Iodine-123 labelled nor-beta-CIT binds to the serotonin transporter in vivo as assessed by biodistribution studies in rats

Flavobacterium aurantiacum NRRL B-184 possesses the ability to degrade aflatoxin B1 in solution and in several food items. Aflatoxin B1 is a potent carcinogen that causes significant economic losses to the agricultural and food industry. The role of trace metal ions (Cu2+, Mn2+, Zn2+, and Co2+) were studied in an effort to understand the enzymatic system involved in aflatoxin B1 degradation by F aurantiacum. The effect of divalent chelators (EDTA and 1,10-phenanthroline [OPT]) in the presence of the trace metal ions was studied as well. Aflatoxin B1 (10 microg/ml) was added to 72-h cultures of F aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). HPLC was used to determine aflatoxin B1 concentration in these cultures. Incubating cells at 30 degrees C with 1 and 10 mM Cu2+, Mn2+, and Zn2+ significantly decreased aflatoxin B degradation after 4 and 24 h (P < 0.05). Decreased degradation was also observed with 1 and 10 mM Cu2+ and Zn2+ after 48 h and with 0.1 mM Cu2+ after 24 and 48 h. Co2+ did not have a significant effect on aflatoxin B1 degradation. EDTA and OPT did not counter the inhibition in the presence of Cu2+. The addition of 1 mM EDTA countered the inhibition by 1 mM Mn2+ after 4 and 24 h, but 1 mM OPT did not counter the inhibition by 10 mM Mn2+ after 4 and 24 h. OPT countered the inhibition by 1 mM Zn2+ after 4 and 48 h. These trace elements inhibit aflatoxin B1 degradation by F aurantiacum. In addition, their presence necessitates higher concentrations (>1 mM) of EDTA and OPT for the removal of their inhibitory effect.     

Renal proliferative and phenotypic changes in rats with two-kidney, one-clip Goldblatt hypertension

Previous research in this laboratory has shown that preweaning and postweaning juvenile meadow voles, Microtus pennsylvanicus, can acquire a spatial task, the Morris water-maze task. The present study examined the influence of age of juvenile acquisition ("before weaning" (BW; Day 10 and 15 after birth) and "after weaning" (AW; Day 20 and 25 after birth)) of a spatial task on subsequent re-acquisition of the same hidden-platform spatial water-maze task. This study also compared sex differences and litter sex-ratio effects on reacquisition performance. Fifteen litters of adults were re-tested in the same water maze 6 weeks after being initially tested as juveniles. All analyses were conducted using a covariate that removed the group differences in the original task performance. Adult voles from female-biased litters, that had previously learned the task at an older juvenile age (AW), reacquired the same task faster than adults that had previously learned the task at a younger juvenile age (BW). In the adult BW group there was also a significant litter sex-ratio effect such that voles born into a female-biased litter re-acquired the task more slowly than did voles born into a male-biased litter. There were no significant sex or litter sex-ratio effects on spatial learning in the AW group. These results show that adult meadow voles can require a spatial task more quickly if they initially learned the task at an older juvenile age, suggestive of a period of infantile amnesia. In addition, these results indicate that the litter sex-ratio can affect adult spatial performance, suggesting that the relative amount of androgens in utero may influence the development of sexually-dimorphic spatial ability in adulthood.     

Uranium Superconductivity Redux

Since the discovery of heavy-fermion superconductivity in uranium compounds in the early 1980s, other uranium compounds have been discovered that are fully as interesting to study. However, as we look forward in the year 2000, we now have higher-purity, single crystals of the element itself. Preliminary resistivity and ac susceptibility measurements show the improved quality of the samples and thus hold the promise of understanding many aspects of its superconductivity, which have remained untouched for almost 25 years.     

Ultra-wideband hybrid-mode feeds

A modified dielectric cone-loaded horn is described that maintains excellent return loss and pattern symmetry over a bandwidth ratio greater than 30:1. The mechanisms responsible for the extremely broadband operation and its application as a feed horn for a reflector antenna are discussed     

Optimized carry lookahead adders with direct feeding

This paper describes improvements to the parallel prefix adder designs and optimization algorithms of Chan, Oklobdzija, Schlag, Thomborson and Wei. Our “direct feeding” (DF) adder design avoids large signal fanouts along critical adder paths. Our “random pruning” heuristic limits the time and space required to find near-optimal DF adders, so that the search process runs in a few minutes on a Sun-4 workstation. Our improved carry lookahead adders are well suited for static CMOS implementation; our improvements may be applied to other parallel prefix CMOS circuits. Simulations with Mentor Graphics' Lsim indicate that our best DIP adders are 12% to 20% faster than the carry lookahead adders presented by Chan et al.     

Collection and Characterization of Soot from an Optical Fiber Preform Torch

To follow the development of particle morphology, silica soot is extracted from four axial positions in the flame of a torch used to manufacture optical fiber preforms by the vaporphase axial deposition method. The soot, collected by three extraction techniques, is analyzed by transmission electron microscopy and gas adsorption to identify which characteristics of the soot morphology are dependent on the sampling technique and which upon the position in the flame. Comparison is also made to other work in which silica soot was extracted from a nondiffusion flame.     

Modelling of electrostatic gate operations in the Kane solid state quantum computer

The nuclear spin quantum computer proposed by Kane [Nature 393 (1998) 133] exploits as a qubit array ³¹P dopants embedded within a silicon matrix. Single-qubit operations are controlled by the application of electrostatic potentials via a set of metallic ‘A’ gates, situated above the donors, on the silicon surface, that tune the resonance frequency of individual nuclear spins, and a globally applied RF magnetic field that flips spins at resonance. Coupling between qubits is controlled by the application of potentials via a set of ‘J’ gates, between the donors, that induce an electron-mediated coupling between nuclear spins. We report the results of the study of the electric field and potential profiles arising within the Kane device from typical gate operations. The extent to which a single nuclear spin can be tuned independently of its neighbours, by operation of an associated A-gate, is examined and key design parameters in the Kane architecture are addressed. Implications for current fabrication strategies involving the implantation of ³¹P atoms are discussed. Solution of the Poisson equation has been carried out by simulation using a TCAD modelling package (Integrated Systems Engineering AG).     

Measuring thermal and mechanical stresses on optical fiber in a DC module using fiber Bragg gratings

Fiber Bragg gratings (FBGs) can be used as sensors to monitor stress and test temperature during the processing and handling of optical fiber. As the FBG experiences a combination of mechanical and thermal loading, the return Bragg wavelength will shift proportionately to the magnitude of the load. This paper discusses the use of these sensors in quantifying induced stress on fiber during the packaging of a dispersion-compensating module (DCM) and the ensuing environmental exposure. There are two potential fiber-failure modes for fiber wound in DCMs, namely microbend-induced attenuation and fiber failure from fatigue. The ability to quantify fiber stress provides a useful feedback tool in the design phase of these modules that can aid in reducing the risk of mechanical and optical failure modes. A practical characterization process was developed to decouple thermal and stress effects on FBGs based on results from current literature and from this study. Uncoated Bragg sensors were found to respond linearly between -40 to 80/spl deg/C. Gratings with a protective polymer recoat departed from the linear behavior of the uncoated gratings below -5/spl deg/C. It was determined that the recoat material places less than 25 MPa (3.6 klbf/in/sup 2/) of axial compression on the fiber at -40/spl deg/C. Four gratings with different Bragg wavelengths were spliced into 10 km of fiber and wound into a DCM. The wind-induced stress on all four gratings quickly relaxed. The module was then thermal cycled between -40 and +75/spl deg/C. The overall stress on each grating was acceptably low for reliability purposes. The maximum stress of 17 MPa (2.5 klbf/in/sup 2/) was observed at the lowest temperature.