Behavioral and neurochemical effects of acute and repeated administration of triadimefon in the male rat

The effects of triadimefon (TDF) were examined in male Sprague-Dawley rats. In this study, the acute administration of TDF (100 mg/kg) was found to significantly increase locomotor activity and induce stereotyped behavior. Acute administration of TDF was also found to significantly increase dopamine (DA) and homovanillic acid (HVA) levels while the dihydroxyphenylacetic acid (DOPAC) level remained unchanged in both the nucleus accumbens (NA) and striatal (ST) tissues when compared to control. Furthermore, DOPAC:DA ratios were significantly reduced in both brain regions suggesting an increase in DA turn overrate. On the other hand, in animals receiving repeated TDF administration, only the HVA level was significantly increased in both the ST and NA. TDF neither competed for binding to D2, D3 or D4 DA receptors nor altered the Kd or the Bmax of [3H] SCH 23390 and [3H] spiperone recognition sites associated with striatal D1 and D2 receptors, respectively. Meanwhile, TDF competed with [3H] GBR 12935 for binding to DA transporter sites with strong affinity, but repeated treatment with TDF had no sustained or cumulative effect on the DA transporter system. These results clearly show that acute TDF-induced behavioral effects may not be via binding to DA receptors, but through the interaction with DA transporter binding sites. Also, TDF does not appear to produce cumulative effects in the parameters evaluated.     

Early stages of polymer crystallization—a dielectric study

The existence and the formation of pre-ordered structures as the initial step during the complex process of polymer crystallization are discussed controversially. Most of the findings and interpretations are based on scattering experiments, which test small density differences between the assumed precursors of the crystals and the surrounding melt. Because of the low contrast the interpretation of experimental results become often speculative. In contrast relaxation experiments are probing motions in the sample and are therefore independent on density contrast. During crystallization, material is transformed from the liquid to the solid state. Consequently, motions typical for a liquid become impossible and do not longer contribute to the measured signal. For pre-ordered structures we expect some changes in mobility too because of the changes in conformation on pre-ordering.We performed dielectric relaxation experiments during isothermal crystallization of PCL. Pronounced effects in ?′ are observed long before changes in crystallinity can be detected. The observations strongly support the idea of pre-order in the polymer melt before the formation of crystals.     

Two- and three-dimensional analysis of closely spaced double-tube tunnels

The two tubes of underground railways in cities are constructed rather close together because of the station configurations. The two tunnel tubes are driven one after the other. The stresses in the linings and in the ground are affected by the driving sequences, especially in soft shaund of shallow tunnels. Hence, a consistent stres--deformation analysis for the tunnels has to take into account the mutual influence of the consecutive tube driving. The paper reports on the results of a finite element approach to these problems for shield-driven tunnels as well as for tunnels driven by excavation and shortcreting. The results are presented in diagrams that show the relative changes in stresses and deformations, in comparison with a single-tunnel analysis. These results show that single-tunnel solutions can be used to find double-tube solutions.     

Accuracy and convergence of a finite element algorithm for laminar boundary layer flow

The Galerkin-weighted residuals formulation is employed to derive an implicit finite element solution algorithm for a generally non-linear initial-boundary value problem. Solution accuracy and convergence with discretization refinement are quantized in several error norms, for the non-linear parabolic partial differential equation system governing laminar boundary layer flow, using linear, quadratic and cubic functions. Richardson extrapolation is used to isolate integration truncation error in all norms, and Newton iteration is employed for all equation solutions performed in double-precision. The mathematical theory supporting accuracy and convergence concepts for linear elliptic equation appears extensible to the non-linear equations characteristic of laminar boundary layer flow.     

Synchronization over fading dispersive channels

An investigation is reported of an acquisition system for digital communication over fading dispersive channels that is optimum in the maximum-likelihood sense. A performance measure for the synchronizer in the acquisition mode is defined. Upper and lower bounds on the performance measure are derived. The effective bounds on parameters, such as signal-to-noise ratio, pulse width and modulation, number of pulses, spread of the channel, and the size of the resolution cell, on the performance of the synchronizer is investigated     

New Wide Band Low Power CMOS Current Conveyors

New Class-A second-generation CMOS current conveyor (CCII) suitable for high frequency applications is proposed. It provides low input impedance and accurate voltage and current tracking. Targeting low power dissipation, the Class-AB version of the proposed Class-A architecture is introduced as well. Simulation results are included.     

Hydrogen production via thermochemical cycles based on sulfur chemistry

A class of closed thermochemical cycles for hydrogen production based on sulfur chemistry is presented. This class is described by the following set of chemical reactions: M+H₂OMO+H₂(low temperature)MO+0.5SM+0.5SO₂(high temperature)M′O+1.5SO₂M′SO₄+.5S (low temperature)M′SO₄rlarr2;M′O+SO₂+0.5O₂(high temperature)Experimental investigation of some of the reactions is presented. Thermodynamic analysis indicates efficiencies of the range of 40–50% and sometimes higher. Not all of the reactions in the proposed cycles have been verified in the literature or through experimentation.     

Serious renal disease in Egypt

We studied serious renal disease in Egypt by registering all 155 patients coming to the nephrology service at the University of Cairo during a period of 62 days in 1993. The patients presented with severe uremic symptoms. Admission creatinine and urea levels were high, 804 mumol/l and 64 mmol/l. Fifteen percent of the patients died; 115 underwent dialysis. Sixty patients presented with chronic renal failure; 53 with acute renal failure, but 24 of these were later found to have end-stage renal failure. Of 29 patients with true acute renal failure, 11 (38%) had pre-renal failure and 7 (24%) post-renal failure. Twenty-one patients were followed up after transplantation and chronic dialysis, another 17 had nephrotic syndrome, 3 hypertension, and one had asymptomatic urinary abnormalities. The most common specific etiology for chronic end-stage renal failure was diabetes mellitus type II in the older patients; second most common was Schistosoma in the younger ones. Most diabetic patients came from the city. All but one Schistosoma patient came from rural Egypt. In the 22 patients who underwent renal biopsy the most common diagnosis was mesangio capillary glomerulonephritis. The prevalence of acute renal failure, particularly iatrogenic-toxic, is increasing.     

Dementia: a serious and enduring mental illness

At the 1997 RCN Congress, the RCN Mental Health and Older People Forum put forward a matter for debate--how the definition of 'serious and enduring mental illness' affects services to people with dementia. Subsequently, the RCN agreed both a position paper, which includes dementia in the definition, and an action plan for dissemination and support of the RCN position. Alison Soliman describes the background to the position paper.     

New family of active RC variable equalisers

A new family of active variable equalisers is introduced. The proposed variable equaliser transfer function is generated from Bode's classical transfer function using a new mathematical transformation. The new circuit uses a single operational amplifier and the required full range of variation is obtained by varying a single resistor Rv from zero to Ro (a reference resistance). The variable equaliser circuit requires a single shaping grounded impedance for realisation.