Zeros, Quality and Space: Trade Theory and Trade Evidence

Bilateral, product-level data exhibit a number of strong patterns that can be used to evaluate international trade theories, notably the spatial incidence of “export zeros” (correlated with distance and importer size), and of export unit values (positively related to distance). We show that leading theoretical trade models fail to explain at least some of these facts, and propose a variant of the Melitz model that can account for all the facts. In our model, high quality firms are the most competitive, with heterogeneous quality increasing with firms’ heterogeneous cost.

Quota restrictions and intra-firm reallocations: evidence from Chinese exports to the US

We study how Chinese textile and clothing firms adjusted the product structure of their exports to the US, as triggered by the termination of Multifiber Arrangement (MFA) quotas. We find that the removal of MFA quotas induced firms to expand their product scope while reducing the concentration on their core product. These effects are strong for domestic and foreign privately-owned firms, but insignificant for state-owned firms

“Dynamic Range” of Inferred Phenotypic HIV Drug Resistance Values in Clinical Practice

Background: ‘Virtual ’ or inferred phenotypes (vPhenotypes) are commonly used to assess resistance to antiretroviral agents in patients failing therapy. In this study, we provide a clinical context for understanding vPhenotype values. Methods: All HIV-infected persons enrolled in the British Columbia Drug Treatment Program with a baseline plasma viral load (pVL) and follow-up genotypic resistance and pVL results were included up to October 29, 2008 (N = 5,277). Change from baseline pVL was determined as a function of Virco vPhenotype, and the ‘‘dynamic range’ ’ (defined here by the 10th and 90th percentiles for fold-change in IC50 amongst all patients) was estimated from the distribution of vPhenotye foldchanges across the cohort. Results: The distribution of vPhenotypes from a large cohort of HIV patients who have failed therapy are presented for all available antiretroviral agents. A maximum change in IC50 of at least 13-fold was observed for all drugs. The dideoxy drugs, tenofovir and most PIs exhibited small ‘‘dynamic ranges’ ’ with values of,4-fold change observed in.99 % of samples. In contrast, zidovudine, lamivudine, emtricitabine and the non-nucleoside reverse transcriptase inihibitors (excluding etravirine) had large dynamic ranges. Conclusion: We describe the populational distribution of vPhenotypes such that vPhenotype results can be interprete

Structural Descriptors of gp120 V3 Loop for the Prediction of HIV-1 Coreceptor Usage

HIV-1 cell entry commonly uses, in addition to CD4, one of the chemokine receptors CCR5 or CXCR4 as coreceptor. Knowledge of coreceptor usage is critical for monitoring disease progression as well as for supporting therapy with the novel drug class of coreceptor antagonists. Predictive methods for inferring coreceptor usage based on the third hypervariable (V3) loop region of the viral gene coding for the envelope protein gp120 can provide us with these monitoring facilities while avoiding expensive phenotypic tests. All simple heuristics (such as the 11/25 rule) as well as statistical learning methods proposed to date predict coreceptor usage based on sequence features of the V3 loop exclusively. Here, we show, based on a recently resolved structure of gp120 with an untruncated V3 loop, that using structural information on the V3 loop in combination with sequence features of V3 variants improves prediction of coreceptor usage. In particular, we propose a distance-based descriptor of the spatial arrangement of physicochemical properties that increases discriminative performance. For a fixed specificity of 0.95, a sensitivity of 0.77 was achieved, improving further to 0.80 when combined with a sequence-based representation using amino acid indicators. This compares favorably with the sensitivities of 0.62 for the traditional 11/25 rule and 0.73 for a prediction based on sequence information as input to a support vector machine and constitutes a statistically significant improvement. A detailed analysis and interpretation of structural features important for classification shows the relevance of several specific hydrogen-bond donor sites and aliphatic side chains to coreceptor specificity towards CCR5 or CXCR4. Furthermore, an analysis of side chain orientation of the specificity-determining residues suggests a major role of one side of the V3 loop in the selection of the coreceptor. The proposed method constitutes the first approach to an improved prediction of coreceptor usage based on an original integration of structural bioinformatics methods with statistical learning

中欧論

千葉大学社会文化科学研究科研究プロジェクト報告書第3集『多民族国家における多文化主義の成立と展開』所

Estimating the Respective Contributions of Human and Viral Genetic Variation to HIV Control

We evaluated the fraction of variation in HIV-1 set point viral load attributable to viral or human genetic factors by using joint host/pathogen genetic data from 541 HIV infected individuals. We show that viral genetic diversity explains 29% of the variation in viral load while host factors explain 8.4%. Using a joint model including both host and viral effects, we estimate a total of 30% heritability, indicating that most of the host effects are reflected in viral sequence variation

Longitudinal community plasma HIV-1 RNA concentrations and incidence of HIV-1 among injecting drug users: prospective cohort study

Objective To examine the relation between plasma HIV-1 RNA concentrations in the community and HIV incidence among injecting drug users

The British economy [March 1989]

Evidence is mixed on whether growth in the economy is beginning to turn down. Nevertheless, the growth of GDP is forecast to fall from last year's high of 4.5% to 2.5% this year. Inflationary expectations are the most immediate cause for concern. But following the Budget there is concern that a relatively restrictive fiscal stance may bear down too heavily on output and employment during the next year

Outlook and appraisal [March 1989]

The Scottish economy is standing up surprisingly well to last year's interest rate rises. Retailing and wholesaling are showing signs of reduced optimism but sales remain strong if below expectations. Manufacturing and Construction remain buoyant. Investment is particularly strong. However, with demand in both the World and British economies falling during 1989, Scotland should be similarly affected. But there are indications that Scottish economic performance might hold up better to such a downturn than on previous occasions. Nevertheless, the outlook does very much depend on whether the current inflationary pressure in Britain can be reduced without the economy being tipped into recession. The probability of a stagflationary outcome appears somewhat greater than when we last reported

The world economy [March 1989]

Growth in the world economy remained strong at the end of last year producing an outturn of around 4% for 1988 as a whole. By the turn of the year there were indications that the down-turn expected in 1989 was already starting to occur in some countries. Yet indications that growth in the world economy may be turning down have not been sufficient to dampen inflationary pressure, nor expectations of a deterioration in inflation rates during 1989. Monetary and fiscal policy have been tightened in several key countries in response to inflationary expectations. This general tightening of policy is expected to contribute to a lowering of world economic growth during 1989 to around 3% and to a moderation of inflation in 1990, but will do little to accelerate the removal of the world's financial imbalances