Moisture susceptibility of high and low compaction dry process crumb rubber modified asphalt mixtures

The field performance of dry process crumb rubber-modified (CRM) asphalt mixtures has been reported to be inconsistent with stripping and premature cracking on the surfacing. One of the concerns is that, because achieving field compaction of CRM material is difficult due to the inherent resilient nature of the rubber particle, nonuniform field compaction may lead to a deficient bond between rubber and bitumen. To assess the influence of compaction, a series of CRM and control mixtures was produced and compacted at two levels: 4% (low, optimum laboratory compaction) and 8% (high, field experience) air void content. The long-term durability, in regard to moisture susceptibility of the mixtures, was assessed by conducting repeated moisture conditioning cycles. Mechanical properties (stiffness, fatigue, and resistance to permanent deformation) were determined in the Nottingham Asphalt Tester. Results indicated that compared with conventional mixtures, the CRM mixtures, regardless of compaction effort, are more susceptible to moisture with the degree of susceptibility primarily depending on the amount of rubber in the mixture, rather than the difference in compaction. This behavior is different from that of conventional mixtures in which, as expected, poorly compacted mixtures were found to be more susceptible to moisture than were well-compacted mixtures

The value of haptic feedback in conventional and robot-assisted minimal invasive surgery and virtual reality training: a current review

BACKGROUND: Virtual reality (VR) as surgical training tool has become a state-of-the-art technique in training and teaching skills for minimally invasive surgery (MIS). Although intuitively appealing, the true benefits of haptic (VR training) platforms are unknown. Many questions about haptic feedback in the different areas of surgical skills (training) need to be answered before adding costly haptic feedback in VR simulation for MIS training. This study was designed to review the current status and value of haptic feedback in conventional and robot-assisted MIS and training by using virtual reality simulation. METHODS: A systematic review of the literature was undertaken using PubMed and MEDLINE. The following search terms were used: Haptic feedback OR Haptics OR Force feedback AND/OR Minimal Invasive Surgery AND/OR Minimal Access Surgery AND/OR Robotics AND/OR Robotic Surgery AND/OR Endoscopic Surgery AND/OR Virtual Reality AND/OR Simulation OR Surgical Training/Education. RESULTS: The results were assessed according to level of evidence as reflected by the Oxford Centre of Evidence-based Medicine Levels of Evidence. CONCLUSIONS: In the current literature, no firm consensus exists on the importance of haptic feedback in performing minimally invasive surgery. Although the majority of the results show positive assessment of the benefits of force feedback, results are ambivalent and not unanimous on the subject. Benefits are least disputed when related to surgery using robotics, because there is no haptic feedback in currently used robotics. The addition of haptics is believed to reduce surgical errors resulting from a lack of it, especially in knot tying. Little research has been performed in the area of robot-assisted endoscopic surgical training, but results seem promising. Concerning VR training, results indicate that haptic feedback is important during the early phase of psychomotor skill acquisitio

A modified footplate for the Kerrison rongeur

Use of the Kerrison rongeur for bone removal in spinal surgery is associated with dural tears and cerebrospinal fluid (CSF) leaks. We report a modification of the Kerrison rongeur footplate designed to reduce the risk of dural tears. A novel footplate was designed by incorporating the following parameters: (1) tapering the footplate to deflect soft tissue downward during positioning of the rongeur underneath the bone, and (2) making the footplate longer and wider than the cutting element to prevent soft tissue from entering into the cutting surface. Stereolithography models of the modified footplate were made and tested in a cadaver. A stainless steel modified footplate was then incorporated into an existing Kerrison rongeur as a working prototype, and tested in 20 laminectomy cases to clinically validate its design. The modified footplate prevented soft tissue from entering the cutting surface of the Kerrison rongeur in the manner intended by its design. No dural tears or CSF leaks were encountered in any instance. Potential soft tissue compression caused by an increase in footplate dimensions was not a significant issue in the rongeur size tested. This modification, however, might not be practical in rongeurs larger than 3 mm. The risk of dural tears and cerebrospinal fluid leaks in spinal surgery may be reduced by this footplate modification of the Kerrison rongeur. Soft tissue compression may limit the incorporation of this modification to rongeurs of 3 mm or smaller. The promising results warrant further tests with a wider range of sizes.Center for Integration of Medicine and Innovative Technology (U.S. Army Medical Research Acquisition Activity Cooperative Agreement No. DAMD17-02-2-0006

Collision sellar lesions: experience with eight cases and review of the literature

The concomitant presence of a pituitary adenoma with a second sellar lesion in patients operated upon for pituitary adenoma is an uncommon entity. Although rare, quite a great variety of lesions have been indentified coexisting with pituitary adenomas. In fact, most combinations have been described before, but an overview with information on the frequency of combined pathologies in a large series has not been published. We present a series of eight collision sellar lesions indentified among 548 transsphenoidally resected pituitary adenomas in two Neurosurgical Departments. The histological studies confirmed a case of sarcoidosis within a non-functioning pituitary adenoma, a case of intrasellar schwannoma coexisting with growth hormone (GH) secreting adenoma, two Rathke’s cleft cysts combined with pituitary adenomas, three gangliocytomas associated with GH-secreting adenomas, and a case of a double pituitary adenoma. The pertinent literature is discussed with emphasis on pathogenetic theories of dual sellar lesions. Although there is no direct evidence to confirm the pathogenetic relationship of collision sellar lesions, the number of cases presented in literature makes the theory of an incidental occurrence rather doubtful. Suggested hypotheses about a common embryonic origin or a potential interaction between pituitary adenomas and the immune system are presented

Cost modelling of onboard cobot-supported item sorting in a picking system

For manual picking processes in warehouses and assembly line feeding, collaborative robots\u2013cobots\u2013hold a potential to support operators and, thereby, enhance performance. However, studies focused on the economic aspects of cobot applications have been scarce. The present paper aims at modelling a new picking system, in which human operators collaborate with cobots during picking (or kitting) activities. It is considered the case of having a cobot on board of the picking trolley or cart, working in parallel with the picker by performing sorting of the picked items. The paper focuses on the economic aspects of this application and presents a model of the relative cost difference between a manual and a cobot-supported process, accounting for the costs associated with operators, equipment, and quality. The relative cost difference is analysed in a numerical example. The findings suggest that the decision to use a cobot sorting mode is robust when there is considerable sorting work to carry out, for example, when there are higher yearly order volumes to handle, and when higher order commonality among orders processed as a batch can be achieved. Future research should focus on implementation challenges and safety issues associated with cobot-supported picking processes