72 research outputs found
Gallium Arsenide (GaAs) Quantum Photonic Waveguide Circuits
Integrated quantum photonics is a promising approach for future practical and
large-scale quantum information processing technologies, with the prospect of
on-chip generation, manipulation and measurement of complex quantum states of
light. The gallium arsenide (GaAs) material system is a promising technology
platform, and has already successfully demonstrated key components including
waveguide integrated single-photon sources and integrated single-photon
detectors. However, quantum circuits capable of manipulating quantum states of
light have so far not been investigated in this material system. Here, we
report GaAs photonic circuits for the manipulation of single-photon and
two-photon states. Two-photon quantum interference with a visibility of 94.9
+/- 1.3% was observed in GaAs directional couplers. Classical and quantum
interference fringes with visibilities of 98.6 +/- 1.3% and 84.4 +/- 1.5%
respectively were demonstrated in Mach-Zehnder interferometers exploiting the
electro-optic Pockels effect. This work paves the way for a fully integrated
quantum technology platform based on the GaAs material system.Comment: 10 pages, 4 figure
Towards an Asymptotic-Safety Scenario for Chiral Yukawa Systems
We search for asymptotic safety in a Yukawa system with a chiral
symmetry, serving as a toy model for the
standard-model Higgs sector. Using the functional RG as a nonperturbative tool,
the leading-order derivative expansion exhibits admissible non-Ga\ssian
fixed-points for which arise from a conformal threshold
behavior induced by self-balanced boson-fermion fluctuations. If present in the
full theory, the fixed-point would solve the triviality problem. Moreover, as
one fixed point has only one relevant direction even with a reduced hierarchy
problem, the Higgs mass as well as the top mass are a prediction of the theory
in terms of the Higgs vacuum expectation value. In our toy model, the fixed
point is destabilized at higher order due to massless Goldstone and fermion
fluctuations, which are particular to our model and have no analogue in the
standard model.Comment: 16 pages, 8 figure
Carvedilol for prevention of restenosis after directional coronary atherectomy : final results of the European carvedilol atherectomy restenosis (EUROCARE) trial
BACKGROUND: In addition to its known properties as a competitive,
nonselective beta and alpha-1 receptor blocker, carvedilol directly
inhibits vascular myocyte migration and proliferation and exerts
antioxidant effects that are considerably greater than those of vitamin E
or probucol. This provides the basis for an evaluation of carvedilol for
the prevention of coronary restenosis. METHODS AND RESULTS: In a
prospective, double-blind, randomized, placebo-controlled trial, 25 mg of
carvedilol was given twice daily, starting 24 h
Asymptotic safety of simple Yukawa systems
We study the triviality and hierarchy problem of a Z_2-invariant Yukawa
system with massless fermions and a real scalar field, serving as a toy model
for the standard-model Higgs sector. Using the functional RG, we look for UV
stable fixed points which could render the system asymptotically safe. Whether
a balancing of fermionic and bosonic contributions in the RG flow induces such
a fixed point depends on the algebraic structure and the degrees of freedom of
the system. Within the region of parameter space which can be controlled by a
nonperturbative next-to-leading order derivative expansion of the effective
action, we find no non-Gaussian fixed point in the case of one or more fermion
flavors. The fermion-boson balancing can still be demonstrated within a model
system with a small fractional flavor number in the symmetry-broken regime. The
UV behavior of this small-N_f system is controlled by a conformal Higgs
expectation value. The system has only two physical parameters, implying that
the Higgs mass can be predicted. It also naturally explains the heavy mass of
the top quark, since there are no RG trajectories connecting the UV fixed point
with light top masses.Comment: 14 pages, 3 figures, v2: references added, typos corrected, minor
numerical correction
Androgens and the breast
Androgens have important physiological effects in women while at the same time they may be implicated in breast cancer pathologies. However, data on the effects of androgens on mammary epithelial proliferation and/or breast cancer incidence are not in full agreement. We performed a literature review evaluating current clinical, genetic and epidemiological data regarding the role of androgens in mammary growth and neoplasia. Epidemiological studies appear to have significant methodological limitations and thus provide inconclusive results. The study of molecular defects involving androgenic pathways in breast cancer is still in its infancy. Clinical and nonhuman primate studies suggest that androgens inhibit mammary epithelial proliferation and breast growth while conventional estrogen treatment suppresses endogenous androgens. Abundant clinical evidence suggests that androgens normally inhibit mammary epithelial proliferation and breast growth. Suppression of androgens using conventional estrogen treatment may thus enhance estrogenic breast stimulation and possibly breast cancer risk. Addition of testosterone to the usual hormone therapy regimen may diminish the estrogen/progestin increase in breast cancer risk but the impact of this combined use on mammary gland homeostasis still needs evaluation
Contribution of human hematopoietic stem cells to liver repair
Immune-deficient mouse models of liver damage allow examination of human stem cell migration to sites of damage and subsequent contribution to repair and survival. In our studies, in the absence of a selective advantage, transplanted human stem cells from adult sources did not robustly become hepatocytes, although some level of fusion or hepatic differentiation was documented. However, injected stem cells did home to the injured liver tissue and release paracrine factors that hastened endogenous repair and enhanced survival. There were significantly higher levels of survival in mice with a toxic liver insult that had been transplanted with human stem cells but not in those transplanted with committed progenitors. Transplantation of autologous adult stem cells without conditioning is a relatively safe therapy. Adult stem cells are known to secrete bioactive factors that suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate recruitment, retention, mitosis, and differentiation of tissue-residing stem cells. These paracrine effects are distinct from the direct differentiation of stem cells to repair tissue. In patients at high risk while waiting for a liver transplant, autologous stem cell therapy could be considered, as it could delay the decline in liver function
Lessons from the epidemiological surveillance program, during the influenza A (H1N1) virus epidemic, in a reference university hospital of Southeastern Brazil
Microhabitat use by three species of egret (Pelecaniformes, Ardeidae) in southern Brazil
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