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We study the interaction of surface acoustic waves with spin waves in ultrathin CoFeB/Pt bilayers. Because of the interfacial Dzyaloshinskii-Moriya interaction (DMI), the spin wave dispersion is nondegenerate for oppositely propagating spin waves in CoFeB/Pt. In combination with the additional nonreciprocity of the magnetoacoustic coupling itself, which is independent of the DMI, highly nonreciprocal acoustic wave transmission through the magnetic film is observed. We systematically characterize the magnetoacoustic wave propagation in a thickness series of CoFeB(d)/Pt samples as a function of magnetic field magnitude and direction, and at frequencies up to 7 GHz. We quantitatively model our results to extract the strength of the DMI and magnetoacoustic driving fields.
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The Large Area Telescope on board the Fermi Gamma-ray Space Telescope has collected the largest ever sample of high-energy cosmic-ray electron and positron events since the beginning of its operation. Potential anisotropies in the arrival directions of cosmic-ray electrons or positrons could be a signature of the presence of nearby sources. We use almost seven years of data with energies above 42 GeV processed with the Pass 8 reconstruction. The present data sample can probe dipole anisotropies down to a level of 10^{-3}. We take into account systematic effects that could mimic true anisotropies at this level. We present a detailed study of the event selection optimization of the cosmic-ray electrons and positrons to be used for anisotropy searches. Since no significant anisotropies have been detected on any angular scale, we present upper limits on the dipole anisotropy. The present constraints are among the strongest to date probing the presence of nearby young and middle-aged sources.
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We report on the search for spectral irregularities induced by oscillations between photons and axionlike-particles (ALPs) in the γ-ray spectrum of NGC 1275, the central galaxy of the Perseus cluster. Using 6 years of Fermi Large Area Telescope data, we find no evidence for ALPs and exclude couplings above 5×10^{-12} GeV^{-1} for ALP masses 0.5â²m_{a}â²5 neV at 95% confidence. The limits are competitive with the sensitivity of planned laboratory experiments, and, together with other bounds, strongly constrain the possibility that ALPs can reduce the γ-ray opacity of the Universe.
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We use joint observations by the Neil Gehrels Swift X-ray Telescope (XRT) and the Fermi Large Area Telescope (LAT) of gamma-ray burst (GRB) afterglows to investigate the nature of the long-lived high-energy emission observed by Fermi LAT. Joint broadband spectral modeling of XRT and LAT data reveal that LAT non-detections of bright X-ray afterglows are consistent with a cooling break in the inferred electron synchrotron spectrum below the LAT and/or XRT energy ranges. Such a break is sufficient to suppress the high-energy emission so as to be below the LAT detection threshold. By contrast, LAT-detected bursts are best fit by a synchrotron spectrum with a cooling break that lies either between or above the XRT and LAT energy ranges. We speculate that the primary difference between GRBs with LAT afterglow detections and the non-detected population may be in the type of circumstellar environment in which these bursts occur, with late-time LAT detections preferentially selecting GRBs that occur in low wind-like circumburst density profiles. Furthermore, we find no evidence of high-energy emission in the LAT-detected population significantly in excess of the flux expected from the electron synchrotron spectrum fit to the observed X-ray emission. The lack of excess emission at high energies could be due to a shocked external medium in which the energy density in the magnetic field is stronger than or comparable to that of the relativistic electrons behind the shock, precluding the production of a dominant synchrotron self-Compton (SSC) component in the LAT energy range. Alternatively, the peak of the SSC emission could be beyond the 0.1-100 GeV energy range considered for this analysis.
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A single-center, double-blind, placebo-controlled, randomized study was conducted to determine the pharmacokinetics, safety, and tolerability of single, rising intramuscular (i.m.) doses and the single maximum tolerated dose of parecoxib sodium, a prodrug of the novel COX-2 selective anti-inflammatory analgesic drug valdecoxib, in 56 healthy male volunteers, ages 18 to 45 years inclusive. Cohorts of up to 6 subjects in each dose schedule were administered either parecoxib sodium (1 mg, 2 mg, 5 mg, 10 mg, 20 mg, or 40 mg) or matching placebo. Following i.m. administration, serial blood samples for measurement of plasma concentrations of parecoxib, valdecoxib, and valdecoxib metabolite (M1) were collected at predetermined intervals (from 15 minutes prior to dose and through 96 hours postdose). Urine collections were obtained for drug assay (from -12 to 0 hours, 0 to 12 hours, and 12 to 24 hours postdose). After i.m. administration, peak plasma concentrations of parecoxib were reached within 15 minutes and then declined rapidly as prodrug was converted to the active moiety, valdecoxib. Change in plasma concentrations of valdecoxib, which declined more slowly (t(1/2) = 5.4-9.9 hours), reflected transformation to several metabolites, one of which was the minor active metabolite M1. As measured by the AUC(0-infinity), Cmax, and XU(0-24) of valdecoxib, parecoxib sodium demonstrated dose proportionality when administered in the range of 1 mg to 40 mg of parecoxib. All single i.m. doses up to the maximum of 40 mg of parecoxib, as well as concentrations of up to 20 mg/ml, were well tolerated.
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Inhibidores de la Ciclooxigenasa/farmacocinética , Isoxazoles/farmacocinética , Adolescente , Adulto , Análisis de Varianza , Antiinflamatorios no Esteroideos/efectos adversos , Antiinflamatorios no Esteroideos/farmacocinética , Área Bajo la Curva , Inhibidores de la Ciclooxigenasa/administración & dosificación , Inhibidores de la Ciclooxigenasa/efectos adversos , Método Doble Ciego , Humanos , Inyecciones Intramusculares , Isoxazoles/administración & dosificación , Isoxazoles/efectos adversos , Masculino , Persona de Mediana Edad , Sulfonamidas/efectos adversos , Sulfonamidas/farmacocinéticaRESUMEN
BACKGROUND: Conventional nonsteroidal anti-inflammatory drugs (NSAIDs) are associated with an increased risk of ulcers and upper gastrointestinal (GI) ulcer complications, which has been attributed to the inhibition of cyclooxygenase-1. These risks are usually increased in elderly populations. Parecoxib sodium is an injectable prodrug of the cyclooxygenase-2-specific inhibitor valdecoxib that has exhibited analgesic activity in previous trials. OBJECTIVE: The purpose of this study was to compare the GI safety and tolerability profile of parecoxib sodium with that of ketorolac, naproxen, and placebo in a 7-day endoscopic trial in elderly subjects. METHODS: This was a randomized, double-blind, double-dummy, placebo-controlled, parallel-group study. After a normal baseline endoscopy, healthy elderly subjects aged 66 to 75 years were randomized to receive i.v. parecoxib sodium (10 mg BID), oral naproxen (500 mg BID), or placebo for 7 days, or placebo for 2 days followed by i.v. ketorolac (15 mg QID) for 5 days. Endoscopy was performed again after 7 days. RESULTS: Among the first 17 subjects enrolled, ulcers were observed in all treatment groups except the parecoxib sodium group (ketorolac, 4/4 subjects; naproxen, 2/4 subjects; and placebo, 2/5 subjects). Four subjects in the ketorolac group and 1 subject in the naproxen group had multiple gastric ulcers or combined gastric and duodenal ulcers. Because of the unexpectedly high incidence of gastroduodenal ulcers observed, the study was terminated early and the randomization blind broken. CONCLUSION: These findings suggest that elderly patients may be at risk for GI ulceration even after short-term use of the conventional NSAIDs ketorolac and naproxen.
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Analgésicos no Narcóticos/efectos adversos , Analgésicos no Narcóticos/uso terapéutico , Antiinflamatorios no Esteroideos/efectos adversos , Antiinflamatorios no Esteroideos/uso terapéutico , Inhibidores de la Ciclooxigenasa/efectos adversos , Inhibidores de la Ciclooxigenasa/uso terapéutico , Mucosa Gástrica/efectos de los fármacos , Isoxazoles/efectos adversos , Isoxazoles/uso terapéutico , Ketorolaco/efectos adversos , Ketorolaco/uso terapéutico , Naproxeno/efectos adversos , Naproxeno/uso terapéutico , Anciano , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Método Doble Ciego , Femenino , Humanos , Infusiones Parenterales , Isoenzimas , Masculino , Proteínas de la Membrana , Úlcera Péptica/inducido químicamente , Prostaglandina-Endoperóxido SintasasRESUMEN
BACKGROUND: Parecoxib sodium is an injectable cyclooxygenase-2-specific inhibitor developed for the treatment of acute pain. The analgesic efficacy of IV and IM parecoxib has been demonstrated in previous pilot studies using the post-oral surgery pain model. OBJECTIVE: This study was conducted to characterize the analgesic efficacy of parecoxib in healthy adults after oral surgery while comparing the efficacy and tolerability of the IV and IM routes of administration. METHODS: This was a double-blind, randomized, parallel-group, placebo- and active-controlled, single-dose, single-center trial. Patients experiencing moderate to severe post-operative pain after the extraction of > or =2 impacted third molars were randomized to receive parecoxib sodium 20 mg IM, 20 mg IV, 40 mg IM, or 40 mg IV; ketorolac tromethamine 60 mg IM; or placebo. Patients assessed pain intensity and pain relief (PR) at baseline and at designated intervals for 24 hours after administration of study medication or until rescue medication was taken. Analgesic efficacy was assessed in terms of time-specific pain intensity difference (PID) and PR, time to onset of analgesia, and time to use of rescue medication. RESULTS: Three hundred four patients were randomized to treatment. Parecoxib sodium 20 and 40 mg IM or IV and ketorolac 60 mg IM were significantly superior to placebo in PID, PR, time to onset of analgesia, and time to use of rescue medication (P < or = 0.05). Equal IV and IM doses of parecoxib were comparable on these measures; however, time to use of rescue medication was longer with IM compared with IV administration. Both doses of parecoxib were comparable to ketorolac 60 mg IM in time to onset of analgesia, but parecoxib 40 mg had a significantly longer duration of action (P < or = 0.05). The few statistically significant differences in PID and PR between parecoxib 40 mg and ketorolac favored ketorolac versus parecoxib 40 mg IV at earlier time points and parecoxib 40 mg IM versus ketorolac at later time points (P < or = 0.05). All treatments were well tolerated. CONCLUSIONS: Parecoxib IV and IM provided effective analgesia. The 40-mg dose was comparable to ketorolac 60 mg on most measures of analgesia but had a longer duration of action.
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Inhibidores de la Ciclooxigenasa/uso terapéutico , Isoxazoles/uso terapéutico , Ketorolaco/uso terapéutico , Tercer Molar/cirugía , Dolor Postoperatorio/tratamiento farmacológico , Adulto , Inhibidores de la Ciclooxigenasa/administración & dosificación , Inhibidores de la Ciclooxigenasa/efectos adversos , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Femenino , Humanos , Inyecciones Intramusculares , Inyecciones Intravenosas , Isoxazoles/administración & dosificación , Isoxazoles/efectos adversos , Ketorolaco/administración & dosificación , Ketorolaco/efectos adversos , Masculino , Persona de Mediana Edad , Dimensión del DolorRESUMEN
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed for the treatment of signs and symptoms of osteoarthritis (OA). Nabumetone and oxaprozin are 2 of the newer NSAIDs and have been shown to have similar safety and efficacy profiles. Nabumetone 1000 mg to 1500 mg once a day (QD) and oxaprozin 1200 mg QD are commonly recommended doses. This study compared the health-related quality of life (HRQOL) of patients receiving oxaprozin 1200 mg QD with that of patients receiving nabumetone 1000 mg QD or nabumetone 1500 mg QD for the treatment of signs and symptoms of OA of the knee. Two similarly designed, independent, randomized, double-masked, placebo-controlled clinical trials were conducted. In trial 1, patients were randomized to receive oxaprozin 1200 mg QD (n = 109), nabumetone 1000 mg QD (n = 110), or placebo (n = 109); in trial 2, patients received oxaprozin 1200 mg QD (n = 116), nabumetone 1500 mg QD (n = 115), or placebo (n = 116). HRQOL was measured by the Medical Outcomes Study Short-Form-36 Health Survey (1-week recall period) at baseline and weeks 2 and 6. Data from the 2 trials were combined to assess differences across the 4 groups in 8 domains and 2 summary scores at baseline, and changes in HRQOL scores at weeks 2 and 6. At week 2, the oxaprozin group showed significantly greater improvement than the placebo group in role physical, vitality, and mental component summary (MCS) scores (P < 0.05), and in physical functioning, bodily pain, social functioning, and physical component summary (PCS) scores (P < 0.01). The nabumetone 1500-mg group showed significantly greater improvement than the placebo group in bodily pain and social functioning (P < 0.05), and in vitality and MCS score (P < 0.01). No significant differences were observed between the nabumetone 1000-mg and placebo groups. At week 2, the oxaprozin group showed a greater change than the nabumetone 1000-mg group in PCS score (P < 0.05). At week 6, oxaprozin treatment resulted in significantly greater improvement than placebo in physical functioning, role physical, and bodily pain (P < 0.05); social functioning, role emotional, and mental health (P < 0.01); and vitality and MCS score (P < 0.001). The nabumetone 1500-mg group showed significantly greater responses than the placebo group in vitality (P < 0.05), mental health (P < 0.01), and MCS score (P < 0.001). The oxaprozin group had significantly better scores than the nabumetone 1500-mg group in the PCS (P < 0.05), and it showed significantly greater improvement than the nabumetone 1000 mg group in role physical and PCS score (P < 0.01) and in role emotional (P < 0.05). No statistically significant differences were found between placebo and nabumetone 1000 mg at week 6. Results of this study suggest that oxaprozin 1200 mg QD has a significant positive impact on the HRQOL of patients with OA of the knee compared with nabumetone 1000 mg QD and placebo.
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Antiinflamatorios no Esteroideos/uso terapéutico , Butanonas/uso terapéutico , Osteoartritis de la Rodilla/tratamiento farmacológico , Propionatos/uso terapéutico , Anciano , Antiinflamatorios no Esteroideos/administración & dosificación , Butanonas/administración & dosificación , Femenino , Humanos , Masculino , Persona de Mediana Edad , Nabumetona , Oxaprozina , Propionatos/administración & dosificación , Calidad de Vida , Ensayos Clínicos Controlados Aleatorios como Asunto , Perfil de Impacto de EnfermedadRESUMEN
This 6-week, multicenter, double-masked, placebo-controlled study compared the efficacy, tolerability, and safety of the recommended starting dose of oxaprozin (1200 mg/d) and a 1500-mg/d dose of nabumetone in the treatment of patients with moderate-to-severe osteoarthritis (OA) of the knee. A total of 347 patients with a mean age of 61.1 years were randomized to receive oxaprozin (116 patients), nabumetone (115 patients), or placebo (116 patients). Adults of either sex who were older than 18 years of age were eligible for entry into the study, if they had had OA of the knee for at least 6 months. Efficacy variables included knee pain on weight bearing, knee pain on motion, patients' and physicians' global assessments of OA, pain intensity as measured on a visual analog scale, and time to walk 50 feet as quickly as possible. Efficacy variables were assessed at baseline and at weeks 1, 2, 4, and 6. Between-group differences in efficacy variables were evident by week 1. Mean improvements were significantly greater with oxaprozin than with placebo for all efficacy variables at all time periods, except knee pain on motion at weeks 2 and 4 and time to walk 50 feet at weeks 1, 2, and 4. Mean improvements were significantly greater with nabumetone than with placebo for all efficacy variables at all time periods, except the following: knee pain on weight bearing at weeks 2, 4 and 6; knee pain on motion at weeks 2 and 4; patients' global assessment at week 4; and pain intensity as measured on a visual analog scale at weeks 2 and 4. There were, however, no significant differences between oxaprozin and nabumetone in any of these efficacy variables. Adverse events were reported by 83 (71.6%) patients who took oxaprozin, by 80 (69.6%) patients who took nabumetone, and by 57 (49.1%) patients who took placebo. Adverse events were reported for significantly more patients taking oxaprozin or nabumetone than placebo. However, adverse events tended to be mild or moderate and rarely resulted in patients withdrawing from the study. Combined with the results of an earlier study, the results of this study showed that a 1500-mg/d dose of nabumetone, which is higher than the recommended starting dose of 1000 mg/d, is required for efficacy equivalent to that of the recommended starting dose of oxaprozin, 1200 mg/d, in relieving the symptoms of OA. Thus nabumetone may require dosage titration from the recommended starting dose. Oxaprozin and nabumetone were found to have similar tolerability profiles, as shown by adverse-event monitoring and withdrawal rates, as well as clinically similar safety profiles, as demonstrated by physical examinations, hematologic and biochemical laboratory testing, hemoccult testing, and adverse-event monitoring and symptom assessment.
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Antiinflamatorios no Esteroideos/uso terapéutico , Butanonas/uso terapéutico , Articulación de la Rodilla , Osteoartritis/tratamiento farmacológico , Propionatos/uso terapéutico , Adulto , Anciano , Antiinflamatorios no Esteroideos/efectos adversos , Butanonas/efectos adversos , Método Doble Ciego , Femenino , Humanos , Masculino , Persona de Mediana Edad , Nabumetona , Oxaprozina , Propionatos/efectos adversosRESUMEN
BACKGROUND: The study was designed to evaluate if there is any evidence of a hyperfibrinolytic bleeding-risk under systemic treatment with prostaglandin E1 (PGE1) of patients with peripheral arterial disease (PAD). PATIENTS AND METHODS: The in vivo effect of PGE1 on the fibrinolytic and hemostatic process was tested on 15 patients before and after treatment with Alprostadil for 21 days using D-dimers (DD), fibrinogen, prothrombin time (PT), partial thromboplastin time (PTT), antithrombin (AT), ProC-Global, plasminogen, plasminogen activator inhibitor activity (PAI), alpha 2-antiplasmin, coagulation factor XII, basal and activated fibrinolytic capacity (fib. cap.). RESULTS: There was no significant difference in DD, fibrinogen, PT, PTT, AT, ProC-Global, plasminogen, PAI, alpha 2-antiplasmin, coagulation factor XII, basal and activated fibrinolytic capacity observed after the treatment. CONCLUSION: Summarizing this study there is no hyperfibrinolytic bleeding-risk after the systemic therapy with Alprostadil to be expected.
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Alprostadil/efectos adversos , Arteriopatías Oclusivas/tratamiento farmacológico , Fibrinólisis/efectos de los fármacos , Fibrinolíticos/efectos adversos , Hemorragia/inducido químicamente , Hemostasis/efectos de los fármacos , Anciano , Anciano de 80 o más Años , Alprostadil/administración & dosificación , Arteriopatías Oclusivas/sangre , Factores de Coagulación Sanguínea/metabolismo , Pruebas de Coagulación Sanguínea , Femenino , Hemorragia/sangre , Humanos , Infusiones Intravenosas , Masculino , Persona de Mediana Edad , Medición de RiesgoRESUMEN
We report on the case of a 22-year-old heroin-dependent diabetic woman. She presented with a gas-forming fungal infection of the kidney caused by Candida tropicalis. The patient was successfully treated by conservative means. Problems in the diagnosis and therapy of this rare disease are discussed.
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Candidiasis/diagnóstico , Diabetes Mellitus Tipo 1/diagnóstico , Nefropatías Diabéticas/diagnóstico , Pielonefritis/diagnóstico , Adulto , Candidiasis/tratamiento farmacológico , Diabetes Mellitus Tipo 1/tratamiento farmacológico , Nefropatías Diabéticas/tratamiento farmacológico , Femenino , Fluconazol/administración & dosificación , Humanos , Sistemas de Infusión de Insulina , Pielonefritis/tratamiento farmacológico , Irrigación Terapéutica , Urodinámica/efectos de los fármacos , Urodinámica/fisiología , UrografíaRESUMEN
We have studied the quasielastic 3He(e,e(')p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e(')p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the A(TL) asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The A(TL) asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.
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We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.
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Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements are presented. These measurements were performed at fixed transferred momentum and energy, q=1502 MeV/c and omega=840 MeV, respectively, for missing momenta p(m) up to 1 GeV/c and missing energies in the continuum region, up to pion threshold; this kinematic coverage is much more extensive than that of any previous experiment. The cross section data are presented along with the effective momentum density distribution and compared to theoretical models.
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Preoperative administration of analgesics may prevent or reduce hyperalgesia and inhibit inflammation and pain by reducing the synthesis of prostaglandins in response to surgical injury. We evaluated in this placebo-controlled study the analgesic efficacy and safety of single doses of parecoxib sodium (20, 40, and 80 mg IV) when administered before oral surgery. Efficacy assessments were recorded during the 24-h period after completion of surgery. All doses of parecoxib sodium were consistently and significantly superior to placebo as measured by time to rescue medication, proportion of patients requiring rescue medication, patient's global assessment, and pain intensity. There were no significant differences between the Parecoxib Sodium 40- and 80-mg groups, suggesting that the analgesic effect of preoperatively administered parecoxib sodium reaches a plateau at 40 mg in this model. Forty-eight percent of the Parecoxib Sodium 40-mg group required rescue medication in the 24-h study period, compared with 93% of patients in the Placebo group. Overall, there were fewer adverse events in parecoxib sodium-treated patients compared with placebo. These findings suggest that preoperative administration of parecoxib sodium, the injectable prodrug of the cyclooxygenase-2 specific inhibitor valdecoxib, is effective, safe, and well tolerated for treating postoperative pain.
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Analgésicos/uso terapéutico , Inhibidores de la Ciclooxigenasa/uso terapéutico , Isoenzimas/metabolismo , Isoxazoles/uso terapéutico , Dolor/prevención & control , Cuidados Preoperatorios , Prostaglandina-Endoperóxido Sintasas/metabolismo , Adolescente , Adulto , Analgésicos/administración & dosificación , Analgésicos/efectos adversos , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa/administración & dosificación , Inhibidores de la Ciclooxigenasa/efectos adversos , Método Doble Ciego , Femenino , Humanos , Inyecciones Intravenosas , Isoxazoles/administración & dosificación , Isoxazoles/efectos adversos , Masculino , Proteínas de la Membrana , Tercer Molar , Procedimientos Quirúrgicos Orales , Dimensión del Dolor , Dolor Postoperatorio/prevención & control , Extracción DentalRESUMEN
The 2H(e,e(')p)n cross section was measured in Hall A of the Thomas Jefferson National Accelerator Facility near the top of the quasielastic peak (x(Bj)=0.964) at a four-momentum transfer squared, Q(2)=0.665 (GeV/c) (2) (omega=0.368 GeV, W=2.057 GeV), and for recoil momenta up to 550 MeV/c. The measured cross section deviates by 1-2sigma from a state-of-the-art calculation at low recoil momenta. At high recoil momenta the cross section is well described by the same calculation; however, in this region, final-state interactions and interaction currents are predicted to be large, and alternative choices of nucleon-nucleon potential and nucleon current operator may result in significant spread in the calculations.
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New data are presented on the p(e,e'p)pi(0) reaction at threshold at a four-momentum transfer of Q(2) = 0.05 GeV(2)/c(2). The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.
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We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.
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We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.