Search Results - (Author, Cooperation:V. Kunin)

2012-08-04

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Actinobacteria/genetics/isolation & purification ; Arabidopsis/classification/growth & development/*microbiology ; Endophytes/*classification/genetics/*isolation & purification ; Genotype ; In Situ Hybridization, Fluorescence ; *Metagenome ; Plant Roots/classification/growth & development/*microbiology ; Proteobacteria/genetics/isolation & purification ; RNA, Ribosomal, 16S/genetics/isolation & purification ; Rhizosphere ; Ribotyping ; Sequence Analysis, DNA ; *Soil Microbiology ; Symbiosis

1573-8620

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract It is well known that the current carriers in a thermally ionized gas vary in composition, but that electrons [1] make the fundamental contribution to the conductivity of the gas, since their mobility is incomparably larger than that of other current-carrying particles. We shall thus be concerned only with electron conductivity. If the gas is under a high pressure in a weak electric field, then in estimating its electrical conductivity by classical means the same concepts are usually employed as those which Drude applied in the theory of metallic conduction. The Drude-Lorentz formula for electrical conductivity was subsequently perfected by Cowling and Chapman who introduced a coefficient to take into account the rate at which the particle interaction forces decrease with distance [2], For electron Coulomb interaction this coefficient takes the value 0.532 instead of 0.500 as compared with the Drude-Lorentz formula. For high pressures and low electric field strengths the electron drift velocity in the field is vanishingly small compared with the mean velocity of random motion, and so it is logical to suppose that the electron free time is independent of the drift velocity, and this supposition leads in the end to the conclusion that Ohm's law is applicable to gases at high pressure in very weak fields. However, we must not overlook the fact that even under the conditions mentioned the conclusion concerning the validity of Ohm's law is only an approximation which becomes less accurate, the lower the gas pressure and the greater the field strength. In what follows the conductivity of the gas is also determined by Drude's method, but with the refinement that in determining the electron free time the drift velocity of these particles in the field is considered.

Electronic Resource

1573-9228

Springer Online Journal Archives 1860-2000

Physics

Abstract It is shown that in the forbidden band of the plasmochemical SiO2 there are electron capture centers with capture cross section 2·10−13cm2, density 2·1019 cm−3, and thermal activation energy 0.41 eV for the process of trap emptying. It is noted that the charge state of the insulator in an external electric field is unstable, this being due to the exchange of electrons between the insulator and the aluminum electrode. An energy band diagram of the structure is deduced from the results of the investigation. The potential barrier heights were found to be 2.78 eV at the Al-SiO2 interface and 4.36 eV at the SiO2-Si interface. The dynamical current-voltage characteristic of the structure is used to determine the density of mobile ions in the insulator, which is found to be S·1013 cm−2 at T=230°C and rate of change 5 mV/sec of the voltage.

Electronic Resource

1573-9228

Springer Online Journal Archives 1860-2000

Physics

Abstract Results are offered from a study of thin film strontium tantalate (SrTa2O6) obtained by vacuum hf deposition. Temperature and frequency dependences of electrical conductivity, ɛ, tan δ, and thermostimulted dielectric depolarization current are studied in Al-SrTa2O6-Al structures. Point defect parameters and their distribution over energy in the dielectric forbidden zone are determined. Polarization and electrical conductivity mechanisms are considered, and it is concluded that strontium tantalate shows promise as a dielectric material for integrated circuits.

Electronic Resource

1573-9228

Springer Online Journal Archives 1860-2000

Physics

Electronic Resource

1573-9228

Springer Online Journal Archives 1860-2000

Physics

Abstract A study was made of the electroabsorption kinetics, as well as of the spectral and field dependences of the contrast and efficiency of modulation of light in Al-SiO2-GaAs-n+-GaP structures near the fundamental absorption edge of GaAs (875–910 nm). Values of the contrast amounting to 10–12 and the modulation efficiency of 30–40% were achieved. It was demonstrated that optical data storage was possible with the aid of an He-Ne laser. Optical memory was observed in Al-SiO2-(n-n+-GaAs structures on application of voltage pulses causing carrier accumulation; the effect was due to the capture of electrons at the SiO2-GaAs interface. The absorption edge of epitaxial GaAs films on GaP substrates had an exponential profile in the photon energy range 1.37≤hν≤1.40 eV infields 0≤E 5≤6.5·104 V/cm. An empirical relationship was obtained for the spectral and field dependences of the absorption coefficient.

Electronic Resource

1573-9228

Springer Online Journal Archives 1860-2000

Physics

Abstract An investigation was made of the Hall and conductivity mobilities of holes in an inversion channel, and the C-V as well as G-V characteristics of Al-SiO2-Si structures were recorded. It was established that the technology of fabrication of MIS structures influenced the parameters of the Si-SiO2 interface. It was found that chemodynamic polishing of silicon plates before oxidation improved significantly the properties of the Si-SiO2 interface. A relationship was found between the density of the surface states (Nss) and the mobility of holes in an inversion channel. It was found that the high mobility of holes at the channel opening threshold was mainly due to a reduction in Nss at the Si-SiO2 interface and in the insulator near this Si-SiO2 interface. In addition to the phonon scattering mechanism, the scattering by the charge in the surface states at the Si-SiO2 interface also played an important role.

Electronic Resource