5,451 research outputs found

    Potential model calculations and predictions for heavy quarkonium

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    We investigate the spectroscopy and decays of the charmonium and upsilon systems in a potential model consisting of a relativistic kinetic energy term, a linear confining term including its scalar and vector relativistic corrections and the complete perturbative one-loop quantum chromodynamic short distance potential. The masses and wave functions of the various states are obtained using a variational technique, which allows us to compare the results for both perturbative and nonperturbative treatments of the potential. As well as comparing the mass spectra, radiative widths and leptonic widths with the available data, we include a discussion of the errors on the parameters contained in the potential, the effect of mixing on the leptonic widths, the Lorentz nature of the confining potential and the possible ccˉc\bar{c} interpretation of recently discovered charmonium-like states.Comment: Physical Review published versio

    A "Sidewinding" Locomotion Gait for Hyper-Redundant Robots

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    This paper considers the kinematics of a novel form of hyper-redundant mobile robot locomotion which is analogous to the 'sidewinding' locomotion of desert snakes. This form of locomotion can be generated by a repetitive travel wave of mechanism bending. Using a continuous backbone curve model, we develop algorithms which enable travel in a uniform direction as well as changes in direction

    Why Rent Control Is Still a Regulatory Taking

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    The Supreme Court has repeatedly declared that land-use regulations that fail to substantially advance legitimate state interests violate the Takings Clause of the Fifth Amendment. This standard seems readily applicable to rent control, a policy that has been shown to exacerbate the problems is intended to remedy, and to impose social heavy costs that would not otherwise exist. Nevertheless, the California Supreme Court has declared that it will not strike down rent control under the substantial advancement standard, nor will it apply a heightened level of scrutiny to such regulations. In response to these rulings, California rental property owners have taken their constitutional claims to federal court. In a series of decisions culminating in Cashman v. City of Cotati, the Ninth Circuit has found rent control laws to violate the Takings Clause under a substantial advancement standard. One of these cases, Lingle v. Chevron, USA, was accepted for review by the United States Supreme Court in October, 2004. The outcome of this case will have major ramifications for rent control and regulatory takings law in the 21st century

    Statistical Error and Legal Error—Type One and Type Two Errors and the Law

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    Knick and the Elephant in the Courtroom: Who Cares Least About Property Rights?

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    In Knick v. Township of Scott, the Supreme Court corrected one of the most egregious and inexplicable blunders of its 230-year history. For more than three decades, plaintiffs who alleged a violation of the Takings Clause by state or local governments were barred from suing for compensation in federal court. The source of this prohibition was Justice Blackmun’s 1985 opinion in Williamson County Regional Planning Commission v. Hamilton Bank of Johnson City—a decision that most scholars and practitioners believe rested on a fundamental misunderstanding of both constitutional text and legal procedure

    Aging Techniques & Population Dynamics of Blue Suckers (Cycleptus elongatus) in the Lower Wabash River

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    The Blue Sucker, Cycleptus elongatus, occurs in large rivers primarily in the Mississippi River basin. Their imperiled status has called attention to the need for its management and protection. Estimating age is crucial for directing management, but past studies have varied in their choice of hard structure, resulting in uncertainty regarding the basic life history of this species. Because the Wabash River Blue Sucker population may be one of few surveyable populations with high abundance and successful reproduction, their demographics can provide a benchmark against which threatened populations can be compared. We harvested Blue Suckers (n = 168) from the lower Wabash River and compared age estimations from multiple hard structures. Otoliths yielded more precise and credible age estimates than other structures. Otoliths assigned ages up to 42 years. Annual mortality was 4.5%, and growth was modeled as TL = 680.29038 ∙ (1 - e( -0.15898 ∙ Age + 5.14037)), where TL = total length (mm) and Age = otolith age (years). Fecundity averaged 110,933 eggs/female. The population length-weight regression was Log10(WT) = 3.323 ∙ Log10(TL) - 5.9592 where WT = weight (g) and TL = total length (mm). Average relative weights followed a declining trend from 2008 to 2019, and this trend was mirrored in the declining average conditions of four other benthic invertivorous fishes in the Wabash River. We suggest that Blue Suckers can serve as bioindicators for the Wabash River ecosystem and their declining relative weights should be regarded as early symptoms of community level change

    Molecular gas in extreme star-forming environments: the starbursts Arp220 and NGC6240 as case studies

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    We report single-dish multi-transition measurements of the 12^CO, HCN, and HCO^+ molecular line emission as well as HNC J=1-0 and HNCO in the two ultraluminous infra-red galaxies Arp220 and NGC6240. Using this new molecular line inventory, in conjunction with existing data in the literature, we compiled the most extensive molecular line data sets to date for such galaxies. The many rotational transitions, with their different excitation requirements, allow the study of the molecular gas over a wide range of different densities and temperatures with significant redundancy, and thus allow good constraints on the properties of the dense gas in these two systems. The mass (~(1-2) x 10^10 Msun) of dense gas (>10^5-6 cm^-3) found accounts for the bulk of their molecular gas mass, and is consistent with most of their IR luminosities powered by intense star bursts while self-regulated by O,B star cluster radiative pressure onto the star-forming dense molecular gas. The highly excited HCN transitions trace a gas phase ~(10-100)x denser than that of the sub-thermally excited HCO^+ lines (for both galaxies). These two phases are consistent with an underlying density-size power law found for Galactic GMCs (but with a steeper exponent), with HCN lines tracing denser and more compact regions than HCO^+. Whether this is true in IR-luminous, star forming galaxies in general remains to be seen, and underlines the need for observations of molecular transitions with high critical densities for a sample of bright (U)LIRGs in the local Universe -- a task for which the HI-FI instrument on board Herschel is ideally suited to do.Comment: 38 pages (preprint ApJ style), 3 figures, accepted for Ap

    Variation of Molecular Line Ratios and Cloud Properties in the Arp 299 Galaxy Merger

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    High resolution observations of 12CO (2.''3), 13CO (3.''9), and HCN (5.''4) J=1--0 in the galaxy merger Arp 299 (IC 694 and NGC 3690) show the line ratios vary dramatically across the system. The 12CO/13CO ratio is unusually large, 60 +- 15, at the IC 694 nucleus, where 12CO emission is very strong, and much smaller, 10 +- 3, in the southern extended disk of that galaxy. Elsewhere, the 12CO/13CO line ratio is 5-20, typical of spiral galaxies. The line ratio variation in the overlap between the two galaxies is smaller, ranging from 10 +- 3 in the east to 20 +- 4 in the west. The 12CO/HCN line ratio also varies across Arp 299, although to a lesser degree. HCN emission is bright towards each galaxy nucleus and in the extranuclear region of active star formation; it was not detected in the IC 694 disk, or the eastern part of the overlap region, leading to lower limits of 25 and 20 respectively. By contrast, at the nuclei of IC 694 and NGC 3690 the ratios are 9 +- 1 and 14 +- 3 respectively. In the western part of the overlap region it is 11 +- 3.Comment: 16 pages, 4 postscript figures, to appear in ApJ Letter

    Work values in cross-national perspective:Some observations from applied research

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