Optimal path planning for nonholonomic robotics systems via parametric optimisation

Abstract. Motivated by the path planning problem for robotic systems this paper considers nonholonomic path planning on the Euclidean group of motions SE(n) which describes a rigid bodies path in n-dimensional Euclidean space. The problem is formulated as a constrained optimal kinematic control problem where the cost function to be minimised is a quadratic function of translational and angular velocity inputs. An application of the Maximum Principle of optimal control leads to a set of Hamiltonian vector field that define the necessary conditions for optimality and consequently the optimal velocity history of the trajectory. It is illustrated that the systems are always integrable when n = 2 and in some cases when n = 3. However, if they are not integrable in the most general form of the cost function they can be rendered integrable by considering special cases. This implies that it is possible to reduce the kinematic system to a class of curves defined analytically. If the optimal motions can be expressed analytically in closed form then the path planning problem is reduced to one of parameter optimisation where the parameters are optimised to match prescribed boundary conditions.This reduction procedure is illustrated for a simple wheeled robot with a sliding constraint and a conventional slender underwater vehicle whose velocity in the lateral directions are constrained due to viscous damping

Comparing different modalities for the diagnosis of incisional hernia: a systematic review

Purpose: Incisional hernia (IH) is the most frequent complication after abdominal surgery. The diagnostic modality, observer, definition, and diagnostic protocol used for the diagnosis of IH potentially influence the reported prevalence. The objective of this systematic review is to evaluate the diagnostic accuracy of different modalities used to identify IH. Methods: Embase, MEDLINE OvidSP, Web of Science, Google Scholar, and Cochrane databases were searched to identify studies diagnosing IH. Studies comparing the IH detection rate of two different diagnostic modalities or inter-observer variability of one modality were included. Quality assessment of studies was done by Cochrane Collaboration’s tool. Article selection and data collection were performed independently by two researchers. PROSPERO registration: CRD42017062307. Results: Fifteen studies representing a total of 2986 patients were included. Inter-observer variation for CT-scan ranged from 11.2 to 69% (n = 678). Disagreement between ultrasound and CT-scan ranged between 6.6 and 17% (n = 221). Ten studies compared physical examination to CT-scan or ultrasound. Disagreement between physical examination and imaging ranged between 7.6 and 39% (n = 1602). Between 15 and 58% of IHs were solely detected by imaging (n = 483). Relative increase in IH prevalence for imaging compared to physical examination ranged from 0.92 to 2.4 (n = 1922). Conclusions: Ultrasound or CT-scan will result in substantial additional IH diagnosis. Lack of consensus regarding the definition of IH might contribute to the disagreement rates. Both the observer and diagnostic modality used could be additional factors explaining varia

Thermal Resonance in Signal Transmission

We use temperature tuning to control signal propagation in simple one-dimensional arrays of masses connected by hard anharmonic springs and with no local potentials. In our numerical model a sustained signal is applied at one site of a chain immersed in a thermal environment and the signal-to-noise ratio is measured at each oscillator. We show that raising the temperature can lead to enhanced signal propagation along the chain, resulting in thermal resonance effects akin to the resonance observed in arrays of bistable systems.Comment: To appear in Phys. Rev.

Sterols sense swelling in lipid bilayers

In the mimetic membrane system of phosphatidylcholine bilayers, thickening (pre-critical behavior, anomalous swelling) of the bilayers is observed, in the vicinity of the main transition, which is non-linear with temperature. The sterols cholesterol and androsten are used as sensors in a time-resolved simultaneous small- and wide angle x-ray diffraction study to investigate the cause of the thickening. We observe precritical behavior in the pure lipid system, as well as with sterol concentrations less than 15%. To describe the precritical behavior we introduce a theory of precritical phenomena.The good temperature resolution of the data shows that a theory of the influence of fluctuations needs modification. The main cause of the critical behavior appears to be a changing hydration of the bilayer.Comment: 11 pages, 7 ps figures included, to appear in Phys.Rev.

Risk Factors for Incarceration in Patients with Primary Abdominal Wall and Incisional Hernias: A Prospective Study in 4472 Patients

_Background_ Incarceration of primary and incisional hernias often results in emergency surgery. The objective of this study was to evaluate the relation of defect size and location with incarceration. Secondary objectives comprised identification of additional patient factors associated with an incarcerated hernia. _Methods_ A registry-based prospective study was performed of all consecutive patients undergoing hernia surgery between September 2011 and February 2016. Multivariate logistic regression was performed to identify risk factors for incarceration. _Results_ In total, 83 (3.5%) of 2352 primary hernias and 79 (3.7%) of 2120 incisional hernias had a non-reducible incarceration. For primary hernias, a defect width of 3–4 cm compared to defects of 0–1 cm was significantly associated with an incarcerated hernia (OR 2.85, 95% CI 1.57–5.18, p = 0.0006). For incisional hernias, a defect width of 3–4 cm compared to defects of 0–2 cm was significantly associated with an incarceration (OR 2.14, 95% CI 1.07–4.31, p = 0.0324). For primary hernias, defects in the peri- and infra-umbilical region portrayed a significantly increased odds for incarceration as compared to supra-umbilical defects (OR 1.98, 95% CI 1.02–3.85, p = 0.043). Additionally, in primary hernias age, BMI, and constipation were associated with incarceration. In incisional hernias age, BMI, female sex, diabetes mellitus and ASA classification were associated with incarceration. _Conclusion_ For primary and incisional hernias, mainly defects of 3–4 cm were associated with incarceration. For primary hernias, mainly defects located in the peri- and infra-umbilical region were associated with incarceration. Based on patient and hernia characteristics, patients with increased odds for incarceration may be selected and these patients may benefit from elective surgical treatment

Comparison of different modalities for the diagnosis of parastomal hernia: a systematic review

Purpose: Parastomal hernia (PSH) is a common complication following stoma formation. The incidence of PSH varies widely due to several factors including differences in diagnostic modality, observer, definition, and classification used for diagnosing PSH. The aim of this systematic review was to evaluate the diagnostic accuracy of the modalities used to identify PSH. Methods: Embase, MEDLINE, Cochrane, Web of Science, and Google Scholar databases were searched. Studies reporting PSH incidence rates detected by two or more different diagnostic modalities or inter-observer variation on one diagnostic modality were included. Article selection and assessment of study quality were conducted independently by two researchers using Cochrane Collaboration’s tool for assessing risk of bias. PROSPERO registration: CRD42018112732. Results: Twenty-nine studies (n = 2514 patients) were included. Nineteen studies compared CT to clinical examination with relative difference in incidence rates ranging from 0.64 to 3.0 (n = 1369). Overall, 79% of studies found an increase in incidence rate when using CT. Disagreement between CT and clinical examination ranged between 0 and 37.3% with pooled inter-modality agreement Kappa value of 0.64 (95% CI 0.52–0.77). Four studies investigated the diagnostic accuracy of ultrasonography (n = 103). Compared with peroperative diagnosis, CT and ultrasonography both seemed accurate imaging modalities with a sensitivity of 83%. Conclusion: CT is an accurate diagnostic modality for PSH diagnosis and increases PSH detection rates, as compared with clinical examination. Studies that specially focus on the diagnostic accuracy are needed and should aim to take patient-reported outcomes into account. A detailed description of the diagnostic approach, modality, definition, and involved observers is prerequisite for future PSH research

Sarcomania? The Inapplicability of Sarcopenia Measurement in Predicting Incisional Hernia Development

Background: Incisional hernia is a frequent complication after abdominal surgery. A risk factor for incisional hernia, related to body composition, is obesity. Poor skeletal muscle mass might also be a risk factor, as it may result in weakness of the abdominal wall. However, it remains unknown if sarcopenia (i.e. low skeletal muscle mass) is a risk factor for incisional hernia. Therefore, this study aims to investigate whether a relation between sarcopenia and incisional hernia exists. Methods: Patients from the STITCH trial, who underwent elective midline laparotomy, were included. Computed tomography examinations performed within 3 months preoperatively were used to measure the skeletal muscle index (SMI; cm2/m2). Primarily, SMI measured continuously, sarcopenia based on previously described cut-off values for the SMI, and sarcopenia as the lowest gender-specific SMI quartile were assessed as measures to predict incisional hernia occurrence. Secondary, the association between these three measures and post-operative complications was investigated. Results: In total, 283 patients (45.2% male; mean age 63.7 years; mean BMI 25.36 kg/m2) were included, of whom 52 (18%) devel

Hyperbaric oxygen therapy improves colorectal anastomotic healing

Purpose: Hyperbaric oxygen treatment (HBOT) has been found to improve the healing of poorly oxygenated tissues. This study aimed to investigate the influence of HBOT on the healing in ischemic colorectal anastomosis. Methods: Forty Wistar rats were randomly divided into a treatment group that received HBOT for 10 consecutive days (7 days before and 3 days after surgery), or in a control group, which did not receive the therapy. Colectomy with an ischemic anastomosis was performed in all rats. In each group, the rats were followed for 3 or 7 days after surgery to determine the influence of HBOT on anastomotic healing. Results: Five rats from each group died during follow-up. No anastomotic dehiscence was seen in the HBOT group, compared to 37.5 % and 28.6 % dehiscence in the control group on postoperative day (POD) 3 and 7, respectively. The HBOT group had a significantly higher bursting pressure (130.9 ± 17.0 mmHg) than the control group (88.4 ± 46.7 mmHg; p = 0.03) on POD 3. On POD 3 and POD 7, the adhesion severity was significantly higher in the control groups than in the HBOT groups (p < 0.005). Kidney function (creatinine level) of the HBOT group was significantly better than of the control group on POD 7 (p = 0.001). Interestingly, a significantly higher number of CD206+ cells (marker for type 2 macrophages) was observed in the HBOT group at the anastomotic area on POD 3. Conclusion: Hyperbaric oxygen enhanced the healing of ischemic anastomoses in rats and improved the postoperative kidney function