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Relative Rates (relative + rate)
Selected AbstractsImpact of Medicare Coverage on Disparities in Access to Simultaneous Pancreas and Kidney TransplantationAMERICAN JOURNAL OF TRANSPLANTATION, Issue 12 2009J. K. Melancon In the setting of disparities in access to simultaneous pancreas and kidney transplantation (SPKT), Medicare coverage for this procedure was initiated July 1999. The impact of this change has not yet been studied. A national cohort of 22 190 type 1 diabetic candidates aged 18,55 for kidney transplantation (KT) alone or SPKT was analyzed. Before Medicare coverage, 57% of Caucasian, 36% of African American and 38% of Hispanic type 1 diabetics were registered for SPKT versus KT alone. After Medicare coverage, these proportions increased to 68%, 45% and 43%, respectively. The overall increase in SPKT registration rate was 27% (95% CI 1.16,1.38). As expected, the increase was more substantial in patients with Medicare primary insurance than those with private insurance (Relative Rate 1.18, 95% CI 1.09,1.28). However, racial disparities were unaffected by this policy change (African American vs. Caucasian: 0.97, 95% CI 0.87,1.09; Hispanic vs. Caucasian: 0.94, 95% CI 0.78,1.05). Even after Medicare coverage, African Americans and Hispanics had almost 30% lower SPKT registration rates than their Caucasian counterparts (95% CI 0.66,0.79 and 0.59,0.80, respectively). Medicare coverage for SPKT succeeded in increasing access for patients with Medicare, but did not affect the substantial racial disparities in access to this procedure. [source] Kinetic study of the gas-phase reaction of the nitrate radical with methyl-substituted thiophenesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2003B. Cabañas The gas-phase reactions of the NO3 radical with 2-methylthiophene, 3-methylthiophene, and 2,5-dimethylthiophene have been studied, using relative and absolute methods at 298 K. Determination of relative rate was performed using Teflon collapsible bag as the reaction chamber and gas chromatography as the analytical tool. For the absolute method, experiments were carried out using fast-flow-discharge technique with detection of NO3 by laser-induced fluorescence. The temperature dependence was studied by the absolute technique for the reactions of NO3 with 2-methylthiophene and 3-methylthiophene in the range 263,335 K. The proposed Arrhenius expressions for the reaction of the nitrate radical with 2-methylthiophene and 3-methylthiophene are k = (4 ± 2) × 10,16 exp[,(2200 ± 100)/T]] cm3 molecule,1 s,1 and k = (3 ± 2) × 10,15 exp[,(1700 ± 200)/T]] cm3 molecule,1 s,1, respectively. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 286,293, 2003 [source] Bacteriotherapy with Lactobacillus plantarum in burnsINTERNATIONAL WOUND JOURNAL, Issue 1 2009Maria C Peral Abstract Bacterial colonisation and infection remain the major causes of delayed healing and graft rejection following burns. Topical treatment is necessary to reduce the incidence of burn wound infection. Silver sulphadiazine (SD-Ag) is an often used microbicidal agent. However, this treatment produces adverse reactions and side-effects. On the basis of experimental data and clinical application of lactobacilli as probiotics, we performed this exploratory study to establish the effectiveness of bacteriotherapy with topical application of the innocuous bacteria Lactobacillus plantarum cultured in De Man, Rogosa and Sharpe medium to provide an alternative method for burn treatment using SD-Ag as a reference. These innocuous bacteria would compete with other bacteria that are wound pathogens and would modify the wound environment and promote tissue repair. Eighty burned patients from the Plastic Surgery and Burns Unit were grouped into infected (delayed) second- and third-degree and non infected (early) third-degree burns and treated with L. plantarum or SD-Ag. The proportion of patients with delayed second-degree burns was 0·71 for L. plantarum and 0·73 for SD-Ag (relative rate: ,2·72%) with respect to the decrease in bacterial load (<105 bacteria/g of tissue), promotion of granulating tissue wound bed and healing. In early third-degree burns, the values were 0·75 for L. plantarum and 0·84 for SD-Ag (relative rate: ,1·07%) in preventing wound infection and promotion of granulation tissue, 0·90 in graft taking for both treatments (relative rate: 0%) and 0·75 for L. plantarum and 0·77 for SD-Ag (relative rate: ,2·60%) in healing. In delayed third-degree burns, values were 0·83 for L. plantarum and 0·71 for SD-Ag (relative rate: +16·90%) with respect to the decrease in the bacterial load (<105 bacteria/g of tissue) and providing a granulating tissue wound bed, 0·90 in graft taking for both treatments (relative rate: 0%) and 0·75 for L. plantarum and 0·64 for SD-Ag (relative rate: + 17·19%) in healing. Although the number of patients (between 12 and 15 per group) did not enable the application of a power statistical test, these results suggest that the L. plantarum treatment should be studied in greater depth and could be used as a valid alternative for the topical treatment of burns. [source] Impacts of land use change on South-east Asian forest butterflies: a reviewJOURNAL OF APPLIED ECOLOGY, Issue 4 2007LIAN PIN KOH Summary 1South-east Asia has the highest relative rate of habitat loss and degradation in the humid tropics. The responses of less ,charismatic' groups, including butterflies, to habitat disturbance remain relatively poorly understood. Many South-east Asian butterflies are endemic to the region and face global extinction if current levels of deforestation were to continue. 2Here, I highlight South-east Asia as a region urgently in need of butterfly conservation research and review empirical studies of the responses of South-east Asian butterflies to land use change. Additionally, I discuss some methodological pitfalls for such studies. Furthermore, I argue for the importance of identifying the ecological correlates of sensitivity of butterfly species to forest modification and the potential biological mechanisms underlying their responses to land use change. 3There has been no consensus among previous studies on the effects of land use change on butterfly communities in South-east Asia. Of the 20 studies I reviewed, seven reported higher species richness/diversity in undisturbed (or the least disturbed) forest than in disturbed habitats, nine reported the opposite trend, three reported no difference and one reported a strong influence of seasonality on the impacts of logging. 4Some of these studies may contain inherent methodological biases resulting from the failure to control for sampling effects, the lack of consideration for the spatial scale of analysis and incomplete sampling of the vertical strata in tropical rainforests. 5Synthesis and applications. Empirical studies of the effects of land use change on tropical forest insects are sorely lacking from South-east Asia. Butterflies are an ideal taxonomic group for such investigations. Future studies should be designed carefully to avoid the methodological pitfalls highlighted here. Determining the ecological correlates of sensitivity of butterflies to forest modification is important for the pre-emptive identification of species of conservation concern and for generating testable hypotheses on the differential responses of species to forest modification. Experimental studies are needed to determine the mechanisms underlying the responses of species to land use change in order to develop effective strategies for the conservation of butterflies in human disturbed landscapes. [source] Changes in miombo woodland cover in and around Sengwa Wildlife Research Area, Zimbabwe, in relation to elephants and fireAFRICAN JOURNAL OF ECOLOGY, Issue 3 2002Isaac N. Mapaure Abstract One of the consequences of impacts of elephants and fire on woodlands is a change in woody cover, which often results in major challenges for wildlife managers. Changes in miombo woodland cover in and around Sengwa Wildlife Research Area (SWRA) between 1958 and 1996 were quantified by analyzing aerial photographs. Woody cover in SWRA decreazed from 95.2% in 1958 to 68.2% in 1996, with a lowest mean of 62.9% in 1983. The annual absolute rate of woody cover change in SWRA increazed from ,1.1% per annum between 1958 and 1964 to a recovery of 1.6% per annum between 1993 and 1996, while the annual relative rate increazed from ,1.1% per annum between 1958 and 1964 to 3.3% per annum between 1993 and 1996. There was a strong negative correlation between elephant densities and woody cover in SWRA, suggesting that loss of woody cover was mainly due to elephants. Woodland recovery after 1983 was due to reductions in elephant populations through legal and illegal off-take and reductions in fire frequency. Surrounding areas experienced less woody cover losses than SWRA, mainly due to tree removal by locals whose densities increazed after the eradication of tsetse fly in the 1970s. Résumé Une des conséquences de l'impact des éléphants et des feux sur les forêts s'exprime par un changement du couvert ligneux qui pose souvent de fameux défis pour les gestionnaires de la faune. Les changements du couvert forestier à Miombo, qui sont survenus à l'intérieur et aux alentours de l'Aire de Recherche sur la Faune de Sengwa (SWRA) entre 1956 et 1996, ont été quantifiés grâce à l'analyse de photos aériennes. Le couvert forestier de la SWRA a diminué de 95.2% en 1958 à 68.2% en 1996, la moyenne la plus basse étant observée en 1983, avec 62.9%. Le taux annuel absolu de changement du couvert forestier dans la SWRA est passé de , 1.1% par an entre 1958 et 1964 à une restauration de 1.6% par an entre 1993 et 1996, tandis que le taux annuel relatif augmentait de , 1.1% par an entre 1958 et 1964 à 3.3% par an entre 1993 et 1996. Il existait une forte corrélation négative entre la densité des éléphants et le couvert forestier de la SWRA, ce qui laisse supposer que la perte de couvert forestier était due principalement aux éléphants. La restauration de la forêt après 1983 était due à des réductions des populations d'éléphants suite à des prélèvements, légaux ou non, et à une baisse de la fréquence des feux. Les zones adjacentes ont subi de moins fortes pertes du couvert forestier que la SWRA, et celles-ci étaient principalement dues à des coupes faites par les locaux dont la densité a augmenté suite à l'éradication de la mouche tsé-tsé dans les années 1970. [source] Evaluation of model compounds,polypropylene film interactions by Fourier transformed infrared spectroscopy (FTIR) methodPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2008Laurent Safa Abstract The interactions of methyl esters, methyl ketones and aldehyde compounds with polypropylene (PP) film were investigated. PP film, placed on a glass vial, was immersed in aqueous solution containing a model flavour compound. After a determined time at 45°C, the PP film was analysed by Fourier transform infrared spectroscopy (FTIR), allowing us to follow the speed of sorption and to quantify its relative rate. ,,For PP films, we observed that the sorption strongly depended on the structure of sorbed molecules. For each functional group of flavour compounds, the sorption increased as the carbon chain number increased. A linear chain of 12,14 carbons favours the sorption more than a linear chain of eight carbons. ,,Concerning functions, the rate of sorption usually decreases from esters to ketones and to aldehydes. ,,High sorption was observed for flavour compounds with a low difference of solubility parameter (SP) value between the film and flavour [(,polymer , ,flavour)2 value]. Furthermore, by using the proposed thermodynamic affinity concept, represented as the contribution of three interactive molecular forces [dispersion (dd), polar (dp) and hydrogen bonding (dh)] between two SP values of film and flavour, packaging materials with high flavour preservation against sorption can be designed. ,,We have a good correlation between the kinetic sorption by FTIR and the SP concept. Copyright © 2007 John Wiley & Sons, Ltd. [source] Consequences of insect herbivory on grape fine root systems with different growth ratesPLANT CELL & ENVIRONMENT, Issue 7 2007T. L. BAUERLE ABSTRACT Herbivory tolerance has been linked to plant growth rate where plants with fast growth rates are hypothesized to be more tolerant of herbivory than slower-growing plants. Evidence supporting this theory has been taken primarily from observations of aboveground organs but rarely from roots. Grapevines differing in overall rates of new root production, were studied in Napa Valley, California over two growing seasons in an established vineyard infested with the sucking insect, grape phylloxera (Daktulosphaira vitifoliae Fitch). The experimental vineyard allowed for the comparison of two root systems that differed in rates of new root tip production (a ,fast grower', Vitis berlandieri × Vitis rupestris cv. 1103P, and a slower-growing stock, Vitis riparia × Vitis rupestris cv. 101,14 Mgt). Each root system was grafted with a genetically identical shoot system (Vitis vinifera cv. Merlot). Using minirhizotrons, we did not observe any evidence of spatial or temporal avoidance of insect populations by root growth. Insect infestations were abundant throughout the soil profile, and seasonal peaks in phylloxera populations generally closely followed peaks in new root production. Our data supported the hypothesis that insect infestation was proportional to the number of growing tips, as indicated by similar per cent infestation in spite of a threefold difference in root tip production. In addition, infested roots of the fast-growing rootstock exhibited somewhat shorter median lifespans (60 d) than the slower-growing rootstock (85 d). Lifespans of uninfested roots were similar for the two rootstocks (200 d). As a consequence of greater root mortality of younger roots, infested root populations in the fast-growing rootstock had an older age structure. While there does not seem to be a trade-off between potential growth rate and relative rate of root infestation in these cultivars, our study indicates that a fast-growing root system may more readily shed infested roots that are presumably less effective in water and nutrient uptake. Thus, differences in root tip production may be linked to differences in the way plants cope with roots that are infested by sucking insects. [source] Price discovery in the options markets: An application of put-call parityTHE JOURNAL OF FUTURES MARKETS, Issue 4 2008Wen-Liang G. Hsieh This study investigates the relative rate of price discovery in Taiwan between index futures and index options, proposing a put-call parity (PCP) approach to recover the spot index embedded in the options premiums. The PCP approach offers the benefits of reducing model risk and alleviating the burden of volatility estimation. Consistent with the trading-cost hypothesis, a dominant tendency is found for futures and a subordinate but non-trivial price discovery from options. The relative weight of options price discovery is sensitive to the methodology employed as the means of inferring the option-implicit spot price. The empirical evidence suggests that the information contained in the PCP-implied spot encompasses that provided by the Black-Scholes-implied spot. © 2008 Wiley Periodicals, Inc. Jrl Fut Mark 28:354, 375, 2008 [source] Disruption of excitation,contraction coupling and titin by endogenous Ca2+ -activated proteases in toad muscle fibresTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Esther Verburg This study investigated the effects of elevated, physiological levels of intracellular free [Ca2+] on depolarization-induced force responses, and on passive and active force production by the contractile apparatus in mechanically skinned fibres of toad iliofibularis muscle. Excitation,contraction (EC) coupling was retained after skinning and force responses could be elicited by depolarization of the transverse-tubular (T-) system. Raising the cytoplasmic [Ca2+] to ,1 ,m or above for 3 min caused an irreversible reduction in the depolarization-induced force response by interrupting the coupling between the voltage sensors in the T-system and the Ca2+ release channels in the sarcoplasmic reticulum. This uncoupling showed a steep [Ca2+] dependency, with 50% uncoupling at ,1.9 ,m Ca2+. The uncoupling occurring with 2 ,m Ca2+ was largely prevented by the calpain inhibitor leupeptin (1 mm). Raising the cytoplasmic [Ca2+] above 1 ,m also caused an irreversible decline in passive force production in stretched skinned fibres in a manner graded by [Ca2+], though at a much slower relative rate than loss of coupling. The progressive loss of passive force could be rapidly stopped by lowering [Ca2+] to 10 nm, and was almost completely inhibited by 1 mm leupeptin but not by 10 ,m calpastatin. Muscle homogenates preactivated by Ca2+ exposure also evidently contained a diffusible factor that caused damage to passive force production in a Ca2+ -dependent manner. Western blotting showed that: (a) calpain-3 was present in the skinned fibres and was activated by the Ca2+exposure, and (b) the Ca2+ exposure in stretched skinned fibres resulted in proteolysis of titin. We conclude that the disruption of EC coupling occurring at elevated levels of [Ca2+] is likely to be caused at least in part by Ca2+ -activated proteases, most likely by calpain-3, though a role of calpain-1 is not excluded. [source] Underutilization of Hepatitis C-Positive Kidneys for Hepatitis C-Positive RecipientsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2010L. M. Kucirka Hepatitis C-positive (HCV(+)) candidates likely derive survival benefit from transplantation with HCV(+) kidneys, yet evidence remains inconclusive. We hypothesized that lack of good survival benefit data has led to wide practice variation. Our goal was to characterize national utilization of HCV(+) kidneys for HCV(+) recipients, and to quantify the risks/benefits of this practice. Of 93,825 deceased donors between 1995 and 2009, HCV(+) kidneys were 2.60-times more likely to be discarded (p < 0.001). However, of 6830 HCV(+) recipients, only 29% received HCV(+) kidneys. Patients over 60 relative rate (RR 0.86), women (RR 0.73) and highly sensitized patients (RR 0.42) were less likely to receive HCV(+) kidneys, while African Americans (RR 1.56), diabetics (RR 1.29) and those at centers with long waiting times (RR 1.19) were more likely to receive them. HCV(+) recipients of HCV(+) kidneys waited 310 days less than the average waiting time at their center, and 395 days less than their counterparts at the same center who waited for HCV(,) kidneys, likely offsetting the slightly higher patient (HR 1.29) and graft loss (HR 1.18) associated with HCV(+) kidneys. A better understanding of the risks and benefits of transplanting HCV(+) recipients with HCV(+) kidneys will hopefully improve utilization of these kidneys in an evidence-based manner. [source] Quantifying the dynamics of sugar concentration in berries of Vitis vinifera cv. Shiraz: a novel approach based on allometric analysisAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2007VICTOR O. SADRAS Abstract Concentrations of key compounds (e.g. sugar) in berries are the net result of relative changes in the amount of compound per berry and berry size. The complex nature of concentrations is widely recognised, but the widespread use of chronological scales for comparisons implies that ontogenetic drift or size-dependent effects are often overlooked. This paper presents an allometric analysis of sugar concentration in berries of cv. Shiraz as a way to formally account for ontogenetic drift. Our starting point is the double-sigmoid growth pattern of a grape berry where we distinguish Phase 1, from flowering to veraison; Phase 2, from veraison to peak berry fresh mass, and Phase 3, after peak fresh mass. Phase 3 explicitly accounts for the late season shrinkage typical of Shiraz berries. We advance an allometric model of sugar per berry with berry fresh mass, rather than time, as descriptor. The condition for an increase in sugar concentration in Phase 2 is that the relative rate of sugar accumulation per berry (RSB) exceeds the relative rate of berry net accumulation of fresh mass (RFM). This is equivalent to an allometric coefficient, calculated as the slope of the regression between amount of sugar per berry and berry mass in a log-log scale, being greater than 1. For Phase 3, the condition for increase of sugar concentration is that a large reduction in berry mass offsets any putative change of sugar per berry, yielding an allometric coefficient < 1. Such an allometric model was tested against measured data from sixteen contrasting crops resulting from the combination of eight water regimes and two seasons. Berry mass peaked between 96 and 105 days after anthesis, and these dates were used to separate Phases 2 and 3. In Phase 2, the relative rate of increase in sugar per berry varied from 0.01 to 0.02 d -1 in comparison to the relative rate of increase in berry fresh mass that varied from 0.0038 to 0.0066 d -1. Sugar per berry thus increased 2.4,3.3 times faster than berry mass, with allometric coefficients between 1.98 and 2.91 accounting for 78% of the variation in the relative rate of change of sugar concentration. In Phase 3, the relative rate of change in sugar per berry was not different from zero (P 0.05) in most cases, whereas the rate of change in berry size ranged from ,0.0013 to ,0.0035 d -1 and was significant (P < 0.05) in 14 out 16 cases. The small changes in sugar per berry and the net loss of berry material yielded allometric coefficients between 0.17 and 1.11, which accounted for 72% of the variation in the relative rate of change in sugar concentration. We conclude that a model, which pivots around peak berry mass, with allometric coefficients above 1 in Phase 2 and below 1 in Phase 3, is suitable to quantitatively account for ontogenetic drift in the dynamics of sugar concentration in berries of Shiraz. This allometric approach demonstrated that sugar per berry during the stage of berry shrinkage is a plastic trait under significant environmental influence. For the same genotype, environmental conditions could determine either, a putative backflow of water accounting for net loss of berry fresh mass (RFM < 0) that could also carry some sugar from berries back to the parent vine (RSB < 0) or a small gain of sugar (RSB 0) closely coupled with a net loss of berry fresh mass (P= 0.003). [source] Interactions between onshore bedrock-channel incision and nearshore wave-base erosion forced by eustasy and tectonicsBASIN RESEARCH, Issue 2 2002N.P. Snyder We explore the response of bedrock streams to eustatic and tectonically induced fluctuations in base level. A numerical model coupling onshore fluvial erosion with offshore wave-base erosion is developed. The results of a series of simulations for simple transgressions with constant rate of sea-level change (SLR) show that response depends on the relative rates of rock uplift (U) and wave-base erosion (,w). Simple regression runs highlight the importance of nearshore bathymetry. Shoreline position during sea-level fall is set by the relative rate of base-level fall (U-SLR) and ,w, and is constant horizontally when these two quantities are equal. The results of models forced by a realistic Late Quaternary sea-level curve are presented. These runs show that a stable shoreline position cannot be obtained if offshore uplift rates exceed ,w. Only in the presence of a relatively stable shoreline position, fluvial profiles can begin to approximate a steady-state condition, with U balanced by fluvial erosion rate (,f). In the presence of a rapid offshore decrease in rock-uplift rate (U), short (,5 km) fluvial channels respond to significant changes in rock-uplift rate in just a few eustatic cycles. The results of the model are compared to real stream-profile data from the Mendocino triple junction region of northern California. The late Holocene sea-level stillstand response exhibited by the simulated channels is similar to the low-gradient mouths seen in the California streams. [source] Ruthenium-Catalyzed Asymmetric Epoxidation of Olefins Using H2O2, Part II: Catalytic Activities and MechanismCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2006Man Kin Tse Dr. Abstract Asymmetric epoxidation of olefins with 30,% H2O2 in the presence of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2 has been studied in detail (pybox=pyridine-2,6-bisoxazoline, pyboxazine=pyridine-2,6-bisoxazine, pydic=2,6-pyridinedicarboxylate). 35 Ruthenium complexes with sterically and electronically different substituents have been tested in environmentally benign epoxidation reactions. Mono-, 1,1-di-, cis - and trans -1,2-di-, tri-, and tetra-substituted aromatic olefins with versatile functional groups can be epoxidized with this type of catalyst in good to excellent yields (up to 100,%) with moderate to good enantioselectivies (up to 84,% ee). Additive and solvent effects as well as the relative rate of reaction with different catalysts have been established. It is shown that the presence of weak organic acids or an electron-withdrawing group on the catalyst increases the reactivity. New insights on the reaction intermediates and reaction pathway of the ruthenium-catalyzed epoxidation are proposed on the basis of density functional theory calculation and experiments. [source] Patterns of Nest Predation on Artificial and Natural Nests in ForestsCONSERVATION BIOLOGY, Issue 2 2004DAWN M. BURKE ave de bosque; depredación de nidos; éxito de nidos; experimento de nidos artificiales; nidos naturales Abstract:,Artificial nest experiments have been used in an attempt to understand patterns of predation affecting natural nests. A growing body of literature suggests that neither relative rates nor patterns of predation are the same for artificial and natural nests. We studied nest predation and daily mortality rates and patterns at real and artificial ground and shrub nests to test the validity of artificial nest experiments. We monitored 1667 artificial and 344 natural nests, over seven trials, in three regions, across 58 sites in Ontario. We controlled for many of the factors thought to be responsible for previously reported differences between predation rates on natural and artificial nests. Although artificial nests in our study resembled natural nests, contained eggs of appropriate size, shape, and color of target bird species, and were placed in similar microhabitats as natural nests, the rates of predation on these nests did not parallel rates on natural nests for any region in terms of absolute rate or pattern. Predation rates on artificial nests did not vary between years, as they tended to for natural nests, and the magnitude of predation pressure on artificial ground nests compared with shrub nests did not show the same pattern as that on natural nests. In general, rates of predation on artificial nests were significantly higher than on natural nests. Our results suggest that conclusions derived from artificial nest studies may be unfounded. Given that many influential ideas in predation theory are based on results of artificial nest experiments, it may be time to redo these experiments with natural nests. Resumen:,Se han utilizado experimentos con nidos artificiales con la intención de entender los patrones de depredación que afectan a los nidos naturales. La bibliografía sugiere que ni las tasas relativas ni los patrones de depredación son iguales para nidos artificiales y naturales. Estudiamos las tasas y patrones de depredación de nidos y de mortalidad diaria en nidos reales y artificiales sobre el suelo y en matorrales para probar la validez de los experimentos con nidos artificiales. Monitoreamos 1667 nidos artificiales y 344 nidos naturales, en siete pruebas, en tres regiones, en 58 sitios en Notario. Controlamos muchos de los factores que se piensa son responsables de diferencias entre tasas de depredación en nidos naturales y artificiales reportadas previamente. Aunque los nidos artificiales en nuestro estudio se asemejaron a nidos naturales, contenían huevos de tamaño, forma y color adecuados para la especie de ave y fueron colocados en microhábitats similares a los de nidos naturales, las tasas de depredación en estos nidos no fueron similares a las tasas en nidos naturales en ninguna región en términos de tasa o patrón absoluto. Las tasas de depredación en nidos artificiales no variaron de un año a otro, como fue la tendencia en nidos naturales, y la magnitud de la presión de depredación en nidos sobre el suelo comparada con nidos en arbustos no mostró el mismo patrón que la depredación en nidos naturales. Nuestros resultados sugieren que las conclusiones derivadas de estudios con nidos artificiales pueden ser infundadas. Debido a que muchas ideas influyentes en la teoría de la depredación se basan en los resultados de experimentos con nidos artificiales, puede haber llegado el momento de volver a realizar estos experimentos utilizando nidos naturales. [source] GENE FLOW AND SPECIES DELIMITATION: A CASE STUDY OF TWO PINE SPECIES WITH OVERLAPPING DISTRIBUTIONS IN SOUTHEAST CHINAEVOLUTION, Issue 8 2010Yong Feng Zhou Species delimitation detected by molecular markers is complicated by introgression and incomplete lineage sorting between species. Recent modeling suggests that fixed genetic differences between species are highly related to rates of intraspecific gene flow. However, it remains unclear whether such differences are due to high levels of intraspecific gene flow overriding the spread of introgressed alleles or favoring rapid lineage sorting between species. In pines, chloroplast (cp) and mitochondrial (mt) DNAs are normally paternally and maternally inherited, respectively, and thus their relative rates of intraspecific gene flow are expected to be high and low, respectively. In this study, we used two pine species with overlapping geographical distributions in southeast China, P. massoniana and P. hwangshanensis, as a model system to examine the association between organelle gene flow and variation within and between species. We found that cpDNA variation across these two pine species is more species specific than mtDNA variation and almost delimits taxonomic boundaries. The shared mt/cp DNA genetic variation between species shows no bias in regard to parapatric versus allopatric species' distributions. Our results therefore support the hypothesis that high intraspecific gene flow has accelerated cpDNA lineage sorting between these two pine species. [source] An analysis of the burning of polyester and vinylester fibre glass compositesFIRE AND MATERIALS, Issue 4 2005P. J. Burchill Abstract An analysis of mass loss and damage depth produced by the combustion of styrenic resins and their fibre glass composites has been undertaken. Mass loss rates at a selected heat flux were found to be linearly related to those at a different heat flux. Given the scatter in the experimental data, these relative rates obeyed the same Arrhenius relationship for both resins and their fibre glass composites. Damage depth in composites was also found to be linearly related to mass loss, and thus may be predicted. It is therefore shown that mass loss and damage depth can be predicted as a function of time at any desired heat flux given that mass loss-time data are available at a specific heat flux. The predictions are limited to consumption of the matrix of about 30% by weight, at which stage the mechanical properties are greatly reduced. Copyright © Commonwealth of Australia 2004. Published by John Wiley & Sons, Ltd. [source] A Computational Study of the Sub-monolayer Growth of PentaceneADVANCED FUNCTIONAL MATERIALS, Issue 13 2006D. Choudhary Abstract A computational study of organic thin-film growth using a combination of ab,initio based energy calculations and kinetic Monte Carlo (KMC) simulations is provided. A lattice-based KMC model is used in which binding energies determine the relative rates of diffusion of the molecules. This KMC approach is used to present "landscapes" or "maps" that illustrate the possible structural outcomes of growing a thin film of small organic molecules, represented as a two-site dimer, on a substrate in which the strength of organic,substrate interactions is allowed to vary. KMC provides a mesoscopic-scale view of sub-monolayer deposition of organic thin films on model substrates, mapped out as a function of the flux of depositing molecules and the temperature of the substrate. The morphology of the crystalline thin films is shown to be a strong function of the molecule,molecule and molecule,substrate interactions. A rich variety of maps is shown to occur in which the small organic molecules either stand up or lie down in a variety of different patterns depending on the nature of the binding to the surface. In this way, it is possible to suggest how to tailor the substrate or the small organic molecule in order to create a desired growth habit. In order to demonstrate how this set of allowable maps is reduced in the case where the set of energy barriers between substrate and organic molecule are reliably known, we have used Gaussian,98 calculations to establish binding energies for the weak van der Waals interactions between a),pairs of pentacene molecules as a function of orientation and b),pentacene and two substrates, silicon surfaces passivated with cyclopentene molecules and a crystalline model of silicon dioxide. The critical nucleation size and the mode of diffusion of this idealized two-site dimer model for pentacene molecules are found to be in good agreement with experimental data. [source] Stereochemical Models for Discussing Additions to ,,, -Unsaturated Aldehydes Organocatalyzed by Diarylprolinol or Imidazolidinone Derivatives , Is There an ,(E)/(Z)-Dilemma'?HELVETICA CHIMICA ACTA, Issue 4 2010Dieter Seebach Abstract The structures of iminium salts formed from diarylprolinol or imidazolidinone derivatives and ,,, -unsaturated aldehydes have been studied by X-ray powder diffraction (Fig.,1), single-crystal X-ray analyses (Table,1), NMR spectroscopy (Tables,2 and 3, Figs.,2,7), and DFT calculations (Helv. Chim. Acta2009, 92, 1, 1225, 2010, 93, 1; Angew. Chem., Int. Ed.2009, 48, 3065). Almost all iminium salts of this type exist in solution as diastereoisomeric mixtures with (E)- and (Z)-configured +NC bond geometries. In this study, (E)/(Z) ratios ranging from 88,:,12 up to 98,:,2 (Tables,2 and 3) and (E)/(Z) interconversions (Figs.,2,7) were observed. Furthermore, the relative rates, at which the (E)- and (Z)-isomers are formed from ammonium salts and ,,, -unsaturated aldehydes, were found to differ from the (E)/(Z) equilibrium ratio in at least two cases (Figs.,4 and 5,,a, and Fig.,6,,a); more (Z)-isomer is formed kinetically than corresponding to its equilibrium fraction. Given that the enantiomeric product ratios observed in reactions mediated by organocatalysts of this type are often ,99,:,1, the (E)-iminium-ion intermediates are proposed to react with nucleophiles faster than the (Z)-isomers (Scheme,5 and Fig.,8). Possible reasons for the higher reactivity of (E)-iminium ions (Figs.,8 and 9) and for the kinetic preference of (Z)-iminium-ion formation are discussed (Scheme,4). The results of related density functional theory (DFT) calculations are also reported (Figs.,10,13 and Table,4). [source] Rate coefficients for the gas-phase reactions of OH radicals with methylbutenols at 298 KINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2004Takashi Imamura The relative-rate method has been used to determine the rate coefficients for the reactions of OH radicals with three C5 biogenic alcohols, 2-methyl-3-buten-2-ol (k1), 3-methyl-3-buten-1-ol (k2), and 3-methyl-2-buten-1-ol (k3), in the gas phase. OH radicals were produced by the photolysis of CH3ONO in the presence of NO. Di- n -butyl ether and propene were used as the reference compounds. The absolute rate coefficients obtained with the two reference compounds agreed well with each other. The O3 and O-atom reactions with the target alcohols were confirmed to have a negligible contribution to their total losses by using two kinds of light sources with different relative rates of CH3ONO and NO2 photolysis. The absolute rate coefficients were obtained as the weighted mean values for the two reference compound systems and were k1 = (6.6 ± 0.5) × 10,11, k2 = (9.7 ± 0.7) × 10,11, and k3 = (1.5 ± 0.1) × 10,10 cm3 molecule,1 s,1 at 298 ± 2 K and 760 torr of air. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 379,385 2004 [source] Stereoselectivity in the Rhodium-Catalysed Reductions of Non-Conjugated DienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Bao Nguyen Abstract The stereochemical course of rhodium-catalysed addition of hydrogen and catecholborane to bicyclo[2.2.1]heptadiene, and of hydrogen to a range of cyclic dienes has been analysed. For hydroboration, the overall catalytic reaction possesses exo -selectivity, but the initial step is endo -selective. For hydrogenation (deuteration), the first step may occur with either exo- or endo- selectivity, depending on the structure of the diene. This enables a distinction to be made between pathways involving prior dissociation of the diene, and direct addition to the complexed diene without full dissociation. The relative ease of hydrogenation of the first and second double bonds varies markedly with reactant structure, and also depends on the choice of catalyst ligands. For dicyclopentadiene, hydrogenation of the cyclopentene double bond is accompanied by rapid alkene isomerisation, as revealed by deuterium addition. The asymmetric hydrogenation of acyclic skipped meso -dienes is reported, demonstrating control of relative rates of the two sequential steps, with ees of up to 53% after the first reduction. [source] Large-scale dynamics in colonization and extinction for breeding birds in BritainJOURNAL OF ANIMAL ECOLOGY, Issue 3 2002Kevin J. Gaston Summary 1A number of generalizations have been made as to the effects of the area of occupancy, population size, dispersal ability and body size of species on their relative rates of local colonization and extinction. 2Here, data on the breeding bird assemblage of Britain are used to test these generalizations. The complete geographical ranges of British birds have been censused twice, in the periods 1968,72 and 1988,91, allowing rates of colonization and extinction between these periods to be estimated. 3The local colonization dynamics of species are influenced independently by their range sizes and the dispersal abilities of adult birds: species with smaller range sizes and larger dispersal distances were more likely to have colonized new areas between the two census periods. 4The local extinction dynamics of species are influenced independently by their population sizes and body masses: species with smaller population sizes and body sizes were more likely to have gone extinct from areas inhabited in the first census period. 5These results remain when controlling for the effects of phylogenetic relatedness. 6These analyses uphold many commonly held generalizations about the correlates of local colonization and extinction, and suggest that the long-term evolutionary history of these bird species has influenced their potential to respond to current ecological conditions. [source] Use of Oral Corticosteroids and Risk of FracturesJOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2000T. P. Van Staa Abstract Treatment with oral corticosteroids is known to decrease bone density but there are few data on the attendant risk of fracture and on the reversibility of this risk after cessation of therapy. A retrospective cohort study was conducted in a general medical practice setting in the United Kingdom (using data from the General Practice Research Database [GPRD]). For each oral corticosteroid user aged 18 years or older, a control patient was selected randomly, who was matched by age, sex, and medical practice. The study comprised 244,235 oral corticosteroid users and 244,235 controls. The average age was 57.1 years in the oral corticosteroid cohort and 56.9 years in the control cohort. In both cohorts 58.6% were female. The most frequent indication for treatment was respiratory disease (40%). The relative rate of nonvertebral fracture during oral corticosteroid treatment was 1.33 (95% confidence interval [CI], 1.29,1.38), that of hip fracture 1.61 (1.47,1.76), that of forearm fracture 1.09 (1.01,1.17), and that of vertebral fracture 2.60 (2.31,2.92). A dose dependence of fracture risk was observed. With a standardized daily dose of less than 2.5 mg prednisolone, hip fracture risk was 0.99 (0.82,1.20) relative to control, rising to 1.77 (1.55,2.02) at daily doses of 2.5,7.5 mg, and 2.27 (1.94,2.66) at doses of 7.5 mg or greater. For vertebral fracture, the relative rates were 1.55 (1.20,2.01), 2.59 (2.16,3.10), and 5.18 (4.25,6.31), respectively. All fracture risks declined toward baseline rapidly after cessation of oral corticosteroid treatment. These results quantify the increased fracture risk during oral corticosteroid therapy, with greater effects on the hip and spine than forearm. They also suggest a rapid offset of this increased fracture risk on cessation of therapy, which has implications for the use of preventative agents against bone loss in patients at highest risk. [source] Multilevel Anthropogenic Cycles of Copper and Zinc: A Comparative Statistical AnalysisJOURNAL OF INDUSTRIAL ECOLOGY, Issue 1-2 2006Barbara Reck Contemporary cycles for copper and zinc are coanalyzed with the tools of exploratory data analysis. One-year analyses (circa 1994) are performed at three discrete spatial levels-country (52 countries that comprise essentially all anthropogenic stocks and flows of the two metals), eight world regions, and the planet as a whole-and are completed both in absolute magnitude and in per capita terms. This work constitutes, to our knowledge, the first multiscale, multilevel analysis of anthropogenic resources throughout their life cycles. The results demonstrate that (1) A high degree of correlation exists between country-level copper and country-level zinc rates of fabrication and manufacturing, entry into use, net addition to in-use stocks, discard, and landfilling; (2) Regional-level rates for copper and zinc cycle parameters show the same correlations as exist at country level; (3) On a per capita basis, countries add to in-use stock almost 50% more copper than zinc; (4) The predominant discard streams for copper and zinc at the global level are different for the two metals, and relative rates of different loss processes differ geographically, so that resource recovery policies must be designed from metalspecific and location-specific perspectives; (5)When absolute magnitudes of life-cycle flows are considered, the standard deviations of the data sets decrease from country level to regional level for both copper and zinc, which is not the case for the per capita data sets, where the statistical properties of the dat sets for both metals approach being independent of spatial level, thus providing a basis for predicting unmeasured per capita metal flow behavior. [source] Solid-solid reactions in series: A modeling and experimental studyAICHE JOURNAL, Issue 9 2009A. K. Suresh Abstract Reactions among particulate solid phases are important and abundant in many materials, chemical, and metallurgical process industries. Many of these are reaction networks, and not single-step reactions as normally assumed. There is no theoretical framework available for the analysis of such systems, and single-reaction models derived from the gas,solid literature continue to be used. Formation of cement clinker in the rotary cement kiln is a prime example of the genre, in which mechanistic aspects play an important role in determining energy efficiency and the composition and nature of the phases that form. In the present study, we formulate a model within the ambit of the "shrinking core" class of models, for reactions in series among solid phases. The model shows the presence of one or two moving fronts in the reacting particle, depending on the relative rates of the processes involved. A single Thiele-type parameter controls the model behavior, at once describing the relative rates of the intermediate formation and consumption processes, and the diffusion-reaction competition for the product formation step. The model has been shown to reduce to the well known single reaction models at the limits of low and high values of the Thiele parameter. Experimental data have been obtained on the calcia-alumina system, an important one in cement manufacture, in the temperature range 1150,1250°C. The model has been fitted to these data and the kinetic parameters determined. The comparison bears out the salient features of the theory, and shows that a degree of diffusion limitation exists for the intermediate conversion step under these conditions. The diffusivity values estimated are in the range of 10,19 to 10,18 m2/s and agree with values found in the literature for similar systems. The rate constant for the intermediate conversion step is of the order of 10,6 s,1. This being among the first such determinations, this value awaits confirmation from other studies. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Correlation of relative rates of chromyl chloride oxidation and chromic acid oxidation of acyclic alkenes versus alkene IPs and HOMOsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2004Donna J. Nelson Abstract Plots of logarithms of relative reaction rates of chromyl chloride oxidation and of chromic acid oxidation of alkenes (log,krel values) versus alkene ionization potentials (IPs) and versus their highest occupied molecular orbital energy levels (HOMOs) demonstrate excellent correlations. Each plot has a similar appearance and shows a single line with a positive slope. The results indicate that the rate-determining step of each title reaction involves an electrophilic attack on the alkene ,-bond without significant steric effects; this supports a proposed 2,+,3 cycloaddition mechanism and disfavors a proposed stepwise 2,+,2 cycloaddition mechanism. Comparison is made with other d0 transition metal complexes that oxidize alkenes. Copyright © 2004 John Wiley & Sons, Ltd. [source] Combining evidence on air pollution and daily mortality from the 20 largest US cities: a hierarchical modelling strategyJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 3 2000Francesca Dominici Reports over the last decade of association between levels of particles in outdoor air and daily mortality counts have raised concern that air pollution shortens life, even at concentrations within current regulatory limits. Criticisms of these reports have focused on the statistical techniques that are used to estimate the pollution,mortality relationship and the inconsistency in findings between cities. We have developed analytical methods that address these concerns and combine evidence from multiple locations to gain a unified analysis of the data. The paper presents log-linear regression analyses of daily time series data from the largest 20 US cities and introduces hierarchical regression models for combining estimates of the pollution,mortality relationship across cities. We illustrate this method by focusing on mortality effects of PM10 (particulate matter less than 10 ,m in aerodynamic diameter) and by performing univariate and bivariate analyses with PM10 and ozone (O3) level. In the first stage of the hierarchical model, we estimate the relative mortality rate associated with PM10 for each of the 20 cities by using semiparametric log-linear models. The second stage of the model describes between-city variation in the true relative rates as a function of selected city-specific covariates. We also fit two variations of a spatial model with the goal of exploring the spatial correlation of the pollutant-specific coefficients among cities. Finally, to explore the results of considering the two pollutants jointly, we fit and compare univariate and bivariate models. All posterior distributions from the second stage are estimated by using Markov chain Monte Carlo techniques. In univariate analyses using concurrent day pollution values to predict mortality, we find that an increase of 10 ,g m -3 in PM10 on average in the USA is associated with a 0.48% increase in mortality (95% interval: 0.05, 0.92). With adjustment for the O3 level the PM10 -coefficient is slightly higher. The results are largely insensitive to the specific choice of vague but proper prior distribution. The models and estimation methods are general and can be used for any number of locations and pollutant measurements and have potential applications to other environmental agents. [source] The Solid State Postcondensation of PET, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2004Barbara Gantillon Abstract Summary: A review of the processes underlying the solid state postcondensation of poly(ethylene terephthalate) (PET) is presented. Fundamental aspects of the reactions are treated, and it is shown that the rate of polycondensation in the solid state depends on the relative rates of two types of diffusion. On the one hand, the diffusion of reaction by-products (physical diffusion) controls the rate of the forward reactions. And on the other hand the diffusion of end-groups (chemical diffusion) allows the reaction to proceed. The transesterification of BHET to form PET. [source] The excess burden of stroke in hospitalized adults with sickle cell disease,AMERICAN JOURNAL OF HEMATOLOGY, Issue 9 2009John J. Strouse This report compares the relative rates and risk factors associated with stroke in adults versus children with sickle cell disease (SCD) in the United States over the last decade. We identified incident strokes in patients with SCD using ICD-9 codes for acute stroke and SCD and the California Patient Discharge Databases. We estimated SCD prevalence by using the incidence of SCD at birth with adjustment for early mortality from SCD. We identified 255 acute strokes (70 primary hemorrhagic and 185 ischemic) among 69,586 hospitalizations for SCD-related complications from 1998 to 2007. The rate of stroke in children [<18 years old (310/100,000 person-years)] was similar to young adults [18,34 years old (360/100,000 person-years)], but much higher in middle-aged [35,64 years old (1,160/100,000 person-years)] and elderly adults [,65 years old (4,700/100,000 person-years)]. Stroke was associated with hypertension in children and hypertension, diabetes mellitus, hyperlipidemia, atrial fibrillation, and renal disease in adults. Most acute strokes (75%) and in-hospital deaths from stroke (91%) occurred in adults. Our results suggest that the rate of stroke in SCD peaks in older adults and is three-fold higher than rates previously reported in African-Americans of similar age (35,64 years) without SCD. Stroke in SCD is associated with several known adult risk factors for ischemic and hemorrhagic stroke. Studies for the primary and secondary prevention of stroke in adults with SCD are urgently needed. Am. J. Hematol. 2009. © 2009 Wiley-Liss, Inc. [source] Has social mobility in Britain decreased?THE BRITISH JOURNAL OF SOCIOLOGY, Issue 2 2010Reconciling divergent findings on income, class mobility Abstract Social mobility has become a topic of central political concern. In political and also media circles it is widely believed that in Britain today mobility is in decline. However, this belief appears to be based on a single piece of research by economists that is in fact concerned with intergenerational income mobility: specifically, with the relation between family income and children's later earnings. Research by sociologists using the same data sources , the British birth cohort studies of 1958 and 1970 , but focusing on intergenerational class mobility does not reveal a decline either in total mobility rates or in underlying relative rates. The paper investigates these divergent findings. We show that they do not result from the use of different subsets of the data or of different analytical techniques. Instead, given the more stable and generally less fluid class mobility regime, it is the high level of income mobility of the 1958 cohort, rather than the lower level of the 1970 cohort, that is chiefly in need of explanation. Further analyses , including ones of the relative influence of parental class and of family income on children's educational attainment , suggest that the economists' finding of declining mobility between the two cohorts may stem, in part at least, from the fact that the family income variable for the 1958 cohort provides a less adequate measure of ,permanent income' than does that for the 1970 cohort. But, in any event, it would appear that the class mobility regime more fully captures the continuity in economic advantage and disadvantage that persists across generations. [source] Intergenerational class mobility in contemporary Britain: political concerns and empirical findings1THE BRITISH JOURNAL OF SOCIOLOGY, Issue 4 2007John H. Goldthorpe Abstract In Britain in recent years social mobility has become a topic of central political concern, primarily as a result of the effort made by New Labour to make equality of opportunity rather than equality of condition a focus of policy. Questions of the level, pattern and trend of mobility thus bear directly on the relevance of New Labour's policy analysis, and in turn are likely be crucial to the evaluation of its performance in government. However, politically motivated discussion of social mobility often reveals an inadequate grasp of both empirical and analytical issues. We provide new evidence relevant to the assessment of social mobility , in particular, intergenerational class mobility , in contemporary Britain through cross-cohort analyses based on the NCDS and BCS datasets which we can relate to earlier cross-sectional analyses based on the GHS. We find that, contrary to what seems now widely supposed, there is no evidence that absolute mobility rates are falling; but, for men, the balance of upward and downward movement is becoming less favourable. This is overwhelmingly the result of class structural change. Relative mobility rates, for both men and women, remain essentially constant, although there are possible indications of a declining propensity for long-range mobility. We conclude that under present day structural conditions there can be no return to the generally rising rates of upward mobility that characterized the middle decades of the twentieth century , unless this is achieved through changing relative rates in the direction of greater equality or, that is, of greater fluidity. But this would then produce rising rates of downward mobility to exactly the same extent , an outcome apparently unappreciated by, and unlikely to be congenial to, politicians preoccupied with winning the electoral ,middle ground'. 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