130 research outputs found
Effects of Pulsed Electric Field (PEF) Preprocessing During Maceration for Red Wine Processing of Idaho Wines: Analysis of Polyphenol Content in Sangiovese Red Wine
The wine industry has created around 70 wineries in Idaho and has had a $209.6 million impact on its economy. The cool climate has made white wines its top-produced wine, however, Idaho has recently been focusing on increasing production of red wines. Sangiovese grapes are a light red color, so producers are interested in increasing the strength of the color pigment. Red wine is produced through the maceration of grapes. Maceration is the process where grapes soak in their juice after being crushed to extract color and flavor from their skins. The maceration time is around 7 days, and producers hope to decrease that time to increase wine production
NGC 3627: a galaxy-dwarf collision?
Group galaxies very often show distinct signs of interaction with both
companion galaxies and the intragroup medium. X-ray observations are
particularly helpful because they provide information on the temperatures and
the densities of the hot gas in galaxies and intergalactic space. This can put
important constraints on the nature and timescales of these interactions. We
use the XMM-Newton X-ray observations of NGC 3627 in the Leo Triplet galaxy
group to explain peculiar features visible in the polarized radio maps. We
analyzed soft X-ray (0.2-1 keV) emission from NGC 3627 to study the
distribution of the hot gas and its temperature in different areas of the
galaxy. Any change throughout the disk can reflect distortions visible in the
radio polarized emission. We also studied two bright point sources that are
probably tightly linked to the evolution of the galaxy. We find an increase in
the temperature of the hot gas in the area of the polarized radio ridge in the
western arm of the galaxy. In the eastern part of the disk we find two
ultra-luminous X-ray sources. We note a large hot gas temperature difference
(by a factor of 2) between the two bar ends. The polarized radio ridge in the
western arm of NGC 3627 is most likely formed by ram-pressure effects caused by
the movement of the galaxy through the intragroup medium. To explain the
distortions visible in the eastern part of the disk in polarized radio maps,
the asymmetry of the bar, and the distortion of the eastern arm, we propose a
recent collision of NGC 3627 with a dwarf companion galaxy.Comment: 8 pages, 6 figures, 5 tables. Accepted for publication in Astronomy
and Astrophysic
Production of ring-like structure in the cocoon of Hercules A
The radio lobes of the radio galaxy Hercules A contain intriguing ring-like
structures concentric with the jet axis. To investigate the occurrence of such
features, we have used hydrodynamic simulations of jets with a range of Mach
numbers (from M=2 to 50) and densities (down to a ratio of 1E-4 relative to the
background) to generate ray-traced images simulating synchrotron emission from
the time-dependent shock structures. We compare these images with observations
of Hercules A, and consider the physical nature and temporal evolution of the
most plausible configurations. We find that the observed ring-like structures
are well explained as nearly annular shocks propagating in the backflow
surrounding the jet. We infer that the jet is oriented at between 30 and 70
degrees to the line of sight, consistent with radio depolarisation observations
of Gizani & Leahy. The observational lack of hot-spots at the extremities of
the radio lobes, and the possible presence of a buried hot-spot near the base
of the western lobe, are explained in terms of the intrinsic brightness
fluctuations and dynamics of the terminal shock of an ultra-light, low Mach
number jet that surges along its axis due to intermittent pinching and
obstruction by turbulent backflow in the cocoon. We conclude from the
appearance of both sides of the Hercules A, that both jets are on the
borderline of becoming fully turbulent.Comment: 25 pages; 11 figures; 2 tables; ApJ submitted & revised. A version
with higher resoluion figures is at
http://www.mso.anu.edu.au/~saxton/show/papers/hera.pd
Fossil AGN jets as ultra high energy particle accelerators
Remnants of AGN jets and their surrounding cocoons leave colossal
magnetohydrodynamic (MHD) fossil structures storing total energies ~10^{60}
erg. The original active galacic nucleus (AGN) may be dead but the fossil will
retain its stable configuration resembling the reversed-field pinch (RFP)
encountered in laboratory MHD experiments.
In an RFP the longitudinal magnetic field changes direction at a critical
distance from the axis, leading to magnetic re-connection there, and to slow
decay of the large-scale RFP field. We show that this field decay induces
large-scale electric fields which can accelerate cosmic rays with an E^{-2}
power-law up to ultra-high energies with a cut-off depending on the fossil
parameters. The cut-off is expected to be rigidity dependent, implying the
observed composition would change from light to heavy close to the cut-off if
one or two nearby AGN fossils dominate. Given that several percent of the
universe's volume may house such slowly decaying structures, these fossils may
even re-energize ultra-high energy cosmic rays from distant/old sources,
offsetting the ``GZK-losses'' due to interactions with photons of the cosmic
microwave background radiation and giving evidence of otherwise undetectable
fossils. In this case the composition would remain light to the highest
energies if distant sources or fossils dominated, but otherwise would be mixed.
It is hoped the new generation of cosmic ray experiments such as the Pierre
Auger Observatory and ultra-high energy neutrino telescopes such as ANITA and
lunar Cherenkov experiments will clarify this.Comment: 11 pages, 6 figures, additional references and explanations. Accepted
for publication in MNRA
Morphological Annotations for Groups in the FIRST Database
The morphology of selected groups of sources in the FIRST (Faint Images of
the Radio Sky at Twenty Centimeters) survey and catalog is examined. Sources in
the FIRST catalog (April 2003 release, 811117 entries) were sorted into
singles, doubles, triples and groups of higher-count membership based on a
proximity criteria. The 7106 groups with four or more components were examined
individually for bent types including, but not limited to, wide-angle tail
(WAT) and narrow-angle tail (NAT) types. In the process of this examination,
ring, double-double (DD), X-shaped, hybrid morphology (HYMOR), giant radio
sources (GRS), and the herein described W-shaped and tri-axial morphology
systems were also identified. For the convenience of the reader separate tables
for distinctive types were generated. A few curiosities were found. For the
16,950 three-component groups and 74,788 two-component groups, catalogs with
probability estimates for bent classification, as determined by pattern
recognition techniques, are presented.Comment: 76 pages, 30 figures Accepted by Astrophysical Journal Supplement
Serie
Recent Developments in Fluorescence Correlation Spectroscopy for Diffusion Measurements in Planar Lipid Membranes
Fluorescence correlation spectroscopy (FCS) is a single molecule technique used mainly for determination of mobility and local concentration of molecules. This review describes the specific problems of FCS in planar systems and reviews the state of the art experimental approaches such as 2-focus, Z-scan or scanning FCS, which overcome most of the artefacts and limitations of standard FCS. We focus on diffusion measurements of lipids and proteins in planar lipid membranes and review the contributions of FCS to elucidating membrane dynamics and the factors influencing it, such as membrane composition, ionic strength, presence of membrane proteins or frictional coupling with solid support
An XMM-Newton Observation of Abell 2597
We report on a 120 ks XMM-Newton observation of the galaxy cluster Abell
2597. Results from both the European Photon Imaging Camera (EPIC) and the
Reflection Grating Spectrometer (RGS) are presented. From EPIC we obtain radial
profiles of temperature, density and abundance, and use these to derive cooling
time and entropy. We illustrate corrections to these profiles for projection
and point spread function (PSF) effects. At the spatial resolution available to
XMM-Newton, the temperature declines by around a factor of two in the central
150 kpc or so in radius, and the abundance increases from about one-fifth to
over one-half solar. The cooling time is less than 10 Gyr inside a radius of
130 kpc. EPIC fits to the central region are consistent with a cooling flow of
around 100 solar masses per year. Broad-band fits to the RGS spectra extracted
from the central 2 arcmin are also consistent with a cooling flow of the same
magnitude; with a preferred low-temperature cut-off of essentially zero. The
data appear to suggest (albeit at low significance levels below formal
detection limits) the presence of the important thermometer lines from Fe XVII
at 15, 17 Angstrom rest wavelength, characteristic of gas at temperatures ~ 0.3
keV. The measured flux in each line is converted to a mass deposition estimate
by comparison with a classical cooling flow model, and once again values at the
level of 100 solar masses per year are obtained. These mass deposition rates,
whilst lower than those of previous generations of X-ray observatories, are
consistent with those obtained from UV data for this object. This raises the
possibility of a classical cooling flow, at the level of around 100 solar
masses per year, cooling from 4 keV by more than two orders of magnitude in
temperature.Comment: 16 pages, 18 figures. Accepted for publication in MNRA
Formation of cold filaments in cooling flow clusters
Emission-lines in the form of filamentary structures is common in bright
clusters characterized by short cooling times. In the Perseus cluster, cold
molecular gas, tightly linked to the H filaments, has been recently
revealed by CO observations. In order to understand the origin of these
filamentary structures, we have investigated the evolution of the hot ICM gas
perturbed by the AGN central activity in a Perseus like cluster. Using
very-high resolution TreeSPH simulations combined with a multiphase model and a
model of plasma bubbles, we have been able to follow the density and
temperature evolution of the disturbed ICM gas around the bubbles. Our
simulations show that a fraction of the gas present at the
center of clusters is trapped and entrained by the rising buoyant bubble to
higher radius where the AGN heating is less efficient. The radiative cooling
makes it cool in a few tens of Myr below , forming cold
filamentary structures in the wake and in the rim of the bubbles.Comment: 4 Pages, 3 figures + online material ; Accepted for publication in
A&A Letters. Higher resolution version may be downloaded here
http://aramis.obspm.fr/~revaz/aa.2007.8915
Alteration assemblages in Martian meteorites: implications for near-surface processes
The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals – which comprise up to 1 vol.% of the meteorites – provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25 – 150 °C) brines. This is consistent with the simple mineralogy of these assemblages – Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays – and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 "rosettes". Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event post-dating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes.
Radiometric dating (K-Ar, Rb-Sr) of the secondary mineral assemblages in one of the nakhlites (Lafayette) suggests that they formed between 0 and 670 Myr, and certainly long after the crystallisation of the host igneous rocks. Crystallisation of ALH84001 carbonate took place 0.5 Gyr after the parent rock. These age ranges and the other research on these assemblages suggest that environmental conditions conducive to near-surface liquid water have been present on Mars periodically over the last 1 Gyr. This fluid activity cannot have been continuous over geological time because in that case much more silicate alteration would have taken place in the meteorite parent rocks and the soluble salts would probably not have been preserved.
The secondary minerals could have been precipitated from brines with seawater-like composition, high bicarbonate contents and a weakly acidic nature. The co-existence of siderite (Fe-carbonate) and clays in the nakhlites suggests that the pCO2 level in equilibrium with the parent brine may have been 50 mbar or more. The brines could have originated as flood waters which percolated through the top few hundred meters of the crust, releasing cations from the surrounding parent rocks. The high sulphur and chlorine concentrations of the martian soil have most likely resulted from aeolian redistribution of such aqueously-deposited salts and from reaction of the martian surface with volcanic acid volatiles.
The volume of carbonates in meteorites provides a minimum crustal abundance and is equivalent to 50–250 mbar of CO2 being trapped in the uppermost 200–1000 m of the martian crust. Large fractionations in 18O between igneous silicate in the meteorites and the secondary minerals (30) require formation of the latter below temperatures at which silicate-carbonate equilibration could have taken place (400°C) and have been taken to suggest low temperatures (e.g. 150°C) of precipitation from a hydrous fluid
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