897 research outputs found
Thermal Transport Model for Heat Sink Design
A document discusses the development of a finite element model for describing thermal transport through microcalorimeter arrays in order to assist in heat-sinking design. A fabricated multi-absorber transition edge sensor (PoST) was designed in order to reduce device wiring density by a factor of four. The finite element model consists of breaking the microcalorimeter array into separate elements, including the transition edge sensor (TES) and the silicon substrate on which the sensor is deposited. Each element is then broken up into subelements, whose surface area subtends 10 10 microns. The heat capacity per unit temperature, thermal conductance, and thermal diffusivity of each subelement are the model inputs, as are the temperatures of each subelement. Numerical integration using the Finite in Time Centered in Space algorithm of the thermal diffusion equation is then performed in order to obtain a temporal evolution of the subelement temperature. Thermal transport across interfaces is modeled using a thermal boundary resistance obtained using the acoustic mismatch model. The document concludes with a discussion of the PoST fabrication. PoSTs are novel because they enable incident x-ray position sensitivity with good energy resolution and low wiring density
Constraints on the Progenitor of SN 2016gkg From Its Shock-Cooling Light Curve
SN 2016gkg is a nearby Type IIb supernova discovered shortly after explosion.
Like several other Type IIb events with early-time data, SN 2016gkg displays a
double-peaked light curve, with the first peak associated with the cooling of a
low-mass extended progenitor envelope. We present unprecedented
intranight-cadence multi-band photometric coverage of the first light-curve
peak of SN 2016gkg obtained from the Las Cumbres Observatory Global Telescope
network, the Asteroid Terrestrial-impact Last Alert System, the Swift satellite
and various amateur-operated telescopes. Fitting these data to analytical
shock-cooling models gives a progenitor radius of ~25-140 solar radii with
~2-30 x 10^-2 solar masses of material in the extended envelope (depending on
the model and the assumed host-galaxy extinction). Our radius estimates are
broadly consistent with values derived independently (in other works) from HST
imaging of the progenitor star. However, the shock-cooling model radii are on
the lower end of the values indicated by pre-explosion imaging. Hydrodynamical
simulations could refine the progenitor parameters deduced from the
shock-cooling emission and test the analytical models.Comment: Accepted by ApJ
Multisite Evaluation of Prediction Models for Emergency Department Crowding Before and During the COVID-19 Pandemic
OBJECTIVE: To develop a machine learning framework to forecast emergency department (ED) crowding and to evaluate model performance under spatial and temporal data drift.
MATERIALS AND METHODS: We obtained 4 datasets, identified by the location: 1-large academic hospital and 2-rural hospital, and time period: pre-coronavirus disease (COVID) (January 1, 2019-February 1, 2020) and COVID-era (May 15, 2020-February 1, 2021). Our primary target was a binary outcome that is equal to 1 if the number of patients with acute respiratory illness that were ED boarding for more than 4 h was above a prescribed historical percentile. We trained a random forest and used the area under the curve (AUC) to evaluate out-of-sample performance for 2 experiments: (1) we evaluated the impact of sudden temporal drift by training models using pre-COVID data and testing them during the COVID-era, (2) we evaluated the impact of spatial drift by testing models trained at location 1 on data from location 2, and vice versa.
RESULTS: The baseline AUC values for ED boarding ranged from 0.54 (pre-COVID at location 2) to 0.81 (COVID-era at location 1). Models trained with pre-COVID data performed similarly to COVID-era models (0.82 vs 0.78 at location 1). Models that were transferred from location 2 to location 1 performed worse than models trained at location 1 (0.51 vs 0.78).
DISCUSSION AND CONCLUSION: Our results demonstrate that ED boarding is a predictable metric for ED crowding, models were not significantly impacted by temporal data drift, and any attempts at implementation must consider spatial data drift
A Tight Correlation Between Millimeter and X-ray Emission in Accreting Massive Black Holes from <100 Milliarcsecond-resolution ALMA Observations
Recent studies have proposed that the nuclear millimeter continuum emission
observed in nearby active galactic nuclei (AGN) could be created by the same
population of electrons that gives rise to the X-ray emission that is
ubiquitously observed in accreting black holes. We present the results of a
dedicated high spatial resolution (60-100 milliarcsecond) ALMA campaign
on a volume-limited ( keV) selected
radio-quiet AGN. We find an extremely high detection rate (25/26 or
), which shows that nuclear emission at mm-wavelengths is
nearly ubiquitous in accreting SMBHs. Our high-resolution observations show a
tight correlation between the nuclear (1-23 pc) 100GHz and the intrinsic X-ray
emission (1 scatter of dex). The ratio between the 100GHz
continuum and the X-ray emission does not show any correlation with column
density, black hole mass, Eddington ratio or star formation rate, which
suggests that the 100GHz emission can be used as a proxy of SMBH accretion over
a very broad range of these parameters. The strong correlation between 100GHz
and X-ray emission in radio-quiet AGN could be used to estimate the column
density based on the ratio between the observed 2-10keV () and 100GHz () fluxes. Specifically, a
ratio strongly
suggests that a source is heavily obscured []. Our work shows the potential of ALMA continuum
observations to detect heavily obscured AGN (up to an optical depth of one at
100GHz, i.e. ), and to identify binary
SMBHs with separations pc, which cannot be probed by current X-ray
facilities.Comment: ApJL in pres
Stability of the monoclinic phase in the ferroelectric perovskite PbZr(1-x)TixO3
Recent structural studies of ferroelectric PbZr(1-x)TixO3 (PZT) with x= 0.48,
have revealed a new monoclinic phase in the vicinity of the morphotropic phase
boundary (MPB), previously regarded as the the boundary separating the
rhombohedral and tetragonal regions of the PZT phase diagram. In the present
paper, the stability region of all three phases has been established from high
resolution synchrotron x-ray powder diffraction measurements on a series of
highly homogeneous samples with 0.42 <=x<= 0.52. At 20K the monoclinic phase is
stable in the range 0.46 <=x<= 0.51, and this range narrows as the temperature
is increased. A first-order phase transition from tetragonal to rhombohedral
symmetry is observed only for x= 0.45. The MPB, therefore, corresponds not to
the tetragonal-rhombohedral phase boundary, but instead to the boundary between
the tetragonal and monoclinic phases for 0.46 <=x<= 0.51. This result provides
important insight into the close relationship between the monoclinic phase and
the striking piezoelectric properties of PZT; in particular, investigations of
poled samples have shown that the monoclinic distortion is the origin of the
unusually high piezoelectric response of PZT.Comment: REVTeX file, 7 figures embedde
A Catalogue of M51 type Galaxy Associations
A catalog of 232 apparently interacting galaxy pairs of the M51 class is
presented. Catalog members were identified from visual inspection of mult-band
images in the IRSA archive. The major findings in the compilation of this
catalog are (1) A surprisingly low number of the main galaxies in M51 systems
are early type spirals and barred spirals. (2) Over 70% of the main galaxies in
M51 systems are 2-armed spirals. (3) Some systems that were classified as M51
types in previous studies are not M51 types as defined in this catalog. There
were a number of systems previously classified as M51 systems for which the
companion is identified as an HII region within the main galaxy or a foreground
star within the Milky Way. (4) It was found that only 18% of the M51 type
companions have redshift measurements in the literature. There is a significant
need for spectroscopic study of the companions in order to improve the value of
the catalog as a sample for studying the effects of M51 type interaction on
galaxy dynamics, morphology, and star formation. Further spectroscopy will also
help constrain the statistics of possible chance projections between foreground
and background galaxies in this catalog. The catalog also contains over 430
additional systems which are classified as "possible M51" systems. The reasons
for classifying certain systems as possible M51 systems are discussed.Comment: 19 pages including 6 figures and tables 3-8, Tables 1 and 2 are found
at http://www.jorcat.com, Accepted for publication in Astrophysics and Space
Scienc
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
The Physical Activity Messaging Framework (PAMF) and Checklist (PAMC): International consensus statement and user guide
Effective physical activity messaging plays an important role in the pathway towards changing physical activity behaviour at a population level. The Physical Activity Messaging Framework (PAMF) and Checklist (PAMC) are outputs from a recent modified Delphi study.
This sought consensus from an international expert panel on how to aid the creation and evaluation of physical activity messages. In this paper, we (1) present an overview of the various concepts within the PAMF and PAMC, (2) discuss in detail how the PAMF and PAMC can be used to create physical activity messages, plan evaluation of messages, and aid understanding and categorisation of existing messages, and (3) highlight areas for future development and research. If adopted, we propose that the PAMF and PAMC could improve physical activity messaging practice by encouraging evidence-based and target population focused messages with clearly stated aims and consideration of potential working pathways.
They could also enhance the physical activity messaging research base by harmonising key messaging terminologies, improving quality of reporting, and aiding collation and synthesis of the evidence
Evaluating housing quality, health and safety using an Internet-based data collection and response system: a cross-sectional study
<p>Abstract</p> <p>Background</p> <p>Typically housing and health surveys are not integrated together and therefore are not representative of population health or national housing stocks. In addition, the existing channels for distributing information about housing and health issues to the general public are limited. The aim of this study was to develop a data collection and response system that would allow us to assess the Finnish housing stock from the points of view of quality, health and safety, and also to provide a tool to distribute information about important housing health and safety issues.</p> <p>Methods</p> <p>The data collection and response system was tested with a sample of 3000 adults (one per household), who were randomly selected from the Finnish Population Register Centre. Spatial information about the exact location of the residences (i.e. coordinates) was included in the database inquiry. People could participate either by completing and returning a paper questionnaire or by completing the same questionnaire via the Internet. The respondents did not receive any compensation for their time in completing the questionnaire.</p> <p>Results</p> <p>This article describes the data collection and response system and presents the main results of the population-based testing of the system. A total of 1312 people (response rate 44%) answered the questionnaire, though only 80 answered via the Internet. A third of the respondents had indicated they wanted feedback. Albeit a majority (>90%) of the respondents reported being satisfied or quite satisfied with their residence, there were a number of prevalent housing issues identified that can be related to health and safety.</p> <p>Conclusions</p> <p>The collected database can be used to evaluate the quality of the housing stock in terms of occupant health and safety, and to model its association with occupant health and well-being. However, it must be noted that all the health outcomes gathered in this study are self-reported. A follow-up study is needed to evaluate whether the occupants acted on the feedback they received. Relying solely on an Internet-based questionnaire for collecting data would not appear to provide an adequate response rate for random population-based surveys at this point in time.</p
Human Papillomavirus Type 16 Entry: Retrograde Cell Surface Transport along Actin-Rich Protrusions
The lateral mobility of individual, incoming human papillomavirus type 16 pseudoviruses (PsV) bound to live HeLa cells was studied by single particle tracking using fluorescence video microscopy. The trajectories were computationally analyzed in terms of diffusion rate and mode of motion as described by the moment scaling spectrum. Four distinct modes of mobility were seen: confined movement in small zones (30–60 nm in diameter), confined movement with a slow drift, fast random motion with transient confinement, and linear, directed movement for long distances. The directed movement was most prominent on actin-rich cell protrusions such as filopodia or retraction fibres, where the rate was similar to that measured for actin retrograde flow. It was, moreover, sensitive to perturbants of actin retrograde flow such as cytochalasin D, jasplakinolide, and blebbistatin. We found that transport along actin protrusions significantly enhanced HPV-16 infection in sparse tissue culture, cells suggesting a role for in vivo infection of basal keratinocytes during wound healing
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