552 research outputs found
Anderson transition in the three dimensional symplectic universality class
We study the Anderson transition in the SU(2) model and the Ando model. We
report a new precise estimate of the critical exponent for the symplectic
universality class of the Anderson transition. We also report numerical
estimation of the function.Comment: 4 pages, 5 figure
Topology dependent quantities at the Anderson transition
The boundary condition dependence of the critical behavior for the three
dimensional Anderson transition is investigated. A strong dependence of the
scaling function and the critical conductance distribution on the boundary
conditions is found, while the critical disorder and critical exponent are
found to be independent of the boundary conditions
Scaling of the conductance distribution near the Anderson transition
The single parameter scaling hypothesis is the foundation of our
understanding of the Anderson transition. However, the conductance of a
disordered system is a fluctuating quantity which does not obey a one parameter
scaling law. It is essential to investigate the scaling of the full conductance
distribution to establish the scaling hypothesis. We present a clear cut
numerical demonstration that the conductance distribution indeed obeys one
parameter scaling near the Anderson transition
Failure of single-parameter scaling of wave functions in Anderson localization
We show how to use properties of the vectors which are iterated in the
transfer-matrix approach to Anderson localization, in order to generate the
statistical distribution of electronic wavefunction amplitudes at arbitary
distances from the origin of disordered systems. For
our approach is shown to reproduce exact diagonalization results
available in the literature. In , where strips of width sites
were used, attempted fits of gaussian (log-normal) forms to the wavefunction
amplitude distributions result in effective localization lengths growing with
distance, contrary to the prediction from single-parameter scaling theory. We
also show that the distributions possess a negative skewness , which is
invariant under the usual histogram-collapse rescaling, and whose absolute
value increases with distance. We find for the
range of parameters used in our study, .Comment: RevTeX 4, 6 pages, 4 eps figures. Phys. Rev. B (final version, to be
published
The effect of food and concurrent chemotherapy on the bioavailability of oral etoposide.
There is no information on the effect of food or concurrent drug administration on the bioavailability of oral etoposide, despite the fact that treatment is frequently administered over several days and most often in combination with other cytotoxic agents. The influence of these factors has been studied in 11 patients, receiving combination cytotoxic therapy for extensive small cell lung carcinoma. Neither food nor concurrent oral or intravenous chemotherapy had a significant effect on the mean plasma concentrations of etoposide, achieved following oral administration. Wide variation in peak plasma concentrations and in area under the concentration time curve (AUC) occurred both between and within patients. It appears unnecessary for patients receiving etoposide (at 100 mg) to fast prior to drug administration. Furthermore, oral etoposide (at 100 mg and at 400 mg) may be given in combination with other cytotoxic agents without compromising its bioavailability
Scaling Theory of Conduction Through a Normal-Superconductor Microbridge
The length dependence is computed of the resistance of a disordered
normal-metal wire attached to a superconductor. The scaling of the transmission
eigenvalue distribution with length is obtained exactly in the metallic limit,
by a transformation onto the isobaric flow of a two-dimensional ideal fluid.
The resistance has a minimum for lengths near l/Gamma, with l the mean free
path and Gamma the transmittance of the superconductor interface.Comment: 8 pages, REVTeX-3.0, 3 postscript figures appended as self-extracting
archive, INLO-PUB-94031
Anderson transition in three-dimensional disordered systems with symplectic symmetry
The Anderson transition in a 3D system with symplectic symmetry is
investigated numerically. From a one-parameter scaling analysis the critical
exponent of the localization length is extracted and estimated to be . The level statistics at the critical point are also analyzed
and shown to be scale independent. The form of the energy level spacing
distribution at the critical point is found to be different from that
for the orthogonal ensemble suggesting that the breaking of spin rotation
symmetry is relevant at the critical point.Comment: 4 pages, revtex, to appear in Physical Review Letters. 3 figures
available on request either by fax or normal mail from
[email protected] or [email protected]
The Anderson transition: time reversal symmetry and universality
We report a finite size scaling study of the Anderson transition. Different
scaling functions and different values for the critical exponent have been
found, consistent with the existence of the orthogonal and unitary universality
classes which occur in the field theory description of the transition. The
critical conductance distribution at the Anderson transition has also been
investigated and different distributions for the orthogonal and unitary classes
obtained.Comment: To appear in Physical Review Letters. Latex 4 pages with 4 figure
Efficacy and toxicity outcomes for patients treated with focal salvage high dose rate brachytherapy for locally recurrent prostate cancer
Introduction
Isolated local recurrence of prostate cancer following primary radiotherapy or brachytherapy may be treated with focal salvage high dose rate brachytherapy, although there remains an absence of high quality evidence to support this approach.
Methods
Men with prostate cancer treated consecutively between 2015 and 2018 using 19 Gy in a single fraction high dose rate brachytherapy (HDR) for locally recurrent prostate cancer were identified from an institutional database. Univariable analysis was performed to evaluate the relationship between patient, disease and treatment factors with biochemical progression free survival (bPFS).
Results
43 patients were eligible for evaluation. Median follow up duration was 26 months (range 1–60). Median bPFS was 35 months (95% confidence interval 25.6–44.4). Kaplan-Meier estimates for bPFS at 1, 2 and 3 years post salvage were 95.2%, 70.6% and 41.8% respectively. On univariable Cox regression analysis, only nadir PSA was significantly associated with bPFS although the majority of patients were also treated with androgen deprivation therapy. Only one late grade 3 genitourinary toxicity was observed.
Conclusion
Focal salvage HDR brachytherapy may provide good biochemical control with a low risk of severe toxicity. Further evaluation within clinical trials are needed to establish its role in the management of locally recurrent prostate cancer
Conductivity of Metallic Si:B near the Metal-Insulator Transition: Comparison between Unstressed and Uniaxially Stressed Samples
The low-temperature dc conductivities of barely metallic samples of p-type
Si:B are compared for a series of samples with different dopant concentrations,
n, in the absence of stress (cubic symmetry), and for a single sample driven
from the metallic into the insulating phase by uniaxial compression, S. For all
values of temperature and stress, the conductivity of the stressed sample
collapses onto a single universal scaling curve. The scaling fit indicates that
the conductivity of si:B is proportional to the square-root of T in the
critical range. Our data yield a critical conductivity exponent of 1.6,
considerably larger than the value reported in earlier experiments where the
transition was crossed by varying the dopant concentration. The larger exponent
is based on data in a narrow range of stress near the critical value within
which scaling holds. We show explicitly that the temperature dependences of the
conductivity of stressed and unstressed Si:B are different, suggesting that a
direct comparison of the critical behavior and critical exponents for stress-
tuned and concentration-tuned transitions may not be warranted
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