2,310 research outputs found

    A cross-sectional analysis of video games and attention deficit hyperactivity disorder symptoms in adolescents

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    BACKGROUND: Excessive use of the Internet has been associated with attention deficit hyperactivity disorder (ADHD), but the relationship between video games and ADHD symptoms in adolescents is unknown. METHOD: A survey of adolescents and parents (n = 72 adolescents, 72 parents) was performed assessing daily time spent on the Internet, television, console video games, and Internet video games, and their association with academic and social functioning. Subjects were high school students in the ninth and tenth grade. Students were administered a modified Young's Internet Addiction Scale (YIAS) and asked questions about exercise, grades, work, and school detentions. Parents were asked to complete the Conners' Parent Rating Scale (CPRS) and answer questions regarding medical/psychiatric conditions in their child. RESULTS: There was a significant association between time spent playing games for more than one hour a day and YIAS (p < 0.001), overall grade point average (p ≤ 0.019), and the "Inattention" and "ADHD" components of the CPRS (p ≤ 0.001 and p ≤ 0.020, respectively). No significant association was found between body mass index (BMI), exercise, number of detentions, or the "Oppositional" and "Hyperactivity" components of CPRS and video game use. CONCLUSION: Adolescents who play more than one hour of console or Internet video games may have more or more intense symptoms of ADHD or inattention than those who do not. Given the possible negative effects these conditions may have on scholastic performance, the added consequences of more time spent on video games may also place these individuals at increased risk for problems in school

    INTERNATIONAL AND INSTITUTIONAL R&D SPILLOVERS: ATTRIBUTION OF BENEFITS AMONG SOURCES FOR BRAZIL'S NEW CROP VARIETIES

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    In general, reported rates of return to agricultural R&D are high, but questions have been raised about upward biases in the evidence. Among the reasons for this bias, insufficient attention to attribution aspects-matching of research benefits and costs-is a pervasive problem, the magnitude of which is illustrated here with new evidence for Brazil. Over the period 1981 to 2003, varietal improvements in upland rice, edible beans, and soybeans yielded benefits attributable to research of $14.8 billion in present value (1999 prices) terms; 6.1 percent of the corresponding value of crop output. If all of those benefits were attributed to Embrapa, a public research corporation accounting for more than half Brazil's agricultural R&D spending, the benefit-cost ratio would be 78:1. If a geometric attribution rule based on genetic histories is used in conjunction with quantitative evidence on the extent of research collaborations to account for the innovative effort of others, the ratio drops substantially to 16:1 (or an internal rate of return of 38.7 percent). The sources of these gains vary markedly among crops and over time, making it hard to generalize about the international and institutional origins of varietal innovations in Brazilian agriculture during the past several decades.Brazil, agricultural R&D, attribution, soybeans, rice, beans, benefit-cost ratios, Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,

    Simulation of a new hybrid Si/SiC power device for harsh environment applications

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    A new power device structure is proposed, conceived to operate in a high temperature, harsh environment, for example within a motor drive application down hole, as an inverter in the engine bay of an electric car, or as a solar inverter in space. The lateral silicon power device resembles a laterally diffused MOSFET (LDMOS), such as those implemented within silicon on insulator (SOI) substrates. However, unlike SOI, the Si thin film has been transferred directly onto a semi-insulating 6H silicon carbide (6H-SiC) substrate via a wafer bonding process. Thermal simulations of the hybrid Si/SiC substrate have shown that the high thermal conductivity of the SiC will have a junction-to-case temperature approximately 4 times less that an equivalent SOI device, reducing the effects of self-heating. Electrical simulations of a 600 V power device, implemented entirely with the silicon thin film, suggest that it will retain the ability of SOI to minimise leakage at high temperature, but does so with 50% less conduction losses
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