On the use of Perfectly Matched Layers at corners for scattering problems with sign-changing coefficients

International audienceWe investigate in a 2D setting the scattering of time-harmonic electromagnetic waves by a plasmonic device, represented as a non dissipative bounded and penetrable obstacle with a negative permittivity. Using the $\texttt{T}$-coercivity approach, we first prove that the problem is well-posed in the classical framework $H^1_{loc}$ if the negative permittivity does not lie in some critical interval whose definition depends on the shape of the device. When the latter has corners, for values inside the critical interval, unusual strong singularities for the electromagnetic field can appear. In that case, well-posedness is obtained by imposing a radiation condition at the corners to select the outgoing black-hole plasmonic wave, that is the one which carries energy towards the corners. A simple and systematic criterion is given to define what is the outgoing solution. Finally, we propose an original numerical method based on the use of Perfectly Matched Layers at the corners. We emphasize that it is necessary to design an $\textit{ad hoc}$ technique because the field is too singular to be captured with standard finite element methods

Specificity of Lower Urinary Tract Symptoms in Neuromyelitis Optica in Comparison With Multiple Sclerosis Patients

Purpose The aim of this study was to describe lower urinary tract symptoms in neuromyelitis optica (NMO), and to compare these data with urinary disorders observed in multiple sclerosis (MS) patients. Methods Retrospective study of data collected from January 1997 to July 2017 using the database from a Neuro-Urology Department of a university hospital. NMO and MS patients were matched for sex, age, and Expanded Disability Status Scale (EDSS) Results Twenty-six patients with NMO were included and compared with 33 MS patients. Mean age was 41.6 years (standard deviation [SD], 14,8), mostly female patients (24 vs. 2 males). Mean EDSS was 4.6 (SD, 1.8) in the 2 groups. In NMO group, 57% of the patients (n=15) had overactive bladder with urgency and urge incontinence and 38.5% (n=10) of them had nocturia. Voiding symptoms was observed in 69.2% of the patients (n=18); 42.3% of NMO patients performed self-intermittent catheterization versus 12.1% in MS patients (P=0.012). Low bladder compliance and severe urinary tract infections (pyelonephritis) were more frequent in NMO than in MS patients (respectively 15% vs. 0%, P=0.016 and 42% vs. 12%, P=0.024). Conclusions Lower urinary tract symptoms, especially overactive bladder and urinary retention, are frequent in NMO. Low bladder compliance, serious urinary infections, and high prevalence of urinary retention requiring self-intermittent catheterization are the main symptoms significantly more frequent than in MS

Eigenvalue problems with sign-changing coefficients

International audienceWe consider a class of eigenvalue problems involving coefficients changing sign on the domain of interest. We describe the main spectral properties of these problems according to the features of the coefficients. Then, under some assumptions on the mesh, we explain how one can use classical finite element methods to approximate the spectrum as well as the eigenfunctions while avoiding spurious modes. We also prove localisation results of the eigenfunctions for certain sets of coefficients.Nous étudions, d’un point de vue théorique et numérique, des problèmes aux valeurs propres mettant en jeu des coefficients dont le signe change sur le domaine d’intérêt

Plasmonic cavity modes: black-hole phenomena captured by Perfectly Matched Layers

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Effectiveness and Complications of Percutaneous Needle Tenotomy with a Large Needle for Muscle Contractures: A Cadaver Study.

Twenty-two percent of institutionalised elderly persons have muscle contractures. Contractures have important functional consequences, rendering hygiene and positioning in bed or in a chair difficult. Medical treatment (such as botulinum toxin injections, physiotherapy or positioning) is not very effective and surgery may be required. Surgery is carried out in the operating theatre, under local or general anaesthesia but is often not possible in fragile patients. Mini-invasive tenotomy could be a useful alternative as it can be carried out in ambulatory care, under local anaesthesia.To evaluate the effectiveness of percutaneous needle tenotomy and the risks of damage to adjacent structures in cadavers.Thirty two doctors who had never practiced the technique (physical medicine and rehabilitation specialists, geriatricians and orthopaedic surgeons) carried out 401 tenotomies on the upper and lower limbs of 8 fresh cadavers. A 16G needle was used percutaneous following location of the tendons. After each tenotomy, a neuro-orthopaedic surgeon and an anatomist dissected the area in order to evaluate the success of the tenotomy and any adjacent lesions which had occurred.Of the 401 tenotomies, 72% were complete, 24.9% partial and 2.7% failed. Eight adjacent lesions occurred (2%): 4 (1%) in tendons or muscles, 3 (0.7%) in nerves and 1 (0.2%) in a vessel.This percutaneous needle technique effectively ruptured the desired tendons, with few injuries to adjacent structures. Although this study was carried out on cadavers, the results suggest it is safe to carry out on patients

Adherence to Anticholinergic Therapy and Clean Intermittent Self-Catheterization in Patients With Multiple Sclerosis

International audiencePurposeTo evaluate adherence to anticholinergic therapy (AT) and clean intermittent self-catheterization (CISC) in patients with multiple sclerosis (MS) and to identify factors associated with poor adherence.MethodsThis single-center study prospectively included 49 patients suffering from MS who had been prescribed AT and/or CISC. Adherence was evaluated using a self-report questionnaire. The Expanded Disability Status Scale (EDSS), Patient Global Impression of Improvement, Mini-Mental State Examination, Urinary Symptom Profile, and Hospital Anxiety and Depression (HAD) instruments were administered, and the number of daily anticholinergic pills and/or catheterizations was noted. Whether patients were receiving concomitant intradetrusor botulinum toxin injections was assessed, as were barriers to treatment, side effects, number of spontaneous micturitions, reasons for the prescription, satisfaction, and difficulties.ResultsOnly 38% of patients were adherent to AT. Experiencing side effects was related to nonadherence (P=0.02). Only 29% of patients were adherent to CISC. More intense voiding dysfunction (P<0.001), a higher frequency of CISC (P=0.03), and a higher EDSS score (P=0.02) were associated with better adherence. Conversely, the HAD score (P<0.001), depression (P<0.001), the persistence of spontaneous micturition (P<0.001), a blocking sensation during catheterization (P=0.04), and the need to adapt one’s posture or gesture to perform catheterization (P=0.04) were associated with poorer adherence.ConclusionsAdherence to AT and CISC was poor in patients with MS suffering from bladder dysfunction. Several factors related to nonadherence were identified in this study, and addressing these factors might help to improve treatment adherence

Lower Urinary Tract Symptoms in Elderly Population With Multiple Sclerosis

Purpose The aim of this study is to compare the clinical and urodynamic characteristics of urinary disorders in multiple sclerosis (MS) patients in a geriatric population with a nongeriatric population. Methods This study was conducted retrospectively between 2010 and 2016. Each patient with MS aged 65 and older was matched with 2 patients with MS aged less than 65 in sex, form of MS, and Expended Disability Status Scale (EDSS). Demographic data, urinary symptoms, treatment, quality of life, repercussion of lower urinary tract symptoms on daily life activities and psychological state and urodynamic parameters were collected. Differences between the 2 populations were evaluated using Student test, chi-square, or Fischer tests. Results Twenty-four patients with MS aged 65 and older (mean age, 69.8 years) were matched with 48 patients aged less than 65 years (mean age, 49.4 years). Maximum urethral closure pressure was lower in the elderly population than in the nongeriatric population (mean±standard deviation [SD]: 35.6±18.5 cm H2O vs. 78.2±52.3 cm H2O, P<0.001). In the male population, there was no statistical difference in any other clinical or urodynamic endpoints. In the female population, voiding symptoms was more described in the nongeriatric population (Urinary Symptom Profile low stream: 3.4±3.5 vs. 1.7±2.4, P=0.04), geriatric population had less urinary treatment (P=0.05). LUTS had less impact on quality of life (Qualiveen: 1.4±1.0 vs. 2.1±0.9, P=0.02) on the geriatric population than in the nongeriatric of female MS patients. Conclusions Geriatric population of MS has few differences of urinary disorders compared to a nongeriatric population with EDSS, sex, and MS form equal. However, the psychological impact of these urinary disorders is less important in female geriatric population

Effect of Transcutaneous Vagus Nerve Stimulation in Erosive Hand Osteoarthritis: Results from a Pilot Trial

International audienceBeyond its effect on vegetative functions, the activation of the vagus nerve inhibits inflammation and reduces pain signaling. The aim of this open-label pilot study was to determine the efficacy and tolerance of transcutaneous auricular VNS (taVNS) on erosive hand osteoarthritis (EHOA) symptoms. Symptomatic EHOA patients with hand pain VAS ≥ 40/100 mm and ≥1 interphalangeal swollen joint(s) were included. The taVNS was performed for 4 weeks using an auricular electrode applied one hour per day and connected to a TENS device with pre-established settings. Clinical efficacy was evaluated by changes between baseline and at 4 weeks with hand pain VAS and the functional index FIHOA score, using a Wilcoxon t-test. The treatment tolerance was also evaluated. Eighteen patients (median age 69 years old, 83% women) were analyzed. At baseline, hand pain VAS was 60 mm [IQR 50; 78.2] and FIHOA 15 [10.7; 20.2]. After 4 weeks, taVNS significantly reduced hand pain VAS, with a median decrease of 23.5 mm [7.7; 37.2] (p = 0.001), as well as FIHOA, with a median decrease of 2 points [0.75; 5.2] (p = 0.01). No serious adverse events were reported. One patient stopped taVNS because of auricular discomfort. This first proof-of-concept trial indicated that taVNS is feasible and may decrease joint inflammation and clinical symptoms in EHOA, arguing for a randomized controlled study versus sham stimulation