Wind trajectory tracing for air pollution studies (AIRPOL)

Wind trajectory computer program, consisting of data handling program and analysis program, traces Los Angeles Basin wind patterns either backward or forward in time. Program may be applicable to other areas

Reversible and irreversible trapping at room temperature in poly(thiophene) thin-film transistors

We measured the bias stress characteristics of poly(thiophene) semi-crystalline thin-film transistors (TFTs) as a function stress times, gate voltages and duty-cycles. At room temperature, the bias stress has two components: a fast reversible component and a slow irreversible component. We hypothesize that the irreversible component is due to charge trapping in the disordered areas of the semiconductor film. At low duty-cycle (<2%), the fast bias stress component is reversed during the off-part of the cycle therefore the observed VT shift in only caused by irreversible trapping. Irreversible trapping follows power-law kinetics with a time exponent approximately equal to 0.37. We use these findings to estimate the lifetime of TFTs used as switches in display backplanes

Experimentally Constrained Molecular Relaxation: The case of hydrogenated amorphous silicon

We have extended our experimentally constrained molecular relaxation technique (P. Biswas {\it et al}, Phys. Rev. B {\bf 71} 54204 (2005)) to hydrogenated amorphous silicon: a 540-atom model with 7.4 % hydrogen and a 611-atom model with 22 % hydrogen were constructed. Starting from a random configuration, using physically relevant constraints, {\it ab initio} interactions and the experimental static structure factor, we construct realistic models of hydrogenated amorphous silicon. Our models confirm the presence of a high frequency localized band in the vibrational density of states due to Si-H vibration that has been observed in a recent vibrational transient grating measurements on plasma enhanced chemical vapor deposited films of hydrogenated amorphous silicon.Comment: 13 pages, 4 figure

Intrinsic hole mobility and trapping in a regio-regular poly(thiophene)

The transport properties of high-performance thin-film transistors (TFT) made with a regio-regular poly(thiophene) semiconductor (PQT-12) are reported. The room-temperature field-effect mobility of the devices varied between 0.004 cm2/V s and 0.1 cm2/V s and was controlled through thermal processing of the material, which modified the structural order. The transport properties of TFTs were studied as a function of temperature. The field-effect mobility is thermally activated in all films at T<200 K and the activation energy depends on the charge density in the channel. The experimental data is compared to theoretical models for transport, and we argue that a model based on the existence of a mobility edge and an exponential distribution of traps provides the best interpretation of the data. The differences in room-temperature mobility are attributed to different widths of the shallow localized state distribution at the edge of the valence band due to structural disorder in the film. The free carrier mobility of the mobile states in the ordered regions of the film is the same in all structural modifications and is estimated to be between 1 and 4 cm2/V s.Comment: 20 pages, 8 figure

The Value of Literacy Practices

The concepts of literacy events and practices have received considerable attention in educational research and policy. In comparison, the question of value, that is, ‘which literacy practices do people most value?’ has been neglected. With the current trend of cross-cultural adult literacy assessment, it is increasingly important to recognise locally valued literacy practices. In this paper we argue that measuring preferences and weighting of literacy practices provides an empirical and democratic basis for decisions in literacy assessment and curriculum development and could inform rapid educational adaptation to changes in the literacy environment. The paper examines the methodological basis for investigating literacy values and its potential to inform cross-cultural literacy assessments. The argument is illustrated with primary data from Mozambique. The correlation between individual values and respondents’ socio-economic and demographic characteristics is explored

Literacy under and over the desk: oppositions and heterogeneity

In this paper I argue that a dominant theme in New Literacy Studies research, the differences between literacy practices inside and outside school, has sometimes involved conflating ‘home literacy’ with private, unregulated ‘vernacular literacy’, and the use of an idealised abstract notion of schooled literacy to represent students’ actual everyday experience in the classroom. Drawing on linguistic ethnographic research in two British primary schools, I use examples of ‘unofficial’ and ‘official’ literacy activities from 10-11 year-olds to show that a wide range of different forms of literacy can be found in the classroom and I argue that the division between ‘vernacular’ and ‘schooled’ is not as clear-cut as is sometimes assumed. My analysis of children’s literacy activities suggests that, on the one hand, unofficial activities orientate towards and index official knowledges and the macro-level institutional order and, on the other hand, official activities are interpenetrated with informal practices and procedures. I also comment on some implications of using the New Literacy Studies ‘events and practices’ conceptual framework for understanding what is going on in classrooms

Higher Descent Data as a Homotopy Limit

We define the 2-groupoid of descent data assigned to a cosimplicial 2-groupoid and present it as the homotopy limit of the cosimplicial space gotten after applying the 2-nerve in each cosimplicial degree. This can be applied also to the case of $n$-groupoids thus providing an analogous presentation of "descent data" in higher dimensions.Comment: Appeared in JHR

Lunar base CELSS: A bioregenerative approach

During the twenty-first century, human habitation of a self-sustaining lunar base could become a reality. To achieve this goal, the occupants will have to have food, water, and an adequate atmosphere within a carefully designed environment. Advanced technology will be employed to support terrestrial life-sustaining processes on the Moon. One approach to a life support system based on food production, waste management and utilization, and product synthesis is outlined. Inputs include an atmosphere, water, plants, biodegradable substrates, and manufacutured materials such as fiberglass containment vessels from lunar resources. Outputs include purification of air and water, food, and hydrogen (H2) generated from methane (CH4). Important criteria are as follows: (1) minimize resupply from Earth; and (2) recycle as efficiently as possible

Shadows and traces in bicategories

Traces in symmetric monoidal categories are well-known and have many applications; for instance, their functoriality directly implies the Lefschetz fixed point theorem. However, for some applications, such as generalizations of the Lefschetz theorem, one needs "noncommutative" traces, such as the Hattori-Stallings trace for modules over noncommutative rings. In this paper we study a generalization of the symmetric monoidal trace which applies to noncommutative situations; its context is a bicategory equipped with an extra structure called a "shadow." In particular, we prove its functoriality and 2-functoriality, which are essential to its applications in fixed-point theory. Throughout we make use of an appropriate "cylindrical" type of string diagram, which we justify formally in an appendix.Comment: 46 pages; v2: reorganized and shortened, added proof for cylindrical string diagrams; v3: final version, to appear in JHR