Background : LAA is the major site of thrombus formation in mitral stenosis; active LAA blood flow and contractile function may be disturbed in MS. TEE is the modality of choice for evaluating LAA and Speckle-tracking echocar- diography (STE) is a recently developed technique for the characterization and quantification of myocardial deformation. It permits measurement of LA and LAA strain and strain rate which can be used to assess the mechanical function of LAA. Objective : To assess the mechanical function of left atrial appendage (LAA) in mitral stenosis (MS) patients with sinus rhythm by 2D speckle tracking strain and strain rate through transesophageal echocardio- graphy (TEE). Patients & Method : Thirty-three patients with moderate to severe MS and sinus rhythm, 38.33 ± 5.66 years as a case group and twen- ty-two age and sex matched healthy volunteers as a control group. All partic- ipants underwent compete conventional transthoracic echocardiography; TEE for assessment of LAA morphology and Doppler flow and speckle tracking strain & strain rate were measured from LAA walls. Results : LAA Doppler flow peak velocities, LAA strain, reservoir strain rate (RSr), conduit strain rate (CSr) and atrial contractile strain rate (ASr) all were significantly lower in patient group. Global Strain of LAA had a negative correlation with LA diameter, pulmonary artery systolic pressure & degree of spontaneous echo contrast and a positive correlation with MS area and LAA Doppler flow. Conclusion : 2D speckle tracking strain and strain rate of LAA is a feasible technique and is significantly reduced in patients with mitral stenosis even with sinus rhythm.
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4) Measurement of the 2D S and Sr: 2D echocardiography images (trans- mit/receive 1.9/4.0 MHz) were obtained from LV apical long axis, 4 chamber, and 2 chamber views with frame rates of 50 - 90 frames/s. Digital data were stored and analyzed off-line. LV endocardial surface was traced manually, and the speckle tracking width was modified in order to cover the whole LV wall thickness so as to obtain curves. Peak LV longitudinal systolic strain (LSS) and Sr (LSSr) were calculated for apical LAX, 4C, and 2C views, and global LV sys- tolic strain (GLSS) and Sr (GLSSr) were calculated through averaging the 3 apic- al views, Longitudinal myocardial strain of PMs was assessed by the free strain method from apical 4chamber view for APM and apical long axis view for PPM .
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LA myocardial feature tracking was performed using dedicated software (TomTec Imaging Systems, 2D CPA MR, Cardiac Performance Analysis, Version 188.8.131.52, Unterschleissheim, Germany). LA endocardial borders were manually traced in the 2- and 4-chamber views using a point-and-click approach when the atrium was at its mini- mum volume after atrial contraction. The atrial endocar- dial border surface was manually delineated and the automated tracking algorithm was applied. Tracking per- formance was visually reviewed to ensure accurate tracking of the atrial myocardium (Figure 1). In case of insufficient automated border tracking, manual adjustments were made to the initial contour and the algorithm was re- applied. The atrium was divided into six segments and av- eraged strain and strain rate profiles were calculated for all segments as previously described . Tracking perform- ance was visually reviewed on a segmental basis. If the tracking quality was not sufficient, e.g. due to the presence of pulmonary veins or left atrial appendage, the corre- sponding segment was excluded from the analysis. Track- ing was repeated for three times in both the 2- and 4- chamber view. LA longitudinal strain and SR results were averaged across all three repetitions in both views. Similar to previous definitions from echocardiographic speckle tracking [11,12] three aspects of atrial strain were analysed (Figure 2): passive strain ( ε e , corresponding to atrial con-
To obtain speci ﬁ c 2D images using STE, digital loops with three successive cardiac cycles were acquired from LVapical 2- chamber (2C), 3-chamber (3C) and 4-chamber (4C) views. The frame rate for these recordings was set at 60 to 90 frames/s. 31,32 After selecting the best-quality two-dimensional image of the cardiac cycle, the LVendocardial border was manually traced at the end-systolic frame. After that, a speckle-tracking region of interest was automatically selected to approximate the myocar- dium between the endocardium and epicardium. The width of the region of interest was adjusted as necessary to accommo- date the total thickness of the LV wall. The LV was divided into 18 segments: 3 levels (basal, mid-cavity and apical), which were further divided into 6 segments (anterior, posterior, lateral, inferior, septal, and anteroseptal). Longitudinal strains for each individual segment were measured and expressed as a bull ’ s- eye, and the software calculated GLS by averaging local strains along the entire LV. 33,34 More negative strain values represent an increased contraction of the myocardium. Normal values of GLS were strati ﬁ ed by age distribution (years) according to references ranges. 30,35
It is important to follow not only the progression of aortic valve obstruction, but also the progression of LV dysfunction by echocardiography in AS patients. Left ventricular ejection fraction (LVEF) is the most common measure of LV systolic function. However, it often remains normal even in symptomatic patients with severe AS. Thus, it is impossible to assess latent changes in LV function using only LVEF. Two-dimensional (2D) speckle tracking echocardiography (STE) is a promising imaging modality, Similar to tissue Doppler imaging (TDI). It permits offline calculation of myocardial velocities and deformation parameters such as strain and strain rate (SR).
Two-dimensional speckle-tracking echocardiography 2D-STE examinations were performed at the end of con- ventional echocardiography for all dogs. The standard left apical long-axis four-chamber and the right paraster- nal short-axis views at the level of papillary muscles were obtained using a frame rate above 60 per second. For each dog, three consecutive cardiac cycles were recorded using one single loop, and digitally stored in a hard disk for offline analysis on a workstation (XStrain™ software for MyLab™ 50 XVision, Esaote, Genova, Italy). The 2D- STE variables included strain, and strain rate. Circumfer- ential strain rate in peak systole (CSR S ), circumferential
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Die vorliegende Arbeit ist unserer Kenntnis nach die erste Arbeit, die anhand einer großen Zahl von Patienten unter klinischen Bedingungen 2D-Strain- Methoden untersucht und diese mit der herkömmlichen Methode des Gewebe- dopplers vergleicht. Die Untersuchung der Tissue Velocity mittels TDI ist in der Tiermedizin bereits in einigen Arbeiten durchgeführt worden (BREITHARDT, 2001; BALOI, 2003; DECKINGER, 2003; EICHENLAUB, 2003; KOFFAS et al., 2003; CHETBOUL et al., 2004b; ZACHERL, 2004; CHETBOUL et al., 2005a; CHETBOUL et al., 2005b; KILLICH et al., 2005; WAGNER, 2005; KILLICH, 2006). Strain Rate und Strain mittels TDI wurden dagegen nur in sehr wenigen Studien an Hunden und Katzen untersucht. In einer Studie von CHETBOUL und Mitarbeitern (2006b) wurden Strain Rate und Strain an relativ wenigen Hundepatienten untersucht, es wurden Referenzwerte erstellt, sowie die Reproduzierbarkeit der Methode evaluiert. Größere Patientenzahlen herzgesunder Hunde und Katzen verschiedener Rassen hatten die Studien von WAGNER (2005) und KILLICH (2006). In experimentellen Studien wurden die 2D-Strain- Methoden an Hunden bereits evaluiert und validiert. Auch hier kamen jeweils nur kleine Patientenzahlen zum Einsatz (TOYODA et al., 2004; KORINEK et al., 2005; LANGELAND et al., 2005; AMUNDSEN et al., 2006). Humanmedizinisch sind diese Methoden bereits validiert und beginnen sich in der Routinediagnostik zu etablieren. Sowohl die Validierung gegen die Goldstandardmethode MRT, als auch der Vergleich mit den konventionellen dopplerbasierten Methoden, sowohl in vivo als auch in vitro, wurde in der Humanmedizin bereits durchgeführt (LEITMAN et al., 2004; INGUL et al., 2005; KORINEK et al., 2005; MODESTO et al., 2005; CHO et al., 2006). Völlig neu an der vorliegenden Studie sind der Vergleich der Einzelpunktmessung mit der Messung von Segmentmittelwerten, der weder in der Tier- noch in der Humanmedizin durchgeführt wurde sowie die Untersuchung der Kurzachsenparameter Rotation und zirkumferenzielle Strain Rate und Strain an Hunden. Studien zu diesen Kurzachsenparametern an Tieren erfolgten ebenfalls nur unter experimentellen Bedingungen an kleinen Patientenzahlen (HELLE-VALLE et al., 2005; NOTOMI et al., 2005).
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In the early deformation, strain hardening is dominant, that is dσ / dε > 0. The adiabatic temperature rises gradually as the plastic work is constantly converted into heat. Therefore, the thermal softening effect increases gradually. If the strain-hardening effect and thermal softening effect reach balance, then dσ / dε = 0, which reaches the critical condition producing ASB, then the thermal softening effect increases continuously. When the thermal softening effect exceeds the strain-hardening effect, that is, dσ / dε < 0, the material will generate local thermoplastic shear instability phenomenon that results in producing ASBs .
In compression test experiments performed by Wright et al., 36) where a data acquisition rate of 100 Hz was applied, the serrated ﬂow and its associated stress drop amplitude were investigated. In addition, the adiabatic heat generated by a single shear event was estimated by evaluating the temporal resolution of a stress drop — a topic that has recently attracted great scientiﬁc interest (see e.g. 37) ). According to Refs. 36, 38 the temperature increase due to adiabatic heating is not suﬃcient to cause a local drop in the viscosity and, therefore, cannot explain serrated ﬂow behavior of shear banding, in particular, with regard to the shear band thick- ness. This conclusion contrasts with that of a recent experi- ment 37) where a tin coating on a metallic glass was used as a
Advanced, robust and convenient strain analysis approach is based on Digital Image Correlation (DIC) . However, in its original ‘tracking’ form it is only capable of following the strain evolution from a reference state. In the absence of such reference, DIC is unable to determine residual stress. The use of high energy synchrotron X-ray diffraction provides the possibility of measuring residual elastic lattice strain, and then deducing stresses by using the material’s elastic properties in the generalized Hooke’s law expression. Thus, the emphasis of synchrotron diffraction data interpretation falls on strain determination from XRD scattering patterns. To streamline and speed up the interpretation of large quantity of data files, a DIC-based approach has been proposed . Whilst that approach offers a reduction in effort and may speed up analysis, further alternative procedures may be proposed for the processing of 2D detector images to achieve efficient extraction of 2D strain states. This forms the core objectives and the results included in the present report.
According to Xiao et al. , despite several research papers on the topic there is not a consensus on the amount of change required in the strain loading rate to effect a change on the strength of concrete. It was found increasing the strain rate increases the ultimate compressive strength of the concrete above that of a static loading rate. Some researchers found an increase of anywhere between 30% and 80% in the ultimate compressive strength, with others claiming an increase of less than 20% and the actual strain rate having no effect on the strength of the concrete. The experimental procedure carried out by Xiao et al.  concluded that differing strain rates have an effect on the ultimate compressive and tensile strength of concrete, while Poisson’s ratio is not obviously dependent on the strain rate. Bischoff and Perry  analysed the dynamic compressive elements of concrete in order to examine the reason for differing results on the effect strain rate has on 25 MPa concrete. Due to the nature of dynamic behavior with varying the strain rates, there are far more factors that can affect the results than a static loading case, including specimen geometry, stress strain distribution throughout the specimen and stress wave propagation effects. Bischoff and Perry  concluded that the confusion about the effect on dynamic strength is because there is a large amount of factors that determine the strength under rapid loading, such as concrete quality, aggregate, age, curing and moisture conditions.
In the second groups G2 (composite with 2% nano carbon) behaves the same behavior as the composite material under the effect of temperature and humidity but it decreased with different rates where the dynamic shear stress of TrHr decreased by 11.73% with increased temperate to 100C° at (T100Hr) , G2 at (TrHr) decreased by rate of 11.4% with increased humidity ratio to 90% at (TrH90) and decreased by 23.8% with increased temperature to T100 and increased humidity to 90% at (T100H90). finally the dynamic shear stress at (TrHr) of G3 decreased by rate of 13.88% with increased temperature to 100C° and 13% with increased humidity to 90 while the dynamic shear stress decreased by 25.3% at T100H90. In all cases with increased temperature and humidity all materials behaves the same behavior .in addition decreased dynamic shear stress because temperature and humidity the shear strain and shear strain rate decreased with different percentage as shown in table (6).
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methodology for generating the flexible tibia, to establish a normative range of strains seen in a homogenous population of young, healthy, male subjects. The flexible tibia was generated by first segmenting the CT scanned tibia to regenerate a 3D solid model of the tibia geometry, then applying the material properties developed from the CT scan Hounsfield Units (HU) values for each element in the finite element model, and finally performing a modal analysis on the finite element model to generate the deformation modes of the tibia model. Strain data from five reference locations around the tibial mid-shaft, and a simulated staple were obtained using subject-specific forward dynamics simulations. The results showed large variability in strain magnitude for a homogenous population. The mean peak and standard deviation for the
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are investigated and the relationship between the mechanical properties of the alloy and its microstructure is explored. The measured strain– stress curves reveal that the dynamic mechanical behaviour of Al–Sc alloy is highly dependent on the strain rate. The ﬂow stress, work hardening rate and strain rate sensitivity increase with increasing strain rate, but the fracture strain and activation volume decrease. The Zerilli–Armstrong fcc constitutive law is used to model the shear ﬂow response of the Al–Sc alloy. A good agreement is found between the predicted and measured shear ﬂow responses. The Al–Sc alloy specimens fracture as a result of shear band formation and crack propagation within the shear band. SEM observations indicate that the fracture features are dominated by a transgranular dimple-like structure. The density and depth of the dimples decrease with increasing strain rate. TEM microstructural observations reveal that the presence of Al 3 Sc precipitated particles in the matrix and
The grain size in the STCR3-processed specimen, regard- ed as the same as that just before the tensile test, is found to be close to that of the cold-rolled Ti–29–13 just before the tensile tests. Except for the grain size factor, the increase in the elongation by the STCR3 processing in Ti–29–13 (Fig. 6) is understandable from the solute-drag deformation model although precise mechanism should be investigated else- where in the near future. The segregation band structure may produce two zones having diﬀerent solute-drag forces for the dislocation gliding. In the zone with lower solute drag force, the local ﬂow stress will be lower although the total ﬂow stress is the same as the STCR3-processsed homogeneous specimen. The lower-drag-force zone will tend to deform more largely than the higher-drag-force zone, resulting in a local strain. In this study, the two zones are in the form of band structure, and the bands are parallel to the tensile direction. This geometric condition will suppress the relax- ation of the local strain. Hence, the higher drag force will facilitate the intergranular cavitation which will be the cause for the lower fracture strain than that in the STCR3-processed
Healthy volunteers were recruited through advertising. Exclusion criteria included history of heart disease, hyper- tension, diabetes, and pregnancy. Volunteers underwent a physical examination, resting electrocardiogram (ECG), CMR with velocity encoded imaging, and exercise stress testing. Volunteers with abnormal stress tests and incom- plete CMR were excluded. Thirty six volunteers were included in this study (13 women and 23 men, mean age 35 years, range 21–65 years). All volunteers were mode- rately physically active but none were reported to be an active athlete. None were obese (mean BMI 24.0, range 18–30). All were in sinus rhythm with a mean resting heart rate 61 beats per minute (44–83) and the mean blood pressure was 127/75 (range 110–145/65–90 mmHg). All patients had normal ejection fraction and cardiac dimensions.
27. Mohiuddin TMG, Lombardo A, Nair RR, Bonetti A, Savini G, Jalil R, Bonini N, Basko DM, Galiotis C, Marzari N, Novoselove KS, Geim AK, Ferrari AC: Uniaxial strain in graphene by Raman spectroscopy: G peak splitting, Gruneisen parameters, and sample orientation. Phys Rev B 2009, 79:205433.
Estimation of side pressure influencing casings in complicated rheological condition in big depths forms the basis of efficie reliable consolidation of the well walls and preparing of pipelines. It is known that before the drilling mine rocks are alw initial strain state. As mine rocks are always under the pressure when determining their strain deformation state their initi state has to be considered. When mass forces are not considered in plane deformation state, then strain state in a
motion of some plate pairs. Table 1 also shows Euler pole estimates from a global GPS study using IGS velocities (Larson et al., 1997) and from the NUVEL-1A plate mo- tion model (DeMets et al., 1994). Angular rotation vectors (plus their covariance matrices) for all plates can be found at http://www.terrapub.co.jp/journals/EPS/ pdf/5210/append.pdf. The table on this website also contains, for each geodetic study, the angular velocities (plus covariance matrices) that were obtained in the inversion and applied to each study to rotate vectors into a global self- consistent reference frame. In general we find a good agree- ment between our model results and NUVEL-1A and, espe- cially, Larson et al. (1997), but also some notable differences exist. Some of these differences are discussed here. We find that the rotation vector for the North America (NA) plate rel- ative to the Pacific plate (PA) is located 5 ◦ more to the east than Larson et al. (1997) found. We believe that this differ- ence may be related to Larson et al.’s (1997) inclusion of the velocity at Fairbanks into their calculation of the rotation vec- tor of NA. When we include Fairbanks on the stable NA plate the weighted RMS for the IGS sites that we use on stable NA increases from 0.11 to 0.27. Therefore, we prefer to consider Fairbanks inside the PA-NA plate boundary zone. The rota- tion rate for the Nazca plate relative to the South America and Pacific plates is significantly lower in this study than in most previous studies. This is in agreement with what is found in recent geodetic studies (Angermann et al., 1999; Norabuena et al., 1999). We find rotation rates for the Arabian and In-
Present investigation demonstrated that the synthesis of nanostructured AISI 304 stainless steel is possible through severe plastic deformation in machining. The effect of cutting speed on deformation characteristics such as plastic strain and strain rate has been studied. Further, investigation reveals that the combined effect of plastic strain and strain rate is critical to the reduction of crystallite size.