A quad 500 MHz waveform digitizer with differential trigger for use in the muon g-2 experiment

We have developed and tested a 4 channel, 500 MHz, 512 k sample, 8 bit waveform digitizer in a FASTCAMAC module. A novel feature is the implementation of a sparse scan during readout with a programmable differential trigger to reduce the data to a manageable level. The differential trigger allows reliable detection of pulses with low threshold in the presence of a variable baseline.     

Copolyperoxides of 2-(acetoacetoxy)ethyl methacrylate with methyl methacrylate and styrene; Synthesis,characterization, thermal analysis,and reactivity ratios

Copolyperoxides of 2-(acetoacetoxy)ethyl methacrylate (AEMA) with styrene (St) and methyl methacrylate (MMA) of different compositions have been synthesized in the presence of 2,2′-azobisisobutyronitrile as a free radical initiator under 100 psi oxygen pressure at 50 °C. The rates of oxidative copolymerization reactions are determined from the oxygen consumption (Δp) against time plot. Highly exothermic thermal degradations of these copolyperoxides are studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and degradation products have been characterised by electron-impact mass spectroscopy (EI-MS). The NMR spectroscopy and EI-MS analysis confirm the alternating peroxy bonds in the main chain. The monomer reactivity ratios are computed by the Fineman–Ross and Kelen–Tüdös methods, using compositions obtained from ¹H and ¹³C NMR analysis. These copolymers can potentially be used as polymeric initiators for the radical polymerization of vinyl monomers, autocombustible fuel. Also, the β-carbonyl moieties along the side chain of the copolyperoxides can be utilized to prepare degradable polyperoxide–metal complexes.     

Electrical,optical and hole transport mechanism in thin films of poly(3-octylthiophene-co-3-hexylthiophene): Synthesis and characterization

The present study demonstrates the designing of copolymer poly(3-octylthiophene-co-3-hexylthiophene) (P3OT-HT) and study of the hole transport mechanism in it. Detailed structural, optical and thermal studies of P3OT-HT discuss its synthesis aspects. Current density–voltage characteristics have been studied at different temperatures (290–110 K) to understand the mechanism of hole transport in P3OT-HT. It has been established that current density in P3OT-HT thin films is governed by space charge limited conduction with traps distributed exponentially in energy and space. Hole mobility is both temperature and electric field dependent arising due to substituent functional groups attached the polymer backbone.     

Liquid crystal order in colloidal suspensions of spheroidal particles by direct current electric field assembly

DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor-like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field-assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self-assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.     

Release kinetics of nisin from biodegradable poly(butylene adipate-co-terephthalate) films into water

The release kinetics of nisin from poly(butylene adipate-co-terephthalate) (PBAT) to distilled water was studied at of 5.6, 22 and 40 °C. The release kinetics of nisin from PBAT film was described using Fick’s second law of diffusion, partition coefficient, and Weibull model. The diffusion coefficients (D) determined were 0.93, 2.29, and 5.78 × 10⁻¹⁰ cm²/s at 5.6, 22, and 40 °C, respectively. The partition coefficients (K) calculated were 0.84, 3.89, and 5.2 × 10³ at 5.6, 22, and 40 °C, respectively. The nisin release data at selected temperatures were fitted with the Weibull model (R² > 0.97) with b and n values ranging from 0.02 to 0.98 and from 0.28 to 0.45, respectively. The temperature dependence of D, K, and Weibull model parameter b was modeled using the Arrhenius equation giving values of activation energy (E_a) of 38.3 kJ mol⁻¹ (for D), 38.5 kJ mol⁻¹ (for K), and 79.5 kJ mol⁻¹ (for b).     

X-ray study of the air-oxidiseda-Ga2Se3 and Ga2Te3 powders

X-ray studies of the stoichiometrically prepareda-Ga₂Se₃ and Ga₂Te₃ are reported after various stages of air-oxidation in the temperature ranges 250 to 825° C and 250 to 650° C respectively. Diffractometric powder data of Ga₂Te₃ are also reported over the complete 2ϑ range with remarkable difference in the relative intensities of the (444) and (642) reflections. Ina-Ga₂Se₃ the oxidation proceeds by formation of the most stable phase, beta-gallium sesquioxide, complete oxidation occurring at 650° C. For Ga₂Te₃ a mixture of Ga₂TeO₆ and TeO₂ is obtained as the intermediate oxidation products in the range 500 to 600° C, while at 450° C some extra lines which could be indexed on the super-lattice cell of Ga₂Te₃, along with Te and unchanged Ga₂Te₃ lines, are observed. Oxidation at the higher temperature of 650° C led to the disappearance of TeO₂ lines leaving Ga₂TeO₆ as the final well-crystallised phase.     

Photomicrographic size distribution determination of non-spherical objects

Equations have been developed for calculating the size distribution of non-spherical objects by using photomicrographs prepared of sections or projections of samples. The equations contain the shape function characteristic of the shape of the objects in the sample which is also determined from the photomicrographs. The equations have been applied to the void size distribution determination in various sandstones and packed beds of beads, as well as to the particle size distribution determination of a sample of common salt. It has been found that the new equations resulted in plausible calculated size distributions in the case of highly anisotropic objects, whereas this was not the case when the sphere model was used as a basis for the calculations. In the case of the salt particles, however, the sphere model was almost equally adequate as the shape function method, because the shape function was, in this case, very nearly spherical.     

Effects of Defects on Charge Transport in Armchair Nanoribbon WS2 Field Effect Transistors

We have studied the WS₂ armchair nanoribbon with various defects like vacancy, edge roughness, twist, turn and ripple and compared how the bandgap changes due to such defects with the bandgap of a nanoribbon with no defects. Materials like WS₂ and other transition metal dichalcogenides (MX₂) have a graphene like layered structure with hexagonal rings and have properties that have attracted a lot of interest. Hence it is essential to study the changes in the band structure of the nanoribbon of WS₂ due to the inclusion of defects like vacancy, rough edge, wrap, ripple and twist for making any device based on WS₂.