439 research outputs found
Limits on the dark matter particle mass from black hole growth in galaxies
I review the properties of degenerate fermion balls and investigate the dark
matter distribution at galactic centers using NFW, Moore and isothermal density
profiles. I show that dark matter becomes degenerate for particles masses of a
few keV at distances less than a few parsec from the center of our galaxy. To
explain the galactic center black hole of mass of and a supermassive black hole of at a redshift of 6.41 in SDSS quasars, the mass of the fermion
ball is assumed to be between and . This constrains the mass of the dark matter particle between
and . The lower limit on the dark matter mass is
improved to about {\rm 6 keV} if exact solutions of Poisson's equation are used
in the isothermal power law case. The constrained dark matter particle could be
interpreted as a sterile neutrino.Comment: 3 pages, To be published in Proceedings of the 11th Marcel Grossmann
meeting on general relativity, 23-29 July 2006, Berlin, German
Comparative Study of Life Histories, Laboratory Rearing, and Immature Stages of \u3ci\u3eEuschistus Servus\u3c/i\u3e and \u3ci\u3eEuschistus Variolarius\u3c/i\u3e (Hemiptera: Pentatomidae)
A comparative study was conducted of the field life histories of Euschistus servus and E. varialarius in southern Illinois, their life cycles under controlled laboratory conditions, and their immature stages.
The results indicate that E. servus is bivoltine and E. variolarius is univoltine. Adults of both species emerged from overwintering sites during early April, began feeding and copulating on leaves of common mullein (Verbascum thapsus) and surrounding vegetation, and reproduced shortly thereafter. Neither eggs and first instars of either species, nor second instars of E. variolarius, were collected in the field. Seasonal occurrences of the adults and subsequent immature stages are discussed for each species. No individuals were found after the first week of November.
Both species were reared on green beans (Phaseolus vulgaris) under a 16L:8D photoperiod and constant temperature of 23 ± 0.06° C. The incubation period averaged 5.8 days for E. servus and 5.4 days for E. variolanus. Durations of the 5 subsequent stadia averaged, respectively, 5, 6, 6.7, 9.3, and 11.5 days for E. servus, and 4.9,5.7,7.8,9.7, and 13.3 days for E. varialarius. Comparisons of incubation period and stadia between the two species showed that only the stadia for the first instars were not statistically different. Total developmental period was longer for E. varialarius than for E. servus.
The external anatomy of the egg and each of the five nymphal instars is described for each species
Solventless substitution chemistry of iron and ruthenium metal carbonyl complexes
ABSTRACT
Solventless reactions of substituted cyclopentadienyl metal carbonyls of iron and ruthenium
with electron donor ligands have been carried out.
The reactions between CpFe(CO)2I and a range of phosphine ligands occurred in melt phase
and yielded two typical compounds : salt product, [CpFe(CO)2PR3]I, and non-salt product,
CpFe(CO)PR3I with the salt product being predominant. The complex [CpFe(CO)2]2 was
used to catalyze these reactions. The progress of the reactions was followed by 1H NMR
spectroscopy. The characterization of products correlates well with the products obtained
when working in solution medium.
The presence of a Me substituent on the Cp ring was found to favour the salt product
formation but generally led to lower rates of reaction.
Solventless reactions between RCpRu(CO)2I (R = H, Me) and solid phosphine ligands were
also carried out. It has been observed that the ruthenium complexes were less reactive
compared with their iron analogues but led to the same types of products namely salt and
non-salt.
The phosphite ligands were found to be less reactive than their phosphine analogues. In fact,
the solventless reactions between RCpM(CO)2I (R = H, Me; M = Fe, Ru) were very slow
even in the presence of [CpFe(CO)2]2 as a catalyst. However, when Me3NO.2H2O was added
to the reaction mixture in solventless conditions, the non-salt product was obtained in a short
period of time at 80oC.
A range of cyclopentadienyl based metal complexes e.g [CpMo(CO)3]2, [MeCpRu(CO)2]2
etc. and palladium based compounds such as PdO, Pd/CaCO3 5% etc. were found to be good
catalysts for the solventless reactions between CpFe(CO)2I and PPh3. Solventless migratory-insertion reactions have been successfully conducted between
CpFe(CO)2CH3 and a range of solid phosphine ligands. Only the acetyl products,
CpFe(CO)[PR3]COCH3 were obtained.
SO2 insertion into RCpFe(CO)2R’ (R = H, CH3; R’ = CH3, CH2Ph) occurred quite easily at
room temperature. However, when R was a carboxylic acid group, CO2H, no reaction took
place. CO insertion into the same systems did not happen in solventless conditions
The Stink Bugs (Hemiptera: Heteroptera: Pentatomidae) of Washington State
Froeschner (1988) recorded 23 species of stink bugs (Hemiptera: Heteroptera: Pentatomidae) from Washington State. Based on material primarily housed in the M. T. James Entomological Collection at Washington State University, the number of species is increased to 51. Three species recorded by Froeschner (1988) were not found in our collections: Apateticus crocatus (Uhler), Chlorochroa rossiana Buxton and Thomas, and Tepa rugulosa (Say). Species recorded from Washington State for the first time are: Apoecilus bracteatus (Fitch), Perillus bioculatus (Fabricius), Podisus maculiventris (Say), P. pallens (Stål), P. placidus Uhler, P. serieventris Uhler, Zicrona caerulea (Linnaeus), Halyomorpha halys (Stål), Brochymena quadripustulata (Fabricius), B. sulcata Van Duzee, Acrosternum hilare (Say), Aelia americana Dallas, Banasa euchlora Stål, B. tumidifrons Thomas and Yonke, Chlorochroa congrua Uhler, Coenus delius (Say), Cosmopepla uhleri Montandon, Dendrocoris pini Montandon, Euschistus servus (Say), E. tristigmus (Say), E. variolarius (Palisot), Holcostethus limbolarius (Say), Neottiglossa sulcifrons Stål, N. undata (Say), Prionosoma podopioides (Uhler), Tepa yerma (Rolston), Trichopepla grossa (Van Duzee), and Amaurochrous vanduzeei Barber and Sailer
Degenerate Fermi gas perturbations at standard background cosmology
The hypothesis of a tiny fraction of the cosmic inventory evolving
cosmologically as a degenerate Fermi gas test fluid at some dominant
cosmological background is investigated. Our analytical results allow for
performing preliminary computations to the evolution of perturbations for
relativistic and non-relativistic test fluids. The density fluctuation,
, the fluid velocity divergence, , and an explicit expression
for the dynamics of the shear stress, , are obtained for a degenerate
Fermi gas in the background regime of radiation. Extensions to the dominance of
matter and to the CDM cosmological background are also investigated
and lessons concerning the formation of large structures of degenerate Fermi
gas are depicted.Comment: 20 pages, 4 figure
Degenerate sterile neutrino dark matter in the cores of galaxies
We study the distribution of fermionic dark matter at the center of galaxies
using NFW, Moore and isothermal density profiles and show that dark matter
becomes degenerate for particle masses of a few {\rm keV} and for distances
less than a few parsec from the center of our galaxy. A compact degenerate core
forms after galaxy merging and boosts the growth of supermassive black holes at
the center of galaxies. To explain the galactic center black hole of mass of
and a supermassive black hole of at a redshift of 6.41 in SDSS quasars, we require a
degenerate core of mass between and . This constrains the mass of the dark matter particle between
and . The lower limit on the dark matter mass is
improved to {\rm 7 keV} if exact solutions of Poisson's equation are used in
the isothermal power law case. We argue that the constrained particle could be
the long sought dark matter of the Universe that is interpreted here as a
sterile neutrino.Comment: 4 pages, 1 figure, Accepted for publication in Astronomy &
Astrophysics Letter
Origin and physics of the highest energy cosmic rays: What can we learn from Radio Astronomy?
Here in this lecture we will touch on two aspects, one the new radio methods
to observe the effects of high energy particles, and second the role that radio
galaxies play in helping us understand high energy cosmic rays. We will focus
here on the second topic, and just review the latest developments in the first.
Radio measurements of the geosynchrotron radiation produced by high energy
cosmic ray particles entering the atmosphere of the Earth as well as radio
\v{C}erenkov radiation coming from interactions in the Moon are another path;
radio observations of interactions in ice at the horizon in Antarctica is a
related attempt. Radio galaxy hot spots are prime candidates to produce the
highest energy cosmic rays, and the corresponding shock waves in relativistic
jets emanating from nearly all black holes observed. We will review the
arguments and the way to verify the ensuing predictions. This involves the
definition of reliable samples of active sources, such as black holes, and
galaxies active in star formation. The AUGER array will probably decide within
the next few years, where the highest energy cosmic rays come from, and so
frame the next quests, on very high energy neutrinos and perhaps other
particles.Comment: 11 pages, To appear in Proceedings of International School of
Astrophysics at Ultra-high Energies, 20-27 June, 2006, Erice, Sicily, Ital
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