High Dielectric Permittivity in AFe1/2_{1 / 2}B1/2_{1 / 2}O3_{3} Nonferroelectric Perovskite Ceramics (A - Ba, Sr, Ca; B - Nb, Ta, Sb)

AFe$_{1 / 2}$B$_{1 / 2}$O$_{3}$(A- Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were synthesized and temperature dependencies of the dielectric permittivity were measured at different frequencies. The experimental data obtained show very high values of the dielectric permittivity in a wide temperature interval that is inherent to so-called high-k materials. The analyses of these data establish a Maxwell-Wagner mechanism as a main source for the phenomenon observed.Comment: 6 pages, 7 figure

Investigation of conformational equilibrium in a series of some 1,3-dioxa-2-phosphorinanes

1. The IR spectra of certain 1,3-dioxa-2-phosphorinanes were studied under conditions of various polarities of the medium and temperatures, and it was shown that 2,4-dimethy1-2-thiono- and 2-chloro-2-thiono-1,3-dioxa-2-phosphorinanes are characterized by stabilization of one conformational form, while for 2-methyl-2-thiono-1,3-dioxa-2-phosphorinane a dynamic equilibrium of two conformers is realized with an appreciable dependence of their amounts on the dielectric permeability of the medium. 2. An equilibrium of three conformers was detected for 2-chloro-4-methyl-2-thiono-1,3-dioxa-2-phosphorinane. It was hypothesized that, together with the "chair" conformation of the ring with axial and equatorial positions of the P=Sbond, the conformer with an equatorial arrangement of the P=S bond and a "boat" form of the ring participates in the equilibrium. © 1973 Consultants Bureau

Perspectives of Single-Wall Carbon Nanotube Production in the Arc Discharge Process

Single-wall carbon nanotubes (SWNTs) promise wide applications in many technical fields. As a result purified SWNT material is sold now on the West market at more than $1000 per 1 gram. Thus developing an effective technology for SWNTs production rises to a very important scientific problem. The perspectives of three existing methods providing raw material in the technology of SWNT production have been analyzed. They are i) pulsed laser evaporation of graphite/metal composites, ii) evaporation of graphite electrodes with metal content in the arc discharge process, and iii) catalytic decomposition of the mixture of CO and metal carbonyl catalyst precursor. The observed dynamics of SWNT market points to replacing the laser method of SWNTs production by the arc process. The conclusion has been made that the technology based on the arc process will be the major one for the fabrication of purified SWNTs at least for the next five years. A reliable estimation of a low price limit of SWNTs was derived from a comparison of two technologies based on the arc discharge process: the first one is the production of SWNTs and the second one is the production of a fullerene mixture С60 + С70. The main conclusion was made that the price of purified SWNTs should always be more by 2-3 times the price of fullerene mixture. The parameters of a lab-scale technology for the production of purified SWNTs are listed. A large-scale application of the developed technology is expected to reduce the price of purified SWNTs by approximately ten times. The methods now employed for the characterization of products containing SWNTs are briefly observed. It is concluded that electron microscopy, thermogravimetric analysis, absorption and Raman spectroscopy, measurement of the specific surface aria, optical microscopy - each in separation is not enough for extensive characterization of a sample containing SWNTs, and all these methods should be used together

Study of the spatial structure of the chloroanhydride of dichloromethylphosphonic acid by a combination of various physical methods

1. In the liquid state, in solution, and in one of its crystalline modifications, the chlorohydrate of dichloromethylphosphonic acid exists as a mixture of two nonrotating isomers of Cs and C1 symmetries (gauche-gauche and gauche-trans orientation of the two CHCl2 group chlorines with respect to the P=O bond). The conformers are individually stabilized in the other crystalline modifications. 2. It is assumed that weak intramolecular bonds of the C-H...O=P type play a role in the stabilizing the conformer with the chlorine in the gauche-trans orientation. © 1977 Plenum Publishing Corporation

The hydrogen bond in dithioacids of pentavalent phosphorus - Communication 2. Intermolecular h-bonds and the conformation of molecules of dithioacids

1. The IR spectra of a number of phosphinic, phosphonic, and phosphoric dithioacids and their solutions in CCl4 were studied in the region of the valence vibrations of the SH group. 2. Molecules of dithioacids in dilute solutions exist primarily in conformations with an intramolecular hydrogen bond SH...S=P. 3. In the investigated compounds associates are formed through a H-bond of the sulfhydryl group with the thiophosphoryl group and the oxygen of the substituent (in the case of phosphonic and phosphoric dithioacids). 4. The spectral characteristics of the H-complexes formed were determined, and the enthalpies of formation of hydrogen bonds were calculated. © 1973 Consultants Bureau

Hypocrates is a genetically encoded fluorescent biosensor for (pseudo)hypohalous acids and their derivatives

The lack of tools to monitor the dynamics of (pseudo)hypohalous acids in live cells and tissues hinders a better understanding of inflammatory processes. Here we present a fluorescent genetically encoded biosensor, Hypocrates, for the visualization of (pseudo)hypohalous acids and their derivatives. Hypocrates consists of a circularly permuted yellow fluorescent protein integrated into the structure of the transcription repressor NemR from Escherichia coli. We show that Hypocrates is ratiometric, reversible, and responds to its analytes in the 106 M-1s-1 range. Solving the Hypocrates X-ray structure provided insights into its sensing mechanism, allowing determination of the spatial organization in this circularly permuted fluorescent protein-based redox probe. We exemplify its applicability by imaging hypohalous stress in bacteria phagocytosed by primary neutrophils. Finally, we demonstrate that Hypocrates can be utilized in combination with HyPerRed for the simultaneous visualization of (pseudo)hypohalous acids and hydrogen peroxide dynamics in a zebrafish tail fin injury model