SO(n + 1) Symmetric Solutions of the Einstein Equations in Higher Dimensions

A method of solving the Einstein equations with a scalar field is presented. It is applied to find higher dimensional vacuum metrics invariant under the group SO(n + 1) acting on n-dimensional spheres.Comment: 11 page

D-dimensional metrics with D-3 symmetries

Hidden symmetry transformations of D-dimensional vacuum metrics with D-3 commuting Killing vectors are studied. We solve directly the Einstein equations in the Maison formulation under additional assumptions. We relate the 4-dimensional Reissner-Nordstr\"om solution to a particular case of the 5-dimensional Gross-Perry metric.Comment: 8 page

Generalization Of The Gross-Perry Metrics

A class of SO(n+1) symmetric solutions of the (N+n+1)-dimensional Einstein equations is found. It contains 5-dimensional metrics of Gross and Perry and Millward.Comment: 9 page

Risk-sensitive events during laparoscopic cholecystectomy: the influence of the integrated operating room and a preoperative checklist tool

Background - Awareness of the relative high rate of adverse events in laparoscopic surgery created a need to safeguard quality and safety of performance better. Technological innovations, such as integrated operating room (OR) systems and checklists, have the potential to improve patient safety, OR efficiency, and surgical outcomes. This study was designed to investigate the influence of the integrated OR system and Pro/cheQ, a digital checklist tool, on the number and type of equipment- and instrument-related risk-sensitive events (RSE) during laparoscopic cholecystectomies. Methods - Forty-five laparoscopic cholecystectomies were analyzed on the number and type of RSE; 15 procedures were observed in the cart-based OR setting, 15 in an integrated OR setting, and 15 in the integrated OR setting while using Pro/cheQ. Results - In the cart-based OR setting and the integrated OR setting, at least one event occurred in 87% of the procedures, which was reduced to 47% in the integrated OR setting when using Pro/cheQ. During 45 procedures a total of 57 RSE was observed—most were caused by equipment that was not switched on or with the wrong settings. In the integrated OR while using Pro/cheQ the number of RSE was reduced by 65%. Conclusions - Using both an integrated OR and Pro/cheQ has a stronger reducing effect on the number of RSE than using an integrated OR alone. The Pro/cheQ tool supported the optimal workflow in a natural way and raised the general safety awareness amongst all members of the surgical team. For tools such as integrated OR systems and checklists to succeed it is pivotal not to underestimate the value of the implementation process. To further improve safety and quality of surgery, a multifaceted approach should be followed, focusing on the performance and competence of the surgical team as a whole.Industrial DesignIndustrial Design Engineerin

Influence of anatomic landmarks in the virtual environment on simulated angled laparoscope navigation

Background - The aim of this study is to investigate the influence of the presence of anatomic landmarks on the performance of angled laparoscope navigation on the SimSurgery SEP simulator. Methods - Twenty-eight experienced laparoscopic surgeons (familiar with 30º angled laparoscope, >100 basic laparoscopic procedures, >5 advanced laparoscopic procedures) and 23 novices (no laparoscopy experience) performed the Camera Navigation task in an abstract virtual environment (CN-box) and in a virtual representation of the lower abdomen (CN-abdomen). They also rated the realism and added value of the virtual environments on seven-point scales. Results - Within both groups, the CN-box task was accomplished in less time and with shorter tip trajectory than the CN-abdomen task (Wilcoxon test, p0.05). In both groups, the CN tasks were perceived as hard work and more challenging than anticipated. Conclusions - Performance of the angled laparoscope navigation task is influenced by the virtual environment surrounding the exercise. The task was performed better in an abstract environment than in a virtual environment with anatomic landmarks. More insight is required into the influence and function of different types of intrinsic and extrinsic feedback on the effectiveness of preclinical simulator training.Industrial DesignIndustrial Design Engineerin

Visuo-spatial ability in colonoscopy simulator training

Visuo-spatial ability is associated with a quality of performance in a variety of surgical and medical skills. However, visuo-spatial ability is typically assessed using Visualization tests only, which led to an incomplete understanding of the involvement of visuo-spatial ability in these skills. To remedy this situation, the current study investigated the role of a broad range of visuo-spatial factors in colonoscopy simulator training. Fifteen medical trainees (no clinical experience in colonoscopy) participated in two psycho-metric test sessions to assess four visuo-spatial ability factors. Next, participants trained flexible endoscope manipulation, and navigation to the cecum on the GI Mentor II simulator, for four sessions within 1 week. Visualization, and to a lesser degree Spatial relations were the only visuo-spatial ability factors to correlate with colonoscopy simulator performance. Visualization additionally covaried with learning rate for time on task on both simulator tasks. High Visualization ability indicated faster exercise completion. Similar to other endoscopic procedures, performance in colonoscopy is positively associated with Visualization, a visuo-spatial ability factor characterized by the ability to mentally manipulate complex visuo-spatial stimuli. The complexity of the visuo-spatial mental transformations required to successfully perform colonoscopy is likely responsible for the challenging nature of this technique, and should inform training- and assessment design. Long term training studies, as well as studies investigating the nature of visuo-spatial complexity in this domain are needed to better understand the role of visuo-spatial ability in colonoscopy, and other endoscopic techniques

Augmented versus Virtual Reality Laparoscopic Simulation: What Is the Difference?: A Comparison of the ProMIS Augmented Reality Laparoscopic Simulator versus LapSim Virtual Reality Laparoscopic Simulator

BACKGROUND: Virtual reality (VR) is an emerging new modality for laparoscopic skills training; however, most simulators lack realistic haptic feedback. Augmented reality (AR) is a new laparoscopic simulation system offering a combination of physical objects and VR simulation. Laparoscopic instruments are used within an hybrid mannequin on tissue or objects while using video tracking. This study was designed to assess the difference in realism, haptic feedback, and didactic value between AR and VR laparoscopic simulation. METHODS: The ProMIS AR and LapSim VR simulators were used in this study. The participants performed a basic skills task and a suturing task on both simulators, after which they filled out a questionnaire about their demographics and their opinion of both simulators scored on a 5-point Likert scale. The participants were allotted to 3 groups depending on their experience: experts, intermediates and novices. Significant differences were calculated with the paired t-test. RESULTS: There was general consensus in all groups that the ProMIS AR laparoscopic simulator is more realistic than the LapSim VR laparoscopic simulator in both the basic skills task (mean 4.22 resp. 2.18, P <0.000) as well as the suturing task (mean 4.15 resp. 1.85, P <0.000). The ProMIS is regarded as having better haptic feedback (mean 3.92 resp. 1.92, P <0.000) and as being more useful for training surgical residents (mean 4.51 resp. 2.94, P <0.000). CONCLUSIONS: In comparison with the VR simulator, the AR laparoscopic simulator was regarded by all participants as a better simulator for laparoscopic skills training on all tested feature

Algebraically special axisymmetric solutions of the higher-dimensional vacuum Einstein equation

A d-dimensional spacetime is "axisymmetric" if it possesses an SO(d-2) isometry group whose orbits are (d-3)-spheres. In this paper, algebraically special, axisymmetric solutions of the higher dimensional vacuum Einstein equation (with cosmological constant) are investigated. Necessary and sufficient conditions for static axisymmetric solutions to belong to different algebraic classes are presented. Then general (possibly time-dependent) axisymmetric solutions are discussed. All axisymmetric solutions of algebraic types II, D, III and N are obtained.Comment: 28 page