Unique Access to u-Channel Physics: Exclusive Backward-Angle Omega Meson Electroproduction.

Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave function. In this Letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive ω electroproduction off the proton, ep→e^{'}pω, at central Q^{2} values of 1.60, 2.45 GeV^{2}, at W=2.21 GeV. The results of our pioneering -u≈-u_{min} study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L/T/LT/TT separations in this never explored kinematic territory. At Q^{2}=2.45 GeV^{2}, the observed dominance of σ_{T} over σ_{L}, is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes: universal nonperturbative objects only accessible through backward-angle kinematics.

Precision Measurement of the Radiative ß Decay of the Free Neutron.

The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the ß decay of the free neutron. We report on the RDK II experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782 keV. The spectral shape was consistent with theory, and we determined a branching ratio of 0.00335±0.00005[stat]±0.00015[syst]. A second detector array of large area avalanche photodiodes directly detected photons from 0.4 to 14 keV. For this array, the spectral shape was consistent with theory, and the branching ratio was determined to be 0.00582±0.00023[stat]±0.00062[syst]. We report the first precision test of the shape of the photon energy spectrum from neutron radiative decay and a substantially improved determination of the branching ratio over a broad range of photon energies.

[Recurrent hypoglycemia due to an occult insulinoma]. / Okkultes Insulinom als Ursache rezidivierender Hypoglykämien.

A 64-year-old woman presented with a history of recurrent hypoglycemia. A prolonged fasting test revealed an increased "amended" insulin-glucose ratio. Transabdominal ultrasound (US), computed tomography (CT) scan, and magnetic resonance imaging (MRI) did not show abnormal results. An insulinoma was suspected based on a contrast-enhanced endoscopic US examination as well as a (68)gallium-DOTA-exendin-4 positron-emission tomography (PET)/CT. The diagnosis of an insulinoma was confirmed histologically after surgical removal of the tumor. Hypoglycemia did not occur during the postoperative period. The prolonged fasting test is the gold standard for the diagnosis of an insulinoma. Novel imaging procedures, such as contrast-enhanced endoscopic US or (68)gallium-DOTA-exendin-4 PET/CT are valuable additions to the diagnostic workup.

Separated response function ratios in exclusive, forward π(±) electroproduction.

The study of exclusive π(±) electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio RL=σL(π-)/σL(π+) is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of RT=σT(π-)/σT(π+) from unity at small -t, to 1/4 at large -t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to perturbative QCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π(±) electroproduction on the deuteron at central Q(2) values of 0.6, 1.0, 1.6 GeV(2) at W=1.95 GeV, and Q(2)=2.45 GeV(2) at W=2.22 GeV. Here, we present the L and T cross sections, with emphasis on RL and RT, and compare them with theoretical calculations. Results for the separated ratio RL indicate dominance of the pion-pole diagram at low -t, while results for RT are consistent with a transition between pion knockout and quark knockout mechanisms.

Measurement of the parity-violating asymmetry in inclusive electroproduction of π- near the Δ0 resonance.

The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Δ)- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d(Δ)- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A(γ)-=-5.2 to +5.2 ppm. The measurement performed in this work leads to A(γ)-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V(ud)/V(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering.

Transverse beam spin asymmetries at backward angles in elastic electron-proton and quasielastic electron-deuteron scattering.

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q² = 0.22 GeV²/c² and 0.63 GeV²/c² at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.

Measurements of the electric form factor of the neutron up to Q2=3.4 GeV2 using the reaction 3He(e,e'n)pp.

The electric form factor of the neutron was determined from studies of the reaction 3He(e,e'n)pp in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2 range over which it is known, we find G(E)(n)=0.0236±0.0017(stat)±0.0026(syst), 0.0208±0.0024±0.0019, and 0.0147±0.0020±0.0014 for Q(2)=1.72, 2.48, and 3.41 GeV2, respectively.

Strange quark contributions to parity-violating asymmetries in the backward angle G0 electron scattering experiment.

We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial-vector current at these four-momentum transfers.

High-resolution spectroscopy of Lambda16N by electroproduction.

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.

Strange magnetism and the anapole structure of the proton.

The violation of mirror symmetry in the weak force provides a powerful tool to study the internal structure of the proton. Experimental results have been obtained that address the role of strange quarks in generating nuclear magnetism. The measurement reported here provides an unambiguous constraint on strange quark contributions to the proton's magnetic moment through the electron-proton weak interaction. We also report evidence for the existence of a parity-violating electromagnetic effect known as the anapole moment of the proton. The proton's anapole moment is not yet well understood theoretically, but it could have important implications for precision weak interaction studies in atomic systems such as cesium.

High resolution spectroscopy of (lambda)(12)B by electroproduction.

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.

Local probe of single phonon dynamics in warm ion crystals.

The detailed characterization of non-trivial coherence properties of composite quantum systems of increasing size is an indispensable prerequisite for scalable quantum computation, as well as for understanding non-equilibrium many-body physics. Here, we show how autocorrelation functions in an interacting system of phonons as well as the quantum discord between distinct degrees of freedoms can be extracted from a small controllable part of the system. As a benchmark, we show this in chains of up to 42 trapped ions, by tracing a single phonon excitation through interferometric measurements of only a single ion in the chain. We observe the spreading and partial refocusing of the excitation in the chain, even on a background of thermal excitations. We further show how this local observable reflects the dynamical evolution of quantum discord between the electronic state and the vibrational degrees of freedom of the probe ion.

Localization and concentration of carcinoembryonic antigen (CEA) in gastrointestinal tumors: correlation with CEA levels in plasma.

In 50 patients with gastrointestinal carcinomas, the following tumor parameters were studied: the concentration and localization of carcinoembryonic antigen (CEA) in tissue, extension, invasion, infiltration, differentiation, and necrosis. CEA concentrations were measured in plasma samples of all patients. In 7 patients with gastric carcinomas, CEA concentrations in tissue were low. Generally, only single cells or cell groups were CEA-positive. Elevated CEA levels in plasma resulted mainly from distant metastases and not from the primary tumor. In 43 colorectal carcinomas, CEA concentrations in tissue varied between 1.5 and 472 microgram/g tissue. They were closely related to the degree of accumulation of CEA-positive necrotic material in the degree of accumulation of CEA-positive necrotic material in the neoplastic glands. In 35 patients with colorectal carcinomas without CEA producing distant metastases, preoperative CEA levels in plasma were normal when tumor necrosis and perineural invasion were absent and CEA concentrations in tissue were low. CEA levels in plasma were regularly elevated when the tumor showed considerable necrosis in the presence of high CEA concentrations in tissue.

Development and Characterization of a High Sensitivity Segmented Fast Neutron Spectrometer (FaNS-2).

We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and 3He proportional counters. It was designed to measure both the flux and spectrum of fast neutrons in the energy range of few MeV to 1 GeV. FaNS-2 utilizes capture-gated spectroscopy to identify neutron events and reject backgrounds. Neutrons deposit energy in the plastic scintillator before capturing on a 3He nucleus in the proportional counters. Segmentation improves neutron energy reconstruction while the large volume of scintillator increases sensitivity to low neutron fluxes. A main goal of its design is to study comparatively low neutron fluxes, such as cosmogenic neutrons at the Earth's surface, in an underground environment, or from low-activity neutron sources. In this paper, we present details of its design and construction as well as its characterization with a calibrated 252Cf source and monoenergetic neutron fields of 2.5 MeV and 14 MeV. Detected monoenergetic neutron spectra are unfolded using a Singular Value Decomposition method, demonstrating a 5% energy resolution at 14 MeV. Finally, we discuss plans for measuring the surface and underground cosmogenic neutron spectra with FaNS-2.

Investigations on the kinetic properties of estrone glucuronyltransferase from pig kidney.

The microsomal fraction of the pig kidney catalyzes the glucuronidation of estrone in the presence of UDP-glucuronic acid. This bireactant system exhibits a sequential type of reaction mechanism. Increasing concentrations of either substrate increase the affinity of the enzyme for the other substrate. The Hill coefficient, n, was calculated to be 1.0 for both estrone and UDP-glucuronic acid. The Kestrone and KUDP-glucuronic acid are 6.6 muM and 254 muM, respectively. The estrone glucuronyltransferase (UDP-glucuronate: 17 beta-oestradiol 3-glucuronosyltransferase, EC 2.4.1.59) exhibits high substrate specificity in that it is inhibited noncompetetively by estradiol-17 beta, estradiol-17 alpha, estriol, testosterone, phenolphthalein and bilirubin; p-nitrophenol and o-aminophenol do not inhibit the glucuronidation of estrone. Mg2+ and Ca2+ were found to be nonessential activators. One of the two products of the reaction, estrone glucuronide, inhibits the enzyme competitively in the presence of increasing concentrations of UDP-glucuronic acid. The other product of the reaction, UDP, inhibits the enzyme noncompetitively with varying estrone concentrations and uncompetitively with varying UDP-glucuronic acid concentrations. Under incubation conditions for the glucuronidation of estrone, the enzyme catalyzes the reverse reaction with estrone glucuronide and UDP as reactants to an extent of about 0.4% of the forward reaction; this reverse reaction is also of a sequential type.

Factors involved in the uptake of corticosterone by rat liver cells.

Isolated rat liver cells take up corticosterone rapidly; the initial rates increase with increasing temperature. A plot of the initial rates against the concentration of corticosterone indicated the presence of saturable and nonsaturable uptake systems. The Eadie-Hofstee plot showed the presence of two saturable and one nonsaturable uptake components. The apparent Kt values of the saturable systems were 64 +/- 40 nM (n = 3) and 1085 +/- 313 nM (n = 12). The nonsaturable system, probably diffusion, contributed 12% to the total uptake between 15 and 72 nM corticosterone, the physiological concentration of the free corticosterone in rat serum. Metabolic inhibitors did not influence the uptake of corticosterone. N-Ethylmaleimide, 1-fluoro-2,4-dinitrobenzene and sodium ethyl mercurithiosalicylate (1 mM each) decreased the uptake by 40%. Iodoacetate did not have any influence. Treatment of cells with phospholipase A inhibited the uptake 35--45%. In the presence of cortisone, cortisol, dexamethasone, aldosterone, testosterone, estradiol-17beta and estrone (2 muM each) the uptake decreased 30--50%. The presence of serum proteins in the external medium inhibits the uptake of corticosterone. These results suggest that corticosterone is transported into the cell and is accumulated. Only the free hormone is available for uptake which in turn may be regulated by protein and lipid components in the plasma membrane of the liver cell.

Doppler versus contrast echocardiography for diagnosis of tricuspid regurgitation.

Sixty-eight patients (mean age 49 years) were studied with contrast echocardiography (CE) and Doppler echocardiography (DE) to evaluate both methods for detecting and grading tricuspid regurgitation (TR). In all patients, right ventricular (RV) angiography was performed. The severity of TR was graded on a 4-point scale. Only 68 of 88 patients who underwent RV angiography (77%) could be evaluated, but 65 of 68 patients who underwent CE (96%) and all 68 who underwent DE (100%) could be evaluated. TR was present in 33 patients as seen on RV angiography. CE and DE correctly diagnosed 27 and 30 patients, respectively, corresponding to a sensitivity of 82% for CE and 91% for DE. Specificity was 100% for CE and 86% for DE. CE and DE grading, respectively, of TR vs RV angiographic grading showed no difference in 50 and 47 patients, a 1-level difference in 8 and 13 and a 2-level difference in 7 and 5 cases. (CE-RV angiography, r = 0.84, p less than 0.001; DE-RV angiography, r = 0.82, p less than 0.001). Thus, CE and DE are accurate methods for routine diagnosis of TR, with DE having higher sensitivity and easier grading. Considering the possibility of false-positive findings of our standard RV angiography, sensitivity and specificity of CE and DE could be even higher.

Effect of recombinant human granulocyte colony-stimulating factor on hemodynamic and cytokine response in a porcine model of Pseudomonas sepsis.

To investigate the effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on sepsis, chronically catheterized conscious pigs were challenged with Pseudomonas aeruginosa (8 x 10(7) colony-forming units kg-1 h-1) for 84 h (Group A, n = 8). Group B (n = 7) also received rhG-CSF at 5 micrograms kg-1 d-1, the first dose being given 30 min before starting bacterial infusion. Two of the animals in Group A died from pulmonary failure, whereas all those treated with rh-GCSF survived. Fever, severe pulmonary hypertension and systemic hypotension--the latter accompanied at first by a transient hypodynamic, and later a hyperdynamic response--were observed in all of the animals. In Group B, however, the rise in temperature, mean pulmonary arterial pressure (at a later stage of the observation), plasma levels of tumor necrosis factor, and endotoxin were significantly less than in Group A. In the rhG-CSF-treated pigs, an initial leukopenia completely recovered within 24 h (p < .05 vs. Group A). These data suggest that rhG-CSF might be beneficial in the treatment of sepsis.

Measurement of tensor polarization in elastic electron-deuteron scattering at large momentum transfer

Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.

Parity violation in elastic electron-proton scattering and the Proton's strange magnetic form factor

We report a new measurement of the parity-violating asymmetry in elastic electron scattering from the proton at backward scattering angles. This asymmetry is sensitive to the strange magnetic form factor of the proton as well as electroweak axial radiative corrections. The new measurement of A = -4.92+/-0.61+/-0.73 ppm provides a significant constraint on these quantities. The implications for the strange magnetic form factor are discussed in the context of theoretical estimates for the axial corrections.