Two-photon absorption in potassium niobate

We report measurements of thermal self-locking of a Fabry-Perot cavity containing a potassium niobate (KNbO3) crystal. We develop a method to determine linear and nonlinear optical absorption coefficients in intracavity crystals by detailed analysis of the transmission lineshapes. These lineshapes are typical of optical bistability in thermally loaded cavities. For our crystal, we determine the one-photon absorption coefficient at 846 nm to be (0.0034 \pm 0.0022) per m and the two-photon absorption coefficient at 846 nm to be (3.2 \pm 0.5) \times 10^{-11} m/W and the one-photon absorption coefficient at 423 nm to be (13 \pm 2) per m. We also address the issue of blue-light-induced-infrared-absorption (BLIIRA), and determine a coefficient for this excited state absorption process. Our method is particularly well suited to bulk absorption measurements where absorption is small compared to scattering. We also report new measurements of the temperature dependence of the index of refraction at 846 nm, and compare to values in the literature.Comment: 8 pages. To appear in J. Opt. Soc. Am.

Poorer mental health is associated with cognitive deficits in old age

Few studies have examined the association between within-person (WP) reaction time (RT) variability and mental health (depression, anxiety, and social dysphoria) in old age. Therefore, we investigated mental health (using the General Health Questionnaire) and cognitive function (mean RT or WP variability) in 257 healthy, community-dwelling adults aged 50-90 years (M = 63.60). The cognitive domains assessed were psychomotor performance, executive function, visual search, and recognition. Structural equation models revealed that for WP variability, but not mean RT, poorer mental health was associated with visual search and immediate recognition deficits in older persons and that these relationships were partially mediated by executive function. The dissociation between mean RT and WP variability provides evidence that the latter measure may be particularly sensitive to the subtle effects of mental health on cognitive function in old age

Combating COVID-19-The role of robotics in managing public health and infectious diseases.

COVID-19 may drive sustained research in robotics to address risks of infectious diseases

Coherent Bayesian analysis of inspiral signals

We present in this paper a Bayesian parameter estimation method for the analysis of interferometric gravitational wave observations of an inspiral of binary compact objects using data recorded simultaneously by a network of several interferometers at different sites. We consider neutron star or black hole inspirals that are modeled to 3.5 post-Newtonian (PN) order in phase and 2.5 PN in amplitude. Inference is facilitated using Markov chain Monte Carlo methods that are adapted in order to efficiently explore the particular parameter space. Examples are shown to illustrate how and what information about the different parameters can be derived from the data. This study uses simulated signals and data with noise characteristics that are assumed to be defined by the LIGO and Virgo detectors operating at their design sensitivities. Nine parameters are estimated, including those associated with the binary system, plus its location on the sky. We explain how this technique will be part of a detection pipeline for binary systems of compact objects with masses up to 20 \sunmass, including cases where the ratio of the individual masses can be extreme.Comment: Accepted for publication in Classical and Quantum Gravity, Special issue for GWDAW-1

Leptonic CP Violation in Supersymmetric Standard Model

We point out the possibility of spontaneous and hard CP-violation in the scalar potential of R-parity broken supersymmetric Standard Model. The existence of spontaneous CP-violation depends crucially on the R-parity breaking terms in the superpotential and, in addition, on the choice of the soft supersymmetry breaking terms. Unlike in theories with R-parity conservation, it is natural, in the context of the present model, for the sneutrinos to acquire (complex) vacuum expectation values. In the context of this model we examine here the global implications, like the strength of the CP-violating interactions and the neutrino masses.Comment: REVTEX, 15 page

Zoonotic potential of simian arteriviruses

Wild nonhuman primates are immediate sources and long-term reservoirs of human pathogens. However, ethical and technical challenges have hampered the identification of novel blood-borne pathogens in these animals. We recently examined RNA viruses in plasma from wild African monkeys and discovered several novel, highly divergent viruses belonging to the family Arteriviridae. Close relatives of these viruses, including simian hemorrhagic fever virus, have caused sporadic outbreaks of viral hemorrhagic fever in captive macaque monkeys since the 1960s. However, arterivirus infection in wild nonhuman primates had not been described prior to 2011. The arteriviruses recently identified in wild monkeys have high sequence and host species diversity, maintain high viremia, and are prevalent in affected populations. Taken together, these features suggest that the simian arteriviruses may be “preemergent” zoonotic pathogens. If not, this would imply that biological characteristics of RNA viruses thought to facilitate zoonotic transmission may not, by themselves, be sufficient for such transmission to occur

Search for Millicharged Particles at SLAC

Particles with electric charge q < 10^(-3)e and masses in the range 1--100 MeV/c^2 are not excluded by present experiments. An experiment uniquely suited to the production and detection of such "millicharged" particles has been carried out at SLAC. This experiment is sensitive to the infrequent excitation and ionization of matter expected from the passage of such a particle. Analysis of the data rules out a region of mass and charge, establishing, for example, a 95%-confidence upper limit on electric charge of 4.1X10^(-5)e for millicharged particles of mass 1 MeV/c^2 and 5.8X10^(-4)e for mass 100 MeV/c^2.Comment: 4 pages, REVTeX, multicol, 3 figures. Minor typo corrected. Submitted to Physical Review Letter

Non-Equilibrium Statistical Physics of Currents in Queuing Networks

We consider a stable open queuing network as a steady non-equilibrium system of interacting particles. The network is completely specified by its underlying graphical structure, type of interaction at each node, and the Markovian transition rates between nodes. For such systems, we ask the question ``What is the most likely way for large currents to accumulate over time in a network ?'', where time is large compared to the system correlation time scale. We identify two interesting regimes. In the first regime, in which the accumulation of currents over time exceeds the expected value by a small to moderate amount (moderate large deviation), we find that the large-deviation distribution of currents is universal (independent of the interaction details), and there is no long-time and averaged over time accumulation of particles (condensation) at any nodes. In the second regime, in which the accumulation of currents over time exceeds the expected value by a large amount (severe large deviation), we find that the large-deviation current distribution is sensitive to interaction details, and there is a long-time accumulation of particles (condensation) at some nodes. The transition between the two regimes can be described as a dynamical second order phase transition. We illustrate these ideas using the simple, yet non-trivial, example of a single node with feedback.Comment: 26 pages, 5 figure

Underreporting of dietary intake by body mass index in premenopausal women participating in the Healthy Women Study

Underreporting patterns by the level of obesity have not been fully assessed yet. The purpose of this study was to examine the differential underreporting patterns on cardiovascular risk factor, macronutrient, and food group intakes by the level of Body Mass Index (BMI). We analyzed cross-sectional baseline nutritional survey data from the population-based longitudinal study, the Healthy Women Study (HWS) cohort. Study subjects included 538 healthy premenopausal women participating in the HWS. Nutrient and food group intakes were assessed by the one-day 24-hour dietary recall and a semi-quantitative food frequency questionnaire, respectively. The ratio of reported energy intake (EI) to estimated basal metabolic rate (BMR) was used as a measure of relative energy reporting status and categorized into tertiles. Overweight group (BMI≥25kg/m2) had a higher ratio of EI to BMR (EI/BMR) than normal weight group (BMI<25kg/m2). Normal weight and overweight groups showed similar patterns in cardiovascular risk factors, nutrient intake, and food group intake by the EI/BMR. Fat and saturated fat intakes as a nutrient density were positively associated with the EI/BMR. Proportion of women who reported higher consumption (≥4 times/wk) of sugar/candy, cream and red meat groups was greater in higher tertiles of the EI/BMR in both BMI groups. Our findings suggest similar patterns of underreporting of cardiovascular risk factors, and macronutrient and food group intakes in both normal and overweight women