Using electric actuation and detection of oscillations in microcantilevers for pressure measurements

Response characteristics of a microcantilever, such as resonant frequency, amplitude, phase and quality factor, can be used for absolute pressure measurements in the range of 10⁻⁴ to 10³ Torr. To this end, it would be very convenient to have the resonance of the microcantilever actuated and detected electrostatically. Herein, we report the nonlinear dynamics of microcantilevers under varying pressure and different gases using the harmonic detection of resonance (HDR) technique [J. Gaillard, M.J. Skove, R. Ciocan, A.M. Rao, Electrical detection of oscillations in 340 microcantilevers and nanocantilevers, Rev. Sci. Instrum. 77 (2006) 073907]. The HDR technique exploits nonlinearities in the cantilever-counter electrode system to allow electrostatic actuation and detection of the responses of the microcantilever to the pressure and gas composition. In particular, the 2nd and 3rd harmonics of the measured charge on the cantilever are investigated. The microcantilever demonstrates a quality factor of 10,000 at 10⁻³ Torr, and a usable response in the range from 10⁻³ to 10³ Torr. The use of different harmonics can enable us to adjust the range of pressures over which the sensor has an efficacious response, enhancing its sensitivity to a particular environment. The experimental results are in reasonable agreement with theoretical calculations, despite the nonlinearities involved.     

Homogeneous asymmetric hydrogenation ofo-chloroacetophenone to enantiomerically pureo-chloro-(1-phenyl)ethanol catalyzed by BINAP-Ru(II) complex

The BINAP-Ru(II) catalyst (2,2-bis(diphenylphosphino)-1,1-binaphthyl)chloro(p-cymene)rutheniun chloride is found to be highly active and enantioselective for homogeneous asymmetric hydrogenation of o-chloroacetophenone to optically pureo-chloro-(1-phenyl)ethanol. In contrast to results of Noyori and coworkers, no organic and inorganic bases are required to obtain high activities and enantioselectivities     

Synthesis of submicron size silver powder for passive components application

Submicron silver powder was prepared from AgNO₃ by a chemical reduction method in the presence of a mixture of caprylic acid and triethanolamine as a surfactant. Hydrazine hydrate (N₂H₄·H₂O) is preferred as a reducing agent. A spherical silver powder with an average particle size of about 150 nm was achieved. Effort was also made to correlate the crystal structure and microstructure evolution of the prepared powders with the resultant thick film characteristics.     

Analysis of Fatty Acid and Lignan Composition of Indian Germplasm of Sesame to Evaluate Their Nutritional Merits

An attempt was made to individually analyze a germplasm collection of 54 indigenous Indian sesame cultivars for fatty acid and lignan composition of their seed oil by gas chromatography and high performance liquid chromatography, respectively. The entries varied in their fatty acid and lignan composition. The mean percentage contents of palmitic, stearic, oleic, linoleic and α‐linolenic acids ranged between 10–22, 5–10, 38–50, 18–43 and less than 1 whereas sesamol, sesamin and sesamolin scored between 3–37, 27–67, 20–59 of the total percentage of lignan, respectively. The highest percentage of α‐linolenic acid (ALA) was obtained in Var‐9 (1.3 % of the total fatty acids). Among the lignans, high sesamin content is considered to be significant, particularly in terms of long shelf life and nutraceutical value of sesame seed oil. The study has broadened our understanding related to differential biochemical composition of the rich sesame germplasms, thereby providing us with a useful groundwork for identifying potential targets and suitable cultivars for genetic engineering approaches to be undertaken in order to improve the nutritional quality of sesame oil, which in turn would be beneficial towards human health.     

Evolution of properties of parts during MIM and sintering of recycled oxide particles

Metal injection moulding (MIM) is an established process for high volume production of complex shaped metallic parts using commercially available feedstocks. The characteristics of parts after moulding, debinding, and sintering cannot be simply predictable from raw materials because the properties get altered with the process parameters and the corresponding levels of porosity during processing steps. In this study, physical properties, microstructure, and mechanical properties of the MIM parts have been characterised to understand the evolution of strength during various steps in MIM processing. Feedstocks with different binder loading show a considerable difference in physical as well as mechanical characteristics. During sintering of parts which have solid loading of grinding sludge, simultaneous in situ reduction and densification takes place, whereas only densification occurs in carbonyl iron parts. It is, therefore, possible to make complex shaped parts of different levels of porosity from downgraded shop floor metallic waste.     

Chemopreventive Effect of Different Ratios of Fish Oil and Corn Oil in Experimental Colon Carcinogenesis

n-3 Polyunsaturated fatty acids (PUFA) have a chemopreventive effect while n-6 PUFA promote carcinogenesis. The effect of these essential fatty acids may be related to oxidative stress. Therefore, the study was designed to evaluate the effect of different ratios of fish oil (FO) and corn oil (CO) in the prevention of colon cancer. Male Wistar rats were divided into control, dimethylhydrazine dihydrochloride (DMH) treated, FO + CO (1:1) and FO + CO (2.5:1). All the groups, except the control received a weekly injection of DMH for 4 weeks. The animals were sacrificed either 48 h later (initiation phase) or kept for 16 weeks (post initiation phase). DMH treatment in the initiation phase animals showed mild to moderate inflammation, decreased ROS and TrxR activity, increased antioxidants, apoptosis and ACF multiplicity. The post initiation study showed severe inflammation with hyperplasia, increased ACF multiplicity and ROS levels, a decrease in antioxidants and apoptosis. The FO + CO (1:1) treated animals showed severe inflammation, a decrease in ROS, an increase in antioxidants and apoptosis in the initiation phase. FO + CO (1:1) in the post initiation phase and FO + CO (2.5:1) in the initiation showed mild inflammation, increased ROS, apoptosis and decreased antioxidants. There was a decrease in ACF multiplicity and ROS levels, increased antioxidants and apoptosis in the post initiation phase study. The present study suggests that FO has a dose- and time-dependent chemopreventive effect in colon cancer mediated through oxidative stress and apoptosis.     

Non-monotonic lattice parameter variation with crystallite size in nanocrystalline solids

An anomalous dependence of the lattice parameter on the crystallite size of nanocrystalline ball-milled powders of metals was observed: lattice contraction followed by lattice expansion with decreasing crystallite size. These data were determined by application of detailed X-ray diffraction measurements. To this end the lattice parameters of the metals investigated – nickel, copper, iron and tungsten – were precisely determined by correcting for influences of stacking faults, in the face-centred cubic metals, as well as by correcting for instrument-related aberrations. The non-monotonic variation of the lattice constant was interpreted as the result of two competing mechanisms: interface-stress-induced contraction vs. expansion as a result of the stress field generated at the crystallite boundary due to the increased excess free volume in the crystallite boundary upon decreasing crystallite size.     

Frequency dependent electrical transport properties of 4,4′,4″-tris(N-3-methylphenyl-N-phenylamine)triphenylamine by impedance spectroscopy

The frequency dependent ac conduction mechanism in 4,4′,4″-tris(N-3-methylphenyl-N-phenylamine)triphenylamine (m-MTDATA) has been studied as a function of applied bias and temperature. The Cole–Cole plot shows a slightly depressed semicircle indicating Debye type relaxation. This result has been explained by an equivalent circuit of the device designed as a two parallel resistor and capacitance network in series with contact resistance. The ac conduction studies under dc bias for hole only devices shows an increase in device conductivity with the increase in bias. The variation of bulk resistance with applied bias indicates Space Charge Limited Conduction (SCLC) mechanism for hole conduction. The hole mobility of the material has also been evaluated from SCLC as 8.859 × 10^?6 cm²/V s. The temperature dependent impedance studies show two activation energies indicating two different phase of the material with a phase transition at 235 K.     

Facile preparation of <Emphasis Type="Italic">Chaetomorpha antennina</Emphasis> based porous polysaccharide–PMMA hybrid material by radical polymerization under microwave irradiation

A hybrid material was prepared from the hot water soluble sulphated polysaccharide of the green seaweed Chaetomorpha antennina (CM_sps) and polymethyl methacrylate (PMMA) by radical polymerization in aqueous medium under microwave irradiation. An insoluble material was formed with the progress of the polymerization. The product was characterized by the IR spectrum and elemental analysis, as well as by acid hydrolysis followed by mass spectrum of the hydrolysate of the hybrid CM_sps–PMMA for confirming the insertion of PMMA. Comprehensive characterization of the product included TGA, XRD, ESI-MS and BET surface analysis. The hybrid material was porous, and formed gel in water–DMSO mixture. It had the crystallinity index of 0.122, and had BET pore diameter of 3.71 nm, a size which is far larger than the molecular diameters of common natural gases and zeolites (0.5–1.0 nm). This material may be useful in the domain of certain adsorption and catalytic applications.     

Hydrazine method of synthesis of γ-Fe2O3 useful in ferrites preparation. Part III – study of hydrogen iron oxide phase in γ-Fe2O3

Direct current electrical conductivity () measurements as a function of temperature have been carried out on -Fe₂O₃ prepared from precursors, iron (II) carboxylatohydrazinates, -FeOOH and hydrazinated -FeOOH. The conductivity variation obeys an Arrhenius equation, _I = \_oe^- E / kT and the plots of log versus 1/T of the as prepared -Fe₂O₃, which are in general linear, during the very first heating up to 350°C and cooling to room temperature (RT) do not overlap. This indicates a hysteresis behavior of conductivity, thereby suggesting involvement of two different conductivity mechanisms. When the heat treated sample was equilibrated in a known partial pressure of moisture at 200°C and then conductivity measured from RT, the log plots during heating and cooling did not overlap and a hysteresis behavior similar to the as prepared -Fe₂O₃ is observed again in the conductivity. Water is considered to be crucial during the synthesis of -Fe₂O₃ through magnetite, Fe₃O₄. Protons, H⁺, are thought to be introduced in the spinel Fe₃O₄ making it defective and the oxidation product of this is -Fe₂O₃ which retains few protons in its spinel structure. From the structural similarity of such proton incorporated -Fe₂O₃ and lithium ferrite, LiFe₅O₈, (Fe³⁺)₈ [Fe³⁺ ₁₂ Li¹⁺ ₄]O₃₂, a formula HFe₅O₈, (Fe³⁺)₈ [Fe³+₁₂H¹+₄]O₃₂ is suggested. A hydrogen iron oxide of formula H_1-xFe_5+x3O₈, where x 0.1 is probably formed as a maximum limit. Protons are removed during the very first heating of the as prepared sample in the present studies and hence the conductivity of proton free -Fe₂O₃ is different and therefore a hysteresis behavior is observed. Moisture equilibration reintroduces the protons. The lithiated samples in the present studies were found to substitute for protons in -Fe₂O₃ and no hysteresis behavior is observed in such samples even after moisture equilibration.