486 research outputs found
Self-steepening of light pulses
Self-steepening of light pulses due to propagation in medium with intensity-dependent index of refractio
Cold guided beams of water isotopologs
Electrostatic velocity filtering and guiding is an established technique to
produce high fluxes of cold polar molecules. In this paper we clarify different
aspects of this technique by comparing experiments to detailed calculations. In
the experiment, we produce cold guided beams of the three water isotopologs
H2O, D2O and HDO. Their different rotational constants and orientations of
electric dipole moments lead to remarkably different Stark shift properties,
despite the molecules being very similar in a chemical sense. Therefore, the
signals of the guided water isotopologs differ on an absolute scale and also
exhibit characteristic electrode voltage dependencies. We find excellent
agreement between the relative guided fractions and voltage dependencies of the
investigated isotopologs and predictions made by our theoretical model of
electrostatic velocity filtering.Comment: 14 pages, 13 figures; small changes to the text, updated reference
Elevated dry-season malaria prevalence associated with fine-scale spatial patterns of environmental risk: a case–control study of children in rural Malawi
Abstract
Background
Understanding the role of local environmental risk factors for malaria in holo-endemic, poverty-stricken settings will be critical to more effectively implement- interventions aimed at eventual elimination. Household-level environmental drivers of malaria risk during the dry season were investigated in rural southern Malawi among children < five years old in two neighbouring rural Traditional Authority (TA) regions dominated by small-scale agriculture.
Methods
Ten villages were randomly selected from TA Sitola (n = 6) and Nsamala (n = 4). Within each village, during June to August 2011, a census was conducted of all households with children under-five and recorded their locations with a geographic position system (GPS) device. At each participating house, a nurse administered a malaria rapid diagnostic test (RDT) to children under five years of age, and a questionnaire to parents. Environmental data were collected for each house, including land cover within 50-m radius. Variables found to be significantly associated with P. falciparum infection status in bivariate analysis were included in generalized linear models, including multivariate logistic regression (MLR) and multi-level multivariate logistic regression (MLLR). Spatial clustering of RDT status, environmental factors, and Pearson residuals from MLR and MLLR were analysed using the Getis-Ord Gi* statistic.
Results
Of 390 children enrolled from six villages in Sitola (n = 162) and four villages in Nsamala (n = 228), 45.6% tested positive (n = 178) for Plasmodium infection by RDT. The MLLR modelled the statistical relationship of Plasmodium positives and household proximity to agriculture ( 2.58, p < 0.01) predominantly within TA Sitola, while residuals from MLLR showed no such clustering.
Conclusion
This study provides evidence for significant, dry-season heterogeneity of malaria prevalence strongly linked to peridomestic land use, and particularly of elevated risk associated with nearby crop production.http://deepblue.lib.umich.edu/bitstream/2027.42/112703/1/12936_2013_Article_3017.pd
The Hyperfine Molecular Hubbard Hamiltonian
An ultracold gas of heteronuclear alkali dimer molecules with hyperfine
structure loaded into a one-dimensional optical lattice is investigated. The
\emph{Hyperfine Molecular Hubbard Hamiltonian} (HMHH), an effective low-energy
lattice Hamiltonian, is derived from first principles. The large permanent
electric dipole moment of these molecules gives rise to long range
dipole-dipole forces in a DC electric field and allows for transitions between
rotational states in an AC microwave field. Additionally, a strong magnetic
field can be used to control the hyperfine degrees of freedom independently of
the rotational degrees of freedom. By tuning the angle between the DC electric
and magnetic fields and the strength of the AC field it is possible to control
the number of internal states involved in the dynamics as well as the degree of
correlation between the spatial and internal degrees of freedom. The HMHH's
unique features have direct experimental consequences such as quantum
dephasing, tunable complexity, and the dependence of the phase diagram on the
molecular state
Electrostatic extraction of cold molecules from a cryogenic reservoir
We present a method which delivers a continuous, high-density beam of slow
and internally cold polar molecules. In our source, warm molecules are first
cooled by collisions with a cryogenic helium buffer gas. Cold molecules are
then extracted by means of an electrostatic quadrupole guide. For ND the
source produces fluxes up to molecules/s with
peak densities up to molecules/cm. For
HCO the population of rovibrational states is monitored by depletion
spectroscopy, resulting in single-state populations up to .Comment: 4 pages, 4 figures, changes to the text, updated figures and
reference
Surface temperature measurements using a thin film thermal array
A thin film device was designed and fabricated to measure surface temperatures. An array of eight integrated thermal sensors are mounted on a 0.002 inch (0.05 mm) Kapton film and multiplexed to obtain an area thermal measurement. The device was tested on a flat plate airfoil and demonstrated a temperature variation of 0.55 C maximum and 0.05 C minimum compared to embedded thermocouples. Future improvements are also discussed
On spin-rotation contribution to nuclear spin conversion in C_{3v}-symmetry molecules. Application to CH_3F
The symmetrized contribution of E-type spin-rotation interaction to
conversion between spin modifications of E- and A_1-types in molecules with
C_{3v}-symmetry is considered. Using the high-J descending of collisional
broadening for accidental rotational resonances between these spin
modifications, it was possible to co-ordinate the theoretical description of
the conversion with (updated) experimental data for two carbon-substituted
isotopes of fluoromethane. As a result, both E-type spin-rotation constants are
obtained. They are roughly one and a half times more than the corresponding
constants for (deutero)methane.Comment: 13 pages with single-spacing, REVTeX, no figures, accepted for
publication in <J. Phys. B
State-to-State Differential and Relative Integral Cross Sections for Rotationally Inelastic Scattering of H2O by Hydrogen
State-to-state differential cross sections (DCSs) for rotationally inelastic
scattering of H2O by H2 have been measured at 71.2 meV (574 cm-1) and 44.8 meV
(361 cm-1) collision energy using crossed molecular beams combined with
velocity map imaging. A molecular beam containing variable compositions of the
(J = 0, 1, 2) rotational states of hydrogen collides with a molecular beam of
argon seeded with water vapor that is cooled by supersonic expansion to its
lowest para or ortho rotational levels (JKaKc= 000 and 101, respectively).
Angular speed distributions of fully specified rotationally excited final
states are obtained using velocity map imaging. Relative integral cross
sections are obtained by integrating the DCSs taken with the same experimental
conditions. Experimental state-specific DCSs are compared with predictions from
fully quantum scattering calculations on the most complete H2O-H2 potential
energy surface. Comparison of relative total cross sections and state-specific
DCSs show excellent agreement with theory in almost all detailsComment: 46 page
Star Formation in M51 Triggered by Galaxy Interaction
We have mapped the inner 360'' regions of M51 in the 158micron [CII] line at
55'' spatial resolution using the Far-infrared Imaging Fabry-Perot
Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO). The emission is
peaked at the nucleus, but is detectable over the entire region mapped, which
covers much of the optical disk of the galaxy. There are also two strong
secondary peaks at ~43% to 70% of the nuclear value located roughly 120'' to
the north-east, and south-west of the nucleus. These secondary peaks are at the
same distance from the nucleus as the corotation radius of the density wave
pattern. The density wave also terminates at this location, and the outlying
spiral structure is attributed to material clumping due to the interaction
between M51 and NGC5195. This orbit crowding results in cloud-cloud collisions,
stimulating star formation, that we see as enhanced [CII] line emission. The
[CII] emission at the peaks originates mainly from photodissociation regions
(PDRs) formed on the surfaces of molecular clouds that are exposed to OB
starlight, so that these [CII] peaks trace star formation peaks in M51. The
total mass of [CII] emitting photodissociated gas is ~2.6x10^{8} M_{sun}, or
about 2% of the molecular gas as estimated from its CO(1-0) line emission. At
the peak [CII] positions, the PDR gas mass to total gas mass fraction is
somewhat higher, 3-17%, and at the secondary peaks the mass fraction of the
[CII] emitting photodissociated gas can be as high as 72% of the molecular
mass.... (continued)Comment: 14 pages, 6 figures, Accepted in ApJ (for higher resolution figures
contact the author
Theory of nuclear spin conversion in ethylene
First theoretical analysis of the nuclear spin conversion in ethylene
molecules (13^CCH4) has been performed. The conversion rate was found equal
approx. 3x10^{-4} 1/s*Torr, which is in qualitative agreement with the recently
obtained experimental value. It was shown that the ortho-para mixing in 13^CCH4
is dominated by the spin-rotation coupling. Mixing of only two pairs of
ortho-para levels were found to contribute significantly to the spin
conversion.Comment: 20 pages, 5 eps figure
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