Phase separation effects and the nematic-isotropic transition in polymer and low molecular weight liquid crystals doped with nanoparticles

Properties of the nematic–isotropic phase transition in polymer and low molecular weight liquid crystals doped with nanoparticles have been studied both experimentally and theoretically in terms of molecular mean-field theory. The variation of the transition temperature and the transition heat with the increasing volume fraction of CdSe quantum dot nanoparticles in copolymer and low molecular weight nematics has been investigated experimentally and the data are interpreted using the results of the molecular theory which accounts for a possibility of phase separation when the system undergoes the nematic–isotropic transition. The theory predicts that the nematic and isotropic phases with different concentrations of nanoparticles may coexist over a broad temperature range, but only if the nanoparticle volume fraction exceeds a certain threshold value which depends on the material parameters. Such unusual phase separation effects are determined by the strong interaction between nanoparticles and mesogenic groups and between nanoparticles themselves

Non-invasive assessment of liver steatosis and fibrosis in HIV/HCV- and HCV- infected patients

Background. Conflicting data have been reported on the prevalence of liver steatosis, its risk factors and its relationship with fibrosis in patients with human immunodeficiency virus (HIV)/hepatitis C virus (HCV) co-infection or with HCV mono-infection. Aim. The study aims were to assess steatosis prevalence and its risk factors in both HCV groups. We also evaluated whether steatosis was linked with advanced fibrosis. Sixty-eight HIV/HCV co-infected and 69 HCV mono-infected patients were consecutively enrolled. They underwent liver ultrasonography and transient elastography. Bright liver echo-pattern was used to diagnose steatosis; advanced fibrosis was defined as liver stiffness ≥ 9.5 kPa and FIB-4 values ≥ 3.25. The optimal stiffness cut-off according to FIB-4 ≥ 3.25 was evaluated by ROC analysis. Results. No significant difference was found in steatosis-prevalence between mono- and co-infected patients (46.3 vs. 51.4%). Steatosis was associated with triglycerides and impaired fasting glucose/diabetes in HCV mono-infected, with lipodystrophy, metabolic syndrome, total-cholesterol and triglycerides in co-infected patients. Stiffness ≥ 9.5 was significantly more frequent in co-infection (P < 0.003). Advanced fibrosis wasn't significantly associated with steatosis. The area under the ROC curve was 0.85 (95% CI 0.79-0.9). On multivariate analysis steatosis was associated with triglycerides in both HCV mono- and co-infected groups (P < 0.02; P < 0.03). Conclusion. Although steatosis was common in both HCV mono- and co-infected patients, it was not linked with advanced fibrosis. Triglycerides were independent predictors of steatosis in either of the HCV-groups. Dietary interventions and lifestyle changes should be proposed to prevent metabolic risk factors

Osteoporosis risk factors in HIV positive women with osteoporosis: A retrospective analysis

Multifactorial risk factors such as HIV/HCV co-infection and antiretroviral therapy (ARV) have been associated with osteoporosis in HIV+ women. We retrospectively analysed which known risk factors were associated with the diagnosis of osteoporosis, according to the WHO definition, in HIV positive women who were followed-up at the AIDS Centre of the University of Palermo, Italy between January 2011 and December 2014. Twenty-one HIV+ women with osteoporosis (13 HIV+ mono-infected and 8 HIV/HCV co-infected females) who underwent dual-energy X-ray absorptiometry (DXA) and liver stiffness assessment were included in the study. No significant differences between the HIV and HIV/HCV group were found regarding liver stiffness and lumbar/femoral osteoporosis scores. In a univariate analysis, we observed a positive linear correlation between LBD score (Lumbar Bone Density) with pre-fractures (p-value = 0.0082), smoke (p-value = 0.0008), alcohol (p-value &lt; 0.0001) and ARV exposure score (p-value = 0.0039), while there were no significant negative linear correlations. In multivariate analysis, pre-fractures, smoke and alcohol were positive predictors of LBD score, while previous antiretroviral therapy (ARV) (years) score was a negative predictor compared to others. Univariate analysis showed a positive linear correlation between FDB (Femoral Bone Density) with smoke (p-value = 0.0303) and alcohol (p-value = 0.0050), while there were no significant negative linear correlations. In multivariate analysis, alcohol was a positive predictor of FDB score compared to others, while ARV score was a negative predictor compared to others. This preliminary study suggests that other factors besides ARV score and liver fibrosis may affect the skeletal system in osteoporotic women with HIV infection. Some of these factors, such as alcohol and smoking, are modifiable. Additional research into impact on osteoporosis in HIV women with osteoporosis is required

Prediction of Anisotropic Single-Dirac-Cones in Bi1−x{}_{1-x}Sbx{}_{x} Thin Films

The electronic band structures of Bi${}_{1-x}$Sb${}_{x}$ thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi${}_{1-x}$Sb${}_{x}$ thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band-gap, which can be used in a general two-dimensional system that has a non-parabolic dispersion relation as in a Bi${}_{1-x}$Sb${}_{x}$ thin film system

The electromagnetic calorimeter of the AMS-02 experiment

The electromagnetic calorimeter (ECAL) of the AMS-02 experiment is a 3-dimensional sampling calorimeter, made of lead and scintillating fibers. The detector allows for a high granularity, with 18 samplings in the longitudinal direction, and 72 sampling in the lateral direction. The ECAL primary goal is to measure the energy of cosmic rays up to few TeV, however, thanks to the fine grained structure, it can also provide the separation of positrons from protons, in the GeV to TeV region. A direct measurement of high energy photons with accurate energy and direction determination can also be provided.Comment: Proceedings of SF2A conference 201

Mixed RG Flows and Hydrodynamics at Finite Holographic Screen

We consider quark-gluon plasma with chemical potential and study renormalization group flows of transport coefficients in the framework of gauge/gravity duality. We first study them using the flow equations and compare the results with hydrodynamic results by calculating the Green functions on the arbitrary slice. Two results match exactly. Transport coefficients at arbitrary scale is ontained by calculating hydrodynamics Green functions. When either momentum or charge vanishes, transport coefficients decouple from each other.Comment: 22 pages, 6 figure

Field-induced polarisation of Dirac valleys in bismuth

Electrons are offered a valley degree of freedom in presence of particular lattice structures. Manipulating valley degeneracy is the subject matter of an emerging field of investigation, mostly focused on charge transport in graphene. In bulk bismuth, electrons are known to present a threefold valley degeneracy and a Dirac dispersion in each valley. Here we show that because of their huge in-plane mass anisotropy, a flow of Dirac electrons along the trigonal axis is extremely sensitive to the orientation of in-plane magnetic field. Thus, a rotatable magnetic field can be used as a valley valve to tune the contribution of each valley to the total conductivity. According to our measurements, charge conductivity by carriers of a single valley can exceed four-fifth of the total conductivity in a wide range of temperature and magnetic field. At high temperature and low magnetic field, the three valleys are interchangeable and the three-fold symmetry of the underlying lattice is respected. As the temperature lowers and/or the magnetic field increases, this symmetry is spontaneously lost. The latter may be an experimental manifestation of the recently proposed valley-nematic Fermi liquid state.Comment: 14 pages + 5 pages of supplementary information; a slightly modified version will appear as an article in Nature physic

Holographic and Wilsonian Renormalization Groups

We develop parallels between the holographic renormalization group in the bulk and the Wilsonian renormalization group in the dual field theory. Our philosophy differs from most previous work on the holographic RG; the most notable feature is the key role of multi-trace operators. We work out the forms of various single- and double-trace flows. The key question, `what cutoff on the field theory corresponds to a radial cutoff in the bulk?' is left unanswered, but by sharpening the analogy between the two sides we identify possible directions.Comment: 31 pages, 3 figures. v2: Minor clarifications. Added reference

Early warning signals of simulated Amazon rainforest dieback

Copyright © The Author(s) 2013. This article is published with open access at Springerlink.comWe test proposed generic tipping point early warning signals in a complex climate model (HadCM3) which simulates future dieback of the Amazon rainforest. The equation governing tree cover in the model suggests that zero and non-zero stable states of tree cover co-exist, and a transcritical bifurcation is approached as productivity declines. Forest dieback is a non-linear change in the non-zero tree cover state, as productivity declines, which should exhibit critical slowing down. We use an ensemble of versions of HadCM3 to test for the corresponding early warning signals. However, on approaching simulated Amazon dieback, expected early warning signals of critical slowing down are not seen in tree cover, vegetation carbon or net primary productivity. The lack of a convincing trend in autocorrelation appears to be a result of the system being forced rapidly and non-linearly. There is a robust rise in variance with time, but this can be explained by increases in inter-annual temperature and precipitation variability that force the forest. This failure of generic early warning indicators led us to seek more system-specific, observable indicators of changing forest stability in the model. The sensitivity of net ecosystem productivity to temperature anomalies (a negative correlation) generally increases as dieback approaches, which is attributable to a non-linear sensitivity of ecosystem respiration to temperature. As a result, the sensitivity of atmospheric CO2 anomalies to temperature anomalies (a positive correlation) increases as dieback approaches. This stability indicator has the benefit of being readily observable in the real world.NERCJoint DECC/Defra Met Office Hadley Centre Climate ProgrammeUniversity of Exete