Method Of Temperature Decrease Research Articles

Catalytic Activity of Crystallographically Characterized Organic–Inorganic Hybrid Containing 1,5-Di-amino-pentane Tetrachloro Manganate with Perovskite Type Structure

Layered 2D organic–inorganic hybrid perovskite (OIHS) of the diammonium series, 1,5 di-aminepentane tetrachloro mangenate ([NH3–(CH2)5–NH3] MnCl4) was prepared by slow evaporation and reducing temperature method and characterized by single crystal X-ray diffraction analysis. Its structure consists of organic cation, [NH3(CH2)5NH3]+2 extended in a zigzag fashion and inorganic anion, [MnCl6]−2 where Mn2+ is coordinated by six Cl− ion in octahedral fashion. The organic and inorganic segments are alternately stacked along c-axis where inorganic layer is extended through corner-shared octahedra sandwiched by the di-aminopentane molecules. The layers (organic and inorganic) were connected to each other through N–H···Cl hydrogen bonds and van-der Waals interaction to build cation–anion–cation cohesion. The hybrid crystal had orthorhombic non-centrosymetric system having I212121 space group with unit cell parameters a = 7.1742(3) A, b = 7.3817(3) A, c = 23.9650(10) A, V = 1269.13 A3 and Z = 4. The hybrid exhibited excellent catalytic activity towards sulphide and alkene oxidation using aqueous H2O2 as an oxidant. OIHS of the diammonium series [NH3–(CH2)5–NH3] MnCl4; 1,5 di-aminepentane tetrachloro mangenate were prepared by slow evaporation and temperature decrease method, characterized by single crystal X-ray diffraction. This complex exhibits excellent catalytic activity towards sulphide oxidation and alkene oxidation using aqueous H2O2 as an oxidant.

The (NH4)H2PO4-KCl-KNO3-H2O system and growth of crystals of the [(NH4),K]H2PO4 solid solutions

On the basis of the known data on the (NH4)H2PO4-KCl-KNO3-H2O system, 65.0 × 9.0 × 8.0-mm3-large crystals of the [K0.75(NH4)0.25]H2PO4 solid solutions are grown on seed by the method of temperature decrease. It is shown that the 60.0 × 17.0 × 10.0 mm3-large KH2PO4 crystals contain impurities: 6.0 × 10−3 wt % Li and 0.1 wt % Na.

Viability and histologic structure of porcine valves after cryopreservation

Background Increased awareness of the limitations of current cardiac valve substitutes has generated a renewed interest in the use of allograft valves. The effects of currently used preservation techniques on the viability of the valve leaflets and the longevity of the implantation however remain controversial. The objective of this study is to analyze the influence of ischemic time, sterilization methods with or without fungicides, and storage procedures on the viability of the valve leaflets and on the histologic structure of the arterial wall, valve leaflet, and myocardium. Methods The tissue sources were hearts from 40 pigs with 1 hour of warm ischemic time. The aortic and pulmonary valves were dissected after 2 or 24 hours of cold ischemic time. They were stored in antibiotic solution for 20 hours at 4°C with or without an antifungal agent. The samples were cryopreserved using a programed temperature decrease method. After 1 week of storage in a liquid nitrogen tank, either in a gas or a liquid phase, the cardiac valves were slowly thawed and examined. Results Pulmonary valves showed greater viability than aortic valves. Decreased cellular viability was observed independent of cold ischemic time, treatment with amphotericin B, or the storage method used. Treatment with or without amphotericin B had no influence on cellular viability. Conversely it was observed that there was greater cellular viability among those valves stored in a liquid phase. As far as the histologic structure of the valve is concerned we did not observe any influence either in the treatment with amphotericin B or the storage method used although it was observed that reduction of the cold ischemic time minimized histologic injury. Conclusions Optimization of preservation methods may decrease the negative effects of cryopreservation on cell viability and histologic structure of the valve.

Growth of single crystals of NaH2PO4 (NaDP), NaH2PO4 · H2O (NaDP · H2O), and NaH2PO4 · 2H2O (NaDP · 2H2O) sodium dihydrogenphosphate based on the analysis of the Na2O-P2O5-H2O phase diagram

The crystallization conditions for the NaH2PO4, NaH2PO4 · H2O, and NaH2PO4 · 2H2O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na2O-P2O5-H2O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H3PO4 and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H2O, and NaDP · 2H2O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H2O single crystals are determined.

Growth of K(DxH1 − x )2PO4 single crystals from solutions in the K2O-P2O5-(D, H)2O system

Based on the analysis of the K2O-P2O5-D2O solubility phase diagram, the optimum conditions of KD2PO4 crystallization—the compositions of mother solutions and the temperature range of crystallization—in the KH2PO4-D2O system have been determined. The technique of K(DxH1 − x)2PO4 growth is developed. The DKDP single crystals with deuterium concentration up to 88 wt % are grown on DKDP seeds from KH2PO4 solutions in D2O by the method of temperature decrease.

In Situ Observation of KB5 Crystal Growth Under Purely Diffusion Gel Systems by Holographic Interferometry

KB5O8.4H2O (KB5) crystals have been grown in an agar-agar gel by temperature decrease method for simulating crystal growth in space. Nucleation and growth have been followed by interferometric holography. A concentration field surrounding the growing crystals was obtained and a Liesegang ring was observed. The pattern are visualized directly to reveal physical phenomena of purely diffusion crystal growth kinetics.

Growth and evaluation of large KDP Single Crystals for High–power harmonic generation by temperature decrease method

AbstractIn the growth of KDP single crystals by the temperature decrease method, the dimensions of equipment for the growth of the crystal whose dimensions are desired for type I and type II phase matching of SHG are discussed, where the (001) plate and (101) plate are used as seed crystals, respectively. It is shown that the equipment has the smallest dimensions in the growth of the crystals for type II with the seeds of the (101) plate. Then the large crystals are grown with the seeds of the (101) plate and their optical characteristics are described.

Growth of Large KDP Single Crystals for Laser Fusion

Large single crystals of potassium dihydrogen phosphate (KDP) have been grown by temperature decrease method for the purpose of a frequency converter in laser fusion. The article describes how large and transparent KDP crystals (about 5cm×5cm×9cm) have been obtained and discusses how to grow much morelarge crystals.

Autoradiography as a tool for studying iron segregation and related defects in KH 2PO 4 single crystals

A dihydrogen phosphate single crystal was grown by the temperature decrease method from a mother liquor doped with the 59Fe tracer. The iron segregation and the crystal perfection were respectively investigated by means of autoradiography and X-ray topography. The iron segregation in the prismatic facets could be related to growth parameters and a good correlation could be established between the X-ray topographs and the autoradiographs. The implication of the iron segregation in generating crystallographic defects and influencing growth kinetics was clearly recognized.

Single crystals of triglycine sulphate containing palladium

Single crystals of TGS doped with Pd2+ have been grown from aqueous solutions using the method of temperature decrease. It was found that the relative growth rate along thec-axis is not constant through the growth process being larger by more than an order of magnitude (in medium size crystals, ca. 30 g) than in pure TGS crystals. Investigation of the domain structure revealed that in the growth pyramids ¦110¦, the crystals are poled in one direction. The internal bias field in these growth pyramids was experimentally found to be of the order of 1 kV/cm. The high internal field excludes the possibility of spontaneous depoling and makes the Pd2+-doped TGS crystals suitable for pyroelectric applications.

A contribution to the study of the influence of impurities on the growth and some physical properties of TGS single crystals

AbstractSingle crystals of TGS doped with Ni2+, Cu2+ and Fe3+ have been prepared under identical conditions by the method of temperature decrease (below the phase transition point). Presentation of the influence of impurities on the development of individual crystal faces is based on goniometric measurements. The influence of impurities on the domain structure of TGS is documented by microphotographs of domain structures and by investigation of the variation with time of the average domain width. It is shown that the distribution of impurities (between the liquid and solid phases) is approximately proportional to the concentrations of metal glycino chelates in the solution. From the results concerning the influence of impurities on various physical properties follows that the degree to which the properties are affected depends not only on the impurity concentration but also on the specific intensity of their action which is due to variations in the binding forces in the structure of TGS.

A crystallizer for growing single crystals from a solution with very precise temperature control

The paper describes a crystallizer for growing single crystals from a solution by the method of temperature decrease; it is intended for studying the influence of growing conditions on the perfection of the crystals and for the actual growing of single crystals with minimum number of defects. The apparatus works in a temperature range of 30 to 80 °C, keeps the set temperature constant with an accuracy of ±0.002°C and automatically performs the temperature decrease at a constant rate of 0.002 °C/day to 5 °C/day. It provides for a wide variability in the volume of crystallization solution, in the stirring regime and in the method of fixing the seed. The design of the mechanical and electronic parts of the apparatus permits reliable operation even when the growing period lasts for several months. A special arrangement prevents a temperature shock when the crystal is removed from the crystallizer. Experience gained over a year of operation is also described.