Inclusive quasielastic electron scattering on 6^6He: a probe of the halo structure

We investigate inclusive electron scattering reactions on two-neutron halo nuclei in the quasielastic region. Expressions for the cross section and structure functions are given assuming that the halo nucleus can be described as a three-body system (${core}+n+n$). The method is applied to $^6$He. We compute cross sections and structure functions, and investigate the kinematic conditions for which the observables are determined either by $\alpha$-knockout or by halo neutron-knockout. The optimal kinematical domain to disantangle the momentum distributions of the various components of the three--body system ($q \lesssim 200$ MeV/c and $\omega < q^2/2M_N + 20$ MeV) are explored.Comment: 10 pages, 3 figures. Physics Letters B, in pres

Electron scattering on two-neutron halo nuclei: The case of 6^6He

The formalism to describe electron scattering reactions on two-neutron halo nuclei is developed. The halo nucleus is described as a three-body system (core+n+n), and the wave function is obtained by solving the Faddeev equations in coordinate space. We discuss elastic and quasielastic scattering using the impulse approximation to describe the reaction mechanism. We apply the method to investigate the case of electron scattering on $^6$He. Spectral functions, response functions, and differential cross sections are calculated for both neutron knockout and $\alpha$ knockout by the electron.Comment: 17 pages, figures include

Cross sections for Coulomb and nuclear breakup of three-body halo nuclei

All possible dissociation cross sections for the loosely bound three-body halo nuclei $^6$He (n+n+$\alpha$) and $^{11}$Li (n+n+$^{9}$Li) are computed as functions of target and beam energy. Both Coulomb and nuclear interactions are included in the same theoretical framework. The measurements agree with the calculations for energies above 100 Mev/nucleon. The largest cross sections correspond to final states with zero or three particles for heavy and with two neutrons for light targets.Comment: 5 pages, 3 figures, revte

Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions

Momentum distributions of particles from nuclear break-up of fast three-body halos are calculated consistently, and applied to $^{11}$Li. The same two-body interactions between the three particles are used to calculate the ground state structure and the final state of the reaction processes. We reproduce the available momentum distributions from $^{11}$Li fragmentation, together with the size and energy of $^{11}$Li, with a neutron-core relative state containing a $p$-state admixture of 20\%-30\%. The available fragmentation data strongly suggest an $s$-state in $^{10}$Li at about 50 keV, and indicate a $p$-state around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file attached at the end of the LaTeX file). To be published in Phys. Rev.

Age-Related Changes in the Epithelial and Stromal Compartments of the Mammary Gland in Normocalcemic Mice Lacking the Vitamin D3 Receptor

The vitamin D3 receptor (VDR) serves as a negative growth regulator during mammary gland development via suppression of branching morphogenesis during puberty and modulation of differentiation and apoptosis during pregnancy, lactation and involution. To assess the role of the VDR in the aging mammary gland, we utilized 12, 14, and 16 month old VDR knockout (KO) and wild type (WT) mice for assessment of integrity of the epithelial and stromal compartments, steroid hormone levels and signaling pathways. Our data indicate that VDR ablation is associated with ductal ectasia of the primary mammary ducts, loss of secondary and tertiary ductal branches and atrophy of the mammary fat pad. In association with loss of the white adipose tissue compartment, smooth muscle actin staining is increased in glands from VDR KO mice, suggesting a change in the stromal microenviroment. Activation of caspase-3 and increased Bax expression in mammary tissue of VDR KO mice suggests that enhanced apoptosis may contribute to loss of ductal branching. These morphological changes in the glands of VDR KO mice are associated with ovarian failure and reduced serum 17β-estradiol. VDR KO mice also exhibit progressive loss of adipose tissue stores, hypoleptinemia and increased metabolic rate with age. These developmental studies indicate that, under normocalcemic conditions, loss of VDR signaling is associated with age-related estrogen deficiency, disruption of epithelial ductal branching, abnormal energy expenditure and atrophy of the mammary adipose compartment

Breakup Reactions of 11Li within a Three-Body Model

We use a three-body model to investigate breakup reactions of 11Li (n+n+9Li) on a light target. The interaction parameters are constrained by known properties of the two-body subsystems, the 11Li binding energy and fragmentation data. The remaining degrees of freedom are discussed. The projectile-target interactions are described by phenomenological optical potentials. The model predicts dependence on beam energy and target, differences between longitudinal and transverse momentum distributions and provides absolute values for all computed differential cross sections. We give an almost complete series of observables and compare with corresponding measurements. Remarkably good agreement is obtained. The relative neutron-9Li p-wave content is about 40%. A p-resonance, consistent with measurements at about 0.5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the momentum distributions are insensitive to target and beam energy with a tendency to increase towards lower energies. The transverse momentum distributions are broader than the longitudinal due to the diffraction process. The absolute values of the cross sections follow the neutron-target cross sections and increase strongly for beam energies decreasing below 100 MeV/u.Comment: 19 pages, 14 figures, RevTeX, psfig.st

The Pauli principle in a three-body cluster model and the momentum distributions after fragmentation of 6He and 11Li

We investigate two simple prescriptions to account for the Pauli principle in a three-body cluster model employing a new method based on an adiabatic hyperspherical expansion to solve the Faddeev equations in coordinate space. The resulting wave functions are computed and compared. They are furthermore tested on halo nuclei by calculations of momentum distributions and invariant mass spectra arising after fragmentation of fast $^6$He and $^{11}$Li in collisions with light targets. The prescriptions are very accurate and the available measured quantities are remarkably well reproduced when final state interactions are included.Comment: 18 pages, LaTex file, 15 postscript figures included using epsf.st

Culture change in elite sport performance teams: Examining and advancing effectiveness in the new era

Reflecting the importance of optimizing culture for elite teams, Fletcher and Arnold (2011) recently suggested the need for expertise in culture change. Acknowledging the dearth of literature on the specific process, however, the potential effectiveness of practitioners in this area is unknown. The present paper examines the activity's precise demands and the validity of understanding in sport psychology and organizational research to support its delivery. Recognizing that sport psychologists are being increasingly utilized by elite team management, initial evidence-based guidelines are presented. Finally, to stimulate the development of ecologically valid, practically meaningful knowledge, the paper identifies a number of future research directions

The effect of iron- and light-limitation on phytoplankton communities of deep chlorophyll maxima of the western Pacific Ocean

The deep chlorophyll maximum (DCM) is a widespread feature in most stratified, oligotrophic waters. In addition to their well-established importance for many surface phytoplankton communities, more recent evidence suggests that iron, light or co-limitation may also be important drivers for some DCM communities. To test this hypothesis, we describe the results from six grow-out experiments, four from the Equatorial Pacific Ocean (between 150°E and 140°W), one in Western Pacific Warm Pool (9°S, 170°E) and one in the middle of the Tasman Sea (36°S). Photosynthetic efficiency (Fv/Fm) and biomass response, including Chl a and phytoplankton community structure (pennate diatoms, photosynthetic eukaryotes, Synechococcus, Prochlorococcus, and major Prochlorococcus ecotypes), were assessed over five days in control, +Fe, +Light or +Fe +Light treatments. Photosynthetic efficiency did not change dramatically in any of the treatments at any of the locations, except at 0°N 140°W where the control and +Fe bottles had elevated efficiency relative to both +Light treatments. Except for some ecotypes of Prochlorococcus (eMIT9313 and eNATL2A), phytoplankton populations were most strongly limited by light in the DCM. Pennate diatoms and other photosynthetic eukaryotes showed the most enhancement with the addition of iron and light at some stations and may be co-limited, but no phytoplankton populations were enhanced by adding iron alone. Although the duration and magnitude of the responses varied depending on initial macronutrient concentrations, they were generally consistent across the locations sampled. These results suggest that light is the primary limiting resource of the DCM for this vast region, but that iron can play an important additive role in limiting phytoplankton populations in locations where flux to the DCM is reduced

Three-body halos. V. Computations of continuum spectra for Borromean nuclei

We solve the coordinate space Faddeev equations in the continuum. We employ hyperspherical coordinates and provide analytical expressions allowing easy computation of the effective potentials at distances much larger than the ranges of the interactions where only s-waves in the different Jacobi coordinates couple. Realistic computations are carried out for the Borromean halo nuclei 6He (n+n+\alpha) for J\pi = 0+-, 1+-, 2+- and 11Li (n+n+9Li) for (1/2)+-, (3/2)+-, (5/2)+-. Ground state properties, strength functions, Coulomb dissociation cross sections, phase shifts, complex S-matrix poles are computed and compared to available experimental data. We find enhancements of the strength functions at low energies and a number of low-lying S-matrix poles.Comment: 35 pages, 14 figure