Measurement of the vortex-core radius by scanning tunneling microscopy

Using a scanning tunneling microscope operated in a spectroscopic mode we imaged flux-line lattices in niobium diselenide at various external magnetic fields. From the evaluation of a large number of tunneling-current profiles taken across the individual vortices we deduced the dependence of the vortex-code radius on the applied magnetic field. It was found that the core radius shows a pronounced decrease with increasing field, even for H/Hc2<<1. This behavior is qualitatively well characterized by self-consistent solutions of the Usadel equations

analyses from a cross-sectional online survey

Objectives Opportunities for men having sex with men (MSM) to meet each other have very much improved by new communication technologies. Meeting venue-based characteristics can impact how many partners are met and how much sexual risk is taken. We analysed the association between physical and virtual venues and the risk for bacterial sexually transmitted infections (bSTIs) among participants in an MSM online survey. Methods Data were collected during 2013/2014 with a survey targeting MSM living in Germany. The impact of the meeting place with the last non-steady anal sex partner on diagnosis with a bSTI in the previous year was analysed using bivariate and multivariate regression analysis, taking into account self-reported HIV status, serostatus communication, condom use, partner number, age and city size. Results The study sample consisted of 8878 respondents (7799 not diagnosed with HIV; 1079 diagnosed with HIV). Meeting partners online was most common (62% HIV−/51% HIV+), followed by sex venues (11% HIV−/25% HIV+); other venues were each reported by 2–6% of the respondents. Venue-dependent proportions reporting bSTIs in the recent year were 2–4 folds higher among men diagnosed with HIV. In multivariate analysis, HIV status was the strongest predictor for bSTIs (OR=5.0; 95% CI 2.8 to 8.7). Compared with meeting partners online, sex (OR 1.6; 95% CI 1.0 to 2.5) and social venues (OR 1.9; 95% CI 1.4 to 2.6) were associated with increased bSTI risk for men not diagnosed with HIV, but the risk when meeting partners by smartphone apps was only of borderline significance (OR 1.5; 95% CI 0.9 to 2.3). For men diagnosed with HIV, bSTI risk increased for sex venues (OR 1.5; 95% CI 1.1 to 2.1), and was lower for non-gay/other venues (OR 0.2; 95% CI 0.1 to 0.5). Conclusions Venues are connected to social-behavioural facets of corresponding sexual encounters, and may be important arenas for differential HIV and STI education, treatment and prevention

Synchronization in a neuronal feedback loop through asymmetric temporal delays

We consider the effect of asymmetric temporal delays in a system of two coupled Hopfield neurons. For couplings of opposite signs, a limit cycle emerges via a supercritical Hopf bifurcation when the sum of the delays reaches a critical value. We show that the angular frequency of the limit cycle is independent of an asymmetry in the delays. However, the delay asymmetry determines the phase difference between the periodic activities of the two components. Specifically, when the connection with negative coupling has a delay much larger than the delay for the positive coupling, the system approaches in-phase synchrony between the two components. Employing variational perturbation theory (VPT), we achieve an approximate analytical evaluation of the phase shift, in good agreement with numerical results.Comment: 5 pages, 4 figure

Are men who have sex with men in Europe protected from hepatitis B?

Hepatitis B vaccination is recommended for men who have sex with men (MSM) in many countries, but information on vaccine coverage is scarce. We studied hepatitis B vaccination programmes and coverage among MSM in Europe to guide prevention. From a large (N = 174 209) pan-European MSM survey (EMIS-2010), we used data on self-reported hepatitis B vaccination, age, education, settlement size and disclosure of the same-sex sexual orientation ('outness'). We excluded participants with a history of hepatitis B. In multilevel (participants, countries) logistic regression models, we calculated adjusted odds ratios (aOR) with 95% confidence intervals (95% CI). We analysed data of 163 987 MSM in 38 European countries: 38.3% were 'out' to all or almost all, 56.4% reported vaccination against hepatitis B and 65.5% lived in countries with free recommended hepatitis B vaccination for MSM. In the final model the odds for being vaccinated increased with outness ('out to all or almost all': aOR 1.76, 95% CI 1.70-1.83 vs. 'out to no one') and with living in countries, where hepatitis B vaccination was recommended and free-of-charge for MSM (aOR 2.21, 95% CI 1.47-3.32 vs. 'no or unclear recommendation'). To increase hepatitis B vaccination coverage among MSM, implementation of MSM-specific recommendations and improvement of the societal climate for MSM is needed

Evalutating the potential of desis to infer plant taxonomical and functional diversities in europwean forests

Abstract. Tackling the accelerated human-induced biodiversity loss requires tools able to map biodiversity and its changes globally. Remote sensing (RS) offers unique capabilities of characterizing Earth surfaces; therefore, it could map plant biodiversity continuously and globally. This approach is supported by the Spectral Variation Hypothesis (SVH), which states that spectra and species (taxonomic and trait) diversities are linked through environmental heterogeneity. In this work, we evaluate the capability of the DESIS hyperspectral imager to capture plant diversity patterns as measured in dedicated plots of the network FunDivEUROPE. We computed functional and taxonomical diversity metrics from field taxonomic, structural, and foliar measurements in vegetation plots sampled in Spain and Romania. In addition, we also computed functional diversity metrics both from the DESIS reflectance factors and from vegetation parameters estimated via inversion of a radiative transfer model. Results showed that only metrics computed from spectral reflectance were able to capture taxonomic variability in the area. However, the lack of sensitivity was related to the insufficient plot size and the lack of spatial match between remote sensing and field data, but also the differences between the information contained in the field traits and remote sensing data, and the potential uncertainties in the remote estimates of vegetation parameters. Thus, while DESIS showed some sensitivity to plant diversity, further efforts are needed to deploy suitable biodiversity evaluation and validation plots and networks that support the development of biodiversity remote sensing products

Prospect inversion for indirect estimation of leaf dry matter content and specific leaf area

Quantification of vegetation properties plays an indispensable role in assessments of ecosystem function with leaf dry mater content (LDMC) and specific leaf area (SLA) being two important vegetation properties. Methods for fast, reliable and accurate measurement of LDMC and SLA are still lacking. In this study, the inversion of the PROSPECT radiative transfer model was used to estimate these two leaf parameters. Inversion of PROSPECT traditionally aims at quantifying its direct input parameters rather than identifying the parameters which can be derived indirectly from the input parameters. The technique has been tested here to indirectly model these parameters for the first time. Biophysical parameters such as leaf area, as well as fresh and dry weights of 137 leaf samples were measured during a field campaign in July 2013 in the mixed mountain forests of the Bavarian Forest National Park, Germany. Reflectance and transmittance of the leaf samples were measured using an ASD field spec III equipped with an integrating sphere. The PROSPECT model was inverted using a look-up table (LUT) approach for the NIR/SWIR region of the spectrum. The retrieved parameters were evaluated using their calculated R2 and normalized root mean square error (nRMSE) values with the field measurements. Among the retrieved variables the lowest nRMSE (0.0899) was observed for LDMC. For both traits higher R2 values (0.83 for LDMC and 0.89 for SLA) were discovered. The results indicate that the leaf traits studied can be quantified as accurately as the direct input parameters of PROSPECT. The strong correlation between the estimated traits and the NIR/SWIR region of the electromagnetic spectrum suggests that these leaf traits could be assessed at canopy and in the landscape by using hyperspectral remote sensing data

Winner-take-all selection in a neural system with delayed feedback

We consider the effects of temporal delay in a neural feedback system with excitation and inhibition. The topology of our model system reflects the anatomy of the avian isthmic circuitry, a feedback structure found in all classes of vertebrates. We show that the system is capable of performing a `winner-take-all' selection rule for certain combinations of excitatory and inhibitory feedback. In particular, we show that when the time delays are sufficiently large a system with local inhibition and global excitation can function as a `winner-take-all' network and exhibit oscillatory dynamics. We demonstrate how the origin of the oscillations can be attributed to the finite delays through a linear stability analysis.Comment: 8 pages, 6 figure

Molecular crowding defines a common origin for the Warburg effect in proliferating cells and the lactate threshold in muscle physiology

Aerobic glycolysis is a seemingly wasteful mode of ATP production that is seen both in rapidly proliferating mammalian cells and highly active contracting muscles, but whether there is a common origin for its presence in these widely different systems is unknown. To study this issue, here we develop a model of human central metabolism that incorporates a solvent capacity constraint of metabolic enzymes and mitochondria, accounting for their occupied volume densities, while assuming glucose and/or fatty acid utilization. The model demonstrates that activation of aerobic glycolysis is favored above a threshold metabolic rate in both rapidly proliferating cells and heavily contracting muscles, because it provides higher ATP yield per volume density than mitochondrial oxidative phosphorylation. In the case of muscle physiology, the model also predicts that before the lactate switch, fatty acid oxidation increases, reaches a maximum, and then decreases to zero with concomitant increase in glucose utilization, in agreement with the empirical evidence. These results are further corroborated by a larger scale model, including biosynthesis of major cell biomass components. The larger scale model also predicts that in proliferating cells the lactate switch is accompanied by activation of glutaminolysis, another distinctive feature of the Warburg effect. In conclusion, intracellular molecular crowding is a fundamental constraint for cell metabolism in both rapidly proliferating- and non-proliferating cells with high metabolic demand. Addition of this constraint to metabolic flux balance models can explain several observations of mammalian cell metabolism under steady state conditions