Plasmas are believed to be possibly the most abundant form of ordinary matter in the Universe, supporting a variety of the wave phenomena, while a dusty plasma is of interest as a non-Hamiltonian ...system of interacting particles. In this Letter, symbolic computation on an observationally/experimentally-supported (2+1)-dimensional generalized variable-coefficient Kadomtsev-Petviashvili-Burgers-type equation is done, for certain dust-acoustic, electron-acoustic, positron-acoustic, magneto-acoustic, dust-magneto-acoustic, ion-acoustic, dust-ion-acoustic and/or quantum-dust-ion-acoustic waves in one of the cosmic/laboratory dusty plasmas. Auto-Bäcklund transformation and families of the solitonic solutions are obtained, for the electrostatic wave potential, perturbation of the magnitude of the magnetic field, fluctuation of electron or ion density, or radial-direction component of the velocity of ions or dust particles, relying on such plasma coefficient functions as the nonlinearity, dispersion, dusty-fluid-viscosity/Burgers-dissipation, geometric-effect and diffraction/transverse-perturbation coefficients. Shock structures presented in this Letter are very close to the experimental results previously reported. Future plasma observations/experiments might verify some other effects offered by our analytic results with respect to those plasma coefficient functions.
Optical fiber communication system is one of the core supporting systems of the modern internet age, and studies on the ultrashort optical pulses are at the forefront of fiber optics, modern optics ...and optical engineering. Hereby, symbolic computation on the recently-proposed generalized higher-order variable-coefficient Hirota equation is performed, for certain ultrashort optical pulses propagating in a nonlinear inhomogeneous fiber. For the complex envelope function associated with the optical-pulse electric field in the fiber, an auto-Bäcklund transformation is worked out, along with a family of the analytic solutions. Both our Bäcklund transformation and analytic solutions depend on the optical-fiber variable coefficients which represent the effects of the first-order dispersion, second-order dispersion, third-order dispersion, Kerr nonlinearity, time delaying, phase modulation and gain/loss. Relevant constraints among those coefficients are also presented. We expect that the work could be of some use for the fiber-optics investigations.
Current studies on the liquids and lattices attract people’s attention. In this Letter, for certain interfacial waves in a two-layer liquid or elastic waves in a lattice, we investigate a ...(3+1)-dimensional generalized Yu-Toda-Sasa-Fukuyama system via building a set of the similarity reductions. In respect of the amplitude or elevation of the relevant wave, our similarity reductions are from that system to a known ordinary differential equation, while dependent on the coefficients in that system.
Nowadays, marine scientists are making use of the Kadomtsev-Petviashvili (KP)-category equations in their investigations from the Straits of Georgia and Gibraltar to the Adriatic Sea, North Sea and ...South China Sea. In fluid mechanics and other fields, the (3+1)-dimensional B-type KP equations have attracted a good size of recent research. For a generalized (3+1)-dimensional variable-coefficient B-type KP equation for the nonlinear waves in fluid mechanics, with symbolic computation, we obtain a variable-coefficient-dependent auto-Bäcklund transformation, along with two variable-coefficient-dependent families of the shock-wave-type solutions.
•We study a generalized (3+1)-dimensional variable-coefficient BKP equation for the nonlinear waves in fluid mechanics.•With symbolic computation, we obtain a variable-coefficient-dependent auto-Bäcklund transformation.•With symbolic computation, we obtain two variable-coefficient-dependent families of the shock-wave-type solutions.
Abstract
As the first web server to analyze various biological sequences at sequence level based on machine learning approaches, many powerful predictors in the field of computational biology have ...been developed with the assistance of the BioSeq-Analysis. However, the BioSeq-Analysis can be only applied to the sequence-level analysis tasks, preventing its applications to the residue-level analysis tasks, and an intelligent tool that is able to automatically generate various predictors for biological sequence analysis at both residue level and sequence level is highly desired. In this regard, we decided to publish an important updated server covering a total of 26 features at the residue level and 90 features at the sequence level called BioSeq-Analysis2.0 (http://bliulab.net/BioSeq-Analysis2.0/), by which the users only need to upload the benchmark dataset, and the BioSeq-Analysis2.0 can generate the predictors for both residue-level analysis and sequence-level analysis tasks. Furthermore, the corresponding stand-alone tool was also provided, which can be downloaded from http://bliulab.net/BioSeq-Analysis2.0/download/. To the best of our knowledge, the BioSeq-Analysis2.0 is the first tool for generating predictors for biological sequence analysis tasks at residue level. Specifically, the experimental results indicated that the predictors developed by BioSeq-Analysis2.0 can achieve comparable or even better performance than the existing state-of-the-art predictors.
The development of kesterite Cu2ZnSn(S,Se)4 thin‐film solar cells is currently hindered by the large deficit of open‐circuit voltage (Voc), which results from the easy formation of CuZn antisite ...acceptor defects. Suppressing the formation of CuZn defects, especially near the absorber/buffer interface, is thus critical for the further improvement of kesterite solar cells. In this paper, it is shown that there is a large disparity between the defects in Cu‐ and Ag‐based kesterite semiconductors, i.e., the CuZn or CuCd acceptor defects have high concentration and are the dominant defects in Cu2ZnSn(S,Se)4 or Cu2CdSnS4, but the AgZn acceptor has only a low concentration and the dominant defects are donors in Ag2ZnSnS4. Therefore, the Cu‐based kesterites always show p‐type conductivity, while the Ag‐based kesterites show either intrinsic or weak n‐type conductivity. Based on this defect disparity and calculated band alignment, it is proposed that the Voc limit of the kesterite solar cells can be overcome by alloying Cu2ZnSn(S,Se)4 with Ag2ZnSn(S,Se)4, and the composition‐graded (Cu,Ag)2ZnSn(S,Se)4 alloys should be ideal light‐absorber materials for achieving higher efficiency kesterite solar cells.
A new strategy is proposed to overcome the Voc bottleneck and increase the efficiency of the kesterite solar cells. This is achieved by forming composition‐graded (Cu1–xAgx)2ZnSn(S,Se)4 alloys as the absorber layer.
Oxidative stress results from an imbalance of the reactive oxygen species/reactive nitrogen species (ROS/RNS) production and the oxidants defense system. Extensive research during the last decades ...has revealed that oxidative stress can mediate cancer initiation and development by leading not only to molecular damage but also to a disruption of reduction-oxidation (redox) signaling. In order to provide a global overview of the redox signaling pathways, which play a role in cancer formation, we conducted a systematic literature search in PubMed and ISI Web of Science and identified 185 relevant reviews published in the last 10 years. The 20 most frequently described pathways were selected to be presented in this systematic review and could be categorized into 3 groups: Intracellular ROS/RNS generating organelles and enzymes, signal transduction cascades kinases/phosphatases and transcription factors. Intracellular ROS/RNS generation organelles are mitochondria, endoplasmic reticulum and peroxisomes. Enzymes, including NOX, COX, LOX and NOS, are the most prominent enzymes generating ROS/RNS. ROS/RNS act as redox messengers of transmembrane receptors and trigger the activation or inhibition of signal transduction kinases/phosphatases, such as the family members of protein tyrosine kinases and protein tyrosine phosphatases. Furthermore, these reactions activate downstream signaling pathways including protein kinase of the MAPK cascade, PI3K and PKC. The kinases and phosphatases regulate the phosphorylation status of transcription factors including APE1/Ref-1, HIF-1α, AP-1, Nrf2, NF-κB, p53, FOXO, STAT, and β-catenin. Finally, we briefly discuss cancer prevention and treatment opportunities, which address redox pathways and further research needs.
The kesterite‐structured semiconductors Cu2ZnSnS4 and Cu2ZnSnSe4 are drawing considerable attention recently as the active layers in earth‐abundant low‐cost thin‐film solar cells. The additional ...number of elements in these quaternary compounds, relative to binary and ternary semiconductors, results in increased flexibility in the material properties. Conversely, a large variety of intrinsic lattice defects can also be formed, which have important influence on their optical and electrical properties, and hence their photovoltaic performance. Experimental identification of these defects is currently limited due to poor sample quality. Here recent theoretical research on defect formation and ionization in kesterite materials is reviewed based on new systematic calculations, and compared with the better studied chalcopyrite materials CuGaSe2 and CuInSe2. Four features are revealed and highlighted: (i) the strong phase‐competition between the kesterites and the coexisting secondary compounds; (ii) the intrinsic p‐type conductivity determined by the high population of acceptor CuZn antisites and Cu vacancies, and their dependence on the Cu/(Zn+Sn) and Zn/Sn ratio; (iii) the role of charge‐compensated defect clusters such as 2CuZn+SnZn, VCu+ZnCu and ZnSn+2ZnCu and their contribution to non‐stoichiometry; (iv) the electron‐trapping effect of the abundant 2CuZn+SnZn clusters, especially in Cu2ZnSnS4. The calculated properties explain the experimental observation that Cu poor and Zn rich conditions (Cu/(Zn+Sn) ≈ 0.8 and Zn/Sn ≈ 1.2) result in the highest solar cell efficiency, as well as suggesting an efficiency limitation in Cu2ZnSn(S,Se)4 cells when the S composition is high.
The physics of lattice defects in kesterite structured Cu2ZnSnS4 and Cu2ZnSnSe4 and chalcopyrite structured CuInSe2 and CuGaSe2 crystals is investigated and compared based on the first‐principles calculations. The influence of shallow acceptor defects, deep donor defects and charge‐compensated defect clusters on the non‐stoichiometry, hole carrier concentration and solar cell efficiency of these materials is revealed.
It was believed that the Se‐rich synthesis condition can suppress the formation of deep‐level donor defect VSe (selenium vacancy) in Sb2Se3 and is thus critical for fabricating high‐efficiency Sb2Se3 ...solar cells. However, here it is shown that by first‐principles calculations the density of VSe increases unexpectedly to 1016 cm−3 when the Se chemical potential increases, so Se‐rich condition promotes rather than suppresses the formation of VSe. Therefore, high density of VSe is thermodynamically inevitable, no matter under Se‐poor or Se‐rich conditions. This abnormal behavior can be explained by a physical concept “defect‐correlation”, i.e., when donor and acceptor defects compensate each other, all defects become correlated with each other due to the formation energy dependence on Fermi level which is determined by densities of all ionized defects. In quasi‐1D Sb2Se3, there are many defects and the complicated defect‐correlation can give rise to abnormal behaviors, e.g., lowering Fermi level and thus decreasing the formation energy of ionized donor VSe2+ in Se‐rich Sb2Se3. Such behavior exists also in Sb2S3. It explains the recent experiments that the extremely Se‐rich condition causes the efficiency drop of Sb2Se3 solar cells, and demonstrates that the common chemical intuition and defect engineering strategies may be invalid in compensated semiconductors.
First‐principles calculations show that the Se‐rich synthesis condition promotes rather than suppresses the formation of selenium vacancy defects in Sb2Se3. To explain such an abnormal behavior, a new physical concept, the defect‐correlation effect, which can be general in compound semiconductors with donor‐acceptor compensation and leads to abnormal defect behavior in Sb2Se3, Sb2S3 and other low‐symmetry or multinary semiconductors, is introduced.
PDF
