445 research outputs found
Use of Focus Groups in Survey Item Development
Focus groups are rapidly gaining popularity as a field research tool. This technique can be particularly effective in survey item development, as illustrated here via development of the Volunteer Work Behaviors Questionnaire. The steps involved in this process, ranging from item generation to finalizing logistics, are outlined. Implications for further research are proposed
A structural role for arginine in proteins: Multiple hydrogen bonds to backbone carbonyl oxygens
We propose that arginine side chains often play a previously unappreciated general structural role in the maintenance of tertiary structure in proteins, wherein the positively charged guanidinium group forms multiple hydrogen bonds to backbone carbonyl oxygens. Using as a criterion for a “structural” arginine one that forms 4 or more hydrogen bonds to 3 or more backbone carbonyl oxygens, we have used molecular graphics to locate arginines of interest in 4 proteins: Arg 180 in Thermus thermophilus manganese superoxide dismutase, Arg 254 in human carbonic anhydrase II, Arg 31 in Streptomyces rubiginosus xylose isomerase, and Arg 313 in Rhodospirillum rubrum ribulose‐1,5‐bisphosphate carboxylase/oxygenase. Arg 180 helps to mold the active site channel of superoxide dismutase, whereas in each of the other enzymes the structural arginine is buried in the “mantle” (i.e., inside, but near the surface) of the protein interior well removed from the active site, where it makes 5 hydrogen bonds to 4 backbone carbonyl oxygens. Using a more relaxed criterion of 3 or more hydrogen bonds to 2 or more backbone carbonyl oxygens, arginines that play a potentially important structural role were found in yeast enolase, Bacillus stearothermophilus glyceraldehyde‐3‐phosphate dehydrogenase, bacteriophage T4 and human lysozymes, Enteromorpha prolifera plastocyanin, HIV‐1 protease, Trypanosoma brucei brucei and yeast triosephosphate isomerases, and Escherichia coli trp aporepressor (but not trp repressor or the trp repressor/operator complex). In addition to helping form the active site funnel in superoxide dismutase, the structural arginines found in this study play such diverse roles as stapling together 3 strands of backbone from different regions of the primary sequence, and tying α‐helix to α‐helix, βturn to β‐turn, and subunit to subunit. Copyright © 1994 The Protein Societ
The Circumstellar Environment of the Early B Protostar G192.16-3.84 and the Discovery of a Low-Mass, Protostellar Core
We have observed the massive star forming region associated with the early B
protostar G192.16-3.84 in NH3(1,1), 22.2 GHz water masers, 1.3 cm continuum
emission, and at 850 microns. The dense gas associated with G192.16 is clumpy,
optically thin, and has a mass of 0.9 Msun. The ammonia core is gravitationally
unstable which may signal that the outflow phase of this system is coming to an
end. Water masers trace an ionized jet 0.8" (1600 AU at a distance of 2 kpc)
north of G192.16. Masers are also located within 500 AU of G192.16, their
velocity distribution is consistent with but does not strongly support the
interpretation that the maser emission arises in a 1000 AU rotating disk
centered on G192.16. Roughly 30" south of G192.16 (0.3 pc) is a compact,
optically thick (optical depth = 1.2) ammonia core (called G192 S3) with an
estimated mass of 2.6 Msun. Based on the presence of 850 micron and 1.2 mm
continuum emission, G192 S3 probably harbors a very young, low-mass protostar
or proto-cluster. The dense gas in the G192 S3 core is likely to be
gravitationally bound and may represent the next site of star formation in this
region.Comment: Astrophysical Journal, in press. 20 pages plus 8 figures (jpg
format). See http://www.aoc.nrao.edu/~dshepher/science.shtml for reprint with
full resolution figure
Counselor Education and Supervision
Abstract: Approaches to mentoring junior faculty in counselor education departments have received minimal attention in the counseling literature. In this article, the authors describe a successful program based on the 10 principles for good mentoring recommended b
Measurement of the Boson Mass
A measurement of the mass of the boson is presented based on a sample of
5982 decays observed in collisions at
= 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a
fit to the transverse mass spectrum, combined with measurements of the
boson mass, the boson mass is measured to be .Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures
(submitted to PRL
Measurement of the Top Quark Mass Using Dilepton Events
The D0 collaboration has performed a measurement of the top quark mass based
on six candidate events for the process t tbar -> b W+ bbar W-, where the W
bosons decay to e nu or mu nu. This sample was collected during an exposure of
the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV
p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2,
consistent with the measurement obtained using single-lepton events.
Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5
GeV/c^2.Comment: 12 pages, 3 figure
Search for Top Squark Pair Production in the Dielectron Channel
This report describes the first search for top squark pair production in the
channel stop_1 stopbar_1 -> b bbar chargino_1 chargino_1 -> ee+jets+MEt using
74.9 +- 8.9 pb^-1 of data collected using the D0 detector. A 95% confidence
level upper limit on sigma*B is presented. The limit is above the theoretical
expectation for sigma*B for this process, but does show the sensitivity of the
current D0 data set to a particular topology for new physics.Comment: Five pages, including three figures, submitted to PRD Brief Report
Search for Production via Trilepton Final States in collisions at TeV
We have searched for associated production of the lightest chargino,
, and next-to-lightest neutralino, , of the
Minimal Supersymmetric Standard Model in collisions at
\mbox{ = 1.8 TeV} using the \D0 detector at the Fermilab Tevatron
collider. Data corresponding to an integrated luminosity of 12.5 \ipb
were examined for events containing three isolated leptons. No evidence for
pair production was found. Limits on
BrBr are
presented.Comment: 17 pages (13 + 1 page table + 3 pages figures). 3 PostScript figures
will follow in a UUEncoded, gzip'd, tar file. Text in LaTex format. Submitted
to Physical Review Letters. Replace comments - Had to resumbmit version with
EPSF directive
Search for a Fourth Generation Charge -1/3 Quark via Flavor Changing Neutral Current Decay
We report on a search for pair production of a fourth generation charge -1/3
quark (b') in pbar p collisions at sqrt(s) = 1.8 TeV at the Fermilab Tevatron
using an integrated luminosity of 93 pb^-1. Both quarks are assumed to decay
via flavor changing neutral currents (FCNC). The search uses the signatures
gamma + 3 jets + mu-tag and 2 gamma + 2 jets. We see no significant excess of
events over the expected background. We place an upper limit on the production
cross section times branching fraction that is well below theoretical
expectations for a b' quark decaying exclusively via FCNC for b' quark masses
up to m(Z) + m(b).Comment: Eleven pages, two postscript figures, submitted to Physical Review
Letter
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