Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure

Performance of a cognitive load inventory during simulated handoffs: Evidence for validity.

BackgroundAdvancing patient safety during handoffs remains a public health priority. The application of cognitive load theory offers promise, but is currently limited by the inability to measure cognitive load types.ObjectiveTo develop and collect validity evidence for a revised self-report inventory that measures cognitive load types during a handoff.MethodsBased on prior published work, input from experts in cognitive load theory and handoffs, and a think-aloud exercise with residents, a revised Cognitive Load Inventory for Handoffs was developed. The Cognitive Load Inventory for Handoffs has items for intrinsic, extraneous, and germane load. Students who were second- and sixth-year students recruited from a Dutch medical school participated in four simulated handoffs (two simple and two complex cases). At the end of each handoff, study participants completed the Cognitive Load Inventory for Handoffs, Paas' Cognitive Load Scale, and one global rating item for intrinsic load, extraneous load, and germane load, respectively. Factor and correlational analyses were performed to collect evidence for validity.ResultsConfirmatory factor analysis yielded a single factor that combined intrinsic and germane loads. The extraneous load items performed poorly and were removed from the model. The score from the combined intrinsic and germane load items associated, as predicted by cognitive load theory, with a commonly used measure of overall cognitive load (Pearson's r = 0.83, p < 0.001), case complexity (beta = 0.74, p < 0.001), level of experience (beta = -0.96, p < 0.001), and handoff accuracy (r = -0.34, p < 0.001).ConclusionThese results offer encouragement that intrinsic load during handoffs may be measured via a self-report measure. Additional work is required to develop an adequate measure of extraneous load

Effect of pH of amine fluoride containing toothpastes on enamel remineralization in vitro

<p>Abstract</p> <p>Background</p> <p>One of the important factors of the demineralization and remineralization equilibrium of enamel is the pH of the surrounding solutions. Effort has been laid in the formulation of different fluoride compounds and the fluoride content in toothpastes but much less is known about the influence of the pH of the toothpastes on their effectiveness. It was therefore the aim of this study to investigate the influence of different pH levels on enamel remineralization in an in vitro experiment using polarization light microscopy and EDX quantitative element analysis.</p> <p>Methods</p> <p>A 5 × 5 mm window on the enamel surface of 40 caries free extracted human premolars was demineralized in a hydroxyethylcellulose solution at pH 4.8. The teeth were divided into 8 groups and the lower half of the window was covered with varnish serving as control. Each group was then immersed in toothpaste slurry containing amine fluoride (1400 ppm) at pH 4.1, 4.5, 5.1 and 6.9 or control toothpaste slurry without fluoride at pH 4.3, 4.7, 5.3 and 7.0. Serial sections were cut through the lesions and investigated with polarization light microscopy and quantitative EDX element analysis.</p> <p>Results</p> <p>The PLM results showed a decreased porous volume of the body of the lesion after incubation with fluoridated toothpaste at pH 4.53 and 5.16. No differences between the experimental window and the control window were found in the other groups. The quantitative element analysis showed no differences in the element content of any of the groups.</p> <p>Conclusion</p> <p>From the results it can be concluded that slightly acidified fluoridated dentifrices may have a certain positive effect on enamel remineralization.</p

Alterations in aortic elasticity in noncompaction cardiomyopathy

Background: Noncompaction cardiomyopathy (NCCM) is a recently recognized disorder frequently associated with systolic and diastolic heart failures. This study was designed to examine aortic stiffness in NCCM patients and to compare these results to age- and gender-matched controls. Methods: A total of 20 patients with typical echocardiographic features of NCCM (age 38 ± 16 years, eight males) were investigated. Their results were compared to 20 age- and gender-matched controls. All subjects underwent a complete two-dimensional transthoracic echocardiographic examination. Systolic (SD) and diastolic (DD) ascending aortic diameters were recorded in M-mode at a level of 3 cm above the aortic valve from a parasternal long-axis view. Aortic stiffness index (β) was calculated as a characteristic of aortic elasticity, as ln(SBP/DBP)/[(SD - DD)/DD], where SBP and DBP are the systolic and diastolic blood pressures, respectively, and ln is the natural logarithm. Results: The number of noncompacted segments in the NCCM patients was 4.6 ± 2.0. NCCM patients had significantly increased left ventricular dimensions and reduced left ventricular ejection fraction. Compared to controls, aortic stiffness index (β) was significantly increased in NCCM patients (8.3 ± 5.2 vs. 3.5 ± 1.1, p < 0.001). Conclusion: Increased aortic stiffness can be observed in patients with NCCM with moderate to severe heart failure. These alterations may be due to neurohormonal changes in heart failure

Alterations in aortic elasticity in noncompaction cardiomyopathy

BACKGROUND: Noncompaction cardiomyopathy (NCCM) is a recently recognized disorder frequently associated with systolic and diastolic heart failures. This study was designed to examine aortic stiffness in NCCM patients and to compare these results to age- and gender-matched controls. METHODS: A total of 20 patients with typical echocardiographic features of NCCM (age 38 +/- 16 years, eight males) were investigated. Their results were compared to 20 age- and gender-matched controls. All subjects underwent a complete two-dimensional transthoracic echocardiographic examination. Systolic (SD) and diastolic (DD) ascending aortic diameters were recorded in M-mode at a level of 3 cm above the aortic valve from a parasternal long-axis view. Aortic stiffness index (beta) was calculated as a characteristic of aortic elasticity, as ln(SBP/DBP)/[(SD - DD)/DD], where SBP and DBP are the systolic and diastolic blood pressures, respectively, and ln is the natural logarithm. RESULTS: The number of noncompacted segments in the NCCM patients was 4.6 +/- 2.0. NCCM patients had significantly increased left ventricular dimensions and reduced left ventricular ejection fraction. Compared to controls, aortic stiffness index (beta) was significantly increased in NCCM patients (8.3 +/- 5.2 vs. 3.5 +/- 1.1, p < 0.001). CONCLUSION: Increased aortic stiffness can be observed in patients with NCCM with moderate to severe heart failure. These alterations may be due to neurohormonal changes in heart failure

New Scores for the Assessment of Mitral Stenosis Using Real-Time Three-Dimensional Echocardiography

Nonsurgical management of patients with symptomatic mitral valve stenosis has been established as the therapeutic modality of choice for two decades. Catheter-based balloon dilation of the stenotic valvular area has been shown, at least, as effective as surgical interventions. Unfavorable results of catheter-based interventions are largely due to unfavorable morphology of the valve apparatus, particularly leaflets calcification and subvalvular apparatus involvement. A mitral valve score has been proposed in Boston, MA, about two decades ago, based on morphologic assessment of mitral valve apparatus by two-dimensional (2D) echocardiography to predict successful balloon dilation of the mitral valve. Several other scores have been developed in the following years in order to more successfully predict balloon dilatation outcome. However, all those scores were based on 2D echocardiography, which is limited by ability to distinguish calcification and subvalvular involvement. The introduction of new matrix-based ultrasound probe has allowed 3D echocardiography (3DE) to provide more detailed morphologic analysis of mitral valve apparatus including calcification and subvalvular involvement. Recently, a new 3DE scoring system has been proposed by our group, which represents an important leap into refinement of the use of echocardiography guiding mitral valve interventions

Value of assessment of tricuspid annulus: real-time three-dimensional echocardiography and magnetic resonance imaging

Aim: To detect the accuracy of real-time three-dimensional echocardiography (RT3DE) and two-dimensional echocardiography (2DE) for tricuspid annulus (TA) assessment compared with magnetic resonance imaging (MRI). Methods: Thirty patients (mean age 34 ± 13 years, 60% males) in sinus rhythm were examined by MRI, RT3DE, and 2DE for TA assessment. End-diastolic and end-systolic TA diameter (TAD) and TA fractional shortening (TAFS) were measured by RT3DE, 2DE, and MRI. End-diastolic and end-systolic TA area (TAA) and TA fractional area changes (TAFAC) were measured by RT3DE and MRI. End-diastolic and end-systolic right ventricular (RV) volumes and ejection fraction (RV-EF) were measured by MRI. Results: The TA was clearly delineated in all patients and visualized as an oval-shaped by RT3DE and MRI. There was a good correlation between TADMRIand TAD3D(r = 0.75, P = 0.001), while TAD2Dwas fairly correlated with TAD3Dand TADMRI(r = 0.5, P = 0.01 for both). There were no significant differences between RT3DE and MRI in TAD, TAA, TAFS, and TAFAC measurements, while TAD2Dand TAFS2Dwere significantly underestimated (P < 0.001). TAFS2Dwas not correlated with RV-EF, while TAFS3Dand TAFAC3Dwere fairly correlated with RV-EF (r = 0.49, P = 0.01, and r = 0.47, P = 0.02 respectively). Conclusion: RT3DE helps in accurate assessment of TA comparable to MRI and may have an important implication in the TV surgical decision-making processes. RT3DE analysis of TA function could be used as a marker of RV function

Conservative surgery for left-sided isolated tubal torsion in pregnancy

We report a case of severe lower abdominal pain in a pregnant woman at 35 weeks and 4 days of gestation. Early diagnosis of an isolated left-sided tubal torsion was established by ultrasound and emergency magnetic resonance imaging (MRI). Subsequent detorsion surgery was able to prevent the need for salpingectomy. The role of emergency imaging and conservative surgery in isolated tubal torsion is discussed

On the Hybrid Extension of CTL and CTL+

The paper studies the expressivity, relative succinctness and complexity of satisfiability for hybrid extensions of the branching-time logics CTL and CTL+ by variables. Previous complexity results show that only fragments with one variable do have elementary complexity. It is shown that H1CTL+ and H1CTL, the hybrid extensions with one variable of CTL+ and CTL, respectively, are expressively equivalent but H1CTL+ is exponentially more succinct than H1CTL. On the other hand, HCTL+, the hybrid extension of CTL with arbitrarily many variables does not capture CTL*, as it even cannot express the simple CTL* property EGFp. The satisfiability problem for H1CTL+ is complete for triply exponential time, this remains true for quite weak fragments and quite strong extensions of the logic