Crop rotation limits Canada thistle, but not Couch grass or annual weeds

Direct weed control of annual as well as perennial weeds was necessary to reduce the amount of weeds in organic crop rotation experiments at three locations in Denmark. For Canada thistle, however, the rotation was the most important controlling factor: the rotation with grass-clover had less thistle biomass than the one without

Worship in small churches

The article advocates and elaborates a theological point of view with respect to worship that is in the interest of the small church and that the small church is in a unique position to advocate. Specific rubrical proposals are made. \u27The means of grace, i.e., the Word and Sacraments, are the central and only indispensable elements in worship. The smaller amount of human resources available to small churches can lead them to focus on these means of grace. This focus is an outstanding strength\u27

Evolution of weak disturbances in inert binary mixtures

The evolution of weak disturbances in inert binary mixtures is determined for the one-dimensional piston problem. The interaction of the dissipative and nonlinear mechanisms is described by Burgers' equation. The binary mixture diffusion mechanisms enter as an additive term in an effective diffusivity. Results for the impulsive motion of a piston moving into an ambient medium and the sinusoidally oscillating piston are used to illustrate the results and elucidate the incorrect behavior pertaining to the associated linear theory

Acoustic disturbances produced by an unsteady spherical diffusion flame

The disturbances produced by a moving spherical diffusion flame are investigated within the framework of a linearized theory. After the flame position and species concentrations are determined, the problem of determining the associated density, pressure, temperature, and velocity fields is delineated. Explicit results for certain limiting situations are discussed

Higher su(N) tensor products

We extend our recent results on ordinary su(N) tensor product multiplicities to higher su(N) tensor products. Particular emphasis is put on four-point couplings where the tensor product of four highest weight modules is considered. The number of times the singlet occurs in the decomposition is the associated multiplicity. In this framework, ordinary tensor products correspond to three-point couplings. As in that case, the four-point multiplicity may be expressed explicitly as a multiple sum measuring the discretised volume of a convex polytope. This description extends to higher-point couplings as well. We also address the problem of determining when a higher-point coupling exists, i.e., when the associated multiplicity is non-vanishing. The solution is a set of inequalities in the Dynkin labels.Comment: 17 pages, LaTe

Development of weeds in organic crop rotation experiments

Weeds are a major problem in organic farming. Preventive as well as curative measures must be utilised to manage the weeds and avoid proliferation. Besides direct weed control measures, many different aspects of planning and management in the cropping system affect the proliferation of weeds. However, it has rarely been investigated how the whole system affects weed populations

X-Ray IGM in the Local Group

Recent observations with the dispersive X-ray spectrometers aboard Chandra and Newton Observatory have begun to probe the properties of the X-ray intergalactic medium (IGM) at small redshifts. Using large quantities (~950 ksec) of spectroscopic data acquired using the RGS aboard Newton Observatory, we investigated the intervening material toward three low redshift, high Galactic latitude AGNs with nominally featureless spectra: Mrk421, PKS2155-304 and 3C273. Each spectrum provides clear evidence for what appears to be a local (z~0), highly ionized absorbing medium betrayed by the OVII 1s-2p resonance transition feature seen at 21.6A (N[OVII] ~ 1E16 cm-2). Measurements are also made for the Lyman alpha transition of the adjacent ionization state, (OVIII; 18.97A), which potentially constrains the absorber's temperature. Finally, in a collisional equilibrium approximation, upper limits to diffuse emission intensities place upper limits on the electron density (ne < 2E-4 cm-3), lower limits on the scale length of the absorber (L > 140 kpc) and lower limits on its mass (M > 5E10 M[sun]). Limits on the absorber's scale length and its velocity distribution lead us to identify it with the Local Group.Comment: 6 pages, 1 table and 2 figs. Latex. To appear in "The IGM/Galaxy Connection: The Distribution of Baryons at z=0" to be published by Kluwer Academic Publishing. Resubmitted with 2 typos corrected, page 5 and figure 2. Thanks to Masao Sako for pointing these ou

The Superpolynomial for Knot Homologies

We propose a framework for unifying the sl(N) Khovanov-Rozansky homology (for all N) with the knot Floer homology. We argue that this unification should be accomplished by a triply graded homology theory which categorifies the HOMFLY polynomial. Moreover, this theory should have an additional formal structure of a family of differentials. Roughly speaking, the triply graded theory by itself captures the large N behavior of the sl(N) homology, and differentials capture non-stable behavior for small N, including knot Floer homology. The differentials themselves should come from another variant of sl(N) homology, namely the deformations of it studied by Gornik, building on work of Lee. While we do not give a mathematical definition of the triply graded theory, the rich formal structure we propose is powerful enough to make many non-trivial predictions about the existing knot homologies that can then be checked directly. We include many examples where we can exhibit a likely candidate for the triply graded theory, and these demonstrate the internal consistency of our axioms. We conclude with a detailed study of torus knots, developing a picture which gives new predictions even for the original sl(2) Khovanov homology.Comment: 46 pages, 30 figures. V2: Minor improvements. To appear in Exp. Mat

An integrated aerodynamic/propulsion study for generic aero-space planes based on waverider concepts

The design of a unified aero-space plane based on waverider technology is analyzed. The overall aerodynamic design and performance of an aero-space plane are discussed in terms of the forebody, scramjet, and afterbody. Other subjects considered in the study are combustion/nozzle optimization, the idealized tip-to-tail waverider model, and the two-dimensional minimum length nozzle. Charts and graphs are provided to show the results of the preliminary investigations

On conformal Jordan cells of finite and infinite rank

This work concerns in part the construction of conformal Jordan cells of infinite rank and their reductions to conformal Jordan cells of finite rank. It is also discussed how a procedure similar to Lie algebra contractions may reduce a conformal Jordan cell of finite rank to one of lower rank. A conformal Jordan cell of rank one corresponds to a primary field. This offers a picture in which any finite conformal Jordan cell of a given conformal weight may be obtained from a universal covering cell of the same weight but infinite rank.Comment: 9 pages, LaTeX, v2: typo corrected, comments added, version to be publishe