Experimental and computational characterization of a modified GEC cell for dusty plasma experiments

A self-consistent fluid model developed for simulations of micro- gravity dusty plasma experiments has for the first time been used to model asymmetric dusty plasma experiments in a modified GEC reference cell with gravity. The numerical results are directly compared with experimental data and the experimentally determined dependence of global discharge parameters on the applied driving potential and neutral gas pressure is found to be well matched by the model. The local profiles important for dust particle transport are studied and compared with experimentally determined profiles. The radial forces in the midplane are presented for the different discharge settings. The differences between the results obtained in the modified GEC cell and the results first reported for the original GEC reference cell are pointed out

Extraction of electromagnetic neutron form factors through inclusive and exclusive polarized electron scattering on polarized 3He target

Inclusive 3He(e,e') and exclusive 3He(e,e'n) processes with polarized electrons and 3He have been theoretically analyzed and values for the magnetic and electric neutron form factors have been extracted. In both cases the form factor values agree well with the ones extracted from processes on the deuteron. Our results are based on Faddeev solutions, modern NN forces and partially on the incorporation of mesonic exchange currents.Comment: 28 pages, 29 Postscript figure

Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium

We report on a measurement of spin-momentum correlations in quasi-elastic scattering of longitudinally polarized electrons with an energy of 720 MeV from vector-polarized deuterium. The spin correlation parameter $A^V_{ed}$ was measured for the $^2 \vec{\rm H}(\vec e,e^\prime p)n$ reaction for missing momenta up to 350 MeV/$c$ at a four-momentum transfer squared of 0.21 (GeV/c)$^2$. The data give detailed information about the spin structure of the deuteron, and are in good agreement with the predictions of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment demonstrates in a most direct manner the effects of the D-state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. for publicatio

Spectral functions of isoscalar scalar and isovector electromagnetic form factors of the nucleon at two-loop order

We calculate the imaginary parts of the isoscalar scalar and isovector electromagnetic form factors of the nucleon up to two-loop order in chiral perturbation theory. Particular attention is paid on the correct behavior of Im $\sigma_N(t)$ and Im $G_{E,M}^V(t)$ at the two-pion threshold $t_0=4 m_\pi^2$ in connection with the non-relativistic 1/M-expansion. We recover the well-known strong enhancement near threshold originating from the nearby anomalous singularity at $t_c = 4m_\pi^2-m_\pi^4/M^2 = 3.98 m_\pi^2$. In the case of the scalar spectral function Im $\sigma_N(t)$ one finds a significant improvement in comparison to the lowest order one-loop result. Higher order $\pi\pi$-rescattering effects are however still necessary to close a remaining 20%-gap to the empirical scalar spectral function. The isovector electric and magnetic spectral functions Im $G_{E,M}^V(t)$ get additionally enhanced near threshold by the two-pion-loop contributions. After supplementing their two-loop results by a phenomenological $\rho$-meson exchange term one can reproduce the empirical isovector electric and magnetic spectral functions fairly well.Comment: 10 pages, 6 figures, submitted to Physical Review

A retrospective analysis of noise-induced hearing loss in the Dutch construction industry

Purpose Noise exposure is an important and highly prevalent occupational hazard in the construction industry. This study examines hearing threshold levels of a large population of Dutch construction workers and compares their hearing thresholds to those predicted by ISO-1999. Methods In this retrospective study, medical records of periodic occupational health examinations of 29,644 construction workers are analysed. Pure-tone audiometric thresholds of noise-exposed workers are compared to a non-exposed control group and to ISO-1999 predictions. Regression analyses are conducted to explore the relationship between hearing loss and noise intensity, noise exposure time and the use of hearing protection. Results Noise-exposed workers had greater hearing losses compared to their non-noise-exposed colleagues and to the reference population reported in ISO-1999. Noise exposure explained only a small proportion of hearing loss. When the daily noise exposure level rose from 80 dB(A) towards 96 dB(A), only a minor increase in hearing loss is shown. The relation of exposure time and hearing loss found was similar to ISO-1999 predictions when looking at durations of 10 years or more. For the first decade, the population medians show poorer hearing than predicted by ISO-1999. Discussion Duration of noise exposure was a better predictor than noise exposure levels, probably because of the limitations in noise exposure estimations. In this population, noise-induced hearing loss was already present at the beginning of employment and increased at the same rate as is predicted for longer exposure duration

Starting a Crossover Kidney Transplantation Program in The Netherlands: Ethical and Psychological Considerations

On April 15th, 2003, the first crossover kidney transplantation took place in The Netherlands. In September of the same year, a national database was established to facilitate kidney exchange between two donor-recipient couples. During 2004, kidneys from living donors will be exchanged between the seven university medical centers in The Netherlands. One of the conditions for successfully implementing this program was the need to address the ethical and psychologic implications involved. In this article we will discuss the ethical and psychologic considerations that are accompanying the practical preparations for the first Dutch crossover transplantation program. We identified five topics of interest: the influence of "donation by strangers" on the motivation and willingness of donor-patient couples, the issue of anonymity, the loss of the possibility of "medical excuses" for unwilling donors, the view that crossover is a first step to commercial organ trade, and the interference with existing organ donation programs. We concluded that whether viewed separately or in combination, these issues do not impede the efficient organization of a crossover program or raise worrying ethical issues. Key Words: Ethics, psychology, crossover transplantation, kidney exchange program. 2004;78: 194 -197) T he Netherlands has a population of 16 million. Approximately 375 to 425 kidneys per year are transplanted from cadaver donors. In addition to cadaver transplants, approximately 200 kidneys from living donors were transplanted during 2003. Although the growing number of available living donors helps prevent the waiting lists from growing further, there are not enough kidneys available to help the 1,300 patients already on the waiting list. After starting dialysis, kidney patients have an average waiting time of 4 years before a kidney becomes available. In the meantime, their health status declines. Currently, the mortality rate of patients on dialysis is approximately 20% per year (1). (Transplantation Living organ donation by family or friends offers an opportunity to reduce the long waiting lists. However, in a third of these cases, the transplantation cannot take place because of ABO incompatibility or donor-specific sensitization (2). A crossover transplantation program offers new hope. The program provides a lifesaving opportunity when a donor cannot give his or her kidney to his or her recipient. If another donor-recipient couple experiences the same problem, the kidneys can be exchanged. In South Korea, such a crossover kidney exchange program has been operating successfully for more than 10 years (3). The United States also has experience with "kidney swapping" (4). In Europe, however, crossover transplantations have been attempted only once in Switzerland, in Romania, and in Rotterdam. This conservative European attitude is in part explained by concerns surrounding the ethical and psychologic implications of crossover transplantation. When a crossover program was initiated in The Netherlands, it was agreed that these concerns should be addressed. A multidisciplinary research effort was conducted to determine the most prominent psychologic and ethical issues that surround crossover kidney exchange and to propose practical solutions. We identified five topics of interest: (1) the influence of "donation by strangers" on the motivation and willingness of donor-patient couples; (2) the issue of anonymity; (3) the loss of the possibility of "medical excuses" for unwilling donors; (4) the view that crossover might be the first step to commercial organ trade; and (5) the interference with existing organ donation programs. Next we describe these five topics in detail and suggest practical solutions. Living Organ Donation by Strangers When discussing the ethical and psychologic issues of a crossover transplantation program, a prominent issue is the possibility of a difference in motivation and willingness of kidney donors and recipients compared with the attitudes of those involved in a direct living donation program. At first glance, crossover donation between two couples is not significantly different from direct living kidney donation. The motivation of the donor is the same: helping a friend or a family member by giving a kidney. The result for the patient is equivalent as well: He or she receives the much needed organ. Furthermore, the medical impact for the four people involved is the same as for the two direct living kidney donors. Psychologically, however, it might matter for those involved whethe

A Measurement of the Electric Form Factor of the Neutron through d⃗(e⃗,e′n)p\vec{d}(\vec{e},e'n)p at Q2=0.5Q^2 = 0.5 (GeV/c)2^2

We report the first measurement of the neutron electric form factor $G_E^n$ via $\vec{d}(\vec{e},e'n)p$ using a solid polarized target. $G_E^n$ was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia, $^{15}$ND$_3$. The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility (TJNAF) in quasi free kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find $G_E^n = 0.04632\pm0.00616 (stat.) \pm0.00341 (syst.)$ at $Q^2 = 0.495$ (GeV/c)$^2$.Comment: Latex2e 5 pages, 3 figure