244 research outputs found
Exploring the Nature of Perfectionism and Middle School Student Achievement
The purpose of this dissertation is to describe a doctoral research study designed to explore the nature of perfectionism and middle school student achievement. Perfectionism is currently perceived as a multi-dimensional construct with both adaptive and maladaptive features. This qualitative research study focuses on the views of nine seventh grade participants who were identified as adaptive or maladaptive perfectionists in a survey of students in one seventh grade cohort using the Almost Perfect Scale-Revised (Slaney, Mobley, Trippi, Ashby, & Johnson, 1996). Each of the participants met with the researcher and completed three individual interviews and two focus group sessions. Data gathered from those meetings were analyzed to answer the following questions: What are the traits of middle school students who are identified as demostrating adaptive perfectionism and maladaptive perfectionism? How do middle school students who are identified as demonstrating adaptive or maladaptive perfectionism view their academic achievement? And, how do middle school students who are identified as demonstrating adaptive or maladaptive perfectionism perceive the impact of parents, teachers and peers on their academic achievement
Cepheid models based on self-consistent stellar evolution and pulsation calculations: the right answer?
We have computed stellar evolutionary models for stars in a mass range
characteristic of Cepheid variables (3) for different
metallicities representative of the Galaxy and the Magellanic Clouds
populations. The stellar evolution calculations are coupled to a linear non
adiabatic stability analysis to get self-consistent mass-period-luminosity
relations. The period - luminosity relation as a function of metallicity is
analysed and compared to the recent EROS observations in the Magellanic Clouds.
The models reproduce the observed width of the instability strips for the SMC
and LMC. We determine a statistical P-L relationship, taking into account the
evolutionary timescales and a mass distribution given by a Salpeter mass
function. Excellent agreement is found with the SMC PL relationship determined
by Sasselov et al. (1997). The models reproduce the change of slope in the P-L
relationship near days discovered recently by the EROS
collaboration (Bauer 1997; Bauer et al. 1998) and thus explain this feature in
term of stellar evolution. Some discrepancy, however, remains for the LMC
Cepheids. The models are also in good agreement with Beat Cepheids observed by
the MACHO and EROS collaborations. We show that most of the 1H/2H Beat Cepheids
have not yet ignited central helium burning; they are just evolving off the
Main Sequence toward the red giant branch.Comment: 18 pages, Latex file, uses aasms4.sty, accepted for publication in
ApJ Letter
Gene mapping in white spruce (P. glauca): QTL and association studies integrating population and expression data
Red Clump Morphology as Evidence Against a New Intervening Stellar Population as the Primary Source of Microlensing Toward the LMC
We examine the morphology of the color-magnitude diagram (CMD) for core
helium-burning (red clump) stars to test the recent suggestion by Zaritsky &
Lin (1997) that an extension of the red clump in the Large Magellanic Cloud
(LMC) toward brighter magnitudes is due to an intervening population of stars
that is responsible for a significant fraction of the observed microlensing
toward the LMC. Using our own CCD photometry of several fields across the LMC,
we confirm the presence of this additional red clump feature, but conclude that
it is caused by stellar evolution rather than a foreground population. We do
this by demonstrating that the feature (1) is present in all our LMC fields,
(2) is in precise agreement with the location of the blue loops in the
isochrones of intermediate age red clump stars with the metallicity and age of
the LMC, (3) has a relative density consistent with stellar evolution and LMC
star formation history, and (4) is present in the Hipparcos CMD for the solar
neighborhood where an intervening population cannot be invoked. Assuming there
is no systematic shift in the model isochrones, which fit the Hipparcos data in
detail, a distance modulus of provides the best fit to our
dereddened CMD.Comment: 21 pages LaTex (aaspp4.sty), including three tables and 9 figures (1
is .ps, 8 are .gif). Accepted for publication by Astronomical Journal on
March 16, 1998. One error corrected and major revisions now lead to an even
stronger argument for the stellar evolutionary origin of features in the LMC
color magnitude diagram, claimed by others to be an intervening stellar
population and major source of microlensing optical depth toward the LM
Gender- and age-related differences in clinical presentation and management of outpatients with stable coronary artery disease
<br>Introduction: Contemporary generalizable data on the demographics and management of outpatients with stable coronary artery disease (CAD) in routine clinical practice are sparse. Using the data from the CLARIFY registry we describe gender- and age-related differences in baseline characteristics and management of these patients across broad geographic regions.</br>
<br>Methods: This international, prospective, observational, longitudinal registry enrolled stable CAD outpatients from 45 countries in Africa, Asia, Australia, Europe, the Middle East, and North, Central, and South America.</br>
<br>Results: Baseline data were available for 33 280 patients. Mean (SD) age was 64 (10.5) years and 22.5% of patients were female. The prevalence of CAD risk factors was generally higher in women than in men. Women were older (66.6 vs 63.4 years), more frequently diagnosed with diabetes (33% vs 28%), hypertension (79% vs 69%), and higher resting heart rate (69 vs 67 bpm), and were less physically active. Smoking and a history of myocardial infarction were more common in men. Women were more likely to have angina (28% vs 20%), but less likely to have undergone revascularization procedures. CAD was more likely to be asymptomatic in older patients perhaps because of reduced levels of physical activity. Prescription of evidence-based medication for secondary prevention varied with age, with patients ≥ 75 years treated less often with beta blockers, aspirin and angiotensin-converting enzyme inhibitors than patients < 65 years.</br>
<br>Conclusions: Important gender-related differences in clinical characteristics and management continue to exist in all age groups of outpatients with stable CAD.</br>
Integrin α8β1 regulates adhesion, migration and proliferation of human intestinal crypt cells via a predominant RhoA/ROCK-dependent mechanism
Background. Integrins are transmembrane αβ heterodimer receptors that function as structural and functional bridges between the cytoskeleton and ECM (extracellular matrix) molecules. The RGD (arginine-glycine-aspartate tripeptide motif)-dependent integrin α8β1 has been shown to be involved in various cell functions in neuronal and mesenchymal-derived cell types. Its role in epithelial cells remains unknown
An integrated palaeoenvironmental investigation of a 6200 year old peat sequence from Ile de la Possession, Iles Crozet, sub-Antarctica
International audienceA 6200 year old peat sequence, cored in a volcanic crater on the sub-Antarctic Ile de la Possession (Iles Crozet), has been investigated, based on a multi-proxy approach. The methods applied are macrobotanical (mosses, seeds and fruits) and diatom analyses, complemented by geochemical (Rock-Eval6) and rock magnetic measurements. The chronology of the core is based on 5 radiocarbon dates. When combining all the proxy data the following changes could be inferred. From the onset of the peat formation (6200 cal yr BP) until ca. 5550 cal yr BP, biological production was high and climatic conditions must have been relatively warm. At ca. 5550 cal yr BP a shift to low biological production occurred, lasting until ca. 4600 cal yr BP. During this period the organic matter is well preserved, pointing to a cold and/or wet environment. At ca. 4600 cal yr BP, biological production increased again. From ca. 4600 cal yr BP until ca. 4100 cal yr BP a “hollow and hummock” micro topography developed at the peat surface, resulting in the presence of a mixture of wetter and drier species in the macrobotanical record. After ca. 4100 cal yr BP, the wet species disappear and a generally drier, acidic bog came into existence. A major shift in all the proxy data is observed at ca. 2800 cal yr BP, pointing to wetter and especially windier climatic conditions on the island probably caused by an intensification and/or latitudinal shift of the southern westerly belt. Caused by a stronger wind regime, erosion of the peat surface occurred at that time and a lake was formed in the peat deposits of the crater, which is still present today
Integrin α6Bβ4 inhibits colon cancer cell proliferation and c-Myc activity
<p>Abstract</p> <p>Background</p> <p>Integrins are known to be important contributors to cancer progression. We have previously shown that the integrin β4 subunit is up-regulated in primary colon cancer. Its partner, the integrin α6 subunit, exists as two different mRNA splice variants, α6A and α6B, that differ in their cytoplasmic domains but evidence for distinct biological functions of these α6 splice variants is still lacking.</p> <p>Methods</p> <p>In this work, we first analyzed the expression of integrin α6A and α6B at the protein and transcript levels in normal human colonic cells as well as colorectal adenocarcinoma cells from both primary tumors and established cell lines. Then, using forced expression experiments, we investigated the effect of α6A and α6B on the regulation of cell proliferation in a colon cancer cell line.</p> <p>Results</p> <p>Using variant-specific antibodies, we observed that α6A and α6B are differentially expressed both within the normal adult colonic epithelium and between normal and diseased colonic tissues. Proliferative cells located in the lower half of the glands were found to predominantly express α6A, while the differentiated and quiescent colonocytes in the upper half of the glands and surface epithelium expressed α6B. A relative decrease of α6B expression was also identified in primary colon tumors and adenocarcinoma cell lines suggesting that the α6A/α6B ratios may be linked to the proliferative status of colonic cells. Additional studies in colon cancer cells showed that experimentally restoring the α6A/α6B balance in favor of α6B caused a decrease in cellular S-phase entry and repressed the activity of c-Myc.</p> <p>Conclusion</p> <p>The findings that the α6Bβ4 integrin is expressed in quiescent normal colonic cells and is significantly down-regulated in colon cancer cells relative to its α6Aβ4 counterpart are consistent with the anti-proliferative influence and inhibitory effect on c-Myc activity identified for this α6Bβ4 integrin. Taken together, these findings point out the importance of integrin variant expression in colon cancer cell biology.</p
Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity
Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by
alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var.
cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging
from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4).
All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show
differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl
esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3
also accepts a wide range of substrates but with very strong preference for producing benzyl acetate.
Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl
acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is
related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating
268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished
activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase
during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in
antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene
(1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the
multiplicity of AAT genes accounts for the great diversity of esters formed in melon
Mapping the coverage of attributes in validated instruments that evaluate primary healthcare from the patient perspective
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