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Search Results: 1 - 10 of 713289 matches for " R.A.L.; "
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Partitions, Compartments and Portals: Cave Development in internally impounded karst masses.
Speleogenesis and Evolution of Karst Aquifers , 2003,
Abstract: Dykes and other vertical bodies can act as aquicludes within bodies of karst rock. These partitions separate isolated bodies of soluble rock called compartments. Speleogenetically each compartment will behave as a small impounded-karst until the partition becomes breached. Breaches through partitions, portals, allow water, air and biota including humans to pass between sections of caves that were originally isolated.
Dating ancient caves and related palaeokarsts
Speleogenesis and Evolution of Karst Aquifers , 2005,
Abstract: There are few cases of open caves that have been reliably dated to ages greater than 65 Ma. This does not mean that such caves are extremely rare, rather it is difficult to reliably establish that a cave, or palaeokarst related to a cave, is this old. Relative dating methods such as: - regional stratigraphic, lithostratigraphic, biostratigraphic, relative climatic, relative isotopic, morphostratigraphic, and regional geomorphic are very useful. They suffer however from significant difficulties, and their results lack the impact of a crisp numerical date. While many of the methods used to date younger caves will not work over the required age range, some isotopic methods and palaeomagnetic methods have been applied with varying degrees of success. While finding something to date and having it dated is difficult enough, producing the date is rarely the end of the story. The difficult issue is not the date or relative correlation itself, but what the date or correlation means. Demonstrating that caves are ancient seems to rapidly become beset with the old adage that “extraordinary claims require extraordinary proof”. The presence of a well-dated or correlated sediment in a cave does not necessarily mean that the cave is that old or older. Perhaps the dated material was stored somewhere in the surrounding environment and deposited much more recently in the cave. A lava flow in a cave must be demonstrated conclusively to be a flow, not a dyke or a pile of weathered boulders washed into the cave. It must be conclusively shown that dated minerals were precipitated in the cave and not transported from elsewhere. There seems little doubt that in the future more ancient caves, or ancient sections of caves, will be identified and that as a result our perception of the age of caves in general will change.
Quartzite dissolution: karst or pseudokarst?
Wray, R.A.L.
Speleogenesis and Evolution of Karst Aquifers , 2007,
Abstract: A wide range of landforms of great similarity to limestone karst is found on many of the world's quartz sandstones and quartzites. These landforms have often been dismissed as pseudokarst, but recent investigation shows that the dissolutional removal of silica, even quartz, under earth-surface conditions is a critical process in their formation. They must therefore be regarded as true karst features. Recognition of these genetically similar forms on quartzose rocks now demands the worldwide adoption of a less restrictive, process-based, karst definition. Direct evidence for this near-surface dissolutional weathering is not common. Examples of this process are reviewed here, along with further evidence for the dissolution of silica from within the quartz sandstones of the Sydney Basin in temperate south-eastern Australia. Some of the complex processes by which dissolution attacks the rock remain unclear. However the solubility, thermodynamics, fluid throughput and physical removal of detritus are all critical factors in the formation of what can only be termed karst on quartzites and quartz sandstone.
The troubles with cupolas
Speleogenesis and Evolution of Karst Aquifers , 2004,
Abstract: Cupolas are dome-shaped solution cavities that occur in karst caves, and have been described in both limestone and gypsum karst. While there has been considerable discussion in the literature concerning the likely origin and significance of these features, there has been little in the way of detailed description of the features themselves and little attention has been given to the definition of the term. Consequently, there are a number of troubles with cupolas: - What is a cupola? Where do cupolas occur? What are cupolas like? Do cupolas occur with particular types of speleogens? Are Cupolas features of Ceilings or features intersected by ceilings? How do cupolas form? But how can these troubles be resolved? Tentative answers are given here to many of these questions but a great deal of basic field observation and theoretical work is required to solve them. The most important step would be more field observation and measurement of cupolas and of the particular suite of speleogens that occur with them. The troubles with cupolas can be solved and in the process we will come to understand a great deal more about the unusual caves in which they occur.
Halls and Narrows: Network caves in dipping limestone, examples from eastern Australia
Osborne, R.A.L.
Speleogenesis and Evolution of Karst Aquifers , 2007,
Abstract: Structurally guided network caves formed in limestones dipping at greater than approximately thirty degrees differ in plan and section from maze caves developed in horizontal to gently dipping limestone. These caves are characterised by the development of large elongate cavities oriented along strike called halls and smaller, short cavities oriented perpendicular to strike called narrows. Halls typically terminate blindly along strike. A range of hall and narrows development is recognised, resulting from increases in dip and differing disposition of joints. Entrances to hall and narrows caves appear to have little genetic relationship to the caves. Hall and narrows caves are common in the steeply dipping Palaeozoic limestones of eastern Australia. While the origin of these caves has yet to be completely explained, many of their features suggest that hydrothermal or artesian water had a role in their development.
Paleokarst: cessation and rebirth?
Osborne, R.A.L.
Speleogenesis and Evolution of Karst Aquifers , 2003,
Abstract: The transformation of active karst into paleokarst by burial, isolation or cessation of process is not necessarily permanent. Paleokarst structures and landforms can be and are exhumed or reactivated, sometimes on numerous occasions. There is not a great deal of similarity between the localities where exhumation and reactivation of paleokarst has been reported. Exhumation and reactivation however have not been reported in many karsts that are similar to those where they have been reported. Exhumation and reactivation appears to be favoured in four situations: - the margins of sedimentary basins overlying grand unconformities, the axes of anticlines, narrow steeply-dipping impounded karsts and where paleokarst fill contains unstable minerals. Six processes are principally responsible for exhumation and reactivation: - per-ascensum speleogenesis, eustatic sea level changes, paragenesis, high density speleogenesis, glaciation, and large-scale meteoric speleogenesis. On some occasions karst landforms, particularly caves or segments of caves, may survive intact and unfilled for geologically significant periods of time. These may be completely isolated from the surface environment, or become reactivated by entrance formation due to breakdown, surface lowering or headward erosion. The intersection and reactivation of ancient open cavities and of exhumed cavities by “modern” caves may be much more common than is currently recognised. If caves have histories as long and as complex as the karsts in which they are developed then many “modern” caves will be composite features composed of interconnected “modern”, relict and exhumed cavities excavated at different times by different processes. Unravelling these histories is the new challenge facing cave science. It will require caves to be studied in a much more detailed, thorough and systematic manner and will also require the application of new technologies in surveying, analysis and dating.
Agronomic Performance of Eight Sweet Melon Cultivars in Three Ecological Zones of Ghana
G.O. Nkansah,R.A.L. Kanton,C. Ametefe,E.B. Quaye
Journal of Agronomy , 2012,
Abstract: In this study, Sweet melons were evaluated in different ecological zones to select those best suited for exporters and other stakeholders in the horticultural industry. The aim of this study was to investigate the performance of eight Sweet melon cultivars (Alpes, Amaral, Kousto, Mirella, Makenna, Anish, Raneen and Alameda) for their growth, yield and fruit quality characters in three different ecological zones (Forest, Coastal and Guinea savanna zones) of Ghana in two seasons (2008 and 2009). The design of the field experiments was Randomized Complete Block Design with factorial combination of eight cultivars and two locations replicated three times. However, in order to obtain information on the effects of season, the results in both seasons were analyzed as a split-split-plot design with season as the main block, location as sub-plot and cultivar as sub-sub plot. Results indicated significant differences in agronomic performance among the varieties in the different ecological zones as well as significant cultivarxlocation interaction. Yield was higher at Binduri (Guinea savanna zone ) and Kade (Forest zone) than at Sogakope (Coastal savanna zone). Cultivars Alameda and Ranneen recorded the highest fruit weight while Alpes had the lowest. Sugar content was lowest at Kade (Forest zone) and highest at Sogakope (Coastal savanna zone). Alpes, Anish, Mirella and Makeenna were found to be early maturing and can be recommended for export due to their earliness. From the studies all the varieties except Makeenna at Kade performed well in all the three agro-ecological zones and thus are suitable for cultivation.
Fisioterapia após substitui??o artroscópica do ligamento cruzado cranial em c?es: II - avalia??o artroscópica e anatomopatológica
Muzzi, L.A.L.;Rezende, C.M.F.;Muzzi, R.A.L.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2009, DOI: 10.1590/S0102-09352009000400008
Abstract: the fascia lata graft in the arthroscopic reconstruction of the cranial cruciate ligament (ccl), the histological characteristics of the graft and the graft-bone interface, and the effects of postoperative physiotherapy by arthroscopic and anatomopathological exams were evaluated. sixteen male mongrel dogs weighing from 19.2 to 26.3kg had the ccl experimentally ruptured and the stifle joint was stabilized by arthroscopical technique with fascia lata as an autogenous graft. eight dogs were included in a postoperative physiotherapy group and the other eight in a temporary immobilization group. arthroscopic and histological examinations showed articular lesions consistent with degenerative joint disease at 60 days after surgery, which was more severe in dogs from the temporary immobilization group. from histological studies, the graft underwent a collagenic reorganization process that was more intense and earlier in dogs from the physiotherapy group. there was a progressive establishment of collagen fiber continuity in the graft-bone interface. it can be concluded that fascia lata graft can be used to replace the ccl by arthroscopic surgery, the graft undergo a ligamentization and osteointegration process, and the postoperative physiotherapy decrease the degenerative joint disease progression and stimulate the ligamentization of the graft.
Fisioterapia após substitui??o artroscópica do ligamento cruzado cranial em c?es: I - avalia??o clínica, radiográfica e ultrassonográfica
Muzzi, L.A.L.;Rezende, C.M.F.;Muzzi, R.A.L.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2009, DOI: 10.1590/S0102-09352009000400007
Abstract: the reconstruction of experimentally ruptured cranial cruciate ligament (ccl) under arthroscopic guidance and the effects of an early postoperative rehabilitation program by clinical, radiographic, and ultrasonographic exams were evaluated. sixteen male mongrel dogs weighing from 19.2 to 26.3kg had the ccl experimentally ruptured and the stifle joint was stabilized by the use of an intracapsular arthroscopical technique with fascia lata as an autogenous graft. eight dogs were included in a postoperative physiotherapy group and the other eight in a temporary immobilization group. from serial clinical, radiographic, and ultrasonographic examinations, no differences between groups were observed, although all dogs had showed signs of degenerative joint disease. limb function was determined after surgery using force platform analysis, and the animals from physiotherapy group had significantly better results during rehabilitation period. it can be concluded that arthroscopic surgery for reconstruction of the cranial cruciate ligament is an efficient method to be used in dogs, in spite of not preventing the degenerative joint disease, and the physiotherapy has beneficial effects on early limb function during the rehabilitation period.
Avalia??o ecodopplercardiográfica da fun??o diastólica em c?es da ra?a Boxer
Cavalcanti, G.A.O.;Muzzi, R.A.L.;Araújo, R.B.;Cherem, M.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2007, DOI: 10.1590/S0102-09352007000500012
Abstract: major diastolics indexes, including the mitral propagation velocity (vp), were evaluated in 36 healthy boxer dogs, 18 males and 18 females, aging from 1.5 to 6-years-old. the aortic root and left atrium ratio, measured in b mode, was 1.17±0.11. the peaks of velocity of waves of the left atrium filling were: systolic 31.41±6.87cm/s, diastolic 73.85±17.04cm/s and atrial reversal 28.90±8.33cm/s. the ratios of the waves of initial ventricular filling were 1.58±0.19 to mitral valve and 1.62±0.29 to tricuspid valve. from the evaluated indexes, the vp was only weakly correlated (r=0.39) with e and a waves of mitral valve and with d, showing itself, relativity, as an independence index. regarding to the vp, no significant differences were seen between the gender of the animals and among the observers. the vp decreased as the age increased, showing mean values of 99.73±16.06cm/s.
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