Laser forming of silicon films using nanoparticle precursor

Polycrystalline silicon films containing cubic silicon crystallites of size 3–4 μm have been formed on nickel substrates by fusing and sintering silicon nanoparticle precursors using a laser. A mechanism for the fusion and sintering of these nanoparticles, resulting in reduced heat input and continuous film formation by surface and grain boundary diffusion, is discussed. Films were characterized by optical microscopy, scanning electron microscopy, energydispersive spectroscopy, and Raman spectroscopy. Films were doped with n- as well as p-type dopants by using a laser doping technique and their current-voltage (I–V) characteristics were measured.     

Al2O3 nanoparticles with and without polyoxometalates as reactive sorbents for the removal of sulphur mustard

Nanoparticles of AP–Al₂O₃ (aerogel produced alumina) have been produced by an alkoxide based synthesis involving aluminum powder, methanol, toluene and water. Thus produced alumina nanoparticles were characterized by N₂-BET, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transformed infra-red spectroscopy and thermogravimetry techniques. The data indicated the formation of nanoparticles of alumina in the size range of 2–30 nm with high surface area (375 m²/g) and microporous–mesoporous characteristics. Thereafter, these nanoparticles were impregnated with polyoxometalates and other reactive chemicals, which have already proven to be effective against sulphur mustard (HD). Adsorptive removal kinetics for HD was monitored by GC–FID (gas chromatograph coupled with flame ionization detector) technique and found to be following pseudo first order reaction kinetics. Among polyoxometalates impregnated alumina nanoparticles based novel mesoporous reactive sorbent systems AP–Al₂O₃ impregnated with 9-molybdo-3-vanadophosphoric acid (10%, w/w) was found to be the most reactive with least half life value (214 min). In addition to this, degradation products of sulphur mustard on prepared mesoporous reactive sorbents were identified using GC/MS technique. Hydrolysis, dehydrohalogenation and oxidation reactions were found to be the route of degradation of sulphur mustard.     

Two-dimensional analytical threshold voltage model for DMG Epi-MOSFET

A two-dimensional (2-D) analytical model of a dual material gate (DMG) epitaxial (Epi)-MOSFET for improved, SCEs, hot electron effects, and carrier transport efficiency is presented. Using a two-region polynomial potential distribution and a universal boundary condition, we calculated the 2-D potential and electric field distribution along the channel. An expression for threshold voltage for short-channel DMG Epi-MOSFETs is also derived. The ratio of gate lengths has been varied to show which gate length ratio gives the best performance. The analytical results have been validated by the 2-D device simulator ATLAS over a wide range of device parameters and bias conditions.     

PREDICTION OF GAS-PHASE HOLDUP IN A BUBBLE COLUMN

Hydrodynamic properties of bubble columns play a significant role in many chemical and biochemical processes. Recent theoretical and experimental work conducted by Krishna et al. (1991, 1994), and Wilkinson et al. (1992) have been examined in conjunction with a bubble column and data for the air-water system operating at ambient conditions. The bubble column is 0.108 m in internal diameter, has a 1.70 m tall test section, and is equipped with a perforated plate distributor having 91 holes of 0.8 mm diameter. The data are taken for five values of the slumped water column height in range from 0.79 to 1.15 m, and for superficial air velocities up to about 0.4 m/s.

The data accord to the qualitative aspects of Krishna et al. model but lead to different values of the bubble swarm rise velocity, and superficial transition air velocity characterizing the transition from homogeneous bubbly flow regime to heterogeneous churn-turbulent flow regime. The quantitative reproduction by the model expressions of these recent works of the experimental data is poor. This may be partly attributed to the geometry of the column, diameter and distributor design.

The qualitative features of Krishna et al. model for the two regimes are confirmed by the present data. For quantitative predictions of gas-phase holdup, a new model is proposed in which the large bubble flow in the churn-turbulent regime is formulated following the drift-flux theory. The proposed theory and experimental data are in good agreement.     

Pineal and 5-methoxyindoles in the regulation of seasonal testicular cycle in Indian palm squirrel, Funambulus pennanti

Effects of late afternoon injections of different doses of melatonin (aMT) and 5-methoxytryptamine (MT) were studied on the testes in sham operated (SO) and pinealectomized (Px) F. pennanti during various reproductive phases. 5-methoxyindoles (MI) in doses 10 and 50 micrograms given for 60 continuous days reduced the weight and activity of the testes in SO and Px animals during the active and regressive phases. During the inactive phase MI administration caused an inhibitory influence on the testes of Px animals. However, during the recrudescence phase no significant effect of MI injections was visible. Both aMT and MT injected for 20 and 40 days respectively failed to influence the testes significantly. Also 1 microgram of the MI had no effect. The results suggest a reproductive phase dependent effect of aMT and MT on the testes of this tropical rodent. The dose and duration of administration are critical and their effects are independent of the pineal gland.     

Grand rounds: sports medicine

Experiments were undertaken to examine the influence of corticosterone on forskolin-stimulated cyclic AMP accumulation in rat cerebral cortical slices. Incubation in vitro of cerebral cortical slices with increasing concentrations of corticosterone (1 nM-100 microM) did not influence basal cyclic AMP response. Despite the lack of effect when used alone, corticosterone attenuated the effect of forskolin (10 microM) on cyclic AMP accumulation with IC50 = 24.1 +/- 5.1 microM. Corticosterone (10 microM) added to the incubation medium, for 10 min, reduced the cyclic AMP accumulation in response to increasing concentrations of forskolin (1 microM-100 microM), the concentration-response curve was shifted to the right by about one order of magnitude. In order to compare the in vitro effect of corticosterone with its effects in vivo in the next experiment the forskolin-induced cyclic AMP accumulation was measured in cerebral cortical slices from rats which were treated with corticosterone or vehicle. Similarly as in in vitro model, single dose of corticosterone (10 mg/kg sc) given to rats 2 h before sacrifice inhibited forskolin-stimulated cyclic AMP accumulation when compared with vehicle-treated control animals. In contrast, prolonged administration of corticosterone (10 mg/kg sc, twice daily for 4 and 7 days) increased forskolin-stimulated cyclic AMP accumulation in rat cerebral cortical slices when measured 2, 24 and 48 h after the administration of the last dose. These findings suggest that glucocorticoids exert multiple actions on the adenylate cyclase-coupled cyclic AMP generating system in the brain, with the ultimate effect being dependent upon amount and duration of exposure to these hormones.     

Ixodid ticks infesting rodents and sheep in diverse biotopes of southern India

A total of 127 rodents were trapped in southern India. Examination of these rodents revealed the presence of 2 species of ticks, Haemaphysalis spinigera and Rhipicephalus ramachandrai. The former species is the principal vector of Kyasanur Forest Disease (KFD) in India, and the latter's role, if any, is unknown. Sheep grazing in 1 of the study area were infested with another ixodid tick. Haemaphysalis intermedia, which is a vector of Bhanja virus in India. The presence of H. spinigera on domestic rats is important from the standpoint of KFD enzootiology. This tick shows a narrow habitat preference but a wide host range. In peridomestic situations, the field rodent Bandicota bengalensis did not harbor any tick species. Contiguity of feral and domestic biotopes in some areas contributed to the transfer of R. ramachandrai from its preferred wild rodent host, Tatera indica, to domestic rats Rattus sp.     

Assessment of iodine deficiency disorders using the 30 cluster approach in the National Capital Territory of Delhi

OBJECTIVE: Iodine Deficiency Disorders (IDD) are a major public health problem in India. The National Capital Territory (NCT) of Delhi is a known iodine deficiency endemic area. The Delhi Government banned the sale of non-iodised salt since 1989. The present study was conducted to assess the status of IDD after 7 years of salt iodisation programme in the state. DESIGN: Cross sectional. METHODOLOGY: The recent indicators recommended by the World Health Organization-United Nations Childrens Fund-International Council for the Control of Iodine Deficiency Disorders (WHO-UNICEF-ICCIDD) were utilized for the assessment of IDD. A total of 30 clusters were selected using population proportionate to size cluster sampling procedure. In each identified cluster, one primary school was selected using random sampling. A total of 6911 school children in the age group of 8-10 years were included for the study. RESULTS: The total goiter prevalence rate was 8.6% while 2.1, 8.4, 17.6 and 71.9% of the children had urinary iodine excretion levels of < 2, 2-4.9, 5-9.9 and 10 and above mcg/dl, respectively. The median urinary iodine excretion was 17 mcg/dl. Of the 1854 salt samples analyzed, salt with a nil iodine content was consumed only by 1.4% of the beneficiaries. Forty one per cent of families consumed salt with an iodine content of less than 15 ppm. CONCLUSION: IDD continues to be a public-health problem in the NCT of Delhi. There is a need of strengthening the existing monitoring system for the quality of iodised salt.