Response of a system of strongly interacting particles to an inhomogeneous external field

We show that a system of N strongly interacting quantum particles in a parabolic confining potential can be unstable under the action of a time-dependent quadrupole external field. The instability leads to the generation or amplification of dipole oscillations. Parameters of the instability are independent of the number of particles and the inter-particle interaction.     

THE PRECURSOR OF INSTABILITY FOR NONLINEAR SYSTEMS AND ITS APPLICATION TO EARTHQUAKE PREDICTION

By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake prediction, we adopt the periodical change of the stress in crust caused by the tide-generating force as the loading and unloading. If we can measure the ratio of the response (such as crust deformation, gravity and seismicity) during the loading period to that during the unloading period, this parameter must contain some characteristic information about the seismogenic process.With nine earthquakes (M≥7) data that occurred in Chinese mainland during 1970-1988, we take the sum of square root o?energy of small earthquakes, which is called the released strain by Benioff, as the response to the tidal loading and unloading. We find that the response ratios of seven earthquakes increase obviously before the main earthquakes.     

A reference‐free stockholder partitioning method based on the force on electrons

We argue that when one divides a molecular property into atom‐in‐a‐molecule contributions, one should perform the division based on the property density of the quantity being partitioned. This is opposition to the normal approach, where the electron density is given a privileged role in defining the properties of atoms‐in‐a‐molecule. Because partitioning each molecular property based on its own property density is inconvenient, we design a reference‐free approach that does not (directly) refer atomic property densities. Specifically, we propose a stockholder partitioning method based on relative influence of a molecule's atomic nuclei on the electrons at a given point in space. The resulting method does not depend on an “arbitrary” choice of reference atoms and it has some favorable properties, including the fact that all of the electron density at an atomic nucleus is assigned to that nucleus and the fact all the atoms in a molecule decay at a uniform asymptotic rate. Unfortunately, the resulting model is not easily applied to spatially degenerate ground states. Furthermore, the practical realizations of this strategy that we tried here gave disappointing numerical results. © 2017 Wiley Periodicals, Inc.     

Mechanism of electrooptic switching time enhancement in ferroelectric liquid crystal/gold nanoparticles dispersion

It is well established that incorporation of nanoparticles (NPs) in the structure of ferroelectric liquid crystals (FLCs) leads to a decrease in their electrooptic response time. Several approaches have been suggested to explain this effect (decrease in rotational viscosity of FLCs, ions enhanced localised electric field, dipole–dipole interaction among NPs and FLC molecules, FLC ordering). In this article, we will report the role of the voltage divider formed by the structural elements of a FLC cell based on ferroelectric liquid crystal/gold nanospheres (FLC/GNSs) dispersion in enhancement of the switching time. Using the impedance spectroscopic measurements, it was demonstrated that the dispersing of GNSs leads to the increase in the voltage drop on FLC/GNSs layer in comparison with the pristine FLC one. Consequently, the electrooptic response time of the FLC/GNSs cell is faster than that of the pristine one. However, the rotational viscosity of the FLC does not depend on the presence of the GNSs.     

Design of optimum response surface experiments for the adsorption of acetic,butyric, and oxalic acids on Amberlyst A21

In this study the adsorption equilibria of acetic, butyric, and oxalic acids onto Amberlyst A21 were investigated experimentally at 25°C. The process was optimized using response surface methodology (RSM). The time to reach the equilibrium state, effects of adsorbent amount, and initial acid concentrations on adsorption efficiency were investigated. Freundlich, Langmuir, and Temkin isotherms were applied to experimental data. The Freundlich isotherm revealed better results than the others. In addition to the main aim of this research, a statistical/mathematical approach – RSM – was utilized to simulate and determine the optimum conditions of acetic, butyric, and oxalic acids removal by Amberlyst A21 using three selected parameters (adsorbent dose, initial dye concentration, and type of acids). The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA). The optimum acid concentration, amount of adsorbent, type of acid, and removal of acid (%) were found by desirability function to be 0.199?mol/L, 1.999?g, butyric acid, and 84.537%, respectively.     

Application of response surface methodology for optimization of the stability of asphaltene particles in crude oil by TiO2/SiO2 nanofluids under static and dynamic conditions

In this work, the onset of asphaltene flocculation for an Iranian crude oil by titration of samples with heptane in the presence and absence of the TiO₂/SiO₂ nanofluids was obtained by Near-IR spectroscopy. Nanoparticles and nanocomposites were characterized by BET, FESEM, EDX, XRD, and XRF analysis. Modeling and optimization of inhibition of asphaltene flocculation process by TiO₂/SiO₂ nanofluids were conducted by response surface methodology (RSM). Under optimum conditions (nanocomposite composition = 0.04 wt% (80%TiO₂:20%SiO₂), salinity = 4.01 wt%, and pH = 3.42), the onset point increased. For nanofluids stability analysis, the optimum nanofluid was compared with the two other nanofluids (SiO₂ and TiO₂) by visual observation method. The results indicated that high stability and surface area of the 80%TiO₂ nanocomposites increase asphaltene adsorption on the particles surface that subsequently increases the onset point. In addition, the optimum nanofluid performance on the carbonate rocks was evaluated by contact angle and core flooding experiments. The 80% TiO₂ nanofluid changed the wettability of carbonate rocks from strongly oil-wet to strongly water-wet condition and also decreased the residual oil saturation and enhanced the oil recovery with an increase in the recovery factor of about 15%.     

A Methylthio‐Functionalized‐MOF Photocatalyst with High Performance for Visible‐Light‐Driven H2 Evolution

Recently, the emergence of photoactive metal–organic frameworks (MOFs) has given great prospects for their applications as photocatalytic materials in visible‐light‐driven hydrogen evolution. Herein, a highly photoactive visible‐light‐driven material for H₂ evolution was prepared by introducing methylthio terephthalate into a MOF lattice via solvent‐assisted ligand‐exchange method. Accordingly, a first methylthio‐functionalized porous MOF decorated with Pt co‐catalyst for efficient photocatalytic H₂ evolution was achieved, which exhibited a high quantum yield (8.90 %) at 420 nm by use sacrificial triethanolamine. This hybrid material exhibited perfect H₂ production rate as high as 3814.0 μmol g^?1 h^?1, which even is one order of magnitude higher than that of the state‐of‐the‐art Pt/MOF photocatalyst derived from aminoterephthalate.     

Biotransformation of soy flour isoflavones by Aspergillus niger NRRL 3122 β-glucosidase enzyme

β-glucosidase enzyme produced from Aspergillus niger NRRL 3122 has been partially purified and characterised. Its molecular weight was 180 KDa. The optimal pH and temperature were 3.98 and 55 °C, respectively. It promoted the hydrolysis of soy flour isoflavone glycosides to their aglycone. Two-level Plackett–Burman design was applied and effective variables for genistein production were determined. Reaction time had a significant positive effect, and pH had a significant negative effect. They were further evaluated using Box–Behnken model. Accordingly, the optimal combination of the major reaction affecting factors was reaction time, 5 h and pH, 4. The concentration of genistein increased by 11.73 folds using this optimal combination. The antioxidant activity of the non-biotransformed and biotransformed soy flour extracts was determined by DPPH method. It was found that biotransformation increased the antioxidant activity by four folds.     

Response surface design as a powerful tool for the development of environmentally benign HPLC methods for the determination of two antihypertensive combinations: Greenness assessment by two green analytical chemistry evaluation tools

Interest in implementing green chemistry principles in analytical chemistry has grown dramatically in the past few years. The solvents used have the major influence on the greenness of the method. Most conventional high‐performance liquid chromatography methods employed utilize solvents that are “hazardous for the environment”. In the present study, two‐factor three‐level response surface design was exploited to develop eco‐friendly chromatographic methods for two different mixtures. The first one was atorvastatin and amlodipine and the second one was amlodipine, perindopril, and indapamide. As it is nontoxic to the environment, ethanol was used as the organic modifier in the mobile phase. The separation of the first mixture was attained using phosphate buffer (pH 7)/ethanol (42:58 v/v), and the second mixture was fully resolved using phosphate buffer (pH 5)/ethanol (40:60 v/v). The use of high‐performance liquid chromatography allows excellent resolution in a short run time, hence, less waste was produced. The greenness of the developed methods was assessed by two evaluation tools, namely, National Environmental Methods Index and analytical eco‐scale, and found to be excellent green analytical methods. Moreover, the developed methods were compared with other reported methods regarding accuracy and greenness and were found to be perfect alternatives to reported methods for separation and quantification of the mixtures.     

Polypeptides with High Zwitterion Density for Safe and Effective Therapeutics

The commonly used “stealth material” poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti‐PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high‐dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase–PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase–PEG conjugates.