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Scaling Symmetry and Integrable Spherical Hydrostatics

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Journal of Modern Physics 2013年第4期4卷 486-494页

作者： Sidney Bludman dallas c. Kennedy Departamento de Astronomía Universidad de Chile Santiago Chile Natick USA

Any symmetry reduces a second-order differential equation to a first integral: variational symmetries of the action (exemplified by central field dynamics) lead to conservation laws, but symmetries of only the equations of motion (exemplified by scale-invariant hydrostatics) yield first-order non-conservation laws between invariants. We obtain these non- conservation laws by extending Noether’s Theorem to non-variational symmetries and present an innovative variational formulation of spherical adiabatic hydrostatics. For the scale-invariant case, this novel synthesis of group theory, hydrostatics, and astrophysics allows us to recover all the known properties of polytropes and define a core radius, inside which polytropes of index n share a common core mass density structure, and outside of which their envelopes differ. The Emden solutions (regular solutions of the Lane-Emden equation) are obtained, along with useful approximations. An appendix discusses the n = 3 polytrope in order to emphasize how the same mechanical structure allows different thermal structures in relativistic degenerate white dwarfs and zero age main sequence stars.

关键词： Lagrangian Mechanics Symmetry Hydrodynamics Astrophysics Stellar Structure

Longwall automation: Delivering enabling technology to achieve safer and more productive underground mining

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International Journal of Mining Science and Technology 2015年第6期25卷 865-876页

作者： Ralston Jonathon c. Reid david c. Dunn Mark T. Hainsworth david W. coal Mining Research Program CSIRO Energy

The ongoing need to deliver improved safety, productivity and environmental benefit in coal mining presents an open challenge as well as a powerful incentive to develop new and improved solutions. This paper assesses the critical role that enabling technologies have played in the delivery of remote and automated capability for longwall mining. A brief historical account is given to highlight key technical contributions which have influenced the direction and development of present-day longwall technology. The current state of longwall automation is discussed with particular attention drawn to the technologies that enable automated capability. Outcomes are presented from an independently conducted case study that assessed the impact that cSIRO＇s LASc longwall automation research has made to the longwall mining industry in Australia. Importantly, this study reveals how uptake of this innova- tive technology has significantly benefitted coal mine productivity, improved working conditions for personnel and enhanced environmental outcomes. These benefits have been widely adopted with cSIRO automation technology being used in 60 per cent of all Australian underground operations. International deployment of the technology is also emerging. The paper concludes with future challenges and opportunities to highfight the ongoing scope for longwall automation research and development.

关键词： Safety Productivity Environment Mining automation Longwall mining Remote mining

Recent research on vasectomy techniques

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Asian Journal of Andrology 2003年第3期5卷 227-230页

作者： david c.Sokal clinical Research Division Family Health International Durham NC 27713 USA

Vasectomy is a commonly used, highly effective method for the control of fertility in the human male. It is almost always performed as an outpatient procedure, is safer than tubal occlusion and has few side effects. The number of people relying on vasectomy as a method of contraception varies widely from country to country. Though vasectomy is highly effective, failures may occur due to re-canalization of the vas, surgical error, anatomical variants or failure of contraception during the post-operative waiting period. One of the disadvantages of this technique is that sperm are present in the posterior end of the vas following surgery and hence patients have to use alternative methods of contraception for a waiting period of 12 weeks to 15 weeks before relying on a vasectomy for contraception. This review summarizes recent research on vasectomy conducted by Family Health International, USA.

关键词： male sterilization vasectomy treatment efficacy safety

cryogenic nanosecond and picosecond high average and peak power(HAPP) pump lasers for ultrafast applications

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High Power Laser Science and Engineering 2016年第2期4卷 37-67页

作者： david c.Brown Sten Tornegrd Joseph Kolis Snake creek Lasers LLC clemson University Department of Chemistry

Using cryogenic laser technology, it is now possible to design and demonstrate lasers that have concomitant high average and peak powers, with near-diffraction-limited beam quality. We refer to these new laser systems as HAPP lasers. In this paper, we review important laser crystal materials properties at cryogenic temperature, with an emphasis on Yb lasers, and discuss the important design considerations, including the laser-induced damage threshold, nonlinear effects and thermal effects. A comprehensive model is presented to describe diode pulsed pumping with arbitrary duration and repetition rate, and is used with the Frantz–Nodvik equation to describe, to first order, the performance of HAPP laser systems. A computer code with representative results is also described.

关键词： cryogenic lasers high-average-power lasers high-peak-power lasers ultrafast lasers Yb lasers

Subordinacy theory for extended cMV matrices

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Science china Mathematics 2022年第3期65卷 539-558页

作者： Shuzheng Guo david Damanik Darren c.Ong School of Mathematical Sciences Ocean University of ChinaQingdao 266100China Department of Mathematics Rice UniversityHoustonTX 77005USA Department of Mathematics Xiamen University MalaysiaSepangSelangor Darul Ehsan 43900Malaysia

We develop subordinacy theory for extended cantero-Moral-Velázquez(cMV) matrices,i.e.,we provide explicit supports for the singular and absolutely continuous parts of the canonical spectral measure associated with a given extended cMV matrix in terms of the presence or absence of subordinate solutions to the generalized eigenvalue *** corollaries and applications of this result are described as well.

关键词： spectral theory subordinacy theory cMV matrix unitary operator carathéodory function

More than mimicry？ Evaluating scope for flicker-fusion as a defensive strategy in coral snake mimics

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current Zoology 2014年第1期60卷 123-130页

作者： Georgia c. TITcOMB david W. KIKUcHI david W. PFENNIG Department of Biology University of North Carolina at Chapel Hill Chapel Hill NC 27599-3280

coral snakes and their mimics often have brightly colored banded patterns, generally associated with warning colora- tion or mimicry. However, such color patterns have also been hypothesized to aid snakes in escaping predators through a ＂flicker-fusion＂ effect. According to this hypothesis, banded color patterns confuse potential predators when a snake transitions from resting to moving because its bands blur together to form a different color. To produce this motion blur, a moving snake＇s bands must transition faster than the critical flicker-fusion rate at which a predator＇s photoreceptors can refresh. It is unknown if coral snakes or their mimics meet this requirement. We tested this hypothesis by measuring the movement speed and color pat- terns of two coral snake mimics, Lampropeltis triangulum campbelli and L. elapsoides, and comparing the frequency of color transitions to the photoreceptor activity of the avian eye. We found that snakes often produced a motion blur, but moving snakes created a blurring effect more often in darker conditions, such as sunrise, sunset, and nighttime when these snakes are often active. Thus, at least two species of coral snake mimics are capable of achieving flicker-fusion, indicating that their color patterns may confer an additional defense aside from mimicry

关键词： coral snake mimicry Flicker-fusion effect cFF Kingsnake Defensive strategy

Why endophenotype development requires families

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chinese Science Bulletin 2011年第32期56卷 3382-3384页

作者： GLAHN david c BLANGERO John Department of Psychiatry Yale University School of Medicine New Haven CT 06511 USA Olin Neuropsychiatry Research center Institute of Living Hartford Hospital CT 06106 USA Department of Genetics Texas Biomedical Research Institute San Antonio TX 78227 USA

Endophenotypes are heritable quantitative traits that are associated with disease liability, can be measured in both affected and unaffected individuals, and provide much greater power to localize and identify risk genes for mental illness than does affection status alone. Traditionally, endophenotypic markers for psychiatric illnesses include in vivo neuroanatomic and functional magnetic resonance imaging measurements and indices of neurocognitive abilities. However, neurocognitive and neuroimaging measures are by no means the only classes of endophenotypes that could be useful for identifying genes for mental illness. Given the advantages of endophenotype-based strategies for elucidating the genetic underpinnings of psychiatric disorders, it would seem prudent to develop a wide range of putative endophenotypes. In order for a measure to be considered a valid endophenotype, it must meet a number of criteria. Specifically, the trait must (1) have moderate to high heritability, (2) be associated with the illness, (3) be independent of clinical state, and (4) impairment must co-segregate with the illness within a family, with non-affected family members showing impairment relative to the general population. While each of these criteria is critical, the heritability and co-segregation requirements are really what differentiate an endophenotype from a simple biomarker. At this time, one requires an experimental design that includes families to demonstrate both heritability and co-segregation. The assertion that novel endophenotypes can not be fully established without family data does not preclude work in unrelated individuals, rather that unrelated samples will only be able to nominate potential candidate endophenotypes that subsequently need to be confirmed in family-based experiments.

关键词：家庭成员稳定精神疾病遗传基础数量性状成像测量生物标志物神经管

Physical activity lowers the risk for acute respiratory infections:Time for recognition

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Journal of Sport and Health Science 2022年第6期11卷 648-655,F0003页

作者： david c.Nieman camila A.Sakaguchi Human Performance Laboratory Appalachian State UniversityNorth Carolina Research CampusKannapolisNC 28081USA

Physical inactivity is a well-established risk factor for chronic diseases,such as cardiovascular disease,cancer,and diabetes *** is a growing awareness that physical inactivity should also be regarded as a risk factor for acute respiratory infections(ARIs).ARIs,such as the common cold,influenza,pneumonia,and coronavirus disease 2019(cOVID-19),are among the most pervasive diseases on earth and cause widespread morbidity and *** in support of the linkage between ARIs and physical inactivity has been strengthened during the cOVID-19 pandemic because of increased scientific ***-scale studies have consistently reported that the risk for severe cOVID-19 outcomes is elevated in cohorts with low physical activity and/or physical fitness,even after adjusting for other risk *** lowered risk for severe cOVID-19 and other ARIs in physically active groups is attributed to exercise-induced immunoprotective effects,including enhanced surveillance of key immune cells and reduced chronic *** consensus groups,including those who submitted the Physical Activity Guidelines for Americans,have not yet given this area of research the respect that is *** is time to add“reduced risk for ARIs”to the“Exercise is Medicine”list of physical activity-related health benefits.

关键词： Acute respiratory infections cOVID-19 Immune system Physical activity Pneumonia

Flow resistance of gravel bed channels

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International Journal of Sediment Research 2014年第1期29卷 126-132页

作者： Wen c.WANG david R.DAWDY Multech Engineering consultants

Existing resistance formulas produce a wide range of friction-factor estimates for gravel bed *** purpose of this paper is to develop a reliable resistance formula in terms of the Darcy-Weisbach friction factor/ Published data were screened and used to establish the *** existing formulas have considered that/is a function of relative roughness D84/R only,where R is the hydraulic radius and D84is the particle size referred to the intermediate diameter that equals or exceeds that of 84 percent of bed *** this paper,/is considered as a function of Froude number in addition to the relative roughness./for D84/R>1 displays a different trend than that for D84/Rc velocity distribution for D84/R>***/formula for D84/R<1 has been established.

关键词： Flow resistance Darcy-Weisbach friction factor Relative roughness Relative submergence Gravel bed channels Open channels