a seasonal climatology of rossby wave breaking in the 320 2000 k layer abstract differential advection in rossby waves can lead to potential vorticity pv p contours on isentropic surfaces folding over in latitude py 0 in a process called rossby wave breaking rwb exploring the properties of rwb may shed light on underlying dynamics and enable quantification of irreversible transport a seasonal climatology of py and rwb statistics is presented for the 320 850 k layer using ncep reanalysis data during 1979 2005 and for the 320 2000 k layer using the met office ukmo data during 1991 2003 a primary goal is to depict the spatial extent and seasonality of rwb maxima this analysis shows seven distinct rwb regimes poleward and equatorward of the subtropical westerly jets poleward and equatorward of the stratospheric polar night jets flanking the equator in the stratosphere and mesosphere equatorward of subtropical monsoon anticyclones and the summertime polar stratosphere a striking pv gradient maximum exists at the equator throughout the layer 360 2000 k flanke

behavior of transversely isotropic shale observed in triaxial tests and brazilian disc tests abstract shale rock is widely distributed in nature and must be taken into account in some rock engineering applications in this research three kinds of experiments namely the conventional triaxial compression test reducing confining pressure test and brazilian test were conducted on a type of shale rock specimen with a horizontal bedding plane and a vertical bedding plane collected from lushan city jiangxi province china to further investigate the bedding effect on the mechanical properties of shale rock an acoustic emission ae monitoring system was used to study the fracture process under the conventional triaxial compression test whereas a digital image correlation dic system was employed to monitor the deformation of disk faces during the failure process under the brazilian test another key issue addressed in this research is the failure process and mechanism of shale specimens with horizontal and vertical bedding planes under the reducing confining pressure test the conventional triaxial compression test shows that the bedding plane could easily affect the elasticity modulus and failure pattern and the failure of the bedding plane can lead to stronger energy release and a higher ae count level the reducing confining pressure test shows that the dissipated energy magnitude of unloading path ii reducing confining pressure and increasing axial stress is much larger than that of unloading path i reducing confining pressure and keeping axial strain constant and that continuous energy input and larger energy dissipation led the specimens under unloading path ii to fail faster than those under unloading path i the brazilian test further revealed that the bedding plane has a significant effect on the tensile strength and failure pattern of shale rock

instability at the winter stratopause a mechanism for the 4 day wave abstract studies using climatological fields in a three dimensional stability model show unstable modes near the polar winter stratopause with periods neat 4 days the calculated modes exhibit equatorward momentum and heat fluxes near the stratopause similar to characteristics of observed 4 day wave events demonstrating that both baroclinic and barotropic processes are important for this instability the baroclinic and baratropic components are considered separately by selectively removing either horizontal or vertical shear from the background flow although both situations reveal instability growth rates are very slow realistic growth rates occur only for climatological flows including both horizontal and vertical shears similar unstable fast moving waves are found near the polar stratopause for several winter months in both hemispheres

influence of water content and anisotropy on the strength and deformability of low porosity meta sedimentary rocks under triaxial compression abstract a reduction of uniaxial compressive strength ucs by the presence of water has been ascertained in many sedimentary rocks and even some metamorphic rocks experimentally this paper reports and discusses the influence of water content and anisotropy on the strength and deformability of two meta sedimentary rocks by triaxial compressive tests before conducting the triaxial tests the physical properties of meta siltstone and meta sandstone specimens have been carefully examined the water contents of both tested rocks are very low for instance 0 17 for meta siltstone and 0 10 for meta sandstone the porosities of the tested rocks are analyzed by the technique of mercury intrusion porosimetry mip it shows that the meta sedimentary rocks have very low porosity 0 18 for meta siltstone and 0 53 for meta sandstone on average the thin section analysis reveals that the meta siltstone contains more hydrophilic substances such as clay minerals than the meta sandstone and both two meta sedimentary rocks are characterized by distinct beddings and laminae even though the water contents of two tested rocks are very low they significantly influence the triaxial compressive strength and deformability the reduction of strength by water content is found to be related to a reduction of friction angle in the mohr coulomb failure criterion while a reduction of mi value in the hoek brown failure criterion on the other hand the influence of water on deformability of tested rocks is reflected as a reduction of young s modulus and increase of poisson s ratio which indicates that the wet meta sedimentary rocks will deform more than that of the dry ones under the same stress condition the experimental studies show that the anisotropy associated with bedding in rock specimens plays a weakening effect on the triaxial compressive strength for both tested rocks appearing more severely for meta siltstone in general the triaxial compression strength of rock specimens with transverse bedding planes is higher than the ones with longitudinal bedding planes no matter for meta siltstone or meta sandstone both dry and wet conditions under the same confining stress with regard to the stiffness both the tangent and secant young s moduli of the two tested rocks with transverse bedding are less than the ones with longitudinal bedding appearing more conspicuously for the meta siltstone the paper also discusses the axial strain calibration by two different measurement techniques one by the linear variant difference transducer lvdt technique and the other one by axial strain gages it shows that the axial strain ratio coefficient k elvdt estrain decays with the deviator stress in our present study the secant modulus estrain is usually about 1 4 1 8 times of elvdt at the peak strength point the correlation between mechanical properties and physical properties of the two tested rocks are also discussed in the paper

model data comparisons of moments of nonbreaking shoaling surface gravity waves the predictions of linear and nonlinear boussinesq shoaling wave models for nonbreaking unidirectional surface gravity waves are compared to field observations with particular emphasis on quantities that may be important for cross shore sediment transport the extensive data sets were obtained on two natural beaches span water depths between 1 and 10 m and include incident wave power spectra with narrow broad and bimodal shapes significant wave heights varied between approximately 30 and 100 cm and peak periods between approximately 8 and 18 s the evolution of total variances of sea surface elevation cross shore velocity and horizontal acceleration is modeled at least qualitatively well by both linear and nonlinear theories only the nonlinear theory predicts the increasingly asymmetric sea surface elevations and horizontal velocities pitched forward wave shapes and the weaker variation of skewness difference between crest and trough profiles which are observed to occur during shoaling the nonlinear theory also models qualitatively well the large skewed accelerations which occur during the passage of asymmetric waves

an enhanced equivalent continuum model for layered rock mass incorporating bedding structure and stress dependence abstract layered rock masses exhibit significant anisotropy in both the deformability and strength properties of this rock mass are largely affected by its bedding structure and also by the stress state change for the purpose of characterizing these salient features using the equivalent continuum concept an enhanced model is proposed in this paper based on the ubiquitous joint model in the enhanced model the intact bedded rock is assumed to behave as a transversely isotropic elastic body a modified anisotropic strength criterion is adopted to describe the direction dependence of the strength of intact bedded rock in addition stress sensitive parameters are utilized for both the intact rock and bedding plane among which the dilation angle and strength parameters of intact rock are influenced by confining pressure and loading history whereas the stiffnesses of bedding planes are closely related to the current normal stress the effect of layer thickness on the mechanical behavior of rock mass is reflected by continuously updating the global stiffness matrix after failure of bedding plane and by conditions for conducting bedding plane related calculations determined by the relative scales between element size and layer thickness preliminary validation of this model is conducted by comparing with the closed form solutions and with laboratory tests generally good agreements can be achieved between numerical simulations and theoretical experimental results which indicate that applicability of the enhanced model on underground engineering issues related to layered rock mass is promising

effect of layer orientation on the failure of layered sandstone under brazilian test conditions abstract the experimental research in this paper focuses at macro scale on the effect of the layer orientation on failure strength and fractures induced by the brazilian tensile test for one particular sandstone sandstone from modave in the south of belgium the variation in the strength the applied energy and the failure pattern are examined as a function of the inclination angle between the layer plane and the loading direction for each sample the length of fractures parallel to the layers as well as corresponding to other directions is measured for the layered sandstone in this study the transition angle range is determined whereby the relative importance of both types of fractures switches

performance of a numerical short wave model abstract a numerical short wave model system based on the boussinesq equations is verified against analytical as well as experimental results for shoaling refraction diffraction and partial reflection processes it is shown that engineers can confidently and responsibly apply such a model system to the study of wave disturbance in coastal regions

skewness in the nearshore zone a comparison of estimates from marsh mcbirney current meters and colocated pressure sensors many of the field studies that have undertaken an investigation of surf zone dynamics e g nearshore sediment transport study canadian coastal sediment study have relied on marsh mcbirney electromagnetic current meters to measure the velocity field data from these instruments have been used to compute higher order moments of the velocity field which are used as an input in many sediment transport models however recent laboratory measurements by aubrey and trowbridge 1985 have raised questions regarding the suitability of marsh mcbirney current meters for surf zone studies and the accuracy of higher order velocity moments fortunately colocated pressure and velocity measurements were made during field programs in effect this provides a calibration check in the field of the performance of these instruments a cross spectral analysis indicates that colocated marsh mcbirney current meter measurements are highly coherent this is true for measurements from inside and outside the surf zone as a result normalized skewness estimates computed with the aid of the bispectrum from these colocated current meter measurements differ by only a few percent a cross spectral analysis between colocated pressure and velocity measurements show a similar distribution of variance for wind wave frequencies observed differences between normalized skewness estimates from colocated pressure and velocity measurements are shown to be consistent with the theoretical expectation that pressure has a nonlinear dependence on velocity these results suggest that the marsh mcbirney current meter is suitable for the estimation of nondimensional velocity moments even in breaking wave conditions

stress state evolution of the brittle upper crust during compressional tectonic inversion as defined by successive quartz vein types high ardenne slate belt germany abstract in the frontal part of the rhenohercynian fold and thrust belt high ardenne slate belt germany two successive types of quartz veins oriented normal and parallel to bedding respectively are interpreted to reflect the early variscan compressional tectonic inversion of the ardenne eifel sedimentary basin fracturing and sealing occurred in lower devonian siliciclastic multilayers under very low grade metamorphic conditions in a brittle upper crust a geometrical and microthermometric analysis of these veins has helped to constrain the kinematic and pressure temperature conditions of both vein types allowing the reconstruction of the stress state evolution in a basin during tectonic inversion it is demonstrated that bedding normal extension veins which developed under low differential stresses and repeatedly opened and sealed crack seal under near lithostatic fluid pressures reflect the latest stage of an extensional stress regime bedding parallel veins which developed at differential stresses that were still low enough to allow the formation of extension veins cross cut the bedding normal veins and preceded the regional fold and cleavage development these veins show a pronounced bedding parallel fabric reflecting bedding normal uplift and bedding parallel shearing under lithostatic to supra lithostatic fluid pressures during the early stages of a compressional stress regime this kinematic history corroborates that fluid overpressures are easy to maintain during compressional tectonic inversion at the onset of orogeny

bonded particle discrete element modeling of mechanical behavior of transversely isotropic rock abstract this paper presents bonded particle discrete element modeling with embedded smooth joints for simulating the mechanical behavior of transversely isotropic rock with systematic verifications and extensions to laboratory and upscaled problems verification was conducted against the analytical solutions in terms of anisotropic elastic and strength behavior the developed model was compared with laboratory observations of three rock types gneiss shale and schist leading to good agreements bonded particle dem modeling successfully captured the failure patterns observed in anisotropic rock in which weak planes play a significant role the model was upscaled to large scale foundation problems subjected to surface line load the study achieved reasonable agreements both for isotropic and anisotropic solutions the results demonstrate that the bonded particle dem with embedded smooth joints can model the equivalent anisotropic medium and it has potential to be applied to problems of larger engineering problems in which anisotropy is important

interannual variability of the 4 day wave and isentropic mixing inside the polar vortex in midwinter of the southern hemisphere upper stratosphere 1 interannual variations of the flow field and large scale horizontal transport and mixing inside the wintertime polar vortex of the southern hemisphere upper stratosphere are investigated using isentropic winds obtained from the u k met office assimilated data for nine years of 1992 2000 we focused on the midwinter july when the polar vortex is not much distorted although an eastward propagating wave called the 4 day wave is observed in some years in the polar region finite time lyapunov exponents are computed and contour advections are done to examine stirring and mixing in the polar region when the 4 day wave has a large amplitude effective mixing through a stretching and folding process is seen inside the polar vortex finite time lyapunov exponents are sometimes as large as the midlatitudes and the material contours of small areas grow exponentially in time on the poleward side of 70 s such mixing properties are not uniform inside the vortex when the wave is not clearly seen on the other hand wind fields are close to a solid body rotation around the pole and mixing is very small lyapunov exponents are small and the material contours grow linearly in time by the stretching due to the meridional shear of the polar night jet such interannual variability of the strength of the mixing is correlated with the variability of the perturbation amplitude of potential vorticity in the polar region

an energetics bedload model for a plane sloping beach local transport bagnold s energetics based sediment transport model for streams is used as a basis for the development of a model for the time varying transport of bedload over a plane sloping bed the sediment transport vector is found to consist of two components the velocity induced transport directed parallel to the instantaneous velocity vector and the gravity induced transport vector directed downslope the model is applied to the case of sediment transport within the surf zone for the separate cases of weak and strong longshore currents relative to the wave bore oscillatory water velocity the results suggest the bagnold s oscillatory sediment transport model which forms the basis for a number of longshore sediment transport models is only correct for the special case of weak longshore currents and near normal incident waves for an artibrary strength longshore current v and a local incident wave angle a the longshore transport rate is found to be proportional to sina v 1 sin sup 2 a v sup 3 where u is the wave induced oscillatory water velocity the model also predicts the onshore offshore sediment rate for weak longshore currents and near normal incident waves the predicted equilibrium beach slope is equal to tanf strong longshore currents and or significant local wave angle conditions however cause amore change in this equilibrium beach slope less authors bailard j a inman d l publication date 1981 03 20 osti identifier 6767919 resource type journal article resource relation journal name j geophys res united states journal volume 86 c3 research org scripps institution of oceanography university of california la jolla california 92093 country of publication united states language english subject 58 geosciences shores sedimentation coastal waters gravitation sediments silt velocity water currents currents surface waters 580500 oceanography 1980 1989

barotropic stability of realistic stratospheric jets abstract the stability of realistic jets is examined in a linearized barotropic model on a sphere approximately non dispersive modes associated with a region of negative basic state absolute vorticity gradient on the poleward side of the jet are examined in detail as in previous studies broader jets and those which peak at higher latitudes produce poleward modes that are less dispersive jet profiles derived from observational data at 10 5 and 2 mb for three southern hemisphere winter months are used in the model and the results are compared with quasi nondispersive features qndf which have been observed in satellite data in the southern hemisphere winter stratosphere characteristics of the barotropically unstable modes compare remarkably well with those of the observed modes the barotropic model results for a month in which these features are not observed indicate the presence of equatorward modes at wavenumbers 3 and 4 which grow considerably faster than the quasi nondispersive poleward modes

fracture mechanical behavior of red sandstone containing a single fissure and two parallel fissures after exposure to different high temperature treatments it is well known to us that the stability and safety of deep underground mining excavations and nuclear waste depositories rely on accurate knowledge of the physical and mechanical properties of representative rocks under the action of high temperature zhang et al in int j plast 34 93 113 2012

mixing processes within the polar night jet abstract lagrangian material line simulations are performed using u k meteorological office assimilated winds and temperatures to examine mixing processes in the middle and lower stratospheric polar night jet during the 1992 southern hemisphere spring and northern hemisphere winter the lagrangian simulations are undertaken to provide insight into the effects of mixing within the polar night jet on observations of the polar vortex made by instruments onboard the upper atmosphere research satellite during these periods a moderate to strong kinematic barrier to large scale isentropic exchange similar to the barrier identified in gcm simulations is identified during both of these periods characteristic timescales for mixing by large scale isentropic motions within the polar night jet range from 20 days in the southern hemisphere lower stratosphere to years in the northern hemisphere middle stratosphere the long mixing timescales found in the northern hemisphere polar night jet do not persist instead

intrusions into the lower stratospheric arctic vortex during the winter of 1991 1992 investigations of the kinematics of the lower stratospheric arctic vortex during the winter of 1991 1992 using the contour advection with surgery technique reveal three distinct events in which there was substantial intrusion of midlatitude air into the vortex in apparent contradiction of the view that the polar vortex constitutes an isolated air mass two of these events in late january and mid february were well documented they were predicted in high resolution forecasts by the european centre for medium range weather forecasts most clearly in experimental forecasts with reduced diffusion direct confirmation of the presence of the intrusions and of their calculated locations was provided by aerosol observations from the airborne differential absorption laser lidar aboard the nasa dc 8 taken as part of the second airborne arctic stratospheric expedition campaign aerosol rich air of midlatitude origin was seen in the expected position of the intrusions the reality of the february event was also confirmed by in situ measurements from the nasa er 2 such events may be significant for the chemical processes taking place within the winter vortex the intrusions were evidently related to the meteorology of the northern stratosphereduring this winter and in particular to persistent tropospheric blocking over the northeastern atlantic ocean and western europe and concomitant ridging into the lower stratospheric vortex in this region nevertheless preliminary investigations have indicated that such events are not uncommon in other northern hemisphere winters although no such events were found in the southern hemisphere during the antarctic winter of 1987

a seasonal climatology of effective diffusivity in the stratosphere a 7 year 1992 1998 seasonal climatology of effective horizontal diffusivity is presented for the stratosphere 350 1900 k as in previous studies the diagnosis is based on the equivalent length of a test tracer advected on isentropic surfaces in this case using the van leer flux limiting scheme driven by the united kingdom meteorological office assimilated winds although the magnitude of equivalent length is resolution dependent its structure is shown to be reasonably robust for quantifying the inhomogeneous mixing in the stratosphere the van leer calculation agrees well with a more expensive spectral transform calculation at a comparable resolution suggesting that the diagnostic is not sensitive to the advection scheme or subgrid representation of the models a first attempt is also made at estimating the implicit numerical diffusion of the van leer scheme which is necessary to convert equivalent length to effective diffusivity compared with the spectral calculations with a constant diffusion coefficient the van leer results show notably greater diffusivity within the winter polar vortices despite the comparable equivalent lengths suggesting that the scheme may be overdiffusing in the vicinities of mobile tracer extrema the climatology of equivalent length is then presented and the seasonal evolution is discussed in detail for the lower middle and upper stratosphere the major mixing barriers winter and summer polar vortices and tropical eddy transport barrier are easily identified as well as the strong mixing regions surf zones generally equivalent length tends to be small in regions of strong zonal wind and large in regions of weak wind large values of equivalent length are observed in the summer lower stratosphere and in the middle stratosphere during the breakup of the polar vortices interhemispheric asymmetry is observed both after the winter polar vortex breakup where in the middle stratosphere the southern hemisphere shows much larger equivalent lengths and in the summer tropical region where larger equivalent lengths are observed in the northern hemisphere likely related to the monsoon circulation a monthly averaged equivalent length climatology is presented and implications for two dimensional stratospheric chemistry transport modeling are discussed

nearshore bar formation by non linear wave processes a comparison of model results and field data abstract analogue wave records and associated wave spectra from field measurements of wave transformation across two nearshore bar systems in georgian bay ontario show considerable growth of energy in the higher harmonics in addition there appears to be a regular spatial pattern of energy transfer between the peak frequency and the first higher harmonics with a length dimension equal to the spacing between the bars the characteristic peak period of moderate and severe storm waves affecting the two beaches 4 0 and 7 0 s and the mean nearshore slopes 0 005 and 0 01 are used as input to a mathematical model which describes the non linear evolution of a shallow water wave and the interaction between the first and second harmonics in the model the mass transport velocities associated with the primary wave and the second harmonic are used to calculate net sediment flux across a two dimensional profile model predictions of bar number and spacing starting with an initially planar slope correlate well with the field measurements for the two sets of wave conditions and mean slopes in addition the model is able to predict profile changes reflecting seasonal changes in wave climate

evaluation of the anisotropy and directionality of a jointed rock mass under numerical direct shear tests abstract the characteristics of the anisotropy and directionality of jointed rock masses are the key to simplifying it as a transversely anisotropic material experimental direct shear tests were performed on stratified rocks cored from granulite rocks the influence of normal stresses and joint orientations was tested and the anisotropy and directionality of the shear strength were evaluated numerical shearing tests on stratified rock models and discrete fractures network dfn models were subsequently conducted in addition the shear anisotropy and directionality in the dfn models were tested and discussed the results demonstrate that the peak shear stress was more sensitive to the inclination angles than the normal stress the stratified rocks in the experimental test showed apparent shear anisotropy and directionality the maximum value of directionality coincided with the direction of the strike of the bedding plane the more apparent the anisotropy was the higher the directionality became the failure patterns of stratified rocks exhibited more complex characteristics under higher normal stress significant variation of the shear strength distribution occurred due to the different orientations of fractures relative to the directions of the shear load the failure patterns of dfn models of varied scales differed and no apparent convergence was discovered the shear strength of the dfn model showed an apparent principal direction the numerical results presented in this paper are valuable for evaluating the prediction of the failure behaviour of rock masses and can be further applied to the study of the failure mechanism of surrounding rock in engineering

failure of transversely isotropic rock under brazilian test conditions abstract the behavior of transversely isotropic rock material was studied under brazilian test conditions for nine different rocks two sandstones one shale two slates one schist and three gneiss both the variation of the strength and the final fracture patterns induced by testing were examined as a function of the inclination angle of the weak planes the combination of the observations for both parameters illustrated clearly the complexity of the failure of such rocks which was summarized by assuming four different trends the four trends for the variation of the strength as a function of the inclination angles range from little or no variation trend 1 i e isotropic behavior for strength to a sharp decrease of the strength from very small angles onwards followed by a leveling off trend 4 trend 2 is characterized by a constant value between 0 and about 45 followed by a linear decrease while trend 3 corresponds to a decrease of the strength over the entire interval but a rather systematic decrease approximating a linear variation different variations were observed among these four trends in terms of the relative lengths of the respective fractures along the weak planes and in any other direction for the rocks investigated there is a cross over from dominant fractures in directions other than the weak planes to dominant fractures along the weak planes for the four trends there are systematic changes in the position of this cross over point i e on average at about an inclination angle of 75 for trend 1 and at about 15 for trend 4 for inclination angles larger than the cross over point the rock specimens failed primarily by splitting between both loading lines

observations of 2 4 day inertia gravity waves from the equatorial troposphere to the f region during the sudden stratospheric warming event of 2009 1 we have observed strong 2 4 day wave activity in the f region peak critical frequency fof2 at 7 5 n obtained from gps radio occultation measurements of the constellation observing system for meteorology ionosphere and climate cosmic satellites and the horizontal component of geomagnetic field variations over tirunelveli 8 7 n 77 8 e 1 75 n dip angle during the sudden stratospheric warming ssw event of 2009 a similar wave is observed strongly in the meridional winds observed by the mf radar at tirunelveli the meridional winds at 9 n and the equator obtained from era interim which is the latest global atmospheric reanalysis produced by the european centre for medium range weather forecasts shows clearly the 2 4 day wave propagating eastward with zonal wave number 6 over the central and eastern pacific both before and during the ssw event and over the indian sector during the ssw event only the potential vorticity pv intrusion at 200 hpa to lower latitudes is near the central pacific before the onset of the ssw event however during the ssw event the pv intrusion is observed more strongly near the indian sector in addition to the weaker intrusion near the central pacific it clearly indicates the rossby wave propagation to equatorial latitudes in the form of pv intrusion and it selectively enhances the periodicities generated owing to equatorial convective heating these waves could propagate to upper heights and cause variations in the mesosphere thermosphere ionosphere system

eulerian measurements of horizontal accelerations in shoaling gravity waves laboratory and field measurements of suspended sediment in the nearshore suggest that fluid accelerations are an important factor in sediment transport by oscillatory waves here eulerian accelerations of the cross shore velocity are calculated from measurements of velocity obtained by an array of bottom mounted electromagnetic flow meters spanning a natural surf zone large shoreward accelerations of brief duration are associated with the steep front faces of both near breaking and breaking waves weaker offshore accelerations of longer duration occur during passage of the more gently sloped rear faces the acceleration field is thus strongly skewed in the shoreward direction power spectra and bispectra indicate as expected that statistics of the acceleration field are significantly influenced by high frequency motions but are rather insensitive to surf beat

palaeozoic clay mineral sedimentation and diagenesis in the dinant and avesnes basins belgium france relationships with variscan tectonism abstract clay mineral investigations have been performed on more than 500 limestones and shales sampled in lower devonian emsian to lower carboniferous namurian outcrops in the dinant and avesnes basins ardenne massif nw europe clay mineral data have been placed in the palaeoenvironmental and structural histories documented by previous lithological stratigraphical palaeontological diagenetic and tectonic contexts the clay associations are dominated by illite and chlorite derived partly from the erosion of land masses surrounding the marine domain the geothermal gradient estimated from correlation with conodont colour alteration index ranges between 40 and 70 c km a diachronous northwards migration of the diagenesis metamorphism interface links to uplift caused by late carboniferous compressional folding and overthrusting associated clay minerals include smectite locally preserved from diagenetic changes mainly by early pore closure that reflect lagoonal or quiet offshore marine conditions smectite and subordinate kaolinite abundances decrease upwards during the devonian in three successive intervals suggesting alternations of sub arid to drier climates the local occurrence of corrensite ordered chlorite smectite mixed layer is attributed to the moderate diagenetic transformation of pre existing smectite

the structure of the polar vortex reconstruction of the airborne antarctic ozone experiment and airborne arctic stratosphere expedition aircraft constituent observations radiative heating rate computations and trajectory calculations are used to generate comparative pictures of the 1987 southern hemisphere sh late winter and 1989 northern hemisphere nh mid winter lower stratospheric polar vortices overall both polar vortices define a region of highly isolated air where the exchange of trace gases occurs principally at the vortex edge through erosional wave activity aircraft measurement showed that 1 between 50 and 100 mbar horizontally stratified long lived tracers such as n20 are displaced downward 2 3 km on the cyclonic poleward side of the jet with the meridional tracer gradient sharpest at the jet core 2 eddy mixing rates computed using parcel ensemble statistics are an order of magnitude or more lower on the cyclonic side of the jet compared to those on the anticyclonic side 3 poleward zonal mean meridional flow on the anticyclonic side of the jet terminates in a descent zone at the jet core despite the similarities between the sh and nh winter vortices there are important differences during the aircraft campaign periods the sh vortex jet core was located roughly 8 o 10 o equatorward of its nh counterpart after pole centering as a result of the arger size of the sh vortex the dynamical heating associated with the jet core descent zone is displaced further from the pole the sh polar vortex can therefore approach radiative equilibrium temperatures over a comparatively larger area than the nh vortex the subsequent widespread formation of polar stratospheric clouds within the much colder sh vortex core gives rise to the interhemispheric differences in the reconstructed h20 noy c10 and 03 species which are affected by polar stratospheric clouds

experimental and theoretical study of the anisotropic properties of shale abstract the effect of bedding plane orientations on shear strength and failure mechanisms of shale is investigated with an emphasis on the shear parameters of the bedding planes this study is based on direct shear tests conducted on directional shale samples obtained from formations which exhibit well developed stratification the tested cylindrical specimens were prepared by coring at 30 intervals from the direction of the bedding planes the results indicate that the anisotropy of the shear strength of shale can be readily observed due to the anisotropic effects of bedding plane orientation and normal stress the shear parameters such as strength cohesion and internal friction angle reach their maximum and the minimum values at 60 and 0 respectively where is the angle between the bedding planes and the coring orientation which is also the direction of normal stress during the laboratory tests it is demonstrated that the bedding planes are weak not only with regards to cementing strength but also with regards to friction three different shear failure modes were built up depending on the shearing angle 1 sliding failure across the bedding planes 2 sliding failure along the bedding planes and 3 sliding failure across the bedding planes combined with tensile splitting along the bedding planes an expression of the shear stress concentration factor of the direct shear model is derived to evaluate the anisotropy of shear strength