Study of 18-cm long single-sided AC-coupled silicon microstripdetectors

The SSC GEM silicon Central Tracker design incorporated 18-cm long single-sided AC-coupled silicon microstrip ladders. Compared to the 12-cm long ladders considered in the preliminary stages of the tracker design, the 18-cm long ladders have the advantage of reduced cost, channel count and overall power consumption, and led to a simplified tracker assembly. However, such long ships also present the challenge of maintaining satisfactory performance. The increased capacitance and series resistance contribute to lower signal-to-noise ratios, longer time walk, higher power consumption per channel and increased probability of crosstalk to neighboring channels. In this paper, an accurate method to calculate the geometric capacitance of the AC-coupled microstrips is presented and the calculated results are compared with measurements, SPICE simulations are performed to predict the noise, the extent of interstrip capacitive coupling and the dispersion of the detector signal due to the finite series resistance of the metal strips and the long length of the detector. The influence of the preamplifier current and the shaping time on the signal and noise levels is also presented. The study concludes that the 18-cm long ladders can successfully satisfy the performance goals of the GEM silicon Central Tracker     

Propagation of a quasi-shear horizontal acoustic wave in Z-Xlithium niobate plates [and conductivity sensor application]

It is found that an acoustic wave which is nearly polarized in the shear horizontal (SH) direction can propagate along the X axis of a Z-cut lithium niobate plate if the ratio h/λ, where h=plate thickness and λ=acoustic wavelength, is less than about 0.5. Attractive properties of this quasi-SH wave include: (1) phase velocity nearly constant for all values of h/λ; (2) ability to propagate in contact with a liquid medium; and (3) electromechanical coupling coefficient as high as 0.15. These properties make the wave attractive for use in a variety of sensor and signal processing applications. An example of sensor applications is illustrated by using the wave to measure conductivity of liquids (aqueous KCl solution). The frequency of a 12-MHz quasi-SH mode oscillator fabricated on a 0.48 wavelength thick Z-X lithium niobate plate is found to vary by more than 80 kHz for variation in KCI concentration from 0 to 0.15%     

Neural networks and blood cell identification

The objective of this project is to propose a method of identifying cells found in human blood and to classify them based upon their morphological features using neural networks. The project focuses on three major blood cell types, namely, erythrocytes, leukocytes and platelets. The data are collected using peripheral blood smears from clinical patients. The image acquisition requires 100x magnification on all the blood smears, the preprocessing involves the use of median and edge enhance filters; the feature extraction is done by performing the wavelet transform on the images. Finally classification of the blood cell types is done using ALOPEX and Back Propagation trained neural networks. The efficacy of both networks is then compared by comparing their outputs and number of iterations required to reach the final result.     

Potential difference and photovoltaic effect arising from distortion of the electron wave function in a GaAs quantum well with a thin AlGaAs barrier

This paper discusses changes in the spectrum and distortion of the electron wave function of a GaAs quantum well when a thin AlGaAs barrier is introduced into it. The potential difference generated across the quantum well by distortion of the electron wave function is calculated, along with its dependence on the position of the barrier in the quantum well. The photovoltaic response of the structure to optical intersubband excitations is also calculated, along with the role of wave function and electronic spectrum distortion as well as intersubband nonradiative transitions in generating this response. The suitability of a GaAs quantum well with a thin barrier for use as an infrared detector is considered. Fiz. Tekh. Poluprovodn. 32, 1246–1250 (October 1998)     

Tomsk complex for neutron-transmutation doping of silicon

All-Union Scientific-Research Institute of Nuclear Physics at the S. M. Kirov Tomsk Polytechnical University. Translated from Atomnaya énergiya, Vol. 79, No. 1, pp. 38–40, July, 1995.     

A microprocessor-based toggle-control lighting system

Analysis, design, practical consideration, and implementation of a microprocessor-based toggle-control lighting system are presented. The system is primarily configured with a power factor corrector (PFC), a square-wave voltage generator, a manually controlled toggle switch, and two relays. Toggling the toggle switch can select a different number of lamps in operation, resulting in a mutual dimming feature. A fluorescent lamp lighting system with this specific ballast gains the merits of lower system cost and more flexibilities in lighting fixture design, as compared to conventional systems     

An inhibitor of DNA topoisomerase I from Xenopus laevis ovaries

A novel, heat-resistant and Pronase-sensitive, inhibitor of eukaryotic DNA topoisomerase I has been purified from Xenopus laevis ovaries. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the most purified fraction revealed three bands with apparent molecular masses of 25, 28.5, and 33.5 kDa. The 25- and 33.5-kDa peptides recovered from an SDS-PAGE gel inhibited X. laevis DNA topoisomerase I. The purified inhibitor was specific to DNA topoisomerase I and did not inhibit other DNA enzymes tested. The inhibitor blocked the catalytic activity of DNA topoisomerase I by interacting with the enzyme, rather than by competing for binding sites on substrate DNA. Binding of DNA topoisomerase I to substrate DNA was blocked by the inhibitor, as was the cleavage reaction catalyzed by DNA topoisomerase I. Inhibition of DNA topoisomerase I was relieved by divalent cations Ca2+, Mg2+, or Mn2+.