BOUND STATES FOR A CLASS OF QUASILINEAR SCALAR FIELD EQUATIONS WITH POTENTIALS VANISHING AT INFINITYDedicated to Professor Constantine M. Dafermos on the occasion of his 70th birthday

We study the existence and non-existence of bound states(i.e.,solutions in W1,p(RN)) for a class of quasilinear scalar field equations of the form-△pu+V(x)|u|p-2 u=a(x)|u|q-2 u,x∈RN,1相似文献   

Ag60纳米颗粒[{Cl@Ag12}@Ag48(dppm)12]的结构(其中dppm=双(二苯基膦基)甲烷

本文合成一种新的双膦连接Ag₆₀纳米团簇[{Cl@Ag₁₂}@Ag₄₈(dppm)₁₂],并通过X射线晶体学进行表征. 二十面体的银处于核心位置,里面是中心氯化物组成,外面有48 个银原子/离子的包裹,顶端是12个双(二苯基膦基)甲烷(dppm)配体. 同时利用密度泛函理论对阳离子[{Cl@Ag₁₂}@Ag₄₈(dppm)₁₂]⁺进行计算,以确定该结构是否对应于核心数n=58的超原子. DFT计算的优化结构与X射线一致,但是HOMO-LUMO的能差并不能保证其超级稳定性.     

Emerging nanocomposite biomaterials as biomedical adsorbents: an overview

Abstract

Biomedicine and pharmacy identify highly important scientific fields within the present time. However, increased advancements in these sciences have influenced the identification of increased levels in environmental degradation through pollution. Pharmaceutical production has influenced increased scientific and public concern regarding the increasing rate of pollution attributed to high levels of toxicological properties within the products. Pharmaceutical compounds are not fully removed through the integration of wastewater treatment plants (WWTP). This renders pharmaceutical compounds, municipal effluents together with hospitals as the major culprits in the development of the majority of the sources that enhance environmental degradation. A wide range of the compounds have been the identified within WWTP effluents, surface water together with ground and drinking water on a global scale. All above has influenced the research development in technological field developing new ways for efficient removal of pharmaceuticals from wastewater produced from the pharmaceuticals or biomedical industries. This situation may be altered through the utilization of adsorbents. Therefore more studies have been published investigating the use of nanocomposite biomaterials for removing the pharmaceutical compounds existing in biomedical effluents.     

Gas-chromatographische Multielementanalyse mit einfachen und fluorierten Di?thyldithiocarbamaten

Zusammenfassung Zur anorganischen Multielementanalyse ist die Gas-Chromatographie von Diäthyldithiocarbamaten geeignet. Mit einem FID können bereits Kationen im 0,6–0,06 ppm-Bereich nach Ausschütteln der wäßrigen Lösungen bestimmt werden. Di(trifluoräthyl)dithiocarbamate zeigen noch höhere Flüchtigkeiten. Eigenschaften und gas-chromatographisches Verhalten einiger dieser Chelate werden angegeben.Die Untersuchungen wurden in dankenswerter Weise durch Sachmittel der Deutschen Forschungsgemeinschaft und des Verbands der Chemischen Industrie unterstützt. Für die Gewährung eines Promotionsstipendiums sei der Friedrich-Ebert-Stiftung ebenfalls gedankt.     

Synthesis, characterization, and study of octanuclear iron-oxo clusters containing a redox-active Fe4O4-cubane core

A one-pot synthetic procedure yields the octanuclear Fe(III) complexes Fe(8)(micro(4-)O)(4)(micro-pz(*))(12)X(40, where X = Cl and pz(*) = pyrazolate anion (pz = C(3)H(3)N(2)-) (1), 4-Cl-pz (2), and 4-Me-pz (3) or X = Br and pz(*) = pz (4). The crystal structures of complexes 1-4, determined by X-ray diffraction, show an Fe(4)O(4)-cubane core encapsulated in a shell composed of four interwoven Fe(micro-pz(*))(3)X units. Complexes 1-4 have been characterized by 1H NMR, infrared, and Raman spectroscopies. M?ssbauer spectroscopic analysis distinguishes the cubane and outer Fe(III) centers by their different isomer shift and quadrupole splitting values. Electrochemical analyses by cyclic voltammetry show four consecutive, closely spaced, reversible reduction processes for each of the four complexes. Magnetic susceptibility studies, corroborated by density functional theory calculations, reveal weak antiferromagnetic coupling among the four cubane Fe centers and strong antiferromagnetic coupling between cubane and outer Fe atoms of 1. The structural similarity between the antiferromagnetic Fe(8)(micro(4-)O)(4) core of 1-4 and the antiferromagnetic units contained in the minerals ferrihydrite and maghemite is demonstrated by X-ray and M?ssbauer data.     

Synthetic membranes (vesicles) in inorganic ion analysis: a review

Vesicles are structures of amphiphile molecules occurring through a self-aggregation process at the molecular or nano scale level with a large structural variety and diverse properties providing a reaction environment for chemical reactions that resembles that of natural systems. Their high versatility and recognized utility in various applications have triggered a interdisciplinary scientific endeavor over their formation, characterization and potential applications with impressive results. However, in the vastness of applications surrounding vesicular structures, their utility in analytical chemistry has only received minor attention. Notwithstanding, studies demonstrating their potential as colorimetric or fluorescence sensors, extraction solvents of inorganic ions or their chelates and stationary phase modifiers in liquid chromatography have appeared. To this end, this article aims to present for the first time the analytical chemistry aspects behind the use of vesicle media with special emphasis on the detection and determination of inorganic ions and encourage further research on this promising field of analytical science.     

Modelling Affinity Chromatography

Abstract

Affinity chromatography plays a significant role in the separation and purification of biologically active macromolecules in laboratory and large-scale applications. There is a need for models which could be used to predict accurately the dynamic behavior of affinity chromatography separations, in order to permit the design, optimization, control, and process scale-up of affinity chromatography systems. Furthermore, the construction and use of such models will contribute to a better fundamental understanding of the physicochemical and biospecific mechanisms involved in affinity chromatography processes. The parameters of the models should be obtainable by using information from a small number of experiments.

This work reviews the modeling of affinity chromatography, and presents general models that could be used to describe the dynamic behavior of the adsorption, wash, and elution stages of affinity chromatography systems. Certain model structures, modeling approaches and operational strategies for systems having porous or nonporous adsorbent particles are also suggested, and experiments are proposed whose data are necessary for parameter estimation and model discrimination studies in affinity chromatography.

Particular emphasis is given to :he modeling of the intrinsic mechanisms of intraparticle diffusion, adsorption, and desorption, because the intrinsic mechanisms are normally independent of the mode of operation (i.e., batch, fixed bed, fluidized bed, continuous countercurrent, or others).     

Generation of the [NiFe] Hydrogenase Active Site (Sulfur's the One!)

Abstract

Chemical and biochemical methods were used to unravel the unprecedented pathway by which the CN ligands of iron in [NiFe] hydrogenase are introduced. Carbamoyl phosphate is the one carbon precursor of these ligands, and reactions involving a protein cysteinyl sulfur are key for processing this precursor into CN ligands.     

Surfactant-enhanced liquid-liquid microextraction coupled to micro-solid phase extraction onto highly hydrophobic magnetic nanoparticles

We are presenting a simplified alternative method for dispersive liquid-liquid microextraction (DLLME) by resorting to the use of surfactants as emulsifiers and micro solid-phase extraction (μ-SPE). In this combined procedure, DLLME of hydrophobic components is initially accomplished in a mixed micellar/microemulsion extractant phase that is prepared by rapidly mixing a non-ionic surfactant and 1-octanol in aqueous medium. Then, and in contrast to classic DLLME, the extractant phase is collected by highly hydrophobic polysiloxane-coated core-shell Fe₂O₃@C magnetic nanoparticles. Hence, the sample components are the target analyte in the DLLME which, in turn, becomes the target analyte of the μ-SPE step. This 2-step approach represents a new and simple DLLME procedure that lacks tedious steps such as centrifugation, thawing, or delicate collection of the extractant phase. As a result, the analytical process is accelerated and the volume of the collected phase does not depend on the volume of the extraction solvent. The method was applied to extract cadmium in the form of its pyrrolidine dithiocarbamate chelate from spiked water samples prior to its determination by FAAS. Detection limits were brought down to the low μg L^?1 levels by preconcentrating 10 mL samples with satisfactory recoveries (96.0–108.0 %).

Protein adsorption in porous adsorbent particles: A multiscale modeling study on inner radial humps in the concentration profiles of adsorbed protein induced by nonuniform ligand density distributions

Recently published results determined from molecular dynamics (MD) modeling and simulation studies have shown that the spatial distribution of the density of immobilized charged ligands in ion‐exchange porous adsorbent particles is most likely nonuniform and the adsorbent particles also exhibit local nonelectroneutrality. In this work, the functional forms of the nonuniform spatial distributions of the density of the immobilized ligands in four different porous adsorbent media that were determined by MD studies were employed in a macroscopic continuum model describing the transport and adsorption of a single protein in the porous particles of the four different adsorbent media. The results clearly show that inner radial humps in the concentration profiles of the adsorbed protein can occur when the spatial distribution of the density of the immobilized ligands in the porous adsorbent particles is nonuniform and also has local maxima or minima along the radial direction in the particle. The results also indicate that the rate at which the equilibrium condition is approached depends significantly on the functional form of the spatial distribution of the density of the immobilized ligands. When adsorption equilibrium has been reached, the concentration profile of the adsorbed protein exhibits the shape of the spatial distribution of the density of the immobilized ligands. The results suggest that the technique of confocal scanning laser microscopy could be used to measure the concentration profile of an adsorbed protein at equilibrium and this measurement could provide the spatial distribution of the density of the immobilized ligands, and such measurements could also be used for quality control of the adsorbent medium. The results in this work have also implications in the modeling, design, analysis, and quality control of systems involving biocatalysis. Furthermore, the results clearly indicate that it is very important to study the dynamic behavior of an adsorption system having a nonuniform spatial distribution in the density of the immobilized charged ligands and where (i) both monovalent and multivalent interactions between the single charged adsorbate and the immobilized charged ligands occur and (ii) the values of the pH and ionic strength are such that the electrophoretic effects are active.