364 research outputs found
Extraction of scattering lengths from final-state interactions
A recently proposed method based on dispersion theory, that allows to extract
the scattering length of a hadronic two-body system from corresponding
final-state interactions, is generalized to the situation where the Coulomb
interaction is present. The steps required in a concrete practical application
are discussed in detail. In addition a thorough examination of the accuracy of
the proposed method is presented and a comparison is made with results achieved
with other methods like the Jost-function approach based on the effective-range
approximation. Deficiencies of the latter method are pointed out. The
reliability of the dispersion theory method for extracting also the effective
range is investigated.Comment: 16 pages, 6 figures, some corrections to text, to appear in Phys.
Rev.
The Transparency of Solar Coronal Active Regions
Resonance scattering has often been invoked to explain the disagreement
between the observed and predicted line ratios of Fe XVII 15.01 A to Fe XVII
15.26 A (the ``3C/3D'' ratio). In this process photons of 15.01, with its much
higher oscillator strength, are preferentially scattered out of the line of
sight, thus reducing the observed line ratio. Recent laboratory measurements,
however, have found significant inner-shell Fe XVI lines at 15.21 and 15.26
Angstroms, suggesting that the observed 3C/3D ratio results from blending.
Given our new understanding of the fundamental spectroscopy, we have
re-examined the original solar spectra, identifying the Fe XVI 15.21 line and
measuring its flux to account for the contribution of Fe XVI to the 15.26 flux.
Deblending brings the 3C/3D ratio into good agreement with the experimental
ratio; hence, we find no need to invoke resonance scattering. Low opacity in Fe
XVII 15.01 also implies low opacity for Fe XV 284.2, ruling out resonance
scattering as the cause of the fuzziness of TRACE and SOHO EIT 284-Angstrom
images. The images must, instead, be unresolved due to the large number of
structures at this temperature. Insignificant resonance scattering implies that
future instruments with higher spatial resolution could resolve the active
region plasma into its component loop structures.Comment: accepted to Ap J Letter
Effective range function below threshold
We demonstrate that the kernel of the Lippmann-Schwinger equation, associated
with interactions consisting of a sum of the Coulomb plus a short range nuclear
potential, below threshold becomes degenerate. Taking advantage of this fact,
we present a simple method of calculating the effective range function for
negative energies. This may be useful in practice since the effective range
expansion extrapolated to threshold allows to extract low-energy scattering
parameters: the Coulomb-modified scattering length and the effective range.Comment: 14 pages, 1 figur
The Nutrition Education Initiative Resource Guide: Examining Effectiveness with Middle School Students and Perceptions of Science Teachers
Background and Purpose: With obesity in children and youth continuing to be a major health problem in the U.S., schools are considered an important setting to implement programs to address the issue but few have focused on middle school students. The purposes of this study were to: 1) determine the effectiveness of a school-based nutrition education program, the Nutrition Education Initiative (NEI) Resource Guide, in improving school lunch eating behaviors of middle school students, and 2) identify science teachers’ perceptions of the materials. Implementation: The project was implemented by 16 middle school science teachers and 309 seventh grade students in a medium-sized north Florida community. The NEI Guide included three conceptual areas (Build a Healthy Base, Choose Sensibly and Aim for Fitness), major concepts, objectives, narrative information, and teaching strategies. Evaluation: Using a pre-/post without control group design, the study involved collecting data via food recall surveys with students, and surveys and interviews with teachers. Data were analyzed using descriptive statistics and paired t-tests. Results: During lunch time, a higher proportion of students met the recommended dietary servings for dairy, meat, vegetables, fruit, juice and grains from pre-test to post-test. Students also significantly increased dietary intake of meat (p< .01), fruit (p< .01) and fruit/juice combined (p< .05); and significantly decreased intake of fried vegetables (p< .001), with decreased fat intake approaching significance (p< .06). Differences in dietary patterns were noted between the two schools studied. Science teachers perceived the NEI Guide as effective; yet they also identified challenges including lack of adequate training, lack of time to implement the materials, and lack of collaboration with the project team. Conclusion: The project outcomes suggest that middle school science teachers can positively impact school lunch eating behaviors of middle school students in selected schools by incorporating nutrition education in their curricula
Atomic data from the IRON Project. I. Electron-impact scattering of Fe17+ using <I>R</I>-matrix theory with intermediate coupling
We present results for electron-impact excitation of F-like Fe calculated using R-matrix theory where an intermediate-coupling frame transformation (ICFT) is used to obtain level-resolved collision strengths. Two such calculations are performed, the first expands the target using 2s2 2p5, 2s 2p6, 2s2 2p4 3l, 2s 2p5 3l, and 2p6 3l configurations while the second calculation includes the 2s2 2p4 4l, 2s 2p5 4l, and 2p6 4l configurations as well. The effect of the additional structure in the latter calculation on the n=3 resonances is explored and compared with previous calculations. We find strong resonant enhancement of the effective collision strengths to the 2s2 2p4 3s levels. A comparison with a Chandra X-ray observation of Capella shows that the n=4 R-matrix calculation leads to good agreement with observation</p
Long‐distance swimming by African lions in Uganda
Earth's most imperiled and iconic wildlife are facing tough decisions under increasing human pressure and limited resources. Swimming across rivers and water bodies filled with high densities of predators may be one such example. In African lions Panthera leo, previous water crossings (recorded in the peer‐reviewed and gray literature, on film, and found using Google Search, and YouTube) have recorded distances ranging from 1 km across Uganda's Kazinga channel located in the Queen Elizabeth National Park six times, and recorded this behavior on film on February 1st 2024. We speculate that three factors could be driving these lions to take long‐distance swims with a high density of crocodiles and hippos Hippopotamus amphibius, namely (1) the lack of lionesses in this ecosystem, (2) intraspecific fights over territory with other male coalitions, and (3) the only other land connection giving lions access to the peninsula is a small road bridge with a strong human presence
The Translation Regulatory Subunit eIF3f Controls the Kinase-Dependent mTOR Signaling Required for Muscle Differentiation and Hypertrophy in Mouse
The mTORC1 pathway is required for both the terminal muscle differentiation and
hypertrophy by controlling the mammalian translational machinery via
phosphorylation of S6K1 and 4E-BP1. mTOR and S6K1 are connected by interacting
with the eIF3 initiation complex. The regulatory subunit eIF3f plays a major
role in muscle hypertrophy and is a key target that accounts for MAFbx function
during atrophy. Here we present evidence that in MAFbx-induced atrophy the
degradation of eIF3f suppresses S6K1 activation by mTOR, whereas an eIF3f mutant
insensitive to MAFbx polyubiquitination maintained persistent phosphorylation of
S6K1 and rpS6. During terminal muscle differentiation a conserved TOS motif in
eIF3f connects mTOR/raptor complex, which phosphorylates S6K1 and regulates
downstream effectors of mTOR and Cap-dependent translation initiation. Thus
eIF3f plays a major role for proper activity of mTORC1 to regulate skeletal
muscle size
Permanent Polymer Coating for in vivo MRI Visualization of Tissue Reinforcement Prostheses
The clinical advantage of MRI visualization of prostheses in soft tissue prolapses is very appealing as over 1?000?000 MRI-transparent synthetic meshes are implanted annually, and postoperative complications such as mesh shrinkage and migration are frequent. Here, the synthesis of a new material composed of a DTPA-Gd complex grafted onto a backbone of PMA via a covalent bond is described (DTPA-Gd-PMA). This new polymer is sprayed onto meshes and gives an MR signal for a long period without any significant release of Gd. In vitro cytocompatibility tests on fibroblasts show limited cytotoxicity. Microscopic investigations indicate that vital cells rapidly colonize the material. Finally, coated meshes implanted in rats are easily recognizable using an MR imaging system
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