Variable-speed generation with the series-resonant converter

Results of study and measurements are presented for a variable-speed generation (VSG) system that uses a series-resonant converter to excite the rotor windings of a doubly-fed generator. The capabilities of this system include maximum-efficiency operation and limited converter rating for a speed range from stand-still (zero RPM) to well beyond synchronous speed, as well as flexibility for line-voltage control, reactive power generation, and synchronization at zero RPM. Measurements of the harmonic distortion are provided showing the superiority of this converter as compared with a VSG system using a conventional cycloconverter or a DC-link converter. A convenient tool for analyzing the operating modes of the system is discussed that can be developed under varying resource conditions     

CD4+ T lymphocytes contribute to protective immunity induced in sheep and goats by Haemonchus contortus gut antigens

"Freezing" is a sudden, unforeseen state of immobility occurring independently of L-Dopa dosage timing and often presents in connection with walking, speech and hand movements. The immobility results from deficits in initiating or simultaneously and sequentially executing movements, in correcting inappropriate movements or planning movements. However, since the progression of motor activity is strongly dependent upon external stimuli, the patient can overcome the freezing phenomena with the aid of certain stimuli or subjective strategies. No consistent relationships have been found with respect to age, length of illness, L-dopa dosis or L-dopa treatment. Neurotransmitter models to explain the freezing phenomena are: a noradrenalin deficiency in locus coeruleus or alternately a dopamine deficiency in substantia nigra, pars compacta, which can possibly be coupled with a GABA deficiency in substantia nigra, pars reticulata. In addition to optimal drug therapy, patients require physiotherapeutical and ergotherapeutical assistance to develop subjectively effective strategies in counteracting freezing during everyday activities.     

Variation of cork quality for wine stoppers across the production regions in Portugal

Cork production and technological quality were characterized following a field sampling covering the whole area of cork oaks in Portugal (six regions), with one site per 20,000 ha of cork oak area (30 sites), using samples taken from the tree at the time of cork stripping (20 trees per site). The following quality parameters were determined: thickness of the raw cork planks, calliper of the cork planks after boiling, cork growth index, i.e., growth of the first 8 complete years, density and porosity. The cork growth index was 28.6 mm, with significant differences between regions and sites within regions. A production cycle of 9 years was applied to 51% of the trees with annual productivity of 0.93 kg m^?2 year^?1 of debarked surface, 30.3 mm raw cork plank thickness, 33.9 mm corkboard calliper, 251 kg m^?3 density and a porosity coefficient of 5.8%. For all the cork quality parameters analysed, the regions and sites within regions were a significant factor of variation. This research covers the natural variability of cork production features for industrial processing, namely for the production of wine stoppers. It is the most extensive work characterizing the geographical variation of cork as an industrial raw-material. The results are useful for optimizing the production cycle and for improving management practices and regulations.     

Thiazolopyrimidine Inhibitors of 2‐Methylerythritol 2,4‐Cyclodiphosphate Synthase (IspF) from Mycobacterium tuberculosis and Plasmodium falciparum

A library of 40 000 compounds was screened for inhibitors of 2‐methylerythritol 2,4‐cyclodiphosphate synthase (IspF) protein from Arabidopsis thaliana using a photometric assay. A thiazolopyrimidine derivative resulting from the high‐throughput screen was found to inhibit the IspF proteins of Mycobacterium tuberculosis, Plasmodium falciparum, and A. thaliana with IC₅₀ values in the micromolar range. Synthetic efforts afforded derivatives that inhibit IspF protein from M. tuberculosis and P. falciparum with IC₅₀ values in the low micromolar range. Several compounds act as weak inhibitors in the P. falciparum red blood cell assay.     

Hyperhomocysteinemia increases intimal hyperplasia in a rat carotid endarterectomy model

PURPOSE: This preliminary study investigated the ability to elevate the serum homocysteine (H[e]) levels and investigated the increases in postoperative neointimal hyperplasia (IH) in an environment with hyperhomocysteinemia and the resultant restenosis in a rat carotid endarterectomy (CEA) model. METHOD: The 9 rats for the control group were fed rat chow, and the 8 rats for the H(e) group were fed H(e)-supplemented rat chow for 2 weeks before and after CEA. The animals underwent anesthesia, and a left common CEA was performed. After 14 days, the serum H(e) levels were measured and the left carotid artery was harvested and elastin stained. Morphometric measurements were used to calculate the area of stenosis of the lumen. The mean and the standard deviation of the mean were determined. The 2 groups were compared with the Mann-Whitney test and a linear regression model. Three additional rats per group were studied, with carotid artery sectioning with double immunohistochemical staining for 5-bromodeoxyuridine (BrdU) and alpha-smooth muscle (alpha-SM) actin. RESULTS: The serum H(e) level in the H(e) group was 36.32 micromol/L +/- 15.28, and in the control group the level was 5.53 micromol/L +/- 2.06 (P =.0007). IH presented as percent lumen stenosis was 21.89% +/- 4.82% in the H(e) group and 4.82% +/- 1.64% in the control group (P =.0007). The linear regression model of the serum H(e) levels and the percent stenosis showed a linear relationship (r2 =.72). The alpha-SM actin staining revealed that nearly all of the cells in the IH area were of smooth muscle or myofibroblast origin and that 10.1% +/- 2.6% of the cells were stained for BrdU in the control group versus 23% +/- 7.1% in the H(e) group. Also, 9.3% +/- 2.6% of the cells in the IH area were stained for BrdU and for alpha-SM actin versus 19.1% +/- 5. 6% stained for both BrdU and alpha-SM actin in the H(e) group. CONCLUSION: This is the first study to examine IH after CEA and hyperhomocysteinemia in rats. The study shows that the elevation of serum H(e) levels can be obtained by feeding rats modified diets with added H(e). The consistent elevation of serum H(e) levels was associated with more than 4 times the amount of IH after a CEA in a rat model.     

The influence of traditional religion on fertility regulation among the Kassena-Nankana of northern Ghana

This article presents findings from a study of the influence of traditional religion on reproductive preferences of Kassena-Nankana lineage heads in northern Ghana. Seven reproductive preference questions were administered to nine lineage heads who are primary practitioners of the cult of soothsaying. With the assistance of soothsayers, interviews were repeated in conjunction with the invocation of religious rites in order to determine the views of ancestral spirits on the seven questions. Pairs of lineage head and ancestral interviews are compared to determine the role of traditional religion in shaping male reproductive preferences. Interview pairs reflect a shared preference for sons, large compounds, and a growing lineage. Findings nonetheless show that some ancestral spirits want small families, some even wanting fewer children than corresponding lineage heads. Spiritual consultations are nondogmatic and open to external ideas and influences, suggesting that family planning introduction will not encounter systematic religious opposition among the Kassena-Nankana.