A new class of nonlinear acoustic phenomena has been observed for acoustic wave interaction with simulated and realistic nonbonded contact interfaces (cracked defects) in solids. “Nonclassical“ ...effects are due to substantially asymmetric stiffness characteristics of the interface for normal stress that results in specific contact acoustic nonlinearity (CAN). The asymmetry in the contact restoring forces causes the stiffness parametric modulation and instability of oscillations, which results in acoustic wave fractional subharmonic generation. The CAN subharmonics and higher harmonics reveal threshold dynamic behaviour, evident hysteresis, and instability effects.
► NDT methods are presented for monitoring the void formation and fatigue behaviour. ► Porosity affects the heat flow, air-coupled guided wave measurements and velocities. ► Final failure starts from ...one of the delaminations caused by accumulated voids. ► The detrimental effect of the two types of porosity on the durability is illustrated.
The effect of evenly distributed voids (dv) and regions of large accumulated voids (lav) on damage evolution and fatigue life during biaxial cyclic loading is studied. Various non-destructive test methods (thermography, microscopy and optical fracture analysis with high-speed photography) are presented for monitoring the void formation, multiaxial fatigue damage mechanisms and final failure process in glass-fibre reinforced plastics (GFRPs) manufactured by a filament winding machine. In addition, air-coupled guided wave measurements (non-contact and single-sided configuration) are applied to a subset of composite tubes for detection of voids and for observing the development of fatigue damages initiated by voids. Thermal imaging during cyclic loading reveals large accumulated voids as well. Variations of stiffness degradation, matrix cracking and guided wave velocities caused by finely distributed or accumulated voids are shown. Finally, the detrimental effect of the two types of porosity on the durability of multiaxially loaded composites is illustrated.
Damage development in and final failure process of glass fibre winding specimens during biaxial fatigue loading are investigated. The phenomena in nominally defect-free tubes and specimens exhibiting ...local fibre waviness in one layer are compared. A subset of wound tubes is analysed using non-destructive testing methods, i.e. air-coupled guided waves, thermography, optical fracture analysis by a high-speed camera, and discrete damage monitoring. Air-coupled guided waves are employed for detection of fibre waviness and for monitoring the failure progress initiated by this waviness. Stiffness degradation due to fatigue damage corresponds to a decline in guided wave velocity. Using infrared inspection, the fibre waviness can be detected in an early stage of fatigue life. Non-destructive evaluation reveals that initiation of final failure in the specimens is caused by local fibre waviness. Finally, the effect of local fibre waviness on the S–N curves of the specimens is illustrated.
CDKL5 deficiency disorder (CDD) is a rare developmental and epileptic encephalopathy. Ganaxolone, a neuroactive steroid, reduces the frequency of major motor seizures in children with CDD. This ...analysis explored the effect of ganaxolone on non-seizure outcomes. Children (2–19 years) with genetically confirmed CDD and ≥ 16 major motor seizures per month were enrolled in a double-blind randomized placebo-controlled trial. Ganaxolone or placebo was administered three times daily for 17 weeks. Behaviour was measured with the Anxiety, Depression and Mood Scale (ADAMS), daytime sleepiness with the Child Health Sleep Questionnaire, and quality of life with the Quality of Life Inventory-Disability (QI-Disability) scale. Scores were compared using ANOVA, adjusted for age, sex, number of anti-seizure mediations, baseline 28-day major motor seizure frequency, baseline developmental skills, and behaviour, sleep or quality of life scores. 101 children with CDD (39 clinical sites, 8 countries) were randomized. Median (IQR) age was 6 (3–10) years, 79.2 % were female, and 50 received ganaxolone. After 17 weeks of treatment, Manic/Hyperactive scores (mean difference 1.27, 95%CI –2.38,-0.16) and Compulsive Behaviour scores (mean difference 0.58, 95%CI -1.14,-0.01) were lower (improved) in the ganaxolone group compared with the placebo group. Daytime sleepiness scores were similar between groups. The total change in QOL score for children in the ganaxolone group was 2.6 points (95%CI -1.74,7.02) higher (improved) than in the placebo group but without statistical significance. Along with better seizure control, children who received ganaxolone had improved behavioural scores in select domains compared to placebo.
•Ganaxolone is a new anti-seizure medication for CDKL5 deficiency disorder.•Compared to the placebo group, children receiving ganaxolone had less hyperactive and compulsive behaviours.-There were nonsignificant, mild improvements in quality of life in the ganaxolone group.-Daytime sleepiness was similar in the placebo and ganaxolone groups.
Damage evolution in wound glass fibre reinforced tubes due to impact (8.4J and 14J) and subsequent biaxial cyclic loading is studied. Nominally defect-free and impact damaged specimens are compared ...to investigate the effect of the impact damage on the fatigue life of multiaxial composites. Non-destructive inspection (air-coupled guided waves, thermography, high-speed photography, and microscopy) is applied to a subset of tubes. Air-coupled guided wave scans for characterisation of the delaminations due to impact agree well with visual inspection. Decline in guided wave velocity is consistent to a decrease in stiffness caused by fatigue damage. Using thermal imaging the impact is detectable during cyclic loading. Strong anomalies of the surface temperature in the vicinity of the impact at the end of the fatigue life correspond to the initiation spot of final failure observed by high-speed imaging. The considerable effect of impact damage on the durability of the specimens is discussed.
Non-destructive methodologies for remote monitoring of fatigue induced by mechanical load in fibre reinforced plastics are presented. Hollow cylinders (glass fibre winding) were stepwise biaxially ...fatigued and measured in single-sided access configurations. Based on conversion of air-coupled ultrasound to guided waves, it is shown that accumulated fatigue damage is accompanied by decrease in phase velocity and increase in attenuation. The change in wave velocity caused by fatigue is shown to correlate closely with measurements of stiffness degradation of the composite. The attenuation of guided waves is affected by crack density which is visually traceable in the transparent composite. Monitoring of cyclic loading of the specimens by thermal imaging and a high-speed camera revealed that the initiation of final failure in the specimens coincides with spots of increased temperature. Air-coupled guided wave area scans allow for observing the development of these areas and other local damage in the composite.
Photoinduced structural variations in single crystals of 2,4-dichloro-trans-cinnamic acid (C9H6Cl2O2, DiClCA) have been investigated using X-ray diffraction (photocrystallography) and optical ...spectroscopic methods. During UV irradiation, which initiates the irreversible dimerization reaction, a loss of the long-range order of the reactant single crystal was found, i.e., that the dimerization is a heterogeneous one. This unexpected result emphasizes the still-existing problem of predicting changes or of remaining periodicity during chemical reactions in the solid state. On the basis of the experimental results, we propose a qualitative kinetic reaction scheme for DiClCA heterogeneous dimerization reaction.
The aim of this paper is to show the possibility of fatigue damage characterization in GFRP-tube-like components by using circumferential plate waves. For that purpose, fatigue tests with different ...loading directions have been conducted and the stiffness degradation has been monitored. After a preset number of loading cycles, non-destructive ultrasonic tests using circumferential plate waves were performed. The correlation between damage induced amplitude changes of the plate waves and stiffness degradation in non-crimped fabric composites is discussed. The results indicate that the technique is applicable to fatigue damage assessment in complex-shaped components of composite materials and is relevant to a wide field of applications.
Medtronic Mosaic porcine bioprosthesis: Assessment of 12-year performance Jamieson, W. R. Eric, MD; Riess, Friedrich-Christian, MD; Raudkivi, Peter J., MD ...
Journal of thoracic and cardiovascular surgery/The Journal of thoracic and cardiovascular surgery/The journal of thoracic and cardiovascular surgery,
08/2011, Letnik:
142, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Background The Mosaic porcine bioprosthesis (Medtronic, Inc, Minneapolis, Minn) was approved in 2000 by the US Food and Drug Administration. Clinical performance was evaluated in 6 centers. Methods ...From 1994 to 2000, 797 patients (mean age 69 years) had aortic valve replacement (AVR) and 232 (mean 67 years) had mitral valve replacement (MVR). Concomitant coronary artery bypass grafting was performed with aortic valve replacement (45.4%) and mitral valve replacement (43.5%). Mean follow-ups were 7.5 years for aortic position and 7.3 years for mitral position. Results Early mortalities were 2.8% for AVR and 3.0% for MVR. Late mortalities were 4.2%/patient-year for AVR and 5.1%/patient-year for MVR. Overall 12-year survivals were 55.8% ± 3.7% for AVR and 43.9% ± 7.4% for MVR. Twelve-year freedoms from valve-related mortality were 87.1% ± 3.1% for AVR and 82.5% ± 7.7% for MVR. Twelve-year freedoms from reoperation were 84.0% ± 3.3% for AVR and 82.5% ± 7.5% for MVR. Freedoms from structural valve deterioration (SVD) by explant reoperation at 12 years for AVR were 93.3% ± 2.6% for patients at least 60 years old and 75.9% ± 9.3% for patients younger than 60 years. Freedoms from SVD by explant reoperation at 10 years for MVR were 95.3% ± 7.8% for patients at least 70 years old and 84.0% ± 9.3% for patients younger than 70 years. Hemodynamic performance data at 1 year for AVR (sizes 21–27 mm) were mean systolic gradient range 13.7 ± 4.8 to 10.3 ± 3.2 mm Hg and effective orifice area range 1.5 ± 0.3 to 2.5 ± 0.4 cm2 . For MVR (sizes 25–31 mm), data were mean diastolic gradient range 6.7 ± 1.7 to 3.7 ± 0.9 mm Hg and effective orifice area range 1.9 ± 0.3 to 2.4 ± 0.6 cm2. Conclusions Overall performance of Mosaic porcine bioprosthesis to 12 years is satisfactory. Freedoms from SVD by explant reoperation were most satisfactory for aortic position in patients at least 60 years old and mitral position in patients at least 70 years old. Overall actuarial freedom from SVD by explant reoperation is encouraging for patients with MVR.
Sex differences in taste aversion learning have been reported for a number of different compounds. It is unknown, however, to what degree, if any, such differences exist when nicotine is the ...aversion-inducing agent. To address this issue, in the present experiment male and female rats were given limited access to saccharin followed by an intraperitoneal (IP) injection of either vehicle or nicotine (0.4, 0.8 or 1.2 mg/kg). Although nicotine induced significant taste aversions in both males and females, the aversions were generally weak at all doses tested. There were no sex differences in the acquisition or strength of the aversions induced by nicotine. The vulnerability to drug abuse has been suggested to be a function of the balance of the rewarding and aversive effects of a drug. Given the relatively weak aversions induced in both sexes and the absence of differences between males and females, it is unlikely that the reported sex difference in the self-administration of nicotine is a function of differences in nicotine's aversive effects. The reported difference in the self-administration of nicotine by males and females is more likely a function of differences in the sensitivity to the rewarding effects of the drug.
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