Regional Strain Research Articles

Dislocation and strain mapping in metamorphic parabolic-graded InGaAs buffers on GaAs

We investigate different architectures for parabolic-graded InGaAs metamorphic buffers grown on GaAs using transmission electron microscopy techniques. The different architectures include InGaP and AlInGaAs/InGaP superlattices with different GaAs substrate misorientations and the inclusion of a strain balancing layer. Our results correlate: (i) the density and distribution of dislocations in the metamorphic buffer and (ii) the strain in the next layer preceding the metamorphic buffer, which varies for each type of architecture. Our findings indicate that the dislocation density in the lower region of the metamorphic layer ranges between 108 and 1010 cm−2, with AlInGaAs/InGaP superlattice samples exhibiting higher values compared to samples with InGaP films. We have identified two waves of dislocations, with threading dislocations typically located lower in the metamorphic buffer (~ 200–300 nm) in comparison to misfit dislocations. The measured localised strain values are in good agreement with theoretical predications. Overall, our results provide a systematic insight into the strain relaxation across different architectures, highlighting the various approaches that can be used to tailor strain in the active region of a metamorphic laser.Graphical abstract

Regional strain homogenized diaphragm based FBG high pressure sensor

Regional strain homogenized diaphragm based FBG high pressure sensor

Mechanical and hemodynamic effects of left bundle branch area versus biventricular pacing in virtual heart failure patients with left bundle branch block

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Dutch Research Council (NWO) Background Left bundle branch area pacing (LBBAP) has been introduced as an alternative, more physiological pacing strategy to biventricular pacing (BiVP). LBBAP can result in selective LBB pacing (sLBBP), non-selective LBB pacing (nsLBBP), or LV septal pacing (LVSP). Direct comparison between the different pacing strategies is challenging due to the practical implications of performing multiple pacing procedures within the same patients, as well as the large heterogeneity of underlying disease in patients. Computational models can be used to perform controlled in silico experiments and to compare all possible pacing modalities under the same conditions. Aim To investigate the effects of LBBAP strategies versus BiVP on cardiac mechanics and hemodynamics in a set of well-defined virtual heart failure patients. Methods An electrophysiological model was used to calculate biventricular electrical activation maps during LBBB and the different pacing strategies. The resulting regional activation times were imposed to the well-validated CircAdapt model of the human four-chamber heart and circulation. A set of virtual patients at different stages of heart failure are then defined within the CircAdapt framework, which is achieved by decreasing the contractility of the LV myocardium, such that LVEF≤35%. The CircAdapt model is then used to compute regional ventricular strain patterns and myocardial work as well as global ventricular pump function during LBBB, BiVP and the different LBBAP modalities. Results Selective LBBP is best at restoring mechanical homogeneity in LV contraction as evidenced by simulated wall strains waveforms (Fig 1, Left). NsLBBP increases septal dyssynchrony and introduces small pre-stretch in the LVfw (1.3±0.3%). This effect is more pronounced in LVSP (2.4±1.4%). In BiVP, pre-stretch occurs only in a single LV free wall (LVfw) segment, but all septal segments display a distinct oscillatory pattern. Work load homogeneity (Fig 1, Center) was best restored in sLBBP (4.9±1.1 kPa). NsLBBP lead to reduced homogeneity (4.9±1.8 kPa). LVSP reduced this further (4.8±2.6kPa), while BiVP performed similarly (4.6±2.6kPa) to LVSP. All modalities vastly improved on the baseline LBBB (4.06±5.6 kPa). Hemodynamically (Fig 1, Right), sLBBP showed greatest improvement in LV function (LVESV:-8.1%; LVEF:+6.8%; MLAP:-16.4%; LVdp/dtmax:+12.8%), followed by nsLBBP (LVESV:-7.2%; LVEF:+6.0%; MLAP:-14.5%; LVdp/dtmax:+12.5%), LVSP (LVESV:-5.6%; LVEF:+4.6%; MLAP:-11.7%; LVdp/dtmax:+12.358%) and finally BiVP (LVESV: -4.6%; LVEF:+3.8%; MLAP:-9.3%; LVdp/dtmax:+9.8%) Conclusion We were able to simulate LBBB and subsequent pacing strategies in virtual heart failure patients. This approach allowed direct comparison of mechanical and hemodynamic effects of BiVP and LBBAP modalities without confounding variables. Our results indicate that all LBBAP modalities perform at least similar to bi-ventricular pacing regardless of mechanical viability.

Association Between Segmental Noninvasive Myocardial Work and Microvascular Perfusion in ST-Segment Elevation Myocardial Infarction: Implications for Left Ventricular Functional Recovery and Clinical Outcomes

Predicting left ventricular recovery (LVR) after acute ST-segment elevation myocardial infarction (STEMI) is of prognostic importance. This study aims to explore the prognostic implications of segmental noninvasive myocardial work (MW) and microvascular perfusion (MVP) after STEMI. In this retrospective study, 112 patients with STEMI who underwent primary percutaneous coronary intervention and transthoracic echocardiography after percutaneous coronary intervention were enrolled. Microvascular perfusion was analyzed by myocardial contrast echocardiography, and segmental MW was analyzed by noninvasive pressure-strain loops. A total of 671 segments with abnormal function at baseline were analyzed. The degrees of MVP were observed following intermittent high-mechanical index impulses: replenishment within 4seconds (normal MVP), replenishment >4seconds and within 10seconds (delayed MVP), and persistent defect (microvascular obstruction). The correlation between MW and MVP was analyzed. The correlation of the MW and MVP with LVR (normalization of wall thickening, >25%) was assessed. The prognostic value of segmental MW and MVP for cardiac events (cardiac death, admission for congestive heart failure, or recurrent myocardial infarction) was evaluated. Normal MVP was seen in 70 segments, delayed MVP in 236, and microvascular obstruction in 365. The segmental MW indices were independently correlated with MVP; 244 (36.4%) segments had segmental LVR at 3-month follow-up. Segmental MW efficiency and MVP were independently associated with segmental LVR (P<.05). The χ2 of combination of segmental MW efficiency and MVP was higher than either index alone for identifying segmental LVR (P<.001). At a median follow-up of 42.0months, cardiac events occurred in 13 patients; all regional MW parameters, high sensitivity troponin I, regional longitudinal strain, and so on were associated with cardiac events. Segmental MW indices are associated with MVP within the infarct zone following reperfused STEMI. Both are independently associated with segmental LVR, and regional MW is associated with cardiac events, providing prognostic value in STEMI patients.

Analysis of prevailing pertussis strains from different regions in China after the application of acellular vaccines.

Analysis of prevailing pertussis strains from different regions in China after the application of acellular vaccines.

Strain Rate Changes during Stress Echocardiography Are the Most Accurate Predictors of Significant Coronary Artery Disease in Patients with Previously Treated Acute Coronary Syndrome.

Dobutamine stress echocardiography (DSE) is a well-established non-invasive investigation for the detection of ischemic myocardial dysfunction. The aim of this study was to evaluate the accuracy of myocardial deformation parameters measured by speckle tracking echocardiography (STE) in predicting culprit coronary artery lesions in patients with prior revascularization and acute coronary syndrome (ACS). We prospectively studied 33 patients with ischemic heart disease, a history of at least one episode of ACS and prior revascularization. All patients underwent a complete stress Doppler echocardiographic examination, including the myocardial deformation parameters of peak systolic strain (PSS), peak systolic strain rate (SR) and wall motion score index (WMSI). The regional PSS and SR were analyzed for different culprit lesions. The mean age of patients was 59 ± 11 years and 72.7% were males. At peak dobutamine stress, the change in regional PSS and SR in territories supplied by the LAD showed smaller increases compared to those in patients without culprit LAD lesions (p < 0.05 for all). Likewise, the regional parameters of myocardial deformation were reduced in patients with culprit LCx lesions compared to those with non-culprit LCx lesions and in patients with culprit RCA legions compared to those with non-culprit RCA lesions (p < 0.05 for all). In the multivariate analysis, the △ regional PSS (1.134 (CI = 1.059-3.315, p = 0.02)) and the △ regional SR (1.566 (CI = 1.191-9.013, p = 0.001)) for LAD territories predicted the presence of LAD lesions. Similarly, in a multivariable analysis, the △ regional PSS and the △SR predicted LCx culprit lesions and RCA culprit lesions (p < 0.05 for all). In an ROC analysis, the PSS and SR had higher accuracies compared to the regional WMSI in predicting culprit lesions. A △ regional SR of -0.24 for the LAD territories was 88% sensitive and 76% specific (AUC = 0.75; p < 0.001), a △ regional PSS of -1.20 was 78% sensitive and 71% specific (AUC = 0.76, p < 0.001) and a △ WMSI of -0.35 was 67% sensitive and 68% specific (AUC = 0.68, p = 0.02) in predicting LAD culprit lesions. Similarly, the △ SR for LCx and RCA territories had higher accuracies in predicting LCx and RCA culprit lesions. The myocardial deformation parameters, particularly the change in regional strain rate, are the most powerful predictors of culprit lesions. These findings strengthen the role of myocardial deformation in increasing the accuracy of DSE analyses in patients with prior cardiac events and revascularization.

Measurement of Brain Strains in a Goat Head Under Impact Loading

Abstract Measurements of brain deformations under dynamic loading are required to understand the biomechanics of traumatic brain injury (TBI). In this work, we have experimentally measured two-dimensional (2D) brain deformations in a sacrificed goat brain under injurious impact loading. To facilitate imaging, the goat head was dissected along the longitudinal midline. Goat head response was studied for sagittal plane rotation. Full-field, 2D deformations in the midsagittal plane of a goat brain were obtained at spatiotemporal resolutions of ∼1 mm and 0.4 ms, respectively. Results elucidate the dynamic strain evolution. The goat brain underwent large deformation. The strain pattern was heterogeneous. Peak strains in various brain regions were established within ∼20 ms, followed by negligible strain development due to the considerable viscous dissipation. The Cerebellum region experienced the highest strain, followed by cortical and subcortical regions. Strain concentration in the goat brain near the stiff membrane of the tentorium was observed. The strains in a brain simulant of a head surrogate (obtained previously) were also compared against the goat brain response. A response in the brain simulant was comparable to the goat brain in terms of strain pattern, peak strains in various substructures, and strain concentration near the membrane. However, the brain simulant was less dissipative than the goat brain. These results enhance the current understanding of the biomechanics of the brain under dynamic loading.

Strain Imaging and Ventricular Arrhythmia.

Ventricular arrhythmia is one of the main causes of sudden cardiac death. Hence, identifying patients at risk of ventricular arrhythmias and sudden cardiac death is important but can be challenging. The indication for an implantable cardioverter defibrillator as a primary preventive strategy relies on the left ventricular ejection fraction as a measure of systolic function. However, ejection fraction is flawed by technical constraints and is an indirect measure of systolic function. There has, therefore, been an incentive to identify other markers to optimize the risk prediction of malignant arrhythmias to select proper candidates who could benefit from an implantable cardioverter defibrillator. Speckle-tracking echocardiography allows for a detailed assessment of cardiac mechanics, and strain imaging has repeatedly been shown to be a sensitive technique to identify systolic dysfunction unrecognized by ejection fraction. Several strain measures, including global longitudinal strain, regional strain, and mechanical dispersion, have consequently been proposed as potential markers of ventricular arrhythmias. In this review, we will provide an overview of the potential use of different strain measures in the context of ventricular arrhythmias.

Dynamic compression behavior of CoCrFeMnNi high-entropy alloy fabricated by direct energy deposition additive manufacturing

High-entropy alloys (HEAs) have attracted significant interest in recent years because of their unique physical properties, which make them suitable for usage in extreme environments. The fabrication of HEAs using metal additive manufacturing (MAM) has shown potential for improving their performance. This study investigates the mechanical properties of CoCrFeMnNi HEA manufactured through direct energy deposition using compression tests conducted at various strain rates ranging from quasi-static to dynamic (10−4 - 4200 s−1). The effect of the strain rate on the mechanical properties was analyzed, and a Johnson-Cook constitutive model was employed to simulate the dynamic compression test using the finite element method. The temperature and strain distributions during high-strain-rate compression were analyzed, reflecting the local temperature rise in the finite element analysis. The comparison of the strain distribution results of the simulation and microstructure after deformation showed that the microstructural behavior was influenced by strain localization, which occurred more prominently at the edge of the material. Because the CoCrFeMnNi HEA had a low stacking fault energy, twin formation was accelerated at high strain rate deformation by easily overcoming the critical twinning stress. The edge region, where strain localization was activated, exhibited a higher twin fraction than the central region (uniform deformation). The partitioned strain in the edge region was absorbed by twin formation, effectively suppressing the formation of the adiabatic shear band. These findings present significant implications for the design and development of MAM-processed HEAs with improved mechanical properties under extreme environments.

Changes in Computed-Tomography-Derived Segmental Left Ventricular Longitudinal Strain After Transcatheter Aortic Valve Implantation

Patients with severe aortic stenosis (AS) may show left ventricular (LV) apical longitudinal strain sparing. Transcatheter aortic valve implantation (TAVI) improves LV systolic function in patients with severe AS. However, the changes in regional longitudinal strain after TAVI have not been extensively evaluated. This study aimed to characterize the effect of the pressure overload relief after TAVI on LV apical longitudinal strain sparing. A total of 156 patients (mean age 80 ± 7years, 53% men) with severe AS who underwent computed tomography before and within 1year after TAVI (mean time to follow-up 50 ± 30days) were included. LV global and segmental longitudinal strain were assessed using feature tracking computed tomography. LV apical longitudinal strain sparing was evaluated as the ratio between the apical and midbasal longitudinal strain and was defined as an LV apical to midbasal longitudinal strain ratio >1. LV apical longitudinal strain remained stable after TAVI (from 19.5 ± 7.2% to 18.7 ± 7.7%, p=0.20), whereas LV midbasal longitudinal strain showed a significant increase (from 12.9 ± 4.2% to 14.2 ± 4.0%, p ≤0.001). Before TAVI, 88% of the patients presented with LV apical strain ratio >1% and 19% presented with an LV apical strain ratio >2. After TAVI, these percentages significantly decreased to 77% and 5% (p=0.009, p ≤0.001), respectively. In conclusion, LV apical sparing of strain is a relatively common finding in patients with severe AS who underwent TAVI and its prevalence decreases after the afterload relief after TAVI.

The mechanism of the present-day crustal deformation in southeast Tibet: from numerical modelling and geodetic observations

SUMMARY The mechanism of present-day crustal deformation in southeast Tibet remains controversial. 3-D high-precision geodetic data can provide significant clues to analyse the key driving forces. Here, we conduct a series of 3-D finite-element modelling to investigate the influences of gravitational collapse, tectonic extrusion and mid-to-lower crustal flow on crustal deformation in southeast Tibet. The numerical results show that the gravitational collapse leads to predominant N-S extension and surface subsidence in the northern region, and predominant NW-SE compression and uplift in the southern region, which can explain the normal-faulting earthquakes in the interior. The gravity-driven horizontal velocity depends on the upper crustal viscosity, while the vertical velocity is determined by mid-to-lower crustal viscosity. The eastward tectonic extrusion causes slight southeastward rotation and predominant E-W compression in the northern region but has a little effect on the deformation in the southern region. By considering the joint effects of gravitational collapse and tectonic extrusion, we simulate the crustal deformation that reconciles with present-day geodetic observations. Both the two driving forces lead to positive shear strain rates along the major fault zones, with more contributions from the tectonic extrusion of the Tibetan Plateau. Constrained by the 3-D geodetic observations, the numerical results argue against the presence of massive fast mid-to-lower crustal flow from the Tibetan Plateau. Overall, the present-day crustal deformation in southeast Tibet is jointly driven by gravitational collapse and tectonic extrusion, which play distinct roles in shaping the faulting kinematics and regional strain partitioning.

Finite element analysis of material deformation behaviour during DRECE: the sheet metal SPD process

The material deformation behaviour during the innovative SPD process called DRECE (Dual Rolls Equal Channel Extrusion) has been analysed by FEM simulations. In the process, a workpiece in the form of a strip is subjected to plastic deformation by passing through the angular channel; however, the workpiece dimensions remain the same after a pass is finished. Performing consecutive passes allow for increasing the effective strain in the material to a required level. In the conducted simulations two various channel angles (108° and 113°) have been taken into consideration, as well as two processing routes, A and C (without and with turning the strip upside-down between consecutive passes, respectively). The analysis of simulation results has revealed that significant strain and stress inhomogeneities across the strip thickness are generated in a single DRECE pass. The die design (the inner and outer corner radius) and friction conditions affect the material flow, reducing significantly the shear strain in the near-surface regions of the strip. The strain inhomogeneity can be effectively reduced by choosing the processing route C. The strain distributions and the corresponding tensile test results have confirmed that the smaller channel die angle allows to generate larger strain and higher strength of the strip but also reduces its ductility more than the die setup with the larger channel die angle.

The novel left atrial appendage strain parameters are associated with thrombosis risk in patients with non-valvular atrial fibrillation.

We sought to explore a novel left atrial appendage (LAA) strain parameter which could represent the cumulative adverse impact of chronic Atrial fibrillation (AF) on the LAA function, and the relationship between the LAA strain parameter and thrombosis risk in patients with non-valvular AF. We enrolled 268 patients with non-valvular AF and 58 sinus rhythm subjects who underwent transesophageal echocardiography in the study. LAA longitudinal strain amplitude (LAA LSA) was defined as the sum of the value of the maximum positive peak strain (LAA PLS) and the absolute value of the minimum negative peak strain (LAA NLS). Dense spontaneous echo contrast (SEC) was defined as grade 3 or 4 SEC. Compared to sinus rhythm group, the global LAA strain parameters were significantly lower in paroxysmal AF (n = 148), and the lowest of them were found in persistent AF (n = 120), which suggested that the global LAA strain parameters could evaluate LAA function in sinus rhythm, paroxysmal AF and persistent AF. Compared with patients in AF without SEC/thrombus (n = 113), the regional and global LAA strain parameters were significantly depressed in AF with SEC/thrombus (n = 155). Multivariate logistic regression analyses showed that LAA global LSA (OR 0.768; 95% CI:0.569, 0.970; p = 0.027) was an independent predicter of the SEC/thrombus. Compared with patients in AF without dense SEC or thrombus (n = 210), the regional and global LAA strain parameters were significantly impaired in the patients with dense SEC/thrombus(n = 58). LAA global LSA (AUC 0.884) had the best predictable accuracy for dense SEC or thrombus, and outperformed LAA PLS, LAA NLS, CHA2DS2-VASc score and conventional LAA functional parameters that have been used in the evaluation blood flow stasis in LAA. LAA LSA showed excellent interobserver and intra-observer agreement beyond LAA PLS and LAA NLS. The novel LAA strain parameters, which were feasible and reproducible parameters for evaluation LAA mechanic function, had good predictive accuracy for blood flow stasis in LAA beyond conventional LAA functional parameters.

Molecular epidemiology of enterically colonizing Escherichia coli with resistance against third-generation cephalosporins isolated from stool samples of European soldiers with concomitant diarrhea on deployment in Western African Mali.

Extended spectrum beta-lactamases (ESBL) are frequently found in Enterobacterales isolates from Western Africa. However, information on the molecular epidemiology of regional ESBL-positive Enterobacterales strains is scarce. In order to provide epidemiological information, ESBL-positive Escherichia coli isolates from stool samples of European soldiers with diarrhea deployed to a field camp in Mali were subjected to whole-genome sequencing (Illumina MiSeq and Oxford Nanopore MinION) and antimicrobial susceptibility testing. With two exemptions, sequence-based analysis suggested an absence of transmission events between soldiers as indicated by a high genetic diversity of isolates and sequence types, confirming previous rep-PCR results. Third-generation cephalosporin resistance was associated with the presence of blaCTX-M-15 genes with (n = 14) and without (n = 5) co-occurring blaTEM-1b genes. Between 0 and 6 virulence and resistance plasmids per isolate were recorded. The detected resistance plasmids could be categorized into five types, which, in turn, share different sequence-identical segments, representing particular antimicrobial resistance gene-associated mobile genetic elements (MGEs). Phenotypic resistance rates within the 19 assessed isolates that showed distinguishable colony morphologies were 94.7% (18/19) against ampicillin-sulbactam and trimethoprim/sulfamethoxazole, 68.4% (13/19) against moxifloxacin, 31.6% (6/19) against ciprofloxacin, 42.1% (8/19) against gentamicin, 31.6% (6/19) against tobramycin, and 21.1% (4/19) against piperacillin-tazobactam and fosfomycin. Virulence-associated genes mediating infectious gastroenteritis were rarely detected. The gene aggR, which is characteristic for enteroaggregative E. coli, was only detected in one single isolate. In summary, we found a variety of different strains and clonal lineages of ESBL-carrying E. coli. Transmission either between soldiers or from common contaminated sources was demonstrated in two cases and played only a minor role in this military field camp, while there were indications that resistance gene bearing MGEs had been exchanged between antimicrobial resistance gene-(ARG-)carrying plasmids.

Immunological and genetic analysis of vaccine strains and regional variants of infectious bronchitis virus is examined.

Abstract Infectious bronchitis virus (IBV) is an acute and highly contagious coronavirus characterized by respiratory and systemic pathology in chickens. Frequent genetic mutation in the spike (S) glycoprotein repeatedly induces regional variants. Although IBV vaccines are extensively utilized in chicken flocks, their efficacy is diminished by variant serotypes and poor cross-protection. To provide restored strategy for the IBV protection, we analyzed the genetic distance between local IBV variants and other coronaviruses, including SARS-CoV-2. We also compared the genetic sequence of the S1 glycoprotein in three commercial vaccine strains. Then, we examined immune responses by vaccine and regional strains in primary chicken embryonic kidney cells and splenocytes. Featured pathways for innate immunity and gene expressions for innate immune response was observed. Our study is expected to provide valid information for vaccine development against emerging variants. Supported by funding from the office of Research Support, Kangwon National University, a 2020 Research Grant from Kangwon National University (no. 520200065), and a National Research Foundation of Korean (NRF) grant funded by the Korea government (MSIT) (no. 2020R1G1A1099715)

PO-01-095 REGIONAL DIFFERENCES IN ATRIAL FIBER STRAINS IN HEART FAILURE PATIENTS WITH AND WITHOUT ATRIAL FIBRILLATION

Left atrial (LA) strain is inhibited by atrial fibrosis, which is a hallmark of atrial fibrillation (AF). Retrospective gated computed tomography (CT) imaging with feature tracking (FT) can measure three-dimensional (3D) local LA strain. Atrial myocardial fiber directions may play an important role in preferred deformation, and therefore atrial fiber strains should be considered. Using the average endocardial fiber architecture from seven hearts imaged ex vivo with high resolution diffusion-tensor magnetic resonance imaging (DT-MRI), the endocardial fiber strain can be measured. To investigate regional and global differences in atrial endocardial fiber strains between heart failure (HF) patients with and without AF. 30 HF patients underwent 10-frame gated CT imaging, and FT was used to measure local endocardial fiber strain (Fig. A). The LA body was classified into five regions using Universal Atrial Coordinates (Fig. B). Global and regional strains were reported as the mean strain over the entire LA body surface and within each region, respectively. The fiber strain range over the cardiac cycle was used to stratify between HF patients with and without AF. The left ventricular ejection fraction (LVEF) and left atrial ejection fraction (LAEF) were calculated from the gated CT images. HF patients with AF had smaller global fiber strain ranges than those without AF (5.9 ± 3.7 % vs 14.2 ± 8.9 %, p = 0.011) (Fig. C). All regions had higher strain ranges in HF patients without AF and the anterior wall exhibited the most significant difference between groups (7.8 ± 4.1 vs 17.9 ± 10.6, p = 0.009). ROC analysis using global strain range to stratify between patient groups gave an AUC of 0.853 (Fig. D). The anterior wall was the region with the highest AUC of 0.842. LVEF was similar between patient groups (p=0.682), however LAEF differed (p=0.002) (Fig. E). Patients with AF had decreased fiber strain ranges globally and regionally compared to those without AF. Strain range in the anterior wall most significantly decreased in the presence of AF, which may suggest a regionally higher fibrosis burden. The LVEF was similar between HF patients with and without AF, however the LAEF differed, which suggests strain differences were driven by LA dysfunction.

Reduced inferior wall longitudinal strain is associated with malignant arrhythmias in non-ischemic heart failure.

Reduced systolic myocardial function in the inferior region of the left ventricle has been suggested to be associated with malignant arrhythmias. We tested this hypothesis in patients with non-ischemic heart failure. Patients with non-ischemic heart failure (left ventricular ejection fraction [LVEF]<35%) were evaluated by 2D-speckle-tracking echocardiography. The regional longitudinal strain was calculated for each of the six left ventricular walls. The reduced regional function was defined as strain below the median. The outcome was a composite of sudden cardiac death, admission with sustained ventricular arrhythmia, resuscitated cardiac arrest, and appropriate therapy from a primary prophylactic implantable cardioverter defibrillator. Time-to-first-event analysis was performed using a Cox model. From two centers, 401 patients were included (median age: 63 years, 72% male) with a median LVEF of 25% (interquartile range [IQR] 20;30), and a median inferior wall strain of -9.0% (-12.5; -5.4). During a median follow-up of 4.0 years, 52 outcomes occurred. After multivariate adjustment for clinical and electrocardiographic parameters, inferior wall strain was independently associated with the outcome (HR 2.50 [1.35; 4.62], p=.003). No independent association was found between the composite outcome and reduced strain in any of the other left ventricular walls, Global Longitudinal Strain (HR 1.66 [0.93; 2.98], p=.09), or LVEF (HR 1.33 [0.75; 2.33], p=.33). Below median strain in the left ventricular inferior region was independently associated with a 2.5-fold increase in the risk of malignant arrhythmias and sudden cardiac death in patients with non-ischemic heart failure.

Simulating hyperelasticity and fractional viscoelasticity in the human heart

Biomechanics plays an important role in the diagnosis and treatment of pathological conditions of the heart. Computational models are paving the way for personalized therapeutic treatment but they rely on accurate constitutive equations for predicting their biomechanical behavior. Even so, viscoelasticity remains under-explored in computational modeling despite experimental observations. To facilitate the viscoelastic modeling of cardiovascular soft tissues, we previously developed a fractional viscoelastic modeling approach, which extends existing hyperelastic models. This has comparable computational costs to the conventional hyperelastic model and only requires two additional material parameters for the viscoelastic response. This approach was demonstrated to be able to accurately capture the viscoelastic response of the human myocardium. However, the numerical properties of this fractional viscoelastic approach have not yet been examined. In this work, we present its implementation in Finite Element Analysis, examine its numerical properties in uniaxial extension and 2D inflation test examples, and examine its physiological implication in a computational model of an idealized left ventricle in a fully idealized circulatory system. Optimal convergence properties were observed and the importance of viscoelasticity during passive filling, ventricular motion, and regional fiber strain and stresses were explained.

Strain-Dependent Morphology of Reactive Astrocytes in Human- and Animal-Vole-Adapted Prions.

Reactive astrogliosis is one of the pathological hallmarks of prion diseases. Recent studies highlighted the influence of several factors on the astrocyte phenotype in prion diseases, including the brain region involved, the genotype backgrounds of the host, and the prion strain. Elucidating the influence of prion strains on the astrocyte phenotype may provide crucial insights for developing therapeutic strategies. Here, we investigated the relationship between prion strains and astrocyte phenotype in six human- and animal-vole-adapted strains characterized by distinctive neuropathological features. In particular, we compared astrocyte morphology and astrocyte-associated PrPSc deposition among strains in the same brain region, the mediodorsal thalamic nucleus (MDTN). Astrogliosis was detected to some extent in the MDTN of all analyzed voles. However, we observed variability in the morphological appearance of astrocytes depending on the strain. Astrocytes displayed variability in thickness and length of cellular processes and cellular body size, suggesting strain-specific phenotypes of reactive astrocytes. Remarkably, four out of six strains displayed astrocyte-associated PrPSc deposition, which correlated with the size of astrocytes. Overall, these data show that the heterogeneous reactivity of astrocytes in prion diseases depends at least in part on the infecting prion strains and their specific interaction with astrocytes.

Strike-slip influenced stratigraphic and structural development of the Foula Sandstone Group, Shetland: implications for offshore Devonian basin development on the northern UK continental shelf

The island of Foula, located 25 km SW of Shetland, preserves a gently folded, 1.6 km thick sequence of Middle Devonian sandstones spectacularly exposed in kilometre-long cliff sections &gt;350 m high. These rocks unconformably overlie likely Precambrian-age amphibolite facies basement rocks that are intruded by sheeted granites. The onshore succession is similar in age to the nearby Lower Clair Group offshore to the west. New mapping, incorporating the use of drone imagery in the inaccessible cliff sections, uses down-plunge projections to show that growth folding and faulting on Foula were contemporaneous with sedimentation during basin filling. The large-scale structural geometry is consistent with the regional constrictional strain due to the sinistral transtension associated with movements along the Walls Boundary–Great Glen fault zone system during the Mid-Devonian. Detrital zircon provenance studies indicate that the Devonian sequences of Foula (and nearby Melby in western Shetland) show similarities with the Clair Group and Orkney successions. We suggest that NE–SW transtensional fold development contemporaneous with regional subsidence in the Devonian basins of Scotland may be more widespread than previously realized. Large, kilometre-scale folds previously interpreted to be related to Permo-Carboniferous inversion may therefore have initiated earlier in the basin evolution sequence than previously realized. Supplementary material: Appendices A, Methodologies; B, Regional stratigraphic correlation table; C, Heavy mineral data; D, Detrital zircon data; and E, 3D virtual outcrop models are available at https://doi.org/10.6084/m9.figshare.c.6442552