3,267 research outputs found
Impact cratering and the Oort cloud
We calculate the expected flux profile of comets into the planetary system
from the Oort cloud arising from Galactic tides and encounters with molecular
clouds. We find that both periodic and sporadic bombardment episodes, with
amplitudes an order of magnitude above background, occur on characteristic
timescales ~25-35 Myr.
Bombardment episodes occurring preferentially during spiral arm crossings may
be responsible both for mass extinctions of life and the transfer of viable
microorganisms from the bombarded Earth into the disturbing nebulae. Good
agreement is found between the theoretical expectations and the age
distribution of large, well-dated terrestrial impact craters of the past 250
million years.
A weak periodicity of ~36 Myr in the cratering record is consistent with the
Sun's recent passage through the Galactic plane, and implies a central plane
density ~0.15 M_Sun pc^(-3). This leaves little room for a significant dark
matter component in the disc
Culture matters: using a cultural contexts of health approach to enhance policy-making
This is the final version of the report. Freely available online from WHO via the link in this recordThis policy brief has been developed in response to the increasing awareness among policy-makers and the public health community of the important relationship between culture and health. By exploring the three key public health areas of nutrition, migration and environment, the policy brief demonstrates how cultural awareness is central to understanding health and well-being and to developing more effective and equitable health policies. Consequently, it argues that public health policy-making has much to gain from applying research from the health-related humanities and social sciencesWorld Health Organisatio
The social construction of 101 non-emergency video relay services for deaf signers
How the police prepare for and engage with a citizen who is deaf and uses British Sign Language (BSL) is a national problem. From the perspective of deaf sign language users, the police remain largely inaccessible and unprepared in how to accommodate their linguistic needs. Four regional forces have responded to this issue by introducing a local solution, a bespoke 101 non-emergency video relay service (101VRS). Independent VRS companies function as the auxiliary service, mediating video calls to a 101 helpline. This service was identified as a simple solution that relied on minimal resourcing and input from the police. In using Pinch and Bijker’s social construction of technology (SCOT) framework, we look at competing interpretations of the 101VRS concept and how this has led to a range of intended and unintended solutions and problems (Pinch TJ and Bijker WE (1984) The social construction of facts and artefacts: or how the sociology of science and the sociology of technology might benefit each other. Social Studies of Science 14(3): 399–441). To maintain the investment in improving access to the police, we recommend harmonization of 101VRS nationally, and ongoing consultation with how front-line services can become better prepared at assisting deaf citizens
Departures From Axisymmetric Morphology and Dynamics in Spiral Galaxies
New HI synthesis data have been obtained for six face-on galaxies with the
Very Large Array. These data and reanalyses of three additional data sets make
up a sample of nine face-on galaxies analyzed for deviations from axisymmetry
in morphology and dynamics. This sample represents a subsample of galaxies
already analyzed for morphological symmetry properties in the R-band. Four
quantitative measures of dynamical nonaxisymmetry are compared to one another
and to the quantitative measures of morphological asymmetry in HI and R-band to
investigate the relationships between nonaxisymmetric morphology and dynamics.
We find no significant relationship between asymmetric morphology and most of
the dynamical measures in our sample. A possible relationship is found,
however, between morphology and dynamical position angle differences between
approaching and receding sides of the galaxy.Comment: 24 pages, 19 figures, AASTeX, accepted for publication in AJ,
postscript figures available at
ftp://culebra.tn.cornell.edu/pub/david/figures.tar.g
On the investigations of galaxy redshift periodicity
In this article we present a historical review of study of the redshift
periodicity of galaxies, starting from the first works performed in the
seventies of the twentieth century until the present day. We discuss the
observational data and methods used, showing in which cases the discretization
of redshifts was observed. We conclude that galaxy redshift periodisation is an
effect which can really exist. We also discussed the redshift discretization in
two different structures: the Local Group of galaxies and the Hercules
Supercluster. Contrary to the previous studies we consider all galaxies which
can be regarded as a structure member disregarding the accuracy of velocity
measurements. We applied the power spectrum analysis using the Hann function
for weighting, together with the jackknife error estimator. In both the
structures we found weak effects of redshift periodisation.Comment: 10 pages, 4 figures, to be published in Part. and Nucl. Lett. 200
Neutral Gas Distribution and Kinematics of the Nearly Face-on Spiral Galaxy NGC 1232
We have analyzed high velocity resolution HI synthesis observations of the
nearly face-on Sc galaxy NGC 1232. The neutral gas distribution extends well
beyond the optical extent of the galaxy. As expected, local peaks in the HI
column density are associated with the spiral arms. Further, the HI column
density drops precipitously near the center of the galaxy. Closed contours in
the velocity field suggest either that the system is warped, or that the
rotation curve declines. The velocity dispersion is approximately constant
throughout the system, with a median value of 9.9 +/- 1.8 km/s. When corrected
for rotational broadening, there is no indication of a radial trend in the
neutral gas velocity dispersion in this galaxy.Comment: 14 pages of text, 10 pages of figures. Accepted to the A
Potent Engineered PLGA Nanoparticles by Virtue of Exceptionally High Chemotherapeutic Loadings
Herein we report the fabrication of engineered poly(lactic acid-co-glycolic acid) nanoparticles via the PRINT® (Particle Replication In Non-wetting Templates) process with high and efficient loadings of docetaxel, up to 40% (w/w) with encapsulation efficiencies >90%. The PRINT process enables independent control of particle properties leading to a higher degree of tailorability than traditional methods. Particles with 40% loading display better in vitro efficacy than particles with lower loadings and the clinical formulation of docetaxel, Taxotere®
Engineering nanomedicines using stimuli-responsive biomaterials
The ability to engineer particles has the potential to shift the paradigm in the creation of new medicines and diagnostics. Complete control over particle characteristics, such as size, shape, mechanical property, and surface chemistry, can enable rapid translation and facilitate the US Food and Drug Administration (FDA) approval of particle technologies for the treatment of cancer, infectious diseases, diabetes, and a host of other major illnesses. The incorporation of natural and artificial external stimuli to trigger the release of drugs enables exquisite control over the release profiles of drugs in a given environment. In this article, we examine several readily scalable top-down methods for the fabrication of shape-specific particles that utilize stimuli-responsive biomaterials for controlled drug delivery. Special attention is given to Particle Replication In Nonwetting Templates (PRINT®) technology and the application of novel triggered-release synthetic and natural polymers
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