What does Isaiah 55:6 mean by "seeking" and "finding" the LORD?

Question: Isaiah 55:6 (ESV):

"Seek the LORD while he may be found; call upon him while he is near;

What does it mean to seek the LORD? What does it mean to find Him?
Answer: The senses (Logos Bible Software) of דָּרַשׁ (seek).

The sense of מָצָא (find).

The context helps  to explain.

Seeking is turning from sin, Finding is God's forgiveness.

Seeking is turning away from our self-made plans, and finding is trusting in God's plans

<code>  Seek the LORD while He can be found,
  Call to Him while He is near.
  7Let the wicked give up his ways,
  The sinful man his plans;
  Let him turn back to the LORD,
  And He will pardon him;
  To our God,
  For he freely forgives.
  8For My plans are not your plans,
  Nor are My ways your ways
       —declares the LORD.
  9But as the heavens are high above the earth,
  So are My ways high above your ways
  And My plans above your plans. (Isa. 55:6–9, JPS)

  11So is the word that issues from My mouth:
  It does not come back to Me unfulfilled,
  But performs what I purpose,
  Achieves what I sent it to do. (Isa. 55:11, JPS)

  5Trust in the LORD with all your heart,
  And do not rely on your own understanding.
  6In all your ways acknowledge Him,
  And He will make your paths smooth.
  7Do not be wise in your own eyes;
  Fear the LORD and shun evil. (Prov. 3:5–7, JPS)
</code>
Comment: Great use of Isaiah 55:7-9, upvoted +1
Answer: God is a spirit, and near to everyone, and he can be found, discovered and experienced by those who seek and call him through their spirit, in "spirit and truth" (John 4:23-24). Seeking him spiritually simply means seeking him earnestly to witness him in one's life. To find God is to have the knowledge (gnosis) of God which means to have a personal acquaintance with him. Humility, repentance, righteousness are generally a prerequisite to find God or receive an answer from him. Those who call or seek him and find him and will have faith and will be saved (Joel 2:32; Rom 10:13).

Jamieson-Fausset-Brown Bible Commentary on Isa 55:6:
The condition and limit in the obtaining of the spiritual benefits (Isa 55:1-3): (1) Seek the Lord. (2) Seek Him while He is to be found
(Isa 65:1; Ps 32:6; Mt 25:1-13; Joh 7:34; 8:21; 2Co 6:2; Heb 2:3;
3:13, 15).
call—casting yourselves wholly on His mercy (Ro 10:13). Stronger than
"seek"; so "near" is more positive than "while He may be found" (Ro
10:8, 9).
near—propitious (Ps 34:18; 145:18).

God is eagerly waiting to be found, as he seeks to save the lost (Luke 15)

Psalms 32:6 Therefore let everyone who is godly offer prayer to you at
a time when you may be found; surely in the rush of great waters, they
shall not reach him.
Isaiah 65:1 I was ready to be sought by those who did not ask for me;
I was ready to be found by those who did not seek me. I said, "Here I
am, here I am," to a nation that was not called by my name.

Vine's Expository Dictionary of New Testament Words    Greek: oida

Know, Known, Knowledge, Unknown:
from the same root as eidon, "to see," is a perfect tense with a
present meaning, signifying, primarily, "to have seen or perceived;"
hence, "to know, to have knowledge of," whether absolutely, as in
Divine knowledge, e.g., Mat 6:8, 32; Jhn 6:6, 64; 8:14; 11:42; 13:11;
18:4; 2Cr 11:31; 2Pe 2:9; Rev 2:2, 9, 13, 19; 3:1, 8, 15; or in the
case of human "knowledge," to know from observation, e.g, 1Th 1:4, 5;
2:1; 2Th 3:7.
The differences between ginosko (No. 1) and oida demand consideration:
(a) ginosko, frequently suggests inception or progress in "knowledge,"
while oida suggests fullness of "knowledge," e.g., Jhn 8:55, "ye have
not known Him" (ginosko), i.e., begun to "know," "but I know Him"
(oida), i.e., "know Him perfectly;" Jhn 13:7, "What I do thou knowest
not now," i.e. Peter did not yet perceive (oida) its significance,
"but thou shalt understand," i.e., "get to know (ginosko), hereafter;"
Jhn 14:7, "If ye had known Me" (ginosko), i.e., "had definitely come
to know Me," "ye would have known My Father also" (oida), i.e., "would
have had perception of:" "from henceforth ye know Him" (ginosko),
i.e., having unconsciously been coming to the Father, as the One who
was in Him, they would now consciously be in the constant and
progressive experience of "knowing" Him; in Mar 4:13, "Know ye not
(oida) this parable? and how shall ye know (ginosko) all the
parables?" (RV), i.e., "Do ye not understand this parable? How shall
ye come to perceive all... " the intimation being that the first
parable is a leading and testing one;
(b) while ginosko frequently implies an active relation between the
one who "knows" and the person or thing "known" (see No. 1, above),
oida expresses the fact that the object has simply come within the
scope of the "knower's" perception; thus in Mat 7:23 "I never knew
you" (ginosko) suggests "I have never been in approving connection
with you," whereas in Mat 25:12, "I know you not" (oida) suggests "you
stand in no relation to Me.

[ESV 1 Corinthians 8:1-3]
1Now concerning food offered to idols: we know that "all of us possess knowledge." This "knowledge" puffs up, but love builds up. 2If anyone imagines that he knows something, he does not yet know as he ought to know. 3But if anyone loves God, he is known by God.

[ESV Proverbs 2:1-11]
1My son, if you receive my words and treasure up my commandments with you, 2making your ear attentive to wisdom and inclining your heart to understanding; 3yes, if you call out for insight and raise your voice for understanding, 4if you seek it like silver and search for it as for hidden treasures, 5then you will understand the fear of the LORD and find the knowledge of God. 6For the LORD gives wisdom; from his mouth come knowledge and understanding; 7he stores up sound wisdom for the upright; he is a shield to those who walk in integrity, 8guarding the paths of justice and watching over the way of his saints. 9Then you will understand righteousness and justice and equity, every good path; 10for wisdom will come into your heart, and knowledge will be pleasant to your soul; 11discretion will watch over you, understanding will guard you,

[ESV Philippians 1:9-10]
9And it is my prayer that your love may abound more and more, with knowledge and all discernment, 10so that you may approve what is excellent, and so be pure and blameless for the day of Christ,


Are both sides of a Avid rotor the same?

Question: i've got a Cotic Roadrat, and the disc mount on the fork is on the right hand side (as you're seated).  However, the front rotor of the avid BB5s (road) i just bought can only be fit on the left fork if I am to follow the installation instructions to the letter - ie rotation must follow the arrow, and the writing must be facing outward.  Can I use this rotor on the right hand side? That is, keep the rotation correct, but have the writing facing inwards?  Are both sides the an avid rotor the same? I assume its the direction of rotation that is the important bit, and not the surface.  Thanks, PB
Comment: I've never heard of disc brakes on the right side. At first I thought you must have the fork on backwards, but I was able to confirm in [their specs](https://www.cotic.co.uk/product/roadrat) and [photographic evidence](https://www.flickr.com/photos/coticltd/10455329913/in/set-72157636896710763) that some roadrats have a right-side front disc brake. More information about their reasoning here: http://www.cotic.co.uk/geek/#ROADHOG_discmount
Answer: Rotors are identical on both sides but are marked to ensure correct rotation as they aren't bi-directional. Few hubs and forks allow for a right hand mounted disc so rotors are only marked for left hand set up. The water and mud shedding capabilities drives the design and direction they should turn.
The earlier Roadrat RB2 was designed for a right hand mounted disc brake (outwards facing on front fork) to negate pressures put on the wheel when braking. The wheel was simply reversed in the drop  out. The new RB3 fork has a left hand mounted disc brake but uses a 9mm thru-axle design which integrates with current 9mm QR hubs. Lawyer lugs achieve the same thing.
Comment: According to their [specifications](https://www.cotic.co.uk/product/roadrat) and [this pic of a roadrat from cotic's flickr](https://www.flickr.com/photos/coticltd/10455329913/in/set-72157636896710763), there are right-side mounted discs on some roadrats.
Comment: Thanks, that's what I wanted to hear. The mount is definitely on the right - I did think I was going mad for a minute.  Opposite to your pick, front-right, rear-left, which surprised me. Its a 2009 model so perhaps before road discs were standardised as mtbs.  Cheers!
Comment: Missed that!! I'll update and only leave the answer to the actual question!
Comment: Does it really matter for road use if its primarily for water and mud shedding ability which determines the rotation?


Higgs boson in space!

Question: Given the fact that the Higgs-like boson has an invariant mass of about 125GeV, could we detect Higgses from Outer Space as we detect photons, neutrinos, protons or cosmic rays? As the Space is the final frontier...Is there any program searching for Higgs resonances from The Outer Space?
Comment: I think I once saw it estimated that at any time there should be about one naturally created Higgs boson in the entire observable universe. If that's true, the rate at which cosmic rays hitting our atmosphere create a Higgs boson would be so low as to never happen. But we need an actual calculation...
Answer: First off, any Higgs resonances we saw would be created in our atmosphere, as the Higgs boson only "lives" for $10^{-22}~\rm s$. So you're really asking about Higgs production due to a primary cosmic ray interacting with our atmosphere.
In order to produce a Higgs boson, cosmic rays of fairly high energies are required. The production of a Higgs boson requires a center of mass energy of at least $m_H$. Since nucleons in the earth's atmosphere are approximately at rest, the center of mass energy of a cosmic ray interacting with a nucleon is given by $$E_{\rm COM}=\sqrt{s}=\sqrt{2mE}$$
where $m\approx 938~\rm GeV$ is the mass of the nucleon and $E$ is the energy of the cosmic ray. For $\sqrt{s}=m_H$, this comes out to about $8.3~\rm TeV$. Even that energy is not enough, because a proton's momentum is spread out among its partons, only one of which is involved in producing a Higgs boson. So you need a proton that is significantly greater than that in energy to have an appreciable chance of producing a Higgs boson. On order $100~\rm TeV$.
Now, at any given place on the earth, cosmic rays of that energy are fairly rare. Looking at the graph for the wikipedia page on cosmic rays suggests that it's on order one per day per square meter.
Furthermore, producing a Higgs boson is a rare event. The Higgs production cross section at the LHC at $\sqrt{s}=7~\rm TeV$ is approximately $10~\rm pb$ and the total proton-proton cross section about $100~\rm mb$. Put together, this means that, when two protons collide with that center of mass energy, the odds of them producing a Higgs boson are roughly $\frac{10~\rm pb}{100~\rm mb}\approx 10^{-10}$. This changes with energy, but it never gets much larger than that, and it's generally smaller for the energy of cosmic rays. So, this gives us on order one Higgs boson per $10^{10}~\rm m^2$ per day.
The surface of the earth is $5\times 10^{14}~\rm m^2$. So, putting all this together, there are optimistically on order $10^4$ Higgs bosons created in the atmosphere every day. Now, this leads to the final problem. Even if we could survey the entire sky for Higgs bosons, the decay of an average Higgs boson is not all that distinctive. The largest decays we could hope to really get much from are $\rm H\rightarrow\gamma\gamma$ (about $10^{-3}$ branching ratio) and $\rm H\rightarrow\mu\mu$ (a few times $10^{-4}$ branching ratio). So if we built an observatory to view the entire sky, we would only get about 10 usable Higgs bosons per day. Keep in mind this was using some rather optimistic rounding. Since realistically we can only survey a tiny portion of the sky to the precision required to identify a Higgs boson, this quickly drops to much less than one a year.
So, trying to do any cosmic ray observations involving the Higgs boson are futile. Cosmic ray observations can be useful in the low energy regime (since there are many, many low energy cosmic rays hitting the earth every second) and the ultra-high energy regime (since those reach center of mass energies significantly beyond those reachable in the LHC), but they are not so useful in the middle regime. The LHC produces more than a billion collisions at $\sqrt{s}=13~\rm TeV$ every second, and has extremely precise instrumentation very close to the collision, allowing for much more data with much greater precision that an cosmic ray observatory could achieve.
Comment: No...I was not implying cosmic rays...I meant   trying to search for a 125GeV line in astrphysical events like Supernovae or galactic centers...
Comment: @riemannium Oh, that's hopeless then. The Higgs decays into *two* photons, so if anything it would be a $62.5~\rm GeV$ line. But since it's only created in ultra-relativistic collisions, those $62.5~\rm GeV$ gammas get Doppler shifted to basically any random old value.
Comment: @Chris  dopler shift would be no problem,  if there was a non explained peak in a specific value. they find positron annihilation http://iopscience.iop.org/article/10.1088/1742-6596/703/1/012001/meta
Comment: @annav By its nature, positron annihilation tends to occur pretty much at rest relative to the medium its in, so the Doppler shift is relatively quite mild: velocities on order $k_BT$ as opposed to velocities very, very close to $c$. Between that and the rarity of Higgs bosons you'd have to take observations for a long, long time to get any sort of peak in the spectrum. I suppose you'd also have problems with multiple scattering of any photons that were created that way.

Higgs boson in space!


Exchange webmail configuration

Question: I am running Outlook Web Access and I need to enforce HTTPS. However, I cannot use forms-based authentication. I have to use HTTP authentication. When a user tries to access to the site via HTTP I need to redirect them to HTTPS and present the http authentication dialog. How can I accomplish this?
Answer: Figured it out already. Create an asp page that redirects to https, and then set the IIS 403.4 error redirect to this file.

Exchange webmail configuration


PCB mounting - flatness

Question: Let's say I have a square PCB with mounting holes near each corner and that the PCB will be mounted to an enclosure with 4 standoffs.  Is there a rule of thumb about how much tolerance I can have on the height of those standoffs?  If the standoffs are not all the same height, then the PCB is going to flex to some degree, so perhaps another way to ask this is how flat does a PCB have to be when it is mounted?
Comment: 1mm or so on a 4" or larger 1.6mm board won't likely cause any problems. The standoffs I usually specify (PEM) have a tolerance of  +.05 –.13mm so there's lots of margin. Thinner boards can easily flex more, but you have to be concerned about the integrity of solder joints to the largest parts in particular, and especially if the package has no "give" (BGA, QFN, 2512 etc.).
Comment: That all depends on your components, how they are mounted, etc, and the type of PCB it is.
Comment: ^this, anyway I'd say that "more than you think" is a quite safe assumption. Have you ever mounted an heatsink on the CPU on a motherboard? PCBs can flex a lot.
Comment: Does rather depend on the  size of the PCB and the magnitude of the error. Some further information would be useful.
Answer: As the comments have mentioned it depends on components, size of board, etc.
As for the board itself, if the standoffs are that irregular then your own strength is going to let you down well before you reach the board's breaking point. A quick look at the datasheet for the boards I get fabricated (from pcbtrain.co.uk, see link below) shows the warp strength is in the region of 50 Kpsi (400+ MPa).
Surface mount components are going to give you the most trouble with bending boards, as others have said. But don't forget things like large electrolytics or bulky connectors. A flexed board is going to have a weak spot. And you'll end up with an oversized capacitor coincidentally placed right on that weak spot. And that oversized cap will sit very close to the chassis that's housing your lovely, new (flexed, but who cares, right?) PCB. And you're going to drop it. And, like a piece of electronic toast, it's going to land upside down, right where that capacitor is pressing against the board. And the board is going to say...
Nothing, because it's broken. At my previous job I have seen it happen regularly in certain mass-produced small electronic devices like pocket and portable radios; the break is ALWAYS in the same place for a given product, and it's invariably a catastrophic failure. In some cases, if the flex is that bad on the board (which you really only get if it's screwed into standoffs, not clipped) you're actually better off not using the anchor point that causes the greatest anomaly.
Datasheet ref: http://www.pcbtrain.co.uk/cp/uploaded/VT481TDSrevA18_9_13.pdf

PCB mounting - flatness


Drupal Views in Glossary mode removing pager

Question: I am adding alphabetical page to the view using glossary mode. I am able to create the alpha pager but the issue is, when I click on the alphabet the alpha pager doesn't appear again. I have to go back to view the alpha pager.
Comment: I am looking for this too. I managed it with some nasty HTML method. Waiting for a better answer.
Comment: Nikhil can you share your mehtod .
Answer: From what I remember, you have to create the Glossary display of the view, and then you set the results page as an Attachment of that view display (attachment being the view display type).
Views ships with a default Glossary view, it's just disabled.  I would suggest enabling that and take a look to see how that does it.
Comment: Chapabu Can you give some idea or link how to create Glossary view and were to enable the default glossary view
Comment: @BLPraveen If you head to the Views list, then scroll down to the bottom.  There will be a view called *Glossary* (or similar) that is disabled by default.  You can either enable that View or clone it and edit it to fit your requirements :)
Answer: I found the solution to this problem.
This link explains how to resolve this issue http://drupal.org/node/349739
Comment: @B L Praveen That link is about Drupal 6. Any idea how to fix this on Drupal 7?
Comment: Its longback I had this issue with one of the website. I never looked it back again.If I could look into the website I can find a solution. I cannot setup on my system to test it.


What is "rational"?

Question: Rational = x
x = ?
I've been defining words for myself for a while and one that I haven't defined rational yet. Anyone have a good definition for one, on a basis of utilitarianism.
Comment: I have one, but not on the basis of utilitarian "diction".
Comment: If one used utilitarianism in order to derive definitions, how could that work? Think about that. But if one uses utilitarianism to derive the definition one may find that the derived definition of rational may not be related to utilitarianism at all.
Comment: @anon I'd argue not, but thank you for the answer nevertheless
Comment: So are you looking for a definition of rational _behaviour_, as opposed to rational _belief_?
Comment: @NikosM. You define words on the basis of connotation (which is essentially a hypothetical as it seems that our knowledge of connotation is based on perception) - you alter the definition of words to bring about good.
Comment: @anon There are multiple dictionaries. None of them define words in such a way that their definitions are axiomatic.
Comment: I suggest to use utilitarian principles in order to derive the definition yourself. How would that work? For example you may take the definition of rational that most people are happy with. But you may find out that this definition of rational is egoistic, thus not aligned with utilitarian principles
Comment: might there be multiple senses to 'rational'?
Comment: @J.G. no. I am looking for the definition of rational on a utilitarian basis. Rational behavior = behavior that is rational (or something to that effect), and the same applies to belief.
Comment: @Swift360 As I understand it, utilitarianism indicates when behaviour is ethical, not rational, while leaving beliefs unassessed.
Comment: A coherent totality of communicable beliefs that are interrelated in discernible "ratios" and correspond, more or less, to causation in their material environment.
Comment: See e.g. [Practical Reason](https://plato.stanford.edu/entries/practical-reason/) as well as [Historicist Theories of Scientific Rationality](https://plato.stanford.edu/entries/rationality-historicist/)
Answer: A coherent totality of communicable beliefs that are interrelated in discernible "ratios" and correspond, more or less, to causation in their material environment.
Answer: Of a belief, having accurate predictive power matching empirical data; or of an action based on such belief, maximising efficacy.
Answer: The term 'rational' is related to the term 'ratio', and implies the ability to effectively measure and balance concepts and ideas. It's a natural analogy to applying principles of geometry to crafts. A man who doesn't measure or calculate well is a sloppy craftsman, and builds (say) weak, wobbly, oddly-proportioned furniture. A man who does measure and calculate well makes sound, sturdy, well-ordered furniture. It's the same with cognitive work. Assessing premises, measuring phrases, calculating intellectual trajectories, etc.: these actions create sound, sturdy, rational arguments.
Answer: Some deep thought on "the principle of reason" can be found in Heidegger's essay The Essence of Ground in Pathmarks.
Quoting from the start and the end to give a flavour of the content.
Page 100

The Problem of Ground

The "principle of reason" as a "supreme principle" seems to preclude
from  the very outset anything like a problem of ground. Yet is the
"principle of  reason" an assertion about ground as such? As a
supreme principle, does it  reveal at all the essence of ground? The
usual, abbreviated version of the  principle states: nihil est sine
ratione, nothing is without reason. Transcribing it positively, this
states: omne ens habet rationem, every being has a reason.  The
principle makes an assertion about beings, and does so with regard
to  something like "ground." Yet what constitutes the essence of
ground is  not determined in this principle. It is presupposed for
this principle as a  self-evident "idea." However, the "supreme"
principle of reason makes use  of the unclarified essence of ground
in yet another way; for the specific character  of principle belonging
to this principle as a "grounding" principle, the  character of
principle belonging to this principium grande (Leibniz) can after
all be delimited originarily only with regard to the essence of
ground.
The "principle of reason" is thus worthy of question both in the way
it  is posed and in terms of the "content" it posits, if the essence
of ground is  indeed now able to become a problem over and above some
indeterminate  general "idea."

Page 132

... looking back to the point of departure of our investigation, we
shall now  discuss briefly whether anything, and if so, what, has been
attained with  regard to the problem of the "principle of reason"
through our attempt at  shedding light upon the "essence" of ground.
The principle means: every  being has its reason [ground]. The
exposition we have given first of all  illuminates why this is so.
Because being, as understood in advance, "intrinsically"
grounds things in an originary manner, every being as a being in  its own way announces "grounds," whether these are specifically
grasped  and determined in an appropriate way or not. Because "ground"
is a transcendental  characteristic of the essence of being in
general, the principle of  reason [ground] is valid for beings.
Ground, however, belongs to the essence  of being because being (not
beings) is given only in transcendence as a  grounding that finds
itself in a projecting of world.
Furthermore, it has become clear with respect to the principle of
reason  [ground] that the "birthplace" of this principle lies neither
in the essence  of proposition nor in propositional truth, but in
ontological truth, i.e., in  transcendence itself. Freedom is the
origin of the principle of reason [ground];  for in freedom, in the
unity of excess and withdrawal, the grounding of  things that develops
and forms itself as ontological truth is grounded.
Coming from this origin we not only understand this principle in its
intrinsic possibility, but we also gain an eye for something
noteworthy and  hitherto unelucidated concerning the way it has been
conceived, something  that is, however, suppressed in the way the
principle is ordinarily formulated.
Answer: A form of obligation which includes moral and extra-moral, but not aesthetic, norms: we are obliged to believe fire is hot.
Comment: this is fun haha
Answer: Thoughts or behavior based on a set of acceptable assumptions following acceptable patterns of thought (a weak variant of being logical).
It is the opposite of irrational, with thoughts or behavior not following from acceptable assumptions, or not following acceptable patterns of thought.
If two people do not agree on assumptions, their thoughts and behaviors may appear irrational to each other. Same if they don't agree on suitable patterns of thought. However as long as they consider each other's assumptions or thoughts pattern mutually acceptable despite of differences, they would still appear rational to each other.
As such a person of science and a person of religion might consider each other as rational, or as irrational if the differences are too pronounced.
While this is subjective, a person may still perceive certain own thoughts or behavior as irrational, this is part of the human condition.
In science people strive to have assumptions backed by observations and math, and using logical patterns of thought. In philosophy, people try to have contradicting free assumptions and using logical patterns of thought backed by philosophers.
Outside of science and philosophy however, people mostly strive to have a large overlap with their peers in what assumptions and patterns of thought they use, to avoid being perceived as irrational. Being "more rational" is typically regarded as a virtue for careers, whereas being too rational can be seen as a negative clashing with other demands in society, such as for compassion.
School education has the goal of grounding people in acceptable assumptions and teaching acceptable patterns of thought (among other goals), ideally still leaving enough freedom for choosing ones own path.
Comment: That sounds pretty close to what I'd want it to be. Thank you very much.

What is "rational"?


Cedar shims disappeared because of COVID-19

Question: I've been hunting for contractor quality cedar shims - the super-wide kind that easily break along the grain. The big box stores don't have them and neither do the local lumber yards. At one of them I visited, they told me that they haven't been able to get them since COVID started. What's the connection? What other materials might be affected by COVID going forward?
Comment: I'm voting to close this question because this is an economics question, not Home Improvement.
Answer: This has been a well-known issue since the pandemic started. Materials have been scarce, and prices have increased dramatically.
This seems to be due to issues on both the supply and the demand sides. Supply has decreased because of obvious issues related to COVID, workers being sick with COVID, factories having to shut down for periods of time, and working at limited capacity due to having to keep physical distance between staff.
Demand has also increased, it seems, because people are stuck at home, and are bored. Seems people either undertake remodeling projects due to being stuck at home and not having other "entertainment" options, and of course having to look at parts of their home they don't like much more know. There is probably also the component of the stimulus money being used on construction projects. Oh, and mortgage interest rates have been at historic lows for a long time, causing more demand on new construction.
Answer: Like PhillipNagel said, the March/April red-alert for COVID caused a lot of production shutdown.  Cedar shingles are not essential work.  Shutdowns like this have largely stopped, even though recent numbers are spectacularly much worse (even in NYS). So the supply chain is working again.
However, demand went insane, on several prongs.
Cooped up at home: DIY home improvement!
Many blue governors and most tech companies have ordered "If you CAN work from home, you MUST work from home". With all that commute time back, people want to do home improvement projects.  They're also just adding space to get a little privacy!   A lot of these people have never done a home improvement project, so they think $8 2x4's are normal.
The building boom for people fleeing cities
In the last 20 years the trend was "New Urbanism": live in the urban core (or in dense-pack suburbs right on top of top-tier transit)... and have no car (or in a family, fewer cars).  Partly for quality-of-life: see actual opera. See top acts at venues you can walk to.  Have face-to-face gatherings of others into obscure interests (where a critical mass of fellows can only be had in big cities).  10,000 fantastic restaurants, and you couldn't even find the city's Applebee's, why would you need to?  And partly for environmental conscience reasons - city living is more sustainable.
Now, everything that makes the city fun is closed.  Proximity to your neighbors is scary. Public transit is radioactive.  Further, giving up cars no longer has the environmental cachet it used to, since electric cars are happening for real now.
So there's a new rush for the suburbs and exurbs, and that's made demand for housing higher than ever.  And of course, that's been soaking up the scarce building materials.
I for one think that trend will reverse once COVID passes.  Which of course puts all the more pressure on homeowners to get their properties sold now - necessitating yet even more home improvement.
Comment: On the "stuck at home" part: My evil twin has upgraded quite a few home WiFi networks because people now find that the "super fast incredible" WiFi by default from a standard Comcast/Xfinity or Verizon router is not super, fast or incredible. But it didn't matter before when the problem was limited to hiccups in cute cat videos. When it becomes hiccups in Zoom calls with the boss or Zoom school, it matters **a lot**. I'm sure there have been plenty of "turn the basement into a real home office" projects too. I'd do that myself, except I never seem to have the time...too busy on SE :-)


How can I let NetworkManager connect to Ethernet when I'm not logged in?

Question: I've a Intel NUC6i3SYH running Debian GNU/Linux Unstable. It's connected to the internet through Ethernet. I'm using NetworkManager, but it only connects to the internet when I'm logged in. How can I set up NetworkManager so that it connects to the internet even when I'm not logged in (so that I could remotely SSH into it)?
Answer: Don't set connection.permissions which restricts the profile to a user.
nmcli connection modify "$PROFILE" connection.permissions ""
Or use the GUI to configure the profile in a similar manner .


Goverment Hacking Bitcoin

Question: Most of the bitcoin community is aware that the U.S. Government "seized" 2 million USD worth of bitcoins at the times current exchange rates. How would the U.S. go about using these. Generally with seized property they set up auctions, but how would that occur.
Answer: Seized items that are not of obvious benefit to the thief eventually get sold at public auction. If they fall into a process that doesn't understand the technology or there are auctioneer agreements then it will be a traditional auction. Value is not likely to be understated or undersold as this will be a very marketable item to advertise.
Stolen goods are also used to attempt interdiction. The government would use the coins in sting operations and in attempts to undermine confidence.

Goverment Hacking Bitcoin


Regarding the $\mathbf{E} × \mathbf{B} $ drift in the Earth's magnetic field

Question: So I have a burning question: The only reason that the $\mathbf{E} × \mathbf{B} $ drift doesn't generate an electric current is because both the electrons and the positive ions move towards the same direction (towards Earth's ionosphere) therefore a charge separation isn't formed? Are opposite velocities the deal breaker for charge separation or am I missing something else?
Comment: The force that comes as the product of the electrical current of the magnetotail being perpendicular to Earth's magnetic field that results in the particles drifting towards Earth
Comment: Can you explain what you mean by ExB drift? I know this as the momentum or equivalently the energy transport of the EM field.
Answer: In uniform crossed magnetic and electric fields, the motion of a charge can be separated into a gyromotion and a constant drift. A constant motion implies zero force, so the charge doesn't affect the drift velocity.
The drift velocity is derived in George K. Parks, Physics of Space Plasmas (1991) pages 93-97, and the derivation is a bit too long to reproduce here, so I'll just give the answer:
$$\mathbf{v} = \frac{\mathbf{E} \times \mathbf{B}}{B^2}.$$
Note that charge doesn't appear in this expression. The Lorentz force on a particle with charge $q$ is
$$ \mathbf{F} = q\mathbf{E} + q\mathbf{v} \times \mathbf{B}.$$
If you substitute the drift velocity in this equation and use $\left(\mathbf{E} \times \mathbf{B}\right) \times \mathbf{B} = \left(\mathbf{E}\cdot\mathbf{B}\right)\mathbf{B} - B^2\mathbf{E}$), you can confirm that $\mathbf{F} = 0.$
Comment: But the E x B field actually acts on the particles and it propels them towards the ionosphere the fact that it doesn't distinguishes between the two charges is irrelevant
Comment: You wanted to know why there is no charge separation, and the answer is that the opposite charges are drifting in the same direction - on average. The $E \times B$ drift applies to the center of the gyromagnetic motion, not the instantaneous motion of each charge.
Answer:
The only reason that the E x B drift doesn't generate an electric current is because both the electrons and the positive ions move towards the same direction...

The ExB-drift is independent of charge, so yes, both ions and electrons will undergo the same ExB-drift velocity.

...therefore a charge separation isn't formed?

Counter streaming particles of opposite charge do not a charge separation make.  Rather, such a scenario leads to a current given by:
$$
\mathbf{j} = \sum_{s} \ n_{s} \ q_{s} \ \mathbf{V}_{s}
$$
where $n_{s}$ is the number density, $q_{s}$ is the total charge (including sign), and $\mathbf{V}_{s}$ is the bulk velocity vector of species $s$.
As an example, if electrons and protons flow in the same direction both at $\mathbf{V}_{o}$, there would be zero net current (assuming quasi-neutrality) because the two species have the opposite charge.  If they flow relative to each other, i.e., $\mathbf{V}_{e} \neq \mathbf{V}_{i}$, then there will be a net current.

Are opposite velocities the deal breaker for charge separation or am I missing something else?

Charge separation in a plasma is generally difficult because it results in electric fields.  Since a plasma is an ionized gas of freely moving electrons and ions, any electric field will quickly act to eliminate itself by doing work on the charged particles.  Most plasmas have incredibly high conductivities, so the lifetime of charge separations are very short.
I think you are confusing flow with charge separation, which are two different phenomena.  Particle species in plasmas can flow relative to each other without generating any charge separation.


Can a Filipino go outside the airport and travel on my own during a layover in Incheon airport without a visa?

Question: If ever I passed through immigration in Incheon (with Filipino citizenship, US tourist visa and LA as my final destination) and my choice of free transit tour is not available or full already, can I commute there on my own instead?
Answer: You can only pass through immigration and thus exit the airport if you can get a visum.
Since the Philippines is not on this list:
https://en.wikipedia.org/wiki/Visa_policy_of_South_Korea
You need to apply for a visum in advance.
Some airports have these "free city tours" for these tours you do not clear immigration and thus does not require a visum.
The fact that you hold a visum for the US does not make a difference for South Korea.
Comment: Hi. Based on my experience, you only need to pass through the immigration (even without prior visa but with connecting flight), once you are granted, you can go on your own or join the super cheap transit tours. The transit tour desk is literally just near the exit so I guess you can leave on your own. I suggest joining the tours but make sure you'll always be prompt in returning to the tour bus or else you'll be left behind. Hope this will help others in the future!


What are these black bugs on my zucchini plant?

Question: I've noticed these black "fruit fly" looking bugs on my plant lately. They appear to fly and they are everywhere. I've taken a few pics. I can't tell if they're doing damage but I want them gone. Can anyone tell me what they are, and a natural remedy to get rid of them?
Answer: I'm going to guess fungus gnats because I always think tiny black bodied winged bugs are fungus gnats but in this case I think I'm right. :)
It looks like you have the plants in containers. Is that how you purchased them or did you pot them yourself? I had purchased a bag of organic potting mix once that was infested with fungus gnat eggs. Once I watered it they came to life. If your potting mix contains compost it's possible they came in the bag. I've only had the problem once with a bag I mail ordered (forget why I bothered to do that.)
At the time I was filming a time lapse video of some grass growing which is how I found them. You can see a portion of my video where I used neem oil to kill the fungus gnats and their larvae on my site. It was pretty effective. You can see the little white dots crawling around the container on the right for the first couple of seconds until I sprayed. Any insecticidal soap I believe will work.
I think the adult flying gnats are harmless but the larvae can feed on the roots. You can also let the potting mix dry out which would kill the larvae as they need moisture. I hear bacillus thuringiensis works too. That's the bacteria they use in mosquito dunks. You dissolve the dunk in your watering can then water the plants.
Comment: Fungus gnats are most likely to be flying in your face rather than resting on a bloom.  Could they be aphids?
Comment: @kevinsky The fungus gnats I had were hanging out on the grass blades. It was my first thought since they were in pots. They also look like those black whinged bugs I saw hanging out with aphids on my spirea in my previous question.  Couldn't get a good photo. Neem killed those too but ants brought back some more green aphids. Hard for me to tell from the photos.
Comment: I saw something similar (like black aphids or something) on my in-door tomatoes. I haven't seen any since I physically removed them once or twice, though (it's been a week or two since I've seen one).


Naming of hydroxides

Question: In naming of compound, for example in strong base; KOH and $\ce{Ca(OH)2}$ have different formula, in potassium hydroxide, one hydroxyl group is attached while in calcium hydroxide two hydroxyl group are present, but both named hydroxide, please explain.
Comment: Related: [Why is CaCl2 called calcium chloride?](http://chemistry.stackexchange.com/q/14141/7951)
Comment: First, do you know why "one hydroxyl group is attached" in KOH and two in $\ce{Ca(OH)2}$?
Comment: Related: [How are ionic formulas written?](http://chemistry.stackexchange.com/q/47104/7951)
Answer: A lot of chemical nomenclature is historic and not very systematic.
Common names for chemicals are often determined by history and don't always completely describe the detailed chemical structure or formula. The theory of chemical bonding and structure was not fully developed until the 20th century but we did a lot of chemistry before that. People got used to common names for things and those names persisted even when more systematic names were developed to introduce more clarity about the relationship between names and formula/structure.
For example, acetone is the commonest name for propan-2-one but the common name gives no indication at all about the chemical structure. Many organic compound have very unwieldy systematic names (reflecting the gargantuan complexity of the chemistry of carbon compounds). Fluoxetine (the active ingredient in prozac) is N-methyl-3-phenyl-3-[4-(trifluoromethyl)phenoxy]propan-1-amine and that is too big even to fit on the pill bottle and even the formula, C17H18F3NO, is a bit of a mouthful despite not giving away a lot of structural information about how the atoms are connected.
In the case of simple inorganic compounds like simple hydroxides the situation is similar. The names arose because they described the key chemical parts making up the compound, in this case a metal (as an ion) and a hydroxide ion (OH-). Rather than the unwieldy but more precise names describing the number of ether part of the compounds, chemists apply a little chemical knowledge and keep simpler names for many compounds. Most chemists know that alkali metals (Na, K etc.) form ions with a single positive charge and, therefore, if they form hydroxides they will only contain one hydroxide. Alkaline earth metals (Mg, Ca etc.) form ions with two positive charges and their compounds will contain two hydroxides. This is because all atoms want to reach the lowest possible energy state, which usually is the elecron structure of noble gases. Since most chemists know this, there is no point in using a more complex and longer name. This isn't always true: transition metals can form ions with several different "oxidation states" (which basically means the charge on the ion in simple ionic compounds: iron for example is commonly found both as Fe2+ and Fe3+) and, in these cases the name needs to contain extra information to help the chemist tell them apart.
Comment: Acetone is the ketone of acetic acid. There are similar (but less common) names such as propione (3-pentanone, from propionic acid), butyrone (4-heptanone, from butyric acid), isovalerone (2,6-dimethyl-4-heptanone, from isovaleric acid), enanthone (7-tridecanone, from enanthic acid), etc.

Naming of hydroxides


Randomising diode

Question: I've been watching Minder DVDs and one of the extras from Series 6 is a Premium Bonds ad from 1986 which explains that their super-duper ERNIE 2 machine uses diodes (I think) that emit pulses at random intervals in order to generate random numbers for the prize draw. Unfortunately, I wasn't able to find the film on Youtube to link to! They were saying that the use of a physical randomising device makes predicting the results of the machine impossible but obviously it was an ad so they were selling a product! How good are these diodes in fact? How inexpensive would they (or similar hardware) be to add to a computer to generate random numbers instead of an algorithm? Would they produce "randomer" numbers than a time-seeded algorithm? I.e. would it be worth the cost of an extra component or are algorithms random enough for most uses?
Comment: For what it is worth, the average PC's PRNG is a bit more thoroughly thought of than just a "time-seeded algorithm". Nice article about Linux also discusses how the CSPRNG works. https://pthree.org/2014/07/21/the-linux-random-number-generator/ (CSPRNG = Cryptographically Secure Pseudo Random Number Generator).
Answer: There is a reasonably good article on Hardware random number generator at wikipedia.
Yes, you may want to add a 'True Random Number Generator' (TRNG) to a computer, and manufacturers do. In some applications, a TRNG is worth a premium price.
For example Sun Microsystems had a hardware random number generator board available as an extra cost option for some of their products, used for example in banking or e-commerce. It was worth paying the extra to generate a large number of truly random numbers at a high rate.
It is described at Sun Microsystems Sun Crypto Accelerator 6000
Software based random numbers use sources of entropy in the system to 'seed' their behaviour (say hard-disk head seek time). However those techniques require reasonable amounts of entropy to give them a good source of randomness. At very high rates of random number generation their isn't enough time to for the systems underlying sources of randomness to provide that. Hence the randomness may be inadequate.
Generating high quality random numbers isn't a problem restricted to web sites and the net. For example ST Micro implement a 'True Random Number Generator' on their STM32F2 and STM32F4 Cortex-M3 and Cortex-M4 Microcontrollers. Those devices are embedded devices, and so are intended to be used to implement cryptographically secure applications.
It is described in  an application note called "AN4230 Application note: STM32F2xx, STM32F4xx random number generation validation using NIST statistical test suite"
It says

The True random number generator peripheral implemented on STM32 ..., and it is based on an analog circuit. This circuit generates a continuous analog noise that feed a Linear Feedback Shift Register (LFSR) in order to produce a 32-bit random number.
The analog circuit is made of several ring oscillators whose outputs are XORed."
Answer: You've asked several sub questions so I'll just address a couple.  The whole topic of hardware random number generation is a huge multi disciplinary subject so'll I'll also further restrict this to diodes(*) and the concept of entropy.
Entropy is unpredictability, or surprisal. It comes from chaotic systems and quantum mechanics.  You can think of it as rolling a die where the single spot is actually a piece of lead rather than paint.  It will fall single spot down most of the time.  But occasionally it will land otherwise.  This is an entropy source with considerable bias as it mainly reads a "6".  Most entropy sources in nature are either biased or have non uniform probability distributions.  The entropy then gets converted to a uniformly distributed set of numbers via post processing and you have your true random number generator (TRNG). Like ERNIE.
The randomising diode is perfect for amateur and professional low rate random number generation.  It's junction breaks down when reverse biased and creates totally unpredictable electrical noise.  You can then process this entropy to extract random numbers.  Maxim have a good application circuit based around a 1N759 Zener diode.  Here's an extract:-

They've measured noise out to 100 MHz.  If this were to be sampled at say 4 bits via a flash ADC, you might expect random numbers in the order of 100 Mbits /s.  This is very much an upper limit as I've never seen a commercial diode based TRNG anywhere this speed.  I'm quite chuffed to achieve 100 kbits /s.
ERNIE 1 used a similar diode like device called a thermionic valve typically used for voltage stabilisation.
You could make the point that a TRNG produces randomer random numbers than a pseudo random number generator (PRNG) but this is somewhat a semantic /philosophical argument.  Some say that a TRNG is effectively the same as a PRNG as their respective outputs will be computationally indistinguishable from random.  However, a PRNG is seeded with a start point and then manipulates this initial value algebraically to produce output.  It you know the seed, you can totally predict the output.  A TRNG has no seed.  The seed is the physical diode itself and our current level of understanding means we cannot predict it's entropic output.  John von Neumann famously said that "Any one who considers arithmetical methods of producing random digits is, of course, in a state of sin."
TRNGs  sound sexy.  The current ERNIE (5) is extremely slow yet is marketed as a wonderful truly unpredictable system drawing upon decades of nostalgia and anthropomorphism.
*Note:  Some say that the emitter base junction in a transistor is a diode which can be used for similar randomness purposes.  I would draw your attention to this question why you shouldn't.
Comment: Is this how one decouples a 100 MHz circuit, by sharing a capacitor?
Comment: @CJDennis Some clarifications:  Actually entropy is uncertainty aka randomness aka irreducible information.  That's the accepted definition of information theory entropy.  You've confusing entropy /randomness with uniformly distributed numbers.  My dodgy die only has one lead spot on the Ace side so it will generally fall  six side up. That's the bias.
Comment: Entropy is not randomness. It takes thousands of rolls to determine if a die is biased or not. If each spot of a die is actually a small piece of lead and the die is otherwise unbiased and with a density less than lead, the spot will cause it to land **6-side down** (1-side up) more often than **1-side down** (6-side up). The level of bias will be determined by the difference in densities between the die and the spots.

Randomising diode


Trunk+Etherchannel group

Question:
The problem encountered in configuring the Trunk+Etherchannel group is that PC1 and PC2 are on different network segments, but I want PC1 to be able to successfully interconnect with PC2 (ping is successful), how should I configure it?
I would really appreciate your help!
Comment: I don't really think the title of this question accurately represents the question.  The port-channel between the switches (and the fact that it's a trunk) does not have anything to do with making two PCs in different broadcast domains able to connect at layer-3.
Comment: Maybe this question will point you in the right direction: https://networkengineering.stackexchange.com/questions/80430/communication-between-different-vlans
Comment: Please add the full switch configs to your question, using the editor's `{}` preformat option.
Comment: Or this one: https://networkengineering.stackexchange.com/questions/28446/how-can-hosts-on-two-different-vlans-communicate
Answer: You need a router in between to act as gateway between the 2 subnets or you need to reconfigure the 2 devices so they are on the same subnet (/22 instead of /24 or similar change) and same VLAN.
Also you left VLAN 88 out of the allowed VLAN list so whatever is in that VLAN won't pass over the trunk.
Comment: Hi FrameHowitzer :
Sorry, I am a beginner in CCNA. Could you please elaborate and guide me in more detail?By the way, I have tried to use OSPF to allow IPs in two different network segments to communicate with each other,but I want to advance to achieve Etherchannel group But encountered a bottleneck, hope to get your help, thank you.
Comment: You probably need to do more research and figure out how to do it all or just hire someone to help you because you seem to have multiple questions about basic setup and configuration. That goes beyond the nature of this site.

If you want help configuring Etherchannel you need to post a new question about that. The configuration you have in your question appears correct and should work fine with the setup you indicated.

Trunk+Etherchannel group


Possible to outsource computations to AWS and utilize results locally?

Question: I'm working on a robot that uses a CNN that needs much more memory than my embedded computer (Jetson TX1) can handle. I was wondering if it would be possible (with an extremely low latency connection) to outsource the heavy computations to EC2 and send the results back to the be used in a Python script. If this is possible, how would I go about it and what would the latency look like (not computations, just sending to and from).
Comment: Hey there! Did you need any more help with this question? You hadn't picked an answer so I thought you might need some more ideas.
Answer: Possible: of course it is.
You can use any kind of RPC to implement this. HTTPS requests, xml-rpc, raw UDP packets, and many more. If you're more interested in latency and small amounts of data, then something UDP based could be better than TCP, but you'd need to build extra logic for ordering the messages and retrying the lost ones. Alternatively something like Zeromq could help.
As for the latency: only you can answer that, because it depends on where you're connecting from. Start up an instance in the region closest to you and run ping, or mtr against it to find out what's the roundtrip time. That's the absolute minimum you can achieve. Your processing time goes on top of that.
Answer: I think it's certainly possible. You would need some scripts or a web server to transfer data to and from. Here is how I think you might achieve it:

Send all your training data to an EC2 instance
Train your CNN
Save the weights and/or any other generated parameters you may need
Construct the CNN on your embedded system and input the weights
from the EC2 instance. Since you won't be needing to do any training
here and won't need to load in the training set, the memory usage
will be minimal.
Use your embedded device to predict whatever you may need

It's hard to give you an exact answer on latency because you haven't given enough information. The exact latency is highly dependent on your hardware, internet connection, amount of data you'd be transferring, software, etc. If you're only training once on an initial training set, you only need to transfer your weights once and thus latency will be negligible. If you're constantly sending data and training, or doing predictions on the remote server, latency will be higher.
Comment: The one thing I'm having trouble with is the actual sending of the data. How could I go about it (assuming the CNN is fully trained) for each frame? Would it be best to send the frame to AWS or something else? Thanks!
Comment: It should be possible to actually reconstruct the model on the embedded device using the weights generated during the training of the model on the server. So all you have to do is transmit that array of weights (maybe only once, at the start), and then do whatever calculations you need on your device. I would *not* recommend sending your test data to AWS each time because that would make things (potentially) slow.
Comment: Thats more of the question I was asking. Right now I'm maxing out at about 3.5FPS due to a lack of memory on the embedded so I was curious if I might be able to bump that up through AWS outsourcing. Seems like doing that >4 times a second though is unlikely. I guess I'll look to slimming down the model instead.
Answer: I am a former employee of CENAPAD-UFC (National Centre of HPC, Federal University of Ceará), so I have something to say about outsourcing computer power.
CENAPAD has a big cluster, and it provides computational power for academic research. There, professors and students send their computation and their data, defined the output and go drink a coffee or two, while the cluster go on with the hard work. After lots of flops, the operation ended and they retrieve it via ssh and go back to their laptops.
For big chunks of computation, you wish to minimize any work that is not a useful computation. One such thing is commumication over detached computers. If you need to know when the computation has ended, let the HPC machine tell you that.
To compute stuff effectively, you may want to go deeper in the machine and performe some kind of distribution. I use OpenMP to distribute computation inside the same machine/thread distribution. To distribute between physically separated computers, but next (latency speaking), I use MPI. I have installed also another cluster in UFC for another department. There, the researchers used only MPI.
Maybe some read about distributed/grid/clusterized computing helps you:

https://en.m.wikipedia.org/wiki/SETI@home ; the first example of massive distributed computing that I ever heard
https://en.m.wikipedia.org/wiki/Distributed_computing
https://en.m.wikipedia.org/wiki/Grid_computing
https://en.m.wikipedia.org/wiki/Supercomputer ; this is CENAPAD like stuff

In my opinion, you wish to use a grid-like computation, with your personal PC working as a master node that may call the EC2 slaves; in this scenario, just use communication from master to slave to send program (if really needed) and data, in such a way that the master will have another thing to do not related with the sent data; also, let the slave tells your master when the computation reached it's end.


Did any Early Church Fathers believe that Mary was without sin?

Question: The immaculate nature of Mary is a doctrine, that holds that the Virgin Mary was free of original sin from the moment of her conception and that she lived a holy and sinless life, but did any of the early church fathers believe that Mary was without sin?
Answer: From a Roman Catholic "Encyclopedia of Theology" I gleaned the following:
The absolute sinlessness of Mary was taught for the first time by Pelagius and Augustine, then that view was expanded into freedom from original sin which was later attributed to Mary.
The belief that Mary was without sin is bound up with the view that Mary was not merely a virgin at the time the Holy Spirit caused her to become pregnant, but the claim that she was perpetually virgin. However:

"There was no fully general consensus before the Council of Ephesus.
It was not taught by Tertullian, Origen or Jerome. But it was upheld
by Irenaeus, the apocryphal writings of Clement of Alexandria, the
Consultationes Zacchaei et Apollonii, and Gregory of Nyssa. ...From
the 4th century on, her perpetual virginity is often mentioned."
(Encyclopedia of Theology Edited by Karl Rahner, p. 896,
article by Michael Schmaus, Burns & Oates, London, 1981)

It was after the 7th century that the formula of "virginity before, in and after giving birth" came into use. This progressed into comparing Mary with Eve. As Eve's disobedience brought ruin, the faith and obedience of Mary brought salvation - Catholics claimed. And Mary's supposed role in the history of salvation was compared with that of the [Catholic] Church (taught by Irenaeus, then Hippolytus and Tertullian but above all by Augustine.

"After some uncertainty about the holiness of Mary, inspired by Lk
2:48, and indeed some negative pronouncements (Cyril of Alexandria),
the absolute sinlessness of Mary was taught for the first time by
Pelagius and Augustine. This thesis was soon expanded into the freedom
from original sin which was then attributed to Mary. In the East,
something similar was taught by Andrew of Crete and John of Damascus.
No express testimony to Mary's freedom from original sin is found in
the West before about A.D. 1000. Bernard of Clairvaux, a fervent
admirer of Mary, and Thomas Aquinas remained doubtful. Theologians
could not harmonize the universal necessity of redemption with the
thesis being developed in Mary's freedom from original sin. In the
course of the controversy William of Ware (c. 1300) and Duns Scotus
developed the notion that Mary remained free from original sin by
virtue of Jesus' redemption...
The doctrinal declaration of the fifth session of the Council of Trent
on original sin stated that it was not the intention of the Council to
include Mary in its teaching on the universality of original sin. In
the 19th century, faith in the freedom of Mary from original sin had
matured so widely that Pius IX could teach it as a dogma in 1854."
(Ibid. p. 897)

It appears that no expression of Mary's freedom from original sin is found in the West before about AD 1000. And it wasn't until the 19th century that faith in the freedom of Mary from original sin had matured to the degree that Pius IX could teach it as a dogma in 1854.  You may thus grasp that Catholic views about Mary took hundreds of years to gradually build up. But the Early Church Fathers that introduced the idea of Mary being absolutely sinless were Pelagius (early 400s, and later declared a heretic) and Augustine (354 - 430 and declared one of the greatest Church Fathers).
Comment: @jaredad7 That extra info. appreciated. I was simply quoting from the official Catholic Encyclopedia which said "the absolute sinlessness of Mary was taught for the first time by Pelagius and Augustine" and, in the West, after A.D.1000. But the Q asked for early Church Fathers, so was Ephraim the Syrian one such? For sure, such ideas would predate official Church Father written statements; that is understood.
Comment: It can't be the case that Pelagius was the first to teach the doctrine. This CA article (https://www.catholic.com/tract/mary-full-of-grace) quotes earlier Fathers. For instance, Ephraim the Syrian wrote, when Pelagius was still just a boy: "You alone and your Mother are more beautiful than any others, for there is no blemish in you nor any stains upon your Mother."
Comment: @jaredad7  Oh, no, the Encyclopedia of Theology I quoted from was published in 1981, edited by the renowned Catholic scholar Karl Rhaner, subtitled, "The Concise Sacramentum Mundi". I would be surprised if such a writing from Ephraim the Syrian was not known in the early 1980s.
Comment: Yes, Ephraim is a Church Father. Are you quoting from the New Advent Catholic Encyclopedia? That one is mostly good, but it is over 100 years old. It may be that this writing from Ephraim was not known to the authors.
Answer: Did any Early Church Fathers believe that Mary was without sin?
There are a few Church Fathers that at least made believed so especially when making a comparison of Mary to Eve.

Mary as the second Eve
This celebrated comparison between Eve, while yet immaculate and incorrupt — that is to say, not subject to original sin — and the Blessed Virgin is developed by:

Justin (Dialogue with Trypho 100),

Irenaeus (Against Heresies III.22.4),

Tertullian (On the Flesh of Christ 17),

Julius Firmicus Maternus (De errore profan. relig xxvi),

Cyril of Jerusalem (Catecheses 12.29),

Epiphanius (Hæres., lxxviii, 18),

Theodotus of Ancyra (Or. in S. Deip n. 11), and

Sedulius (Carmen paschale, II, 28).

The absolute purity of Mary
Patristic writings on Mary's purity abound.

The Fathers call Mary the tabernacle exempt from defilement and corruption (Hippolytus, "Ontt. in illud, Dominus pascit me");

Origen calls her worthy of God, immaculate of the immaculate, most complete sanctity, perfect justice, neither deceived by the persuasion of the serpent, nor infected with his poisonous breathings ("Hom. i in diversa");

Ambrose says she is incorrupt, a virgin immune through grace from every stain of sin ("Sermo xxii in Ps. cxviii);

Maximus of Turin calls her a dwelling fit for Christ, not because of her habit of body, but because of original grace ("Nom. viii de Natali Domini");

Theodotus of Ancyra terms her a virgin innocent, without spot, void of culpability, holy in body and in soul, a lily springing among thorns, untaught the ills of Eve, nor was there any communion in her of light with darkness, and, when not yet born, she was consecrated to God ("Orat. in S. Dei Genitr.").

In refuting Pelagius St. Augustine declares that all the just have truly known of sin "except the Holy Virgin Mary, of whom, for the honour of the Lord, I will have no question whatever where sin is concerned" (On Nature and Grace 36).

Mary was pledged to Christ (Peter Chrysologus, "Sermo cxl de Annunt. B.M.V.");

it is evident and notorious that she was pure from eternity, exempt from every defect (Typicon S. Sabae);

she was formed without any stain (St. Proclus, "Laudatio in S. Dei Gen. ort.", I, 3);

she was created in a condition more sublime and glorious than all other natures (Theodorus of Jerusalem in Mansi, XII, 1140);

when the Virgin Mother of God was to be born of Anne, nature did not dare to anticipate the germ of grace, but remained devoid of fruit (John Damascene, "Hom. i in B. V. Nativ.", ii).

The Syrian Fathers never tire of extolling the sinlessness of Mary. St. Ephraem considers no terms of eulogy too high to describe the excellence of Mary's grace and sanctity: "Most holy Lady, Mother of God, alone most pure in soul and body, alone exceeding all perfection of purity ...., alone made in thy entirety the home of all the graces of the Most Holy Spirit, and hence exceeding beyond all compare even the angelic virtues in purity and sanctity of soul and body . . . . my Lady most holy, all-pure, all-immaculate, all-stainless, all-undefiled, all-incorrupt, all-inviolate spotless robe of Him Who clothes Himself with light as with a garment . . . flower unfading, purple woven by God, alone most immaculate" ("Precationes ad Deiparam" in Opp. Graec. Lat., III, 524-37).

To St. Ephraem she was as innocent as Eve before her fall, a virgin most estranged from every stain of sin, more holy than the Seraphim, the sealed fountain of the Holy Ghost, the pure seed of God, ever in body and in mind intact and immaculate ("Carmina Nisibena").

Jacob of Sarug says that "the very fact that God has elected her proves that none was ever holier than Mary; if any stain had disfigured her soul, if any other virgin had been purer and holier, God would have selected her and rejected Mary". It seems, however, that Jacob of Sarug, if he had any clear idea of the doctrine of sin, held that Mary was perfectly pure from original sin ("the sentence against Adam and Eve") at the Annunciation.
St. John Damascene (Or. i Nativ. Deip., n. 2) esteems the supernatural influence of God at the generation of Mary to be so comprehensive that he extends it also to her parents. He says of them that, during the generation, they were filled and purified by the Holy Ghost, and freed from sexual concupiscence. Consequently according to the Damascene, even the human element of her origin, the material of which she was formed, was pure and holy. This opinion of an immaculate active generation and the sanctity of the "conceptio carnis" was taken up by some Western authors; it was put forward by Petrus Comestor in his treatise against St. Bernard and by others. Some writers even taught that Mary was born of a virgin and that she was conceived in a miraculous manner when Joachim and Anne met at the golden gate of the temple (Trombelli, "Mari SS. Vita", Sect. V, ii, 8; Summa aurea, II, 948. Cf. also the "Revelations" of Catherine Emmerich which contain the entire apocryphal legend of the miraculous conception of Mary.
From this summary it appears that the belief in Mary's immunity from sin in her conception was prevalent amongst the Fathers, especially those of the Greek Church. The rhetorical character, however, of many of these and similar passages prevents us from laying too much stress on them, and interpreting them in a strictly literal sense. The Greek Fathers never formally or explicitly discussed the question of the Immaculate Conception.
Comment: CJ is back to posting duplicates... wish you'd waited before writing this up


PID 1 in Docker persistance

Question: I have set up a Kippo server to run in a docker container. Everything runs fine,until you kill the container. Killing the container(by restarting the machine or through docker kill) makes it unusable with STDERR "Another twistd server is running, PID 1". How can I solve this problem? I don't have issues to reset the file system of the container or something like this because everything I want is logged to a database. Thank you very much
Answer: Within Docker, each container runs in its own PID namespace.  This means that the process started by the dockerfile will always be PID 1, and PIDs will count upwards from there.
twistd expects that PIDs are non-deterministic enough that it can check to see if another twistd is "already running" by simply comparing to see if the PID is the same.  Since, in Docker, the PID will always be 1, this check always succeeds, and twistd thinks it shouldn't start up.  If the container exits un-cleanly, twistd won't get the opportunity to clean up its .pid file, and the state will be preserved within the container's filesystem.
Since the Docker daemon will namespace containers and prevent two matching twistd processes from starting up at the same time anyway, the .pid file and its related checking is not actually useful at all, so you should disable it.  You can disable it by changing your command line to include the --pidfile= option (exactly as such, nothing after the "=") before the plugin name.  I'm not familiar with Kippo, but for twistd web this would be twistd --pidfile= web.
I hope that this helps!
Comment: I have already specified a pidfile which is removed if something goes wrong. My problem is that after killing the container(not stopping it) twistd has the issue,not the kippo. And since kippo runs through twistd,kippo can't run. Can I somehow remove all the pid files and the container starts as a brand new?
Comment: Change the `twistd` command line that runs kippo in the way I described in my answer and there will be no need to delete the pid files, as they will be neither written nor checked.
Comment: Glad to hear it - thanks for following up, and thanks for using Twisted!
Answer: It sounds like your pid1 in the container is not properly cleaning up after itself when it is told to stop. This likely means it does not remove its pidfile, so when you go to start the container again it refuses to start.
One way to handle this may be to introduce something like supervisord that can handle receiving the stop signal, and then gracefully shut down the kippo server.
Another solution might be to simply start the container in read-only mode. In read-only mode, the container doesn't get a write layer, and the root filesystem is simply read-only. Kippo may, however, refuse to start if it can't create a pidfile to begin with. (see docker run --read-only)
Yet another solution would be to set up an ENTRYPOINT script that removes the pidfile before calling exec on kippo.
Comment: Kippo won't run in read only mode because some keys must be generated. I will try to provide them at building. Also, I don't think that the kippo.pid is the issue because it gets removed if it already exists. Where can I find the twistd pidfile?

PID 1 in Docker persistance


Different SSL Certificate Authorities for domains and subdomains?

Question: Our main site www.example.com has a regular VeriSign SSL certificate. However, we need ssl for our dev environment for accurate testing. Is it possible to use another ssl from a different (cheaper) provider for our dev.example.com and stage.example.com domains? We have a load balancer with different ip's so having unique IP's should not be an issue.
Comment: You want to host prod, dev and staging on the same machine? o_O
Comment: well no, they are on separate machines, but we have our analytics.example.com and other similarly named applications on the same machine.
Answer: Yes
It is most certainly possible. I've worked with a few companies who buy expensive certificates (eg. Extended Validation certificates) for production sites, and cheaper certificates (Domain Validated certificates), sometimes from different Certificate Authorities, for development and testing purposes.
That being said, you might want to approach this a little differently though, especially when considering an "accurate testing" motive
First of all, SSL certificates primarily provide 3 things:

Encryption
Integrity
Authenticity

The first feature, encryption, is provided no matter what CA you choose. A 2048-bit CSR signed by DigiSign provides just as strong encryption as a 2048-bit CSR signed by VeriSign.
The second feature, integrity, lies in the nature of the connection, that is: an encrypted message exchange between a client and a trusted server. So without the confidence in the Encryption and Authenticity, integrity of the message exchange cannot be achieved. Furthermore a message digest is calculated to ensure that the message is the same before encryption and after decryption
The third feature, authenticity, is determined by the trust relationship between the CA that issued your SSL certificate (eg. VeriSign), and the user (the client). This is important, because client software might trust one CA but not another. An example might be: testing a secure web application on a mobile device. The mobile device trusts the CA that issued your "test"-certificate, but as soon as you go into production everything breaks, because the CA that issued your production certificate is not trusted by the mobile device.
A possible solution (and one that I would often recommend), is the use of wildcard certificates, a certificate that matches a wildcard subdomain component, like: *.example.com. This way you can secure www.example.com, analytics.example.com, dev.analytics.com etc., all with the same certificate.
Wildcard certificates are pretty expensive, but if you have a handful of sites or more, it might be worth your while
Comment: Great notes! Don't overlook self-signed certificates in IIS7 as the cheapest means of adding SSLs to development & staging sites for testing!
Comment: @ChrisAnton if the technical part (encryption), is the only worry, then yeah, self-signed certificates is without doubt the cheapest option :-)
Comment: @ChrisAnton: You can get free Class 1 SSL certificates at StartSLL, and they are recognised by all major browsers.
Answer: It will depend on your LB config and your webserver choice and config but yes it should be possible to have different certificates on each subdomain.


Average momentum in quantum mechanics over some finite interval of space

Question: Why can't the expectation value of momentum be computed over some finite interval of space? Something like, $$ \int_a^b \psi^* \hat{p}\psi ~\mathrm{d}x.\tag{1}$$  I understand that usually we compute expectation value over all space, but does the above quantity mean anything? Also, I am not assuming that $[a,b]$ is the width of some box that the particle is confined to.
Comment: Because that isn't the definition of expectation value? By definition, the expectation value of an operator is the value that one would obtain if one repeated the same experiment on infinite identical copies of the same system and took the average of all the results. Given this, $\langle p \rangle$ is defined as integral over all space. Now, if the wave-function itself is non-zero only in the range $(b,a)$, then it would be what you said above.
Answer:
Technically, OP's eq. (1) is the expectation value
$$ \langle \hat{A} \rangle ~:=~ \int_{\mathbb{R}} \!\mathrm{d}x~\psi^{\ast} \hat{A}\psi \tag{i}$$
of a non-Hermitian operator
$$ \hat{A}~:=~ 1_{[a,b]}(\hat{x})\hat{p}.\tag{ii}$$
Here $x\mapsto 1_{[a,b]}(x)$ denotes the characteristic/indicator function for the interval $[a,b]\subseteq \mathbb{R}$. We assume $a<b$.
$\hat{A}$ is non-Hermitian, since $\hat{x}$ and $\hat{p}$ do not commute
$$ [\hat{x},\hat{p}]~=~i\hbar~{\bf 1}.\tag{iii} $$
Formally, to get a Hermitian operator/observable, consider e.g. instead the symmetrized operator
$$ \hat{B}~:=~\frac{1}{2}\left\{1_{[a,b]}(\hat{x}),~\hat{p}\right\}_+
~:=~\frac{1}{2}\left(1_{[a,b]}(\hat{x}) \hat{p}+\hat{p}1_{[a,b]}(\hat{x})\right)
~=~\hat{A} +\frac{i\hbar}{2}\left(\delta(\hat{x}\!-\!b)-\delta(\hat{x}\!-\!a)\right).\tag{iv}
$$
If there exist some boundary conditions such that
$$\psi(a)~=~0~=~\psi(b), \tag{v}$$
(e.g. because of an infinite potential at $x=a$ and $x=b$), then the operators $\hat{A}$ and $\hat{B}$ are effectively the same.
\psi
Fun fact: If the wave function $\psi\in\mathbb{R}$ is differentiable, real, and vanishes $\psi(\pm\infty)=0$ at infinity, then the expectation value vanishes
$$ \langle \hat{B} \rangle~\stackrel{(\text{iv})}{=}~
\frac{1}{2}\int_a^b \!\mathrm{d}x\left(\psi^{\ast} (\hat{p}\psi) + (\hat{p}\psi)^{\ast}\psi\right)~\stackrel{(\text{vii})}{=}~\int_a^b \!\mathrm{d}x ~mj~=~0, \tag{vi}$$
where
$$j~:=~\frac{1}{2m}\left(\psi^{\ast} \hat{p}\psi-\psi \hat{p}\psi^{\ast}\right)~=~0\tag{vii}$$
is the probability current.
Comment: Thanks so much for your answer. Could you please tell me what $1_{[a,b]}(\hat{x})$? Is it $\Theta(\hat{x} -a) - \Theta(\hat{x}-b)$? Where $\Theta$ is the step function.
Comment: $\uparrow$ Yes.
Comment: If I compute $\langle \hat{B} \rangle$ for $\psi(x,0)=e^{-x^2}$ I get zero* for any $[a,b]$ (Of course this is a wave packet with zero mean momentum).  Does $\hat{B}$ have any physical interpretation, for e.g., measuring momentum only in a fixed region of space and then calculating the momentum average over many measurements.

*Hopefully I did the calculation correctly.
Comment: Okay, thinking about this a bit, $\hat{B}$ will always give zero because of integration by parts, at least when $\psi$ is real.
Comment: $\uparrow$ Right, when $\psi$ is real
Comment: Okay I feel like I have come around in a circle because the integrand in (vi) is the probability current of a unit mass particle.
Comment: Apologies for making this thread so long. There is an extra factor of 2 in (vi) after the equality (vii).
Answer: A wavefunction gives you the probability of a particle to be seen somewhere. If it's not confined to be in some region, like a potential well or something, then it has a probability to be seen anywhere in the space. That's why the integration runs from $-\infty$ to $+\infty$ (remember that you could never pinpoint a quantum mechanical particle in space). That can be converted to a finite volume of space if the confinement is strong. For example, in the case of a particle in an infinite potential well, the boundary condition is that the wavefunction should vanish at the potential well boundaries.
But, in reality, there are no such infinite potential traps where you can confine a particle to.  All potentials available are finite. So, the condition that the wavefunction should vanish at the boundary is no longer valid, which means that, the wavefunction could spread out of the boundary (called quantum tunneling). Such wavefunctions are called unnormalized. That's why you integrate over the entire space for getting the probability and hence the expectation value of the particle.


3 black wires to new dimmer switch

Question: I have a switch controlling two lights in hallway. I purchased the Lutron C-L DimmerScL-153PH-WH. I have 3 black wires and 1 copper wire coming out of wall.  The old switch was not connected to the copper wire. The 3 black were connected to the switch with just an on/off toggle.  How do I connect my new dimmer to the 3 black coming out of wall?
Comment: Are there two switches that control the lights (3-way)?
Comment: You probably should've marked things. The extra black probably feeds something downstream. You'll need to determine which black feeds the light circuit and which is the source hot.
Comment: Are any of the wires connected to the same terminal?
Answer: Are there some white wires in the back of the box?  If so, surely the blacks are:

One black (and partner neutral) which comes from power source.  It will be hot all the time, even when separated from the others.
One black (and partner white) going to other things such as receptacles, light switches and the like, things intended to be always-hot.
One black (and its partner white) going to the lamp - the one controlled by the switch. If you wire power source to this, the lamp will be on all the time.

The normal connection is to a) hook up all grounds.    b) attach the black/hot going to the lamp, to one of the switch terminals.  c) tie the power-source and the "other stuff" hot to each other.  d) Tie those two to the other terminal on the switch.
How to tie 2 wires to one terminal
Comment: I don't see how that could work, codewise. People often neglect the mush in the back of the box.
Comment: I assumed that there were no neutrals in the box based on the wording of the question. Could have been mistaken, though.

3 black wires to new dimmer switch


When to use "has/have had" in a sentence?

Question: I often see sentences like:

I have had this car for 5 years.
I have had Ice cream.

I googled it but didn't understood it well.
Comment: Recommended reading: http://ell.stackexchange.com/questions/13255/canonical-post-2-what-is-the-perfect-and-how-should-i-use-it
Answer: These are instances of the present perfect: http://www.englishpage.com/verbpage/presentperfect.html
As you can see in the page linked above, there are many, complex rules governing when to use the present perfect.
Your examples may be particularly confusing because they use the same word "have" in two different ways.  The first "have" in each sentence is the auxiliary "have" required for the present perfect.  The second "have" is "have" used in the sense of ownership (eg, "I have 2 cars").  Its present perfect form is "had."
It might clarify to think of similar sentences using a different main verb: "love".

I have loved this car for 5 years.
I have always loved Ice cream.
Answer: I have had this car for 5 years.
I have had the ice cream.
Both the sentences are in the present perfect. The word "have" is an auxiliary verb.  The word "had" is the past participle of the verb "have".
The main verb " have" in the form of the past participle has been used in different senses in these sentences.  In the former sentence, it's a stative verb and it implies to own, whereas in the latter it's a dynamic verb and it means to eat.
The present perfect in the first sentence shows the state of your having (owning) this car that started in the past and continues in the present. It's been 5 years since you had (owned) this car.
The present perfect in the second sentence is indicative of recently finished action of having (eating) the ice cream.


Who is responsible for getting developers in the same team to work together?

Question: In a team of 9, 2 of the Senior Developers do not see eye to eye, professionally and personally, the relationship has deteriorated even before a Scrum Master has joined the team.
What is the responsibility of the Scrum Master here?
What is the responsibility of management here?
Answer: It does not matter about the development methods or the titles of roles that the development method creates. Leadership needs to intervene between two team members in conflict. They don't need to like each other but they need to work well together. Leadership should, at first, enable them to work out their differences on their own. If that fails, then leadership needs to facilitate as a mediator to resolve whatever ails them. If that fails, remove and replace...either both of them or one of them, whatever makes the most business sense.
Comment: I know agile has some set of rules around organization structure. I don't really know all of them. In my world, an employee reports to someone. It is that someone who bears the responsibility of resolving conflict. Whether someone else jumps in to help before it gets to that person is immaterial. But when a formal intervention is required, it needs to go up the reporting chain.
Comment: @TobySpeight, I attempted to keep my answer development methodology agnostic. That's why I wrote "leadership." However that gets defined, leadership should cover it.
Comment: Sure: both our answers are useful (I was more specific because of the [tag:scrum-master] tag on the question).  And I did misread "leadership" as implying "management", when that's not necessarily the case.  Leadership is certainly one of the attributes of a good Scrum Master.
Comment: Who tries to intervene first, is it the SM in one of the teams, or a manager who hears it first?

We're struggling with weak management, feels like Scrum Masters are accountable for everything and not just coaching Agile and Scrum and leading the team and org to deliver value.
Comment: I take a similar but different viewpoint in my answer: management has a role, but only after the scrum master has exhausted the possibilities for resolving this within the team.
Answer: Part of the Scrum Master's role is to coach the team towards higher performance.  To this end, you should be helping developers find ways to accommodate disagreements and advance the Team's goals rather than getting stuck on personal differences.
This is the kind of individual coaching that's best done mid-sprint, when you are less involved with the team-level coaching you tend to be doing at the start and end of each sprint.  Keep it low-key, rather than calling out the behaviour in public.  And listen as well as speak - find out whether these two really have a personality clash or whether they are both genuinely trying to promote what's best for the team and its product.
It's also important to know when to stop.  Coaching is a two-way thing, and if some of your developers are totally uninterested in being part of a team, and don't accept the need to work together, then you will need to involve their line-management.  At that point, however, you'll be able to explain to the manager(s) how you have attempted to resolve the problem, and that it really is an issue that needs to be escalated.
Comment: Very good. This is something I usually avoid, individual developer coaching. I usually focus with the teams and the org. I leave individual behavior issues to line management.
It's something I should work on, currently I have too many teams.
Answer: Very often the responsibilities of the management and the scrum master overlap, and this is good as it shows they have an alignment on team goals. I'm a firm believer that all managers should know how to coach their team members, not only on career growth, but also on conflict resolution - and this is something scrum masters should also promote and do. So this is how I approached the same issue in the past; I hope it will spark some ideas for your current setup:
Root cause

I think the most important thing here is to understand the root cause of the issue. Why are these 2 developers having issues when working together? Is it an expectations management problem, or are they competing for something? By figuring this out first the next steps will be clearer.

Scrum Master as a mediator

On the team level, the scrum master can aid the relationship by acting as a mediator in a meeting to ease the differences between the 2 developers and coach them to understand that it is okay to disagree with each other, but that they should commit anyways to work together.

Democratic agreement

Include them in the decision making: go into a meeting room and show them the problem on a white board and actively ask them for ideas to make the situation better. How the best case scenario looks like? And the worst? By making them part of the solution you'll get a much more longer commitment to whatever outcome they decide.

Experiment mindset

With these kind of interpersonal issues it is always recommendable to keep an experiment mindset, so you don't need to solve the issue and make them love each other; your goal is to make the situation 1% better by trying something out that may change if we see it is not working. Keep the ball rolling, keep the solution alive, changing and adapting.

Management

All of the above also applies to management, it is a collaboration between the scrum master and the management to make the situation better. The management should use the 1on1 meetings to go deeper into the root cause of the problem and help them find middle ground - perhaps even adding it as an item in their career goals to work on this.

Let go

Having said that, we should also accept that sometimes people cannot work well together and investing the time and effort on fixing this may not be the best thing for the business or the team. Sometimes it is better to have a hole in the team, than an ***hole


What is the magnitude of the force on a charged particle due to electromagnetic radiation?

Question: Suppose there is an electromagnetic wave moving forward in the $\mathbf{\hat{k}}$ direction.  Its electric/magnetic field components are given by:
$$\mathbf{E} = E_0 \sin(kz - \omega t) \mathbf{\hat{i}}$$
$$\mathbf{B} = B_0 \sin(kz - \omega t) \mathbf{\hat{j}}$$
If a particle of charge $q$ was lying on the wave's trajectory, the Lorentz force law says that the force is given $\mathbf{F} = q(\mathbf{E} + \mathbf{v} \times \mathbf{B})$. However, is an electromagnetic wave a combination of both E and B fields, requiring both fields to be plugged into the equation, or does the force on the electron only depend on one of the fields, and is  an EM wave only either an electric field or a magnetic field at one instant?
Edit: changed x to z in expression for EM wave.
Answer: Note. As indicated by user23660, the EM wave must be transverse which means the $x$'s in your phases should instead be $z$'s.
At a given time $t$ and spatial point $\mathbf x = (x,y,z)$, the electromagnetic wave you consider is a combination of both of the fields;
\begin{align}
  \mathbf E(t,\mathbf x) &= E_0\sin(kz-\omega t) \hat{\mathbf x} \\
  \mathbf B(t,\mathbf x) &= B_0\sin(kz-\omega t) \hat{\mathbf y}
\end{align}
There are some special points at which both of the fields vanish though.  In particular, any time the argument of the $\sin$ is an integer multiple of $\pi$;
\begin{align}
  kz-\omega t = n\pi, \qquad n\in\mathbb Z
\end{align}
As a result, a particle sitting in the wave will experience both of the fields at once, and both of these fields will have to be plugged into the Lorentz force equation.  Explicitly, Newton's Second Law along with the Lorentz force equation with both fields plugged in gives us the following equation of motion:
\begin{align}
  \ddot{\mathbf x} =\frac{q}{m}(E_0\sin(kz-\omega t) \hat{\mathbf x} +B_0\sin(kz-\omega t)\dot{\mathbf x}\times\hat{\mathbf y}).
\end{align}
In components, this can be written as the following system of coupled differential equations:
\begin{align}
  \ddot x &= \omega_0\sin(kz-\omega t)(c - \dot z) \\
  \ddot y &= 0 \\
  \ddot z &= \omega_0\sin(kz-\omega t) \dot x
\end{align}
where I've used the relationship $E_0 = cB_0$ and I have defined
\begin{align}
  \omega_0 = \frac{qB_0}{m}.
\end{align}
As far as I can tell, this is a pretty nasty system, and I'm not sure if the general solution can be written in closed form (although admittedly I haven't really tried very hard to figure that out.)  It's actually not so bad since $y$ is completely decoupled from $x$ and $z$, and it's differential equation simply implies constant velocity in $y$.  This leaves a pair of coupled equations for $x$ and $z$.
Comment: It feels like the kind of system that should have some cute solution. Now I'm curious...
Comment: @DavidZ Yea I agree.  I'm surprised I've never seen this problem tackled before in standard books, but perhaps I haven't really payed enough attention.  I'd be curious to know if you find a clever method of solution.
Comment: Indeed, I'll let you know if I find anything.
Comment: If you consider the relativistic motion, ii will have analytical solution. https://deepblue.lib.umich.edu/bitstream/handle/2027.42/70253/PHPAEN-10-5-2155-1.pdf?sequence=2            This paper equation 13
Comment: But indeed, recently my EM hw require us to solve the nonrelativisitc motion. That's your differential eqn, I don't know how to solve it.
Comment: See https://physics.stackexchange.com/questions/275930/motion-of-charged-particle-in-em-wave and http://iopscience.iop.org/article/10.1088/0305-4470/9/11/008/meta
Answer: In linear polarization, the electron is accelerated by the electric field in x-direction, and therefore moves in the y-magnetic field of the wave. In the far field both fields are always present and reverse synchronously, so the electron performs an oscillation in the z-direction with doubled frequency. This oscillation vanishes with circularly polarized light. If you are interested in details, look here https://www.researchgate.net/publication/259232654_Inherent_Energy_Loss_of_the_Thomson_Scattering
The formula for ω0 in the preceding answer makes no sense, because the magnetic component of the wave is not constant.


lead in concrete stains

Question: I live in an old lake house built about 1938 to 1940 and the entire slab is concrete and stained red, I was told that lead was used in the concrete when the slab was poured.  Is this true and how do I cover it up and seal in the lead
Comment: In all my years, I have never seen concrete poured with color added so it is throughout the concrete. Even if it was added as a topcoat, I have not seen that done in all the old homes I have worked on. Nor have I ever heard of lead making concrete red, but then again, maybe I can learn something....
Comment: Hello, and welcome to Home Improvement. If an answer is helpful, please click the large check mark next to it to accept. And, please [take our tour](//diy.stackexchange.com/tour) so you'll know how best to participate here.
Answer: Is it true? Try a lead testing kit, commonly available at hardware stores - while primarily intended to test paint, I'd have to think it would give some indication. For a more definitive test you can probably send a sample to a lab. Red Lead was a common pigment, yes. Whether or not that was what was used on your slab, only testing will tell.
Whether you even need to seal in the hypothetical lead is debatable - the primary concerns with lead paint are children eating flaking paint or dust - if the slab does have lead but is not crumbling away and being eaten or inhaled, there isn't a pathway for the hypothetical lead to get into you.
Answer: To be safe, just buy an epoxy coat for concrete floors from your home improvement store. It's easy to mix the 2 part epoxy and spread and I've done numerous floors with it. Sika makes a great product and you can use it with or without color flakes. Warning. It will stink pretty bad for a day or two as it cures. Be very careful to start the furthest corner from where you back out the door, and work the room back and forth evenly because you do not want to trap an area that you can't reach or end up walking through it! You will never get it off your shoes.

lead in concrete stains


Playwritting with vim

Question: I've started using vim for things besides programming, (taking notes, etc.) but something I haven't been able to replace final draft with vim yet just because there are so many things I need, so I was looking to see if any of you had taken a stab at this issue.Just to give you an idea of the features I am looking for: auto indention, different modes for different things like dialogue, character names, etc, changing my font to courier for specific. Another thing I'd like that I don't have in final draft is custom auto completion for commonly used words, names, and phrases. If something like this doesn't exist if you guys knew of any implementations of the features described above or resources to help me figure out how to implement them myself that would also be helpful. Also I use neovim if that matters.
Comment: Do you know about **Fountain**? http://fountain.io/ It's a plain-text markup language for screenplays. I don't know if it would be usable or useful for playwriting or not, but it might be worth a look. There's a vim syntax plugin for Fountain files too: http://www.vim.org/scripts/script.php?script_id=3880
Comment: I have a similar issue and I solved it using Latex. With minimal markup you get your text nicely formatted in a neat pdf and with some effort you can make your own commands to speed up writing for oft recurring situation (start a new act,  open dialog etc.) I would put It as an answer if the question were reopened, illustrating why latex + vim make a great combo. This seems a sensible question for this site and I don't see it as too broad
Answer: I think you could create your own filetype (.play?) and define custom indent and syntax for it. See :help filetype, :help indent and :help syntax. You can also read the Steve Losh book "Learn Vimscript the Hard Way". It has some chapters on Vim filetypes.
Vim and Neovim inherit the font family and size from your terminal but you can use bold, italics and two types of underline.
The ins-completion feature provides dictionary completion. You can add k{dict} to your $MYVIMRC file like so:
set complete=ken,kes

And now, when you press Ctrl+N in insertion mode a pop-up with words from English and Spanish will appear.
See :help 'complete' for more details.
Now if you are using Neovim I recomend you to try deoplete, an asynchronous auto-completion engine. It provides dictionary completion among others an you can write your own sources. So, for dictionary completion you could declare something like:
let g:deoplete#sources={
  \ 'play': ['dictionary']
  \ }

Playwritting with vim