421 research outputs found
Gas gain on single wire chambers filled with pure isobutane at low pressure
The gas gain of single-wire chambers filled with isobutane, with cell
cross-section 12x12 mm and wire diameters of 15, 25, 50 and 100 m, has
been measured at pressures ranging 12-92 Torr. Contrary to the experience at
atmospheric pressure, at very low pressures the gas gain on thick wires is
higher than that on thin wires at the same applied high voltage as was recently
shown. Bigger wire diameters should be used in wire chambers operating at very
low pressure if multiple scattering on wires is not an issue.Comment: 9 pages, 6 figure
High-Resolution Measurements of Intersystem Bands of Carbon Monoxide toward X Persei
In an echelle spectrum of X Per acquired with the Space Telescope Imaging
Spectrograph we have identified individual rotational lines of 11
triplet-singlet (intersystem) absorption bands of ^12CO. Four bands provide
first detections for interstellar clouds. From a comparison with the zeta Oph
sight line we find that X Per is obscured by a higher 12CO column density of
1.4 x 10^16 cm-2. Together with the high spectral resolution of 1.3 km s-1,
this allows (i) an improved measurement of previously published f-values for
seven bands, and (ii) an extraction of the first astrophysical oscillator
strengths for d-X (8-0), (9-0), and (10-0), as well as for e-X (12-0). The
^13CO d-X (12-0) band, previously suspected to exist toward zeta Oph, is now
readily resolved and modeled. Our derived intersystem f-values for ^12CO
include a few mild (leq 34%) disagreements with recent predictions from a
perturbation analysis calculated for the interstellar excitation temperature.
Overall, the comparison confirms the superiority of employing multiple singlet
levels in the calculations of mixing coefficients over previous single-level
predictions.Comment: 11 pages (incl. 1 figure). Accepted by ApJ Letter
FUSE Measurements of Interstellar Fluorine
The source of fluorine is not well understood, although core-collapse
supernovae, Wolf-Rayet stars, and asymptotic giant branch stars have been
suggested. A search for evidence of the nu process during Type II supernovae is
presented. Absorption from interstellar F I is seen in spectra of HD 208440 and
HD 209339A acquired with the Far Ultraviolet Spectroscopic Explorer. In order
to extract the column density for F I from the line at 954 A, absorption from
H2 has to be modeled and then removed. Our analysis indicates that for H2
column densities less than about 3 x 10^20 cm^-2, the amount of F I can be
determined from lambda 954. For these two sight lines, there is no clear
indication for enhanced F abundances resulting from the nu process in a region
shaped by past supernovae.Comment: 17 pages, 4 figures, accepted for publication in Ap
P17-01. HIV-specific immune responses induced by a single dose of HIV DNA vaccine in Rhesus macaques
Precision planar drift chambers and cradle for the TWIST muon decay spectrometer
To measure the muon decay parameters with high accuracy, we require an array
of precision drift detector layers whose relative position is known with very
high accuracy. This article describes the design, construction and performance
of these detectors in the TWIST (TRIUMF Weak Interaction Symmetry Test)
spectrometer.Comment: 44 pages, 16 Postscript figures, LaTeX2e, uses Elsevier class
elsart.cls, package graphicx, submitted to Nuclear Instruments & Methods in
Physics Researc
Measurement of two-halo neutron transfer reaction p(Li,Li)t at 3 MeV
The p(\nuc{11}{Li},\nuc{9}{Li})t reaction has been studied for the first time
at an incident energy of 3 MeV delivered by the new ISAC-2 facility at
TRIUMF. An active target detector MAYA, build at GANIL, was used for the
measurement. The differential cross sectionshave been determined for
transitions to the \nuc{9}{Li} ground andthe first excited states in a wide
range of scattering angles. Multistep transfer calculations using different
\nuc{11}{Li} model wave functions, shows that wave functions with strong
correlations between the halo neutrons are the most successful in reproducing
the observation.Comment: 6 pages, 3 figures, submitted to Physical Review Letter
Pseudogap temperature as a Widom line in doped Mott insulators
The pseudogap refers to an enigmatic state of matter with unusual physical
properties found below a characteristic temperature in hole-doped
high-temperature superconductors. Determining is critical for
understanding this state. Here we study the simplest model of correlated
electron systems, the Hubbard model, with cluster dynamical mean-field theory
to find out whether the pseudogap can occur solely because of strong coupling
physics and short nonlocal correlations. We find that the pseudogap
characteristic temperature is a sharp crossover between different
dynamical regimes along a line of thermodynamic anomalies that appears above a
first-order phase transition, the Widom line. The Widom line emanating from the
critical endpoint of a first-order transition is thus the organizing principle
for the pseudogap phase diagram of the cuprates. No additional broken symmetry
is necessary to explain the phenomenon. Broken symmetry states appear in the
pseudogap and not the other way around.Comment: 6 pages, 4 figures and supplementary information; published versio
Some discussions on functionalist housing and its economics in Romania by Lhe late 1950s and early 1960s
This paper proposes an analysis of the Romanian architectural practices in the late 1950's and early 1960's by considering the availability of financial resources. I premise that echoes of Moscow's approaches to the built environment overlapped the Bucharest politicians' priorities, whose lack of constancy in economic decision-making exacerbated itself as the urban construction programs advanced. From the Romanian authorities' point of view, therefore, raising the mass housing profitability could save important financial resources for other investments in heavy industry, while maintaining the appearance of a social state. Similarities between Soviet and Romanian modernist building projects suggested a coherent approach to housing throughout the bloc. However, this article will show that functionalist architectural modernism -cheap and fast to erect- also proved beneficial for Gheorghe Gheorghiu-Dej's economic plans, which questions urban construction projects' political agendas and the professional tensions between architects and economists. Therefore, investigating the functionalist architecture opens up several lines of inquiry: to what extent Nikita Khrushchev's housing program was transferred in Romania; the tortuous policies of the Romanian state's leadership in the field of housing as well as how local bureaucratic or professional actors appropriated, interpreted and adjusted such programs; and, the economic costs of the new functionalist approach to urban dwelling. In this way, this article reads the making of functionalist mass housing programs by the late 1950s to assess the Soviets' part in building the Romanian cities. To this end, the article contributes to the recent scholarly literature on multiple modernities
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