Conductance and persistent current of a quantum ring coupled to a quantum wire under external fields

The electronic transport of a noninteracting quantum ring side-coupled to a quantum wire is studied via a single-band tunneling tight-binding Hamiltonian. We found that the system develops an oscillating band with antiresonances and resonances arising from the hybridization of the quasibound levels of the ring and the coupling to the quantum wire. The positions of the antiresonances correspond exactly to the electronic spectrum of the isolated ring. Moreover, for a uniform quantum ring the conductance and the persistent current density were found to exhibit a particular odd-even parity related with the ring-order. The effects of an in-plane electric field was also studied. This field shifts the electronic spectrum and damps the amplitude of the persistent current density. These features may be used to control externally the energy spectra and the amplitude of the persistent current.Comment: Revised version, 7 pages and 9 figures. To appear in Phys. Rev.

Properties of the peaks of second harmonic light through Fibonacci-class ferroelectric domains

After establishing the method of constructing a class of one-dimensional (1D) Fibonacci-class quasiperiodic (FC(n)) ferroelectric domains system, we have studied the properties of the electric field of the second harmonic generation (SHG) by means of the small-signal approximation in the case of the vertically transmission. It was found that only the second harmonic light (SHL) peaks which were indexed by two special integers q and p would be the brightest and the spectra whose positions were decided by successive FC(n) integers qF and pF were perfect self-similar without considering the dispersive effect of the refractive index on SHL. The effect of the vacancies for some special spectral lines was also studied generally. The analytic results were confirmed by the numerical simulations

Localized states of acoustic waves in three-dimensional periodic composites with point defects

Acoustic point defect states in the three-dimensional simple-cubic arrays of water spheres embedded in a mercury host are studied. Two kinds of defects are introduced, one is a sphere defect created by changing its radius, and another is a cubic defect obtained by replacing one of the spheres with a cube. The results show that a defect band appears in the band gap of the perfect crystals. The calculations show that the defect modes are localized around the defect. The influence of the filling fraction and the geometry of the defect on the defect modes are investigated in detail. Copyright Springer-Verlag Berlin/Heidelberg 2003

Spatiotemporal patterns of precipitation based on the Bayesian maximum entropy method in a typical catchment of the Heihe River watershed, northwest China

Precipitation patterns are vital to water resource management and hydrological research, especially in the upper reaches of inland rivers in arid and semiarid areas. However, estimating spatiotemporal precipitation patterns at a basin scale is challenging due to limited observations. In this study, spatiotemporal patterns of precipitation amount, frequency, duration, and intensity at different time scales from 2014 to 2019 are estimated using the Bayesian maximum entropy method in the Tianlaochi catchment of the Heihe River watershed, northwest China. The study's results show that the annual average precipitation amount was 535.9 mm from 2014 to 2019, with precipitation amount between May and September accounting for 85.9% of the annual precipitation amount. For daily precipitation, the average frequency rate of light precipitation is highest at 59.55%, however, the average contribution rate of moderate precipitation is highest at 50.33%. The spatial distribution of precipitation is characterized by high-value areas concentrated in the central valley and low-value areas located at the catchment's outlet. The most important driving factors of precipitation patterns are elevation, relative humidity, and wind direction. These outcomes can be used to establish accurate hydrological models in the catchment and provide support for water resource management in the Heihe River watershed

Soybean oil-based shape-memory polyurethanes: Synthesis and characterization

Shape-memory polymers (SMPs) have wide range of applications due to their ability to sense environmental stimuli and reshape from a temporary shape to a permanent shape. Plant oil-based polymeric materials are highly concerned in recent years in consideration of petroleum depletion and environmental pollution. However, plant oil-based polymers are rarely investigated regarding their shape-memory characteristics though bio-based SMPs are highly desired nowadays. In this study, a series of soybean oil-based shape-memory polyurethanes (SSMPUs) are prepared through a mild chemo-enzymatic synthetic route, and their properties are fully characterized with tensile testing, DSC, dynamic mechanical analysis (DMA), and shape-memory testing. Results show that SSMPUs are soft rubbers with tensile strength in the range of 1.92.2?MPa and glass transition temperature in the range of 25 degrees C, and possess good shape recoveries at RT when stretching ratio is 10, 20, and 30%, respectively. This work would promote the development of high-value-added plant oil-based shape-memory polyurethanes

Soybean Oil-Based Polyurethane Networks: Shape-Memory Effects and Surface Morphologies

Vegetable oil-based shape-memory polyurethane networks are an emerging class of bio-based functional materials with great potential applications. In this study, a series of different structural soybean oil polyols were synthesized, and utilized to fabricate polyurethane networks by reacting with 1,6-diisocyanatohexane. The soybean oil-based polyurethanes (SOPUs) were characterized with differential scanning calorimetry (DSC), dynamic mechanical tests (DMA), tensile testing, shape-memory testing, and atomic force microscopy (AFM). It was found that SOPUs with a preserved triglyceride structure were fixed in a temporary shape at -20 A degrees C, while others were fixed in temporary shapes at 4 A degrees C. Although the recovery speeds were different, all the samples could completely regain their permanent shapes at 37 A degrees C (human body temperature). Furthermore, different SOPUs exhibited different surface structures, which might provide the materials with additional values

Remote Sensing-Based Approach for the Assessing of Ecological Environmental Quality Variations Using Google Earth Engine: A Case Study in the Qilian Mountains, Northwest China

Due to climate change and human activities, the eco-environment quality (EEQ) of eco-fragile regions has undergone massive change, especially in the Tibet Plateau. The Qilian Mountains (QLM) region is an essential ecological function zone in the northeastern Tibet Plateau, which plays a vital role in northwestern China’s eco-environmental balance. However, EEQ changes in the QLM during the 21st century remain poorly understood. In this study, the spatiotemporal variations of the EEQ in the QLM were analyzed from 2000 to 2020 using a remote sensing ecological index (RSEI). The EEQ driving factors are identified by the geographic detector, and the spatial influence of critical factors is represented by a geographically weighted regression model. The results show low EEQ in the QLM. From 2000 to 2020, the EEQ initially slightly improved, then deteriorated, and finally gradually recovered. Spatially, the EEQ shows an increasing trend from northwest to southeast. Moran’s I of EEQ remains at around 0.95, representing high spatial aggregation. “High–High” and “Low–Low” clustering features dominate in the local spatial autocorrelation, indicating the EEQ of the QLM is polarized. Precipitation is the dominant positive factor in the EEQ, with a q statistics exceeding 0.644. Furthermore, the key factors (precipitation, distance to towns, distance to roads) affecting EEQ in different periods vary significantly in space. From results we can draw the conclusion that the natural factors mainly control the spatial patterns of EEQ, while the human factors mainly impact the temporal trend of EEQ, the EEQ in the QLM has been significantly improved since 2015. Our findings can provide theoretical support for future eco-environmental protection and restoration in the QLM

Enzymatic synthesis of oleic acid-based epoxy monomer for the production of value added polymers

An oleic acid-based epoxy monomer was synthesized by reacting 2-hydroxyethyl acrylate with epoxy stearic acid and an immobilized lipase. NMR, electrospray ionization mass spectrometry and gel permeation chromatography were used to characterize the intermediates and products. 2-(Acryloyloxy) ethyl epoxy stearate was synthesized with a yield of 87 % w/w. After free radical polymerization, epoxy stearic acid-grafted epoxy polymer with molecular weight of 15,150 g/mol was obtained; the final yield was 81 % w/w

Development and Evaluation of a PSMA-Targeted Nanosystem Co-Packaging Docetaxel and Androgen Receptor siRNA for Castration-Resistant Prostate Cancer Treatment

Primary prostate cancer (PC) progresses to castration-resistant PC (CRPC) during androgen deprivation therapy (ADR) in early stages of prostate cancer. Thus, rather than blocking the androgen-related pathway further, docetaxel (DTX)-based therapy has become the most effective and standard first-line chemotherapy for CRPC. Although the therapy is successful in prolonging the survival of patients with CRPC, chemotherapy resistance develops due to the abnormal activation of the androgen receptor (AR) signaling pathway. Thus, to optimize DTX efficacy, continued maximum suppression of androgen levels and AR signaling is required. Here, we designed a prostate-specific membrane antigen (PSMA)-targeted nanosystem to carry both DTX and AR siRNA (Di-PP/AR-siRNA/DTX) for CRPC treatment. Specifically, DTX was encapsulated into the hydrophobic inner layer, and the AR siRNA was then condensed with the cationic PEI block in the hydrophilic outer layer of the PEI-PLGA polymeric micelles. The micelles were further coated with PSMA-targeted anionic polyethylene glycol-polyaspartic acid (Di-PEG-PLD). In vitro and in vivo results demonstrated that the resulting Di-PP/AR-siRNA/DTX exhibited prolonged blood circulation, selective targeting, and enhanced antitumor effects. Consequently, Di-PP/AR-siRNA/DTX holds great potential for efficient CRPC treatment by combining chemotherapy and siRNA silencing of androgen-related signaling pathways

The optimum elastic wave band gaps in three dimensional phononic crystals with local resonance

Using multiple-scattering theory, we investigate the optimization of the elastic wave band gaps of three dimensional three-component phononic crystals with local resonance. The optimum gaps of two systems including Au spheres coated with Pb embedded in Si matrix and Pb spheres coated with plastic embedded in Si matrix are obtained by tuning the ratio of the inner and the outer radii of the coating layers. It also shows that the elastic wave band gaps for the two systems versus the filling fractions and the radius ratio display different features. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2004