842 research outputs found
Helping education undergraduates to use appropriate criteria for evaluating accounts of motivation
The aim of the study was to compare students in a control group with those in a treatment group with respect to evaluative comments on psychological accounts of motivation. The treatment group systematically scrutinized the nature and interpretation of evidence that supported different accounts, and the assumptions, logic, coherence and clarity of accounts. Content analysis of 74 scripts (using three categories) showed that the control group students made more assertions than either evidential or evaluative points, whereas the treatment group used evaluative statements as often as they used assertion. The findings provide support for privileging activities that develop understanding of how knowledge might be contested, and suggest a need for further research on pedagogies to serve this end. The idea is considered that such understanding has a pivotal role in the development of critical thinking
A New Approach to Measuring Estrogen Exposure and Metabolism in Epidemiologic Studies
Endogenous estrogen plays an integral role in the etiology of breast and endometrial cancer, and conceivably ovarian cancer. However, the underlying mechanisms and the importance of patterns of estrogen metabolism and specific estrogen metabolites have not been adequately explored. Long-standing hypotheses, derived from laboratory experiments, have not been tested in epidemiologic research because of the lack of robust, rapid, accurate measurement techniques appropriate for large-scale studies. We have developed a stable isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS(2)) method that can measure concurrently all 15 estrogens and estrogen metabolites (EM) in urine and serum with high sensitivity (level of detection=2.5-3.0fmol EM/mL serum), specificity, accuracy, and precision [laboratory coefficients of variation (CV\u27s) \u3c or =5% for nearly all EM]. The assay requires only extraction, a single chemical derivatization, and less than 0.5mL of serum or urine. By incorporating enzymatic hydrolysis, the assay measures total (glucuronidated+sulfated+unconjugated) EM. If the hydrolysis step is omitted, the assay measures unconjugated EM. Interindividual differences in urinary EM concentrations (pg/mL creatinine), which reflect total EM production, were consistently large, with a range of 10-100-fold for nearly all EM in premenopausal and postmenopausal women and men. Correlational analyses indicated that urinary estrone and estradiol, the most commonly measured EM, do not accurately represent levels of total urinary EM or of the other EM. In serum, all 15 EM were detected as conjugates, but only 5 were detected in unconjugated form. When we compared our assay methods with indirect radioimmunoassays for estrone, estradiol, and estriol and enzyme-linked immunosorbent assays for 2-hydroxyestrone and 16alpha-hydroxyestrone, ranking of individuals agreed well for premenopausal women [Spearman r (r(s))=0.8-0.9], but only moderately for postmenopausal women (r(s)=0.4-0.8). Our absolute readings were consistently lower, especially at the low concentrations characteristic of postmenopausal women, possibly because of improved specificity. We are currently applying our EM measurement techniques in several epidemiologic studies of premenopausal and postmenopausal breast cancer
A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector
We describe a compact, ultra-clean device used to deploy radioactive sources
along the vertical axis of the KamLAND liquid-scintillator neutrino detector
for purposes of calibration. The device worked by paying out and reeling in
precise lengths of a hanging, small-gauge wire rope (cable); an assortment of
interchangeable radioactive sources could be attached to a weight at the end of
the cable. All components exposed to the radiopure liquid scintillator were
made of chemically compatible UHV-cleaned materials, primarily stainless steel,
in order to avoid contaminating or degrading the scintillator. To prevent radon
intrusion, the apparatus was enclosed in a hermetically sealed housing inside a
glove box, and both volumes were regularly flushed with purified nitrogen gas.
An infrared camera attached to the side of the housing permitted real-time
visual monitoring of the cable's motion, and the system was controlled via a
graphical user interface.Comment: Revised author affiliations, corrected typos, made minor improvements
to text, and revised reference
Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND
Radioactive isotopes produced through cosmic muon spallation are a background
for rare-event detection in detectors, double--decay experiments,
and dark-matter searches. Understanding the nature of cosmogenic backgrounds is
particularly important for future experiments aiming to determine the pep and
CNO solar neutrino fluxes, for which the background is dominated by the
spallation production of C. Data from the Kamioka liquid-scintillator
antineutrino detector (KamLAND) provides valuable information for better
understanding these backgrounds, especially in liquid scintillators, and for
checking estimates from current simulations based upon MUSIC, FLUKA, and
GEANT4. Using the time correlation between detected muons and neutron captures,
the neutron production yield in the KamLAND liquid scintillator is measured to
be . For other isotopes,
the production yield is determined from the observed time correlation related
to known isotope lifetimes. We find some yields are inconsistent with
extrapolations based on an accelerator muon beam experiment.Comment: 16 pages, 20 figure
Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector
We report a measurement of the neutrino-electron elastic scattering rate from
8B solar neutrinos based on a 123 kton-day exposure of KamLAND. The
background-subtracted electron recoil rate, above a 5.5 MeV analysis threshold
is 1.49+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a
pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a
spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1.
The analysis threshold is driven by 208Tl present in the liquid scintillator,
and the main source of systematic uncertainty is due to background from
cosmogenic 11Be. The measured rate is consistent with existing measurements and
with Standard Solar Model predictions which include matter enhanced neutrino
oscillation.Comment: 6 pages, 3 figure
Search for the Invisible Decay of Neutrons with KamLAND
The Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) is used in a
search for single neutron or two neutron intra-nuclear disappearance that would
produce holes in the -shell energy level of C nuclei. Such holes
could be created as a result of nucleon decay into invisible modes (),
e.g. or . The de-excitation of the corresponding
daughter nucleus results in a sequence of space and time correlated events
observable in the liquid scintillator detector. We report on new limits for
one- and two-neutron disappearance: years
and years at 90% CL. These results
represent an improvement of factors of 3 and over previous
experiments.Comment: 5 pages, 3 figure
Phase 2a safety and immunogenicity testing of DNA and recombinant modified vaccinia ankara virus vaccines expressing virus-like particles
Measurement of Neutrino Oscillation with KamLAND: Evidence of Spectral Distortion
We present results of a study of neutrino oscillation based on a 766 ton-year
exposure of KamLAND to reactor anti-neutrinos. We observe 258 \nuebar\
candidate events with energies above 3.4 MeV compared to 365.2 events expected
in the absence of neutrino oscillation. Accounting for 17.8 expected background
events, the statistical significance for reactor \nuebar disappearance is
99.998%. The observed energy spectrum disagrees with the expected spectral
shape in the absence of neutrino oscillation at 99.6% significance and prefers
the distortion expected from \nuebar oscillation effects. A two-neutrino
oscillation analysis of the KamLAND data gives \DeltaMSq =
7.9 eV. A global analysis of data from KamLAND
and solar neutrino experiments yields \DeltaMSq =
7.9 eV and \ThetaParam =
0.40, the most precise determination to date.Comment: 5 pages, 4 figures; submitted to Phys.Rev.Letter
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