Science.gov

Sample records for basic mechanical properties

  1. 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.

  2. Determination of basic physical and mechanical properties of basaltic rocks from P-wave velocity

    NASA Astrophysics Data System (ADS)

    Karakuş, Askeri; Akatay, Mahmut

    2013-12-01

    Physical and mechanical properties of basaltic rocks used as main building material in historical buildings in Diyarbakir show great diversity depending on the place of origin. Especially, earthquake studies as well as restoration jobs and civil engineers and architects who work on building dynamics need to know basic material properties of basaltic rocks that are the main building material. In this study, the basalt samples obtained from 18 different locations of the Diyarbakir area were tested in order to estimate the main material properties of basalts used in historical buildings without collecting samples from them. Subsequently, statistical relationships between the nondestructive P-wave velocity and other properties of basalts were investigated. Consequently, highly correlated models (R2 = 0.717-0.890) were obtained between P-wave velocity and density, porosity, uniaxial compressive strength, Brazilian tensile strength, modulus of elasticity and Poisson's ratio.

  3. Nature's amazing biopolymer: basic mechanical and hydrological properties of soil affected by plant exudates

    NASA Astrophysics Data System (ADS)

    Naveed, Muhammad; Roose, Tiina; Raffan, Annette; George, Timothy; Bengough, Glyn; Brown, Lawrie; Keyes, Sam; Daly, Keith; Hallett, Paul

    2016-04-01

    Plant exudates are known to have a very large impact on soil physical properties through changes in mechanical and hydrological processes driven by long-chain polysaccharides and surface active compounds. Whilst these impacts are well known, the basic physical properties of these exudates have only been reported in a small number of studies. We present data for exudates obtained from barley roots and chia seeds, incorporating treatments examining biological decomposition of the exudates. When these exudates were added to a sandy loam soil, contact angle and drop penetration time increased exponentially with increasing exudate concentration. These wetting properties were strongly correlated with both exudate density and zero-shear viscosity, but not with exudate surface tension. Water holding capacity and water repellency of exudate mixed soil tremendously increased with exudate concentration, however they were significantly reduced on decomposition when measured after 14 days of incubation at 16C. Mechanical stability greatly increased with increasing exudate amendment to soils, which was assessed using a rheological amplitude sweep test near saturation, at -50 cm matric potential (field capacity) using indentation test, and at air-dry condition using the Brazilian test. This reflects that exudates not only attenuate plant water stress but also impart mechanical stability to the rhizosphere. These data are highly relevant to the understanding and modelling of rhizosphere development, which is the next phase of our research.

  4. Basic Engineer Equipment Mechanic.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the skills needed by basic engineer equipment mechanics. Addressed in the four individual units of the course are the following topics: mechanics and their tools (mechanics, hand tools, and power…

  5. A Three-Scale Model of Basic Mechanical Properties of Nafion

    NASA Astrophysics Data System (ADS)

    Kafka, V.; Vokoun, D.

    2015-01-01

    The mechanical properties of Nafion are explained and modeled on the basis of Kafka's general mesomechanical model and confronted with experimental results. In this approach, Nafion is looked upon as a composite consisting of three constituents: a crystalline Nafion, amorphous Nafion, and water. Taking into account the degree of hydration, its elastic, elastic-plastic, and hysteretic properties are discussed and modeled. It is shown how the interaction between the three constituents manifests itself on the macroscale.

  6. Basic properties and variability

    NASA Technical Reports Server (NTRS)

    Querci, Francois R.

    1987-01-01

    Giant and supergiant M, S, and C stars are discussed in this survey of research. Basic properties as determined by spectra, chemical composition, photometry, or variability type are discussed. Space motions and space distributions of cool giants are described. Distribution of these stars in our galaxy and those nearby is discussed. Mira variables in particular are surveyed with emphasis on the following topics: (1) phase lag phenomenon; (2) Mira light curves; (3) variations in color indices; (4) determination of multiple periods; (5) correlations between quantities such as period length, light-curve shape, infrared (IR) excess, and visible and IR color diagram; (6) semiregular (SR) variables and different time scales in SR light variations; (7) irregular variable Lb and Lc stars; (8) different time-scale light variations; (9) hydrogen-deficient carbon (HdC) stars, in particular RCB stars; and (10) irreversible changes and rapid evolution in red variable stars.

  7. Basic thermal-mechanical properties and thermal shock, fatigue resistance of swaged + rolled potassium doped tungsten

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxin; Yan, Qingzhi; Lang, Shaoting; Xia, Min; Ge, Changchun

    2014-09-01

    The potassium doped tungsten (W-K) grade was achieved via swaging + rolling process. The swaged + rolled W-K alloy exhibited acceptable thermal conductivity of 159.1 W/m K and ductile-to-brittle transition temperature of about 873 K while inferior mechanical properties attributed to the coarse pores and small deformation degree. Then the thermal shock, fatigue resistance of the W-K grade were characterized by an electron beam facility. Thermal shock tests were conducted at absorbed power densities varied from 0.22 to 1.1 GW/m2 in a step of 0.22 GW/m2. The cracking threshold was in the range of 0.44-0.66 GW/m2. Furthermore, recrystallization occurred in the subsurface of the specimens tested at 0.66-1.1 GW/m2 basing on the analysis of microhardness and microstructure. Thermal fatigue tests were performed at 0.44 GW/m2 up to 1000 cycles and no cracks emerged throughout the tests. Moreover, recrystallization occurred after 1000 cycles.

  8. Basic concepts in mechanical ventilation.

    PubMed

    Carbery, Catherine

    2008-03-01

    Mechanical ventilatory support is a major component of the clinical management of critically ill patients admitted into intensive care. Closely linked with the developments within critical care medicine, the use of ventilatory support has been increasing since the polio epidemics in the 1950s (Lassen 1953). Initially used to provide controlled mandatory ventilation, today with advances in technology, most mechanical ventilators are triggered by the patient, increasing the awareness of the complexity of patient/ventilator interaction (Tobin 1994). Though ventilator appearance and design may have changed quite significantly and the variety of options for support extensive, the basic concepts of mechanical ventilatory support of the critically ill patient remains unchanged. This paper aims to outline these concepts so as to gain a better understanding of mechanical ventilatory support.

  9. Basic Mechanisms of the Epilepsies.

    ERIC Educational Resources Information Center

    Jasper, Herbert H., Ed.; And Others

    A collection of highly technical scientific articles by international basic and clinical neuroscientists constitutes a review of their knowledge of the brain and nervous system, particularly the aspects related to loss of brain function control and its explosive discharges which cause epileptic seizures. Anatomy, biophysics, biochemistry, and…

  10. Basic Mechanisms of Solar Variability

    NASA Technical Reports Server (NTRS)

    Sofia, Sabatino

    1990-01-01

    In order to simulate the behavior of a changing Sun in a realistic way, researchers have used a perturbation analysis (the results are summarized in Endal et al. 1985). In this approach, they use a standard solar model and then vary several of the model parameters to mimic the sudden or gradual change of some physical property within the Sun. The evolution following the perturbation is followed in a physically self-consistent way, that is, hydrostatic and thermal processes occur in their normal timescales. This treatment has allowed us to determine the sensitivity of the various global parameters to physical processes affecting the solar interior, and it has guided us in defining the least complex global solar model which can address the question of climatically significant variability. Not surprisingly, magnetic fields play the crucial role. The current status of the model, what researchers have already learned from it, and the future prospects are discussed.

  11. Auto Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Carter, Thomas G., Sr.

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 14 terminal objectives for a basic automotive mechanics course. The materials were developed for a two-semester course (2 hours daily) designed to provide training in the basic fundamentals in diagnosis and repair including cooling system and…

  12. Diesel Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Tidwell, Joseph

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 12 terminal objectives for a basic diesel mechanics course. The course is designed as a two-semester (2 hour daily) course for 10th graders interested in being diesel service and repair mechanics; it would serve as the first year of a 3-year…

  13. Basic mechanisms of neurodegeneration: a critical update

    PubMed Central

    Jellinger, Kurt A

    2010-01-01

    Abstract Neurodegenerative diseases are characterized by progressive dysfunction of specific populations of neurons, determining clinical presentation. Neuronal loss is associated with extra and intracellular accumulation of misfolded proteins, the hallmarks of many neurodegenerative proteinopathies. Major basic processes include abnormal protein dynamics due to deficiency of the ubiquitin–proteosome–autophagy system, oxidative stress and free radical formation, mitochondrial dysfunction, impaired bioenergetics, dysfunction of neurotrophins, ‘neuroinflammatory’ processes and (secondary) disruptions of neuronal Golgi apparatus and axonal transport. These interrelated mechanisms lead to programmed cell death is a long run over many years. Neurodegenerative disorders are classified according to known genetic mechanisms or to major components of protein deposits, but recent studies showed both overlap and intraindividual diversities between different phenotypes. Synergistic mechanisms between pathological proteins suggest common pathogenic mechanisms. Animal models and other studies have provided insight into the basic neurodegeneration and cell death programs, offering new ways for future prevention/treatment strategies. PMID:20070435

  14. Basic mechanisms governing solar-cell efficiency

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.; Neugroschel, A.; Sah, C. T.

    1976-01-01

    The efficiency of a solar cell depends on the material parameters appearing in the set of differential equations that describe the transport, recombination, and generation of electrons and holes. This paper describes the many basic mechanisms occurring in semiconductors that can control these material parameters.

  15. Gasoline Engine Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of five terminal objectives presented in this curriculum guide for a basic gasoline engine mechanics course at the secondary level. (For the intermediate course guide see CE 010 946.) The materials were developed for a two semester (2 hours daily)…

  16. Basic mechanisms for the new millennium

    SciTech Connect

    Dressendorfer, P.V.

    1998-09-01

    This part of the Short Course will review the basic mechanisms for radiation effects in semiconductor devices. All three areas of radiation damage will be considered -- total dose, displacement effects, and single event effects. Each of these areas will be discussed in turn. First an overview and background will be provided on the historical understanding of the damage mechanism. Then there will be a discussion of recent enhancements to the understanding of those mechanisms and an up-to-date picture provided of the current state of knowledge. Next the potential impact of each of these damage mechanisms on devices in emerging technologies and how the mechanisms may be used to understand device performance will be described, with an emphasis on those likely to be of importance in the new millennium. Finally some additional thoughts will be presented on how device scaling expected into the next century may impact radiation hardness.

  17. Basicity, Catalytic and Adsorptive Properties of Hydrotalcites

    NASA Astrophysics Data System (ADS)

    Figueras, Francois

    Solid bases have numerous potential applications, not only as catalyst for the manufacture of fine chemicals, in refining and petrochemistry, but also for adsorption and anion exchange. The present processes use liquid bases, typically alcoholic potash, and require neutralisation of the reaction medium at the end of the reaction, with production of salts. The substitution of these liquid bases by solids would provide cleaner and safer processes, due to the reduction of salts, and facilitate separation of the products and recycling of the catalyst. This chapter reviews the recent ideas on the modification of the basic properties of hydrotalcites by anion exchange and on the catalytic properties of solid bases as catalysts. Many examples of successful applications are given, with emphasis to industrial processes recently presented such as isomerisation of olefins. The basic properties of hydrotalcites can also be used to carry the exchange of toxic anions, humic acids or dyes, and have driven recent developments proposing HDT as drug carriers.

  18. Basic mechanisms of calcific aortic valve disease.

    PubMed

    Mathieu, Patrick; Boulanger, Marie-Chloé

    2014-09-01

    Calcific aortic valve disease (CAVD) is the most common heart valve disorder. There is no medical treatment to prevent and/or promote the regression of CAVD. Hence, it is of foremost importance to delineate and understand the key basic underlying mechanisms involved in CAVD. In the past decade our comprehension of the underpinning processes leading to CAVD has expanded at a fast pace. Hence, our understanding of the basic pathobiological processes implicated in CAVD might lead eventually to the development of novel pharmaceutical therapies for CAVD. In this review, we discuss molecular processes that are implicated in fibrosis and mineralization of the aortic valve. Specifically, we address the role of lipid retention, inflammation, phosphate signalling and osteogenic transition in the development of CAVD. Interplays between these different processes and the key regulation pathways are discussed along with their clinical relevance.

  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. The basics and underlying mechanisms of mucoadhesion.

    PubMed

    Smart, John D

    2005-11-03

    Mucoadhesion is where two surfaces, one of which is a mucous membrane, adhere to each other. This has been of interest in the pharmaceutical sciences in order to enhance localised drug delivery, or to deliver 'difficult' molecules (proteins and oligonucleotides) into the systemic circulation. Mucoadhesive materials are hydrophilic macromolecules containing numerous hydrogen bond forming groups, the carbomers and chitosans being two well-known examples. The mechanism by which mucoadhesion takes place has been said to have two stages, the contact (wetting) stage followed by the consolidation stage (the establishment of the adhesive interactions). The relative importance of each stage will depend on the individual application. For example, adsorption is a key stage if the dosage form cannot be applied directly to the mucosa of interest, while consolidation is important if the formulation is exposed to significant dislodging stresses. Adhesive joint failure will inevitably occur as a result of overhydration of a dosage form, or as a result of epithelia or mucus turnover. New mucoadhesive materials with optimal adhesive properties are now being developed, and these should enhance the potential applications of this technology.

  1. 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.

  2. Two basic Uncertainty Relations in Quantum Mechanics

    SciTech Connect

    Angelow, Andrey

    2011-04-07

    In the present article, we discuss two types of uncertainty relations in Quantum Mechanics-multiplicative and additive inequalities for two canonical observables. The multiplicative uncertainty relation was discovered by Heisenberg. Few years later (1930) Erwin Schroedinger has generalized and made it more precise than the original. The additive uncertainty relation is based on the three independent statistical moments in Quantum Mechanics-Cov(q,p), Var(q) and Var(p). We discuss the existing symmetry of both types of relations and applicability of the additive form for the estimation of the total error.

  3. Two basic Uncertainty Relations in Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Angelow, Andrey

    2011-04-01

    In the present article, we discuss two types of uncertainty relations in Quantum Mechanics-multiplicative and additive inequalities for two canonical observables. The multiplicative uncertainty relation was discovered by Heisenberg. Few years later (1930) Erwin Schrödinger has generalized and made it more precise than the original. The additive uncertainty relation is based on the three independent statistical moments in Quantum Mechanics-Cov(q,p), Var(q) and Var(p). We discuss the existing symmetry of both types of relations and applicability of the additive form for the estimation of the total error.

  4. Basic mechanism for abrupt monsoon transitions

    PubMed Central

    Levermann, Anders; Schewe, Jacob; Petoukhov, Vladimir; Held, Hermann

    2009-01-01

    Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and abrupt changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to abrupt changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, R c, no conventional monsoon can develop; above R c, two stable regimes exist. We identify a nondimensional parameter l that defines the threshold and makes monsoon systems comparable with respect to the character of their abrupt transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute R c for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation. PMID:19858472

  5. Basic mechanism for abrupt monsoon transitions.

    PubMed

    Levermann, Anders; Schewe, Jacob; Petoukhov, Vladimir; Held, Hermann

    2009-12-08

    Monsoon systems influence the livelihood of hundreds of millions of people. During the Holocene and last glacial period, rainfall in India and China has undergone strong and abrupt changes. Though details of monsoon circulations are complicated, observations reveal a defining moisture-advection feedback that dominates the seasonal heat balance and might act as an internal amplifier, leading to abrupt changes in response to relatively weak external perturbations. Here we present a minimal conceptual model capturing this positive feedback. The basic equations, motivated by observed relations, yield a threshold behavior, robust with respect to addition of other physical processes. Below this threshold in net radiative influx, R(c), no conventional monsoon can develop; above R(c), two stable regimes exist. We identify a nondimensional parameter l that defines the threshold and makes monsoon systems comparable with respect to the character of their abrupt transition. This dynamic similitude may be helpful in understanding past and future variations in monsoon circulation. Within the restrictions of the model, we compute R(c) for current monsoon systems in India, China, the Bay of Bengal, West Africa, North America, and Australia, where moisture advection is the main driver of the circulation.

  6. Urethral sensation: basic mechanisms and clinical expressions.

    PubMed

    Birder, Lori A; de Wachter, Stefan; Gillespie, James; Wyndaele, Jean Jacques

    2014-04-01

    A prerequisite for conscious bladder control is adequate sensory input to the central nervous system, and it is well established that changes in sensory mechanisms can give rise to disturbances in bladder function. Impulses related to the desire to void are believed to course through the pelvic nerves, and those for sensation of a full bladder course through the pudendal nerves. The sense of imminent micturition most probably resides in the urethra, and the desire to void comes from stretching the bladder wall. In addition, a variety of structures play an important role in terms of urethral closure (such as the urethral epithelium, vasculature and smooth muscle) that are necessary to maintain continence. This overview will discuss mechanisms related in part to the urethra involved in activation of bladder reflexes and sensation with a discussion on the mucosa (urothelium and underlying lamina propria) and underlying cellular structures.

  7. Basic failure mechanisms in advanced composites

    NASA Technical Reports Server (NTRS)

    Mullin, J. V.; Mazzio, V. F.; Mehan, R. L.

    1972-01-01

    Failure mechanisms in carbon-epoxy composites are identified as a basis for more reliable prediction of the performance of these materials. The approach involves both the study of local fracture events in model specimens containing small groups of filaments and fractographic examination of high fiber content engineering composites. Emphasis is placed on the correlation of model specimen observations with gross fracture modes. The effects of fiber surface treatment, resin modification and fiber content are studied and acoustic emission methods are applied. Some effort is devoted to analysis of the failure process in composite/metal specimens.

  8. Basic failure mechanisms in advanced composites

    NASA Technical Reports Server (NTRS)

    Mullin, J. V.; Mazzio, V. F.; Mehan, R. L.

    1971-01-01

    Fundamental failure mechanisms in carbon-epoxy composites were studied for more reliable prediction of the performance of these materials. Single and multiple fiber specimens were tested under tensile loads, and the sequence of failure events was observed. Parameters such as resin crack sensitivity, fiber surface treatment and variations in fibers from batch to batch are being evaluated. The analysis of bulk composite fracture processes using acoustic emission techniques is being studied in order to correlate microscopic observations with bulk composite behavior. Control of the fracture process through matrix and interface modification is being attempted, and study of failure processes in composite/metal specimens is being conducted. Most of the studies involved DEN 438 epoxy novolac as the matrix, but some experiments are now underway using the higher temperature resin ERLA 4617.

  9. "Basic MR Relaxation Mechanisms & Contrast Agent Design"

    PubMed Central

    De León-Rodríguez, Luis M.; Martins, André F.; Pinho, Marco; Rofsky, Neil; Sherry, A. Dean

    2015-01-01

    The diagnostic capabilities of magnetic resonance imaging (MRI) have undergone continuous and substantial evolution by virtue of hardware and software innovations and the development and implementation of exogenous contrast media. Thirty years since the first MRI contrast agent was approved for clinical use, a reliance on MR contrast media persists largely to improve image quality with higher contrast resolution and to provide additional functional characterization of normal and abnormal tissues. Further development of MR contrast media is an important component in the quest for continued augmentation of diagnostic capabilities. In this review we will detail the many important considerations when pursuing the design and use of MR contrast media. We will offer a perspective on the importance of chemical stability, particularly kinetic stability, and how this influences one's thinking about the safety of metal-ligand based contrast agents. We will discuss the mechanisms involved in magnetic resonance relaxation in the context of probe design strategies. A brief description of currently available contrast agents will be accompanied by an in-depth discussion that highlights promising MRI contrast agents in development for future clinical and research applications. Our intention is to give a diverse audience an improved understanding of the factors involved in developing new types of safe and highly efficient MR contrast agents and, at the same time, provide an appreciation of the insights into physiology and disease that newer types of responsive agents can provide. PMID:25975847

  10. Clinical Science-linking basic science to disease mechanisms.

    PubMed

    Touyz, Rhian M

    2017-04-01

    For more than 50 years, Clinical Science has been at the interface linking basic science to disease mechanisms. Here, Rhian Touyz, the Editor-in-Chief, describes the journal, its aims and scope, and recent developments.

  11. Catch-Up Growth: Basic Mechanisms.

    PubMed

    Griffin, Ian J

    2015-01-01

    The neuroendocrine model of catch-up growth has been well studied in a number of animal models. During nutritional inadequacy, which invariably precedes catch-up growth, growth hormone (GH) levels increase under the influence of the oxygenic 'hunger signal' ghrelin. This increase in GH would usually be accompanied by an increase in IGF-1. However, malnutrition also induces the nutritionally responsive proteins sirtuin 1 (SIRT1) and fibroblast growth factor 21 (FGF21) that block GH signal transduction in the liver by blocking the JAK/STAT pathway, limiting IGF-1 production. The result is that GH's action is shifted from hepatic effects to effects in other tissues (for example muscle and adipose) and shifted away from IGF-1-mediated effects and towards GH-mediated effects. Once nutrients become more available, SIRT1 and FGF21 levels, and hepatic GH sensitivity return to normal, and production of IGF-1 resumes. This shifts GH signaling away from GH-mediated effects, and towards IGF-1-mediated effects both in the liver and in other tissues. It presumably leads to greatly increased IGF-1 signaling that would have been expected without the prior episode of nutritional inadequacy. Although much work remains to be done, it does appear that ghrelin is increased in in utero and postnatal malnutrition, that elevations in ghrelin may be prolonged after malnutrition resolves, and that higher ghrelin levels are associated with increased rates of catch-up growth. Prolonged increases in circulating ghrelin and GH, combined with a rapid return in hepatic GH sensitivity would provide an elegant mechanism to drive catch-up growth after periods of nutritional insufficiency.

  12. Magnetic dipole discharges. I. Basic properties

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R.

    2013-08-15

    A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup −3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.

  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. Literature Survey: Basic Mechanisms of Explosive Compounds in Wastewater.

    DTIC Science & Technology

    1984-05-01

    of absorption of radiation and the H 202 concentration is given by the Beer - Lambert law: I = 1 10- H202 CH202 (16)0 where I is the source intensity... BASIC MECHANISMS OF EXPLOSIVE COM.POUNDS IN WASTEWATER Contract Number DAAK11-83-C-0006 Prepared by: David W. DeBerry Alfred Viebbeck Dean Meidrum A May...NUMBERDXTH-TE-CR-84279 4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED BASIC MECHANISMS OF EXPLOSIVE COMPOUNDS IN FINAL WASTEWATER 13 Dec. 1982

  15. 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

  16. Basic Gasoline Engine Mechanics. Florida Vocational Program Guide.

    ERIC Educational Resources Information Center

    University of South Florida, Tampa. Dept. of Adult and Vocational Education.

    This packet contains a program guide and Career Merit Achievement Plan (Career MAP) for the implementation of a basic gasoline engine mechanics program in Florida secondary and postsecondary schools. The program guide describes the program content and structure, provides a program description, lists job titles under the program, and includes a…

  17. Basic mechanisms for adverse cardiovascular events associated with air pollution

    PubMed Central

    Chin, Michael T.

    2015-01-01

    Air pollution is a significant cause of cardiovascular morbidity and mortality worldwide. Although the epidemiologic association between air pollution exposures and exacerbation of cardiovascular disease is well established, the mechanisms by which these exposures promote cardiovascular disease are incompletely understood. In this review I will give an overview of the components of air pollution, an overview of the cardiovascular effects of air pollution exposure and a review of the basic mechanisms that are activated by exposure to promote cardiovascular disease. PMID:25552258

  18. Basic mechanism of transcription by RNA polymerase II

    PubMed Central

    Svetlov, Vladimir; Nudler, Evgeny

    2012-01-01

    RNA polymerase II-like enzymes carry out transcription of genomes in Eukaryota, Archaea, and some viruses. They also exhibit fundamental similarity to RNA polymerases from bacteria, chloroplasts, and mitochondria. In this review we take an inventory of recent studiesilluminating different steps of basic transcription mechanism, likely common for most multi-subunit RNA polymerases. Through the amalgamation of structural and computational chemistry data we attempt to highlight the most feasible reaction pathway for the two-metal nucleotidyl transfer mechanism, and to evaluate the way catalysis can be linked to translocation in the mechano-chemical cycle catalyzed by RNA polymerase II. PMID:22982365

  19. 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

  20. Dimensional psychiatry: mental disorders as dysfunctions of basic learning mechanisms.

    PubMed

    Heinz, Andreas; Schlagenhauf, Florian; Beck, Anne; Wackerhagen, Carolin

    2016-08-01

    It has been questioned that the more than 300 mental disorders currently listed in international disease classification systems all have a distinct neurobiological correlate. Here, we support the idea that basic dimensions of mental dysfunctions, such as alterations in reinforcement learning, can be identified, which interact with individual vulnerability and psychosocial stress factors and, thus, contribute to syndromes of distress across traditional nosological boundaries. We further suggest that computational modeling of learning behavior can help to identify specific alterations in reinforcement-based decision-making and their associated neurobiological correlates. For example, attribution of salience to drug-related cues associated with dopamine dysfunction in addiction can increase habitual decision-making via promotion of Pavlovian-to-instrumental transfer as indicated by computational modeling of the effect of Pavlovian-conditioned stimuli (here affectively positive or alcohol-related cues) on instrumental approach and avoidance behavior. In schizophrenia, reward prediction errors can be modeled computationally and associated with functional brain activation, thus revealing reduced encoding of such learning signals in the ventral striatum and compensatory activation in the frontal cortex. With respect to negative mood states, it has been shown that both reduced functional activation of the ventral striatum elicited by reward-predicting stimuli and stress-associated activation of the hypothalamic-pituitary-adrenal axis in interaction with reduced serotonin transporter availability and increased amygdala activation by aversive cues contribute to clinical depression; altogether these observations support the notion that basic learning mechanisms, such as Pavlovian and instrumental conditioning and Pavlovian-to-instrumental transfer, represent a basic dimension of mental disorders that can be mechanistically characterized using computational modeling and

  1. Properties of the zeros of generalized basic hypergeometric polynomials

    NASA Astrophysics Data System (ADS)

    Bihun, Oksana; Calogero, Francesco

    2015-11-01

    We define the generalized basic hypergeometric polynomial of degree N in terms of the generalized basic hypergeometric function, by choosing one of its parameters to allow the termination of the series after a finite number of summands. In this paper, we obtain a set of nonlinear algebraic equations satisfied by the N zeros of the polynomial. Moreover, we obtain an N × N matrix M defined in terms of the zeros of the polynomial, which, in turn, depend on the parameters of the polynomial. The eigenvalues of this remarkable matrix M are given by neat expressions that depend only on some of the parameters of the polynomial; that is, the matrix M is isospectral. Moreover, in case the parameters that appear in the expressions for the eigenvalues of M are rational, the matrix M has rational eigenvalues, a Diophantine property.

  2. BASIC PROPERTIES OF REFERENCE CROSSPLY CARBON-FIBER COMPOSITE

    SciTech Connect

    Corum, J.M.

    2001-01-11

    This report provides basic in-air property data and correlations-tensile, compressive, shear, tensile fatigue, and tensile creep-for a reference carbon-fiber composite being characterized as a part of the Durability of Carbon-Fiber Composites Project at Oak Ridge National Laboratory. The overall goal of the project, which is sponsored by the Department of Energy's Office of Advanced Automotive Materials and is closely coordinated with the Advanced Composites Consortium, is to develop durability-based design guidance for polymeric composites for automotive structural applications. The composite addressed here is a {+-}45{degree} crossply consisting of continuous Thornel T300 fibers in a Baydur 420 IMR urethane matrix. Basic tensile, compressive, and shear properties are tabulated for the temperature range from {minus}40 to 120 C. Fatigue response at room-temperature and 120 C are presented, and creep and creep rupture at room temperature only are reported. In all cases, two fiber orientations--0/90{degree} and {+-}45{degree}--relative to the specimen axes are addressed. The properties and correlations presented are interim in nature. They are intended as a baseline for planning a full durability test program on this reference composite.

  3. 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.

  4. Pathobiology of human cerebrovascular malformations: basic mechanisms and clinical relevance.

    PubMed

    Gault, Judith; Sarin, Hemant; Awadallah, Nabil A; Shenkar, Robert; Awad, Issam A

    2004-07-01

    Cerebrovascular malformations affect more than 3% of the population, exposing them to a lifetime risk of hemorrhagic stroke, seizures, and focal neurological deficits. Cerebral cavernous malformations (CCMs) exhibit an immature vessel wall, a brittle hemorrhagic tendency, and epileptogenesis, whereas arteriovenous malformations (AVMs) lack capillary beds and manifest apoplectic bleeding under high-flow conditions. There are also more benign venous anomalies, capillary malformations, and lesions with mixed and transitional features. Advances have been made toward understanding the natural history, radiological and pathological correlates, and clinical management. Yet, mechanisms of lesion genesis and clinical manifestations remain largely unknown, and the clinical behavior in individual patients is highly unpredictable. Lesion pathogenesis likely involves abnormal assembly or maintenance of blood vessels, resulting in dysmorphic vessel phenotypes. Familial CCM disease is in part caused by mutations in a cytoskeletal-related protein that is likely integral to interendothelial cell connectivity and maturation of the vascular wall. Rare familial forms of AVM disease have been correlated with two different transforming growth factor-beta receptor components, possibly causing disturbance in signaling during vascular assembly. Relevance of these mechanisms to the more common and otherwise identical sporadic CCM and AVM lesions is being explored. In this report, basic mechanisms of vasculogenesis and angiogenesis and how they possibly relate to the common cerebrovascular malformation lesions are reviewed. Novel concepts are discussed related to the cellular, molecular, and genetic substrates in CCM and AVM as well as to how this knowledge can be applied to predict, explain, and possibly modify clinical disease manifestations.

  5. Excitation transfer through open quantum networks: Three basic mechanisms

    NASA Astrophysics Data System (ADS)

    Campos Venuti, Lorenzo; Zanardi, Paolo

    2011-10-01

    A variety of open quantum networks are currently under intense examination to model energy transport in photosynthetic systems. Here, we study the coherent transfer of a quantum excitation over a network incoherently coupled with a structured and small environment that effectively models the photosynthetic reaction center. Our goal is to distill a few basic, possibly universal, mechanisms or effects that are featured in simple energy-transfer models. In particular, we identify three different phenomena: the congestion effect, the asymptotic unitarity, and the staircase effects. We begin with few-site models, in which these effects can be fully understood, and then proceed to study more complex networks similar to those employed to model energy transfer in light-harvesting complexes.

  6. Solvation of polymers as mutual association. II. Basic thermodynamic properties

    NASA Astrophysics Data System (ADS)

    Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.

    2013-04-01

    The theory of equilibrium solvation of polymers B by a relatively low molar mass solvent A, developed in the simplest form in Paper I, is used to explore some essential trends in basic thermodynamic properties of solvated polymer solutions, such as the equilibrium concentrations of solvated polymers AiB and free solvent molecules A, the mass distribution φ _{{AiB}}(i) of solvated clusters, the extent of solvation of the polymer Φsolv, the solvation transition lines T_{solv}(φ _{{B}}o), the specific heat CV, the osmotic second virial coefficient B2, phase stability boundaries, and the critical temperatures associated with closed loop phase diagrams. We discuss the differences between the basic thermodynamic properties of solvated polymers and those derived previously for hierarchical mutual association processes involving the association of two different species A and B into AB complexes and the subsequent polymerization of these AB complexes into linear polymeric structures. The properties of solvated polymer solutions are also compared to those for solutions of polymers in a self-associating solvent. Closed loop phase diagrams for solvated polymer solutions arise in the theory from the competition between the associative and van der Waals interactions, a behavior also typical for dispersed molecular and nanoparticle species that strongly associate with the host fluid. Our analysis of the temperature dependence of the second osmotic virial coefficient reveals that the theory must be generalized to describe the association of multiple solvent molecules with each chain monomer, and this complex extension of the present model will be developed in subsequent papers aimed at a quantitative rather than qualitative treatment of solvated polymer solutions.

  7. Flavonoid basics: chemistry, sources, mechanisms of action, and safety.

    PubMed

    Corcoran, Michael P; McKay, Diane L; Blumberg, Jeffrey B

    2012-01-01

    In our efforts to understand how various dietary factors can influence the risk and progression of chronic disease, much recent research has focused on phytochemicals. Phytochemicals are defined as nonessential nutrients found in plant-based food, many of which have been established as bioactive and thus may affect human health. The largest group of phytochemicals is the polyphenols, comprised principally of the flavonoids, which are characterized chemically by two benzene rings joined by a linear carbon chain. Evidence from observational studies indicates that regular consumption of foods containing flavonoids may reduce the risk several chronic conditions, including neurodegenerative diseases, atherosclerosis, and certain forms of cancer. These results have generated considerable interest in flavonoids, although much basic information about their nutrient characteristics in humans remains limited, e.g., their bioavailability and metabolism, interactions with other dietary factors, mechanisms of action, and intakes associated with specific health outcomes. Although flavonoids are commonly defined as dietary antioxidants and their putative health benefits commonly attributed to this mechanism, it now appears their principal actions are mediated in vivo via other biochemical and molecular pathways.

  8. Basic mechanisms controlling the sweeping efficiency of propagating current sheets

    NASA Astrophysics Data System (ADS)

    Berkery, J. W.; Choueiri, E. Y.

    2006-02-01

    The basic mechanisms controlling the sweeping efficiency of propagating current sheets are investigated through experiments and analytical modelling. The sweeping efficiency of a current sheet in a parallel plate gas-fed pulsed plasma accelerator is defined as the ratio of the current sheet mass to the total available propellant mass. Permeability of neutrals through the sheet, and leakage of mass out of the sheet and into a cathode wake, decrease the sweeping efficiency. The sweeping efficiency of current sheets in argon, neon, helium and hydrogen propellants at different initial pressures was determined through measurements of sheet velocity with high speed photography and of sheet mass with laser interferometry. The mechanism that controls the sweeping efficiency of propagating current sheets was found to be an interplay of two processes: the flux of mass entering the sheet and the leakage of mass at the cathode, with the former dependent on the degree of permeability and the latter dependent on the level of ion current as determined by the ion Hall parameter.

  9. Gastric sensitivity and reflexes: basic mechanisms underlying clinical problems.

    PubMed

    Azpiroz, Fernando; Feinle-Bisset, Christine; Grundy, David; Tack, Jan

    2014-02-01

    Both reflex and sensory mechanisms control the function of the stomach, and disturbances in these mechanisms may explain the pathophysiology of disorders of gastric function. The objective of this report is to perform a literature-based critical analysis of new, relevant or conflicting information on gastric sensitivity and reflexes, with particular emphasis on the comprehensive integration of basic and clinical research data. The stomach exerts both phasic and tonic muscular (contractile and relaxatory) activity. Gastric tone determines the capacity of the stomach and mediates both gastric accommodation to a meal as well as gastric emptying, by partial relaxation or progressive recontraction, respectively. Perception and reflex afferent pathways from the stomach are activated independently by specific stimuli, suggesting that the terminal nerve endings operate as specialized receptors. Particularly, perception appears to be related to stimulation of tension receptors, while the existence of volume receptors in the stomach is uncertain. Reliable techniques have been developed to measure gastric perception and reflexes both in experimental and clinical conditions, and have facilitated the identification of abnormal responses in patients with gastric disorders. Gastroparesis is characterised by impaired gastric tone and contractility, whereas patients with functional dyspepsia have impaired accommodation, associated with antral distention and increased gastric sensitivity. An integrated view of fragmented knowledge allows the design of pathophysiological models in an attempt to explain disorders of gastric function, and may facilitate the development of mechanistically orientated treatments.

  10. 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.

  11. Oscillating plasma bubbles. I. Basic properties and instabilities

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2012-08-15

    Plasma bubbles are created in an ambient discharge plasma. A bubble is a plasma volume of typically spherical shape, which is separated from the ambient plasma by a negatively biased grid of high transparency. Ions and electrons from the ambient plasma flow into the bubble volume. In steady state the flow of particles and currents is divergence-free, which is established by the plasma potential inside the bubble. The grid has two sheaths, one facing the ambient plasma, the other the bubble plasma. The inner sheath is observed to become unstable, causing the plasma potential in the bubble to oscillate. The instability arises from an excess of ions and a deficiency of electrons. Its frequency is in the range of the ion plasma frequency but depends on all parameters which influence the charge density in the sheath. When the grid voltage is very negative, electrons cannot enter the outer sheath, and the inner sheath becomes a virtual anode which reflects ions such that the bubble interior is empty. When an electron source is placed into the bubble it can neutralize the ions and the bubble refills. Without plasma sources or sinks the bubble plasma is extremely sensitive to perturbations by probes. Modified current-voltage characteristics of Langmuir and emissive probes are demonstrated. A sequence of papers first describes the basic steady-state properties, then the time evolution of bubbles, the effects of electron sources in bubbles, and the role of the grid and bubble geometry. The physics of plasma bubbles is important to several fields of basic plasma physics such as sheaths, sheath instabilities, diagnostic probes, electrostatic confinement, and current and space charge neutralization of beams.

  12. Basic mechanisms of migraine and its acute treatment.

    PubMed

    Edvinsson, Lars; Villalón, Carlos M; MaassenVanDenBrink, Antoinette

    2012-12-01

    Migraine is a neurovascular disorder characterized by recurrent unilateral headaches accompanied by nausea, vomiting, photophobia and phonophobia. Current theories suggest that the initiation of a migraine attack involves a primary event in the central nervous system (CNS), probably involving a combination of genetic changes in ion channels and environmental changes, which renders the individual more sensitive to environmental factors; this may, in turn, result in a wave of cortical spreading depression (CSD) when the attack is initiated. Genetically, migraine is a complex familial disorder in which the severity and the susceptibility of individuals are most likely governed by several genes that vary between families. Early PET studies have suggested the involvement of a migraine active region in the brainstem. Migraine headache is associated with trigeminal nerve activation and calcitonin gene-related peptide (CGRP) release from the trigeminovascular system. Administration of triptans (5-HT(1B/1D) receptor agonists) causes the headache to subside and the levels of CGRP to normalize. Moreover, administration of CGRP receptor antagonists aborts the headache. Recent immunohistochemical and pharmacological results suggest that the trigeminal system has receptors for CGRP; further, 5-HT(1B/1D) receptors, which inhibit the action of CGRP in pain transmission when activated, have been demonstrated. This offers an explanation for the treatment response. The present review provides an updated analysis of the basic mechanisms involved in the pathophysiology of migraine and the various pharmacological approaches (including 5-HT(1B/1D) receptor agonists, CGRP receptor antagonists and glutamate receptor antagonists) that have shown efficacy for the acute treatment of this disorder.

  13. 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.

  14. Information as a basic property of the universe.

    PubMed

    Stonier, T

    1996-01-01

    A theory is proposed which considers information to be a basic property of the universe the way matter and energy are. Operationally--just as energy is defined in terms of its capacity to perform work--so is information defined in terms of its capacity to organize a system. Pure energy can perform no 'useful' (entropy reducing) work without a concomitant input of information. Conversely, all expenditures of energy lead to a reorganization of the universe, hence to a change in its information status. Energy and information are interconvertible; physicists have been able to ignore the information parameter principally for two major reasons. First, historically, just as there was no need to define energy prior to the advent of increasingly complex, powered machinery and cannons (Galileo was a military engineer), so was there no need until the 20th Century to define information. It was the telephone engineers who first preoccupied themselves with developing a theory of information. The second reason is that physicists invented accounting devices such as potential energy and entropy to explain the apparent disappearance of energy yet maintain the law of the conservation of energy. The proposed theory would consider that what is conserved is the sum of information and energy. The mathematical relationship between information and entropy is provided by the equation: I = (Io)e-S/k while the conversion of energy into information involves the relationship: 1 J/degree K = 10(23) bits (approximately) Acceptance of the theory would require paradigm shifts in a number of interrelated areas.

  15. Strength/Brittleness Classification of Igneous Intact Rocks Based on Basic Physical and Dynamic Properties

    NASA Astrophysics Data System (ADS)

    Aligholi, Saeed; Lashkaripour, Gholam Reza; Ghafoori, Mohammad

    2017-01-01

    This paper sheds further light on the fundamental relationships between simple methods, rock strength, and brittleness of igneous rocks. In particular, the relationship between mechanical (point load strength index I s(50) and brittleness value S 20), basic physical (dry density and porosity), and dynamic properties (P-wave velocity and Schmidt rebound values) for a wide range of Iranian igneous rocks is investigated. First, 30 statistical models (including simple and multiple linear regression analyses) were built to identify the relationships between mechanical properties and simple methods. The results imply that rocks with different Schmidt hardness (SH) rebound values have different physicomechanical properties or relations. Second, using these results, it was proved that dry density, P-wave velocity, and SH rebound value provide a fine complement to mechanical properties classification of rock materials. Further, a detailed investigation was conducted on the relationships between mechanical and simple tests, which are established with limited ranges of P-wave velocity and dry density. The results show that strength values decrease with the SH rebound value. In addition, there is a systematic trend between dry density, P-wave velocity, rebound hardness, and brittleness value of the studied rocks, and rocks with medium hardness have a higher brittleness value. Finally, a strength classification chart and a brittleness classification table are presented, providing reliable and low-cost methods for the classification of igneous rocks.

  16. Multidimensional Generalized Functions in Aeroacoustics and Fluid Mechanics. Part 1; Basic Concepts and Operations

    NASA Technical Reports Server (NTRS)

    Farassat, Fereidoun; Myers, Michael K.

    2011-01-01

    This paper is the first part of a three part tutorial on multidimensional generalized functions (GFs) and their applications in aeroacoustics and fluid mechanics. The subject is highly fascinating and essential in many areas of science and, in particular, wave propagation problems. In this tutorial, we strive to present rigorously and clearly the basic concepts and the tools that are needed to use GFs in applications effectively and with ease. We give many examples to help the readers in understanding the mathematical ideas presented here. The first part of the tutorial is on the basic concepts of GFs. Here we define GFs, their properties and some common operations on them. We define the important concept of generalized differentiation and then give some interesting elementary and advanced examples on Green's functions and wave propagation problems. Here, the analytic power of GFs in applications is demonstrated with ease and elegance. Part 2 of this tutorial is on the diverse applications of generalized derivatives (GDs). Part 3 is on generalized Fourier transformations and some more advanced topics. One goal of writing this tutorial is to convince readers that, because of their powerful operational properties, GFs are absolutely essential and useful in engineering and physics, particularly in aeroacoustics and fluid mechanics.

  17. 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.

  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. 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.

  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. [Basic mechanisms: structure, function and metabolism of plasma lipoproteins].

    PubMed

    Errico, Teresa L; Chen, Xiangyu; Martin Campos, Jesús M; Julve, Josep; Escolà-Gil, Joan Carles; Blanco-Vaca, Francisco

    2013-01-01

    The aim of this work is to present basic information on the lipoprotein physiology. The protein fraction of lipoproteins consists of several apolipoproteins and enzymes whose functions are lipid transport and metabolism. Classification of lipoproteins is based on their density. Chylomicrons, VLDL, IDL, LDL and HDL can be isolated by ultracentrifugation. Both chylomicrons- and VLDL-triglycerides are transported from the intestine and liver, respectively, to the peripheral tissues. The metabolism of VLDL originates IDL and LDL. LDL is the main transporter of cholesterol to extrahepatic tissues. HDL mobilizes cholesterol from peripheral tissues to the liver where it is secreted to bile as free cholesterol or bile salts, a process termed reverse cholesterol transport. Lipoprotein metabolism can be regulated by nuclear receptors that regulate the expression of genes involved in triglyceride and apolipoprotein metabolism.

  3. The Elusive Memristor: Properties of Basic Electrical Circuits

    ERIC Educational Resources Information Center

    Joglekar, Yogesh N.; Wolf, Stephen J.

    2009-01-01

    We present an introduction to and a tutorial on the properties of the recently discovered ideal circuit element, a memristor. By definition, a memristor M relates the charge "q" and the magnetic flux [phi] in a circuit and complements a resistor R, a capacitor C and an inductor L as an ingredient of ideal electrical circuits. The properties of…

  4. 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.

  5. Osteoarthritis pain mechanisms: Basic studies in animal models

    PubMed Central

    Zhang, Rui-Xin; Ren, Ke; Dubner, Ronald

    2013-01-01

    Osteoarthritis (OA) is a complex and painful disease of the whole joint. At present there are no satisfying agents for treating OA. The current standard of care mainly involves managing and alleviating its symptoms. Mechanisms of OA pain have been studied in rodent knee OA models produced by intra-knee injection of the chondrocyte glycolytic inhibitor mono-iodoacetate, surgery, or spontaneous development in some species. These models are clinically relevant in terms of histological damage and functional changes, and are used to study mechanisms underlying mechanical, thermal, ambulatory, body weight supporting-evoked, and ongoing OA pain. Recent peripheral, spinal, and supraspinal biochemical and electrophysiological studies in these models suggest that peripheral pro-inflammatory mediators and neuropeptides sensitize knee nociceptors. Spinal cytokines and neuropeptides promote OA-associated pain, and peripheral and spinal cannabinoids inhibit OA pain respectively through cannabinoid-1 (CB1) and CB1/CB2 receptors. TRPV1 and metalloproteinases contribute and supraspinal descending facilitation of 5-HT/5-HT 3 receptors may also contribute to OA pain. Conditioned place preference tests demonstrate that OA pain induces aversive behaviors suggesting brain involvement in OA pain. During OA, brain functional connectivity is enhanced, but at present it is unclear how this change is related to OA pain. PMID:23973145

  6. The Basic Physical Mechanism for Disconnection Events(DEs)

    NASA Astrophysics Data System (ADS)

    Brandt, J. C.

    2004-11-01

    Disconnection Events (DEs) are arguably the most dramatic phenomena in cometary physics. The entire plasma tail disconnects from the head, and image sequences have been available for approximately one century. Many details were known to Barnard (1899, 1908, 1920) and his contemporaries. Modern DE studies began with the rediscovery of the phenomena by Niedner & Brandt (1978) and their proposal that the physical mechanism was the severing of the magnetic field lines by magnetic reconnection at crossings of the heliospheric current sheet (HCS). While many areas of investigation-direct spacecraft observations (Niedner & Schwingenschuh 1987; Verigin et al. 1987; Kirsch et al. 1989); associations of DEs with solar-wind features (Niedner & Brandt 1979; Yi et al. 1994; Brandt et al. 1999); and magnetohydrodynamic (MHD) simulations of DEs (Yi et al. 1996)-strongly supported this physical mechanism, areas of concern or disagreement remained (e.g., Farnham & Meech 1994; Wegmann 1995, 1998, 2000). Recent results seem to resolve the problems in all areas. The associations of DEs with solar-wind features have been extensively reinvestigated (Niedner et al. 2005). In particular, many high-speed streams are not associated with the HCS (as many as 40%) and these high-speed streams are definitely not associated with DEs. Finally, Konz et al. (2004) have reproduced DEs at crossings of the HCS using plasma-neutral gas simulations with anomalous resistivity. The new evidence strongly confirms the sunward, magnetic reconnection physical mechanism proposed by Niedner & Brandt (1978).

  7. Reversible atomic processes as basic mechanisms of the glass transition

    PubMed Central

    Ye, Feng; Sprengel, Wolfgang; Wunderlich, Rainer K.; Fecht, Hans-Jörg; Schaefer, Hans-Eckhardt

    2007-01-01

    Reversible formation and disappearance of vacant spaces (vacancy-type defects) in bulk Zr57Cu15.4Ni12.6Nb5Al10 glass are directly evidenced by high-resolution, time-differential dilatometry studies. The vacancy kinetics are strongly temperature-dependent, with an effective migration enthalpy of HVM = 3.34 eV. This may explain the strong temperature dependence of glass properties such as viscosity. The results presented here are of general importance for understanding amorphous condensed matter and biomaterials and for the technical development of amorphous steels. PMID:17664428

  8. 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.

  9. Intrahepatic Cholangiocarcinoma Progression: Prognostic Factors and Basic Mechanisms

    PubMed Central

    Sirica, Alphonse E.; Dumur, Catherine I.; Campbell, Deanna J. W.; Almenara, Jorge A.; Ogunwobi, Olorunseun O.; Dewitt, Jennifer L.

    2013-01-01

    In this review, we will examine various molecular biomarkers for their potential to serve as independent prognostic factors for predicting survival outcome in postoperative patients with progressive intrahepatic cholangiocarcinoma. Specific rodent models of intrahepatic cholangiocarcinoma that mimic relevant cellular, molecular, and clinical features of the human disease are also described, not only in terms of their usefulness in identifying molecular pathways and mechanisms linked to cholangiocarcinoma development and progression, but also for their potential value as preclinical platforms for suggesting and testing novel molecular strategies for cholangiocarcinoma therapy. Last, recent studies aimed at addressing the role of desmoplastic stroma in promoting intrahepatic cholangiocarcinoma progression are highlighted in an effort to underline the potential value of targeting tumor stromal components together with that of cholangiocarcinoma cells as a novel therapeutic option for this devastating cancer. PMID:19896103

  10. Some basic fracture mechanics concepts in functionally graded materials

    NASA Astrophysics Data System (ADS)

    Jin, Z.-H.; Batra, R. C.

    1996-08-01

    In this paper, the crack-tip fields in a general nonhomogeneous material are summarized. The fracture toughness and R-curve of functionally graded materials (FGMs) are studied based on the crack-bridging concept and a rule of mixtures. It is shown that the fracture toughness is significantly increased when a crack grows from the ceramic-rich region into the metal-rich region in an alumina-nickel FGM. By applying the concept of the toughening mechanism to the study of the strength behavior of FGMs, it is found that the residual strength of the alumina-nickel FGM with an edge crack on the ceramic side is quite notch insensitive.

  11. Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications.

    PubMed

    Lei, Xin Gen; Zhu, Jian-Hong; Cheng, Wen-Hsing; Bao, Yongping; Ho, Ye-Shih; Reddi, Amit R; Holmgren, Arne; Arnér, Elias S J

    2016-01-01

    Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

  12. Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

    PubMed Central

    Lei, Xin Gen; Zhu, Jian-Hong; Cheng, Wen-Hsing; Bao, Yongping; Ho, Ye-Shih; Reddi, Amit R.; Holmgren, Arne; Arnér, Elias S. J.

    2015-01-01

    Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate “paradoxical” outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of “antioxidant” nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that “paradoxical” roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways. PMID:26681794

  13. Cryogenic compressive properties of basic epoxy resin systems

    SciTech Connect

    Markley, F.W.; Hoffman, J.A.; Muniz, D.P.

    1985-09-01

    The compressive properties of short cylindrical samples of many different epoxy resin systems have been measured at ambient temperature and at 77/sup 0/K. These are pure resin systems of known chemistry, without the inorganic fillers or fibrous reinforcements needed in final cryogenic systems. Of course, chemically incorporated modifiers such as flexibilizing resins have been included. This data should make possible inferences about cryogenic properties from molecular structures and provide specific data useful to formulators and end users. Measurements on some other plastics such as PTFE, Polyimides, and UHMWPE have been made for comparison purposes.

  14. Stimulating immune responses to fight cancer: Basic biology and mechanisms.

    PubMed

    O'Byrne, Kenneth

    2015-04-01

    Chronic inflammation is now recognized as a major cause of malignant disease. In concert with various mechanisms (including DNA instability), hypoxia and activation of inflammatory bioactive lipid pathways and pro-inflammatory cytokines open the doorway to malignant transformation and proliferation, angiogenesis, and metastasis in many cancers. A balance between stimulatory and inhibitory signals regulates the immune response to cancer. These include inhibitory checkpoints that modulate the extent and duration of the immune response and may be activated by tumor cells. This contributes to immune resistance, especially against tumor antigen-specific T-cells. Targeting these checkpoints is an evolving approach to cancer immunotherapy, designed to foster an immune response. The current focus of these trials is on the programmed cell death protein 1 (PD-1) receptor and its ligands (PD-L1, PD-L2) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). Researchers have developed anti-PD-1 and anti-PDL-1 antibodies that interfere with the ligands and receptor and allow the tumor cell to be recognized and attacked by tumor-infiltrating T-cells. These are currently being studied in lung cancer. Likewise, CTLA-4 inhibitors, which have had success treating advanced melanoma, are being studied in lung cancer with encouraging results.

  15. Prolactin secretion patterns: basic mechanisms and clinical implications for reproduction.

    PubMed

    Egli, Marcel; Leeners, Brigitte; Kruger, Tillmann H C

    2010-11-01

    Prolactin (PRL) is one of the most versatile hormones in the mammalian body affecting reproductive, sexual, metabolic, immune, and other functions. It is therefore not surprising that the neural control of PRL secretion is complex, involving the coordinated actions of several hypothalamic nuclei. A plethora of experimental data exists on the hypothalamic control of hormone secretion under various physiological stimuli. There have been even mathematical models and computer studies published, which help to understand the complex hypothalamic-pituitary network. Nevertheless, the putative role of PRL for human reproduction still has to be clarified. Here, we review data on the underlying mechanisms controlling PRL secretion using both experimental and mathematical approaches. These investigations primarily focus on rhythmic secretion in rats during early pregnancy or pseudopregnancy, and they point to the important role of oxytocin as a crucial PRL-releasing factor. Recent data on human studies and their theoretical and clinical implications are reviewed as well. In particular, studies demonstrating a sustained PRL surge after sexual climax in males and females are presented, indicating possible implications for both sexual satiation and reproductive functions. Taking these data together, there is evidence for the hypothesis that the PRL surge induced by sexual activity, together with the altered PRL rhythmic pattern, is important for successful initialization of pregnancy not only in rodents but also possibly in humans. However, further investigations are needed to clarify such a role in humans.

  16. Thermoelastic waves and ratcheting - basic mechanism of global tectonics

    NASA Astrophysics Data System (ADS)

    Kalenda, Pavel; Ostřihanský, Lubor; Wandrol, Ivo; Frydrýšek, Karel; Kopf, Tomáš; Neumann, Libor

    2013-04-01

    The deformation measurement of rock mass in the depth and mathematical modelling solved the old question of Wegeneŕs theory "What is the main engine for the lithosphere movement?". The solar energy, which reaches the Earth, is two orders higher than the energy of all earthquakes and volcanoes. Only a small part of the solar energy is accumulated in the rocks and the thermal wave created by the solar irradiation penetrates the subsurface layers. The thermal expansions of rocks give rise to excitation of the thermoelastic waves, which are observable in depths as well as in the whole lithosphere plate. The thermoelastic waves with diurnal and annual periods are well observable. The limit cases were modeled by the Simulation-Based Reliability Assessment (SBRA) method (probabilistic Monte Carlo approach). The upper limit corresponds with slow slip events, tremors, creep or earthquakes, the lower limit corresponds with opening of cracks and faults, which can be filled by ratchets. Such mechanism leads to the non-reversible expansions of rocks and spreading of the ocean floor.

  17. Basic mechanisms of augmentation of antidepressant effects with thyroid hormone.

    PubMed

    Lifschytz, Tsuri; Segman, Ronen; Shalom, Galit; Lerer, Bernard; Gur, Eitan; Golzer, Tanya; Newman, Michael E

    2006-02-01

    The thyroid hormone triiodothyronine (T3) has been used both to augment and accelerate the clinical effects of antidepressants, particularly the tricyclics. More recent work indicates that it may have similar actions with regard to the SSRIs. Two main mechanisms have been put forward to explain its antidepressant actions, (a) an action at the nuclear level involving stimulation of gene transcription, (b) an action at the cell membrane level involving potentiation of neurotransmission. In particular, there is considerable evidence for potentiation by T3 of the actions of the neurotransmitter 5-HT or serotonin. This evidence, which is mainly based on in vivo microdialysis studies, is reviewed, and evidence based on human and animal neuroendocrine studies considered. The effects of T3, alone and together with the SSRI fluoxetine, on mRNA levels for the 5-HT1A and 5-HT1B autoreceptors, which mediate serotonergic neurotransmission by feedback actions at the levels of cell firing(somatodendritic 5-HT1A autoreceptors) and neurotransmitter release (nerve terminal 5-HT1B autoreceptors) were also determined. Administration of a combination of fluoxetine and T3 induced reductions in the transcription of these autoreceptors, which may explain the clinical potentiating effects of this combination, and thus link the nuclear and neurotransmitter hypotheses of T3 action.

  18. Advances in understanding basic mechanisms of epilepsy and seizures.

    PubMed

    Jefferys, John G R

    2010-12-01

    Sixty years ago the clinical neurophysiology of epilepsy had progressed to the stage that it posed questions that could be addressed by major advances in cellular electrophysiology made around the that time. However, it took about 25-30 years to build up serious momentum in understanding the mechanisms of epileptic discharges. Over the past 2-3 decades developments in pharmacology and molecular biology have substantially increased the depth and complexity of our insights into the nervous system in general and the epileptic brain in particular. One of the biggest advances in our understanding of the brain is in its plasticity in the adult - that is its ability to modify its structure and function. The current state of play is that for most chronic epileptic foci it is possible to identify multiple differences from normal brain tissue in both the structure and function of neurons, neuronal networks and glia. This review will chart some of this progress to give an idea of the pace of advances over the decades.

  19. Basic mechanisms leading to focal emphysema in coal workers' pneumoconiosis

    SciTech Connect

    Rom, W.N. )

    1990-10-01

    Coal miners develop focal emphysema characterized by dilatation of second- and third-order respiratory bronchioles with coal mine dust-laden macrophages infiltrating the wall. A reticulin network with small amounts of collagen and atrophy of smooth muscle occurs. To evaluate the mechanisms of lung injury associated with this lesion, 17 long-term non- or ex-smoking West Virginia underground coal miners underwent bronchoalveolar lavage (BAL) and were compared to healthy nonsmoker and smoker controls. The coal miners had evidence of an alveolar macrophage-neutrophil alveolitis with a significant increase in neutrophils/microliter of epithelial lining fluid and an increased gallium lung scan index (206 +/- 26 units). Alveolar macrophages lavaged from coal miners spontaneously released exaggerated amounts of superoxide anion and hydrogen peroxide in vitro compared to nonsmoking controls. Coal workers had significantly elevated levels of neutrophil elastase in BAL fluid complexed with alpha 1-antitrypsin (P less than 0.01) and normal levels of alpha 1-antitrypsin. An accumulation of activated, dust-laden inflammatory cells with increased release of oxidants and elastase may contribute to the development of focal emphysema identified at postmortem in miners with coal workers' pneumoconiosis.

  20. The heart in sepsis: from basic mechanisms to clinical management.

    PubMed

    Rudiger, Alain; Singer, Mervyn

    2013-03-01

    Septic shock is characterized by circulatory compromise, microcirculatory alterations and mitochondrial damage, which all reduce cellular energy production. In order to reduce the risk of major cell death and a diminished likelihood of recovery, adaptive changes appear to be activated. As a result, cells and organs may survive in a non-functioning hibernation-like condition. Sepsis-induced cardiac dysfunction may represent an example of such functional shutdown. Sepsis-induced myocardial dysfunction is common, corresponds to the severity of sepsis, and is reversible in survivors. Its mechanisms include the attenuation of the adrenergic response at the cardiomyocyte level, alterations of intracellular calcium trafficking and blunted calcium sensitivity of contractile proteins. All these changes are mediated by cytokines. Treatment includes preload optimization with sufficient fluids. However, excessive volume loading is harmful. The first line vasopressor recommended at present is norepinephrine, while vasopressin can be started as a salvage therapy for those not responding to catecholamines. During early sepsis, cardiac output can be increased by dobutamine. While early administration of catecholamines might be necessary to restore adequate organ perfusion, prolonged administration might be harmful. Novel therapies for sepsis-induced cardiac dysfunction are discussed in this article. Cardiac inotropy can be increased by levosimendan, istaroxime or omecamtiv mecarbil without greatly increasing cellular oxygen demands. Heart rate reduction with ivabradine reduces myocardial oxygen expenditure and ameliorates diastolic filling. Beta-blockers additionally reduce local and systemic inflammation. Advances may also come from metabolic interventions such as pyruvate, succinate or high dose insulin substitutions. All these potentially advantageous concepts require rigorous testing before implementation in routine clinical practice.

  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. 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.

  3. Predicting blood:air partition coefficients using basic physicochemical properties.

    PubMed

    Buist, Harrie E; Wit-Bos, Lianne de; Bouwman, Tialda; Vaes, Wouter H J

    2012-02-01

    Quantitative Property Property Relationships (QPPRs) for human and rat blood:air partition coefficients (PBAs) have been derived, based on vapour pressure (Log(VP)), the octanol:water partition coefficient (Log(K(OW))) and molecular weight (MW), using partial least squares multilinear modelling. These parameters are all included in the standard data to be submitted under REACH. The chemical dataset consisted of volatile organic chemicals, principally aliphatic hydrocarbons, benzene derivatives with one aromatic ring, and ethers, with and without halogen atoms. Other chemicals represented were cyclic hydrocarbons and carbonic acid esters. Separate rat and human models were derived, as well as mixed ones. Log(VP) and Log(K(OW)) contributed most to the prediction of Log(PBA) in the three-parameter model, while the contribution of MW was relatively small. Still, the three-parameter model differed significantly from the two-parameter model and performed better. Its performance was comparable to that of models published in public literature, which are based on more complex molecular parameters or on measured olive:oil air and saline/water:air partition coefficients. Since, based on the available data for humans, rats, mice, dogs and rabbits, existence of interspecies differences of PBAs cannot be clearly excluded, the use of separate models for each species is advisable. Concluding, the three-parameter human model Log(PBA)=6.96-1.04 Log(VP)-0.533 Log(K(OW))-0.00495MW and the three-parameter rat model 6.16-0.888 Log(VP)-0.521 Log(K(OW))-0.00201MW provide robust and reliable models for predicting PBA values of volatile organic chemicals using commonly available chemical properties of molecules.

  4. An Experimental and Theoretical Investigation of the Magnetization Properties and Basic Electromechanics of Ferrofluids,

    DTIC Science & Technology

    The purpose of this study is to investigate the basic magnetization processes and properties of ferrofluids and to apply these findings to the...In basic ferrofluid properties studies, the authors have discovered a previously unreported agglomeration effect in commercially available 200 Gauss...water-base ferrofluid . Upon the application of a uniform or non-uniform magnetic field, A.C. (60 Hz) or D.C., and any strength from 5 Oe to 230 Oe

  5. Magnetic antenna excitation of whistler modes. I. Basic properties

    SciTech Connect

    Urrutia, J. M.; Stenzel, R. L.

    2014-12-15

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  6. General study and basic properties of causal symmetries

    NASA Astrophysics Data System (ADS)

    García-Parrado, Alfonso; Senovilla, José M. M.

    2004-01-01

    We fully develop the concept of causal symmetry introduced in our earlier publication (2003 Class. Quantum Grav. 20 L139). A causal symmetry is a transformation of a Lorentzian manifold (V, g) which maps every future-directed vector onto a future-directed vector. We prove that the set of all causal symmetries is not a group under the usual composition operation but a submonoid of the diffeomorphism group of V. Therefore, the infinitesimal generating vector fields of causal symmetries—causal-preserving vector fields—are associated with local one-parameter groups of transformations which are causal symmetries only for positive values of the parameter—one-parameter submonoids of causal symmetries. The pull-back of the metric under each causal symmetry results in a new rank-2 future tensor, and we prove that there is always a set of null directions canonical to the causal symmetry. As a result of this it makes sense to classify causal symmetries according to the number of independent canonical null directions. This classification is maintained at the infinitesimal level where we find the necessary and sufficient conditions for a vector field to be causal preserving. They involve the Lie derivatives of the metric tensor and of the canonical null directions. In addition, we prove the stability property of these equations under the repeated application of the Lie operator. Monotonicity properties, constants of motion and conserved currents can be defined or built using causal preserving vector fields. Some illustrative examples are presented.

  7. Magnetic antenna excitation of whistler modes. I. Basic properties

    NASA Astrophysics Data System (ADS)

    Urrutia, J. M.; Stenzel, R. L.

    2014-12-01

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  8. 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.

  9. Effect of adding sodium hexametaphosphate liquefier on basic properties of calcium phosphate cements.

    PubMed

    Hesaraki, S; Zamanian, A; Moztarzadeh, F

    2009-02-01

    Sodium hexametaphosphate (Na-HMP) is a common liquefying agent widely used in the ceramics industry for modifying the rheological behavior of ceramic slurries. The objective of this study was to investigate the influence of Na-HMP on several properties of calcium phosphate cements (CPCs). Various types of CPCs were prepared by mixing the same powder, namely, a mixture of tetracalcium phosphate and dicalcium phosphate anhydrate, with various liquids, namely, distilled water, Na(2)HPO(4) solutions, and Na-HMP solutions. The setting time, mechanical strength, rheological properties, and injectability of the cement pastes were examined in this work. Also, X-ray diffractometry (XRD) and scanning electron microscopy (SEM) techniques were employed for phase analysis and morphological evaluations, respectively. The results showed that, compared to CPCs made with water and Na(2)HPO(4) solutions, the CPC pastes made with Na-HMP solutions had improved stability and injectability but prolonged setting times. The XRD and SEM studies showed that Na-HMP inhibited the growth of apatite crystals during soaking of the cements in Ringer's solution. Thus, the CPC made with Na-HMP solution had lower compressive strength than those made with water or Na(2)HPO(4) solutions. Although Na-HMP could improve the injectability and stability of the CPC paste, it impaired other basic properties of the cement. Thus, it is not an appropriate liquefier additive.

  10. A homogeneous sample of binary galaxies: Basic observational properties

    NASA Technical Reports Server (NTRS)

    Karachentsev, I. D.

    1990-01-01

    A survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies. Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f(solar), with the mean value (7.8 plus or minus 0.7) f(solar). Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12 plus or minus 0.02 and characteristic merger timescale 0.2 H(exp -1) may significantly influence the rate of dynamical evolution of galaxies.

  11. Basic properties of solitary waves in granular crystals

    NASA Astrophysics Data System (ADS)

    Hasan, M. Arif; Nemat-Nasser, Sia

    We consider a chain of lightly contacting identical spherical elastic granules and provide explicit analytical expressions to fully characterize solitary waves (SWs) that may be generated in the chain by an impact or an applied shock force. These SWs consist of individual packages of linear momentum/energy transmitted across the granules through Hertzian contacts. They are nonlinear translational waves (involving no vibrations) that propagate through the granular chain without distortion, i.e., without any temporal evolution in shape or size. In particular, we focus on a fully-formed SW and provide analytical expressions for the associated peak value as well as the time variation of the granules' displacement, velocity, acceleration, and compressive contact force acting across any two contacting granules. In addition, by considering a SW as an "effective particle", we provide explicit analytical expressions for its linear momentum, total energy, equivalent (or effective) mass and effective velocity. All of the above mentioned results are shown to depend only on the peak value of the SW's contact force and the properties of the granules, i.e., their diameter, density, and elastic moduli. Then we provide a simple recipe to calculate the peak value of the SW's contact force in terms of a given shock force. Finally, we check by numerical simulations the accuracy of the analytical predictions.

  12. 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.

  13. 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.

  14. Basic properties of steel plant dust and technological properties of direct reduction

    NASA Astrophysics Data System (ADS)

    She, Xue-Feng; Wang, Jing-Song; Xue, Qing-Guo; Ding, Yin-Gui; Zhang, Sheng-Sheng; Dong, Jie-Ji; Zeng, Hui

    2011-06-01

    Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas (OG) sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 μm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces (BF) if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250°C for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the briquettes were kept at 1250°C for 6 min.

  15. What the Sun Has Taught Us About Basic Properties of Matter

    SciTech Connect

    Basu, Sarbani

    2012-03-07

    The Sun is an immensely large object formed out of many tons of gas. Yet the Sun can help us learn about some of the basic properties of matter. The structure of the Sun is governed not only by macrophysics such as hydrostatic equilibrium, convective and radiative heat transport, but also by microphysics such as nuclear reaction rates and the equation of state of the material that forms the Sun. Knowledge of the detailed structure of the Sun can therefore help us constrain the basic properties of matter. Helioseismology, the study of solar pulsations, has given us the means to get a detailed picture of the solar interior. In this talk I shall discuss how helioseismology has allowed us to determine details of solar structure, and in turn allowing us to study basic properties of matter.

  16. Microstructure in linear elasticity and scale effects: a reconsideration of basic rock mechanics and rock fracture mechanics

    NASA Astrophysics Data System (ADS)

    Exadaktylos, George E.; Vardoulakis, Ioannis

    2001-06-01

    An account on the role of higher order strain gradients in the mechanical behavior of elastic-perfectly brittle materials, such as rocks, is given that is based on a special grade-2 elasticity theory with surface energy as this was originated by Casal and Mindlin and further elaborated by the authors. The fundamental idea behind the theory is that the effect of the granular and polycrystalline nature of geomaterials (i.e. their microstructural features) on their macroscopic response may be modeled through the concept of volume cohesion forces, as well as surface forces rather than through intractable statistical mechanics concepts of the Boltzmann type. It is shown that the important phenomena of the localization of deformation in macroscopically homogeneous rocks under uniform tractions and of dependence of rock behavior on the specimen's dimensions, commonly known as size or scale effect, can be interpreted by using this 'non-local', higher order theory. These effects are demonstrated for the cases of the unidirectional tension test, and for the small circular hole under uniform internal pressure commonly known as the inflation test. The latter configuration can be taken as a first order approximation of the indentation test that is frequently used for the laboratory or in situ characterization of geomaterials. In addition, it is shown that the solution of the three basic crack deformation modes leads to cusping of the crack tips that is caused by the action of 'cohesive' double forces behind and very close to the tips, that tend to bring the two opposite crack lips in close contact, and further, it is demonstrated that the fracture toughness depends on the size of the crack, and thus it is not a fundamental property of the material. This latter outcome agrees with experimental results which indicate that materials with smaller cracks are more resistant to fracture than those with larger cracks.

  17. Teaching Basic Quantum Mechanics in Secondary School Using Concepts of Feynman Path Integrals Method

    ERIC Educational Resources Information Center

    Fanaro, Maria de los Angeles; Otero, Maria Rita; Arlego, Marcelo

    2012-01-01

    This paper discusses the teaching of basic quantum mechanics in high school. Rather than following the usual formalism, our approach is based on Feynman's path integral method. Our presentation makes use of simulation software and avoids sophisticated mathematical formalism. (Contains 3 figures.)

  18. MoH 101: Basic Concepts in the Mechanics of Hearing

    NASA Astrophysics Data System (ADS)

    Bergevin, Christopher; Epp, Bastian; Meenderink, Sebastiaan W. F.

    2011-11-01

    We provide a synopsis of selected questions and answers from the second triennial Mechanics of Hearing 101 session held at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The MoH 101 session offers a non-intimidating forum for students, postdocs, and others new to the field to explore issues and ideas relevant to the Workshop. We have augmented the discussion content by giving some basic background and references.

  19. 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.

  20. 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.

  1. 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.

  2. Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

    2016-03-01

    Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

  3. Mechanical Properties of Infrared Transmitting Materials

    DTIC Science & Technology

    1978-01-01

    72-0170, 1972. Touloukian , Y. S., Ed., "Thermophysical Properties of Matter" series. A Comprehensive Compilation of Data by the Thermophysical...Research Projects Agency, 675 North Randolph Street, Arlington, VA 22203-2114. DARPA ltr, 20 Mar 1980 RIA-78-0291 2 01010695 2 Iviecnanica Properties of...336 2. GOVT ACCESSION NO 3. RECIPIENT’S CATALOG NUMBER 4. TITLE (end Subtitle) Mechanical Properties of Infrared Transmitting Materials 5

  4. 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.

  5. 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.

  6. Osteoarthritis year in review 2014: mechanics--basic and clinical studies in osteoarthritis.

    PubMed

    Moyer, R F; Ratneswaran, A; Beier, F; Birmingham, T B

    2014-12-01

    The purpose of this review was to highlight recent research in mechanics and osteoarthritis (OA) by summarizing results from selected studies spanning basic and clinical research methods. Databases were searched from January 2013 through to March 2014. Working in pairs, reviewers selected 67 studies categorized into four themes--mechanobiology, ambulatory mechanics, biomechanical interventions and mechanical risk factors. Novel developments in mechanobiology included the identification of cell signaling pathways that mediated cellular responses to loading of articular cartilage. Studies in ambulatory mechanics included an increased focus on instrumented knee implants and progress in computational models, both emphasizing the importance of muscular contributions to load. Several proposed biomechanical interventions (e.g., shoe insoles and knee braces) produced variable changes in external knee joint moments during walking, while meta-analysis of randomized clinical trials did not support the use of lateral wedge insoles for decreasing pain. Results from high quality randomized trials suggested diet with or without exercise decreased indicators of knee joint load during walking, whereas similar effects from exercise alone were not detected with the measures used. Data from longitudinal cohorts suggested mechanical alignment was a risk factor for incidence and progression of OA, with the mechanism involving damage to the meniscus. In combination, the basic and clinical studies highlight the importance of considering multiple contributors to joint loading that can evoke both protective and damaging responses. Although challenges clearly exist, future studies should strive to integrate basic and clinical research methods to gain a greater understanding of the interactions among mechanical factors in OA and to develop improved preventive and therapeutic strategies.

  7. Physical properties of basic hydrogen peroxide solutions for use in singlet oxygen generators

    NASA Astrophysics Data System (ADS)

    Bakshin, Victor V.; Kalinovsky, V. V.; Konovalov, V. V.; Nikolaev, V. D.; Sobolev, R. E.; Shornikov, L. N.

    1998-12-01

    The physical properties of basic hydrogen peroxide solutions (BHP) such as viscosity, density, and freezing temperature as well as their variation during laser operation have been experimentally investigated. In these experiments (30 - 50%) commercial hydrogen peroxides have been used, containing stabilizers and an alkali of the following composition: 81.5% KOH and 5.5% K2CO3. The use of these substances for generation of singlet oxygen in the COIL has shown their good ability to operate. Consideration has been given to the possibilities of the basic hydrogen peroxide solutions recovery during the industrial COIL operation.

  8. 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

  9. 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.

  10. Air pollution and adverse cardiac remodeling: clinical effects and basic mechanisms

    PubMed Central

    Liu, Yonggang; Goodson, Jamie M.; Zhang, Bo; Chin, Michael T.

    2015-01-01

    Exposure to air pollution has long been known to trigger cardiovascular events, primarily through activation of local and systemic inflammatory pathways that affect the vasculature. Detrimental effects of air pollution exposure on heart failure and cardiac remodeling have also been described in human populations. Recent studies in both human subjects and animal models have provided insights into the basic physiological, cellular and molecular mechanisms that play a role in adverse cardiac remodeling. This review will give a brief overview of the relationship between air pollution and cardiovascular disease, describe the clinical effects of air pollution exposure on cardiac remodeling, describe the basic mechanisms that affect remodeling as described in human and animal systems and will discuss future areas of investigation. PMID:26042051

  11. Mechanical properties of artificial tracheas composed of a mesh cylinder and a spiral stent.

    PubMed

    Kawaguchi, S; Nakamura, T; Shimizu, Y; Masuda, T; Takigawa, T; Liu, Y; Ueda, H; Sekine, T; Matsumoto, K

    2001-12-01

    Much work has been done on the materials used for mesh-type artificial tracheas, but a precise mechanical evaluation of these structures has not yet been performed. In the present study, we determined the mechanical properties of typical mesh-type artificial tracheas and compared them with those of native trachea. Four types of artificial trachea were made and used for the mechanical tests. The basic frame of all the specimens was composed of a mesh cylinder and a spiral stent. The specimen whose mesh was sealed with collagen sponge showed almost the same behavior in the force-strain curve under compression, suggesting that collagen sealing has little effect on mechanical properties. Agreement between measured and estimated mechanical properties was good, especially in the low strain region, suggesting that artificial tracheas can be designed in terms of mechanical properties by mainly considering the basic frame structure.

  12. 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).

  13. 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.

  14. 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.

  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. The Acid Hydrolysis Mechanism of Acetals Catalyzed by a Supramolecular Assembly in Basic Solution

    SciTech Connect

    Pluth, Michael D.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-09-24

    A self-assembled supramolecular host catalyzes the hydrolysis of acetals in basic aqueous solution. The mechanism of hydrolysis is consistent with the Michaelis-Menten kinetic model. Further investigation of the rate limiting step of the reaction revealed a negative entropy of activation ({Delta}S{double_dagger} = -9 cal mol{sup -1}K{sup -1}) and an inverse solvent isotope effect (k(H{sub 2}O)/k(D{sub 2}O) = 0.62). These data suggest that the mechanism of hydrolysis that takes place inside the assembly proceeds through an A-2 mechanism, in contrast to the A-1 mechanism operating in the uncatalyzed reaction. Comparison of the rates of acetal hydrolysis in the assembly with the rate of the reaction of unencapsulated substrates reveals rate accelerations of up to 980 over the background reaction for the substrate diethoxymethane.

  17. 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

  18. 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

  19. 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.

  20. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced By Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Taminger, Karen M. B.; Begley, Matthew

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties have been demonstrated for electron beam deposited aluminum and titanium alloys that are comparable to wrought products, although the microstructures of the deposits exhibit features more typical of cast material. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. In the current study, mechanical properties and resulting microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Material performance was evaluated based on tensile properties and results were compared with properties of Al 2219 wrought products. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains, typically with interior dendritic structures, which were described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  1. Mechanical properties testing and results for thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Cruse, Thomas A.; Johnsen, B. P.; Nagy, Andrew

    1995-01-01

    The paper reports on several years of mechanical testing of thermal barrier coatings. The test results were generated to support the development of durability models for the coatings in heat engine applications. The test data that are reviewed include modulus, static strength, and fatigue strength data. The test methods and results are discussed, along with the significant difficulties inherent in mechanical testing of thermal barrier coating materials. The materials include 7 percent wt. and 8 percent wt. yttria, partially stabilized zirconia as well as a cermet material. Both low pressure plasma spray and electron-beam physical vapor deposited coatings were tested. The data indicate the basic trends in the mechanical properties of the coatings over a wide range of isothermal conditions. Some of the trends are correlated with material density.

  2. Simulated Hail Ice Mechanical Properties and Failure Mechanism at Quasi-Static Strain Rates

    NASA Astrophysics Data System (ADS)

    Swift, Jonathan M.

    Hail is a significant threat to aircraft both on the ground and in the air. Aeronautical engineers are interested in better understanding the properties of hail to improve the safety of new aircraft. However, the failure mechanism and mechanical properties of hail, as opposed to clear ice, are not well understood. A literature review identifies basic mechanical properties of ice and a failure mechanism based upon the state of stress within an ice sphere is proposed. To better understand the properties of Simulated Hail Ice (SHI), several tests were conducted using both clear and cotton fiber reinforced ice. Pictures were taken to show the internal crystal structure of SHI. SHI crush tests were conducted to identify the overall force-displacement trends at various quasi-static strain rates. High speed photography was also used to visually track the failure mechanism of spherical SHI. Compression tests were done to measure the compression strength of SHI and results were compared to literature data. Fracture toughness tests were conducted to identify the crack resistance of SHI. Results from testing clear ice samples were successfully compared to previously published literature data to instill confidence in the testing methods. The methods were subsequently used to test and characterize the cotton fiber reinforced ice.

  3. [Research on basic questions of intellectual property rights of acupuncture and moxibustion].

    PubMed

    Dong, Guo-Feng; Wu, Xiao-Dong; Han, Yan-Jing; Meng, Hong; Wang, Xin

    2011-12-01

    Along with the modernization and internationalization of acupuncture-moxibustion (acu-moxibustion), the issue of intellectual property rights has been becoming prominent and remarkable increasingly. In the present paper, the authors explain the basic issues of acu-moxibustion learning from the concept, scope, subject, object, contents and acquisition way of intellectual property rights. To make clear these questions will help us inherit and carry forward the existing civilization achievements of acu-moxibustion, and unceasingly bring forth new ideas and further improvement in clinical application, so as to serve the people's health in a better way.

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. Development of procedures for calculating stiffness and damping properties of elastomers in engineering applications. Part 1: Verification of basic methods

    NASA Technical Reports Server (NTRS)

    Chiang, T.; Tessarzik, J. M.; Badgley, R. H.

    1972-01-01

    The primary aim of this investigation was verification of basic methods which are to be used in cataloging elastomer dynamic properties (stiffness and damping) in terms of viscoelastic model constants. These constants may then be used to predict dynamic properties for general elastomer shapes and operating conditions, thereby permitting optimum application of elastomers as energy absorption and/or energy storage devices in the control of vibrations in a broad variety of applications. The efforts reported involved: (1) literature search; (2) the design, fabrication and use of a test rig for obtaining elastomer dynamic test data over a wide range of frequencies, amplitudes, and preloads; and (3) the reduction of the test data, by means of a selected three-element elastomer model and specialized curve fitting techniques, to material properties. Material constants thus obtained have been used to calculate stiffness and damping for comparison with measured test data. These comparisons are excellent for a number of test conditions and only fair to poor for others. The results confirm the validity of the basic approach of the overall program and the mechanics of the cataloging procedure, and at the same time suggest areas in which refinements should be made.

  10. Optical and mechanical properties of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Marcus, Matthew S.

    The experiments presented in this thesis provide insight into the optical and mechanical properties of carbon nanotubes. In the process of studying the properties of carbon nanotube structures we also discovered some interesting features of intermittent contact atomic force microscopy. Phase data from non-contact AFM reveals in-plane material properties . In the process of characterizing carbon nanotubes with an intermittent contact AFM (ICAFM), we discovered something quite interesting: ICAFM is sensitive to in-plane properties. We found that phase contrast in ICAFM reveals in-plane mechanical properties of the poly-di-acetylene films. Our measurements are possible because, during ICAFM, the cantilever tip oscillates not just perpendicular but also parallel to the sample surface along the long axis of the cantilever. Understanding photo-induced conductivity changes in carbon nanotubes . The basic process for using a nanotube as a photo-detector involves using light to change the conductivity of the nanotube, typically measured as a change in current. We review the different mechanisms for how light changes the conductivity of a nanotube, and then focus on a photo-gating mechanism. In a photo-gating mechanism, light interacts with the nanotube's environment changing the conductivity of the nanotube. Thermally driven oscillations play a significant role in chemical vapor deposition growth. The elevated temperatures during the CVD growth thermally drive nanotube oscillations with amplitudes on the order of 80nm. Nanotubes suspended a small distance above the substrate will often oscillate with an amplitude as large as the suspension height and interact with the substrate. The large binding energy between the nanotube and the substrate causes the nanotube to become stuck: the nanotube is no longer suspended. Using data from CVD growths on our suspended structures we are able to extract a Young's modulus value for our nanotubes which both validates the thermally driven

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. Basic properties of transformation remanent magnetization due to the Verwey transition of magnetite

    NASA Astrophysics Data System (ADS)

    Sato, M.; Mochizuki, N.; Tsunakawa, H.

    2010-12-01

    Recent explorations of Mars and Moon have observed many magnetic anomalies which probably recorded ancient magnetic fields. Many authors have pointed out a correlation between magnetic anomaly patterns and geological features, especially impact craters (e.g. Acuna et al., 1999; Mitchell et al., 2007). Although impact-origin magnetic signatures can give key information of the planetary dynamo evolution, details of shock remanent magnetization (SRM) acquisition mechanisms have not been revealed yet. One of the plausible mechanisms of SRM is transformation remanent magnetization (TrRM). Nagata et al. (1963) found that magnetite acquire remanence by heating through the Verwey transition in a magnetic field (inverse thermoremanent magnetization, ITRM). Ozima et al. (1963) measured field dependence of the intensity of ITRM which was produced by warming from 123 K to room temperature. Dunlop (2006, 2007) studied intensity and stability of TrRM as a function of grain size. However, there have been only a few systematic studies of TrRM concerning magnetic field record. Focusing on the Verwey transition, we have conducted TrRM experiments to examine basic magnetic properties of parallelism, proportionality and stability. In the experiment, natural rock samples containing multi-domain (MD) magnetite grains and crushed magnetite samples were used. They were cooled down from room temperature to a temperature lower than the Verwey transition temperature (Tv) and then warmed back to room temperature in a weak DC field or zero-filed. In the present study, three types of transformation remanences are defined: (1) transformation remanent magnetization (TrRM) which is acquired by cooling and warming in a constant DC field, (2) transformation warming remanent magnetization (TrWRM) which is acquired by cooling in zero field and warming in a DC field, and (3) transformation cooling remanent magnetization (TrCRM) which is acquired by cooling in a DC field and warming in zero field. We

  17. Design considerations in mechanical face seals for improved performance. 1: Basic configurations

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P.; Greiner, H. F.

    1977-01-01

    Basic assembly configurations of the mechanical face seal are described and some advantages associated with each are listed. The various forms of seal components are illustrated, and functions pointed out. The technique of seal pressure balancing and its application are described; and the concept of the PV factor, its different forms and limitations are discussed. Brief attention is given to seal lubrication since it is covered in detail in a companion paper. Finally, the operating conditions for various applications of low pressure seals (aircraft transmissions) are listed, and the seal failure mode of a particular application is discussed.

  18. 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.

  19. Thermodynamics and statistical mechanics. [thermodynamic properties of gases

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. ERBB receptors: from oncogene discovery to basic science to mechanism-based cancer therapeutics.

    PubMed

    Arteaga, Carlos L; Engelman, Jeffrey A

    2014-03-17

    ERBB receptors were linked to human cancer pathogenesis approximately three decades ago. Biomedical investigators have since developed substantial understanding of the biology underlying the dependence of cancers on aberrant ERBB receptor signaling. An array of cancer-associated genetic alterations in ERBB receptors has also been identified. These findings have led to the discovery and development of mechanism-based therapies targeting ERBB receptors that have improved outcome for many cancer patients. In this Perspective, we discuss current paradigms of targeting ERBB receptors with cancer therapeutics and our understanding of mechanisms of action and resistance to these drugs. As current strategies still have limitations, we also discuss challenges and opportunities that lie ahead as basic scientists and clinical investigators work toward more breakthroughs.

  8. Basic physical properties/structure of polystyrene-polyisobutylene-polystyrene triblock copolymers

    SciTech Connect

    Kaszas, G.

    1993-12-31

    Polystyrene-b-polyisobutylene-b-polystyrene (PSt-PIB-PSt) triblock copolymers, with various molecular architectures, have been synthesized to establish basic physical properties/structure correlations for this novel thermoplastics elastomer (TPE). The test results have confirmed that these triblock copolymers have a unique combination of physical properties which is currently unavailable on the TPE market. The fully saturated character of the PIB backbone provides excellent ozone resistance. Barrier, electrical, and low-temperature properties, were measured, and found to be equivalent to those of conventional butyl vulcanizates. The low initial modules of PIB, and the fact that the PSt content can be kept low without significant loss in tensile properties, renders the material soft. The high incompatibility of PIB and PSt allows the overall chain length and, therefore, the melt viscosity, to be kept low. This could bring an important advantage, in processing, over other TPE`s. The combination of the above properties, and the inherent properties of PIB, makes this material in excellent candidate for wire and cable coating, seal and gasket, adhesive and vibration damping applications.

  9. 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

  10. 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.

  11. 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.

  12. Basic properties of somatosensory-evoked responses in the dorsal hippocampus of the rat

    PubMed Central

    Bellistri, Elisa; Aguilar, Juan; Brotons-Mas, Jorge R; Foffani, Guglielmo; de la Prida, Liset Menendez

    2013-01-01

    The hippocampus is a pivotal structure for episodic memory function. This ability relies on the possibility of integrating different features of sensory stimuli with the spatio-temporal context in which they occur. While recent studies now suggest that somatosensory information is already processed by the hippocampus, the basic mechanisms still remain unexplored. Here, we used electrical stimulation of the paws, the whisker pad or the medial lemniscus to probe the somatosensory pathway to the hippocampus in the anaesthetized rat, and multisite electrodes, in combination with tetrode and intracellular recordings, to look at the properties of somatosensory hippocampal responses. We found that peripheral and lemniscal stimulation elicited small local field potential responses in the dorsal hippocampus about 35–40 ms post-stimulus. Current source density analysis established the local nature of these responses, revealing associated synaptic sinks that were consistently confined to the molecular layer (ML) of the dentate gyrus (DG), with less regular activation of the CA1 stratum lacunosum moleculare (SLM). A delayed (40–45 ms), potentially active, current source that outlasted the SLM sink was present in about 50% cases around the CA1 pyramidal cell layer. Somatosensory stimulation resulted in multi-unit firing increases in the majority of DG responses (79%), whereas multi-unit firing suppression was observed in the majority of CA1 responses (62%). Tetrode and intracellular recordings of individual cells confirmed different firing modulation in the DG and the CA1 region, and verified the active nature of both the early ML sink and delayed somatic CA1 source. Hippocampal responses to somatosensory stimuli were dependent on fluctuations in the strength and composition of synaptic inputs due to changes of the ongoing local (hippocampal) and distant (cortical) state. We conclude that somatosensory signals reach the hippocampus mainly from layer II entorhinal cortex to

  13. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced by Electron Beam Freeform Fabrication

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Tainger, Karen M.

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties demonstrated for electron beam deposited aluminum and titanium alloys are comparable to wrought products, although the microstructures of the deposits exhibit cast features. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. Tensile mechanical properties and microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains with interior dendritic structures, described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  14. Basic failure mechanisms in advanced composites. [composed of epoxy resins reinforced with carbon fibers

    NASA Technical Reports Server (NTRS)

    Mazzio, V. F.; Mehan, R. L.; Mullin, J. V.

    1973-01-01

    The fundamental failure mechanisms which result from the interaction of thermal cycling and mechanical loading of carbon-epoxy composites were studied. This work was confined to epoxy resin uniderictionally reinforced with HTS carbon fibers, and consists of first identifying local fiber, matrix and interface failure mechanisms using the model composite specimen containing a small number of fibers so that optical techniques can be used for characterization. After the local fracture process has been established for both mechanical loading and thermal cycling, engineering composite properties and gross fracture modes are then examined to determine how the local events contribute to real composite performance. Flexural strength in high fiber content specimens shows an increase in strength with increased thermal cycling. Similar behavior is noted for 25 v/o material up to 200 cycles; however, there is a drastic reduction after 200 cycles indicating a major loss of integrity probably through the accumulation of local cleavage cracks in the tensile region.

  15. LORETA Neurofeedback in the Precuneus: Operant Conditioning in Basic Mechanisms of Self-Regulation.

    PubMed

    Cannon, Rex L; Baldwin, Debora R; Diloreto, Dominic J; Phillips, Sherman T; Shaw, Tiffany L; Levy, Jacob J

    2014-10-01

    Low-resolution brain electomagnetic tomography (LORETA) neurofeedback provides a mechanism to influence the electrical activity of the brain in intracranial space. The aim of this study was to determine the effects of LORETA neurofeedback (LNFB) in the precuneus as a mechanism for improving self-regulation in controls and a heterogeneous diagnostic group (DX). Thirteen participants completed between 10 and 20 sessions of LNFB training in a 3-voxel cluster in the left precuneus. The participants included 5 nonclinical university students, and 8 adults with heterogeneous psychiatric diagnoses. We assessed the effects of LNFB with neurophysiological measures as well as pre- and post-Personality Assessment Inventory (PAI) subscales and selected subtests from the Delis-Kaplan Executive Function System (DKEFS). There was a significant total relative power increase at the precuneus for baseline contrasts for the control group. The DX group did not reach significant levels. All participants showed improvements in executive functions and tended to report significantly less psychopathology. The basic neural mechanisms of self-regulation are poorly understood. The data obtained in this study demonstrate that LNFB in a heterogeneous population enhances executive functions while concordantly decreasing endorsement of psychological symptoms. The alpha frequency in the brain may represent integrative functioning relative to operant efficiency and self-regulatory mechanisms.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Vitamin D3 for the Treatment of Epilepsy: Basic Mechanisms, Animal Models, and Clinical Trials

    PubMed Central

    Pendo, Kevin; DeGiorgio, Christopher M.

    2016-01-01

    There is increasing evidence supporting dietary and alternative therapies for epilepsy, including the ketogenic diet, modified Atkins diet, and omega-3 fatty acids. Vitamin D3 is actively under investigation as a potential intervention for epilepsy. Vitamin D3 is fat-soluble steroid, which shows promise in animal models of epilepsy. Basic research has shed light on the possible mechanisms by which Vitamin D3 may reduce seizures, and animal data support the efficacy of Vitamin D3 in rat and mouse models of epilepsy. Very little clinical data exist to support the treatment of human epilepsy with Vitamin D3, but positive findings from preliminary clinical trials warrant larger Phase I and II clinical trials in order to more rigorously determine the potential therapeutic value of Vitamin D3 as a treatment for human epilepsy. PMID:28008324

  1. Linking properties to microstructure through multiresolution mechanics

    NASA Astrophysics Data System (ADS)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. The value of basic research insights into atrial fibrillation mechanisms as a guide to therapeutic innovation: a critical analysis.

    PubMed

    Heijman, Jordi; Algalarrondo, Vincent; Voigt, Niels; Melka, Jonathan; Wehrens, Xander H T; Dobrev, Dobromir; Nattel, Stanley

    2016-04-01

    Atrial fibrillation (AF) is an extremely common clinical problem associated with increased morbidity and mortality. Current antiarrhythmic options include pharmacological, ablation, and surgical therapies, and have significantly improved clinical outcomes. However, their efficacy remains suboptimal, and their use is limited by a variety of potentially serious adverse effects. There is a clear need for improved therapeutic options. Several decades of research have substantially expanded our understanding of the basic mechanisms of AF. Ectopic firing and re-entrant activity have been identified as the predominant mechanisms for arrhythmia initiation and maintenance. However, it has become clear that the clinical factors predisposing to AF and the cellular and molecular mechanisms involved are extremely complex. Moreover, all AF-promoting and maintaining mechanisms are dynamically regulated and subject to remodelling caused by both AF and cardiovascular disease. Accordingly, the initial presentation and clinical progression of AF patients are enormously heterogeneous. An understanding of arrhythmia mechanisms is widely assumed to be the basis of therapeutic innovation, but while this assumption seems self-evident, we are not aware of any papers that have critically examined the practical contributions of basic research into AF mechanisms to arrhythmia management. Here, we review recent insights into the basic mechanisms of AF, critically analyse the role of basic research insights in the development of presently used anti-AF therapeutic options and assess the potential value of contemporary experimental discoveries for future therapeutic innovation. Finally, we highlight some of the important challenges to the translation of basic science findings to clinical application.

  7. 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.

  8. 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

  9. Fundamental Entangling Operators in Quantum Mechanics and Their Properties

    NASA Astrophysics Data System (ADS)

    Dao-Ming, Lu

    2016-07-01

    For the first time, we introduce so-called fundamental entangling operators e^{iQ1 P2} and e^{iP1 Q2 } for composing bipartite entangled states of continuum variables, where Q i and P i ( i = 1, 2) are coordinate and momentum operator, respectively. We then analyze how these entangling operators naturally appear in the quantum image of classical quadratic coordinate transformation ( q 1, q 2) → ( A q 1 + B q 2, C q 1 + D q 2), where A D- B C = 1, which means even the basic coordinate transformation ( Q 1, Q 2) → ( A Q 1 + B Q 2, C Q 1 + D Q 2) involves entangling mechanism. We also analyse their Lie algebraic properties and use the integration technique within an ordered product of operators to show they are also one- and two- mode combinatorial squeezing operators.

  10. Studies of Basic Electronic Properties of CdTe-Based Solar Cells and Their Evolution During Processing and Stress: Final Technical Report, 16 October 2001 - 31 August 2005

    SciTech Connect

    Kaydanov, V. I.; Ohno, T. R.

    2007-02-01

    This report describes basic issues behind CdTe/CdS cell performance and stability, such as the nature and electronic properties of impurities and defects that control the majority carrier concentration, mechanisms of dopant compensation, recombination processes, their nature and properties, migration and transformation of defects under various processing, stress, and operating conditions. We believe that a better basic understanding of the specific influence of grain boundaries, especially for fine-grain materials such as those making up CdTe-based cells, is now one of the most important issues we must address. We need to clarify the role of grain boundaries in forming the film electronic properties, as well as those of the p-n junction.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  12. 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.

  13. 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

  14. Functional coupling as a basic mechanism of feedback regulation of cardiac energy metabolism.

    PubMed

    Saks, V A; Kuznetsov, A V; Vendelin, M; Guerrero, K; Kay, L; Seppet, E K

    2004-01-01

    In this review we analyze the concepts and the experimental data on the mechanisms of the regulation of energy metabolism in muscle cells. Muscular energetics is based on the force-length relationship, which in the whole heart is expressed as a Frank-Starling law, by which the alterations of left ventricle diastolic volume change linearly both the cardiac work and oxygen consumption. The second basic characteristics of the heart is the metabolic stability--almost constant levels of high energy phosphates, ATP and phosphocreatine, which are practically independent of the workload and the rate of oxygen consumption, in contrast to the fast-twitch skeletal muscle with no metabolic stability and rapid fatigue. Analysis of the literature shows that an increase in the rate of oxygen consumption by order of magnitude, due to Frank-Starling law, is observed without any significant changes in the intracellular calcium transients. Therefore, parallel activation of contraction and mitochondrial respiration by calcium ions may play only a minor role in regulation of respiration in the cells. The effective regulation of the respiration under the effect of Frank-Starling law and metabolic stability of the heart are explained by the mechanisms of functional coupling within supramolecular complexes in mitochondria, and at the subcellular level within the intracellular energetic units. Such a complex structural and functional organisation of heart energy metabolism can be described quantitatively by mathematical models.

  15. Role of the synthesis route on the properties of hybrid LDH-graphene as basic catalysts

    NASA Astrophysics Data System (ADS)

    Álvarez, Mayra G.; Tichit, Didier; Medina, Francesc; Llorca, Jordi

    2017-02-01

    Layered double hydroxides (LDH or HT) or their derived mixed oxides present marked acid-base properties useful in catalysis, but they lead to agglomerate inducing a weak accessibility to the active sites. In this study we report the preparation and characterization of HT/Graphene (HT/rGO) nanocomposites as active and selective basic catalysts for the acetone condensation reaction. The graphene high specific surface area and structural compatibility with the HT allowed increasing the number and accessibility of the active sites and activity of this later. Two series of HT/rGO nanocomposites with 0.5 ≤ HT/rGO ≤ 10 mass ratio were prepared by: i) direct HT coprecipitation in the presence of GO; ii) self-assembly of preformed HT with GO. The prepared HT/rGO nanocomposites were dried either in air at 80 °C or freeze-dried. A series of characterizations showed the great influence of the preparation method and HT/rGO mass ratio on both the nanocomposite structure and catalytic activity. An optimum activity was observed for a HT/rGO = 10 catalyst. Particularly, the highest catalytic activity was found in those nanocomposites obtained by coprecipitation and freeze dried (3 times more active than bulk HT) which can be connected to their structure with a better accessibility to the basic sites.

  16. Finite-element analysis of the effect of basic hip movements on the mechanical stimulus within a proximal femur.

    PubMed

    Tovar-López, Francisco Javier; Domínguez-Hernández, Víctor Manuel; Diez-García, María Del Pilar; Araujo-Monsalvo, Víctor Manuel

    2014-07-01

    Osteoporosis is a serious and multifactorial disease. The number of people affected with osteoporosis is increasing due to the lengthening of life expectancy. Currently, unlike the genetic, nutritional and hormonal factors that have been the focus of most studies of osteoporosis, mechanical stimuli that potentially can produce an increase in bone strength have not been well studied. Studies suggest that the relationship between the health of the bone and mechanical stimuli occurs through bone adaptive remodeling, which is activated by means of the shear stress transmitted by the interstitial fluid flow. The present work consists of a finite element analysis of a femur to simulate the basic movements of the hip (flexion, extension, abduction, and adduction) to compare the shear stresses in a common zone of fracture and in the critical mechanical strength zones of the femoral head. A comparison of the distribution and magnitude of the shear stresses was performed to estimate the movement that could induce a more rapid adaptive bone remodeling. This study is the first step in the development of a physical therapy for a preventive rehabilitation that helps to prevent patients with low bone mineral density to avoid suffering osteoporosis hip fractures. The finite element model was constructed using a free-access three-dimensional standardized femur obtained from the Instituti Ortopedici Rizzoli, Bologna, Italy. The mechanical properties and the muscular forces were obtained from a specialized bibliography. We conclude that the movements that exhibit a higher mean value and a good shear stress distribution in the femoral neck are hip extension and abduction.

  17. Absolute Configuration Determination by Quantum Mechanical Calculation of Chiroptical Spectra: Basics and Applications to Fungal Metabolites.

    PubMed

    Superchi, Stefano; Scafato, Patrizia; Górecki, Marcin; Pescitelli, Gennaro

    2017-03-10

    The application of quantum mechanical simulation of chiroptical properties, i.e. electronic circular dichroism (ECD), optical rotation (OR), and vibrational circular dichroism (VCD), to the assignment of the absolute configuration of chiral naturally occurring metabolites of fungal origin, is reviewed. The fundamentals of such chiroptical spectroscopies as well as the specific experimental and computational issues allied to the application of their ab initio calculation is reported. Some examples, related to the use of the ECD, VCD, and OR techniques and highlighting the practical application of the methods, are also described.

  18. Cannabinoid-Induced Hyperemesis: A Conundrum—From Clinical Recognition to Basic Science Mechanisms

    PubMed Central

    Darmani, Nissar A.

    2010-01-01

    Cannabinoids are used clinically on a subacute basis as prophylactic agonist antiemetics for the prevention of nausea and vomiting caused by chemotherapeutics. Cannabinoids prevent vomiting by inhibition of release of emetic neurotransmitters via stimulation of presynaptic cannabinoid CB1 receptors. Cannabis-induced hyperemesis is a recently recognized syndrome associated with chronic cannabis use. It is characterized by repeated cyclical vomiting and learned compulsive hot water bathing behavior. Although considered rare, recent international publications of numerous case reports suggest the contrary. The syndrome appears to be a paradox and the pathophysiological mechanism(s) underlying the induced vomiting remains unknown. Although some traditional hypotheses have already been proposed, the present review critically explores the basic science of these explanations in the clinical setting and provides more current mechanisms for the induced hyperemesis. These encompass: (1) pharmacokinetic factors such as long half-life, chronic exposure, lipid solubility, individual variation in metabolism/excretion leading to accumulation of emetogenic cannabinoid metabolites, and/or cannabinoid withdrawal; and (2) pharmacodynamic factors including switching of the efficacy of Δ9-THC from partial agonist to antagonist, differential interaction of Δ9-THC with Gs and Gi signal transduction proteins, CB1 receptor desensitization or downregulation, alterations in tissue concentrations of endocannabinoid agonists/inverse agonists, Δ9-THC-induced mobilization of emetogenic metabolites of the arachidonic acid cascade, brainstem versus enteric actions of Δ9-THC, and/or hypothermic versus hyperthermic actions of Δ9-THC. In addition, human and animal findings suggest that chronic exposure to cannabis may not be a prerequisite for the induction of vomiting but is required for the intensity of emesis. PMID:27713347

  19. Basic Phenomenological Theory of the Optical Properties of Thin Films (Osnovy Fenomenologicheskoi Teorii Opticheskikh Svoistv Tonkikh Pokrytii),

    DTIC Science & Technology

    The optical properties of thin films used in interferometry are examined from the viewpoint of phenomenological theory to assist in revealing the...nature of the basic optical properties of thin films and in preparing the groundwork for determination of the causes of the numberous anomalies inherent

  20. 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.

  1. 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.

  2. Synthetic melanin films: Assembling mechanisms, scaling behavior, and structural properties

    NASA Astrophysics Data System (ADS)

    Lorite, Gabriela S.; Coluci, Vitor R.; da Silva, Maria Ivonete N.; Dezidério, Shirlei N.; Graeff, Carlos Frederico O.; Galva~O, Douglas S.; Cotta, Mônica A.

    2006-06-01

    In this work we report on the surface characterization of melanin thin films prepared using both water-based and organic solvent-based melanin syntheses. Atomic force microscopy (AFM) analysis of these films suggests that the organic solvent synthesis provides relatively planar basic melanin structures; these basic structures generate surface steps with height in the range of 2-3 nm and small tendency to form larger aggregates. The scaling properties obtained from the AFM data were used to infer the assembling mechanisms of these thin films which depend on the solvent used for melanin synthesis. The behavior observed in organic solvent-based melanin suggests a diffusion-limited aggregation process. Thus films with good adhesion to the substrate and smoother morphologies than water-prepared melanin films are obtained. Electronic structure calculations using a conductorlike screening model were also performed in order to elucidate the microscopic processes of thin film formation. Our results suggest that the agglomerates observed in hydrated samples originate from reaction with water at specific locations on the surface most likely defects on the planar structure.

  3. 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%.

  4. 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.

  5. 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.

  6. 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.

  7. Triadic closure as a basic generating mechanism of communities in complex networks

    NASA Astrophysics Data System (ADS)

    Bianconi, Ginestra; Darst, Richard K.; Iacovacci, Jacopo; Fortunato, Santo

    2014-10-01

    Most of the complex social, technological, and biological networks have a significant community structure. Therefore the community structure of complex networks has to be considered as a universal property, together with the much explored small-world and scale-free properties of these networks. Despite the large interest in characterizing the community structures of real networks, not enough attention has been devoted to the detection of universal mechanisms able to spontaneously generate networks with communities. Triadic closure is a natural mechanism to make new connections, especially in social networks. Here we show that models of network growth based on simple triadic closure naturally lead to the emergence of community structure, together with fat-tailed distributions of node degree and high clustering coefficients. Communities emerge from the initial stochastic heterogeneity in the concentration of links, followed by a cycle of growth and fragmentation. Communities are the more pronounced, the sparser the graph, and disappear for high values of link density and randomness in the attachment procedure. By introducing a fitness-based link attractivity for the nodes, we find a phase transition where communities disappear for high heterogeneity of the fitness distribution, but a different mesoscopic organization of the nodes emerges, with groups of nodes being shared between just a few superhubs, which attract most of the links of the system.

  8. 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.

  9. 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

  10. Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

    NASA Astrophysics Data System (ADS)

    Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

    2013-09-01

    We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the <100>, <110>, <111> in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

  11. 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

  12. Ketosis and diabetic ketoacidosis in response to SGLT2 inhibitors: Basic mechanisms and therapeutic perspectives.

    PubMed

    Qiu, Hongyu; Novikov, Aleksandra; Vallon, Volker

    2017-01-18

    Inhibitors of the sodium-glucose cotransporter SGLT2 are a new class of antihyperglycemic drugs that have been approved for the treatment of type 2 diabetes mellitus (T2DM). These drugs inhibit glucose reabsorption in the proximal tubules of the kidney thereby enhancing glucosuria and lowering blood glucose levels. Additional consequences and benefits include a reduction in body weight, uric acid levels, and blood pressure. Moreover, SGLT2 inhibition can have protective effects on the kidney and cardiovascular system in patients with T2DM and high cardiovascular risk. However, a potential side effect that has been reported with SGLT2 inhibitors in patients with T2DM and particularly during off-label use in patients with type 1 diabetes is diabetic ketoacidosis. The US Food and Drug Administration recently warned that SGLT2 inhibitors may result in euglycemic ketoacidosis. Here, we review the basic metabolism of ketone bodies, the triggers of diabetic ketoacidosis, and potential mechanisms by which SGLT2 inhibitors may facilitate the development of ketosis or ketoacidosis. This provides the rationale for measures to lower the risk. We discuss the role of the kidney and potential links to renal gluconeogenesis and uric acid handling. Moreover, we outline potential beneficial effects of modestly elevated ketone body levels on organ function that may have therapeutic relevance for the observed beneficial effects of SGLT2 inhibitors on the kidney and cardiovascular system.

  13. Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag.

    PubMed

    Han, Chong; Jiao, Yanan; Wu, Qianqian; Yang, Wangjin; Yang, He; Xue, Xiangxin

    2016-08-01

    Basic oxygen furnace slag (BOFS) has the potential to remove hexavalent chromium (Cr(VI)) from wastewater by a redox process due to the presence of minerals containing Fe(2+). The effects of the solution pH, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system and X-ray diffractometer (XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe(2+) released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe(2+) responsible for Cr(VI) removal was primarily derived from the dissolution of FeO and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum (CaSO4·2H2O) could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe(2+) and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps.

  14. Study of the mechanism of spatter produced by basic welding electrodes

    SciTech Connect

    Chen, J.H.; Sun, Z.C.; Fan, D.

    1996-10-01

    In this work a device was made to control the current at three stages of short circuiting welding: at the beginning of short circuiting, during the overall period of short circuiting, including the breaking stage, and at the arc reinitiating stage. By investigating the effects of these currents on the spatter produced by basic welding electrodes, the decisive parameter which determined spatter quantities was identified as the current at the short circuit breaking stage. On the basis of the experimental results from the combined effect of short circuiting current and the oxygen potential in the covering, it was found that the major process causing spatter was the explosion of CO gas bubbles, which resulted in the breakage of the short circuiting bridge. The high density of current intensified this explosion and increased the spatter quantity. The spatter mechanism caused by the explosion of gases was identified by studying the metal transfer using laser back-light, high-speed photography and x-ray, high-speed photography to record two images simultaneously, along with arc sound and arc voltage oscillographs.

  15. Networked buffering: a basic mechanism for distributed robustness in complex adaptive systems.

    PubMed

    Whitacre, James M; Bender, Axel

    2010-06-15

    A generic mechanism--networked buffering--is proposed for the generation of robust traits in complex systems. It requires two basic conditions to be satisfied: 1) agents are versatile enough to perform more than one single functional role within a system and 2) agents are degenerate, i.e. there exists partial overlap in the functional capabilities of agents. Given these prerequisites, degenerate systems can readily produce a distributed systemic response to local perturbations. Reciprocally, excess resources related to a single function can indirectly support multiple unrelated functions within a degenerate system. In models of genome:proteome mappings for which localized decision-making and modularity of genetic functions are assumed, we verify that such distributed compensatory effects cause enhanced robustness of system traits. The conditions needed for networked buffering to occur are neither demanding nor rare, supporting the conjecture that degeneracy may fundamentally underpin distributed robustness within several biotic and abiotic systems. For instance, networked buffering offers new insights into systems engineering and planning activities that occur under high uncertainty. It may also help explain recent developments in understanding the origins of resilience within complex ecosystems.

  16. Basic properties of calcium phosphate cement containing atelocollagen in its liquid or powder phases.

    PubMed

    Miyamoto, Y; Ishikawa, K; Takechi, M; Toh, T; Yuasa, T; Nagayama, M; Suzuki, K

    1998-01-01

    The basic properties of calcium phosphate cement (CPC) containing atelocollagen, the main component of the organic substrate in bone, were studied in an initial evaluation for the fabrication of modified CPC. The setting time of conventional CPC (c-CPC) was prolonged to over 100 min when c-CPC contained 1% or more atelocollagen. The diametral tensile strength (DTS) of c-CPC decreased linearly with the collagen content, descending to below the detection limit when the c-CPC contained 3% or more atelocollagen. Therefore, use of c-CPC as the base cement seems inappropriate for the fabrication of atelocollagen-containing CPC. In contrast, the cement set at 9-34 min when fast-setting CPC (FSCPC) was used as the base cement and contained 1-5% atelocollagen, respectively. Although addition of atelocollagen resulted in the decrease of DTS of the set mass, the DTS was approximately the same, 6-8 MPa, at contents of atelocollagen between 1% and 5%. When atelocollagen was added to FSCPC, the handling property was improved significantly. The paste also became more adhesive with increase in atelocollagen content. These properties are desirable for its use in surgical procedures since, for example, bony defects can be filled easily and without a space interposed between the bone and cement paste. Although there are some disadvantages for the addition of atelocollagen to CPC, it can be accepted as long as FSCPC was used as the base cement. We conclude that further evaluations of the effects of atelocollagen, such as biocompatibility, bone synthesis, and bone replacement behaviour should be done, using FSCPC as the base cement.

  17. Basic mechanisms of radiation effects in the natural space radiation environment

    SciTech Connect

    Schwank, J.R.

    1994-06-01

    Four general topics are covered in respect to the natural space radiation environment: (1) particles trapped by the earth`s magnetic field, (2) cosmic rays, (3) radiation environment inside a spacecraft, (4) laboratory radiation sources. The interaction of radiation with materials is described by ionization effects and displacement effects. Total-dose effects on MOS devices is discussed with respect to: measurement techniques, electron-hole yield, hole transport, oxide traps, interface traps, border traps, device properties, case studies and special concerns for commercial devices. Other device types considered for total-dose effects are SOI devices and nitrided oxide devices. Lastly, single event phenomena are discussed with respect to charge collection mechanisms and hard errors. (GHH)

  18. 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.

  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. 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.

  1. 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.

  2. 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

  3. Cytophilic and cytotoxic properties of human eosinophil peroxidase plus major basic protein.

    PubMed Central

    Samoszuk, M. K.; Petersen, A.; Gidanian, F.; Rietveld, C.

    1988-01-01

    The cytophilic and cytotoxic properties of an acetate-buffered solution of human eosinophil peroxidase (EPO) plus major basic protein (MBP) were studied to determine the cytotoxic potential of localized eosinophil degranulation in human tissues. When incubated with EPO + MBP for 5 minutes, viable cells of six unrelated types (Sp 2/0; HeLa; human gastric adenocarcinoma; acute lymphocytic leukemia; IM-9; benign lymphoid hyperplasia) developed varying degrees of cytochemically detectable deposits of EPO on the cell membranes. A single-step propidium iodide exclusion assay was then used to show that EPO + MBP in the absence of hydrogen peroxide is substantially cytotoxic only to the acute lymphocytic leukemia and IM-9 cells. In the presence of 0.003% hydrogen peroxide, EPO + MBP was cytotoxic to five types of cells. It is concluded that human EPO in the presence of MBP has an affinity for the membrane of diverse cell types. The toxicity of EPO + MBP is markedly enhanced by the presence of hydrogen peroxide. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 PMID:3414778

  4. Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

    SciTech Connect

    Xu, Wen-Sheng; Freed, Karl F.

    2015-07-14

    The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.

  5. Basic physical properties of the close binary V497 Cep in the open cluster NGC 7160

    NASA Astrophysics Data System (ADS)

    Yakut, K.; Tarasov, A. E.; İbanoğlu, C.; Harmanec, P.; Kalomeni, B.; Holmgren, D. E.; Božić, H.; Eenens, P.

    2003-07-01

    New light and radial-velocity curves of V497 Cep , a binary in the open cluster NGC 7160, were obtained and the linear ephemeris of the system was refined to HJD (Min I) = (2 446 299.1596 +/- 0.0064) + (1.2028287d +/- 0.0000015d ) x E. The first light and radial-velocity curve solutions allowed us to derive the basic physical properties of this astrophysically important binary. It was found that the observed light variation of V497 Cep consists of a strong ellipticity effect and a small contribution from grazing eclipses. A comparison of masses and radii of V497 Cep with theoretical evolutionary tracks indicates that both binary components are very close to the zero-age main sequence. A comparison of disentangled line profiles of the He I 6678 line with synthetic, rotationally broadened line profiles indicates that the rotation of both stars is synchronized with the orbital revolution as expected. This finding increases the credibility of our solutions. We find E(B-V)=0fm39 . The distance to the cluster NGC 7160 was found to be about 760 (+/- 100) pc which agrees well with other available estimates. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/1087

  6. Aging properties of films of plasticized vital wheat gluten cast from acidic and basic solutions.

    PubMed

    Olabarrieta, Idoia; Cho, Sung-Woo; Gällstedt, Mikael; Sarasua, Jose-Ramon; Johansson, Eva; Hedenqvist, Mikael S

    2006-05-01

    In order to understand the mechanisms behind the undesired aging of films based on vital wheat gluten plasticized with glycerol, films cast from water/ethanol solutions were investigated. The effect of pH was studied by casting from solutions at pH 4 and pH 11. The films were aged for 120 days at 50% relative humidity and 23 degrees C, and the tensile properties and oxygen and water vapor permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion and reverse-phase high-performance liquid chromatography, and the film structure was revealed by optical and scanning electron microscopy. The pH 11 film was mechanically more stable with time than the pH 4 film, the latter being initially very ductile but turning brittle toward the end of the aging period. The protein solubility and infrared spectroscopy measurements indicated that the protein structure of the pH 4 film was initially significantly less polymerized/aggregated than that of the pH 11 film. The polymerization of the pH 4 film increased during storage but it did not reach the degree of aggregation of the pH 11 film. Reverse-phase chromatography indicated that the pH 11 films were to some extent deamidated and that this increased with aging. At the same time a large fraction of the aged pH 11 film was unaffected by reducing agents, suggesting that a time-induced isopeptide cross-linking had occurred. This isopeptide formation did not, however, change the overall degree of aggregation and consequently the mechanical properties of the film. During aging, the pH 4 films lost more mass than the pH 11 films mainly due to migration of glycerol but also due to some loss of volatile mass. Scanning electron and optical microscopy showed that the pH 11 film was more uniform in thickness and that the film structure was more homogeneous than that of the pH 4 film. The oxygen permeability was also lower for the pH 11 film. The

  7. 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

  8. On the Acquisition of Some Basic Word Spelling Mechanisms in a Deep (French) and a Shallow (Spanish) System

    ERIC Educational Resources Information Center

    Carrillo, Maria Soledad; Alegria, Jesus; Marin, Javier

    2013-01-01

    An experiment was carried out to compare the time course of the acquisition of two basic spelling mechanisms in Spanish, a shallow system, and French, a deep system. The first was lexical. It relies on the orthographic lexicon, a hypothetical structure containing the orthographic representations of words accessible for word spelling. To evaluate…

  9. 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

  10. 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.

  11. Mechanical Properties of High Purity Niobium - Novel Measurements

    SciTech Connect

    Ganapati Myneni

    2003-09-01

    One of the procedures to improve the performance of superconducting niobium cavities is a heat treatment for several hours in an ultrahigh vacuum at temperatures between 800C and 1400C for hydrogen degassing or post-purification, respectively. However, it was recently observed with Spallation Neutron Source Project (SNS) prototype cavities, that a heat treatment at 800 C for even 1 hour degraded the mechanical properties of RRR niobium, in particular the yield strength. This lower strength resulted in cavity deformations during handling thus affecting both their resonant frequency and field profile. In addition to lowering the yield strength, it was observed in some lots of material that the Young's modulus was also apparently reduced by a factor of 2 as a result of the hydrogen outgassing at 800 C. Surprisingly, material received at other national laboratories exhibited similar anomalous behavior even without any heat treatments in vacuum. Based on these observations a multi-institutional collaborative basic research activity on high RRR niobium (determination of Nb yield strength as a function of grain size, work hardening, chemical composition, and heat treatment temperature) has been initiated by JLAB to gain a better understanding of the material properties affecting the mechanical behavior In this contribution, a brief review of the measurements at JLAB, at the Materials Science and Engineering Department of the University of Virginia, at the Analytical Chemistry and Metallurgy Divisions of the National Institute of Standard and Technology, Gaithersburg and in the Department of Physics, SUNY, Albany are presented. The measurements include yield strength, hardness, ultrasonic velocity, crystallographic structure, microstructure, determination of interstitial contents using internal friction; particular emphasis is placed on determining the hydrogen concentration in the niobium via Cold Neutron Prompt Gamma-Ray Activation Analysis and Neutron Incoherent

  12. 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

  13. Polymer Basics: Classroom Activities Manipulating Paper Clips to Introduce the Structures and Properties of Polymers

    ERIC Educational Resources Information Center

    Umar, Yunusa

    2014-01-01

    A simple and effective hands-on classroom activity designed to illustrate basic polymer concepts is presented. In this activity, students build primary structures of homopolymers and different arrangements of monomers in copolymer using paper clips as monomers. The activity supports formation of a basic understanding of polymer structures,…

  14. Basic properties of sintering dust from iron and steel plant and potassium recovery.

    PubMed

    Zhan, Guang; Guo, Zhancheng

    2013-06-01

    With the production of crude steel, China produces several million tons of sintering dusts which contain a great deal of valuable metals such as, K, Na, Zn, Pb. If discharged directly without adequate treatment, these elements can lead to adverse effects on the environment. Therefore, it is very necessary to determine how to separate these elements from the dust before discharge. Several physical and chemical detection methods were used to study the basic properties of sintering dust. At the same time, preliminary experiments on the recovery of the potassium resources from the sintering dust were carried out. The mean particle size of the electrostatic precipitator (ESP) dust determined by a laser granulometer was 41.468 microm. Multi-point BET and single-point BET analysis showed that the surface area of the ESP dust was 2.697 m2/g. XRD measurements detected the following phases in the ESP dust: Fe2O3, Fe3O4, KCl and NaCl, and Fe2O3, Fe3O4 and SiO2 in the water-washed dust. SEM-EDS results proved that in the ESP dust, K mostly existed in the form of KCl particles without being coated. Leaching experiments showed that the KCl in the ESP dust could be separated and recovered by water leaching and fractional crystallization. Through the recovery experiments, the yield of K-Na vaporized crystalline salt was 18.56%, in which the mass fractions of KCl, NaCl, CaSO4 and K2SO4 were about 61.03%, 13.58%, 14.03% and 9.97%, respectively. This process is technically viable and considerable in economic benefit. There was almost no secondary pollution produced in the whole recovery process.

  15. 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.

  16. a Brief Survey on Basic Properties of Thin Films for Device Application

    NASA Astrophysics Data System (ADS)

    Rao, M. C.; Shekhawat, M. S.

    Thin film materials are the key elements of continued technological advances made in the fields of optoelectronic, photonic and magnetic devices. Thin film studies have directly or indirectly advanced many new areas of research in solid state physics and chemistry which are based on phenomena uniquely characteristic of the thickness, geometry and structure of the film. The processing of materials into thin films allows easy integration into various types of devices. Thin films are extremely thermally stable and reasonably hard, but they are fragile. On the other hand organic materials have reasonable thermal stability and are tough, but are soft. Thin film mechanical properties can be measured by tensile testing of freestanding films and by the micro beam cantilever deflection technique, but the easiest way is by means of nanoindentation. Optical experiments provide a good way of examining the properties of semiconductors. Particularly measuring the absorption coefficient for various energies gives information about the band gaps of the material. Thin film materials have been used in semiconductor devices, wireless communications, telecommunications, integrated circuits, rectifiers, transistors, solar cells, light-emitting diodes, photoconductors and light crystal displays, lithography, micro- electromechanical systems (MEMS) and multifunctional emerging coatings, as well as other emerging cutting technologies.

  17. 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.

  18. Basic Psychological Skills Usage and Competitive Anxiety Responses: Perceived Underlying Mechanisms

    ERIC Educational Resources Information Center

    Wadey, Ross; Hanton, Sheldon

    2008-01-01

    This study examined the relationship between basic psychological skills usage (i.e., goal-setting, imagery, self-talk, and relaxation) and the intensity and directional dimensions of competitive anxiety. Semistructured interviews were used on a sample of 15 elite athletes (M age = 24.3 years, SD = 4.2) from a variety of team and individual sports.…

  19. Automotive Mechanics. COM-LINK. Competency Based Vocational Curricula with Basic Skills and Academic Linkages.

    ERIC Educational Resources Information Center

    Brown, Desmond

    This competency-based module uses the Ocean County (New Jersey) Vocational-Technical Schools curriculum-infused model for infusing basic skills instruction into vocational education. The model demonstrates the relationship of vocational skills to communication, mathematics, and science. The document begins with a philosophy statement; preface; a…

  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. Attractive mechanical properties of a lightweight highly sensitive bi layer thermistor: polycarbonate/organic molecular conductor

    NASA Astrophysics Data System (ADS)

    Laukhina, E.; Lebedev, V.; Rovira, C.; Laukhin, V.; Veciana, J.

    2016-03-01

    The paper covers some of the basic mechanical characteristics of a recently developed bi layer thermistor: polycarbonate/(001) oriented layer of organic molecular conductor α’-(BEDT-TTF)2IxBr3-x, were BEDT-TTF=bis(ethylenedithio)tetrathiafulvalen. The nano and macro mechanical properties have been studied in order to use this flexible, low cost thermistor in sensing applications by proper way. The nano-mechanical properties of the temperature sensitive semiconducting layer of α’-(BEDT-TTF)2IxBr3-x were tested using nanoindentation method. The value of Young's modulus in direction being perpendicular to the layer plan was found as 9.0 ±1.4 GPa. The macro mechanical properties of the thermistor were studied using a 5848 MicroTester. The tensile tests showed that basic mechanical characteristics of the thermistor are close to those of polycarbonate films. This indicates a good mechanical strength of the developed sensor. Therefore, the thermistor can be used in technologies that need to be instrumented with highly robustness lightweight low cost temperature sensors. The paper also reports synthetic details on fabricating temperature sensing e-textile. As the temperature control is becoming more and more important in biomedical technologies like healthcare monitoring, this work strongly contributes on the ongoing research on engineering sensitive conducting materials for biomedical applications.

  2. 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…

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Organizational stressors and basic psychological needs: The mediating role of athletes' appraisal mechanisms.

    PubMed

    Bartholomew, K J; Arnold, R; Hampson, R J; Fletcher, D

    2017-02-07

    This article reports the first study to quantitatively examine the relationships between the demands encountered by athletes that are associated with the organization within which they are operating, cognitive appraisals, and basic psychological need experiences. Three hundred and fifteen high-level British athletes completed a multisection questionnaire which assessed each of the aforementioned constructs. A series of path analyses provided valuable insight into the way in which the three dimensions (ie, frequency, intensity, and duration) of five organizational stressor categories were evaluated by athletes and, in turn, how such threat or challenge appraisals predicted feelings of need satisfaction and need frustration. Moreover, cognitive stress appraisals were found to mediate the relationship between organizational stressors and psychological need experiences. The role of secondary control appraisals was also explored and found to mediate the relationship between primary cognitive appraisals and basic psychological need experiences. Study limitations, proposed future research directions, and the implications of the findings for applied practitioners are discussed.

  11. 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.

  12. 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.

  13. 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)

  14. 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.

  15. Agricultural Mechanics. V-A-1 to V-E-1. Basic V.A.I.

    ERIC Educational Resources Information Center

    Texas A and M Univ., College Station. Vocational Instructional Services.

    This packet contains five units of informational materials and transparency masters with accompanying scripts, skill sheets, and safety tests for teacher and student use in an agricultural mechanics course in vocational agriculture. The first unit introduces the agricultural mechanics shop, covering the following topics: importance of agricultural…

  16. Ground and excited state properties of high performance anthocyanidin dyes-sensitized solar cells in the basic solutions

    NASA Astrophysics Data System (ADS)

    Prima, Eka Cahya; Yuliarto, Brian; Suyatman, Dipojono, Hermawan Kresno

    2015-09-01

    The aglycones of anthocyanidin dyes were previously reported to form carbinol pseudobase, cis-chalcone, and trans-chalcone due to the basic levels. The further investigations of ground and excited state properties of the dyes were characterized using density functional theory with PCM(UFF)/B3LYP/6-31+G(d,p) level in the basic solutions. However, to the best of our knowledge, the theoretical investigation of their potential photosensitizers has never been reported before. In this paper, the theoretical photovoltaic properties sensitized by dyes have been successfully investigated including the electron injections, the ground and excited state oxidation potentials, the estimated open circuit voltages, and the light harvesting efficiencies. The results prove that the electronic properties represented by dyes' LUMO-HOMO levels will affect to the photovoltaic performances. Cis-chalcone dye is the best anthocyanidin aglycone dye with the electron injection spontaneity of -1.208 eV, the theoretical open circuit voltage of 1.781 V, and light harvesting efficiency of 56.55% due to the best HOMO-LUMO levels. Moreover, the ethanol solvent slightly contributes to the better cell performance than the water solvent dye because of the better oxidation potential stabilization in the ground state as well as in the excited state. These results are in good agreement with the known experimental report that the aglycones of anthocyanidin dyes in basic solvent are the high potential photosensitizers for dye-sensitized solar cell.

  17. Ground and excited state properties of high performance anthocyanidin dyes-sensitized solar cells in the basic solutions

    SciTech Connect

    Prima, Eka Cahya; Yuliarto, Brian; Suyatman; Dipojono, Hermawan Kresno

    2015-09-30

    The aglycones of anthocyanidin dyes were previously reported to form carbinol pseudobase, cis-chalcone, and trans-chalcone due to the basic levels. The further investigations of ground and excited state properties of the dyes were characterized using density functional theory with PCM(UFF)/B3LYP/6-31+G(d,p) level in the basic solutions. However, to the best of our knowledge, the theoretical investigation of their potential photosensitizers has never been reported before. In this paper, the theoretical photovoltaic properties sensitized by dyes have been successfully investigated including the electron injections, the ground and excited state oxidation potentials, the estimated open circuit voltages, and the light harvesting efficiencies. The results prove that the electronic properties represented by dyes’ LUMO-HOMO levels will affect to the photovoltaic performances. Cis-chalcone dye is the best anthocyanidin aglycone dye with the electron injection spontaneity of −1.208 eV, the theoretical open circuit voltage of 1.781 V, and light harvesting efficiency of 56.55% due to the best HOMO-LUMO levels. Moreover, the ethanol solvent slightly contributes to the better cell performance than the water solvent dye because of the better oxidation potential stabilization in the ground state as well as in the excited state. These results are in good agreement with the known experimental report that the aglycones of anthocyanidin dyes in basic solvent are the high potential photosensitizers for dye-sensitized solar cell.

  18. Influence of Basicity on High-Chromium Vanadium-Titanium Magnetite Sinter Properties, Productivity, and Mineralogy

    NASA Astrophysics Data System (ADS)

    Zhou, Mi; Yang, Songtao; Jiang, Tao; Xue, Xiangxin

    2015-05-01

    The effect of basicity on high-chromium vanadium-titanium magnetite (V-Ti-Cr) sintering was studied via sintering pot tests. The sinter rate, yield, and productivity were calculated before determining sinter strength (TI) and reduction degradation index (RDI). Furthermore, the effect of basicity on V-Ti-Cr sinter mineralogy was clarified using metallographic microscopy, x-ray diffraction, and scanning electron microscopy-energy-dispersive x-ray spectroscopy. The results indicate that increasing basicity quickly increases the sintering rate from 25.4 mm min-1 to 28.9 mm min-1, yield from 75.3% to 87.2%, TI from 55.4% to 64.8%, and productivity from 1.83 t (m2 h)-1 to 1.94 t (m2 h)-1 before experiencing a slight drop. The V-Ti-Cr sinter shows complex mineral composition, with main mineral phases such as magnetite, hematite, silicate (dicalcium silicate, Ca-Fe olivine, glass), calcium and aluminum silico-ferrite (SFCA/SFCAI) and perovskite. Perovskite is notable because it lowers the V-Ti sinter strength and RDI. The well intergrowths between magnetite and SFCA/SFCAI, and the decrease in perovskite and secondary skeletal hematite are the key for improving TI and RDI. Finally, a comprehensive index was calculated, and the optimal V-Ti-Cr sinter basicity also for industrial application was 2.55.

  19. Meaning, Memory, and Multiplication: Integrating Patterns and Properties with Basic Facts

    ERIC Educational Resources Information Center

    Ploger, Don; Hecht, Steven

    2012-01-01

    Although learning mathematics certainly depends upon accurate understanding of the facts of multiplication, it requires much more. This study examines the relationship between a meaningful understanding of arithmetic operations and the mastery of basic facts. The study began with a joke about a mistaken mathematical fact. The children appreciated…

  20. 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.

  1. An outline for a vocabulary of nominal properties and examinations--basic and general concepts and associated terms.

    PubMed

    Nordin, Gunnar; Dybkaer, René; Forsum, Urban; Fuentes-Arderiu, Xavier; Schadow, Gunther; Pontet, Françoise

    2010-11-01

    Scientists of disciplines in clinical laboratory sciences have long recognized the need for a common language for efficient and safe request of investigations, reporting of results, and communication of experience and scientific achievements. Widening the scope, most scientific disciplines, not only clinical laboratory sciences, rely to some extent on various nominal examinations, in addition to measurements. The 'International vocabulary of metrology--Basic and general concepts and associated terms' (VIM) is designed for metrology, science of measurement. The aim of the proposed vocabulary is to suggest definitions and explanations of concepts and terms related to nominal properties, i.e., properties that can be compared for identity with other properties of the same kind-of-property, but that have no magnitude.

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. Numerical Prediction of Microstructure and Mechanical Properties During the Hot Stamping Process

    NASA Astrophysics Data System (ADS)

    Kan, Dongbin; Liu, Lizhong; Hu, Ping; Ma, Ning; Shen, Guozhe; Han, Xiaoqiang; Ying, Liang

    2011-08-01

    Numerical simulation and prediction of microstructures and mechanical properties of products is very important in product development of hot stamping parts. With this method we can easily design changes of hot stamping products' properties prior to the manufacturing stage and this offers noticeable time and cost savings. In the present work, the hot stamping process of a U-channel with 22MnB5 boron steels is simulated by using a coupled thermo-mechanical FEM program. Then with the temperature evolution results obtained from the simulation, a model is applied to predict the microstructure evolution during the hot stamping process and mechanical properties of this U-channel. The model consists of a phase transformation model and a mechanical properties prediction model. The phase transformation model which is proposed by Li et al is used to predict the austenite decomposition into ferrite, pearlite, and bainite during the cooling process. The diffusionless austenite-martensite transformation is modeled using the Koistinen and Marburger relation. The mechanical properties prediction model is applied to predict the products' hardness distribution. The numerical simulation is evaluated by comparing simulation results with the U-channel hot stamping experiment. The numerically obtained temperature history is basically in agreement with corresponding experimental observation. The evaluation indicates the feasibility of this set of methods to be used to guide the optimization of hot stamping process parameters and the design of hot stamping tools.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Correlation of basic oil quality indices and electrical properties of model vegetable oil systems.

    PubMed

    Prevc, Tjaša; Cigić, Blaž; Vidrih, Rajko; Poklar Ulrih, Nataša; Šegatin, Nataša

    2013-11-27

    Model vegetable oil mixtures with significantly different basic oil quality indices (free fatty acid, iodine, and Totox values) were prepared by adding oleic acids, synthetic saturated triglycerides, or oxidized safflower oil ( Carthamus tinctorius ) to the oleic type of sunflower oil. Dielectric constants, dielectric loss factors, quality factors, and electrical conductivities of model lipids were determined at frequencies from 50 Hz to 2 MHz and at temperatures from 293.15 to 323.15 K. The dependence of these dielectric parameters on basic oil quality indices was investigated. Adding oleic acids to sunflower oil resulted in lower dielectric constants and conductivities and higher quality factors. Reduced iodine values resulted in increased dielectric constants and quality factors and decreased conductivities. Higher Totox values resulted in higher dielectric constants and conductivities at high frequencies and lower quality factors. Dielectric constants decreased linearly with temperature, whereas conductivities followed the Arrhenius law.

  19. Basic Knowledge for Market Principle: Approaches to the Price Coordination Mechanism by Using Optimization Theory and Algorithm

    NASA Astrophysics Data System (ADS)

    Aiyoshi, Eitaro; Masuda, Kazuaki

    On the basis of market fundamentalism, new types of social systems with the market mechanism such as electricity trading markets and carbon dioxide (CO2) emission trading markets have been developed. However, there are few textbooks in science and technology which present the explanation that Lagrange multipliers can be interpreted as market prices. This tutorial paper explains that (1) the steepest descent method for dual problems in optimization, and (2) Gauss-Seidel method for solving the stationary conditions of Lagrange problems with market principles, can formulate the mechanism of market pricing, which works even in the information-oriented modern society. The authors expect readers to acquire basic knowledge on optimization theory and algorithms related to economics and to utilize them for designing the mechanism of more complicated markets.

  20. Prestressed F-actin networks cross-linked by hinged filamins replicate mechanical properties of cells

    NASA Astrophysics Data System (ADS)

    Gardel, M. L.; Nakamura, F.; Hartwig, J. H.; Crocker, J. C.; Stossel, T. P.; Weitz, D. A.

    2006-02-01

    We show that actin filaments, shortened to physiological lengths by gelsolin and cross-linked with recombinant human filamins (FLNs), exhibit dynamic elastic properties similar to those reported for live cells. To achieve elasticity values of comparable magnitude to those of cells, the in vitro network must be subjected to external prestress, which directly controls network elasticity. A molecular requirement for the strain-related behavior at physiological conditionsis a flexible hinge found in FLNa and some FLNb molecules. Basic physical properties of the in vitro filamin-F-actin network replicate the essential mechanical properties of living cells. This physical behavior could accommodate passive deformation and internal organelle trafficking at low strains yet resist externally or internally generated high shear forces. cytoskeleton | cell mechanics | nonlinear rheology

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Teaching the basics of autophagy and mitophagy to redox biologists—Mechanisms and experimental approaches

    PubMed Central

    Zhang, Jianhua

    2015-01-01

    Autophagy is a lysosomal mediated degradation activity providing an essential mechanism for recycling cellular constituents, and clearance of excess or damaged lipids, proteins and organelles. Autophagy involves more than 30 proteins and is regulated by nutrient availability, and various stress sensing signaling pathways. This article provides an overview of the mechanisms and regulation of autophagy, its role in health and diseases, and methods for its measurement. Hopefully this teaching review together with the graphic illustrations will be helpful for instructors teaching graduate students who are interested in grasping the concepts and major research areas and introducing recent developments in the field. PMID:25618581

  7. Teaching the basics of autophagy and mitophagy to redox biologists--mechanisms and experimental approaches.

    PubMed

    Zhang, Jianhua

    2015-01-01

    Autophagy is a lysosomal mediated degradation activity providing an essential mechanism for recycling cellular constituents, and clearance of excess or damaged lipids, proteins and organelles. Autophagy involves more than 30 proteins and is regulated by nutrient availability, and various stress sensing signaling pathways. This article provides an overview of the mechanisms and regulation of autophagy, its role in health and diseases, and methods for its measurement. Hopefully this teaching review together with the graphic illustrations will be helpful for instructors teaching graduate students who are interested in grasping the concepts and major research areas and introducing recent developments in the field.

  8. 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.

  9. 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.

  10. Dependence of the basic properties of meso-nitro-substituted derivatives of β-octaethylporphyrin on the nature of substituents

    NASA Astrophysics Data System (ADS)

    Pukhovskaya, S. G.; Ivanova, Yu. B.; Nam, Dao The; Vashurin, A. S.

    2014-10-01

    Spectrophotometric titration is used to study the basic properties of a series of porphyrins with a continuously increasing degree of macrocycle deformation resulting from the introduction of strong electron-withdrawing substituents: 2,3,7,8,12,13,17,18-octaethylporphyrin ( I), 5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrin ( II), 5,15-dinitro-2,3,7,8,12,13,17,18-octaethylporphyrin ( III), 5,10,15-trinitro-2,3,7,8,12,13,17,18-octaethylporphyrin ( IV), and 5,10,15,20-tetranitro-2,3,7,8,12,13,17,18-octaethylporphyrin ( V). It is found that the values of log K b (total basicity constants) obtained for the investigated compounds consistently diminish with an increase in the number of meso-substituents: 11.85 ( I) > 10.45 ( II) > 10.31 ( III) > 10.23 ( IV) > 9.56 ( V). It is shown that two opposing factors, the steric and electronic effects of the substituents, change the basic properties of the above series of compounds.

  11. 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

  12. 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.

  13. Linking Basic Skills to Entry-Level Auto Mechanic & Auto Body Worker Tasks. Instructional Resources. Assessments.

    ERIC Educational Resources Information Center

    Benavidez, Charlotte; Miyatake, George

    This project first identified the duties and tasks required of an entry-level auto mechanic (AM) and an auto body worker (ABW), using a modified DACUM (Developing a Curriculum) occupational analysis process. In this process, a panel of local, expert workers determined the essential duties and tasks of their occupations. Next, the panel identified…

  14. Basic Mechanisms of Radiation Effects on Electronic Materials, Devices, and Integrated Circuits

    DTIC Science & Technology

    1982-08-01

    such changes on de’ ice properties. To gain detailed insight regarding the effects that occur when an integrated circuit is placed in a radiation...the interaction produces energetic free elec- trons. The energy range in which photoelectr~ ic collisions dominate depends on the atomic number Z of...neutron energy dependent, as discussed in Sec- ticn 3.0, this makes it difficult to compare directly results obtained by workers using different radiation

  15. A novel mechanism for poisoning of metal oxide SCR catalysts: base-acid explanation correlated with redox properties.

    PubMed

    Chang, Huazhen; Li, Junhua; Su, Wenkang; Shao, Yuankai; Hao, Jiming

    2014-09-11

    A novel mechanism is proposed for the poisoning effect of acid gases and N2O formation on SCR catalysts involving base-acid properties correlated with redox ability of M-O or M-OH (M = Ce or V) of metal oxides and the strength of their basicity responsible for resistance to HCl and SO2 at medium and low temperatures.

  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. Advances in classification, basic mechanisms and clinical science in ankylosing spondylitis and axial spondyloarthritis.

    PubMed

    Robinson, P C; Benham, H

    2015-02-01

    The field of spondyloarthritis (SpA) has seen huge advances over the past 5 years. The classification of axial disease has been redefined by the axial SpA criteria that incorporate disease captured before radiographic damage is evident as well as established erosive sacroiliac joint disease. Our knowledge of genetics and basic immunological pathways has progressed significantly. In addition, revolutionary progress has been achieved with the availability of tumour necrosis factor inhibitors for treating patients with moderate to severe disease. In parallel, several of novel biomarkers have been identified that show significant promise for the future. Advances in magnetic resonance imaging have helped define positive disease. We have identified that T1 and short tau inversion recovery sequences are best for the diagnosis of axial SpA, and gadolinium contrast is not additive for diagnosis. Progress has been made in identifying potential agents and strategies that reduce radiographic progression. Several referral strategies aimed at appropriate identification of patients have been trialled and found to be effective. There is still substantial work ahead, but the advances of the last 5 years have made a huge and tangible difference at the clinical coalface, and we suggest that this trend will continue.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

    SciTech Connect

    Cressault, Y.

    2015-05-15

    This paper has for objectives to present the radiative and the transport properties for people beginning in thermal plasmas. The first section will briefly recall the equations defined in numerical models applied to thermal plasmas; the second section will particularly deal with the estimation of radiative losses; the third part will quickly present the thermodynamics properties; and the last part will concern the transport coefficients (thermal conductivity, viscosity and electrical conductivity of the gas or mixtures of gases). We shall conclude the paper with a discussion about the validity of these results the lack of data for some specific applications, and some perspectives concerning these properties for non-equilibrium thermal plasmas.

  4. [Phenomenology and mechanisms of changes in the basic functions of the human body in weightlessness].

    PubMed

    Grigor'ev, A I; Egorov, A D

    1988-01-01

    In the course of the space era the duration of manned flights increased from 108 minutes to 326 days. During the flights a large number of biomedical investigations were carried out to study the phenomenology and mechanisms of space flight effects on the human body. It was demonstrated that exposure to microgravity produced most significant changes. Short-term effects include space adaptation syndrome changes associated with fluid shifts and changes in movement coordination. Long-term effects involve various changes in the musculoskeletal system, cardiovascular system, metabolism and its regulation, endocrine system, blood and immunity system. This paper describes symptom-complexes that are consistently observed in space flight, discusses mechanisms of changes and adaptation of vital physiological systems, and outlines main periods of changes during and after flight.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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).

  13. 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.

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. Basic mechanism for biorientation of mitotic chromosomes is provided by the kinetochore geometry and indiscriminate turnover of kinetochore microtubules

    PubMed Central

    Zaytsev, Anatoly V.; Grishchuk, Ekaterina L.

    2015-01-01

    Accuracy of chromosome segregation relies on the ill-understood ability of mitotic kinetochores to biorient, whereupon each sister kinetochore forms microtubule (MT) attachments to only one spindle pole. Because initial MT attachments result from chance encounters with the kinetochores, biorientation must rely on specific mechanisms to avoid and resolve improper attachments. Here we use mathematical modeling to critically analyze the error-correction potential of a simplified biorientation mechanism, which involves the back-to-back arrangement of sister kinetochores and the marked instability of kinetochore–MT attachments. We show that a typical mammalian kinetochore operates in a near-optimal regime, in which the back-to-back kinetochore geometry and the indiscriminate kinetochore–MT turnover provide strong error-correction activity. In human cells, this mechanism alone can potentially enable normal segregation of 45 out of 46 chromosomes during one mitotic division, corresponding to a mis-segregation rate in the range of 10−1–10−2 per chromosome. This theoretical upper limit for chromosome segregation accuracy predicted with the basic mechanism is close to the mis-segregation rate in some cancer cells; however, it cannot explain the relatively low chromosome loss in diploid human cells, consistent with their reliance on additional mechanisms. PMID:26424798

  20. The basic mechanism behind the hurricane-free warm tropical ocean

    NASA Astrophysics Data System (ADS)

    Yuan, Z.; Qian, Y.-K.; Wu, J.; Qi, J.

    2010-01-01

    No hurricane is detected in the tropics off the Brazilian coast due to the lack of initial conditions (e.g., the weak vertical shear of horizontal wind) despite that high sea surface temperature is available. According to previous studies, the initial conditions (as the ingredients of hurricane's embryo) are related so that the thick warm-and-moist layer (due to the updraft vapour) below a cold-and-dry layer frames the convective instability which enhances diabatic processes accompanied by tropical cyclones with the weak vertical shear. So the basic question is how, starting with an internal-disturbance-free balance-situation, external forces create the rapidly-upward acceleration of moist air at the warm sea surface. The answer is revealed by the vertical-momentum equation which shows that boosted by the external-force-induced significant lower-layer equatorial westerly wind (LLEWW), the upward (unit-mass) acceleration could be as significant as the midlatitude Coriolis force. Besides creating cyclonic vortices through the upward acceleration and diabatic processes, the external-force-induced significant-LLEWW could directly create cyclonic wind shears along with easterly jets for the low-level cyclonic vorticity through reducing the peak value of zonally-homogeneous trade easterlies (centered at the Equator between the Northern and Southern Hemisphere subtropical high-belts). We emphasize external forces to avoid the ''chicken-and-egg'' problem accompanying nonlinear interactions of internal-forcing processes. The external-force-induced significant-LLEWW could result from the deflection of the cross-equatorial flow characterized by the seasonal shift coincident with that of locations of most embryos. This significant cross-equatorial flow is driven by the significant differential heating between the largest continent with the highest plateau and the largest ocean with the warm pool located to the east and on the equatorward side of the continent on the rotating

  1. Metallic syntactic foams synthesis, characterization and mechanical properties

    NASA Astrophysics Data System (ADS)

    Castro, Gerhard

    In this study, we report two procedures for producing lab-scale syntactic steel by melt infiltration of millimeter-sized alumina microspheres: mechanical pressure infiltration and gravity-fed infiltration. Both methods yield foam with uniform distributions of microspheres and negligible unintended porosity. The most critical parameters in the manufacture of the syntactic steel foams are the melt temperature and the preheat temperature of the microspheres prior to infiltration. The preheatment temperature of the microspheres must be close to the melting temperature of steel. Syntactic steel foams with relative density of about half of solid steel densities were produced using monosized microspheres randomly situated in a mold. Microspheres with a diameter of 1.27 mm were used for the mechanical pressure infiltration method and microspheres with a diameter of 4.45 mm for the gravity-fed infiltration method. Different steel chemical compositions were selected to produce steel foams of different inherent yield strength: including several ferritic-pearlitic steels and one TRIP steel (TRansformation-Induced Plasticity). The resultant foams were characterized by chemical and microstructural analysis. The microstructure of the samples consisted of blends of ferritic and pearlitic constituents in varying proportions for the ferritic-pearlitic steels, while the cast TRIP steel matrix presented an austenitic microstructure. The basic mechanical properties of the steel syntactic foams were studied under compression loading. The pearlitic syntactic foams have greater compression strength and energy absorption capacity than the ferritic syntactic foams, but the TRIP steel syntactic foam exhibited the highest compression strength and highest energy absorption capacity. The properties of the steel syntactic foams were compared to those of other steel foams, aluminum foams and other cellular structures reported in the literature. We present also the compression and impact behavior

  2. 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.

  3. Platelet-derived sphingosine-1-phosphate and inflammation: from basic mechanisms to clinical implications.

    PubMed

    Vito, Clara Di; Hadi, Loubna Abdel; Navone, Stefania Elena; Marfia, Giovanni; Campanella, Rolando; Mancuso, Maria Elisa; Riboni, Laura

    2016-07-01

    Beyond key functions in hemostasis and thrombosis, platelets are recognized as key players of inflammation, an underlying feature of a variety of diseases. In this regard, platelets act as a circulating source of several pro- and anti-inflammatory molecules, which are secreted from their intracellular stores upon activation. Among them, mounting evidence highlights a crucial role of sphingosine-1-phosphate (S1P), a multifunctional sphingoid mediator. S1P-induced pleiotropic effects include those crucial in inflammatory processes, such as the maintenance of the endothelial barrier integrity, and leukocyte activation and recruitment at the injured site. This review outlines the peculiar features and molecular mechanisms that allow platelets for acting as a unique factory that produces and stores S1P in large quantities. A particular emphasis is placed on the autocrine and paracrine roles of S1P derived from the "inflamed" platelets, highlighting the role of its cross-talk with endothelial and blood cells involved in inflammation, and the mechanisms of its contribution to the development and progression of inflammatory diseases. Finally, potential clinical implications of platelet-derived S1P as diagnostic tool of inflammatory severity, and as therapeutic target in inflammation are discussed.

  4. Immunological analogy between allograft rejection, recurrent abortion and pre-eclampsia - the same basic mechanism?

    PubMed

    Wilczyński, Jacek R

    2006-07-01

    There are still controversies concerning the role of immunological mechanisms engaged both in recurrent abortions (RA) and pre-eclampsia (PE). According to some opinions, recurrent miscarriage is comparable to organ-specific autoimmune disease. Analysis of immune reactions shows that graft rejection shares many similar mechanisms with RA and PE. This fact allows us to conclude that rejection of transplanted alloantigenic organs and pregnancy loss have probably the same evolutionary origin. Subsets and functions of immunocompetent cells (T CD4, suppressor gammadeltaT, cytotoxic T CD8, Treg, Tr1, uterine NK cells), over-activation of innate immunity (activation of NK cytotoxic cells, macrophages, neutrophils and complement), changes of Th1/Th2 cytokine balance (IL-2, IL-12, IL-15, IL-18, IFNgamma, TNFalpha vs. IL-4, IL-10, TGFbeta), importance of HLA-G molecule, CD200/CD200R interaction, over-expression of adhesion molecules, fgl2 prothrombinase activation and stimulation of IDO and HO expression, all suggest that RA and PE are syndromes of fetal allograft rejection, and not organ-specific autoimmune diseases. According to that supposition, an analogy might exist between acute graft rejection and recurrent abortion, and between chronic graft rejection and pre-eclampsia.

  5. High basicity adsorbents from solid residue of cellulose and synthetic polymer co-pyrolysis for phenol removal: Kinetics and mechanism

    NASA Astrophysics Data System (ADS)

    Lorenc-Grabowska, Ewa; Rutkowski, Piotr

    2014-10-01

    The activated carbons (ACs) produced from solid residue of cellulose and synthetic polymer co-pyrolysis (CACs) and commercial activated carbon from coconut shell (GC) were used for phenol removal. The adsorption kinetics and mechanism were investigated. All studied activated carbons are predominantly microporous and are characterized by basic surface characteristics. Surface area SBET varies between 1235 and 1499 m2/g, whereas the pHPZC changes from 7.70 to 10.63. The bath adsorption of phenol (P) was carried out at ambient temperature. The equilibrium time and equilibrium sorption capacity were determined. It was found that the boundary layer effect is bigger in AC with high basic characteristics of the surface. The rate controlling step is the intraparticle diffusion in CACs only, whereas in ACs with higher amount of acidic functionalities the adsorbate-surface interaction influences the rate of kinetic as well. The equilibrium isotherms are L2 type for commercial AC and L4 for CACs. The CACs are characterized by very high adsorption capacity that vary between 312 and 417 mg/g. The main mechanism of phenol adsorption is micropore filling within pores smaller than 1.4 nm. In the absence of solvent effect further adsorption of phenol on CACs takes place. The enhanced adsorption is due to dispersive/repulsive interaction induced by oxygen functionalities.

  6. Basic effects of pulp refining on fiber properties--a review.

    PubMed

    Gharehkhani, Samira; Sadeghinezhad, Emad; Kazi, Salim Newaz; Yarmand, Hooman; Badarudin, Ahmad; Safaei, Mohammad Reza; Zubir, Mohd Nashrul Mohd

    2015-01-22

    The requirement for high quality pulps which are widely used in paper industries has increased the demand for pulp refining (beating) process. Pulp refining is a promising approach to improve the pulp quality by changing the fiber characteristics. The diversity of research on the effect of refining on fiber properties which is due to the different pulp sources, pulp consistency and refining equipment has interested us to provide a review on the studies over the last decade. In this article, the influence of pulp refining on structural properties i.e., fibrillations, fine formation, fiber length, fiber curl, crystallinity and distribution of surface chemical compositions is reviewed. The effect of pulp refining on electrokinetic properties of fiber e.g., surface and total charges of pulps is discussed. In addition, an overview of different refining theories, refiners as well as some tests for assessing the pulp refining is presented.

  7. Flux composition, microstructure and mechanical properties of HY-100 SAW weldments

    SciTech Connect

    Brothers, D.G.; Kettell, K.W.; Fox, A.G.

    1994-12-31

    The mechanical properties of submerged arc welds (SAW) on high strength steels are sensitive to weld-metal chemistry and thus the chemical composition of the welding consumables. Consumable chemistry determines the size, distribution, and composition of the nonmetallic inclusions present in the weld metal which together with cooling rate determines weld-metal microstructure and thus mechanical properties. Multirun submerged arc welds were made on HY-100 steel and all-weld variables were kept constant except the flux composition for which five different commercial fluxes were investigated. The basicity of each flux was calculated and correlated with weld-metal chemistry and it was found that lower basicity fluxes appeared to generate a higher oxygen activity in the weld-metal leading to more pronounced oxidation of carbon, manganese, and silicon and thus loss of weld-metal yield strength. Inclusion analyses showed the inclusion in the weld-metals to contain MnO, Al{sub 2}O{sub 3}, SiO{sub 2}, and TiO{sub 2}. These results suggest that the optimum flux for welding high-strength steels should have a high enough basicity and MnO content to avoid the loss of alloying elements from the weld metal due to high oxygen activity and to generate sufficient numbers of non-metallic inclusions to keep the DBTT low by forming significant amounts of acicular ferrite.

  8. Basic properties of coals and other solids. Final report, September 1, 1989--August 30, 1992

    SciTech Connect

    Arnett, E.M.

    1992-12-31

    The previous project dissected the heats of interactions of a series of coals into components that represented Bronsted acidity, hydrogen-bonding acidity and dispersion force interactions through comparison with the simple prototype solid acids: sulfonic acid resin, silica, and graphitized carbon black respectively. The present grant has emphasized the interaction of basic components in the coal with strong Bronsted acids and boron trichloride, a very strong Lewis acid, with a brief examination of the interactions of the coals with phenols as weaker hydrogen-bonding acids. We have also compared several coals with liquids derived from them at Wilsonville and Exxon. Finally, we have examined the effect of citric acid washing on several coals.

  9. [Concepts of basic physics that every cardiovascular surgeon should know: part I - mechanics of fluids].

    PubMed

    Oliveira, Marcos Aurélio Barboza de; Alves, Fernanda Tomé; Silva, Marcos Vinícius Pinto e; Croti, Ulisses Alexandre; Godoy, Moacir Fernandes de; Braile, Domingo Marcolino

    2010-01-01

    The professional activity that the cardiovascular surgeon performs is much more than a simple gesture to mechanically operate the patient's heart. There is in every act of intraoperative most notions of physiology and physics than we generally realize. This paper discusses, in the light of mathematics, on the dynamics of fluids, ie blood, focused on invasive measurements of blood pressure, the effect of vessel size on its internal resistance and the flow passing through it in conversion of various units of measurements of pressure and resistance, blood viscosity and its relationship to the vessel, hemodilution, differences in laminar and turbulent flow, velocity and blood pressure and wall tension after a stenosis and the origin of poststenotic aneurysm. This study is not to enable the reader to the knowledge of all physics, but to show it as a useful tool in explaining phenomena known in the routine of cardiovascular surgery.

  10. Magnetorheological fluid template for basic studies of mechanical-chemical effects during polishing

    NASA Astrophysics Data System (ADS)

    Miao, Chunlin; Bristol, Kirk M.; Marino, Anne E.; Shafrir, Shai N.; DeGroote, Jessica E.; Jacobs, Stephen D.

    2007-09-01

    We developed a new magnetorheological (MR) fluid for studying the relative contributions of mechanics and chemistry in polishing hard materials. The base carrier fluid is a mixture of two non-aqueous liquids. At conventional carbonyl iron (CI) magnetic particle concentrations, removal rates with this formulation were unacceptably low for the polycrystalline optical ceramic aluminum oxynitride (ALON). We overcame this problem by creating a high magnetic solids concentration suspension consisting of a blend of large and small CI particles. Our test bed for experiments was a magnetorheological finishing (MRF) spot-taking machine (STM) that can only polish spots into a non-rotating part. We demonstrated that, using this new MR fluid formulation, we could substantially increase peak removal rates on ALON with small additions of nonmagnetic, nanodiamond abrasives. Material removal with this fluid was assumed to be predominately driven by mechanics. With the addition of small amounts of DI water to the base fluid containing nanodiamonds, the peak removal rate showed an additional increase, presumably due to the altered fluid rheology and possibly chemical interactions. It is possible, however, that this result is due to increased fluid viscosity as well. Interestingly, the microtexture on the surfaces of the ALON grains (albeit-two different ALON parts) showed distinctly different features when spotted with nanodiamonds or with nanodiamonds and water, and an understanding of this phenomenon is the goal of future work. In this paper we describe the difficult fluid viscosity issues that were addressed in creating a viable, high removal rate, non-aqueous MR fluid template that could be pumped in the STM for several days of experiments.

  11. A novel mechanism underlying the basic defensive response of macrophages against Mycobacterium infection.

    PubMed

    Iyoda, Takuya; Takada, Muneaki; Fukatsu, Yoshinobu; Kumokoshi, Shunsuke; Fujisawa, Tatsuya; Shimada, Tomokazu; Shimokawa, Noriko; Matsunaga, Takuya; Makino, Kimiko; Doi, Norio; Terada, Hiroshi; Fukai, Fumio

    2014-05-01

    Following inhalation of Mycobacterium tuberculosis, including bacillus Calmette-Guérin (BCG), pathogens enter and grow inside macrophages by taking advantage of their phagocytic mechanisms. Macrophages often fail to eliminate intracellular M. tuberculosis, leading to the induction of host macrophage death. Despite accumulating evidence, the molecular mechanisms underlying M. tuberculosis infection-induced cell death remain controversial. In this study, we show the involvement of two distinct pathways triggered by TLR2 and β2 integrin in BCG infection-induced macrophage apoptosis. First, BCG infection induced activation of ERK1/2, which in turn caused phosphorylation/activation of the proapoptotic protein Bim in mouse macrophage-like Raw 264.7 cells. BCG-infected Raw cells treated with U0126, an MEK/ERK inhibitor, led to the suppression of Bim phosphorylation alongside a remarkable increase in the number of viable macrophages. Small interfering RNA-mediated knockdown of Bim rescued the macrophages from the apoptotic cell death induced by BCG infection. Stimulation with Pam3CSK, a TLR2 agonist, induced macrophage apoptosis with a concomitant increase in the phosphorylation/activation of MEK/ERK and Bim. These observations indicate the important role of the TLR2/MEK/ERK/Bim pathway in BCG infection-induced macrophage apoptosis. Second, we used the β2 integrin agonists C3bi and fibronectin to show that the β2 integrin-derived signal was involved in BCG infection-induced apoptosis, independent of MEK/ERK activation. Interestingly, latex beads coated with Pam3CSK and C3bi were able to induce apoptosis in macrophages to the same extent and specificity as that induced by BCG. Taken together, two distinct pattern-recognition membrane receptors, TLR2 and β2 integrin, acted as triggers in BCG infection-induced macrophage apoptosis, in which MEK/ERK activation played a crucial role following the engagement of TLR2.

  12. 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.

  13. 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.

  14. 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.

  15. Incretin-Based Therapies for Diabetic Complications: Basic Mechanisms and Clinical Evidence

    PubMed Central

    Kawanami, Daiji; Matoba, Keiichiro; Sango, Kazunori; Utsunomiya, Kazunori

    2016-01-01

    An increase in the rates of morbidity and mortality associated with diabetic complications is a global concern. Glycemic control is important to prevent the development and progression of diabetic complications. Various classes of anti-diabetic agents are currently available, and their pleiotropic effects on diabetic complications have been investigated. Incretin-based therapies such as dipeptidyl peptidase (DPP)-4 inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RA) are now widely used in the treatment of patients with type 2 diabetes. A series of experimental studies showed that incretin-based therapies have beneficial effects on diabetic complications, independent of their glucose-lowering abilities, which are mediated by anti-inflammatory and anti-oxidative stress properties. Based on these findings, clinical studies to assess the effects of DPP-4 inhibitors and GLP-1RA on diabetic microvascular and macrovascular complications have been performed. Several but not all studies have provided evidence to support the beneficial effects of incretin-based therapies on diabetic complications in patients with type 2 diabetes. We herein discuss the experimental and clinical evidence of incretin-based therapy for diabetic complications. PMID:27483245

  16. Incretin-Based Therapies for Diabetic Complications: Basic Mechanisms and Clinical Evidence.

    PubMed

    Kawanami, Daiji; Matoba, Keiichiro; Sango, Kazunori; Utsunomiya, Kazunori

    2016-07-29

    An increase in the rates of morbidity and mortality associated with diabetic complications is a global concern. Glycemic control is important to prevent the development and progression of diabetic complications. Various classes of anti-diabetic agents are currently available, and their pleiotropic effects on diabetic complications have been investigated. Incretin-based therapies such as dipeptidyl peptidase (DPP)-4 inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RA) are now widely used in the treatment of patients with type 2 diabetes. A series of experimental studies showed that incretin-based therapies have beneficial effects on diabetic complications, independent of their glucose-lowering abilities, which are mediated by anti-inflammatory and anti-oxidative stress properties. Based on these findings, clinical studies to assess the effects of DPP-4 inhibitors and GLP-1RA on diabetic microvascular and macrovascular complications have been performed. Several but not all studies have provided evidence to support the beneficial effects of incretin-based therapies on diabetic complications in patients with type 2 diabetes. We herein discuss the experimental and clinical evidence of incretin-based therapy for diabetic complications.

  17. 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.

  18. 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.

  19. 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.

  20. Basic evaluation on physical properties of experimental fluorinated soft lining materials.

    PubMed

    Kasuga, Yuta; Takahashi, Hidekazu; Akiba, Norihisa; Minakuchi, Shunsuke; Matsushita, Nariko; Hishimoto, Munemitsu

    2011-01-01

    The purpose of the present study was to compare the properties required for the clinical application of soft lining materials containing a fluorinated monomer versus that of conventional materials in an effort to develop a new soft lining material with long-term stable viscoelastic properties. Four soft lining materials were examined. Two experimental materials containing dodecafluoroheptyl methacrylate (SR12F) or tridecafluorooctyl methacrylate (SR13F) were prepared. Two commercial soft lining materials, one acrylic-based and one silicone rubber-based, were selected as reference materials. Shore A hardness, viscoelastic properties, water sorption, solubility, and staining resistance were evaluated. The Shore A hardness and the displacements were analyzed with two-way analysis of variance (ANOVA) and Tukey's HSD test. The water sorption, the solubility and the color change were analyzed with one-way ANOVA and Tukey's HSD test. The significance level was set at 0.05. SR12F and SR13F showed greater viscous flow, low water sorption, low solubility, and good staining resistance compared to the commercial products. The results indicate that the soft lining materials containing fluorinated monomers might have a potentially long-term stable viscoelastic behavior.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Distinct structural and mechanical properties of the nuclear lamina in Hutchinson-Gilford progeria syndrome.

    PubMed

    Dahl, Kris Noel; Scaffidi, Paola; Islam, Mohammad F; Yodh, Arjun G; Wilson, Katherine L; Misteli, Tom

    2006-07-05

    The nuclear lamina is a network of structural filaments, the A and B type lamins, located at the nuclear envelope and throughout the nucleus. Lamin filaments provide the nucleus with mechanical stability and support many basic activities, including gene regulation. Mutations in LMNA, the gene encoding A type lamins, cause numerous human diseases, including the segmental premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). Here we show that structural and mechanical properties of the lamina are altered in HGPS cells. We demonstrate by live-cell imaging and biochemical analysis that lamins A and C become trapped at the nuclear periphery in HGPS patient cells. Using micropipette aspiration, we show that the lamina in HGPS cells has a significantly reduced ability to rearrange under mechanical stress. Based on polarization microscopy results, we suggest that the lamins are disordered in the healthy nuclei, whereas the lamins in HGPS nuclei form orientationally ordered microdomains. The reduced deformability of the HGPS nuclear lamina possibly could be due to the inability of these orientationally ordered microdomains to dissipate mechanical stress. Surprisingly, intact HGPS cells exhibited a degree of resistance to acute mechanical stress similar to that of cells from healthy individuals. Thus, in contrast to the nuclear fragility seen in lmna null cells, the lamina network in HGPS cells has unique mechanical properties that might contribute to disease phenotypes by affecting responses to mechanical force and misregulation of mechanosensitive gene expression.

  8. 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.

  9. 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.

  10. Rheology, processing, and mechanical properties of thermoplastic/graphite fiber composites

    SciTech Connect

    Scobbo, J.J. Jr.

    1989-01-01

    Various cause and effect relations between the rheology, processing and mechanical properties of poly(ether ether ketone) (PEEK) and poly(arylene sulfide) (PAS) matrix composites were studied. The test methods and characterization schemes used emphasize novel techniques for characterizing composites that have not been used previously. A dynamic mechanical analyzer has been modified and used to characterize transition temperatures of the neat matrix resins and the 60 volume percent continuous graphite fiber reinforced composites. Transitions related to local order may have been found in PEEK at 380{degree}C and PAS at 345{degree}C. Transitions such as these have not been reported previously using dynamic mechanical analysis. Basic rheological behavior of the resins has been studied using dynamic mechanical analysis. Similar dynamic tests were performed on PEEK and PAS matrix unidirectional prepreg tape-based laminates. Tests were performed for the first time in simple shear with the matrix in the melt state. Simple shear deformation is of interest because it represents flow behavior of laminated composites in processing operations such as thermoforming. A simple model of resin layers between fibrous plates describes the observed behavior. A bending mode dynamic test has been developed to determine laminate softening temperatures. This test has been shown to be beneficial in the characterization of composite elastic properties at room temperature. The test requires less material and labor than other more common mechanical property tests. Processing studies were conducted where the radiative heating of laminates was simulated to determine optimum thermoforming cycle times.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. Irradiation response on mechanical properties of neutron irradiated F82H

    NASA Astrophysics Data System (ADS)

    Shiba, K.; Suzuki, M.; Hishinuma, A.

    1996-10-01

    Tensile and Charpy impact properties of neutron irradiated F82H (Fe8Cr2WVTa) with and without boron have been investigated to obtain the basic irradiation response on mechanical properties in low damage regime less than 1 dpa at the temperature ranging from 300° to 590°C. Boron-doped steel was used for the helium effect due to (n, α) reaction. Typical irradiation hardening was observed at 300°C. The irradiation above 520°C did not reveal increase in yield stress, but the specimen irradiated at 590°C showed some reduction in elongation in room temperature tensile testing. Slight difference in the tensile properties between boron-doped and boron-free were observed at 590°C. No changes in ductile brittle transition temperature (DBTT) occurred at a temperature between 335° and 460°C by Charpy impact testing.

  16. Effects of temperature and strain rate on the mechanical properties of hexagonal boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Han, Tongwei; Luo, Ying; Wang, Chengyuan

    2014-01-01

    The effect of temperature and strain rate on mechanical properties remains an open topic in research of hexagonal boron nitride (h-BN) nanosheets. To examine these fundamental issues we have performed molecular dynamics simulations to record the stress-strain curves in tensile tests and measure Young's modulus, fracture strength and fracture strain in armchair and zigzag directions. Comparing the results obtained at different temperatures and strain rates we have quantified the effects of the two factors on the tensile properties of the h-BN nanosheets. The influence of crystal orientation is also examined in the present study. It is found that the h-BN nanosheets are basically an anisotropic material whose tensile properties vary substantially with temperature and strain rate. In particular, a yielding platform is observed for the h-BN nanomaterial at relatively low temperature.

  17. 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.

  18. 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.

  19. 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).

  20. Basic Fourier properties for generalized phase shifting and some interesting detuning insensitive algorithms

    NASA Astrophysics Data System (ADS)

    Téllez-Quiñones, Alejandro; Malacara-Doblado, Daniel; García-Márquez, Jorge

    2011-07-01

    In this manuscript, some interesting properties for generalized or nonuniform phase-shifting algorithms are shown in the Fourier frequency space. A procedure to find algorithms with equal amplitudes for their sampling function transforms is described. We also consider in this procedure the finding of algorithms that are orthogonal for all possible values in the frequency space. This last kind of algorithms should closely satisfy the first order detuning insensitive condition. The procedure consists of the minimization of functionals associated with the desired insensitivity conditions.

  1. Basic Fourier properties for generalized phase shifting and some interesting detuning insensitive algorithms.

    PubMed

    Téllez-Quiñones, Alejandro; Malacara-Doblado, Daniel; García-Márquez, Jorge

    2011-07-20

    In this manuscript, some interesting properties for generalized or nonuniform phase-shifting algorithms are shown in the Fourier frequency space. A procedure to find algorithms with equal amplitudes for their sampling function transforms is described. We also consider in this procedure the finding of algorithms that are orthogonal for all possible values in the frequency space. This last kind of algorithms should closely satisfy the first order detuning insensitive condition. The procedure consists of the minimization of functionals associated with the desired insensitivity conditions.

  2. The spacing calculator software—A Visual Basic program to calculate spatial properties of lineaments

    NASA Astrophysics Data System (ADS)

    Ekneligoda, Thushan C.; Henkel, Herbert

    2006-05-01

    A software tool is presented which calculates the spatial properties azimuth, length, spacing, and frequency of lineaments that are defined by their starting and ending co-ordinates in a two-dimensional (2-D) planar co-ordinate system. A simple graphical interface with five display windows creates a user-friendly interactive environment. All lineaments are considered in the calculations, and no secondary sampling grid is needed for the elaboration of the spatial properties. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the programme defines a window that depends on the mode value of the length distribution of the lineaments in a study area. This makes the results more consistent, compared to the manual method of spacing calculation. Histograms are provided to illustrate and elaborate the distribution of the azimuth, length and spacing. The core of the tool is the spacing calculation between neighbouring parallel lineaments, which gives direct information about the variation of block sizes in a given category of structures. The 2-D lineament frequency is calculated for the actual area that is occupied by the lineaments.

  3. 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).

  4. Mechanical And Thermal Properties Of Optical Materials - A Review

    NASA Astrophysics Data System (ADS)

    Ballard, Stanley S.

    1980-02-01

    In selecting an optical material, the instrument designer's first consideration is optical properties, especially transmission region but also homogeneity, freedom from birefringence, perhaps refractive index and dispersion. Next in his hierarchy are the other physical properties: mechanical, thermal, and chemical (solubility, for example). In this review article, the several properties are listed, and data sources are given. No single compilation or handbook contains all the desired data, so many references are quoted. This review covers materials useful in the ultraviolet and esuecially the infrared spectral regions; it does not include the standard glasses used in the visible region.

  5. [Functional properties of taste bud cells. Mechanisms of afferent neurotransmission in Type II taste receptor cells].

    PubMed

    Romanov, R A

    2013-01-01

    Taste Bud cells are heterogeneous in their morphology and functionality. These cells are responsible for sensing a wide variety of substances and for associating detected compounds with a different taste: bitter, sweet, salty, sour and umami. Today we know that each of the five basic tastes corresponds to distinct cell populations organized into three basic morpho-functional cell types. In addition, some receptor cells of the taste bud demonstrate glia-related functions. In this article we expand on some properties of these three morphological receptor cell types. Main focus is devoted to the Type II cells and unusual mechanism for afferent neurotransmission in these cells. Taste cells of the Type II consist of three populations detecting bitter, sweet and umami tastes, and, thus, evoke a serious scientific interest.

  6. 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

  7. 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

  8. 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.

  9. 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

  10. Assessing the functional mechanical properties of bioengineered organs with emphasis on the lung.

    PubMed

    Suki, Béla

    2014-09-01

    Recently, an exciting new approach has emerged in regenerative medicine pushing the forefront of tissue engineering to create bioartificial organs. The basic idea is to create biological scaffolds made of extracellular matrix (ECM) that preserves the three-dimensional architecture of an entire organ. These scaffolds are then used as templates for functional tissue and organ reconstruction after re-seeding the structure with stem cells or appropriately differentiated cells. In order to make sure that these bioartificial organs will be able to function in the mechanical environment of the native tissue, it is imperative to fully characterize their mechanical properties and match them with those of the normal native organs. This mini-review briefly summarizes modern measurement techniques of mechanical function characterized mostly by the material or volumetric stiffness. Micro-scale and macro-scale techniques such as atomic force microscopy and the tissue strip stress-strain approach are discussed with emphasis on those that combine mechanical measurements with structural visualization. Proper micro-scale stiffness helps attachment and differentiation of cells in the bioartificial organ whereas macro-scale functionality is provided by the overall mechanical properties of the construct. Several approaches including failure mechanics are also described, which specifically probe the contributions of the main ECM components including collagen, elastin, and proteoglycans to organ level ECM function. Advantages, drawbacks, and possible pitfalls as well as interpretation of the data are given throughout. Finally, specific techniques to assess the functionality of the ECM of bioartificial lungs are separately discussed.

  11. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  12. Mechanical properties of tricalcium phosphate-alumina composites

    NASA Astrophysics Data System (ADS)

    Sakka, S.; Ben Ayed, F.; Bouaziz, J.

    2012-02-01

    Tricalcium phosphate and alumina powder were mixed in order to elaborate biphasic ceramics composites. This study deals to produce bioceramics composites sintered at various temperatures for differents times. The characterization of samples, before and after the sintering process was investigated, using X-Ray diffraction, scanning electronic microscopy, 31P and 27Al nuclear magnetic resonance and differential thermal analysis. Mechanical properties of biphasic composites were studied using Brazilian test. The tricalcium phosphate - 75 wt% alumina composites mechanical resistance increased with sintered temperature. The mechanical resistance reach it's optimum value (8.6 MPa) at 1550°C for two hours.

  13. Interspecific comparison of the mechanical properties of mussel byssus.

    PubMed

    Brazee, Shanna L; Carrington, Emily

    2006-12-01

    Byssally tethered mussels are found in a variety of habitats, including rocky intertidal, salt marsh, subtidal, and hydrothermal vents. One key to the survival of mussels in these communities is a secure attachment, achieved by the production of byssal threads. Although many studies have detailed the unique biomechanical properties of byssal threads, only a few prevalent species have been examined. This study assesses the variation in the mechanical properties of byssus in a broad range of mussel species from diverse environments, including intertidal and subtidal Mytilus edulis, Modiolus modiolus, Geukensia demissa, Bathymodiolus thermophilus, and Dreissena polymorpha. A tensometer was used to measure quasi-static and dynamic mechanical properties of individual threads, and several aspects of morphology were quantified. The results indicate that thread mechanical properties vary among mussel species, and several novel properties were observed. For example, of the species examined, D. polymorpha threads were the strongest, stiffest, least resilient, and fastest to recover after partial deformation. Threads of M. modiolus were characterized by the presence of two distinct yield regions prior to tensile failure. This comparative study not only provides insight into the ecological limitations and evolution of mussels, but also suggests new models for the design of novel biomimetic polymers.

  14. Physical and mechanical properties of the lunar soil (a review)

    NASA Astrophysics Data System (ADS)

    Slyuta, E. N.

    2014-09-01

    We review the data on the physical and mechanical properties of the lunar soil that were acquired in the direct investigations on the lunar surface carried out in the manned and automatic missions and in the laboratory examination of the lunar samples returned to the Earth. In justice to the American manned program Apollo, we show that a large volume of the data on the properties of the lunar soil was also obtained in the Soviet automatic program Lunokhod and with the automatic space stations Luna-16, -20, and -24 that returned the lunar soil samples to the Earth. We consider all of the main physical and mechanical properties of the lunar soil, such as the granulometric composition, density and porosity, cohesion and adhesion, angle of internal friction, shear strength of loose soil, deformation characteristics (the deformation modulus and Poisson ratio), compressibility, and the bearing capacity, and show the change of some properties versus the depth. In most cases, the analytical dependence of the main parameters is presented, which is required in developing reliable engineering models of the lunar soil. The main physical and mechanical properties are listed in the summarizing table, and the currently available models and simulants of the lunar soil are reviewed.

  15. Nonmetallic impurities improve mechanical properties of vapor-deposited tungsten

    NASA Technical Reports Server (NTRS)

    Chin, J.; Weinberg, A. F.; Lindgren, J. R.

    1972-01-01

    Mechanical properties of vapor deposited tungsten are improved by selective incorporation of various nonmetallic impurities. Addition of trace quantities of carbon, nitrogen, or oxygen can significantly increase both low and high temperature yield strength without greatly affecting ductile-to-brittle transition temperature.

  16. Variations in the mechanical properties of Alouatta palliata molar enamel.

    PubMed

    Darnell, Laura A; Teaford, Mark F; Livi, Kenneth J T; Weihs, Timothy P

    2010-01-01

    Teeth have provided insights into many topics including primate diet, paleobiology, and evolution, due to the fact that they are largely composed of inorganic materials and may remain intact long after an animal is deceased. Previous studies have reported that the mechanical properties, chemistry, and microstructure of human enamel vary with location. This study uses nanoindentation to map out the mechanical properties of Alouatta palliata molar enamel on an axial cross-section of an unworn permanent third molar, a worn permanent first molar, and a worn deciduous first molar. Variations were then correlated with changes in microstructure and chemistry using scanning electron microscopy and electron microprobe techniques. The hardness and Young's modulus varied with location throughout the cross-sections from the occlusal surface to the dentin-enamel junction (DEJ), from the buccal to lingual sides, and also from one tooth to another. These changes in mechanical properties correlated with changes in the organic content of the tooth, which was shown to increase from approximately 6% near the occlusal surface to approximately 20% just before the DEJ. Compared to human enamel, the Alouatta enamel showed similar microstructures, chemical constituents, and magnitudes of mechanical properties, but showed less variation in hardness and Young's modulus, despite the very different diet of this species.

  17. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    PubMed Central

    Pithon, Matheus Melo; Ferraz, Caio Souza; Rosa, Francine Cristina Silva; Rosa, Luciano Pereira

    2015-01-01

    OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60) (20 KGy) gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination), Group 2 (70°GL alcohol), Group 3 (autoclave), Group 4 (ultraviolet), Group 5 (peracetic acid) and Group 6 (glutaraldehyde). After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL), and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05). CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties. PMID:26154462

  18. A biodegradable polymer nanocomposite: Mechanical and barrier properties

    NASA Astrophysics Data System (ADS)

    Lilichenko, N.; Maksimov, R. D.; Zicans, J.; Merijs Meri, R.; Plume, E.

    2008-01-01

    The preparation of an environmentally friendly nanocomposite based on plasticized potato starch and unmodified montmorillonite clay is described. Data on the influence of montmorillonite concentration on the mechanical properties of the materials obtained are reported. The effective elastic constants of the nanocomposites are calculated. The calculation results are compared with experimental data. The influence of montmorillonite content on the moisture permeability is also investigated.

  19. Barrier and Mechanical Properties of Starch-Clay Nanocomposite Films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The poor barrier and mechanical properties of biopolymer-based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch-clay nano-composites were synthesized by a melt extrusion method. Natural (MMT) and organically modifi...

  20. Mechanical shear and tensile properties of selected biomass stems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lignocellulosic biomass, such as big bluestem, corn stalk, intermediate wheat grass and switchgrass stem are abundant and dominant species in the Midwest region of US. There is a need to understand the mechanical properties for these crops for better handling and processing of the biomass feedstocks...

  1. Thermal treatment and mechanical properties of aluminum-2021

    NASA Technical Reports Server (NTRS)

    Brennecke, M. W.

    1970-01-01

    Mechanical properties, after thermal treatments, are summarized for sheet and plate of copper-rich, high-strength, heat-treatable aluminum-2021. The alloy is quench sensitive, quench rate and variations in aging affect corrosion behavior. Aging effects on yield strength, tensile strength, and elongation of sheet and plate are compared.

  2. Mechanical and physical properties of modern boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1978-01-01

    The results of accurate measurements of the modern boron fiber's Young's modulus, flexural modulus, shear modulus, and Poisson's ratio are reported. Physical property data concerning fiber density, thermal expansion, and resistance obtained during the course of the mechanical studies are also given.

  3. Processing dependence of mechanical properties of metallic glass nanowires

    SciTech Connect

    Zhang, Qi; Li, Mo; Li, Qi-Kai

    2015-02-16

    Compared to their crystalline counterparts, nanowires made of metallic glass have not only superb properties but also remarkable processing ability. They can be processed easily and cheaply like plastics via a wide range of methods. To date, the underlying mechanisms of how these different processing routes affect the wires' properties as well as the atomic structure remains largely unknown. Here, by using atomistic modeling, we show that different processing methods can greatly influence the mechanical properties. The nanowires made via focused ion beam milling and embossing exhibit higher strength but localized plastic deformation, whereas that made by casting from liquid shows excellent ductility with homogeneous deformation but reduced strength. The different responses are reflected sensitively in the underlying atomic structure and packing density, some of which have been observed experimentally. The presence of the gradient of alloy concentration and surface effect will be discussed.

  4. A review of mechanical and electromechanical properties of piezoelectric nanowires.

    PubMed

    Espinosa, Horacio D; Bernal, Rodrigo A; Minary-Jolandan, Majid

    2012-09-04

    Piezoelectric nanowires are promising building blocks in nanoelectronic, sensing, actuation and nanogenerator systems. In spite of great progress in synthesis methods, quantitative mechanical and electromechanical characterization of these nanostructures is still limited. In this article, the state-of-the art in experimental and computational studies of mechanical and electromechanical properties of piezoelectric nanowires is reviewed with an emphasis on size effects. The review covers existing characterization and analysis methods and summarizes data reported in the literature. It also provides an assessment of research needs and opportunities. Throughout the discussion, the importance of coupling experimental and computational studies is highlighted. This is crucial for obtaining unambiguous size effects of nanowire properties, which truly reflect the effect of scaling rather than a particular synthesis route. We show that such a combined approach is critical to establish synthesis-structure-property relations that will pave the way for optimal usage of piezoelectric nanowires.

  5. Determining the Mechanical Properties of Lattice Block Structures

    NASA Technical Reports Server (NTRS)

    Wilmoth, Nathan

    2013-01-01

    Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was found to be extremely brittle from the casting process and only compression testing was completed. Future shape memory alloy lattice block structures will utilize an adjusted material composition that will provide a better quality casting. The testing effort resulted in baseline mechanical property data from the conventional titanium material for comparison to shape memory alloy materials once suitable castings are available.

  6. Moisture effect on mechanical properties of polymeric composite materials

    NASA Astrophysics Data System (ADS)

    Airale, A. G.; Carello, M.; Ferraris, A.; Sisca, L.

    2016-05-01

    The influence of moisture on the mechanical properties of fibre-reinforced polymer matrix composites (PMCs) was investigated. Four materials had been take into account considering: both 2×2-Twill woven carbon fibre or glass fibre, thermosetting matrix (Epoxy Resin) or thermoplastic matrix (Polyphenylene Sulfide). The specimens were submitted for 1800 hours to a hygrothermic test to evaluate moisture absorption on the basis of the Fick's law and finally tested to verify the mechanical properties (ultimate tensile strength). The results showed that the absorbed moisture decreases those properties of composites which were dominated by the matrix or the interface, while was not detectable the influence of water on the considered fibre. An important result is that the diffusion coefficient is highest for glass/PPS and lowest for carbon/epoxy composite material. The results give useful suggestions for the design of vehicle components that are exposed to environmental conditions (rain, snow and humidity).

  7. Mechanical property determination of high conductivity metals and alloys

    NASA Technical Reports Server (NTRS)

    Harrod, D. L.; Vandergrift, E.; France, L.

    1973-01-01

    Pertinent mechanical properties of three high conductivity metals and alloys; namely, vacuum hot pressed grade S-200E beryllium, OFHC copper and beryllium-copper alloy no. 10 were determined. These materials were selected based on their possible use in rocket thrust chamber and nozzle hardware. They were procured in a form and condition similar to that which might be ordered for actual hardware fabrication. The mechanical properties measured include (1) tension and compression stress strain curves at constant strain rate (2) tensile and compressive creep, (3) tensile and compressive stress-relaxation behavior and (4) elastic properties. Tests were conducted over the temperature range of from 75 F to 1600 F. The resulting data is presented in both graphical and tabular form.

  8. Basic Properties of Conductivity and Normal Hall Effect in the Periodic Anderson Model

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinji; Miyake, Kazumasa

    2016-04-01

    Exact formulas of diagonal conductivity σxx and Hall conductivity σxy are derived from the Kubo formula in hybridized two-orbital systems with arbitrary band dispersions. On the basis of the theoretical framework for the Fermi liquid based on these formulas, the ground-state properties of the periodic Anderson model with electron correlation and weak impurity scattering are studied on the square lattice. It is shown that imbalance of the mass-renormalization factors causes remarkable increase in σxx and σxy in the valence-fluctuation regime as the f level increases while the cancellation of the renormalization factors causes slight increase in σxx and σxy in the Kondo regime. The Hall coefficient RH shows almost constant behavior in both the regimes. Near half filling, RH is expressed by the total hole density as R{H} = 1/(bar{n}{hole}e) while RH approaches zero near quarter filling, which reflects the curvature of the Fermi surface. These results hold as far as the damping rate for f electrons is less than about 10% of the renormalized hybridization gap. From these results we discuss pressure dependence of residual resistivity and normal Hall effect in Ce- and Yb-based heavy electron systems.

  9. Basic properties of a liquidt in anode solid oxide fuel cell

    SciTech Connect

    Harry Abernathy; RandallGemmen; KirkGerdes; Mark Koslowske; ThomasTao

    2010-12-17

    An unconventional high temperature fuel cell system, the liquidt in anode solid oxide fuel cell(LTA-SOFC), is discussed. A thermodynamic analysis of a solid oxide fuel cell with a liquid metal anode is developed. Pertinent thermo chemical and thermo physical properties of liquid tin in particular are detailed. An experimental setup for analysis of LTA-SOFC anode kinetics is described, and data for a planar cell under hydrogen indicated an effective oxygen diffusion coefficient of 5.3×10−5 cm2 s−1 at 800 ◦C and 8.9×10−5 cm2 s−1 at 900 ◦C. This value is similar to previously reported literature values for liquid tin. The oxygen conductivity through the tin, calculated from measured diffusion coefficients and theoretical oxygen solubility limits, is found to be on the same order of thatofyttria-stabilizedzirconia(YSZ), a traditional SOFC electrolyte material. As such,the ohmicloss due to oxygen transport through the tin layer must be considered in practical system cell design since the tin layer will usually be at least as thick as the electrolyte.

  10. Characterization of the Basic Operational Properties of the Capillary Plasma Electrode (CPE) Discharge

    NASA Astrophysics Data System (ADS)

    Lopez, Jose; Zhu, Weidong; Figus, Margaret; Becker, Kurt

    2008-10-01

    Various approaches have been pursued to create stable atmospheric pressure discharges by extending the lifetime of the diffuse phase of the discharge to hundreds of microseconds. Previous research showed that the stability of the diffuse mode is dependent on the frequency (in the kHz range), gas type, power, mode of the excitation, and geometrical confinement. The Capillary Plasma Electrode (CPE) discharge is able to produce stable atmospheric pressure nonequilibrium plasmas. The CPE is similar in design to a barrier-electrode discharge, but has perforated dielectrics. This configuration, aside from exhibiting a diffuse mode of operation, also exhibits the so-called ``capillary jet'' mode, in which the capillaries ``turn on'' and a bright plasma jet emerges from the capillaries. The capillary jets from adjacent capillaries overlap so that the discharge appears uniform when the electrode contains an array of holes. There appears to be a threshold frequency for the capillary jet formation, which is strongly dependent on the L/D ratio of the capillaries, where D is the diameter of a capillary and L its length. This current work explores these modes of operation of the CPE by characterizing the electrical and optical emission properties of this discharge.

  11. Chemical treatment of olive pomace: effect on acid-basic properties and metal biosorption capacity.

    PubMed

    Martín-Lara, M A; Pagnanelli, F; Mainelli, S; Calero, M; Toro, L

    2008-08-15

    In this study, olive pomace, an agricultural waste that is very abundant in Mediterranean area, was modified by two chemical treatments in order to improve its biosorption capacity. Potentiometric titrations and IR analyses were used to characterise untreated olive pomace (OP), olive pomace treated by phosphoric acid (PAOP) and treated by hydrogen peroxide (HPOP). Acid-base properties of all investigated biosorbents were characterised by two main kinds of active sites, whose nature and concentration were determined by a mechanistic model assuming continuous distribution for the proton affinity constants. Titration modelling denoted that all investigated biosorbents (OP, PAOP and HPOP) were characterised by the same kinds of active sites (carboxylic and phenolic), but with different total concentrations with PAOP richer than OP and HPOP. Single metal equilibrium studies in batch reactors were carried out to determine the capacity of these sorbents for copper and cadmium ions at constant pH. Experimental data were analysed and compared using the Langmuir isotherm. The order of maximum uptake capacity of copper and cadmium ions on different biosorbents was PAOP>HPOP>OP. The maximum adsorption capacity of copper and cadmium, was obtained as 0.48 and 0.10 mmol/g, respectively, for PAOP. Metal biosorption tests in presence of Na(+) in solution were also carried out in order to evaluate the effect of chemical treatment on biomass selectivity. These data showed that PAOP is more selective for cadmium than the other sorbents, while similar selectivity was observed for copper.

  12. Influence of mechanical activation of steel powder on its properties

    NASA Astrophysics Data System (ADS)

    Vaulina, O. Yu; Darenskaia, E. A.; Myachin, Y. V.; Vasilyeva, I. E.; Kulkov, S. N.

    2017-02-01

    It has been studied properties of stainless steel based powders after mechanical activation using planetary ball milling technique. It have been shown that after one minute mechanical activation porosity of sintered steel is less than 5%, which is less than the porosity of the sintered steel powder without mechanical activation. The sample without activation has austenite state, which changes after activation toaustenite and ferrite mixtures. X-ray analysis confirmed that the mechanical activation leads to a change in the phase state of the samples: the samples without activation of the FCC structure (γ-Fe), after activation - FCC (γ-Fe) and BCC (α-Fe). The hardness increases at increasing activation time from 800 MPa for the sample without mechanical activation to 1250 MPa for the sample with the activation time of 10 minutes.

  13. Do Non-Collagenous Proteins Affect Skeletal Mechanical Properties?

    PubMed Central

    Morgan, Stacyann; Poundarik, Atharva A.; Vashishth, Deepak

    2015-01-01

    The remarkable mechanical behavior of bone is attributed to its complex nanocomposite structure that, in addition to mineral and collagen, comprises a variety of non-collagenous matrix proteins or NCPs. Traditionally, NCPs have been studied as signaling molecules in biological processes including bone formation, resorption and turnover. Limited attention has been given to their role in determining the mechanical properties of bone. Recent studies have highlighted that NCPs can indeed be lost or modified with aging, diseases and drug therapies. Homozygous and heterozygous mice models of key NCP provide a useful approach to determine the impact of NCPs on bone morphology as well as matrix quality, and to carry out detailed mechanical analysis for elucidating the pathway by which NCPs can affect the mechanical properties of bone. In this article, we present a systematic analysis of a large cohort of NCPs on bone’s structural and material hierarchy, and identify three principal pathways by which they determine bone’s mechanical properties. These pathways include alterations of bone morphological parameters crucial for bone’s structural competency, bone quality changes in key matrix parameters (mineral and collagen), and a direct role as load bearing structural proteins. PMID:26048282

  14. Porcine bladder acellular matrix (ACM): protein expression, mechanical properties.

    PubMed

    Farhat, Walid A; Chen, Jun; Haig, Jennifer; Antoon, Roula; Litman, Jessica; Sherman, Christopher; Derwin, Kathleen; Yeger, Herman

    2008-06-01

    Experimentally, porcine bladder acellular matrix (ACM) that mimics extracellular matrix has excellent potential as a bladder substitute. Herein we investigated the spatial localization and expression of different key cellular and extracellular proteins in the ACM; furthermore, we evaluated the inherent mechanical properties of the resultant ACM prior to implantation. Using a proprietary decellularization method, the DNA contents in both ACM and normal bladder were measured; in addition we used immunohistochemistry and western blots to quantify and localize the different cellular and extracellular components, and finally the mechanical testing was performed using a uniaxial mechanical testing machine. The mean DNA content in the ACM was significantly lower in the ACM compared to the bladder. Furthermore, the immunohistochemical and western blot analyses showed that collagen I and IV were preserved in the ACM, but possibly denatured collagen III in the ACM. Furthermore, elastin, laminin and fibronectin were mildly reduced in the ACM. Although the ACM did not exhibit nucleated cells, residual cellular components (actin, myosin, vimentin and others) were still present. There was, on the other hand, no significant difference in the mean stiffness between the ACM and the bladder. Although our decellularization method is effective in removing nuclear material from the bladder while maintaining its inherent mechanical properties, further work is mandatory to determine whether these residual DNA and cellular remnants would lead to any immune reaction, or if the mechanical properties of the ACM are preserved upon implantation and cellularization.

  15. Mechanical Properties of Non-Accreting Neutron Star Crusts

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey L.; Heyl, J. S.

    2013-01-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from Soft Gamma-ray Repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ˜0.1 and a shear modulus of ˜1030 dyne cm-2 at a density of ρ = 1014g cm-3 for simulations with an initially perfect BCC lattice. With these crustal properties and the observed properties of PSR J2124-3358 the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone can not be ruled out for triggering the energy in SGR bursts.

  16. Mechanical properties of non-accreting neutron star crusts

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey; Heyl, Jeremy

    2012-11-01

    The mechanical properties of a neutron star crust, such as breaking strain and shear modulus, have implications for the detection of gravitational waves from a neutron star as well as bursts from soft Gamma-ray repeaters (SGRs). These properties are calculated here for three different crustal compositions for a non-accreting neutron star that results from three different cooling histories, as well as for a pure iron crust. A simple shear is simulated using molecular dynamics to the crustal compositions by deforming the simulation box. The breaking strain and shear modulus are found to be similar in the four cases, with a breaking strain of ˜0.1 and a shear modulus of ˜1030 dyne cm-2 at a density of ρ = 1014 g cm-3 for simulations with an initially perfect body-centred cubic (BCC) lattice. With these crustal properties and the observed properties of PSR J2124-3358, the predicted strain amplitude of gravitational waves for a maximally deformed crust is found to be greater than the observational upper limits from LIGO. This suggests that the neutron star crust in this case may not be maximally deformed or it may not have a perfect BCC lattice structure. The implications of the calculated crustal properties of bursts from SGRs are also explored. The mechanical properties found for a perfect BCC lattice structure find that crustal events alone cannot be ruled out for triggering the energy in SGR bursts.

  17. Floc properties of polyaluminum ferric chloride in water treatment: The effect of Al/Fe molar ratio and basicity.

    PubMed

    Cao, Baichuan; Gao, Baoyu; Wang, Mengmeng; Sun, Xiaomei; Wang, Jin

    2015-11-15

    Producing flocs with desired properties is significant for contaminants removal in water treatment works. In this study, an inorganic composite coagulant, polyaluminum ferric chloride (PAFC), was prepared and used in surface water treatment, and the influence of Al/Fe molar ratio and basicity (B) on floc properties was investigated. The contribution of metal species analysis showed a competition relationship between Al and Fe in the pre-hydrolysis, while the monomeric contents decreased with the increase of B value. The investigation of floc properties was conducted on a laser scattering instrument, in terms of floc size, strength, recovery capacity and fractal dimension (Df). The largest floc size and the highest growth rate was achieved when Al/Fe=7:1 and B=1.5. Floc formed at the Al/Fe ratios of 5:1 and 7:1 were considered to be more compact. Meanwhile, the Df value increased when B value was increased. At Al/Fe=7:1 and B=1.5, strongest flocs were obtained. During the breakage period, the Df value increased. As lower shear was replaced, the floc size decreased continuously, with a further increase of Df value. However, after breakage at higher shear, all of the PAFC flocs showed capacity for regrowth and loose structures were formed.

  18. Ultrasonic evaluation of the physical and mechanical properties of granites.

    PubMed

    Vasconcelos, G; Lourenço, P B; Alves, C A S; Pamplona, J

    2008-09-01

    Masonry is the oldest building material that survived until today, being used all over the world and being present in the most impressive historical structures as an evidence of spirit of enterprise of ancient cultures. Conservation, rehabilitation and strengthening of the built heritage and protection of human lives are clear demands of modern societies. In this process, the use of nondestructive methods has become much common in the diagnosis of structural integrity of masonry elements. With respect to the evaluation of the stone condition, the ultrasonic pulse velocity is a simple and economical tool. Thus, the central issue of the present paper concerns the evaluation of the suitability of the ultrasonic pulse velocity method for describing the mechanical and physical properties of granites (range size between 0.1-4.0 mm and 0.3-16.5 mm) and for the assessment of its weathering state. The mechanical properties encompass the compressive and tensile strength and modulus of elasticity, and the physical properties include the density and porosity. For this purpose, measurements of the longitudinal ultrasonic pulse velocity with distinct natural frequency of the transducers were carried out on specimens with different size and shape. A discussion of the factors that induce variations on the ultrasonic velocity is also provided. Additionally, statistical correlations between ultrasonic pulse velocity and mechanical and physical properties of granites are presented and discussed. The major output of the work is the confirmation that ultrasonic pulse velocity can be effectively used as a simple and economical nondestructive method for a preliminary prediction of mechanical and physical properties, as well as a tool for the assessment of the weathering changes of granites that occur during the serviceable life. This is of much interest due to the usual difficulties in removing specimens for mechanical characterization.

  19. An Introduction to the Mechanical Properties of Ceramics

    NASA Astrophysics Data System (ADS)

    Green, David J.

    1998-09-01

    Over the past twenty-five years ceramics have become key materials in the development of many new technologies as scientists have been able to design these materials with new structures and properties. An understanding of the factors that influence their mechanical behavior and reliability is essential. This book will introduce the reader to current concepts in the field. It contains problems and exercises to help readers develop their skills. This is a comprehensive introduction to the mechanical properties of ceramics, and is designed primarily as a textbook for advanced undergraduates in materials science and engineering. It will also be of value as a supplementary text for more general courses and to industrial scientists and engineers involved in the development of ceramic-based products, materials selection and mechanical design.

  20. Chirality-Mediated Mechanical and Structural Properties of Oligopeptide Hydrogels

    SciTech Connect

    Taraban, Marc B.; Feng, Yue; Hammouda, Boualem; Hyland, Laura L.; Yu, Y. Bruce

    2012-10-29

    The origin and the effects of homochirality in the biological world continuously stimulate numerous hypotheses and much debate. This work attempts to look at the biohomochirality issue from a different angle - the mechanical properties of the bulk biomaterial and their relation to nanoscale structures. Using a pair of oppositely charged peptides that co-assemble into hydrogels, we systematically investigated the effect of chirality on the mechanical properties of these hydrogels through different combinations of syndiotactic and isotactic peptides. It was found that homochirality confers mechanical advantage, resulting in a higher elastic modulus and strain yield value. Yet, heterochirality confers kinetic advantage, resulting in faster gelation. Structurally, both homochiral and heterochiral hydrogels are made of fibers interconnected by lappet-like webs, but the homochiral peptide fibers are thicker and denser. These results highlight the possible role of biohomochirality in the evolution and/or natural selection of biomaterials.

  1. Mechanical Properties of Nanotextured Titanium Orthopedic Screws for Clinical Applications.

    PubMed

    Descamps, Stephane; Awitor, Komla O; Raspal, Vincent; Johnson, Matthew B; Bokalawela, Roshan S P; Larson, Preston R; Doiron, Curtis F

    2013-06-01

    In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and [Formula: see text]. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.

  2. Nano-palpation AFM and its quantitative mechanical property mapping.

    PubMed

    Nakajima, Ken; Ito, Makiko; Wang, Dong; Liu, Hao; Nguyen, Hung Kim; Liang, Xiaobin; Kumagai, Akemi; Fujinami, So

    2014-06-01

    We review nano-palpation atomic force microscopy, which offers quantitative mechanical property mapping especially for soft materials. The method measures force-deformation curves on the surfaces of soft materials. The emphasis is placed on how both Hertzian and Derjaguin-Muller-Toporov contact mechanics fail to reproduce the experimental curves and, alternatively, how the Johnson-Kendall-Roberts model does. We also describe the force-volume technique for obtaining a two-dimensional map of mechanical properties, such as the elastic modulus and adhesive energy, based on the above-mentioned analysis. Finally, we conclude with several counterpart measurements, which describe the viscoelastic nature of soft materials, and give examples, including vulcanized isoprene rubber and the current status of ISO standardization.

  3. Mechanical Properties of Iron Alumininides Intermetallic Alloy with Molybdenum Addition

    SciTech Connect

    Zuhailawati, H.; Fauzi, M. N. A.

    2010-03-11

    In this work, FeAl-based alloys with and without molybdenum addition were fabricated by sintering of mechanically alloyed powders in order to investigate the effect of molybdenum on iron aluminide mechanical properties. Bulk samples were prepared by mechanical alloying for 4 hours, pressing at 360 MPa and sintering at 1000 deg. C for 2 hours. The specimens were tested in compression at room temperature using Instron machine. The phase identification and microstructure of the consolidated material was examined by x-ray diffraction and scanning electron microscope correspondingly. Results show that 2.5 wt%Mo addition significantly increased the ultimate stress and ultimate strain in compressive mode due to solid solution hardening. However, the addition of Mo more than 2.5 wt% was accompanied by a reduction in both properties caused by the presence of Mo-rich precipitate particles.

  4. Mechanical Properties of Materials with Nanometer Scale Microstructures

    SciTech Connect

    William D. Nix

    2004-10-31

    We have been engaged in research on the mechanical properties of materials with nanometer-scale microstructural dimensions. Our attention has been focused on studying the mechanical properties of thin films and interfaces and very small volumes of material. Because the dimensions of thin film samples are small (typically 1 mm in thickness, or less), specialized mechanical testing techniques based on nanoindentation, microbeam bending and dynamic vibration of micromachined structures have been developed and used. Here we report briefly on some of the results we have obtained over the past three years. We also give a summary of all of the dissertations, talks and publications completed on this grant during the past 15 years.

  5. One of the Distinctive Properties of Ionic Liquids over Molecular Solvents and Inorganic Salts: Enhanced Basicity Stemming from the Electrostatic Environment and "Free" Microstructure

    SciTech Connect

    Yang, Qiwei; Xing, Huabin; Bao, Zongbi; Su, Baogen; Zhang, Zhiguo; Yang, Yiwen; Dai, Sheng; Ren, Qilong

    2014-01-01

    The basicity of ionic liquids (ILs) underlies many important IL-based processes including the dissolution and conversion of cellulose, the capture of CO2, and metal catalysis. In this work, we have disclosed the nature of the basicity of ILs, i.e., the difference between the basicity of IL and the basicity of the molecular solvent and inorganic salt, through a quantitative electrostatic and electronic analysis of the molecular surface for the first time. The results reveal one of the distinctive properties of ILs (enhanced basicity over molecular solvents and inorganic salts with the same basic site) stemming from their special electrostatic environment and microstructure. The enhancement is significant, from either the electrostatic aspect or the covalent aspect of basicity. The peculiar electrostatic environment of ILs leads to stronger basicity than similar molecular solvents, and the relatively freer microstructure of ILs contributes to the enhancement of basicity over their inorganic analogues. These results are highly instructive for better understanding the unique value of ILs and designing novel ILs to improve the efficiency of basicity-related processes.

  6. Mechanical Properties of the TiAl IRIS Alloy

    NASA Astrophysics Data System (ADS)

    Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

    2016-12-01

    This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

  7. Acidic and basic properties of zeolite-containing cracking catalyst in the process of butene-1 isomerization

    NASA Astrophysics Data System (ADS)

    Mursalova, L. A.; Guseinova, E. A.; Adzhamov, K. Yu.

    2016-08-01

    The process of butene-1 isomerization in the presence of two groups of samples of zeolite-containing catalyst (ZCC) that earlier participated in the traditional and oxidative catalytic cracking of vacuum gasoil is investigated. It is established that the nature of the reaction mixture and conditions of the cracking process are key factors in forming the acidic and basic properties of the catalyst. It is shown that the highest activity in the butene-1 isomerization into cis-/ trans-butene-2 is demonstrated by ZCC samples that participated in the oxidative catalytic cracking (oxycracking). It is suggested that the enhanced catalytic activity of this group of ZCC samples was related to the availability of acid-base centers in the form of radical-like oxygen along with protic- and aprotic-type acidic centers in the structure of the oxidative compaction products.

  8. Structures and Mechanical Properties of Natural and Synthetic Diamonds

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1998-01-01

    A revolution in the diamond technology is in progress, as the low-pressure process becomes an industrial reality. It will soon be possible to take advantage of the demanding properties of diamond to develop a myriad of new applications, particularly for self-lubricating, wear-resistant, and superhard coatings. The production of large diamond films or sheets at low cost, a distinct possibility in the not-too-distant future, may drastically change tribology technology, particularly regarding solid lubricants and lubricating materials and systems. This paper reviews the structures and properties of natural and synthetic diamonds to gain a better understanding of the tribological properties of diamond and related materials. Atomic and crystal structure, impurities, mechanical properties, and indentation hardness of diamond are described.

  9. Dielectric breakdown properties of hot SF6/He mixtures predicted from basic data

    NASA Astrophysics Data System (ADS)

    Wang, Weizong; Tu, Xin; Mei, Danhua; Rong, Mingzhe

    2013-11-01

    Sulfur hexafluoride (SF6) gas has a quite high global warming potential and hence it is required that applying any substitute for SF6 gas. Much interest in the use of a mixture of helium and SF6 as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF6. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF6/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF6 and pure hot He and experimental results and previous calculations. The addition of He to SF6 was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF6/He mixtures.

  10. Basic properties and potential regulators of the apical K+ channel in macula densa cells

    PubMed Central

    1994-01-01

    These studies examine the properties of an apical potassium (K+) channel in macula densa cells, a specialized group of cells involved in tubuloglomerular feedback signal transmission. To this end, individual glomeruli with thick ascending limbs (TAL) and macula densa cells were dissected from rabbit kidney and the TAL covering macula densa cells was removed. Using patch clamp techniques, we found a high density (up to 54 channels per patch) of K+ channels in the apical membrane of macula densa cells. An inward conductance of 41.1 +/- 4.8 pS was obtained in cell-attached patches (patch pipette, 140 mM K+). In inside- out patches (patch pipette, 140 mM; bath, 5 mM K+), inward currents of 1.1 +/- 0.1 pA (n = 11) were observed at 0 mV and single channel current reversed at a pipette potential of -84 mV giving a permeability ratio (PK/PNa) of over 100. In cell-attached patches, mean channel open probability (N,Po, where N is number of channels in the patch and Po is single channel open probability) was unaffected by bumetanide, but was reduced from 11.3 +/- 2.7 to 1.6 +/- 1.3 (n = 5, p < 0.02) by removal of bath sodium (Na+). Simultaneous removal of bath Na+ and calcium (Ca2+) prevented the Na(+)-induced decrease in N.Po indicating that the effect of Na+ removal on N.Po was probably mediated by stimulation of Ca2+ entry. This interpretation was supported by studies where ionomycin, which directly increases intracellular Ca2+, produced a fall in N.Po from 17.8 +/- 4.0 to 5.9 +/- 4.1 (n = 7, p < 0.02). In inside- out patches, the apical K+ channel was not sensitive to ATP but was directly blocked by 2 mM Ca2+ and by lowering bath pH from 7.4 to 6.8. These studies constitute the first single channel observations on macula densa cells and establish some of the characteristics and regulators of this apical K+ channel. This channel is likely to be involved in macula densa transepithelial Cl- transport and perhaps in the tubuloglomerular feedback signaling process. PMID

  11. Aminosilanes grafted to basic alumina as CO2 adsorbents--role of grafting conditions on CO2 adsorption properties.

    PubMed

    Bali, Sumit; Leisen, Johannes; Foo, Guo Shiou; Sievers, Carsten; Jones, Christopher W

    2014-11-01

    Solid oxide-supported amine sorbents for CO2 capture are amongst the most rapidly developing classes of sorbent materials for CO2 capture. Herein, basic γ supports are used as hosts for amine sites through the grafting of 3-aminopropyltrimethoxysilane to the alumina surface under a variety of conditions, yielding the expected surface-grafted alkylamine groups, as demonstrated by FTIR spectroscopy and (29)Si and (13)C cross-polarization magic-angle spinning (CPMAS NMR) spectroscopy. Grafting amine sites on the surface in the presence of water leads to a high density of amine sites on the surface whereas simultaneously creating a unique type of aluminum species on the surface, as demonstrated by both 1D and 2D (27)Al MAS NMR spectroscopy. The thus prepared sorbents result in higher CO2 adsorption capacities and amine efficiencies compared to sorbents prepared in the absence of water or similar amine loading sorbents prepared using silica supports. In situ FTIR spectra of the sorbents exposed to CO2 at various pressures show no distinct difference in the nature of the adsorbed CO2 species on alumina- versus silica-supported amines, whereas water adsorption isotherms show that the improved performance of the amine-grafted alumina support is not a consequence of retained water on the more hydrophobic aminoalumina materials. The findings demonstrate that amine-grafted, basic alumina materials can be tuned to be more efficient than the corresponding silica-supported materials at comparable amine loadings, further demonstrating that the properties of amine sites can be tuned by controlling or adjusting the support surface properties.

  12. DNA origami compliant nanostructures with tunable mechanical properties.

    PubMed

    Zhou, Lifeng; Marras, Alexander E; Su, Hai-Jun; Castro, Carlos E

    2014-01-28

    DNA origami enables fabrication of precise nanostructures by programming the self-assembly of DNA. While this approach has been used to make a variety of complex 2D and 3D objects, the mechanical functionality of these structures is limited due to their rigid nature. We explore the fabrication of deformable, or compliant, objects to establish a framework for mechanically functional nanostructures. This compliant design approach is used in macroscopic engineering to make devices including sensors, actuators, and robots. We build compliant nanostructures by utilizing the entropic elasticity of single-stranded DNA (ssDNA) to locally bend bundles of double-stranded DNA into bent geometries whose curvature and mechanical properties can be tuned by controlling the length of ssDNA strands. We demonstrate an ability to achieve a wide range of geometries by adjusting a few strands in the nanostructure design. We further developed a mechanical model to predict both geometry and mechanical properties of our compliant nanostructures that agrees well with experiments. Our results provide a basis for the design of mechanically functional DNA origami devices and materials.

  13. Spatial memory and path integration studied by self-driven passive linear displacement. I. Basic properties.

    PubMed

    Israël, I; Grasso, R; Georges-Francois, P; Tsuzuku, T; Berthoz, A

    1997-06-01

    According to path integration, the brain is able to compute the distance of a traveled path. In this research we applied our previously reported method for studying memory of linear distance, a crucial mechanism in path integration; our method is based on the overt reconstruction of a passive transport. Passive transport is a special case of navigation in which no active control is performed. Blindfolded subjects were first asked to travel 2 m forward, in darkness, by driving with a joystick the robot on which they were seated. The results show that all subjects but two undershot this distance, i.e., overestimated their own displacement. Then, subjects were submitted to a passive linear forward displacement along 2, 4, 6, 8, or 10 m, and had to reproduce the same distance, still blindfolded. The results show that the distance of the stimulus was accurately reproduced, as well as stimulus duration, peak velocity, and velocity profile. In this first condition, the imposed velocity profile was triangular and therefore stimulus distance and duration were correlated. In a second condition, it was shown that distance was correctly reproduced also when the information about stimulus duration was kept constant. Here, different velocity profiles were used as stimuli, and most subjects also reproduced the velocity profile. Statistical analyses indicated that distance was not reproduced as a consequence of duration, peak velocity, or velocity profile reproduction, but was uniquely correlated to stimulus distance. The previous hypothesis of a double integration of the otolith signal to provide a distance estimate can explain our results. There was a large discrepancy between the accuracy with which the subjects matched the velocity profiles and that of distance reproduction. It follows that, whereas the dynamics of passive motion are stored and available to further use, distance is independently estimated. It is concluded that vestibular and somatosensory signals excited by

  14. Mechanical properties of Municipal Solid Waste by SDMT

    SciTech Connect

    Castelli, Francesco; Maugeri, Michele

    2014-02-15

    Highlights: • The adoption of the SDMT for the measurements of MSW properties is proposed. • A comparison between SDMT results and laboratory tests was carried out. • A good reliability has been found in deriving waste properties by SDMT. • Results seems to be promising for the friction angle and Young’s modulus evaluation. - Abstract: In the paper the results of a geotechnical investigation carried on Municipal Solid Waste (MSW) materials retrieved from the “Cozzo Vuturo” landfill in the Enna area (Sicily, Italy) are reported and analyzed. Mechanical properties were determined both by in situ and laboratory large-scale one dimensional compression tests. While among in situ tests, Dilatomer Marchetti Tests (DMT) is used widely in measuring soil properties, the adoption of the DMT for the measurements of MSW properties has not often been documented in literature. To validate its applicability for the estimation of MSW properties, a comparison between the seismic dilatometer (SDMT) results and the waste properties evaluated by laboratory tests was carried out. Parameters for “fresh” and “degraded waste” have been evaluated. These preliminary results seems to be promising as concerns the assessment of the friction angle of waste and the evaluation of the S-wave in terms of shear wave velocity. Further studies are certainly required to obtain more representative values of the elastic parameters according to the SDMT measurements.

  15. Mechanical Properties of Nanostructured Materials Determined Through Molecular Modeling Techniques

    NASA Technical Reports Server (NTRS)

    Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The potential for gains in material properties over conventional materials has motivated an effort to develop novel nanostructured materials for aerospace applications. These novel materials typically consist of a polymer matrix reinforced with particles on the nanometer length scale. In this study, molecular modeling is used to construct fully atomistic models of a carbon nanotube embedded in an epoxy polymer matrix. Functionalization of the nanotube which consists of the introduction of direct chemical bonding between the polymer matrix and the nanotube, hence providing a load transfer mechanism, is systematically varied. The relative effectiveness of functionalization in a nanostructured material may depend on a variety of factors related to the details of the chemical bonding and the polymer structure at the nanotube-polymer interface. The objective of this modeling is to determine what influence the details of functionalization of the carbon nanotube with the polymer matrix has on the resulting mechanical properties. By considering a range of degree of functionalization, the structure-property relationships of these materials is examined and mechanical properties of these models are calculated using standard techniques.

  16. Mechanical Properties in a Bamboo Fiber/PBS Biodegradable Composite

    NASA Astrophysics Data System (ADS)

    Ogihara, Shinji; Okada, Akihisa; Kobayashi, Satoshi

    In recent years, biodegradable plastics which have low effect on environment have been developed. However, many of them have lower mechanical properties than conventional engineering plastics. Reinforcing them with a natural fiber is one of reinforcing methods without a loss of their biodegradability. In the present study, we use a bamboo fiber as the reinforcement and polybutylenesuccinate (PBS) as the matrix. We fabricate long fiber unidirectional composites and cross-ply laminate with different fiber weight fractions (10, 20, 30, 40 and 50wt%). We conduct tensile tests to evaluate the mechanical properties of these composites. In addition, we measure bamboo fiber strength distribution. We discuss the experimentally-obtained properties based on the mechanical properties of the constituent materials. Young's modulus and tensile strength in unidirectional composite and cross-ply laminate increase with increasing fiber weight fraction. However, the strain at fracture showed decreasing tendency. Young's modulus in fiber and fiber transverse directions are predictable by the rules of mixture. Tensile strength in fiber direction is lower than Curtin's prediction of strength which considers distribution of fiber strength. Young's modulus in cross-ply laminate is predictable by the laminate theory. However, analytical prediction of Poisson's ratio in cross-ply laminate by the laminate theory is lower than the experimental results.

  17. Mechanical properties and microstructure of centrifugally cast alloy 718

    NASA Astrophysics Data System (ADS)

    Michel, D. J.; Smith, H. H.

    1985-07-01

    The relationship between the microstructure and mechanical properties of alloy 718 was investigated for two discs centrifugally cast at 50 and 200 rpm and given a duplex age heat treatment. The results of mechanical property tests at temperatures from 426 to 649 °C showed that the tensile yield and ultimate strength levels of both castings were similar. However, the creep-rupture properties were considerably enhanced for the casting produced at 200 rpm. Comparison of the radial and transverse creep properties of each disc indicated that creep life was generally independent of orientation, but ductility was greatest for specimens oriented transverse to the radial direction of the casting. Fatigue crack propagation performance was not greatly influenced by orientation or mold speed parameters and was comparable to wrought alloy 718 when compared on the basis of stress intensity factor range. The centrifugal casting process was found to produce a homogeneous microstructure free of porosity but with the expected segregation of solute alloying elements to Laves and carbide phases. The effect of the as-cast microstructure on the mechanical behavior and the potential influence of hot isostatic pressing to improve the microstructure are discussed.

  18. Evolution of mechanical properties in ErT2 films.

    SciTech Connect

    Browning, James Frederick; Bond, Gillian Mary; Knapp, James Arthur

    2010-04-01

    The mechanical properties of rare earth tritide films evolve as tritium decays into {sup 3}He, which forms bubbles that influence long-term film stability in applications such as neutron generators. Ultralow load nanoindentation, combined with finite-element modeling to separate the mechanical properties of the thin films from their substrates, has been used to follow the mechanical properties of model ErT{sub 2} films as they aged. The size of the growing {sup 3}He bubbles was followed with transmission electron microscopy, while ion beam analysis was used to monitor total T and {sup 3}He content. The observed behavior is divided into two regimes: a substantial increase in layer hardness but elasticity changed little over {approx}18 months, followed by a decrease in elastic stiffness and a modest decease in hardness over the final 24 months. We show that the evolution of properties is explained by a combination of dislocation pinning by the bubbles, elastic softening as the bubbles occupy an increasing fraction of the material, and details of bubble growth modes.

  19. Mechanical properties of several iron-nickel meteorites

    SciTech Connect

    Mulford, Roberta N; El - Dasher, Bassem

    2011-01-06

    Iron-nickel meteorites exhibit a unique lamellar microstructure, consisting of small regions with steep-iron-nickel composition gradients. The microstructure arises as a result of slow cooling in a planetary core or other large mass. The microstructure is further influenced by variable concentrations of other elements such as phosphorous which may have influenced cooling and phase separation. Mechanical properties of these composite structures have been investigated using Vickers and spherical indentation, x-ray fluorescence, and EBSD. Direct observation of mechanical properties in these highly structured materials provides a valuable supplement to bulk measurements, which frequently exhibit large variation in dynamic properties, even within a single sample. 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. This was ascribed to the extreme work-hardening evident in the EBSD measurements. Additional specimens from the Canyon Diablo fall (type IAB, coarse octahedrite) and several fine octahedrite meteorites, from the Muonionalusta meteorite (IVA) and Gibeon fall (IVA), have been examined to establish a range of error on the previously measured yield, to determine the extent to which deformation upon reentry contributes to yield, and to establish the degree to which the strength varies as a function of microstructure.

  20. Imaging-Based Methods for Non-invasive Assessment of Bone Properties Influenced by Mechanical Loading.

    PubMed

    Macintyre, Norma J; Lorbergs, Amanda L

    2012-01-01

    Purpose: To describe the most common in vivo imaging-based research tools used to assess bone properties that are influenced by mechanical loading associated with exercise, habitual physical activity, or disease states. Bone is a complex metabolically active tissue that adapts to changes in mechanical loading by altering the amount and spatial organization of mineral. Method: Using a narrative review design, the authors provide an overview of bone biology and biomechanics to emphasize the importance of bone size scale, porosity, and degree of mineralization when interpreting measures acquired using quantitative ultrasound (QUS), dual-energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI), and finite element analysis (FEA). For each imaging modality, basic imaging principles, typical outcome measures associated with changes in mechanical loading, and salient features for physiotherapists are described. Main Results: While each imaging modality has strengths and limitations, currently CT-based methods are best suited for determining the effects of mechanical loading on bone properties—particularly in the peripheral skeleton. Conclusions: Regardless of the imaging technology used, the physiotherapist must carefully consider the assumptions of the imaging-based method, the clinical context, the nature of the change in mechanical loading, and the expected time course for change in bone properties.

  1. Mechanical properties of high-temperature brazed titanium materials

    SciTech Connect

    Lugscheider, E.; Broich, U.

    1995-05-01

    The mechanical properties of commercial titanium CPTi and Ti-Al6-V4 joints, brazed with Ti-based filler metals in the system Ti(Zr)-Cu-Ni-(Pd) are evaluated by tensile test at various temperatures, as well as by fatigue test at room temperature. The influence of the microstructure in the brazing zone on the mechanical properties of the joints was assessed by conducting metallographic analysis. A vacuum furnace and an induction heating furnace were used for the production of the metallographic and tensile samples. The results from the mechanical and metallographic investigations revealed a strong dependence of the tensile strength of the titanium joints on the microstructure of the brazing zone. The presence of the brittle intermetallic Ti-Cu and Ti-Ni phases in the brazing zone leads to the weakening of the joint. However, for the formation of these intermetallic phases can be avoided by using adequate brazing process parameters and by optimizing the joint clearance. In that case, it is possible to fabricate titanium joints with Ti-based filler metals that have excellent mechanical properties comparable to those of the base metal.

  2. Loops determine the mechanical properties of mitotic chromosomes

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Heermann, Dieter W.

    2013-03-01

    In mitosis, chromosomes undergo a condensation into highly compacted, rod-like objects. Many models have been put forward for the higher-order organization of mitotic chromosomes including radial loop and hierarchical folding models. Additionally, mechanical properties of mitotic chromosomes under different conditions were measured. However, the internal organization of mitotic chromosomes still remains unclear. Here we present a polymer model for mitotic chromosomes and show how chromatin loops play a major role for their mechanical properties. The key assumption of the model is the ability of the chromatin fibre to dynamically form loops with the help of binding proteins. Our results show that looping leads to a tight compaction and significantly increases the bending rigidity of chromosomes. Moreover, our qualitative prediction of the force elongation behaviour is close to experimental findings. This indicates that the internal structure of mitotic chromosomes is based on self-organization of the chromatin fibre. We also demonstrate how number and size of loops have a strong influence on the mechanical properties. We suggest that changes in the mechanical characteristics of chromosomes can be explained by an altered internal loop structure. YZ gratefully appreciates funding by the German National Academic Foundation (Studienstiftung des deutschen Volkes) and support by the Heidelberg Graduate School for Mathematical and Computational Methods in the Sciences (HGS MathComp).

  3. Effects of sintering atmosphere on the physical and mechanical properties of modified BOF slag glass

    NASA Astrophysics Data System (ADS)

    Dai, Wen-bin; Li, Yu; Cang, Da-qiang; Zhou, Yuan-yuan; Fan, Yong

    2014-05-01

    This study proposes an efficient way to utilize all the chemical components of the basic oxygen furnace (BOF) slag to prepare high value-added glass-ceramics. A molten modified BOF slag was converted from the melting BOF slag by reducing it and separating out iron component in it, and the modified BOF slag was then quenched in water to form glasses with different basicities. The glasses were subsequently sintered in the temperature range of 600-1000°C in air or nitrogen atmosphere for 1 h. The effects of different atmospheres on the physical and mechanical properties of sintered samples were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and by conducting experiment on evaluating the sintering shrinkage, water absorption and bulk density. It is found that the kinetics of the sintering process is significantly affected by sintering atmosphere. In particular, compared with sintering in air atmosphere, sintering in N2 atmosphere promotes the synergistic growth of pyroxene and melilite crystalline phases, which can contribute to better mechanical properties and denser microstructure.

  4. Woven glass fabric reinforced laminates based on polyolefin wastes: Thermal, mechanical and dynamic-mechanical properties

    NASA Astrophysics Data System (ADS)

    Russo, Pietro; Acierno, Domenico; Simeoli, Giorgio; Lopresto, Valentina

    2014-05-01

    Potentialities of polyolefin wastes in place of virgin polypropylene to produce composite laminates have been investigated. Plaques reinforced with a woven glass fabric were prepared by film-stacking technique and systematically analyzed in terms of thermal, mechanical and dynamic-mechanical properties. In case of PP matrices, the use of a typical compatibilizer to improve the adhesion at the interface has been considered. Thermal properties emphasized the chemical nature of plastic wastes. About mechanical properties, static tests showed an increase of flexural parameters for compatibilized systems due to the coupling effect between grafted maleic anhydride and silane groups on the surface of the glass fabric. These effects, maximized for composites based on car bumper wastes, is perfectly reflected in terms of storage modulus and damping ability of products as determined by single-cantilever bending dynamic tests.

  5. Mechanical properties of normal versus cancerous breast cells

    PubMed Central

    Smelser, Amanda M.; Macosko, Jed C.; O’Dell, Adam P.; Smyre, Scott; Bonin, Keith

    2016-01-01

    A cell’s mechanical properties are important in determining its adhesion, migration, and response to the mechanical properties of its microenvironment and may help explain behavioral differences between normal and cancerous cells. Using fluorescently labeled peroxisomes as microrheological probes, the interior mechanical properties of normal breast cells were compared to a metastatic breast cell line, MDA-MB-231. To estimate the mechanical properties of cell cytoplasms from the motions of their peroxisomes, it was necessary to reduce the contribution of active cytoskeletal motions to peroxisome motion. This was done by treating the cells with blebbistatin, to inhibit myosin II, or with sodium azide and 2-deoxy-D-glucose, to reduce intracellular ATP. Using either treatment, the peroxisomes exhibited normal diffusion or subdiffusion, and their mean squared displacements (MSDs) showed that the MDA-MB-231 cells were significantly softer than normal cells. For these two cell types, peroxisome MSDs in treated and untreated cells converged at high frequencies, indicating that cytoskeletal structure was not altered by the drug treatment. The MSDs from ATP-depleted cells were analyzed by the generalized Stokes–Einstein relation to estimate the interior viscoelastic modulus G* and its components, the elastic shear modulus G′ and viscous shear modulus G″, at angular frequencies between 0.126 and 628rad/s. These moduli are the material coefficients that enter into stress–strain relations and relaxation times in quantitative mechanical models such as the poroelastic model of the interior regions of cancerous and non-cancerous cells. PMID:25929519

  6. Mechanical and tribological properties of ion beam-processed surfaces

    SciTech Connect

    Kodali, Padma

    1998-01-01

    The intent of this work was to broaden the applications of well-established surface modification techniques and to elucidate the various wear mechanisms that occur in sliding contact of ion-beam processed surfaces. The investigation included characterization and evaluation of coatings and modified surfaces synthesized by three surface engineering methods; namely, beam-line ion implantation, plasma-source ion implantation, and DC magnetron sputtering. Correlation among measured properties such as surface hardness, fracture toughness, and wear behavior was also examined. This dissertation focused on the following areas of research: (1) investigating the mechanical and tribological properties of mixed implantation of carbon and nitrogen into single crystal silicon by beam-line implantation; (2) characterizing the mechanical and tribological properties of diamond-like carbon (DLC) coatings processed by plasma source ion implantation; and (3) developing and evaluating metastable boron-carbon-nitrogen (BCN) compound coatings for mechanical and tribological properties. The surface hardness of a mixed carbon-nitrogen implant sample improved significantly compared to the unimplanted sample. However, the enhancement in the wear factor of this sample was found to be less significant than carbon-implanted samples. The presence of nitrogen might be responsible for the degraded wear behavior since nitrogen-implantation alone resulted in no improvement in the wear factor. DLC coatings have low friction, low wear factor, and high hardness. The fracture toughness of DLC coatings has been estimated for the first time. The wear mechanism in DLC coatings investigated with a ruby slider under a contact stress of 1 GPa was determined to be plastic deformation. The preliminary data on metastable BCN compound coatings indicated high friction, low wear factor, and high hardness.

  7. The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

    PubMed

    Gong, Kemeng; Qu, Shuxin; Liu, Yumei; Wang, Jing; Zhang, Yongchao; Jiang, Chongxi; Shen, Ru

    2016-08-01

    Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements.

  8. Micro-mechanical properties of bio-materials

    NASA Astrophysics Data System (ADS)

    Zakiev, V.; Markovsky, A.; Aznakayev, E.; Zakiev, I.; Gursky, E.

    2005-09-01

    Investigation of physical-mechanical characteristics of stomatologic materials (ceramics for crowns, silver amalgam, cements and materials on a polymeric basis) properties by the modern methods and correspondence their physical-mechanical properties to the physical-mechanical properties of native teeth is represented. The universal device "Micron-Gamma" is built for this purpose. This device allows investigate the physical-mechanical characteristics of stomatologic materials (an elastic modulus, micro-hardness, destruction energy, resistance to scratching) by the methods of continuous indentation, scanning and pricking. A new effective method as well as its device application for the investigation of surface layers of materials and their physical-mechanical properties by means of the constant indenting of an indenter is realized. This method is based on the automatic registration of loading (P) on the indenter with the simultaneous measurement of its indentation depth (h). The results of investigations are presented on a loading diagram P=f(h) and as a digital imaging on the PC. This diagram allows get not only more diverse characteristics in the real time regime but also gives new information about the stomatologic material properties. Therefore, we can to investigate the wide range of the physical-mechanical properties of stomatologic materials. "Micron-alpha" is digital detection device for light imaging applications. It enables to detect the very low material surface relief heights and restoration of surface micro topography by a sequence data processing of interferential data of partially coherent light also. "Micron-alpha" allows: to build 2D and 3D imaging of a material surface; to estimate the quantitatively characteristics of a material surface; to observe the imaging interferential pictures both in the white and in the monochromatic light; to carry out the investigation of blood cells, microbes and biological macromolecules profiles. The method allows

  9. Brain Mechanical Property Measurement Using MRE with Intrinsic Activation

    PubMed Central

    Pattison, Adam J.; McGarry, Matthew D.; Perreard, Irina M.; Swienckowski, Jessica G.; Eskey, Clifford J.; Lollis, S. Scott; Paulsen, Keith D.

    2013-01-01

    Problem Addressed Many pathologies alter the mechanical properties of tissue. Magnetic resonance elastography (MRE) has been developed to noninvasively characterize these quantities in vivo. Typically, small vibrations are induced in the tissue of interest with an external mechanical actuator. The resulting displacements are measured with phase contrast sequences and are then used to estimate the underlying mechanical property distribution. Several MRE studies have quantified brain tissue properties. However, the cranium and meninges, especially the dura, are very effective at damping externally applied vibrations from penetrating deeply into the brain. Here, we report a method, termed ‘intrinsic activation’, that eliminates the requirement for external vibrations by measuring the motion generated by natural blood vessel pulsation. Methodology A retrospectively gated phase contrast MR angiography sequence was used to record the tissue velocity at eight phases of the cardiac cycle. The velocities were numerically integrated via the Fourier transform to produce the harmonic displacements at each position within the brain. The displacements were then reconstructed into images of the shear modulus based on both linear elastic and poroelastic models. Results, Significance and Potential Impact The mechanical properties produced fall within the range of brain tissue estimates reported in the literature and, equally important, the technique yielded highly reproducible results. The mean shear modulus was 8.1 kPa for linear elastic reconstructions and 2.4 kPa for poroelastic reconstructions where fluid pressure carries a portion of the stress. Gross structures of the brain were visualized, particularly in the poroelastic reconstructions. Intra-subject variability was significantly less than the inter-subject variability in a study of 6 asymptomatic individuals. Further, larger changes in mechanical properties were observed in individuals when examined over time than when

  10. Genetic Deletion of TREK-1 or TWIK-1/TREK-1 Potassium Channels does not Alter the Basic Electrophysiological Properties of Mature Hippocampal Astrocytes In Situ.

    PubMed

    Du, Yixing; Kiyoshi, Conrad M; Wang, Qi; Wang, Wei; Ma, Baofeng; Alford, Catherine C; Zhong, Shiying; Wan, Qi; Chen, Haijun; Lloyd, Eric E; Bryan, Robert M; Zhou, Min

    2016-01-01

    We have recently shown that a linear current-to-voltage (I-V) relationship of membrane conductance (passive conductance) reflects the intrinsic property of K(+) channels in mature astrocytes. While passive conductance is known to underpin a highly negative and stable membrane potential (V M) essential for the basic homeostatic function of astrocytes, a complete repertoire of the involved K(+) channels remains elusive. TREK-1 two-pore domain K(+) channel (K2P) is highly expressed in astrocytes, and covalent association of TREK-1 with TWIK-1, another highly expressed astrocytic K2P, has been reported as a mechanism underlying the trafficking of heterodimer TWIK-1/TREK-1 channel to the membrane and contributing to astrocyte passive conductance. To decipher the individual contribution of TREK-1 and address whether the appearance of passive conductance is conditional to the co-expression of TWIK-1/TREK-1 in astrocytes, TREK-1 single and TWIK-1/TREK-1 double gene knockout mice were used in the present study. The relative quantity of mRNA encoding other astrocyte K(+) channels, such as Kir4.1, Kir5.1, and TREK-2, was not altered in these gene knockout mice. Whole-cell recording from hippocampal astrocytes in situ revealed no detectable changes in astrocyte passive conductance, V M, or membrane input resistance (R in) in either kind of gene knockout mouse. Additionally, TREK-1 proteins were mainly located in the intracellular compartments of the hippocampus. Altogether, genetic deletion of TREK-1 alone or together with TWIK-1 produced no obvious alteration in the basic electrophysiological properties of hippocampal astrocytes. Thus, future research focusing on other K(+) channels may shed light on this long-standing and important question in astrocyte physiology.

  11. Genetic Deletion of TREK-1 or TWIK-1/TREK-1 Potassium Channels does not Alter the Basic Electrophysiological Properties of Mature Hippocampal Astrocytes In Situ

    PubMed Central

    Du, Yixing; Kiyoshi, Conrad M.; Wang, Qi; Wang, Wei; Ma, Baofeng; Alford, Catherine C.; Zhong, Shiying; Wan, Qi; Chen, Haijun; Lloyd, Eric E.; Bryan, Robert M. Jr.; Zhou, Min

    2016-01-01

    We have recently shown that a linear current-to-voltage (I-V) relationship of membrane conductance (passive conductance) reflects the intrinsic property of K+ channels in mature astrocytes. While passive conductance is known to underpin a highly negative and stable membrane potential (VM) essential for the basic homeostatic function of astrocytes, a complete repertoire of the involved K+ channels remains elusive. TREK-1 two-pore domain K+ channel (K2P) is highly expressed in astrocytes, and covalent association of TREK-1 with TWIK-1, another highly expressed astrocytic K2P, has been reported as a mechanism underlying the trafficking of heterodimer TWIK-1/TREK-1 channel to the membrane and contributing to astrocyte passive conductance. To decipher the individual contribution of TREK-1 and address whether the appearance of passive conductance is conditional to the co-expression of TWIK-1/TREK-1 in astrocytes, TREK-1 single and TWIK-1/TREK-1 double gene knockout mice were used in the present study. The relative quantity of mRNA encoding other astrocyte K+ channels, such as Kir4.1, Kir5.1, and TREK-2, was not altered in these gene knockout mice. Whole-cell recording from hippocampal astrocytes in situ revealed no detectable changes in astrocyte passive conductance, VM, or membrane input resistance (Rin) in either kind of gene knockout mouse. Additionally, TREK-1 proteins were mainly located in the intracellular compartments of the hippocampus. Altogether, genetic deletion of TREK-1 alone or together with TWIK-1 produced no obvious alteration in the basic electrophysiological properties of hippocampal astrocytes. Thus, future research focusing on other K+ channels may shed light on this long-standing and important question in astrocyte physiology. PMID:26869883

  12. Structural and mechanical properties of mandibular condylar bone.

    PubMed

    van Eijden, T M G J; van der Helm, P N; van Ruijven, L J; Mulder, L

    2006-01-01

    The trabecular bone of the mandibular condyle is structurally anisotropic and heterogeneous. We hypothesized that its apparent elastic moduli are also anisotropic and heterogeneous, and depend on trabecular density and orientation. Eleven condyles were scanned with a micro-CT system. Volumes of interest were selected for the construction of finite element models. We simulated compressive and shear tests to determine the principal mechanical directions and the apparent elastic moduli. Compressive moduli were relatively large in directions acting in the sagittal plane, and small in the mediolateral direction. The degree of mechanical anisotropy ranged from 4.7 to 10.8. Shear moduli were largest in the sagittal plane and smallest in the transverse plane. The magnitudes of the moduli varied with the condylar region and were proportional to the bone volume fraction. Furthermore, principal mechanical direction correlated significantly with principal structural direction. It was concluded that variation in trabecular structure coincides with variation in apparent mechanical properties.

  13. Enzymatic treatment of mechanical pulp fibers for improving papermaking properties.

    PubMed

    Wong, K K; Richardson, J D; Mansfield, S D

    2000-01-01

    Three enzyme preparations (crude cellulase, laccase, and proteinase) were evaluated for their potential to improve the papermaking properties of mechanical pulp. After treating a long fibre-rich fraction of the pulp with enzyme, the fibres were recombined with untreated fines for handsheet making and testing. None of the enzymes altered the retention of fines or the consolidation of the furnish mix during handsheet formation. All three enzymes increased tensile stiffness index, which is a measure of the initial resistance of the handsheets to strain. Only the laccase preparation, an enzyme that modifies pulp lignin, consistently increased fibre bonding to enhance other strength properties of the handsheets.

  14. Constitutive Modeling of the Mechanical Properties of Optical Fibers

    NASA Technical Reports Server (NTRS)

    Moeti, L.; Moghazy, S.; Veazie, D.; Cuddihy, E.

    1998-01-01

    Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

  15. Imaging and mechanical property measurements of kerogen via nanoindentation

    NASA Astrophysics Data System (ADS)

    Zeszotarski, Jonathan C.; Chromik, Richard R.; Vinci, Richard P.; Messmer, Marie C.; Michels, Raymond; Larsen, John W.

    2004-10-01

    Most analyses of kerogens rely on samples that have been isolated by dissolving the rock matrix. The properties of the kerogen before and after such isolation may be different and all sample orientation information is lost. We report a method of measuring kerogen mechanical properties in the rock matrix without isolation. An atomic force microscope (AFM) based nanoindenter is used to measure the hardness and reduced modulus of the kerogen within Woodford shale. The same instrument also provides useful images of polished rock sections on a submicrometer scale. Measurements were carried out both parallel and perpendicular to the bedding plane.

  16. Review of research on the mechanical properties of the human tooth

    PubMed Central

    Zhang, Ya-Rong; Du, Wen; Zhou, Xue-Dong; Yu, Hai-Yang

    2014-01-01

    ‘Bronze teeth' reflect the mechanical properties of natural teeth to a certain extent. Their mechanical properties resemble those of a tough metal, and the gradient of these properties lies in the direction from outside to inside. These attributes confer human teeth with effective mastication ability. Understanding the various mechanical properties of human teeth and dental materials is the basis for the development of restorative materials. In this study, the elastic properties, dynamic mechanical properties (visco-elasticity) and fracture mechanical properties of enamel and dentin were reviewed to provide a more thorough understanding of the mechanical properties of human teeth. PMID:24743065

  17. Electrical and dielectric properties of bovine trabecular bone--relationships with mechanical properties and mineral density.

    PubMed

    Sierpowska, J; Töyräs, J; Hakulinen, M A; Saarakkala, S; Jurvelin, J S; Lappalainen, R

    2003-03-21

    Interrelationships of trabecular bone electrical and dielectric properties with mechanical characteristics and density are poorly known. While electrical stimulation is used for healing fractures, better understanding of these relations has clinical importance. Furthermore, earlier studies have suggested that bone electrical and dielectric properties depend on the bone density and could, therefore, be used to predict bone strength. To clarify these issues, volumetric bone mineral density (BMDvol), electrical and dielectric as well as mechanical properties were determined from 40 cylindrical plugs of bovine trabecular bone. Phase angle, relative permittivity, loss factor and conductivity of wet bovine trabecular bone were correlated with Young's modulus, yield stress, ultimate strength, resilience and BMDvol. The reproducibility of in vitro electrical and dielectric measurements was excellent (standardized coefficient of variation less than 1%, for all parameters), especially at frequencies higher than 1 kHz. Correlations of electrical and dielectric parameters with the bone mechanical properties or density were frequency-dependent. The relative permittivity showed the strongest linear correlations with mechanical parameters (r > 0.547, p < 0.01, n = 40, at 50 kHz) and with BMDvol (r = 0.866, p < 0.01, n = 40, at 50 kHz). In general, linear correlations between relative permittivity and mechanical properties or BMDvol were highest at frequencies over 6 kHz. In addition, a significant site-dependent variation of electrical and dielectric characteristics, mechanical properties and BMDvol was revealed in bovine femur (p < 0.05, Kruskall-Wallis H-test). Based on the present results, we conclude that the measurement of electrical and dielectric properties provides quantitative information that is related to bone quantity and quality.

  18. Spectroscopic comparison of effects of electron radiation on mechanical properties of two polyimides

    NASA Technical Reports Server (NTRS)

    Long, Edward R., Jr.; Long, Sheila Ann T.

    1987-01-01

    The differences in the radiation durabilities of two polyimide materials, Du Pont Kapton and General Electric Ultem, are compared. An explanation of the basic mechanisms which occur during exposure to electron radiation from analyses of infrared (IR) and electron paramagnetic resonance (EPR) spectroscopic data for each material is provided. The molecular model for Kapton was, in part, established from earlier modeling for Ultem (pp. 1293-1298 of IEEE Transactions on Nuclear Science, December 1984). Techniques for understanding the durability of one complex polymer based on the understanding of a different and equally complex polymer are demonstrated. The spectroscopic data showed that the primary radiation-generated change in the tensile properties of Ultem (a large reduction in tensile elongation) was due to crosslinking, which followed the capture by phenyl radicals of hydrogen atoms removed from gem-dimethyl groups. In contrast, the tensile properties of Kapton remained unchanged because radical-radical recombination, a self-mending process, took place.

  19. Evaluation of the compressive mechanical properties of endoluminal metal stents.

    PubMed

    Schrader, S C; Beyar, R

    1998-06-01

    The mechanical properties of metal stents are important parameters in the consideration of stent design, matched to resist arterial recoil and vascular spasm. The purpose of this study was to develop a system for a standardized quantitative evaluation of the mechanical characteristics of various coronary stents. Several types of stents were compressed by external hydrostatic pressure. The stent diameter was assessed by placing a pair of small ultrasonic sono-crystals on the stent. From pressure-strain diagrams the ultimate strength and radial stiffness for each stent were determined. For all stents, except the MICRO-II and the Wiktor stent, the diameter decreased homogeneously until an ultimate compressive strength was exceeded, causing an abrupt collapse. Expanded to 3 mm, the mechanical behavior of the beStent, the Crown and the Palmaz-Schatz stent (PS153-series) were comparable. The spiral articulated Palmaz-Schatz stent showed twice the strength (1.26 atm) of the PS-153 (0.65 atm). The NIR stent yielded a maximum strength of 1.05 atm. The MICRO-II and the Wiktor stent did not collapse abruptly but rather showed a continuous decline of diameter with increasing external pressure. The Cardiocoil stent behaved in a fully elastic manner and showed the largest radial stiffness. Difference in mechanical properties between stents were documented using a new device specifically developed for that purpose. These mechanical stent parameters may have important clinical implications.

  20. Crosstalk between focal adhesions and material mechanical properties governs cell mechanics and functions.

    PubMed

    Fusco, Sabato; Panzetta, Valeria; Embrione, Valerio; Netti, Paolo A

    2015-09-01

    Mechanical properties of materials strongly influence cell fate and functions. Focal adhesions are involved in the extremely important processes of mechanosensing and mechanotransduction. To address the relationship between the mechanical properties of cell substrates, focal adhesion/cytoskeleton assembly and cell functions, we investigated the behavior of NIH/3T3 cells over a wide range of stiffness (3-1000kPa) using two of the most common synthetic polymers for cell cultures: polyacrylamide and polydimethylsiloxane. An overlapping stiffness region was created between them to compare focal adhesion characteristics and cell functions, taking into account their different time-dependent behavior. Indeed, from a rheological point of view, polyacrylamide behaves like a strong gel (elastically), whereas polydimethylsiloxane like a viscoelastic solid. First, focal adhesion characteristics and dynamics were addressed in terms of material stiffness, then cell spreading area, migration rate and cell mechanical properties were correlated with focal adhesion size and assembly. Focal adhesion size was found to increase in the whole range of stiffness and to be in agreement in the overlapping rigidity region for the investigated materials. Cell mechanics directly correlated with focal adhesion lengths, whereas migration rate followed an inverse correlation. Cell spreading correlated with the substrate stiffness on polyacrylamide hydrogel, while no specific trend was found on polydimethylsiloxane. Substrate mechanics can be considered as a key physical cue that regulates focal adhesion assembly, which in turn governs important cellular properties and functions.

  1. Stretchable polyurethane sponge reinforced magnetorheological material with enhanced mechanical properties

    NASA Astrophysics Data System (ADS)

    Ge, Lin; Xuan, Shouhu; Liao, Guojiang; Yin, Tiantian; Gong, Xinglong

    2015-03-01

    A stretchable magnetorheological material (SMRM) consisting of micro-meter carbonyl iron (CI) particles, low cross-linking polyurethane (PU) polymer and porous PU sponge has been developed. Due to the presence of the PU sponge, the high-performance MR material can be reversibly stretched or bent, just as MR elastomers. When the CI content increases to 80 wt%, the magnetic induced modulus of the MR material can reach as high as 7.34 MPa and the corresponding relative MR effect increases to 820%. A possible strengthening mechanism of the SMRM was proposed. The attractive mechanical properties make the SMRM a promising candidate for future high-performance devices.

  2. Failure criterion for materials with spatially correlated mechanical properties.

    PubMed

    Faillettaz, J; Or, D

    2015-03-01

    The role of spatially correlated mechanical elements in the failure behavior of heterogeneous materials represented by fiber bundle models (FBMs) was evaluated systematically for different load redistribution rules. Increasing the range of spatial correlation for FBMs with local load sharing is marked by a transition from ductilelike failure characteristics into brittlelike failure. The study identified a global failure criterion based on macroscopic properties (external load and cumulative damage) that is independent of spatial correlation or load redistribution rules. This general metric could be applied to assess the mechanical stability of complex and heterogeneous systems and thus provide an important component for early warning of a class of geophysical ruptures.

  3. Structure and mechanical properties of liquid crystalline filaments

    SciTech Connect

    Eremin, Alexey; Nemes, Alexandru; Stannarius, Ralf; Schulz, Mario; Nadasi, Hajnalka; Weissflog, Wolfgang

    2005-03-01

    The formation of stable freely suspended filaments is an interesting peculiarity of some liquid crystal phases. So far, little is known about their structure and stability. Similarly to free-standing smectic films, an internal molecular structure of the mesophase stabilizes these macroscopically well-ordered objects with length to diameter ratios of 10{sup 3} and above. In this paper, we report observations of smectic liquid crystal fibers formed by bent-shaped molecules in different mesophases. Our study, employing several experimental techniques, focuses on mechanical and structural aspects of fiber formation such as internal structure, stability, and mechanical and optical properties.

  4. 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.

  5. Dynamic Mechanical Properties of Natural Rubber/Polyaniline Composites

    NASA Astrophysics Data System (ADS)

    Najidha, S.; Predeep, P.; Saxena, N. S.

    2008-04-01

    The Dynamic Mechanical properties of polymer composite containing Natural Rubber (NR) as the matrix and polyaniline as filler has been studied. The composites were prepared by mechanical mixing in a roll mill and vulcanized in a hot press. The dynamic modulus such as tanδ, storage modulus and loss modulus of the composite were evaluated. The glass transition (Tg) temperature of the Natural Rubber phase in the composite was shifted to lower temperature indicating that the polyaniline content strongly affects the behavior of the composite. Addition of polyaniline lowered the crosslinking degree, but produced a reinforcing effect in the elastomer.

  6. Influence of Water Content on Mechanical Properties of Rock in Both Saturation and Drying Processes

    NASA Astrophysics Data System (ADS)

    Zhou, Zilong; Cai, Xin; Cao, Wenzhuo; Li, Xibing; Xiong, Cheng

    2016-08-01

    Water content has a pronounced influence on the properties of rock materials, which is responsible for many rock engineering hazards, such as landslides and karst collapse. Meanwhile, water injection is also used for the prevention of some engineering disasters like rock-bursts. To comprehensively investigate the effect of water content on mechanical properties of rocks, laboratory tests were carried out on sandstone specimens with different water contents in both saturation and drying processes. The Nuclear Magnetic Resonance technique was applied to study the water distribution in specimens with variation of water contents. The servo-controlled rock mechanics testing machine and Split Hopkinson Pressure Bar technique were used to conduct both compressive and tensile tests on sandstone specimens with different water contents. From the laboratory tests, reductions of the compressive and tensile strength of sandstone under static and dynamic states in different saturation processes were observed. In the drying process, all of the saturated specimens could basically regain their mechanical properties and recover its strength as in the dry state. However, for partially saturated specimens in the saturation and drying processes, the tensile strength of specimens with the same water content was different, which could be related to different water distributions in specimens.

  7. Mechanical properties and failure behaviors of the interface of hybrid graphene/hexagonal boron nitride sheets

    PubMed Central

    Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

    2016-01-01

    Hybrid graphene/h-BN sheet has been fabricated recently and verified to possess unusual physical properties. During the growth process, defects such as vacancies are unavoidably present at the interface between graphene and h-BN. In the present work, typical vacancy defects, which were located at the interface between graphene and h-BN, were studied by density functional theory. The interface structure, mechanical and electronic properties, and failure behavior of the hybrid graphene/h-BN sheet were investigated and compared. The results showed that the formation energy of the defective graphene/h-BN interface basically increased with increasing inflection angles. However, Young’s modulus for all graphene/h-BN systems studied decreased with the increase in inflection angles. The intrinsic strength of the hybrid graphene/h-BN sheets was affected not only by the inflection angles, but also by the type of interface connection and the type of defects. The energy band structure of the hybrid interface could be tuned by applying mechanical strain to the systems. These results demonstrated that vacancies introduced significant effects on the mechanical and electronic properties of the hybrid graphene/h-BN sheet. PMID:27527371

  8. Prediction of Mechanical Properties of Polymers With Various Force Fields

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Clancy, Thomas C.; Gates, Thomas S.

    2005-01-01

    The effect of force field type on the predicted elastic properties of a polyimide is examined using a multiscale modeling technique. Molecular Dynamics simulations are used to predict the atomic structure and elastic properties of the polymer by subjecting a representative volume element of the material to bulk and shear finite deformations. The elastic properties of the polyimide are determined using three force fields: AMBER, OPLS-AA, and MM3. The predicted values of Young s modulus and shear modulus of the polyimide are compared with experimental values. The results indicate that the mechanical properties of the polyimide predicted with the OPLS-AA force field most closely matched those from experiment. The results also indicate that while the complexity of the force field does not have a significant effect on the accuracy of predicted properties, small differences in the force constants and the functional form of individual terms in the force fields determine the accuracy of the force field in predicting the elastic properties of the polyimide.

  9. Quantitative ultrasonic evaluation of mechanical properties of engineering materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    Current progress in the application of ultrasonic techniques to nondestructive measurement of mechanical strength properties of engineering materials is reviewed. Even where conventional NDE techniques have shown that a part is free of overt defects, advanced NDE techniques should be available to confirm the material properties assumed in the part's design. There are many instances where metallic, composite, or ceramic parts may be free of critical defects while still being susceptible to failure under design loads due to inadequate or degraded mechanical strength. This must be considered in any failure prevention scheme that relies on fracture analysis. This review will discuss the availability of ultrasonic methods that can be applied to actual parts to assess their potential susceptibility to failure under design conditions.

  10. A Review of the Mechanical Properties of Concrete Containing Biofillers

    NASA Astrophysics Data System (ADS)

    Ezdiani Mohamad, Mazizah; Mahmood, Ali A.; Min, Alicia Yik Yee; Khalid, Nur Hafizah A.

    2016-11-01

    Sustainable construction is a rapidly increasing research area. Investigators of all backgrounds are using industrial and agro wastes to replace Portland cement in concrete to reduce greenhouse emissions and the corresponding decline in general health. Many types of wastes have been used as cement replacements in concrete including: fly ash, slag and rice husk ash in addition to others. This study investigates the possibility of producing a sustainable approach to construction through the partial replacement of concrete using biofillers. This will be achieved by studying the physical and mechanical properties of two widely available biological wastes in Malaysia; eggshell and palm oil fuel ash (POFA). The mechanical properties tests that were studied and compared are the compression, tensile and flexural tests.

  11. On the mechanical properties of selenite glass nanocomposites

    NASA Astrophysics Data System (ADS)

    Bar, Arun Kr.; Kundu, Ranadip; Roy, Debasish; Bhattacharya, Sanjib

    2016-05-01

    In this paper the room temperature micro-hardness of selenite glass-nanocomposites has been measured using a Vickers and Knoop micro hardness tester where the applied load varies from 0.01N to 0.98 N. A significant indentation size effect was observed for each sample at relatively low indentation test loads. The classical Meyer's law and the proportional specimen resistance model were used to analyze the micro-hardness behavior. It was found that the selenite glass-nanocomposite becomes harder with increasing CuI composition and the work hardening coefficient and mechanical properties like Young modulus, E, were also calculated. Our results open the way for the preparation, application and investigation of significant mechanical properties of new type of glass-nanocomposites.

  12. Computer simulations of the mechanical properties of metals.

    PubMed

    Schiøtz, J; Vegge, T

    1999-01-01

    Atomic-scale computer simulations can be used to gain a better understanding of the mechanical properties of materials. In this paper we demonstrate how this can be done in the case of nanocrystalline copper, and give a brief overview of how simulations may be extended to larger length scales. Nanocrystline metals are metals with grain sizes in the nanometre range, they have a number of technologically interesting properties such as much increased hardness and yield strength. Our simulations show that the deformation mechanisms are different in these materials than in coarse-grained materials. The main deformation is occurring in the grain boundaries, and only little dislocation activity is seen inside the grains. This leads to a hardening of the material as the grain size is increased, and the volume fraction of grain boundaries is decreased.

  13. Ultrasound Study of the Mechanical Properties of the Arterial Wall

    NASA Astrophysics Data System (ADS)

    Bernal Restrepo, Miguel

    Arterial elasticity has become an important predictor of cardiovascular diseases and mortality in the past few of decades. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels. In vivo approaches, even though have shown correlation of diseases and mortality with arterial elasticity in population studies, are not widely used as a clinical tool for the diagnosis and follow up of patients. Ex vivo techniques have focused their efforts on studying the mechanical properties of the arterial tissue in different axes. These techniques are usually destructive testing methods which can not be applied in an in vivo setting. In this work we present two different approaches to the characterization of the mechanical properties of arterial wall. One of the methodologies presented here uses piezoelectric elements attached to the arterial wall to measure the strain and the stresses in two directions (circumferential and longitudinal) as the arteries are pressurized. The second part of this works focuses on a technique that uses ultrasound radiation force to generate mechanical waves in the arterial wall. These waves are measured and analyzed in the frequency domain to determine the different modes of propagation and from there, estimate the material properties of the wall tissue. This technique has a high temporal resolution which will allow the dynamic study of the elastic and viscous properties throughout the heart cycle. At the same time the method posses a high spatial resolution allowing the characterization of different vascular segments within the arterial tree. We are currently working on the implementation of this methodology in a clinical system for the translation into a clinical setting.

  14. Mechanical properties of polymeric composites with carbon dioxide particles

    NASA Astrophysics Data System (ADS)

    Moskalyuk, O. A.; Samsonov, A. M.; Semenova, I. V.; Smirnova, V. E.; Yudin, V. E.

    2017-02-01

    Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO2 raises the flexural modulus of the nanocomposites by 30%.

  15. ORMOSIL thin films: tuning mechanical properties via a nanochemistry approach.

    PubMed

    Palmisano, Giovanni; Le Bourhis, Eric; Ciriminna, Rosaria; Tranchida, Davide; Pagliaro, Mario

    2006-12-19

    The mechanical properties (hardness and elastic modulus) of organically modified silicate thin films can be finely tuned by varying the degree of alkylation and thus the fraction of six- and four-membered siloxane rings in the organosilica matrix. This opens the way to large tunability of parameters that are of crucial practical importance for films that are finding increasing application in numerous fields ranging from microelectronics to chemical sensing.

  16. Mechanical and thermophysical properties of hot-pressed SYNROC B

    SciTech Connect

    Hoenig, C.L.; Newkirk, H.W.; Otto, R.A.; Brady, R.L.; Brown, A.E.; Ulrich, A.R.; Lum, R.C.

    1981-05-06

    The optimal SYNROC compositons for use with commercial waste are reviewed. Large amounts of powder (about 2.5 kg) were prepared by convention al ceramic operations to test the SYNROC concept on a processing scale. Samples, 15.2 cm in diameter, were hot pressed in graphite, and representative samples were cut for microstructural evaluations. Measured mechanical and thermophysical properties did not vary significantly as a function of sample location and were typical of titanate ceramic materials.

  17. High Strain Rate Mechanical Properties of Glassy Polymers

    DTIC Science & Technology

    2012-07-25

    Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2012-008 High Strain Rate...TITLE AND SUBTITLE High Strain Rate Mechanical Properties of Glassy Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...1990s, a range of experimental data has been generated describing the response of glassy polymers to high strain rate loading in compression. More

  18. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    NASA Astrophysics Data System (ADS)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  19. Mechanical properties of D0 Run IIB silicon detector staves

    SciTech Connect

    Lanfranco, Giobatta; Fast, James; /Fermilab

    2001-06-01

    A proposed stave design for the D0 Run IIb silicon tracker outer layers featuring central cooling channels and a composite shell mechanical structure is evaluated for self-deflection and deflection due to external loads. This paper contains an introduction to the stave structure, a section devoted to composite lamina and laminate properties and finally a section discussing the beam deflections expected for assembled staves using these laminates.

  20. Interface Characteristics and the Mechanical Properties of Metal Matrix Composites.

    DTIC Science & Technology

    1987-09-28

    oxide were identified to most probably be y - A120 3 or the MgAI20 4 type spinel. Details are given in Appendix K. Summary -. The research reported ...Zecas aT Austit. INTERFACE CHARACTERISTICS AND THE MECHANICAL PROPERTIES OF METAL MATRIX COMPOSITES UTCMSE-87-3 Office of Naval Research Technical Report ...THIS PAGE (When Date Entered) READ INSTRUCTIONSREPORT DOCUMENTATION PAGE I RE COSPLETIOR~BEFORE MPLETING FORM VI REPORT NUMBER 2. GOVT ACCESSION NO., 3

  1. Effect of Preheating on the Mechanical Properties of Resin Composites

    PubMed Central

    Uctasli, Mine Betül; Arisu, Hacer Deniz; Lasilla, Lippo VJ; Valittu, Pekka K.

    2008-01-01

    Objectives The purpose of this study was to compare the flexural strength and modulus of two commercial resin composites, at room temperature and 40, 45 and 50°C prior to light polymerization with standard and step-cure protocols. Methods One nanohybrid (Grandio, VOCO, Cuxhaven, Germany), and microhybrid composite resin (Filtek Z250, 3M ESPE, St. Paul, MN, USA) were used. The materials were inserted into rectangular moulds at room temperature or preheated to a temperature of 40, 45 or 50°C and cured with standard or step-cure protocols with high intensity halogen (Elipar Highlight, 3M-ESPE, St. Paul, MN, USA). Ten specimens were prepared for each preheating and light curing protocol. A three-point bending test was performed using a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed by one-way analysis of variance and Tukey’s post hoc tests (P<.05) to examine the effect of curing protocol and preheating. Pearson’s correlation test was used to determine the correlation between tested mechanical properties and preheating. Results There were no statistically significant difference between tested mechanical properties of the materials, curing protocols and temperature of the materials. No significant correlation was found between preheating and tested mechanical properties. Conclusions The mechanical properties of the tested materials did not changed by preheating so the tested materials could be preheated because of the other potential clinical advantages like more adaptation to the cavity walls. PMID:19212532

  2. The mechanical properties of density graded hemp/polyethylene composites

    NASA Astrophysics Data System (ADS)

    Dauvegis, Raphaël; Rodrigue, Denis

    2015-05-01

    In this work, the production and mechanical characterization of density graded biocomposites based on high density polyethylene and hemp fibres was performed. The effect of coupling agent addition (maleated polyethylene) and hemp content (0-30%) was studied to determine the effect of hemp distribution (graded content) inside the composite (uniform, linear, V and Λ). Tensile and flexural properties are reported to compare the structures, especially in terms of their stress-strain behaviors under tensile loading.

  3. A comparison of mechanical properties of some foams and honeycombs

    NASA Technical Reports Server (NTRS)

    Bhat, Balakrishna T.; Wang, T. G.

    1990-01-01

    A comparative study is conducted of the mechanical properties of foam-core and honeycomb-core sandwich panels, using a normalizing procedure based on common properties of cellular solids and related properties of dense solids. Seven different honeycombs and closed-foam cells are discussed; of these, three are commercial Al alloy honeycombs, one is an Al-alloy foam, and two are polymeric foams. It is concluded that ideal, closed-cell foams may furnish compressive strengths which while isotropic can be fully comparable to the compressive strengths of honeycombs in the thickness direction. The shear strength of ideal closed-cell foams may be superior to the shear strength of honeycombs.

  4. Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong

    2017-01-01

    This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.

  5. Rubber-toughened cyanate composites - Properties and toughening mechanism

    NASA Technical Reports Server (NTRS)

    Yang, P. C.; Woo, E. P.; Laman, S. A.; Jakubowski, J. J.; Pickelman, D. M.; Sue, H. J.

    1991-01-01

    Earlier work by Young et al. (1990) has shown that Dow experimental cyanate ester resin XU71787.02 is readily toughenable by rubber. A particularly effective rubber for this purpose is an experimental core-shell rubber which toughens the polymer by inducing shear yielding. This paper describes an investigation into the toughening mechanism in the corresponding carbon-fiber composite systems and the effect of fibers on composite properties. Resin-fiber interfacial shear strengths have been successfully correlated to the compressive strengths after impact and other key properties of composites based on rubber-toughened cyanate and several carbon fibers. The differences in the properties are explained by the difference in the functioning of the rubber particles during the fracture process.

  6. High-Mn steel weldment mechanical properties at 4 K

    SciTech Connect

    Chan, J.W.; Sunwoo, A.J.; Morris, J.W. Jr.

    1988-06-01

    Advanced high-field superconducting magnets of the next generation of magnetic confinement fusion devices will require structural alloys with high yield strength and high toughness at cryogenic temperatures. Commercially available alloys used in the current generation of magnets, such as 300 series stainless steels, do not have the required properties. N-strengthened, high-Mn alloys meet base plate requirements in the as-rolled condition. However, the property changes associated with weld microstructural and chemical changes in these alloys have not been well characterized. In this work welding induced cryogenic mechanical property changes of an 18Mn-16Cr-5Ni-0.2N alloy are correlated with as-solidified weld microstructures and chemistries. 30 refs., 12 figs., 3 tabs.

  7. Protocol dependence of mechanical properties in granular systems.

    PubMed

    Inagaki, S; Otsuki, M; Sasa, S

    2011-11-01

    We study the protocol dependence of the mechanical properties of granular media by means of computer simulations. We control a protocol of realizing disk packings in a systematic manner. In 2D, by keeping material properties of the constituents identical, we carry out compaction with various strain rates. The disk packings exhibit the strain rate dependence of the critical packing fraction above which the pressure becomes non-zero. The observed behavior contrasts with the well-studied jamming transitions for frictionless disk packings. We also observe that the elastic moduli of the disk packings depend on the strain rate logarithmically. Our results suggest that there exists a time-dependent state variable to describe macroscopic material properties of disk packings, which depend on its protocol.

  8. Structure and mechanical properties of Octopus vulgaris suckers

    PubMed Central

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N.; Mazzolai, Barbara

    2014-01-01

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers. PMID:24284894

  9. Relationships between supercontraction and mechanical properties of spider silk.

    PubMed

    Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

    2005-12-01

    Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of 'unfrozen' molecular chains (as in polyethylene terephthalate) or the 'broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

  10. [Mechanical properties of wiredrawn Ag-Pd-Cu alloys].

    PubMed

    Hasegawa, T; Miyagawa, Y; Nakamura, K

    1989-01-01

    Nine experimental Ag-Pd-Cu ternary alloys, containing 20-30 wt% Pd and 10-20 wt% Cu, were cast into rods 4.5 mm in diameter using an original vacuum/argon-pressure oxide-free casting technique. Test samples 2.0 mm in diameter were made from the rods by wire-drawing. After softening and hardening heat treatments, mechanical properties (modulus of elasticity, elastic limit, proof stress, tensile strength, elongation, and Vickers hardness) of the samples were measured to analyze the effects of composition and fifteen sets of correlations between the mechanical properties on the condition that few internal casting defects existed. After softening heat treatment, values of hardness and strength increased with increasing Cu and Pd contents, while they increased approximately with increasing Pd content after hardening heat treatment. After softening and hardening heat treatments, tensile strength ranged from 44.4 to 60.7 and from 68.1 to 89.1 kgf/mm2, respectively. Values of elongation were more than 10% even after hardening heat treatment. Fourteen out of fifteen correlation coefficients (r) were statistically significant (p less than 0.01). One of the regression lines derived was as follows. Tensile strength (kgf/mm2) = 9.1 +/- 0.305 Hv (r = 0.990) Moreover, the mechanical properties observed in this investigation were compared with those of ordinarily cast samples with the same compositions.

  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. Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes

    NASA Astrophysics Data System (ADS)

    Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

    2007-03-01

    The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

  13. Reconstruction of Sedimentary Rock Based on MechanicalProperties

    SciTech Connect

    Jin, Guodong; Patzek, Tad W.; Silin, Dmitry B.

    2004-05-04

    We describe a general, physics-based approach to numericalreconstruction of the geometrical structure and mechanical properties ofnatural sedimentary rock in 3D. Our procedure consists of three mainsteps: sedimentation, compaction, and diagenesis, followed by theverification of rock mechanical properties. The dynamic geologicprocesses of grain sedimentation and compaction are simulated by solvinga dimensionless form of Newton's equations of motion for an ensemble ofgrains. The diagenetic rock transformation is modeled using a cementationalgorithm, which accounts for the effect of rock grain size on therelative rate of cement overgrowth. Our emphasis is on unconsolidatedsand and sandstone. The main input parameters are the grain sizedistribution, the final rock porosity, the type and amount of cement andclay minerals, and grain mechanical properties: the inter-grain frictioncoefficient, the cement strength, and the grain stiffness moduli. We usea simulated 2D Fontainebleau sandstone to obtain the grain mechanicalproperties. This Fontainebleau sandstone is also used to study theinitiation, growth, and coalescence of micro-cracks under increasingvertical stress. The box fractal dimension of the micro-crackdistribution, and its variation with the applied stress areestimated.

  14. Mechanical Properties of a Primary Cilium Measured by Resonant Oscillation

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    Primary cilia are ubiquitous mammalian cellular substructures implicated in an ever-increasing number of regulatory pathways. The well-established `ciliary hypothesis' states that physical bending of the cilium (for example, due to fluid flow) initiates signaling cascades, yet the mechanical properties of the cilium remain incompletely measured, resulting in confusion regarding the biological significance of flow-induced ciliary mechanotransduction. In this work we measure the mechanical properties of a primary cilium by using an optical trap to induce resonant oscillation of the structure. Our data indicate 1), the primary cilium is not a simple cantilevered beam, 2), the base of the cilium may be modeled as a nonlinear rotatory spring, the linear spring constant `k' of the cilium base calculated to be (4.6 +/- 0.62)*10-12 N/rad and nonlinear spring constant ` α' to be (-1 +/- 0.34) *10-10 N/rad2 , and 3) the ciliary base may be an essential regulator of mechanotransduction signalling. Our method is also particularly suited to measure mechanical properties of nodal cilia, stereocilia, and motile cilia, anatomically similar structures with very different physiological functions.

  15. Relationships between supercontraction and mechanical properties of spider silk

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Shao, Zhengzhong; Vollrath, Fritz

    2005-12-01

    Typical spider dragline silk tends to outperform other natural fibres and most man-made filaments. However, even small changes in spinning conditions can have large effects on the mechanical properties of a silk fibre as well as on its water uptake. Absorbed water leads to significant shrinkage in an unrestrained dragline fibre and reversibly converts the material into a rubber. This process is known as supercontraction and may be a functional adaptation for the silk's role in the spider's web. Supercontraction is thought to be controlled by specific motifs in the silk proteins and to be induced by the entropy-driven recoiling of molecular chains. In analogy, in man-made fibres thermal shrinkage induces changes in mechanical properties attributable to the entropy-driven disorientation of `unfrozen' molecular chains (as in polyethylene terephthalate) or the `broken' intermolecular hydrogen bonds (as in nylons). Here we show for Nephila major-ampullate silk how in a biological fibre the spinning conditions affect the interplay between shrinkage and mechanical characteristics. This interaction reveals design principles linking the exceptional properties of silk to its molecular orientation.

  16. Structure and mechanical properties of Octopus vulgaris suckers.

    PubMed

    Tramacere, Francesca; Kovalev, Alexander; Kleinteich, Thomas; Gorb, Stanislav N; Mazzolai, Barbara

    2014-02-06

    In this study, we investigate the morphology and mechanical features of Octopus vulgaris suckers, which may serve as a model for the creation of a new generation of attachment devices. Octopus suckers attach to a wide range of substrates in wet conditions, including rough surfaces. This amazing feature is made possible by the sucker's tissues, which are pliable to the substrate profile. Previous studies have described a peculiar internal structure that plays a fundamental role in the attachment and detachment processes of the sucker. In this work, we present a mechanical characterization of the tissues involved in the attachment process, which was performed using microindentation tests. We evaluated the elasticity modulus and viscoelastic parameters of the natural tissues (E ∼ 10 kPa) and measured the mechanical properties of some artificial materials that have previously been used in soft robotics. Such a comparison of biological prototypes and artificial material that mimics octopus-sucker tissue is crucial for the design of innovative artificial suction cups for use in wet environments. We conclude that the properties of the common elastomers that are generally used in soft robotics are quite dissimilar to the properties of biological suckers.

  17. Novel F-releasing Composite with Improved Mechanical Properties

    PubMed Central

    Ling, L.; Xu, X.; Choi, G.-Y.; Billodeaux, D.; Guo, G.; Diwan, R.M.

    2009-01-01

    In recent years, the authors have been developing novel fluoride-releasing dental composites containing ternary zirconium fluoride chelates. The aim of this study was to improve the physical and mechanical properties of these composites by improving the formulation of the monomers and photoinitiators. The hypothesis was that reduction of hydrophilic monomers and improvement of the photoinitiators could reduce water sorption and significantly increase the mechanical properties of the composite. The degree of conversion of the composites containing different compositions of photoinitiators was studied by Fourier transform near-infrared spectroscopy (FT-NIR). Ten experimental composites containing different compositions of ethoxylated bisphenol-A dimethacrylate (EBPADMA), 1,6-hexanediol dimethacrylate (HDDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]-propane (BisGMA) were tested for flexural strength, viscosity, and water sorption. The experimental composite containing 20% synthesized fluoride-releasing monomer, 30% BisGMA, 30% EBPADMA, and 20% HDDMA showed significantly higher fluoride release and recharge, but physical and mechanical properties similar to those of the control composite containing 40% BisGMA, 40% EBPADMA, and 20% HDDMA. PMID:19131323

  18. Enhanced mechanical properties of nanocomposites at low graphene content.

    PubMed

    Rafiee, Mohammad A; Rafiee, Javad; Wang, Zhou; Song, Huaihe; Yu, Zhong-Zhen; Koratkar, Nikhil

    2009-12-22

    In this study, the mechanical properties of epoxy nanocomposites with graphene platelets, single-walled carbon nanotubes, and multi-walled carbon nanotube additives were compared at a nanofiller weight fraction of 0.1 +/- 0.002%. The mechanical properties measured were the Young's modulus, ultimate tensile strength, fracture toughness, fracture energy, and the material's resistance to fatigue crack propagation. The results indicate that graphene platelets significantly out-perform carbon nanotube additives. The Young's modulus of the graphene nanocomposite was approximately 31% greater than the pristine epoxy as compared to approximately 3% increase for single-walled carbon nanotubes. The tensile strength of the baseline epoxy was enhanced by approximately 40% with graphene platelets compared to approximately 14% improvement for multi-walled carbon nanotubes. The mode I fracture toughness of the nanocomposite with graphene platelets showed approximately 53% increase over the epoxy compared to approximately 20% improvement for multi-walled carbon nanotubes. The fatigue resistance results also showed significantly different trends. While the fatigue suppression response of nanotube/epoxy composites degrades dramatically as the stress intensity factor amplitude is increased, the reverse effect is seen for graphene-based nanocomposites. The superiority of graphene platelets over carbon nanotubes in terms of mechanical properties enhancement may be related to their high specific surface area, enhanced nanofiller-matrix adhesion/interlocking arising from their wrinkled (rough) surface, as well as the two-dimensional (planar) geometry of graphene platelets.

  19. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    PubMed Central

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  20. Effect of viscosity, basicity and organic content of composite flocculant on the decolorization performance and mechanism for reactive dyeing wastewater.

    PubMed

    Wang, Yuanfang; Gao, Baoyu; Yue, Qinyan; Wang, Yan

    2011-01-01

    A coagulation/flocculation process using the composite flocculant polyaluminum chloride-epichlorohydrin dimethylamine (PAC-EPI-DMA) was employed for the treatment of an anionic azo dye (Reactive Brilliant Red K-2BP dye). The effect of viscosity (eta), basicity (B = [OH]/[Al]) and organic content (W(P)) on the flocculation performance as well as the mechanism of PAC-EPI-DMA flocculant were investigated. The eta was the key factor affecting the dye removal efficiency of PAC-EPI-DMA. PAC-EPI-DMA with an intermediate eta (2400 mPa x sec) gave higher decolorization efficiency by adsorption bridging and charge neutralization due to the co-effect of PAC and EPI-DMA polymers. The W(P) of the composite flocculant was a minor important factor for the flocculation. The adsorption bridging of PAC-EPI-DMA with eta of 300 or 4300 mPa x sec played an important role with the increase of W(P), whereas the charge neutralization of them was weaker with the increase of W(P). There was interaction between W(P) and B on the removal of reactive dye. The composite flocculant with intermediate viscosity and organic content was effective for the treatment of reactive dyeing wastewater, which could achieve high reactive dye removal efficiency with low organic dosage.

  1. Mechanical properties of several magnesium and aluminum composites. Final report

    SciTech Connect

    Tsangarakis, N.; Taleghani, B.

    1992-12-01

    Several composites of magnesium and aluminum alloys were tested in order to assess and evaluate their mechanical properties. The magnesium alloys were AZ91 C, ZE41 A, and commercially pure magnesium, reinforced with 40% by volume continuous graphite fiber. The tensile properties of these composites were not superior to those of unreinforced magnesium and estimates of their fracture toughness were low. The matrices of the aluminum composites were 2124-T6, 6061-T4, 2124-T4, and 2219-T4. The reinforcements were either particulate or whiskers of silicon carbide or boron carbide and their volume content was 15% to 30%. The aluminum composites which were reinforced with silicon carbide particulate exhibited improved yield and ultimate tensile stresses, as well as tensile elastic modulus over the unreinforced aluminum alloys. The 2124-T4/B4C/25p composite exhibited the highest ultimate tensile strength which was 511 MPa. The composite which was reinforced with whiskers of silicon carbide exhibited an endurance limit which was 20% higher than that of the matrix alloy. The compressive properties and fracture toughness of some of these aluminum composites were not improved over those of the unreinforced matrix alloy.... Composites, Mechanical properties.

  2. Measurement of the Mechanical Properties of Intact Collagen Fibrils

    NASA Astrophysics Data System (ADS)

    Mercedes, H.; Heim, A.; Matthews, W. G.; Koob, T.

    2006-03-01

    Motivated by the genetic disorder Ehlers-Danlos syndrome (EDS), in which proper collagen synthesis is interrupted, we are investigating the structural and mechanical properties of collagen fibrils. The fibrous glycoprotein collagen is the most abundant protein found in the human body and plays a key role in the extracellular matrix of the connective tissue, the properties of which are altered in EDS. We have selected as our model system the collagen fibrils of the sea cucumber dermis, a naturally mutable tissue. This system allows us to work with native fibrils which have their proteoglycan complement intact, something that is not possible with reconstituted mammalian collagen fibrils. Using atomic force microscopy, we measure, as a function of the concentration of divalent cations, the fibril diameter, its response to force loading, and the changes in its rigidity. Through these experiments, we will shed light on the mechanisms which control the properties of the sea cucumber dermis and hope to help explain the altered connective tissue extracellular matrix properties associated with EDS.

  3. Hierarchical graphene nanoribbon assemblies feature unique electronic and mechanical properties

    NASA Astrophysics Data System (ADS)

    Xu, Zhiping; Buehler, Markus J.

    2009-09-01

    Graphene nanoribbons present intriguing electronic properties due to their characteristic size and edge shape, and have been suggested for a wide range of applications from electronics to electromechanical systems. To bridge the scales from their nanostructural geometry—the key for their unique properties—to the requirements critical for large-scale electronics and device applications, here we propose a de novo hierarchical material assembled from functionalized graphene nanoribbons stabilized through hydrogen bonds, mimicking the structure of beta-sheet proteins. By investigating their mechanical and electronic properties through first principles calculations, we demonstrate that hierarchical graphene nanoribbons not only preserve the unique electronic properties of individual graphene nanoribbons in the bulk, but are also energetically and mechanically stable. Specifically, we find that the energy gap of the bulk material shrinks as the width of the constituting graphene nanoribbons increases. The tuning of bulk material properties through controlling the nanostructure enables the synthesis of a broader class of biomimetic multifunctional mechanomutable and electromutable nanomaterials for electromechanical applications.

  4. Effects of acido-basic support properties on the catalytic hydrogenation of acetylene on gold nano-particles

    NASA Astrophysics Data System (ADS)

    Manda, Abdullah Ahmed

    Metallic gold nanoparticles supported on gamma-Al2O 3 and magnesia-alumina mixed oxide, with different magnesia content have been prepared by sol-gel method and characterized by different techniques (inductive coupled plasma-mass spectroscopy (ICP-MS), XRD, BET surface area analysis, transmission electron microscopy (TEM), CO2 and NH 3 temperature programmed desorption (TPD), H2 temperature programmed reduction (TPR) and FTIR of adsorbed CO2). Such systems were found to produce catalysts with controllable acidity, varying from catalyst possessing large density of acidic and low density of basic sites, others with acidic and basic sites of equal strength and density, and others with large basic and low acid sites densities, respectively. The catalytic assessment of the generated acidity was carried out using 2-propanol decomposition as a test reaction. The results obtained indicate that the presence of magnesia and reduced gold nanopartilces has imparted the catalysts, 1%Au/4%Mg-Al 2O3 and 1%Au/8%Mg-Al2O3, with significant base-catalytic properties. Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on gamma-Al2O3 and gold supported on alumina-magnisia mixed oxide with different gold content; 1%Au/gamma-Al 2O3, 1%Au/15%Mg-Al2O3, 2%Au/15%Mg-Al 2O3 and 4%Au/15%Mg-Al2O3. The effect of the H2/C2H2 ratio was studied over a range of values. The catalytic activity and selectivity towards ethylene and other products were investigated at different reaction temperatures. Acetylene hydrogenation was investigated in the presence and absence of ethylene in stream. It is investigated that the adsorption of the triple bond is preferred over the double bond and during selective catalytic (SCR) of C2H2 the two hydrocarbons do not compete for the same adsorption sites. The deactivation of catalysts was studied by temperature programmed oxidation (TPO). Higher content of coke over 1%Au/Al2O3 catalyst was investigated in contrast to

  5. Mechanical properties and failure behavior of phosphorene with grain boundaries

    NASA Astrophysics Data System (ADS)

    Sorkin, V.; Zhang, Y. W.

    2017-02-01

    Using the density-functional tight-binding method, we studied the effect of grain boundaries on the mechanical properties and failure behavior of phosphorene. We found that the high-angle tilt boundaries with a higher density of (5∣7) defect pairs (oriented along the armchair direction) are stronger than the low-angle tilt boundaries with a lower defect density, and similarly the high-angle boundaries with a higher density of (4∣8) defect pairs (oriented along the zigzag direction) are stronger than the low-angle boundaries with a lower defect density. The failure is due to the rupture of the most pre-strained bonds in the heptagons of the (5∣7) defect pair or octagons of the (4∣8) pairs. The high-angle grain boundaries are better at accommodating the pre-strained bonds in heptagon and octagon defects, leading to a higher failure stress and strain. The results cannot be described by a Griffith-type fracture mechanics criterion, since this does not take into account the bond pre-stretching. Interestingly, these anomalous mechanical and failure characteristics of tilt grain boundaries in phosphorene are also shared by graphene and hexagonal boron nitride, signifying that they may be universal for 2D materials. The findings revealed here may be useful in tuning the mechanical properties of phosphorene via defect engineering for specific applications.

  6. Anomalous magnetic properties of mechanically milled cobalt oxide nanoparticles.

    PubMed

    Mishra, S R; Dubenko, I; Losby, J; Ghosh, l K; Khan, M; Ali, N

    2005-12-01

    Defect induced magnetic properties of CoO nanoparticles produced via mechanical ball milling have been assessed by detailed magnetic measurements. A progressive decrease in the particle size and a concomitant increase in the induced strain have been observed with the milling times. The mechanically milled nanoparticles of CoO exhibit anomalous magnetic properties such as FM hysteresis when compared with the unmilled CoO sample. The presence of weak ferromagnetism, with a highest value of magnetization of 0.532 emu/g at 10 K in the 100 h milled sample, is attributed to the uncompensated surface spins resulting from induced surface defects via mechanical milling. The ZFC coercive force, measured at 10 K, increases with milling time reaching a maximum value of 1066 Oe for the 100 h milled sample. The temperature dependent field-cooled (FC) and zero-field-cooled (ZFC) magnetic measurements indicate a presence of an exchange bias field arising from uncompensated moments generated by mechanical strain and the antiferromagnetic (AFM) core. The exchange bias field measured at 10 K reaches a value 210 Oe for the 50 h milled sample and decreases upon prolonged milling. The exchange bias field vanishes at a temperature approximately 200 K, a temperature much lower than the Neel temperature of CoO (TN approximately 291 K). The observed anomalous magnetic behavior of CoO could be interpreted in terms of the exchanged bias FM-AFM model.

  7. Mechanical properties of tricalcium phosphate-fluorapatite-alumina composites

    NASA Astrophysics Data System (ADS)

    Bouslama, N.; Ben Ayed, F.; Bouaziz, J.

    2009-11-01

    This study deals to produce tricalcium phosphate - fluorapatite composites sintering at various temperatures (1300∘ C, 1350∘ C and 1400∘ C) and with different alumina additives amounts (2.5 wt%, 5 wt%, 7.5 wt%, 10 wt% and 20 wt%). The characterization of samples before and after sintering was investigated, using X-ray diffraction, infrared spectroscopy, scanning electronic microscopy and by analysis using 31P and 27Al nuclear magnetic resonance. Mechanical properties have been measured by Brazilian test. The evolution of composite rupture strength was studied as a function of sintering temperature. The effect of sintering on the mechanical properties was measured with the change in composition and microstructure of the composite. The mechanical resistances of composites were increased with the temperatures and with concentrations of alumina. At 1350∘ C, the mechanical resistance reaches its maximum value with 5 wt% Al2O3 (13.6 MPa) whereas the optimum density is about 90% with 2.5 wt% Al2O3.

  8. Length-dependent mechanical properties of gold nanowires

    PubMed Central

    Han, Jing; Fang, Liang; Sun, Jiapeng; Han, Ying; Sun, Kun

    2012-01-01

    The well-known “size effect” is not only related to the diameter but also to the length of the small volume materials. It is unfortunate that the length effect on the mechanical behavior of nanowires is rarely explored in contrast to the intensive studies of the diameter effect. The present paper pays attention to the length-dependent mechanical properties of 〈111〉-oriented single crystal gold nanowires employing the large-scale molecular dynamics simulation. It is discovered that the ultrashort Au nanowires exhibit a new deformation and failure regime-high elongation and high strength. The constrained dislocation nucleation and transient dislocation slipping are observed as the dominant mechanism for such unique combination of high strength and high elongation. A mechanical model based on image force theory is developed to provide an insight to dislocation nucleation and capture the yield strength and nucleation site of first partial dislocation indicated by simulation results. Increasing the length of the nanowires, the ductile-to-brittle transition is confirmed. And the new explanation is suggested in the predict model of this transition. Inspired by the superior properties, a new approach to strengthen and toughen nanowires-hard/soft/hard sandwich structured nanowires is suggested. A preliminary evidence from the molecular dynamics simulation corroborates the present opinion. PMID:23284186

  9. Mechanical Properties of Mineralized Collagen Fibrils As Influenced By Demineralization

    SciTech Connect

    Balooch, M.; Habelitz, S.; Kinney, J.H.; Marshall, S.J.; Marshall, G.W.

    2009-05-11

    Dentin and bone derive their mechanical properties from a complex arrangement of collagen type-I fibrils reinforced with nanocrystalline apatite mineral in extra- and intrafibrillar compartments. While mechanical properties have been determined for the bulk of the mineralized tissue, information on the mechanics of the individual fibril is limited. Here, atomic force microscopy was used on individual collagen fibrils to study structural and mechanical changes during acid etching. The characteristic 67 nm periodicity of gap zones was not observed on the mineralized fibril, but became apparent and increasingly pronounced with continuous demineralization. AFM-nanoindentation showed a decrease in modulus from 1.5 GPa to 50 MPa during acid etching of individual collagen fibrils and revealed that the modulus profile followed the axial periodicity. The nanomechanical data, Raman spectroscopy and SAXS support the hypothesis that intrafibrillar mineral etches at a substantially slower rate than the extrafibrillar mineral. These findings are relevant for understanding the biomechanics and design principles of calcified tissues derived from collagen matrices.

  10. Equivalent mechanical properties of textile monolayers from discrete asymptotic homogenization

    NASA Astrophysics Data System (ADS)

    Goda, Ibrahim; Assidi, Mohamed; Ganghoffer, Jean-François

    2013-12-01

    The determination of the effective mechanical moduli of textiles from mechanical measurements is usually difficult due to their discrete architecture, which makes micromechanical analyses a relevant alternative to access those properties. Micropolar continuum models describing the effective mechanical behavior of woven fabric monolayers are constructed from the homogenization of an identified repetitive pattern of the textile within a representative unit cell. The interwoven yarns within the textile are represented as a network of trusses connected by nodes at their crossover points. These trusses have extensional and bending rigidities to allow for yarn stretching and flexion, and a transverse shear deformation is additionally considered. Interactions between yarns at the crossover points are captured by beam segments connecting the nodes. The woven fabric is modeled after homogenization as an anisotropic planar continuum with two preferred material directions in the mean plane of the textile. Based on the developed methodology, the effective mechanical properties of plain weave and twill are evaluated, including their bending moduli and characteristic flexural lengths. A satisfactory agreement is obtained between the effective moduli obtained by homogenization and numerical values obtained by finite element simulations performed over periodic unit cells.

  11. Mechanical Properties of Type IV Pili in P. Aeruginosa

    NASA Astrophysics Data System (ADS)

    Lu, Shun; Touhami, Ahmed; Scheurwater, Edie; Harvey, Hanjeong; Burrows, Lori; Dutcher, John

    2009-03-01

    Type IV pili (Tfp) are thin flexible protein filaments that extend from the cell membrane of bacteria such as Pseudomonas aeruginosa and Neisseria gonorrhoeae. The mechanical properties of Tfp are of great importance since they allow bacteria to interact with and colonize various surfaces. In the present study, we have used atomic force microscopy (AFM) for both imaging and pulling on Tfp from P. aeruginosa (PAO1) and from its PilA, PilT, and FliC mutants. A single pilus filament was mechanically stretched and the resulting force-extension profiles were fitted using the worm-like-chain (WLC) model. The statistical distributions obtained for contour length, persistence length, and number of pili per bacteria pole, were used to evaluate the mechanical properties of a single pilus and the biogenesis functions of different proteins (PilA, PilT) involved in its assembly and disassembly. Importantly, the persistence length value of ˜ 1 μm measured in the present study, which is consistent with the curvature of the pili observed in our AFM images, is significantly lower than the value of 5 μm reported earlier by Skerker et al. (1). Our results shed new light on the role of mechanical forces that mediate bacteria-surface interactions and biofilm formation. 1- J.M. Skerker and H.C. Berg, Proc. Natl. Acad. Sci. USA, 98, 6901-6904 (2001).

  12. Mechanical and thermal properties of nanoparticle filled epoxy nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Su

    2007-12-01

    One of the potential advantages of nanoparticle filled thermosets is the unique combination of mechanical properties that can be obtained. There have been several reports of improved ductility and toughness in brittle thermoset polymers due to the addition of equiaxed nanoparticles. The mechanisms leading to these improvements, however, are poorly understood. In the present study, a model system of nanoscale alumina filled bisphenol A based epoxy with two interface conditions was used to highlight the mechanisms leading to significant improvements in ductility, toughness, modulus and fatigue crack propagation resistance. It was found that the interfacial condition is critical to controlling the mechanical properties of the nanocomposites. Well-bonded APTES-Al 2O3 (3-aminopropyltriethoxysilane treated alumina) nanoparticle filled epoxy nanocomposites showed significant improvements in tensile ductility (max 39%), fracture toughness (max 26%) and fatigue crack propagation resistance, while exhibiting an increase in modulus and maintained strength. Poorly-bonded NT-Al2O3 (non-treated) nanoparticle filled epoxy nanocomposites only showed improvements in fatigue crack propagation resistance and modulus. Fracture morphology and theoretical predictions were used to study the mechanisms. The key mechanism, that significantly improved the ductility or tensile toughness of the treated nanocomposites and distinguished the treated nanocomposites from the untreated nanocomposites, is crack deflection. Crack deflection occurred much more for the well-bonded nanocomposites due to the stronger particle/matrix adhesion. Furthermore, it was found that crack deflection, interfacial debonding and particle pull-out were critical for composites with a weak interface, but that a stronger interface lead to additional mechanisms of further crack deflection, plastic deformation, microcracking and as a result a further improvement in mechanical properties. In addition, higher thermal

  13. AFM Manipulation of Viruses: Substrate Interactions and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Falvo, M. R.; Superfine, R.; Washburn, S.; Finch, M.; Taylor, R. M.; Chi, V.; Brooks, F. P.; Ferrari, F.; Samulski, R.

    1996-03-01

    Using an AFM tip as a manipulation tool, we have translated, rotated, and dissected individual Tobacco Mosaic Virus (TMV) and Adenovirus particles. We have implemented a teleoperation system which allows manual control of the relative tip-sample position while also allowing conventional AFM operation for imaging resulting structure. Using simple tip trajectories to bend the rod-shaped TMV, we observed a variety of resulting structures and mechanical failures. The distributed adhesive interaction between the virus and the sample surface, as well as the local tip-virus interaction affect the distortion in the shape of the virus. Experiments were performed in air as well as in liquid on graphite and Si substrates. The in-liquid experiments allow tuning of the environmental conditions, including osmolarity and pH, which are known to profoundly affect the virus structure. A continuum mechanical model relating mechanical properties to observations provides insight into the constraints for successful nondestructive manipulation.

  14. Size Dependent Mechanical Properties of Monolayer Densely Arranged Polystyrene Nanospheres.

    PubMed

    Huang, Peng; Zhang, Lijing; Yan, Qingfeng; Guo, Dan; Xie, Guoxin

    2016-12-13

    In contrast to macroscopic materials, the mechanical properties of polymer nanospheres show fascinating scientific and application values. However, the experimental measurements of individual nanospheres and quantitative analysis of theoretical mechanisms remain less well performed and understood. We provide a highly efficient and accurate method with monolayer densely arranged honeycomb polystyrene (PS) nanospheres for the quantitatively mechanical characterization of individual nanospheres on the basis of atomic force microscopy (AFM) nanoindentation. The efficiency is improved by 1-2 orders, and the accuracy is also enhanced almost by half-order. The elastic modulus measured in the experiments increases with decreasing radius to the smallest nanospheres (25-35 nm in radius). A core-shell model is introduced to predict the size dependent elasticity of PS nanospheres, and the theoretical prediction agrees reasonably well with the experimental results and also shows a peak modulus value.

  15. Manipulation of individual viruses: friction and mechanical properties.

    PubMed Central

    Falvo, M R; Washburn, S; Superfine, R; Finch, M; Brooks, F P; Chi, V; Taylor, R M

    1997-01-01

    We present our results on the manipulation of individual viruses using an advanced interface for atomic force microscopes (AFMs). We show that the viruses can be dissected, rotated, and translated with great facility. We interpret the behavior of tobacco mosaic virus with a mechanical model that makes explicit the competition between sample-substrate lateral friction and the flexural rigidity of the manipulated object. The manipulation behavior of tobacco mosaic virus on graphite is shown to be consistent with values of lateral friction observed on similar interfaces and the flexural rigidity expected for macromolecular assemblies. The ability to manipulate individual samples broadens the scope of possible studies by providing a means for positioning samples at specific binding sites or predefined measuring devices. The mechanical model provides a framework for interpreting quantitative measurements of virus binding and mechanical properties and for understanding the constraints on the successful, nondestructive AFM manipulation of delicate samples. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 PMID:9138585

  16. The fundamental role of mechanical properties in the progression of cancer disease and inflammation

    NASA Astrophysics Data System (ADS)

    Mierke, Claudia Tanja

    2014-07-01

    The role of mechanical properties in cancer disease and inflammation is still underinvestigated and even ignored in many oncological and immunological reviews. In particular, eight classical hallmarks of cancer have been proposed, but they still ignore the mechanics behind the processes that facilitate cancer progression. To define the malignant transformation of neoplasms and finally reveal the functional pathway that enables cancer cells to promote cancer progression, these classical hallmarks of cancer require the inclusion of specific mechanical properties of cancer cells and their microenvironment such as the extracellular matrix as well as embedded cells such as fibroblasts, macrophages or endothelial cells. Thus, this review will present current cancer research from a biophysical point of view and will therefore focus on novel physical aspects and biophysical methods to investigate the aggressiveness of cancer cells and the process of inflammation. As cancer or immune cells are embedded in a certain microenvironment such as the extracellular matrix, the mechanical properties of this microenvironment cannot be neglected, and alterations of the microenvironment may have an impact on the mechanical properties of the cancer or immune cells. Here, it is highlighted how biophysical approaches, both experimental and theoretical, have an impact on the classical hallmarks of cancer and inflammation. It is even pointed out how these biophysical approaches contribute to the understanding of the regulation of cancer disease and inflammatory responses after tissue injury through physical microenvironmental property sensing mechanisms. The recognized physical signals are transduced into biochemical signaling events that guide cellular responses, such as malignant tumor progression, after the transition of cancer cells from an epithelial to a mesenchymal phenotype or an inflammatory response due to tissue injury. Moreover, cell adaptation to mechanical alterations, in

  17. Spherical agglomerates of lactose with enhanced mechanical properties.

    PubMed

    Lamešić, Dejan; Planinšek, Odon; Lavrič, Zoran; Ilić, Ilija

    2017-01-10

    The aim of this study was to prepare spherical agglomerates of lactose and to evaluate their physicochemical properties, flow properties, particle friability and compaction properties, and to compare them to commercially available types of lactose for direct compression (spray-dried, granulated and anhydrous β-lactose). Porous spherical agglomerates of α-lactose monohydrate with radially arranged prism-like primary particles were prepared exhibiting a high specific surface area. All types of lactose analysed had passable or better flow properties, except for anhydrous β-lactose, which had poor flowability. Particle friability was more pronounced in larger granulated lactose particles; however, particle structure was retained in all samples analysed. The mechanical properties of spherical agglomerates of lactose, in terms of compressibility, established with Walker analysis, and compactibility, established with a compactibility profile, were found to be superior to any commercially available types of lactose. Higher compactibility of spherical agglomerates of lactose is ascribed to significantly higher particle surface area due to a unique internal structure with higher susceptibility to fragmentation.

  18. Mechanical and hydraulic properties of rocks related to induced seismicity

    USGS Publications Warehouse

    Witherspoon, P.A.; Gale, J.E.

    1977-01-01

    Witherspoon, P.A. and Gale, J.E., 1977. Mechanical and hydraulic properties of rocks related to induced seismicity. Eng. Geol., 11(1): 23-55. The mechanical and hydraulic properties of fractured rocks are considered with regard to the role they play in induced seismicity. In many cases, the mechanical properties of fractures determine the stability of a rock mass. The problems of sampling and testing these rock discontinuities and interpreting their non-linear behavior are reviewed. Stick slip has been proposed as the failure mechanism in earthquake events. Because of the complex interactions that are inherent in the mechanical behavior of fractured rocks, there seems to be no simple way to combine the deformation characteristics of several sets of fractures when there are significant perturbations of existing conditions. Thus, the more important fractures must be treated as individual components in the rock mass. In considering the hydraulic properties, it has been customary to treat a fracture as a parallel-plate conduit and a number of mathematical models of fracture systems have adopted this approach. Non-steady flow in fractured systems has usually been based on a two-porosity model, which assumes the primary (intergranular) porosity contributes only to storage and the secondary (fracture) porosity contributes only to the overall conductivity. Using such a model, it has been found that the time required to achieve quasi-steady state flow in a fractured reservoir is one or two orders of magnitude greater than it is in a homogeneous system. In essentially all of this work, the assumption has generally been made that the fractures are rigid. However, it is clear from a review of the mechanical and hydraulic properties that not only are fractures easily deformed but they constitute the main flow paths in many rock masses. This means that one must consider the interaction of mechanical and hydraulic effects. A considerable amount of laboratory and field data is now

  19. An Experimental Investigation of Shale Mechanical Properties Through Drained and Undrained Test Mechanisms

    NASA Astrophysics Data System (ADS)

    Islam, Md. Aminul; Skalle, Paal

    2013-11-01

    Shale mechanical properties are evaluated from laboratory tests after a complex workflow that covers tasks from sampling to testing. Due to the heterogeneous nature of shale, it is common to obtain inconsistent test results when evaluating the mechanical properties. In practice, this variation creates errors in numerical modeling when test results differ significantly, even when samples are from a similar core specimen. This is because the fundamental models are based on the supplied test data and a gap is, therefore, always observed during calibration. Thus, the overall goal of this study was to provide additional insight regarding the organization of the non-linear model input parameters in borehole simulations and to assist other researchers involved in the rock physics-related research fields. To achieve this goal, the following parallel activities were carried out: (1) perform triaxial testing with different sample orientations, i.e., 0°, 45°, 60°, and 90°, including the Brazilian test and CT scans, to obtain a reasonably accurate description of the anisotropic properties of shale; (2) apply an accurate interpretative method to evaluate the elastic moduli of shale; (3) evaluate and quantify the mechanical properties of shale by accounting for the beddings plane, variable confinement pressures, drained and undrained test mechanisms, and cyclic versus monotonic test effects. The experimental results indicate that shale has a significant level of heterogeneity. Postfailure analysis confirmed that the failure plane coincides nicely with the weak bedding plane. The drained Poisson’s ratios were, on average, 40 % or lower than the undrained rates. The drained Young’s modulus was approximately 48 % that of the undrained value. These mechanical properties were significantly impacted by the bedding plane orientation. Based on the Brazilian test, the predicted tensile strength perpendicular to the bedding plane was 12 % lower than the value obtained using the

  20. Size effects on mechanical and thermal properties of thin films

    NASA Astrophysics Data System (ADS)

    Alam, Md Tarekul

    Materials, from electronic to structural, exhibit properties that are sensitive to their composition and internal microstructures such as grain and precipitate sizes, crystalline phases, defects and dopants. Therefore, the research trend has been to obtain fundamental understanding in processing-structure-properties to develop new materials or new functionalities for engineering applications. The advent of nanotechnology has opened a new dimension to this research area because when material size is reduced to nanoscale, properties change significantly from the bulk values. This phenomenon expands the problem to 'size-processing-structure-propertiesfunctionalities'. The reinvigorated research for the last few decades has established size dependency of the material properties such as thermal conductivity, Young's modulus and yield strength, electrical resistivity, photo-conductance etc. It is generally accepted that classical physical laws can be used to scale down the properties up to 25-50 nm length-scale, below which their significant deviation or even breakdown occur. This dissertation probes the size effect from a different perspective by asking the question, if nanoscale size influences one physical domain, why it would not influence the coupling between two or more domains? Or in other words, if both mechanical and thermal properties are different at the nanoscale, can mechanical strain influence thermal conductivity? The hypothesis of size induced multi-domain coupling is therefore the foundation of this dissertation. It is catalyzed by the only few computational studies available in the literature while experimental validations have been non-existent owing to experimental challenges. The objective of this research is to validate this hypothesis, which will open a novel avenue to tune properties and functionalities of materials with the size induced multi-domain coupling. Single domain characterization itself is difficult at the nanoscale due to specimen

  1. 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.

  2. Mechanical properties of lunar regolith and lunar soil simulant

    NASA Technical Reports Server (NTRS)

    Perkins, Steven W.

    1989-01-01

    Through the Surveyor 3 and 7, and Apollo 11-17 missions a knowledge of the mechanical properties of Lunar regolith were gained. These properties, including material cohesion, friction, in-situ density, grain-size distribution and shape, and porosity, were determined by indirect means of trenching, penetration, and vane shear testing. Several of these properties were shown to be significantly different from those of terrestrial soils, such as an interlocking cohesion and tensile strength formed in the absence of moisture and particle cementation. To characterize the strength and deformation properties of Lunar regolith experiments have been conducted on a lunar soil simulant at various initial densities, fabric arrangements, and composition. These experiments included conventional triaxial compression and extension, direct tension, and combined tension-shear. Experiments have been conducted at low levels of effective confining stress. External conditions such as membrane induced confining stresses, end platten friction and material self weight have been shown to have a dramatic effect on the strength properties at low levels of confining stress. The solution has been to treat these external conditions and the specimen as a full-fledged boundary value problem rather than the idealized elemental cube of mechanics. Centrifuge modeling allows for the study of Lunar soil-structure interaction problems. In recent years centrifuge modeling has become an important tool for modeling processes that are dominated by gravity and for verifying analysis procedures and studying deformation and failure modes. Centrifuge modeling is well established for terrestrial enginering and applies equally as well to Lunar engineering. A brief review of the experiments is presented in graphic and outline form.

  3. Brush-Coated Nanoparticle Polymer Thin Films: structure-mechanical-optical properties

    SciTech Connect

    Green, Peter F.

    2014-08-15

    Our work was devoted to understanding the structure and properties of a class of thin film polymer nanocomposites (PNCs). PNCs are composed of polymer hosts into which nanoparticles (metallic nanoparticles, quantum dots, nanorods, C60, nanotubes) are incorporated. PNCs exhibit a diverse range of functional properties (optical, electronic, mechanical, biomedical, structural), determined in part by the chemical composition of the polymer host and the type of nanoparticle. The properties PNCs rely not only on specific functional, size-dependent, behavior of the nanoparticles, but also on the dispersion, and organizational order in some cases, inter-nanoparticle separation distances, and on relative interactions between the nanoparticles and the host. Therefore the scientific challenges associated with understanding the interrelations between the structure and function/properties of PNCs are far more complex than may be understood based only on the knowledge of the compositions of the constituents. The challenges of understanding the structure-function behavior of PNCs are further compounded by the fact that control of the dispersion of the nanoparticles within the polymer hosts is difficult; one must learn how to disperse inorganic particles within an organic host. The goal of this proposal was to develop an understanding of the connection between the structure and the thermal (glass transition), mechanical and optical properties of a specific class of PNCs. Specifically PNCs composed of polymer chain grafted gold nanoparticles within polymer hosts. A major objective was to understand how to develop basic principles that enable the fabrication of functional materials possessing optimized morphologies and combinations of materials properties.

  4. The mechanical properties of human ribs in young adult.

    PubMed

    Pezowicz, Celina; Głowacki, Maciej

    2012-01-01

    A good understanding of thoracic biomechanics is important for complete examination and control of chest behaviour under conditions of physiological and pathological work, and under the impact of external forces leading to traumatic loading of the chest. The purpose of the study was to analyse the mechanical properties of human ribs obtained from individuals under the age of 25 with scoliosis deformation and to correlate them with geometric properties of ribs. Thirty three fragments of ribs (9th to 12th) were tested in three-point bending. Rib fragments were collected intraoperatively from female patients treated for scoliosis in the thoracic, thoracolumbar, and lumbar spine. The results were used to determine the maximum failure force, stiffness, and Young's modulus. A significant relationship was found between the age and elastic modulus of the ribs. The analysis was carried out for two age groups, i.e., between the ages of 10 and 15 and between the ages of 16 and 22, and statistically significant differences were obtained for Young's modulus (p = 0.0001) amounting to, respectively, 2.79 ± 1.34 GPa for the first group and 7.44 ± 2.85 GPa for the second group. The results show a significant impact of age on the mechanical properties of ribs.

  5. Enhancing the Mechanical Properties of Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  6. Measurement of Mechanical Properties of Cantilever Shaped Materials

    PubMed Central

    Finot, Eric; Passian, Ali; Thundat, Thomas

    2008-01-01

    Microcantilevers were first introduced as imaging probes in Atomic Force Microscopy (AFM) due to their extremely high sensitivity in measuring surface forces. The versatility of these probes, however, allows the sensing and measurement of a host of mechanical properties of various materials. Sensor parameters such as resonance frequency, quality factor, amplitude of vibration and bending due to a differential stress can all be simultaneously determined for a cantilever. When measuring the mechanical properties of materials, identifying and discerning the most influential parameters responsible for the observed changes in the cantilever response are important. We will, therefore, discuss the effects of various force fields such as those induced by mass loading, residual stress, internal friction of the material, and other changes in the mechanical properties of the microcantilevers. Methods to measure variations in temperature, pressure, or molecular adsorption of water molecules are also discussed. Often these effects occur simultaneously, increasing the number of parameters that need to be concurrently measured to ensure the reliability of the sensors. We therefore systematically investigate the geometric and environmental effects on cantilever measurements including the chemical nature of the underlying interactions. To address the geometric effects we have considered cantilevers with a rectangular or circular cross section. The chemical nature is addressed by using cantilevers fabricated with metals and/or dielectrics. Selective chemical etching, swelling or changes in Young's modulus of the surface were investigated by means of polymeric and inorganic coatings. Finally to address the effect of the environment in which the cantilever operates, the Knudsen number was determined to characterize the molecule-cantilever collisions. Also bimaterial cantilevers with high thermal sensitivity were used to discern the effect of temperature variations. When appropriate

  7. Investigation on mechanical properties of basalt composite fabrics (experiment study)

    NASA Astrophysics Data System (ADS)

    Talebi Mazraehshahi, H.; Zamani, H.

    2010-06-01

    To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with

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

    PubMed

    Lomakin, Joseph; Huber, Patricia A; Eichler, Christian; Arakane, Yasuyuki; Kramer, Karl J; Beeman, Richard W; Kanost, Michael R; Gehrke, Stevin H

    2011-02-14

    We determined the relationship between composition and mechanical properties of elytra (modified forewings that are composed primarily of highly sclerotized dorsal and less sclerotized ventral cuticles) from the beetles Tribolium castaneum (red flour beetle) and Tenebrio molitor (yellow mealworm). Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult eclosion, the elytron of Tenebrio is ductile and soft with a Young's modulus (E) of 44 ± 8 MPa, but it becomes brittle and stiff with an E of 2400 ± 1100 MPa when fully tanned. With increasing tanning, dynamic elastic moduli (E') increase nearly 20-fold, whereas the frequency dependence of E' diminishes. These results support the hypothesis that cuticle tanning involves cross-linking of components, while drying to minimize plasticization has a lesser impact on cuticular stiffening and frequency dependence. Suppression of the tanning enzymes laccase-2 (TcLac2) or aspartate 1-decarboxylase (TcADC) in Tribolium altered mechanical characteristics consistent with hypotheses that (1) ADC suppression favors formation of melanic pigment with a decrease in protein cross-linking and (2) Lac2 suppression reduces both cuticular pigmentation and protein cross-linking.

  9. Mechanical properties of borophene films: a reactive molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Quy Le, Minh; Mortazavi, Bohayra; Rabczuk, Timon

    2016-11-01

    The most recent experimental advances could provide ways for the fabrication of several atomic thick and planar forms of boron atoms. For the first time, we explore the mechanical properties of five types of boron films with various vacancy ratios ranging from 0.1-0.15, using molecular dynamics simulations with ReaxFF force field. It is found that the Young’s modulus and tensile strength decrease with increasing the temperature. We found that boron sheets exhibit an anisotropic mechanical response due to the different arrangement of atoms along the armchair and zigzag directions. At room temperature, 2D Young’s modulus and fracture stress of these five sheets appear in the range 63-136 N m-1 and 12-19 N m-1, respectively. In addition, the strains at tensile strength are in the ranges of 9%-14%, 11%-19%, and 10%-16% at 1, 300, and 600 K, respectively. This investigation not only reveals the remarkable stiffness of 2D boron, but establishes relations between the mechanical properties of the boron sheets to the loading direction, temperature and atomic structures.

  10. Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair

    NASA Astrophysics Data System (ADS)

    Lyphout, Christophe; Fasth, Angelica; Nylen, Per

    2014-02-01

    The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young's modulus and thus a tool for Design Practice for repair applications.

  11. Study on Thermal and Mechanical Properties of EPDM Insulation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Shui; Xu, Jin-Sheng; Chen, Xiong; Jiang, Jing

    As the most common insulation material of solid rocket motors, thermal and mechanical properties of ethylene propylene diene monomer (EPDM) composite are inspected in the study. Referring to the results of thermogravimetric analysis (TGA), composition and morphology of EPDM composite in different thermal degradation degree are investigated by scanning electron microscope (SEM) to inspect the mechanism of thermal insulation. Mechanical properties of EPDM composite in the state of pyrolysis are investigated by uniaxial tensile tests. At the state of initial pyrolysis, composite belongs to the category of hyperelastic-viscoelastic material. The tendency of tensile strength increased and elongation decreased with increasing of heating temperature. Composite behaves as the linear rule at the state of late pyrolysis, which belongs to the category of bittle. The elasticity modulus of curves are almost the same while the heating temperature ranges from 200°C to 300°C, and then gradually go down. The tensile strength of pyrolytic material reach the highest at the heating temperature of 300°C, and the virgin material has the largest elongation.

  12. Mechanical properties for irradiated face-centred cubic nanocrystalline metals.

    PubMed

    Xiao, X Z; Song, D K; Chu, H J; Xue, J M; Duan, H L

    2015-05-08

    In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling the behaviours of GBs. The elastic-viscoplastic self-consistent method with considering grain size distribution is developed to transit the microscopic behaviour of individual grains to the macroscopic properties of nanocrystals (NCs). The proposed theory is applied to model the mechanical properties of irradiated NC copper, and the feasibility and efficiency have been validated by comparing with experimental data. Numerical results show that: (i) irradiation-induced defects can lead to irradiation hardening in the GIs, but the hardening effect decreases with the grain size due to the increasing absorption of defects by GBs. Meanwhile, the absorbed defects would make the GBs softer than the unirradiated case. (ii) There exists a critical grain size for irradiated NC metals, which separates the grain size into the irradiation hardening dominant region (above the critical size) and irradiation softening dominant region (below the critical size). (iii) The distribution of grain size has a significant influence on the mechanical behaviours of both irradiated and unirradiated NCs. The proposed model can offer a valid theoretical foundation to study the irradiation effect on NC materials.

  13. CO2 sequestration utilizing basic-oxygen furnace slag: Controlling factors, reaction mechanisms and V-Cr concerns.

    PubMed

    Su, Tung-Hsin; Yang, Huai-Jen; Shau, Yen-Hong; Takazawa, Eiichi; Lee, Yu-Chen

    2016-03-01

    Basic-oxygen furnace slag (BOF-slag) contains >35% CaO, a potential component for CO2 sequestration. In this study, slag-water-CO2 reaction experiments were conducted with the longest reaction duration extending to 96hr under high CO2 pressures of 100-300kg/cm(2) to optimize BOF-slag carbonation conditions, to address carbonation mechanisms, and to evaluate the extents of V and Cr release from slag carbonation. The slag carbonation degree generally reached the maximum values after 24hr slag-water-CO2 reaction and was controlled by slag particle size and reaction temperature. The maximum carbonation degree of 71% was produced from the experiment using fine slag of ≤0.5mm under 100°C and a CO2 pressure of 250kg/cm(2) with a water/slag ratio of 5. Vanadium release from the slag to water was significantly enhanced (generally >2 orders) by slag carbonation. In contrast, slag carbonation did not promote chromium release until the reaction duration exceeded 24hr. However, the water chromium content was generally at least an order lower than the vanadium concentration, which decreased when the reaction duration exceeded 24hr. Therefore, long reaction durations of 48-96hr are proposed to reduce environmental impacts while keeping high carbonation degrees. Mineral textures and water compositions indicated that Mg-wüstite, in addition to CaO-containing minerals, can also be carbonated. Consequently, the conventional expression that only considered carbonation of the CaO-containing minerals undervalued the CO2 sequestration capability of the BOF-slag by ~20%. Therefore, the BOF-slag is a better CO2 storage medium than that previously recognized.

  14. Mechanical Properties of ZnSe for the FEANICS Module

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2006-01-01

    Mechanical and physical properties of ZnSe windows to be used with the FEANICS (Flow Enclosure Accommodating Novel Investigations in Combustion of Solids) experiments were measured in order to determine design allowables. In addition, the literature on crack growth properties was summarized. The average Young's modulus, Poisson's ratio, equibiaxial fracture strength, flaw size, grain size, Knoop hardness, Vicker's hardness, and branching constant were 74.3 +/- 0.1 GPa, 0.31, 57.8 +/- 6.5 MPa, 21 4 mm, 43 +/- 9 micron, 0.97 +/- 0.02 GPa, 0.97 +/- 0.02 GPa, and 1.0 +/- 0.1 MPam(exp 0.5), respectively. The properties of current ZnSe made by chemical vapor deposition are in good agreement with those measured in the 1970's. The hardness of CVD ZnSe windows is about one twentieth of the sapphire window being replaced, and about one-sixth of that of window glass. Thus the ZnSe window must be handled with great care. The large grain size relative to the inherent crack size implies the need to use single crystal crack growth properties in the design process. In order to determine the local failure stresses in one of the test specimens, a solution for the stresses between the support ring and the edge of a circular plate load between concentric rings was derived.

  15. Low-temperature mechanical properties of glass/epoxy laminates

    NASA Astrophysics Data System (ADS)

    Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

    2014-01-01

    Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

  16. Mechanical properties of biological specimens explored by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kasas, S.; Longo, G.; Dietler, G.

    2013-04-01

    The atomic force microscope is a widely used surface scanning apparatus capable of reconstructing at a nanometric scale resolution the 3D morphology of biological samples. Due to its unique sensitivity, it is now increasingly used as a force sensor, to characterize the mechanical properties of specimens with a similar lateral resolution. This unique capability has produced, in the last years, a vast increase in the number of groups that have exploited the versatility and sensitivity of the instrument to explore the nanomechanics of various samples in the fields of biology, microbiology and medicine. In this review we outline the state of the art in this field, reporting the most interesting recent works involving the exploration of the nanomechanical properties of various biological samples.

  17. Low-temperature mechanical properties of glass/epoxy laminates

    SciTech Connect

    Reed, R. P.; Madhukar, M.; Thaicharoenporn, B.; Martovetsky, N. N.

    2014-01-27

    Selected mechanical properties of glass/epoxy laminate candidates for use in the electrical turn and ground insulation of the ITER Central solenoid (CS) modules were measured. Short-beam shear and flexural tests have been conducted on various E-glass cloth weaves/epoxy laminates at 295 and 77 K. Types of glass weave include 1581, 7500, 7781, and 38050, which represent both satin and plain weaves. The epoxy, planned for use for vacuum-pressure impregnation of the CS module, consists of an anhydride-cured bisphenol F resin system. Inter-laminar shear strength, flexural elastic modulus, and flexural strength have been measured. The data indicate that these properties are dependent on the volume percent of glass. Short-beam shear strength was measured as a function of the span-to-thickness ratio for all laminates at 77 K. Comprehensive fractography was conducted to obtain the failure mode of each short-beam shear test sample.

  18. Evaluation of the mechanical and architectural properties of glenoid bone.

    PubMed

    Mimar, Raghad; Limb, David; Hall, Richard M

    2008-01-01

    Successful glenoid fixation in shoulder arthroplasty is partly dependent on the properties of the underlying bone. Therefore, mapping of the glenoid surface and locating the bone with the highest quality, in terms of mechanical properties and morphology, is a key requirement in ensuring effective fixation. To this end, an investigation was undertaken to study the relationship between indentation behavior and the quality of the glenoid bone. Nineteen embalmed glenoids were obtained from human cadavers (mean age at death, 82 years). Each specimen was tested using a cylindrical indentor at 11 predetermined points to investigate load-displacement behavior. Microcomputed tomography analysis was performed to ascertain the bone volume (BV)/total volume (TV) fraction of the trabecular bone and the subchondral thickness. Statistical analysis showed that both strength and modulus varied with indentation position. Significant relationships were found between either strength or modulus and BV/TV or subchondral thickness, although the explained variance was relatively low.

  19. Estimation of mechanical properties of nanomaterials using artificial intelligence methods

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, V.; Garg, A.; Wong, C. H.; Tai, K.

    2014-09-01

    Computational modeling tools such as molecular dynamics (MD), ab initio, finite element modeling or continuum mechanics models have been extensively applied to study the properties of carbon nanotubes (CNTs) based on given input variables such as temperature, geometry and defects. Artificial intelligence techniques can be used to further complement the application of numerical methods in characterizing the properties of CNTs. In this paper, we have introduced the application of multi-gene genetic programming (MGGP) and support vector regression to formulate the mathematical relationship between the compressive strength of CNTs and input variables such as temperature and diameter. The predictions of compressive strength of CNTs made by these models are compared to those generated using MD simulations. The results indicate that MGGP method can be deployed as a powerful method for predicting the compressive strength of the carbon nanotubes.

  20. Mechanical properties of nacre and highly mineralized bone.

    PubMed

    Currey, J D; Zioupos, P; Davies, P; Casino, A

    2001-01-07

    We compared the mechanical properties of 'ordinary' bovine bone, the highly mineralized bone of the rostrum of the whale Mesoplodon densirostris, and mother of pearl (nacre) of the pearl oyster Pinctada margaritifera. The rostrum and the nacre are similar in having very little organic material. However, the rostral bone is much weaker and more brittle than nacre, which in these properties is close to ordinary bone. The ability of nacre to outperform rostral bone is the result of its extremely well-ordered microstructure, with organic material forming a nearly continuous jacket round all the tiny aragonite plates, a design well adapted to produce toughness. In contrast, in the rostrum the organic material, mainly collagen, is poorly organized and discontinuous, allowing the mineral to join up to form, in effect, a brittle stony material.