Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation

The H(-) injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ～38 mA beam current in the linac at 60 Hz with a pulse length of up to ～1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.     

Modeling and simulation of gas separations with spiral-wound membranes

Models for gas separations with spiral-wound membranes are developed and found to exhibit good agreement with experiments performed on N₂/O₂ mixtures. The two-dimensional (2D) model can be accurately approximated by a one-dimensional (1D) surrogate model when the spacer widths are chosen to make the channel pressure drops small. Subsequently, the separation of propane/propylene mixtures from the recycle purge stream of a polypropylene reactor is investigated. Assuming ideal gas is found to lead to significant overestimations in membrane stage cuts (sometimes more than 10%), an extent comparable to that associated with extrapolating constant olefin permeance from a low-pressure condition. While olefin permeance can change significantly with pressure, using a constant-permeance formulation can result in a small (< 2.5%) underprediction in stage cut if the value for the permeance is taken from the feed condition. Finally, membrane properties and costs necessary for a viable separation process are discussed.     

Biasing technique via bulk terminal for minimum supply CMOS amplifiers

A biasing technique for minimum supply CMOS amplifiers is proposed. The bulk terminals of the input transistors of a pseudo-differential amplifier are exploited in a switched-capacitor control loop to set the quiescent current. Simulations on a design powered with 0.7 V show that the performance obtained is comparable to that of a traditional differential pair supplied with 1 V.     

CMOS multiplier for grounded capacitors

A CMOS circuit suited particularly to magnifying the value of a grounded unit capacitor is presented. The multiplication factor is achieved through the gain of current mirrors and its maximum value is limited solely by power consumption constraints. Solutions are then developed to reduce power dissipation, to enable the detection of small unit capacitances, and to enlarge the operating frequency bandwidth     

Symbolic factorization methodology for multistage amplifier transfer functions

In this paper, we discuss a symbolic simplification methodology to derive approximated factorized forms of the transfer function of multistage amplifiers in the complex frequency domain. The developed approach is useful for hand calculation and is also suitable to be implemented in symbolic computer‐aided design tools. Although the proposed methodology is mainly intended for the analysis and design of operational transconductance amplifiers, it can straightforwardly be applied to the small‐signal analysis of any analog linear circuit. Design examples are provided to verify the effectiveness of the proposed approach implemented through a Matlab function. Copyright © 2015 John Wiley & Sons, Ltd.     

Antioxidative effects of phenolic extracts from chestnut leaves,catkins and spiny burs in streptozotocin-treated rat pancreatic β-cells

Oxidative stress plays a central role in the onset of diabetes which is characterised by progressive pancreatic β-cell failure. We studied the ability of phenolic extracts prepared from chestnut leaf, catkin and spiny burs to prevent oxidative stress-induced β-cell (Rin-5F) death. The Rin-5F cell death was induced by treatment with the diabetogenic agent streptozotocin (STZ) and the protective effects of the chestnut extracts were assessed after cells treatment with a STZ/extracts mixture. The chestnut extracts increased cell viability by protecting DNA from oxidative damage and by enhancing the natural antioxidant system. Moreover, the chestnut extracts had a significant impact on the cell’s redox-status which was observed as an increase in the levels of reduced glutathione. Chestnut extracts were capable of inhibiting lipid peroxidation, which was manifested as a lowering of malondialdehyde levels. We concluded that chestnut extracts increased cell viability after STZ treatment as a result of their antioxidative properties.