708 research outputs found

    Effect of variation on knowledge accumulation in the internationalization process

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    This article examines the effect of variation - in the geographical operations - of international business operations on experiential knowledge development in the internationalization of the firm. Based on learning theory, this article develops five hypotheses on the effects of variation on three interrelated components of international experiential knowledge: internationalization knowledge, business knowledge and institutional knowledge. The LISREL analysis indicates that variation has a positive effect on the accumulation of experiential knowledge in internationalizing firms. In particular, it demonstrates that internationalization knowledge is a key variable which mediates the effect of variation on the other two knowledge variables

    Long-Term Effects of Placental Growth on Overweight and Body Composition

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    Obesity is programmed in utero and small babies generally have small placentas. In some circumstances, an undernourished fetus can expand its placental surface to extract more nutrients. We hypothesize that this results in an imbalanced nutrient supply to the fetus leading to obesity. To determine whether placental size determines overweight and body composition, we studied 2003 subjects in adult life. Associations between placental surface area and indices of overweight were restricted to people who carried the Pro12Pro genotype of the PPARĪ³2 gene. For every 1 SD increase in placental surface area, the odds ratio for overweight was 1.37 (95% CI 1.10 to 1.71; P = 0.005). Expansion of the placental surface in compensation for fetal undernutrition increases the risk of overweight and a higher body fat percentage in people carrying the Pro12Pro genotype. We suggest that similar underlying multifactorial mechanisms affect the development of obesity in general

    The relationship between umbilical cord length and chronic rheumatic heart disease: a prospective cohort study.

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    BACKGROUND: One previous, preliminary study reported that the length of the umbilical cord at birth is related to the risk of developing chronic rheumatic heart disease in later life. We sought to replicate this finding. DESIGN: Prospective, population-based birth cohort. METHODS: We traced 11,580 individuals born between 1915 and 1929 in Uppsala, Sweden. We identified cases with a main or secondary diagnosis of chronic rheumatic heart disease in the Swedish national inpatient, outpatient or death registers. Archived obstetric records provided data on umbilical cord length, gestational age, birthweight and placental weight. RESULTS: There were 136 patients with chronic rheumatic heart disease (72 men and 64 women) with a mean age at first hospital admission of 68Ā years (range 36-92). There was evidence of a positive association between umbilical cord length and risk of subsequent chronic rheumatic heart disease. The overall hazard ratio in the Swedish study (1.13, 95% confidence interval 1.01 to 1.27) was similar to that of the previous study, with some suggestion of larger effect in men than in women. No other birth characteristics were predictive except for weak evidence of a protective effect of higher birthweight in men. CONCLUSIONS: People with longer umbilical cords at birth are more likely to develop chronic rheumatic heart disease in later life. As longer umbilical cords have more spiral arteries and a higher vascular resistance, we hypothesize that the increased pressure load on the heart leads to changes in endothelial biology and increased vulnerability to the autoimmune process initiated by infection with Ī²-haemolytic streptococci

    Scanned Potential Microscopy of Edge and Bulk Currents in the Quantum Hall Regime

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    Using an atomic force microscope as a local voltmeter, we measure the Hall voltage profile in a 2D electron gas in the quantum Hall (QH) regime. We observe a linear profile in the bulk of the sample in the transition regions between QH plateaus and a distinctly nonlinear profile on the plateaus. In addition, localized voltage drops are observed at the sample edges in the transition regions. We interpret these results in terms of theories of edge and bulk currents in the QH regime.Comment: 4 pages, 5 figure

    Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2

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    The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis
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