Research and Modeling of Viscoelastic Behavior of Elastomeric Nanocomposites

The paper presents results of studying mechanical properties of polymer composites depending on types of filler particles (granular - carbon black, nanodiamonds; layered - graphene plates; fibrous - single-walled nanotubes). These nanofillers differ greatly from each other in their structure and geometry. A significant difference in behavior of nanocomposites was revealed even with little introduction of particles into the elastomer. The highest level of reinforcement of the matrix was obtained when single-wall nanotubes and detonation nanodiamonds were used as fillers. The viscoelastic properties and the Mullins softening effect [1-4] were investigated in experiments performed with material samples subjected to complex uniaxial cyclic deformation. In these experiments, the amplitude of deformations was changed step by step; and at each step a time delay was specified to complete rearrangement processes of the material structure. It was found that a pronounced softening effect after the first cycle of deformation and significant hysteresis losses occur in the material filled with single-walled nanotubes. These characteristics are insignificant for the rest of nanocomposites until elongation increases twofold. In accordance with the obtained results, a new version of the mathematical model to describe properties of the viscoelastic polymer materials was proposed. The constants of the constitutive relations were calculated for each material; the theoretical and experimental load curves were compared. As a result, the introduced model is able to describe the behavior of elastomeric nanocomposites with a high accuracy. Moreover, this model is relatively easy to use, suitable for a wide range of strain rates and stretch ratios and does not require the entire history of deformation as needed for integral models of viscoelasticity.

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Multicoating Inhomogeneities Problem for Effective Viscoelastic Properties of Particulate Composite Materials

Journal of Engineering Materials and Technology ◽

10.1115/1.3086336 ◽

2009 ◽

Vol 131 (2) ◽

Cited By ~ 13

Author(s):

Yao Koutsawa ◽

Mohammed Cherkaoui ◽

El Mostafa Daya

Keyword(s):

Loss Modulus ◽

Micromechanical Model ◽

Polymer System ◽

High Capacity ◽

Viscoelastic Behavior ◽

Particulate Composite ◽

Micromechanical Modeling ◽

High Loss ◽

Wide Range ◽

The Matrix

The present work extends the multicoated micromechanical model of Lipinski et al. (2006, “Micromechanical Modeling of an Arbitrary Ellipsoidal Multi-Coated Inclusion,” Philos. Mag., 86(10), pp. 1305–1326) in the quasistatic domain to compute the effective material moduli of a viscoelastic material containing multicoated spherical inclusions displaying elastic or viscoelastic behavior. Losses are taken into account by introducing the frequency-dependent complex stiffness tensors of the viscoelastic matrix and the multicoated inclusions. The advantage of the micromechanical model is that it is applicable to the case of nonspherical multicoated inclusions embedded in anisotropic materials. The numerical simulations indicate that with proper choice of material properties, it is possible to engineer multiphase polymer system to have a high-loss modulus (good energy dissipation characteristics) for a wide range of frequencies without substantially degrading the stiffness of the composite (storage modulus). The numerical analyses show also that with respect to the relative magnitudes of the loss factors and the storage moduli of the matrix, inclusion and coating, the overall properties of the viscoelastic particulate composite are dominated by the properties of the matrices in some frequency ranges. The model can thus be a suitable tool to explore a wide range of microstructures for the design of materials with high capacity to absorb acoustic and vibrational energies.

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Soft-Tissue-Mimicking Using Hydrogels for the Development of Phantoms

Gels ◽

10.3390/gels8010040 ◽

2022 ◽

Vol 8 (1) ◽

pp. 40

Author(s):

Aitor Tejo-Otero ◽

Felip Fenollosa-Artés ◽

Isabel Achaerandio ◽

Sergi Rey-Vinolas ◽

Irene Buj-Corral ◽

...

Keyword(s):

Mechanical Properties ◽

Soft Tissues ◽

Mechanical Response ◽

Viscoelastic Behavior ◽

Linear Elastic ◽

Lack Of Information ◽

Wide Range ◽

Significant Difference ◽

Promising Solution ◽

Living Tissues

With the currently available materials and technologies it is difficult to mimic the mechanical properties of soft living tissues. Additionally, another significant problem is the lack of information about the mechanical properties of these tissues. Alternatively, the use of phantoms offers a promising solution to simulate biological bodies. For this reason, to advance in the state-of-the-art a wide range of organs (e.g., liver, heart, kidney as well as brain) and hydrogels (e.g., agarose, polyvinyl alcohol –PVA–, Phytagel –PHY– and methacrylate gelatine –GelMA–) were tested regarding their mechanical properties. For that, viscoelastic behavior, hardness, as well as a non-linear elastic mechanical response were measured. It was seen that there was a significant difference among the results for the different mentioned soft tissues. Some of them appear to be more elastic than viscous as well as being softer or harder. With all this information in mind, a correlation between the mechanical properties of the organs and the different materials was performed. The next conclusions were drawn: (1) to mimic the liver, the best material is 1% wt agarose; (2) to mimic the heart, the best material is 2% wt agarose; (3) to mimic the kidney, the best material is 4% wt GelMA; and (4) to mimic the brain, the best materials are 4% wt GelMA and 1% wt agarose. Neither PVA nor PHY was selected to mimic any of the studied tissues.

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Validation of the Applied Biosystems 7500 Fast Instrument for Detection of Listeria Species with the SureTect Listeria Species PCR Assay

Journal of AOAC International ◽

10.5740/jaoacint.15-0283 ◽

2016 ◽

Vol 99 (2) ◽

pp. 407-416

Author(s):

Jonathan Cloke ◽

Julia Arizanova ◽

David Crabtree ◽

Helen Simpson ◽

Katharine Evans ◽

...

Keyword(s):

Reference Method ◽

Probability Of Detection ◽

Stainless Steel Surface ◽

Pcr Assay ◽

Listeria Species ◽

Surface Samples ◽

Wide Range ◽

Significant Difference ◽

The Matrix ◽

Level 2

Abstract The Thermo Scientific™ SureTect™ Listeria species Real-Time PCR Assay was certified during 2013 by the AOAC Research Institute (RI) Performance Tested MethodsSM program as a rapid method for the detection of Listeria species from a wide range of food matrixes and surface samples. A method modification study was conducted in 2015 to extend the matrix claims of the product to a wider range of food matrixes. This report details the method modification study undertaken to extend the use of this PCR kit to the Applied Biosystems™ 7500 Fast PCR Instrument and Applied Biosystems RapidFinder™ Express 2.0 software allowing use of the assay on a 96-well format PCR cycler in addition to the current workflow, using the 24-well Thermo Scientific PikoReal™ PCR Instrument and Thermo Scientific SureTect software. The method modification study presented in this report was assessed by the AOAC-RI as being a level 2 method modification study, necessitating a method developer study on a representative range of food matrixes covering raw ground turkey, 2% fat pasteurized milk, and bagged lettuce as well as stainless steel surface samples. All testing was conducted in comparison to the reference method detailed in International Organization for Standardization (ISO) 6579:2002. No significant difference by probability of detection statistical analysis was found between the SureTect Listeria species PCR Assay or the ISO reference method methods for any of the three food matrixes and the surface samples analyzed during the study.

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Biochemical and molecular characterization of Alternaria alternata isolates highly resistant to procymidone from broccoli and cabbage

Phytopathology Research ◽

10.1186/s42483-021-00092-z ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Bingran Wang ◽

Tiancheng Lou ◽

Lingling Wei ◽

Wenchan Chen ◽

Longbing Huang ◽

...

Keyword(s):

Alternaria Alternata ◽

Single Point ◽

Sodium Dodecyl ◽

Cross Resistance ◽

Molecular Characteristics ◽

Single Point Mutation ◽

Wide Range ◽

Significant Difference ◽

Leaf Blights ◽

High Level

AbstractAlternaria alternata, a causal agent of leaf blights and spots on a wide range of hosts, has a high risk of developing resistance to fungicides. Procymidone, a dicarboximide fungicide (DCF), has been widely used in controlling Alternaria leaf blights in China for decades. However, the resistance of A. alternata against DCFs has rarely been reported from crucifer plants. A total of 198 A. alternata isolates were collected from commercial fields of broccoli and cabbage during 2018–2019, and their sensitivities to procymidone were determined. Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant (ProHR) and procymidone-sensitive (ProS) isolates, and also between ProHR isolates from broccoli and cabbage. Compared with ProS isolates, the mycelial growth rate, sporulation capacity and virulence of most ProHR isolates were reduced; ProHR isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate (SDS); all ProHR isolates showed a reduced sensitivity to hydrogen peroxide (H2O2) except for the isolate B102. Correlation analysis revealed a positive cross-resistance between procymidone and iprodione, or fludioxonil. When treated with 10 μg/mL of procymidone, both mycelial intracellular glycerol accumulations (MIGAs) and relative expression of AaHK1 in ProS isolates were higher than those in ProHR isolates. Sequence alignment of AaHK1 from ten ProHR isolates demonstrated that five of them possessed a single-point mutation (P94A, V612L, E708K or Q924STOP), and four isolates had an insertion or a deletion in their coding regions. No significant difference in biochemical characteristics was observed among ProHR isolates from two different hosts, though mutations in AaHK1 of the cabbage-originated ProHR isolates were distinct from those of the broccoli-originated ProHR isolates.

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Antifungal Activity of Propyl Disulfide from Neem (Azadirachta indica) in Vapor and Agar Diffusion Assays against Anthracnose Pathogens (Colletotrichum gloeosporioides and Colletotrichum acutatum) in Mango Fruit

Microorganisms ◽

10.3390/microorganisms9040839 ◽

2021 ◽

Vol 9 (4) ◽

pp. 839

Author(s):

Muhammad Rafiullah Khan ◽

Vanee Chonhenchob ◽

Chongxing Huang ◽

Panitee Suwanamornlert

Keyword(s):

Antifungal Activity ◽

Mycelial Growth ◽

Colletotrichum Gloeosporioides ◽

Colletotrichum Acutatum ◽

Model Parameters ◽

Pathogenicity Test ◽

Agar Diffusion ◽

Wide Range ◽

Significant Difference ◽

Diffusion Assay

Microorganisms causing anthracnose diseases have a medium to a high level of resistance to the existing fungicides. This study aimed to investigate neem plant extract (propyl disulfide, PD) as an alternative to the current fungicides against mango’s anthracnose. Microorganisms were isolated from decayed mango and identified as Colletotrichum gloeosporioides and Colletotrichum acutatum. Next, a pathogenicity test was conducted and after fulfilling Koch’s postulates, fungi were reisolated from these symptomatic fruits and we thus obtained pure cultures. Then, different concentrations of PD were used against these fungi in vapor and agar diffusion assays. Ethanol and distilled water were served as control treatments. PD significantly (p ≤ 0.05) inhibited more of the mycelial growth of these fungi than both controls. The antifungal activity of PD increased with increasing concentrations. The vapor diffusion assay was more effective in inhibiting the mycelial growth of these fungi than the agar diffusion assay. A good fit (R2, 0.950) of the experimental data in the Gompertz growth model and a significant difference in the model parameters, i.e., lag phase (λ), stationary phase (A) and mycelial growth rate, further showed the antifungal efficacy of PD. Therefore, PD could be the best antimicrobial compound against a wide range of microorganisms.

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A Threat of Farmers’ Suicide and the Opportunity in Organic Farming for Sustainable Agricultural Development in India

Sustainability ◽

10.3390/su11082400 ◽

2019 ◽

Vol 11 (8) ◽

pp. 2400 ◽

Cited By ~ 4

Author(s):

Karthikeyan Mariappan ◽

Deyi Zhou

Keyword(s):

Organic Farming ◽

Tamil Nadu ◽

Agricultural Development ◽

Small Scale ◽

Conventional Farming ◽

Wide Range ◽

Significant Difference ◽

Small Scale Farmers ◽

The Cost ◽

Input Cost

Agriculture is the main sources of income for humans. Likewise, agriculture is the backbone of the Indian economy. In India, Tamil Nadu regional state has a wide range of possibilities to produce all varieties of organic products due to its diverse agro-climatic condition. This research aimed to identify the economics and efficiency of organic farming, and the possibilities to reduce farmers’ suicides in the Tamil Nadu region through the organic agriculture concept. The emphasis was on farmers, producers, researchers, and marketers entering the sustainable economy through organic farming by reducing input cost and high profit in cultivation. A survey was conducted to gather data. One way analysis of variance (ANOVA) has been used to test the hypothesis regards the cost and profit of rice production. The results showed that there was a significant difference in profitability between organic and conventional farming methods. It is very transparent that organic farming is the leading concept of sustainable agricultural development with better organic manures that can improve soil fertility, better yield, less input cost and better return than conventional farming. The study suggests that by reducing the cost of cultivation and get a marginal return through organic farming method to poor and small scale farmers will reduce socio-economic problems such as farmers’ suicides in the future of Indian agriculture.

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4K 3-dimensional video microscope system (orbeye) for transsphenoidal pituitary surgery

Acta Neurochirurgica ◽

10.1007/s00701-021-04762-x ◽

2021 ◽

Author(s):

Roman Rotermund ◽

Jan Regelsberger ◽

Katharina Osterhage ◽

Jens Aberle ◽

Jörg Flitsch

Keyword(s):

3D Visualization ◽

Remission Rate ◽

Subjective Evaluation ◽

Pituitary Surgery ◽

Image Resolution ◽

Wide Range ◽

Significant Difference ◽

Duration Of Surgery ◽

Video Microscope ◽

Transsphenoidal Pituitary Surgery

Abstract Background In previous reports on experiences with an exoscope, this new technology was not found to be applicable for transsphenoidal pituitary surgery. As a specialized center for pituitary surgery, we were using a 4K 3D video microscope (Orbeye, Olympus) to evaluate the system for its use in transsphenoidal pituitary surgery in comparison to conventional microscopy. Method We report on 296 cases performed with the Orbeye at a single institution. An observational study was conducted with standardized subjective evaluation by the surgeons after each procedure. An objective measurement was added to compare the exoscopic and microscopic methods, involving surgery time and the initial postoperative remission rate in matched cohorts. Results The patients presented with a wide range of pathologies. No serious events or minor complications occurred based on the usage of the 4K 3D exoscope. There was no need for switching back to the microscope in any of the cases. Compared to our microsurgically operated collective, there was no significant difference regarding duration of surgery, complications, or extent of resection. The surgeons rated the Orbeye beneficial in regard to instrument size, positioning, surgeon’s ergonomics, learning curve, image resolution, and high magnification. Conclusions The Orbeye exoscope presents with optical and digital zoom options as well as a 4K image resolution and 3D visualization resulting in better depth perception and flexibility in comparison to the microscope. Split screen mode offers the complementary benefit of the endoscope which may increase the possibilities of lateral view but has to be evaluated in comparison to endoscopic transsphenoidal procedures in the next step.

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Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽

10.3390/met11040548 ◽

2021 ◽

Vol 11 (4) ◽

pp. 548 ◽

Cited By ~ 1

Author(s):

Leonid Agureev ◽

Valeriy Kostikov ◽

Zhanna Eremeeva ◽

Svetlana Savushkina ◽

Boris Ivanov ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Elastic Modulus ◽

Strength Properties ◽

Alumina Nanoparticles ◽

Metal Powders ◽

Wide Range ◽

The Matrix ◽

Spark Plasma ◽

Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

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A smart passive MR damper with a hybrid powering system for impact mitigation: An experimental study

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20988085 ◽

2021 ◽

pp. 1045389X2098808

Author(s):

S. Jin ◽

L. Deng ◽

J. Yang ◽

S. Sun ◽

D. Ning ◽

...

Keyword(s):

Impact Velocity ◽

Mr Damper ◽

Damping Force ◽

Softening Effect ◽

Impact Speed ◽

Impact Mitigation ◽

Passive Damper ◽

Comparison Results ◽

Wide Range ◽

The Impact

This paper presents a smart passive MR damper with fast-responsive characteristics for impact mitigation. The hybrid powering system of the MR damper, composed of batteries and self-powering component, enables the damping of the MR damper to be negatively proportional to the impact velocity, which is called rate-dependent softening effect. This effect can keep the damping force as the maximum allowable constant force under different impact speed and thus improve the efficiency of the shock energy mitigation. The structure, prototype and working principle of the new MR damper are presented firstly. Then a vibration platform was used to characterize the dynamic property and the self-powering capability of the new MR damper. The impact mitigation performance of the new MR damper was evaluated using a drop hammer and compared with a passive damper. The comparison results demonstrate that the damping force generated by the new MR damper can be constant over a large range of impact velocity while the passive damper cannot. The special characteristics of the new MR damper can improve its energy dissipation efficiency over a wide range of impact speed and keep occupants and mechanical structures safe.

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Estimating the number of usability problems affecting medical devices: modelling the discovery matrix

BMC Medical Research Methodology ◽

10.1186/s12874-020-01091-y ◽

2020 ◽

Vol 20 (1) ◽

Author(s):

Vincent Vandewalle ◽

Alexandre Caron ◽

Coralie Delettrez ◽

Renaud Périchon ◽

Sylvia Pelayo ◽

...

Keyword(s):

Medical Devices ◽

Market Access ◽

Real Life ◽

Usability Testing ◽

Probability Of Detection ◽

Usability Problems ◽

Usability Problem ◽

Wide Range ◽

The Matrix ◽

Problem Detection

Abstract Background Usability testing of medical devices are mandatory for market access. The testings’ goal is to identify usability problems that could cause harm to the user or limit the device’s effectiveness. In practice, human factor engineers study participants under actual conditions of use and list the problems encountered. This results in a binary discovery matrix in which each row corresponds to a participant, and each column corresponds to a usability problem. One of the main challenges in usability testing is estimating the total number of problems, in order to assess the completeness of the discovery process. Today’s margin-based methods fit the column sums to a binomial model of problem detection. However, the discovery matrix actually observed is truncated because of undiscovered problems, which corresponds to fitting the marginal sums without the zeros. Margin-based methods fail to overcome the bias related to truncation of the matrix. The objective of the present study was to develop and test a matrix-based method for estimating the total number of usability problems. Methods The matrix-based model was based on the full discovery matrix (including unobserved columns) and not solely on a summary of the data (e.g. the margins). This model also circumvents a drawback of margin-based methods by simultaneously estimating the model’s parameters and the total number of problems. Furthermore, the matrix-based method takes account of a heterogeneous probability of detection, which reflects a real-life setting. As suggested in the usability literature, we assumed that the probability of detection had a logit-normal distribution. Results We assessed the matrix-based method’s performance in a range of settings reflecting real-life usability testing and with heterogeneous probabilities of problem detection. In our simulations, the matrix-based method improved the estimation of the number of problems (in terms of bias, consistency, and coverage probability) in a wide range of settings. We also applied our method to five real datasets from usability testing. Conclusions Estimation models (and particularly matrix-based models) are of value in estimating and monitoring the detection process during usability testing. Matrix-based models have a solid mathematical grounding and, with a view to facilitating the decision-making process for both regulators and device manufacturers, should be incorporated into current standards.

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