3,199 research outputs found

    Land Quality in an International Comparison: It's Importance in Measuring Productivity

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    The purpose of this paper has been to present quality-adjusted values for land in the United States and nine European countries using price and quantity data for 1990. Disregarding such differences in the quality-adjusted land input would generate biased estimates of the land input and thus of total factor productivity. Land quality adjustments could potentially be enhanced further with additional data on soil characteristics, climate, and other productivity-related characteristics.total factor productivity, hedonic techniques, soil stress, quality-adjusted land, Productivity Analysis,

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    Scheme Independence and the Exact Renormalization Group

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    We compute critical exponents in a Z2Z_2 symmetric scalar field theory in three dimensions, using Wilson's exact renormalization group equations expanded in powers of derivatives. A nontrivial relation between these exponents is confirmed explicitly at the first two orders in the derivative expansion. At leading order all our results are cutoff independent, while at next-to-leading order they are not, and the determination of critical exponents becomes ambiguous. We discuss the possible ways in which this scheme ambiguity might be resolved.Comment: 15 pages, TeX with harvmac, 2 figures in compressed postscript; presentation of first section revised, several minor errors corrected, two references adde

    Hadrons with Charm and Beauty

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    By combining potential models and QCD spectral sum rules (QSSR), we discuss the spectroscopy of the (bcˉ)(b\bar c) mesons and of the (bcq)(bcq), (ccq)(ccq) and (bbq)(bbq) baryons (q≡d{q}\equiv {d} or ss), the decay constant and the (semi)leptonic decay modes of the BcB_c meson. For the masses, the best predictions come from potential models and read: MBc=(6255±20)M_{B_c} = (6255 \pm 20)~MeV, MBc∗=(6330±20)M_{B^*_c} = (6330 \pm 20)~MeV, MΛ(bcu)=(6.93±0.05)M_{\Lambda(bcu)} = (6.93\pm 0.05)~GeV, MΩ(bcs)=(7.00±0.05)M_{\Omega(bcs)} = (7.00\pm 0.05)~GeV, MΞ∗(ccu)=(3.63±0.05)M_{\Xi^*(ccu)} =(3.63\pm 0.05)~GeV and MΞ∗(bbu)=(10.21±0.05)M_{\Xi^*(bbu)} = (10.21\pm 0.05)~GeV. The decay constant fBc=(2.94±0.21)fπf_{B_c} = (2.94 \pm 0.21) f_\pi is well determined from QSSR and leads to: Γ(Bc→Μττ)=(3.0±0.4)(Vcb/0.037)2\Gamma(B_c \rightarrow \nu_\tau \tau) = (3.0 \pm 0.4)( V_{cb}/0.037 )^2 ×1010\times 10^{10} s−1^{-1}.The uses of the vertex sum rules for the semileptonic decays of the BcB_c show that the tt-dependence of the form factors is much stronger than predicted by vector meson dominance. It also predicts the almost equal strength of about 0.30 ×1010\times 10^{10} sec−1^{-1} for the semileptonic rates BcB_c into Bs,Bs∗,ηcB_s, B^*_s,\eta_c and J/ψ\psi. Besides these phenomenological results, we also show explicitly how the Wilson coefficients of the ⟚αsG2⟩\langle\alpha_s G^2\rangle and ⟹G3⟩\langle G^3\rangle gluon condensates already contain the full heavy quark- (⟹QˉQ⟩\langle\bar QQ\rangle) and mixed- (⟹QˉGQ⟩\langle\bar QGQ\rangle) condensate contributions in the OPE.}Comment: 32 pages, LaTeX, no changes in the 1994 paper, latex errors corrected in 201

    Abnormal neuromuscular transmission in an infantile myasthenic syndrome

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    A term infant required intubation for respiratory depression. Examination revealed hypotonia and areflexia with intact extraocular movements. Electrodiagnostic studies demonstrated defective neuromuscular transmission characterized by borderline low motor evoked amplitudes, profound decremental responses at all stimulation rates, and moderate facilitation (50 to 740%) 15 seconds after 5 seconds of 50 Hz stimulation. Repetitive muscle action potential responses were not recorded following stimulation of nerves by single shocks. Sensory evoked responses and needle electromyographic findings were normal, as were acetylcholine receptor antibody levels. Results of muscle histochemical analyses, including acetylcholinesterase stains, were normal. End-plate histometric analyses demonstrated only a slight reduction in mean synaptic vesicle diameter compared with that in an adult control subject. In vitro muscle contractile properties, stimulating the muscle directly, were normal. Anticholinesterase medications were ineffective. Guanidine produced clinical deterioration. The amplitude of motor evoked responses progressively declined, whereas the percentage of decrement and amount of post-tetanic facilitation increased. Although the nature of the transmission defect was not identified, the data are consistent with abnormal acetylcholine resynthesis, mobilization, or storage without abnormality of release or receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50308/1/410160107_ftp.pd

    Study protocol for a randomised controlled trial of invasive versus conservative management of primary spontaneous pneumothorax

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    INTRODUCTION: Current management of primary spontaneous pneumothorax (PSP) is variable, with little evidence from randomised controlled trials to guide treatment. Guidelines emphasise intervention in many patients, which involves chest drain insertion, hospital admission and occasionally surgery. However, there is evidence that conservative management may be effective and safe, and it may also reduce the risk of recurrence. Significant questions remain regarding the optimal initial approach to the management of PSP

    The experience of long-term opiate maintenance treatment and reported barriers to recovery: A qualitative systematic review

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    Background/Aim: To inform understanding of the experience of long-term opiate maintenance and identify barriers to recovery. Methods: A qualitative systematic review. Results: 14 studies in 17 papers, mainly from the USA (65%), met inclusion criteria, involving 1,088 participants. Studies focused on methadone prescribing. Participants reported stability; however, many disliked methadone. Barriers to full recovery were primarily ‘inward focused'. Conclusion: This is the first review of qualitative literature on long-term maintenance, finding that universal service improvements could be made to address reported barriers to recovery, including involving ex-users as positive role models, and increasing access to psychological support. Treatment policies combining harm minimisation and abstinence-orientated approaches may best support individualised recovery

    Investigation of Stilbenoids as Potential Therapeutic Agents for Rotavirus Gastroenteritis

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    Rotavirus (RV) infections cause severe diarrhea in infants and young children worldwide. Vaccines are available but cost prohibitive for many countries and only reduce severe symptoms. Vaccinated infants continue to shed infectious particles, and studies show decreased efficacy of the RV vaccines in tropical and subtropical countries where they are needed most. Continuing surveillance for new RV strains, assessment of vaccine efficacy, and development of cost effective antiviral drugs remain an important aspect of RV studies. This study was to determine the efficacy of antioxidant and anti-inflammatory stilbenoids to inhibit RV replication. Peanut (A. hypogaea) hairy root cultures were induced to produce stilbenoids, which were purified by high performance countercurrent chromatography (HPCCC) and analyzed by HPLC. HT29.f8 cells were infected with RV in the presence stilbenoids. Cell viability counts showed no cytotoxic effects onHT29.f8 cells. Viral infectivity titers were calculated and comparatively assessed to determine the effects of stilbenoid treatments. Two stilbenoids, trans-arachidin-1 and trans-arachidin-3, show a significant decrease in RV infectivity titers.Western blot analyses performed on the infected cell lysates complemented the infectivity titrations and indicated a significant decrease in viral replication. These studies show the therapeutic potential of the stilbenoids against RV replication
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