Design and evaluation of an optically triggered monolithic sampleand hold circuit using GaAs MESFET technology

The design and evaluation of an optically triggered, fully integrated sample and hold circuit (OS/H) is described. Measured results are presented that demonstrate operation of this circuit at 250 Ms/s and with effective resolution approaching 8 bits. The integrated circuit, which measures 2.1 mm×1.4 mm, is realized in -1.0-V threshold, 20-GHz ft GaAs MESFET technology, consumes approximately 200 mW of power, and requires one optical address. The OS/H will find applications in high precision, hybrid, and integrated signal processing systems where high speed, high levels of parallelism, and low timing jitter are important. Measured results of a series photoconducting (Auston switch) OS/H realized in the same technology are presented for comparison purposes     

Some electrohydrodynamic effects in fluid dispersions

Under the combined influence of applied shear and electric fields, the macroscopic behavior of suspensions reflects coupling of the two fields which produces stresses at the phase boundaries. These stresses in turn cause motion and/or deformation of the suspended phase. Electrohydrodynamic (EHD) factors which govern these motions and deformations are reviewed in detail. both in a general theoretical context and also in terms of extensive experimental observations. Throughout an attempt has been made to relate the microscopic behaviour (including interactions) of the suspended phase to macroscopically observable or bulk properties of the suspension as a whole.The phenomena reviewed here are important to a large number of colloidal problems of interest to the physical, biological and earth sciences.     

Mobilities of some positive and negative hydrogen ions in He and H2

Mobilities of H⁺ and H^? in He and in H₂, and of H⁺₂ and H⁺₃ in He, are calculated from ion-neutral potentials derived from theory and ion-beam scattering. Agreement with experiment is reasonable except for H^? in H₂ and H⁺₂ in He, which present unexplained puzzles.     

Well depths of XeF− and XeCl− from ion transport data

Mobility and diffusion data for F^? and Cl^? ions in Xe gas at 300 K are used to test the well depths and the “width” of the XeF^? well previously obtained by a fit to differential scattering cross sections.     

The Landau-Lifshitz equation,elliptic curves and the ward transform

The Landau-Lifshitz (LL) equation is studied from a point of view that is close to that of Segal and Wilson's work on KdV. The LL hierarchy is defined and shown to exist using a dressing transformation that involves parameters ₁, ₂, ₃ that live on an elliptic curve . The crucial role of the groupK ₂ × ₂ of translations by the half-periods of and its non-trivial central extension is brought out and an analogue of Birkhoff factorisation for -equivariant loops in is given. This factorisation theorem is given two treatments, one in terms of the geometry of an infinite-dimensional Grassmannian, and the other in terms of the algebraic geometry of bundles over . Further, a Ward-like transform between a class of holomorphic vector bundles on the total spaceZ of a line-bundle over and solutions of LL is constructed. An appendix is devoted to a careful definition of the Grassmannian of the Frechet spaceC (S ¹).     

Light streak tracking of optically trapped thin microdisks

Nonspherical particles can uniquely probe soft system dynamics. We show that laser tweezers stably trap thin coinlike microdisks in 3D with an edge-on orientation. Scattered light forms a streak that we track using a fast camera to measure the disk's angular displacement. Linearly polarized tweezers rotationally trap a birefringent disk, and we measure its harmonically bound Brownian rotation over 5 decades in time. Near a surface, the disk exhibits a translational-orientational switchback oscillation. Circularly polarized tweezers rotate the disk and streak, yielding a colloidal lighthouse.     

Measurements of F2 and xF(nu)(3) - xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe Data in a Physics Model-Independent Way

We report on the extraction of the structure functions F2 and DeltaxF(3) = xF(nu)(3)-xF(nu;)(3) from CCFR nu(mu)-Fe and nu;(mu)-Fe differential cross sections. The extraction is performed in a physics model-independent (PMI) way. This first measurement of DeltaxF(3), which is useful in testing models of heavy charm production, is higher than current theoretical predictions. The ratio of the F2 (PMI) values measured in nu(mu) and mu scattering is in agreement (within 5%) with the predictions of next-to-leading-order parton distribution functions using massive charm production schemes, thus resolving the long-standing discrepancy between the two sets of data.     

Some recent studies at Coventry University sonochemistry centre

Three main areas of research at Coventry University are discussed: the uses of power ultrasound in polymer science (for both synthesis and degradation) and its effects on catalytic reactivity and radical production in solution.     

Self-assembly of boehmite nanopetals to form 3D high surface area nanoarchitectures

A flower-like boehmite nanostructure was prepared through a template-free chemical route by the self-assembly process of nanosize petals 800–1000 nm long, 200–250 nm wide, 20–50 nm thick and having an average crystallite size of about 2.21 nm. X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), DTA/TGA analyses and Brunauer–Emmet–Teller (BET-N₂) analyses were used in order to characterize the product obtained. XRD results exhibited that the obtained nanostructures composed of pure orthorhombic AlOOH phase. The effects of Cl⁻ ions and TEA on the growth of boehmite three-dimensional nanoarchitectures in the presence of NO₃^-\mathrm{NO}_{3}^{-} ions were investigated. BET analyses of as-prepared material demonstrate that this nanostructure material has a high specific surface area, as high as 123 m² g⁻¹.