730 research outputs found
The future of the subsurface chlorophyll-a maximum in the Canada Basin-A model intercomparison
Six Earth system models and three ocean-ice-ecosystem models are analyzed to evaluate magnitude and depth of the subsurface Chl-a maximum (SCM) in the Canada Basin and ratio of surface to subsurface Chl-a in a future climate scenario. Differences in simulated Chl-a are caused by large intermodel differences in available nitrate in the Arctic Ocean and to some extent by ecosystem complexity. Most models reproduce the observed SCM and nitracline deepening and indicate a continued deepening in the future until the models reach a new state with seasonal ice-free waters. Models not representing a SCM show either too much nitrate and hence no surface limitation or too little nitrate with limited surface growth only. The models suggest that suppression of the nitracline and deepening of the SCM are caused by enhanced stratification, likely driven by enhanced Ekman convergence and freshwater contributions with primarily large-scale atmospheric driving mechanisms. The simulated ratio of near-surface Chl-a to depth-integrated Chl-a is slightly decreasing in most areas of the Arctic Ocean due to enhanced contributions of subsurface Chl-a. Exceptions are some shelf areas and regions where the continued ice thinning leaves winter ice too thin to provide a barrier to momentum fluxes, allowing winter mixing to break up the strong stratification. Results confirm that algorithms determining vertically integrated Chl-a from surface Chl-a need to be tuned to Arctic conditions, but likely require little or no adjustments in the future
Measuring Black Hole Spin using X-ray Reflection Spectroscopy
I review the current status of X-ray reflection (a.k.a. broad iron line)
based black hole spin measurements. This is a powerful technique that allows us
to measure robust black hole spins across the mass range, from the stellar-mass
black holes in X-ray binaries to the supermassive black holes in active
galactic nuclei. After describing the basic assumptions of this approach, I lay
out the detailed methodology focusing on "best practices" that have been found
necessary to obtain robust results. Reflecting my own biases, this review is
slanted towards a discussion of supermassive black hole (SMBH) spin in active
galactic nuclei (AGN). Pulling together all of the available XMM-Newton and
Suzaku results from the literature that satisfy objective quality control
criteria, it is clear that a large fraction of SMBHs are rapidly-spinning,
although there are tentative hints of a more slowly spinning population at high
(M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of
the spins of stellar-mass black holes in X-ray binaries. In general,
reflection-based and continuum-fitting based spin measures are in agreement,
although there remain two objects (GROJ1655-40 and 4U1543-475) for which that
is not true. I end this review by discussing the exciting frontier of
relativistic reverberation, particularly the discovery of broad iron line
reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and
MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk
reflection, this detection of reverberation demonstrates that future large-area
X-ray observatories such as LOFT will make tremendous progress in studies of
strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The
Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds
a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the
referencing of the discovery of soft lags in 1H0707-495 (which were in fact
first reported in Fabian et al. 2009
Pancreatic lipase immunoreactivity in serum of dogs with diabetic ketoacidosis
BACKGROUND : Diabetic ketoacidosis (DKA) is a relatively common endocrine disorder in dogs and is routinely associated with concurrent pancreatic injury.
OBJECTIVES : The aims of this study were to determine the prevalence of pancreatic injury in dogs with DKA based on measurement of pancreatic lipase immunoreactivity in serum (PLI); compare demographic, clinicopathologic, and ultrasonographic findings in dogs with and without evidence of concurrent pancreatic injury; determine the impact of pancreatic injury on duration of hospitalization and short-term outcome. ANIMALS : One hundred and nineteen dogs with DKA with or without concurrent pancreatic injury. METHODS : Retrospective study. Dogs with DKA were divided into three groups on the basis of PLI results: positive for pancreatic injury (PLIpos), negative for pancreatic injury (PLIneg), and not tested (PLIna). Demographics, clinicopathologic test results, findings on abdominal ultrasonography (AUS), duration of hospitalization, and short-term outcome were compared between the three groups. RESULTS : Based on serum PLI activity, 45 dogs (73%) with DKA had evidence of concurrent pancreatic injury. Median total carbon dioxide was significantly lower in the PLIpos dogs compared to the PLIneg dogs. There was fair agreement (j = 0.26) between serum PLI activity and AUS. Evidence of pancreatic injury was not associated with significantly longer periods of hospitalization (PLIpos median 6 days, range 4–7 days, PLIneg median 4 days, range 3–6 days) and did not influence
short-term outcome (PLIpos failure to survive to discharge 11/45, 24%, PLIneg failure to survive to discharge 2/17, 12%).
CLINICAL IMPORTANCE : Concurrent pancreatic injury is common in dogs with DKA, but did not affect prognosis in this population of dogs.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1939-1676hb2017Production Animal Studie
Effect of the momentum dependence of nuclear symmetry potential on the transverse and elliptic flows
In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck
transport model, effect of the momentum dependence of nuclear symmetry
potential on nuclear transverse and elliptic flows in the neutron-rich reaction
Sn+Sn at a beam energy of 400 MeV/nucleon is studied. We find
that the momentum dependence of nuclear symmetry potential affects the rapidity
distribution of the free neutron to proton ratio, the neutron and the proton
transverse flows as a function of rapidity. The momentum dependence of nuclear
symmetry potential affects the neutron-proton differential transverse flow more
evidently than the difference of neutron and proton transverse flows as well as
the difference of proton and neutron elliptic flows. It is thus better to probe
the symmetry energy by using the difference of neutron and proton flows since
the momentum dependence of nuclear symmetry potential is still an open
question. And it is better to probe the momentum dependence of nuclear symmetry
potential by using the neutron-proton differential transverse flow and the
rapidity distribution of the free neutron to proton ratio.Comment: 6 pages, 6 figures, to be published by EPJ
Sensitivity of deexcitation energies of superdeformed secondary minima to the density dependence of symmetry energy with the relativistic mean-field theory
The relationship between deexcitation energies of superdeformed secondary
minima relative to ground states and the density dependence of the symmetry
energy is investigated for heavy nuclei using the relativistic mean field (RMF)
model. It is shown that the deexcitation energies of superdeformed secondary
minima are sensitive to differences in the symmetry energy that are mimicked by
the isoscalar-isovector coupling included in the model. With deliberate
investigations on a few Hg isotopes that have data of deexcitation energies, we
find that the description for the deexcitation energies can be improved due to
the softening of the symmetry energy. Further, we have investigated
deexcitation energies of odd-odd heavy nuclei that are nearly independent of
pairing correlations, and have discussed the possible extraction of the
constraint on the density dependence of the symmetry energy with the
measurement of deexcitation energies of these nuclei.Comment: 14 pages, 3 figure
Feline exocrine pancreatic insufficiency : a retrospective study of 150 cases
BACKGROUND : Little information is available about the clinical presentation and response to treatment of cats with exocrine
pancreatic insufficiency (EPI).
OBJECTIVES : To describe the signalment, clinical signs, concurrent diseases, and response to treatment of cats with EPI.
ANIMALS : One hundred and fifty cats with EPI.
METHODS : Retrospective case series.
RESULTS : Questionnaires were sent to 261 veterinarians, and 150 (57%) were returned with data suitable for statistical
analysis. The median age of the cats with EPI was 7.7 years. The median body condition score was 3 of 9. Ninety-two of
119 cats (77%) had hypocobalaminemia, and 56 of 119 cats (47%) had increased and 6 of 119 cats (5%) had decreased
serum folate concentrations. Clinical signs included weight loss (91%), unformed feces (62%), poor hair coat (50%), anorexia
(45%), increased appetite (42%), lethargy (40%), watery diarrhea (28%), and vomiting (19%). Eighty-seven cats
(58%) had concurrent diseases. Treatment response was reported to be good in 60%, partial in 27%, and poor in 13% of
121 cats. Trypsin-like immunoreactivity <4 lg/L was associated with a positive response to treatment (OR, 3.2; 95% CI,
1.5–7.0; P = .004). Also, cobalamin supplementation improved the response to treatment (OR, 3.0; 95% CI, 1.4–6.6;
P = .006).
CONCLUSIONS AND CLINICAL IMPORTANCE : Exocrine pancreatic insufficiency in cats often has a different clinical presentation
than in dogs. The age range for EPI in cats is wide, and many cats can be ≤5 years of age. Most cats respond well to appropriate
treatment for EPI, and cobalamin supplementation appears to be necessary for a good response.Some of the results of this study were presented at the 2012
American College of Veterinary Internal Medicine Forum, New
Orleans, LA.http://www.sherpa.ac.uk/romeo/issn/0891-6640/am2017Production Animal Studie
Absence of lattice strain anomalies at the electronic topological transition in zinc at high pressure
High pressure structural distortions of the hexagonal close packed (hcp)
element zinc have been a subject of controversy. Earlier experimental results
and theory showed a large anomaly in lattice strain with compression in zinc at
about 10 GPa which was explained theoretically by a change in Fermi surface
topology. Later hydrostatic experiments showed no such anomaly, resulting in a
discrepancy between theory and experiment. We have computed the compression and
lattice strain of hcp zinc over a wide range of compressions using the
linearized augmented plane wave (LAPW) method paying special attention to
k-point convergence. We find that the behavior of the lattice strain is
strongly dependent on k-point sampling, and with large k-point sets the
previously computed anomaly in lattice parameters under compression disappears,
in agreement with recent experiments.Comment: 9 pages, 6 figures, Phys. Rev. B (in press
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
Spectroscopic Coronal Observations during the Total Solar Eclipse of 11 July 2010
The flash spectrum of the solar chromosphere and corona was measured with a
slitless spectrograph before, after, and during the totality of the solar
eclipse, of 11 July 2010, at Easter Island, Chile. This eclipse took place at
the beginning of the Solar Cycle 24, after an extended minimum of solar
activity. The spectra taken during the eclipse show a different intensity ratio
of the red and green coronal lines compared with those taken during the total
solar eclipse of 1 August 2008, which took place towards the end of the Solar
Cycle 23. The characteristic coronal forbidden emission line of forbidden Fe
XIV (5303 {\AA}) was observed on the east and west solar limbs in four areas
relatively symmetrically located with respect to the solar rotation axis.
Subtraction of the continuum flash-spectrum background led to the
identification of several extremely weak emission lines, including forbidden Ca
XV (5694 {\AA}), which is normally detected only in regions of very high
excitation, e.g., during flares or above large sunspots. The height of the
chromosphere was measured spectrophotometrically, using spectral lines from
light elements and compared with the equivalent height of the lower
chromosphere measured using spectral lines from heavy elements.Comment: 14 pages, 8 figures, 1 table; Solar Physics, 2012, Februar
Patterns in rational base number systems
Number systems with a rational number as base have gained interest
in recent years. In particular, relations to Mahler's 3/2-problem as well as
the Josephus problem have been established. In the present paper we show that
the patterns of digits in the representations of positive integers in such a
number system are uniformly distributed. We study the sum-of-digits function of
number systems with rational base and use representations w.r.t. this
base to construct normal numbers in base in the spirit of Champernowne. The
main challenge in our proofs comes from the fact that the language of the
representations of integers in these number systems is not context-free. The
intricacy of this language makes it impossible to prove our results along
classical lines. In particular, we use self-affine tiles that are defined in
certain subrings of the ad\'ele ring and Fourier
analysis in . With help of these tools we are able to
reformulate our results as estimation problems for character sums
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