2,543 research outputs found
PROFILES OF TARIFFS IN GLOBAL AGRICULTURAL MARKETS
High protection for agricultural commodities in the form of tariffs continues to be the major factor restricting world trade. The large differences in average tariffs across countries make it possible for farmers in one country to benefit from tariff protection while farmers in other countries lose income because of lower prices resulting from those tariffs. This report provides the first comprehensive analysis of agricultural tariffs and tariff-rate quotas (limits on imported goods) across a large number of countries and commodities and finds that high average tariffs create barriers to markets for U.S. and other farmers.market access, megatariffs, tariff profiles, over-quota tariffs, in-quota tariffs, tariff-rate quotas, World Trade Organization, International Relations/Trade,
Spatial and temporal variation in crop diversity in agroforestry homegardens of southern Ethiopia
A key assumption in many homegarden studies is that homegardens are ecologically and socio-economically sustainable due to their species diversity. The precise relation between diversity and sustainability is still heavily debated, however. A basic question is how diversity in homegardens can best be characterized in view of the various dimensions of species diversity and their variation in time and space. This paper assesses different types of species diversity in the homegardens of Sidama region of southern Ethiopia. In a survey of crop species in 144 homegardens a total of 78 cultivated crop species (excluding trees) belonging to 10 functional groups were recorded; there were on average 16 crop species and 8 functional groups per farm. Within homegardens, plots differ in species composition and crop diversity. Four types of homegarden systems are distinguished differing in both type and area-share of dominant species, relative orientation at subsistence or cash production and overall crop diversity. The gradual replacement of enset by maize and of coffee by more financially attractive cash crops khat and pineapple causes a decrease in overall crop diversity. Our data demonstrate that it is incorrect to consider homegardens as generic systems with a uniform distribution of species diversity: important within and between homegarden variation exists. Ecological and socio-economic sustainability is not just related to species diversity per se, but rather to more specific features such as presence of keystone species and diversity in functional species groups. Socio-economic sustainability in terms of adjustment to socio-economic change implies dynamics in species diversit
The Evolution of Quasar CIV and SiIV Broad Absorption Lines Over Multi-Year Time Scales
We investigate the variability of CIV 1549A broad absorption line (BAL)
troughs over rest-frame time scales of up to ~7 yr in 14 quasars at redshifts
z>2.1. For 9 sources at sufficiently high redshift, we also compare CIV and
SiIV 1400A absorption variation. We compare shorter- and longer-term
variability using spectra from up to four different epochs per source and find
complex patterns of variation in the sample overall. The scatter in the change
of absorption equivalent width (EW), Delta EW, increases with the time between
observations. BALs do not, in general, strengthen or weaken monotonically, and
variation observed over shorter (<months) time scales is not predictive of
multi-year variation. We find no evidence for asymmetry in the distribution of
Delta EW that would indicate that BALs form and decay on different time scales,
and we constrain the typical BAL lifetime to be >~30 yr. The BAL absorption for
one source, LBQS 0022+0150, has weakened and may now be classified as a
mini-BAL. Another source, 1235+1453, shows evidence of variable, blue continuum
emission that is relatively unabsorbed by the BAL outflow. CIV and SiIV BAL
shape changes are related in at least some sources. Given their high
velocities, BAL outflows apparently traverse large spatial regions and may
interact with parsec-scale structures such as an obscuring torus. Assuming BAL
outflows are launched from a rotating accretion disk, notable azimuthal
symmetry is required in the outflow to explain the relatively small changes
observed in velocity structure over times up to 7 yr
Comparing the efficiency of base and multiplicative selection indices for yield and quality traits in Cassava: Article Retracted by the Authors
The efficiency of two selection indices; base index and the multiplicative index was compared to determine the effectiveness of each in identifying superior genotypes in cassava (Manihot esculent Crantz) population. Genotypic data on various yield and quality traits among 570 cassava genotypes were used to construct these selection indices. The efficiency of these indices was compared by determining the performance means of each genotype for studied traits and computing selection differentials of each index. Best linear unbiased predictions (BLUPs) for dry matter content and harvest index were also used for comparison of the two selection indices. The base index produced high-performance means of all five studied traits and proved to be more efficient compared to the multiplicative index in the improvement of cassava genotypes. In addition, the base index produced high selection differentials for three out of five studied traits. It was concluded that the base index is useful in cassava germplasm selectio
Improving Usability of Social and Behavioral Sciences’ Evidence: A Call to Action for a National Infrastructure Project for Mining Our Knowledge
Over the last century, the social and behavioral sciences have accumulated a vast storehouse of knowledge with the potential to transform society and all its constituents. Unfortunately, this knowledge has accumulated in a form (e.g., journal papers) and scale that makes it extremely difficult to search, categorize, analyze, and integrate across studies. In this commentary based on a National Science Foundation-funded workshop, we describe the social and behavioral sciences’ knowledge-management problem. We discuss the knowledge-scale problem and how we lack a common language, a common format to represent knowledge, a means to analyze and summarize in an automated way, and approaches to visualize knowledge at a large scale. We then describe that we need a collaborative research program between information systems, information science, and computer science (IICS) researchers and social and behavioral science (SBS) researchers to develop information system artifacts to address the problem that many scientific disciplines share but that the social and behavioral sciences have uniquely not addressed
A Randomized Dietary Intervention to Increase Colonic and Peripheral Blood Short-Chain Fatty Acids Modulates the Blood B- and T-cell Compartments in Healthy Humans
BACKGROUND: Short-chain fatty acids (SCFA) have immune-modulating effects in animal models of disease. However, there is limited evidence that this may occur in humans. OBJECTIVES: This study aimed to determine the effects of increased exposure to SCFA via dietary manipulation on colonic fermentation and adaptive immune cells. METHODS: Twenty healthy, young adults (18-45 years of age) underwent a blinded, randomized, cross-over dietary intervention, consuming a high-SCFA producing diet and matched low-SCFA diet for 21 days with 21-day wash-out in between. SCFA were provided through resistant starch, inulin and apple cider vinegar. Blood and 3-day total fecal output were collected at baseline and at the end of each diet. Gas chromatography was used to measure fecal and plasma SCFA. Flow cytometry was used for peripheral blood immuno-phenotyping. RESULTS: High-SCFA diet was associated with significantly (paired samples Wilcoxon test) higher median [IQR] fecal SCFA concentrations (86.6 [59.0] vs 75.4 [56.2] µmol/g, P = 0.02) and significantly lower median fecal ammonia concentrations (26.2 [14.7] vs 33.4 [18.5] µmol/g, P = 0.04) than the low-SCFA diet. Plasma propionate (9.87 [12.3] vs 4.72 [7.6] µmol/L, P = 0.049) and butyrate (2.85 [1.35] vs 2.02 [1.29] µmol/L, P = 0.03) were significantly higher after high-SCFA diet than after low-SCFA diet. Blood total B cells (184 [112] vs 199 [143] cells/µL, P = 0.04), naive B cells (83 [66] vs 95 [89] cells/µL, P = 0.02), Th1 cells (22 [19] vs 29 [16] cells/µL, P = 0.03) and mucosal-associated invariant T (MAIT) cells (62 [83] vs 69 [114] cells/µL, P = 0.02) were significantly lower after high-SCFA diet than low-SCFA diet. CONCLUSION: Increasing colonic and peripheral blood SCFA has discrete effects on circulating immune cells in healthy humans following 3-week intervention. Further studies, e.g., in patients with inflammatory disease, are necessary to determine if these changes have immunomodulatory effects, whether these are therapeutically beneficial, and whether prolonged intake might be required. Clinical trial registry: Australian New Zealand Clinical trials registry: ACTRN12618001054202.
Development and Validation of a Predictive Model of Acute Glucose Response to Exercise in Individuals With Type 2 Diabetes
Background: Our purpose was to develop and test a predictive model of the acute glucose response to exercise in individuals with type 2 diabetes.
Design and methods: Data from three previous exercise studies (56 subjects, 488 exercise sessions) were combined and used as a development dataset. A mixed-effects Least Absolute Shrinkage Selection Operator (LASSO) was used to select predictors among 12 potential predictors. Tests of the relative importance of each predictor were conducted using the Lindemann Merenda and Gold (LMG) algorithm. Model structure was tested using likelihood ratio tests. Model accuracy in the development dataset was assessed by leave-one-out cross-validation.
Prospectively captured data (47 individuals, 436 sessions) was used as a test dataset. Model accuracy was calculated as the percentage of predictions within measurement error. Overall model utility was assessed as the number of subjects with ≤ 1 model error after the third exercise session. Model accuracy across individuals was assessed graphically. In a post-hoc analysis, a mixed-effects logistic regression tested the association of individuals\u27 attributes with model error.
Results: Minutes since eating, a non-linear transformation of minutes since eating, post-prandial state, hemoglobin A1c, sulfonylurea status, age, and exercise session number were identified as novel predictors. Minutes since eating, its transformations, and hemoglobin A1c combined to account for 19.6% of the variance in glucose response. Sulfonylurea status, age, and exercise session each accounted for \u3c1.0% of the variance. In the development dataset, a model with random slopes for pre-exercise glucose improved fit over a model with random intercepts only (likelihood ratio 34.5, p \u3c 0.001). Cross-validated model accuracy was 83.3%. In the test dataset, overall accuracy was 80.2%. The model was more accurate in pre-prandial than postprandial exercise (83.6% vs. 74.5% accuracy respectively). 31/47 subjects had ≤1 model error after the third exercise session. Model error varied across individuals and was weakly associated with within-subject variability in pre-exercise glucose (Odds ratio 1.49, 95% Confidence interval 1.23-1.75).
Conclusions: The preliminary development and test of a predictive model of acute glucose response to exercise is presented. Further work to improve this model is discussed
Population genetics of trypanosoma brucei rhodesiense: clonality and diversity within and between foci
African trypanosomes are unusual among pathogenic protozoa in that they can undergo their complete morphological life cycle in the tsetse fly vector with mating as a non-obligatory part of this development. Trypanosoma brucei rhodesiense, which infects humans and livestock in East and Southern Africa, has classically been described as a host-range variant of the non-human infective Trypanosoma brucei that occurs as stable clonal lineages. We have examined T. b. rhodesiense populations from East (Uganda) and Southern (Malawi) Africa using a panel of microsatellite markers, incorporating both spatial and temporal analyses. Our data demonstrate that Ugandan T. b. rhodesiense existed as clonal populations, with a small number of highly related genotypes and substantial linkage disequilibrium between pairs of loci. However, these populations were not stable as the dominant genotypes changed and the genetic diversity also reduced over time. Thus these populations do not conform to one of the criteria for strict clonality, namely stability of predominant genotypes over time, and our results show that, in a period in the mid 1990s, the previously predominant genotypes were not detected but were replaced by a novel clonal population with limited genetic relationship to the original population present between 1970 and 1990. In contrast, the Malawi T. b. rhodesiense population demonstrated significantly greater diversity and evidence for frequent genetic exchange. Therefore, the population genetics of T. b. rhodesiense is more complex than previously described. This has important implications for the spread of the single copy T. b. rhodesiense gene that allows human infectivity, and therefore the epidemiology of the human disease, as well as suggesting that these parasites represent an important organism to study the influence of optional recombination upon population genetic dynamics
Human and animal Trypanosomes in Côte d'Ivoire form a single breeding population.
BACKGROUND: Trypanosoma brucei is the causative agent of African Sleeping Sickness in humans and contributes to the related veterinary disease, Nagana. T. brucei is segregated into three subspecies based on host specificity, geography and pathology. T. b. brucei is limited to animals (excluding some primates) throughout sub-Saharan Africa and is non-infective to humans due to trypanolytic factors found in human serum. T. b. gambiense and T. b. rhodesiense are human infective sub-species. T. b. gambiense is the more prevalent human, causing over 97% of human cases. Study of T. b. gambiense is complicated in that there are two distinct groups delineated by genetics and phenotype. The relationships between the two groups and local T. b. brucei are unclear and may have a bearing on the evolution of the human infectivity traits. METHODOLOGY/PRINCIPAL FINDINGS: A collection of sympatric T. brucei isolates from Côte d'Ivoire, consisting of T. b. brucei and both groups of T. b. gambiense have previously been categorized by isoenzymes, RFLPs and Blood Incubation Infectivity Tests. These samples were further characterized using the group 1 specific marker, TgSGP, and seven microsatellites. The relationships between the T. b. brucei and T. b. gambiense isolates were determined using principal components analysis, neighbor-joining phylogenetics, STRUCTURE, FST, Hardy-Weinberg equilibrium and linkage disequilibrium. CONCLUSIONS/SIGNIFICANCE: Group 1 T. b. gambiense form a clonal genetic group, distinct from group 2 and T. b. brucei, whereas group 2 T. b. gambiense are genetically indistinguishable from local T. b. brucei. There is strong evidence for mating within and between group 2 T. b. gambiense and T. b. brucei. We found no evidence to support the hypothesis that group 2 T. b. gambiense are hybrids of group 1 and T. b. brucei, suggesting that human infectivity has evolved independently in groups 1 and 2 T. b. gambiense
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