78 research outputs found

    Self-consistent field theory of polarized BEC: dispersion of collective excitation

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    We suggest the construction of a set of the quantum hydrodynamics equations for the Bose-Einstein condensate (BEC), where atoms have the electric dipole moment. The contribution of the dipole-dipole interactions (DDI) to the Euler equation is obtained. Quantum equations for the evolution of medium polarization are derived. Developing mathematical method allows to study effect of interactions on the evolution of polarization. The developing method can be applied to various physical systems in which dynamics is affected by the DDI. Derivation of Gross-Pitaevskii equation for polarized particles from the quantum hydrodynamics is described. We showed that the Gross-Pitaevskii equation appears at condition when all dipoles have the same direction which does not change in time. Comparison of the equation of the electric dipole evolution with the equation of the magnetization evolution is described. Dispersion of the collective excitations in the dipolar BEC, either affected or not affected by the uniform external electric field, is considered using our method. We show that the evolution of polarization in the BEC leads to the formation of a novel type of the collective excitations. Detailed description of the dispersion of collective excitations is presented. We also consider the process of wave generation in the polarized BEC by means of a monoenergetic beam of neutral polarized particles. We compute the possibilities of the generation of Bogoliubov and polarization modes by the dipole beam.Comment: 16 pages, 15 figures. arXiv admin note: substantial text overlap with arXiv:1106.082

    New insights into the genetic etiology of Alzheimer's disease and related dementias

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    Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

    Experimental progress in positronium laser physics

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    Global, regional, and national age-sex-specific mortality and life expectancy, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017

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    BACKGROUND: Assessments of age-specific mortality and life expectancy have been done by the UN Population Division, Department of Economics and Social Affairs (UNPOP), the United States Census Bureau, WHO, and as part of previous iterations of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD). Previous iterations of the GBD used population estimates from UNPOP, which were not derived in a way that was internally consistent with the estimates of the numbers of deaths in the GBD. The present iteration of the GBD, GBD 2017, improves on previous assessments and provides timely estimates of the mortality experience of populations globally. METHODS: The GBD uses all available data to produce estimates of mortality rates between 1950 and 2017 for 23 age groups, both sexes, and 918 locations, including 195 countries and territories and subnational locations for 16 countries. Data used include vital registration systems, sample registration systems, household surveys (complete birth histories, summary birth histories, sibling histories), censuses (summary birth histories, household deaths), and Demographic Surveillance Sites. In total, this analysis used 8259 data sources. Estimates of the probability of death between birth and the age of 5 years and between ages 15 and 60 years are generated and then input into a model life table system to produce complete life tables for all locations and years. Fatal discontinuities and mortality due to HIV/AIDS are analysed separately and then incorporated into the estimation. We analyse the relationship between age-specific mortality and development status using the Socio-demographic Index, a composite measure based on fertility under the age of 25 years, education, and income. There are four main methodological improvements in GBD 2017 compared with GBD 2016: 622 additional data sources have been incorporated; new estimates of population, generated by the GBD study, are used; statistical methods used in different components of the analysis have been further standardised and improved; and the analysis has been extended backwards in time by two decades to start in 1950. FINDINGS: Globally, 18·7% (95% uncertainty interval 18·4–19·0) of deaths were registered in 1950 and that proportion has been steadily increasing since, with 58·8% (58·2–59·3) of all deaths being registered in 2015. At the global level, between 1950 and 2017, life expectancy increased from 48·1 years (46·5–49·6) to 70·5 years (70·1–70·8) for men and from 52·9 years (51·7–54·0) to 75·6 years (75·3–75·9) for women. Despite this overall progress, there remains substantial variation in life expectancy at birth in 2017, which ranges from 49·1 years (46·5–51·7) for men in the Central African Republic to 87·6 years (86·9–88·1) among women in Singapore. The greatest progress across age groups was for children younger than 5 years; under-5 mortality dropped from 216·0 deaths (196·3–238·1) per 1000 livebirths in 1950 to 38·9 deaths (35·6–42·83) per 1000 livebirths in 2017, with huge reductions across countries. Nevertheless, there were still 5·4 million (5·2–5·6) deaths among children younger than 5 years in the world in 2017. Progress has been less pronounced and more variable for adults, especially for adult males, who had stagnant or increasing mortality rates in several countries. The gap between male and female life expectancy between 1950 and 2017, while relatively stable at the global level, shows distinctive patterns across super-regions and has consistently been the largest in central Europe, eastern Europe, and central Asia, and smallest in south Asia. Performance was also variable across countries and time in observed mortality rates compared with those expected on the basis of development. INTERPRETATION: This analysis of age-sex-specific mortality shows that there are remarkably complex patterns in population mortality across countries. The findings of this study highlight global successes, such as the large decline in under-5 mortality, which reflects significant local, national, and global commitment and investment over several decades. However, they also bring attention to mortality patterns that are a cause for concern, particularly among adult men and, to a lesser extent, women, whose mortality rates have stagnated in many countries over the time period of this study, and in some cases are increasing

    Robot technology in dentistry, part one of a systematic review: literature characteristics

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    Objectives: To provide dental practitioners and researchers with a comprehensive and transparent evidence-based overview of the characteristics of literature regarding initiatives of robot technology in dentistry. Data: All articles in which robot technology in dentistry is described, except for non-scientific articles and articles containing secondary data (reviews). Amongst others, the following data were extracted: type of study, level of technological readiness, authors’ professional background and the subject of interaction with the robot. Sources: Bibliographic databases PubMed, Embase, and Scopus were surveyed. A reference search was conducted. The search timeline was between January 1985 and October 2020. Study selection: A total of 911 articles were screened on title and abstract of which 161 deemed eligible for inclusion. Another 71 articles were excluded mainly because of unavailability of full texts or the sole use of secondary data (reviews). Four articles were included after hand searching the reference lists. In total, 94 articles were included for analysis. Conclusions: Since 2013 an average of six articles per year concern robot initiatives in dentistry, mostly originating from East Asia (57%). The vast majority of research was categorized as either basic theoretical or basic applied research (80%). Technology readiness levels did not reach higher than three (proof of concept) in 55% of all articles. In 84%, the first author of the included articles had a technical background and in 36%, none of the authors had a dental or medical background. The overall quality of literature, especially in terms of clinical validation, should be considered as low.Learning & Autonomous Contro

    Mineralogy and chemistry of cored sediments from active margin off southwestern Taiwan

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    The cored sediments sampled by R/V Marion Dufrense are mostly muds consisting mainly of quartz, feldspar, illite, chlorite + kaolinite and calcite. Authigenic carbonates mainly composed of aragonite, calcite, dolomite and associated with Fe-montmorillonite and pyrite occur in core samples collected from station MD-052911 (22 degrees 15.6' N, 119 degrees 51.0' E) at 2137-2140 cm and 2237-2240 cm depth which may be formed via sulfate reduction by CH4. In general Illite/Quartz intensity ratios of the sediments show little variation with core depth indicating the relatively constant abundance of illite in the source rock on Taiwan. The cored sediments have higher average Al2O3, Sigma FeO and MgO but lower SiO2, Na2O, and CaO contents when compared with upper continental crust (UCC). High field strength elements (Zr, Hf, Y, Nb and Ta) are also depleted in the cored sediments. CaO, Sr, Mn and Pb in the core samples collected from station MD-052912 (22 degrees 21.5' N, 119 degrees 48.5' E) tend to decrease with depth which may be essentially related to the decrease of biogenic CaCO3 with core depth. The La/Th, La/Sc, Th/Sc ratios of the cored sediments are similar to those of UCC, however the (La/Yb)(N) ratios of the cored sediments are higher. The cored sediments display similar REE patterns with LREE enrichment and negative Eu anomaly reflecting a felsic nature of the source rock which can also be identified in the La-Th-Sc plot. The chemistry of the sediments can be deduced using a mixing model involved four end members i.e., shale, greywacke, quartzite and limestone
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