Multigroup diffusion preconditioners for multiplying fixed-source transport problems

Several preconditioners based on multigroup di usion are developed for application to multiplying fi xed-source transport problems using the discrete ordinates method. By starting from standard, one-group, diff usion synthetic acceleration (DSA), a multigroup diff usion preconditioner is constructed that shares the same fi ne mesh as the transport problem. As a cheaper but effective alternative, a two-grid, coarse-mesh, multigroup diff usion preconditioner is examined, for which a variety of homogenization schemes are studied to generate the coarse mesh operator. Finally, a transport-corrected diff usion preconditioner based on application of the Newton-Shulz algorithm is developed. The results of several numerical studies indicate the coarse-mesh, diff usion preconditioners work very well. In particular, a coarse-mesh, transport-corrected, diff usion preconditioner reduced the computational time of multigroup GMRES by up to a factor of 17 and outperformed best-case Gauss-Seidel results by over an order of magnitude for all problems studied

Solving eigenvalue response matrix equations with nonlinear techniques

This paper presents new algorithms for use in the eigenvalue response matrix method (ERMM) for reactor eigenvalue problems. ERMM spatially decomposes a domain into independent nodes linked via boundary conditions approximated as truncated orthogonal expansions, the coefficients of which are response functions. In its simplest form, ERMM consists of a two-level eigenproblem: an outer Picard iteration updates the k-eigenvalue via balance, while the inner λ -eigenproblem imposes neutron balance between nodes. Efficient methods are developed for solving the inner λ-eigenvalue problem within the outer Picard iteration. Based on results from several diffusion and transport benchmark models, it was found that the Krylov-Schur method applied to the λ -eigenvalue problem reduces Picard solver times (excluding response generation) by a factor of 2–5. Furthermore, alternative methods, including Picard acceleration schemes, Steffensen’s method, and Newton’s method, are developed in this paper. These approaches often yield faster k-convergence and a need for fewer k-dependent response function evaluations, which is important because response generation is often the primary cost for problems using responses computed online (i.e., not from a precomputed database). Accelerated Picard iteration was found to reduce total computational times by 2–3 compared to the unaccelerated case for problems dominated by response generation. In addition, Newton’s method was found to provide nearly the same performance with improved robustness

Use of mutants to dissect the role of ethylene signalling in organ senescence and the regulation of yield in Arabidopsis thaliana

The role of ethylene in regulating organ senescence in Arabidopsis has been investigated by studying the development of mutants that have an attenu- ated capacity to perceive the gas. The onset of leaf senescence and floral organ abscission was delayed in the ethylene-insensitive mutant etr1. The photosynthetic life span of rosette leaves was similarly extended in the gain- of-function mutant ers2, and this mutant also exhibited a delay in the timing of pod dehiscence primarily as a con- sequence of an extension in the final stages of senescence. A detailed analysis of yield revealed that whilst thousand grain weight was increased, by as much as 20 %, in etr1, ein4, and the loss-of-function mutant etr2, only the latter showed a significant increase in total weight of seeds produced per plant. The other studied mutants exhibited a reduction in total seed yield of almost 40 %. These observations are discussed in the context of the possible role of ethylene in regulating organ senescence and their significance in the breeding of crop plants with enhanced phenotypic characteristics

Psychopathy and offending behaviour: findings from the national survey of prisoners in England and Wales

There is debate about whether the psychopath's criminal behaviour is a consequence of abnormal personality traits or a symptom of psychopathy. The aim of this study was to examine independent associations between offending behaviour over the lifetime and psychopathy in a representative sample of male and female offenders. A two-stage survey was carried out among prisoners in all prisons in England and Wales. Psychopathy was measured using the PCL-R in the second stage among 497 male and female prisoners. Independent relationships between the four factors of psychopathy and lifetime offences were examined using multiple regression. Two models of association were compared to test the effects of the fourth (antisocial) factor. Factor 1 (interpersonal) was not associated with any category of serious offending behaviour. Affective deficiency (Factor 2) was independently associated with violent and acquisitive offending in men. The contribution of the antisocial factor to associations with total PCL-R scores, together with its strong intercorrelations with Factor 3 (lifestyle), suggest that it is an integral component of the psychopathy construct. The findings also demonstrate the dilemma of colinearity between the third and fourth factors of psychopathy and their relationship with criminal behaviour, especially in men. Keywords: Psychopathy; offending behaviour; prisoners; criminality; factor-structure; gende

Personality disorder and offending behaviour: findings from the national survey of male prisoners in England and Wales

Previous studies have related mental disorder and antisocial personality disorder to criminal behaviour, but little is known about the associations with other personality disorders. The aim of this study was to examine independent associations between offending behaviour over the lifetime and personality disorder in a representative sample of male offenders. A two-stage survey was carried out among prisoners in all prisons in England and Wales. DSM-IV personality disorder was measured using SCID-II in the second stage among 391 male prisoners. Independent relationships between personality disorder scores and lifetime offences were examined using multiple regression. Findings demonstrated several independent relationships between personality disorders and offending behaviour. Strongest associations were found between the conduct disorder and adult antisocial components of antisocial personality disorder, with no evidence that these were the consequence of the other Axis II disorders. Future research should investigate the functional links between personality disorder and offending behaviour

EFFECTS OF RISK ON OPTIMAL NITROGEN FERTILIZATION DATES IN WINTER WHEAT PRODUCTION AS AFFECTED BY DISEASE AND NITROGEN SOURCE

Optimal fertilization dates were found for two nitrogen sources in the presence of two diseases for wheat farmers with different risk preferences. Risk was independent of fertilization date. Ammonium Nitrate and Urea-Ammonium Nitrate did not affect risk differently. Ammonium Nitrate applied on March 9 was optimal regardless of risk preferences.Crop Production/Industries,

Disinfection of Spacecraft Potable Water Systems by Photocatalytic Oxidation Using UV-A Light Emitting Diodes

Ultraviolet (UV) light has long been used in terrestrial water treatment systems for photodisinfection and the removal of organic compounds by several processes including photoadsorption, photolysis, and photocatalytic oxidation/reduction. Despite its effectiveness for water treatment, UV has not been explored for spacecraft applications because of concerns about the safety and reliability of mercury-containing UV lamps. However, recent advances in ultraviolet light emitting diodes (UV LEDs) have enabled the utilization of nanomaterials that possess the appropriate optical properties for the manufacture of LEDs capable of producing monochromatic light at germicidal wavelengths. This report describes the testing of a commercial-off-the-shelf, high power Nichia UV-A LED (250mW A365nnJ for the excitation of titanium dioxide as a point-of-use (POD) disinfection device in a potable water system. The combination of an immobilized, high surface area photocatalyst with a UV-A LED is promising for potable water system disinfection since toxic chemicals and resupply requirements are reduced. No additional consumables like chemical biocides, absorption columns, or filters are required to disinfect and/or remove potentially toxic disinfectants from the potable water prior to use. Experiments were conducted in a static test stand consisting of a polypropylene microtiter plate containing 3mm glass balls coated with titanium dioxide. Wells filled with water were exposed to ultraviolet light from an actively-cooled UV-A LED positioned above each well and inoculated with six individual challenge microorganisms recovered from the International Space Station (ISS): Burkholderia cepacia, Cupriavidus metallidurans, Methylobacterium fujisawaense, Pseudomonas aeruginosa, Sphingomonas paucimobilis and Wautersia basilensis. Exposure to the Nichia UV-A LED with photocatalytic oxidation resulted in a complete (>7-log) reduction of each challenge bacteria population in <180 minutes of contact time. With continued advances in the design and manufacture of UV-A LEDs and semi-conducting photocatalysts, LED activated photochemical process technology promises to extend its application to spacecraft environmental systems

EFFECTS OF RISK, DISEASE, AND NITROGEN SOURCE ON OPTIMAL NITROGEN FERTILIZATION RATES IN WINTER WHEAT PRODUCTION

Interactions among nitrogen (N) fertilization rate, N source, and disease severity can affect mean yield and yield variance in conservation tillage wheat production. A Just-Pope model was used to evaluate the effects of N rate, N source, and disease on the spring N-fertilization decision. Ammonium nitrate (AN) was the utility-maximizing N source regardless of risk preferences. The net-return-maximizing AN rate was 92 lb N/acre, providing $0.52/acre higher net returns than the best alternative N source (urea). If a farmer could anticipate a higher than average Take-All infection, the difference in optimal net-returns between AN and urea would increase to$35.11/acre.Crop Production/Industries,

Measurement of dynamic full-field internal stresses through surface laser Doppler vibrometry

We present a method for evaluating internal dynamic stresses in a solid vibrating body from measurements of surface motion. The method relies on the same mathematics as boundary element method: A boundary reciprocity integral represents interior motion as a surface integral of boundary motion times the Green’s function. The surface motions are measured with a laser vibrometer rather than simulated, giving a direct measurement of internal motions and internal dynamic stresses. Experimental results on a flexing beam demonstrate that stresses measured in this fashion match those calculated from elementary theory