Measuring Feedback in Damped Lyman Alpha Systems

We measure feedback (heating rates) in damped Lyman alpha systems from the cooling rate of the neutral gas. Since cooling occurs through [C II] 158 micron emission, we infer cooling from C II^{*} 1335.7 absorption lines detected with HIRES on the Keck I telescope. The inferred heating rates are about 30 times lower than for the Galaxy ISM. At z = 2.8, the implied star formation rate per unit area is 10^{-2.4+-0.3} solar masses per kpc^{2} per year, and the the star formation rate per unit comoving volume is 10^{-0.8+-0.2} solar masses per Mpc^{3} per year. This is the first measurement of star formation rates in objects likely to be the progenitors of current galaxies.Comment: 7 pages, 5 figures, Proceedings of the ESO/ECF/STScI Workshop on Deep Field

Generating and evaluating a novel genetic resource in wheat in diverse environments

The principal objective of the project is to develop composite cross populations of wheat based on a wide range of key parent varieties. The parents will be selected partly on past knowledge of successful performance in terms of yield, quality and disease resistance and partly on the basis of molecular ancestry to try to ensure as wide range of diversity as possible. Following parental inter-crossing in all possible combinations, progeny population samples will be exposed to a range of widely different agricultural environments and systems through several seasons of, largely, natural selection. Performance of the population samples will be compared at different stages against both the parents grown as pure stands and as physical mixtures. Our objective is to increase the sustainability and competitiveness of organic and other extensive farming systems by developing genetically diverse wheat populations that will respond rapidly to on-farm selection for improved productivity and yield. It is well established that modern varieties of wheat perform poorly under the conditions and management options encountered in organic farming systems. This is due to a number of factors including poor competition against weeds, narrow resistance against pests and disease, inability to efficiently utilise soil bound nutrients and the lack of genetic flexibility to buffer against environmental variation. To develop a conventional, new wheat breeding programme, from start to release of adapted varieties, would take many years. The approach we propose can deliver this material quickly. This will be achieved through the production of appropriate composite-cross populations of winter wheat. The research will provide material adapted to basic organic conditions that can then be further selected on-farm. This will also be of benefit to non-organic farms as the populations will posses broad resistance to pests and disease and improved competitive ability against weeds, so minimising the need for crop protection inputs. The research will deliver a unique insight into the evolution of genetically diverse wheat populations, under a diverse range of environments, which will allow the elucidation of gene x environment interactions. In addition, it will provide information on the characters of winter wheat that confer improved productivity under a diversity of environmental conditions. Samples of the resulting winter wheat composite cross populations will be placed in the gene bank at the John Innes Centre. Overall objective: To increase the sustainability and competitiveness of both non-organic and organic farming systems by developing genetically diverse wheat populations that will respond rapidly to on-farm selection for improved productivity and yield. 1. To generate six distinct, highly heterogeneous composite-cross populations of winter wheat for further development and selection. The populations will comprise; one with parental material selected for good milling potential, one with parents selected for high yield potential and one comprising both sets of parent material. Each of these populations will then be split to either include or exclude heritable male sterility. 2. To evaluate the performance and evolution of composite-cross populations over time under a diverse range of environmental conditions and identify characteristics that confer improved productivity in these environments. 3. To track the genetic changes that accompany selection, so providing a better understanding of the assemblages of traits that underlie improved productivity in diverse environments. 4. To provide genetically diverse crop material for further selection by farmers and as a resource for future publicly funded research. 5. To disseminate the results to the scientific community and industr

Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology

We probe the physical conditions in high redshift galaxies, specifically, the Damped Lyman-alpha Systems (DLAs) using neutral carbon (CI) fine structure lines and molecular hydrogen (H2). We report five new detections of CI and analyze the CI in an additional 2 DLAs with previously published data. We also present one new detection of H2 in a DLA. We present a new method of analysis that simultaneously constrains \emph{both} the volume density and the temperature of the gas, as opposed to previous studies that a priori assumed a gas temperature. We use only the column density of CI measured in the fine structure states and the assumption of ionization equilibrium in order to constrain the physical conditions in the gas. We present a sample of 11 CI velocity components in 6 DLAs and compare their properties to those derived by the global CII* technique. The resulting median values for this sample are: = 69 cm^{-3}, = 50 K, and = 3.86 cm^{-3} K, with standard deviations, sigma_{n(HI)} = 134 cm^{-3}, sigma_T = 52 K, and sigma_{log(P/k)} = 3.68 cm^{-3} K. This can be compared with the integrated median values for the same DLAs : = 2.8 cm^{-3}, = 139 K, and = 2.57 cm^{-3} K, with standard deviations sigma_{n(HI)} = 3.0 cm^{-3}, sigma_T = 43 K, and sigma_{log(P/k)} = 0.22 cm^{-3} K. Interestingly, the pressures measured in these high redshift CI clouds are similar to those found in the Milky Way. We conclude that the CI gas is tracing a higher-density, higher-pressure region, possibly indicative of post-shock gas or a photodissociation region on the edge of a molecular cloud. We speculate that these clouds may be direct probes of the precursor sites of star formation in normal galaxies at high redshift.Comment: Accepted for publication in Ap

Companion cropping for organic field vegetables (OF0181)

Typical organic crop rotations are extensive with at least one year in four as a fertility building crop. However, the economic viability of organic systems may be compromised by having 75% or less of the farm productive at one time, limited further by the absence of the Arable Area Payments Scheme, particularly Set-aside, for vegetable crops. In addition, the system gives rise to a high fertility/low fertility sequence which is inefficient in terms of nutrient management (particularly nitrogen). To try to address this, the use of permanent beds of companion crop grown alongside the vegetable crops has been developed under various conditions around the world and is perceived as a possible alternative in organic husbandry. Companion crops also have the potential to reduce the impact of pests and weeds. A potential disadvantage of companion crops is competition with crop plants for space, light, water and nutrients. The companion crop, therefore, is likely to have to be mown or grazed to control competition and encourage nutrient transfer. On the positive side, companion crops have the potential to reduce the impact of pests, and weeds. The challenge is, therefore, to develop appropriate crop layouts and machinery to balance these interactions and result in profitable crop production. Project OF0181 was delivered with Elm Farm Research Centre and was guided by a Steering Group. The core of the project was the further development and evaluation of a seven-crop companion crop system initially developed by Professor Martin Wolfe at Wakelyns Agroforesty, Fressingfield, Suffolk, a Soil Association registered organic farm. The system was based on 1.5 m beds, with three 20 cm vegetable rows alternating with 30 cm leguminous companion strips. Within each bed, there was a seven-course crop rotation: potatoes, alliums, Umbellifers, spring oats, legumes, brassicas and spring wheat. To establish and manage this system, Martin Wolfe and his co-workers (P. J. & M. J. Wards) had by spring 1999 developed a range of purpose-built machinery including a strip rotavator, 3 row precision seed drill, straight tine or L-blade strip cultivator with/without discs, rotary strip mower, strip irrigator and a strip compost spreader. Two large experiments were established at Wakelyns in spring 1999; it was planned that these be continued for the full three years of the project. One experiment compared a factorial combination of a) three companion crops: white clover, vetch and nil, b) companion crop mowings left to fall, or deflected onto the vegetable rows, and c) the presence or absence of added composted manure. A second experiment compared factorial combinations of winter cover crops of rye and vetch grown in the vegetable rows with additional approved inputs of phosphorus and potassium. All seven crops were grown but assessments were made only on brassicas, alliums and carrots. Conclusions Companion cropping has the potential to improve economic viability, and pest, disease and annual weed control in organic cropping systems, particularly in field vegetables which are not supported by the Arable Area Payment Scheme. However, in practice, in project OF0181 these benefits were not realised: • Grass weeds were favoured and were difficult to control once established. • There were problems with seedbed preparation and crop establishment; these may be less on lighter soils. • Some crop species were better suited to companion cropping. In 2000 and 2001, there was: - a high yield in both years from beetroot, spinach, chard and kale; - a high yield in one year from Brassicas (some cabbage, swede, turnip), endive, lettuce, parsley and parsnip; - a low yield in both years from Allium crops (leeks, onions), Brassica (sprouts, some cabbage, calabrese), carrots, celeriac, broad and dwarf beans. • Clover used soil available nitrogen in preference to fixed nitrogen, starving less competitive crops such as alliums of the nutrient and resulting in very low yields. • Even with reliable yields, companion cropping in the form tested may only be suited to small-scale labour-intensive production. A system with greater spatial separation of companion and vegetable crops, with vegetables and companion crops grown alone in separate beds or strips, may give the reported benefits of companion cropping with less competition and be practical for large scale production

Target absent trials in configural contextual cuing

In contextual cueing (CC), reaction times to find targets in repeated displays are faster than in displays that have never been seen before. This has been demonstrated using target-distractor configurations, global background colors, naturalistic scenes and the co-variation of target with distractors. The majority of CC studies have used displays where the target is always present. This paper investigates what happens when the target is sometimes absent. Experiment 1 shows that, although configural CC occurs in displays when the target is always present, there is no CC when the target is always absent. Experiment 2 shows that there is no CC when the same spatial layout can be both target present and target absent on different trials. The presence of distractors in locations that contain targets on other trials appears to interfere with CC and even disrupts the expression of previously learned contexts (Experiments 3-5). The results show that it is the target-distractor associations that are important in producing CC and, consistent with a response selection account, changing the response type from an orientation task to a detection task removes the CC effect

Crater production on Venus and Earth by asteroid and comet impact

New calculations of the collision probabilities of asteroids and comets with Venus were carried out based on the orbits of the known Venus-crossing asteroids and comets. For comparison, asteroid and comet collision probabilities and cratering rates on the Earth and Moon were recalculated and the estimated cratering rates on Venus were normalized to those of the Earth

Education and Labor Market Consequences of Teenage Childbearing: Evidence Using the Timing of Pregnancy Outcomes and Community Fixed Effects

The question of whether giving birth as a teenager has negative economic consequences for the mother remains controversial despite substantial research. In this paper, we build upon existing literature, especially the literature that uses the experience of teenagers who had a miscarriage as the appropriate comparison group. We show that miscarriages are not random events, but rather are likely correlated with (unobserved) community-level factors, casting some doubt on previous findings. Including community-level fixed effects in our specifications lead to important changes in our estimates. By making use of information on the timing of miscarriages as well as birth control choices preceding the teenage pregnancies we construct more relevant control groups for teenage mothers. We find evidence that teenage childbearing likely reduces the probability of receiving a high school diploma by 5 to 10 percentage points, reduces annual income as a young adult by $1,000 to$2,400, and may increase the probability of receiving cash assistance and decrease years of schooling.teen pregnancy, economic consequences, human capital