Inverse identification of hyperelastic constitutive parameters of skeletal muscles via optimization of AI techniques.

Studies on the deformation characteristics and stress distribution in loaded skeletal muscles are of increasing importance. Reliable prediction of hyperelastic material parameters requires an inverse process, which possesses challenges. This work proposes two inverse procedures to identify the hyperelastic material parameters of skeletal muscles. The first one integrates nonlinear finite element method (FEM), random forest (RF) model, and Bayesian optimization (BO) algorithm. The other one integrates FEM, RF and hybrid Grid Search (GS), and Random Search (RS) algorithm. FEM models are first established to simulate nonlinear deformation of skeletal muscles subject to compression based on nonlinear mechanics principals. A dataset of nonlinear relationship between the nominal stress and principal stretch of skeletal muscles is created using our FEM models and the nonlinear relationship is learned through RF model. The BO, hybrid GS and RS algorithms are used to adjust the major model parameters in RF. Then the optimized RF is utilized to predict hyperelastic material parameters of skeletal muscles, with the help of uniaxial compression experiments. Intensive studies also have been carried out to compare the RF-BO approach with RF-Search approach, and the comparison results show that RF-BO approach is an effective and accurate approach to identify the hyperelastic material parameters of skeletal muscles. The present RF-BO model can be further extended for the predictions of constitutive parameters of other types of nonlinear soft materials.

Bone remodeling analysis for a swine skull at continuous scale based on the smoothed finite element method.

In order to study bone response during chewing, bone remodeling analysis at a continuous scale is performed to a swine skull obtained using µCT. The smoothed finite element method (S-FEM) is utilized to replace the finite element method (FEM) in bone remodeling as it is solving the "overly-stiff" problem in FEM by introducing strain smoothing technology to soften the stiffness matrix. Three S-FEM models with different levels of softening effects are developed, including node-based, edge-based, and face-based, which leads to various bone remodeling results for a better understanding of the remodeling process. During the remodeling process, the strain energy density is used as the mechanical stimulus, and the surface elements or smoothing domains are regarded as cortical bone. Under the action of mechanical stimuli, cortical bone and cancellous bone have been remodeled. In remodeling progress, ES-FEM shows close results as compared with the experimental µCT in nodal bone density distribution, FEM and FS-FEM are close to the µCT experimental model in average nodal density. In summary, the combined use of several methods provides more angles for the description of bone remodeling.

Perfectly matched layer absorbing boundary conditions for Euler equations with oblique mean flows modeled with smoothed particle hydrodynamics.

Absorbing boundary conditions (ABCs) play a critical role in the simulation of sound or wave propagation problems. This paper proposes a technique of space-time transformed perfectly matched layer (PML) boundary condition implemented in a widely used mesh-free method called smoothed particle hydrodynamic (SPH) method, to absorb the outgoing sound waves with oblique shear mean flow. Special consideration is given to the particle features of the SPH, and the PMLs are formulated to correct the truncation error of SPH and absorb the outgoing wave at the same time, aiming to reduce the storage and computational cost in the infinite computational domain. Because the group velocity and phase velocity of the outgoing sound waves in the PMLs may be in different directions, exponentially growing pseudo reflections can result. The authors thus employ space-time transformation to eliminate the reflections effectively in PML boundaries for stable solutions. Moreover, a uniform framework of PML absorbing boundary conditions for Euler equations in the cases of arbitrary oblique mean flow and static media is derived. Finally, the present PML-SPH method with this stable absorbing boundary is applied to simulate sound waves propagating with mean flow. The obtained numerical results agree very well with the reference results.

A high-fidelity 3D S-FEM stress analysis of a highly heterogeneous swine skull.

Fracture healing and growth of the bones are highly related to the stress level. Numerical analysis of stresses is the most effective means to determine the stress level, but it usually requires sufficient resolution to ensure an accurate description of geometry features of bones. In this paper, high-fidelity smoothed finite element method (S-FEM) skull models are created using computed tomography (CT) and micro-computed tomography (µCT) images of a juvenile pig skull. The material properties of the heterogeneous bone are modeled by a varying distribution of Young's modulus mapped to each element and smoothing domain to accurately capture the high heterogeneity. Different types of S-FEM models, including node-based, edge-based, and face-based, are developed for this high-fidelity modeling work. It is found that S-FEM has higher accuracy, in terms of displacements, stresses, and strain energy, compared to the traditional finite element method (FEM). Graphical abstract.

A compact perfectly matched layer algorithm for acoustic simulations in the time domain with smoothed particle hydrodynamic method.

This paper focuses on the development of absorbing boundary conditions and their implementation in the smoothed particle hydrodynamics (SPH) method for wave propagation problems. A compact perfectly matched layer (C-PML) approach is formulated for transient acoustic problems in an infinite space using SPH models with a computational domain of finite dimensions. The proposed approach is based on the concept of fictitious physical damping acting within the additional perfectly matched layers (PMLs) to absorb outgoing waves to practically eliminate the reflection of waves from the boundary of the finite computational domain. To reduce the amount of computations resulting from the layers and improve the computational stability with respect to time, the C-PML algorithm uses the time exponential differencing scheme with small PML domains implemented in an SPH code for transient analyses of waves propagating in acoustic media. Tests of Gaussian pulse sound wave propagation are conducted to demonstrate the effectiveness of the proposed algorithm. The results show that the C-PML algorithm with SPH can absorb the outgoing wave with fewer layers than the conventional PML algorithm. The influence of the thickness of the PML layers, attenuation coefficient, and smoothing length on the C-PML algorithm are analyzed.

[Application and analysis of abdominal aortic branch malperfusion pattern in thoracic endovascular aortic repair for Stanford B aortic dissection].

OBJECTIVE: To evaluate the efficiency of thoracic endovascular aortic repair (TEVAR) in dealing with abdominal aortic branch malperfusion based on the analysis of aortic computed tomography angiography (CTA) images in pre- and post-TEVAR. METHODS: Retrospective analysis from September 2015 to March 2016 in single institution to 32 patients, diagnosed as Stanford B aortic dissection with abdominal aortic branch malperfusion, CTA images in pre- and post-TEVAR were collected. Based on the aortic branch malperfusion pattern redefined by Nagamine, we identified and characterized branch malperfusion pattern for four abdominal aortic branches (celiac trunk, superior mesenteric artery, bilateral renal artery) in statistical analysis. RESULTS: In the four abdominal aortic branches (total 128 branches), 86 branches (67.2%) expressed with Class I patterns, in which subtype I-b presented with 0.8%, subtype I-c with 5.5%; 14 branches (10.9%) expressed with Class II patterns, in which subtype II-b-1 with 3.9%, subtype II-b-2 with 3.1%; 16 branches (12.5%) expressed with Class III patterns, all with subtype III-a, no subtype III-b and III-c presented. The remaining 12 branches were normal. The 100% successful rate of TEVAR obtained in 32 patients performed. The mean following-up was 4 months. Aortic CTA showed that among the 14 "high-risk" abdominal aortic branch malperfusion, 13 (92.9%) with obvious branch malperfusion in post-TEVAR were observed to improve, and the remaining one branch malperfusion (7.1%) was observed to change from subtype I-b to I-c. CONCLUSION: Few ratios in abdominal aortic branches suffered with obvious malperfusion complicated by Stanford B aortic dissection. For branches with "high-risk" malperfusion pattern, optimal changes were observed in abdominal aortic branch without revascularization in post-TEVAR, as well other branches with non-"high-risk" pattern perfusion were mostly stable in post-TEVAR. It could be of profound benefit to extend branch malperfusion patterns redefined by Nagamine in clinical practice to assess aortic dissection and in further guide for revascularization or not.

Insulin-like growth factor I reduces the occurrence of necrotizing enterocolitis by reducing inflammatory response and protecting intestinal mucosal barrier in neonatal rats model.

OBJECTIVE: To observe the effect of enteral supplement of insulin-like growth factor I (IGF-1) on dynamic changes of TLR4, NF-κB, IL-6, SIgA and MUC2 in intestinal tissues of neonatal rats, and to investigate the protective effects and possible mechanisms of IGF-1 on necrotizing enterocolitis (NEC). MATERIALS AND METHODS: Specific pathogen free (SPF) neonatal Sprague Dawley (SD) rats aged 3 days old were randomly divided into 3 groups, namely, normal control group, NEC model group and IGF-1 intervention group. In NEC group, the neonatal NEC rat models were established using artificial feeding, hypoxia and cold stimulation. In IGF-1 intervention group, the models were established by means of artificial feeding plus hypoxia and cold stimulation, and IGF-1 (22 ug/L) at a physiological concentration similar to the breast milk was added to milk replacer for intervention. The rats in the three groups were killed after the blood was collected from the heart at 24, 48 and 72 h, respectively, following the establishment of models; then, 3 cm of the terminal ilea were dissected and used for histopathological examination, RT-PCR and ELISA studies after hematoxylin and eosin (HE) staining. RESULTS: Symptoms in IGF-1 intervention group were significantly relieved, and the incidence rate of NEC was lowered remarkably. In NEC model group, the peak expression of TLR4 mRNA occurred later than that of NF-κB mRNA and IL-6, and the expressions of TLR4 mRNA, NF-κB mRNA and IL-6 were decreased at 72 h after IGF-1 intervention. In NEC model group, the expression of MUC2 showed a transient decrease, the expression of SIgA was on the decline, but the expressions of MUC2 and SIgA were increased after IGF-1 intervention. CONCLUSIONS: The enteral administration of IGF-1 at a physiological concentration can ameliorate the clinical symptoms in neonatal NEC rat models and decrease the occurrence rate. The possible mechanism is that IGF-1 down-regulates the TLR4 mRNA expression to inhibit the production of inflammatory mediators, and it up-regulates the expressions of MUC2 and SIgA to protect the mechanical and immuno-barrier functions of the intestinal mucous.

[Efficacy of endovascular repair in patients with abdominal aortic aneurysm complicating acute aortic syndrome].

OBJECTIVE: To evaluate the efficacy of simultaneous thoracic endovascular aortic repair (TEVAR) and endovascular aneurysm repair (EVAR) on abdominal aortic aneurysm (AAA) patients complicating acute aortic syndrome (AAS). METHODS: Data of 17 patients (16 men, mean age (65.2±6.9) years old) , who underwent simultaneous TEVAR and EVAR between September 2010 and June 2015 in Beijing Anzhen Hospital, were retrospectively reviewed.All patients were diagnosed with concomitant AAA and AAS by preoperative CTA.All abdominal aortic lesions were AAA and all thoracic aortic lesions were AAS.Under local anesthesia, simultaneous TEVAR and EVAR were performed and emergent simultaneous endovascular repair was performed in 2 patients.Follow up was made at 1 month, 3 months, 6 months, and yearly after the procedure.Procedure success rate, procedure related complications were evaluated. RESULTS: Procedure was successful in all patients.The length of thoracic coverage was (21.0±4.6) cm.The operation time was 150(120, 170) min, and the hospitalization time was 7 (6, 12) d. After a mean of 27.0(5.5, 44.5) months follow up, there were no acute cardiopulmonary complications and contrast induced nephropathy.One patient developed spinal cord ischemia and resolved after treatment.One patient was died for aneurysm rupture at 6 months post operation.One patient developed type Ⅰb endoleak for expansion of right iliac artery at 9 months post operation and was successfully sealed by iliac stent-graft extension. CONCLUSIONS: Combined TEVAR and EVAR can be performed successfully in patients with AAA complicating AAS.When anatomically feasible, simultaneous TEVAR and EVAR can be considered as a effective and safe therapy alternative to patients with multilevel aortic diseases.

Review of molecular and mechanical interactions in the aortic valve and aorta: implications for the shared pathogenesis of aortic valve disease and aortopathy.

Aortic valve disease (AVD) and aortopathy are associated with substantial morbidity and mortality, representing a significant cardiovascular healthcare burden worldwide. These mechanobiological structures are morphogenetically related and function in unison from embryonic development through mature adult tissue homeostasis, serving both coordinated and distinct roles. In addition to sharing common developmental origins, diseases of the aortic valve and proximal thoracic aorta often present together clinically. Current research efforts are focused on identifying etiologic factors and elucidating pathogenesis, including genetic predisposition, maladaptive cell-matrix remodeling processes, and hemodynamic and biomechanical perturbations. Here, we review the impact of these processes as they pertain to translational research efforts, emphasizing the overlapping relationship of these two disease processes. The successful application of new therapeutic strategies and novel tissue bioprostheses for AVD and/or aortopathy will require an understanding and integration of molecular and biomechanical processes for both diseases.

Production of secoisolariciresinol from defatted flaxseed by bacterial biotransformation.

AIMS: Secoisolariciresinol (SECO) is increasingly recognized for potential clinical application because of its preventive effects against breast and colon cancers, atherosclerosis and diabetes, and its production through biotransformation has been attempted. However, previously reported bacteria all required stringent anaerobic culture conditions, precluding large-scale production. Here, we report the isolation and characterization of bacteria that produce SECO under less stringent anaerobic culture conditions. METHODS AND RESULTS: Using defatted flaxseed as raw material, we isolated a facultative anaerobic bacterium from human faeces that hydrolysed secoisolariciresinol diglucoside-3-hydroxy-3-methyl glutaric acid (SDG-HMGA) oligomers in flaxseed to produce SECO. Both conventional assays and 16S rRNA gene sequence analysis demonstrated its close relatedness with Bacteroides uniformis. The transformation efficiency of SDG in defatted flaxseed to SECO was more than 80% by this bacterial strain. We investigated factors that might influence fermentation, such as redox potential and pH, for large-scale fermentation of defatted flaxseed to produce SECO. CONCLUSIONS: The method to produce SECO through biotransformation of defatted flaxseed with this bacterial strain is highly efficient and economic. SIGNIFICANCE AND IMPACT OF THE STUDY: This bacterial strain can transform SDG to SECO under less stringent anaerobic culture conditions, which will greatly facilitate industry-scale production of SECO.

Levels and profiles of unintentionally produced persistent organic pollutants in surface soils from Shanxi province, China.

Six species of unintentionally produced persistent organic pollutions comprised of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, polychlorinated naphthalenes, hexachlorobenzene and pentachlorobenzene in soils collected from Shanxi province, China were determined. The sum toxic equivalent ranged from 0.14 to 2.20 with an average of 0.94 pg TEQ/g. Polychlorinated dibenzo-p-dioxins/furans contributed the most toxic proportion to the total toxic equivalent. CB-126 was the most toxic contributor to polychlorinated biphenyls. CN66/67 and CN73 are the dominant toxic congeners to polychlorinated naphthalenes. From the patterns, it was speculated that thermal related industries were possible sources of unintentionally produced persistent organic pollutions.

Identification and validation of quantitative trait loci conferring tan spot resistance in the bread wheat variety Ernie.

Tan spot, caused by Pyrenophora tritici-repentis, is a foliar disease of wheat, and it can inflict serious reduction in grain yield and quality. The bread wheat variety Ernie was found to be immune to this disease in Australia, and its genetic control was investigated by quantitative trait loci (QTL) analysis using a doubled haploid population. Eight QTL were identified in this population from three independent trials, and four of them were derived from the parent Ernie. The most significant QTL was located on chromosome arm 2BS, explaining 38.2, 29.8 and 36.2% of the phenotypic variance, respectively, in these trials. The effects of the 2BS QTL were further validated in four additional populations. The presence of this single QTL reduced disease severity by between 29.2 and 67.1% with an average of 50.5%. The significant effects of this QTL and its consistent detection across all the trials with different genetic backgrounds make it an ideal target for breeding programmes as well as for its further characterization. Data from this study also showed that neither plant height nor heading date significantly affects tan spot resistance.

Identifiable range of osseointegration of dental implants through resonance frequency analysis.

This paper aims to determine the identifiable stiffness range of interfacial tissue of dental implants by means of resonance frequency analysis. Two structural models of the Implant-Tissue-Bone system are built and the lowest two resonance frequencies of these two models are analyzed by Finite Element Method in the software Abaqus. The effects of four key parameters, i.e. the geometry, boundary constrain, material property of the bone and the interfacial tissue, to the resonance frequencies are examined in great detail. An intensive parametric study is conducted to reveal quantitative relationships between the resonance frequencies and these parameters. It is found that when the Young's modulus of the interfacial tissue is less than 15MPa, the resonance frequencies are dominantly affected by the interfacial tissue but not the other three parameters. This finding is extremely important to imply that the lowest two resonance frequencies of the Implant-Tissue-Bone system can be accurately determining the osseointegration of dental implants without worrying about all the other factors, as long as the Young's modulus of the interfacial tissue is in the range of 1-15MPa. However, beyond this range the measured resonance frequencies are affected by all these parameters, and need to be properly interpreted.

The mutL mutation in Pseudomonas aeruginosa isolates reveals multidrug-resistant traits and possible evolutionary trends.

To evaluate the genetic differences and possible evolutionary trends of clinical multidrug-resistant (MDR) strains, Pseudomonas aeruginosa isolates were characterized by pulsed-field gel electrophoresis (PFGE) and evolutionary distances were estimated. A total of 85.7% of the P. aeruginosa isolates were MDR strains. Strains with the PFGE pattern A predominated; all were susceptible to amikacin and cefepime but resistant to levofloxacin and meropenem (except strain PA45 which was sensitive to meropenem). PFGE pattern H or P strains exhibited resistance to six to eight different antibiotics. PFGE pattern I or J strains were susceptible to all antibiotics tested. Two imperfect six base-pair tandem repeats, CTGGCG and CTGGCC, were found in the mutL gene. In conclusion, MDR characteristics and PFGE profiles were clearly correlated with the mutL phylogenetic tree. This indicates that mutations in mutL might contribute to genetic stability in adaptation by changing the MDR traits. Phylogenetic analysis of mutL revealed the MDR relatedness of P. aeruginosa strains.

Identification of infarct core and penumbra in acute stroke using CT perfusion source images.

BACKGROUND AND PURPOSE: CT perfusion (CTP) mapping has been reported to be useful in the differentiation of the infarct core and ischemic penumbra. However, the value of the CTP source imaging (CTP-SI) during the arterial and venous phases has not been fully investigated. The purpose of this study was to develop a CTP-SI methodology for acute ischemic stroke and compare its efficacy with cerebral blood flow (CBF) and cerebral blood volume (CBV) in predicting infarct core and penumbra. MATERIALS AND METHODS: CT examinations, including non-contrast-enhanced CT, CTP, and CT angiography (CTA), were performed in 42 patients with symptoms of stroke for <9 hours. The Alberta Stroke Program Early CT Score (ASPECTS) was analyzed on the arterial phase CTP-SI and venous phase CTP-SI and then compared with the ASPECTS on CBF and CBV for efficacy assessment. RESULTS: The ASPECTS on the arterial phase CTP-SI was closely correlated with the ASPECTS on CBF, the Pearson correlation coefficient was 0.88 (P < .001), and the concordance correlation coefficient was 0.7603 (95% confidence interval [CI], 0.6331-0.8476). The ASPECTS on the venous phase CTP-SI revealed a significant correlation with the ASPECTS on CBV, the Pearson correlation coefficient was 0.92 (P < .001), and the concordance correlation coefficient was 0.8880 (95% CI, 0.8148-0.9334). Significant differences were shown between the arterial phase CTP-SI/ venous phase CTP-SI (P < .001) and CBF/CBV (P < .001). CONCLUSIONS: This study provides preliminary evidence that the arterial phase and venous phase CTP-SI mismatch model could possibly be applied to ischemic regions in the acute stage of stroke to determine penumbra and infarct core.

Transport of biomolecules in asymmetric nanofilter arrays.

We propose a theoretical model for describing the electric-field-driven migration of rod-like biomolecules in nanofilters comprising a periodic array of shallow passages connecting deep wells. The electrophoretic migration of the biomolecules is modeled as transport of point-sized Brownian particles, with the orientational degree of freedom captured by an entropy term. Using appropriate projections, the formulation dimensionality is reduced to one physical dimension, requiring minimal computation and making it ideal for device design and optimization. Our formulation is used to assess the effect of slanted well walls on the energy landscape and resulting molecule mobility. Using this approach, we show that asymmetry in the well shape, such as a well with one slanted and one vertical wall, may be used for separation using low-frequency alternating-current fields because the mobility of a biomolecule is different in the two directions of travel. Our results show that, compared to methods using direct-current fields, the proposed method remains effective at higher field strengths and can achieve comparable separation using a significantly shorter device.

Rapid identification of elastic modulus of the interface tissue on dental implants surfaces using reduced-basis method and a neural network.

This paper proposes a rapid inverse analysis approach based on the reduced-basis method (RBM) and neural network (NN) to identify the "unknown" elastic modulus (Young's modulus) of the interfacial tissue between a dental implant and the surrounding bones. In the present RBM-NN approach, a RBM model is first built to compute displacement responses of dental implant-bone structures subjected to a harmonic loading for a set of "assumed" Young's moduli. The RBM model is then used to train a NN model that is used for actual inverse analysis in real-time. Actual experimental measurements of displacement responses are fed into the trained NN model to inversely determine the "true" elastic modulus of the interfacial tissue. As an example, a physical model of dental implant-bone structure is built and inverse analysis is conducted to verify the present RBM-NN approach. Based on numerical simulation and actual experiments, it is confirmed that the identified results are very accurate, reliable, and the computational saving is very significant. The present RBM-NN approach is found robust and efficient for inverse material characterizations in noninvasive and/or nondestructive evaluations.

p73 expression and its clinical significance in colorectal cancer.

OBJECTIVE: To explore p73 mRNA and p73 protein expression and their clinical significance in colorectal cancer. METHOD: p73 mRNA and p73 protein expression were detected using hybridization in situ and immunohistochemical method in cancerous tissue from 60 patients of colorectal cancer and in paracancerous tissue from 23 patients among the corresponding 60 patients of colorectal cancer. Quantitative analysis was performed using Smartscape image analysis system. RESULTS: Compared with paracancerous tissue, p73 mRNA and p73 protein expression in cancerous tissue was increased with a statistically significant difference (P < 0.01) and was associated with differentiation level and lymphatic metastasis. CONCLUSION: High expression of p73 mRNA and p73 protein in colorectal cancer may be involved in the progression of colorectal cancer and p73 mRNA and p73 protein may serve as a potential index to predict differentiation level and prognosis of colorectal cancer.

Application of independent component analysis to dynamic contrast-enhanced imaging for assessment of cerebral blood perfusion.

Dynamic contrast-enhanced (DCE) imaging is widely used for in vivo assessment of the cerebral blood perfusion. In this work, we investigate the use of independent component analysis (ICA) on DCE imaging data for assessment of cerebral blood perfusion, without any prior knowledge of the underlying tissue vasculature and arterial input function. The minimum description length (MDL) criterion and principle component analysis (PCA) were employed to reduce the dimension of the data. An oscillating index method was used to select the components of interest. Numerical simulation and patient case studies were carried out to investigate the performance of ICA. The results show that ICA is able to extract physiologically meaningful components from the DCE imaging data. The advantages of ICA include its efficiency of computation, clarity of obtained component maps, and no need of the manually selected input function. The obtained independent component maps can provide reliable reference to identify the arterial and venous structure, and allow better demarcation of the tumor territories. The potential of ICA to be a useful clinical tool for diagnosis of cerebral vascular disease and for the assessment of treatment response has been demonstrated.

Prediction of recovery from a post-traumatic coma state by diffusion-weighted imaging (DWI) in patients with diffuse axonal injury.

INTRODUCTION: To determine whether diffusion-weighted magnetic resonance (MR) imaging findings combined with initial clinical factors indicate the depth of shearing lesions in the brain structure and therefore relate to coma duration in diffuse axonal injury (DAI). METHODS: A total of 74 adult patients (48 male and 26 female) with DAI were examined with conventional MR imaging and diffusion-weighted MR imaging between 2 hours and 20 days after injury. Apparent diffusion coefficient (ADC) maps were obtained and the mean ADC values of each region of interest (ROI) were measured using MRI console software. The involvement of the brainstem, deep gray matter, and corpus callosum was determined for each sequence separately as well as for the combination of all sequences. The correlations between MR imaging findings indicating the presence of apparent brain injury combined with initial clinical factors were determined. RESULTS: Clinical characteristics, such as initial score on the Glasgow coma scale (GCS), age and number of all lesions, and ADC scores were predictive of the duration of coma. CONCLUSION: It was possible to predict post-traumatic coma duration in DAI from cerebral MR imaging findings combined with clinical prognostic factors in the acute to subacute stage after head injury. Age, ADC scores, GCS score and number of lesions were highly significant in predicting coma duration. The technique presented here might provide a tool for in vivo detection of DAI to allow the prediction of the coma duration during the early stages in patients with traumatic brain injury.