Non-Amontons behavior of friction in single contacts

We report on the frictional properties of a single contact between a glassy polymer lens and a flat silica substrate covered either by a disordered or by a self-assembled alkylsilane monolayer. We find that, in contrast to common belief, the Amontons proportionality between frictional and normal stresses does not hold. Besides, we observe that the velocity dependence of the sliding stress is strongly sensitive to the structure of the silane layer. Analysis of the frictional rheology observed on both disordered and self-assembled monolayers suggests that dissipation is controlled by the plasticity of a glass-like interfacial layer in the former case, and by pinning of polymer chains on the substrate in the latter one.Comment: submitted to Eur. Phys. J.

Urodynamic Evaluation in Multiple System Atrophy: A Retrospective Cohort Study.

Background: Urological dysfunction in patients with multiple system atrophy (MSA) is one of the main manifestations of autonomic failure. Urodynamic examination is clinically relevant since underlying pathophysiology of lower urinary tract (LUT) dysfunction can be variable. Objective: Evaluation of the pathophysiology of urological symptoms and exploration of differences in urodynamic patterns of LUT dysfunction between MSA-P and MSA-C. Methods: Retrospective study of patients with possible and probable MSA who were referred for urodynamic studies between 2004 and 2019. Demographic data, medical history, physical examination and urodynamic studies assessing storage and voiding dysfunction were obtained. Results: Seventy-four patients were included in this study (MSA-P 64.9% n = 48; median age 62.5 (IQR 56.8-70) years). Detrusor overactivity during filling phase was noted in 58.1% (n = 43) of the patients. In the voiding phase, detrusor sphincter dyssynergia and detrusor underactivity were observed in 24.6% (n = 17) and in 62.1% (n = 41) of the patients, respectively. A postmicturition residual volume of over 100 ml was present in 71.4% (n = 50) of the patients. Comparison of MSA subtypes showed weaker detrusor contractility in MSA-P compared to MSA-C [pdetQmax 26.2 vs. 34.4 cmH20, P = 0.04]. In 56.2% (n = 41) of patients pathophysiology of LUT dysfunction was deemed to be neurogenic and consistent with the diagnosis of MSA. In 35.6% (n = 26) urodynamic pattern suggested other urological co-morbidities. Conclusion: Urodynamic evaluation is an important tool to analyze the pattern of LUT dysfunction in MSA. Impaired detrusor contractility was seen more in MSA-P which needs to be investigated in further studies

Development of Reacted Channel During Flow of CO2 Rich Water Along a Cement Fracture

AbstractLab scale experiments were performed to characterize how coupling between reaction and flow affect time-dependent flux of CO2-rich water along leaky wells. The core flow system applies confining stress to a cement core with a single tensile fracture while CO2-rich water is injected at constant rate and elevated pore pressure. Results show no significant variation in pressure differential, despite the development of a texturally distinct calcium depleted channel along the fracture surfaces which is bounded by thin rims of precipitation. Silicon rich material remains in the channel and prevents wormhole development and large increases in aperture. Implications for time-dependent CO2 leakage are that even with high fluid flux, the leak does not get appreciably worse

Intraoperative 3-D mapping of parathyroid adenoma using freehand SPECT

Background: Freehand single photon emission computed tomography (fSPECT) is a three-dimensional (3-D) tomographic imaging modality based on data acquisition with a handheld detector that is moved freely, in contrast to conventional, gantry-mounted gamma camera systems. In this pilot study, we evaluated the feasibility of fSPECT for intraoperative 3-D mapping in patients with parathyroid adenomas. Methods: Three patients (range 30 to 45 years) diagnosed with hyperparathyroidism (one primary and two tertiary) underwent parathyroid scintigraphy with technetium-99m sestamibi (99mTc-MIBI) to localize parathyroid adenomas. Two patients were referred with persistent hyperparathyroidism after conventional parathyroidectomy. In all three patients, a planar scintigraphy of the neck was performed 10 min after injection (p.i.) followed by SPECT/CT (Symbia T2, Siemens Healthcare) and a correlative ultrasound 2 h p.i. 99mTc-MIBI scan was performed the day before surgery in two patients and at the same day in one patient. fSPECT images were acquired intraoperatively using declipse SPECT (SurgicEyeTM). Results: A total of five parathyroid adenomas were successfully located with SPECT/CT. fSPECT allowed intraoperative detection of all adenomas, and successful parathyroidectomy was accomplished. Parathyroid hormone level decreased intraoperatively in all three patients, on average, by 79% (range 72% to 91%). Conclusion: In this preliminary study, we could demonstrate that intraoperative localization of parathyroid adenomas is feasible using the freehand SPECT technology, thus allowing an image-guided parathyroidectomy

Naïve and informed views on the nature of scientific inquiry in large-scale assessments: Two sides of the same coin or different currencies

Many models in the field of epistemic cognition conceptualize students' views as being on a continuum between the poles of naïve and informed views. Against this background, the aim of the present study was to find out whether views on the nature of scientific inquiry (NOSI views) should be conceptualized and quantitatively assessed in a more multiplistic manner, considering naïve and informed views in their own, separate dimensions. Based on a competence model defining three inquiry methods, we developed a Likert-scaled questionnaire containing 10 scales, each assessing one NOSI view. We administered the questionnaire to a sample of 802 students in the lower and upper levels of secondary school. Based on structural equation modeling, the analyses confirmed a 10-dimensional model, distinguishing between each naïve and informed views as the only adequate representation of the data. Latent class analysis and interview data revealed four profiles of NOSI views in the data, which differed with regard to their agreement or disagreement with different naïve and informed views. We interpret these findings as evidence that supports more multiplistic models, with relevance to conceptualizing, measuring, and fostering NOSI views. We derive future directions of nature of science and NOSI research linking basic and applied research using experimental studies. © 2019 The Author. Journal of Research in Science Teaching published by Wiley Periodicals, Inc

Preface – Special issue: Multiple system atrophy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41652/1/702_2005_Article_376.pd