Unstable Substrate Research Articles

Dynamics and kinematics of ant locomotion: do wood ants climb on level surfaces?

The biomechanics of running in small animals have remained poorly characterized because of the difficulty of recording three-dimensional ground reaction forces. Available techniques limit investigations to animals with a body mass above 1 g. Here we present, for the first time, single-leg ground reaction forces of ants (body mass 10 mg), measured with a custom-built miniature force plate. We investigated forces and high-speed kinematics for straight level runs (average speed: 8.4 cm s(-1)) of Formica polyctena workers. The major finding was that the time course of ground reaction forces strongly differed from previous observations of larger insects. Maximum vertical force was reached during the first third of the tripod contact phase. During this period the body was decelerated predominantly by the front legs. Subsequently, the front legs pulled and accelerated the body. This 'climbing' type of stride may be useful on the bumpy and unstable substrates that the animals face in their natural habitats, and may therefore also occur on level ground. Propulsive forces were generated predominantly by the front and hind legs. Dragging of the gaster on the substrate resulted in a breaking momentum, which was compensated by the legs. Future investigations will reveal, whether the identified pattern is due to specialization.

Spatial and seasonal changes of net plankton and zoobenthos in Lake Tonle Sap, Cambodia

To clarify spatial and seasonal differences in net plankton and zoobenthos in Lake Tonle Sap, Cambo- dia, quantitative surveys were carried out at 14 stations in the north and south basins in high- and low-water seasons during 2003-2005. In the phytoplankton communities, a diatom Aulacoseira granulata dominated throughout the lake in the high-water seasons, while blue-green algae, mostly composed of Microcystis, surpassed other algae in the low-water season when the lake water was very turbid and the Secchi disk readings were only a few centimeters. In the low-water seasons, a bloom of floating blue-green algae occurred everywhere, especially prominent in the coastal areas. Protozoans and rotifers dominated the zoo- plankton communities. In the open-water stations, diversity was higher in high-water seasons in phytoplankton, while it was not significantly different between seasons in zoo- plankton. Composition of plankton communities in Lake Tonle Sap appears to have changed little since the 1950s, at least in phytoplankton, while the phytoplankton density appears to be higher in the present study. Among the mac- rozoobenthos, mollusks, oligochaetes and chironomids dominated in density, and mollusks exceeded others in bio- mass in both basins and seasons. The total densities of macrozobenthos were not high, being fewer than 1,300 m -2 throughout the stations and seasons. Possible reasons for the low zoobenthos abundance in the lake may include high predation pressures by benthivorous fish or unfavorable unstable and flocculant substrates.

Ecological aspects of endemic plant populations on Klang Gates quartz ridge, a habitat island in Peninsular Malaysia

The population characteristics of Aleisanthia rupestris (Rubiaceae), Eulalia milsumii (Poaceae) and Ilex praetermissa (Aquifoliaceae), endemic to the Klang Gates quartz ridge north-east of Kuala Lumpur, Malaysia were studied. Whereas their narrow, natural distribution within species-poor communities in drier, less fertile conditions on the ridge can be explained by the selection of adaptive traits and reduced plant competition compared to the more extensive, surrounding richer forest communities on more fertile soils, recent disturbances altering site conditions have diminished their populations. Populations were compared among various terrain and site conditions (ridge spine or rockface, exposed or sheltered) on less disturbed and very disturbed portions of the ridge. A. rupestris was scarce or absent in sites shaded by taller vegetation, probably an inability to establish in conditions associated with deeper soil development. I. praetermissa appeared specially adapted to rockfaces where unstable substrates and poor soil development may restrict competition with other plants. All three species were adversely affected to varying degrees by disturbance and altered site conditions; invasive, fast-spreading, thicket-forming, weeds in disturbed sites on gentler terrain on the ridge spine appear to be especially detrimental to A. rupestris and E. milsumii establishment. Although the larger plant size of I. praetermissa compared to the other two species could mean it is less likely to be shaded out by invading weedy species, residual adults as well as new regeneration may not adapt to changed site conditions following disturbance. Distinguishing between adaptation (of both adults and new regeneration) to changed environmental conditions following disturbance, and ability in competing for space and resources against invading weedy species, is relevant.

Role of a Conserved Pore Residue in the Formation of a Prehydrolytic High Substrate Affinity State in the AAA+ Chaperone ClpA

The AAA+ protease ClpAP, consisting of the ClpA chaperone and the ClpP protease, processively unfolds and translocates its substrates into its proteolytic core, where they are cleaved. Unfolding and efficient translocation require ATP-dependent conformational changes in ClpA's D2 loop, where the conserved GYVG motif resides. To explore the role of the essential tyrosine of this motif, we investigated how two mutations at this residue (Y540C and Y540A) affect the rate at which the enzyme processes unstructured substrates. The mutations decrease ClpA's ability to process unfolded or unstable protein substrates but have only mild effects on the rates of ATP hydrolysis or hydrolysis of small peptide substrates. The mutants' substrate binding properties were also characterized, using single molecule fluorescence microscopy. The single-molecule studies demonstrate that the conserved tyrosine is essential for the formation of the prehydrolytic, high substrate affinity conformation observed in wild-type ClpA. Together, the results support a model in which destabilization of the high substrate affinity conformation of ClpA makes translocation less efficient and uncouples it from ATP hydrolysis.

Post-disturbance erosion impacts carbon fluxes and plant succession on recent tropical landslides

Tropical landslides are suitable locations to study short-term carbon (C) fluxes because of the rapid changes that occur for the first few years following initial disruption of the slope. Because of the high heterogeneity among landslide soils and plant re-colonization patterns, we measured C fluxes from 30 landslides in the Luquillo Experimental Forest in northeastern Puerto Rico from 8–13 months after landslide formation. Post-landslide erosion resulted in significantly higher soil output on dioritic than on volcaniclastic soils, with no temporal decline in soil output during the study. Much more C was found in landslide soils than in plant biomass, and we estimate that 6–24% of the soil C standing stock would erode from our plots within 1 year. Even the relatively small amount of C in plant matter was in flux, with four to five times plant C standing stock deposited into the plots as plant litter and two times standing stock leaving our plots in 1 year. This rapid turnover of C is indicative of highly unstable substrates that likely stabilize over successional time. We combined our short-term study with past chronosequence studies to project long-term carbon movement in landslides. We suggest that landslides in Puerto Rico represent a net down slope movement of C despite deposition from surrounding forest soils, litter from the surrounding landscape and in situ successional re-growth.

Fermentative production of l‐glycerol 3‐phosphate utilizing a Saccharomyces cerevisiae strain with an engineered glycerol biosynthetic pathway

Interest in L-glycerol 3-phosphate (L-G3P) production via microbial fermentation is due to the compound's potential to replace the unstable substrate dihydroxyacetone phosphate (DHAP) in one-pot enzymatic carbohydrate syntheses. A Saccharomyces cerevisiae strain with deletions in both genes encoding specific L-G3Pases (GPP1 and GPP2) and multicopy overexpression of L-glycerol 3-phosphate dehydrogenase (GPD1) was studied via small-scale (100 mL) batch fermentations under quasi-anaerobic conditions. Intracellular accumulation of L-G3P reached extremely high levels (roughly 200 mM) but thereafter declined. Extracellular L-G3P was also detected and its concentration continuously increased throughout the fermentation, such that most of the total L-G3P was found outside the cells as fermentation concluded. Moreover, in spite of the complete elimination of specific L-G3Pase activity, the strain showed considerable glycerol formation suggesting unspecific dephosphorylation as a mechanism to relieve cells of intracellular L-G3P accumulation. Up-scaling the process employed fed-batch fermentation with repeated glucose feeding, plus an aerobic growth phase followed by an anaerobic product accumulation phase. This produced a final product titer of about 325 mg total L-G3P per liter of fermentation broth.

Influencing the binding configuration of sucrose in the active sites of chicory fructan 1-exohydrolase and sugar beet fructan 6-exohydrolase.

The hydrolytic plant enzymes of family 32 of glycoside hydrolases (GH32), including acid cell wall type invertases (EC 3.2.1.26), fructan 1-exohydrolases (1-FEH; EC 3.2.1.153) and fructan 6-exohydrolases (6-FEH; EC 3.2.1.154), are very similar at the molecular and structural levels, but are clearly functionally different. The work presented here aims at understanding the evolution of enzyme specificity and functional diversity in this family by means of site-directed mutagenesis. It is demonstrated for the first time that invertase activity can be introduced in an S101L mutant of chicory (Cichorium intybus) 1-FEH IIa by influencing the orientation of Trp 82. At high sucrose and enzyme concentrations, a shift is proposed from a stable inhibitor configuration to an unstable substrate configuration. In the same way, invertase activity was introduced in Beta vulgaris 6-FEH by introducing an acidic amino acid in the vicinity of the acid-base catalyst (F233D mutant), creating a beta-fructofuranosidase type of enzyme with dual activity against sucrose and levan. As single amino acid substitutions can influence the donor substrate specificity of FEHs, it is predicted that plant invertases and FEHs may have diversified by introduction of a very limited number of mutations in the common ancestor.

Late Neoproterozoic carbonate productivity in a rifting context: the Adoudou Formation and its associated bimodal volcanism onlapping the western Saghro inlier, Morocco

Abstract An interval of episodic carbonate productivity, lithostratigraphically recognized as the ‘Calcaires inférieurs’ (upper member of the Adoudou Formation), took place across the Neoproterozoic–Cambrian transition onlapping the western Saghro inlier, Morocco. Sedimentation of the ‘Calcaires inférieurs’ was highly variable: in relatively stable substrates, a peritidal-dominated mixed platform is recorded where deposition was primarily controlled by autocyclic processes and accommodation space availability, whereas, in unstable substrates, the tectonic activity associated with the inherited block-faulting basement led to deposition of complex slide sheets composed of penecontemporaneous isoclinal folds and disrupted strata. The uppermost part of the ‘Calcaires inférieurs’ displays a negative δ 13 C shift reaching values of −6.5‰. This shift may represent the δ 13 C excursion to −6‰ that marks the Neoproterozoic–Cambrian boundary in the western Anti-Atlas. Two volcanic episodes bracketed the carbonate productivity. They consist of lower basaltic flows and an upper rhyolitic ignimbrite, with a SiO 2 gap between 52 and 74 wt%. The basic rocks resemble those of tholeiitic magmas in continental rifts. The felsic rocks show high light to heavy rare earth element abundances and negative Nb, Ta, P and Ti anomalies, and were probably generated as a result of either fractional crystallization coupled with relative crustal contamination, or from a different magmatic source. The lower basic flows of tholeiitic affinity predated and geochemically differ from the alkaline magmatism of the Alougoum volcanic complex (Boho jbel) that surrounds the neighbouring Bou-Azzer inlier.

Stability of reef framework and post settlement mortality as the structuring factor for recovery of Malakal Bay Reef, Palau, Micronesia: 25 years after a severe COTS outbreak

Corals in Malakal Bay reefs were devastated in the 1979 Crown of Thorns Starfish (COTS) outbreak. It has been almost 30 years since the outbreak and coral cover at the study sites have not come close to the cover before the outbreak. A question is asked: what factors may contribute to the slow recovery of these reefs: recruitment or post-settlement mortality? Two habitat types within the reef systems were monitored using coral transplants to determine if corals can survive in these environments and recruitment tiles to see if there are larvae coming into the system. The study revealed that coral survivorship is high in the fore reef areas compared to the reef channel slopes and that larvae is not a limiting factor to natural recovery. Stability of the reef framework, i.e. unstable rubble substrate, and possibly high post settlement mortality, are the structuring factors that determine the recovery process in these reef systems and possibly so for similar habitats in other reef systems throughout Palau.

Palaeoecology of solitary corals in soft-substrate habitats: the example of Cunnolites (upper Santonian, Eastern Alps)

The upper Santonian Hofergraben Member (Eastern Alps) provides an example of a soft-substrate habitat suited mainly for solitary corals (Cunnolites), for colonial forms of solitary coral-like shape (Placosmilia, Diploctenium), and for colonial corals of high sediment resistance (e.g. Actinacis, Pachygyra). The Hofergraben Member consists mainly of silty-sandy marls of wave-dominated, low-energy shore zone to shallow neritic environments. Substrates of soft to firm mud supported level-bottoms of non-rudist bivalves, gastropods, solitary corals, colonial corals, rudists, echinoids, and benthic foraminifera. Boring and/or encrustation of fossils overall are scarce. In the marls, Cunnolites is common to abundant. Both a cupolate shape and a lightweight construction of the skeleton aided the coral to keep afloat soft substrata. Cunnolites taphocoenoses are strongly dominated by small specimens (about 1–3 cm in diameter). Cunnolites was immobile and mostly died early in life upon, either, smothering during high-energy events, rapid sedimentation associated with river plumes, or by toppling and burial induced by burrowing. Comparatively few large survivor specimens may show overgrowth margins interpreted as records of partial mortality from episodic sedimentation or tilting on unstable substrate. Scattered pits and scalloped surfaces on large Cunnolites may have been produced, in some cases at least, by predators (durophagous fish?). Post-mortem, large Cunnolites provided benthic islands to corals, epifaunal bivalves and bryozoans. In a single documented case of probable in vivo contact of Cunnolites with the colonial coral Actinastraea, the latter prevailed.

Uncertainty on the Use of Aldosterone Antagonists for Primary Therapy for Sudden Cardiac Death in the Setting of Implanted Devices

In the early development of therapy for acute myocardial infarction, it was thought that once the necrotic process had been completed (usually within 24 hours of coronary artery occlusion), additional therapies could not affect outcome. However, after completion of the necrotic process, the myocardial infarction may thin and stretch (involving lengthwise slippage of myocytes), a phenomenon referred to as myocardial infarct expansion. This process causes local left ventricular cavity dilatation followed by gradual global left ventricular dilatation and lengthwise (eccentric) hypertrophy of the noninfarcted tissue. Apoptosis (programmed cell death) and some attempt of the myocardium to regenerate, especially at the infarct border zone, may also contribute to this remodeling process of the ventricle. If the left ventricle remodels in such a way that it becomes very dilated, then the prognosis is poor, and heart failure is more likely to occur.1 These later processes of myocardial infarct expansion and left ventricular remodeling became the target of therapies such as angiotensin-converting enzyme (ACE) inhibition that could be initiated after 24 hours of coronary occlusion. ACE inhibition, angiotensin receptor blockade, and long-term β-blockade have become standard pharmacological approaches for postinfarction left ventricular dysfunction and heart failure. Response by Pitt and Pitt p 2989 Ventricular arrhythmias can occur in both the acute and chronic phases of acute myocardial infarction and can lead to sudden cardiac death (SCD). Reentrant arrhythmias may arise at the border zone of infarcts, causing monomorphic ventricular tachycardia that may occur years after the index infarction. Recurrent myocardial ischemia resulting in an unstable substrate may contribute to polymorphic ventricular tachycardia or ventricular fibrillation. Agents such as β-blockers that are anti-ischemic may reduce sudden death by quieting this unstable substrate. In the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II, implantable defibrillators were shown to reduce mortality in post–myocardial infarction patients with …

Calcium carbonate seafloor precipitates from the outer shelf to slope facies of the Lower Triassic (Smithian-Spathian) Union Wash Formation, California, USA: Sedimentology and palaeobiologic significance

Formerly aragonite seafloor fans from the Lower Triassic (Smithian-Spathian) Union Wash Formation of east-central California were examined to determine the processes active during their growth. The seafloor fans were deposited in an outer shelf to slope environment along the western margin of Pangaea, and are contained within two stratigraphic intervals. The lower precipitate-bearing interval is 130 m thick, comprised of micritic limestone, and contains precipitates that fall into 2 end-member morphologies: 1) laminated precipitate masses that contain distinct hemispheres or fans; and 2) precipitate masses that are composed of a complex interlocking mosaic of hemispheres or fans. Precipitates found in the bedded, lower half of the interval are typically 2–3 cm tall and 10–20 cm wide, and are commonly undercut, disturbed, and, in the case of the interlocking mosaics of hemispheres, show evidence of entrainment and transport by density currents. Precipitates are larger in the upper, massive portion of the lower precipitate-bearing interval and occur only as interlocking hemisphere/fan mosaics. Fans and hemispheres attain heights as tall as 30 cm, and precipitate bodies, made of interlocking mosaics of hemispheres and fans, attain thicknesses of up to 50 cm and widths of 1–2 m. Chaotic bedding, broken precipitates, and brecciation of precipitate bodies imply an unstable and mobile substrate. The upper precipitate-bearing interval is 30 m thick, comprised of bivalve-, ammonoid- and microgastropod-bearing wackestone, and is separated from lower precipitate-bearing strata by 23 m of interbedded shale and calcareous siltstone. Much of the upper precipitate-bearing unit was deposited by subaqueous debris flows, as suggested by multiple breccias contained within the interval. Seafloor cements are found in undisturbed units and rarely within breccia clasts, suggesting that precipitates formed locally as well as higher on the shelf. Precipitate growth was likely the result of an increase in the saturation state of calcium carbonate in Early Triassic oceans, related to widespread oceanic anoxia. The presence of unusual carbonates during the period, and their correlation with depauperate faunas in the equivalent shallow facies of the Virgin Limestone, suggest that the remarkable oceanographic conditions associated with precipitate growth likely dampened the biotic recovery in the region until those conditions disappeared in the Middle Triassic.

Multi‐stemmed trees in subtropical coastal dune forest: Survival strategy in response to chronic disturbance

AbstractQuestions: Is multi‐stemming a survival strategy in response to chronic disturbance? Is multi‐stemming under phylogenetic control? What environmental factors are associated with multi‐stemming? When do trees initiate growth of multiple stems? Do multi‐stemmed trees have limited stature?Location: Subtropical Indian Ocean coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park, northeastern South Africa.Methods: Tree physiognomy and environmental conditions were sampled in 20 transects that were 300 m long and 5 m wide.Results: 38.9 % of trees were multi‐stemmed, with no correlation between multi‐stemming and taxonomic grouping. The multi‐stemming trait was most associated with stem decumb‐ency and substrate erosion and multi‐stemmed individuals were less common in protected dune slacks. Trees at Cape Vidal appear to facultatively produce multiple stems from an early stage. There was no trade‐off between tree height and stem number.Conclusions: Coastal winds and the unstable dune substrate are important environmental correlates of multi‐stemming. Both short stature and the high incidence of multi‐stemming are related to the tree‐disturbance interaction. The taxonomically widespread phenotypic plasticity in this trait indicates the importance of multi‐stemming to tree survival even under low levels of disturbance.

Петрофитные сообщества высокогорных известняковых массивов Западного Кавказа

The paper presents description of new syntaxa of pertrophyte associations from West Caucasus lime­stone massifs. The work is based on the author’s long-term observations between years 1998 and 2003, made in the basins of the rivers Belaya, Bolshaja Laba and Malaya Laba within the National Nature Park «Bol­shoi Tkhach» and limestone massifs of Caucasian State Natural Biosphere Reserve. Original geobotanical rele­veйs have been used for the classification. Collec­tion and material processing involved Braun-Blanqet me­thod. The size of sampling plots varied from 4 to 25 m2. The paper is based upon 120 releveés. New syntaxa names have been given in accordance with the Code of Phytosociological Nomenclature (Weber et al., 2000). Ass. Veronica minutae—Chaerophylletum humilis Onipchenko 2002 is common for upper alpine belt of the Reserve and distributed over mobile calcareous screes at 2400—2800 m alt. occupying small areas of Oshten, Fisht, Pshekha-Su and Yatygvarta mountains. Ass. Helianthemetum cani ass. nov. includes open chionophobic groupings of alpine belt, developing on windward mountain slopes and crests at 2000—2800 m alt., occurs on rocky outcrops and dry sedentary screes, and covers significant areas of Lagonaki Pla­teau, mountains Bolshoi Tkhach, Yatygvarta and Snegovalka Ridge. These open associations preferen­tially occupy slopes of «warm» (southern, southern-west, southern-east) expositions of different abruptness from almost horizontal up to 70° (in average 25°). Ass. Saxifragetum sibiricae typicum Onipchenko et Lubez­nova 2002 includes chionophytic groupings of seden­tary screes, characterized by significant snow accu­mulation in winter, forms patches of vegetation around snowbeds and glaciers of Lagonaki Plateau in the Reserve, occurs sporadically on the studied territory. Ass. Saxifragetum sibiricae arabidetosum caucasicae subass. nov. combines open communities of alpine belt at unstable damp rocky substrates and predominantly occupies abrupt slopes (20—35°) of northern—nor­thern-east exposition of damp, slightly mobile screes close to glaciers at 2000—2700 м alt. on Lagonaki Plateau in the Reserve. Ass. Saxifrago cartilagineae—Asplenietum rutae-murariae ass. nov. occurs on rocks in subalpine belt predominantly on abrupt slopes (20—90°, average 69°) of different expositions at 1400—1700 m alt. on Lagonaki Plateau in the Reserve. Ass. Valeriana saxicolae—Helianthemetum cani ass. nov. includes plant communities of limestone rocks occupying abrupt slopes (20—70°, in average 53°) of predominantly southern expositions at 2000—2700 m alt. on Lagonaki Plateau, Triu-Yatygvarta massif, mountain Bolshoi Tkhach.

Arsenic in soils and plants of woodland regenerated on an arsenic-contaminated substrate: A sustainable natural remediation?

Plant As accumulation at three As-polluted sites where spontaneous re-vegetation has taken place is examined. Each site had a different source of soil As (coal fly ash, LeBlanc process waste, canal dredging). Plant analysis indicates that soil-plant As transfer is poor at each site. Any mobile As is retained in root tissues, with little transfer to shoots. Bryophytes, pteridophytes, herbaceous and woody plants sampled at each site predominantly showed As concentrations of <3 mg kg(-1) dry wt, whilst total soil As ranged between 50 and 220 mg kg(-1) dry wt. Risk associated with food chain transfer at these sites is low when compared to other routes such as direct ingestion/inhalation of As-contaminated particulates re-entrained from an unvegetated or unstable substrate.

Preparation of Crystalline TiO2 Thin Film Photocatalysts on Polycarbonate Substrates by a RF-magnetron Sputtering Deposition Method

Abstract Crystalline TiO2 thin films were successfully prepared on thermally unstable polycarbonate substrates without any inorganic or organic binders at low temperature (ca. 353 K) by a RF-magnetron sputtering deposition method. The anatase structure of TiO2 could be confirmed by XRD measurements. These thin films showed high transparency and mechanical stability and were not susceptible to peeling by scratching or bending. These TiO2 thin films prepared on polycarbonate substrates also exhibited photoinduced superhydrophilicity under UV light irradiation.

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy

Upper Cretaceous–Paleocene conifer woods from Big Bend National Park, Texas

Conifer wood types from the Upper Cretaceous Aguja and Javelina Formations and the Paleocene Black Peaks Formation of Big Bend National Park, Texas, are briefly described. The Big Bend conifer woods represent the largest assemblage of late Cretaceous conifer wood thus far described from the western interior of North America, and include samples with characteristics of the Araucariaceae and Cheirolepidiaceae, and Cupressaceae and Podocarpaceae. Cupressaceae/Podocarpaceae types of the Maastrichtian Javelina Formation have, on average, narrower rings than those of the Campanian Aguja Formation, consistent with the drier climate already proposed for the Javelina Formation. Angiosperm wood assemblages differ between the lower shale and upper shale members of the Aguja Formation, the Javelina Formation, and the Black Peaks, so do the conifer assemblages. The Big Bend conifer woods differ from those described from other western interior localities and document more variation in growth ring types than previously recognized for the whole of the northern hemisphere Late Cretaceous. The sizes of some logs and width of their growth rings suggest that some trees might have reached diameters of 1 m in approximately 80 years. Woods of the Cupressaceae/Podocarpaceae type show that the strategy of having juvenile wood with narrower tracheids and less distinct growth rings than in mature wood occurred in the Late Cretaceous. The incidence of compression wood in mature trunk wood is relatively high and may reflect either unstable substrates or frequent storms with high winds.

Room temperature synthesis of nano-carbons using an electrochemical technique of organicsolution

Room temperature synthesis of nano-carbons, i.e., whiskers, wires, onions and tubes, hasbeen achieved by an electrochemical process under a liquid phase of organic solution with ametal catalyst. The electrochemical method supplies athermal energy to the reactantscontrary to ordinary methods, i.e., this method creates nano-carbons directly transferringelectrons at the electrode in the condensed phase, and the temperature does not increaseduring the synthesis. The nano-carbons with various structures were obtained by usingC2H5OH with solution under a high electric field. The metal catalyst plays an important role inthe nano-carbon growth in the present method, in a similar way to the usualmethods. By virtue of the low temperature synthesis, this technique has greatadvantages in nano-scale interconnections and large area field emission cathodesof nano-carbons in next-generation devices on a thermally unstable substrate.

Development of Equatorial Delta-Front Patch Reefs During the Neogene, Borneo

Abstract Miocene patch reefs formed in turbid waters associated with high siliciclastic input at the seaward margin of the equatorial Mahakam Delta in eastern Borneo, SE Asia. Patch reefs were initiated on unstable substrates on localized low-relief bathymetric highs associated with delta-front channels or distributary mouthbars in the process of abandonment. Patch reefs developed only in shallow waters, formed low-relief buildups, lacked rigid frameworks, and had gently sloping margins. Although the biodiversity of the patch reefs may be comparable with that of clear-water systems, all the organisms present were adapted to turbid-water areas associated with siliciclastic, and sometimes nutrient, influx. The patch reefs were transient features, and their demise was influenced by increased siliciclastic and nutrient input, perhaps at times associated with deepening. Carbonate production and bioherm or patch-reef development can occur in turbid-water delta-front areas as localized or more regionally extensive units during any phases of eustatic sea level. However, development and preservation of turbid-water carbonates is most likely during relative transgression or perhaps late lowstand periods. This is in contrast with common highstand carbonates from clear-water shelves, where nearly pure carbonates interdigitate with siliciclastics. It is the interplay between factors such as tectonics, eustasy, delta lobe switching, shelf currents, and amount and size fraction of siliciclastic influx that ultimately controlled carbonate development and preservation.