211 research outputs found
Discovery enabled by in-situ synchrotron X-ray techniques
Understanding the complex mechanism of nanocrystal formation and transformation in solutions represents a challenge in materials science. For example, formation of colloidal noble metal nanocrystals from homogeneous liquid solutions involves many complicated processes that are poorly understood. The absence of enough knowledge of nanoparticle formation in liquid media is due to the difficulty in developing effective tools to “see through” solvents and probe chemical and physical events in the liquids. This situation also leads to challenging barriers that prevent the synthesis of functional nanoparticles with precisely tailored properties and better understanding of the dependence of nanoparticles’ performance on their physical parameters including shape and crystalline phase. The exceptional penetration power of the high-flux, high-energy X-ray beams in liquid solutions and reaction vessels (e.g., glass flasks) enables the direct probing of nanophase evolution in large-volume reactors that are usually used in conventional wet chemistry laboratories. The weak absorption of the high-energy X-ray beams in reactants and solvent molecules eliminates the possible side reactions during nanoparticle growth and transformation. As a result, time-resolved, high-energy synchrotron X-ray techniques represent one class of ideal methods for noninvasive probing of growth/transformation mechanism of colloidal nanocrystals in conventional reactors. In this presentation, the time-resolved high-energy synchrotron X-ray diffraction is demonstrated to monitor the nanophase evolution involved in the synthesis of colloidal Ag nanocubes and the physical/chemical transformation of colloidal Ag nanowires to nanoparticles/nanotubes. Use of the Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH11357
Morphology of Graphene on SiC(000-1) Surfaces
Graphene is formed on SiC(000-1) surfaces (the so-called C-face of the
crystal) by annealing in vacuum, with the resulting films characterized by
atomic force microscopy, Auger electron spectroscopy, scanning Auger microscopy
and Raman spectroscopy. Morphology of these films is compared with the graphene
films grown on SiC(0001) surfaces (the Si-face). Graphene forms a terraced
morphology on the C-face, whereas it forms with a flatter morphology on the
Si-face. It is argued that this difference occurs because of differing
interface structures in the two cases. For certain SiC wafers, nanocrystalline
graphite is found to form on top of the graphene.Comment: Submitted to Applied Physics Letters; 9 pages, 3 figures; corrected
the stated location of Raman G line for NCG spectrum, to 1596 cm^-
Vertical distributions of soil microbial biomass carbon: a global dataset
Soil microbial biomass carbon (SMBC) is important in regulating soil organic carbon (SOC) dynamics along soil profiles by mediating the decomposition and formation of SOC. The dataset (VDMBC) is about the vertical distributions of SOC, SMBC, and soil microbial quotient (SMQ = SMBC/SOC) and their relations to environmental factors across five continents. Data were collected from literature, with a total of 289 soil profiles and 1040 observations in different soil layers compiled. The associated environment data collectd include climate, ecosystem types, and edaphic factors. We developed this dataset by searching the Web of Sciene and the China National Knowledge Infrastructure from the year of 1970 to 2019. All the data in this dataset met two creteria: 1) there were at least three mineral soil layers along a soil profile, and 2) SMBC was measured using the fumigation extraction method. The data in tables and texts were obtained from literature directly, and the data in figures were extracted by using the GetData Graph digitizer software version 2.25. When climate and soil properties were not available from publications, we obtainted the data from the World Weather Information Service (https://worldweather.wmo.int/en/home.html) and SoilGrids at a spatial resolution of 250 meters (version 0.5.3, https://soilgrids.org). The units of all the variables were converted to the standard international units or commonly used ones and the values were transformed correspondingly. For example, the value of soil organic matter (SOM) was converted to SOC by using the equation (SOC = SOM × 0.58). This dataset can be used in predicting global SOC changes along soil profiles by using the multi-layer soil carbon models. It can also be used to analyse how soil microbial biomass changes with plant roots as well as the composition, structure, and functions of soil microbial communities along soil profiles at large spatial scales. This dataset offers opportunities to improve our prediction of SOC dynamics under global changes and to advance our understanding of the environmental controls
Graphene formed on SiC under various environments: Comparison of Si-face and C-face
The morphology of graphene on SiC {0001} surfaces formed in various
environments including ultra-high vacuum, 1 atm of argon, and 10^-6 to 10^-4
Torr of disilane is studied by atomic force microscopy, low-energy electron
microscopy, and Raman spectroscopy. The graphene is formed by heating the
surface to 1100 - 1600 C, which causes preferential sublimation of the Si
atoms. The argon atmosphere or the background of disilane decreases the
sublimation rate so that a higher graphitization temperature is required, thus
improving the morphology of the films. For the (0001) surface, large areas of
monolayer-thick graphene are formed in this way, with the size of these areas
depending on the miscut of the sample. Results on the (000-1) surface are more
complex. This surface graphitizes at a lower temperature than for the (0001)
surface and consequently the growth is more three-dimensional. In an atmosphere
of argon the morphology becomes even worse, with the surface displaying
markedly inhomogeneous nucleation, an effect attributed to unintentional
oxidation of the surface during graphitization. Use of a disilane environment
for the (000-1) surface is found to produce improved morphology, with
relatively large areas of monolayer-thick graphene.Comment: 22 pages, 11 figures, Proceedings of STEG-2 Conference; eliminated
Figs. 4 and 7 from version 1, for brevity, and added Refs. 18, 29, 30, 31
together with associated discussio
Association Between Participation in Annual Physical Examinations and Risk Factors for Noncommunicable Diseases in Adults with Disabilities: Evidence from Shanghai, China
The relationships between regular participation in annual physical examinations and the risk factors for noncommunicable diseases (NCDs) among adults with disabilities remains unclear. To address this gap, we used data from 130,899 individuals with disabilities in Shanghai (2014-2016) and evaluated four risk factors for NCDs: hypertension, hyperglycemia, hyperlipidemia, and being overweight. Overall, 4540 individuals participated in annual physical examinations across all three years and 11,388 missed examinations in 2015 (group without regular participation). Chi-squared tests and binary logistic regression were used to assess differences in patient characteristics and explore correlations between variables. Significant differences in age (χ2 = 102.620, p \u3c 0.01), place of residence (χ2 = 94.308, p \u3c 0.01), educational level (χ2 = 59.884, p \u3c 0.01), marital status (χ2 = 16.414, p \u3c 0.01) and disability type (χ2 = 56.499, p \u3c 0.01) and severity (χ2 = 45.464, p \u3c 0.01) were found between those who participated in regular physical examinations and those who did not. Regular participation was associated with reduced incidences of hypertension (odds ratio 0.799, 95% confidence interval (CI): 0.733-0.871) and hyperlipidemia (0.347, 95% CI: 0.307-0.392), but not with the incidence of diabetes (1.049, 95% CI: 0.944-1.166) or being overweight (0.907, 95% CI: 0.812-1.014). Hence, regular participation in annual physical examinations had different associations with risk factors for NCDs
Simuliranje i upravljačka strategija 5.6 kV 17-razniskog STATCOM sustava uz SVG uvjet
To achieve high-voltage reactive power compensation, a 5.6kV 17-level STATCOM under SVG Condition is presented. In this paper, we use a cascaded H-bridge multilevel star-connection converter whose system structure and circuit schematic are described. Then by using the phase-shifted carrier modulation strategy and the active-reactive current decoupling method, the STATCOM performs quite well. Moreover modulation strategy of the 17-level STATCOM based on the active disturbance rejection control (ADRC) is presented and the analytical formulas are described. For implementation, control strategy for DC bus voltage balance in cascaded H-bridge multilevel converters, time average distribution method and extreme value offset method are applied in our design. Finally, simulation results demonstrate that the proposed 17-level STATCOM is capable of reactive power compensation, simultaneous controlling and balancing the DC side voltages during the work and verify that high-voltage reactive power can be accurately and effectively compensated.Za postizanje kompenzacije jalove snage uz visoki napon, predstavljen je STATCOM s 5.6 kV i 17-razina uz SVG uvjet. U ovom radu koristimo kaskadni višerazinski H-mosni pretvarač u zvijezda spoju uz opisane strukturu i shemu spoja. Zatim korištenjem strategije modulacije s fazno-pomaknutim signalom nosioca i metode rasprezanja radno-jalove struje, STATCOM pokazuje prilično dobro vladanje. Uz to, prikazana je strategija modulacije 17-razinskog STATCOM-a zasnovana na upravljanju s aktivnim odbacivanjem smetnji (ADRC) te su opisane analitičke formule. Za implementaciju, u naš dizajn primjenjene su upravljačka strategija balansiranja napona DC sabirnice u kaskadnom višerazinskom H-mosnom pretvaraču te metoda vremenskog uprosječavanja razdiobe i metoda ekstremne vrijednosti pomaka. Konačno, simulacijski rezultati pokazuju da je predloženi 17-razinski STATCOM sposoban za kompenzaciju jalove snage, istovremeno upravljanje i balansiranje napona DC strane u radu te potvrđuju da je jalovu snagu uz visoki napon moguće točno i djelotvorno kompenzirati
Red-Fleshed Apple Anthocyanin Extracts Attenuate Male Reproductive System Dysfunction Caused by Busulfan in Mice
In this research, we analyzed the effect of an intragastrical oral administration of red-fleshed apple anthocyanin extract (RAAE) on busulfan-treated mice. First, we showed that the most abundant component in RAAE was cyanidin 3-O-galactoside. To determine the effect of the RAAE, the mice were divided into control and four other different concentrations of RAAE feeding treatment groups (BA0, no RAAE; BA.1, 0.1 mg/kg; BA1, 1 mg/kg; and BA5, 5 mg/kg) following busulfan injection. We observed that RAAE treatments displayed ameliorative effects on male reproductive system dysfunction caused by busulfan, such as recovering the irregular arrangements of seminiferous tubules, increasing the number of spermatogonia and spermatocytes, improving sperm concentration by 3-fold in BA.1, and improving sperm motility by 2-fold in BA1. The liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis showed significant up- or downregulation of certain metabolites, such as lysophosphatidylcholine (LysoPC), L-arginine, glycine, anandamide, and L-carnitine, which could contribute to the positive effects of RAAE, especially in PBA1 (plasma of BA1) and PBA5 (plasma of BA5). Taken together, the results indicate that 1 mg/kg of RAAE is a suitable concentration for rescuing spermatogenesis in mice. The research suggests that RAAE could be a potential nutraceutical for protecting spermatogenesis after busulfan therapy in cancer
Hydrogen-Rich Saline Attenuates Brain Injury Induced by Cardiopulmonary Bypass and Inhibits Microvascular Endothelial Cell Apoptosis Via the PI3K/Akt/GSK3β Signaling Pathway in Rats
Comprehensive investigation of Quantum Oscillations in Semimetal Using an ac Composite Magnetoelectric Technique with Ultrahigh Sensitivity
Quantum oscillation (QO), a physical phenomenon that reflects the
characteristics of the Fermi surface and transport fermions, has been
extensively observed in metals and semimetals through various approaches, like
magnetostriction, magnetization, resistivity, and thermoelectric power.
However, only some allowed oscillation frequencies can be revealed by each
individual method, particularly in semimetals with intricate Fermi pockets and
associated magnetic breakdown phenomena. In this paper, we present the
application of an ac composite magnetoelectric (ME) technique to measure the
QOs of a topological nodal-line semimetal, ZrSiS, which possesses six
fundamental QO frequencies. By employing the ME technique with a maximum
magnetic field of 13 T and a minimum temperature of 2 K, we are able to capture
all the fundamental frequencies and most of the permissible magnetic breakdown
frequencies. In comparison, some of the frequencies were missing in the
aforementioned four methods under identical measurement conditions. Remarkably,
a series of magnetic breakdown frequencies around 8000 T were revealed even in
a magnetic field as low as 7.5 T. These findings highlight the ME technique as
an ultrahigh-sensitive tool for studying Dirac Fermions and other topological
semimetals with complex Fermi surfaces.Comment: 22 pages, 4 figure
Red-fleshed apple flavonoid extract alleviates CCl4-induced liver injury in mice
In recent years, the global incidence of liver damage has increased. Despite the many known health benefits of red-fleshed apple flavonoids, their potential liver-protective effects have not yet been investigated. In this study, we analyzed the composition of red-fleshed apple flavonoid extract (RAFE) by high-performance liquid chromatography (HPLC). We then induced liver damage in mice with carbon tetrachloride (CCl4) and performed interventions with RAFE to analyze its effect on liver damage, using bifendate as a positive control. The results showed that catechin was the most abundant flavonoid in ‘XJ4’ RAFE (49.346 mg/100 g). In liver-injured mice, the liver coefficients converged to normal levels following RAFE intervention. Moreover, RAFE significantly reduced the enzymatic activity levels of glutamic oxaloacetic transaminase (ALT), glutamic alanine transaminase (AST), and alkaline phosphatase (ALP) in mouse serum. Furthermore, RAFE significantly increased the content or enzyme activity level of total glutathione, total antioxidant capacity, and superoxide dismutase, and significantly decreased the content of malondialdehyde in the liver of mice. In parallel, we performed histopathological observations of mouse livers for each group. The results showed that RAFE restored the pathological changes caused by CCl4 around the central hepatic vein in mice and resulted in tightly bound hepatocytes. The recovery effect of RAFE was dose-dependent in the liver tissue. Regarding intestinal microorganisms, we found that RAFE restored the microbial diversity in liver-injured mice, with a similar microbial composition in the RAFE intervention group and normal group. RAFE reduced the ratio of Firmicutes to Bacteroidetes, increased the levels of probiotic bacteria, such as Lactobacillus acidophilus, and Clostridium, and reduced the levels of harmful bacteria, such as Erysipelothrix Rosenbach. Therefore, RAFE ameliorated CCl4-induced liver damage by modulating the abundance and composition of intestinal microorganisms in mice. In conclusion, RAFE alleviated CCl4-induced liver damage in mice, with H-RAFE (5 mg kg–1) significantly improving liver damage in mice but M-RAFE (1 mg kg–1) significantly improving the imbalance of intestinal microorganisms in mice. Our research suggests that RAFE could be employed for the adjuvant treatment and prevention of liver damage, and may have important applications in food and medicine
- …