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Letteratura scientifica selezionata sul tema "QMA DMA"

Autore: Grafiati

Pubblicato: 10 agosto 2024

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Articoli di riviste sul tema "QMA DMA"

Xu, Jiahui, Guichen Li, Ruiyang Bi, Haoyu Rong, and Changlun Sun. "Explanation on the Abnormal Behavior during the Nanoindentation Holding Stages by Amplifying Oscillation." Advances in Civil Engineering 2022 (January 18, 2022): 1–11. http://dx.doi.org/10.1155/2022/8886965.

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Recently, the holding states of nanoindentation experiments have been widely used to analyze the time-dependent deformations of various rocks, and the dynamic mechanical analysis (DMA) method seems to be more applicable than the quasi-static mechanical analysis (QMA) method when the influence of creep deformation on mechanical properties of rocks was analyzed. However, the former method causes an abnormal behavior during the creep holding stages that was not clearly interpreted.2 Consequently, in this study, by amplifying the oscillation of the DMA method, the mechanical mechanism of this phenomenon was explained. Experimental results confirm that the rheological deformation of rocks consists of the creep deformation (depth increasing) and the elastic aftereffect deformation (depth decreasing) during the creep time with small oscillation; once the elastic aftereffect deformation exceeds the creep deformation, the abnormal behavior can be observed. Besides, some other abnormal behaviors might be found for other rock materials when the DMA method with different oscillations is used, which illustrates the complexity and limitation of applying this method. Thus, the QMA method was recommended to investigate the above questions in future studies.

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Schweighardt, Attila, and Balázs Vehovszky. "Comparison of different methods for dynamic characterization of porous-elastic materials." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 4 (2023): 4848–58. http://dx.doi.org/10.3397/in_2023_0688.

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Acoustical simulation of porous-elastic materials requires several properties to be characterized, one of them is the dynamic mechanical behavior of the structure. For this goal, quasi-static mechanical analysis (QMA) is the generally used method executed in the ca. 20-60 Hz frequency range, resulting constant (averaged) mechanical properties. Polymer-based materials, however, are well-known from their time- and frequency-dependent behavior. This implies the need for having frequency-dependent data in a wider frequency range, but the error induced by the fluid motion inside the pores increases with frequency. For that reason, dynamic mechanical analysis (DMA) together with frequency-temperature superposition method was chosen to analyze the possibility of extending the evaluable frequency range. Different measurement setups and strategies were tested and evaluated to minimize the errors coming from machine resonances and other influencing factors, and results were compared to those obtained from the classical QMA measurements. It was finally proven, that with thoroughly chosen technique, DMA can give high quality results for porous-elastic materials as well, in a remarkably wide frequency range.

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Lin, Lu Bin, Qing Yun Yu, Zhuo Qun Gu, Xiao Ze Jiang, and Mei Fang Zhu. "Reduction-Degradable Shell Cross-Linked Micelle with pH-Responsive Cores Prepared via Click Chemistry." Materials Science Forum 848 (March 2016): 527–31. http://dx.doi.org/10.4028/www.scientific.net/msf.848.527.

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A well-defined poly [(ethylene glycol)-block-2-(dimethylamino) ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEG-b-DMA-b-DEA) triblock copolymer was synthesized via atom transfer radical polymerization (ATRP) by successively polymerization of DMA and DEA monomers using a PEG-based macroinitiator, and obtained copolymer was then converted to be PEG-b-P(DMA-co-QDMA)-b-PDEA copolymer with “clickable” moieties in the middle block by the quaternization with propargyl bromide. Those copolymers prepared were characterized by proton Nuclear Magnetic Resonance (1H NMR) and Gel Permeation Chromatography (GPC), and its self-assembly behavior and subsequently fixation with bis-(azidoethyl) disulfide via click chemistry resulting reduction-sensitive shell-cross-linked (SCL) micelle in purely aqueous solution were investigated by Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The results show the micellar structure could be effectively cross-linked via click chemistry and also be dissociated at reduction condition, which may realize it's potential application as novel drug delivery carriers.

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Turgeman Dahan, Noy, Jean-Jacques Vatine, Irit Weissman-Fogel, Hana Karpin, Sharon Shmuely, and Tami Bar-Shalita. "Quantitative Dynamic Allodynograph—A Standardized Measure for Testing Dynamic Mechanical Allodynia in Chronic Limb Pain." Sensors 23, no. 18 (2023): 7949. http://dx.doi.org/10.3390/s23187949.

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Background: Dynamic mechanical allodynia (DMA) is both a symptom and a central sensitization sign, yet no standardized method for quantifying the DMA area has been reported. This study aimed to establish psychometric properties for Quantitative Dynamic Allodynography (QDA), a newly developed protocol measuring the DMA area as a percentage of the body surface. Methods: Seventy-eight patients aged 18–65 diagnosed with chronic complex regional pain syndrome (CRPS) participated in this study. Test–retest reliability was conducted twice, one week apart (N = 20), and inter-rater (N = 3) reliability was conducted on 10 participants. Disease severity (CRPS Severity Score, CSS), pain intensity (VAS), and quality of life (SF-36) measures were utilized to test construct validity. Results: High inter-rater reliability (intraclass correlation coefficient (ICC) = 0.96, p < 0.001) and test–retest reliability (r = 0.98, p < 0.001) were found. Furthermore, the QDA score was found to be correlated with the CSS (r = 0.47, p < 0.001), VAS (r = 0.37, p < 0.001), and the SF-36 physical health total (r = −0.47, p < 0.001) scores. Conclusion: The QDA is the first developed reliable and valid protocol for measuring DMA in a clinical setting and may be used as a diagnostic and prognostic measure in clinics and in research, advancing the pain precision medicine approach.

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Zhu, Shu Yu, Zhong Li Niu, Xiao Ting Zhang, et al. "Doxorubicin Loading Capacity of Shell Cross-Linked Micelles with pH-Responsive Core as Anticancer Drug Delivery Nanocarriers." Materials Science Forum 898 (June 2017): 2366–72. http://dx.doi.org/10.4028/www.scientific.net/msf.898.2366.

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Detailed studies were performed to probe the effects of the cross-linking layer microstructure of pH-responsive shell cross-linked (SCL) micelles on the loading capacity of doxorubicin (DOX). Well-defined poly [(ethylene glycol)-block-2-(dimethylamino) ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEG-b-P(DMA- co-QDMA)-b-PDEA) copolymer with “clickable” moieties in the middle block by the quaternization with propargyl bromide dissolved molecularly in acidic solution; micellization occurred at alkaline solution to form three-layer “onionlike” micelles constituting PDEA cores, P(DMA-co-QDMA) inner shells, and PEG coronas. Two types of cross-linker bearing azide group: 1,6-bisazidehexane and bis-(azidoethyl) disulfide were utilized to prepare the SCL micelles with different cross-linking layer microstructure via click chemistry at basic aqueous media. The results showed that two types of SCL micelles possessed excellent stability. In neutral solution, these SCL micelles still maintained structural integrity, and the average hydrodynamic diameter of SCL micelles 1 and SCL micelles 2 increased to 80 nm and 90 nm, respectively. In the acidic solution, due to the complete protonated of the PDEA core, the sizes of the two types of SCL micelles increased to 95 nm and 110 nm, respectively, which were favorable for the diffusion of the encapsulated drug in the core. Moreover, the cross-linking degree had no effect on the size of SCL micelles. The loading efficiency and loading content of the SCL micelles were significantly better than those of the uncross-linked micelles, and loading capacity did not vary with degree of cross-linking. However, the SCL micelles 1 demonstrated better loading capacity. This study could be a guidance for the future research on the effects of the cross-linking layer microstructure on controlled doxorubicin release.

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Zhu, Kai, Chongshi Gu, Jianchun Qiu, Wanxin Liu, Chunhui Fang, and Bo Li. "Determining the Optimal Placement of Sensors on a Concrete Arch Dam Using a Quantum Genetic Algorithm." Journal of Sensors 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/2567305.

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Structural modal identification has become increasingly important in health monitoring, fault diagnosis, vibration control, and dynamic analysis of engineering structures in recent years. Based on an analysis of traditional optimization algorithms, this paper proposes a novel sensor optimization criterion that combines the effective independence (EFI) method with the modal strain energy (MSE) method. Considering the complex structure and enormous degrees of freedom (DOFs) of modern concrete arch dam, a quantum genetic algorithm (QGA) is used to optimize the corresponding sensor network on the upstream surface of a dam. Finally, this study uses a specific concrete arch dam as an example and determines the optimal sensor placement using the proposed method. By comparing the results with the traditional optimization methods, the proposed method is shown to maximize the spatial intersection angle among the modal vectors of sensor network and can effectively resist ambient perturbations, which will make the identified modal parameters more precise.

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Fitriansyah, Sani Nurlaela, Rika Hartati, and Irda Fidrianny. "Effect of Different Solvent on Phytochemical Content, Tyrosinase Inhibition and Antioxidant Activities of Campolay (Pouteria campechiana kunth. [Baehni.])." Open Access Macedonian Journal of Medical Sciences 10, A (2022): 158–63. http://dx.doi.org/10.3889/oamjms.2022.8204.

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BACKGROUND: Pouteria campechiana leaves are reported to have phenol and flavonoid compounds. Phenolic and flavonoid compounds can act as tyrosinase inhibitor and antioxidant. AIM: The purpose of this study was to compare phytochemical content, tyrosinase inhibition, antioxidant activities, and determine of marker compound from P. campechiana leaves extract with different polarities solvent. METHODS: In addition, the content of marker compound from P. campechaina leaves extract was determined by HPLC. RESULTS: The highest total phenolic content (TPC) 7.83 GAE/100 g extract, IC50 of tyrosinase 171.512 ± 1.352 and IC50 of DPPH 0.968 ± 0.008 was given by ethanolic extract (DE). Meanwhile ethyl acetate extract (DEA) had the highest of total flavonoid content 2.544 ± 0.554 QEA/100 g extract. The TPC correlated with tyrosinase inhibitory activity and antioxidant activity. CONCLUSION: Quercitrin was as marker compound from P. campechiana leaves extract, and quercitrin content in the DEA of P. campechiana leaves was 3.539%, while in the DE was 0.153%.

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Zhu, Kai, Chongshi Gu, Jianchun Qiu, and Hao Li. "The Analysis of the Concrete Gravity Dam’s Foundation Uplift Pressure under the Function of Typhoon." Mathematical Problems in Engineering 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/2834192.

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How to evaluate the seepage safety status of the concrete gravity dam under the function of short-period heavy rainfall and the possible historical extreme reservoir water level during typhoon is an important issue considering the dam safety-monitoring. Based on analysis of the monitoring series of the foundation uplift pressure, this paper assumed the influential process of antecedent reservoir water level and rainfall as a process of normal distribution and introduced the mutation factor to reflect the uprush feature of uplift pressure under the function of high-influential typhoon. Moreover, the corresponding hysteresis days and influential days of the model are optimized with quantum genetic algorithm (QGA) to raise the fitting and prediction accuracy. It is verified that the new statistical model for fitting can obtain higher multiple correlation coefficient (0.972) compared with the traditional statistical model (0.925) and could also perfectly predict the uprush feature of the pressure during the typhoon, which is of certain theoretical and practical application value in the future.

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Schneider, Bruna Celestino, Janaína Vieira dos Santos Motta, Ludmila Correa Muniz, et al. "Desenho de um questionário de frequência alimentar digital autoaplicado para avaliar o consumo alimentar de adolescentes e adultos jovens: coortes de nascimentos de Pelotas, Rio Grande do Sul." Revista Brasileira de Epidemiologia 19, no. 2 (2016): 419–32. http://dx.doi.org/10.1590/1980-5497201600020017.

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RESUMO: Objetivo: Artigo metodológico com o objetivo de descrever a construção de um questionário de frequência alimentar (QFA) digital autoaplicado, desenvolvido para as coortes de nascimentos de Pelotas de 1982 e 1993. Métodos: O instrumento foi criado com base em QFAs anteriormente utilizados nas duas coortes em acompanhamentos nos anos de 2004 e 2008. O QFA foi elaborado incluindo 88 alimentos e/ou preparações cujas frequências foram agrupadas em categorias desde o valor mínimo de consumo de nunca ou < 1 vez/mês até o máximo de ≥ 5 vezes/dia. As opções fechadas relativas à porção foram construídas considerando recordatórios de 24 horas (R24Hs) anteriormente aplicados à subamostra da coorte de 1993. Três alternativas de porção foram construídas: igual, menos ou mais. A porção igual foi descrita com base no percentil 50 do consumo de cada alimento, obtido a partir das distribuições das porções constantes nos R24H. Fotos das porções relativas ao percentil 50 de cada alimento foram também incluídas ao formato do programa. Resultados: Esse QFA digital incluiu alimentos e preparações que atendem aos objetivos das pesquisas atuais. A aparência do programa foi atrativa à equipe de trabalho e também aos participantes do estudo. O tempo médio de aplicação de 12 minutos e a facilidade de preenchimento possibilitaram que vários participantes respondessem às questões ao mesmo tempo. Além disso, o instrumento dispensou a necessidade de entrevistador e a dupla entrada de dados em programa específico. Conclusão: Recomenda-se o uso dessa mesma estratégia em outros estudos, adaptando-a aos diferentes contextos e situações.

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Abd-Al Wahhab, Iman, Sarmad Nory Gany, and Hussein Abdul Kadhim. "Assessment of RBCs membrane protective activity of citicoline and eicosapentanoic- decosahexanoic acid in osmotic fragility model." AL-QADISIYAH MEDICAL JOURNAL 10, no. 18 (2017): 118–21. http://dx.doi.org/10.28922/qmj.2014.10.18.118-121.

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Abstract (sommario):

Different organic compounds possess a good membranes stabilizing effects that protect cells like erythrocytes from strains exerted by change in medium osmolarity . These changes in tonicity could predispose RBCs for hemolysis . This disorder could be assessed by osmotic fragility test . From those compounds that widen osmotic fragility test values are citicoline (membrane phospholipids precursor) and polyunsaturated fatty acids EPA-DHA. Assessment of these compounds on osmotic fragility test revealed that both of citicoline and EPA-DHA will protect RBCs from hemolysis for a wider range than values of the control blank. Although these effects were statistically not significant on considering statistical correlation test, however, the differences were important on considering t test for the range of saline concentration between 0.4-0.5 at P<0.05 . From the overall results, both citicoline and pufa induced a significant change in statbility of RBCs membrane upon exposure of osmotic effects in the saline concentration between 0.4-0.5. Further evaluation of citicoline and EPA- DHA effects may be necessary before recommending the use these compounds in protection against hemolytic diseases.

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