32,849 research outputs found
Portable electrophoresis apparatus using minimum electrolyte
An electrophoresis unit for use in conducting electrophoretic analysis of specimens is described. The unit includes a sealable container in which a substrate mounted specimen is suspended in an electrolytic vapor. A heating unit is employed to heat a supply of electrolyte to produce the vapor. The substrate is suspended within the container by being attached between a pair of clips which also serve as electrodes to which a direct current power source may be connected
Tracking and data handling for the pioneer iii and pioneer iv firings
Tracking and data handling systems for Pioneer III space probe and Pioneer IV lunar probe firing
The dominant X-ray wind in massive star binaries
We investigate which shocked wind is responsible for the majority of the
X-ray emission in colliding wind binaries, an issue where there is some
confusion in the literature, and which we show is more complicated than has
been assumed. We find that where both winds rapidly cool (typically close
binaries), the ratio of the wind speeds is often more important than the
momentum ratio, because it controls the energy flux ratio, and the faster wind
is generally the dominant emitter. When both winds are largely adiabatic
(typically long-period binaries), the slower and denser wind will cool faster
and the stronger wind generally dominates the X-ray luminosity.Comment: 4 pages, 1 figure, accepted by A&A Letter
The Cluster Wind from Local Massive Star Clusters
Results of a study of the theoretically predicted and observed X-ray
properties of local massive star clusters are presented, with a focus on
understanding the mass and energy flow from these clusters into the ISM via a
cluster wind. A simple theoretical model, based on the work of Chevalier &
Clegg (1985), is used to predict the theoretical cluster properties, and these
are compared to those obtained from recent Chandra observations. The model
includes the effect of lower energy transfer efficiency and mass-loading. In
spite of limited statistics, some general trends are indicated; the observed
temperature of the diffuse X-ray emission is lower than that predicted from the
stellar mass and energy input rates, but the predicted scaling of X-ray
luminosity with cluster parameters is seen. The implications of these results
are discussed.Comment: 9 pages, 6 figues, accepted for publication in MNRA
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Trace gas transport in the subsurface of Mars
The ExoMars Trace Gas Orbiter (TGO) will have the capability of detecting and characterizing a broad suite of trace gases in the atmosphere of Mars. Interpreting the results of this mission will require an understanding of how these trace gases are transported from their sources, which may be deep underground, to the atmosphere. Here we present results of modeling designed to measure the timescales of release from putative subsurface methane sources. These transport timescales are far longer than mixing times in the atmosphere and could be up to 10 million years
Galaxies in Clusters: the Observational Characteristics of Bow-Shocks, Wakes and Tails
The dynamical signatures of the interaction between galaxies in clusters and
the intracluster medium (ICM) can potentially yield significant information
about the structure and dynamical history of clusters. To develop our
understanding of this phenomenon we present results from numerical modelling of
the galaxy/ICM interaction, as the galaxy moves through the cluster. The
simulations have been performed for a broad range, of ICM temperatures (kT =
1,4 and 8 keV), representative of poor clusters or groups through to rich
clusters. There are several dynamical features that can be identified in these
simulations; for supersonic galaxy motion, a leading bow-shock is present, and
also a weak gravitationally focussed wake or tail behind the galaxy (analogous
to Bondi-Hoyle accretion). For galaxies with higher mass-replenishment rates
and a denser interstellar medium (ISM), the dominant feature is a dense
ram-pressure stripped tail. In line with other simulations, we find that the
ICM/galaxy ISM interaction can result in complex time- dependent dynamics, with
ram-pressure stripping occurring in an episodic manner. In order to facilitate
this comparison between the observational consequences of dynamical studies and
X-ray observations we have calculated synthetic X-ray flux and hardness maps
from these simulations. These calculations predict that the ram-pressure
stripped tail will usually be the most visible feature, though in nearby
galaxies the bow-shock preceding the galaxy should also be apparent in deeper
X-ray observations. We briefly discuss these results and compare with X-ray
observations of galaxies where there is evidence of such interactions.Comment: 14 pages, 8 diagrams, MNRAS (in press
Probing the wind-wind collision in Gamma Velorum with high-resolution Chandra X-ray spectroscopy: evidence for sudden radiative braking and non-equilibrium ionization
We present a new analysis of an archived Chandra HETGS X-ray spectrum of the
WR+O colliding wind binary Gamma Velorum. The spectrum is dominated by emission
lines from astrophysically abundant elements: Ne, Mg, Si, S and Fe. From a
combination of broad-band spectral analysis and an analysis of line flux ratios
we infer a wide range of temperatures in the X-ray emitting plasma (~4-40 MK).
As in the previously published analysis, we find the X-ray emission lines are
essentially unshifted, with a mean FWHM of 1240 +/- 30 km/s. Calculations of
line profiles based on hydrodynamical simulations of the wind-wind collision
predict lines that are blueshifted by a few hundred km/s. The lack of any
observed shift in the lines may be evidence of a large shock-cone opening
half-angle (> 85 degrees), and we suggest this may be evidence of sudden
radiative braking. From the R and G ratios measured from He-like
forbidden-intercombination-resonance triplets we find evidence that the Mg XI
emission originates from hotter gas closer to the O star than the Si XIII
emission, which suggests that non-equilibrium ionization may be present.Comment: 22 pages, 14 figures. Accepted for publication in MNRA
Thin Film Formation During Splashing of Viscous Liquids
After impact onto a smooth dry surface, a drop of viscous liquid initially
spreads in the form of a thick lamella. If the drop splashes, it first emits a
thin fluid sheet that can ultimately break up into droplets causing the splash.
Ambient gas is crucial for creating this thin sheet. The time for sheet
ejection, , depends on impact velocity, liquid viscosity, gas pressure
and molecular weight. A central air bubble is trapped below the drop at
pressures even below that necessary for this sheet formation. In addition, air
bubbles are entrained underneath the spreading lamella when the ejected sheet
is present. Air entrainment ceases at a lamella velocity that is independent of
drop impact velocity as well as ambient gas pressure.Comment: 8 pages, 11 figure
Simulations of the Effects of Stripping and Accretion on Galaxy Haloes in Clusters
We present results from a series of hydrodynamic simulations investigating
ram pressure stripping of galactic haloes as the host galaxy falls radially
into a cluster. We perform a parameter study comprising of variations in
initial gas content, gas injection rate (via stellar mass loss processes),
galaxy mass and amplitude of infall. From the simulation results we track
variations in both physical quantities (e.g. gas mass) and directly observable
quantities (e.g. X-ray luminosities). The luminosity of the galaxy's X-ray halo
is found to compare favourably with the observationally determined correlation
with optical blue band luminosity (L_X:L_B) relation. Factors affecting the
X-ray luminosity are explored and it is found that the gas injection rate is a
dominant factor in determining the integrated luminosity. Observational
properties of the material stripped from the galaxy, which forms an X-ray wake,
are investigated and it is found that wakes are most visible around galaxies
with a substantial initial gas content, during their first passage though the
cluster. We define a statistical skewness measure which may be used to
determine the direction of motion of a galaxy using X-ray observations.
Structures formed in these simulations are similar to the cold fronts seen in
observation of cluster mergers where a sharp increase in surface brightness is
accompanied by a transition to a cooler region.Comment: Accepted for publication in MNRAS. 19 pages, 21 figure
Differential Relationship between Physical Activity and Intake of Added Sugar and Nutrient-Dense Foods: A Cross-Sectional Analysis
A curvilinear relationship exists between physical activity (PA) and dietary energy intake (EI), which is reduced in moderately active when compared to inactive and highly active individuals, but the impact of PA on eating patterns remains poorly understood. Our goal was to establish the relationship between PA and intake of foods with varying energy and nutrient density. Data from the 2009–2010 United States National Health and Nutrition Examination Survey were used to include a Dietary Screener Questionnaire for estimated intakes of added sugar, fruits and vegetables, whole grains, fiber, and dairy. Participants (n = 4766; 49.7% women) were divided into sex-specific quintiles based on their habitual PA. After adjustment for age, body mass index, household income, and education, intakes were compared between PA quartiles, using the lowest activity quintile (Q1) as reference. Women in the second to fourth quintile (Q2-Q4) consumed less added sugar from sugary foods (+2 tsp/day) and from sweetened beverages (+2 tsp/day; all p \u3c 0.05 vs. Q1). In men, added sugar intake was elevated in the highest activity quintile (Q5: +3 ± 1 tsp/day, p = 0.007 vs. Q1). Fruit and vegetable intake increased (women: Q1-Q4 +0.3 ± 0.1 cup eq/day; p \u3c 0.001; men: Q1-Q3 +0.3 ± 0.1 cup eq/day, p = 0.002) and stagnated in higher quintiles. Dairy intake increased with PA only in men (Q5: +0.3 ± 0.1 cup eq/day, p \u3c 0.001 vs. Q1). Results demonstrate a differential relationship between habitual PA and dietary intakes, whereby moderate but not necessarily highest PA levels are associated with reduced added sugar and increased nutrient-dense food consumption. Future research should examine specific mechanisms of food choices at various PA levels to ensure dietary behaviors (i.e., increased sugary food intake) do not negate positive effects of PA
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