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Selected AbstractsCorrelations among Extinction Risks Assessed by Different Systems of Threatened Species CategorizationCONSERVATION BIOLOGY, Issue 6 2004JULIAN J. O'GRADY análisis de viabilidad poblacional; categorías de amenaza; especies en peligro; riesgo de extinción Abstract:,Many different systems are used to assess levels of threat faced by species. Prominent ones are those used by the World Conservation Union, NatureServe, and the Florida Game and Freshwater Fish Commission (now the Florida Fish and Wildlife Conservation Commission). These systems assign taxa a threat ranking by assessing their demographic and ecological characteristics. These threat rankings support the legislative protection of species and guide the placement of conservation programs in order of priority. It is not known, however, whether these assessment systems rank species in a similar order. To resolve this issue, we assessed 55 mainly vertebrate taxa with widely differing life histories under each of these systems and determined the rank correlations among them. Moderate, significant positive correlations were seen among the threat rankings provided by the three systems (correlations 0.58,0.69). Further, the threat rankings for taxa obtained using these systems were significantly correlated to their rankings based on predicted probability of extinction within 100 years as determined by population viability analysis (correlations 0.28,0.37). The different categorization systems, then, yield related but not identical threat rankings, and these rankings are associated with predicted extinction risk. Resumen:,Se utilizan muchos sistemas diferentes para evaluar los niveles de amenaza que enfrentan las especies. Son prominentes los utilizados por World Conservation Union, NatureServe Heritage y Florida Game and Freshwater Fish Commission (ahora Florida Fish and Wildlife Conservation Commission). Estos sistemas asignan una categoría de amenaza a los taxa mediante la evaluación de sus características demográficas y ecológicas. Estas categorías de amenaza sustentan a la protección legislativa de especies y guían la definición de prioridades en programas de conservación. Sin embargo, se desconoce si estos sistemas de evaluación categorizan a las especies en orden similar. Para resolver este tema, evaluamos 55 taxa, principalmente de vertebrados, con historias de vidas muy diferentes con cada uno de estos sistemas y determinamos las correlaciones entre las categorías. Hubo correlaciones positivas moderadas entre las categorías de amenaza proporcionadas por los tres sistemas (correlaciones 0.58-0.69). Más aun, las categorías de amenaza proporcionados por estos sistemas estuvieron correlacionadas significativamente con las categorías definidas con base en la probabilidad de extinción pronosticada en 100 años determinada por análisis de viabilidad poblacional (correlaciones 0.28-0.37). Por lo tanto, los diferentes sistemas de categorización están proporcionando categorías de amenazas relacionadas pero no idénticas, y estas categorías están relacionadas con el riesgo de extinción pronosticado. [source] Reinvestigation of the Mechanism of gem -Diacylation: Chemoselective Conversion of Aldehydes to Various gem -Diacylates and Their Cleavage under Acidic and Basic ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2005Veerababurao Kavala Abstract The mechanism of gem -diacylate formation has been studied extensively using tetrabutylammonium tribromide (TBATB) as the catalyst. The reaction proceeds by a nucleophilic attack of an anhydride on an aldehydic carbonyl group, nucleophilic attack of the hemiacylate intermediate on a second molecule of the anhydride, followed by an intermolecular attack of a second acetate group to regenerate the anhydride. gem -Diacylates of various aliphatic and aromatic aldehydes were obtained directly from the reaction of a variety of aliphatic and aromatic acid anhydrides in the presence of a catalytic quantity of tetrabutylammonium tribromide (TBATB) under solvent-free conditions. A significant electronic effect was observed during its formation as well as deprotection to the corresponding aldehyde. Chemoselective gem -diacylation of the aromatic aldehyde containing an electron-donating group has been achieved in the presence of an aldehyde containing an electron-withdrawing group. Deprotection of the gem -diacylate to the parent carbonyl compound can be accomplished in methanol in presence of the same catalyst. Here again, chemoselective deprotection of the gem -diacylate of a substrate containing an electrondonating group has been achieved in the presence of a substrate containing an electron-withdrawing group. Both the acid and base stability order of the various gem -diacylates examined follow a similar order. The stability order determined from the present study is: gem -dibenzoate > gemdipivalate > gem -diisobutyrate > gem -diacetate > gem -dipropionate. All the gem -diacylals are more stable under basic conditions than acidic condition. No correlation was found between the stability order and the pKa's of the corresponding acids; rather, the stability order is directly related to the steric crowding around the carbonyl carbon. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Evidence against ,2 -adrenoceptors mediating relaxation in rat thoracic aortae: ,2 -agonists relaxation depends on interaction with ,1 -adrenoceptorsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2006Enrique F. Castillo Abstract In rat aorta, the presence of functional ,2 -adrenoceptors (,2 -AR) was investigated in ring preparations preconstricted with ,1 -adrenergic and non- ,1 -adrenergic agonists. Particularly, the hypothetical interference of ,2 -AR agonists with ,1 -AR-mediated vasoconstriction was evaluated. Relaxant and contractile responses to ,2 -AR agonists were obtained. In endothelium-intact and endothelium-denuded aortic rings preconstricted with phenylephrine (1 × 10,6 m), the imidazoline derivatives, clonidine and UK14304, induced relaxations with similar order of potencies (,log EC50) and maxima relaxant effects respectively. Pretreatment with the NO synthase inhibitor, NG -nitro- l -arginine methyl ester (l -NAME) had no effect on the relaxant responses to clonidine and UK14304. In phenylephrine-constricted rings with endothelium, relaxations to clonidine and UK 14304 were not antagonized by the selective ,2 -AR antagonist, rauwolscine (,1 × 10,6 m). Clonidine and UK 14304 induced only contractions on endothelium-intact and endothelium-denuded aortic rings contracted with prostaglandin F2, (3 × 10,7 m). Moreover, clonidine and UK 14304-induced relaxation of endothelium-denuded arteries precontracted with methoxamine but not with serotonin. Finally, the concentration,contraction curves to clonidine and UK 14304 in endothelium-denuded aortic rings were significantly shifted to the right by the ,1D -AR selective antagonist, BMY 7378, and rauwolscine. The pA2 and pKB values for BMY 7378 and rauwolscine, respectively, against endothelium-independent actions of clonidine and UK 14304 were characteristic of an effect on the ,1D -AR. The other selective ,2 -AR agonist tested BHT 933 (an azepine derivative), lacks considerable relaxant and contractile effects in rat aorta. The results provide no evidence for the presence of functional ,2 -AR in rat aorta. Respectively, the relaxant and contractile effects of the imidazoline derivatives, clonidine and UK 14304, may be due to an adjustable (in relation to the agonist-dependent active state of the ,1 -AR), inhibitory and excitatory, interaction with ,1 -ARs. [source] Effect of Alkyl Side-Chain Length on Photovoltaic Properties of Poly(3-alkylthiophene)/PCBM Bulk HeterojunctionsADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Abay Gadisa Abstract The morphological, bipolar charge-carrier transport, and photovoltaic characteristics of poly(3-alkylthiophene) (P3AT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side-chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3-butylthiophene) (P3BT, m,=,4), poly(3-pentylthiophene) (P3PT, m,=,5), and poly(3-hexylthiophene) (P3HT, m,=,6). Solar cells with these blends deliver similar order of photo-current yield (exceeding 10,mA cm,2) irrespective of side-chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole-only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field-effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells. [source] A study on degradation kinetics of ascorbic acid in drumstick (Moringa olifera) leaves during cookingJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2005Nisha P Bineesh Abstract The kinetics of ascorbic acid degradation in drumstick (Moringa olifera) leaves as well as in pure ascorbic acid solutions at the initial concentrations present in drumstick leaves over a temperature range of 50,120 °C (isothermal temperature process) has been studied. The degradation kinetics of ascorbic acid was also evaluated in normal open-pan cooking, pressure-cooking and a newly developed and patented fuel-efficient eco cooker (non-isothermal heating process). The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in the temperature. The temperature dependence of degradation was adequately modelled by the Arrhenius equation. A mathematical model was developed using the isothermal kinetic parameters obtained to predict the losses of ascorbic acid from the time,temperature data of the non-isothermal heating/processing method. The results obtained indicate the ascorbic acid degradation is of similar order of magnitude in all the methods of cooking. Copyright © 2005 Society of Chemical Industry [source] Teaching of Anatomy of Genital Organs in the Large AnimalsANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005G. M. Constantinescu At the University of Missouri-Columbia, USA, teaching the anatomy of genital organs in large (and in small) animals is clinically oriented. In the male horse, ox, and pig, the descriptive anatomy of the structures is taught in that order as they are listed in Nomina Anatomica Veterinaria. Clinical correlates are immediately mentioned in relation to each of the following structures. The testicle, epididymis, ductus deferens, spermatic cord, and tunics of spermatic cord and testis are correlated to the castration, criptorchidism, ectopic testicles, and inguinal herniae, as well as to the landmarks and approaches to different clinical techniques. The penis and male urethra are correlated to the prolapse of the prepuce, ulcerative posthitis, balanitis, penile deviation, penischisis, persistent penile frenulum, short retractor penis muscle, catheterization of the urethra, the contagious equine metritis (CEM), etc. In the female horse, ox and pig, following the similar order as in the male species, the ovary and the salpinx are correlated to the diagnosis of pregnancy by rectal exploration, ovarian hypoplasia, ectopic pregnancy, and ovariectomy. The uterus is correlated to the different aspects of metritis and endometritis, to the retained placenta, pyometra, uterine torsion, uterine prolapse and eversion, Caesarian section, diagnosis of pregnancy and different stages of oestrus by rectal exploration, double external ostium of the cervix, distocia, and the assessment of possible difficulties in the birth process. The vagina and vestibulum vaginae are correlated to the gaertneritis, vaginal and cervical prolapse, vaginitis, catheterization of the urinary bladder, and pelvimetry. The vulva and clitoris are correlated to vulvitis, balanitis, distocia, episiotomy, and transmissible genital diseases. Different kinds of udder diseases (mastitis) are based on the thorough knowledge of the anatomy of the udder including the blood and nerve supply and the lymphatic system. The two techniques of epidural anesthesia (Magda and Farquharson in ruminants) and subsacral anaesthesia (Popescu) for diagnosis and treatment purposes are explained in detail. [source] Learning, governance and economic policy1BRITISH JOURNAL OF POLITICS & INTERNATIONAL RELATIONS, Issue 4 2003Hugh Pemberton This article examines the relationship between economic policy networks and policy learning during the 1960s, using recently released files to flesh out the operation of both networks and learning. It finds that policy failure in the 1950s brought into being a new policy network which was able to secure a radical shift in the economic policy of the core executive in the early 1960s. However, it then proved impossible to craft, implement and sustain a coherent and enduring set of new policies within the new policy framework due to the ability of competing networks to resist central control. This leads to three conclusions. First, peripheral actors may obtain influence over policy-making in the core executive by means of a policy network. Second, policy learning does not necessarily generate policy change of a similar order because, whilst networks may facilitate learning, competing networks may block the translation of this learning into effective policies. Third, ,governance' is not solely a phenomenon of the years since 1979: in the 1960s the British core executive was already operating within a polity characterised by fragmentation, inter-dependency and self-organising policy networks. [source] The Returns to Education: MacroeconomicsJOURNAL OF ECONOMIC SURVEYS, Issue 2 2003Barbara Sianesi We offer an extensive summary and a critical discussion of the empirical literature on the impact of human capital on macro-economic performance, with a particular focus on UK policy. We also highlight methodological issues and make recommendations for future research priorities. Taking the studies as a whole, the evidence that human capital increases productivity is compelling, though still largely divided on whether the stock of education affects the long-run level or growth rate of GDP. A one-year increase in average education is found to raise the level of output per capita by between three and six percent according to augmented neo-classical specifications, while leading to an over one percentage point faster growth according to estimates from the new-growth theories. Still, over the short-run planning horizon (four years) the empirical estimates of the change in GDP are of similar orders of magnitude in the two approaches. The impact of increases at different levels of education appear to depend on the level of a country's development, with tertiary education being the most important for growth in OECD countries. Education is found to yield additional indirect benefits to growth. More preliminary evidence seems to indicate that type, quality and efficiency of education matter for growth too. [source] | |||||||||||||