Phys.Rev.Lett.86:2963-2966,2001 High-precision H(e,e'p)pi0 measurements at Q2=0.126 (GeV/c)2 are reported,
which allow the determination of quadrupole amplitudes in the gamma* N->Delta
transition; ...they simultaneously test the reliability of electroproduction
models. The derived quadrupole-to-dipole amplitude ratios, Rsm=(-6.5 +-
0.2{stat+sys} +- 2.5{mod}) % and Rem=(-2.1 +- 0.2{stat+sys} +- 2.0{mod}) %, are
dominated by model error. Previous Rsm and Rem results should be reconsidered
after the model uncertainties associated with the method of their extraction
are taken into account.
Large productivity gains have been observed in Chinese agriculture following the transition from collective farming to household contracting. Using a model of mutual monitoring in an egalitarian ...production team, the authors estimate that labor supervision absorbed about 10-20 percent of total labor time for a sample of Chinese agricultural teams during 1970-76. These agency costs are lower than comparable estimates derived from aggregate data. Copyright 1993 by University of Chicago Press.
Although 85% of HIV-positive adolescents reside in sub-Saharan Africa, little is known about the psychosocial and mental health factors affecting their daily well-being. Identifying these contextual ...variables is key to development of culturally appropriate and effective interventions for this understudied and high-risk population. The purpose of this study was to identify salient psychosocial and mental health challenges confronted by HIV-positive youth in a resource-poor Tanzanian setting. A total of 24 qualitative interviews were conducted with a convenience sample of adolescents aged 12-24 receiving outpatient HIV care at a medical center in Moshi, Tanzania. All interviews were audio-recorded, transcribed, and coded using thematic analysis. Psychosocial challenges identified included loss of one or more parents, chronic domestic abuse, financial stressors restricting access to medical care and education, and high levels of internalized and community stigma among peers and other social contacts. Over half of youth (56%) reported difficulties coming to terms with their HIV diagnosis and espoused related feelings of self-blame. These findings highlight the urgent need to develop culturally proficient programs aimed at helping adolescents cope with these manifold challenges. Results from this study guided the development of Sauti ya Vijana (The Voice of Youth), a 10-session group mental health intervention designed to address the psychosocial and mental health needs of HIV-positive Tanzanian youth.
Phys.Rev.C58:3205-3211,1998 The coincidence cross-section and the interference structure function, R_LT,
were measured for the 12C(e,e'p) 11B reaction at quasielastic kinematics and
central momentum ...transfer of q=400 MeV/c. The measurement was at an opening
angle of theta_pq=11 degrees, covering a range in missing energy of E_m = 0 to
65 MeV. The R_LT structure function is found to be consistent with zero for E_m
> 50 MeV, confirming an earlier study which indicated that R_L vanishes in this
region. The integrated strengths of the p- and s-shell are compared with a
Distorted Wave Impulse Approximation calculation. The s-shell strength and
shape are compared with a Hartree Fock-Random Phase Approximation calculation.
The DWIA calculation overestimates the cross sections for p- and s-shell proton
knockout as expected, but surprisingly agrees with the extracted R_LT value for
both shells. The HF-RPA calculation describes the data more consistently, which
may be due to the inclusion of 2-body currents in this calculation.
This paper examines the provision of campaign contributions made by economic interests to incumbents seeking reelection in the 1984, 1986, and 1988 California Assembly elections. The study tests ...whether the distribution of campaign contributions by specific industrial sectors corresponds to legislator possession of the policy property rights associated with membership on relevant Assembly standing committees. A nonparametric statistical model compares the distribution of campaign contributions from groups within a given industrial sector to members of relevant policy committees with the distribution of contributions from all other contributor classes. The empirical analysis confirms that committee assignments significantly affect the allocation of special interest resources in Assembly elections, substantiating the importance of institutional considerations in influencing special interest activity. Copyright 1998 by Kluwer Academic Publishers
Phys.Rev.Lett. 80 (1998) 452-455; Erratum-ibid. 82 (1999) 2221 Recoil proton polarization observables were measured for both the p($\vec
{\rm e}$,e$^\prime\vec{\rm p}\,$) and d($\vec {\rm ...e}$,e$^\prime\vec{\rm
p}\,)$n reactions at two values of Q$^2$ using a newly commissioned proton
Focal Plane Polarimeter at the M.I.T.-Bates Linear Accelerator Center. The
hydrogen and deuterium spin-dependent observables $D_{\ell\ell}$ and
$D_{{\ell}t}$, the induced polarization $P_n$ and the form factor ratio
$G^p_E/G^p_M$ were measured under identical kinematics. The deuterium and
hydrogen results are in good agreement with each other and with the plane-wave
impulse approximation (PWIA).
Phys. Rev. Lett. 80 (1998) 456-459 The first measurements of the induced proton polarization, P_n, for the 12C
(e,e'\vec{p}) reaction are reported. The experiment was performed at quasifree
...kinematics for energy and momentum transfer (\omega,q) \approx (294 MeV, 756
MeV/c) and sampled a recoil momentum range of 0-250 MeV/c. The induced
polarization arises from final-state interactions and for these kinematics is
dominated by the real part of the spin-orbit optical potential. The
distorted-wave impulse approximation provides good agreement with data for the
1p_{3/2} shell. The data for the continuum suggest that both the 1s_{1/2} shell
and underlying l > 1 configurations contribute.
Phys.Rev.Lett. 78 (1997) 3824-3827 We report the first measurement of the parity-violating asymmetry in elastic
electron scattering from the proton. The asymmetry depends on the neutral weak
magnetic ...form factor of the proton which contains new information on the
contribution of strange quark-antiquark pairs to the magnetic moment of the
proton. We obtain the value $G_M^Z= 0.34 \pm 0.09 \pm 0.04 \pm 0.05$ n.m. at
$Q^2=0.1$ (GeV/c)^2$.
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