730 research outputs found

    The evolution of interdisciplinarity in physics research

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    Science, being a social enterprise, is subject to fragmentation into groups that focus on specialized areas or topics. Often new advances occur through cross-fertilization of ideas between sub-fields that otherwise have little overlap as they study dissimilar phenomena using different techniques. Thus to explore the nature and dynamics of scientific progress one needs to consider the large-scale organization and interactions between different subject areas. Here, we study the relationships between the sub-fields of Physics using the Physics and Astronomy Classification Scheme (PACS) codes employed for self-categorization of articles published over the past 25 years (1985-2009). We observe a clear trend towards increasing interactions between the different sub-fields. The network of sub-fields also exhibits core-periphery organization, the nucleus being dominated by Condensed Matter and General Physics. However, over time Interdisciplinary Physics is steadily increasing its share in the network core, reflecting a shift in the overall trend of Physics research.Comment: Published version, 10 pages, 8 figures + Supplementary Informatio

    Processing and Transmission of Information

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    Contains reports on seven research projects.Lincoln Laboratory, Purchase Order DDL B-00337U.S. ArmyU.S. NavyU.S. Air Force under Air Force Contract AF19(604)-7400National Institutes of Health (Grant MH-04737-02

    Good Quantum Convolutional Error Correction Codes And Their Decoding Algorithm Exist

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    Quantum convolutional code was introduced recently as an alternative way to protect vital quantum information. To complete the analysis of quantum convolutional code, I report a way to decode certain quantum convolutional codes based on the classical Viterbi decoding algorithm. This decoding algorithm is optimal for a memoryless channel. I also report three simple criteria to test if decoding errors in a quantum convolutional code will terminate after a finite number of decoding steps whenever the Hilbert space dimension of each quantum register is a prime power. Finally, I show that certain quantum convolutional codes are in fact stabilizer codes. And hence, these quantum stabilizer convolutional codes have fault-tolerant implementations.Comment: Minor changes, to appear in PR

    Young star clusters in M31

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    In our study of M31's globular cluster system with MMT/Hectospec, we have obtained high-quality spectra of 85 clusters with ages less than 1 Gyr. With the exception of Hubble V, the young cluster in NGC 205, we find that these young clusters have kinematics and spatial distribution consistent with membership in M31's young disk. Preliminary estimates of the cluster masses and structural parameters, using spectroscopically derived ages and HST imaging, confirms earlier suggestions that M31 has clusters similar to the LMC's young populous clusters.Comment: 4 pages, 1 figure, contributed talk at "Galaxies in the Local Volume" conference in Sydney, July 200

    Impact mass flow sensor for monitoring peanut harvest yields

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    Yield monitoring systems for harvesting machines and methods that can provide yield monitoring of crops are described. Machines include those that pneumatically convey crop through the machine such as peanut harvesting machines. The yield monitoring system includes a force sensor that can be located in conjunction with a duct of the harvesting machine such that impact of the crop materials on an impact plate within the duct will be registered by the force sensor. This registration can be used to determine a mass flow rate for the crop, which can be correlated to yield of the crop. The systems can include additional components such as optical monitors, moisture sensors, and pressure sensors

    Processing and Transmission of Information

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    Contains research objectives and reports on four research projects.Lincoln Laboratory, Purchase Order DDL B-00306U. S. ArmyU. S. NavyU. S. Air Force under Air Force Contract AF19(604)-7400National Science Foundation (Grant B-16526)National Institutes of Health (Grant MP-4737

    Conflito trabalho-família, auto eficácia parental e estilos parentais percebidos em pais e mães da cidade de Talca no Chile

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    The relationship between levels of work-family conflict, parental self-efficacy and perceived parenting styles in a group of 43 school children and both working parents is analyzed, controlling for socio-demographic variables. Also, gender differences are identified in the variables and the relationship between them in relation to the number of children. Three instruments were applied to the sample for measuring the referred variables. A significant and negative relationship is observed between levels of work-family conflict and parental self-efficacy (r = -0.484, P <0.001). The authoritarian parenting style has greater association with self-efficacy (r = 0.301, P = 0.005). A significant and negative relationship between self-efficacy and number of children (r = -0.257, P = 0.017) is reported. Finally, it is concluded that women have greater work-family conflict than men.Se analiza la relación existente entre los niveles de conflicto trabajo-familia, autoeficacia parental y estilos parentales percibidos en un grupo de 43 niños estudiantes y ambos padres trabajadores, controlando las variables sociodemográficas. Así mismo, se identifican las diferencias por género en las variables, y la relación que existe entre ellas con respecto al número de hijos. A la muestra le fueron aplicados tres instrumentos de medición de las variables referidas. Se observa una relación significativa y negativa entre los niveles de conflicto trabajo-familia y la autoeficacia parental (r= -0,484; p<0,001). El estilo parental autoritario presenta mayor asociación con autoeficacia (r=0,301; p=0,005). Se reporta una relación significativa y negativa entre autoeficacia y número de hijos (r=-0,257; p=0,017). Finalmente se reporta que las mujeres presentan mayor conflicto trabajo-familia que los hombres.Analisa-se a relação existente entre os níveis de conflito trabalho-família, auto eficácia parental e estilos parentais percebidos em um grupo de 43 crianças estudantes de pais trabalhadores, controlando as variáveis sociodemográficas. Assim mesmo, identificam-se as diferenças por gênero nas variáveis, e a relação que existe entre elas com respeito ao número de filhos. Foram aplicados à mostra três instrumentos de medição das variáveis referidas. Observa-se uma relação significativa e negativa entre os níveis de conflito trabalho-família e a auto eficácia parental (r= -0,484; p<0,001). O estilo parental autoritário apresenta maior associação com autoeficácia (r=0,301; p=0,005). Reporta-se uma relação significativa e negativa entre autoeficácia e número de filhos (r=-0,257; p=0,017). Finalmente reporta-se que as mulheres apresentam maior conflito trabalho-família que os homens

    Active Tension Network model suggests an exotic mechanical state realized in epithelial tissues.

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    Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal - "isogonal" - deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit y embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena
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