Glacial thermohaline circulation states of the northern Atlantic: The compatibility of modelling and observations

We present 3He data froma repeat section across Drake Passage, fromthree sections off the South American continent in the Pacific, at 28?S, 35?S, and 43?S, and fromthree sections in the Atlantic, eastward of the Malvinas, close to 35?W, and near the Greenwich Meridian. In Drake Passage, a distinct high-3He signal is observed that is centered just above the boundary of the Lower and the Upper Circumpolar Deep Water (LCDW, UCDW), and is concentrated towards the northern continental slope. 3He concentrations in the Antarctic Circumpolar Current (ACC) upstream of Drake Passage (World Ocean Circulation Experiment section P19 at 88?W) are markedly lower than those found in Drake Passage, and a regional source of primordial helium in the path of the ACC that might cause the high-3He feature can be ruled out. We explain the feature by addition of high-3He waters present at the 43?S Pacific section. This supports a previous, similar interpretation of a low-salinity anomaly in Drake Passage (Naveira Garabato et al., Deep- Sea Research I 49 (2002) 681), that is strongly related to the high-3He feature. Employing multiparameter water mass analysis (including 3He as a parameter), we find that deep waters as met at the 43?S Pacific section, flowing south along the South American continental slope, contribute substantially to the ACC waters in Drake Passage (fractions exceed 50% locally). Lesser, but laterally more extended contributions are found east of the Malvinas, and still smaller ones are present at 35?W and at the Greenwich Meridian. Using velocity measurements from one of the two Drake Passage sections, we estimate the volume transport of these waters to be 7.071.2 Sv, but the average transport may be somewhat lower as the other realization had a less pronounced signal. The enhanced 3He signature in Drake Passage is essentially confined north of the Polar Front. Further downstreamthe signature crosses this front, to the extent that at 35?W the contributions south and north of it are of similar magnitude. At the same time, the 3He levels north of the front are reduced due to a substantial admixture of low-3He North Atlantic Deep Water, such that 3He becomes highest south of the front. The flow of Southeast Pacific deep slope waters entering the ACC constitutes the predominant exit pathway of the primordial helium released in the deep Pacific, and represents a considerable fraction of the deep water return flow fromthe Pacific into the ACC. Therefore and also because the density range of the added deep slope waters is intermediate between those of UCDW and LCDW, they must be considered a distinct water mass. r 2003 Elsevier Ltd. All rights reserved

Sharing data from clinical trials: the rationale for a controlled access approach.

The move towards increased transparency around clinical trials is welcome. Much focus has been on under-reporting of trials and access to individual patient data to allow independent verification of findings. There are many other good reasons for data sharing from clinical trials. We describe some key issues in data sharing, including the challenges of open access to data. These include issues in consent and disclosure; risks in identification, including self-identification; risks in distorting data to prevent self-identification; and risks in analysis. These risks have led us to develop a controlled access policy, which safeguards the rights of patients entered in our trials, guards the intellectual property rights of the original researchers who designed the trial and collected the data, provides a barrier against unnecessary duplication, and ensures that researchers have the necessary resources and skills to analyse the data

A preliminary investigation into psychophysiological effects of threatening a perceptually embodied rubber hand in healthy human participants

Background and aims: Threatening a perceptually embodied rubber hand with noxious stimuli has been shown to generate levels of anxiety similar to that experienced when a real hand is threatened. The aim of this study was to investigate skin conductance response, self-reported anxiety and the incidence, type and location of sensations when a perceptually embodied rubber was exposed to threatening and non-threatening stimuli. Methods: A repeated measures cross-over design was used whereby 20 participants (>18 years, 14 females) received a threatening (syringe needle) and non-threatening (soft brush) stimulus to a perceptually embodied rubber hand. Perceptual embodiment was achieved using a soft brush to synchronously stroke the participant’s real hand (out of view) and a rubber hand (in view). Then the investigator approached the rubber hand with a syringe needle (threat) or soft brush (non-threat). Results: Repeated measures ANOVA found that approaching the perceptually embodied rubber hand with either stimulus produced statistically significant reductions in the rated intensity of response to the following questions (p<0.01): ‘How strongly does it feel like the rubber hand is yours?’; ‘How strongly does it feel like the rubber hand is part of your body?’; and ‘How strongly does it feel you can move the rubber hand?’. However, there were no statistically significant differences in scores between needle and brush stimuli. Repeated measures ANOVA on skin conductance response found statistically significant effects for experimental Events (baseline; stroking; perceptual embodiment; stimuli approaching rubber hand; stimuli touching rubber hand; p<0.001) but not for Condition (needle versus brush p=0.964) or experimental Event x Condition interaction (p=0.160). Ten of the 20 participants (50%) reported that they experienced a sensation arising from the rubber hand when the rubber hand was approached and touched by either the needle and/or brush but these sensations lacked precision in location, timing, and nature. Conclusion and Implications: Our preliminary findings suggest that the increase in arousal in response to stimuli entering the peripersonal space may not be selective for threat. There was tentative evidence that more intense sensations were experienced when a perceptually embodied rubber hand was approached by a threatening stimulus. Our findings provide initial insights and should serve as a catalyst for further research

Exploring Graphs with Time Constraints by Unreliable Collections of Mobile Robots

A graph environment must be explored by a collection of mobile robots. Some of the robots, a priori unknown, may turn out to be unreliable. The graph is weighted and each node is assigned a deadline. The exploration is successful if each node of the graph is visited before its deadline by a reliable robot. The edge weight corresponds to the time needed by a robot to traverse the edge. Given the number of robots which may crash, is it possible to design an algorithm, which will always guarantee the exploration, independently of the choice of the subset of unreliable robots by the adversary? We find the optimal time, during which the graph may be explored. Our approach permits to find the maximal number of robots, which may turn out to be unreliable, and the graph is still guaranteed to be explored. We concentrate on line graphs and rings, for which we give positive results. We start with the case of the collections involving only reliable robots. We give algorithms finding optimal times needed for exploration when the robots are assigned to fixed initial positions as well as when such starting positions may be determined by the algorithm. We extend our consideration to the case when some number of robots may be unreliable. Our most surprising result is that solving the line exploration problem with robots at given positions, which may involve crash-faulty ones, is NP-hard. The same problem has polynomial solutions for a ring and for the case when the initial robots' positions on the line are arbitrary. The exploration problem is shown to be NP-hard for star graphs, even when the team consists of only two reliable robots

A Genome-Wide Association Study of Neuroticism in a Population-Based Sample

Neuroticism is a moderately heritable personality trait considered to be a risk factor for developing major depression, anxiety disorders and dementia. We performed a genome-wide association study in 2,235 participants drawn from a population-based study of neuroticism, making this the largest association study for neuroticism to date. Neuroticism was measured by the Eysenck Personality Questionnaire. After Quality Control, we analysed 430,000 autosomal SNPs together with an additional 1.2 million SNPs imputed with high quality from the Hap Map CEU samples. We found a very small effect of population stratification, corrected using one principal component, and some cryptic kinship that required no correction. NKAIN2 showed suggestive evidence of association with neuroticism as a main effect (p<10(-6)) and GPC6 showed suggestive evidence for interaction with age (p approximate to 10(-7)). We found support for one previously-reported association (PDE4D), but failed to replicate other recent reports. These results suggest common SNP variation does not strongly influence neuroticism. Our study was powered to detect almost all SNPs explaining at least 2% of heritability, and so our results effectively exclude the existence of loci having a major effect on neuroticism

Testing the adequacy of a single-value Monte Carlo simulation for space-time interaction of crime

The goal of this study is to determine the number of iterations (r) required in a Monte Carlo based space-time interaction analysis of crime data sets, in order to test the adequacy of using a single value of 999 iterations. A case study of burglary crime data sets is presented in which Knox test is used for the analysis of space-time interactions. The outcomes of this analysis demonstrate that the use of a single value, such as 999, does not always represent the most appropriate number of iterations especially when multiple ST neighbourhood sizes are involved. This analysis opens further research opportunities into determining the best strategy to defining the expected distribution in a space-time interaction analysis of crime