3,838 research outputs found
Perch or plankton: top-down control of Daphnia by yellow perch ( Perca flavescens ) or Bythotrephes cederstroemi in an inland lake?
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73542/1/j.1365-2427.2001.00716.x.pd
Composite Accretion Disk and White Dwarf Photosphere Analyses of the FUSE and HST Observations of EY Cygni
We explore the origin of FUSE and HST STIS far UV spectra of the dwarf nova,
EY Cyg, during its quiescence using \emph{combined} high gravity photosphere
and accretion disk models as well as model accretion belts. The best-fitting
single temperature white dwarf model to the FUSE plus HST STIS spectrum of EY
Cygni has TK, log , with an Si abundance of 0.1 x
solar and C abundance of 0.2 x solar but the distance is only 301 pc. The
best-fitting composite model consists of white dwarf with TK,
log , plus an accretion belt with TK covering 27% of
the white dwarf surface with V km/s. The accretion belt
contributes 63% of the FUV light and the cooler white dwarf latitudes
contribute 37%. This fit yields a distance of 351 pc which is within 100 pc of
our adopted distance of 450 pc. EY Cyg has very weak C {\sc iv} emission and
very strong N {\sc v} emission, which is atypical of the majority of dwarf
novae in quiescence. We also conducted a morphological study of the
surroundings of EY Cyg using direct imaging in narrow nebular filters from
ground-based telescopes. We report the possible detection of nebular material^M
associated with EY Cygni. Possible origins of the apparently large N {\scv}/C
{\sc iv} emission ratio are discussed in the context of nova explosions,
contamination of the secondary star and accretion of nova abundance-enriched
matter back to the white dwarf via the accretion disk or as a descendant of a
precursor binary that survived thermal timescale mass transfer. The scenario
involving pollution of the secondary by past novae may be supported by the
possible presence of a nova remnant-like nebula around EY Cyg.Comment: To appear in AJ, Oct. 2004. 5 figures, including 2 color ones (2D
pictures
Aerodynamic Flight-Test Results for the Adaptive Compliant Trailing Edge
The aerodynamic effects of compliant flaps installed onto a modified Gulfstream III airplane were investigated. Analyses were performed prior to flight to predict the aerodynamic effects of the flap installation. Flight tests were conducted to gather both structural and aerodynamic data. The airplane was instrumented to collect vehicle aerodynamic data and wing pressure data. A leading-edge stagnation detection system was also installed. The data from these flights were analyzed and compared with predictions. The predictive tools compared well with flight data for small flap deflections, but differences between predictions and flight estimates were greater at larger deflections. This paper describes the methods used to examine the aerodynamics data from the flight tests and provides a discussion of the flight-test results in the areas of vehicle aerodynamics, wing sectional pressure coefficient profiles, and air data
Effect of development of antibodies to hla and cytomegalovirus mismatch on lung transplantation survival and development of bronchiolitis obliterans syndrome
AbstractObjective: A retrospective analysis was performed to examine the role of HLA antibodies and cytomegalovirus mismatch on the development of bronchiolitis obliterans syndrome and survival after lung transplantation. Methods: Of 339 consecutive lung transplantations performed over a 102-month interval, 301 patients survived at least 3 months. There was a minimum follow-up period of 13 months. Bronchiolitis obliterans syndrome was defined as a decline in forced expiratory volume in 1 second less than 80% of posttransplantation baseline and/or histologic presence of obliterative bronchiolitis and was defined as occurring “early” if documented within 3 years of transplantation. Variables analyzed included preoperative donor and recipient cytomegalovirus status and the development of antibodies to human leukocyte antigens after transplantation. Microcytotoxicity was used to determine the presence of antibodies to human leukocyte antigens. Variables were subjected to Kaplan-Meier analysis to determine their impact on freedom from bronchiolitis obliterans syndrome and survival. Results: The development of antibodies to human leukocyte antigens after transplantation correlated significantly with bronchiolitis obliterans syndrome (P = .02). The development of antibodies to human leukocyte antigens did not affect survival (P = .33) unless they were detected within 2 years of transplantation (P = .04). There was greater frequency of early bronchiolitis obliterans syndrome in cytomegalovirus seronegative patients who received allografts from seropositive donors compared with all other combinations (P = .02). There was also a trend toward worse survival of cytomegalovirus seronegative patients who received allografts from seropositive donors (P = .13). Conclusion: These data suggest that bronchiolitis obliterans syndrome is the result of an immune-mediated process in which HLA antibodies and cytomegalovirus may play a significant role. (J Thorac Cardiovasc Surg 1998;116:812-20
Stars on the edge: Galactic tides and the outskirts of the Sculptor dwarf spheroidal
Stars far beyond the half-light radius of a galaxy suggest the existence of a
mechanism able to move stars out of the region where most star formation has
taken place. The formation of these "stellar halos" are usually ascribed to the
effects of early mergers or Galactic tides, although fluctuations in the
gravitational potential due to stellar feedback is also a possible candidate
mechanism. A Bayesian algorithm is used to find new candidate members in the
extreme outskirts of the Sculptor dwarf galaxy. Precise metallicities and
radial velocities for two distant stars are measured from their spectra taken
with the Gemini South GMOS spectrograph. The radial velocity, proper motion and
metallicity of these targets are consistent with Sculptor membership. As a
result, the known boundary of the Sculptor dwarf extends now out to an
elliptical distance of half-light radii, which corresponds to a
projected physical distance of kpc. As reported in earlier work, the
overall distribution of radial velocities and metallicities indicate the
presence of a more spatially and kinematically dispersed metal-poor population
that surrounds the more concentrated and colder metal-rich stars. Sculptor's
density profile shows a "kink" in its logarithmic slope at a projected distance
of arcmin (620 pc), which we interpret as evidence that Galactic tides
have helped to populate the distant outskirts of the dwarf. We discuss further
ways to test and validate this tidal interpretation for the origin of these
distant stars.Comment: 10 pages, 4 figures, submitted to MNRA
Effects of creatine loading on electromyographic fatigue threshold during cycle ergometry in college-aged women
This is the publisher's version, also found at http://www.jissn.com/content/4/1/20The purpose of this study was to examine the effects of 5 days of Creatine (Cr) loading on the
electromyographic fatigue threshold (EMGFT) in college-aged women. Fifteen healthy college-aged
women (mean ± SD = 22.3 ± 1.7 yrs) volunteered to participate in this double-blind, placebocontrolled
study and were randomly placed into either placebo (PL – 10 g of flavored dextrose
powder; n = 8) or creatine (Cr – 5 g di-creatine citrate plus 10 g of flavored dextrose powder; n
= 7; Creatine Edge, FSI Nutrition) loading groups. Each group ingested one packet 4 times per day
(total of 20 g/day) for 5 days. Prior to and following supplementation, each subject performed a
discontinuous incremental cycle ergometer test to determine their EMGFT value, using bipolar
surface electrodes placed on the longitudinal axis of the right vastus lateralis. Subjects completed a
total of four, 60 second work bouts (ranging from 100–350 W). The EMG amplitude was averaged
over 10 second intervals and plotted over the 60 second work bout. The resulting slopes from each
successive work bouts were used to calculate EMGFT. A two-way ANOVA (group [Cr vs. PL] ×
time [pre vs. post]) resulted in a significant (p = 0.031) interaction. Furthermore, a dependent
samples t-test showed a 14.5% ± 3.5% increase in EMGFT from pre- to post-supplementation with
Cr (p = 0.009), but no change for the PL treatment (-2.2 ± 5.8%; p = 0.732). In addition, a significant
increase (1.0 ± 0.34 kg; p = 0.049) in weight (kg) was observed in the Cr group but no change for
PL (-0.2 kg ± 0.2 kg). These findings suggest that 5 days of Cr loading in women may be an effective
strategy for delaying the onset of neuromuscular fatigue during cycle ergometry
Effect of sex on torque, recovery, EMG, and MMG responses to fatigue
The purpose of the present investigation was to examine the effect of sex on maximal voluntary isometric contraction (MVIC) torque and the EMG and MMG responses as a result of fatiguing, intermittent, submaximal (65% of MVIC), isometric elbow flexion muscle contractions. Methods: Eighteen men and women performed MVIC trials before (pretest), after (posttest), and 5-min after (5-min recovery) performing 50 intermittent, submaximal isometric muscle contractions. Surface electromyographic (EMG) and mechanomyographic (MMG) signals were simultaneously recorded from the biceps brachii muscle. Results: As a result of the fatiguing workbout torque decreased similarly from pretest to posttest for both the men (24.0%) and women (23.3%). After 5-min of recovery, torque had partially recovered for the men, while torque had returned to pretest levels for the women. For both sexes, from pretest to posttest EMG mean power frequency and MMG amplitude decreased, but returned to pretest levels after 5-min of recovery. Conclusions: In the present study, there were sex-related differences in muscle fatigue that were not associated with the EMG or MMG responses
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