Origin of lead in eight Central European peat bogs determined from isotope ratios,strengths, and operation times of regional pollution sources

Lead originating from coal burning, gasoline burning, and ore smelting was identified in 210Pb-dated profiles through eight peat bogs distributed over an area of 60,000 km2. The Sphagnum-dominated bogs were located mainly in mountainous regions of the Czech Republic bordering with Germany, Austria, and Poland. Basal peat 14C-dated at 11,000 years BP had a relatively high 206Pb/207Pb ratio (1.193). Peat deposited around 1800 AD had a lower 206Pb/207Pb ratio of 1.168-1.178, indicating that environmental lead in Central Europe had been largely affected by human activity (smelting) even before the beginning of the Industrial Revolution. Five of the sites exhibited a nearly constant 206Pb/207Pb ratio (1.175) throughout the 19th century, resembling the "anthropogenic baseline" described in Northern Europe (1.17). At all sites, the 206Pb/207Pb ratio of peat decreased at least until 1980; at four sites, a reversal to more radiogenic values (higher 206Pb/207Pb), typical of easing pollution, was observed in the following decade (1980-1990). A time series of annual outputs for 14 different mining districts dispersing lead into the environment has been constructed for the past 200 years. The production of Ag-Pb, coal, and leaded gasoline peaked in 1900, 1980, and 1980, respectively. In contrast to other European countries, no peak in annual Pb accumulation rates was found in 1900, the year of maximum ore smelting. The highest annual Pb accumulation rates in peat were consistent with the highest Pb emission rates from coal-fired power plants and traffic (1980). Although maximum coal and gasoline production coincided in time, their isotope ratios were unique. The mean measured 206Pb/207Pb ratios of local coal, ores, and gasoline were 1.19, 1.16, and 1.11, respectively. A considerable proportion of coal emissions, relative to gasoline emisions, was responsible for the higher 206Pb/207Pb ratios in the recent atmosphere (1.15) compared to Western Europe (1.10). As in West European countries, the gasoline sold in the Czech Republic during the Communist era (1948-1989) contained an admixture of low-radiogenic Precambrian lead from Australia.     

Fiducial optimization for minimal target registration error in image-guided neurosurgery

This paper presents new methods for the optimal selection of anatomical landmarks and optimal placement of fiducial markers in image-guided neurosurgery. These methods allow the surgeon to optimally plan fiducial marker locations on routine diagnostic images before preoperative imaging and to intraoperatively select the set of fiducial markers and anatomical landmarks that minimize the expected target registration error (TRE). The optimization relies on a novel empirical simulation-based TRE estimation method built on actual fiducial localization error (FLE) data. Our methods take the guesswork out of the registration process and can reduce localization error without additional imaging and hardware. Our clinical experiments on five patients who underwent brain surgery with a navigation system show that optimizing one marker location and the anatomical landmarks configuration reduced the TRE. The average TRE values using the usual fiducials setup and using the suggested method were 4.7 mm and 3.2 mm, respectively. We observed a maximum improvement of 4 mm. Reducing the target registration error has the potential to support safer and more accurate minimally invasive neurosurgical procedures.     

Single-path routing for life time maximization in multi-hop wireless networks

Energy-aware routing is important in multi-hop wireless networks that are powered by battery, e.g., wireless sensor networks. To maximize the network survivability, the energy efficiency of paths must be taken into account for route selection. Simple heuristics such as choosing paths with minimal energy consumption are ineffective, because the energy of the nodes on such paths may deplete quickly. The issue is particularly serious for the networks with regular traffic pattern as in monitoring sensor applications. Existing solutions to this issue typically adopt the multi-path routing approach, in which multiple paths are set up between source and destination and one (or all) of the paths is (are) used at a certain moment. However, this approach involves high overhead for establishment and management of multiple paths. In this paper, we present a static single-path routing scheme which uses one energy-efficient path for each communicating peer throughout the network lifetime, eliminating the overhead of multi-path routing. It is theoretically proved that our routing scheme achieves a constant factor approximate of the optimal solution. We compare the performance of the proposed scheme with that of multi-path routing via simulations. Despite the use of single static path, the proposed scheme outperforms existing multi-path routing schemes and produces performance close to the optimal multi-path solution, particularly in heavily loaded networks and multiple-gateway networks.     

Feeling Better About Doing Worse: Social Comparisons Within Romantic Relationships.

The authors examined the role of closeness between self and partner in determining the impact of social comparisons within intimate relationships. To the extent that one's partner is a central aspect of one's identity, one may be able to restore one's positive self-regard following an upward comparison with the partner by turning to the relationship as a self-affirmational resource. Studies 1 and 2 examined reactions to imagined comparisons; Studies 3 and 4 examined reactions to actual comparison feedback. Across studies, closeness moderated the impact of upward comparisons with the partner; that is, higher closeness participants responded to a more successful partner by focusing on their relationship-related strengths. However, closeness did not moderate the impact of downward comparisons with the partner. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Minimizing the expected response time of an idled server on a line

We address the problem of where to locate an idle server in a one-dimensional system where the arrival of demands for service have both spatial and temporal uncertainty. In such a system it is reasonable to have an idle server make an anticipatory move in order to better position itself for the next demand. However, moving all the way to its home base, or even moving at all, might delay the service for a demand which arrives during the move. We develop an analytical model to optimize the destination of an anticipatory move based upon the location of the server. Insights into the impact of system parameters as well as empirical examples are given.     

On the identity of the smallest random variable

We compute and analyze the probability that a particular random variable will assume the smallest value among a set of random variables. This work was motivated by wanting to predict the 'winner' in R&D and patent 'races' Some general results and comparative statics are provided. For symmetric distributions we derive bounds on the probabilities of interest. We compute the probabilities of who will be the smallest (fastest) for normal, lognormal, Weibull, Pareto, binomial and PH-distributions. We also analyze several models of multivariate exponential distributions.     

On the allocation of uncertainty-reduction effort to minimize total variability

Manufacturing processes and projects often consist of a series of activities with uncertain durations. The resulting uncertainty of the process or project impedes planning and disrupts the supply chain. Suppose that the uncertainty of the duration of individual activities can be reduced at a cost. We wish to minimize the variability of the sum of these durations, i.e., the variability of the project's duration. Using mean-preserving transformations, we derive the optimal budget allocation among individual activities for separable and non-separable cost functions, and also explore the implications of statistical dependence on the allocation     

Thick Protective UHTC Coatings for SiC-Based Structures: Process Establishment

A new process to form thick and dense ultra-high-temperature ceramic (UHTC) composite coatings over SiC surfaces is described. Coatings of ZrB₂/SiC/(ZrC) thicker than 100 μm are formed by a reaction-bonded SiC (RBSC) approach based on Si infiltration into ZrB₂/C preform coating. The residual Si, typically found in RBSC, can be eliminated efficiently to provide a coating material that performs at temperatures above 1500°C. The process is performed at 1500°C in Ar at ambient pressure. The interface between the in situ formed SiC and the Zr phases is very tight, as is the interface with the substrate.
The ZrB₂ particles used in this process are rearranged in their morphology and an additional new phase containing Zr–C is formed. The coatings exhibit excellent integrity, hardness, and bonding to the tested substrates. A preliminary oxidation study indicates good protection of substrates at 1500°C under both passive and active oxidation conditions, provided that the coatings have sufficient thickness.     

Encoding morphology in oxide nanostructures during their growth

Programmable control over the overall structure of SnO(2) nanowires grown by vapor-solid synthesis is shown to be possible by pulse modulating the flow rate of the carrier gas in which oxygen (one of the reactants) is entrained. The control is shown to depend on the local oscillation of the supersaturation condition for the SnO vapor (another reactant) in the vicinity of the growing nanostructure. The latter triggers dramatic, reproducible oscillations in the lateral dimensions of the nanostructure and in the direction of its growth. The method provides a means for producing predictable morphological and compositional variations in 1D nanostructures, thereby potentially resulting in a high yield of custom-designed nanostructures.     

Controlled release of propham from plastic granules

Urea–formaldehyde granules containing propham, a volatile herbicide, have been tested in the laboratory as well as in the field as a suitable controlled release system. The advantages of such a system compared to the present commonly used formulas are being demonstrated.