Benefits of a marketing cooperative in transition agriculture: Mórakert purchasing and service co-operative

The paper analyses the potential benefits of marketing cooperatives in Hungary, employing a transaction cost economics framework. We found that the purchased quantity, the existence of contracts, flexibility and trust are the most important factors farmers consider when selling their products via a cooperative. The most striking result is that diversification has positive influences on the share of cooperatives in farmers’ sale. Furthermore, farmers with larger bargaining power have less willingness to sell their product to the cooperative. Surprisingly, asset specificity has rather negative effects on the share of cooperatives in members’ sales

The [4+2]‐Cycloaddition of α‐Nitrosoalkenes with Thiochalcones as a Prototype of Periselective Hetero‐Diels–Alder Reactions—Experimental and Computational Studies

The [4+2]‐cycloadditions of α‐nitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styryl‐substituted 4H‐1,5,2‐oxathiazines in moderate to good yields. Of the eight conceivable hetero‐Diels–Alder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the α‐nitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bis‐heterocyclic [4+2]‐cycloadducts. The experiments are supported by high‐level DFT calculations that were also extended to related hetero‐Diels–Alder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2‐dithiin and 2H‐thiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process

The 8Li Calibration Source for the Sudbury Neutrino Obervatory

A calibration source employing 8Li (t_1/2 = 0.838s) has been developed for use with the Sudbury Neutrino Observatory (SNO). This source creates a spectrum of beta particles with an energy range similar to that of the SNO 8B solar neutrino signal. The source is used to test the SNO detector's energy response, position reconstruction and data reduction algorithms. The 8Li isotope is created using a deuterium-tritium neutron generator in conjunction with a 11B target, and is carried to a decay chamber using a gas/aerosol transport system. The decay chamber detects prompt alpha particles by gas scintillation in coincidence with the beta particles which exit through a thin stainless steel wall. A description is given of the production, transport, and tagging techniques along with a discussion of the performance and application of the source.Comment: 11 pages plus 9 figures, Sumbitted to Nuclear Instruments and Methods

Chaotic flow and efficient mixing in a micro-channel with a polymer solution

Microscopic flows are almost universally linear, laminar and stationary because Reynolds number, $Re$, is usually very small. That impedes mixing in micro-fluidic devices, which sometimes limits their performance. Here we show that truly chaotic flow can be generated in a smooth micro-channel of a uniform width at arbitrarily low $Re$, if a small amount of flexible polymers is added to the working liquid. The chaotic flow regime is characterized by randomly fluctuating three-dimensional velocity field and significant growth of the flow resistance. Although the size of the polymer molecules extended in the flow may become comparable with the micro-channel width, the flow behavior is fully compatible with that in a table-top channel in the regime of elastic turbulence. The chaotic flow leads to quite efficient mixing, which is almost diffusion independent. For macromolecules, mixing time in this microscopic flow can be three to four orders of magnitude shorter than due to molecular diffusion.Comment: 8 pages,7 figure

Chemical sensitivity to the ratio of the cosmic-ray ionization rates of He and H2 in dense clouds

Aim: To determine whether or not gas-phase chemical models with homogeneous and time-independent physical conditions explain the many observed molecular abundances in astrophysical sources, it is crucial to estimate the uncertainties in the calculated abundances and compare them with the observed abundances and their uncertainties. Non linear amplification of the error and bifurcation may limit the applicability of chemical models. Here we study such effects on dense cloud chemistry. Method: Using a previously studied approach to uncertainties based on the representation of rate coefficient errors as log normal distributions, we attempted to apply our approach using as input a variety of different elemental abundances from those studied previously. In this approach, all rate coefficients are varied randomly within their log normal (Gaussian) distribution, and the time-dependent chemistry calculated anew many times so as to obtain good statistics for the uncertainties in the calculated abundances. Results: Starting with so-called ``high-metal'' elemental abundances, we found bimodal rather than Gaussian like distributions for the abundances of many species and traced these strange distributions to an extreme sensitivity of the system to changes in the ratio of the cosmic ray ionization rate zeta\_He for He and that for molecular hydrogen zeta\_H2. The sensitivity can be so extreme as to cause a region of bistability, which was subsequently found to be more extensive for another choice of elemental abundances. To the best of our knowledge, the bistable solutions found in this way are the same as found previously by other authors, but it is best to think of the ratio zeta\_He/zeta\_H2 as a control parameter perpendicular to the ''standard'' control parameter zeta/n\_H.Comment: Accepted for publicatio

Magnetic moments of W 5d in Ca2CrWO6 and Sr2CrWO6 double perovskites

We have investigated the magnetic moment of the W ion in the ferrimagnetic double perovskites Sr2CrWO6 and Ca2CrWO6 by X-ray magnetic circular dichroism (XMCD) at the W L(2,3) edges. In both compounds a finite negative spin and positive orbital magnetic moment was detected. The experimental results are in good agreement with band-structure calculations for (Sr/Ca)2CrWO6 using the full-potential linear muffin-tin orbital method. It is remarkable, that the magnetic ordering temperature, TC, is correlated with the magnetic moment at the 'non-magnetic' W atom.Comment: accepted for publicatio

Multiscale Simulation of History Dependent Flow in Polymer Melt

We have developed a new multiscale simulation technique to investigate history-dependent flow behavior of entangled polymer melt, using a smoothed particle hydrodynamics simulation with microscopic simulators that account for the dynamics of entangled polymers acting on each fluid element. The multiscale simulation technique is applied to entangled polymer melt flow around a circular obstacle in a two-dimensional periodic system. It is found that the strain-rate history-dependent stress of the entangled polymer melt affects its flow behavior, and the memory in the stress causes nonlinear behavior even in the regions where ${\rm Wi} \le 1$. The spatial distribution of the entanglements $$ is also investigated. The slightly low entanglement region is observed around the obstacle and is found to be broaden in the downstream region.Comment: 4 pages, 3 figure

CN and HCN in Dense Interstellar Clouds

We present a theoretical investigation of CN and HCN molecule formation in dense interstellar clouds. We study the gas-phase CN and HCN production efficiencies from the outer photon-dominated regions (PDRs) into the opaque cosmic-ray dominated cores. We calculate the equilibrium densities of CN and HCN, and of the associated species C+, C, and CO, as functions of the far-ultraviolet (FUV) optical depth. We consider isothermal gas at 50 K, with hydrogen particle densities from 10^2 to 10^6 cm^-3. We study clouds that are exposed to FUV fields with intensities 20 to 2*10^5 times the mean interstellar FUV intensity. We assume cosmic-ray H2 ionization rates ranging from 5*10^-17 s^-1, to an enhanced value of 5*10^-16 s^-1. We also examine the sensitivity of the density profiles to the gas-phase sulfur abundance.Comment: Accepted for publication in ApJ, 33 pages, 8 figure