A new peat bog testate amoeba transfer function and quantitative palaeohydrological reconstructions from southern Patagonia

Testate amoebae have been extensively used as proxies for environmental change and palaeoclimate reconstructions in European and North American peatlands. The presence of these micro-organisms near the peat surface is generally significantly linked to the local water table depth (WTD) and therefore preservation of the amoeba shells downcore allows for water table reconstructions over millennia. In the last decades, attention for the palaeoecology of the southern Patagonian peat bogs has increased, partly because of the particular climatological setting under the influence of the southern westerlies. These atypical peat bogs are characterised by a wide range of water tables, from wet hollows to hummocks exceeding 100 cm above the water table, and a dominance of Sphagnum magellanicum on low lawns up to the highest hummocks. Here we present the first transfer function for this region that allows for reliable WTD reconstructions, along with 2k-year palaeorecords from local peat bogs.A modern dataset (155 samples) was sampled along transects from five bogs in 2012 and 2013. Measurements of WTD, pH and conductivity were taken for all samples. Transfer function model was based on the 2012 dataset while the 2013 samples served as an independent test set to validate the model. Besides the standard leave-one- out cross-validation we applied leave-one-site-out and leave-one transect-out cross-validation, which are effective means of verifying the degree of clustering in the dataset. To assure the environmental gradient had been evenly sampled we quantified the root-mean-squared error of prediction (RMSEP) individually for segments of this gradient.Ordinations showed a clear hydrological gradient in amoeba assemblages, with the dominant Assulina muscorum at the dry end and Amphitrema wrightianum and Difflugia globulosa at the wet end. Taxa as Nebela certesi and Nebela cockayni, possibly exclusive to the southern hemisphere, were identified and their optima and tolerances were determined. Canonical correspondence analysis showed that WTD was the most important environmental variable, accounting for 18% of the variance in amoeba assemblages. A weighted averaging-partial least squares model showed best performance in cross-validation and using the 2013 data as an independent test set. Any spatial autocorrelation was minimal although the model still appeared less effective in predicting WTD for sites not included in the training set. The segment-wise RMSEP showed that the WTD gradient was generally evenly sampled with RMSEP below 15 cm for most of the gradient, much lower than the standard deviation of the mean of all WTDs (26 cm).Preliminary results from peat cores sampled from the same peat bogs show surprisingly stable water tables over the last 2k years in Andorra bog but more variation in nearby Tierra Australis bog. Peat accumulation rates in Andorra bog are among the highest recorded in temperate bogs with around 4 m of peat accumulated during the last 2000 year

Age and Grip Strength Predict Hand Dexterity in Adults.

In the scientific literature, there is much evidence of a relationship between age and dexterity, where increased age is related to slower, less nimble and less smooth, less coordinated and less controlled performances. While some suggest that the relationship is a direct consequence of reduced muscle strength associated to increased age, there is a lack of research that has systematically investigated the relationships between age, strength and hand dexterity. Therefore, the aim of this study was to examine the associations between age, grip strength and dexterity. 107 adults (range 18-93 years) completed a series of hand dexterity tasks (i.e. steadiness, line tracking, aiming, and tapping) and a test of maximal grip strength. We performed three phases of analyses. Firstly, we evaluated the simple relationships between pairs of variables; replicating the existing literature; and found significant relationships of increased age and reduced strength; increased age and reduced dexterity, and; reduced strength and reduced dexterity. Secondly, we used standard Multiple Regression (MR) models to determine which of the age and strength factors accounted for the greater variance in dexterity. The results showed that both age and strength made significant contributions to the data variance, but that age explained more of the variance in steadiness and line tracking dexterity, whereas strength explained more of the variance in aiming and tapping dexterity. In a third phase of analysis, we used MR analyses to show an interaction between age and strength on steadiness hand dexterity. Simple Slopes posthoc analyses showed that the interaction was explained by the middle to older aged adults showing a relationship between reduced strength and reduced hand steadiness, whereas younger aged adults showed no relationship between strength and steadiness hand dexterity. The results are discussed in terms of how age and grip strength predict different types of hand dexterity in adults

Bimodal granulocyte transit time through the human lung demonstrated by deconvolution analysis

AbstractThe lungs are an important site of granulocyte pooling. The aim of the study is to quantify pulmonary vascular granulocyte transit time using deconvolution analysis, as has previously been performed to measure pulmonary red cell transit time. Granulocyte and red cell studies were performed in separate groups of patients. Both cell types were labelled with Tc-99m, which for granulocyte labelling was complexed with hexamethylpropyleneamine oxime (HMPAO). The red cell impulse response function (IRF) was monoexponential with a median transit time of 4·3 s. The granulocyte IRF was biexponential in 19 of 22 subjects, 18 of whom had systemic inflammation (inflammatory bowel disease, systemic vasculitis or graft-vs-host disease) and four were controls without inflammatory disease. The median transit time of the fast component ranged from 20 to 25 s and of the slow component 120–138 s in the four patient groups. The fraction of cells undergoing slow transit correlated significantly with (a) mean granulocyte transit time and (b) the fraction showing shape change in vitro. We conclude that granulocyte transit time through the pulmonary circulation is bimodal and that shape-changed (activated) cells transit more slowly that non-activated cells. The size of the fraction undergoing slow transit is closely related to mean granulocyte transit time and is an important determinant of the size of the pulmonary vascular granulocyte pool

Representational task formats and problem solving strategies in kinematics and work

Previous studies have reported that students employed different problem solving approaches when presented with the same task structured with different representations. In this study, we explored and compared students’ strategies as they attempted tasks from two topical areas, kinematics and work. Our participants were 19 engineering students taking a calculus-based physics course. The tasks were presented in linguistic, graphical, and symbolic forms and requested either a qualitative solution or a value. The analysis was both qualitative and quantitative in nature focusing principally on the characteristics of the strategies employed as well as the underlying reasoning for their applications. A comparison was also made for the same student’s approach with the same kind of representation across the two topics. Additionally, the participants’ overall strategies across the different tasks, in each topic, were considered. On the whole, we found that the students prefer manipulating equations irrespective of the representational format of the task. They rarely recognized the applicability of a ‘‘qualitative’’ approach to solve the problem although they were aware of the concepts involved. Even when the students included visual representations in their solutions, they seldom used these representations in conjunction with the mathematical part of the problem. Additionally, the students were not consistent in their approach for interpreting and solving problems with the same kind of representation across the two topical areas. The representational format, level of prior knowledge, and familiarity with a topic appeared to influence their strategies, their written responses, and their ability to recognize qualitative ways to attempt a problem. The nature of the solution does not seem to impact the strategies employed to handle the problem

`NMR Crystallization': in-situ NMR techniques for time-resolved monitoring of crystallization processes

Solid-state NMR spectroscopy is a well-established and versatile technique for studying structural and dynamic properties of solids, and there is considerable potential to exploit the power and versatility of solid-state NMR for in-situ studies of chemical processes. However, a number of technical challenges are associated with adapting this technique for in-situ studies, depending on the process of interest. Recently, an in-situ solid-state NMR strategy for monitoring the evolution of crystallization processes has been developed and has proven to be a promising approach for identifying the sequence of distinct solid forms present as a function of time during crystallization from solution, and for the discovery of new polymorphs. The latest development of this technique, called “CLASSIC” NMR, allows simultaneous measurement of both liquid-state and solid-state NMR spectra as a function of time, thus yielding complementary information on the evolution of both the liquid phase and the solid phase during crystallization from solution. This article gives an overview of the range of NMR strategies that are currently available for in-situ studies of crystallization processes, with examples of applications that highlight the potential of these strategies to deepen our understanding of crystallization phenomena

Source of gold in Neoarchean orogenic-type deposits in the North Atlantic Craton, Greenland: Insights for a proto-source of gold in sub-seafloor

Given that gold (Au) mostly remained in the incipient Earth mantle until ca. 3.9–3.8 Ga, a “proto-source” of gold may have been present in the dominantly mafic crust precursor born through first-stage melting of the early Earth mantle. In south-westernmost Greenland, a fragment of the North Atlantic Craton is characterised by greenstone belts comprising mafic volcanic and magmatic rocks, and harzburgite cumulates that were emplaced at ca.3.0 Ga prograde amphibolite-facies metamorphic assemblages and caused local dissolution of arsenopyrite. During this retrograde tectono-metamorphic stage, in gold-rich shear zones, the Re- Os geochronometer in arsenopyrite was reset to a Neoarchean age while invisible gold was liberated and deposited as free gold with 2.66 Ga pyrite (Re-Os isochron ages). The initial Os isotope ratios of Neoarchean arsenopyrite ($^{187}$Os/$^{188}$Os$_{i}$ = 0.13 ± 0.02) and gold-bearing pyrite (0.12 ± 0.02) overlap with the estimated ($^{187}$Os/$^{188}$Os ratio of the Mesoarchean mantle (0.11 ± 0.01) and preclude contribution of radiogenic crustal Os from evolved lithologies in the accretionary arc complex, but instead, favour a local contribution in Os from basaltic rocks and serpentinised harzburgite protoliths by metamorphic fluids. Thus, the ca. 2.66 Ga lode gold mineralisation identified in the North Atlantic Craton may illustrate a gold endowment in shear zones in Earth’s stabilizing continental crust at the time of the 2.75–2.55 Ga Global Gold Event, through metamorphic upgrading of bulk gold which had originally been extracted from the Mesoarchean mantle and concentrated in hydrothermal arsenopyrite deposits in oceanic crust beneath the overall reduced Mesoarchean ocean

Altered functional brain network connectivity and glutamate system function in transgenic mice expressing truncated Disrupted-in-Schizophrenia 1

Considerable evidence implicates DISC1 as a susceptibility gene for multiple psychiatric diseases. DISC1 has been intensively studied at the molecular, cellular and behavioral level, but its role in regulating brain connectivity and brain network function remains unknown. Here, we utilize a set of complementary approaches to assess the functional brain network abnormalities present in mice expressing a truncated Disc1 gene (Disc1tr Hemi mice). Disc1tr Hemi mice exhibited hypometabolism in the prefrontal cortex (PFC) and reticular thalamus along with a reorganization of functional brain network connectivity that included compromised hippocampal–PFC connectivity. Altered hippocampal–PFC connectivity in Disc1tr Hemi mice was confirmed by electrophysiological analysis, with Disc1tr Hemi mice showing a reduced probability of presynaptic neurotransmitter release in the monosynaptic glutamatergic hippocampal CA1–PFC projection. Glutamate system dysfunction in Disc1tr Hemi mice was further supported by the attenuated cerebral metabolic response to the NMDA receptor (NMDAR) antagonist ketamine and decreased hippocampal expression of NMDAR subunits 2A and 2B in these animals. These data show that the Disc1 truncation in Disc1tr Hemi mice induces a range of translationally relevant endophenotypes underpinned by glutamate system dysfunction and altered brain connectivity

Gravity, p-branes and a spacetime counterpart of the Higgs effect

We point out that the worldvolume coordinate functions $\hat{x}^\mu(\xi)$ of a $p$-brane, treated as an independent object interacting with dynamical gravity, are Goldstone fields for spacetime diffeomorphisms gauge symmetry. The presence of this gauge invariance is exhibited by its associated Noether identity, which expresses that the source equations follow from the gravitational equations. We discuss the spacetime counterpart of the Higgs effect and show that a $p$-brane does not carry any local degrees of freedom, extending early known general relativity features. Our considerations are also relevant for brane world scenarios.Comment: 5 pages, RevTeX. v2 (30-IV-03) with additional text and reference

Tracking Black Holes in Numerical Relativity

This work addresses and solves the problem of generically tracking black hole event horizons in computational simulation of black hole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing black hole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon, as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the black hole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary black hole system. In this first such three dimensional analysis, we establish both qualitative and quantitative physics for the asymmetric collision; including: 1. Bounds on the topology of the throat connecting the holes following merger, 2. Time of merger, and 3. Continuous accounting for the surface of section areas of the black hole sources.Comment: 14 pages, 16 figure