2,770 research outputs found
Correlation between a loss of auxin signaling and a loss of proliferation in maize antipodal cells
The plant life cycle alternates between two genetically active generations: the diploid sporophyte and the haploid gametophyte. In angiosperms the gametophytes are sexually dimorphic and consist of only a few cells. The female gametophyte, or embryo sac, is comprised of four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In some species the antipodal cells are indistinct and fail to proliferate, so many aspects of antipodal cell function and development have been unclear. In maize and many other grasses, the antipodal cells proliferate to produce a highly distinct cluster at the chalazal end of the embryo sac that persists at the apex of the endosperm after fertilization. The antipodal cells are a site of auxin accumulation in the maize embryo sac. Analysis of different families of genes involved in auxin biosynthesis, distribution, and signaling for expression in the embryo sac demonstrates that all steps are expressed within the embryo sac. In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells. Mutant analysis shows a correlation between a loss of auxin signaling and a loss of proliferation of the antipodal cells. The leaf polarity mutant Laxmidrib1 causes a lack of antipodal cell proliferation coupled with a loss of DR5 and PIN1a expression in the antipodal cells
Physical characteristics and non-keplerian orbital motion of "propeller" moons embedded in Saturn's rings
We report the discovery of several large "propeller" moons in the outer part
of Saturn's A ring, objects large enough to be followed over the 5-year
duration of the Cassini mission. These are the first objects ever discovered
that can be tracked as individual moons, but do not orbit in empty space. We
infer sizes up to 1--2 km for the unseen moonlets at the center of the
propeller-shaped structures, though many structural and photometric properties
of propeller structures remain unclear. Finally, we demonstrate that some
propellers undergo sustained non-keplerian orbit motion. (Note: This arXiv
version of the paper contains supplementary tables that were left out of the
ApJL version due to lack of space).Comment: 9 pages, 4 figures; Published in ApJ
Are General and Strategic Measures of Organizational Context and Leadership Associated with Knowledge and Attitudes toward Evidence-Based Practices in Public Behavioral Health Settings? A Cross-Sectional Observational Study
Background: Examining the role of modifiable barriers and facilitators is a necessary step toward developing effective implementation strategies. This study examines whether both general (organizational culture, organizational climate, and transformational leadership) and strategic (implementation climate and implementation leadership) organizational-level factors predict therapist-level determinants of implementation (knowledge of and attitudes toward evidence-based practices).
Methods: Within the context of a system-wide effort to increase the use of evidence-based practices (EBPs) and recovery-oriented care, we conducted an observational, cross-sectional study of 19 child-serving agencies in the City of Philadelphia, including 23 sites, 130 therapists, 36 supervisors, and 22 executive administrators. Organizational variables included characteristics such as EBP initiative participation, program size, and proportion of independent contractor therapists; general factors such as organizational culture and climate (Organizational Social Context Measurement System) and transformational leadership (Multifactor Leadership Questionnaire); and strategic factors such as implementation climate (Implementation Climate Scale) and implementation leadership (Implementation Leadership Scale). Therapist-level variables included demographics, attitudes toward EBPs (Evidence-Based Practice Attitudes Scale), and knowledge of EBPs (Knowledge of Evidence-Based Services Questionnaire). We used linear mixed-effects regression models to estimate the associations between the predictor (organizational characteristics, general and strategic factors) and dependent (knowledge of and attitudes toward EBPs) variables.
Results: Several variables were associated with therapistsâ knowledge of EBPs. Clinicians in organizations with more proficient cultures or higher levels of transformational leadership (idealized influence) had greater knowledge of EBPs; conversely, clinicians in organizations with more resistant cultures, more functional organizational climates, and implementation climates characterized by higher levels of financial reward for EBPs had less knowledge of EBPs. A number of organizational factors were associated with the therapistsâ attitudes toward EBPs. For example, more engaged organizational cultures, implementation climates characterized by higher levels of educational support, and more proactive implementation leadership were all associated with more positive attitudes toward EBPs.
Conclusions: This study provides evidence for the importance of both general and strategic organizational determinants as predictors of knowledge of and attitudes toward EBPs. The findings highlight the need for longitudinal and mixed-methods studies that examine the influence of organizational factors on implementation
Simplified R-Symmetry Breaking and Low-Scale Gauge Mediation
We argue that some of the difficulties in constructing realistic models of
low-scale gauge mediation are artifacts of the narrow set of models that have
been studied. In particular, much attention has been payed to the scenario in
which the Goldstino superfield in an O'Raifeartaigh model is responsible for
both supersymmetry breaking and R-symmetry breaking. In such models, the
competing problems of generating sufficiently massive gauginos while preserving
an acceptably light gravitino can be quite challenging. We show that by sharing
the burdens of breaking supersymmetry and R-symmetry with a second field, these
problems are easily solved even within the O'Raifeartaigh framework. We present
explicit models realizing minimal gauge mediation with a gravitino mass in the
eV range that are both calculable and falsifiable.Comment: 31 pages, 4 figures, references added, minor change
A Complementary Marriage of Perspectives: Understanding Organizational Social Context Using Mixed Methods
Background: Organizational factors impact the delivery of mental health services in community settings. Mixed-methods analytic approaches have been recommended, though little research within implementation science has explicitly compared inductive and deductive perspectives to understand their relative value in understanding the same constructs. The purpose of our study is to use two different paradigmatic approaches to deepen our understanding of organizational social context. We accomplish this by using a mixed-methods approach in an investigation of organizational social context in community mental health clinics.
Methods: Nineteen agencies, representing 23 sites, participated. Enrolled participants included 130 therapists, 36 supervisors, and 22 executive administrators. Quantitative data was obtained via the Organizational Social Context (OSC) measure. Qualitative data, comprised of direct observation with spot sampling generated from agency visits, was coded using content analysis and grounded theory. The present study examined elements of organizational social context that would have been missed if only quantitative data had been obtained and utilized mixed methods to investigate if stratifying observations based on quantitative ratings from the OSC resulted in the emergence of differential themes.
Results: Four of the six OSC constructs were commonly observed in field observations (i.e., proficiency, rigidity, functionality, stress), while the remaining two constructs were not frequently observed (i.e., resistance, engagement). Constructs emerged related to organizational social context that may have been missed if only quantitative measurement was employed, including those around the physical environment, commentary about evidence-based practice initiatives, leadership, cultural diversity, distrust, and affect. Stratifying agencies by âbest,â âaverage,â and âworstâ organizational social context impacted interpretation for three constructs (affect, stress, and leadership).
Conclusions: Results support the additive value of integrating inductive and deductive perspectives in implementation science research. This synthesis of approaches facilitated a more comprehensive understanding and interpretation of the findings than would have been possible if either methodology had been employed in isolation
Scalable Focused Ion Beam Creation of Nearly Lifetime-Limited Single Quantum Emitters in Diamond Nanostructures
The controlled creation of defect center---nanocavity systems is one of the
outstanding challenges for efficiently interfacing spin quantum memories with
photons for photon-based entanglement operations in a quantum network. Here, we
demonstrate direct, maskless creation of atom-like single silicon-vacancy (SiV)
centers in diamond nanostructures via focused ion beam implantation with nm lateral precision and nm positioning accuracy relative to a
nanocavity. Moreover, we determine the Si+ ion to SiV center conversion yield
to and observe a 10-fold conversion yield increase by additional
electron irradiation. We extract inhomogeneously broadened ensemble emission
linewidths of GHz, and close to lifetime-limited single-emitter
transition linewidths down to MHz corresponding to -times
the natural linewidth. This demonstration of deterministic creation of
optically coherent solid-state single quantum systems is an important step
towards development of scalable quantum optical devices
Neutral B Meson Mixing in Unquenched Lattice QCD
We study and mixing in unquenched lattice QCD employing the MILC
collaboration gauge configurations that include u, d, and s sea quarks based on
the improved staggered quark (AsqTad) action and a highly improved gluon
action. We implement the valence light quarks also with the AsqTad action and
use the nonrelativistic NRQCD action for the valence b quark. We calculate
hadronic matrix elements necessary for extracting CKM matrix elements from
experimental measurements of mass differences and . We
find , MeV and MeV. We also update previous results for decay
constants and obtain MeV, MeV and
. The new lattice results lead to updated values
for the ratio of CKM matrix elements and for the Standard
Model prediction for with reduced errors. We
determine and .Comment: 12 pages, 10 postscript figures, version to appear in Phys.Rev.D. Two
new figures, Fig.6 and Fig.10, added. Result on branching fraction Br(B_s
\rightarrow mu^+, mu^-) added. Other results on decay constants and on \xi
unchange
Effects of growth rate, size, and light availability on tree survival across life stages: a demographic analysis accounting for missing values and small sample sizes.
The data set supporting the results of this article is available in the Dryad repository, http://dx.doi.org/10.5061/dryad.6f4qs. Moustakas, A. and Evans, M. R. (2015) Effects of
growth rate, size, and light availability on tree survival across life stages: a demographic analysis accounting for missing values.Plant survival is a key factor in forest dynamics and survival probabilities often vary across life stages. Studies specifically aimed at assessing tree survival are unusual and so data initially designed for other purposes often need to be used; such data are more likely to contain errors than data collected for this specific purpose
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