Relationship between the timing of seedbed preparation and the efficacy of pre-emergence flaming

The field experiments were conducted in 1995 and 1996. Seedbed preparation was done with a rotary tiller to 15-20 cm depth either 5-7 days prior to sowing of carrot or at the day of sowing. In both cases, flaming was done 8 days after sowing

Overwintering and regrowth of Sonchus arvensis roots in Finland as affected by fragmentation and burial in three different soil types

In this study the effect of root fragmentation, burial depth and soil type on overwintering and regrowth of Sonchus arvensis L. (perennial sow-thistle) was studied

The comparative politics of courts and climate change

Disappointment with international efforts to find legal solutions to climate change has led to the emergence of a new generation of climate policy. This includes the emergence of courts as new ‘battlefields in climate fights’. Cross-national comparative analysis of the United Kingdom, Canada and Australia supplements research that has found that litigation plays an important governance gap-filling role in jurisdictions without comprehensive national-level climate change policies. The inductive research design identifies patterns in climate change litigation. The three countries illustrate the varieties of climate policies, and thus serve as a useful entry point for thinking more generally about the interplay between climate politics and legal mobilisation. To improve theoretical understandings of the role of courts in climate change politics, the range of litigants and the variety of cases brought to courts under the umbrella of the term ‘climate change litigation’ are identified

A dynamical mean-field theory study of stripe order and d-wave superconductivity in the two-dimensional Hubbard model

We use cellular dynamical mean-field theory with extended unit cells to study the ground state of the two-dimensional repulsive Hubbard model at finite doping. We calculate the energy of states with d-wave superconductivity coexisting with spatially uniform magnetic order and find that they are energetically favoured in a large doping region as compared to the uniform solution. We study the spatial form of the superconducting and magnetic order parameters at different doping values.Comment: 11 pages, 6 figure

Neural networks and MIMD-multiprocessors

Two artificial neural network models are compared. They are the Hopfield Neural Network Model and the Sparse Distributed Memory model. Distributed algorithms for both of them are designed and implemented. The run time characteristics of the algorithms are analyzed theoretically and tested in practice. The storage capacities of the networks are compared. Implementations are done using a distributed multiprocessor system

Productivity and job flows: heterogeneity of new hires and continuing jobs in the business cycle

This paper focuses on tenure driven productivity dynamics of a firm-worker match as a potential explanation of "unemployment volatility puzzle". We let new matches and continuing jobs differ by their productivity levels and by their sensitivity to aggregate productivity shocks. As a result, new matches have a higher destruction rate and lower, but more volatile, wages than old matches, as new hires receive technology associated with the latest vintage. Our contribution is to produce model driven stickiness of old jobs’ wages which does not rely on ad hoc assumptions on wage rigidity. In our model, an aggregate productivity shock generates a persistent productivity difference between the two types of matches, creating an incentive to open new productive vacancies and to destroy old matches that are temporarily less productive. The model produces a well behaving Beveridge curve, despite endogenous job destruction, and more volatile vacancies and unemployment, without a need to rely on differing wage setting mechanisms of new and continuing jobs. Price rigidities do not alter the basic mechanism and the transmission of monetary policy shock is very similar to the standard New Keynesian model with search frictions. JEL Classification: E24, E32, J64Beveridge curve, job flows, Matching, monetary policy shock, nominal rigidities, productivity shocks, tenure, vintage structure

Response of Sonchus arvensis to mechanical and cultural weed control

In order to study the biology and physical control of Sonchus arvensis, a 3-year field experiment was established in 2001 at Vihti, southern Finland

Simultaneous Triggered Collapse of the Presolar Dense Cloud Core and Injection of Short-Lived Radioisotopes by a Supernova Shock Wave

Cosmochemical evidence for the existence of short-lived radioisotopes (SLRI) such as $^{26}$Al and $^{60}$Fe at the time of the formation of primitive meteorites requires that these isotopes were synthesized in a massive star and then incorporated into chondrites within $\sim 10^6$ yr. A supernova shock wave has long been hypothesized to have transported the SLRI to the presolar dense cloud core, triggered cloud collapse, and injected the isotopes. Previous numerical calculations have shown that this scenario is plausible when the shock wave and dense cloud core are assumed to be isothermal at $\sim 10$ K, but not when compressional heating to $\sim 1000$ K is assumed. We show here for the first time that when calculated with the FLASH2.5 adaptive mesh refinement (AMR) hydrodynamics code, a 20 km/sec shock wave can indeed trigger the collapse of a 1 $M_\odot$ cloud while simultaneously injecting shock wave isotopes into the collapsing cloud, provided that cooling by molecular species such as H$_2$O, CO$_2$, and H$_2$ is included. These calculations imply that the supernova trigger hypothesis is the most likely mechanism for delivering the SLRI present during the formation of the solar system.Comment: 12 pages, 4 color figures. Astrophysical Journal Letters (in press

Effect of conservation tillage and peat application on weed infestation on a clay soil

Amendment of soil with peat is an attempt to avoid crop yield variation in the transition to conservation tillage, as it improves seedbed conditions and crop growth in drought-sensitive clay soils. Weed infestations were compared in 1999-2000 between the original and peat-amended clay (Typic Cryaquept, very fine, illitic or mixed) under different autumn tillage systems in an oats-barley rotation. In a field experiment, sphagnum peat (H = 4) had been spread (0.02 m 3 m -2 ) on the soil surface in August 1995. Tillage treatments included mouldboard ploughing (to 20 cm) and stubble cultivations of different working depths (8 or 15 cm) and intensity (once or twice). Weed biomass and density were assessed by an area of 1 m 2 per field plot in August 1999-2000 and June 2000. The 1999 season was dry, but soil moisture conditions were more favourable in 2000. Peat application tended to increase the number of volunteer oats and Chenopodium album in 1999, while decreasing Galium spurium biomass. Ploughing significantly increased the abundance of Chenopodium album and Lamium purpureum in barley (Hordeum vulgare) in 1999. Weed infestation was much lower in 2000, and tillage effect on Chenopodium album was minor in oats (Avena sativa). Growth of Lamium purpureum and Fumaria officinalis was stimulated in ploughed soils both years. Intensity and working depth of stubble cultivation had no significant effect on weeds

Managing Sonchus arvensis using mechanical and cultural methods

Perennial sow-thistle (Sonchus arvensis L.) represents an increasing problem in Finland. Options for mechanical and cultural control of S. arvensis were studied in a field experiment on clay soil under organic production. The experiment consisted of different crop sequences: spring cereal (barley, Hordeum vulgare L., in 2001, oats, Avena sativa L., in 2002) with or without inter-row hoeing and/or stubble cultivation, bare fallow, fibre hemp (Cannabis sativa L.), and ley with mowing. In 2003 the entire field was sown to spring wheat. Crop plant and Sonchus shoot density and dry mass prior to cereal harvest and crop yield were assessed. The control effect was rated: bare fallow > ley > cereal with or without inter-row hoeing > poor growth fibre hemp. Bare fallow was an effective but costly way to reduce S. arvensis infestation. Introduction of a regularly mown green fallow or silage ley in the crop rotation is advisable. Mechanical weed control by inter-row hoeing in cereals limits S. arvensis growth. Infestation might also be reduced by stubble cultivation in autumn. When managing S. arvensis using mechanical and cultural methods, appropriate options, including a competitive crop, should be chosen for the specific field and rotation