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排序方式: 共有159条查询结果,搜索用时 15 毫秒
1.
Marcos R. Guilherme Adriano V. Reis Alexandre T. Paulino André R. Fajardo Edvani C. Muniz Elias B. Tambourgi 《应用聚合物科学杂志》2007,105(5):2903-2909
This contribution describes the absorption percentage of Pb2+ and Cu2+ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal‐absorption tests, upon sequential pH variation, indicated that the SH has pH‐sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (? COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb2+, 81.99% for Cu2+ in water and 63.64% for Pb2+, and 76.67% for Cu2+ in saline water with 0.1 mol kg?1 ionic strength. A replicated 22 full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal‐absorption results demonstrated that the SH is a convenient material for absorption of Pb2+ and Cu2+ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
2.
S. Travis Waller David Fajardo Melissa Duell Vinayak Dixit 《Networks and Spatial Economics》2013,13(4):427-443
This work introduces a novel formulation of system optimal dynamic traffic assignment that captures strategic route choice in users under demand uncertainty. We define strategic route choice to be that users choose a path prior to knowing the true travel demand which will be experienced (therefore users consider the full set of possible demand scenarios). The problem is formulated based on previous work by Ziliaskopoulos (Transp Sci 34(1):37–49, 2000). The resulting novel formulation requires substantial enhancement to account for path-based flows and scenario-based stochastic demands. Further, a numerical demonstration is presented on a network with different demand loading profiles. Finally, model complexity, implications on scalability and future research directions are discussed. 相似文献
3.
We report a study in which dyads use Instant Messaging to agree a preference among a set of three apartments. The information given to participants is partially overlapping, and contains a “hidden profile” (HP), such that a single apartment emerges as the best according to an unweighted sum of feature values only if dyad members pool information that is presented to only one of them. When dyads were additionally provided with a shared online spreadsheet, their decision strategy was more likely to be compensatory and relatively exhaustive, even if the distribution of importance among the cues in which the apartments vary meant that a “fast and frugal” heuristic such as take-the-best would be a rational strategy. This study shows the potential of classic experimental tasks, the HP task in particular, for understanding technological constraints on group decision making and signals the importance of understanding decision-making strategies, and the potential of fast and frugal heuristics, for informing the design of decision support systems. 相似文献
4.
André R. Fajardo Silvia L. Fávaro Adley F. Rubira Edvani C. Muniz 《Reactive and Functional Polymers》2013,73(12):1662-1671
The formation of a novel type of hydrogel that combines chemically and physically crosslinked networks in a dual-network approach is presented here. Chitosan (CHT) and chondroitin sulfate (CS) were chemically modified with glycidyl methacrylate (GMA) and then crosslinked. The chemical hydrogels (CHT- and CS-gel) were deposited in different vials filled with CS or CHT stock solutions to form the dual-network hydrogels. FTIR, TGA and XRD analyses were used to characterize the chemical and the dual-network hydrogels. The percentages of CS or CHT complexed to the CHT- and CS-gel networks were calculated from the HPLC data. SEM images and swelling assays indicated that the formation of a secondary network by polyelectrolyte complexation changes the morphologies and liquid uptake capacities of the chemical hydrogels. Hence, the data and discussion presented here enable the formation of dual-network hydrogels with very interesting properties, such as the ability to interact with charged specimens (i.e., drugs, proteins or metal ions), a desirable feature for a wide range of applications. 相似文献
5.
BJ Hillman KD Nash DB Witzke LL Fajardo D Davis 《Canadian Metallurgical Quarterly》1998,209(2):323-326
STUDY OBJECTIVE: To determine whether quantitative measurement of end-tidal carbon dioxide (ETCO2) can differentiate between cardiac and obstructive causes of respiratory distress. DESIGN: Prospective observational study. SETTING: Emergency department (ED) of a tertiary care hospital. PATIENTS: Adult patients who presented to the ED with moderate-to-severe dyspnea. Patients were excluded if they were unable to cooperate with the performance of peak expiratory flow rate (PEFR) or ETCO2 tests, were younger than 18 years of age, or had received prehospital intervention for their respiratory distress. INTERVENTIONS: Physicians obtained an ETCO2 level and PEFR prior to ED pharmacologic intervention. A hand-held capnometer with digital read-out was used to obtain the ETCO2 level. The patient's age, sex, initial vital signs, breath sounds and medication history, the presence or absence of diaphoresis and/or orthopnea, the duration of symptoms, the chest radiograph interpretation, and final diagnosis were also recorded. MEASUREMENTS and RESULTS: Forty-two patients were eligible for inclusion in the analysis. The mean ETCO2 level was 31.1+/-9.4 mm Hg; the mean PEFR was 161.3+/-53.1 L/min. The ETCO2 levels for pulmonary edema/congestive heart failure (CHF) patients differed significantly from those of asthma/COPD patients (27.1+/-7.8 mm Hg vs 33.4+/-9.6 mm Hg; p=0.0375). However, no single ETCO2 level was found to be a reliable predictor of diagnosis. CONCLUSION: ETCO2 levels for pulmonary edema/CHF patients differ significantly from those of asthma/COPD patients. However, no single ETCO2 level reliably differentiates between the two disease processes. 相似文献
6.
D.M. Bastidas E. Cano S. Fajardo E. Campo-Montero J.M. Bastidas 《Corrosion Science》2008,50(6):1785-1788
The tarnishing originated on a hammered gold mask was analysed. Red tarnishing was observed after three years of storage in an indoor environment in the Gold Museum of Banco de la República, Bogotá, Colombia. Silver sulphide (Ag2S) and silver sulphate (Ag2SO4) compounds were identified as the origin of the tarnishing phenomenon, which is attributed to environmental contamination. Atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS) techniques were used. 相似文献
7.
Pérez AA Farías SS Strobl AM Pérez LB López CM Piñeiro A Roses O Fajardo MA 《The Science of the total environment》2007,376(1-3):51-59
Baseline concentration levels of As, B, Ca, Cd, Cr, Cu, Co, Fe, Mg, Mn, Mo, Ni, P, Pb, Se, V, and Zn were determined for Porphyra columbina and Ulva sp. collected from three locations along San Jorge Gulf, in Patagonia Argentina. Elements were quantified by inductively coupled plasma-optical emission spectrometry, with the exception of lead and cadmium in some samples which were determined by electrothermal atomic absorption spectrometry. Three stations with different exposure degree to human activities, Bahía Solano, the mouth of Arroyo La Mata stream and Punta Maqueda, were selected as sampling points. The results showed a wide range of metal retention capacity between the two studied species. Regarding the levels of pollutants found in the researched sites, Punta Maqueda seemed to be less influenced by anthropogenic activities than the other two sites except for Cd. Taking into account their toxicities seasonal variations in Pb and Cd levels were studied in both algae in Punta Maqueda. Maximum concentrations of Cd (9.8 microg g(-1) dry wt.) were observed in P. columbina during winter, and maximum levels of Pb (0.82 microg g(-1) dry wt.) were detected in Ulva sp. during summer. Legislative and health safety aspects were evaluated for Cd and Pb. 相似文献
8.
María de Lourdes Contreras‐Pacheco Fernando Santacruz‐Ruvalcaba Jorge A. García‐Fajardo José de Jesús Sánchez G. Mario A. Ruíz L. Mirna Estarrón‐Espinosa Arturo Castro‐Castro 《International Journal of Food Science & Technology》2013,48(10):2111-2118
Dioscorea spp. tubers are known commonly as camote de cerro to the state of Jalisco, México. Besides its use as food, it contains diosgenin, a raw material used widely for synthesising steroid hormones. The purpose of the present research was to determine diosgenin contents by gas chromatography‐mass spectrometry (GC‐MS), as well as physical and chemical characteristics of sixty Dioscorea spp. accessions cultivated in mesh shade coming from eleven localities in the state of Jalisco. Extraction protocol for diosgenin was maceration combined with ethanol 80%. Significant statistical differences for diosgenin content were found between accessions, finding levels between 0.02 and 0.16 mg kg?1 in dry basis. Length, weight tuber, proportion pulp/skin, percentage of pulp and percentage of skin showed significant differences. Chemical composition based in fresh weight presented in moisture percentage a range of 71.93–83.26%, crude protein 1.42–1.74%, ashes 0.80–1.16%, lipid 0.13–0.17%, crude fibre 3.80–4.02% and total carbohydrates 13.97–25.44%. Results show that tubers from Jalisco can be an important source of nutrients for consumers. 相似文献
9.
10.
Irene Martín Teresa GarcíaVioleta Fajardo María RojasNicolette Pegels Pablo E. HernándezIsabel González Rosario Martín 《Meat science》2009
A real-time polymerase chain reaction assay using primers targeting the porcine-specific mitochondrial 12S rRNA gene and universal eukaryotic primers amplifying a conserved fragment of the nuclear 18S rRNA gene has been developed for the detection and quantification of porcine DNA in food and feedstuffs. The 18S rRNA primers were used as endogenous control for the total content of PCR-amplifiable DNA in the sample. The assay was tested on DNA extracted from raw and heat-treated binary mixtures of porcine tissues in a plant matrix, and on DNA extracted from reference feedstuff samples. Analysis of experimental mixtures demonstrated the suitability of the assay for the detection and quantification of porcine DNA in mixtures containing as little as 0.1%. 相似文献