Environmental exposure as an independent risk factor of chronic bronchitis in northwest Russia

Peer reviewe

Electric Field-Tuned Topological Phase Transition in Ultra-Thin Na3Bi - Towards a Topological Transistor

The electric field induced quantum phase transition from topological to conventional insulator has been proposed as the basis of a topological field effect transistor [1-4]. In this scheme an electric field can switch 'on' the ballistic flow of charge and spin along dissipationless edges of the two-dimensional (2D) quantum spin Hall insulator [5-9], and when 'off' is a conventional insulator with no conductive channels. Such as topological transistor is promising for low-energy logic circuits [4], which would necessitate electric field-switched materials with conventional and topological bandgaps much greater than room temperature, significantly greater than proposed to date [6-8]. Topological Dirac semimetals(TDS) are promising systems in which to look for topological field-effect switching, as they lie at the boundary between conventional and topological phases [3,10-16]. Here we use scanning probe microscopy/spectroscopy (STM/STS) and angle-resolved photoelectron spectroscopy (ARPES) to show that mono- and bilayer films of TDS Na3Bi [3,17] are 2D topological insulators with bulk bandgaps >400 meV in the absence of electric field. Upon application of electric field by doping with potassium or by close approach of the STM tip, the bandgap can be completely closed then re-opened with conventional gap greater than 100 meV. The large bandgaps in both the conventional and quantum spin Hall phases, much greater than the thermal energy kT = 25 meV at room temperature, suggest that ultrathin Na3Bi is suitable for room temperature topological transistor operation

Obesity surgery and risk of colorectal and other obesity-related cancers: An English population-based cohort study

Background: The association between obesity surgery (OS) and cancer risk remains unclear. We investigated this association across the English National Health Service. A population-based Swedish study has previously suggested that OS may increase the risk of developing colorectal cancer (CRC). Methods: A retrospective observational study of individuals who underwent OS (surgery cohort) or diagnosed with obesity, but had no OS (no-surgery cohort) (1997–2013) were identified using Hospital Episode Statistics. Subsequent diagnosis of CRC, breast, endometrial, kidney and lung cancer, as well as time ‘at risk’, were determined by linkage to National Cancer Registration & Analysis Service and Office of National Statistics data, respectively. Standardised incidence ratios (SIR) in relation to OS were calculated. Results: 1 002 607 obese patients were identified, of whom 3.9% (n = 39 747) underwent OS. In the no-surgery obese population, 3 237 developed CRC (SIR 1.12 [95% CI 1.08–1.16]). In those who underwent OS, 43 developed CRC (SIR 1.26 [95% CI 0.92–1.71]). The OS cohort demonstrated decreased breast cancer risk (SIR 0.76 [95% CI 0.62–0.92]), unlike the no surgery cohort (SIR 1.08 [95% CI 1.04–1.11]). Increased risk of endometrial and kidney cancer was observed in surgery and no-surgery cohorts. Conclusions: CRC risk is increased in individuals diagnosed as obese. Prior obesity surgery was not associated with an increased CRC risk. However, the OS population was small, with limited follow-up. Risk of breast cancer after OS is reduced compared with the obese no-surgery population, while the risk of endometrial and kidney cancers remained elevated after OS

Characterization of collective ground states in single-layer NbSe2

Layered transition metal dichalcogenides (TMDs) are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge density wave (CDW) order and superconductivity. In bulk NbSe2 a CDW sets in at TCDW = 33 K and superconductivity sets in at Tc = 7.2 K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single 2D layer of NbSe2 by means of low temperature scanning tunneling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and electrical transport measurements. We demonstrate that 3x3 CDW order in NbSe2 remains intact in 2D. Superconductivity also still remains in the 2D limit, but its onset temperature is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of {\Delta} = 4 meV at the Fermi energy, which is accessible via STS due to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing new insight into CDW formation and superconductivity in this model strongly-correlated system.Comment: Nature Physics (2015), DOI:10.1038/nphys352

Surface modification of battery electrodes via electroless deposition with improved performance for Na-ion batteries

Sodium-ion batteries (SIBs) are emerging as potential stationary energy storage devices due to the abundance and low cost of sodium. A simple and energy efficient strategy to develop electrodes for SIBs with a high charge/discharge rate is highly desirable. Here we demonstrate that by surface modification of Ge, using electroless deposition in SbCl3/ionic liquids, the stability and performance of the anode can be improved. This is due to the formation of GexSb1−x at the surface leading to better diffusion of Na, and the formation of a stable twin organic and inorganic SEI which protects the electrode. By judicious control of the surface modification, an improvement in the capacity to between 50% and 300% has been achieved at high current densities (0.83–8.4 A g−1) in an ionic liquid electrolyte NaFSI-[Py1,4]FSI. The results clearly demonstrate that an electroless deposition based surface modification strategy in ionic liquids offers exciting opportunities in developing superior energy storage devices

Characterisation of the solid electrolyte interface during lithiation/delithiation of germanium in an ionic liquid

In this paper, we present investigations of the interface of electrodeposited Ge during lithiation/delithiation in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide containing 0.5 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI/[Py1,4]TFSI). Cyclic voltammetry (CV) and infrared spectroscopy were used to study the electrochemistry and the changes in the electrolyte during the Li intercalation/deintercalation processes. From infrared spectroscopic analysis, it was found that the TFSI− anion decomposes during the lithiation process, resulting in the formation of a solid–liquid interface (SEI) layer. X-ray photoelectron spectroscopy was used to analyse the composition of the SEI layer and the changes in the electrodeposited germanium. Furthermore, atomic force microscopy (AFM) was used to evaluate the changes in the SEI layer which showed that the SEI layer was inhomogenous and changed during the lithiation/delithiation processes

Understanding pH-Dependent Selectivity of Alamethicin K18 Channels by Computer Simulation

Alamethicin K18 is a covalently linked alamethicin dimer in which the glutamine residue at position 18 in each helix has been replaced by a lysine residue. As described in previous work, channels formed by this peptide show pH-dependent selectivity. The maximum anion selectivity of the putative octameric conducting state is obtained at pH 7 or lower. Inasmuch as no change in selectivity is seen between pH 7 and pH 3, and because protons are expected to be in equilibrium with the open state of the channel during a selectivity measurement, the channel is believed to be fully charged (i.e., all eight lysines protonated) at pH 7. In an effort to understand how such a highly charged channel structure is stable in membranes and why it is not more selective for anions, we have performed a number of computer simulations of the system. Molecular dynamics simulations of 10 ns each of the octameric bundle in a lipid bilayer environment are presented, with either zero, four, or eight lysines charged in the absence of salt, and with eight lysines charged in the presence of 0.5 M and 1 M KCl. When no salt is present and all lysines are charged, on average 1.9 Cl(−) ions are inside the channel and the channel significantly deforms. With 0.5 M KCl present, 2.9 Cl(−) ions are inside the channel. With 1 M KCl present, four Cl(−) ions are present and the channel maintains a regular structure. Poisson-Boltzmann calculations on models of the octameric channel also predict an average of 2–4 Cl(−) ions near the lysine residues as a function of ionic strength. These counterions lower the apparent charge of the channel, which may underlie the decrease in selectivity observed experimentally with increasing salt concentrations. We suggest that to increase the selectivity of Alm K18 channels, positive charges could be engineered in a narrower part of the channel

Determining molecular structures and conformations directly from electron diffraction using a genetic algorithm

A global optimization strategy, based upon application of a genetic algorithm (GA), is demonstrated as an approach for determining the structures of molecules possessing significant conformational flexibility directly from gas-phase electron diffraction data. In contrast to the common approach to molecular structure determination, based on trial-and-error assessment of structures available from quantum chemical calculations, the GA approach described here does not require expensive quantum mechanical calculations or manual searching of the potential energy surface of the sample molecule, relying instead upon simple comparison between the experimental and calculated diffraction pattern derived from a proposed trial molecular structure. Structures as complex as all-trans retinal and p-coumaric acid, both important chromophores in photosensing processes, may be determined by, this approach. In the examples presented here, we find that the GA approach con determine the correct conformation of a flexible molecule described by I I independent torsion angles. We also demonstrate applications to samples comprising a mixture of two distinct molecular conformations. With these results we conclude that applications of this approach ore very promising in elucidating the structures of large molecules directly from electron diffraction data