Effective range function below threshold

We demonstrate that the kernel of the Lippmann-Schwinger equation, associated with interactions consisting of a sum of the Coulomb plus a short range nuclear potential, below threshold becomes degenerate. Taking advantage of this fact, we present a simple method of calculating the effective range function for negative energies. This may be useful in practice since the effective range expansion extrapolated to threshold allows to extract low-energy scattering parameters: the Coulomb-modified scattering length and the effective range.Comment: 14 pages, 1 figur

Wikis, blogs and podcasts: a new generation of Web-based tools for virtual collaborative clinical practice and education

BACKGROUND: We have witnessed a rapid increase in the use of Web-based 'collaborationware' in recent years. These Web 2.0 applications, particularly wikis, blogs and podcasts, have been increasingly adopted by many online health-related professional and educational services. Because of their ease of use and rapidity of deployment, they offer the opportunity for powerful information sharing and ease of collaboration. Wikis are Web sites that can be edited by anyone who has access to them. The word 'blog' is a contraction of 'Web Log' – an online Web journal that can offer a resource rich multimedia environment. Podcasts are repositories of audio and video materials that can be "pushed" to subscribers, even without user intervention. These audio and video files can be downloaded to portable media players that can be taken anywhere, providing the potential for "anytime, anywhere" learning experiences (mobile learning). DISCUSSION: Wikis, blogs and podcasts are all relatively easy to use, which partly accounts for their proliferation. The fact that there are many free and Open Source versions of these tools may also be responsible for their explosive growth. Thus it would be relatively easy to implement any or all within a Health Professions' Educational Environment. Paradoxically, some of their disadvantages also relate to their openness and ease of use. With virtually anybody able to alter, edit or otherwise contribute to the collaborative Web pages, it can be problematic to gauge the reliability and accuracy of such resources. While arguably, the very process of collaboration leads to a Darwinian type 'survival of the fittest' content within a Web page, the veracity of these resources can be assured through careful monitoring, moderation, and operation of the collaborationware in a closed and secure digital environment. Empirical research is still needed to build our pedagogic evidence base about the different aspects of these tools in the context of medical/health education. SUMMARY AND CONCLUSION: If effectively deployed, wikis, blogs and podcasts could offer a way to enhance students', clinicians' and patients' learning experiences, and deepen levels of learners' engagement and collaboration within digital learning environments. Therefore, research should be conducted to determine the best ways to integrate these tools into existing e-Learning programmes for students, health professionals and patients, taking into account the different, but also overlapping, needs of these three audience classes and the opportunities of virtual collaboration between them. Of particular importance is research into novel integrative applications, to serve as the "glue" to bind the different forms of Web-based collaborationware synergistically in order to provide a coherent wholesome learning experience

Warming Can Boost Denitrification Disproportionately Due to Altered Oxygen Dynamics

Background: Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to reduce eutrophication effects. However, potential responses of denitrification to warming are poorly understood. Although several studies have reported increased denitrification rates with rising temperature, the impact of temperature on denitrification seems to vary widely between systems. Methodology/Principal Findings: We explored the effects of warming on denitrification rates using microcosm experiments, field measurements and a simple model approach. Our results suggest that a three degree temperature rise will double denitrification rates. By performing experiments at fixed oxygen concentrations as well as with oxygen concentrations varying freely with temperature, we demonstrate that this strong temperature dependence of denitrification can be explained by a systematic decrease of oxygen concentrations with rising temperature. Warming decreases oxygen concentrations due to reduced solubility, and more importantly, because respiration rates rise more steeply with temperature than photosynthesis. Conclusions/Significance: Our results show that denitrification rates in aquatic ecosystems are strongly temperature dependent, and that this is amplified by the temperature dependencies of photosynthesis and respiration. Our result

Evidence-based Kernels: Fundamental Units of Behavioral Influence

This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior

Towards eco-friendly crop protection: natural deep eutectic solvents and defensive secondary metabolites

Plant science

Half-shell scattering by a screened Coulomb potential

We investigate the physical half-shell T matrix for scattering by a smoothly screened Coulomb potential. In particular, we study the Kowalski-Noyes half-shell extension function Flhs(p;k) in the limit that the screening radius a tends to infinity. For the Coulomb potential the half-shell scattering cross section is a discontinuous (step) function of the off-shell momentum p at the on-shell point p=k. For the screened Coulomb potential (with screening of the Hulthén form, for l=0) we find that the half-shell cross section exhibits almost a step behavior near p=k: Its magnitude varies dramatically in an interval, the width of which is of the order of the inverse screening radius a. We discuss physical implications of this result

Formulas for the δ-shell-plus-Coulomb potential for all partial waves

Closed forms are given for a large number of quantities occurring in the theory of potential scattering in an arbitrary partial-wave state l for the cases (i) the δ-shell potential V(r)=−λR−2δ(r−R), and (ii) the δ-shell plus Coulomb potential. Furthermore, the trajectories of the poles of the total T operator in the complex k plane, with varying complex λ, are investigated in detail for zero, repulsive, and attractive Coulomb force, respectively. Expressions are given for the effective-range parameters, and the Coulomb-modified effective-range parameters, for all l, with application to the NN system, and the Nα system, respectively. The connection between Coulomb-level shifts and effective-range parameters is considered. Improvements on the standard small-shift approximation, which is relatively poor, are suggested

Transmission of stimulus-locked responses in two coupled phase oscillators

A model of two n:m coupled phase oscillators is studied, where both oscillators are subject to random forces, but only one oscillator is repetitively stimulated with a pulsatile stimulus. The focus of the paper is on transmission of transient responses as well as transient synchronization and desynchronization, which are stimulus locked, i.e., tightly time locked to the stimulus. A bistability or multistability of stable synchronized states of the two-phase oscillators (modulo 2pi) occurs due to the n:m coupling. Accordingly, after stimulation the two oscillators may tend to qualitatively different stable states, which leads to a cross-trial (CT) response clustering (i.e., a switching between qualitatively different poststimulus responses across trials) of either one of the oscillators or both. A stochastic CT phase resetting analysis allows one to detect such transient responses and provides a reliable estimation of the transmission time. In contrast, CT averaging (averaging over an ensemble of responses), CT standard deviation, and CT cross correlation fail in studying the transmission of such stimulus-locked responses, even in the simpler case of 1:1 coupling. In particular, even though being used as golden standard for the analysis of evoked responses in medicine and neuroscience, CT averaging typically causes severe artifacts and misinterpretations