The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized 8.5GeV photons impinging on a hydrogen target which is contained within a detector with near-complete ...coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson rho(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. Here we confirm a high degree of s-channel helicity conservation at small squared four-momentum transfer t and are able to extract the t-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full t range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced rho(770) differ by two units are negligible for -t<0.5GeV2/c2.
Gastroesophageal reflux is a common condition caused mainly by motility disorders of the upper gastrointestinal tract. The most effective therapy combines acid suppression with a promotility agent. ...Nizatidine is a well-tolerated and effective histamine-2 (H
2)-receptor antagonist used to suppress gastric acid secretion. Animal and human studies have conclusively demonstrated that nizatidine also has prokinetic activity comparable to that of cisapride, and its effect is evident <1 hour after administration of doses commonly used in clinical practice. This prokinetic activity occurs through noncompetitive inhibition of acetylcholine; this inhibition approximates the inhibition caused by neostigmine. Nizatidine appears to possess a prokinetic mechanism that may be helpful in treating patients with gastroesophageal reflux.
We report a measurement of the $\pi^-$ photoproduction beam asymmetry for the reaction $\vec{\gamma} p \rightarrow \pi^- \Delta^{++}$ using data from the GlueX experiment in the photon beam energy ...range 8.2--8.8 GeV. The asymmetry $\Sigma$ is measured as a function of four-momentum transfer $t$ to the $\Delta^{++}$ and compared to phenomenological models. We find that $\Sigma$ varies as a function of $t$: negative at smaller values and positive at higher values of $|t|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. Furthermore, this is the first measurement of the process at this energy.
Inflammatory pseudotumor of the liver is a rare benign lesion that usually has been discovered at laparotomy and treated by hepatic resection. We report a case of hepatic pseudotumor that was treated ...without surgery and that subsequently spontaneously resolved. Hepatic pseudotumor occur in all age groups, but most commonly in middle-aged adults, with a 3.5:1 male predominance. Presenting symptoms are 1 or 2 months of fever (66%), abdominal pain (51%), and weight loss (21%). Most often, the lesions are solitary encapsulated tumors composed of whorled laminated fibrous stroma and chronic inflammatory infiltrate. Our report provides documentation of spontaneous resolution of a hepatic pseudotumor.
Pentane, a product of lipid peroxidation, has been detected in situations involving ischemic injury. Such injury may be limited if lipid peroxidation can be controlled by antioxidants. The role of ...lipid peroxidation in chronic heart failure (CHF) was assessed by measuring breath pentane in patients with CHF vs. age matched controls. The effect of a free radical scavenger on pentane released during CHF was also measured. Pentane levels were correlated with the daily dose of captopril, a sulfhydril-containing drug used to treat CHF, which is an angiotensin converting enzyme inhibitor. To separate the scavenging effects of captopril from the pharmacologic effects of converting enzyme inhibitors, a crossover study using a nonsulfhydril inhibitor was used. Patients with CHF excreted (p < 0.005) high concentrations of pentane (5.7 +/- 2.1 vs. control 3.6 +/- 1.2 nmol/l). Patients treated with captopril also had significantly higher (p < 0.05) excretion of pentane than the control patients (4.7 +/- 1.3 vs. 3.6 +/- 1.2 nmol/l). The dose of captopril was inversely proportional to the concentration of pentane excreted (r = 0.55, p < 0.05). Pentane excretion during captopril therapy was significantly lower before (p < 0.01) and after (p < 0.02) nonsulfhydril inhibitor therapy.
breath pentane is elevated in CHF and it can be reduced by a free radical scavenger. This reduction of pentane excretion is not a converting enzyme inhibitor class effect.
To investigate whether reperfusion after myocardial ischaemia leads to free-radical-mediated peroxidation of membrane lipids and cell damage, we measured pentane, a product of lipid peroxidation, in ...the breath of 10 healthy control subjects and in 20 consecutive patients with suspected acute myocardial infarction. 10 of these patients showed no myocardial damage on electrocardiography (patient control group) and 10 satisfied standard diagnostic criteria for acute myocardial infarction. The three groups were wellmatched for age, sex, underlying disase, and smoking habits. The time from onset of chest pain to breath collection was similar in the patients control and acute myocardial infarction was higher (p<0·0001) in the acute myocardial infarction group (4·96 1·15 nmol/l) than in the patient control (1·96 1·04 nmol/l) and healthy control groups (1·71 0·87 nmol/l). Lipid peroxidation during acute myocardial infarction reflects action of oxygen radicals and their potential for contribution to the pathogenesis of tissue damage.
The GlueX beamline and detector Adhikari, S.; Akondi, C. S.; Austregesilo, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Volume:
987
Journal Article
Peer reviewed
Open access
The GlueX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a ...scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 $μs$. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. Here, we describe the photon beam, the GlueX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation.
We report measurements of the photon beam asymmetry $\Sigma$ for the reaction $\vec{\gamma} p\to K^+\Sigma^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected using ...a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $\Sigma$ was measured as a function of the Mandelstam variable $t$, and a single value of $\Sigma$ was extracted for events produced in the $u$-channel. These are the first exclusive measurements of the photon beam asymmetry $\Sigma$ for the reaction in this energy range. For the $t$-channel, the measured beam asymmetry is close to unity over the $t$-range studied, $-t=(0.1-1.4)~$(GeV/$c$)$^{2}$, with an average value of $\Sigma = 1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{*}$(892) Regge trajectory. A value of $\Sigma = 0.41 \pm 0.09$ is obtained for the $u$-channel integrated up to $-u=2.0$~(GeV/$c$)$^{2}$.
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