Magneto-shear modes and a.c. dissipation in a two-dimensional Wigner crystal

The a.c. response of an unpinned and finite 2D Wigner crystal to electric fields at an angular frequency $\omega$ has been calculated in the dissipative limit, $\omega \tau \ll 1$, where $\tau ^{-1}$ is the scattering rate. For electrons screened by parallel electrodes, in zero magnetic field the long-wavelength excitations are a diffusive longitudinal transmission line mode and a diffusive shear mode. A magnetic field couples these modes together to form two new magneto-shear modes. The dimensionless coupling parameter $\beta =2(c_{t}/c_{l})|\sigma_{xy}/\sigma_{xx}|$ where $c_{t}$ and $c_{l}$ are the speeds of transverse and longitudinal sound in the collisionless limit and $\sigma_{xy}$ and $\sigma_{xx}$ are the tensor components of the magnetoconductivity. For $\beta \geqslant 1$, both the coupled modes contribute to the response of 2D electrons in a Corbino disk measurement of magnetoconductivity. For $\beta \gg 1$, the electron crystal rotates rigidly in a magnetic field. In general, both the amplitude and phase of the measured a.c. currents are changed by the shear modulus. In principle, both the magnetoconductivity and the shear modulus can be measured simultaneously.Comment: REVTeX, 7 pp., 4 eps figure

The impact of diet-based glycaemic response and glucose regulation on cognition: evidence across the lifespan

The brain has a high metabolic rate and its metabolism is almost entirely restricted to oxidative utilisation of glucose. These factors emphasise the extreme dependence of neural tissue on a stable and adequate supply of glucose. Whereas initially it was thought that only glucose deprivation (i.e. under hypoglycaemic conditions) can affect brain function, it has become apparent that low-level fluctuations in central availability can affect neural and consequently, cognitive performance. In the present paper the impact of diet-based glycaemic response and glucose regulation on cognitive processes across the lifespan will be reviewed. The data suggest that although an acute rise in blood glucose levels has some short-term improvements of cognitive function, a more stable blood glucose profile, which avoids greater peaks and troughs in circulating glucose is associated with better cognitive function and a lower risk of cognitive impairments in the longer term. Therefore, a habitual diet that secures optimal glucose delivery to the brain in the fed and fasting states should be most advantageous for the maintenance of cognitive function. Although the evidence to date is promising, it is insufficient to allow firm and evidence-based nutritional recommendations. The rise in obesity, diabetes and metabolic syndrome in recent years highlights the need for targeted dietary and lifestyle strategies to promote healthy lifestyle and brain function across the lifespan and for future generations. Consequently, there is an urgent need for hypothesis-driven, randomised controlled trials that evaluate the role of different glycaemic manipulations on cognition

Bistability and Hysteresis of Intersubband Absorption in Strongly Interacting Electrons on Liquid Helium

We study nonlinear inter-subband microwave absorption of electrons bound to the liquid helium surface. Already for a comparatively low radiation intensity, resonant absorption due to transitions between the two lowest subbands is accompanied by electron overheating. The overheating results in a significant population of higher subbands. The Coulomb interaction between electrons causes a shift of the resonant frequency, which depends on the population of the excited states and thus on the electron temperature $T_e$. The latter is determined experimentally from the electron photoconductivity. The experimentally established relationship between the frequency shift and $T_e$ is in reasonable agreement with the theory. The dependence of the shift on the radiation intensity introduces nonlinearity into the rate of the inter-subband absorption resulting in bistability and hysteresis of the resonant response. The hysteresis of the response explains the behavior in the regime of frequency modulation, which we observe for electrons on liquid $^3$He and which was previously seen for electrons on liquid $^4$He

Epidemiology of Any and Vaccine-Type Anogenital Human Papillomavirus Among 13-26-Year-Old Young Men After HPV Vaccine Introduction

PURPOSE: The aims of this study were to determine prevalence of and factors associated with any human papillomavirus (HPV) and vaccine-type HPV among young men after vaccine introduction, stratified by vaccination status. METHODS: Young men were recruited from clinical sites from 2013 to 2015, completed a survey, and were tested for 36 anogenital HPV types. We determined factors associated with ≥1 HPV type among all participants, and vaccine-type HPV (HPV6, 11, 16, and/or 18) among all, vaccinated and unvaccinated participants, using multivariable regression. RESULTS: Mean age was 21.5 years and 26% had received at least one HPV vaccine dose. HPV prevalence was lower in vaccinated versus unvaccinated young men (50.5% vs. 62.6%, p = .03). HPV positivity was discordant by anogenital site. At both sites, 59.4% were positive for ≥1 HPV type and 26.0% for ≥1 4-valent vaccine type. In multivariable logistic regression, factors associated with ≥1 HPV type among all participants were frequency of oral sex (odds ratio [OR] = 1.80, 95% confidence interval [CI] = 1.00-3.24), recent smoking (OR = 1.84, CI = 1.17-2.90), and sexually transmitted infection history (OR = 1.56, CI = 1.02-2.38). Factors associated with vaccine-type HPV among all participants were white versus black race (OR = 1.91, CI = 1.10-3.34) and gonorrhea history (OR = 2.52, CI = 1.45-4.38); among vaccinated participants were private versus Medicaid insurance (OR = 5.6, CI = 1.46-20.4) and private versus no insurance (OR = 15.9, CI = 3.06-83.3); and among unvaccinated participants was gonorrhea history (OR = 1.83, CI = 1.03-3.24). CONCLUSIONS: Anogenital HPV prevalence was high and vaccination rates low among young men 2-4 years after vaccine introduction, underscoring the urgency of increasing vaccination rates and vaccinating according to national guidelines

Atomic clocks with suppressed blackbody radiation shift

We develop a nonstandard concept of atomic clocks where the blackbody radiation shift (BBRS) and its temperature fluctuations can be dramatically suppressed (by one to three orders of magnitude) independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies v1 and v2) which are exposed to the same thermal environment, there exists a "synthetic" frequency v_{syn} (v1-e12 v2) largely immune to the BBRS. As an example, it is shown that in the case of ion 171Yb+ it is possible to create a clock in which the BBRS can be suppressed to the fractional level of 10^{-18} in a broad interval near room temperature (300\pm 15 K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies v1 and v2. Here the frequency v_{syn} is generated as one of the components of the comb spectrum and can be used as an atomic standard.Comment: 5 pages, 2 figure

Pengaruh Kompensasi dan Lingkungan Kerja pada Loyalitas Karyawan Berdasarkan Jenis Kelamin

This study aimed to examine the effect of compensation and work environment on employee loyalty by gender either simultaneously or partially.73 Respondnts as employees is determined using the method of saturated samples. Data were obtained through questionnaires,were analyzed using discriminant analysis techniques (discriminant analysis). Based on the analysis it was found that compensation and work environment simultaneously significant effect on employee loyalty. Partially compensated significant effect on employee loyalty. The working environment is partially no significant effect on employee loyalty

Quantum interference-induced stability of repulsively bound pairs of excitations

We study the dynamics of two types of pairs of excitations which are bound despite their strong repulsive interaction. One corresponds to doubly occupied sites in one-dimensional Bose-Hubbard systems, the so-called doublons. The other is pairs of neighboring excited spins in anisotropic Heisenberg spin-1/2 chains. We investigate the possibility of decay of the bound pairs due to resonant scattering by a defect or due to collisions of the pairs. We find that the amplitudes of the corresponding transitions are very small. This is a result of destructive quantum interference and explains the stability of the bound pairs.Comment: 12 pages, 3 figure

Cooperative Hydration of Pyruvic Acid in Ice

About 3.5 ± 0.3 water molecules are still involved in the exothermic hydration of 2-oxopropanoic acid (PA) into its monohydrate (2,2-dihydroxypropanoic acid, PAH) in ice at 230 K. This is borne out by thermodynamic analysis of the fact that Q_H(T) = [PAH]/[PA] becomes temperature independent below ∼250 K (in chemically and thermally equilibrated frozen 0.1 ≤ [PA]/M ≤ 4.6 solutions in D_2O), which requires that the enthalpy of PA hydration (ΔHH ∼ −22 kJ mol^(-1)) be balanced by a multiple of the enthalpy of ice melting (ΔH_M = 6.3 kJ mol^(-1)). Considering that:  (1) thermograms of frozen PA solutions display a single endotherm, at the onset of ice melting, (2) the sum of the integral intensities of the ^1δ_(PAH) and ^1δ_(PA) methyl proton NMR resonances is nearly constant while, (3) line widths increase exponentially with decreasing temperature before diverging below ∼230 K, we infer that PA in ice remains cooperatively hydrated within interstitial microfluids until they vitrify