Ion beam induced formation of nanocrystalline silicon in pulsed laser deposited SiOX thin films

Synthesis and structural studies of nanocrystalline silicon grown in pulsed laser deposited SiO_X films is reported. The effect of high energy heavy ion beam irradiation on these films is studied using 100 MeV Ag ions. The structural studies were carried out using micro Raman spectroscopy, GAXRD, FTIR, TEM, HRTEM, SAED and EDX. The occurrence of phase separation in non-stoichiometric silicon oxide by means of ion beam irradiation leading to the formation of silicon nanocrystals in the films is confirmed by the results. HRTEM results reveal the structure of silicon phase formed after ion beam treatment and the particle size can be controlled up to 2-3 nm. A detailed analysis by micro Raman and HRTEM studies suggest the presence of crystallite size distribution. The results of GAXRD and SAED confirm the formation of cubic phase of silicon with two different lattice parameters. The studies conclude that the size of the nanocrystals can be controlled by varying deposition and ion irradiation parameters.     

Kinetics of adsorption of sulfur mustard on Al2O3 nanoparticles with and without impregnants

BACKGROUND: Chemical warfare (CW) agents are highly toxic compounds and have been used in war to produce physical immobilization, so safe and effective ways to detoxify them without endangering human life or the environment is of great concern. One of the important ways to achieve protection against CW agents contaminating air is to utilize suitable adsorbent materials, e.g. activated carbon, nanoparticles, etc. In the present study nanoparticles, synthesized through sol–gel processes and loaded with reactive compounds have been used for the degradation of CW agents and to understand their adsorption kinetics using Fickian and linear driving force models. RESULTS: Nanoparticles of AP‐Al₂O₃ (aerogel‐produced alumina) in the size range 2–30 nm with high surface area (375 m² g^?1) were produced by an alkoxide‐based synthesis, and then characterized using N₂‐Brunauer–Emmet–Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. Thereafter, these were impregnated, and finally tested for kinetics of adsorption of sulfur mustard (HD) under static conditions. The kinetics was studied using linear driving force and Fickian diffusion models and the kinetics parameters determined. CONCLUSION: AP‐Al₂O₃ with 10% impregnation of 9‐molybdo‐3‐vanadophosphoric acid (10%, w/w) showed the maximum uptake (640 mg g^?1) of HD. The highest adsorption potential indicated that the adsorption was due not only to physisorption but also involved chemisorption. Values of the diffusional exponent indicated the mechanism to be Fickian and anomalous. Hydrolysis, dehydrochlorination and oxidation reactions (identified using gas chromatography‐mass spectrometry (GC/MS)) were found to be the route of degradation of HD over the prepared nanoparticle based adsorbents. Copyright © 2009 Society of Chemical Industry     

Enalapril-induced renal artery thrombosis in unilateral renal artery stenosis

Intravascular adhesion of leucocytes plays a role in the pathogenesis of acute and chronic vascular disease. Regular aerobic exercise seems to protect against vascular disease. Since leucocyte adhesion is mediated by integrins, we tested the hypothesis that surface expression of the integrin adhesive receptors LFA-1 (cd11a/cd18), MAC-1 (cd11b/cd18), gp 150/95 (cd11c/cd18), and VLA-4 (cd29/cd49) is decreased by moderate endurance exercise. Surface expression of integrins was measured by FACS analysis in 19 healthy subjects (16 males, 3 females, 36.6 +/- 8.7 years, 177.1 +/- 7.5 cm, 70.3 +/- 8.1 kg) before and after submaximal exercise (3 h run) using monoclonal antibodies against cd11a, cd11b, cd11c, cd18, cd29 and cd49. In addition, we compared resting integrin expression in this group with a group of sedentary subjects (19 males, 6 females, 29.3 +/- 5.3 years). White blood cell count increased from 5300 ml(-1) to 9740 ml(-1) during exercise (P < 0.001). Nevertheless, the expression (indicated by the mean log fluorescence) of cd11a (94 +/- 24 vs. 78 +/- 14) and cd18 (128 +/- 31 vs. 102 +/- 21) on lymphocytes and of cd11a (104 +/- 25 vs. 85 +/- 16), cd11c (497 +/- 171 vs. 408 +/- 126) cd29 (109 +/- 16 vs. 89 +/- 16), cd49 (69 +/- 8 vs. 54 +/- 11) on monocytes was decreased after exercise (all P < 0.05). In contrast, integrin expression on granulocytes was not altered by exercise. Comparison of exercising and sedentary subjects showed a significantly decreased expression of integrins in exercising subjects. Our results demonstrate that moderate exercise leads to decreased expression of integrin receptors on leucocytes. This decreased expression of adhesion molecules may result in decreased adhesion and infiltration of leucocytes into the vessel wall. This phenomenon may play a role in the beneficial effect of moderate exercise in prevention of acute and chronic vascular disease.     

Synthesis and compressive behavior of Cr2GeC up to 48 GPa

M_n+1AX_n compounds have gathered huge momentum because of its exciting properties. In this paper we report the synthesis of ternary layered ceramic Cr₂GeC, a 211 M_n+1AX_n compound by hot-pressing. Scanning electron microscopy and X-ray diffraction have been employed to characterize the new synthesized phase. High-pressure compressibility of Cr₂GeC were measured using diamond anvil cell and synchrotron radiation at room temperature up to 48 GPa. No phase transformation was observed in the experimental pressure range. The bulk modulus of Cr₂GeC calculated using the Birch–Murnaghan equation of state is 169 ± 3 GPa, with K′ = 3.05 ± 0.15.     

Hydrogen peroxide sensing properties of PVA/TiO2/I2 nanocomposite‐based free standing membranes

The nanocomposite of titanium‐di‐oxide (TiO₂)/iodine (I₂) in polyvinyl alcohol (PVA) matrix has been explored to be used in hydrogen peroxide (H₂O₂) sensing applications for the first time. The proposed nanocomposite can be easily casted in the form of thin film on glass substrates as well as free standing membranes. These nanocomposite films and membranes exhibit reduced resistance values and easily observable colour changes in the presence of H₂O₂. The films also exhibit significant quenching in photoluminescence emission properties upon H₂O₂ exposure. These sensor responses have been attributed to redox reactions at nanocomposite films and H₂O₂ interface. This study indicates an easy to fabricate, flexible and environmental friendly sensing platform for H₂O₂. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42257.     

Studies on corrosion control of naphtha fractions in overhead condensing system using laboratory distillation device

Corrosion in the overhead condensing system of atmospheric distillation units is a common occurrence in petroleum refineries worldwide. These corrosion problems are influenced by the presence of three phases: vapours, liquid hydrocarbons and aqueous phase containing hydrochloric acid formed during distillation by decomposition of chloride salts of calcium and magnesium.Present studies highlight the corrosion control of naphtha fractions of Bombay High and Dubai crude oils in laboratory distillation device by chemical treatment using various corrosion inhibitors having different functional groups. These studies were carried out using two phase systems (aqueous-hydrocarbon) in the distillation device having facilities for monitoring the corrosion and temperatures in vapour condensing region and liquid condensate. Corrosion monitoring was carried out by potentiodynamic polarization technique and dissolved iron analysis using inductively coupled plasma atomic emission spectroscopy (ICPAES). Experimental findings indicate that Dubai naphtha fraction is more corrosive in nature when compared to Bombay High naphtha. This observation can also be explained on the basis of characterization of both crude oils and their naphtha fractions. At normally recommended dosage level as in refinery overhead systems, water soluble corrosion inhibitors are more effective than hydrocarbon soluble ones in the vapour condensing region as well as in the liquid condensate of both naphtha fractions.     

A Novel FRFT Beamformer for Rayleigh Faded Channels

A method of optimal beamforming for flat Rayleigh faded channels using the Fractional Fourier Transform (FRFT) is considered in this paper. It has been demonstrated through simulations that optimal beamforming with FRFT allows smaller mean-square errors in restoring signals degraded with linear time-or frequency variant distortions and Additive White Gaussian Noise. This is made possible by the additional flexibility that comes with free parameter ‘a’ of the fractional Fourier transform as oppose to the classical Fourier transform (FT). The method is especially useful in moving source problems, where Doppler Effect produces frequency shift when the source is moving, as in mobile and wireless communication where user produces the frequency shift while moving. In this paper it is shown through simulations that beamforming in fractional domain reduces BER as compared to time or frequency domain.     

CLAMP: Efficient class-based sampling for flexible flow monitoring

With an increasing requirement to classify traffic and track security threats, newer flexible and efficient ways are needed for collecting traffic statistics and monitoring network flows. However, traditional solutions based on packet sampling do not provide the flexibility required for these applications. For example, operators are often interested in observing as many unique flows as possible; however, random packet sampling is inherently biased towards large flows. Operators may also be interested in increasing the fidelity of flow measurements for a certain class of flows; such flexibility is lacking in today’s packet sampling frameworks. In this paper, we propose a novel architecture called CLAMP that provides an efficient framework to implement class-based sampling. At the heart of CLAMP is a novel data structure we propose called composite Bloom filter (CBF) that consists of a set of Bloom filters working together to encapsulate various class definitions. In particular, we show the flexibility and efficacy of CLAMP by implementing a simple two-class size-based sampling. We also consider different objectives such as maximizing flow coverage and improving the accuracy of certain class of flows. In comparison to previous approaches that implement simple size-based sampling, our architecture requires substantially lower amounts of memory (up to 80×) and achieves higher flow coverage (up to 8× more flows) under specific configurations.     

Thiocompounds as simulants of sulphur mustard for testing of protective barriers

The protective potential of protective devices such as respirators, suits, gloves, and overboots is widely evaluated using the standard colorimetric test (spot disc breakthrough time test, also called SD BTT) involving sulfur mustard (SM) as the challenge chemical. The vesicant nature of SM makes the test inconvenient and poses stringent safety demands. Moreover, such tests are allowed only at a limited number of facilities, causing delay in product development and supply. This prompted the present study on the search for suitable SM simulant responsive to SD BTT test. The diffusivities at BTT (D_BTT) of 10 commercially available thiocompounds through butyl rubber (IIR) were compared vis‐a‐vis D_BTT of SM. For three representative thiocompounds, namely methyl (phenyl thio)acetate, 2‐chloroethyl phenyl sulfide (2‐CEPS) and phenyl‐n‐propyl sulfide (PNPS), the transport parameters through IIR were obtained. PNPS and 2‐CEPS were further compared with respect to D_BTT in elastomers such as IIR, ethylene–propylene–diene methylene rubber, polydimethylsiloxane, nitrile rubber, polybutadiene, and natural rubber. 2‐CEPS showed generally same order of D_BTT as SM implying its potential use as a simulant. The transport parameters for various 2‐CEPS/elastomer systems were also determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009