Radiation Damping Effects in Two Level Maser Oscillators

Several experiments [1,2] have noted recently that when an inverted two-level spin system was permitted to radiate spontaneously, the resulting oscillation was characterized by an appreciable amplitude modulation. The phenomenon was first believed to be the result of interference of different spin packets in an inhomogeneously broadened spectrum [1]. A theoretical analysis (which will be reported separately) shows that this is not the case. The spins are not independent but are coupled together by means of their radiation field. This explanation has since been by its original authors

Understanding what you are doing: A new angle on CAS?

Powerful Computer Algebra Systems (CAS) are often used only with reluctance in early undergraduate mathematics teaching, partly because of concerns that they may not encourage students to understand what they are doing. In this exploratory study, a version of a CAS that has been designed for secondary school students was used, with a view to considering the value of this sort of student learning support for first year undergraduate students enrolled in degree programs other than mathematics. Workshops were designed to help students understand aspects of elementary symbolic manipulation, through the use of the Algebra mode of an algebraic calculator, the Casio Algebra FX 2.0. The Algebra mode of this calculator allows a user to undertake elementary algebraic manipulation, routinely providing all intermediate results, in contrast to more powerful CAS software, which usually provides simplified results only. The students were volunteers from an introductory level unit, designed to provide a bridge between school and university studies of mathematics and with a focus on algebra and calculus. The two structured workshop sessions focussed respectively on the solution of linear equations and on relationships between factorising and expanding; attention focussed on using the calculators as personal learning devices. Following the workshops, structured interviews were used to systematically record student reactions to the experience. As a result of the study, the paper offers advice on the merits of using algebraic calculators in this sort of way

Graphics calculator use in examinations: accident or design?

As graphics calculators become more available, interest will focus on how to incorporate them appropriately into curriculum structures, and particularly into examinations. We describe and exemplify a typology of use of graphics calculators in mathematics examinations, from the perspective of people designing examinations, together with some principles for the awarding of partial credit to student responses. This typology can be used to help design examinations in which students are permitted to use graphics calculators as well as to interrogate existing examination practice

Symbolic manipulation on a TI-92: New threat or hidden treasures?

The availability of hand held devices that can undertake symbolic manipulation is a recent phenomenon, potentially of great significance for both the algebra and calculus curriculum in the secondary and lower undergraduate years. The significance to date of symbolic manipulation for mathematics is described, and parallels drawn with the significance of arithmetic skills for the primary school. It is suggested that, while symbolic manipulation is central to mathematics, many students develop only a restricted competence with the associated mathematical ideas. The Texas Instruments TI-92 is used to suggest some potential beneficial uses of technology that involves symbolic manipulation

Flowering and pollination studies with European plum (Prunus domestica L.) cultivars

One of the most important factors affecting the financial outcome of commercial fruit growing is the success of pollination and fertilization, which in turn are dependent on weather conditions, activity of pollinators and the compatibility and overlap in flowering of the cultivars. Before introducing new cultivars, it is obviously important to know the compatibility and flowering characteristics of the genotypes. In order to find out these attributes of seven new and four established plum cultivars, pollen germination tests, hand pollinations and flowering phenology observations were carried out. ‘Prosser 84’ had 70% pollen germination. ‘Opal’ had just 3%, probably due to aged pollen. ‘Anna Späth’ flowered over a short period (13 days) and ‘1468’ and ‘DCA BO 46’ over long (19 days) periods; the overlap of all cultivars was relatively good. With ‘1468’, ‘Victory’, ‘Anna Späth’ and ‘Prosser 84’ flowering intensity varied between years, ‘Jubileum’, ‘V70032’, ‘Tita’ and ‘DCA BO 46’ flowered regularly, the others were intermediate. ‘1468’ and ‘WJ 65’ flowered early, ‘Prosser 84’ and ‘DCA BO 46’ late and the rest fell in between. ‘Victoria’ proved to be self-fertile, ‘Jubileum’, ‘V70032’ and ‘1468’ semi self-fertile. Fruit set percentages after June drop of all crosses were rather low; varying between 0 and 28%. With ‘Tita’, fruit drop occurred approximately two weeks later than with the other cultivar

The Consequences of Caregiving: Does Employment Make a Difference?

While a number of studies have examined the consequences of caregiving among employed women, surprisingly little research has explicitly compared how consequences differ between employed and not employed women. Moreover, very little research in this area has distinguished between part-time and full- time employment. This paper examines these issues drawing on the 1996 General Social Survey of Canada. The sample for this study consists of women aged 25 to 64 who reported providing care to one or more people aged 65+ because of a long-term physical disability (n=426). Three employment status groups (full-time, part-time and not employed) are compared on positive consequences, burden, guilt, job adjustment, postponed opportunities, and social and economic consequences. Results reveal significant differences between the three employment categories indicating that employment, both full and part-time, is associated with higher burden, guilt and social and economic consequences.caregiving; employment status; GSS

The \u3cem\u3emir-51\u3c/em\u3e Family of MicroRNAs Functions in Diverse Regulatory Pathways in \u3cem\u3eCaenorhbditis elegans\u3c/em\u3e

The mir-51 family of microRNAs (miRNAs) in C. elegans are part of the deeply conserved miR-99/100 family. While loss of all six family members (mir-51-56) in C. elegans results in embryonic lethality, loss of individual mir-51 family members results in a suppression of retarded developmental timing defects associated with the loss of alg-1. The mechanism of this suppression of developmental timing defects is unknown. To address this, we characterized the function of the mir-51 family in the developmental timing pathway. We performed genetic analysis and determined that mir-51 family members regulate the developmental timing pathway in the L2 stage upstream of hbl-1. Loss of the mir-51 family member, mir-52, suppressed retarded developmental timing defects associated with the loss of let-7 family members and lin-46. Enhancement of precocious defects was observed for mutations in lin-14, hbl-1, and mir-48(ve33), but not later acting developmental timing genes. Interestingly, mir-51 family members showed genetic interactions with additional miRNA-regulated pathways, which are regulated by the let-7 and mir-35 family miRNAs, lsy-6, miR-240/786, and miR-1. Loss of mir-52 likely does not suppress miRNA-regulated pathways through an increase in miRNA biogenesis or miRNA activity. We found no increase in the levels of four mature miRNAs, let-7, miR-58, miR-62 or miR-244, in mir-52 or mir-52/53/54/55/56 mutant worms. In addition, we observed no increase in the activity of ectopic lsy-6 in the repression of a downstream target in uterine cells in worms that lack mir-52. We propose that the mir-51 family functions broadly through the regulation of multiple targets, which have not yet been identified, in diverse regulatory pathways in C. elegans

Research on ion beam diagnostics Final report

Research on ion beam diagnostic