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961.
Hydrothermal activity in the Tulancingo–Acoculco Caldera Complex,central Mexico: Exploratory studies
Aída López-Hernández Gerardo García-Estrada Gerardo Aguirre-Díaz Eduardo González-Partida Hugo Palma-Guzmán José L. Quijano-León 《Geothermics》2009
Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo–Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 °C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He3/He4 ratios. 相似文献
962.
Luis Gerardo de la Fraga Oliver Schütze 《International Journal of Computer Vision》2009,81(2):119-127
In this article we propose a new method to calibrate directly the camera by which it was taken an image of a cuboid, and to
find at the same time the orientation and side lengths of the cuboid. This is a highly non-linear optimization problem that
is solved directly using a heuristic called differential evolution. We show in this paper that this problem is very difficult
if one tries to solve it with a conventional scalar optimization procedure. Although differential evolution is a heuristic,
we find valid results in 100% of the executions. We test our method with synthetic and real images. 相似文献
963.
Fern Y. Hunt Michael A. Galler Jonathan W. Martin 《Journal of Coatings Technology》1998,70(880):45-53
The role of pigment particle size, pigment volume concentration, and dispersion in gloss loss of paint films on weathered
surfaces is unclear. Because reproducible and cost effective data are difficult to obtain, an approach based on computer simulation
and modeling is a promising supplementary tool. We describe the simulation of a painted surface consisting of pigment particles
of known size, pigment volume concentration and dispersion, situated in a binder that erodes over time due to exposure to
ultraviolet radiation. Pigment particle size, geometry, pigment volume concentration, and pigment particle dispersion are
parameters of the model. Our purpose is to illustrate how simulation can be used to aid the development of formulation strategies
for the design of coatings with desirable gloss characteristics. 相似文献
964.
Comparative estimation of the reproduction number for pandemic influenza from daily case notification data
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Gerardo Chowell Hiroshi Nishiura Luís M.A Bettencourt 《Journal of the Royal Society Interface》2007,4(12):155-166
The reproduction number, R, defined as the average number of secondary cases generated by a primary case, is a crucial quantity for identifying the intensity of interventions required to control an epidemic. Current estimates of the reproduction number for seasonal influenza show wide variation and, in particular, uncertainty bounds for R for the pandemic strain from 1918 to 1919 have been obtained only in a few recent studies and are yet to be fully clarified. Here, we estimate R using daily case notifications during the autumn wave of the influenza pandemic (Spanish flu) in the city of San Francisco, California, from 1918 to 1919. In order to elucidate the effects from adopting different estimation approaches, four different methods are used: estimation of R using the early exponential-growth rate (Method 1), a simple susceptible-exposed-infectious-recovered (SEIR) model (Method 2), a more complex SEIR-type model that accounts for asymptomatic and hospitalized cases (Method 3), and a stochastic susceptible-infectious-removed (SIR) with Bayesian estimation (Method 4) that determines the effective reproduction number Rt at a given time t. The first three methods fit the initial exponential-growth phase of the epidemic, which was explicitly determined by the goodness-of-fit test. Moreover, Method 3 was also fitted to the whole epidemic curve. Whereas the values of R obtained using the first three methods based on the initial growth phase were estimated to be 2.98 (95% confidence interval (CI): 2.73, 3.25), 2.38 (2.16, 2.60) and 2.20 (1.55, 2.84), the third method with the entire epidemic curve yielded a value of 3.53 (3.45, 3.62). This larger value could be an overestimate since the goodness-of-fit to the initial exponential phase worsened when we fitted the model to the entire epidemic curve, and because the model is established as an autonomous system without time-varying assumptions. These estimates were shown to be robust to parameter uncertainties, but the theoretical exponential-growth approximation (Method 1) shows wide uncertainty. Method 4 provided a maximum-likelihood effective reproduction number 2.10 (1.21, 2.95) using the first 17 epidemic days, which is consistent with estimates obtained from the other methods and an estimate of 2.36 (2.07, 2.65) for the entire autumn wave. We conclude that the reproduction number for pandemic influenza (Spanish flu) at the city level can be robustly assessed to lie in the range of 2.0-3.0, in broad agreement with previous estimates using distinct data. 相似文献
965.
Ma Inmaculada González-Martín César Fernández Bermejo José Miguel Hernández Hierro Carlos I. Sánchez González 《Food Control》2009,20(8):752-755
In the present work a study was made of the use of near infra-red spectroscopy (NIRS) technology with a remote reflectance fibre–optic probe for the analysis of hydroxyproline in cured pork sausages (salchichón and chorizo) and dry cured beef (cecina). The presence of the amino acid hydroxyproline was used as an analytical criterion to assess the amount of collagen from connective tissues versus lean meat (muscle). The fibre–optic probe was placed directly on the sample with no previous treatment or manipulation.The regression method employed was that of modified partial least squares (MPLS). The equation developed for a total of 80 samples (salchichón, chorizo and cecina) allowed the determination of the hydroxyproline content within a range of 0–0.74%. The multiple correlation coefficient (RSQ) and standard error of prediction corrected (SEP(C)) obtained were respectively 0.772 and 0.05%. The predicted values of hydroxyproline in unknown samples using NIRS technology and applying the fibre–optic probe directly on the sample without previous treatment were comparable to those obtained using the chemical method. 相似文献
966.
A total of 634 samples of oranges, tangerines, peaches, nectarines, khakis and watermelons were collected from an Agricultural Valencia Community Cooperative during the May 2001 to April 2003 campaigns and they were analysed for 15 pesticides among those recommended for pest treatment. A conventional multiresidue analytical procedure based on ethyl acetate extraction was used followed by gas chromatography coupled to a nitrogen phosphorus detector for routine analysis; and mass spectrometry was performed for confirmation. Recovery studies with spiked samples at 0.5 mg kg-1 for each pesticide ranged from 52% for acephate to 87% for fenthion with a standard deviation <20%. Limits of quantification ranged from 0.1 to 100 microg kg-1. A total of 43% of samples contained pesticide residues; and 5% exceeded the maximum residue levels (MRLs). Nine of the pesticides studied were found. Malathion, which was the most frequently detected, was found in 121 samples (19%) at 0.002-4.25 mg kg-1; followed by fenthion in 104 samples (16%) at 0.005-2.3 mg kg-1; and methidation in 68 samples (10%) at 0.008-1.3 mg kg-1. Khaki showed the highest contamination rates with 60% of contaminated samples that exceeded more often the MRLs; and fenthion was the pesticide more frequently detected in all the commodities studied at levels above the European MRLs. The estimated daily intakes of each pesticide calculated from the results obtained were much lower than the acceptable daily intakes. 相似文献
967.
Avelina Fernández Eva Soriano Gracia López-Carballo Pierre Picouet Elsa Lloret Rafael Gavara Pilar Hernández-Muñoz 《Food research international (Ottawa, Ont.)》2009,42(8):1105-1112
Silver nanoparticles have been formed in fluff pulp and nanostructured Lyocell fibres by immersion in silver nitrate, and a subsequent transformation of the adsorbed silver ions into elementary silver nanoparticles by physical (thermal/UV) or chemical (sodium borohydride) methods. Microscopy revealed that nanoparticles generated by physical methods were regular in shape and efficiently dispersed, while the chemical reduction produced highly aggregated nanoparticles. Nanoparticle size has been found relevant to guarantee high antimicrobial activity, being the samples with big aggregated silver nanoparticles almost inefficient. Indeed a satisfactory correlation between silver ion release and the antimicrobial efficiency against Escherichia coli and Staphylococcus aureus could be confirmed, and furthermore, the highest concentrations tested were efficient to reduce the microbial load in poultry exudates. This work demonstrates that especially designed absorbent materials could be optimised to preserve aseptic conditions during manipulation, leading to feasible applications of a silver based nanotechnology in food technology. 相似文献
968.
Javier M Obando‐Ulloa Mohammad‐Mahdi Jowkar Eduard Moreno M Kazem Souri Juan A Martínez María C Bueso Antonio J Monforte J Pablo Fernández‐Trujillo 《Journal of the science of food and agriculture》2009,89(10):1743-1753
BACKGROUND: This paper characterizes the quality traits at harvest and the changes associated with fruit senescence based on fruit physiological behaviour (climacteric or non‐climacteric) found in a collection of near‐isogenic lines (NILs) of melon (Cucumis melo L.). Data from both stages of postharvest development were analyzed by univariate and multivariate statistical analysis. RESULTS: The principal components and random forest analyses of the fruit quality traits allowed the best classification of the NILs by time (harvest, senescence), or by climacteric behaviour at harvest, but not at the senescent stage. The overall quality profile of the non‐climacteric senescent melons was, in general, very different from that of the climacteric ones, and was in accord with a longer storage life. Most of the taste quality traits (individual sugars or sucrose equivalents, titratable acidity and the citric, oxalacetic, glutamic and succinic acids) and the traits related to skin, flesh and juice colour parameters (chroma, hue angle) helped to distinguish the climacteric NILs from the non‐climacteric ones independently of the time considered. CONCLUSIONS: The time had a stronger effect on quality than the physiological behaviour. The discrimination by climacteric or non‐climacteric behaviour was usually better at harvest than at the senescent stage irrespective of the methodology used. Principal component analysis was the best multivariate method to discriminate by time and physiological behaviour followed by random forest and linear discriminant analysis. Copyright © 2009 Society of Chemical Industry 相似文献
969.
Silvia Cerri Cristina Ghezzi Gerardo Ongari Stefania Croce Micol Avenali Roberta Zangaglia Donato A. Di Monte Enza Maria Valente Fabio Blandini 《International journal of molecular sciences》2021,22(4)
Heterozygous mutations in the GBA gene, encoding the lysosomal enzyme glucocerebrosidase (GCase), are the strongest known genetic risk factor for Parkinson’s disease (PD). The molecular mechanisms underlying the increased PD risk and the variable phenotypes observed in carriers of different GBA mutations are not yet fully elucidated. Extracellular vesicles (EVs) have gained increasing importance in neurodegenerative diseases since they can vehiculate pathological molecules potentially promoting disease propagation. Accumulating evidence showed that perturbations of the endosomal–lysosomal pathway can affect EV release and composition. Here, we investigate the impact of GCase deficiency on EV release and their effect in recipient cells. EVs were purified by ultracentrifugation from the supernatant of fibroblast cell lines derived from PD patients with or without GBA mutations and quantified by nanoparticle tracking analysis. SH-SY5Y cells over-expressing alpha-synuclein (α-syn) were used to assess the ability of patient-derived small EVs to affect α-syn expression. We observed that defective GCase activity promotes the release of EVs, independently of mutation severity. Moreover, small EVs released from PD fibroblasts carrying severe mutations increased the intra-cellular levels of phosphorylated α-syn. In summary, our work shows that the dysregulation of small EV trafficking and alpha-synuclein mishandling may play a role in GBA-associated PD. 相似文献
970.
Guy Guday Ievgen S. Donskyi Mohammad Fardin Gholami Gerardo Algara‐Siller Felix Witte Andreas Lippitz Wolfgang E. S. Unger Beate Paulus Jürgen P. Rabe Mohsen Adeli Rainer Haag 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(12)
A new method for top‐down, one‐pot, gram‐scale production of high quality nanographene by incubating graphite in a dilute sodium hypochlorite solution at only 40 °C is reported here. The produced sheets have only 4 at% oxygen content, comparable with nanographene grown by chemical vapor deposition. The nanographene sheets are covalently functionalized using a nondestructive nitrene [2+1] cycloaddition reaction that preserves their π‐conjugated system. Statistical analyses of Raman spectroscopy and X‐ray photoelectron spectroscopy indicate a low number of sp3 carbon atoms on the order of 2% before and 4% after covalent functionalization. The nanographene sheets are significantly more conductive than conventionally prepared nanographene oxide, and conductivity further increases after covalent functionalization. The observed doping effects and theoretical studies suggest sp2 hybridization for the carbon atoms involved in the [2+1] cycloaddition reaction leading to preservation of the π‐conjugated system and enhancing conductivity via n‐type doping through the bridging N‐atom. These methods are easily scalable, which opens the door to a mild and efficient process to produce high quality nanographenes and covalently functionalize them while retaining or improving their physicochemical properties. 相似文献