251 research outputs found
Social Cohesion in Omaha
How are you feeling today? a physician asks, and the answer to that question can become the basis for a serious analysis of the general well-being of the individual. Similarly, we now ask the question: What makes a community? and state that the answer can lead us to important levels of analysis into the nature of the ongoing social order
Social Participation and Life Satisfaction of Senior Citizens
This is the second in a series of three surveys relating social participation and life satisfaction as reported by residents of five high-rise apartment buildings in the city of Omaha, These buildings (towers) are available to low-income senior citizens, and are operated under the direction of the Omaha Housing Authority. Recreational facilities and activities are provided by the City of Omaha Parks, Recreation and Public Property Department and it was at their request that this study was undertaken by the Urban Studies Center at the University of Nebraska at Omaha
Flavor Changing Supersymmetry Interactions in a Supernova
We consider for the first time R-parity violating interactions of the Minimal
Standard Supersymmetric Model involving neutrinos and quarks (``flavor changing
neutral currents'', FCNC's) in the infall stage of stellar collapse. Our
considerations extend to other kinds of flavor changing neutrino reactions as
well. We examine non-forward neutrino scattering processes on heavy nuclei and
free nucleons in the supernova core. This investigation has led to four
principal original discoveries/products: (1) first calculation of neutrino
flavor changing cross sections for spin one half (e.g. free nucleon) and spin
zero nuclear targets; (2) discovery of nuclear mass number squared (A squared)
coherent amplification of neutrino-quark FCNC's; (3) analysis of FCNC-induced
alteration of electron capture and weak/nuclear equilibrium in the collapsing
core; and (4) generalization of the calculated cross sections (mentioned in 1)
for the case of hot heavy nuclei to be used in collapse/supernova and neutrino
transport simulations. The scattering processes that we consider allow electron
neutrinos to change flavor during core collapse, thereby opening holes in the
electron neutrino sea, which allows electron capture to proceed and results in
a lower core electron fraction. A lower electron fraction implies a lower
homologous core mass, a lower shock energy, and a greater nuclear
photo-disintegration burden for the shock. In addition, unlike the standard
supernova model, the core now could have net muon and/or tau lepton numbers.
These effects could be significant even for supersymmetric couplings below
current experimental bounds.Comment: 22 pages, 7 figures, typos corrected, abstract modifided, minor
additions to conten
Using VO tools to investigate distant radio starbursts hosting obscured AGN in the HDF(N) region
A 10-arcmin field around the HDF(N) contains 92 radio sources >40 uJy,
resolved by MERLIN+VLA at 0".2-2".0 resolution. 55 have Chandra X-ray
counterparts including 18 with a hard X-ray photon index and high luminosity
characteristic of a type-II (obscured) AGN. >70% of the radio sources have been
classified as starbursts or AGN using radio morphologies, spectral indices and
comparisons with optical appearance and MIR emission. Starbursts outnumber
radio AGN 3:1. This study extends the VO methods previously used to identify
X-ray-selected obscured type-II AGN to investigate whether very luminous radio
and X-ray emission originates from different phenomena in the same galaxy. The
high-redshift starbursts have typical sizes of 5--10 kpc and star formation
rates of ~1000 Msun/yr. There is no correlation between radio and X-ray
luminosities nor spectral indices at z>~1.3. ~70% of both the radio-selected
AGN and the starburst samples were detected by Chandra. The X-ray luminosity
indicates the presence of an AGN in at least half of the 45 cross-matched radio
starbursts, of which 11 are type-II AGN including 7 at z>1.5. This distribution
overlaps closely with the X-ray detected radio sources which were also detected
by SCUBA. Stacked 1.4-GHz emission at the positions of radio-faint X-ray
sources is correlated with X-ray hardness. Most extended radio starbursts at
z>1.3 host X-ray selected obscured AGN. Radio emission from most of these
ultra-luminous objects is dominated by star formation but it contributes less
than 1/3 of their X-ray luminosity. Our results support the inferences from
SCUBA and IR data, that at z>1.5, star formation is an order of magnitude more
extended and more copious, it is closely linked to AGN activity and it is
triggered differently, compared with star formation at lower redshifts.Comment: 24 pages, 12 figures, uses graphicx, rotating, natbib, supertabular
packages and aa.cls. Accepted for publication in A&
Madelung Fluid Model for The Most Likely Wave Function of a Single Free Particle in Two Dimensional Space with a Given Average Energy
We consider spatially two dimensional Madelung fluid whose irrotational
motion reduces into the Schr\"odinger equation for a single free particle. In
this respect, we regard the former as a direct generalization of the latter,
allowing a rotational quantum flow. We then ask for the most likely wave
function possessing a given average energy by maximizing the Shannon
information entropy over the quantum probability density. We show that there
exists a class of solutions in which the wave function is self-trapped,
rotationally symmetric, spatially localized with finite support, and spinning
around its center, yet stationary. The stationarity comes from the balance
between the attractive quantum force field of a trapping quantum potential
generated by quantum probability density and the repulsive centrifugal force of
a rotating velocity vector field. We further show that there is a limiting case
where the wave function is non-spinning and yet still stationary. This special
state turns out to be the lowest stationary state of the ordinary Schr\"odinger
equation for a particle in a cylindrical tube classical potential.Comment: 19 page
Preliminary study of the influence of red blood cells morphometry on the species determinism of domestic animals
Aim: This survey was realized on cattle, sheep, goats, horses, and dogs, in order to study the influence of three morphometric parameters: the diameter, the circumference and the surface of red blood cells on the determinism of these species.
Materials and Methods: For each species, blood samples were taken from 15 adult female by jugular venipuncture with confection of blood smears on microscope slides immediately after blood collection and stained according to the method of May-GrĂĽndwald Giemsa. Morphometric study was realized using the software OPTIKA Pro Vision. To better describe the results, the statistical analysis was assessed by using the descriptive Boxplots test, ANOVA, and the Student's t-test.
Results: The morphometric parameters of red blood cells are biggest in dogs followed by horses, cattle, and sheep, while goats have the lowest ones.
Conclusion: This investigation allowed us to show that from a drop of blood we can have an idea about the animal species taking into account the diameter, the circumference, and the surface of erythrocytes
An XMM-Newton Study of the Hard X-ray Sky
We report on the spectral properties of a sample of 90 hard X-ray selected
serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80
10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified
with 0.1<z<2 and most of them are classified as broad line AGNs. A simple model
consisting of power law modified by Galactic absorption offers an acceptable
fit to ~65% of the source spectra. This fit yields an average photon index of
~1.55 over the whole sample. We also find that the mean slope of the
QSOs in our sample turns out to remain nearly constant (~1.8-1.9)
between 0<z<2, with no hints of particular trends emerging along z. An
additional cold absorption component with 10^(21)<Nh<10^(23) cm^(-2) is
required in ~30% of the sources. Considering only subsamples that are complete
in flux, we find that the observed fraction of absorbed sources (i.e. with
Nh>~10^(22) cm^(-2)) is ~30%, with little evolution in the range 2<F(2-10)<80
10^(-14) erg/cm2/s. Interestingly, this value is a factor ~2 lower than
predicted by the synthesis models of the CXB. This finding, detected for the
first time in this survey, therefore suggests that most of the heavily obscured
objects which make up the bulk of the CXB will be found at lower fluxes
(F(2-10)< 10^(-14) erg/cm2/s). This mismatch together with other recent
observational evidences which contrast with CXB model predictions suggest that
one (or more) of the assumptions usually included in these models need to be
revised.Comment: 20 pages, 13 figures, accepted for publication in A&
Characterization of AGN and their hosts in the Extended Groth Strip: a multiwavelength analysis
We have employed a reliable technique of classification of Active Galactic
Nuclei (AGN) based on the fit of well-sampled spectral energy distributions
(SEDs) with a complete set of AGN and starburst galaxy templates. We have
compiled ultraviolet, optical, and infrared data for a sample of 116 AGN
originally selected for their X-ray and mid-infrared emissions (96 with single
detections and 20 with double optical counterparts). This is the most complete
compilation of multiwavelength data for such a big sample of AGN in the
Extended Groth Strip (EGS). Through these SEDs, we are able to obtain highly
reliable photometric redshifts and to distinguish between pure and
host-dominated AGN. For the objects with unique detection we find that they can
be separated into five main groups, namely: Starburst-dominated AGN (24 % of
the sample), Starburst-contaminated AGN (7 %), Type-1 AGN (21 %), Type-2 AGN
(24 %), and Normal galaxy hosting AGN (24 %). We find these groups concentrated
at different redshifts: Type-2 AGN and Normal galaxy hosting AGN are
concentrated at low redshifts, whereas Starburst-dominated AGN and Type-1 AGN
show a larger span. Correlations between hard/soft X-ray and ultraviolet,
optical and infrared luminosities, respectively, are reported for the first
time for such a sample of AGN spanning a wide range of redshifts. For the 20
objects with double detection the percentage of Starburst-dominated AGN
increases up to 48%.Comment: 38 pages, 8 figures, 5 tables. Accepted by A
On the X-ray properties of submm-selected galaxies
We present an analysis of the X-ray properties of 35 submm galaxies(SMGs) in
the CDF-N. Using a sample of robust 850micron-selected galaxies, with accurate
positions from Spitzer and/or radio counterparts, we find 16 objects (45+/-8%)
with significant X-ray detections in the 2Ms Chandra data. 6 of these SMGs
(~17+/-6%) have measured X-ray luminosities or upper limits consistent with
those expected based on the far-infrared (FIR) or radio-derived star formation
rate (SFR), and hence with the X-rays coming solely from star formation. In
another 7 sources (20+/-7%) a dominant AGN contribution to the X-ray emission
is required, while in 3 more it is unclear whether stellar process or accretion
are responsible. Stacking of the X-ray undetected SMGs reveals a highly
significant detection. If due to star formation, this corresponds to an average
X-ray derived SFR of ~150 Msun/yr. We deduce that the AGN fraction in SMGs
based on X-ray observations is 20-29 (+/-7) %, which is towards the lower limit
of previous estimates. Spectral analysis shows that in general the SMGs are not
heavily obscured in the X-ray but most of the SMGs classfied as AGN show
absorption with N_H in excess of 10^22 cm^-2. Of the secure AGN, the bolometric
luminosity appears to be dominated by the AGN in only 3 cases. In ~85% of the
SMGs, the X-ray spectrum effectively rules out an AGN contribution that
dominates the bolometric emission, even if the AGN is Compton thick. The
evidence therefore suggests that intense star formation accounts for both the
FIR and X-ray emission in most SMGs. We argue that, rather than having an
especially high AGN fraction or duty cycle, SMGs have a high X-ray detection
rate at very faint fluxes partly because of their high star formation rates
and, in rarer cases, because the submm emission is from an AGN.(abridged)Comment: 12 pages, 5 figures, accepted for publication in MNRA
A Correlation Between the Ionization State of the Inner Accretion Disk and the Eddington Ratio of Active Galactic Nuclei
X-ray reflection features observed from the innermost regions of accretion
disks in Active Galactic Nuclei (AGNs) allow important tests of accretion
theory. In recent years it has been possible to use the Fe K line and
reflection continuum to parametrize the ionization state of the irradiated
inner accretion disk. Here, we collect 10 measurements of xi, the disk
ionization parameter, from 8 AGNs with strong evidence for reflection from the
inner accretion disk and good black hole mass estimates. We find strong
statistical evidence (98.56% confidence) for a nearly linear correlation
between xi and the AGN Eddington ratio. Moreover, such a correlation is
predicted by a simple application of alpha-disk accretion theory, albeit with a
stronger dependence on the Eddington ratio. The theory shows that there will be
intrinsic scatter to any correlation as a result of different black hole spins
and radii of reflection. There are several possibilities to soften the
predicted dependence on the Eddington ratio to allow a closer agreement with
the observed correlation, but the current data does not allow for an unique
explanation. The correlation can be used to estimate that MCG-6-30-15 should
have a highly ionized inner accretion disk, which would imply a black hole spin
of ~0.8. Additional measurements of xi from a larger sample of AGNs are needed
to confirm the existence of this correlation, and will allow investigation of
the accretion disk/corona interaction in the inner regions of accretion disks.Comment: 21 pages, 2 figures, accepted by Ap
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