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排序方式: 共有3016条查询结果,搜索用时 15 毫秒
901.
Cliff Randell Sara Price Yvonne Rogers Eric Harris Geraldine Fitzpatrick 《Personal and Ubiquitous Computing》2004,8(3-4):177-183
The Ambient Horn is a novel handheld device designed to support children learning about habitat distributions and interdependencies in an outdoor woodland environment. The horn was designed to emit non-speech audio sounds representing ecological processes. Both symbolic and arbitrary mappings were used to represent the processes. The sounds are triggered in response to the childrens location in certain parts of the woodland. A main objective was to provoke children into interpreting and reflecting upon the significance of the sounds in the context in which they occur. Our study of the horn being used showed the sounds to be provocative, generating much discussion about what they signified in relation to what the children saw in the woodland. In addition, the children appropriated the horn in creative ways, trying to scoop up new sounds as they walked in different parts of the woodland. 相似文献
902.
Andria SE Richardson JN Kaval N Zudans I Seliskar CJ Heineman WR 《Analytical chemistry》2004,76(11):3139-3144
We report herein an attenuated total reflectance (ATR) absorbance-based spectroelectrochemical sensor for tris(2,2'-bipyridyl)ruthenium(II) ion [Ru(bpy)(3)(2+)] that employs ultrathin (24-50 nm) Nafion films as the charge-selective layer. This film serves to sequester and preconcentrate the analyte at the optically transparent electrode surface such that it can be efficiently detected optically via electrochemical modulation. Our studies indicate that use of ultrathin films in tandem with continuous flow of sample solution through the cell compartment leads to a 100-500-fold enhancement in detection limit (10 nM) compared to earlier absorbance-based spectroelectrochemical sensors ( approximately 1-5 microM); markedly shorter analysis times also result. We report the dependence of the measured absorbance on sample flow rate and Nafion film thickness, and also provide calibration curves that illustrate the linear range and detection limits of the sensor using a 24 nm film at a constant sample flow rate of 0.07 mL/min. 相似文献
903.
The present work describes a novel, fully automated method, based on on-line solid-phase extraction-liquid chromatography-electrospray tandem mass spectrometry (SPE-LC-ESI-MS-MS), which allows the unequivocal identification and quantification of the most environmentally relevant estrogens (estradiol, estrone, estriol, estradiol-17-glucuronide, estradiol-17-acetate, estrone-3-sulfate, ethynyl estradiol, diethylstilbestrol) in natural and treated waters at levels well below those of concern (limits of quantification between 0.02 and 1.02 ng/L). The method is highly precise, with relative standard deviations varying between 1.43 and 3.89%, and accurate (recovery percentages >74 %). This method was used to track the presence and fate of the target compounds in a waterworks and to evaluate the removal efficiency of the treatment processes applied. Only estrone and estrone-3-sulfate were detected in the river water used as source (at 0.68 and 0.33 ng/L, respectively). After progressive removal through the various treatment steps, none of them were detected in the finished drinking water. In addition to selectivity, sensitivity, repeatability, and automation (up to 15 samples plus 6 calibration solutions and 1 blank can be analyzed unattended), this technique offers fairly high throughput (analysis time per sample is 60 min), low time and solvent consumption, and ease of use. 相似文献
904.
The objective of this study was to determine whether the addition of iron and vitamin A (VA) to corn flour, supplied through a national enrichment program since 1993, allows preschoolers to achieve an adequate intake of these nutrients. Data from the assessment of 196 children (4-6 year old) from Valencia, Venezuela is presented, including socio-demographic, anthropometric, anemia, VA deficiency (by conjunctival impression cytology (CIC) and serum retinol), and food intake. 92% of the children lived in poverty. 12% were below the norm for weight-for-height. 13% had anemia, 9% had VA deficiency according to CIC, and 0.5% according to serum retinol (< 0.70 mumol/L), 30% were at risk of VA deficiency (0.70-1.05 mmol/L). 17%, 37%, and 5% of the sample had an insufficient intake (< 80% of RDA) of energy, iron, and VA, respectively. When excluding from the analysis the amount of iron and VA from corn flour enrichment, an additional 38% and 10% of the sample showed deficient intakes of each nutrient, respectively. According to the weight-for-height indicator, iron intake was significantly lower in undernourished children (p < 0.05) than in those normal or above the norm; this was not so for VA. It is concluded that iron enrichment contributes to the improvement of the intake of this nutrient but is not enough to provide an adequate amount of it; and that the addition of VA does not seem to have an important effect on the diet of this age group. 相似文献
905.
906.
Electrografting of poly [N-vinylcarbazole-co-methylmethacrylate] onto high tenacity carbon fiber (TENAX HTA 5000) was carried
out under preparative constant current electrolysis conditions by using anode and cathode as fiber towings. The surface morphology
of the electrografted carbon fibers was determined by scanning electron microscopy (SEM). FTIR reflectance measurements (FTIR-ATR)
were applied for the characterization of chemical composition on the electrografted thin film surface on carbon fiber. The
efficiency of the electrocopolymerization on carbon fiber surfaces under preparative constant current electrolysis conditions
were evaluated, i.e., current density (charge) vs. thickness, yield and morphology. 相似文献
907.
Almgren S Nilsson E Erlandsson B Isaksson M 《The Science of the total environment》2006,368(2-3):804-813
It is of interest to know the spatial variation and the amount of (137)Cs e.g. in case of an accident with a radioactive discharge. In this study, the spatial distribution of the quarterly (137)Cs deposition over Sweden due to nuclear weapons fallout (NWF) during the period 1962-1966 was determined by relating the measured deposition density at a reference site to the amount of precipitation. Measured quarterly values of (137)Cs deposition density per unit precipitation at three reference sites and quarterly precipitation at 62 weather stations distributed over Sweden were used in the calculations. The reference sites were assumed to represent areas with different quarterly mean precipitation. The extent of these areas was determined from the distribution of the mean measured precipitation between 1961 and 1990 and varied according to seasonal variations in the mean precipitation pattern. Deposition maps were created by interpolation within a geographical information system (GIS). Both integrated (total) and cumulative (decay corrected) deposition densities were calculated. The lowest levels of NWF (137)Cs deposition density were noted in north-eastern and eastern parts of Sweden and the highest levels in the western parts of Sweden. Furthermore the deposition density of (137)Cs, resulting from the Chernobyl accident was determined for an area in western Sweden based on precipitation data. The highest levels of Chernobyl (137)Cs in western Sweden were found in the western parts of the area along the coast and the lowest in the east. The sum of the deposition densities from NWF and Chernobyl in western Sweden was then compared to the total activity measured in soil samples at 27 locations. Comparisons between the predicted values of this study show a good agreement with measured values and other studies. 相似文献
908.
Analysis of products, mechanisms of reaction, and some functional properties of soy protein hydrolysates 总被引:11,自引:0,他引:11
Sara E. Molina Ortiz Mara Cristina An 《Journal of the American Oil Chemists' Society》2000,77(12):1293-1301
Soybean protein isolates were hydrolyzed with papain, bromelain, cucurbita, hieronymin, and pomiferin. The highest hydrolysis
rate for cucurbita and the lowest for papain was detected at 720 min. Gel filtration, reversed-phase liquid chromatography,
and electrophoresis showed that the action of each protease was different. Pomiferin acted on the native structure of β-conglycinin
and glycinin, generating a large number of small hydrolysis products with hydrophilic and hydrophobic characteristics. The
hydrolysates obtained with cucurbita showed residual structures that were almost intact and very similar to the substrate
and contained a low number of small peptides. The hydrolyzates obtained with papain, bromelain, and hieronymin had hydrolysis
products with structures similar to the partially hydrolyzed native isolate. The molecular masses of these products were similar
to or lower than the controls. Polypeptides of low molecular mass were also detected. The prevalence of one-by-one and zipper
mechanisms was suggested for cucurbita and pomiferin, respectively. For the other proteases both mechanisms were likely to
coexist. The solubility of hydrolysates and their ability to form and stabilize foams correlated well with the structural
properties and with the suggested mechanisms of hydrolysis. The best properties were presented by the hydrolysates prepared
with cucurbita. Foaming ability for pomiferin hydrolysates was as high as that for unhydrolyzed soy isolate, but the foams
were extremely unstable. 相似文献
909.
Raque-Bogdan Trisha L.; Ericson Sara K.; Jackson John; Martin Helena M.; Bryan Nicole A. 《Canadian Metallurgical Quarterly》2011,58(2):272
Research shows a strong link between adult attachment and mental and physical health, but little is known about the mechanisms that underlie these relationships. The present study examined self-compassion and mattering, two constructs from positive psychology literature, as potential mediators. Using survey data from a sample of 208 college students, relationships among attachment, self-compassion, mattering, and functional health were explored. Correlational analyses indicated that attachment anxiety and avoidance were strongly related to the mental health component of functional health. Mediation analyses indicated that mattering and self-compassion mediated the relationships between attachment orientation (i.e., levels of avoidance and anxiety) and mental health. These findings suggest that individuals' abilities to be kind toward themselves and their sense of belonging and being important to others are pathways through which attachment orientation relates to mental health. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
910.
Protective effect of hydroxytyrosol and its predominant plasmatic human metabolites against endothelial dysfunction in human aortic endothelial cells 下载免费PDF全文