A seamless, extended DG approach for advection-diffusion problems on unbounded domains

We propose and analyze a seamless extended Discontinuous Galerkin (DG) discretization of advection-diffusion equations on semi-infinite domains. The semi-infinite half line is split into a finite subdomain where the model uses a standard polynomial basis, and a semi-unbounded subdomain where scaled Laguerre functions are employed as basis and test functions. Numerical fluxes enable the coupling at the interface between the two subdomains in the same way as standard single domain DG interelement fluxes. A novel linear analysis on the extended DG model yields unconditional stability with respect to the P\'eclet number. Errors due to the use of different sets of basis functions on different portions of the domain are negligible, as highlighted in numerical experiments with the linear advection-diffusion and viscous Burgers' equations. With an added damping term on the semi-infinite subdomain, the extended framework is able to efficiently simulate absorbing boundary conditions without additional conditions at the interface. A few modes in the semi-infinite subdomain are found to suffice to deal with outgoing single wave and wave train signals more accurately than standard approaches at a given computational cost, thus providing an appealing model for fluid flow simulations in unbounded regions.Comment: 27 pages, 8 figure

Incremental Convex Planarity Testing

AbstractAn important class of planar straight-line drawings of graphs are convex drawings, in which all the faces are drawn as convex polygons. A planar graph is said to be convex planar if it admits a convex drawing. We give a new combinatorial characterization of convex planar graphs based on the decomposition of a biconnected graph into its triconnected components. We then consider the problem of testing convex planarity in an incremental environment, where a biconnected planar graph is subject to on-line insertions of vertices and edges. We present a data structure for the on-line incremental convex planarity testing problem with the following performance, where n denotes the current number of vertices of the graph: (strictly) convex planarity testing takes O(1) worst-case time, insertion of vertices takes O(log n) worst-case time, insertion of edges takes O(log n) amortized time, and the space requirement of the data structure is O(n)

Effectiveness of osteopathic interventions in chronic non-specific low back pain: A systematic review and meta-analysis.

Background: Chronic low back pain (CLBP) is a frequent cause of disability and it represents a medical, social and economic burden globally. Therefore, we assessed effectiveness of osteopathic interventions in the management of NS-CLBP for pain and functional status. Methods: A systematic review and meta-analysis were conducted. Findings were reported following the PRISMA statement. Six databases were searched for RCTs. Studies were independently assessed using a standardized form. Each article was assessed using the Cochrane risk of bias (RoB) tool. Effect size (ES) were calculated at post-treatment and at 12 weeks' follow up. We used GRADE to assess quality of evidence. Results: 10 articles were included. Studies investigated osteopathic manipulative treatment (OMT, n = 6), myofascial release (MFR, n = 2), craniosacral treatment (CST, n = 1) and osteopathic visceral manipulation (OVM, n = 1). None of the study was completely judged at low RoB. Osteopathy revealed to be more effective than control interventions in pain reduction (ES: -0.59; 95% CI: -0.81, -0.36; P < 0.00,001) and in improving functional status (ES: -0.42; 95% 95% CI: -0.68, -0.15; P = 0.002). Moderate-quality evidence suggested that MFR is more effective than control treatments in pain reduction (ES: -0.69; 95% CI: -1.05, -0.33; P = 0.0002), even at follow-up (ES: -0.73; 95% CI: -1.09, -0.37; P < 0.0001). Low-quality evidence suggested superiority of OMT in pain reduction (ES: -0.57; 95% CI: -0.90, -0.25; P = 0.001) and in changing functional status (ES: -0.34; 95% CI: -0.65, -0.03; P = 0.001). Very low-quality evidence suggested that MFR is more effective than control interventions in functional improvements (ES: -0.73; 95% CI: -1.25, -0.21; P = 0.006). Conclusion: Results strengthen evidence that osteopathy is effective in pain levels and functional status improvements in NS-CLBP patients. MFR reported better level of evidence for pain reduction if compared to other interventions. Further high-quality RCTs, comparing different osteopathic modalities, are recommended to produce better-quality evidence

Effect of obesity and low back pain on spinal mobility: a cross sectional study in women

<p>Abstract</p> <p>Background</p> <p>obesity is nowadays a pandemic condition. Obese subjects are commonly characterized by musculoskeletal disorders and particularly by non-specific chronic low back pain (cLBP). However, the relationship between obesity and cLBP remains to date unsupported by an objective measurement of the mechanical behaviour of the spine and its morphology in obese subjects. Such analysis may provide a deeper understanding of the relationships between function and the onset of clinical symptoms.</p> <p>Purpose</p> <p>to objectively assess the posture and function of the spine during standing, flexion and lateral bending in obese subjects with and without cLBP and to investigate the role of obesity in cLBP.</p> <p>Study design</p> <p>Cross-sectional study</p> <p>Patient sample</p> <p>thirteen obese subjects, thirteen obese subjects with cLBP, and eleven healthy subjects were enrolled in this study.</p> <p>Outcome measures</p> <p>we evaluated the outcome in terms of angles at the initial standing position (START) and at maximum forward flexion (MAX). The range of motion (ROM) between START and MAX was also computed.</p> <p>Methods</p> <p>we studied forward flexion and lateral bending of the spine using an optoelectronic system and passive retroreflective markers applied on the trunk. A biomechanical model was developed in order to analyse kinematics and define angles of clinical interest.</p> <p>Results</p> <p>obesity was characterized by a generally reduced ROM of the spine, due to a reduced mobility at both pelvic and thoracic level; a static postural adaptation with an increased anterior pelvic tilt. Obesity with cLBP is associated with an increased lumbar lordosis.</p> <p>In lateral bending, obesity with cLBP is associated with a reduced ROM of the lumbar and thoracic spine, whereas obesity on its own appears to affect only the thoracic curve.</p> <p>Conclusions</p> <p>obese individuals with cLBP showed higher degree of spinal impairment when compared to those without cLBP. The observed obesity-related thoracic stiffness may characterize this sub-group of patients, even if prospective studies should be carried out to verify this hypothesis.</p

Skeletal muscle characteristics and motor performance after 2-year growth hormone treatment in adults with prader-willi syndrome.

Context:In adults with Prader-Willi syndrome (PWS), abnormal body composition with decreased lean body mass and skeletal muscle (SM) volume has been related to altered GH secretion and may possibly contribute to greatly reduced motor capacity.Objective:The scope of the study was to test the hypothesis that GH treatment has favorable effects on SM characteristics and motor performance in adults with PWS.Design, Setting, and Participants:Fifteen obese PWS subjects (nine males and six females; age range, 19–35 y; body mass index, 37.7–59.9 kg/m2) were investigated before and after 12 (GH12) and 24 (GH24) months of GH treatment.Main Outcome Measures:SM cross-sectional area and SM attenuation were determined with computed tomography at the lumbar and midthigh levels. Maximal isometric handgrip strength and isokinetic knee extension peak torque were measured. Motor performance was evaluated with different indoor walking tests, whereas exercise endurance was assessed with a treadmill incremental test to exhaustion.Results:A condition of severe GH deficiency was found in six patients (40%). GH treatment significantly increased lean body mass (GH12, P &lt; .05; GH24, P &lt; .05), reduced percentage of body fat (GH12, P &lt; .05; GH24, P &lt; .05), and augmented SM cross-sectional area and SM attenuation of both lumbar (GH12, P &lt; .01; GH24, P &lt; .001) and thigh muscles (GH24, P &lt; .05). Handgrip strength increased by 7% at GH12 (P &lt; .05) and by 13% at GH24 (P &lt; .001). Peak torque of knee extension extrapolated at zero angular velocity was significantly higher at GH24 (P &lt; .01), and exercise endurance rose by 13% (P &lt; .05) and 17% (P &lt; .05) before exhaustion at GH12 and GH24, respectively, whereas no change was detected with walking tests. No significant difference in the response to GH treatment was detected between patients with and without GH deficiency.Conclusion:Long-term GH treatment in adult PWS patients improves body composition and muscle size and quality and increases muscle strength and exercise tolerance independently from the GH secretory status

Mechanisms underlying center of pressure displacements in obese subjects during quiet stance

<p>Abstract</p> <p>Objective</p> <p>the aim of this study was to assess whether reduced balance capacity in obese subjects is secondary to altered sensory information.</p> <p>Design</p> <p>cross sectional study.</p> <p>Subjects</p> <p>44 obese (BMI = 40.6 ± 4.6 kg/m², age = 34.2 ± 10.8 years, body weight: 114,0 ± 16,0 Kg, body height 167,5 ± 9,8 cm) and 20 healthy controls (10 females, 10 males, BMI: 21.6 ± 2.2 kg/m², age: 30.5 ± 5.5 years, body weight: 62,9 ± 9,3 Kg, body height 170,1 ± 5,8 cm) were enrolled.</p> <p>Measurements</p> <p>center of pressure (CoP) displacements were evaluated during quiet stance on a force platform with eyes open (EO) and closed (EC). The Romberg quotient (EC/EO) was computed and compared between groups.</p> <p>Results</p> <p>we found statistically significant differences between obese and controls in CoP displacements (p < 0.01) and no statistically significant differences in Romberg quotients (p > 0.08).</p> <p>Conclusion</p> <p>the increased CoP displacements in obese subjects do not need an hypothesis about altered sensory information. The integration of different sensory inputs appears similar in controls and obese. In the latter, the increased mass, ankle torque and muscle activity may probably account for the higher CoP displacements.</p

Postural adaptations to long-term training in Prader-Willi patients

<p>Abstract</p> <p>Background</p> <p>Improving balance and reducing risk of falls is a relevant issue in Prader-Willi Syndrome (PWS). The present study aims to quantify the effect of a mixed training program on balance in patients with PWS.</p> <p>Methods</p> <p>Eleven adult PWS patients (mean age: 33.8 ± 4.3 years; mean BMI: 43.3 ± 5.9 Kg/m2) attended a 2-week training program including balance exercises during their hospital stay. At discharge, Group 1 (6 patients) continued the same exercises at home for 6 months, while Group 2 (5 patients) quitted the program. In both groups, a low-calorie, well-balanced diet of 1.200 kcal/day was advised. They were assessed at admission (PRE), after 2 weeks (POST1) and at 6-month (POST2). The assessment consisted of a clinical examination, video recording and 60-second postural evaluation on a force platform. Range of center of pressure (CoP) displacement in the antero-posterior direction (RANGE_APindex) and the medio-lateral direction (RANGE_MLindex) and its total trajectory length were computed.</p> <p>Results</p> <p>At POST1, no significant changes in all of the postural parameters were observed. At completion of the home program (POST2), the postural assessment did not reveal significant modifications. No changes in BMI were observed in PWS at POST2.</p> <p>Conclusions</p> <p>Our results showed that a long-term mixed, but predominantly home-based training on PWS individuals was not effective in improving balance capacity. Possible causes of the lack of effectiveness of our intervention include lack of training specificity, an inadequate dose of exercise, an underestimation of the neural and sensory component in planning rehabilitation exercise and failed body weight reduction during the training. Also, the physiology of balance instability in these patients may possibly compose a complex puzzle not affected by our exercise training, mainly targeting muscle weakness.</p