627 research outputs found
APPROACH E: CHANGING MARKET SUPPLY BY RESTRICTING INPUTS
Agricultural and Food Policy,
Credit Risks and European Government Bond Markets: A Panel Data Econometric Analysis
A fixed effects panel data estimation of the determinants of European government default risk is undertaken. Credit risk of sovereign debt is assessed by comparing yields on benchmark government bonds with high-quality private risk represented by interest rate swap yields. Using a new data-set from the European Commission (DG2's AMECO database), we find government default risk to depend positively on changes in the debt to GDP ratio and the variability of inflation and negatively on lagged inflation and changes in taxable capacity. Finally, there is evidence for persistence of government bond yield spreads reflecting differences in cross-country government default risk.Bond Market; Bonds; Government Bonds; Interest Rates; Interest; Yield
Cooperative WebLab in chemical engineering between France and Brazil: Validation of the methodology
A WebLab is an experiment operated remotely via Internet. Besides the strictly technical aspects of such an experiment, which may contribute to the learning of Chemical Engineering fundamentals, there is also important feedback when teams of students of two different countries are working together: the WebLab becomes an intercultural experience, enhancing the communication skills of the students. A WebLab between Universidade Federal de São Carlos (DEQ/UFSCar) and the Ecole Nationale Supérieure d’Ingénieurs en Arts Chimiques et Technologiques (ENSIACET) is presented in this work. A mass transfer experiment in a bench scale reactor (stirred and aerated) had to be studied by mixed teams, thus emulating challenges that will be common in future working environments. In order to perform the experiment, students in Brazil and in France were put into groups. The students had to make decisions about the procedure for executing the experiments. All the students were able to control the equipment, no matter where they were physically. Students communicated using video conference software. The students' and teachers' opinions of this experience were very positive. This methodology is an important contribution to the education of engineers in a world integrated by modern communication technologies
Seeing the fields through the weeds: introducing the WeedEco R package for comparing past and present arable farming systems using functional weed ecology
The functional ecology of arable weeds provides a way of comparing present-day and past farming regimes. This paper presents the R package WeedEco, an open-source resource which allows users to compare their archaeobotanical dataset against three previously published arable weed models to understand fertility, disturbance or a combination of both. The package provides functions for data organisation, classification and visualisation, allowing users to enter raw archaeobotanical data, obtain trait values from the functional trait dataset, conduct discriminant analysis and plot the results against the relevant present-day model. Using data from the early medieval site of Stafford in the UK, the paper provides a detailed example of the use of the package, demonstrating its different functions, as well as how the results can be interpreted
NikR mediates nickel-responsive transcriptional induction of urease expression in Helicobacter pylori
The important human pathogen Helicobacter pylori requires the abundant
expression and activity of its urease enzyme for colonization of the
gastric mucosa. The transcription, expression, and activity of H. pylori
urease were previously demonstrated to be induced by nickel
supplementation of growth media. Here it is demonstrated that the HP1338
protein, an ortholog of the Escherichia coli nickel regulatory protein
NikR, mediates nickel-responsive induction of urease expression in H.
pylori. Mutation of the HP1338 gene (nikR) of H. pylori strain 26695
resulted in significant growth inhibition of the nikR mutant in the
presence of supplementation with NiCl(2) at > or =100 microM, whereas the
wild-type strain tolerated more than 10-fold-higher levels of NiCl(2).
Mutation of nikR did not affect urease subunit expression or urease enzyme
activity in unsupplemented growth media. However, the nickel-induced
increase in urease subunit expression and urease enzyme activity observed
in wild-type H. pylori was absent in the H. pylori nikR mutant. A similar
lack of nickel responsiveness was observed upon removal of a 19-bp
palindromic sequence in the ureA promoter, as demonstrated by using a
genomic ureA::lacZ reporter gene fusion. In conclusion, the H. pylori NikR
protein and a 19-bp operator sequence in the ureA promoter are both
essential for nickel-responsive induction of urease expression in H.
pylori
Recommended from our members
Competing risks and deposit insurance governance convergence
Why do policies often seem to converge across countries at the same time? This question has been studied extensively in the diffusion literature. However, past research has not examined complex choice environments, especially where there are many alternatives. This article fills this gap in the literature. I show how Fine and Gray's Competing Risks Event History Analysis can be used to tease apart the causes of policy convergence. I apply the method to an examination of the reasons why, from the mid-1990s to 2007, many countries created independent deposit insurers. I find an interaction between international recommendations and regional peers' choices, particularly in the European Union. However, convergence appears to slow under the particular conditions of a banking crisis, regardless of how well independence is promoted. Possibly due to electoral incentives, democracies seem to have been more likely to create independent insurers. Ultimately, I demonstrate how competing risks analysis can help enable future research on policy choices, complementing methods previously applied in political economy. © The Author(s) 2013
Ward Identities, B-> \rho Form Factors and |V_ub|
The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward
identities in a general vector meson dominance framework, predicting vector
meson couplings involved. The long distance contributions are discussed which
results to obtain form factors and |V_ub|. A detailed comparison is given with
other approaches.Comment: 30 pages+four postscript figures, an Appendix adde
Characterizing COVID-19 clinical phenotypes and associated comorbidities and complication profiles
Purpose Heterogeneity has been observed in outcomes of hospitalized patients with coronavirus disease 2019 (COVID-19). Identification of clinical phenotypes may facilitate tailored therapy and improve outcomes. The purpose of this study is to identify specific clinical phenotypes across COVID-19 patients and compare admission characteristics and outcomes. Methods This is a retrospective analysis of COVID-19 patients from March 7, 2020 to August 25, 2020 at 14 U.S. hospitals. Ensemble clustering was performed on 33 variables collected within 72 hours of admission. Principal component analysis was performed to visualize variable contributions to clustering. Multinomial regression models were fit to compare patient comorbidities across phenotypes. Multivariable models were fit to estimate associations between phenotype and in-hospital complications and clinical outcomes. Results The database included 1,022 hospitalized patients with COVID-19. Three clinical phenotypes were identified (I, II, III), with 236 [23.1%] patients in phenotype I, 613 [60%] patients in phenotype II, and 173 [16.9%] patients in phenotype III. Patients with respiratory comorbidities were most commonly phenotype III (p = 0.002), while patients with hematologic, renal, and cardiac (all p<0.001) comorbidities were most commonly phenotype I. Adjusted odds of respiratory, renal, hepatic, metabolic (all p<0.001), and hematological (p = 0.02) complications were highest for phenotype I. Phenotypes I and II were associated with 7.30- fold (HR:7.30, 95% CI:(3.11-17.17), p<0.001) and 2.57-fold (HR:2.57, 95% CI:(1.10-6.00), p = 0.03) increases in hazard of death relative to phenotype III. Conclusion We identified three clinical COVID-19 phenotypes, reflecting patient populations with different comorbidities, complications, and clinical outcomes. Future research is needed to determine the utility of these phenotypes in clinical practice and trial design
Stream food web response to a salmon carcass analogue addition in two central Idaho, U.S.A. streams
Pacific salmon and steelhead once contributed large amounts of marine-derived carbon, nitrogen and phosphorus to freshwater ecosystems in the Pacific Northwest of the United States of America (California, Oregon, Washington and Idaho). Declines in historically abundant anadromous salmonid populations represent a significant loss of returning nutrients across a large spatial scale. Recently, a manufactured salmon carcass analogue was developed and tested as a safe and effective method of delivering nutrients to freshwater and linked riparian ecosystems where marine-derived nutrients have been reduced or eliminated.We compared four streams: two reference and two treatment streams using salmon carcass analogue(s) (SCA) as a treatment. Response variables measured included: surface streamwater chemistry; nutrient limitation status; carbon and nitrogen stable isotopes; periphyton chlorophyll a and ash-free dry mass (AFDM); macroinvertebrate density and biomass; and leaf litter decomposition rates. Within each stream, upstream reference and downstream treatment reaches were sampled 1 year before, during, and 1 year after the addition of SCA.Periphyton chlorophyll a and AFDM and macroinvertebrate biomass were significantly higher in stream reaches treated with SCA. Enriched stable isotope (δ15N) signatures were observed in periphyton and macroinvertebrate samples collected from treatment reaches in both treatment streams, indicating trophic transfer from SCA to consumers. Densities of Ephemerellidae, Elmidae and Brachycentridae were significantly higher in treatment reaches. Macroinvertebrate community composition and structure, as measured by taxonomic richness and diversity, did not appear to respond significantly to SCA treatment. Leaf breakdown rates were variable among treatment streams: significantly higher in one stream treatment reach but not the other. Salmon carcass analogue treatments had no detectable effect on measured water chemistry variables.Our results suggest that SCA addition successfully increased periphyton and macroinvertebrate biomass with no detectable response in streamwater nutrient concentrations. Correspondingly, no change in nutrient limitation status was detected based on dissolved inorganic nitrogen to soluble reactive phosphorus ratios (DIN/SRP) and nutrient-diffusing substrata experiments. Salmon carcass analogues appear to increase freshwater productivity.Salmon carcass analogues represent a pathogen-free nutrient enhancement tool that mimics natural trophic transfer pathways, can be manufactured using recycled fish products, and is easily transported; however, salmon carcass analogues should not be viewed as a replacement for naturally spawning salmon and the important ecological processes they provide
The Determination of alpha_s from Tau Decays Revisited
We revisit the determination of alpha_s(m_tau) using a fit to inclusive tau
hadronic spectral moments in light of (1) the recent calculation of the
fourth-order perturbative coefficient K_4 in the expansion of the Adler
function, (2) new precision measurements from BABAR of e+e- annihilation cross
sections, which decrease the uncertainty in the separation of vector and
axial-vector spectral functions, and (3) improved results from BABAR and Belle
on tau branching fractions involving kaons. We estimate that the fourth-order
perturbative prediction reduces the theoretical uncertainty, introduced by the
truncation of the series, by 20% with respect to earlier determinations. We
discuss to some detail the perturbative prediction and show that the effect of
the incomplete knowledge of the series is reduced by using the so-called
contour-improved calculation, as opposed to fixed-order perturbation theory
which manifests convergence problems. The corresponding theoretical
uncertainties are studied at the tau and Z mass scales. Nonperturbative
contributions extracted from the most inclusive fit are small, in agreement
with earlier determinations. Systematic effects from quark-hadron duality
violation are estimated with simple models and found to be within the quoted
systematic errors. The fit gives alpha_s(m_tau) = 0.344 +- 0.005 +- 0.007,
where the first error is experimental and the second theoretical. After
evolution to M_Z we obtain alpha_s(M_Z) = 0.1212 +- 0.0005 +- 0.0008 +- 0.0005,
where the errors are respectively experimental, theoretical and due to the
evolution. The result is in agreement with the corresponding NNNLO value
derived from essentially the Z width in the global electroweak fit. The
alpha_s(M_Z) determination from tau decays is the most precise one to date.Comment: 22 pages, 7 figure
- …