The preparation of high-purity and -quality gallium nitride nanowires is accomplished by a catalytic growth using gallium and ammonium. A series of catalysts and different reaction parameters were ...applied to systematically optimize and control the vapor−liquid−solid (VLS) growth of the nanowires. The resulting nanowires show predominantly wurtzite phase; they were up to several micrometers in length, typically with diameters of 10−50 nm. A minimum nanowire diameter of 6 nm has been achieved. Temperature dependence of photoluminescence spectra of the nanowires revealed that the emission mainly comes from wurtzite GaN with little contribution from the cubic phase. Moreover, the thermal quenching of photoluminescence was much reduced in the GaN nanowires. The Raman spectra showed five first-order phonon modes. The frequencies of these peaks were close to those of the bulk GaN, but the modes were significantly broadened, which is indicative of the phonon confinement effects associated with the nanoscale dimensions of the system. Additional Raman modes, not observed in the bulk GaN, were found in the nanowires. The field emission study showing notable emission current with low turn-on field suggests potential of the GaN nanowires in field emission applications. This work opens a wide route toward detailed studies of the fundamental properties and potential applications of semiconductor nanowires.
Vegetation indices are valuable in many fields of geosciences. Conventional, visible-near infrared, indices are often limited by the effects of atmosphere, background soil conditions, and saturation ...at high levels of vegetation. In this study, we will establish the theoretical basis for our new passive microwave vegetation indices (MVIs) based on data from the Advanced Microwave Scanning Radiometer (AMSR-E) on the Aqua satellite. Through the analysis of numerical simulations by surface emission model, the Advanced Integral Equation Model (AIEM), we found that bare soil surface emissivities at different frequencies can be characterized by a linear function with parameters that are dependent on the pair of frequencies used. This makes it possible to minimize the surface emission signal and maximize the vegetation signal when using multi-frequency radiometer measurements. Using a radiative transfer model (
ω–
τ model), a linear relationship between the brightness temperatures observed at two adjacent radiometer frequencies can be derived. The intercept and slope of this linear function depend only on vegetation properties and can be used as vegetation indices. These can be derived from the dual-frequency and dual-polarization satellite measurements under assumption that there is no significant impact of the polarization dependence on the vegetation signals. To demonstrate the potential of the new microwave vegetation indices, we compared them with the Normalized Difference of Vegetation Index (NDVI) derived using MODIS the optical sensor at continental and global scales. The major purpose of this paper is to describe the concept and techniques involved in these newly developed MVIs and explore the general relationships between these MVIs and NDVI. In this first investigation, the information content of NDVI and MVIs, both are qualitative indices, was compared by examining its response in global pattern and to seasonal vegetation phenology. The results indicate that the MVIs can provide significant new information since the microwave measurements are sensitive not only to the leafy part of vegetation properties but also to the properties of the overall vegetation canopy when the microwave sensor can “see” through it. In combination with conventional optical sensor derived vegetation indices, they provide a possible complementary dataset for monitoring global short vegetation and seasonal phenology from space.
White muscle concentrations of As, Cd, Cu, Fe, Se, and Zn were investigated in Atlantic- and Indian-bigeye tuna (BET) (Thunnus obesus) from 6 regions. As and Cd muscle concentrations were ...significantly higher in the Indian-BET than in the Atlantic-BET, whereas the Indian-BET caught in the waters off South Africa revealed the highest As, Se, and Zn muscle concentrations. Accordingly, multidimensional scaling separated them into two oceanic groups. Positive linear relationships between muscle Cd concentration and fork length (FL) were established in both oceans. For the other elements, only muscle-Fe and FL relationship was found in the Atlantic-BET. 10.3% of BET > 145 cm FL from both oceans possessed muscle Cd concentrations exceeding the food safety limit (0.1 μg g−1 wet weight) set by the European Commission. Increased Cd, Cu and Zn pollution was found in the Atlantic Ocean compared with previous data, with higher levels found in the Indian Ocean.
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•Bigeye tuna (BET) muscle metal levels reflect their geographical sampling sites.•Higher BET-As and -Cd muscle levels found in Indian Ocean than in Atlantic Ocean.•Positive relationships between muscle Cd levels and size revealed in the two Oceans.•10% of bigeye tuna > 145 cm had muscle Cd levels exceeding the food safety limit.•The muscle concentrations showed global oceanic metal pollution in recent 20 years.
Abstract
Because mergers of black hole–neutron star (BH–NS) binaries are widely argued to produce both gravitational and electromagnetic waves, these binaries are among the most attractive systems in ...the era of multi-messenger astronomy. In this paper we explore the charging processes of a moving BH in two types of charged surroundings and propose a new charging scenario differing from the elegant mechanism of Wald. During the inspiral of such a binary, the NS is strongly magnetized and the BH is moving inward. By considering this moving BH charging scenario, we find that the BH will increasingly accumulate enough net charge to light up the binary system at the inspiral stage. This charging process is universal no matter whether the BH spins or not. We show that our BH charging scenario can physically explain the BH’s unipolar inductor mechanism in a BH–NS binary system. We calculate electromagnetic emission luminosities due to various energy dissipation mechanisms and find that the electric dipole radiation of the BH makes a dominant contribution to electromagnetic emission at the final stage of inspiral if the BH spins slowly.
Previously, we reported that Akt inactivation determines the sensitivity of hepatocellular carcinoma (HCC) cells to bortezomib. In this study, we report that cancerous inhibitor of protein ...phosphatase 2A (CIP2A), a cellular inhibitor of protein phosphatase 2A (PP2A), mediates the apoptotic effect of bortezomib in HCC. Silencing PP2A by small interference RNA (siRNA) abolishes bortezomib-induced down-regulation of phospho-Akt and apoptosis. Bortezomib increases PP2A activity in sensitive HCC cells, including Sk-Hep1, Hep3B and Huh-7, but not in resistant PLC5 cells. Bortezomib down-regulates CIP2A in a dose- and time-dependent manner in all sensitive HCC cells, whereas no alterations in CIP2A were found in resistant PLC5 cells. Knockdown of CIP2A by siRNA restored bortezomib's effects on apoptosis and PP2A activity in PLC5 cells. Moreover, over-expression of CIP2A up-regulated phospho-Akt and protected Sk-Hep1 cells from bortezomib-induced apoptosis. It is significant that, ectopic expression of CIP2A decreased Akt-related PP2A activity, whereas silencing CIP2A increased this activity, indicating that CIP2A negatively regulates Akt-related PP2A activity in HCC cells, furthermore, our in vivo data showed that bortezomib down-regulates CIP2A and up-regulates PP2A activity in Huh-7 tumors, but not in PLC5 tumors. In conclusion, inhibition of CIP2A determines the effects of bortezomib on apoptosis and PP2A-dependent Akt inactivation in HCC.
This study was performed to evaluate the subjective and objective functional outcomes of patients who had undergone submandibular gland-sparing neck dissection. All data were obtained from patients ...treated in a single hospital. Seventy-seven patients who had undergone complete submandibular gland sparing (CSGS) were included in the study. Cancer prognosis items were recorded. The subjective outcomes included patient self-evaluation of mouth dryness and the evaluation of the presence of saliva secretion following the application of digital pressure. Saliva scintigraphy served as the objective test. Self-reported xerostomia was compared between the CSGS patients and a control group of patients who had undergone unilateral submandibular gland removal (USGR; n = 74). In the CSGS group, local recurrence occurred in 3.8% of the 80 cancer sites, and neck recurrence occurred in 5.9% of neck dissection sites. Regarding the subjective measurements, 7.0% of the CSGS patients reported xerostomia and 91.9% demonstrated saliva secretion by digital pressure. Scintigraphy revealed actively secreting glands, with 42.9% of them showing normal gland function; none of the patients had severe xerostomia. The relative risk of dry mouth was significantly higher in the USGR patients than in the CSGS patients (P < 0.001). Submandibular gland sparing during neck dissection was found to result in satisfactory saliva secretion, with a relatively small risk of local or neck recurrence.
This case report describes 26‐year‐old woman who had multiple clusters of pale‐pink lichenoid papules since childhood and the accompanying itching was intense. Skin biopsy revealed obvious fissures ...had formed under the epidermis. The patient was diagnosed with epidermolysis bullosa pruriginosa and was successfully treated with tofacitinib.
In high-dimensional multivariate regression problems, enforcing low rank in the coefficient matrix offers effective dimension reduction, which greatly facilitates parameter estimation and model ...interpretation. However, commonly used reduced-rank methods are sensitive to data corruption, as the low-rank dependence structure between response variables and predictors is easily distorted by outliers. We propose a robust reduced-rank regression approach for joint modelling and outlier detection. The problem is formulated as a regularized multivariate regression with a sparse mean-shift parameterization, which generalizes and unifies some popular robust multivariate methods. An efficient thresholding-based iterative procedure is developed for optimization. We show that the algorithm is guaranteed to converge and that the coordinatewise minimum point produced is statistically accurate under regularity conditions. Our theoretical investigations focus on non-asymptotic robust analysis, demonstrating that joint rank reduction and outlier detection leads to improved prediction accuracy. In particular, we show that redescending ψ-functions can essentially attain the minimax optimal error rate, and in some less challenging problems convex regularization guarantees the same low error rate. The performance of the proposed method is examined through simulation studies and real-data examples.
The effects of Zr, Er and Cr additions on the microstructures, mechanical properties and corrosion resistance of Al–Zn–Mg–Cu alloy were investigated. The combined additions of Zr, Er and Cr to ...Al–Zn–Mg–Cu alloy led to the formation of coherent Zn, Mg, Cu, Cr-containing Al3(Zr, Er). These 15–25nm secondary precipitates remarkably inhibited the recrystallization of Al matrix, and numerous fine subgrain boundaries were retained. Compared to the partial recrystallized Al–Zn–Mg–Cu–Zr alloy, the unrecrystallized Al–Zn–Mg–Cu–Zr–Er–Cr alloy exhibited higher resistance to intergranular corrosion and stress corrosion with the improved mechanical properties and fracture toughness. The synergetic effects of Zr, Er and Cr on the precipitates, recrystallization and corrosion resistance of ultra-high strength Al–Zn–Mg–Cu alloys have been discussed.
CsV3 Sb5 is a newly discovered Z2 topological kagome metal showing the coexistence of a charge-density-wave (CDW)-like order at T* = 94 K and superconductivity (SC) at Tc = 2.5 K at ambient pressure. ...Here, we study the interplay between CDW and SC in CsV3 Sb5 via measurements of resistivity, dc and ac magnetic susceptibility under various pressures up to 6.6 GPa. We find that the CDW transition decreases with pressure and experience a subtle modification at Pc1 ≈ 0.6 – 0.9 GPa before it vanishes completely at Pc2 ≈ 2 GPa . Correspondingly, Tc(P) displays an unusual M -shaped double dome with two maxima around Pc1 and Pc2 , respectively, leading to a tripled enhancement of Tc to about 8 K at 2 GPa. The obtained temperature-pressure phase diagram resembles those of unconventional superconductors, illustrating an intimated competition between CDW-like order and SC. The competition is found to be particularly strong for the intermediate pressure range Pc1 ≤ P ≤ Pc2 as evidenced by the broad superconducting transition and reduced superconducting volume fraction. The modification of CDW order around Pc1 has been discussed based on the band structure calculations. This work not only demonstrates the potential to raise Tc of the V-based kagome superconductors, but also offers more insights into the rich physics related to the electron correlations in this novel family of topological kagome metals.
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