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1.
Annu Rev Biomed Eng ; 26(1): 67-91, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38211326

RESUMO

Low-field magnetic resonance imaging (MRI) has recently experienced a renaissance that is largely attributable to the numerous technological advancements made in MRI, including optimized pulse sequences, parallel receive and compressed sensing, improved calibrations and reconstruction algorithms, and the adoption of machine learning for image postprocessing. This new attention on low-field MRI originates from a lack of accessibility to traditional MRI and the need for affordable imaging. Low-field MRI provides a viable option due to its lack of reliance on radio-frequency shielding rooms, expensive liquid helium, and cryogen quench pipes. Moreover, its relatively small size and weight allow for easy and affordable installation in most settings. Rather than replacing conventional MRI, low-field MRI will provide new opportunities for imaging both in developing and developed countries. This article discusses the history of low-field MRI, low-field MRI hardware and software, current devices on the market, advantages and disadvantages, and low-field MRI's global potential.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Sistemas Automatizados de Assistência Junto ao Leito , Software , Imageamento por Ressonância Magnética/métodos , Humanos , Processamento de Imagem Assistida por Computador/métodos , Desenho de Equipamento , Aprendizado de Máquina , Calibragem
2.
Cereb Cortex ; 34(1)2024 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-38100334

RESUMO

Functional connectome has revealed remarkable potential in the diagnosis of neurological disorders, e.g. autism spectrum disorder. However, existing studies have primarily focused on a single connectivity pattern, such as full correlation, partial correlation, or causality. Such an approach fails in discovering the potential complementary topology information of FCNs at different connection patterns, resulting in lower diagnostic performance. Consequently, toward an accurate autism spectrum disorder diagnosis, a straightforward ambition is to combine the multiple connectivity patterns for the diagnosis of neurological disorders. To this end, we conduct functional magnetic resonance imaging data to construct multiple brain networks with different connectivity patterns and employ kernel combination techniques to fuse information from different brain connectivity patterns for autism diagnosis. To verify the effectiveness of our approach, we assess the performance of the proposed method on the Autism Brain Imaging Data Exchange dataset for diagnosing autism spectrum disorder. The experimental findings demonstrate that our method achieves precise autism spectrum disorder diagnosis with exceptional accuracy (91.30%), sensitivity (91.48%), and specificity (91.11%).


Assuntos
Transtorno do Espectro Autista , Conectoma , Doenças do Sistema Nervoso , Humanos , Conectoma/métodos , Transtorno do Espectro Autista/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Encéfalo/diagnóstico por imagem , Mapeamento Encefálico/métodos
3.
Cereb Cortex ; 34(3)2024 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-38494887

RESUMO

The early diagnosis of autism spectrum disorder (ASD) has been extensively facilitated through the utilization of resting-state fMRI (rs-fMRI). With rs-fMRI, the functional brain network (FBN) has gained much attention in diagnosing ASD. As a promising strategy, graph convolutional networks (GCN) provide an attractive approach to simultaneously extract FBN features and facilitate ASD identification, thus replacing the manual feature extraction from FBN. Previous GCN studies primarily emphasized the exploration of topological simultaneously connection weights of the estimated FBNs while only focusing on the single connection pattern. However, this approach fails to exploit the potential complementary information offered by different connection patterns of FBNs, thereby inherently limiting the performance. To enhance the diagnostic performance, we propose a multipattern graph convolution network (MPGCN) that integrates multiple connection patterns to improve the accuracy of ASD diagnosis. As an initial endeavor, we endeavored to integrate information from multiple connection patterns by incorporating multiple graph convolution modules. The effectiveness of the MPGCN approach is evaluated by analyzing rs-fMRI scans from a cohort of 92 subjects sourced from the publicly accessible Autism Brain Imaging Data Exchange database. Notably, the experiment demonstrates that our model achieves an accuracy of 91.1% and an area under ROC curve score of 0.9742. The implementation codes are available at https://github.com/immutableJackz/MPGCN.


Assuntos
Transtorno do Espectro Autista , Transtorno Autístico , Humanos , Transtorno do Espectro Autista/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Bases de Dados Factuais , Curva ROC
4.
Cereb Cortex ; 34(3)2024 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-38466115

RESUMO

Mild cognitive impairment plays a crucial role in predicting the early progression of Alzheimer's disease, and it can be used as an important indicator of the disease progression. Currently, numerous studies have focused on utilizing the functional brain network as a novel biomarker for mild cognitive impairment diagnosis. In this context, we employed a graph convolutional neural network to automatically extract functional brain network features, eliminating the need for manual feature extraction, to improve the mild cognitive impairment diagnosis performance. However, previous graph convolutional neural network approaches have primarily concentrated on single modes of brain connectivity, leading to a failure to leverage the potential complementary information offered by diverse connectivity patterns and limiting their efficacy. To address this limitation, we introduce a novel method called the graph convolutional neural network with multimodel connectivity, which integrates multimode connectivity for the identification of mild cognitive impairment using fMRI data and evaluates the graph convolutional neural network with multimodel connectivity approach through a mild cognitive impairment diagnostic task on the Alzheimer's Disease Neuroimaging Initiative dataset. Overall, our experimental results show the superiority of the proposed graph convolutional neural network with multimodel connectivity approach, achieving an accuracy rate of 92.2% and an area under the Receiver Operating Characteristic (ROC) curve of 0.988.


Assuntos
Doença de Alzheimer , Disfunção Cognitiva , Humanos , Imageamento por Ressonância Magnética , Doença de Alzheimer/diagnóstico por imagem , Neuroimagem , Encéfalo/diagnóstico por imagem , Disfunção Cognitiva/diagnóstico por imagem
5.
Bioinformatics ; 39(9)2023 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-37647657

RESUMO

MOTIVATION: A critical issue in drug benefit-risk assessment is to determine the frequency of side effects, which is performed by randomized controlled trails. Computationally predicted frequencies of drug side effects can be used to effectively guide the randomized controlled trails. However, it is more challenging to predict drug side effect frequencies, and thus only a few studies cope with this problem. RESULTS: In this work, we propose a neighborhood-regularization method (NRFSE) that leverages multiview data on drugs and side effects to predict the frequency of side effects. First, we adopt a class-weighted non-negative matrix factorization to decompose the drug-side effect frequency matrix, in which Gaussian likelihood is used to model unknown drug-side effect pairs. Second, we design a multiview neighborhood regularization to integrate three drug attributes and two side effect attributes, respectively, which makes most similar drugs and most similar side effects have similar latent signatures. The regularization can adaptively determine the weights of different attributes. We conduct extensive experiments on one benchmark dataset, and NRFSE improves the prediction performance compared with five state-of-the-art approaches. Independent test set of post-marketing side effects further validate the effectiveness of NRFSE. AVAILABILITY AND IMPLEMENTATION: Source code and datasets are available at https://github.com/linwang1982/NRFSE or https://codeocean.com/capsule/4741497/tree/v1.


Assuntos
Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Humanos , Algoritmos , Benchmarking , Distribuição Normal , Probabilidade
6.
J Appl Toxicol ; 44(6): 818-832, 2024 06.
Artigo em Inglês | MEDLINE | ID: mdl-38272789

RESUMO

Titanium dioxide nanoparticles (TiO2 NPs) can cause apoptosis in TM4 cells; however, the underlying mechanism has not been entirely elucidated. The purpose of this study was to investigate the effects of TiO2 NPs on ROS, Ca2+ level, p38/AKT/mTOR pathway, and apoptosis in TM4 cells and to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. After exposure to different concentrations (0, 50, 100, 150, and 200 µg/mL) of TiO2 NPs for 24 h, cell viability, ROS, Ca2+ level, Ca2+-ATPase activity, p38/AKT/mTOR pathway-related proteins, apoptosis rate, and apoptosis-related proteins (Bax, Bcl-2, Caspase 3, Caspase 9, and p53) were detected. The ROS scavenger NAC was used to determine the effect of ROS on Ca2+ level. The Ca2+ chelator BAPTA-AM was used to evaluate the role of Ca2+ in p38/AKT/mTOR pathway and apoptosis. TiO2 NPs significantly inhibited cell viability, increased ROS level, and elevated Ca2+ level while suppressing Ca2+-ATPase activity. TiO2 NPs regulated the p38/AKT/mTOR pathway via increasing p-p38 level and decreasing p-AKT and p-mTOR levels. TiO2 NPs significantly enhanced the apoptosis. NAC attenuated Ca2+ overload and reduction in Ca2+-ATPase activity caused by TiO2 NPs. BAPTA-AM alleviated TiO2 NPs-induced abnormal expression of p38/AKT/mTOR pathway-related proteins. BAPTA-AM assuaged the apoptosis caused by TiO2 NPs. Altogether, this study revealed that TiO2 NPs elevated intracellular Ca2+ level through ROS accumulation. Subsequently, the heightened intracellular Ca2+ level was observed to exert regulation over the p38/AKT/mTOR pathway, ultimately culminating in apoptosis. These results provides a complementary understanding to the mechanism of TiO2 NPs-induced apoptosis in TM4 cells.


Assuntos
Apoptose , Cálcio , Sobrevivência Celular , Proteínas Proto-Oncogênicas c-akt , Espécies Reativas de Oxigênio , Transdução de Sinais , Serina-Treonina Quinases TOR , Titânio , Proteínas Quinases p38 Ativadas por Mitógeno , Titânio/toxicidade , Apoptose/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Cálcio/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Animais , Linhagem Celular , Transdução de Sinais/efeitos dos fármacos , Camundongos , Nanopartículas Metálicas/toxicidade , Nanopartículas/toxicidade
7.
Sensors (Basel) ; 24(8)2024 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-38676130

RESUMO

To enhance the precision of evaluating the operational status of SF6 high-voltage circuit breakers (HVCBs) and devise judicious maintenance strategies, this study introduces an operational state assessment method for SF6 HVCBs grounded in the integrated data-driven analysis (IDDA) model. The relative degradation weight (RDW) is introduced as a metric for quantifying the relative significance of distinct indicators concerning the operational condition of SF6 HVCBs. A data-driven model, founded on critical factor stability (CFS), is formulated to convert environmental indicators into quantitative computations. Furthermore, an optimized fuzzy inference (OFI) system is devised to streamline the system architecture and enhance the processing speed of continuous indicators. Ultimately, the efficacy of the proposed model is substantiated through validation, and results from instance analyses underscore that the presented approach not only attains heightened accuracy in assessment compared to extant analytical methodologies but also furnishes a dependable foundation for prioritizing maintenance sequences across diverse components.

8.
Magn Reson Med ; 90(5): 2198-2210, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37382188

RESUMO

PURPOSE: Multinuclear MRI/S is of increasing interest. Currently, most multinuclear receive array coils are constructed by nesting multiple single-tuned array coils or using switching elements to control the operating frequency, in which case more than one set of conventional isolation preamplifiers and associated decoupling circuits is required. These conventional configurations rapidly become complicated when greater numbers of channels or nuclei are needed. In this work, a novel coil decoupling mechanism is proposed to enable broadband decoupling for array coils with one set of preamplifiers. METHODS: Instead of using conventional isolation preamplifiers, a high-input impedance preamplifier is proposed to create broadband decoupling of the array elements. A matching network consisting of a single inductor-capacitor-capacitor multi-tuned network and a wire-wound transformer was used to interface the surface coil to the high-impedance preamplifier. To validate the concept, the proposed configuration was compared to the conventional preamplifier decoupling configuration on both bench and scanner. RESULTS: 2 The approach can provide more than 15dB decoupling over a range of 25MHz, covering the Larmor frequencies of 23 Na and 2 H at 4.7T. This multi-tuned prototype obtained 61% and 76% of the imaging SNR at 2 H and 23 Na respectively, 76 and 89% in a higher loading test phantom, when compared to the conventional single-tuned preamplifier decoupling configuration. CONCLUSION: With the multinuclear array operation and decoupling achieved using only one layer of array coil and preamplifiers, this work provides a simple approach of building high element-count arrays to enable accelerated imaging or SNR improvement from multiple nuclei.


Assuntos
Aumento da Imagem , Imageamento por Ressonância Magnética , Impedância Elétrica , Desenho de Equipamento , Imagens de Fantasmas
9.
Magn Reson Med ; 87(3): 1136-1149, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34687086

RESUMO

PURPOSE: This study is to investigate time-resolved 13 C MR spectroscopy (MRS) as an alternative to imaging for assessing pyruvate metabolism using hyperpolarized (HP) [1-13 C]pyruvate in the human brain. METHODS: Time-resolved 13 C spectra were acquired from four axial brain slices of healthy human participants (n = 4) after a bolus injection of HP [1-13 C]pyruvate. 13 C MRS with low flip-angle excitations and a multichannel 13 C/1 H dual-frequency radiofrequency (RF) coil were exploited for reliable and unperturbed assessment of HP pyruvate metabolism. Slice-wise areas under the curve (AUCs) of 13 C-metabolites were measured and kinetic analysis was performed to estimate the production rates of lactate and HCO3- . Linear regression analysis between brain volumes and HP signals was performed. Region-focused pyruvate metabolism was estimated using coil-wise 13 C reconstruction. Reproducibility of HP pyruvate exams was presented by performing two consecutive injections with a 45-minutes interval. RESULTS: [1-13 C]Lactate relative to the total 13 C signal (tC) was 0.21-0.24 in all slices. [13 C] HCO3- /tC was 0.065-0.091. Apparent conversion rate constants from pyruvate to lactate and HCO3- were calculated as 0.014-0.018 s-1 and 0.0043-0.0056 s-1 , respectively. Pyruvate/tC and lactate/tC were in moderate linear relationships with fractional gray matter volume within each slice. White matter presented poor linear regression fit with HP signals, and moderate correlations of the fractional cerebrospinal fluid volume with pyruvate/tC and lactate/tC were measured. Measured HP signals were comparable between two consecutive exams with HP [1-13 C]pyruvate. CONCLUSIONS: Dynamic MRS in combination with multichannel RF coils is an affordable and reliable alternative to imaging methods in investigating cerebral metabolism using HP [1-13 C]pyruvate.


Assuntos
Imageamento por Ressonância Magnética , Ácido Pirúvico , Isótopos de Carbono , Humanos , Cinética , Espectroscopia de Ressonância Magnética , Reprodutibilidade dos Testes
10.
Magn Reson Med ; 85(6): 3497-3509, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33314274

RESUMO

PURPOSE: B1+ shimming is an important method for mitigating B1 inhomogeneity in high-field MRI. Using independent power amplifiers for each transmit (Tx) element is the preferred method for B1 shimming but comes with a high cost. Conversely, the simplest approach to control a Tx array is by using coaxial cables of varying length in the Tx chain, but this approach is cumbersome and impractical for dynamic shimming. In this article, a system is described that enables dynamic, phase-only, eight-channel B1+ steering on a 7T MR scanner with only two power amplifiers. METHODS: Power dividers were utilized to first split the existing two-channel Tx signal into eight channels. Digitally controlled phase shifters on each channel were designed to provide independent phase shifts with a resolution of 22.5° (from 0°, 22.5° … 337.5°). To validate the system, an eight-channel body dipole array was simulated and constructed for bench and 7T imaging and evaluation. RESULTS: The phase conjugate B1+ steering method was employed at three different spatial positions in simulation, bench measurements, and scanner measurements-all with matching results. At the desired points, regions with homogenous B1+ were generated, indicating good Tx steering to the selected region. CONCLUSION: The described system can be used as a simple retrofit to existing hardware to provide phase control while avoiding the need to manually switch cables and without requiring independent power amplifiers for each channel, thus demonstrating the ability to perform dynamic B1+ shimming with increased degrees of freedom but without significantly increased hardware cost.


Assuntos
Amplificadores Eletrônicos , Imageamento por Ressonância Magnética , Simulação por Computador , Desenho de Equipamento , Imagens de Fantasmas
11.
Int J Mol Sci ; 22(4)2021 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-33567582

RESUMO

Cyclophilin (Cyp) and Ca2+/calcineurin proteins are cellular components related to fungal morphogenesis and virulence; however, their roles in mediating the pathogenesis of Botrytis cinerea, the causative agent of gray mold on over 1000 plant species, remain largely unexplored. Here, we show that disruption of cyclophilin gene BcCYP2 did not impair the pathogen mycelial growth, osmotic and oxidative stress adaptation as well as cell wall integrity, but delayed conidial germination and germling development, altered conidial and sclerotial morphology, reduced infection cushion (IC) formation, sclerotial production and virulence. Exogenous cyclic adenosine monophosphate (cAMP) rescued the deficiency of IC formation of the ∆Bccyp2 mutants, and exogenous cyclosporine A (CsA), an inhibitor targeting cyclophilins, altered hyphal morphology and prevented host-cell penetration in the BcCYP2 harboring strains. Moreover, calcineurin-dependent (CND) genes are differentially expressed in strains losing BcCYP2 in the presence of CsA, suggesting that BcCyp2 functions in the upstream of cAMP- and Ca2+/calcineurin-dependent signaling pathways. Interestingly, during IC formation, expression of BcCYP2 is downregulated in a mutant losing BcJAR1, a gene encoding histone 3 lysine 4 (H3K4) demethylase that regulates fungal development and pathogenesis, in B. cinerea, implying that BcCyp2 functions under the control of BcJar1. Collectively, our findings provide new insights into cyclophilins mediating the pathogenesis of B. cinerea and potential targets for drug intervention for fungal diseases.


Assuntos
Botrytis/patogenicidade , Ciclofilinas/metabolismo , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Phaseolus/microbiologia , Doenças das Plantas/microbiologia , Esporos Fúngicos/crescimento & desenvolvimento , Adaptação Fisiológica , Ciclofilinas/genética , Proteínas Fúngicas/genética , Perfilação da Expressão Gênica , Folhas de Planta/microbiologia , Virulência
12.
New Phytol ; 225(2): 930-947, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31529514

RESUMO

Histone 3 Lysine 4 (H3K4) demethylation is ubiquitous in organisms, however the roles of H3K4 demethylase JARID1(Jar1)/KDM5 in fungal development and pathogenesis remain largely unexplored. Here, we demonstrate that Jar1/KDM5 in Botrytis cinerea, the grey mould fungus, plays a crucial role in these processes. The BcJAR1 gene was deleted and its roles in fungal development and pathogenesis were investigated using approaches including genetics, molecular/cell biology, pathogenicity and transcriptomic profiling. BcJar1 regulates H3K4me3 and both H3K4me2 and H3K4me3 methylation levels during vegetative and pathogenic development, respectively. Loss of BcJAR1 impairs conidiation, appressorium formation and stress adaptation; abolishes infection cushion (IC) formation and virulence, but promotes sclerotium production in the ΔBcjar1 mutants. BcJar1 controls reactive oxygen species (ROS) production and proper assembly of Sep4, a core septin protein and virulence determinant, to initiate infection structure (IFS) formation and host penetration. Exogenous cAMP partially restored the mutant appressorium, but not IC, formation. BcJar1 orchestrates global expression of genes for ROS production, stress response, carbohydrate transmembrane transport, secondary metabolites, etc., which may be required for conidiation, IFS formation, host penetration and virulence of the pathogen. Our work systematically elucidates BcJar1 functions and provides novel insights into Jar1/KDM5-mediated H3K4 demethylation in regulating fungal development and pathogenesis.


Assuntos
Botrytis/genética , Botrytis/patogenicidade , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Histonas/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Adaptação Fisiológica , Botrytis/crescimento & desenvolvimento , Parede Celular/metabolismo , Sequência Conservada , AMP Cíclico/metabolismo , Desmetilação , Regulação para Baixo/genética , Ontologia Genética , Modelos Biológicos , Micélio/crescimento & desenvolvimento , Micélio/metabolismo , Oxirredução , Oxigênio/metabolismo , Esporos Fúngicos/metabolismo , Estresse Fisiológico , Virulência/genética
13.
Aging (Albany NY) ; 16(11): 10004-10015, 2024 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-38862259

RESUMO

OBJECTIVE: A neurodevelopmental illness termed as the autism spectrum disorder (ASD) is described by social interaction impairments. Previous studies employing resting-state functional imaging (rs-fMRI) identified both hyperconnectivity and hypoconnectivity patterns in ASD people. However, specific patterns of connectivity within and between networks linked to ASD remain largely unexplored. METHODS: We utilized a meticulously selected subset of high-quality data, comprising 45 individuals diagnosed with ASD and 47 HCs, obtained from the ABIDE dataset. The pre-processed rs-fMRI time series signals were partitioned into ninety regions of interest. We focused on eight intrinsic connectivity networks and further performed intra- and inter-network analysis. Finally, support vector machine was used to discriminate ASD from HC. RESULTS: Through different sparsities, ASD exhibited significantly decreased intra-network connectivity within default mode network and dorsal attention network, increased connectivity between limbic network and subcortical network, and decreased connectivity between default mode network and limbic network. Using the classifier trained on altered intra- and inter-network connectivity, multivariate pattern analyses classified the ASD from HC with 71.74% accuracy, 70.21% specificity and 75.56% sensitivity in 10% sparsity of functional connectivity. CONCLUSIONS: ASD showed characteristic reorganization of the brain networks and this provided new insight into the underlying process of the functional connectome dysfunction in ASD.


Assuntos
Transtorno do Espectro Autista , Encéfalo , Imageamento por Ressonância Magnética , Humanos , Transtorno do Espectro Autista/fisiopatologia , Transtorno do Espectro Autista/diagnóstico por imagem , Masculino , Feminino , Adulto , Encéfalo/diagnóstico por imagem , Encéfalo/fisiopatologia , Adulto Jovem , Máquina de Vetores de Suporte , Rede Nervosa/fisiopatologia , Rede Nervosa/diagnóstico por imagem , Conectoma , Adolescente
14.
Foods ; 13(10)2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38790866

RESUMO

This study investigated the effects of ultrasound-assisted immersion freezing (UIF) at different power rates (0, 200, 400, and 600 W) on the changes in beef quality and flavor after braising. The results demonstrated that UIF treatment at 400 W significantly reduced the juice loss (cooking loss decreased from 49.04% to 39.74%) and fat oxidation (TBARS value decreased from 0.32 mg/kg to 0.20 mg/kg) of braised beef. In addition, the tenderness (hardness value decreased from 5601.50 g to 2849.46 g) and color stability of braised beef were improved after UIF treatment. The flavor characteristics of braised beef were characterized using an electronic nose and an electronic tongue. The PCA analysis data showed that the cumulative contribution rates of the first and second principal components were 85% and 93.2%, respectively, with the first principal component accounting for a higher proportion. The UIF-400 W group had the highest concentration for the first principal component, and the differentiation was not significant compared to the control group. The total amino acid values of different power UIF treatment groups were improved compared to the AF treatment group, indicating that UIF can effectively reduce the losses caused by freezing. The results demonstrate that ultrasound-assisted freezing treatment is beneficial in enhancing the tenderness and flavor attributes of beef after braising, providing new insights into the processing of meat products with desirable quality characteristics.

15.
Sci Rep ; 14(1): 3307, 2024 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-38332252

RESUMO

Eliminating conventional pulsed B0-gradient coils for magnetic resonance imaging (MRI) can significantly reduce the cost of and increase access to these devices. Phase shifts induced by the Bloch-Siegert shift effect have been proposed as a means for gradient-free, RF spatial encoding for low-field MR imaging. However, nonlinear phasor patterns like those generated from loop coils have not been systematically studied in the context of 2D spatial encoding. This work presents an optimization algorithm to select an efficient encoding trajectory among the nonlinear patterns achievable with a given hardware setup. Performance of encoding trajectories or projections was evaluated through simulated and experimental image reconstructions. Results show that the encodings schemes designed by this algorithm provide more efficient spatial encoding than comparison encoding sets, and the method produces images with the predicted spatial resolution and minimal artifacts. Overall, the work demonstrates the feasibility of performing 2D gradient-free, low-field imaging using the Bloch-Siegert shift which is an important step towards creating low-cost, point-of-care MR systems.


Assuntos
Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Imageamento por Ressonância Magnética/métodos , Processamento de Imagem Assistida por Computador/métodos , Algoritmos , Artefatos , Imagens de Fantasmas
16.
Adv Colloid Interface Sci ; 326: 103122, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38513432

RESUMO

The performance of nano- and micro-porous materials in capturing and releasing fluids, such as during CO2 geo-storage and water/gas removal in fuel cells and electrolyzers, is determined by their wettability in contact with the solid. However, accurately characterizing wettability is challenging due to spatial variations in dynamic forces, chemical heterogeneity, and surface roughness. In situ measurements can potentially measure wettability locally as a contact angle - the angle a denser phase (e.g water) contacts solid in the presence of a second phase (e.g. hydrogen, air, CO2) - but suffer from difficulties in accurately capturing curvatures, contact areas, and contact loops of multiphase fluids. We introduce a novel extended topological method for in situ contact angle measurement and provide a comparative review of current geometric and topological methods, assessing their accuracy on ideal surfaces, porous rocks containing CO2, and water in gas diffusion layers. The new method demonstrates higher accuracy and reliability of in situ measurements for uniformly wetting systems compared to previous topological approaches, while geometric measurements perform best for mixed-wetting domains. This study further provides a comprehensive open-source platform for in situ characterization of wettability in porous materials with implications for gas geo-storage, fuel cells and electrolyzers, filtration, and catalysis.

17.
Artigo em Inglês | MEDLINE | ID: mdl-38082622

RESUMO

Low-impedance preamplifier decoupling is commonly used in RF coil array construction to minimize coupling between elements through mutual impedance. The trap circuit is an essential component in preamp decoupling techniques, but becomes a limiting factor in constructing multi-tuned, multi-nuclear coil arrays. In principle, it is possible to double-tune or multi-tune the trap circuits, but will add complexity and loss. We present a broadband decoupling approach using high impedance preamplifiers. A dual-tuned prototype four-channel array using this approach which targets 2H and 23 Na at 4.7T, has been previously constructed, evaluated and reported. Without any retuning of the array, the same setup is tested at the 23Na and 31P frequencies for 3T. Initial bench measurements and Chemical Shift Imaging (CSI) results are acquired and presented in this study.Clinical Relevance- This study could reduce the complexity of multi-nuclear array coil design.


Assuntos
Imageamento por Ressonância Magnética , Ondas de Rádio , Desenho de Equipamento , Impedância Elétrica
18.
Adv Colloid Interface Sci ; 304: 102654, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35468356

RESUMO

Capillary imbibition, such as plant roots taking up water, reservoir rocks absorbing brine and a tissue paper wiping stains, is pervasive occurred in nature, engineering and industrial fields, as well as in our daily life. This phenomenon is earliest modeled through the process that wetting liquid is spontaneously propelled by capillary pressure into regular geometry models. Recent studies have attracted more attention on capillary-driven flow models within more complex geometries of the channel, since a detailed understanding of capillary imbibition dynamics within irregular geometry models necessitates the fundamentals to fluid transport mechanisms in porous media with complex pore topologies. Herein, the fundamentals and concepts of different capillary imbibition models in terms of geometries over the past 100 years are reviewed critically, such as circular and non-circular capillaries, open and closed capillaries with triangular/rectangular cross-sections, and heterogeneous geometries with axial variations. The applications of these models with appropriate conditions are discussed in depth accordingly, with a particular emphasize on the capillary flow pattern as a consequence of capillary geometry. In addition, a universal model is proposed based on the dynamic wetting condition and equivalent cylindrical geometry to describe the capillary imbibition process in terms of various solid topologies. Finally, future research is suggested to focus on analyzing the dynamics during corner flow, the snap-off of wetting fluid, the capillary rise of non-Newtonian fluids and applying accurate physical simulation methods on capillary-driven flow processes. Generally, this review provides a comprehensive understanding of the capillary-driven flow models inside various capillary geometries and affords an overview of potential advanced developments to enhance the current understanding of fluid transport mechanisms in porous media.


Assuntos
Capilares , Porosidade , Molhabilidade
19.
J Colloid Interface Sci ; 608(Pt 3): 2330-2338, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34774316

RESUMO

HYPOTHESIS: Emerging energy-related technologies deal with multiscale hierarchical structures, intricate surface morphology, non-axisymmetric interfaces, and complex contact lines where wetting is difficult to quantify with classical methods. We hypothesise that a universal description of wetting on multiscale surfaces can be developed by using integral geometry coupled to thermodynamic laws. The proposed approach separates the different hierarchy levels of physical description from the thermodynamic description, allowing for a universal description of wetting on multiscale surfaces. THEORY AND SIMULATIONS: The theoretical framework is presented followed by application to limiting cases of wetting on multiscale surfaces. Limiting cases include those considered in the Wenzel, Cassie-Baxter, and wicking state models. Wetting characterisation of multiscale surfaces is explored by conducting simulations of a fluid droplet on a structurally rough surface and a chemically heterogeneous surface. FINDINGS: The underlying origin of the classical wetting models is shown to be rooted within the proposed theoretical framework. Integral geometry provides a topological-based wetting metric that is not contingent on any type of wetting state. The wetting metric is demonstrated to account for multiscale features along the common line in a scale consistent way; providing a universal description of wetting for multiscale surfaces.

20.
ACS Appl Mater Interfaces ; 14(16): 18393-18408, 2022 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-35418225

RESUMO

A new type of nano-SnFe2O4 with stable lattice-oxygen and abundant surface defects anchored on ultra-thin graphene-like porous carbon networks (SFO@C) is prepared for the first time by an interesting freezing crystallization salt template method. The functional composite has excellent rate performance and long-term cycle stability for lithium-ion battery (LIB) anodes due to the stable structure, improved conductivity, and shortened migrating distance for lithium-ions, which are derived from the higher lattice-oxygen of SnFe2O4, abundant porous carbon networks and surface defects, and smaller nanoparticles. Under the ultra-high current density of 10, 15, and 20 A g-1 cycling for 1000 times, the SFO@C can provide high reversible capacities of 522.2, 362.5, and 361.1 mAh g-1, respectively. The lithium-ion storage mechanism of the composite was systematically studied for the first time by in situ X-ray diffraction (XRD), ex situ XRD and scanning electron microscopy (SEM), and density functional theory (DFT) calculations. The results indicate that the existence of Li2O and metallic Fe during the lithiation/delithiation process is a key reason for reducing the initial lithium-ion storage reversibility but increasing the rate performance and capacity stability in the subsequent cycles. DFT calculations show that lithium-ions are more easily adsorbed on the (111) crystal plane with a much lower adsorption energy of -7.61 eV than other planes, and the Fe element is the main acceptor of electrons. Moreover, the kinetics investigation indicates that the lithium-ion intercalation and deintercalation in SFO@C are mainly controlled by the pseudocapacitance behavior, which is favorable to enhancing the rate performance. The research provides a new strategy for designing LIB electrode materials with a stable structure and outstanding lithium-ion storage performance.

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