Ion transport studies in calcium alginate gels by magnetic resonance microscopy

Polyelectrolyte biopolymers such as calcium alginate are becoming increasingly important for the recovery of heavy metals from aqueous solutions. To understand the mechanism of ion transport in these biopolymer systems, the transport of copper ions into calcium alginate gels was investigated using proton nuclear magnetic resonance (NMR) microscopy. Copper ion transport was imaged using an inversion recovery technique which utilizes the paramagnetic effect of copper on water proton relaxation times. Diffusion experiments were performed in a diffusion cell designed to approximate a semi-infinite slab geometry at temperatures between 278 and 313 K using copper reservoir concentrations between 10 and 60 mM. The diffusion coefficient of copper in these gels was calculated from the NMR data to fit a combined diffusion-reaction model involving a diffusion term (D) and a kinetic binding term (k). At 23 °C, the diffusion coefficients in 1, 2, and 3% (w/v) gels were 3.1 · 10⁻¹⁰, 2.0 · 10⁻¹⁰, and 1.4 · 10⁻¹⁰ m²/s, respectively. The activation energy for diffusion in the 2% (w/v) gel was 28 kJ/mol.     

A novel A/D converter using resonant tunneling diodes

A large-signal resonant tunneling diode (RTD) model is used to simulate the performance of a 2-b A/D converter. Results from the theoretical analysis, the breadboard circuit demonstration, and the SPICE3 simulation are discussed. It is shown that the unique folding characteristics of the vertically integrated RTD greatly reduce the complexity of the A/D converter circuit, making analog-to-digital conversion at tens-of-gigahertz rates possible     

Array processor supercomputers

The authors describe the range of hardware variations of array processors, a form of SIMD (simple instruction stream, multiple dates stream architecture), comparing and contrasting the significant differences among them and briefly illustrating the wide range of algorithms that can effectively utilize them. Three applications are reviewed. The first application, image convolution, represents the traditional numerically computationally intensive areas of application. SIMD array processors are sufficiently powerful to process digital imagery in real time easily. The second application, an example of real-time database management, is the air traffic control problem. The problem cannot be solved today by networks of computers that are successfully used in similar, less time-critical applications. With an array processor there is sufficient real time remaining after the present system tasks are accomplished to realize additional system enhancements. The third application area, graph algorithms, which is more theoretical, is representative of problems for which the simplicity of the array processor solution results in an execution time better than the best theoretical case for a conventional sequential implementation     

Optimization of HfSiON using a design of experiment (DOE) approach on 0.45 V Vt Ni-FUSI CMOS transistors

We report for the first time that the optimization of a HfSiON process on Ni-FUSI devices is best tackled using a design of experiments (DOE [Myers RH, Montgomery. Response surface methodology. New York, DC: Wiley; 1995]) approach. We show that a DOE allows for directly linking process parameters to relevant short channel performance metrics. By tuning the SiO₂ thickness, HfSiO thickness, Hf concentration, nitridation parameters and by using response surface modeling (RSM), we report an improvement of 12%/17% in nMOS/pMOS drive current (I_dsat 600/255 uA/μm at I_off = 20 pA/μm and V_dd = 1.1 V) over our reference process. In parallel, we demonstrate that by selecting the right parameters, plasma nitridation can outperform thermal nitridation with NH_3. We believe that this new approach will be useful for device engineers and can be easily applied.     

Study of charmless hadronic B meson decays to pseudoscalar-vector final states

We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.     

Observation of the Omega(0)(c) Charmed Baryon at CLEO

The CLEO experiment at the CESR collider has used 13.7 fb(-1) of data to search for the production of the Omega(0)(c) (css ground state) in e(+)e(-) collisions at square root of (s) approximately 10.6 GeV. The modes used to study the Omega(0)(c) are Omega(-)pi(+), Omega(-)pi(+)pi(0), Xi-K-pi(+)pi(+), Xi0K-pi(+), and Omega(-)pi(+)pi(+)pi(-). We observe a signal of 40.4+/-9.0(stat) events at a mass of 2694.6+/-2.6(stat)+/-1.9(syst) MeV/c(2), for all modes combined.     

Synthesis of heterosubstituted hexaarylbenzenes via asymmetric carbonylative couplings of benzyl halides

[structure: see text]. Asymmetric carbonylative couplings of benzyl halides have been shown to give heterosubstituted 1,3-diarylacetones in moderate to high yields. These asymmetric ketones were converted via Knoevenagel condensations to tetraarylcyclopentadienones, and further conversion via dehydro-Diels-Alder cycloadditions gave highly heterofunctionalized hexaarylbenzenes with uniquely functionalized aryl groups at the para positions of the central benzene. This method allows control of the substituents on each of four unique pendent aryl group positions, giving rise to substitution patterns not available using symmetrical 1,3-diarylacetones.