turbulence measurements over a sand wave in lower chesapeake bay virginia u s a abstract measurements of turbulent shear stress 5 cm above a sediment bed are described for five stations distributed along a transverse profile of an estuarine sand wave in lower chesapeake bay virginia u s a time series analyses of the velocity data reveal three kinds of constituents 1 components of long period 2 wind wave components and 3 turbulence the energy in the turbulent part of the records is highly attenuated in comparison with that of the low frequency components furthermore at all except the lowermost frequencies the energy contained in the horizontal component of the flow is less than that contained in the vertical component the excess energy at the low frequency part of the spectrum as compared to the high frequency part is explained by 1 the input of energy from wind waves 2 damping of turbulence or 3 both causes the first evidently is the main cause suspended sediments and stable density stratification reduce turbulence but they act mainly on the vertical component a schematic model presented here indicates that oscillating flow over a rugose bed induces additional fluctuations in the vertical component estimates of reynolds shear stress are small and most are negative time series plots of the reynolds stress show 1 small spikes in all records in which the instantaneous shear stresses are very close to zero and 2 intermittent large spikes in most instances within a spike the fluctuating horizontal component of the turbulent velocity u and the vertical counterpart w are of the same sign and w u these results are in agreement with the proposed model of flow over rippled surfaces the findings and concepts developed in the study indicate that even though a flow over the bed actually produces a significant boundary shear stress it cannot be properly measured very close to the bottom based on the reynolds stress idea when making nearbed measurements in turbulent flows in open waters with tidal currents surface waves stable density structures a rugose bed and with sediment in suspension one may encounter a reduction in turbulence and a degradation of the usual correlation between u and w under these conditions the profile method for determining the shear stress using mean flow values may be more reliable

sediment transport predictions for the english channel using numerical models output from an hydrodynanmic numerical model salomon breton 1991 a b has been combined with various empirical formulae to derive sediment transport rates and directions the predictions are compared with radioactive sand tracer experiments demonstrating the applicability of gadd et al s 1978 expression the derived bedload transport pattern for the area is consistent with sedimentological and geomorphological evidence but provides improved resolution a bedload parting zone is identified for the central english channel this is well defined for sand movement but seabed material present over this area gravel is not predicted to move significantly the area is non erosive over which fine grained sediments are being transported a bedload convergence is located to the southwest of the dover strait not in the strait itself as proposed previously a transport pathway bypassing the convergence along the french coastline which is supported by radioactive tracer experiments could be responsible for sand transfer from the english channel to the southern north sea

probability distribution of turbulent kinetic energy dissipation rate in ocean observations and approximations the probability distribution of turbulent kinetic energy dissipation rate in stratified ocean usually deviates from the classic lognormal distribution that has been formulated for and often observed in unstratified homogeneous layers of atmospheric and oceanic turbulence our measurements of vertical profiles of micro scale shear collected in the east china sea northern bay of bengal to the south and east of sri lanka and in the gulf stream region show that the probability distributions of the dissipation rate r in the pycnoclines r 1 4 m is the averaging scale can be successfully modeled by the burr type xii probability distribution in weakly stratified boundary layers lognormal distribution of r is preferable although the burr is an acceptable alternative the skewness sk and the kurtosis k of the dissipation rate appear to be well correlated in a wide range of sk and k variability

flow and sediment transport induced by tide propagation 2 the wavy bottom case 1 a model is formulated to describe the flow field locally induced by the propagation of a tidal wave and to evaluate the sediment transport the three dimensional reynolds averaged momentum equations are considered and coriolis terms are retained since they affect the tide propagation turbulent reynolds stresses are described by means of the boussinesq assumption and the eddy viscosity is assumed to be an assigned function of the distance from the sea bed the effects of wind waves on sediment transport are taken into account and both the bed load and the suspended load are computed a comparison of the obtained results with laboratory data and field measurements shows that the model provides a reliable and accurate description of both the velocity field and sediment transport and does not require high computational costs

intermittency of near bottom turbulence in tidal flow on a shallow shelf u s office of naval research n00014 05 1 0245 spanish ministry of education and science fis2008 03608 major state program of china for basic research 2006cb400602 catalan institute for water research icra

the modelling of the free surface flow of water over topography abstract a numerical model is developed for the flow of water over a bottom topography that is characteristic of sandwaves found in the coastal and river estuary environment turbulence closure is achieved at the level of the turbulence energy equation and the reynolds stresses are parameterised in terms of a gradient transfer law and an assumed partitioning of the turbulence energy between different components of the flow the pressure derives from both hydrostatic and hydrodynamic contributions an experiment is performed for steady state flow over a sequence of asymmetrical sandwaves and it is shown that there is flow separation over the lee slope of a sandwave in this case it is shown further that flow separation is a consequence of the inclusion of the hydrodynamic pressure contribution a comparison is also made between non hydrostatically and hydrostatically determined values of other mean and turbulent flow quantities

giant sand waves on the taiwan banks southern taiwan strait distribution morphometric relationships and hydrologic influence factors in a tide dominated environment abstract giant sand waves heights 10 m are widely developed on the taiwan banks the distribution pattern morphotypes and morphometric relationships of which have not yet been fully clarified based on multi beam bathymetric swath data covering 780 line km of survey track giant sand waves with heights up to 22 5 m and wavelengths up to 2115 m have been recorded the relationship between height h and wavelength l of the complete data set follows the regression trend of hmean 0 0625 l0 8152 r 0 94 which is in good general agreement with a previously determined average global trend of hmean 0 0677 l0 8098 this global trend did not include any data from the china seas the giant sand waves have been grouped into four morphotypes namely double crested symmetric symmetric asymmetric and asymmetric forms the individual bedform morphotypes and their spatial distribution were investigated in relation to water depth textural characteristics of the sediment and the hydrodynamic conditions recorded by several 25 hour repeated ship based current observations the relationship between mean water depth d and mean sand wave height h and mean wavelength l on the taiwan banks are hmean 0 29d r 0 35 and lmean 36d r 0 42 respectively with increasing water depth the shape of the sand wave becomes gentler it is found that the coarser sediment median grain size of 0 51 0 54 mm and stronger flow in the present study may contribute to the larger h d and l d ratios at the given water depths than other sand wave fields and flows of varying from equal to unequal northerly and southerly components correspond with sand waves from symmetrical to asymmetrical forms a decrease in velocity and a veering in direction of flows have been observed over the giant sand waves indicating the interaction between large bedforms and the near bed water layer in the study area

spatial variability of bottom types in the lower chesapeake bay and adjoining estuaries and inner shelf abstract the spatial distributions of the bed textural and morphologic properties that influence boundary layer roughness characteristics in the lower chesapeake bay the lower portions of the york james and elizabeth rivers and the adjacent inner continental shelf were systematically mapped a high resolution fully corrected side scan sonar mapping system 100 khz was used for remote acoustic detection of bottom roughness supported by ground truthing by direct in situ observations by divers these complementary methods proved to be especially effective in detecting a wide range of roughness controlling bed surface properties at various scales fine scale variations in sediment size and associated bottom texture are considered to be the main source of heterogeneity in nikuradse skin friction roughness a wide variety of small and intermediate scale morphologic elements provide meso scale and small scale distributed form drag roughness depending upon location the distributed roughness may be either biogenic or hydrodynamically induced by currents and waves although anthropogenic roughness prevails in certain instances e g port areas in terms of particular combinations of roughness scales and types combined sonar and diver observation data allow the beds to be systematically but qualitatively classified into 10 bottom types each of which is associated with a particular type of subenvironment

shear velocity estimates in rough bed open channel flow shear velocity u is an important parameter in geophysical flows in particular with respect to sediment transport dynamics in this study we investigate the feasibility of applying five standard methods the logarithmic mean velocity profile the reynolds stress profile the turbulent kinetic energy tke profile the wall similarity and spectral methods that were initially developed to estimate shear velocity in smooth bed flow to turbulent flow over a loose bed of coarse gravel d 50 15cm under sub threshold conditions the analysis is based on quasi instantaneous three dimensional 3d full depth velocity profiles with high spatial and temporal resolution that were measured with an acoustic doppler velocity profiler advp in an open channel the results of the analysis confirm the importance of detailed velocity profile measurements for the determination of shear velocity in rough bed flows results from all methods fall into a range of 20 variability and no systematic trend between methods was observed local and temporal variation in the loose bed roughness may contribute to the variability of the logarithmic profile method results estimates obtained from the tke and reynolds stress methods reasonably agree most results from the wall similarity method are within 10 of those obtained by the tke and reynolds stress methods the spectral method was difficult to use since the spectral energy of the vertical velocity component strongly increased with distance from the bed in the inner layer this made the choice of the reference level problematic mean shear stress for all experiments follows a quadratic relationship with the mean velocity in the flow the wall similarity method appears to be a promising tool for estimating shear velocity under rough bed flow conditions and in field studies where other methods may be difficult to apply this method allows for the determination of u from a single point measurement at one level in the intermediate range 036 copyright c 2013 john wiley sons ltd

turbulence and internal waves at the equator part ii details of a single event abstract in the low richardson number shear flow above the pacific equatorial undercurrent a single vertical microstructure profile intersected the overturning crest of a packet of high horizontal wavenumber waves the observed dissipation rates within the overturning wave were so high that if they were representative of the volume averaged rate the total wave energy would have been dissipated within a single buoyancy period the chaotic structure and temperature fluctuations with horizontal scales less than 2 m of the two wave crests and troughs west of the overturning wave crest suggest that recent mixing had occurred there wave crests and troughs east of the overturning wave crest showed little or no sign of turbulent mixing similar high horizontal wavenumber waves believed to be shear instability waves have been observed in low richardson number regions of the midlatitude seasonal thermocline although the equatorial waves have a horizontal wavelength appropriate for shear instability waves t

flexural rigidity and shoot reconfiguration determine wake length behind saltmarsh vegetation patches vegetation patches play an important role in controlling sediment deposition in shallow aquatic environments such as coastal saltmarshes and fluvial systems however predicting deposition around vegetation patches is difficult due to the complexity of patch morphology and their dynamic interaction with the flow here we incorporate a biomechanical model parameterized using field data within a 3d computational fluid dynamics cfd model which allows prediction of individual shoot reconfiguration within patches due to flow forcing the model predicts velocity attenuation and bed shear stresses within the wake of the patch which agree spatially with accretion patterns measured in the field using terrestrial lidar the model is applied to sparse patches of suaeda maritima located in saltmarshes of coastal habitats to explore the role of i shoot distribution ii patch geometry iii shoot flexural rigidity and iv bulk flow velocity in determining the length of the predicted wake region we demonstrate that for suaeda maritima with intermediate rigidity the vertical shear layer over the vegetation controls the length of the predicted wake region consequently reconfiguration due to flexural rigidity strongly impacts on wake length confounding the relationship between patch height and wake length a simplified model for predicting wake length based on shoot reconfiguration is applied to the simulation data and shows good agreement the results demonstrate that the observed wake characteristics can be well explained by intraspecific variability in flexural rigidity thus demonstrating the importance of biomechanical traits in determining flow vegetation sediment interactions

geometry and migration characteristics of bedforms under waves and currents part 1 sandwave morphodynamics abstract in this paper the geometric and migration characteristics of sandwaves generated under the combined effect of waves and currents are described description and analysis of the flow structure along the centerline of developed sandwaves are also presented the velocity distribution along the sandwave is used to explain in part the size and shape characteristics of the ripples superimposed upon the sandwaves as discussed in the companion paper catano lopera y and garcia m h in press geometry and migration characteristics of bedforms under waves and currents part 2 ripples superimposed upon sandwaves coastal engineering doi 10 1016 j coastaleng 2006 03 008 variation in roughness height along the considered bed feature is also discussed for a particular experiment velocity measurements within the fluid were recorded with an acoustic doppler velocimeter adv an acoustic level sensor was employed to determine surface wave characteristics such as amplitude and period 3d mapping of the bottom was done via a 32 composite element array of sub aquatic acoustic sensors seatek multiple transducer arrays bottom records were statistically analyzed to obtain height length migration rates of ripples and sandwaves and vertical growth rate of sandwaves experiments were conducted for the mobility factor and the reynolds wave number within the ranges 10

kahlke r d 1999 the history of the origin evolution and dispersal of the late pleistocene mammuthus coelodonta faunal complex in eurasia large mammals the last glacial was characterized by some of the most cold adapted large mammals ever known eurasian glacial faunas were typified by the presence of the mammoth and the woolly rhinoceros which gave rise to the so named mammuthus coelodonta faunal complex kahlke s approach focuses on the origin of the various faunal elements that constituted this terminal cold stage the essence of this book is to document the evolutionary history of the faunal complex and in turn to throw light on the ecological conditions that preceded the last glacial maximum in eurasia the

the history of the origin evolution and dispersal of the late pleistocene mammuthus coelodonta faunal complex in eurasia large mammals

measurements of the reynolds stress components close to a marine sand bank abstract soulsby r l 1981 measurements of the reynolds stress components close to a marine sand bank mar geol 42 35 47 observations of turbulence have been made at a height of 65 cm above the sea bed in water 42 m deep on the edge of the skerries sand bank off southwest england the observations extended over a 4 h period from the time of maximum flood velocity to slack water electromagnetic current meters were used to measure the streamwise u cross stream v and vertical w velocity components while simultaneously a conventional current meter measured the speed and direction 5 m below the water surface ratios of u2 1 2 v2 1 2 and w2 1 2 to shear velocity agreed with accepted values for laboratory and atmospheric flows near to the surface the current was found to flow across the bank while near the bed it ran nearly parallel to the isobaths consequently the bottom current was directed 480 clockwise of the surface current the azimuth of the reynolds stress uw vw near the bed lay between these directions and was directed about 60 anticlockwise of the near bed current this balanced the cross stream as well as the streamwise shear a lateral shear stress uv associated with the bank was observed taken together with previous measurements of the velocity distribution over the bank this yielded a value for lateral eddy viscosity of 1 2 105 cm2 s 1 the scale over which this acts is of the order 1 km and the value is appreciably smaller than reported values deduced for larger scales the veering of the current acts to lessen the bottom current convergence associated with coriolis and curvature effects and may contribute to lateral sorting by preferentially carrying finer sediment toward the crest of the bank the lateral eddy viscosity coefficient may be useful in assessing the diffusion of sediment on or off the bank

geometry and migration characteristics of bedforms under waves and currents part 2 ripples superimposed on sandwaves this paper presents results of a series of detailed measurements of geometric and migrating characteristics of ripples superimposed upon sandwaves under the action of combined waves and currents velocity measurements within the fluid surface wave characteristics and 3d mapping of the bottom were recorded with an acoustic doppler velocimeter adv an acoustic water level sensor and a 32 composite element array of sub aquatic acoustic sensors respectively bottom records were statistically analyzed to obtain height length and migration rates of ripples experiments examined ripple heights and wavelengths for the mobility factors as defined in eq 4 and the reynolds wave number within the ranges 10 88 and 16 103 rew 5 105 respectively measured values were compared with laboratory and field data together with semi empirical and analytical formulae from the literature good correlation was obtained when plotting measured ripple length and length in dimensionless form as a function of the reynolds wave number rew under a given hydraulic condition it was observed that ripples with different geometric characteristics may coexist at different locations over the sandwave ripple steepness is presented as a function of the shields parameter although characterized with rather large scatter finally average ripple migration speed is presented as a function of the shields parameter and the mobility number

measurements of turbulence in the benthic boundary layer over a gravel bed it is now generally recognized that the mathematical description of sediment dynamics will be improved through an understanding of geophysical turbulence in this study therefore the turbulence characteristics of the benthic boundary layer over coarse sediments are examined as a step towards the realization of such a description examination of the turbulence has been conducted using spectral correlation quadrant and statistical analyses and a number of features have been identified mean eddy length scales obtained using spectral and autocorrelation techniques were found to be similar the interpretation of the duration and interval between the intermittent bursting events scaled using outer flow variables was found to be dependent upon the sampling interval autocorrelation analysis revealed a high correlation between bedload transport and the instantaneous horizontal flow component rather than instantaneous kinematic stress from the standpoint of developing prognostic transport models based on physically realistic benthic flow processes it is considered that turbulence measurements will lead to such formulation

mechanisms for linear sandbank formation and maintenance in relation to dynamical oceanographic observations abstract theories associated with flow in the vicinity of headlands and sandbanks together with proposed mechanisms for sandbank formation and maintenance are reviewed to exemplify water and sand movement around a sandbank on a tidally dominated shelf tidal currents in the vicinity of a headland associated linear sandbank are described these data are integrated with sedimentological information on bedforms and grain size distributions the sandbank under detailed investigation the scarweather sands is located along the northern coastline of the bristol channel uk which is an area susceptible to high energy inputs the maximum spring tidal range here is around 10m and a 6000km fetch is available for storm wave approach from the atlantic ocean but the area is 460km from the shelf break detailed observations are presented from 11 long term current meter stations located within 10km of the sandbank currents are described in terms of residual water circulation shallow water harmonics and tidal ellipse characteristics bedload transport paths are inferred from the distribution of bedforms grain size and m2 m4 tidal current interactions transport vectors are predicted from near bed current meter observations combined with empirically derived formulae it is demonstrated that water circulation and sand transport paths form part of a clockwise eddy system around the sandbank mechanisms controlling the location and the characteristics of this particular sandbank are shown to be explicable in terms of a combination of models for sandbank formation and maintenance the results of the present study are thought to be applicable directly to headland associated sandbanks elsewhere it is shown on the basis of theoretical considerations that the pattern of residual water movement and possibly sand transport around this sandbank could be extended to continental shelves on a global basis

investigation of deep sea shelf sandbank dynamics driven by highly energetic tidal flows abstract in this paper we describe a numerical modelling study carried out to investigate the prevailing sediment dynamics of two large sandbanks located at a site designated for future development of tidal stream energy extraction in the inner sound channel of pentland firth scotland uk a calibrated and validated 3d delft3d hydrodynamic model covering pentland firth channel was combined with a morphodynamic model the sea bed changes occurring around the sandbanks during a period of two spring neap tidal cycles are described and discussed in detail it was found that both sandbanks which are located in a deep shelf region depths 18 m are morphodynamically active and their existence and integrity are strongly linked with the existing hydrodynamic regime

microstructure measurements in natural waters methodology and applications abstract modern approaches to microstructure data processing including wavelet denoising are discussed the wavelet procedure is applied to small scale shear signals before estimating the dissipation rate e and to the temperature density profiles used to calculate thorpe scales microstructure data obtained on the mediterranean shelf of catalonia are used to illustrate various approaches to the thorpe displacement calculations it is suggested that the weibull probability function is an appropriate model for the thorpe scale distribution microstructure measurements from the upper layer of the boadella reservoir catalonia spain support this finding a new analytical approximation for the 1d panchev kesich spectrum is deduced and the results of e computation are compared with spectral fitting by the widely used nasmyth spectrum applying the kraichnan spectral model to compute e from temperature spectra in the convective viscous sub range is examined as an alternative to the batchelor spectrum microstructure measurements taken in lake banyoles catalonia spain and in the north atlantic were used for spectral calculations statistical analysis of eddy kb and thermal k diffusivities measured on a shallow shelf of the black sea shows the importance of process orientated domain averaging of the diffusivities in obtaining good correspondence between kb and k in active turbulent regions in weakly turbulent stratified interior layers the averaged kb and k differ significantly which may point to the inapplicability of isotropic formulae used for e and temperature dissipation estimates as well as to a dependence of the mixing efficiency on the richardson number or in some cases on regions of fossil turbulence

on the formation of sand waves and sand banks a fully three dimensional model is proposed for the generation of tidal sand waves and sand banks from small bottom perturbations of a flat seabed subject to tidal currents the model predicts the conditions leading to the appearance of both tidal sand waves and sand banks and determines their main geometrical characteristics a finite wavelength of both sand waves and sand banks is found around the critical conditions thus opening the possibility of performing a weakly nonlinear stability analysis able to predict the equilibrium amplitude of the bottom forms as shown by previous works on the subject the sand wave crests turn out to be orthogonal to the direction of the main tidal current the present results also show that in the northern hemisphere sand bank crests are clockwise or counter clockwise rotated with respect to the main tidal current depending on the counter clockwise or clockwise rotation of the velocity vector induced by the tide only for unidirectional or quasi unidirectional tidal currents are sand banks always counter clockwise rotated the predictions of the model are supported by comparisons with field data finally the mechanisms leading to the appearance of sand waves and sand banks are discussed in the light of the model findings in particular it is shown that the growth of sand banks is not only induced by the depth averaged residual circulation which is present around the bedforms and is parallel to the crests of the bottom forms a steady drift of the sediment from the troughs towards the crests is also driven by the steady velocity component orthogonal to the crests which is present close to the bottom and can be quantified only by a three dimensional model while the former mechanism appears to trigger the formation of counter clockwise sand banks only the latter mechanism can give rise to both counter clockwise and clockwise rotated sand banks

cave bears carnivora ursidae from the middle and late pleistocene of serbia a revision abstract cave bear remains are known from 36 caves and other karst features and from one open air site in serbia the sites vary greatly by their morphology and size position altitude stratigraphy and diversity of the fossil fauna the cave bear stands out as a dominant species at the majority of the sites at a number of sites it is the single species found there are only few sites where herbivores or predators remains exceed those of the cave bears the majority of cave bear remains originate from the late pleistocene deposits previously they have been identified as ursus spelaeus we present a morphology and metric study of cave bears from three sites two recently discovered localities of middle pleistocene age and the risovaca cave which may be regarded as the reference site for the late pleistocene mammals in the region based on a large number of collected remains and published data the remains of the middle pleistocene spelaeoid bears are described from mala balanica cave eastern serbia and an open air site at ruma brickyard northern serbia for the first time considering the size and morphology of cheek teeth and metapodial bones these cave bears are identified as ursus spelaeus deningeroides the cheek teeth morphology and size as well as metapodial bones metric relate the cave bear from the risovaca cave to the advanced evolutive type of the cave bear established in central and eastern europe ursus spelaeus ingressus

an introduction to the middle and upper pleistocene loess paleosol sequence at ruma brickyard vojvodina serbia abstract six loess units and five paleosols are preserved in the 20 m thick exposure of middle and late pleistocene sediments at ruma brickyard vojvodina serbia amino acid geochronology provides stratigraphic correlations between loess paleosol units sl l1 s1 sl l2 s2 sl l3 s3 and sl l4 at ruma with loess of glacial cycles b c and d and e respectively at other central and southeastern european localities the profile represents one of the best potential sections in the region for reconstructing detailed paleoclimates and paleoenvironments of the last ca 350 000 yr initial sedimentological magnetic and malacological evidence indicate many episodes of drier conditions in the region than in other parts of central and southeastern europe during the later part of the middle and late pleistocene

the effects of suspended sediment on turbulence within an estuarine turbidity maximum predictions of cohesive sediment transport are hampered by poor understanding of the effects of sediment suspensions upon the nature of near bed turbulence in this study current velocities associated turbulence and flow characteristics were measured within an estuarine turbidity maximum during two spring ebb tides measurements at two heights both within and above a near bed high concentration layer show the importance of intermittent internal waves the ratio of vertical to horizontal turbulence intensities exceeded 1 0 when waves were present the waves were more significant above the layer than within it comparison between the turbulent kinetic energy and the reynolds stresses showed inactive turbulence occurring at stresses less than about 0 2 n m 2 during these periods negative suspended sediment fluxes occurred indicating that the turbulence could enhance settling of the sediment the effect of the intermittent internal waves on the turbulent bursting structure and their interaction with the concentration profile appears to increase the variability of the reynolds fluxes of suspended sediment and cause downwards reynolds fluxes especially beneath the lutocline

a skeleton of steppe mammoth mammuthus trogontherii pohlig from drmno near kostolac serbia abstract the kostolac mammoth was discovered in 2009 in pleistocene deposits adjacent to the drmno open cast lignite mine in the serbian danube basin on the basis of cranial and dental features the individual is identified as the so called steppe mammoth mammuthus trogontherii the remains are those of an old male of estimated age around 62 years and comprise one of the most complete and best preserved known skeletons of this species and the first from the region skeletal height is estimated as around four metres and body mass 9 5 t the excellent preservation of the skeleton provides new information about the osteology of m trogontherii an evolutionary intermediate between the better known ancestral mammoth mammuthus meridionalis and woolly mammoth mammuthus primigenius the find is also remarkable for the articulated condition of the skeleton the animal occupying a crouching posture which is probably little altered from its original death position this and the depositional environment of the skeleton a broad fast flowing river suggest that the animal died in relatively shallow water and was very rapidly buried in river sediments based on the known european record of typical large sized m trogontherii of this kind the age of the kostolac skeleton and its enclosing sediments is between 1 0 and 0 4 ma

steppe lion remains imported by ice age spotted hyenas into the late pleistocene perick caves hyena den in northern germany upper pleistocene remains of the ice age steppe lion panthera leo spelaea goldfuss 1810 have been found in the perick caves sauerland karst nw germany bones from many hyenas and their imported prey dating from the lower to middle weichselian have also been recovered from the perick cave hyena den these are commonly cracked or exhibit deep chew marks the absence of lion cub bones in contrast to hyena and cave bear cub remains in the perick caves and other caves of northern germany excludes the possibility that p leo spelaea used the cave for raising cubs only in the wilhelms cave was a single skeleton of a cub found in a hyena den evidence of the chewing nibbling and cracking of lion bones and crania must have resulted from the importation and destruction of lion carcasses 4 of the prey fauna similar evidence was preserved at other hyena den caves and open air sites in germany the bone material from the perick and other central european caves points to antagonistic hyena and lion conflicts similar to clashes of their modern african relatives

turbulent flow over three dimensional dunes 2 fluid and bed stresses 1 dunes formed in response to fluid flow exert a total boundary stress on the fluid that is made up of form drag and skin friction the latter of which is generally considered important for predicting sediment transport and dune evolution previous research has used various methods to estimate the total stress and its subcomponents with recent work suggesting the application of a spatial average to the equations of motion a complete three dimensional 3 d form of this analysis is derived and applied to recent measurements of turbulent open channel flow over 3 d dunes spatial averages of reynolds shear stresses over 3 d dunes cannot be used to predict total boundary shear stress however estimations of total boundary shear stress from the spatially averaged equations of motion agree with not only the sum of form drag and skin friction but also the direct measurements of average free surface slope form induced stresses from secondary circulations augment the relatively low reynolds shear stresses over the 3 d dunes these low turbulence levels have ramifications for sediment transport predictions in that use of the total boundary shear stress in prediction of sediment transport over 3 d dunes must account for these low turbulence levels so as not to overpredict transport rates

the janda cavity at fruska gora the first cave assemblage from the southeast pannonian lowland vojvodina serbia abstract the recently discovered janda cavity yielded the first large mammal fossil assemblage of the late pleistocene age in the southeast pannonian lowland vojvodina outside the karst region of serbia the cavity is formed in the badenian reef limestone on the northern hillside of the fruska gora mountain the paper provides a paleontological description and taphonomic data on mammal remains collected from the loose sediments or scree herbivores are represented by bison priscus bojanus 1827 which is the most abundant species followed by megaloceros giganteus blumenbach 1803 and equus germanicus nehring 1884 with several remains of mammuthus sp and coelodonta antiquitatis blumenbach 1799 carnivores are represented by ursus spelaeus ingressus rabeder et al 2004 crocuta crocuta spelaea goldfuss 1823 panthera leo spelaea goldfuss 1810 as well as canis lupus linnaeus 1758 wolf remains are characterized by their large size almost reaching the size of hyenas which is in contrast with the finds of rather small pleistocene wolves from the caves in the mountainous part of serbia the faunal composition and the presence of mostly grazing forms among the herbivores indicate glacial conditions and an open landscape in the surroundings of the site during the formation of the janda cavity infill taphonomic observations indicate the cave hyena as a dominant bone accumulating agent in contrast to other cave hyena sites in serbia where mostly small and medium sized prey remains were accumulated prey preference for large and extra large mammals is noted it is supposed that this is the consequence of the differences between mountainous and lowland landscapes and environments climatic conditions different composition of animal and plant associations and also in different modes of competitions between predators