Ikaite of sediment cores from the Zaire deep-sea fan

Most concentration profiles of sulfate in continental margin sediments show constant or continuously increasing gradients from the benthic boundary layer down to the deep sulfate reduction zone. However, a very marked change in this gradient has been observed several meters below the surface at many locations, which has been attributed to anoxic sulfide oxidation or to non-local transport mechanisms of pore waters. The subject of this study is to investigate whether this feature could be better explained by non-steady state conditions in the pore-water system. To this end, data are presented from two gravity cores recovered from the Zaire deep-sea fan. The sediments at this location can be subdivided into two sections. The upper layer, about 10 m thick, consists of stratified pelagic deposits representing a period of continuous sedimentation over the last 190 kyr. It is underlain by a turbidite sequence measuring several meters in thickness, which contains large crystals of authigenic calcium carbonate (ikaite: CaCO3·6H2O). Ikaite delta13C values are indicative of a methane carbon contribution to the CO2 pool. Radiocarbon ages of these minerals, as well as of the adjacent bulk sediments, provide strong evidence that the pelagic sediments have overthrust the lower section as a coherent block. Therefore, the emplacement of a relatively undisturbed sediment package is postulated. Pore-water profiles show the depth of the sulfate-methane transition zone within the turbiditic sediments. By the adaptation of a simple transport-reaction model, it is shown that the change in the geochemical environmental conditions, resulting from this slide emplacement, and the development towards a new steady state are fully sufficient to explain all features related to the pore-water profiles, particularly, [SO4]2- and dissolved inorganic carbon (DIC). The model shows that the downslope transport took place about 300 yr ago.

Lead 210 concentrations in sediments of the Arabian Sea

In order to evaluate bioturbation in abyssal Arabian-Sea sediments of the Indus fan profiles of 210Pb (half-life: 22.3 yr) and 234Th (half-life: 24.1 d) were measured in cores collected during September and October 1995 and April 1997, respectively. The density and composition of epibenthic megafauna and lebensspuren were determined in vertical seafloor photographs during April 1997. Mean eddy-diffusive mixing coefficients according to the distribution of excess 210Pb ( 210Pb-DB) were 0.072±0.028, 0.068±0.055, 0.373±0.119, 0.037±0.009 and 0.079±0.119 cm**2 yr**-1 in the northern, western, central, eastern and southern abyssal Arabian sea, respectively. Mean eddy-diffusive mixing coefficients according to the distribution of excess 234Th (234Th-DB) were 0.53, 1.64 and 0.47 cm**2 yr**-1 in the northern, western and central abyssal Arabian Sea, respectively. Mobile epibenthic megafauna at the western, northern, central and southern study sites were dominated by ophiuroids, holothurians, ophiuroids and natant decapods (the respective densities were 100, 82, 29 and 6 individuals 1000 m**-2). The northern study site was characterized by a high abundance of spoke traces and fecal casts. The central site showed spoke traces and many tracks. The southern site displayed the highest abundance of spoke traces, whereas at the western site hardly any lebensspuren were observed. There is evidence for at least two functional endmember communities in the Arabian Sea. In the northwestern Arabian Sea (WAST) vertical particle displacement seems to be dominated by macrofauna and primarily eddy-diffusive. In the southern Arabian Sea (SAST) non-local and 'incidental' mixing due to spoke-trace producers might become more important and superimpose reduced eddy-diffusive mixing. With respect to biological data CAST is an intermediate location. Given the biological data, average 210Pb-DB is higher and decimeter-scale variability of 210Pb-DB smaller at CAST than expected. These findings indicate that in a mixture of both endmember communities the organisms may interact in way that increases values of biodiffusivity, as reflected by 210Pb-DB, and reduces decimeter-scale 210Pb-DB heterogeneity in comparison to the simple sum of the isolated effects of the endmembers. For time scales <100 years there was no evidence for a relationship between food supply (POC flux) and bioturbation intensity, as reflected by 210Pb-DB and 234Th-DB. Bioturbation intensity should be controlled primarily by the composition of the benthic fauna, its specific adaptation to the environmental setting, and the abundance of each species of the benthic community. Food supply can have only an indirect influence on bioturbation intensity. In certain parts of the ocean the a priori overall positive relationship between POC flux and biodiffusivity might include restricted intervals displaying no or even negative relations.

Biogenic silica and silicic acid benthic fluxes of a North-eastern Atlantic Abyssal Locality

Within the framework of the EU-funded BENGAL programme, the effects of seasonality on biogenic silica early diagenesis have been studied at the Porcupine Abyssal Plain (PAP), an abyssal locality located in the northeast Atlantic Ocean. Nine cruises were carried out between August 1996 and August 1998. Silicic acid (DSi) increased downward from 46.2 to 213 µM (mean of 27 profiles). Biogenic silica (BSi) decreased from ca. 2% near the sediment-water interface to <1% at depth. Benthic silicic acid fluxes as measured from benthic chambers were close to those estimated from non-linear DSi porewater gradients. Some 90% of the dissolution occurred within the top 5.5 cm of the sediment column, rather than at the sediment-water interface and the annual DSi efflux was close to 0.057 mol Si/m**2/yr. Biogenic silica accumulation was close to 0.008 mol Si/m**2/yr and the annual opal delivery reconstructed from sedimentary fluxes, assuming steady state, was 0.065 mol Si/m**2/yr. This is in good agreement with the mean annual opal flux determined from sediment trap samples, averaged over the last decade (0.062 mol Si/m**2/yr). Thus ca. 12% of the opal flux delivered to the seafloor get preserved in the sediments. A simple comparison between the sedimentation rate and the dissolution rate in the uppermost 5.5 cm of the sediment column suggests that there should be no accumulation of opal in PAP sediments. However, by combining the BENGAL high sampling frequency with our experimental results on BSi dissolution, we conclude that non-steady state processes associated with the seasonal deposition of fresh biogenic particles may well play a fundamental role in the preservation of BSi in these sediments. This comes about though the way seasonal variability affects the quality of the biogenic matter reaching the seafloor. Hence it influences the intrinsic dissolution properties of the opal at the seafloor and also the part played by non-local mixing events by ensuring the rapid transport of BSi particles deep into the sediment to where saturation is reached.

Mobilities, Entanglements, Transformations. Outline of a Research Project on Pottery Practices in Neolithic Wetland Sites of the Swiss Plateau

A large number of later Neolithic sites (3900–3500BC) in Switzerland, Southern Germany and Eastern France offer outstandingly well preserved archaeological materials from cultural layers. Due to the wide use of dendrochronology, settlement remains and artefact assemblages can now be placed into a precise and fixed chronological framework, thus presenting a unique case within prehistoric archaeology. In earlier research, chronological and regional units were constructed on the basis of pottery. These spacial and temporal units of typical pottery sets were understood as Neolithic cultures, as culturally more or less homogenous entities connected with (ethnic) identities. Today, with a larger data corpus of excavated settlements at hand, we can begin to understand that this period of the past was in fact characterised by a multitude of cultural entanglements and transformations. This is indicated by the occurrence of local and non-local pottery styles in one and the same settlement: for example typically local Cortaillod pottery is found together with NMB-styled pottery in settlements at Lake Neuchâtel or Michelsberg pottery is regularly occurring in settlements at Lake Constance where Pfyn pottery style is the typical local one. These and many more examples show that there must have been complex entanglements of social ties expanding between Eastern France, Southern Germany and the Swiss Plateau. Given these circumstances the former notions of Neolithic culture should be critically revised. Therefore, in late 2014, the Prehistoric Archaeology Department at the Archaeological Institute of University of Berne started a four-year research project funded by Swiss National Science Foundation in late 2014: ‘Mobilities, Entanglements and Transformations in Neolithic Societies of the Swiss Plateau (3900-3500 BC)’. It’s objective is to address the topic sketched above by adopting a mixed methods research (MMR)-design combining qualitative and quantitative approaches from archaeology and archaeometry. The approach is theoretically based on Pierre Bourdieu’s reflexive sociology and his concept of habitus but includes further concepts of practice theories. By shifting the focus to the movement of people, ideas and things – to pottery production practices in contexts of mobility – a deeper understanding of the transformative capacities of encounters can be achieved. This opens the path for new insights of Neolithic societies including social, cultural and economic dynamics that were underestimated in former research.

Optimized edge appearance probability for cooperative localization based on tree-reweighted nonparametric belief propagation

Nonparametric belief propagation (NBP) is a well-known particle-based method for distributed inference in wireless networks. NBP has a large number of applications, including cooperative localization. However, in loopy networks NBP suffers from similar problems as standard BP, such as over-confident beliefs and possible nonconvergence. Tree-reweighted NBP (TRW-NBP) can mitigate these problems, but does not easily lead to a distributed implementation due to the non-local nature of the required so-called edge appearance probabilities. In this paper, we propose a variation of TRWNBP, suitable for cooperative localization in wireless networks. Our algorithm uses a fixed edge appearance probability for every edge, and can outperform standard NBP in dense wireless networks.

A Video-Aware FEC-Based Unequal Loss Protection Scheme for RTP Video Streaming

A video-aware unequal loss protection (ULP) system for protecting RTP video streaming in bursty packet loss networks is proposed. Just considering the relevance of the frame, the state of the channel and the bitrate constraints of the protection bitstream, our algorithm selects in real time the most suitable frames to be protected through forward error correction (FEC) techniques. It benefits from a wise RTP encapsulation that allows working at a frame level without requiring any further process than that of parsing RTP headers, so it is perfectly suitable to be included in commercial transmitters. The simulation results show how our proposed ULP technique outperforms non-smart schemes.

Discernment of bee pollen loads using computer vision and one-class classification techniques

In this paper, we propose a system for authenticating local bee pollen against fraudulent samples using image processing and classification techniques. Our system is based on the colour properties of bee pollen loads and the use of one-class classifiers to reject unknown pollen samples. The latter classification techniques allow us to tackle the major difficulty of the problem, the existence of many possible fraudulent pollen types. Also presented is a multi-classifier model with an ambiguity discovery process to fuse the output of the one-class classifiers. The method is validated by authenticating Spanish bee pollen types, the overall accuracy of the final system of being 94%. Therefore, the system is able to rapidly reject the non-local pollen samples with inexpensive hardware and without the need to send the product to the laboratory.

Analysis of the influence of the plasma thermodynamic regime in the spectrally resolved and mean radiative opacity calculations of carbon plasmas in a wide range of density and temperature

In this work the spectrally resolved, multigroup and mean radiative opacities of carbon plasmas are calculated for a wide range of plasma conditions which cover situations where corona, local thermodynamic and non-local thermodynamic equilibrium regimes are found. An analysis of the influence of the thermodynamic regime on these magnitudes is also carried out by means of comparisons of the results obtained from collisional-radiative, corona or Saha–Boltzmann equations. All the calculations presented in this work were performed using ABAKO/RAPCAL code.

Asymptotic stability of a mathematical model of cell population

We consider a simplified system of a growing colony of cells described as a free boundary problem. The system consists of two hyperbolic equations of first order coupled to an ODE to describe the behavior of the boundary. The system for cell populations includes non-local terms of integral type in the coefficients. By introducing a comparison with solutions of an ODE's system, we show that there exists a unique homogeneous steady state which is globally asymptotically stable for a range of parameters under the assumption of radially symmetric initial data.

On a mathematical model of tumor growth based on cancer stem cells

We consider a simple mathematical model of tumor growth based on cancer stem cells. The model consists of four hyperbolic equations of first order to describe the evolution of different subpopulations of cells: cancer stem cells, progenitor cells, differentiated cells and dead cells. A fifth equation is introduced to model the evolution of the moving boundary. The system includes non-local terms of integral type in the coefficients. Under some restrictions in the parameters we show that there exists a unique homogeneous steady state which is stable.

A gradient-enhanced large-deformation continuum damage model for fibre-reinforced materials

A non-local gradient-based damage formulation within a geometrically non-linear setting is presented. The hyperelastic constitutive response at local material point level is governed by a strain energy which is additively composed of an isotropic matrix and of an anisotropic fibre-reinforced material, respectively. The inelastic constitutive response is governed by a scalar [1–d]-type damage formulation, where only the anisotropic elastic part is assumed to be affected by the damage. Following the concept in Dimitrijević and Hackl [28], the local free energy function is enhanced by a gradient-term. This term essentially contains the gradient of the non-local damage variable which, itself, is introduced as an additional independent variable. In order to guarantee the equivalence between the local and non-local damage variable, a penalisation term is incorporated within the free energy function. Based on the principle of minimum total potential energy, a coupled system of Euler–Lagrange equations, i.e., the balance of linear momentum and the balance of the non-local damage field, is obtained and solved in weak form. The resulting coupled, highly non-linear system of equations is symmetric and can conveniently be solved by a standard incremental-iterative Newton–Raphson-type solution scheme. Several three-dimensional displacement- and force-driven boundary value problems—partially motivated by biomechanical application—highlight the mesh-objective characteristics and constitutive properties of the model and illustratively underline the capabilities of the formulation proposed

A gradient-enhanced continuum damage model with application to fibre-reinforced tissues at finite strains

A non-local gradient-based damage formulation within a geometrically non-linear set- ting is presented. The hyperelastic constitutive response at local material point level is governed by a strain energy function which is additively composed by an isotropic neo-Hookean matrix and by an anisotropic fibre-reinforced material based on the model proposed by T. Gasser, R. Ogden, and G. Holzapfel.

Electronic structure and transport properties of atomic NiO spinvalves

Ab initio quantum transport calculations show that short NiO chains suspended in Ni nanocontacts present a very strong spin-polarization of the conductance.The generalized gradient approximation we use here predicts a similar polarization of the conductance as the one previously computed with non-local exchange, confirming the robustness of the result. Their use as nanoscopic spinvalves is proposed.

Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries

Context. Classical supergiant X-ray binaries (SGXBs) and supergiant fast X-ray transients (SFXTs) are two types of high-mass X-ray binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors’ stellar wind can provide the required information to accomplish an adequate test of these theories. However, such analyses are scarce. Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J17544-2619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 ± 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e< 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (ν∞ = 1500 km s-1 in IGR J17544-2619 and ν∞ = 700 km s-1 in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.

Pollen profiles from a Late Palaeolithic site in the community of Bad Buchau-Kappel, Baden-Wuerttemberg, Germany

Excavations were carried out in a Late Palaeolithic site in the community of Bad Buchau-Kappel between 2003 and 2007. Archaeological investigations covered a total of more than 200 m**2. This site is the product of what likely were multiple occupations that occurred during the Late Glacial on the Federsee shore in this location. The site is situated on a mineral ridge that projected into the former Late Glacial lake Federsee. This beach ridge consists of deposits of fine to coarse gravel and sand and was surrounded by open water, except for a connection to the solid shore on the south. A lagoon lay between the hook-shaped ridge and the shore of the Federsee. This exposed location provided optimal access to the water of the lake. In addition, the small lagoon may have served as a natural harbor for landing boats or canoes. Sedimentological and palynological investigations document the dynamic history of the location between 14,500 and 11,600 years before present (cal BP). Evidence of the deposition of sands, gravels and muds since the Bølling Interstadial is provided by stratigraphic and palynological analyses. The major occupation occurred in the second half of the Younger Dryas period. Most of the finds were located on or in the sediments of the ridge; fewer finds occurred in the surrounding mud, which was also deposited during the Younger Dryas. Direct dates on some bone fragments, however, demonstrate that intermittent sporadic occupations also took place during the two millennia of the Meiendorf, Bølling, and Allerød Interstadials. These bones were reworked during the Younger Dryas and redeposited in the mud. A 14C date from one bone of 11,600 years ago (cal BP) places the Late Palaeolithic occupation of the ridge at the very end of the Younger Dryas, which is in agreement with stratigraphic observations. Stone artifacts, numbering 3,281, comprise the majority of finds from the site. These include typical artifacts of the Late Palaeolithic, such as backed points, short scrapers, and small burins. There are no bipointes or Malaurie-Points, which is in accord with the absolute date of the occupation. A majority of the artifacts are made from a brown chert that is obtainable a few kilometers north of the site in sediments of the Graupensandrinne. Other raw materials include red and green radiolarite that occur in the fluvioglacial gravels of Oberschwaben, as well as quartzite and lydite. The only non-local material present is a few artifacts of tabular chert from the region near Kelheim in Bavaria. A unique find consists of two fragments of a double-barbed harpoon made of red deer antler, which was found in the Younger Dryas mud. It is likely, but not certain, that this find belongs to the same assemblage as the numerous stone artifacts. Although not numerous, animal bones were also found in the excavations. Most of them lay in sediments of the Younger Dryas, but several 14C dates place some of these bones in earlier periods, including the Meiendorf, Bølling, and Allerød Interstadials. These bones were reworked by water and redeposited in mud sediments during the Younger Dryas. As a result, it is difficult to attribute individual bones to particular chronological positions without exact dates. Species that could be identified include wild horse (Equus spec.), moose or elk (Alces alces), red deer (Cervus elaphus), roe deer (Capreolus capreolus), aurochs or bison (Bos spec.), wild boar (Sus scrofa), as well as birds and fish, including pike (Esox Lucius).