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Sample records for extracting mechanical properties

  1. Antimicrobial, Optical and Mechanical Properties of Chitosan-Starch Films with Natural Extracts.

    PubMed

    Lozano-Navarro, Jessica I; Díaz-Zavala, Nancy P; Velasco-Santos, Carlos; Martínez-Hernández, Ana L; Tijerina-Ramos, Beatriz I; García-Hernández, Margarita; Rivera-Armenta, José L; Páramo-García, Ulises; Reyes-de la Torre, Adriana I

    2017-05-05

    Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan-starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV-VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications.

  2. Antimicrobial, Optical and Mechanical Properties of Chitosan–Starch Films with Natural Extracts

    PubMed Central

    Lozano-Navarro, Jessica I.; Díaz-Zavala, Nancy P.; Velasco-Santos, Carlos; Martínez-Hernández, Ana L.; Tijerina-Ramos, Beatriz I.; García-Hernández, Margarita; Rivera-Armenta, José L.; Páramo-García, Ulises; Reyes-de la Torre, Adriana I.

    2017-01-01

    Natural extracts possess several kinds of antioxidants (anthocyanins, betalains, thymol, carvacrol, and resveratrol) that have also demonstrated antimicrobial properties. In order to study these properties, extracts from cranberry, blueberry, beetroot, pomegranate, oregano, pitaya, and resveratrol (from grapes) were obtained. Growth inhibition tests of mesophilic aerobes, coliforms, and fungi were conducted in films prepared from the extracts in accordance with Mexican Official Norms (NOM). Optical properties such as transparency and opacity, mechanical properties, and pH were also analyzed in these materials. The films with beetroot, cranberry, and blueberry extracts demonstrated the best antimicrobial activity against various bacteria and fungi in comparison with unmodified chitosan–starch film. This study shows that the addition of antioxidants improved the antimicrobial performance of these films. It was also found that antimicrobial properties are inherent to the films. These polymers combined with the extracts effectively inhibit or reduce microorganism growth from human and environmental contact; therefore, previous sterilization could be unnecessary in comparison with traditional plastics. The presence of extracts decreased transmittance percentages at 280 and 400 nm, as well as the transparency values, while increasing their opacity values, providing better UV–VIS light barrier properties. Despite diminished glass transition temperatures (Tg), the values obtained are still adequate for food packaging applications. PMID:28475151

  3. Extracting the mechanical properties of microtubules from thermal fluctuation measurements on an attached tracer particle.

    PubMed

    Taute, Katja M; Pampaloni, Francesco; Florin, Ernst-Ludwig

    2010-01-01

    The mechanical properties of microtubules have been the subject of intense study during recent decades because of their importance to the many cell functions that they are involved in. Observations of microtubule thermal fluctuations have proven to be a reliable method to extract mechanical properties because they provide intrinsic calibration. While analysis of the entire microtubule shape is limited by spatial resolution to very long microtubules, we show that even for short microtubules, one can obtain high-precision fluctuation information from one point along the contour by the use of tracer particles attached to the microtubule. The information is sufficient to extract key mechanical parameters such as stiffness and first mode relaxation time. In this article, we discuss sample preparation as well as measurements and data analysis.

  4. CMOS-MEMS Test-Key for Extracting Wafer-Level Mechanical Properties

    PubMed Central

    Chuang, Wan-Chun; Hu, Yuh-Chung; Chang, Pei-Zen

    2012-01-01

    This paper develops the technologies of mechanical characterization of CMOS-MEMS devices, and presents a robust algorithm for extracting mechanical properties, such as Young’s modulus, and mean stress, through the external electrical circuit behavior of the micro test-key. An approximate analytical solution for the pull-in voltage of bridge-type test-key subjected to electrostatic load and initial stress is derived based on Euler’s beam model and the minimum energy method. Then one can use the aforesaid closed form solution of the pull-in voltage to extract the Young’s modulus and mean stress of the test structures. The test cases include the test-key fabricated by a TSMC 0.18 μm standard CMOS process, and the experimental results refer to Osterberg’s work on the pull-in voltage of single crystal silicone microbridges. The extracted material properties calculated by the present algorithm are valid. Besides, this paper also analyzes the robustness of this algorithm regarding the dimension effects of test-keys. This mechanical properties extracting method is expected to be applicable to the wafer-level testing in micro-device manufacture and compatible with the wafer-level testing in IC industry since the test process is non-destructive. PMID:23235449

  5. Extraction of mechanical properties of foot plantar tissues using ultrasound indentation associated with genetic algorithm.

    PubMed

    Ling, Hang-Yin; Choi, Pong-Chi; Zheng, Yong-ping; Lau, Kin-Tak

    2007-08-01

    This paper demonstrates the use of ultrasound indentation technique for estimating the mechanical properties of foot plantar tissues in virtue of the reconstruction of the force response using genetic algorithm (GA) from an indentation test based on a quasi-linear viscoelastic (QLV) model. The indentation test on the plantar tissues covering the right first metatarsal head of a normal subject was carried out to verify the feasibility of the GA for the extraction of the tissue properties. The QLV properties of the plantar tissues were determined by the GA with a fixed Poisson's ratio. Such results were then compared with those obtained using a classical optimization method. Moreover, the GA was further employed to simultaneously determine the QLV properties as well as the Poisson's ratio of the plantar tissues. The correlations between the QLV properties and the Poisson's ratio are discussed.

  6. Analytical model for extracting mechanical properties of a single cell in a tapered micropipette

    NASA Astrophysics Data System (ADS)

    He, J. H.; Xu, W.; Zhu, L.

    2007-01-01

    A simple solid mechanical model has been developed to extract the mechanical properties of a single cell in a tapered micropipette. This analytical model is derived using the definition of elastic modulus and force equilibrium. Using the authors' model, an elastic modulus of 21.80±4.91Pa, a Poisson ratio of 0.46±0.03, and a friction coefficient of 0.0274±0.0077 are extracted for a neutrophil cell. The model is verified by finite element software and shows good agreement with experiments. The biophysical basis of the model and application in microfluidic channels for cancer cell research are discussed, while a comparison is made with other models.

  7. Mechanical and thermal properties of polylactic acid composites reinforced with cellulose nanoparticles extracted from kenaf fibre

    NASA Astrophysics Data System (ADS)

    Ketabchi, Mohammad Reza; Khalid, Mohammad; Thevy Ratnam, Chantara; Walvekar, Rashmi

    2016-12-01

    Different approaches have been attempted to use biomass as filler for production of biodegradable polymer composites. In this study, cellulose nanoparticles (CNP) extracted from kenaf fibres were used to produce polylactic acid (PLA) based biodegradable nanocomposites. CNP concentration was varied from 1-5 wt. % and blended with PLA using Brabender twin-screw compounder. Effects of CNP loading on the mechanical, thermal and dynamic properties of PLA were investigated. Studies on the morphological properties and influence of CNP loading on the properties of CNP/PLA nanocomposite were also conducted. The results show an adequate compatibility between CNP and PLA matrix. Moreover, addition of 3 wt. % of CNP improved the PLA tensile strength by 25%.

  8. The effect of soxhlet extraction on morphology and mechanical properties of Poly(DVB)polyHIPE

    NASA Astrophysics Data System (ADS)

    Pakeyangkoon, Pornsri; Nithitanakul, Manit

    2007-03-01

    PolyHIPE (Polymerized High Internal Phase Emulsion) is a novel porous polymer, which is microporous materials and produce by polymerization of the continuous phase of system. Poly(DVB)PolyHIPE using two different system of three-component surfactant (S20M and S80M) with various porogenic solvents including T, CB, CB/T and PE has been successfully prepared. The phase morphology, mechanical properties and surface area measurement were investigated. After polymerization of continuous phase, the porous materials with interconnected were obtained. The cell size and surface area were found to improve by using various solvent, this is due to the ability of porogenic solvent and mixture of surfactant which prevent the Ostwald ripening (coalescence) of system. Moreover, the surface area and mechanical properties of the resulting materials were found to be depended on the soxhlet time. It can be concluded that the suitable soxhlet time for extraction was 6-12 hours and at this condition, high surface area with highest mechanical properties was obtained as compare to others conditions.

  9. Antimicrobial and physical-mechanical properties of agar-based films incorporated with grapefruit seed extract.

    PubMed

    Kanmani, Paulraj; Rhim, Jong-Whan

    2014-02-15

    The use of synthetic petroleum based packaging films caused serious environmental problems due to their difficulty in recycling and poor biodegradability. Therefore, present study was aimed to develop natural biopolymer-based antimicrobial packaging films as an alternative for the synthetic packaging films. As a natural antimicrobial agent, grapefruit seed extract (GSE) has been incorporated into agar to prepare antimicrobial packaging film. The films with different concentrations of GSE were prepared by a solvent casting method and the resulting composite films were examined physically and mechanically. In addition, the films were characterized by FE-SEM, XRD, FT-IR and TGA. The incorporation of GSE caused increase in color, UV barrier, moisture content, water solubility and water vapor permeability, while decrease in surface hydrophobicity, tensile strength and elastic modulus of the films. As the concentration of GSE increased from 0.6 to 13.3 μg/mL, the physical and mechanical properties of the films were affected significantly. The addition of GSE changed film microstructure of the film, but did not influence the crystallinity of agar and thermal stability of the agar-based films. The agar/GSE films exhibited distinctive antimicrobial activity against three test food pathogens, such as Listeria monocytogenes, Bacillus cereus and Escherichia coli. These results suggest that agar/GSE films have potential to be used in an active food packaging systems for maintaining food safety and extending the shelf-life of the packaged food.

  10. Mechanical properties, water sorption characteristics, and compound release of grape seed extract-incorporated resins

    PubMed Central

    EPASINGHE, Don Jeevanie; YIU, Cynthia Kar Yung; BURROW, Michael Francis

    2017-01-01

    Abstract Objective This study evaluated the effect of grape seed extract (GSE) incorporation on the mechanical properties, water sorption, solubility, and GSE release from the experimental adhesive resins. Material and Methods An experimental comonomer mixture, consisting of 40% Bis-GMA, 30% Bis MP, 28% HEMA, 0.26% camphorquinone and 1% EDMAB, was used to prepare four GSE-incorporated adhesive resins at concentrations of 0.5, 1, 1.5, and 2 wt%. The neat resin without GSE was used as the control. Six resin beams (25 mm x 2 mm x 2 mm) per group were prepared for flexural strength and modulus of elasticity evaluations using a universal testing machine at a crosshead speed of 1 mm/min. Five disks (6 mm in diameter and 2 mm in thickness) per group were used for microhardness measurements using a Leitz micro-hardness tester with Leica Qgo software. Five disks (7 mm in diameter and 2 mm in thickness) per group were prepared and stored in deionized water for 28 days. Water sorption, solubility, and GSE release in deionized water were calculated for each GSE-incorporated adhesive at the end of 28th day. Data was evaluated using one-way ANOVA and Tukey multiple comparisons. Results Flexural strength, modulus of elasticity and microhardness of GSE-incorporated adhesive decreased significantly with incorporation of 1.5% of GSE (p<0.05). Addition of GSE had no effect on the water sorption of the adhesive resins (p=0.33). The solubility of the resin also increased significantly with incorporation of 1.5% of GSE (p<0.05). Quantities of GSE release increased with increased concentration of GSE in the adhesive resin. Conclusion Up to 1% of GSE can be incorporated into a dental adhesive resin without interfering with the mechanical properties or solubility of the resins. PMID:28877280

  11. Extracting mechanical properties of copper coatings on oxidized silicon substrates by nanoindentation

    NASA Astrophysics Data System (ADS)

    Moharrami, N.; Oila, A.; Bull, S. J.

    2014-08-01

    The thickness of the copper coatings that are used for the manufacture of conducting tracks in microelectronic devices are being aggressively scaled down and there is a need to monitor the mechanical response of metallization at a scale comparable to the material microstructure. When using indentation tests to assess the properties of thin films, the plastic zone dimensions are of a similar scale to the grain size. For the purposes of designs based on continuum mechanics approaches it is usually required that the grain size is much smaller than the deforming volume, which is not always observed in practice. Considerable differences between predicted and observed performance can be seen depending on the material tested and its grain size; the extent of oxidation of the copper after deposition is critical, as is that of its underlying silicon substrate. Whereas it is possible to make good measurements of metallization properties on stiff substrates such as silicon there are serious issues with the reliability of Young's modulus and hardness data from coatings on device quality wafers which may have been oxidized prior to use. The effects of grain size, shape and orientation on the mechanical response of metallic thin films used for semiconductor metallization on oxidized silicon are presented in this paper. The appropriate conditions for the successful use of continuum mechanics are discussed and the importance of considering the consequences of crystallographic anisotropy and oxidation on the selection of suitable design data is presented with regards to copper coatings.

  12. Influence of mechanical grinding on lithium insertion and extraction properties of iron silicide/silicon composites

    NASA Astrophysics Data System (ADS)

    Usui, Hiroyuki; Nouno, Kazuma; Takemoto, Yuya; Nakada, Kengo; Ishii, Akira; Sakaguchi, Hiroki

    2014-12-01

    We prepared composite electrodes of iron silicide/Si by using mechanical grinding for mixtures of ferrosilicon and Si followed by gas-deposition, and investigated their electrochemical properties as Li-ion battery anode. With increasing the mechanical grinding time, the phase transformation from FeSi to FeSi2 took place more significantly, and the composite electrode showed better cycle stabilities. There was no remarkable difference in mechanical properties and electronic conductivity between FeSi and FeSi2. On the other hand, the FeSi2 electrode exhibited about three times larger capacities in comparison with the FeSi electrode. In addition, a result of our first principle calculation indicates that Li-ion can diffuse more easily in FeSi2 lattice than in FeSi lattice. It is suggested that the better cyclability of the composite electrodes was attributed to the moderate reactivity of FeSi2 with Li and the smooth Li-ion diffusion in it.

  13. Mechanical properties, phenolic composition and extractability indices of Barbera grapes of different soluble solids contents from several growing areas.

    PubMed

    Torchio, Fabrizio; Cagnasso, Enzo; Gerbi, Vincenzo; Rolle, Luca

    2010-02-15

    Phenolic compounds, extractable from grape skins and seeds, have a notable influence on the quality of red wines. Many studies have clearly demonstrated the relationship between the phenolic composition of the grape at harvest time and its influence on the phenolic composition of the red wine produced. In many previous works the evolution of phenolic composition and relative extractability was normally studied on grapes sampled at different times during ripening, but at the same date the physiological characteristics of grape berries in a vineyard are often very heterogeneous. Therefore, the main goal of the study is to investigate the differences among mechanical properties, phenolic composition and relative extractability of Vitis vinifera L. cv Barbera grape berries, harvested at the same date from several vineyards, and calibrated according to their density at three levels of soluble solids (A=235+/-8, B=252+/-8 and C=269+/-8 g L(-1) sugar) with the aim of studying the influence of ripeness stages and growing locations on these parameters. Results on mechanical properties showed that the thickness of the berry skin (Sp(sk)) was the parameter most affected by the different level of sugars in the pulp, while different skin hardnesses, evaluated by the break skin force (F(sk)), were related to the cultivation sites. The latter were also observed to influence the mechanical characteristics of seeds. Generally, the anthocyanin content increased with the level of soluble solids, while the increase in the tannin content of the berry skin and seeds was less marked. However, significant changes in flavanols reactive to vanillin in the seeds were found. The cellular maturity index (EA%) was little influenced by the soluble solids content of grapes. Copyright 2009 Elsevier B.V. All rights reserved.

  14. Impact of postharvest dehydration process of winegrapes on mechanical and acoustic properties of the seeds and their relationship with flavanol extraction during simulated maceration.

    PubMed

    Río Segade, Susana; Torchio, Fabrizio; Gerbi, Vincenzo; Quijada-Morín, Natalia; García-Estévez, Ignacio; Giacosa, Simone; Escribano-Bailón, M Teresa; Rolle, Luca

    2016-05-15

    This study represents the first time that the extraction of phenolic compounds from the seeds is assessed from instrumental texture properties for dehydrated grapes. Nebbiolo winegrapes were postharvest dehydrated at 20°C and 41% relative humidity. During the dehydration process, sampling was performed at 15%, 30%, 45% and 60% weight loss. The extractable fraction and extractability of phenolic compounds from the seeds were determined after simulated maceration. The evolution of mechanical and acoustic attributes of intact seeds was also determined during grape dehydration to evaluate how these changes affected the extraction of phenolic compounds. The extractable content and extractability of monomeric flavanols and proanthocyanidins, as well as the galloylation percentage of flavanols, might be predicted easily and quickly from the mechanical and acoustic properties of intact seeds. This would help in decision-making on the optimal dehydration level of winegrapes and the best management of winemaking of dehydrated grapes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Hypoglycemic property of acidic polysaccharide extracted from Saccharina japonica and its potential mechanism.

    PubMed

    Wang, Jing; Jin, Weihua; Zhang, Wenjing; Hou, Yun; Zhang, Hong; Zhang, Quanbin

    2013-06-05

    In the present study, a sulfated polysaccharide fucoidan extracted from Saccharina japonica was administered to normal and alloxan-diabetic rats/mice, and its effects on glycemia, insulin and serum lipid levels were evaluated. Fucoidan administered at 200 or 1200 mg/kg body weight/day could significantly reduce the blood glucose level by 22% and 34%, respectively, in alloxan-induced diabetic rats. Serum insulin levels in diabetic mice were increased by the administration of fucoidan (P<0.05). The results of an oral glucose tolerance test (OGTT) revealed that fucoidan treatment had some effect on glucose disposal after 15 days of treatment. Furthermore, fucoidan altered plasma lipid levels by lowering cholesterol, triglyceride and plasma low-density lipoprotein concentrations, while elevating plasma high-density lipoprotein cholesterol at 100 or 300 mg/kg body weight/day. The results suggested that fucoidan exhibited a considerable hypoglycemic effect, possibly by stimulating pancreatic release of insulin and/or by reducing insulin metabolism. Our results indicated that fucoidan could be developed as a potential oral hypoglycemic agents or functional food for the management of diabetes.

  16. Alterations in the mechanical properties of the extracted human teeth to be used as biological restorations on storing them in different storage media: an in vitro study.

    PubMed

    Kantoor, Pallavi; Srivastava, Nikhil; Rana, Vivek; Adlakha, Vivek K

    2015-08-01

    Total or partial loss of tooth structure occured due to caries or trauma. The decayed or fractured tooth is restored with appropriate restorative materials. A range of restorative materials are available in the market today, but each of them has one or the other drawbacks, viz. color mismatch, variable wear resistance, and strength. Therefore, there has always been a quest to use a restorative material which has properties as close to natural tooth as possible. Extracted human teeth have been tried as restorative materials with good success rate, but their storage has been a problem due to change in physical properties. To evaluate the changes in the mechanical properties of the extracted human teeth to be used as biological restoration upon storing them in different storage media and to compare their effectiveness. Five hundred and twenty extracted human teeth (samples) included in the study were equally distributed and randomly stored in different storage media (saline, artificial saliva, ORS, coconut water, and eye solution), and their mechanical properties were checked at different time intervals (7, 14, and 30 days) using universal testing machine and Vickers hardness test. None of the storage media used in the study significantly altered mechanical properties of the stored extracted human teeth except the hardness which was substantially reduced after storing for 30 days. Of the 4 media tested, eye solution was found to be the best, while artificial saliva was found to be least effective as storage media. It was also concluded that storage time of the extracted teeth to be used as biological restorations should not exceed more than 3-4 weeks as beyond this time, mechanical properties namely hardness get altered significantly. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Mechanical Properties of Transcription

    NASA Astrophysics Data System (ADS)

    Sevier, Stuart A.; Levine, Herbert

    2017-06-01

    The mechanical properties of transcription have recently been shown to play a central role in gene expression. However, a full physical characterization of this central biological process is lacking. In this Letter, we introduce a simple description of the basic physical elements of transcription where RNA elongation, RNA polymerase rotation, and DNA supercoiling are coupled. The resulting framework describes the relative amount of RNA polymerase rotation and DNA supercoiling that occurs during RNA elongation. Asymptotic behavior is derived and can be used to experimentally extract unknown mechanical parameters of transcription. Mechanical limits to transcription are incorporated through the addition of a DNA supercoiling-dependent RNA polymerase velocity. This addition can lead to transcriptional stalling and resulting implications for gene expression, chromatin structure and genome organization are discussed.

  18. Aleurites moluccana (L.) Willd. Leaves: Mechanical Antinociceptive Properties of a Standardized Dried Extract and Its Chemical Markers

    PubMed Central

    Quintão, Nara L. M.; Meyre-Silva, Christiane; Silva, Gislaine F.; Antonialli, Carla S.; Rocha, Lilian W.; Lucinda-Silva, Ruth M.; Malheiros, Angela; Souza, Márcia M.; Cechinel Filho, Valdir; Bresolin, Tania M. B.

    2011-01-01

    Seeking to develop a new analgesic phytomedicine, a spray-dried extract (SDE) of Aleurites moluccana (L.) Willd. leaves was developed in scale up (5 kg). The SDE was standardized at 3% w/w in relation to the flavonoid 2′′-O-rhamnosylswertisin. The SDE batches were evaluated in relation to their physical, physiochemical, and pharmacological characteristics. The results demonstrated the reproducibility of the scale up SDE process which, when dosed orally, reduced carrageenan-induced mechanical hypernociception, with an ID50% of 443 mg/kg. Similar results were obtained with animals injected with complete Freund's adjuvant (CFA), in which SDE caused inhibition of 48 ± 4%. SDE was effective in preventing prostaglandin E2 (PGE2)-induced mechanical hypernociception (inhibition of 26 ± 10% and 33 ± 3%, at 250 and 500 mg/kg, respectively). Swertisin and 2′′-O-rhamnosylswertisin isolated from the own extract were effective in inhibiting the hypernociceptive response induced by carrageenan (70 ± 2% and 50 ± 5%, resp.). Furthermore, 2′′-O-rhamnosylswertisin was capable of significantly inhibiting the mechanical sensitization induced by CFA or PGE2, with inhibitions of 25 ± 3% and 94 ± 6%, respectively. These results suggest that the effects of SDE are related, at least in part, to the presence of these flavonoids. PMID:21660087

  19. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  20. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  1. Keratins extracted from Merino wool and Brown Alpaca fibres: thermal, mechanical and biological properties of PLLA based biocomposites.

    PubMed

    Fortunati, E; Aluigi, A; Armentano, I; Morena, F; Emiliani, C; Martino, S; Santulli, C; Torre, L; Kenny, J M; Puglia, D

    2015-02-01

    Keratins extracted from Merino wool (KM) and Brown Alpaca fibres (KA) by sulphitolysis and commercial hydrolyzed keratins (KH) were used as fillers in poly(l-lactic) acid based biocomposites processed by solvent casting in chloroform. Different contents (1 wt.% and 5 wt.%) of keratins were considered and the morphological, thermal, mechanical, chemical and biological behaviours of the developed PLLA biocomposites were investigated. The results confirmed that surface morphologies of biocomposites revealed specific round-like surface topography function of different microsized keratin particles in different weight contents, such as the analysis of bulk morphologies which confirmed a phase adhesion strictly dependent by the keratin source. Transparency and thermal responses were deeply affected by the presence of the different keratins and their interaction with the PLLA matrix. Tensile test results underlined the possibility to modulate the mechanical behaviour of PLLA selecting the keratin type and content in order to influence positively the elastic and/or plastic response. It was demonstrated that surface characteristics of PLLA/KA systems also influenced the bovine serum albumin adsorption, moreover PLLA and PLLA biocomposites based on different kinds of keratins supported the culture of human bone-marrow mesenchymal stem cells, indicating that these biocomposites could be useful materials for medical applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Influence of the protocol used for fibroin extraction on the mechanical properties and fiber sizes of electrospun silk mats.

    PubMed

    Aznar-Cervantes, Salvador D; Vicente-Cervantes, Daniel; Meseguer-Olmo, Luis; Cenis, José L; Lozano-Pérez, A Abel

    2013-05-01

    Silk fibroin (SF) was regenerated using three of the most common protocols described in the bibliography for the dissolution of raw SF (LiBr 9.3M, CaCl2 50 wt.% or CaCl2:EtOH:H2O 1:2:8 in molar ratio). The integrity of regenerated SF in aqueous solution was analyzed by SDS-PAGE and different profiles of degradation were observed depending on the protocol used. This fact was found to affect also the aqueous solubility of the freeze dried protein. These different SFs were used to produce electrospun mats using SF solutions of SF 17 wt.% in 1,1,1,1',1',1'-hexafluoro-2-propanol (HFIP) and significant differences in fiber sizes, elongation and ultimate strength values were found. This work provides a global overview of the manner that different methods of SF extraction can affect the properties of electrospun SF-mats and consequently it should be considered depending on the use they are going to be made for.

  3. Mechanical properties of viruses.

    PubMed

    de Pablo, Pedro J; Mateu, Mauricio G

    2013-01-01

    Structural biology techniques have greatly contributed to unveil the relationships between structure, properties and functions of viruses. In recent years, classic structural approaches are being complemented by single-molecule techniques such as atomic force microscopy and optical tweezers to study physical properties and functions of viral particles that are not accessible to classic structural techniques. Among these features are mechanical properties such as stiffness, intrinsic elasticity, tensile strength and material fatigue. The field of virus mechanics is contributing to materials science by investigating some physical parameters of "soft" biological matter and biological nano-objects. Virus mechanics studies are also starting to unveil the biological implications of physical properties of viruses. Growing evidence indicate that viruses are subjected to internal and external forces, and that they may have adapted to withstand and even use those forces. This chapter describes what is known on the mechanical properties of virus particles, their structural determinants, and possible biological implications, of which several examples are provided.

  4. Mechanisms of Analgesic and Anti-Inflammatory Properties of Annona muricata Linn. (Annonaceae) Fruit Extract in Rodents

    PubMed Central

    Ishola, Ismail O.; Olusayero, Abayomi Micheal; Ochieng, Charles O.

    2014-01-01

    Abstract Unripe fruit of Annona muricata Linn. (Annonaceae) (soursop) is used in traditional African medicine for the treatment of neuralgia, rheumatism, and arthritic pain. This study sought to investigate the analgesic and anti-inflammatory effects of lyophilized fruit extract of Annona muricata (AM) in rodents. The analgesic activity was evaluated using the mouse writhing, formalin, and hot-plate tests while the anti-inflammatory action was investigated using the carrageenan-induced rat paw edema and xylene-induced ear edema tests. Pretreatment with AM (50, 100, and 200 mg/kg, p.o.) produced dose-dependent (P<.001) inhibition of writhes and formalin-induced pain in the late phase. AM and morphine produced time-course increase in pain threshold in hot-plate test. However, the analgesic effect elicited by AM was reversed (P<.05) by naloxone pretreatment. Similarly, the time-dependent increase in paw circumference induced by carrageenan was inhibited by AM treatment with peak effect (0.23±0.10 cm; P<.001, 200 mg/kg; 6 h), which was comparatively similar to that of diclofenac treated. Further, the xylene-induced ear edema was significantly reduced by AM (50 or 100 mg/kg) pretreatment; however, the anti-inflammatory effect elicited by AM was prevented by pretreatment of mice with NG-nitro-l-arginine (20 mg/kg, i.p., nitric-oxide synthase inhibitor) 15 min before AM (200 mg/kg, p.o.). The in vitro cyclooxygenase assay also showed that AM produced concentration-dependent inhibition of both cyclooxygenase (COX)-1 and COX-2 activity by 39.44%±0.05% and 55.71%±0.12%, respectively, at 100 μg/mL. In conclusion, A. muricata possesses analgesic effect through interaction with opioidergic pathway and anti-inflammatory property through inhibition of chemical mediators of inflammation. PMID:25133801

  5. Mechanisms of analgesic and anti-inflammatory properties of Annona muricata Linn. (Annonaceae) fruit extract in rodents.

    PubMed

    Ishola, Ismail O; Awodele, Olufunsho; Olusayero, Abayomi Micheal; Ochieng, Charles O

    2014-12-01

    Unripe fruit of Annona muricata Linn. (Annonaceae) (soursop) is used in traditional African medicine for the treatment of neuralgia, rheumatism, and arthritic pain. This study sought to investigate the analgesic and anti-inflammatory effects of lyophilized fruit extract of Annona muricata (AM) in rodents. The analgesic activity was evaluated using the mouse writhing, formalin, and hot-plate tests while the anti-inflammatory action was investigated using the carrageenan-induced rat paw edema and xylene-induced ear edema tests. Pretreatment with AM (50, 100, and 200 mg/kg, p.o.) produced dose-dependent (P<.001) inhibition of writhes and formalin-induced pain in the late phase. AM and morphine produced time-course increase in pain threshold in hot-plate test. However, the analgesic effect elicited by AM was reversed (P<.05) by naloxone pretreatment. Similarly, the time-dependent increase in paw circumference induced by carrageenan was inhibited by AM treatment with peak effect (0.23±0.10 cm; P<.001, 200 mg/kg; 6 h), which was comparatively similar to that of diclofenac treated. Further, the xylene-induced ear edema was significantly reduced by AM (50 or 100 mg/kg) pretreatment; however, the anti-inflammatory effect elicited by AM was prevented by pretreatment of mice with N(G)-nitro-l-arginine (20 mg/kg, i.p., nitric-oxide synthase inhibitor) 15 min before AM (200 mg/kg, p.o.). The in vitro cyclooxygenase assay also showed that AM produced concentration-dependent inhibition of both cyclooxygenase (COX)-1 and COX-2 activity by 39.44%±0.05% and 55.71%±0.12%, respectively, at 100 μg/mL. In conclusion, A. muricata possesses analgesic effect through interaction with opioidergic pathway and anti-inflammatory property through inhibition of chemical mediators of inflammation.

  6. A time domain technique for mechanism extraction

    NASA Technical Reports Server (NTRS)

    Dominek, Allen K.; Peters, Leon, Jr.; Burnside, Walter D.

    1987-01-01

    The properties of scattered fields from a structure can be better evaluated from the characteristics of the individual scatterers. Decomposition techniques can be classified either as a matrix or an integral formulation. With either formulation, aspect pattern of frequency information of a scattering center can be obtained. Emphasis is placed on an integral (time domain) isolation extraction technique to obtain the frequency characteristics of scattering mechanisms. This technique has its origins in the time domain interpretation of scattered fields.

  7. Impact of several pre-treatments on the extraction of phenolic compounds in winegrape varieties with different anthocyanin profiles and skin mechanical properties.

    PubMed

    Río Segade, Susana; Torchio, Fabrizio; Giacosa, Simone; Ricauda Aimonino, Davide; Gay, Paolo; Lambri, Milena; Dordoni, Roberta; Gerbi, Vincenzo; Rolle, Luca

    2014-08-20

    This study was performed to evaluate and compare the effects of different pre-treatments of whole grape berries (freezing with dry ice or in a cold room, steam blanching with different exposure times, and microwave heating with different exposure times and microwave power density) on total content of some phenolic compounds and the composition of individual anthocyanins released into the pulp during the treatment and those extracted during the maceration step. Two red winegrape varieties with different proportions of di- and trisubstituted anthocyanins were used (Nebbiolo and Barbera, respectively). Pulp-extracted anthocyanins were more significantly influenced by the pre-treatment. The results highlighted that freezing with dry ice, followed by freezing in a cold room and steam blanching for 5 min, have a great potential from an industrial point of view. They facilitated the extraction of anthocyanins in the must prior to maceration, when compared with the control samples, increasing their total content (+37.8-83.6%), and modifying the anthocyanin profile through the enrichment in the most stable compounds (+2.8-6.6% malvidin derivatives) to the detriment of others more prone to oxidation (-0.8-11.0% cyanidin derivatives). In Nebbiolo winegrapes, an improved extraction of low- and high-molecular weight flavanols into the pulp was also observed (+60.4-73.4%). Significant relationships between the phenolic composition of treated berries and the corresponding skin mechanical properties were also studied, but they were variety dependent. Discriminant analysis permitted a correct classification of the samples according to the variety and pre-treatment.

  8. The effects of bone and pore volume fraction on the mechanical properties of PMMA/bone biopsies extracted from augmented vertebrae.

    PubMed

    Kinzl, M; Boger, A; Zysset, P K; Pahr, D H

    2011-10-13

    Vertebroplasty forms a porous PMMA/bone composite which was shown to be weaker and less stiff than pure PMMA. It is not known what determines the mechanical properties of such composites in detail. This study investigated the effects of bone volume fraction (BV/TV), cement porosity (PV/(TV-BV), PV…pore volume) and cement stiffness. Nine human vertebral bodies were augmented with either standard or low-modulus PMMA cement and scanned with a HR-pQCT system before and after augmentation. Fourteen cylindrical PMMA/bone biopsies were extracted from the augmented region, scanned with a micro-CT system and tested in compression until failure. Micro-finite element (FE) models of the complete biopsies, of the trabecular bone alone as well as of the porous cement alone were generated from CT images to gain more insight into the role of bone and pores. PV/(TV-BV) and experimental moduli of standard/low-modulus cement (R(2)=0.91/0.98) as well as PV/(TV-BV) and yield stresses (R(2)=0.92/0.83) were highly correlated. No correlation between BV/TV (ranging from 0.057 to 0.138) and elastic moduli was observed (R(2)< 0.05). Interestingly, the micro-FE models of the porous cement alone reproduced the experimental elastic moduli of the standard/low-modulus cement biopsies (R(2)=0.75/0.76) more accurately than the models with bone (R(2)=0.58/0.31). In conclusion, the mechanical properties of the biopsies were mainly determined by the cement porosity and the cement material properties. The study showed that bone tissue inside the biopsies was mechanically "switched off" such that load was carried essentially by the porous PMMA.

  9. Selective adsorption of Pb(II) from aqueous solution using porous biosilica extracted from marine diatom biomass: Properties and mechanism

    NASA Astrophysics Data System (ADS)

    Qi, Yarong; Wang, Jingfeng; Wang, Xin; Cheng, Jay Jiayang; Wen, Zhiyou

    2017-02-01

    Biosilica with a surface area of 143 m2 g-1 derived from marine diatoms was prepared using an easy two-step method involving washing with dilute acid and baking. The extracted biosilica was used to remove divalent lead ions, i.e., Pb(II), from aqueous solution. The effects on Pb(II) adsorption of initial pH, shaking speed, and adsorbent loading were investigated. The adsorption of Pb(II) in the presence of other ions was also investigated. The biosilica showed a high adsorption capacity with high selectivity for Pb(II). The experimental maximum adsorption capacity was 108.2-120.4 mg g-1 at an adsorbent loading of 1 g L-1. The adsorption process was best described by the Langmuir model. The adsorbent selectively adsorbed Pb(II) from binary ion systems in the presence of Cu(II), Cd(II), Ni(II), and Ag(I). The results of this study show that biosilica extracted from fresh marine diatoms is a more efficient and selective adsorbent for Pb(II) than other inorganic adsorbents.

  10. Mechanical properties of wood

    Treesearch

    David Kretschmann

    2010-01-01

    The mechanical properties presented in this chapter were obtained from tests of pieces of wood termed “clear” and “straight grained” because they did not contain characteristics such as knots, cross grain, checks, and splits. These test pieces did have anatomical characteristics such as growth rings that occurred in consistent patterns within each piece. Clear wood...

  11. Mechanical properties of wood

    Treesearch

    David W. Green; Jerrold E. Winandy; David E. Kretschmann

    1999-01-01

    The mechanical properties presented in this chapter were obtained from tests of small pieces of wood termed “clear” and “straight grained” because they did not contain characteristics such as knots, cross grain, checks, and splits. These test pieces did have anatomical characteristics such as growth rings that occurred in consistent patterns within each piece. Clear...

  12. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  13. Mechanical Properties of Cells

    NASA Technical Reports Server (NTRS)

    Bradley, Robert; Becerril, Joseph; Jeevarajan, Anthony

    2007-01-01

    Many physiologic and pathologic processes alter the biomechanical properties of the tissue they affect, and these changes may be manifest at the single cell level. The normal and abnormal mechanical properties of a given cell type can be established with the aid of an atomic force microscope (AFM), nonetheless, consistency in the area of the tip has been a mayor limitation of using the AFM for quantitative measurements of mechanical properties. This project attempts to overcome this limitation by using materials with a known elastic modulus, which resembles the one of the cell, to create force-deformation curves to calculate the area of indentation by means of Hooke s Law (sigma = E(epsilon)), which states that stress (sigma) is proportional to the strain (epsilon) where the constant of proportionality, E, is called the Young s modulus, also referred as the elastic modulus. Hook s Law can be rearranged to find the area of indentation (Area= Force/ E(epsilon)), where the indentation force is defined by the means of the added mass spring calibration method.

  14. Mechanical Properties of Aerogels

    NASA Technical Reports Server (NTRS)

    Parmenter, Kelly E.; Milstein, Frederick

    1995-01-01

    Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response

  15. The mechanical behavior of PMMA/bone specimens extracted from augmented vertebrae: a numerical study of interface properties, PMMA shrinkage and trabecular bone damage.

    PubMed

    Kinzl, M; Boger, A; Zysset, P K; Pahr, D H

    2012-05-11

    Recently published compression tests on PMMA/bone specimens extracted after vertebral bone augmentation indicated that PMMA/bone composites were not reinforced by the trabecular bone at all. In this study, the reasons for this unexpected behavior should be investigated by using non-linear micro-FE models. Six human vertebral bodies were augmented with either standard or low-modulus PMMA cement and scanned with a HR-pQCT system before and after augmentation. Six cylindrical PMMA/bone specimens were extracted from the augmented region, scanned with a micro-CT system and tested in compression. Four different micro-FE models were generated from these images which showed different bone tissue material behavior (with/without damage), interface behavior (perfect bonding, frictionless contact) and PMMA shrinkage due to polymerization. The non-linear stress-strain curves were compared between the different micro-FE models as well as to the compression tests of the PMMA/bone specimens. Micro-FE models with contact between bone and cement were 20% more compliant compared to those with perfect bonding. PMMA shrinkage damaged the trabecular bone already before mechanical loading, which further reduced the initial stiffness by 24%. Progressing bone damage during compression dominated the non-linear part of the stress-strain curves. The micro-FE models including bone damage and PMMA shrinkage were in good agreement with the compression tests. The results were similar with both cements. In conclusion, the PMMA/bone interface properties as well as the initial bone damage due to PMMA polymerization shrinkage clearly affected the stress-strain behavior of the composite and explained why trabecular bone did not contribute to the stiffness and strength of augmented bone.

  16. Antioxidant properties of fermented mango leaf extracts.

    PubMed

    Park, Anna; Ku, Taekyu; Yoo, Ilsou

    2015-01-01

    Antioxidant properties of mango (Mangifera indica) leaves were evaluated. Hydroalcoholic leaf extracts that were lyophilized were subsequently fermented with either Lactobacillus casei or effective microorganisms (EM) such as probiotic bacteria and/or other anaerobic organisms. Antioxidant properties were measured as a function of the mango leaf extract concentration in the fermentation broth. Tests for radical scavenging using the 1,1-diphenyl-2-picrylhydrazyl radical showed higher antioxidant activity for Lactobacillus- and EM-fermented mango leaf extracts than for the synthetic antioxidant butylated hydroxytoluene. Antioxidant activity generally increased with increasing fermented extract concentration as did the fermented extracts' polyphenol and flavonoid contents. Fermented extracts reduced reactive oxygen species generation by lipopolysaccharide in RAW 264.7 cells when measured via fluorescence of dichlorodihydrofluorescein acetate treated cells using flow cytometry. RAW 264.7 cells also showed a concentration-dependent cytotoxic effect of the fermented extracts using the 3-(4,5-dimethylthialol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Inhibition of mushroom tyrosinase activity as well as nitrite scavenging by the fermented extracts increased as fermented extract concentrations increased. Tyrosinase activity was assayed with 3,4-dihydroxyphenylalanine as substrate. Nitrite scavenging was assessed via measurement of inhibition of chromophore production from nitrite-naphthylamine-sulfanilic acid mixtures. The antioxidant properties of fermented mango leaf extracts suggest the fermented extracts may be useful in developing health food and fermentation-based beauty products.

  17. Mechanical Properties of MEMS Materials

    DTIC Science & Technology

    2004-03-01

    thermal strain for polysilicon (data points) compared with bulk silicon (Thermophysical Properties of Matter, Volume 13, Y. S. Touloukian , Editor...AFRL-IF-RS-TR-2004-76 Final Technical Report March 2004 MECHANICAL PROPERTIES OF MEMS MATERIALS Johns Hopkins University...TITLE AND SUBTITLE MECHANICAL PROPERTIES OF MEMS MATERIALS 6. AUTHOR(S) W. N. Sharpe, Jr., K. J. Hemker - Dept of Mechanical Engineering R. L

  18. The Mechanical Properties of Nanowires

    PubMed Central

    Wang, Shiliang; Shan, Zhiwei

    2017-01-01

    Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed. PMID:28435775

  19. Mechanical properties of aspen

    Treesearch

    R.P.A. Johnson

    1947-01-01

    The clear wood of aspen has inherent properties of merit. Several of these properties are familiar to a large proportion of the general public, for some of the common types of matches are made of this wood. The requirements of wood for matches are exacting in that the wood must combine straightness of grain, ease of splitting, ease of working, and toughness. To meet...

  20. Mechanisms of aqueous extraction of soybean oil.

    PubMed

    Campbell, K A; Glatz, C E

    2009-11-25

    Aqueous extraction processing (AEP) of soy is a promising green alternative to hexane extraction processing. To improve AEP oil yields, experiments were conducted to probe the mechanisms of oil release. Microscopy of extruded soy before and after extraction with and without protease indicated that unextracted oil is sequestered in an insoluble matrix of denatured protein and is released by proteolytic digestion of this matrix. In flour from flake, unextracted oil is contained as intact oil bodies in undisrupted cells, or as coalesced oil droplets too large to pass out of the disrupted cellular matrix. Our results suggest that emulsification is an important extraction mechanism that reduces the size of these droplets and increases yield. Protease and SDS were both successful in increasing extraction yields. We propose that this is because they disrupt a viscoelastic protein film at the droplet interface, facilitating droplet disruption. An extraction model based on oil droplet coalescence and the formation of a viscoelastic film was able to fit kinetic extraction data well.

  1. Mechanical Properties of Axons

    NASA Astrophysics Data System (ADS)

    Bernal, Roberto; Pullarkat, Pramod A.; Melo, Francisco

    2007-07-01

    The mechanical response of PC12 neurites under tension is investigated using a microneedle technique. Elastic response, viscoelastic relaxation, and active contraction are observed. The mechanical model proposed by Dennerll et al. [J. Cell Biol. 109, 3073 (1989).JCLBA30021-952510.1083/jcb.109.6.3073], which involves three mechanical devices—a stiff spring κ coupled with a Voigt element that includes a less stiff spring k and a dashpot γ—has been improved by adding a new element to describe the main features of the contraction of axons. This element, which represents the action of molecular motors, acts in parallel with viscous forces defining a global tension response of axons T against elongation rates δ˙k. Under certain conditions, axons show a transition from a viscoelastic elongation to active contraction, suggesting the presence of a negative elongation rate sensitivity in the curve T vs δ˙k.

  2. The antimicrobial properties of ginseng and ginseng extracts.

    PubMed

    Kachur, Karina; Suntres, Zacharias E

    2016-01-01

    Ginseng is commonly used in traditional Chinese medicine as a tonic and an adaptogen to reduce fatigue and boost the immune system. In recent years, ginseng extracts are shown to have both bacteriostatic and bactericidal actions and seem to exert their effects by several mechanisms, including disruption of biofilms, inhibition of quorum-sensing and virulence factors, and altering motility. Also, ginseng extracts are shown to have antifungal properties as demonstrated by their ability to inhibit the growth of several mold and yeast species. Extracts from ginseng root have a strong antiviral activity against the RNA viruses in cell cultures and animal models. In addition to the antimicrobial activities, ginseng extracts are shown to possess immunomodulatory properties involved in the amelioration of infections. The present paper describes the antimicrobial effects of ginseng and its extracts.

  3. MECHANICAL PROPERTIES OF WROUGHT TUNGSTEN

    DTIC Science & Technology

    Mechanical properties of wrought tungsten vol. II. Creep rupture test data from 1500 to 5000 F, and tensile test data from room temperature to 5000 F at various strain rates for tungsten sheet material.

  4. Mechanical properties of nanophase metals

    SciTech Connect

    Siegel, R.W.; Fougere, G.E.

    1994-11-01

    Nanophase metals have grain-size dependent mechanical properties that are significantly different than those of their coarse-grained counterparts. Pure metals are much stronger and apparently less ductile than conventional ones; intermetallics are also strengthened, but they tend toward increased ductility at the smallest grain sizes. These property changes are primarily related to grain size limitations, but they are also affected by the large percentage of atoms in grain boundaries and other microstructural features. Strengthening appears to result from a limitation of dislocation activity, while increased ductility probably relates to grain boundary sliding. A brief overview of our present understanding of the mechanical properties of nanophase metals is presented.

  5. Mechanical properties of nanophase materials

    SciTech Connect

    Siegel, R.W.; Fougere, G.E.

    1993-11-01

    It has become possible in recent years to synthesize new materials under controlled conditions with constituent structures on a nanometer size scale (below 100 nm). These novel nanophase materials have grain-size dependent mechanical properties significantly different than those of their coarser-grained counterparts. For example, nanophase metals are much stronger and apparently less ductile than conventional metals, while nanophase ceramics are more ductile and more easily formed than conventional ceramics. The observed mechanical property changes are related to grain size limitations and/or the large percentage of atoms in grain boundary environments; they can also be affected by such features as flaw populations, strains and impurity levels that can result from differing synthesis and processing methods. An overview of what is presently known about the mechanical properties of nanophase materials, including both metals and ceramics, is presented. Some possible atomic mechanisms responsible for the observed behavior in these materials are considered in light of their unique structures.

  6. [Mechanism of action of St. Johns wort extract].

    PubMed

    Müller, W E; Singer, A; Wonnemann, M

    2000-12-14

    Over the last few years St-John's wort preparations have been used in large quantities in Germany for treating mild to moderate depression. In the meantime the antidepressive action of these extracts has been proved in numerous placebo-controlled studies. Furthermore, a considerably lower adverse effect rate compared with classic antidepressants has been established. Analogously to other antidepressants, subchronic St-John's wort treatment of rats showed significant down-regulation of beta receptor density and a significant increase in 5HT2 receptors. The extract also exhibited antidepressant activity in animal pharmacological models of depression. Interest is now focused on identifying the underlying pharmacological mechanisms of action of this phytotherapeutic agent. Like other working parties, we were only able to identify a weak inhibitory effect of the extract and the pure substance hypericin on the monoamine oxidases A and B. Similarly to synthetic antidepressants, St-John's wort exerts marked inhibitory effects on synaptosomal uptake of serotonin and noradrenaline. However, dopamine and uptake and neuronal uptake of GABA and L-glutamate are also inhibited. These effects may mainly be attributed to the substance hyperforin contained in the extract. An additional, as yet unknown, pharmacological mechanism of action of St-John's wort extracts is beginning to emerge. Although hyperforin shows similar properties to classical antidepressants, there are indications of a novel mechanism of action. Our laboratory is currently investigating the means by which St-John's wort extract, or its constituent hyperforin, develops its antidepressant action.

  7. Changes in triphasic mechanical properties of proteoglycan-depleted articular cartilage extracted from osmotic swelling behavior monitored using high-frequency ultrasound.

    PubMed

    Wang, Q; Zheng, Y P; Niu, H J

    2010-03-01

    This study aims to obtain osmosis-induced swelling strains of normal and proteoglycan (PG) depleted articular cartilage using an ultrasound system and to investigate the changes in its mechanical properties due to the PG depletion using a layered triphasic model. The swelling strains of 20 cylindrical cartilage-bone samples collected from different bovine patellae were induced by decreasing the concentration of bath saline and monitored by the ultrasound system. The samples were subsequently digested by a trypsin solution for approximately 20 min to deplete proteoglycans, and the swelling behaviors of the digested samples were measured again. The bi-layered triphasic model proposed in our previous study (Wang et al., J Biomech Eng-Trans ASME 2007; 129: 413-422) was used to predict the layered aggregate modulus Ha from the data of depth-dependent swelling strain, fixed charge density and water content. It was found that the region near the bone, for the normal specimens, had a significantly higher aggregate modulus (Ha1 = 20.6 +/- 18.2 MPa) in comparison with the middle zone and the surface layer (Ha2 = 7.8 +/- 14.5 MPa and Ha3 = 3.6 +/- 3.2 MPa, respectively) (p < 0.001). The normalized thickness of the deep layer h1 was 0.68 +/- 0.20. After the trypsin digestion, the parametric values decreased to Ha1 = 13.6 +/- 9.6 MPa, Ha2 = 6.7 +/- 11.5 MPa, Ha3 = 2.7 +/- 3.2 MPa, and h1 = 0.57 +/- 0.28. Other models were also used to analyze data and the results were compared. This study showed that high-frequency ultrasound measurement combined with the triphasic modeling was capable of nondestructively quantifying the alterations in the layered mechanical properties of the proteoglycan-depleted articular cartilage.

  8. Mechanical properties of graphene papers

    NASA Astrophysics Data System (ADS)

    Liu, Yilun; Xie, Bo; Zhang, Zhong; Zheng, Quanshui; Xu, Zhiping

    2012-04-01

    Graphene-based paper materials attract particular interests recently owing to their outstanding properties, the key of which is their layer-by-layer hierarchical structures similar to many biological materials such as bone, teeth and nacre, combining intralayer strong sp2 bonds and interlayer crosslinks for efficient load transfer. Here we firstly study the mechanical properties of various interlayer and intralayer crosslinks through first-principles calculations, and then perform continuum model analysis for the overall mechanical properties of graphene-based paper materials. We find that there is a characteristic length scale l0, defined as √{Dh0/4G}, where D is the stiffness of the graphene sheet, h0 and G are height of interlayer crosslink and shear modulus respectively. When the size of the graphene sheets exceeds 3l0, the tension-shear (TS) chain model, which is widely used for nanocomposites, fails to predict the overall mechanical properties of the graphene-based papers. Instead we proposed here a deformable tension-shear (DTS) model by considering elastic deformation of graphene sheets, also the interlayer and intralayer crosslinks. The DTS is then applied to predict the mechanical properties of graphene papers under tensile loading. According to the results we thus obtain, optimal design strategies are proposed for graphene papers with ultrahigh stiffness, strength and toughness.

  9. Changes in hair properties by Eucalyptus extract.

    PubMed

    Mamada, Akira; Ishihama, Mariko; Fukuda, Reiko; Inoue, Shigeto

    2008-01-01

    A long-term usage investigation of a scalp lotion containing Eucalyptus extract, which increases the amount of ceramide in the skin, was carried out to explore the change in physical properties of the hair fiber. Half-head or whole-head usage studies of a scalp lotion with Eucalyptus extract were carried out for the following groups: Japanese female, Japanese senior female, Japanese male, and Caucasian female panelists. As a result, the improvement in hair luster and bounce in the root part of the hair were recognized by the panelists after the long-term application of the scalp lotion with Eucalyptus extract. Measurement of hair gloss intensity and bending stress at the root suggests that this improvement is based on changes in these physical properties. These results indicate that the recognition of panelists is based on an actual change in the hair fiber properties. The efficacy of Eucalyptus extract is expressed regardless of race, age, or gender, since similar results were confirmed in all panelist groups. In order to investigate the cause of these phenomena, we measured the elasticity (Young's modulus) of the new-growth part of the cortex in Eucalyptus extract-treated hair and placebo hair by the nano-indentation method of atomic force microscopy (AFM). These results suggest that the Young's modulus of the new-growth part of the cortex in Eucalyptus extract treated-hair increases in comparison with placebo hair. The IR spectra of treated samples of hair show changes that appear to confirm a decrease in the alpha-helix structure and an increase in the beta-sheet structure.

  10. Mechanical Properties of Respiratory Muscles

    PubMed Central

    Sieck, Gary C.; Ferreira, Leonardo F.; Reid, Michael B.; Mantilla, Carlos B.

    2014-01-01

    Striated respiratory muscles are necessary for lung ventilation and to maintain the patency of the upper airway. The basic structural and functional properties of respiratory muscles are similar to those of other striated muscles (both skeletal and cardiac). The sarcomere is the fundamental organizational unit of striated muscles and sarcomeric proteins underlie the passive and active mechanical properties of muscle fibers. In this respect, the functional categorization of different fiber types provides a conceptual framework to understand the physiological properties of respiratory muscles. Within the sarcomere, the interaction between the thick and thin filaments at the level of cross-bridges provides the elementary unit of force generation and contraction. Key to an understanding of the unique functional differences across muscle fiber types are differences in cross-bridge recruitment and cycling that relate to the expression of different myosin heavy chain isoforms in the thick filament. The active mechanical properties of muscle fibers are characterized by the relationship between myoplasmic Ca2+ and cross-bridge recruitment, force generation and sarcomere length (also cross-bridge recruitment), external load and shortening velocity (cross-bridge cycling rate), and cross-bridge cycling rate and ATP consumption. Passive mechanical properties are also important reflecting viscoelastic elements within sarcomeres as well as the extracellular matrix. Conditions that affect respiratory muscle performance may have a range of underlying pathophysiological causes, but their manifestations will depend on their impact on these basic elemental structures. PMID:24265238

  11. [Mechanical properties of thermoplastic materials].

    PubMed

    Zhang, Ning; Bai, Yu-xing; Zhang, Kun-ya

    2010-09-14

    To investigate the mechanical properties of various brands of thermoplastic materials under different test conditions so as to analyze their influencing factors so as to provide a reference for improving the effect of invisible orthodontics. Three brands of thermoplastic materials, DR, Biolon and Erkodent, were selected. They were tested by Instron testing machine to measure their maximal stress and modulus under different processing modes, including pre-thermoforming, post-thermoforming and dipped in artificial saliva for two weeks after thermoforming. The data were analyzed by SPSS 11.5. Analyzed the mechanical properties change-trend under each test condition. The modulus (MPa) and maximum stress (MPa) of control group were significantly higher than those of thermoforming group (DR: 9.63±0.68 vs 7.85±0.61, 267±8 vs 199±6; Erkodent: 8.28±0.28 vs 7.59±0.45, 226±6 vs 199±6; Biolon: 8.85±0.41 vs 7.07±0.22, 237±6 vs 169±7, all P<0.05). The modulus (MPa) and maximum stress (MPa) of thermoforming group were significantly lower than those of saliva immersion group (DR: 7.85±0.61 vs 9.14±0.41, 199±6 vs 243±7; Erkodent: 7.59 ± 0.45 vs 8.38±0.29, 199±6 vs 212±7; Biolon: 7.07±0.22 vs 7.90±0.31, 169±7 vs 197±5, all P<0.05). The different brands of thermoplastic materials have different mechanical properties. The different processing modes influence the mechanical properties of thermoplastic materials. The mechanical properties decrease after thermoforming and increase after saliva immersion.

  12. Mechanical properties of composite materials

    NASA Technical Reports Server (NTRS)

    Thornton, H. Richard; Cornwell, L. R.

    1993-01-01

    A composite material incorporates high strength, high modulus fibers in a matrix (polymer, metal, or ceramic). The fibers may be oriented in a manner to give varying in-plane properties (longitudinal, transverse-stress, strain, and modulus of elasticity). The lay-up of the composite laminates is such that a center line of symmetry and no bending moment exist through the thickness. The laminates are tabbed, with either aluminum or fiberglass, and are ready for tensile testing. The determination of the tensile properties of resin matrix composites, reinforced by continuous fibers, is outlined in ASTM standard D 3039, Tensile Properties of Oriented Fiber Composites. The tabbed flat tensile coupons are placed into the grips of a tensile machine and load-deformation curves plotted. The load-deformation data are translated into stress-strain curves for determination of mechanical properties (ultimate tensile strength and modulus of elasticity).

  13. Influence of grape pomace extract incorporation on chitosan films properties.

    PubMed

    Ferreira, Andreia S; Nunes, Cláudia; Castro, Alichandra; Ferreira, Paula; Coimbra, Manuel A

    2014-11-26

    Chitosan has been studied as a renewable polymer to form edible films allowing the incorporation of functional compounds. The aim of this work was to evaluate the effects in the chitosan films properties of the incorporation of grape pomace extracts: 0.15% of hot water extract (mainly polysaccharides), 0.15 and 0.3% of chloroform extract (wax), and 0.3 and 0.75% of n-hexane extract (oil). The evaluation of the surface morphology revealed that the films with the aqueous extract had the most homogeneous and smoother topography. The incorporation of higher proportion of wax and oil led to changes in mechanical properties of the films, namely lower resistance and stiffness. The chitosan-based films with 0.75% oil demonstrated a 75% decrease of solubility in water, due to their hydrophobicity, as confirmed by the contact angle and surface free energy measurements. The hydrophobic films showed higher antioxidant capacity in organic medium (ABTS and DPPH assays) whereas the most hydrophilic films showed an improvement in FRAP and reducing power assays. Therefore, all the chitosan-based films prepared by incorporation of these grape pomace extracts are promising for food shelf life extension.

  14. B cell antigen extraction is regulated by physical properties of antigen-presenting cells

    PubMed Central

    2017-01-01

    Antibody production and affinity maturation are driven by B cell extraction and internalization of antigen from immune synapses. However, the extraction mechanism remains poorly understood. Here we develop DNA-based nanosensors to interrogate two previously proposed mechanisms, enzymatic liberation and mechanical force. Using antigens presented by either artificial substrates or live cells, we show that B cells primarily use force-dependent extraction and resort to enzymatic liberation only if mechanical forces fail to retrieve antigen. The use of mechanical forces renders antigen extraction sensitive to the physical properties of the presenting cells. We show that follicular dendritic cells are stiff cells that promote strong B cell pulling forces and stringent affinity discrimination. In contrast, dendritic cells are soft and promote acquisition of low-affinity antigens through low forces. Thus, the mechanical properties of B cell synapses regulate antigen extraction, suggesting that distinct properties of presenting cells support different stages of B cell responses. PMID:27923880

  15. Anti-fatigue properties of tartary buckwheat extracts in mice.

    PubMed

    Jin, Hong-Mei; Wei, Ping

    2011-01-01

    Anti-fatigue properties of tartary buckwheat extracts (TBE) was investigated in male Kunming mice. The animals were divided into four groups. The first group, designated as the control group (control), was administered with distilled water by gavage every day for 28 days. The other three groups, designated as TBE treatment groups, were administered with TBE of 60, 120 and 240 mg/kg body weight, respectively, by gavage every day for 28 days. Exhaustive swimming time, blood lactic acid (BLA), blood urea nitrogen (BUN), tissue glycogen, glutathione peroxidase (GPx) and superoxide dismutase (SOD) of mice after swimming were determined. The results showed that tartary buckwheat extracts had anti-fatigue properties, which extended the exhaustive swimming time of mice, effectively inhibiting the increase of BLA, decreasing the level of BUN, increasing the tissue glycogen content and the activities of SOD and GPx of mice. However, further study is needed to elucidate the exact mechanism of the effect of TBE on fatigue.

  16. Woven TPS Mechanical Property Evaluation

    NASA Technical Reports Server (NTRS)

    Gonzales, Gregory Lewis; Kao, David Jan-Woei; Stackpoole, Margaret M.

    2013-01-01

    Woven Thermal Protection Systems (WTPS) is a relatively new program funded by the Office of the Chief Technologist (OCT). The WTPS approach to producing TPS architectures uses precisely engineered 3-D weaving techniques that allow tailoring material characteristics needed to meet specific mission requirements. A series of mechanical tests were performed to evaluate performance of different weave types, and get a better understanding of failure modes expected in these three-dimensional architectures. These properties will aid in material down selection and guide selection of the appropriate WTPS for a potential mission.

  17. Mechanical Properties of Viral Capsids

    NASA Astrophysics Data System (ADS)

    Zandi, Roya; Reguera, David

    2005-03-01

    Viral genomes, whether they involve RNA or DNA molecules, are invariably protected by a rigid, single-protein-thick, shell referred to as ``capsid.'' Viral capsids are known to tolerate wide ranges of pH and salt conditions and to withstand internal pressures as high as 100 atms. We study the mechanical properties of viral capsids, calling explicit attention to the inhomogeneity of the shells that is inherent in their being discrete/polyhedral rather than continuous/spherical. We analyze the distribution of stress in these capsids due to isotropic internal pressure (arising, for instance, from genome confinement and/or osmotic activity), and compare the results with appropriate generalizations of classical elasticity theory. We also examine the competing mechanisms for viral shell failure, e.g., in-plane crack formation vs radial bursting. The biological consequences of the special stabilities and stress distributions of viral capsids are also discussed.

  18. Mechanical Properties of Niobium Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  19. Understanding extractive bleed : wood extractives: distribution, properties, and classes

    Treesearch

    Edward Burke; Norm Slavik; Tony Bonura; Dennis Connelly; Tom Faris; Arnie Nebelsick; Brent Stuart; Sam Williams; Alex C. Wiedenhoeft

    2010-01-01

    Color, odor, and natural durability of heartwood are characteristics imparted by a class of chemicals in wood known collectively extractives. Wood is converted by the tree from sapwood to heartwood by the deposition of extractives, typically many years after the growth ring undergoing this change was formed by the tree. Extractives are thus not a part of the wood...

  20. Mechanical properties of metal dihydrides

    SciTech Connect

    Schultz, Peter A.; Snow, Clark S.

    2016-02-04

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides, $\\text{M}{{\\text{H}}_{2}}$ {$\\text{M}$ = Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. Finally, the source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.

  1. Mechanical properties of metal dihydrides

    DOE PAGES

    Schultz, Peter A.; Snow, Clark S.

    2016-02-04

    First-principles calculations are used to characterize the bulk elastic properties of cubic and tetragonal phase metal dihydrides,more » $$\\text{M}{{\\text{H}}_{2}}$$ {$$\\text{M}$$ = Sc, Y, Ti, Zr, Hf, lanthanides} to gain insight into the mechanical properties that govern the aging behavior of rare-earth di-tritides as the constituent 3H, tritium, decays into 3He. As tritium decays, helium is inserted in the lattice, the helium migrates and collects into bubbles, that then can ultimately create sufficient internal pressure to rupture the material. The elastic properties of the materials are needed to construct effective mesoscale models of the process of bubble growth and fracture. Dihydrides of the scandium column and most of the rare-earths crystalize into a cubic phase, while dihydrides from the next column, Ti, Zr, and Hf, distort instead into the tetragonal phase, indicating incipient instabilities in the phase and potentially significant changes in elastic properties. We report the computed elastic properties of these dihydrides, and also investigate the off-stoichiometric phases as He or vacancies accumulate. As helium builds up in the cubic phase, the shear moduli greatly soften, converting to the tetragonal phase. Conversely, the tetragonal phases convert very quickly to cubic with the removal of H from the lattice, while the cubic phases show little change with removal of H. Finally, the source and magnitude of the numerical and physical uncertainties in the modeling are analyzed and quantified to establish the level of confidence that can be placed in the computational results, and this quantified confidence is used to justify using the results to augment and even supplant experimental measurements.« less

  2. Functional properties of spice extracts obtained via supercritical fluid extraction.

    PubMed

    Leal, Patrícia F; Braga, Mara E M; Sato, Daisy N; Carvalho, João E; Marques, Marcia O M; Meireles, M Angela A

    2003-04-23

    In the present study the antioxidant, anticancer, and antimycobacterial activities of extracts from ginger (Zingiber officinale Roscoe), rosemary (Rosmarinus officinalis L.), and turmeric (Curcuma longa L.) were evaluated. The extracts were obtained using supercritical CO(2) with and without ethanol and/or isopropyl alcohol as cosolvent. The extracts' antioxidant power was assessed using the reaction between beta-carotene and linolenic acid, the antimycobacterial activity against M. tuberculosis was measured by the MABA test, and their anticancer action was tested against nine human cancer ancestries: lung, breast, breast resistant, melanoma, colon, prostate, leukemia, and kidney. The rosemary extracts exhibited the strongest antioxidant and the lowest antimycobacterial activities. Turmeric extracts showed the greatest antimycobacterial activity. Ginger and turmeric extracts showed selective anticancer activities.

  3. Evaluation of Antioxidant and Antiangiogenic Properties of Caesalpinia Echinata Extracts

    PubMed Central

    da Silva Gomes, Elisangela Christhianne Barbosa; Jimenez, George Chaves; da Silva, Luis Claudio Nascimento; de Sá, Fabrício Bezerra; de Souza, Karen Pena Cavalcanti; Paiva, Gerson S.; de Souza, Ivone Antônia

    2014-01-01

    Natural products contain important combinations of ingredients, which may to some extent help to modulate the effects produced by oxidation substrates in biological systems. It is known that substances capable of modulating the action of these oxidants on tissue may be important allies in the control of neovascularization in pathological processes. The aim of this study was to evaluate the antioxidant and antiangiogenic properties of an ethanol extract of Caesalpinia echinata. The evaluation of antioxidant properties was tested using two methods (DPPH inhibition and sequestration of nitric oxide). The antiangiogenic properties were evaluated using the inflammatory angiogenesis model in the corneas of rats. The extract of C. echinata demonstrated a high capacity to inhibit free radicals, with IC50 equal to 42.404 µg/mL for the DPPH test and 234.2 µg/mL for nitric oxide. Moreover, it showed itself capable of inhibiting the inflammatory angiogenic response by 77.49%. These data suggest that biochemical components belonging to the extract of C. echinata interfere in mechanisms that control the angiogenic process, mediated by substrates belonging to the arachidonic acid cascade, although the data described above also suggest that the NO buffer may contribute to some extent to the reduction in the angiogenic response. PMID:24563668

  4. Optical and mechanical properties of cellulose nanopaper structures

    NASA Astrophysics Data System (ADS)

    Tsalagkas, Dimitrios; Zhai, Lindong; Kim, Hyun Chan; Kim, Jaehwan

    2017-04-01

    The objectives of this study are to prepare and investigate the optical and tensile properties of the obtained cellulose nanopaper structures. A ball mill mechanical pretreatment combined with a wet pulverization process by using an aqueous counter collision machine were used to extract CNFs from softwood and hardwood bleached kraft pulps. Cellulose nanofiber (CNF) nanopapers were fabricated via vacuum filtration and oven drying method. The mechanical and optical properties of the fabricated nanopaper were investigated by using tensile test and UV-vis spectrometer. Results have shown that the softwood sample demonstrated better mechanical properties than the hardwood sample. UV-vis transmittance measurements did not indicate significant differences.

  5. Mechanical Properties of Nanocrystal Supercrystals

    SciTech Connect

    Tam, Enrico; Podsiadlo, Paul; Shevchenko, Elena; Ogletree, D. Frank; Delplancke-Ogletree, Marie-Paule; Ashby, Paul D.

    2009-12-30

    Colloidal nanocrystals attract significant interest due to their potential applications in electronic, magnetic, and optical devices. Nanocrystal supercrystals (NCSCs) are particularly appealing for their well ordered structure and homogeneity. The interactions between organic ligands that passivate the inorganic nanocrystal cores critically influence their self-organization into supercrystals, By investigating the mechanical properties of supercrystals, we can directly characterize the particle-particle interactions in a well-defined geometry, and gain insight into both the self-assembly process and the potential applications of nanocrystal supercrystals. Here we report nanoindentation studies of well ordered lead-sulfide (Pbs) nanocrystal supercrystals. Their modulus and hardness were found to be similar to soft polymers at 1.7 GPa and 70 MPa respectively and the fractures toughness was 39 KPa/m1/2, revealing the extremely brittle nature of these materials.

  6. Visual-adaptation-mechanism based underwater object extraction

    NASA Astrophysics Data System (ADS)

    Chen, Zhe; Wang, Huibin; Xu, Lizhong; Shen, Jie

    2014-03-01

    Due to the major obstacles originating from the strong light absorption and scattering in a dynamic underwater environment, underwater optical information acquisition and processing suffer from effects such as limited range, non-uniform lighting, low contrast, and diminished colors, causing it to become the bottleneck for marine scientific research and projects. After studying and generalizing the underwater biological visual mechanism, we explore its advantages in light adaption which helps animals to precisely sense the underwater scene and recognize their prey or enemies. Then, aiming to transform the significant advantage of the visual adaptation mechanism into underwater computer vision tasks, a novel knowledge-based information weighting fusion model is established for underwater object extraction. With this bionic model, the dynamical adaptability is given to the underwater object extraction task, making them more robust to the variability of the optical properties in different environments. The capability of the proposed method to adapt to the underwater optical environments is shown, and its outperformance for the object extraction is demonstrated by comparison experiments.

  7. Mechanical Properties of Primary Cilia

    NASA Astrophysics Data System (ADS)

    Battle, Christopher; Schmidt, Christoph F.

    2013-03-01

    Recent studies have shown that the primary cilium, long thought to be a vestigial cellular appendage with no function, is involved in a multitude of sensory functions. One example, interesting from both a biophysical and medical standpoint, is the primary cilium of kidney epithelial cells, which acts as a mechanosensitive flow sensor. Genetic defects in ciliary function can cause, e.g., polycystic kidney disease (PKD). The material properties of these non-motile, microtubule-based 9 +0 cilia, and the way they are anchored to the cell cytoskeleton, are important to know if one wants to understand the mechano-electrochemical response of these cells, which is mediated by their cilia. We have probed the mechanical properties, boundary conditions, and dynamics of the cilia of MDCK cells using optical traps and DIC/fluorescence microscopy. We found evidence for both elastic relaxation of the cilia themselves after bending and for compliance in the intracellular anchoring structures. Angular and positional fluctuations of the cilia reflect both thermal excitations and cellular driving forces.

  8. Energy transfer properties and mechanisms

    SciTech Connect

    Barker, J.R.

    1992-10-20

    The overall objective of the research carried out under this program is to determine the principles of collisional energy transfer and use them in predictive models and theories. In order to accomplish this goal, energy transfer properties must be determined and then analyzed to discern the underlying principles involved. In this laboratory, the experimental determination of energy transfer parameters is based on techniques that use physical properties to monitor the amount of energy in excited molecules. These techniques differ from chemical methods, based on unimolecular reaction studies, which are susceptible to interferences from complex chemical mechanisms and other complications. The physical methods have their own weaknesses and limitations, however, and much of our effort has been directed toward gaining a better understanding of these deficiencies. Two physical techniques have been proved to be particularly useful: time-resolved infrared fluorescence (IRF) and time-dependent thermal lensing (TDTL). As described later, we will shortly begin work using resonance enhanced multiphoton ionization (REMPI) techniques to investigate energy transfer in bulbs and half collisions'' in free jets. We also have completed some experiments and model calculations which explore the approximations we previously have used in calculating infrared emission from highly excited molecules.

  9. Mechanical properties of warped membranes

    NASA Astrophysics Data System (ADS)

    Kosmrlj, Andrej; Xiao, Kechao; Weaver, James C.; Vlassak, Joost J.; Nelson, David R.

    2014-03-01

    We explore how a frozen background metric affects the mechanical properties of solid planar membranes at zero temperature. Our focus is a special class of ``warped membranes'' with a preferred random height profile characterized by random Gaussian variables h(q) in Fourier space with zero mean and variance < | h(q) | 2 > q-m . Using statistical physics tools to treat this quenched random disorder, we find that in the linear response regime, similar to thermally fluctuating polymerized membranes, an increasing scale-dependent effective bending rigidity, while the Young and the shear moduli are reduced. Compared to flat plates of the same thickness t, the bending rigidity of warped membranes is increased by a factor hv / t while the in-plane elastic moduli are reduced by t /hv , where hv =√{< | h(x) | 2 > } describes the frozen height fluctuations. Interestingly, hv is system size dependent for warped membranes characterized with m > 2 . Numerical results show good agreement with theoretical predictions, which are now being tested experimentally, where warped membranes are prepared with 3D printers.

  10. Neuroprotective and neurochemical properties of mint extracts.

    PubMed

    López, Víctor; Martín, Sara; Gómez-Serranillos, Maria Pilar; Carretero, Maria Emilia; Jäger, Anna K; Calvo, Maria Isabel

    2010-06-01

    Mints are aromatic plants with a tradition as medicinal remedies and culinary herbs. With the aim of investigating potential central nervous system (CNS) activities of traditional medicinal plants, four species and one hybrid of the genus Mentha (M. aquatica, M. longifolia, M. pulegium, M. suaveolens and M. x piperita) were selected. Methanolic extracts of the plants were tested for protective effects against hydrogen-peroxide-induced toxicity in PC12 cells, antioxidant activity (by ABTS and X/XO methods) and neurochemical properties (MAO-A inhibition, AChE inhibition and affinity to the GABA(A) receptor). Mentha x piperita and Mentha aquatica produced significant (p < 0.05) protection of the PC12 cells against oxidative stress. All the plants exhibited antioxidant and MAO-A inhibitory activities, M. x piperita being the most active. M. aquatica showed the highest affinity to the GABA(A)-receptor assay. Results demonstrate that mints might have effect on the CNS. (c) 2009 John Wiley & Sons, Ltd.

  11. Molecular Mechanism of Cyclodextrin Mediated Cholesterol Extraction

    PubMed Central

    López, Cesar A.; de Vries, Alex H.; Marrink, Siewert J.

    2011-01-01

    The depletion of cholesterol from membranes, mediated by β-cyclodextrin (β-CD) is well known and documented, but the molecular details of this process are largely unknown. Using molecular dynamics simulations, we have been able to study the CD mediated extraction of cholesterol from model membranes, in particular from a pure cholesterol monolayer, at atomic resolution. Our results show that efficient cholesterol extraction depends on the structural distribution of the CDs on the surface of the monolayer. With a suitably oriented dimer, cholesterol is extracted spontaneously on a nanosecond time scale. Additional free energy calculations reveal that the CDs have a strong affinity to bind to the membrane surface, and, by doing so, destabilize the local packing of cholesterol molecules making their extraction favorable. Our results have implications for the interpretation of experimental measurements, and may help in the rational design of efficient CD based nano-carriers. PMID:21455285

  12. Properties of wood-plastic composites (WPCs) reinforced with extracted and delignified wood flour

    Treesearch

    Yao Chen; Nicole M. Stark; Mandla A. Tshabalala; Jianmin Gao; Yongming Fan

    2014-01-01

    The water sorption and mechanical properties of wood-plastic composites (WPCs) made of extracted and delignified wood flour (WF) has been investigated. WF was prepared by extraction with the solvent systems toluene/ethanol (TE), acetone/water (AW), and hot water (HW), and its delignification was conducted by means of sodium chlorite/acetic acid (AA) solution. A 2 4...

  13. Extraction kinetics and properties of proanthocyanidins from pomegranate peel

    USDA-ARS?s Scientific Manuscript database

    With an objective of developing a safe and efficient method to extract proanthocyanidins products from pomegranate peel for use in nutraceuticals or as food additives, the effects of extraction parameters on the production efficiency, product properties, and extraction kinetics were systematically s...

  14. Research on mechanical properties of corn stalk

    NASA Astrophysics Data System (ADS)

    Zhang, Kaifei; He, Yujing; Zhang, Hongmei; Li, He

    2017-03-01

    Many domestic scholars have studied on straw utilization from lodging resistance, by breeding agricultural experts to optimization parameters, which selected by agricultural mechanical experts and efficient utilization after the harvest crush. Therefore, the study of the mechanical properties of corn stalks has great prospects. It can provide the basis for the design of agricultural machinery and comprehensive utilization of straw that study the relationship between the properties of the corn stalk and the mechanical properties. In this paper, the radial compression and bending mechanical properties of corn stalk was conducted by universal material testing machine, which contributes to the increase of corn crop and provides basis for the development of equipment.

  15. Mechanical algal disruption for efficient biodiesel extraction

    NASA Astrophysics Data System (ADS)

    Krehbiel, Joel David

    Biodiesel from algae provides several benefits over current biodiesel feedstocks, but the energy requirements of processing algae into a useable fuel are currently so high as to be prohibitive. One route to improving this is via disruption of the cells prior to lipid extraction, which can significantly increase energy recovery. Unfortunately, several obvious disruption techniques require more energy than can be gained. This dissertation examines the use of microbubbles to improve mechanical disruption of algal cells using experimental, theoretical, and computational methods. New laboratory experiments show that effective ultrasonic disruption of algae is achieved by adding microbubbles to an algal solution. The configuration studied flows the solution through a tube and insonifies a small section with a high-pressure ultrasound wave. Previous biomedical research has shown effective cell membrane damage on animal cells with similar methods, but the present research is the first to extend such study to algal cells. Results indicate that disruption increases with peak negative pressure between 1.90 and 3.07 MPa and with microbubble concentration up to 12.5 x 107 bubbles/ml. Energy estimates of this process suggest that it requires only one-fourth the currently most-efficient laboratory-scale disruption process. Estimates of the radius near each bubble that causes disruption (i.e. the disruption radius) suggest that it increases with peak negative pressure and is near 9--20 microm for all cases tested. It is anticipated that these procedures can be designed for better efficiency and efficacy, which will be facilitated by identifying the root mechanisms of the bubble-induced disruption. We therefore examine whether bubble expansion alone creates sufficient cell deformation for cell rupture. The spherically-symmetric Marmottant model for bubble dynamics allows estimation of the flow regime under experimental conditions. Bubble expansion is modeled as a point source of

  16. Antimicrobial Properties of Teas and Their Extracts in vitro.

    PubMed

    Siddiqui, Md Wasim; Sharangi, A B; Singh, J P; Thakur, Pran K; Ayala-Zavala, J F; Singh, Archana; Dhua, R S

    2016-07-03

    Tea has recently received the attention of pharmaceutical and scientific communities due to the plethora of natural therapeutic compounds. As a result, numerous researches have been published in a bid to validate their biological activity. Moreover, major attention has been drawn to antimicrobial activities of tea. Being rich in phenolic compounds, tea has the preventive potential for colon, esophageal, and lung cancers, as well as urinary infections and dental caries, among others. The venture of this review was to illustrate the emerging findings on the antimicrobial properties of different teas and tea extracts, which have been obtained from several in vitro studies investigating the effects of these extracts against different microorganisms. Resistance to antimicrobial agents has become an increasingly important and urgent global problem. The extracts of tea origin as antimicrobial agents with new mechanisms of resistance would serve an alternative way of antimicrobial chemotherapy targeting the inhibition of microbial growth and the spread of antibiotic resistance with potential use in pharmaceutical, cosmetic, and food industries.

  17. Canola Proteins for Human Consumption: Extraction, Profile, and Functional Properties

    PubMed Central

    Tan, Siong H; Mailer, Rodney J; Blanchard, Christopher L; Agboola, Samson O

    2011-01-01

    Canola protein isolate has been suggested as an alternative to other proteins for human food use due to a balanced amino acid profile and potential functional properties such as emulsifying, foaming, and gelling abilities. This is, therefore, a review of the studies on the utilization of canola protein in human food, comprising the extraction processes for protein isolates and fractions, the molecular character of the extracted proteins, as well as their food functional properties. A majority of studies were based on proteins extracted from the meal using alkaline solution, presumably due to its high nitrogen yield, followed by those utilizing salt extraction combined with ultrafiltration. Characteristics of canola and its predecessor rapeseed protein fractions such as nitrogen yield, molecular weight profile, isoelectric point, solubility, and thermal properties have been reported and were found to be largely related to the extraction methods. However, very little research has been carried out on the hydrophobicity and structure profiles of the protein extracts that are highly relevant to a proper understanding of food functional properties. Alkaline extracts were generally not very suitable as functional ingredients and contradictory results about many of the measured properties of canola proteins, especially their emulsification tendencies, have also been documented. Further research into improved extraction methods is recommended, as is a more systematic approach to the measurement of desired food functional properties for valid comparison between studies. PMID:21535703

  18. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, U.

    1995-04-25

    A composition and method are disclosed of preparing YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T{sub c}. About 5-20% additions give rise to substantially improved mechanical properties.

  19. Enhancement of mechanical properties of 123 superconductors

    DOEpatents

    Balachandran, Uthamalingam

    1995-01-01

    A composition and method of preparing YBa.sub.2 Cu.sub.3 O.sub.7-x superconductor. Addition of tin oxide containing compounds to YBCO superconductors results in substantial improvement of fracture toughness and other mechanical properties without affect on T.sub.c. About 5-20% additions give rise to substantially improved mechanical properties.

  20. Anti-Fatigue Properties of Tartary Buckwheat Extracts in Mice

    PubMed Central

    Jin, Hong-Mei; Wei, Ping

    2011-01-01

    Anti-fatigue properties of tartary buckwheat extracts (TBE) was investigated in male Kunming mice. The animals were divided into four groups. The first group, designated as the control group (control), was administered with distilled water by gavage every day for 28 days. The other three groups, designated as TBE treatment groups, were administered with TBE of 60, 120 and 240 mg/kg body weight, respectively, by gavage every day for 28 days. Exhaustive swimming time, blood lactic acid (BLA), blood urea nitrogen (BUN), tissue glycogen, glutathione peroxidase (GPx) and superoxide dismutase (SOD) of mice after swimming were determined. The results showed that tartary buckwheat extracts had anti-fatigue properties, which extended the exhaustive swimming time of mice, effectively inhibiting the increase of BLA, decreasing the level of BUN, increasing the tissue glycogen content and the activities of SOD and GPx of mice. However, further study is needed to elucidate the exact mechanism of the effect of TBE on fatigue. PMID:21954324

  1. Calendula extract: effects on mechanical parameters of human skin.

    PubMed

    Akhtar, Naveed; Zaman, Shahiq Uz; Khan, Barkat Ali; Amir, Muhammad Naeem; Ebrahimzadeh, Muhammad Ali

    2011-01-01

    The aim of this study was to evaluate the effects of newly formulated topical cream of Calendula officinalis extract on the mechanical parameters of the skin by using the cutometer. The Cutometer 580 MPA is a device that is designed to measure the mechanical properties of the skin in response to the application of negative pressure. This non-invasive method can be useful for objective and quantitative investigation of age related changes in skin, skin elasticity, skin fatigue, skin hydration, and evaluation of the effects of cosmetic and antiaging topical products. Two creams (base and formulation) were prepared for the study. Both the creams were applied to the cheeks of 21 healthy human volunteers for a period of eight weeks. Every individual was asked to come on week 1, 2, 3, 4, 5, 6, 7, and 8 and measurements were taken by using Cutometer MPA 580 every week. Different mechanical parameters of the skin measured by the cutometer were; R0, R1, R2, R5, R6, R7, and R8. These were then evaluated statistically to measure the effects produced by these creams. Using ANOVA, and t-test it was found that R0, and R6 were significant (p <0.05) whereas R1, R2, R5, R7, R8 were insignificant (p > 0.05). The instrumental measurements produced by formulation reflected significant improvements in hydration and firmness of skin.

  2. Hot environment effects on alloy mechanical properties

    NASA Technical Reports Server (NTRS)

    Davidson, J. M.; Aning, K.; Tien, J. K.

    1976-01-01

    Prolonged high temperature performance of structural alloys requires joint attention to both corrosion and mechanical properties, and to their possible interactions. In this interpretive review paper, we provide a systematic compaction of theories and key observations on corrosion-mechanical properties interactions, from early single crystal work in the 1930s to recent studies on superalloys in nonoxidizing, oxidizing and hot corrosive environments. Particular attention is paid to environmental effects on creep, stress rupture and fatigue properties.

  3. Effects of Hot-Pressure Extraction Time on Composition and Gelatin Properties of Chicken Bone Extracts.

    PubMed

    Yue, Jian-Ying; Wang, Jin-Zhi; Zhang, Chun-Hui; Jia, Wei; Li, Xia; Sun, Zhen

    2017-03-29

    Hot-pressure extraction was utilized in this study to extract proteins from chicken bones at 130 °C. The obtained extracts were further used to prepare gelatin gels. Results demonstrated that the extraction time can significantly affect the composition of the chicken bone extracts (P < 0.05). High-performance liquid chromatography (HPLC) analysis indicated that the protein fraction of molecular weight (MW) >30 KDa was only visible in the extracts collected between 40 and 60 min. The highest contents of hydroxyproline, imino acids, and hydrophobic amino acids were all achieved in the chicken bone extracts after 120 min of extraction, being 3.9, 7.7, and 16.0 mg/g, respectively. The prepared gelatin properties were evaluated in terms of viscosity, storage and loss modulus, stability, gel strength, and their microstructures. Results indicated that gelatins made from chicken bone extracts of 20, 40, and 60 min extraction had better properties compared to that of 90 and 120 min. Significant correlations were identified between gelatin's composition and properties (P < 0.05). The abundance of proteins with MW of <10 KDa and 10 to 30 KDa was found to be the predominant factor that can affect the gelatin's properties. This study illustrated a promising and natural way to obtain edible gelatins from chicken bones.

  4. Antiviral properties of extract of Opuntia streptacantha.

    PubMed

    Ahmad, A; Davies, J; Randall, S; Skinner, G R

    1996-05-01

    An extract of the cactus plant Opuntia streptacantha inhibited intracellular virus replication and inactivated extracellular virus. Inhibition of virus replication also occurred following pre-infection treatment--a favourable finding in terms of in-vivo limitation of virus disease. There was inhibition of both DNA and RNA virus replication, for example, herpes simplex virus, equine herpes virus, pseudorabies virus, influenza virus, respiratory syncytial virus and human immunodeficiency virus, with normal protein synthesis in uninfected cells at extract concentrations which were 15-fold in excess of 50% viral inhibitory concentrations (1 mg/ml). The active inhibitory component(s) of the extract appeared to be protein in nature and resided mainly in the wall of the plant rather than in the cuticle or inner sap. The extract was non-toxic on oral administration to mice, horses and human patients; the non-toxicity of intravenous administration of 70 mg to a mouse representing at least fifty tissue culture 50% viral inhibitory dosages encourages clinical trial of this extract in virus disease of human and veterinary species.

  5. Effects of hemicellulose pre-extraction and cellulose nanofiber on the properties of rice straw pulp.

    PubMed

    Hasanjanzadeh, Hadi; Hedjazi, Sahab; Ashori, Alireza; Mahdavi, Saeed; Yousefi, Hossein

    2014-07-01

    The aim of this study was to evaluate the influence of mild alkaline pre-extraction on the hemicelluloses removal of rice straw. In addition, the performance of cellulose nanofibers (CNFs) addition on some physico-mechanical properties obtained from extracted and un-extracted (control) samples were investigated. An optimum compromise was found as operating conditions (10% soda, 50°C, and 90min) that provided moderate hemicelluloses removal (48.1%). The residual extracted rice straw particles were subjected to soda-anthraquinone pulping at 160°C for 30-60min with 6 to 18% active alkali charge. Compared with the control samples, the screened yield and Kappa number for extracted pulps decreased slightly. Extracted samples showed better air resistance compared with the un-extracted (control) pulps. However, pre-extraction was found to negatively impact on some mechanical properties such as decrease in burst and tensile indices while addition of CNFs and refining of fibers could improve the strength properties considerably. In general, the addition of CNFs in any concentrations considerably enhanced tensile and burst indices of the sheets in extracted and un-extracted conditions, compared with the unfilled ones. The improvement in mechanical properties was considered one of the key benefits brought by CNFs reinforcement. On the other hand, the stretch properties of the beaten pulps are higher than those of control samples. SEM observations showed that CNFs were deposited on the voids between the rice straw fibers. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Mechanical property characterization of polymeric composites reinforced by continuous microfibers

    NASA Astrophysics Data System (ADS)

    Zubayar, Ali

    Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear

  7. The Antinociceptive Properties of the Corydalis yanhusuo Extract

    PubMed Central

    Wang, Lien; Zhang, Yan; Wang, Zhiwei; Gong, Nian; Kweon, Tae Dong; Vo, Benjamin; Wang, Chaoran; Zhang, Xiuli; Chung, Jae Yoon; Alachkar, Amal; Liang, Xinmiao; Luo, David Z.; Civelli, Olivier

    2016-01-01

    Corydalis yanhusuo. W.T. extracts (YHS) are widely used for the treatment of pain and inflammation. There are a few studies that assessed the effects of YHS in pain assays; however, none of these studies has systematically compared its activities in the different pain animal modes namely: acute, inflammatory and chronic pain. Furthermore, little is known about the mechanism of YHS activity in these assays. The aim of this study was to systematically evaluate the antinociceptive properties of YHS by testing it in four standardized pain assays and to investigate its mechanism. YHS antinociceptive properties were analyzed in the tail flick, the formalin paw licking, the von Frey filament and the hot box assays after spinal nerve ligation, which monitors acute nociceptive, persistent inflammatory and chronic neuropathic pain, respectively. YHS pharmacological profile was determined by screening it against a battery of G-protein coupled receptors and its mechanism of action was studied using knock-out mice. Our study shows that YHS, at a non-sedative dose, increases the tail flick latency in the tail flick assay without resulting in development of tolerance. YHS also decreases paw licking time in the formalin assay. Further, YHS increases paw withdraw threshold and latency in the von Frey filament and the hot box assays, respectively. In vitro, YHS exhibits prominent dopamine receptor antagonistic properties. In dopamine D2 receptor knockout mice, its antinociceptive effects are attenuated in acute and neuropathic pain but not inflammatory pain assays. Our results therefore indicate that YHS effectively attenuates acute, inflammatory and neuropathic pain, without causing tolerance. The effects on acute and neuropathic pain, but not inflammatory pain, are at least partially mediated through dopamine D2 receptor antagonism. Since YHS is a dietary supplement commercially available in the United States, our data suggest that it might be a candidate for alternative pain

  8. Bioactive phytochemicals in wheat: Extraction, analysis, processing, and functional properties

    USDA-ARS?s Scientific Manuscript database

    Whole wheat provides a rich source of bioactive phytochemicals namely, phenolic acids, carotenoids, tocopherols, alkylresorcinols, arabinoxylans, benzoxazinoids, phytosterols, and lignans. This review provides information on the distribution, extractability, analysis, and nutraceutical properties of...

  9. Molecular interaction mechanisms in reverse micellar extraction of microbial transglutaminase.

    PubMed

    Yu, Tingting; Lin, Mingxiang; Wan, Junfen; Cao, Xuejun

    2017-08-18

    Reverse micellar extraction is an efficient and economical alternative for protein purification. In this study, microbial transglutaminase (MTGase) from crude materials was purified using reverse micellar extraction, and the molecular interaction mechanism in reverse micellar extraction of MTGase was explored. By using a molecular simulation study, the interaction mechanism of forward extraction was investigated. The molecular simulation results reveal the interaction of MTGase-water-surfactant is the major driving force for the forward extraction. Further, the effect of ionic strength on molecular interactions in backward extraction was investigated using 1H low-field nuclear magnetic resonance (LF-NMR) and circular dichroism (CD) spectra. In backward extraction, the interactions between water and the other two molecules (MTGase and surfactant molecules) are enhanced while the interactions between target molecules (MTGase) and the other two molecules (water and surfactant molecules) are weakened as the ionic strength increases. Moreover, the effect of size exclusion on backward extraction was also investigated. The results demonstrate size exclusion has limit effect at high ionic strength, and the weakened interaction of MTGase-water-surfactant is the main reason causing the release of the target molecules in backward extraction. This work might provide valuable reference to the MTGase purification and downstream processing. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Antioxidant properties of prepared blueberry (Vaccinium myrtillus) extracts.

    PubMed

    Faria, Ana; Oliveira, Joana; Neves, Patrícia; Gameiro, Paula; Santos-Buelga, Celestino; de Freitas, Victor; Mateus, Nuno

    2005-08-24

    A blueberry extract (A) and two anthocyanin-derived extracts (B and C) were prepared. The contents of polyphenols, flavonoids, anthocyanins, and anthocyanin-derived pigments of the extracts were determined for the first time. The pigment profile of blueberry extract A corresponded to 15 anthocyanins, whereas extract B was mainly composed of anthocyanin-pyruvic acid adducts of the blueberry original anthocyanins and extract C was mainly composed of the respective vinylpyranoanthocyanin-catechins (portisins). The extracts' abilities to inhibit lipid peroxidation, induced by 2,2'-azobis(2-methyl-propanimidamide) dihydrochloride in a liposomal membrane system were examined. The antioxidant capacities of the extracts were evaluated through monitoring oxygen consumption and by measuring the formation of conjugated dienes. All of the extracts provided protection of membranes against peroxyl radicals by increasing the induction time of oxidation. This effect increased with the polyphenol content and with the structural complexity of the anthocyanin-derived pigments of the extracts. The pigments present in extract C seemed to induce a higher protection of the liposome membranes toward oxidation. In addition, the antiradical properties and the reducing power of the extracts were determined by using DPPH and FRAP methods, respectively. The results from these assays were in agreement with those obtained with the liposome membranes.

  11. Hepatoprotective properties of Bauhinia variegata bark extract.

    PubMed

    Bodakhe, Surendra H; Ram, Alpana

    2007-09-01

    Bauhinia variegata (Leguminosae) commonly known as Kachnar, is widely used in Ayurveda as tonic to the liver. The present work was carried out to assess the potential of Bauhinia variegata bark as hepatoprotective agent. The hepatoprotective activity was investigated in carbon tetrachloride (CCl(4)) intoxicated Sprague-Dawley rats. Bauhinia variegata alcoholic Stem Bark Extract (SBE) at different doses (100 and 200 mg/kg) were administered orally to male Sprague-Dawley rats weighing between 100-120 g. The effect of SBE on the serum marker enzymes, viz., AST, ALT, ALP and GGT and liver protein and lipids were assessed. The extract exhibited significant hepatoprotective activity. Hence, B. variegata appears to be a promising hepatoprotective agent.

  12. Extraction of polycyclic aromatic hydrocarbons from soot and sediment: solvent evaluation and implications for sorption mechanism.

    PubMed

    Jonker, Michiel T O; Koelmans, Albert A

    2002-10-01

    Soot contains high levels of toxic compounds such as polycyclic aromatic hydrocarbons (PAHs). Extraction of PAHs from soot for quantitative analysis is difficult because the compounds are extremely tightly bound to the sorbent matrix. This study was designed to investigate the effect of solvent type on PAH extraction yield, to identify the most optimal solvent for PAH extraction from soot, and to gain insight into the mechanism of PAH sorption to soot in aquatic environments. To that end, different types of soot as well as coal, charcoal, and sediments containing soot-like material were extracted with seven organic solvents. Large differences in extraction recoveries were observed among solvents, with relative values as low as 16% as compared to the best extracting solvent. These differences were much larger for soot than for sediments. Dichloromethane, which to date is the most widely used solvent for soot and sediment extractions, appeared to be the overall worst extractant, whereas toluene/methanol (1:6) gave the best results. Based on extraction yields and solvent properties, extraction of PAHs from soot was explained by a two-step mechanism involving swelling of the sorbent matrix and subsequent displacement of sorbates by solvent molecules. Due to the low displacement capacity of water, desorption of PAHs from soot in the aquatic environment will be strongly limited. Moreover, a certain fraction of the total PAH mass on soot is suggested to be physically entrapped, making it unavailable for partitioning to the aqueous phase.

  13. Microstructure and mechanical properties of sheep horn.

    PubMed

    Zhu, Bing; Zhang, Ming; Zhao, Jian

    2016-07-01

    The sheep horn presents outstanding mechanical properties of impact resistance and energy absorption, which suits the need of the vehicle bumper design, but the mechanism behind this phenomenon is less investigated. The microstructure and mechanical properties of the sheep horn of Small Tailed Han Sheep (Ovis aries) living in northeast China were investigated in this article. The effect of sampling position and orientation of the sheep horn sheath on mechanical properties were researched by tensile and compression tests. Meanwhile, the surface morphology and microstructure of the sheep horn were observed using scanning electron microscopy (SEM). The formation mechanism of the mechanical properties of the sheep horn was investigated by biological coupling analysis. The analytical results indicated that the outstanding mechanical properties of the sheep horn are determined by configuration, structure, surface morphology and material coupling elements. These biological coupling elements make the sheep horn possess super characteristics of crashworthiness and energy absorption through the internal coupling mechanism. We suppose that these findings would make a difference in vehicle bumper design. Microsc. Res. Tech. 79:664-674, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  14. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation of the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix hybridized with secondary S-glass or Kevlar 49 fiber composites is presented. The specimen stress-strain behavior was determined, showing that mechanical properties of intraply hybrid composites can be measured with available methods such as the ten-degree off-axis test for intralaminar shear, and conventional tests for tensile, flexure, and Izod impact properties. The results also showed that combinations of high modulus graphite/S-glass/epoxy matrix composites exist which yield intraply hybrid laminates with the best 'balanced' properties, and that the translation efficiency of mechanical properties from the constituent composites to intraply hybrids may be assessed with a simple equation.

  15. Mechanical properties of low tantalum alloys

    NASA Technical Reports Server (NTRS)

    Kortovich, C. S.

    1982-01-01

    The mechanical property behavior of equiaxed cast B-1900 + Hf alloy as a function of tantalum content was studied. Tensile and stress rupture characterization was conducted on cast to size test bars containing tantalum at the 4.3% (standard level), 2.2% and 0% levels. Casting parameters were selected to duplicate conditions used to prepare test specimens for master metal heat qualification. The mechanical property results as well as results of microstructural/phase analysis of failed test bars are presented.

  16. [Mechanisms of algal inhibition by rice straw extract].

    PubMed

    Feng, Jing; Zhu, Qing; Wu, Wei-zhong; Rui, Ke-jian; Li, Yan-bo

    2008-12-01

    An indoor experiment was conducted to investigate the inhibition effects and mechanisms of rice straw extracts to the harmful bloom-forming algae, Microcystis aeruginosa. It was found that there were algae inhibitory chemicals in rice straw. The inhabitation ratio of rice straw extract to Microcystis was 69.3% when stored at a low temperature of - 4 degrees C for 4 days with a concentration of 2.5 g/L. The algal inhibition depends on both chemicals and biological responses from decomposed rice straw extracts. Their relative contributions to the algal inhibition depended on decomposition pathway and time. Algal inhibitory chemicals played more important roles in anaerobic decomposed rice straw extracts than aerobic decomposed ones in the algal-inhibition process. For anaerobically decomposed straw extracts, if stored for 15 and 30 days with the concentration of 1.5 g/L, the inhabitation ratio of rice straw to Microcystis was 83% and 46% respectively. However, for aerobically decomposed straw extracts, the biologic mechanism was more important. The inhibition effects of biologic mechanism increased with the decomposition time. For aerobically decomposed straw extracts, if stored for 15 and 30 days with the concentration of 1.5 g/L, the inhabitation ratio of rice straw to Microcystis was 81% and 93% respectively.

  17. Mechanical deformation mechanisms and properties of amyloid fibrils.

    PubMed

    Choi, Bumjoon; Yoon, Gwonchan; Lee, Sang Woo; Eom, Kilho

    2015-01-14

    Amyloid fibrils have recently received attention due to their remarkable mechanical properties, which are highly correlated with their biological functions. We have studied the mechanical deformation mechanisms and properties of amyloid fibrils as a function of their length scales by using atomistic simulations. It is shown that the length of amyloid fibrils plays a role in their deformation and fracture mechanisms in such a way that the competition between shear and bending deformations is highly dependent on the fibril length, and that as the fibril length increases, so does the bending strength of the fibril while its shear strength decreases. The dependence of rupture force for amyloid fibrils on their length is elucidated using the Bell model, which suggests that the rupture force of the fibril is determined from the hydrogen bond rupture mechanism that critically depends on the fibril length. We have measured the toughness of amyloid fibrils, which is shown to depend on the fibril length. In particular, the toughness of the fibril with its length of ∼3 nm is estimated to be ∼30 kcal mol(-1) nm(-3), comparable to that of a spider silk crystal with its length of ∼2 nm. Moreover, we have shown the important effect of the pulling rate on the mechanical deformation mechanisms and properties of amyloid fibril. It is found that as the pulling rate increases, so does the contribution of the shear effect to the elastic deformation of the amyloid fibril with its length of <10 nm. However, we found that the deformation mechanism of the amyloid fibril with its length of >15 nm is almost independent of the pulling rate. Our study sheds light on the role of the length scale of amyloid fibrils and the pulling rate in their mechanical behaviors and properties, which may provide insights into how the excellent mechanical properties of protein fibrils can be determined.

  18. Extensive screening for herbal extracts with potent antioxidant properties.

    PubMed

    Niwano, Yoshimi; Saito, Keita; Yoshizaki, Fumihiko; Kohno, Masahiro; Ozawa, Toshihiko

    2011-01-01

    This paper summarizes our research for herbal extracts with potent antioxidant activity obtained from a large scale screening based on superoxide radical (O(2) (•-)) scavenging activity followed by characterization of antioxidant properties. Firstly, scavenging activity against O(2) (•-) was extensively screened from ethanol extracts of approximately 1000 kinds of herbs by applying an electron spin resonance (ESR)-spin trapping method, and we chose four edible herbal extracts with prominently potent ability to scavenge O(2) (•-). They are the extracts from Punica granatum (Peel), Syzygium aromaticum (Bud), Mangifera indica (Kernel), and Phyllanthus emblica (Fruit). These extracts were further examined to determine if they also scavenge hydroxyl radical ((•)OH), by applying the ESR spin-trapping method, and if they have heat resistance as a desirable characteristic feature. Experiments with the Fenton reaction and photolysis of H(2)O(2) induced by UV irradiation demonstrated that all four extracts have potent ability to directly scavenge (•)OH. Furthermore, the scavenging activities against O(2) (•-) and (•)OH of the extracts of P. granatum (peel), M. indica (kernel) and P. emblica (fruit) proved to be heat-resistant.The results of the review might give useful information when choosing a potent antioxidant as a foodstuff. For instance, the four herbal extracts chosen from extensive screening possess desirable antioxidant properties. In particular, the extracts of the aforementioned three herbs are expected to be suitable for food processing in which thermal devices are used, because of their heat resistance.

  19. Physical and mechanical properties of stony meteorites

    NASA Astrophysics Data System (ADS)

    Slyuta, E. N.

    2017-01-01

    The method for experimental research of physical and mechanical properties of stony meteorites is considered. Experimental data on the physical and mechanical properties of samples of three ordinary chondrites are reported. Ordinary chondrites are characterized by a well-defined three-dimensional (spatial) anisotropy of physical and mechanical properties, when a compression strength in one of the directions significantly exceeds that in the other two directions. A measured compression strength of ordinary chondrites is in the range from 105 to 203 MPa, while a tensile strength is in the range from 18 to 31 MPa. As follows from the available published data on the strength of carbonaceous chondrites, they are drastically different in properties from ordinary chondrites. The observed critical aerodynamic loads do not exceed a measured tensile strength value of ordinary chondrites, which is actually the upper limit restricting the maximum aerodynamic load for ordinary chondrites.

  20. Mechanical properties of active polyacrylonitrile gels

    NASA Astrophysics Data System (ADS)

    Marra, Steven P.; Ramesh, Kaliat T.; Douglas, Andrew S.

    1999-05-01

    The ability of some polymeric gels to shrink and swell with changes in their environment makes them of interest in many applications such as artificial muscles and drug delivery systems. While much work has been done to study the behavior and properties of these gels, little information is available regarding the full constitutive description of the mechanical and actuation properties. This work is focused on developing constitutive descriptions of the mechanical properties of such gels, and to determine how these properties change due to changes in the environment. Since these gels can undergo finite elastic deformations, uniaxial tests do not provide sufficient property information and a combination of loading conditions must be used. A biaxial testing system has been developed to test thin sheets of these films, and includes the ability to monitor and change the environmental conditions around the specimen. Initial tests were performed on latex to determine the quality of the testing apparatus. Preliminary results on a polyacrylonitrile gel are presented.

  1. IMMUNO-MODULATORY PROPERTIES OF PREBIOTICS EXTRACTED FROM vernonia amygdalina.

    PubMed

    Im, Ezeonu; Ae, Asuquo; Bn, Ukwah; Po, Ukoha

    2016-01-01

    Vernonia amygdalina, commonly called bitter-leaf, is widely consumed in many parts of Africa, and Nigeria, in particular. The leaf extract has been reported to have antimicrobial, anti-plasmodial, anti-helminthic, as well as prebiotic properties, but its immuno-modulatory effects have not been well-studied, neither have the prebiotics been identified. This study evaluated the immuno-modulatory properties of the aqueous leaf extract and identified the prebiotic components. The immuno-modulatory potential was evaluated by monitoring the effects of oral administration of the extract on immunological, haematological and lipid profiles of Rattus norvegicus, while the prebiotic components were identified by thin layer chromatography (TLC), following liquid-liquid fractionation of the extract. Consumption of the extract caused significant increases in CD4+-, white blood cell-, total lymphocyte- and high density lipid (HDL) counts; decreases in low density lipid (LDL) and triglycerides and no significant effect on haemoglobin (Hb) and packed cell volume (PCV) in the blood of test animals. The water-soluble fraction of the extract contained most of the phyto-constituents of the extract and Thin Layer Chromatographic analysis of the fraction revealed the presence of fructo-oligosaccharide and galacto-oligosaccharide prebiotics. The results from this study have shown that the aqueous leaf extract of V. amygdalina has positive immune-modulatory and haematologic effects and contains some important prebiotic compounds.

  2. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    PubMed

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  3. Assessing mechanical properties from cone indentation hardness

    NASA Astrophysics Data System (ADS)

    Dicarlo, Anthony Albert

    This dissertation investigates methods for assessing the mechanical properties of materials using hardness values obtained from cone indentations. A broad range of isotropic metallic materials was simulated using finite element analysis. In particular, the elastic and plastic bulk properties, which define the stress-strain behavior of materials that exhibit power law hardening, are studied. Other investigators have found that the Young's modulus, E, can be determined from the unloading data of a cone indentation. Therefore, the remaining properties of interest, in this study, are the yield strength, Y, and the work hardening exponent, n. Atkins and Tabor have conducted pioneering work in the area of determining the stress-strain behavior of a metallic material from cone indentation experiments. This work has been re-visited in this study using computational models implementing an expanded range of mechanical properties. Consequently, discrepancies in this prediction method were uncovered when the mechanical properties were outside of the original range studied. As a result, two new prediction methods have been developed using the data collected from the finite element simulations in conjunction with a regression technique. The first method correlates the non-dimensional hardness values, H/E, collected from five cone indentations to the non-dimensional mechanical properties, Y/E and n. The second method is similar in principle, but uses two hardness values as opposed to five. The yield strength can be estimated with a priori knowledge of E. Both of these methods are compared to the method developed by Atkins and Tabor. Although the majority of the work mentioned is focused on the macro-scale, bulk mechanical properties, there is some investigation of meso-scale cone indentations. At the meso-scale, the number of geometric dislocations is significant enough to noticeably increase the strength of a material. This length scale effect is studied for various angled cone

  4. Biomolecular motor modulates mechanical property of microtubule.

    PubMed

    Kabir, Arif Md Rashedul; Inoue, Daisuke; Hamano, Yoshimi; Mayama, Hiroyuki; Sada, Kazuki; Kakugo, Akira

    2014-05-12

    The microtubule (MT) is the stiffest cytoskeletal filamentous protein that takes part in a wide range of cellular activities where its mechanical property plays a crucially significant role. How a single biological entity plays multiple roles in cell has been a mystery for long time. Over the recent years, it has been known that modulation of the mechanical property of MT by different cellular agents is the key to performing manifold in vivo activities by MT. Studying the mechanical property of MT thus has been a prerequisite in understanding how MT plays such diversified in vivo roles. However, the anisotropic structure of MT has been an impediment in obtaining a precise description of the mechanical property of MT along its longitudinal and lateral directions that requires employment of distinct experimental approach and has not been demonstrated yet. In this work, we have developed an experimental system that enabled us to investigate the effect of tensile stress on MT. By using our newly developed system, (1) we have determined the Young's modulus of MT considering its deformation under applied tensile stress and (2) a new role of MT associated motor protein kinesin in modulating the mechanical property of MT was revealed for the first time. Decrease in Young's modulus of MT with the increase in interaction with kinesin suggests that kinesin has a softening effect on MT and thereby can modulate the rigidity of MT. This work will be an aid in understanding the modulation of mechanical property of MTs by MT associated proteins and might also help obtain a clear insight of the endurance and mechanical instability of MTs under applied stress.

  5. Effective mechanical properties of hexagonal boron nitride nanosheets.

    PubMed

    Boldrin, L; Scarpa, F; Chowdhury, R; Adhikari, S

    2011-12-16

    We propose an analytical formulation to extract from energy equivalence principles the equivalent thickness and in-plane mechanical properties (tensile and shear rigidity, and Poisson's ratio) of hexagonal boron nitride (h-BN) nanosheets. The model developed provides not only very good agreement with existing data available in the open literature from experimental, density functional theory (DFT) and molecular dynamics (MD) simulations, but also highlights the specific deformation mechanisms existing in boron nitride sheets, and their difference with carbon-based graphitic systems.

  6. Properties of vermicompost aqueous extracts prepared under different conditions.

    PubMed

    Hanc, Ales; Boucek, Jiri; Svehla, Pavel; Dreslova, Marketa; Tlustos, Pavel

    2016-09-23

    The aim of this work was to determine the influence of aeration and time of extraction on the agrochemical properties of aqueous extracts from vermicomposts made from horse manure (M) and apple pomace (P) waste. There were two extract treatments: stirring without aeration (S), and stirring with aeration (A) for 48 h. Aeration significantly increased the levels of electrical conductivity (EC) and the concentration of [Formula: see text], [Formula: see text], and macro-elements in the extracts. In the (A) treatment, the extraction efficiency of K and Mg increased twofold, and the extraction efficiency of Ca and P increased by one-third compared with the (S) treatment. Simultaneously, the extracts prepared under aeration were characteristic with a higher pH value compared with non-aerated variants. The EC and content of macro-elements in the extracts increased proportionally with time. Their highest growth was found within the first 6 h. After 48 h, the highest release of macro-elements into the extract was found in the case of the horse manure under stirring with aeration.

  7. Mechanical properties of nanoparticles: basics and applications

    NASA Astrophysics Data System (ADS)

    Guo, Dan; Xie, Guoxin; Luo, Jianbin

    2014-01-01

    The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.

  8. Mechanical properties of septal cartilage homografts

    SciTech Connect

    Glasgold, M.J.; Kato, Y.P.; Christiansen, D.; Hauge, J.A.; Glasgold, A.I.; Silver, F.H.

    1988-10-01

    The compressive mechanical properties of untreated and chemically and physically treated nasal septum homografts were determined. Mechanical properties of control, saline-, thimerosal (Merthiolate)- and Alcide-treated specimens were similar. At high strains, the stiffness of treated cartilage ranged from 12.8 to 22.5 MPa and was unaffected by storage time. In comparison, irradiated and freeze-dried nasal septum exhibited stiffnesses of 35 and 37.5 MPa, respectively, after approximately 1 month of storage. These values of stiffness were significantly different from controls at a 0.95 confidence level. On the basis of these results, it was concluded that Alcide and Merthiolate treatment did not alter the compressive mechanical properties of cartilage and that a combination of these treatments may adequately sterilize and preserve nasal septum homografts.

  9. Physical and mechanical properties of hemp seed

    NASA Astrophysics Data System (ADS)

    Taheri-Garavand, A.; Nassiri, A.; Gharibzahedi, S.

    2012-04-01

    The current study was conducted to investigate the effect of moisture content on the post-harvest physical and mechanical properties of hemp seed in the range of 5.39 to 27.12% d.b. Results showed that the effect of moisture content on the most physical properties of the grain was significant (P<0.05). The results of mechanical tests demonstrated that the effect of loading rate on the mechanical properties of hemp seed was not significant. However, the moisture content effect on rupture force and energy was significant (P<0.01). The lowest value of rupture force was obtained at the highest loading rate (3mm min-1)and in the moisture content of 27.12% d.b. Moreover, the interaction effects of loading rate and moisture content on the rupture force and energy of hemp seed were significant (P<0.05).

  10. [Antimicrobial properties of extracts from Rhizophora mangle L].

    PubMed

    Rojas Hernández, N M; Coto Pérez, O

    1978-01-01

    Aqueous and alcoholic extracts are obtained from the roots, leaves and stems of ruddy mangrove-tree (Rhizophora mangle L.), a very common plant in Cuban coasts and to which different curative properties are attributed in our popular medicine. The inhibitory activity of these extracts on the growth of different human pathogenic organisms, among which are bacteria, fungii and yeasts, is reported. For this determination, a method of diffusion in an agar medium with holes in which 50 ml of each extract in question were poured was used; the size in millimeters of the inhibitory halo found in each species and the concentration of the dilution in broth for Mycobacterium strains are reported.

  11. Platform construction and extraction mechanism study of magnetic mixed hemimicelles solid-phase extraction.

    PubMed

    Xiao, Deli; Zhang, Chan; He, Jia; Zeng, Rong; Chen, Rong; He, Hua

    2016-12-07

    Simple, accurate and high-throughput pretreatment method would facilitate large-scale studies of trace analysis in complex samples. Magnetic mixed hemimicelles solid-phase extraction has the power to become a key pretreatment method in biological, environmental and clinical research. However, lacking of experimental predictability and unsharpness of extraction mechanism limit the development of this promising method. Herein, this work tries to establish theoretical-based experimental designs for extraction of trace analytes from complex samples using magnetic mixed hemimicelles solid-phase extraction. We selected three categories and six sub-types of compounds for systematic comparative study of extraction mechanism, and comprehensively illustrated the roles of different force (hydrophobic interaction, π-π stacking interactions, hydrogen-bonding interaction, electrostatic interaction) for the first time. What's more, the application guidelines for supporting materials, surfactants and sample matrix were also summarized. The extraction mechanism and platform established in the study render its future promising for foreseeable and efficient pretreatment under theoretical based experimental design for trace analytes from environmental, biological and clinical samples.

  12. Platform construction and extraction mechanism study of magnetic mixed hemimicelles solid-phase extraction

    NASA Astrophysics Data System (ADS)

    Xiao, Deli; Zhang, Chan; He, Jia; Zeng, Rong; Chen, Rong; He, Hua

    2016-12-01

    Simple, accurate and high-throughput pretreatment method would facilitate large-scale studies of trace analysis in complex samples. Magnetic mixed hemimicelles solid-phase extraction has the power to become a key pretreatment method in biological, environmental and clinical research. However, lacking of experimental predictability and unsharpness of extraction mechanism limit the development of this promising method. Herein, this work tries to establish theoretical-based experimental designs for extraction of trace analytes from complex samples using magnetic mixed hemimicelles solid-phase extraction. We selected three categories and six sub-types of compounds for systematic comparative study of extraction mechanism, and comprehensively illustrated the roles of different force (hydrophobic interaction, π-π stacking interactions, hydrogen-bonding interaction, electrostatic interaction) for the first time. What’s more, the application guidelines for supporting materials, surfactants and sample matrix were also summarized. The extraction mechanism and platform established in the study render its future promising for foreseeable and efficient pretreatment under theoretical based experimental design for trace analytes from environmental, biological and clinical samples.

  13. Platform construction and extraction mechanism study of magnetic mixed hemimicelles solid-phase extraction

    PubMed Central

    Xiao, Deli; Zhang, Chan; He, Jia; Zeng, Rong; Chen, Rong; He, Hua

    2016-01-01

    Simple, accurate and high-throughput pretreatment method would facilitate large-scale studies of trace analysis in complex samples. Magnetic mixed hemimicelles solid-phase extraction has the power to become a key pretreatment method in biological, environmental and clinical research. However, lacking of experimental predictability and unsharpness of extraction mechanism limit the development of this promising method. Herein, this work tries to establish theoretical-based experimental designs for extraction of trace analytes from complex samples using magnetic mixed hemimicelles solid-phase extraction. We selected three categories and six sub-types of compounds for systematic comparative study of extraction mechanism, and comprehensively illustrated the roles of different force (hydrophobic interaction, π-π stacking interactions, hydrogen-bonding interaction, electrostatic interaction) for the first time. What’s more, the application guidelines for supporting materials, surfactants and sample matrix were also summarized. The extraction mechanism and platform established in the study render its future promising for foreseeable and efficient pretreatment under theoretical based experimental design for trace analytes from environmental, biological and clinical samples. PMID:27924944

  14. Electron extraction mechanisms of a micro-ECR neutralizer

    NASA Astrophysics Data System (ADS)

    Takao, Yoshinori; Hiramoto, Kenta; Nakagawa, Yuichi; Kasagi, Yusuke; Koizumi, Hiroyuki; Komurasaki, Kimiya

    2016-07-01

    Three-dimensional particle simulations have been conducted to analyze the mechanisms of electron extraction through the orifices of a 4.2 GHz microwave discharge microneutralizer, using a xenon electron cyclotron resonance plasma. The dimensions of the neutralizer are 20 × 20 × 4 mm3, and a ring-shaped microwave antenna and permanent magnets are employed for its discharges. The numerical model is composed of a particle-in-cell simulation with a Monte Carlo collision algorithm for charged particle motions, a finite-difference time-domain method for microwaves, and a finite element analysis for magnetostatic fields. The simulation results have shown that the electrostatic field inside the plasma source has a dominant effect on electron extraction. The extracted electrons move along the magnetic field line to the orifice entrances and the E × B drift at the orifice edge induces electron extraction.

  15. Stainless Steel Microstructure and Mechanical Properties Evaluation

    SciTech Connect

    Switzner, Nathan T

    2010-06-01

    A nitrogen strengthened 21-6-9 stainless steel plate was spinformed into hemispherical test shapes. A battery of laboratory tests was used to characterize the hemispheres. The laboratory tests show that near the pole (axis) of a spinformed hemisphere the yield strength is the lowest because this area endures the least “cold-work” strengthening, i.e., the least deformation. The characterization indicated that stress-relief annealing spinformed stainless steel hemispheres does not degrade mechanical properties. Stress-relief annealing reduces residual stresses while maintaining relatively high mechanical properties. Full annealing completely eliminates residual stresses, but reduces yield strength by about 30%.

  16. Mechanical Properties of Ingot Nb Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  17. Silk Fibroin Degradation Related to Rheological and Mechanical Properties.

    PubMed

    Partlow, Benjamin P; Tabatabai, A Pasha; Leisk, Gary G; Cebe, Peggy; Blair, Daniel L; Kaplan, David L

    2016-05-01

    Regenerated silk fibroin has been proposed as a material substrate for biomedical, optical, and electronic applications. Preparation of the silk fibroin solution requires extraction (degumming) to remove contaminants, but results in the degradation of the fibroin protein. Here, a mechanism of fibroin degradation is proposed and the molecular weight and polydispersity is characterized as a function of extraction time. Rheological analysis reveals significant changes in the viscosity of samples while mechanical characterization of cast and drawn films shows increased moduli, extensibility, and strength upon drawing. Fifteen minutes extraction time results in degraded fibroin that generates the strongest films. Structural analysis by wide angle X-ray scattering (WAXS) and Fourier transform infrared spectroscopy (FTIR) indicates molecular alignment in the drawn films and shows that the drawing process converts amorphous films into the crystalline, β-sheet, secondary structure. Most interesting, by using selected extraction times, films with near-native crystallinity, alignment, and molecular weight can be achieved; yet maximal mechanical properties for the films from regenerated silk fibroin solutions are found with solutions subjected to some degree of degradation. These results suggest that the regenerated solutions and the film casting and drawing processes introduce more complexity than native spinning processes.

  18. Antitumor effects and mechanisms of Ganoderma extracts and spores oil

    PubMed Central

    Chen, Chun; Li, Peng; Li, Ye; Yao, Guan; Xu, Jian-Hua

    2016-01-01

    Ganoderma lucidum is a popular herbal medicine used in China to promote health. Modern studies have disclosed that the active ingredients of Ganoderma can exhibit several effects, including antitumor effects and immunomodulation. The present study evaluated the antitumor effects of self-prepared Ganoderma extracts and spores oil, and investigated the possible underlying mechanisms by observing the effects of the extracts and oil on topoisomerases and the cell cycle. The results showed that Ganoderma extracts and spores oil presented dose-dependent inhibitory effects on tumor cells. The half maximal inhibitory concentration (IC50) values of Ganoderma extracts on HL60, K562 and SGC-7901 cells for 24 h were 0.44, 0.39 and 0.90 mg/ml, respectively; for Ganoderma spores oil, the IC50 values were 1.13, 2.27 and 6.29 mg/ml, respectively. In the in vivo study, the inhibitory rates of Ganoderma extracts (4 g/kg/d, intragastrically) on S180 and H22 cells were 39.1 and 44.6%, respectively, and for Ganoderma spores oil (1.2 g/kg/d, intragastrically) the inhibitory rates were 30.9 and 44.9%, respectively. Ganoderma extracts and spores oil inhibited the activities of topoisomerase I and II. Ganoderma spores oil was shown block the cell cycle at the transition between the G1 and S phases and induce a marked decrease in cyclin D1 levels in K562 cells, with no significant change in cyclin E level. These results suggest that the Ganoderma extracts and spores oil possessed antitumor effects in the in vitro and in vivo studies. The antitumor mechanisms of the extracts and spores oil were associated with inhibitory effects on topoisomerase I and II activities, and for Ganoderma spores oil, the antitumor effects may also be associated with decreased cyclin D1 levels, thus inducing G1 arrest in the cell cycle. PMID:27900038

  19. Electrochemical study of the mechanism of lanthanide extraction with thenoyltrifluoroacetone.

    PubMed

    Yu, W H; Freiser, H

    1989-01-01

    Current-scan polarography at the ascending-water electrode (AWE) was used to examine the electrochemical behavior of HTTA and La(3+), both in the absence and presence of neutral ligands, TOPO or MBDPO, and the light this sheds on the mechanism of extraction of lanthanides with HTTA, as well as the role played by mixed-ligand chelate formation.

  20. Mechanical properties of polygonal carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Ling; Cao, Dapeng

    2012-08-01

    A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the transition-state theory model to predict the critical strain of P-CNTs at given experimental conditions. It is expected that this work could provide feasible means to manipulate the mechanical properties of novel P-CNTs and facilitate the mechanical application of nanostructures as potential electronic devices.A group of polygonal carbon nanotubes (P-CNTs) have been designed and their mechanical behavior was investigated by classical molecular dynamics simulations. The research aimed at exploring the effects of structure, temperature, and strain rate on the mechanical properties. The results indicate that the Young's modulus of P-CNTs is lower than those of circumcircle carbon nanotubes (C-CNT). Moreover, with an increase in the number of sides to the polygons, the Young's modulus increases and is much closer to that of C-CNT. The effects of temperature and strain rate on the mechanical properties of P-CNTs show that the higher temperature and slower strain rate result in a lower critical strain and weaker tensile strength. In addition, it was found that the critical strains of P-CNTs are dependent on the tube size. Finally, we used the

  1. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  2. Yellow Mealworm Protein for Food Purposes - Extraction and Functional Properties

    PubMed Central

    Zhao, Xue; Vázquez-Gutiérrez, José Luis; Johansson, Daniel P.; Landberg, Rikard; Langton, Maud

    2016-01-01

    A protocol for extraction of yellow mealworm larvae proteins was established, conditions were evaluated and the resulting protein extract was characterised. The freeze-dried yellow mealworm larvae contained around 33% fat, 51% crude protein and 43% true protein on a dry matter basis. The true protein content of the protein extract was about 75%, with an extraction rate of 70% under optimised extraction conditions using 0.25 M NaOH, a NaOH solution:ethanol defatted worm ratio of 15:1 mL/g, 40°C for 1 h and extraction twice. The protein extract was a good source of essential amino acids. The lowest protein solubility in distilled water solution was found between pH 4 and 5, and increased with either increasing or decreasing pH. Lower solubility was observed in 0.5 M NaCl solution compared with distilled water. The rheological tests indicated that temperature, sample concentration, addition of salt and enzyme, incubation time and pH alterations influenced the elastic modulus of yellow mealworm protein extract (YMPE). These results demonstrate that the functional properties of YMPE can be modified for different food applications. PMID:26840533

  3. Yellow Mealworm Protein for Food Purposes - Extraction and Functional Properties.

    PubMed

    Zhao, Xue; Vázquez-Gutiérrez, José Luis; Johansson, Daniel P; Landberg, Rikard; Langton, Maud

    2016-01-01

    A protocol for extraction of yellow mealworm larvae proteins was established, conditions were evaluated and the resulting protein extract was characterised. The freeze-dried yellow mealworm larvae contained around 33% fat, 51% crude protein and 43% true protein on a dry matter basis. The true protein content of the protein extract was about 75%, with an extraction rate of 70% under optimised extraction conditions using 0.25 M NaOH, a NaOH solution:ethanol defatted worm ratio of 15:1 mL/g, 40°C for 1 h and extraction twice. The protein extract was a good source of essential amino acids. The lowest protein solubility in distilled water solution was found between pH 4 and 5, and increased with either increasing or decreasing pH. Lower solubility was observed in 0.5 M NaCl solution compared with distilled water. The rheological tests indicated that temperature, sample concentration, addition of salt and enzyme, incubation time and pH alterations influenced the elastic modulus of yellow mealworm protein extract (YMPE). These results demonstrate that the functional properties of YMPE can be modified for different food applications.

  4. Probing cell mechanical properties with microfluidic devices

    NASA Astrophysics Data System (ADS)

    Rowat, Amy

    2012-02-01

    Exploiting flow on the micron-scale is emerging as a method to probe cell mechanical properties with 10-1000x advances in throughput over existing technologies. The mechanical properties of cells and the cell nucleus are implicated in a wide range of biological contexts: for example, the ability of white blood cells to deform is central to immune response; and malignant cells show decreased stiffness compared to benign cells. We recently developed a microfluidic device to probe cell and nucleus mechanical properties: cells are forced to deform through a narrow constrictions in response to an applied pressure; flowing cells through a series of constrictions enables us to probe the ability of hundreds of cells to deform and relax during flow. By tuning the constriction width so it is narrower than the width of the cell nucleus, we can specifically probe the effects of nuclear physical properties on whole cell deformability. We show that the nucleus is the rate-limiting step in cell passage: inducing a change in its shape to a multilobed structure results in cells that transit more quickly; increased levels of lamin A, a nuclear protein that is key for nuclear shape and mechanical stability, impairs the passage of cells through constrictions. We are currently developing a new class of microfluidic devices to simultaneously probe the deformability of hundreds of cell samples in parallel. Using the same soft lithography techniques, membranes are fabricated to have well-defined pore distribution, width, length, and tortuosity. We design the membranes to interface with a multiwell plate, enabling simultaneous measurement of hundreds of different samples. Given the wide spectrum of diseases where altered cell and nucleus mechanical properties are implicated, such a platform has great potential, for example, to screen cells based on their mechanical phenotype against a library of drugs.

  5. Extensive screening for herbal extracts with potent antioxidant properties

    PubMed Central

    Niwano, Yoshimi; Saito, Keita; Yoshizaki, Fumihiko; Kohno, Masahiro; Ozawa, Toshihiko

    2011-01-01

    This paper summarizes our research for herbal extracts with potent antioxidant activity obtained from a large scale screening based on superoxide radical (O2•−) scavenging activity followed by characterization of antioxidant properties. Firstly, scavenging activity against O2•− was extensively screened from ethanol extracts of approximately 1000 kinds of herbs by applying an electron spin resonance (ESR)-spin trapping method, and we chose four edible herbal extracts with prominently potent ability to scavenge O2•−. They are the extracts from Punica granatum (Peel), Syzygium aromaticum (Bud), Mangifera indica (Kernel), and Phyllanthus emblica (Fruit). These extracts were further examined to determine if they also scavenge hydroxyl radical (•OH), by applying the ESR spin-trapping method, and if they have heat resistance as a desirable characteristic feature. Experiments with the Fenton reaction and photolysis of H2O2 induced by UV irradiation demonstrated that all four extracts have potent ability to directly scavenge •OH. Furthermore, the scavenging activities against O2•− and •OH of the extracts of P. granatum (peel), M. indica (kernel) and P. emblica (fruit) proved to be heat-resistant. The results of the review might give useful information when choosing a potent antioxidant as a foodstuff. For instance, the four herbal extracts chosen from extensive screening possess desirable antioxidant properties. In particular, the extracts of the aforementioned three herbs are expected to be suitable for food processing in which thermal devices are used, because of their heat resistance. PMID:21297917

  6. Mechanical properties of thermoelectric lanthanum telluride from quantum mechanics

    NASA Astrophysics Data System (ADS)

    Li, Guodong; Aydemir, Umut; Wood, Max; Goddard, William A., III; Zhai, Pengcheng; Zhang, Qingjie; Snyder, G. Jeffrey

    2017-07-01

    Lanthanum telluride (La3Te4) is an n-type high-performance thermoelectric material in the high temperature range, but its mechanical properties remain unknown. Since we want robust mechanical properties for their integration into industrial applications, we report here quantum mechanics (QM) simulations to determine the ideal strength and deformation mechanisms of La3Te4 under pure shear deformations. Among all plausible shear deformation paths, we find that shearing along the (0 0 1)/< \\text{1} 0 0> slip system has the lowest ideal shear strength of 0.99 GPa, making it the most likely slip system to be activated under pressure. We find that the long range La-Te ionic interactions play the predominant role in resisting shear deformation. To enhance the mechanical strength, we suggest improving the long ionic La-Te bond stiffness to strengthen the ionic La-Te framework in La3Te4 by a defect-engineering strategy, such as partial substitution of La by Ce or Pr having isotypic crystal structures. This work provides the fundamental information to understand the intrinsic mechanics of La3Te4.

  7. Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites

    DTIC Science & Technology

    2001-11-01

    Montmorillonite Composites DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report: TITLE: Nanophase and...Mechanical Properties of Unsaturated Polyester / Montmorillonite Composites A. Baran Inceoglu and Ulku Yilmazer Middle East Technical University, Chemical...analysed the nature of the curing agent on structure. Kornmann, Berglund and Giannelis [8] studied nanocomposites based on montmorillonite modified

  8. Mechanical properties of fully hydrogenated graphene sheets

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Mirnezhad, M.; Rouhi, H.

    2015-01-01

    Graphane is a two-dimensional structure consisting of a flat monolayer graphene sheet fully covered with hydrogen atoms attached to its carbon atoms in an alternating pattern. The unique properties of graphane make it suitable for different applications. In this paper, the mechanical properties of the most stable conformer of graphane, the so-called chair-like, are extensively investigated using density functional theory (DFT) scheme within the framework of the generalized gradient approximation (GGA) and the well-known Perdew-Burke-Ernzerhof (PBE) exchange correlation. It is shown that the hydrogenation has significant influences on the mechanical properties of graphene sheet. In particular, it is found that the elastic, bulk and shear moduli and Poisson's ratio of the chair-graphane are significantly smaller than those of graphene.

  9. Extracting dielectric spectroscopic properties from microwave-induced thermoacoustic signals.

    PubMed

    Shiyu Liu; Hao Nan; Dolatsha, Nemat; Arbabian, Amin

    2016-08-01

    Available data on the dielectric properties of biological tissue across a frequency range adds an extra degree of freedom of contrast besides the baseline structural information obtained by conventional imaging techniques. In this paper, we propose a new methodology to non-invasively extract the normalized effective conductivity of samples over a large frequency range using microwave-induced thermoacoustic (TA) signals. Additionally, a calibration approach has been adopted to remove the frequency dependency of the experimental setup errors as well as the RF power variation. The linear relationship between the TA signal amplitude on the absorbed microwave power is used to extract the properties of samples. Saline phantoms with various concentration are used to mimic different tissue materials in the proof-of-concept experiment. The extracted normalized effective conductivity by the proposed method matches the theoretical calculations as well as the direct contact measurements by a dielectric probe.

  10. Mechanical Properties of Doubly Stabilized Microtubule Filaments

    PubMed Central

    Hawkins, Taviare L.; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L.

    2013-01-01

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5′ [(α, β)-methyleno] triphosphate, guanosine-5′-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules. PMID:23561528

  11. Improvement of mechanical properties of glass substrates

    NASA Astrophysics Data System (ADS)

    Karbay, Ismail Hakki Cengizhan; Budakoglu, Refika; Zayim, Esra Ozkan

    2015-12-01

    This paper aims to enhance the mechanical and optical properties of glass substrates with thin films by the sol-gel method. TiO2-SiO2 binary system and Ta2O5 were deposited on glass substrates with high transparency. Ring-on-ring flexure and scratch tests were the main mechanical characterization tests. Herein, we report that the thin films can be used to enhance the mechanical properties of the glass substrates efficiently and effectively. TiO2-SiO2 binary system shows more than two times and Ta2O5 thin films show nearly three times better ultimate strength in the ring-on-ring flexure test. Besides, Ta2O5 thin film samples show superior scratch resistance. Additionally, the finite element method was also used to check the conformity in the application of mechanical properties of composite materials. It is also worth noting that, the finite element method can be used to accurately analyze the mechanical stability of composite materials. The use of the finite element method can reduce the total number of experimental trials without losing reliability.

  12. Isotropic microscale mechanical properties of coral skeletons

    PubMed Central

    Pasquini, Luca; Molinari, Alan; Fantazzini, Paola; Dauphen, Yannicke; Cuif, Jean-Pierre; Levy, Oren; Dubinsky, Zvy; Caroselli, Erik; Prada, Fiorella; Goffredo, Stefano; Di Giosia, Matteo; Reggi, Michela; Falini, Giuseppe

    2015-01-01

    Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata, were investigated by nanoindentation. The hardness HIT and Young's modulus EIT were determined from the analysis of several load–depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, EIT in the 76–77 GPa range, and HIT in the 4.9–5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in HIT is observed between the species. Different from corals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections. PMID:25977958

  13. Mechanical properties of doubly stabilized microtubule filaments.

    PubMed

    Hawkins, Taviare L; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L

    2013-04-02

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5' [(α, β)-methyleno] triphosphate, guanosine-5'-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules.

  14. Mechanical Properties of Polymer Nano-composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  15. Food mechanical properties and dietary ecology.

    PubMed

    Berthaume, Michael A

    2016-01-01

    Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by "toughness," or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement-limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non-linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement-limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet.

  16. Correlation of Cell and Substrate Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Setton, Tedhar; Levine, Joshua; Levine, Joseph; Guan, E.; Collazo, Lourdes; Ge, Shouren; Entcheva, Emilia; Rafailovich, Miriam

    2003-03-01

    The mechanical properties of neonatal rat ventricular fibroblasts plated onto elastomer surfaces were studied in vitro and correlated to the mechanical response of the substrate. In order to differentiate the response of the cells to mechanical as opposed to mechanical modifications in their environment, only the rheological properties of the substrates were modified. In the case of entangled polymers this can be accomplished either by varying the molecular weight or the thickness of polymer films spun cast onto rigid supports. Scanning lateral force microscopy, which has been shown to be an effective technique for measuring relative modulii of surfaces(1) was used to track the mechanical response of the substrates as a function of processing procedures, molecular weight, both in liquid, air, and following fibronectin incubation. The response of the living cells was then compared to that of the underlying substrate. The samples were then stained and the distribution of actin correlated to the mechanical response. 1. S. Ge et al. Phys. Rev. Lett. 11, (2000)2340

  17. Antibacterial mechanism and activities of black pepper chloroform extract.

    PubMed

    Zou, Lan; Hu, Yue-Ying; Chen, Wen-Xue

    2015-12-01

    Black pepper extracts reportedly inhibit food spoilage and food pathogenic bacteria. This study explored the antimicrobial activity of black pepper chloroform extract (BPCE) against Escherichia coli and Staphylococcus aureus. The antibacterial mechanism of BPCE was elucidated by analyzing the cell morphology, respiratory metabolism, pyruvic acid content, and ATP levels of the target bacteria. Scanning electron micrographs showed that the bacterial cells were destroyed and that plasmolysis was induced. BPCE inhibited the tricarboxylic acid pathway of the bacteria. The extract significantly increased pyruvic acid concentration in bacterial solutions and reduced ATP level in bacterial cells. BPCE destroyed the permeability of the cell membrane, which consequently caused metabolic dysfunction, inhibited energy synthesis, and triggered cell death.

  18. Microstructure and Mechanical Properties of Porous Mullite

    NASA Astrophysics Data System (ADS)

    Hsiung, Chwan-Hai Harold

    Mullite (3 Al2O3 : 2 SiO2) is a technologically important ceramic due to its thermal stability, corrosion resistance, and mechanical robustness. One variant, porous acicular mullite (ACM), has a unique needle-like microstructure and is the material platform for The Dow Chemical Company's diesel particulate filter AERIFY(TM). The investigation described herein focuses on the microstructure-mechanical property relationships in acicular mullites as well as those with traditional porous microstructures with the goal of illuminating the critical factors in determining their modulus, strength, and toughness. Mullites with traditional pore morphologies were made to serve as references via slipcasting of a kaolinite-alumina-starch slurry. The starch was burned out to leave behind a pore network, and the calcined body was then reaction-sintered at 1600C to form mullite. The samples had porosities of approximately 60%. Pore size and shape were altered by using different starch templates, and pore size was found to influence the stiffness and toughness. The ACM microstructure was varied along three parameters: total porosity, pore size, and needle size. Total porosity was found to dominate the mechanical behavior of ACM, while increases in needle and pore size increased the toughness at lower porosities. ACM was found to have much improved (˜130%) mechanical properties relative to its non-acicular counterpart at the same porosity. A second set of investigations studied the role of the intergranular glassy phase which wets the needle intersections of ACM. Removal of the glassy phase via an HF etch reduced the mechanical properties by ˜30%, highlighting the intergranular phase's importance to the enhanced mechanical properties of ACM. The composition of the glassy phase was altered by doping the ACM precursor with magnesium and neodymium. Magnesium doping resulted in ACM with greatly reduced fracture strength and toughness. Studies showed that the mechanical properties of the

  19. Mechanical Properties of Fe-Ni Meteorites

    NASA Astrophysics Data System (ADS)

    Roberta, Mulford; El Dasher, B.

    2010-10-01

    Iron-nickel meteorites exhibit a unique lamellar microstructure, Widmanstatten patterns, consisting of small regions with steep-iron-nickel composition gradients.1,2 The microstructure arises as a result of extremely slow cooling in a planetary core or other large mass. Mechanical properties of these structures have been investigated using microindentation, x-ray fluorescence, and EBSD. Observation of local mechanical properties in these highly structured materials supplements bulk measurements, which can exhibit large variation in dynamic properties, even within a single sample. 3 Accurate mechanical properties for meteorites may enable better modeling of planetary cores, the likely origin of these objects. Appropriate values for strength are important in impact and crater modeling and in understanding the consequences of observed impacts on planetary crusts. Previous studies of the mechanical properties of a typical iron-nickel meteorite, a Diablo Canyon specimen, indicated that the strength of the composite was higher by almost an order of magnitude than values obtained from laboratory-prepared specimens.4 This was ascribed to the extreme work-hardening evident in the EBSD measurements. This particular specimen exhibited only residual Widmanstatten structures, and may have been heated and deformed during its traverse of the atmosphere. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and examples from the Muonionalusta meteorite and Gibeon fall ( both IVA, fine octahedrite), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon re-entry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure. 1. A. Christiansen, et.al., Physica Scripta, 29 94-96 (1984.) 2. Goldstein and Ogilvie, Geochim Cosmochim Acta, 29 893-925 (1965.) 3. M. D. Furnish, M.B. Boslough, G.T. Gray II, and J.L. Remo, Int. J. Impact Eng

  20. Elastic proteins: biological roles and mechanical properties.

    PubMed Central

    Gosline, John; Lillie, Margo; Carrington, Emily; Guerette, Paul; Ortlepp, Christine; Savage, Ken

    2002-01-01

    The term 'elastic protein' applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is 'stretchy', or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber-like proteins (e.g. resilin and elastin) that function in the storage of elastic-strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology. PMID:11911769

  1. Bioactive properties of wood knot extracts on cultured human cells.

    PubMed

    Phelan, Martha; Aherne, S Aisling; Wong, Alfred; O'Brien, Nora M

    2009-12-01

    Not all felled wood is converted to timber or pulp, with the remaining material being a rich source of relatively unexplored and unexploited potentially novel bioactive compounds. Therefore the potential bioactive effects of two softwood knot (the part of the branch encased in the tree stem) extracts--namely, Pinus banksiana Lamb. (Jack pine) and Picea sitchensis (Bong.) Carr. (Sitka spruce)--were investigated by (1) determining their effects on the viability and antioxidant status of human Jurkat T cells, (2) investigating potential cytoprotective and genoprotective effects against oxidative stress in cultured cells, and (3) assessing their effects on concanavalin A (ConA)-induced interleukin-2 (IL-2) production. Initially, both Jack pine knot and Sitka spruce knot extracts were shown to possess strong antioxidant activity as determined by the ferric reducing antioxidant power assay. When added to Jurkat cells, Jack pine knot extract was more toxic compared with Sitka spruce knot extract, with concentrations that resulted in 50% cell death of 153.0 microg/mL and 376.1 microg/mL, respectively. Supplementation of Jurkat cells with wood knot extracts did not affect their glutathione content or catalase activity. Pretreatment of Jurkat cells with Sitka spruce or Jack pine knot extracts protected against H(2)O(2)-induced cell injury. However, none of the extracts protected against H(2)O(2)-induced DNA damage. Jack pine knots, at a concentration of 30 microg/mL, significantly suppressed ConA-induced IL-2 production. Although total phenol content did not differ between the two extracts, gas chromatography analysis did show variation in the types of constituents present. Further research is warranted to elucidate the selective bioactive properties of these softwood knot extracts.

  2. Chemical composition and cytotoxic properties of Clinacanthus nutans root extracts.

    PubMed

    Teoh, Peik Lin; Cheng, Angelina Ying Fang; Liau, Monica; Lem, Fui Fui; Kaling, Grace P; Chua, Fern Nie; Cheong, Bo Eng

    2017-12-01

    Clinacanthus nutans Lindau (Acanthaceae) is a medicinal plant that has been reported to have anti-inflammatory, antiviral, antimicrobial and antivenom activities. In Malaysia, it has been widely claimed to be effective in various cancer treatments but scientific evidence is lacking. This study investigates the chemical constituents, anti-proliferative, and apoptotic properties of C. nutans root extracts. The roots were subjected to solvent extraction using methanol and ethyl acetate. The anti-proliferative effects of root extracts were tested at the concentrations of 10 to 50 μg/mL on MCF-7 and HeLa by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay for 72 h. Morphological changes were observed under light microscope. Pro-apoptotic effects of root extracts were examined using flow cytometric analysis and RT-PCR. The chemical compositions of root extracts were detected using GC-MS. The proliferation of MCF-7 cells was inhibited with the IC50 values of 35 and 30 μg/mL, respectively, for methanol and ethyl acetate root extracts. The average inhibition of HeLa cells was ∼25%. Induction of apoptosis in MCF-7 was supported by chromatin condensation, down-regulation of BCL2 and unaltered expression of BAX. However, only ethyl acetate extract caused the loss of mitochondrial membrane potential. GC-MS analysis revealed the roots extracts were rich with terpenoids and phytosterols. The results demonstrated that root extracts promote apoptosis by suppressing BCL2 via mitochondria-dependent or independent manner. The identified compounds might work solely or cooperatively in regulating apoptosis. However, further studies are required to address this.

  3. Mechanical properties of crosslinked polymer coatings

    NASA Technical Reports Server (NTRS)

    Csernica, Jeffrey

    1994-01-01

    The objectives of this experiment are to: fabricate and test thin films to explore relations between a polymer's structure and its mechanical properties; expose students to testing methods for hardness and impact energy that are simple to perform and which have results that are easy to comprehend; show importance of polymer properties in materials that students frequently encounter; illustrate a system which displays a tradeoff between strength and impact resistance, the combination of which would need to be optimized for a particular application; and to expose students to coatings technology and testing.

  4. Mechanism and analyses for extracting photosynthetic electrons using exogenous quinones - what makes a good extraction pathway?

    PubMed

    Longatte, G; Rappaport, F; Wollman, F-A; Guille-Collignon, M; Lemaître, F

    2016-08-04

    Plants or algae take many benefits from oxygenic photosynthesis by converting solar energy into chemical energy through the synthesis of carbohydrates from carbon dioxide and water. However, the overall yield of this process is rather low (about 4% of the total energy available from sunlight is converted into chemical energy). This is the principal reason why recently many studies have been devoted to extraction of photosynthetic electrons in order to produce a sustainable electric current. Practically, the electron transfer occurs between the photosynthetic organism and an electrode and can be assisted by an exogenous mediator, mainly a quinone. In this regard, we recently reported on a method involving fluorescence measurements to estimate the ability of different quinones to extract photosynthetic electrons from a mutant of Chlamydomonas reinhardtii. In the present work, we used the same kind of methodology to establish a zone diagram for predicting the most suitable experimental conditions to extract photoelectrons from intact algae (quinone concentration and light intensity) as a function of the purpose of the study. This will provide further insights into the extraction mechanism of photosynthetic electrons using exogenous quinones. Indeed fluorescence measurements allowed us to model the capacity of photosynthetic algae to donate electrons to an exogenous quinone by considering a numerical parameter called "open center ratio" which is related to the Photosystem II acceptor redox state. Then, using it as a proxy for investigating the extraction of photosynthetic electrons by means of an exogenous quinone, 2,6-DCBQ, we suggested an extraction mechanism that was globally found consistent with the experimentally extracted parameters.

  5. Immunomodulatory properties of Olea europaea leaf extract in intestinal inflammation.

    PubMed

    Vezza, Teresa; Algieri, Francesca; Rodríguez-Nogales, Alba; Garrido-Mesa, José; Utrilla, M Pilar; Talhaoui, Nassima; Gómez-Caravaca, Ana María; Segura-Carretero, Antonio; Rodríguez-Cabezas, M Elena; Monteleone, Giovanni; Gálvez, Julio

    2017-10-01

    Extracts from olive (Olea europaea) leaves are used in Mediterranean traditional medicine as anti-inflammatory agents. They contain antioxidant phenolic compounds, such as oleuropeoside, which could be interesting for the treatment of inflammatory conditions associated with oxidative stress in humans, including inflammatory bowel disease. The anti-inflammatory effects of olive leaf extract (0.5-25 mg/kg) were studied in two mice models of colitis (DSS and DNBS). Olive leaf extract (0.1-100 μg/mL) immunomodulatory effects were also investigated in different cell types and in ex vivo organ cultures of mucosal explants of healthy donors and Crohn's disease (CD) patients. The extract showed effect in both colitis models reducing the expression of proinflammatory mediators (IL-1β, TNF-α, and iNOS), and improving the intestinal epithelial barrier integrity restoring the expression of ZO-1, MUC-2, and TFF-3. These effects were confirmed in vitro. Furthermore, it reduced the production of proinflammatory mediators (IL-1β, IL-6, IL-8, and TNF-α) in intestinal mucosal samples from CD patients. Olive leaf extract presented intestinal anti-inflammatory activity in colitis mouse models, maybe be related to its immunomodulatory properties and the capacity to restore the intestinal epithelial barrier. Besides, the extract could also regulate the activity of cells involved in the inflammatory response. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Investigation of antioxidant properties of Nasturtium officinale (watercress) leaf extracts.

    PubMed

    Ozen, Tevfik

    2009-01-01

    The objective of this study was to examine the in vitro and in vivo antioxidative properties of aqueous and ethanolic extracts of the leaf of Nasturtium officinale R. Br. (watercress). Extracts were evaluated for total antioxidant activity by ferric thiocyanate method, total reducing power by potassium ferricyanide reduction method, 1,1-diphenyl-2-picrylhydrazyl (DPPH*) radical scavenging activities, superoxide anion radical scavenging activities in vitro and lipid peroxidation in vivo. Those various antioxidant activities were compared to standards such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and alpha-tocopherol. The ethanolic extract was found as the most active in total antioxidant activity, reducing power, DPPH* radicals and superoxide anion radicals scavenging activities. Administration of the ethanol extract to rats decreased lipid peroxidation in liver, brain and kidney. These results lead to the conclusion that N. officinale extracts show relevant antioxidant activity by means of reducing cellular lipid peroxidation and increasing antioxidant activity, reducing power, free radiacal and superoxide anion radical scavenging activities. In addition, total phenolic compounds in the aqueous and ethanolic extract of N. officinale were determined as pyrocatechol.

  7. Assessment of Cholinergic Properties of Ashwagandha Leaf-Extract in the Amnesic Mouse Brain

    PubMed Central

    Gautam, Akash; Wadhwa, Renu; Thakur, Mahendra K.

    2016-01-01

    Background In our earlier study, we have shown the memory enhancing and scopolamine-induced amnesia recovery properties of Ashwagandha leaf extract using behavioral paradigm and expression analysis of synaptic plasticity genes. Purpose However, the exact mechanism through which Ashwagandha demonstrates these effects is still unknown. Methods In the present study, we hypothesized that the alcoholic extract of Ashwagandha leaves (i-Extract) possesses cholinergic properties, which in turn inhibit the anti-cholinergic nature of scopolamine. Therefore, the potential of i-Extract to recover from the scopolamine-induced cholinergic deficits was assessed by measuring acetylcholine (neurotransmitter) and Arc (synaptic activity-related gene) expression level in the mouse brain. Results The enzymatic activity of acetyl cholinesterase and choline acetyltransferase was assessed through colorimetric assays, and expression level of Arc protein was examined by Western blotting. Furthermore, mRNA level of these genes was examined by semi-quantitative reverse-transcriptase PCR. We observed that the treatment of i-Extract in scopolamine-induced amnesic mouse attenuates scopolamine-induced detrimental alterations in the cholinergic system. Conclusion Thus, our study provided biochemical and molecular evidence of cholinergic properties of Ashwagandha leaf extract during brain disorders associated with cholinergic dysfunction. PMID:27647956

  8. Assessment of Cholinergic Properties of Ashwagandha Leaf-Extract in the Amnesic Mouse Brain.

    PubMed

    Gautam, Akash; Wadhwa, Renu; Thakur, Mahendra K

    2016-07-01

    In our earlier study, we have shown the memory enhancing and scopolamine-induced amnesia recovery properties of Ashwagandha leaf extract using behavioral paradigm and expression analysis of synaptic plasticity genes. However, the exact mechanism through which Ashwagandha demonstrates these effects is still unknown. In the present study, we hypothesized that the alcoholic extract of Ashwagandha leaves (i-Extract) possesses cholinergic properties, which in turn inhibit the anti-cholinergic nature of scopolamine. Therefore, the potential of i-Extract to recover from the scopolamine-induced cholinergic deficits was assessed by measuring acetylcholine (neurotransmitter) and Arc (synaptic activity-related gene) expression level in the mouse brain. The enzymatic activity of acetyl cholinesterase and choline acetyltransferase was assessed through colorimetric assays, and expression level of Arc protein was examined by Western blotting. Furthermore, mRNA level of these genes was examined by semi-quantitative reverse-transcriptase PCR. We observed that the treatment of i-Extract in scopolamine-induced amnesic mouse attenuates scopolamine-induced detrimental alterations in the cholinergic system. Thus, our study provided biochemical and molecular evidence of cholinergic properties of Ashwagandha leaf extract during brain disorders associated with cholinergic dysfunction.

  9. Mechanical properties of functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Q.; Liu, B.; Chen, Y. L.; Jiang, H.; Hwang, K. C.; Huang, Y.

    2008-10-01

    Carbon nanotubes (CNTs) used to reinforce polymer matrix composites are functionalized to form covalent bonds with the polymer in order to enhance the CNT/polymer interfaces. These bonds destroy the perfect atomic structures of a CNT and degrade its mechanical properties. We use atomistic simulations to study the effect of hydrogenization on the mechanical properties of single-wall carbon nanotubes. The elastic modulus of CNTs gradually decreases with the increasing functionalization (percentage of C-H bonds). However, both the strength and ductility drop sharply at a small percentage of functionalization, reflecting their sensitivity to C-H bonds. The cluster C-H bonds forming two rings leads to a significant reduction in the strength and ductility. The effect of carbonization has essentially the same effect as hydrogenization.

  10. Rhenium Mechanical Properties and Joining Technology

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.; Biaglow, James A.

    1996-01-01

    Iridium-coated rhenium (Ir/Re) provides thermal margin for high performance and long life radiation cooled rockets. Two issues that have arisen in the development of flight Ir/Re engines are the sparsity of rhenium (Re) mechanical property data (particularly at high temperatures) required for engineering design, and the inability to directly electron beam weld Re chambers to C103 nozzle skirts. To address these issues, a Re mechanical property database is being established and techniques for creating Re/C103 transition joints are being investigated. This paper discusses the tensile testing results of powder metallurgy Re samples at temperatures from 1370 to 2090 C. Also discussed is the evaluation of Re/C103 transition pieces joined by both, explosive and diffusion bonding. Finally, the evaluation of full size Re transition pieces, joined by inertia welding, as well as explosive and diffusion bonding, is detailed.

  11. Advanced mechanical properties of graphene paper

    NASA Astrophysics Data System (ADS)

    Ranjbartoreh, Ali R.; Wang, Bei; Shen, Xiaoping; Wang, Guoxiu

    2011-01-01

    Graphene paper (GP) has been prepared by flow-directed assembly of graphene nanosheets. The mechanical properties of as-prepared GPs were investigated by tensile, indentation, and bending tests. Heat treated GPs demonstrate superior hardness, ten times that of synthetic graphite, and two times that of carbon steel; besides, their yielding strength is significantly higher than that of carbon steel. GPs show extremely high modulus of elasticity during bending test; in the range of a few terapascal. The high strength and stiffness of GP is ascribed to the interlocking-tile microstructure of individual graphene nanosheets in the paper. These outstanding mechanical properties of GPs could lead to a wide range of engineering applications.

  12. Mechanical properties of intra-ocular lenses

    NASA Astrophysics Data System (ADS)

    Ehrmann, Klaus; Kim, Eon; Parel, Jean-Marie

    2008-02-01

    Cataract surgery usually involves the replacement of the natural crystalline lens with a rigid or foldable intraocular lens to restore clear vision for the patient. While great efforts have been placed on optimising the shape and optical characteristics of IOLs, little is know about the mechanical properties of these devices and how they interact with the capsular bag once implanted. Mechanical properties measurements were performed on 8 of the most commonly implanted IOLs using a custom build micro tensometer. Measurement data will be presented for the stiffness of the haptic elements, the buckling resistance of foldable IOLs, the dynamic behaviour of the different lens materials and the axial compressibility. The biggest difference between the lens types was found between one-piece and 3-piece lenses with respect to the flexibility of the haptic elements

  13. Investigation of Mechanical Properties and Interfacial Mechanics of Crystalline Nanomaterials

    NASA Astrophysics Data System (ADS)

    Qin, Qingquan

    Nanowires (NWs) and nanotubes (NTs) are critical building blocks of nanotechnologies. The operation and reliability of these nanomaterials based devices depend on their mechanical properties of the nanomaterials, which is therefore important to accurately measure the mechanical properties. Besides, the NW--substrate interfaces also play a critical role in both mechanical reliability and electrical performance of these nanodevices, especially when the size of the NW is small. In this thesis, we focus on the mechanical properties and interface mechanics of three important one dimensional (1D) nanomaterials: ZnO NWs, Ag NWs and Si NWs. For the size effect study, this thesis presents a systematic experimental investigation on the elastic and failure properties of ZnO NWs under different loading modes: tension and buckling. Both tensile modulus (from tension) and bending modulus (from buckling) were found to increase as the NW diameter decreased from 80 to 20 nm. The elastic modulus also shows loading mode dependent; the bending modulus increases more rapidly than the tensile modulus. The tension experiments showed that fracture strain and strength of ZnO NWs increase as the NW diameter decrease. A resonance testing setup was developed to measure elastic modulus of ZnO NWs to confirm the loading mode dependent effect. A systematic study was conducted on the effect of clamping on resonance frequency and thus measured Young's modulus of NWs via a combined experiment and simulation approach. A simple scaling law was provided as guidelines for future designs to accurate measure elastic modulus of a cantilevered NW using the resonance method. This thesis reports the first quantitative measurement of a full spectrum of mechanical properties of five-fold twinned Ag NWs including Young's modulus, yield strength and ultimate tensile strength. In situ tensile testing of Ag NWs with diameters between 34 and 130 nm was carried out inside a SEM. Young's modulus, yield strength and

  14. Mechanical Properties of Palm Fiber Mattress

    NASA Astrophysics Data System (ADS)

    Li, Yu-Qian; Wu, Jia-Yu; Gu, Hao-Wei; Chen, Zong-Yong; Shi, Xiao-Bing; Liao, Ting-Mao; An, Cheng; Yuan, Hong; Liu, Ren-Huai

    2016-05-01

    Palm fiber mattress is increasingly accepted by many families. This study aims at evaluating the mechanical properties of palm fiber mattress. Two experiments were conduct to investigate the Young's modulus of palm fiber mattress in three directions. In addition, finite element models were established to characterize palm fiber mattress under uniform distributed pressure. Finally, results from finite element analysis are presented to illustrate that the thick mattress will stick with human body curve perfectly, which can support vertebral column effectively.

  15. Mechanical property characterization of intraply hybrid composites

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sinclair, J. H.

    1979-01-01

    An investigation was conducted to characterize the mechanical properties of intraply hybrids made from graphite fiber/epoxy matrix (primary composites) hybridized with varying amounts of secondary composites made from S-glass or Kevlar 49 fibers. The tests were conducted using thin laminates having the same thickness. The specimens for these tests were instrumented with strain gages to determine stress-strain behavior. Significant results are included.

  16. Compositional Determinants of Mechanical Properties of Enamel

    PubMed Central

    Baldassarri, M.; Margolis, H.C.; Beniash, E.

    2008-01-01

    Dental enamel is comprised primarily of carbonated apatite, with less than 1% w/w organic matter and 4-5% w/w water. To determine the influence of each component on the microhardness and fracture toughness of rat incisor enamel, we mechanically tested specimens in which water and organic matrix were selectively removed. Tests were performed in mid-sagittal and transverse orientations to assess the effect of the structural organization on enamel micromechanical properties. While removal of organic matrix resulted in up to a 23% increase in microhardness, and as much as a 46% decrease in fracture toughness, water had a significantly lesser effect on these properties. Moreover, removal of organic matrix dramatically weakened the dentino-enamel junction (DEJ). Analysis of our data also showed that the structural organization of enamel affects its micromechanical properties. We anticipate that these findings will help guide the development of bio-inspired nanostructured materials for mineralized tissue repair and regeneration. PMID:18573984

  17. Mechanical Properties of Additively Manufactured Thick Honeycombs

    PubMed Central

    Hedayati, Reza; Sadighi, Mojtaba; Mohammadi Aghdam, Mohammad; Zadpoor, Amir Abbas

    2016-01-01

    Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions. PMID:28773735

  18. Determinants of the mechanical properties of bones

    NASA Technical Reports Server (NTRS)

    Martin, R. B.

    1991-01-01

    The mechanical properties of bones are governed by the same principles as those of man-made load-bearing structures, but the organism is able to adapt its bone structure to changes in skeletal loading. In this overview of the determinants of the strength and stiffness of bone, a continuum approach has been taken, in which the behavior of a macroscopic structure depends on its shape and size, and on the mechanical properties of the material within. The latter are assumed to depend on the composition (porosity and mineralization) and organization (trabecular or cortical bone architecture, collagen fiber orientation, fatigue damage) of the bone. The effects of each of these factors are reviewed. Also, the possible means of non-invasively estimating the strength or other mechanical properties of a bone are reviewed, including quantitative computed tomography, photon absorptiometry, and ultrasonic measurements. The best estimates of strength have been obtained with photon absorptiometry and computed tomography, which at best are capable of accounting for 90% of the strength variability in a simple in vitro test, but results from different laboratories have been highly variable.

  19. Measurement of material mechanical properties in microforming

    NASA Astrophysics Data System (ADS)

    Yun, Wang; Xu, Zhenying; Hui, Huang; Zhou, Jianzhong

    2006-02-01

    As the rapid market need of micro-electro-mechanical systems engineering gives it the wide development and application ranging from mobile phones to medical apparatus, the need of metal micro-parts is increasing gradually. Microforming technology challenges the plastic processing technology. The findings have shown that if the grain size of the specimen remains constant, the flow stress changes with the increasing miniaturization, and also the necking elongation and the uniform elongation etc. It is impossible to get the specimen material properties in conventional tensile test machine, especially in the high precision demand. Therefore, one new measurement method for getting the specimen material-mechanical property with high precision is initiated. With this method, coupled with the high speed of Charge Coupled Device (CCD) camera and high precision of Coordinate Measuring Machine (CMM), the elongation and tensile strain in the gauge length are obtained. The elongation, yield stress and other mechanical properties can be calculated from the relationship between the images and CCD camera movement. This measuring method can be extended into other experiments, such as the alignment of the tool and specimen, micro-drawing process.

  20. Database of Mechanical Properties of Textile Composites

    NASA Technical Reports Server (NTRS)

    Delbrey, Jerry

    1996-01-01

    This report describes the approach followed to develop a database for mechanical properties of textile composites. The data in this database is assembled from NASA Advanced Composites Technology (ACT) programs and from data in the public domain. This database meets the data documentation requirements of MIL-HDBK-17, Section 8.1.2, which describes in detail the type and amount of information needed to completely document composite material properties. The database focuses on mechanical properties of textile composite. Properties are available for a range of parameters such as direction, fiber architecture, materials, environmental condition, and failure mode. The composite materials in the database contain innovative textile architectures such as the braided, woven, and knitted materials evaluated under the NASA ACT programs. In summary, the database contains results for approximately 3500 coupon level tests, for ten different fiber/resin combinations, and seven different textile architectures. It also includes a limited amount of prepreg tape composites data from ACT programs where side-by-side comparisons were made.

  1. Evaluation of the Hypoglycemic Properties of Anacardium humile Aqueous Extract

    PubMed Central

    Urzêda, Márcio A.; Marcussi, Silvana; Silva Pereira, Luciana L.; França, Suzelei C.; Pereira, Ana Maria S.; Pereira, Paulo S.; da Silva, Saulo L.; Guimarães, César L. S.; Calderon, Leonardo A.; Stábeli, Rodrigo G.; Soares, Andreimar M.; Couto, Lucélio B.

    2013-01-01

    The antihyperglycemic effects of several plant extracts and herbal formulations which are used as antidiabetic formulations have been described and confirmed to date. The main objective of this work was to evaluate the hypoglycemic activity of the aqueous extract of Anacardium humile. Although the treatment of diabetic animals with A. humile did not alter body weight significantly, a reduction of the other evaluated parameters was observed. Animals treated with A. humile did not show variation of insulin levels, possibly triggered by a mechanism of blood glucose reduction. Levels of ALT (alanine aminotransferase) decreased in treated animals, suggesting a protective effect on liver. Levels of cholesterol were also reduced, indicating the efficacy of the extract in reestablishing the balance of nutrients. Moreover, a kidney protection may have been achieved due to the partial reestablishment of blood glucose homeostasis, while no nephrotoxicity could be detected for A. humile. The obtained results demonstrate the effectiveness of A. humile extracts in the treatment of alloxan-induced diabetic rats. Therefore, A. humile aqueous extract, popularly known and used by diabetic patients, induced an improvement in the biochemical parameters evaluated during and following treatment of diabetic rats. Thus, a better characterization of the medicinal potential of this plant will be able to provide a better understanding of its mechanisms of action in these pathological processes. PMID:23737820

  2. In vitro release properties of encapsulated blueberry (Vaccinium ashei) extracts.

    PubMed

    Flores, Floirendo P; Singh, Rakesh K; Kerr, William L; Phillips, Dennis R; Kong, Fanbin

    2015-02-01

    We aimed to determine the effect of encapsulation on the release properties of blueberry extracts during simulated gastrointestinal digestion. An ethanolic pomace extract was microencapsulated with whey protein isolate via spray drying. The in vitro release of monomeric anthocyanins, phenolics and ferric reducing antioxidant activity of the microcapsules (W) were evaluated for the microcapsules and two non-encapsulated systems: ethanolic pomace extract (P) and freeze-dried juice (F). Concentrations of anthocyanin and phenolics were normalised prior to digestion. Results showed that antioxidant activity was in the order of: F>W>P. Regardless of encapsulation, more phenolics were released from W and P than F. Anthocyanin concentration decreased after intestinal digestion for W, but remained constant for P and F. MALDI-MS showed similar spectra for P and F but not for W. The spray-dried product has comparable release characteristics to freeze-dried juice, and may be investigated for food applications.

  3. [Immunostimulatory properties of mistletoe extracts and their application in oncology].

    PubMed

    Wrotek, Sylwia; Skawiński, Robert; Kozak, Wiesław

    2014-10-23

    For a long time cancer immunotherapy was overshadowed by chemotherapy and radiotherapy. Recently, "Science", one of the world's top scientific journals, named the stimulation of the body's own immune system to fight cancer cells as the "breakthrough of the year". In Germany, Switzerland and Austria, extracts derived from mistletoe (Viscum album L.) such as Iscador, Abnobaviscum, Helixor, Iscar, Iscucin and Isorel have been used in oncology for many years. These extracts have immunomodulating and immunostimulating properties, as demonstrated by experimental studies as well as in clinical trials. The aim of our paper is to present immunological disorders associated with cancer, which can be counteracted by treatment with extracts derived from mistletoe. Although these drugs cannot replace conventional cancer treatment, they may improve the patient's quality and length of life.

  4. [Properties of commercial licorice extracts used as a food additive].

    PubMed

    Iida, Kenji; Uematsu, Yoko; Suzuki, Kumi; Yasuno, Tetsuko; Hirata, Keiko; Ito, Kouichi

    2007-08-01

    Properties of eight commercial licorice extracts used as a food additive (sweetener, listed in the List of Existing Food Additives in the Japanese Food Sanitation Law) were surveyed. Residue on ignition ranged from 0.3 to 12.4%, and pH ranged from 4.1 to 6.8, amount of glycyrrhizin, which is the major component in licorice extract, ranged from 10.9 to 77.4%, sodium ranged from 0.1 to 1.2%, potassium ranged from 0.3 to 5.0%, and ammonium nitrogen ranged from 0.03 to 2.5%. These results indicated that various products were distributed on the market. Differences in the manufacturing process may contribute to the variations of product properties.

  5. Antioxidative and Cardioprotective Properties of Anthocyanins from Defatted Dabai Extracts

    PubMed Central

    Khoo, Hock Eng; Azlan, Azrina; Nurulhuda, M. Halid; Ismail, Amin; Abas, Faridah; Hamid, Muhajir; Roowi, Suri

    2013-01-01

    This study aimed to determine anthocyanins and their antioxidative and cardioprotective properties in defatted dabai parts. Anthocyanins in crude extracts and extract fractions of defatted dabai peel and pericarp were quantified using UHPLC, while their antioxidant capacity and oxidative stress inhibition ability were evaluated by using DPPH and CUPRAC assays as well as linoleic acid oxidation system, hemoglobin oxidation, and PARP-1 inhibition ELISA. Cardioprotective effect of the defatted dabai peel extract was evaluated using hypercholesterolemic-induced New Zealand white rabbits. Six anthocyanins were detected in the defatted dabai peel, with the highest antioxidant capacities and oxidative stress inhibition effect compared to the other part. The defatted dabai peel extract has also inhibited lipid peroxidation (plasma MDA) and elevated cellular antioxidant enzymes (SOD and GPx) in the tested animal model. Major anthocyanin (cyanidin-3-glucoside) and other anthocyanins (pelargonidin-3-glucoside, malvidin-3-glucoside, cyanidin-3-galactoside, cyanidin-3-arabinoside, and peonidin-3-glucoside) detected in the defatted dabai peel are potential future nutraceuticals with promising medicinal properties. PMID:24368926

  6. Machining as a mechanical property test revisited

    NASA Astrophysics Data System (ADS)

    Smith, David L.

    There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, strain rate and temperature, an opportunity exists for using plane-strain cutting as a mechanical property test for measuring flow properties of metals. The feasibility of using plane-strain cutting to measure flow properties of metals is revisited in the light of recent data showing controllability of the deformation conditions in chip formation by systematic variation of process input parameters. A method is outlined as to how the deformation conditions can be varied by changing the process parameters. The method is applied to cutting of commercially pure copper (FCC), iron (BCC) and zinc (HCP). Forces and chip geometries are measured, in conjunction with particle image velocimetry characterization of the deformation using high speed image sequences. The flow stresses are estimated from these measurements. The measured flow stress and its dependence on strain are shown to agree well with prior measurements of these parameters using conventional tests, and flow stress inferred from hardness characterization. The method is also demonstrated to be able to measure properties of metals that recrystallize at room temperature (zinc), wherein quasi-static tests predict much lower strength. Sources of variability and uncertainty in the application of this measurement technique are discussed. Future work in the context of further

  7. Antioxidant Properties of Artemisia annua Extracts in Model Food Emulsions

    PubMed Central

    Skowyra, Monika; Gallego, Maria Gabriela; Segovia, Francisco; Almajano, Maria Pilar

    2014-01-01

    Artemisia annua is currently the only commercial source of the sesquiterpene lactone artemisinin. Although artemisinin is a major bioactive component present in this Chinese herb, leaf flavonoids have shown a variety of biological activities. The polyphenolic profile of extract from leaves of A. annua was assessed as a source of natural antioxidants. Total phenolic content and total flavonoid content were established and three assays were used to measure the antioxidant capacity of the plant extract. The measurement of scavenging capacity against the 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) were 314.99 µM Trolox equivalents (TE)/g DW, 736.26 µM TE/g DW and 212.18 µM TE/g DW, respectively. A. annua extracts also showed good antioxidant properties in 10% sunflower oil-in-water emulsions during prolonged storage (45 days) at 32 °C. Artemisia extract at 2 g/L was as effective as butylated hydroxyanisole (BHA) at 0.02 g/L in slowing down the formation of hydroperoxides as measured by peroxide value and thiobarbituric acid reactive substances. The results of this study indicate that extract of A. annua may be suitable for use in the food matrix as substitutes for synthetic antioxidants. PMID:26784667

  8. Antioxidant Properties of Artemisia annua Extracts in Model Food Emulsions.

    PubMed

    Skowyra, Monika; Gallego, Maria Gabriela; Segovia, Francisco; Almajano, Maria Pilar

    2014-03-03

    Artemisia annua is currently the only commercial source of the sesquiterpene lactone artemisinin. Although artemisinin is a major bioactive component present in this Chinese herb, leaf flavonoids have shown a variety of biological activities. The polyphenolic profile of extract from leaves of A. annua was assessed as a source of natural antioxidants. Total phenolic content and total flavonoid content were established and three assays were used to measure the antioxidant capacity of the plant extract. The measurement of scavenging capacity against the 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical cation, the oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP) were 314.99 µM Trolox equivalents (TE)/g DW, 736.26 µM TE/g DW and 212.18 µM TE/g DW, respectively. A. annua extracts also showed good antioxidant properties in 10% sunflower oil-in-water emulsions during prolonged storage (45 days) at 32 °C. Artemisia extract at 2 g/L was as effective as butylated hydroxyanisole (BHA) at 0.02 g/L in slowing down the formation of hydroperoxides as measured by peroxide value and thiobarbituric acid reactive substances. The results of this study indicate that extract of A. annua may be suitable for use in the food matrix as substitutes for synthetic antioxidants.

  9. Antioxidant properties of xanthones extracted from the pericarp of Garcinia mangostana (Mangosteen): A theoretical study

    NASA Astrophysics Data System (ADS)

    Thong, Nguyen Minh; Quang, Duong Tuan; Bui, Ngoc Hoa Thi; Dao, Duy Quang; Nam, Pham Cam

    2015-04-01

    A theoretical study on antioxidant properties of fourteen xanthones extracted from the pericarp of G. Mangostana has been performed. Three main reaction mechanisms are investigated: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SETPT) and sequential proton loss electron transfer (SPLET). The Osbnd H bond dissociation enthalpy (BDE), ionization energy (IE), proton affinity (PA) and electron transfer energy (ETE) parameters were computed in gas phase and water. The results show that HAT would be the most favorable mechanism for explaining antioxidant activity of xanthones in gas phase, whereas the SPLET mechanism is thermodynamically favored in water.

  10. Mechanical Properties Characterization at the Nanoscale

    NASA Astrophysics Data System (ADS)

    Fong, Hanson; Sopp, Jeffery; Sarikaya, Mehmet

    2001-05-01

    Nanoindentation is an unique technique that characterizes mechanical properties of materials down to the nanometer scale. With a force range from nanoNewtons to milliNewtons, unique properties of surface structures and thin films in the mesoscale can be routinely quantifieds. With technology continually pushing toward smaller feature size in electronic and mechanical devices as well as biomaterials applications, nanoindentation has become an invaluable method to measure these characteristic features. Here, we report its application in the study the biological hard tissues. For example, using engineered metallic indentation tips, the elastic properties of the 20 nm protein layer in the biocomposite of the abalone shell was measured. The elastic modulus was found to be exceptionally high compared to most synthetic polymers. With the combination of AFM imaging nanoindentation, we were able to measure the difference in deformation behavior at the mesoscale between normal and genetically altered mouse enamel. These measurements were complementary in determining the growth defects resulting from genetically modified enamel proteins. Details of these results and future prospects will be discussed.

  11. Multi-axial mechanical properties of human trabecular bone.

    PubMed

    Rincón-Kohli, Liliana; Zysset, Philippe K

    2009-06-01

    In the context of osteoporosis, evaluation of bone fracture risk and improved design of epiphyseal bone implants rely on accurate knowledge of the mechanical properties of trabecular bone. A multi-axial loading chamber was designed, built and applied to explore the compressive multi-axial yield and strength properties of human trabecular bone from different anatomical locations. A thorough experimental protocol was elaborated for extraction of cylindrical bone samples, assessment of their morphology by micro-computed tomography and application of different mechanical tests: torsion, uni-axial traction, uni-axial compression and multi-axial compression. A total of 128 bone samples were processed through the protocol and subjected to one of the mechanical tests up to yield and failure. The elastic data were analyzed using a tensorial fabric-elasticity relationship, while the yield and strength data were analyzed with fabric-based, conewise generalized Hill criteria. For each loading mode and more importantly for the combined results, strong relationships were demonstrated between volume fraction, fabric and the elastic, yield and strength properties of human trabecular bone. Despite the reviewed limitations, the obtained results will help improve the simulation of the damage behavior of human bones and bone-implant systems using the finite element method.

  12. Antiophidian properties of the aqueous extract of Mikania glomerata.

    PubMed

    Maiorano, Victor A; Marcussi, Silvana; Daher, Maristela A F; Oliveira, Clayton Z; Couto, Lucélio B; Gomes, Odair A; França, Suzelei C; Soares, Andreimar M; Pereira, Paulo S

    2005-12-01

    Aqueous extracts, prepared from dried or fresh roots, stems or leaves of Mikania glomerata, a plant found in Mata Atlântica in Southeastern Brazil, were able to efficiently neutralize different toxic, pharmacological, and enzymatic effects induced by venoms from Bothrops and Crotalus snakes. Phospholipase A(2) activity and the edema induced by Crotalus durissus terrificus venom were inhibited around 100 and approximately 40%, respectively, although this inhibition was only partial for Bothrops venoms. The hemorrhagic activity of Bothrops venoms (Bothrops altenatus, Bothrops moojeni, Bothrops neuwiedi, and Bothrops jararacussu) was significantly inhibited by this vegetal species, while the clotting activity of Crotalus durissus terrificus, Bothrops jararacussu, and Bothrops neuwiedi venoms was totally inhibited. Although, the mechanism of action of Mikania glomerata extract is still unknown, the finding that no visible change was detected in the electrophoretic pattern of snake venom after incubation with the extract excludes proteolytic degradation as a potential mechanism. Since the extract of Mikania glomerata significantly inhibited the studied snake venoms, it may be used as an alternative treatment to serumtherapy and, in addition, as a rich source of potential inhibitors of PLA(2)s, metalloproteases and serineproteases, enzymes involved in several physiopathological human and animal diseases.

  13. Mechanical Properties of Nylon Harp Strings

    PubMed Central

    Lynch-Aird, Nicolas; Woodhouse, Jim

    2017-01-01

    Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young’s modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young’s modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings. PMID:28772858

  14. Mechanical Properties of Nylon Harp Strings.

    PubMed

    Lynch-Aird, Nicolas; Woodhouse, Jim

    2017-05-04

    Monofilament nylon strings with a range of diameters, commercially marketed as harp strings, have been tested to establish their long-term mechanical properties. Once a string had settled into a desired stress state, the Young's modulus was measured by a variety of methods that probe different time-scales. The modulus was found to be a strong function of testing frequency and also a strong function of stress. Strings were also subjected to cyclical variations of temperature, allowing various thermal properties to be measured: the coefficient of linear thermal expansion and the thermal sensitivities of tuning, Young's modulus and density. The results revealed that the particular strings tested are divided into two groups with very different properties: stress-strain behaviour differing by a factor of two and some parametric sensitivities even having the opposite sign. Within each group, correlation studies allowed simple functional fits to be found to the key properties, which have the potential to be used in automated tuning systems for harp strings.

  15. Design of monoliths through their mechanical properties.

    PubMed

    Podgornik, Aleš; Savnik, Aleš; Jančar, Janez; Krajnc, Nika Lendero

    2014-03-14

    Chromatographic monoliths have several interesting properties making them attractive supports for analytics but also for purification, especially of large biomolecules and bioassemblies. Although many of monolith features were thoroughly investigated, there is no data available to predict how monolith mechanical properties affect its chromatographic performance. In this work, we investigated the effect of porosity, pore size and chemical modification on methacrylate monolith compression modulus. While a linear correlation between pore size and compression modulus was found, the effect of porosity was highly exponential. Through these correlations it was concluded that chemical modification affects monolith porosity without changing the monolith skeleton integrity. Mathematical model to describe the change of monolith permeability as a function of monolith compression modulus was derived and successfully validated for monoliths of different geometries and pore sizes. It enables the prediction of pressure drop increase due to monolith compressibility for any monolith structural characteristics, such as geometry, porosity, pore size or mobile phase properties like viscosity or flow rate, based solely on the data of compression modulus and structural data of non-compressed monolith. Furthermore, it enables simple determination of monolith pore size at which monolith compressibility is the smallest and the most robust performance is expected. Data of monolith compression modulus in combination with developed mathematical model can therefore be used for the prediction of monolith permeability during its implementation but also to accelerate the design of novel chromatographic monoliths with desired hydrodynamic properties for particular application.

  16. Electrical and Mechanical Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Bao, Wenzhong

    Graphene is an exciting new atomically-thin two-dimensional (2D) system of carbon atoms organized in a hexagonal lattice structure. This "wonder material" has been extensively studied in the last few years since it's first isolation in 2004. Its rapid rise to popularity in scientific and technological communities can be attributed to a number of its exceptional properties. In this thesis I will present several topics including fabrication of graphene devices, electrical and mechanical properties of graphene. I will start with a brief introduction of electronic transport in nanosclae system including quantum Hall effect, followed by a discussion of fundamental electrical and mechanical properties of graphene. Next I will describe how graphene devices are produced: from the famous "mechnical exfoliation" to our innovative "scratching exfoliation" method, together with the traditional lithography fabrication for graphene devices. We also developed a lithography-free technique for making electrical contacts to suspended graphene devices. Most of the suspended devices presented in this thesis are fabricated by this technique. Graphene has remarkable electrical properties thanks to its crystal and band structures. In Chapter 3, I will first focus on proximity-induced superconductivity in graphene Josephson transistors. In this section we investigate electronic transport in single layer graphene coupled to superconducting electrodes. We observe significant suppression in the critical current I c and large variation in the product IcR n in comparison to theoretic prediction; both phenomena can be satisfactorily accounted for by premature switching in underdamped Josephson junctions. Another focus of our studies is quantum Hall effect and many body physics in graphene in suspended bilayer and trilayer graphene. We demonstrate that symmetry breaking of the first 3 Landau levels and fractional quantum Hall states are observed in both bilayer and trilayer suspended graphene

  17. PICA Variants with Improved Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Thornton, Jeremy; Ghandehari, Ehson M.; Fan, Wenhong; Stackpoole, Margaret; Chavez-Garcia, Jose

    2011-01-01

    Phenolic Impregnated Carbon Ablator (PICA) is a member of the family of Lightweight Ceramic Ablators (LCAs) and was developed at NASA Ames Research Center as a thermal protection system (TPS) material for the Stardust mission probe that entered the Earth s atmosphere faster than any other probe or vehicle to date. PICA, carbon fiberform base and phenolic polymer, shows excellent thermal insulative properties at heating rates from about 250 W/sq cm to 1000 W/sq cm. The density of standard PICA - 0.26 g/cu cm to 0.28 g/cu cm - can be changed by changing the concentration of the phenolic resin. By adding polymers to the phenolic resin before curing it is possible to significantly improve the mechanical properties of PICA without significantly increasing the density.

  18. Mechanical properties of CuNi films

    SciTech Connect

    Brueckner, W.; Macionczyk, F.; Reiss, G. |

    1997-05-01

    CuNi alloys are widely used for precision resistors and thermocouples. Recently, they have been applied to low resistance thin film components. The mechanical properties of resistive CuNi films sputtered on both silicon wafers and flexible Kapton foils are important for reliability and lifetime of resistors. Studies of stress-temperature dependence and stress relaxation, stress-strain measurements and scanning scratch tests were performed to investigate film stresses, elastic properties, plastic flow, stress for crack initiation and film adhesion. The growth and annealing stresses were found to be tensile and can be seen as the reason for resistance degradation by stress relaxation due to plastic flow. The strains for crack initiation of 0.2% to 0.7% depending on film thickness and annealing restrict the application in resistors on flexible substrates. The film adhesion can be improved by a NiCr base-layer.

  19. Quantifying tissue mechanical properties using photoplethysmography

    SciTech Connect

    Akl, Tony; Wilson, Mark A.; Ericson, Milton Nance; Cote, Gerard L.

    2014-01-01

    Photoplethysmography (PPG) is a non-invasive optical method that can be used to detect blood volume changes in the microvascular bed of tissue. The PPG signal comprises two components; a pulsatile waveform (AC) attributed to changes in the interrogated blood volume with each heartbeat, and a slowly varying baseline (DC) combining low frequency fluctuations mainly due to respiration and sympathetic nervous system activity. In this report, we investigate the AC pulsatile waveform of the PPG pulse for ultimate use in extracting information regarding the biomechanical properties of tissue and vasculature. By analyzing the rise time of the pulse in the diastole period, we show that PPG is capable of measuring changes in the Young s Modulus of tissue mimicking phantoms with a resolution of 4 KPa in the range of 12 to 61 KPa. In addition, the shape of the pulse can potentially be used to diagnose vascular complications by differentiating upstream from downstream complications. A Windkessel model was used to model changes in the biomechanical properties of the circulation and to test the proposed concept. The modeling data confirmed the response seen in vitro and showed the same trends in the PPG rise and fall times with changes in compliance and vascular resistance.

  20. Green tea extract: possible mechanism and antibacterial activity on skin pathogens.

    PubMed

    Sharma, Anjali; Gupta, Sonal; Sarethy, Indira P; Dang, Shweta; Gabrani, Reema

    2012-11-15

    Camellia sinensis (tea) is known for its therapeutic properties (anti-inflammatory, anti-microbial, anti-tumour, anti-oxidative and anti-ageing). Although, anti-microbial properties of green tea have been studied, its role against bacterial strains related to skin infections and mechanism of action is not well understood. We focussed on exploring anti-microbial activity and the basic mechanism of aqueous green tea leaf extract on selected bacterial strains. Staphylococcus epidermidis, Micrococcus luteus, Brevibacterium linens, Pseudomonas fluorescens and Bacillus subtilis were found to be sensitive to green tea extract via disc diffusion assay (zone of inhibition ≥7 mm). Minimal inhibitory concentration (MIC) was determined via nitro blue tetrazolium (NBT) assay (0.156-0.313 mg/ml). Moreover, the aqueous extract was found to be not toxic to the Vero cell-line up to a concentration of 500 μg/ml. The effect of aqueous extract on adhesion of different bacteria to Vero cells indicated that it inhibits the adhesion at its MIC value.

  1. Design and mechanical properties of insect cuticle.

    PubMed

    Vincent, Julian F V; Wegst, Ulrike G K

    2004-07-01

    Since nearly all adult insects fly, the cuticle has to provide a very efficient and lightweight skeleton. Information is available about the mechanical properties of cuticle-Young's modulus of resilin is about 1 MPa, of soft cuticles about 1 kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of sclerotised cuticle ranges between 25 and 80 kgf mm(-2); density is 1-1.3 kg m(-3)-and one of its components, chitin nanofibres, the Young's modulus of which is more than 150 GPa. Experiments based on fracture mechanics have not been performed although the layered structure probably provides some toughening. The structural performance of wings and legs has been measured, but our understanding of the importance of buckling is lacking: it can stiffen the structure (by elastic postbuckling in wings, for example) or be a failure mode. We know nothing of fatigue properties (yet, for instance, the insect wing must undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical performance and efficiency of cuticle can be analysed and compared with those of other materials using material property charts and material indices. Presented in this paper are four: Young's modulus-density (stiffness per unit weight), specific Young's modulus-specific strength (elastic hinges, elastic energy storage per unit weight), toughness-Young's modulus (fracture resistance under various loading conditions), and hardness (wear resistance). In conjunction with a structural analysis of cuticle these charts help to understand the relevance of microstructure (fibre orientation effects in tendons, joints and sense organs, for example) and shape (including surface structure) of this fibrous composite for a given function. With modern techniques for analysis of structure and material, and emphasis on nanocomposites and self-assembly, insect cuticle should be the archetype for composites at all levels of scale.

  2. In Vitro Chemopreventive Properties of Green Tea, Rooibos and Honeybush Extracts in Skin Cells.

    PubMed

    Magcwebeba, Tandeka U; Swart, Pieter; Swanevelder, Sonja; Joubert, Elizabeth; Gelderblom, Wentzel C A

    2016-11-25

    The chemopreventive properties of the herbal teas rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) have been demonstrated on mouse skin in vivo but the underlying mechanisms are not clear. The aim of the current study was to determine the anti-proliferative and pro-apoptotic activity of methanol and aqueous extracts of rooibos and two Cyclopia species in different skin cells, using green tea (Camellia sinensis) as a benchmark. Extracts were also characterised for their major individual polyphenols by high performance liquid chromatography and spectroscopically for the total polyphenol (TP) groups. The methanol extract of rooibos, containing higher levels of polyphenols than its aqueous extract, displayed similar activity to green tea as it selectively targeted premalignant cells by inhibiting cell proliferation at lower concentrations whilst inducing apoptosis via membrane depolarisation at higher concentrations. Specific roles of the major rooibos dihydrochalcones and flavanol/proanthocyanidin-type (FLAVA) compounds are likely to be involved. The aqueous extracts of the Cyclopia species were more active against cell proliferation and at inducing apoptosis which was associated with a higher FLAVA content and a reduced TP/FLAVA ratio. In contrast, their methanol extracts exhibited a cytoprotective effect against apoptosis which was related to their monomeric xanthone and flavanone content. The underlying chemopreventive properties of green tea and the herbal teas appear to be associated with diverse and complex monomeric/polymeric polyphenolic cell interactions.

  3. Efficacy of Punica granatum L. hydroalcoholic extract on properties of dyed hair exposed to UVA radiation.

    PubMed

    Dario, Michelli Ferrera; Pahl, Richard; de Castro, Jordana Rodrigues; de Lima, Fernando Soares; Kaneko, Telma Mary; Pinto, Claudinéia A S O; Baby, André Rolim; Velasco, Maria Valéria Robles

    2013-03-05

    The solar radiation promotes color fading of natural and dyed hair by free radical generation, which oxidize the pigments, and it has been proposed the incorporation of antioxidants in order to reduce the alterations of hair color. Due to its high content of polyphenols and tannins, which are potent antioxidants, the hydroalcoholic extract of Punica granatum L. (pomegranate) was used in this research. Hair care formulations containing pomegranate extract were applied to red dyed hair tresses, and these were exposed to UVA radiation. Non-ionic silicone emulsion presenting color protection properties were also used for comparison purpose between the results obtained with different treatments, including silicone in combination with the pomegranate extract. The pomegranate extract at 5.0% and 10.0%w/w was effective in preventing the hair color fading in 37.6% and 60.8%, respectively, but the association of hydroalcoholic extract and non-ionic silicone emulsion is not encouraged. Mechanical properties were not affected by UVA radiation, since significant differences in breaking strength were not observed. Considering the conditions which the tresses have been exposed, it was concluded that the pomegranate extract at 10.0% w/w in hair care formulations are effective in reducing color fading of red dyed hair.

  4. Mechanical properties of low dimensional materials

    NASA Astrophysics Data System (ADS)

    Saini, Deepika

    Recent advances in low dimensional materials (LDMs) have paved the way for unprecedented technological advancements. The drive to reduce the dimensions of electronics has compelled researchers to devise newer techniques to not only synthesize novel materials, but also tailor their properties. Although micro and nanomaterials have shown phenomenal electronic properties, their mechanical robustness and a thorough understanding of their structure-property relationship are critical for their use in practical applications. However, the challenges in probing these mechanical properties dramatically increase as their dimensions shrink, rendering the commonly used techniques inadequate. This dissertation focuses on developing techniques for accurate determination of elastic modulus of LDMs and their mechanical responses under tensile and shear stresses. Fibers with micron-sized diameters continuously undergo tensile and shear deformations through many phases of their processing and applications. Significant attention has been given to their tensile response and their structure-tensile properties relations are well understood, but the same cannot be said about their shear responses or the structure-shear properties. This is partly due to the lack of appropriate instruments that are capable of performing direct shear measurements. In an attempt to fill this void, this dissertation describes the design of an inexpensive tabletop instrument, referred to as the twister, which can measure the shear modulus (G) and other longitudinal shear properties of micron-sized individual fibers. An automated system applies a pre-determined twist to the fiber sample and measures the resulting torque using a sensitive optical detector. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers. Two industrially important fibers, IM7 carbon fiber and KevlarRTM 119, were found to have G = 17 and 2.4 GPa, respectively. In addition to measuring the shear

  5. Mechanical properties of phosphorene nanoribbons and oxides

    SciTech Connect

    Hao, Feng; Chen, Xi

    2015-12-21

    Mechanical properties of phosphorene nanoribbons and oxides are investigated by using density functional theory. It is found that the ideal strength of nanoribbon decreases in comparison with that of 2D phosphorene. The Young's modulus of armchair nanoribbon has a remarkable size effect because of the edge relaxations. The analysis of the stress-strain relation indicates that, owing to chemisorbed oxygen atoms, the ideal strength and Young's modulus of 2D phosphorene oxide are greatly reduced along the zigzag direction, especially upon high oxidation ratios. In addition, strain and oxidation have significant impacts on phonon dispersion.

  6. Passive mechanical properties of ovine rumen tissue

    NASA Astrophysics Data System (ADS)

    Waite, Stephen J.; Cater, John E.; Walker, Cameron G.; Amirapu, Satya; Waghorn, Garry C.; Suresh, Vinod

    2016-05-01

    Mechanical and structural properties of ovine rumen tissue have been determined using uniaxial tensile testing of tissue from four animals at five rumen locations and two orientations. Animal and orientation did not have a significant effect on the stress-strain response, but there was a significant difference between rumen locations. Histological studies showed two orthogonal muscle layers in all regions except the reticulum, which has a more isotropic structure. A quasi-linear viscoelastic model was fitted to the relaxation stage for each region. Model predictions of the ramp stage had RMS errors of 13-24% and were within the range of the experimental data.

  7. Physical and Mechanical Properties of Glass--Reinforced Plastics,

    DTIC Science & Technology

    REINFORCED PLASTICS , REVIEWS), GLASS TEXTILES, MECHANICAL PROPERTIES, ELECTRICAL PROPERTIES, SILICONE PLASTICS , POLYESTER PLASTICS , PHENOLIC... PLASTICS , EPOXY RESINS, TEST METHODS, NONDESTRUCTIVE TESTING, FIRE RESISTANT MATERIALS, POLYVINYL CHLORIDE, USSR

  8. Task-specific thioglycolate ionic liquids for heavy metal extraction: Synthesis, extraction efficacies and recycling properties.

    PubMed

    Platzer, Sonja; Kar, Mega; Leyma, Raphlin; Chib, Sonia; Roller, Alexander; Jirsa, Franz; Krachler, Regina; MacFarlane, Douglas R; Kandioller, Wolfgang; Keppler, Bernhard K

    2017-02-15

    Eight novel task-specific ionic liquids (TSILs) based on the thioglycolate anion designed for heavy metal extraction have been prepared and characterized by (1)H and (13)C NMR, UV-Vis, infrared, ESI-MS, conductivity, viscosity, density and thermal properties. Evaluation of their time-resolved extraction abilities towards cadmium(II) and copper(II) in aqueous solutions have been investigated where distribution ratios up to 1200 were observed. For elucidation of the IL extraction mode, crystals were grown where Cd(II) was converted with an excess of S-butyl thioglycolate. It was found by X-ray diffraction analysis that cadmium is coordinated by five oxygen and one sulfur donor atoms provided by two thioglycolate molecules and one water molecule. Leaching behavior of the hydrophobic ionic liquids into aqueous systems was studied by TOC (total dissolved organic carbon) measurements. Additionally, the immobilization on polypropylene was elucidated and revealed slower metal extraction rates and similar leaching behavior. Finally, recovery processes for cadmium and copper after extraction were performed and recyclability was successfully proven for both metals. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

  9. Method for improving the extraction properties of a tributyl phosphate solution

    DOEpatents

    Martin, Earl C.; Bruns, Lester E.

    1976-01-01

    A method for improving the extraction properties of a tributyl phosphate extractant used for reprocessing irradiated nuclear reactor fuel (Purex Process) containing degradation products of tributyl phosphate by contacting the extractant with diazomethane in a suitable solvent whereby the degradation products are esterified to triester phosphates which have extraction properties similar to those of tributyl phosphate.

  10. Electron Extraction Mechanisms of a Micro ECR Neutralizer

    NASA Astrophysics Data System (ADS)

    Takao, Yoshinori; Hiramoto, Kenta; Nakagawa, Yuichi; Kasagi, Yusuke; Koizumi, Hiroyuki; Komurasaki, Kimiya

    2015-09-01

    A neutralizer is one of the indispensable components for ion propulsion systems. To design a better performance neutralizer the mechanisms of electron extraction from its plasma source through orifices should be elucidated. In the present study, three-dimensional particle simulations have been carried out for a 4.2-GHz microwave discharge neutralizer, where the size of the discharge chamber is 20 × 20 × 4 mm3 and a xenon electron cyclotron resonance plasma is employed. The numerical model is composed of a particle-in-cell simulation with a Monte Carlo collision algorithm for the kinetics of charged particles, a finite-difference time-domain method for the electromagnetic fields of microwaves, and a finite element analysis for the magnetostatic fields of permanent magnets. The calculations were conducted at the gas pressure of 1 mTorr and the absorbed power of 0.3 W. The simulation results have indicated that the electrostatic field of the plasma has a dominant influence on the electron extraction, where electrons are not extracted unless the effect of the electrostatic field is taken into account in the calculations. This work was supported in part by JSPS KAKENHI Grant No. 25289304. Part of the simulations was performed on the KDK computer system at RISH, Kyoto University.

  11. Antiatherogenic properties of acetone extract of Alpinia zerumbet seeds.

    PubMed

    Chompoo, Jamnian; Upadhyay, Atul; Gima, Shinichi; Fukuta, Masakazu; Tawata, Shinkichi

    2012-05-25

    Oxidation of low-density lipoprotein (LDL) is the principal risk factor for the development of atherosclerosis. In this study, we used several methods to investigate the ability of the acetone extract from rhizomes, stems, leaves, flowers, pericarps and seeds of Alpinia zerumbet to inhibit atherosclerosis in vitro. The seed extract had the strongest activity against tyrosinase, pancreatic lipase (PL), 15-lipoxygenase (15-LO) and LDL oxidation activities (IC₅₀ = 2.30 ± 0.02, 5.00 ± 0.07, 1.29 ± 0.07 and 15.40 ± 0.86 μg/mL, respectively), amongst all different parts. It also had similar effects to the positive controls. Most of the extracts showed partial agonistic properties towards estrogenic activity. Cholest-4-ene-3,6-dione, a steroid present only in the seed extract seems to be the compound responsible for these activities. The results showed that cholest-4-ene-3,6-dione had similar ability to curcumin and quercetin against PL and LDL oxidation (IC₅₀ = 19.50 ± 1.17 and 16.12 ± 1.43 μg/mL, respectively). Furthermore, cholest-4-ene-3,6-dione (IC₅₀ = 34.21 ± 1.31 μg/mL) had higher inhibition against 15-LO than quercetin (IC₅₀ = 54.79 ± 1.12 μg/mL).

  12. Coronal Jet Plasma Properties and Acceleration Mechanisms

    NASA Astrophysics Data System (ADS)

    Farid, Samaiyah; Reeves, Kathy; Savcheva, Antonia; Soto, Natalia

    2017-08-01

    Coronal jets are transient eruptions of plasma typically characterized by aprominent long spire and a bright base, and sometimes accompanied by a small filament. Jets are thought to be produced by magnetic reconnection when small-scale bipolar magnetic fields emerge into an overlying coronal field or move into a locally unipolar region. Coronal jets are commonly divided into two categories: standard jets and blowout jets, and are found in both quiet and active regions. The plasma properties of jets vary across type and location, therefore understanding the underlying acceleration mechanisms are difficult to pin down. In this work, we examine both blow-out and standard jets using high resolution multi-wavelength data. Although reconnection is commonly accepted as the primary acceleration mechanism, we also consider the contribution chromospheric evaporation to jet formation. We use seven coronal channels from SDO/AIA , Hinode/XRT Be-thin and IRIS slit-jaw data. In addition, we separate the Fe-XVIII line from the SDO/94Å channel. We calculate plasma properties including velocity, Alfven speed, and density as a function of wavelength and Differential Emission Measure (DEM). Finally, we explore the magnetic topology of the jets using Coronal Modeling System (CMS) to construct potential and non-linear force free models based on the flux rope insertion method.

  13. Braiding Simulation and Prediction of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Pickett, Anthony K.; Sirtautas, Justas; Erber, Andreas

    2009-12-01

    Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to ‘take-up’ the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso- model analysis and validation again analytical and test measurements are presented.

  14. Study of Anti Cancer Property of Scrophularia striata Extract on the Human Astrocytoma Cell Line (1321)

    PubMed Central

    Ardeshiry lajimi, Abdulreza; Rezaie-Tavirani, Mostafa; Mortazavi, Seyed Alireza; Barzegar, Mansoureh; Moghadamnia, Seyed Hasan; Rezaee, Mohamad Bagher

    2010-01-01

    There are considerable efforts to identify naturally occurring substances as new drugs in cancer therapy. Many components of medicinal plants have been identified that possess substantial anticancerous properties. This prompted us to investigate the effect of Scrophularia striata (an Iranian species belonging to the Scrophulariace family) extract on the growth of astrocyte cancer cell line (1321). The 1321 cell line were seeded in 96-well culture plates in the presence and absence of various concentrations of either leaf and seed filtered and unfiltered extract of Scrophularia striata to determine their probable anticancer effects in comparison with etoposide (chemical anticancer reagent). filtered leaf extract of S. Striata showed strong anticancer effect on 1321cell line as compared to control group (cells not exposed to extracts), and even the group (adenocarcinoma gastric cell line) exposed to etoposide. Unlike the leaf extract, the seed extract activated cell proliferation in all experiments. Flow cytometry findings indicated that apoptosis is the mechanism by which the leaf extract inhibits cell proliferation. Our findings indicate that both leaves and seeds of S. Striata contain both anti cancer and cell growth enhancing agents. PMID:24381605

  15. Mechanical Properties of the Seismogenic Zone

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.

    Understanding the processes that dictate the evolution of frictional strength during the seismic cycle is a central problem in characterizing the seismic potential of faults and in relating earthquake source parameters such as stress drop to recurrence interval and geologic and geodetic fault slip rates. Laboratory friction experiments provide insight into the mechanisms of fault healing, and results of these studies provide the fundamental underpinnings of the rate- and state-friction laws. Frictional healing is the mechanism(s) associated with fault restrengthening following failure, where time-, slip- and velocity-dependent processes dictate the evolution of real contact area at grain junctions within fault gouge. The objective of this work is to illuminate the micromechanics of frictional healing and the relation between mechanical and hydraulic properties of fault gouge. Four main dissertation chapters are combined with three additional collaborative works describing research on the fundamental processes that govern earthquakes and tectonic faulting. Chapter one is focused on the role of water during repetitive stick-slip frictional sliding, with particular emphasis on the grain scale mechanisms of frictional restrengthening. A micromechanical model for gouge deformation is developed, based on the interpretation of mechanical and microstructural observations. Chapter two describes the role of pore fluid pressure during earthquake nucleation and dynamic rupture. Experiments were performed on synthetic granular fault gouge under a range of hydrological boundary conditions from drained to undrained. The experiments demonstrate that when gouge layers are deformed under undrained boundary conditions, time-dependent strengthening and the magnitude of stress drop increase, when compared with drained conditions. I conclude that under undrained conditions, a series of feedback processes between pore fluid depressurization and stress enhanced pressure solution creep

  16. Lunar surface mechanical properties from Surveyor data.

    NASA Technical Reports Server (NTRS)

    Jones, R. H.

    1971-01-01

    During the Surveyor program spacecraft were successfully landed at five widely separated lunar locations. Recent computer simulations of each landing have provided more comprehensive data on the mechanical properties of the lunar surface than have been obtained previously by this method of analysis. Results show that the variations in surface bearing pressure observed at the various lunar sites are probably due to surface slope effects and do not necessarily indicate differences in soil properties at these sites. Estimates of cohesion at two sites give almost identical results and further support the conclusion that the soil properties at all sites are probably very similar. Surface pressures that resist horizontal (plowing) motion are largely due to cohesion, and density and gravitational contributions are small. It is concluded that the lunar surface bearing strength is essentially zero at the surface and, for zero surface slope, increases with penetration depth at a rate of 1.87 (plus or minus 0.33) N/cu cm. The cohesion of the lunar soil is estimated to be between 0.11 and 0.17 N/sq cm.

  17. Mechanical properties of 3D ceramic nanolattices

    NASA Astrophysics Data System (ADS)

    Meza, Lucas

    Developments in advanced nanoscale fabrication techniques have allowed for the creation of 3-dimensional hierarchical structural meta-materials that can be designed with arbitrary geometry. These structures can be made on length scales spanning multiple orders of magnitude, from tens of nanometers to hundreds of microns. The smallest features are controllable on length scales where materials have been shown to exhibit size effects in their mechanical properties. Combining novel nanoscale mechanical properties with a 3-dimensional architecture enables the creation of new classes of materials with tunable and unprecedented mechanical properties. We present the fabrication and mechanical deformation of hollow tube alumina nanolattices that were fabricated using two-photon lithography direct laser writing (DLW), atomic layer deposition (ALD), and oxygen plasma etching. Nanolattices were designed in a number of different geometries including octet-truss, octahedron, and 3D Kagome. Additionally, a number of structural parameters were varied including tube wall thickness (t) , tube major axis (a) , and unit cell size (L) . The resulting nanolattices had a range of densities from ρ = 4 to 250 mg/cm3. Uniaxial compression and cyclic loading tests were performed on the nanolattices to obtain the yield strength and modulus. In these tests, a marked change in the deformation response was observed when the wall thickness was reduced below 20nm; thick-walled nanolattices (t>20nm) underwent catastrophic, brittle failure, which transitioned to a gradual, ductile-like deformation as wall thickness was reduced. Thick-walled nanolattices also exhibited no recovery after compression, while thin-walled structures demonstrated notable recovery, with some recovering by 98% after compression to 50% strain and by 80% when compressed to 90% strain. Across all geometries, unit cell sizes, and wall thicknesses, we found a consistent power law relation between strength and modulus with

  18. Phytochemistry and medicinal properties of Phaleria macrocarpa (Scheff.) Boerl. extracts

    PubMed Central

    Altaf, Rabia; Asmawi, Mohammad Zaini Bin; Dewa, Aidiahmad; Sadikun, Amirin; Umar, Muhammad Ihtisham

    2013-01-01

    Phaleria macrocarpa, commonly known as Mahkota dewa is a medicinal plant that is indigenous to Indonesia and Malaysia. Extracts of P. macrocarpa have been used since years in traditional medicine that are evaluated scientifically as well. The extracts are reported for a number of valuable medicinal properties such as anti-cancer, anti-diabetic, anti-hyperlipidemic, anti-inflammatory, anti-bacterial, anti-fungal, anti-oxidant and vasorelaxant effect. The constituents isolated from different parts of P. macrocarpa include Phalerin, gallic acid, Icaricide C, magniferin, mahkoside A, dodecanoic acid, palmitic acid, des-acetylflavicordin-A, flavicordin-A, flavicordin-D, flavicordin-A glucoside, ethyl stearate, lignans, alkaloids andsaponins. The present review is an up-to-date summary of occurrence, botanical description, ethnopharmacology, bioactivity and toxicological studies related to P. macrocarpa. PMID:23922460

  19. HTML Extraction Algorithm Based on Property and Data Cell

    NASA Astrophysics Data System (ADS)

    Purnamasari, Detty; Wayan Simri Wicaksana, I.; Harmanto, Suryadi; Yuniar Banowosari, Lintang

    2013-06-01

    The data available on the Internet is in various models and formats. One form of data representation is a table. Tables extraction is used in process more than one table on the Internet from different sources. Currently the effort is done by using copy-paste that is not automatic process. This article presents an approach to prepare the area, so tables in HTML format can be extracted and converted into a database that make easier to combine the data from many resources. This article was tested on the algorithm 1 used to determine the actual number of columns and rows of the table, as well as algorithm 2 are used to determine the boundary line of the property. Tests conducted at 100 tabular HTML format, and the test results provide the accuracy of the algorithm 1 is 99.9% and the accuracy of the algorithm 2 is 84%.

  20. Reversible work extraction in a hybrid opto-mechanical system

    NASA Astrophysics Data System (ADS)

    Elouard, Cyril; Richard, Maxime; Auffèves, Alexia

    2015-05-01

    With the progress of nano-technology, thermodynamics also has to be scaled down, calling for specific protocols to extract and measure work. Usually, such protocols involve the action of an external, classical field (the battery) of infinite energy, that controls the energy levels of a small quantum system (the calorific fluid). Here we suggest a realistic device to reversibly extract work in a battery of finite energy : a hybrid optomechanical system. Such devices consist of an optically active two-level quantum system interacting strongly with a nano-mechanical oscillator that provides and stores mechanical work, playing the role of the battery. We identify protocols where the battery exchanges large, measurable amounts of work with the quantum emitter without getting entangled with it. When the quantum emitter is coupled to a thermal bath, we show that thermodynamic reversibility is attainable with state-of-the-art devices, paving the road towards the realization of a full cycle of information-to-energy conversion at the single bit level.

  1. Mechanical properties of the beetle elytron, a biological composite material

    USDA-ARS?s Scientific Manuscript database

    We determined the relationship between composition and mechanical properties of elytral (modified forewing) cuticle of the beetles Tribolium castaneum and Tenebrio molitor. Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult ecl...

  2. Mechanical properties of kenaf composites using dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Loveless, Thomas A.

    Natural fibers show potential to replace glass fibers in thermoset and thermoplastic composites. Kenaf is a bast-type fiber with high specific strength and great potential to compete with glass fibers. In this research kenaf/epoxy composites were analyzed using Dynamic Mechanical Analysis (DMA). A three-point bend apparatus was used in the DMA testing. The samples were tested at 1 hertz, at a displacement of 10 ?m, and at room temperature. The fiber volume content of the kenaf was varied from 20% - 40% in 5% increments. Ten samples of each fiber volume fraction were manufactured and tested. The flexural storage modulus, the flexural loss modulus, and the loss factor were reported. Generally as the fiber volume fraction of kenaf increased, the flexural storage and flexural loss modulus increased. The loss factor remained relatively constant with increasing fiber volume fraction. Woven and chopped fiberglass/epoxy composites were manufactured and tested to be compared with the kenaf/epoxy composites. Both of the fiberglass/epoxy composites reported higher flexural storage and flexural loss modulus values. The kenaf/epoxy composites reported higher loss factor values. The specific flexural storage and specific flexural loss modulus were calculated for both the fiberglass and kenaf fiber composites. Even though the kenaf composites reported a lower density, the fiberglass composites reported higher specific mechanical properties.

  3. Preparation and functional properties of extracts from bee bread.

    PubMed

    Nagai, Takeshi; Nagashima, Toshio; Myoda, Takao; Inoue, Reiji

    2004-06-01

    Three extracts, namely hot-water fraction (HWF), water-soluble fraction (WSF), and ethanol-soluble fraction (ESF), were prepared from fresh bee bread imported from Lithuania. The protein and total phenolic contents of these samples were very high. Among them, WSF at 100% concentration showed the highest antioxidative ability and scavenging ability. On the other hand, ESF at 10% concentration possessed the highest ability against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals. Bee bread will apply more and more as health food and medicine due to its functional properties such as antioxidative ability and scavenging activities of reactive oxygen species.

  4. Different neurophysiological mechanisms underlying word and rule extraction from speech.

    PubMed

    De Diego Balaguer, Ruth; Toro, Juan Manuel; Rodriguez-Fornells, Antoni; Bachoud-Lévi, Anne-Catherine

    2007-11-14

    The initial process of identifying words from spoken language and the detection of more subtle regularities underlying their structure are mandatory processes for language acquisition. Little is known about the cognitive mechanisms that allow us to extract these two types of information and their specific time-course of acquisition following initial contact with a new language. We report time-related electrophysiological changes that occurred while participants learned an artificial language. These changes strongly correlated with the discovery of the structural rules embedded in the words. These changes were clearly different from those related to word learning and occurred during the first minutes of exposition. There is a functional distinction in the nature of the electrophysiological signals during acquisition: an increase in negativity (N400) in the central electrodes is related to word-learning and development of a frontal positivity (P2) is related to rule-learning. In addition, the results of an online implicit and a post-learning test indicate that, once the rules of the language have been acquired, new words following the rule are processed as words of the language. By contrast, new words violating the rule induce syntax-related electrophysiological responses when inserted online in the stream (an early frontal negativity followed by a late posterior positivity) and clear lexical effects when presented in isolation (N400 modulation). The present study provides direct evidence suggesting that the mechanisms to extract words and structural dependencies from continuous speech are functionally segregated. When these mechanisms are engaged, the electrophysiological marker associated with rule-learning appears very quickly, during the earliest phases of exposition to a new language.

  5. Metal Additive Manufacturing: A Review of Mechanical Properties (Postprint)

    DTIC Science & Technology

    2016-04-21

    AFRL-RX-WP-JA-2017-0156 METAL ADDITIVE MANUFACTURING : A REVIEW OF MECHANICAL PROPERTIES (POSTPRINT) John J. Lewandowski and...2012 – 19 March 2016 4. TITLE AND SUBTITLE METAL ADDITIVE MANUFACTURING : A REVIEW OF MECHANICAL PROPERTIES (POSTPRINT) 5a. CONTRACT NUMBER...data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples

  6. Environmental properties set cell mechanics and morphology

    NASA Astrophysics Data System (ADS)

    Janmey, Paul

    2012-02-01

    Many cell types are sensitive to mechanical signals that are produced either by application of exogenous force to their surfaces, or by the resistance that their surroundings place on forces generated by the cells themselves. Cell morphology, motility, proliferation, and protein expression all change in response to substrate stiffness. Changing the elastic moduli of substrates alters the formation of focal adhesions, the assembly of actin filaments into bundles, and the stability of intermediate filaments. The range of stiffness over which different primary cell types respond can vary over a wide range and generally reflects the elastic modulus of the tissue from which these cells were isolated. Mechanosensing depends on the type of adhesion receptor by which the cell binds, and therefore on both the molecular composition of the extracellular matrix and the nature of its link to the cytoskeleton. Many cell types can alter their own stiffness to match that of the substrate to which they adhere. The maximal elastic modulus that cells such as fibroblasts can attain is similar to that of crosslinked actin networks at the concentrations in the cell cortex. The precise mechanisms of mechanosensing are not well defined, but they presumably require an elastic connection between cell and substrate, mediated by transmembrane proteins. The viscoelastic properties of different extracellular matrices and cytoskeletal elements strongly influence the response of cells to mechanical signals, and the unusual non-linear elasticity of many biopolymer gels, characterized by strain-stiffening, leads to novel mechanisms by which cells alter their stiffness by engagement of molecular motors that produce internal stresses. Cell cortical elasticity is dominated by cytoskeletal polymer networks and can be modulated by internal tension. Simultaneous control of substrate stiffness and adhesive patterns suggests that stiffness sensing occurs on a length scale much larger than single molecular

  7. Extracting surface phonon properties from the electronic spectral function

    NASA Astrophysics Data System (ADS)

    Plummer, Ward

    2005-03-01

    Angle resolved photoemission measurements have revealed an enhancement in the electron-phonon coupling (EPC) for two- dimensional surface states and quantum-well states in thin films. A recent theoretical advancement by J. Shi [1] has developed a method for the direct extraction of the momentum dependent Eliashberg function from the high-resolution photoemission data. The origin of the enhanced EPC at surfaces and interfaces will be explored as well as schemes to tune the EPC by modification of the surface electronic and vibrational properties. The implications of EPC on physical properties will be discussed, including the lifetime of electronic states near the Fermi energy. 1. Junren Shi et al., Phys. Rev. Lett. 92, 186401 (2004). The work at UT supported by NSF- DMR 0105232. Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725.

  8. Morphology, orientation, and mechanical properties of gelatin films

    SciTech Connect

    Blanton, T.N.; Tsou, A.H.

    1996-12-31

    Gelatin is a polypeptide derived from degradation and disorganization of collagen fibers and is the primary binder in photographic emulsions. Gelatin provides the mechanical integrity and strength to the photographic emulsion allowing for packaging, handling, and photofinishing operations. Gelatin films generated from aqueous-solution casting can exist in a semicrystalline or an amorphous state. When a gelatin solution is cooled below its helix-coil transition temperature, partial renaturation of gelatin to form triple helices can occur. The degree of renaturation in a coated film is dependent upon the drying temperature and the drying rate. During the drying process, gelatin crystals can be formed by lateral association of the triple helices through a mechanism of nucleation and growth of a fringed micelle structure. X-ray scattering techniques have been utilized to examine the morphology and orientation of gelatin films. Based on X-ray diffraction data, it is observed that aggregates of triple-helix rods lie parallel to the film plane but are symmetrically distributed within the film plane. Since a material`s physical and mechanical properties are related to its structure, it is necessary to understand and to characterize the morphological development in gelatin film formation. In this study, an X-ray diffractometer and pole figure goniometer were utilized to examine the structural development and orientation anisotropy in solid-state gelatin films. Also, in this study, the in-plane mechanical properties of a gelatin film were determined from a uniaxial tensile test, and the gelatin film properties in the thickness direction were extracted from an indentation test based on the finite element analysis of the indentation results using a viscoelastic material model.

  9. Mechanical properties of high-strength concrete

    NASA Astrophysics Data System (ADS)

    Mokhtarzadeh, Alireza

    This report summarizes an experimental program conducted to investigate production techniques and mechanical properties of high strength concrete in general and to provide recommendations for using these concretes in manufacturing precast/prestressed bridge girders. Test variables included total amount and composition of cementitious material (portland cement, fly ash, and silica fume), type and brand of cement, type of silica fume (dry densified and slurry), type and brand of high-range water-reducing admixture, type of aggregate, aggregate gradation, maximum aggregate size, and curing. Tests were conducted to determine the effects of these variables on changes in compressive strength and modulus of elasticity over time, splitting tensile strength, modulus of rupture, creep, shrinkage, and absorption potential (as an indirect indicator of permeability). Also investigated were the effects of test parameters such as mold size, mold material, and end condition. Over 6,300 specimens were cast from approximately 140 mixes over a period of 3 years.

  10. Mechanical properties of icosahedral virus capsids

    NASA Astrophysics Data System (ADS)

    Vliegenthart, G. A.; Gompper, G.

    2007-12-01

    Virus capsids are self-assembled protein shells in the size range of 10 to 100 nanometers. The shells of DNA-viruses have to sustain large internal pressures while encapsulating and protecting the viral DNA. We employ computer simulations to study the mechanical properties of crystalline shells with icosahedral symmetry that serve as a model for virus capsids. The shells are positioned on a substrate and deformed by a uni-axial force excerted by a small bead. We predict the elastic response for small deformations, and the buckling transitions at large deformations. Both are found to depend strongly on the number N of elementary building blocks (capsomers), and the Föppl-von Kármán number γ which characterizes the relative importance of shear and bending elasticity.

  11. Material modeling of biofilm mechanical properties.

    PubMed

    Laspidou, C S; Spyrou, L A; Aravas, N; Rittmann, B E

    2014-05-01

    A biofilm material model and a procedure for numerical integration are developed in this article. They enable calculation of a composite Young's modulus that varies in the biofilm and evolves with deformation. The biofilm-material model makes it possible to introduce a modeling example, produced by the Unified Multi-Component Cellular Automaton model, into the general-purpose finite-element code ABAQUS. Compressive, tensile, and shear loads are imposed, and the way the biofilm mechanical properties evolve is assessed. Results show that the local values of Young's modulus increase under compressive loading, since compression results in the voids "closing," thus making the material stiffer. For the opposite reason, biofilm stiffness decreases when tensile loads are imposed. Furthermore, the biofilm is more compliant in shear than in compression or tension due to the how the elastic shear modulus relates to Young's modulus. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Potential Properties of Plant Sprout Extracts on Amyloid β

    PubMed Central

    Okada, Mizue; Okada, Yoshinori

    2016-01-01

    The aim of this study is to examine the amyloid β (Aβ) inhibition mechanism of plant sprouts' aqueous extracts (PSAE). In this study, we screened the effects of five plant sprouts' extracts on Aβ (1–42) structure modification using gel electrophoresis. In PSAE, no band of Aβ monomer was recognized in Japanese butterbur. Similarly, the Aβ monomer band became light in buckwheat, red cabbage, broccoli, and brussels. The neuroprotective effects of PSAE were evaluated by measuring levels of Aβ in mixtures (Aβ  and PSAE) with Aβ ELISA assay. The treatment with PSAE decreased Aβ levels. The results indicated that the levels of red cabbage, Japanese butterbur, and broccoli were 9.6, 28.0, and 44.0%, respectively. The lowest value was observed with buckwheat. Furthermore, we carried out a Congo Red (CR) and Aβ binding experiment of PSAE to confirm the modification mechanism of PSAE. The correlation coefficient for the absorption spectrum peak of CR was found to be bigger than 0.8 (r = 0.882) which proved that the Aβ levels could be attributed to the peak of CR. In conclusion, we demonstrated that treatment with PSAE effectively decreases Aβ concentration. Thus, the mechanism that decreased the Aβ levels may be modification by PSAE. PMID:27429807

  13. Potential Properties of Plant Sprout Extracts on Amyloid β.

    PubMed

    Okada, Mizue; Okada, Yoshinori

    2016-01-01

    The aim of this study is to examine the amyloid β (Aβ) inhibition mechanism of plant sprouts' aqueous extracts (PSAE). In this study, we screened the effects of five plant sprouts' extracts on Aβ (1-42) structure modification using gel electrophoresis. In PSAE, no band of Aβ monomer was recognized in Japanese butterbur. Similarly, the Aβ monomer band became light in buckwheat, red cabbage, broccoli, and brussels. The neuroprotective effects of PSAE were evaluated by measuring levels of Aβ in mixtures (Aβ  and PSAE) with Aβ ELISA assay. The treatment with PSAE decreased Aβ levels. The results indicated that the levels of red cabbage, Japanese butterbur, and broccoli were 9.6, 28.0, and 44.0%, respectively. The lowest value was observed with buckwheat. Furthermore, we carried out a Congo Red (CR) and Aβ binding experiment of PSAE to confirm the modification mechanism of PSAE. The correlation coefficient for the absorption spectrum peak of CR was found to be bigger than 0.8 (r = 0.882) which proved that the Aβ levels could be attributed to the peak of CR. In conclusion, we demonstrated that treatment with PSAE effectively decreases Aβ concentration. Thus, the mechanism that decreased the Aβ levels may be modification by PSAE.

  14. Antioxidant properties and phytochemical characteristics of extracts from Lactuca indica.

    PubMed

    Wang, Sheng-Yang; Chang, Hsing-Ning; Lin, Kai-Ti; Lo, Chiu-Ping; Yang, Ning-Sun; Shyur, Lie-Fen

    2003-02-26

    Lactuca indica (Compositae) is an edible wild vegetable, used as a folk medicine in anti-inflammatory, antibacterial, and other medications in Asia. This is the first scientific evaluation of the chemopreventive therapeutic properties of L. indica using five antioxidation assay systems. An extract from L. indica was found to possess significant free radical scavenging activity, effectively protecting phix174 supercoiled DNA against strand cleavage and reducing oxidative stress in human promyelocytic leukemia HL-60 cells. Moreover, extracts of L. indica almost totally inhibited nitric oxide production and the mRNA expression of inducible nitric oxide synthase, at a dosage of 100 microg/mL, in LPS-stimulated macrophage RAW264.7 cells. Bioactivity-guided chromatographic fractionation and metabolite profiling coupled with spectroscopic analyses revealed that the six phenolic compounds, that is, protocatechulic acid (1), methyl p-hydroxybenzoate (2), caffeic acid (3), 3,5-dicaffeoylquinic acid (4), luteolin 7-O-beta-glucopyranoside (5), and quercetin 3-O-beta-glucopyranoside (6), are the major antioxidative constituents in the L. indica extract.

  15. Phenolic profiles and antioxidant properties of apple skin extracts.

    PubMed

    Huber, G M; Rupasinghe, H P V

    2009-01-01

    Lipid oxidation, especially the oxidation of polyunsaturated fatty acids, is a significant issue in the food industry impacting both food quality and health of consumers. Apple skin was investigated as a source of natural antioxidants. The phenolic compound composition and antioxidant properties of 21 selected apple genotypes were evaluated. The lipid stabilizing ability of the apple skin extracts was examined using an aqueous emulsion system of methyl linolenate. The total phenolic concentrations determined by high-performance liquid chromatography tandem mass spectrometry of methanolic extracts of skins of the apple genotypes varied from 150 to 700 mg/100 g DW. The antioxidant capacity measured by Folin-Ciocalteu (16.2 to 34.1 mg GAE/100 g DW), ferric reducing antioxidant power (1.3 to 3.3 g TE/100 g DW), oxygen radical absorbance capacity (5.2 to 14.2 g TE/100 g DW), and percent inhibition of oxidation of methyl linolenate (73.8% to 97.2%) varied among the apple genotypes. The apple skin extracts, specifically the crab apple varieties such as "Dolgo," were revealed to be effective inhibitors of oxidation of polyunsaturated fatty acid in a model system and thus can be considered as a potential source of natural food antioxidants.

  16. Empirical extraction of mechanisms underlying real world network generation

    NASA Astrophysics Data System (ADS)

    Itzhack, Royi; Muchnik, Lev; Erez, Tom; Tsaban, Lea; Goldenberg, Jacob; Solomon, Sorin; Louzoun, Yoram

    2010-11-01

    The generation mechanisms of real world networks have been described using multiple models. The mathematical features of these models are usually extrapolated from statistical properties of a snapshot of these networks. We here propose an alternative method based on direct measurement of a sequence of consecutive snapshots to uncover the dynamics underlying real world generation. We assume that the probability of adding a node or an edge depends only on local features surrounding the newly added node/edge, and directly measure the contribution of these features to the node/edge addition probability. These measurements are performed using newly defined N-node local structures. Each N-node local structure represents the configuration of edges surrounding a newly added edge. The N-node local structure measurements reproduce for some networks the now classical addition of edges between high degree node mechanisms. It also provides quantitative estimates of more complex mechanisms driving other networks’ evolution, such as the effect of common first and second neighbors. This new methodology reveals the relative importance of different generation mechanisms. We show, for example, that the main mechanism driving hyperlink addition between two websites is the existence of a third website linking to both the source and the target of the new hyperlink.

  17. Mechanical properties of nanostructure of biological materials

    NASA Astrophysics Data System (ADS)

    Ji, Baohua; Gao, Huajian

    2004-09-01

    Natural biological materials such as bone, teeth and nacre are nanocomposites of protein and mineral with superior strength. It is quite a marvel that nature produces hard and tough materials out of protein as soft as human skin and mineral as brittle as classroom chalk. What are the secrets of nature? Can we learn from this to produce bio-inspired materials in the laboratory? These questions have motivated us to investigate the mechanics of protein-mineral nanocomposite structure. Large aspect ratios and a staggered alignment of mineral platelets are found to be the key factors contributing to the large stiffness of biomaterials. A tension-shear chain (TSC) model of biological nanostructure reveals that the strength of biomaterials hinges upon optimizing the tensile strength of the mineral crystals. As the size of the mineral crystals is reduced to nanoscale, they become insensitive to flaws with strength approaching the theoretical strength of atomic bonds. The optimized tensile strength of mineral crystals thus allows a large amount of fracture energy to be dissipated in protein via shear deformation and consequently enhances the fracture toughness of biocomposites. We derive viscoelastic properties of the protein-mineral nanostructure and show that the toughness of biocomposite can be further enhanced by the viscoelastic properties of protein.

  18. Mechanical properties of semiconductors and their alloys

    NASA Astrophysics Data System (ADS)

    Sher, A.; Berding, M. A.; Paxton, A. T.; Krishnamurthy, S.; Chen, A.-B.

    1992-02-01

    A wide range of subjects have been treated in this contract. We have devoted time to the development and applications of two first principles computational methods: one, the full-potential linear muffin tin orbital (FP-LMTO) method is somewhat mature and highly accurate, while the other, linear combination of atomic orbitals (LCAO), is less accurate but more flexible and is easily incorporated into the other calculations we have in place, e.g., surface Green's function methods and CPA. Tight binding has also been used. These methods have been applied to solve a host of mechanical-property problems including elastic constants, cleavage energies, sublimation energies, interactions between surface atoms relating to their surface order-disorder state and growth theory, surface segregation, bulk order-disorder theory and phase stability, the effect of dislocations on electronic transport and electro-optic properties of semiconductors, the Ni-Al intermetallic phase diagram, planar fault energies in L12 alloys, high-performance structural metal alloy design, and a contribution to understanding the Jones theory of metal alloying. Many of these subjects have been brought to publishable conclusions. Whenever possible, we have presented our detailed results in the form of preprints and reprints, with only brief summaries of the work given here. In instances where the research is incomplete, we have given somewhat longer expositions.

  19. Mechanical properties of nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Shen, Z. H.; Hess, P.; Huang, J. P.; Lin, Y. C.; Chen, K. H.; Chen, L. C.; Lin, S. T.

    2006-06-01

    Nanocrystalline diamond (NCD) films with thicknesses in the range of 0.12-1.5 μm were deposited on silicon substrates in CH4/H2/O2 gas mixtures by microwave plasma-enhanced chemical vapor deposition. The morphology and structure of these NCD films were analyzed by field-emission scanning electron microscopy, x-ray diffraction (XRD), and ultraviolet-Raman spectroscopy. The lower limit of the grain size in the NCD films was estimated to be 10 nm from the XRD measurements. These grains are embedded in a columnar-type structure. The elastic and mechanical properties of the NCD films were determined by measuring the dispersion of laser-induced surface acoustic waves. The densities were in the range of 3.41+/-0.11 g/cm3 and Young's moduli varied between 674+/-34 and 953+/-48 GPa, depending on the growth time and deposition conditions. It is concluded that oxygen may have a significant positive effect on the elastic properties of NCD films. The growth rate decreases sharply for an oxygen content in the source gas in excess of about 4%.

  20. Biodegradable compounds: Rheological, mechanical and thermal properties

    NASA Astrophysics Data System (ADS)

    Nobile, Maria Rossella; Lucia, G.; Santella, M.; Malinconico, M.; Cerruti, P.; Pantani, R.

    2015-12-01

    Recently great attention from industry has been focused on biodegradable polyesters derived from renewable resources. In particular, PLA has attracted great interest due to its high strength and high modulus and a good biocompatibility, however its brittleness and low heat distortion temperature (HDT) restrict its wide application. On the other hand, Poly(butylene succinate) (PBS) is a biodegradable polymer with a low tensile modulus but characterized by a high flexibility, excellent impact strength, good thermal and chemical resistance. In this work the two aliphatic biodegradable polyesters PBS and PLA were selected with the aim to obtain a biodegradable material for the industry of plastic cups and plates. PBS was also blended with a thermoplastic starch. Talc was also added to the compounds because of its low cost and its effectiveness in increasing the modulus and the HDT of polymers. The compounds were obtained by melt compounding in a single screw extruder and the rheological, mechanical and thermal properties were investigated. The properties of the two compounds were compared and it was found that the values of the tensile modulus and elongation at break measured for the PBS/PLA/Talc compound make it interesting for the production of disposable plates and cups. In terms of thermal resistance the compounds have HDTs high enough to contain hot food or beverages. The PLA/PBS/Talc compound can be, then, considered as biodegradable substitute for polystyrene for the production of disposable plates and cups for hot food and beverages.

  1. Mechanical and biological properties of keratose biomaterials.

    PubMed

    de Guzman, Roche C; Merrill, Michelle R; Richter, Jillian R; Hamzi, Rawad I; Greengauz-Roberts, Olga K; Van Dyke, Mark E

    2011-11-01

    The oxidized form of extractable human hair keratin proteins, commonly referred to as keratose, is gaining interest as a biomaterial for multiple tissue engineering studies including those directed toward peripheral nerve, spinal cord, skin, and bone regeneration. Unlike its disulfide cross-linked counterpart, kerateine, keratose does not possess a covalently cross-linked network structure and consequently displays substantially different characteristics. In order to understand its mode(s) of action and potential for clinical translatability, detailed characterization of the composition, physical properties, and biological responses of keratose biomaterials are needed. Keratose was obtained from end-cut human hair fibers by peracetic acid treatment, followed by base extraction, and subsequent dialysis. Analysis of lyophilized keratose powder determined that it contains 99% proteins by mass with amino acid content similar to human hair cortex. Metallic elements were also found in minute quantities. Protein oxidation led to disulfide bond cleavage and drastic reduction of free thiols due to conversion of sulfhydryl to sulfonic acid, chain fragmentation, and amino acid modifications. Mass spectrometry identified the major protein constituents as a heterogeneous mixture of 15 hair keratins (type I: K31-35 and K37-39, and type II: K81-86) with small amounts of epithelial keratins which exist in monomeric, dimeric, multimeric, and even degraded forms. Re-hydration with PBS enabled molecular assembly into an elastic solid-like hydrogel. Highly-porous scaffolds formed by lyophilization of the gel had the compression behavior of a cellular foam material and reverted back to gel upon wetting. Cytotoxicity assays showed that the EC50 for various cell lines were attained at 8-10 mg/mL keratose, indicating the non-toxic nature of the material. Implantation in mouse subcutaneous tissue pockets demonstrated that keratose resorption follows a rectangular hyperbolic regression

  2. Mechanical properties of DNA-like polymers

    PubMed Central

    Peters, Justin P.; Yelgaonkar, Shweta P.; Srivatsan, Seergazhi G.; Tor, Yitzhak; James Maher, L.

    2013-01-01

    The molecular structure of the DNA double helix has been known for 60 years, but we remain surprisingly ignorant of the balance of forces that determine its mechanical properties. The DNA double helix is among the stiffest of all biopolymers, but neither theory nor experiment has provided a coherent understanding of the relative roles of attractive base stacking forces and repulsive electrostatic forces creating this stiffness. To gain insight, we have created a family of double-helical DNA-like polymers where one of the four normal bases is replaced with various cationic, anionic or neutral analogs. We apply DNA ligase-catalyzed cyclization kinetics experiments to measure the bending and twisting flexibilities of these polymers under low salt conditions. Interestingly, we show that these modifications alter DNA bending stiffness by only 20%, but have much stronger (5-fold) effects on twist flexibility. We suggest that rather than modifying DNA stiffness through a mechanism easily interpretable as electrostatic, the more dominant effect of neutral and charged base modifications is their ability to drive transitions to helical conformations different from canonical B-form DNA. PMID:24013560

  3. Photopatterning the mechanical properties of polydimethylsiloxane films

    NASA Astrophysics Data System (ADS)

    Cotton, D. P. J.; Popel, A.; Graz, I. M.; Lacour, S. P.

    2011-03-01

    Silicone rubber films with graded and localized mechanical properties are prepared using two-part polydimethylsiloxane (PDMS) elastomer, photoinhibitor compounds and conventional photolithography. First the un-cross-linked PDMS is mixed with benzophenone. The resulting positive photosensitive material is then exposed through a mask to UV light from a conventional mask aligner. Cross-linking of the UV exposed elastomer is inhibited, leading to softer regions than the surrounding unexposed matrix. By empirically fitting the nonlinear, hyperelastic Mooney-Rivlin model to experimentally measured stress-strain curves we determine the equivalent tensile modulus (E) of the rubber film. We show the PDMS tensile modulus can then be adjusted in the 0.65-2.9 MPa range by decreasing the UV exposure dose (from 24 000 to 0 mJ cm-2). Further, using a patterned UV mask, we can locally define differential regions of tensile modulus within a single PDMS rubber film. We demonstrate that "hard islands" (E ≈ 2.9 MPa) of 100 μm minimum diameter can be patterned within a 100-μm-thick, single "soft" PDMS rubber membrane (E ≈ 0.65 MPa) cured at 150 °C for 24 h. Thin gold film conductors patterned directly onto the photopatterned PDMS are stretchable and withstand uniaxial cycling to tens of percent strain. The mechanically "pixellated" PDMS rubber film provides an improved substrate with built-in strain relief for stretchable electronics.

  4. Trabecular Bone Mechanical Properties and Fractal Dimension

    NASA Technical Reports Server (NTRS)

    Hogan, Harry A.

    1996-01-01

    Countermeasures for reducing bone loss and muscle atrophy due to extended exposure to the microgravity environment of space are continuing to be developed and improved. An important component of this effort is finite element modeling of the lower extremity and spinal column. These models will permit analysis and evaluation specific to each individual and thereby provide more efficient and effective exercise protocols. Inflight countermeasures and post-flight rehabilitation can then be customized and targeted on a case-by-case basis. Recent Summer Faculty Fellowship participants have focused upon finite element mesh generation, muscle force estimation, and fractal calculations of trabecular bone microstructure. Methods have been developed for generating the three-dimensional geometry of the femur from serial section magnetic resonance images (MRI). The use of MRI as an imaging modality avoids excessive exposure to radiation associated with X-ray based methods. These images can also detect trabecular bone microstructure and architecture. The goal of the current research is to determine the degree to which the fractal dimension of trabecular architecture can be used to predict the mechanical properties of trabecular bone tissue. The elastic modulus and the ultimate strength (or strain) can then be estimated from non-invasive, non-radiating imaging and incorporated into the finite element models to more accurately represent the bone tissue of each individual of interest. Trabecular bone specimens from the proximal tibia are being studied in this first phase of the work. Detailed protocols and procedures have been developed for carrying test specimens through all of the steps of a multi-faceted test program. The test program begins with MRI and X-ray imaging of the whole bones before excising a smaller workpiece from the proximal tibia region. High resolution MRI scans are then made and the piece further cut into slabs (roughly 1 cm thick). The slabs are X-rayed again

  5. In Vivo Penetration Mechanics and Mechanical Properties of Mouse Brain Tissue at Micrometer Scales

    PubMed Central

    Sharp, Andrew A.; Ortega, Alicia M.; Restrepo, Diego; Curran-Everett, Douglas; Gall, Ken

    2010-01-01

    Substantial advancement in the understanding of the neuronal basis of behavior and the treatment of neurological disorders has been achieved via the implantation of various devices into the brain. To design and optimize the next generation of neuronal implants while striving to minimize tissue damage, it is necessary to understand the mechanics of probe insertion at relevant length scales. Unfortunately, a broad based understanding of brain-implant interactions at the necessary micrometer scales is largely missing. This paper presents a generalizable description of the micrometer scale penetration mechanics and material properties of mouse brain tissue in vivo. Cylindrical stainless steel probes were inserted into the cerebral cortex and olfactory bulb of mice. The effects of probe size, probe geometry, insertion rate, insertion location, animal age and the presence of the dura and pia on the resulting forces were measured continuously throughout probe insertion and removal. Material properties (modulus, cutting force, and frictional force) were extracted using mechanical analysis. The use of rigid, incompressible, cylindrical probes allows for a general understanding of how probe design and insertion methods influence the penetration mechanics of brain tissue in vivo that can be applied to the quantitative design of most future implantable devices. PMID:19224718

  6. Paullinia pinnata extracts rich in polyphenols promote vascular relaxation via endothelium-dependent mechanisms.

    PubMed

    Zamble, Alexis; Carpentier, Marie; Kandoussi, Abdelmejid; Sahpaz, Sevser; Petrault, Olivier; Ouk, Tawarak; Hennuyer, Nathalie; Fruchart, Jean-Charles; Staels, Bart; Bordet, Régis; Duriez, Patrick; Bailleul, François; Martin-Nizard, Françoise

    2006-04-01

    Paullinia pinnata L. (Sapindaceae) is an African tropical plant whose roots and leaves are used in traditional medicine for many purposes, especially for erectile dysfunction, but its action mechanism is unknown. P. pinnata root and leaf methanolic extracts are rich in phenolic compounds. This study shows that both extracts are highly antioxidative and induce a slight transcriptional activity of peroxisome proliferator activated receptor-alpha. They also increased and decreased endothelial nitric oxide synthase and endothelin-1 mRNA levels in bovine aortic endothelial cells, respectively. In this study P. pinnata methanolic extracts in cumulative doses elicited in a dose-dependent manner the relaxation of phenylephrine precontracted isolated rat aortic rings. N-nitro-L-arginine methyl ester significantly attenuated the capacity of both extracts to induce arterial relaxation, indicating that this arterial relaxation was mediated by endothelial nitric oxide release. It could be suggested that the arterial relaxation induced by both extracts could be mainly linked to their capacities to inhibit nitric oxide oxidation through their antioxidant properties.

  7. Mechanical Properties of a Single Cancellous Bone Trabeculae Taken from Bovine Femur

    NASA Astrophysics Data System (ADS)

    Enoki, Shinichi; Sato, Mitsuhiro; Tanaka, Kazuto; Katayama, Tsutao

    The increase of patients with osteoporosis is becoming a social problem, thus it is an urgent issue to find its prevention and treatment methods. Since cancellous bone is metabolically more active than cortical bone, cancellous bone is often used for diagnosis of osteoporosis and has received much attention within the study of bone. Bone is a hierarchically structured material and its mechanical properties vary at different structural levels, therefore it is important to break down the mechanical testing of bone according to the various levels within bone material. Mechanical properties of cancellous bone is said to be depended on quantities and orientation of trabecular bone. It is supposed that mechanical properties of trabecular bone are constant without depending on any structural arrangement and parts. However, such assumption has not been established in studies of trabecular bone. Furthermore test results have a large margin of error caused by insufficient shape assessment. In this study, three point bending tests of single cancellous bone trabeculae extracted from bovine femur were conducted to evaluate the effects of directions to the femur major axis direction on the mechanical properties. X-ray μCT was used to obtain shape of trabecular bone specimens. Furthermore compression tests of cancellous bone specimens, which were extracted in 10mm cubic geometry, were conducted for evaluation of directional properties.There were small difference in the elastic modulus of the trabecular bones which were extracted in parallel and in perpendicular to the major axis of femur. Considering from the results that the cancellous bone specimens, which were extracted in 10mm cubic geometry, have different elastic properties depending on the tested directions; the bone structure has larger influence than bone material property on the mechanical properties of cancellous bone.

  8. Mechanical properties of hydroxyapatite single crystals from nanoindentation data

    PubMed Central

    Zamiri, A.; De, S.

    2011-01-01

    In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

  9. Mechanical properties of hydroxyapatite single crystals from nanoindentation data.

    PubMed

    Zamiri, A; De, S

    2011-02-01

    In this paper we compute elastoplastic properties of hydroxyapatite single crystals from nanoindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young's modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from the existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals.

  10. Inhibitory mechanisms of two Uncaria tomentosa extracts affecting the Wnt-signaling pathway.

    PubMed

    Gurrola-Díaz, Carmen Magdalena; García-López, Pedro Macedonio; Gulewicz, Krzysztof; Pilarski, Radoslaw; Dihlmann, Susanne

    2011-06-15

    Uncaria tomentosa ("uña de gato"; "cat's claw"), a woody vine native to the Amazon rainforest, is commonly used in South American traditional medicine to treat a broad spectrum of diseases. Although recent studies have reported anti-inflammatory and anti-proliferative properties of different alkaloids extracted from this plant, the underlying molecular mechanisms of these effects have not been elucidated yet. Our study investigates the inhibitory mechanisms of Uncaria tomentosa extracts on the Wnt-signaling pathway, a central regulator of development and tissue homoeostasis. A modified cell-based luciferase assay for screening inhibitors of the Wnt-pathway was used for analysis. Three cancer cell lines displaying different levels of aberrant Wnt-signaling activity were transfected with Wnt-signaling responsive Tcf-reporter plasmids and treated with increasing concentrations of two Uncaria tomentosa bark extracts. Wnt-signaling activity was assessed by luciferase activity and by expression of Wnt-responsive target genes. We show that both, an aqueous and an alkaloid-enriched extract specifically inhibit Wnt-signaling activity in HeLa, HCT116 and SW480 cancer cells resulting in reduced expression of the Wnt-target gene: c-Myc. The alkaloid-enriched extract (B/S(rt)) was found to be more effective than the aqueous extract (B/W(37)). The strongest effect was observed in SW480 cells, displaying the highest endogenous Wnt-signaling activity. Downregulation of Wnt-signaling by a dominant negative-TCF-4 variant in non-cancer cells rendered the cells insensitive towards treatment with B/S(rt). B/Srt was less toxic in non-cancer cells than in cancer cells. Our data suggest that the broad spectrum of pharmacological action of Uncaria tomentosa involves inhibition of the Wnt-signaling pathway, downstream of beta-Catenin activity.

  11. Modification of Propellant Binder Network for Improvement of Mechanical Properties

    DTIC Science & Technology

    1984-12-01

    Propellant November 1982 to Binder Network for 71 November 1984 Improvement of Mechanical Properties December 1984 Author: Polymer Research Institute 4...determine the possibility of improving mechanical properties of energetic propellants via bimodal and/or multimodal * binder network formation. * 3.0... mechanical properties . 4.5 Effect of Temperature Improvements in stress/strain properties of all the polymer/PEG 8000 bimodal systems tend to be griater at 25

  12. Mechanical properties of β-HMX.

    PubMed

    Gallagher, Hugh G; Miller, John C; Sheen, David B; Sherwood, John N; Vrcelj, Ranko M

    2015-01-01

    For a full understanding of the mechanical properties of a material, it is essential to understand the defect structures and associated properties and microhardness indentation is a technique that can aid this understanding. The Vickers hardness on (010), {011} and {110} faces lay in the range of 304-363 MPa. The Knoop Hardnesses on the same faces lay in the range 314-482 MPa. From etching of three indented surfaces, the preferred slip planes have been identified as (001) and (101). For a dislocation glide, the most likely configuration for dislocation movement on the (001) planes is (001) [100] (|b| = 0.65 nm) and for the (101) plane as (101) [Formula: see text] (|b| = 1.084 nm) although (101) [010] (|b| = 1.105 nm) is possible. Tensile testing showed that at a stress value of 2.3 MPa primary twinning occurred and grew with increasing stress. When the stress was relaxed, the twins decreased in size, but did not disappear. The twinning shear strain was calculated to be 0.353 for the (101) twin plane. HMX is considered to be brittle, compared to other secondary explosives. Comparing HMX with a range of organic solids, the values for hardness numbers are similar to those of other brittle systems. Under the conditions developed beneath a pyramidal indenter, dislocation slip plays a major part in accommodating the local deformation stresses. Graphical abstractHMX undergoing tensile testing.

  13. On the mechanical properties of tooth enamel under spherical indentation.

    PubMed

    Chai, Herzl

    2014-11-01

    The mechanical properties of tooth enamel generally exhibit large variations, which reflect its structural and material complexity. Some key properties were evaluated under localized contact, simulating actual functioning conditions. Prominent cusps of extracted human molar teeth were polished down ~0.7 mm below the cusp tip and indented by tungsten carbide balls. The internal damage was assessed after unloading from longitudinal or transverse sections. The ultimate tensile stress (UTS) was determined using a novel bilayer specimen. The damage is characterized by penny-like radial cracks driven by hoop stresses and cylindrical cracks driven along protein-rich interrod materials by shear stresses. Shallow cone cracks typical of homogeneous materials which may cause rapid tooth wear under repeat contact are thus avoided. The mean stress vs. indentation strain curve is highly nonlinear, attributable to plastic shearing of protein between and within enamel rods. This curve is also affected by damage, especially radial cracks, the onset of which depends on ball radius. Several material properties were extracted from the tests, including shear strain at the onset of ring cracks γ(F) (=0.14), UTS (=119 MPa), toughness K(C) (=0.94 MPa m(1/2)), a crack propagation law and a constitutive response determined by trial and error with the aid of a finite-element analysis. These quantities, which are only slightly sensitive to anatomical location within the enamel region tested, facilitate a quantitative assessment of crown failure. Causes for variations in published UTS and K(C) values are discussed.

  14. Physicochemical properties of modified citrus pectins extracted from orange pomace.

    PubMed

    Venzon, Simoni Spohr; Canteri, Maria Helene Giovanetti; Granato, Daniel; Junior, Bogdan Demczuk; Maciel, Giselle Maria; Stafussa, Ana Paula; Haminiuk, Charles Windson Isidoro

    2015-07-01

    Modified pectin is a polysaccharide rich in galacturonic acid altered by pH adjustment and thermal treatment used especially as an anti-cancer agent. The aim of this work was to study the physical and chemical properties of modified pectins extracted from orange pomace with citric and nitric acids. The galacturonic acid content, degree of esterification, Fourier Transform Infrared Spectroscopy profile, molecular weight, intrinsic viscosity, rheological properties and antioxidant activity of the pectins were evaluated. The modification process caused the de-esterification of pectins and a decrease of molecular weight due to removal of neutral sugars, maintaining the linear chain of galacturonic acid. Such changes also caused a significant increase in the in vitro antioxidant activity (p ≤ 0.05) and influenced the rheological properties of pectin, reducing its viscosity. This work showed that the modification of pectin from orange pomace with citric and nitric acids altered its structural and physical characteristics as well as its biological activity toward a free-radical.

  15. Mechanical properties of thermal protection system materials.

    SciTech Connect

    Hardy, Robert Douglas; Bronowski, David R.; Lee, Moo Yul; Hofer, John H.

    2005-06-01

    An experimental study was conducted to measure the mechanical properties of the Thermal Protection System (TPS) materials used for the Space Shuttle. Three types of TPS materials (LI-900, LI-2200, and FRCI-12) were tested in 'in-plane' and 'out-of-plane' orientations. Four types of quasi-static mechanical tests (uniaxial tension, uniaxial compression, uniaxial strain, and shear) were performed under low (10{sup -4} to 10{sup -3}/s) and intermediate (1 to 10/s) strain rate conditions. In addition, split Hopkinson pressure bar tests were conducted to obtain the strength of the materials under a relatively higher strain rate ({approx}10{sup 2} to 10{sup 3}/s) condition. In general, TPS materials have higher strength and higher Young's modulus when tested in 'in-plane' than in 'through-the-thickness' orientation under compressive (unconfined and confined) and tensile stress conditions. In both stress conditions, the strength of the material increases as the strain rate increases. The rate of increase in LI-900 is relatively small compared to those for the other two TPS materials tested in this study. But, the Young's modulus appears to be insensitive to the different strain rates applied. The FRCI-12 material, designed to replace the heavier LI-2200, showed higher strengths under tensile and shear stress conditions. But, under a compressive stress condition, LI-2200 showed higher strength than FRCI-12. As far as the modulus is concerned, LI-2200 has higher Young's modulus both in compression and in tension. The shear modulus of FRCI-12 and LI-2200 fell in the same range.

  16. Cytoprotective properties of traditional Chinese medicinal herbal extracts in hydrogen peroxide challenged human U373 astroglia cells.

    PubMed

    Steele, Megan L; Truong, John; Govindaraghavan, Suresh; Ooi, Lezanne; Sucher, Nikolaus J; Münch, Gerald

    2013-04-01

    Age is the leading risk factor for many of the most prevalent and devastating diseases including neurodegenerative diseases. A number of herbal medicines have been used for centuries to ameliorate the deleterious effects of ageing-related diseases and increase longevity. Oxidative stress is believed to play a role in normal ageing as well as in neurodegenerative processes. Since many of the constituents of herbal extracts are known antioxidants, it is believed that restoring oxidative balance may be one of the underlying mechanisms by which medicinal herbs can protect against ageing and cognitive decline. Based on the premise that astrocytes are key modulators in the progression of oxidative stress associated neurodegenerative diseases, 13 herbal extracts purported to possess anti-ageing properties were tested for their ability to protect U373 human astrocytes from hydrogen peroxide induced cell death. To determine the contribution of antioxidant activity to the cytoprotective ability of extracts, total phenol content and radical scavenging capacities of extracts were examined. Polygonum multiflorum, amongst others, was identified as possessing potent antioxidant and cytoprotective properties. Not surprisingly, total phenol content of extracts was strongly correlated with antioxidant capacity. Interestingly, when total phenol content and radical scavenging capacities of extracts were compared to the cytoprotective properties of extracts, only moderately strong correlations were observed. This finding suggests the involvement of multiple protective mechanisms in the beneficial effects of these medicinal herbs. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Extraction of petroleum hydrocarbons from soil by mechanical shaking

    SciTech Connect

    Schwab, A.P.; Su, J.; Wetzel, S.; Pekarek, S.; Banks, M.K.

    1999-06-01

    A shaking extraction method for petroleum hydrocarbons in soil was developed and compared to Soxhlet extraction. Soxhlet extraction is an EPA-approved method for volatile and semivolatile organic contaminants from solid materials, but it has many disadvantages including long extraction periods and potential loss of volatile compounds. When field-moist soils are used, variability in subsamples is higher, and the extraction of hydrocarbons with a nonpolar solvent may be less efficient. A shaking method was designed to fill the need for simpler and more efficient extraction of petroleum hydrocarbons from soil. A systematic study of extraction conditions was performed for various soil types, soil weights, solvents, extraction times, and extraction cycles. The results were compared to those for Soxhlet extraction. Shaking 1 g of soil with a sequence of three 10-mL aliquots of dichloromethane or acetone was found to be equivalent to Soxhlet extraction for total petroleum hydrocarbons and polycyclic aromatic hydrocarbons. Shaking with acetone was more consistent than all other methods for the extraction of specific compounds from aged, contaminated soil. The shaking method appears to be applicable to a wide range of soil types and petroleum contaminants but should be compared to Soxhlet extraction for new conditions.

  18. Antioxidant properties of various solvent extracts of potato peel, sugar beet pulp and sesame cake.

    PubMed

    Mohdaly, Adel A A; Sarhan, Mohamed A; Smetanska, Iryna; Mahmoud, Awad

    2010-01-30

    Growing interest in the replacement of synthetic food antioxidants by natural ones has fostered research on vegetable sources and screening of raw materials to identify new antioxidants. The food-processing industry generates substantial quantities of phenolic-rich by-products that could be valuable natural sources of antioxidants. In this study the antioxidant properties and total phenolic, flavonoid and flavonol contents of three industrial by-products, sugar beet pulp, sesame cake and potato peel, extracted with various solvents were examined. Since different antioxidant compounds have different mechanisms of action, several methods were used to assess the antioxidant efficacy of extracts. Among the six solvents tested, methanol gave the highest extract yield of potato peel and sugar beet pulp, while diethyl ether gave the highest extract yield of sesame cake. Methanol exhibited the highest extraction ability for phenolic compounds, with total phenolics amounting to 2.91, 1.79 and 0.81 mg gallic acid equivalent g(-1) dry weight in potato peel, sugar beet pulp and sesame cake extracts respectively, and also showed the strongest antioxidant capacity in the three assays used. All three methods proved that potato peel extract had the highest antioxidant activity owing to its high content of phenolic compounds and flavonoids. On the basis of the results obtained, potato peel, sugar beet pulp and sesame cake extracts could serve as natural antioxidants owing to their significant antioxidant activity. Therefore they could be used as preservative ingredients in the food and/or pharmaceutical industries. (c) 2009 Society of Chemical Industry.

  19. Mechanical Properties of Nuclear Fuel Surrogates using Picosecond Laser Ultrasonics

    SciTech Connect

    David Hurley; Marat Khafizov; Farhad Farzbod; Eric Burgett

    2013-05-01

    Detailed understanding between microstructure evolution and mechanical properties is important for designing new high burnup nuclear fuels. In this presentation we discuss the use of picosecond ultrasonics to measure localize changes in mechanical properties of fuel surrogates. We develop measurement techniques that can be applied to investigate heterogeneous elastic properties caused by localize changes in chemistry, grain microstructure caused by recrystallization, and mechanical properties of small samples prepared using focused ion beam sample preparation. Emphasis is placed on understanding the relationship between microstructure and mechanical properties

  20. Possible antiosteoporotic mechanism of Cicer arietinum extract in ovariectomized rats

    PubMed Central

    Fahmy, Sohair R; Soliman, Amel M; Sayed, Amany A; Marzouk, Mohamed

    2015-01-01

    Objective: The present study aimed to throw the light on the anti-osteoprotic mechanism of Cicer arietinum extract (CAE) seeds against ovariectomized (OVX) rats. Methods: Seventy female rats were divided into two groups. The first group (14 rats/group) represented normal rats (Sham operated) while the second group (56 rats/group) underwent bilateral ovariectomy (OVX). After one week of recovery from ovariectomy surgery, the second group was randomly subdivided into 4 subgroups (14 rats/ each subgroup). The rats administered orally; distilled water (vehicle) (1st subgroup), Cicer arietinum extract (CAE) (500 or 1000 mg/kg body weight/day) (2nd and 3rd subgroups), alendronate (6.5 mg/kg mg/kg body weight) as a positive control one time/week (4rh subgroup), daily for 10 weeks. Results: The present study demonstrated that ovariectomy caused significant decrease in bone mineral; density (BMD) and content (BMC), Bone-specific alkaline phosphatase (BALP), calcium (Ca), phosphorus (P), parathyroid hormone (PTH) and calcitonin levels. Furthermore, ovariectomy induced significant elevation of tartrate-resistant acid phosphatase 5b (TRAP 5b) and receptor activator of nuclear factor (NF-kappa β) ligand (RANKL) concentration. Conversely, osteoprotegerin (OPG) and OPG/RANKL ratio were decreased following ovariectomy. The present work suggests that CAE has antiosteoporotic action against ovariectomy effects and its activity may results from its phytochemical and/or phytoestrogen contents. Conclusion: The ongoing study speculates that the CAE exerts its action through regulation of RANK/RANKL/OPG system. As, CAE not only promotes osteoblast differentiation, but also up-regulates OPG and downregulates RANKL secretion in osteoblasts, subsequently prevents bone loss and osteoporosis. PMID:26097532

  1. Possible antiosteoporotic mechanism of Cicer arietinum extract in ovariectomized rats.

    PubMed

    Fahmy, Sohair R; Soliman, Amel M; Sayed, Amany A; Marzouk, Mohamed

    2015-01-01

    The present study aimed to throw the light on the anti-osteoprotic mechanism of Cicer arietinum extract (CAE) seeds against ovariectomized (OVX) rats. Seventy female rats were divided into two groups. The first group (14 rats/group) represented normal rats (Sham operated) while the second group (56 rats/group) underwent bilateral ovariectomy (OVX). After one week of recovery from ovariectomy surgery, the second group was randomly subdivided into 4 subgroups (14 rats/ each subgroup). The rats administered orally; distilled water (vehicle) (1st subgroup), Cicer arietinum extract (CAE) (500 or 1000 mg/kg body weight/day) (2nd and 3rd subgroups), alendronate (6.5 mg/kg mg/kg body weight) as a positive control one time/week (4(rh) subgroup), daily for 10 weeks. The present study demonstrated that ovariectomy caused significant decrease in bone mineral; density (BMD) and content (BMC), Bone-specific alkaline phosphatase (BALP), calcium (Ca), phosphorus (P), parathyroid hormone (PTH) and calcitonin levels. Furthermore, ovariectomy induced significant elevation of tartrate-resistant acid phosphatase 5b (TRAP 5b) and receptor activator of nuclear factor (NF-kappa β) ligand (RANKL) concentration. Conversely, osteoprotegerin (OPG) and OPG/RANKL ratio were decreased following ovariectomy. The present work suggests that CAE has antiosteoporotic action against ovariectomy effects and its activity may results from its phytochemical and/or phytoestrogen contents. The ongoing study speculates that the CAE exerts its action through regulation of RANK/RANKL/OPG system. As, CAE not only promotes osteoblast differentiation, but also up-regulates OPG and downregulates RANKL secretion in osteoblasts, subsequently prevents bone loss and osteoporosis.

  2. Mechanical properties of cervical dura mater.

    PubMed

    Mazgajczyk, Emilia; Ścigała, Krzysztof; Czyż, Marcin; Jarmundowicz, Włodzimierz; Będziński, Romuald

    2012-01-01

    The aim of the study was to determine experimentally the stress as strain function as well as the orthotropy and heterogeneity of porcine dura mater of the cervical spinal cord. Material was divided into groups based on the place of collection, considering the dorsal side and ventral side, specifying the number of cervical vertebra, and the direction of tension of the sample - longitudinal or circumferential. Experimental studies were conducted with the MTS Synergie 100 testing machine. The tensile test was performed for each sample at a speed of 2 mm/min until the sample's break. There were determined the characteristics of stress as a function of strain in particular samples. Distribution maps of the stress and strain values at the characteristic points were then drawn (the beginning and the end of the linear range of the stress-strain characteristic and the point corresponding to the complete sample damage) for each set of samples, taking account of their collection place and direction of tension. The results confirmed the orthotropy of mechanical properties of dura mater. Stress and strain differed also in the value at the height of each vertebra and exhibited diversification on the ventral side compared to dorsal one.

  3. Fluid Mechanical Properties of Silkworm Fibroin Solutions

    NASA Astrophysics Data System (ADS)

    Matsumoto, Akira

    2005-11-01

    The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

  4. Mechanical properties of lattice grid composites

    NASA Astrophysics Data System (ADS)

    Fan, Hualin; Fang, Daining; Jin, Fengnian

    2008-08-01

    An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid composite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.

  5. Mechanical Properties of the Upper Airway

    PubMed Central

    Strohl, Kingman P.; Butler, James P.; Malhotra, Atul

    2013-01-01

    The importance of the upper airway (nose, pharynx, and larynx) in health and in the pathogenesis of sleep apnea, asthma, and other airway diseases, discussed elsewhere in the Comprehensive Physiology series, prompts this review of the biomechanical properties and functional aspects of the upper airway. There is a literature based on anatomic or structural descriptions in static circumstances, albeit studied in limited numbers of individuals in both health and disease. As for dynamic features, the literature is limited to studies of pressure and flow through all or parts of the upper airway and to the effects of muscle activation on such features; however, the links between structure and function through airway size, shape, and compliance remain a topic that is completely open for investigation, particularly through analyses using concepts of fluid and structural mechanics. Throughout are included both historically seminal references, as well as those serving as signposts or updated reviews. This article should be considered a resource for concepts needed for the application of biomechanical models of upper airway physiology, applicable to understanding the pathophysiology of disease and anticipated results of treatment interventions. PMID:23723026

  6. Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics.

    PubMed

    Napper, Imogen E; Bakir, Adil; Rowland, Steven J; Thompson, Richard C

    2015-10-15

    Cosmetic products, such as facial scrubs, have been identified as potentially important primary sources of microplastics to the marine environment. This study characterises, quantifies and then investigates the sorptive properties of plastic microbeads that are used as exfoliants in cosmetics. Polyethylene microbeads were extracted from several products, and shown to have a wide size range (mean diameters between 164 and 327 μm). We estimated that between 4594 and 94,500 microbeads could be released in a single use. To examine the potential for microbeads to accumulate and transport chemicals they were exposed to a binary mixture of (3)H-phenanthrene and (14)C-DDT in seawater. The potential for transport of sorbed chemicals by microbeads was broadly similar to that of polythene (PE) particles used in previous sorption studies. In conclusion, cosmetic exfoliants are a potentially important, yet preventable source of microplastic contamination in the marine environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Physicochemical and functional properties of gelatin extracted from Yak skin.

    PubMed

    Xu, Mengqi; Wei, Lixin; Xiao, Yuancan; Bi, Hongtao; Yang, Hongxia; Du, Yuzhi

    2017-02-01

    Different molecular weight distribution (MWD) gelatin was extracted from Yak skin after enzymatic pretreatments and their physicochemical and functional properties (SDS-PAGE, UV-vis absorption spectra, DSC, FT-IR, Amino acid analysis, AFM, emulsibility and foamability) were analyzed. The gelatin was extracted by pepsin and got different MWD of Yak skin gelatin by controlling the enzymolysis time. The SDS-PAGE showed the MWD of the Yak skin gelatin. The UV-vis absorption turned out that the broad MWD of Yak skin gelatin had a higher maximum absorption peaks. The FT-IR and AFM indicated that the gelatin structures and microstructures changed with the change of the MWD. The broad MWD of the Yak skin gelatin had a higher denaturation temperature (TD), and it was higher than most of the other mammals and marine biological gelatin. The broad MWD gelatin also had higher imino acids (proline and hydroxyproline) contents and lower foamability and emulsibility compared to the narrow MWD gelatin. These findings, obtained for the first time for Yak skin gelatin, showed that it has great potential for application as an alternative to commercial gelatin due to its good thermotolerance, particularly in the applications of the biological materials, stabilizer of thermo-tolerant and so on. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Inhibition properties of propolis extracts to some clinically important enzymes.

    PubMed

    Baltas, Nimet; Yildiz, Oktay; Kolayli, Sevgi

    2016-01-01

    The present study was conducted to envisage inhibition effects of propolis on the crucial enzymes, urease, xanthine oxidase (XO) and acetylcholinesterase (AChE). Some of the antioxidant properties of the propolis samples were determined using the total phenolic content (TPE) and total flavonoids in the eight different ethanolic propolis extracts (EPE) samples. Inhibition values of the enzymes were expressed as inhibition concentration (IC50; mg/mL or μg/mL) causing 50% inhibition of the enzymes with donepezil, acetohydroxamic acid and allopurinol as reference inhibitors. All the propolis extracts exhibited variable inhibition effects on these enzymes, but the higher the phenolic contents the lower the inhibitions values (IC50 = 0.074 to 1.560 mg/mL). IC50 values of the P5 propolis sample having the highest TPE, obtained from Zonguldak, for AChE, urease and XO were 0.081 ± 0.009, 0.080 ± 0.006 and 0.074 ± 0.011 μg/mL, respectively. The EPE proved to be a good source of inhibitor agents that can be used as natural inhibitors to serve human health.

  9. Anthelmintic properties of extracts from Artemisia plants against nematodes.

    PubMed

    Khan, S; Afshan, K; Mirza, B; Miller, J E; Manan, A; Irum, S; Rizvi, S S R; Qayyum, M

    2015-06-01

    Artemisia plant genus, natural inhabitant of northern Punjab Pakistan, is well known for its anthelmintic properties; many Artemisia species have not been so far scientifically proved. The aim of this study was to assess in vitro anthelmintic activity of Artemisia indica and Artemisia roxburghiana against mixed infection of gastrointestinal nematodes in small ruminants. This study is first scientifically proven study on anthelmintic activity of A. indica and A. roxburghiana. Five different concentrations (50, 25, 12.5, 6.25 and 3.75 mg/mL) accompanied by negative control (PBS) and positive control (albendazole, 10%) were used to carry out the egg hatch inhibition assay, larval mortality assay and adult worm mortality assay. The Baermann technique was used first time in larval mortality assay and proved to be effective. The results revealed that methanolic extracts of both A. indica and A. roxburghiana, showed maximum anthelmintic activity at concentration of 50 mg/ml by egg hatch inhibition (85±21.2; 80±28.3), larvae mortality (18±2.8; 17±4.2) and adult worm mortality (8.5±2.1; 8±2.8) assays. However, at concentration of 50 mg/ml both plant extracts in comparison to albendazole showed statistically insignificant (p≤0.05) results. The A. indica showed higher anthelmintic activity at all concentrations as compared to A. roburghiana. It has been concluded both plants exhibit anthelmintic activity and further evaluation of these plants should be carried out to purify the active ingredients for anthelmintic activity. Moreover, the decoctions of these plants could be used to GINs after confirming anthelmintic properties through in vivo.

  10. Mechanical properties of spindle poles are symmetrically balanced

    PubMed Central

    Suzuki, Kazuya; Itabashi, Takeshi; Ishiwata, Shin’ichi

    2017-01-01

    The metaphase spindle is organized for accurate chromosome segregation. One of the fundamental features of the spindle across the species is its symmetrical shape; the spindle consists of two polar arrays of microtubules at both ends. Although it has been suggested that the formation of the bipolar shape requires force balance coordination by molecular motors, i.e., kinesins and dyneins, quantitative analysis for the pole mechanics has not been conducted. Here, we demonstrate that it is not only the shape but also the stiffness and microtubule density of the pairs of pole regions are symmetrically balanced in single spindles self-assembled in Xenopus egg extracts. We found that the inhibition of dynein functions dramatically reduced the stiffness and microtubule density in the pole region. By contrast, the inhibition of one of the kinesins, Eg5, which is the antagonistic motor protein of dynein, increased the value of these parameters. Moreover, the inhibition of both dynein and Eg5 recovered these parameter values to those of non-treated spindle poles. We also found that, when one pole structure was held widened with the use of two glass microneedles, the opposite pole structure spontaneously widened, resulting in the formation of the barrel-like shaped spindle. The values of stiffness and microtubule density in the manipulated pole region decreased, following the spontaneous decrement of those in the paired unmanipulated pole region. These results suggest that the spindle possesses a mechanism to dynamically maintain its symmetry in mechanical properties. PMID:28409085

  11. Mechanical properties of spindle poles are symmetrically balanced.

    PubMed

    Suzuki, Kazuya; Itabashi, Takeshi; Ishiwata, Shin'ichi

    2017-01-01

    The metaphase spindle is organized for accurate chromosome segregation. One of the fundamental features of the spindle across the species is its symmetrical shape; the spindle consists of two polar arrays of microtubules at both ends. Although it has been suggested that the formation of the bipolar shape requires force balance coordination by molecular motors, i.e., kinesins and dyneins, quantitative analysis for the pole mechanics has not been conducted. Here, we demonstrate that it is not only the shape but also the stiffness and microtubule density of the pairs of pole regions are symmetrically balanced in single spindles self-assembled in Xenopus egg extracts. We found that the inhibition of dynein functions dramatically reduced the stiffness and microtubule density in the pole region. By contrast, the inhibition of one of the kinesins, Eg5, which is the antagonistic motor protein of dynein, increased the value of these parameters. Moreover, the inhibition of both dynein and Eg5 recovered these parameter values to those of non-treated spindle poles. We also found that, when one pole structure was held widened with the use of two glass microneedles, the opposite pole structure spontaneously widened, resulting in the formation of the barrel-like shaped spindle. The values of stiffness and microtubule density in the manipulated pole region decreased, following the spontaneous decrement of those in the paired unmanipulated pole region. These results suggest that the spindle possesses a mechanism to dynamically maintain its symmetry in mechanical properties.

  12. Mechanical properties of the porcine growth plate vary with developmental stage.

    PubMed

    Wosu, Roxanne; Sergerie, Kim; Lévesque, Martin; Villemure, Isabelle

    2012-03-01

    The objectives of this study were to extract the intrinsic mechanical properties of the growth plate at four different stages of growth and to compare two different methods of extracting these properties. Porcine distal ulnar growth plate samples were obtained from newborn, 4-, 8-, and 18-week (W) pigs and were tested using stress relaxation tests under unconfined compression. A four-parameter curve fitting procedure was developed to extract mechanical properties using the Transversely Isotropic Biphasic Elastic model(TIBPE) (Cohen et al. in J Biomech Eng Trans Asme 120(4):491-496, 1998) and the Differential Evolution (DE) optimization algorithm (Price et al. Natural computing series, Springer, Germany 2005). Optimization was done on all experimental curves for the first method and on one average experimental curve per developmental stage in the second. The 4-week stage was studied in two subgroups (a) and (b) due to distinct differences in mechanical properties. Intrinsic mechanical properties of the growth plate varied nonlinearly with developmental stage. Both methods showed that transverse and out-of-plane Young's moduli (E (1), E (3)) decrease with developmental stage, whereas transverse permeability (k (1)) increases. The exception is a sharp increase in stiffness and reduction in permeability at the 4W(a) stage, which may be associated with rapid porcine developmental changes at the 3-4 week period. The second method provides a more reliable representation of the average mechanical behavior, whereas the first method allows statistical comparison of optimized mechanical properties. This study characterizes, for the first time, the variation in growth plate mechanical properties for the same animal (porcine) and bone (ulna) model with developmental stage and provides new insight into the progression of musculoskeletal diseases during growth spurts in response to mechanical loading.

  13. Anticholinesterase and Antioxidative Properties of Aqueous Extract of Cola acuminata Seed In Vitro

    PubMed Central

    Akinyemi, Ayodele J.; Omojokun, Olasunkanmi S.; Oyeleye, Idowu S.

    2014-01-01

    Background. Cola acuminata seed, a commonly used stimulant in Nigeria, has been reportedly used for the management of neurodegenerative diseases in folklore without scientific basis. This study sought to investigate the anticholinesterase and antioxidant properties of aqueous extracts from C. acuminata seed in vitro. Methodology. The aqueous extract of C. acuminata seed was prepared (w/v) and its effect on acetylcholinesterase (AChE) and butyrylcholinesterase activities, as well as some prooxidant (FeSO4, sodium nitroprusside (SNP), and quinolinic acid (QA)) induced lipid peroxidation in rat brain in vitro, was investigated. Results. The results revealed that C. acuminata seed extract inhibited AChE (IC50 = 14.6 μg/mL) and BChE (IC50 = 96.2 μg/mL) activities in a dose-dependent manner. Furthermore, incubation of rat's brain homogenates with some prooxidants caused a significant increase P < 0.05 in the brain malondialdehyde (MDA) content and inhibited MDA production dose-dependently and also exhibited further antioxidant properties as typified by their high radicals scavenging and Fe2+ chelating abilities. Conclusion. Inhibition of AChE and BChE activities has been the primary treatment method for mild Alzheimer's disease (AD). Therefore, one possible mechanism through which the seed exerts its neuroprotective properties is by inhibiting cholinesterase activities as well as preventing oxidative-stress-induced neurodegeneration. However, this is a preliminary study with possible physiological implications. PMID:25506036

  14. Artocarpin-enriched (Artocarpus altilis) Heartwood Extract Provides Protection Against UVB-induced Mechanical Damage in Dermal Fibroblasts.

    PubMed

    Tiraravesit, Narisara; Humbert, Philippe; Robin, Sophie; Tissot, Marion; Viennet, Céline; Viyoch, Jarupa

    2017-10-01

    This study aimed to evaluate the protective effect of artocarpin-enriched (Artocarpus altilis) heartwood extract on the mechanical properties of UVB-irradiated fibroblasts. Human skin fibroblasts were pretreated with 50 μg/mL(-1) extract and later irradiated with UVB (200 mJ/cm(-2) ). They were then cultured within three-dimensional of free-floating and tense collagen lattices. The pretreatment of fibroblasts with the extract prior to UVB radiation showed cells protection against UVB-induced suppression of α-SMA expression, fibroblast migration and contraction. These results reveal that the extract prevents mechanical damages induced by UVB irradiation in fibroblast-embedded collagen lattices, and therefore, has a potential as a natural photo-protectant. © 2017 The American Society of Photobiology.

  15. Auxetic oesophageal stents: structure and mechanical properties.

    PubMed

    Ali, Murtaza Najabat; Busfield, James J C; Rehman, Ihtesham U

    2014-02-01

    Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure

  16. Cell Mechanosensitivity: Mechanical Properties and Interaction with Gravitational Field

    PubMed Central

    Ogneva, I. V.

    2013-01-01

    This paper addressed the possible mechanisms of primary reception of a mechanical stimulus by different cells. Data concerning the stiffness of muscle and nonmuscle cells as measured by atomic force microscopy are provided. The changes in the mechanical properties of cells that occur under changed external mechanical tension are presented, and the initial stages of mechanical signal transduction are considered. The possible mechanism of perception of different external mechanical signals by cells is suggested. PMID:23509748

  17. Cell mechanosensitivity: mechanical properties and interaction with gravitational field.

    PubMed

    Ogneva, I V

    2013-01-01

    This paper addressed the possible mechanisms of primary reception of a mechanical stimulus by different cells. Data concerning the stiffness of muscle and nonmuscle cells as measured by atomic force microscopy are provided. The changes in the mechanical properties of cells that occur under changed external mechanical tension are presented, and the initial stages of mechanical signal transduction are considered. The possible mechanism of perception of different external mechanical signals by cells is suggested.

  18. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti-Ag sintered alloys.

    PubMed

    Chen, Mian; Zhang, Erlin; Zhang, Lan

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti-Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti-Ag phase, residual pure Ag and Ti were the mainly phases in Ti-Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti-Ag(S10) sintered alloy. The mechanical test indicated that Ti-Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti-Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti-Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution.

  19. Evaluation of wound healing properties of Arrabidaea chica Verlot extract.

    PubMed

    Jorge, Michelle Pedroza; Madjarof, Cristiana; Gois Ruiz, Ana Lúcia Tasca; Fernandes, Alik Teixeira; Ferreira Rodrigues, Rodney Alexandre; de Oliveira Sousa, Ilza Maria; Foglio, Mary Ann; de Carvalho, João Ernesto

    2008-08-13

    Arrabidaea chica Verlot. (Bignoniaceae), popularly known as Crajiru, has been traditionally used as wound healing agent. Investigate in vitro and in vivo healing properties of Arrabidaea chica leaves extract (AC). AC was evaluated in vitro in fibroblast growth stimulation (0.25-250 microg/mL) and collagen production stimulation (250 microg/mL) assays. Allantoin (0.25-250 microg/mL) and vitamin C (25 microg/mL) were used as controls respectively. DPPH and Folin-Ciocalteau assays were used for antioxidant evaluation, using trolox (0.25-250 microg/mL) as reference antioxidant. To study wound healing properties in rats, AC (100mg/mL, 200 microL/wound/day) was topically administered during 10 days and wound area was evaluated every day. Allantoin (100mg/mL, 200 microL/wound/day) was used as standard drug. After treatment, wound sites were removed for histopathological analysis and total collagen determination. AC stimulated fibroblast growth in a concentration dependent way (EC50=30 microg/mL), increased in vitro collagen production and demonstrated moderate antioxidant capacity. In vivo, AC reduced wound size in 96%, whereas saline group showed only 36% wound healing. AC efficiency seems to involve fibroblast growing stimulus and collagen synthesis both in vitro and in vivo, beyond moderate scavenging activity, corroborating Crajiru folk use.

  20. Flexible Mechanical Conveyors for Regolith Extraction and Transport

    NASA Technical Reports Server (NTRS)

    Walton, Otis R.; Vollmer, Hubert J.

    2013-01-01

    A report describes flexible mechanical conveying systems for transporting fine cohesive regolith under microgravity and vacuum conditions. They are totally enclosed, virtually dust-free, and can include enough flexibility in the conveying path to enable an expanded range of extraction and transport scenarios, including nonlinear drill-holes and excavation of enlarged subsurface openings without large entry holes. The design of the conveyors is a modification of conventional screw conveyors such that the central screw-shaft and the outer housing or conveyingtube have a degree of bending flexibility, allowing the conveyors to become nonlinear conveying systems that can convey around gentle bends. The central flexible shaft is similar to those used in common tools like a weed whacker, consisting of multiple layers of tightly wound wires around a central wire core. Utilization of compliant components (screw blade or outer wall) increases the robustness of the conveying, allowing an occasional oversized particle to pass hough the conveyor without causing a jam or stoppage

  1. Statistical mechanical description of supercritical fluid extraction and retrograde condensation

    NASA Astrophysics Data System (ADS)

    Park, S. J.; Kwak, T. Y.; Mansoori, G. A.

    1987-07-01

    The phenomena of supercritical fluid extraction (SFE) and its reverse effect, which is known as retrograde condensation (RC), have found new and important applications in industrial separation of chemical compounds and recovery and processing of natural products and fossil fuels. Full-scale industrial utilization of SFE/RC processes requires knowledge about thermodynamic and transport characteristics of the asymmetric mixtures involved and the development of predictive modeling and correlation techniques for performance of the SFE/RC system under consideration. In this report, through the application of statistical mechanical techniques, the reasons for the lack of accuracy of existing predictive approaches are described and they are improved. It is demonstrated that these techniques also allow us to study the effect of mixed supercritical solvents on the solubility of heavy solutes (solids) at different compositions of the solvents, pressures, and temperatures. Fluid phase equilibrium algorithms based on the conformal solution van der Waals mixing rules and different equations of state are presented for the prediction of solubilities of heavy liquid in supercritical gases. It is shown that the Peng-Robinson equation of state based on conformal solution theory can predict solubilites of heavy liquid in supercritical gases more accurately than the van der Waals and Redlich-Kwong equations of state.

  2. Antihemorrhagic, antinucleolytic and other antiophidian properties of the aqueous extract from Pentaclethra macroloba.

    PubMed

    da Silva, Jocivânia O; Coppede, Juliana S; Fernandes, Vanessa C; Sant'ana, Carolina D; Ticli, Fábio K; Mazzi, Maurício V; Giglio, José R; Pereira, Paulo S; Soares, Andreimar M; Sampaio, Suely V

    2005-08-22

    Several Brazilian plants have been utilized in folk medicine as active agents against various effects induced by snake venoms. The inhabitants of the Amazon region use, among others, the macerated bark of a plant popularly named "Pracaxi" (Pentaclethra macroloba Willd) to combat these effects. We report now the antihemorrhagic properties against snake venoms of the aqueous extract of Pentaclethra macroloba (EPema). EPema exhibited full inhibition of hemorrhagic and nucleolytic activities induced by several snake venoms. Additionally, partial inhibition of myotoxic, lethal, phospholipase and edema activities of snake venoms and its isolated PLA(2)s by EPema is reported. In vivo tests showed that EPema is able to totally inhibit a Bothrops jararacussu metalloprotease (BjussuMP-I) induced hemorrhage, suggesting interaction of the extract compounds with this high molecular weight protein. The extract did induce neither hemorrhage nor death in mice when administered alone by i.m. route. When administered separately by i.m. route, the extract did not induce death in mice at 12.5--300 mg/kg doses. Other assays demonstrated that EPema was unable to inhibit fibrinogenolytic and coagulant activities of Bothrops atrox venom. Although the mechanism of action of EPema is still unknown, the finding that no visible change was detected in the electrophoretic pattern of snake venom after incubation with the extract excludes proteolytic degradation as a potential mechanism. The search for new inhibitors of venom metalloproteases and DNAases are a relevant task. Investigation of snake venom inhibitors can provide useful tools for the elucidation of the action mechanisms of purified toxins. Furthermore, these inhibitors can be used as molecular models for development of new therapeutical agents in the treatment of ophidian accidents.

  3. Rectangular waveguide material characterization: anisotropic property extraction and measurement validation

    NASA Astrophysics Data System (ADS)

    Crowgey, Benjamin Reid

    for characterization of a sample filling the cross-section of a waveguide. Due to the rectangular nature of the waveguide, typically three different samples are manufactured from the same material in order to characterize the six complex material parameters. The second technique for measuring the electromagnetic properties of a biaxially anisotropic material sample uses a reduced-aperture waveguide sample holder designed to accommodate a cubical sample. All the tensor material parameters can then be determined by measuring the reflection and transmission coefficients of a single sample placed into several orientations. The parameters are obtained using a root-searching algorithm by comparing theoretically computed and measured reflection and transmission coefficients. The theoretical coefficients are determined using a mode matching technique. The first technique for characterizing the electromagnetic properties of gyromagnetic materials considers requires filling the cross-section of a waveguide. The material parameters are extracted from the measured reflection and transmission coefficients. Since the cross-sectional dimensions of waveguides become prohibitively large at low frequencies, and it is at these frequencies that the gyromagnetic properties are most pronounced, sufficiently large samples may not be available. Therefore, the second technique uses a reduced-aperture sample holder that does not require the sample to fill the entire cross section of the guide. The theoretical reflection and transmission coefficients for both methods are determined using a mode matching technique. A nonlinear least squares method is employed to extract the gyromagnetic material parameters. Finally, this dissertation introduces a waveguide standard that acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the NRW technique. A genetic algorithm is used to optimize the all

  4. Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites

    DTIC Science & Technology

    2010-03-15

    technical report 3. DATES COVERED (From - To) From Ol-Jan-2007 to 31 -Dec-2009 4. TITLE AND SUBTITLE Modeling of Mechanical Properties of Advanced ...for puj^Ux^ r^Wse_- dC5+rvioockd>v^ <JMT4MTLC4<JSI . 13. SUPPLEMENTARY NOTES 14. ABSTRACT Mechanical properties of advanced nanostructured...Modeling of Mechanical Properties of Advanced Nanostructured Ceramic Composites Program Officer: Larry Kabacoff CO-PI Information Number of Co-PIs

  5. Mechanical Properties of Several Magnesium and Aluminum Composites

    DTIC Science & Technology

    1992-12-01

    34AD-A262 481 ARMY RESEARCH LABORATORY Mechanical Properties of Several Magnesium and Aluminum Composites Nikos Tsangarakis and Barmac Taleghani ARL...ESJEI L .PwmOM N.ajmns Mechanical Properties of Several Magnesium and Aluminum Composites 2.AUIwORU Nikos Tsangarakis and Barmac Taleghani 7. PERONUMMN...Several composites of magnesiumn and aluminum alloys were tested In order to assess and evaluate their mechanical properties . The magnesium alloys were

  6. Mechanical Properties of Ceramics for High Temperature Applications

    DTIC Science & Technology

    1976-12-01

    U.S. DEPARTMENT OF COMMERCE National Technical Information Service AD-A034 262 MFIHANICAL PROPERTIES OF CERAMICS FOR HIGH TEMPERATURE APPLICATIONS...Atlantic Treaty Organization 7 rue Ancelle, 92200 Neujily sur Seinle, France 6.TtlcMECHANICAL PROPERTIES OF CERAMICS FOR HIGH TEMPERATURE APPLICATIONS...whlichi are outlined onl thle Outside Back Covers of all AGARI) publications. 13. Key words/Descriptors . Ceramics Fracture properties Mechanical properties

  7. In vitro studies to evaluate the wound healing properties of Calendula officinalis extracts.

    PubMed

    Nicolaus, Christoph; Junghanns, Susanne; Hartmann, Anja; Murillo, Renato; Ganzera, Markus; Merfort, Irmgard

    2017-01-20

    Calendula officinalis (pot marigold) flower extracts have a long-lasting tradition in ethnopharmacology. Currently, the European Medicines Agency (EMA) has approved its lipophilic and aqueous alcoholic extracts as traditional medicinal products for the treatment of minor inflammation of the skin and as an aid in the healing of minor wounds. The purpose of this study was to analyse the molecular mechanism of the wound healing effects of Calendula extracts, which may reflect the phytomedicines currently used in the market. The effect of three different extracts from Calendula flowers (n-hexanic, ethanolic, aqueous) on the inflammatory phase of wound healing was studied in human immortalized keratinocytes and human dermal fibroblasts. An electrophoretic mobility shift assay on NF-κB-DNA binding, qRT-PCR and ELISA experiments were performed. The effect of Calendula extracts on the new tissue formation phase of wound healing was evaluated by studying the migratory properties of these extracts, triterpene mixtures and single compounds in human immortalized keratinocytes using the scratch assay. Finally, the effect of the extracts on the formation of granulation tissue in wound healing was studied using bacterial collagenase isolated from Clostridium histolyticum and the determination of soluble collagen in the supernatant of human dermal fibroblasts. The n-hexanic and the ethanolic extracts from Calendula flowers influence the inflammatory phase by activating the transcription factor NF-κB and by increasing the amount of the chemokine IL-8, both at the transcriptional and protein level, in human immortalized keratinocytes. The migration of the keratinocytes during the new tissue formation phase was only marginally influenced in the scratch assay. However, it can be assumed that the granulation tissue was affected, as the ethanolic extract inhibited the activity of collagenase in vitro and enhanced the amount of collagen in the supernatant of human dermal fibroblasts

  8. Mechanical Extraction of Power From Ocean Currents and Tides

    NASA Technical Reports Server (NTRS)

    Jones, Jack; Chao, Yi

    2010-01-01

    A proposed scheme for generating electric power from rivers and from ocean currents, tides, and waves is intended to offer economic and environmental advantages over prior such schemes, some of which are at various stages of implementation, others of which have not yet advanced beyond the concept stage. This scheme would be less environmentally objectionable than are prior schemes that involve the use of dams to block rivers and tidal flows. This scheme would also not entail the high maintenance costs of other proposed schemes that call for submerged electric generators and cables, which would be subject to degradation by marine growth and corrosion. A basic power-generation system according to the scheme now proposed would not include any submerged electrical equipment. The submerged portion of the system would include an all-mechanical turbine/pump unit that would superficially resemble a large land-based wind turbine (see figure). The turbine axis would turn slowly as it captured energy from the local river flow, ocean current, tidal flow, or flow from an ocean-wave device. The turbine axis would drive a pump through a gearbox to generate an enclosed flow of water, hydraulic fluid, or other suitable fluid at a relatively high pressure [typically approx.500 psi (approx.3.4 MPa)]. The pressurized fluid could be piped to an onshore or offshore facility, above the ocean surface, where it would be used to drive a turbine that, in turn, would drive an electric generator. The fluid could be recirculated between the submerged unit and the power-generation facility in a closed flow system; alternatively, if the fluid were seawater, it could be taken in from the ocean at the submerged turbine/pump unit and discharged back into the ocean from the power-generation facility. Another alternative would be to use the pressurized flow to charge an elevated reservoir or other pumped-storage facility, from whence fluid could later be released to drive a turbine/generator unit at a

  9. Understanding nanoscale mechanical properties of materials using ultrafast EUV photoacoustics

    NASA Astrophysics Data System (ADS)

    Hoogeboom-Pot, K.; Turgut, E.; Shaw, J.; Hernandez-Charpak, J.; Murnane, M.; Kapteyn, H.; Nardi, D.

    2014-03-01

    How do the elastic properties of materials evolve as a nanostructure builds up layer by layer? A host of questions in nanoscience, nanotechnology, quantum dot systems and more rely on an answer to this issue; but our ability to probe mechanical properties is severely constrained at dimensions below 100 nm. With tabletop high harmonic generation (HHG), we overcome these limitations by extending non-destructive visible photoacoustics to extreme ultraviolet (EUV) wavelengths. The short wavelength of EUV light, combined with the coherence and ultrashort pulses of HHG creates a unique and powerful probe of nanostructured materials on their intrinsic length and time scales. We study a series of ultrathin bilayer (10-nm Ni/0-6-nm Ta) nanostructures on SiO2 substrates. A femtosecond infrared pulse excites longitudinal acoustic waves (LAWs) within the nanostructures and surface acoustic waves (SAWs) in the substrate. Diffraction of a time-delayed EUV probe pulse monitors the dynamics. LAW resonances are directly related to the bilayer thickness and effective speed of sound; their dependence on Ta-layer thickness reveals that the LAW velocities of both Ni and Ta differ from bulk values. The changing mass of Ta also affects the SAW frequency, allowing us to extract nanoscale densities. This work was supported by the SRC Contract 2012-OJ-2304, by NSF Award No.: DGE 1144083, and used facilities provided by the NSF Engineering Research Center in EUV Science and Technology.

  10. Anxiolytic property of hydro-alcohol extract of Lactuca sativa and its effect on behavioral activities of mice.

    PubMed

    Harsha, Singapura Nagesh; Anilakumar, Kandangath Raghavan

    2013-01-01

    Lactuca sativa, belonging to the Asteraceae family, is a leafy vegetable known for its medicinal properties. This study aimed to understand the mechanism of Lactuca sativa extract with respect to pharmacological action.We investigated the anxiolytic effects of hydro-alcoholic extract of leaves of Lactuca sativa on mice. The behavioral tests performed on mice models to assess anti-anxiety properties were: open field test (OFT), elevated plus maze test (EPM), elevated T maze test, and marble burying test. Increased locomotor activity and time spent in the "open-arm" were observed in extract fed group. Malondialdehyde (MDA) and nitrite levels were decreased, catalase and glutathione levels were increased in Lactuca sativa treated mice. The data obtained in the present study suggests that the extract of Lactuca sativa can afford significant protection against anxiolytic activity.

  11. Anxiolytic property of hydro-alcohol extract of Lactuca sativa and its effect on behavioral activities of mice

    PubMed Central

    Harsha, Singapura Nagesh; Anilakumar, Kandangath Raghavan

    2013-01-01

    Lactuca sativa, belonging to the Asteraceae family, is a leafy vegetable known for its medicinal properties. This study aimed to understand the mechanism of Lactuca sativa extract with respect to pharmacological action.We investigated the anxiolytic effects of hydro-alcoholic extract of leaves of Lactuca sativa on mice. The behavioral tests performed on mice models to assess anti-anxiety properties were: open field test (OFT), elevated plus maze test (EPM), elevated T maze test, and marble burying test. Increased locomotor activity and time spent in the “open-arm” were observed in extract fed group. Malondialdehyde (MDA) and nitrite levels were decreased, catalase and glutathione levels were increased in Lactuca sativa treated mice. The data obtained in the present study suggests that the extract of Lactuca sativa can afford significant protection against anxiolytic activity. PMID:23554792

  12. Antioxidant properties of the methanol extracts from the leaves of Paullinia pinnata.

    PubMed

    Jimoh, F O; Sofidiya, M O; Afolayan, A J

    2007-12-01

    Paullinia pinnata is an African woody vine widely used in traditional medicine for the treatment of malaria. In order to throw more light into its mechanisms of pharmacological actions, the in vitro antioxidant activities of the methanol extract of its leaves were evaluated using different testing systems. Its scavenging activities on 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radicals as well as its ferric ion reducing power were assessed. The results showed that P. pinnata possessed strong scavenging activity and moderate reducing power. The total phenol, flavonoid, and proanthocyanidin contents of the extracts were very close to those reported for most medicinal plants and showed good correlation with its antioxidant activities. These properties are probably part of the reasons why P. pinnata is effective in folk medicine.

  13. Mechanical properties of non-woven glass fiber geopolymer composites

    NASA Astrophysics Data System (ADS)

    Rieger, D.; Kadlec, J.; Pola, M.; Kovářík, T.; Franče, P.

    2017-02-01

    This experimental research focuses on mechanical properties of non-woven glass fabric composites bound by geopolymeric matrix. This study investigates the effect of different matrix composition and amount of granular filler on the mechanical properties of final composites. Matrix was selected as a metakaolin based geopolymer hardened by different amount of potassium silicate activator. The ceramic granular filler was added into the matrix for investigation of its impact on mechanical properties and workability. Prepared pastes were incorporated into the non-woven fabrics by hand roller and final composites were stacked layer by layer to final thickness. The early age hardening of prepared pastes were monitored by small amplitude dynamic rheology approach and after 28 days of hardening the mechanical properties were examined. The electron microscopy was used for detail description of microstructural properties. The imaging methods revealed good wettability of glass fibers by geopolymeric matrix and results of mechanical properties indicate usability of these materials for constructional applications.

  14. Bioactive glass/hydroxyapatite composites: mechanical properties and biological evaluation.

    PubMed

    Bellucci, Devis; Sola, Antonella; Anesi, Alexandre; Salvatori, Roberta; Chiarini, Luigi; Cannillo, Valeria

    2015-06-01

    Bioactive glass/hydroxyapatite composites for bone tissue repair and regeneration have been produced and discussed. The use of a recently developed glass, namely BG_Ca/Mix, with its low tendency to crystallize, allowed one to sinter the samples at a relatively low temperature thus avoiding several adverse effects usually reported in the literature, such as extensive crystallization of the glassy phase, hydroxyapatite (HA) decomposition and reaction between HA and glass. The mechanical properties of the composites with 80wt.% BG_Ca/Mix and 20wt.% HA are sensibly higher than those of Bioglass® 45S5 reference samples due to the presence of HA (mechanically stronger than the 45S5 glass) and to the thermal behaviour of the BG_Ca/Mix, which is able to favour the sintering process of the composites. Biocompatibility tests, performed with murine fibroblasts BALB/3T3 and osteocites MLO-Y4 throughout a multi-parametrical approach, allow one to look with optimism to the produced composites, since both the samples themselves and their extracts do not induce negative effects in cell viability and do not cause inhibition in cell growth.

  15. Antidepressant properties of bioactive fractions from the extract of Crocus sativus L.

    PubMed

    Wang, Yang; Han, Ting; Zhu, Yu; Zheng, Cheng-Jian; Ming, Qian-Liang; Rahman, Khalid; Qin, Lu-Ping

    2010-01-01

    The aim of this study was to investigate the antidepressant properties of stigmas and corms of Crocus sativus L. The aqueous ethanol extract of C. sativus corms was fractionated on the basis of polarity. Among the different fractions, the petroleum ether fraction and dichloromethane fraction at doses of 150, 300, and 600 mg/kg showed significant antidepressant-like activities in dose-dependent manners, by means of behavioral models of depression. The immobility time in the forced swimming test and tail suspending test was significantly reduced by the two fractions, without accompanying changes in ambulation when assessed in the open-field test. By means of a gas chromatography-mass spectrometry technique, twelve compounds of the petroleum ether fraction were identified. These data show that administration of C. sativus corms extract produces antidepressant-like effects. Aqueous stigmas extract also exerted antidepressive effects in the behavioral models. Crocin 1 and crocin 2 of the aqueous stigmas extract were identified by a reversed-phase HPLC analysis. In addition, the bioactive compound crocin 1 in this herb was quantitatively determined. The data indicate that antidepressant-like properties of aqueous stigma extracts may be due to crocin 1, giving support to the validity of the use of this plant in traditional medicine. All these results suggest that the low polarity parts of C. sativus corms should be considered as a new plant material for curing depression, which merit further studies regarding antidepressive-like activities of chemical compounds isolated from the two fractions and mechanism of action.

  16. Mechanical properties determination of AM components

    NASA Astrophysics Data System (ADS)

    Dzugan, J.; Sibr, M.; Konopík, P.; Procházka, R.; Rund, M.

    2017-02-01

    Characterisation of engineering materials and components is a crucial part for design and save service life utilization. Due to components processing technologies and exploitation conditions local properties can significantly vary from location to location over larger components as well as over small material volumes with gradual material changes such as welds, coatings or additively manufactured parts. The current paper is dealing with local properties characterisation for additively manufacture (AM) components by micro tensile test (M-TT). Components produced by additive manufacturing techniques yield properties variation in dependence of the considered location within the component regarding to direction in relation to deposition process. Properties vary over the thickness, length, angle or contacts with the supporting structures necessary for a successful components production by additive manufacturing techniques. The properties differences are mainly related to varying heating/reheating and cooling conditions at various locations of usually very complex parts produced mainly by these technologies. The standard testing procedures fail to characterize such local properties of complex shaped objects due to large size requirements on specimens. Therefore, new techniques have to be established for such detailed local characterizations. Results of miniaturized tensile tests application for local properties and orientations are shown here.

  17. Composition analysis and antioxidant properties of black garlic extract.

    PubMed

    Lu, Xiaoming; Li, Ningyang; Qiao, Xuguang; Qiu, Zhichang; Liu, Pengli

    2017-04-01

    Black garlic produced from fresh garlic under controlled high temperature and humidity has strong antioxidant properties. To determine these compounds, five fractions (from F1 to F5) were separated and purified by elution with chloroform:methanol at different ratios (8:1, 6:1, 4:1, 2:1, and 0:1; v/v). The antioxidant activity of each fraction was analyzed. The results showed that F3 and F4 had higher phenolic contents and stronger 2,2-diphenyl-2-picrylhydrazyl radical scavenging activity than the others. Seven purified individual components were further separated using semipreparation high-performance liquid chromatography from these two intensely antioxidant fractions (F3 and F4), their structures were elucidated by high-performance liquid chromatography coupled to diode array detection, electrospray ionization, mass spectrometry, (1)H nuclear magnetic resonance, and (13)C nuclear magnetic resonance spectrometry. Three compounds including adenosine, uridine, and 2-acetylpyrrole were first identified in black garlic, except for 5-hydroxymethylfurfural, (1S, 3S)-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid, and (1R, 3S)-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid. The cellular antioxidant activities of uridine, adenosine, carboline alkaloids, 5-hydroxymethylfurfural, and ethyl acetate extracts were consistent with the results of in vitro experimental antioxidant properties. The results provide useful information for understanding the health benefits of black garlic products. Copyright © 2016. Published by Elsevier B.V.

  18. Mechanical properties of materials at micro/nano scales

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Hua

    Mechanical properties of materials in small dimensions, including the depth-dependent hardness at the nano/micrometer scales, and the mechanical characterization of thin films and nanotubes, are reported. The surface effect on the depth-dependent nano/microhardness was studied and an apparent surface stress was introduced to represent the energy dissipated per unit area of a solid surface. A plastic bearing ratio model was proposed for the nanoindentation of rough surfaces. The energy dissipation occurring at the indented surface is among the factors that cause the Indentation Size Effect (ISE) at the micro/nanometer scales. Furthermore, an elastic-plastic bearing ratio model was developed for nanoindentation of rough surfaces with a flat indenter tip. The theoretical predictions agree with the experimental results and finite element simulations, from which the elastic constant and the surface hardness were extracted. The surface hardness exhibits an inverse ISE due to the interaction of asperities. The nanoindentation tests on Highly Oriented Pyrolytic Graphite (HOPG) may lead to the formation of carbon tubes, which are rolled up by the delaminated graphite layers. The nanoindentation loading-unloading curves reveal single pop-in and multiple pop-in phenomena, which is induced by fracture of the graphite layers and/or by delamination between the layers. From the load at pop-in, the fracture strength of the layers and/or the bonding strength between the layers can be estimated by the elastic field model for Hertzian contact including sliding friction for transverse isotropy. Two novel methods were developed to estimate the mechanical properties of films, including the Raman spectra method for the estimation of residual stresses in thin ferroelectric films and the microbridge testing method for the mechanical characterization of trilayer thin films. Mechanical characterization was also carried out on Tobacco Mosaic Virus (TMV) nanotubes with each being comprised of

  19. Characterisation of antibacterial Australian medicinal plant extracts by investigation of the mechanism of action and the effect of interfering substances.

    PubMed

    Tomlinson, Steven; Palombo, Enzo A

    2005-01-01

    Propidium iodide (PI) uptake and salt tolerance assays were used to investigate the mechanism of antibacterial action of an extract of the leaves of Eremophila duttonii, a traditional Australian medicinal plant previously shown to have potent bactericidal activity against Gram positive bacteria. The extract compromised the integrity of the cytoplasmic membrane of Staphylococcus aureus , leading to increased membrane permeability (indicated by uptake of PI) and a decrease in ability to exclude NaCl. The bactericidal action of the E. duttonii extract was concluded to be due to its membrane-active properties. The effect of contaminants on the efficacy of this extract and other medicinal plant extracts was also investigated. Organic contaminants (bakers' yeast and skim milk powder) decreased the efficacy of all extracts investigated, while hard water had no effect. Greater understanding of the biocidal properties of the plant extracts investigated may determine if they have medical, industrial or environmental applications. ((c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).

  20. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

    1998-01-01

    Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  1. Antiobesogenic and Antiatherosclerotic Properties of Caralluma fimbriata Extract.

    PubMed

    Kamalakkannan, Soundararajan; Rajendran, Ramaswamy; Venkatesh, Ramasamy V; Clayton, Paul; Akbarsha, Mohammad A

    2010-01-01

    There is evidence that the principles present in the widely consumed Indian food plant C. fimbriata extract (CFE) suppress appetite, and provide antiobesogenic and metabolic benefits. The Diet-Induced Obesity (DIO) rat model was used to investigate CFE's anorexigenic effects. Rats were randomly divided into three groups: (i) untreated control (C), (ii) control for cafeteria diet (CA), and (iii) cafeteria diet fed + CFE treated. Rats in the test group received cafeteria diet and CFE from day one onwards. CFE was administered by gavage at three doses (25, 50, 100 mg/Kg BW per day) for 90 days. The antiobesogenic effects of CFE were evaluated by monitoring changes in feed intake, body weight, serum lipid and hormonal (leptin) profiles, fat pads, and liver weight. Antiatherosclerotic effects were measured by histology. CFE induced significant and dose-dependent inhibition of food intake, with dose-related prevention of gains in body weight, liver weight, and fat pad mass. Alterations in serum lipid profiles associated with weight gain were similarly inhibited, as were the typical increases in serum leptin levels. These data substantiate CFE's reported anorexigenic effects. CFE treatment also conferred protection against atherogenesis. We conclude that CFE possesses antiobesogenic and antiatherosclerotic properties.

  2. Antiobesogenic and Antiatherosclerotic Properties of Caralluma fimbriata Extract

    PubMed Central

    Kamalakkannan, Soundararajan; Rajendran, Ramaswamy; Venkatesh, Ramasamy V.; Clayton, Paul; Akbarsha, Mohammad A.

    2010-01-01

    There is evidence that the principles present in the widely consumed Indian food plant C. fimbriata extract (CFE) suppress appetite, and provide antiobesogenic and metabolic benefits. The Diet-Induced Obesity (DIO) rat model was used to investigate CFE's anorexigenic effects. Rats were randomly divided into three groups: (i) untreated control (C), (ii) control for cafeteria diet (CA), and (iii) cafeteria diet fed + CFE treated. Rats in the test group received cafeteria diet and CFE from day one onwards. CFE was administered by gavage at three doses (25, 50, 100 mg/Kg BW per day) for 90 days. The antiobesogenic effects of CFE were evaluated by monitoring changes in feed intake, body weight, serum lipid and hormonal (leptin) profiles, fat pads, and liver weight. Antiatherosclerotic effects were measured by histology. CFE induced significant and dose-dependent inhibition of food intake, with dose-related prevention of gains in body weight, liver weight, and fat pad mass. Alterations in serum lipid profiles associated with weight gain were similarly inhibited, as were the typical increases in serum leptin levels. These data substantiate CFE's reported anorexigenic effects. CFE treatment also conferred protection against atherogenesis. We conclude that CFE possesses antiobesogenic and antiatherosclerotic properties. PMID:21234320

  3. Wave-Mechanical Properties of Stationary States.

    ERIC Educational Resources Information Center

    Holden, Alan

    This monograph is a review of the quantum mechanical concepts presented in two other monographs, "The Nature of Atoms" and "Bonds Between Atoms," by the same author. It is assumed the reader is familiar with these ideas. The monograph sketches only those aspects of quantum mechanics that are of most direct use in picturing and calculating the…

  4. Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens)

    Treesearch

    H.Q. Yu; Z.H. Jiang; C.Y. Hse; T.F. Shupe

    2008-01-01

    Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens). Selected physical and mechanical properties of 4?6 year old moso bamboo (Phyllostachys pubescens) grown in Zhejiang, China were investigated at different vertical and horizontal positions. Two way analysis of variance and Tukey?s mean comparison...

  5. Mechanical properties of a polyamide 6-reinforced PTFE composite

    NASA Astrophysics Data System (ADS)

    Li, J.

    2009-05-01

    Polytetrafluoroethylene (PTFE) blends with polyamide 6 (PA6) in various ratios were prepared in a corotating twin-screw extruder, where PTFE acted as a polymer matrix and PA6 as a disperse phase, and the morphology and mechanical properties of the blends were investigated by using SEM. With increasing content of PA6 in the blends, their flexural properties improved. The interfacial adhesion promoted the creation of an interphase between the PTFE and PA6 and led to improved mechanical properties of the material. The mechanical properties of the blends were optimum at 30 vol.% PA6.

  6. Investigation of mechanical properties of pavement through electromagnetic techniques

    NASA Astrophysics Data System (ADS)

    Benedetto, Andrea; Tosti, Fabio; D'Amico, Fabrizio

    2014-05-01

    Ground-penetrating radar (GPR) is considered as one of the most flexible geophysical tools that can be effectively and efficiently used in many different applications. In the field of pavement engineering, GPR can cover a wide range of uses, spanning from physical to geometrical inspections of pavements. Traditionally, such inferred information are integrated with mechanical measurements from other traditional (e.g. plate bearing test) or non-destructive (e.g. falling weight deflectometer) techniques, thereby resulting, respectively, in time-consuming and low-significant measurements, or in a high use of technological resources. In this regard, the new challenge of retrieving mechanical properties of road pavements and materials from electromagnetic measurements could represent a further step towards a greater saving of economic resources. As far as concerns unpaved and bound layers it is well-known that strength and deformation properties are mostly affected, respectively, by inter-particle friction and cohesion of soil particles and aggregates, and by bitumen adhesion, whose variability is expressed by the Young modulus of elasticity. In that respect, by assuming a relationship between electromagnetic response (e.g. signal amplitudes) and bulk density of materials, a reasonable correlation between mechanical and electric properties of substructure is therefore expected. In such framework, a pulse GPR system with ground-coupled antennae, 600 MHz and 1600 MHz centre frequencies was used over a 4-m×30-m test site composed by a flexible pavement structure. The horizontal sampling resolution amounted to 2.4×10-2 m. A square regular grid mesh of 836 nodes with a 0.40-m spacing between the GPR acquisition tracks was surveyed. Accordingly, a light falling weight deflectometer (LFWD) was used for measuring the elastic modulus of pavement at each node. The setup of such instrument consisted of a 10-kg falling mass and a 100-mm loading plate so that the influence domain

  7. Atomic Force Microscopy Measurements of the Mechanical Properties of Cell Walls on Living Bacterial Cells

    NASA Astrophysics Data System (ADS)

    Bailey, Richard; Mullin, Nic; Turner, Robert; Foster, Simon; Hobbs, Jamie

    2014-03-01

    Staphylococcus aureus is a major cause of infection in humans, including the Methicillin resistant strain, MRSA. However, very little is known about the mechanical properties of these cells. Our investigations use AFM to examine live S. aureus cells to quantify mechanical properties. These were explored using force spectroscopy with different trigger forces, allowing the properties to be extracted at different indentation depths. A value for the cell wall stiffness has been extracted, along with a second, higher value which is found upon indenting at higher forces. This higher value drops as the cells are exposed to high salt, sugar and detergent concentrations, implying that this measurement contains a contribution from the internal turgor pressure. We have monitored these properties as the cells progress through the cell cycle. Force maps were taken over the cells at different stages of the growth process to identify changes in the mechanics throughout the progression of growth and division. The effect of Oxacillin has also been studied, to better understand its mechanism of action. Finally mutant strains of S. aureus and a second species Bacillus subtilis have been used to link the mechanical properties of the cell walls with the chain lengths and substructures involved.

  8. Mechanical Properties of 23 Species of Eastern Hardwoods.

    Treesearch

    B. A. Bendtsen; R. L. Ethington

    1975-01-01

    Important mechanical properties of clear, straight-grained wood of 23 species are tabulated, along with coefficients of variation. These property estimates can be used to match up species with kind of material needed for a specific job, or to search for substitutes for a presently used species. Some of the species appear, with allowable properties, in two published...

  9. Mechanical and physical properties of plasma-sprayed stabilized zirconia

    NASA Technical Reports Server (NTRS)

    Siemers, P. A.; Mehan, R. L.

    1983-01-01

    Physical and mechanical properties were determined for plasma-sprayed MgO- or Y2O3-stabilized ZrO2 thermal barrier coatings. Properties were determined for the ceramic coating in both the freestanding condition and as-bonded to a metal substrate. The properties of the NiCrAlY bond coating were also investigated.

  10. Electronic, thermal and mechanical properties of carbon nanotubes.

    PubMed

    Dresselhaus, M S; Dresselhaus, G; Charlier, J C; Hernández, E

    2004-10-15

    A review of the electronic, thermal and mechanical properties of nanotubes is presented, with particular reference to properties that differ from those of the bulk counterparts and to potential applications that might result from the special structure and properties of nanotubes. Both experimental and theoretical aspects of these topics are reviewed.

  11. Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

    NASA Astrophysics Data System (ADS)

    Mohan, Nisha

    Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of

  12. Mechanical properties of UV irradiated rat tail tendon (RTT) collagen.

    PubMed

    Sionkowska, Alina; Wess, Tim

    2004-04-01

    The mechanical properties of RTT collagen tendon before and after UV irradiation have been investigated by mechanical testing (Instron). Air-dried tendon were submitted to treatment with UV irradiation (wavelength 254 nm) for different time intervals. The changes in such mechanical properties as breaking strength and percentage elongation have been investigated. The results have shown, that the mechanical properties of the tendon were greatly affected by time of UV irradiation. Ultimate tensile strength and ultimate percentage elongation decreased after UV irradiation of the tendon. Increasing UV irradiation leads to a decrease in Young's modulus of the tendon.

  13. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.

    2000-01-01

    Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  14. How divergence mechanisms influence disassortative mixing property in biology

    NASA Astrophysics Data System (ADS)

    Xu, Chunsui; Liu, Zengrong; Wang, Ruiqi

    2010-02-01

    The duplication-divergence mechanism of network growth has been widely investigated, especially in gene and protein networks. Both the duplication and divergence have a key role in biological network evolution. However, the relative roles of these mechanisms in the influence of disassortative property in protein interaction networks remain to be clarified. It has been shown that duplication can indeed make protein networks evolve towards disassortative networks. To make the relationship between the disassortative property and the duplication-divergence mechanism more clear, we further discuss how the divergence mechanism influences the disassortative property. We tested four different divergence mechanisms, i.e., node deletion, edge deletion, edge addition, and edge rewiring to study their effects on disassortative property. Our study highlights the crucial roles of different divergence evolution mechanisms.

  15. Mechanical properties of natural cartilage and tissue-engineered constructs.

    PubMed

    Little, Christopher James; Bawolin, Nahshon Kenneth; Chen, Xiongbiao

    2011-08-01

    There has been much research over the past two decades with the aim of engineering cartilage constructs for repairing or restoring damaged cartilage. To engineer healthy neocartilage, the constructs must have mechanical properties matching those of native cartilage as well as appropriate for the loading conditions of the joint. This article discusses the mechanical behavior of native cartilage and surveys different types of tensile, compressive, and shear tests with their limitations. It also comprehensively reviews recent work and achievements in developing the mathematical models representing the mechanical properties of both native and engineered cartilage. Different methods for enhancing the mechanical properties of engineered cartilage are also discussed, including scaffold design, mechanical stimulation, and chemical stimulation. This article concludes with recommendations for future research aimed at achieving engineered cartilage with mechanical properties matching those found in native cartilage.

  16. The Antiinflammatory and Antiarthritic Properties of Ethanol Extract of Hedera helix

    PubMed Central

    Rai, Anuradha

    2013-01-01

    The ethanol Hedera helix plant extract was tested for its antiinflammatory properties. Intraperitoneal injections of 7.5 ml/kg wt ethanol extract showed antiinflammatory activity with 88.89% inhibition as compared to reference drug diclofenac, which showed 94.44% inhibition in formalin-induced paw oedema. As formalin-induced paw oedema closely resembles human arthritis, the antiarthritic property of ethanol extract of Hedera helix was also investigated. The visible reduction in arthritic symptoms by extract of Hedera helix suggests the potential of the plant extract against inflammation and arthritis. PMID:23901168

  17. Microbial DNA extraction from intestinal biopsies is improved by avoiding mechanical cell disruption

    PubMed Central

    Carbonero, Franck; Nava, Gerardo M.; Benefiel, Ann C.; Greenberg, Eugene; Gaskins, H. Rex

    2011-01-01

    Currently, standard protocols for microbial DNA extraction from intestinal tissues do not exist. We assessed the efficiency of a commercial kit with and without mechanical disruption. Better quality DNA was obtained without mechanical disruption. Thus, it appears that bead-beating is not required for efficient microbial DNA extraction from intestinal biopsies. PMID:21820015

  18. Lunar soil properties and soil mechanics

    NASA Technical Reports Server (NTRS)

    Mitchell, J. K.; Houston, W. N.

    1974-01-01

    The long-range objectives were to develop methods of experimentation and analysis for the determination of the physical properties and engineering behavior of lunar surface materials under in situ environmental conditions. Data for this purpose were obtained from on-site manned investigations, orbiting and softlanded spacecraft, and terrestrial simulation studies. Knowledge of lunar surface material properties are reported for the development of models for several types of lunar studies and for the investigation of lunar processes. The results have direct engineering application for manned missions to the moon.

  19. Complex rheological properties of a water-soluble extract from the fronds of the black tree fern, Cyathea medullaris.

    PubMed

    Goh, Kelvin K T; Matia-Merino, Lara; Hall, Christopher E; Moughan, Paul J; Singh, Harjinder

    2007-11-01

    A water-soluble extract was obtained from the fronds of a New Zealand native black tree fern (Cyathea medullaris or Mamaku in Māori). The extract exhibited complex rheological behavior. Newtonian, shear-thinning, shear-thickening, thixotropic, antithixotropic, and viscoelastic behaviors were observed depending on polymer concentration, shear rate, and shear history. The extract also displayed rod-climbing and self-siphoning properties typical of viscoelastic fluids. Such complex rheological properties have been reported in synthetic or chemically modified polymers but are less frequent in unmodified biopolymers. Although Mamaku extract obtained from the pith of the fern has been traditionally used by the Māori in New Zealand for treating wounds and diarrhea among other ailments, this material has never been characterized before. This study reports on the chemical composition of the extract and on its viscoelastic properties through rotational and oscillatory rheological measurements. Explanations of the mechanism behind the rheological properties were based on transient network models for associating polymers.

  20. Physical and mechanical properties of icebergs

    SciTech Connect

    Gammon, P.H.; Bobby, W.; Gagnon, R.E.; Russell, W.E.

    1983-05-01

    Physical and mechanical characteristics of iceberg ice were studied from samples collected near the shores of eastern Newfoundland. Although the physical characteristics show considerable diversity, iceberg ice has some common features and is generally porous, lacks significant concentrations of dissolved materials, contains internal cracks and has an irregular interlocking grain structure. A review of mechanical testing of ice was carried out and an experimental setup was devised to reduce effects of improper contact between specimen and loading apparatus. Uniaxial compressive strength for iceberg ice was determined and compared with that for lake ice. The strength of iceberg ice was higher than that of lake ice but Young's Modulus for lake ice was higher.

  1. Mechanical Properties of Normal and Diseased Cerebrovascular System

    PubMed Central

    Ebrahimi, Ali P.

    2009-01-01

    Background: Blood vessel mechanics has traditionally been of interest to researchers and clinicians. Changes in mechanical properties of arteries have been associated with various diseases. Objective: To provide a comprehensive review directed towards understanding the basic biomechanical properties of cerebral arteries under normal and diseased conditions. Methods: Literature review supplemented by personal knowledge. Results: The mechanical properties of vascular tissue may depend on several factors including macromolecular volume fraction, molecular orientation, and volume or number of cells such as smooth muscle cells. Mechanical properties of a blood vessel have been characterized using different methods such as in vitro tensile testing, non-invasive ultrasound examination, and mathematical models. Experiments are complicated by the variation in properties and content of materials that make up the vessel wall and more challenging as the size of the vessel of interest decreases. Therapeutic interventions aiming to alter the mechanical response are either pharmaceutical: including calcium channel blockers, angiotensin converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), and β-blockers; or, mechanical interventions such as angioplasty, stent placement, mechanical thrombectomy, or embolization procedures. Conclusion: It is apparent from the literature that macromolecular and cellular mechanics of blood vessels are not fully understood. Therefore, further studies are necessary to better understand contribution of these mechanisms to the overall mechanics of the vascular tissue. PMID:22518247

  2. Effective Mechanical Properties of Fuzzy Fiber Composites

    DTIC Science & Technology

    2012-03-16

    fibers’’. Numerical examples of compositesmade of epoxy resin , carbonfibers and carbon nanotubes are presented and the impact of the carbon nanotubes...allows us to compute effective properties of composites with multiple types of ??fuzzy fibers??. Numerical examples of composites made of epoxy resin ...length (Fig. 1 in [42]). The CNTs have inter- nal radius 0.51 nm and external radius 0.85 nm. The ‘‘fuzzy fibers’’ are embedded in EPIKOTE 862 resin . The

  3. Composite propellant technology research: Mechanical property characterization

    NASA Technical Reports Server (NTRS)

    Bower, Mark V.

    1991-01-01

    Proof for the existence of a single Poisson's ratio function in isotropic linear viscoelastic materials is presented. An in-depth discussion is given of three dimensional viscoelastic material properties and their relationships to linear isotropic and orthotropic viscoelastic materials. A discussion of the alternate invariant definition as used by Abaqus and how it relates to the form used by Dr. S. Peng is presented.

  4. Mechanical Properties of Infrared Transmitting Materials

    DTIC Science & Technology

    1978-01-01

    William L. Gaiser, Eglin Air Force Base Dr. George Hayes, Naval Weapons Center, China Lake Dr. Dale Holter , U.S. Army Missile Command Prof. Ray...Laboratory; and numerical work has been performed at Systems, Science and Software ; California Research Technology; shock Hydrodynamics; General Atomic...Hageman, 6. A. Gurtman, and M. Baker, "Influence of ABM Material Properties on Erosion Resulting from Particle Impact," Systems, Science, and Software

  5. Supramolecular Polymer Nanocomposites - Improvement of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hinricher, Jesse; Neikirk, Colin; Priestley, Rodney

    2015-03-01

    Supramolecular polymers differ from traditional polymers in that their repeat units are connected by hydrogen bonds that can reversibly break and form under various stimuli. They can be more easily recycled than conventional materials, and their highly temperature dependent viscosities result in reduced energy consumption and processing costs. Furthermore, judicious selection of supramolecular polymer architecture and functionality allows the design of advanced materials including shape memory and self-healing materials. Supramolecular polymers have yet to see widespread use because they can't support much weight due to their inherent mechanical weakness. In order to address this issue, the mechanical strength of supramolecular polymer nanocomposites based on ureidopyrmidinone (UPy) telechelic poly(caprolactone) doped with surface activated silica nanoparticles was investigated by tensile testing and dynamic mechanical analysis. The effects of varying amounts and types of nanofiller surface functionality were investigated to glean insight into the contributions of filler-filler and filler-matrix interactions to mechanical reinforcement in supramolecular polymer nanocomposites. MRSEC NSF DMR 0819860 (PI: Prof. N. Phuan Ong) REU Site Grant: NSF DMR-1156422 (PI: Prof. Mikko Haataja)

  6. Assessment of structural, thermal, and mechanical properties of portlandite through molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Hajilar, Shahin; Shafei, Behrouz

    2016-12-01

    The structural, thermal, and mechanical properties of portlandite, the primary solid phase of ordinary hydrated cement paste, are investigated using the molecular dynamics method. To understand the effects of temperature on the structural properties of portlandite, the coefficients of thermal expansion of portlandite are determined in the current study and validated with what reported from the experimental tests. The atomic structure of portlandite equilibrated at various temperatures is then subjected to uniaxial tensile strains in the three orthogonal directions and the stress-strain curves are developed. Based on the obtained results, the effect of the direction of straining on the mechanical properties of portlandite is investigated in detail. Structural damage analysis is performed to reveal the failure mechanisms in different directions. The energies of the fractured surfaces are calculated in different directions and compared to those of the ideal surfaces available in the literature. The key mechanical properties, including tensile strength, Young's modulus, and fracture strain, are extracted from the stress-strain curves. The sensitivity of the obtained mechanical properties to temperature and strain rate is then explored in a systematic way. This leads to valuable information on how the structural and mechanical properties of portlandite are affected under various exposure conditions and loading rates.

  7. Extracting accurate strain measurements in bone mechanics: A critical review of current methods.

    PubMed

    Grassi, Lorenzo; Isaksson, Hanna

    2015-10-01

    Osteoporosis related fractures are a social burden that advocates for more accurate fracture prediction methods. Mechanistic methods, e.g. finite element models, have been proposed as a tool to better predict bone mechanical behaviour and strength. However, there is little consensus about the optimal constitutive law to describe bone as a material. Extracting reliable and relevant strain data from experimental tests is of fundamental importance to better understand bone mechanical properties, and to validate numerical models. Several techniques have been used to measure strain in experimental mechanics, with substantial differences in terms of accuracy, precision, time- and length-scale. Each technique presents upsides and downsides that must be carefully evaluated when designing the experiment. Moreover, additional complexities are often encountered when applying such strain measurement techniques to bone, due to its complex composite structure. This review of literature examined the four most commonly adopted methods for strain measurements (strain gauges, fibre Bragg grating sensors, digital image correlation, and digital volume correlation), with a focus on studies with bone as a substrate material, at the organ and tissue level. For each of them the working principles, a summary of the main applications to bone mechanics at the organ- and tissue-level, and a list of pros and cons are provided.

  8. Mechanical and microwave absorbing properties of carbon-filled polyurethane.

    PubMed

    Kucerová, Z; Zajícková, L; Bursíková, V; Kudrle, V; Eliás, M; Jasek, O; Synek, P; Matejková, J; Bursík, J

    2009-01-01

    Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

  9. Manufacturing and mechanical properties of calcium phosphate biomaterials

    NASA Astrophysics Data System (ADS)

    Laasri, S.; Taha, M.; Hlil, E. K.; Laghzizil, A.; Hajjaji, A.

    2012-10-01

    In this study, the influence of powder manufacturing and sintering temperature on densification, microstructure and mechanical properties of dense β-tricalcium phosphate (β-TCP) bioceramic has been studied. Densification results show that the β-TCP can be sintered at 1160 °C for 3 hours to have good density and high performance mechanic properties (Vickers hardness, toughness and Young's modulus). X-ray diffraction and SEM microscopy are used to check the microstructure changes during the sintering temperature. The used processing of β-TCP ceramic improved its densification, microstructure homogeneity and mechanical properties.

  10. Fine-Scale Mechanical Properties of Sliding Solids.

    DTIC Science & Technology

    1987-02-28

    UNCLASSIFIED DRJ45-4-C-0006 F/0 26/11 ML E~Em***smRn loI 1.05 w4 AV. -w q ! WvI% %111.2nE~% 03TI ElLE CP - 1NE-CALE MECHANICAL PROPERTIES OF - 0 SLIDING...LAI 4Th Approved for Public Release; distribution unlimited f 4,rm 6mw "%U FINE-SCALE MECHANICAL PROPERTIES OF SLIDING SOLIDS Final Technical Report by...experiments specifically designed to -investigate the mechanical properties of materials at the submicroscopic level. The first part deals with

  11. Effect of fabricated density and bamboo species on physical-mechanical properties of bamboo fiber bundle reinforced composites

    Treesearch

    Jiulong Xie; Jinqiu Qi; Tingxing Hu; Cornelis F. De Hoop; Chung Yun Hse; Todd F. Shupe

    2016-01-01

    Bamboo stems were subjected to a mechanical treatment process for the extraction of bamboo fiber bundles. The fiber bundles were used as reinforcement for the fabrication of high-performance composites with phenolic resins as matrix. The influence of fabricated density and bamboo species on physical–mechanical properties of bamboo fiber bundle reinforced composites (...

  12. Elastic properties and mechanical tension of graphene

    NASA Astrophysics Data System (ADS)

    Ramírez, R.; Herrero, C. P.

    2017-01-01

    Room-temperature simulations of graphene have been performed as a function of the mechanical tension of the layer. Finite-size effects are accurately reproduced by an acoustic dispersion law for the out-of-plane vibrations that, in the long-wave limit, behaves as ρ ω2=σ k2+κ k4 . The fluctuation tension σ is finite (˜0.1 N/m) even when the external mechanical tension vanishes. Transverse vibrations imply a duplicity in the definition of the elastic constants of the layer, as observables related to the real area of the surface may differ from those related to the in-plane projected area. This duplicity explains the variability of experimental data on the Young modulus of graphene based on electron spectroscopy, interferometric profilometry, and indentation experiments.

  13. The mechanical and strength properties of diamond.

    PubMed

    Field, J E

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of

  14. The mechanical and strength properties of diamond

    NASA Astrophysics Data System (ADS)

    Field, J. E.

    2012-12-01

    Diamond is an exciting material with many outstanding properties; see, for example Field J E (ed) 1979 The Properties of Diamond (London: Academic) and Field J E (ed) 1992 The Properties of Natural and Synthetic Diamond (London: Academic). It is pre-eminent as a gemstone, an industrial tool and as a material for solid state research. Since natural diamonds grew deep below the Earth's surface before their ejection to mineable levels, they also contain valuable information for geologists. The key to many of diamond's properties is the rigidity of its structure which explains, for example, its exceptional hardness and its high thermal conductivity. Since 1953, it has been possible to grow synthetic diamond. Before then, it was effectively only possible to have natural diamond, with a small number of these found in the vicinity of meteorite impacts. Techniques are now available to grow gem quality synthetic diamonds greater than 1 carat (0.2 g) using high temperatures and pressures (HTHP) similar to those found in nature. However, the costs are high, and the largest commercially available industrial diamonds are about 0.01 carat in weight or about 1 mm in linear dimension. The bulk of synthetic diamonds used industrially are 600 µm or less. Over 75% of diamond used for industrial purposes today is synthetic material. In recent years, there have been two significant developments. The first is the production of composites based on diamond; these materials have a significantly greater toughness than diamond while still maintaining very high hardness and reasonable thermal conductivity. The second is the production at low pressures by metastable growth using chemical vapour deposition techniques. Deposition onto non-diamond substrates was first demonstrated by Spitsyn et al 1981 J. Cryst. Growth 52 219-26 and confirmed by Matsumoto et al 1982 Japan J. Appl. Phys. 21 L183-5. These developments have added further to the versatility of diamond. Two other groups of materials

  15. Mechanical properties of intermediate filament proteins

    PubMed Central

    Charrier, Elisabeth E.; Janmey, Paul A.

    2016-01-01

    Purified intermediate filament proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filament form viscoelastic gels. The crosslinks holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking non-linear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large stains resembling those that soft tissues undergo in vivo. Individual Ifs can be stretched to more than 2 or 3 times their resting length without breaking. At least ten different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of IF on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations. PMID:26795466

  16. Mechanical properties of alumina porcelain during heating

    NASA Astrophysics Data System (ADS)

    Šín, Peter; Podoba, Rudolf; ŠtubÅa, Igor; Trník, Anton

    2014-11-01

    The mechanical strength and Young's modulus of green alumina porcelain (50 wt. % of kaolin, 25 wt. % of Al2O3, and 25 wt. % of feldspar) were measured during heating up to 900 °C and 1100 °C, respectively. To this end, we used the three point-bending method and modulated force thermomechanical analysis (mf-TMA). The loss liberation - of the physically bound water (20 - 250 °C) strengthens the sample and Young's modulus increases its values significantly. The dehydroxylation that takes place in the range of 400 - 650 °C causes a slight decrease in Young's modulus. On the other hand, the mechanical strength slightly increases in this temperature range, although it has a sudden drop at 420 °C. Beyond the dehydroxylation range, above 650 °C, both Young's modulus and mechanical strength increase. Above 950 °C, a sharp increase of Young's modulus is caused by the solid-state sintering and the new structure created by the high-temperature reactions in metakaolinite.

  17. Fructus Ligustri Lucidi (FLL) ethanol extract increases bone mineral density and improves bone properties in growing female rats.

    PubMed

    Lyu, Ying; Feng, Xin; Zhao, Pengling; Wu, Zhenghao; Xu, Hao; Fang, Yuehui; Hou, Yangfeng; Denney, Liya; Xu, Yajun; Feng, Haotian

    2014-11-01

    Osteoporosis is a chronic disease affecting millions of people worldwide. It is generally accepted that acquisition of a high peak bone mass (PBM) early in life can reduce the risk of osteoporosis later in life. The aims of this study were to investigate the effects of Fructus Ligustri Lucidi (FLL) ethanol extract on bone mineral density and its mechanical properties in growing female rats and to explore the underlying mechanisms. The rats were given different doses of FLL extract mixed with AIN-93G formula (0.40, 0.65 and 0.90 %), and a group given AIN-93G diet treatment only was used as control. The intervention lasted for 16 weeks until the animals were about 5 months old, the time when the animals almost reach their PBM. Our results showed that FLL treatment increased bone mineral density and improved bone mechanical properties in the growing female rats in a dose-dependent manner. In addition, FLL treatment significantly decreased the serum bone-resorbing marker, CTX-I, while significantly increasing serum 25(OH)D3 and thereby increasing Ca absorption and Ca retention. Intriguingly, both in vivo and in vitro results demonstrated that FLL treatment could reduce the RANKL/OPG ratio. In conclusion, FLL ethanol extract exerted beneficial effects on peak bone mass acquisition and the improvement of bone mechanical properties by favoring Ca metabolism and decreasing the RANKL/OPG ratio.

  18. Physicochemical and phytochemical properties of cold and hot water extraction from Hibiscus sabdariffa.

    PubMed

    Ramirez-Rodrigues, Milena M; Plaza, Maria L; Azeredo, Alberto; Balaban, Murat O; Marshall, Maurice R

    2011-04-01

    Hibiscus cold (25 °C) and hot (90 °C) water extracts were prepared in various time-temperature combinations to determine equivalent extraction conditions regarding their physicochemical and phytochemical properties. Equivalent anthocyanins concentration was obtained at 25 °C for 240 min and 90 °C for 16 min. Total phenolics were better extracted with hot water that also resulted in a higher antioxidant capacity in these extracts. Similar polyphenolic profiles were observed between fresh and dried hibiscus extracts. Hibiscus acid and 2 derivatives were found in all extracts. Hydroxybenzoic acids, caffeoylquinic acids, flavonols, and anthocyanins constituted the polyphenolic compounds identified in hibiscus extracts. Two major anthocyanins were found in both cold and hot extracts: delphynidin-3-sambubioside and cyanidin-3-sambubioside. In general, both cold and hot extractions yielded similar phytochemical properties; however, under cold extraction, color degradation was significantly lower and extraction times were 15-fold longer. Hibiscus beverages are prepared from fresh or dried calyces by a hot extraction and pasteurized, which can change organoleptic, nutritional, and color attributes. Nonthermal technologies such as dense phase carbon dioxide may maintain their fresh-like color, flavor, and nutrients. This research compares the physicochemical and phytochemical changes resulting from a cold and hot extraction of fresh and dried hibiscus calyces and adds to the knowledge of work done on color, quality attributes, and antioxidant capacity of unique tropical products. In addition, the research shows how these changes could lead to alternative nonthermal processes for hibiscus.

  19. Physicochemical, nutritional, and antimicrobial properties of wine grape (cv. Merlot) pomace extract-based films.

    PubMed

    Deng, Qian; Zhao, Yanyun

    2011-04-01

    Wine grape pomace (WGP) (cv. Merlot) extract-based films were studied in terms of their physicochemical, mechanical, water barrier, nutritional, and antibacterial properties. Pomace extract (PE) was obtained by hot water extraction and had a total soluble solid of 3.6% and pH 3.65. Plant-based polysaccharides, low methoxyl pectin (LMP, 0.75% w/w), sodium alginate (SA, 0.3% w/w), or Ticafilm (TF, 2% w/w), was added into PE for film formation, respectively. Elongation at break and tensile strength were 23% and 4.04 MPa for TF-PE film, 25% and 1.12 MPa for SA-PE film, and 9.89% and 1.56 MPa for LMP-PE film. Water vapor permeability of LMP-PE and SA-PE films was 63 and 60 g mm m(-2) d(-1) kPa, respectively, lower than that of TF-PE film (70 g mm m(-2) d(-1) kPa) (P<0.05). LMP-PE film had higher water solubility, indicated by the haze percentage of water after 24 h of film immersion (52.8%) than that of TF-PE (25.7%) and SA-PE (15.9%) films, and also had higher amount of released phenolics (96.6%) than that of TF-PE (93.8%) and SA-PE (80.5%) films. PE films showed antibacterial activity against both Escherichia coli and Listeria innocua, in which approximate 5-log reductions in E. coli and 1.7- to 3.0-log reductions in L. innocua were observed at the end of 24 h incubation test compared with control. This study demonstrated the possibility of utilizing WGP extracts as natural, antimicrobial, and antioxidant promoting film-forming material for various food applications.   WGP extract-based edible films with the addition of a small amount of commercial polysaccharides showed attractive color and comparable mechanical and water barrier properties to other edible films. The films also demonstrated their potential antioxidant and antimicrobial functions. Hence, they may be used as colorful wraps or coatings for food, pharmaceutical, or other similar applications.

  20. Probing the mechanical properties of dental porcelain through nanoindentation

    NASA Astrophysics Data System (ADS)

    Manda, Marianthi; Moschakis, Nikolaos; Konstantinidis, Avraam; Christophilos, Demetrios; Papadopoulou, Lambrini; Koidis, Petros; Aifantis, Elias

    2012-11-01

    The purpose of this short communication is to report on some micro/nanoscale aspects of the mechanical behavior of dental porcelain. Specimens were characterized by micro-Raman spectroscopy and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Massive nanoindentation experiments on the surface of the specimens were performed, and typical load-displacement or load-depth (P-h) curves were obtained, which in turn were used to determine the Young modulus (E) and nanoindentation hardness (n-H), based on the Oliver-Pharr method [1]. Statistical analyses were carried out to determine the Spearman’s rank correlation coefficient (Spearman’s ρ), along with non-parametric linear regression analysis by employing Kolmogorov-Smirnov and Two-Step Cluster tests. Densification due to grain boundary diffusion and open-pore elimination was revealed by SEM. EDS analysis indicated a leucite-dispersed silicate glass matrix, as well as its contamination by traces of other minerals. Raman spectroscopy supported the EDS assignments. The P-h curves suggested that inelastic deformation and material flow increases at larger depths. Spearman’s ρ value showed strong dependence of E and n-H on h, indicating the occurrence of a size effect. The logarithmic data of E and n-H as functions of h were fitted by using linear regression analysis. The data did not obey a normal distribution (as the Kolmogorov-Smirnov test showed) due to the chemical heterogeneity involved. The Two-Step Cluster analysis indicated clustering in four groups associated with the chemical heterogeneity of the surface. Similar works using nanoindentation to determine the mechanical properties of dental materials can be found, for example, in [2, 3]. Corresponding methods for extracting the values of E and n-H from P-h experimental curves can be found, for example, in [4-6].

  1. Mechanical properties of different types of space maintainers

    NASA Astrophysics Data System (ADS)

    Beldiman, M.-A.; Mârţu, I.; Leiţoiu, B.; Luchian, I.; Lupescu, O.; Bârcă, E. S.

    2015-11-01

    Currently, inside the oral cavity, the dental space maintainers are subjected to forces exerted on them when performing various functions; therefore, it is important to know how each of these mechanisms behave and respond to forces that are applied directly to them. The mechanical properties of the materials used in dentistry are defined by a set of characteristics representing the behaviour of their particular working conditions and it is qualitatively expressed by a number of parameters.The study aimed to determine the pressing force that can be taken by four 4 types of space maintainers frequently used in practice - fixed and removable, applied on four samples realized with human teeth extracted for orthodontic purposes. Static tests were carried out on a machine type short WDW-5 EC with a maximum force of 5 kN and a loading speed of 5 mm/min by a special testing machine, with an innovative appliance; data recording was automatically performed, using a computer with a special program that present the specific diagrams. Experimental determinations included the following aspects: to determine the maximum force that can be supported by each sample, and to observe the deformations. The values obtained indicate that the best option in terms of behavior under the conditions specified is the removable appliance, and the less functional version is the fixed space maintainer using brackets. According to tests conducted, the fracture strength was found to be more important for fixed space maintainers (band and loop, for example) so, in practice is using more frequent these types of space maintainers.

  2. Coupled thermo-hydro-mechanical modeling of heat extraction from the Tattapani geothermal field, India

    NASA Astrophysics Data System (ADS)

    Nand Pandey, Sachchida; Vishal, Vikram

    2017-04-01

    Modeling of coupled thermo-hydro-mechanical processes in enhanced geothermal systems is presented using the finite element method of modeling for a 3-D domain. The reservoir consists of a single horizontal fracture surrounded by low permeable rock matrix. The flow is imposed on a fracture plane, consisting of a doublet system. The reservoir rock mechanical properties were taken from the field data of the Tattapani geothermal field, India. We investigate the effects of injection temperature and mass flow rate on the energy output. The results indicate that temperature and pressure changes within the reservoirs occur due to injection of cold water. The temperature drop and fluid overpressure inside the reservoirs/fracture affect the transport properties of the fracture. The spatial-temporal variations of fracture aperture inside the reservoir greatly impact the thermal drawdown and therefore net energy output. The results showed that maximum aperture evolution occurs near the injection zone than the production zone. The fracture aperture evolution is a result of combined effects of thermal stress and fluid overpressure inside the fracture. The fracture opening reduces the injection pressure required to circulate the fixed volume of water. The effects of the injection temperature on heat extraction were also analyzed under different reservoir formations. The results indicate that reservoir permeability plays a significant role on heat extraction, highlighting the important effect of water losses. For each factor, it is concluded that thermal breakthrough primarily depends on injection temperate, mass flow rate, reservoir permeability and well distances. The results of this study can help in choosing the operational parameters for successful operation of geothermal system. The study will also be helpful to optimize the EGS performance under varying reservoir conditions.

  3. Inhibitory effects and mechanisms of Hydrilla verticillata (Linn.f.) Royle extracts on freshwater algae.

    PubMed

    Zhang, T-T; He, M; Wu, A-P; Nie, L-W

    2012-03-01

    To pursue an effective way to control freshwater algae, four extracts from a submerged macrophyte Hydrilla verticillata (Linn.f.) Royle were tested to study its inhibitory effects on Anabaena flos-aquae FACHB-245 and Chlorella pyrenoidosa Chick FACHB-9. Extract with the highest inhibiting ability was further studied in order to reveal the inhibitory mechanism. The results demonstrated that H. verticillata extracts inhibited the growth of A. flos-aquae and C. pyrenoidosa, and methanol extract had the highest inhibiting ability. The mechanism underlying the algal growth inhibition involves the superoxide anion radical generation that induces the damage of cell wall and release of intracellular components.

  4. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    PubMed

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  5. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing

    PubMed Central

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  6. Pectin from Abelmoschus esculentus: optimization of extraction and rheological properties.

    PubMed

    Chen, Yi; Zhang, Jian-Guo; Sun, Han-Ju; Wei, Zhao-Jun

    2014-09-01

    Response surface methodology (RSM) was applied to optimize the parameters of pectin extraction from okra pods. The extracted okra pectin was then investigated by steady-shear and oscillatory rheological measurements. Statistical analysis showed that the linear term of the liquid-solid ratio, the quadratic term of the pH, and the linear term of the extraction time showed highly significant effects on pectin yield. The optimal extraction conditions that maximized the pectin yield within the experimental range of the variables researched were a pH of 3.9, an extraction time of 64 min, an extraction temperature of 60°C, and a liquid-solid ratio of 42:1. Under these conditions, the pectin yield was predicted to be 2.71%. At a liquid-solid ratio less than 2.5% w/w in aqueous solution, the pectin extracted from okra presented non-Newtonian shear-thinning behavior and could be well described by the Cross model. The okra pectin showed predominantly viscous responses (G'

  7. Toxicity and properties of the extract from Sarcocystis cruzi cysts.

    PubMed

    Saito, M; Taguchi, K; Shibata, Y; Kobayashi, T; Shimura, K; Itagaki, H

    1995-12-01

    The extract from Sarcocystis cruzi cysts in bovine muscle was subcutaneously injected to mice, guinea pigs, chickens, and rabbits to detect its toxicity. Only rabbits showed reactions after administration of the extract at a dose of 25 micrograms. The main clinical signs of the rabbits were depression, reduction in body temperature and intermittent diarrhea and the hematological findings observed were elevation in WBC, RBC, PCV, TP, BUN, AST, AUT and creatinine values and reduction in glucose, K+ and pH of blood. The extract, crude toxin, was a water soluble, acid-alkali stable and thermolabile protein and estimated to be a molecular mass of 15-16 kd.

  8. Mechanical properties of ISABELLE superconducting coils

    SciTech Connect

    Thompson, P.; Bertsche, A.; Fuhrmann, J.; Greene, A.; Grove, E.; Repeta, L.; Short, F.; Tannenbaum, M.; Wanderer, P.

    1981-01-01

    As a part of the manufacturing processes, several mechanical measurements are made on ISABELLE dipoles. These are done both to control the process and to provide information for the evaluation of the behavior of the completed magnets. This paper discusses the Young's Modulus (E = 1-3 x 10/sup 6/ psi), the thermal contraction of the coil assembly (..delta..L/L = 290 +- 17 x 10/sup -5/ at 77/sup 0/K), and the loss of applied prestress with time (approx. 20% for times 20 days).

  9. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Kalatur, Ekaterina Narikovich, Anton; Buyakova, Svetlana E-mail: kulkov@ispms.tsc.ru; Kulkov, Sergey E-mail: kulkov@ispms.tsc.ru

    2014-11-14

    The article studies the porous ceramics consisting of ultra-fine ZrO{sub 2} powders. The porosity of ceramic samples varied from 15% to 80%. The structure of the ceramic materials had a cellular configuration. The distinctive feature of all experimentally obtained strain diagrams is their nonlinearity at low deformations characterized by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations shown in strain diagrams is due to the mechanical instability of cellular elements of the ceramic framework.

  10. Annealing and Mechanical Properties of ECAP Tantalum

    DTIC Science & Technology

    2011-03-01

    deformation. 9.0 References 1 J. M. O’Brien and W. F. Hosford . “Grain Refinement of Tantalum, Copper and Zirconium by Equal Channal Angular...pp. 205-217. 10 S. Nemat-Nasser and J.B. Isaacs, Acta Materialia 45 (3) (1997) pp.907-919. 11 W. F. Hosford , The Mechanics of Crystals and...O’Brien and W. F. Hosford , AFRL-MN-EG-TR-2007-7000, Technical Report, Eglin AFB, FL, November 2006, Contract No. F08651-02-C-0023. 17 P. S

  11. Mechanical Properties of Gradient Structure Mg Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Hongliang; Yang, Jiang; Zhou, Hao; Moering, Jordan; Yin, Zhe; Gong, Yulan; Zhao, KunYu

    2017-09-01

    In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.

  12. Mechanical Properties of Gradient Structure Mg Alloy

    NASA Astrophysics Data System (ADS)

    Chen, Hongliang; Yang, Jiang; Zhou, Hao; Moering, Jordan; Yin, Zhe; Gong, Yulan; Zhao, KunYu

    2017-07-01

    In this work, a surface mechanical attrition treatment (SMAT) process was applied to AZ31B magnesium alloy at room temperature. This method produced a gradient structure on the treated AZ31B, in which the grains of the topmost layer are refined to nanoscale sizes. A combination of nanocrystallites at the surface and coarse-grains in the center are the main features of this structure. This structure results in an excellent combination of both strength and ductility. The highest yield strength for the 30 minutes SMAT AZ31B samples increased to 249 ± 5 MPa and the uniform elongation decreased to 9.3 ± 0.8 pct, whereas the original yield strength was only 147 ± 4 MPa and the uniform elongation was 15.4 ± 1.1 pct. Microstructural observations, stress relaxation tests, and hardness tests were used to verify the results. Additionally, there is a specific volume fraction of gradient structure to achieve the best mechanical performance, which is shown to be in the range of 9.3 to 14 pct for the AZ31B alloy.

  13. Mechanical properties of plastics predetermined by empirical method

    NASA Technical Reports Server (NTRS)

    Lohr, J. J.; Parker, J. A.

    1964-01-01

    To predetermine the mechanical properties of rigid plastics as a function of plasticizer content and composition, a set of equations has been empirically derived. These relate strain rate, yield stress, temperature, and weight fraction of the plasticizer.

  14. Influence of initial flaws on the mechanical properties of nacre.

    PubMed

    Anup, S

    2015-06-01

    Nacre is a bio-composite made up of hard mineral and soft protein, and has excellent mechanical properties. This paper examines the effect of naturally occurring defects (initial flaws) in nacre on its mechanical properties such as toughness and strength. A random fuse model is developed incorporating initial flaws. Numerical simulations show that initial flaws affect different mechanical properties at different rates. The variation in the experimentally obtained mechanical properties of nacre reported in the literature is shown to be due to initial flaws. The stress in the mineral and protein increases due to initial flaws, but by different amounts. The results obtained in this study are useful for gaining insight into the failure of nacre and development of nacre-inspired composites.

  15. Resource Letter MPF-1: Mechanical Properties of Fluids

    ERIC Educational Resources Information Center

    Stanley, R. C.

    1974-01-01

    Presents an annotated bibliography concerning the mechanical properties of fluids, including topics for use at elementary, secondary, undergraduate, and graduate levels. Indicates that the material can particularly help college physicists in improving course contents in specified fields of physics. (CC)

  16. Tailoring of mechanical properties of hydroformed aluminum tubes

    SciTech Connect

    Hong, Sung-tae; Lavender, Curt A.

    2007-07-06

    Tailoring of the mechanical properties of hydroformed aluminum 6063-T4 tubes to those of aluminum 6063-T6 was performed by heat treatment. Quasi-static tensile tests and a SEM analysis were conducted to evaluate the change of the mechanical properties. The experimental results of the hydroformed tubes in T4 condition (before the heat treatment) show significant variations of the mechanical properties along the length due to the different extents of work hardening by hydroforming. The experimental results of the hydroformed tubes in T6 condition (after the heat treatment) show that the precipitation hardening successfully removed the effects of the non-uniform work hardening and resulted in the uniform mechanical properties in the tube.

  17. Modified Polypropylene with Improved Physical-Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Chervakov, D. O.; Bashtanyk, P. I.; Burmistr, M. V.

    2015-03-01

    The use of mixtures of benzoyl peroxide and polysiloxane polyol compounds as polypropylene modifiers is suggested. It is established that, in such a way, its physical-mechanical properties can be changed purposefully.

  18. Characterising Mechanical Properties of Braided and Woven Textile Composite Beams

    NASA Astrophysics Data System (ADS)

    Dauda, Benjamin; Oyadiji, S. Olutunde; Potluri, Prasad

    2009-02-01

    The focus of this paper is on the manufacture of textile composite beams and on the determination of their mechanical properties. This includes investigating the effects of fibre orientation on the mechanical properties of braided and woven textile composites. Composites were manufactured from nominally identical constituents and identical consolidation processes, leaving as the only variables, variations caused by the different fibre architecture of the preform. The repeatability and, hence, reliability of this approach is demonstrated. Results obtained show that fibre architecture affects composite strength and extensibility. Composites with woven preforms are practically linear up to catastrophic failure while composites with braided preforms exhibit non-linearity prior to failure. Also the mechanical properties of the textile composite beams were determined. Results show that by tailoring the braid angle and pick density of braided and woven composite performs, the mechanical properties of the composite beams can be controlled to suit end-use requirement.

  19. Properties of rice stem extracts obtained by using subcritical fluids.

    PubMed

    Tangkhavanich, Boonnakhom; Kobayashi, Takashi; Adachi, Shuji

    2013-01-01

    Rice stems were subjected to a subcritical fluid treatment at 230 °C, using ethanol or acetone at a dilution of 0-100% in water. The obtained extracts were determined for their yield, carbohydrate content, phenolic content, DPPH radical scavenging ability, and color. The highest yield and carbohydrate content were achieved with the subcritical 20% (v/v) organic solvent, while the highest phenolic content was obtained with subcritical 80% (v/v) acetone. The highest radical scavenging ability was achieved with subcritical 60% (v/v) ethanol and 80% (v/v) acetone. The lightness of the extracts obtained with subcritical ethanol and acetone was negatively correlation with their radical scavenging ability (R=-0.85). The relationship between the lightness and phenolic content of the extracts was not significant, suggesting that other substances in the extract could also possess radical scavenging ability.

  20. Properties of herbal extracts against Propionibacterium acnes for biomedical application

    NASA Astrophysics Data System (ADS)

    Lim, Youn-Mook; Kim, Sung Eun; Kim, Yong Soo; Shin, Young Min; Jeong, Sung In; Jo, Sun-Young; Gwon, Hui-Jeong; Park, Jong-seok; Nho, Young-Chang; Kim, Jong-Cheol; Kim, Seong-Jang; Shin, HeungSoo

    2012-10-01

    Propionibacterium acnes (P. acnes), one of the anaerobic bacterium, causes inflammatory acne. To find a novel medication for treating the inflammation caused by P. acnes, we investigated the anti-bacterial and anti-inflammatory activities of several herbal extracts against P. acnes. The aqueous extracts from five dried herbs, Phellodendron amurense Rupr., Paeonia lactiflora Pallas., Houttuynia cordata Thunb., Agrimonia pilosa Ledeb. and Glycyrrhiza uralensis Fisch., were prepared and mixed. In this experiment, 1 mg/ml of the herbal extract mixture caused a decrease in the growth of P. acnes and reduced the production of pro-inflammatory cytokines, TNF-α, IL-8, IL-1β and IL-6, in human monocytic THP-1 cells treated with heat-killed P. acnes. Therefore, this herbal extract mixture may possess both anti-bacterial and anti-inflammatory activities against P. acnes and can be a novel therapeutic agent for treating inflammatory acne.

  1. Mechanical Properties of Bovine Rhodopsin and Bacteriorhodopsin: Possible Roles in Folding and Function†

    PubMed Central

    Sapra, K. Tanuj; Park, Paul S.-H.; Palczewski, Krzysztof; Muller, Daniel J.

    2008-01-01

    Molecular interactions and mechanical properties that contribute to the stability and function of proteins are complex and of fundamental importance. In this study, we used single-molecule dynamic force spectroscopy (DFS) to explore the interactions and the unfolding energy landscape of bovine rhodopsin and bacteriorhodopsin. An analysis of the experimental data enabled the extraction of parameters that provided insights into the kinetic stability and mechanical properties of these membrane proteins. Individual structural segments of rhodopsin and bacteriorhodopsin have different properties. A core of rigid structural segments was observed in rhodopsin but not in bacteriorhodopsin. This core may reflect differences in mechanisms of protein folding between the two membrane proteins. The different structural rigidity of the two proteins may also reflect their adaptation to differing functions. PMID:18266338

  2. [Plant extracts with cytostatic properties growing in Cuba. I].

    PubMed

    Lopez Abraham, A M; Rojas Hernandez, N M; Jimenez Misas, C A

    1979-01-01

    The cytostatic activity of aqueous, alcoholic and ketonic extracts of 9 species of superior plants of the families Fitolacaceae, Compositae, Moraceae, Zingiberaceae, Martiniaceae, Mirtaceae, Verbenaceae and Annonaceae was assessed. The Kubas microbiologic method and the fungus Ascomiceto Neurospora crassa were used in the assessment. The fungus growth was measured in millimeters. Inhibition percentages for every case regarding control are reported. The best results were obtained from Annona muricata, Costus spiralis, Cecropia peltata, Xanthium chinense and Pluchea adorata extracts.

  3. [Plant extracts with cytostatic properties growing in Cuba. II].

    PubMed

    Lopez Abraham, A M; Rojas Hernandez, N M; Jimenez Misas, C A

    1979-01-01

    The study of the cytostatic activity of aqueous, alcoholic and ketonic extracts from 18 parts of 9 species of superior plants of the families Araceae, Borraginacease, Burseraceae, Cesalpinaceae, Meliaceae, Compositae, Rebiaceae, Cruciferaceae and Verbenaceae using the microbiologic method of described by Kubas in 1972 is pursued. The best results were obtained from Hamelia patens. Lippia alba, Lepidium virginicum, Cassia ligustrina, Bursera simaruba and Heliotropium campechianum extracts.

  4. Microstructure and mechanical properties of neoprene montmorillonite nanocomposites

    NASA Astrophysics Data System (ADS)

    Yeh, Meng-Heng; Hwang, Weng-Sing; Cheng, Lin-Ri

    2007-03-01

    To investigate the microstructure and mechanical properties of neoprene-montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of montmorillonite enhances the mechanical properties of neoprene significantly.

  5. Processing effects on the mechanical properties of tungsten heavy alloys

    NASA Technical Reports Server (NTRS)

    Kishi, Toshihito; German, R. M.

    1990-01-01

    Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

  6. Primate dietary ecology in the context of food mechanical properties.

    PubMed

    Coiner-Collier, Susan; Scott, Robert S; Chalk-Wilayto, Janine; Cheyne, Susan M; Constantino, Paul; Dominy, Nathaniel J; Elgart, Alison A; Glowacka, Halszka; Loyola, Laura C; Ossi-Lupo, Kerry; Raguet-Schofield, Melissa; Talebi, Mauricio G; Sala, Enrico A; Sieradzy, Pawel; Taylor, Andrea B; Vinyard, Christopher J; Wright, Barth W; Yamashita, Nayuta; Lucas, Peter W; Vogel, Erin R

    2016-09-01

    Substantial variation exists in the mechanical properties of foods consumed by primate species. This variation is known to influence food selection and ingestion among non-human primates, yet no large-scale comparative study has examined the relationships between food mechanical properties and feeding strategies. Here, we present comparative data on the Young's modulus and fracture toughness of natural foods in the diets of 31 primate species. We use these data to examine the relationships between food mechanical properties and dietary quality, body mass, and feeding time. We also examine the relationship between food mechanical properties and categorical concepts of diet that are often used to infer food mechanical properties. We found that traditional dietary categories, such as folivory and frugivory, did not faithfully track food mechanical properties. Additionally, our estimate of dietary quality was not significantly correlated with either toughness or Young's modulus. We found a complex relationship among food mechanical properties, body mass, and feeding time, with a potential interaction between median toughness and body mass. The relationship between mean toughness and feeding time is straightforward: feeding time increases as toughness increases. However, when considering median toughness, the relationship with feeding time may depend upon body mass, such that smaller primates increase their feeding time in response to an increase in median dietary toughness, whereas larger primates may feed for shorter periods of time as toughness increases. Our results emphasize the need for additional studies quantifying the mechanical and chemical properties of primate diets so that they may be meaningfully compared to research on feeding behavior and jaw morphology. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Mechanical properties of henequen fibre/epoxy resin composites

    NASA Astrophysics Data System (ADS)

    Gonzalez-Murillo, C.; Ansell, M. P.

    2009-07-01

    By using surface-treated and untreated henequen fibres and an epoxy resin, composites were made by compression moulding, and their mechanical properties and failure modes were determined experimentally in tension, bending, and impact loading. The results obtained show that the treatment of fibre surface does not improve the bond between the fibres and the resin matrix, and the general mechanical properties of the composites are similar.

  8. Evaluation of a sequential extraction process used for determining mercury binding mechanisms to coal combustion byproducts

    SciTech Connect

    James D. Noel; Pratim Biswas; Daniel E. Giammar

    2007-07-15

    This study evaluated the selectivity and effectiveness of a sequential extraction process used to determine mercury binding mechanisms to various materials that are present in coal combustion byproducts. A six-step sequential extraction process was applied to laboratory-synthesized materials with known mercury concentrations and binding mechanisms. These materials were calcite, hematite, goethite, and titanium dioxide. Fly ash from a full-scale coal-fired power plant was also investigated. The concentrations of mercury were measured using inductively coupled plasma (ICP) mass spectrometry, whereas the major elements were measured by ICP atomic emission spectrometry. The materials were characterized by X-ray powder diffraction and scanning electron microscopy with energy dispersive spectroscopy. The sequential extraction procedure provided information about the solid phases with which mercury was associated in the solid sample. The procedure effectively extracted mercury from the target phases. The procedure was generally selective in extracting mercury. However, some steps in the procedure extracted mercury from nontarget phases, and others resulted in mercury redistribution. Iron from hematite and goethite was only leached in the reducible and residual extraction steps. Some mercury associated with goethite was extracted in the ion exchangeable step, whereas mercury associated with hematite was extracted almost entirely in the residual step. Calcium in calcite and mercury associated with calcite were primarily removed in the acidsoluble extraction step. Titanium in titanium dioxide and mercury adsorbed onto titanium dioxide were extracted almost entirely in the residual step. 42 refs., 13 figs., 2 tabs.

  9. Measuring the mechanical properties of molecular conformers

    NASA Astrophysics Data System (ADS)

    Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

    2015-09-01

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

  10. Mechanical properties of rare earth stannate pyrochlores

    NASA Astrophysics Data System (ADS)

    Feng, J.; Xiao, B.; Qu, Z. X.; Zhou, R.; Pan, W.

    2011-11-01

    The RE2Sn2O7 series compounds (RE = La, Nb, Sm, Gd, Er, Yb) with a pyrochlore structure are prepared by co-precipitation method. The bulk, shear, Young's moduli, B/G, and Poisson's ratios are calculated using density functional theory and also measured by ultrasonic resonance method. The theoretical values of lattice constants and mechanical moduli are smaller than experimental results. The electronic structures of RE2Sn2O7 are analogous to RE2Zr2O7. La2Sn2O7 exhibits stronger ionic bonds than others. The covalent interactions are slightly enhanced in the heavy rare earth stannate pyrochlores. The Vickers harnesses of RE2Sn2O7 are measured experimentally, which are smaller than theoretical predictions.

  11. Measuring the mechanical properties of molecular conformers.

    PubMed

    Jarvis, S P; Taylor, S; Baran, J D; Champness, N R; Larsson, J A; Moriarty, P

    2015-09-21

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

  12. Mechanical properties of hydroxyapatite/mica composite.

    PubMed

    Nordström, E G; Herø, H; Jørgensen, R B

    1994-01-01

    Bend specimens of the inorganic synthetic materials hydroxyapatite (HA) and a composite of hydroxyapatite/muscovite mica have been prepared and tested mechanically. Sintering followed by hot isostatic pressing (HIP) without encapsulation gave an increased strength for HA alone, but no significant increase in strength compared with sintering alone for HA/mica composites. The bend strength of the HA/mica composite was inferior to that of HA alone, the reason being inadequate bonding between HA and mica. HIP in glass capsules and an increased cold compaction pressure tended to improve the bend strength of the composite. Corrosion in tris for 7 d did not affect the bend strength of the investigated materials significantly.

  13. Effective elastic mechanical properties of single layer graphene sheets.

    PubMed

    Scarpa, F; Adhikari, S; Srikantha Phani, A

    2009-02-11

    The elastic moduli of single layer graphene sheet (SLGS) have been a subject of intensive research in recent years. Calculations of these effective properties range from molecular dynamic simulations to use of structural mechanical models. On the basis of mathematical models and calculation methods, several different results have been obtained and these are available in the literature. Existing mechanical models employ Euler-Bernoulli beams rigidly jointed to the lattice atoms. In this paper we propose truss-type analytical models and an approach based on cellular material mechanics theory to describe the in-plane linear elastic properties of the single layer graphene sheets. In the cellular material model, the C-C bonds are represented by equivalent mechanical beams having full stretching, hinging, bending and deep shear beam deformation mechanisms. Closed form expressions for Young's modulus, the shear modulus and Poisson's ratio for the graphene sheets are derived in terms of the equivalent mechanical C-C bond properties. The models presented provide not only quantitative information about the mechanical properties of SLGS, but also insight into the equivalent mechanical deformation mechanisms when the SLGS undergoes small strain uniaxial and pure shear loading. The analytical and numerical results from finite element simulations show good agreement with existing numerical values in the open literature. A peculiar marked auxetic behaviour for the C-C bonds is identified for single graphene sheets under pure shear loading.

  14. Antioxidant Properties of Berberis aetnensis C. Presl (Berberidaceae) Roots Extract and Protective Effects on Astroglial Cell Cultures

    PubMed Central

    Campisi, Agata; Bonfanti, Roberta; Raciti, Giuseppina; Amodeo, Andrea; Mastrojeni, Silvana; Ragusa, Salvatore; Iauk, Liliana

    2014-01-01

    Berberis aetnensis C. Presl (Berberidaceae) is a bushy-spiny shrub common on Mount Etna (Sicily). We demonstrated that the alkaloid extract of roots of B. aetnensis C. Presl contains prevalently berberine and berbamine, possesses antimicrobial properties, and was able to counteract the upregulation evoked by glutamate of tissue transglutaminase in primary rat astroglial cell cultures. Until now, there are no reports regarding antioxidant properties of B. aetnensis C. Presl collected in Sicily. Air-dried, powdered roots of B. aetnensis C. Presl were extracted, identified, and quantified by HPLC. We assessed in cellular free system its effect on superoxide anion, radicals scavenging activity of antioxidants against free radicals like the 1,1-diphenyl-2-picrylhydrazyl radical, and the inhibition of xanthine oxidase activity. In primary rat astroglial cell cultures, exposed to glutamate, we evaluated the effect of the extract on glutathione levels and on intracellular production of reactive oxygen species generated by glutamate. The alkaloid extract of B. aetnensis C. Presl inhibited superoxide anion, restored to control values, the decrease of GSH levels, and the production of reactive oxygen species. Potent antioxidant activities of the alkaloid extract of roots of B. aetnensis C. Presl may be one of the mechanisms by which the extract is effective against health disorders associated to oxidative stress. PMID:25177720

  15. Antioxidant properties of Berberis aetnensis C. Presl (Berberidaceae) roots extract and protective effects on astroglial cell cultures.

    PubMed

    Campisi, Agata; Acquaviva, Rosaria; Bonfanti, Roberta; Raciti, Giuseppina; Amodeo, Andrea; Mastrojeni, Silvana; Ragusa, Salvatore; Iauk, Liliana

    2014-01-01

    Berberis aetnensis C. Presl (Berberidaceae) is a bushy-spiny shrub common on Mount Etna (Sicily). We demonstrated that the alkaloid extract of roots of B. aetnensis C. Presl contains prevalently berberine and berbamine, possesses antimicrobial properties, and was able to counteract the upregulation evoked by glutamate of tissue transglutaminase in primary rat astroglial cell cultures. Until now, there are no reports regarding antioxidant properties of B. aetnensis C. Presl collected in Sicily. Air-dried, powdered roots of B. aetnensis C. Presl were extracted, identified, and quantified by HPLC. We assessed in cellular free system its effect on superoxide anion, radicals scavenging activity of antioxidants against free radicals like the 1,1-diphenyl-2-picrylhydrazyl radical, and the inhibition of xanthine oxidase activity. In primary rat astroglial cell cultures, exposed to glutamate, we evaluated the effect of the extract on glutathione levels and on intracellular production of reactive oxygen species generated by glutamate. The alkaloid extract of B. aetnensis C. Presl inhibited superoxide anion, restored to control values, the decrease of GSH levels, and the production of reactive oxygen species. Potent antioxidant activities of the alkaloid extract of roots of B. aetnensis C. Presl may be one of the mechanisms by which the extract is effective against health disorders associated to oxidative stress.

  16. Mechanical properties of Inconel 617 and 618

    SciTech Connect

    McCoy, H E; King, J F

    1985-02-01

    Inconel 617 and 618 were evaluated for application in high-temperature gas-cooled reactors (HTGRs). Techniques were developed for making sound welds, and tests were performed on base and weld metals. Specimens of both materials were aged to 20,000 h to evaluate thermal stability. Short-term tensile tests on alloy 617 showed that aging severely reduced the strain at fracture at both ambient and elevated temperatures. The impact energy at ambient temperature was severely degraded by aging. Creep tests showed that fracture occurred at 593 through 704{sup 0}C after only 1 to 2% strain, and higher strains were noted at higher temperatures. There was no detectable difference between the creep behavior in air and that in HTGR helium environments. Inconel alloy 618 had excellent stability during aging. Fracture strains in short-term tensile tests and impact energies in impact tests remained high after aging. The creep properties of alloy 618 were equivalent in air and in HTGR helium. Both alloys were carburized during creep testing in HTGR helium, and the rate of carburization became rather high at 760{sup 0}C and higher temperatures. 49 figures, 20 tables.

  17. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties

    PubMed Central

    Carroll, Chad C.

    2015-01-01

    Exercising individuals commonly consume analgesics but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling. PMID:26509485

  18. Analgesic Drugs Alter Connective Tissue Remodeling and Mechanical Properties.

    PubMed

    Carroll, Chad C

    2016-01-01

    Exercising individuals commonly consume analgesics, but these medications alter tendon and skeletal muscle connective tissue properties, possibly limiting a person from realizing the full benefits of exercise training. I detail the novel hypothesis that analgesic medications alter connective tissue structure and mechanical properties by modifying fibroblast production of growth factors and matrix enzymes, which are responsible for extracellular matrix remodeling.

  19. Data for prediction of mechanical properties of aspen flakeboards

    Treesearch

    C. G. Carll; P. Wang

    1983-01-01

    This research compared two methods of producing flakeboards with uniform density distribution (which could then be used to predict bending properties of flakeboards with density gradients). One of the methods was suspected of producing weak boards because it involved exertion of high pressures on cold mats. Although differences were found in mechanical properties of...

  20. Mechanical and physical properties of agro-based fiberboard

    Treesearch

    S. Lee; T.F. Shupe; C.Y. Hse

    2006-01-01

    In order to better utilize agricultural fibers as an alternative resource for composite panels, several variables were investigated to improve mechanical and physical properties of agm-based fiberboard. This study focused on the effect of fiber morphology, slenderness ratios (UD), and fiber mixing combinations on panel properties. The panel construction types were also...

  1. Study of the effect of gamma irradiation on a commercial polycyclooctene I. Thermal and mechanical properties

    NASA Astrophysics Data System (ADS)

    García-Huete, N.; Laza, J. M.; Cuevas, J. M.; Vilas, J. L.; Bilbao, E.; León, L. M.

    2014-09-01

    A gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals able to induce chain scission or recombination of radicals, which induces annihilation, branching or crosslinking processes. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of 60Co at different doses (25-200 kGy). After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane. Furthermore, thermal properties were evaluated before and after Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as mechanical properties were measured by Dynamic Mechanical Thermal Analysis (DMTA). The results showed the variations of the properties depending on the irradiation dose. Finally, a first approach to evaluate qualitatively the shape memory behaviour of all irradiated PCO samples was performed by a visually monitoring shape recovery process.

  2. Analysis on the Physicochemical Properties of Ginkgo biloba Leaves after Enzymolysis Based Ultrasound Extraction and Soxhlet Extraction.

    PubMed

    Zhang, Chang-Wei; Wang, Cheng-Zhang; Tao, Ran

    2016-01-15

    In this study, high performance liquid chromatography (HPLC), ultraviolet (UV), thermagravimetric analyzer (TGA), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), and scanning electron microscope (SEM) were used as measurement techniques, contents of chemical composition, pyrolytic products, thermal stability, morphological characterization of Ginkgo biloba leaves (GBL) acted as the index, and physicochemical properties of GBL after enzymolysis based ultrasound extraction (EBUE) and Soxhlet extraction were studied. The detection results of chemical composition revealed that contents of general flavone, soluble protein, soluble total sugar and protein in the GBL declined significantly after EBUE, and contents of polyprenols and crude fat obviously reduced as well after Soxhlet extraction. Py-GC-MS results indicated that total GC contents of micromolecules with carbon less than 12 from 54.0% before EBUE decline to 8.34% after EBUE. Total GC contents of long-chain fatty acids with carbon less than 20 from 43.0% before EBUE reduced to 27.0% after Soxhlet extraction. Thermal stability results showed that GBL after Soxhlet extraction was easier to decompose than GBL before EBUE. SEM results illustrated that surface structure of GBL was damaged severely after EBUE, compared with GBL before EBUE, while organic solvent extraction had little influence on the morphological characterization of GBL after Soxhlet extraction compared with GBL after EBUE.

  3. Mechanical properties of human trabecular bone lamellae quantified by nanoindentation.

    PubMed

    Zysset, P K; Guo, X E; Hoffler, C E; Moore, K E; Goldstein, S A

    1998-12-01

    Improved preventive and therapeutic strategies for skeletal diseases such as osteoporosis rely on a better understanding of the mechanical properties of trabecular bone and their influence on cell mediated adaptation processes. The mechanical properties of trabecular bone are determined by composition as well as structural (trabecular architecture), microstructural (trabecular packets) and nanostructural (lamellae) organization. Density is the major predictor of the mechanical properties of trabecular structures and has been extended to the concept of fabric to include architectural anisotropy and improve even further the power of prediction. Recent advances in QCT and MRI technologies allow for precise assessment of 3D trabecular architecture and the mechanical consequences of structural changes can be increasingly well quantified by the means of computational methods. While single trabeculae have been tested using various techniques with contrasting results, little is known about the intrinsic mechanical properties of trabecular bone lamellae on which these computational methods rely. For instance, water and mineral content have a significant effect on the elastic, viscous, yield and postyield properties of bone tissue. In addition, collagen fiber orientation affects the mechanics of single remodeling units. Variations in composition and organization determined by age, accumulated damage or disease may therefore reduce the mechanical integrity of trabecular bone and deserve more attention. The aim of this work was to utilize a nanoindentation technique to quantify elastic modulus and hardness of human trabecular bone lamellae.

  4. Mechanical properties of dental investment materials.

    PubMed

    Low, D; Swain, M V

    2000-07-01

    Measurement of the elastic modulus (E) of investment materials has been difficult because of their low strength. However, these values are essential for engineering simulation and there are many methods available to assess the elasticity of materials. The present study compared two different methods with one of the methods being non-destructive in nature and can be used for specimens prepared for other tests. Two different types of investment materials were selected, gypsum-and phosphate-bonded. Method 1 is a traditional three-point bending test. Twelve rectangular bars with dimension of (70 x 9 x 3 mm) were prepared and placed on supports 56.8 mm apart. The test was conducted at a cross-head speed of 1 mm/min by use of a universal testing machine. The load applied to the test specimen and the corresponding deflection were measured until the specimen fractured. The E value was calculated from a linear part of the stress-strain plot. Method 2 is an ultra micro-indentation system to determine near surface properties of materials with nanometer resolution. The measurement procedure was programmed such that the specimens were indented with an initial contact force of 5 mN then followed by a maximum force of 500 mN. Measurement consisted of 10 indentations conducted with a spherical stainless steel indenter (R = 250 microm) that were equally spaced (500 microm). The E value rose asymptotically with depth of penetration and would approach the three-point bending test value at approximately four time's maximum contact depth for both materials. Both methods are practical ways of measuring the E of investment materials.

  5. Fluid mechanical properties of flames in enclosures

    SciTech Connect

    Rotman, D.A.; Pindera, M.Z.; Oppenheim, A.K.

    1988-07-01

    In an enclosure where the reacting medium is initially at rest, the flame first generates a flowfield that then gets stretched, i.e., its front is pulled along the surface by the flowfield in which it then finds itself residing. A methodology developed for numerical modeling of such fields is described. Of key significance in this respect is the zero Mach number model/endash/a reasonable idealization in view of the relatively high temperature, and hence sound speed, that exists, concomitantly with a comparatively low particle velocity, in the confinement of a combustion chamber. According to this model, the density gradient in the field is nullified, while across the flame front it approaches infinity. One has thus two regimes: one of the unburned medium and the other of the burned gas, each of spatially uniform density, separated by a flame front interface. The latter is endowed with four properties, of which the first two are purely kinematic and the others dynamic in nature, namely: 1) it is advected at the local velocity of flow; 2) it self-advances at the normal burning speed, the eigenvalue of the system; 3) it acts as the velocity source due to the exothermicity of the combustion process; and 4) it acts as the vorticity source due to the baroclinic effect generated by the pressure gradient along its surface and the density gradient across it. A solution obtained for a flame propagating in an oblong rectangular enclosure demonstrates that the latter has a significant influence upon the formation of the well known tulip shape. 12 refs., 4 figs.

  6. Relationship between microstructure, material distribution, and mechanical properties of sheep tibia during fracture healing process.

    PubMed

    Gao, Jiazi; Gong, He; Huang, Xing; Fang, Juan; Zhu, Dong; Fan, Yubo

    2013-01-01

    The aim of this study was to investigate the relationship between microstructural parameters, material distribution, and mechanical properties of sheep tibia at the apparent and tissue levels during the fracture healing process. Eighteen sheep underwent tibial osteotomy and were sacrificed at 4, 8, and 12 weeks. Radiographs and micro-computed tomography (micro-CT) scanning were taken for microstructural assessment, material distribution evaluation, and micro-finite element analysis. A displacement of 5% compressive strain on the longitudinal direction was applied to the micro-finite element model, and apparent and tissue-level mechanical properties were calculated. Principle component analysis and linear regression were used to establish the relationship between principle components (PCs) and mechanical parameters. Visible bony callus formation was observed throughout the healing process from radiographic assessment. Apparent mechanical property increased at 8 weeks, but tissue-level mechanical property did not increase significantly until 12 weeks. Three PCs were extracted from microstructural parameters and material distribution, which accounted for 87.592% of the total variation. The regression results showed a significant relationship between PCs and mechanical parameters (R>0.8, P<0.05). Results of this study show that microstructure and material distribution based on micro-CT imaging could efficiently predict bone strength and reflect the bone remodeling process during fracture healing, which provides a basis for exploring the fracture healing mechanism and may be used as an approach for fractured bone strength assessment.

  7. Mechanical properties of lanthanum and yttrium chromites

    SciTech Connect

    Paulik, S.W.; Armstrong, T.R.

    1996-12-31

    In an operating high-temperature (1000{degrees}C) solid oxide fuel cell (SOFC), the interconnect separates the fuel (P(O{sub 2}){approx}10{sup -16} atm) and the oxidant (P(O2){approx}10{sup 0.2} atm), while being electrically conductive and connecting the cells in series. Such severe atmospheric and thermal demands greatly reduce the number of viable candidate materials. Only two materials, acceptor substituted lanthanum chromite and yttrium chromite, meet these severe requirements. In acceptor substituted chromites (Sr{sup 2+} or Ca{sup 2+} for La{sup 3+}), charge compensation is primarily electronic in oxidizing conditions (through the formation of Cr{sup 4+}). Under reducing conditions, ionic charge compensation becomes significant as the lattice becomes oxygen deficient. The formation of oxygen vacancies is accompanied by the reduction of Cr{sup 4+} ions to Cr{sup 3+} and a resultant lattice expansion. The lattice expansion observed in large chemical potential gradients is not desirable and has been found to result in greatly reduced mechanical strength.

  8. Measuring the mechanical properties of molecular conformers

    PubMed Central

    Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

    2015-01-01

    Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules. PMID:26388232

  9. Porosity and mechanical properties of zirconium ceramics

    SciTech Connect

    Buyakova, S. Kulkov, S.; Sablina, T.

    2015-11-17

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO{sub 2}(MgO), ZrO{sub 2}(Y{sub 2}O{sub 3}) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO{sub 2} powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO{sub 2} grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  10. Porosity and mechanical properties of zirconium ceramics

    NASA Astrophysics Data System (ADS)

    Buyakova, S.; Sablina, T.; Kulkov, S.

    2015-11-01

    Has been studied a porous ceramics obtained from ultra-fine powders. Porous ceramic ZrO2(MgO), ZrO2(Y2O3) powder was prepared by pressing and subsequent sintering of compacts homologous temperatures ranging from 0.63 to 0.56 during the isothermal holding duration of 1 to 5 hours. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials produced from plasma-sprayed ZrO2 powder was represented as a system of cell and rod structure elements. Cellular structure formed by stacking hollow powder particles can be easily seen at the images of fracture surfaces of obtained ceramics. There were three types of pores in ceramics: large cellular hollow spaces, small interparticle pores which are not filled with powder particles and the smallest pores in the shells of cells. The cells generally did not have regular shapes. The size of the interior of the cells many times exceeded the thickness of the walls which was a single-layer packing of ZrO2 grains. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformation on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

  11. Mechanical Properties of Nanoscopic Lipid Domains

    SciTech Connect

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; Stanley, Christopher; Lindner, Benjamin; Heberle, Frederick A.; Perticaroli, Stefania; Feygenson, Mikhail; Egami, Takeshi; Standaert, Robert F.; Smith, Jeremy C.; Myles, Dean A. A.; Ohl, Michael; Katsaras, John

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approaches with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.

  12. Mechanical Properties of Nanoscopic Lipid Domains

    DOE PAGES

    Nickels, Jonathan D.; Cheng, Xiaolin; Mostofian, Barmak; ...

    2015-09-28

    We found that the lipid raft hypothesis presents insight into how the cell membrane organizes proteins and lipids to accomplish its many vital functions. Yet basic questions remain about the physical mechanisms that lead to the formation, stability, and size of lipid rafts. Thus, much interest has been generated in the study of systems that contain similar lateral heterogeneities, or domains. In the current work we present an experimental approach that is capable of isolating the bending moduli of lipid domains. This is accomplished using neutron scattering and its unique sensitivity to the isotopes of hydrogen. Combining contrast matching approachesmore » with inelastic neutron scattering, we isolate the bending modulus of ~13 nm diameter domains residing in 60 nm unilamellar vesicles, whose lipid composition mimics the mammalian plasma membrane outer leaflet. Importantly, the bending modulus of the nanoscopic domains differs from the modulus of the continuous phase surrounding them. Moreover, from additional structural measurements and all-atom simulations, we also determine that nanoscopic domains are in-register across the bilayer leaflets. Taken together, these results inform a number of theoretical models of domain/raft formation and highlight the fact that mismatches in bending modulus must be accounted for when explaining the emergence of lateral heterogeneities in lipid systems and biological membranes.« less

  13. Mechanism of electrodialytic ion transport through solvent extraction membranes

    SciTech Connect

    Moskvin, L.N.; Shmatko, A.G.; Krasnoperov, V.M.

    1987-02-01

    The authors construct a mathematical model for electrodialysis and solvent extraction via an ion-selective ion exchange membrane and accounts for the electrochemical, ion exchange, and diffusional behavior of the processes including their dependence on component concentration and current and voltage. The model is tested against experimental data for the electrodialytic transport of anionic platinum complexes of chlorides from hydrochloric acid solution through tributylphosphate membranes. The platinum concentration in the aqueous solution was determined by gamma spectroscopy obtained via platinum 191 as a radiotracer.

  14. Multiresponse Optimization and Prediction of Antioxidant Properties of Aqueous Ginger Extract

    PubMed Central

    Makanjuola, Solomon Akinremi; Enujiugha, Victor Ndigwe; Omoba, Olufunmilayo Sade

    2016-01-01

    The influence of extraction temperature, powder concentration, and extraction time on the antioxidant properties of aqueous ginger extract was investigated. The possibility of estimating the antioxidant properties of the extract from its absorbance and colour properties was also investigated. Results indicated that powder concentration was the most significant factor to consider in optimizing antioxidant extraction. However, temperature and time still influenced the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity while extraction temperature influenced the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the extract. Using the total phenol content, total flavonoid content, ABTS radical scavenging activity, and DPPH radical scavenging activity of the extract, the multiresponse optimization condition for extraction of antioxidant based on the experimental range studied is 96°C, 2.10 g/100 mL, and 90 min. The absorbance of the ginger extract at 610 nm could be exploited for rapid estimation of its total flavonoid and polyphenol with a R2 of 0.713 and 0.753, respectively. PMID:28078258

  15. Mechanical and microstructural properties of "wet" alginate and composite films containing various carbohydrates.

    PubMed

    Harper, B Allison; Barbut, Shai; Smith, Alexandra; Marcone, Massimo F

    2015-01-01

    Composite "wet" alginate films were manufactured from alginate-carbohydrate solutions containing 5% alginate and 0.25% pectin, carrageenan (kappa or iota), potato starch (modified or unmodified), gellan gum, or cellulose (extracted or commercial). The "wet" alginate films were used as a model to understand co-extruded alginate sausage casings that are currently being used by several sausage manufacturers. The mechanical, optical, and microstructural properties of the calcium cross-linked composite films were explored. In addition, the water holding capacity and textural profile analysis properties of the alginate-carbohydrate gels were studied. The results indicate that the mechanical properties of "wet" alginate films/casings can be modified by adding various carbohydrates to them. Alginate films with pectin, carrageenan, and modified potato starch had significantly (P < 0.05) greater elongation values than pure alginate films. The alginate-pectin films also had greater (P < 0.05) tensile strengths than the pure alginate films. Alginate films with extracted cellulose, commercial cellulose, and modified potato starch had lower (P < 0.05) puncture force, distance, and work values than the alginate control films. Transmission electron microscopy images showed a very uniform alginate network in the control films. Several large cellulose fibers were visible in the films with extracted cellulose, while the cellulose fibers in the films with commercial cellulose were difficult to distinguish. Despite these apparent differences in cellulose fiber length, the 2 cellulose films had similar puncture and tensile properties.

  16. Evaluation of a sequential extraction process used for determining mercury binding mechanisms to coal combustion byproducts.

    PubMed

    Noel, James D; Biswas, Pratim; Giammar, Daniel E

    2007-07-01

    Leaching of mercury from coal combustion byproducts is a concern because of the toxicity of mercury. Leachability of mercury can be assessed by using sequential extraction procedures. Sequential extraction procedures are commonly used to determine the speciation and mobility of trace metals in solid samples and are designed to differentiate among metals bound by different mechanisms and to different solid phases. This study evaluated the selectivity and effectiveness of a sequential extraction process used to determine mercury binding mechanisms to various materials. A six-step sequential extraction process was applied to laboratory-synthesized materials with known mercury concentrations and binding mechanisms. These materials were calcite, hematite, goethite, and titanium dioxide. Fly ash from a full-scale power plant was also investigated. The concentrations of mercury were measured using inductively coupled plasma (ICP) mass spectrometry, whereas the major elements were measured by ICP atomic emission spectrometry. The materials were characterized by X-ray powder diffraction and scanning electron microscopy with energy dispersive spectroscopy. The sequential extraction procedure provided information about the solid phases with which mercury was associated in the solid sample. The procedure effectively extracted mercury from the target phases. The procedure was generally selective in extracting mercury. However, some steps in the procedure extracted mercury from nontarget phases, and others resulted in mercury redistribution. Iron from hematite and goethite was only leached in the reducible and residual extraction steps. Some mercury associated with goethite was extracted in the ion exchangeable step, whereas mercury associated with hematite was extracted almost entirely in the residual step. Calcium in calcite and mercury associated with calcite were primarily removed in the acid-soluble extraction step. Titanium in titanium dioxide and mercury adsorbed onto

  17. Antimicrobial mechanisms against Acinetobacter calcoaceticus of rat polymorphonuclear leukocyte granule extract.

    PubMed Central

    Loeffelholz, M J; Modrzakowski, M C

    1988-01-01

    The antimicrobial mechanisms of rat polymorphonuclear leukocyte granule extract and isolated extract fractions against Acinetobacter calcoaceticus were examined. Crude granule extract and a fraction containing low-molecular-weight cationic peptides (peak D) reduced the viability of A. calcoaceticus and inhibited the uptake of radiolabeled macromolecule precursors by cells. The inhibitory activity observed with peak D was not as great as that of crude granule extract containing equivalent amounts of peak D protein. Crude extract also inhibited incorporation of uracil into trichloroacetic acid-precipitable material, while no isolated fraction, including peak D, had any substantial effect on incorporation. The antimicrobial activities of crude granule extract were more sensitive to boiling than those of isolated peak D. Preincubation of A. calcoaceticus with either crude granule extract or a fraction (peak B) possessing proteolytic activity but lacking any antimicrobial activity caused cells to become sensitive to a subinhibitory concentration of actinomycin D, suggesting that granule extract and peak B increase the outer membrane permeability of A. calcoaceticus. The antimicrobial granule extract fraction, peak D, did not affect outer membrane permeability. These results suggest that rat polymorphonuclear leukocyte granule extract reduces the viability of A. calcoaceticus by inhibiting the transport and incorporation of macromolecule precursors and that either whole granule extract is required for complete antimicrobial activity or an unidentified component is responsible for antimicrobial activity in addition to peak D. The granule extract activity that increases outer membrane permeability does not appear to be directly responsible for the observed decrease in viability. PMID:2449397

  18. Papermaking properties of aspen ultrahigh-yield mechanical pulps

    Treesearch

    J. N. McGovern; T. H. Wegner

    1991-01-01

    Eleven types of aspen ultra-high-yield (90% and above) mechanical pubs were evaluated for their chemical compositions (including sulfur), handsheet strength, and optical properties, fiber length indices, and fiberizing energies. The pulping processes were stone groundwood, pressurized stone groundwood, refiner mechanical, thermomechanical, chemimechanical (alkaline...

  19. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  20. Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites

    NASA Technical Reports Server (NTRS)

    Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

  1. Dynamic monitoring of cell mechanical properties using profile microindentation

    PubMed Central

    Guillou, L.; Babataheri, A.; Puech, P.-H.; Barakat, A. I.; Husson, J.

    2016-01-01

    We have developed a simple and relatively inexpensive system to visualize adherent cells in profile while measuring their mechanical properties using microindentation. The setup allows simultaneous control of cell microenvironment by introducing a micropipette for the delivery of soluble factors or other cell types. We validate this technique against atomic force microscopy measurements and, as a proof of concept, measure the viscoelastic properties of vascular endothelial cells in terms of an apparent stiffness and a dimensionless parameter that describes stress relaxation. Furthermore, we use this technique to monitor the time evolution of these mechanical properties as the cells’ actin is depolymerized using cytochalasin-D. PMID:26857265

  2. Anti-inflammatory and neuroactive properties of selected fruit extracts.

    PubMed

    Heim, Kelly C; Angers, Paul; Léonhart, Sebastien; Ritz, Barry W

    2012-09-01

    Epidemiological evidence supports inverse associations between fruit and vegetable intake and incidence of cardiovascular disease and neurodegeneration. Dietary botanicals with salient health benefits include berries and leafy vegetables. Molecular pharmacology research has ascribed these benefits primarily to phenolic constituents and antioxidant activity. The current investigation sought to eluicidate pharmacologic activity of two novel preparations of berry and spinach extracts in vitro. Blueberry and cranberry exhibited the greatest antioxidant activity. In a dose-dependent manner, a proprietary mixture of cranberry and blueberry extracts inhibited inhibitor of κB kinase β, a central node in inflammatory signal transduction. A proprietary mixture of blueberry, strawberry, and spinach extracts inhibited prolyl endopeptidase, a regulator of central neuropeptide stability and an emerging therapeutic target in neurology and psychiatry. These results indicate specific molecular targets of blended dietary plants with potential relevance to inflammation and neurological health.

  3. Radioprotective property of an aqueous extract from valeriana wallichii

    PubMed Central

    Katoch, Omika; Kaushik, Shikha; Kumar, Mysore Sadashiv Yogendra; Agrawala, Paban K.; Misra, Kshipra

    2012-01-01

    Objectives: Preparations of herbal drugs have drawn considerable interest in scientific community in recent years for the treatment of several stress related health problems including radiation-injury. Materials and Methods: An aqueous extract from Valeriana wallichii containing hesperidin as one of its major constituent was evaluated for its ability to protect against radiation-injury in model systems like plasmid deoxyribonucleic acid (DNA) and cultured human fibroblast cells. Results: The extract was found to significantly counter radiation-induced free radicals at 4 h after 5 Gy irradiation, reduced prolonged oxidative stress led increase in mitochondrial mass, enhanced reproductive viability of cultured cells and protected against radiation-induced DNA damage in solution. Discussion: Further studies are required to validate the radioprotective ability of the extract and to develop a safer radioprotective agent. PMID:23248568

  4. Optimization of mechanical extraction conditions for producing grape seed oil

    USDA-ARS?s Scientific Manuscript database

    In the United States, over 150 thousand metric tons of dried grape seeds containing 13-19% of oil are produced every year, as a byproduct from processing of about 5.8 million metric tons of grapes. The health promoting properties of grape seed oil is due to the presence of many bioactive components ...

  5. Mechanism of cytotoxicity by Psoralea corylifolia extract in human breast carcinoma cells.

    PubMed

    Rajan, Vasumathy; Tripathi, Jyoti; Variyar, Prasad; Pandey, Badri Narain

    2014-01-01

    Psoralea corylifolia has been widely used in herbal medicine, and a few studies show its anticancer activity. However, the detailed mechanism of the anticancer activity of P. corylifolia seed extract (PC extract) was not studied. This study evaluates the anticancer activity and underlying mechanism of PC extract in a human breast cancer cell line (MCF7). PC extract caused a concentration-dependent decrease in the proliferation of MCF7 cells and an increase in apoptotic death as measured by annexin-V-FITC and TUNEL assays. Increased cleavage of poly(ADP-ribose) polymerase in cells treated with PC extract further confirmed the apoptotic mode of cell death. There was a decrease (~2-fold) of mitochondrial membrane potential in cells treated with PC extract. In cells treated with PC extract, an increase in intracellular reactive oxygen species (ROS) and a decrease in mitochondrial ROS was observed. A significant decrease in ATP (~1.8-fold) was observed in extract-treated cells. Moreover, MCF7 cells treated with extract showed cleavage of caspase-9 and caspase-7, upregulation of Bax, release of cytochrome-c, and loss of mitochondrial integrity. Taken together, these results suggest the involvement of the mitochondrial pathway in PC extract-induced apoptosis in MCF7 cells.

  6. Mechanical Properties and Durability of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  7. Mechanical Properties and Durability of "Waterless Concrete"

    NASA Technical Reports Server (NTRS)

    Toutanji, Houssam; Grugel, Richard N.

    2008-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Iron can be used to reinforce the sulfur concrete. Sulfur concrete specimens were cycled between liquid nitrogen (approximately 191 C) and room temperature (approximately 21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (approximately 21 C) and approximately 101 C. Test results showed that due to temperature cycling, compressive strength of cycled specimens was 20% of those non-cycled. Microscopic examination of the fracture surfaces from the cycled samples showed clear de-bonding of the sulfur from the aggregate material whereas it was seen well bonded in those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fibers from lunar regolith simulant was melted in a 25 cc Pt-Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to 1 hour. Glass fibers were cast from the melt into graphite crucibles and were annealed for a couple of hours at 600 C. Glass fibers and small rods were pulled from the melt. The glass melt wets the ceramic rod and long continuous glass fibers were easily hand drawn. The glass fibers were immediately coated with a protective polymer to maintain the mechanical strength. The glass fibers were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fiber showed to

  8. Mechanical properties of carbon nanotube/polymer composites

    NASA Astrophysics Data System (ADS)

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-10-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

  9. Mechanical properties of carbon nanotube/polymer composites

    PubMed Central

    Arash, B.; Wang, Q.; Varadan, V. K.

    2014-01-01

    The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region. PMID:25270167

  10. Mechanical properties of carbon nanotubes and their polymer nanocomposites.

    PubMed

    Miyagawa, Hiroaki; Misra, Manjusri; Mohanty, Amar K

    2005-10-01

    More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.

  11. A simple auxetic tubular structure with tuneable mechanical properties

    NASA Astrophysics Data System (ADS)

    Ren, Xin; Shen, Jianhu; Ghaedizadeh, Arash; Tian, Hongqi; Xie, Yi Min

    2016-06-01

    Auxetic materials and structures are increasingly used in various fields because of their unusual properties. Auxetic tubular structures have been fabricated and studied due to their potential to be adopted as oesophageal stents where only tensile auxetic performance is required. However, studies on compressive mechanical properties of auxetic tubular structures are limited in the current literature. In this paper, we developed a simple tubular structure which exhibits auxetic behaviour in both compression and tension. This was achieved by extending a design concept recently proposed by the authors for generating 3D metallic auxetic metamaterials. Both compressive and tensile mechanical properties of the auxetic tubular structure were investigated. It was found that the methodology for generating 3D auxetic metamaterials could be effectively used to create auxetic tubular structures as well. By properly adjusting certain parameters, the mechanical properties of the designed auxetic tubular structure could be easily tuned.

  12. Salt-leached silk scaffolds with tunable mechanical properties.

    PubMed

    Yao, Danyu; Dong, Sen; Lu, Qiang; Hu, Xiao; Kaplan, David L; Zhang, Bingbo; Zhu, Hesun

    2012-11-12

    Substrate mechanical properties have remarkable influences on cell behavior and tissue regeneration. Although salt-leached silk scaffolds have been used in tissue engineering, applications in softer tissue regeneration can be encumbered with excessive stiffness. In the present study, silk-bound water interactions were regulated by controlling processing to allow the preparation of salt-leached porous scaffolds with tunable mechanical properties. Increasing silk-bound water interactions resulted in reduced silk II (β-sheet crystal) formation during salt-leaching, which resulted in a modulus decrease in the scaffolds. The microstructures as well as degradation behavior were also changed, implying that this water control and salt-leaching approach can be used to achieve tunable mechanical properties. Considering the utility of silk in various fields of biomedicine, the results point to a new approach to generate silk scaffolds with controllable properties to better mimic soft tissues by combining scaffold preparation methods and silk self-assembly in aqueous solutions.

  13. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    SciTech Connect

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  14. Mechanical Properties and Tableting Behavior of Amorphous Solid Dispersions.

    PubMed

    Patel, Sarsvat; Kou, Xiang; Hou, Hao Helen; Huang, Ye Bill; Strong, John C; Zhang, Geoff G Z; Sun, Changquan Calvin

    2017-01-01

    Amorphous solid dispersions (ASDs) consisting of acetaminophen (APAP) and copovidone were systematically studied to identify effects of drug loading and moisture content on mechanical properties, thermal properties, and tableting behavior. ASDs containing APAP at different levels were prepared by film casting and characterized by differential scanning calorimetry and nanoindentation. The glass transition temperature (Tg) continuously decreased with increasing amount of APAP, but the hardness of ASDs was increased at a low APAP content and reduced at high APAP content. This in turn significantly influenced tablet quality. Water reduced both the hardness and Tg of ASDs, and the APAP loading level corresponding to the transition to the softening mechanism was lower at a higher relative humidity. Overall, the mechanical properties, rather than the thermal properties, better represent the plasticization/antiplasticization effect of small molecule to ASDs. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  15. Effect of vitro preservation on mechanical properties of brain tissue

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Yi-fan; Liu, Li-fu; Niu, Ying; Ma, Jian-li; Wu, Cheng-wei

    2017-05-01

    To develop the protective devices for preventing traumatic brain injuries, it requires the accurate characterization of the mechanical properties of brain tissue. For this, it necessary to elucidate the effect of vitro preservation on the mechanical performance of brain tissue as usually the measurements are carried out in vitro. In this paper, the thermal behavior of brain tissue preserved for various period of time was first investigated and the mechanical properties were also measured. Both reveals the deterioration with prolonged preservation duration. The observations of brain tissue slices indicates the brain tissue experiences karyorrhexis and karyorrhexis in sequence, which accounts for the deterioration phenomena.

  16. Mechanical Properties of Isotactic Polypropylene Modified with Thermoplastic Potato Starch

    NASA Astrophysics Data System (ADS)

    Knitter, M.; Dobrzyńska-Mizera, M.

    2015-05-01

    In this paper selected mechanical properties of isotactic polypropylene (iPP) modified with potato starch have been presented. Thermoplastic starch (TPS) used as a modifier in the study was produced from potato starch modified with glycerol. Isotactic polypropylene/thermoplastic potato starch composites (iPP/TPS) that contained 10, 30, 50 wt.% of modified starch were examined using dynamic mechanical-thermal analysis, static tensile, Brinell hardness, and Charpy impact test. The studies indicated a distinct influence of a filler content on the mechanical properties of composites in comparison with non-modified polypropylene.

  17. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    PubMed Central

    Petersen, Richard C.; Liu, Perng-Ru

    2016-01-01

    Photocure fiber-reinforced composites (FRCs) with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC) for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p < 1.1×10−5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity. PMID:27642629

  18. Extracts and constituents of Leontopodium alpinum enhance cholinergic transmission: Brain ACh increasing and memory improving properties

    PubMed Central

    Hornick, Ariane; Schwaiger, Stefan; Rollinger, Judith M.; Vo, Nguyen Phung; Prast, Helmut; Stuppner, Hermann

    2012-01-01

    Leontopodium alpinum (‘Edelweiss’) was phytochemically investigated for constituents that might enhance cholinergic neurotransmission. The potency to increase synaptic availability of acetylcholine (ACh) in rat brain served as key property for the bioguided isolation of cholinergically active compounds using different chromatographic techniques. The dichlormethane (DCM) extract of the root, fractions and isolated constituents were injected i.c.v. and the effect on brain ACh was detected via the push–pull technique. The DCM extract enhanced extracellular ACh concentration in rat brain and inhibited acetylcholinesterase (AChE) in vitro. The extracellular level of brain ACh was significantly increased by the isolated sesquiterpenes, isocomene and 14-acetoxyisocomene, while silphiperfolene acetate and silphinene caused a small increasing tendency. Only silphiperfolene acetate showed in vitro AChE inhibitory activity, thus suggesting the other sesquiterpenes to stimulate cholinergic transmission by an alternative mechanism of action. Isocomene was further investigated with behavioural tasks in mice. It restored object recognition in scopolamine-impaired mice and showed nootropic effects in the T-maze alternation task in normal and scopolamine-treated mice. Additionally, this sesquiterpene reduced locomotor activity of untreated mice in the open field task, while the activity induced by scopolamine was abolished. The enhancement of synaptic availability of ACh, the promotion of alternation, and the amelioration of scopolamine-induced deficit are in accordance with a substance that amplifies cholinergic transmission. Whether the mechanism of action is inhibition of AChE or another pro-cholinergic property remains to be elucidated. Taken together, isocomene and related constituents of L. alpinum deserve further interest as potential antidementia agents in brain diseases associated with cholinergic deficits. PMID:18541221

  19. Coupling of mechanical and electronic properties of carbon nanotubes.

    PubMed

    Cristancho, Dahiyana; Benitez, Laura; Seminario, Jorge M

    2013-12-01

    Because of the potential importance of carbon nanotubes (CNT) in renewable energy and other fields, molecular orbital ab initio calculations are used to study the relation between mechanical and electronic properties of such structures. We estimate a modulus of elasticity of 1.3 TPa and find out that the mechanism of CNT structure deformation is dependent on their chirality. Armchair and chiral nanotubes have ductile deformation fracture while zigzag have both ductile and brittle; on the other hand armchair nanotubes fracture and form two caps while chiral nanotubes adopt a helical-structure conformation. In addition, the energy gap between occupied and unoccupied molecular orbitals increases when nanotubes are under plastic deformation. This strong coupling between mechanical and electrical properties can be used to tune CNT mechanically to specific electronic bandgaps, affecting directly their electromagnetic absorption properties.

  20. Mechanics of intraply hybrid composites - Properties, analysis and design

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    A mechanics theory is developed for predicting the physical thermal, hygral and mechanical properties (including various strengths) of unidirectional intraply hybrid composites (UIHC) based on unidirectional properties of the constituent composites. Procedures are described which can use this theory in conjunction with composite mechanics computer codes and general purpose structural analysis finite element programs for the analysis/design of structural components made from intraply hybrid angleplied laminates (IHAL). Comparisons with limited data show that this theory predicts mechanical properties of UIHC and flexural stiffnesses of IHAL which are in good agreement with experimental data. The theory developed herein makes it possible to design and optimize structural components from IHAL based on a large class of available constituent fibers.

  1. Significantly enhanced mechanical properties in AlN helix

    NASA Astrophysics Data System (ADS)

    Zhang, Xinghong; Zhao, Chaoliang; Yao, Tai; Zhou, Shanbao; Han, Jiecai; Li, Jiajie; Gao, Tangling; Wang, Xianjie; Zheng, Kun; Song, Bo

    2017-07-01

    To safely and reliably use aluminum nitride (AlN) helices in the fabrication of novel micro/nanodevices, it is very important to know their mechanical properties. Herein, we investigate the mechanical properties of individual AlN helices using an in situ tensile-bending test. Tensile tests reveal that an AlN helix has an average ε of ∼4.7 ± 0.8% elastic deformation before a typical brittle fracture occurs. The bending test shows a two-step mechanical feature—linear-elastic followed by an elastic-plastic process—with an average ε bent of ∼54.5 ± 0.6%. Our results provide direct cognition about the mechanical properties of AlN helices and their benefit to the design of AlN-based flexible micro/nanodevices.

  2. Processing, texture and mechanical properties of sintered silicon carbide

    NASA Technical Reports Server (NTRS)

    Landfermann, H.; Hausner, H.

    1988-01-01

    With regard to its favorable properties, in particular those shown at high temperatures, silicon carbide is of great interest for applications related to the construction of engines and turbines. Thus, silicon carbide could replace heat-resisting alloys with the objective to achieve a further increase in operational temperature. The present investigation is concerned with approaches which can provide silicon carbide material with suitable properties for the intended applications, taking into account the relations between characteristics of the raw material, material composition, sinter conditions, and results of the sintering process. The effects of density and texture formation on the mechanical properties are studied. It is found that a dense material with a fine-grained microstructure provides optimal mechanical properties, while any deviation from this ideal condition can lead to a considerable deterioration with respect to the material properties.

  3. Mechanical properties of jennite: A theoretical and experimental study

    SciTech Connect

    Moon, Juhyuk; Yoon, Seyoon; Monteiro, Paulo J.M.

    2015-05-15

    The objective of this study is to determine the mechanical properties of jennite. To date, several hypotheses have been proposed to predict the structural properties of jennite. For the first time as reported herein, the isothermal bulk modulus of jennite was measured experimentally. Synchrotron-based high-pressure x-ray diffraction experiments were performed to observe the variation of lattice parameters under pressure. First-principles calculations were applied to compare with the experimental results and predict additional structural properties. Accurately measured isothermal bulk modulus herein (K{sub 0} = 64(2) GPa) and the statistical assessment on experimental and theoretical results suggest reliable mechanical properties of shear and Young's modulus, Poisson's ratio, and elastic tensor coefficients. Determination of these fundamental structural properties is the first step toward greater understanding of calcium–silicate–hydrate, as well as provides a sound foundation for forthcoming atomic level simulations.

  4. Relating Interface Evolution to Interface Mechanics Based on Interface Properties

    NASA Astrophysics Data System (ADS)

    Verma, Devendra; Biswas, Sudipta; Prakash, Chandra; Tomar, Vikas

    2017-01-01

    The current article focuses on recent work done in understanding the role of processing techniques on interface evolution and connecting interface evolution to interface thickness-dependent properties. Special emphasis is placed on interface evolution during the sintering process of tungsten ( W). Sintering with additives such as nickel significantly changes grain boundary properties in W, leading to issues such as grain boundary embrittlement. When one has to mechanically describe properties of polycrystalline W with an account of the influence of grain boundary embrittlement, one must explicitly consider grain boundary properties. This issue is the focus of the present work on the mechanical properties of interfaces. Overall, a phase field modeling-based approach is shown to be an excellent computational tool for predicting the interface evolution. The influences of the interface thickness, chemistry, and orientation of phases around interfaces are analyzed using extended finite element simulations for polycrystalline W.

  5. Air-coupled non-contact mechanical property determination of drug tablets.

    PubMed

    Akseli, Ilgaz; Cetinkaya, Cetin

    2008-07-09

    A non-contact/non-destructive technique for determining the mechanical properties of coated drug tablets is presented. In the current measurement approach, air-coupled excitation and laser interferometric detection are utilized and their effectiveness in characterizing the mechanical properties of a drug tablet by examining its vibrational resonance frequencies is demonstrated. The drug tablet is vibrated via an acoustic field of an air-coupled transducer in a frequency range sufficiently high to excite its several vibrational modes (harmonics). The tablet surface vibrational responses at measurement points are acquired by a laser vibrometer in a non-contact manner. An iterative computational procedure based on the finite element method is developed to extract the mechanical properties of the coated tablet from a subset of its measured resonance frequencies. The mechanical properties measured by this technique are compared to those obtained by a standard contact ultrasonic measurement method and a good agreement is found. Sensitivities of the resonance frequencies to the changes in the tablet mechanical properties are also obtained and discussed. The presented non-destructive technique requires no physical contact with the tablet and operates in the microsecond time-scale. Therefore, it could be employed for rapid monitoring and characterization applications.

  6. Brain mechanisms for extracting spatial information from smell.

    PubMed

    Porter, Jess; Anand, Tarini; Johnson, Brad; Khan, Rehan M; Sobel, Noam

    2005-08-18

    Forty years ago, von Békésy demonstrated that the spatial source of an odorant is determined by comparing input across nostrils, but it is unknown how this comparison is effected in the brain. To address this, we delivered odorants to the left or right of the nose, and contrasted olfactory left versus right localization with olfactory identification during brain imaging. We found nostril-specific responses in primary olfactory cortex that were predictive of the accuracy of left versus right localization, thus providing a neural substrate for the behavior described by von Békésy. Additionally, left versus right localization preferentially engaged a portion of the superior temporal gyrus previously implicated in visual and auditory localization, suggesting that localization information extracted from smell was then processed in a convergent brain system for spatial representation of multisensory inputs.

  7. Cytotoxic Properties of Some Medicinal Plant Extracts from Mazandaran, Iran

    PubMed Central

    Nemati, Farkhondeh; Dehpouri, Abbas Ali; Eslami, Bahman; Mahdavi, Vahid; Mirzanejad, Sepideh

    2013-01-01

    Background It was shown that plants derived agents are being used for treatment of cancer. In this study, crude ethanolic extract of Consolida orientalis L., Ferula assa-foetida L., Coronilla varia L., Orobanche orientalis G. Beck were screened in vitro for cytotoxic activity on Hela (Human cervical carcinoma) cell line. Objectives We performed the present study to evaluate the in vitro cytotoxic activity of four plant extracts that we gathered from north of Iran, Mazandaran Materials and Methods Hela cells were treated with various concentrations of individual samples (0.0312, 0.0625, 0.125, 0.25, 0.5, 1, 2.5, 5, 7.5 and 10 mg/ml) for 72 hours. Cell proliferation measured by MTT assay. Results Result from the performed assay showed that ethanolic extract of Consolida orientalis L., Ferula assa-foetida L., Coronilla varia L. has more significant cytotoxicity effect on Hela cell line than Orobanche orientalis G. Beck. Conclusions Extracts of the Consolida orientalis L., Ferula assa-foetida L., Coronilla varia L. could be considered as potential sources of anticancer compounds but further studies are necessary for isolation and identification of biologically active substances. PMID:24719689

  8. Mechanical property characterization of bilayered tablets using nondestructive air-coupled acoustics.

    PubMed

    Akseli, Ilgaz; Dey, Dipankar; Cetinkaya, Cetin

    2010-03-01

    A noncontact/nondestructive air-coupled acoustic technique to be potentially used in mechanical property determination of bilayer tablets is presented. In the reported experiments, a bilayer tablet is vibrated via an acoustic field of an air-coupled transducer in a frequency range sufficiently high to excite several vibrational modes (harmonics) of the tablet. The tablet vibrational transient responses at a number of measurement points on the tablet are acquired by a laser vibrometer in a noncontact manner. An iterative computational procedure based on the finite element method is utilized to extract the Young's modulus, the Poisson's ratio, and the mass density values of each layer material of a bilayer tablet from a subset of the measured resonance frequencies. For verification purposes, a contact ultrasonic technique based on the time-of-flight data of the longitudinal (pressure) and transverse (shear) acoustic waves in each layer of a bilayer tablet is also utilized. The extracted mechanical properties from the air-coupled acoustic data agree well with those determined from the contact ultrasonic measurements. The mechanical properties of solid oral dosage forms have been shown to impact its mechanical integrity, disintegration profile and the release rate of the drug in the digestive tract, thus potentially affecting its therapeutic response. The presented nondestructive technique provides greater insight into the mechanical properties of the bilayer tablets and has the potential to identify quality and performance problems related to the mechanical properties of the bilayer tablets early on the production process and, consequently, reduce associated cost and material waste.

  9. Mechanical and water barrier properties of glutenin films influenced by storage time.

    PubMed

    Hernández-Muñoz, Pilar; López-Rubio, Amparo; Del-Valle, Valeria; Almenar, Eva; Gavara, Rafael

    2004-01-14

    The goal of this work was to study the effect of storage time on the functional properties of glutenin films plasticized with selected hydrophilic low molecular weight compounds: glycerol (GL), triethanolamine (TEA), and sorbitol (S). Glutenins were extracted from wheat gluten, and films were cast from film-forming solutions. The glutenin-based films were homogeneous, flexible, translucent, and easy to handle. Films were stored in an environmental chamber at 50 +/- 5% realtive humidity and 23 +/- 2 degrees C. Optical, mechanical, and water vapor permeability properties were monitored at regular intervals for 16 weeks. Films plasticized with GL and TEA had similar mechanical and water vapor barrier properties during the first few days of fabrication. Films plasticized with S were stronger, with better water vapor barrier properties. Mechanical and water vapor permeability properties of films plasticized with GL changed dramatically over time, whereas the properties of films plasticized with TEA and S remained stable during storage. Color properties of films plasticized with GL, TEA, and S did not change within the time period studied.

  10. Mechanical properties that influence antimicrobial peptide activity in lipid membranes.

    PubMed

    Marín-Medina, Nathaly; Ramírez, Diego Alejandro; Trier, Steve; Leidy, Chad

    2016-12-01

    Antimicrobial peptides are small amphiphilic proteins found in animals and plants as essential components of the innate immune system and whose function is to control bacterial infectious activity. In order to accomplish their function, antimicrobial peptides use different mechanisms of action which have been deeply studied in view of their potential exploitation to treat antibiotic-resistant bacterial infections. One of the main mechanisms of action of these peptides is the disruption of the bacterial membrane through pore formation, which, in some cases, takes place via a monomer to oligomer cooperative transition. Previous studies have shown that lipid composition, and the presence of exogenous components, such as cholesterol in model membranes or carotenoids in bacteria, can affect the potency of distinct antimicrobial peptides. At the same time, considering the membrane as a two-dimensional material, it has been shown that membrane composition defines its mechanical properties which might be relevant in many membrane-related processes. Nevertheless, the correlation between the mechanical properties of the membrane and antimicrobial peptide potency has not been considered according to the importance it deserves. The relevance of these mechanical properties in membrane deformation due to peptide insertion is reviewed here for different types of pores in order to elucidate if indeed membrane composition affects antimicrobial peptide activity by modulation of the mechanical properties of the membrane. This would also provide a better understanding of the mechanisms used by bacteria to overcome antimicrobial peptide activity.

  11. Extraction, composition and functional properties of pennycress (Thlaspi arvense L.) press cake protein

    USDA-ARS?s Scientific Manuscript database

    This study compared two methods for extracting the protein in pennycress (Thlaspi arvense L.) press cake and determined the composition and functional properties of the protein products. Proteins in pennycress press cake were extracted by using the conventional alkali solubilization-acid precipitati...

  12. Some Antifungal Properties of Sorbic Acid Extracted from Berries of Rowan (Sorbus Aucuparia).

    ERIC Educational Resources Information Center

    Brunner, Ulrich

    1985-01-01

    The food preservative sorbic acid can be extracted from Eurasian mountain ash berries (commercially available) and used to show antifungal properties in microbiological investigations. Techniques for extraction, purification, ultraviolet analysis, and experiments displaying antifungal activity are described. A systematic search for similar…

  13. Some Antifungal Properties of Sorbic Acid Extracted from Berries of Rowan (Sorbus Aucuparia).

    ERIC Educational Resources Information Center

    Brunner, Ulrich

    1985-01-01

    The food preservative sorbic acid can be extracted from Eurasian mountain ash berries (commercially available) and used to show antifungal properties in microbiological investigations. Techniques for extraction, purification, ultraviolet analysis, and experiments displaying antifungal activity are described. A systematic search for similar…

  14. Comparison of the milk-clotting properties of three plant extracts.

    PubMed

    Mazorra-Manzano, Miguel A; Perea-Gutiérrez, Teresa C; Lugo-Sánchez, María E; Ramirez-Suarez, Juan C; Torres-Llanez, María J; González-Córdova, Aarón F; Vallejo-Cordoba, Belinda

    2013-12-01

    Several proteases from plant sources have been proposed as milk coagulants, however, limited research has been done on their milk-clotting properties. The effect of temperature on the milk-clotting activity of kiwi fruit, melon and ginger extracts was evaluated, as well as the effects of the different extracts on curd properties. Melon extracts showed high milk-clotting activity over a broad temperature range (45-75 °C) while kiwi fruit and ginger extracts showed high activity over a narrower temperature range, with a maximum at 40 and 63 °C, respectively. Curds produced using kiwi extracts had textural properties comparable with those obtained using commercial rennet, while melon extracts produced a fragile gel and low curd yield. The milk-clotting behavior of the three plant extracts was related to the protease specificity present in these extracts. The kiwi proteases displayed chymosin-like properties and thus hold the best potential for use as a milk coagulant in cheese production. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Effect of extraction temperature on composition, structure and functional properties of flaxseed gum.

    PubMed

    Kaushik, Pratibha; Dowling, Kim; Adhikari, Raju; Barrow, Colin J; Adhikari, Benu

    2017-01-15

    Flaxseed gum (FG) was extracted at four different temperatures (30, 50, 70 and 90°C). Chemical composition and structural features of FG extracted at different temperatures were investigated to determine the effect of temperature. Content of acidic monosaccharides and denatured protein increased with increasing FG extraction temperature. The ratio of neutral to acidic monosaccharides decreased from 6.7 to 5.7 as the extraction temperature was increased from 30 to 90°C. Physiochemical and functional properties, including zeta-potential, surface morphology, emulsifying activity index (EAI) and emulsion stability index (ESI), water absorption capacity (WAC) and fat absorption capacity (FAC) of FG samples, were also investigated as a function of extraction temperature. EAI and WAC of FG samples reduced significantly with rise in extraction temperature. Our study suggests that FG extracted at different temperatures may be specifically targeted for different applications, such as for emulsification or gel formation in food systems.

  16. Characterization and Antioxidant Properties of Six Algerian Propolis Extracts: Ethyl Acetate Extracts Inhibit Myeloperoxidase Activity

    PubMed Central

    Boufadi, Yasmina Mokhtaria; Soubhye, Jalal; Riazi, Ali; Rousseau, Alexandre; Vanhaeverbeek, Michel; Nève, Jean; Boudjeltia, Karim Zouaoui; Van Antwerpen, Pierre

    2014-01-01

    Because propolis contains many types of antioxidant compounds such as polyphenols and flavonoids, it can be useful in preventing oxidative damages. Ethyl acetate extracts of propolis from several Algerian regions show high activity by scavenging free radicals, preventing lipid peroxidation and inhibiting myeloperoxidase (MPO). By fractioning and assaying ethyl acetate extracts, it was observed that both polyphenols and flavonoids contribute to these activities. A correlation was observed between the polyphenol content and the MPO inhibition. However, it seems that kaempferol, a flavonoid, contributes mainly to the MPO inhibition. This molecule is in a high amount in the ethyl acetate extract and demonstrates the best efficiency towards the enzyme with an inhibiting concentration at 50% of 4 ± 2 μM. PMID:24514562

  17. Characterization and antioxidant properties of six Algerian propolis extracts: ethyl acetate extracts inhibit myeloperoxidase activity.

    PubMed

    Boufadi, Yasmina Mokhtaria; Soubhye, Jalal; Riazi, Ali; Rousseau, Alexandre; Vanhaeverbeek, Michel; Nève, Jean; Boudjeltia, Karim Zouaoui; Van Antwerpen, Pierre

    2014-02-07

    Because propolis contains many types of antioxidant compounds such as polyphenols and flavonoids, it can be useful in preventing oxidative damages. Ethyl acetate extracts of propolis from several Algerian regions show high activity by scavenging free radicals, preventing lipid peroxidation and inhibiting myeloperoxidase (MPO). By fractioning and assaying ethyl acetate extracts, it was observed that both polyphenols and flavonoids contribute to these activities. A correlation was observed between the polyphenol content and the MPO inhibition. However, it seems that kaempferol, a flavonoid, contributes mainly to the MPO inhibition. This molecule is in a high amount in the ethyl acetate extract and demonstrates the best efficiency towards the enzyme with an inhibiting concentration at 50% of 4 ± 2 µM.

  18. Structural properties for determining mechanisms of toxic action

    SciTech Connect

    Bradbury, S.P.; Lipnick, R.L.

    1989-01-01

    The results of a workshop co-sponsored by EPA through the Health and Environmental Review Division, Office of Toxic Substances and the Environmental Research Laboratory-Duluth, of the Office of Research and Development are briefly summarized as an introduction to a series of manuscripts dealing with the structural properties of chemicals that determine their toxic mechanisms. Results of the workshop are intended to be incorporated in an expert system to predict mechanisms from chemical structure and aid in predictive toxicology applications in the Agency. The goal of the workshop was to review current understanding of fundamental mechanisms, and develop an initial knowledge base on chemical features and properties from which toxic mechanisms could be predicted from structure. Areas addressed included general anesthesia, or narcosis, oxidative phosphorylation uncoupling, electrophile and free-radical reactivity, and a variety of pesticide-based mechanisms.

  19. Metal Additive Manufacturing: A Review of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  20. Mechanical properties of basement membrane in health and disease.

    PubMed

    Miller, R Tyler

    2017-01-01

    Physical properties are differentiated characteristics of tissues that are essential to their function. For example, the function of bone depends on its rigidity, and the function of skin depends on its elasticity. The aggregate physical properties of tissues are determined by a collaborative relationship between their cells and matrix and are the product of genetic programs, circulating chemical signals, physical signals, and age. The mechanical properties of matrix and basement membranes in biologic systems are difficult to understand in detail because of their complexity and technical limitations of measurements. Matrix may contain fibrillary collagens, network collagens, other fibrillar proteins such as elastin, fibronectin, and laminins, proteoglycans, and can be a reservoir for growth factors. In each tissue and in different regions of the same tissue, matrix composition can vary. The goal of measuring the mechanical properties of matrix is to understand the physical environment experienced by specific cell types to be able to control cell behavior in vivo and for tissue engineering. At this time, such precise analysis is not possible. The general elastic properties of tissues are now better characterized, and model systems using limited numbers of matrix constituents permit improved understanding of the physical behavior of matrix and its effects on cells. This review will describe model systems for understanding problems of matrix elasticity, focus on a relatively new aspect of matrix mechanics, strain-stiffening, and the interactions of cells with matrix to produce overall tissue mechanical properties.

  1. [Bone biopsy needles: mechanical properties, needle design and specimen quality].

    PubMed

    Keulers, A; Cunha-Cruz, V C; Bruners, P; Penzkofer, T; Braunschweig, T; Schmitz-Rode, T; Mahnken, A

    2011-03-01

    To quantitatively analyze differences in mechanical properties, needle design including signs of wear, subjective handling and specimen quality of bone biopsy needles. In this study 19 different bone biopsy systems (total 38; 2 /type) were examined. With each biopsy needle five consecutive samples were obtained from vertebral bodies of swine. During puncture a force-torques sensor measured the mechanical properties and subjective handling was assessed. Before and after each biopsy the needles were investigated using a profile projector and signs of wear were recorded. Afterwards, a pathologist semi-quantitatively examined the specimen regarding sample quality. The overall evaluation considered mechanical properties, needle wear, subjective handling and sample quality. Differences were assessed for statistical significance using ANOVA and t-test. Needle diameter (p = 0.003) as well as needle design (p = 0.008) affect the mechanical properties significantly. Franseen design is significantly superior to other needle designs. Besides, length reduction recorded by the profile projector, as a quality criterion showed notable distinctions in between the needle designs. Bone biopsy needles vary significantly in performance. Needle design has an important influence on mechanical properties, handling and specimen quality. Detailed knowledge of those parameters would improve selecting the appropriate bone biopsy needle. © Georg Thieme Verlag KG Stuttgart · New York.

  2. Enhanced Microbial, Functional and Sensory Properties of Herbal Yogurt Fermented with Korean Traditional Plant Extracts

    PubMed Central

    Joung, Jae Yeon; Lee, Ji Young; Ha, Young Sik; Shin, Yong Kook; Kim, Younghoon; Kim, Sae Hun; Oh, Nam Su

    2016-01-01

    This study evaluated the effects of two Korean traditional plant extracts (Diospyros kaki THUNB. leaf; DK, and Nelumbo nucifera leaf; NN) on the fermentation, functional and sensory properties of herbal yogurts. Compared to control fermentation, all plant extracts increased acidification rate and reduced the time to complete fermentation (pH 4.5). Supplementation of plant extracts and storage time were found to influence the characteristics of the yogurts, contributing to increased viability of starter culture and phenolic compounds. In particular, the increase in the counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was highest (2.95 and 1.14 Log CFU/mL respectively) in DK yogurt. Furthermore, supplementation of the plant extracts significantly influenced to increase the antioxidant activity and water holding capacity and to produce volatile compounds. The higher antioxidant activity and water holding capacity were observed in NN yogurt than DK yogurt. Moreover, all of the sensory characteristics were altered by the addition of plant extracts. Addition of plant extracts increased the scores related to flavor, taste, and texture from plain yogurt without a plant extract, as a result of volatile compounds analysis. Thus, the overall preference was increased by plant extracts. Consequently, supplementation of DK and NN extracts in yogurt enhanced the antioxidant activity and physical property, moreover increased the acceptability of yogurt. These findings demonstrate the possibility of using plant extracts as a functional ingredient in the manufacture of herbal yogurt. PMID:27499669

  3. Effect of extraction process on composition, oxidative stability and rheological properties of purslane seed oil.

    PubMed

    Delfan-Hosseini, Sasan; Nayebzadeh, Kooshan; Mirmoghtadaie, Leila; Kavosi, Maryam; Hosseini, Seyede Marzieh

    2017-05-01

    Purslane seed oil could be considered as potential nutritious oil due to its desirable fatty acid composition and other biological active compounds. In this study the effect of three extraction procedure including solvent extraction, cold pressing and microwave pretreatment (MW) followed by cold pressing on oil yield, physicochemical properties, oxidative stability and rheological behaviors of oil was investigated. Solvent extracted oil had the highest extraction yield (72.31%). Pretreatment by microwave before cold press extraction resulted in an increase in extraction yield, total phenolic compound (TPC) and antioxidant activity. Cold press extracted oil had the lowest oxidative stability (4.64h). This property was greatly enhanced by microwave irradiation, so that the longest oxidative stability was found in MW-cold press extracted oil with 9.67h. Furthermore, all extracted oils demonstrated Newtonian flow behaviors. MW-cold press extracted oil had the greatest apparent viscosity and highest sensitivity to temperature changes (Ea=29.18kJ/mol(-1)).

  4. Enhanced Microbial, Functional and Sensory Properties of Herbal Yogurt Fermented with Korean Traditional Plant Extracts.

    PubMed

    Joung, Jae Yeon; Lee, Ji Young; Ha, Young Sik; Shin, Yong Kook; Kim, Younghoon; Kim, Sae Hun; Oh, Nam Su

    2016-01-01

    This study evaluated the effects of two Korean traditional plant extracts (Diospyros kaki THUNB. leaf; DK, and Nelumbo nucifera leaf; NN) on the fermentation, functional and sensory properties of herbal yogurts. Compared to control fermentation, all plant extracts increased acidification rate and reduced the time to complete fermentation (pH 4.5). Supplementation of plant extracts and storage time were found to influence the characteristics of the yogurts, contributing to increased viability of starter culture and phenolic compounds. In particular, the increase in the counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was highest (2.95 and 1.14 Log CFU/mL respectively) in DK yogurt. Furthermore, supplementation of the plant extracts significantly influenced to increase the antioxidant activity and water holding capacity and to produce volatile compounds. The higher antioxidant activity and water holding capacity were observed in NN yogurt than DK yogurt. Moreover, all of the sensory characteristics were altered by the addition of plant extracts. Addition of plant extracts increased the scores related to flavor, taste, and texture from plain yogurt without a plant extract, as a result of volatile compounds analysis. Thus, the overall preference was increased by plant extracts. Consequently, supplementation of DK and NN extracts in yogurt enhanced the antioxidant activity and physical property, moreover increased the acceptability of yogurt. These findings demonstrate the possibility of using plant extracts as a functional ingredient in the manufacture of herbal yogurt.

  5. The fracture properties and toughening mechanisms of bone and dentin

    NASA Astrophysics Data System (ADS)

    Koester, Kurt John

    The mechanical properties of bone and dentin and in particular their fracture properties, are the subject of intense research. The relevance of these properties is increasing as our population ages and fracture incidence impacts the lives of a greater portion of the population. A robust framework is needed to understand the fracture properties of bone and dentin to guide researchers as they attempt to characterize the effects of aging, disease, and pharmaceutical treatments on the properties of these mineralized tissues. In the present work, this framework is provided and applied to human bone, human dentin, and animal bone. In situ electron microscopy was also used to identify the salient toughening mechanisms in bone and dentin. It was found that bone and dentin are extrinsically toughened materials and consequently their fracture properties are best characterized utilizing a crack-growth resistance approach. A description of the different mechanical measurements commonly employed when using small animal models (rats and mice) to evaluate the influence of drug therapies on bone fragility is provided. A study where these properties were measured for a large population of wild-type rats and mice was also conducted. Given my findings, it was determined that for the most complete understanding of small animal bone it was necessary to measure strength and toughness. Strength measurements probe the flaw distribution and toughness measurements to evaluate the resistance to facture in the presence of a single dominant worst-case flaw.

  6. The antioxidant mechanisms underlying the aged garlic extract- and S-allylcysteine-induced protection.

    PubMed

    Colín-González, Ana L; Santana, Ricardo A; Silva-Islas, Carlos A; Chánez-Cárdenas, Maria E; Santamaría, Abel; Maldonado, Perla D

    2012-01-01

    Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo--in diverse experimental animal models associated to oxidative stress--and in vitro conditions--using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor--a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels.

  7. The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection

    PubMed Central

    Colín-González, Ana L.; Santana, Ricardo A.; Silva-Islas, Carlos A.; Chánez-Cárdenas, Maria E.; Santamaría, Abel; Maldonado, Perla D.

    2012-01-01

    Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo—in diverse experimental animal models associated to oxidative stress—and in vitro conditions—using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor—a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels. PMID:22685624

  8. Mechanical cell disruption for lipid extraction from microalgal biomass.

    PubMed

    Halim, Ronald; Rupasinghe, Thusitha W T; Tull, Dedreia L; Webley, Paul A

    2013-07-01

    Cell disruption is an integral part of the downstream operation required to produce biodiesel from microalgae. This study investigated the use of ultrasonication and high-pressure homogenization (HPH) as cell disruption methods for two microalgal species, Tetraselmis suecica (TS) and Chlorococcum sp. (C sp.). The kinetics of cell disruption followed a first-order model (0.65extraction resulted in 5-8-fold increase in lipid yield and 3-5-fold increase in triglyceride yield. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Probiotic Properties of Lyophilized Cell Free Extract of Lactobacillus casei.

    PubMed

    Saadatzadeh, Afrooz; Fazeli, Mohamma Reza; Jamalifar, Hossein; Dinarvand, Rassoul

    2013-08-01

    In recent years there have been considerable interests in the use of probiotic live cells for nutritional and therapeutic purposes. This strategy can be concomitant with some limitations such as survival of live cell during the GI-transit and their effective delivery to target tissues upon ingestion. Several attempts have been made to overcome these limitations such as their microencapsulation, spray-drying and lyophilization. In this study extract of cultured probiotics without cells was evaluated for its antimicrobial effects, antioxidant activity, and its stability. In this work the potential of lyophilized-cell-free-probiotic-extract (LPE) as a suitable alternative strategy for the preparation of probiotic-products was investigated. The main aim of this study was to find out the antibacterial and antioxidant activity of LPE and also its stability. LPE was obtained by centrifugation and subsequent lyophilization of the collected supernatant from culture media of Lactobacillus casei. An enzymatic reagent-kit was used for detection of its content of lactic acid. Antibacterial test was performed using agar cup-plat-method, the DPPH scavenging -assay was used to determine its antioxidant activity and during a storage course, LPE was under a long-term stability study. Results showed that, LPE had more antipathogenic effects, antioxidant activity, and stability during storage-time when compared to fresh probiotic-extract. Employing the LPE as a new approach, gives novel concept of probiotic-products in food and medical marketing.

  10. Probiotic Properties of Lyophilized Cell Free Extract of Lactobacillus casei

    PubMed Central

    Saadatzadeh, Afrooz; Fazeli, Mohamma Reza; Jamalifar, Hossein; Dinarvand, Rassoul

    2013-01-01

    Background In recent years there have been considerable interests in the use of probiotic live cells for nutritional and therapeutic purposes. This strategy can be concomitant with some limitations such as survival of live cell during the GI-transit and their effective delivery to target tissues upon ingestion. Several attempts have been made to overcome these limitations such as their microencapsulation, spray-drying and lyophilization. Objectives In this study extract of cultured probiotics without cells was evaluated for its antimicrobial effects, antioxidant activity, and its stability. Materials and Methods In this work the potential of lyophilized-cell-free-probiotic-extract (LPE) as a suitable alternative strategy for the preparation of probiotic-products was investigated. The main aim of this study was to find out the antibacterial and antioxidant activity of LPE and also its stability. LPE was obtained by centrifugation and subsequent lyophilization of the collected supernatant from culture media of Lactobacillus casei. An enzymatic reagent-kit was used for detection of its content of lactic acid. Antibacterial test was performed using agar cup-plat-method, the DPPH scavenging -assay was used to determine its antioxidant activity and during a storage course, LPE was under a long-term stability study. Results Results showed that, LPE had more antipathogenic effects, antioxidant activity, and stability during storage-time when compared to fresh probiotic-extract. Conclusions Employing the LPE as a new approach, gives novel concept of probiotic-products in food and medical marketing. PMID:24624202

  11. Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

    NASA Astrophysics Data System (ADS)

    Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

    2017-03-01

    The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

  12. Antioxidant, antimicrobial, antiparasitic, and cytotoxic properties of various Brazilian propolis extracts

    PubMed Central

    Barreto, Gabriele de Abreu; Costa, Samantha Serra; Andrade, Luciana Nalone; Amaral, Ricardo Guimarães; Carvalho, Adriana Andrade; Padilha, Francine Ferreira; Barbosa, Josiane Dantas Viana

    2017-01-01

    Propolis is known for its biological properties and its preparations have been continuously investigated in an attempt to solve the problem of their standardization, an issue that limits the use of propolis in food and pharmaceutical industries. The aim of this study was to evaluate in vitro antioxidant, antimicrobial, antiparasitic, and cytotoxic effects of extracts of red, green, and brown propolis from different regions of Brazil, obtained by ethanolic and supercritical extraction methods. We found that propolis extracts obtained by both these methods showed concentration-dependent antioxidant activity. The extracts obtained by ethanolic extraction showed higher antioxidant activity than that shown by the extracts obtained by supercritical extraction. Ethanolic extracts of red propolis exhibited up to 98% of the maximum antioxidant activity at the highest extract concentration. Red propolis extracts obtained by ethanolic and supercritical methods showed the highest levels of antimicrobial activity against several bacteria. Most extracts demonstrated antimicrobial activity against Staphylococcus aureus. None of the extracts analyzed showed activity against Escherichia coli or Candida albicans. An inhibitory effect of all tested ethanolic extracts on the growth of Trypanosoma cruzi Y strain epimastigotes was observed in the first 24 h. However, after 96 h, a persistent inhibitory effect was detected only for red propolis samples. Only ethanolic extracts of red propolis samples R01Et.B2 and R02Et.B2 showed a cytotoxic effect against all four cancer cell lines tested (HL-60, HCT-116, OVCAR-8, and SF-295), indicating that red propolis extracts have great cytotoxic potential. The biological effects of ethanolic extracts of red propolis revealed in the present study suggest that red propolis can be a potential alternative therapeutic treatment against Chagas disease and some types of cancer, although high activity of red propolis in vitro needs to be confirmed by

  13. Antioxidant, antimicrobial, antiparasitic, and cytotoxic properties of various Brazilian propolis extracts.

    PubMed

    Dantas Silva, Rejane Pina; Machado, Bruna Aparecida Souza; Barreto, Gabriele de Abreu; Costa, Samantha Serra; Andrade, Luciana Nalone; Amaral, Ricardo Guimarães; Carvalho, Adriana Andrade; Padilha, Francine Ferreira; Barbosa, Josiane Dantas Viana; Umsza-Guez, Marcelo Andres

    2017-01-01

    Propolis is known for its biological properties and its preparations have been continuously investigated in an attempt to solve the problem of their standardization, an issue that limits the use of propolis in food and pharmaceutical industries. The aim of this study was to evaluate in vitro antioxidant, antimicrobial, antiparasitic, and cytotoxic effects of extracts of red, green, and brown propolis from different regions of Brazil, obtained by ethanolic and supercritical extraction methods. We found that propolis extracts obtained by both these methods showed concentration-dependent antioxidant activity. The extracts obtained by ethanolic extraction showed higher antioxidant activity than that shown by the extracts obtained by supercritical extraction. Ethanolic extracts of red propolis exhibited up to 98% of the maximum antioxidant activity at the highest extract concentration. Red propolis extracts obtained by ethanolic and supercritical methods showed the highest levels of antimicrobial activity against several bacteria. Most extracts demonstrated antimicrobial activity against Staphylococcus aureus. None of the extracts analyzed showed activity against Escherichia coli or Candida albicans. An inhibitory effect of all tested ethanolic extracts on the growth of Trypanosoma cruzi Y strain epimastigotes was observed in the first 24 h. However, after 96 h, a persistent inhibitory effect was detected only for red propolis samples. Only ethanolic extracts of red propolis samples R01Et.B2 and R02Et.B2 showed a cytotoxic effect against all four cancer cell lines tested (HL-60, HCT-116, OVCAR-8, and SF-295), indicating that red propolis extracts have great cytotoxic potential. The biological effects of ethanolic extracts of red propolis revealed in the present study suggest that red propolis can be a potential alternative therapeutic treatment against Chagas disease and some types of cancer, although high activity of red propolis in vitro needs to be confirmed by

  14. Mechanical properties of bimetallic crystalline and nanostructured nanowires.

    PubMed

    Hou, Marc; Melikhova, Oksana; Pisov, Stoyan

    2008-01-01

    Nanowires are basic components of interconnects at the nanoscale level in electronic as well as in electromechanical devices. Presently, there is a fast growing interest in their synthesis as well as in their mechanical testing. Focused ion beams now allow machining pillars with diameters as small as a few tens of nanometres and nanoindenter systems allow measuring strains at the atomic scale and compressive stresses up to the 10 GPa range. Such pillars typically contain less than millions of atoms, which makes their modelling and the modelling of their mechanical properties at the atomic scale realistic. A few Molecular Dynamics studies are presently available, discussing deformation mechanisms in thin narrow crystalline nanowires, but the literature about nanoalloy wires and nanostructured wires, as they can be synthesized from clusters, is almost non-existent. In the latter, the dislocation activity may be inhibited, leading to specific mechanical properties. By means of large scale computations, we use Ni3A1 to discuss the mechanical properties of crystalline and nanostructured nanowires. We also compare wires to their bulk counterparts. Both isothermal and isoenergetic whereby mechanical work converts into heat in the system-deformation mechanisms are considered. The comparison between pair correlation functions, stress distributions, configuration analysis and strain stress relations capture most of the stress-induced evolution mechanisms of nanowires with different diameters and structures, including elastic properties, dislocation activity, grain rotation and boundary motion, local melting, superplasticity and fracture. A structural transition which may be martensitic is predicted for the first time at the nanoscale level, suggesting possible shape memory properties of nanoalloy nanowires.

  15. Microstructural influences on the mechanical properties of solder

    SciTech Connect

    Morris, J.W. Jr.; Goldstein, J.L.F.; Mei, Z.

    1993-04-01

    Intent of this book is to review analytic methods for predicting behavior of solder joints, based on continuum mechanics. The solder is treated as a continuous, homogeneous body, or composite of such bodies, whose mechanical behavior is uniform and governed by simple constitutive equations. The microstructure of a solder joint influences its mechanical properties in 3 ways: it governs deformation and failure; common solders deform inhomogeneously; and common solders are microstructurally unstable. The variety of microstructures often found in solder joints are briefly reviewed, and some of the ways are discussed in which the microstructure influences the common types of high-temperature mechanical behavior. 25 figs, 40 refs.

  16. Mapping the mechanical properties of cholesterol-containing supported lipid bilayers with nanoscale spatial resolution.

    PubMed

    Shamitko-Klingensmith, Nicole; Molchanoff, Kelley M; Burke, Kathleen A; Magnone, George J; Legleiter, Justin

    2012-09-18

    It has been demonstrated that many biological processes are influenced by mechanical changes in membranes comprised of a variety of lipid components. As a result, the ability to map physicomechanical properties of surfaces with high temporal and spatial resolution is desirable. Tapping mode atomic force microscopy (AFM) has proven to be a useful technique for imaging biological surfaces due to its ability to operate in solution; however, access to information concerning the mechanical properties of these surfaces can also be obtained by reconstructing the time-resolved tip/sample force interactions during the imaging process. An advantage of such an approach is the direct correlation of topographical features with mechanical properties. Reconstruction of the tip/sample force is achievable by a technique called scanning probe acceleration microscopy (SPAM), which treats the cantilever as an accelerometer. The acceleration, which is directly related to the tip/sample force, of the cantilever is obtained by taking the second derivative of the cantilever deflection signal during a tapping mode AFM experiment in solution with standard cantilevers. Herein, we describe the applicability of SPAM to study mechanical properties of supported lipid bilayers with nanoscale spatial resolution via numerical simulations and experiment. The maximum and minimum tapping forces respond to changes in specific surface mechanical properties. Furthermore, we demonstrate how these changes can be used to map relative changes in the Young's modulus and adhesive properties of supported total brain lipid extract bilayers containing exogenous cholesterol. Finally, the ability of SPAM to distinguish nanoscale lipid raft domains based on changes in local mechanical properties is demonstrated.

  17. Solvent extraction of cadmium and zinc from sulphate solutions: Comparison of mechanical agitation and ultrasonic irradiation.

    PubMed

    Daryabor, Mahboubeh; Ahmadi, Ali; Zilouei, Hamid

    2017-01-01

    This research was conducted to evaluate the potential of ultrasonic irradiation during the solvent extraction of metals, and comparing its efficiency with a mechanically stirred system (MSSX). The simultaneous extraction of zinc and cadmium from sulphate solutions was investigated by di-(2-ethylhexyl) phosphoric acid (D2EHPA) as an organic extractant which was diluted (20%) in kerosene at the organic: aqueous phase ratio of 1:1 and the temperature of 25°C. The influence of some critical parameters, including contact time, solution pH, ultrasonic power, and zinc/cadmium ratio were investigated on the extraction of the metals. Results show that D2EHPA selectively extract zinc rather than cadmium in both mechanically and ultrasonically mixed systems. It was also found that increase of ultrasonic power from 10 to 120W cause a small decrease in zinc extraction; while, at low and high levels of the induced power, cadmium extraction was significantly decreased. Results also show that maximum extraction amounts of zinc (88.7%) and cadmium (68.2%) by the MSSX system occurred at the pH of 3 and the contact times of 3 and 20min, respectively. Although capability of extraction in the ultrasonically assisted solvent extraction (USAX) system for both metals was higher, the selectivity was lower than that of MSSX system under different conditions especially in high zinc/cadmium ratios. It can be concluded that physical effects (i.e. mixing) inducing at low ultrasonic powers (below 60W) mainly results in increasing solvent extraction rate, while the chemical actions applied at the higher powers have a negative outcome on the extraction rate particularly for cadmium. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-11-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  19. Passive and active mechanical properties of biotemplated ceramics revisited.

    PubMed

    Van Opdenbosch, Daniel; Fritz-Popovski, Gerhard; Plank, Johann; Zollfrank, Cordt; Paris, Oskar

    2016-10-13

    Living nature and human technology apply different principles to create hard, strong and tough materials. In this review, we compare and discuss prominent aspects of these alternative strategies, and demonstrate for selected examples that nanoscale-precision biotemplating is able to produce uncommon mechanical properties as well as actuating behavior, resembling to some extent the properties of the original natural templates. We present and discuss mechanical testing data showing for the first time that nanometer-precision biotemplating can lead to porous ceramic materials with deformation characteristics commonly associated with either biological or highly advanced technical materials. We also review recent findings on the relation between hierarchical structuring and humidity-induced directional motion. Finally, we discuss to which extent the observed behavior is in agreement with previous results and theories on the mechanical properties of multiscale hierarchical materials, as well as studies of highly disperse technical materials, together with an outlook for further lines of investigation.

  20. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties

    PubMed Central

    Avinash, M. B.; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T.

    2015-01-01

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50–300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties. PMID:26525957

  1. Build-in Electric Field Induced Mechanical Property Change

    NASA Astrophysics Data System (ADS)

    Chien, Te-Yu; Liu, Jian; Yost, Andrew J.; Chakhalian, Jacques; Freeland, John W.; Guisinger, Nathan P.

    Mechanical properties describe how materials respond to external stress. Microscopically, many intrinsic and extrinsic factors, such as bond length and strength (intrinsic) and grain boundaries (extrinsic), may affect the mechanical property of the materials. In this study, we observed a change of fracturing behavior of Nb-doped SrTiO3 in a Schottky barrier near the interfaces with metallic LaNiO3 films. Through cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S) experiments and theoretical analysis, the observed fractured topography could be explained by the change of the bond length caused alternation of mechanical property inside the Schottky barrier. Same model could also explain the widely observed dielectric dead layer for SrTiO3 in contact with metal electrodes.

  2. Bioinspired Reductionistic Peptide Engineering for Exceptional Mechanical Properties.

    PubMed

    Avinash, M B; Raut, Devaraj; Mishra, Manish Kumar; Ramamurty, Upadrasta; Govindaraju, T

    2015-11-03

    A simple solution-processing and self-assembly approach that exploits the synergistic interactions between multiple hydrogen bonded networks and aromatic interactions was utilized to synthesize molecular crystals of cyclic dipeptides (CDPs), whose molecular weights (~0.2 kDa) are nearly three orders of magnitude smaller than that of natural structural proteins (50-300 kDa). Mechanical properties of these materials, measured using the nanoindentation technique, indicate that the stiffness and strength are comparable and sometimes better than those of natural fibres. The measured mechanical responses were rationalized by recourse to the crystallographic structural analysis and intermolecular interactions in the self-assembled single crystals. With this work we highlight the significance of developing small molecule based bioinspired design strategies to emulate biomechanical properties. A particular advantage of the successfully demonstrated reductionistic strategy of the present work is its amenability for realistic industrial scale manufacturing of designer biomaterials with desired mechanical properties.

  3. Microstructure and mechanical properties of Al-1050 during incremental ECAP

    NASA Astrophysics Data System (ADS)

    Salamati, M.; Tamimi, S.; Moturu, S.; Sivaswamy, G.; Qarni, M.; Rosochowski, A.

    2017-05-01

    Incremental ECAP is a new method of ECAP process were the severe shear deformation is incrementally applied on the sample resulting in grain refining and new texture developing. The fundamental objective of the present work is an observation of effect of different passes of I-ECAP on microstructure and mechanical properties of AA1050 billet. To that end, 8 pass of I-ECAP have been carried out using Bc route and microstructure evolution and mechanical properties of the I-ECAPed samples have been studied. The EBSD and TEM analyses indicates that I-ECAP is as capable as conventional ECAP to grain refinements and a UFG structure is resulted after I-ECAP cycles. Tensile testing and hardness measurements indicates that mechanical properties of the Al-1050 billets increases dramatically by increasing the I-ECAP passes.

  4. Method of predicting mechanical properties of decayed wood

    DOEpatents

    Kelley, Stephen S.

    2003-07-15

    A method for determining the mechanical properties of decayed wood that has been exposed to wood decay microorganisms, comprising: a) illuminating a surface of decayed wood that has been exposed to wood decay microorganisms with wavelengths from visible and near infrared (VIS-NIR) spectra; b) analyzing the surface of the decayed wood using a spectrometric method, the method generating a first spectral data of wavelengths in VIS-NIR spectra region; and c) using a multivariate analysis to predict mechanical properties of decayed wood by comparing the first spectral data with a calibration model, the calibration model comprising a second spectrometric method of spectral data of wavelengths in VIS-NIR spectra obtained from a reference decay wood, the second spectral data being correlated with a known mechanical property analytical result obtained from the reference decayed wood.

  5. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  6. Mechanical properties and fiber type composition of chronically inactive muscles

    NASA Technical Reports Server (NTRS)

    Roy, R. R.; Zhong, H.; Monti, R. J.; Vallance, K. A.; Kim, J. A.; Edgerton, V. R.

    2000-01-01

    A role for neuromuscular activity in the maintenance of skeletal muscle properties has been well established. However, the role of activity-independent factors is more difficult to evaluate. We have used the spinal cord isolation model to study the effects of chronic inactivity on the mechanical properties of the hindlimb musculature in cats and rats. This model maintains the connectivity between the motoneurons and the muscle fibers they innervate, but the muscle unit is electrically "silent". Consequently, the measured muscle properties are activity-independent and thus the advantage of using this model is that it provides a baseline level (zero activity) from which regulatory factors that affect muscle cell homeostasis can be defined. In the present paper, we will present a brief review of our findings using the spinal cord isolation model related to muscle mechanical and fiber type properties.

  7. Phase imaging of mechanical properties of live cells (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wax, Adam

    2017-02-01

    The mechanisms by which cells respond to mechanical stimuli are essential for cell function yet not well understood. Many rheological tools have been developed to characterize cellular viscoelastic properties but these typically require direct mechanical contact, limiting their throughput. We have developed a new approach for characterizing the organization of subcellular structures using a label free, noncontact, single-shot phase imaging method that correlates to measured cellular mechanical stiffness. The new analysis approach measures refractive index variance and relates it to disorder strength. These measurements are compared to cellular stiffness, measured using the same imaging tool to visualize nanoscale responses to flow shear stimulus. The utility of the technique is shown by comparing shear stiffness and phase disorder strength across five cellular populations with varying mechanical properties. An inverse relationship between disorder strength and shear stiffness is shown, suggesting that cell mechanical properties can be assessed in a format amenable to high throughput studies using this novel, non-contact technique. Further studies will be presented which include examination of mechanical stiffness in early carcinogenic events and investigation of the role of specific cellular structural proteins in mechanotransduction.

  8. Impact of hemicellulose pre-extraction for bioconversion on birch Kraft pulp properties.

    PubMed

    Helmerius, Jonas; von Walter, Jonas Vinblad; Rova, Ulrika; Berglund, Kris A; Hodge, David B

    2010-08-01

    The combination of hemicellulose extraction with chemical pulping processes is one approach to generate a sugar feedstock amenable to biochemical transformation to fuels and chemicals. Extractions of hemicellulose from silver birch (Betula pendula) wood chips using either water or Kraft white liquor (NaOH, Na(2)S, and Na(2)CO(3)) were performed under conditions compatible with Kraft pulping, using times ranging between 20 and 90 min, temperatures of 130-160 degrees C, and effective alkali (EA) charges of 0-7%. The chips from select extractions were subjected to subsequent Kraft pulping and the refined pulps were made into handsheets. Several metrics for handsheet strength properties were compared with a reference pulp made without an extraction step. This study demonstrated that white liquor can be utilized to extract xylan from birch wood chips prior to Kraft cooking without decreasing the pulp yield and paper strength properties, while simultaneously impregnating cooking alkali into the wood chips. However, for the alkaline conditions tested extractions above pH 10 resulted in low concentrations of xylan. Water extractions resulted in the highest final concentrations of xylan; yielding a liquor without the presence of toxic or inhibitory inorganics and minimal soluble aromatics that we demonstrate can be successfully enzymatically hydrolyzed to monomeric xylose and fermented to succinic acid. However, water extractions were found to negatively impact some pulp properties including decreases in compression strength, bursting strength, tensile strength, and tensile stiffness while exhibiting minimal impact on elongation and slight improvement in tearing strength index.

  9. Mechanical properties of complex biological systems using AFM-based force spectroscopy

    NASA Astrophysics Data System (ADS)

    Graham, John Stephen

    An atomic force microscope (AFM) was designed and built to study the mechanical properties of small collagen fibrils and the plasma membrane of living cells. Collagen is a major component of bone, skin and connective tissues, and is abundant in the extracellular matrix (ECM). Because of its abundance, an understanding of how disease affects collagen mechanics is crucial in disease prevention efforts. Two levels of type I collagen structure were investigated, subfibrils (on the order of 1 mum in length) and longer fibrils. Comparisons were made between measurements of wild-type (wt) collagen and collagen from the mouse model of osteogenesis imperfecta (OI). Significant differences between OI and wt collagen were observed, primarily that intermolecular bonds in OI collagen fibrils are weaker than in wt, or not ruptured, as in the case of OI subfibrils. As cells interact with collagen in the ECM, the mechanical properties of the plasma membrane are also of great interest. Membrane tethers were extracted from living cells under varied conditions in order to assess the contributions of membrane-associated macromolecules such as the actin cytoskeleton and the glycocalyx, and intracellular signaling. Tether extraction force was found to be sensitive to all of these altered conditions, suggesting that tether extraction may be used to monitor various cellular processes.

  10. Mechanical Properties of Lower Limb Tendons and Ligaments in Primates.

    DTIC Science & Technology

    1982-07-01

    AD-Ri28 797 MECHANICAL PROPERTIES OF LOWER LIMB TENDONS AND i/i LIGAMENTS IN PRIMATES(U) MICHIGAN STATE UNIV EAST LANSING DEPT OF BIOMECHAlNICS D J...filottifj by &task ember) Lower Limb Tendons and Ligaments Hysteresis Chimpanzee 316io"chanical. Response Relaxation 1bratory Loads Miechanical Stress...tweoey an Idwoth, by Week Member) Ibis report covers a study of the material property characteristics of four ligaments and tendons from the lover limbs

  11. Influence of physiological effort of growth and chemical composition on antler bone mechanical properties.

    PubMed

    Landete-Castillejos, T; Currey, J D; Estevez, J A; Gaspar-López, E; Garcia, A; Gallego, L

    2007-11-01

    Antler is a good model to study bone biology both because it is accessible and because it grows and is shed every year. Previous studies have shown that chemical composition changes as the antler is grown, implying constraints in mineral availability and the physiological effort made to grow it. This study aimed at examining antler mechanical properties to assess whether they reflect physiological effort and whether they are associated with precise mineral bone composition rather than just ash content, which is usually the main factor affecting mechanical properties. We examined Young's modulus of elasticity (E), strength, and work to maximum load, as well as bone mineral composition, along the antler shaft. Then we compared trends between antlers from two populations: captive, well-fed, health-managed deer (n=15), and free-ranging deer with lower food quality and no health treatment (n=10). Greater E, strength and work were found for better fed and health managed deer. In addition, antler chemical composition of both populations differed in Na, Mg, K, Fe and Si, and marginally in Zn, but not in ash or Ca content. Significant and clear divergent trends in mechanical properties supporting greater physiological exhaustion in free-ranging deer were found for all mechanical variables. Detailed models showed that, in addition to ash content, independent factors extracted from principal component analyses on composition affected E and strength, but not work to maximum load. The results suggest that there is an association between bone chemical composition and mechanical properties independently of ash content.

  12. Transient dynamic mechanical properties of resilin-based elastomeric hydrogels

    PubMed Central

    Li, Linqing; Kiick, Kristi L.

    2014-01-01

    The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young's modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (<15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels. PMID:24809044

  13. Mechanical property quantification of endothelial cells using scanning acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Shelke, A.; Brand, S.; Kundu, T.; Bereiter-Hahn, J.; Blase, C.

    2012-04-01

    The mechanical properties of cells reflect dynamic changes of cellular organization which occur during physiologic activities like cell movement, cell volume regulation or cell division. Thus the study of cell mechanical properties can yield important information for understanding these physiologic activities. Endothelial cells form the thin inner lining of blood vessels in the cardiovascular system and are thus exposed to shear stress as well as tensile stress caused by the pulsatile blood flow. Endothelial dysfunction might occur due to reduced resistance to mechanical stress and is an initial step in the development of cardiovascular disease like, e.g., atherosclerosis. Therefore we investigated the mechanical properties of primary human endothelial cells (HUVEC) of different age using scanning acoustic microscopy at 1.2 GHz. The HUVECs are classified as young (tD < 90 h) and old (tD > 90 h) cells depending upon the generation time for the population doubling of the culture (tD). Longitudinal sound velocity and geometrical properties of cells (thickness) were determined using the material signature curve V(z) method for variable culture condition along spatial coordinates. The plane wave technique with normal incidence is assumed to solve two-dimensional wave equation. The size of the cells is modeled using multilayered (solid-fluid) system. The propagation of transversal wave and surface acoustic wave are neglected in soft matter analysis. The biomechanical properties of HUVEC cells are quantified in an age dependent manner.

  14. Membrane mechanical properties of synthetic asymmetric phospholipid vesicles.

    PubMed

    Lu, Li; Doak, William J; Schertzer, Jeffrey W; Chiarot, Paul R

    2016-09-13

    Synthetic lipid vesicles have served as important model systems to study cellular membrane biology. Research has shown that the mechanical properties of bilayer membranes significantly affects their biological behavior. The properties of a lipid bilayer are governed by lipid acyl chain length, headgroup type, and the presence of membrane proteins. However, few studies have explored how membrane architecture, in particular trans-bilayer lipid asymmetry, influences membrane mechanical properties. In this study, we investigated the effects of lipid bilayer architecture (i.e. asymmetry) on the mechanical properties of biological membranes. This was achieved using a customized micropipette aspiration system and a novel microfluidic technique previously developed by our team for building asymmetric phospholipid vesicles with tailored bilayer architecture. We found that the bending modulus and area expansion modulus of the synthetic asymmetric bilayers were up to 50% larger than the values acquired for symmetric bilayers. This was caused by the dissimilar lipid distribution in each leaflet of the bilayer for the asymmetric membrane. To the best of our knowledge, this is the first report on the impact of trans-bilayer asymmetry on the area expansion modulus of synthetic bilayer membranes. Since the mechanical properties of bilayer membranes play an important role in numerous cellular processes, these results have significant implications for membrane biology studies.

  15. Controlling Mechanical Properties of Bis-leucine Oxalyl Amide Gels

    NASA Astrophysics Data System (ADS)

    Chang, William; Carvajal, Daniel; Shull, Kenneth

    2011-03-01

    is-leucine oxalyl amide is a low molecular weight gelator capable of gelling polar and organic solvents. A fundamental understanding of self-assembled systems can lead to new methods in drug delivery and the design of new soft material systems. An important feature of self-assembled systems are the intermolecular forces between solvent and gelator molecule; by changing the environment the gel is in, the mechanical properties also change. In this project two variables were considered: the degree of neutralization present for the gelator molecule from neutral to completely ionized, and the concentration of the gelator molecule, from 1 weight percent to 8 weight percent in 1-butanol. Mechanical properties were studied using displacement controlled indentation techniques and temperature sweep rheometry. It has been found that properties such as the storage modulus, gelation temperature and maximum stress allowed increase with bis-leucine oxalyl amide concentration. The results from this study establish a 3-d contour map between the gelator concentration, the gelator degree of ionization and mechanical properties such as storage modulus and maximum stress allowed. The intermolecular forces between the bis-leucine low molecular weight gelator and 1-butanol govern the mechanical properties of the gel system, and understanding these interactions will be key to rationally designed self-assembled systems.

  16. Investigation of mechanical properties of cryogenically treated music wire

    NASA Astrophysics Data System (ADS)

    Heptonstall, A.; Waller, M.; Robertson, N. A.

    2015-08-01

    It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO—the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article, we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For the samples we studied, we conclude that there is no significant difference in the properties of interest for application in gravitational wave detectors.

  17. The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

    PubMed

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

    2016-09-16

    Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties.

  18. Characterization of Local Mechanical Properties of Polymer Thin Films and Polymer Nanocomposites via AFM indentations

    NASA Astrophysics Data System (ADS)

    Cheng, Xu

    AFM indentation has become a tool with great potential in the characterization of nano-mechanical properties of materials. Thanks to the nanometer sized probes, AFM indentation is capable of capturing the changes of multiple properties within the range of tens of nanometers, such task would otherwise be difficult by using other experiment instruments. Despite the great potentials of AFM indentation, it operates based on a simple mechanism: driving the delicate AFM probe to indent the sample surface, and recording the force-displacement response. With limited information provided by AFM indentation, efforts are still required for any practice to successfully extract the desired nano-scale properties from specific materials. In this thesis, we focus on the mechanical properties of interphase between polymer and inorganic materials. It is known that in nanocomposites, a region of polymer exist around nanoparticles with altered molecular structures and improved properties, which is named as interphase polymer. The system with polymer thin films and inorganic material substrates is widely used to simulate the interphase effect in nanocomposites. In this thesis, we developed an efficient and reliable method to process film/substrate samples and characterize the changes of local mechanical properties inside the interphase region with ultra-high resolution AFM mechanical mapping technique. Applying this newly developed method, the interphase of several film/substrate pairs were examined and compared. The local mechanical properties on the other side of the polymer thin film, the free surface side, was also investigated using AFM indentation equipped with surface modified probes. In order to extract the full spectrum of local elastic modulus inside the surface region in the range of only tens of nanometers, the different contact mechanics models were studied and compared, and a Finite Element model was also established. Though the film/substrate system has been wide used as

  19. Mechanical Properties and Fractography of Electroslag Remelted 300M Steel.

    DTIC Science & Technology

    1983-03-01

    the minimum requirements. Charpy impact energy values shown in Table 3 varied from a high of 22 ft-lb for the L-T orientation to 9 ft-lb for the S-L...specimen orientations are shown in Figures la and lb. 3 ’ab 4. MECHANICAL PROPERTIES OF 300M AND 4340 STEELS Impact emp. Orien- i.?% Y.S. U.T.S. Eon...AMMRC TR 83-13 IAD II MECHANICAL PROPERTIES AND FRACTOGRAPHY OF ELECTROSLAG REMELTED 300M STEEL 0 f ALBERT A. ANCTIL METALS RESEARCH DIVISION March

  20. Improvement of Mechanical Properties in Natural Rubber with Organic Fillers

    NASA Astrophysics Data System (ADS)

    Gonzales-Fernandes, M.; Bastos, Andrade C. G.; Esper, F. J.; Valenzuela-Diaz, F. R.; Wiebeck, H.

    When added to polymeric matrices, organophilic clay transforms the performance of the resulting composites. A natural rubber matrix with different loads was prepared as bentonite chocolate B modified by sodification and treated with ammonium quaternary salt with cellulose charge, cardboard and palm fiber. After the mixture of natural rubber in a roller mill with the additives and subsequent addition of loads individually, plates were vulcanized for fabricating specimens. We measured the mechanical properties of traction and the interlayer distances analyzed by XRD. The aim of the paper is to show that the composite obtained improved in mechanical properties as compared to plates without the addition of loads.

  1. Mechanical Properties and Durability of CNT Cement Composites

    PubMed Central

    Camacho, María del Carmen; Galao, Oscar; Baeza, Francisco Javier; Zornoza, Emilio; Garcés, Pedro

    2014-01-01

    In the present paper, changes in mechanical properties of Portland cement-based mortars due to the addition of carbon nanotubes (CNT) and corrosion of embedded steel rebars in CNT cement pastes are reported. Bending strength, compression strength, porosity and density of mortars were determined and related to the CNT dosages. CNT cement paste specimens were exposed to carbonation and chloride attacks, and results on steel corrosion rate tests were related to CNT dosages. The increase in CNT content implies no significant variations of mechanical properties but higher steel corrosion intensities were observed. PMID:28788536

  2. Elastic properties of graphene obtained by computational mechanical tests

    NASA Astrophysics Data System (ADS)

    Hartmann, Markus A.; Todt, Melanie; Rammerstorfer, Franz G.; Fischer, Franz D.; Paris, Oskar

    2013-09-01

    The basic building block of many carbon nanostructures like fullerenes, carbon onions or nanotubes is the truly two-dimensional material graphene. Commercial finite element codes, widely used to predict the mechanical properties of these structures, rely on the knowledge of the mechanical properties of the basic material. In this paper using an atomistic simulation approach we determine the membrane and bending stiffness of graphene, as well as the corresponding effective parameters: the effective elastic modulus E=2.4\\ \\text{TPa} , Poisson ratio \

  3. Antioxidant properties of various solvent extracts from purple basil

    NASA Astrophysics Data System (ADS)

    Yeşiloğlu, Yeşim; Şit, Latifşah

    2012-09-01

    Water, ethanol and acetone extracts from leaves and flowers of purple basil, one of the most popular spices consumed in the Thrace region of Turkey, were tested in vitro for their ability to inhibit peroxidation of lipids, to scavenge DPPH, hydrogen peroxide, superoxide anion, to reduce Fe(III) to Fe(II) and to chelate Fe(II) ions. The results showed that purple basil contained naturally occurring antioxidant components and possessed antioxidant activity which may be attributed to its lipid peroxidation inhibitory, radical scavenging and metal chelating activities. It was concluded that purple basil might be a potential source of antioxidants.

  4. Stevia rebaudiana ethanolic extract exerts better antioxidant properties and antiproliferative effects in tumour cells than its diterpene glycoside stevioside.

    PubMed

    López, Víctor; Pérez, Sergio; Vinuesa, Arturo; Zorzetto, Christian; Abian, Olga

    2016-04-01

    Steviol glycosides are currently being used as natural sweeteners by the food industry and Stevia rebaudiana has long been used as a sweet plant in South America for patients suffering from diabetes. In this study, a Stevia rebaudiana ethanolic extract (SREE) was prepared, analysed and tested for antioxidant activity in terms of free radical scavenging properties and antiproliferative effects in cervix (HeLa), pancreatic (MiaPaCa-2) and colonic (HCT116) cancer cells. The antiproliferative mechanism was confirmed by testing the effects on cyclin D1-CDK4. Bioassays were also performed for the diterpene glycoside stevioside. Our results demonstrate that the extract acts as an antioxidant being able to scavenge free radicals, but this activity was not due to stevioside. The extract also induced cell death in the three cell lines, being more active against cervix cancer cells (HeLa); however, the concentration of stevioside needed to produce antiproliferative effects was higher than the amount of steviol glycosides found in a lower dose of extract inducing cell death. In addition, the extract clearly inhibited CDK4 whereas stevioside did not, concluding that the antiproliferative activity of stevia may be due to inhibition of cyclin-dependent kinases performed by other compounds of the extract.

  5. Physical and mechanical properties of Tunisian women hair.

    PubMed

    Sayahi, E; Harizi, T; Msahli, S; Sakli, F

    2016-10-01

    Mechanical analysis of human hair may provide the dermatologists with several markers of considerable diagnostic importance. The aim of this study was to analyse the physical and mechanical properties of Tunisian women's hair. Surface characteristics were determined with scanning electron microscopy (SEM). Mechanical properties were studied using the Miniature Tensile Tester Model 675 (MTT675), and the Fibre Dimensional Analysis Unit Model 765 (FDAS765) of Dia-Stron, UK, was used to measure the cross-sectional area. The cross-sectional area, stress at break, strain at break, elastic modulus and total work were 4643.21 ± 817 μm(2) , 201 ± 11.26 MPa, 47.3 ± 3.6%, 3.1 ± 0.16 GPa, and 9 ± 2.2 mJ, respectively. The effects of the factors 'hair curliness' and 'age' on the physical and mechanical properties were studied. The cross-sectional area and the break load are influenced by the factors 'age' and 'curl type', whereas Young's modulus shows a significant dependency only on the age. Tunisian women hair presented good mechanical properties as shown by a greater breaking stress and higher breaking strain. Both curl type and age are important factors to consider when evaluating the behaviour of hair. © 2016 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  6. Hierarchical structure and mechanical properties of remineralized dentin.

    PubMed

    Chen, Yi; Wang, Jianming; Sun, Jian; Mao, Caiyun; Wang, Wei; Pan, Haihua; Tang, Ruikang; Gu, Xinhua

    2014-12-01

    It is widely accepted that the mechanical properties of dentin are significantly determined by its hierarchical structure. The current correlation between the mechanical properties and the hierarchical structure was mainly established by studying altered forms of dentin, which limits the potential outcome of the research. In this study, dentins with three different hierarchical structures were obtained via two different remineralization procedures and at different remineralization stages: (1) a dentin structure with amorphous minerals incorporated into the collagen fibrils, (2) a dentin with crystallized nanominerals incorporated into the collagen fibrils, and (3) a dentin with an out-of-order mineral layer filling the collagen fibrils matrix. Nanoindentation tests were performed to investigate the mechanical behavior of the remineralized dentin slides. The results showed that the incorporation of the crystallized nanominerals into the acid-etched demineralized organic fibrils resulted in a remarkable improvement of the mechanical properties of the dentin. In contrast, for the other two structures, i.e. the amorphous minerals inside the collagen fibrils and the out-of-order mineral layer within the collagen fibrils matrix, the excellent mechanical properties of dentin could not be restored. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Mechanical properties of carbon fiber composites for applications in space

    NASA Astrophysics Data System (ADS)

    Hana, P.; Inneman, A.; Daniel, V.; Sieger, L.; Petru, M.

    2015-01-01

    This article describes method of measurement mechanical properties of carbon fiber composites in space. New material structures are specifically designed for use on space satellites. Composite structures will be exposed to cosmic radiation in Earth orbit on board of a '2U CubeSat' satellite. Piezoelectric ceramic sensors are used for detection mechanical vibrations of composite test strip. A great deal of attention is paid to signal processing using 8-bit microcontroler. Fast Fourier Transformation is used. Fundamental harmonic frequencies and damping from on-board measurements will serve as the input data for terrestrial data processing. The other step of elaboration data is creation of the physical model for evaluating mechanical properties of Carbon composite - Piezoelectric ceramic system. Evaluation of anisotropic mechanical properties of piezoelectric ceramics is an interesting secondary outcome of the investigation. Extreme changes in temperature and the effect of cosmic rays will affect the mechanical properties and durability of the material used for the external construction of satellites. Comparative terrestrial measurements will be performed.

  8. Artificial insect wings with biomimetic wing morphology and mechanical properties.

    PubMed

    Liu, Zhiwei; Yan, Xiaojun; Qi, Mingjing; Zhu, Yangsheng; Huang, Dawei; Zhang, Xiaoyong; Lin, Liwei

    2017-09-26

    The pursuit of a high lift force for insect-scale flapping-wing micro aerial vehicles (FMAVs) requires that their artificial wings possess biomimetic wing features which are close to those of their natural counterpart. In this work, we present both fabrication and testing methods for artificial insect wings with biomimetic wing morphology and mechanical properties. The artificial cicada (Hyalessa maculaticollis) wing is fabricated through a high precision laser cutting technique and a bonding process of multilayer materials. Through controlling the shape of the wing venation, the fabrication method can achieve three-dimensional wing architecture, including cambers or corrugations. Besides the artificial cicada wing, the proposed fabrication method also shows a promising versatility for diverse wing types. Considering the artificial cicada wing's characteristics of small size and light weight, special mechanical testing systems are designed to investigate its mechanical properties. Flexural stiffness, maximum deformation rate and natural frequency are measured and compared with those of its natural counterpart. Test results reveal that the mechanical properties of the artificial cicada wing depend strongly on its vein thickness, which can be used to optimize an artificial cicada wing's mechanical properties in the future. As such, this work provides a new form of artificial insect wings which can be used in the field of insect-scale FMAVs.

  9. Effect of sodium hypochlorite on dentine mechanical properties. A review.

    PubMed

    Pascon, Fernanda Miori; Kantovitz, Kamila Rosamilia; Sacramento, Patrícia Almada; Nobre-dos-Santos, Marinês; Puppin-Rontani, Regina Maria

    2009-12-01

    The aim of this study was to carry out a review on the effect of sodium hypochlorite (NaOCl) on the mechanical properties of root dentine. The authors searched the Cochrane Library, Embase, PubMed and the Web of Science for papers published from 1984 to 2008. The main search terms used were: dentine, root canal dentine, sodium hypochlorite, mechanical analysis, elastic modulus, hardness, roughness, flexural strength, compressive strength. The inclusion criteria were studies that evaluated the effect of NaOCl solution, used as an irrigant in endodontics, on the mechanical properties of root dentine. Those studies that were considered to be unrelated to the question addressed, that had investigated NaOCl as a deproteinizing agent, had not evaluated the effect of NaOCl on the mechanical properties of dentine, and that indirectly verified the effect of NaOCl on endodontically treated teeth were excluded. The selected papers were assigned to a score (A-C), according to predetermined criteria. A total of 16 papers were selected, and nine papers were included in the critical appraisal. Five papers were classified as grade A, 4 as grade B, and no paper was classified as grade C. Based on this review, the authors suggest that there is strong evidence showing that sodium hypochlorite adversely alters the mechanical properties of root dentine, when used as an endodontic irrigant.

  10. Characterization of High Temperature Mechanical Properties Using Laser Ultrasound

    SciTech Connect

    David Hurley; Stephen Reese; Farhad Farzbod; Rory Kennedy

    2012-05-01

    Mechanical properties are controlled to a large degree by defect structures such as dislocations and grain boundaries. These microstructural features involve a perturbation of the perfect crystal lattice (i.e. strain fields). Viewed in this context, high frequency strain waves (i.e. ultrasound) provide a natural choice to study microstructure mediated mechanical properties. In this presentation we use laser ultrasound to probe mechanical properties of materials. This approach utilizes lasers to excite and detect ultrasonic waves, and as a consequence has unique advantages over other methods—it is noncontacting, requires no couplant or invasive sample preparation (other than that used in metallurgical analysis), and has the demonstrated capability to probe microstructure on a micron scale. Laser techniques are highly reproducible enabling sophisticated, microstructurally informed data analysis. Since light is being used for generation and detection of the ultrasonic wave, the specimen being examined is not mechanically coupled to the transducer. As a result, laser ultrasound can be carried out remotely, an especially attractive characteristic for in situ measurements in severe environments. Several examples involving laser ultrasound to measure mechanical properties in high temperature environments will be presented. Emphasis will be place on understanding the role of grain microstructure.

  11. Influence of Moisture on Mechanical Properties of Cellulose Insulation Paper

    NASA Astrophysics Data System (ADS)

    Wang, Y. Y.; Tian, M.; Xu, H. X.; Fan, P.

    2014-01-01

    This paper aims to investigate the impact of moisture on mechanical properties of insulation paper. According to the molecular modeling approach proposed by Theodorou, the amorphous cellulose models of insulation paper with different moisture contents were built up to calculate mechanical parameters and hydrogen bond networks. And relevant conclusions could be drawn through further analysis on these calculation results: water molecules can destroy hydrogen bond network between the neighboring cellulose molecules, which might be responsible for the significant decrease of Young's modulus and other mechanical parameters, while no appreciable effect of intramolecular hydrogen bonds on mechanical properties was detected. Thus tensile tests were also carried out to study the moisture influence on the Young's modulus, by which the result of the simulation was approved.

  12. Mechanical and Electrical Properties of Cryo-worked Cu

    NASA Astrophysics Data System (ADS)

    Bettinali, Livio; Tosti, Silvano; Pizzuto, Aldo

    2014-01-01

    For manufacturing the magnets of fusion machines pure copper of both high mechanical resistance and electrical conductivity is required. Though high purity copper guarantees high electrical conductivity, its mechanical properties may be not suitable for the applications in tokamaks. In this view, a new procedure developed for obtaining high purity copper with excellent mechanical strength is described in this work. Samples of oxygen free copper (OFC) have been worked by pressing in liquid nitrogen (77 K). It has been verified that the mechanical properties of the worked metal are strongly dependent on the strain rate. Very low strain rates permitted to attain values of tensile yield strength (550 MPa) significantly higher than those obtained by traditional cold-working at room temperature (450 MPa). The electrical conductivity of the cryo-worked Cu decreases with the tensile yield strength even though the hardest samples of tensile yield strength of 550 MPa exhibit still acceptable values of conductivity (about 94 % IACS at room temperature).

  13. Interaction mechanism between green tea extract and human α-amylase for reducing starch digestion.

    PubMed

    Miao, Ming; Jiang, Bo; Jiang, Huan; Zhang, Tao; Li, Xingfeng

    2015-11-01

    This study evaluated the inhibitory effects of the green tea extract on human pancreatic α-amylase activity and its molecular mechanism. The green tea extract was composed of epicatechin (59.2%), epigallocatechin gallate (14.6%) and epicatechin gallate (26.2%) as determined by HPLC analysis. Enzyme activity measurement showed that % inhibition and IC50 of the green tea extract (10%, based on starch) were 63.5% and 2.07 mg/ml, respectively. The Michaelis-Menten constant remained unchanged but the maximal velocity decreased from 0.43 (control) to 0.07 mg/(ml × min) (4 mg/ml of the green tea extract), indicating that the green tea extract was an effective inhibitor against α-amylase with a non-competitive mode. The fluorescence data revealed that the green tea extract bound with α-amylase to form a new complex with static quenching mechanism. Docking study showed the epicatechin gallate in the green tea extract presented stronger affinity than epigallocatechin gallate, with more number of amino acid residues involved in amylase binding with hydrogen bonds and Van der Waals forces. Thus, the green tea extract could be used to manipulate starch digestion for potential health benefits.

  14. Surface Effects on the Mechanical Properties of Si-nanorods

    NASA Astrophysics Data System (ADS)

    Wu, Shi-Yu; Liu, Shudun; Jayanthi, C. S.; Zhang, Zhenyu

    2000-03-01

    Mechanical properties of Si-nanorods of various sizes are studied using an order(N) non-orthogonal tight-binding molecular dynamics [1]. As the size of the nanorod decreases, we find an evolution in the surface reconstruction pattern and change in the structural and elastic properties. In particular, we examine how the surface effects modify and eventually lead to the break down of the scaling behavior of the elastic properties of Si-nanorods. [1] C.S. Jayanthi, S.Y. Wu, J. Cocks, N.S. Luo, Z.L. Xie, M. Menon and G. Yang, Phys. Rev. B57, 3799(1998).

  15. Mechanical properties of sorbents depending on nanopore sizes

    NASA Astrophysics Data System (ADS)

    Kolesnikova, A. S.

    2017-07-01

    The effect of the nanopore size on the mechanical properties of a porous carbon material with the density of 1.4 g/cm3 is discussed. The atomistic models of porous carbon materials depending on the nanopore size are constructed. The numerical experiments are implemented with using the molecular mechanical method based on the Brenner potential. The Young's moduli are evaluated for porous carbon structures at certain nanopore dimensions and are found to decrease with the enlarging nanopores.

  16. Antioxidant properties of Mediterranean food plant extracts: geographical differences.

    PubMed

    Schaffer, S; Schmitt-Schillig, S; Müller, W E; Eckert, G P

    2005-03-01

    Locally grown, wild food plants seasonally contribute a considerable portion of the daily diet in certain Mediterranean areas and it has been suggested that the beneficial effects of the Mediterranean diet on human health partly originate from the antioxidant effect of flavonoid-rich food plants. The nutrient content of most wild plants is higher than that of cultivated ones and may vary depending on the prevailing environmental conditions. Accordingly, three local Mediterranean plant foods (i.e. Cichorium intybus, Sonchus oleraceus, Papaver rhoeas) were collected in Greece (Crete), southern Italy, and southern Spain in order to assess possible differences in their in vitro antioxidant potential. The biological assays revealed diverse intra-plant specific antioxidant effects for the tested extracts ranging from no activity to almost complete protection. Furthermore, substantial differences in the polyphenol content were found for the nutritionally used part of the same plant originating from different locations. However, no clear correlations between the polyphenol content and the extracts' antioxidant activities were found. Taken together, the data suggest that certain local Mediterranean plant foods possess promising antioxidant activity and that the observed biological effects are possibly influenced by the geographically-dependent environmental conditions prevailing during plant growth.

  17. Antioxidant properties of rice bran oil-based extraction products

    USDA-ARS?s Scientific Manuscript database

    Rice bran oil has many properties that make it an attractive functional food ingredient. Compared with other oils, rice bran oil is relatively rich in tocopherols, tocotrienols, and y-oryzanol, all of which have been shown to have numerous desirable health effects. The same compounds thought to co...

  18. Anti Tumoral Properties of Punica Granatum (Pomegranate) Peel Extract on Different Human Cancer Cells.

    PubMed

    Modaeinama, Sina; Abasi, Mozhgan; Abbasi, Mehran Mesgari; Jahanban-Esfahlan, Rana

    2015-01-01

    Medicinal plants, especially examples rich in polyphenolic compounds, have been suggested to be chemopreventive on account of antioxidative properties. Punica granatum (PG) (pomegranate) is a well known fruit in this context, but its cytotoxicity in cancer cells has not been extensively studied. Here, we investigated the antiproliferative properties of a peel extract of PG from Iran in different human cancer cells. A methanolic extract of pomegranate peel (PPE) was prepared. Total phenolic content(TPC) and total flavonoid conetnt (TFC) were determined by colorimetric assays. Antioxidant activity was determined by DPPH radical scavenging activity. The cytotoxicity of different doses of PPE (0, 5, 20, 100, 250, 500, 1000 μg/ml) was evaluated by MTT assays with A549 (lung non small cell cancer), MCF-7 (breast adenocarcinoma), SKOV3 (ovarian cancer), and PC-3 (prostate adenocarcinoma) cells. Significant (P<0.01) or very significant (P<0.0001) differences were observed in comparison with negative controls at all tested doses (5-1000 μg/ml). In all studied cancer cells, PPE reduced the cell viability to values below 40%, even at the lowest doses. In all cases, IC50 was determined at doses below 5μg/ml. In this regard, MCF-7 breast adenocarcinoma cells were the most responsive cells to antiprolifreative effects of PPE with a maximum mean growth inhibition of 81.0% vs. 69.4%, 79.3% and 77.5% in SKOV3, PC-3 and A549 cells, respectively. Low doses of PPE exert potent anti-proliferative effects in different human cancer cells and it seems that MCF-7 breast adenocarcinoma cells are the most cells and SKOV3 ovarian cancer cells the least responsive in this regard. However, the mechanisms of action need to be addressed.

  19. Effect of extraction methods on the properties and antioxidant activities of Chuanminshen violaceum polysaccharides.

    PubMed

    Dong, Hongmin; Lin, Shang; Zhang, Qing; Chen, Hong; Lan, Weijie; Li, Huiyan; He, Jingliu; Qin, Wen

    2016-12-01

    The yields, properties and antioxidant activities of polysaccharides extracted from Chuanminshen violaceum (CVPs) by various methods including heated reflux extraction (HRE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), were evaluated. The results indicated that the yield of the polysaccharides (34.59%) obtained by MAE was higher than those obtained by other methods. Polysaccharides extracted by all three methods had similar physicochemical characteristics and FT-IR spectra. However, SEM images of particles of Chuanminshen violaceum treated by the three different methods were significantly different. Compared with HRE, UAE and MAE resulted in CVPs with lower molecular weight distributions and higher reducing power and scavenging abilities for ABTS (+) and DPPH. CVPs obtained by UAE had reduced scavenging abilities for DPPH compared to those obtained by MAE. These data indicated that MAE resulted in better extraction yields for CVPs and also resulted in CVPs with higher bioactivity. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Inhibitory Properties of Aqueous Ethanol Extracts of Propolis on Alpha-Glucosidase

    PubMed Central

    Zhang, Hongcheng; Wang, Guangxin; Beta, Trust; Dong, Jie

    2015-01-01

    The objective of the present study was to evaluate the inhibitory properties of various extracts of propolis on alpha-glucosidase from baker's yeast and mammalian intestine. Inhibitory activities of aqueous ethanol extracts of propolis were determined by using 4-nitrophenyl-D-glucopyranoside, sucrose and maltose as substrates, and acarbose as a positive reference. All extracts were significantly effective in inhibiting α-glucosidase from baker's yeast and rat intestinal sucrase in comparison with acarbose (P < 0.05). The 75% ethanol extracts of propolis (75% EEP) showed the highest inhibitory effect on α-glucosidase and sucrase and were a noncompetitive inhibition mode. 50% EEP, 95%, EEP and 100% EEP exhibited a mixed inhibition mode, while water extracts of propolis (WEP) and 25% EEP demonstrated a competitive inhibition mode. Furthermore, WEP presented the highest inhibitory activity against maltase. These results suggest that aqueous ethanol extracts of propolis may be used as nutraceuticals for the regulation of postprandial hyperglycemia. PMID:25767553

  1. Quadriceps Muscle Mechanical Simulator for Training of Vastus Medialis Obliquus and Vastus Lateralis Obliquus Mechanical Properties

    PubMed Central

    Irmak, Rafet; Irmak, Ahsen; Biçer, Gökhan

    2014-01-01

    Objectives: In classical anatomy quadriceps muscle has four heads. Clinical studies have demostrated 6 heads of this muscle. These heads were demostrated seperately not only by their functional properties,but also by innervation and kinesiological properties. In our previous study we have developed and demostrated electrophysiological properties of vastus medialis obliquus by an electronic patient simulator. The purpose of this study is to develop a mechanical simulator which can be used to demostrate mechanical properties of 6 heads of quadriceps muscle and the screw home mechanism. Methods: Quadriceps femoris muscle has 6 heads: rectus femoris, vastus intermedius, vastus medialis obliquus, vastus medialis longus, vastus lateralis obliquus and vastus lateralis longus. The fundamental mechanical properties of each head is seperated by insersio and angle of pull. Main design principle was to demostrate all heads with insersio and angle of pull properties. Second design principle was to demostrate the screw-home mechanism which is the result of difference in articular surfaces of medial and lateral of condyles of femur. Results: Final design of the simulator consists of three planes for demostration of angle of pull and pulling forces (patellar plane, proximal and distal planes) of each heads. On each plane channels were graved as origo and insersio for demostration of angle of pull. Distal plane was movable for demostration of pulling forces in different angels of knee flexion and extention. Also proximal plane was adjustable to demostrate different sitting and standing positions. Srew home mechanism was demostrated by specially designed hingle mechanism. Left and right side hingle mechanisms have different radii as femoral condyles and this difference can cause rotation in terminal extension as in the screw home mechanism. Conclusion: Vastus medialis obliquus, vastus lateralis obliquus and screw-home mechanism have clinical significance. We were not able to find

  2. Modified Gellan Gum hydrogels with tunable physical and mechanical properties

    PubMed Central

    Coutinho, Daniela F.; Sant, Shilpa; Shin, Hyeongho; Oliveira, João T.; Gomes, Manuela E.; Neves, Nuno M.; Khademhosseini, Ali; Reis, Rui L.

    2010-01-01

    Gellan Gum (GG) has been recently proposed for tissue engineering applications. GG hydrogels are produced by physical crosslinking methods induced by temperature variation or by the presence of divalent cations. However, physical crosslinking methods may yield hydrogels that become weaker in physiological conditions due to the exchange of divalent cations by monovalent ones. Hence, this work presents a new class of GG hydrogels crosslinkable by both physical and chemical mechanisms. Methacrylate groups were incorporated in the GG chain, leading to the production of a methacrylated gellan gum (MeGG) hydrogel with highly tunable physical and mechanical properties. The chemical modification was confirmed by proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared spectroscopy (FTIR-ATR). The mechanical properties of the developed hydrogel networks, with Young’s modulus values between 0.15 and 148 kPa, showed to be tuned by the different crosslinking mechanisms used. The in vitro swelling kinetics and hydrolytic degradation rate was dependent on the crosslinking mechanisms used to form the hydrogels. Three-dimensional (3D) encapsulation of NIH-3T3 fibroblast cells in MeGG networks demonstrated in vitro biocompatibility confirmed by high cell survival. Given the highly tunable mechanical and degradation properties of MeGG, it may be applicable for a wide range of tissue engineering approaches. PMID:20663552

  3. Stacking order dependent mechanical properties of graphene/MoS{sub 2} bilayer and trilayer heterostructures

    SciTech Connect

    Elder, Robert M. E-mail: mahesh.neupane.ctr@mail.mil; Neupane, Mahesh R. E-mail: mahesh.neupane.ctr@mail.mil; Chantawansri, Tanya L.

    2015-08-17

    Transition metal dichalcogenides (TMDC) such as molybdenum disulfide (MoS{sub 2}) are two-dimensional materials that show promise for flexible electronics and piezoelectric applications, but their weak mechanical strength is a barrier to practical use. In this work, we perform nanoindentation simulations using atomistic molecular dynamics to study the mechanical properties of heterostructures formed by combining MoS{sub 2} with graphene. We consider both bi- and tri-layer heterostructures formed with MoS{sub 2} either supported or encapsulated by graphene. Mechanical properties, such as Young's modulus, bending modulus, ultimate tensile strength, and fracture strain, are extracted from nanoindentation simulations and compared to the monolayer and homogeneous bilayer systems. We observed that the heterostructures, regardless of the stacking order, are mechanically more robust than the mono- and bi-layer MoS{sub 2}, mainly due to the mechanical reinforcement provided by the graphene layer. The magnitudes of ultimate strength and fracture strain are similar for both the bi- and tri-layer heterostructures, but substantially larger than either the mono- and bi-layer MoS{sub 2}. Our results demonstrate the potential of graphene-based heterostructures to improve the mechanical properties of TMDC materials.

  4. Designed biomaterials to mimic the mechanical properties of muscles.

    PubMed

    Lv, Shanshan; Dudek, Daniel M; Cao, Yi; Balamurali, M M; Gosline, John; Li, Hongbin

    2010-05-06

    The passive elasticity of muscle is largely governed by the I-band part of the giant muscle protein titin, a complex molecular spring composed of a series of individually folded immunoglobulin-like domains as well as largely unstructured unique sequences. These mechanical elements have distinct mechanical properties, and when combined, they provide the desired passive elastic properties of muscle, which are a unique combination of strength, extensibility and resilience. Single-molecule atomic force microscopy (AFM) studies demonstrated that the macroscopic behaviour of titin in intact myofibrils can be reconstituted by combining the mechanical properties of these mechanical elements measured at the single-molecule level. Here we report artificial elastomeric proteins that mimic the molecular architecture of titin through the combination of well-characterized protein domains GB1 and resilin. We show that these artificial elastomeric proteins can be photochemically crosslinked and cast into solid biomaterials. These biomaterials behave as rubber-like materials showing high resilience at low strain and as shock-absorber-like materials at high strain by effectively dissipating energy. These properties are comparable to the passive elastic properties of muscles within the physiological range of sarcomere length and so these materials represent a new muscle-mimetic biomaterial. The mechanical properties of these biomaterials can be fine-tuned by adjusting the composition of the elastomeric proteins, providing the opportunity to develop biomaterials that are mimetic of different types of muscles. We anticipate that these biomaterials will find applications in tissue engineering as scaffold and matrix for artificial muscles.

  5. Characterization of mechanical and biochemical properties of developing embryonic tendon

    PubMed Central

    Marturano, Joseph E.; Arena, Jeffrey D.; Schiller, Zachary A.; Georgakoudi, Irene; Kuo, Catherine K.

    2013-01-01

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration. PMID:23576745

  6. Characterization of mechanical and biochemical properties of developing embryonic tendon.

    PubMed

    Marturano, Joseph E; Arena, Jeffrey D; Schiller, Zachary A; Georgakoudi, Irene; Kuo, Catherine K

    2013-04-16

    Tendons have uniquely high tensile strength, critical to their function to transfer force from muscle to bone. When injured, their innate healing response results in aberrant matrix organization and functional properties. Efforts to regenerate tendon are challenged by limited understanding of its normal development. Consequently, there are few known markers to assess tendon formation and parameters to design tissue engineering scaffolds. We profiled mechanical and biological properties of embryonic tendon and demonstrated functional properties of developing tendon are not wholly reflected by protein expression and tissue morphology. Using force volume-atomic force microscopy, we found that nano- and microscale tendon elastic moduli increase nonlinearly and become increasingly spatially heterogeneous during embryonic development. When we analyzed potential biochemical contributors to modulus, we found statistically significant but weak correlation between elastic modulus and collagen content, and no correlation with DNA or glycosaminoglycan content, indicating there are additional contributors to mechanical properties. To investigate collagen cross-linking as a potential contributor, we inhibited lysyl oxidase-mediated collagen cross-linking, which significantly reduced tendon elastic modulus without affecting collagen morphology or DNA, glycosaminoglycan, and collagen content. This suggests that lysyl oxidase-mediated cross-linking plays a significant role in the development of embryonic tendon functional properties and demonstrates that changes in cross-links alter mechanical properties without affecting matrix content and organization. Taken together, these data demonstrate the importance of functional markers to assess tendon development and provide a profile of tenogenic mechanical properties that may be implemented in tissue engineering scaffold design to mechanoregulate new tendon regeneration.

  7. Physico-mechanical properties of plywood bonded with ecological adhesives from Acacia mollissima tannins and lignosulfonates

    NASA Astrophysics Data System (ADS)

    Rhazi, Naima; Oumam, Mina; Sesbou, Abdessadek; Hannache, Hassan; Charrier-El Bouhtoury, Fatima

    2017-06-01

    The objective of this research was to develop ecological adhesives for bonding plywood panels using lignosulfonates, a common waste product of the wood pulp industry, and natural tannin extracted from Moroccan bark of Acacia mollissima using different process. Natural tannin and lignin were used in wood adhesives formulation to substitute resins based on phenol and formaldehyde. To achieve this, the lignosulfonates were glyoxalated to enhance their reactivity and the used tannins obtained by three different extraction methods were compared with commercial mimosa tannin. The proportion of Acacia mollissima tannins and lignosulfonates, the pressing time, the pressing temperature, and the pressure used were studied to improve mechanical properties, and bonding quality of plywood panel. The properties of plywood panels produced with these adhesives were tested in accordance with normative tests. Thus, the tensile strength, and the shear strength were measured. The results showed that the performance of the plywood panels made using biobased tannin adhesives was influenced by physical conditions such as pressure, press temperature as well as by chemical conditions, such as the tannin-lignin ratio. It exhibited excellent mechanical properties comparable to commercially available phenol-formaldehyde plywood adhesives. This study showed that biobased adhesives formulations presented good and higher mechanical performance and no formaldehyde emission. Contribution to the topical issue "Materials for Energy harvesting, conversion and storage II (ICOME 2016)", edited by Jean-Michel Nunzi, Rachid Bennacer and Mohammed El Ganaoui

  8. Effect of tooth bleaching agents on protein content and mechanical properties of dental enamel.

    PubMed

    Elfallah, Hunida M; Bertassoni, Luiz E; Charadram, Nattida; Rathsam, Catherine; Swain, Michael V

    2015-07-01

    This study investigated the effect of two bleaching agents, 16% carbamide peroxide (CP) and 35% hydrogen peroxide (HP), on the mechanical properties and protein content of human enamel from freshly extracted teeth. The protein components of control and treated enamel were extracted and examined on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Marked reduction of the protein matrix and random fragmentation of the enamel proteins after bleaching treatments was found. The mechanical properties were analyzed with Vickers indentations to characterize fracture toughness, and nanoindentation to establish enamel hardness, elastic modulus and creep deformation. Results indicate that the hardness and elastic modulus of enamel were significantly reduced after treatment with CP and HP. After bleaching, the creep deformation at maximum load increased and the recovery upon unloading reduced. Crack lengths of CP and HP treated enamel were increased, while fracture toughness decreased. Additionally, the microstructures of fractured and indented samples were examined with field emission gun scanning electron microscopy (FEG-SEM) showing distinct differences in the fracture surface morphology between pre- and post-bleached enamel. In conclusion, tooth bleaching agents can produce detrimental effects on the mechanical properties of enamel, possibly as a consequence of damaging or denaturing of its protein components.

  9. Exciton transport, charge extraction, and loss mechanisms in organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Scully, Shawn Ryan

    Organic photovoltaics have attracted significant interest over the last decade due to their promise as clean low-cost alternatives to large-scale electric power generation such as coal-fired power, natural gas, and nuclear power. Many believe power conversion efficiency targets of 10-15% must be reached before commercialization is possible. Consequently, understanding the loss mechanisms which currently limit efficiencies to 4-5% is crucial to identify paths to reach higher efficiencies. In this work, we investigate the dominant loss mechanisms in some of the leading organic photovoltaic architectures. In the first class of architectures, which include planar heterojunctions and bulk heterojunctions with large domains, efficiencies are primarily limited by the distance photogenerated excitations (excitons) can be transported (termed the exciton diffusion length) to a heterojunction where the excitons may dissociate. We will discuss how to properly measure the exciton diffusion length focusing on the effects of optical interference and of energy transfer when using fullerenes as quenching layers and show how this explains the variety of diffusion lengths reported for the same material. After understanding that disorder and defects limit exciton diffusion lengths, we suggest some approaches to overcome this. We then extensively investigate the use of long-range resonant energy transfer to increase exciton harvesting. Using simulations and experiments as support, we discuss how energy transfer can be engineered into architectures to increase the distance excitons can be harvested. In an experimental model system, DOW Red/PTPTB, we will show how the distance excitons are harvested can be increased by almost an order of magnitude up to 27 nm from a heterojunction and give design rules and extensions of this concept for future architectures. After understanding exciton harvesting limitations we will look at other losses that are present in planar heterojunctions. One of

  10. Pharmaceutical properties of calycosin, the major bioactive isoflavonoid in the dry root extract of Radix astragali.

    PubMed

    Gao, JunQing; Liu, Zong Jun; Chen, Tao; Zhao, DeQiang

    2014-09-01

    Radix astragali (Fabaceae astragalus propinquus Schischkin) is a Chinese medicinal herb traditionally used for the treatment of several diseases. Calycosin is the major bioactive chemical in the dry root extract of this medical plant. This work presents a brief overview of recent reports on the potential effects of calycosin on several diseases and the possible mechanisms of action of this chemical. This review gathers information from the scientific literature (before 1 June 2013) that was compiled from various databases, such as Science Direct, PubMed, Google Scholar, and Scopus. The potential pharmaceutical properties of calycosin in the treatment of tumors, inflammation, stroke, and cardiovascular diseases have gained increasing attention in the recent years. The literature survey showed that calycosin exhibits promising effects for the treatment of several diseases and that these effects may be due to its isoflavonoid and phytoestrogenic properties. The effects of calycosin most likely result from its interaction with the ER receptors on the cell membrane and the modulation of the MAPK signaling pathway. Calycosin exhibits great potential as a therapeutic drug and may be a successful example of the standardization and modernization of traditional Chinese herbal medicine.

  11. Effects of hot water pre-extraction on surface properties of bagasse soda pulp.

    PubMed

    Cordeiro, Nereida; Ashori, Alireza; Hamzeh, Yahya; Faria, Marisa

    2013-03-01

    In this work, the effects of hot water pre-extraction of depithed bagasse on the soda pulping and surface properties were studied. The conditions of hot water pre-extraction were: maximum temperature 170 °C, heat-up time 90 min, time at maximum temperature 10 min, and solid to liquor ratio (S:L) 1:8. Consequently, the pre-extracted and un-extracted bagasse chips were subjected to soda pulping at 160 °C for 1h with 11, 14 and 17% active alkali charge and an S:L of 1:5. The results showed that the hot water pre-extraction increased bagasse surface texture porosity by hemicellulose degradation. Therefore, the delignification was faster for pulping of pre-extracted samples. At a certain charge of alkali, pre-extracted samples showed higher screened yield and lower Kappa number. For instance, at 17% alkali charge, pre-extracted bagasse gave 11.3% higher pulp yield compared with the un-extracted ones. Inverse gas chromatography (IGC) results showed that the hot water pre-extraction changed the active sites on the bagasse surface, decreasing the dispersive energy and the basicity character, and affected the particle morphology. The pulping process decreased the hydrophobicity and the basicity of the bagasse surface. The surfaces of un-extracted and pre-extracted bagasse pulps had similar properties but different morphology. The pulps present higher surface area and permeability with more reactive capacity. Copyrigh