726 research outputs found
Effects of confinement on the permanent electric-dipole moment of Xe atoms in liquid Xe
Searches for permanent electric-dipole moments (EDM) of atoms provide
important constraints on competing extensions to the standard model of
elementary particles. Recently proposed experiment with liquid Xe [M.V.
Romalis and M.P. Ledbetter, Phys. Rev. Lett. \textbf{87}, 067601 (2001)] may
significantly improve present limits on the EDMs. To interpret experimental
data in terms of CP-violating sources, one must relate measured atomic EDM to
various model interactions via electronic-structure calculations. Here we study
density dependence of atomic EDMs. The analysis is carried out in the framework
of the cell model of the liquid coupled with relativistic atomic-structure
calculations. We find that compared to an isolated atom, the EDM of an atom of
liquid Xe is suppressed by about 40%
Atomic Parity Nonconservation: Electroweak Parameters and Nuclear Structure
There have been suggestions to measure atomic parity nonconservation (PNC)
along an isotopic chain, by taking ratios of observables in order to cancel
complicated atomic structure effects. Precise atomic PNC measurements could
make a significant contribution to tests of the Standard Model at the level of
one loop radiative corrections. However, the results also depend upon certain
features of nuclear structure, such as the spatial distribution of neutrons in
the nucleus. To examine the sensitivity to nuclear structure, we consider the
case of Pb isotopes using various recent relativistic and non-relativistic
nuclear model calculations. Contributions from nucleon internal weak structure
are included, but found to be fairly negligible. The spread among present
models in predicted sizes of nuclear structure effects may preclude using Pb
isotope ratios to test the Standard Model at better than a one percent level,
unless there are adequate independent tests of the nuclear models by various
alternative strong and electroweak nuclear probes. On the other hand,
sufficiently accurate atomic PNC experiments would provide a unique method to
measure neutron distributions in heavy nuclei.Comment: 44 pages, INT Preprint DOE/ER/40561-050-INT92-00-1
Statistical analysis of environmental variability within the CELSS breadboard project's biomass production chamber
Variability in the aerial and root environments of NASA's Breadboard Project's Biomass Production Chamber (BPC) was determined. Data from two lettuce and two potato growouts were utilized. One growout of each crop was conducted prior to separating the upper and lower chambers; the other was subsequent to separation. There were little or no differences in pH, EC, or solution temperature between the upper and lower chamber or within a chamber. Variation in the aerial environment within a chamber was two to three times greater than variation between chambers for air temperature, relative humidity, and PPF. High variability in air velocity, relative to tray position, was observed. Separating the BPC had no effect on PPF, air velocity, solution temperature, pH, or EC. Separation reduced the gradient in air temperature and relative humidity between the upper and lower chambers, but increased the variability within a chamber. Variation between upper and lower chambers was within 5 percent of environmental set-points and of little or no physiological significance. In contrast, the variability within a chamber limits the capability of the BPC to generate statistically reliable data from individual tray treatments at this time
A Randomized Clinical Trial of Vapocoolant for Pediatric Immunization Pain Relief
OBJECTIVES: The purpose of the current study was to evaluate the effectiveness of vapocoolant for preschoolers’ immunization injection pain relief.
STUDY DESIGN: 57 4- to 6-year-old children were randomized to vapocoolant alone or typical care conditions. Pain was measured at baseline and at injection via self-report, caregiver-report, nurse-report, and an observational scale.
RESULTS: Self-report suggested that children in the vapocoolant alone condition demonstrated stronger increases in pain from baseline to injection than typical care. All other measures showed significant increases in pain from baseline to injection, but none indicted treatment effects.
CONCLUSIONS: Consistent with prior studies, vapocoolant might not be an effective pain-management intervention for children’s intramuscular injections
Long-term monitoring of the radio-galaxy M87 in gamma-rays: joint analysis of MAGIC, VERITAS and Fermi-LAT data
M87 was discovered in the very-high-energy band (VHE, E > 100 GeV) with HEGRA
in 2003, long before its emission was detected in the high-energy band (HE, E >
100 MeV) with Fermi-LAT in 2009, opening the window to a new family of
extragalactic sources with tilted jets. After a series of major VHE flares in
2005, 2008, and 2010, which were detected in multiple bands, the source has
been found in a low activity state, interrupted only by comparatively
smaller-scale flares. MAGIC and VERITAS, two stereoscopic Cherenkov telescope
arrays located at Roque de los Muchachos Observatory (Canary Islands, Spain)
and the Fred Lawrence Whipple Observatory (Arizona, US), have monitored M87
continuously and in coordination for more than 10 years. In this work, we
present the data for 4 years of MAGIC and VERITAS observations corresponding to
2019, 2020, 2021 and 2022. The resulting light curves are shown in daily and
monthly scales where no significant variability is observed. In addition, we
show the first joint analysis using combined event data from the two VHE
instruments and Fermi-LAT to compute the spectral energy distribution
Randomized Clinical Trial of Distraction for Infant Immunization Pain
Distraction has been shown to be an effective technique for managing pain in children; however, few investigations have examined the utility of this technique with infants. The goal of the current study was to investigate the effectiveness of movie distraction in reducing infants’ immunization distress. Participants were 136 infants (range = 1 to 21 months; M = 7.6 months, SD = 5.0 months) and their parents, all of whom were recruited when presenting for routine vaccinations. The parent-child dyads were randomly assigned to either a Distraction or Typical Care control condition. Infant and adult behaviors were assessed using a visual analog scale and a behavioral observation rating scale. Results indicated parents in the Distraction group engaged in higher rates of distraction than those in the Typical Care group, whereas there was no difference in the behavior of nurses in the Distraction and Typical Care groups. In addition, infants in the Distraction group displayed fewer distress behaviors than infants in the Typical Care group both prior to and during recovery from the injection. Findings suggest that a simple and practical distraction intervention can provide some distress relief to infants during routine injections
Galaxy Zoo: the effect of bar-driven fuelling on the presence of an active galactic nucleus in disc galaxies
We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19756 disc galaxies at 0.01<z<0.05 which have been visually examined for the presence of a bar. Within this sample, AGN host galaxies have a higher overall percentage of bars (51.8 per cent) than inactive galaxies exhibiting central star formation (37.1 per cent). This difference is primarily due to known effects: that the presence of both AGN and galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16 per cent of the average barred AGN fraction. Using the /MBH ratio as a measure of AGN strength, we show that barred AGNs do not exhibit stronger accretion than unbarred AGNs at a fixed mass and colour. The data are consistent with a model in which bar-driven fuelling does contribute to the probability of an actively growing black hole, but in which other dynamical mechanisms must contribute to the direct AGN fuelling via smaller, non-axisymmetric perturbation
Solar Jet Hunter: a citizen science initiative to identify coronal jets in EUV data sets
Context. Solar coronal jets seen in EUV are ubiquitous on the Sun, have been
found in and at the edges of active regions, at the boundaries of coronal
holes, and in the quiet Sun. Jets have various shapes, sizes, brightness,
velocities and duration in time, which complicates their detection by automated
algorithms. So far, solar jets reported in the Heliophysics Event Knowledgebase
(HEK) have been mostly reported by humans looking for them in the data, with
different levels of precision regarding their timing and positions. Aims. We
create a catalogue of solar jets observed in EUV at 304 {\AA} containing
precise and consistent information on the jet timing, position and extent.
Methods. We designed a citizen science project, "Solar Jet Hunter", on the
Zooniverse platform, to analyze EUV observations at 304 {\AA} from the Solar
Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA). We created movie
strips for regions of the Sun in which jets have been reported in HEK and ask
the volunteers to 1) confirm the presence of at least one jet in the data and
2) report the timing, position and extent of the jet. Results. We report here
the design of the project and the results obtained after the analysis of data
from 2011 to 2016. 365 "coronal jet" events from HEK served as input for the
citizen science project, equivalent to more than 120,000 images distributed
into 9,689 "movie strips". Classification by the citizen scientists resulted
with only 21% of the data containing a jet, and 883 individual jets being
identified. Conclusions. We demonstrate how citizen science can enhance the
analysis of solar data with the example of Solar Jet Hunter. The catalogue of
jets thus created is publicly available and will enable statistical studies of
jets and related phenomena. This catalogue will also be used as a training set
for machines to learn to recognize jets in further data sets
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