羧基化改性煤的离子交换性能

对马来酸酐改性制成的长焰煤加合物的阳离子交换性进行研究,并同氧化煤和工业吸附剂作了对比,表明其亲质子基团的解离范围宽(pK3.6～6.5)。从水溶液中吸附多价金属阳离子的能力取决于阳离子交换剂的表面性质:该加合物对Cr、Fe、Pb的吸附活性高于КБ-4阳离子树脂。     

Applications,Enrollment, Attendance,and Student Performance in Rebuilt School Facilities: A Case Study

Public school construction represents a significant portion of all construction spending in the United States; yet, the average age of United States’ public schools is 42 years old. This article focuses on magnet schools in a large urban school district in the United States. The study examines whether construction, building age, and building condition have an impact on magnet applications, enrollment, attendance, and student achievement measures. Twenty-eight magnet elementary schools in the school district were chosen for analysis. The experimental group (n=14) included all magnet elementary schools (kindergarten to 5^th grade [K-5]) rebuilt under three school bond programs. The control group (n=14) included randomly selected elementary schools (K-5) from the 32 remaining elementary schools in the district that were not rebuilt. Multiple regressions were conducted using building and student data gathered during the 2011-2012 school year. Results indicate that building composite score and building age had no observable predictive effects on magnet applications, student enrollment, or student attendance, in both groups. However, student achievement was positively affected by building composite score as measured by the ability to predict state percentile ranking. This study supports that building and maintaining high quality educational facilities has the potential to raise student achievement levels.     

Modal dynamics in multimode fibers

The dynamics of modes and their states of polarizations in multimode fibers as a function of time, space, and wavelength are experimentally and theoretically investigated. The results reveal that the states of polarizations are displaced in Poincaré sphere representation when varying the angular orientations of the polarization at the incident light. Such displacements, which complicate the interpretation of the results, are overcome by resorting to modified Poincaré sphere representation. With such modification it should be possible to predict the output modes and their state of polarization when the input mode and state of polarization are known.     

New UK guidance on the use of concrete in aggressive ground

The UK guidance for specification of concrete in aggressive ground has been revised following the discovery of the thaumasite form of sulfate attack in the foundations to highway bridges in England in 1998. Interim advice was issued in the Report of the Thaumasite Expert Group in January 1999. Following consultation with industry, a new BRE Special Digest 1 was published in September 2001 (to replace Digest 363) and parallel amendments to the current BS 5328 were drafted. New concepts are introduced for ground assessment and concrete specification. Allowance is now made for the oxidation of sulfides in the ground and there is a new classification for the aggressive chemical environment. Concrete specification additionally takes into account the required structural performance level, the carbonate content of aggregates, and the need for additional protective measures. Compatible guidance is being put in place for the UK Highways Agency and for BS 8500, the UK complementary standard to the European Standard BS EN 206-1, which will replace BS 5328 in December 2003.     

I.T. Education for humanities students: The Lampeter approach

In 1984, a new course, Information Studies, was introduced at Saint David's University College, Lampeter. This project attempted to provide an academic course of study into the application and implications of Information Technology (I.T.). The course was offered to students as a full Bachelor of Arts, Part One, option course and could be chosen as one of the three subjects studied in Year One of the Bachelor of Arts degree course. Several factors made the enterprise unusual. Firstly, Lampeter has only faculties of Arts and Technology. Students are offered a range of subjects from the arts, social sciences, divinity and theology and there was no expectation by students for a technology course. Secondly, most of these students had not previously followed advanced courses in science or technology. By adopting a methodical approach to the development of Information Studies it was intended to tailor the course as closely as possible to the original concept and to the needs of the students. The content of the course has therefore reflected the current developments in I.T., and student activity has been that which will increase useful knowledge and skills for the students. In addition, because of the unusual factors noted above, serious consideration was given to the organization and presentation of the course. In order to compensate for the “insecurity” generated by technical topics in general, and computers in particular, particular sensitivity was maintained by the lecturers and tutors who presented the course. Nevertheless, Information Studies had to cater for beginners without losing its credibility as a degree subject while attempting to maintain both the practical and the intellectual aspects of the course. This has allowed students to learn new skills of I.T. and at the same time apply these to their knowledge and understanding of other fields. The project was a working research activity. As with the most educational developments it did not have the luxury of a controlled environment and so a scheme of “Action Research” was planned. This involved analysing, evaluating and modifying the programme continuously. Analysis of student's coursework and written examination results has shown that the student scores in Information Studies are not significantly different from their marks in other Part One degree courses, nor is there any significant difference between the performance of female and male students.     

Units of DNA replication in S-phase human cells

Current methods of physical mapping allow the estimation of genomic distances (i.e. DNA contents) from linear distances between DNA markers in interphase nuclei, and in this study we estimated the size of focal centers of DNA replication in cultured S-phase human cells. Our results indicate that the conformation of S-phase chromosome fibres in the range of contour lengths 0.1-3.0 microns fits the random walk model and, therefore, the quantitative methods of interphase mapping can be applied to the estimation of sizes of replication units. The obtained data show the existence of multiple non-clustered small units less than 150 kb in size, equivalent to small replicons detected by fiber DNA radioautography, and also a significant fraction of big units more than 500 kb in size, representing groups of small replicons and/or big replicons. These big units are detected as chains of small replication foci, probably reflecting the structural chromatin organization in well-known loop domains, since the experimentally induced decrease of replicons to the average size 12 kb does not lead to any change in the pattern of indicated chains.