Nerve root compression has been suggested as one important pathogenetic factor in low-back pain syndromes and sciatica. The underlying pathophysiologic mechanisms are, however, incompletely known, ...partly because of the lack of experimental data on this topic. In the present study, a model for experimental compression of the porcine sacrococcygeal cauda equina is presented. The model consists of surgical exposure of the cauda equina and compression of the cauda equina toward the ventral aspect of the spinal canal by an inflatable balloon fixed to the spine. This compression system was shown to have a high accuracy in pressure transmission from the balloon to the cauda equina. The gross and microscopic neural anatomy and the vascular anatomy of the porcine cauda equina were analyzed with light microscopic and ink-perfusion techniques. The porcine cauda equina showed a close anatomic resemblance to the human lumbosacral cauda equina. The presented model offers unique possibilities for experimental studies on nerve root compression injury because of the easy surgical exposure and the sufficient length of the nerve roots. In separate studies, this model, along with investigations of solute transport to the nerve tissue and of impulse propagation, has been used to analyze the effects of acute, graded compression on blood flow and edema formation in the cauda equina. The porcine cauda equina would also be particularly suitable for chronic compression studies because any neurologic deficit acquired would be restricted to the tail.
This paper presents an overview of the role of remote sensing technology in the context of the United Nations Framework Convention on Climate Change (UNFCCC) Kyoto Protocol and is based largely on ...discussions held at an international workshop in MI, USA, and the report that followed A. Rosenqvist, M. Imhoff, T. Milne, C. Dobson (Eds.), Remote Sensing and the Kyoto Protocol: A Review of Available and Future Technology for Monitoring Treaty Compliance, Workshop Report, Ann Arbor, MI, USA, 20–22 October 1999, 2000a, 159 pp. Available at
http://www.eecs.umich.edu/kyoto. The implications of significant decisions pertaining to the definition of the key terms
forest and afforestation, reforestation and deforestation (ARD) activities taken at the conference of parties (COP 6:2 and COP 7) meetings in Bonn and Marrakesh, respectively in 2001 are also discussed. Past, current and near-future remote sensing instruments with applications appropriate to Kyoto requirements are short listed; research topics that need to be advanced to support use of these are outlined, and future actions recommended.
River floodplains are the dominant wetland habitat in the Amazon river basin, providing important habitation for aquatic flora and fauna, and playing a key role in sustaining regional fish ...production. The annual inundation pulse has been identified as the dominant environmental factor affecting aquatic biota on the floodplain, and the characteristics of this pulse, in terms of timing, duration and amplitude, vary spatially on the floodplain as a function of fluctuations in river stage height and topography. River floodplains are furthermore globally significant sources of methane (CH 4 ) and other trace gases essential to climate regulation. Refined information on wetland distributions and dynamics are currently needed to improve estimates of habitat availability and to calculate regional contributions of trace gases, especially CH 4, to the troposphere. This paper describes how multitemporal time series of spaceborne L-band Synthetic Aperture Radar (SAR) data from the Japanese Earth Resource Satellite 1 (JERS-1) were used to generate a model of the spatial and temporal variation of inundation on the floodplain of a typical black water river in the Central Brazilian Amazon and how this model was utilized, together with in situ measurements of river stage heights and CH4 fluxes, to model regional estimates of CH 4 emissions. We also demonstrate how a JERS-1 SAR time series can be used to map the spatial variation of flood duration on the floodplain, a key factor controlling local variations in plant biodiversity. For both applications, the availability of adequate time series of satellite sensor data is the prime factor affecting the reliability and accuracy of the flood models and the spatial details of the flood duration map. The availability of in situ data, especially daily river height measurements, was also critical for the development of the flooding model and for the subsequent decoupling of the model from the satellite sensor data.
Two JERS-1 Synthetic Aperture Radar (SAR) mosaics covering central Africa were investigated with respect to their potential usefulness for studies of seasonal flooding dynamics in the Congo river ...basin. The mosaic quality was initially evaluated with respect to geometric and radiometric accuracy, as well as to the temporal composition of the data used in the mosaic assembly. The investigation revealed no major defects that should prevent utilization of the data for hydrological applications. The state of flooding captured in each of the two mosaics-preferably portraying the Congo and its tributaries during their annual maximum and minimum water marks-was furthermore evaluated by examining river stage information. Stage data contemporary with the satellite acquisitions (1996) were derived from the TOPEX/POSEIDON Radar Altimeter and supplemented by historical in situ records. The results suggest that the SAR mosaics may serve well to appraise the maximum extents of flooding in the Congo river basin, but quite poorly to assess the dynamics and ranges of the variations. It was reckoned that a minimum of three acquisitions within 1 year would be required to better describe the complex hydrology in the region. The validation uncertainty in rivers where only historical in situ data were available was evident, thus stressing the utility and future potential of radar altimetry to provide substitute measurements of river stages. important transport routes in the basin, although the occurrence of islands, and rapids make large stretches of the main channel unnavigable. to the Amazon river, which is subject to large annual variations in the seasonal changes in the Congo water levels are less pronounced. to differences in the timing of the wet and dry seasons in the southern hemispheres. The Congo crosses the equator twice and flood-waves
Large floodplains in the tropics, like the Congo river basin in Central Africa, are interesting ecosystems that function as water storage and faunistic and florensis habitat. Moreover, they host a ...series of bio-chemical processes, such as methane emission, which have a significance in global change issues. Characterization of these complex ecosystems can be tackled from different view points, such as bio-chemistry, geology, climatology, hydrology, geomorphology, floristics and forest structure. In this paper we focus on forest structure aspects and report about an approach for mapping two thematic classes - the swamp forest and lowland rain forest - by radar remote sensing at regional scale and high spatial resolution. The proposed solution hinges on the recent availability of a large radar mosaic acquired over Central Africa wall-to-wall by the Synthetic Aperture Radar instrument on board the ESA ERS-1 satellite. The focal points and main issues of this study are: the global mapping approach, using continuous spatial sampling over the region of interest; the signal processing techniques; the up-scaling to wide area of local area classification and (more critical) validation techniques. Results achieved so far already show that blanket radar coverage of the tropics can provide thematic information on the forest composition of a whole ecosystem at an unprecedented level of detail and accuracy.
Global carbon observations is a fundamental requirement in the context of the Terrestrial Carbon Observation (TCO) theme within the Integrated Global Carbon Observation (IGCO) theme of Integrated ...Global Observation Strategy Partners (IGOS-P), for quantitative estimation of key biophysical parameters such as net primary productivity (NPP), carbon stocks and their changes in time. In support to this major international effort, NASDA, through its Earth Observation Research Center (EORC), is planning global systematic data observations using the Phased-Array L-band Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS) from 2004. Like its predecessor - the JERS-1 SAR - the PALSAR instrument will operate in the longer L-band wavelength range (23.5 cm), with added polarimetric features making it attractive for assessment of regenerating and lower-density above-ground biomass, and changes therein. In addition to ALOS, the Global Imager (GLI) instrument onboard the Advanced Earth Observing Satellite-II (ADEOS-II), launched successfully in December 2002, will be used to estimate annual change of global NPP at 1 km and 250 m spatial resolutions. Notable is that the six terrestrial channels on GLI operate with the same wavelength as Landsat ETM+ and MODIS, but all with a spatial resolution of 250 m. This paper describes the preliminary study on the applicability and improvement of data sets from PALSAR on ALOS and GLI on ADEOS-11 for terrestrial carbon observation.
Multi-temporal JERS-1 SAR (Japanese Earth Resource Satellite 1 Synthetic Aperture Radar) data have been used in this study to investigate the temporal and spatial characteristics of irrigated rice in ...LHH-band SAR data. The two test sites chosen represent areas that are characterized by manual and mechanical planting practices that turn out to have a significant effect on the L-band backscatter. The results show a clear relationship between L-band backscatter and plant growth in manually planted areas. A dynamic range of about 8dB has been measured with no apparent saturation of the signal. Areas in which mechanical planting is practiced, however, display a more complex relationship where the radar response is strongly dependent on parameters related to the spatial distribution of the plants. The backscatter displays a strong dependency on planting orientation and plant spacing, where fields planted in the radar illumination direction with a certain plant spacing display extreme dynamic ranges of up to more than 20dB due to resonant scattering. Fields planted in other directions generally experience attenuation of the signal and dynamic ranges do not change by more than a few decibels. Despite these artifacts, however, a correlation between plant growth and backscatter has been observed for all fields, independent of plant spacing and field orientation.
Introduction Treatment of osteoporosis is becoming more effective, but methods to identify patients who are most suitable for investigation and treatment are still being debated. Should any type of ...fracture have higher priority for investigation of osteoporosis than any other? Is the number of previous fractures useful information?
Material and methods We investigated 303 consecutive women patients between 55 and 75 years of age who had a newly diagnosed low-energy fracture. They answered a questionnaire on previous fractures which also dealt with risk factors. Bone mineral density (BMD) was measured at the hip, lumbar spine, and forearm.
Results The distribution of fracture location was: distal forearm 56%, proximal humerus 12%, vertebra 18%, and hip 13%, all with similar age. Half of the subjects had had at least one previous fracture before the index fracture, 19% had had two previous fractures, and 6% had had three or more previous fractures. Patients with vertebral or hip fracture had lower BMD and had had more previous fractures than patients with forearm or humerus fractures. There was an inverse correlation between number of fractures and BMD. Osteoporosis was present in one-third of patients with forearm fracture, in one-half of those with hip or humerus fracture, and in two-thirds of those with vertebral fracture.
Interpretation Vertebral fractures were the strongest marker of low BMD and forearm fractures the weakest. The number of previous fractures is helpful information for finding the most osteoporotic patient in terms of severity. Investigation of osteoporosis therefore seems warranted in every woman between the ages of 55 and 75 with a recent low-energy fracture, with highest priority being given to those with vertebral, hip, or multiple fractures.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK, VSZLJ
PDF