675 research outputs found
Experimental f-value and isotopic structure for the Ni I line blended with [OI] at 6300A
We have measured the oscillator strength of the Ni I line at 6300.34 \AA,
which is known to be blended with the forbidden [O I] 6300 line, used
for determination of the oxygen abundance in cool stars. We give also
wavelengths of the two isotopic line components of Ni and Ni
derived from the asymmetric laboratory line profile. These two line components
of Ni I have to be considered when calculating a line profile of the 6300 \AA\
feature observed in stellar and solar spectra. We also discuss the labelling of
the energy levels involved in the Ni I line, as level mixing makes the
theoretical predictions uncertain.Comment: Accepted for publication in ApJLetter
The intersection between the Mid-Atlantic Ridge and the Vema Fracture zone in the North Atlantic
Near 11°N, the Mid-Atlantic Ridge is offset by the Verna Fracture. The hypothesis of sea-floor spreading has suggested that the fracture is a transform fault, and this has been confirmed by the first motion studies of recent earthquakes along the fracture. The fault zone is developed as a deep and narrow east-west trending through, bordered on the south side by a high and steep rocky wall representing an uplifted slice of crust...
Competition between Magnetic and Structural Transition in CrN
CrN is observed to undergo a paramagnetic to antiferromagnetic transition
accompanied by a shear distortion from cubic NaCl-type to orthorhombic
structure. Our first-principle plane wave and ultrasoft pseudopotential
calculations confirm that the distorted antiferromagnetic phase with spin
configuration arranged in double ferromagnetic sheets along [110] is the most
stable. Antiferromagnetic ordering leads to a large depletion of states around
Fermi level, but it does not open a gap. Simultaneous occurence of structural
distortion and antiferromagnetic order is analyzed.Comment: 10 pages, 10 figure
Family ties: Maternal-offspring attachment and young adult nonmedical prescription opioid use
Background: Nonmedical prescription drug use is prevalent among young adults, yet little is known about modifiable determinants of use. We examined whether maternal-offspring attachment reported at mean age 21 was associated with nonmedical prescription opioid use at mean age 26, and investigated whether a history of depressive symptoms and substance use played a role in associations between maternal-offspring attachment and nonmedical prescription opioid use. Methods: We used data from the Growing Up Today Study, a longitudinal cohort of United States adolescents followed into young adulthood. Maternal-offspring attachment was reported by young adults and their mothers, and defined as mutual low, mutual medium or high, and dissonant. Analyses were carried out in the full sample using generalized estimating equation models, and in a sibling subsample, using conditional fixed effects models to control for stable aspects of the family environment. Results: Analyses with the full sample and the sibling subsample both showed that mutual medium/high maternal-offspring attachment at age 21 was associated with lower odds of nonmedical prescription opioid use at age 26 (RR = 0.74; 95% CI = 0.57–0.97 in full sample). The association was partly mediated by mean age 23 offspring smoking, heavy episodic drinking, and illicit drug use. Conclusions: Promoting reciprocal attachment in the maternal-offspring dyad should be investigated as a strategy to prevent nonmedical prescription opioid use by young adulthood. Even in young adulthood, programs that target both parents and offspring may have greater impact on offspring substance use than programs that target offspring alone
Magnetization steps in Zn_(1-x)Mn_xO: Four largest exchange constants and single-ion anisotropy
Magnetization steps (MST's) from Mn pairs in several single crystals of
Zn_(1-x)Mn_xO (0.0056<=x<=0.030, and in one powder (x=0.029), were observed.
The largest two exchange constants, J1/kB=-18.2+/-0.5K and J1'/kB=-24.3+/-0.6K,
were obtained from large peaks in the differential susceptibility, dM/dH,
measured in pulsed magnetic fields, H, up to 500 kOe. These two largest J's are
associated with the two inequivalent classes of nearest neighbors (NN's) in the
wurtzite structure. The 29% difference between J1 and J1' is substantially
larger than 13% in CdS:Mn, and 15% in CdSe:Mn. The pulsed-field data also
indicate that, despite the direct contact between the samples and a
superfluid-helium bath, substantial departures from thermal equilibrium
occurred during the 7.4 ms pulse. The third- and fourth-largest J's were
determined from the magnetization M at 20 mK, measured in dc magnetic fields H
up to 90 kOe. Both field orientations H||c and H||[10-10] were studied. (The
[10-10] direction is perpendicular to the c-axis, [0001].) By definition,
neighbors which are not NN's are distant neighbors (DN's). The largest DN
exchange constant (third-largest overall), has the value J/kB=-0.543+/-0.005K,
and is associated with the DN at r=c. Because this is not the closest DN, this
result implies that the J's do not decrease monotonically with the distance r.
The second-largest DN exchange constant (fourth-largest overall), has the value
J/kB=-0.080 K. It is associated with one of the two classes of neighbors that
have a coordination number z=12, but the evidence is insufficient for a
definite unique choice. The dependence of M on the direction of H gives
D/kB=-0.039+/-0.008K, in fair agreement with -0.031 K from earlier EPR work.Comment: 12 pages, 10 figures. Submitted to PR
Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V_2O_3
Magnetic correlations in all four phases of pure and doped vanadium
sesquioxide V_2O_3 have been examined by magnetic thermal neutron scattering.
While the antiferromagnetic insulator can be accounted for by a Heisenberg
localized spin model, the long range order in the antiferromagnetic metal is an
incommensurate spin-density-wave, resulting from a Fermi surface nesting
instability. Spin dynamics in the strongly correlated metal are dominated by
spin fluctuations in the Stoner electron-hole continuum. Furthermore, our
results in metallic V_2O_3 represent an unprecedentedly complete
characterization of the spin fluctuations near a metallic quantum critical
point, and provide quantitative support for the SCR theory for itinerant
antiferromagnets in the small moment limit. Dynamic magnetic correlations for
energy smaller than k_BT in the paramagnetic insulator carry substantial
magnetic spectral weight. However, the correlation length extends only to the
nearest neighbor distance. The phase transition to the antiferromagnetic
insulator introduces a sudden switching of magnetic correlations to a different
spatial periodicity which indicates a sudden change in the underlying spin
Hamiltonian. To describe this phase transition and also the unusual short range
order in the paramagnetic state, it seems necessary to take into account the
orbital degrees of freedom associated with the degenerate d-orbitals at the
Fermi level in V_2O_3.Comment: Postscript file, 24 pages, 26 figures, 2 tables, accepted by Phys.
Rev.
The complex TIE between macrophages and angiogenesis
Macrophages are primarily known as phagocytic immune cells, but they also play a role in diverse processes, such as morphogenesis, homeostasis and regeneration. In this review, we discuss the influence of macrophages on angiogenesis, the process of new blood vessel formation from the pre-existing vasculature. Macrophages play crucial roles at each step of the angiogenic cascade, starting from new blood vessel sprouting to the remodelling of the vascular plexus and vessel maturation. Macrophages form promising targets for both pro- and anti-angiogenic treatments. However, to target macrophages, we will first need to understand the mechanisms that control the functional plasticity of macrophages during each of the steps of the angiogenic cascade. Here, we review recent insights in this topic. Special attention will be given to the TIE2-expressing macrophage (TEM), which is a subtype of highly angiogenic macrophages that is able to influence angiogenesis via the angiopoietin-TIE pathway
A deeply branching thermophilic bacterium with an ancient acetyl-CoA pathway dominates a subsurface ecosystem
<div><p>A nearly complete genome sequence of <em>Candidatus</em> ‘Acetothermum autotrophicum’, a presently uncultivated bacterium in candidate division OP1, was revealed by metagenomic analysis of a subsurface thermophilic microbial mat community. Phylogenetic analysis based on the concatenated sequences of proteins common among 367 prokaryotes suggests that <em>Ca.</em> ‘A. autotrophicum’ is one of the earliest diverging bacterial lineages. It possesses a folate-dependent Wood-Ljungdahl (acetyl-CoA) pathway of CO<sub>2</sub> fixation, is predicted to have an acetogenic lifestyle, and possesses the newly discovered archaeal-autotrophic type of bifunctional fructose 1,6-bisphosphate aldolase/phosphatase. A phylogenetic analysis of the core gene cluster of the acethyl-CoA pathway, shared by acetogens, methanogens, some sulfur- and iron-reducers and dechlorinators, supports the hypothesis that the core gene cluster of <em>Ca.</em> ‘A. autotrophicum’ is a particularly ancient bacterial pathway. The habitat, physiology and phylogenetic position of <em>Ca.</em> ‘A. autotrophicum’ support the view that the first bacterial and archaeal lineages were H<sub>2</sub>-dependent acetogens and methanogenes living in hydrothermal environments.</p> </div
Measurements of Dihadron Correlations Relative to the Event Plane in Au+Au Collisions at GeV
Dihadron azimuthal correlations containing a high transverse momentum (\pt)
trigger particle are sensitive to the properties of the nuclear medium created
at RHIC through the strong interactions occurring between the traversing parton
and the medium, i.e. jet-quenching. Previous measurements revealed a strong
modification to dihadron azimuthal correlations in Au+Au collisions with
respect to \pp\ and \dAu\ collisions. The modification increases with the
collision centrality, suggesting a path-length dependence to the jet-quenching
effect. This paper reports STAR measurements of dihadron azimuthal correlations
in mid-central (20-60\%) Au+Au collisions at \snn=200~GeV as a function of
the trigger particle's azimuthal angle relative to the event plane,
\phis=|\phit-\psiEP|. The azimuthal correlation is studied as a function of
both the trigger and associated particle \pt. The subtractions of the
combinatorial background and anisotropic flow, assuming Zero Yield At Minimum
(\zyam), are described. The away-side correlation is strongly modified, and the
modification varies with \phis, which is expected to be related to the
path-length that the away-side parton traverses. The pseudo-rapidity (\deta)
dependence of the near-side correlation, sensitive to long range \deta
correlations (the ridge), is also investigated. The ridge and jet-like
components of the near-side correlation are studied as a function of \phis.
The ridge appears to drop with increasing \phis while the jet-like component
remains approximately constant. ...Comment: 50 pages, 39 figures, 6 table
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