In this paper, detailed investigations of the electronic and optical properties of a Janus SnSSe monolayer under a biaxial strain and electric field using ab initio methods are presented.

The heat resistance of Campylobacter jejuni strains AR6 and L51 and the heat resistance of Campylobacter coli strains DR4 and L6 were measured over the temperature range from 50 to 60°C by two methods. Isothermal measurements yielded D 55 values in the range from 4.6 to 6.6 min and z values in the range from 5.5 to 6.3°C. Dynamic measurements using differential scanning calorimetry (DSC) during heating at a rate of 10°C/min yielded D 55 values of 2.5 min and 3.4 min and z values of 6.3°C and 6.5°C for AR6 and DR4, respectively. Both dynamic and isothermal methods yielded mean D 55 values that were substantially greater than those reported previously (0.75 to 0.95 min). DSC analysis of each strain during heating at a rate of 10°C/min yielded a complex series of overlapping endothermic peaks, which were assigned to cell wall lipids, ribosomes, and DNA. Measurement of the decline in the numbers of CFU in calorimetric samples as they were heated showed that the maximum rate of cell death occurred at 56 to 57°C, which is close to the value predicted mathematically from the isothermal measurements of D and z (61°C). Both estimates were very close to the peak m 1 values, 60 to 62°C, which were tentatively identified with unfolding of the 30S ribosome subunit, showing that cell death in C. jejuni and C. coli coincided with unfolding of the most thermally labile regions of the ribosome. Other measurements indicated that several essential proteins, including the ␣ and ␤ subunits of RNA polymerase, might also unfold at the same time and contribute to cell death.Thermophilic Campylobacter species, particularly Campylobacter jejuni and to a lesser extent Campylobacter coli, are the most important cause of bacterial gastroenteritis in the developed world (5, 11). This is surprising because campylobacters are considered to be poor survivors in the environment. In particular, they are considered to be more heat and radiation sensitive than most bacteria, including other gram-negative food-borne pathogens, such as Salmonella spp. and Escherichia coli (8). They are also considered to be sensitive to drying and are unable to multiply at temperatures below 31°C (6, 22). However, there have been few detailed studies that have determined D and z values. In this study our goals were to examine the heat resistance of several strains of C. jejuni and C. coli over the temperature range from 50 to 60°C and to investigate the mechanism of heat damage by use of differential scanning calorimetry (DSC). MATERIALS AND METHODSStrains. Two strains of C. jejuni and two strains of C. coli were examined. C. jejuni AR6, an isolate from poultry feces, was supplied by D. Newell (Food and Environmental Safety, Veterinary Laboratories Agency, Weybridge, United Kingdom). C. jejuni L51 and C. coli L6 were isolated from broiler chickens on a slaughter line. C. coli DR4, which was isolated from retail chicken, was obtained from T. Humphrey (University of Bristol, Bristol, United Kingdom) and was found previously to be particularly heat resistant when it was...

Two-dimensional graphene-based van der Waals heterostructures have received considerable interest because of their intriguing characteristics compared with the constituent single-layer two-dimensional materials. Here, we investigate the interfacial characteristics, Schottky contact, and optical performance of graphene/Ga 2 SSe van der Waals (vdW) heterostructure using first-principles calculations. The effects of stacking patterns, electric gating, and interlayer coupling on the interfacial properties of graphene/Ga 2 SSe heterostructures are also examined. Our results demonstrate that the Dirac cone of graphene is well preserved at the point in all stacking patterns due to the weak vdW interactions, which keep the heterostructures feasible such that they can be obtained in further experiments. Moreover, depending on the stacking patterns, a small band gap of about 13-17 meV opens in graphene and has a high carrier mobility, indicating that the graphene/Ga 2 SSe heterostructures are potential candidates for future high-speed nanoelectronic applications. In the ground state, the graphene/Ga 2 SSe heterostructures form an n-type Schottky contact. The transformation from an n-type to a p-type Schottky contact or to an Ohmic contact can be forced by electric gating or by varying the interlayer coupling. Our findings could provide physical guidance for designing controllable Schottky nanodevices with high electronic and optical performances.

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