The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Robert W Snow - One of the best experts on this subject based on the ideXlab platform.
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a Spatial national health facility database for public health sector planning in kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized.
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A Spatial national health facility database for public health sector planning in Kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized. Methods A disparate series of contemporary lists of health service providers were used to update a public health facility database of Kenya last compiled in 2003. These new lists were derived primarily through the national distribution of antimalarial and antiretroviral commodities since 2006. A combination of methods, including global positioning systems, was used to map service providers. These Spatially-referenced data were combined with high-resolution population maps to analyze disparity in geographic access to public health care. Findings The updated 2008 database contained 5,334 public health facilities (67% ministry of health; 28% mission and nongovernmental organizations; 2% local authorities; and 3% employers and other ministries). This represented an overall increase of 1,862 facilities compared to 2003. Most of the additional facilities belonged to the ministry of health (79%) and the majority were dispensaries (91%). 93% of the health facilities were Spatially referenced, 38% using global positioning systems compared to 21% in 2003. 89% of the population was within 5 km Euclidean distance to a public health facility in 2008 compared to 71% in 2003. Over 80% of the population outside 5 km of public health service providers was in the sparsely settled pastoralist areas of the country. Conclusion We have shown that, with concerted effort, a relatively complete inventory of mapped health services is possible with enormous potential for improving planning. Expansion in public health care in Kenya has resulted in significant increases in geographic access although several areas of the country need further improvements. This information is key to future planning and with this paper we have released the digital Spatial database in the public domain to assist the Kenyan Government and its partners in the health sector.
Abdisalan M Noor - One of the best experts on this subject based on the ideXlab platform.
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a Spatial national health facility database for public health sector planning in kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized.
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A Spatial national health facility database for public health sector planning in Kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized. Methods A disparate series of contemporary lists of health service providers were used to update a public health facility database of Kenya last compiled in 2003. These new lists were derived primarily through the national distribution of antimalarial and antiretroviral commodities since 2006. A combination of methods, including global positioning systems, was used to map service providers. These Spatially-referenced data were combined with high-resolution population maps to analyze disparity in geographic access to public health care. Findings The updated 2008 database contained 5,334 public health facilities (67% ministry of health; 28% mission and nongovernmental organizations; 2% local authorities; and 3% employers and other ministries). This represented an overall increase of 1,862 facilities compared to 2003. Most of the additional facilities belonged to the ministry of health (79%) and the majority were dispensaries (91%). 93% of the health facilities were Spatially referenced, 38% using global positioning systems compared to 21% in 2003. 89% of the population was within 5 km Euclidean distance to a public health facility in 2008 compared to 71% in 2003. Over 80% of the population outside 5 km of public health service providers was in the sparsely settled pastoralist areas of the country. Conclusion We have shown that, with concerted effort, a relatively complete inventory of mapped health services is possible with enormous potential for improving planning. Expansion in public health care in Kenya has resulted in significant increases in geographic access although several areas of the country need further improvements. This information is key to future planning and with this paper we have released the digital Spatial database in the public domain to assist the Kenyan Government and its partners in the health sector.
Peter W Gething - One of the best experts on this subject based on the ideXlab platform.
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a Spatial national health facility database for public health sector planning in kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized.
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A Spatial national health facility database for public health sector planning in Kenya in 2008
International Journal of Health Geographics, 2009Co-Authors: Abdisalan M Noor, Victor A Alegana, Peter W Gething, Robert W SnowAbstract:Background Efforts to tackle the enormous burden of ill-health in low-income countries are hampered by weak health information infrastructures that do not support appropriate planning and resource allocation. For health information systems to function well, a reliable inventory of health service providers is critical. The Spatial Referencing of service providers to allow their representation in a geographic information system is vital if the full planning potential of such data is to be realized. Methods A disparate series of contemporary lists of health service providers were used to update a public health facility database of Kenya last compiled in 2003. These new lists were derived primarily through the national distribution of antimalarial and antiretroviral commodities since 2006. A combination of methods, including global positioning systems, was used to map service providers. These Spatially-referenced data were combined with high-resolution population maps to analyze disparity in geographic access to public health care. Findings The updated 2008 database contained 5,334 public health facilities (67% ministry of health; 28% mission and nongovernmental organizations; 2% local authorities; and 3% employers and other ministries). This represented an overall increase of 1,862 facilities compared to 2003. Most of the additional facilities belonged to the ministry of health (79%) and the majority were dispensaries (91%). 93% of the health facilities were Spatially referenced, 38% using global positioning systems compared to 21% in 2003. 89% of the population was within 5 km Euclidean distance to a public health facility in 2008 compared to 71% in 2003. Over 80% of the population outside 5 km of public health service providers was in the sparsely settled pastoralist areas of the country. Conclusion We have shown that, with concerted effort, a relatively complete inventory of mapped health services is possible with enormous potential for improving planning. Expansion in public health care in Kenya has resulted in significant increases in geographic access although several areas of the country need further improvements. This information is key to future planning and with this paper we have released the digital Spatial database in the public domain to assist the Kenyan Government and its partners in the health sector.
Brice Isableu - One of the best experts on this subject based on the ideXlab platform.
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sport skill specific expertise biases sensory integration for Spatial Referencing and postural control
Journal of Motor Behavior, 2018Co-Authors: Michalis Thalassinos, Giorgos Fotiadis, Fotini Arabatzi, Brice Isableu, Vassilia HatzitakiAbstract:ABSTRACTThe authors asked how sport expertise modulates visual field dependence and sensory reweighting for controlling posture. Experienced soccer athletes, ballet dancers, and nonathletes performed (a) a Rod and Frame test and (b) a 100-s bipedal stance task during which vision and proprioception were successively or concurrently disrupted in 20-s blocks. Postural adaptation was assessed in the mean center of pressure displacement, root mean square of center of pressure velocity and ankle muscles integrated electromyography activity. Soccer athletes were more field dependent than were nonathletes. During standing, dancers were more destabilized by vibration and required more time to reweigh sensory information compared with the other 2 groups. These findings reveal a sport skill–specific bias in the reweighing of sensory inputs for Spatial orientation and postural control.
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individual differences in the ability to identify select and use appropriate frames of reference for perceptuo motor control
Neuroscience, 2010Co-Authors: Brice Isableu, Nicolas Vuillerme, Theophile Ohlmann, J Cremieux, B Amblard, M A GrestyAbstract:The causes of the interindividual differences (IDs) in how we perceive and control Spatial orientation are poorly understood. Here, we propose that IDs partly reflect preferred modes of Spatial Referencing and that these preferences or "styles" are maintained from the level of Spatial perception to that of motor control. Two groups of experimental subjects, one with high visual field dependency (FD) and one with marked visual field independency (FI) were identified by the Rod and Frame Test, which identifies relative dependency on a visual frame of reference (VFoR). FD and FI subjects were tasked with standing still in conditions of increasing postural difficulty while visual cues of self-orientation (a visual frame tilted in roll) and self-motion (in stroboscopic illumination) were varied and in darkness to assess visual dependency. Postural stability, overall body orientation and modes of segmental stabilization relative to either external (space) or egocentric (adjacent segments) frames of reference in the roll plane were analysed. We hypothesized that a moderate challenge to balance should enhance subjects' reliance on VFoR, particularly in FD subjects, whereas a substantial challenge should constrain subjects to use a somatic-vestibular based FoR to prevent falling in which case IDs would vanish. The results showed that with increasing difficulty, FD subjects became more unstable and more disoriented shown by larger effects of the tilted visual frame on posture. Furthermore, their preference to coalign body/VFoR coordinate systems lead to greater fixation of the head-trunk articulation and stabilization of the hip in space, whereas the head and trunk remained more stabilized in space with the hip fixed on the leg in FI subjects. These results show that FD subjects have difficulties at identifying and/or adopting a more appropriate FoR based on proprioceptive and vestibular cues to regulate the coalignment of posturo/exocentric FoRs. The FI subjects' resistance in the face of altered VFoR and balance challenge resides in their greater ability to coordinate movement by coaligning body axes with more appropriate FoRs (provided by proprioceptive and vestibular co-variance).
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assessment of visual field dependence comparison between the mechanical 3d rod and frame test developed by oltman in 1968 with a 2d computer based version
Journal of Vestibular Research-equilibrium & Orientation, 2008Co-Authors: Brice Isableu, Marc Gueguen, Benoit Fourre, Guillaume Giraudet, Michelange AmorimAbstract:The identification of subject's perceptual style regarding multisensory integration is a central issue for Spatial perception and sensorimotricity. In Spatial orientation studies, the weighting of visual frame of reference (visual field dependence) is classically assessed by using verticality perception tasks, and especially the mechanical 3D rod-and-frame test (3D RFT). The validation of a 2D computer-based version of the RFT by virtue of its portability would facilitate the identification of modes of Spatial Referencing for the design and evaluation of sensory and motor rehabilitation programs. We question here whether the computerized 2D RFT yields frame effects similar (in amplitude, direction) and correlated to those induced by the mechanical 3D RFT. In both devices, 35 young and healthy males' subjects were seated and tasked with aligning a rod to the gravity vertical within a square frame that was tilted at 18 ◦ . The results showed significantly larger rod deviations from the verticality in the 3D RFT. 3D and 2D RFT errors significantly correlated but shared a small amount of common variance (r 2 = 0.35). In addition, left-right tilt asymmetry changes from one device to another. These results suggest that the mechanical 3D RFT for verticality perception remains a more robust test for identifying the subject's perceptual style.
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Assessment of visual field dependence: comparison between the mechanical 3D rod-and-frame test developed by Oltman in 1968 with a 2D computer-based version.
Journal of Vestibular Research, 2008Co-Authors: Brice Isableu, Marc Gueguen, Benoit Fourre, Guillaume Giraudet, Michelange AmorimAbstract:The identification of subject's perceptual style regarding multisensory integration is a central issue for Spatial perception and sensorimotricity. In Spatial orientation studies, the weighting of visual frame of reference (visual field dependence) is classically assessed by using verticality perception tasks, and especially the mechanical 3D rod-and-frame test (3D RFT). The validation of a 2D computer-based version of the RFT by virtue of its portability would facilitate the identification of modes of Spatial Referencing for the design and evaluation of sensory and motor rehabilitation programs. We question here whether the computerized 2D RFT yields frame effects similar (in amplitude, direction) and correlated to those induced by the mechanical 3D RFT. In both devices, 35 young and healthy males' subjects were seated and tasked with aligning a rod to the gravity vertical within a square frame that was tilted at 18 degrees . The results showed significantly larger rod deviations from the verticality in the 3D RFT. 3D and 2D RFT errors significantly correlated but shared a small amount of common variance (r;{2} = 0.35). In addition, left-right tilt asymmetry changes from one device to another. These results suggest that the mechanical 3D RFT for verticality perception remains a more robust test for identifying the subject's perceptual style.
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Differential integration of kinaesthetic signals to postural control.
Experimental Brain Research, 2006Co-Authors: Brice Isableu, Nicolas VuillermeAbstract:The purpose of the present experiment was to identify whether non-visual sensory cues involved in the maintenance of balance control could be weighted differently from one subject to another in condition during which kinaesthetic signals, stemming from the ankle proprioceptors and plantar pressure somatosensory sensors, were altered. A large population of blindfolded healthy young university students (n = 140) were asked to sway as little as possible on: (1) a firm support (Firm condition) and (2) an unstable support used to impair the exploitation of the kinematic ankle proprioceptive and plantar pressure somatosensation (Foam condition). Centre of foot pressure (CoP) displacements were recorded using a force platform. Analyses of the surface area, range, and mean velocity of the CoP displacements showed significant negative correlations between the postural sway observed in the Firm condition and the increase in postural sway observed in the Foam condition. In other words, the alteration of ankle proprioception had a greater destabilising effect in subjects exhibiting the smallest CoP displacements when standing in a normal proprioception condition. The present findings suggest that the exploitation of the kinaesthetic relationships to postural control varied from one subject to another, hence evidencing the need to introduce differential approach to assess the general impact of preferential modes of Spatial Referencing in postural control.
H.l. Tanenbaum - One of the best experts on this subject based on the ideXlab platform.
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Predictive scheduling algorithms for real-time feature extraction and Spatial Referencing: application to retinal image sequences
IEEE transactions on bio-medical engineering, 2004Co-Authors: Gang Lin, Charles V. Stewart, Badrinath Roysam, Kenneth Fritzsche, Gehua Yang, H.l. TanenbaumAbstract:Real-time Spatial Referencing is an important alternative to tracking for designing Spatially aware ophthalmic instrumentation for procedures such as laser photocoagulation and perimetry. It requires independent, fast registration of each image frame from a digital video stream (1024 /spl times/ 1024 pixels) to a Spatial map of the retina. Recently, we have introduced a Spatial Referencing algorithm that works in three primary steps: 1) tracing the retinal vasculature to extract image feature (landmarks); 2) invariant indexing to generate hypothesized landmark correspondences and initial transformations; and 3) alignment and verification steps to robustly estimate a 12-parameter quadratic Spatial transformation between the image frame and the map. The goal of this paper is to introduce techniques to minimize the amount of computation for successful Spatial Referencing. The fundamental driving idea is to make feature extraction subservient to registration and, therefore, only produce the information needed for verified, accurate transformations. To this end, the image is analyzed along one-dimensional, vertical and horizontal grid lines to produce a regular sampling of the vasculature, needed for step 3) and to initiate step 1). Tracing of the vascular is then prioritized hierarchically to quickly extract landmarks and groups (constellations) of landmarks for indexing. Finally, the tracing and Spatial Referencing computations are integrated so that landmark constellations found by tracing are tested immediately. The resulting implementation is an order-of-magnitude faster with the same success rate. The average total computation time is 31.2 ms per image on a 2.2-GHz Pentium Xeon processor.
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frame rate Spatial Referencing based on invariant indexing and alignment with application to online retinal image registration
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2003Co-Authors: Hong Shen, Gang Lin, Charles V. Stewart, Badrinath Roysam, H.l. TanenbaumAbstract:This paper describes an algorithm to continually and accurately estimate the absolute location of a diagnostic or surgical tool (such as a laser) pointed at the human retina, from a series of image frames. We treat the problem as a registration problem using diagnostic images to build a Spatial map of the retina and then registering each online image against this map. Since the image location where the laser strikes the retina is easily found, this registration determines the position of the laser in the global coordinate system defined by the Spatial map. For each online image, the algorithm computes similarity invariants, locally valid despite the curved nature of the retina, from constellations of vascular landmarks. These are detected using a high-speed algorithm that iteratively traces the blood vessel structure. Invariant indexing establishes initial correspondences between landmarks from the online image and landmarks stored in the Spatial map. Robust alignment and verification steps extend the similarity transformation computed from these initial correspondences to a global, high-order transformation. In initial experimentation, the method has achieved 100 percent success on 1024 /spl times/ 1024 retina images. With a version of the tracing algorithm optimized for speed on 512 /spl times/ 512 images, the computation time is only 51 milliseconds per image on a 900MHz PentiumIII processor and a 97 percent success rate is achieved. The median registration error in either case is about 1 pixel.
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frame rate Spatial Referencing based on invariant indexing and alignment with application to laser retinal surgery
Computer Vision and Pattern Recognition, 2001Co-Authors: Hong Shen, Gang Lin, Charles V. Stewart, Badrinath Roysam, H.l. TanenbaumAbstract:The paper describes a fast feature-based algorithm for accurately estimating the absolute location of a surgical tool (a laser), pointed at the curved human retina, from a series of image frames. The method is capable of a 91% success rate with just a third of the feature extraction computation, taking 37 ms overall per image on a 900 MHz Pentium III. The success rate approaches 100% when the feature extraction is allowed to run to completion. The median error is 0.92 pixels with 512/spl times/512 8-bit image frames. Making a significant break from prior incremental tracking-based efforts, we propose a framework that involves extensive offline precomputation to build a "Spatial map" and high-speed online "Spatial Referencing" to rapidly register each surgical image with this Spatial map. The Spatial Referencing technique is designed around the idea of quasi-invariant indexing. Similarity invariants, locally valid despite the curved nature of the retina, are computed from constellations of vascular landmarks. These are detected using a high-speed algorithm that recursively traces the blood vessel structure. Invariant indexing establishes initial correspondences between landmarks from the online image and landmarks stored in the Spatial map. Alignment and verification steps gradually extend the similarity transformation computed from these initial correspondences to a global, high-order transformation. The Spatial map is precomputed to contain mosaics, distance maps and an invariant database, all designed to make these Spatial Referencing computations extremely fast.