bluuebunny/crossref_metadata_2025 huggingface dataset:
Low‐Mg calcite marine cement in Cretaceous turbidites: origin, spatial distribution and relationship to seawater chemistry
Authors: HENDRY JAMES P. , TREWIN NIGEL H. , FALLICK ANTHONY E.
Published: June 2006

Lower Cretaceous (Hauterivian) bioclastic sandstone turbidites in the Scapa Member (North Sea Basin) were extensively cemented by low‐Mg calcite spars, initially as rim cements and subsequently as concretions. Five petrographically distinct cement stages form a consistent paragenetic sequence across the Scapa Field. The dominant and pervasive second cement stage accounts for the majority of concretions, and is the focus of this study. Stable‐isotope characterization of the cement is hampered by the presence of calcitic bioclasts and of later cements in sponge spicule moulds throughout the concretions. Nevertheless, trends from whole‐rock data, augmented by cement separates from synlithification fractures, indicate an early calcite δ18O value of+0·5 to ‐1·5‰ PDB. As such, the calcite probably precipitated from marine pore fluids shortly after turbidite deposition. Carbon isotopes (δ13C=0 to ‐2‰ PDB) and petrographic data indicate that calcite formed as a consequence of bioclastic aragonite dissolution. Textural integrity of calcitic nannoplankton in the sandstones demonstrates that pore fluids remained at or above calcite saturation, as expected for a mineral‐controlled transformation.

Electron probe microanalyses demonstrate that early calcite cement contains <2 mol% MgCO3, despite its marine parentage. Production of this cement is ascribed to a combination of an elevated aragonite saturation depth and a lowered marine Mg2+/Ca2+ ratio in early Cretaceous ‘calcite seas’, relative to modern oceans. Scapa cement compositions concur with published models in suggesting that Hauterivian ocean water had a Mg2+/Ca2+ ratio of ≤1. This is also supported by consideration of the spatial distribution of early calcite cement in terms of concretion growth kinetics. In contrast to the dominant early cement, late‐stage ferroan, 18O‐depleted calcites were sourced outwith the Scapa Member and precipitated after 1–2 km of burial.

Our results emphasize that bioclast dissolution and low‐Mg calcite cementation in sandstone reservoirs should not automatically be regarded as evidence for uplift and meteoric diagenesis.
Was Phanerozoic reef history controlled by the distribution of non‐enzymatically secreted reef carbonates (microbial carbonate and biologically induced cement)?
Authors: WEBB GREGORY E.
Published: June 2006

Throughout most of the Phanerozoic, reef rigidity resulted as much, or more, from early lithification by microbial carbonates and biologically induced cements (non‐enzymatic carbonates) than from biological encrustation of, or by, large, enzymatically secreted metazoan skeletons. Reef framework is divided into four categories: (1) skeletal metazoan; (2) non‐skeletal microbialite (stromatolite and thrombolite); (3) calcimicrobe; and (4) biocementstone, in which small or delicate organisms serve as scaffolds for rigid cement crusts. The last three categories are dominated by non‐enzymatic carbonates. Skeletal framework and non‐skeletal microbialite framework were the most abundant framework types through the Phanerozoic. The composition and abundance of skeletal framework was controlled largely by mass extinction events, but most reefs consisted of both microbialite and skeletal organisms in a mutually beneficial relationship. Microbialite framework was abundant throughout the Palaeozoic and early Mesozoic, but declined after the Jurassic. Calcimicrobe framework was important during the Cambrian‐Early Ordovician and Devonian and biocementstone framework was important from the late Mississippian to the Late Triassic.

The Phanerozoic history of reefs does not correlate well with the stratigraphic distribution of large, skeletal ‘reef builders’, or with a variety of physicochemical parameters, including sea‐level history, Wilson Cycle or global climate cycles. Because non‐enzymatic carbonates result from induction by non‐obligate calcifiers, and not enzymatic precipitation by obligate calcifiers, the distribution of these carbonates was controlled to a larger extent by temporal changes in physicochemical parameters affecting the saturation state of sea water with respect to carbonate minerals. Changes in pCO2, Ca/Mg ratios, cation concentrations and temperature may have affected the abundance of non‐enzymatic carbonates and, hence, reefs, independently from the effects of these same parameters and mass extinction events on skeletal reef biota. The decline in abundance of reefal microbialite and absence of calcimicrobe and biocementstone reef framework after the Jurassic may be a result of relatively low saturation states of sea water owing to increased removal and sequestration of finite marine carbonate resources by calcareous plankton since the Jurassic. Reef history is difficult to correlate with temporal changes in specific global parameters because these parameters affect skeletal biota and biologically induced carbonate precipitation independently. Hence, reef history was regulated not just by skeletal reef biota, but by parameters governing non‐enzymatic carbonates.
Internal structure of aeolian dunes in Abu Dhabi determined using ground‐penetrating radar
Authors: BRISTOW CHARLIE , PUGH JONATHAN , GOODALL TIM
Published: June 2006

A ground‐penetrating radar survey of aeolian dunes in the Al Liwa area of Abu Dhabi reveals a variety of dipping reflectors which are interpreted as primary sedimentary structures. The interpretation of the radar profiles has been confirmed by bulldozing trenches through the study area and comparing logged sections in the trenches with the radar profiles. NNW— SSE‐orientated radar profiles, approximately parallel to the prevailing wind direction, show two sets of dipping reflectors which are interpreted as sets of cross‐stratification and second‐ and third‐order bounding surfaces. Radar profiles orientated WSW—ENE across the prevailing wind direction are dominated by concave‐up reflectors which are interpreted as trough‐shaped scours and sets of trough cross‐stratification produced by oblique progradation of barchanoid dunes. Nested troughs, with small sets of trough cross‐stratification within larger troughs, may be due to reactivation following wind reversal, or the superposition of small dunes on larger dunes and the fill of large dune troughs by smaller dunes. Convex‐upwards reflectors are interpreted as linear spurs on the convex portions of sinuous dunes or erosional remnants between troughs. Overall there is a tendency for the larger second‐order bounding surfaces to dip downwind, which confirms Brookfield's ideas of the relative migration paths of dunes and draa.
Regional setting and role of meteoric water in dolomite formation and diagenesis in an evaporite basin: studies in the Zechstein (Permian) deposits of Poland
Authors: PERYT TADEUSZ M. , SCHOLLE PETER A.
Published: June 2006

The Zechstein Basin of Poland was an area of widespread cyclical deposition of carbonates and evaporites during Late Permian time. The Zechstein shelves, along both the northern and the southern margins of the basin, were sites of shallow‐water sedimentation during the formation of the Main Dolomite and Platy Dolomite, two widespread carbonate units. These units consist of oolitic, peloidal, skeletal, micritic and evaporitic carbonates formed in depositional settings ranging from open marine to coastal (lagoonal, sabkha and salina). Although originally deposited as limestones, the Main Dolomite and Platy Dolomite are inferred to have been completely replaced by dolomite through very early stage (essentially penecontemporaneous) reflux of hypersaline brines.

The dolomites of the two basin margins, however, have very different petrographic and isotopic characteristics. Many northern shelf dolomites show early stage calcitization (dedolomitization) and even, in some cases, evidence of a subsequent redolomitization event. These northern shelf samples also have a broad range of carbon and oxygen isotopic ratios (up to 12%0for oxygen). Samples from the southern shelf, on the other hand, are petrographically much simpler; they do not show complex calcitization and redolomitization patterns. Likewise, their isotopic values are much more tightly clustered, with only about a 5%0range of oxygen isotopic ratios.

The differences between dolomites of the same age from the northern and southern margins are best explained by regional variations in river water influx during episodic exposure events associated with regional or global sea‐level fluctuations. The distribution of clastic terrigenous materials and palaeokarstic features indicate that areas of the northern shelf had extensive river input, an influx largely lacking on the southern shelf. Early formed dolomites appear to have been calcitized during sea‐level lowstands through the infiltration of meteoric fluids into the evaporitic dolomites created during the previous highstand. In some cases, redolomitization occurred when meteoric fluids were again replaced by hypersaline brines during subsequent sea‐level highstands.

Although repeated sea‐level fluctuations are clearly evident in these strata, it is likely that associated climatic changes (rainfall variations) also played a role in forming these complex diagenetic patterns. Age‐equivalent strata from Texas and New Mexico (from sites at much lower palaeolatitudes) show no such alteration patterns; samples from Greenland (slightly higher palaeolatitudes) show even more intense diagenetic alteration during depositional cycles. Thus, the examination of patterns of diagenesis may be useful in interpreting ancient, palaeolatitudinally sensitive climate patterns.
Epitaxial salt reefs and mushrooms in the southern Dead Sea
Authors: TALBOT C. J. , STANLEY W. , SOUB R. , AL‐SADOUN N.
Published: June 2006

Salt usually accumulates in shallow ephemeral brines as simple flat beds. However, in permanent brines deepening in solar evaporation ponds in the southern Dead Sea, salt accumulation is complicated by the growth of isolated vegetable‐like salt structures and networks of polygonal salt walls. These walls divide large salt ponds, which are easily homogenized by wind, into thousands of small compartments that are less easy to mix. Instead, brines in the compartments stratify when a surficial layer about 10 cm thick supersaturates and floats above the cumulate floors on brines that are merely saturated.

Salt reef growth in the southern Dead Sea has previously been attributed to mixing of ions common to brines already in the ponds and those pumped in from the northern basin (with or without subsurface brines rising through the pond floors). A new factor is emphasized here that, whatever the origins of the brines, salt reefs remain emergent by epitaxis, the in situ growth of crystalline substrates already in the surficial supersaturated layer.

Epitaxis can be invisible in crystal clear brines and prolongs the obvious crystallization season by replacing sedimentation of grains nucleated and grown on the brine surface as the dominant mechanism of deposition. Salt reefs develop botryoidal overhangs that can merge into salt platforms that roof over deep brines. Salt shallows on the reef platforms and around the pond shores are both characterized by the deposition of the thin flat beds with vertical palisade textures well known from other ephemeral brines. Salt reefs are interpreted as tepee structures which have grown by epitaxis as fast as saturated brines have deepened around them. Epitaxis may also account for the rapid deposition of thick beds of pure salt in rifts that open to oceans.

Local histories of salt reef compartmentalization can be read from the shapes of reefs that record their relative rates of growth and drowning. Rather than diminish evaporation area, damp emergent salt reefs act as giant transpirative pumps that accelerate salt crystallization and reconfigure the evaporation ponds into areas smaller than thought necessary by chemical engineers. The natural end of reef formation may be when shallow brines on hollow reef platforms become ephemeral on solid salt flats. Former salt reefs are likely to be distinguishable in the undeformed geological record by their botryoidal layers of nonvertical chevron crystals.
Transition from foreland‐ to piggyback‐basin deposition, Plio‐Pleistocene Upper Siwalik Group, Shinghar Range, NW Pakistan
Authors: PIVNIK DAVID A. , KHAN M. JAVED
Published: June 2006

Plio‐Pleistocene synorogenic deposits of the Upper Siwalik Group in the Shinghar Range (Trans‐Indus Salt Ranges) of north‐western Pakistan record the transition from foreland‐basin to piggyback‐basin deposition on the hangingwall of the Salt Range thrust. The Siwalik and Upper Siwalik Groups are over 4 km thick in the Shinghar Range. The lower 3 km consists of the Miocene Siwalik Group, which was deposited by a south‐flowing foreland trunk stream, the palaeo‐Indus River. The upper 1·5 km consists of the Upper Siwalik Group, which is herein divided into three members. The lowest member includes deposits of the south‐flowing palaeo‐Indus River and is distinguished from the underlying Siwalik Group by the first appearance of conglomerate. The transition from the lower member to the middle member is interpreted as recording uplift on the Salt Range thrust. As the Salt Range thrust was active, the palaeo‐Indus River was bifurcated to the east and west around the embryonic Shinghar Range and overbank and lacustrine deposition occurred, represented by the middle member. When the Shinghar Range achieved significant topography, the upper member was deposited by streams transporting gravel and sand that flowed north and west out of the range and into a piggyback basin that formed on the hangingwall of the Salt Range thrust. New and previously published palaeomagnetic stratigraphy and fission‐track ages from volcaniclastic deposits within the Upper Siwalik Group provide tight constraints on the chronology of sedimentary‐facies transitions and timing of uplift of the Shinghar Range. The integration of sedimentological and geochronological data indicates that motion on the Salt Range thrust and repositioning of the Indus River began at ∼1·0 Ma.
Thermokarst‐lake‐basin sediments, Tuktoyaktuk Coastlands, western arctic Canada
Authors: MURTON JULIAN B.
Published: June 2006

Three stages of deposition are distinguished in thermokarst‐lake‐basin sequences in ice‐rich permafrost of the Tuktoyaktuk Coastlands, western arctic Canada: (1) widespread retrogressive thaw slumping around lake margins that rapidly transports upland sediments into thermokarst lakes, forming a distinctive basal unit of impure sand and/or diamicton; (2) a reduction or cessation of slumping‐because of the pinching out of adjacent ground ice, slump stabilization or climatic cooling, that reduces the input of clastic sediment, permitting reworking of sediment around lake margins and suspension settling, principally in basin centres; (3) lakes drain and deposition may continue by gelifluction and accumulation ofin situpeat or aeolian sand.

Radiocarbon dating of detrital peat and wood from a progradational sequence (basal unit) defines a lateral younging trend in the direction of progradation. A progradation rate is calculated to be ∼ 4 cm yr−1, consistent with rapid deposition during stage (1) above. The nonuniform nature of the trend is attributed to episodic influxes of old organic material by slumping and reworking by waves and currents.

In comparison with thermokarst‐lake‐basin sequences previously described in Alaska, Canada and Siberia, the middle unit of those in the Tuktoyaktuk Coastlands is similar, whereas the basal unit is generally thicker and, by contrast, often contains diamicton. These differences are attributed, respectively, to larger‐scale resedimentation of upland sediments by retrogressive thaw slumping and debris‐flow deposition in thermokarst lakes in the Tuktoyaktuk Coastlands. Compared with the sediments within supraglacial lakes in areas of moderate to high relief, the middle unit of thermokarst‐lake‐basin sequences in the Tuktoyaktuk Coastlands lacks clastic varves and the basal unit is much thinner and texturally less variable. These differences are attributed to higher relief and larger volumes of meltwater and glacigenic sediment in supraglacial lakes, which promote more suspension settling and resedimentation of glacigenic sediment than in thermokarst lakes in the Tuktoyaktuk Coastlands.

It may be impossible to distinguish glacial and periglacial thermokarst‐lake‐basin sediments in permafrost areas of incomplete deglaciation. Not only is it often difficult to distinguish intrasedimental and buried glacier ice, but the depositional processes associated with thaw of both ice types are presumably the same and the host sediments very similar.
Internal architecture and sedimentary evolution of coarse‐grained, turbidite channel‐levee complexes, Early Eocene Regência Canyon, Espírito Santo Basin, Brazil
Authors: BRUHN CARLOS H. L. , WALKER ROGER G.
Published: June 2006

Successions of Early Eocene coarse‐grained turbidites up to 400 m thick fill fault‐controlled canyons along the eastern Brazilian continental margin. They form part of a Late Albian to Early Eocene transgressive succession characterized by onlapping, deepening‐upward sedimentation. In the Lagoa Parda oil field (Regência Canyon, Espírito Santo Basin) the turbidite facies consist mostly of unstratified conglomerate and sandstone, with interbedded bioturbated mudstone and thin‐bedded, stratified sandstone. Within the main Regência Canyon, the coarser grained facies occur within 38 deeply incised channels. The fills are 9 to >50 m thick, 210 to >1050 m wide and >1 km long. The finer grained facies build asymmetrical levees that are higher and thicker on the left side (looking downstream) of their channels, probably as an effect of the Coriolis force (to the left in the Southern Hemisphere). Nine levee successions up to 50 m thick are associated with the 20 youngest channels. The deposits filling the low‐sinuosity Lagoa Parda channels record successive channel abandonment through relatively rapid avulsions. Avulsions of unleveed channels took place randomly, but channels with well‐developed levees show preferential avulsion to the right (looking downstream), opposite to the direction of preferential levee growth.

Lagoa Parda channels can be grouped into three complexes 20–100 m thick. These complexes have an estimated duration of about 140 000 years. It is suggested that control of the development of individual channel complexes was related to variation in sediment supply, in turn probably related to climatic changes. The deposition of each channel complex would have followed an increase in sediment supply into the Regência Canyon through delta/fan‐delta and littoral drift systems, which in turn would have responded to phases of higher denudation rates in the high‐relief, ancestral coastal ranges of south‐eastern Brazil.

Overall, the three Lagoa Parda channel complexes form a turbidite succession characterized by channel fills that become narrower, thinner and finer grained upward. These trends were induced mostly by a longer term (>400 000 years) decrease in sediment supply, which in turn resulted from the combined effects of a long‐term (second‐order) trend of sea‐level rise, and the decreasing fault activity at the basin margin and source area.
Marine‐derived dolomite in the shallowly buried temperate Port Campbell Limestone (Miocene), Otway Basin, Australia
Authors: NICOLAIDES STELIOS
Published: June 2006

The Miocene Port Campbell Limestone in the Otway Basin (Port Campbell Embayment), south‐eastern Australia, is a shallowly buried (<350 m), temperate carbonate grainstone which consists primarily of benthonic foraminifera, bryozoans, brachiopods, echinoids and planktonic foraminifera. Volumetrically insignificant calcite cements include scalenohedral, blocky and syntaxial overgrowths. Dolomite is present in variable amounts (1–25%), scattered throughout the unit as euhedral rhombs, usually comprising <2% of the whole rock volume. The dolomite post‐dates the calcite cements and is mainly an interparticle cement with crystal size varying between 10 and 150 μm (mean 50 μm). Under cathodoluminescence the dolomite rhombs have a dull core and a nonluminescent outer rim.

The dolomite is nonstoichiometric, Ca‐rich (Ca54–62Mg38–46), with high trace element concentrations. The Mn concentrations range from 0 to 310 p.p.m. in the crystal cores (mean 140 p.p.m.) and 80–240 p.p.m. in the crystal rims (mean 140 p.p.m.). The Fe concentrations increase from the crystal cores (range 640–5690 p.p.m.; mean 2030 p.p.m.) to the crystal rims (range 2840–9440 p.p.m.; mean 6040 p.p.m.), whereas the Sr concentrations decrease from the crystal cores (range 690–1510 p.p.m.; mean 1280 p.p.m.) to the crystal rims (620–1240 p.p.m.; mean 930 p.p.m.). The δ13CPDB values of the dolomite range between +2.5 and +2.6%, whereas the δ18OPDB values range from +0.3% to+0.6%.

This dolomite occurrence supports the idea that marine or near‐marine dolomite can form not only syndepositionally, but also in the shallow subsurface of temperate units, soon after sediment deposition, under reducing conditions. The fine‐grained, low‐permeability nature of the Port Campbell Limestone contributed to the reducing conditions at shallow depth, the high trace element concentrations of the dolomite (especially in Fe) and the near marine composition of the dolomitizing fluids, as large volumes of meteoric water were inhibited.
Anatomy and evolution of a Lower Cretaceous alluvial plain: sedimentology and palaeosols in the upper Blairmore Group, south‐western Alberta, Canada
Authors: MCCARTHY PAUL J. , MARTINI I. PETER , LECKIE DALE A.
Published: June 2006

The Lower Cretaceous (Albian) upper Blairmore Group is part of a thick clastic wedge that formed adjacent to the rising Cordillera in south‐western Alberta. Regional transgressive intervals are superimposed on the overall regressive succession. Alluvial conglomerates, sandstones and mudstones were deposited in east‐north‐eastward draining fluvial systems, orientated transverse to the basin axis. Five facies associations have been identified: igneous pebble conglomerate, thick sandstone, interbedded lenticular sandstone and mudstone, thick mudstone with thin sandstone interlayers, and fossiliferous sandstone and mudstone. The facies associations are interpreted as gravelly fluvial channels, sandy fluvial channels, sand‐dominated floodplains, mud‐dominated floodplains, and marine shoreline deposits, respectively.

Five types of palaeosols are recognized in the upper Blairmore Group based on lithology, the presence of pedogenic features (clay coatings, root traces, ferruginous nodules, slickensides, carbonate nodules) and degree of horizonization. The regional distribution of the various types of palaeosols enables a refinement of the palaeoenvironmental reconstruction permitting an assessment of the controls on floodplain evolution. In source‐proximal areas, palaeosol development was inhibited by high rates of sedimentation. In source‐distal locations, poor drainage resulting from high watertables, low topography and lower rates of sedimentation also inhibited palaeosol development. The best‐developed palaeosols (containing Bt horizons) occur in intermediate alluvial plain positions (tectonic hinge zone) where the floodplains were most stable due to a balance between sedimentation, erosion and subsidence rates. Extrapolating from the upper Blairmore Group suggests that the tectonic hinge zone of continental foreland basins can be established by palaeosol analysis. At the hinge zone, soil development is controlled primarily by climate and tectonics and their effect on sediment supply, whereas closer to the palaeoshoreline, relative sea level fluctuations, resulting in poor drainage, may have a more significant influence.
Formation of silica oncoids around geysers and hot springs at El Tatio, northern Chile
Authors: Jones Brian , Renaut Robin W.
Published: June 2006

Siliceous oncoids, up to 4 cm in diameter, are common on the laterally extensive sinter aprons that surround the spectacular geysers and hot springs at El Tatio in northern Chile. Many of these complex oncoids developed close to geyser and spring vents that discharge boiling water. Internally the oncoids, which are composed of precipitated amorphous silica, are formed of complex arrays of spicules and concentric laminae as well as detrital volcanic grains. Spicular growth is dominant in most examples. The formation and growth of the spicules and concentric laminae were mediated by a microbial community which included filamentous microbes, mucus, and possibly bacteria. The microbes and mucus were silicified by replacement and encrustation. In some laminae the filamentous microbes lay parallel to the growth surface; in other laminae most filaments forming the thin mats were suberect. Amorphous silica precipitated between the filaments occluded porosity and commonly disguised the microbial fabric.

The oncoids grew on the proximal sinter aprons around the geyser vents and hot spring pools. Most growth took place subaerially with the silica delivered to the precipitation sites by splashing water from the geysers and/or periodic shallow flooding of the discharge aprons. Unlike silica oncoids at other geothermal sites, vertical growth of oncoids that formed in some rimstone pools was not limited by water depth.
Phases of the Adoption of Innovation in Organizations: Effects of Environment, Organization and Top Managers1
Authors: Damanpour Fariborz , Schneider Marguerite
Published: June 2006

Multidimensional empirical examinations of the adoption of innovations in organizations, and the influence of factors within each dimension on the phases of adoption, are scarce. This study examines the effects of environmental, organizational and top managers' characteristics on the initiation, adoption decision and implementation of innovation. Using a sample of approximately 1200 public organizations in the United States, we found that while each dimension accounts for unique variance in the adoption of innovation, organizational characteristics and top managers' attitudes toward innovation have a stronger influence than environmental and top managers' demographic characteristics. We also found no difference in the direction of effects of any antecedent, but did find differences in the significance of effects of several antecedents, on the phases of innovation adoption. We discuss the implications of these findings and suggest ideas for future research.
CONSCIOUS OBJECTIONS: GOD AND THE CONSCIOUSNESS DEBATES
Authors: Birkett Kirsten
Published: June 2006

Abstract. Consciousness studies are dogged with religious overtones, and many researchers fight hard against Christian ideas of soul or anything supernatural. This gives many studies on consciousness a particular relevance to religious belief. Many writers assume that, if consciousness can be explained physically, religious belief in a soul—and perhaps religious belief itself—must be false. Theorists of consciousness grapple with questions of materialism and reduction in trying to understand how the physical brain can produce the bizarre sensations that we call ourselves. In this essay I discuss the problems in trying to separate religion from science in such a “fuzzy” area as consciousness. I look at the question of what precisely theories of consciousness are trying to explain. I consider theories from David Chalmers, Daniel Dennett, and Roger Penrose as examples of different approaches. Although all of these are materialistically based, I argue that they do not necessarily demonstrate the nonexistence of a soul and also that religious belief does not necessarily require belief in a nonmaterial soul. I conclude with a discussion of why a physical/ materialist explanation of consciousness is desired and how religious bias is still a problem in this scientific/philosophical field.
NATURALIZING TRANSCENDENCE IN THE NEW COSMOLOGIES OF EMERGENCE
Authors: Braxton Donald M.
Published: June 2006

Abstract. Recent discourse on emergence within the natural sciences offers a superior alternative to traditional notions of transcendence. Emergence is a term of common parlance in the natural sciences. It designates moments when various systems develop an internal dynamic that generates an entirely new level of complexity, a qualitatively different mode of existence that cannot simply be reduced to its constituent parts. To the natural scientist, emergence is an expression of transcendence without reference to final causality or central organizing principle. Autopoietic emergence is more congruent with contemporary understandings of the universe than the traditional anthropomorphizing concept of teleological design. In this article I offer both an interpretation of emergence as a new category for the interpretation of divinity and an explanation for traditional anthropomorphism rooted in contemporary cognitive sciences.
Release of glial fibrillary acidic protein is related to the neurovascular status in acute ischemic stroke
Authors: Wunderlich M. T. , Wallesch C. W. , Goertler M.
Published: June 2006

This study aimed at an analysis of glial fibrillary acidic protein (GFAP) in acute ischemic stroke, its association with the neurovascular status and its potential value as monitoring parameter. In 53 consecutive patients, serial venous blood samples were taken on admission, 6, 12, 18, 24, 48, 72, 96, and 120 h after stroke onset. The neurovascular status was assessed by repetitive extracranial and transcranial duplex sonography. Neurologic deficits were quantified by the National Institutes of Health stroke scale, and functional outcome was assessed with the modified Rankin Scale. Mean GFAP values were elevated from admission on with highest levels 48 h after stroke onset. GFAP release was highly correlated with severity of neurologic deficits and infarct volume. In patients with persistent middle cerebral artery occlusion, GFAP increased significantly compared with patients with normal sonographic findings (P = 0.019) and recanalization after thrombolysis resulted in a significant reduced increase (P = 0.038). GFAP concentrations were associated with the functional outcome after 3 months. Release kinetics of GFAP are associated with patients clinical deficits and infarct volume, depend on the neurovascular status on admission and on early recanalization after thrombolysis, and may be used as an additional predictor of the early course and functional outcome.
THE EFFECT OF THE PLANT HORMONE ABSCISIC ACID ON LIPID BILAYER MEMBRANES
Authors: LEA E. J. A. , COLLINS J. C.
Published: June 2006

Summary

In the presence of the plant hormone 2‐cis,4‐transabscisic acid, bimolecular lipid membranes exhibited conductance fluctuations of the type associated with channels. Under a voltage clamp of 100 mV, channels were observed of mean conductance 0‐4 × 10−10S and mean lifetime 0·2 msec.

Membrane conductance was measured as a function of concentration of abscisic acid and a log‐log plot of the data revealed a linear relationship. The slope of the regression line was 0·52 ± 0·08 with Pearson's product moment 0·85.

An analysis of current fluctuations is presented.

The results are discussed in terms of a process in which multimeric channels are generated from abscisic acid monomers and in which channels are destroyed by collision.
PHOTOSYNTHESIS, RESPIRATION AND WATER CONTENT IN BRYOPHYTES
Authors: DILKS T. J. K. , PROCTOR M. C. F.
Published: June 2006

Summary

Response curves of photosynthesis to water content of bryophytes of dry habitats (e.g. Tortula intermedia, Camptothecium lutescens) show an optimum, with photosynthesis declining again at high water contents. Respiration may be stimulated by water stress, but is unaffected by high water contents. The steep portions of the photosynthesis and respiration curves lie within a similar range at low water contents. Some species of constantly moist habitats (e.g. Pellia epiphylla, Hookeria lucens) show photosynthesis increasing progressively to water contents of 500 to 1000 % of dry weight, and affected at much lower water deficits than respiration as the plant dries out. The response of photosynthesis and respiration to water potential is broadly similar in the two groups. In the species investigated there was generally measurable photosynthesis at –60 to – 100 bar, but little or none at – 150 to –200 bar. Respiration continues to somewhat lower water potentials of which the limits were not determined.

Field measurements of the water content of shoots of five species over a period of 12 months showed much greater variation in Tortula muralis than in the woodland species. Maximum water contents in the field generally lay close to the optima of the photosynthesis response curves. The lower water contents recorded in these and in published data are considered in relation to sorption isotherms for bryophytes and other plant materials.

The water associated with bryophyte shoots can be divided into (1) water within the cell walls (apoplast water), (2) water within the cytoplasm (symplast water), and (3) external capillary water. Changes in water content below about –200 bar take place chiefly within (1), between c.– 200 and c. ‐ 2 bar within (2), and at higher water potentials chiefly within (3). Water movement within the shoots is physiologically important; the distribution and movement of water are mediated by the geometry of the capillary spaces of the cell walls and the plant surface. In species with papillose leaves, rates of capillary conduction in the interstices between the papillae are more than sufficient to balance evaporation. Conduction within the cell walls is likely to be important in species with non‐papillose leaves, hut other pathways may also be involved, and water movement in these species requires further investigation.
Failure of Plasma Atrial Natriuretic Peptide Levels to Increase During Exercise in Patients with Chronic Atrial Fibrillation
Authors: KELLY PAUL A. , MacAULAY‐HUNTER ESTHER , ASTRIDGE PENELOPE S. , LOWRY PHILIP J. , PERRINS E. JOHN , KAYE GERRY C.
Published: June 2006

It is generally accepted that plasma atrial natriuretic peptide release occurs secondary to atrial stretch. The influence of coordinated atrial contraction (AC) upon this process is not fully appreciated. The aim of the study was to determine the importance of coordinated AC upon peripheral atrial natriuretic peptide levels (α‐hANP) during exercise. Peripheral α‐hANP levels were measured at rest and during exercise in 12 patients with complete heart block (CHB) and permanent rate responsive pacemakers. Seven patients had coordinated AC and five had chronic atrial fibrillation (AE). Each patient performed three treadmill exercise tests. Maximal inspired oxygen volume (VO2 max) was determined during test 1. Tests 2 and 3 were performed to 70% VO2 max, the pacemaker being programmed to either VVI or VVIR mode. Plasma α‐hANP was measured using a two‐site immunoradiometric assay. At rest there was a small but significant difference between the two patient groups: AF 60.2 pg/mL versus AC 97.6 pg/mL; P = 0.03. During exercise in the AC patients, there was a significant increase in α‐hANP levels, in VVIR mode, to 238.4 pg/mL, and in VVI mode, to 207.9 pg/mL, P = 0.002 and 0.003, respectively. In those patients with chronic AF, there was no significant rise or fall in α‐hANP levels in either pacing mode, VVIR 65.2 pg/mL, VVI 46.6 pg/mL. Previous workers have suggested that α‐hANP release by nonfunctioning atria is normal. We have shown that the presence of coordinated AC is required for the release of α‐hANP during exercise in patients with CHB, and that this appears to be independent of ventricular rate.
Age and Sex Related Changes in Heart Rate to Ventilation Coupling: Implications for Rate Adaptive Pacemaker Algorithms
Authors: RICKLI HANS , MacCARTER DEAN J. , MAIRE RENÉ , AMANN FRANZ W. , CANDINAS RETO
Published: June 2006

Minute ventilation (VE) controlled rate adaptive pacemakers determine the paced rate increase during exercise by measuring changes in transthoracic impedance that have been shown to correlate well with VE. To determine the normal coupling of heart rate (HR) to VE, this relationship was evaluated in 30 younger and 25 older, healthy subjects using peak cardiopulmonary exercise testing. After determining the anaerobic threshold (AT), the linear HR to VE slope was determined both below and above the AT. In addition, the entire curve of the HR to VE relationship was assessed by a “best fit” regression analysis method. The relationship of HR to VE was more often logarithmic in younger as compared to older subjects. The HR to VE slope below the AT was always steeper than above the AT in younger subjects. Females of both age subgroups demonstrated a significantly greater slope below and above the AT. For the appropriate programming of VE controlled, rate responsive pacemakers, one should take into consideration age‐ and sex‐specific differences in the HR to VE relationship throughout exercise. Therefore, age‐ and sex‐specific programmable features for rate responsive parameters should be incorporated into pacemakers using VE controlled rate adaptive algorithms.
Retromammary Implantation of an ICD Using a Single Lead System: An Alternative Approach to Pectoral Implantation in Women
Authors: GADHOKE ARUN , ROTH JAMES A.
Published: June 2006

Pectoral ICD implantation, although feasible with the release of smaller devices, can be cosmetically disturbing to some patients due to the device protruding under the skin. An ICD was implanted using the retromammary approach in a 25‐year‐old female patient. Retromammary implantation of an ICD is feasible and offers an alternative approach in women.
New Onset Complete Heart Block and Corrected Transposition of Great Arteries in the Seventh Decade
Authors: YEŞİL MURAT , BAYATA SERDAR , POSTACI NURSEN , AKSOY IBRAHIM
Published: June 2006

A 65‐year‐old female was hospitalized for syncope due to new onset complete heart block. An apical holosystolic murmur was detected on physical examination. Echocardiography revealed corrected transposition of great arteries, and Ebstein‐like anomaly with regurgitation at the left‐sided tricuspid valve. A single chamber (VVI) pacemaker was implanted and patient has been asymptomatic thereafter.
Comparison of Defibrillation Efficacy Using Biphasic Waveforms Delivered from Various Capacitances/Pulse Widths
Authors: LIN JACK H. , STOTTS LARRY J. , ROSBOROUGH JOHN P. , FREDERICK HOLGAR
Published: June 2006

The efficacy of the biphasic waveform shock for the defibrillation of the ventricular myocardium has been reported by researchers and physicians. Although many authors have suggested that biphasic waveforms delivered from lower capacitances and shorter pulse widths could result in the reduction of the energy required for sucessful defibrillation, no report has described the smallest capacitance and pulse width yielding the lowest DFT. In the study, we compared efficacies of the biphasic waveform shocks and DFT safety margins among five different capacitances (175 μf, 125 μf, 100 μf, 75 μf, and 50 μf) combined with 1–3 pulse widths. These experiments perfomed in six dogs used an endocardial lead/subcutaneous patch defibrillation electrode system. The average DFTs at E50 for 175 μf (6.5/3.5 ms), 125 μf (6.5/3.5 ms), 100 μf (6.0/3.0 ms), 75 μf (4.0/2.0) ms, and 50 μf (3.0/2.0 ms) were 8.5, 10.0, 11.0, 14.0, and 16.5 J, respectively. These results indicate that a biphasic waveform delivered from a larger capacitance with a proper pulse width could achieve a higher defibrillation efficacy. All DFTs at E50 for all waveforms were compared to their deliverable energies and maximum stored energies. This comparison indicated a narrow DFT safety margin with capacitances below 100 μf. Therefore, it is concluded that higher energy and higher leading edge voltage are required for a biphasic waveform delivered from a smaller capacitance with a shorter pulse width. Since the current capacitor technology provides a maximum voltage of 750 V using two capacitors in series, with the electrode impedance system used in this study, smaller capacitors appear to have a decreased probability of defibrillation success at a given energy.
Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators: How Many Attempts Are Useful?
Authors: FRIES ROLAND , HEISEL ARMIN , KALWEIT GERHARD , JUNG JENS , SCHIEFFER HERMANN
Published: June 2006

The purpose of this study was to determine the termination and acceleration rates for 1 to 6 attempts of antitachycardia pacing (ATP) delivered by ICD in order to terminate spontaneously occurring VTs. Twenty‐four ICD recipients with active ATP programs, including a maximum of six ATP sequences and spontaneously occurring VTs during follow‐up, were investigated. During a mean follow‐up of 42 ± 15 months (range, 17–63 months) 413 spontaneous VT episodes (17 ± 14; range, 1–49 per patient) resulting in appropriate ATP delivery by the ICD occurred. ATP successfully terminated 328 episodes (80 %) with a mean number of 1.6 ± 1.1 pacing sequences. Eighty episodes (19%) were accelerated by ATP and 5 (1%) were unresponsive to ATP. The ATP success decreased until the third ATP sequence (59%→ 31%→ 24%), but increased again in the fourth to sixth attempt (46%→ 46%→ 29%). The acceleration rate increased from sequence one to sequence three (8%→ 13%→ 28%), but decreased significantly in further ATP attempts (19%→ 0%→ 0%). The mean time delays until redetection or termination after 4, 5, and 6 attempts of ATP were 22 ± 5 seconds, 37 ± 2 seconds, and 41 ± 9 seconds, respectively. Nine patients (37%) used ≥3 ATP attempts during follow‐up and all of them had a therapeutic benefit from it. Five out of 13 VTs (38%) treated with ≥4 attempts could ultimately be terminated by ATP. The results of this study demonstrate that the first ATP sequence is the most effective and that > 4 ATP attempts may be useful in a minority of patients. There seems to be a low risk of VT acceleration by the fourth to sixth ATP sequence. Because of the associated time delay, a high number of ATP attempts should only be programmed in patients with hemodynamically well‐tolerated stable VTs.
Complications Associated with Pectoral Implantation of Cardioverter Defibrillators
Authors: GOLD MICHAEL R. , PETERS ROBERT W. , JOHNSON JAMES W. , SHOROFSKY STEPHEN R. ,   for the WORLD‐WIDE JEWEL INVESTIGATORS
Published: June 2006

Pectoral placement of ICD pulse generators is now routine after downsizing of these devices. However, the safety of this approach is not well documented. The aim of this study was to evaluate complications in a large cohort of patients undergoing initial pectoral ICD implantation. The subjects for this study were 1,000 consecutive patients receiving a Medtronic Jewel ICD at 93 centers worldwide. Cumulative follow‐up for all patients was 634 patient‐years, with 64.9% of patients followed for 6 months or longer. The complications evaluated were erosion, pocket hematoma, seroma, wound infection, dehiscence, device migration, lead fracture, and dislodgment. In this series, 1.8% of patients experienced a pocket complication with only 3 (0.3%) erosions and 2 (0.2%) infections. Lead complications were observed in 2.1% of subjects, most commonly early dislodgment of the RV lead. We conclude that pectoral implantation of a downsized ICD system can be performed with a low rate of complications. However, careful attention to anchoring techniques and close early monitoring is important given the 1.7% rate of lead dislodgment that occurred primarily during the first month following implantation.
Patients' Attitudes Toward Implanted Defibrillator Shocks
Authors: AHMAD MAHA , BLOOMSTEIN LAUREN , ROELKE MARC , BERNSTEIN ALAN D. , PARSONNET VICTOR
Published: June 2006

In addition to its beneficial effect on patient survival, the implanted cardioverter defibriliator (ICD) changes a patient's life physically, socially, and psychologically. For improved patient management, it is important to understand the quality‐of‐life changes that accompany this mode of treatment. To this end, 119 patients were surveyed retrospectively and interviewed concurrently regarding their emotional, physical, and behavioral responses to ICD shocks and to the device itself. Most (55%) correctly estimated the total number of shocks they had received within a 10% margin. They found the shocks severe, 79% assigning a score between 3 and 5 on a scale of 1–5. Common descriptions of the shock sensation were a blow to the body or a spasm causing the entire body to jump. Most patients tolerated the shocks as life saving, but 23% dreaded shocks and 5% even said they would rather be without the ICD and take their chances. After a shock, 50% of patients called their physician and 42% continued their daily routine. Thirty percent went to a hospital emergency room or called a rescue service. Sixty‐five percent had no preshock prodromes. Fifty‐four percent were interested in the programmable option of a warning signal prior to a shock, while 31 % preferred no warning. Of the 74% who were advised not to drive after implantation, 29% drove anyway. Five patients were shocked while driving with no resulting accidents. We conclude that most patients find ICD shocks moderately uncomfortable, but they tolerate them because of the lifesaving protection provided by the device.
Assessing the Psychosocial Impact of the ICD: A National Survey of Implantable Cardioverter Defibrillator Health Care Providers
Authors: SEARS SAMUEL F. , TODARO JOHN F. , URIZAR GUIDO , LEWIS TARA SAIA , SIROIS BRIAN , WALLACE ROBYN , SOTILE WAYNE , CURTIS ANNE B. , CONTI JAMIE B.
Published: June 2006

The implantable cardioverter defibrillator (ICD) provides a survival advantage over antiarrhythmic medications for patients with life‐threatening ventricular arrhythmias. However, the effect of ICD therapy on quality‐of‐life and psychosocial functioning are not as well understood. Health care providers (e.g., physicians, nurses) can serve as a valuable source of information related to these ICD outcomes. The purpose of this study was to investigate health care provider perceptions regarding: (1) the quality‐of‐life and psychosocial functioning of their ICD recipients, (2) the concerns or problems reported by ICD recipients, and (3) the degree of provider comfort in managing these concerns. The final sample of health care providers (n = 261) rated ICD recipients' global quality‐of‐life and psychosocial functioning, and specific concerns about health care, lifestyle, special population adjustment, marital and family adjustment, and emotional well‐being. With regard to quality‐of‐life, health care providers reported that the majority of ICD recipients were functioning better (38%) or about the same (47%) than before implantation. However, health care providers reported that 15% of recipients experienced worse quality‐of‐life postimplantation. Similarly, health care providers indicated that 10%‐20% of ICD recipients experienced worse emotional functioning and strained family relationships. Moreover, issues related to driving, dealing with ICD shocks, and depression were the most common ICD recipient concerns. Significant differences were noted between physicians and nurses/other health care professionals on a wide range of psychosocial issues. Health care providers generally reported the most comfort dealing with traditional medical issues (i.e., patient adherence), and the least comfort in managing emotional well‐being issues (e.g., depression and anxiety). These results suggest that routine attention to ICD quality‐of‐life and psychosocial outcomes is indicated for health care providers who care for ICD recipients.