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The texture of polycrystalline material is the preferred orientation distribution of its crystallites. As an intrinsic feature of metals, alloys, ceramics and polymers, texture strongly affects many properties of polycrystalline materials. It will make the material exhibit significant anisotropy in properties, consequently affecting its service performance. Therefore, texture is regarded as one of the essential parameters for describing a full microstructural characterization of polycrystalline materials. Texture determination is usually based on the pole figure measurements by X-ray, synchrotron radiation, electron back-scatter diffraction and neutron diffraction. Among these techniques, neutron diffraction offers many advantages in texture characterization due to the low absorption coefficient of neutrons. For example, it enables the use of sample environment devices to investigate texture evolution during in-situ high temperature or loading processes of materials. The first neutron texture diffractometer in China has been built at the China Advanced Research Reactor (CARR), due to strong demand for texture measurement with neutrons from the domestic user community. This instrument is mainly applied to study texture in commonly used industrial materials and engineering components. As the study of texture evolution during in-situ loading processes is extremely important for a deeper understanding of the deformation modes and performance evolution mechanisms of materials under various deformation processes and service environment. A specialized in-situ loading device was designed and developed based on the neutron texture diffractometer of CARR, capable of applying a maximum loading force of 10 kN, with a continuously adjustable loading rate ranging from 0.01 to 3 mm/min. In order to realize real-time measurement of the microstructure and bulk texture evolution in polycrystalline materials during in-situ tensile and compression processes, this loading device can be rotated around neutron texture diffractometer Euler cradle χ angle from 0° to 90° and along the tensile axis rotated from 0° to 360°. The texture evolution of hot-extruded Mg-1.2Al-0.3Ca-0.47Mn (MMK1) alloy during in-situ tensile process was studied using this device, and it was found that the intensity of the (0002) basal texture continuously increased with increasing of tensile displacement, indicating that the device’s capability to measure texture evolution of polycrystalline materials during in-situ loading processes. The design and development of this in-situ loading device at the CARR neutron texture diffractometer provide crucial technical support for investigating the relationship between microstructure and mechanical properties of polycrystalline materials, especially the laws and mechanisms of material structure evolution under external load condition.

Enterococcus faecalis is the main pathogen causing refractory apical periodontitis (RAP). This bacterium can tolerate harsh environments and trigger periapical immune inflammatory responses that result in persistent infection inside and outside the root canal. Adhesion to the dentin wall of root canals and the subsequent formation of biofilms significantly enhances the drug resistance and anti-erosion ability of Enterococcus faecalis, which is the key factor mediating its pathogenesis. The adhesion of Enterococcus faecalis to dentin involves non-specific adhesion and specific adhesion, and the latter is mediated by adhesion-related virulence factors, mainly including the adhesin of collagen from enterococci (Ace), extracellular surface protein (Esp), gelatinase (GelE), serine protease (SprE), endocarditis and biofilm associated pilus (Ebp) and aggregation substance (AS), which is regulated by multiple two-component systems. The two-component system Fsr can promote the expression of gelE and sprE when the cell population density increases. GelE can further reduce Ace, while the two-component system GrvRS directly downregulates ace expression in response to the serum environment. The two-component systems CroRS and WalRK may also promote and inhibit the expression of various virulence factors, including ace and gelE, thus affecting the adhesion of Enterococcus faecalis. In addition, the mechanochemical preparation and the internal environment of the root canal can also influence the adhesion of Enterococcus faecalis to dentin. Avoiding the introduction of Enterococcus faecalis and using adhesion-interfering medications during root canal treatment can effectively prevent the adhesion of Enterococcus faecalis, and a variety of activated irrigation protocols can also be effective at increasing the clearance of Enterococcus faecalis from the root canal. The design of rational drugs targeting key factors involved in and regulators of the adhesion of Enterococcus faecalis to dentin is expected to provide new ideas and strategies for root canal infection control. The present paper reviews the adhesion of Enterococcus faecalis to dentin and its influencing factors.

Residual stress is a key factor that directly affects fatigue, stress corrosion, fretting wear and other performance of engineering materials and components. However, it is difficult to accurately obtain the distribution of the deep residual stress field of the components using theoretical analysis and traditional non-destructive testing methods, which greatly hinders the development of advanced components. Due to the high penetration ability of thermal neutrons, neutron diffraction is an excellent engineering tool for providing mapping of residual stresses nondestructively in bulk components. Therefore, neutron diffraction was the most suitable non-destructive technique to characterize the deep residual stresses distribution. Therefore, National Important Project on Scientific Instrument and Equipment “the Neutron Diffractometer for Residual Stress and Defect in Materials and Components” was funded to built Engineering and Scientific Stress Diffractometer at China Advanced Research Reactor (CARR), which will serve the development of national important equipments, provide testing technique for manufacturing process of large-scale component and accumulate technical data for new material design. In order to fully play the role of Engineering and Scientific Stress Diffractometer in residual stress characterization of the engineering components, the mostly used crystal planes and the required wavelength for diffraction angle of about 90° of steel, nickel, copper, aluminum and titanium were analyzed. Thus, the optimal wavelength of the diffractometer was chosen to be around 0.164 nm, which satisfies the residual stress measurement for most commonly used metal materials. With this wavelength, the error of Fe(211) diffraction peak position was used as figure of Merit for the optics optimization. Optimized optics was obtained by tuning the horizontal and vertical focusing parameters. The neutron flux at the sample position that measured at the optimized optics with wavelength of 0.164 nm is a key parameter for the intensity performance of diffractometer. The activation method is the most commonly used technique to measure the distribution of neutron flux, which has the advantages of flexibility, adaptability, wide sensitivity and small disturbance to neutron field. In this work, the neutron flux at the sample is 3.0×107 cm−2·s−1 (±4.5%) at full reactor power of 60 MW. The resolution at the diffraction angle of about 90° is 0.42% by analyzing Fe(211) diffraction peak. The position resolution of the area detector was tested using a cadmium plate with three slit with known size. The horizontal position resolution is (1.44±0.03) mm. In this work, the optical optimization and performance calibration of Engineering and Scientific Stress Diffractometer at CARR were completed, which provides an experimental foundation for the instrument operation.

BACKGROUND: Laboratory studies have indicated that a cholesterol metabolite and selective estrogen receptor modulator, 27-hydroxycholesterol (27HC), may be important in breast cancer etiology and explain associations between obesity and postmenopausal breast cancer risk. Epidemiologic evidence for 27HC in breast cancer risk is limited, particularly in multiethnic populations. METHODS: In a nested case-control study of 1470 breast cancer cases and 1470 matched controls within the Multiethnic Cohort Study, we examined associations of pre-diagnostic circulating 27HC with breast cancer risk among African American, Japanese American, Native Hawaiian, Latino, and non-Latino White postmenopausal females. We used multivariable logistic regression adjusted for age, education, parity, body mass index, and smoking status. Stratified analyses were conducted across racial and ethnic groups, hormone receptor (HR) status, and use of lipid-lowering drugs. We assessed interactions of 27HC with steroid hormones. RESULTS: 27HC levels were inversely related to breast cancer risk (odds ratio [OR] 0.80; 95% confidence interval [CI] 0.58, 1.12), but the association was not statistically significant in the full model. Directions of associations differed by racial and ethnic group. Results suggested an inverse association with HR-negative breast cancer (OR 0.46; 95% CI 0.20, 1.06). 27HC interacted with testosterone, but not estrone, on risk of breast cancer; 27HC was only inversely associated with risk among those with the highest levels of testosterone (OR 0.46; 95% CI 0.24, 0.86). CONCLUSION: This is the first US study to examine circulating 27HC and breast cancer risk and reports a weak inverse association that varies across racial and ethnic groups and testosterone level.

Liquid metal phase change materials have the advantages of high thermal conductivity and high volumetric latent heat, which are expected to address the growing challenges of thermal management of advanced electronics. In previous studies, the effect of radiative heat transfer from fins of a phase change heat sink on thermal management performance has rarely been considered. In this study, radiative coating materials with high emissivity were prepared and coated on the fins of the liquid metal phase change heat sink. The effect of radiative heat transfer on the performance of liquid metal phase change heat sink was investigated. The experimental results of continuous heating under natural convection conditions show that the introduction of the radiative coating with an emissivity of 0.9298 can extend the time for the surface temperature of the heat source to reach 100 °C by 9.4%, while shortening the recovery time of the phase change heat sink by 14.9%. The results of high-power cyclic heating indicate that the high emissivity coating can reduce the peak temperature by 16.6 °C in the tenth working cycle. A simplified numerical model was subsequently developed and validated to determine the specific effects of phase change and radiative heat transfer on the overall thermal control performance. The radiation-enhanced liquid metal phase change heat sink proposed in this study is simple and maintenance-free. It is expected to address the thermal management issues of electronic devices that cannot use active cooling or operate in thin-air environments. [ABSTRACT FROM AUTHOR]

Genome mining of biosynthetic pathways with no identifiable core enzymes can lead to discovery of the so-called unknown (biosynthetic route)-unknown (molecular structure) natural products. Here we focused on a conserved fungal biosynthetic pathway that lacks a canonical core enzyme and used heterologous expression to identify the associated natural product, a highly modified cyclo-arginine-tyrosine dipeptide. Biochemical characterization of the pathway led to identification of a new arginine-containing cyclodipeptide synthase (RCDPS), which was previously annotated as a hypothetical protein and has no sequence homology to non-ribosomal peptide synthetase or bacterial cyclodipeptide synthase. RCDPS homologs are widely encoded in fungal genomes; other members of this family can synthesize diverse cyclo-arginine-Xaa dipeptides, and characterization of a cyclo-arginine-tryptophan RCDPS showed that the enzyme is aminoacyl-tRNA dependent. Further characterization of the biosynthetic pathway led to discovery of new compounds whose structures would not have been predicted without knowledge of RCDPS function.