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1.
J Colloid Interface Sci ; 606(Pt 2): 1077-1086, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34487930

RESUMO

HYPOTHESIS: Droplet wetting on a solid substrate is affected by the surface heterogeneity. Introducing patterned wettability on the solid substrate is expected to engender anisotropic wetting morphologies, thereby manipulating droplet wetting behaviors. However, when the droplet size is comparable with that of the surface heterogeneity, the wetting morphologies cannot be depicted by the quintessential Cassie's theory but should be possible to be predicted from the perspective of thermodynamics via surface energy minimization. METHODS: Here, we investigate the equilibrium droplet shapes on chemically patterned substrates by using an analytical model, phase-field simulations, and experiments. The former two methods are sharp and diffuse interface treatments, respectively, which both are based on minimizing the free energy of the system. The experimental results are obtained by depositing droplets on chemically patterned glass substrates. FINDINGS: Various anisotropic wetting shapes are found from the three methods. Excellent agreement is observed between different methods, showing the possibility to quantify the anisotropic wetting droplet morphologies on patterned substrates by present methods. We also address a series of non-rotationally symmetric droplet shapes, which is the first resport about these special wetting morphologies. Furthermore, we reveal the anisotropic wetting shapes in a quasi-equilibrium evaporation process.


Assuntos
Propriedades de Superfície , Anisotropia , Simulação por Computador , Molhabilidade
2.
Sci Total Environ ; 804: 150165, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34509853

RESUMO

This paper is based on the fact that some climatic variables show a preferential directionality and grant a markedly anisotropic character to the weathering system acting on rocks. The aim of this work is to quantify the anisotropic degree of the weathering system and its effects on rock erosion. For this purpose, a new methodology based on the vector analysis of directional and time-dependent parameters is proposed to quantify the annual or seasonal anisotropy of the weathering system. Results show that, on the one hand, wind-driven rain and solar radiation are the most anisotropic variables, being north and east the most intense directions for wind-driven rain and southeast for solar radiation, in the case of the San José Tower, the reference monument of this study. On the other hand, the ranking from the most to the least eroded façades of the tower are: east (maximum recession depth of 26.77 mm) > south (15.53 mm) ≈ west (13.56 mm) > north (6.37 mm). Solar radiation and indirect processes arising therefrom are the most important weathering agents in the semiarid Mediterranean climate, whilst wind-driven rain is the main erosion factor especially due to its torrential character. According to our results, weathering and erosion agents are strongly anisotropic, which emphasizes the importance of integrating the anisotropic character of the weathering system in preventive strategies against surface deterioration of monuments. In this sense, this paper advances the United Nations' 2030 Agenda for Sustainable Development.


Assuntos
Chuva , Tempo (Meteorologia) , Anisotropia , Espanha , Vento
3.
J Nanosci Nanotechnol ; 21(6): 3306-3311, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-34739786

RESUMO

Magnetic nanoparticles (MNPs) subjected to external alternating magnetic field can induce heat in MNPs due to hysteresis, which is usually employed for tumor hyperthermia. An effective hyperthermia treatment should selectively kill the tumor cells without damaging the ambient healthy tissue. Hence, it is important for hyperthermia to correctly control the alternating magnetic field-induced temperature of MNPs in the tumor. This work develops a thermal model to analyze various forms of temperature-rise with time in magnetic nanoparticles for tumor hyperthermia. Results show that there are horizontal, linear rise, square root, exponential decay and abrupt temperature-rise lines with time in MNPs. The horizontal, linear rise, and square root temperature lines with time are consistent with the available experimental data. It is worthily noted that the form of abrupt temperaturerise with time can result in harm to the normal cells or tissue. If the abrupt temperature-rise does not be controlled and predicted well.


Assuntos
Hipertermia Induzida , Nanopartículas de Magnetita , Nanopartículas , Anisotropia , Humanos , Hipertermia , Campos Magnéticos , Temperatura
4.
J Int Med Res ; 49(10): 3000605211047071, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34719991

RESUMO

OBJECTIVE: To study the characteristics of point-by-point destruction of white matter tracts in patients using automated fiber tract quantification (AFQ). METHODS: Thirty-four classic trigeminal neuralgia (CTN) patients and 34 healthy control (HC) subjects underwent 3.0 T diffusion tensor magnetic resonance imaging and T1-weighted imaging. The fractional anisotropy (FA) and mean diffusivity (MD) of 100 nodes of 20 fiber tracts were analyzed by AFQ, and the correlations of the FA and MD with the visual analogue scale (VAS) pain score were assessed. RESULTS: The FA values of the left thalamic radiation (middle segment), left corticospinal tract, callosum forceps minor, and right uncinate fasciculus were significantly lower in CTN patients than in the HC group. The MD of the left thalamic tract (middle segment), left corticospinal tract, right superior longitudinal fasciculus, and left superior longitudinal fasciculus (anterior segment) were significantly higher in the CTN group. Additionally, the VAS pain score in CTN patients was positively correlated with FA and negatively correlated with MD. CONCLUSION: Specific fiber tract nodes were damaged in CTN patients, which was related to the VAS pain score. Multi-node quantitative studies of fiber tract damage are valuable for understanding the white matter tract damage pattern in CTN patients.


Assuntos
Neuralgia do Trigêmeo , Substância Branca , Anisotropia , Encéfalo , Corpo Caloso , Imagem de Tensor de Difusão , Humanos , Neuralgia do Trigêmeo/diagnóstico por imagem , Substância Branca/diagnóstico por imagem
6.
Isr Med Assoc J ; 23(10): 625-630, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34672443

RESUMO

BACKGROUND: Only a small proportion of schizophrenia patients present with catatonic symptoms. Imaging studies suggest that brain motor circuits are involved in the underlying pathology of catatonia. However, data about diffusivity dysregulation of these circuits in catatonic schizophrenia are scarce. OBJECTIVES: To assess the involvement of brain motor circuits in schizophrenia patients with catatonia. METHODS: Diffusion tensor imaging (DTI) was used to measure white matter signals in selected brain regions linked to motor circuits. Relevant DTI data of seven catatonic schizophrenia patients were compared to those of seven non-catatonic schizophrenia patients, matched for sex, age, and education level. RESULTS: Significantly elevated fractional anisotropy values were found in the splenium of the corpus callosum, the right peduncle of the cerebellum, and the right internal capsule of the schizophrenia patients with catatonia compared to those without catatonia. This finding showed altered diffusivity in selected motor-related brain areas. CONCLUSIONS: Catatonic schizophrenia is associated with dysregulation of the connectivity in specific motoric brain regions and corresponding circuits. Future DTI studies are needed to address the neural correlates of motor abnormalities in schizophrenia-related catatonia during the acute and remitted state of the illness to identify the specific pathophysiology of this disorder.


Assuntos
Imagem de Tensor de Difusão/métodos , Córtex Motor , Esquizofrenia Catatônica , Adulto , Anisotropia , Cerebelo/diagnóstico por imagem , Cerebelo/fisiopatologia , Conectoma/métodos , Corpo Caloso/diagnóstico por imagem , Corpo Caloso/fisiopatologia , Correlação de Dados , Manual Diagnóstico e Estatístico de Transtornos Mentais , Feminino , Humanos , Cápsula Interna/diagnóstico por imagem , Cápsula Interna/fisiopatologia , Masculino , Córtex Motor/diagnóstico por imagem , Córtex Motor/fisiopatologia , Escalas de Graduação Psiquiátrica , Esquizofrenia Catatônica/diagnóstico , Esquizofrenia Catatônica/fisiopatologia
7.
Int J Comput Assist Radiol Surg ; 16(11): 1947-1956, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34694572

RESUMO

PURPOSE: The viscoelasticity (storage modulus and loss modulus) of living tissues is known to be related to diseases. Magnetic resonance elastography (MRE) is a quantitative method for non-invasive measuring viscoelasticity. The viscoelasticity is calculated from the elastic wave images using an inversion algorithm. The estimation accuracy of the inversion algorithm is degraded by background noise. This study aims to propose novel inversion algorithms that are applicable for noisy elastic wave images. METHODS: The proposed algorithms are based on the Voigt-type viscoelastic equation. The algorithms are designed to improve the noise robustness by avoiding direct differentiation of measurement data by virtue of Green's formula. Similarly, stabilization is introduced to the curl-operator which works to eliminate the compression waves in measurement data. To clarify the characteristics of the algorithms, the proposed algorithms were compared with the conventional algorithms using isotropic and anisotropic voxel numerical simulations and phantom experimental data. RESULTS: From the results of the numerical simulations, normalized errors of stiffness of proposed algorithms were 3% or less. The proposed algorithms mostly showed better results than the conventional algorithms despite noisy elastic wave images. From the gel phantom experiment, we confirmed the same tendency as the characteristics of the algorithms observed in the numerical simulation results. CONCLUSION: We have developed a novel inversion algorithm and evaluated it quantitatively. The results confirm that the proposed algorithms are highly quantitative and noise-robust methods for estimating storage and loss modulus regardless of noise, voxel anisotropy, and propagation direction. Therefore, the proposed algorithms will appropriate to various three-dimensional MRE systems.


Assuntos
Técnicas de Imagem por Elasticidade , Algoritmos , Anisotropia , Humanos , Imageamento por Ressonância Magnética , Imagens de Fantasmas
8.
J Biomed Opt ; 26(10)2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34617423

RESUMO

SIGNIFICANCE: A non-destructive technique for accurately characterizing the spatial distribution of optical properties of soft tissue membranes may give improved outcomes in many tissue engineering applications. AIM: This study aimed to develop a non-destructive macroscopic imaging technique that is sensitive to optical anisotropy, typical of fibrous components in soft tissue membranes, and can address some of the difficulties caused by the complex turbid nature of these tissues. APPROACH: A near-infrared Mueller matrix imaging polarimeter employing logarithm decomposition was developed and used to conduct transmission measurements of all the polarization properties across the full thickness of bovine pericardium tissue. RESULTS: The full Mueller matrix was measured across a 70 mm × 70 mm sample of calf bovine pericardium and revealed significant retardance (linear and circular) and depolarization in this tissue. Regions with a uniform axis of optical anisotropy were identified. Mueller matrix imaging demonstrated that the exhibited circular retardance was sufficient to lead to possible misinterpretation of apparent fiber orientation when using conventional polarization imaging techniques for such tissues. CONCLUSIONS: Mueller matrix imaging can identify regional distributions of optical anisotropy in calf bovine pericardium. This new capability is a promising development in non-destructive imaging for tissue selection.


Assuntos
Diagnóstico por Imagem , Imagem Óptica , Animais , Anisotropia , Bovinos
9.
BMC Pediatr ; 21(1): 440, 2021 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-34625051

RESUMO

BACKGROUND: Conventional diffusion weighted imaging (DWI) is a promising non-invasive tool in the evaluation of infants with symptomatic urinary tract infections (UTI). The use of multiparametric diffusion tensor imaging (DTI) provides further information on renal pathology by reflecting renal microstructure. However, its potential to characterize and distinguish between renal lesions, such as acute pyelonephritic lesions, permanent renal damages or dysplastic changes has not been shown. This study aimed to evaluate the potential of multiparametric DTI for characterization of renal lesions with purpose to distinguish acute pyelonephritis from other renal lesions in young infants with their first UTI. METHODS: Nine kidneys in seven infants, age 1.0-5.6 months, with renal lesions i.e. uptake reductions, on acute scintigraphy performed after their first UTI, were included. The DTI examinations were performed during free breathing without sedation. The signal in the lesions and in normal renal tissue was measured in the following images: b0, b700, apparent diffusion coefficient (ADC), and fractional anisotropy (FA). In addition, DTI tractographies were produced for visibility. RESULTS: There was a difference between lesions and normal tissue in b700 signal (197 ± 52 and 164 ± 53, p = 0.011), ADC (1.22 ± 0.11 and 1.45 ± 0.15 mm2/s, p = 0.008), and FA (0.18 ± 0.03 and 0.30 ± 0.10, p = 0.008) for all nine kidneys. Six kidneys had focal lesions with increased b700 signal, decreased ADC and FA indicating acute inflammation. In three patients, the multiparametric characteristics of the lesions were diverging. CONCLUSION: Multiparametric DTI has the potential to further characterize and distinguish acute pyelonephritis from other renal lesions in infants with symptomatic UTI.


Assuntos
Imagem de Tensor de Difusão , Infecções Urinárias , Anisotropia , Imagem de Difusão por Ressonância Magnética , Humanos , Lactente , Rim/diagnóstico por imagem , Infecções Urinárias/diagnóstico por imagem
10.
Cell Rep ; 37(3): 109841, 2021 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-34624207

RESUMO

Nonstructural protein 1 (nsp1) is a coronavirus (CoV) virulence factor that restricts cellular gene expression by inhibiting translation through blocking the mRNA entry channel of the 40S ribosomal subunit and by promoting mRNA degradation. We perform a detailed structure-guided mutational analysis of severe acute respiratory syndrome (SARS)-CoV-2 nsp1, revealing insights into how it coordinates these activities against host but not viral mRNA. We find that residues in the N-terminal and central regions of nsp1 not involved in docking into the 40S mRNA entry channel nonetheless stabilize its association with the ribosome and mRNA, both enhancing its restriction of host gene expression and enabling mRNA containing the SARS-CoV-2 leader sequence to escape translational repression. These data support a model in which viral mRNA binding functionally alters the association of nsp1 with the ribosome, which has implications for drug targeting and understanding how engineered or emerging mutations in SARS-CoV-2 nsp1 could attenuate the virus.


Assuntos
COVID-19/genética , Regulação Viral da Expressão Gênica , SARS-CoV-2/genética , Proteínas não Estruturais Virais/metabolismo , Anisotropia , COVID-19/imunologia , Análise Mutacional de DNA , Feminino , Perfilação da Expressão Gênica , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Humanos , Cinética , Mutação , Fenótipo , Mutação Puntual , Biossíntese de Proteínas , Domínios Proteicos , Estabilidade de RNA , Subunidades Ribossômicas Menores de Eucariotos/metabolismo , Ribossomos/metabolismo
11.
Nutrients ; 13(10)2021 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-34684410

RESUMO

BACKGROUND: Determining optimal nutritional regimens in extremely preterm infants remains challenging. This study aimed to evaluate the effect of a new nutritional regimen and individual macronutrient intake on white matter integrity and neurodevelopmental outcome. METHODS: Two retrospective cohorts of extremely preterm infants (gestational age < 28 weeks) were included. Cohort B (n = 79) received a new nutritional regimen, with more rapidly increased, higher protein intake compared to cohort A (n = 99). Individual protein, lipid, and caloric intakes were calculated for the first 28 postnatal days. Diffusion tensor imaging was performed at term-equivalent age, and cognitive and motor development were evaluated at 2 years corrected age (CA) (Bayley-III-NL) and 5.9 years chronological age (WPPSI-III-NL, MABC-2-NL). RESULTS: Compared to cohort A, infants in cohort B had significantly higher protein intake (3.4 g/kg/day vs. 2.7 g/kg/day) and higher fractional anisotropy (FA) in several white matter tracts but lower motor scores at 2 years CA (mean (SD) 103 (12) vs. 109 (12)). Higher protein intake was associated with higher FA and lower motor scores at 2 years CA (B = -6.7, p = 0.001). However, motor scores at 2 years CA were still within the normal range and differences were not sustained at 5.9 years. There were no significant associations with lipid or caloric intake. CONCLUSION: In extremely preterm born infants, postnatal protein intake seems important for white matter development but does not necessarily improve long-term cognitive and motor development.


Assuntos
Cognição , Dieta , Proteínas na Dieta/administração & dosagem , Ingestão de Alimentos , Lactente Extremamente Prematuro/crescimento & desenvolvimento , Destreza Motora , Substância Branca/crescimento & desenvolvimento , Anisotropia , Imagem de Tensor de Difusão , Ingestão de Energia , Feminino , Humanos , Fórmulas Infantis , Recém-Nascido , Masculino , Estudos Retrospectivos , Substância Branca/diagnóstico por imagem
12.
Br J Radiol ; 94(1126): 20201315, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34491821

RESUMO

OBJECTIVE: To investigate the feasibility of magnetic resonance diffusion kurtosis imaging (DKI) and intravoxel incoherent motion (IVIM) for distinguishing Type 1 and 2 of papillary renal cell carcinoma (PRCC). METHODS: A total of Type 1 (n = 20) and Type 2 (n = 16) of PRCC were examined by pathology. For DKI and IVIM, mean diffusivity (MD), fractional anisotropy (FA), mean kurtosis (MK), kurtosis anisotropy (KA), radial kurtosis (RK), diffusivity (D), pseudodiffusivity (D*) and perfusion fraction (f) were performed in assessment of type of PRCC. RESULTS: The mean SNRs of IVIM and DKI images at b = 1500 and 2000 s/mm2 were 8.6 ± 0.8 and 7.8 ± 0.6. Statistically significant differences were observed in MD and D values (1.11 ± 0.23 vs 0.73 ± 0.13, 0.91 ± 0.24 vs 0.49 ± 0.13, p < 0.05) between Type 1 and Type 2 of PRCC, while comparable FA, RK, D* and f values were found between Type 1 and Type 2 of PRCC (p > 0.05). Statistically significant differences were observed in MK and KA values (1.23 ± 0.16 vs 1.91 ± 0.26, 1.49 ± 0.19 vs 2.36 ± 0.39, p < 0.05) between Type 1 and Type 2 of PRCC. Areas of MD, MK, KA and D values under ROC curves for differentiating Type 1 and Type 2 of PRCC were 0.836, 0.818, 0.881 and 0.766, respectively. Using MD, MK, KA and D values of 0.93, 1.64, 1.94, 0.68 as the threshold value for differentiating Type 1 from Type 2 of PRCC, the best result obtained had a sensitivity of 85.0%, 80.0%, 90.0%, 85.0%, a specificity 75.0%, 68.7%, 87.5%, 81.2%, and an accuracy of 83.3%, 80.5%, 88.9%, 86.1%, respectively. CONCLUSION: DKI and IVIM are feasible techniques for distinguishing type of PRCC, given an adequate SNR of IVIM and DKI images. ADVANCES IN KNOWLEDGE: 1. MD and D values are higher for Type 1 of PRCC and lower for Type 2 of PRCC.2. MK and KA values are higher for Type 2 of PRCC and lower for Type 1 of PRCC.3. DKI and IVIM can be used as clinical biomarker for PRCC type's differential diagnosis, given an adequate SNR.


Assuntos
Carcinoma de Células Renais/diagnóstico por imagem , Imagem de Difusão por Ressonância Magnética/métodos , Neoplasias Renais/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Anisotropia , Diagnóstico Diferencial , Estudos de Viabilidade , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
13.
Neurol India ; 69(4): 889-893, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34507407

RESUMO

Background: Hirayama disease (HD) is a motor neuron disease and occasionally is associated with lower limb hyper-reflexia. Corticospinal tract dysfunction can be evaluated by diffusion tensor imaging (DTI), but there is paucity of study in HD. Objective: We report corticospinal tract functions using DTI in the patients with HD and correlate with clinical findings. Materials and Methods: The patients with HD diagnosed on the basis of clinical and electromyography findings were included. Their age, duration of illness, side of initial involvement, and progression were noted. Presence of lower limb hyper-reflexia, and cervical spine magnetic resonance imaging (MRI) findings were noted. Cranial MRI was done and DTI findings at internal capsule, cerebral peduncle, pons, and pyramid were noted. Results: In total, 10 patients with HD and 5 matched controls were evaluated. The apparent diffusion coefficient (7.03 ± 0.27 vs 6.83 ± 0.36), fractional anisotropy (0.79 ± 0.04 vs 0.82 ± 0.05), axial diffusivity (5.08 ± 0.08 vs 5.04 ± 0.07), and radial diffusivity (3.79 ± 0.05 vs 3.76 ± 0.05) between HD patients and controls were not different in internal capsule. These values were also not significantly different in cerebral peduncle, pons, and pyramid. These values were also not significantly different between the severe and less severely affected sides. The fractional anisotropy did not correlate with lower limb hyper-reflexia (P = 1.00) and spinal cord atrophy (P = 0.60). Conclusion: DTI study in HD patients did not reveal corticospinal tract involvement in brain.


Assuntos
Imagem de Tensor de Difusão , Atrofias Musculares Espinais da Infância , Anisotropia , Humanos , Tratos Piramidais/diagnóstico por imagem
14.
Mater Sci Eng C Mater Biol Appl ; 129: 112339, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34579931

RESUMO

Electrospun scaffolds combine suitable structural characteristics that make them strong candidates for their use in tissue engineering. These features can be tailored to optimize other physiologically relevant attributes (e.g. mechanical anisotropy and cellular affinity) while ensuring adequate degradation rates of the biomaterial. Here, we present the fabrication of microstructured scaffolds by using a combination of micropatterned electrospinning collectors (honeycomb- or square-patterned) and poly(lactic acid) (PLA)-based copolymers (linear or star-shaped). The resulting materials showed appropriate macropore size and fiber alignment that were key parameters to enhance their anisotropic properties in protraction. Moreover, their elastic modulus, which was initially similar to that of soft tissues, gradually changed in hydrolytic conditions, matching the degradation profile in a 2- to 3-month period. Finally, honeycomb-structured scaffolds exhibited enhanced cellular proliferation compared to standard electrospun mats, while cell colonization was shown to be guided by the macropore contour. Taking together, these results provide new insight into the rational design of microstructured materials that can mimic the progressive evolution of properties in soft tissue regeneration.


Assuntos
Engenharia Tecidual , Tecidos Suporte , Anisotropia , Materiais Biocompatíveis , Poliésteres
15.
Nano Lett ; 21(19): 8043-8050, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34550704

RESUMO

Two-dimensional (2D) trigonal selenium (t-Se) has become a new member in 2D semiconducting nanomaterial families. It is composed of well-aligned one-dimensional Se atomic chains bonded via van der Waals (vdW) interaction. The contribution of this unique anisotropic nanostructure to its mechanical properties has not been explored. Here, for the first time, we combine experimental and theoretical analyses to study the anisotropic mechanical properties of individual 2D t-Se nanosheets. It was found that its fracture strength and Young's modulus parallel to the atomic chain direction are much higher than along the transverse direction, which was attributed to the weak vdW interaction between Se atomic chains as compared to the covalent bonding within individual chains. Additionally, two distinctive fracture modes along two orthogonal loading directions were identified. This work provides important insights into the understanding of anisotropic mechanical behaviors of 2D semiconducting t-Se and opens new possibilities for future applications.


Assuntos
Nanoestruturas , Selênio , Anisotropia , Módulo de Elasticidade , Humanos
16.
Molecules ; 26(18)2021 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-34576970

RESUMO

Imaging of the electrical conductivity distribution inside the human body has been investigated for numerous clinical applications. The conductivity tensors of biological tissue have been obtained from water diffusion tensors by applying several models, which may not cover the entire phenomenon. Recently, a new conductivity tensor imaging (CTI) method was developed through a combination of B1 mapping, and multi-b diffusion weighted imaging. In this study, we compared the most recent CTI method with the four existing models of conductivity tensors reconstruction. Two conductivity phantoms were designed to evaluate the accuracy of the models. Applied to five human brains, the conductivity tensors using the four existing models and CTI were imaged and compared with the values from the literature. The conductivity image of the phantoms by the CTI method showed relative errors between 1.10% and 5.26%. The images by the four models using DTI could not measure the effects of different ion concentrations subsequently due to prior information of the mean conductivity values. The conductivity tensor images obtained from five human brains through the CTI method were comparable to previously reported literature values. The images by the four methods using DTI were highly correlated with the diffusion tensor images, showing a coefficient of determination (R2) value of 0.65 to 1.00. However, the images by the CTI method were less correlated with the diffusion tensor images and exhibited an averaged R2 value of 0.51. The CTI method could handle the effects of different ion concentrations as well as mobilities and extracellular volume fractions by collecting and processing additional B1 map data. It is necessary to select an application-specific model taking into account the pros and cons of each model. Future studies are essential to confirm the usefulness of these conductivity tensor imaging methods in clinical applications, such as tumor characterization, EEG source imaging, and treatment planning for electrical stimulation.


Assuntos
Condutividade Elétrica , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Anisotropia , Imagens de Fantasmas
17.
Comput Biol Med ; 138: 104863, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34562679

RESUMO

The arrhythmogenic role of discrete cardiac propagation may be assessed by comparing discrete (fine-grained) and equivalent continuous (coarse-grained) models. We aim to develop an optimization algorithm for estimating the smooth conductivity field that best reproduces the diffusion properties of a given discrete model. Our algorithm iteratively adjusts local conductivity of the coarse-grained continuous model by simulating passive diffusion from white noise initial conditions during 3-10 ms and computing the root mean square error with respect to the discrete model. The coarse-grained conductivity field was interpolated from up to 300 evenly spaced control points. We derived an approximate formula for the gradient of the cost function that required (in two dimensions) only two additional simulations per iteration regardless of the number of estimated parameters. Conjugate gradient solver facilitated simultaneous optimization of multiple conductivity parameters. The method was tested in rectangular anisotropic tissues with uniform and nonuniform conductivity (slow regions with sinusoidal profile) and random diffuse fibrosis, as well as in a monolayer interconnected cable model of the left atrium with spatially-varying fibrosis density. Comparison of activation maps served as validation. The results showed that after convergence the errors in activation time were < 1 ms for rectangular geometries and 1-3 ms in the atrial model. Our approach based on the comparison of passive properties (<10 ms simulation) avoids performing active propagation simulations (>100 ms) at each iteration while reproducing activation maps, with possible applications to investigating the impact of microstructure on arrhythmias.


Assuntos
Algoritmos , Anisotropia , Simulação por Computador , Difusão
18.
Int J Mol Sci ; 22(17)2021 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-34502249

RESUMO

The replacement of damaged or degenerated articular cartilage tissue remains a challenge, as this non-vascularized tissue has a very limited self-healing capacity. Therefore, tissue engineering (TE) of cartilage is a promising treatment option. Although significant progress has been made in recent years, there is still a lack of scaffolds that ensure the formation of functional cartilage tissue while meeting the mechanical requirements for chondrogenic TE. In this article, we report the application of flock technology, a common process in the modern textile industry, to produce flock scaffolds made of chitosan (a biodegradable and biocompatible biopolymer) for chondrogenic TE. By combining an alginate hydrogel with a chitosan flock scaffold (CFS+ALG), a fiber-reinforced hydrogel with anisotropic properties was developed to support chondrogenic differentiation of embedded human chondrocytes. Pure alginate hydrogels (ALG) and pure chitosan flock scaffolds (CFS) were studied as controls. Morphology of primary human chondrocytes analyzed by cLSM and SEM showed a round, chondrogenic phenotype in CFS+ALG and ALG after 21 days of differentiation, whereas chondrocytes on CFS formed spheroids. The compressive strength of CFS+ALG was higher than the compressive strength of ALG and CFS alone. Chondrocytes embedded in CFS+ALG showed gene expression of chondrogenic markers (COL II, COMP, ACAN), the highest collagen II/I ratio, and production of the typical extracellular matrix such as sGAG and collagen II. The combination of alginate hydrogel with chitosan flock scaffolds resulted in a scaffold with anisotropic structure, good mechanical properties, elasticity, and porosity that supported chondrogenic differentiation of inserted human chondrocytes and expression of chondrogenic markers and typical extracellular matrix.


Assuntos
Alginatos/química , Materiais Biocompatíveis/química , Quitosana/química , Hidrogéis/química , Engenharia Tecidual/métodos , Tecidos Suporte/química , Agrecanas/genética , Agrecanas/metabolismo , Anisotropia , Proteína de Matriz Oligomérica de Cartilagem/genética , Proteína de Matriz Oligomérica de Cartilagem/metabolismo , Diferenciação Celular , Proliferação de Células , Condrócitos/metabolismo , Condrogênese , Colágeno/metabolismo , Colágeno Tipo II/genética , Colágeno Tipo II/metabolismo , Força Compressiva , Feminino , Glicosaminoglicanos/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Cultura Primária de Células , Eletricidade Estática
19.
Int J Mol Sci ; 22(17)2021 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-34502469

RESUMO

In this review article, tissue engineering and regenerative medicine are briefly explained and the importance of scaffolds is highlighted. Furthermore, the requirements of scaffolds and how they can be fulfilled by using specific biomaterials and fabrication methods are presented. Detailed insight is given into the two biopolymers chitosan and collagen. The fabrication methods are divided into two categories: isotropic and anisotropic scaffold fabrication methods. Processable biomaterials and achievable pore sizes are assigned to each method. In addition, fiber spinning methods and textile fabrication methods used to produce anisotropic scaffolds are described in detail and the advantages of anisotropic scaffolds for tissue engineering and regenerative medicine are highlighted.


Assuntos
Materiais Biocompatíveis/química , Colágeno/química , Têxteis , Engenharia Tecidual , Tecidos Suporte/química , Animais , Anisotropia , Humanos , Porosidade
20.
J Mech Behav Biomed Mater ; 124: 104805, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34474321

RESUMO

PURPOSE: Proper understanding of skin biomechanics, viscoelasticity and investigation of skin tension vectors is necessary to find optimal incision lines. Great tension across a healing wound after any surgical procedure might lead to forming hypertrophic scars. The aim of the study was to investigate tension lines in volar forearm skin in young males and females, in order to ensure best incision line. METHODS: Five biomechanical and viscoelastic parameters were measured using a hand-held myotonometer: Oscillation Frequency [Hz], Dynamic Stiffness [N/m], Logarithmic Decrement of tissue's natural oscillation, Mechanical Stress Relaxation Time [ms], and Creep. Measurements were taken in four different directions; Along Forearm, Across Forearm, Along Langer's Line and Across Langer's Line. RESULTS: Significant main effects for direction were found for Oscillation Frequency (p < 0.001, η2 = 0.371) [Hz], Dynamic Stiffness (p < 0.001, η2 = 0.522) [N/m], Logarithmic Decrement (p < 0.001, η2 = 0.083), Mechanical Stress Relaxation Time (p < 0.001, η2 = 0.494) [ms] and Creep (p < 0.001, η2 = 0.480). For each parameter except for logarithmic decrement results obtained Along Langers Line and Across Forearm were significantly different to Across Langers Line and Along Forearm (p < 0.001, d = -2.76 - 2.66). Significant main effects for sex were found for logarithmic decrement Along Forearm (p < 0.001, d = 1.698) and Across Langer's Line (p = 0.021, d = 1.697). CONCLUSIONS: Our results suggested that optimal incision line for this age group in males and females could potentially be performed diagonally i.e. Across Langer's Line or parallel i.e. Along Forearm to forearm axis. These directions would provide the lowest tension across a healing wound and possibly minimalize the risk of hypertrophic scarring post incision.


Assuntos
Antebraço , Fenômenos Fisiológicos da Pele , Anisotropia , Feminino , Humanos , Masculino , Pele , Estresse Mecânico
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