Natural Dynamic Processes Research Articles

Scour process due to symmetric dam spillways crossing jets

The presence of a dam in a river deeply modifies the natural dynamic process, including sediment transport, debris flow and flow regime occurring both in the upstream and in the downstream branches. Thus a dam cannot be considered as an isolated element in the context of a river, and the study of all the cited phenomena has to be conducted taking its presence into account. In particular, it affects both the global and the local river erosive mechanisms. Moreover, risk management policy considers, among other variables, that in all likelihood toe erosion is the one affecting dam failures. In this perspective, even the local scour phenomenon due to plunging jets assumes a particular importance for all river engineers and has to be carefully taken into consideration in order to prevent structural risks and to correctly design protection measurements downstream of hydraulic structures. Previous studies extensively analysed both scour geometry and flow features due to one single jet. The present paper aims to study both the flow features and the scour hole lengths in the case in which two symmetric crossing jets are used. In particular, experiments were conducted by varying hydraulic and geometric parameters: jet discharge, tailwater depth, jet vertical angle and the angle between the crossing jets. Moreover, it was experimentally proven that the vertical distance of the jet crossing point from the water surface deeply influences the scour hole length. A comparison of scour hole morphology due to an equivalent single jet geometric condition is also proposed, in order to understand under what conditions crossing jets reduce the scour depth.

Effects of age and composition of field-produced biofilms on oyster larval setting

Lack of success in restoring the native Eastern oyster, Crassostrea virginica, to Chesapeake Bay has been linked to the low occurrence of oyster larval setting in tributaries to the Bay. Among the many potential factors that could affect efforts to produce oysters through aquaculture or supplementation of shell beds is substratum condition. The present study examined larval setting on field-produced biofilms from Little Wicomico River (Virginia, USA) to assess whether bacterial community structure (examined by terminal restriction fragment length polymorphism, T-RFLP) or other characteristics of contemporary biofilms in this tributary (biofilm age and mass, algal abundance, and percentage organic matter) inhibited setting of larval oysters. The structure of the natural and heterogenous bacterial community in the biofilms and the success of oyster set were correlated, suggesting that specific microbial species may play a role in oyster setting. Larval set increased with biofilm age and mass, suggesting that established field-produced biofilms have no inhibitory effect. In contrast, the percentage of organic matter was negatively correlated with oyster set, whereas chlorophyll a concentration had no observed effect. The study expands prior knowledge by providing a more realistic timeframe for biofilm development (weeks as opposed to days), recounting effects of biofilms that are more representative of the natural dynamic and disturbance processes that would be expected to occur on submerged structures, and by incorporating seasonal and spatial variation. An important negative effect observed during the study period was heavy predation by Stylochus ellipticus on newly set oysters. Overall, the results of this study, which is the first assessment of the effects of biofilms produced naturally within a Chesapeake Bay tributary, suggest that the absence of large numbers of oysters in Little Wicomico River is not related to microbes or other specific characteristics of biofilms that develop on suitable setting substrata, but rather to heavy predation of newly set larvae.

Fish habitat rehabilitation using wood in the world

To provide river managers and researchers with practical knowledge about fish rehabilitation, various studies of fish habitat rehabilitation that used wood were reviewed. The review focuses on fish responses, wood installation methods, and geomorphic features of the rehabilitation sites. Most studies were conducted in moderately sized (small and medium) streams with relatively high bed gradients and aimed to improve the habitats of salmonid species. In this stream type, structures spanning the full (log dam) and partial (log deflector) width of the river were most common, and wood structures that created pools and covers were successful in improving fish habitat. Some projects were conducted in moderately sized low-gradient streams, in which wooden devices used to create instream cover were effective for fish assemblages. There were few studies in other aquatic ecosystems. However, well-designed large wood structures, known as engineered log jams, were used in rehabilitation projects for large rivers. In slack-water or lentic systems such as side-channels, estuaries, and reservoirs, small and large wood structures that created cover were used to improve habitat for many fish species. For successful fish habitat rehabilitation projects, the hydrogeomorphic conditions of rehabilitation sites should be carefully examined to avoid physical failure of wood structures. Although artificial wood structures can be used to improve fish habitat in various aquatic ecosystems, they should be considered to be a complementary or interim habitat enhancement technique. The recovery of natural dynamic processes at the watershed scale is the ultimate target of restoration programs.

Relative importance of dynamical and chemical contributions to Arctic wintertime ozone

We present the first complete budget of the interannual variability in Arctic springtime ozone taking into account anthropogenic chemical and natural dynamical processes. For the winters 1991/1992 to 2003/2004 the Arctic chemical ozone loss is available from observations. This work investigates the dynamical supply of ozone to the Arctic polar vortex due to mean transport processes for the same winters. The ozone supply is quantified in a vortex‐averaged framework using estimates of diabatic descent over winter. We find that the interannual variability of both dynamical ozone supply and chemical ozone loss contribute, in equal shares, to the variability of the total ozone change. Moreover, together they explain nearly all of the interannual variability of Arctic springtime column ozone. Variability in planetary wave activity, characterized by the Eliassen‐Palm flux at 100 hPa, contributes significantly to the variability of ozone supply, chemical ozone loss and total springtime ozone.

Microanalytical flow-through method for assessment of the bioavailability of toxic metals in environmental samples

The application of a recently proposed microanalytical flow-through system for on-line sequential extraction of heavy metals from solid samples of environmental interest is described. Using various extraction schemes (a nitric acid scheme, a two-stage extraction scheme using two reagents applied in the BCR procedure) and comparison with the common batch sequential BCR procedure, the suitability of the system for fast screening of solid environmental samples is demonstrated. By pumping leaching agents sequentially through the sample held in a micro cartridge, the different metal fractions present can be assessed in less than an hour. Method evaluation was performed using SRM 1648 urban particulate matter and BCR 701 lake sediment reference material certified for extractable metals. The need for and design of laboratory internal reference material suitable for simulating the natural (dynamic) processes of metal release into the environment is also discussed. For the first time correlation is sought between fractionation techniques and physiologically based methods for assessment of the bioaccessibility of metals in biomatrices.

Integrated management of artificially created salt marshes in the Wadden Sea of Schleswig-Holstein, Germany

In the about 10,000 km2 large Wadden Sea 353 km2 of salt marshes exist. The great majority of these are artificial, i.e. developed through accretion enhancement techniques. Salt marshes in the Wadden Sea have a high coastal defence value as well as ecological significance. High salt marshes in front of sea walls reduce the wave-impact on the dikes and, therewith, the danger of breaching. At the same time, the salt marshes have a high ecological value, e.g., as resting places for migratory birds. In consequence, for coastal defence, salt marshes should be created and/or maintained. For nature protection, natural dynamic processes (incl. erosion) should prevail. To anticipate this possible conflict among coastal defence and environmental administration, in Schleswig-Holstein an interdepartmental working group established a salt marsh management concept. For information of the interested parties and for monitoring of the concept, an integrated salt marsh board was established, consisting of representatives from public administration and local interest groups (NGO's, dike and water boards, municipalities). Five years after implementation of the concept, this board established a first progress report. Although the concept was, in the beginning, met with great scepticism, five years of practical experience demonstrate that it functions well. The salt marshes are stable or growing, i.e. the management measures are successful. As a planning instrument, the concept is unambiguous, i.e. provides clear guidelines on how to manage the salt marshes. Finally, as an instrument of participation, the salt marsh board is valued positively by all members.

Ecological quality objectives for the Dutch sector of the North Sea, an outline of a policy under development

We describe the process of formulating ecological quality objectives for the Dutch sector of the North Sea and the future steps that have to be taken before they can be translated into management measures. The project ‘North Sea Ecosystem Objectives’ started in January 1999 with the distinction of twelve rather broad objectives. They range from ‘natural dynamic processes’ (e.g. transport of sand and sediment), through aspects of ‘biodiversity’ (e.g. fish fauna and sea birds) to issues of ‘human perception’ (e.g. open horizon and panoramic view). The objectives were worked out on the basis of available scientific information and concretised into ecological targets. We highlight the targets for the fish fauna as an example. After consultation of the stakeholders, the effects of the various human activities in relation to the ecological objectives have been classified according to type and seriousness. Fisheries turned out to be by far the number one on the list of intervening activities. Shipping is also high on the list. Eutrophication is a serious factor in the coastal zone, whereas large-scale sand extraction will cause problems in the near future. During the next phase of the project, policy decisions will be made on the most relevant set of ecological targets, possible management measures and ways of implementation. With regard to the most problematic activity (i.e. fisheries; particularly beam trawling on flatfish), a first start has been made with a discussion on several options for measures meant to spare fish populations, nursery areas and bottom fauna. Due to the international context of fisheries management, measures regarding fisheries on the NCP will always need international agreement.

Alternative stable states of macrophytes versus phytoplankton in two interconnected impoundments of the New Danube (Vienna, Austria)

Natural dynamic processes leading to a shift from algal to macrophyte domination in the two impoundments of the New Danube flood-relief channel are associated with and explained by a theory of bi-stable states. Changes are largely caused by alterations of water level and hence the retention times of the impoundments. Implications for water quality evaluation are discussed using the concept of potential water column concentrations of phosphorus. Calculations indicate the importance of macrophytes as structures that can buffer nutrient concentrations, via uptake and storage in plant tissues Results are contrasted with similar hut anthropogenically-induced forward and reverse shifts in the nearby Old Danube seepage lake, and implications for lake management are discussed.

The transformation of dynamic parameters of oil-contaminated sediments of North European Russia

The study of dynamic parameters of terrigenious material was carried out in subaqueous areas of the North European Russia and in the coastal Pechorskoe sea including Pechora river delta. The areas are characterized by extremely wide spreading of fluxes, lakes, marshes. This is the intensive exploited oil-gas area. The geological survey and the existence of pooled recoverable hydrocarbons are accompanied by the pollution of the natural environments and upper lithosphere. The main oil-pollution is accumulated in soils and sediments of small flows. The periodic processes (high-flood, snow thaw) include the contaminated sediments in transfer. According by the natural investigations of the spreading range of oil-pollutions connected with terrigenious material can be highly essential.The experimental work was based on the comparison of structural and dynamic characteristics of polluted sediments and the same sediments purified from oil-products. The average breaking and accumulated velocities for the sediments of different lithology with various concentrations of oil-products were determined. Parallel we determined : the character of interaction of mineral and oil parts (morphological forms of oil-contaminents), the quantitive and qualitative composition of oil-products in different size fractions of sediments.The dynamic of moderately oil-contaminated sediments is governed by natural dynamical processes. At 10 and more times background concentrations, oil-products influence to the structural changes of sediments and as a result to the processes of transfer and accumulation.The results of investigations allow us to predict the distance of migration, possible zones of accumulation and the scale of oil-pollution in bottom sediments.

A three‐dimensional simulation of the Antarctic ozone hole: Impact of anthropogenic chlorine on the lower stratosphere and upper troposphere

We have developed a global three‐dimensional transport‐chemical model of the stratosphere (called the Study of Transport and chemical Reactions in the Stratosphere (STARS)) which includes a representation of the formation of polar stratospheric clouds (PSCs) and heterogeneous reactions on the surfaces of PSCs and sulfate aerosols. The formation of the observed springtime “Antarctic ozone hole” is well reproduced by the model. A maximum of 40% total ozone depletion occurs in October. Calculated ozone and chlorine concentrations are consistent with satellite observations. After the breakdown of the polar vortex in December, air with depleted ozone is transported to midlatitudes in the southern hemisphere, resulting in a 2–4% ozone decrease at 50°S in December and a 1% decrease in the sub tropics. Ozone‐poor air masses are also transported to the troposphere and produce a significant decrease in upper tropospheric ozone. Model calculations show that the calculated ozone depletion is not significantly modified when type I PSC particles are assumed to be liquid ternary solutions (H2SO4/HNO3/H2O) rather than solid nitric acid trihydrates. Ice particles (type II PSCs) sediment into the troposphere, producing a large decrease in the concentrations of stratospheric HNO3 and NO2. As a result, the conversion of ClO into ClONO2 is reduced, and the concentration of reactive chlorine remains high for two additional weeks. The ozone column abundance is reduced by an additional 10% during the month of October. The model results show that the ozone minimum observed in Antarctica several decades ago (preindustrial chlorine levels) is produced by (natural) dynamical processes. Under these conditions the polar ozone depletion caused by chemical processes was very small (maximum of 3%) in October. In November the ozone concentration even increased above 22 km in response to PSC processes.

Influence of Site and Stand Factors on the Distribution of Crustose Lichens Of The Caliciales in a Suboceanic Spruce Forest Area in Central Norway

The distribution of crustose Caliciales has been surveyed in 100 spruce forest patches in Sør-Trøndelag, central Norway. Relationships between occurrence of the species and a number of site and stand variables were analysed by detrended correspondence analysis (DCA) and direct gradient analysis. Species diversity7 was significantly higher in old forests and in forests at higher altitudes compared to young forests and forests at lower altitudes. Old trees and snags are considered to be the most important structural components in old forests promoting species diversity of the Caliciales. Threatened or vulnerable species, such as Chaenotheca gracilliina, Cybebe gracilenta, Sclerophora coniophaea and S. peronella were confined to forest on rich soils showing no correlation with forest stand age. Chaenotheca brachypoda and C. trichialis were found to be the most typical old forest species among the Caliciales. Humidiphilous species are considered to be less affected by forestry in a humid climate. A change in forestry practice towards methods imitating the natural dynamic processes is considered necessary to maintain species diversity of the Caliciales in boreal forests.

INFLUENCE OF SITE AND STAND FACTORS ON THE DISTRIBUTION OF CRUSTOSE LICHENS OF THE CALICIALES IN A SUBOCEANIC SPRUCE FOREST AREA IN CENTRAL NORWAY

The distribution of crustose Caliciales has been surveyed in 100 spruce forest patches in Sør-Trøndelag, central Norway. Relationships between occurrence of the species and a number of site and stand variables were analysed by detrended correspondence analysis (DCA) and direct gradient analysis. Species diversity was significantly higher in old forests and in forests at higher altitudes compared to young forests and forests at lower altitudes. Old trees and snags are considered to be the most important structural components in old forests promoting species diversity of the Caliciales. Threatened or vulnerable species, such as Chaenotheca gracillima, Cybebe gracilenta, Sclerophora coniophaeaand S. peronellawere confined to forest on rich soils showing no correlation with forest stand age. Chaenotheca brachypodaand C. trichialiswere found to be the most typical old forest species among the Caliciales. Humidiphilous species are considered to be less affected by forestry in a humid climate. A change in forestry practice towards methods imitating the natural dynamic processes is considered necessary to maintain species diversity of the Caliciales in boreal forests.

Crustal evolution of the Rhinegraben area. 1. Exploring the lower crust in the Rhinegraben rift by unified geophysical experiments

Abstract Unified geophysical investigations of the lithosphere in the Rhinegraben rift system have revealed new details of the lower crust and its role in the rifting process. The new findings allow an assessment of the compatibility of four different geophysical notions and properties of the lower crust: 1. (1) the lower crust as the layer beneath the Conrad discontinuity with a P-wave velocity of about 6.5 km/s or greater (refraction seismics); 2. (2) the laminated band of reflections, as seen in the near-vertical reflection seismic experiments in many parts of the continents; 3. (3) the ductile part of the crust below the brittle-ductile transition, devoid of earthquakes in seismically active regions; 4. (4) the electrical conductivity of the lower crust indicative of dry or wet conditions, or still unknown conduction phenomena. In the Rhinegraben area the lamination of the lower crust serves as an outstanding marker of deep tectonic activity during the rifting process, in which the crust of the Rhinegraben rift system has been subjected to three different natural dynamic processes: (1) Uplift by 2 to 3 km with subsequent erosion of the Rhinegraben shoulders (Black Forest and Vosges Mountains) caused decompression possibly leading to the formation of a low-velocity/high-electrical-conductivity zone right on top of the laminated lower crust beneath the elevated shoulders of the Black Forest. (2) The brittle crystalline wedge of the graben proper subsided nearly undeformed into the lower crust, which became about 5 to 7 km thinner below the graben than below the shoulders. (3) The deepest hypocentres in the Black Forest (Dinkelberg area), if projected onto the neighbouring reflection profile, would be located 7 to 8 km within the laminated lower crust beneath the southern Black Forest, indicating a discrepancy between the top of the lower crust as defined by the brittle-ductile transition as seen by the deepest earthquakes and by the top of the laminated reflection band. The Rhinegraben rift system reveals the properties and behaviour of the lower crust under a wide variety of tectonic situations.

Antarctic ozone decreases: A dynamical cause?

A hypothesis is advanced that natural dynamical processes might explain much of the observed late winter ozone decreases over Antarctica. For this to be the case, sometime after 1979 there must have been a substantial reduction of the wintertime planetary‐scale disturbance activity in the Southern Hemisphere troposphere. The expected stratospheric response to such a natural process is to reduce wintertime polar ozone, prolong the life of the polar vortex, reduce the transport of ozone out of the middle stratosphere, and to increase the possibility of polar rising motion shortly after the return of the sun to high latitudes. All of these effects are in qualitative agreement with the observed ozone changes.

Relationship between cry and social support in preterm and term infants

We investigated a shock vein of the Yamato 791384 L6 chondrite to clarify the nature and sequence of the dynamic processes that resulted from the shock events. The chondritic host-rock of Y-791384 mainly consists of olivine (Fa24–25), low-Ca pyroxene (Fs18–22), albitic feldspar (An9–10Ab84–86Or5–7), troilite and metallic Fe–Ni. The shock vein contains majorite (or majorite-pyropess) and magnesiowüstite (+ minor jadeite) as high-pressure polymorphs. Two different dynamic events were recorded in the shock vein. The majorite grain contained vitrified (Mg,Fe)SiO3-perovskite inclusions. The (Mg,Fe)SiO3-perovskite was crystallized from a chondritic melt, and is a remnant of a first dynamic event. The majorite and magnesiowüstite were also crystallized directly from a chondritic melt but induced by a second dynamic event. The pressure condition for the first and second dynamic events would be >~24 GPa and <~22 GPa, respectively. Pervasive feather-shaped olivine (Fa16) nucleated on the magnesiowüstite and majorite. This feather-shaped olivine is evidence for rapidly grown olivine from the melt related to the shock event. Phase relations deduced from high-pressure melting experiments of the Allende meteorite and peridotite indicate that the magnesiowüstite and majorite + olivine pair cannot coexist at equilibrium condition. The disequilibrium assemblage reflects a decompression stage. These features demonstrate the complexity of events during a natural dynamic process.

Grand Isle Barrier Island, Louisiana--Human Activity in Natural Dynamic System: ABSTRACT

Grand Isle, Louisiana, is a recently formed barrier End_Page 1692------------------------------ island developed by the marine reworking of the seaward edge of the Lafourche delta, the last major deltaic deposit laid down by the Mississippi River prior to the development of its present delta. Marine reworking of the deltaic front provides sediment which is moved northeasterly and northwesterly away from the deltaic front by longshore currents to form barrier spits and chains of barrier islands, such as Isles Dernieres on the west and Grand Isle-Grand Terre Islands. Grand Isle became a subaerial deposit about 700 years ago and began to lengthen and grow southeasterly by ridge accretion. Its shape and location are controlled primarily by interaction of the longshore currents in the surf zone and the tidal-pass currents that interrupt them. Changes in the tidal channels, such as position or depth, drastically affect the action of the longshore currents. This has been dramatically shown at Grand Isle during 1970. High winds in the summer of 1970 and Hurricane Camille in 1969 deepened and changed the location of the tidal channels northeast and southwest of the island. As a result, accelerated erosion at the island's southwest end has removed several acres of a state park, moved the Gulf shoreline inland 300 ft, and caused the loss or removal of seve al beachfront homes. The causeway to the island and a large marina are threatened. Government money has been made available for jetty construction and for eventual sand-pumping operations to reduce erosion and restore the beach. Destruction of the Lafourche delta and construction of the ephemeral and migrating barrier islands on its flanks provided sites attractive for development by man. The desire for permanency of the developed sites is in conflict with the natural dynamic shoreline processes. End_of_Article - Last_Page 1693------------

Der Islam im Mittelalter (review)

BOOK REVIEWS 251 when compared with the fact that genetic processes issue in results which are so different from their origin. This view of motion carries him at last to a theology which is rather unique in the history of thought.., and which lays emphasis on the intelligibility of nature as the moving force of its operations and of our own understanding of it (pp. x-ix). Woodbridge's exposition of Aristotle's naturalism as "the history of the soul" and "the life of reason" is a beautiful summary of his many inspiring expositions of Aristotle's writings, and to those of us who were privileged to hear them, this little volume is precious as a reminder of Woodbridge's art and insight. Randall describes in his Introduction the excitement at Columbia that Woodbridge and Aristotle, at work together, aroused in several generations of students. But Woodbridge himself published little of his work, so that this volume is a rare book in several senses. Even more interesting to historians and more indicative of Woodbridge's style of work are the notes that fortunately accompany the lectures. Woodbridge had a special conception of the Organon as a basic element of the so-called Metaphysics, of the De Anima as a part of the Physics, of the world as "the earth's spherical horizon," and of all of this as provided with built-in movers, none of them "automatic" in our sense. Man with his soul illustrates the natural dynamic or genetic process. And he is clearly the best illustration of it, because of the fact that in him this process is carried to that consummation where the desire for theory is actualized in definite concrete form. Here attained vision is found to be the discovery of the light by which he walks and lives. Here are discovered the conditions of change and movements. Here is developed the logical framework, which to be sure does nothing, but is nonetheless that without which nothing could be done. Here are found the conditions without which what can be could never become what is. These conditions are not material conditions, they are not bodies of matter. They are not grasped with the hand or seen with the eye. They are thinss of the mind, as we say. They are logical because they are what is finally said by man in his theory. And they have the effect of releasing power as nothing else releases it. They do not push and pull a man about, but when once they are there, in his mind, all his being pushed and pulled is seen to be in consequence of them. They are in him an unmoved mover (p. 166). "It is at last the logical that moves the world" (p. 166). This is Woodbridge's version of "the Creative Logos." HERBERTW. SCHNEIDER Claremont, CaliIornia Der Islam im MiUelalter. By Gustav Edmund yon Grunebanm. (Ziirich und Stuttgart: ArtemisVerlag [1963]. Pp. 649 [1] = Die Bibliothek des Morgenlandes. ["Anmerkungen": pp. 443-601; "Bibliographie" and "Register": pp. 602-649.] Sfr 39.50) Obwohl der Islam fast framer als eine der drei monotheistisehen Hauptreligionen die ibm gebiihrende Anerkennung gefunden hat, trat im 20. Jahrhundert das Interesse ftir ihn seltsamerweise stark in den Hintergrund. Nattirlich gilt das nur ftir den Westen und alle nichtarabischen I~nder, wo trotz der kriegeriSchen Verwicklungen und Revolutionen in Algerien, Tunis and Marokko, yon Aegypten ganz zu schweigen, die Beschi4ftigung mit dem Mohammedanismus auf einen kleinen Kreis von Spezialisten beschriinkt blieb. Dies war eine der bedenklichen Folgen der Ueberspezialisierung unserer Zeit, die einer Zusammenschau der entscheidenden kulturhistorischen Ereignisse den fruehtbaren Boden entzog. Glticklicherweise hat das Werk des hervorragenden Arabisten G. E. yon Grunebaum, der jahrelang als Professor an der Chicagoer Universit~t gewirkt hat und jetzt als Professor ffir Gesehiehte dem "Near Eastern Center" der Universit~t von Kalifornien vorsteht, diesem wissenschaftlichen Parochialismus ein Ende bereitet. Grunebaum, der zuerst im Jahre 1937 mit der Abhandlung "Die Wirklichkeitsweite der frfih-arabisehen Dichtung" hervortrat und sp~ter (1955) das Werk Kritik und Dichtkunst. ~gtudien zur arabischen Literaturgeschichte verSffentliehte, hat in zwei Bfichern, die in den Jahren 1961 und 1962 herauskamen, zuerst die groasen kulturgeschichtliehen Zusammenh~nge beleuchtet. Die Titel dieser Abhandlungen...