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In this work we report on the aerosol synthesis of photocatalytic powder nanostructures of core-shell Si-ZnS particles. Submicron Si particles were prepared in the form of an aqueous dispersion by disintegration of the semiconductor-grade silicon powder in the cavitation Water Jet Mill disintegrator. Adding zinc acetate converted aqueous dispersion medium into a solution of Zn(Ac)2in various concentrations. The thus prepared liquid dispersion was then transformed into aerosol microdroplets with an average size of 3.5 microns in the Omron NE-U17 nebulizer. These were subsequently transported by flowing gas into the vigorously stirred aqueous solution of sodium sulfide. At impact of these aerosol “microreactors” the two liquid reactants produce zinc sulphide. Due to heterogeneous nucleation the insoluble phase of ZnS is precipitated on the phase surface of the silicon carrier particles contained in the microdroplets. As the amount of Zn(Ac)2in a microdroplet is limited, so is the extent of the precipitation reaction and the thickness of the container can be regulated by Zn(Ac)2concentration in the liquid dispersion. The obtained liquid dispersion of core-shell particles of Si-ZnS was dryed by controlled vacuum sublimation and stabilized in the form of lamellar nanoaggregates with a relatively high surface area. The final material enables easy handling and shows significantly higher photocatalytic activity than TiO2Evonik P25 standard.

Molecular dynamics simulations of Ribonuclease Sa yield properties that are compared to data extracted from crystallography and NMR. Similar distributions of static/average as well as dynamic properties are found. The pattern of fluctuations in the backbone torsions as revealed by order parameters is conserved between different techniques. The character of concerted displacements between the different techniques is qualitatively similar. The extent of variation of conformation during the simulations is much higher than is observed by any other technique and is confined to a subspace that differs from that describing the major variation in the observed structures. The functional motions deduced are composed of a highly mobile His85 coupled to a less mobile Glu54 as forming the catalytic diad, in concert with the motion of loops lining the active site. Two of these loops have been found to exist in three distinct conformational substates: the C-terminal part of the α−β2 loop from NMR and the β2−β3 loop in the simulations. The simulations present a view of the dynamics of Rnase Sa that is different but complementary to NMR and X-ray, and together the data reveal a more comprehensive picture of the protein's “real” dynamics than from any method alone.

The dynamics of the enzyme ribonuclease-Sa as a function of temperature has been explored through a series of molecular dynamics simulations. Long-range expansion and short-range contraction of the structure lends the protein a solidlike core and a liquidlike exterior as the temperature is increased. The trend in magnitudes of fluctuations of atoms are biphasic across the 150−200K region and are increasingly non-Brownian in character as the temperature is increased. The mobility of solvent molecules is much higher than the protein atoms, even though the solvent mobility displays behavior which is dampened relative to behavior in bulk water. The region of the active site that binds the base of the nucleotide ligand shows low plasticity relative to regions that interact with the sugar−phosphate part. This suggests that the enzyme is preorganized dynamically:  regions with low plasticity confer specificity while the more flexible regions have the fluidity to facilitate energetically inexpensive conformational rearrangements such as those required to achieve the transition state. Below 200K the dynamics are characterized by low amplitude harmonic motions that involve concerted motions that involve small groups of atoms. Above 200K, the dynamics are dominated by large amplitude anharmonic motions which involve long-range correlations including breathing and twisting modes such as those required for ligand binding/release/activation. The temperature-dependent transition in the character of the dynamics at ~200K reflects the ease with which the system hops among barriers giving rise to enhanced diffusion across phase space. This enhanced plasticity is catalyzed by a significant increase in the mobility of solvent water molecules and the associated increase in frequency of different hydrogen bond arrangements and may facilitate the onset of significantly enhanced functionality above the transition temperature.

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An explicit expression describing the kinetics of distribution and, in some cases, biological activity in drugs and other anthropogenic chemicals in a four-compartment system consisting of a catenary chain of alternating aqueous and lipoid phases is derived. Substitution of the transport rate parameters by their appropriate relations to the reference partition coefficient converts the kinetic equations into the quantitative structure-time-activity relationship (QSTAR) or its fixed-time equivalent, QSAR. The resulting expression describes satisfactorily the published data on antibacterial activity ofn-alkyl amines as a function of their hydrophobicity. The hydrophobicity-activity profile consists of two or three smoothly connected linear parts. The model can be used in drug design, pharmacokinetics, and toxicology for description of the distribution of compounds in simple biosystems and in environmental sciences to predict the fate and effects of anthropogenic chemicals in ecological systems.

The serum levels of folic acid and vitamin B12were estimated in 3 groups of subjects: Group 1 consisted of 59 elderly patients screened from 152 consecutive hospital admissions from homes for the aged and from a geriatric center; Group 2 consisted of 51 geriatric patients admitted to the hospital from their own homes; and Group 3 (controls) consisted of 100 younger healthy subjects who were not in the hospital. Medication with drugs known to interfere with the biologic assay of these vitamins was the chief reason for eliminating all but 59 of the 152 patients tested originally for Group 1.