11,577 research outputs found
E 0336-248 : A New BL Lac Object Found by an Old Einstein
We obtained new ROSAT HRI and optical observations in the field of the
Einstein X-ray source E 0336-248, which we use to identify it as a 19th
magnitude BL Lacertae object at z=0.251 with an X-ray luminosity of 10^45
erg/s. It is also a 14 mJy radio source at 20 cm. An emission-line galaxy at
z=0.043 that was previously considered a Seyfert identification for E 0336-248
is shown instead to be an unrelated, non-active H II region galaxy that lies 78
arcseconds from the X-ray source. The resolution of this historical case of
mistaken identity illustrates that discoveries of non-AGN emission-line
galaxies with high X-ray luminosity should be tested carefully. The properties
of E 0336-248 are similar to those of other X-ray selected BL Lacs, including
its location in an apparent group or cluster of galaxies. Somewhat unusual is
the weak contribution of nonstellar optical light relative to the starlight in
the spectrum of its host galaxy, which raises once again the possibility that
even high-luminosity BL Lac objects may be difficult to identify in X-ray
selected samples. We discuss a possible manifestation of this problem that
appeared in the recent literature.Comment: To appear in the Astronomical Journal. 8 pages including figures
(uses psfig.tex, also included
Stratospheric Variability and Trends in Models Used for the IPCC AR4
Atmosphere and ocean general circulation model (AOGCM) experiments for the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) are analyzed to better understand model variability and assess the importance of various forcing mechanisms on stratospheric trends during the 20th century. While models represent the climatology of the stratosphere reasonably well in comparison with NCEP reanalysis, there are biases and large variability among models. In general, AOGCMs are cooler than NCEP throughout the stratosphere, with the largest differences in the tropics. Around half the AOGCMs have a top level beneath ~2 hPa and show a significant cold bias in their upper levels (~10 hPa) compared to NCEP, suggesting that these models may have compromised simulations near 10 hPa due to a low model top or insufficient stratospheric levels. In the lower stratosphere (50 hPa), the temperature variability associated with large volcanic eruptions is absent in about half of the models, and in the models that do include volcanic aerosols, half of those significantly overestimate the observed warming. There is general agreement on the vertical structure of temperature trends over the last few decades, differences between models are explained by the inclusion of different forcing mechanisms, such as stratospheric ozone depletion and volcanic aerosols. However, even when human and natural forcing agents are included in the simulations, significant differences remain between observations and model trends, particularly in the upper tropical troposphere (200 hPa–100 hPa), where, since 1979, models show a warming trend and the observations a cooling trend
Fractional Operators, Dirichlet Averages, and Splines
Fractional differential and integral operators, Dirichlet averages, and
splines of complex order are three seemingly distinct mathematical subject
areas addressing different questions and employing different methodologies. It
is the purpose of this paper to show that there are deep and interesting
relationships between these three areas. First a brief introduction to
fractional differential and integral operators defined on Lizorkin spaces is
presented and some of their main properties exhibited. This particular approach
has the advantage that several definitions of fractional derivatives and
integrals coincide. We then introduce Dirichlet averages and extend their
definition to an infinite-dimensional setting that is needed to exhibit the
relationships to splines of complex order. Finally, we focus on splines of
complex order and, in particular, on cardinal B-splines of complex order. The
fundamental connections to fractional derivatives and integrals as well as
Dirichlet averages are presented
Transport in Almost Integrable Models: Perturbed Heisenberg Chains
The heat conductivity kappa(T) of integrable models, like the one-dimensional
spin-1/2 nearest-neighbor Heisenberg model, is infinite even at finite
temperatures as a consequence of the conservation laws associated with
integrability. Small perturbations lead to finite but large transport
coefficients which we calculate perturbatively using exact diagonalization and
moment expansions. We show that there are two different classes of
perturbations. While an interchain coupling of strength J_perp leads to
kappa(T) propto 1/J_perp^2 as expected from simple golden-rule arguments, we
obtain a much larger kappa(T) propto 1/J'^4 for a weak next-nearest neighbor
interaction J'. This can be explained by a new approximate conservation law of
the J-J' Heisenberg chain.Comment: 4 pages, several minor modifications, title change
Resting state correlates of subdimensions of anxious affect
Resting state fMRI may help identify markers of risk for affective disorder. Given the comorbidity of anxiety and depressive disorders and the heterogeneity of these disorders as defined by DSM, an important challenge is to identify alterations in resting state brain connectivity uniquely associated with distinct profiles of negative affect. The current study aimed to address this by identifying differences in brain connectivity specifically linked to cognitive and physiological profiles of anxiety, controlling for depressed affect. We adopted a two-stage multivariate approach. Hierarchical clustering was used to independently identify dimensions of negative affective style and resting state brain networks. Combining the clustering results, we examined individual differences in resting state connectivity uniquely associated with subdimensions of anxious affect, controlling for depressed affect. Physiological and cognitive subdimensions of anxious affect were identified. Physiological anxiety was associated with widespread alterations in insula connectivity, including decreased connectivity between insula subregions and between the insula and other medial frontal and subcortical networks. This is consistent with the insula facilitating communication between medial frontal and subcortical regions to enable control of physiological affective states. Meanwhile, increased connectivity within a frontoparietal-posterior cingulate cortex-precunous network was specifically associated with cognitive anxiety, potentially reflecting increased spontaneous negative cognition (e.g., worry). These findings suggest that physiological and cognitive anxiety comprise subdimensions of anxiety-related affect and reveal associated alterations in brain connectivity
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Nurses’ Knowledge and Perception of Resident Mobility in Long-Term Care Facilities
Background: Decreased mobility for patients in long-term care (LTC) can lead to a slew of health-related issues such as sedentariness, cognitive decline, increased falls, and pressure injuries. Lack of perception and/or knowledge of the importance of mobility can lead to care of omission by nurses towards their patients. Educational interventions are effective to increase nurse’s knowledge base and perceived importance of resident mobility.
Purpose: The purpose of this quality improvement project was to assess the effect of an in-person educational intervention on the nurses’ perception and understanding of the importance of mobility for LTC residents.
Methods: One thirty-minute PowerPoint educational intervention was developed based on the most recent recommendations form several evidence-based peer reviewed articles. It was completed by 31 nurses throughout eight sessions over a two-day period in December 2020. Participants completed five perception questions and five knowledge base questions before and after the educational intervention. The effectiveness of intervention was analyzed using a paired t-test for perception questions and McNemar’s P-test for knowledge base questions.
Results: Thirty-one participants completed the pre and post education questionnaire. Results showed that there is a positive perception increase and at least a 50% increase in knowledge scores after the educational intervention.
Conclusion: An in-person educational intervention had a positive impact on LTC nurses’ perception and knowledge towards mobility. Future projects should focus on sustainment of this through annual competencies
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Doubled haploid ramets via embryogenesis of haploid tissue cultures
Tissue culture in the oil palm business is generally concerned with the multiplication
(clonal production) of dura, pisifera and tenera palms. These are all normal diploids
(2n=2x=36). Sumatra Bioscience has pioneered haploid tissue culture of oil palm
(n=x=18). Haploid oil palm is the first step in producing doubled haploid palms
which in turn provide parental lines for F1 hybrid production. Chromosome doubling
is known to occur during embryogenesis in other haploid cultures, e.g. barley anther
culture. Haploid tissue cultures in oil palm were therefore set up to investigate and
exploit spontaneous chromosome doubling during embryogenesis. Flow cytometry of
embryogenic tissue showed the presence of both haploid (n) and doubled haploid (2n)
cells indicating spontaneous doubling. Completely doubled haploid ramets were
regenerated suggesting that doubling occurred during the first mitoses of
embryogenesis. This is the first report of doubled haploid production in oil palm via
haploid tissue culture. The method provides a means of producing a range of doubled
haploids in oil palm from the 1,000 plus haploids available at Sumatra Bioscience, in
addition the method also produced doubled haploid (and haploid) clones.
1
Spin hydrodynamics in the S = 1/2 anisotropic Heisenberg chain
We study the finite-temperature dynamical spin susceptibility of the
one-dimensional (generalized) anisotropic Heisenberg model within the
hydrodynamic regime of small wave vectors and frequencies. Numerical results
are analyzed using the memory function formalism with the central quantity
being the spin-current decay rate gamma(q,omega). It is shown that in a generic
nonintegrable model the decay rate is finite in the hydrodynamic limit,
consistent with normal spin diffusion modes. On the other hand, in the gapless
integrable model within the XY regime of anisotropy Delta < 1 the behavior is
anomalous with vanishing gamma(q,omega=0) proportional to |q|, in agreement
with dissipationless uniform transport. Furthermore, in the integrable system
the finite-temperature q = 0 dynamical conductivity sigma(q=0,omega) reveals
besides the dissipationless component a regular part with vanishing
sigma_{reg}(q=0,omega to 0) to 0
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