520 research outputs found

    Efficacy of Hibiscus Cannabinus L. (kenaf) Crude Seed Powder and its Methanol Extract in Water Purification

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    The efficiencies of hibiscus cannabinus (kenaf) powder and methanol extract were studied in water purification. Two turbidity levels namely, high (160NTU) and low (49NTU) were considered. The water samples were taken from an open pond used for irrigation farming in Custom area of Maiduguri, Nigeria. In this study, the powdered cannabinus was discovered to be more effective in removing high turbidity water, with an efficiency of 96.0% against the extract with 85.6%. However, in low turbidity water, the methanol extract performed better, with a turbidity removal efficiency of 89.4% compared to 84.4%, if the cannabinus powder is used. Another parameter studied was the pH of the water which remains unaffected after the treatment at 7.0. The outcome of the performance of this natural coagulant and alum when compared indicated that alum also performed better on high turbidity water than low turbid water with a removal efficiency of 98.8% and 95.7% respectively. Alum slightly affected the pH of the water from original value of 7.0 to 5.5, which makes the water more acidic after treatment. It appears that natural coagulants of plant origin remain the best option engineers are left with, if the current emphasis on millennium development goal on clean water supply for all is to be achieved. Keywords: , Cannabinus, Coagulation, Water Purificatio

    Implicit complexity for coinductive data: a characterization of corecurrence

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    We propose a framework for reasoning about programs that manipulate coinductive data as well as inductive data. Our approach is based on using equational programs, which support a seamless combination of computation and reasoning, and using productivity (fairness) as the fundamental assertion, rather than bi-simulation. The latter is expressible in terms of the former. As an application to this framework, we give an implicit characterization of corecurrence: a function is definable using corecurrence iff its productivity is provable using coinduction for formulas in which data-predicates do not occur negatively. This is an analog, albeit in weaker form, of a characterization of recurrence (i.e. primitive recursion) in [Leivant, Unipolar induction, TCS 318, 2004].Comment: In Proceedings DICE 2011, arXiv:1201.034

    Itinerant Electron Ferromagnetism in the Quantum Hall Regime

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    We report on a study of the temperature and Zeeman-coupling-strength dependence of the one-particle Green's function of a two-dimensional (2D) electron gas at Landau level filling factor ν=1\nu =1 where the ground state is a strong ferromagnet. Our work places emphasis on the role played by the itinerancy of the electrons, which carry the spin magnetization and on analogies between this system and conventional itinerant electron ferromagnets. We discuss the application to this system of the self-consistent Hartree-Fock approximation, which is analogous to the band theory description of metallic ferromagnetism and fails badly at finite temperatures because it does not account for spin-wave excitations. We go beyond this level by evaluating the one-particle Green's function using a self-energy, which accounts for quasiparticle spin-wave interactions. We report results for the temperature dependence of the spin magnetization, the nuclear spin relaxation rate, and 2D-2D tunneling conductances. Our calculations predict a sharp peak in the tunneling conductance at large bias voltages with strength proportional to temperature. We compare with experiment, where available, and with predictions based on numerical exact diagonalization and other theoretical approaches.Comment: 29 pages, 20 figure

    Ernst Freund as Precursor of the Rational Study of Corporate Law

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    Gindis, David, Ernst Freund as Precursor of the Rational Study of Corporate Law (October 27, 2017). Journal of Institutional Economics, Forthcoming. Available at SSRN: https://ssrn.com/abstract=2905547, doi: https://dx.doi.org/10.2139/ssrn.2905547The rise of large business corporations in the late 19th century compelled many American observers to admit that the nature of the corporation had yet to be understood. Published in this context, Ernst Freund's little-known The Legal Nature of Corporations (1897) was an original attempt to come to terms with a new legal and economic reality. But it can also be described, to paraphrase Oliver Wendell Holmes, as the earliest example of the rational study of corporate law. The paper shows that Freund had the intuitions of an institutional economist, and engaged in what today would be called comparative institutional analysis. Remarkably, his argument that the corporate form secures property against insider defection and against outsiders anticipated recent work on entity shielding and capital lock-in, and can be read as an early contribution to what today would be called the theory of the firm.Peer reviewe

    Trial outcomes and information for clinical decision-making: a comparative study of opinions of health professionals

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    Background: Trials are robust sources of data for clinical practice, however, trial outcomes may not reflect what is important to communicate for decision making. The study compared clinicians’ views of outcomes to include in a core outcome set for colorectal cancer (CRC) surgery, with what clinicians considered important information for clinical practice (core information). Methods: Potential outcomes/information domains were identified through systematic literature reviews, reviews of hospital information leaflets and interviews with patients. These were organized into 6 categories, and used to design a questionnaire survey that asked surgeons and nurses from a sample of CRC centers to rate the importance of each domain as an outcome or as information on a 9-point Likert scale. Respondents were re-surveyed (round 2) following group feedback (Delphi methods). Comparisons were made by calculating the difference in mean scores between the outcomes and information domains, and paired t-tests were used to explore the difference between mean scores of the 6 outcome/information categories. Results: Data sources identified 1216 outcomes/information of CRC surgery that informed a 94 item questionnaire. First round questionnaires were returned from 63/81 (78%) of centers. Clinicians rated 76/94 (84%) domains of higher importance to measure in trials than to information to communicate to patients in Round 1. This was reduced to 24/47 (51%) in Round 2. The greatest difference was evident in domains about survival, which was rated much more highly as a trial outcome than important piece of information for decision-making (mean difference 2.3, 95% CI 1.9-2.8, p<0.0001). Specific complications and quality-of-life domains were rated similarly (mean difference 0.18, 95% CI -0.1-0.4, p=0.2 and 0.2, 95% CI -0.1-0.5, p=0.2 respectively). Conclusions: Whilst clinicians want to measure key outcomes in trials, they rate these as less important to communicate in decision-making with patients. This discrepancy needs to be explored and addressed to maximize the impact of trials on clinical practice

    Transverse energy production and charged-particle multiplicity at midrapidity in various systems from sNN=7.7\sqrt{s_{NN}}=7.7 to 200 GeV

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    Measurements of midrapidity charged particle multiplicity distributions, dNch/dηdN_{\rm ch}/d\eta, and midrapidity transverse-energy distributions, dET/dηdE_T/d\eta, are presented for a variety of collision systems and energies. Included are distributions for Au++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200, 130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, Cu++Cu collisions at sNN=200\sqrt{s_{_{NN}}}=200 and 62.4 GeV, Cu++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV, U++U collisions at sNN=193\sqrt{s_{_{NN}}}=193 GeV, dd++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV, 3^{3}He++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV, and pp++pp collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV. Centrality-dependent distributions at midrapidity are presented in terms of the number of nucleon participants, NpartN_{\rm part}, and the number of constituent quark participants, NqpN_{q{\rm p}}. For all AA++AA collisions down to sNN=7.7\sqrt{s_{_{NN}}}=7.7 GeV, it is observed that the midrapidity data are better described by scaling with NqpN_{q{\rm p}} than scaling with NpartN_{\rm part}. Also presented are estimates of the Bjorken energy density, εBJ\varepsilon_{\rm BJ}, and the ratio of dET/dηdE_T/d\eta to dNch/dηdN_{\rm ch}/d\eta, the latter of which is seen to be constant as a function of centrality for all systems.Comment: 706 authors, 32 pages, 20 figures, 34 tables, 2004, 2005, 2008, 2010, 2011, and 2012 data. v2 is version accepted for publication in Phys. Rev.

    ϕ\phi meson production in dd++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

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    The PHENIX experiment has measured ϕ\phi meson production in dd++Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV using the dimuon and dielectron decay channels. The ϕ\phi meson is measured in the forward (backward) dd-going (Au-going) direction, 1.2<y<2.21.2<y<2.2 (2.2<y<1.2-2.2<y<-1.2) in the transverse-momentum (pTp_T) range from 1--7 GeV/cc, and at midrapidity y<0.35|y|<0.35 in the pTp_T range below 7 GeV/cc. The ϕ\phi meson invariant yields and nuclear-modification factors as a function of pTp_T, rapidity, and centrality are reported. An enhancement of ϕ\phi meson production is observed in the Au-going direction, while suppression is seen in the dd-going direction, and no modification is observed at midrapidity relative to the yield in pp++pp collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor indicating similar cold-nuclear-matter effects.Comment: 484 authors, 16 pages, 12 figures, 6 tables. v1 is the version accepted for publication in Phys. Rev. C. Data tables for the points plotted in the figures are given in the paper itsel

    Cross Section and Transverse Single-Spin Asymmetry of η\eta Mesons in p+pp^{\uparrow}+p Collisions at s=200\sqrt{s}=200 GeV at Forward Rapidity

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    We present a measurement of the cross section and transverse single-spin asymmetry (ANA_N) for η\eta mesons at large pseudorapidity from s=200\sqrt{s}=200~GeV p+pp^{\uparrow}+p collisions. The measured cross section for 0.5<pT<5.00.5<p_T<5.0~GeV/cc and 3.0<η<3.83.0<|\eta|<3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries ANA_N have been measured as a function of Feynman-xx (xFx_F) from 0.2<xF<0.70.2<|x_{F}|<0.7, as well as transverse momentum (pTp_T) from 1.0<pT<4.51.0<p_T<4.5~GeV/cc. The asymmetry averaged over positive xFx_F is AN=0.061±0.014\langle{A_{N}}\rangle=0.061{\pm}0.014. The results are consistent with prior transverse single-spin measurements of forward η\eta and π0\pi^{0} mesons at various energies in overlapping xFx_F ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p+pp^{\uparrow}+p collisions.Comment: 484 authors, 13 pages, 11 figures, 4 tables, 2008 data. v2 is version accepted by Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be)publicly available at http://www.phenix.bnl.gov/papers.htm
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