THE CONJUGATE OF A SINGULAR FUNCTIONAL DIFFERENTIAL OPERATOR

An explicit representation of the conjugate of a singular functional differential operator is given. Some theorems and their corollaries are proven

Mechanisms of cross and multiple herbicide resistance in Alopecurus myosuroides and Lolium rigidum

L’Alopecurus myosuroides et le Lolium rigidum ont développé des résistances croisées et multiples à des herbicides ayant différents modes d'action et provenant de diverses classes chimiques. Un biotype d'Amyosuroides, Peldon AI, possède une capacité élevée de dégradation métabolique des herbicides de types urée substituée et aryloxypheno-xypropionate (APP), lui conférant une résistance croisée non reliée à la cible d'action. Un biotype australien de L. rigidum, SLR 31, possède de multiples mécanismes de résistance, comprenant à la fois des mécanismes de résistance croisée non reliés à la cible et d'autres reliés à la cible. La majorité des individus de la population SLR 31 a une capacité élevée de dégradation métabolique du chlorsulfuron et du diclofop-méthyl, en plus d'un mécanisme associé à une altération de la membrane cellulaire, lequel est corrélé avec la résistance à plusieurs herbicides de types APP et cyclohexanedione (CHD). De plus, une faible proportion des individus de cette population possède une cible d'action modifiée conférant une grande résistance à tous les APP et CHD. Bien que la biologie d'A. myosuroides et de L. rigidum présente beaucoup de points communs, ces deux espèces ne sont pas uniques. Nous prédisons que les résistances aux herbicides de type croisée non reliée à la cible et les résistances multiples vont se développer chez d'autres espèces. Les implications potentielles de ces types de résistance justifient l'adoption de mesures préventives.Alopecurus myosuroides and Lolium rigidum have developed resistance to herbicides with several modes of action in many herbicide classes. A. myosuroides biotype Peldon A1 from England exhibits non-target site cross resistance to substituted urea and aryloxyphenoxypropionate herbicides (APP) due to enhanced metabolism. L. rigidum biotype SLR 31 from Australia has multiple resistance mechanisms, including both non-target site cross resistance and target site cross resistance. The majority of the SLR 31 population has enhanced metabolism of chlorsulfuron and diclofop-methyl and a mechanism correlated with altered plasma membrane response, which correlates with resistance to some APP and cyclohexanedione (CHD) herbicides. A small proportion of the population also has target site cross resistance to APP and CHD herbicides. While A myosuroides and L. rigidum share common biological elements, they are not unique. Non-target site cross resistance and multiple herbicide resistance is predicted to develop in other weed species. The repercussions of cross and multiple resistance warrant proactive measures to prevent or delay onset

Management of herbicide-resistant wild oat (Avena fatua) patches

Non-Peer ReviewedA study was conducted at a 64-ha site in western Canada to determine how preventing seed shed from herbicide-resistant wild oat affects patch expansion over a 6-yr period. Seed shed was prevented in two patches and allowed to occur in two patches (untreated controls). Annual patch expansion was determined by seed bank sampling and mapping. All crop management practices were performed by the grower. Area of treated patches increased by 35% over the 6-yr period, whereas untreated patches increased by 330%. Patch expansion was attributed mainly to natural seed dispersal (untreated) or seed movement by equipment at time of seeding (untreated and treated). Extensive seed shed from plants in untreated patches before harvest or control of resistant plants by alternative herbicides minimized seed movement by the combine harvester. Although both treated and untreated patches were relatively stable over time in this cropping system, preventing seed production and shed in herbicide-resistant wild oat patches can markedly slow the rate of patch expansion

Current state of herbicide resistance in Canada

Non-Peer ReviewedBiotypes of wild oat (Avena fatua L.) resistant to Group 1 herbicides in the prairie provinces, and biotypes of chickweed [Stellaria media (L.) Vill.] and kochia [Kochia scoparia (L.) Schrad.] in western Canada and pigweed (Amaranthus) species in Ontario resistant to Group 2 herbicides are most abundant and widespread. Evolution of resistance in these biotypes is attributable to frequent use of herbicides from these two respective groups. Increasing incidence of wild oat populations with multiple-group resistance will threaten the future effectiveness of herbicides of different modes of action. Proactive or reactive management for herbicide resistance in weeds must consider the risks of herbicides of different modes of action to select for resistance and the differing propensity of herbicides to be metabolized in herbicide-resistant biotypes when rotating among herbicides, must meet criteria for effective herbicide mixtures, and should incorporate agronomic practices in cropping systems that help reduce weed seed production and spread

Bisimple monogenic orthodox semigroups

We give a complete description of the structure of all bisimple orthodox semigroups generated by two mutually inverse elements

Calcitonin gene-related peptide receptor antagonist BIBN 4096 BS for the acute treatment of migraine

Background: Calcitonin gene–related peptide (CGRP) may have a causative role in migraine. We therefore hypothesized that a CGRP-receptor antagonist might be effective in the treatment of migraine attacks. Methods: In an international, multicenter, double-blind, randomized clinical trial of BIBN 4096 BS, a highly specific and potent nonpeptide CGRP-receptor antagonist, 126 patients with migraine received one of the following: placebo or 0.25, 0.5, 1, 2.5, 5, or 10 mg of BIBN 4096 BS intravenously over a period of 10 minutes. A group-sequential adaptive treatment-assignment design was used to minimize the number of patients exposed. Results: The 2.5-mg dose was selected, with a response rate of 66 percent, as compared with 27 percent for placebo (P=0.001). The BIBN 4096 BS group as a whole had a response rate of 60 percent. Significant superiority over placebo was also observed with respect to most secondary end points: the pain-free rate at 2 hours; the rate of sustained response over a period of 24 hours; the rate of recurrence of headache; improvement in nausea, photophobia, phonophobia, and functional capacity; and the time to meaningful relief. An effect was apparent after 30 minutes and increased over the next few hours. The overall rate of adverse events was 25 percent after the 2.5-mg dose of the drug and 20 percent for the BIBN 4096 BS group as a whole, as compared with 12 percent for placebo. The most frequent side effect was paresthesia. There were no serious adverse events. Conclusions: The CGRP antagonist BIBN 4096 BS was effective in treating acute attacks of migraine

Alberta field survey of herbicide-resistant weeds

Non-Peer ReviewedIn 2001, 236 fields were randomly selected throughout the ecoregions of Alberta and surveyed for grass and broadleaf weeds resistant to Group 1 (ACCase inhibitor) or Group 2 (ALS inhibitor) herbicides. Nearly 20% of surveyed fields had a herbicide-resistant weed biotype. Only 5% of producers with resistant biotypes were aware of their occurrence. This survey serves as a baseline for determining future trends in weed resistance in Alberta

Influence of plant growth regulator application and nitrogen fertilization on oat yield and stand-ability

Non-Peer Reviewe

Social and cultural origins of motivations to volunteer a comparison of university students in six countries

Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces

Management practices influencing herbicide resistance in wild oat (Avena fatua)

Non-Peer ReviewedA 3-year study was conducted in Wheatland County, Alberta to determine if agronomic practices of growers influenced the occurrence of herbicide resistance in wild oat. Wild oat seeds were collected in 33 fields in 1997, and in 31 fields in each of 1998 and 1999 (one field per grower). Seedlings were screened for resistance to two acetyl-CoA carboxylase (ACCase) inhibitors (Group 1), imazamethabenz, an acetolactate synthase (ALS) inhibitor (Group 2), and triallate, a thiocarbamate herbicide (Group 8). A questionnaire on herbicide resistance awareness and management practices was completed by each grower. Both ACCase and ALS inhibitor resistance in wild oat were linked to a lack of crop rotation diversity. In addition, ALS inhibitorresistant wild oat was associated with conservation-tillage systems and recent use of herbicides with that mode of action. Results of this study suggest that timely tillage and inclusion of fall-seeded and perennial forage crops in rotations will effectively slow the selection of resistance in this grass species