124924859
Direct Observation of SU(N) Orbital Magnetism
2486417
Precision test of mass-ratio variations with lattice-confined ultracold molecules.
We propose a precision measurement of time variations of the proton-electron mass ratio using ultracold molecules in an optical lattice. Vibrational energy intervals are sensitive to changes of the mass ratio. In contrast to measurements that use hyperfine-interval-based atomic clocks, the scheme discussed here is model independent and does not require separation of time variations of different physical constants. The possibility of applying the zero-differential-Stark-shift optical lattice technique is explored to measure vibrational transitions at high accuracy.
25651519
New limits on coupling of fundamental constants to gravity using 87Sr optical lattice clocks.
The 1S0-3P0 clock transition frequency nuSr in neutral 87Sr has been measured relative to the Cs standard by three independent laboratories in Boulder, Paris, and Tokyo over the last three years. The agreement on the 1 x 10(-15) level makes nuSr the best agreed-upon optical atomic frequency. We combine periodic variations in the 87Sr clock frequency with 199Hg+ and H-maser data to test local position invariance by obtaining the strongest limits to date on gravitational-coupling coefficients for the fine-structure constant alpha, electron-proton mass ratio mu, and light quark mass. Furthermore, after 199Hg+, 171Yb+, and H, we add 87Sr as the fourth optical atomic clock species to enhance constraints on yearly drifts of alpha and mu.
31462099
Precision stabilization of femtosecond lasers to high-finesse optical cavities
We report on direct stabilization of a femtosecond laser by a high-finesse passive optical cavity. Detailed comparison of two distinct stabilization schemes leads to new understanding of the optimum conditions for cavity stabilization and limitations on the ability to transfer the frequency stability of the cavity to the microwave domain. The stability of the frequency comb is explored in both the optical and the radio frequency domain. With an independent, stable cw laser, we verify that the linewidth and stability of the optical comb components, respectively, reach below 300 Hz and 53 10 ˛14 at 1 s averaging time, both limited by the
7079909
Convergent Evolution of a New Arsenic Binding Site in the ArsR/SmtB Family of Metalloregulators*
Acidithiobacillus ferrooxidans has an arsenic resistance operon that is controlled by an As(III)-responsive transcriptional repressor, AfArsR, a member of the ArsR/SmtB family of metalloregulators. AfArsR lacks the As(III) binding site of the ArsRs from plasmid R773 and Escherichia coli, which have a Cys32-Val-Cys34-Asp-Leu-Cys37 sequence in the DNA binding site. In contrast, it has three cysteine residues, Cys95, Cys96, and Cys102, that are not present in the R773 and E. coli ArsRs. The results of direct As(III) binding measurements and x-ray absorption spectroscopy show that these three cysteine residues form a 3-coordinate As(III) binding site. DNA binding studies indicate that binding of As(III) to these cysteine residues produces derepression. Homology modeling indicates that As(III) binding sites in AfArsR are located at the ends of antiparallel C-terminal helices in each monomer that form a dimerization domain. These results suggest that the As(III)-S3 binding sites in AfArsR and R773 ArsR arose independently at spatially distinct locations in their three-dimensional structures.
2120691
Optical interferometers with reduced sensitivity to thermal noise
Thermal phase noise in optical interferometry can be compensated by exploiting coherence for underlying stochastic displacements and strains. The phase upon reflection from a fluctuating mirror's surface can thereby have reduced sensitivity to thermal noise.
111121123
Irradiation studies of Gb/s optical links developed for the front-end read-out of the ATLAS liquid argon calorimeter
Abstract In the baseline read-out scheme of the ATLAS liquid argon calorimeter, approximately 1500 unidirectional Gigavit/s (Gb/s) optical links are used to transfer data from teh calorimeter to receivers in data acquisition electronics situated up to 200 metres away. In the architecture of the link currently under development, VCSEL's (Vertical Cavity Surface Emitting Laser diodes) mounted on-detector are coupled to PIN-photodiodes located in receivers through graded-index multimode optical fibres. Over 10 years of ATLAS running, the components of the emitter will be exposed to high levels of neutron (1.7 × 10 13 n (1MeV Si) cm −2 ) and gamma (800 Gy) radiation. Their performance has been explored using neutron and gamma facilities and the results of these studies are presented in this paper. No significant levels of radiation are expected for the receiving part of the link.
109908952
Cryogenic digital data links for the liquid argon time projection chamber
In this paper we present the cryogenic functionality of the components of data links for the Liquid Argon Time Projection Chamber (LArTPC), a potential far site detector technology of the Long-Baseline Neutrino Experiment (LBNE). We have confirmed that an LVDS driver can drive a 20-meter CAT5E twisted pair up to 1 gigabit per second at the liquid nitrogen temperature (77 K). We have verified that a commercial-off-the-shelf (COTS) serializer, a laser diode driver, laser diodes, optical fibers and connectors, and field-programming gate arrays (FPGA`s) continue to function at 77 K. A variety of COTS resistors and capacitors have been tested at 77 K. All tests we have conducted show that the cryogenic digital data links for the liquid argon time projection chamber are promising.
6496614
Response of a 0.25 μm thin-film silicon-on-sapphire CMOS technology to total ionizing dose
The radiation response of a 0.25 μm silicon-on-sapphire CMOS technology is characterized at the transistor and circuit levels utilizing both standard and enclosed layout devices. The threshold-voltage shift is less than 170 mV and the leakage-current increase is less than 1 nA for individual standard-layout nMOSFET and pMOSFET devices at a total dose of 100 krad(SiO2). The increase in power supply current at the circuit level was less than 5%, consistent with the small change in off-state transistor leakage current. The technology exhibits good characteristics for use in the electronics of the ATLAS experiment at the Large Hadron Collider.
30481535
A compact apparatus for muon lifetime measurement and time dilation demonstration in the undergraduate laboratory
We describe a compact apparatus for measuring the charge-averaged lifetime of atmospheric muons in plastic scintillator using low-cost, low-power electronics. We present measurements of the stopping rate of atmospheric muons as a function of altitude to demonstrate relativistic time dilation. The apparatus is designed for the advanced undergraduate physics laboratory and is suitable for field measurements.
63008679
CDRD High Rate Data Links Program