Regulated cascode switched-current memory cell

A new sampled-current signal processing cell is presented. When operated with its memory transistor in saturation it can be designed with high signal swing and low supply voltage. Alternatively, with the addition of a simple clock circuit to produce nearly constant switch charge injection, the memory transistor may be operated in nonsaturation to improve accuracy.<>     

Intentional overstress trimming of active semiconductor devices

An alternative methodology for adjusting the performance of electronic systems to ensure that they are operating according to the required specifications is described. Intentional electrical overstress is employed to systematically adjust the performance of integrated devices and circuits. It is shown that such an approach can trim selected circuits even after they have been assembled into packages. The trimming approach discussed is based upon the introduction of systematic and repeatable changes in transistor parameters by energetic pulses applied between appropriate terminals of the device. A preliminary reliability assessment of the technique has been performed, and the available results are discussed     

A simultaneous SAXS/WAXS and stress-strain study of polyethylene deformation at high strain rates

An experimental system has been commissioned which allows the collection of time-resolved simultaneous two-dimensional small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS) and stress-strain data with a temporal resolution of 40 ms during the drawing of synthetic polymers. X-ray data collection is achieved via two CCD-based area detectors which are positioned in order to maximize the amount of scattering that can be observed from a particular sample. True stress-strain measurements are obtained from video extensometer and load cell measurements. The system was used at the Daresbury SRS to study the structural changes which occur in a sample of isotropic high-density polyethylene when subjected to an overall strain rate of ≈ 3 s⁻¹. It is shown that the onset of both a partial stress-induced crystal phase change and micro-voiding in the sample can be directly correlated to the point of yield in the true stress-strain curve. © 1997 Elsevier Science Ltd.     

Computer-based engineering of thermostabilized antibody fragments

We used the molecular modeling program Rosetta to identify clusters of amino acid substitutions in antibody fragments (scFvs and scAbs) that improve global protein stability and resistance to thermal deactivation. Using this methodology, we increased the melting temperature (T_m) and resistance to heat treatment of an antibody fragment that binds to the Clostridium botulinum hemagglutinin protein (anti-HA33). Two designed antibody fragment variants with two amino acid replacement clusters, designed to stabilize local regions, were shown to have both higher T_m compared to the parental scFv and importantly to retain full antigen binding activity after 2 hr of incubation at 70°C. The crystal structure of one thermostabilized scFv variants was solved at 1.6 Å and shown to be in close agreement with the RosettaAntibody model prediction.     

Economic growth through entrepreneurship: Determinants of self-employed income across regional economies

Knowledge of the determinants of self-employment income is critical to entrepreneurial development strategies if the development goal is to increase incomes not just employment. Using American Community Survey data, unconditional quantile regression is used to investigate differences in the relationship between entrepreneurial income and an array of individual, industry, and regional characteristics across the self-employment income distribution. Personal attributes, such as education, race, age, and gender, both explain differences in self-employment income and vary in importance across the income distribution. Regional agglomerative effects are significantly positive and stronger at the upper end of the self-employed income distribution.     

Removal of Metals and Acidity from Acid Mine Drainage Using Municipal Wastewater and Activated Sludge

Co-treatment of acid mine drainage (AMD) and municipal wastewater (MWW) using the activated sludge process is an innovative approach to AMD remediation that utilizes the alkalinity of MWW and the adsorptive properties of the wastewater particulates and activated sludge biomass to buffer acidity and remove metals. The capacity of these materials to treat AMD was investigated in batch mode metal removal tests using high-strength synthetic AMD (pH 2.8, Al 120–200 mg/L, Cu 18–30 mg/L, Fe 324–540 mg/L, Mn 18–30 mg/L, and Zn 36–60 mg/L). Using material from a range of MWW treatment plants, the performance of screened and settled MWW, activated sludges with mixed liquor suspended solids (MLSS) concentrations of 2.0 and 4.0 g/L, and return activated sludges with 6.0 and 7.4 g/L MLSS were compared. Similar trends were observed for the MWW and activated sludges, with removal efficiency generally decreasing in the order Al = Cu > Mn > Zn > Fe. Trends in Fe removal using settled MWW and activated sludges were highly variable, with removal <30 %. Using activated sludges, average removal efficiencies for Al, Cu, Mn, and Zn were 10–65 %, 20–60 %, 10–25 %, and 0–20 %, respectively. Sludge solids concentration was an important controlling factor in metal removal, with removal of Al, Cu, Mn, and Zn increasing significantly with solids concentration. Municipal wastewaters had greater neutralization capacities than activated sludges at high AMD loading ratios. Mixing AMD with screened MWW gave the highest removal efficiency for all metals, achieving average removal of 90–100 % for Al, Cu, and Fe, 65–100 % for Zn, and 60–75 % for Mn. These empirical findings are useful for developing process design parameters in co-treatment systems. Utilizing MWW and activated sludge to remediate AMD can potentially reduce materials and energy requirements and associated costs.