确定时间序列分段点的方法研究

现有的时间序列分段线性表示一般把局部极值点作为分段点,但是局部极值点并不能完全刻画时间序列的状态变化,根据时间序列线性分段的基本思想,提出在确定局部极值点的基础上引入斜率差值大的分段点,以便得到较高的拟合精度。新的分段点通过比较相邻序列段的斜率实现,斜率差值越大,该点的状态改变越明显。实验证明该方法拟合误差小,有很好的实用性。     

Identifying the Activity Origin of a Cobalt Single-Atom Catalyst for Hydrogen Evolution Using Supervised Learning

Single-atom catalysts (SACs) have become the forefront of energy conversion studies, but unfortunately, the origin of their activity and the interpretation of the synchrotron spectrograms of these materials remain ambiguous. Here, systematic density functional theory computations reveal that the edge sites—zigzag and armchair—are responsible for the activity of the graphene-based Co (cobalt) SACs toward hydrogen evolution reaction (HER). Then, edge-rich (E)-Co single atoms (SAs) were rationally synthesized guided by theoretical results. Supervised learning techniques are applied to interpret the measured synchrotron spectrum of E-Co SAs. The obtained local environments of Co SAs, 65.49% of Co-4N-plane, 13.64% in Co-2N-armchair, and 20.86% in Co-2N-zigzag, are consistent with Athena fitting. Remarkably, E-Co SAs show even better HER electrocatalytic performance than commercial Pt/C at high current density. Using the joint effort of theoretical modeling, thorough characterization of the catalysts aided by supervised learning, and catalytic performance evaluations, this study not only uncovers the activity origin of Co SACs for HER but also lays the cornerstone for the rational design and structural analysis of nanocatalysts.     

Electrospinning from a convex needle with multiple jet toward better controlling and enhanced production rate

Multiple jet was successfully generated from a convex needle spinneret based on a conventional electrospinning setup. A convex channel was created in the front part of the needle to generate a limited free surface in the electrospinning process. A high flow rate was implemented with more than one polymer jet being produced, resulting in the production rate 2–3 times higher than conventional electrospinning. Finer nanofibers were produced from the convex needle when the applied voltage was 19 kV. The electric field intensity distribution of this spinneret was analyzed and compared with conventional needle spinneret by Comsol Multiphysics modeling. The research work has demonstrated that scaling up the production rate of nanofibers from needle-based free surface electrospinning is possible. It will benefit further development of electrospinning with enhanced throughput and more precise controlling. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48014.     

Magnetic properties of the mixed spinel Co1+x Si x Fe2−2x O4

The structural and magnetic properties of the mixed spinel Co_1+x Si _x Fe_2?2x O₄ system for 0·1≤x≤0·6 have been studied by means of X-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. X-ray intensity calculations indicate that Si⁴⁺ ions occupy only tetrahedral (A) sites replacing Fe³⁺ ions, and the added Co²⁺ ions substitute for (B) site Fe³⁺ ions. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at the A and B sites, forx≤0·3. The Mössbauer intensity data shows that Si possesses a preference for the A site of the spinel. The variation of the saturation magnetic moment per formula unit measured at 300 K with the Si content, is explained on the basis of Neel’s collinear spin ordering model forx≤0·3 which is supported by Mössbauer, and X-ray data. The Curie temperature decreases nearly linearly with increase of the Si content, forx=0·1–0·6.     

Particle-liquid mass transfer in three phase sparged reactor

Particle-liquid mass transfer in a three phase sparged reactor has been studied over a wide range of particle sizes, for the chum-turbulent regime. The particle-liquid Sherwood number has been correlated in the usual form with the Reynolds and Schmidt numbers. Use of the hindered particle settling velocity in the Reynolds number yields good agreement (±20%) with the present as well as most of the literature data. The proposed correlation also holds for power law non-Newtonian liquids when the effective viscosity is used.     

In vitro isolation and identification of human immunodeficiency virus (HIV) variants with reduced sensitivity to C-2 symmetrical inhibitors of HIV type 1 protease

Protease inhibitors are another class of compounds for treatment of human immunodeficiency virus (HIV)-caused disease. The emergence of resistance to the current anti-HIV drugs makes the determination of potential resistance to protease inhibitors imperative. Here we describe the isolation of an HIV type 1 (HIV-1) resistant to an HIV-protease inhibitor. Serial passage of HIV-1 (strain RF) in the presence of the inhibitor, [2-pyridylacetylisoleucylphenylalanyl-psi (CHOH)]2 (P9941), failed to yield a stock of virus with a resistance phenotype. However, variants of the virus with 6- to 8-fold reduced sensitivity to P9941 were selected by using a combination of plaque assay and endpoint titration. Genetic analysis and computer modeling of the variant proteases revealed a single change in the codon for amino acid 82 (Val-->Ala), which resulted in a protease with lower affinity and reduced sensitivity to this inhibitor and certain, but not all, related inhibitors.     

Counteracting HIV-1 protease drug resistance: structural analysis of mutant proteases complexed with XV638 and SD146, cyclic urea amides with broad specificities

The long-term therapeutic benefit of HIV antiretroviral therapy is still threatened by drug-resistant variants. Mutations in the S1 subsite of the protease are the primary cause for the loss of sensitivity toward many HIV protease inhibitors, including our first-generation cyclic urea-based inhibitors DMP323 and DMP450. We now report the structures of the three active-site mutant proteases V82F, I84V, and V82F/I84V in complex with XV638 and SD146, two P2 analogues of DMP323 that are 8-fold more potent against the wild type and are able to inhibit a broad panel of drug-resistant variants [Jadhav, P. K., et al. (1997) J. Med. Chem. 40, 181-191]. The increased efficacy of XV638 and SD146 is due primarily to an increase in P2-S2 interactions: 30-40% more van der Waals contacts and two to four additional hydrogen bonds. Furthermore, because these new interactions do not perturb other subsites in the protease, it appears that the large complementary surface areas of their P2 substituents compensate for the loss of P1-S1 interactions and reduce the probability of selecting for drug-resistant variants.     

The cultural origins of western depression

Focusing on the British cultural vocabulary of guilt, fatigue, energy, stress and depression; this paper argues that such vocabularies have their own unique histories and meanings; deeply embedded, in this instance, within "white British and western European" institutions. Predicated on a western epistemology, these constructs developed in response to prevailing concerns at different periods in western history; but are now assumed to be universal natural entities that await further scientific research and investigation. The cross-cultural validity of depression as a universal disorder is therefore dubious and needs an extensive re-examination.     

Development of In Situ Gelling Inserts by Lyophilization for Nasal Delivery of Terbutaline Sulfate

The aim of present study was development and in vitro characterization of sponge like, in situ gelling inserts of terbutaline sulfate by lyophilization for nasal administration to avoid first-pass metabolism. The inserts were investigated for thickness, water uptake, moisture absorption, drug content, in vitro drug release, histopathology, scanning electron microscopy analysis, and powder X-ray diffraction. The developed inserts were smooth in appearance with uniform thickness and drug content. The inserts exhibited satisfactory water uptake and extended drug release up to 10?h. Hence, inserts could be used as a viable alternative to improve therapeutic efficacy of terbutaline sulfate.