2,598 research outputs found
Alternative Mathematical Technique to Determine LS Spectral Terms
We presented an alternative computational method for determining the
permitted LS spectral terms arising from electronic configurations. This
method makes the direct calculation of LS terms possible. Using only basic
algebra, we derived our theory from LS-coupling scheme and Pauli exclusion
principle. As an application, we have performed the most complete set of
calculations to date of the spectral terms arising from electronic
configurations, and the representative results were shown. As another
application on deducing LS-coupling rules, for two equivalent electrons, we
deduced the famous Even Rule; for three equivalent electrons, we derived a new
simple rule.Comment: Submitted to Phys. Rev.
Systematic computation of crystal field multiplets for X-ray core spectroscopies
We present a new approach to computing multiplets for core spectroscopies,
whereby the crystal field is constructed explicitly from the positions and
charges of surrounding atoms. The simplicity of the input allows the
consideration of crystal fields of any symmetry, and in particular facilitates
the study of spectroscopic effects arising from low symmetry environments. The
interplay between polarization directions and crystal field can also be
conveniently investigated. The determination of the multiplets proceeds from a
Dirac density functional atomic calculation, followed by the exact
diagonalization of the Coulomb, spin-orbit and crystal field interactions for
the electrons in the open shells. The eigenstates are then used to simulate
X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering spectra.
In examples ranging from high symmetry down to low symmetry environment,
comparisons with experiments are done with unadjusted model parameters as well
as with semi-empirically optimized ones. Furthermore, predictions for the RIXS
of low-temperature MnO and for Dy in a molecular complex are proposed.Comment: Accepted for publication in Phys. Rev.
Pacific 187Os/188Os isotope chemistry and U-Pb geochronology: synchroneity of global Os isotope change across OAE 2
Studies of OAE 2 sections beyond the Atlantic Ocean, Western Interior Seaway (WIS) and European pelagic shelf are limited. Here, we present initial osmium isotope stratigraphy (187Os/188Os–Osi) from two proto-Pacific sites that span the Cenomanian–Turonian boundary interval (CTBI): the Yezo Group (YG) section, Hokkaido, Japan, and the Great Valley Sequence (GVS), California, USA; to evaluate the 187Os/188Os seawater chemistry of the proto-Pacific. Additionally we combine new 206Pb/238U zircon CA-ID-TIMS geochronology from five volcanic tuff horizons of the Yezo Group section to test and facilitate inter-basinal integration with the WIS using radio-isotopically constrained age–depth models for both sections, and quantitatively constrain the absolute timing and duration of events across the CTBI. The YG shows an almost identical Osi profile to that of the WIS, and very similar to that of other sites of the proto-Atlantic and European pelagic oceans (Turgeon and Creaser, 2008 and Du Vivier et al., 2014). The characteristics of the Osi profile are radiogenic and heterogeneous (∼0.55–0.85) prior to the OAE 2, and synchronous with the inferred OAE 2 onset the Osi abruptly become unradiogenic and remain relatively homogeneous (∼0.20–0.30) before showing a gradual return to more radiogenic View the MathML source throughout the middle to late OAE 2. A206Pb/238U zircon age of an interbedded tuff (HK017) in the adjacent horizon to the first unradiogenic Osi value constrains the age of the Osi inflection at 94.44±0.14 Ma. This age, including uncertainty, agrees with the interpolated age of the same point in the Osi profile (94.28±0.25 Ma) in the only other dated OAE 2 section, the WIS; indicating a coeval shift in seawater chemistry associated with volcanism at the OAE 2 onset at the levels of temporal resolution (ca. 0.1 Myr). Further, prior to the onset of OAE 2 an enhanced radiogenic inflection in the Osi profile of the YG is correlative, within uncertainty, with a similar trend in the WIS based on the U–Pb age–depth model. The interpolated ages, 94.78±0.12 Ma and 94.66±0.25 Ma for this Osi inflection in the YG and WIS, respectively, indicate that palaeocirculation was sufficient to simultaneously influence transbasinal seawater chemistry. In contrast, the pre-OAE 2 Osi profile for the GVS is disparate to that of the YG and those of the proto-Atlantic and European pelagic shelf locations. We interpret the pre OAE 2 heterogeneous Osi values (0.30–0.95) to record a palaeobasin that was regionally influenced interchangeably by both unradiogenic (hydrothermal flux) and radiogenic (continental flux) Os. We conclude that the Osi profiles from the proto-Pacific sections record both trends that are consistent globally (OAE 2 onset, syn and post OAE 2), but also show regional differences (pre OAE 2) between OAE 2 sections worldwide. As such the Osi profiles coupled with U–Pb geochronology facilitate the correlation of OAE 2 stratigraphy, and demonstrate both regional and global ocean dynamics
GMRT observations of the field of INTEGRAL X-ray sources- II (newly discovered hard X-ray sources)
We have conducted low-frequency radio observations with the Giant Metrewave
Radio Telescope (GMRT) of 40 new hard X-ray sources discovered by the INTEGRAL
satellite. This survey was conducted in order, to study radio emissions from
these sources, to provide precise position and to identify new microquasar
candidates. From our observations we find that 24 of the X-ray sources have
radio candidates within the INTEGRAL error circle. Based on the radio
morphology, variability and information available from different wavelengths,
we categorize them as seventeen Galactic sources (4 unresolved, 7 extended, 6
extended sources in diffuse region) and seven extragalactic sources (2
unresolved, 5 extended). Detailed account for seventeen of these sources was
presented in earlier paper. Based on the radio data for the remaining sources
at 0.61 GHz, and the available information from NVSS, DSS, 2MASS and NED, we
have identified possible radio counterparts for the hard X-ray sources. The
three unresolved sources, viz IGR J173030601, IGR J174643213, and IGR
J184060539 are discussed in detail. These sources have been identified as
X-ray binaries with compact central engine and variable in X-ray and in the
radio, and are most likely microquasar candidates. The remaining fourteen
sources have extended radio morphology and are either diffuse Galactic regions
or extragalactic in origin.Comment: 9 pages, 7 figures, submitted to A&A. submitted to A&
Radio continuum and far-infrared emission from the galaxies in the Eridanus group
The Eridanus galaxies follow the well-known radio-FIR correlation. Majority
(70%) of these galaxies have their star formation rates below that of the Milky
Way. The galaxies having a significant excess of radio emission are identified
as low luminosity AGNs based on their radio morphologies obtained from the GMRT
observations. There are no powerful AGNs (L{20cm} > 10^{23} W Hz^{-1}) in the
group. The two most far-infrared and radio luminous galaxies in the group have
optical and HI morphologies suggestive of recent tidal interactions. The
Eridanus group also has two far-infrared luminous but radio-deficient galaxies.
It is believed that these galaxies are observed within a few Myr of the onset
of an intense star formation episode after being quiescent for at least a 100
Myr. The upper end of the radio luminosity distribution of the Eridanus
galaxies (L_{20cm} ~ 10^{22} W Hz^{-1}) is consistent with that of the field
galaxies, other groups, and late-type galaxies in nearby clusters.Comment: 16 pages; Accepted for publication in Journal of Astroph. & Astron.
March, 200
Predicting Post-Deployment Family Adaptation in U.S. Navy Families
Background: Although military families worldwide face changes that include adapting to peace and wartime deployments, few studies have explored how military families adapt to the post-deployment return of a service member.
Objectives: To identify variables that predicted post-deployment adaptation of U.S. Navy families.
Methods: A mixed method study guided by the Roy Adaptation Model included a convenience sample of 142 spouses of service members recently returned from deployment. The degree to which length of deployment, prior deployments, and years married, number of children, participation in religious and family support groups, communication, race, and interdependence predicted post-deployment family adaptation was tested. Multiple regression analysis and content analysis were used to analyze quantitative and qualitative data to better understand post- deployment adaptation of military families.
Results: Post-deployment family adaptation was significantly predicted by having been previously deployed and by scores measuring family interdependence. Content analysis of qualitative responses from 10 spouses indicated that 90% experienced integrated adaptive responses.
Conclusions: Family interdependence and prior deployments predicted levels of post-deployment family adaptation. Families who give time to adjust, communicate, and resume family routines experienced levels of adaptive response
Nascent starbursts in synchrotron-deficient galaxies with hot dust
Three nearby galaxies which have abnormally high infrared to radio continuum
ratios, NGC 1377, IC 1953 and NGC 4491, are investigated with a view to
understanding the physical origin of their peculiarity. We review the existing
data and present new radio continuum measurements along with near-infrared
integral-field spectroscopy and molecular gas observations. The three galaxies
have low luminosities but starburst-like infrared colors; in NGC 1377, no
synchrotron emission is detected at any wavelength; in IC 1953, the observed
synchrotron component is attributable to the spiral disk alone, and is lacking
in the central regions; the radio spectrum of NGC 4491 is unusually flat. We
also compare and contrast them with NGC 4418, a heavily extinguished galaxy
which shares some attributes with them. After examining various scenarios, we
conclude that these galaxies are most likely observed within a few Myr of the
onset of an intense star formation episode after being quiescent for at least ~
100 Myr. This starburst, while heating the dust, has not produced optical
signatures nor a normal amount of cosmic rays yet. We briefly discuss the
statistics of such galaxies and what they imply for star formation surveys.Comment: accepted for publication in ApJ -- 38 pages of text, 8 tables, 12
figures (fig. 1, 7 and 10 degraded
The Environments of Low and High Luminosity Radio Galaxies at Moderate Redshifts
In the local Universe, high-power radio galaxies live in lower density
environments than low-luminosity radio galaxies. If this trend continues to
higher redshifts, powerful radio galaxies would serve as efficient probes of
moderate redshift groups and poor clusters. Photometric studies of radio
galaxies at 0.3 < z < 0.5 suggest that the radio luminosity-environment
correlation disappears at moderate redshifts, though this could be the result
of foreground/background contamination affecting the photometric measures of
environment. We have obtained multi-object spectroscopy of in the fields of 14
lower luminosity (L_1.4GHz
1.2x10^25 W/Hz) radio galaxies at z ~ 0.3 to spectroscopically investigate the
link between the environment and the radio luminosity of radio galaxies at
moderate redshifts. Our results support the photometric analyses; there does
not appear to be a correlation between the luminosity of a radio galaxy and its
environment at moderate redshifts. Hence, radio galaxies are not efficient
signposts for group environments at moderate redshifts.Comment: 7 pages, 9 figures, Accepted for publication in A
Book Reviews
Reviews of the following books: Hardliners: A History of the Emery-Waterhouse Company by Edgar Allen Beem and Charles L. Hildreth, Jr.; L.L. Bean: The Making of an American Icon by Leon Gorman; Eminent Mainers: Succinct Biographies of Thousands of Amazing Mainers, Mostly Dead and a Few People from Away Who Have Done Something Useful Within the State Maine; Compiled by Arthur Douglas Stover and Maine: Downeast and Different: An Illustrated History by Neil Rolde; ; The Rangeley and Its Region: The Famous Boat and Lakes of Western Maine by Stephen A. Cole; Voyages: A Maine Franco-American Reader, edited by Nelson Madore and Barry Rodrigu
FIRBACK IV: Towards the nature of the 170microns source population
We present a detailed study of the brighter ( detections) sources
in the 170m FIRBACK northern N1 ISO survey, with the help of complementary
data in the optical, radio, and mid-IR domain. For 82% of them, an optical
galaxy counterpart is identified, either as the unique source of the IR
emission, or as part of a multiple identification. With less than 15% of AGNs,
these sources are essentially local, moderate starbursters with a dominating
cold dust component. and represent a population of cold galaxies rather
neglected up to now. Their colours do not match those of the far-IR Cosmic IR
Background (CIB), to which they contribute less than 5%. The bulk of the
sources contributing to the CIB is thus to be searched for in more distant
galaxies, possibly counterparts of the fainter FIRBACK sources still under
study. These bright, local, galaxies however play an important role in the
evolution of IR galaxies: they dominate the number counts at high 170 m
fluxes, and represent half of the contribution at 250 mJy. Although not
particularly massive (typically M*), they form more stars than a typical spiral
galaxy and many are bulge dominated, that could represent the remnant of a
former merger. The fainter part of this population may represent the missing
link with the higher-z sources found in sub-mm observations.Comment: 40 pages, 10 figures, accepted for publication in Astronomy &
Astrophysic
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