Mercury and metal(loid) deposition to remote Nova Scotia lakes from both local and distant sources

Kejimkujik National Park, in Nova Scotia, Canada, is a sensitive region for metal(loid) contamination, such as mercury, in part due to long-range atmospheric deposition from global and regional industrial centers. The region is remote from industrial centres, but is downwind of major pollution sources in the Eastern United States and Canada, and historically had numerous gold mining sites. Due to a paucity of long-term atmospheric deposition monitoring in this region, little is known about the response of Kejimkujik lakes to multiple changing global, regional and local atmospheric Hg and metal(loid) sources. Here, we used multiple lake sediment cores to reconstruct anthropogenic depositional fluxes of metal(loid)s of concern for the last ~210years. Results showed that Kejimkujik lake sediments are highly enriched in lead (Pb), antimony (Sb) and tin (Sn), with post-industrial metal(loid) concentrations being >4-fold greater than natural baseline levels (prior to ~1800) and moderately enriched in silver (Ag), bismuth (Bi), cadmium (Cd), copper (Cu), mercury (Hg), rubidium (Rb), tellurium (Te), thallium (Tl), vanadium (V), tungsten (W) and zinc (Zn), with post-industrial metal(loid) concentrations being between 1.5 and 4-fold greater than natural baseline levels (prior to ~1800). Lake sediment core reconstructions of total atmospheric Hg deposition matched well with Hg wet deposition monitoring data from the overlapped period (1997-2010) being 9.1±2.7μg/m²/yr and 7.0±0.7μg/m²/yr respectively. Lakes closest to historic gold mining sites show spikes in Ag, Cd, Sb, Tl, Zn and W during mining periods (~1880 and 1950). Most of the enriched metal(loid)s (EF >1.5) (Ag, Bi, Cu, Hg, Pb, Sb, Sn, V and W) do not appear affected by redox and remobilisation issues. For the other enriched metal(loid)s (EF >1.5) (Cd, Tl, and Zn), remobilisation from upper sediments appears to be occurring within these acidic and DOC rich Kejimkujik lakes.

New experimental platform to study high density laser-compressed matter

We have developed a new experimental platform at the Linac Coherent Light Source (LCLS) which combines simultaneous angularly and spectrally resolved x-ray scattering measurements. This technique offers a new insights on the structural and thermodynamic properties of warm dense matter. The < 50 fs temporal duration of the x-ray pulse provides near instantaneous snapshots of the dynamics of the compression. We present a proof of principle experiment for this platform to characterize a shock-compressed plastic foil. We observe the disappearance of the plastic semi-crystal structure and the formation of a compressed liquid ion-ion correlation peak. The plasma parameters of shock-compressed plastic can be measured as well, but requires an averaging over a few tens of shots.

Effects of different regimens to lower blood pressure on major cardiovascular events in older and younger adults: meta-analysis of randomised trials

OBJECTIVE

To quantify the relative risk reductions achieved with different regimens to lower blood pressure in younger and older adults.

DESIGN

Meta-analyses and meta-regression analyses used to compare the effects on the primary outcome between two age groups (<65 v > or =65 years). Evidence for an interaction between age and the effects of treatment sought by fitting age as a continuous variable and estimating overall effects across trials.

PRIMARY OUTCOME

total major cardiovascular events.

RESULTS

31 trials, with 190 606 participants, were included. The meta-analyses showed no clear difference between age groups in the effects of lowering blood pressure or any difference between the effects of the drug classes on major cardiovascular events (all P> or =0.24). Neither was there any significant interaction between age and treatment when age was fitted as a continuous variable (all P>0.09). The meta-regressions also showed no difference in effects between the two age groups for the outcome of major cardiovascular events (<65 v > or =65; P=0.38).

CONCLUSIONS

Reduction of blood pressure produces benefits in younger (<65 years) and older (> or =65 years) adults, with no strong evidence that protection against major vascular events afforded by different drug classes varies substantially with age.

fMRI study of episodic memory in relapsing-remitting MS: correlation with T2 lesion volume

OBJECTIVE

To determine whether memory loss in patients with multiple sclerosis (MS) results from faulty encoding or retrieval, we correlated extent of T2-weighted lesion involvement with brain activation patterns on fMRI scans obtained while patients performed a verbal episodic memory task.

METHODS

We performed a neurologic examination, neuropsychological testing, and an event-related fMRI scan on 36 patients with relapsing-remitting MS. In addition, we obtained T2-weighted structural MRI scans to measure lesion volume. We performed a regression analysis to examine the association between lesion volume and regional brain activation.

RESULTS

Increasing lesion volume correlated with increasing magnitude of brain activation, primarily in the left frontal and parietal association cortices. Significant correlations of function with lesion volume were primarily observed during the memory retrieval phase of the task.

CONCLUSIONS

These results extend previous fMRI studies in multiple sclerosis (MS) by demonstrating an association between greater disease burden and increased neural recruitment during episodic memory. In addition, the stronger correlations observed between lesion volume and brain activation during retrieval than encoding would suggest that retrieval processes are more affected by MS-related cerebral pathology.