1,123 research outputs found
Multiple packets of neutral molecules revolving for over a mile
The level of control that one has over neutral molecules in beams dictates
their possible applications. Here we experimentally demonstrate that
state-selected, neutral molecules can be kept together in a few mm long packet
for a distance of over one mile. This is accomplished in a circular arrangement
of 40 straight electrostatic hexapoles through which the molecules propagate
over 1000 times. Up to 19 packets of molecules have simultaneously been stored
in this ring structure. This brings the realization of a molecular low-energy
collider within reach
Typing Supernova Remnants Using X-ray Line Emission Morphologies
We present a new observational method to type the explosions of young
supernova remnants (SNRs). By measuring the morphology of the Chandra X-ray
line emission in seventeen Galactic and Large Magellanic Cloud SNRs with a
multipole expansion analysis (using power ratios), we find that the
core-collapse SNRs are statistically more asymmetric than the Type Ia SNRs. We
show that the two classes of supernovae can be separated naturally using this
technique because X-ray line morphologies reflect the distinct explosion
mechanisms and structure of the circumstellar material. These findings are
consistent with recent spectropolarimetry results showing that core-collapse
SNe are intrinsically more asymmetric.Comment: 4 pages, 1 figure, accepted for publication in ApJ
High accuracy theoretical investigations of CaF, SrF, and BaF and implications for laser-cooling
The NL-eEDM collaboration is building an experimental setup to search for the
permanent electric dipole moment of the electron in a slow beam of cold barium
fluoride molecules [Eur. Phys. J. D, 72, 197 (2018)]. Knowledge of molecular
properties of BaF is thus needed to plan the measurements and in particular to
determine an optimal laser-cooling scheme. Accurate and reliable theoretical
predictions of these properties require incorporation of both high-order
correlation and relativistic effects in the calculations. In this work
theoretical investigations of the ground and the lowest excited states of BaF
and its lighter homologues, CaF and SrF, are carried out in the framework of
the relativistic Fock-space coupled cluster (FSCC) and multireference
configuration interaction (MRCI) methods. Using the calculated molecular
properties, we determine the Franck-Condon factors (FCFs) for the transition, which was successfully used for
cooling CaF and SrF and is now considered for BaF. For all three species, the
FCFs are found to be highly diagonal. Calculations are also performed for the
transition recently
exploited for laser-cooling of CaF; it is shown that this transition is not
suitable for laser-cooling of BaF, due to the non-diagonal nature of the FCFs
in this system. Special attention is given to the properties of the
state, which in the case of BaF causes a leak channel, in contrast
to CaF and SrF species where this state is energetically above the excited
states used in laser-cooling. We also present the dipole moments of the ground
and the excited states of the three molecules and the transition dipole moments
(TDMs) between the different states.Comment: Minor changes; The following article has been submitted to the
Journal of Chemical Physics. After it is published, it will be found at
https://publishing.aip.org/resources/librarians/products/journals
The Bridgwater Infant Welfare Centre, 1922-1939: from an authoritarian concern with 'welfare mothers' to a more inclusive community health project?
The infant welfare movement in Britain has received considerable scholarly attention but continues to generate controversy and debate. Many of the services began with nineteenth-century voluntary initiative but were later developed by local authorities. Critics have drawn attention to the limitations of such provision; arguing that it was predicated on unattractive assumptions about class and gender roles. Under this interpretation working-class mothers were viewed with suspicion and targeted for advice aimed at inculcating middle-class standards of childcare and housekeeping. This paper accepts that there was an authoritarian character to much of the early welfare work but suggests that over time this gave way to more inclusive approaches that sought to provide clients with the services that met their real rather than assumed needs. This paper reviews the recent historiography, develops an overview of national trends, and then takes a detailed look at the Bridgwater Infant Welfare Centre. The case study benefi ts from unusually comprehensive records and, by drawing on evidence from a small Somerset town, adds to our understanding of infant welfare work that has previously been developed from research on major urban centres.Wellcome Trust Fellowshi
Six Years of Chandra Observations of Supernova Remnants
We present a review of the first six years of Chandra X-ray Observatory
observations of supernova remnants. From the official "first-light" observation
of Cassiopeia A that revealed for the first time the compact remnant of the
explosion, to the recent million-second spectrally-resolved observation that
revealed new details of the stellar composition and dynamics of the original
explosion, Chandra observations have provided new insights into the supernova
phenomenon. We present an admittedly biased overview of six years of these
observations, highlighting new discoveries made possible by Chandra's unique
capabilities.Comment: 82 pages, 28 figures, for the book Astrophysics Update
A brief history of contact in fostering and adoption:Practice and power, and the coming of the mobile phone
Design and Initial Performance of the Prototype for the BEACON Instrument for Detection of Ultrahigh Energy Particles
The Beamforming Elevated Array for COsmic Neutrinos (BEACON) is a planned
neutrino telescope designed to detect radio emission from upgoing air showers
generated by ultrahigh energy tau neutrino interactions in the Earth. This
detection mechanism provides a measurement of the tau flux of cosmic neutrinos.
We have installed an 8-channel prototype instrument at high elevation at
Barcroft Field Station, which has been running since 2018, and consists of 4
dual-polarized antennas sensitive between 30-80 MHz, whose signals are
filtered, amplified, digitized, and saved to disk using a custom data
acquisition system (DAQ). The BEACON prototype is at high elevation to maximize
effective volume and uses a directional beamforming trigger to improve
rejection of anthropogenic background noise at the trigger level. Here we
discuss the design, construction, and calibration of the BEACON prototype
instrument. We also discuss the radio frequency environment observed by the
instrument, and categorize the types of events seen by the instrument,
including a likely cosmic ray candidate event.Comment: 21 pages, 20 figure
Mammographic screening for young women with a family history of breast cancer: knowledge and views of those at risk
Although the effectiveness of mammography for women under the age of 50 years with a family history of breast cancer (FHBC) has not yet been proven, annual screening is being offered to these women to manage breast cancer risk. This study investigates women's awareness and interpretation of their familial risk and knowledge and views about mammographic screening. A total of 2231 women from 21 familial/breast/genetics centres who were assessed as moderate risk (17–30% lifetime risk) or high risk (>30% lifetime risk) completed a questionnaire before their mammographic screening appointment. Most women (70%) believed they were likely, very likely or definitely going to develop breast cancer in their lifetime. Almost all women (97%) understood that the purpose of mammographic screening was to allow the early detection of breast cancer. However, 20% believed that a normal mammogram result meant there was definitely no breast cancer present, and only 4% understood that screening has not been proven to save lives in women under the age of 50 years. Women held positive views on mammography but did not appear to be well informed about the potential disadvantages. These findings suggest that further attention should be paid to improving information provision to women with an FHBC being offered routine screening
Validation of ACE and OSIRIS ozone and NO2 measurements using ground-based instruments at 80 degrees N
The Optical Spectrograph and Infra-Red Imager System (OSIRIS) and the Atmospheric Chemistry Experiment (ACE) have been taking measurements from space since 2001 and 2003, respectively. This paper presents intercomparisons between ozone and NO2 measured by the ACE and OSIRIS satellite instruments and by ground-based instruments at the Polar Environment Atmospheric Research Laboratory (PEARL), which is located at Eureka, Canada (80A degrees N, 86A degrees W) and is operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC). The ground-based instruments included in this study are four zenith-sky differential optical absorption spectroscopy (DOAS) instruments, one Bruker Fourier transform infrared spectrometer (FTIR) and four Brewer spectrophotometers. Ozone total columns measured by the DOAS instruments were retrieved using new Network for the Detection of Atmospheric Composition Change (NDACC) guidelines and agree to within 3.2%. The DOAS ozone columns agree with the Brewer spectrophotometers with mean relative differences that are smaller than 1.5%. This suggests that for these instruments the new NDACC data guidelines were successful in producing a homogenous and accurate ozone dataset at 80A degrees N. Satellite 14-52 km ozone and 17-40 km NO2 partial columns within 500 km of PEARL were calculated for ACE-FTS Version 2.2 (v2.2) plus updates, ACE-FTS v3.0, ACE-MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) v1.2 and OSIRIS SaskMART v5.0x ozone and Optimal Estimation v3.0 NO2 data products. The new ACE-FTS v3.0 and the validated ACE-FTS v2.2 partial columns are nearly identical, with mean relative differences of 0.0 +/- 0.2% and -0.2 +/- 0.1% for v2.2 minus v3.0 ozone and NO2, respectively. Ozone columns were constructed from 14-52 km satellite and 0-14 km ozonesonde partial columns and compared with the ground-based total column measurements. The satellite-plus-sonde measurements agree with the ground-based ozone total columns with mean relative differences of 0.1-7.3%. For NO2, partial columns from 17 km upward were scaled to noon using a photochemical model. Mean relative differences between OSIRIS, ACE-FTS and ground-based NO2 measurements do not exceed 20%. ACE-MAESTRO measures more NO2 than the other instruments, with mean relative differences of 25-52%. Seasonal variation in the differences between NO2 partial columns is observed, suggesting that there are systematic errors in the measurements and/or the photochemical model corrections. For ozone spring-time measurements, additional coincidence criteria based on stratospheric temperature and the location of the polar vortex were found to improve agreement between some of the instruments. For ACE-FTS v2.2 minus Bruker FTIR, the 2007-2009 spring-time mean relative difference improved from -5.0 +/- 0.4% to -3.1 +/- 0.8% with the dynamical selection criteria. This was the largest improvement, likely because both instruments measure direct sunlight and therefore have well-characterized lines-of-sight compared with scattered sunlight measurements. For NO2, the addition of a +/- 1A degrees latitude coincidence criterion improved spring-time intercomparison results, likely due to the sharp latitudinal gradient of NO2 during polar sunrise. The differences between satellite and ground-based measurements do not show any obvious trends over the missions, indicating that both the ACE and OSIRIS instruments continue to perform well
Progress report no. 2
Statement of responsibility on title-page reads: Editors: I.A. Forbes, M.J. Driscoll, N.C. Rasmussen, D.D. Lanning and I. Kaplan; Contributors: S.T. Brewer, G.J. Brown, P.DeLaquil, III, M.J. Driscoll, I.A. Forbes, C.W. Forsberg, E.P. Gyftopoulos, P.L. Hendrick, C.S. Kang, I. Kaplan, J.L. Klucar, D.D. Lanning, T.C. Leung, E.A. Mason, N.R. Ortiz, N.A. Passman, N.C. Rasmussen, I.C. Rickard, V.C. Rogers, G.E. Sullivan, A.T. Supple, and C. P. TzanosIncludes bibliographical referencesProgress report; June 30, 1971U.S. Atomic Energy Commission contract AT(11-1)306
- …