Directing role of functional groups in selective generation of C-H center dot center dot center dot pi interactions: In situ cryo-crystallographic studies on benzyl derivatives

The in situ cryo-crystallization study of benzyl derivatives reveals that the molecular packing in these compounds is either through methylene (sp(3)) C-H center dot center dot center dot pi or aromatic (sp(2)) C-H center dot center dot center dot pi interactions depending on the level of acidity of the benzyl proton. These studies of low melting compounds bring out the subtle features of such weak interactions and point to the directional preferences depending on the nature (electron withdrawing, polarizability) of the neighbouring functional group.

An in situ EXAFS investigation of bimetallic Cu---Ni/γ-Al2O3 catalysts

In situ EXAFS investigations have been carried out on Ni/γ-Al2O3 and Cu---Ni/γ-Al2O3 catalysts with different metal loadings, and prepared by different procedures. As-prepared Ni/γ-Al2O3 on calcination gives NiO and NiAl2O4-like phases on the surface, the proportion of the latter increasing with the increase in calcination temperature; the proportion of the NiO-like phase, on the other hand, increases with the metal loading. The reducibility of Ni/γ-Al2O3 to give metallic Ni on the surface directly depends on the proportion of the NiO-like phase present before reduction. Co-impregnating with Cu suppresses the formation of the surface aluminate and thereby favours the reduction to metallic Ni. This conclusion is clearly substantiated by our studies of bimetallic catalysts containing varying Cu/Ni ratios and also those prepared by the two-stage impregnation procedure.

In-situ crystallization studies of gels in the ZrO2---SiO2 system

The in-situ investigation of amorphous gels is important in understanding the evolution of structures and the influence of environmental factors on crystallization. In this paper, the ZrO2---SiO2 system has been studied in-situ under electron beam heating. The study reveals that both the size of the ZrO2 particles and the presence of hydroxyl ions influence the nature of the crystalline phase of the ZrO2 particles formed.

A furnace for in situ synchrotron Laue diffraction and its application to studies of solid-state phase transformations

The design of a new microfurnace for use for Laue diffraction studies of solid-state transformations is described. The furnace operates in the temperature range 298-573 K with a thermal stability of about ± 0.1 K. The potential of the synchrotron-radiation Laue diffraction technique for studies of structural phase transitions is demonstrated. Experimental data on phase transitions in caesium periodate, potassium tetrachlorozincate and pentaerythritol are presented.

An electron spectroscopic study of the adsorption of nitrogen on a Ni/TiO2 catalyst prepared in situ in the spectrometer: evidence for dissociative adsorption in the strong-metal-support-interaction (SMSI) state

Nitrogen is dissociatively adsorbed on an annealed Ni/TiO2 surface just as on a Ti–Ni alloy surface while it is molecularly adsorbed on a Ni/Al2O3 surface.

An in situ electron microscope investigation of the icosahedral-to-decagonal quasicrystalline transformation in Al-20 at.% Mn

The solid-state transformation behaviour of the icosahedral phase in rapidly solidified Al-20 at.% Mn has been investigated by in situ heating experiments in the transmission electron microscope. As-rapidly-solidified Al-20 at.% Mn consists mainly of a dendritic icosahedral phase, with a small amount of interdendritic f.c.c. agr-Al. During subsequent heat treatment at temperatures below about 500°C, the dendritic icosahedral phase grows and consumes the interdendritic agr-Al. At about 500°C the decagonal phase nucleates near icosahedral dendrite and grain boundaries and then grows into the icosahedral matrix by lateral motion of ledges 10-20 nm high across facet planes normal to the twofold symmetry axes. At about 600°C the decagonal phase transforms into a crystalline phase. The present study suggests that solid-state decomposition of the icosahedral phase is the mechanism of decagonal phase formation in as-rapidly-solidified Al-Mn alloys.

Potassamide induced in situ alkylation of 5,6-dihydroisoquinolines: Structure of products

Potassamide induced in situ alkylation of 1-alkyl- 4-cyano-3-methoxy-5,6-dihydroisoquinolines (2a & 2b) with alkyl iodides (CH3I, CH3CH2I & cyclohexyl iodide) gave the 5-alkyl- and 5,9-dialkyl-5,6-dihydroisoquinolines (4–ad & 3a–e), isoquinoline derivatives, (5a–b) and diastereomeric mixture of 4- alkyl-1,2,3,4-tetrahydroisoquinolin-3(2H)-ones (6a–e & 6′a–e). Structures were assigned on the basis of spectral data [Mass, 1H & 13C NMR, 2D NOESY & HC-COLOC]. Amide induced in situ alkylation of compounds 3a and 4a with CH3I gave in almost quantitative yield the dimethylated compounds 3d and 3a respectively. While KNH2/liq.NH3 methylation of 1,2- dihydroisoquinoline, 1 with CH3I gave the mixture of compounds, 6a & 6′a and the isoquinoline derivative 5a, NaH/benzene reaction of 1 with CH3I gave exclusively 5a. N-methylation of the mixture of compounds 6a & 6′a with NaH/CH3I gave the methylated derivatives, 7 & 8. A suitable mechanism has been proposed for the formation of products.

Strong metal-support interaction in Ni/TiO2 catalysts: in situ EXAFS and related studies

In situ EXAFS and X-ray diffraction investigations of Ni/TiO2 catalysts show that NiTiO3 is formed as an intermediate during calcination of catalyst precursors prepared by the wet-impregnation method; the intermediate is not formed when ion-exchange method is used for the preparation. On hydrogen reduction, NiTiO3 gives rise to Ni particles dispersed in the TiO2(rutile) matrix. The occurrence of the anatase-rutile transformation of the TiO2 support, the formation and subsequent decomposition/reduction of NiTiO3 as well as the unique interface properties of the Ni particles are all factors of importance in giving rise to metal-support interaction. Active TiO2(anatase) prepared from gel route gives an additional species involving Ni3+.

Potassamide induced in situ benzylation of 5,6-dihydroisoquinolines: Structure of novel products

Potassamide induced in situ benzylation of 1-alkyl-4-cyano-3-methoxy-5,6-dihydroisoquinolines (1a-b) with benzyl iodide gave the 5-benzyl-, 5,9-dibenzyl- and 4,4-dibenzyl-5,6-dihydroisoquinolines (9a-b, 8a-b and 10a-b), isoquinoline derivatives (4a-b) and diastereomeric mixture of 4-benzyl-1,2,3,4-tetrahydroisoquinolin-3(2H)-ones (11a-b & 11'a-b). Structures were assigned on the basis of spectral data [Mass, H-1 & C-13 NMR, 2D NOESY]. A few reactions carried out to transform the diastereomeric mixture of compounds 11a and 11's to the spirobenzylisoquinoline system 7a isomeric with naturally occurring ochotensane system ga are discussed.

Potassamide induced in situ alkylation of 5,6-dihydroisoquinoline with allyl bromide and Michael acceptors

Potassamide induced in situ alkylation of 4-cyano-3-methoxy-1-methyl-5, 6-dihydroisoquinoline (1a) with allyl bromide gives the 5-allyl- and 5,9-diallyl-5,6-dihydroisoquinolines (1c and 1d), isoquinoline derivative 2 and 4-allyl-1, 2, 3, 4-tetrahydroisoquinolin-3(2H)-one (3a). However, potassamide induced in situ alkylation of In with buten-2-one, mesityl oxide and acrylonitrile results in the formation of only 5-alkylated 5,6-dihydroisoquinoline derivatives 1e-g along with fully aromatised compound 2.

Non-viral ex vivo hepatic gene transfer by in situ lipofection of liver and intraperitoneal transplantation of hepatocytes

Perfusion of liver with plasmid DNA-lipofectin complexes via the portal vein results in efficient accumulation of the vector in hepatocytes. Such hepatocytes, when administered intraperitoneally into a hepatectomized rat, repopulate the liver and express the transgene efficiently. This procedure obviates the need for large-scale hepatocyte culture for ex vivo gene transfer. Further, intraperitoneal transplantation is a simple and cost-effective strategy of introducing genetically modified hepatocytes into liver. Thus, in situ lipofection of liver and intraperitoneal transfer of hepatocytes can be developed into a novel method of non-viral ex vivo gene transfer technique that has applications in the treatment of metabolic disorders of liver and hepatic gene therapy.

Susceptibility of sperm chromatin to acid denaturation in situ: A study in endogenous FSH-deprived adult male bonnet monkeys (Macaca radiata)

Acid denaturation of calf thymus DNA in vitro followed by acridine orange (AO) binding induced a 112% increase in the emission of red, a 58% decrease in green, and a consequential decrease in the ratio of green:red fluorescences from 1.7 to 0.9. This metachromatic property of AO on binding to DNA following acid denaturation was utilized to study the susceptibility of normal and ovine follicle-stimulating hormone (oFSH) actively immunized bonnet monkey spermatozoa voided throughout the year. For analyses, the scattergram generated by the emission of red and green fluorescences by 10,000 AO-bound sperm from each semen sample was divided into 4 quadrant zones representing percentage cells fluorescing high green-low red (Q1), high green-high red (Q2), low green-low red (Q3) and low green-high red. (Q4). Normal monkey sperm obtained during the months of July-December exhibited 76, 13, and 11% cells in Q2, Q3, and Q4 quadrants, respectively. However, during January-June, when the females of the species are markedly subfertile, noncycling, and amenorrhoeic, the spermatozoa ejaculated by the male monkeys exhibited 38, 39, and 23% sperm in Q2, Q3, and Q4, respectively, the differences being highly significant (p < .01-.001). FSH deprivation induced significant shifts in fluorescence emissions, from respective controls, with 39, 33, and 28% cells in Q2, Q3, and Q4, respectively, during July-December, and 15, 48, and 37% sperm in Q2, Q3, and Q4 quadrants, respectively, during January-June. It is postulated that the altered kinetics of germ cell transformations and the deficient spermiogenesis observed earlier following FSH deprivation in these monkeys may have induced the enhanced susceptibility to acid denaturation in sperm.

Synthesis of single-walled carbon nanotubes using binary (Fe, Co, Ni) alloy nanoparticles prepared in situ by the reduction of oxide solid solutions

Passing a H-2-CH4 mixture over oxide spinels containing two transition elements as in Mg0.8MyMz'Al2O4 (M, M' = Fe, Co or Ni, y + z = 0.2) at 1070 degrees C produces small alloy nanoparticles which enable the formation of carbon nanotubes. Surface area measurements are found to be useful for assessing the yield and quality of the nanotubes. Good-quality single-walled nanotubes (SWNTs) have been obtained in high yields with the FeCo alloy nanoparticles, as evidenced by transmission electron microscope images and surface area measurements. The diameter of the SWNTs is in the 0.8-5 nm range, and the multiwalled nanotubes, found occasionally, possess very few graphite layers. (C) 1999 Elsevier Science B.V. All rights reserved.

In-situ power monitoring scheme and its application in dynamic voltage and threshold scaling for digital CMOS integrated circuits

An in-situ power monitoring technique for Dynamic Voltage and Threshold scaling (DVTS) systems is proposed which measures total power consumed by load circuit using sleep transistor acting as power sensor. Design details of power monitor are examined using simulation framework in UMC 90nm CMOS process. Experimental results of test chip fabricated in AMS 0.35µm CMOS process are presented. The test chip has variable activity between 0.05 and 0.5 and has PMOS VTH control through nWell contact. Maximum resolution obtained from power monitor is 0.25mV. Overhead of power monitor in terms of its power consumption is 0.244 mW (2.2% of total power of load circuit). Lastly, power monitor is used to demonstrate closed loop DVTS system. DVTS algorithm shows 46.3% power savings using in-situ power monitor.

In situ synthesis of Al2O3-ZrO2-SiCW ceramic matrix composites by carbothermal reduction of natural silicates

In situ formations of Al2O3 + ZrO2 + SiCW ternary composite powders have been obtained by carbothermal reduction of a mixture of Sillimanite. Kaolin and Zircon using two different carbon sources. Products formed were mixtures of alumina and zirconia along with silicon carbide in the form of whiskers. The effects of composition of the reactants, the role of fineness of the starting precursors and the nature of the carbon Source on the final product powder obtained are presented. XRD and SEM analyses indicate complete reaction of the precursors to yield Al2O3 + ZrO2 + SiCW as product powders, with the SiC having whisker morphology. It is also seen that zirconia could be stabilised to some extent in the tetragonal form without any stabilising agent by tailoring the starting materials and their composition. (C) 2002 Published by Elsevier Science B.V.