Miracle-dz/UniFAR-FTUs huggingface dataset:
A dual origin for the hydrothermal component in a metalliferous sediment core from the Mid-Atlantic Ridge

A highly metalliferous sediment core collected from TAG, 26°N Mid-Atlantic Ridge has been analyzed for uranium series isotopes, rare earth elements (REE), and radiogenic isotopes. Two types of deposition of hydrothermal material have been identified and characterized. The first is sulfide material which has been rapidly deposited and is sometimes clearly turbiditic. This material exhibits high U/Fe and Eu/Sm ratios and low 230Th/Fe and REE/Fe ratios. It is proposed that U is incorporated into the sulfides by diffusion through the oxidized coating with reductive fixation near the sulfide/oxide boundary. The second hydrothermal component is particulate fallout from the neutrally buoyant plume which is diluted by the background pelagic sedimentation. This component exhibits U/Fe ratios around 2 × 10−5, an order of magnitude greater than reported plume particulate levels, but the 230Th/Fe, REE/Fe and Eu/Sm ratios are similar to plume values. Nd and Pb isotopes have been used to differentiate the hydrothermal and pelagic end-members within this sediment core.
The eclogite to garnetite transition — Experimental and thermodynamic constraints

We have found that the forms of the experimentally determined phase diagrams for pyroxene-garnet transformations require the volume changes for these reactions to be much smaller at 130 kbar (400 km) than at 1 atm. Using these . volume data we calculated the width of the eclogite-garnetite transition in natural quartz tholeiite and alkali olivine basalt compo- sitions taking account of mixing in multicom- ponent pyroxene and garnet phases. We find that the eclogite-garnetite transition does not exhi- bit any discontinuity in bulk sound velocity in the pressure range 110 to 230 kbar. In addition, this velocity, when plotted as a function of pressure, possesses a curvature which is in the opposite sense to that given by the Preliminary Reference Earth Model (PREM). This phase transi- tion, therefore, does not appear to be a satis- factory model for the 400 km seismic discon- tinuity.
On Why Thylakoids Energize Atp Formation Using Either Delocalized or Localized Proton Gradients – a Ca 2+ + + Mediated Role in Thylakoid Stress Responses

By the early 1970s, the chemiosmotic hypothesis of Peter Mitchell was widely accepted by bioenergetics researchers as the best conceptual scheme to explain how ATP is formed in oxidative and photosynthetic phosphorylation. At about the same time, however, work from a few laboratories suggested that some aspects of that elegant, relatively simple hypothesis required revision – not abandonment, but refinement to accommodate more complex movements of protons in the ATP formation mechanism than originally envisioned by Peter Mitchell. In some situations it appeared that protons were constrained to localized domains rather than always delocalized within an enclosed vesicle as envisioned by chemiosmosis. This minireview tells that story from my perspective, as one of the researchers involved in the experimental approaches that revealed more complex energy coupling proton flux patterns. Ionic conditions during isolated thylakoid storage were found to reversibly switch the˜µ H + gradient driving ATP formation between delocalized and localized energy coupling modes. Thylakoid accessible Ca 2+ ions proved to be the switching factor that was responding to the ionic conditions in the storage treatment. The mechanism of Ca 2+ was at least partially demystified when it was shown that the reversible switching betweeñ µ H + energy coupling modes involved Ca 2+ interactions with the 8 kDa CF 0 (the H + channel) subunit in a type of H + flux gating action. Other experiments showed that the Ca 2+ gating of H + flux into the lumen may be a critical regulatory factor in controlling the lumen pH and thereby help regulate the activity of the violaxanthin de-epoxidase enzyme, a key part of the chloroplast photoprotective response to over-energization (excess light) stress. Ion gradient-coupled membrane bioenergetics – emergence of a new paradigm A new era in cell membrane bioenergetics began in August 1960 at a meeting in Prague, Czechoslovakia – the International Conference on Membrane Transport and Metabolism – where Robert K. Crane presented his concept that glucose transport into intestinal cells was powered by a Na +-glucose co-transport. This is told in an interesting historical article by Robert Crane about this topic (Crane 1983). He was the first to propose (diagrammed in Figure 4 of Crane's article) that the energy contained in the Na + concentration gradient acted on a carrier protein, not directly on the glucose molecule. Other models being proposed and studied often held that the glucose was somehow covalently changed, that is, activated. …
Glaciohydraulic supercooling in Iceland

We present evidence of glaciohydraulic supercooling under jokulhlaup and ablation- dominated conditions from two temperate Icelandic glaciers. Observations show that freezing of sediment-laden meltwater leads to intraglacial debris entrainment during normal and extreme hydrologic regimes. Intraglacial frazil ice propagation under normal ablation-dominated conditions can trap copious volumes of sediment, which forms anomalously thick sections of debris-rich ice. Glaciohydraulic supercooling plays an important role in intraglacial debris entrainment and should be given more attention in models of basal ice development. Extreme jokulhlaup conditions can result in significant intraglacial sediment accretion by supercooling, which may explain the concentration of englacial sediments deposited in Heinrich layers in the North Atlantic during the last glaciation.
Knowleuye-Baseu Seyentation Of Road Scenes

A rule-based expert system is being developed to segment and label the major elements in digitized images of simple road scenes. The system acts on a set of uniform regions, generated by the split-and-merge algorithm, which may be regarded dS a non-standard primal sketch. Simple descriptors attached to regions and to boundaries between regions are referenced by the rule base, which incorporates general Knowledge of the typical benavior of the split-and-merge algorithm, as well as specific knowledge of the scene domain. The rules merge oversegmented regions to form an essentially correct description of the scene. The system is intended to investigate tne limits of applicability of methods which do riot introduce an explicit tnree-dimensional (3D) representation
Deliver us from Evil : The Effects of Mortality Salience and Reminders of 9 / 11 on Support for President

This is the fixed version of an article made available by an organization that acts as a publisher by formally and exclusively declaring the article "published". If it is an "early release" article (formally identified as being published even before the compilation of a volume issue and assignment of associated metadata), it is citable via some permanent identifier(s), and final copy-editing, proof corrections, layout, and typesetting have been applied.
Polycyclic aromatic hydrocarbons (PAHs) in the aquatic ecosystems of Soweto and Lenasia

Polycyclic aromatic hydrocarbons (PAHs) in the aquatic ecosystems of Soweto and Lenasia Polycyclic aromatic hydrocarbons (PAHs) are fused benzene rings containing only hydrogen and carbon atoms. The aim of the study is to determine the concentrations and origins of the 16 priority PAHs, and the ecotoxicological effects they may have on the aquatic ecosystem and possible risk to the human population.
Carbon 14 dating of groundwater in confined aquifers: Implications of aquitard diffusion

The influence of diffusive losses into fine-grained aquitards on the 14C age interpretation of groundwater in long, thin confined aquifers is examined. An analytical model is developed by coupling two one-dimensional steady state differential equations, one representing advective-dispersive transport in the aquifer and the other representing diffusion into the aquitards. The results indicate that aquitard diffusion is a mechanism that can cause a significant reduction in 14C concentrations in a confined aquifer. Groundwater velocities derived from 14C measurements that are unadjusted for diffusion would therefore be underestimated. The error that ensues is highly sensitive to the aquifer thickness and the magnitude of the diffusion coefficient. In contrast, the steady-state distribution of 14C is shown to be relatively insensitive to the magnitude of the longitudinal dispersivity value of the aquifer. Dispersivities representative of the upper range of values that have been reported in the literature produced a negligible difference in steady state 14C concentration compared to results obtained using small dispersivities. An equation is presented which permits the adjustment of 14C data to account for diffusion, providing that the aquifer-aquitard system is not stratigraphically complex and heterogeneous. The analysis can be extended to include age-dating isotopes that have half-lives different from that of 14C. The results of this study also apply to age dating in fractured porous media.
Superimposed electrical stimulation decreases maximal grip force.

AIM The purpose of this study was to assess maximal grip force in two conditions of voluntary muscular contraction (MVC) and electrical stimulation superimposed on voluntary muscular contraction (SES) to better understand mechanisms and effectiveness of electrical stimulation of the hand. There is conflicting evidence regarding the effectiveness of electrical stimulation superimposed on voluntary muscular contraction on improving maximal force. Increased knowledge of the physiologic and mechanical effects of electrical stimulation applied during voluntary muscular contraction can lead to refinement of its clinical application. METHODS Twenty subjects (36+/-13 years; 17 males and 3 females) participated in this study. All subjects were undergoing physical therapy within a hand rehabilitation center. They were instructed to randomly perform three grip determinations in both voluntary muscular contraction and superimposed electrical stimulation conditions to elicit maximal grip force of the unaffected hand. Force was assessed using a handheld dynamometer. Subjective force and contraction were assessed just after sessions as well as pain and discomfort using a visual analogue scale. RESULTS The mean force values were 22+/-7 kg and 30+/-1 kg for the superimposed electrical stimulation and voluntary muscular contraction conditions, respectively. Analyses of the force measures showed that force was weaker in the superimposed electrical stimulation condition (P<0.001). Patients rated their pain and discomfort at 0+/-0 mm and 4+/-2.9 mm, respectively. CONCLUSION Maximal grip force is reduced when electrical stimulation is superimposed to voluntary muscular contraction. This result could be explained by unbalanced muscular synergies at the hand due to SES, confirming these synergies as essential to produce maximal grip force.
Tipping Points in a Dynamic Stochastic IAM

We use a dynamic stochastic general equilibrium model of integrated climate and economy (DSICE) to account for abrupt and irreversible climate change. We model a climate shock in the form of a stochastic tipping point. We investigate the impact of the tipping point externality on optimal mitigation policy.We conclude that the optimal mitigation policy depends on the dynamic pattern of the impact. In the case of abrupt and irreversible climate change with a permanent impact, the optimal policy implies a constant anti-tipping effort to prevent the catastrophe, calling for immediate limitations on emissions.
Epidemic dynamics and antigenic evolution in a single season of influenza A

We use a mathematical model to study the evolution of influenza A during the epidemic dynamics of a single season. Classifying strains by their distance from the epidemic-originating strain, we show that neutral mutation yields a constant rate of antigenic evolution, even in the presence of epidemic dynamics. We introduce host immunity and viral immune escape to construct a non-neutral model. Our population dynamics can then be framed naturally in the context of population genetics, and we show that departure from neutrality is governed by the covariance between a strain's fitness and its distance from the original epidemic strain. We quantify the amount of antigenic evolution that takes place in excess of what is expected under neutrality and find that this excess amount is largest under strong host immunity and long epidemics.
Petrogenesis of the Flood-Basalt Sequence at Noril'sk, North Central Siberia

The 3500-m-thick sequence of volcanic rocks at Noril'sk, formed during a brief interval (∼1 m.y.) at the Permian/Triassic time boundary (∼251 Ma), represents the earliest part of the ∼6500-m-thick sequence presently ascribed to the Siberian flood-basalt province. It is composed of picritic and basaltic lavas of both low-Ti and high-Ti parentage. Extensive geological, geochemical, and isotopic study of the lava sequence and related intrusions allows detailed reconstruction of its petrogenesis. Various crustal-related processes-fractionation, crustal contamination, sulfide separation, and magma mixing-participated in the formation of the lavas. The geochemical and isotopic characteristics indicative of these processes, as well as mantle-related signatures of lava compositions, are discussed. Based on these characteristics, detailed interpretations of lava genesis and evolution throughout the Noril'sk sequence are presented. Eight varieties of lavas are recognized to be primitive, similar in composition to p.
Precipitation of dolomite using sulphate‐reducing bacteria from the Coorong Region, South Australia: significance and implications

Dolomite was successfully precipitated in culture experiments that simulated microbiogeochemical conditions prevailing during late stages of evaporation in ephemeral, hypersaline dolomitic lakes of the Coorong region, South Australia. Analyses of lake‐ and pore‐water samples document rapid geochemical changes with time and depth in both dolomitic and non‐dolomitic lakes. Extremely high sulphate and magnesium ion concentrations in lake waters decline rapidly with depth in pore waters throughout the sulphate‐reduction zone, whereas carbonate concentrations in pore waters reach levels up to 100 times those of normal sea water. Ultimately, sulphate is totally consumed and no solid sulphate is recorded in the dolomitic lake sediments. ‘Most probable number’ calculations of lake sediment samples record the presence of large populations of sulphate‐reducing bacteria, whereas sulphur‐isotope analyses of lake‐water samples indicate microbial fractionation in all the lakes studied. Viable populations of microbes from the lake sediments were cultured in anoxic conditions in the laboratory. Samples were then injected into vials containing sterilized clastic or carbonate grains, or glass beads, immersed in a solution that simulated the lake water. Falls in the levels of sulphate and rising pH in positive vials were interpreted as indicating active bacterial sulphate reduction accompanied by increased concentrations of carbonate. Within 2 months, sub‐spherical, sub‐micron‐size crystals of dolomite identical to those of lake sediments were precipitated. It is concluded that bacterial sulphate reduction overcomes kinetic constraints on dolomite formation by removing sulphate and releasing magnesium and calcium ions from neutral ion pairs, and by generating elevated carbonate concentrations, in a hypersaline, strongly electrolytic solution. The results demonstrate that bacterial sulphate reduction controls dolomite precipitation in both the laboratory experiments and lake sediments. It is proposed that dolomite formation, through bacterial sulphate reduction, provides a process analogue applicable to thick platformal dolostones of the past, where benthic microbial communities were the sole or dominant colonizers of shallow marine environments.
Human‐activity‐enhanced formation of organic aerosols by biogenic hydrocarbon oxidation

Tropospheric aerosol can affect climate and the chemistry of the atmosphere. Organic particulates form a significant fraction of the atmospheric suspended matter over forested areas and may originate to a large extent from the oxidation of natural hydrocarbons. A three-dimensional global model of the troposphere is used to evaluate the contribution to the global organic aerosol (OA) source of the secondary organic aerosol (SOA) derived from the ozonolysis of biogenic volatile organic compounds (BVOC) and its evolution since preindustrial times. BVOC have been represented by a mixture of α- and β-pinenes, and their aerosol-forming parameters and chemical reactivities versus O3, OH, and NO3 have been estimated using laboratory information. An important factor in SOA formation is the deposition of condensable aerosol oxidation products onto preexisting organic aerosol, and this has been taken into account. The thus-calculated source of SOA is evaluated to have increased from 17–28 Tg/yr in preindustrial times to 61–79 Tg/yr at present. This threefold to fourfold enhancement of the formation of organic aerosol from natural BVOC is attributed to an increase in ozone and organic aerosol from anthropogenic sources. The main uncertainties involved in our calculations are related to the composition of BVOC emissions and the details of their aerosol formation capabilities.
Measurements and statistical modelling of spectrum occupancy

Although results from a number of spectrum occupancy surveys have been published in recent years, the associated modelling has concentrated on a single quantity representative of a band (service allocation). The congestion Q, defined as the fraction of channels within an allocated band with observed levels exceeding a given threshold or as the percentage of all channel samples that exceed a given threshold is essentially equal to the unconditional probability q that a random sample is above the threshold. From this definition its complement p = 1-q can be identified. This paper presents results from two recent experimental investigations at a quiet rural site in Wiltshire. Rapid scans of small bands of frequencies were used to measure mean durations of clear channels and slower scans were used to examine the whole of the HF spectrum from 5 to 29 MHz to determine whether there are preferred sub-bands within particular service allocations. Both investigations suggested the need for a statistical model involving additional variables other than p or q.
OLIVINE SHEAR STRENGTH AT HIGH PRESSURE AND ROOM TEMPERATURE

The shear strength of olivine (forsterite) varies from 1.77 kb at 5.5 kb coafining pressure to 15.2 kb at 50 kb confining pressure in room temperature shearing tests at strain rates from 1/sec to 10.3/sec. Extreme grain granulation, increased undulatory extinction, diffuse X-ray patterns and refractive index reductions up to 0.030 are found in sheared pellets. Extreme microfracturing and absence of recrystalization or gliding indicate predominantly brittle behavior.
Supraglacial drainage and its relationship to structure, with particular reference to Charles Rabots Bre, Okstindan, Norway

The small, steep glacier Charles Rabots Bre has an exceptionally well-developed drainage pattern. Deeply incised channels, many of which have highly sinuous meanders, and moulins are common; because of the stagnant nature of the ice, they survive from year to year. The factors affecting the development of the supraglacial drainage system, and its relationship with open and closed crevasses, foliation, and stratification are discussed, and several stages of evolution are recognised.
An idealized model of nitrogen recycling in marine sediments

A model of the interdependent processes involved in nitrogen mineralization in marine sediments is presented, based on data collected in the sandy sediments of the North Sea. It relates the flux of organic material deposited in the sediments to the release of dissolved nitrogen to the overlying water, given the mixing conditions undergone by the solid and interstitial phases of the sediment under the action of physical or biological processes. Although idealized, the model can be useful in predicting the trends of variation in the relative importance of ammonification, nitrification, and denitrification, as a result of variations in the organic matter input to the bottom. It shows that, at low input of organic matter, most nitrogen release occurs as nitrate, whereas, at higher input, ammonium release prevails. Denitrification reaches a plateau above a certain input of organic material. It can involve an appreciable proportion (more than about 30 percent of the flux) of remineralized nitrogen only at high organic input and when a high nitrate concentration exists in the overlying water.
Relative contribution of outdoor and indoor particle sources to indoor concentrations

The effect of indoor particle sources on indoor particle size distributions and concentrations was previously investigated using real-time indoor and outdoor particle size distribution data collected in four homes in Boston in 1996. These data demonstrated the importance of indoor sources (i.e., cooking, cleaning, and movement of people) and air exchange rates on observed indoor concentrations. As part of the continued analyses of these data, a simple physical model was used to determine the source emission and infiltration rates for specific particle sizes. Decay rates were also estimated. Cooking, cleaning, and indoor work (characterized by movement of people) significantly increased PM(0.7-10) concentrations by 0.27, 0.27, and 0.25 μm3 cm-3 min-1, respectively. Cooking was the only variable significantly associated with generation of particles less than 0.5 μm in diameter. Outdoor particles (0.02−0.5 and 0.7−10 μm) were found to contribute significantly to indoor particle levels. Effective penetration .