704 research outputs found
Developmental toxicity of combined ethylbenzene and methylethylketone administered by inhalation to rats
Pregnant Sprague–Dawley rats were exposed to ethylbenzene (EB; 0, 250, or 1000 ppm) and methylethylketone (MEK; 0, 1000, or 3000 ppm), alone and in combination, by inhalation, for 6 h/day, during days 6–20 of gestation. Maternal toxicity, evidenced by decreased in body weight gain and food consumption, tended to be greater after simultaneous exposures to the high concentrations of 1000 ppm EB and 3000 ppm MEK, when compared to the treatments with individual compounds. No significant increase in embryo/fetal lethality or incidence of malformations and variations was observed in any of the treatment groups. Fetal body weight was significantly reduced after individual treatment with 1000 ppm EB or 3000 ppm MEK, and in the combined groups. There was no evidence of interaction between EB and MEK in causing developmental toxicity
Long-term follow-up of intratympanic methylprednisolone versus gentamicin in patients with unilateral Menière’s disease
Objectives: To determine whether long term (>48 months)
symptomatic vertigo control is sustained in patients with
Menie`re’s disease from a previous comparative trial of
intratympanic methylprednisolone versus gentamicin, and if the two treatments remain nonsignificantly different at longterm follow-up.
Study Design: Mail survey recording vertigo frequency in
the previous one and six months, further intratympanic
treatment received, and validated symptom questionnaires.
Setting: Outpatient hospital clinic setting.
Patients: Adult patients with definite unilateral refractory Menie`re’s disease, who previously received in tratympanic treatment in a comparative trial.
Intervention: A survey of trial participants who received
intratympanic gentamicin (40 mg/mL) or methylprednisolone
(62.5 mg/mL).
Outcome measures: Primary: number of vertigo attacks in
the 6 months prior to receiving this survey compared with
the 6 months before the first trial injection.
Secondary: : Number of vertigo attacks over the previous 1 month; validated symptom questionnaire scores of tinnitus, dizziness, vertigo, aural fullness, and functional disability.
Results: Average follow-up was 70.8 months (standard
deviation 17.0) from the first treatment injection. Vertigo attacks in the 6 months prior to receiving the current survey reduced by 95% compared to baseline in both drug groups (intention-to-treat analysis, both p<0.001). No significant difference between drugs was found for the primary and secondary outcomes. Eight participants (methylprednisolone ¼ 5 and gentamicin ¼ 3) required further injections for relapse after completing the original trial.
Conclusion: Intratympanic methylprednisolone treatment provides effective long-lasting relief of vertigo, without the known inner-ear toxicity associated with gentamicin. There are no significant differences between the two treatments at long term follow-up
Bridges of hope? : Canadian voluntary agencies and the Third World
Published in French under the title: Ponts de l'espoir
Pleiotropic actions of suramin on the proliferation of human breast-cancer cells in vitro
Suramin, a non‐specific growth factor antagonist, is currently under investigation for treatment of cancer patients. We studied its action on 6 different human breast‐cancer cell lines in vitro. In complete growth medium, pleiotropic effects were observed with respect to cell proliferation, i.e. suramin is stimulatory at low concentrations and inhibitory at higher concentrations, for 4 of the 6 cell lines studied. The various cell lines showed marked differences with respect to the antiproliferative action of suramin, the Evsa‐T cells being by far the most sensitive ones. A suramin concentration of 100 μg/ml brought about a 100% stimulation of the proliferation of ZR/HERc cells, ZR 75.1 cells ectopically expressing a human epidermal growth factor receptor (EGF‐R) cDNA. Although less pronounced (10 to 60% stimulation), a similar response was observed for the parent ZR 75.1 cells, as well as for T‐47D and MDA‐MB‐231 cells. The non‐specificity of the action of suramin was established by the observation that suramin‐induced inhibition of cell proliferation could be abolished by insulin‐like growth factor‐1 (IGF‐I) or basic fibroblast growth factor (bFGF), and even by estradiol, both in complete growth medium and under defined serum‐free conditions. Our data indicate that suramin exerts pleiotropic effects on the proliferation of human breast cancer cells in vitro, and confirm the non‐specific nature of its action. The stimulatory effect of low concentrations of suramin on the proliferation of breast cancer cells may have important consequences for breast cancer patients treated with suramin. Copyrigh
Rolling tachyon solution of two-dimensional string theory
We consider a classical (string) field theory of matrix model which was
developed earlier in hep-th/9207011 and subsequent papers. This is a
noncommutative field theory where the noncommutativity parameter is the string
coupling . We construct a classical solution of this field theory and show
that it describes the complete time history of the recently found rolling
tachyon on an unstable D0 brane.Comment: 19 pages, 2 figures, minor changes in text and additional references,
correction of decay time (version to appear in JHEP.
The importance of self-consistency in determining interface properties of S-I-N and D-I-N structures
We develop a method to solve the Bogoliubov de Gennes equation for
superconductors self-consistently, using the recursion method. The method
allows the pairing interaction to be either local or non-local corresponding to
and --wave superconductivity, respectively. Using this method we examine
the properties of various and interfaces. In particular we
self-consistently calculate the spatially varying density of states and the
superconducting order parameter. We see that changing the strength of the
insulating barrier, at the interface, does not, in the case of an --wave
superconductor, dramatically, change the low energy local density of states, in
the superconducting region near the interface. This is in stark contrast to
what we see in the case of a interface where the local particle density
of states is changed dramatically. Hence we deduce that in calculating such
properties as the conductance of and structures it is far more
important to carry out a self-consistent calculations in the --wave case.Comment: 14 pages, 8 figures, submitted to special issue of "Superlattices and
Microstructures
Inhomogeneous tachyon dynamics and the zipper
We study the process of inhomogeneous tachyon condensation in an intersecting
D1- and anti-D1-brane system using an effective tachyon DBI action. By
switching to the Hamiltonian formalism, we numerically solve for the dynamical
evolution of the system at a small intersection angle. We find that the decay
proceeds indefinitely and resembles the action of two zippers moving away from
the intersection point at the speed of light, zipping the branes together and
leaving inhomogeneous tachyon matter behind. We also discuss the range of
validity of our analysis and discuss the relation of the D1-anti-D1 description
of the system to one in terms of an intersecting D1-D1-brane pair.Comment: 23 pages, 12 figures. v2: added references; v3: more references,
published versio
A Matrix Model Dual of Type 0B String Theory in Two Dimensions
We propose that type 0B string theory in two dimensions admits a dual
description in terms of a one dimensional bosonic matrix model of a hermitian
matrix. The potential in the matrix model is symmetric with respect to the
parity-like Z_2 transformation of the matrix. The two sectors in the theory,
namely the NSNS and RR scalar sectors correspond to two classes of operators in
the matrix model, even and odd under the Z_2 symmetry respectively. We provide
evidence that the matrix model successfully reconstructs the perturbative
S-matrix of the string theory, and reproduces the closed string emission
amplitude from unstable D-branes. Following recent work in two dimensional
bosonic string, we argue that the matrix model can be identified with the
theory describing N unstable D0-branes in type 0B theory. We also argue that
type 0A theory is described in terms of the quantum mechanics of
brane-antibrane systems.Comment: Latex, 20 pages, typos corrected, explanations added, references
adde
Rolling Tachyon Boundary State, Conserved Charges and Two Dimensional String Theory
The boundary state associated with the rolling tachyon solution on an
unstable D-brane contains a part that decays exponentially in the asymptotic
past and the asymptotic future, but it also contains other parts which either
remain constant or grow exponentially in the past or future. We argue that the
time dependence of the latter parts is completely determined by the requirement
of BRST invariance of the boundary state, and hence they contain information
about certain conserved charges in the system. We also examine this in the
context of the unstable D0-brane in two dimensional string theory where these
conserved charges produce closed string background associated with the discrete
states, and show that these charges are in one to one correspondence with the
symmetry generators in the matrix model description of this theory.Comment: LaTeX file, 37 pages; v3: references added; v4: minor change
Strings from Tachyons
We propose a new interpretation of the c=1 matrix model as the world-line
theory of N unstable D-particles, in which the hermitian matrix is provided by
the non- abelian open string tachyon. For D-particles in 1+1-d string theory,
we find a direct quantitative match between the closed string emission due to a
rolling tachyon and that due to a rolling eigenvalue in the matrix model. We
explain the origin of the double-scaling limit, and interpret it as an extreme
representative of a large equivalence class of dual theories. Finally, we
define a concrete decoupling limit of unstable D-particles in IIB string theory
that reduces to the c=1 matrix model, suggesting that 1+1-d string theory
represents the near-horizon limit of an ultra-dense gas of IIB D-particles.Comment: 30 pages, 4 figures; v2: added references, improved discussion of
Liouville boundary states, v3: small correction
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