An investigation into the relationship between preceding break crops and weed populations in barley crops in organic ley/arable rotations

This report was presented at the UK Organic Research 2002 Conference. The relationship between weed populations and cereal crops following nine organic break crops was investigated in field trials in Warwickshire, Aberdeenshire and Ceredigion in 2001. Weed biodiversity was high on all sites and varied between sites in terms of species present. Severity of weed infestation differed significantly between sites and between cereals following different break crops. The impact of break crop species on the incidence and severity of the weed burden in the following cereal is discussed in relation to the field trials at the three sites

Incoherent pion photoproduction on the deuteron with polarization observables I: Formal expressions

Formal expressions are developed for the general five-fold differential cross section of incoherent $\pi$-photoproduction on the deuteron including beam and target polarization. The polarization observables of the cross section are described by various beam, target and beam-target asymmetries for polarized photons and/or polarized deuterons. They are given as bilinear hermitean forms in the reaction matrix elements divided by the unpolarized cross section. In addition, the corresponding observables for the semi-exclusive reaction $\vec d(\vec \gamma,\pi)NN$ are also given.Comment: 11 pages, 1 figur

Incoherent single pion electroproduction on the deuteron with polarization effects

Incoherent pion electroproduction on the deuteron is studied from threshold up to the second resonance region with special emphasis on the influence of final state interaction, in particular on polarization observables. The elementary $\gamma N\to\pi N$ amplitude is taken from the MAID-2003 model. Final state interaction is included by considering complete rescattering in the final $NN$ and $\pi N$ subsystems. Their influence on the structure functions governing the semi-exclusive differential cross section, where besides the scattered electron only the produced pion is detected, is investigated in detail. For charged pion-production the effect of $NN$-rescattering is moderate whereas $\pi N$-rescattering is almost negligible, except very close to threshold. $NN$-rescattering appears much stronger in neutral pion production for which the primary mechanism is the elimination of a significant spurious coherent contribution in the impulse approximation. Sizeable effects are also found in some of the polarization structure functions for beam and/or target polarizations.Comment: 20 pages including 14 figure

Psychic Distance and Country Image in Exporter–Importer Relationships

Conflicting evidence on the issue of psychic distance (PD) in international business relationships suggests the existence of misunderstood boundary conditions to its effect. This article argues that country image (CI) is a contingent factor to the effect of PD. Expectancy–value theory provides the theoretical foundations for this argument. Based on structural equation modeling, analyses for a sample of 358 exporter–importer relationships in the global wine industry provide empirical support. Product-related CI mitigates the negative impact of PD on the relational exchange orientation (REO) between firms. Specifically, a high level of PD dampens REO when product-related CI is poor, whereas a strong product-related CI helps firms facing such PD conditions to build REO irrespective. People-related CI has an indirect effect on REO through product-related CI. Our study contributes to explaining the paradox of distance and offers a fresh perspective on how to handle the issue of PD when relevant

Variability of the Centimeter-Submillimeter Spectrum and Polarization of 3C 273 during Outburst

Original article can be found at: http://www.journals.uchicago.edu/ApJ/--Copyright University of Chicago Press/ AASCentimeter to submillimeter total flux and polarization monitoring data are used to investigate the nature of a prominent flare in the quasar 3C 273 during 1995/6. After removal of the quiescent level, the resulting “flare spectra" are well fitted by a simple homogeneous synchrotron source model, which in turn allows the movement of the self-absorption turnover to be tracked during the flare. Both the flare amplitude/time delay relationship and the overall spectral evolution are qualitatively consistent with existing models. The early evolution of the spectrum is best determined and is shown to be in excellent agreement with the Compton stage of the Marscher & Gear shock model. However, the polarization behavior during the flare is different at millimeter and centimeter wavelengths and the observations are difficult to reconcile with a simple transverse shock. They are, however, consistent with a conical shock for which the observed polarization properties vary with distance along the jet. Such variations may be caused, for example, by a change in cone angle owing to disruption caused by the growing component of the magnetic field parallel to the jet axis or by a moderate change in viewing angle.Peer reviewe

Understanding Consumers’ Inferences from Price and Nonprice Information in the Online Lodging Purchase Decision

The sustained success of variable pricing for revenue management (RM) is dependent on the creation of appropriate price points at which to sell a given product offering. To date, few studies have considered the impact of nonprice information on consumer reaction to price, and none have investigated the relative weights that consumers assign to price and the nonprice information available to them during different phases of the purchase choice process. This exploratory study uses a combination of eye tracking and retrospective think-aloud (RTA) interviews to examine how consumers consider the price and nonprice content generated by the firm and the nonprice information generated by other consumers during two distinct phases of the online choice process: browsing and deliberation. This study’s findings suggest that during browsing, firm-generated content appears to be very influential, particularly the image selected to represent the property in search results. Both firm-generated and user-generated content play a role in hotel choice during deliberation, with the interplay among several types of information being an important indication of value for consumers