1-(2-chlorophenyl) ethanol (CPE) is of health and environmental concern due to its toxicity and its use as an intermediate in pharmaceutical manufacturing. The current work deals with the catalytic reductive dechlorination and detoxification of CPE by Pd/Fe bimetal. CPE was effectively dechlorinated to l-phenyl ethanol (PE) accompanied by the equivalent release of chloride. The extent of CPE dechlorination increased with temperature, Fe dosage and Pd loading. A decrease in solution pH increased CPE dechlorination, resulting presumably from an increase in hydrogen production. Under the specific conditions of 20 g/L Pd/Fe, 0.10% Pd (w/w) and initial pH 5-6, the CPE dechlorination was completed within 145 rain. The dechlorination followed a pseudo-first-order kinetics with an activation energy of 56.7 kJ/mol. The results of toxicity testing showed that CPE was very toxic to Chlorella, whereas PE showed little toxicity. The toxicity of the reaction solution declined gradually and the promoting effects on Chlorella intensified consequently with the dechlorination process. Thus, the reductive dechlorination of CPE to PE by Pd/Fe was a detoxification process. It may be used to effectively reduce the toxicological effects of CPE-contaminated wastewater, thereby enhancing the performance of subsequent biological processes in wastewater treatment. 相似文献
Cognitive outcomes at age 11 of 131 Romanian adoptees from institutions were compared with 50 U.K. adopted children. Key findings were of both continuity and change: (1) marked adverse effects persisted at age 11 for many of the children who were over 6 months on arrival; (2) there was some catch-up between ages 6 and 11 for the bottom 15%; (3) there was a decrease of 15 points for those over 6 months on arrival, but no differentiation within the 6-42-month range; (4) there was marked heterogeneity of outcome but this was not associated with the educational background of the adoptive families. The findings draw attention to the psychological as well as physical risks of institutional deprivation. 相似文献
Developmental trajectories of personal and collective self-concept were examined among American Indian adolescents. Personal self-concept (self-esteem) and collective self-concept (American Indian identity, Euro-American identity, community-mindedness) were assessed 6 times over 3 years in 4 cohorts of adolescents from 3 American Indian cultural groups (N=1,252). An accelerated longitudinal design was used to estimate developmental trajectories from 14 to 19 years; parallel-process and covariate models were used to examine variation in trajectories. Both personal and collective self-concepts were generally positive and showed small gains; they were moderately related to one another and differentially related to cultural group, gender, and perceived social support. The findings highlight the complexity of self-concept for American Indian youth and the significance of both personal and collective identity. 相似文献
The effectiveness of an explicit, systematic reading intervention for first-grade students whose home language was Spanish and who were at risk for reading difficulties was examined. Participants were 69 students in 20 classrooms in 7 schools from 3 districts who initially did not pass the screening in Spanish and were randomly assigned within schools to a treatment or comparison group; after 7 months, 64 students remained in the study. The intervention matched the language of instruction of their core reading program (Spanish). Treatment groups of 3 to 5 students met daily for 50 min and were provided systematic and explicit instruction in oral language and reading by trained bilingual intervention teachers. Comparison students received the school's standard intervention for struggling readers. Observations during core reading instruction provided information about the reading instruction and language use of the teachers. There were no differences between the treatment and comparison groups in either Spanish or English on any measures at pretest, but there were significant posttest differences in favor of the treatment group for the following outcomes in Spanish: Letter-Sound Identification (d = 0.72), Phonological Awareness composite (d = 0.73), Woodcock Language Proficiency Battery-Revised Oral Language composite (d = 0.35), Word Attack (d = 0.85), Passage Comprehension (d = 0.55), and two measures of reading fluency (d = 0.58-0.75). 相似文献
This paper presents the preliminary work for developing guidelines to ensure that industry-sponsored projects in first-year courses aid, not hamper, retention of students. Specifically, the overall research plan includes the following steps: (1) investigating the appropriateness of industry projects in a required introduction to engineering design course (approximately 1000 students per year), (2) assessing the impact of industry-sponsored projects on first-year students' learning and retention, and (3) promoting an awareness of issues involved in successfully introducing industry projects in the first year. It is expected that the outcomes of this work will result in guidelines widely applicable by other institutions looking into or currently using industry projects in the first year, thereby addressing the recognized national need of increasing retention rates, especially amongst women and minorities.
This paper covers a review of potential factors affecting industry-sponsored projects' appropriateness at the first year, and related preliminary data. 相似文献
The BSc in computer aided product design (CAPD) course at the University of Wolverhampton was conceived as a collaborative venture in 1989 between the School of Engineering and the School of Art and Design. The award was at the forefront of forging interdisciplinary collaboration at undergraduate level in the field of product design. It has integrated engineering design from the former with industrial design from the latter, developing a mixture of traditional, technical and design skills using the computer.
The current paper discusses the use of formal methods of delivery on the CAPD course together with the integration of industrial product design and engineering design from a case study and project approach. It progresses from a formal approach through a transitional stage to an innovative method of delivery and assessment.
In providing the framework to this innovative approach the paper utilizes examples of students’ case studies, projects and design competitions that rely upon the use of three-dimensional (3D modelling) and both traditional prototyping and rapid prototyping techniques in developing the product design artefact. Combined with this is the utilization of a design process model that combines both product design and industrial design methodologies.
The changing attitude of staff in the education of CAPD students, with respect to the integration of formal methods and innovative methods in case study and project scenarios, is also discussed. 相似文献
Study of plant roots and the diversity of soil micro biota, such as bacteria, fungi and microfauna associated with them, is important for understanding the ecological complexities between diverse plants, microbes, soil and climates and their role in phytoremediation of contaminated soils. The arbuscular mycorrhizal fungi (AMF) are universal and ubiquitous rhizosphere mi- croflora forming symbiosis with plant roots and acting as biofertilizers, bioprotactants, and biodegraders. In addition to AMF, soils also contain various antagonistic and beneficial bacteria such as root pathogens, plant growth promoting rhizobacteria including free-living and symbiotic N-fixers, and mycorrhiza helping bacteria. Their potential role in phytoremediation of heavy metal (HM) contaminated soils and water is becoming evident although there is need to completely understand the ecological complexities of the plant-microbe-soil interactions and their better exploitation as consortia in remediation strategies employed for contaminated soils. These multitrophic root microbial associations deserve multi-disciplinary investigations using molecular, biochemical, and physiological techniques. Ecosystem restoration of heavy metal contaminated soils practices need to incorporate microbial biotechnology research and development. This review highlights the ecological complexity and diversity of plant-microbe-soil combinations, particularly AM and provides an overview on the recent developments in this area. It also discusses the role AMF play in phytorestoration of HM contaminated soils, i.e. mycorrhizoremediation. 相似文献
Leakage currents, tiny currents flowing from an everyday-life appliance through the body to the ground, can cause a non-adequate perception (called electrocutaneous sensation, ECS) or even pain and should be avoided.
Safety standards for low-frequency range are based on experimental results of current thresholds of electrocutaneous sensations, which however show a wide range between about 50 pA (rms) and 1000 μA (rms). In order to be able to explain these differences, the perception threshold was measured repeatedly in experiments with test persons under identical experimental setup, but by means of different methods (measuring strategies), namely: direct adjustment, classical threshold as amperage of 50% perception probability, and confidence rating procedure of signal detection theory. The current is injected using a I cm2 electrode at the highly touch sensitive part of the index fingertip.
These investigations show for the first time that the threshold of electrocutaneous sensations is influenced both by adaptation to the non-adequate stimulus and individual, emotional factors. Theretbre, classical methods, on which the majority of the safety investigations are based, cannot be used to determine a leakage current threshold.
The confidence rating procedure of the modem signal detection theory yields a value of 179.5 μA (rms) at 50 Hz power supply net frequency as the lower end of the 95% confidence range considering the variance in the investigated group. This value is expected to be free of adaptation influences, and is distinctly lower than the European limits and supports the stricter regulations of Canada and USA. 相似文献