1,666 research outputs found
Controlled Phenylhydrazine-Induced Reticulocytosis in the Rat
Author Institution: Department of Physiology, Ohio State University, College of Medicine, Columbus, Ohio 43210The pattern of development of phenylhydrazine-induced rat reticulocytosis was studied over a period of nine days. Intraperitoneal injections of phenylhydrazine (4 mg/100 gm) every other day caused a fall in hematocrit which leveled off at 60% of normal by the fifth day. Increased erythropoiesis was indicated by a three-fold increase in the number of circulating reituclocytes after the first three injections. The immediate response was the release of stored mature reticulocytes from the bone marrow. As the anemia progressed, more and more young reticulocytes appeared until 70 to 85% of the red cells in the peripheral circulation were reticulocytes and 20% of these were juvenile forms
A Cross-Sectional Study of Myopia and Morning Melatonin Status in Northern Irish Adolescent Children
Purpose. Previous studies have demonstrated an association between melatonin status and both refractive error and axial length in young adult myopes. This study aimed to determine if this relationship extends to a younger adolescent cohort. Methods. Healthy children aged 12–15 years provided morning saliva samples before attending Ulster University (55°N) for cycloplegic autorefraction and axial length measures. Participants completed questionnaires describing recent sleep habits and physical activity. Salivary melatonin was quantified using high-performance liquid chromatography-tandem mass spectrometry. Data collection for all participants occurred over a 1-week period (April 2021). Results. Seventy participants aged 14.3 (95% CI: 14.2—14.5) years were categorised by spherical equivalent refraction [SER] (range: −5.38DS to +1.88DS) into two groups; myopic SER ≤ −0.50DS (n = 22) or nonmyopic −0.50DS < SER ≤ +2.00DS (n = 48). Median morning salivary melatonin levels were 4.52 pg/ml (95% CI: 2.60–6.02) and 4.89 pg/ml (95% CI: 3.18–5.66) for myopic and nonmyopic subjects, respectively, and did not differ significantly between refractive groups ( = 0.91). Melatonin levels were not significantly correlated with SER, axial length, sleep, or activity scores (Spearman’s rank, all > 0.39). Higher levels of physical activity were associated with higher sleep quality (Spearman’s rank, ρ = −0.28, = 0.02). Conclusion. The present study found no significant relationship between morning salivary melatonin levels and refractive error or axial length in young adolescents. This contrasts with outcomes from a previous study of adults with comparable methodology, season of data collection, and geographical location. Prospective studies are needed to understand the discrepancies between adult and childhood findings and evaluate whether melatonin levels in childhood are indicative of an increased risk for future onset of myopia and/or faster axial growth trajectories and myopia progression in established myopes. Future work should opt for a comprehensive dim-light melatonin onset protocol to determine circadian phase
An excess power statistic for detection of burst sources of gravitational radiation
We examine the properties of an excess power method to detect gravitational
waves in interferometric detector data. This method is designed to detect
short-duration (< 0.5 s) burst signals of unknown waveform, such as those from
supernovae or black hole mergers. If only the bursts' duration and frequency
band are known, the method is an optimal detection strategy in both Bayesian
and frequentist senses. It consists of summing the data power over the known
time interval and frequency band of the burst. If the detector noise is
stationary and Gaussian, this sum is distributed as a chi-squared (non-central
chi-squared) deviate in the absence (presence) of a signal. One can use these
distributions to compute frequentist detection thresholds for the measured
power. We derive the method from Bayesian analyses and show how to compute
Bayesian thresholds. More generically, when only upper and/or lower bounds on
the bursts duration and frequency band are known, one must search for excess
power in all concordant durations and bands. Two search schemes are presented
and their computational efficiencies are compared. We find that given
reasonable constraints on the effective duration and bandwidth of signals, the
excess power search can be performed on a single workstation. Furthermore, the
method can be almost as efficient as matched filtering when a large template
bank is required. Finally, we derive generalizations of the method to a network
of several interferometers under the assumption of Gaussian noise.Comment: 22 pages, 6 figure
Plans for the LIGO-TAMA Joint Search for Gravitational Wave Bursts
We describe the plans for a joint search for unmodelled gravitational wave
bursts being carried out by the LIGO and TAMA collaborations using data
collected during February-April 2003. We take a conservative approach to
detection, requiring candidate gravitational wave bursts to be seen in
coincidence by all four interferometers. We focus on some of the complications
of performing this coincidence analysis, in particular the effects of the
different alignments and noise spectra of the interferometers.Comment: Proceedings of the 8th Gravitational Wave Data Analysis Workshop,
Milwaukee, WI, USA. 10 pages, 3 figures, documentclass ``iopart'
Localisation of massive fermions on the brane
We construct an explicit model to describe fermions confined on a four
dimensional brane embedded in a five dimensional anti-de Sitter spacetime. We
extend previous works to accommodate massive bound states on the brane and
exhibit the transverse structure of the fermionic fields. We estimate
analytically and calculate numerically the fermion mass spectrum on the brane,
which we show to be discrete. The confinement life-time of the bound states is
evaluated, and it is shown that existing constraints can be made compatible
with the existence of massive fermions trapped on the brane for durations much
longer than the age of the Universe.Comment: 20 pages, LaTeX-RevTex, 15 figures, submitted to PR
Searching for periodic sources with LIGO
We investigate the computational requirements for all-sky, all-frequency
searches for gravitational waves from spinning neutron stars, using archived
data from interferometric gravitational wave detectors such as LIGO. These
sources are expected to be weak, so the optimal strategy involves coherent
accumulaton of signal-to-noise using Fourier transforms of long stretches of
data (months to years). Earth-motion-induced Doppler shifts, and intrinsic
pulsar spindown, will reduce the narrow-band signal-to-noise by spreading power
across many frequency bins; therefore, it is necessary to correct for these
effects before performing the Fourier transform. The corrections can be
implemented by a parametrized model, in which one does a search over a discrete
set of parameter values. We define a metric on this parameter space, which can
be used to determine the optimal spacing between points in a search; the metric
is used to compute the number of independent parameter-space points Np that
must be searched, as a function of observation time T. The number Np(T) depends
on the maximum gravitational wave frequency and the minimum spindown age
tau=f/(df/dt) that the search can detect. The signal-to-noise ratio required,
in order to have 99% confidence of a detection, also depends on Np(T). We find
that for an all-sky, all-frequency search lasting T=10^7 s, this detection
threshhold is at a level of 4 to 5 times h(3/yr), where h(3/yr) is the
corresponding 99% confidence threshhold if one knows in advance the pulsar
position and spin period.Comment: 18 pages, LaTeX, 12 PostScript figures included using psfig.
Submitted to Phys. Rev.
The driver landscape of sporadic chordoma.
Chordoma is a malignant, often incurable bone tumour showing notochordal differentiation. Here, we defined the somatic driver landscape of 104 cases of sporadic chordoma. We reveal somatic duplications of the notochordal transcription factor brachyury (T) in up to 27% of cases. These variants recapitulate the rearrangement architecture of the pathogenic germline duplications of T that underlie familial chordoma. In addition, we find potentially clinically actionable PI3K signalling mutations in 16% of cases. Intriguingly, one of the most frequently altered genes, mutated exclusively by inactivating mutation, was LYST (10%), which may represent a novel cancer gene in chordoma.Chordoma is a rare often incurable malignant bone tumour. Here, the authors investigate driver mutations of sporadic chordoma in 104 cases, revealing duplications in notochordal transcription factor brachyury (T), PI3K signalling mutations, and mutations in LYST, a potential novel cancer gene in chordoma
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