237 research outputs found
Precision determination of band offsets in strained InGaAs/GaAs quantum wells by C-V-profiling and Schroedinger-Poisson self-consistent simulation
The results of measurements and numerical simulation of charge carrier
distribution and energy states in strained quantum wells In_xGa_{1-x}As/GaAs
(0.06 < x < 0.29) by C-V-profiling are presented. Precise values of conduction
band offsets for these pseudomorphic QWs have been obtained by means of
self-consistent solution of Schroedinger and Poisson equations and following
fitting to experimental data. For the conduction band offsets in strained
In_xGa_{1-x}As/GaAs - QWs the expression DE_C(x) = 0.814x - 0.21x^2 has been
obtained.Comment: 9 pages, 12 figures, RevTeX
Remote frequency measurement of the 1S0-3P1 transition in laser cooled Mg-24
We perform Ramsey-Bord\'e spectroscopy on laser-cooled magnesium atoms in
free fall to measure the 1S0 \rightarrow 3P1 intercombination transition
frequency. The measured value of 655 659 923 839 730 (48) Hz is consistent with
our former atomic beam measurement (Friebe et al 2008 Phys. Rev. A 78 033830).
We improve upon the fractional accuracy of the previous measurement by more
than an order of magnitude to 7e-14. The magnesium frequency standard was
referenced to a fountain clock of the Physikalisch-Technische Bundesanstalt
(PTB) via a phase-stabilized telecom fiber link and its stability was
characterized for interrogation times up to 8000 s. The high temperature of the
atomic ensemble leads to a systematic shift due to the motion of atoms across
the spectroscopy beams. In our regime, this leads to a counterintuitive
reduction of residual Doppler shift with increasing resolution. Our theoretical
model of the atom-light interaction is in agreement with the observed effect
and allows us to quantify its contribution in the uncertainty budget.Comment: 16 pages, 8 figures. Accepted in New Journal of Physic
Amplitude to phase conversion of InGaAs pin photo-diodes for femtosecond lasers microwave signal generation
When a photo-diode is illuminated by a pulse train from a femtosecond laser,
it generates microwaves components at the harmonics of the repetition rate
within its bandwidth. The phase of these components (relative to the optical
pulse train) is known to be dependent on the optical energy per pulse. We
present an experimental study of this dependence in InGaAs pin photo-diodes
illuminated with ultra-short pulses generated by an Erbium-doped fiber based
femtosecond laser. The energy to phase dependence is measured over a large
range of impinging pulse energies near and above saturation for two typical
detectors, commonly used in optical frequency metrology with femtosecond laser
based optical frequency combs. When scanning the optical pulse energy, the
coefficient which relates phase variations to energy variations is found to
alternate between positive and negative values, with many (for high harmonics
of the repetition rate) vanishing points. By operating the system near one of
these vanishing points, the typical amplitude noise level of commercial-core
fiber-based femtosecond lasers is sufficiently low to generate state-of-the-art
ultra-low phase noise microwave signals, virtually immune to amplitude to phase
conversion related noise.Comment: 7 pages, 6 figures, submitted to Applied Physics
Inclusive Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions
Inclusive differential cross sections and
for the production of \kzeros, \lambdazero, and
\antilambda particles are measured at HERA in proton-induced reactions on C,
Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to
GeV in the proton-nucleon system. The ratios of differential
cross sections \rklpa and \rllpa are measured to be and , respectively, for \xf . No significant dependence upon the
target material is observed. Within errors, the slopes of the transverse
momentum distributions also show no significant
dependence upon the target material. The dependence of the extrapolated total
cross sections on the atomic mass of the target material is
discussed, and the deduced cross sections per nucleon are
compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table
The rationale of opportunistic bilateral salpingectomies (OBS) during benign gynaecological and obstetric surgery : a consensus text of the Flemish Society of Obstetrics and Gynaecology (VVOG)
Ovarian cancer (OC), is a disease difficult to diagnose in an early stage implicating a poor prognosis. The 5-year
overall survival in Belgium has not changed in the last 18 years and remains 44 %. There is no effective screening
method (secondary prevention) to detect ovarian cancer at an early stage. Primary prevention of ovarian cancer
came in the picture through the paradigm shift that the fallopian tube is often the origin of ovarian cancer and
not the ovary itself. Opportunistic bilateral salpingectomy (OBS) during benign gynaecological and obstetric
surgery might have the potential to reduce the risk of ovarian cancer by as much as 65 %. Bilateral risk-reducing
salpingectomy during a benign procedure is feasible, safe, appears to have no impact on the ovarian function and
seems to be cost effective. The key question is whether we should wait for a RCT or implement OBS directly in our
daily practice. Guidelines regarding OBS within our societies are therefore urgently needed. Our recommendation
is to inform all women without a child wish, undergoing a benign gynaecological or obstetrical surgical procedure
about the pro’s and the con’s of OBS and advise a bilateral salpingectomy. Furthermore, there is an urgent need
for a prospective registry of OBS. The present article is the consensus text of the Flemish Society of Obstetrics and
Gynaecology (VVOG) regarding OBS
Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope
The scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI) and hyperspectral cathodoluminescence imaging (CL) provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively, with a spatial resolution of tens of nanometres. EBSD provides crystal orientation, crystal phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended defects over a large area of a given sample. CL reveals the influence of crystal structure, composition and strain on intrinsic luminescence and/or reveals defect-related luminescence. Dark features are also observed in CL images where carrier recombination at defects is non-radiative. The combination of these techniques is a powerful approach to clarifying the role of crystallography and extended defects on a materials' light emission properties. Here we describe the EBSD, ECCI and CL techniques and illustrate their use for investigating the structural and light emitting properties of UV-emitting nitride semiconductor structures. We discuss our investigations of the type, density and distribution of defects in GaN, AlN and AlGaN thin films and also discuss the determination of the polarity of GaN nanowires
Estimating the potential survival gains by eliminating socioeconomic and sex inequalities in stage at diagnosis of melanoma.
BACKGROUND: Although inequalities in cancer survival are thought to reflect inequalities in stage at diagnosis, little evidence exists about the size of potential survival gains from eliminating inequalities in stage at diagnosis. METHODS: We used data on patients diagnosed with malignant melanoma in the East of England (2006-2010) to estimate the number of deaths that could be postponed by completely eliminating socioeconomic and sex differences in stage at diagnosis after fitting a flexible parametric excess mortality model. RESULTS: Stage was a strong predictor of survival. There were pronounced socioeconomic and sex inequalities in the proportion of patients diagnosed at stages III-IV (12 and 8% for least deprived men and women and 25 and 18% for most deprived men and women, respectively). For an annual cohort of 1025 incident cases in the East of England, eliminating sex and deprivation differences in stage at diagnosis would postpone approximately 24 deaths to beyond 5 years from diagnosis. Using appropriate weighting, the equivalent estimate for England would be around 215 deaths, representing 11% of all deaths observed within 5 years from diagnosis in this population. CONCLUSIONS: Reducing socioeconomic and sex inequalities in stage at diagnosis would result in substantial reductions in deaths within 5 years of a melanoma diagnosis.This article is an independent research supported by different
funding bodies, beyond the authors’ own employing organisations.
MJR was partially funded by a Cancer Research UK Postdoctoral
Fellowship (CRUK_A13275). GL is supported by a Postdoctoral
Fellowship award by the National Institute for Health Research
(NIHR PDF-2011-04-047) to end of 2014 and a Cancer Research
UK Clinician Scientist Fellowship award (A18180) from January
2015. The views expressed in this publication are those of the
authors and not necessarily those of the National Health Service
(NHS), the National Institute for Health Research, the Department
of Health, Cancer Research UK, or any other organisation. We
thank all staff at the National Cancer Registration Service, Public
Health England, Eastern Office, who helped collect and code data
used in this study. We particularly acknowledge the help of Dr
Clement H Brown and Dr Brian A Rous who were responsible for
staging.This is the final published version. It first appeared at http://www.nature.com/bjc/journal/v112/n1s/full/bjc201550a.html
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