12 research outputs found
Recommended from our members
Fall 1979
New Ideas in Tree Care (page 3) \u27Wonder Water\u27 (6) Herbicides: Are They Safe? (9) University of Massachusetts Turfgrass Field Day (10) The Shade Tree Laboratories of Massachusetts--Origin and Public Services (11) Do Pesticides Cause Allergies (14) Federal Noxious Weed Act Funded (18) Your Opinion Please (18
A New Monte Carlo Algorithm for Protein Folding
We demonstrate that the recently proposed pruned-enriched Rosenbluth method
(P. Grassberger, Phys. Rev. E 56 (1997) 3682) leads to extremely efficient
algorithms for the folding of simple model proteins. We test them on several
models for lattice heteropolymers, and compare to published Monte Carlo
studies. In all cases our algorithms are faster than all previous ones, and in
several cases we find new minimal energy states. In addition to ground states,
our algorithms give estimates for the partition sum at finite temperatures.Comment: 4 pages, Latex incl. 3 eps-figs., submitted to Phys. Rev. Lett.,
revised version with changes in the tex
Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF).
International audienceEnergy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations
Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)
Declining Acidic Deposition Begins Reversal of Forest-Soil Acidification in the Northeastern U.S. and Eastern Canada
Decreasing
trends in acidic deposition levels over the past several
decades have led to partial chemical recovery of surface waters. However,
depletion of soil Ca from acidic deposition has slowed surface water
recovery and led to the impairment of both aquatic and terrestrial
ecosystems. Nevertheless, documentation of acidic deposition effects
on soils has been limited, and little is known regarding soil responses
to ongoing acidic deposition decreases. In this study, resampling
of soils in eastern Canada and the northeastern U.S. was done at 27
sites exposed to reductions in wet SO<sub>4</sub><sup>2–</sup> deposition of 5.7–76%, over intervals of 8–24 y. Decreases
of exchangeable Al in the O horizon and increases in pH in the O and
B horizons were seen at most sites. Among all sites, reductions in
SO<sub>4</sub><sup>2–</sup> deposition were positively correlated
with ratios (final sampling/initial sampling) of base saturation (<i>P</i> < 0.01) and negatively correlated with exchangeable
Al ratios (<i>P</i> < 0.05) in the O horizon. However,
base saturation in the B horizon decreased at one-third of the sites,
with no increases. These results are unique in showing that the effects
of acidic deposition on North American soils have begun to reverse