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41.
Franzoni MB Acosta RH Pastawski HM Levstein PR 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2012,370(1976):4713-4733
Nuclear spins are promising candidates for quantum information processing because their good isolation from the environment precludes the rapid loss of quantum coherence. Many strategies have been developed to further extend their decoherence times. Some of them make use of decoupling techniques based on the Carr-Purcell and Carr-Purcell-Meiboom-Gill pulse sequences. In many cases, when applied to inhomogeneous samples, they yield a magnetization decay much slower than that of the Hahn echo. However, we have proved that these decays cannot be associated with longer decoherence times, as coherences remain frozen. They result from coherences recovered after their storage as local polarization and thus they can be used as memories. We show here how this freezing of the coherent state, which can subsequently be recovered after times longer than the natural decoherence time of the system, can be generated in a controlled way with the use of field gradients. A similar behaviour of homogeneous samples in inhomogeneous fields is demonstrated. It is emphasized that the effects of inhomogeneities in solid-state nuclear magnetic resonance, independently of their origin, should not be disregarded, as they play a crucial role in multipulse sequences. 相似文献
42.
Horacio Toniolo Jeff Derry Ken Irving William Schnabel 《Canadian Metallurgical Quarterly》2010,136(11):935-939
Rivers located on the North Slope of Alaska’s Brooks Range are typically not well characterized with respect to basic hydraulic and sedimentological data. In order to obtain basic hydrosedimentological information on the Anaktuvuk River, a pristine stream located in the Colville River basin, we conducted an extensive field campaign from late May to early June 2009. The study reach was located at N69°27.785′, W151°09.858′, latitude and longitude, respectively. The Anaktuvuk River flows north from the Brooks Range to the Colville River, drains an area of 7,058?km2, and encompasses 2,063 m of vertical relief. During the field campaign, the field crew measured discharge and water-surface slope, collected water samples, and characterized bed sediment. As a result of fieldwork and laboratory work, we present an initial rating curve for the Anaktuvuk River, as well as the calculated roughness coefficient and suspended sediment concentrations. In addition, we compare the observed bankfull discharges with the bankfull discharge predicted by a recently published model. 相似文献
43.
Bernal RA Agrawal R Peng B Bertness KA Sanford NA Davydov AV Espinosa HD 《Nano letters》2011,11(2):548-555
We characterized the elastic properties of GaN nanowires grown along different crystallographic orientations. In situ transmission electron microscopy tensile tests were conducted using a MEMS-based nanoscale testing system. Complementary atomistic simulations were performed using density functional theory and molecular dynamics. Our work establishes that elasticity size dependence is limited to nanowires with diameters smaller than 20 nm. For larger diameters, the elastic modulus converges to the bulk values of 300 GPa for c-axis and 267 GPa for a- and m-axis. 相似文献
44.
45.
Bao Zhang Serge Gavras Anumalasetty V. Nagasekhar Carlos Horacio Cáceres Mark A. Easton 《Metallurgical and Materials Transactions A》2014,45(10):4386-4397
3D numerical images of the intergranular percolating eutectic of two binary alloys, Mg-0.62 at. pctLa and Mg-0.60 at. pctNd, created using dual beam FIB tomography, were incorporated into an FEM code to model their tensile behavior. Due to its high volume fraction (29.9 pct), the behavior of the Mg-La network was akin to that of a stretch-dominated micro-truss structure, whereas the Mg-Nd’s, with a relatively low volume fraction (7.5 pct), mimicked that of a bending-dominated structure. The 3D network contributed some 37 MPa to the strength of the Mg-La alloy casting, whereas it only added about 1.4 MPa to the Mg-Nd’s. The model predictions based on the binary alloys were verified using cast-to-shape specimens of the Mg-La and two ternary Mg-La-Nd alloys, subjected to a flash-annealing aiming at breaking up the continuity of the 3D network, while preserving the rest of the microstructure unchanged. The flash-annealed specimens exhibited a decrease in strength that matched closely the computed values. Implications regarding alloy design involving the eutectic network and solid solution hardening of more complex alloys are discussed. 相似文献
46.
Virginia Melo-Ruiz Yomas Quirino-Barreda Concepcion Calvo-Carrillo Karina Sanchez-Herrera Horacio Sandoval-Trujillo 《化学与化工:英文版》2013,(12):1181-1187
Edible insects, escamoles ant eggs of the Formicidae family are consumed by cultural tradition at rural communities and by sensory characteristics at high class restaurants of Mexico; however, people ignore the importance of insect consumption in the nutrition of humans. Laboratory spectroscopy methods in food analysis represent benefits in time and precision. The aim of this study is to assess macronutrients and micronutrients of escamoles and eggs by spectroscopic methods to inform population the benefits they provide in health and to mention the advantage in the use of these techniques at laboratory work. Samples were gather the second week of March and April 2012, at Hidalgo State and analyze moisture and macronutrients by AOAC (Association of Official Analytical Chemistry) methods, amino acids by cation exchange chromatography, tryptophan was determined by a colorimeter method, fatty acids by GC (gas chromatography) using helium as a carrier (AOAC), fat soluble vitamins A, D and E by HPLC (high performance liquid chromatography), and minerals by atomic absorption spectrophotometers and phosphorus by colorimeter (AOAC). Data showed high amount in proteins, lipids and minerals; low in fiber and soluble carbohydrates; contained all essential amino acids. Fatty acids contain monounsaturated and polyunsaturated. Fat soluble vitamins A, D and E. Minerals: sodium, phosphorus, potassium, magnesium, calcium and manganese. Escamoles ant eggs include polyunsaturated fatty acids essential for mental development, vitamin A to prevent eye diseases, vitamin E as antioxidant and vitamin D involved in calcium absorption that low intake, impair grow and bone health. Iron and zinc contained anemia. Regarding the laboratory benefits, needs less expensive chemicals, testing is clean, rapid and easy results of multiple samples, but it is required to handle by qualified chemists. In conclusion, data may change according to biotic and abiotic conditions of the environment; however, escamoles have all nutrients in adequate balance to improve human health; and provide faster and precise results. 相似文献
47.
Psychrotrophic bacteria behaviour, when gamma irradiation is applied with shelf-life extension purposes to a fresh squid product, was modelled. In this regard, the effect of gamma irradiation at 0, 1.8, 3.3 and 5.8 kGy on psychrotrophic microorganisms in vacuum-packed squid (Illex argentinus) rings was analysed during storage at 4–5 °C. First-order kinetics satisfactorily described the radio-induced inactivation of the initial psychrotrophs population. The growth of surviving bacteria during storage was fitted to two empirical models: modified Gompertz model and a polynomial expression dependent on irradiation dose and storage time. In turn, the influence of irradiation dose on kinetic parameters of Gompertz model was described by second order polynomials. Both proposed models satisfactorily described the behaviour of psychrotrophs as affected by gamma irradiation, allowing accurate shelf-life predictions for doses up to 5.3 kGy. Considering the predictions accuracy, complete Gompertz model was preferred and model validation was done for irradiation at 4.8 kGy. 相似文献
48.
Ana I Pardo‐García Ana M Martínez‐Gil Horacio López‐Córcoles Amaya Zalacain Rosario Salinas 《Journal of the science of food and agriculture》2013,93(5):1147-1155
BACKGROUND: The present work was carried out because there is only a small amount of literature on how the volatile composition of tomatoes can be modified by the effect of exogenous substances in contact with tomato plants. This work studies how eugenol and guaiacol, either by foliar application and/or in the surrounding atmosphere, can affect the volatile composition of this fruit. An important work of this study was also conduced to validate the analytical method [headspace stir bar sorptive extraction–gas chromatography–mass spectrometry (HS‐SBSE‐GC‐MS)] to determine the composition of the volatiles in tomato. RESULTS: Analytical method validation parameters such as linearity, limit of detection, limit of quantification, and recovery proved that this method is suitable for the analysis of tomato volatiles. Their eugenol and guaiacol content changed, with an increase of 200 and 35 times, respectively, when foliar treatment was used, and an increase of 10, in both cases, when plants were in contact with the contaminated atmosphere. As consequence of the treatments other volatile compounds changed considerably. CONCLUSION: For first time, a HS‐SBSE‐GC‐MS method was successfully validated for the study of volatiles in tomatos. Results suggests that exogenous compounds in contact with the plants, such as eugenol and guaiacol, can be absorbed changing the global volatile composition of fruits, which could produce a negative or positive effect in their aroma. © 2012 Society of Chemical Industry 相似文献
49.
David Hernndez-Silva Joaquín Cantn-Sandoval Francisco Juan Martínez-Navarro Horacio Prez-Snchez Sofia de Oliveira Victoriano Mulero Francisca Alcaraz-Prez María Luisa Cayuela 《International journal of molecular sciences》2022,23(18)
Telomere shortening is the main molecular mechanism of aging, but not the only one. The adaptive immune system also ages, and older organisms tend to develop a chronic pro-inflammatory status with low-grade inflammation characterized by chronic activation of the innate immune system, called inflammaging. One of the main stimuli that fuels inflammaging is a high nutrient intake, triggering a metabolic inflammation process called metainflammation. In this study, we report the anti-inflammatory activity of several senolytic drugs in the context of chronic inflammation, by using two different zebrafish models: (i) a chronic skin inflammation model with a hypomorphic mutation in spint1a, the gene encoding the serine protease inhibitor, kunitz-type, 1a (also known as hai1a) and (ii) a non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH) model with inflammation induced by a high-fat diet. Our results show that, although these models do not manifest premature aging, the senolytic drugs dasatinib, navitoclax, and venetoclax have an anti-inflammatory effect that results in the amelioration of chronic inflammation. 相似文献
50.
Horacio Irán Solís-Cisneros Carlos Alberto Hernández-Gutiérrez Enrique Campos-González Máximo López-López 《半导体学报》2024,45(5):052501-1-052501-10
This work reports the growth and characterization of p-AlInN layers doped with Mg by plasma-assisted molecular beam epitaxy (PAMBE). AlInN was grown with an Al molar fraction of 0.80 by metal-modulated epitaxy (MME) with a thickness of 180 nm on Si(111) substrates using AlN as buffer layers. Low substrate temperatures were used to enhance the incorporation of indium atoms into the alloy without clustering, as confirmed by X-ray diffraction (XRD). Cathodoluminescence measurements revealed ultraviolet (UV) range emissions. Meanwhile, Hall effect measurements indicated a maximum hole mobility of 146 cm2/(V∙s), corresponding to a free hole concentration of 1.23 × 1019 cm−3. The samples were analyzed by X-ray photoelectron spectroscopy (XPS) estimating the alloy composition and extracting the Fermi level by valence band analysis. Mg-doped AlInN layers were studied for use as the electron-blocking layer (EBL) in LED structures. We varied the Al composition in the EBL from 0.84 to 0.96 molar fraction to assess its theoretical effects on electroluminescence, carrier concentration, and electric field, using SILVACO Atlas. The results from this study highlight the importance and capability of producing high-quality Mg-doped p-AlInN layers through PAMBE. Our simulations suggest that an Al content of 0.86 is optimal for achieving desired outcomes in electroluminescence, carrier concentration, and electric field. 相似文献