Polyamino acids and cytochrome C anchored rhodium complexes

Polyamino acids (amino acid = valine, alanine, lysine and arginine) and the protein cytochrome C (Cyt C) have been treated with [Rh(CO)₂Cl]₂ (1) to give polymersupportedcis-dicarbonyl species. The polymer-supported rhodium complexes, characterised on the basis of infrared and ESCA data, have been found to undergo reversible decarbonylation reaction. The Cyt C-supported rhodium complex acts as a hydrogenation catalyst of low to moderate activity. In the hydrogenation of 3-methyl cyclohexanone no stereoselectivity has been observed.     

Chemical ionization mass spectra of chlorine-substituted aryl-propio- and -butyro-nitriles: Occurrence of an unusual radical-induced cyclization process

The chemical ionization (CI) induced reactions in certain chlorine-containing aryl-substituted alkyl nitriles have been studied using different reagent gases including ND₃ and CD₄ and with the help of collisional activation spectra. A few fragmentations can be explained only on the basis of protonation of or electrophilic attachment to neutral products formed in the CI source. A detailed investigation of the unusual dehalogenation and dehydrohalogenation reactions occurring in some of these molecules has shown that radical-induced cyclization processes give rise to these ions.     

A Convenient Synthesis of 3-Nitro-2-pyrrolines: Regioselective Oxidations of Substituted Pyrrolidines to Pyrrolines+

A regiospecific oxidation of 3-nitro-4-substituted phenyl pyrrolidines with KMnO₄ to 3-nitro-4-substituted phenyl 2-pyrrolines and the hydroxymethylations of 3-nitro-4-substituted phenyl pyrrolidines have been described.     

Microscopic TV holography for MEMS deflection and 3-D surface profile characterization

Recent industrial demands for greater product quality in the fields of microelements and micro-electro-mechanical systems (MEMS) generate new challenges for metrology. The fast-growing MEMS industry requires a robust non-destructive quantitative measurement system for the characterization of their performance, reliability and integrity. A microscopic TV holographic system using a long working distance microscope with an extended zoom range has been developed for microelements and MEMS deformation and 3-D surface profile analysis. The system is capable of evaluating both rough and smooth surfaces. Noisy wrapped phase map is a usual problem in speckle interferometry. We have compared several phase-shifting algorithms for evaluation of speckle phase for their usefulness in generating less-noisy phase maps. The experimental results on a MEMS pressure sensor for out-of-plane deflection and 3-D surface profile analysis are presented.     

High diffusion length silicon germanium alloy thin films deposited by pulsed rf PECVD method

Hydrogenated amorphous silicon germanium (a-Si_1?xGe_x:H) alloy thin films were deposited in a rf (13.56 MHz) powered plasma CVD system from a mixture of silane, germane and hydrogen. The rf power was pulsed at a frequency of 1356 Hz with the duty cycle (Q) ranging from 50% to 100%. The Ge content in the films, found in the range 40–45%, was deduced from Raman spectra. The band gaps E_g of the films were in between 1.44 and 1.48 eV. We find a good correlation between the ambipolar diffusion length (L_d) and the microstructure factor ($R^1$) for different duty cycles. At Q = 75% the $R^1$ value is lowest (0.14) which correlates well with the maximum value of L_d (100 nm), the highest L_d value reported for a-Si_1?xGe_x:H films with E_g = 1.44 eV. It was also found to be very stable under light soaking. Powder incorporation within the films was also studied. Quality of the films is determined by two opposing effects viz. size of the powders incorporated into the films from the plasma and the bombardment of energetic ions and neutrals. Best transport properties were found at an optimum duty cycle of 75%.     

Two-wavelength micro-interferometry for 3-D surface profiling

Three-dimensional non-contact optical techniques for rapid and accurate mapping of micro-machined surfaces are important for the optoelectronic industry. Interferometry is a well-established technique for 3-D surface profiling. The conventional interferometric surface profilers using a single wavelength offer excellent vertical resolution, but a serious limitation to their use is that they can only handle smooth profiles and step heights less than half a wavelength. In this paper we describe a two-wavelength micro-interferometric setup for 3-D surface profile characterization of smooth as well as rough micro-specimens. The method removes ambiguity associated with the single-wavelength data and also extends the phase measurement range compared to the conventional single-wavelength interferometry. Seven-phase step algorithm is used for quantitative fringe analysis. The design of the system along with experimental results on smooth and rough micro-specimens is presented.     

The Baylis-Hillman chemistry in aqueous media: elucidation of mechanism for synthesis of ether side-product leads to an efficient approach to C-O bond formation

The formation of an ether from the Baylis-Hillman (BH) adduct during the BH reaction of 5-isoxazolecarboxaldehydes is a common phenomenon if the reaction is allowed to proceed for longer periods. The amount of formation of such ethers depends on the acrylates used and is most significant for tert-butyl acrylates. A study of the plausible mechanism for the formation of these side-products led to reactions of acetates of BH adducts with phenol in aqueous media to yield the corresponding 3-phenoxy alk-2-enoates in good yields. The successful translation of solution phase methodology to solid phase for application towards combinatorial chemistry is discussed.     

Solitary waves in a class of sine-Gordon-type equations

A new class of sine-Gordon-type Lagrangians is studied for solitary-wave solutions. The potential is a series with N terms, N varying from 1 to ∞, and N=1 corresponding to the usual sine-Gordon form. The large- and small-x limits of the solutions are obtained analytically for arbitrary N. The large-x behaviour is shown to be distinct for N even or odd. Also, the solutions for arbitrarily large but finite N are found to differ exponentially from the N=∞ solution, for asymptotically large x.     

Photopolymerization of methyl methaerylate initiated by benzil in non-aqueous media

Summary Kinetics of polymerization of methyl methacrylate initiated by photolysis of benzil with 420 nm radiation, have been investigated at 35 °C. The rate of monomer disappearance has been followed gravimetrically and the chain-length of the polymer formed, measured by viscometry. The dependence of the rate of polymerization and quantum yield of monomer conversion on the concentrations of the monomer and the initiator, absorbed light-intensity etc. has been studied in detail. A kinetic scheme has been proposed in the light of experimental results, involving i) a primary photochemical act of excitation of the sensitizer producing free radicals by hydrogen abstraction, ii) initiation of polymerization by free radicals generated and iii) termination of the active chain by mutual combination involving either coupling or disproportionation.With 3 figures and 2 tables