We have performed a comparative study of resonance Raman scattering in transition-metal dichalcogenides 2H-MX 2 semiconductors (M ¼ Mo, W; X ¼ S, Se) and single-layer MoS 2. Raman spectra were collected using excitation wavelengths 633 nm (1.96 eV), 594 nm (2.09 eV), 532 nm (2.33 eV), 514 nm (2.41 eV), and 488 nm (2.54 eV). In bulk-MoS 2 and WS 2 , the resonant energies appear to coincide with their exciton excitations. The resonance can be fine tuned by varying sample temperatures, which confirms its excitonic origin in both MoS 2 and WS 2. Temperature dependence of Raman intensities is analyzed in the context of resonance Raman theory, which agrees well with the existing absorption data. While in WSe 2 , the resonance has been observed in a wider range of excitations from 633 to 514 nm, which cannot be explained with its excitonic energies of 1.6 and 2.0 eV. It is considered that additional excitonic bands induced by band splitting are involved in the inter-band transitions and substantially extend the resonance energy range. The Raman resonance energy range remains unchanged in single-layer MoS 2 compared with that in the bulk sample. However, most phonon modes in single-layer MoS 2 are significantly broadened or strongly suppressed under resonance conditions. This change could be related to the modification of acoustic modes by the substrate. V

The causal relationship between persistent high-risk human papillomavirus infection and cervical cancer is widely accepted. HR-HPV DNA testing, alone or in combination with Pap smear testing, may have a role in primary screening. The screening results (VIA, VILI, Pap, and HR-HPV DNA) of 9,057 women in rural China were analyzed to determine the screening performance for the detection of CIN31. All screening strategies had comparable AUCs (0.9). Cotesting strategies had the overall highest sensitivity for CIN31 (99.4%), followed by HR-HPV DNA testing alone (96.3%), Pap alone (80.2%), and reflex testing (75.4%). Reflex testing had the highest specificity (96.7%), followed by Pap alone (93.3%), HR-HPV DNA testing alone (85.5%), and both cotesting strategies (LSIL: 84.8%, HSIL: 84.8%). Of the single-test strategies, HR-HPV DNA testing had a higher sensitivity (96.3% vs. 80.2%) compared with Pap testing. The specificity of the Pap test was higher (93.3% vs. 85.5%) and it had a lower percent referred for colposcopy (7.8% vs. 15.8%) than HR-HPV DNA testing. HR-HPV DNA testing with a 10.0 cutoff point (relative light units/cutoff ratio) had a sensitivity (85.2%) and specificity (90.6%) estimate comparable to Pap testing. A single-test primary screening strategy with adequate performance would permit less frequent screening and be most appropriate. Of the primary screening strategies investigated in this setting in China, the performance of HR-HPV DNA testing with an increased cutoff-point might best meet these criteria.Cervical cancer is one of the most common cancers among women 1 with much of the disease burden occurring in lowresource countries. In 2002, $490,000 new cases of cervical cancer were diagnosed worldwide with 409,000 (83%) of cases and 86% of deaths in low-resource countries.2 The relatively high rates of cervical cancer-related morbidity and mortality in low-resource countries are largely due to lack of infrastructure and resources necessary for routine Papanicolaou (Pap) screening, histological diagnosis, and ablative or excisional treatment procedures. 3Once in a lifetime, Pap test lacks sensitivity for the detection of precancerous lesions in reproductive-aged women

By combining temperature-dependent x-ray diffraction (XRD) with temperature-dependent Raman scattering, we have characterized the structural transitions and lattice dynamics of the hybrid organic–inorganic perovskite CH3NH3PbI3. The XRD measurements cover distinct phases between 15 K and 370 K and demonstrate a general positive thermal expansion. Clear anomalies are found around the transition temperatures. The temperature evolution of the lattice constants reveals that the transition at 160 K/330 K is of the first-/second-order type. Raman measurements uncover three strong low-frequency modes, which can be ascribed to the vibration of the Pb/I atoms. The temperature evolution of the modes clearly catches these transitions at 160 K and 330 K, and confirms the transition types, which are exactly consistent with the XRD results. The present study may set an experimental basis to understand the high conversion efficiency in methylammonium lead iodide.

The shock‐compression responses of PTFE (polytetrafluoroethylene)/Al granular composites subjected to planar shock waves of various pressures are investigated. A 57‐mm diameter single‐stage gas‐gun and 50‐mm diameter plane‐wave lenses are employed to perform planar shock wave experiments. High frequency manganin piezoresistance stress gauges are used to monitor the stress (regarded as pressure in consideration of the high pressure state) at four Lagrangian positions of the PTFE/Al granular composites specimens. Planar shock wave experiments show characteristics of densification at measured input pressure of 0.5 GPa to 1.27 GPa using single‐stage gas‐gun and shock‐induced reaction (SIR) indicated by growth of shock pressure and specific volume expansion at measured input pressure of 7.29 GPa to 12.25 GPa using plane‐wave lenses. The pressure and relative volume states behind the shock wave front are calculated from the experimental recorded pressure profiles using Lagrangian analysis method, which are used to determine the reaction ratios under different shock pressures by comparing with partial reacted Hugoniot calculations. It was shown that the reaction ratios obtained in this research have good agreement with the thermochemical modeling calculations. The corresponding results indicate that the shock‐induced reactions of PTFE/Al granular composites occur in the shock wave rising period and the reaction ratios are intimately related to the shock wave pressure.

The recently discovered layered BiS 2 -based superconductors have attracted a great deal of interest due to their structural similarity to cuprate and iron-pnictide

In this study, the digital image correlation method(with Newton-Raphson iteration method) is used to measure the in-plane deformation of poly-crystal aluminum. When the specimen is exerted a tensile load, the strain distribution of the specimen surface will be inhomogeneous. The micro-deformation of the poly-crystal aluminum is studied under a SEM(scanning electron microscope), a series of images of the micro crystal are captured during the loading process. By using digital image correlation to analyze the images, the displacement and strain of a micro-crystal are obtained, which provide important data for further analysis of the inhomogeneous properties of the poly-crystal aluminum.

In this paper, we studied stacked mL + nL graphene layers using Raman scattering spectroscopy. Our results indicate that the 2D band from stacked graphene can be considered as a superposition of those from the constituent nL and mL graphene layers, and a blueshift in the 2D band is observed when n or m = 1. The blueshift increases with the number of stacked layers and can be well understood by the reduction of Fermi velocity in the single layer graphene, as studied in the 1L + 1L (or twisted bilayer) case. As the number of stacked layers changes from 1 to 5, the Fermi velocity in the single layer graphene reduces to about 85% of its initial value. This study shows a convenient way to realize the modification of the Fermi velocity in free-stacking graphene and is of significance to the applications of graphene-based heterostructures.

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