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Fluid dynamics models complement expensive experiments with limited measurement accuracy that investigate the mass transport in PEM water electrolysis. Here, a first-principle microscale model for oxygen transport is successfully validated that accounts for (1) uncertain transport processes in catalyst layers, (2) numerically challenging capillary-dominated two-phase flow and (3) bubble detachments in channels. We developed algorithms for the stochastic generation of geometries and for the coupling of flow and transport processes. The flow model is based on the volume of fluid method and reproduces experimentally measured pressure drops and bubble velocities within minichannels with a 30% and 20% accuracy, respectively, provided that the capillary number is above 2.1 × 10−7. At lower capillary numbers, excessive spurious currents occur. Correspondingly, two-phase flow simulations within the porous transport layers are stable at current densities above 0.5 A cm−2and match operando gas saturation measurements within a 20% margin at relevant locations. The simulated bubble detachments occur at pore throats that agree with porosimetry and microfluidic experiments. The presented model allows explaining and optimizing mass transport processes in channels and porous transport layers. These were found to be negligibly sensitive to transport resistances within the catalyst layer, providing information on boundary conditions for future catalyst layer models.

The vadose zone is subject to dynamic boundary conditions in the form of infiltration and evaporation. A better understanding of implications for flow and solute transport, arising from these dynamic boundary conditions in combination with heterogeneous structure, will help to improve the prediction of the fate of solutes. We present laboratory experiments and numerical simulations of heterogeneous porous media under unsaturated conditions where controlled, temporally varying precipitation and evaporation are applied to study the effect of dynamic boundary conditions on solute transport in the presence of material interfaces. Dye tracers Eosine Y and Brilliant Blue FCF are utilized to visualize solute transport and analyze redistribution processes in a flow cell. Water and solute fluxes in and out of the flow cell are quantified. While in dynamic experiments application of small infiltration rates (significantly below the saturated hydraulic conductivities of the materials) led to a reversal of transport paths between infiltration and succeeding evaporation, larger infiltration rates altered downward transport such that flow and transport paths differed from those observed during evaporation. Differences in transport paths ultimately led to a redistribution and trapping of solute in one material which manifested as pronounced tailing in breakthrough curves. Trapping was induced not by the formation of a stagnant zone as result of large parameter contrast but by an interplay of dynamic boundary conditions and material heterogeneity. This study thereby highlights the importance to consider dynamic boundary conditions in predictions of solute leaching. Laboratory studies of solute transport in heterogeneous porous media under dynamic boundary conditions are conductedCombination of dynamic boundary conditions and material heterogeneity affects solute leaching in experiments and can induce strong tailingStudy highlights importance of consideration of dynamic boundary conditions in predictions of solute leaching

Removing water from porous Vycor glass resolves the near-IR (NIR) spectrum revealing that the emissivity of nanoporous silicas derives from two energetically distinct silanol, SiOH(H2O)x, and siloxane, SiOSi(H2O)y, surface sites. The occurrence of isosbestic points and emission lifetimes independent of a water content implies that these sites do not randomly interact with water but are associated with a specific number of water molecules on the silica surface. Integer relationships between NIR absorptions that are overtones of the SiOH(H2O)xand SiOSi(H2O)yvibrations and the excitation spectra of the SiOH(H2O)xand SiOSi(H2O)yfluorescence indicate a facile exchange of electronic and vibrational energy with the majority of the excitation energy stored as O–H vibrational energy in a 14–15 Å layer of water on the silica surface. CO2quenches the SiOH(H2O)x, and SiOSi(H2O)yexcited states by a proton transfer mechanism which initiates the CO2/CH4conversion. Although individual O–H vibrations do not have sufficient energy to promote the more energetic steps in the conversion, higher-order composite overtones indicate the presence of nonlinear processes that promote the transfer of hydrogen atoms and hydride ions from the silica/H2O surface sustaining the CO2/CH4conversion.

We develop an efficient computational model for simulating fluid invasion patterns emerging in variable aperture fractures. This two‐dimensional model takes into account the effect of capillary force on the fluid‐fluid interfaces and viscous pressure drop in both fluid phases. The pressure distribution is solved at each time step based on mass balance and local cubic law, considering an imposed pressure jump condition at the fluid‐fluid interface. This pressure jump corresponds to the Laplace pressure which includes both terms related to the out‐of‐plane (aperture‐spanning) curvature and to the in‐plane curvature. Simulating a configuration that emulates viscous fingering in two‐dimensional random porous media confirms that the model accounts properly for the role of viscous forces. Furthermore, direct comparison with previously obtained experimental results shows that the model reproduces the observed drainage patterns in a rough fracture reasonably well. The evolutions of tip location, the inlet pressures, and the invading phase fractal dimensions are analyzed to characterize the transition from capillary fingering to viscous fingering regimes. A radial injection scenario of immiscible invasion is also studied with varying modified capillary number and viscosity ratio, showing displacement patterns ranging from capillary fingering to viscous fingering to stable displacement. Such simulations using two contact angles show that the invading phase becomes more compact when the wetting condition changes from strong to weak drainage, as already observed in 2‐D porous media. The model can be used to bridge the gap in spatial scales of two‐phase flow between pore‐scale modeling approaches and the continuum Darcy‐scale models. The flow of two or more fluids in fractured media is an important process involved in many industrial and environmental applications in the subsurface with examples spanning from contaminant transport to petroleum recovery to geological storage of carbon dioxide. Understanding and controlling two‐phase flow in fractures is critical from both the scientific and technological points of view. In this study, we focus on the displacement of one fluid by another immiscible one in a rough fracture, a fundamental process underlying two‐phase flow in fractured media. We develop an efficient computational model for simulating fluid invasion patterns emerging in rough fractures. This model takes into account the effect of capillary force on the fluid‐fluid interfaces and viscous pressure drop in both fluid phases. Direct comparison with experimental results shows that the model output matches the observed patterns reasonably well. In addition, generic simulations demonstrate the ability of the model to produce flow patterns that fall into regimes whose dependence on the viscosity ratio and capillary number is similar to that of the classical phase diagram. The model can be used to bridge the gap in spatial scales of two‐phase flow between pore‐scale modeling approaches and the continuum Darcy‐scale models. An efficient, intermediate‐scale model is developed for dynamic, immiscible displacement in rough geological fracturesThe model reproduces essential features of experimentally observed drainage patterns from capillary to viscous fingeringThe model is advantageous over CFD approaches in computational efficiency and accuracy, especially in low to medium capillary number flows

Two‐phase flow involving non‐Newtonian fluids in fractured media is of vital importance in many natural processes and subsurface engineering applications, such as rock grouting, groundwater remediation, and enhanced oil recovery. Yet, how the displacement dynamics is impacted by the non‐Newtonian rheology remains an open question. Here, we conduct primary drainage experiments in which a shear‐thinning Xanthan gum solution displaces a silicone oil in a transparent rough fracture for a wide range of shear‐thinning property (controlled by polymer concentration) and flow rates. We first evaluate the effects of shear‐thinning property on displacement efficiency. Based on qualitative and quantitative analyses of the observed fluid morphologies, we present an experimental phase diagram of the obtained displacement patterns. We characterize a novel displacement pattern where the fluid‐fluid interface changes from stable (plug flow) to unstable (fingering) as the fracture aperture, averaged over the transverse direction, varies along the mean flow direction. We demonstrate that the existence of this mixed displacement pattern can be explained by local viscosity heterogeneity induced by the coupling of the shear‐thinning behavior and the spatial variability of apertures. Finally, we propose a theoretical model elucidating the mechanisms behind the flow regime transitions. The interface stability criterion predicted by this model exhibits good agreement with the experimental measurements, and stresses the potentially important role of fluid rheology, coupled to aperture variability, in immiscible displacements in rough fractures. These findings provide new insights into the dynamics of immiscible two‐phase flows with non‐Newtonian effects, and has potential implications for the aforementioned engineering applications. We conduct drainage experiments in which a shear‐thinning fluid displaces a Newtonian fluid in a transparent rough fractureWe present an experimental phase diagram of displacement patterns in the space of flow rate and shear‐thinning rheological propertyWe propose a theoretical model of stability criterion and elucidate the mechanisms behind the flow regime transitions We conduct drainage experiments in which a shear‐thinning fluid displaces a Newtonian fluid in a transparent rough fracture We present an experimental phase diagram of displacement patterns in the space of flow rate and shear‐thinning rheological property We propose a theoretical model of stability criterion and elucidate the mechanisms behind the flow regime transitions

Models for flow in environmental systems are subject to uncertainty. Models can thus be interpreted as hypotheses on the validity of the underlying model assumptions. One important source of uncertainty in models for flow and transport processes in the subsurface is the model concept. While uncertain model parameters or forcing terms can be captured as random processes and random fields, this type of uncertainty cannot be included into a model in a straightforward manner. This is particularly true if established model descriptions of a given process are not known or are still being debated. In this contribution, we outline several examples of subsurface flow and transport modeling where uncertainty of the model concept plays an important role. We discuss the need for the development of methods and standards to deal with this type of uncertainty in model hypothesis testing. Uncertainty about processes in a model is a key source of uncertainty in many subsurface modelsOngoing research on alternative modeling approaches for flow and transport should be taken up in formulations of structural model errorsMethods are needed to deal with uncertainty about model concepts

Groundwater recharge is the main forcing of regional groundwater flow. In traditional partial‐differential‐equation (pde)‐based models that treat aquifers as separate compartments, groundwater recharge needs to be defined as a boundary condition or it is a coupling condition to other compartments. Integrated models that treat the vadose and phreatic zones as a continuum allow for a more sophisticated calculation of subsurface fluxes, as feedbacks between both zones are captured. However, they do not contain an explicit groundwater‐recharge term so it needs to be estimated by post‐processing. Groundwater recharge consists of changes in groundwater storage and of the flux crossing the water table, which can be calculated based on hydraulic gradients. We introduce a method to evaluate the change of groundwater storage by a time‐cumulative water balance over the depth section of water table fluctuations, avoiding the use of a specific yield. We demonstrate the approach first by a simple 1‐D vertical model that does not allow for lateral outflow and illustrates the ambiguity of computing groundwater recharge by different methods. We then apply the approach to a 3‐D model with a complex topography and subsurface structure. The latter example shows that groundwater recharge is highly variable in space and time with notable differences between regional and local estimates. Local heterogeneity of topography or subsurface properties results in complex redistribution patterns of groundwater. In fully integrated models, river‐groundwater exchange flow may severely bias the estimate of groundwater recharge. We, therefore, advise masking out groundwater recharge at river locations. We introduce a method to calculate groundwater recharge efficiently and consistently in fully integrated hydrological modelsWe estimate contributions to groundwater recharge based on groundwater‐storage changes and the flux crossing the water tableWe emphasize the importance of numerical models to capture the spatially and temporally complex nature of groundwater recharge We introduce a method to calculate groundwater recharge efficiently and consistently in fully integrated hydrological models We estimate contributions to groundwater recharge based on groundwater‐storage changes and the flux crossing the water table We emphasize the importance of numerical models to capture the spatially and temporally complex nature of groundwater recharge

The Hsp90 chaperone is a central node of protein homeostasis, activating many diverse client proteins. Hsp90 functions as a molecular clamp that closes and opens in response to the binding and hydrolysis of ATP. Crystallographic studies have defined distinct conformational states of the mechanistic core, implying structural changes that have not yet been observed in solution. Here we engineered one-nanometer fluorescence probes based on photoinduced electron transfer into the yeast Hsp90 to observe these motions. We found that the ATPase activity of the chaperone was reflected in the kinetics of specific structural rearrangements at remote positions that acted cooperatively. Nanosecond single-molecule fluorescence fluctuation analysis uncovered that critical structural elements that undergo rearrangement were mobile on a sub-millisecond time scale. We identified a two-step mechanism for lid closure over the nucleotide-binding pocket. The activating co-chaperone Aha1 mobilized the lid of apo Hsp90, suggesting an early role in the catalytic cycle.

Editors of several journals in the field of hydrology met during the Assembly of the International Association of Hydrological Sciences—IAHS (within the Assembly of the International Union of Geodesy and Geophysics—IUGG) in Prague in June 2015. This event was a follow-up of a similar meeting held in July 2013 in Gothenburg (as reported by Blöschl et al. [2014]). These meetings enable the group of editors to review the current status of the journals and the publication process, and share thoughts on future strategies. Journals were represented in the 2015 meeting through their editors, as shown in the list of authors. The main points on fostering innovation and improving impact assessment in journal publications in hydrology are communicated in this joint editorial published in the above journals.

It has recently been shown that the anisotropy in nanocrystalline FINEMET-type magnets, induced by their crystallization under tensile stress, can originate from the magnetoelastic coupling within the crystallites or can have its source in directional diatomic ordering which occurs also within the volume of nanocrystalline phase in the present work the temperature dependence of this anisotropy has been investigated for a series of initially amorphous Fe73,5Cu3Nb3Si15,2B7-ribbon samples (Vacuumschmelze, GmbH), nanocrystallized at various temperature-time-stress conditions. It has been assumed that the obtained results will allow to judge which of the mechanisms mentional above governs in reality the considered anisotropy. An analysis of the results obtained show that diatomic directional ordering within the volume of the nanocrystalline phase seems to be very likely the origin of the stress-anneal-induced anisotropy in Finemet-type magnets. This analysis has been performed assuming that the anisotropy originating from the atomic ordering should scale with the square of saturation magnetization in the high temperature range (in the vicinity of critical temperature - Curie point of the nanocrystalline phase) and with the cube of this quantity at low temperatures. Quite satisfactory agreement has been obtained for the best fit of the experimental data to the polynomial consisting of the two above terms.

Abstract: Background and study aims: Patients with achalasia or malignancies of the head and neck are at increased risk for esophageal squamous cell carcinoma. The discussion of a screening and surveillance program is controversial. The aim of the present study was to determine the diagnostic potential of Lugol chromoendoscopy combined with brush cytology to diagnose esophageal squamous cell carcinoma and high-grade dysplasia. Secondly, the benefit of additional biomarkers was investigated. Patients and methods: A total of 61 patients (21 patients with achalasia and 40 patients with malignancies of the head and neck) were included. Chromoendoscopy with 1.2% Lugol iodine solution with targeted biopsies and brush cytology processed by digital image cytometry (DICM) and fluorescence in situ hybridization (FISH) from unstained lesions (USLs) and stained mucosa were performed. Results: Six of the 61 patients had USLs ≥2 cm. Four patients had high-grade dysplasia (HGD) or carcinoma in situ (CIS). One patient with HGD and one patient with CIS were detected only after Lugol chromoendoscopy. The sensitivity and specificity for detected HGD or CIS in USLs ≥2 cm were 100% and 96.5%. No dysplasia was found in USLs <2 cm. DNA ploidy by DNA cytometry and p53 loss of heterozygosity (LOH) by fluorescence in situ hybridization showed no additional impact on diagnostic accuracy. Conclusions: Lugol chromoendoscopy enhances the detection rate of high-risk lesions with dysplasia or carcinoma in situ in large unstained lesions. Biomarkers such as aneuploidy and p53 LOH from brush cytology were not of additional benefit in this setting.

BACKGROUND AND STUDY AIMS: The reference surveillance method in patients with Barrett's esophagus is careful endoscopic observation, with targeted as well as random four-quadrant biopsies. Autofluorescence endoscopy (AFE) may make it easier to locate neoplasia. The aim of this study was to elucidate the diagnostic accuracy of surveillance with AFE-guided plus four-quadrant biopsies in comparison with the conventional approach. PATIENTS AND METHODS: A total of 187 of 200 consecutive Barrett's esophagus patients who were initially enrolled (73 % male, mean age 67 years, mean Barrett's segment length 4.6 cm), who underwent endoscopy for Barrett's esophagus in four study centers, were randomly assigned to undergo either AFE-targeted biopsy followed by four-quadrant biopsies or conventional endoscopic surveillance, also including four-quadrant biopsies (study phase 1). After exclusion of patients with early cancer or high-grade dysplasia, who underwent endoscopic or surgical treatment, as well as those who declined to participate in phase 2 of the study, 130 patients remained. These patients were examined again with the alternative method after a mean of 10 weeks, using the same methods described. The main study parameter was the detection of early cancer/adenocarcinoma or high-grade dysplasia (HGD), comparing both approaches in study phase 1; the secondary study aim in phase 2 was to assess the additional value of the AFE-guided approach after conventional surveillance, and vice versa. Test accuracy measures were derived from study phase 1. RESULTS: In study phase 1, the AFE and conventional approaches yielded adenocarcinoma/HGD rates of 12 % and 5.3 %, respectively, on a per-patient basis. With AFE, four previously unrecognized adenocarcinoma/HGD lesions were identified (4.3 % of the patients); with the conventional approach, one new lesion (1.1 %) was identified. Of the 19 adenocarcinoma/HGD lesions detected during AFE endoscopy in study phase 1, eight were visualized, while 11 were only detected using untargeted four-quadrant biopsies (sensitivity 42 %). Of the 766 biopsies classified at histology as being nonneoplastic, 58 appeared suspicious (specificity 92 %, positive predictive value 12 %, negative predictive value 98.5 %). In study phase 2, AFE detected two further lesions in addition to the initial alternative approach in 3.2 % of cases, in comparison with one lesion with conventional endoscopy (1.7 %). CONCLUSIONS: In this referral Barrett's esophagus population with a higher prevalence of neoplastic lesions, the AFE-guided approach improved the diagnostic yield for neoplasia in comparison with the conventional approach using four-quadrant biopsies. However, AFE alone was not suitable for replacing the standard four-quadrant biopsy protocol.

We demonstrate the potential of modern confocal fluorescence microscopy in combination with quenched peptide-based fluorescence probes for sensitive detection of p53 antibodies directly in homogeneous solution. Single tryptophan (Trp) residues in the sequences of short, synthetic peptide epitopes of the human p53 protein efficiently quench the fluorescence of an oxazine fluorophore attached to the amino terminal ends of the peptides. The fluorescence quenching mechanism is thought to be a photoinduced electron transfer reaction from Trp to the dye enabled by the formation of intramolecular complexes between dye and Trp. Specific recognition of the epitope by the antibody confines the conformational flexibility of the peptide. Consequently, complex formation between dye and Trp is abolished and fluorescence is recovered. Using fluorescence correlation spectroscopy (FCS), antibody binding can be monitored observing simultaneously two parameters: the diffusional mobility of the peptide as well as the quenching amplitude induced by the conformational flexibility of the peptide change significantly upon antibody binding. Furthermore, we demonstrate that the strong fluorescence increase upon binding can also be used to directly detect p53 autoantibodies from human blood serum samples in fluorescence intensity time traces. Our data demonstrate that new refined single-molecule fluorescence techniques in combination with quenched peptide epitopes open new possibilities for the reliable detection of antibody binding events in homogeneous solution.

This mini-review describes how single-molecule sensitive fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET) reactions can be successfully applied to monitor conformational dynamics in biopolymers. Single-pair FRET experiments are ideally suited to study conformational dynamics occurring on the nanometer scale, e.g. during protein folding or unfolding. In contrast, conformational dynamics with functional significance, for example occurring in enzymes at work, often appear on much smaller spatial scales of up to several Angströms. Our results demonstrate that selective PET-reactions between fluorophores and amino acids or DNA nucleotides represent a versatile tool to measure small-scale conformational dynamics in biopolymers on a wide range of time scales, extending from nanoseconds to seconds, at the single-molecule level. That is, the monitoring of conformational dynamics of biopolymers with temporal resolutions comparable to those within reach using new techniques of molecular dynamic simulations. Furthermore, we demonstrate that the strong distance dependence of charge separation reactions on the sub-nanometer scale can be used to develop conformationally flexible PET-biosensors. These sensors enable the detection of specific target molecules in the sub-picomolar range and allow one to follow their molecular binding dynamics with temporal resolution.

We derive a large scale mixing parameter for a displacement process of one fluid by another immiscible one in a two-dimensional heterogeneous porous medium. The mixing of the displacing fluid saturation due to the heterogeneities of the permeabilities is captured by a dispersive flux term in the large scale homogeneous flow equation. By making use of the stochastic approach we develop a definition of the dispersion coefficient and apply a Eulerian perturbation theory to determine explicit results to second order in the fluctuations of the total velocity. We apply this method to a uniform flow configuration as well as to a radial one. The dispersion coefficient is found to depend on the mean total velocity and can therefore be time varying. The results are compared to numerical multi-realization calculations. We found that the use of single phase flow stochastics cannot capture all phenomena observed in the numerical simulations.

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Upscaling is the term used to describe the process of going from a fine scale, detailed model of a physical system to a coarser scale, less detailed description. It is particularly appropriate in modelling flows in natural porous media (for example in the oil industry or in groundwater flows) because the fluctuations in flow properties of geological systems occur on many length scales from microns to kilometres whereas we often only need to resolve the flow on the scale of tens or hundreds of metres. There is a great deal of uncertainty about the actual spatial distribution of the geological heterogeneities in a given system, which leads to uncertainty in performance prediction. Currently the only way to predict the statistics of the predicted performance is to sample realisations of the geological heterogeneity and then run these through a deterministic numerical flow simulation and thereby sample the flow statistics. Although in some cases it is possible to construct some moments of the distribution analytically. In this paper we suggest an alternative strategy, which is to derive the probability distribution of the saturation and its time evolution. We propose a path integral solution for this and indicate how upscaling (or renormalisation) of this path integral formulation can be done formally to give the appropriate, upscaled probability distribution. In this paper we establish the formalism of the path integral for the nonlinear Buckley–Leverett problem but at this stage we only present upscaling for a much simpler linear transport problem. The advantage of this path integral is that it gives an explicit representation of the entire probability distribution from which all other information (e.g., moments) can be obtained.

Although bats are nocturnal, many species emerge from roosts to forage during twilight, despite a presumed high risk of predation at this time. Here, we describe twilight foraging by a maternity colony of Schneider's leafnosed bat (Hipposideros speoris)in the dry zone of Sri Lanka and determine the dietary benefits of such behavior. Bats usually began foraging during dusk, sometimes before sunset, and also foraged during twilight in the morning. Mean use of available twilight by four radio‐tagged bats was 75 percent. Twilight foraging made up, on average, 47 percent of the total foraging time of these bats (range = 25–96%), although twilight consisted of only 12 percent of the available time between sunset and sunrise the next morning. Eight species of potential predators (7 birds and 1 mammal) were observed within a 1 km radius of the colony, of which 5 species are predicted to regularly capture bats. Bats took a wide diversity of prey (11 insect orders, including at least 27 families, and spiders) that ranged in wing length from 2.0 to 54.0 mm. Major orders in the diet were Coleoptera, Lepidoptera, and Diptera. Prey of secondary importance included Hemiptera, Hymenoptera, Isoptera, and Neuroptera. Bats captured large numbers of insects that were only available or had marked peaks in abundance during twilight. These groups included small, swarming insects (especially flies) that have peaks in flight activity at dusk and dawn, large diurnal species (especially dragonflies) that have crepuscular activity, and winged termites that emerge in swarms at dusk. Access to these insects was a clear benefit of twilight foraging.

Background:The endoscopic biopsy is a prerequisite for histopathologic diagnosis. Various types of forceps are used to obtain tissue specimens. The aim of this study was to assess and compare the diagnostic quality of biopsy specimens obtained with a conventional forceps and a Multibite forceps. Methods:In a prospective, partially blinded, and randomized trial that included 250 patients referred for diagnostic upper and/or lower endoscopy, 510 biopsy specimens obtained with the Multibite forceps were compared with 520 specimens obtained with a conventional forceps. An experienced, blinded pathologist evaluated the specimens for diameter, depth of specimen, artifacts, anatomic orientation, vitality, general histologic quality, and diagnostic quality. Statistical analysis was performed by using the Fisher exact test. A pvalue of < 0.05 was regarded as significant. Results:There were no statistically significant differences between the specimens obtained with the 2 forceps. The pvalues for the evaluated parameters were as follows: diameter 0.45, depth of specimen 0.56, artifacts 1.0, pathoanatomic orientation 0.40, vitality 0.45, and histologic diagnostic quality 0.53. Conclusion:The quality of biopsy specimens obtained with the Multibite forceps is comparable with that of specimens taken with a conventional forceps. Use of the Multibite forceps saves time in that 4 specimens can be obtained in 1 pass in situations in which a large number of specimens are needed or when the potential for transmission of infection is of concern. (Gastrointest Endosc 2001;54:600-4.)

Summary: Globally unique hexactinellid sponge reefs occur on the continental shelf off British Columbia, Canada. They cover about 425 km2 of seafloor on the continental shelf off British Columbia (Canada) in water depths between 165 and 240 metres and occur on a low-angle deep shelf, iceberg scoured seafloor, characterized by very low sedimentation rates and very stable environmental conditions. The sponge bioherms are up to 19 metres high with steep flanks, whereas the biostromes are 2–10 metres thick and many kilometres wide. They all consist of dense populations of only seven hexactinellid species. Three of them, all hexactinosan species (Aphrocallistes vastus, Heterochone calyx, Farrea occa) are the main frambuilders, composing a true rigid framework of sponge skeletons encased in a organic rich matrix of modern clay baffled by the sponges. Growth rates of hexactinosan sponges range in the order of 0–7 centimetres per year. The base of the oldest sponge reefs date from approximately 9000 years b.p. Different invertebrate and fish faunas occupy the reefs than occur on adjacent seafloor areas and some species appear to use the sponge reef complex structures as refugia where they can hide. Sidescan sonar data and direct observation by manned submersible clearly show that large areas of sponge reefs have been heavily damaged by seafloor trawling in the past decade. These unique extant siliceous sponge reefs can be used as a modern analogue for a better understanding and interpretation of fossil siliceous sponge reefs, known from many ages and many locations world wide.

Summary: Liassic sponge mounds of the central High Atlas (Rich area, northern Morocco) have a stratigraphic range from the Lower/Upper Sinemurian boundary interval up to the lower parts of the Lower Pliensbachian (Carixian). The base of Liassic sponge mounds consists of a transgressive discontinuity, i.e., a condensed section of microbioclastic wackestones with firm- and hardgrounds, ferruginous stromatolites, sponge spicules and ammonites. The top of Liassic sponge mounds is an irregular palaeorelief covered by cherty marl-limestone rhythmites, namely hemipelagic spicular wackestones with radiolaria. In the Rich area, section Foum Tillicht, the sponge mound succession has a total thickness of about 250 meters. Within this succession we distinguished between three mound intervals. The lower mound interval shows only small, meter-scale sponge mounds consisting of boundstones with lyssakine sponges, commensalicTerebella and the problematicumRadiomura. This interval forms a shallowing-upward sequence culminating in a bedded facies withTubiphytes, calcareous algae (Palaeodasycladus), sponge lithoclasts, coated grains, and thin rims of marine cement. The middle mound interval is aggradational with decametric mounds and distinct thrombolitic textures and reefal cavities. The mound assemblage here consists of hexactinellid sponges, lithistid demosponges, non-rigid demosponges,Radiomura, Serpula (Dorsoserpula), Terebella, encrusting bryozoa, and minor contributions by calcareous sponges, and excavating sponges (typeAka). Thrombolites are dendrolitic and may reach sizes of several tens of centimeters, similar to the maximum size of siliceous sponges. The upper mound interval appears retrogradational and geometries change upsection from mound shapes to flat lenses and level-bottom, biostromal sponge banks. The biotic assemblage is similar to that of the middle mound interval and there is no difference between mound and bank communities. The demise of sponge mounds is successive from regional spread in the Sinemurian to more localised spots in the Lower Pliensbachian. This reduction correlates with an increasing influence of pelagic conditions. At Foum Tillicht, sponge mounds lack any photic contribution and there is virtually no differentiation into subcommunities between mound surface and cavity dwelling organisms. There is some evidence that the heterotrophic food web of mound communities was sourced by oxygen minimum zone edge effects, namely microbial recycling of essential elements such as N and P. Basin geometry suggests a waterdepth of several 100's of meters, well below the photic zone and possibly only controlled by the depth range of the oxygen minimum zone. Palaeoceanographic conditions of well-stratified deeper water masses diminished gradually during widespread transgression across the Sinemurian to Pliensbachian boundary culminating in the Lower Pliensbachianibex ammonite zone.

Abstract: Traditionally, the medial superior olive, a mammalian auditory brainstem structure, is considered to encode interaural time differences, the main cue for localizing low-frequency sounds. Detection of binaural excitatory and inhibitory inputs are considered as an underlying mechanism. Most small mammals, however, hear high frequencies well beyond 50 kHz and have small interaural distances. Therefore, they can not use interaural time differences for sound localization and yet possess a medial superior olive. Physiological studies in bats revealed that medial superior olive cells show similar interaural time difference coding as in larger mammals tuned to low-frequency hearing. Their interaural time difference sensitivity, however, is far too coarse to serve in sound localization. Thus, interaural time difference sensitivity in medial superior olive of small mammals is an epiphenomenon. We propose that the original function of the medial superior olive is a binaural cooperation causing facilitation due to binaural excitation. Lagging inhibitory inputs, however, suppress reverberations and echoes from the acoustic background. Thereby, generation of antagonistically organized temporal fields is the basic and original function of the mammalian medial superior olive. Only later in evolution with the advent of larger mammals did interaural distances, and hence interaural time differences, became large enough to be used as cues for sound localization of low-frequency stimuli.

Abstract.: We analyze the movement of a solute cloud in a saturated aquifer, resulting from a point-like instantaneous solute injection. Physical heterogeneities of the medium due to spatial variations of the hydraulic conductivity, as well as the chemical heterogeneities due to variations in the linear adsorption coefficient and the degradation rate, are modeled as spatial stochastic processes with exponential autocorrelation functions. Furthermore, cross-correlations between the chemical properties and the conductivity are taken into account. For large transport times, the movement of the solute cloud is characterized by its center-of-mass velocity, by the macroscopic dispersion constant, and the macroscopic degradation rate. These quantities are evaluated using perturbation theory and two different averaging procedures. The first procedure derives the large-scale properties from the central moments of the concentration distribution in a given aquifer realization, and averages over the ensemble afterwards. The second method which is mathematically less demanding obtains large scale transport coefficients from the central moments of the ensemble-averaged concentration distribution. Under the assumption that both prescriptions lead to the same macro-scale quantities, the second approach is usually preferred in literature. The present paper is an extension of the work of Metzger et al. (1996). We show that the two averaging procedures lead to different results in one-dimensional systems, whereas the difference vanishes for higher dimensions. Taking into account the influence of small scale dispersion, we give explicit results for the macroscopic parameters characterizing the solute plume. We analyze the various contributions to these parameters and show how the physical origin of these contributions can be traced back uniquely to fluctuations in the retardation factor, in the flow field, and in the degradation rate, and to the cross-correlations between these inhomogeneities, respectively.

Sinusförmig deformierte Sedimentgänge (sinusoidally deformed veins, SDVs) sind ein besonderes Deformationsgefüge im Unteren Muschelkalk des Germanischen Beckens. Dieses Deformationsgefüge ist ein typischer Bestandteil von Kalk-Mergel Wechsellagerungen. Es entstand unter flacher, mehrere Dezimeter mächtiger Sedimentbedeckung, unterhalb der Bioturbationszone, aber noch innerhalb der Zone fortschreitender plastischer Vertikalkompaktion. Zwei aufeinanderfolgende Prozesse führten zur Ausbildung der SDVs: 1) Die mergeligen Kalke erfuhren eine spontane Schrumpfung, und es wurde Sediment injiziert. Dadurch entstand ein astiges Injektionsgefüge aus passiv gefüllten, vorwiegend vertikal orientierten Schrumpfrissen und horizontalen Verastelungen, die sich unter aktiver Verdrängung des Nebensedimentes ausbreiteten. Das injizierte Material war ein Tonschlamm mit wenig Quarz-Silt und stammt vermutlich aus dem unmittelbaren Unter- und Überlager. Die Injektionen sind in der Regel gangparallel feingeschichtet. 2) Nachfolgend wurde die Injektionsstruktur unidirektional oder bidirektional deformiert. Die damit einhergehende, einheitliche Deformation von Rhizocorallium Bohrgängen legt nahe, daß lateral wirkende Scherkräfte und nicht etwa vertikaler Kompaktionsdruck die sinusförmige Deformation verursachten. Sporadisch erfolgte eine teilweise Verflüssigung und Homogenisierung des Sedimentes. Ein bidirektionales Deformationsgefüge macht Erdbeben als Auslöse-Mechanismus wahrscheinlich. Unidirektionale Gefüge können als Folge-Erscheinung gravitativen Sedimentkriechens aufgefaßt werden. Das Sedimentkriechen erfolgte in Richtung der Akkumulationszentren, wahrscheinlich aufgrund kurzfristig auftretender, lateraler Massen-Ungleichgewichte. Das vergleichsweise seltene Auftreten solcher sinusförmig deformierter Injektionsstrukturen deutet auf einen besonderen rheologischen Zustand unter flacher Sedimentbedeckung hin (Korngröße, Tongehalt, Porenwasserdruck, Menge und Art organischer Substanz). Sinusförmig deformierte Gänge sind als Bestandteil sogenannter 'molar-tooth' -Gefüge ein wichtiges Element einiger meso- und neoproterozoischer Kalkmergelsteine.

Single-unit responses to tonal stimulation with interaural disparities were recorded in the nuclei of the superior olivary complex (SOC) and the central nucleus of the inferior colliculus (ICC) of the echolocating bat, Molossus ater. Seventy-six units were recorded from the ICC and 74 from the SOC; of the SOC units, 31 were histologically verified in the medial superior olive (MSO), 10 in the lateral superior olive (LSO), and 33 in unidentified areas of the SOC. Best frequencies (BFs) of the units ranged from 10.3 to 89.6 kHz, and Q10 dB values ranged from 2 to 70 dB. Most ICC neurons responded phasically to stimulus onset and were either inhibitory/excitatory [I/E; (53)] or excitatory/excitatory [E/E; (21)] units. In the MSO, 23 units responded tonically and 7 phasically on, 18 were E/E or E/OF (facilitatory for other input) units, and 11 were I/E neurons. All LSO neurons responded in a "chopper" fashion, and the binaural neurons were E/I units. In E/E units the excitatory response to binaural stimulation was frequently larger than the sum of the monaurally evoked responses. Many neurons with E/I or I/E inputs had very steep binaural impulse-count functions and were sensitive to small interaural intensity differences. Twenty-eight units (24%) responded with a change in firing rate of at least 20% to interaural time differences of +/- 500 microseconds. Within this sample, 11 units (8 from ICC, 2 from MSO, and 1 from SOC) were sensitive to interaural time differences of only +/- 50 microseconds. Of these 11 units, 10 were I/E units responding phasically only to stimulus onset and were also sensitive to intensity differences (delta I), being suppressed completely by the inhibitory input over a delta I range of 20 dB or less. Of 117 units tested in the ICC and SOC nuclei, 86 units (76%) were not sensitive to interaural time disparities within +/- 500 microseconds. Because the BFs of these units sensitive to interaural transient time differences (delta t) ranged between 18 and 90 kHz, responses were elicited by pure tones, and responses did not change periodically with the period equal to that of the stimulus frequency, we conclude that the neurons reacted to interaural differences of stimulus-onset time (transient time difference) but not to phase differences (ongoing time difference). Sensitivity to interaural time differences was also correlated with interaural intensity differences.(ABSTRACT TRUNCATED AT 400 WORDS)

The postnatal development of midbrain tonotopy was investigated in the inferior colliculus (IC) of the south Indian CF-FM batHipposideros speoris. The developmental progress of the three-dimensional frequency representation was determined by systematic stereotaxic recordings of multiunit clusters from the 1st up to the 7th postnatal week. Additional developmental measures included the tuning characteristics of single units (Figs. 3f; 4f; 5f), the analysis of the vocalised pulse repertoire (Figs. 3e, 4e, 5e), and morphometric reconstructions of the brains of all experimental animals (Fig. 1).

1.Two hipposiderid bats,H. bicolor andH. speoris, were observed in their natural foraging areas in Madurai (South India). Both species hunt close together near the foliage of trees and bushes but they differ in fine structure of preferred hunting space:H. bicolor hunts within the foliage, especially whenH. speoris is active at the same time, whereasH. speoris never flies in dense vegetation but rather in the more open area (Fig. 1, Table 1).2.Both species emit CF/FM-sounds containing only one harmonic component in almost all echolocation situations. The CF-parts of CF/FM-sounds are species specific within a band of 127–138 kHz forH. speoris and 147–159 kHz forH. bicolor (Tables 2 and 3).3.H. speoris additionally uses a complex harmonic sound during obstacle avoidance and during laboratory tests for Doppler shift compensation.H. bicolor consistently emits CF/FM-sounds in these same situations (Fig. 2).4.Both hipposiderid bats respond to Doppler shifts in the returning echoes by lowering the frequency of the emitted sounds (Fig. 3). However, Doppler compensations are incomplete as the emitted frequencies are decreased by only 55% and 56% (mean values) of the full frequency shifts byH. speoris andH, bicolor, respectively.5.The differences in Doppler shift compensation, echolocating and hunting behavior suggest thatH. speoris is less specialized on echolocation with CF/FM-sounds thanH. bicolor.

1.Audiograms are recorded from one non-echolocating and nine echolocating sympatrically living bat species of South India. These species areCynopterus sphinx (non-echolocating),Tadarida aegyptiaca, Taphozous melanopogon, T. kachhensis, Rhinopoma hardwickei, Pipistrellus dormeri, P. mimus, Hipposideros speoris, H. bicolor andMegaderma lyra.2.InRhinopoma hardwickei a highly sensitive frequency range was found which is narrowly tuned to the frequency band of the bat's CF-echolocation call (32–35 kHz, Fig. 3). In hipposiderids a ‘filter’ narrowly tuned to the frequency of the CF-part of the CF-FM echolocation sounds (137.5 kHz inH. speoris and 151.5 kHz inH. bicolor, Fig. 5) could be recorded from deeper parts of IC.3.In the echolocating species the best frequency of the audiograms closely matched with that frequency range in the echolocation calls containing most energy.4.In bat species foraging flying prey best frequencies of audiograms and height of preferred foraging areas are inversely related, i.e. bat species hunting high above canopy have lower best frequencies than those foraging close to or within canopy (Fig. 6).5.A hypothesis is forwarded explaining how fluttering target detection by constant frequency echolocation might have evolved from long distance echolocation by pure tone signals.

1.When catching flying prey under laboratory conditionsRhinolophus ferrumequinum typically emit FM-CF-FM signals (Fig. 2). Except for the last two sounds during approach and final buzz the FM-parts are fainter than the CF-component by a factor of 0.76+-14 (Fig. 1). The final FM-part was undetectable in some signals emitted during approach (Fig. 3).2.In obstacle avoidance flights both, preceding and final FM-parts are prominent and louder than the CF-part by a factor of 1.14 to 1.63 (Fig. 1 and 3). Bandwidths of the FM-components increased from ca. 3.5 to 12 kHz for the starting and from 12 to 20 kHz on the average for the final FM-sweep (Table 1).3.In the open field during cruising flightsNyctalus noctula emits pure tones of 22.5 to 25.0 kHz without any frequency modulated components and a duration of 10 to 50 ms (Fig. 4). Brief frequency modulated signals sweeping from ca. 50 to 20 kHz in about 1–2 ms are emitted during pursuit of prey (Fig. 4).4.Under laboratory conditionsNyctalus noctula does not emit pure tones and is not able to catch flying prey in a flight chamber 10.5×3.5×2.15 m in size. During flights towards a landing platformNyctalus noctula invariably emits brief frequency modulated pulses. During an individual flight the structure is not changed (Fig. 5).5.InNyctalus noctula specific features of the echolocation pulses, e.g. frequency range swept through, presence of harmonics and double pulses (Fig. 6) are maintained during an individual flight. These specific characteristics of the signal may be used to identify echoes belonging to its own emitted echolocation pulse.

1.In horseshoe bats temporal response patterns to pure tone stimuli (10–100 kHz, 20 ms duration, 0.5 ms rise/fall-time) of 149 cochlear nucleus units (DCN and PVCN) have been recorded.2.Distribution of the units' Best Frequencies (BF): low frequency neurons 26% (BF 10–65 kHz); FM-frequency neurons 20% (BF 65–81 kHz, i.e. frequencies occurring in the FM-part of the bat's echo signal); filter frequency neurons 52% (BF 81–88 kHz, i.e. frequencies occurring in the CF-part of the bat's echo signal); high frequency neurons 2% (BF > 88 kHz) (Table 1).3.According to PST-histograms the neurons were classified as: sustained responders (28%, Fig. 1D, E); transient responders (51%, Fig. 1A–C); negative responders (4%, Fig. 1F) and complex responders (17%, Fig. 2–4). In the latter class response patterns drastically change with stimulus frequency and intensity. These units have suppressory sidebands on one or both sides of the excitatory field, sometimes overlapping and enclosing the excitatory area (Fig. 2 and 4). Frequently excitatory response patterns display simultaneous inhibitory processes the latency and duration of which depend on stimulus parameters.4.In a few complex responders two or more excitatory areas exist, the BF of which may be harmonically related (Fig. 3 and 4).5.Tuning curves of four auditory nerve fibers are reported showing two separate excitatory areas: a broad less sensitive one from 37 to 79 kHz (low frequency tail) and a narrow, more sensitive one from 82 to 90 kHz (Fig. 5).

The responses of 230 single neurons in the inferior colliculus of the horseshoebat to single tones have been studied, emphasizing systematic analysis of the effective frequency bands, dynamic properties and the time course of responses. Distribution of the units' best excitatory frequencies (BEF) is: low frequency neurons 23% (BEF 3–65 kHz); FM-frequency neurons 25% (BEF 65–81 kHz, i.e., frequencies occurring in the FM-part of the bat's echo signal); filter neurons 45% (BEF 81–88 kHz, i.e., frequencies occurring in the stabilized CF-part of the bat's echo=reference frequency (RF)); high frequency neurons about 7% (BEF > 88 kHz). Tuning curves show conventional shapes (Fig. 1), apart from those of filter neurons, which are extremely narrow. Accordingly, Q10dB-values (BEF divided by the bandwidth of the tuning curve at 10 dB above threshold) are 80–450 in filter neurons (Fig. 2). Response patterns (Fig. 3) are similar to those of Nucleus cochlearis units (transient, sustained, negative and complex responders) with an increased percentage of complex responders up to 38% and a decreased number of transient responders.

For echolocation,Rhinolophus ferrumequinum emits orientation sounds, each of which consists of a long constant-frequency (CF) component and short frequency-modulated (FM) components. The CF component is about 83 kHz and is used for Doppler-shift compensation. In this bat, single auditory nerve fibers and cochlear nuclear neurons tuned at about 83 kHz show low threshold and very sharp filter characteristics. The slopes of their tuning curves ranged between 1,000 and 3,500 dB/octave and their Q-10 dB values were between 20 and 400, 140 on the average (Figs. 3–5). The peripheral auditory system is apparently specialized for the reception and fine frequency analysis of the CF component in orientation sounds and Doppler-shift compensated echoes. This specialization is not due to suppression or inhibition comparable to lateral inhibition, but due to the mechanical specialization of the cochlea. Peripheral auditory neurons with the best frequency between 77 and 87 kHz showed not only on-responses, but also off-responses to tonal stimuli (Figs. 1, 2, and 6). The off-responses with a latency comparable to that of N1-off were not due to a rebound from either suppression or inhibition, but probably due to a mechanical transient occurring in the cochlea at the cessation of a tone burst.

Summary: Morphological and geochemical comparisons between modern cryptic microbialites from Lizard Island/Great Barrier Reef and fossil counterparts in the Upper Jurassic (Southern Germany, Dobrogea/Romania) and late Lower Cretaceous (Aptian/Albian from Cantabria/Spain) spongiolitic environments show that there are common factors controlling the crust formations mostly independent of light despite of diverging (paleo-) oceanographic positions as well as relationships of competitors. Factors such as increased alkalinity, oligotrophy, and reduced allochthonous deposition are of major importance. Thrombolitic microbialites are interpreted as biologically induced and therefore calcified in isotopic equilibrium with the surrounding sea water. Corresponding with shallowing upward cycles, microbial mats which produce stromatolitic peloidal crusts become more important. Different biomarkers are introduced for the first time extracted and analyzed from spongiolitic limestones of Lower Kimmeridgian age from Southern Germany.

Summary: A benthic community of sessile metazoans dominated by coralline sponges (e.g.Acanthochaetetes andVaceletia) is found within a Cenomanian-Turonian deep water hardground succession cropping out at the coastal area of the Bay of Biscay near Santander. The characteristic K-strategic community exhibits a very close taxonomic relationship with modern communities from the Pacific realm, which allows for a comparison with Recent environmental conditions. The sponge community was associated with automicrites, microbialites, and thin mineralized limonitic biofilms. This biofacies is typically found in cryptic niches of reefal buildups (“telescoping”). The iron-rich biofilms had a strong electrochemical corrosive ability which explains the distinct submarine dissolution patterns. The hardground conditions are controlled, in part, by strong contour current regimes linked with extremely oligotrophic water masses. This system was established during the drowning of a distal carbonate ramp during the early Middle Cenomanian (A.rhotomagenese zone). In the uppermost portion of the hardground (Late Cenomaian, upperR. cushmani zone) the coralline sponge community was replaced by thick limonitic stromatolites with numerous encrusting foraminifera (Miniacina-type) and by colonies of the problematic iron bacteriumFrutexites. This event is accompanied by an increase of terrigenous influx and detrital glauconite, indicating a fundamental change in food web, and terminates the sponge dominated basal hardground interval. Thehardground was buried by hemipelagic sediments during the Middle Turonian (upperR. kallesi zone).

Summary: This research report contains nine case studies (part II to X) dealing with Palaeozoic and Mesozoic mud mounds, microbial reefs, and modern zones of active micrite production, and two parts (I and XI) summarizing the major questions and results. The formation of different types ofin situ formed micrites (automicrites) in close association with siliceous sponges is documented in Devonian, Carboniferous, Triassic, Jurassic and Cretaceous mounds and suggests a common origin with a modern facies found within reef caves. Processes involved in the formation of autochthonous micrites comprise: (i) calcifying mucus enriched in Asp and Glu, this type presumably is linked to the formation of stromatolites, thrombolites and massive fabrics; (ii) protein-rich substances within confined spaces (e.g. microcavities) result in peloidal pockets, peloidal coatings and peloidal stromatolites, and (iii) decay of sponge soft tissues, presumably enriched with symbiotic bacteria, lead to the micropeloidal preservation of parts of former sponge bodies. As a consequence, there is strong evidence that the primary production of micrite in place represents the initial cause for buildup development. The mode of precipitation corresponds to biologically-induced, matrix-mediated mineralization which results in high-Mg-calcites, isotopically balanced with inorganic cements or equilibrium skeletal carbonates, respectively. If distinct automicritic fabrics are absent, the source or origin of micrite remains questionable. However, the co-occurring identifiable components are inadequate, by quantity and physiology, to explain the enhanced accumulation of fine-grained calcium carbonate. The stromatolite reefs from the Permian Zechstein Basin are regarded as reminiscent of ancestral (Precambrian) reef facies, considered the precursor of automicrite/sponge buildups. Automicrite/sponge buildups represent the basic Phanerozoic reef type. Analogous facies are still present within modern cryptic reef habitats, where the biocalcifying carbonate factory is restricted in space.