The paper considers the usability of the World Wide Web in the light of a decade of research into the usability of hypertext and hypermedia systems. The concepts of virtual hierarchies and virtual networks are introdu...
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The paper considers the usability of the World Wide Web in the light of a decade of research into the usability of hypertext and hypermedia systems. The concepts of virtual hierarchies and virtual networks are introduced as a mechanism for alleviating some of the shortcomings inherent in the current implementations of the web, without violating its basic philosophy. It is suggested that virtual hierarchies and virtual networks will assist users to find task-relevant information more easily and quickly and also help web authors to ensure that their pages are targeted at the users who wish to see them. The paper first analyses the published work on hypermedia usability, identifying the assumptions that underlie this research and relating them to the assumptions underlying the web. Some general conclusions are presented about both hypermedia usability principles and their applicability to the web. These results are coupled with problems identified from other sources to produce a requirements list for improving web usability. A possible solution is then presented which utilizes the capabilities of existing distributed information management software to permit web users to create virtual hierarchies and virtual networks. Some ways in which these virtual structures assist searchers to find useful information, and thus help authors to publicize their information more effectively, are described. The explanation is illustrated by examples taken from the GENIE Service, an implementation of some of the ideas. This uses the World Wide Web as a means of allowing global environmental change researchers throughout the world to find data that may be relevant to their research. (C) 1997 Academic Press Limited.
The pulsatile catheter (PUCA) pump is an intraventricular blood pump that can be introduced into the left ventricular cavity through a superficial artery (trans arterially) or directly through the thoracic aorta durin...
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The pulsatile catheter (PUCA) pump is an intraventricular blood pump that can be introduced into the left ventricular cavity through a superficial artery (trans arterially) or directly through the thoracic aorta during open chest conditions. When positioned, the pump aspirates blood from the left ventricle and transports it into the ascending aorta. A pneumatic driving system allows the blood to be ejected in early diastole of every second or third heart beat. The main goal of this study was to develop an easy, fast, safe surgical introduction technique. Four different means of catheter introduction were tested in 20 acute open chest experiments with calves: introduction without any guidance at all, introduction by x-ray guidance only, introduction using a guide wire plus x-ray guidance, and introduction using a guiding pressure catheter. Introducing the PUCA pump catheter into the left ventricular cavity using a pigtail guiding pressure catheter proved to be easy. The large bore pump catheter followed the guiding catheter and passed the aortic valve well. The position of the PUCA pump could be monitored from the pressure patterns derived from the guiding catheter.
Improving productivity in a creative venture such as research and development can be quite a challenge. The phrase \"reengineering\" process development may be perceived negatively. Many people see reenginee...
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Improving productivity in a creative venture such as research and development can be quite a challenge. The phrase \"reengineering\" process development may be perceived negatively. Many people see reengineering as a euphemism for layoffs, while to others it is just another business fad. However, reengineering does offer opportunities to try new ways of doing things. This, article outlines a more growth-oriented approach and offers guidance that, if implemented with a positive attitude, can ensure success for all concerned — employee, management, and shareholder alike.
The indications, technique and results of cryotherapy for potentially hazardous paraspinal haemangiomas that would otherwise have to be treated surgically are described. Two men with back pain which limited work activ...
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The indications, technique and results of cryotherapy for potentially hazardous paraspinal haemangiomas that would otherwise have to be treated surgically are described. Two men with back pain which limited work activity were treated by cryotherapy as an alternative to surgical therapy. Magnetic resonance imaging (MRI) was utilized for diagnosis and planning. Intraprocedural ultrasound was also utilized for guidance and monitoring. Techniques that were adapted from prostate cryotherapy with special probes are described. MRI proved crucial and essential for both diagnosis and planning. Laparoscopic ultrasound was also helpful. Both patients improved clinically and neither has required surgery with follow-up of over 1 year. No complications occurred. Image-guided cryotherapy, with at least 1 year follow-up, has been valuable to alleviate symptoms, avoid surgery, and permit patients to resume work.
Improvements in gray-scale ultrasound resolution and the proliferation of sensitive duplex Doppler and color flow capabilities on modern ultrasound machines, as well as the development of intravascular ultrasound syst...
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Improvements in gray-scale ultrasound resolution and the proliferation of sensitive duplex Doppler and color flow capabilities on modern ultrasound machines, as well as the development of intravascular ultrasound systems, have rendered ultrasonography valuable in the performance of diagnostic and interventional vascular procedures. Advantages of ultrasonography include the general ones of portability, relatively low cost, and lack of exposure to ionizing radiation. Ultrasound also confers more specific advantages of accurate real-time visualization, localization, and characterization of palpable and nonpalpable vascular structures, of adjacent anatomy and pathology, and of angiographic devices, as well as rapid confimation and characterization of blood flow. In this article, some of the techniques and applications relevant to this powerful tool will be discussed.
Practical management guidelines for occupational health physicians are needed for the individual support of employees with low-back pain. In this study the level of evidence regarding the efficacy of intervention with...
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Practical management guidelines for occupational health physicians are needed for the individual support of employees with low-back pain. In this study the level of evidence regarding the efficacy of intervention with vocational outcome parameters was assessed. In a systematic literature search, 40 randomized clinical trials on different types of intervention were retrieved. Their internal validity and statistical power criteria were assessed. The randomization procedure, blinding of patients, and sample size were problematic in most studies. For patients with acute low-back pain limited or moderate evidence was found for the efficacy of no bed rest, a short period of bed rest, and spinal manipulation. For chronic patients limited evidence was found for the efficacy of antidepressants. For the other types of intervention, studies with sufficient statistical power were lacking. Such studies are needed before more-detailed evidence-based guidelines can be formulated for occupational health care.
This study examined the behavior of rat tendon fibroblasts, baby hamster kidney fibroblasts, macrophage-like P388D1 cells, and neurons from rat dorsal root ganglia, cultured on fibronectin strands 0.2-5 mu m in diamet...
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This study examined the behavior of rat tendon fibroblasts, baby hamster kidney fibroblasts, macrophage-like P388D1 cells, and neurons from rat dorsal root ganglia, cultured on fibronectin strands 0.2-5 mu m in diameter. We investigated cell spreading, orientation, formation of focal contacts, the speed of cell movement, and the speed of neurite outgrowth in cells cultured on fibronectin strands, glass covered with fibronectin, and plain. nontreated glass. Fibronectin strands significantly promoted cell spreading and caused a marked alignment of all kinds of cells to the direction of the liber. The fibers caused the alignment of actin filaments in fibroblasts and focal contacts in fibroblasts and macrophages and increased polymerization of F-actin in cells. Fibronectin fibers also increased the speed and persistence of cell movement and the rate of neurite outgrowth. Macrophages grown on fibronectin fibers produced numerous actin-rich microspikes and adopted a polarized, migratory phenotype. These findings indicate that fibronectin strands, resembling natural components of the extracellular matrix, are more effective in activating Various types of cells than two-dimensional, fibronectin-covered substrata. The results also confirm the suitability of the three-dimensionally oriented fibronectin form for use in clinical practice.
The discussion presented on the various shielding effectiveness measurement techniques for EMI shielding components shows the lack of industry consensus in this area. Efforts such as the IEEE EMC Society P1302 project...
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ISBN:
(纸本)0780339886
The discussion presented on the various shielding effectiveness measurement techniques for EMI shielding components shows the lack of industry consensus in this area. Efforts such as the IEEE EMC Society P1302 project will provide some help in the EMI gasket area. Similarly, the IEEE STD 299 revision effort may provide guidance in the smaller shielded enclosure area. ASTM D 4935 revisions and the new ASTM transfer impedance gasket test method should help as well. However, consensus industry standards do not exist for shielding effectiveness. Most ofthe established, legitimized measurement standards have limitations or shortcomings that have led to unrestrained and undisciplined modifications. It is time for those interested in shielding effectiveness measurement to get involved with standards developing organizations such as the IEEE EMC Society, to help create better EMI measurement standards.
The Air Force program, Smart Tactical Autonomous guidance (STAG), has as its central concept, the use of passive millimeter wave imagery (PMMW) to enable an autonomous vehicle to perform its own smart guidance and att...
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ISBN:
(纸本)081942479X
The Air Force program, Smart Tactical Autonomous guidance (STAG), has as its central concept, the use of passive millimeter wave imagery (PMMW) to enable an autonomous vehicle to perform its own smart guidance and attack. The algorithms on board the vehicle use image flow to derive the necessary range information for obtaining real time navigation updates. The results of a natural-imagery feasibility program will be reported, aimed at validating the STAG approach. PMMW imagery will be taken from land-based vantage points that mimic the geometry of an airborne, down looking, sensor. Essentially, hardware-in-the-loop simulation will be performed, where PMMW data will be real, and the loop extends over many miles of outdoor terrain. The only departure from an actual mission will be that it is not real-time. All imagery will be gathered using frame times consistent with existing camera capabilities. Image flow and other data processing will be done off-line. The key ingredients will be the sequences of imagery and the computer processing of that imagery. The means for accomplishing both have been developed under the STAG program. The camera to be used operates at W-band and consists of an f/l, refractive, telecentric, image forming system with a 30 cm diameter input aperture. Image flow involves a model whose parameters are determined via automated pixel tracking from frame to frame. Passive range maps are then generated, and navigation is accomplished through the subsequent correlation of these maps with reference elevation maps. Automatic target recognition is also addressed.
The purpose of this study was to test the feasibility of MR-guided percutaneous ethanol ablation of liver tissue on a .2-T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then...
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The purpose of this study was to test the feasibility of MR-guided percutaneous ethanol ablation of liver tissue on a .2-T open MR scanner. Needles were placed by MR guidance first into an ex vivo sheep liver and then into livers of three anesthetized pigs, and injection of 10 ml of 96% alcohol was performed. T1 fast low-angle shot (FLASH), T2 turbo spin echo (TSE), and T1 spin echo (SE) images were obtained after incremental volumes of injection. In one pig, simultaneous injection of saline into normal liver was also performed with subsequent pathological correlation. Ethanol-infiltrated liver was hypointense to liver on all sequences, whereas saline caused no tissue signal changes on T1 SE and either isointense or hyperintense changes on T2 TSE images. Pathological examination confirmed ethanol-induced acute liver changes as compared with the control. MR guidance of needle placement and monitoring of ethanol effects on liver tissue is feasible. This may have implications for potential MR-guided hepatic tumor ablation.
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