Lack of evidence for an involvement of nucleus accumbens dopamine D1 receptors in the initiation of heroin self-administration in the rat

The involvement of dopamine D1 receptor systems in the reinforcing properties of opiate reward was studied by examining the effect of the dopamine D1 antagonist SCH23390 on the initiation of heroin self-administration in rats. The D1 antagonist was administered daily systemically or locally in the nucleus accumbens (NAC), after which the animals were allowed to self-administer heroin (IV) in a 3-h session for 5 consecutive days. Systemic treatment with SCH23390 (0.17 and 0.5 mg.kg-1) significantly decreased heroin intake during initiation of heroin self-administration, while a dose of 0.06 mg.kg-1 was not effective. Local administration of SCH23390 (0.5 and 2.5 micrograms/site) in the NAC did not affect heroin intake. Both systemic and intra-accumbal administration of SCH23390 dose dependently decreased motor behavior measured in a small open field. The attenuation of heroin intake during initiation of heroin self-administration by blockade of dopamine D1 receptor systems may be due to a decrease in the reinforcing effects of heroin or more likely to a reduction in non-reinforcement-related behavior. The dopamine D1 receptors present in the NAC are probably not involved in opiate reward.     

Selected Experiences with Irrigation Management Transfer: Economic Implications

After three decades of rapid increases in investment in irrigation systems, there has been an almost equally dramatic decline in irrigation investment, brought about by relatively low grain prices, rising construction costs and increased concern about the environment. As governments have been forced to reduce their public expenditures, many of them are now instituting programmes to transfer either complete or partial responsibility for management of public irrigation systems to local water users. This paper explores this transfer process in Indonesia, Colombia, New Zealand and Nigeria. From this sample it can be hypothesized that in countries where governments have had the political will to increase water fees to close to the real O&M cost, the process of irrigation management transfer has been smoother. This reflects the fact that water users are encouraged to take over management responsibility in order to reduce water costs. An equally important inducement for water users to accept additional management responsibility is better, more dependable delivery services from irrigation agencies.     

Phase transformation-induced grain refinement in rapidly solidified ultra-high-carbon steels

Superplastic forming offers a promising approach for reducing the cost of high-performance metal components with complex shapes. Severe thermomechanical deformation is one method for producing the fine grain structure needed to permit superplastic forming economically. Our approach to generating fine-grained microstructures is by cyclic heat treatment of rapidly solidified material. First, a metastable structure is produced by rapid quenching of the liquid metal. Then, solid-state phase transformations at modest temperatures are employed to refine this structure. In the ultra-high-carbon steels (UHCS) studied, the brittle as-cast structure of martensite and austenite was transformed, after cyclic heat treatment, to a ductile mixture of 1-μm ferrite and 0.25-μm carbide. Varying the heat-treat temperatures by 100 °C within the transformation range had little effect on the scale of the microstructure. Higher C resulted in coarser carbide spheroids, addition of Al refined the microstructure, and the finest mean carbide size was obtained with an intermediate level (5 pct) of Cr. Refinement of the martensite plates retained austenite via cyclic tempering and austenitization was found to be the key step in the overall mechanism for phase transformation-induced grain refinement in rapidly solidified UHCS.     

Evaluating performance tradeoffs between fine-grained andcoarse-grained alternatives

Recent simulation based studies suggest that while superpipelines and superscalars are equally capable of exploiting fine grained concurrency, multiprocessors are better at exploiting coarse grained parallelism. An analytical model that is more flexible and less costly in terms of run time than simulation, is proposed as a tool for analyzing the tradeoff between superpipelined processors, superscalar processors, and multiprocessors. The duality of superpipelines and superscalars is examined in detail. The performance limit for these systems has been derived and it supports the fetch bottleneck observation of previous researchers. Common characteristics of utilization curves for such systems are examined. Combined systems, such as superpipelined multiprocessors and superscalar multiprocessors, are also analyzed. The model shows that the number of pipelines (or processors) at which the maximum throughput is obtained is, as memory access time increases, increasingly sensitive to the ratio of memory access time to network access delay. Further, as a function of interiteration dependence distance, optimum throughput is shown to vary nonlinearly, whereas the corresponding optimum number of processors varies linearly. The predictions from the analytical model agree with similar results published using simulation based techniques     

Dynamic response of an electronically shuttered CCD imager

The dynamic response of an electronically shuttered charge-coupled device (CCD) imager to nanosecond voltage pulses has been investigated. Measurements show that the shutter can be dynamically opened and closed in nanosecond times. For the shutter opening, simulations indicate that the collection of photoelectrons occurs in times much shorter than that needed to form the steady-state depletion region under the CCD well. In addition, the shutter closing occurs faster than the reconstitution of the p-buried (shutter) layer. Simulations further indicate that electric fields created in the neutral substrate by the shutter clocks enable photogenerated charge collection/rejection on nanosecond time scales despite the fact that the depletion-region formation and collapse take much longer times.     

Processing and Properties of Tungsten Heavy AUoys with Ni48Al12Fe40 Inteimetallic Matrix

The superior ballistic penetration behavior of Depleted Uranium (DU) alloys compared to W-Ni-Fe heavy alloys (WHA) has been attributed to a self-sharpening behavior in DU where failure occurs along adiabatic shear bands. Since adiabatic shear represents a plastic flow instability condition between competing processes of thermal softening and work-hardening, cracking along these bands will occur more readily if the matrix were to embrittle with increased temperature along these shear bands. While conventional materials exhibit decreasing strength and increasing ductility with increasing temperature, certain Ll₂+f.c.c intermetaHic compounds such as Ni-12Al-40Fe(at.%) exhibit 'anomalous' behavior where sharply decreased ductility and gradually decreasing strength is observed with increasing temperatures. Hence, tungsten heavy alloys that utilize such intermetaHic matrices have potential to fail by adiabatic shear under high strain rate conditions. Heavy alloys with different weight fractions of tungsten and intermetaHic matrix were investigated. A processing sequence was developed for these novel heavy alloys such that the alloys tested consistently exhibited densities in excess of 97.5% of the theoretical. Such heavy alloys exhibit significantly increased flow stress levels compared to conventional heavy alloys and shear localization during dynamic testing. Further, failure along the shear bands occurred almost immediately following initiation of shear localization. These novel heavy alloys exhibit promise to duplicate the self-sharpening behavior of DU alloys.     

Examining changes in HRV in response to varying ambient temperature

The present study is designed to examine changes in HRV in response to ambient temperature change in college-aged men and women. We hypothesize that the VLFP (very-low-frequency power) component would be increased in the cold environment whereas the HFP (high-frequency power) component would be reduced in the hot environment with no differences between baseline and the cold condition.     

Characterization, modeling, and minimization of transient thresholdvoltage shifts in MOSFETs

MOSFETs subjected to large-signal gate-source voltage pulses on microsecond to millisecond time scales exhibit transient threshold voltage shifts which relax over considerably longer periods of time. This problem is important in high-accuracy analog circuits where it can cause errors at the 12 b level and above. In this paper, transient threshold voltage shifts are characterized with respect to their dependence on stress amplitude and duration, relaxation time, gate bias, substrate bias, drain voltage, temperature, and channel width and length. In contrast to previous studies, threshold voltage shifts are measured at time and voltage scales relevant to analog circuits, and are shown to occur even when the effects of Fowler-Nordheim tunneling, avalanche injection, hot carriers, trap generation, self-heating, mobile ions, and dipolar polarizations are absent. A new model is proposed in which channel charge carriers tunnel to and from near-interface oxide traps by one of three parallel pathways. Transitions may occur elastically, by direct tunneling between the silicon band edges and an oxide trap, or inelastically, by tunneling in conjunction with a thermal transition in the insulator or at the Si-SiO₂ interface. Simulations based on this model show excellent agreement with experimental results. The threshold voltage shifts are also shown to be correlated with 1/f noise, in corroboration of the tunneling model. Techniques for the minimization and modeling of errors in circuits are presented     

Calisto: A low-power single-chip multiprocessor communications platform

The convergence of voice, data, and multimedia transport with traditional telephony demands reliable and high-quality voice over packet services. Calisto leverages multiprocessor parallelism and low-power integration to enable multichannel communications gateways that support such VoP services.     

Thyroid-stimulating hormone and total thyroxine concentrations in euthyroid, sick euthyroid and hypothyroid dogs

Canine thyroid-stimulating hormone (cTSH) was measured in a variety of clinical cases (n = 72). The cases were classified as euthyroid, sick euthyroid, hypothyroid or hypothyroid on nonthyroidal therapy on the basis of their history, clinical signs, laboratory results (including total thyroxine concentrations and, where indicated, thyroid-releasing hormone [TRH] stimulation tests) and response to appropriate therapy. Additional samples were taken during some of the TRH stimulation tests to measure the response of cTSH concentrations following TRH administration. A reference range (0 to 0.41 ng/ml) was calculated from the basal concentrations of cTSH in a group of 41 euthyroid dogs. Six of nine cases of confirmed hypothyroidism had basal cTSH concentrations above the reference range, whereas the remainder were within the normal range. One of these three remaining cases was a pituitary dwarf and did not show a rise in cTSH concentration following TRH stimulation. In contrast, only one of a group of six hypothyroid dogs that had been on non-thyroidal treatment within the previous four weeks had increased concentrations of basal cTSH. This study also found that five of a group of 16 dogs with sick euthyroid syndrome had increased cTSH concentrations. It was concluded that cTSH measurements are a useful additional diagnostic test in cases of suspected hypothyroidism in dogs but that dynamic testing is still required to confirm the diagnosis of hypothyroidism.