Modification of Graphene Properties due to Electron-Beam Irradiation

The authors report micro-Raman investigation of changes in the single and bilayer graphene crystal lattice induced by the low and medium energy electron-beam irradiation (5 and 20 keV). It was found that the radiation exposures results in appearance of the strong disorder D band around 1345 1/cm indicating damage to the lattice. The D and G peak evolution with the increasing radiation dose follows the amorphization trajectory, which suggests graphene's transformation to the nanocrystalline, and then to amorphous form. The results have important implications for graphene characterization and device fabrication, which rely on the electron microscopy and focused ion beam processing.Comment: 13 pages and 4 figure

Charm production nearby threshold in pA-interactions at 70 GeV

The results of the SERP-E-184 experiment at the U-70 accelerator (IHEP, Protvino) are presented. Interactions of the 70 GeV proton beam with C, Si and Pb targets were studied to detect decays of charmed $D^0$, $\overline D^0$, $D^+$, $D^-$ mesons and $\Lambda _c^+$ baryon near their production threshold. Measurements of lifetimes and masses are shown a good agreement with PDG data. The inclusive cross sections of charm production and their A-dependencies were obtained. The yields of these particles are compared with the theoretical predictions and the data of other experiments. The measured cross section of the total open charm production ($\sigma _{\mathrm {tot}}(c\overline c)$ = 7.1 $\pm$ 2.3(stat) $\pm$1.4(syst) $\mu$b/nucleon) at the collision c.m. energy $\sqrt {s}$ = 11.8 GeV is well above the QCD model predictions. The contributions of different species of charmed particles to the total cross section of the open charm production in proton-nucleus interactions vary with energy.Comment: 4 pages, 6 pages, 38th International Conference on High Energy Physics 3-10 August 2016, Chicago, US

Practical guidelines for standardising the measurement of resting metabolism by indirect calorimetry: a literature review

Accurate resting metabolic rate readings are essential for dietary planning and body composition monitoring not only for healthy individuals but also for athletes. A number of factors can alter resting metabolic rate during its measurement by indirect calorimetry. The methodology used may affect the results of the study. A clear standardisation of this procedure is needed to obtain the most accurate results.Purpose: To review the literature to determine the optimal subject condition and methodology for the resting metabolism measurement procedure using indirect calorimetry.Materials and methods: A literature search was conducted in PubMed, MEDLINE and Cochrane Library databases. The query included key words and logical phrases: “calorimetry”, “indirect calorimetry”, “resting metabolic rate”, “energy metabolism”, “basal metabolism”, “standards”. Only Englishlanguage studies and human studies were considered. Additional information was identified because of the review and included in the review.Results: the parameters of standardization during the resting metabolism measurement procedure are described: consumption of food, ethanol, caffeine, nicotine; daily activities and physical activity; body position in space and environmental conditions during the measurement; actions of the specialist performing the procedure, etc. The article outlines effective methods for measuring resting metabolism to obtain the most accurate results in both athletes and non-athletes.Conclusion: an attempt has been made to formulate precise methodological rules for standardization and recommendations for measuring resting metabolism by indirect calorimetry

Quantum Brownian motion under rapid periodic forcing

We study the steady state behaviour of a confined quantum Brownian particle subjected to a space-dependent, rapidly oscillating time-periodic force. To leading order in the period of driving, the result of the oscillating force is an effective static potential which has a quantum dissipative contribution, $V_{QD}$, which adds on to the classical result. This is shown using a coherent state representation of bath oscillators. $V_{QD}$ is evaluated exactly in the case of an Ohmic dissipation bath. It is strongest for intermediate values of the damping, where it can have pronounced effects.Comment: 11 Pages and 3 figures, Content change

Direct Observation of Martensitic Phase-Transformation Dynamics in Iron by 4D Single-Pulse Electron Microscopy

The in situ martensitic phase transformation of iron, a complex solid-state transition involving collective atomic displacement and interface movement, is studied in real time by means of four-dimensional (4D) electron microscopy. The iron nanofilm specimen is heated at a maximum rate of ∼10^(11) K/s by a single heating pulse, and the evolution of the phase transformation from body-centered cubic to face-centered cubic crystal structure is followed by means of single-pulse, selected-area diffraction and real-space imaging. Two distinct components are revealed in the evolution of the crystal structure. The first, on the nanosecond time scale, is a direct martensitic transformation, which proceeds in regions heated into the temperature range of stability of the fcc phase, 1185−1667 K. The second, on the microsecond time scale, represents an indirect process for the hottest central zone of laser heating, where the temperature is initially above 1667 K and cooling is the rate-determining step. The mechanism of the direct transformation involves two steps, that of (barrier-crossing) nucleation on the reported nanosecond time scale, followed by a rapid grain growth typically in ∼100 ps for 10 nm crystallites

Polar optical phonons in wurtzite spheroidal quantum dots: Theory and application to ZnO and ZnO/MgZnO nanostructures

Polar optical-phonon modes are derived analytically for spheroidal quantum dots with wurtzite crystal structure. The developed theory is applied to a freestanding spheroidal ZnO quantum dot and to a spheroidal ZnO quantum dot embedded into a MgZnO crystal. The wurtzite (anisotropic) quantum dots are shown to have strongly different polar optical-phonon modes in comparison with zincblende (isotropic) quantum dots. The obtained results allow one to explain and accurately predict phonon peaks in the Raman spectra of wurtzite nanocrystals, nanorods (prolate spheroids), and epitaxial quantum dots (oblate spheroids).Comment: 11 page