Effect of bed surface roughness on longitudinal dispersion in artificial open channels

In several empirical and modelling studies on river hydraulics, dispersion was negatively correlated to surface roughness. In this study, it was aimed to investigate the influence of surface roughness on longitudinal dispersion under controlled conditions. In artificial flow channels with a length of 104 m, tracer experiments with variations in channel bed material were performed. By use of measured tracer breakthrough curves, average flow velocity, mean longitudinal dispersion, and mean longitudinal dispersivity were calculated. Longitudinal dispersion coefficients ranged from 0·018 m² s^?1 in channels with smooth bed surface up to 0·209 m² s^?1 in channels with coarse gravel as bed material. Longitudinal dispersion was linearly related to mean flow velocity. Accordingly, longitudinal dispersivities ranged between 0·152 ± 0·017 m in channels with smooth bed surface and 0·584 ± 0·015 m in identical channels with a coarse gravel substrate. Grain size and surface roughness of the channel bed were found to correlate positively to longitudinal dispersion. This finding contradicts several existing relations between surface roughness and dispersion. Future studies should include further variation in surface roughness to derive a better‐founded empirical equation forecasting longitudinal dispersion from surface roughness. Copyright © 2011 John Wiley & Sons, Ltd.     

Paleomagnetic correlation of sedimentary sequences: The use of secular geomagnetic variations for the differentiation and correlation of Holocene Aral Sea deposits

The paper presents results demonstrating the possibility of using data on paleosecular magnetic variations for correlation of young deposits. Using Holocene deposits of the Aral Sea as an example, it is shown that the combination of paleo-and petromagnetic data can be used to reliably correlate sections in presently isolated parts of a basin, as well as to correlate paleohydrologic events and estimate their age with regard for absolute radiocarbon datings. It is established that the most significant drop in the Aral Sea level occurred more than 2000–2500 yr ago and less significant drops that occurred later are dated at about 1500, 750–1050, and 270–500 yr ago.     

Imperfect fluid Friedmannian cosmology

The bulk viscosity is introduced into the frame of ordinary Friedmannian cosmology (under highly idealized assumption of the constant coefficient of bulk viscosity). Explicit solutions are given for the viscous flat universe filled with the dust-substratum and for the viscous radiative universe. The problem, how does the introduction of viscosity affect the appearance of singularity, is briefly discussed.     

循化-德地区新生代盆地发育及其对高原增生的指示

循化-贵德地区的循化盆地、贵德盆地和同仁盆地与拉鸡山和西秦岭北缘逆冲带相邻分布.盆地沉积地层主要由渐新统西宁群、渐新统上部至上新统贵德群和下更新统组成.它们由不整合界面分隔,划分为3个盆地相.盆地相1为西宁群,盆地相2为贵德群查让组、下东山组、贺尔加组和甘家砾岩组,盆地相3为共和组及下更新统.3个盆地相均在其中下部或底部发育湖泊沉积,向上转变为冲积扇-辫状河平原沉积体系,呈现出粒径向上不断加大的反序、进积沉积序列.盆地沉积、古流和沉积物碎屑成分分析表明,研究区在西宁群(盆地相1)沉积时期发育大型湖泊沉积盆地,盆地沉积物源主要来自于南侧的西秦岭逆冲带,而拉鸡山逆冲带处于沉积基准面之下,接受沉积;在贵德群(盆地相2)沉积时期,逆冲作用向北迁移,拉鸡山逆冲隆升,研究区盆地分割,主要沿拉鸡山逆冲带南北两侧发育点源扩散型冲积扇-辫状河平原沉积.研究区盆山系统演化对青藏高原远端增生过程具有重要的指示意义.研究结果表明,青藏高原新生代向北东的增生作用在渐新世(29～21.4Ma)已抵达西秦岭北缘地区,增生过程主要表现为向北的单向褶皱逆冲增厚隆升和前缘前陆盆地充填;中新世至上新世(20.8～2.6Ma)高原增生作用跨过研究区可能抵达祁连北缘和六盘山地区,增生过程主要表现为双向基底卷入式逆冲增厚隆升和分割式前陆盆地充填上新世至早更新世(2.6～1.7 Ma)高原远端主要表现为区域剥蚀夷平与山间盆地加积充填.     

The non-agricultural economy in post-socialist rural Romania: The insights and perceptions of national, regional and local institutions

This study evaluates some aspects of the socio-economic transformation of rural Romania with reference to the views of representative organisations (at national, regional and local levels) and other experts. Interviews conducted in ten communes of nine Romanian counties (‘judete’) focus attention on the advantages and disadvantages of system change experienced since 1989; the most important problems and constraints for future socio-economic change; and appropriate policies and perspectives for development in the immediate future. Wherever appropriate the claims of interviewees are substantiated through reference to statistics, drawn in many cases from Chambers of Commerce & Industry (CCI). Local level representatives presented much more negative views on recent change than their national and regional level counterparts, but all agreed on the crucial problem of capital shortage. Thus while specific programmes to assist rural areas are justified, they cannot fully succeed until the national economy is able to grow more rapidly and attract greater foreign investment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Small landslide types and controls in glacial deposits: Lower Skagit river drainage,northern cascade range,Washington

Observations of 167 small, shallow landslides spanning a 22-year period on extensively logged slopes of Quaternary terraces in the lower Skagit and Baker Valleys, Washington, shows that there is a relationship between the common slope failures in this area and the slope angle, stratigraphy, and logging practices. Landslide frequency increases upvalley, as do mean annual precipitation and the frequency of perched water tables. Debris slides are most common, occur on steep slopes (>50%) composed of sand and gravel, and are most abundant in areas previously logged by the clear—cut method. Debris flows occur on shallower slopes (>30%) where the stratigraphy leads to perched water tables. Debris flows larger than 600 m² in area appear to be unrelated to logging practices. Slump flows, described here for the first time, occur on similar slope angles and stratigraphic situations as debris flows. They differ mainly by the presence of semiconsolidated material, usually till, at the slide head. Where till is breached—commonly along road cuts—water infiltration is increased, saturating underlying fine-grained deposits, which then fail by debris flowage. Secondary slumping of till happens when the slope steepens during debris flow failure. Small landslides surrounding Lake Shannon may contribute up to 80% of the total particulate matter yield to the fluvial system at present, increasing lake sedimentation by a rate of 5 mm/yr.     

Prospects for gradiometric aiding of inertial survey systems

The state of current and proposed moving-base gravity gradiometer instruments is briefly reviewed. The review perspective is directed toward their deployment as a source of additional gravimetric data during inertial surveys. In such gradiometer-aided surveys, the additional gravity gradient information could be used to:

1. Improve surveyed gravity vector accuracy
2. Extend the interval between zero velocity update stops
3. Accomplish varying combinations of the above.

The paper examines potential survey improvements associated with gradiometers having noise levels observed in laboratory prototypes. The additional improvements possible with future gradiometers are also discussed. These results are interpreted in light of present and likely future inertial survey system technology.     

Remanent magnetization of a Pliensbachian limestone sequence at Bakonycsernye (Hungary)

Remanent coercivity spectra derived from IRM acquisition curves and thermal demagnetization of the IRM indicate that magnetite, haematite and minor amounts of goethite determine the magnetic properties of the Pliensbachian limestones at Bakonycsernye. These limestones have been sampled at approximately 7-cm intervals along a 10-m stratigraphic section which covers the whole Pliensbachian stage (Lower Jurassic) without any recognizable break in sedimentation. The primary natural remanent magnetization (NRM) is carried by detrital particles of magnetite and haematite, but it is seriously overprinted by a normal magnetization which originates from secondary haematite with a wide range of blocking temperatures. This haematite is believed to have formed diagenetically during one of the Mesozoic periods of normal polarity. However, the reversal pattern obtained after NRM thermal demagnetization at temperatures ≥450°C is thought to be characteristic of the Pliensbachian stage.     

Biochemie und Feinstruktur Fossiler Knochen aus Bituminösen Schichten

Zusammenfassung Eingangs wird kurz das Untersuchungsmaterial, seine stratigraphische Eingliederung und seine lokale Herkunft skizziert. Sämtliches Wirbelmaterial wurde aus bituminösen Schichten verschiedenen Alters entnommen. Bei der Bestimmung des Gehalts an organischer Substanz dor Wirbelknochen trennte ich zwischen ursprünglicher, d. h. knocheneigener organischer Substanz und aus dem Sediment eingewanderter organischer Substanz während der Einbettung der Knochen bzw. später.Chemismus und Feinstruktur der fossilen Wirbelknochen zeigen keine wesentlichen Unterschiede gegenüber den rezenten. Lediglich die Aminosäuren Histidin und Methionin fehlen unter denjenigen, die das rezente Kollagen enthält. Auf Grund ihres einerseits mengenmäßigen geringen Vorhandenseins im Kollagen und andererseits wesentlich unbeständigeren Charakters ist ihr Fehlen verständlich. Die röntgenographische Untersuchung der Knochen mit dem Zählrohrgoniometer und die polarisationsmikroskopische Betrachtung der Knochendünnschliffe zeigt, daß keine knochenfremden Mineralien in die Knochen eingewandert bzw. dort auskristallisiert sind. Elektronenmikroskopische Untersuchungen wurden gleichfalls an den Knochen durchgeführt. Die bisherigen vorläufigen Ergebnisse lassen noch nicht klar genug erkennen, ob die Veränderung der Knollagenstruktur auf das absolute geologische Alter der Knochen oder auf die nicht völlig identische Einbettung derselben in die bituminösen Schichten oder den Chemismus bzw. Bitumengehalt des Sediments zurückzuführen ist.Der unterschiedliche Feinbau der Wirbelknochen läßt eine verschieden starke Adsorptionsfähigkeit für Bitumen erkennen. Den höchsten Gehalt an Bitumen zeigt die Zone der inneren Generallamellen und das umgewandelte Gewebe der Chordascheide und des Chordagewebes bei den Ichthyosaurierwirbeln.

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The author analysed vertebrae taken from strata of different geological age. For some specified reasons only bones of bituminous layers have been analysed. These layers and the localities are: the bituminous schist of the Middle Alpine Trias (Anisian/Ladinian) of the Monte San Giorgio (Kanton Tessin, Switzerland), the Lias epsilon (Posidonomya Shales, Toarcium) of Holzmaden (Baden-Württemberg, Germany), and the bituminous swamps of Rancho La Brea (USA). It has turned out that under these special conditions of bedding the collagenous structure has been preserved to a great extent, and no migration of minerals out of the sediments into the bones has taken place. This could be proved by the use of an X-ray-counting goniometer (Zählrohrgoniometer).Comparing analyses of vertebrae taken from non-bituminous layers showed that in the those cases the collagenous structure had been destroyed, and thatThis means that the bitumen must have acted as a protecting film on the bones.

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Résumé Au départ seront brièvement esquissés le matériel de recherche, son enchaînement stratigraphique et son origine locale. L'ensemble du matériel vertébral a été retiré de couches bitumineuses d'âges différents. Par la détermination du contenu de la substance organique des vertèbres, j'ai séparé la substance primitive, c'est-à-dire organique propre aux os, du sédiment, de la substance organique implantée pendant le gisement des os ou après.Par rapport aux vertèbres actuelles, le chimisme et la configuration intime (constitution intime) des vertèbres fossiles n'offrent pas de différences essentielles. Simplement, parmi les acides aminés, l'histidine et la méthionine font défaut parmi ceux que contient le collagène récent. En raison de leur existence en faible quantité d'une part, et de leur caractère essentiellement labile d'autre part, leur absence est compréhensible.L'exploration radiographique des os au compteur goniomètrique et l'examen micropolarographique des coupes minces osseuses montrent qu'aucune substance minérale étrangère n'a été implantée dans les os, ou fixée. Des recherches au microscope électronique ont également été menées sur les os. Les résultats jusque là provisoires ne font pas encore assez clairement ressortir si la transformation de la structure du collagène est à rapporter à l'âge géologique absolu des os ou à leur localisation (Einbettung) non parfaitement identique dans les couches bitumineuses, ou encore au chimisme, disons plutôt au contenu bitumineux du sédiment.La constitution intime différente des vertèbres fait apparaître un potentiel d'adsorption variable pour les bitumes. C'est dans la zone des lamelles générales intérieures (inneren Generallamellen) et dans le tissu transformé (umgewandelte) de la gaine et des tissus chordaux des vertèbres d'Ichthyosaure que l'on trouve la plus grande teneur en bitumes.

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