1,456 research outputs found
Synthesis of the Beryllium 3131A Spectral Region
The Beryllium spectral region of the Sun, Procyon and 4 stars in the open
cluster NGC6633 up to Teff = 7500K have been synthesised using ATLAS9 model
atmospheres and the MOOG spectral synthesis program.
The line list used for these syntheses has been modified from the ATLAS9 line
list to improve the quality of the fits in light of the improved opacities in
the new version of the MOOG code.
Significant changes have been made to the Mn I line at ATLAS9 wavelength
3131.037A and an OH line has been added at 3131.358A. In addition there are a
number of minor changes to gf-values throughout the synthesised region thus
improving the fit for the spectra across the temperature range considerably.Comment: 4 pages, 3 figures. To appear in the proceedings of the Workshop
"ATLAS 12 and related codes", Trieste, July 11-15, 200
The Li Overabundance of J37: Diffusion or Accretion?
In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633,
an iron poor analogue of the better studied Hyades and Praecepe open clusters,
was announced. This unique star was thought to be the smoking gun for the
action of diffusion, models of which predict a narrow "Li-peak" at
approximately the correct temperature. However, with more detailed studies into
J37s abundance pattern this star provides firm evidence for the accretion of
planetesimals or other material from the circumstellar environment of new born
stars.
Thanks to the specific predictions made about the behaviour of Be abundances,
(the most striking of which being no Be in super-Li-rich dwarfs subject to
diffusion) the opposing diffusion/accretion predictions can be tested.
Initial modelling of the Be line indicates that J37 is as Be rich as it is Li
rich; log N(Be) = 2.25 +/- 0.25, and so is broadly consistent with an
accretion-fuelled enhancement. However, that both Li and Be are enhanced by
much more than the iron-peak elements (as determined in previous studies)
suggests that diffusion also plays a role in increasing the abundances of Li
and Be specifically.
Furthermore, a new data set from the UVES/UT2 combination has allowed the
elemental abundance of Iron to be measured, and the set of preliminary stellar
parameters determined; Teff ~ 7340 K, log g ~ 4.1, microturbulence ~ 4.3 km/s,
[Fe/H] ~ 0.50. This again provides distinct evidence for the effects of
accretion in J37 and requires a new synthesis of the Be doublet.Comment: 5 pages, 2 figures. Poster presented at IAU Symposium 224 "The A Star
Puzzle", 7-13 July 2004, Poprad, Slovaki
Beryllium Enhancement as Evidence for Accretion in a Lithium-Rich F Dwarf
The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual
pattern of photospheric abundances, including an order of magnitude enhancement
of lithium and iron-peak elements, but an under-abundance of carbon. As a
consequence of its thin convection zone these anomalies have been attributed to
either radiative diffusion or the accretion of hydrogen-depleted material. By
comparing high resolution VLT/UVES spectra of J37 (and other F stars in NGC
6633) with syntheses of the Be ii doublet region at 3131 Ang, we establish that
J37 also has a Be abundance (A(Be)=3.0+/-0.5) that is at least ten times the
cosmic value. This contradicts radiative diffusion models that produce a Li
over-abundance, as they also predict photospheric Be depletion. Instead, since
Be is a highly refractory element, it supports the notion that J37 is the first
clear example of a star that has accreted volatile-depleted material with a
composition similar to chondritic meteorites, although some diffusion may be
necessary to explain the low C and O abundances.Comment: Accepted for publication in MNRAS letters, 5 page
Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
Existing determinations show that n(C)/n(Fe) is more than a factor of 10
below solar in the atmospheres of three white dwarfs that appear to be
externally-polluted. These results are not easily explained if the stars have
accreted interstellar matter, and we re-interpret these measurements as
evidence that these stars have accreted asteroids of a chrondritic composition.Comment: 23 pages, 6 figures, accepted for Ap
Acceptability of a moringa-added complementary soft porridge to caregivers in Hammanskraal, Gauteng province and Lebowakgomo, Limpopo province, South Africa
Objectives: This study determined caregivers’ (mothers’) acceptability and perceptions of a soft, white maize porridge (traditional complementary food (TCF)) that was modified by substituting maize meal with Moringa oleifera Lam. leaf powder at different levels, 1%, 2% and 3% weight for weight (w/w).
Design: A cross-sectional study was conducted.
Setting: The study was conducted in Stinkwater, Hammanskraal, Gauteng province (25° 23’ 59.99” S: 28° 16’ 60.00” E) and Ga-Mphahlele village, Lebowakgomo, Limpopo province (24°18’0.83”S: 29°32’33.61”E), South Africa.
Subjects: Sixty mothers were sampled, separately, from Hammanskraal and Lebowakgomo communities.
Outcome measures: The sensory acceptability of the complementary soft porridges was evaluated by caregivers from Hammanskraal and Lebowakgomo communities using a five-point facial hedonic scale (n = 60 per study area). A series of three focus-group discussions were conducted per study area (n = 12 persons per group) to assess caregivers’ perceptions on the inclusion of moringa in complementary foods.
Results: Sensory evaluation results showed that the acceptability of the two traditional complementary foods decreased as the level of moringa leaf powder increased. Caregivers indicated in the focus-group discussions that moringa-based soft porridges had a bitter taste, which would not be suitable for children. Only the Lebowakgomo modified traditional complementary food (MTCF) containing 1% of moringa was rated similar in overall acceptability to the corresponding TCF (control). Nevertheless, all caregivers expressed willingness to use moringa in complementary foods provided they would be trained on how to process it.
Conclusions: Varying product formulation and processing methods may contribute to increased acceptability of moringa-based foods. Overall, moringa appears to have the potential for use in complementary foods
Waist-to-Height Ratio Is More Predictive of Years of Life Lost than Body Mass Index
Objective: Our aim was to compare the effect of central obesity (measured by waist-to-height ratio, WHtR) and total obesity (measured by body mass index, BMI) on life expectancy expressed as years of life lost (YLL), using data on British adults.
Methods: A Cox proportional hazards model was applied to data from the prospective Health and Lifestyle Survey (HALS) and the cross sectional Health Survey for England (HSE). The number of years of life lost (YLL) at three ages (30, 50, 70 years) was found by comparing the life expectancies of obese lives with those of lives at optimum levels of BMI and WHtR.
Results: Mortality risk associated with BMI in the British HALS survey was similar to that found in US studies. However, WHtR was a better predictor of mortality risk. For the first time, YLL have been quantified for different values of WHtR. This has been done for both sexes separately and for three representative ages.
Conclusion: This study supports the simple message ‘‘Keep your waist circumference to less than half your height’’. The use of WHtR in public health screening, with appropriate action, could help add years to life
Live Cell Imaging Unveils Multiple Domain Requirements for In Vivo Dimerization of the Glucocorticoid Receptor
Glucocorticoids are essential for life, but are also implicated in disease pathogenesis and may produce unwanted effects when given in high doses. Glucocorticoid receptor (GR) transcriptional activity and clinical outcome have been linked to its oligomerization state. Although a point mutation within the GR DNA-binding domain (GRdim mutant) has been reported as crucial for receptor dimerization and DNA binding, this assumption has recently been challenged. Here we have analyzed the GR oligomerization state in vivo using the number and brightness assay. Our results suggest a complete, reversible, and DNA-independent ligand-induced model for GR dimerization. We demonstrate that the GRdim forms dimers in vivo whereas adding another mutation in the ligand-binding domain (I634A) severely compromises homodimer formation. Contrary to dogma, no correlation between the GR monomeric/dimeric state and transcriptional activity was observed. Finally, the state of dimerization affected DNA binding only to a subset of GR binding sites. These results have major implications on future searches for therapeutic glucocorticoids with reduced side effects.Fil: Presman, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Ogara, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Stortz, Martin Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Alvarez, Lautaro Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; ArgentinaFil: Pooley, John R.. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados Unidos. University of Bristol; Reino UnidoFil: Schiltz, R. Louis. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados UnidosFil: Grøntved, Lars. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados UnidosFil: Johnson, Thomas A.. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados UnidosFil: Mittelstadt, Paul R.. National Cancer Institute. Laboratory of Immune Cell Biology; Estados UnidosFil: Ashwell, Jonathan D.. National Cancer Institute. Laboratory of Immune Cell Biology; Estados UnidosFil: Ganesan, Sundar. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados Unidos. National Institute of Allergy and Infectious Diseases; Estados UnidosFil: Burton, Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; ArgentinaFil: Levi, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Hager, Gordon L.. National Cancer Institute. Laboratory of Receptor Biology and Gene Expression; Estados UnidosFil: Pecci, Adali. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentin
Subunit interactions within the T-cell antigen receptor: clues from the study of partial complexes.
4-Aminopyridinium picrate
In the title compound, C5H7N2
+·C6H2N3O7
−, the 4-aminopyridinium cation is essentially planar (r.m.s. deviation = 0.002 Å). The three nitro groups in the picrate anion are twisted away from the attached benzene ring [dihedral angles = 24.1 (1), 9.3 (3) and 21.4 (1)°]. In the crystal structure, the ions are linked into a three-dimensional network by N—H⋯O and C—H⋯O hydrogen bonds
4-tert-Butylpyridinium picrate
In the title compound, C9H14N+·C6H2N3O7
−, the three nitro groups of the picrate anion are twisted out of the plane of the attached benzene ring; the dihedral angles are 32.8 (2), 10.5 (4) and 12.3 (4)°. The pyridinium cations and picrate anions are linked via bifurcated N—H⋯(O,O) hydrogen bonds. The ionic pairs are linked into a ribbon-like structure along [101] by C—H⋯O hydrogen bonds
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