The correlates of the digital divide and their impact on college student learning

By focusing on two dimensions of the digital divide—computer use and computer knowledge, this study explores four research questions: (1) What are the undergraduates doing with the computers they use at colleges? (2) How do undergraduates perform in regard to computer knowledge and skills? (3) With what is the digital divide among college students correlated? (4) What consequences does the digital divide have for student academic performance? In order to answer these research questions, a national survey was conducted. The survey investigated 3083 first-year college students of 12 4-year universities in Taiwan. A total of 2719 of them completed the questionnaires resulting in a response rate of 88.2%. In this study, the digital divide is measured in terms of computer use, which includes a variety of purposes for using computers and academic-related work as a proportion of total computer hours, and computer knowledge. Multiple regressions and a generalized ordered logit, i.e. a partial proportional odds model, are employed. The main findings include the following: (1) Undergraduates use computers not only for fulfilling their academic requirements and searching for information, but also for entertainment. On average, undergraduates spend about 19 h per week using computers, of which 5 h are academic-related. (2) Most undergraduates perform at the middle average level in terms of computer knowledge. (3) No significant differences among correlates in relating to demographic and socioeconomic family background were found in predicting the various purposes in using computers. (4) Students who are female, whose fathers and/or whose mothers are from minorities, whose fathers are blue-collar workers or unemployed, who study in the fields of the humanities and social sciences, and who enter private universities are at a disadvantage in terms of computer skills and knowledge. However, female students, students whose mothers were less educated and students who enroll in private universities are more focused computer users in terms of allocating time to academic-related work. (5) Computer knowledge and devotion to using computers for academic-related work have a moderate effect on college student learning, while the various other uses of computers do not. Of the different kinds of computer knowledge, it is the knowledge of software that helps students to learn the most.     

A semantic enriched data model for sensor network interoperability

One of the main open issues in the development of applications for sensor network management is the definition of interoperability mechanisms among the several monitoring systems and heterogeneous data. Interesting researches related to integration techniques have taken place, they are primary based on the adoption of sharing data mechanisms. In the last years, the Service-Oriented Architecture (SOA) approach has become predominant in many sensor network projects as it enables the cooperation and interoperability of different sensor platforms at an higher level of abstraction. In this paper we propose a novel architecture for the interoperability of sensor networks, which is based on web services technologies and on a common data model enriched with semantic concepts and annotations. The proposed architecture allows the development of complex decision support system applications by integration of heterogeneous data, accessible through services, according to standard data format and standard protocols.     

Study of the NOχ reaction with reducing gases on Fe/ZrO2 catalyst

The Fe/ZrO₂ catalyst (1% Fe by weight) shows a strong adsorption capacity toward the nitric oxide (at room temperature the ratio NOFe is ca. 0.5) as a consequence of the formation of a highly dispersed iron phase after reduction at 500–773 K. Nitric oxide is adsorbed mainly as nitrosyl species on the reduced surface where the Fe²⁺ sites are prevailing, but it is easily oxidised by oxygen forming nitrito and nitrato species adsorbed on the support. However, in the presence of a reducing gas such as hydrogen, carbon monoxide, propane and ammonia at 473–573 K the Fe-nitrosyl species react producing nitrogen, nitrous oxide, carbon dioxide and water, as detected by FTIR and mass spectrometers. The results show that nitric oxide reduction is more facile with hydrogen containing molecules than with CO, probably due the co-operation of spillover effects. Experiments carried out with the same gases in the presence of oxygen show, however, a reduced dissociative activity of the surface iron sites toward the species NO_χ formed by NO oxidation and therefore the reactivity is shifted to higher temperatures.     

Occurrence of Listeria monocytogenes in green table olives

Microbiological safety of green table olives from different cultivars, prepared by both the Spanish-style and biological methods and fermented with starter cultures of lactic acid bacteria (Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus pentosus), was investigated. The fermentation process was monitored by measuring pH values, titratable acidities, and growth of lactic acid bacteria over time. During fermentation, lactic acid bacteria and yeasts were major microbial populations. Microbiological safety was evaluated by analysis for Listeria monocytogenes with the use of an enrichment method during storage (from 55 days to 18 months). Results demonstrated that L. monocytogenes can survive and grow in green table olives. L. monocytogenes was found in one of the commercial (thermally treated) samples analyzed and in all samples older than 2 months, irrespective of olive cultivar, lactic acid bacteria starter used, pH and titratable acidity of brine samples, or treatment applied.     

Mercury(II) removal using polymer inclusion membranes containing Cyanex 471X

BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the development of membrane extraction‐based methodologies for its separation. The specific advantages (effective carrier immobilization, easy preparation, versatility, and good mechanical properties) of polymer inclusion membranes (PIMs) make them suitable for this purpose. In this work a novel procedure using PIMs for mercury separation with a commercial available extractant (Cyanex 471X) is described and evaluated through the determination of the efficiency parameters (permeability, selectivity, stability) and membrane characterization. RESULTS: Using a membrane composed of 30% cellulose triacetate (CTA), 60% 2‐nitrophenyl octyl ether (NPOE), and 10% w/w Cyanex 471X a 0.1 mmol dm^?3 Hg(II) solution prepared in 0.01 mol dm^?3 HCl was transported to a 0.05 mol dm^?3 NaCl solution at pH 12.3 with permeability values in the feed and strip phases of 0.25 and 0.15 cm min^?1, respectively. A diffusive Fickian‐type mechanism was inferred from the results. High separation factors ranging between 2 and 5900, less than 11% of competing metal ions transported, active transport of the metal ion and a successful reuse of the PIM were achieved. CONCLUSION: Optimized PIMs using Cyanex 471X represent an interesting alternative for Hg(II) removal from waters showing high efficiency factors and easy implementation. Copyright © 2009 Society of Chemical Industry     

迷失在塑料袋时代

让人看着舒服的塑料袋是有的:极富装饰感的设计、洁净的外表、内里装了精致的礼品或是衣物,看似不经意地拎在手里,心里却是在享受着袋子里面那一份钟爱的物品带来的喜悦,这时候的塑料袋是实用而知趣的,毫不张扬,却恰如其分地代表了主人的品位。当印有高尚品牌标志的塑料袋     

Diffraction of x rays in capillary optics

Propagation of x rays generated by a small-diameter incoherent source through the capillary waveguide that satisfies the multimode condition is studied with the Fresnel-Kirchhoff diffraction theory. The strong influence of diffraction on the propagation is demonstrated. The diffraction phenomenon is manifested by the appearance of diffraction fringes in both the guide channel and the far-field zone of the capillary output. Experimental data that confirm such behavior of the x-ray radiation is also presented. The results confirm the interference effects recently observed in some experiments on the grazing reflections of x rays in single- and multiple-capillary optics.     

Survey of the pollution in a coastal area of the Tyrrhenian Sea. aerial photography, physico-chemical and microbiological investigations and mutagenic monitoring

Investigations were carried out in a coastal area of the Tyrrhenian Sea, which receives wastes from a chemical manufacturing industry. Industrial wastes are combined with domestic sewage prior to discharge into the sea. Warm and alkaline wastewaters carry large amounts of whitish suspended solids, mainly composed of calcium carbonate, calcium sulphate and magnesium hydroxide, which are responsible for an evident visual pollution of the sandy shore and of the facing sea-water body. Alterations of physical parameters (temperature and pH values) were found to affect the investigated coastal area only to a limited extent. Conversely, aerial photographic investigations afforded a more complete picture of pollution spreading. Infrared and chiefly water-penetration images provided information on the underwater environment, and the resulting findings could be correlated with the particle size analysis of sediment samples. Faecal streptococci represented a considerable proportion of total heterotrophic bacteria in waste and sea-water, whereas concentration of total and faecal coliforms was relatively low. These figures suggested a possible selective inactivation of bacteria in industrial waters, which was supported by the findings of survival tests with three bacterial species (E. coli, Strep. faecalis and S. typhi). Survival of a virus (type 1 poliovirus) and of a virus antigen (hepatitis B surface antigen or HBsAg) was also investigated under various conditions. Clearance of industrial solids around some bacterial colonies growing in agar plates could be ascribed to aspecific acidification of the medium by bacterial metabolism. Finally, unconcentrated samples of the industrial wastewater failed to elicit any toxic or mutagenic effects for his⁻ strains of S. typhimurium, both in the presence and absence of rat liver microsomal preparations.     

Differences in X-ray absorption due to cadmium treatment in Saponaria officinalis leaves

A method for detecting cadmium uptake in leaves of Saponaria officinalis doped with a solution of cadmium acetate is described. The technique based on the exposure of dried leaves to X-rays of a wavelength close to that of the metal K-edge could be useful for phytoremediation studies as it could reveal the bioaccumulation in plants due to the treatment either in vivo or in vitro with heavy metals. X-ray microradiography measurements are in agreement with those from peroxidase enzyme assay utilized to follow the oxidative damage induced by heavy metals. At present, as we will see in this report, microradiography has still poorer sensitivity in comparison with enzyme assay, but it has the advantage of being faster, not destructive, and usable even at very high doping levels, where the enzyme assay technique results are fully saturated. Further analysis of the optical density values could lead to a quantitative measurement of the heavy metal in the sample. Thus, the technology developed in this article could be useful for tracing the intake in phytoremediation studies.     

Laboratory septic tank performance response to electrolytic stimulation

This research investigated the effects of electrolytic stimulation on the performance of two laboratory-scale septic tanks. The tanks were fed a synthetic solution that included cellulose, peptone trypticase, beef extract, and urea. After a baseline period with no passed current, currents ranging from 100 to 500 mA were passed through the electrodes. The chemical oxygen demand (COD) removal efficiency from the tanks improved when a current was passed, with higher removal efficiencies observed at higher levels of passed current. Hydrolytic reactions resulted in ammonia and phosphate levels in the tanks that were higher than the influent. At currents > 300 mA, these hydrolytic reactions were suppressed, resulting in phosphate levels similar to the influent and ammonia levels lower than the influent because of the settling of ammonia-containing components of the feed solution. A slight increase in nitrate levels was observed when a current was passed, indicating minimal stimulation of nitrification activity. Abiotic studies confirmed that the COD can be removed via electrolysis and the removal was proportional to the passed current. Under the conditions of this study, the primary benefit of electrolytic stimulation of the septic tank is enhanced COD removal.