293 research outputs found
Energy-dependent relative charge transfer cross sections of Cs+ + Rb(5s, 5p)
Magneto optical trap recoil ion momentum spectroscopy is used to measure
energy-dependent charge exchange cross sections in the Cs+ + Rb(5s, 5p) system
over a range of projectile energies from 3.2 to 6.4 keV. The measurements are
kinematically complete and yield cross sections that are differential in
collision energy, scattering angle, and initial and final states
The Combined Effects of Pulsed Magnetic Radiation (Diapulse) and Chemotherapy on Tumor Bearing Mice. The Measurement of Rodent Palatal Explants as a Device for Measurement of the Biologic Effects of Nonionic Radiation (EMR)
Simultaneous treatment utilizing pulsed radiowave and cancer chemotherapy significantly extended the life span of mice with Lewis lung transplanted carcinoma. In comparison with nontreated controls, the combination of hydroxyurea and whole body nonionizing EM radiation (at 27.12 MHz) produced differential enhancement of longevity depending on hydroxyurea combined with highest power output achieved by pulsing the radiation 600 times per second; at a 3.9% duty cycle, peak watts = 975 produced the mean extension of life 67% greater than that of the group treated with hydroxyurea alone
The Effect of Multigrade Classes on Cognitive and non- Cognitive Skills. Causal Evidence Exploiting Minimum Class Size Rules in Italy
We analyse how schooling in multigrade classes affects the formation of student cognitive and non-cognitive skills. Our identification strategy is based on some institutional features of the Italian educational system establishing a minimum number of students per class. Classes that do not reach the minimum number of pupils are organized in multigrade classes. In addition, the Italian law also establishes a maximum number of students for multigrade classes, which implies that class size in multigrade classes is very similar to class size in small single grade classes with a number of students just above the minimum size. Using census data on 5th grade Italian students, we find that pupils in multigrade classrooms obtain worse test scores both in literacy and numeracy standardised tests compared to comparable pupils in single grade classroom. While the effect is small and not always statistically significant for the literacy score, we find a large and highly statistically significant effect on the numeracy score. We also find that pupils placed in multigrade classes tend to have a more external centred locus of control. Our results are robust to different specifications including controls for class size and a number of student and school characteristics
Measurement of the interaction strength in a Bose-Fermi mixture with 87Rb and 40K
A quantum degenerate, dilute gas mixture of bosonic and fermionic atoms was
produced using 87Rb and 40K. The onset of degeneracy was confirmed by observing
the spatial distribution of the gases after time-of-flight expansion. Further,
the magnitude of the interspecies scattering length between the doubly spin
polarized states of 87Rb and 40K, |a_RbK|, was determined from
cross-dimensional thermal relaxation. The uncertainty in this collision
measurement was greatly reduced by taking the ratio of interspecies and
intraspecies relaxation rates, yielding |a_RbK| = 250 +/- 30 a_0, which is a
lower value than what was reported in [M. Modugno et al., Phys. Rev. A 68,
043626 (2003)]. Using the value for |a_RbK| reported here, current T=0 theory
would predict a threshold for mechanical instability that is inconsistent with
the experimentally observed onset for sudden loss of fermions in [G. Modugno et
al., Science 297, 2240 (2002)].Comment: RevTeX4 + 4 eps figures; Replaced with published versio
A Concept for a High-Energy Gamma-ray Polarimeter
We present a concept for an imaging gamma-ray polarimeter operating from ~50
MeV to ~1 GeV. Such an instrument would be valuable for the study of
high-energy pulsars, active galactic nuclei, supernova remnants, and gamma-ray
bursts. The concept makes use of pixelized gas micro-well detectors, under
development at Goddard Space Flight Center, to record the electron-positron
tracks from pair-production events in a large gas volume. Pixelized micro-well
detectors have the potential to form large-volume 3-D track imagers with ~100
micron (rms) position resolution at moderate cost. The combination of high
spatial resolution and a continuous low-density gas medium permits many
thousands of measurements per radiation length, allowing the particle tracks to
be imaged accurately before multiple scattering masks their original
directions. The polarization of the incoming radiation may then be determined
from the azimuthal distribution of the electron-positron pairs. We have
performed Geant4 simulations of these processes to estimate the polarization
sensitivity of a simple telescope geometry at 100 MeV.Comment: 12 pages, 10 figures, to appear in Proc. SPIE 5165, "X-Ray and
Gamma-Ray Instrumentation for Astronomy XIII
Ion-lithium collision dynamics studied with an in-ring MOTReMi
We present a novel experimental tool allowing for kinematically complete
studies of break-up processes of laser-cooled atoms. This apparatus, the
'MOTReMi', is a combination of a magneto-optical trap (MOT) and a Reaction
Microscope (ReMi). Operated in an ion-storage ring, the new setup enables to
study the dynamics in swift ion-atom collisions on an unprecedented level of
precision and detail. In first experiments on collisions with 1.5 MeV/amu
O-Li the pure ionization of the valence electron as well as
ionization-excitation of the lithium target has been investigated
Coherent Population Trapping with Controlled Interparticle Interactions
We investigate Coherent Population Trapping in a strongly interacting
ultracold Rydberg gas. Despite the strong van der Waals interactions and
interparticle correlations, we observe the persistence of a resonance with
subnatural linewidth at the single-particle resonance frequency as we tune the
interaction strength. This narrow resonance cannot be understood within a
meanfield description of the strong Rydberg--Rydberg interactions. Instead, a
many-body density matrix approach, accounting for the dynamics of interparticle
correlations, is shown to reproduce the observed spectral features
Experimental determination of the Compton profile of C60 through binary encounter electron spectroscopy
The method of 0° electron spectroscopy was used to study binary encounter electrons resulting from hard collisions between 1.5 MeV/u C6+ ions and the electrons in a C60 vapor target. The Compton profile of C60 was then extracted from the electron spectra using an impulse approximation treatment. The experimental results are in excellent agreement with theoretical Compton profiles of C60. The C60 Compton profile is compared with that of atomic carbon, as well as those for graphite and diamond.Peer reviewe
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