835 research outputs found
Adjudication Acts of State in Suits Against Foreign Sovereigns: A Political Question Analysis
We discuss how one can identify CP violation (and conservation) in multi-Higgs-doublet potentials. After a brief review of CP violation in the 2HDM, we refer to the fact that for NHDM with N ≥ 3 the well known methods useful in the case N = 2 have not been generalized in order to provide a set of well defined necessary and sufficient conditions for CP conservation. We then present a simple method, proposed by the authors, to be used in such cases. Two non-trivial examples based on an S3-symmetric three-doublet model are analyzed by means of this new method.publishedVersio
Differential antifungal activity of human and cryptococcal melanins with structural discrepancies
Indexación: Scopus.Melanin is a pigment found in all biological kingdoms, and plays a key role in protection against ultraviolet radiation, oxidizing agents, and ionizing radiation damage. Melanin exerts an antimicrobial activity against bacteria, fungi, and parasites. We demonstrated an antifungal activity of synthetic and human melanin against Candida sp. The members of the Cryptococcus neoformans and C. gattii species complexes are capsulated yeasts, which cause cryptococcosis. For both species melanin is an important virulence factor. To evaluate if cryptococcal and human melanins have antifungal activity against Cryptococcus species they both were assayed for their antifungal properties and physico-chemical characters. Melanin extracts from human hair and different strains of C. neoformans (n = 4) and C. gattii (n = 4) were investigated. The following minimum inhibitory concentrations were found for different melanins against C. neoformans and C. gattii were (average/range): 13.7/(7.8-15.6) and 19.5/(15.6-31.2) μg/mL, respectively, for human melanin; 273.4/(125- > 500) and 367.2/(125.5- > 500) μg/mL for C. neoformans melanin and 125/(62.5-250) and 156.2/(62-250) μg/mL for C. gattii melanin. Using Scanning Electron Microscopy we observed that human melanin showed a compact conformation and cryptococcal melanins exposed an amorphous conformation. Infrared spectroscopy (FTIR) showed some differences in the signals related to C-C bonds of the aromatic ring of the melanin monomers. High Performance Liquid Chromatography established differences in the chromatograms of fungal melanins extracts in comparison with human and synthetic melanin, particularly in the retention time of the main compound of fungal melanin extracts and also in the presence of minor unknown compounds. On the other hand, MALDI-TOF-MS analysis showed slight differences in the spectra, specifically the presence of a minor intensity ion in synthetic and human melanin, as well as in some fungal melanin extracts. We conclude that human melanin is more active than the two fungal melanins against Cryptococcus. Although some physico-chemical differences were found, they do not explain the differences in the antifungal activity against Cryptococcus of human and cryptococcal melanins. More detailed studies on the structure should be considered to associate structure and antifungal activity.https://www.frontiersin.org/articles/10.3389/fmicb.2017.01292/ful
Dark matter in a CP-violating three-Higgs-doublet model with S3 symmetry
In spite of the success of the Standard Model of particle physics, there are some theoretical predictions which are not yet fully established experimentally, as well as some experimental observations which cannot be fitted within its theoretical framework, thus requiring physics beyond the Standard Model. One of these is a hypothetical nonluminous form of matter–dark matter. Models with an extended scalar electroweak sector yield plausible dark matter candidates. In this paper we study a specific model, C-III-a, from a family of S3 -symmetric three-Higgs-doublet models. The model consists of two active SU(2) doublets and an inert one. The latter is inert due to a Z2 symmetry that survives the breaking of S3 , and would accommodate a dark matter particle. We explore the model numerically, based on theoretical and experimental constraints. After applying a number of successive checks over the parameter space we found a viable dark matter mass region in the range [ 6.5 ; 44.5 ] GeV . This region is drastically different from the Higgs-like dark matter states that have been proposed: the well-known inert doublet model and models with three scalar doublets, with one or two inert doublets. Furthermore, the C-III-a model allows for spontaneous C P violation. This means that the scalar potential explicitly conserves CP . However, in order to generate a realistic Cabibbo-Kobayashi-Maskawa matrix we need to introduce complex Yukawa couplings.publishedVersio
Incompressible Quantum Liquids and New Conservation Laws
In this letter we investigate a class of Hamiltonians which, in addition to
the usual center-of-mass (CM) momentum conservation, also have center-of-mass
position conservation. We find that regardless of the particle statistics, the
energy spectrum is at least q-fold degenerate when the filling factor is ,
where and are coprime integers. Interestingly the simplest Hamiltonian
respecting this type of symmetry encapsulates two prominent examples of novel
states of matter, namely the fractional quantum Hall liquid and the quantum
dimer liquid. We discuss the relevance of this class of Hamiltonian to the
search for featureless Mott insulators.Comment: updated version, to be published by PR
The Fulling-Unruh effect in general stationary accelerated frames
We study the generalized Unruh effect for accelerated reference frames that
include rotation in addition to acceleration. We focus particularly on the case
where the motion is planar, with presence of a static limit in addition to the
event horizon. Possible definitions of an accelerated vacuum state are examined
and the interpretation of the Minkowski vacuum state as a thermodynamic state
is discussed. Such athermodynamic state is shown to depend on two parameters,
the acceleration temperature and a drift velocity, which are determined by the
acceleration and angular velocity of the accelerated frame. We relate the
properties of Minkowski vacuum in the accelerated frame to the excitation
spectrum of a detector that is stationary in this frame. The detector can be
excited both by absorbing positive energy quanta in the "hot" vacuum state and
by emitting negative energy quanta into the "ergosphere" between the horizon
and the static limit. The effects are related to similar effects in the
gravitational field of a rotating black hole.Comment: Latex, 39 pages, 5 figure
Design and Tests of 500kW RF Windows for the ITER LHCD System
In the frame of a R\&D effort conducted by CEA toward the design and the
qualification of a 5 GHz LHCD system for the ITER tokamak, two 5 GHz 500 kW/5 s
windows have been designed, manufactured and tested at high power in
collaboration with the National Fusion Research Institute (NFRI). The window
design rely on a symmetrical pill-box concept with a cylindrical beryllium
oxide ceramic brazed on an actively water cooled copper skirt. The ceramic RF
properties have been measured on a test sample to get realistic values for
guiding the design. Low power measurements of the manufactured windows show
return losses below-32 dB and insertion losses between-0.01 dB and-0.05 dB,
with an optimum frequency shifted toward lower frequencies. High power tests
conducted at NFRI show unexpected total power loss for both windows. The
ceramic temperature during RF pulses has been found to reach unexpected high
temperature, preventing these windows to be used under CW conditions. A
post-mortem RF analysis of samples taken from one window shows that the
dielectric properties of the ceramic were not the ones measured on the
manufacturer sample, which partly explain the differences with the reference
modelling
Design and RF measurements of a 5 GHz 500 kW window for the ITER LHCD system
International audienceCEA/IRFM is conducting R&D efforts in order to validate the critical RF components of the 5 GHz ITER LHCD system, which is expected to transmit 20 MW of RF power to the plasma. Two 5 GHz 500 kW BeO pill-box type window prototypes have been manufactured in 2012 by the PMB Company, in close collaboration with CEA/IRFM. Both windows have been validated at low power, showing good agreement between measured and modeling, with a return loss better than 32 dB and an insertion loss below 0.05 dB. This paper reports on the window RF design and the low power measurements. The high power tests up to 500kW have been carried out in March 2013 in collaboration with NFRI. Results of these tests are also reported. In the current ITER LHCD design, 20 MW Continuous Wave (CW) of Radio-Frequency power at 5 GHz are expected to be generated and transmitted to the plasma. In order to separate the vacuum vessel pressure from the cryostat waveguide pressure, forty eight 5 GHz 500kW CW windows are to be assembled on the waveguides at the equatorial port flange. For nuclear safety reasons, forty eight additional windows could be located in the cryostat section, to separate and monitor the cryostat waveguide pressure from the exterior transmission line pressure. These windows are identified as being one of the main critical components for the ITER LHCD system since first ITER LHCD studies [1] [2] [3] or more recently [4] [5] , and clearly require an important R&D effort. In this context and even if the LHCD system is not part of the construction baseline, the CEA/IRFM is conducting a R&D effort in order to validate a design and the performances of these RF windows. In order to begin the assessment of this need, two 5 GHz 500 kW/5 s pill-box type windows prototypes have been manufactured in 2012 by the PMB Company in close collaboration with the CEA/IRFM [6]. The section 2 of this paper reports the RF and mechanical design of a 5 GHz window. Some features of the mechanical design and the experimental RF measurements at low power are reported in section 3. High power results, made in collaboration with NFRI, are detailed in section 4. The development of CW windows is discussed in the conclusion. 2-RF AND MECHANICAL DESIGN The proposed 5 GHz RF window is based on a pill-box design [2] , i.e. a ceramic brazed in portion of a circular waveguide, connected on either side to a rectangular waveguide section. Typical design rules of thumb of such device are circular section diameter about the same size of the diagonal of the rectangular waveguide (cf. FIGURE 1). Without taking into account the ceramic, the circular section length is approximately half a guided wavelength of the circular TE 11 mode, in order for the device to act as a half-wave transformer. Once optimized, taking into account the ceramic, matching is correct only for a narrow band of frequency and is very sensitive to the device dimensions and the ceramic relative permittivity. The heat losses in the ceramic, which have to be extracted by an active water cooling, depends on the inside electric field topology and of ceramic dielectric loss (loss tangent). Undesirable modes due to parasitic resonances can be excited in the ceramic volume, raising the electric field an
Broad white matter impairment in multiple system atrophy.
Multiple system atrophy (MSA) is a rare neurodegenerative disorder characterized by the widespread aberrant accumulation of α-synuclein (α-syn). MSA differs from other synucleinopathies such as Parkinson's disease (PD) in that α-syn accumulates primarily in oligodendrocytes, the only source of white matter myelination in the brain. Previous MSA imaging studies have uncovered focal differences in white matter. Here, we sought to build on this work by taking a global perspective on whole brain white matter. In order to do this, in vivo structural imaging and diffusion magnetic resonance imaging were acquired on 26 MSA patients, 26 healthy controls, and 23 PD patients. A refined whole brain approach encompassing the major fiber tracts and the superficial white matter located at the boundary of the cortical mantle was applied. The primary observation was that MSA but not PD patients had whole brain deep and superficial white matter diffusivity abnormalities (p < .001). In addition, in MSA patients, these abnormalities were associated with motor (Unified MSA Rating Scale, Part II) and cognitive functions (Mini-Mental State Examination). The pervasive whole brain abnormalities we observe suggest that there is widespread white matter damage in MSA patients which mirrors the widespread aggregation of α-syn in oligodendrocytes. Importantly, whole brain white matter abnormalities were associated with clinical symptoms, suggesting that white matter impairment may be more central to MSA than previously thought
The Association between Serum Serine and Glycine and Related-Metabolites with Pancreatic Cancer in a Prospective Cohort Study
Background: Serine and glycine play an important role in the folate-dependent one-carbon metabolism. The metabolism of serine and glycine has been shown to be associated with cancer cell proliferation. No prior epidemiologic study has investigated the associations for serum levels of serine and glycine with pancreatic cancer risk.
Methods: We conducted a nested case-control study involved 129 incident pancreatic cancer cases and 258 individually matched controls within a prospective cohort study of 18,244 male residents in Shanghai, China. Glycine and serine and related metabolites in pre-diagnostic serum were quantified using gas chromatography-tandem mass spectrometry. A conditional logistic regression method was used to evaluate the associations for serine, glycine, and related metabolites with pancreatic cancer risk with adjustment for potential confounders.
Results: Odds ratios (95% confidence intervals) of pancreatic cancer for the highest quartile of serine and glycine were 0.33 (0.14–0.75) and 0.25 (0.11–0.58), respectively, compared with their respective lowest quartiles (both p’s < 0.01). No significant association with risk of pancreatic cancer was observed for other serine- or glycine related metabolites including cystathionine, cysteine, and sarcosine.
Conclusion: The risk of pancreatic cancer was reduced by more than 70% in individuals with elevated levels of glycine and serine in serum collected, on average, more than 10 years prior to cancer diagnosis in a prospectively designed case-control study. These novel findings support a protective role of serine and glycine against the development of pancreatic cancer in humans that might have an implication for cancer prevention.publishedVersio
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