Although both obesity and ageing are risk factors for cognitive impairment, there is no evidence in Chile on how obesity levels are associated with cognitive function. Therefore, the aim of the present study was to investigate the association between adiposity levels and cognitive impairment in older Chilean adults. This cross-sectional study includes 1384 participants, over 60 years of age, from the Chilean National Health Survey 2009–2010. Cognitive impairment was evaluated using the Mini-Mental State Examination. BMI and waist circumference (WC) were used as measures of adiposity. Compared with people with a normal BMI, the odds of cognitive impairment were higher in participants who were underweight (OR 4·44; 95 % CI 2·43, 6·45; P < 0·0001), overweight (OR 1·86; 95 % CI 1·06, 2·66; P = 0·031) and obese (OR 2·26; 95 % CI 1·31, 3·21; P = 0·003). The associations were robust after adjustment for confounding variables. Similar results were observed for WC. Low and high levels of adiposity are associated with an increased likelihood of cognitive impairment in older adults in Chile.

We propose a new method for preparing atom probe tomography specimens from nanoparticles using a fusible bismuth–indium–tin alloy as an embedding medium. Iron nanoparticles synthesized by the sodium borohydride reduction method were chosen as a model system. The as-synthesized iron nanoparticles were embedded within the fusible alloy using focused ion beam milling and ion-milled to needle-shaped atom probe specimens under cryogenic conditions. An atom probe analysis revealed boron atoms in a detected iron nanoparticle, indicating that boron from the sodium borohydride reductant was incorporated into the nanoparticle during its synthesis.

Precisely measured neutron star masses and especially radii would provide unique constraints on the properties of cold matter at several times nuclear density. Observations using the Rossi X-ray Timing Explorer suggest that such measurements might be possible using thermonuclear X-ray bursts. Here we discuss the prospects for mass and radius constraints, with a particular focus on potential systematic errors.

Gate current plays an important role in determining the characteristics and limiting performance of GaN-based field effect transistors. In GaN-based HFETs, the gate current limits the gate voltage swing and, hence, the maximum device current. Since the electron transport across the wide band gap barrier layer involves trapping, under certain bias conditions, the gate current leads to the threshold voltage shifts and causes reliability problems. Under reverse bias, the gate leakage in GaN-based HFET dominates the minimum (pinch-off) drain current. Insulating gate HFETs (i.e. Metal Oxide Heterostructure Field Effect Transistors – MOSHFETs) have the gate leakage currents 4 – 6 orders of magnitude lower than HFETs, even at elevated temperatures up to 300 °C. In this paper, we report on the gate current characteristics in these devices at room and elevated temperatures. We propose a semi-empirical model for the current-voltage characteristics in these devices, which is in good agreement with experimental data. Our data also show that both tunneling and temperature activation are important factors in MOSHFETs. These results are important for possible applications of GaN MOSHFETs in high power amplifiers and power switches as well as in non-volatile memory devices and integrated circuits that will operate in a much wider temperature range than conventional silicon and GaAs devices.

Recent experiments on single crystals of the compounds CeRh1−xCoxIn5 and PrOs4Sb12 are briefly reviewed. The temperature-composition (T-x) phase diagram of the heavy fermion pseudoternary system CeRh1−xCoxIn5, delineating the regions in which superconductivity, antiferromagnetism, and the coexistence of these two phenomena occur, has been established. Entropy vs x isotherms and residual resistivity vs x plots exhibit peaks near the critical concentration xcr ≈ 0.8 at which the Néel temperature appears to vanish (quantum critical point). The filled skutterudite compound PrOs4Sb12 exhibits unconventional superconductivity below Tc = 1.85 K that involves heavy fermion quasiparticles with an effective mass m* ≈ 50 me, where me is the mass of the free electron. The unconventional superconducting state appears to consist of several distinct superconducting phases and to break time reversal symmetry. A high field ordered phase occurs below ∼ 1 K and between ∼ 4.5 T and ∼ 15 T that appears to be associated with quadrupolar order. The heavy fermion state and superconductivity in PrOs4Sb12 may originate from the interaction between Pr3+ electric quadrupole moments and the charges of the conduction electrons. When Ru is substituted for Os in PrOs4Sb12, a minimum in Tc occurs at Pr(Os0.4Ru0.6)4Sb12, suggesting a competition between two types of superconductivity.

Laser-produced electron–positron pair production has been under discussion in the literature since 1969. Large numbers of positrons have been generated by lasers for a few years in studies which are also related to the studies of the physics of the fast ignitor laser fusion concept. For electron–positron pair production in vacuum due to vacuum polarization as predicted by Heisenberg (1934) with electrostatic fields, high-frequency laser fields with intensities around 1028 W/cm2 are necessary and may be available within a number of years. A similar electron acceleration by gravitation near black holes denoted as Hawking–Unruh radiation was discussed in 1985 by McDonald. The conditions are considered in view of the earlier work on pair production, change of statistics for electrons in relativistic black body radiation, and an Einstein recoil mechanism with a consequence of a physical foundation of the fine structure constant.