A novel synthesis of 2'-hydroxy-1',3'-xylyl crown ethers

Six novel 2' - hydroxy - 1',3' - xylyl crown ethers (8a–e and 13)1 have been synthesized utilizing the allyl group to protect the OH function during the cyclization reaction. The macrocycles 6a-e were formed in yields of 26 to 52%, by intermolecular reaction of 4 - chloro - 2,6 - bis(bromomethyl) - 1 - (2 - propenyloxy)benzene (5) with polyethylene glycols; 6a was also obtained by an intramolecular cyclization reaction of monotosylate 14.\ud A 30-membered ring with a 2' - hydroxy - 1',3' - xylyl sub-unit was obtained in 87% yield by reaction of ditosylate 9 with bis [2 - (o - hydroxyphenoxy)ethyl]ether (11) in the presence of cesium fluoride. The synthesis of crown ethers with a 2' - hydroxy - 1',3' - xylyl sub-unit (1c–e, H for CH3) by demethylation of the corresponding 2'-methoxy crown ethers 1c–e with lithium iodide were unsuccessful; it would appear that the demethylation reaction is restricted to 15- and 18-membered rings. One of the 2' - hydroxy - 1',3' - xylyl crown ethers 8d forms a crystalline 1:1-complex with water

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

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

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

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

Density-Matrix approach to a Strongly Coupled Two-Component Bose-Einstein Condensate

The time evolution equations for average values of population and relative phase of a strongly coupled two component BEC is derived analytically. The two components are two hyper-fine states coupled by an external laser that drives fast Rabi oscillations between these states. Specifically, this derivation incorporates the two-mode model proposed in [1] for the strongly coupled hyper-fine states of Rb. The fast Rabi cycle is averaged out and rate equations are derived that represents the slow dynamics of the system. These include the collapse and revival of Rabi oscillations and their subsequent dependence on detuning and trap displacement as reported in experiments of [1]. A proposal to create stable vortices is also given.Comment: 11 Latex pages, 2 figures (Figure 3 was removed and the text chnaged accordingly

A New Dental Superalloy System: V. Embrittling Phase Transformations

The σ phase is rich in Ta. When the Ta concentration is less than 14%, σ does not interfere with the slip mechanism; when the Ta concentration is more than 15%, σ interferes with the slip mechanism. The coherent α-Co 3Ta phase forms at Ta concentrations of less than 15%, whereas incoherent γ-Co 2Ta forms only at higher Ta concentrations. The interface between σ and the matrix is an important factor in the failure mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67929/2/10.1177_00220345740530013301.pd

The ASK Network: developing a virtuous cycle of subsurface data and knowledge exchange

Knowledge of the subsurface is essential in delivering successful construction and regeneration projects. Inadequate understanding of subsurface ground conditions can constrain effective development of urban areas and is a key factor in project delay and overspending. Improving this situation demands much better use, and re-use, of subsurface data and knowledge. The establishment of ASK subsurface data and knowledge exchange network has led to substantial improvements in how urban subsurface data is reported and exchanged between the public and private sectors. Implementation of the GSPEC standardised digital data reporting format has improved the integrity and accessibility of data. ASK and GSPEC are enabling the expansion and exchange of high quality systematic subsurface datasets, improving development of robust 3D ground models which can be used to promote more cost effective and better informed ground engineering investigations, and monitoring and regulation of resources in the urban environment. The work underway in Glasgow is acting as a standard for change, both within the UK and Europe

Spin dynamics of a trapped spin-1 Bose Gas above the Bose-Einstein transition temperature

We study collective spin oscillations in a spin-1 Bose gas above the Bose-Einstein transition temperature. Starting from the Heisenberg equation of motion, we derive a kinetic equation describing the dynamics of a thermal gas with the spin-1 degree of freedom. Applying the moment method to the kinetic equation, we study spin-wave collective modes with dipole symmetry. The dipole modes in the spin-1 system are found to be classified into the three type of modes. The frequency and damping rate are obtained as functions of the peak density. The damping rate is characterized by three relaxation times associated with collisions.Comment: 19 pages, 5 figur

Measurement of the Forward Cross Section of p(n,d)y at 190 MeV

This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit