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In this paper, we formed two BC2P/MoS2 van der Waals (vdW) heterostructures, namely BC2P/MoS2-a and -b heterostructures by stacking the MoS2 and BC2P monolayers. First, by analyzing binding energies, flat average differential charge density and elastic constants of two vdW heterostructures, their structures and formation possibility were studied. Two vdW heterostructures are semiconductors with their indirect band gaps as 0.774/1.405 eV and 1.028/1.458 (direct) eV under the GGA-PBE/HSE06 functional, respectively. Moreover, they are two-dimensional materials with close hardness to the graphene. Especially, two vdW heterostructures possess very high absorption coefficients (> 30%) and low reflection coefficients (< 4%) for the visible light, which makes them as novel and potential two-dimensional materials in the application of optoelectronic, electronic and photovoltaics devices. [ABSTRACT FROM AUTHOR]

Poisson-Boltzmann electrostatics is a well established model in biophysics; however, its application to large-scale biomolecular processes such as protein-protein encounter is still limited by the efficiency and memory constraints of existing numerical techniques. In this article, we present an efficient and accurate scheme that incorporates recently developed numerical techniques to enhance our computational ability. In particular, a boundary integral equation approach is applied to discretize the linearized Poisson-Boltzmann equation; the resulting integral formulas are well conditioned and are extended to systems with arbitrary numbers of biomolecules. The solution process is accelerated by Krylov subspace methods and a new version of the fast multipole method. In addition to the electrostatic energy, fast calculations of the forces and torques are made possible by using an interpolation procedure. Numerical experiments show that the implemented algorithm is asymptotically optimal O(N) in both CPU time and required memory, and application to the acetylcholinesterase-fasciculin complex is illustrated.

The gating motion of the human nicotinic acetylcholine receptor (nAChR) alpha 7 was investigated with normal mode analysis (NMA) of two homology models. The first model, referred to as model 1, was built from both the Lymnaea stagnalis acetylcholine binding protein (AChBP) and the transmembrane (TM) domain of the Torpedo marmorata nAChR. The second model, referred to as model C, was based solely on the recent electron microscopy structure of the T. marmorata nAChR. Despite structural differences, both models exhibit nearly identical patterns of flexibility and correlated motions. In addition, both models show a similar global twisting motion that may represent channel gating. The similar results obtained for the two models indicate that NMA is most sensitive to the contact topology of the structure rather than its finer detail. The major difference between the low-frequency motions sampled for the two models is that a symmetrical pore-breathing motion, favoring channel opening, is present as the second most dominant motion in model 1, whilst largely absent from model C. The absence of this mode in model C can be attributed to its less symmetrical architecture. Finally, as a further goal of the present study, an approximate open channel model, consistent with many experimental findings, has been produced. (c) 2005 Elsevier Ltd. All rights reserved.

The electrostatic interaction among molecules solvated in ionic solution is governed by the Poisson-Boltzmann equation (PBE). Here the hypersingular integral technique is used in a boundary element method (BEM) for the three-dimensional (3D) linear PBE to calculate the Maxwell stress tensor on the solvated molecular surface, and then the PB forces and torques can be obtained from the stress tensor. Compared with the variational method (also in a BEM frame) that we proposed recently, this method provides an even more efficient way to calculate the full intermolecular electrostatic interaction force, especially for macromolecular systems. Thus, it may be more suitable for the application of Brownian dynamics methods to study the dynamics of protein/protein docking as well as the assembly of large 3D architectures involving many diffusing subunits. The method has been tested on two simple cases to demonstrate its reliability and efficiency, and also compared with our previous variational method used in BEM. (c) 2005 American Institute of Physics.

C18H21NO8S, monoclinic, P121/c1 (no. 14), a = 21.069(5) Å, b = 11.494(3)Å, c = 7.996(2)Å, β = 97.257(3)°, V = 1920.9Å3, Z = 4, Rgt(F) = 0.044, wRref(F2) = 0.124, T = 298 K.

Considered in this paper is an inverse Robin problem governed by a steady-state diffusion equation. By the Robin inverse problem, one wants to recover the unknown Robin coefficient on an inaccessible boundary from Cauchy data measured on the accessible boundary. In this paper, instead of reconstructing the Robin coefficient directly, we compute first the Cauchy data on the inaccessible boundary which is a linear inverse problem, and then compute the Robin coefficient through Newton's law. For the Cauchy problem, a parameter-dependent coupled complex boundary method (CCBM) is applied. The CCBM has its own merits, and this is particularly true when it is applied to the Cauchy problem. With the introduction of a positive parameter, we can prove the regularized solution is uniformly bounded with respect to the regularization parameter which is a very good property because the solution can now be reconstructed for a rather small value of the regularization parameter. For the problem of computing the Robin coefficient from the recovered Cauchy data, a least square output Tikhonov regularization method is applied to Newton's law to obtain a stable approximate Robin coefficient. Numerical results are given to show the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The elastic and structural properties of nanolaminate Zr2InC are studied by first-principles, and it is shown that, for any used modes, including the generalized gradient approximation (GGA) and localized density approximation, there always exists an ultraincompressibility along c axis between 70 GPa and 400 GPa. Such anomalous behavior is originated from the slowdown of core-valence charge transfer. The rapid shift of Zr atom along c axis also contributed much to the ultraincompressibility as it is greatly reduced once the Zr atom shift suspends along c axis above about 400 GPa. Both the elastic constants and the phononic vibrational frequencies investigations confirmed the structural unstable simultaneously. The Poisson's ratio investigations observed a higher ionic or weaker covalent contribution in interatomic bonding and the degree of ionicity increases with pressure. [ABSTRACT FROM AUTHOR]

OBJECTIVE: DJ-1 is a negative regulator of PTEN and plays a role in tumorigenesis. Abnormal miR-203 expression is associated with pancreatic cancer. Bioinformatics analysis showed a targeted relationship between miR-203 and DJ-1 3'-UTR. This study investigated whether miR-203 regulates DJ-1 expression and its role in pancreatic cancer cell proliferation, apoptosis, and cisplatin (DDP) resistance. MATERIALS AND METHODS: The Dual-Luciferase reporter gene assay validated the targeted regulation between miR-203 and DJ-1. The DDP-resistant cell line SW1990/DDP was established and divided into miR-NC group and miR- 203 mimic group followed by analysis of the expression of DJ-1, PTEN and p-AKT, cell apoptosis, and proliferation. RESULTS: There was a targeted relationship between miR-203 and DJ-1 mRNA. The expression of miR-203 in SW1990/DDP cells was significantly lower than that in SW1990 cells, while the expression of DJ-1 mRNA and protein was significantly higher than that in SW1990 cells. Compared with miR-NC group, the expression of DJ-1 and p-AKT protein in SW1990/DDP cells was significantly decreased in miR-203 mimic transfection group, while the expression of PTEN was significantly increased with increased cell apoptosis and decreased cell proliferation, as well as reduced DDP resistance. CONCLUSIONS: The decreased expression of miR-203 and the increased expression of DJ-1 is associated with drug resistance in pancreatic cancer cells. Elevated miR-203 can inhibit the expression of DJ-1, affect the activity of PTEN-PI3K/AKT pathway, inhibit the proliferation of pancreatic cancer cells, induce cell apoptosis, and reduce DDP resistance of pancreatic cancer cells. [ABSTRACT FROM AUTHOR]

Bioluminescence tomography (BLT) aims at the determination of the distribution of a bioluminescent source quantitatively. The mathematical problem involved is an inverse source problem and is ill-posed. With the Tikhonov regularization, an optimization problem is formed for the light source reconstruction and it is usually solved by gradient-type methods. However, such iterative methods are often locally convergent and thus the solution accuracy depends largely on initial guesses. In this paper, we reformulate the reduced regularized optimal problem as a nonlinear equation and apply a homotopy method, which is a powerful tool for solving nonlinear problem due to its globally convergent property, to it. Numerical experiments show that the application of the homotopy technique is feasible and can produce satisfactory approximate solutions for a very large range of initial guesses. [ABSTRACT FROM PUBLISHER]

Abstract: Since February 2012, CO2, H2O, and wind data at 10 Hz have been measured by the open‐path eddy covariance systems at 8, 16, 47, 80, 140, 200, and 280 m above ground level on the 325 m Beijing meteorological tower. Analysis of the data from 2013 to 2016 indicates that the annual averaged CO2 concentration increased and the local and regional CO2 emission decreased with the sequestration of background CO2 concentration. The maximum values occurred during winter, and the minimum values occurred during summer. During spring, summer, and autumn, there was a constant CO2 flux layer from 47 m to 140 m. However, during winter, CO2 flux increased with height, and the maximum appeared at approximately 140 m and then decreased with height. Above 47 m, the CO2 fluxes were represented as the net efflux, and below 16 m, the fluxes were near zero or a net uptake. At all observed heights, the diurnal variation in the CO2 concentration displayed a clear cycle with a peak corresponding to the morning transportation rush hour. The local wavelet power spectra of the CO2 concentration, CO2 flux, and other meteorological elements identified significant cross‐wavelet powers near the 24 h and 365 day bands for the CO2 concentration and flux with temperature, wind speed, friction velocity, and turbulent kinetic energy. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To study the expression profile and role of microRNA miR-34a in Leukemia stem cells (LSC) and during its metastasis. We examined upon the enforced expression of miR-34a in TIM3 positive leukemia stem cells and study the impact of leukemia stem cells and its metastasis. PATIENTS AND METHODS: Samples were collected from acute myeloid leukemia (AML) children along with controls. Immunohistochemistry analysis was performed with TIM3 antibody followed by Sorting of TIM3 positive cells by flow cytometry and the expression level of miR-34a was quantified by qRT-PCR assay. RESULTS: Immunohistochemistry in accordance with Sorting of TIM3 positive cells by flow cytometry concludes that the leukemia stem cells (LSC) were present in the samples. Induced expression of miR-34a in TIM3 positive leukemia stem cells (LSC), inhibits the clonogenic expansion, tumor progression and metastasis of leukemia. CONCLUSIONS: The enforced expression of miR-34a in TIM3 positive leukemia stem cells inhibits the leukemia stem cells and its metastasis. Our study illustrates that miR-34a is a key regulator and which will be developed as a novel therapeutic agent against leukemia stem cells (LSC). [ABSTRACT FROM AUTHOR]