2,637 research outputs found
Balance in Family Triads:How Intergenerational Relationships Affect the Adult Sibling Relationship
In order to understand the interdependency between intergenerational and adult sibling relationships, a family systems perspective is applied to identify a smaller?empirically analyzable?relational unit of analysis, that is, the sibling?parent?sibling triad. Using balance theory, triadic configurations are derived that represent enhancement, compensation, and loyalty conflicts. The hypotheses are tested for three relational dimensions: support exchange, contact, and conflict. Multilevel analyses of 549 sibling?parent?sibling triads from the Netherlands Kinship Panel data show strong evidence for enhancement, whereas some indication was obtained for sibling relationships being affected by loyalty conflicts. The results underscore and substantiate interdependency between intergenerational and adult sibling relationships
On the classification of type D spacetimes
We give a classification of the type D spacetimes based on the invariant
differential properties of the Weyl principal structure. Our classification is
established using tensorial invariants of the Weyl tensor and, consequently,
besides its intrinsic nature, it is valid for the whole set of the type D
metrics and it applies on both, vacuum and non-vacuum solutions. We consider
the Cotton-zero type D metrics and we study the classes that are compatible
with this condition. The subfamily of spacetimes with constant argument of the
Weyl eigenvalue is analyzed in more detail by offering a canonical expression
for the metric tensor and by giving a generalization of some results about the
non-existence of purely magnetic solutions. The usefulness of these results is
illustrated in characterizing and classifying a family of Einstein-Maxwell
solutions. Our approach permits us to give intrinsic and explicit conditions
that label every metric, obtaining in this way an operational algorithm to
detect them. In particular a characterization of the Reissner-Nordstr\"{o}m
metric is accomplished.Comment: 29 pages, 0 figure
Pulmonary Effects of Neonatal Hydrocortisone Treatment in Ventilator-Dependent Preterm Infants
Background/Objective. Hydrocortisone, administered to ventilated preterm neonates to facilitate extubation, has no adverse long-term effects, but short-term pulmonary effects have not been described previously. In the present study, we analyzed effects of hydrocortisone on ventilator settings and FiO2 in ventilator-dependent preterm infants. Patients and Methods. Fifty-five preterm children were included in this retrospective cohort study. Hydrocortisone was administered at a postnatal age of > 7 days to treat chronic lung disease (CLD). Ventilator settings before and after hydrocortisone administration were recorded as well as FiO2 at 36 weeks' gestational age. Presence of cerebral palsy was assessed at a mean corrected age of 24.1 months. Results. Hydrocortisone administered at a median postnatal age of 14 days significantly reduced FiO2 from a median of 0.39 to 0.30, mean airway pressure (MAP) from a median of 10.0 cm H2O to 7.6 cm H2O, and PaCO2 from a median of 53.5 mmHg to 47 mmHg. Extubation was achieved in all patients. CLD at 36 weeks was present in 11 of the 52 patients (21.1%). None developed cerebral palsy. Conclusions. Hydrocortisone was effective in reducing the FiO2, MAP, and PaCO2 and facilitated extubation. Hydrocortisone was not associated with cerebral palsy
Complete classification of purely magnetic, non-rotating and non-accelerating perfect fluids
Recently the class of purely magnetic non-rotating dust spacetimes has been
shown to be empty (Wylleman, Class. Quant. Grav. 23, 2727). It turns out that
purely magnetic rotating dust models are subject to severe integrability
conditions as well. One of the consequences of the present paper is that also
rotating dust cannot be purely magnetic when it is of Petrov type D or when it
has a vanishing spatial gradient of the energy density. For purely magnetic and
non-rotating perfect fluids on the other hand, which have been fully classified
earlier for Petrov type D (Lozanovski, Class. Quant. Grav. 19, 6377), the fluid
is shown to be non-accelerating if and only if the spatial density gradient
vanishes. Under these conditions, a new and algebraically general solution is
found, which is unique up to a constant rescaling, which is spatially
homogeneous of Bianchi type , has degenerate shear and is of Petrov type
I( in the extended Arianrhod-McIntosh classification.
The metric and the equation of state are explicitly constructed and
properties of the model are briefly discussed. We finally situate it within the
class of normal geodesic flows with degenerate shear tensor.Comment: 12 pages; introduction partly rewritten, notation made more clear,
table of results adde
Detailed Radio to Soft Gamma-ray Studies of the 2005 Outburst of the New X-ray Transient XTE J1818-245
XTE J1818-245 is an X-ray nova that experienced an outburst in 2005, first
seen by the RXTE satellite. The source was observed simultaneously at various
wavelengths up to soft gamma-rays with the INTEGRAL satellite, from 2005
February to September. X-ray novae are extreme systems that often harbor a
black hole, and are known to emit throughout the electromagnetic spectrum when
in outburst. We analyzed radio, (N)IR, optical, X-ray and soft gamma-ray
observations and constructed simultaneous broad-band X-ray spectra. Analyzing
both the light curves in various energy ranges and the hardness-intensity
diagram enabled us to study the long-term behavior of the source. Spectral
parameters were typical of the Soft Intermediate States and the High Soft
States of a black hole candidate. The source showed relatively small spectral
variations in X-rays with considerable flux variation in radio. Spectral
studies showed that the accretion disc cooled down from 0.64 to 0.27 keV in 100
days and that the total flux decreased while the relative flux of the hot
medium increased. Radio emission was detected several times, and,
interestingly, five days after entering the HSS. Modeling the spectral energy
distribution from the radio to the soft gamma-rays reveals that the radio
flares arise from several ejection events. XTE J1818-245 is likely a black hole
candidate transient source that might be closer than the Galactic Bulge. The
results from the data analysis trace the physical changes that took place in
the system at a maximum bolometric luminosity of (0.4-0.9)e38 erg/s (assuming a
distance between 2.8-4.3 kpc) and they are discussed within the context of disc
and jet models.Comment: Accepted for publication in Astronomy and Astrophysics. 11 Figures, 3
Table
- …