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Intermediate Values (intermediate + value)
Selected AbstractsEffect of dietary protein and energy levels on growth, oxygen consumption, haemolymph and digestive gland carbohydrates, nitrogen excretion and osmotic pressure of Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles (Crustacea, Decapoda; Penaeidae)AQUACULTURE RESEARCH, Issue 7 2001C Rosas Abstract The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ,1 were fed at 20% of shrimp body weight of two sizes: < 1 g and >,1 g. Both species showed a optimum P/E ratio of 36 mg kJ,1 (33,44% protein and 6,23% carbohydrate) in juveniles <,1 g. For shrimp >,1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ,1 (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ,1 (33,44% protein and 6,23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2,3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ,1 diet and lower values (O/N = 73) with a 36-mg kJ,1 diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus <,1 g fed with 36 mg kJ,1 and the lowest in L. vannamei <,1 g fed with 31 mg kJ,1. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles <,1 g of both species are more affected by the P/E ratio than juveniles >,1 g. All results showed that juveniles >,1 g of both species are less dependent of P/E ratio than juveniles <,1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds. [source] Superior temporal lobe dysfunction and frontotemporal dysconnectivity in subjects at risk of psychosis and in first-episode psychosisHUMAN BRAIN MAPPING, Issue 12 2009Nicolas A. Crossley Abstract Background: Superior temporal lobe dysfunction is a robust finding in functional neuroimaging studies of schizophrenia and is thought to be related to a disruption of fronto-temporal functional connectivity. However, the stage of the disorder at which these functional alterations occur is unclear. We addressed this issue by using functional MRI (fMRI) to study subjects in the prodromal and first episode phases of schizophrenia. Methods: Subjects with an at risk mental state (ARMS) for psychosis, a first psychotic episode (FEP), and controls were studied using fMRI while performing a working memory task. Activation in the superior temporal gyrus (STG) was assessed using statistical parametric mapping, and its relationship to frontal activation was examined using dynamic causal modeling. Results: The STG was differentially engaged across the three groups. There was deactivation of this region during the task in controls, whereas subjects with FEP showed activation and the response in subjects with ARMS was intermediately relative to the two other groups. There were corresponding differences in the effective connectivity between the STG and the middle frontal gyrus across the three groups, with a negative coupling between these areas in controls, a positive coupling in the FEP group, and an intermediate value in the ARMS group. Conclusions: A failure to deactivate the superior temporal lobe during tasks that engage prefrontal cortex is evident at the onset of schizophrenia and may reflect a disruption of fronto-temporal connectivity. Qualitatively similar alterations are evident in people with prodromal symptoms of the disorder. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Spatial patterns in species,area relationships and species distribution in a West African forest,savanna mosaicJOURNAL OF BIOGEOGRAPHY, Issue 4 2005Thomas Hovestadt Abstract Aim, To investigate the relationship between the slope z of the species,area relationship (SAR) and the intensity of spatial patterns in species number and dissimilarity for woody plants with different modes of seed dispersal. According to island theory we expect, for any given archipelago, steeper slopes and more pronounced spatial patterns for groups of less dispersive species. Location, Ivory Coast, West Africa. Methods, In a West African forest,savanna mosaic we collected presence,absence data for woody plant species in 49 forest islands. The parameters of the SARs were fitted by nonlinear regressions and then compared for plant species aggregated according to their mode of seed dispersal. We used the Mantel test to calculate the intensity of spatial patterns in species number, i.e. residual deviation from SAR, and species dissimilarity. Results, The z -value for bird-dispersed species was lower (0.11) than that for wind-dispersed species (0.27), with mammal-dispersed species taking an intermediate value (0.16). This result suggests that, as a group, bird-dispersed species are better colonizers. The spatial pattern in species number as well as species similarity was more pronounced for bird- compared with wind-dispersed species. Main conclusions, The standard interpretation of the theory of island biogeography claims that shallow slopes in the SAR imply low isolation of islands, i.e. good dispersal abilities of species. The results of our study appear to contradict this statement. The contradiction can eventually be resolved by a more detailed account of the colonization process, i.e. by distinguishing between dispersal and consecutive establishment of populations. [source] Origin of Crude Oil in the Lunnan Region, Tarim BasinACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010LI Sumei Abstract: The oil source of the Tarim Basin has been controversial over a long time. This study characterizes the crude oil and investigates the oil sources in the Lunnan region, Tarim Basin by adopting compound specific isotopes of n -alkanes and biomarkers approaches. Although the crude oil has a good correlation with the Middle-Upper Ordovician (O2+3) source rocks and a poor correlation with the Cambrian-Lower Ordovician (,-O1) based on biomarkers, the ,13C data of n -alkanes of the Lunnan oils show an intermediate value between ,-O1 and O2+3 genetic affinity oils, which suggests that the Lunnan oils are actually of an extensively mixed source. A quantification of oil mixing was performed and the results show that the contribution of the Cambrian-Lower Ordovician source rocks ranges from 11% to 70% (averaging 36%), slightly less than that of the Tazhong uplift. It is suggested that the inconsistency between the biomarkers and ,13C in determining the oil sources in the Lunnan Region results from multiple petroleum charge episodes with different chemical components in one or more episode(s) and different sources. The widespread marine mixed-source oil in the basin indicates that significant petroleum potential in deep horizons is possible. To unravel hydrocarbons accumulation mechanisms for the Lunnan oils is crucial to further petroleum exploration and exploitation in the region. [source] Social anxiety disorder: what are we losing with the current diagnostic criteria?ACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2010A. S. Filho Filho AS, Hetem LAB, Ferrari MCF, Trzesniak C, Martín-Santos R, Borduqui T, de Lima Osório F, Loureiro SR, Busatto Filho G, Zuardi AW, Crippa JAS. Social anxiety disorder: what are we losing with the current diagnostic criteria? Objective:, To assess the rate of comorbidities and the functional impairment associated with the social anxiety disorder (SAD), with an emphasis on the so-called subthreshold clinical signs and symptoms. Method:, Psychiatric comorbidities and psychosocial functioning were evaluated in 355 volunteers (college students) who had been diagnosed as SAD (n = 141), Subthreshold SAD (n = 92) or Controls (n = 122). Results:, The rate of comorbidities was 71.6% in the SAD group and 50% in subjects with Subthreshold SAD, both significantly greater than Controls (28.7%). Concerning psychosocial functioning, the SAD group had higher impairment than the other two groups in all domains evaluated, and subjects with Subthreshold SAD presented intermediate values. Conclusion:, The rates of psychiatric comorbidities and the impairment of psychosocial functioning increase progressively along the spectrum of social anxiety. The fact that Subthreshold SAD causes considerable disability and suffering in comparison with control subjects justifies a review of the validity of the diagnostic criteria. [source] DIFFERENTIAL PERFORMANCE AMONG LDH-B GENOTYPES IN RANA LESSONAE TADPOLESEVOLUTION, Issue 5 2000Hansjürg Hotz Abstract The European pool frog, Rana lessonae, is widely polymorphic for two common alleles (b, e) at the lactate dehydrogenase-B (LDH-B) locus. We compared fitness-related larval life-history traits among LDH-B genotypes, which originated from segregation in heterozygous parents, in an artificial pond experiment where tadpoles of R. lessonae from a Swiss population were raised together with tadpoles of the hemiclonal hybrid R. esculenta at two densities. In R. lessonae, LDH-B e/e homozygotes at each density had a higher proportion of metamorphs among survivors, reached metamorphosis earlier, and were heavier at metamorphosis than b/b homozygotes; b/e heterozygotes had intermediate values. That e/e individuals were superior to b/b in both time to and mass at metamorphosis is surprising because these two life-history traits are thought to reflect a performance trade-off; e/e genotypes apparently compensated for shorter time to metamorphosis by a higher growth rate. The two alleles showed the same performance ranking when combined in hybrids with a R. ridibunda allele: When R. esculenta from Swiss populations reared in the same ponds had received the e allele rather than the b allele from their R. lessonae parent, they reached metamorphosis earlier, but did not differ in mass at metamorphosis. The degree of linkage disequilibrium in the source population of the eight R. lessonae used as parents of the R. lessonae tadpoles is unknown, so we cannot exclude the possibility that the performance differences are caused by some anonymous tightly linked gene, rather than the LDH-B locus, that constitutes the genomically localized target of natural selection. A causal involvement of LDH-B is plausible, nevertheless, because this enzyme takes part in the central energy-metabolizing processes and has been reported to underlie fitness differences in other animals; also, differential performance of LDH-B genotypes has been observed in R. lessonae larvae from another population. The present results suggest strong directional selection for allele e; the sum of available data, including an independent laboratory experiment, suggests that partial environment-dependent overdominance combined with balancing selection favoring e/e homozygotes under some and b/b homozygotes under other conditions may be partially responsible for the broad maintenance of the LDH-B polymorphism in R. lessonae. [source] Do woodlice and earthworms interact synergistically in leaf litter decomposition?FUNCTIONAL ECOLOGY, Issue 1 2005MARTIN ZIMMER Summary 1In laboratory microcosms, we investigated the influence of diversity of both leaf litter and detritivores on decomposition processes. Either woodlice or earthworms, or a combination of woodlice and earthworms, fed on leaf litter of either oak or alder, or oak and alder for 8 weeks. Mass loss of leaf litter, soil microbial respiration and soil nutrient concentrations were determined every 2 weeks. 2For four out of seven decomposition parameters, the joint effects of woodlice and earthworms were stronger than the sum of single-species effects when they had fed on alder litter. When feeding on oak litter, however, woodlice and earthworms together revealed lower decomposition rates than predicted from their single effects. Joint effects of detritivores on decomposition of mixed litter were always lower than predicted from the sum of their effects. 3In mixed-litter assays, we obtained intermediate values of decomposition parameters, indicating that doubling the species richness of leaf litter from one to two species did not promote decomposition processes. Effects of mixing litter were, thus, mostly additive; essentially only when earthworms fed on mixed litter we observed, mostly positive, non-additive effects of diverse litter. 4Our findings provide evidence for a potential effect on ecosystem functioning through joint action of detritivores even at low species diversity, while litter diversity seems to be less significant. On high-quality litter, isopods and earthworms are not functionally redundant but act synergistically on litter decomposition. The effects of detritivore diversity on ecosystem processes, however, are context-specific and depend on the quality and diversity of the available food sources, and on species-specific characteristics of the detritivores. [source] Impact of land use on the hydraulic properties of the topsoil in a small French catchmentHYDROLOGICAL PROCESSES, Issue 17 2010E. Gonzalez-Sosa Abstract The hydraulic properties of the topsoil control the partition of rainfall into infiltration and runoff at the soil surface. They must be characterized for distributed hydrological modelling. This study presents the results of a field campaign documenting topsoil hydraulic properties in a small French suburban catchment (7 km2) located near Lyon, France. Two types of infiltration tests were performed: single ring infiltration tests under positive head and tension-disk infiltration using a mini-disk. Both categories were processed using the BEST,Beerkan Estimation of Soil Transfer parameters,method to derive parameters describing the retention and hydraulic conductivity curves. Dry bulk density and particle size data were also sampled. Almost all the topsoils were found to belong to the sandy loam soil class. No significant differences in hydraulic properties were found in terms of pedologic units, but the results showed a high impact of land use on these properties. The lowest dry bulk density values were obtained in forested soils with the highest organic matter content. Permanent pasture soils showed intermediate values, whereas the highest values were encountered in cultivated lands. For saturated hydraulic conductivity, the highest values were found in broad-leaved forests and small woods. The complementary use of tension-disk and positive head infiltration tests highlighted a sharp increase of hydraulic conductivity between near saturation and saturated conditions, attributed to macroporosity effect. The ratio of median saturated hydraulic conductivity to median hydraulic conductivity at a pressure of , 20 mm of water was about 50. The study suggests that soil texture, such as used in most pedo-transfer functions, might not be sufficient to properly map the variability of soil hydraulic properties. Land use information should be considered in the parameterizations of topsoil within hydrological models to better represent in situ conditions, as illustrated in the paper. Copyright © 2010 John Wiley & Sons, Ltd. [source] Single value of serum transferrin receptor is not diagnostic for the absence of iron stores in anaemic patients with rheumatoid arthritisINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 3 2003S. Siebert Summary Serum transferrin receptor (sTfR) concentrations were measured in anaemic patients with rheumatoid arthritis (RA). Serum transferrin receptor concentrations were positively correlated with the percentage of hypochromic cells and negatively correlated with MCH. There was a weak correlation with serum ferritin (sFn) concentration but not with reticulocyte count. Thus, high concentrations of sTfR indicate iron-deficient erythropoiesis rather than levels of storage iron in the tissues. Patients were divided into three groups on the basis of sFn concentration: those with probable tissue iron deficiency, those with adequate iron stores and those with intermediate values of sFn which did not allow classification. The median sTfR concentration was significantly higher in the iron-deficient group than in the other two groups but because of overlap between the three groups, a single sTfR value was of limited value in determining the level of storage iron in an individual with RA. [source] A modelling strategy for the analysis of clinical trials with partly missing longitudinal dataINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 3 2003Ian R. White Abstract Standard statistical analyses of randomized controlled trials with partially missing outcome data often exclude valuable information from individuals with incomplete follow-up. This may lead to biased estimates of the intervention effect and loss of precision. We consider a randomized trial with a repeatedly measured outcome, in which the value of the outcome on the final occasion is of primary interest. We propose a modelling strategy in which the model is successively extended to include baseline values of the outcome, then intermediate values of the outcome, and finally values of other outcome variables. Likelihood-based estimation of random effects models is used, allowing the incorporation of data from individuals with some missing outcomes. Each estimated intervention effect is free of non-response bias under a different missing-at-random assumption. These assumptions become more plausible as the more complex models are fitted, so we propose using the trend in estimated intervention effects to assess the nature of any non-response bias. The methods are applied to data from a trial comparing intensive case management with standard case management for severely psychotic patients. All models give similar estimates of the intervention effect and we conclude that non-response bias is likely to be small. Copyright © 2003 Whurr Publishers Ltd. [source] Digestibility and nitrogen retention of diets containing different levels of fibre in local (Mong Cai), F1 (Mong Cai × Yorkshire) and exotic (Landrace × Yorkshire) growing pigs in VietnamJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 7-8 2007N. T. Len Summary Total tract digestibility and nitrogen retention of three diets containing different levels of fibre [200, 260 and 320 g/kg neutral detergent fibre (NDF) in dry matter] were determined in three breeds of growing pig at an initial age of approximately 3.5 months. The breeds were local (Mong Cai, MC), F1 crossbred (MC × Yorkshire) and exotic (Landrace × Yorkshire, LY), allocated at random within breed (block) to double 3 × 3 Latin squares. The main fibrous ingredients of the experimental diets were rice bran, cassava residue meal and non-dehulled groundnut cake meal. Digestibility of organic matter (OM), crude protein (CP), NDF, crude fibre, gross energy (GE) and ether extract (EE) decreased as the level of dietary NDF increased (p < 0.001). The r2 values for the relationship between NDF level and digestibility of OM, CP, GE and EE were 83%, 83%, 80% and 82% respectively. On average, an increase in NDF content of 1% unit resulted in a decrease in OM, CP, GE and EE digestibility of 0.67%, 0.75%, 0.50% and 0.42% units respectively. Digestibility of energy and nutrients was the highest for MC and the lowest for LY (p < 0.01), with intermediate values for F1. There was a negative effect of NDF level on nitrogen (N) retained as a proportion of intake (p < 0.05). Nitrogen retention and utilization were significantly higher (p < 0.001) for LY than for MC and F1 pigs. [source] Role of habitat degradation in determining fish distribution and abundance along the lowland Warta River, PolandJOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2007A. Kruk Summary The distribution and abundance of fish collected in 1996,1998 are compared in three river sections X, Y and Z in the 808-km-long Warta River, Poland. The upper section, X, was least human-modified, the middle section, Y, was the most polluted by industry and regulated, and the downstream section, Z, was moderately disturbed. The differences between X and Y in concentrations of dissolved oxygen, volatile phenols and nitrite nitrogen, and in the index of availability of hiding places, were highly significant because these parameters were several times worse in the Y section; in the Z section they assumed intermediate values. Although the abundance of certain fish species was changing along the downstream river gradient (i.e. differed the most between X and Z), both the Kohonen artificial neural network (SOM) and assemblage indices showed the biggest differences between X and Y, thus confirming the crucial role of the degradation of aquatic environment in shaping fish assemblages. The latter result ensued from the reaction of the rheophilic burbot, stone loach, gudgeon, chub and dace, which were most abundant in X, almost absent in Y and reoccurring in Z (although less numerous when compared with X). The opposite was recorded for mud loach, tench, ide and silver bream, which were most abundant in the degraded section Y, probably because of weak competition with the almost-absent rheophils. The abundance of two generalists, roach and pike, was similar in all three sections, i.e. changed neither along the downstream nor in the degradation gradient. [source] Intangible effort and performance: the case of the French wine industryAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2010Paul Amadieu This study investigates to what extent intangible investments have a positive impact on French wine companies' financial performance. French wine companies are small- and medium-sized enterprises (SMEs), so the task is (a) to measure their intangible expenses and capital, and (b) to estimate their impact on companies' performances. The authors then analyze the effect of property structures (cooperatives and corporations) and business activities on the intensity of the relationship between intangibility and performance. Relationships between intangibles and performance were tested empirically by means of a questionnaire carried out in 2005,2006. Questionnaire data were completed using financial statements for 207 companies whose activity included one or more stages in the production and marketing of wine. Using MANOVA and the production function approach, the authors found evidence that intangible proxies had a negative impact on the firms' economic performance measurements and a positive impact on commercial performance for intermediate values of intangible ratios. They also found that production functions were very different with regard to legal status and business activity, but that the negative impact of intangible proxies remained. © 2010 Wiley Periodicals, Inc. [source] The relationship of oocyte diameter and incubation temperature to incubation time in temperate freshwater fish speciesJOURNAL OF FISH BIOLOGY, Issue 3 2009F. Teletchea Based on the analysis of six egg variables and incubation temperature of 65 temperate freshwater fish species, the possible relationships between oocyte diameter, incubation time and incubation temperature were reassessed and compared to the results obtained from marine fishes. Most freshwater species have eggs (mean ±s.d. 2·19 ± 1·52 mm) larger than marine species, that are chiefly demersal and develop stuck to various substrata, such as plants or rocks. A strong negative relationship was found between incubation time (t, days) and incubation temperature (T, ° C): t = 186·23e,0·197T (r2= 0·87). A strong dependence of incubation time on oocyte diameter (Ø, mm) and incubation temperature was also found and was defined as: log10t= 3·002 + 0·599 log10Ø, 1·91 log10 (T + 2), which explained 92% of the variance of the data set. Five major groups of species were defined based on the principal component analysis (PCA) of four quantitative variables. There were two distinct groups of salmonids, displaying demersal and non-adhesive eggs with a long incubation time at low temperature, the eggs of which required a high number of degree-days. There was a large group of species possessing small, mostly demersal and adhesive eggs developing at high temperature during a short period of time, and requiring a low number of degree-days. Between these two extremes, there was a fourth group displaying intermediate values and a fifth group including three species with large, adhesive and demersal eggs incubating at high temperatures during a short period of time. The burbot Lota lota displayed an unusual combination of variables compared to the remaining species in the data set. [source] Correlating dough elastic recovery during sheeting with flour analyses and rheological propertiesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2008DanQiu Ren Abstract The dough rheological behaviors of three flours having different chemical and physical properties were measured, as were changes in thickness and snapback (thickness of the machined dough sheet relative to the roll gap), immediately following sheeting. Dough snapback was determined to be a function of processing parameters, reduction ratio, and dough rest time, as well as different flour properties. The predication equation for dough snapback is based on multiple flour properties and sheeting conditions. Higher protein flours normally have stronger dough properties and larger snapback, compared with low protein flours, but also depend on the protein quality. The snapback will increase either with increased protein content, reduction ratio, or reduced rest time. Dough snapback using flour made by blending two flours 50/50 had intermediate values between the two original flours. Among the variables, Mixograph work, reduction ratio, and dough rest time were the main factors affecting the elastic characteristics of the doughs. Minimum snapback occurred with the weakest flour experiencing the longest rest time and the smallest reduction ratio. A linear 7-factor equation was found to predict the snapback of several flours, by combining reduction ratio, dough rest time, Mixograph work, peak height, and mixing time, Alveograph P/L, and protein content. Only three factor combinations of Mixograph work, reduction ratio, and rest time were needed to develop a second order equation for predicting snapback. Copyright © 2008 Society of Chemical Industry [source] Sample size and the detection of a hump-shaped relationship between biomass and species richness in Mediterranean wetlandsJOURNAL OF VEGETATION SCIENCE, Issue 2 2006J.L. Espinar Abstract Questions: What is the observed relationship between biomass and species richness across both spatial and temporal scales in communities of submerged annual macrophytes? Does the number of plots sampled affect detection of hump-shaped pattern? Location: Doñana National Park, southwestern Spain. Methods: A total of 102 plots were sampled during four hydrological cycles. In each hydrological cycle, the plots were distributed randomly along an environmental flooding gradient in three contrasted microhabitats located in the transition zone just below the upper marsh. In each plot (0.5 m × 0.5 m), plant density and above- and below-ground biomass of submerged vegetation were measured. The hump-shaped model was tested by using a generalized linear model (GLM). A bootstrap procedure was used to test the effect of the number of plots on the ability to detect hump-shaped patterns. Result: The area exhibited low species density with a range of 1,9 species and low values of biomass with a range of 0.2 -87.6 g-DW/0.25 m2. When data from all years and all microhabitats were combined, the relationships between biomass and species richness showed a hump-shaped pattern. The number of plots was large enough to allow detection of the hump-shaped pattern across microhabitats but it was too small to confirm the hump-shaped pattern within each individual microhabitat. Conclusion: This study provides evidence of hump-shaped patterns across microhabitats when GLM analysis is used. In communities of submerged annual macrophytes in Mediterranean wetlands, the highest species density occurs in intermediate values of biomass. The bootstrap procedure indicates that the number of plots affects the detection of hump-shaped patterns. [source] mtDNA perspective of chromosomal diversification and hybridization in Peters' tent-making bat (Uroderma bilobatum: Phyllostomidae)MOLECULAR ECOLOGY, Issue 11 2003Federico G. Hoffmann Abstract We compared sequence variation in the complete mitochondrial cytochrome -b gene with chromosomal and geographical variation for specimens of Peters' tent-making bat (Uroderma bilobatum). Three different chromosomal races have been described in this species: a 2n = 42 race from South America east of the Andes, a 2n = 44 from NW Central America and 2n = 38 from the rest of Central America and NW South America. The deepest nodes in the tree were found within the South American race (42 race), which is consistent with a longer history of this race. Average distance among races ranged from 2.5 to 2.9%, with the highest amount of intraracial variation found within the 2n = 42 race (1.7%), intermediate values within the 2n = 38 race (0.9%) and lowest within the 2n = 44 race (0.5%). Variation among chromosomal races accounted for over 55% of molecular variance, whereas variation among populations within races accounted for 6%. The 2n = 38 and 2n = 44 races hybridize in the coastal lowlands of Honduras, near the Gulf of Fonseca. Introgression between these two races is low (two introgressed individuals in 45 examined). Clinal variation across the hybrid zone for the cytochrome -b of U. bilobatum, is similar to clinal variation reported for chromosomes and isozymes of this species. Mismatch distribution analyses suggests that geographical isolation and karyological changes have interplayed in a synergistic fashion. Fixation of the alternative chromosomal rearrangements in geographical isolation and secondary contact is the most likely mechanism accounting for the hybrid zone between the 2n = 38 and 2n = 44 races. If a molecular clock is assumed, with rates ranging from 2.3 to 5.0% per million years, then isolation between these races occurred within the last million years, implying a relatively recent origin of the extant diversity in Uroderma bilobatum. None the less, the three chromosomal races probably represent three different biological species. [source] Magnetic field-dependence study of the magnetocaloric properties of a superparamagnetic nanoparticle system: a Monte Carlo simulationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008D. Serantes Abstract The influence of the applied magnetic field on the magnetocaloric properties of a fine magnetic particle system has been studied using a Monte Carlo technique. By simulating zero field cooling (ZFC) curves under different strengths of the applied magnetic field, we have analyzed the variation of the entropy for temperatures above the maximum of the ZFC curves, where the process is reversible. The entropy curves have been observed to behave in a different fashion at low values of the magnetic field, where the peak only slightly shifts to higher temperatures with increasing fields. For larger fields, the peak rapidly shifts to higher temperatures, while the overall shape of the curve broadens over a wide temperature range. It is also observed that the blocking temperature as a function of the magnetic field shows the feature of a change from a bell-like shape to a monotonically decreasing function, resembling what is found experimentally for intermediate values of the sample concentration. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synergism between plant viruses: a mathematical analysis of the epidemiological implicationsPLANT PATHOLOGY, Issue 6 2001X.-S. Zhang Many virus diseases of plants are caused by a synergistic interaction between viruses within the host plant. Such synergism can induce symptoms more severe than would be caused by additive effects. In a synergistic interaction, the virus titre of both, one, or neither virus may be enhanced and, as a consequence, the rate of disease spread may be affected. An epidemiological model was developed in which transmission and loss rates were attributed to the different virus infection possibilities. Sharing the same host population implies competition, and this imposes an increased constraint on the survival of both viruses. It was shown that, in order to ensure virus survival in a mixed infection, the basic reproductive number should exceed a critical value which is larger than unity (R0 > Rc > 1). Here R0 is used in the same sense as in the absence of superinfection. Increased virulence (equivalent to disease severity) in dually infected plants decreases the opportunities for both viruses to coexist, while increased virus transmission from dually infected plants increases such opportunities. The net effect of increased virulence and increased virus transmission on virus persistence was neutral if synergism caused the same proportional effect on both. Total host abundance was, however, reduced. The opportunity for virus persistence was increased if the enhancement of transmission exceeded that of virulence. Indeed, by this mechanism a virus which was nonviable alone could invade and persist in a chronic epidemic of another virus. Where the effect on virulence is greater than that on transmission, the viruses are likely to exclude each other, especially when the transmission rates of both viruses have intermediate values. In such cases, the final outcome is determined by both the parameter values and the initial state. [source] Recruitment of Ca2+ release channels by calcium-induced Ca2+ release does not appear to occur in isolated Ca2+ release sites in frog skeletal muscleTHE JOURNAL OF PHYSIOLOGY, Issue 3 2002Karine Fénelon Ca2+ release from the sarcoplasmic reticulum (SR) in skeletal muscle in response to small depolarisations (e.g. to -60 mV) should be the sum of release from many isolated Ca2+ release sites. Each site has one SR Ca2+ release channel activated by its associated T-tubular voltage sensor. The aim of this study was to evaluate whether it also includes neighbouring Ca2+ release channels activated by Ca-induced Ca2+ release (CICR). Ca2+ release in frog cut muscle fibres was estimated with the EGTA/phenol red method. The fraction of SR Ca content ([CaSR]) released by a 400 ms pulse to -60 mV (denoted fCa) provided a measure of the average Ca2+ permeability of the SR associated with the pulse. In control experiments, fCa was approximately constant when [CaSR] was 1500-3000 ,m (plateau region) and then increased as [CaSR] decreased, reaching a peak when [CaSR] was 300-500 ,m that was 4.8 times larger on average than the plateau value. With 8 mm of the fast Ca2+ buffer BAPTA in the internal solution, fCa was 5.0-5.3 times larger on average than the plateau value obtained before adding BAPTA when [CaSR] was 300-500 ,m. In support of earlier results, 8 mm BAPTA did not affect Ca2+ release in the plateau region. At intermediate values of [CaSR], BAPTA resulted in a small, if any, increase in fCa, presumably by decreasing Ca inactivation of Ca2+ release. Since BAPTA never decreased fCa, the results indicate that neighbouring channels are not activated by CICR with small depolarisations when [CaSR] is 300-3000 ,m. [source] Male-mediated introgression of Bos indicus genes into Argentine and Bolivian Creole cattle breedsANIMAL GENETICS, Issue 5 2000G Giovambattista The geographic distribution and frequency of Bos taurus and Bos indicus Y chromosome haplotypes amongst Argentine and Bolivian Creole cattle breeds were studied, using cytogenetic and molecular genetic techniques. A complete correspondence between Y chromosome morphology and the haplotype of the Y-linked microsatellite marker INRA 124 was found in all males examined. The taurine and indicine haplotypes were detected in 85·7 and 14·3% of the males studied, respectively, although these frequencies varied amongst the different breeds examined. The geographic distribution of this polymorphism suggests a pattern of zebu introgression in South America. The highest frequencies of the Zebu Y-chromosome are found in Brazilian populations (43,90%), in the eastern part of the continent, while it is absent in the southermost breeds from Uruguay and Argentina. Bolivan breeds, at the centre of the continent, exhibit intermediate values (17,41%). This east/west and north/south gradient of male Zebu introgression could be explained by historical events and environmental factors. [source] Effect of different levels of Quebracho tannin on nitrogen utilization and growth performance of Najdi sheep fed alfalfa (Medicago sativa) hay as a sole dietANIMAL SCIENCE JOURNAL, Issue 5 2009Soliman N. AL-DOBAIB ABSTRACT A commercial tannin source (Quebracho tannin, QT), containing 75% condensed tannins (CT) in dry matter (DM) was used to evaluate the effects of addition of different levels of QT to alfalfa hay on the in vitro degradation kinetics of organic matter (OM) and nitrogen (N) in experiment 1 (Exp. 1), N utilization and microbial N synthesis (MNS) in experiment 2 (Exp. 2) and growth performance of growing Najdi lambs in experiment 3 (Exp. 3). Alfalfa hay was treated with QT at the levels of 0, 1, 2 and 3% of DM to form four treatments of QT0, QT1, QT2 and QT3 to have actual levels of CT being 0, 0.75, 1.5 and 2.25% of DM, respectively. Degradation rate and the effective degradability of N were significantly decreased (P < 0.05) for QT2 and QT3 as compared with the QT0. In Exp. 2, digestibility coefficients for OM, neutral detergent fiber and acid detergent fiber were significantly decreased (P < 0.05) at QT3, whereas QT1 and QT2 showed no difference toQT0. In the metabolism trial (Exp. 2), digested N (DN) and urinary N (UN) excretion for QT2 and QT3 were significantly decreased (P < 0.05) compared to QT0 and QT1. The DN and UN as percentage of N intake were 79.2, 76.9, 75.5 and 69.8%; and 24.4, 22.6, 19.9 and 19.6% for QT0, QT1, QT2 and QT3, respectively. QT2 had the highest MNS and the lowest value was in QT3, the MNS of the treatments were 18.1, 18.7, 19.2 and 15.8 g/day for QT0, QT1, QT2 and QT3, respectively. In the growth trial of 56 days duration (Exp. 3, n = 24 lambs), the addition of QT at the level of QT2 enhanced (P < 0.05) the average daily gain and feed conversion rate compared with the QT0, while, QT1 and QT3 had intermediate values. It is concluded that alfalfa hay treated with QT at the level of 2% of DM could be used to protect alfalfa N from ruminal degradation that would lead to improve growth performance of lambs. [source] Comparison of carcass composition among Japanese Black, Holstein and their crossbred steers fattening on farmANIMAL SCIENCE JOURNAL, Issue 5 2004Fumio MUKAI ABSTRACT Carcass composition among Japanese Black, Holstein and their crossbreed (F1), by Holstein mated with Japanese Black sires, was compared by using carcass components of fattening steers collected at eight carcass processing factories. The least squares means of 14 retail cuts, total weights of retail cuts, trimmed fat and bones, and six carcass traits measured at 6th,7th rib section were used for the comparison and examined the expression of heterosis. The comparison was performed at the same level of left-side carcass weight and under 10 mm fat cover on each retail cut. Japanese Black had the heaviest total weight of retail cuts, followed by F1 and then Holstein. By contrast, non-edible parts, trimmed fat and bones, were heavier in the order of Holstein, F1 and Japanese Black. Of the retail cuts, so called higher-priced cuts, such as Shoulder-Chuck-Roll, Tender-Loin, Rib-Chuck-Roll, Strip-Loin and Sirloin-Butt surrounding the spinal column, were heavier in Japanese Black than Holstein. Although F1 showed intermediate values for almost all traits, Tender-Loin, Rib-Chuck-Roll and Strip-Loin of F1 were similar to those of Japanese Black rather than the mid-parent averages. It reflects that at least the average parent heterosis of 2.3,4.3% might be expressed in these higher-priced cuts. The classification of breeds was carried out by the canonical discriminant analysis using 20 carcass measurements. By the canonical variates, breeds can be effectively discriminated with misdiscrimination rate of 11.6%. When the comparison is made at the carcass weight constant, Japanese Black has characteristics for producing superior carcass quality as well as meat quality. [source] Microsatellite evolution in modern humans: a comparison of two data sets from the same populationsANNALS OF HUMAN GENETICS, Issue 2 2000L. JIN We genotyped 64 dinucleotide microsatellite repeats in individuals from populations that represent all inhabited continents. Microsatellite summary statistics are reported for these data, as well as for a data set that includes 28 out of 30 loci studied by Bowcock et al. (1994) in the same individuals. For both data sets, diversity statistics such as heterozygosity, number of alleles per locus, and number of private alleles per locus produced the highest values in Africans, intermediate values in Europeans and Asians, and low values in Americans. Evolutionary trees of populations based on genetic distances separated groups from different continents. Corresponding trees were topologically similar for the two data sets, with the exception that the (,,)2 genetic distance reliably distinguished groups from different continents for the larger data set, but not for the smaller one. Consistent with our results from diversity statistics and from evolutionary trees, population growth statistics Sk and ,, which seem particularly useful for indicating recent and ancient population size changes, confirm a model of human evolution in which human populations expand in size and through space following the departure of a small group from Africa. [source] Transfer prices and the structure of intra-firm tradeCANADIAN JOURNAL OF ECONOMICS, Issue 1 2000Vibhas Madan In this paper the structure of intra-firm trade within the context of transfer price manipulation by a multinational firm is endogenized. ,High' and ,low' values of host-country tax rates give rise to intra-firm trade in final goods and intermediate inputs, and ,intermediate' values of the tax rate are associated with intra-firm trade in either the intermediate inputs or the final goods only. Higher tariffs and stricter local content restrictions bias intra-firm trade towards intermediate-good trade and final-good trade, respectively. In the presence of endogenous transfer prices host-country sales may increase if the multinational faces stricter trade restrictions and higher host-country tax rates. JEL Classification: F23, F12 Prix de cession interne et structure du commerce itnra-firme. Ce mémoire endogénéise la structure du commerce intra-firme dans le contexte d'un modèle qui permet la manipulation du prix de cession interne par une firme plurinationale. Des taux de taxation hauts et bas par le pays hôte entraînent un commerce international intra-firme tant dans les biens finaux que dans les intrants intermédiaires; des taux moyens de taxation sont associés à un commere intra-firme soit dans les intrants intermédiaires, soit dans les biens finaux mais pas dans les deux. Des droits de douane élevés et des restrictions sur le contenu intérieur plus importantes créent des distorsions en faveur du commerce intra-firme dans les biens intermédiaires et dans les biens finaux respectivement. Quand il existe des prix de cession interne endogènes, les ventes de la firme nationale peuvent s'accroître si la firme plurinationale fait face à des restrictions au commerce plus importantes et à des taux de taxation plus élevés de la part du pays hôte. 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