High-frequency capacitance-voltage characteristics of amorphous (undoped)/crystalline silicon heterostructures

A numerical procedure is presented for calculating high-frequency capacitance variation with bias in amorphous (undoped)/crystalline silicon heterojunction. The results of the model calculations using this procedure have been reported, for different p silicon substrates. These have been compared with the corresponding capacitance variations in the other limiting case, in which the heterostructure acts like an MIS structure. The effect of interface states on the capacitance characteristics has also been studied. In the second part, we report the results of 1 MHz capacitance measurements on various amorphous (undoped)/crystalline silicon heterostructures.

Studies on the macroconida of microsporum-canis-characteristics of invitro amino-acid incorporativing system

The characteristics of an in vitro polyuridylic acid dependent amino acid incorporating system prepared from germinating macroconidia of Microsporum canis are described. The incorporation of 14C-phenylalanine into polyphenylalanine is dependent on S-30 extract, adenosine triphosphate, magnesium ions and polyuridylic acid. Incorporation is slightly enhanced by yeast transfer ribonucleic acid and pyruvate kinase. The system is highly sensitive to ribonuclease, puromycin and miconazole (an antifungal agent), moderately sensitive to sodium fluoride and much less sensitive to phenethylalcohol, cycloheximide, chloramphenicol and deoxyribonuclease. Cell-free extract from ungerminated conidia has less capacity to synthesize the protein and during germination a marked increase in the protein synthetic activity is observed. The results from experiments wherein ribosomes and S-100 fraction from germinated and ungerminated spores are interchanged, revealed that the defect in the extract from the ungerminated spore is in the ribosomes.

Complex Permittivity Characteristics of Epoxy Nanocomposites at Low Frequencies

The complex permittivity characteristics of epoxy nanocomposite systems were examined and an attempt has been made to understand the underlying physics governing some of the unique macroscopic dielectric behaviors. The experimental investigations were performed using two different nanocomposite systems with low filler concentrations over the frequency range of 10(-2)-400 Hz, but for some cases, the data has been reported upto 10(6) Hz for a better understanding of the behaviors. Results demonstrate that nanocomposites do possess unique permittivity behaviors as compared to those already known for unfilled polymer and microcomposite systems. The nanocomposite real permittivity and tan delta values are found to be lower than that of unfilled epoxy. In addition, results show that interfacial polarization and charge carrier mobilities are suppressed in epoxy nanocomposite systems. The complex permittivity spectra coupled with the ac conductivity characteristics with respect to frequency was found to be sufficient to identify several of the nanocomposite characteristics like the reduction in permittivity values, reduction in the interfacial polarization mechanisms and the electrical conduction behaviors. Analysis of the results are also performed using electric modulus formalisms and it has been seen that the nanocomposite dielectric behaviors at low frequencies can also be explained clearly using this formalism.

Stress-strain characteristics of Tress-strain characteristics of reinforcing steel bars under cyclic loading

This paper presents test results for 22 high strength deformed bars and nine mild steel bars subjected to monotonic repeated and reversed axial loading to determine the stress-strain behavior. Equations have been proposed for the stress-strain curves and have been compared with test results. Satisfactory agreement was obtained.

Stress-Strain Characteristics of Reinforcing Steel Bars Under Cyclic Loading

This paper presents test results for 22 high strength deformed bars and nine mild steel bars subjected to monotonic repeated and reversed axial loading to determine the stress-strain behavior. Equations have been proposed for the stress-strain curves and have been compared with test results. Satisfactory agreement was obtained.

Spectroscopic properties of molecules related to hindered isomers of retinal

Proton and12C NMR study of molecules related to retinal has been carried out. The characteristic differences in spectral behaviour among 7-trans and 7-cis isomers have been established which would be useful in determining the structure of new isomers and identifying components in a mixture. Through coupling constant measurements and DNMR study it is clearly established that 7-cis isomers of β-ionyl derivatives and in turn 7-cis isomers of retinyl derivatives prefer a non-planar arrangement and this non-planarity brings about resonance destabilisation.

Reactivity Of Pph3 Toward Ruiiruiiicl(O2car)4 - Syntheses, Molecular-Structures, And Spectroscopic And Electrochemical Properties Of Ruiiruiii(Oh2)Cl(Mecn)(O2car)4(Pph3)2 And Ruii2(Oh2)(Mecn)2(O2car)4(Pph3)2

By the reaction of Ru2Cl(O2CAr)4 (1) and PPh3 in MeCN-H2O the diruthenium(II,III) and diruthenium(II) compounds of the type Ru2(OH2)Cl(MeCN)(O2CAr)4(PPh3)2 (2) and Ru2(OH2)(MeCN)2(O2CAr)4(PPh3)2 (3) were prepared and characterized by analytical, spectral, and electrochemical data (Ar is an aryl group, C6H4-p-X; X = H, OMe, Me, Cl, NO2). The molecular structure of Ru2(OH2)Cl(MeCN)(O2CC6H4-p-OMe)4(PPh3)2 was determined by X-ray crystallography. Crystal data are as follows: triclinic, P1BAR, a = 13.538 (5) angstrom, b = 15.650 (4) angstrom, c = 18.287 (7) angstrom, alpha = 101.39 (3)-degrees, beta = 105.99 (4)-degrees, gamma = 97.94 (3)-degrees, V = 3574 angstrom 3, Z = 2. The molecule is asymmetric, and the two ruthenium centers are clearly distinguishable. The Ru(III)-Ru(II), Ru(III)-(mu-OH2), and Ru(II)-(mu-OH2) distances and the Ru-(mu-OH2)-Ru angle in [{Ru(III)Cl(eta-1-O2CC6H4-p-OMe)(PPh3)}(mu-OH2)(mu-O2CC6H4-p-OMe)2{Ru(II)(MeCN)(eta-1-O2CC6H4-p-OMe)(PPh3)}] are 3.604 (1), 2.127 (8), and 2.141 (10) angstrom and 115.2 (5)-degrees, respectively. The compounds are paramagnetic and exhibit axial EPR spectra in the polycrystalline form. An intervalence transfer (IT) transition is observed in the range 900-960 nm in chloroform in these class II type trapped mixed-valence species 2. Compound 2 displays metal-centered one-electron reduction and oxidation processes near -0.4 and +0.6 V (vs SCE), respectively in CH2Cl2-TBAP. Compound 2 is unstable in solution phase and disproportionates to (mu-aquo)diruthenium(II) and (mu-oxo)diruthenium(III) complexes. The mechanistic aspects of the core conversion are discussed. The molecular structure of a diruthenium(II) compound, Ru2(OH2)(MeCN)2(O2CC6H4-p-NO2)4(PPh3)2.1.5CH2Cl2, was obtained by X-ray crystallography. The compound crystallizes in the space group P2(1)/c with a = 23.472 (6) angstrom, b = 14.303 (3) angstrom, c = 23.256 (7) angstrom, beta = 101.69 (2)-degrees, V = 7645 angstrom 3, and Z = 4. The Ru(II)-Ru(II) and two Ru(II)-(mu-OH2) distances and the Ru(II)-(mu-OH2)-Ru(II) angle in [{(PPh3)-(MeCN)(eta-1-O2CC6H4-p-NO2)Ru}2(mu-OH2)(mu-O2CC6H4-p-NO2)2] are 3.712 (1), 2.173 (9), and 2.162 (9) angstrom and 117.8 (4)-degrees, respectively. In both diruthenium(II,III) and diruthenium(II) compounds, each metal center has three facial ligands of varying pi-acidity and the aquo bridges are strongly hydrogen bonded with the eta-1-carboxylato facial ligands. The diruthenium(II) compounds are diamagnetic and exhibit characteristic H-1 NMR spectra in CDCl3. These compounds display two metal-centered one-electron oxidations near +0.3 and +1.0 V (vs SCE) in CH2Cl2-TBAP. The overall reaction between 1 and PPh3 in MeCN-H2O through the intermediacy of 2 is of the disproportionation type. The significant role of facial as well as bridging ligands in stabilizing the core structures is observed from electrochemical studies.

Spectroscopic evidence for the removal of mobile holes on Fe doping in YBa2Cu3-xFexO7-δ

X-ray absorption spectra at the oxygen K edge using the total yield technique are reported for YBa2Cu3O6.9 and YBa2Cu2.7Fe0.3O6.9. A comparison of the two spectra reveals that the mobile holes in YBa2Cu3O7-δ are removed and localized on Fe doping. Fe thus enters the lattice primarily in the formally trivalent oxidation state.

Synthetic, spectroscopic, magnetic, and x-ray structural studies on a vitamin B6-amino acid Schiff base complex, aqua(5'-phosphopyridoxylidenetyrosinato)copper(II) tetrahydrate

A Schiff base metal complex, [Cu(II)(PLP-DL-tyrosinato)(H2O)].4H2O (PLP = pyridoxal phosphate), with the molecular formula CuC17O13N2H27P has been prepared and characterized by magnetic, spectral, and X-ray structural studies. The compound crystallizes in the triclinic space group P1BAR with a = 8.616 (2) angstrom, b = 11.843 (3) angstrom, c = 12.177 (3) angstrom, alpha = 103.40 (2)degrees, beta = 112.32 (2)degrees, gamma = 76.50 (1)degrees, and Z = 2. The structure was solved by the heavy-atom method and refined by least-squares techniques to a final R value of 0.057 for 3132 independent reflections. The coordination geometry around Cu(II) is distorted square pyramidal with phenolic oxygen, imino nitrogen, and carboxylate oxygen from the Schiff base ligand and water oxygen as basal donor atoms. The axial site is occupied by a phosphate oxygen from a neighboring molecule, thus resulting in a one-dimensional polymer. The structure reveals pi-pi interaction of the aromatic side chain of the amino acid with the pyridoxal pi system. A comparative study is made of this complex with similar Schiff base complexes. The variable-temperature magnetic behavior of this compound shows a weak antiferromagnetic interaction.

Infrared spectroscopic study of the phase transitions in CsNO3, RbNO3 and NH4NO3

Phase transitions of CsNO3 (II-I), RbNO3 (IV-III-II) and NH4NO3 (V-IV-III-II-I) have been studied by i.r. spectroscopy. The study has provided useful information on the changes in the dispositions of the ions during the phase transitions.

Experimental evaluation of the aeroacoustic characteristics of a source of pulsating gas flow

Amongv arioums ethodtsh,e t ransmissliionne o r thei mpedantcueb em ethohda sb eenm ospt opulafro r thee xperimenetavla luatioonf thea cousticiaml pedanocef a terminatioTnh. ee xistinmg ethodisn,c luding theo nesre porteeda rlierb, y thea uthorrse quirleo catioonf thes oundp ressumrei nima nd/orm axima, or elsem akeu se0 f somei terativep rocedureTsh. e presenpt aperd ealsw ith a methodo f analysios f standinwga vews hichd oesn otd epenodn anyo f thesein volvepdr ocedureIts i.s applicabtloe thec aseo f stationarays w ella sm ovingm ediaI.t enableosn to evaluatteh e impedancoef anyp assivbel ackb ox,a s well as the aeroacoustcich aracteristicosf a sourceo f pulsatingg asf low, with the leaste xperimentawl ork andc omputatiotinm ea ndw itht hee xtraa dvantagoef usinga givenim pedanctueb ef or wavelengtahss largea s fourt imesit s lengthA. methodo f externaml easuremenntost, involvinugs eo f anyi mpedance tubef, or evaluatintgh ea eroacouscthica racteristoicf as sourcoef pulsatingga sf lowi s alsod ealtw ith, based on the definition of attenuation or insertion loss of a muffler.