Can student claim verbal or physical harassments one year after my graduation to the university? Can this claim revoke my degree?

Question: I graduated from a U.S university one year ago. If one year after my graduation a person or a group of persons claim(s) to the university that I harassed them (verbally or physically), could this claim lead to the revoking of my degree?
Comment: As for the first part, you need to look at the rules and laws in place at the institution. We don't know those, and even if we did, this sounds way too much like legal advice for me to be comfortable giving you advice.
Comment: For the second part, see [What are the criteria for degree revocation?](https://academia.stackexchange.com/questions/153661/what-are-the-criteria-for-degree-revocation)
Comment: https://academia.stackexchange.com/a/153665/ Should be answered here.
Answer: Universities and colleges are governed by their own rules. I would be surprised if a degree revocation would be possible based on bad behavior alone, even if the bad behavior would  be criminal. Bad behavior is usually sanctioned in other ways such as expulsion or suspension, or by going through the criminal or civil justice system. After graduation, the institution itself is usually not in a position to sanction the now ex-student in a meaningful way. They could kick the ex-student out of the alumni association and send a letter of reprimand, maybe. Redress for a victim would need to go through the criminal or civil court system.
Degree revocation usually needs to be based on some type of grievous academic misconduct, such as repeated cheating on examinations or serious plagiarism in a thesis.
However, without knowing your institution and the rules of that institution, nobody here can answer this question.
Answer: People can claim whatever they want, and a claim by itself should be no basis for disciplinary action. Now, if their claim is substantiated with evidence, the consequences will depend on the severity of your actions. "Verbal or physical harassment" (your words) covers a wide range of behavior, from saying something others don't like, to stalking (I don't really know what other behaviors could be incldued under "physical harassment": if you physically touched people, that'd be assault.) It is unlikely to result in the revocation of a degree at any university I know of. But there might still be consequences if the act was illegal, e.g. if you stalked, you might still get a restraining order issued against you, etc.


Mezuzos on an "eruv"

Question: What we colloquially call an "eruv" is actually intended to be a halachic doorway (tzurath hapethach) to count as a partition delineating a reshuth hayachid (private domain). As such, every post should really be obligated in a "mezuza" (see Chazon Ish Hilchos Mezuza 172; see also, however, Sefer Chovas haDar 5:1, both cited here). Leniencies are suggested where there is a threat that the mezuza scroll might be defaced by the public. Are there any Rabbis, communities (or private eruvim, for that matter) that do indeed put mezuzoth in the posts?
Answer: We live in a square made up of 8 buildings with 4 entrances.
We have doorposts connected by a string at every entrance, as an Eruv.
When a neighbour - some 15 years ago - made a bris at home and invited Reb Chaim Kanievsky שליט"א to be Sandek, he noticed this.
He paskened that we need a Mezuza at each entrance.
As a result we replaced the string with a solid lintel. Why? 1. Aligning a Mezuza under a string is next to impossible. 2. Strings snap and then the Mezuzah has to be refastened; a pain when it's solidly affixed to prevent vandalism.
As to why a regular Eruv does not have Mezuzot on every entrance, I've been told that these doorposts are not for entering and exiting and thus do not need a Mezuza.
See Kitzur Shulchan Aruch סימן יא - הלכות מזוזה:

אַךְ אִם יֵשׁ אֵיזֶה פֶתַח שֶׁאֵינוֹ עָשׂוּי אֶלָּא לְהַכְנִיס דֶּרֶךְ שָׁם אֵיזֶה מַשָּׂא לִפְרָקִים וְיֵשׁ שָׁם פֶּתַח אַחֵר לִכְנִיסָה וִיצִיאָה, אֲזַי הַפֶּתַח הֶעָשׂוּי רַק לְהַכְנִיס מַשָּׂאוֹת, פָּטוּר

Doors that are rarely used - e.g. for deliveries only - are exempt from Mezuza if there are other entrances that are usually used.
Comment: Do you check them every 25 years?
Comment: As in "שְׁתֵּי פְעָמִים בַּיּוֹבֵל"? I've been wondering if it's sensible to wait that long...
Comment: I don't think I've ever seen an *eruv* that didn't include at least some sections that are entered and exited. (It's probably worth pointing out that just because one doesn't notice the doorway, doesn't mean one hasn't entered/exited it.)
Comment: @Loewian, absolutely - and IIRC the fancier Eruvs have real doorways with doors that can actually block streets, and I suspect they have Mezuzoth; I'll keep an eye out for them and report back.

Mezuzos on an "eruv"


Does sexual arousal really release testerone?

Question: So I have been told that the more sexual stimulation created by a male, the more testosterone his body produces. Is this true?
Comment: This seems like something that belongs on skeptics exchange.
Answer: Yes, testosterone is produced more when you have sexual stimulation. This is because testosterone is produced in the testicles, which are responsible for sexual reproduction. When a male is aroused, his testosterone levels will spike up, due to the fact that it stimulates the chemicals moving around in the guy's testicles. In a 2012 study, it was discovered by British researchers that levels of testerone increased in almost forty percent of men after visiting a sex club. http://www.dailymail.co.uk/news/article-2239621/Researchers-test-mens-testosterone-levels-rise-arousal--visiting-sex-club.html


Flag for a modified meeting with Exchange Web Services

Question: I trying to find a way to determine if meeting details have changed so I can update the records of it in a database that is used to display the details for the meetings on a web site.
I know there is Appointment.LastModifiedTime but that also changes when a response is returned. I want something that will change only if there was an update to the meeting details.
I've seen Appointment.IsUnmodified and tested it with a new meeting but it still returned false.
Does anyone know of a reliable way to check this?
On a side note, is there any id associated with an item that I can use as a reference in the db? I've been using itemID, but i read that under certain circumstances that will change. Is that true?
Answer: You can store the ChangeKey along with the UniqueId in the database.


How to monitor DHCP leased ip address

Question: I have Ubuntu server 12.10 as DRBL and CloneZilla. How can I find out how many IP addresses have been assigned to the clients. How do I control/monitor the DHCP daemon service(stop/start/status)?
Answer: To monitor Dhcp leases just type in terminal :
gedit /var/lib/dhcp/dhcpd.leases

Comment: Is `gedit` really the best way to peek into that file? First, it requires a desktop environment, which is usually not present on a server installation. Second: launching an editor suggests this file could be modified, but I'm pretty sure that editing it can cause nothing but trouble.
Comment: This is sometimes on `/var/lib/NetworkManager/*.lease`
Comment: Why Gedit? Just use `cat /var/lib/dhcp/dhcpd.leases`
Answer: All the answers above are partial. And to be honest there is no simple solution. 1) You can parse the dhcpd.leases database file and get information on active leases, but

you will not get information on any FIXED addresses (assigned by a line like:
host switch1      { hardware ethernet a1:b2:c3:d7:2f:bc ; fixed-address switch1.mydomain.com; }

and this also is not really giving any information on when was the last time a dhcp ack was sent to the machine.

2) on the other hand you can parse the dhcpd.log file to search for ack lines (they look like this):
2017-03-12T08:44:52.421174+01:00, Linuxx, info, dhcpd: DHCPACK on 10.0.0.63 to 68:ab:35:59:9c:a1 via 10.0.0.1

Which is giving you information on DHCPD requests and replies but there is no information about actual leases (time, status).
What you should really do is to do BOTH. First parse the log file, and then update the file with information obtained from dhcpd.leases file with database for missing information like lease start-end etc.
Now: I have played circa 2 full workdays till I have created a solution which creates a HTML table with ALL active leases, both FIXED and dynamic. Here is the code that you can place in your cgi-bin folder or wherever.
#!/usr/bin/perl
#####################################################################################
# list dhcpd active leases
#   - both "fixed" addresses which are normally not placed into leases database
#   - and dynamically given leases which are present in leases DB
# working for isc-dhcpd-server service but should also work for other compatible
# dhcpd servers.
# produces HTML or CSV list of leases
# in shell can pipe to lynx:
#   ./dhcp-leases.pl | lynx -stdin
#
# written by Marcin Gosiewski, BV Grupa s.c. Poland <firstname.lastname@example.com> http://www.bvsystemy.pl/
# based on portions of code by Jason Antman <email@example.com>
#
# to make it work change the $logfilename and $leasedbname below and modify
# the regexp in second part of code (see below) to match your log lines format
# also you can optionally turn off reverse dns lookup (see below) which speeds up the process
# of table creation and is useless unless you have reverse dns populated for
# your fixed or dynamic leases
#
# CHANGELOG:
#     2017-03-13: initial version
#     2019-08-15: extended for @logprog by Jim Klimov
use Socket;
use strict;
use warnings;
no warnings 'uninitialized';

# adjust this to match your files location: both log file and leases
# database. We use 2 last log files from logrotate, but you can add as many as you want
my @logfilenames = ( "/var/log/LOCALAPP.dhcpd.log.1", "/var/log/LOCALAPP.dhcpd.log" );
# Alternately, on systems without explicit log (e.g. with systemd journals), use empty array of files:
### my @logfilenames = ( ); # if empty, use output from logprog below
my @logprog = qw ( sudo journalctl --no-pager -lu dhcpd );
# Delegate rights for logprog as root, e.g.
#   echo 'www-data  ALL=(root)  NOPASSWD:/usr/bin/journalctl --no-pager -lu dhcpd' > /etc/sudoers.d/www-journalctl
my $leasedbname = "/var/lib/dhcp/dhcpd.leases";
my %data = ();
# optional, can be modified to produce local time
use Time::Local;
use POSIX 'strftime';
my $now = time();
# local variables, lease information stored here
my $ip="";
my $status="";
my $interface="";
my $sdate="";         # beginning of lease
my $stime="";
my $edate="";         # end of lease
my $etime="";
my $adate="";         # last update (ACK) sent to requesting server
my $atime="";
my $mac="";
my $hostname="";
my $dnsname="";       # reverse dns lookup for host

#######################################################################
# first gather data from logfile for all ACK actions
#######################################################################

# collect all lines from log files into memory...
my @lines = (); my @loglines=();
if (scalar @logfilenames > 0) {
 foreach my $logfilename (@logfilenames)
 {
  open LOGFILE, '<', $logfilename;
  chomp(@loglines = <LOGFILE>);
  #printf "LINES1: " . scalar @loglines . " in " .$logfilename . "\n";
  push(@lines, @loglines);
  close(LOGFILE);
 }
} else {
  open LOGPROG, '-|', join (' ', @logprog) or die "Could not pipe from logprog";
  chomp(@loglines = <LOGPROG>);
  #printf "LINES1: " . scalar @loglines . " in " .$logfilename . "\n";
  push(@lines, @loglines);
  close(LOGPROG);
}
@loglines=();
#printf "TOTAL LINES: " . scalar @lines . "\n";
foreach my $line (@lines)
{
  if ( $line !~ m/dhcpd[^:]*: DHCPACK/) { next;}
  #printf "LINE: $line\n";

  ###############################
  # Modify the following line to make regexp capture 6 groups from log line:
  # 1 - date
  # 2 - time
  # 3 - ip
  # 4 - mac
  # 5 - hostname if available
  # 6 - interface
  #$line =~ m/(^.{10})T(.{8}).+,\ dhcpd: DHCPACK on (\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}) to ((?:[0-9a-f]{2}[:-]){5}[0-9a-f]{2}.*) via (.+)/;
  $line =~ m/(^.{10})T(.{8}).+,\ dhcpd: DHCPACK on (\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}) to ((?:[0-9a-f]{2}[:-]){5}[0-9a-f]{2}) (.*)via (.+)/;
  #$line =~ m/^(.{6}) (.{8})\ .+,?\ dhcpd[^:]*: DHCPACK on (\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}) to ((?:[0-9a-f]{2}[:-]){5}[0-9a-f]{2}) (.*)via (.+)/;
  # process the input
  $adate="$1";
  $atime="$2";
  $ip="$3";
  $mac="$4";
  $hostname="$5";
  $interface="$6";
  #add some 'known' facts:
  $status="ACK";
  $sdate="";    #"FOREVER";
  $stime="";
  $edate="";
  $etime="";

  #create/update record for this mac_addr
  #you can add extra check here if the IP address is not duplicated within
  #ack history and choose only the newer one.

  $data{"$mac"}->{'ip'} = "$ip";
  $data{"$mac"}->{'status'} = "$status";
  $data{"$mac"}->{'interface'} = "$interface";
  $data{"$mac"}->{'adate'} = "$adate";
  $data{"$mac"}->{'atime'} = "$atime";
  $data{"$mac"}->{'sdate'} = "$sdate";
  $data{"$mac"}->{'stime'} = "$stime";
  $data{"$mac"}->{'edate'} = "$edate";
  $data{"$mac"}->{'etime'} = "$etime";
  $data{"$mac"}->{'mac'} = "$mac";
  if (length($hostname) > 0) {
    $hostname =~ s/^\ *\(*//;
    $hostname =~ s/\)*\ *$//;
  }
  $data{"$mac"}->{'hostname'} = "$hostname";
}
#close(LOGFILE);

#######################################################################
# gather data from lease database for dynamic addresses
# update the records (for existing) or add new records
#######################################################################

my $isdata = 0;
my $type = "";

#this information is not present in leases database so we just set
#it to default values
$interface="dhcpd";
$status="ACTIVE";
$adate="-";
$atime="";

open LEASEDB, $leasedbname or die $!;
foreach my $line (<LEASEDB>)
{
  chomp($line);
  $isdata = 1 if $line =~ /^lease /;
  $isdata = 0 if $line =~ /^}/;

  if ($isdata)
  {
    if ($line =~ /^lease/)
    {
      $ip = (split(" ", $line))[1];
    }
    elsif ($line =~ /^  starts/)
    {
      ($sdate, $stime) = (split(" ", $line))[2,3];
      $sdate =~ s/\//-/g;
      $stime =~ s/;//;
    }
    elsif ($line =~ /^  ends/)
    {
      ($type, $edate, $etime) = (split(" ", $line))[1,2,3];
      if($type eq "never;")
      {
        $edate="forever";
        $etime=" ";
      }
      else
      {
        $edate =~ s/\//-/g;
        $etime =~ s/;//;
      }
    }
    elsif ($line =~ /^  hardware ethernet/)
    {
            $mac = (split(" ", $line))[2];
            $mac =~ s/;//;
    }
    elsif ($line =~ /^  client-hostname/)
    {
            $hostname = (split(/\"/, $line))[1];
    }
    elsif($mac ne "")
    {
        #we have parsed the whole record, no more matching entries
        #data is collected to variables. now push the record.

        #now let's decide if we are updating the record or creating
        #new record

        # check against lease date, do not add expired leases
        # convert lease end time to local time/date and compare with $now
        my $y=0; my $m=0; my $d=0; my $H=0; my $M=0; my $S=0;
        my $edatetime = $now;
        ($y, $m, $d) = split("-", $edate);
        ($H, $M, $S) = split(":", $etime);
        $edatetime = timelocal($S,$M,$H,$d,$m-1,$y);
        if($edatetime >= $now)
        {
          # now check if record exists
          if(!defined($data{"$mac"}->{'mac'}))
          {
            #record does not exist, fill up default data
            $data{"$mac"}->{'mac'} = "$mac";
            $data{"$mac"}->{'interface'} = "$interface";
            $data{"$mac"}->{'ip'} = "$ip";
            $data{"$mac"}->{'hostname'} = "$hostname";
          }
          # record exists, let's check if we should update
          $data{"$mac"}->{'status'} = "$status";
          $data{"$mac"}->{'sdate'} = "$sdate";
          $data{"$mac"}->{'stime'} = "$stime";
          $data{"$mac"}->{'edate'} = "$edate";
          $data{"$mac"}->{'etime'} = "$etime";
          $data{"$mac"}->{'hostname'} = "$hostname";
          #we do NOT update ACK time because we do not have it
          #do NOT uncomment below
          #$data{"$mac"}->{'adate'} = "$adate";
          #$data{"$mac"}->{'atime'} = "$atime";

        }
    }
  }
}
close(LEASEDB);

#######################################################################
# sort data
#######################################################################

#we sort by IP but you can sort by anything.
my @sorted = sort { ($data{$a}{'ip'}) cmp ($data{$b}{'ip'}) } %data;

#######################################################################
# Print out everything to the HTML table
#######################################################################

my $hostnamelong="";

printf "Content-type: text/html\n\n";
printf "<title>Aktywne dzierzawy DHCP</title>\n";
printf "\n";
printf "\n";
printf "
\n";
printf "
IP	Status	Interface	Lease time	ACK time	Mac	Host
\n";
foreach my $key (@sorted) {
    if($data{$key}{'mac'} eq "") { next ; }

    # BEGIN reverse dns lookup
    # can optionally turn off reverse dns lookup (comment out below lines) which speeds up the process
    # of table creation and is useless unless you have reverse dns populated for
    # your fixed or dynamic leases uncomment single line below instead:
    #
    # version without reverse dns lookup:
    # $hostnamelong = $data{$key}{'hostname'};
    #
    # version with reverse dns lookup:
    # BEGIN
    $dnsname = gethostbyaddr(inet_aton($data{$key}{'ip'}), AF_INET);
    if($data{$key}{'hostname'} ne "")
    {
      $hostnamelong = $data{$key}{'hostname'} . " | " . $dnsname;
    }
    else
    {
      $hostnamelong = $dnsname;
    }
    $dnsname = "";
    # END

    printf "
";
    printf "" . $data{$key}{'ip'} ."	";
    printf "" . $data{$key}{'status'} ."	";
    printf "" . $data{$key}{'interface'} ."	";
    printf "" . $data{$key}{'sdate'} . " " . $data{$key}{'stime'} ." - ";
    printf $data{$key}{'edate'} . " " . $data{$key}{'etime'} ."	";
    printf "" . $data{$key}{'adate'} . " " . $data{$key}{'atime'} . "	";
    printf "" . $data{$key}{'mac'} ."	";
    printf "" . $hostnamelong ."	";
    printf "
\n";
}

printf "
\n";
printf "\n";

# END of programm

Please note, that:
1) the above script needs slight modification before running in YOUR environment, you have to modify the files locations, and one regex depending on your log file format. See comment in script.
2) the above script is not checking whether the IP is not repeated in ACK table, if 2 different machines got the same address within last days. This is by design (what I personally needed to see each mac address which was present in my network during last days) - you can easily modify it, there is a ready section for this in code, just add one condition.
Hope you like it.
Comment: I would like to use this script. However, I don't have a log file as the dhcpd.leases file came from another computer. Can I still use it? I tried using an empty array for the log file but running it just returned an empty table with headers.
Comment: to frakman1: without log file the script is rather useless. you will not have any usefull information without it.
Comment: What are you calling "useful information"? What is the log file being used for? I don't need an ACK since the dhcpd.leases file tells me about every device that was granted a lease. I can just assume that they got it. Also, dhcpd.leases isn't just for active leases. It's for all leases, past and present. Most DHCP monitoring scripts only use dhcpd.leases and dhcpd.conf for their analysis.
Comment: to frakman1: please read the above post carefully. If you do not need the information in the log files: feel free to ignore it. I need information from both the leases file and the log as described at the top of the post above. over and out.
Answer: The script used to control the DHCP daemon depends on which one you're using. I'm assuming isc-dhcp-server. Then it would be:
service isc-dhcp-server stop
service isc-dhcp-server start
service isc-dhcp-server status

If that doesn't work, look in /etc/init for a config file named after dhcp, and use that. Say your config file is called dhcpd3.conf, then you'd replace isc-dhcp-server in the above commands with dhcpd3.
To see "how many ip addresses have been assigned to clients", which was your original request, you can do this:
grep "^lease" /var/lib/isc-dhcp-server/dhcpd.leases |sort |uniq |wc -l

This will plainly give you the number of assigned addresses.
Again, if you get an error about /var/lib/isc-dhcp-server not being findable, look in /var/lib and replace it with something suggestind a dhcp server, usually dhcp or dhcp3
Note that as mentioned in another answer, this will miss the distinction between assigned and active  (i.e. with a system using them at the moment) addresses. Also, if a client is forcefully shutdown and doesn't release the lease, you will also get unused addresses reported as assigned.
Comment: Found this to be helpful, new to running my own DHCP Server. I also found `dhcp-lease-list --lease /var/lib/dhcp/dhcpd.leases` to be helpful. Running hostapd and isc-dhcp-server on ubuntu, Pine64 Board.
Answer: To list all the active Clients IP's you can use nmap. It can list both DHCP as well as static clients.
you can install nmap in your PC with
sudo apt-get install nmap

Then to list all the active clients you can do like ,
 nmap -v -sP 192.168.0.0/255

here the IP's from 0 to 255 will be scanned and active IP's will be showup.
The better network monitor I can found my self is nethogs.
you can get it by installing with
sudo apt-get install nethogs

Then simply
sudo nethogs <connection_name>

Can show the traffic monitor in your terminal.
hope this can help you.
Comment: Big difference between assigned and active though, this will miss a lot of the inactive ones
Answer: If you are using isc-dhcp-server on UBUNTU 14.04 headless server
To control the isc-dhcp-server
service isc-dhcp-server stop
service isc-dhcp-server start
service isc-dhcp-server status

To monitor the isc-dhcp-server
This method will work on a headless server (non-GUI) for "assigned DHCP leases only", login, enter the following command from the terminal
cat /var/lib/dhcp/dhcpd.leases
If NMAP has been installed enter this command from the terminal
nmap -v -sP 192.168.0.0/24
This method will work on this subnet and scan 256 addressees, and output IP and MAC addresses. This will respond if the HOST is down with an IP Address that has no assignment and will respond with MAC and IP Address if the HOST is up.
Depending on if a switch or router is between the PC and the network, and depending what "network layer 2/3/4" router or switch operates at.
tail -f /var/log/syslog will output DHCP addresses being actively assigned.
tcpdump -i eth0 port 67 or port 68 -e -n will capture DHCP packets on port 67 and port 68 on network interface eth0
If DHCPDUMP has been installed enter this command from the terminal
dhcpdump -i eth0 will DUMP "as it implies" DHCP information from the server to the client.

How to monitor DHCP leased ip address


Child tax credit: should I file as a non-filer?

Question: I have not filed taxes the past 2 years due to no income, but my daughter and I have been claimed by the person who is supporting us. I haven't received any stimulus money for me or my child and he has not either. He says he isn't going to claim me on 2021 taxes and that I should file as a non-filer to receive the child tax credit that starts in July since non-filers can receive it. Is this accurate? Should I file for it to receive the $250 per month for my child? And yes I am in the USA. I just don't want to end up owing for something if I get it.
Answer: Non-filers can enter their info here at IRS.gov, to start getting the monthly payments.
But I question whether or not you are truly a non-filer, if you were a dependent on someone's return. On another page, it says that the non-filer form is not for "someone who can be claimed as a dependent" on another person's tax form. In this article, you can explore whether or not you can be claimed as a dependent. Note that even if your benefactor does not plan to claim you as a dependent, that's a separate question from whether he can claim you.
It's too bad this is complicated. If you have time, you could make an appointment to visit an IRS Taxpayer Assistance Center.
Regarding the worry about being overpaid by the IRS, there is some protection from having to repay in the event of overpayments. Please see this FAQ, question 6:

Q H6. How do I know if I qualify for the full repayment protection for
filers based on income during 2021?
Answer: First of all, if someone can claim you as a dependent (i.e. meets the conditions in the law to claim you as a dependent), then you cannot claim dependents and you cannot get the Child Tax Credit or stimulus payments. This is true even if nobody actually claims you on their tax return.
You said that he isn't going to claim you as a dependent for 2021, but that doesn't tell us whether he can claim you. If he can claim you but just chooses not to, you still cannot claim dependents and you cannot qualify for the Child Tax Credit or Recovery Rebate Credit. On the other hand, if he can't claim you (i.e. he does not meet the requirements to claim you as a dependent), and you can verify that you meet the requirements to claim your daughter as your dependent, including providing more than half of her support, then you should qualify for the Child Tax Credit, and you can file for the advance credit in 2021.


Bijection between countable ordinals and reals

Question: The set of all countable ordinals is $\omega_1$, which has a cardinality of $\aleph_1$. When accepting the continuum hypothesis, $2^{\aleph_0} = \aleph_1$, so a bijection between countable ordinals and real numbers exists. Is there any known bijection of this type?
Comment: I don't understand either, but for a different reason.  If there was a "known bijection of this type" then the continuum hypothesis would no longer have to be accepted, right?  It would be proven?
Comment: I think that an answer with involves forcing arguments might merit this question with a [set-theory] tag, rather than an [elementary-set-theory] tag after all.
Comment: I am not sure I understand your question. Are you asking whether, from the mere knowledge that there is a bijection, we can actually define one? In general, this depends on what notion of definability you are working with. There are models of set theory where there are (very) explicitly definable such bijections, and there are other models where no bijection is definable in quite a general sense.
Answer: The use of the term "known bijection" is unclear. If you mean an explicit formula in the language of set theory that $\sf ZFC$ proves it to be a bijection, then the answer is no. If that would have existed then the continuum hypothesis would have been a theorem, rather than a consistent sentence.
Under certain assumptions, for example $V=L$, there is a definable bijection, and one can say, if so, that there is a statement in the language of set theory which under the additional axiom $V=L$, defines a bijection between $\omega_1$ and $\mathcal P(\omega)$.
However, in general there is no parameter free $\varphi$ such that $\sf ZFC+CH$ proves that $\varphi$ defines a bijection. Assume by contradiction that $\varphi(x,y)$ defines such a bijection (so $x\subseteq\omega$ and $y<\omega_1$). $\newcommand{\forces}{\mathrel{\Vdash}}$
Now consider $V\models\sf ZFC+CH$, and let $\Bbb P=2^{<\omega}$ in $V$ be the Cohen forcing adding a single real, whose canonical name is $\dot r$. Let $G$ is a generic filter, then $V[G]$ is also a model of $\sf ZFC+CH$.
Therefore in $V[G]$ the formula $\varphi(x,y)$ still defines a bijection, therefore there is some $\alpha<\omega_1$ and $p\in G$ such that $p\forces\varphi(\dot r,\check\alpha)$. Let $m,n$ two integers not in the domain of $p$ (recall that a condition is a partial function from $\omega$ into $2$ with a finite domain) and consider the $2$-cycle $(m\ n)$ as a permutation of $\omega$. By standard arguments this permutation extends to the forcing and the names, and we have, $$p\forces\varphi(\dot r,\check\alpha)\iff\pi p\forces\varphi(\pi\dot r,\pi\check\alpha)=p\forces\varphi(\pi\dot r,\check\alpha).$$
Therefore $p$ forces that $\varphi$ does not define a bijection. This is a contradiction to the assumption that it does.

Note: If we allow parameters, then of course that such formula exists, since we just need to write as a formula in $\varphi(x,y,u)$ that $u$ is a bijection between $\mathcal P(\omega)$ and $\omega_1$ and that $u(x)=y$. That clearly creates circularity in the question, so I only treated the parameter free case.
Of course one can define a whole wide spectrum of allowed parameters, real numbers, countable sets of real numbers, and so on and so forth. I have only dealt with the simplest case in my above answer, and there might be a positive answer if we use strong enough parameterization; but my suspicion is that any such answer would amount to encoding the bijection in one way or another.
Comment: Re your first paragraph: Well, that's not quite clear. We could have an explicit formula that only works under $\mathsf{CH}$. For example, there is an explicit formula defining a well-ordering of a set of reals, but the formula only gives us a well-ordering of $\mathbb R$ iff $\mathbb R=\mathbb R^L$.
Comment: Re your closing note: But there is much in between no parameters and alloing the bijection as a parameter. There are formulas with reals as parameters, or with ordinals, or with stationary sets. There is a whole subfield of set theory that works on defining well-orderings from such parameters under specific situations.
Comment: @Andres: Yes, I meant that it is provable from $\sf ZFC+CH$, not from a stronger theory (as I mention in the second paragraph).
Comment: As for the second comment, yes. I agree with that as well. But the spectrum becomes too large for an answer on MSE, I believe. On an answer on MO, I'd feel comfortable giving this answer and the needed variants for various parameters (I had to think about the parameter free proof a few minutes to begin with, going further would require more work, of course). But on MSE my preference is to try and give either hints or relatively full explanations. So doing all that seemed like too much for just an answer. I'll edit your comment in, by the way.


Questions about the site

Question: Is there a chat room for this site? Are you allowed to ask a question of a question, ie., seek further clarification to an answer to your question? Are you allowed to razzle dazzle your posts with colours, photos, etc., using the editor above? Okay that's THREE questions. :-)
Answer: Usually it's best to ask questions separately (it's fine; there's no quota :-) ), but I'll go ahead and answer these together since they're short.

Is there a chat room for this site?

There sure is!  Our main chat room is V'dibarta Bam, which you can reach from anywhere on the site by clicking on the blue Stack Exchange logo in the top left corner and then clicking on the "chat" link.  (This is also where you can easily move between the main and meta sites, and access other sites in the network.)  Please come to chat any time you like.  Conversation is pretty free-flowing and might be about anything from posts on the site to current events to people's Shabbat plans to just plain chit-chat.

Are you allowed to ask a question of a question, ie., seek further clarification to an answer to your question?

Yes.  This is, in fact, what comments are designed for; despite how it may look sometimes, comments aren't for extended conversations.  (That's what chat is for.)  It takes 50 reputation to leave a comment in general (this is an anti-spam measure), so you're close, but you can always comment on your own posts and I think you can comment on answers to your own questions.  It sounds like that's what you want to do in this case, so please try it and let us know if it worked.  (You can, for example, try to comment on this answer to your meta post.)
If what you're looking for is more of a follow-up that goes beyond the scope of the original question, then you should consider posting a new question rather than a comment. It can be helpful, in that case, to include an explicit link to the first question in the second.

Are you allowed to razzle dazzle your posts with colours, photos, etc., using the editor above?

Well, I don't think markdown actually supports colors (if you meant text color) and that's probably a good thing, but as you can see from the posting interface, it does support images.  Of course you shouldn't be gratuitous, but that feature is there because sometimes a photo or drawing is really important to understanding something.  So yes, feel free to use images where doing so helps your post, but save LOLCats and the like for other venues. :-)
Comment: Thanks @IsaacMoses.
Comment: I'm feeling a little odd about something. I noticed my answer got a -2 vote or something. People rate my comments/questions? That's a little off-putting. Can you explain the voting business? I don't want to be an annoyance. I want to add value.

Questions about the site


Why the standard error of the mean never gets to zero even when the sample has the same size as the population?

Question: Why, when we calculate the standard error of the mean for a hypothetical sample with the same size as the population, the value is not equal to zero, if the sample in this case is identical to the population?
Comment: See e.g. https://en.wikipedia.org/wiki/Standard_error  for the finite population correction which ensures zero standard error whenever the sample is complete.
Comment: The formula you're using is for infinite populations.
Answer: If the sample has the same size as the population, either some units from the population are sampled multiple times, or the sample is in fact the whole population.
In the former case, the sample mean provides an estimate of the population mean, in which case a different sample would likely yield a different estimate of the population mean. Thus, the standard error of the estimate should be greater than zero (unless the sample has zero variance, of course).
In the latter case, there is no need to estimate the population mean, because the population mean can simply be calculated. This statistic has a variance of zero; it will not vary if we sample again using the same sampling procedure. Thus, the standard error is zero in that case.
Answer: When sampling from finite population, the standard error of the mean $\frac{\sigma}{\sqrt{n}}$ must me multiplied with the finite population correction (FPC) $\sqrt{\frac{N - n}{N - 1}}$ where $N$ is the population size and $n$ the sample size. Hence, the corrected standard error of the mean is:
$$
\frac{\sigma}{\sqrt{n}}\sqrt{\frac{N - n}{N - 1}}
$$
and because $\lim_{n\rightarrow N}\sqrt{\frac{N - n}{N - 1}} = 0$, the standard error of the mean goes to zero, as the other posts explained.
Note that if you work with the sample variance using Bessel's correction ($n-1$) then the FPC is $\sqrt{\frac{N-n}{N}}$ (see here for a derivation).
Answer: The reason that this does not happen is that we apply formula's that assume that the sample size is much smaller than the population size.

A sample is often regarded as taken from an infinite population and, when used as an estimate for the mean of the population, the estimate of the mean of the population has an estimated variance of $$ \text{var}(\bar{x})  = \frac{1}{n-1} \sum (y_i - \bar{y} )^2  $$
This assumes that the population can be regarded as infinite. When this assumption is false then this formula is not correct. And it is also incorrect to state that the variance does not get to zero.
When you estimate the mean of a finite population and you get to sample the entire population, then you can determine the population mean with 100% accuracy and the standard error should be zero.


Why is 的 mandatory in the sentence 坐四十五分钟的二百七路

Question: I have troubles trying to figure out why 的 should be present (and its position) in the following sentence:
...,然后坐四十五分钟的二百七路
As far as I know, 的 is used to modify nouns. What is that particle modifying?
Answer: 二百七路 sounds like  a bus route number. That would make it a noun
的 is acting as the preposition 'of' in this context.  It connects the quantity complement "四十五分钟" to the noun 二百七路 (45 minutes of route 207)

[坐] [四十五分钟] [的] [二百七路]
[ride] [45 minutes] [of] [route 207 (bus)]

Example of quantity complement complements verb:

坐 (v) 四十五分钟 (quantity complement)
坐 (v) 二百七路 (n) 四十五分钟 (quantity complement)

坐四十五分钟的公共汽車 can be reduced to 坐四十五分钟公共汽車 by omitting 的. Which mean 坐四十五分钟的二百七路 can also be reduced to 坐四十五分钟二百七路
Answer: I'll proceed to dissect the clause 坐四十五分钟的二百七路 using systemic grammar:
<code>   坐     四十五分钟     的    二百七路
1. \-----------Predicate----------/
2. \P/   \---------Object---------/                P: Predicator
3.       \Modifier/    的    \Head/
</code>
The clause can be analyzed using 3 levels.
As you can see, the object in this clause if constructed using the Modifier-的-Head pattern.
The predicator is 坐, meaning ride.
The modified noun (head) is 二百七路, which literally translate into "207 Line", presumably a bus route.
The modifier here acts as an adjective, describing the "207 Line", with the quality of 四十五分钟, which is "45 minutes".

See, if we take out the modifier (四十五分钟的), the clause is simplified into:
<code>坐二百七路
</code>
The meaning would simply be: Take (ride) the 207 Line.
This sentence makes sense, and this is a hint that 的 was used as a particle for the Modifier-Head construct and not as a possessive particle.
Answer: As explained in other answers, 的 in 坐四十五分钟的二百七路[sic, 1] is customary and frequently used. However, as a native speaker, I don't find it "mandatory" as you said. The following sounds fine to me:
先坐四十五分钟二百七路,然后步行300米到达目的地

1: the notation of "二百七路" feels rather unorthodox to me. At least in where I live, if you mean 207, it is usually called 二零七(路), or rarely, 二百零七, but never 二百七. And if you mean 270, although it is called 二百七 sometimes, it's mostly in prices or amount of cash. Otherwise, as a bus route, you would call it 二七零, or rarely, 二百七十.


Missing languages (e.g. Portuguese) option on Google Pixel 6's Live Caption

Question: According to Android Police - Google's Pixel 6 might play interpreter on your next vacation,

The feature will get a dedicated location in Settings -> System and will apparently support 55 different languages to varying degrees, most of which it will only support in a limited way via the camera. According to the list published, only Spanish, Portuguese, Japanese, Italian, German, French, and English will get particularly good support for Live Translate's various features.

Trying to download a Portuguese language file to use with live caption translation on Pixel 6, but I can only see: French (already installed so you can't see it in the screenshot), German, Italian, and Japanese.

I recall I saw on some forum that Portuguese is also an option. Does anyone know more about this?
Answer: Live Transcribe currently supports Portuguese and many languages whereas live caption just supports 4 languages which don't include Portuguese.


pool pump wiring size

Question: The pump is 115v 9 amp draw. The run length from breaker box to outlet is between 70 and 75'. I have a coil of 14/2 left over from my barn wiring project. I've done some online checking and think I am ok with this setup but you can never have too much info. Thanks for the help.
Comment: Is this a cord-and-plug connected pool pump, or a hardwired one? Is the pool a storable type or a permanent pool, and if it's storable, what size is it?
Answer: Sorry to disagree with Harper on this but I would always run a minimum of 12-gauage wire for a 9-Amp pool pump with a circuit run of 75-feet.  The pool pump is going to be considered a continuous load. This will require a buffer factor of at least 25%. A continuous load at 75' would require another deration factor. A pool pump is not an incidental load.  14-guage wire is designed to carry minimal loads.  And a pool pump/motor is an expensive item.  We shouldn't take a chance on taxing that motor with inadequate wiring.
Answer: You can't use interior wire (NM aka Romex) for outdoor, underground or outside conduit applications.  As an example if the cable contains that paper wadding, that's a big no-go.  You need UF cable if direct burying, or that or THWN-2/XHHW individual wires for conduit.
#14 NM is generally white (rarely black). UF is gray.
Voltage drop wise, that sounds fine.  You don't even need to think about voltage drop til at least 60' on a 120V circuit, and even then only if you are running at hard circuit limits (which you should not) and believe in 3% (which you should not).
Given that you are well under 15A, and 3% isn't that important for a panel-final load run, you are fine.

pool pump wiring size


Can I use "left eye" and "right eye" in my sample as two different subjects?

Question: My data is as follows. I have two groups of patients. Patients in each group had a different type of eye surgery. 5 variables were measured on patients in each group. I want to compare those variables between the two groups using a permutation test or MANOVA. The eye on which the surgery was done does not really matter in the analysis. However, Patient 2 in group A for example, had the surgery on both eyes and therefore has those 5 variables measured twice, one time on each eye. Can I consider patient 2 Left and patient 2 Right as two different observations? Same for patient 31 in group B.
$$
\begin{array}
\hline
 \text{Patient} & \text{Surgery type} & \text{Side} & \text{V1}& \ldots & V5\\
  1 & \text{A} & \text{Left}  & 91 & \ldots & 22\\
   2 & \text{A} & \text{Left}  & 87 & \ldots & 19\\
 2 & \text{A} & \text{Right}  & 90 & \ldots & 23\\
 . & . & . &\\
  31 & \text{B} & \text{Left}  & 90 & \ldots & 17\\
   31 & \text{B} & \text{Right}  & 88 & \ldots & 19\\
 32 & \text{B} & \text{Right}  & 91 & \ldots & 24\\
 . & . & . &\\
\hline
\end{array}
$$
Comment: Your test may be accomplished by something similar to a matched pair test, unbalanced randomized block design. But before I guess further, could you please elaborate on your data, what is it what is looks like etc.?
Comment: Thanks. I am trying to present my data in a nice table format here on the blog but I still didn't figure out how. I will make sure to present my data in details in my next question. I would like to reiterate that both eyes had the same type of surgery, so are in the same group.
Comment: I have made a sample table, you can now edit it to show your data.
Comment: @suncoolsu, the question is answerable without the data.  What is your intent in having the OP post data?
Comment: @Iterator I agree and you have already answered it (and I have upvoted it :-)). I was just curious to see the data and what kind of models could be fit on the data.
Comment: @suncoolsu No problem. Unfortunately, any models will be affected by the assumptions, and we don't really know whether or not both eyes are treated the same as they would be if there were just one eye involved.  Maybe the OP will come back with an EDA question or a hypothesis testing question.  :)
Comment: I have edited my question and posted the details of my data.
Answer: I would not recommend it.  Not being a domain expert, I can still identify three things that would reduce the independence of the outcomes:

Both eyes were treated at (almost) the same time.  While this is not necessarily a problem, it affects the other assumptions of independence.  What's more, the surgical team may have opted to treat both in the same way or may make a decision about one eye with consideration of aspects of the other eye.
Both eyes were treated by the same surgical team (surgeon and everyone else involved)
Both eyes are subject to the same patient "factors", i.e. anything that would be intrinsic to the patient that could affect outcomes, such as compliance with other treatments, overall health, etc.

If anything about the outcome could be attributed to the surgical team or the patient, then there's a problem.
Answer: Because all the answers so far are negative (in terms of advocating using less than the full data set or in suggesting limited uses for the two-eye cases), let's see what can be done.  For that, we need a probability model.
Consider a single response variable, $Y$ (one of V1 through V5, apparently).  As a point of departure, suppose the response depends on several factors, including

An average or "typical" response $\mu$.
A random patient-specific factor, $\varepsilon$, with zero mean.
Perhaps an indicator that both eyes were involved, $X_2$.
A surgery type factor, $X_s$, which ought to be an attribute of the eye, but which appears to be constant within each patient (thereby limiting our ability to identify this factor).
A factor for any systematic difference between the right and the left, $X_e$.
For each eye, a random variation from the expected response in that eye, $\delta$, with zero mean and independent of the patient factor $\varepsilon$.

It is implicit here that the experiment was designed in certain standard ways: namely, that patients were randomly selected from a specified population; that the determination to treat the left eye, right eye, or both, was either randomized or can be assumed independent of other factors; etc.  Changes to these assumptions would require concomitant changes in the model.
According to this model, the response expected of eye $j$ ($j \in {\text{right}, \text{left}}$) within patient $i$ is
$$Y(i,j) = \mu + \beta_2 X_2(i,j) + \beta_s X_s(i,j) + \beta_e X_e(j) + \varepsilon(i) + \delta(j).$$
This looks like a somewhat complex partially nested mixed model.  Fitting the parameters $\mu$, $\beta_2$ and $\beta_s$ can be done with maximum likelihood (or possibly generalized least squares regression).
I offer this purely as an illustration, to show how one might profitably think about this problem and arrive at a way to exploit the dataset to the fullest.  Some of my assumptions may be incorrect and should be modified; additional interactions may be needed; some thought may be required about how best to handle potential differences between eyes.  (It's unlikely there's a universal difference between left and right, but maybe there's a difference related to the patient's dominant eye, for instance.)
The point is that there does not appear to be any reason either to limit the analysis to one eye per patient or to use ad hoc analytical methods.  Standard methodology appears to be applicable and a good way to use it begins by modeling the experiment.
Comment: I think it's important to add that the assumption of independence can and should be tested, if using the samples with binocular treatments.  Such testing for dependence should be done *before* running ahead with a model, for two reasons: 1: If there is some dependence, then this could be very interesting.  2: Understanding the dependence could lead to a better model.
Comment: @Iterator Your good suggestion is exactly what I was hoping this discussion would prompt: when we contemplate how to model our data, we often get insight into what assumptions are being made and need to be tested.
Comment: @whuber Good start. As always, you are right about "mixed-model-ish" treatment! I agree with you that we should not "
throw away" any data.
Answer: I agree with the others that two eyes of the same patient are not independent. However, I do not per se agree on using only one sample. After all that is throwing away precious samples.
In a somewhat similar situation (some of my patients were operated again on the
same tumour) I do use their samples.

For the (iterated/repeated cross) validation I make sure the splitting is done patient-wise.
I cannot state the effective (statistical) sample size. For me that is anyways no problem due to more samples of some patients. I have hundreds of spectra for each sample, and they are neither repeated (they are taken from different places) nor independent. So I don't loose anything here.
I sometimes use the number of patients as conservative bound for the effective (statistical) sample size: at least the patients are independent
You may weigh the samples so that each patient enters the analysis with the same weight.
Answer: I concur with @iterator. If a large proportion had surgery on both eyes, I'd do some sort of matched pairs. If only a small proportion had surgery on both eyes, I'd probably just not use either eye for those people, but certainly not both.
Comment: Peter's right.  Actually, the set could be quite interesting in itself: conditioned on needing to operate on *both* eyes, were outcomes any worse?  The reason we advocate not assuming independence is that there are a lot of reasons why this *could* be wrong.  If there's a large enough sample, test for independence.  The insight could be very interesting & practically useful.
Answer: One point to add to the comments of iterator and peter. When analyzing the overall data set, you should use only the data from one eye for patients who were operated on both (because the outcome for the two eyes is unlikely to be independent). Which eye? Use a randomization method, so you don't choose the one with the better (or worse) outcome, which would influence (bias) the results.
As part of a separate study, you might want to look at only patients with good outcome in one eye and not in the other, and try to see is there are any hints about what causes the difference.


HP ProLiant ML370 G6 shows no sign of life after RAM upgrade

Question: I have power issues with my HP ProLiant ML370 G6 server after Ram upgrade. This server has been running without interruption for a very long time and when we decided to power it off to upgrade RAM we couldn't power  it on again. It looks like th MB recives no power. In the trobleshooting process we replaced one of our redundant power supplies with a new one. Nothing changed. All leds on the MB are off. Power supply leds are off. Though power supply fans are spinning. I've already tried basic trobleshooting operations for this kind of problems (change power outlet and cable, disconnect any internal component like ram or hard drives). In the end we stopped even tring to power it on and we abbandoned the server with all its components diconnected in a storage room for 3 months.
Now we decided to give it another chance and when we plugged it on again, mb leds and power button led were on and i could even power it on. Ofcourse we got boot errors for the components missing so I tried to power it back off by pressing for a few seconds the power button but it didn't work and i had to directly unplug it. Now we are back at the beginning because the server is dead again.
Considering this do you think that the power backplane is the problem? maybe it's capacitors  decharged during this last 3 months and that's the reason why I could power it on for a few minutes?
I also have to tell you that the power button seems damaged. It looks like its always pressed in. Do you think that a damaged power button could cause the total interruption of power to the MB? I thought that when the power button is damaged maybe you cannot turn the server on but you can atleast see some leds on the MB on.
Any suggestions? Thanks
Comment: Probably nothing, these have been end-of-support for a long time already.
Comment: This falls into the _"why are you asking the internet?"_ category.
Comment: What did HP support say?
Comment: Just wanted to narrow down which component failed. Changing the power backplane board it's not like changing the entire mainboard. Considering how old this server is i defenetly won't change the MB, but if the backplane board is damaged i would consider repairing it.
Answer: Call HP please, for support or to buy a part.
For the symptom you have I would suspect a problem with the mainboard.
A bestpractice is to always restart a system before an maintenance, to know the state of the system. As usually if the uptime is more than a year you could have bad condensator on the mainboard, but having the server at off, and restarted reset those components, that allow you to know if your server is still functional before an intervention inside it.
I do a lot of upgrade for customer and I usually told them to restart the day before I come to make sure I dont fall on a bad surprise after the maintenance.
Answer: This is becoming an old server. G6 dates back to 2009.
You clearly don't have support, but you can try a few troubleshooting techniques.
See: ProLiant DL380 G7 won't boot, solid amber power LED
and look at: HP DL380 G7 Will Not Power On
But here's a (lengthy) troubleshooting procedure to try first if you have access to the machine.

Remove the power supply units and swap them.

Test to see if the system will boot...
If that doesn't work:

Remove all power supplies from the chassis
Locate the System Maintenance Switch on the motherboard - It's a set of 10 DIP switches.
Turn switch #6 switch on.
Insert all power supply units.
Power on the server and allow it to idle for 3 minutes.
Power the server off.
Remove all power supplies.
Return DIP switch #6 to off (original) position.
Reinsert the power supplies.
Power the server on.

Test to see if the system will boot...
If that doesn't work:

Remove all power supplies from the chassis
Turn DIP switches #1, 5 and 6 switch on.
Insert all power supply units.
Power on the server and allow it to idle for 3 minutes.
Power the server off.
Remove all power supplies.
Return DIP switches #1, 5 and 6 to off (original) position.
Reinsert the power supplies.
Power the server on.

Test to see if the system will boot...
Comment: This troubleshooting procedure didn't work as no power reaches the NVRAM. This is not a boot problem. HP provides no support. 3 months ago a colleague tried to fix it  while reciving indications from  HP by phone, they told him to disconnect RAM and fan chage and after that they suggested to replace the MB.
Comment: Ok. Get someone to come evaluate the hardware or replace it. The systems are modular, so you can also replace the power switch. Also see: https://serverfault.com/a/825614/13325


Car overheated, found no coolant, now it won't crank

Question: So I have a 2004 Toyota Camry, and a few weeks ago I was driving home then I started smelling this foul burning smell, I didn't think nothing of it ... I thought it was others cars because I was on the interstate. So I got off the exit and was just hitting an traffic light then all the sudden my car stopped and wouldn't crank back on... I (of course) freaked out and realized the burning smell was me( basically my car overheated). But long story short.. I took my car to Pep boys. The guy gave me a (1 minute) review then told me to start my car and he smelt it and said "burning" and then he realized my car didn't have water/coolant and immediately said it was the head gasket and I need a new engine. But I didn't think that was the reason because my car wasn't leaking and my oil was just fine, I didn't have the symptoms of a head gasket like no bubble on the stick, my oil wasn't milky, and it wasn't leaking plus etc. Not only that I just got my oil changed a week before the incident. So I went to a friend for a second opinion and he was saying it wasn't  head gasket and that Pep boys was trying to scam me. He took a look at my car and we both put water in it and tried to crank it up but no hope. But I didn't smell any burning. Also no dashboard light came on. So we did some research and we're both thinking it's the water pump and the timing belt.... but it doesn't make sense because I still don't know where my coolant/ water has ran off too. Could someone please help me !!?
Comment: *tried to crank it up but no hope* could you please be more accurate with that you mean when you say this? If you means the engine turns but won't start then say so. If you mean the engine doesn't turn, then say so
Comment: Maybe you ran it so long without coolant that it seized up.
Comment: When you try to start the car what happens.

Does it Crank (engine turns) but not catch/sputter/try start, or does it not crank at all (i.e. engine wont turn at all). If the engine does not turn at all, disconnect the spark plugs and remove them and try to turn the engine manually from the Crank pulley. If it does turn without any hard resistance then engine is probably "ok", something else may be preventing the starter from starting activating.

I say engine is probably ok, but head could be warped or etc, but will likely still run.
Comment: No temperature gauge or warning light of over-heat before you ruined the engine ?
Answer: A head gasket can fail where there's a breach between the cylinder and the cooling jacket. When that happens it burns coolant. So it's very possible you have a bad head gasket. It's also possible you have a coolant leak and that's what caused the over heating. Try rotating the engine by hand using a socket and large ratchet on the front crankshaft bolt. If the engine won't rotate, it's toast.
Answer: If you run the car out of coolant your head gasket will very often fail.
When no coolant are circulating and the engine is running the cylinder head will heat up and expand,this will compress the head gasket and strech the head bolts.
When the engine cools down and the cylinder head contracts a lot less pressure will keep the head gasket sealed to the sylinderhead/engine block as the head bolts have been streched too far from the heat they where exposed to.
The next time you start the engine the head gasket will fail.
if you see the failiure before the engine overheats too bad you might avoid changing the head gasket and head bolts.
If you fill coolant and the head gasket is blown you might get liquid in the cylinders this is uncompressable so it might stop the engine from cranking over,if this is the case remove the sparkplugs to get the liquid out.
Answer: I want to add some answer on it.

If your car won't crank (meaning the engine won't even turn).
= your cylinder head is still good probably bending a bit (you just need to resurface). But the the other like crankshaft, crankshaft bearing, or even cylinder piston could wrap that makes your engine won't even crank

Head gasket will not making your engine stuck. Unless you have a very bad luck that head gasket suck into chamber and making it stuck (won't happens in hundred years).

The burning.
If you smell burning oil = please check again your engine oil level, check from oil lever not warning light. if your engine drown to empty, then your car is almost 50/50 the crankshaft is wrapped (please check)

The coolant.
Please check the water pipe.. it could be the water come out from leaking water pipe or radiator itself.. but this is overshadowed by a fact your engine won't crank.

So i suggest you do overhaul your engine if your car won't even cranked (the motor starter like stalling).
sometimes you can be lucky that crankshaft didn't wrap but just need undersized or oversized because wrapped bearing.
check again with mechanic that understands the situation, and the shop with fully equip not only showing oil packing on the shop

Car overheated, found no coolant, now it won’t crank


Will AI based test automation tools make selenium webdriver obsolete in few years?

Question: I have a fear that in few years  companies will deploy AI based robotic process test automation tools and my java selenium  programming skills will become obsolete.
Comment: your question is more of a conversation starter, thus any answer would be "Opinion-based" , which does not fit the purpose of Stack Exchange. I would suggest the How to Ask guide and create one or more focused questions. https://stackoverflow.com/help/how-to-ask
Answer: It is hard to predict the future. You might need new (AI) skills to work on new projects. Keep in mind old projects exist for a long time. Some programmers still program in Cobol and are paid very well today.
I recently switched to a government employer and they are living at least 15 years in the past. My previously un-used Selenium skills translated very well to this environment. Before the majority here trusts AI testing tools it needs to be an international standard first, this will probably take another 10 years. Using Machine Learning to automate people is also still frowned upon here.
If programmers and testers will be fully replaced by AI, that means most jobs will be replaced by AI. Thus we need to redesign society. Jobs will be no more. Although I hope this will go faster, I do not expect this to happen within my working lifetime (25 years left).
My advice is to keep researching and experiment with new tools in the market.
Answer: I think the concept of being valued for the java skill shows that you are missing the point of being agile. The 4 main pillars of Agile way of working are

Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan

You should not be tied to a specific set of tools but should be skilled to investigate, research and identify the best solution for the problem in-hand. For example try investigating the benefits of using protractor for an angular website, the postman for API testing, and other tools that overcome the complexity and bottlenecks of current solutions.
The tools and technology will evolve rapidly , and as an engineer  your task is to identify the best solution that is applicable to your context as testing or any activity is context depended. For example, if it's a simple one page single frame wapplication you don't have to complicate it with huge framework and designs and cause proliferation of classes.
Coming back to the question
Software testing has different scopes on different levels. Most AI tools concentrate mainly on functional UI testing but have huge maintenance bottleneck as the test case and
test coverage grows.
Also, AI solution lacks UX/UI experience testing capability, that's why we have exploratory test cloud still in the testing pyramid.

Summary

In the current state AI is still in the learning phase and its long time before it could be completely trusted to be matured enough.
We still need human intervension
If in future if AI becomes matured enough , you as a quality engineer should be more than happy to replace current implementations with AI or any better tools that would be more beneficial compared to the effort involved in the migration.

Also:
Java-selenium skill set is not a non-acquirable valued skill that makes someone a highly demanded non-replacable resource:
What makes work valuable are :

Debugging skills
Fast learning skills
Critical thinking skills
Collaboration skills
Team skill


Can I play Day Z on My Raspberry Pi?

Question: I know I can play Minecraft on my raspberry pi, but is Day Z possible or would I need a gaming computer? Though I have a tight wallet ...
Answer: We are able to play a version of Minecraft on the Raspberry Pi because the developers of Minecraft ported a version of the game to run on the Pi.
After doing some quick research on DayZ using Google; all indications show that DayZ is a Microsoft PC based game at this time.  There was some discussion about Bohemian Interactive supporting game consoles (XBox) in the future.
I recommend that you post your wishes for supporting a version of the game for the Raspberry Pi on the games forum.
Answer: DayZ is a Windows game. The raspberry pi does not run Windows. You will not be able to play Day Z on a raspberry pi.
Answer: The Raspberry Pi is not powerful enough to run Day Z and is also not a Windows machine, which Day Z requires.
Answer: If you are interested in using the Raspberry Pi as a gaming computer I would suggest using the Retropie distro.
Although I am unfamiliar with the game DayZ (I would guess zombies ...) you may find games for the retropie which satisfy your gaming needs.
Answer: Download steam on your pi. You can remote play with your PC using the rapper pi as a display and controller

Can I play Day Z on My Raspberry Pi?


Gimp fuzzy selector selection not being removed on delete

Question: I've done this precise thing before, but for some reason after selecting with the fuzzy selector the portion of the image I want to remove and hitting the delete key, it's not being removed.. Am I in some kind of weird mode? I am able to copy the selection but not cut it. I can fill it but erase it.. Any ideas?
Comment: so strange. I reopened to try what you are saying and it's just working as usual now.. If you answer the question I'll give you the points because that was good thinking.
Answer: A guess: Your layer has no alpha channel(=no transparency possible) and you try to delete a part which already has the background color. Insert the alpha channel. It works if your color mode is RGB.


gzip file in the finder

Question: Is it possible to add gzip (or any other command-line commands) as an option when you right-click on files in the Finder? There is a "Compress" option, but it makes a zip.
Comment: I found a similar question with a basic example. Leaving it here in case anyone finds it useful: https://apple.stackexchange.com/questions/425140/mac-os-x-10-14-6-add-option-to-right-click-menu-in-finder
Answer: You can use the Automator application to create a Quick Action, which can execute gzip (or any other command-line commands) as an option when you right-click on files or folders in the Finder application. The quick action needs to be stored as a .workflow file in your ~/Library/Services folder. Below is a example, where the gzip -r command can be executed on selected files. The AppleScript can be modified to execute other commands.

Note: This example was done using macOS Monterey version 12.5. I also tested using macOS High Sierra version 10.13.6. Prior to macOS Mojave version 10.14, Quick Actions are referred to a Services.

The AppleScript may seem lengthly, but has the following features:

There is a popup dialog that prompts the user confirm before executing the command.
There is a popup message when an error occurs. This message is currently truncated to 2000 characters.
Complete error messages can be viewed using the Console application.
The Finder application updates the window containing the selected files after executing the command.

The image below shows how the Quick Action is configured in the Automator application.

Below is the AppleScript that is partially shown in the above image.
to truncateReturns from userstring
    repeat while (userstring ends with return)
        if userstring = return then return ""
        set userstring to text from beginning to item -2 of userstring
    end repeat
    return userstring
end truncateReturns

to replaceCharacters of userstring over maxlength by endstring
    if userstring ends with return then
        set userstring to truncateReturns from userstring
    end if
    if length of userstring > maxlength then
        set userstring to (text from beginning to item maxlength of userstring)
        set userstring to (truncateReturns from userstring) & endstring
    end if
    return userstring
end replaceCharacters

on finderLogger(input)
    set logger to "printf"
    repeat with listitem in input
        set liststr to listitem as string
        if liststr = "<date>" then
            set liststr to (do shell script "date  +'%Y-%m-%d %H:%M:%S'" as string)
        end if
        set logger to logger & " " & quoted form of liststr
    end repeat
    set logger to logger & " >> ~/Library/Logs/Finder.log"
    set stdout to do shell script logger
    return stdout
end finderLogger

to fileInfo for thelink given following:followingBoolean
    set thequoted to quoted form of thelink
    if followingBoolean is false then
        set cmd to "if [ -L " & thequoted & " ];then echo LNK;fi"
        set followingBoolean to (do shell script cmd) is not "LNK"
    end if

    if followingBoolean is false then
        set linkFolderHFS to (do shell script "dirname " & thequoted) as POSIX file as text
        set linkFileHFS to (do shell script "basename " & thequoted) as POSIX file as text
        tell application "Finder" to set thefile to file linkFileHFS of folder linkFolderHFS
    else
        set linkFullHFS to thelink as POSIX file as text
        tell application "Finder" to set thefile to alias linkFullHFS
    end if
    return thefile
end fileInfo

on run {input, parameters}
    set cmd to "gzip -r"
    set messagetext to "Do you want run gzip on"
    set wait to 3600
    set maxlength to 2000
    considering numeric strings
        if system version of (system info) < "10.14" then
            set workflowname to "service gzip"
        else
            set workflowname to "quick action gzip"
        end if
    end considering

    try
        set filecount to count of input
        if filecount = 0 then error "The list of items was empty."

        set filelist to ""
        set fullpath to ""
        repeat with currentfile in input
            set fullpath to POSIX path of currentfile
            if length of fullpath > 1 and text -1 of fullpath = "/" then
                set fullpath to text 1 thru -2 of fullpath
            end if
            set filelist to filelist & " " & quoted form of fullpath
        end repeat

        if filecount is not equal to 1 then
            set messagetext to messagetext & " " & filecount & " items?"
        else
            set fullinfo to fileInfo for fullpath without following
            set displayname to displayed name of fullinfo
            set filekind to kind of fullinfo
            set messagetext to messagetext & return & """ & displayname & "" " & filekind & "?"
        end if
        tell application "Finder"
            activate
            with timeout of wait + 100 seconds
                set status to display dialog messagetext buttons {"Stop", "Continue"} with icon caution giving up after wait
            end timeout
        end tell
        if gave up of status then error "Time out occurred after wait for Continue button to selected."
        if button returned of status is not equal to "Continue" then return input
        set fullcommand to cmd & filelist & " 2>&1"
        set stdout to do shell script fullcommand
    on error errmsg number errnum
        try
            finderLogger({"%s %s: %s\\n", "<date>", workflowname, errmsg})
            error (replaceCharacters of errmsg over maxlength by "…")
        on error errmsg number errnum
            tell application "Finder"
                activate
                with timeout of wait + 100 seconds
                    display alert errmsg as critical giving up after wait
                end timeout
            end tell
        end try
    end try
    try
        tell application "Finder"
            activate
            tell front window
                update every item with necessity
            end tell
        end tell
    end try
    return input
end run

The image below shows an error message appearing in the Finder log.

Below are the corresponding images taken from macOS High Sierra version 10.13.6.

I should also point out that if you are not interested in having a popup to confirm and being notified when an error occurs, then you could simply modify this answer to use the command gzip -r.
Comment: I believe originally the menu item did appear in the right-click menu directly. However, this was changed to appear under "Services", then finally under "Quick Actions". So I do not know how to make the menu item appear in the right-click menu directly when using your version of macOS.
Comment: Here is an [image](https://imgur.com/a/JINTCAb) of Snow Leopard installed in a virtual machine. The Automator application window shows a service which just creates a popup. The Finder application window shows this service exists in the `~/Library/Services` folder. The next [image](https://imgur.com/a/EBxd3wf) shows right clicking on a file in the Finder application window. The `MyTest` service does appear directly in the menu. This final [image](https://imgur.com/a/EzCKrZt) shows the popup generated when `MyTest` is selected.
Comment: That worked! It actually saves in ~/Library/Services automatically, so you don't even need to worry about that. Do you know how to make the menu item appear in the right-click menu directly instead of under "Quick Actions"?
Comment: I saw some tutorials where it showed up directly in the right-click menu. I could not determine what exactly they did differently. Maybe it was a different version.
Comment: As I already stated, originally the menu item did appear in the right-click menu directly. For example, this is true if you are using OS X Snow Leopard version 10.6.8. So you are viewing old tutorials. (I happen to have Snow Leopard installed in a VirtualBox virtual machine so I can verify what I have posted in this comment.)

gzip file in the finder


Is there a way to overwrite a saved file in firebase storage?

Question: I am dealing with profile pictures in my ionic 1 App. I am searching for a way to update a file in firebase storage such that the download link remains the same.
Is it possible or any other way to achieve the required?
Answer: You can't update the file and maintain the same public download link--it's a different file, so it's assumed that you might want to change the access permissions
Just re-fetch the URL and download the file once it's been updated (it's actually returned in the metadata returned on upload, so you can send it to other apps right after you change it, no need to grab the URL separately):
var file = ... // use the Blob or File API
ref.put(file).then(function(snapshot) {
  var url = snapshot.downloadURL;
});

Answer: As the other answer says, basically you cant update the image without it changing the permissions.
BUT, if you change your rules for the path where your image is stored to say
allow read: if true;
allow write: if request.auth != null;

this basically makes it where anyone with the link can see the image. This will let you see the new image from the old download link.
But just know that this also means anybody with this link can see the image, not just people from your app.
Answer: Hey so I was dealing with something similar recently. According to the docs there isn't a direct way to overwrite an existing file but I did find a way to do this and retrieve a new url. Here is how I store and update.
const storeFile = async (file) => {
    const ref = firebase.firestore.collection('bin').doc();
    const id = ref.id;
    const storageRef = firebase.storage().ref().child('bin/' + id)
    await storageRef.put(file)
}

const updateFile = async (id, file) => {
    const storageRef = firebase.storage().ref('/path').child(id);
    // Put the new file in the same child ref.
    await storageRef.put(file);
    // Get the new URL
    const url = await storageRef.getDownloadURL();
    return url;
}

Comment: What is `id` here?
Comment: @MarkusAmaltheaMagnuson Usually I will store the file under a unique id. I'll either create an id in firestore, or use a uuid generator. I will update my answer
Answer: File update should be made on https://console.cloud.google.com/storage and after replacing the file with same name, then it's metadata should be updated with the firebaseStorageDownloadTokens key and previously used token.


what accentuates a mode shift in your melodic line?

Question: Aside from the underlying chords that are played, is it imperative to start and end your melody on the same note within your piece to indicate a modal tone? if so can you still use all the notes in the scale you use up and down loosely and not lose the sound of your mode as long as you started and end on the note that indicates the mode you want to emphasize?
Answer: No
You don't have to start or end on the same note. But bear in mind that chord progressions and melodies work differently.
Every melody or set of chord progressions suggests the mode. This is important to understand.
Example with chords: if you play: II - V you know what I is.
Example with a melody: by using triads or fifths you can suggest a root without playing it. Especially if you use a M7.
This also works the other way around, you can play in the key of C and suggest -for example- D minor, even if you use Dorian. Miles Davis' So What is a great example of this.
Answer: The tonic note of a scale is merely and only the MOST CHARACTERISTIC note of that scale. It does not have to sound in order for the scale to be discerned, as plenty of other notes in the scale serve to also delineate that scale.
Let's use an example from modern pop music:  Hootie and the Blowfish.  The singer's melodies are banal, uninteresting, naive, trivial, mostly BECAUSE they slam the tonic note so relentlessly.
Think of it this way:  moving away from the tonic note creates tension, while moving toward the tonic note resolves tension.  Western music, in both harmony and melody, is about creating then resolving tension.  The melody can range FAR AFIELD from the ostensible tonic, without breaking the "mood" of the stated key.  Whether it finds its way back or not doesn't really matter, in terms of the listener's perception of key or modality.


What are problems of many hidden layers?

Question: Is there any problem if we use too many hidden layers in Neural Network? Can anyone simply describe what problems can occur if we have too many hidden layers.
Answer: The gradient diminishes fast in very deep architectures, so the usual style of backpropagation doesn't work well. Backpropagated errors become very small after a few layers, which makes learning ineffective. This can be solved by pretraining, e.g. starting with initial weights that are close to the final solution.
Answer: If we increase the number of hidden layers then the neural network complexity increases.
Moreover many application can be solved using one or two hidden layer. But for multiple hidden layers, proportionality plays a vital role. Also if hidden layer are increased then total time for training will also increase. Overfitting may arise due to network complexity.
But if you aim is to achieve accuracy then multiple hidden layers can do that.
Comment: W/ so many free parameters (due to the multiple hidden layers) you will need *a lot* of data or the "accuracy" will only be due to overfitting. You will need to cross validate to get an unbiased estimate of the accuracy you really have.


Windows Domain controller as dns

Question: Im creating my first domain and joining pcs to the domain. Why do I need to specify my dc as the dns to join a pc to that domain?
Answer: You don't have to do that. You could first setup a DNS servers, e.g. BIND, and then setup your Active Directory. The first windows server you promote to be the domain controller will need to write a lot of entries into the DNS so it requires quite a lot of privileges. This is quite complex and Microsoft likes it to just work so it provides its own DNS server which it will install when promoting your first server to DC.
You can find tutorials on the Internet where it is explained how to use a separate DNS server for your Active Directory environment.
Answer: Active Directory Domain Services (AD DS) uses Domain Name System (DNS) name resolution services to make it possible for clients to locate domain controllers and for the domain controllers that host the directory service to communicate with each other.
Answer: I believe this has to do with the lookup zones for the DNS.
As the way DNS works, when you search for a query (I.E a hostname such as yourcompany.com) you start from the DNS server you are pointed to (in most cases that would be your DNS server in the LAN) and if the DNS server you are pointing to doesn't know the answer, he will ask the next DNS server, until he either reaches the root DNS servers or until he gets some reply from the DNS servers on the way/the root DNS servers.
More on how DNS works HERE
Now, as probably no other DNS know your domain, and there is no DC locator in any public DNS, you need to point your DNS to the DC you have created as that DC is the only one who can resolve the hostname "yourcompany.com", and tell you where it is located.

Windows Domain controller as dns


Fix Python error while launching QGIS 3.28

Question: I have installed QGIS 3.28 (Windows 10) and I am getting some errors while launching it.
This error is related to pyplugin_installer :

An error occurred during execution of following code:
import pyplugin_installer
traceback.print_exception() failed
Python version:
QGIS version:
3.28.8-Firenze 'Firenze', 5ac45272b58
Python path:

I have QGIS 3.18 already installed and it works fine.
I have tried to set PYTHONPATH but I still get the same results.
Answer: Fixed after changing the user in QGIS.


What can be done to mitigate risk to property from large trees other than removal?

Question: There are 3 oak trees that need to be removed as they pose risks
to personal safety and property during windstorm. The last windstorm (dec. 2019, AK) produced 120 m/h gusts. The quote is $6k due to complexity  plus a crane will need to be utilized to accomplish the task.
Is there anything else could be done?
Comment: In some locations you need permission to fell an oak as they are protected.
Comment: Sounds like a courtyard with building on four sides. Here in the piney woods ( many experts available) , they cut large trees ( 100' by 3 ' diameter) using a boom truck that can reach 50' feet from any roadway or lawn, and lower the pieces of tree by rope.. I have had 10 trees removed . One in the summer cost $600 to cut and remove . It may be worth getting other estimates.
Comment: The one removed in summer was a "baby" ; 100' by only 18" diameter.
Comment: Thank  you all. They estimated it at 5K.
Comment: You're welcome, but please [take the tour](https://diy.stackexchange.com/tour) so you know how this network operates. "Thank you" comments are discouraged.
Answer: Your question is a bit broad since you've provided very little detail about the situation, but hiring an arborist to guide structural pruning would almost entirely eliminate risk of blowdown.
We have large white oaks in our neighborhood, and they're rarely blown completely down, but they do tend to lose large, long, high branches in severe storms. Shortening or removing those would substantially reduce risk. Obviously there's still cost involved, but perhaps quite a bit less, and you get to keep some beautiful trees.
Comment: I have a huge oak at my home we had it pruned by a licensed arborists when we purchased this place 5 years ago. Last year we had a really bad snow storm and we lost a few branches but nothing worth removing the tree, we had the arborists come back and take care of one branch that needed removal and trim a few others he said needed it but the 2nd trip was 450$ the first was a little over 1000 maybe 1200 but we still have our tree I would agree with Isherwood that ti would be less expensive and probably look better to keep the tree with some professional care it made it through the storm.+
Comment: +1 for recommending an arborist. They always want to coat the cut areas with some special protection to keep bugs and moisture out.
Comment: I've been told recently that sealing wounds is no longer advisable, which was news to me. [Here's an article that mentions it](https://s3.wp.wsu.edu/uploads/sites/403/2015/03/wound-sealer.pdf). It's more about knowing where to cut, I think.
Answer: You could get an engineer to devise a steel collar with steel rope that could prevent the trees from falling in a certain direction.  Depending on the location / size of the trees / structures you could devise something that allows you to retain the trees.
Comment: So guy wires to the ground? Have you seen this done anywhere? I'm curious about the anchoring that would be required. I'd expect that a large concrete structure would be needed.


Pentesting file Upload feature

Question: The file(resume) upload feature is accepting any sort of files. I have uploaded the PHP shell into it. How do I again access to that uploaded file? I'm bruteforcing the web directory to check for uploaded file path. Is my approach correct?
Comment: dany I would suggest checking how the file viewer works - do you browse straight to this file? Is there a parameter that includes the relative local file path? Or is the file stored in a database? Besides that, do you know for a fact that PHP is installed, or are you just assuming this? Also check out [this post](http://security.stackexchange.com/a/11992/33) regarding other potential attacks regarding file uploads, besides just file execution.
Answer: Your approach is fine for finding vulnerable systems, but it's likely not vulnerable.
The file you uploaded isn't guaranteed to be in any publicly accessible directory. It may be stored outside of the document root of the web server, then read via a PHP script that streams the content back to you.
In such a case, there's no way to make the web server run the script as a PHP script, because the PHP module won't execute anything outside of its base directory (document root).
Answer: There is no guarantee that the file you uploaded is also available through the webserver. It might be that the path to where the file is stored is protected and cannot be browsed.
Comment: ok..any other solution to ..pentest that feature?
Answer: What I usually do depends on the exact type of app.  If it's a user contributed content application where the uploaded files are visible after upload, then just upload something safe, find where it's uploaded through standard application functionality, and that's your location.
Assuming here that that's not the case you have a couple of options.  If you can identify the product in use (assuming it's a packaged app) then a good approach is download the app or the documentation and find out the default location from that.
If it's bespoke then you're likely back to the bruteforcing approach that you're currently using. as @lucas-kauffman and @polynomial have mentioned, it's possible/probable that the application uploads outside of the web root, in which case you won't be able to directly access the content.
Of course there's other things you could do as part of a pentest with a file upload feature that could still be interesting.  A standard one you may not yet have tried is uploading eicar to check the A-V on the upload facility, in a lot of cases they won't have any.

Pentesting file Upload feature


Resources for connections between dependent type theory and LCCC

Question: Can someone recommend introductory articles/papers on the connections between dependent type theory and locally cartesian closed category? Many Thanks!
Comment: The original paper by Seely is quite readable: [Locally cartesian closed categories and type theory](https://www.math.mcgill.ca/rags/LCCC/LCCC.pdf).
Answer: The original interpretation of dependent type theory in lcccs by Seely suffers from coherence problems. There are a range of techniques with have been invented to solve them. In most cases the interpretation of a type $\Gamma
\vdash A \textit{ type}$ is no longer an object in the slice $\mathbf S/\Gamma$ over the interpretation of $\Gamma$, instead the interpetation of $A$ will be a fibered functor $A:y(\Gamma)\to \partial_1$ where $\partial_1$ is the codomain fibration of the base. The fibered Yoneda lemma tells us that there is an equivalence $$Fib_\mathbf S(y\Gamma,\partial_1) = \mathbf S/\Gamma$$
The extra data which a fibered functor $A:y(\Gamma)\to \partial_1$ carries around is a choice of pullbacks of its display map in $\mathbf S/\Gamma$, and this is what is needed to solve the coherence problem. You asked for references, so here are some:

On the interpretation of type theory in locally cartesian closed categories by Martin Hoffman explains the coherence problem in Selly's semantic and explains how one can solve it.

More generally, the constructions in Hoffman's paper is just a way to associate a model of dependent type theory to a lcccs. You may want to read about such models in general. There are many different ones, but they are all essentially equivalent. E.g. there are categories with families, categories with attributes and split comprehension categories.

The later chapters of Jacobs Categorical Logic and Type Theory talk about comprehension and split comprehension categories. They do not discuss the canonical splitting of the self-indexing $\partial_1$ though.

Natural Models of Homotopy Type Theory by Awodey discusses the interpretation of $\Sigma,\Pi$ and extensional equality in a category in a really nice way.

Categories with Families Unityped, Simply Typed, and Dependently Typed by Castellan, Lairambault, Dybjer discusses in detail the 2-equivalence between the 2-category of lcccs and the 2-category of democatric categories with families which admit $\Pi,\Sigma,=,\mathbf 1$. I believe they also show that the syntax of Martin-Löf dependent type theory yields a 2-initial (in the non-strict sense) category with families. Together with the 2-equivalence to lcccs one can conclude that the category of contexts of MLTT with $\Pi,\Sigma,\mathbf 1,=$ is 2-intial in lccc.

The shorter article The biequivalence of lccc and MLTT by Clairambault, Dybjer is only about the relation between lcccs and MLTT, so it is exactly what you are looking for.


Stability of delta sigma modulator with high frequency signal input

Question: What happens to the high frequency part of a signal (in the region where the quantization noise is high) requantized with a delta sigma modulator, let's say with $$STF = 1$$ and $$NTF = (1-z^{-1})^N$$? I assume it is just lost into the shaped quantization noise, but does it affect also the stability of the modulator?
In particular I know that MASH structures rely on the fact that the signal is still present inside the secondary modulator superposed to the added quantization noise. Does this "high frequency signal" (the quantization noise of the previous stage of the MASH) affect the stability of the modulator? The literature always assume the first order delta sigma is unconditionally stable, but also in presence of an input high frequency signal? My doubts arise from the fact that the high frequency part of the spectrum is used to stuff shaped noise, if this portion of the spectrum is already occupied by the signal itself does that mean that there is less "space" available and this could lead to stability problems?
Answer: There are no stability problems if the spectrum of a reasonable amplitude input signal extends into the 'noisy' region. The converter is stable in the presence of large voltage swings there anyway, a little extra additive input makes little difference.
With enough amplitude, it is possible to overload a sigma delta modulator, but this is just normal behaviour, any device has an overload level.
Given that the signal recovery filter after a sigma delta modulator removes, essentially completely, all the noisy region of the spectrum, it would be possible to overload the converter and not realise it, if looking at the filtered output signal alone.


Gnome Left Menu Gone

Question: Months ago I changed kernels temporarily from 3.10.0-1160.11.1.el7.x86_64 to 5.8.0-1.el7.elrepo.x86_64 then I reverted back to 3.10.0-1160.11.1.el7.x86_64 within a few hours.  Once I loaded up 3.10.0-1160.11.1.el7.x86_64 I ended up losing the Super Key feature and "Left menu".  I am using CentOS7 and now have to click the "Applications" and select tools that way.
What I realized is  3.10.0-1160.11.1.el7.x86_64 is using Gnome 3.28.2. So Kernel 5.8.0-1.el7.elrepo.x86_64 likely had a newer Gnome version which created a conflict.
I feel like there is a repair command I can run or something to get the left menu bar and "Windows" search key back.
Any ideas how to get it back?  This is a total pita.
Answer: I guess when I changed kernels it changed to GNOME classic.  So I logged out, clicked the gear icon then selected Gnome and vioala!

Gnome Left Menu Gone


What is the best Y level for diamonds?

Question: Is there a specific y level for diamonds so that they occur the most? I am having trouble because some people will say Y level 10 or Y level 14 and so on. I just want to know if there is a designated Y level for diamonds or something.
Answer: diamonds naturally spawn at level 12. Therefore if you mine at a lower level you will run into more diamonds than if you mine on level 12.
Comment: do we have any proof that it is Y level 12?
Answer: Below level about 15 (12 if you want to be exact) diamonds become more common, however below level 4 they start to get less common. Since the higher the safer in mining, it is recommended to mine about 10 - 12, but if you really want you can go to 6 - 9.

What is the best Y level for diamonds?


The reason behind circular motion of vehicles

Question: In all the textbooks and internet resources that I've ever read , most of them explains role if friction in circular motion of an object (let's says a cycle), from the frame of the cyclist i.e. with the help of centrifugal pseudo force. I think they do this because it's more  intuitive and easy to understand.
However I want to Visualise it from the ground frame. The best explanation I gave myself is that without friction no change in the path of my cycle can be observed (ignoring everything other than gravity) so there has to be something with the help of which I'm able to continuously turn.
But it feels dry and it was only to satisfy my thirst.
Please share your views on this problem. And possibly explain it without any maths.
Comment: related: https://physics.stackexchange.com/questions/265556/friction-in-circular-motion
Answer: This might help, I promise no maths...
We imagine your cycle going straight. To make it turn to the left, we have to either pull it or push it leftwards so it will start turning in a circle. And as long as we wish it to continue going in a circle, we have to keep pushing or pulling it ever to its left.
Where does this leftward force come from? If you had a friend in the middle of the circle with a rope and he tied one end of it to your bike frame and pulled on the other end, he could make you swing around and around in a circle by applying a constant pulling force towards the center of the circle, and around you go. But as soon as he lets go of the rope and thereby stops pulling on the bike, you and the bike will depart in a straight line.
Without a friend with a rope, you must instead rely on the friction force between the bike's tires and the pavement to push sideways on the bike and bend its path into a circle. The process by which a cyclist turns a bike is complex and has been written about extensively here, but the important point you need to know is this:
the bike leans to the left, and as it tracks around into a turn it is pushing sideways towards the right on the pavement- and here it is- the pavement is pushing sideways on the tire to the left, thereby providing the sideways force needed to bend the bike's path into a turn.
Comment: Nice math free answer. +1 from me.
Comment: So that was the important point I was missing. So the cycle has to lean atleast a little bit to even start curving it's path. By leaning we are basically creating a component which can push the road sideways. And then friction will oppose this push and we will use this sidewise stopping force as the step we step in to, to make the turn.(feel what I'm tryna say). This also means that without friction, I'll disbalance if a lean , the instant gravity can't balance my torque, since there is no friction to help. Lol without Friction I can't even start the cycle.
Comment: But is circular motion in a cycle even possible without leaning?
Comment: certainly, if you have a friend with a rope!
Answer: If an object is to change its velocity, it must experience a resultant force, that is a push or pull from another body. For a bicycle on level ground, that resultant force must be horizontal, and the only forces usually available are (a) from the ground; we call that force 'friction' (b) air resistance, which, unless there is a wind blowing, acts in the opposite direction to the cyclist's velocity.
So if you want to increase your speed you need a frictional force from the ground in your forward direction; you obtain this by pedalling at an appropriate rate.
If you want to follow a circular path you steer accordingly, and a 'sideways' frictional force from the road provides the centripetal force needed to change your velocity (because in order to go in a circle the direction of the velocity vector has to keep changing. Although the magnitude of the velocity may stay the same, the change in direction means that there is a change in velocity – an acceleration! And, as you know, for a body to accelerate there must be a resultant force.