56,376 research outputs found
The Orion constellation as an installation - An innovative three dimensional teaching and learning environment
Visualising the three dimensional distribution of stars within a
constellation is highly challenging for both students and educators, but when
carried out in an interactive collaborative way it can create an ideal
environment to explore common misconceptions about size and scale within
astronomy. We present how the common table top activities based upon the Orion
constellation miss out on this opportunity. Transformed into a walk-through
Orion installation that includes the position of our Solar system, it allows
the students to fully immerse themselves within the model and experience
parallax. It enables participants to explore within the installation many other
aspects of astronomy relating to sky culture, stellar evolution, and stellar
timescales establishing an innovative learning and teaching environment.Comment: 2 pages, submitted to The Physics Teacher - Colum
Study of a quasi-microscope design for planetary landers
The Viking Lander fascimile camera, in its present form, provides for a minimum object distance of 1.9 meters, at which distance its resolution of 0.0007 radian provides an object resolution of 1.33 millimeters. It was deemed desirable, especially for follow-on Viking missions, to provide means for examing Martian terrain at resolutions considerably higher than that now provided. This led to the concept of quasi-microscope, an attachment to be used in conjunction with the fascimile camera to convert it to a low power microscope. The results are reported of an investigation to consider alternate optical configurations for the quasi-microscope and to develop optical designs for the selected system or systems. Initial requirements included consideration of object resolutions in the range of 2 to 50 micrometers, an available field of view of the order of 500 pixels, and no significant modifications to the fascimile camera
Matter formed at the BNL relativistic heavy ion collider
We suggest that the "new form of matter" found just above by RHIC is
made up of tightly bound quark-antiquark pairs, essentially 32 chirally
restored (more precisely, nearly massless) mesons of the quantum numbers of
, , and . Taking the results of lattice gauge
simulations (LGS) for the color Coulomb potential from the work of the
Bielefeld group and feeding this into a relativistic two-body code, after
modifying the heavy-quark lattice results so as to include the
velocity-velocity interaction, all ground-state eigenvalues of the 32 mesons go
to zero at just as they do from below as predicted by the vector
manifestation (VM in short) of hidden local symmetry. This could explain the
rapid rise in entropy up to found in LGS calculations. We argue that how
the dynamics work can be understood from the behavior of the hard and soft
glue.Comment: Final versio
Sums and differences of four k-th powers
We prove an upper bound for the number of representations of a positive
integer as the sum of four -th powers of integers of size at most ,
using a new version of the Determinant method developed by Heath-Brown, along
with recent results by Salberger on the density of integral points on affine
surfaces. More generally we consider representations by any integral diagonal
form. The upper bound has the form , whereas earlier
versions of the Determinant method would produce an exponent for of order
in this case. Furthermore, we prove that the number of
representations of a positive integer as a sum of four -th powers of
non-negative integers is at most for
, improving upon bounds by Wisdom.Comment: 18 pages. Mistake corrected in the statement of Theorem 1.2. To
appear in Monatsh. Mat
Emotional intelligence and locus of control of adult patients with breast cancer receiving treatment
Background: This article investigates emotional intelligence and locus of control in an adult breast cancer population receiving treatment. Gaining insight into these constructs will contribute to improving breast cancer patients’ psychological well-being and to reducing physical vulnerability to disease before and during treatment.Method: The researcher used an exploratory, descriptive and correlational approach. Nonprobability purposive sampling was employed. Sixty-seven breast cancer patients receiving treatment participated in the research. A biographical questionnaire, the Schutte Emotional Intelligence Scale, and the Rotter Internal-External Locus of Control Scale were used to measure the constructs explored in this article. Descriptive and inferential statistics were used to analyse the data.Results: The sample yielded above-average levels of emotional intelligence and an internal locus of control. The results indicate a statistically and practically significant negative correlation between emotional intelligence and locus of control. The significant association found between higher and lower emotional intelligence groups and internal and external locus of control groups also confirmed these results.Conclusion: Having an understanding of the psychosocial variables that impact on individuals diagnosed with a chronic illness, in this case breast cancer, can assist interventionists working in the field of positive psychology. While the stressors and challenges that breast cancer patients face are well documented, this article highlights the strength factors emotional intelligence and locus of control as important mediators in the treatment and management of breast cancer
Analysis of ALOPE data from Superflux
Remote sensing data collected with the airborne lidar oceanographic probing experiment (ALOPE) laser fluorosensor during the Superflux 1 and Superflux 2 experiments were analyzed using two techniques. A qualitative technique which requires no supplementary data provided a near-real-time estimate of relative abundance of the golden-brown and green phytoplankton color groups. Contour plots developed for the later mission are used to demonstrate the utility of this technique. A quantitative technique which requires supplementary data to define the attenuation coefficient provides chlorophyll a concentration by color group. The sum of the golden-brown and green chlorophyll a data yields total chlorophyll a values which may be compared with in situ data. As expected, the golden-brown population was dominant in the Chesapeake Bay and the Bay plume whereas the green population was dominant in shelf waters
Time-Reversal-Violating Schiff Moment of 199Hg
We calculate the Schiff moment of the nucleus 199Hg, created by pi-N-N
vertices that are odd under parity (P) and time-reversal (T). Our approach,
formulated in diagrammatic perturbation theory with important core-polarization
diagrams summed to all orders, gives a close approximation to the expectation
value of the Schiff operator in the odd-A Hartree-Fock-Bogoliubov ground state
generated by a Skyrme interaction and a weak P- and T-odd pion-exchange
potential. To assess the uncertainty in the results, we carry out the
calculation with several Skyrme interactions (the quality of which we test by
checking predictions for the isoscalar-E1 strength distribution in 208Pb) and
estimate most of the important diagrams we omit.Comment: 13 pages, 7 figure
Heterocyst placement strategies to maximize growth of cyanobacterial filaments
Under conditions of limited fixed-nitrogen, some filamentous cyanobacteria
develop a regular pattern of heterocyst cells that fix nitrogen for the
remaining vegetative cells. We examine three different heterocyst placement
strategies by quantitatively modelling filament growth while varying both
external fixed-nitrogen and leakage from the filament. We find that there is an
optimum heterocyst frequency which maximizes the growth rate of the filament;
the optimum frequency decreases as the external fixed-nitrogen concentration
increases but increases as the leakage increases. In the presence of leakage,
filaments implementing a local heterocyst placement strategy grow significantly
faster than filaments implementing random heterocyst placement strategies. With
no extracellular fixed-nitrogen, consistent with recent experimental studies of
Anabaena sp. PCC 7120, the modelled heterocyst spacing distribution using our
local heterocyst placement strategy is qualitatively similar to experimentally
observed patterns. As external fixed-nitrogen is increased, the spacing
distribution for our local placement strategy retains the same shape while the
average spacing between heterocysts continuously increases.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher-authenticated version
will be available onlin
Observation of Buried Phosphorus Dopants near Clean Si(100)-(2x1) with Scanning Tunneling Microscopy
We have used scanning tunneling microscopy to identify individual phosphorus
dopant atoms near the clean silicon (100)-(2x1) reconstructed surface. The
charge-induced band bending signature associated with the dopants shows up as
an enhancement in both filled and empty states and is consistent with the
appearance of n-type dopants on compound semiconductor surfaces and passivated
Si(100)-(2x1). We observe dopants at different depths and see a strong
dependence of the signature on the magnitude of the sample voltage. Our results
suggest that, on this clean surface, the antibonding surface state band acts as
an extension of the bulk conduction band into the gap. The positively charged
dimer vacancies that have been observed previously appear as depressions in the
filled states, as opposed to enhancements, because they disrupt these surface
bands.Comment: 4 pages, 3 figures. TeX for OSX from Wierde
Predicting the hypervelocity star population in Gaia
Hypervelocity stars (HVSs) are amongst the fastest objects in our Milky Way.
These stars are predicted to come from the Galactic center (GC) and travel
along unbound orbits across the Galaxy. In the coming years, the ESA satellite
Gaia will provide the most complete and accurate catalogue of the Milky Way,
with full astrometric parameters for more than billion stars. In this
paper, we present the expected sample size and properties (mass, magnitude,
spatial, velocity distributions) of HVSs in the Gaia stellar catalogue. We
build three Gaia mock catalogues of HVSs anchored to current observations,
exploring different ejection mechanisms and GC stellar population properties.
In all cases, we predict hundreds to thousands of HVSs with precise proper
motion measurements within a few tens of kpc from us. For stars with a relative
error in total proper motion below , the mass range extends to ~ but peaks at ~ . The majority of Gaia HVSs will
therefore probe a different mass and distance range compared to the current
non-Gaia sample. In addition, a subset of a few hundreds to a few thousands of
HVSs with ~ will be bright enough to have a precise
measurement of the three-dimensional velocity from Gaia alone. Finally, we show
that Gaia will provide more precise proper motion measurements for the current
sample of HVS candidates. This will help identifying their birthplace narrowing
down their ejection location, and confirming or rejecting their nature as HVSs.
Overall, our forecasts are extremely encouraging in terms of quantity and
quality of HVS data that can be exploited to constrain both the Milky Way
potential and the GC properties.Comment: 17 pages, 18 figures, accepted for publication in MNRA
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