751 research outputs found
A contribution to the study of sex-determination in the anura
The problem of sex -determination possesses
a peculiar fascination for the student of. animate
Nature and the fact that it remains as yet unsolved,
permits one to set out on the great adventure of its
solution with high hopes and, if one is young, with
confidence.But with the experience of the difficulties
and complexities of the subject comes a chastened
mind, and at the journey's end one is left with just
the hope that in the results of the work which has
enslaved by its all -absorbing fascination, there may
be found some suggestion as to the direction in which
the truth of the matter really lies.In this study the question of sex- determination is approached through a consideration of the abnormalities of the reproductive system which have
been recorded in Zoological literature. Often an
appreciation of the abnormal can illumine the mechanism of the normal.The typical sexual characters are first
briefly described, so as to furnish standards to
which the abnormalities may be referred. The abnormalities are then tabulated and analysed. A
brief consideration of the embryology of the reproductive system naturally follows and the investigation is brought to a close by a review of what is
known of the sex-ratio. An account is given of certain experiments.It is intended to demonstrate that the abnormalities obviously suggest that in the case of the
frog, sex is not irreversible; that the facts of embryology lend support to this view; and that a .study of
the variations of the sex -ratio supplies conclusive
proof that sax- reversal can and does occur. The graduated degrees of abnormality as portrayed, are shown . to provide a clear view of the process by which sex-reversal is effected
Phase I trial of intravesical Suramin in recurrent superficial transitional cell bladder carcinoma
Suramin is an antitrypanosomal agent with antineoplastic activity, but with serious systemic side effects. We administered Suramin intravesically to determine a concentration with low toxicity but with evidence of a pharmacodynamic effect, to recommend a dose level for phase II trials. This was an open-labelled, nonrandomised dose-escalation phase I study. In all, 12 patients with a history of recurrent superficial bladder cancer were grouped into four dose levels (10â150âmgâmlâ1 in 60âml saline). Six catheter instillations at weekly intervals were used. Cystoscopy and biopsy were performed before and 3 months after the start of treatment. Suramin was assayed using high-performance liquid chromatography, vascular endothelial growth factor (VEGF) using ELISA (enzyme-linked immunosorbent assay), and urinary protein profile using surface-enhanced laser desorption ionisation mass spectroscopy (SELDI). Minimal systemic absorption of Suramin was found at the highest dose of 150âmgâmlâ1. Urinary VEGF was affected by Suramin at doses above 50âmgâmlâ1, corresponding to the estimated threshold of saturation of Suramin binding to urine albumin. SELDI showed a specific disappearance of urinary protein peaks during treatment. Intravesical Suramin shows lack of toxicity and low systemic absorption. The results of this phase I trial support expanded clinical trials of efficacy at a dose of 100âmgâmlâ1 intravesically
Global Characteristics of X-Ray Flashes and X-Ray-Rich GRBs Observed by HETE-2
We describe and discuss the global properties of 45 gamma-ray bursts (GRBs)
observed by HETE-2 during the first three years of its mission, focusing on the
properties of X-Ray Flashes (XRFs) and X-ray-rich GRBs (XRRs). We find that the
numbers of XRFs, XRRs, and GRBs are comparable. We find that the durations and
the sky distributions of XRFs and XRRs are similar to those of GRBs. We also
find that the spectral properties of XRFs and XRRs are similar to those of
GRBs, except that the values of the peak energy of the
burst spectrum in , the peak energy flux \Fp, and the energy
fluence of XRFs are much smaller -- and those of XRRs are smaller -- than
those of GRBs. Finally, we find that the distributions of all three kinds of
bursts form a continuum in the [(2-30 keV),(30-400) keV]-plane, the
[(2-400 keV), ]-plane, and the [(50-300 keV),
]-plane. These results provide strong evidence that all three
kinds of bursts arise from the same phenomenon.Comment: 33 pages, 15 figures, submitted to Ap
HETE-2 Observation of two gamma-ray bursts at z > 3
GRB 020124 and GRB 030323 constitute half the sample of gamma-ray bursts with
a measured redshift greater than 3. This paper presents the temporal and
spectral properties of these two gamma-ray bursts detected and localized with
HETE-2. While they have nearly identical redshifts (z=3.20 for GRB 020124, and
z=3.37 for GRB 030323), these two GRBs span about an order of magnitude in
fluence, thus sampling distinct regions of the GRB luminosity function. The
properties of these two bursts are compared with those of the bulk of the GRB
population detected by HETE-2. We also discuss the energetics of GRB 020124 and
GRB 030323 and show that they are compatible with the Epeak - Eiso relation
discovered by Amati et al. (2002). Finally, we compute the maximum redshifts at
which these bursts could have been detected by HETE-2 and we address various
issues connected with the detection and localization of high-z GRBs.Comment: 19 pages, 4 figures, submitted to Ap
HETE Observations of the Gamma-Ray Burst GRB030329: Evidence for an Underlying Soft X-ray Component
An exceptionally intense gamma-ray burst, GRB030329, was detected and
localized by the instruments on board the High Energy Transient Explorer
satellite (HETE) at 11:37:14 UT on 29 March 2003. The burst consisted of two
\~10s pulses of roughly equal brightness and an X-ray tail lasting >100s. The
energy fluence in the 30-400 keV energy band was 1.08e-4 erg/cm2, making
GRB030329 one of the brightest GRBs ever detected. Communication of a 2 arcmin
error box 73 minutes after the burst allowed the rapid detection of a
counterpart in the optical, X-ray, radio and the ensuing discovery of a
supernova with most unusual characteristics. Analyses of the burst lightcurves
reveal the presence of a distinct, bright, soft X-ray component underlying the
main GRB: the 2-10 keV fluence of this component is ~7e-6 erg/cm2. The main
pulses of GRB030329 were preceded by two soft, faint, non-thermal bumps. We
present details of the HETE observations of GRB030329.Comment: 22 pages, 5 figures, to be published in ApJ 617, no. 2 (10 December
2004). Referee comments have been incorporated; results of improved spectral
analysis are include
Scientific Highlights of the HETE-2 Mission
The HETE-2 mission has been highly productive. It has observed more than 250
GRBs so far. It is currently localizing 25 - 30 GRBs per year, and has
localized 43 GRBs to date. Twenty-one of these localizations have led to the
detection of X-ray, optical, or radio afterglows, and as of now, 11 of the
bursts with afterglows have known redshifts. HETE-2 has confirmed the
connection between GRBs and Type Ic supernovae, a singular achievement and
certainly one of the scientific highlights of the mission so far. It has
provided evidence that the isotropic-equivalent energies and luminosities of
GRBs are correlated with redshift, implying that GRBs and their progenitors
evolve strongly with redshift. Both of these results have profound implications
for the nature of GRB progenitors and for the use of GRBs as a probe of
cosmology and the early universe. HETE-2 has placed severe constraints on any
X-ray or optical afterglow of a short GRB. It is also solving the mystery of
"optically dark' GRBs, and revealing the nature of X-ray flashes.Comment: 10 pages, 9 figures, to appear in proc. "The Restless High-Energy
Universe", Royal Tropical Institute, Amsterdam; revised text, added ref
X-ray Flashes or soft Gamma-ray Bursts? The case of the likely distant XRF 040912
In this work, we present a multi-wavelength study of XRF 040912, aimed at
measuring its distance scale and the intrinsic burst properties. We performed a
detailed spectral and temporal analysis of both the prompt and the afterglow
emission and we estimated the distance scale of the likely host galaxy. We then
used the currently available sample of XRFs with known distance to discuss the
connection between XRFs and classical Gamma-ray Bursts (GRBs). We found that
the prompt emission properties unambiguously identify this burst as an XRF,
with an observed peak energy of E_p=17+/-13 keV and a burst fluence ratio
S(2-30keV)/S(30-400keV)>1. A non-fading optical source with R~24 mag and with
an apparently extended morphology is spatially consistent with the X-ray
afterglow, likely the host galaxy. XRF 040912 is a very dark burst since no
afterglow optical counterpart is detected down to R>25 mag (3 sigma limiting
magnitude) at 13.6 hours after the burst. The host galaxy spectrum detected
from 3800A to 10000A, shows a single emission line at 9552A. The lack of any
other strong emission lines blue-ward of the detected one and the absence of
the Ly alpha cut-off down to 3800A are consistent with the hypothesis of the
[OII] line at redshift z=1.563+/-0.001. The intrinsic spectral properties rank
this XRF among the soft GRBs in the E_peak-E_iso diagram. Similar results were
obtained for most XRFs at known redshift. Only XRF 060218 and XRF 020903
represent a good example of instrinsic XRF(i-XRF) and are possibly associated
with a different progenitor population. This scenario may calls for a new
definition of XRFs.Comment: 10 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
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