46 research outputs found
Scaling up pro-environmental agricultural practice using agglomeration payments: Proof of concept from an agent-based model
Rates of adoption of pro-environmental practices in agriculture in many parts of the world are low. In some cases, this is attributable to the private costs borne by farmers to adopt these practices, often well in advance of any benefits - public or private - that they may bring. Monetary incentives, such as through payments-for-ecosystem services (PES) programs, may be of assistance, and in this study we examine the potential for a recent innovation (the agglomeration payment) to improve adoption of pro-environmental practice in a rural agricultural context. Agglomeration payments include bonus payments for adoption by neighboring farms, which may help to encourage both compliance with the program they promote as well as the overall diffusion of the program across rural contexts. We develop an abstract agent-based model (ABM) of an agglomeration payment program to encourage adoption of the pro-environment practice of conservation agriculture (CA). We find that agglomeration payments have the potential to improve levels of adoption of pro-environmental practice per program dollar, and may help to reduce required spending on project monitoring and enforcement
Stability of two-component alkali clusters formed on helium nanodroplets
The stability of two-component clusters consisting of light (Na or K) and
heavy (Rb or Cs) alkali atoms formed on helium nanodroplets is studied by
femtosecond laser ionization in combination with mass spectrometry.
Characteristic stability patterns reflecting electron shell-closures are
observed in dependence of the total number of atoms contained in the mixed
clusters. Faster decay of the stability of mixed clusters compared to the pure
light ones as a function of size indicates a destabilizing effect of heavy
alkali atoms on light alkali clusters, presumably due to second order
spin-orbit interaction
Wave packet dynamics of potassium dimers attached to helium nanodroplets
The dynamics of vibrational wave packets excited in K dimers attached to
superfluid helium nanodroplets is investigated by means of femtosecond
pump-probe spectroscopy. The employed resonant three-photon-ionization scheme
is studied in a wide wavelength range and different pathways leading to
K-formation are identified. While the wave packet dynamics of the
electronic ground state is not influenced by the helium environment,
perturbations of the electronically excited states are observed. The latter
reveal a strong time dependence on the timescale 3-8 ps which directly reflects
the dynamics of desorption of K off the helium droplets
Formation and dynamics of van der Waals molecules in buffer-gas traps
We show that weakly bound He-containing van der Waals molecules can be
produced and magnetically trapped in buffer-gas cooling experiments, and
provide a general model for the formation and dynamics of these molecules. Our
analysis shows that, at typical experimental parameters, thermodynamics favors
the formation of van der Waals complexes composed of a helium atom bound to
most open-shell atoms and molecules, and that complex formation occurs quickly
enough to ensure chemical equilibrium. For molecular pairs composed of a He
atom and an S-state atom, the molecular spin is stable during formation,
dissociation, and collisions, and thus these molecules can be magnetically
trapped. Collisional spin relaxations are too slow to affect trap lifetimes.
However, helium-3-containing complexes can change spin due to adiabatic
crossings between trapped and untrapped Zeeman states, mediated by the
anisotropic hyperfine interaction, causing trap loss. We provide a detailed
model for Ag3He molecules, using ab initio calculation of Ag-He interaction
potentials and spin interactions, quantum scattering theory, and direct Monte
Carlo simulations to describe formation and spin relaxation in this system. The
calculated rate of spin-change agrees quantitatively with experimental
observations, providing indirect evidence for molecular formation in
buffer-gas-cooled magnetic traps.Comment: 20 pages, 13 figure
Increased Serum and Musculotendinous Fibrogenic Proteins following Persistent Low-Grade Inflammation in a Rat Model of Long-Term Upper Extremity Overuse.
We examined the relationship between grip strength declines and muscle-tendon responses induced by long-term performance of a high-repetition, low-force (HRLF) reaching task in rats. We hypothesized that grip strength declines would correlate with inflammation, fibrosis and degradation in flexor digitorum muscles and tendons. Grip strength declined after training, and further in weeks 18 and 24, in reach limbs of HRLF rats. Flexor digitorum tissues of reach limbs showed low-grade increases in inflammatory cytokines: IL-1ÎČ after training and in week 18, IL-1α in week 18, TNF-α and IL-6 after training and in week 24, and IL-10 in week 24, with greater increases in tendons than muscles. Similar cytokine increases were detected in serum with HRLF: IL-1α and IL-10 in week 18, and TNF-α and IL-6 in week 24. Grip strength correlated inversely with IL-6 in muscles, tendons and serum, and TNF-α in muscles and serum. Four fibrogenic proteins, TGFB1, CTGF, PDGFab and PDGFbb, and hydroxyproline, a marker of collagen synthesis, increased in serum in HRLF weeks 18 or 24, concomitant with epitendon thickening, increased muscle and tendon TGFB1 and CTGF. A collagenolytic gelatinase, MMP2, increased by week 18 in serum, tendons and muscles of HRLF rats. Grip strength correlated inversely with TGFB1 in muscles, tendons and serum; with CTGF-immunoreactive fibroblasts in tendons; and with MMP2 in tendons and serum. Thus, motor declines correlated with low-grade systemic and musculotendinous inflammation throughout task performance, and increased fibrogenic and degradative proteins with prolonged task performance. Serum TNF-α, IL-6, TGFB1, CTGF and MMP2 may serve as serum biomarkers of work-related musculoskeletal disorders, although further studies in humans are needed
Salud de los trabajadores
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