8,830 research outputs found
Searching for Very High Energy Emission from Pulsars Using the High Altitude Water Cherenkov (HAWC) Observatory
There are currently over 160 known gamma-ray pulsars. While most of them are
detected only from space, at least two are now seen also from the ground. MAGIC
and VERITAS have measured the gamma ray pulsed emission of the Crab pulsar up
to hundreds of GeV and more recently MAGIC has reported emission at
TeV. Furthermore, in the Southern Hemisphere, H.E.S.S. has detected the Vela
pulsar above 30 GeV. In addition, non-pulsed TeV emission coincident with
pulsars has been detected by many groups, including the Milagro Collaboration.
These GeV-TeV observations open the possibility of searching for
very-high-energy (VHE, > 100GeV) pulsations from gamma-rays pulsars in the HAWC
field of view.Comment: Presented at the 34th International Cosmic Ray Conference (ICRC2015),
The Hague, The Netherlands. See arXiv:1508.03327 for all HAWC contribution
Betalains and phenolic compounds of leaves and stems of Alternanthera brasiliana and Alternanthera tenella
Betacyanins and phenolic compounds from acetonitrile:acidified water extracts of Alternanthera brasiliana and Alternanthera tenella were characterized and quantified using a high-performance liquid chromatography system coupled with diode array and electrospray mass spectrometry detection. Four betacyanins (amaranthine, isoamaranthine, betanin and isobetanin) were tentatively identified and quantified. Twenty eight phenolic compounds of four different families (hydroxybenzoic and hydroxycinnamic acids, flavones and flavonols) were separated and characterized on the basis of their accurate MS and MS/MS information out of which ten compounds were confirmed by authentic standards. These plant species could be considered as an especially rich source of natural bioactive compounds and potential food colorants. A. brasiliana showed the highest betacyanin and polyphenols content (89 μg/g and 35,243 μg/g, respectively). Among polyphenols, flavonols were the more abundant (kaempferol-glucoside, kaempferol-rutinoside and kaempferol-rhamnosyl-rhamnosyl-glycoside). Meanwhile, A. tenella showed a different polyphenols profile with flavones as major compounds (glucopyranosil-vitexin and vitexin). As a novelty, pentosyl-vitexin and pentosyl-isovitexin were detected for the first time in Alternanthera plants. Both A. brasiliana and A. tenella leaves showed high total polyphenol content and in vitro antioxidant activity (FRAP). These results provide an analytical base concerning the phenolic and betalains composition and the antioxidant properties of two members of the promising Alternanthera gender, for subsequent applications, such as functional food ingredients.Fil: Deladino, Lorena. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Alvarez, I.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: De Ancos, B.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Sánchez Moreno, C.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Molina García, A. D.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Schneider Teixeira, Aline. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; Españ
Objective Quantification of Posterior Capsule Opacification after Cataract Surgery, with Optical Coherence Tomography
PURPOSE: To evaluate posterior capsule opacification (PCO) in humans after
cataract surgery with intraocular lens (IOL) implantation, by using optical
coherence tomography (OCT-1). METHODS: Sixty-six eyes with PCO and 20 eyes with a
normal posterior capsule were analyzed. A 3-mm-long horizontal scan of the
posterior capsule was obtained. Measurements at three points and their average
were recorded. Intraoperator and interoperator reliabilities were assessed.
Investigated was peak intensity (PI) and posterior capsule thickening (PCT), with
PCT indicating the distance between two reflectivity spikes, with an approximate
axial resolution of 10 microm. Results were compared with visual acuity (VA) and
PCO type. RESULTS: Intraoperator reliability was 0.59 and 0.97 for average PI and
PCT, respectively. The interoperator concordance correlation coefficient was 0.70
and 0.82 for average PI and PCT, respectively. Median (interquartile range)
intensities of the reflectivity spike were 16.88 (dB) (range, 12.88-20.41) and
11.9 (8.58-14.28), respectively, in the PCO and control eyes (P = 0.001). PCT was
found in PCO eyes (median: 86.13 microm; range, 46.33-115.33), whereas no second
spike appeared in control eyes (P = 0.001). The area under the receiver operating
characteristic curve of the average PCT for differentiating pearl-type from
fibrosis-type PCO was 0.87 (P = 0.001). For a cutoff point of 55.3 microm, the
sensitivity was 97.5%, and the specificity was 69%. Worse VA correlated
significantly only with larger PCT (r(o) = 0.66; P = 0.01). CONCLUSIONS: OCT-1
appears useful to quantitate PCO. In addition, this system seems to discriminate
between different types of PCO. PCT may be a previously unrecognized factor in VA
degradation
Atomic motions in the -region of glass-forming polymers: Molecular versus Mode Coupling Theory approach
We present fully atomistic Molecular Dynamics simulation results on a
main-chain polymer, 1,4-Polybutadiene, in the merging region of the -
and -relaxations. A real space analysis reveals the occurrence of
localized motions (``-like'') in addition to the diffusive structural
relaxation. A molecular approach provides a direct connection between the local
conformational changes reflected in the atomic motions and the secondary
relaxations in this polymer. Such local processes occur just in the time window
where the -process of the Mode Coupling Theory is expected. We show that
the application of this theory is still possible, and yields an unusually large
value of the exponent parameter. This result might originate from the
competition between two mechanisms for dynamic arrest: intermolecular packing
and intramolecular barriers for local conformational changes
(``-like'').Comment: 10 pages, 6 figure
The use of cosmic muons in detecting heterogeneities in large volumes
The muon intensity attenuation method to detect heterogeneities in large
matter volumes is analyzed. Approximate analytical expressions to estimate the
collection time and the signal to noise ratio, are proposed and validated by
Monte Carlo simulations. Important parameters, including point spread function
and coordinate reconstruction uncertainty are also estimated using Monte Carlo
simulations.Comment: 8 pages, 11 figures, submetted to NIM
Retinal thickness study with optical coherence tomography in patients with diabetes
To quantitatively assess retinal thickness by optical coherence
tomography (OCT) in normal subjects and patients with diabetes. This study was
intended to determine which retinal thickness value measured with OCT best
discriminates between diabetic eyes, with and without macular edema. METHODS: OCT
retinal thickness was measured by a manual technique in a total of 26 healthy
volunteers (44 control eyes) and 85 patients with diabetes (148 eyes) with the
clinical diagnosis of no diabetic retinopathy (45 eyes), nonproliferative
diabetic retinopathy without clinically significant macular edema (CSME; 54
eyes), proliferative diabetic retinopathy without CSME (21 eyes), and 28 eyes
with diabetic retinopathy with CSME. Independent predictors of the presence of
CSME were quantified by using univariate and multivariate logistic regression
analyses. Receiver operating characteristic (ROC) curves were generated to
evaluate and compare the predictor variables. The correlation of retinal
thickness measurements and visual acuity was calculated. RESULTS: There were
statistically significant differences in foveal thickness between control eyes
and all the other eye groups (P = 0.001). Diabetic eyes with CSME had a
statistically significant greater thickness in each of the areas compared with
the other groups. In a multivariate logistic regression model, foveal thickness
was a strong and independent predictor of CSME (odds ratio [OR], 1.037; 95%
confidence interval [CI] 1.02-1.05). The area under the ROC curve of this
predictor variable was 0.94 (P = 0.001). For a cutoff point of 180 microm, the
sensitivity was 93%, and specificity was 75%. Foveal thickness correlated with
visual acuity in a log minimum angle of resolution (logMAR) scale (Spearman's rho
= 0.9, P = 0.001). CONCLUSIONS: These results suggest that foveal thickening over
180 microm measured by OCT may be useful for the early detection of macular
thickening and may be an indicator for a closer follow-up of the patient with
diabetes
Magnetic Instabilities and Phase Diagram of the Double-Exchange Model in Infinite Dimensions
Dynamical mean-field theory is used to study the magnetic instabilities and
phase diagram of the double-exchange (DE) model with Hund's coupling J_H >0 in
infinite dimensions. In addition to ferromagnetic (FM) and antiferromagnetic
(AF) phases, the DE model supports a broad class of short-range ordered (SRO)
states with extensive entropy and short-range magnetic order. For any site on
the Bethe lattice, the correlation parameter q of a SRO state is given by the
average q=, where theta_i is the angle between any spin and
its neighbors. Unlike the FM (q=0) and AF (q=1) transitions, the transition
temperature of a SRO state (T_{SRO}) with 0<q<1 cannot be obtained from the
magnetic susceptibility. But a solution of the coupled Green's functions in the
weak-coupling limit indicates that a SRO state always has a higher transition
temperature than the AF for all fillings p<1 and even than the FM for 0.26\le p
\le 0.39. For 0.39<p<0.73, where both the FM and AF phases are unstable for
small J_H, a SRO phase has a non-zero T_{SRO} except close to p=0.5. As J_H
increases, T_{SRO} eventually vanishes and the FM dominates. For small J_H, the
T=0 phase diagram is greatly simplified by the presence of the SRO phase. A SRO
phase is found to have lower energy than either the FM or AF phases for 0.26\le
p0 but appears for J_H\neq 0. For
p near 1, PS occurs between an AF with p=1 and either a SRO or a FM phase. The
stability of a SRO state at T=0 can be understood by examining the interacting
DOS,which is gapped for any nonzero J_H in an AF but only when J_H exceeds a
critical value in a SRO state.Comment: 38 pages, 11 figures, submitted to New Journal of Physic
Cirrus high-definition optical coherence tomography compared with Stratus optical coherence tomography in glaucoma diagnosis
To compare the retinal nerve fiber layer (RNFL) evaluation using Cirrus
optical coherence tomography (OCT) and Stratus OCT in glaucoma diagnosis.
METHODS: One hundred thirty normal and 86 patients with glaucoma were included in
this prospective study. The signal strengths of the OCTs were evaluated. The
sensitivities and specificities of global RNFL average thickness were compared in
the four quadrants and in each clock hour sector. Receiver operating
characteristic (ROC) curves, areas under the ROC (AUC), and the likelihood ratio
(LR) were plotted for RNFL thickness. Agreement between the OCTs was calculated
by using the Bland-Altman method and kappa (kappa) coefficient. RESULTS:
Twenty-three percent of all cases examined with Stratus OCT and 1.9% examined
with Cirrus OCT had a signal strength below 6 (P = 0.01). In cases with signal
strengths > or =6, the mean signal strength was higher with Cirrus OCT than with
Stratus OCT (P = 0.01). The RNFL measurements by Cirrus were thicker than those
of Stratus OCT (P < 0.05). The AUCs were 0.829 for Stratus and 0.837 for Cirrus
OCT (P = 0.706) for global RNFL average. LRs were similar in both OCTs in global
RNFL classification but varied in quadrants. The widths of the limits of
agreement varied between 42.16 and 97.79 microm. There was almost perfect
agreement (kappa = 0.82) in the average RNFL classification. CONCLUSIONS: Cirrus
OCT has better scan quality than Stratus OCT, especially in glaucomatous eyes. In
cases with good-quality scans, the sensitivity and specificity, and AUCs were
similar. The best agreement was in the global average RNFL classification. The
widths of limits of agreements exceed the limits of resolution of the OCTs
Determinación e incidencia del fondo geoquímico de las pizarras areniscosas del Tremadociense sobre las concentraciones minerales. Zócalo de la rama sur de la Ibérica. (Prov. de Soria y Zaragoza)
The metallogenic study carried out in the upper formations of the Tremadocian on the occidental branch of the bedrock of the Iberian Range, has allowed us to classify as sinsedimentary - epigenetic many of the mineral occurrences of Pb, Cu, Zn, Ag and Sb present. As these occurrences are associated with the sandy shales ("micropsammofilitas-psammitas"), their geochemical background (in Pb, Cu, Zn, Ag and Sb) could be determined as well as their infIuence on the concentration of minerals present. The elements, were anaIysed in more than 240 sandy shales fram: La Alameda (Soria); Embid de Ariza, Bubierca and Pardos (Zaragoza).
The background on these clements was shown to be higher than that of the sandstones; compared with the shales, the concentration of Pb and Zn was slightly higher (16-25 p.p.m. and 92-115 p.p.m. respectively) and substantially so in the case of Ag (0.31-0.77 p.p.m.) and Sb (6-15 p.p.m.). The concentration of Cu was the same.
The Iines of regression corroborate the evidence of the metallogenic studies. The geochemical metallotect, together with the tectonic and stratigraphical metallotects represent necessary, but not sufficient conditions to justify the mineral concentrations in La Alameda and Bubierca; we must also employ the paleogeographical metallotect resulting in the formation of shallow.El estudio metalogénico realizado en las formaciones superiores dcl Tremadociense, pertenecientes a la rama occidental del zócalo de la Cordillera Ibérica, ha permitido clasificar, como sinsedimentarios-epigenéticos a muchos de los indicios minerales de Pb, Cu, Zn, Ag y Sb. Al ir ligados cstos últimos a pizarras areniscosas (micropsammofilitas-psammitas) se ha determinado el fondo geoquímico (en Pb, Cu, Zn, Ag y Sb) en ellas y la incidencia que tiene sobre las concentraciones minerales. Se analizan estos elementos en más de 240 pizarras arcniscosas procedentes de: La Alameda (Soria); Embid de Ariza, Bubierca y Pardos (Zaragoza).
El fondo obtenido para estos elementos es superior al que corresponde a las areniscas; respecto a las pizarras. el fondo es ligeramente superior para el Pb (16-25 p.p.m.) y el Zn (92-115 p.p.m.); muy superior para la Ag (0.31-0.77 p.p.m.) y el Sb (6-15 p.p.m.) y ligeramente del mismo orden para el Cu.
Las rectas de regresión confirman los estudios metalogénicos. El metalotecto geoquímico, junto con los metaloctectos tectónico y litoestratigráfico, constitiyen condiciones necesarias para justificar las concentraciones minerales en La Alameda y Bubierca pero no suficientes. debiendo invocar además el metalotecto paleogeográfico relacionado con la formación de un alta fondo
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Comparison of thermistor linearization techniques for accurate temperature measurement in phase change materials
Alternate energy technologies are developing rapidly in the recent years. A significant part of this trend is the development of different phase change materials (PCMs). Proper utilization of PCMs requires accurate thermal characterization. There are several methodologies used in this field. This paper stresses the importance of accurate temperature measurements during the implementation of T-history method. Since the temperature sensor size is also important thermistors have been selected as the sensing modality. Two thermistor linearization techniques, one based on Wheatstone bridge and the other based on simple serial-parallel resistor connection, are compared in terms of achievable temperature accuracy through consideration of both, nonlinearity and self-heating errors. Proper calibration was performed before T-history measurement of RT21 (RUBITHERM® GmbH) PCM. Measurement results suggest that the utilization of serial-parallel resistor connection gives better accuracy (less than ±0.1°C) in comparison with the Wheatstone bridge based configuration (up to ±1.5°C)
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