Hydraulic Redistribution from Wet to Drying Roots of Potatoes (Solanum tubersosum L.) During Partial Rootzone Drying

Hydraulic redistribution, redistribution of water upward or downward within a soil profile through roots as a consequence of root-soil water potential gradients, can be an important mechanism in transporting chemical signals (i.e. abscisic acid) to the shoot for stomatal closure or in maintaining the root system during dry periods of partial rootzone drying (PRD). PRD involves alternate irrigation to two sides of a plant root system. The study reported here investigated the occurrence and magnitude of hydraulic redistribution in glasshouse-grown potatoes (Solanum tuberosum L.) under PRD. Deuterium labelled water was applied to only one half of the root system to field capacity at tuber initiation. The roots from the drying side of the dual pot were extracted at 3, 6, 12, 18 and 24 h following watering by the dry sieving method. Water from the roots was extracted by azeotropic distillation and analysed for hydrogen isotope ratios. Hydraulic redistribution occurred the most at night when stomatal conductance was considerably lower and leaf water potential was higher (less negative). The magnitude of the redistributed water, however, did not exceed 3.5%, indicating limited water redistribution under PRD. The observed water redistribution would probably be of little significance for the survival of roots present in the upper drier portion of the soil under higher water demanding conditions but its role in sending the chemical signals to the shoot to conserve water by reducing transpiration would be of particular significance during drying periods of partial rootzone drying

A gauge model for quantum mechanics on a stratified space

In the Hamiltonian approach on a single spatial plaquette, we construct a quantum (lattice) gauge theory which incorporates the classical singularities. The reduced phase space is a stratified K\"ahler space, and we make explicit the requisite singular holomorphic quantization procedure on this space. On the quantum level, this procedure furnishes a costratified Hilbert space, that is, a Hilbert space together with a system which consists of the subspaces associated with the strata of the reduced phase space and of the corresponding orthoprojectors. The costratified Hilbert space structure reflects the stratification of the reduced phase space. For the special case where the structure group is $\mathrm{SU}(2)$, we discuss the tunneling probabilities between the strata, determine the energy eigenstates and study the corresponding expectation values of the orthoprojectors onto the subspaces associated with the strata in the strong and weak coupling approximations.Comment: 38 pages, 9 figures. Changes: comments on the heat kernel and coherent states have been adde

A review of the tractive performance of wheeled tractors and soil management in lowland intensive rice production.

This paper reviews the cultivation practices and tractive performance using wheeled tractors, and how these interact with soil management, in lowland intensive rice production. The paper explores the issues of long term sustainable soil use, the energy inputs required, environmental impact and changes in approach to agronomy and links these to the tractor operations carried out as part of rice production. The paddy soil environment demonstrates very significant changes in soil properties with depth, in particular soil density, penetrometer resistance, soil structure and pore interconnectivity, water content and movement, and soil biology. This is related to the management of the soil hard pan in relation to machinery operations and machinery use. One of the issues appears to be that the hard pan can be deeper than required with consequently unnecessarily high energy inputs. The tractive performance of wheeled tractors on different surface conditions is considered with respect to tractive efficiency and maintenance of a soil hard pan that has the required characteristics for sustainable production. Alternatives to conventional tyres, cage wheels and tracks, are considered. The cultivation operations are evaluated in relation to soil management, crop requirements and energy use. Variation in hard pan characteristics may be disadvantageous and provides opportunities for precision operations

What do young athletes implicitly understand about psychological skills?

One reason sport psychologists teach psychological skills is to enhance performance in sport; but the value of psychological skills for young athletes is questionable because of the qualitative and quantitative differences between children and adults in their understanding of abstract concepts such as mental skills. To teach these skills effectively to young athletes, sport psychologists need to appreciate what young athletes implicitly understand about such skills because maturational (e.g., cognitive, social) and environmental (e.g., coaches) factors can influence the progressive development of children and youth. In the present qualitative study, we explored young athletes’ (aged 10–15 years) understanding of four basic psychological skills: goal setting, mental imagery, self-talk, and relaxation. Young athletes (n = 118: 75 males and 43 females) completed an open-ended questionnaire to report their understanding of these four basic psychological skills. Compared with the older youth athletes, the younger youth athletes were less able to explain the meaning of each psychological skill. Goal setting and mental imagery were better understood than self-talk and relaxation. Based on these findings, sport psychologists should consider adapting interventions and psychoeducational programs to match young athletes’ age and developmental level

VERITAS: the Very Energetic Radiation Imaging Telescope Array System

The Very Energetic Radiation Imaging Telescope Array System (VERITAS) represents an important step forward in the study of extreme astrophysical processes in the universe. It combines the power of the atmospheric Cherenkov imaging technique using a large optical reflector with the power of stereoscopic observatories using arrays of separated telescopes looking at the same shower. The seven identical telescopes in VERITAS, each of aperture 10 m, will be deployed in a filled hexagonal pattern of side 80 m; each telescope will have a camera consisting of 499 pixels with a field of view of 3.5 deg VERITAS will substantially increase the catalog of very high energy (E > 100GeV) gamma-ray sources and greatly improve measurements of established sources.Comment: 44 pages, 16 figure

Squark-, Slepton- and Neutralino-Chargino coannihilation effects in the low-energy effective MSSM

Within the low-energy effective Minimal Supersymmetric extension of the Standard Model (effMSSM) we calculate the neutralino relic density taking into account slepton-neutralino, squark-neutralino and neutralino/chargino- neutralino coannihilation channels. By including squark (stop and sbottom) coannihilation channels we extend our comparative study to all allowed coannihilations and obtain the general result that all of them give sizable contributions to the reduction of the neutralino relic density. Due to these coannihilation processes some models (mostly with large neutralino masses) enter into the cosmologically interesting region for relic density, but other models leave this region. Nevertheless, in general, the predictions for direct and indirect dark matter detection rates are not strongly affected by these coannihilation channels in the effMSSM.Comment: 14 pages, 10 figures, corrected and to be published in Phys. Rev.

Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Nucleosome conformation dictates the histone code

Histone post-translational modifications (PTMs) play a critical role in chromatin regulation. It has been proposed that these PTMs form localized 'codes' that are read by specialized regions (reader domains) in chromatin-associated proteins (CAPs) to regulate downstream function. Substantial effort has been made to define [CAP: histone PTM] specificities, and thus decipher the histone code and guide epigenetic therapies. However, this has largely been done using the reductive approach of isolated reader domains and histone peptides, which cannot account for any higher-order factors. Here, we show that the [BPTF PHD finger and bromodomain: histone PTM] interaction is dependent on nucleosome context. The tandem reader selectively associates with nucleosomal H3K4me3 and H3K14ac or H3K18ac, a combinatorial engagement that despite being in cis is not predicted by peptides. This in vitro specificity of the BPTF tandem reader for PTM-defined nucleosomes is recapitulated in a cellular context. We propose that regulatable histone tail accessibility and its impact on the binding potential of reader domains necessitates we refine the 'histone code' concept and interrogate it at the nucleosome level