Ultrasonic propagation through aqueous solutions of acetates

Using the pulse method in the range of 2 to 26Mc's the ultrasonic absorption, velocity and the adiabatic compressibility have been studied in eleven aqueous acetate solutions up to a concentration of 1 mole/litre. The substances studied are the acetates of lithium, sodium, potassium, ammonium, magnesium, calcium, strontium, barium, zinc, cadmium and lead. Absorption in mercuric acetate has been studied only at 2 and 6 Mc/s. Two regions of relaxation are noticed, one below 10 Mc/s and the other between 10 and 26 Mc/s. The first relaxation is ascribed to the dissociation reaction of the salt and the second one to the monomerdimer reaction of the acetic acid formed by the hydrolysis of the salt in water.

Cloning, expression, purification, crystallization and preliminary X-ray crystallographic study of the putative SAICAR synthetase (PH0239) from Pyrococcus horikoshii OT3

The study of proteins involved in de novo biosynthesis of purine nucleotides is central in the development of antibiotics and anticancer drugs. In view of this, a protein from the hyperthermophile Pyrococcus horikoshii OT3 was isolated, purified and crystallized using the microbatch method. Its primary structure was found to be similar to that of SAICAR synthetase, which catalyses the seventh step of de novo purine biosynthesis. A diffraction-quality crystal was obtained using Hampton Research Crystal Screen II condition No. 34, consisting of 0.05 M cadmium sulfate hydrate, 0.1 M HEPES buffer pH 7.5 and 1.0 M sodium acetate trihydrate, with 40%(v/v) 1,4-butanediol as an additive. The crystal belonged to space group P3(1), with unit-cell parameters a = b = 95.62, c = 149.13 angstrom. Assuming the presence of a hexamer in the asymmetric unit resulted in a Matthews coefficient (V-M) of 2.3 angstrom(3) Da(-1), corresponding to a solvent content of about 46%. A detailed study of this protein will yield insights into structural stability at high temperatures and should be highly relevant to the development of antibiotics and anticancer drugs targeting the biosynthesis of purine nucleotides.

Studies on design, fabrication and reliability assessment of embedded passives on a high-density interconnect (HDI) organic substrate using a sequential build-up process

One of the foremost design considerations in microelectronics miniaturization is the use of embedded passives which provide practical solution. In a typical circuit, over 80 percent of the electronic components are passives such as resistors, inductors, and capacitors that could take up to almost 50 percent of the entire printed circuit board area. By integrating passive components within the substrate instead of being on the surface, embedded passives reduce the system real estate, eliminate the need for discrete and assembly, enhance electrical performance and reliability, and potentially reduce the overall cost. Moreover, it is lead free. Even with these advantages, embedded passive technology is at a relatively immature stage and more characterization and optimization are needed for practical applications leading to its commercialization.This paper presents an entire process from design and fabrication to electrical characterization and reliability test of embedded passives on multilayered microvia organic substrate. Two test vehicles focusing on resistors and capacitors have been designed and fabricated. Embedded capacitors in this study are made with polymer/ceramic nanocomposite (BaTiO3) material to take advantage of low processing temperature of polymers and relatively high dielectric constant of ceramics and the values of these capacitors range from 50 pF to 1.5 nF with capacitance per area of approximately 1.5 nF/cm(2). Limited high frequency measurement of these capacitors was performed. Furthermore, reliability assessments of thermal shock and temperature humidity tests based on JEDEC standards were carried out. Resistors used in this work have been of three types: 1) carbon ink based polymer thick film (PTF), 2) resistor foils with known sheet resistivities which are laminated to printed wiring board (PWB) during a sequential build-up (SBU) process and 3) thin-film resistor plating by electroless method. Realization of embedded resistors on conventional board-level high-loss epoxy (similar to 0.015 at 1 GHz) and proposed low-loss BCB dielectric (similar to 0.0008 at > 40 GHz) has been explored in this study. Ni-P and Ni-W-P alloys were plated using conventional electroless plating, and NiCr and NiCrAlSi foils were used for the foil transfer process. For the first time, Benzocyclobutene (BCB) has been proposed as a board level dielectric for advanced System-on-Package (SOP) module primarily due to its attractive low-loss (for RF application) and thin film (for high density wiring) properties.Although embedded passives are more reliable by eliminating solder joint interconnects, they also introduce other concerns such as cracks, delamination and component instability. More layers may be needed to accommodate the embedded passives, and various materials within the substrate may cause significant thermo -mechanical stress due to coefficient of thermal expansion (CTE) mismatch. In this work, numerical models of embedded capacitors have been developed to qualitatively examine the effects of process conditions and electrical performance due to thermo-mechanical deformations.Also, a prototype working product with the board level design including features of embedded resistors and capacitors are underway. Preliminary results of these are presented.

Crystal structure of 2-thiophene-2-yl-3(thiophene-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one and the synthesis, spectral and thermal studies of its transition metal(II) complexes

The synthesis of manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of a new ligand 2-thiophene-2-yl-3(thiophene-2-carboxylidene-amino)-1,2-dihydroquinazolin-4(3H)-one (TTCADQ) is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.-vis., i.r., 1D n.m.r., 2D hetcor and e.p.r.) and thermal studies. The formation of 1,2-dihydroquinazolin-4(3H)-one rather than hydrazone, in the reaction of aromatic aldehyde and o-aminobenzoylhydrazide is proved by single crystal X-ray diffraction and 2D hetcor n.m.r. studies. On the basis of elemental analysis, u.v.-vis.spectroscopy and magnetic moment studies, six coordinate geometry for all the complexes was proposed. The i.r. spectral studies reveal the bidentate behaviour of the ligand.

Controlled photoluminescence from self-assembled semiconductor-metal quantum dot hybrid array films

Thin films of hybrid arrays of cadmium selenide quantum dots and polymer grafted gold nanoparticles have been prepared using a BCP template. Controlling the dispersion and location of the respective nanoparticles allows us to tune the exciton-plasmon interaction in such hybrid arrays and hence control their optical properties. The observed photoluminescence of the hybrid array films is interpreted in terms of the dispersion and location of the gold nanoparticles and quantum dots in the block copolymer matrix.

Ionic conductivity and dielectric measurements in single crystal β---AgI

Ionic conductivity measurements have been made on pure, copper-doped and cadmium-doped single crystals. Dielectric measurements in the frequency range 30Hz–100Hz showed that there was no anomalously to be (0.64 ± 0.02) eV and migration energies for silver ion intersitials and vacancies in the c direction to be (0.41 ± 0.02) eV and (0.50 ± 0.02) eV respectively. ESR measurements have shown that copper exists as Cu+ in these crystals. Dielectric measurements in the frequency range (OHz–100KHz showed that there was no anomalously high value for ε as reported earlier.

Photoconductivity in β-AgI

Excitation spectra and transient and steady-state photoconductivity have been studied in undoped and 0.8-mole% Cu-doped single-crystal β-AgI between 150 and 260°K. A single peak in the spectral response was found to occur in each case, at 2.88 eV for undoped and at 2.81 eV for copper-doped specimens at 260 K, the difference being due to a decrease in band gap. The anisotropy due to polarization of incident radiation parallel or perpendicular to the c direction, which is a measure of the energy difference between the Γ9 and Γ7 levels in the valence band, was found to be 0.010 eV. Transient-photoconductivity experiments showed that the hole lifetime was 6 μ sec at 300°K, an order of magnitude larger than the electron lifetime. The hole drift mobility was found to be 12±2 cm2/ V sec at 300°K and limited by traps at a depth of 0.51±0.01 eV with concentration (3-5)×109/cm3 and capture cross section 10-11 cm2. The study of photoconductivity decay versus temperature revealed the presence of shallow hole traps at 0.14±0.02 eV with concentration greater than 1016/cm3 and capture cross section 10-19 cm2. The steady-state photoconductivity was determined by the deep hole traps at 0.51 eV, and showed the presence of shallow electron traps at a depth of 0.28 eV. The trap distribution was found to be substantially the same in pure and copper-doped specimens, indicating the monovalent substitutional role of copper. The effects of iodine annealing, cadmium doping, and heating above the transition temperature were also studied. The possible nature of the traps is discussed.

Casting and heat treatment variables of Al–7Si–Mg alloy

A review of the research work that has been carried out thus far relating the casting and heat treatment variables to the structure and mechanical properties of Al–7Si–Mg (wt-%) is presented here. Although specifications recommend a wide range of magnesium contents and a fairly high content of iron, a narrow range of magnesium contents, closer to either the upper or lower specified limits depending on the properties desired, and a low iron content will have to be maintained to obtain optimum and consistent mechanical properties. A few studies have revealed that the modification of eutectic silicon slightly increases ductility and fracture toughness and also that the effect of modification is predominant at low iron content. Generally, higher solidification rates give superior mechanical properties. Delayed aging (the time elapsed between quenching and artificial aging during precipitation hardening) severely affects the strength of the alloy. The mechanism of delayed aging can be explained on the basis of Pashley's kinetic model. It has been reported that certain trace additions (cadmium, indium, tin, etc.) neutralise the detrimental effect of delayed aging. In particular, it should be noted that delayed aging is not mentioned in any of the specifications. With reference to the mechanism by which trace additions neutralise the detrimental effect of delayed aging, various hypotheses have been postulated, of which impurity–vacancy interaction appears to be the most widely accepted.

Brush plated CdSe films and their photoelectrochemical characteristics

The brush plating technique has been employed for the first time to obtain CdSe films on Ti and conducting glass substrates. These films have been annealed in an argon atmosphere and their structural, optical and photoelectrochemical properties are discussed. The power conversion efficiency has been found to be 7.43% under an illumination of 80 mW cm-2. A peak quantum efficiency of 0.64 is obtained for an incident wavelength of 720 nm. Donor concentration of 3.42 x 10(17) cm-3, electron mobility of 3 cm2 V-1 s-1 and minority carrier diffusion length of 0.013 mum have been obtained.

Influence of deviation from stoichiometry on the photoluminescence in CdTe doped with indium

Low temperature photoluminescence of vacuum and cadmium annealed CdTe:In is reported here. A new peak at similar to 1.14 eV related to transitions from the conduction band to an acceptor involving a tellurium vacancy has been observed.

Advances in storage batteries

Over the years, new power requirements for telecommunication, space, automotive and traction applications have arisen which need to be met. Although lead-acid and nickel-cadmium storage batteries continue to be the work horses with limited advances, associated environmental hazards and recycling are still the issues to be resolved. As a result, lead-acid and nickel-cadmium storage batteries have declined in importance whilst nickel-metal hydride and lithium secondary batteries with superior performances have shown greater acceptability in newer applications. These developments are reflected in this article.

Crystal structure of nonadentate tricompartmental ligand derived from pyridine-2,6-dicarboxylic acid: Spectroscopic, electrochemical and thermal investigations of its transition metal(II) complexes

The coordinating behavior of a new dihydrazone ligand, 2,6-bis(3-methoxysalicylidene) hydrazinocarbonyl]pyridine towards manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) has been described. The metal complexes were characterized by magnetic moments, conductivity measurements, spectral (IR, NMR, UV-Vis, FAB-Mass and EPR) and thermal studies. The ligand crystallizes in triclinic system, space group P-1, with alpha=98.491(10)degrees, beta=110.820(10)degrees and gamma=92.228(10)degrees. The cell dimensions are a=10.196(7)angstrom, b=10.814(7)angstrom, c=10.017(7)angstrom, Z=2 and V=1117.4(12). IR spectral studies reveal the nonadentate behavior of the ligand. All the complexes are neutral in nature and possess six-coordinate geometry around each metal center. The X-band EPR spectra of copper(II) complex at both room temperature and liquid nitrogen temperature showed unresolved broad signals with g(iso) = 2.106. Cyclic voltametric studies of copper(II) complex at different scan rates reveal that all the reaction occurring are irreversible. (C) 2011 Elsevier B.V. All rights reserved.

Characterization of alkyl chain conformation in an intercalated cationic lipid bilayer by IR spectroscopy

A structural analysis of alkyl chain conformation of an intercalated cationic lipid bilayer is described. Dialkyl dimethylammonium ions (di-C(n)DA) were ion exchanged into the galleries of layered cadmium thiophosphate to give Cd0.83PS3(di-C(n)DA)(0.34). The grafting density and interlayer expansions were identical to those for the intercalated single chain alkyl trimethylammonium (C(n)TA) bilayers. The increased methylene chain density in the galleries, however, forces the intercalated lipid to adopt a more trans ordered structure. Progression bands arising from the coupling of vibrational modes of trans methylene units are used to establish the extent of trans registry. Two types of ordered structures of the intercalated cationic lipid may be distinguished. One in which both alkyl chains adopt an all-trans geometry, and one in which the methylene bond adjacent to the headgroup on one of the alkyl chains is gauche. The latter structure is typically found in the crystalline state of these cationic lipids. The concentrations of the two structures were determined from the ratio of the intensities of the progression bands and were found to remain unchanged with temperature.

Solvothermal routes to capped oxide and chalcogenide nanoparticles

We review our recent contributions to the use of solvothermal methods for the preparation of different oxide and chalcogenide nanoparticles. We have prepared sub 10-nm,gamma-Fe2O3 ZnFe2O4, and CoFe2O4 particles by the decomposition of the corresponding cupferron complexes in the presence of n-octylamine or n-dodecylamine in solvothermal toluene. Similarly, dodecanethiol-capped chalcogenide nanoparticles of CdSe have been prepared by reacting cadmium stearates with H2Se under solvothermal conditions. The H2Se is generated in situ by the reduction of Se by tetralin. Using this latter technique, we have also been able to prepare PbSe and PbI2 in toluene under solvothermal conditions, albeit in bulk (rather than nanocrystalline) form. In the preparation of PbI2, HI is prepared by the in situ reduction of I-2 by tetralin.

A layered chlorophosphate, Na-3[Cd4Cl3(HPO4)(2)(H2PO4)(4)], containing Na+ ions in the interlamellar space

Reaction between CdCl2.H2O and NaH2PO4.H2O Under hydrothermal conditions gives rise to a new cadmium chlorophosphate of the formula Na-3[Cd4Cl3(HPO4)(2)(H2PO4)(4)] I. This material crystallizes in the orthorhombic system with space group Fmm2(no. 42). I has macroanionic layers of [Cd4Cl3(HPO4)(2)(H2PO4)(4)](3-) with Na+ ions in the interlamellar space. The discovery of such compounds suggests that metathetic reactions carried out under hydrothermal conditions may provide a novel route for the synthesis of new open-framework structures.