A glimpse of gluons through deeply virtual compton scattering on the proton.

The internal structure of nucleons (protons and neutrons) remains one of the greatest outstanding problems in modern nuclear physics. By scattering high-energy electrons off a proton we are able to resolve its fundamental constituents and probe their momenta and positions. Here we investigate the dynamics of quarks and gluons inside nucleons using deeply virtual Compton scattering (DVCS)-a highly virtual photon scatters off the proton, which subsequently radiates a photon. DVCS interferes with the Bethe-Heitler (BH) process, where the photon is emitted by the electron rather than the proton. We report herein the full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the regime where the scattering is expected to occur off a single quark, measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.

Rosenbluth Separation of the π

We report the first longitudinal-transverse separation of the deeply virtual exclusive π^{0} electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions dσ_{L}/dt, dσ_{T}/dt, dσ_{LT}/dt, and dσ_{TT}/dt are extracted as a function of the momentum transfer to the recoil system at Q^{2}=1.75 GeV^{2} and x_{B}=0.36. The ed→edπ^{0} cross sections are found compatible with the small values expected from theoretical models. The en→enπ^{0} cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity generalized parton distributions of the nucleon. By combining these results with previous measurements of π^{0} electroproduction off the proton, we present a flavor decomposition of the u and d quark contributions to the cross section.

Rosenbluth Separation of the π

We present deeply virtual π^{0} electroproduction cross-section measurements at x_{B}=0.36 and three different Q^{2} values ranging from 1.5 to 2 GeV^{2}, obtained from Jefferson Lab Hall A experiment E07-007. The Rosenbluth technique is used to separate the longitudinal and transverse responses. Results demonstrate that the cross section is dominated by its transverse component and, thus, is far from the asymptotic limit predicted by perturbative quantum chromodynamics. Nonetheless, an indication of a nonzero longitudinal contribution is provided by the measured interference term σ_{LT}. Results are compared with several models based on the leading-twist approach of generalized parton distributions (GPDs). In particular, a fair agreement is obtained with models in which the scattering amplitude includes convolution terms of chiral-odd (transversity) GPDs of the nucleon with the twist-3 pion distribution amplitude. This experiment, together with previous extensive unseparated measurements, provides strong support to the exciting idea that transversity GPDs can be accessed via neutral pion electroproduction in the high-Q^{2} regime.

Measurements of parity-violating asymmetries in electron-deuteron scattering in the nucleon resonance region.

We report on parity-violating asymmetries in the nucleon resonance region measured using inclusive inelastic scattering of 5-6 GeV longitudinally polarized electrons off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the Δ(1232). They provide a verification of quark-hadron duality-the equivalence of the quark- and hadron-based pictures of the nucleon-at the (10-15)% level in this electroweak observable, which is dominated by contributions from the nucleon electroweak γZ interference structure functions. In addition, the results provide constraints on nucleon resonance models relevant for calculating background corrections to elastic parity-violating electron scattering measurements.

New precision limit on the strange vector form factors of the proton.

The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV2 and beam energy E(b) = 3.48 GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.

Tensor correlations measured in 3He(e,e' pp)n.

We have measured the 3He(e,e' pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs by using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum p(tot). For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low p(tot) and rises to approximately 0.5 at large p(tot). This shows the dominance of tensor over central correlations at this relative momentum.

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.

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.

Compton-scattering cross section on the proton at high momentum transfer.

Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s=5-11 and -t=2-7 GeV2 with a statistical accuracy of a few percent. The scaling power for the s dependence of the cross section at fixed center-of-mass angle was found to be 8.0+/-0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.

Measurements of the proton elastic-form-factor ratio mu pG p E/G p M at low momentum transfer.

High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected.

Deeply virtual compton scattering off the neutron.

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

Regulation of the early expression of the Xenopus nodal-related 1 gene, Xnr1.

The Xenopus nodal related-1 (Xnr1) gene has a complex expression pattern in embryos, with two temporal phases. In the first phase, transcripts are first detected in perinuclear sites in the vegetal region of the blastula. During gastrulation, this expression disappears and transcripts become localised to the dorsal marginal zone. Expression stops and then restarts in a second phase at neurula and tailbud stages, firstly in two symmetric patches near the posterior end of the notochord, and then asymmetrically in a large domain in the left lateral plate mesoderm. In this study, we have investigated the regulation of the early phase of expression of Xnr1. We show that the T-box transcription factor VegT can induce Xnr1. It had previously been shown that Xnr1 can induce VegT in ectoderm cells and we show that the early expression of Xnr1 is regulated by an autoregulatory loop. By inspection of the Xnr1 promoter sequence, we have identified two non-palindromic T-box-binding sites, which are 10 bp apart. Using mutational analysis, we have shown that these elements are required for the VegT induction of Xnr1. The Xnr1 promoter shows striking homologies with the Xnr3 promoter. In particular, two elements that are required for Wnt signaling are conserved between these two promoters, but the two T-box sites are not conserved, and Xnr3 is not induced by VegT. A region of the promoter containing the T-box sites and the Wnt sites is sufficient to drive expression of a reporter gene in a dorsal domain in transgenic Xenopus at the gastrula stage. We show that this pattern of expression of the transgene in gastrulae is not dependent on the T-box sites.

Expression pattern of a novel hyaluronidase during Xenopus embryogenesis.

We have isolated a cDNA encoding a novel hyaluronidase, which is expressed during embryogenesis. The encoded protein was expressed as a fusion polypeptide with glutathione S-transferase, and the affinity-purified fusion protein was shown to possess hyaluronidase activity with a pH optimum about pH 4.0. The expression of the XEH1 gene was analysed by in situ hybridization, and was first apparent in scattered cells in a broad ventral region of late gastrula embryos. As development proceeded through to tailbud stages, the domain of expression became progressively more restricted, eventually being located in the developing liver rudiment near the primary hepatic cavity. The results reveal the dynamic regulation of the contrasting activities of hyaluronan synthesis and degradation during early morphogenetic movements.

Psychiatric intensive care in acute psychosis.

We have reviewed the development of psychiatric intensive care, focusing on organizational factors and the causes of psychiatric violence, suggesting guidelines for rapid tranquillization. The economics of running a psychiatric intensive care unit were subjected to an analysis of fixed, semi-fixed and variable costs. Variable costs (treatment and patient numbers) were shown to be more open to manipulation and possible cost savings.

Similar properties of fetal and adult amine transporters in the rat brain.

A variety of drug classes, including psychomotor stimulants and antidepressants, interact with monoamine transporters in order to exert their effects. Although these transporters have been extensively characterized in the adult brain, little is known about uptake mechanisms in the fetal system. High affinity dopamine (DA) and serotonin (5-HT) uptake in the striatum and frontal cortex, respectively, were examined in rat fetuses (embryonic day 20; E-20). These results were then compared to uptake in adult rat synaptosomal preparations of the same regions. The data indicate that the fetal (E-20) uptake mechanism is sodium-dependent. Furthermore, the potency of various agents to inhibit transporter function was assessed. These drugs produced a concentration-dependent inhibition of uptake, and the resulting IC50 values were not significantly different from those obtained in the adult preparations. Our results provide evidence that the affinity of monoamine uptake inhibitors for fetal (E-20) DA and 5-HT transporters is similar to that observed with adult transporters. This observation has broad implications when considering neuronal development and in utero exposure to drugs that exert their effects through these transporters.

A "biofeedback" approach to the treatment of chronic polydipsia.

A novel behavioral method is described for the treatment of psychogenic polydipsia in a patient suffering from chronic schizophrenia. The patient was given feedback on serum sodium concentration, likely physical consequences, and the value of reducing fluid intake. An ABAB single-case design was used, with changes in sodium concentration (charted by the patient during the treatment phases) as the dependent variable. The patient showed substantially increased sodium concentration, which was maintained despite the withdrawal of feedback. This behavioral method appears promising in settings where restriction of fluid intake is not practical or ethical.

Differing neurotoxic potencies of methamphetamine, mazindol, and cocaine in mesencephalic cultures.

The potent reinforcing effects of methamphetamine and cocaine are thought to be mediated by their interactions with CNS dopamine neurons. Both stimulants share the ability to block dopamine uptake potently, and methamphetamine can release cytoplasmic dopamine as well. There is also abundant evidence demonstrating the neurotoxic effects of methamphetamine. There are, however, limited studies that attempt to discern the neurotoxic mechanisms of these agents. The purpose of the present study was to characterize and compare the chronic in vitro effects of methamphetamine, cocaine, and the dopamine uptake blocker, mazindol, on cultured fetal mesencephalic dopamine neurons. Our studies examined biochemical mechanisms to evaluate the contribution of reuptake blockade versus release of dopamine. Using a dispersed cell preparation of fetal mesencephalon, cultures were treated for 5 days with the three uptake blockers. Dopamine function was assessed by measuring high-affinity [3H]dopamine uptake and by examining cultures for the presence of tyrosine hydroxylase-immunopositive neurons. Nonspecific neurotoxicity was assessed by staining for neuron-specific enolase and measuring lactate dehydrogenase activity. The results indicate that repeated administration of high concentrations of methamphetamine (10(-4) and 10(-3) M) caused a generalized neurotoxicity whereas the effects of 10(-5) M methamphetamine appeared to be specific to dopamine cells. Likewise, treatment of the cultures with mazindol (10(-6) M) resulted in reduced dopamine uptake while not significantly affecting neuron-specific enolase or tyrosine hydroxylase immunostaining. On the other hand, repeated exposure to cocaine (10(-5) and 10(-4) M) did not alter dopaminergic function in these cultures. The different mechanisms of action of these stimulants may explain the differences in neurotoxic potency of these compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term cocaine administration is not neurotoxic to cultured fetal mesencephalic dopamine neurons.

The psychostimulants cocaine and methamphetamine produce their euphoric effects through an interaction with the mesolimbic dopamine system. Methamphetamine, unlike cocaine, has been shown to be neurotoxic to both dopaminergic and serotonergic systems. We have previously determined that a 6 day exposure to methamphetamine causes neuronal damage to tyrosine hydroxylase-immunopositive cells in our tissue culture model of the mesencephalon. Over the same exposure period, cocaine neither impaired neuronal function nor altered dopamine cell survival. To test whether a longer exposure period to cocaine would alter dopamine function, we added cocaine (100 microM) to the cultures once daily for either 8 or 11 days and examined changes in dopamine uptake, cell survival and morphology 24 h after the last administration. Cocaine did not produce any signs of neurotoxicity in the mesencephalic cultures.

'Ecstasy' psychosis and flashbacks.

We report three cases of flashbacks and one case of recurrent psychosis experienced by three MDMA users. We draw the attention of clinicians to the combination of adverse effects observed with this drug of abuse and to the advisability of prolonged treatment should they occur.

Douglas House. Seven years' experience of a community hostel ward.

Of 24 residents of a ten-bed, community-based hostel ward suffering chronic psychiatric illness, nine have been resettled in the community, with four more expected to follow them. Five residents have made Douglas House their home but another six have manifested behavioural disturbance necessitating return to hospital wards. We found community discharge to be associated with illnesses having good prognostic features, while organic illness militated against such placement. Indicators of a prior history of behavioural disturbance seem to predict difficulties in managing a patient in this environment.