Showing papers by "Government College published in 1995"

Diamond polytypes in the chemical vapor deposited diamond films

Abstract: Micro‐Raman spectroscopy and x‐ray diffraction measurements have been used to identify the presence of hexagonal diamond polytypes in chemical vapor deposited diamond films. The presence of additional reflections, in addition to the normal cubic diamond reflections in the diffraction spectra and bands at 1306 and 1193 cm−1 in the Raman spectra, are attributed to the presence of diamond 6H polytype. The presence of the 1324 cm−1 band in addition to the main diamond peak in the expanded spectra is attributed to regions with hexagonal symmetry, thus supporting the presence of hexagonal diamond polytypes. The compressive strain in diamond layers on the Si substrate is believed to create regions of hexagonal symmetry and vice versa.

Effect of addition of Zn impurities on the electronic conduction in semiconducting Se80−xTe20Znx glasses

Abstract: A study of the effect of the addition of Zn impurities on the electronic transport properties of melt-quenched semiconducting glasses in the system Se80-xTe20Znx (x = 0, 1, 2 and 4) has been undertaken for the first time. Measurements of the temperature dependence of the d.c. conductivity and the frequency and temperature dependence of the d.c. conductivity [sgrave]a.c.(ω) and dielectric relaxation have been made in the temperature interval 180–450 K and frequency range 500 Hz–10 kHz. It is revealed that [sgrave]a.c.(ω) is proportional to ω s . The temperature dependence of [sgrave]a.c.(ω) and the parameter s is reasonably interpreted by the correlated-barrier-hopping model. The analysis of the results shows that the electronic conduction in compositions with x = 0 and 1 takes place by a bipolaron-hopping process in the whole temperature range of study. The addition of higher concentrations of Zn impurities (x = 2 and 4) induces new types of defects which contribute predominantly to single-polaro...

Electronic conduction in vitreous semiconductors in the pseudo-binary system (As2S3)1-x(PbS)x

Abstract: AC conductivity and dielectric relaxation measurements of the bulk amorphous compositions in the pseudo-binary system (As2S3)1-x(PbS)x (x = 0, 0.1, 0.4 and 0.5) in the frequency range 500 Hz-10 kHz and in the temperature span 180–450 K are reported. The temperature dependence of the ac conductivity, σac(ω), has a broad structure at all frequencies in compositions with x = 0.1, 0.4 and 0.5 whose peak position is not thermally activated. A similar structure was also observed in the data on the dielectric constant, ϵ1, which peaked at a frequency of 1 kHz in the composition with x = 0.5. Analysis of the results using the correlated barrier hopping model revealed that the electronic conduction takes place by single polaron and bipolaron hopping processes at high and low temperatures, respectively, in compositions containing Pb. The microstructure and phase-separation in the glasses containing Pb influence the electrical transport and dielectric dispersion. This study has revealed the possible presence of a phase transformation at around 300 K at a frequency of 1 kHz in the dielectric dispersion behaviour of composition with x = 0.5.

Doping of chalcogenide glassy semiconductor by implanting Ni ions

Abstract: An amorphous chalcogenide semiconductor, Pb 20 Ge 19 Se 61 , has been doped by bombardment with 75 MeV Ni ions at fluences of 2 × 10 13 and 5 × 10 13 ions/cm 2 . The ion-induced effect on the electronic properties of the bombarded and annealed semiconductor has been studied by measuring the dc electrical conductivity and thermoelectric power. It is found that Ni atoms with incomplete electronic 3d shells induce deep trap states near the Fermi level which contribute to the electronic conduction process by a variable-range hopping mechanism. The carrier transport remains p-type in the bombarded (annealed) sample. However, significant changes in the temperature dependence of the thermoelectric power were observed. It is important to observe that a small fraction of the implanted Ni (0.2 at.%) introduced by ion-implantation at MeV energy can induce doping effects in bulk chalcogenide glass samples.

Electronic conduction in MeV energy ion-beam irradiated semiconducting glass Pb20Ge19Se61

Abstract: The semiconducting glass Pb20Ge19Se61 has been irradiated with a 75 MeV 58Ni6+ ion-beam at room temperature with fluences 2 × 1013 and 5 × 1013 ions/cm2. Irradiation-induced effects on the electronic conduction process in the bombarded and sequentially annealed (at 100–220°C) semiconductor have been investigated by measurements of the temperature dependence of the d.c. conductivity, and frequency (100Hz-10kHz) and temperature dependence of the a.c. conductivity and dielectric relaxation in the temperature span 180K-450K. An analysis of the data revealed that the Ni-ion induced defects/complexes in the bombarded semiconductor become electrically active on annealing and introduce localized states near the Fermi level which exhibit variable-range hopping conduction. Irradiation and subsequent annealing introduces inhomogeneity into the semiconductor with a distribution of simple defects and clusters in the bulk of the material. The results of a.c. conductivity and dielectric relaxation support this ...

Inhibitors of blood platelet cAMP phosphodiesterase: a QSAR analysis.

Abstract: A quantitative structure-activity relationship (QSAR) analysis of two related series of the derivatives of 7-substituted imidazo [4,5-b]-quinolin-2-one active as inhibitors of human blood platelet cAMP phosphodiesterase (PDE) is presented with a view to reflecting upon the parametric requirements of the side chain as well as of the N-1 and N-3 substitutions on the heterocycle. For the first series (Figure 1) consisting of 114 congeners and having a more flexible functionalized side chain at the 7-position and only binary variations (Me or H) at N-1 and N-3, it has been shown that bulk (Vw), of the functionalized side chain tends to potentiate the inhibitory activity of a derivative while positions N-1 and N-3 should better remain unsubstituted, as reflected through the dummy variables. A similar analysis of the compounds of the second series (Figure 2), where a less flexible side chain is linked through a basic nitrogen, has provided a parabolic dependence of inhibition activity on Vw. From this relationship, a limiting size of the side chain, seems to be necessary for triggering a minimal response.

Resonance Line Radiation from Spin Polarized Sodium and Potassium Atoms

Abstract: There is a growing interest in the study of spin effects in atomic collision processes as it can help to analyze the different interactions involved and also provide a stringent test for theoretical models. However, due to the rather complicated experimental techniques employed for measurements of the spin states of collision systems before and after a collision, only relatively simple cases have so far been investigated. For a more complete description of the research work devoted to such problems reviews of Moisewitch and Smith (1968), Bederson (1969), Blum and Kleinpoppen (1975, 1976, 1983), Chen and Gallagher (1978), Heddle and Gallagher (1989), Kessler (1991), Teubner and Weigold (1992) and research papers by Kleinpoppen (1971), Moores and Norcross (1972), Tripathi and Mathur (1973), Jitschin et al. (1984) and Anderson and Bartschat (1993) may be consulted.

Knowledge of college girls on child health.

Abstract: In Kumbakonam Tamil Nadu State in India 384 final-year female students attending the Government College for Women completed a questionnaire so the researcher could assess their knowledge of prenatal and childhood immunizations breast feeding weaning oral rehydration solution (ORS) and feeding during diarrhea. 53.2% were from an urban area 17.9% from a semi-urban area and 28.9% from a rural area. Most students (88.8%) did not know the purpose of prenatal immunization yet most (71.1%) knew the correct dose for prenatal immunization and that it should be given (91.9%). 92.4% answered incorrectly about childhood immunizations. Yet most (88.8%) knew that childhood immunizations were supposed to be administered. Only 5.7% knew the purpose and doses of these immunizations. The students tended not to know the common terms for the vaccine preventable diseases. All the students knew that breast feeding is good. Most students (72.9%) knew that breast feeding has a great nutritive value and that it prevents common infections. 79.7% knew that weaning should begin before the infant is 6 months old. 68.2% were familiar with the inexpensive nutritive locally available weaning foods. 82.4% were familiar with ORS. 37% knew that continued feeding during diarrhea is desirable. 32.8% wanted to withhold food during diarrhea. Even though the questions were based on the message spread via mass media (especially TV) the overall level of awareness on child health was poor. These findings suggest the need for child health education directed towards the public and in colleges.