[Effect of sintering temperature on mechanical properties of dental zirconia toughened alumina ceramics].

PubMed

Fan, Jiang-Yuan; Lin, Ting-Ting; Hu, Fang-Xuan; Zheng, Rui-Bin; Fan, Fan; Ma, Jian-Feng

2017-04-01

To investigate the effect of sintering temperature on mechanical properties of dental zirconia toughened alumina (ZTA) ceramics prepared by gel-casting technique. The samples prepared by gel-casting were sintered at 1100, 1200, 1250, 1300 and 1400degrees centigrade for each group. The flexural strength, fracture toughness, Vickers hardness and brittleness index were obtained and microscopic morphology of each group was observed under scanning electron microscope (SEM). The data were statistically analyzed using SPSS 19.0 software package. The flexural strength, fracture toughness and Vickers hardness increased with the increasing sintering temperature during 1100~1400degrees centigrade. The lowest brittleness index (0.74±0.16) μm -1/2 was observed in group sintered at 1200degrees centigrade and the highest (2.76±0.14) μm -1/2 was at 1400degrees centigrade (P<0.05), while the flexural strength of these two groups was (46.89±3.24) MPa and (349.64±54.72) MPa, respectively. The ZTA dental ceramics exhibit good machinability with proper sintering temperature (1200degrees centigrade) and the strength meets the requirement of clinical application.

Relationship between dynamical entropy and energy dissipation far from thermodynamic equilibrium.

PubMed

Green, Jason R; Costa, Anthony B; Grzybowski, Bartosz A; Szleifer, Igal

2013-10-08

Connections between microscopic dynamical observables and macroscopic nonequilibrium (NE) properties have been pursued in statistical physics since Boltzmann, Gibbs, and Maxwell. The simulations we describe here establish a relationship between the Kolmogorov-Sinai entropy and the energy dissipated as heat from a NE system to its environment. First, we show that the Kolmogorov-Sinai or dynamical entropy can be separated into system and bath components and that the entropy of the system characterizes the dynamics of energy dissipation. Second, we find that the average change in the system dynamical entropy is linearly related to the average change in the energy dissipated to the bath. The constant energy and time scales of the bath fix the dynamical relationship between these two quantities. These results provide a link between microscopic dynamical variables and the macroscopic energetics of NE processes.

Relationship between dynamical entropy and energy dissipation far from thermodynamic equilibrium

PubMed Central

Green, Jason R.; Costa, Anthony B.; Grzybowski, Bartosz A.; Szleifer, Igal

2013-01-01

Connections between microscopic dynamical observables and macroscopic nonequilibrium (NE) properties have been pursued in statistical physics since Boltzmann, Gibbs, and Maxwell. The simulations we describe here establish a relationship between the Kolmogorov–Sinai entropy and the energy dissipated as heat from a NE system to its environment. First, we show that the Kolmogorov–Sinai or dynamical entropy can be separated into system and bath components and that the entropy of the system characterizes the dynamics of energy dissipation. Second, we find that the average change in the system dynamical entropy is linearly related to the average change in the energy dissipated to the bath. The constant energy and time scales of the bath fix the dynamical relationship between these two quantities. These results provide a link between microscopic dynamical variables and the macroscopic energetics of NE processes. PMID:24065832

Statistical fluctuations in pedestrian evacuation times and the effect of social contagion

NASA Astrophysics Data System (ADS)

Nicolas, Alexandre; Bouzat, Sebastián; Kuperman, Marcelo N.

2016-08-01

Mathematical models of pedestrian evacuation and the associated simulation software have become essential tools for the assessment of the safety of public facilities and buildings. While a variety of models is now available, their calibration and test against empirical data are generally restricted to global averaged quantities; the statistics compiled from the time series of individual escapes ("microscopic" statistics) measured in recent experiments are thus overlooked. In the same spirit, much research has primarily focused on the average global evacuation time, whereas the whole distribution of evacuation times over some set of realizations should matter. In the present paper we propose and discuss the validity of a simple relation between this distribution and the microscopic statistics, which is theoretically valid in the absence of correlations. To this purpose, we develop a minimal cellular automaton, with features that afford a semiquantitative reproduction of the experimental microscopic statistics. We then introduce a process of social contagion of impatient behavior in the model and show that the simple relation under test may dramatically fail at high contagion strengths, the latter being responsible for the emergence of strong correlations in the system. We conclude with comments on the potential practical relevance for safety science of calculations based on microscopic statistics.

Building on the Legacy of Professor Keenan. Entropy An Intrinsic Property of Matter

NASA Astrophysics Data System (ADS)

Gyftopoulos, Elias P.

2008-08-01

In the scientific and engineering literature, entropy—the distinguishing feature of thermodynamics from other branches of physics—is viewed with skepticism, and thought to be not a physical property of matter—like mass or energy—but a measure either of disorder in a system, or of lack of information about the physics of a system in a thermodynamic equilibrium state, and a plethora of expressions are proposed for its analytical representation. In this article, I present briefly two revolutionary nonstatistical expositions of thermodynamics (revolutionary in the sense of Thomas Kuhn, The Structure of Scientific Revolutions, U. Chicago Press, 1970) that apply to all systems (both macroscopic and microscopic, including one spin or a single particle), to all states (thermodynamic equilibrium, and not thermodynamic equilibrium), and that disclose entropy as an intrinsic property of matter. The first theory is presented without reference to quantum mechanics even though quantum theoretic ideas are lurking behind the exposition. The second theory is a unified quantum theory of mechanics and thermodynamics without statistical probabilities, that is, I am not presenting another version of statistical quantum mechanics.

Microscopic Electron Variations Measured Simultaneously By The Cluster Spacecraft

NASA Astrophysics Data System (ADS)

Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Beloff, N.

Data is used from the Particle Correlator experiments running on each of the four Cluster spacecraft so as to determine common microscopic behaviour in the elec- tron population observed over the macroscopic Cluster separations. The Cluster par- ticle correlator experiments operate by forming on board Auto Correlation Functions (ACFs) generated from short time series of electron counts obtained, as a function of electron energy, from the PEACE HEEA sensor. The information on the microscopic variation of the electron flux covers the frequency range DC up to 41 kHz (encom- passing typical electron plasma frequencies and electron gyro frequencies and their harmonics), the electron energy range is that covered by the PEACE HEEA sensor (within the range 1 eV to 26 keV). Results are presented of coherent electron struc- tures observed simultaneously by the four spacecraft in the differing plasma interac- tion regions and boundaries encountered by Cluster. As an aid to understanding the plasma interactions, use is made of numerical simulations which model both the un- derlying statistical properties of the electrons and also the manner in which particle correlator experiments operate.

Interlaboratory study for nickel alloy 625 made by laser powder bed fusion to quantify mechanical property variability.

PubMed

Brown, Christopher U; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2016-08-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser-powder-bed-fusion additive manufacturing machines. The tensile specimens were heat treated and tensile tests conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to 4 times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure.

Interlaboratory study for nickel alloy 625 made by laser powder bed fusion to quantify mechanical property variability

PubMed Central

Brown, Christopher U.; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2017-01-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser-powder-bed-fusion additive manufacturing machines. The tensile specimens were heat treated and tensile tests conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to 4 times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure. PMID:28243032

Interlaboratory Study for Nickel Alloy 625 Made by Laser Powder Bed Fusion to Quantify Mechanical Property Variability

NASA Astrophysics Data System (ADS)

Brown, Christopher U.; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

2016-08-01

Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser powder bed fusion-additive manufacturing machines. The tensile specimens were heat treated and tensile tests were conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to four times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure.

Relating triggering processes in lab experiments with earthquakes.

NASA Astrophysics Data System (ADS)

Baro Urbea, J.; Davidsen, J.; Kwiatek, G.; Charalampidou, E. M.; Goebel, T.; Stanchits, S. A.; Vives, E.; Dresen, G.

2016-12-01

Statistical relations such as Gutenberg-Richter's, Omori-Utsu's and the productivity of aftershocks were first observed in seismology, but are also common to other physical phenomena exhibiting avalanche dynamics such as solar flares, rock fracture, structural phase transitions and even stock market transactions. All these examples exhibit spatio-temporal correlations that can be explained as triggering processes: Instead of being activated as a response to external driving or fluctuations, some events are consequence of previous activity. Although different plausible explanations have been suggested in each system, the ubiquity of such statistical laws remains unknown. However, the case of rock fracture may exhibit a physical connection with seismology. It has been suggested that some features of seismology have a microscopic origin and are reproducible over a vast range of scales. This hypothesis has motivated mechanical experiments to generate artificial catalogues of earthquakes at a laboratory scale -so called labquakes- and under controlled conditions. Microscopic fractures in lab tests release elastic waves that are recorded as ultrasonic (kHz-MHz) acoustic emission (AE) events by means of piezoelectric transducers. Here, we analyse the statistics of labquakes recorded during the failure of small samples of natural rocks and artificial porous materials under different controlled compression regimes. Temporal and spatio-temporal correlations are identified in certain cases. Specifically, we distinguish between the background and triggered events, revealing some differences in the statistical properties. We fit the data to statistical models of seismicity. As a particular case, we explore the branching process approach simplified in the Epidemic Type Aftershock Sequence (ETAS) model. We evaluate the empirical spatio-temporal kernel of the model and investigate the physical origins of triggering. Our analysis of the focal mechanisms implies that the occurrence of the empirical laws extends well beyond purely frictional sliding events, in contrast to what is often assumed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

More, R.M.

A new statistical model (the quantum-statistical model (QSM)) was recently introduced by Kalitkin and Kuzmina for the calculation of thermodynamic properties of compressed matter. This paper examines the QSM and gives (i) a numerical QSM calculation of pressure and energy for aluminum and comparison to existing augmented-plane-wave data; (ii) display of separate kinetic, exchange, and quantum pressure terms; (iii) a study of electron density at the nucleus; (iv) a study of the effects of the Kirzhnitz-Weizsacker parameter controlling the gradient terms; (v) an analytic expansion for very high densities; and (vi) rigorous pressure theorems including a general version of themore » virial theorem which applies to an arbitrary microscopic volume. It is concluded that the QSM represents the most accurate and consistent theory of the Thomas-Fermi type.« less

Uncertainty quantification in nanomechanical measurements using the atomic force microscope

Treesearch

Ryan Wagner; Robert Moon; Jon Pratt; Gordon Shaw; Arvind Raman

2011-01-01

Quantifying uncertainty in measured properties of nanomaterials is a prerequisite for the manufacture of reliable nanoengineered materials and products. Yet, rigorous uncertainty quantification (UQ) is rarely applied for material property measurements with the atomic force microscope (AFM), a widely used instrument that can measure properties at nanometer scale...

Droplets and the three-phase contact line at the nano-scale. Statics and dynamics

NASA Astrophysics Data System (ADS)

Yatsyshin, Petr; Sibley, David; Savva, Nikos; Kalliadasis, Serafim

2014-11-01

Understanding the behaviour of the solid-liquid-vapour contact line at the scale of several tens of molecular diameters is important in wetting hydrodynamics with applications in micro- and nano-fluidics, including the design of lab-on-a-chip devices and surfaces with specific wetting properties. Due to the fluid inhomogeneity at the nano-scale, the application of continuum-mechanical approaches is limited, and a natural way to remedy this is to seek descriptions accounting for the non-local molecular-level interactions. Density Functional Theory (DFT) for fluids offers a statistical-mechanical framework based on expressing the free energy of the fluid-solid pair as a functional of the spatially varying fluid density. DFT allows us to investigate small drops deposited on planar substrates whilst keeping track of the microscopic structural details of the fluid. Starting from a model of intermolecular forces, we systematically obtain interfaces, surface tensions, and the microscopic contact angle. Using a dynamic extension of equilibrium DFT, we investigate the diffusion-driven evolution of the three-phase contact line to gain insight into the dynamic behaviour of the microscopic contact angle, which is still under debate.

Agent-based model with multi-level herding for complex financial systems

NASA Astrophysics Data System (ADS)

Chen, Jun-Jie; Tan, Lei; Zheng, Bo

2015-02-01

In complex financial systems, the sector structure and volatility clustering are respectively important features of the spatial and temporal correlations. However, the microscopic generation mechanism of the sector structure is not yet understood. Especially, how to produce these two features in one model remains challenging. We introduce a novel interaction mechanism, i.e., the multi-level herding, in constructing an agent-based model to investigate the sector structure combined with volatility clustering. According to the previous market performance, agents trade in groups, and their herding behavior comprises the herding at stock, sector and market levels. Further, we propose methods to determine the key model parameters from historical market data, rather than from statistical fitting of the results. From the simulation, we obtain the sector structure and volatility clustering, as well as the eigenvalue distribution of the cross-correlation matrix, for the New York and Hong Kong stock exchanges. These properties are in agreement with the empirical ones. Our results quantitatively reveal that the multi-level herding is the microscopic generation mechanism of the sector structure, and provide new insight into the spatio-temporal interactions in financial systems at the microscopic level.

Agent-based model with multi-level herding for complex financial systems

PubMed Central

Chen, Jun-Jie; Tan, Lei; Zheng, Bo

2015-01-01

In complex financial systems, the sector structure and volatility clustering are respectively important features of the spatial and temporal correlations. However, the microscopic generation mechanism of the sector structure is not yet understood. Especially, how to produce these two features in one model remains challenging. We introduce a novel interaction mechanism, i.e., the multi-level herding, in constructing an agent-based model to investigate the sector structure combined with volatility clustering. According to the previous market performance, agents trade in groups, and their herding behavior comprises the herding at stock, sector and market levels. Further, we propose methods to determine the key model parameters from historical market data, rather than from statistical fitting of the results. From the simulation, we obtain the sector structure and volatility clustering, as well as the eigenvalue distribution of the cross-correlation matrix, for the New York and Hong Kong stock exchanges. These properties are in agreement with the empirical ones. Our results quantitatively reveal that the multi-level herding is the microscopic generation mechanism of the sector structure, and provide new insight into the spatio-temporal interactions in financial systems at the microscopic level. PMID:25669427

Bulk and surface properties of liquid Al-Cr and Cr-Ni alloys.

PubMed

Novakovic, R

2011-06-15

The energetics of mixing and structural arrangement in liquid Al-Cr and Cr-Ni alloys has been analysed through the study of surface properties (surface tension and surface segregation), dynamic properties (chemical diffusion) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of statistical mechanical theory in conjunction with quasi-lattice theory. The Al-Cr phase diagram exhibits the existence of different intermetallic compounds in the solid state, while that of Cr-Ni is a simple eutectic-type phase diagram at high temperatures and includes the low-temperature peritectoid reaction in the range near a CrNi(2) composition. Accordingly, the mixing behaviour in Al-Cr and Cr-Ni alloy melts was studied using the complex formation model in the weak interaction approximation and by postulating Al(8)Cr(5) and CrNi(2) chemical complexes, respectively, as energetically favoured.

Safety of Microsurgery Under Loupes Versus Microscope: A Head-to-Head Comparison of 2 Surgeons With Similar Experiences.

PubMed

Ehanire, Tosan; Singhal, Dhruv; Mast, Bruce; Leyngold, Mark

2018-01-24

Microsurgery is performed using either the operating microscope or loupe magnification. Use of the operating microscope is considered the "criterion standard"; however, loupes are emerging as a safe and reliable technique to perform microsurgery. The purpose of this study was to analyze the safety of microsurgery under loupe magnification compared with the microscope. Previous studies discussing the safety of loupe magnification during microsurgery have been published; however, this is the first study to compare free flap outcomes from 2 surgeons at the same institution, each using their respective technique. The outcomes were compared by retrospective chart review of 116 patients, and 148 microvascular free tissue transfers were performed between January 1, 2013, and July 15, 2016, by 2 surgeons (D.S.) and (M.L.). Patients' demographics, free flap failure rate, and other surgical complications were analyzed. Statistical significance was determined by unpaired t test, and χ analysis was used to determine statistical significance in proportions between groups. Thirty-eight percent of flaps were performed under ×3.5 loupe magnification and 62% under the operating microscope. Most free flaps used were deep inferior epigastric perforator or muscle sparing transverse rectus abdominis flaps (52%) for breast reconstruction, remainder of free flaps included ALT, radial forearm, and latissimus dorsi for a variety of reconstructive applications. There was no significant difference between the loupes and microscope groups in intraoperative anastomotic revision rate (27% vs 17%), postoperative arterial or venous thrombosis (4.4% vs 2.6%, 5.4% vs 2.2%), flap loss (3.6% vs 2.2%), or median length of stay (6 days vs 6.5 days). The loupe magnification group had statistically significant shorter setup time (20 minutes, P < 0.01). Consistent with previously reported studies, we found no statistical difference in free flap outcomes and safety under loupe magnification compared with the operating microscope. This is the first study to demonstrate these findings with 2 microsurgeons both in their first 3 years in practice, with similar training and experience, operating at the same institution and given the same resources, each using either microscopes or loupes for microsurgery.

Reaction rates for mesoscopic reaction-diffusion kinetics

DOE PAGES

Hellander, Stefan; Hellander, Andreas; Petzold, Linda

2015-02-23

The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In thismore » paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. Finally, we show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.« less

Reaction rates for mesoscopic reaction-diffusion kinetics

PubMed Central

Hellander, Stefan; Hellander, Andreas; Petzold, Linda

2016-01-01

The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results. PMID:25768640

Time interval between successive trading in foreign currency market: from microscopic to macroscopic

NASA Astrophysics Data System (ADS)

Sato, Aki-Hiro

2004-12-01

Recently, it has been shown that inter-transaction interval (ITI) distribution of foreign currency rates has a fat tail. In order to understand the statistical property of the ITI dealer model with N interactive agents is proposed. From numerical simulations it is confirmed that the ITI distribution of the dealer model has a power law tail. The random multiplicative process (RMP) can be approximately derived from the ITI of the dealer model. Consequently, we conclude that the power law tail of the ITI distribution of the dealer model is a result of the RMP.

Photon Localization and Dicke Superradiance in Atomic Gases

NASA Astrophysics Data System (ADS)

Akkermans, E.; Gero, A.; Kaiser, R.

2008-09-01

Photon propagation in a gas of N atoms is studied using an effective Hamiltonian describing photon-mediated atomic dipolar interactions. The density P(Γ) of photon escape rates is determined from the spectrum of the N×N random matrix Γij=sin⁡(xij)/xij, where xij is the dimensionless random distance between any two atoms. Varying disorder and system size, a scaling behavior is observed for the escape rates. It is explained using microscopic calculations and a stochastic model which emphasizes the role of cooperative effects in photon localization and provides an interesting relation with statistical properties of “small world networks.”

Dental enamel defect diagnosis through different technology-based devices.

PubMed

Kobayashi, Tatiana Yuriko; Vitor, Luciana Lourenço Ribeiro; Carrara, Cleide Felício Carvalho; Silva, Thiago Cruvinel; Rios, Daniela; Machado, Maria Aparecida Andrade Moreira; Oliveira, Thais Marchini

2018-06-01

Dental enamel defects (DEDs) are faulty or deficient enamel formations of primary and permanent teeth. Changes during tooth development result in hypoplasia (a quantitative defect) and/or hypomineralisation (a qualitative defect). To compare technology-based diagnostic methods for detecting DEDs. Two-hundred and nine dental surfaces of anterior permanent teeth were selected in patients, 6-11 years of age, with cleft lip with/without cleft palate. First, a conventional clinical examination was conducted according to the modified Developmental Defects of Enamel Index (DDE Index). Dental surfaces were evaluated using an operating microscope and a fluorescence-based device. Interexaminer reproducibility was determined using the kappa test. To compare groups, McNemar's test was used. Cramer's V test was used for comparing the distribution of index codes obtained after classification of all dental surfaces. Cramer's V test revealed statistically significant differences (P < .0001) in the distribution of index codes obtained using the different methods; the coefficients were 0.365 for conventional clinical examination versus fluorescence, 0.961 for conventional clinical examination versus operating microscope and 0.358 for operating microscope versus fluorescence. The sensitivity of the operating microscope and fluorescence method was statistically significant (P = .008 and P < .0001, respectively). Otherwise, the results did not show statistically significant differences in accuracy and specificity for either the operating microscope or the fluorescence methods. This study suggests that the operating microscope performed better than the fluorescence-based device and could be an auxiliary method for the detection of DEDs. © 2017 FDI World Dental Federation.

SPY: a new scission-point model based on microscopic inputs to predict fission fragment properties

NASA Astrophysics Data System (ADS)

Panebianco, Stefano; Dubray, Nöel; Goriely, Stéphane; Hilaire, Stéphane; Lemaître, Jean-François; Sida, Jean-Luc

2014-04-01

Despite the difficulty in describing the whole fission dynamics, the main fragment characteristics can be determined in a static approach based on a so-called scission-point model. Within this framework, a new Scission-Point model for the calculations of fission fragment Yields (SPY) has been developed. This model, initially based on the approach developed by Wilkins in the late seventies, consists in performing a static energy balance at scission, where the two fragments are supposed to be completely separated so that their macroscopic properties (mass and charge) can be considered as fixed. Given the knowledge of the system state density, averaged quantities such as mass and charge yields, mean kinetic and excitation energy can then be extracted in the framework of a microcanonical statistical description. The main advantage of the SPY model is the introduction of one of the most up-to-date microscopic descriptions of the nucleus for the individual energy of each fragment and, in the future, for their state density. These quantities are obtained in the framework of HFB calculations using the Gogny nucleon-nucleon interaction, ensuring an overall coherence of the model. Starting from a description of the SPY model and its main features, a comparison between the SPY predictions and experimental data will be discussed for some specific cases, from light nuclei around mercury to major actinides. Moreover, extensive predictions over the whole chart of nuclides will be discussed, with particular attention to their implication in stellar nucleosynthesis. Finally, future developments, mainly concerning the introduction of microscopic state densities, will be briefly discussed.

AGN jets under the microscope: A divide? Doctoral Thesis Award Lecture 2011

NASA Astrophysics Data System (ADS)

Karouzos, M.; Britzen, S.; Witzel, A.; Zensus, A. J.; Eckart, A.

2012-06-01

A new paradigm for active galactic jet kinematics has emerged through detailed investigations of BL Lac objects using very long baseline radio interferometry. In this new scheme, most, if not all, jet components appear to remain stationary with respect to the core but show significant non-radial motions. This paper presents results from our kinematic investigation of the jets of a statistically complete sample of radio-loud flat-spectrum active galaxies, focusing on the comparison between the jet kinematic properties of BL Lacs and flat-spectrum radio-quasars. It is shown that there is a statistically significant difference between the kinematics of the two AGN classes, with BL Lacs showing more bent jets, that are wider and show slower movement along the jet axis, compared to flat-spectrum radio-quasars. This is interpreted as evidence for helically structured jets.

Symmetry breaking gives rise to energy spectra of three states of matter

PubMed Central

Bolmatov, Dima; Musaev, Edvard T.; Trachenko, K.

2013-01-01

A fundamental task of statistical physics is to start with a microscopic Hamiltonian, predict the system's statistical properties and compare them with observable data. A notable current fundamental challenge is to tell whether and how an interacting Hamiltonian predicts different energy spectra, including solid, liquid and gas phases. Here, we propose a new idea that enables a unified description of all three states of matter. We introduce a generic form of an interacting phonon Hamiltonian with ground state configurations minimising the potential. Symmetry breaking SO(3) to SO(2), from the group of rotations in reciprocal space to its subgroup, leads to emergence of energy gaps of shear excitations as a consequence of the Goldstone theorem, and readily results in the emergence of energy spectra of solid, liquid and gas phases. PMID:24077388

Statistical mechanics of self-driven Carnot cycles.

PubMed

Smith, E

1999-10-01

The spontaneous generation and finite-amplitude saturation of sound, in a traveling-wave thermoacoustic engine, are derived as properties of a second-order phase transition. It has previously been argued that this dynamical phase transition, called "onset," has an equivalent equilibrium representation, but the saturation mechanism and scaling were not computed. In this work, the sound modes implementing the engine cycle are coarse-grained and statistically averaged, in a partition function derived from microscopic dynamics on criteria of scale invariance. Self-amplification performed by the engine cycle is introduced through higher-order modal interactions. Stationary points and fluctuations of the resulting phenomenological Lagrangian are analyzed and related to background dynamical currents. The scaling of the stable sound amplitude near the critical point is derived and shown to arise universally from the interaction of finite-temperature disorder, with the order induced by self-amplification.

Statistical Mechanics of the Human Placenta: A Stationary State of a Near-Equilibrium System in a Linear Regime.

PubMed

Lecarpentier, Yves; Claes, Victor; Hébert, Jean-Louis; Krokidis, Xénophon; Blanc, François-Xavier; Michel, Francine; Timbely, Oumar

2015-01-01

All near-equilibrium systems under linear regime evolve to stationary states in which there is constant entropy production rate. In an open chemical system that exchanges matter and energy with the exterior, we can identify both the energy and entropy flows associated with the exchange of matter and energy. This can be achieved by applying statistical mechanics (SM), which links the microscopic properties of a system to its bulk properties. In the case of contractile tissues such as human placenta, Huxley's equations offer a phenomenological formalism for applying SM. SM was investigated in human placental stem villi (PSV) (n = 40). PSV were stimulated by means of KCl exposure (n = 20) and tetanic electrical stimulation (n = 20). This made it possible to determine statistical entropy (S), internal energy (E), affinity (A), thermodynamic force (A / T) (T: temperature), thermodynamic flow (v) and entropy production rate (A / T x v). We found that PSV operated near equilibrium, i.e., A ≺≺ 2500 J/mol and in a stationary linear regime, i.e., (A / T) varied linearly with v. As v was dramatically low, entropy production rate which quantified irreversibility of chemical processes appeared to be the lowest ever observed in any contractile system.

Comparison of spring characteristics of titanium-molybdenum alloy and stainless steel

PubMed Central

Salehi, Anahita; Asatourian, Armen

2017-01-01

Background Titanium-molybdenum alloy (TMA) and stainless steel (SS) wires are commonly used in orthodontics as arch-wires for tooth movement. However, plastic deformation phenomenon in these arch-wires seems to be a major concern among orthodontists. This study aimed to compare the mechanical properties of TMA and SS wires with different dimensions. Material and Methods Seventy-two wire samples (36 TMA and 36 SS) of three different sizes (19×25, 17×25 and 16×22) were analyzed in vitro, with 12 samples in each group. Various mechanical properties of the wires, including spring-back, bending moment and stiffness were determined using a universal testing machine. Student’s t-test showed statistically significant differences in the mean values of all the groups. In addition, metallographic comparison of SS and TMA wires was conducted under an optical microscope. Results The degree of stiffness of 16×22-sized SS and TMA springs was found to be 12±2 and 5±0.4, respectively, while the bending moment was estimated to be 1927±352 (gm-mm) and 932±16 (gm-mm), respectively; the spring-back index was determined to be 0.61±0.2 and 0.4±.09, respectively (p<0.001). There were no statistically significant differences in spring-back index in larger dimensions of the wires. Conclusions Systematic analysis indicated that springs made of TMA were superior compared to those made of SS. Although both from economic and functionality viewpoints the use of TMA is suggested, further clinical investigations are recommended. Key words:Bending moment, optical microscope, spring-back, stainless steel, stiffness, titanium‒molybdenum alloy. PMID:28149469

Maximum Entropy Methods as the Bridge Between Microscopic and Macroscopic Theory

NASA Astrophysics Data System (ADS)

Taylor, Jamie M.

2016-09-01

This paper is concerned with an investigation into a function of macroscopic variables known as the singular potential, building on previous work by Ball and Majumdar. The singular potential is a function of the admissible statistical averages of probability distributions on a state space, defined so that it corresponds to the maximum possible entropy given known observed statistical averages, although non-classical entropy-like objective functions will also be considered. First the set of admissible moments must be established, and under the conditions presented in this work the set is open, bounded and convex allowing a description in terms of supporting hyperplanes, which provides estimates on the development of singularities for related probability distributions. Under appropriate conditions it is shown that the singular potential is strictly convex, as differentiable as the microscopic entropy, and blows up uniformly as the macroscopic variable tends to the boundary of the set of admissible moments. Applications of the singular potential are then discussed, and particular consideration will be given to certain free-energy functionals typical in mean-field theory, demonstrating an equivalence between certain microscopic and macroscopic free-energy functionals. This allows statements about L^1-local minimisers of Onsager's free energy to be obtained which cannot be given by two-sided variations, and overcomes the need to ensure local minimisers are bounded away from zero and +∞ before taking L^∞ variations. The analysis also permits the definition of a dual order parameter for which Onsager's free energy allows an explicit representation. Also, the difficulties in approximating the singular potential by everywhere defined functions, in particular by polynomial functions, are addressed, with examples demonstrating the failure of the Taylor approximation to preserve relevant shape properties of the singular potential.

On the correlation between microscopic structural heterogeneity and embrittlement behavior in metallic glasses

PubMed Central

Li, Weidong; Gao, Yanfei; Bei, Hongbin

2015-01-01

In order to establish a relationship between microstructure and mechanical properties, we systematically annealed a Zr-based bulk metallic glass (BMG) at 100 ~ 300 °C and measured their mechanical and thermal properties. The as-cast BMG exhibits some ductility, while the increase of annealing temperature and time leads to the transition to a brittle behavior that can reach nearly-zero fracture energy. The differential scanning calorimetry did not find any significant changes in crystallization temperature and enthalpy, indicating that the materials still remained fully amorphous. Elastic constants measured by ultrasonic technique vary only slightly with respect to annealing temperature and time, which does obey the empirical relationship between Poisson’s ratio and fracture behavior. Nanoindentation pop-in tests were conducted, from which the pop-in strength mapping provides a “mechanical probe” of the microscopic structural heterogeneities in these metallic glasses. Based on stochastically statistic defect model, we found that the defect density decreases with increasing annealing temperature and annealing time and is exponentially related to the fracture energy. A ductile-versus-brittle behavior (DBB) model based on the structural heterogeneity is developed to identify the physical origins of the embrittlement behavior through the interactions between these defects and crack tip. PMID:26435318

On the correlation between microscopic structural heterogeneity and embrittlement behavior in metallic glasses

DOE PAGES

Li, Weidong; Gao, Yanfei; Bei, Hongbin

2015-10-05

To establish a relationship between microstructure and mechanical properties, we systematically annealed a Zr-based bulk metallic glass (BMG) at 100 ~ 300°C and measured their mechanical and thermal properties. The as-cast BMG exhibits some ductility, while the increase of annealing temperature and time leads to the transition to a brittle behavior that can reach nearly-zero fracture energy. The differential scanning calorimetry did not find any significant changes in crystallization temperature and enthalpy, indicating that the materials still remained fully amorphous. Elastic constants measured by ultrasonic technique vary only slightly with respect to annealing temperature and time, which does obey themore » empirical relationship between Poisson’s ratio and fracture behavior. Nanoindentation pop-in tests were conducted, from which the pop-in strength mapping provides a “mechanical probe” of the microscopic structural heterogeneities in these metallic glasses. Based on stochastically statistic defect model, we found that the defect density decreases with increasing annealing temperature and annealing time and is exponentially related to the fracture energy. A ductile-versus-brittle behavior (DBB) model based on the structural heterogeneity is developed to identify the physical origins of the embrittlement behavior through the interactions between these defects and crack tip.« less

Simulation of transmission electron microscope images of biological specimens.

PubMed

Rullgård, H; Ofverstedt, L-G; Masich, S; Daneholt, B; Oktem, O

2011-09-01

We present a new approach to simulate electron cryo-microscope images of biological specimens. The framework for simulation consists of two parts; the first is a phantom generator that generates a model of a specimen suitable for simulation, the second is a transmission electron microscope simulator. The phantom generator calculates the scattering potential of an atomic structure in aqueous buffer and allows the user to define the distribution of molecules in the simulated image. The simulator includes a well defined electron-specimen interaction model based on the scalar Schrödinger equation, the contrast transfer function for optics, and a noise model that includes shot noise as well as detector noise including detector blurring. To enable optimal performance, the simulation framework also includes a calibration protocol for setting simulation parameters. To test the accuracy of the new framework for simulation, we compare simulated images to experimental images recorded of the Tobacco Mosaic Virus (TMV) in vitreous ice. The simulated and experimental images show good agreement with respect to contrast variations depending on dose and defocus. Furthermore, random fluctuations present in experimental and simulated images exhibit similar statistical properties. The simulator has been designed to provide a platform for development of new instrumentation and image processing procedures in single particle electron microscopy, two-dimensional crystallography and electron tomography with well documented protocols and an open source code into which new improvements and extensions are easily incorporated. © 2011 The Authors Journal of Microscopy © 2011 Royal Microscopical Society.

Urban growth simulation from "first principles".

PubMed

Andersson, Claes; Lindgren, Kristian; Rasmussen, Steen; White, Roger

2002-08-01

General and mathematically transparent models of urban growth have so far suffered from a lack in microscopic realism. Physical models that have been used for this purpose, i.e., diffusion-limited aggregation, dielectric breakdown models, and correlated percolation all have microscopic dynamics for which analogies with urban growth appear stretched. Based on a Markov random field formulation we have developed a model that is capable of reproducing a variety of important characteristic urban morphologies and that has realistic microscopic dynamics. The results presented in this paper are particularly important in relation to "urban sprawl," an important aspect of which is aggressively spreading low-density land uses. This type of growth is increasingly causing environmental, social, and economical problems around the world. The microdynamics of our model, or its "first principles," can be mapped to human decisions and motivations and thus potentially also to policies and regulations. We measure statistical properties of macrostates generated by the urban growth mechanism that we propose, and we compare these to empirical measurements as well as to results from other models. To showcase the open-endedness of the model and to thereby relate our work to applied urban planning we have also included a simulated city consisting of a large number of land use classes in which also topographical data have been used.

Cluster properties of the one-dimensional lattice gas: the microscopic meaning of grand potential.

PubMed

Fronczak, Agata

2013-02-01

Using a concrete example, we demonstrate how the combinatorial approach to a general system of particles, which was introduced in detail in an earlier paper [Fronczak, Phys. Rev. E 86, 041139 (2012)], works and where this approach provides a genuine extension of results obtained through more traditional methods of statistical mechanics. We study the cluster properties of a one-dimensional lattice gas with nearest-neighbor interactions. Three cases (the infinite temperature limit, the range of finite temperatures, and the zero temperature limit) are discussed separately, yielding interesting results and providing alternative proof of known results. In particular, the closed-form expression for the grand partition function in the zero temperature limit is obtained, which results in the nonanalytic behavior of the grand potential, in accordance with the Yang-Lee theory.

Quantification of Nanoscale Density Fluctuations in Biological Cells/Tissues: Inverse Participation Ratio (IPR) Analysis of Transmission Electron Microscopy Images and Implications for Early-Stage Cancer Detection

NASA Astrophysics Data System (ADS)

Pradhan, Prabhakar; Damania, Dhwanil; Joshi, Hrushikesh; Taflove, Allen; Roy, Hemant; Dravid, Vinayak; Backman, Vadim

2010-03-01

We report a study of the nanoscale mass density fluctuations of biological cells and tissues by quantifying their nanoscale light-localization properties. Transmission electron microscope (TEM) images of human cells and tissues are used to construct corresponding effective disordered optical lattices. Light-localization properties are studied by statistical analysis of the inverse participation ratio (IPR) of the eigenfunctions of these optical lattices at the nanoscales. Our results indicate elevation of the nanoscale disorder strength (e.g., refractive index fluctuations) in early carcinogenesis. Importantly, our results demonstrate that the increase in the nanoscale disorder represents the earliest structural alteration in cells undergoing carcinogenesis known to-date. Potential applications of the technique for early stage cancer detection will be discussed.

Non-Gaussianity in a quasiclassical electronic circuit

NASA Astrophysics Data System (ADS)

Suzuki, Takafumi J.; Hayakawa, Hisao

2017-05-01

We study the non-Gaussian dynamics of a quasiclassical electronic circuit coupled to a mesoscopic conductor. Non-Gaussian noise accompanying the nonequilibrium transport through the conductor significantly modifies the stationary probability density function (PDF) of the flux in the dissipative circuit. We incorporate weak quantum fluctuation of the dissipative LC circuit with a stochastic method and evaluate the quantum correction of the stationary PDF. Furthermore, an inverse formula to infer the statistical properties of the non-Gaussian noise from the stationary PDF is derived in the classical-quantum crossover regime. The quantum correction is indispensable to correctly estimate the microscopic transfer events in the QPC with the quasiclassical inverse formula.

Charge frustration in complex fluids and in electronic systems

NASA Astrophysics Data System (ADS)

Carraro, Carlo

1997-02-01

The idea of charge frustration is applied to describe the properties of such diverse physical systems as oil-water-surfactant mixtures and metal-ammonia solutions. The minimalist charge-frustrated model possesses one energy scale and two length scales. For oil-water-surfactant mixtures, these parameters have been determined starting from the microscopic properties of the physical systems under study. Thus, microscopic properties are successfully related to the observed mesoscopic structure.

Fluid leakage near the percolation threshold

NASA Astrophysics Data System (ADS)

Dapp, Wolf B.; Müser, Martin H.

2016-02-01

Percolation is a concept widely used in many fields of research and refers to the propagation of substances through porous media (e.g., coffee filtering), or the behaviour of complex networks (e.g., spreading of diseases). Percolation theory asserts that most percolative processes are universal, that is, the emergent powerlaws only depend on the general, statistical features of the macroscopic system, but not on specific details of the random realisation. In contrast, our computer simulations of the leakage through a seal—applying common assumptions of elasticity, contact mechanics, and fluid dynamics—show that the critical behaviour (how the flow ceases near the sealing point) solely depends on the microscopic details of the last constriction. It appears fundamentally impossible to accurately predict from statistical properties of the surfaces alone how strongly we have to tighten a water tap to make it stop dripping and also how it starts dripping once we loosen it again.

Acquisition of basic microsurgery skills using home-based simulation training: A randomised control study.

PubMed

Malik, Mohsan M; Hachach-Haram, Nadine; Tahir, Muaaz; Al-Musabi, Musab; Masud, Dhalia; Mohanna, Pari-Naz

2017-04-01

Acquisition of fine motor skills required in microsurgery can be challenging in the current training system. Therefore, there is an increased demand for novel training and assessment methods to optimise learning outside the clinical setting. Here, we present a randomised control trial of three microsurgical training models, namely laboratory tabletop training microscope (Laboratory Microscope, LM), low-cost jewellers microscope (Home Microscope, HM) and iPad trainer (Home Tablet, HT). Thirty-nine participants were allocated to four groups, control n = 9, LM n = 10, HM n = 10 and HT n = 10. The participants performed a chicken femoral artery anastomosis at baseline and at the completion of training. The performance was assessed as follows: structured assessment of microsurgery skills (SAMS) score, time taken to complete anastomosis and time for suture placement. No statistically significant difference was noted between the groups at baseline. There was a statistically significant improvement in all training arms between the baseline and post-training for SAMS score, time taken to complete the anastomosis and time per suture placement. In addition, a reduction was observed in the leak rate. No statistical difference was observed among the training arms. Our study demonstrated that at the early stages of microsurgical skill acquisition, home training using either the jewellers microscope or iPad produces comparable results to laboratory-based training using a tabletop microscope. Therefore, home microsurgical training is a viable, easily accessible cost-effective modality that allows trainees to practice and take ownership of their technical skill development in this area. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Scanning SQUID microscope with an in-situ magnetization/demagnetization field for geological samples

NASA Astrophysics Data System (ADS)

Du, Junwei; Liu, Xiaohong; Qin, Huafeng; Wei, Zhao; Kong, Xiangyang; Liu, Qingsong; Song, Tao

2018-04-01

Magnetic properties of rocks are crucial for paleo-, rock-, environmental-magnetism, and magnetic material sciences. Conventional rock magnetometers deal with bulk properties of samples, whereas scanning microscope can map the distribution of remanent magnetization. In this study, a new scanning microscope based on a low-temperature DC superconducting quantum interference device (SQUID) equipped with an in-situ magnetization/demagnetization device was developed. To realize the combination of sensitive instrument as SQUID with high magnetizing/demagnetizing fields, the pick-up coil, the magnetization/demagnetization coils and the measurement mode of the system were optimized. The new microscope has a field sensitivity of 250 pT/√Hz at a coil-to-sample spacing of ∼350 μm, and high magnetization (0-1 T)/ demagnetization (0-300 mT, 400 Hz) functions. With this microscope, isothermal remanent magnetization (IRM) acquisition and the according alternating field (AF) demagnetization curves can be obtained for each point without transferring samples between different procedures, which could result in position deviation, waste of time, and other interferences. The newly-designed SQUID microscope, thus, can be used to investigate the rock magnetic properties of samples at a micro-area scale, and has a great potential to be an efficient tool in paleomagnetism, rock magnetism, and magnetic material studies.

Multiresolution multiscale active mask segmentation of fluorescence microscope images

NASA Astrophysics Data System (ADS)

Srinivasa, Gowri; Fickus, Matthew; Kovačević, Jelena

2009-08-01

We propose an active mask segmentation framework that combines the advantages of statistical modeling, smoothing, speed and flexibility offered by the traditional methods of region-growing, multiscale, multiresolution and active contours respectively. At the crux of this framework is a paradigm shift from evolving contours in the continuous domain to evolving multiple masks in the discrete domain. Thus, the active mask framework is particularly suited to segment digital images. We demonstrate the use of the framework in practice through the segmentation of punctate patterns in fluorescence microscope images. Experiments reveal that statistical modeling helps the multiple masks converge from a random initial configuration to a meaningful one. This obviates the need for an involved initialization procedure germane to most of the traditional methods used to segment fluorescence microscope images. While we provide the mathematical details of the functions used to segment fluorescence microscope images, this is only an instantiation of the active mask framework. We suggest some other instantiations of the framework to segment different types of images.

Transport properties at fluids interfaces: a molecular study for a macroscopic modelling

NASA Astrophysics Data System (ADS)

Russo, Antonio; Morciano, Matteo; Sibley, David N.; Nold, Andreas; Goddard, Benjamin D.; Asinari, Pietro; Kalliadasis, Serafim

2017-11-01

Rapid developments in the field of micro- and nano-fluidics require detailed analysis of the properties of matter at the molecular level. But despite numerous works in the literature, appropriate macroscopic relations able to integrate a microscopic description of fluid and soft matter properties at liquid-vapour and multi-fluid interfaces are missing. As a consequence, studies on interfacial phenomena and micro-device designs often rely on oversimplified assumptions, e.g. that the viscosities can be considered constant across interfaces. In our work, we present non-equilibrium MD simulations to scrutinise efficiently and systematically, through the tools of statistical mechanics, the anisotropic properties of fluids, namely density variations, stress tensor, and shear viscosity, at the fluid interfaces between liquid and vapour and between two partially miscible fluids. Our analysis has led to the formulation of a general relation between shear viscosity and density variations validated for a wide spectrum of interfacial fluid problems. In addition, it provides a rational description of other interfacial quantities of interest, including surface tension and its origins, and more generally, it offers valuable insight of molecular transport phenomena at interfaces.

In Vitro Tissue Differentiation using Dynamics of Tissue Mechanical Properties

NASA Astrophysics Data System (ADS)

Lin, Wei-Chiang; Phillips, Paul J.

2002-03-01

Dynamics of tissue mechanical properties of various human tissue types were studied at macroscopic as well as microscopic level in vitro. This study was conducted to enable the development of a feedback system based on dynamics of tissue mechanical properties for intraoperative guidance for tumor treatment (e.g., RF ablation of liver tumor) and noninvasive tumor localization. Human liver tissues, including normal, cancerous, and cirrhotic tissues, were obtained from patients receiving liver transplant or tumor resection at Vanderbilt University Medical Center with the approval of the Vanderbilt Institutional Review Board. Tissue samples, once resected from the patients, were snap-frozen using liquid nitrogen and stored at -70 oC. Measurements of the mechanical properties of these tissue samples were conducted at the University of Tennessee at Knoxville. Dynamics of tissue mechanical properties were measured from both native and thermally coagulated tissue samples at macroscopic and microscopic level. Preliminary results suggest the dynamics of mechanical properties of normal liver tissues are very different from those of cancerous liver tissues. The correlation between the dynamics of mechanical properties at macroscopic level and those at microscopic level is currently under investigation.

Microscopic investigation of cavitation erosion damage in metals

NASA Technical Reports Server (NTRS)

Hackworh, J. V.; Adler, W. F.

1974-01-01

The results of research to identify the cavitation erosion damage mechanisms at the microscopic level for three metals (aluminum, stainless steel, and titanium) representing a range of properties and microstructure are presented. The metals were exposed to cavitation generated in distilled water by a 20-kHz ultrasonic facility operating at a vibration amplitude of 2 mils. Representative properties of the metals and experimental details are summarized. Replicas of the eroded surfaces of the specimens obtained periodically during exposure were examined with a transmission electron microscope to follow progression of the erosion damage and identify dominant erosion mechanisms as a function of exposure time. Eroded surfaces of selected specimens were also examined with a scanning electron microscope to assist in the interpretation.

On the role of fluctuations in the modeling of complex systems.

NASA Astrophysics Data System (ADS)

Droz, Michel; Pekalski, Andrzej

2016-09-01

The study of models is ubiquitous in sciences like physics, chemistry, ecology, biology or sociology. Models are used to explain experimental facts or to make new predictions. For any system, one can distinguish several levels of description. In the simplest mean-field like description the dynamics is described in terms of spatially averaged quantities while in a microscopic approach local properties are taken into account and local fluctuations for the relevant variables are present. The properties predicted by these two different approaches may be drastically different. In a large body of research literature concerning complex systems this problem is often overlooked and simple mean-field like approximation are used without asking the question of the robustness of the corresponding predictions. The goal of this paper is twofold, first to illustrate the importance of the fluctuations in a self-contained and pedagogical way, by revisiting two different classes of problems where thorough investigations have been conducted (equilibrium and non-equilibrium statistical physics). Second, we present our original research on the dynamics of population of annual plants which are competing among themselves for just one resource (water) through a stochastic dynamics. Depending on the observable considered, the mean-field like and microscopic approaches agree or totally disagree. There is not a general criterion allowing to decide a priori when the two approaches will agree.

Optical design and system characterization of an imaging microscope at 121.6 nm

NASA Astrophysics Data System (ADS)

Gao, Weichuan; Finan, Emily; Kim, Geon-Hee; Kim, Youngsik; Milster, Thomas D.

2018-03-01

We present the optical design and system characterization of an imaging microscope prototype at 121.6 nm. System engineering processes are demonstrated through the construction of a Schwarzschild microscope objective, including tolerance analysis, fabrication, alignment, and testing. Further improvements on the as-built system with a correction phase plate are proposed and analyzed. Finally, the microscope assembly and the imaging properties of the prototype are demonstrated.

Combined use of optical and electron microscopic techniques for the measurement of hygroscopic property, chemical composition, and morphology of individual aerosol particles.

PubMed

Ahn, Kang-Ho; Kim, Sun-Man; Jung, Hae-Jin; Lee, Mi-Jung; Eom, Hyo-Jin; Maskey, Shila; Ro, Chul-Un

2010-10-01

In this work, an analytical method for the characterization of the hygroscopic property, chemical composition, and morphology of individual aerosol particles is introduced. The method, which is based on the combined use of optical and electron microscopic techniques, is simple and easy to apply. An optical microscopic technique was used to perform the visual observation of the phase transformation and hygroscopic growth of aerosol particles on a single particle level. A quantitative energy-dispersive electron probe X-ray microanalysis, named low-Z particle EPMA, was used to perform a quantitative chemical speciation of the same individual particles after the measurement of the hygroscopic property. To validate the analytical methodology, the hygroscopic properties of artificially generated NaCl, KCl, (NH(4))(2)SO(4), and Na(2)SO(4) aerosol particles of micrometer size were investigated. The practical applicability of the analytical method for studying the hygroscopic property, chemical composition, and morphology of ambient aerosol particles is demonstrated.

Nanocellulose Fragmentation Mechanisms and Inversion of Chirality from the Single Particle to the Cholesteric Phase.

PubMed

Nyström, Gustav; Arcari, Mario; Adamcik, Jozef; Usov, Ivan; Mezzenga, Raffaele

2018-05-22

Understanding how nanostructure and nanomechanics influence physical material properties on the micro- and macroscale is an essential goal in soft condensed matter research. Mechanisms governing fragmentation and chirality inversion of filamentous colloids are of specific interest because of their critical role in load-bearing and self-organizing functionalities of soft nanomaterials. Here we provide a fundamental insight into the self-organization across several length scales of nanocellulose, an important biocolloid system with wide-ranging applications as structural, insulating, and functional material. Through a combined microscopic and statistical analysis of nanocellulose fibrils at the single particle level, we show how mechanically and chemically induced fragmentations proceed in this system. Moreover, by studying the bottom-up self-assembly of fragmented carboxylated cellulose nanofibrils into cholesteric liquid crystals, we show via direct microscopic observations that the chirality is inverted from right-handed at the nanofibril level to left-handed at the level of the liquid crystal phase. These results improve our fundamental understanding of nanocellulose and provide an important rationale for its application in colloidal systems, liquid crystals, and nanomaterials.

Visualization of cortical, subcortical, and deep brain neural circuit dynamics during naturalistic mammalian behavior with head-mounted microscopes and chronically implanted lenses

PubMed Central

Resendez, Shanna L.; Jennings, Josh H.; Ung, Randall L.; Namboodiri, Vijay Mohan K.; Zhou, Zhe Charles; Otis, James M.; Nomura, Hiroshi; McHenry, Jenna A.; Kosyk, Oksana; Stuber, Garret D.

2016-01-01

Genetically encoded calcium indicators for visualizing dynamic cellular activity have greatly expanded our understanding of the brain. However, due to light scattering properties of the brain as well as the size and rigidity of traditional imaging technology, in vivo calcium imaging has been limited to superficial brain structures during head fixed behavioral tasks. This limitation can now be circumvented by utilizing miniature, integrated microscopes in conjunction with an implantable microendoscopic lens to guide light into and out of the brain, thus permitting optical access to deep brain (or superficial) neural ensembles during naturalistic behaviors. Here, we describe procedural steps to conduct such imaging studies using mice. However, we anticipate the protocol can be easily adapted for use in other small vertebrates. Successful completion of this protocol will permit cellular imaging of neuronal activity and the generation of data sets with sufficient statistical power to correlate neural activity with stimulus presentation, physiological state, and other aspects of complex behavioral tasks. This protocol takes 6–11 weeks to complete. PMID:26914316

On the way to a microscopic derivation of covariant density functionals in nuclei

NASA Astrophysics Data System (ADS)

Ring, Peter

2018-02-01

Several methods are discussed to derive covariant density functionals from the microscopic input of bare nuclear forces. In a first step there are semi-microscopic functionals, which are fitted to ab-initio calculations of nuclear matter and depend in addition on very few phenomenological parameters. They are able to describe nuclear properties with the same precision as fully phenomenological functionals. In a second step we present first relativistic Brueckner-Hartree-Fock calculations in finite nuclei in order to study properties of such functionals, which cannot be obtained from nuclear matter calculations.

Properties of nanocrystalline Si layers embedded in structure of solar cell

NASA Astrophysics Data System (ADS)

Jurečka, Stanislav; Imamura, Kentaro; Matsumoto, Taketoshi; Kobayashi, Hikaru

2017-12-01

Suppression of spectral reflectance from the surface of solar cell is necessary for achieving a high energy conversion efficiency. We developed a simple method for forming nanocrystalline layers with ultralow reflectance in a broad range of wavelengths. The method is based on metal assisted etching of the silicon surface. In this work, we prepared Si solar cell structures with embedded nanocrystalline layers. The microstructure of embedded layer depends on the etching conditions. We examined the microstructure of the etched layers by a transmission electron microscope and analysed the experimental images by statistical and Fourier methods. The obtained results provide information on the applied treatment operations and can be used to optimize the solar cell forming procedure.

The structural properties of PbF2 by molecular dynamics

NASA Astrophysics Data System (ADS)

Chergui, Y.; Nehaoua, N.; Telghemti, B.; Guemid, S.; Deraddji, N. E.; Belkhir, H.; Mekki, D. E.

2010-08-01

This work presents the use of molecular dynamics (MD) and the code of Dl_Poly, in order to study the structure of fluoride glass after melting and quenching. We are realized the processing phase liquid-phase, simulating rapid quenching at different speeds to see the effect of quenching rate on the operation of the devitrification. This technique of simulation has become a powerful tool for investigating the microscopic behaviour of matter as well as for calculating macroscopic observable quantities. As basic results, we calculated the interatomic distance, angles and statistics, which help us to know the geometric form and the structure of PbF2. These results are in experimental agreement to those reported in literature.

The uncertain trajectory of a pilot-wave

NASA Astrophysics Data System (ADS)

Nachbin, Andre

2015-11-01

Yves Couder (Paris 7) and coworkers reported on walking droplets on the surface of a vibrating bath. John Bush (MIT) and coworkers also produced laboratory experiments which were compared to theoretical predictions. Both groups discussed the pilot-wave properties previously thought to be peculiar to the microscopic, quantum realm. Of particular interest is the wavelike statistics for pilot-wave dynamics in a confined domain. We present a one dimensional water wave model for a droplet bouncing in a confined domain. The mathematical model makes use of conformal mapping which allows for the presence of submerged barriers. The computational simulations produce tunneling events. Work supported by CNPq grant 454027/2008-7 and by FAPERJ Cientistas do Nosso Estado grant 102917/2011.

Optimal detection pinhole for lowering speckle noise while maintaining adequate optical sectioning in confocal reflectance microscopes

PubMed Central

Rajadhyaksha, Milind

2012-01-01

Abstract. Coherent speckle influences the resulting image when narrow spectral line-width and single spatial mode illumination are used, though these are the same light-source properties that provide the best radiance-to-cost ratio. However, a suitable size of the detection pinhole can be chosen to maintain adequate optical sectioning while making the probability density of the speckle noise more normal and reducing its effect. The result is a qualitatively better image with improved contrast, which is easier to read. With theoretical statistics and experimental results, we show that the detection pinhole size is a fundamental parameter for designing imaging systems for use in turbid media. PMID:23224184

Scanning laser microscope for imaging nanostructured superconductors

NASA Astrophysics Data System (ADS)

Ishida, Takekazu; Arai, Kohei; Akita, Yukio; Miyanari, Mitsunori; Minami, Yusuke; Yotsuya, Tsutomu; Kato, Masaru; Satoh, Kazuo; Uno, Mayumi; Shimakage, Hisashi; Miki, Shigehito; Wang, Zhen

2010-10-01

The nanofabrication of superconductors yields various interesting features in superconducting properties. A variety of different imaging techniques have been developed for probing the local superconducting profiles. A scanning pulsed laser microscope has been developed by the combination of the XYZ piezo-driven stages and an optical fiber with an aspheric focusing lens. The scanning laser microscope is used to understand the position-dependent properties of a superconducting MgB 2 stripline of length 100 μm and width of 3 μm under constant bias current. Our results show that the superconducting stripline can clearly be seen in the contour image of the scanning laser microscope on the signal voltage. It is suggested from the observed image that the inhomogeneity is relevant in specifying the operating conditions such as detection efficiency of the sensor.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments.

PubMed

Espinosa, G; Rodríguez, R; Gil, J M; Suzuki-Vidal, F; Lebedev, S V; Ciardi, A; Rubiano, J G; Martel, P

2017-03-01

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments

NASA Astrophysics Data System (ADS)

Espinosa, G.; Rodríguez, R.; Gil, J. M.; Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Rubiano, J. G.; Martel, P.

2017-03-01

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.

WETTABILITY AND IMBIBITION: MICROSCOPIC DISTRIBUTION OF WETTING AND ITS CONSEQUENCES AT THE CORE AND FIELD SCALES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jill S. Buckley; Norman R. Morrow; Chris Palmer

2003-02-01

The questions of reservoir wettability have been approached in this project from three directions. First, we have studied the properties of crude oils that contribute to wetting alteration in a reservoir. A database of more than 150 different crude oil samples has been established to facilitate examination of the relationships between crude oil chemical and physical properties and their influence on reservoir wetting. In the course of this work an improved SARA analysis technique was developed and major advances were made in understanding asphaltene stability including development of a thermodynamic Asphaltene Solubility Model (ASM) and empirical methods for predicting themore » onset of instability. The CO-Wet database is a resource that will be used to guide wettability research in the future. The second approach is to study crude oil/brine/rock interactions on smooth surfaces. Contact angle measurements were made under controlled conditions on mica surfaces that had been exposed to many of the oils in the CO-Wet database. With this wealth of data, statistical tests can now be used to examine the relationships between crude oil properties and the tendencies of those oils to alter wetting. Traditionally, contact angles have been used as the primary wetting assessment tool on smooth surfaces. A new technique has been developed using an atomic forces microscope that adds a new dimension to the ability to characterize oil-treated surfaces. Ultimately we aim to understand wetting in porous media, the focus of the third approach taken in this project. Using oils from the CO-Wet database, experimental advances have been made in scaling the rate of imbibition, a sensitive measure of core wetting. Application of the scaling group to mixed-wet systems has been demonstrated for a range of core conditions. Investigations of imbibition in gas/liquid systems provided the motivation for theoretical advances as well. As a result of this project we have many new tools for studying wetting at microscopic and macroscopic scales and a library of well-characterized fluids for use in studies of crude oil/brine/rock interactions.« less

Synthesis Properties and Electron Spin Resonance Properties of Titanic Materials (abstract)

NASA Astrophysics Data System (ADS)

Cho, Jung Min; Lee, Jun; Kim, Tak Hee; Sun, Min Ho; Jang, Young Bae; Cho, Sung June

2009-04-01

Titanic materials were synthesized by hydrothermal method of TiO2 anatase in 10M LiOH, 10M NaOH, and 14M KOH at 130° C for 30 hours. Alkaline media were removed from the synthesized products using 0.1N HCl aqueous solution. The as-prepared samples were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, Brunauer-Emmett-Teller isotherm, and electron spin resonance. Different shapes of synthesized products were observed through the typical electron microscope and indicated that the formation of the different morphologies depends on the treatment conditions of highly alkaline media. Many micropores were observed in the cubic or octahedral type of TiO2 samples through the typical electron microscope and Langmuir adsorption-desorption isotherm of liquid nitrogen at 77° K. Electron spin resonance studies have also been carried out to verify the existence of paramagnetic sites such as oxygen vacancies on the titania samples. The effect of alkali metal ions on the morphologies and physicochemical properties of nanoscale titania are discussed.

Surface properties for α-cluster nuclear matter

NASA Astrophysics Data System (ADS)

Castro, J. J.; Soto, J. R.; Yépez, E.

2013-03-01

We introduce a new microscopic model for α-cluster matter, which simulates the properties of ordinary nuclear matter and α-clustering in a curved surface of a large but finite nucleus. The model is based on a nested icosahedral fullerene-like multiple-shell structure, where each vertex is occupied by a microscopic α-particle. The novel aspect of this model is that it allows a consistent description of nuclear surface properties from microscopic parameters to be made without using the leptodermous expansion. In particular, we show that the calculated surface energy is in excellent agreement with the corresponding coefficient of the Bethe-Weizäcker semi-empirical mass formula. We discuss the properties of the surface α-cluster state, which resembles an ultra cold bosonic quantum gas trapped in an optical lattice. By comparing the surface and interior states we are able to estimate the α preformation probability. Possible extensions of this model to study nuclear dynamics through surface vibrations and departures from approximate sphericity are mentioned.

Osmotic Pressure in Ionic Microgel Dispersions

NASA Astrophysics Data System (ADS)

Denton, Alan R.; Tang, Qiyun

2015-03-01

Microgels are microscopic gel particles, typically 10-1000 nm in size, that are swollen by a solvent. Hollow microgels (microcapsules) can encapsulate cargo, such as dye molecules or drugs, in their solvent-filled cavities. Their sensitive response to environmental conditions (e.g., temperature, pH) and influence on flow properties suit microgels to widespread applications in the chemical, pharmaceutical, food, and consumer care industries. When dispersed in water, polyelectrolyte gels become charged through dissociation of counterions. The electrostatic contribution to the osmotic pressure inside and outside of ionic microgels influences particle swelling and bulk materials properties, including thermodynamic, structural, optical, and rheological properties. Within the primitive and cell models of polyelectrolyte solutions, we derive an exact statistical mechanical formula for the contribution of mobile microions to the osmotic pressure within ionic microgels. Using Poisson-Boltzmann theory, we validate this result by explicitly calculating ion distributions across the surface of an ionic microgel and the electrostatic contribution to the osmotic pressure. Within a coarse-grained one-component model, we further chart the limits of the cell model for salty dispersions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

Quantum Foundations of Quantum Information

NASA Astrophysics Data System (ADS)

Griffiths, Robert

2009-03-01

The main foundational issue for quantum information is: What is quantum information about? What does it refer to? Classical information typically refers to physical properties, and since classical is a subset of quantum information (assuming the world is quantum mechanical), quantum information should--and, it will be argued, does--refer to quantum physical properties represented by projectors on appropriate subspaces of a quantum Hilbert space. All sorts of microscopic and macroscopic properties, not just measurement outcomes, can be represented in this way, and are thus a proper subject of quantum information. The Stern-Gerlach experiment illustrates this. When properties are compatible, which is to say their projectors commute, Shannon's classical information theory based on statistical correlations extends without difficulty or change to the quantum case. When projectors do not commute, giving rise to characteristic quantum effects, a foundation for the subject can still be constructed by replacing the ``measurement and wave-function collapse'' found in textbooks--an efficient calculational tool, but one giving rise to numerous conceptual difficulties--with a fully consistent and paradox free stochastic formulation of standard quantum mechanics. This formulation is particularly helpful in that it contains no nonlocal superluminal influences; the reason the latter carry no information is that they do not exist.

Stochastic model of financial markets reproducing scaling and memory in volatility return intervals

NASA Astrophysics Data System (ADS)

Gontis, V.; Havlin, S.; Kononovicius, A.; Podobnik, B.; Stanley, H. E.

2016-11-01

We investigate the volatility return intervals in the NYSE and FOREX markets. We explain previous empirical findings using a model based on the interacting agent hypothesis instead of the widely-used efficient market hypothesis. We derive macroscopic equations based on the microscopic herding interactions of agents and find that they are able to reproduce various stylized facts of different markets and different assets with the same set of model parameters. We show that the power-law properties and the scaling of return intervals and other financial variables have a similar origin and could be a result of a general class of non-linear stochastic differential equations derived from a master equation of an agent system that is coupled by herding interactions. Specifically, we find that this approach enables us to recover the volatility return interval statistics as well as volatility probability and spectral densities for the NYSE and FOREX markets, for different assets, and for different time-scales. We find also that the historical S&P500 monthly series exhibits the same volatility return interval properties recovered by our proposed model. Our statistical results suggest that human herding is so strong that it persists even when other evolving fluctuations perturbate the financial system.

How multiplicity determines entropy and the derivation of the maximum entropy principle for complex systems.

PubMed

Hanel, Rudolf; Thurner, Stefan; Gell-Mann, Murray

2014-05-13

The maximum entropy principle (MEP) is a method for obtaining the most likely distribution functions of observables from statistical systems by maximizing entropy under constraints. The MEP has found hundreds of applications in ergodic and Markovian systems in statistical mechanics, information theory, and statistics. For several decades there has been an ongoing controversy over whether the notion of the maximum entropy principle can be extended in a meaningful way to nonextensive, nonergodic, and complex statistical systems and processes. In this paper we start by reviewing how Boltzmann-Gibbs-Shannon entropy is related to multiplicities of independent random processes. We then show how the relaxation of independence naturally leads to the most general entropies that are compatible with the first three Shannon-Khinchin axioms, the (c,d)-entropies. We demonstrate that the MEP is a perfectly consistent concept for nonergodic and complex statistical systems if their relative entropy can be factored into a generalized multiplicity and a constraint term. The problem of finding such a factorization reduces to finding an appropriate representation of relative entropy in a linear basis. In a particular example we show that path-dependent random processes with memory naturally require specific generalized entropies. The example is to our knowledge the first exact derivation of a generalized entropy from the microscopic properties of a path-dependent random process.

A comparison of microscopic ink characteristics of 35 commercially available surgical margin inks.

PubMed

Milovancev, Milan; Löhr, Christiane V; Bildfell, Robert J; Gelberg, Howard B; Heidel, Jerry R; Valentine, Beth A

2013-11-01

To compare microscopic characteristics of commercially available surgical margin inks used for surgical pathology specimens. Prospective in vitro study. Thirty-five different surgical margin inks (black, blue, green, orange, red, violet, and yellow from 5 different manufacturers). Inks were applied to uniform, single-source, canine cadaveric full-thickness ventral abdominal tissue blocks. Tissue blocks and ink manufacturers were randomly paired and each color was applied to a length of the cut tissue margin. After drying, tissues were fixed in formalin, and 3 radial slices were obtained from each color section and processed for routine histologic evaluation, yielding 105 randomly numbered slides with each manufacturer's color represented in triplicate. Slides were evaluated by 5 blinded, board-certified veterinary anatomic pathologists using a standardized scoring scheme. Statistical analyses were performed to evaluate for ink manufacturer effects on scores, correlation among different subjective variables, and pathologist agreement. Black and blue had the most consistently high scores whereas red and violet had the most consistently low overall scores, across all manufacturers. All colors tested, except yellow, had statistically significant differences in overall scores among individual manufacturers. Overall score was significantly correlated to all other subjective microscopic scores evaluated. The average Spearman correlation coefficient among the 10 pairwise pathologists overall ink scores was 0.60. There are statistically significant differences in microscopic ink characteristics among manufacturers, with a notable degree of inter-pathologist agreement. © Copyright 2013 by The American College of Veterinary Surgeons.

Effects of intraoral aging on surface properties of coated nickel-titanium archwires.

PubMed

Rongo, Roberto; Ametrano, Gianluca; Gloria, Antonio; Spagnuolo, Gianrico; Galeotti, Angela; Paduano, Sergio; Valletta, Rosa; D'Antò, Vincenzo

2014-07-01

To evaluate the effects of intraoral aging on surface properties of esthetic and conventional nickel-titanium (NiTi) archwires. Five NiTi wires were considered for this study (Sentalloy, Sentalloy High Aesthetic, Superelastic Titanium Memory Wire, Esthetic Superelastic Titanium Memory Wire, and EverWhite). For each type of wire, four samples were analyzed as received and after 1 month of clinical use by an atomic force microscope (AFM) and a scanning electronic microscope (SEM). To evaluate sliding resistance, two stainless steel plates with three metallic or three monocrystalline brackets, bonded in passive configuration, were manufactured; four as-received and retrieved samples for every wire were pulled five times at 5 mm/min for 1 minute by means of an Instron 5566, recording the greatest friction value (N). Data were analyzed by one-way analysis of variance and by Student's t-test. After clinical use, surface roughness increased considerably. The SEM images showed homogeneity for the as-received control wires; however, after clinical use esthetic wires exhibited a heterogeneous surface with craters and bumps. The lowest levels of friction were observed with the as-received Superelastic Titanium Memory Wire on metallic brackets. When tested on ceramic brackets, all the wires exhibited an increase in friction (t-test; P < .05). Furthermore, all the wires, except Sentalloy, showed a statistically significant increase in friction between the as-received and retrieved groups (t-test; P < .05). Clinical use of the orthodontic wires increases their surface roughness and the level of friction.

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models.

PubMed

Elben, A; Vermersch, B; Dalmonte, M; Cirac, J I; Zoller, P

2018-02-02

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Rényi Entropies from Random Quenches in Atomic Hubbard and Spin Models

NASA Astrophysics Data System (ADS)

Elben, A.; Vermersch, B.; Dalmonte, M.; Cirac, J. I.; Zoller, P.

2018-02-01

We present a scheme for measuring Rényi entropies in generic atomic Hubbard and spin models using single copies of a quantum state and for partitions in arbitrary spatial dimensions. Our approach is based on the generation of random unitaries from random quenches, implemented using engineered time-dependent disorder potentials, and standard projective measurements, as realized by quantum gas microscopes. By analyzing the properties of the generated unitaries and the role of statistical errors, with respect to the size of the partition, we show that the protocol can be realized in existing quantum simulators and used to measure, for instance, area law scaling of entanglement in two-dimensional spin models or the entanglement growth in many-body localized systems.

Replication of Cancellation Orders Using First-Passage Time Theory in Foreign Currency Market

NASA Astrophysics Data System (ADS)

Boilard, Jean-François; Kanazawa, Kiyoshi; Takayasu, Hideki; Takayasu, Misako

Our research focuses on the annihilation dynamics of limit orders in a spot foreign currency market for various currency pairs. We analyze the cancellation order distribution conditioned on the normalized distance from the mid-price; where the normalized distance is defined as the final distance divided by the initial distance. To reproduce real data, we introduce two simple models that assume the market price moves randomly and cancellation occurs either after fixed time t or following the Poisson process. Results of our model qualitatively reproduce basic statistical properties of cancellation orders of the data when limit orders are cancelled according to the Poisson process. We briefly discuss implication of our findings in the construction of more detailed microscopic models.

"Breath figures" on leaf surfaces-formation and effects of microscopic leaf wetness.

PubMed

Burkhardt, Juergen; Hunsche, Mauricio

2013-01-01

"Microscopic leaf wetness" means minute amounts of persistent liquid water on leaf surfaces which are invisible to the naked eye. The water is mainly maintained by transpired water vapor condensing onto the leaf surface and to attached leaf surface particles. With an estimated average thickness of less than 1 μm, microscopic leaf wetness is about two orders of magnitude thinner than morning dewfall. The most important physical processes which reduce the saturation vapor pressure and promote condensation are cuticular absorption and the deliquescence of hygroscopic leaf surface particles. Deliquescent salts form highly concentrated solutions. Depending on the type and concentration of the dissolved ions, the physicochemical properties of microscopic leaf wetness can be considerably different from those of pure water. Microscopic leaf wetness can form continuous thin layers on hydrophobic leaf surfaces and in specific cases can act similar to surfactants, enabling a strong potential influence on the foliar exchange of ions. Microscopic leaf wetness can also enhance the dissolution, the emission, and the reaction of specific atmospheric trace gases e.g., ammonia, SO2, or ozone, leading to a strong potential role for microscopic leaf wetness in plant/atmosphere interaction. Due to its difficult detection, there is little knowledge about the occurrence and the properties of microscopic leaf wetness. However, based on the existing evidence and on physicochemical reasoning it can be hypothesized that microscopic leaf wetness occurs on almost any plant worldwide and often permanently, and that it significantly influences the exchange processes of the leaf surface with its neighboring compartments, i.e., the plant interior and the atmosphere. The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past.

Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki, E-mail: toshiaki.tanigaki.mv@hitachi.com

2015-02-16

Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44 pm.

Microscopic properties of ionic liquid/organic semiconductor interfaces revealed by molecular dynamics simulations.

PubMed

Yokota, Yasuyuki; Miyamoto, Hiroo; Imanishi, Akihito; Takeya, Jun; Inagaki, Kouji; Morikawa, Yoshitada; Fukui, Ken-Ichi

2018-05-09

Electric double-layer transistors based on ionic liquid/organic semiconductor interfaces have been extensively studied during the past decade because of their high carrier densities at low operation voltages. Microscopic structures and the dynamics of ionic liquids likely determine the device performance; however, knowledge of these is limited by a lack of appropriate experimental tools. In this study, we investigated ionic liquid/organic semiconductor interfaces using molecular dynamics to reveal the microscopic properties of ionic liquids. The organic semiconductors include pentacene, rubrene, fullerene, and 7,7,8,8-tetracyanoquinodimethane (TCNQ). While ionic liquids close to the substrate always form the specific layered structures, the surface properties of organic semiconductors drastically alter the ionic dynamics. Ionic liquids at the fullerene interface behave as a two-dimensional ionic crystal because of the energy gain derived from the favorable electrostatic interaction on the corrugated periodic substrate.

A Bottom-Up Approach to Understanding Protein Layer Formation at Solid-Liquid Interfaces

PubMed Central

Kastantin, Mark; Langdon, Blake B.; Schwartz, Daniel K.

2014-01-01

A common goal across different fields (e.g. separations, biosensors, biomaterials, pharmaceuticals) is to understand how protein behavior at solid-liquid interfaces is affected by environmental conditions. Temperature, pH, ionic strength, and the chemical and physical properties of the solid surface, among many factors, can control microscopic protein dynamics (e.g. adsorption, desorption, diffusion, aggregation) that contribute to macroscopic properties like time-dependent total protein surface coverage and protein structure. These relationships are typically studied through a top-down approach in which macroscopic observations are explained using analytical models that are based upon reasonable, but not universally true, simplifying assumptions about microscopic protein dynamics. Conclusions connecting microscopic dynamics to environmental factors can be heavily biased by potentially incorrect assumptions. In contrast, more complicated models avoid several of the common assumptions but require many parameters that have overlapping effects on predictions of macroscopic, average protein properties. Consequently, these models are poorly suited for the top-down approach. Because the sophistication incorporated into these models may ultimately prove essential to understanding interfacial protein behavior, this article proposes a bottom-up approach in which direct observations of microscopic protein dynamics specify parameters in complicated models, which then generate macroscopic predictions to compare with experiment. In this framework, single-molecule tracking has proven capable of making direct measurements of microscopic protein dynamics, but must be complemented by modeling to combine and extrapolate many independent microscopic observations to the macro-scale. The bottom-up approach is expected to better connect environmental factors to macroscopic protein behavior, thereby guiding rational choices that promote desirable protein behaviors. PMID:24484895

Characterization of platelet adhesion under flow using microscopic image sequence analysis.

PubMed

Machin, M; Santomaso, A; Cozzi, M R; Battiston, M; Mazzuccato, M; De Marco, L; Canu, P

2005-07-01

A method for quantitative analysis of platelet deposition under flow is discussed here. The model system is based upon perfusion of blood platelets over an adhesive substrate immobilized on a glass coverslip acting as the lower surface of a rectangular flow chamber. The perfusion apparatus is mounted onto an inverted microscope equipped with epifluorescent illumination and intensified CCD video camera. Characterization is based on information obtained from a specific image analysis method applied to continuous sequences of microscopical images. Platelet recognition across the sequence of images is based on a time-dependent, bidimensional, gaussian-like pdf. Once a platelet is located,the variation of its position and shape as a function of time (i.e., the platelet history) can be determined. Analyzing the history we can establish if the platelet is moving on the surface, the frequency of this movement and the distance traveled before its resumes the velocity of a non-interacting cell. Therefore, we can determine how long the adhesion would last which is correlated to the resistance of the platelet-substrate bond. This algorithm enables the dynamic quantification of trajectories, as well as residence times, arrest and release frequencies for a high numbers of platelets at the same time. Statistically significant conclusions on platelet-surface interactions can then be obtained. An image analysis tool of this kind can dramatically help the investigation and characterization of the thrombogenic properties of artificial surfaces such as those used in artificial organs and biomedical devices.

The stability of cellulose: a statistical perspective from a coarse-grained model of hydrogen-bond networks.

PubMed

Shen, Tongye; Gnanakaran, S

2009-04-22

A critical roadblock to the production of biofuels from lignocellulosic biomass is the efficient degradation of crystalline microfibrils of cellulose to glucose. A microscopic understanding of how different physical conditions affect the overall stability of the crystalline structure of microfibrils could facilitate the design of more effective protocols for their degradation. One of the essential physical interactions that stabilizes microfibrils is a network of hydrogen (H) bonds: both intrachain H-bonds between neighboring monomers of a single cellulose polymer chain and interchain H-bonds between adjacent chains. We construct a statistical mechanical model of cellulose assembly at the resolution of explicit hydrogen-bond networks. Using the transfer matrix method, the partition function and the subsequent statistical properties are evaluated. With the help of this lattice-based model, we capture the plasticity of the H-bond network in cellulose due to frustration and redundancy in the placement of H-bonds. This plasticity is responsible for the stability of cellulose over a wide range of temperatures. Stable intrachain and interchain H-bonds are identified as a function of temperature that could possibly be manipulated toward rational destruction of crystalline cellulose.

Networking—a statistical physics perspective

NASA Astrophysics Data System (ADS)

Yeung, Chi Ho; Saad, David

2013-03-01

Networking encompasses a variety of tasks related to the communication of information on networks; it has a substantial economic and societal impact on a broad range of areas including transportation systems, wired and wireless communications and a range of Internet applications. As transportation and communication networks become increasingly more complex, the ever increasing demand for congestion control, higher traffic capacity, quality of service, robustness and reduced energy consumption requires new tools and methods to meet these conflicting requirements. The new methodology should serve for gaining better understanding of the properties of networking systems at the macroscopic level, as well as for the development of new principled optimization and management algorithms at the microscopic level. Methods of statistical physics seem best placed to provide new approaches as they have been developed specifically to deal with nonlinear large-scale systems. This review aims at presenting an overview of tools and methods that have been developed within the statistical physics community and that can be readily applied to address the emerging problems in networking. These include diffusion processes, methods from disordered systems and polymer physics, probabilistic inference, which have direct relevance to network routing, file and frequency distribution, the exploration of network structures and vulnerability, and various other practical networking applications.

Microscopic hematuria and calculus-related ureteral obstruction.

PubMed

Stewart, D P; Kowalski, R; Wong, P; Krome, R

1990-01-01

The evaluation of patients with ureteral calculi in the emergency department has historically included urinalysis (UA) and intravenous pyelograms (IVP). This retrospective study was done to determine if a statistically significant relationship existed between the degree of calculus-related ureteral obstruction, proven by IVP, and the presence or absence of microscopic hematuria. Urine red blood cells were recorded as less than 3 rbc/hpf (negative) or greater than or equal to 3 rbc/hpf (positive). IVPs were recorded as nonsevere or severe. IVP criteria were based on the presence or absence of extravasation, greater than 2-hour ureteral filling times, and a numerical scoring system of 1 to 4 for ureteral or calyceal dilatation and nephrogenic effect. Eighty-nine men (72%) had non-severe obstructions and 34 (28%) had severe obstructions. Twenty-five women (68%) had nonsevere obstructions and 12 (32%) had severe obstructions. Of the 28 patients with normal UAs, 11 had severe ureteral obstructions and 17 had nonsevere ureteral obstructions. There were no statistically significant differences between the presence or absence of significant microscopic hematuria and the presence or absence of severe ureteral obstruction. Microscopic hematuria is neither sensitive nor specific in determining the degree of calculus-related ureteral obstruction.

The Scanning Optical Microscope: An Overview

NASA Astrophysics Data System (ADS)

Kino, G. S.; Corte, T. R.; Xiao, G. Q.

1988-07-01

In the last few years there has been a resurgence in research on optical microscopes. One reason stems from the invention of the acoustic microscope by Quate and Lemons,1 and the realization that some of the same principles could be applied to the optical microscope. The acoustic microscope has better transverse definition for the same wavelength than the standard optical microscope and at the same time has far better range definition. Consequently, Kompfner, who was involved with the work on the early acoustic microscope, decided to try out similar scanning microscope principles with optics, and started a group with Wilson and Sheppard to carry out such research at Oxford.2 Sometime earlier, Petran et a13 had invented the tandem scanning microscope which used many of the same principles. Now, in our laboratory at Stanford, these ideas on the tandem scanning microscope and the scanning optical microscope are converging. Another aspect of this work, which stems from the earlier experience with the acoustic microscope, involves measurement of both phase and amplitude of the optical beam. It is also possible to use scanned optical microscopy for other purposes. For instance, an optical beam can be used to excite electrons and holes in semiconductors, and the generated current can be measured. By scanning the optical beam over the semiconductor, an image can be obtained of the regions where there is strong or weak electron hole generation. This type of microscope is called OBIC (Optical Beam Induced Current). A second application involves fluorescent imaging of biological materials. Here we have the excellent range definition of a scanning optical microscope which eliminates unwanted glare from regions of the material where the beam is unfocused.3 A third application is focused on the heating effect of the light beam. With such a system, images can be obtained which are associated with changes in the thermal properties of a material, changes in recombination rates in semiconductors, and differences in material properties associated with either acoustic or thermal effects.4,5 Thus, the range of scanning optical microscopy applications is very large. In the main, the most important applications have been to semiconductors and to biology.

A hybrid scanning force and light microscope for surface imaging and three-dimensional optical sectioning in differential interference contrast.

PubMed

Stemmer, A

1995-04-01

The design of a scanned-cantilever-type force microscope is presented which is fully integrated into an inverted high-resolution video-enhanced light microscope. This set-up allows us to acquire thin optical sections in differential interference contrast (DIC) or polarization while the force microscope is in place. Such a hybrid microscope provides a unique platform to study how cell surface properties determine, or are affected by, the three-dimensional dynamic organization inside the living cell. The hybrid microscope presented in this paper has proven reliable and versatile for biological applications. It is the only instrument that can image a specimen by force microscopy and high-power DIC without having either to translate the specimen or to remove the force microscope. Adaptation of the design features could greatly enhance the suitability of other force microscopes for biological work.

[Strategy of molecular design of drugs: the unification of macro-properties and micro-structures of a molecule].

PubMed

Guo, Zong-Ru

2008-03-01

The interaction of a drug with the organism involves both the disposition of a drug by the organism and the action of a drug on the organism. The disposition of various exogenous substances, including drugs, complies with general rules. The underlying physical and chemical changes to different drugs in view of time and space, i. e. pharmacokinetics, share common characteristics, that is the tout ensemble of a molecule and its macroscopic properties convey direct effect on the pharmacokinetic behavior as the tendency and consequence of biological evolution. The action of a drug on the organism, on the other hand, implicates the physico-chemical binding of a drug molecule to the target protein, which induces pharmacological and toxicological effects. The biological reactions, no matter beneficial or adverse, are all specific and individual manifestation of the drug molecule and determined by the interactive binding between definitive atoms or groups of the drug molecule and the macromolecular target in three-dimension. Such critical atoms, groups, or fragments responsible for the interaction reflect the microscopic structures of drug molecules and are called pharmacophore. In this context, a drug molecule is presumed as an assembly of macroscopic property and microscopic structure, with the macroscopic properties determining the absorption, distribution, metabolism and elimination of drugs and the microscopic structure coining pharmacological action. The knowledge of the internal relationship between macroscopy/microscopy and PK/PD conduces to comprehension of drug action and guides molecular drug design, because this conception facilitates the identification of structural features necessary for biological response, and the determination of factors modulating the physico-chemical and pharmacokinetic properties. The factors determining macro-properties include molecular weight, solubility, charge, lipophilicity (partition), and polar surface area, etc., which are destined by molecular scaffolds and/or side chain(s) apart from pharmacophore. The features of micro-structures contributing to specific activity contain hydrogen bonding donor and acceptor, positive and negative charge centers, hydrophobic centers and centers of aromatic rings. Different combinations and spacial arrangements of these features determine the distinct activity presented. The macro-property and micro-structure are integrated into a single molecule, and are inseparable. The macro-property reflects overall contribution of atoms and groups in the micro-structure. On the other hand, structural changes aimed to adjust macroscopic property usually alter the relative position of the microscopic structure. The goal of molecular drug design is to integrate the macroscopic and microscopic factors in optimized manner. In the early stage of molecular design, both macroscopic property and microscopic structure should be considered to make pharmacodynamics, pharmacokinetics, and physico-chemical properties in optimal match. Therefore, it required the existence of structural overlapping among acceptable pharmacokinetics, visible developing potential and specific pharmacodynamics. The larger the scope of overlapping, the higher the possibility to be a drug.

Automated Image Analysis of Lung Branching Morphogenesis from Microscopic Images of Fetal Rat Explants

PubMed Central

Rodrigues, Pedro L.; Rodrigues, Nuno F.; Duque, Duarte; Granja, Sara; Correia-Pinto, Jorge; Vilaça, João L.

2014-01-01

Background. Regulating mechanisms of branching morphogenesis of fetal lung rat explants have been an essential tool for molecular research. This work presents a new methodology to accurately quantify the epithelial, outer contour, and peripheral airway buds of lung explants during cellular development from microscopic images. Methods. The outer contour was defined using an adaptive and multiscale threshold algorithm whose level was automatically calculated based on an entropy maximization criterion. The inner lung epithelium was defined by a clustering procedure that groups small image regions according to the minimum description length principle and local statistical properties. Finally, the number of peripheral buds was counted as the skeleton branched ends from a skeletonized image of the lung inner epithelia. Results. The time for lung branching morphometric analysis was reduced in 98% in contrast to the manual method. Best results were obtained in the first two days of cellular development, with lesser standard deviations. Nonsignificant differences were found between the automatic and manual results in all culture days. Conclusions. The proposed method introduces a series of advantages related to its intuitive use and accuracy, making the technique suitable to images with different lighting characteristics and allowing a reliable comparison between different researchers. PMID:25250057

The way from microscopic many-particle theory to macroscopic hydrodynamics.

PubMed

Haussmann, Rudolf

2016-03-23

Starting from the microscopic description of a normal fluid in terms of any kind of local interacting many-particle theory we present a well defined step by step procedure to derive the hydrodynamic equations for the macroscopic phenomena. We specify the densities of the conserved quantities as the relevant hydrodynamic variables and apply the methods of non-equilibrium statistical mechanics with projection operator techniques. As a result we obtain time-evolution equations for the hydrodynamic variables with three kinds of terms on the right-hand sides: reversible, dissipative and fluctuating terms. In their original form these equations are completely exact and contain nonlocal terms in space and time which describe nonlocal memory effects. Applying a few approximations the nonlocal properties and the memory effects are removed. As a result we find the well known hydrodynamic equations of a normal fluid with Gaussian fluctuating forces. In the following we investigate if and how the time-inversion invariance is broken and how the second law of thermodynamics comes about. Furthermore, we show that the hydrodynamic equations with fluctuating forces are equivalent to stochastic Langevin equations and the related Fokker-Planck equation. Finally, we investigate the fluctuation theorem and find a modification by an additional term.

Effects of Al3(Sc,Zr) and Shear Band Formation on the Tensile Properties and Fracture Behavior of Al-Mg-Sc-Zr Alloy

NASA Astrophysics Data System (ADS)

Huang, Hongfeng; Jiang, Feng; Zhou, Jiang; Wei, Lili; Qu, Jiping; Liu, Lele

2015-11-01

The mechanical properties and microstructures of Al-6Mg-0.25Sc-0.1Zr alloy (wt.%) during annealing were investigated by means of uniaxial tensile testing, optical microscope, scanning electron microscope, transmission electron microscope, and high-resolution transmission electron microscope. The results show that a large number of micro and grain-scale shear bands form in this alloy after cold rolling. As the tensile-loading force rises, strain softening would generate in shear bands, resulting in the occurrence of shear banding fracture in cold-rolled Al-Mg-Sc-Zr alloys. Recrystallization takes place preferentially in shear bands during annealing. Due to the formation of coarse-grain bands constructed by new subgrains, recrystallization softening tends to occur in these regions. During low-temperature annealing, recrystallization is inhibited by nano-scale Al3(Sc,Zr) precipitates which exert significant coherency strengthening and modulus hardening. However, the strengthening effect of Al3(Sc,Zr) decreases with the increasing of particle diameter at elevated annealing temperature. The mechanical properties of the recrystallized Al-Mg-Sc-Zr alloy decrease to a minimum level, and the fracture plane exhibits pure ductile fracture characteristics.

Relationship between microscopic dynamics in traffic flow and complexity in networks.

PubMed

Li, Xin-Gang; Gao, Zi-You; Li, Ke-Ping; Zhao, Xiao-Mei

2007-07-01

Complex networks are constructed in the evolution process of traffic flow, and the states of traffic flow are represented by nodes in the network. The traffic dynamics can then be studied by investigating the statistical properties of those networks. According to Kerner's three-phase theory, there are two different phases in congested traffic, synchronized flow and wide moving jam. In the framework of this theory, we study different properties of synchronized flow and moving jam in relation to complex network. Scale-free network is constructed in stop-and-go traffic, i.e., a sequence of moving jams [Chin. Phys. Lett. 10, 2711 (2005)]. In this work, the networks generated in synchronized flow are investigated in detail. Simulation results show that the degree distribution of the networks constructed in synchronized flow has two power law regions, so the distinction in topological structure can really reflect the different dynamics in traffic flow. Furthermore, the real traffic data are investigated by this method, and the results are consistent with the simulations.

Identification of phases, symmetries and defects through local crystallography

DOE PAGES

Belianinov, Alex; He, Qian; Kravchenko, Mikhail; ...

2015-07-20

Here we report that advances in electron and probe microscopies allow 10 pm or higher precision in measurements of atomic positions. This level of fidelity is sufficient to correlate the length (and hence energy) of bonds, as well as bond angles to functional properties of materials. Traditionally, this relied on mapping locally measured parameters to macroscopic variables, for example, average unit cell. This description effectively ignores the information contained in the microscopic degrees of freedom available in a high-resolution image. Here we introduce an approach for local analysis of material structure based on statistical analysis of individual atomic neighbourhoods. Clusteringmore » and multivariate algorithms such as principal component analysis explore the connectivity of lattice and bond structure, as well as identify minute structural distortions, thus allowing for chemical description and identification of phases. This analysis lays the framework for building image genomes and structure–property libraries, based on conjoining structural and spectral realms through local atomic behaviour.« less

Technique to quantitatively measure magnetic properties of thin structures at <10 NM spatial resolution

DOEpatents

Bajt, Sasa

2003-07-08

A highly sensitive and high resolution magnetic microscope images magnetic properties quantitatively. Imaging is done with a modified transmission electron microscope that allows imaging of the sample in a zero magnetic field. Two images from closely spaced planes, one in focus and one slightly out of focus, are sufficient to calculate the absolute values of the phase change imparted to the electrons, and hence obtain the magnetization vector field distribution.

Probing Chemical Properties of Interstitial Micro-fluids in Ice

NASA Astrophysics Data System (ADS)

Cheng, J.; Colussi, A. J.; Hoffmann, M. R.

2007-12-01

Liquid is present as microscopic channels in polycrystalline ice at sub-freezing and even sub-eutectic temperatures. Not only do chemicals tend to concentrate substantially in this microscopic liquid phase, but local physicochemical properties may also differ widely from the bulk counterparts, therefore critically affecting the thermodynamics and kinetics of chemical processes occurring in frozen media such as snow, frost, and frost- flowers. This phenomenon has important implications in atmospheric chemistry such as affecting the composition of the atmospheric boundary layer in snow-covered regions. A method using con-focal laser scanning microscope equipped with a cryostat has been developed to measure physicochemical properties of the microscopic liquid phase in ice that are not readily extrapolated from the bulk data. The experimental setup allows for monitoring the freezing process of an aqueous solution with a sub- second time resolution and a submicron 3D spatial resolution. The physicochemical properties (e.g. viscosity, polarity, and acidity) can, in theory, be deduced from features of the fluorescence spectra of particular fluorescent indicators. For example, the acidity change during the freezing and melting process of electrolyte solutions has been monitored in real time by a pH-dependent dual emission fluorescent probe C-SNARF-1. The effects of temperature, freezing rate, and added electrolytes such as ammonium sulfate, sodium chloride and zwitterions are also examined. The findings complement the theory and previous experimental evidence of freezing hydrolysis.

Effect of process parameters on microstructure and mechanical properties of friction stir welded joints: A review

NASA Astrophysics Data System (ADS)

Wanare, S. P.; Kalyankar, V. D.

2018-04-01

Friction stir welding is emerging as a promising technique for joining of lighter metal alloys due to its several advantages over conventional fusion welding processes such as low thermal distortion, good mechanical properties, fine weld joint microstructure, etc. This review article mainly focuses on analysis of microstructure and mechanical properties of friction stir welded joints. Various microstructure characterization techniques used by previous researchers such as optical microscopes, x-ray diffraction, electron probe microscope, transmission electron microscope, scanning electron microscopes with electron back scattered diffraction, electron dispersive microscopy, etc. are thoroughly overviewed and their results are discussed. The effects of friction stir welding process parameters such as tool rotational speed, welding speed, tool plunge depth, axial force, tool shoulder diameter to tool pin diameter ratio, tool geometry etc. on microstructure and mechanical properties of welded joints are studied and critical observations are noted down. The microstructure examination carried out by previous researchers on various zones of welded joints such as weld zone, heat affected zone and base metal are studied and critical remarks have been presented. Mechanical performances of friction stir welded joints based on tensile test, micro-hardness test, etc. are discussed. This article includes exhaustive literature review of standard research articles which may become ready information for subsequent researchers to establish their line of action.

Resistive switching phenomena: A review of statistical physics approaches

DOE PAGES

Lee, Jae Sung; Lee, Shinbuhm; Noh, Tae Won

2015-08-31

Here we report that resistive switching (RS) phenomena are reversible changes in the metastable resistance state induced by external electric fields. After discovery ~50 years ago, RS phenomena have attracted great attention due to their potential application in next-generation electrical devices. Considerable research has been performed to understand the physical mechanisms of RS and explore the feasibility and limits of such devices. There have also been several reviews on RS that attempt to explain the microscopic origins of how regions that were originally insulators can change into conductors. However, little attention has been paid to the most important factor inmore » determining resistance: how conducting local regions are interconnected. Here, we provide an overview of the underlying physics behind connectivity changes in highly conductive regions under an electric field. We first classify RS phenomena according to their characteristic current–voltage curves: unipolar, bipolar, and threshold switchings. Second, we outline the microscopic origins of RS in oxides, focusing on the roles of oxygen vacancies: the effect of concentration, the mechanisms of channel formation and rupture, and the driving forces of oxygen vacancies. Third, we review RS studies from the perspective of statistical physics to understand connectivity change in RS phenomena. We discuss percolation model approaches and the theory for the scaling behaviors of numerous transport properties observed in RS. Fourth, we review various switching-type conversion phenomena in RS: bipolar-unipolar, memory-threshold, figure-of-eight, and counter-figure-of-eight conversions. Finally, we review several related technological issues, such as improvement in high resistance fluctuations, sneak-path problems, and multilevel switching problems.« less

Physicochemical and microscopic characterization of implant–abutment joints

PubMed Central

Lopes, Patricia A.; Carreiro, Adriana F. P.; Nascimento, Rubens M.; Vahey, Brendan R.; Henriques, Bruno; Souza, Júlio C. M.

2018-01-01

Objective: The purpose of this study was to investigate Morse taper implant–abutment joints by chemical, mechanical, and microscopic analysis. Materials and Methods: Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant–abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant–abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant–abutment joints. Statistics: Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Results: Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant–abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Conclusions: Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant–abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication. PMID:29657532

Imaging properties and its improvements of scanning/imaging x-ray microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeuchi, Akihisa, E-mail: take@spring8.or.jp; Uesugi, Kentaro; Suzuki, Yoshio

A scanning / imaging X-ray microscope (SIXM) system has been developed at SPring-8. The SIXM consists of a scanning X-ray microscope with a one-dimensional (1D) X-ray focusing device and an imaging (full-field) X-ray microscope with a 1D X-ray objective. The motivation of the SIXM system is to realize a quantitative and highly-sensitive multimodal 3D X-ray tomography by taking advantages of both the scanning X-ray microscope using multi-pixel detector and the imaging X-ray microscope. Data acquisition process of a 2D image is completely different between in the horizontal direction and in the vertical direction; a 1D signal is obtained with themore » linear-scanning while the other dimensional signal is obtained with the imaging optics. Such condition have caused a serious problem on the imaging properties that the imaging quality in the vertical direction has been much worse than that in the horizontal direction. In this paper, two approaches to solve this problem will be presented. One is introducing a Fourier transform method for phase retrieval from one phase derivative image, and the other to develop and employ a 1D diffuser to produce an asymmetrical coherent illumination.« less

Characteristics of biochar: Microchemical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amonette, James E.; Joseph, Stephen

2009-03-13

Biochars, being derived from a variety of biological feedstocks that have been thermally degraded under a range of conditions, exhibit a correspondingly large range in composition and chemistry. Due in part to the somewhat chaotic nature of the thermal process itself, this chemical heterogeneity extends to the microscopic scale even within a single biochar. Thus, in the strictest sense, each biochar made under a particular feedstock/process combination presents a unique mixture of phases and microenvironments that gives rise to a unique set of chemical properties. In some respects, the chemical complexity of biochars rivals that of incipient soils. In thismore » chapter we focus on the chemical complexity of biochar as manifested primarily at a microscopic and molecular scale. We start by describing the biochar-formation process and how this influences the composition and nature of the solid phases, entrained oils, and their organization at the microscopic level. We then proceed to discuss the range of surface chemistries exhibited by biochars in terms of functional groups and electrochemical properties. We conclude with a discussion of the influence of these properties on the sorption of aqueous species at biochar surfaces.« less

Scaling of chaos in strongly nonlinear lattices.

PubMed

Mulansky, Mario

2014-06-01

Although it is now understood that chaos in complex classical systems is the foundation of thermodynamic behavior, the detailed relations between the microscopic properties of the chaotic dynamics and the macroscopic thermodynamic observations still remain mostly in the dark. In this work, we numerically analyze the probability of chaos in strongly nonlinear Hamiltonian systems and find different scaling properties depending on the nonlinear structure of the model. We argue that these different scaling laws of chaos have definite consequences for the macroscopic diffusive behavior, as chaos is the microscopic mechanism of diffusion. This is compared with previous results on chaotic diffusion [M. Mulansky and A. Pikovsky, New J. Phys. 15, 053015 (2013)], and a relation between microscopic chaos and macroscopic diffusion is established.

Density dependence of the nuclear energy-density functional

NASA Astrophysics Data System (ADS)

Papakonstantinou, Panagiota; Park, Tae-Sun; Lim, Yeunhwan; Hyun, Chang Ho

2018-01-01

Background: The explicit density dependence in the coupling coefficients entering the nonrelativistic nuclear energy-density functional (EDF) is understood to encode effects of three-nucleon forces and dynamical correlations. The necessity for the density-dependent coupling coefficients to assume the form of a preferably small fractional power of the density ρ is empirical and the power is often chosen arbitrarily. Consequently, precision-oriented parametrizations risk overfitting in the regime of saturation and extrapolations in dilute or dense matter may lose predictive power. Purpose: Beginning with the observation that the Fermi momentum kF, i.e., the cubic root of the density, is a key variable in the description of Fermi systems, we first wish to examine if a power hierarchy in a kF expansion can be inferred from the properties of homogeneous matter in a domain of densities, which is relevant for nuclear structure and neutron stars. For subsequent applications we want to determine a functional that is of good quality but not overtrained. Method: For the EDF, we fit systematically polynomial and other functions of ρ1 /3 to existing microscopic, variational calculations of the energy of symmetric and pure neutron matter (pseudodata) and analyze the behavior of the fits. We select a form and a set of parameters, which we found robust, and examine the parameters' naturalness and the quality of resulting extrapolations. Results: A statistical analysis confirms that low-order terms such as ρ1 /3 and ρ2 /3 are the most relevant ones in the nuclear EDF beyond lowest order. It also hints at a different power hierarchy for symmetric vs. pure neutron matter, supporting the need for more than one density-dependent term in nonrelativistic EDFs. The functional we propose easily accommodates known or adopted properties of nuclear matter near saturation. More importantly, upon extrapolation to dilute or asymmetric matter, it reproduces a range of existing microscopic results, to which it has not been fitted. It also predicts a neutron-star mass-radius relation consistent with observations. The coefficients display naturalness. Conclusions: Having been already determined for homogeneous matter, a functional of the present form can be mapped onto extended Skyrme-type functionals in a straightforward manner, as we outline here, for applications to finite nuclei. At the same time, the statistical analysis can be extended to higher orders and for different microscopic (ab initio) calculations with sufficient pseudodata points and for polarized matter.

Pancam and Microscopic Imager observations of dust on the Spirit Rover: Cleaning events, spectral properties, and aggregates

USGS Publications Warehouse

Vaughan, Alicia F.; Johnson, Jeffrey R.; Herkenhoff, Kenneth E.; Sullivan, Robert; Landis, Geoffrey A.; Goetz, Walter; Madsen, Morten B.

2010-01-01

This work describes dust deposits on the Spirit Rover over 2000 sols through examination of Pancam and Microscopic Imager observations of specific locations on the rover body, including portions of the solar array, Pancam and Mini-TES calibration targets, and the magnets. This data set reveals the three "cleaning events" experienced by Spirit to date, the spectral properties of dust, and the tendency of dust particles to form aggregates 100 um and larger.

Effect of reduced graphene oxide-carbon nanotubes hybrid nanofillers in mechanical properties of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Sa, Kadambinee; Mahakul, Prakash C.; Subramanyam, B. V. R. S.; Raiguru, Jagatpati; Das, Sonali; Alam, Injamul; Mahanandia, Pitamber

2018-03-01

Graphene and carbon nanotubes (CNTs) have tremendous interest as reinforcing fillers due to their excellent physical properties. However, their reinforcing effect in polymer matrix is limited due to agglomeration of graphene and CNTs within the polymer matrix. Mechanical properties by the admixture of reduced graphene oxide (rGO) and CNTs in Poly (methyl methacrylate) (PMMA) prepared by solution mixing method has been investigated. The prepared samples are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The hybrid composite shows improvement in the mechanical properties compared to rGO/PMMA and MWCNTs/PMMA composites due to better interaction between rGO-MWCNTs and polymer matrix.

Machine learning approach for automated screening of malaria parasite using light microscopic images.

PubMed

Das, Dev Kumar; Ghosh, Madhumala; Pal, Mallika; Maiti, Asok K; Chakraborty, Chandan

2013-02-01

The aim of this paper is to address the development of computer assisted malaria parasite characterization and classification using machine learning approach based on light microscopic images of peripheral blood smears. In doing this, microscopic image acquisition from stained slides, illumination correction and noise reduction, erythrocyte segmentation, feature extraction, feature selection and finally classification of different stages of malaria (Plasmodium vivax and Plasmodium falciparum) have been investigated. The erythrocytes are segmented using marker controlled watershed transformation and subsequently total ninety six features describing shape-size and texture of erythrocytes are extracted in respect to the parasitemia infected versus non-infected cells. Ninety four features are found to be statistically significant in discriminating six classes. Here a feature selection-cum-classification scheme has been devised by combining F-statistic, statistical learning techniques i.e., Bayesian learning and support vector machine (SVM) in order to provide the higher classification accuracy using best set of discriminating features. Results show that Bayesian approach provides the highest accuracy i.e., 84% for malaria classification by selecting 19 most significant features while SVM provides highest accuracy i.e., 83.5% with 9 most significant features. Finally, the performance of these two classifiers under feature selection framework has been compared toward malaria parasite classification. Copyright © 2012 Elsevier Ltd. All rights reserved.

Microscopic approaches to liquid nitromethane detonation properties.

PubMed

Hervouët, Anaïs; Desbiens, Nicolas; Bourasseau, Emeric; Maillet, Jean-Bernard

2008-04-24

In this paper, thermodynamic and chemical properties of nitromethane are investigated using microscopic simulations. The Hugoniot curve of the inert explosive is computed using Monte Carlo simulations with a modified version of the adaptative Erpenbeck equation of state and a recently developed intermolecular potential. Molecular dynamic simulations of nitromethane decomposition have been performed using a reactive potential, allowing the calculation of kinetic rate constants and activation energies. Finally, the Crussard curve of detonation products as well as thermodynamic properties at the Chapman-Jouguet (CJ) point are computed using reactive ensemble Monte Carlo simulations. Results are in good agreement with both thermochemical calculations and experimental measurements.

Microcellular nanocomposite injection molding process

Treesearch

Mingjun Yuan; Lih-Sheng Turng; Rick Spindler; Daniel Caulfield; Chris Hunt

2003-01-01

This study aims to explore the processing benefits and property improvements of combining nanocomposites with microcellular injection molding. The molded parts produced based on the Design of Experiments (DOE) matrices were subjected to tensile testing, impact testing, and Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Dynamic Mechanical...

Low vibration high numerical aperture automated variable temperature Raman microscope

DOE PAGES

Tian, Y.; Reijnders, A. A.; Osterhoudt, G. B.; ...

2016-04-05

Raman micro-spectroscopy is well suited for studying a variety of properties and has been applied to wide- ranging areas. Combined with tuneable temperature, Raman spectra can offer even more insights into the properties of materials. However, previous designs of variable temperature Raman microscopes have made it extremely challenging to measure samples with low signal levels due to thermal and positional instability as well as low collection efficiencies. Thus, contemporary Raman microscope has found limited applicability to probing the subtle physics involved in phase transitions and hysteresis. This paper describes a new design of a closed-cycle, Raman microscope with full polarizationmore » rotation. High collection efficiency, thermal and mechanical stability are ensured by both deliberate optical, cryogenic, and mechanical design. Measurements on two samples, Bi 2Se 3 and V 2O 3, which are known as challenging due to low thermal conductivities, low signal levels and/or hysteretic effects, are measured with previously undemonstrated temperature resolution.« less

Low vibration high numerical aperture automated variable temperature Raman microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Y.; Reijnders, A. A.; Osterhoudt, G. B.

Raman micro-spectroscopy is well suited for studying a variety of properties and has been applied to wide- ranging areas. Combined with tuneable temperature, Raman spectra can offer even more insights into the properties of materials. However, previous designs of variable temperature Raman microscopes have made it extremely challenging to measure samples with low signal levels due to thermal and positional instability as well as low collection efficiencies. Thus, contemporary Raman microscope has found limited applicability to probing the subtle physics involved in phase transitions and hysteresis. This paper describes a new design of a closed-cycle, Raman microscope with full polarizationmore » rotation. High collection efficiency, thermal and mechanical stability are ensured by both deliberate optical, cryogenic, and mechanical design. Measurements on two samples, Bi 2Se 3 and V 2O 3, which are known as challenging due to low thermal conductivities, low signal levels and/or hysteretic effects, are measured with previously undemonstrated temperature resolution.« less

Automated system for characterization and classification of malaria-infected stages using light microscopic images of thin blood smears.

PubMed

Das, D K; Maiti, A K; Chakraborty, C

2015-03-01

In this paper, we propose a comprehensive image characterization cum classification framework for malaria-infected stage detection using microscopic images of thin blood smears. The methodology mainly includes microscopic imaging of Leishman stained blood slides, noise reduction and illumination correction, erythrocyte segmentation, feature selection followed by machine classification. Amongst three-image segmentation algorithms (namely, rule-based, Chan-Vese-based and marker-controlled watershed methods), marker-controlled watershed technique provides better boundary detection of erythrocytes specially in overlapping situations. Microscopic features at intensity, texture and morphology levels are extracted to discriminate infected and noninfected erythrocytes. In order to achieve subgroup of potential features, feature selection techniques, namely, F-statistic and information gain criteria are considered here for ranking. Finally, five different classifiers, namely, Naive Bayes, multilayer perceptron neural network, logistic regression, classification and regression tree (CART), RBF neural network have been trained and tested by 888 erythrocytes (infected and noninfected) for each features' subset. Performance evaluation of the proposed methodology shows that multilayer perceptron network provides higher accuracy for malaria-infected erythrocytes recognition and infected stage classification. Results show that top 90 features ranked by F-statistic (specificity: 98.64%, sensitivity: 100%, PPV: 99.73% and overall accuracy: 96.84%) and top 60 features ranked by information gain provides better results (specificity: 97.29%, sensitivity: 100%, PPV: 99.46% and overall accuracy: 96.73%) for malaria-infected stage classification. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

A perspective on the interfacial properties of nanoscopic liquid drops.

PubMed

Malijevský, Alexandr; Jackson, George

2012-11-21

The structural and interfacial properties of nanoscopic liquid drops are assessed by means of mechanical, thermodynamical, and statistical mechanical approaches that are discussed in detail, including original developments at both the macroscopic level and the microscopic level of density functional theory (DFT). With a novel analysis we show that a purely macroscopic (static) mechanical treatment can lead to a qualitatively reasonable description of the surface tension and the Tolman length of a liquid drop; the latter parameter, which characterizes the curvature dependence of the tension, is found to be negative and has a magnitude of about a half of the molecular dimension. A mechanical slant cannot, however, be considered satisfactory for small finite-size systems where fluctuation effects are significant. From the opposite perspective, a curvature expansion of the macroscopic thermodynamic properties (density and chemical potential) is then used to demonstrate that a purely thermodynamic approach of this type cannot in itself correctly account for the curvature correction of the surface tension of liquid drops. We emphasize that any approach, e.g., classical nucleation theory, which is based on a purely macroscopic viewpoint, does not lead to a reliable representation when the radius of the drop becomes microscopic. The description of the enhanced inhomogeneity exhibited by small drops (particularly in the dense interior) necessitates a treatment at the molecular level to account for finite-size and surface effects correctly. The so-called mechanical route, which corresponds to a molecular-level extension of the macroscopic theory of elasticity and is particularly popular in molecular dynamics simulation, also appears to be unreliable due to the inherent ambiguity in the definition of the microscopic pressure tensor, an observation which has been known for decades but is frequently ignored. The union of the theory of capillarity (developed in the nineteenth century by Gibbs and then promoted by Tolman) with a microscopic DFT treatment allows for a direct and unambiguous description of the interfacial properties of drops of arbitrary size; DFT provides all of the bulk and surface characteristics of the system that are required to uniquely define its thermodynamic properties. In this vein, we propose a non-local mean-field DFT for Lennard-Jones (LJ) fluids to examine drops of varying size. A comparison of the predictions of our DFT with recent simulation data based on a second-order fluctuation analysis (Sampayo et al 2010 J. Chem. Phys. 132 141101) reveals the consistency of the two treatments. This observation highlights the significance of fluctuation effects in small drops, which give rise to additional entropic (thermal non-mechanical) contributions, in contrast to what one observes in the case of planar interfaces which are governed by the laws of mechanical equilibrium. A small negative Tolman length (which is found to be about a tenth of the molecular diameter) and a non-monotonic behaviour of the surface tension with the drop radius are predicted for the LJ fluid. Finally, the limits of the validity of the Tolman approach, the effect of the range of the intermolecular potential, and the behaviour of bubbles are briefly discussed.

Correlation between macro- and nano-scopic measurements of carbon nanostructured paper elastic modulus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omar, Yamila M.; Al Ghaferi, Amal, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae; Chiesa, Matteo, E-mail: aalghaferi@masdar.ac.ae, E-mail: mchiesa@masdar.ac.ae

2015-07-20

Extensive work has been done in order to determine the bulk elastic modulus of isotropic samples from force curves acquired with atomic force microscopy. However, new challenges are encountered given the development of new materials constructed of one-dimensional anisotropic building blocks, such as carbon nanostructured paper. In the present work, we establish a reliable framework to correlate the elastic modulus values obtained by amplitude modulation atomic force microscope force curves, a nanoscopic technique, with that determined by traditional macroscopic tensile testing. In order to do so, several techniques involving image processing, statistical analysis, and simulations are used to find themore » appropriate path to understand how macroscopic properties arise from anisotropic nanoscale components, and ultimately, being able to calculate the value of bulk elastic modulus.« less

Key Factors Influencing the Energy Absorption of Dual-Phase Steels: Multiscale Material Model Approach and Microstructural Optimization

NASA Astrophysics Data System (ADS)

Belgasam, Tarek M.; Zbib, Hussein M.

2018-06-01

The increase in use of dual-phase (DP) steel grades by vehicle manufacturers to enhance crash resistance and reduce body car weight requires the development of a clear understanding of the effect of various microstructural parameters on the energy absorption in these materials. Accordingly, DP steelmakers are interested in predicting the effect of various microscopic factors as well as optimizing microstructural properties for application in crash-relevant components of vehicle bodies. This study presents a microstructure-based approach using a multiscale material and structure model. In this approach, Digimat and LS-DYNA software were coupled and employed to provide a full micro-macro multiscale material model, which is then used to simulate tensile tests. Microstructures with varied ferrite grain sizes, martensite volume fractions, and carbon content in DP steels were studied. The impact of these microstructural features at different strain rates on energy absorption characteristics of DP steels is investigated numerically using an elasto-viscoplastic constitutive model. The model is implemented in a multiscale finite-element framework. A comprehensive statistical parametric study using response surface methodology is performed to determine the optimum microstructural features for a required tensile toughness at different strain rates. The simulation results are validated using experimental data found in the literature. The developed methodology proved to be effective for investigating the influence and interaction of key microscopic properties on the energy absorption characteristics of DP steels. Furthermore, it is shown that this method can be used to identify optimum microstructural conditions at different strain-rate conditions.

Microstructure and mechanical properties of a Ti-microalloyed low-carbon stainless steel treated by quenching-partitioning-tempering process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, S.T., E-mail: xst-2007@163.com; Liu, Z.Y.; Wang, Z.

Quenching-partitioning-tempering (Q-P-T) process was used to treat a Ti-microalloyed low-carbon stainless steel after cold rolling. In addition to martensite, ferrite and retained austenite, TiN, coarse TiC, fine TiC, (Fe,Cr){sub 3}C and ultra-fine TiC precipitates were formed after the Q-P-T treatment. Based on field emission-scanning electron microscope (FESEM) and transmission electron microscope (TEM) observations, thermodynamic, crystallographic and statistical analyses were used to reveal the precipitation behaviors of these particles. The effects of partitioning-tempering (P-T) temperature and time on the microstructure and mechanical properties of Q-P-T treated specimens were specially studied. The coarsening and spheroidization of (Fe,Cr){sub 3}C particles during P-T stagemore » were obviously retarded by large Cr addition. The retained austenite was obtained significantly with appropriate P-T parameters. The precipitation of ultra-fine TiC particles in the martensite during the P-T stage at 500 °C induced a secondary hardening. - Highlights: • Some fine TiC with 30–70 nm precipitated in austenite during partial austenization. • A part of fine TiC had K-S OR with martensite after Q-P-T treatment. • A part of fine TiC had a OR specially deviating from K-S OR with martensite. • Coarsening and spheroidization of (Fe,Cr){sub 3}C were retarded during P-T stage. • Ultra-fine TiC with < 10 nm precipitated in martensite during P-T stage at 500 °C.« less

Key Factors Influencing the Energy Absorption of Dual-Phase Steels: Multiscale Material Model Approach and Microstructural Optimization

NASA Astrophysics Data System (ADS)

Belgasam, Tarek M.; Zbib, Hussein M.

2018-03-01

The increase in use of dual-phase (DP) steel grades by vehicle manufacturers to enhance crash resistance and reduce body car weight requires the development of a clear understanding of the effect of various microstructural parameters on the energy absorption in these materials. Accordingly, DP steelmakers are interested in predicting the effect of various microscopic factors as well as optimizing microstructural properties for application in crash-relevant components of vehicle bodies. This study presents a microstructure-based approach using a multiscale material and structure model. In this approach, Digimat and LS-DYNA software were coupled and employed to provide a full micro-macro multiscale material model, which is then used to simulate tensile tests. Microstructures with varied ferrite grain sizes, martensite volume fractions, and carbon content in DP steels were studied. The impact of these microstructural features at different strain rates on energy absorption characteristics of DP steels is investigated numerically using an elasto-viscoplastic constitutive model. The model is implemented in a multiscale finite-element framework. A comprehensive statistical parametric study using response surface methodology is performed to determine the optimum microstructural features for a required tensile toughness at different strain rates. The simulation results are validated using experimental data found in the literature. The developed methodology proved to be effective for investigating the influence and interaction of key microscopic properties on the energy absorption characteristics of DP steels. Furthermore, it is shown that this method can be used to identify optimum microstructural conditions at different strain-rate conditions.

Topologically invariant macroscopic statistics in balanced networks of conductance-based integrate-and-fire neurons.

PubMed

Yger, Pierre; El Boustani, Sami; Destexhe, Alain; Frégnac, Yves

2011-10-01

The relationship between the dynamics of neural networks and their patterns of connectivity is far from clear, despite its importance for understanding functional properties. Here, we have studied sparsely-connected networks of conductance-based integrate-and-fire (IF) neurons with balanced excitatory and inhibitory connections and with finite axonal propagation speed. We focused on the genesis of states with highly irregular spiking activity and synchronous firing patterns at low rates, called slow Synchronous Irregular (SI) states. In such balanced networks, we examined the "macroscopic" properties of the spiking activity, such as ensemble correlations and mean firing rates, for different intracortical connectivity profiles ranging from randomly connected networks to networks with Gaussian-distributed local connectivity. We systematically computed the distance-dependent correlations at the extracellular (spiking) and intracellular (membrane potential) levels between randomly assigned pairs of neurons. The main finding is that such properties, when they are averaged at a macroscopic scale, are invariant with respect to the different connectivity patterns, provided the excitatory-inhibitory balance is the same. In particular, the same correlation structure holds for different connectivity profiles. In addition, we examined the response of such networks to external input, and found that the correlation landscape can be modulated by the mean level of synchrony imposed by the external drive. This modulation was found again to be independent of the external connectivity profile. We conclude that first and second-order "mean-field" statistics of such networks do not depend on the details of the connectivity at a microscopic scale. This study is an encouraging step toward a mean-field description of topological neuronal networks.

On the microscopic fluctuations driving the NMR relaxation of quadrupolar ions in water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carof, Antoine; Salanne, Mathieu; Rotenberg, Benjamin, E-mail: benjamin.rotenberg@upmc.fr

Nuclear Magnetic Resonance (NMR) relaxation is sensitive to the local structure and dynamics around the probed nuclei. The Electric Field Gradient (EFG) is the key microscopic quantity to understand the NMR relaxation of quadrupolar ions, such as {sup 7}Li{sup +}, {sup 23}Na{sup +}, {sup 25}Mg{sup 2+}, {sup 35}Cl{sup −}, {sup 39}K{sup +}, or {sup 133}Cs{sup +}. Using molecular dynamics simulations, we investigate the statistical and dynamical properties of the EFG experienced by alkaline, alkaline Earth, and chloride ions at infinite dilution in water. Specifically, we analyze the effect of the ionic charge and size on the distribution of the EFGmore » tensor and on the multi-step decay of its auto-correlation function. The main contribution to the NMR relaxation time arises from the slowest mode, with a characteristic time on the picosecond time scale. The first solvation shell of the ion plays a dominant role in the fluctuations of the EFG, all the more that the ion radius is small and its charge is large. We propose an analysis based on a simplified charge distribution around the ion, which demonstrates that the auto-correlation of the EFG, hence the NMR relaxation time, reflects primarily the collective translational motion of water molecules in the first solvation shell of the cations. Our findings provide a microscopic route to the quantitative interpretation of NMR relaxation measurements and open the way to the design of improved analytical theories for NMR relaxation for small ionic solutes, which should focus on water density fluctuations around the ion.« less

Influence of olive and rosemary leaves extracts on chemically induced liver cirrhosis in male rats

PubMed Central

Al-Attar, Atef M.; Shawush, Nessreen A.

2014-01-01

The current study was undertaken to evaluate the protective activity of olive and rosemary leaves extracts on experimental liver cirrhosis induced by thioacetamide (TAA) in Wistar male rats. Highly significant decline in the values of body weight gain and highly statistically increase of liver/body weight ratio were noted in rats treated with TAA. Furthermore, the levels of serum alanine aminotransferase, aspartate aminotransferase, gamma glutamyl transferase, alkaline phosphatase and total bilirubin were statistically increased. Additionally, light microscopic examination of liver sections from rats treated with TAA showed a marked increase in the extracellular matrix collagen content and bridging fibrosis was prominent. There were bundles of collagen surrounding the lobules that resulted in large fibrous septa and distorted tissue architecture. Interestingly, the findings of this experimental study indicated that the extracts of olive and rosemary leaves and their combination possess hepatoprotective properties against TAA-induced hepatic cirrhosis by inhibiting the physiological and histopathological alterations. Moreover, these results suggest that the hepatoprotective effects of these extracts may be attributed to their antioxidant activities. PMID:25737646

Entropy, a Unifying Concept: from Physics to Cognitive Psychology

NASA Astrophysics Data System (ADS)

Tsallis, Constantino; Tsallis, Alexandra C.

Together with classical, relativistic and quantum mechanics, as well as Maxwell electromagnetism, Boltzmann-Gibbs (BG) statistical mechanics constitutes one of the main theories of contemporary physics. This theory primarily concerns inanimate matter, and at its generic foundation we find nonlinear dynamical systems satisfying the ergodic hypothesis. This hypothesis is typically guaranteed for systems whose maximal Lyapunov exponent is positive. What happens when this crucial quantity is zero instead? We suggest here that, in what concerns thermostatistical properties, we typically enter what in some sense may be considered as a new world — the world of living systems — . The need emerges, at least for many systems, for generalizing the basis of BG statistical mechanics, namely the Boltzmann-Gibbs-von Neumann-Shannon en-tropic functional form, which connects the oscopic, thermodynamic quantity, with the occurrence probabilities of microscopic configurations. This unifying approach is briefly reviewed here, and its widespread applications — from physics to cognitive psychology — are overviewed. Special attention is dedicated to the learning/memorizing process in humans and computers. The present observations might be related to the gestalt theory of visual perceptions and the actor-network theory.

Acousto-Optic Tunable Filter Hyperspectral Microscope Imaging Method for Characterizing Spectra from Foodborne Pathogens.

USDA-ARS?s Scientific Manuscript database

Hyperspectral microscope imaging (HMI) method, which provides both spatial and spectral characteristics of samples, can be effective for foodborne pathogen detection. The acousto-optic tunable filter (AOTF)-based HMI method can be used to characterize spectral properties of biofilms formed by Salmon...

Identifying local characteristic lengths governing sound wave properties in solid foams

NASA Astrophysics Data System (ADS)

Tan Hoang, Minh; Perrot, Camille

2013-02-01

Identifying microscopic geometric properties and fluid flow through opened-cell and partially closed-cell solid structures is a challenge for material science, in particular, for the design of porous media used as sound absorbers in building and transportation industries. We revisit recent literature data to identify the local characteristic lengths dominating the transport properties and sound absorbing behavior of polyurethane foam samples by performing numerical homogenization simulations. To determine the characteristic sizes of the model, we need porosity and permeability measurements in conjunction with ligament lengths estimates from available scanning electron microscope images. We demonstrate that this description of the porous material, consistent with the critical path picture following from the percolation arguments, is widely applicable. This is an important step towards tuning sound proofing properties of complex materials.

Current–Voltage Characterization of Individual As-Grown Nanowires Using a Scanning Tunneling Microscope

PubMed Central

2013-01-01

Utilizing semiconductor nanowires for (opto)electronics requires exact knowledge of their current–voltage properties. We report accurate on-top imaging and I–V characterization of individual as-grown nanowires, using a subnanometer resolution scanning tunneling microscope with no need for additional microscopy tools, thus allowing versatile application. We form Ohmic contacts to InP and InAs nanowires without any sample processing, followed by quantitative measurements of diameter dependent I–V properties with a very small spread in measured values compared to standard techniques. PMID:24059470

Current-voltage characterization of individual as-grown nanowires using a scanning tunneling microscope.

PubMed

Timm, Rainer; Persson, Olof; Engberg, David L J; Fian, Alexander; Webb, James L; Wallentin, Jesper; Jönsson, Andreas; Borgström, Magnus T; Samuelson, Lars; Mikkelsen, Anders

2013-11-13

Utilizing semiconductor nanowires for (opto)electronics requires exact knowledge of their current-voltage properties. We report accurate on-top imaging and I-V characterization of individual as-grown nanowires, using a subnanometer resolution scanning tunneling microscope with no need for additional microscopy tools, thus allowing versatile application. We form Ohmic contacts to InP and InAs nanowires without any sample processing, followed by quantitative measurements of diameter dependent I-V properties with a very small spread in measured values compared to standard techniques.

eSIP: A Novel Solution-Based Sectioned Image Property Approach for Microscope Calibration

PubMed Central

Butzlaff, Malte; Weigel, Arwed; Ponimaskin, Evgeni; Zeug, Andre

2015-01-01

Fluorescence confocal microscopy represents one of the central tools in modern sciences. Correspondingly, a growing amount of research relies on the development of novel microscopic methods. During the last decade numerous microscopic approaches were developed for the investigation of various scientific questions. Thereby, the former qualitative imaging methods became replaced by advanced quantitative methods to gain more and more information from a given sample. However, modern microscope systems being as complex as they are, require very precise and appropriate calibration routines, in particular when quantitative measurements should be compared over longer time scales or between different setups. Multispectral beads with sub-resolution size are often used to describe the point spread function and thus the optical properties of the microscope. More recently, a fluorescent layer was utilized to describe the axial profile for each pixel, which allows a spatially resolved characterization. However, fabrication of a thin fluorescent layer with matching refractive index is technically not solved yet. Therefore, we propose a novel type of calibration concept for sectioned image property (SIP) measurements which is based on fluorescent solution and makes the calibration concept available for a broader number of users. Compared to the previous approach, additional information can be obtained by application of this extended SIP chart approach, including penetration depth, detected number of photons, and illumination profile shape. Furthermore, due to the fit of the complete profile, our method is less susceptible to noise. Generally, the extended SIP approach represents a simple and highly reproducible method, allowing setup independent calibration and alignment procedures, which is mandatory for advanced quantitative microscopy. PMID:26244982

Differentiating gold nanorod samples using particle size and shape distributions from transmission electron microscope images

NASA Astrophysics Data System (ADS)

Grulke, Eric A.; Wu, Xiaochun; Ji, Yinglu; Buhr, Egbert; Yamamoto, Kazuhiro; Song, Nam Woong; Stefaniak, Aleksandr B.; Schwegler-Berry, Diane; Burchett, Woodrow W.; Lambert, Joshua; Stromberg, Arnold J.

2018-04-01

Size and shape distributions of gold nanorod samples are critical to their physico-chemical properties, especially their longitudinal surface plasmon resonance. This interlaboratory comparison study developed methods for measuring and evaluating size and shape distributions for gold nanorod samples using transmission electron microscopy (TEM) images. The objective was to determine whether two different samples, which had different performance attributes in their application, were different with respect to their size and/or shape descriptor distributions. Touching particles in the captured images were identified using a ruggedness shape descriptor. Nanorods could be distinguished from nanocubes using an elongational shape descriptor. A non-parametric statistical test showed that cumulative distributions of an elongational shape descriptor, that is, the aspect ratio, were statistically different between the two samples for all laboratories. While the scale parameters of size and shape distributions were similar for both samples, the width parameters of size and shape distributions were statistically different. This protocol fulfills an important need for a standardized approach to measure gold nanorod size and shape distributions for applications in which quantitative measurements and comparisons are important. Furthermore, the validated protocol workflow can be automated, thus providing consistent and rapid measurements of nanorod size and shape distributions for researchers, regulatory agencies, and industry.

Diamond Quantum Nanoemitters: Cross Discipline Research on Hyperbolic Optical Systems for Control of Quantum Nanoemitters

DTIC Science & Technology

2017-05-05

results of this project there are: (1) the investigation of the effect of phonons on the optical properties of solid state emitters. A microscopic ...In  what  follows  we  list  the  main  results  and  undergoing  research.   2. Results 2.1   Microscopic  modeling...fluorescent  markers   for   biological   measurements.   Here,   we   present   a   first-­‐principles   microscopic   description

Fabrication and In Situ Transmission Electron Microscope Characterization of Free-Standing Graphene Nanoribbon Devices.

PubMed

Wang, Qing; Kitaura, Ryo; Suzuki, Shoji; Miyauchi, Yuhei; Matsuda, Kazunari; Yamamoto, Yuta; Arai, Shigeo; Shinohara, Hisanori

2016-01-26

Edge-dependent electronic properties of graphene nanoribbons (GNRs) have attracted intense interests. To fully understand the electronic properties of GNRs, the combination of precise structural characterization and electronic property measurement is essential. For this purpose, two experimental techniques using free-standing GNR devices have been developed, which leads to the simultaneous characterization of electronic properties and structures of GNRs. Free-standing graphene has been sculpted by a focused electron beam in transmission electron microscope (TEM) and then purified and narrowed by Joule heating down to several nanometer width. Structure-dependent electronic properties are observed in TEM, and significant increase in sheet resistance and semiconducting behavior become more salient as the width of GNR decreases. The narrowest GNR width we obtained with the present method is about 1.6 nm with a large transport gap of 400 meV.

Another look through Heisenberg’s microscope

NASA Astrophysics Data System (ADS)

Boughn, Stephen; Reginatto, Marcel

2018-05-01

Heisenberg introduced his famous uncertainty relations in a seminal 1927 paper entitled The Physical Content of Quantum Kinematics and Mechanics. He motivated his arguments with a gedanken experiment, a gamma ray microscope to measure the position of a particle. A primary result was that, due to the quantum nature of light, there is an inherent uncertainty in the determinations of the particle’s position and momentum dictated by an indeterminacy relation, δ qδ p∼ h. Heisenberg offered this demonstration as ‘a direct physical interpretation of the [quantum mechanical] equation {{pq}}-{{qp}}=-{{i}}{\\hslash }’ but considered the indeterminacy relation to be much more than this. He also argued that it implies limitations on the very meanings of position and momentum and emphasised that these limitations are the source of the statistical character of quantum mechanics. In addition, Heisenberg hoped but was unable to demonstrate that the laws of quantum mechanics could be derived directly from the uncertainty relation. In this paper, we revisit Heisenberg’s microscope and argue that the Schrödinger equation for a free particle does indeed follow from the indeterminacy relation together with reasonable statistical assumptions.

An electron microscope for the aberration-corrected era.

PubMed

Krivanek, O L; Corbin, G J; Dellby, N; Elston, B F; Keyse, R J; Murfitt, M F; Own, C S; Szilagyi, Z S; Woodruff, J W

2008-02-01

Improved resolution made possible by aberration correction has greatly increased the demands on the performance of all parts of high-end electron microscopes. In order to meet these demands, we have designed and built an entirely new scanning transmission electron microscope (STEM). The microscope includes a flexible illumination system that allows the properties of its probe to be changed on-the-fly, a third-generation aberration corrector which corrects all geometric aberrations up to fifth order, an ultra-responsive yet stable five-axis sample stage, and a flexible configuration of optimized detectors. The microscope features many innovations, such as a modular column assembled from building blocks that can be stacked in almost any order, in situ storage and cleaning facilities for up to five samples, computer-controlled loading of samples into the column, and self-diagnosing electronics. The microscope construction is described, and examples of its capabilities are shown.

Rheological and structural properties of sea cucumber Stichopus japonicus during heat treatment

NASA Astrophysics Data System (ADS)

Gao, Xin; Xue, Dongmei; Zhang, Zhaohui; Xu, Jiachao; Xue, Changhu

2005-07-01

Changes in tissue structure, rheological properties and water content of raw and heated sea cucumber meat were studied. Sea cucumber Stichopus japonicus was heated at 25°C , 70°C and 100°C water for 5 min. The structural changes were observed using a light microscope and the rheological parameters (rupture strength, adhesive strength and deformation) determined using a texture meter. Microscopic photograph revealed that the structural change of heated meat was greater than that of raw meat. The rupture strength, adhesive strength and deformation of raw meat were smaller than those of the heated meat. Meanwhile, rheological parameters showed positive correlation with heating temperature. These changes are mainly caused by thermal denaturation and gelatinization of collagen during heating. These changes were also evidenced in observations using a light microscope and differential scanning calorimetry.

Constitutive models for static and dynamic response of geotechnical materials

NASA Astrophysics Data System (ADS)

Nemat-Nasser, S.

1983-11-01

The objective of this research program has been to develop realistic macroscopic constitutive relations which describe static and dynamic properties of geotechnical materials (soils and rocks). To this end a coordinated theoretical and experimental activity has been followed. The theoretical work includes a balanced combination of statistical microscopic (at the grain size level) modeling and a nonclassical elasto-plastic macroscopic formulation. The latter includes the effects of internal friction, plastic compressibility, and pressure sensitivity, as well as anisotropy which is commonly observed in geotechnical materials. The following specific goals have been sought: (1) to develop three-dimensional constitutive relations under ordinary or high pressures (such as those induced by blasting or tectonic forces which may cause a large amount of densification by relative motion and possible crushing of grains); and (2) to examine and characterize the behavior of saturated granular materials under dynamic loading. The latter item includes characterization of possible liquefaction and subsidence which may be induced in granular materials under confining pressure by ground vibration or passage of waves. The theoretical work has been carefully coordinated with key experiments in order to: (1) understand the basic physics of the process, both at macroscopic and microscopic levels; (2) to verify the corresponding theoretical predictions; and (3) to establish relevant material parameters.

The Ising Decision Maker: a binary stochastic network for choice response time.

PubMed

Verdonck, Stijn; Tuerlinckx, Francis

2014-07-01

The Ising Decision Maker (IDM) is a new formal model for speeded two-choice decision making derived from the stochastic Hopfield network or dynamic Ising model. On a microscopic level, it consists of 2 pools of binary stochastic neurons with pairwise interactions. Inside each pool, neurons excite each other, whereas between pools, neurons inhibit each other. The perceptual input is represented by an external excitatory field. Using methods from statistical mechanics, the high-dimensional network of neurons (microscopic level) is reduced to a two-dimensional stochastic process, describing the evolution of the mean neural activity per pool (macroscopic level). The IDM can be seen as an abstract, analytically tractable multiple attractor network model of information accumulation. In this article, the properties of the IDM are studied, the relations to existing models are discussed, and it is shown that the most important basic aspects of two-choice response time data can be reproduced. In addition, the IDM is shown to predict a variety of observed psychophysical relations such as Piéron's law, the van der Molen-Keuss effect, and Weber's law. Using Bayesian methods, the model is fitted to both simulated and real data, and its performance is compared to the Ratcliff diffusion model. (c) 2014 APA, all rights reserved.

Optimization of mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy by heat treatment.

PubMed

Bao, Mianmian; Liu, Ying; Wang, Xiaoyan; Yang, Lei; Li, Shengyi; Ren, Jing; Qin, Gaowu; Zhang, Erlin

2018-03-01

Previous study has shown that Ti-3Cu alloy shows good antibacterial properties (>90% antibacterial rate), but the mechanical properties still need to be improved. In this paper, a series of heat-treatment processes were selected to adjust the microstructure in order to optimize the properties of Ti-3Cu alloy. Microstructure, mechanical properties, biocorrosion properties and antibacterial properties of wrought Ti-3Cu alloy at different conditions was systematically investigated by X-ray diffraction, optical microscope, scanning electron microscope, transmission electron microscopy, electrochemical measurements, tensile test, fatigue test and antibacterial test. Heat treatment could significantly improve the mechanical properties, corrosion resistance and antibacterial rate due to the redistribution of copper elements and precipitation of Ti 2 Cu phase. Solid solution treatment increased the yield strength from 400 to 740 MPa and improved the antibacterial rate from 33% to 65.2% while aging treatment enhanced the yield strength to 800-850 MPa and antibacterial rate (>91.32%). It was demonstrated that homogeneous distribution and fine Ti 2 Cu phase plays a very important role in mechanical properties, corrosion resistance and antibacterial properties.

Thermal conductivity and dielectric functions of alkali chloride XCl (X = Li, Na, K and Rb): a first-principles study

NASA Astrophysics Data System (ADS)

Xu, M.; Yang, J. Y.; Liu, L. H.

2016-07-01

The macroscopic physical properties of solids are fundamentally determined by the interactions among microscopic electrons, phonons and photons. In this work, the thermal conductivity and infrared-visible-ultraviolet dielectric functions of alkali chlorides and their temperature dependence are fully investigated at the atomic level, seeking to unveil the microscopic quantum interactions beneath the macroscopic properties. The microscopic phonon-phonon interaction dominates the thermal conductivity which can be investigated by the anharmonic lattice dynamics in combination with Peierls-Boltzmann transport equation. The photon-phonon and electron-photon interaction intrinsically induce the infrared and visible-ultraviolet dielectric functions, respectively, and such microscopic processes can be simulated by first-principles molecular dynamics without empirical parameters. The temperature influence on dielectric functions can be effectively included by choosing the thermally equilibrated configurations as the basic input to calculate the total dipole moment and electronic band structure. The overall agreement between first-principles simulations and literature experiments enables us to interpret the macroscopic thermal conductivity and dielectric functions of solids in a comprehensive way.

Nonadditive entropy Sq and nonextensive statistical mechanics: Applications in geophysics and elsewhere

NASA Astrophysics Data System (ADS)

Tsallis, Constantino

2012-06-01

The celebrated Boltzmann-Gibbs (BG) entropy, S BG = -kΣi p i ln p i, and associated statistical mechanics are essentially based on hypotheses such as ergodicity, i.e., when ensemble averages coincide with time averages. This dynamical simplification occurs in classical systems (and quantum counterparts) whose microscopic evolution is governed by a positive largest Lyapunov exponent (LLE). Under such circumstances, relevant microscopic variables behave, from the probabilistic viewpoint, as (nearly) independent. Many phenomena exist, however, in natural, artificial and social systems (geophysics, astrophysics, biophysics, economics, and others) that violate ergodicity. To cover a (possibly) wide class of such systems, a generalization (nonextensive statistical mechanics) of the BG theory was proposed in 1988. This theory is based on nonadditive entropies such as S_q = kfrac{{1 - sumnolimits_i {p_i^q } }} {{q - 1}}left( {S_1 = S_{BG} } right). Here we comment some central aspects of this theory, and briefly review typical predictions, verifications and applications in geophysics and elsewhere, as illustrated through theoretical, experimental, observational, and computational results.

Macroscopic characterisations of Web accessibility

NASA Astrophysics Data System (ADS)

Lopes, Rui; Carriço, Luis

2010-12-01

The Web Science framework poses fundamental questions on the analysis of the Web, by focusing on how microscopic properties (e.g. at the level of a Web page or Web site) emerge into macroscopic properties and phenomena. One research topic on the analysis of the Web is Web accessibility evaluation, which centres on understanding how accessible a Web page is for people with disabilities. However, when framing Web accessibility evaluation on Web Science, we have found that existing research stays at the microscopic level. This article presents an experimental study on framing Web accessibility evaluation into Web Science's goals. This study resulted in novel accessibility properties of the Web not found at microscopic levels, as well as of Web accessibility evaluation processes themselves. We observed at large scale some of the empirical knowledge on how accessibility is perceived by designers and developers, such as the disparity of interpretations of accessibility evaluation tools warnings. We also found a direct relation between accessibility quality and Web page complexity. We provide a set of guidelines for designing Web pages, education on Web accessibility, as well as on the computational limits of large-scale Web accessibility evaluations.

On microscopic theory of radiative nuclear reaction characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamerdzhiev, S. P.; Achakovskiy, O. I., E-mail: oachakovskiy@ippe.ru; Avdeenkov, A. V.

2016-07-15

A survey of some results in the modern microscopic theory of properties of nuclear reactions with gamma rays is given. First of all, we discuss the impact of Phonon Coupling (PC) on the Photon Strength Function (PSF) because it represents the most natural physical source of additional strength found for Sn isotopes in recent experiments that could not be explained within the standard HFB + QRPA approach. The self-consistent version of the Extended Theory of Finite Fermi Systems in the Quasiparticle Time Blocking Approximation is applied. It uses the HFB mean field and includes both the QRPA and PC effectsmore » on the basis of the SLy4 Skyrme force. With our microscopic E1 PSFs, the following properties have been calculated for many stable and unstable even–even semi-magic Sn and Ni isotopes as well as for double-magic {sup 132}Sn and {sup 208}Pb using the reaction codes EMPIRE and TALYS with several Nuclear Level Density (NLD) models: (1) the neutron capture cross sections; (2) the corresponding neutron capture gamma spectra; (3) the average radiative widths of neutron resonances. In all the properties considered, the PC contribution turned out to be significant, as compared with the standard QRPA one, and necessary to explain the available experimental data. The results with the phenomenological so-called generalized superfluid NLD model turned out to be worse, on the whole, than those obtained with the microscopic HFB + combinatorial NLD model. The very topical question about the M1 resonance contribution to PSFs is also discussed.Finally, we also discuss the modern microscopic NLD models based on the self-consistent HFB method and show their relevance to explain the experimental data as compared with the phenomenological models. The use of these self-consistent microscopic approaches is of particular relevance for nuclear astrophysics, but also for the study of double-magic nuclei.« less

A mini-review on econophysics: Comparative study of Chinese and western financial markets

NASA Astrophysics Data System (ADS)

Zheng, Bo; Jiang, Xiong-Fei; Ni, Peng-Yun

2014-07-01

We present a review of our recent research in econophysics, and focus on the comparative study of Chinese and western financial markets. By virtue of concepts and methods in statistical physics, we investigate the time correlations and spatial structure of financial markets based on empirical high-frequency data. We discover that the Chinese stock market shares common basic properties with the western stock markets, such as the fat-tail probability distribution of price returns, the long-range auto-correlation of volatilities, and the persistence probability of volatilities, while it exhibits very different higher-order time correlations of price returns and volatilities, spatial correlations of individual stock prices, and large-fluctuation dynamic behaviors. Furthermore, multi-agent-based models are developed to simulate the microscopic interaction and dynamic evolution of the stock markets.

Multi-scale quantum point contact model for filamentary conduction in resistive random access memories devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lian, Xiaojuan, E-mail: xjlian2005@gmail.com; Cartoixà, Xavier; Miranda, Enrique

2014-06-28

We depart from first-principle simulations of electron transport along paths of oxygen vacancies in HfO{sub 2} to reformulate the Quantum Point Contact (QPC) model in terms of a bundle of such vacancy paths. By doing this, the number of model parameters is reduced and a much clearer link between the microscopic structure of the conductive filament (CF) and its electrical properties can be provided. The new multi-scale QPC model is applied to two different HfO{sub 2}-based devices operated in the unipolar and bipolar resistive switching (RS) modes. Extraction of the QPC model parameters from a statistically significant number of CFsmore » allows revealing significant structural differences in the CF of these two types of devices and RS modes.« less

Scattering properties of normal and cancerous tissues from human stomach based on phase-contrast microscope

NASA Astrophysics Data System (ADS)

Zhang, Hui; Li, Zhifang; Li, Hui

2012-12-01

In order to study scattering properties of normal and cancerous tissues from human stomach, we collect images for human gastric specimens by using phase-contrast microscope. The images were processed by the way of mathematics morphology. The equivalent particle size distribution of tissues can be obtained. Combining with Mie scattering theory, the scattering properties of tissues can be calculated. Assume scattering of light in biological tissue can be seen as separate scattering events by different particles, total scattering properties can be equivalent to as scattering sum of particles with different diameters. The results suggest that scattering coefficient of the cancerous tissue is significantly higher than that of normal tissue. The scattering phase function is different especially in the backscattering area. Those are significant clinical benefits to diagnosis cancerous tissue

Failure of cement hydrates: freeze-thaw and fracture

NASA Astrophysics Data System (ADS)

Ioannidou, Katerina; Del Gado, Emanuela; Ulm, Franz-Josef; Pellenq, Roland

Mechanical and viscoelastic behavior of concrete crucially depends on cement hydrates, the ``glue'' of cement. Even more than the atomistic structure, the mesoscale amorphous texture of cement hydrates over hundreds of nanometers plays a crucial role for material properties. We use simulations that combine information of the nano-scale building units of cement hydrates and on their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles.Our mesoscale model was able to reconcile different experimental results ranging from small-angle neutron scattering, SEM, adsorption/desorption of N2, and water to nanoindentation and gain the new fundamental insights into the microscopic origin of the properties measured. Our results suggest that heterogeneities developed during the early stages of hydration persist in the structure of C-S-H, impacting the rheological and mechanical performance of the hardened cement paste. In this talk I discuss recent investigation on failure mechanism at the mesoscale of hardened cement paste such as freeze-thaw and fracture. Using correlations between local volume fractions and local stress we provide a link between structural and mechanical heterogeneities during the failure mechanisms.

Effects of Laser Shock Processing on Morphologies and Mechanical Properties of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion

PubMed Central

Zhang, Lei; Lu, Jin-Zhong; Zhang, Yong-Kang; Ma, Hai-Le; Luo, Kai-Yu; Dai, Feng-Ze

2017-01-01

Effects of laser shock processing (LSP) on the cavitation erosion resistance of laser weldments were investigated by optical microscope (OM), scanning electron microscope (SEM) observations, roughness tester, micro hardness tester, and X-ray diffraction (XRD) technology. The morphological microstructures were characterized. Cumulative mass loss, incubation period, erosion rate, and damaged surface areas were monitored during cavitation erosion. Surface roughness, micro-hardness, and residual stress were measured in different zones. Results showed that LSP could improve the damage of morphological microstructures and mechanical properties after cavitation erosion. The compressive residual stresses were generated during the process of LSP, which was an effective guarantee for the improvement of the above mentioned properties. PMID:28772652

Characterization of Strong Light-Matter Coupling in Semiconductor Quantum-Dot Microcavities via Photon-Statistics Spectroscopy

NASA Astrophysics Data System (ADS)

Schneebeli, L.; Kira, M.; Koch, S. W.

2008-08-01

It is shown that spectrally resolved photon-statistics measurements of the resonance fluorescence from realistic semiconductor quantum-dot systems allow for high contrast identification of the two-photon strong-coupling states. Using a microscopic theory, the second-rung resonance of Jaynes-Cummings ladder is analyzed and optimum excitation conditions are determined. The computed photon-statistics spectrum displays gigantic, experimentally robust resonances at the energetic positions of the second-rung emission.

Evaluation of a recently developed noncontact specular microscope in comparison with conventional pachymetry devices.

PubMed

Módis, László; Szalai, Eszter; Németh, Gábor; Berta, András

2010-01-01

The study was conducted to assess the central corneal thickness (CCT) of the healthy cornea with a recently developed noncontact specular microscope (EM-3000; Tomey) and compare the results with those measured with a contact specular microscope and an ultrasound pachymeter. Agreement between measurements taken by 2 investigators was also studied. The right eyes of 41 healthy individuals who had negative history of contact lens wear, ophthalmic disease, or ocular surgery were examined. The CCT was determined sequentially with a noncontact specular microscope, a contact specular microscope (EM-1000; Tomey), and an ultrasound pachymeter (AL-2000; Tomey). Each evaluation with the specular microscopes was performed by 2 independent operators. A significant difference was detected in pachymetry measurements among the 3 instruments (p=0.01; analysis of variance). The mean CCT values were lower measured with the ultrasound pachymeter (537+/-30 microm) than the contact endothelial microscope (543+/-37 microm, p=0.17, Student t-test) and the noncontact microscope (549+/-33 microm, p<0.0001) (operator 1). There was no statistically significant difference in CCT measurements between the 2 endothelial microscopes (p=0.19). We found significant correlations (p<0.0001) in thickness measurements between each pair of instruments (r=0.91, noncontact microscopy and ultrasound pachymetry; r=0.74, noncontact and contact microscopy; r=0.72, contact microscopy and ultrasound pachymetry; Spearman rank correlation). The strong correlations among the 3 pachymetry devices suggest that the tested instruments provide reliable measurements; however, they cannot be used interchangeably.

A comparative study of a (0-3) connectivity type composite and core-shell structure of CoFe2O4 - BaTiO3 based on microstructure and magnetic property

NASA Astrophysics Data System (ADS)

Das, Avisek; Gorige, Venkataiah

2018-04-01

In this work CoFe2O4 (CFO)-BaTiO3 (BTO) composite and core-shell CFO-BTO have been prepared to investigate the effect of microstructure on the magnetic properties. Detailed microstructure analysis has been carried out using X-ray diffraction, field emission scanning electron microscope and transmission electron microscope. Although uniform distribution of CFO is found in BTO matrix for the composite sample, magnetization and coercivity values are more enhanced in core-shell CFO-BTO.

X-ray Microscopic Characterization of Protein Crystals

NASA Technical Reports Server (NTRS)

Hu, Z. W.; Holmes, A.; Thomas, B.R.; Chernov, a. A.; Chu, Y. S.; Lai, B.

2004-01-01

The microscopic mapping of the variation in degree of perfection and in type of defects in entire protein crystals by x-rays may well be a prerequisite for better understanding causes of lattice imperfections, the growth history, and properties of protein crystals. However, x-ray microscopic characterization of bulk protein crystals, in the as-grown state, is frequently more challenging than that of small molecular crystals due to the experimental difficulties arising largely from the unique features possessed by protein crystals. In this presentation, we will illustrate ssme recent activities in employing coherence-based phase contrast x-ray imaging and high-angular-resolution diffraction techniques for mapping microdefects and the degree of perfection of protein crystals, and demonstrate a correlation between crystal perfection, diffraction phenomena., and crystallization conditions. The observed features and phenomena will be discussed in context to gain insight into the nature of defects, nucleation and growth, and the properties of protein crystals.

Automatic analysis and quantification of fluorescently labeled synapses in microscope images

NASA Astrophysics Data System (ADS)

Yona, Shai; Katsman, Alex; Orenbuch, Ayelet; Gitler, Daniel; Yitzhaky, Yitzhak

2011-09-01

The purpose of this work is to classify and quantify synapses and their properties in the cultures of a mouse's hippocampus, from images acquired by a fluorescent microscope. Quantification features include the number of synapses, their intensity and their size characteristics. The images obtained by the microscope contain hundreds to several thousands of synapses with various elliptic-like shape features and intensities. These images also include other features such as glia cells and other biological objects beyond the focus plane; those features reduce the visibility of the synapses and interrupt the segmentation process. The proposed method comprises several steps, including background subtraction, identification of suspected centers of synapses as local maxima of small neighborhoods, evaluation of the tendency of objects to be synapses according to intensity properties at their larger neighborhoods, classification of detected synapses into categories as bulks or single synapses and finally, delimiting the borders of each synapse.

Advanced Microscopic Integrated Thermocouple Arrays

NASA Technical Reports Server (NTRS)

Pettigrew, Penny J.

1999-01-01

The purpose of this research is to develop and refine a technique for making microscopic thermocouple arrays for use in measuring the temperature gradient across a solid-liquid interface during the solidification process. Current thermocouple technology does not allow for real-time measurements across the interface due to the prohibitive size of available thermocouples. Microscopic thermocouple arrays will offer a much greater accuracy and resolution of temperature measurements across the solid-liquid interface which will lead to a better characterization of the solidification process and interface reaction which affect the properties of the resulting material.

Examination of silicon solar cells by means of the Scanning Laser Acoustic Microscope (SLAM)

NASA Technical Reports Server (NTRS)

Vorres, C.; Yuhas, D. E.

1981-01-01

The Scanning Laser Acoustic Microscope produces images of internal structure in materials. The acoustic microscope is an imaging system based upon acoustic rather than electromagnetic waves. Variations in the elastic propertis are primarily responsible for structure visualized in acoustic micrographs. The instrument used in these investigations is the SONOMICROSCOPE 100 which can be operated at ultrasonic frequencies of from 30 MHz to 500 MHz. The examination of the silicon solar cells was made at 100 MHz. Data are presented in the form of photomicrographs.

Quantitative measurement of piezoelectric coefficient of thin film using a scanning evanescent microwave microscope.

PubMed

Zhao, Zhenli; Luo, Zhenlin; Liu, Chihui; Wu, Wenbin; Gao, Chen; Lu, Yalin

2008-06-01

This article describes a new approach to quantitatively measure the piezoelectric coefficients of thin films at the microscopic level using a scanning evanescent microwave microscope. This technique can resolve 10 pm deformation caused by the piezoelectric effect and has the advantages of high scanning speed, large scanning area, submicron spatial resolution, and a simultaneous accessibility to many other related properties. Results from the test measurements on the longitudinal piezoelectric coefficient of PZT thin film agree well with those from other techniques listed in literatures.

Note: long-range scanning tunneling microscope for the study of nanostructures on insulating substrates.

PubMed

Molina-Mendoza, Aday J; Rodrigo, José G; Island, Joshua; Burzuri, Enrique; Rubio-Bollinger, Gabino; van der Zant, Herre S J; Agraït, Nicolás

2014-02-01

The scanning tunneling microscope (STM) is a powerful tool for studying the electronic properties at the atomic level, however, it is of relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting of conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies.

Thermophysical ESEM and TEM Characterization of Carbon Fibers CTE, Spectroscopy and Roughness Studies at High Temperatures

NASA Technical Reports Server (NTRS)

Ochoa, Ozden O.

2004-01-01

Accurate determination of the transverse properties of carbon fibers is important for assessment and prediction of local material as well as global structural response of composite components. However the measurements are extremely difficult due to the very small diameters of the fibers (few microns only) and must be conducted within a microscope. In this work, environmental scanning electron microscope (ESEM) and transmission electron microscope (TEM) are used to determine the transverse coefficient of thermal expansion of different carbon fibers as a function of temperature.

Multi-Scale Low-Entropy Method for Optimizing the Processing Parameters during Automated Fiber Placement

PubMed Central

Han, Zhenyu; Sun, Shouzheng; Fu, Hongya; Fu, Yunzhong

2017-01-01

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of micro-system could be taken into account synthetically. Taking a carbon fiber/epoxy prepreg as an example, mechanical properties of macro–meso–scale are obtained by Finite Element Method (FEM). A multi-scale energy transfer model is then established to input the macroscopic results into the microscopic system as its boundary condition, which can communicate with different scales. Furthermore, microscopic characteristics, mainly micro-scale adsorption energy, diffusion coefficient entropy–enthalpy values, are calculated under different processing parameters based on molecular dynamics method. Low-entropy region is then obtained in terms of the interrelation among entropy–enthalpy values, microscopic mechanical properties (interface adsorbability and matrix fluidity) and processing parameters to guarantee better fluidity, stronger adsorption, lower energy consumption and higher energy quality collaboratively. Finally, nine groups of experiments are carried out to verify the validity of the simulation results. The results show that the low-entropy optimization method can reduce void content effectively, and further improve the mechanical properties of laminates. PMID:28869520

Multi-Scale Low-Entropy Method for Optimizing the Processing Parameters during Automated Fiber Placement.

PubMed

Han, Zhenyu; Sun, Shouzheng; Fu, Hongya; Fu, Yunzhong

2017-09-03

Automated fiber placement (AFP) process includes a variety of energy forms and multi-scale effects. This contribution proposes a novel multi-scale low-entropy method aiming at optimizing processing parameters in an AFP process, where multi-scale effect, energy consumption, energy utilization efficiency and mechanical properties of micro-system could be taken into account synthetically. Taking a carbon fiber/epoxy prepreg as an example, mechanical properties of macro-meso-scale are obtained by Finite Element Method (FEM). A multi-scale energy transfer model is then established to input the macroscopic results into the microscopic system as its boundary condition, which can communicate with different scales. Furthermore, microscopic characteristics, mainly micro-scale adsorption energy, diffusion coefficient entropy-enthalpy values, are calculated under different processing parameters based on molecular dynamics method. Low-entropy region is then obtained in terms of the interrelation among entropy-enthalpy values, microscopic mechanical properties (interface adsorbability and matrix fluidity) and processing parameters to guarantee better fluidity, stronger adsorption, lower energy consumption and higher energy quality collaboratively. Finally, nine groups of experiments are carried out to verify the validity of the simulation results. The results show that the low-entropy optimization method can reduce void content effectively, and further improve the mechanical properties of laminates.

Design, Fabrication and Testing of Multilayer Coated X-Ray Optics for the Water Window Imaging X-Ray Microscope

NASA Technical Reports Server (NTRS)

Spencer, Dwight C.

1996-01-01

Hoover et. al. built and tested two imaging Schwarzschild multilayer microscopes. These instruments were constructed as prototypes for the "Water Window Imaging X-Ray Microscope," which is a doubly reflecting, multilayer x-ray microscope configured to operate within the "water window." The "water window" is the narrow region of the x-ray spectrum between the K absorption edges of oxygen (lamda = 23.3 Angstroms) and of carbon (lamda = 43.62 Angstroms), where water is relatively highly transmissive and carbon is highly absorptive. This property of these materials, thus permits the use of high resolution multilayer x-ray microscopes for producing high contrast images of carbon-based structures within the aqueous physiological environments of living cells. We report the design, fabrication and testing of multilayer optics that operate in this regime.

Nanoindentation of orthodontic archwires: The effect of decontamination and clinical use on hardness, elastic modulus and surface roughness.

PubMed

Alcock, Joseph P; Barbour, Michele E; Sandy, Jonathan R; Ireland, Anthony J

2009-08-01

The purpose of this research was to investigate the effects of decontamination and clinical exposure on the elastic moduli, hardness and surface roughness of two frequently used orthodontic archwires, namely 0.020in.x0.020in. heat activated (martensitic active) nickel titanium archwires and 0.019in.x0.025in. austenitic stainless steel archwires. This study was a prospective clinical trial in which 20 consecutive patients requiring an archwire change as part of their course of orthodontic fixed appliance therapy, had either a nickel titanium or stainless steel archwire fitted as deemed clinically necessary. The effect of clinical use was determined by comparing distal end cuts of the "as received" archwires before and after decontamination, with the same retrieved archwires following clinical use and decontamination. Hardness, elastic modulus and surface roughness were determined using an atomic force microscope (AFM) coupled with a nanoindenter. The results showed that the decontamination regimen and clinical use had no statistically significant effect on the nickel titanium archwires, but did have a statistically significant effect on the steel archwires. Decontamination of the steel wires significantly increased the observed surface hardness (p=0.01) and reduced the surface roughness (p=0.02). Clinical use demonstrated a statistically significant increase in the observed elastic modulus (p<0.001) and a decrease in surface roughness (p=0.001). At present it is difficult to predict the clinical significance of these statistically significant changes in archwire properties on orthodontic tooth movement.

Evidence of the most stretchable egg sac silk stalk, of the European spider of the year Meta menardi.

PubMed

Lepore, Emiliano; Marchioro, Andrea; Isaia, Marco; Buehler, Markus J; Pugno, Nicola M

2012-01-01

Spider silks display generally strong mechanical properties, even if differences between species and within the same species can be observed. While many different types of silks have been tested, the mechanical properties of stalks of silk taken from the egg sac of the cave spider Meta menardi have not yet been analyzed. Meta menardi has recently been chosen as the "European spider of the year 2012", from the European Society of Arachnology. Here we report a study where silk stalks were collected directly from several caves in the north-west of Italy. Field emission scanning electron microscope (FESEM) images showed that stalks are made up of a large number of threads, each of them with diameter of 6.03 ± 0.58 µm. The stalks were strained at the constant rate of 2 mm/min, using a tensile testing machine. The observed maximum stress, strain and toughness modulus, defined as the area under the stress-strain curve, are 0.64 GPa, 751% and 130.7 MJ/m(3), respectively. To the best of our knowledge, such an observed huge elongation has never been reported for egg sac silk stalks and suggests a huge unrolling microscopic mechanism of the macroscopic stalk that, as a continuation of the protective egg sac, is expected to be composed by fibres very densely and randomly packed. The Weibull statistics was used to analyze the results from mechanical testing, and an average value of Weibull modulus (m) is deduced to be in the range of 1.5-1.8 with a Weibull scale parameter (σ(0)) in the range of 0.33-0.41 GPa, showing a high coefficient of correlation (R(2) = 0.97).

Evidence of the Most Stretchable Egg Sac Silk Stalk, of the European Spider of the Year Meta menardi

PubMed Central

Lepore, Emiliano; Marchioro, Andrea; Isaia, Marco; Buehler, Markus J.; Pugno, Nicola M.

2012-01-01

Spider silks display generally strong mechanical properties, even if differences between species and within the same species can be observed. While many different types of silks have been tested, the mechanical properties of stalks of silk taken from the egg sac of the cave spider Meta menardi have not yet been analyzed. Meta menardi has recently been chosen as the “European spider of the year 2012”, from the European Society of Arachnology. Here we report a study where silk stalks were collected directly from several caves in the north-west of Italy. Field emission scanning electron microscope (FESEM) images showed that stalks are made up of a large number of threads, each of them with diameter of 6.03±0.58 µm. The stalks were strained at the constant rate of 2 mm/min, using a tensile testing machine. The observed maximum stress, strain and toughness modulus, defined as the area under the stress-strain curve, are 0.64 GPa, 751% and 130.7 MJ/m3, respectively. To the best of our knowledge, such an observed huge elongation has never been reported for egg sac silk stalks and suggests a huge unrolling microscopic mechanism of the macroscopic stalk that, as a continuation of the protective egg sac, is expected to be composed by fibres very densely and randomly packed. The Weibull statistics was used to analyze the results from mechanical testing, and an average value of Weibull modulus (m) is deduced to be in the range of 1.5–1.8 with a Weibull scale parameter (σ 0) in the range of 0.33–0.41 GPa, showing a high coefficient of correlation (R2 = 0.97). PMID:22347380

Assessment of changes in crystallization properties of pressurized milk fat.

PubMed

Staniewski, Bogusław; Smoczyński, Michał; Staniewska, Katarzyna; Baranowska, Maria; Kiełczewska, Katarzyna; Zulewska, Justyna

2015-04-01

The aim of the study was to demonstrate the use of fractal image analysis as a possible tool to monitor the effect of pressurization on the crystallization pattern of anhydrous milk fat. This approach can be useful when developing new products based on milk fat. The samples were subjected to different hydrostatic pressure (100, 200, 300, and 400 MPa) and temperature (10 and 40 °C) treatments. The crystallization microphotographs were taken with a scanning electron microscope. The image analysis of scanning electron microscope photographs was done to determine a fractal dimension. Milk-fat pressurization under the applied parameters resulted in slight, but statistically significant, changes in the course of crystallization curves, related to the triacylglycerol fraction crystallizing in the lowest temperature (I exothermic effect). These changes were dependent on the value of pressure but not dependent on the temperatures applied during the process of pressurization (at either 10 or 40 °C). In turn, significant differences were observed in crystallization images of milk-fat samples subjected to this process compared with the control sample. The results of additional fractal analysis additionally demonstrated the highest degree of irregularity of the surface of the crystalline form for the nonpressurized sample and the samples pressurized at 200 and 300 MPa at 10 °C. The lowest value of fractal dimension-indicative of the least irregularity-was achieved for the fat samples pressurized at 400 MPa, 10 °C and at 100 MPa, 40 °C. The possibilities of wider application of the fractal analysis for the evaluation of effects of parameters of various technological processes on crystallization properties of milk fat require further extensive investigations. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Nd:YOV4 laser polishing on WC-Co HVOF coating

NASA Astrophysics Data System (ADS)

Giorleo, L.; Ceretti, E.; Montesano, L.; La Vecchia, G. M.

2017-10-01

WC/Co coatings are widely applied to different types of components due to their extraordinary performance properties including high hardness and wear properties. In industrial applications High Velocity Oxy-Fuel (HVOF) technique is extensively used to deposit hard metal coatings. The main advantage of HVOF compared to other thermal spray techniques is the ability to accelerate the melted powder particles of the feedstock material at a relatively high velocity, leading to obtain good adhesion and low porosity level. However, despite the mentioned benefits, the surface finish quality of WC-Co HVOF coatings results to be poor (Ra higher than 5 µm) thus a mechanical polishing process is often needed. The main problem is that the high hardness of coating leads the polishing process expensive in terms of time and tool wear; moreover polishing becomes difficult and not always possible in case of limited accessibility of a part, micro dimensions or undercuts. Nowadays a different technique available to improve surface roughness is the laser polishing process. The polishing principle is based on focused radiation of a laser beam that melts a microscopic layer of surface material. Compared to conventional polishing process (as grinding) it ensures the possibility of avoiding tool wear, less pollution (no abrasive or liquids), no debris, less machining time and coupled with a galvo system it results to be more suitable in case of 3D complex workpieces. In this paper laser polishing process executed with a Nd:YOV4 Laser was investigated: the effect of different process parameters as initial coating morphology, laser scan speed and loop cycles were tested. Results were compared by a statistical approach in terms of average roughness along with a morphological analysis carried out by Scanning Electron Microscope (SEM) investigation coupled with EDS spectra.

Effect of texturing on polarization switching dynamics in ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Zhukov, Sergey; Genenko, Yuri A.; Koruza, Jurij; Schultheiß, Jan; von Seggern, Heinz; Sakamoto, Wataru; Ichikawa, Hiroki; Murata, Tatsuro; Hayashi, Koichiro; Yogo, Toshinobu

2016-01-01

Highly (100),(001)-oriented (Ba0.85Ca0.15)TiO3 (BCT) lead-free piezoelectric ceramics were fabricated by the reactive templated grain growth method using a mixture of plate-like CaTiO3 and BaTiO3 particles. Piezoelectric properties of the ceramics with a high degree of texture were found to be considerably enhanced compared with the BCT ceramics with a low degree of texture. With increasing the Lotgering factor from 26% up to 94%, the piezoelectric properties develop towards the properties of a single crystal. The dynamics of polarization switching was studied over a broad time domain of 8 orders of magnitude and was found to strongly depend on the degree of orientation of the ceramics. Samples with a high degree of texture exhibited 2-3 orders of magnitude faster polarization switching, as compared with the ones with a low degree of texture. This was rationalized by means of the Inhomogeneous Field Mechanism model as a result of the narrower statistical distribution of the local electric field values in textured media, which promotes a more coherent switching process. The extracted microscopic parameters of switching revealed a decrease of the critical nucleus energy in systems with a high degree of texture providing more favorable switching conditions related to the enhanced ferroelectric properties of the textured material.

Sub-micron materials characterization using near-field optics

NASA Astrophysics Data System (ADS)

Blodgett, David Wesley

1998-12-01

High-resolution sub-surface materials characterization and inspection are critical in the microelectronics and thin films industries. To this end, a technique is described that couples the bulk property measurement capabilities of high-frequency ultrasound with the high-resolution surface imaging capabilities of the near-field optical microscope. Sensing bulk microstructure variations in the material, such as grain boundaries, requires a detection footprint smaller than the variation itself. The near-field optical microscope, with the ability to exceed the diffraction limit in optical resolution, meets this requirement. Two apertureless near-field optical microscopes, on-axis and off-axis illumination, have been designed and built. Near-field and far-field approach curves for both microscopes are presented. The sensitivity of the near-field approach curve was 8.3 muV/nm. Resolution studies for the near-field microscope indicate optical resolutions on the order of 50 nm, which exceeds the diffraction limit. The near-field microscope has been adapted to detect both contact-transducer-generated and laser-generated ultrasound. The successful detection of high-frequency ultrasound with the near-field optical microscope demonstrates the potential of this technique.

Helioseismic and neutrino data-driven reconstruction of solar properties

NASA Astrophysics Data System (ADS)

Song, Ningqiang; Gonzalez-Garcia, M. C.; Villante, Francesco L.; Vinyoles, Nuria; Serenelli, Aldo

2018-06-01

In this work, we use Bayesian inference to quantitatively reconstruct the solar properties most relevant to the solar composition problem using as inputs the information provided by helioseismic and solar neutrino data. In particular, we use a Gaussian process to model the functional shape of the opacity uncertainty to gain flexibility and become as free as possible from prejudice in this regard. With these tools we first readdress the statistical significance of the solar composition problem. Furthermore, starting from a composition unbiased set of standard solar models (SSMs) we are able to statistically select those with solar chemical composition and other solar inputs which better describe the helioseismic and neutrino observations. In particular, we are able to reconstruct the solar opacity profile in a data-driven fashion, independently of any reference opacity tables, obtaining a 4 per cent uncertainty at the base of the convective envelope and 0.8 per cent at the solar core. When systematic uncertainties are included, results are 7.5 per cent and 2 per cent, respectively. In addition, we find that the values of most of the other inputs of the SSMs required to better describe the helioseismic and neutrino data are in good agreement with those adopted as the standard priors, with the exception of the astrophysical factor S11 and the microscopic diffusion rates, for which data suggests a 1 per cent and 30 per cent reduction, respectively. As an output of the study we derive the corresponding data-driven predictions for the solar neutrino fluxes.

Investigation of the Radial Compression of Carbon Nanotubes with a Scanning Probe Microscope

NASA Astrophysics Data System (ADS)

Shen, Weidian; Jiang, Bin; Han, Bao Shan; Xie, Si-Shen

2001-03-01

Carbon nanotubes have attracted great interest since they were first synthesized. The tubes have substantial promise in a variety of applications due to their unique properties. Efforts have been made to characterize the mechanical properties of the tubes. However, previous work has concentrated on the tubes’ longitudinal properties, and studies of their radial properties lag behind. We have operated a scanning probe microscope, NanoScopeTM IIIa, in the indentation/scratching mode to carry out a nanoindentation test on the top of multiwalled carbon nanotubes. We measured the correlation between the radial stress and the tube compression, and thereby determined the radial compressive elastic modulus at different compressive forces. The measurements also allowed us to estimate the radial compressive strength of the tubes. Support of this work by an Eastern Michigan University Faculty Research Fellowship and by the K. C. Wong Education Foundation, Hong Kong is gratefully acknowledged.

Analytical scanning evanescent microwave microscope and control stage

DOEpatents

Xiang, Xiao-Dong; Gao, Chen; Duewer, Fred; Yang, Hai Tao; Lu, Yalin

2013-01-22

A scanning evanescent microwave microscope (SEMM) that uses near-field evanescent electromagnetic waves to probe sample properties is disclosed. The SEMM is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The SEMM has the ability to map dielectric constant, loss tangent, conductivity, electrical impedance, and other electrical parameters of materials. Such properties are then used to provide distance control over a wide range, from to microns to nanometers, over dielectric and conductive samples for a scanned evanescent microwave probe, which enable quantitative non-contact and submicron spatial resolution topographic and electrical impedance profiling of dielectric, nonlinear dielectric and conductive materials. The invention also allows quantitative estimation of microwave impedance using signals obtained by the scanned evanescent microwave probe and quasistatic approximation modeling. The SEMM can be used to measure electrical properties of both dielectric and electrically conducting materials.

Analytical scanning evanescent microwave microscope and control stage

DOEpatents

Xiang, Xiao-Dong; Gao, Chen; Duewer, Fred; Yang, Hai Tao; Lu, Yalin

2009-06-23

A scanning evanescent microwave microscope (SEMM) that uses near-field evanescent electromagnetic waves to probe sample properties is disclosed. The SEMM is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The SEMM has the ability to map dielectric constant, loss tangent, conductivity, electrical impedance, and other electrical parameters of materials. Such properties are then used to provide distance control over a wide range, from to microns to nanometers, over dielectric and conductive samples for a scanned evanescent microwave probe, which enable quantitative non-contact and submicron spatial resolution topographic and electrical impedance profiling of dielectric, nonlinear dielectric and conductive materials. The invention also allows quantitative estimation of microwave impedance using signals obtained by the scanned evanescent microwave probe and quasistatic approximation modeling. The SEMM can be used to measure electrical properties of both dielectric and electrically conducting materials.

Role of fluoridated carbamide peroxide whitening gel in the remineralization of demineralized enamel: An in vitro study.

PubMed

Bollineni, Swetha; Janga, Ravi Kumar; Venugopal, L; Reddy, Indukuri Ravikishore; Babu, P Ravisekhar; Kumar, Sunil S

2014-05-01

The use of self-administered carbamide peroxide bleaching gels has become increasingly popular for whitening of discolored vital teeth. Studies have reported that its use may induce increased levels of sensitivity and surface roughness of the tooth due to demineralization. This study evaluates the effect of fluoride addition to the bleaching agent - its remineralizing capacity and alterations in the whitening properties. Twenty-four extracted lower third molar teeth, with the pretreatment shade determined, were taken up in the study. Each tooth was sectioned into four and labeled as groups A, B, C, and D. The tooth quadrants in group A-C were demineralized; groups A and B were treated with 10% carbamide peroxide gel (group-A without fluoride and group-B with 0.463% fluoride addition) (no further treatment was carried out for group c) group-D remained as the control. The post-treatment shade was determined. The tooth samples were sectioned (approximately 200 μm) for evaluation under a light microscope. The depth of demineralization was analyzed at five different equidistant points. Statistical analysis was carried out with t-tests, accepting ≤0.05 as significant. Addition of fluoride caused remineralization of demineralized enamel. The tooth whitening system showed that the remineralization properties did not affect the whitening properties.

Comparison of fluorescence microscopy and solid-phase cytometry methods for counting bacteria in water

USGS Publications Warehouse

Lisle, John T.; Hamilton, Martin A.; Willse, Alan R.; McFeters, Gordon A.

2004-01-01

Total direct counts of bacterial abundance are central in assessing the biomass and bacteriological quality of water in ecological and industrial applications. Several factors have been identified that contribute to the variability in bacterial abundance counts when using fluorescent microscopy, the most significant of which is retaining an adequate number of cells per filter to ensure an acceptable level of statistical confidence in the resulting data. Previous studies that have assessed the components of total-direct-count methods that contribute to this variance have attempted to maintain a bacterial cell abundance value per filter of approximately 106 cells filter-1. In this study we have established the lower limit for the number of bacterial cells per filter at which the statistical reliability of the abundance estimate is no longer acceptable. Our results indicate that when the numbers of bacterial cells per filter were progressively reduced below 105, the microscopic methods increasingly overestimated the true bacterial abundance (range, 15.0 to 99.3%). The solid-phase cytometer only slightly overestimated the true bacterial abundances and was more consistent over the same range of bacterial abundances per filter (range, 8.9 to 12.5%). The solid-phase cytometer method for conducting total direct counts of bacteria was less biased and performed significantly better than any of the microscope methods. It was also found that microscopic count data from counting 5 fields on three separate filters were statistically equivalent to data from counting 20 fields on a single filter.

Generation of dense statistical connectomes from sparse morphological data

PubMed Central

Egger, Robert; Dercksen, Vincent J.; Udvary, Daniel; Hege, Hans-Christian; Oberlaender, Marcel

2014-01-01

Sensory-evoked signal flow, at cellular and network levels, is primarily determined by the synaptic wiring of the underlying neuronal circuitry. Measurements of synaptic innervation, connection probabilities and subcellular organization of synaptic inputs are thus among the most active fields of research in contemporary neuroscience. Methods to measure these quantities range from electrophysiological recordings over reconstructions of dendrite-axon overlap at light-microscopic levels to dense circuit reconstructions of small volumes at electron-microscopic resolution. However, quantitative and complete measurements at subcellular resolution and mesoscopic scales to obtain all local and long-range synaptic in/outputs for any neuron within an entire brain region are beyond present methodological limits. Here, we present a novel concept, implemented within an interactive software environment called NeuroNet, which allows (i) integration of sparsely sampled (sub)cellular morphological data into an accurate anatomical reference frame of the brain region(s) of interest, (ii) up-scaling to generate an average dense model of the neuronal circuitry within the respective brain region(s) and (iii) statistical measurements of synaptic innervation between all neurons within the model. We illustrate our approach by generating a dense average model of the entire rat vibrissal cortex, providing the required anatomical data, and illustrate how to measure synaptic innervation statistically. Comparing our results with data from paired recordings in vitro and in vivo, as well as with reconstructions of synaptic contact sites at light- and electron-microscopic levels, we find that our in silico measurements are in line with previous results. PMID:25426033

Effect of 0.2 and 0.5% Ti on the microstructure and mechanical properties of 13Cr supermartensitic stainless steel

NASA Astrophysics Data System (ADS)

Lian, Yong; Huang, Jinfeng; Zhang, Jin; Zhang, Cheng; Gao, Wen; Zhao, Chao

2015-11-01

The effect that a 0, 0.2, and 0.5 wt.% titanium content has on the microstructure and mechanical properties of 13Cr supermartensitic stainless steel was investigated using an optical microscope, transmission electron microscope, and X-ray diffraction. The resultant microstructures of the three steels were tempered martensite with a reversed austenite dispersed throughout the matrix. Additionally, the formation of Cr-rich carbides was suppressed by stable Ti(C, N), which improved the strength without severely decreasing in the Ti-microalloyed steel toughness. Nano-precipitation of Ni3Ti was found for the 0.5 wt.% Ti steel during tempering, which significantly increased the strength, but decreased the toughness. The reversed austenite volume fraction also significantly influenced the mechanical properties.

The Impact of Microfibril Orientations on the Biomechanics of Plant Cell Walls and Tissues.

PubMed

Ptashnyk, Mariya; Seguin, Brian

2016-11-01

The microscopic structure and anisotropy of plant cell walls greatly influence the mechanical properties, morphogenesis, and growth of plant cells and tissues. The microscopic structure and properties of cell walls are determined by the orientation and mechanical properties of the cellulose microfibrils and the mechanical properties of the cell wall matrix. Viewing the shape of a plant cell as a square prism with the axis aligning with the primary direction of expansion and growth, the orientation of the microfibrils within the side walls, i.e. the parts of the cell walls on the sides of the cells, is known. However, not much is known about their orientation at the upper and lower ends of the cell. Here we investigate the impact of the orientation of cellulose microfibrils within the upper and lower parts of the plant cell walls by solving the equations of linear elasticity numerically. Three different scenarios for the orientation of the microfibrils are considered. We also distinguish between the microstructure in the side walls given by microfibrils perpendicular to the main direction of the expansion and the situation where the microfibrils are rotated through the wall thickness. The macroscopic elastic properties of the cell wall are obtained using homogenization theory from the microscopic description of the elastic properties of the cell wall microfibrils and wall matrix. It is found that the orientation of the microfibrils in the upper and lower parts of the cell walls affects the expansion of the cell in the lateral directions and is particularly important in the case of forces acting on plant cell walls and tissues.

Microleakage of different temporary filling materials in primary teeth.

PubMed

Odabas, Mesut Enes; Tulunoglu, Ozlem; Ozalp, Serife Ozdemir; Bodur, Haluk

2009-01-01

The aim of this study was to compare the sealing properties of IRM, Coltosol, Cavit G, Adhesor and Clip, which used as temporary filling material in coronal access openings in extracted human primary teeth. Standardized access cavities of 2 x 2 mm were prepared in the eighty-four, caries-free human primary anterior teeth. The teeth were divided randomly into five groups of 16 teeth each. Temporary restorative materials Group A: IRM (Dentsply), Group B: Coltosol (Coltone), Group C: Cavit G (3M), Group D: Adhesor (Spofa Dental) and Group E: Clip (Voco) were applied according to the manufacturer's directions. The specimens were immersed silver nitrate and placed in film developer under fluorescent for 24 hours. The sectioned specimens were evaluated under a digital microscope at x 20 magnifications and blindly scored for microleakage. Clip presented the least microleakage value whereas; Adhesor and IRM presented the higher microleakage values. There were statistically significant differences between Clip and the others groups, while there were no statistically significant differences in microleakage between IRM, Adhesor, Coltosol and Cavit G. However the leakage scores of Clip and Cavit G were congruent (p = 0.454). Amongst the five materials, Clip exhibited a better sealing ability.

A brief introduction to computer-intensive methods, with a view towards applications in spatial statistics and stereology.

PubMed

Mattfeldt, Torsten

2011-04-01

Computer-intensive methods may be defined as data analytical procedures involving a huge number of highly repetitive computations. We mention resampling methods with replacement (bootstrap methods), resampling methods without replacement (randomization tests) and simulation methods. The resampling methods are based on simple and robust principles and are largely free from distributional assumptions. Bootstrap methods may be used to compute confidence intervals for a scalar model parameter and for summary statistics from replicated planar point patterns, and for significance tests. For some simple models of planar point processes, point patterns can be simulated by elementary Monte Carlo methods. The simulation of models with more complex interaction properties usually requires more advanced computing methods. In this context, we mention simulation of Gibbs processes with Markov chain Monte Carlo methods using the Metropolis-Hastings algorithm. An alternative to simulations on the basis of a parametric model consists of stochastic reconstruction methods. The basic ideas behind the methods are briefly reviewed and illustrated by simple worked examples in order to encourage novices in the field to use computer-intensive methods. © 2010 The Authors Journal of Microscopy © 2010 Royal Microscopical Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gantayat, S., E-mail: subhra-gantayat@rediffmail.com; Rout, D.; Swain, S. K.

The effect of the functionalization of multiwalled carbon nanotube on the structure and electrical properties of composites was investigated. Samples based on epoxy resin with different weight percentage of MWCNTs were prepared and characterized. The interaction between MWCNT & epoxy resin was noticed by Fourier transform infrared spectroscopy (FTIR). The structure of functionalized multiwalled carbon nanotube (f-MWCNT) reinforced epoxy composite was studied by field emission scanning electron microscope (FESEM). The dispersion of f-MWCNT in epoxy resin was evidenced by high resolution transmission electron microscope (HRTEM). Electrical properties of epoxy/f-MWCNT nanocomposites were measured & the result indicated that the conductivity increasedmore » with increasing concentration of f-MWCNTs.« less

Tribological characterization of TiN coatings prepared by magnetron sputtering

NASA Astrophysics Data System (ADS)

Makwana, Nishant S.; Chauhan, Kamlesh V.; Sonera, Akshay L.; Chauhan, Dharmesh B.; Dave, Divyeshkumar P.; Rawal, Sushant K.

2018-05-01

Titanium nitride (TiN) coating deposited on aluminium and brass pin substrates using RF reactive magnetron sputtering. The structural properties and surface morphology were characterized by X-ray diffraction (XRD), atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM). There was formation of (101) Ti2N, (110) TiN2 and (102) TiN0.30 peaks at 3.5Pa, 2Pa and 1.25Pa sputtering pressure respectively. The tribological properties of coating were inspected using pin on disc tribometer equipment. It was observed that TiN coated aluminium and brass pins demonstrated improved wear resistance than uncoated aluminium and brass pins.

A Novel Preparation Method of SiC Reinforced Aluminum Composite Through Vertical Rotatory Furnace

NASA Astrophysics Data System (ADS)

Nassar, Amal Ebrahim; Nassar, Eman Ebrahim; Younis, Mona Ahmed

2018-04-01

The aluminum composite was prepared successfully by stirring using internal blade installed inside a vertical rotatory furnace. Pure aluminum was used as matrix and silicon carbide particles with 10 weight percentage as reinforcement. To evaluate the efficiency of the suggested stirrer, the microstructure of the samples was analyzed using scanning electron microscope, image analyzer software available with optical microscope and energy dispersive X-ray spectroscopy analysis. Furthermore, mechanical properties were studied by measuring ultimate and yield strength, wear resistance, hardness and porosity. It was found that the particle distribution was enhanced and consequently improved the mechanical properties of the composite.

Anion-exchange membranes derived from quaternized polysulfone and exfoliated layered double hydroxide for fuel cells

NASA Astrophysics Data System (ADS)

Liu, Wan; Liang, Na; Peng, Pai; Qu, Rong; Chen, Dongzhi; Zhang, Hongwei

2017-02-01

Layered double hydroxides (LDH) are prepared by controlling urea assisted homogeneous precipitation conditions. Morphology and crystallinity of LDHs are confirmed by X-ray diffraction and scanning electron microscope. After LDHs are incorporated into quaternized polysulfone membranes, transmission electron microscope is used to observe the exfoliated morphology of LDH sheets in the membranes. The properties of the nanocomposite membranes, including water uptake, swelling ratio, mechanical property and ionic conductivity are investigated. The nanocomposite membrane containing 5% LDH sheets shows more balanced performances, exhibiting an ionic conductivity of 2.36×10-2 S cm-1 at 60 °C.

Hybrid Al/steel-joints manufactured by ultrasound enhanced friction stir welding (USE-FSW): Process comparison, nondestructive testing and microscopic analysis

NASA Astrophysics Data System (ADS)

Thomä, M.; Wagner, G.; Straß, B.; Wolter, B.; Benfer, S.; Fürbeth, W.

2017-03-01

The process of friction stir welding (FSW) is an innovative joining technique, which proved its potential in joining dissimilar metals that are poorly fusion weldable. This ability opens a wide range for applications in industrial fields, where weight reduction by partial substitution of conventional materials through lightweight materials is a current central aim. As a consequence of this, the realization of aluminum / steel-joints is of great interest. For this material compound, several friction stir welds were carried out by different researchers for varying Al/steel-joints, whereas the definition of optimal process parameters as well as the increase of mechanical properties was in the focus of the studies. To achieve further improved properties for this dissimilar joint a newly developed hybrid process named “ultrasound enhanced friction stir welding (USE-FSW)” was applied. In this paper the resulting properties of Al/steel-joints using FSW and USE-FSW will be presented and compared. Furthermore, first results by using the nondestructive testing method “computer laminography” to analyze the developed joining area will be shown supplemented by detailed light-microscopic investigations, scanning electron microscopic analysis, and EDX.

[Study of the reliability in one dimensional size measurement with digital slit lamp microscope].

PubMed

Wang, Tao; Qi, Chaoxiu; Li, Qigen; Dong, Lijie; Yang, Jiezheng

2010-11-01

To study the reliability of digital slit lamp microscope as a tool for quantitative analysis in one dimensional size measurement. Three single-blinded observers acquired and repeatedly measured the images with a size of 4.00 mm and 10.00 mm on the vernier caliper, which simulatated the human eye pupil and cornea diameter under China-made digital slit lamp microscope in the objective magnification of 4 times, 10 times, 16 times, 25 times, 40 times and 4 times, 10 times, 16 times, respectively. The correctness and precision of measurement were compared. The images with 4 mm size were measured by three investigators and the average values were located between 3.98 to 4.06. For the images with 10.00 mm size, the average values fell within 10.00 ~ 10.04. Measurement results of 4.00 mm images showed, except A4, B25, C16 and C25, significant difference was noted between the measured value and the true value. Regarding measurement results of 10.00 mm iamges indicated, except A10, statistical significance was found between the measured value and the true value. In terms of comparing the results of the same size measured at different magnifications by the same investigator, except for investigators A's measurements of 10.00 mm dimension, the measurement results by all the remaining investigators presented statistical significance at different magnifications. Compared measurements of the same size with different magnifications, measurements of 4.00 mm in 4-fold magnification had no significant difference among the investigators', the remaining results were statistically significant. The coefficient of variation of all measurement results were less than 5%; as magnification increased, the coefficient of variation decreased. The measurement of digital slit lamp microscope in one-dimensional size has good reliability,and should be performed for reliability analysis before used for quantitative analysis to reduce systematic errors.

Australian thrips of the Haplothrips lineage (Insecta: Thysanoptera)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mound, Laurence A.; Minaei, Kambiz

2007-12-01

Water is important and ubiquitous and surprisingly not understood. Just because is it common, does not mean its understood "Poets say science takes away from the beauty of the stars-mere globs of gas atoms. I too can see the stars on a desert night, and feel them. But do I see less or more? ... What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it." - Richard P. Feynman, The Feynmanmore » Lectures on Physics, 1963. (Cited in the introduction to Chapter 3 of "The Snowflake, Winter's Secret Beauty, Text by Kenneth Libbrecht, Photography by Patricia Rasmussen.) 1. Highlight the fact that water is still one of the most active and challenging research areas in chemistry and physics 2. Describe in general terms why water is unique from the point of view of its properties o Large dipole-moment o Very polarizable o Involved in is own chemistry (e.g. auto ionization defining the pH scale) • Atomic view: o Oxygen and Hydrogen. o Hydrogen is a quantum mechanical in nature. Classical physics is no good. o Water’s Charge-charge interaction described by classical physics laws (e.g. Coulomb) o The statistical mechanics of water. Why counting is important. o You need the full arsenal of theoretical methods to understand water • Waters well known bulk properties do not explain waters anomalies o Surface tension, heat capacity • Understanding the microscopic nature of water and how this gives rise to the known bulk quantities is the thrust of state-of-the-art research o Hydrogen bonding o Liquid structure o The so-called “spherical cow” model gets you no where with water o There are 10s-100s of different water models available in the scientific literature. It is a hard business • All of life takes place at the interfaces of solid, liquid, and gas o Biology takes advantage of waters varying properties in different geometries (e.g. confined, surfaces, etc. o Water behaves differently in confined environments • Water is the most abundant greenhouse gas o How does a microscopic understanding of water impact our knowledge of the radiation budget of the earth o How does a microscopic understanding of water impact our knowledge of weather.« less

Limits of agreement between the optical pachymeter and a noncontact specular microscope.

PubMed

Ogbuehi, Kelechi C; Almubrad, Turki M

2005-07-01

To determine the limits of agreement between central corneal thickness (CCT) measurements made with the slit lamp-attached optical pachymeter and the SP2000P noncontact specular microscope. Triplicate readings for CCT were obtained for each of 130 (right) eyes of 130 patients, using the slit lamp-attached optical pachymeter and then the SP2000P noncontact specular microscope. The average CCT measured by each method was compared. Subsequently, the mean difference between both sets of measurements was assessed, and the 95% confidence interval (limits of agreement) between both techniques was determined. The mean +/- SD CCT measured by the optical pachymeter was 543 +/- 34 microm and 532 +/- 34 microm for the specular microscope. We found a statistically significant (P < 0.001) mean bias of 10 mum between CCT values measured with both types of equipment, with the optical pachymeter returning the higher values. The coefficient of variation was 6.3% for the optical pachymeter and 6.4% for the specular microscope. The right eye CCT measurements made by the optical pachymeter are, on average, 10 mum thicker than those made with the SP2000P specular microscope, which suggests that both pieces of equipment cannot be used interchangeably to monitor CCT changes in patients. Excluding left eye measurements, the reliability of the optical pachymeter is identical to that of the noncontact specular microscope.

Multi-scale mechanics of granular solids from grain-resolved X-ray measurements

NASA Astrophysics Data System (ADS)

Hurley, R. C.; Hall, S. A.; Wright, J. P.

2017-11-01

This work discusses an experimental technique for studying the mechanics of three-dimensional (3D) granular solids. The approach combines 3D X-ray diffraction and X-ray computed tomography to measure grain-resolved strains, kinematics and contact fabric in the bulk of a granular solid, from which continuum strains, grain stresses, interparticle forces and coarse-grained elasto-plastic moduli can be determined. We demonstrate the experimental approach and analysis of selected results on a sample of 1099 stiff, frictional grains undergoing multiple uniaxial compression cycles. We investigate the inter-particle force network, elasto-plastic moduli and associated length scales, reversibility of mechanical responses during cyclic loading, the statistics of microscopic responses and microstructure-property relationships. This work serves to highlight both the fundamental insight into granular mechanics that is furnished by combined X-ray measurements and describes future directions in the field of granular materials that can be pursued with such approaches.

Microscopic Spin Model for the STOCK Market with Attractor Bubbling on Regular and Small-World Lattices

NASA Astrophysics Data System (ADS)

Krawiecki, A.

A multi-agent spin model for changes of prices in the stock market based on the Ising-like cellular automaton with interactions between traders randomly varying in time is investigated by means of Monte Carlo simulations. The structure of interactions has topology of a small-world network obtained from regular two-dimensional square lattices with various coordination numbers by randomly cutting and rewiring edges. Simulations of the model on regular lattices do not yield time series of logarithmic price returns with statistical properties comparable with the empirical ones. In contrast, in the case of networks with a certain degree of randomness for a wide range of parameters the time series of the logarithmic price returns exhibit intermittent bursting typical of volatility clustering. Also the tails of distributions of returns obey a power scaling law with exponents comparable to those obtained from the empirical data.

Influence of the local environment on Mn acceptors in GaAs

NASA Astrophysics Data System (ADS)

Lee, Donghun; Gohlke, David; Benjamin, Anne; Gupta, Jay A.

2015-04-01

As transistors continue to shrink toward nanoscale dimensions, their characteristics are increasingly dependent on the statistical variations of impurities in the semiconductor material. The scanning tunneling microscope (STM) can be used to not only study prototype devices with atomically precise placement of impurity atoms, but can also probe how the properties of these impurities depend on the local environment. Tunneling spectroscopy of Mn acceptors in GaAs indicates that surface-layer Mn act as a deep acceptor, with a hole binding energy that can be tuned by positioning charged defects nearby. Band bending induced by the tip or by these defects can also tune the ionization state of the acceptor complex, evident as a ring-like contrast in STM images. The interplay of these effects is explored over a wide range of defect distances, and understood using iterative simulations of tip-induced band bending.

Mutual information, neural networks and the renormalization group

NASA Astrophysics Data System (ADS)

Koch-Janusz, Maciej; Ringel, Zohar

2018-06-01

Physical systems differing in their microscopic details often display strikingly similar behaviour when probed at macroscopic scales. Those universal properties, largely determining their physical characteristics, are revealed by the powerful renormalization group (RG) procedure, which systematically retains `slow' degrees of freedom and integrates out the rest. However, the important degrees of freedom may be difficult to identify. Here we demonstrate a machine-learning algorithm capable of identifying the relevant degrees of freedom and executing RG steps iteratively without any prior knowledge about the system. We introduce an artificial neural network based on a model-independent, information-theoretic characterization of a real-space RG procedure, which performs this task. We apply the algorithm to classical statistical physics problems in one and two dimensions. We demonstrate RG flow and extract the Ising critical exponent. Our results demonstrate that machine-learning techniques can extract abstract physical concepts and consequently become an integral part of theory- and model-building.

Long-Term Evolution of Email Networks: Statistical Regularities, Predictability and Stability of Social Behaviors.

PubMed

Godoy-Lorite, Antonia; Guimerà, Roger; Sales-Pardo, Marta

2016-01-01

In social networks, individuals constantly drop ties and replace them by new ones in a highly unpredictable fashion. This highly dynamical nature of social ties has important implications for processes such as the spread of information or of epidemics. Several studies have demonstrated the influence of a number of factors on the intricate microscopic process of tie replacement, but the macroscopic long-term effects of such changes remain largely unexplored. Here we investigate whether, despite the inherent randomness at the microscopic level, there are macroscopic statistical regularities in the long-term evolution of social networks. In particular, we analyze the email network of a large organization with over 1,000 individuals throughout four consecutive years. We find that, although the evolution of individual ties is highly unpredictable, the macro-evolution of social communication networks follows well-defined statistical patterns, characterized by exponentially decaying log-variations of the weight of social ties and of individuals' social strength. At the same time, we find that individuals have social signatures and communication strategies that are remarkably stable over the scale of several years.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daily, Michael D.; Olsen, Brett N.; Schlesinger, Paul H.

In mammalian cells cholesterol is essential for membrane function, but in excess can be cytototoxic. The cellular response to acute cholesterol loading involves biophysical-based mechanisms that regulate cholesterol levels, through modulation of the “activity” or accessibility of cholesterol to extra-membrane acceptors. Experiments and united atom (UA) simulations show that at high concentrations of cholesterol, lipid bilayers thin significantly and cholesterol availability to external acceptors increases substantially. Such cholesterol activation is critical to its trafficking within cells. Here we aim to reduce the computational cost to enable simulation of large and complex systems involved in cholesterol regulation, such as those includingmore » oxysterols and cholesterol-sensing proteins. To accomplish this, we have modified the published MARTINI coarse-grained force field to improve its predictions of cholesterol-induced changes in both macroscopic and microscopic properties of membranes. Most notably, MARTINI fails to capture both the (macroscopic) area condensation and membrane thickening seen at less than 30% cholesterol and the thinning seen above 40% cholesterol. The thinning at high concentration is critical to cholesterol activation. Microscopic properties of interest include cholesterol-cholesterol radial distribution functions (RDFs), tilt angle, and accessible surface area. First, we develop an “angle-corrected” model wherein we modify the coarse-grained bond angle potentials based on atomistic simulations. This modification significantly improves prediction of macroscopic properties, most notably the thickening/thinning behavior, and also slightly improves microscopic property prediction relative to MARTINI. Second, we add to the angle correction a “volume correction” by also adjusting phospholipid bond lengths to achieve a more accurate volume per molecule. The angle + volume correction substantially further improves the quantitative agreement of the macroscopic properties (area per molecule and thickness) with united atom simulations. However, this improvement also reduces the accuracy of microscopic predictions like radial distribution functions and cholesterol tilt below that of either MARTINI or the angle-corrected model. Thus, while both of our forcefield corrections improve MARTINI, the combined angle and volume correction should be used for problems involving sterol effects on the overall structure of the membrane, while our angle-corrected model should be used in cases where the properties of individual lipid and sterol models are critically important.« less

Towards a theory of cortical columns: From spiking neurons to interacting neural populations of finite size.

PubMed

Schwalger, Tilo; Deger, Moritz; Gerstner, Wulfram

2017-04-01

Neural population equations such as neural mass or field models are widely used to study brain activity on a large scale. However, the relation of these models to the properties of single neurons is unclear. Here we derive an equation for several interacting populations at the mesoscopic scale starting from a microscopic model of randomly connected generalized integrate-and-fire neuron models. Each population consists of 50-2000 neurons of the same type but different populations account for different neuron types. The stochastic population equations that we find reveal how spike-history effects in single-neuron dynamics such as refractoriness and adaptation interact with finite-size fluctuations on the population level. Efficient integration of the stochastic mesoscopic equations reproduces the statistical behavior of the population activities obtained from microscopic simulations of a full spiking neural network model. The theory describes nonlinear emergent dynamics such as finite-size-induced stochastic transitions in multistable networks and synchronization in balanced networks of excitatory and inhibitory neurons. The mesoscopic equations are employed to rapidly integrate a model of a cortical microcircuit consisting of eight neuron types, which allows us to predict spontaneous population activities as well as evoked responses to thalamic input. Our theory establishes a general framework for modeling finite-size neural population dynamics based on single cell and synapse parameters and offers an efficient approach to analyzing cortical circuits and computations.

Multispectral detection of cutaneous lesions using spectroscopy and microscopy approaches

NASA Astrophysics Data System (ADS)

Borisova, E.; Genova-Hristova, Ts.; Troyanova, P.; Pavlova, E.; Terziev, I.; Semyachkina-Glushkovskaya, O.; Lomova, M.; Genina, E.; Stanciu, G.; Tranca, D.; Avramov, L.

2018-02-01

Autofluorescence, diffuse-reflectance and transmission spectral, and microscopic measurements were made on different cutaneous neoplastic lesions, namely basal cell carcinoma, squamous cell carcinoma, malignant melanoma, and dysplastic and benign lesions related. Spectroscopic measurements were made on ex vivo tissue samples, and confocal microscopy investigations were made on thin tissue slices. Fluorescence spectra obtained reveal statistically significant differences between the different benign, dysplastic and malignant lesions by the level of emission intensity, as well by spectral shape, which are fingerprints applicable for differentiation algorithms. In reflectance mode the most significant differences are related to the influence of skin pigments - melanin and hemoglobin. Transmission spectroscopy mode gave complementary optical properties information about the tissue samples investigated to that one of reflectance and absorption spectroscopy. Using autofluorescence detection of skin lesions we obtain very good diagnostic performance for distinguishing of nonmelanoma lesions. Using diffuse reflectance and transmission spectroscopy we obtain significant tool for pigmented pathologies differentiation, but it is a tool with moderate sensitivity for non-melanoma lesions detection. One could rapidly increase the diagnostic accuracy of the received combined "optical biopsy" method when several spectral detection techniques are applied in common algorithm for lesions' differentiation. Specific spectral features observed in each type of lesion investigated on micro and macro level would be presented and discussed. Correlation between the spectral data received and the microscopic features observed would be discussed in the report.

Diagnostic value and cost utility analysis for urine Gram stain and urine microscopic examination as screening tests for urinary tract infection.

PubMed

Wiwanitkit, Viroj; Udomsantisuk, Nibhond; Boonchalermvichian, Chaiyaporn

2005-06-01

The aim of this study was to evaluate the diagnostic properties of urine Gram stain and urine microscopic examination for screening for urinary tract infection (UTI), and to perform an additional cost utility analysis. This descriptive study was performed on 95 urine samples sent for urine culture to the Department of Microbiology, Faculty of Medicine, Chulalongkorn University. The first part of the study was to determine the diagnostic properties of two screening tests (urine Gram stain and urine microscopic examination). Urine culture was set as the gold standard and the results from both methods were compared to this. The second part of this study was to perform a cost utility analysis. The sensitivity of urine Gram stain was 96.2%, the specificity 93.0%, the positive predictive value 94.3% and the negative predictive value 95.2%. False positives occurred with a frequency of 7.0% and false negatives 3.8%. For the microscopic examination, the sensitivity was 65.4%, specificity 74.4%, positive predictive value 75.6% and negative predictive value 64.0%. False positives occurred with a frequency of 25.6% and false negatives 34.6%. Combining urine Gram stain and urine microscopic examination, the sensitivity was 98.1%, specificity 74.4%, positive predictive value 82.3% and negative predictive value 97.0%. False positives occurred with a frequency of 25.6% and false negatives 1.9%. However, the cost per utility of the combined method was higher than either urine microscopic examination or urine Gram stain alone. Urine Gram stain provided the lowest cost per utility. Economically, urine Gram stain is the proper screening tool for presumptive diagnosis of UTI.

Effect of heat treatment procedure on magnetic and magnetocaloric properties of Ni43Mn46In11 melt spun ribbons

NASA Astrophysics Data System (ADS)

Kaya, M.; Elerman, Y.; Dincer, I.

2018-07-01

The effect of heat treatment on the structural, magnetic and magnetocaloric properties of Ni43Mn46In11 melt-spun ribbons was systematically investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), magnetic force microscope (MFM) and magnetic measurements. From the XRD studies, tetragonal and cubic phases were detected at room temperature for as-spun, quenched and slow-cooled ribbons. Furthermore, it was observed, upon annealing martensite transition temperatures increased when compared to the as-spun ribbon. To avoid magnetic hysteresis losses in the vicinity of the structural transition region, the magnetic entropy changes-ΔS m of the investigated ribbons were evaluated from temperature-dependent magnetisation-M(T) curves on cooling for different applied magnetic fields. The maximum ΔS m value was found to be 6.79 J kg-1 K-1 for the quenched ribbon in the vicinity of structural transition region for a magnetic field change of 50 kOe.

Using an ultrasound elasticity microscope to map three-dimensional strain in a porcine cornea.

PubMed

Hollman, Kyle W; Shtein, Roni M; Tripathy, Sakya; Kim, Kang

2013-08-01

An ultrasound elasticity microscope was used to map 3-D strain volume in an ex vivo porcine cornea to illustrate its ability to measure the mechanical properties of this tissue. Mechanical properties of the cornea play an important role in its function and, therefore, also in ophthalmic diseases such as kerataconus and corneal ectasia. The ultrasound elasticity microscope combines a tightly focused high-frequency transducer with confocal scanning to produce high-quality speckle over the entire volume of tissue. This system and the analysis were able to generate volume maps of compressional strain in all three directions for porcine corneal tissue, more information than any previous study has reported. Strain volume maps indicated features of the cornea and mechanical behavior as expected. These results constitute a step toward better understanding of corneal mechanics and better treatment of corneal diseases. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Anion-exchange membranes derived from quaternized polysulfone and exfoliated layered double hydroxide for fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wan; Liang, Na; Peng, Pai

2017-02-15

Layered double hydroxides (LDH) are prepared by controlling urea assisted homogeneous precipitation conditions. Morphology and crystallinity of LDHs are confirmed by X-ray diffraction and scanning electron microscope. After LDHs are incorporated into quaternized polysulfone membranes, transmission electron microscope is used to observe the exfoliated morphology of LDH sheets in the membranes. The properties of the nanocomposite membranes, including water uptake, swelling ratio, mechanical property and ionic conductivity are investigated. The nanocomposite membrane containing 5% LDH sheets shows more balanced performances, exhibiting an ionic conductivity of 2.36×10{sup −2} S cm{sup −1} at 60 °C. - Graphical abstract: Anion-exchange membrane based onmore » quaternized polysulfone and exfoliated layered double hydroxide is optically transparent and has good ionic properties.« less

A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

NASA Astrophysics Data System (ADS)

Hussnain, Ali; Singh Rawat, Rajdeep; Ahmad, Riaz; Hussain, Tousif; Umar, Z. A.; Ikhlaq, Uzma; Chen, Zhong; Shen, Lu

2015-02-01

Nano-crystalline tungsten nitride thin films are synthesized on AISI-304 steel at room temperature using Mather-type plasma focus system. The surface properties of the exposed substrate against different deposition shots are examined for crystal structure, surface morphology and mechanical properties using X-ray diffraction (XRD), atomic force microscope, field emission scanning electron microscope and nano-indenter. The XRD results show the growth of WN and WN2 phases and the development of strain/stress in the deposited films by varying the number of deposition shots. Morphology of deposited films shows the significant change in the surface structure with different ion energy doses (number of deposition shots). Due to the effect of different ion energy doses, the strain/stress developed in the deposited film leads to an improvement of hardness of deposited films.

Traceable measurements of small forces and local mechanical properties

NASA Astrophysics Data System (ADS)

Campbellová, Anna; Valtr, Miroslav; Zůda, Jaroslav; Klapetek, Petr

2011-09-01

Measurement of local mechanical properties is an important topic in the fields of nanoscale device fabrication, thin film deposition and composite material development. Nanoindentation instruments are commonly used to study hardness and related mechanical properties at the nanoscale. However, traceability and uncertainty aspects of the measurement process often remain left aside. In this contribution, the use of a commercial nanoindentation instrument for metrology purposes will be discussed. Full instrument traceability, provided using atomic force microscope cantilevers and a mass comparator (normal force), interferometer (depth) and atomic force microscope (area function) is described. The uncertainty of the loading/unloading curve measurements will be analyzed and the resulting uncertainties for quantities, that are computed from loading curves such as hardness or elastic modulus, are studied. For this calculation a combination of uncertainty propagation law and Monte Carlo uncertainty evaluations are used.

Realization of a four-step molecular switch in scanning tunneling microscope manipulation of single chlorophyll-a molecules

PubMed Central

Iancu, Violeta; Hla, Saw-Wai

2006-01-01

Single chlorophyll-a molecules, a vital resource for the sustenance of life on Earth, have been investigated by using scanning tunneling microscope manipulation and spectroscopy on a gold substrate at 4.6 K. Chlorophyll-a binds on Au(111) via its porphyrin unit while the phytyl-chain is elevated from the surface by the support of four CH3 groups. By injecting tunneling electrons from the scanning tunneling microscope tip, we are able to bend the phytyl-chain, which enables the switching of four molecular conformations in a controlled manner. Statistical analyses and structural calculations reveal that all reversible switching mechanisms are initiated by a single tunneling-electron energy-transfer process, which induces bond rotation within the phytyl-chain. PMID:16954201

Molecular dynamics simulations of salicylate effects on the micro- and mesoscopic properties of a dipalmitoylphosphatidylcholine bilayer†

PubMed Central

Song, Yuhua; Guallar, Victor; Baker, Nathan A.

2008-01-01

Salicylate, an amphiphilic molecule and a popular member of non-steroidal antiinflammatory drug family, is known to affect hearing through reduction of the electromechanical coupling in the outer hair cells of the ear. This reduction of electromotility by salicylate has been widely studied but the molecular mechanism of the phenomenon is still unknown. In this study, we investigated one aspect of salicylate’s action; namely, the perturbation of electrical and mechanical membrane properties by salicylate in the absence of cytoskeletal or membrane-bound motor proteins such as prestin. In particular, we simulated the interaction of salicylate with a dipalmitoylphosphatidylcholine (DPPC) bilayer via atomically-detailed molecular dynamics simulations to observe the effect of salicylate on the microscopic and mesoscopic properties of the bilayer. The results demonstrate that salicylate interacts with the bilayer by associating at the water-DPPC interface in a nearly perpendicular orientation and penetrating more deeply into the bilayer than either sodium or chloride. This association has several affects on the membrane properties. First, binding of salicylate to the membrane displaces chloride from the bilayer-water interface. Second, salicylate influences the electrostatic potential and dielectric properties of the bilayer, with significant changes at the water-lipid bilayer interface. Third, salicylate association results in structural changes including decreased head group area per lipid and increased lipid tail order. However, salicylate does not significantly alter the mechanical properties of the DPPC bilayer; bulk compressibility, area compressibility, and bending modulus were only perturbed by small, statistically-insignificant amounts, by the presence of salicylate. The observations from these simulations are in qualitative agreement with experimental data and support the conclusion that salicylate influences the electrical but not the mechanical properties of DPPC membranes. PMID:16216066

Low-energy nuclear spectroscopy in a microscopic multiphonon approach

NASA Astrophysics Data System (ADS)

Lo Iudice, N.; Ponomarev, V. Yu; Stoyanov, Ch; Sushkov, A. V.; Voronov, V. V.

2012-04-01

The low-lying spectra of heavy nuclei are investigated within the quasiparticle-phonon model. This microscopic approach goes beyond the quasiparticle random-phase approximation by treating a Hamiltonian of separable form in a microscopic multiphonon basis. It is therefore able to describe the anharmonic features of collective modes as well as the multiphonon states, whose experimental evidence is continuously growing. The method can be put in close correspondence with the proton-neutron interacting boson model. By associating the microscopic isoscalar and isovector quadrupole phonons with proton-neutron symmetric and mixed-symmetry quadrupole bosons, respectively, the microscopic states can be classified, just as in the algebraic model, according to their phonon content and their symmetry. In addition, these states disclose the nuclear properties which are to be ascribed to genuine shell effects, not included in the algebraic approach. Due to its flexibility, the method can be implemented numerically for systematic studies of spectroscopic properties throughout entire regions of vibrational nuclei. The spectra and multipole transition strengths so computed are in overall good agreement with the experimental data. By exploiting the correspondence of the method with the interacting boson model, it is possible to embed the microscopic states into this algebraic frame and, therefore, face the study of nuclei far from shell closures, not directly accessible to merely microscopic approaches. Here, it is shown how this task is accomplished through systematic investigations of magnetic dipole and, especially, electric dipole modes along paths moving from the vibrational to the transitional regions. The method is very well suited to the study of well-deformed nuclei. It provides reliable descriptions of low-lying magnetic as well as electric multipole modes of nuclei throughout the rare-earth and actinide regions. Attention is focused here on the low-lying 0+ states produced in large abundance in recent experiments. The analysis shows that the quasiparticle-phonon model accounts for the occurrence of so many 0+ levels and discloses their nature.

Quantifying fluctuations in economic systems by adapting methods of statistical physics

NASA Astrophysics Data System (ADS)

Stanley, H. E.; Gopikrishnan, P.; Plerou, V.; Amaral, L. A. N.

2000-12-01

The emerging subfield of econophysics explores the degree to which certain concepts and methods from statistical physics can be appropriately modified and adapted to provide new insights into questions that have been the focus of interest in the economics community. Here we give a brief overview of two examples of research topics that are receiving recent attention. A first topic is the characterization of the dynamics of stock price fluctuations. For example, we investigate the relation between trading activity - measured by the number of transactions NΔ t - and the price change GΔ t for a given stock, over a time interval [t, t+ Δt] . We relate the time-dependent standard deviation of price fluctuations - volatility - to two microscopic quantities: the number of transactions NΔ t in Δ t and the variance WΔ t2 of the price changes for all transactions in Δ t. Our work indicates that while the pronounced tails in the distribution of price fluctuations arise from WΔ t, the long-range correlations found in ∣ GΔ t∣ are largely due to NΔ t. We also investigate the relation between price fluctuations and the number of shares QΔ t traded in Δ t. We find that the distribution of QΔ t is consistent with a stable Lévy distribution, suggesting a Lévy scaling relationship between QΔ t and NΔ t, which would provide one explanation for volume-volatility co-movement. A second topic concerns cross-correlations between the price fluctuations of different stocks. We adapt a conceptual framework, random matrix theory (RMT), first used in physics to interpret statistical properties of nuclear energy spectra. RMT makes predictions for the statistical properties of matrices that are universal, that is, do not depend on the interactions between the elements comprising the system. In physics systems, deviations from the predictions of RMT provide clues regarding the mechanisms controlling the dynamics of a given system, so this framework can be of potential value if applied to economic systems. We discuss a systematic comparison between the statistics of the cross-correlation matrix C - whose elements Cij are the correlation-coefficients between the returns of stock i and j - and that of a random matrix having the same symmetry properties. Our work suggests that RMT can be used to distinguish random and non-random parts of C; the non-random part of C, which deviates from RMT results provides information regarding genuine cross-correlations between stocks.

A Low-Cost Digital Microscope with Real-Time Fluorescent Imaging Capability.

PubMed

Hasan, Md Mehedi; Alam, Mohammad Wajih; Wahid, Khan A; Miah, Sayem; Lukong, Kiven Erique

2016-01-01

This paper describes the development of a prototype of a low-cost digital fluorescent microscope built from commercial off-the-shelf (COTS) components. The prototype was tested to detect malignant tumor cells taken from a living organism in a preclinical setting. This experiment was accomplished by using Alexa Fluor 488 conjugate dye attached to the cancer cells. Our prototype utilizes a torch along with an excitation filter as a light source for fluorophore excitation, a dichroic mirror to reflect the excitation and pass the emitted green light from the sample under test and a barrier filter to permit only appropriate wavelength. The system is designed out of a microscope using its optical zooming property and an assembly of exciter filter, dichroic mirror and transmitter filter. The microscope is connected to a computer or laptop through universal serial bus (USB) that allows real-time transmission of captured florescence images; this also offers real-time control of the microscope. The designed system has comparable features of high-end commercial fluorescent microscopes while reducing cost, power, weight and size.

A Low-Cost Digital Microscope with Real-Time Fluorescent Imaging Capability

PubMed Central

Hasan, Md. Mehedi; Wahid, Khan A.; Miah, Sayem; Lukong, Kiven Erique

2016-01-01

This paper describes the development of a prototype of a low-cost digital fluorescent microscope built from commercial off-the-shelf (COTS) components. The prototype was tested to detect malignant tumor cells taken from a living organism in a preclinical setting. This experiment was accomplished by using Alexa Fluor 488 conjugate dye attached to the cancer cells. Our prototype utilizes a torch along with an excitation filter as a light source for fluorophore excitation, a dichroic mirror to reflect the excitation and pass the emitted green light from the sample under test and a barrier filter to permit only appropriate wavelength. The system is designed out of a microscope using its optical zooming property and an assembly of exciter filter, dichroic mirror and transmitter filter. The microscope is connected to a computer or laptop through universal serial bus (USB) that allows real-time transmission of captured florescence images; this also offers real-time control of the microscope. The designed system has comparable features of high-end commercial fluorescent microscopes while reducing cost, power, weight and size. PMID:27977709

Size determination of Acipenser ruthenus spermatozoa in different types of electron microscopy.

PubMed

Psenicka, Martin; Tesarová, Martina; Tesitel, Jakub; Nebesárová, Jana

2010-07-01

In this study three types of scanning electron microscopes were used for the size determination of spermatozoa of sterlet Acipenser ruthenus - high vacuum scanning electron microscope (SEM, JEOL 6300), environmental scanning electron microscope (ESEM, Quanta 200 FEG), field emission scanning electron microscope (FESEM, JEOL 7401F) with cryoattachment Alto 2500 (Gatan) and transmission electron microscope (TEM, JEOL 1010). The use of particular microscopes was tied with different specimen preparation techniques. The aim of this study was to evaluate to what degree the type of used electron microscope can influence the size of different parts of spermatozoa. For high vacuum SEM the specimen was prepared using two slightly different procedures. After chemical fixation with 2.5% glutaraldehyde in 0.1M phosphate buffer and post-fixation by 1% osmium tetroxide, the specimen was dehydrated by acetone series and dried either by critical point method or by means of t-butylalcohol. For ESEM fresh, unfixed material was used, which was dropped on microscopic copper grids. In FESEM working in cryo-mode the specimen was observed in a frozen state. Ultrathin sections from chemically fixed and Epon embedded specimens were prepared for TEM observation. Distinct parts of sterlet spermatozoa were measured in each microscope and the data obtained was statistically processed. Results confirmed that the classical chemical procedure of specimen preparation for SEM including critical point drying method led to a significant contraction of all measured values, which could deviate up to 30% in comparison with values measured on the fresh chemically untreated specimen in ESEM. Surprisingly sperm dimensions determinated on ultrathin sections by TEM are comparable with values obtained in ESEM or FESEM. Copyright 2010 Elsevier Ltd. All rights reserved.

Football fever: goal distributions and non-Gaussian statistics

NASA Astrophysics Data System (ADS)

Bittner, E.; Nußbaumer, A.; Janke, W.; Weigel, M.

2009-02-01

Analyzing football score data with statistical techniques, we investigate how the not purely random, but highly co-operative nature of the game is reflected in averaged properties such as the probability distributions of scored goals for the home and away teams. As it turns out, especially the tails of the distributions are not well described by the Poissonian or binomial model resulting from the assumption of uncorrelated random events. Instead, a good effective description of the data is provided by less basic distributions such as the negative binomial one or the probability densities of extreme value statistics. To understand this behavior from a microscopical point of view, however, no waiting time problem or extremal process need be invoked. Instead, modifying the Bernoulli random process underlying the Poissonian model to include a simple component of self-affirmation seems to describe the data surprisingly well and allows to understand the observed deviation from Gaussian statistics. The phenomenological distributions used before can be understood as special cases within this framework. We analyzed historical football score data from many leagues in Europe as well as from international tournaments, including data from all past tournaments of the “FIFA World Cup” series, and found the proposed models to be applicable rather universally. In particular, here we analyze the results of the German women’s premier football league and consider the two separate German men’s premier leagues in the East and West during the cold war times as well as the unified league after 1990 to see how scoring in football and the component of self-affirmation depend on cultural and political circumstances.

Impact of Gastric Acid Induced Surface Changes on Mechanical Behavior and Optical Characteristics of Dental Ceramics.

PubMed

Kulkarni, Aditi; Rothrock, James; Thompson, Jeffery

2018-01-14

To test the impact of exposure to artificial gastric acid combined with toothbrush abrasion on the properties of dental ceramics. Earlier research has indicated that immersion in artificial gastric acid has caused increased surface roughness of dental ceramics; however, the combined effects of acid immersion and toothbrush abrasion and the impact of increased surface roughness on mechanical strength and optical properties have not been studied. Three commercially available ceramics were chosen for this study: feldspathic porcelain, lithium disilicate glass-ceramic, and monolithic zirconium oxide. The specimens (10 × 1 mm discs) were cut, thermally treated as required, and polished. Each material was divided into four groups (n = 8 per group): control (no exposure), acid only, brush only, acid + brush. The specimens were immersed in artificial gastric acid (50 ml of 0.2% [w/v] sodium chloride in 0.7% [v/v] hydrochloric acid mixed with 0.16 g of pepsin powder, pH = 2) for 2 minutes and rinsed with deionized water for 2 minutes. The procedure was repeated 6 times/day × 9 days, and specimens were stored in deionized water at 37°C. Toothbrush abrasion was performed using an ISO/ADA design brushing machine for 100 cycles/day × 9 days. The acid + brush group received both treatments. Specimens were examined under SEM and an optical microscope for morphological changes. Color and translucency were measured using spectrophotometer CIELAB coordinates (L*, a*, b*). Surface gloss was measured using a gloss meter. Surface roughness was measured using a stylus profilometer. Biaxial flexural strength was measured using a mechanical testing machine. The data were analyzed by one-way ANOVA followed by Tukey's HSD post hoc test (p < 0.05). Statistically significant changes were found for color, gloss, and surface roughness for porcelain and e.max specimens. No statistically significant changes were found for any properties of zirconia specimens. The acid treatment affected the surface roughness, color, and gloss of porcelain and e.max ceramics. The changes in translucency and mechanical strength for all materials were not statistically significant. Zirconia ceramic showed resistance to all treatments. © 2018 by the American College of Prosthodontists.

Multiscale modelling and analysis of collective decision making in swarm robotics.

PubMed

Vigelius, Matthias; Meyer, Bernd; Pascoe, Geoffrey

2014-01-01

We present a unified approach to describing certain types of collective decision making in swarm robotics that bridges from a microscopic individual-based description to aggregate properties. Our approach encompasses robot swarm experiments, microscopic and probabilistic macroscopic-discrete simulations as well as an analytic mathematical model. Following up on previous work, we identify the symmetry parameter, a measure of the progress of the swarm towards a decision, as a fundamental integrated swarm property and formulate its time evolution as a continuous-time Markov process. Contrary to previous work, which justified this approach only empirically and a posteriori, we justify it from first principles and derive hard limits on the parameter regime in which it is applicable.

Microstructures and properties of rapidly solidified alloys

NASA Technical Reports Server (NTRS)

Shechtman, D.; Horowitz, E.

1984-01-01

The microstructure and properties of rapidly solidified aluminum alloys were researched. The effects of powder and flake chemistry and morphology and alternative consolidation processing parameters are being conducted. Samples of the powders being utilized were obtained for comprehensive metallurgical characterization. Seven aluminum alloys in the form of thin foils were studied by a variety of techniques including optical metallography, scanning electron microscope, and transmission electron microscope. Details of the microstructural characteristics are presented along with a discussion of the solidification process. A better understanding of the microstructure of the rapidly solidified aluminum alloys prepared by a variety of techniques such as roller quenching, the vacuum atomized procedure, ultrasonically atomized in inert atmospheres, and atomized in flue gas was provided.

Quality Control of Laser-Beam-Melted Parts by a Correlation Between Their Mechanical Properties and a Three-Dimensional Surface Analysis

NASA Astrophysics Data System (ADS)

Grimm, T.; Wiora, G.; Witt, G.

2017-03-01

Good correlations between three-dimensional surface analyses of laser-beam-melted parts of nickel alloy HX and their mechanical properties were found. The surface analyses were performed with a confocal microscope, which offers a more profound surface data basis than a conventional, two-dimensional tactile profilometry. This new approach results in a wide range of three-dimensional surface parameters, which were each evaluated with respect to their feasibility for quality control in additive manufacturing. As a result of an automated surface analysis process by the confocal microscope and an industrial six-axis robot, the results are an innovative approach for quality control in additive manufacturing.

Enhanced mechanical properties of hydrothermal carbamated cellulose nanocomposite film reinforced with graphene oxide.

PubMed

Gan, Sinyee; Zakaria, Sarani; Syed Jaafar, Sharifah Nabihah

2017-09-15

Cellulose carbamate (CC) was synthesized via hydrothermal process and mixed with graphene oxide (GO) to form a homogeneous cellulose matrix nanocomposite films. The properties of CC/GO nanocomposite films fabricated using simple solution-mixing method with different GO loadings were studied. Transmission electron microscope analysis showed the exfoliation of self-synthesized GO nanosheets within the CC matrix. X-ray diffraction results confirmed the crystalline structure of CC/GO films as the CC/GO mass ratio increased from 100/0 to 100/4. The mechanical properties of CC/GO film were significantly improved as compared to neat CC film. From thermogravimetric analysis result, the introduction of GO enhanced the thermal stability and carbon yields. The 3D homogeneous porous structures of the CC/GO films were observed under Field emission scanning electron microscope. These improvements in nanocomposite film properties could be confirmed by Fourier transform infrared spectroscopy due to the strong and good interactions between CC and GO. Copyright © 2017 Elsevier Ltd. All rights reserved.

Barrier properties of nano silicon carbide designed chitosan nanocomposites.

PubMed

Pradhan, Gopal C; Dash, Satyabrata; Swain, Sarat K

2015-12-10

Nano silicon carbide (SiC) designed chitosan nanocomposites were prepared by solution technique. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used for studying structural interaction of nano silicon carbide (SiC) with chitosan. The morphology of chitosan/SiC nanocomposites was investigated by field emission scanning electron microscope (FESEM), and high resolution transmission electron microscope (HRTEM). The thermal stability of chitosan was substantially increased due to incorporation of stable silicon carbide nanopowder. The oxygen permeability of chitosan/SiC nanocomposites was reduced by three folds as compared to the virgin chitosan. The chemical resistance properties of chitosan were enhanced due to the incorporation of nano SiC. The biodegradability was investigated using sludge water. The tensile strength of chitosan/SiC nanocomposites was increased with increasing percentage of SiC. The substantial reduction in oxygen barrier properties in combination with increased thermal stability, tensile strength and chemical resistance properties; the synthesized nanocomposite may be suitable for packaging applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Hao; Lee, H. S.; Sarahan, M. C.

Grain boundaries (GBs) in complex oxides such as perovskites have been shown to readily accommodate nonstoichiometry changing the electrostatic potential at the boundary plane and effectively controlling material properties such as capacitance, magnetoresistance and superconductivity. Understanding and quantifying exactly how variations in atomic scale nonstoichiometry at the boundary plane extend to the practical mesoscale operating length of the system is therefore critical for improving the overall properties. Bicrystals of SrTiO 3 were fabricated to provide the model GB model structures that are analysed in this paper. We show that statistical analysis of aberration-corrected scanning transmission electron microscope images acquired frommore » a large area of GB is an effective routine to understanding the variation in boundary structure that occurs to accommodate nonstoichiometry. In the case of the SrTiO 3 22.6° Σ13 (510)/[100] GB analysed here, the symmetric atomic structures observed from a micron-long GB can be categorized as two different competing structural arrangements, with and without a rigid-body translation along the boundary plane. How this quantified experimental approach can provide direct insights into the GB energetics is further confirmed from the first principles density functional theory, and the effect of nonstoichiometry in determining the GB energies is quantified.« less

Infrared spectroscopy, nano-mechanical properties, and scratch resistance of esthetic orthodontic coated archwires.

PubMed

da Silva, Dayanne Lopes; Santos, Emanuel; Camargo, Sérgio de Souza; Ruellas, Antônio Carlos de Oliveira

2015-09-01

To evaluate the material composition, mechanical properties (hardness and elastic modulus), and scratch resistance of the coating of four commercialized esthetic orthodontic archwires. The coating composition of esthetic archwires was assessed by Fourier-transform infrared spectroscopy (FTIR). Coating hardness and elastic modulus were analyzed with instrumented nano-indentation tests. Scratch resistance of coatings was evaluated by scratch test. Coating micromorphologic characteristics after scratch tests were observed in a scanning electron microscope. Statistical differences were investigated using analysis of variance and Tukey post hoc test. The FTIR results indicate that all analyzed coatings were markedly characterized by the benzene peak at about 1500 cm(-1). The coating hardness and elastic modulus average values ranged from 0.17 to 0.23 GPa and from 5.0 to 7.6 GPa, respectively. Scratch test showed a high coating elasticity after load removal with elastic recoveries >60%, but different failure features could be observed along the scratches. The coatings of esthetic archwires evaluated are probably a composite of polyester and polytetrafluoroethylene. Delamination, crack propagation, and debris generation could be observed along the coating scratches and could influence its durability in the oral environment.

Spectral Properties and Dynamics of Gold Nanorods Revealed by EMCCD Based Spectral-Phasor Method

PubMed Central

Chen, Hongtao; Digman, Michelle A.

2015-01-01

Gold nanorods (NRs) with tunable plasmon-resonant absorption in the near-infrared region have considerable advantages over organic fluorophores as imaging agents. However, the luminescence spectral properties of NRs have not been fully explored at the single particle level in bulk due to lack of proper analytic tools. Here we present a global spectral phasor analysis method which allows investigations of NRs' spectra at single particle level with their statistic behavior and spatial information during imaging. The wide phasor distribution obtained by the spectral phasor analysis indicates spectra of NRs are different from particle to particle. NRs with different spectra can be identified graphically in corresponding spatial images with high spectral resolution. Furthermore, spectral behaviors of NRs under different imaging conditions, e.g. different excitation powers and wavelengths, were carefully examined by our laser-scanning multiphoton microscope with spectral imaging capability. Our results prove that the spectral phasor method is an easy and efficient tool in hyper-spectral imaging analysis to unravel subtle changes of the emission spectrum. Moreover, we applied this method to study the spectral dynamics of NRs during direct optical trapping and by optothermal trapping. Interestingly, spectral shifts were observed in both trapping phenomena. PMID:25684346

Electronic structure and microscopic model of V(2)GeO(4)F(2)-a quantum spin system with S = 1.

PubMed

Rahaman, Badiur; Saha-Dasgupta, T

2007-07-25

We present first-principles density functional calculations and downfolding studies of the electronic and magnetic properties of the oxide-fluoride quantum spin system V(2)GeO(4)F(2). We discuss explicitly the nature of the exchange paths and provide quantitative estimates of magnetic exchange couplings. A microscopic modelling based on analysis of the electronic structure of this systems puts it in the interesting class of weakly coupled alternating chain S = 1 systems. Based on the microscopic model, we make inferrences about its spin excitation spectra, which needs to be tested by rigorous experimental study.

Highly dispersible diamond nanoparticles for pretreatment of diamond films on Si substrate

NASA Astrophysics Data System (ADS)

Zhao, Shenjie; Huang, Jian; Zhou, Xinyu; Ren, Bing; Tang, Ke; Xi, Yifan; Wang, Lin; Wang, Linjun; Lu, Yicheng

2018-03-01

High quality diamond film on Si substrate was synthesized by coating diamond nanoparticles prepared by polyglycerol grafting (ND-PG) dispersion as pre-treatment method. Transmission electron microscope indicates that ND-PG is much more dispersible than untreated nanoparticles in organic solvents. The surface morphology was characterized by scanning electron microscope while atomic force microscope was conducted to measure the surface roughness. Microstructure properties were carried out by Raman spectroscopy and X-ray diffraction. The results revealed an increase in nucleation density, an acceleration of growth rate and an improvement of film crystalline quality by using spin-coating ND-PG pretreatment.

Development of 1500mm Wide Wrought Magnesium Alloys by Twin Roll Casting Technique in Turkey

NASA Astrophysics Data System (ADS)

Duygulu, Ozgur; Ucuncuoglu, Selda; Oktay, Gizem; Temur, Deniz Sultan; Yucel, Onuralp; Kaya, Ali Arslan

Magnesium alloy AZ31, AZ61, AZ91, AM50 and AM60 sheets were produced by twin roll casting first time in Turkey. Sheets of 4.5-6.5mm thick and 1500mm width were successfully achieved. Microstructure of the sheet was analyzed by optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). Semi-quantitative analyses were performed by SEM-EDS. In addition, X-ray studies were performed for both characterization and texture purposes. Mechanical properties were investigated by tensile tests and also hardness measurements. Homogenization and annealing heat treatments were performed on the produced sheets.

Magnetostructural Properties of Colossal Magnetoresistance Manganites Under External Magnetic Fields and Uniaxial Pressure

NASA Astrophysics Data System (ADS)

Kaplan, Michael; Zimmerman, George

2002-03-01

In the colossal magnetoresistance manganites the transport and magnetostructural properties are tightly connected [1,2]. Many magnetic field induced structural phase transitions and anomalous magnetoacoustical properties continue to be discovered in various manganite derivatives. Nevertheless the mechanism of structural transitions and microscopic theory of corresponding anomalous properties are still to be completely understood. Here we present a microscopic model of magnetic field and uniaxial pressure induced structural phase transitions in lightly doped manganites. The model is based on the cooperative Jahn-Teller effect which takes into account the Mn3+-ground doublet and excited triplet electronic states. Numerous calculations for different orientation magnetic field suggest the explanations of the origin of the structural transitions and of the measured magnetostriction data. The calculations for the two-sublattice antiferrodistortive crystals under uniaxial pressure support the idea of metaelasticity - a property typical for Jahn-Teller antiferroelastics. 1.Y. Tokura, ed. Colossal Magnetoresistance Oxides. Gordon & Breach, London, 2000. 2.M. Kaplan, G. Zimmerman, eds. Vibronic Interactions: Jahn-Teller Effect in Crystal and Molecules. NATO Science Series, Dordrecht/Boston/London, 2001

Electron microscopic changes of detrusor in benign enlargement of prostate and its clinical correlation.

PubMed

Yadav, Sher Singh; Bhattar, Rohit; Sharma, Lokesh; Banga, Gautam; Sadasukhi, Trilok Chandra

2017-01-01

To study the ultra structural changes in bladder musculature in cases of BPE and their clinical relevance. In this descriptive longitudinal, controlled, observational study patients were enrolled into three groups, group 1, group 2A and group 2B. Control group (group-1) consisted of age matched normal male patients, who underwent surveillance or diagnostic cystoscopy for microscopic hematuria or irritative symptoms. Case group (group-2) comprised of patients with BPE, undergoing TURP. Case group (group-2) was further classified into: Category 2A (patients not on catheter) and cat-egory 2B (patients on catheter). All relevant clinical parameters like IPSS, prostate size, Qmax, PVR were recorded. Cystoscopy and bladder biopsy were performed in all patients. Various ultrastructural parameters like myocytes, fascicular pattern, interstitial tissue, nerve hypertrophy and cell junction pattern were analyzed under electron microscope and they were clinically correlated using appropriate statistical tests. Control group had significant difference as compared to case group in terms of baseline parameters like IPSS, flow rate and prostate size, both preoperatively and postoperatively, except for PVR, which was seen only preoperatively. There was statistically significant difference in ultrastructural patterns between case and control group in all five electron microscopic patterns. However, no significant difference was found between the subcategories of case groups. BPE is responsible for ultra structural changes in detrusor muscle and these changes remain persistent even after TURP. Nerve hypertrophy, which was not thoroughly discussed in previous studies, is also one of the salient feature of this study. Copyright® by the International Brazilian Journal of Urology.

Quantitatively characterizing the microstructural features of breast ductal carcinoma tissues in different progression stages by Mueller matrix microscope.

PubMed

Dong, Yang; Qi, Ji; He, Honghui; He, Chao; Liu, Shaoxiong; Wu, Jian; Elson, Daniel S; Ma, Hui

2017-08-01

Polarization imaging has been recognized as a potentially powerful technique for probing the microstructural information and optical properties of complex biological specimens. Recently, we have reported a Mueller matrix microscope by adding the polarization state generator and analyzer (PSG and PSA) to a commercial transmission-light microscope, and applied it to differentiate human liver and cervical cancerous tissues with fibrosis. In this paper, we apply the Mueller matrix microscope for quantitative detection of human breast ductal carcinoma samples at different stages. The Mueller matrix polar decomposition and transformation parameters of the breast ductal tissues in different regions and at different stages are calculated and analyzed. For more quantitative comparisons, several widely-used image texture feature parameters are also calculated to characterize the difference in the polarimetric images. The experimental results indicate that the Mueller matrix microscope and the polarization parameters can facilitate the quantitative detection of breast ductal carcinoma tissues at different stages.

Effects of long memory in the order submission process on the properties of recurrence intervals of large price fluctuations

NASA Astrophysics Data System (ADS)

Meng, Hao; Ren, Fei; Gu, Gao-Feng; Xiong, Xiong; Zhang, Yong-Jie; Zhou, Wei-Xing; Zhang, Wei

2012-05-01

Understanding the statistical properties of recurrence intervals (also termed return intervals in econophysics literature) of extreme events is crucial to risk assessment and management of complex systems. The probability distributions and correlations of recurrence intervals for many systems have been extensively investigated. However, the impacts of microscopic rules of a complex system on the macroscopic properties of its recurrence intervals are less studied. In this letter, we adopt an order-driven stock model to address this issue for stock returns. We find that the distributions of the scaled recurrence intervals of simulated returns have a power-law scaling with stretched exponential cutoff and the intervals possess multifractal nature, which are consistent with empirical results. We further investigate the effects of long memory in the directions (or signs) and relative prices of the order flow on the characteristic quantities of these properties. It is found that the long memory in the order directions (Hurst index Hs) has a negligible effect on the interval distributions and the multifractal nature. In contrast, the power-law exponent of the interval distribution increases linearly with respect to the Hurst index Hx of the relative prices, and the singularity width of the multifractal nature fluctuates around a constant value when Hx<0.7 and then increases with Hx. No evident effects of Hs and Hx are found on the long memory of the recurrence intervals. Our results indicate that the nontrivial properties of the recurrence intervals of returns are mainly caused by traders' behaviors of persistently placing new orders around the best bid and ask prices.

Expert and novice categorization of introductory physics problems

NASA Astrophysics Data System (ADS)

Wolf, Steven Frederick

Since it was first published 30 years ago, Chi et al.'s seminal paper on expert and novice categorization of introductory problems led to a plethora of follow-up studies within and outside of the area of physics [Chi et al. Cognitive Science 5, 121 -- 152 (1981)]. These studies frequently encompass "card-sorting" exercises whereby the participants group problems. The study firmly established the paradigm that novices categorize physics problems by "surface features" (e.g. "incline," "pendulum," "projectile motion,"... ), while experts use "deep structure" (e.g. "energy conservation," "Newton 2,"... ). While this technique certainly allows insights into problem solving approaches, simple descriptive statistics more often than not fail to find significant differences between experts and novices. In most experiments, the clean-cut outcome of the original study cannot be reproduced. Given the widespread implications of the original study, the frequent failure to reproduce its findings warrants a closer look. We developed a less subjective statistical analysis method for the card sorting outcome and studied how the "successful" outcome of the experiment depends on the choice of the original card set. Thus, in a first step, we are moving beyond descriptive statistics, and develop a novel microscopic approach that takes into account the individual identity of the cards and uses graph theory and models to visualize, analyze, and interpret problem categorization experiments. These graphs are compared macroscopically, using standard graph theoretic statistics, and microscopically, using a distance metric that we have developed. This macroscopic sorting behavior is described using our Cognitive Categorization Model. The microscopic comparison allows us to visualize our sorters using Principal Components Analysis and compare the expert sorters to the novice sorters as a group. In the second step, we ask the question: Which properties of problems are most important in problem sets that discriminate experts from novices in a measurable way? We are describing a method to characterize problems along several dimensions, and then study the effectiveness of differently composed problem sets in differentiating experts from novices, using our analysis method. Both components of our study are based on an extensive experiment using a large problem set, which known physics experts and novices categorized according to the original experimental protocol. Both the size of the card set and the size of the sorter pool were larger than in comparable experiments. Based on our analysis method, we find that most of the variation in sorting outcome is not due to the sorter being an expert versus a novice, but rather due to an independent characteristic that we named "stacker" versus "spreader." The fact that the expert-novice distinction only accounts for a smaller amount of the variation may partly explain the frequent null-results when conducting these experiments. In order to study how the outcome depends on the original problem set, our problem set needed to be large so that we could determine how well experts and novices could be discriminated by considering both small subsets using a Monte Carlo approach and larger subsets using Simulated Annealing. This computationally intense study relied on our objective analysis method, as the large combinatorics did not allow for manual analysis of the outcomes from the subsets. We found that the number of questions required to accurately classify experts and novices could be surprisingly small so long as the problem set was carefully crafted to be composed of problems with particular pedagogical and contextual features. In order to discriminate experts from novices in a categorization task, it is important that the problem sets carefully consider three problem properties: The chapters that problems are in (the problems need to be from a wide spectrum of chapters to allow for the original "deep structure" categorization), the processes required to solve the problems (the problems must required different solving strategies), and the difficulty of the problems (the problems must be "easy"). In other words, for the experiment to be "successful," the card set needs to be carefully "rigged" across three property dimensions.

Laboratory comparison of the mechanical properties of TRUShape with several nickel-titanium rotary instruments.

PubMed

Elnaghy, A M; Elsaka, S E

2017-08-01

To assess and compare the mechanical properties of TRUShape (TRS) with several nickel-titanium rotary instruments. Cyclic fatigue, torsional resistance, flexibility and surface microhardness of TRS (size 25, 0.06v taper), ProTaper Next X2 (PTN X2, size 25, 0.06 taper), ProTaper Gold (PTG F2; size 25, 0.08 taper) and ProTaper Universal (PTU F2; size 25, 0.08 taper) instruments were evaluated. The topographical structures of the fracture surfaces of instruments were assessed using a scanning electron microscope. The cyclic fatigue resistance, torsional resistance and microhardness data were analysed using one-way analysis of variance (anova) and Tukey's post hoc tests. The fragment length and bending resistance data were analysed statistically with the Kruskal-Wallis H-test and Mann-Whitney U-tests. The statistical significance level was set at P < 0.05. PTN and PTG instruments revealed significantly higher resistance to cyclic fatigue than TRS and PTU instruments (P < 0.001). PTN instruments revealed significantly higher torsional resistance compared with the other instruments (P < 0.001). PTG instrument had significantly higher flexibility than the other tested brands (P < 0.05). However, for microhardness, the PTU had significantly higher surface microhardness values compared with other tested brands (P < 0.05). TRS instruments had lower resistance to cyclic fatigue and lower flexibility compared with PTG and PTN instruments. TRS, PTG and PTU instruments had lower resistance to torsional stress than PTN instruments. TRS and PTG instruments had comparable surface microhardness. © 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Development of Functional Surfaces on High-Density Polyethylene (HDPE) via Gas-Assisted Etching (GAE) Using Focused Ion Beams.

PubMed

Sezen, Meltem; Bakan, Feray

2015-12-01

Irradiation damage, caused by the use of beams in electron and ion microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on electron/ion beam irradiation. Nevertheless, it is possible to turn degradation-dependent physical/chemical changes from negative to positive use when materials are intentionally exposed to beams. Especially, controllable surface modification allows tuning of surface properties for targeted purposes and thus provides the use of ultimate materials and their systems at the micro/nanoscale for creating functional surfaces. In this work, XeF2 and I2 gases were used in the focused ion beam scanning electron microscope instrument in combination with gallium ion etching of high-density polyethylene surfaces with different beam currents and accordingly different gas exposure times resulting at the same ion dose to optimize and develop new polymer surface properties and to create functional polymer surfaces. Alterations in the surface morphologies and surface chemistry due to gas-assisted etching-based nanostructuring with various processing parameters were tracked using high-resolution SEM imaging, complementary energy-dispersive spectroscopic analyses, and atomic force microscopic investigations.

Interference Confocal Microscope Integrated with Spatial Phase Shifter.

PubMed

Wang, Weibo; Gu, Kang; You, Xiaoyu; Tan, Jiubin; Liu, Jian

2016-08-24

We present an interference confocal microscope (ICM) with a new single-body four-step simultaneous phase-shifter device designed to obtain high immunity to vibration. The proposed ICM combines the respective advantages of simultaneous phase shifting interferometry and bipolar differential confocal microscopy to obtain high axis resolution, large dynamic range, and reduce the sensitivity to vibration and reflectance disturbance seamlessly. A compact single body spatial phase shifter is added to capture four phase-shifted interference signals simultaneously without time delay and construct a stable and space-saving simplified interference confocal microscope system. The test result can be obtained by combining the interference phase response and the bipolar property of differential confocal microscopy without phase unwrapping. Experiments prove that the proposed microscope is capable of providing stable measurements with 1 nm of axial depth resolution for either low- or high-numerical aperture objective lenses.

Properties study of cotton stalk fiber/gypsum composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Guozhong; Yu Yanzhen; Zhao Zhongjian

This manuscript addresses treating cotton stalk fiber surface with styrene acrylic emulsion, which improves the interfacial combined state of cotton stalk fiber/gypsum composite effectively and improves its mechanical properties notably. Mixes less slag, ordinary Portland cement, etc., to modify gypsum base. The electron microscope was utilized to analyze and research on the effect on composite properties of the abovementioned mixtures.

Microscopic fluorescence spectral analysis of basal cell carcinomas

NASA Astrophysics Data System (ADS)

He, Qingli; Lui, Harvey; Zloty, David; Cowan, Bryce; Warshawski, Larry; McLean, David I.; Zeng, Haishan

2007-05-01

Background and Objectives. Laser-induced autofluorescence (LIAF) is a promising tool for cancer diagnosis. This method is based on the differences in autofluorescence spectra between normal and cancerous tissues, but the underlined mechanisms are not well understood. The objective of this research is to study the microscopic origins and intrinsic fluorescence properties of basal cell carcinoma (BCC) for better understanding of the mechanism of in vivo fluorescence detection and margin delineation of BCCs on skin patients. A home-made micro- spectrophotometer (MSP) system was used to image the fluorophore distribution and to measure the fluorescence spectra of various microscopic structures and regions on frozen tissue sections. Materials and Methods. BCC tissue samples were obtained from 14 patients undergoing surgical resections. After surgical removal, each tissue sample was immediately embedded in OCT medium and snap-frozen in liquid nitrogen. The frozen tissue block was then cut into 16-μm thickness sections using a cryostat microtome and placed on microscopic glass slides. The sections for fluorescence study were kept unstained and unfixed, and then analyzed by the MSP system. The adjacent tissue sections were H&E stained for histopathological examination and also served to help identify various microstructures on the adjacent unstained sections. The MSP system has all the functions of a conventional microscope, plus the ability of performing spectral analysis on selected micro-areas of a microscopic sample. For tissue fluorescence analysis, 442nm He-Cd laser light is used to illuminate and excite the unstained tissue sections. A 473-nm long pass filter was inserted behind the microscope objective to block the transmitted laser light while passing longer wavelength fluorescence signal. The fluorescence image of the sample can be viewed through the eyepieces and also recorded by a CCD camera. An optical fiber is mounted onto the image plane of the photograph port of the microscope to collect light from a specific micro area of the sample. The collected light is transmitted via the fiber to a disperserve type CCD spectrometer for spectral analysis. Results. The measurement results showed significant spectral differences between normal and cancerous tissues. For normal tissue regions, the spectral results agreed with our previous findings on autofluorescence of normal skin sections. For the cancerous regions, the epidermis showed very weak fluorescence signal, while the stratum corneum exhibited fluorescence emissions peaking at about 510 nm. In the dermis, the basal cell island and a band of surrounding areas showed very weak fluorescence signal, while distal dermis above and below the basal cell island showed greater fluorescence signal but with different spectral shapes. The very weak autofluorescence from the basal cell island and its surrounding area may be attributed to their degenerative properties that limited the production of collagens. Conclusions. The obtained microscopic results very well explain the in vivo fluorescence properties of BCC lesions in that they have decreased fluorescence intensity compared to the surrounding normal skin. The intrinsic spectra of various microstructures and the microscopic fluorescence images (corresponding fluorophore distribution in tissue) obtained in this study will be used for further theoretical modeling of in vivo fluorescence spectroscopy and imaging of skin cancers.

Connecting macroscopic dynamics with microscopic properties in active microtubule network contraction

NASA Astrophysics Data System (ADS)

Foster, Peter J.; Yan, Wen; Fürthauer, Sebastian; Shelley, Michael J.; Needleman, Daniel J.

2017-12-01

The cellular cytoskeleton is an active material, driven out of equilibrium by molecular motor proteins. It is not understood how the collective behaviors of cytoskeletal networks emerge from the properties of the network’s constituent motor proteins and filaments. Here we present experimental results on networks of stabilized microtubules in Xenopus oocyte extracts, which undergo spontaneous bulk contraction driven by the motor protein dynein, and investigate the effects of varying the initial microtubule density and length distribution. We find that networks contract to a similar final density, irrespective of the length of microtubules or their initial density, but that the contraction timescale varies with the average microtubule length. To gain insight into why this microscopic property influences the macroscopic network contraction time, we developed simulations where microtubules and motors are explicitly represented. The simulations qualitatively recapitulate the variation of contraction timescale with microtubule length, and allowed stress contributions from different sources to be estimated and decoupled.

Local oxidation using scanning probe microscope for fabricating magnetic nanostructures.

PubMed

Takemura, Yasushi

2010-07-01

Local oxidation technique using atomic force microscope (AFM) was studied. The local oxidation of ferromagnetic metal thin films was successfully performed by AFM under both contact and dynamic force modes. Modification of magnetic and electrical properties of magnetic devices fabricated by the AFM oxidation was achieved. Capped oxide layers deposited on the ferromagnetic metal films are advantageous for stable oxidation due to hydrophilic surface of oxide. The oxide layer is also expected to prevent magnetic devices from degradation by oxidation of ferromagnetic metal. As for modification of magnetic property, the isolated region of CoFe layer formed by nanowires of CoFe-oxide exhibited peculiar characteristic attributed to the isolated magnetization property and pinning of domain wall during magnetization reversal. Temperature dependence of current-voltage characteristic of the planar-type tunnel junction consisting of NiFe/NiFe-oxide/NiFe indicated that the observed current was dominated by intrinsic tunneling current at the oxide barrier.

Structural and magnetic properties of chromium doped zinc ferrite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sebastian, Rintu Mary; Thankachan, Smitha; Xavier, Sheena

2014-01-28

Zinc chromium ferrites with chemical formula ZnCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared by Sol - Gel technique. The structural as well as magnetic properties of the synthesized samples have been studied and reported here. The structural characterizations of the samples were analyzed by using X – Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The single phase spinel cubic structure of all the prepared samples was tested by XRD and FTIR. The particle size was observed to decrease from 18.636 nm to 6.125more » nm by chromium doping and induced a tensile strain in all the zinc chromium mixed ferrites. The magnetic properties of few samples (x = 0.0, 0.4, 1.0) were investigated using Vibrating Sample Magnetometer (VSM)« less

Morphological and mechanical properties of styrene butadiene rubber/nano copper nanocomposites

NASA Astrophysics Data System (ADS)

Harandi, Maryam Hadizadeh; Alimoradi, Fakhrodin; Rowshan, Gholamhussein; Faghihi, Morteza; Keivani, Maryam; Abadyan, Mohamadreza

In this research, rubber based nanocomposites with presence of nanoparticle has been studied. Styrene butadiene rubber (SBR)/nanocopper (NC) composites were prepared using two-roll mill method. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images showed proper dispersion of NC in the SBR matrix without substantial agglomeration of nanoparticles. To evaluate the curing properties of nanocomposite samples, swelling and cure rheometric tests were conducted. Moreover, the rheological studies were carried out over a range of shear rates. The effect of NC particles was examined on the thermal behavior of the SBR using thermal gravimetric analysis (TGA). Furthermore, tensile tests were employed to investigate the capability of nanoparticles to enhance mechanical behavior of the compounds. The results showed enhancement in tensile properties with incorporation of NC to SBR matrix. Moreover, addition of NC increased shear viscosity and curing time of SBR composites.

Mechanical properties of the rust layer induced by impressed current method in reinforced mortar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Care, S.; Nguyen, Q.T.; L'Hostis, V.

This paper describes the mechanical effects of rust layer formed in reinforced mortar through accelerated tests of corrosion. The morphological and physico-chemical properties (composition, structures) of the corrosion system were characterized at different stages by using optical microscope and scanning electron microscope coupled with energy dispersive spectroscopy. The corrosion pattern was mainly characterized by a rust layer confined at the interface between the steel and the mortar. Expansion coefficient of rust products was determined from the rust thickness and the Faraday's law. Furthermore, in order to understand the mechanical effects of corrosion on the damage of mortar, displacement field measurementsmore » were obtained by using digital image correlation. An analytical model (hollow cylinder subjected to inner and outer pressures) was used with a set of experimental data to deduce the time of cracking and the order of magnitude of the mechanical properties of the rust layer.« less

Adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by selective laser melting technique.

PubMed

Ye, Ye; Jiao, Ting; Zhu, Jiarui; Sun, Jian

2018-01-24

The purpose of the study was to evaluate the adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by the selective laser melting (SLM) technique. Twenty pairs of edentulous casts were randomly and evenly divided into two groups, and manufacturing of the Co-Cr alloy maxillary complete denture base was conducted either by the SLM technique or by the conventional method. The base-cast sets were transversally sectioned into three sections at the distal canines, mesial of the first molars and the posterior palatal zone. The gap between the metal base and cast was measured in these three sections with a stereoscopic microscope, and the data were analysed using t tests. A total of five specimens of 5 mm diameter were fabricated with the Co-Cr alloy by SLM and the traditional casting technology. A scanning electron microscope (SEM) was used to evaluate the differences in microstructure between these specimens. There was no statistical difference between the three sections in all four groups (P > 0.05). At the region of the canines, the clearance value for the SLM Co-Cr alloy group was larger than that of the conventional method group (P < 0.05). At the mesial of the first molar region and the posterior palatal zone, there was no statistical difference between the gaps observed in the two groups (P > 0.05). The SLM Co-Cr alloy has a denser microstructure behaviour and less casting defect than the cast Co-Cr alloy. The SLM technique showed initial feasibility for the manufacture of dental bases of complete dentures, but large sample studies are needed to prove its reliability in clinical applications. The mechanical properties and microstructure of the denture frameworks prepared by selective laser melting indicate that these dentures are appropriate for clinical use.

Novel Starch-PVA Polymer for Microparticle Preparation and Optimization Using Factorial Design Study

PubMed Central

Chattopadhyay, Helen; De, Amit Kumar; Datta, Sriparna

2015-01-01

The aim of our present work was to optimize the ratio of a very novel polymer, starch-polyvinyl alcohol (PVA), for controlled delivery of Ornidazole. Polymer-coated drug microparticles were prepared by emulsion method. Microscopic study, scanning electron microscopic study, and atomic force microscopic study revealed that the microparticles were within 10 micrometers of size with smooth spherical shape. The Fourier transform infrared spectroscopy showed absence of drug polymer interaction. A statistical 32 full factorial design was used to study the effect of different concentration of starch and PVA on the drug release profile. The three-dimensional plots gave us an idea about the contribution of each factor on the release kinetics. Hence this novel polymer of starch and polyvinyl alcohol can be utilized for control release of the drug from a targeted delivery device. PMID:27347511

Nonlinear field equations for aligning self-propelled rods.

PubMed

Peshkov, Anton; Aranson, Igor S; Bertin, Eric; Chaté, Hugues; Ginelli, Francesco

2012-12-28

We derive a set of minimal and well-behaved nonlinear field equations describing the collective properties of self-propelled rods from a simple microscopic starting point, the Vicsek model with nematic alignment. Analysis of their linear and nonlinear dynamics shows good agreement with the original microscopic model. In particular, we derive an explicit expression for density-segregated, banded solutions, allowing us to develop a more complete analytic picture of the problem at the nonlinear level.

Probing Quark-Gluon-Plasma properties with a Bayesian model-to-data comparison

NASA Astrophysics Data System (ADS)

Cai, Tianji; Bernhard, Jonah; Ke, Weiyao; Bass, Steffen; Duke QCD Group Team

2016-09-01

Experiments at RHIC and LHC study a special state of matter called the Quark Gluon Plasma (QGP), where quarks and gluons roam freely, by colliding relativistic heavy-ions. Given the transitory nature of the QGP, its properties can only be explored by comparing computational models of its formation and evolution to experimental data. The models fall, roughly speaking, under two categories-those solely using relativistic viscous hydrodynamics (pure hydro model) and those that in addition couple to a microscopic Boltzmann transport for the later evolution of the hadronic decay products (hybrid model). Each of these models has multiple parameters that encode the physical properties we want to probe and that need to be calibrated to experimental data, a task which is computationally expensive, but necessary for the knowledge extraction and determination of the models' quality. Our group has developed an analysis technique based on Bayesian Statistics to perform the model calibration and to extract probability distributions for each model parameter. Following the previous work that applies the technique to the hybrid model, we now perform a similar analysis on a pure-hydro model and display the posterior distributions for the same set of model parameters. We also develop a set of criteria to assess the quality of the two models with respect to their ability to describe current experimental data. Funded by Duke University Goldman Sachs Research Fellowship.

Effect of solution and post-mortem time on mechanical and histological properties of liver during cold preservation.

PubMed

Ayyildiz, Mehmet; Aktas, Ranan Gulhan; Basdogan, Cagatay

2014-01-01

In liver transplantation, the donor and recipient are in different locations most of the time, and longer preservation periods are inevitable. Hence, the choice of the preservation solution and the duration of the preservation period are critical for the success of the transplant surgery. In this study, we examine the mechanical and histological properties of the bovine liver tissue stored in Lactated Ringer's (control), HTK and UW solutions as a function of preservation period. The mechanical experiments are conducted with a shear rheometer on cylindrical tissue samples extracted from 3 bovine livers and the change in viscoelastic material properties of the bovine liver is characterized using the fractional derivative Kelvin-Voigt Model. Also, the histological examinations are performed on the same liver samples under a light microscope. The results show that the preservation solution and period have a significant effect on the mechanical and histological properties of the liver tissue. The storage and loss shear moduli, the number of the apoptotic cells, the collagen accumulation, and the sinusoidal dilatation increase, and the glycogen deposition decreases as the preservation period is longer. Based on the statistical analyses, we observe that the liver tissue is preserved well in all three solutions for up to 11 h. After then, UW solution provides a better preservation up to 29 h. However, for preservation periods longer than 29 h, HTK is a more effective preservation solution based on the least amount of change in mechanical properties. On the other hand, the highest correlation between the mechanical and histological properties is observed for the liver samples preserved in UW solution.

Bio-inspired enhancement of friction and adhesion at the polydimethylsiloxane-intestine interface and biocompatibility characterization.

PubMed

Zhang, Hongyu; Wang, Yi; Vasilescu, Steven; Gu, Zhibin; Sun, Tao

2017-05-01

An active navigation of self-propelled miniaturized robot along the intestinal tract without injuring the soft tissue remains a challenge as yet. Particularly in this case an effective control of the interfacial friction and adhesion between the material used and the soft tissue is crucial. In the present study, we investigated the frictional and adhesive properties between polydimethylsiloxane (PDMS, microscopically patterned with micro-pillar arrays and non-patterned with a flat surface) and rabbit small intestinal tract using a universal material tester. The friction coefficient-time plot and adhesive force-time plot were recorded during the friction test (sliding speed: 0.25mm/s; normal loading: 0.4N) and adhesion test (preloading: 0.5N; hoisting speed: 2.5×10 -3 mm/s). In addition, biocompatibility of the PDMS samples was characterized in terms of cell morphology (scanning electron microscope) and cell cytotoxicity (alamarBlue assay) using human vascular endothelial cells (HUVECs). The results demonstrated that the interfacial friction (0.27 vs 0.19) and adhesion (34.9mN vs 26.7mN) were greatly increased using microscopically patterned PDMS, in comparison with non-patterned PDMS. HUVECs adhered to and proliferated on non-patterned/microscopically patterned PDMS very well, with a relative cell viability of about 90% following seeding at 1d, 3d, and 5d. The favorable enhancement of the frictional and adhesive properties, along with the excellent biocompatibility of the microscopically patterned PDMS, makes it a propitious choice for clinical application of self-propelled miniaturized robots. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of total carbon on microscopic soil properties and implications for crop production

USDA-ARS?s Scientific Manuscript database

Soil structure is a dynamic property affected by physical, chemical, and microbiological processes. Addition of organic matter to soils and the use of different management practices have been reported to impact soil structure and crop production. Moderation in soil temperature and increases in mic...

Exploring Solid-State Structure and Physical Properties: A Molecular and Crystal Model Exercise

ERIC Educational Resources Information Center

Bindel, Thomas H.

2008-01-01

A crystal model laboratory exercise is presented that allows students to examine relations among the microscopic-macroscopic-symbolic levels, using crystalline mineral samples and corresponding crystal models. Students explore the relationship between solid-state structure and crystal form. Other structure-property relationships are explored. The…

Mechanical properties of bovine cortical bone based on the automated ball indentation technique and graphics processing method.

PubMed

Zhang, Airong; Zhang, Song; Bian, Cuirong

2018-02-01

Cortical bone provides the main form of support in humans and other vertebrates against various forces. Thus, capturing its mechanical properties is important. In this study, the mechanical properties of cortical bone were investigated by using automated ball indentation and graphics processing at both the macroscopic and microstructural levels under dry conditions. First, all polished samples were photographed under a metallographic microscope, and the area ratio of the circumferential lamellae and osteons was calculated through the graphics processing method. Second, fully-computer-controlled automated ball indentation (ABI) tests were performed to explore the micro-mechanical properties of the cortical bone at room temperature and a constant indenter speed. The indentation defects were examined with a scanning electron microscope. Finally, the macroscopic mechanical properties of the cortical bone were estimated with the graphics processing method and mixture rule. Combining ABI and graphics processing proved to be an effective tool to obtaining the mechanical properties of the cortical bone, and the indenter size had a significant effect on the measurement. The methods presented in this paper provide an innovative approach to acquiring the macroscopic mechanical properties of cortical bone in a nondestructive manner. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reservoir zonation based on statistical analyses: A case study of the Nubian sandstone, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

El Sharawy, Mohamed S.; Gaafar, Gamal R.

2016-12-01

Both reservoir engineers and petrophysicists have been concerned about dividing a reservoir into zones for engineering and petrophysics purposes. Through decades, several techniques and approaches were introduced. Out of them, statistical reservoir zonation, stratigraphic modified Lorenz (SML) plot and the principal component and clustering analyses techniques were chosen to apply on the Nubian sandstone reservoir of Palaeozoic - Lower Cretaceous age, Gulf of Suez, Egypt, by using five adjacent wells. The studied reservoir consists mainly of sandstone with some intercalation of shale layers with varying thickness from one well to another. The permeability ranged from less than 1 md to more than 1000 md. The statistical reservoir zonation technique, depending on core permeability, indicated that the cored interval of the studied reservoir can be divided into two zones. Using reservoir properties such as porosity, bulk density, acoustic impedance and interval transit time indicated also two zones with an obvious variation in separation depth and zones continuity. The stratigraphic modified Lorenz (SML) plot indicated the presence of more than 9 flow units in the cored interval as well as a high degree of microscopic heterogeneity. On the other hand, principal component and cluster analyses, depending on well logging data (gamma ray, sonic, density and neutron), indicated that the whole reservoir can be divided at least into four electrofacies having a noticeable variation in reservoir quality, as correlated with the measured permeability. Furthermore, continuity or discontinuity of the reservoir zones can be determined using this analysis.

Statistical mechanics of neocortical interactions: A scaling paradigm applied to electroencephalography

NASA Astrophysics Data System (ADS)

Ingber, Lester

1991-09-01

A series of papers has developed a statistical mechanics of neocortical interactions (SMNI), deriving aggregate behavior of experimentally observed columns of neurons from statistical electrical-chemical properties of synaptic interactions. While not useful to yield insights at the single-neuron level, SMNI has demonstrated its capability in describing large-scale properties of short-term memory and electroencephalographic (EEG) systematics. The necessity of including nonlinear and stochastic structures in this development has been stressed. In this paper, a more stringent test is placed on SMNI: The algebraic and numerical algorithms previously developed in this and similar systems are brought to bear to fit large sets of EEG and evoked-potential data being collected to investigate genetic predispositions to alcoholism and to extract brain ``signatures'' of short-term memory. Using the numerical algorithm of very fast simulated reannealing, it is demonstrated that SMNI can indeed fit these data within experimentally observed ranges of its underlying neuronal-synaptic parameters, and the quantitative modeling results are used to examine physical neocortical mechanisms to discriminate high-risk and low-risk populations genetically predisposed to alcoholism. Since this study is a control to span relatively long time epochs, similar to earlier attempts to establish such correlations, this discrimination is inconclusive because of other neuronal activity which can mask such effects. However, the SMNI model is shown to be consistent with EEG data during selective attention tasks and with neocortical mechanisms describing short-term memory previously published using this approach. This paper explicitly identifies similar nonlinear stochastic mechanisms of interaction at the microscopic-neuronal, mesoscopic-columnar, and macroscopic-regional scales of neocortical interactions. These results give strong quantitative support for an accurate intuitive picture, portraying neocortical interactions as having common algebraic or physics mechanisms that scale across quite disparate spatial scales and functional or behavioral phenomena, i.e., describing interactions among neurons, columns of neurons, and regional masses of neurons.

Are dragon-king neuronal avalanches dungeons for self-organized brain activity?

NASA Astrophysics Data System (ADS)

de Arcangelis, L.

2012-05-01

Recent experiments have detected a novel form of spontaneous neuronal activity both in vitro and in vivo: neuronal avalanches. The statistical properties of this activity are typical of critical phenomena, with power laws characterizing the distributions of avalanche size and duration. A critical behaviour for the spontaneous brain activity has important consequences on stimulated activity and learning. Very interestingly, these statistical properties can be altered in significant ways in epilepsy and by pharmacological manipulations. In particular, there can be an increase in the number of large events anticipated by the power law, referred to herein as dragon-king avalanches. This behaviour, as verified by numerical models, can originate from a number of different mechanisms. For instance, it is observed experimentally that the emergence of a critical behaviour depends on the subtle balance between excitatory and inhibitory mechanisms acting in the system. Perturbing this balance, by increasing either synaptic excitation or the incidence of depolarized neuronal up-states causes frequent dragon-king avalanches. Conversely, an unbalanced GABAergic inhibition or long periods of low activity in the network give rise to sub-critical behaviour. Moreover, the existence of power laws, common to other stochastic processes, like earthquakes or solar flares, suggests that correlations are relevant in these phenomena. The dragon-king avalanches may then also be the expression of pathological correlations leading to frequent avalanches encompassing all neurons. We will review the statistics of neuronal avalanches in experimental systems. We then present numerical simulations of a neuronal network model introducing within the self-organized criticality framework ingredients from the physiology of real neurons, as the refractory period, synaptic plasticity and inhibitory synapses. The avalanche critical behaviour and the role of dragon-king avalanches will be discussed in relation to different drives, neuronal states and microscopic mechanisms of charge storage and release in neuronal networks.

Heat capacity of the neutron star inner crust within an extended nuclear statistical equilibrium model

NASA Astrophysics Data System (ADS)

Burrello, S.; Gulminelli, F.; Aymard, F.; Colonna, M.; Raduta, Ad. R.

2015-11-01

Background: Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Present theoretical calculations employ the quasiparticle mean-field Hartree-Fock-Bogoliubov theory with temperature-dependent occupation numbers for the quasiparticle states. Purpose: Finite temperature stellar matter is characterized by a whole distribution of different nuclear species. We want to assess the importance of this distribution on the calculation of heat capacity in the inner crust. Method: Following a recent work, the Wigner-Seitz cell is mapped into a model with cluster degrees of freedom. The finite temperature distribution is then given by a statistical collection of Wigner-Seitz cells. We additionally introduce pairing correlations in the local density BCS approximation both in the homogeneous unbound neutron component, and in the interface region between clusters and neutrons. Results: The heat capacity is calculated in the different baryonic density conditions corresponding to the inner crust, and in a temperature range varying from 100 KeV to 2 MeV. We show that accounting for the cluster distribution has a small effect at intermediate densities, but it considerably affects the heat capacity both close to the outer crust and close to the core. We additionally show that it is very important to consider the temperature evolution of the proton fraction for a quantitatively reliable estimation of the heat capacity. Conclusions: We present the first modelization of stellar matter containing at the same time a statistical distribution of clusters at finite temperature, and pairing correlations in the unbound neutron component. The effect of the nuclear distribution on the superfluid properties can be easily added in future calculations of the neutron star cooling curves. A strong influence of resonance population on the heat capacity at high temperature is observed, which deserves to be further studied within more microscopic calculations.

Maximizing information exchange between complex networks

NASA Astrophysics Data System (ADS)

West, Bruce J.; Geneston, Elvis L.; Grigolini, Paolo

2008-10-01

Science is not merely the smooth progressive interaction of hypothesis, experiment and theory, although it sometimes has that form. More realistically the scientific study of any given complex phenomenon generates a number of explanations, from a variety of perspectives, that eventually requires synthesis to achieve a deep level of insight and understanding. One such synthesis has created the field of out-of-equilibrium statistical physics as applied to the understanding of complex dynamic networks. Over the past forty years the concept of complexity has undergone a metamorphosis. Complexity was originally seen as a consequence of memory in individual particle trajectories, in full agreement with a Hamiltonian picture of microscopic dynamics and, in principle, macroscopic dynamics could be derived from the microscopic Hamiltonian picture. The main difficulty in deriving macroscopic dynamics from microscopic dynamics is the need to take into account the actions of a very large number of components. The existence of events such as abrupt jumps, considered by the conventional continuous time random walk approach to describing complexity was never perceived as conflicting with the Hamiltonian view. Herein we review many of the reasons why this traditional Hamiltonian view of complexity is unsatisfactory. We show that as a result of technological advances, which make the observation of single elementary events possible, the definition of complexity has shifted from the conventional memory concept towards the action of non-Poisson renewal events. We show that the observation of crucial processes, such as the intermittent fluorescence of blinking quantum dots as well as the brain’s response to music, as monitored by a set of electrodes attached to the scalp, has forced investigators to go beyond the traditional concept of complexity and to establish closer contact with the nascent field of complex networks. Complex networks form one of the most challenging areas of modern research overarching all of the traditional scientific disciplines. The transportation networks of planes, highways and railroads; the economic networks of global finance and stock markets; the social networks of terrorism, governments, businesses and churches; the physical networks of telephones, the Internet, earthquakes and global warming and the biological networks of gene regulation, the human body, clusters of neurons and food webs, share a number of apparently universal properties as the networks become increasingly complex. Ubiquitous aspects of such complex networks are the appearance of non-stationary and non-ergodic statistical processes and inverse power-law statistical distributions. Herein we review the traditional dynamical and phase-space methods for modeling such networks as their complexity increases and focus on the limitations of these procedures in explaining complex networks. Of course we will not be able to review the entire nascent field of network science, so we limit ourselves to a review of how certain complexity barriers have been surmounted using newly applied theoretical concepts such as aging, renewal, non-ergodic statistics and the fractional calculus. One emphasis of this review is information transport between complex networks, which requires a fundamental change in perception that we express as a transition from the familiar stochastic resonance to the new concept of complexity matching.

Multiscale Modelling and Analysis of Collective Decision Making in Swarm Robotics

PubMed Central

Vigelius, Matthias; Meyer, Bernd; Pascoe, Geoffrey

2014-01-01

We present a unified approach to describing certain types of collective decision making in swarm robotics that bridges from a microscopic individual-based description to aggregate properties. Our approach encompasses robot swarm experiments, microscopic and probabilistic macroscopic-discrete simulations as well as an analytic mathematical model. Following up on previous work, we identify the symmetry parameter, a measure of the progress of the swarm towards a decision, as a fundamental integrated swarm property and formulate its time evolution as a continuous-time Markov process. Contrary to previous work, which justified this approach only empirically and a posteriori, we justify it from first principles and derive hard limits on the parameter regime in which it is applicable. PMID:25369026

[Morphofunctional properties of the peripheral blood and bone marrow cells of rats following a flight on board the Kosmos-936 biosatellite].

PubMed

Kozinets, G I; Korol'kov, V I; Britvan, I I; Bykova, I A; Spitsyna, N E

1983-01-01

Morphofunctional properties of peripheral blood cells of Cosmos-936 rats were examined, using morphological, interferometric and electron microscopic techniques. As follows from the morphological data, immediately after recovery the weightless rats showed symptoms of a stress reaction which disappeared by R+3. The centrifuged rats exhibited less expressed symptoms of this sort. The percentage of bone marrow cell distribution was shifted towards enhanced myelopoiesis and diminished erythropoiesis. By the end of the readaptation period the ratio of bone marrow cell composition returned to normal. Interferometric and electron microscopic examinations did not reveal any irreversible changes in the structure and function of cells that may be caused by zero-g.

A Cost-Effective Fluorescence Mini-Microscope with Adjustable Magnifications for Biomedical Applications

PubMed Central

Zhang, Yu Shrike; Ribas, João; Nadhman, Akhtar; Aleman, Julio; Selimović, Šeila; Lesher-Perez, Sasha Cai; Wang, Ting; Manoharan, Vijayan; Shin, Su-Ryon; Damilano, Alessia; Annabi, Nasim; Dokmeci, Mehmet Remzi; Takayama, Shuichi; Khademhosseini, Ali

2015-01-01

We have designed and fabricated a miniature microscope from off-the-shelf components and webcam, with built-in fluorescence capability for biomedical applications. The mini-microscope was able to detect both biochemical parameters such as cell/tissue viability (e.g. Live/Dead assay), and biophysical properties of the microenvironment such as oxygen levels in microfabricated tissues based on an oxygen-sensitive fluorescent dye. This mini-microscope has adjustable magnifications from 8-60X, achieves a resolution as high as <2 μm, and possesses a long working distance of 4.5 mm (at a magnification of 8X). The mini-microscope was able to chronologically monitor cell migration and analyze beating of microfluidic liver and cardiac bioreactors in real time, respectively. The mini-microscope system is cheap, and its modularity allows convenient integration with a wide variety of pre-existing platforms including but not limited to, cell culture plates, microfluidic devices, and organs-on-a-chip systems. Therefore, we envision its widespread applications in cell biology, tissue engineering, biosensing, microfluidics, and organs-on-chips, which can potentially replace conventional bench-top microscopy where long-term in situ and large-scale imaging/analysis is required. PMID:26282117

A cost-effective fluorescence mini-microscope for biomedical applications.

PubMed

Zhang, Yu Shrike; Ribas, João; Nadhman, Akhtar; Aleman, Julio; Selimović, Šeila; Lesher-Perez, Sasha Cai; Wang, Ting; Manoharan, Vijayan; Shin, Su-Ryon; Damilano, Alessia; Annabi, Nasim; Dokmeci, Mehmet Remzi; Takayama, Shuichi; Khademhosseini, Ali

2015-01-01

We have designed and fabricated a miniature microscope from off-the-shelf components and a webcam, with built-in fluorescence capability for biomedical applications. The mini-microscope was able to detect both biochemical parameters, such as cell/tissue viability (e.g. live/dead assay), and biophysical properties of the microenvironment such as oxygen levels in microfabricated tissues based on an oxygen-sensitive fluorescent dye. This mini-microscope has adjustable magnifications from 8-60×, achieves a resolution as high as <2 μm, and possesses a long working distance of 4.5 mm (at a magnification of 8×). The mini-microscope was able to chronologically monitor cell migration and analyze beating of microfluidic liver and cardiac bioreactors in real time, respectively. The mini-microscope system is cheap, and its modularity allows convenient integration with a wide variety of pre-existing platforms including, but not limited to, cell culture plates, microfluidic devices, and organs-on-a-chip systems. Therefore, we envision its widespread application in cell biology, tissue engineering, biosensing, microfluidics, and organs-on-chips, which can potentially replace conventional bench-top microscopy where long-term in situ and large-scale imaging/analysis is required.

Microscopic observation of magnetic bacteria in the magnetic field of a rotating permanent magnet.

PubMed

Smid, Pieter; Shcherbakov, Valeriy; Petersen, Nikolai

2015-09-01

Magnetotactic bacteria are ubiquitous and can be found in both freshwater and marine environments. Due to intracellular chains of magnetic single domain particles, they behave like swimming compass needles. In external magnetic fields like the Earth's magnetic field, a torque is acting on the chain. This will cause the bacterium to be rotated and aligned with the external field. The swimming direction of magnetotactic bacteria can be controlled with external magnetic fields, which makes it convenient to study them under a light microscope. Usually, a special set of coils arranged around a light microscope is used to control the swimming magnetotactic bacteria. Here, we present a simple mechanical system with a permanent magnet, which produces a rotating magnetic field of nearly constant amplitude in the focal plane of a light microscope. The device is placed beside the light microscope and easily adaptable to almost any microscope and thus convenient for field experiments. To describe the trajectories qualitatively, a theoretical model of the trajectories is presented. This device can be used to control the swimming direction of magnetotactic bacteria and also for studying their magnetic and hydrodynamic properties.

Microscopy imaging device with advanced imaging properties

DOEpatents

Ghosh, Kunal; Burns, Laurie; El Gamal, Abbas; Schnitzer, Mark J.; Cocker, Eric; Ho, Tatt Wei

2015-11-24

Systems, methods and devices are implemented for microscope imaging solutions. One embodiment of the present disclosure is directed toward an epifluorescence microscope. The microscope includes an image capture circuit including an array of optical sensor. An optical arrangement is configured to direct excitation light of less than about 1 mW to a target object in a field of view of that is at least 0.5 mm.sup.2 and to direct epi-fluorescence emission caused by the excitation light to the array of optical sensors. The optical arrangement and array of optical sensors are each sufficiently close to the target object to provide at least 2.5 .mu.m resolution for an image of the field of view.

Indentation-Enabled In Situ Mechanical Characterization of Micro/Nanopillars in Electron Microscopes

NASA Astrophysics Data System (ADS)

Guo, Qiang; Fu, Xidan; Guo, Xiaolei; Liu, Zhiying; Shi, Yan; Zhang, Di

2018-04-01

Indentation-enabled micro/nanomechanical characterization of small-scale specimens provides powerful new tools for probing materials properties that were once unattainable by conventional experimental methods. Recent advancement in instrumentation further allows mechanical testing to be carried out in situ in electron microscopes, with high spatial and temporal resolution. This review discusses the recent development of nanoindentation-enabled in situ mechanical testing in electron microscopes, with an emphasis on the study of micro/nanopillars. Focus is given to novel applications beyond simple compressive and tensile testing that have been developed in the past few years, and limitations and possible future research directions in this field are proposed and discussed.

Microscopy imaging device with advanced imaging properties

DOEpatents

Ghosh, Kunal; Burns, Laurie; El Gamal, Abbas; Schnitzer, Mark J.; Cocker, Eric; Ho, Tatt Wei

2016-10-25

Systems, methods and devices are implemented for microscope imaging solutions. One embodiment of the present disclosure is directed toward an epifluorescence microscope. The microscope includes an image capture circuit including an array of optical sensor. An optical arrangement is configured to direct excitation light of less than about 1 mW to a target object in a field of view of that is at least 0.5 mm.sup.2 and to direct epi-fluorescence emission caused by the excitation light to the array of optical sensors. The optical arrangement and array of optical sensors are each sufficiently close to the target object to provide at least 2.5 .mu.m resolution for an image of the field of view.

Microscopy imaging device with advanced imaging properties

DOEpatents

Ghosh, Kunal; Burns, Laurie; El Gamal, Abbas; Schnitzer, Mark J.; Cocker, Eric; Ho, Tatt Wei

2016-11-22

Systems, methods and devices are implemented for microscope imaging solutions. One embodiment of the present disclosure is directed toward an epifluorescence microscope. The microscope includes an image capture circuit including an array of optical sensor. An optical arrangement is configured to direct excitation light of less than about 1 mW to a target object in a field of view of that is at least 0.5 mm.sup.2 and to direct epi-fluorescence emission caused by the excitation light to the array of optical sensors. The optical arrangement and array of optical sensors are each sufficiently close to the target object to provide at least 2.5 .mu.m resolution for an image of the field of view.

Microscopy imaging device with advanced imaging properties

DOEpatents

Ghosh, Kunal; Burns, Laurie; El Gamal, Abbas; Schnitzer, Mark J.; Cocker, Eric; Ho, Tatt Wei

2017-04-25

Systems, methods and devices are implemented for microscope imaging solutions. One embodiment of the present disclosure is directed toward an epifluorescence microscope. The microscope includes an image capture circuit including an array of optical sensor. An optical arrangement is configured to direct excitation light of less than about 1 mW to a target object in a field of view of that is at least 0.5 mm.sup.2 and to direct epi-fluorescence emission caused by the excitation light to the array of optical sensors. The optical arrangement and array of optical sensors are each sufficiently close to the target object to provide at least 2.5 .mu.m resolution for an image of the field of view.

A Novel Method to Reconstruct the Force Curve by Higher Harmonics of the First Two Flexural Modes in Frequency Modulation Atomic Force Microscope (FM-AFM).

PubMed

Zhang, Suoxin; Qian, Jianqiang; Li, Yingzi; Zhang, Yingxu; Wang, Zhenyu

2018-06-04

Atomic force microscope (AFM) is an idealized tool to measure the physical and chemical properties of the sample surfaces by reconstructing the force curve, which is of great significance to materials science, biology, and medicine science. Frequency modulation atomic force microscope (FM-AFM) collects the frequency shift as feedback thus having high force sensitivity and it accomplishes a true noncontact mode, which means great potential in biological sample detection field. However, it is a challenge to establish the relationship between the cantilever properties observed in practice and the tip-sample interaction theoretically. Moreover, there is no existing method to reconstruct the force curve in FM-AFM combining the higher harmonics and the higher flexural modes. This paper proposes a novel method that a full force curve can be reconstructed by any order higher harmonics of the first two flexural modes under any vibration amplitude in FM-AFM. Moreover, in the small amplitude regime, short range forces are reconstructed more accurately by higher harmonics analysis compared with fundamental harmonics using the Sader-Jarvis formula.

Practical three color live cell imaging by widefield microscopy

PubMed Central

Xia, Jianrun; Kim, Song Hon H.; Macmillan, Susan

2006-01-01

Live cell fluorescence microscopy using fluorescent protein tags derived from jellyfish and coral species has been a successful tool to image proteins and dynamics in many species. Multi-colored aequorea fluorescent protein (AFP) derivatives allow investigators to observe multiple proteins simultaneously, but overlapping spectral properties sometimes require the use of sophisticated and expensive microscopes. Here, we show that the aequorea coerulescens fluorescent protein derivative, PS-CFP2 has excellent practical properties as a blue fluorophore that are distinct from green or red fluorescent proteins and can be imaged with standard filter sets on a widefield microscope. We also find that by widefield illumination in live cells, that PS-CFP2 is very photostable. When fused to proteins that form concentrated puncta in either the cytoplasm or nucleus, PSCFP2 fusions do not artifactually interact with other AFP fusion proteins, even at very high levels of over-expression. PSCFP2 is therefore a good blue fluorophore for distinct three color imaging along with eGFP and mRFP using a relatively simple and inexpensive microscope. PMID:16909160

An estimate of biofilm properties using an acoustic microscope.

PubMed

Good, Morris S; Wend, Christopher F; Bond, Leonard J; Mclean, Jeffrey S; Panetta, Paul D; Ahmed, Salahuddin; Crawford, Susan L; Daly, Don S

2006-09-01

Noninvasive measurements over a biofilm, a three-dimensional (3-D) community of microorganisms immobilized at a substratum, were made using an acoustic microscope operating at frequencies up to 70 MHz. The microscope scanned a 2.5-mm by 2.5-mm region of a living biofilm having a nominal thickness of 100 microm. Spatial variation of surface heterogeneity, thickness, interior structure, and biomass were estimated. Thickness was estimated as the product of the speed of sound of the medium and the interim between the highest signal peak and that of the substratum plane without biofilm. The thickest portions of biofilm were 145 microm; however, slender structures attributed as streamers extended above, with one obtaining a 274-microm height above the substratum. Three-dimensional iso-contours of amplitude were used to estimate the internal structure of the biofilm. Backscatter amplitude was examined at five zones of increasing height from the substratum to examine biomass distribution. Ultrasound-based estimates of thickness were corroborated with optical microscopy. The experimental acoustic and optical systems, methods used to estimate biofilm properties, and potential applications for the resulting data are discussed.

Microscopic Description of Spontaneous Emission in Stark Chirped Rapid Adiabatic Passages

NASA Astrophysics Data System (ADS)

Shi, Xuan; Yuan, Hao; Zhao, Hong-Quan

2018-01-01

A microscopic approach describing the effect of spontaneous emission in the stark-chirped rapid adiabatic passages (SCRAPs) for quantum computation is presented. Apart from the phenomenological model, this microscopic one can investigate the dependence of the population dynamics both on the temperature of the environment and the decay rate γ. With flux-biased Josephson qubits as a specifical example, we study the efficiency of the SCRAP for realizing the basic Pauli-X and iSWAP gates. Our results show clearly that the behavior of the population transfer described by the microscopic model is similar with the phenomenological one at zero temperature. In the limit of very high temperature, the population probabilities of the qubit states exhibit strong stability properties. High efficiency for the quantum gate manipulations in SCRAPs is available against the weak decay rate γ ≪ 1 at low temperature.

Advantages of using newly developed quartz contact lens with slit illumination from operating microscope.

PubMed

Kiyokawa, Masatoshi; Sakuma, Toshiro; Hatano, Noriko; Mizota, Atsushi; Tanaka, Minoru

2009-06-01

The purpose of this article is to report the characteristics and advantages of using a newly designed quartz contact lens with slit illumination from an operating microscope for intraocular surgery. The new contact lens is made of quartz. The lens is convex-concave and is used in combination with slit illumination from an operating microscope. The optical properties of quartz make this lens less reflective with greater transmittance. The combination of a quartz contact lens with slit illumination provided a brighter and wider field of view than conventional lenses. This system enabled us to perform bimanual vitrectomy and scleral buckling surgery without indirect ophthalmoscope. Small intraocular structures in the posterior pole or in the periphery were detected more easily. In conclusion, the newly designed quartz lens with slit beam illumination from an operating microscope provided a bright, clear and wide surgical field, and allowed intraocular surgery to be performed more easily.

An investigation of nitride precipitates in archaeological iron artefacts from Poland.

PubMed

Kedzierski, Z; Stepiński, J; Zielińska-Lipiec, A

2010-03-01

The paper describes the investigations of nitride precipitates in a spearhead and a sword found in the territory of Poland, in cremation graveyards of the Przeworsk Culture, dated to the Roman Period. Three different techniques of the examination of nitride precipitates were employed: optical microscope, scanning electron microscope (scanning electron microscope with energy dispersive X-ray spectrometer) and transmission electron microscope. Two types of precipitates have been observed, and their plate-like shape was demonstrated. The large precipitate has been confirmed to be gamma'-Fe(4)N, whereas the small one has been identified as alpha''-Fe(16)N(2). The origin of nitride precipitates in archaeological iron artefacts from Poland is probably a result of the manufacturing process or cremation as part of burial rites. An examination of available iron artefacts indicates that nitride precipitates (have only limited effect on mechanical properties) influence the hardness of metal only to a very limited degree.

Confocal Raman microscopy and multivariate statistical analysis for determination of different penetration abilities of caffeine and propylene glycol applied simultaneously in a mixture on porcine skin ex vivo.

PubMed

Mujica Ascencio, Saul; Choe, ChunSik; Meinke, Martina C; Müller, Rainer H; Maksimov, George V; Wigger-Alberti, Walter; Lademann, Juergen; Darvin, Maxim E

2016-07-01

Propylene glycol is one of the known substances added in cosmetic formulations as a penetration enhancer. Recently, nanocrystals have been employed also to increase the skin penetration of active components. Caffeine is a component with many applications and its penetration into the epidermis is controversially discussed in the literature. In the present study, the penetration ability of two components - caffeine nanocrystals and propylene glycol, applied topically on porcine ear skin in the form of a gel, was investigated ex vivo using two confocal Raman microscopes operated at different excitation wavelengths (785nm and 633nm). Several depth profiles were acquired in the fingerprint region and different spectral ranges, i.e., 526-600cm(-1) and 810-880cm(-1) were chosen for independent analysis of caffeine and propylene glycol penetration into the skin, respectively. Multivariate statistical methods such as principal component analysis (PCA) and linear discriminant analysis (LDA) combined with Student's t-test were employed to calculate the maximum penetration depths of each substance (caffeine and propylene glycol). The results show that propylene glycol penetrates significantly deeper than caffeine (20.7-22.0μm versus 12.3-13.0μm) without any penetration enhancement effect on caffeine. The results confirm that different substances, even if applied onto the skin as a mixture, can penetrate differently. The penetration depths of caffeine and propylene glycol obtained using two different confocal Raman microscopes are comparable showing that both types of microscopes are well suited for such investigations and that multivariate statistical PCA-LDA methods combined with Student's t-test are very useful for analyzing the penetration of different substances into the skin. Copyright © 2016 Elsevier B.V. All rights reserved.

Leg ischaemia before circulatory arrest alters brain leucocyte count and respiratory chain redox state.

PubMed

Yannopoulos, Fredrik S; Arvola, Oiva; Haapanen, Henri; Herajärvi, Johanna; Miinalainen, Ilkka; Jensen, Hanna; Kiviluoma, Kai; Juvonen, Tatu

2014-03-01

Remote ischaemic preconditioning and its neuroprotective abilities are currently under investigation and the method has shown significant effects in several small and large animal studies. In our previous studies, leucocyte filtration during cardiopulmonary bypass reduced cerebrocortical adherent leucocyte count and mitigated cerebral damage after hypothermic circulatory arrest (HCA) in piglets. This study aimed to obtain and assess direct visual data of leucocyte behaviour in cerebral vessels after hypothermic circulatory arrest following remote ischaemic preconditioning. Twelve native stock piglets were randomized into a remote ischaemic preconditioning group (n = 6) and a control group (n = 6). The intervention group underwent hind-leg ischaemia, whereas the control group received a sham-treatment before a 60-min period of hypothermic circulatory arrest. An intravital microscope was used to obtain measurements from the cerebrocortical vessel in vivo. It included three sets of filters: a violet filter to visualize microvascular perfusion and vessel diameter, a green filter for visualization of rhodamine-labelled leucocytes and an ultraviolet filter for reduced nicotinamide adenine dinucleotide (NADH) analysis. The final magnification on the microscope was 400. After the experiment, cerebral and cerebellar biopsies were collected and analysed with transmission electron microscope by a blinded analyst. In the transmission electron microscope analysis, the entire intervention group had normal, unaffected rough endoplasmic reticulum's in their cerebellar tissue, whereas the control group had a mean score of 1.06 (standard deviation 0.41) (P = 0.026). The measured amount of adherent leucocytes was lower in the remote ischaemic preconditioning group. The difference was statistically significant at 5, 15 and 45 min after circulatory arrest. Statistically significant differences were seen also in the recovery phase at 90 and 120 min after reperfusion. Nicotinamide adenine dinucleotide autofluorescence had statistically significant differences at 10 min after cooling and at 120 and 180 min after hypothermic circulatory arrest. Remote ischaemic preconditioning seems to provide better mitochondrial respiratory chain function as indicated by the higher NADH content. It simultaneously provides a reduction of adherent leucocytes in cerebral vessels after hypothermic circulatory arrest. Additionally, it might provide some degree of cellular organ preservation as implied by the electron microscopy results.

Consistent integration of experimental and ab initio data into molecular and coarse-grained models

NASA Astrophysics Data System (ADS)

Vlcek, Lukas

As computer simulations are increasingly used to complement or replace experiments, highly accurate descriptions of physical systems at different time and length scales are required to achieve realistic predictions. The questions of how to objectively measure model quality in relation to reference experimental or ab initio data, and how to transition seamlessly between different levels of resolution are therefore of prime interest. To address these issues, we use the concept of statistical distance to define a measure of similarity between statistical mechanical systems, i.e., a model and its target, and show that its minimization leads to general convergence of the systems' measurable properties. Through systematic coarse-graining, we arrive at appropriate expressions for optimization loss functions consistently incorporating microscopic ab initio data as well as macroscopic experimental data. The design of coarse-grained and multiscale models is then based on factoring the model system partition function into terms describing the system at different resolution levels. The optimization algorithm takes advantage of thermodynamic perturbation expressions for fast exploration of the model parameter space, enabling us to scan millions of parameter combinations per hour on a single CPU. The robustness and generality of the new model optimization framework and its efficient implementation are illustrated on selected examples including aqueous solutions, magnetic systems, and metal alloys.

HyphArea--automated analysis of spatiotemporal fungal patterns.

PubMed

Baum, Tobias; Navarro-Quezada, Aura; Knogge, Wolfgang; Douchkov, Dimitar; Schweizer, Patrick; Seiffert, Udo

2011-01-01

In phytopathology quantitative measurements are rarely used to assess crop plant disease symptoms. Instead, a qualitative valuation by eye is often the method of choice. In order to close the gap between subjective human inspection and objective quantitative results, the development of an automated analysis system that is capable of recognizing and characterizing the growth patterns of fungal hyphae in micrograph images was developed. This system should enable the efficient screening of different host-pathogen combinations (e.g., barley-Blumeria graminis, barley-Rhynchosporium secalis) using different microscopy technologies (e.g., bright field, fluorescence). An image segmentation algorithm was developed for gray-scale image data that achieved good results with several microscope imaging protocols. Furthermore, adaptability towards different host-pathogen systems was obtained by using a classification that is based on a genetic algorithm. The developed software system was named HyphArea, since the quantification of the area covered by a hyphal colony is the basic task and prerequisite for all further morphological and statistical analyses in this context. By means of a typical use case the utilization and basic properties of HyphArea could be demonstrated. It was possible to detect statistically significant differences between the growth of an R. secalis wild-type strain and a virulence mutant. Copyright © 2010 Elsevier GmbH. All rights reserved.

4D microscope-integrated OCT improves accuracy of ophthalmic surgical maneuvers

NASA Astrophysics Data System (ADS)

Carrasco-Zevallos, Oscar; Keller, Brenton; Viehland, Christian; Shen, Liangbo; Todorich, Bozho; Shieh, Christine; Kuo, Anthony; Toth, Cynthia; Izatt, Joseph A.

2016-03-01

Ophthalmic surgeons manipulate micron-scale tissues using stereopsis through an operating microscope and instrument shadowing for depth perception. While ophthalmic microsurgery has benefitted from rapid advances in instrumentation and techniques, the basic principles of the stereo operating microscope have not changed since the 1930's. Optical Coherence Tomography (OCT) has revolutionized ophthalmic imaging and is now the gold standard for preoperative and postoperative evaluation of most retinal and many corneal procedures. We and others have developed initial microscope-integrated OCT (MIOCT) systems for concurrent OCT and operating microscope imaging, but these are limited to 2D real-time imaging and require offline post-processing for 3D rendering and visualization. Our previously presented 4D MIOCT system can record and display the 3D surgical field stereoscopically through the microscope oculars using a dual-channel heads-up display (HUD) at up to 10 micron-scale volumes per second. In this work, we show that 4D MIOCT guidance improves the accuracy of depth-based microsurgical maneuvers (with statistical significance) in mock surgery trials in a wet lab environment. Additionally, 4D MIOCT was successfully performed in 38/45 (84%) posterior and 14/14 (100%) anterior eye human surgeries, and revealed previously unrecognized lesions that were invisible through the operating microscope. These lesions, such as residual and potentially damaging retinal deformation during pathologic membrane peeling, were visualized in real-time by the surgeon. Our integrated system provides an enhanced 4D surgical visualization platform that can improve current ophthalmic surgical practice and may help develop and refine future microsurgical techniques.

Covariant density functional theory: predictive power and first attempts of a microscopic derivation

NASA Astrophysics Data System (ADS)

Ring, Peter

2018-05-01

We discuss systematic global investigations with modern covariant density functionals. The number of their phenomenological parameters can be reduced considerable by using microscopic input from ab-initio calculations in nuclear matter. The size of the tensor force is still an open problem. Therefore we use the first full relativistic Brueckner-Hartree-Fock calculations in finite nuclear systems in order to study properties of such functionals, which cannot be obtained from nuclear matter calculations.

Molecular Model of a Quantum Dot Beyond the Constant Interaction Approximation

NASA Astrophysics Data System (ADS)

Temirov, Ruslan; Green, Matthew F. B.; Friedrich, Niklas; Leinen, Philipp; Esat, Taner; Chmielniak, Pawel; Sarwar, Sidra; Rawson, Jeff; Kögerler, Paul; Wagner, Christian; Rohlfing, Michael; Tautz, F. Stefan

2018-05-01

We present a physically intuitive model of molecular quantum dots beyond the constant interaction approximation. It accurately describes their charging behavior and allows the extraction of important molecular properties that are otherwise experimentally inaccessible. The model is applied to data recorded with a noncontact atomic force microscope on three different molecules that act as a quantum dot when attached to the microscope tip. The results are in excellent agreement with first-principles simulations.

Demonstration of a plenoptic microscope based on laser optical feedback imaging.

PubMed

Glastre, Wilfried; Hugon, Olivier; Jacquin, Olivier; Guillet de Chatellus, Hugues; Lacot, Eric

2013-03-25

A new kind of plenoptic imaging system based on Laser Optical Feedback Imaging (LOFI) is presented and is compared to another previously existing device based on microlens array. Improved photometric performances, resolution and depth of field are obtained at the price of a slow point by point scanning. Main properties of plenoptic microscopes such as numerical refocusing on any curved surface or aberrations compensation are both theoretically and experimentally demonstrated with a LOFI-based device.

A 25% tannic acid solution as a root canal irrigant cleanser: a scanning electron microscope study.

PubMed

Bitter, N C

1989-03-01

A scanning electron microscope was used to evaluate the cleansing properties of a 25% tannic acid solution on the dentinal surface in the pulp chamber of endodontically prepared teeth. This was compared with the amorphous smear layer of the canal with the use of hydrogen peroxide and sodium hypochlorite solution as an irrigant. The tannic acid solution removed the smear layer more effectively than the regular cleansing agent.

Observation of microscopic dynamics of phase transition in ferroelectric crystals using fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Sedarous, Salah S.

1996-03-01

Despite the large quantity of data on the macroscopic changes in the physical properties of ferroelectric crystals during phase transition, there is a continued need for understanding their microscopic origin. Here we describe a novel method for examining the microscopic dynamics of the ferroelectric phase transition using time-resolved fluorescence spectroscopy. The fluorescence properties of organic chromophores embedded in the ferroelectric crystals triglycine sulfate and potassium dihydrogen phosphate are altered in response to the structural phase transitions. The lifetime and the fractional intensity decay show large changes around Tc and the order of the phase transition is readily recovered (first or second order). To explain the fluorescence lifetime data we present a novel theoretical model based on the concept of polaritons in these crystals. Deactivation of the excited state chromophore involves the participation of the vibrational modes of the chromophore. These modes are coupled to the polarization dispersion of the matrix and facilitate the coupling of the excited state to the collective modes in the crystal. The net result is the flow of energy from the excited state chromophore to the lattice phonon. The data indicate that changes in fluorescence lifetime can be used to examine directly the collective modes in these crystals. Our work provides important insight into the emergence of macroscopic phase transition behavior out of microscopic fluctuations.

Plasmodium malariae in the Colombian Amazon region: you don't diagnose what you don't suspect.

PubMed

Niño, Carlos Hernando; Cubides, Juan Ricardo; Camargo-Ayala, Paola Andrea; Rodríguez-Celis, Carlos Arturo; Quiñones, Teódulo; Cortés-Castillo, Moisés Tomás; Sánchez-Suárez, Lizeth; Sánchez, Ricardo; Patarroyo, Manuel Elkin; Patarroyo, Manuel Alfonso

2016-11-29

Malaria is a worldwide public health problem; parasites from the genus Plasmodium spp. are the aetiological agent of this disease. The parasite is mainly diagnosed by microscope-based techniques. However, these have limited sensitivity. Many asymptomatic infections are sub-microscopic and can only be detected by molecular methods. This study was aimed at comparing nested PCR results to those obtained by microscope for diagnosing malaria and to present epidemiological data regarding malaria in Colombia's Amazon department. A total of 1392 blood samples (taken by venepuncture) from symptomatic patients in Colombia's Amazon department were analysed in parallel by thick blood smear (TBS) test and nested PCR for determining Plasmodium spp. infection and identifying infecting species, such as Plasmodium vivax, Plasmodium malariae and/or Plasmodium falciparum. Descriptive statistics were used for comparing the results from both tests regarding detection of the disease, typing infecting species and their prevalence in the study region. Bearing the microscope assay in mind as gold standard, PCR diagnosis performance was evaluated by statistical indicators. The present study revealed great differences between both diagnostic tests, as well as suggesting high P. malariae prevalence from a molecular perspective. This differed profoundly from previous studies in this region of Colombia, usually based on the TBS test, suggesting that diagnosis by conventional techniques could lead to underestimating the prevalence of certain Plasmodium spp. having high circulation in this area. The present results highlight the need for modifying state malaria surveillance schemes for more efficient strategies regarding the detection of this disease in endemic areas. The importance of PCR as a back-up test in cases of low parasitaemia or mixed infection is also highlighted.

Wear at the titanium-titanium and the titanium-zirconia implant-abutment interface: a comparative in vitro study.

PubMed

Stimmelmayr, Michael; Edelhoff, Daniel; Güth, Jan-Frederik; Erdelt, Kurt; Happe, Arndt; Beuer, Florian

2012-12-01

The purpose of this study was to determine and measure the wear of the interface between titanium implants and one-piece zirconia abutments in comparison to titanium abutments. 6 implants were secured into epoxy resin blocks. The implant interface of these implants and 6 corresponding abutments (group Zr: three one-piece zirconia abutments; group Ti: three titanium abutments) were examined by a microscope and scanning electron micrograph (SEM). Also the implants and the abutments were scanned by 3D-Micro Computer Tomography (CT). The abutments were connected to the implants and cyclically loaded with 1,200,000 cycles at 100N in a two-axis fatigue testing machine. Afterwards, all specimens were unscrewed and the implants and abutments again were scanned by microscope, SEM and CT. The microscope and SEM images were compared, the CT data were superimposed and the wear was calculated by inspection software. The statistical analysis was carried out with an unpaired t-test. Abutment fracture or screw loosening was not observed during cyclical loading. Comparing the microscope and SEM images more wear was observed on the implants connected to zirconia abutments. The maximum wear on the implant shoulder calculated by the inspection software was 10.2μm for group Zr, and 0.7μm for group Ti. The influence of the abutment material on the measured wear was statistically significant (p≤0.001; Levene-test). Titanium implants showed higher wear at the implant interface following cyclic loading when connected to one-piece zirconia implant abutments compared to titanium abutments. The clinical relevance is not clear; hence damage of the internal implant connection could result in prosthetic failures up to the need of implant removal. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Efficacy of clinical and radiological methods to identify second mesiobuccal canals in maxillary first molars.

PubMed

Abuabara, Allan; Baratto-Filho, Flares; Aguiar Anele, Juliana; Leonardi, Denise Piotto; Sousa-Neto, Manoel Damião

2013-01-01

The success of endodontic treatment depends on the identification of all root canals. Technological advances have facilitated this process as well as the assessment of internal anatomical variations. The aim of this study was to compare the efficacy of clinical and radiological methods in locating second mesiobuccal canals (MB2) in maxillary first molars. Fifty patients referred for analysis; access and clinical analysis; cone-beam endodontic treatment of their maxillary first molars were submitted to the following assessments: analysis; access and clinical analysis; cone-beam computed tomography (CBCT); post-CBCT clinical analysis; clinical analysis using an operating microscope; and clinical analysis after Start X ultrasonic inserts in teeth with negative results in all previous analyses. Periapical radiographic analysis revealed the presence of MB2 in four (8%) teeth, clinical analysis in 25 (50%), CBCT analysis in 27 (54%) and clinical analysis following CBCT and using an operating microscope in 27 (54%) and 29 (58%) teeth, respectively. The use of Start X ultrasonic inserts allowed one to detect two additional teeth with MB2 (62%). According to Vertucci's classification 48% of the mesiobuccal canals found were type I, 28% type II, 18% type IV and 6% type V. Statistical analysis showed no significant differences (p > 0.5) in the ability of CBCT to detect MB2 canals when compared with clinical assessment with or without an operating microscope. A significant difference (p < 0.001)was found only between periapical radiography and clinical/CBCT evaluations. Combined use of different methods increased the detection ofthe second canal in MB roots, but without statistical difference among CBCT, operating microscope, Start X and clinical analysis.

Effect of different catalyst preparation methods on the synthesis of carbon nanotubes with the flame pyrolysis method

NASA Astrophysics Data System (ADS)

Guo, Yonghong; Zhai, Gang; Ru, Yu; Wu, Chuyu; Jia, Xiaowei; Sun, Yaping; Yu, Jiawen; Kang, Zhizhong; Sun, Baomin

2018-03-01

The Flame pyrolysis method used to synthesize carbon nanotubes was studied in this work. In order to improve the quality of synthesized carbon nanotubes, it is important to change the corresponding natures of the catalyst. Two catalyst preparation methods, namely, the sol-gel method and the impregnation method, were compared in this experiment. The properties of the catalyst are analyzed in depth by energy dispersive spectrometer (EDS), x-ray diffraction (XRD), temperature program reduction (TPR). The generation of carbon nanotubes was systematically analysed through scanning electron microscope (SEM), molecule dynamics (MD), raman spectroscopy and transmission electron microscope (TEM). The results show that the catalysts prepared by the impregnation method are stickier, dispersed and easier to dip onto the probe or substrate, which is beneficial for the large-scale production of carbon tubes. The specific surface area of alumina is larger and the iron and molybdenum oxide are more evenly dispersed on the surface of alumina. The carbon nanotubes produced by the catalysts prepared by impregnation method are flatter and have less impurities. The ratio of ID/IG+ is 29.7% lower than that of the sol-gel method in the Raman spectra. The TEM statistics show that the average diameter of the carbon tubes decreases by 23.3%. Therefore, the impregnation method can improve the quality of carbon nanotubes in the case of a similar degree of difficulty in the preparation of the catalyst.

Towards a theory of cortical columns: From spiking neurons to interacting neural populations of finite size

PubMed Central

Gerstner, Wulfram

2017-01-01

Neural population equations such as neural mass or field models are widely used to study brain activity on a large scale. However, the relation of these models to the properties of single neurons is unclear. Here we derive an equation for several interacting populations at the mesoscopic scale starting from a microscopic model of randomly connected generalized integrate-and-fire neuron models. Each population consists of 50–2000 neurons of the same type but different populations account for different neuron types. The stochastic population equations that we find reveal how spike-history effects in single-neuron dynamics such as refractoriness and adaptation interact with finite-size fluctuations on the population level. Efficient integration of the stochastic mesoscopic equations reproduces the statistical behavior of the population activities obtained from microscopic simulations of a full spiking neural network model. The theory describes nonlinear emergent dynamics such as finite-size-induced stochastic transitions in multistable networks and synchronization in balanced networks of excitatory and inhibitory neurons. The mesoscopic equations are employed to rapidly integrate a model of a cortical microcircuit consisting of eight neuron types, which allows us to predict spontaneous population activities as well as evoked responses to thalamic input. Our theory establishes a general framework for modeling finite-size neural population dynamics based on single cell and synapse parameters and offers an efficient approach to analyzing cortical circuits and computations. PMID:28422957

Physicochemical and microscopic characterization of implant-abutment joints.

PubMed

Lopes, Patricia A; Carreiro, Adriana F P; Nascimento, Rubens M; Vahey, Brendan R; Henriques, Bruno; Souza, Júlio C M

2018-01-01

The purpose of this study was to investigate Morse taper implant-abutment joints by chemical, mechanical, and microscopic analysis. Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant-abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant-abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant-abutment joints. Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05. Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant-abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa). Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant-abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication.

Electronic holographic moire in the micron range

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Sciammarella, Federico M.

2001-06-01

The basic theory behind microscopic electronic holographic moire is presented. Conditions of observation are discussed, and optimal parameters are established. An application is presented as an example where experimental result are statistically analyzed and successfully correlated with an independent method of measurement of the same quantity.

Microscopes and computers combined for analysis of chromosomes

NASA Technical Reports Server (NTRS)

Butler, J. W.; Butler, M. K.; Stroud, A. N.

1969-01-01

Scanning machine CHLOE, developed for photographic use, is combined with a digital computer to obtain quantitative and statistically significant data on chromosome shapes, distribution, density, and pairing. CHLOE permits data acquisition about a chromosome complement to be obtained two times faster than by manual pairing.

Modeling of Yb3+/Er3+-codoped microring resonators

NASA Astrophysics Data System (ADS)

Vallés, Juan A.; Gălătuş, Ramona

2015-03-01

The performance of a highly Yb3+/Er3+-codoped phosphate glass add-drop microring resonator is numerically analyzed. The model assumes resonant behaviour of both pump and signal powers and the dependences of pump intensity build-up inside the microring resonator and of the signal transfer functions to the device through and drop ports are evaluated. Detailed equations for the evolution of the rare-earth ions levels population densities and the propagation of the optical powers inside the microring resonator are included in the model. Moreover, due to the high dopant concentrations considered, the microscopic statistical formalism based on the statistical average of the excitation probability of the Er3+ ion in a microscopic level has been used to describe energy-transfer inter-atomic mechanisms. Realistic parameters and working conditions are used for the calculations. Requirements to achieve amplification and laser oscillation within these devices are obtainable as a function of rare earth ions concentration and coupling losses.

RIPL - Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations

NASA Astrophysics Data System (ADS)

Capote, R.; Herman, M.; Obložinský, P.; Young, P. G.; Goriely, S.; Belgya, T.; Ignatyuk, A. V.; Koning, A. J.; Hilaire, S.; Plujko, V. A.; Avrigeanu, M.; Bersillon, O.; Chadwick, M. B.; Fukahori, T.; Ge, Zhigang; Han, Yinlu; Kailas, S.; Kopecky, J.; Maslov, V. M.; Reffo, G.; Sin, M.; Soukhovitskii, E. Sh.; Talou, P.

2009-12-01

We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released in January 2009, and is available on the Web through http://www-nds.iaea.org/RIPL-3/. This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations. The numerical data and computer codes included in RIPL-3 are arranged in seven segments: MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi et al. (2003). DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic and γ-ray decay probabilities available from ENSDF in October 2007. NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab. OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment. LEVEL DENSITIES contains phenomenological parameterizations based on the modified Fermi gas and superfluid models and microscopic calculations which are based on a realistic microscopic single-particle level scheme. Partial level densities formulae are also recommended. All tabulated total level densities are consistent with both the recommended average neutron resonance parameters and discrete levels. GAMMA contains parameters that quantify giant resonances, experimental gamma-ray strength functions and methods for calculating gamma emission in statistical model codes. The experimental GDR parameters are represented by Lorentzian fits to the photo-absorption cross sections for 102 nuclides ranging from 51V to 239Pu. FISSION includes global prescriptions for fission barriers and nuclear level densities at fission saddle points based on microscopic HFB calculations constrained by experimental fission cross sections.

RIPL - Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capote, R.; Herman, M.; Oblozinsky, P.

We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released inmore » January 2009, and is available on the Web through (http://www-nds.iaea.org/RIPL-3/). This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations. The numerical data and computer codes included in RIPL-3 are arranged in seven segments: MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi et al. (2003). DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic and {gamma}-ray decay probabilities available from ENSDF in October 2007. NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab. OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment. LEVEL DENSITIES contains phenomenological parameterizations based on the modified Fermi gas and superfluid models and microscopic calculations which are based on a realistic microscopic single-particle level scheme. Partial level densities formulae are also recommended. All tabulated total level densities are consistent with both the recommended average neutron resonance parameters and discrete levels. GAMMA contains parameters that quantify giant resonances, experimental gamma-ray strength functions and methods for calculating gamma emission in statistical model codes. The experimental GDR parameters are represented by Lorentzian fits to the photo-absorption cross sections for 102 nuclides ranging from {sup 51}V to {sup 239}Pu. FISSION includes global prescriptions for fission barriers and nuclear level densities at fission saddle points based on microscopic HFB calculations constrained by experimental fission cross sections.« less

RIPL-Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capote, R.; Herman, M.; Capote,R.

We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released inmore » January 2009, and is available on the Web through http://www-nds.iaea.org/RIPL-3/. This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations. The numerical data and computer codes included in RIPL-3 are arranged in seven segments: MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi et al. (2003). DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic and {gamma}-ray decay probabilities available from ENSDF in October 2007. NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab. OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment. LEVEL DENSITIES contains phenomenological parameterizations based on the modified Fermi gas and superfluid models and microscopic calculations which are based on a realistic microscopic single-particle level scheme. Partial level densities formulae are also recommended. All tabulated total level densities are consistent with both the recommended average neutron resonance parameters and discrete levels. GAMMA contains parameters that quantify giant resonances, experimental gamma-ray strength functions and methods for calculating gamma emission in statistical model codes. The experimental GDR parameters are represented by Lorentzian fits to the photo-absorption cross sections for 102 nuclides ranging from {sup 51}V to {sup 239}Pu. FISSION includes global prescriptions for fission barriers and nuclear level densities at fission saddle points based on microscopic HFB calculations constrained by experimental fission cross sections.« less

Effect of Microscopic Damage Events on Static and Ballistic Impact Strength of Triaxial Braid Composites

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Binienda, Wieslaw K.; Arnold, William A.; Roberts, Gary d.; Goldberg, Robert K.

2008-01-01

In previous work, the ballistic impact resistance of triaxial braided carbon/epoxy composites made with large flat tows (12k and 24k) was examined by impacting 2 X2 X0.125" composite panels with gelatin projectiles. Several high strength, intermediate modulus carbon fibers were used in combination with both untoughened and toughened matrix materials. A wide range of penetration thresholds were measured for the various fiber/matrix combinations. However, there was no clear relationship between the penetration threshold and the properties of the constituents. During some of these experiments high speed cameras were used to view the failure process, and full-field strain measurements were made to determine the strain at the onset of failure. However, these experiments provided only limited insight into the microscopic failure processes responsible for the wide range of impact resistance observed. In order to investigate potential microscopic failure processes in more detail, quasi-static tests were performed in tension, compression, and shear. Full-field strain measurement techniques were used to identify local regions of high strain resulting from microscopic failures. Microscopic failure events near the specimen surface, such as splitting of fiber bundles in surface plies, were easily identified. Subsurface damage, such as fiber fracture or fiber bundle splitting, could be identified by its effect on in-plane surface strains. Subsurface delamination could be detected as an out-of-plane deflection at the surface. Using this data, failure criteria could be established at the fiber tow level for use in analysis. An analytical formulation was developed to allow the microscopic failure criteria to be used in place of macroscopic properties as input to simulations performed using the commercial explicit finite element code, LS-DYNA. The test methods developed to investigate microscopic failure will be presented along with methods for determining local failure criteria that can be used in analysis. Results of simulations performed using LS-DYNA will be presented to illustrate the capabilities and limitations for simulating failure during quasi-static deformation and during ballistic impact of large unit cell size triaxial braid composites.

Correction to verdonck and tuerlinckx (2014).

PubMed

2015-01-01

Reports an error in "The Ising Decision Maker: A binary stochastic network for choice response time" by Stijn Verdonck and Francis Tuerlinckx (Psychological Review, 2014[Jul], Vol 121[3], 422-462). An inaccurate assumption in Appendix B (provided in the erratum) led to an oversimplified result in Equation 18 (the diffusion equations associated with the microscopically defined dynamics). The authors sincerely thank Rani Moran for making them aware of the problem. Only the expression of the diffusion coefficient D is incorrect, and should be changed, as indicated in the erratum. Both the cause of the problem and the solution are also explained in the erratum. (The following abstract of the original article appeared in record 2014-31650-006.) The Ising Decision Maker (IDM) is a new formal model for speeded two-choice decision making derived from the stochastic Hopfield network or dynamic Ising model. On a microscopic level, it consists of 2 pools of binary stochastic neurons with pairwise interactions. Inside each pool, neurons excite each other, whereas between pools, neurons inhibit each other. The perceptual input is represented by an external excitatory field. Using methods from statistical mechanics, the high-dimensional network of neurons (microscopic level) is reduced to a two-dimensional stochastic process, describing the evolution of the mean neural activity per pool (macroscopic level). The IDM can be seen as an abstract, analytically tractable multiple attractor network model of information accumulation. In this article, the properties of the IDM are studied, the relations to existing models are discussed, and it is shown that the most important basic aspects of two-choice response time data can be reproduced. In addition, the IDM is shown to predict a variety of observed psychophysical relations such as Piéron's law, the van der Molen-Keuss effect, and Weber's law. Using Bayesian methods, the model is fitted to both simulated and real data, and its performance is compared to the Ratcliff diffusion model. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

Applications of Real Space Crystallography in Characterization of Dislocations in Geological Materials in a Scanning Electron Microscope (SEM)

NASA Astrophysics Data System (ADS)

Kaboli, S.; Burnley, P. C.

2017-12-01

Imaging and characterization of defects in crystalline materials is of significant importance in various disciplines including geoscience, materials science, and applied physics. Linear defects such as dislocations and planar defects such as twins and stacking faults, strongly influence many of the properties of crystalline materials and also reflect the conditions and degree of deformation. Dislocations have been conventionally imaged in thin foils in a transmission electron microscope (TEM). Since the development of field emission scanning electron microscopes (FE-SEM) with high gun brightness and small spot size, extensive efforts have been dedicated to the imaging and characterization of dislocations in semi-conductors using electron channeling contrast imaging (ECCI) in the SEM. The obvious advantages of using SEM over TEM include easier and non-destructive sample preparation and a large field of view enabling statistical examination of the density and distribution of dislocations and other defects. In this contribution, we extend this technique to geological materials and introduce the Real Space Crystallography methodology for imaging and complete characterization of dislocations based on bend contour contrast obtained by ECCI in FE-SEM. Bend contours map out the distortion in the crystal lattice across a deformed grain. The contrast of dislocations is maximum in the vicinity of bend contours where crystal planes diffract at small and positive deviations from the Bragg positions (as defined by Bragg's law of electron diffraction). Imaging is performed in a commercial FE-SEM equipped with a standard silicon photodiode backscattered (BSE) detector and an electron backscatter diffraction (EBSD) system for crystal orientation measurements. We demonstrate the practice of this technique in characterization of a number of geological materials in particular quartz, forsterite olivine and corundum, experimentally deformed at high pressure-temperature conditions. This new approach in microstructure characterization of deformed geologic materials in FE-SEM, without the use of etching or decoration techniques, has valuable applications to both experimentally deformed and naturally deformed specimens.

A Novel SPM Probe with MOS Transistor and Nano Tip for Surface Electric Properties

NASA Astrophysics Data System (ADS)

Lee, Sang H.; Lim, Geunbae; Moon, Wonkyu

2007-03-01

In this paper, the novel SPM (Scanning Probe Microscope) probe with the planar MOS (Metal-Oxide-Semiconductor) transistor and the FIB (Focused Ion Beam) nano tip is fabricated for the surface electric properties. Since the MOS transistor has high working frequency, the device can overcome the speed limitation of EFM (Electrostatic Force Microscope) system. The sensitivity is also high, and no bulky device such as lock-in-amplifier is required. Moreover, the nano tip with nanometer scale tip radius is fabricated with FIB system, and the resolution can be improved. Therefore, the probe can rapidly detect small localized electric properties with high sensitivity and high resolution. The MOS transistor is fabricated with the common semiconductor process, and the nano tip is grown by the FIB system. The planar structure of the MOS transistor makes the fabrication process easier, which is the advantage on the commercial production. Various electric signals are applied using the function generator, and the measured data represent the well-established electric properties of the device. It shows the promising aspect of the local surface electric property detection with high sensitivity and high resolution.

Tuning critical failure with viscoelasticity: How aftershocks inhibit criticality in an analytical mean field model of fracture.

NASA Astrophysics Data System (ADS)

Baro Urbea, J.; Davidsen, J.

2017-12-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible of deformation. Avalanche models involving critical failure have determined universality classes in different systems: from slip events in crystalline and amorphous materials to the jamming of granular media or the fracture of brittle materials. However, not all empirical failure processes exhibit the trademarks of critical failure. As an example, the statistical properties of ultrasonic acoustic events recorded during the failure of porous brittle materials are stationary, except for variations in the activity rate that can be interpreted in terms of aftershock and foreshock activity (J. Baró et al., PRL 2013).The rheological properties of materials introduce dissipation, usually reproduced in atomistic models as a hardening of the coarse-grained elements of the system. If the hardening is associated to a relaxation process the same mechanism is able to generate temporal correlations. We report the analytic solution of a mean field fracture model exemplifying how criticality and temporal correlations are tuned by transient hardening. We provide a physical meaning to the conceptual model by deriving the constitutive equation from the explicit representation of the transient hardening in terms of a generalized viscoelasticity model. The rate of 'aftershocks' is controlled by the temporal evolution of the viscoelastic creep. At the quasistatic limit, the moment release is invariant to rheology. Therefore, the lack of criticality is explained by the increase of the activity rate close to failure, i.e. 'foreshocks'. Finally, the avalanche propagation can be reinterpreted as a pure mathematical problem in terms of a stochastic counting process. The statistical properties depend only on the distance to a critical point, which is universal for any parametrization of the transient hardening and a whole category of fracture models.

The Logic of Quantum Measurements

NASA Astrophysics Data System (ADS)

Vanni, Leonardo; Laura, Roberto

2013-07-01

We apply our previously developed formalism of contexts of histories, suitable to deal with quantum properties at different times, to the measurement process. We explore the logical implications which are allowed by the quantum theory, about the realization of properties of the microscopic measured system, before and after the measurement process with a given pointer value.

Computer Simulations and Theoretical Studies of Complex Systems: from complex fluids to frustrated magnets

NASA Astrophysics Data System (ADS)

Choi, Eunsong

Computer simulations are an integral part of research in modern condensed matter physics; they serve as a direct bridge between theory and experiment by systemactically applying a microscopic model to a collection of particles that effectively imitate a macroscopic system. In this thesis, we study two very differnt condensed systems, namely complex fluids and frustrated magnets, primarily by simulating classical dynamics of each system. In the first part of the thesis, we focus on ionic liquids (ILs) and polymers--the two complementary classes of materials that can be combined to provide various unique properties. The properties of polymers/ILs systems, such as conductivity, viscosity, and miscibility, can be fine tuned by choosing an appropriate combination of cations, anions, and polymers. However, designing a system that meets a specific need requires a concrete understanding of physics and chemistry that dictates a complex interplay between polymers and ionic liquids. In this regard, molecular dynamics (MD) simulation is an efficient tool that provides a molecular level picture of such complex systems. We study the behavior of Poly (ethylene oxide) (PEO) and the imidazolium based ionic liquids, using MD simulations and statistical mechanics. We also discuss our efforts to develop reliable and efficient classical force-fields for PEO and the ionic liquids. The second part is devoted to studies on geometrically frustrated magnets. In particular, a microscopic model, which gives rise to an incommensurate spiral magnetic ordering observed in a pyrochlore antiferromagnet is investigated. The validation of the model is made via a comparison of the spin-wave spectra with the neutron scattering data. Since the standard Holstein-Primakoff method is difficult to employ in such a complex ground state structure with a large unit cell, we carry out classical spin dynamics simulations to compute spin-wave spectra directly from the Fourier transform of spin trajectories. We conclude the study by showing an excellent agreement between the simulation and the experiment.

Microstructural modification of pure Mg for improving mechanical and biocorrosion properties.

PubMed

Ahmadkhaniha, D; Järvenpää, A; Jaskari, M; Sohi, M Heydarzadeh; Zarei-Hanzaki, A; Fedel, M; Deflorian, F; Karjalainen, L P

2016-08-01

In this study, the effect of microstructural modification on mechanical properties and biocorrosion resistance of pure Mg was investigated for tailoring a load-bearing orthopedic biodegradable implant material. This was performed utilizing the friction stir processing (FSP) in 1-3 passes to refine the grain size. Microstructure was examined in an optical microscope and scanning electron microscope with an electron backscatter diffraction unit. X-ray diffraction method was used to identify the texture. Mechanical properties were measured by microhardness and tensile testing. Electrochemical impedance spectroscopy was applied to evaluate corrosion behavior. The results indicate that even applying a single pass of FSP refined the grain size significantly. Increasing the number of FSP passes further refined the structure, increased the mechanical strength and intensified the dominating basal texture. The best combination of mechanical properties and corrosion resistance were achieved after three FSP passes. In this case, the yield strength was about six times higher than that of the as-cast Mg and the corrosion resistance was also improved compared to that in the as-cast condition. Copyright © 2016 Elsevier Ltd. All rights reserved.

The influence of voltage applied between the electrodes on optical and morphological properties of the InGaN thin films grown by thermionic vacuum arc.

PubMed

Özen, Soner; Şenay, Volkan; Pat, Suat; Korkmaz, Şadan

2016-01-01

The aim of this research is to investigate the optical and morphological properties of the InGaN thin films deposited onto amorphous glass substrates in two separate experiments with two different voltages applied between the electrodes, i.e. 500 and 600 V by means of the thermionic vacuum arc technique. This technique is original for thin film deposition and it enables thin film production in a very short period of time. The optical and morphological properties of the films were investigated by using field emission scanning electron microscope, atomic force microscope, spectroscopic ellipsometer, reflectometer, spectrophotometer, and optical tensiometer. Optical properties were also supported by empirical relations. The deposition rates were calculated as 3 and 3.3 nm/sec for 500 and 600 V, respectively. The increase in the voltage also increased the refractive index, grain size, root mean square roughness and surface free energy. According to the results of the wetting experiments, InGaN samples were low-wettable, also known as hydrophobic. © Wiley Periodicals, Inc.

Characterization of grain boundary conductivity of spin-sprayed ferrites using scanning microwave microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myers, J.; Nicodemus, T.; Zhuang, Y., E-mail: yan.zhuang@wright.edu

2014-05-07

Grain boundary electrical conductivity of ferrite materials has been characterized using scanning microwave microscope. Structural, electrical, and magnetic properties of Fe{sub 3}O{sub 4} spin-sprayed thin films onto glass substrates for different length of growth times were investigated using a scanning microwave microscope, an atomic force microscope, a four-point probe measurement, and a made in house transmission line based magnetic permeameter. The real part of the magnetic permeability shows almost constant between 10 and 300 MHz. As the Fe{sub 3}O{sub 4} film thickness increases, the grain size becomes larger, leading to a higher DC conductivity. However, the loss in the Fe{sub 3}O{submore » 4} films at high frequency does not increase correspondingly. By measuring the reflection coefficient s{sub 11} from the scanning microwave microscope, it turns out that the grain boundaries of the Fe{sub 3}O{sub 4} films exhibit higher electric conductivity than the grains, which contributes loss at radio frequencies. This result will provide guidance for further improvement of low loss ferrite materials for high frequency applications.« less

Superfluid drag in the two-component Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Sellin, Karl; Babaev, Egor

2018-03-01

In multicomponent superfluids and superconductors, co- and counterflows of components have, in general, different properties. A. F. Andreev and E. P. Bashkin [Sov. Phys. JETP 42, 164 (1975)] discussed, in the context of He3/He4 superfluid mixtures, that interparticle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly, the drag can be both positive (entrainment) and negative (counterflow). The effect is known to have crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars and rotational responses of Bose mixtures of ultracold atoms to magnetic responses of multicomponent superconductors. Although substantial literature exists that includes the drag interaction phenomenologically, only a few regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly correlated regimes where the ratio of coflow and counterflow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

Preservation of viscoelastic properties of rabbit vocal folds after implantation of hyaluronic Acid-based biomaterials.

PubMed

Choi, Jeong-Seok; Kim, Nahn Ju; Klemuk, Sarah; Jang, Yun Ho; Park, In Suh; Ahn, Kyung Hyun; Lim, Jae-Yol; Kim, Young-Mo

2012-09-01

To compare the rheological characteristics of structurally different hyaluronic acid (HA)-based biomaterials that are presently used for phonosurgery and to investigate their influence on the viscoelastic properties of vocal folds after implantation in an in vivo rabbit model. In vitro and in vivo rheometric investigation. Experimental laboratory, Inha and Seoul National Universities. Viscoelastic shear properties of 3 HA-based biomaterials (Rofilan, Restylane, and Reviderm) were measured with a strain-controlled rheometer. These biomaterials were injected into the deep layers of rabbit vocal folds, and viscoelastic moduli of the injected vocal folds were determined 2 months after the injection. The vocal fold specimens were observed using a light microscope and a transmission electron microscope. All HA-based biomaterials showed similar levels of shear viscosity, which were slightly higher than that of human vocal folds reported in previous studies. Compared with noninjected control vocal folds, there were no significant differences in the magnitudes of both elastic shear modulus (G') and viscous modulus (G") of injected vocal folds among all of the materials. Light microscopic images showed that all materials were observed in the deep layers of vocal folds and electron scanning images revealed that injected HA particles were homogeneously distributed in regions of collagenous fibers. HA-based biomaterials could preserve the viscoelastic properties of the vocal folds, when they were injected into vocal folds in an in vivo rabbit model. However, further studies on the influence of the biomaterials on the viscoelasticity of human vocal folds in ECM surroundings are still needed.

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites

PubMed Central

Li, Feng; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

2018-01-01

Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca3(PO4)2, TixPy, and Ti3O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed. PMID:29659504

Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites.

PubMed

Li, Feng; Jiang, Xiaosong; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

2018-04-16

Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca₃(PO₄)₂, Ti x P y , and Ti₃O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

Multivariate statistical analysis of low-voltage EDS spectrum images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, I.M.

1998-03-01

Whereas energy-dispersive X-ray spectrometry (EDS) has been used for compositional analysis in the scanning electron microscope for 30 years, the benefits of using low operating voltages for such analyses have been explored only during the last few years. This paper couples low-voltage EDS with two other emerging areas of characterization: spectrum imaging and multivariate statistical analysis. The specimen analyzed for this study was a finished Intel Pentium processor, with the polyimide protective coating stripped off to expose the final active layers.

In situ microscopy of the self-assembly of branched nanocrystals in solution

DOE PAGES

Sutter, Eli; Tkachenko, Alexei V.; Sutter, Peter; ...

2016-04-04

Here, solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components. Liquid environments are key to self-assembly since they allow suspended nanocrystals to diffuse and interact freely, but they also complicate experiments. Real-time observations with single-particle resolution could have transformative impact on our understanding of nanocrystal self-assembly. Here we use real-time in situ imaging by liquid-cell electron microscopy to elucidate the nucleation and growth mechanism and properties of linear chains of octapod-shaped nanocrystals in their native solution environment. Statistical mechanics modelling based on these observations and using the measured chain-length distribution clarifiesmore » the relative importance of dipolar and entropic forces in the assembly process and gives direct access to the interparticle interaction. Our results suggest that monomer-resolved in situ imaging combined with modelling can provide unprecedented quantitative insight into the microscopic processes and interactions that govern nanocrystal self-assembly in solution.« less

In situ microscopy of the self-assembly of branched nanocrystals in solution

NASA Astrophysics Data System (ADS)

Sutter, Eli; Sutter, Peter; Tkachenko, Alexei V.; Krahne, Roman; de Graaf, Joost; Arciniegas, Milena; Manna, Liberato

2016-04-01

Solution-phase self-assembly of nanocrystals into mesoscale structures is a promising strategy for constructing functional materials from nanoscale components. Liquid environments are key to self-assembly since they allow suspended nanocrystals to diffuse and interact freely, but they also complicate experiments. Real-time observations with single-particle resolution could have transformative impact on our understanding of nanocrystal self-assembly. Here we use real-time in situ imaging by liquid-cell electron microscopy to elucidate the nucleation and growth mechanism and properties of linear chains of octapod-shaped nanocrystals in their native solution environment. Statistical mechanics modelling based on these observations and using the measured chain-length distribution clarifies the relative importance of dipolar and entropic forces in the assembly process and gives direct access to the interparticle interaction. Our results suggest that monomer-resolved in situ imaging combined with modelling can provide unprecedented quantitative insight into the microscopic processes and interactions that govern nanocrystal self-assembly in solution.

Structure–property relationships in atomic-scale junctions: Histograms and beyond

DOE PAGES

Mark S. Hybertsen; Venkataraman, Latha

2016-03-03

Over the past 10 years, there has been tremendous progress in the measurement, modeling and understanding of structure–function relationships in single molecule junctions. Numerous research groups have addressed significant scientific questions, directed both to conductance phenomena at the single molecule level and to the fundamental chemistry that controls junction functionality. Many different functionalities have been demonstrated, including single-molecule diodes, optically and mechanically activated switches, and, significantly, physical phenomena with no classical analogues, such as those based on quantum interference effects. Experimental techniques for reliable and reproducible single molecule junction formation and characterization have led to this progress. In particular, themore » scanning tunneling microscope based break-junction (STM-BJ) technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Furthermore, harnessing fundamental link chemistry has provided the necessary chemical control over junction formation, enabling measurements that revealed clear relationships between molecular structure and conductance characteristics.« less

Structure–property relationships in atomic-scale junctions: Histograms and beyond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark S. Hybertsen; Venkataraman, Latha

Over the past 10 years, there has been tremendous progress in the measurement, modeling and understanding of structure–function relationships in single molecule junctions. Numerous research groups have addressed significant scientific questions, directed both to conductance phenomena at the single molecule level and to the fundamental chemistry that controls junction functionality. Many different functionalities have been demonstrated, including single-molecule diodes, optically and mechanically activated switches, and, significantly, physical phenomena with no classical analogues, such as those based on quantum interference effects. Experimental techniques for reliable and reproducible single molecule junction formation and characterization have led to this progress. In particular, themore » scanning tunneling microscope based break-junction (STM-BJ) technique has enabled rapid, sequential measurement of large numbers of nanoscale junctions allowing a statistical analysis to readily distinguish reproducible characteristics. Furthermore, harnessing fundamental link chemistry has provided the necessary chemical control over junction formation, enabling measurements that revealed clear relationships between molecular structure and conductance characteristics.« less

Multiscale analysis of replication technique efficiency for 3D roughness characterization of manufactured surfaces

NASA Astrophysics Data System (ADS)

Jolivet, S.; Mezghani, S.; El Mansori, M.

2016-09-01

The replication of topography has been generally restricted to optimizing material processing technologies in terms of statistical and single-scale features such as roughness. By contrast, manufactured surface topography is highly complex, irregular, and multiscale. In this work, we have demonstrated the use of multiscale analysis on replicates of surface finish to assess the precise control of the finished replica. Five commercial resins used for surface replication were compared. The topography of five standard surfaces representative of common finishing processes were acquired both directly and by a replication technique. Then, they were characterized using the ISO 25178 standard and multiscale decomposition based on a continuous wavelet transform, to compare the roughness transfer quality at different scales. Additionally, atomic force microscope force modulation mode was used in order to compare the resins’ stiffness properties. The results showed that less stiff resins are able to replicate the surface finish along a larger wavelength band. The method was then tested for non-destructive quality control of automotive gear tooth surfaces.

Fabrication and electric measurements of nanostructures inside transmission electron microscope.

PubMed

Chen, Qing; Peng, Lian-Mao

2011-06-01

Using manipulation holders specially designed for transmission electron microscope (TEM), nanostructures can be characterized, measured, modified and even fabricated in-situ. In-situ TEM techniques not only enable real-time study of structure-property relationships of materials at atomic scale, but also provide the ability to control and manipulate materials and structures at nanoscale. This review highlights in-situ electric measurements and in-situ fabrication and structure modification using manipulation holder inside TEM. Copyright © 2011 Elsevier B.V. All rights reserved.

Quantitative Phase Imaging in a Volume Holographic Microscope

NASA Astrophysics Data System (ADS)

Waller, Laura; Luo, Yuan; Barbastathis, George

2010-04-01

We demonstrate a method for quantitative phase imaging in a Volume Holographic Microscope (VHM) from a single exposure, describe the properties of the system and show experimental results. The VHM system uses a multiplexed volume hologram (VH) to laterally separate images from different focal planes. This 3D intensity information is then used to solve the transport of intensity (TIE) equation and recover phase quantitatively. We discuss the modifications to the technique that were made in order to give accurate results.

Mapping flexible protein domains at subnanometer resolution with the atomic force microscope.

PubMed

Müller, D J; Fotiadis, D; Engel, A

1998-06-23

The mapping of flexible protein domains with the atomic force microscope is reviewed. Examples discussed are the bacteriorhodopsin from Halobacterium salinarum, the head-tail-connector from phage phi29, and the hexagonally packed intermediate layer from Deinococcus radiodurans which all were recorded in physiological buffer solution. All three proteins undergo reversible structural changes that are reflected in standard deviation maps calculated from aligned topographs of individual protein complexes. Depending on the lateral resolution (up to 0.8 nm) flexible surface regions can ultimately be correlated with individual polypeptide loops. In addition, multivariate statistical classification revealed the major conformations of the protein surface.

Emergent Societal Effects of Crimino-Social Forces in an Animat Agent Model

NASA Astrophysics Data System (ADS)

Scogings, Chris J.; Hawick, Ken A.

Societal behaviour can be studied at a causal level by perturbing a stable multi-agent model with new microscopic behaviours and observing the statistical response over an ensemble of simulated model systems. We report on the effects of introducing criminal and law-enforcing behaviours into a large scale animat agent model and describe the complex spatial agent patterns and population changes that result. Our well-established predator-prey substrate model provides a background framework against which these new microscopic behaviours can be trialled and investigated. We describe some quantitative results and some surprising conclusions concerning the overall societal health when individually anti-social behaviour is introduced.

A microscopic model of the Stokes-Einstein relation in arbitrary dimension.

PubMed

Charbonneau, Benoit; Charbonneau, Patrick; Szamel, Grzegorz

2018-06-14

The Stokes-Einstein relation (SER) is one of the most robust and widely employed results from the theory of liquids. Yet sizable deviations can be observed for self-solvation, which cannot be explained by the standard hydrodynamic derivation. Here, we revisit the work of Masters and Madden [J. Chem. Phys. 74, 2450-2459 (1981)], who first solved a statistical mechanics model of the SER using the projection operator formalism. By generalizing their analysis to all spatial dimensions and to partially structured solvents, we identify a potential microscopic origin of some of these deviations. We also reproduce the SER-like result from the exact dynamics of infinite-dimensional fluids.

A Comparison of the Flexural and Impact Strengths and Flexural Modulus of CAD/CAM and Conventional Heat-Cured Polymethyl Methacrylate (PMMA).

PubMed

Al-Dwairi, Ziad N; Tahboub, Kawkab Y; Baba, Nadim Z; Goodacre, Charles J

2018-06-13

The introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) technology to the field of removable prosthodontics has recently made it possible to fabricate complete dentures of prepolymerized polymethyl methacrylate (PMMA) blocks, which are claimed to be of better mechanical properties; however, no published reports that have evaluated mechanical properties of CAD/CAM PMMA. The purpose of this study was to compare flexural strength, impact strength, and flexural modulus of two brands of CAD/CAM PMMA and a conventional heat-cured PMMA. 45 rectangular specimens (65 mm × 10 mm × 3 mm) were fabricated (15 CAD/CAM AvaDent PMMA specimens from AvaDent, 15 CAD/CAM Tizian PMMA specimens from Shütz Dental, 15 conventional Meliodent PMMA specimens from Heraeus Kulzer) and stored in distilled water at (37  ± 1°C) for 7 days. Specimens (N = 15) in each group were subjected to the three-point bending test and impact strength test, employing the Charpy configuration on unnotched specimens. The morphology of the fractured specimens was studied under a scanning electron microscope (SEM). Statistical analysis was performed using one-way ANOVA and Tukey pairwise multiple comparisons with 95% confidence interval. The Schütz Dental specimens showed the highest mean flexural strength (130.67 MPa) and impact strength (29.56 kg/m 2 ). The highest mean flexural modulus was recorded in the AvaDent group (2519.6 MPa). The conventional heat-cured group showed the lowest mean flexural strength (93.33 MPa), impact strength (14.756 kg/m 2 ), and flexural modulus (2117.2 MPa). Differences in means of flexural properties between AvaDent and Schütz Dental specimens were not statistically significant (p > 0.05). As CAD/CAM PMMA specimens exhibited improved flexural strength, flexural modulus, and impact strength in comparison to the conventional heat-cured groups, CAD/CAM dentures are expected to be more durable. Different brands of CAD/CAM PMMA may have inherent variations in mechanical properties. © 2018 by the American College of Prosthodontists.

Mechanical properties of dental resin/composite containing urchin-like hydroxyapatite.

PubMed

Liu, Fengwei; Sun, Bin; Jiang, Xiaoze; Aldeyab, Sultan S; Zhang, Qinghong; Zhu, Meifang

2014-12-01

To investigate the reinforcing effect of urchin-like hydroxyapatite (UHA) in bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin (without silica nanoparticles) and dental composites (with silica nanoparticles), and explore the effect of HA filler morphologies and loadings on the mechanical properties. UHA was synthesized by a facile method of microwave irradiation and studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis (TGA). Mechanical properties of the dental resin composites containing silanized UHA were tested by a universal mechanical testing machine. Analysis of variance was used for the statistical analysis of the acquired data. The fracture morphologies of tested composites were observed by SEM. Composites with silanized irregular particulate hydroxyapatite (IPHA) and hydroxyapatite whisker (HW) were prepared for comparative studies. Impregnation of lower loadings (5 wt% and 10 wt%) of silanized UHA into dental resin (without silica nanoparticles) substantially improved the mechanical properties; higher UHA loadings (20 wt% and 30 wt%) of impregnation continuously improved the flexural modulus and microhardness, while the strength would no longer be increased. Compared with silanized IPHA and HW, silanized UHA consisting of rods extending radially from center were embedded into the matrix closely and well dispersed in the composite, increasing filler-matrix interfacial contact area and combination. At higher filler loadings, UHA interlaced together tightly without affecting the mobility of monomer inside, which might bear higher loads during fracture of the composite, leading to higher strengths than those of dental resins with IPHA and HW. Besides, impregnation of silanized UHA into dental composites (with silica nanoparticles) significantly improved the strength and modulus. UHA could serve as novel reinforcing HA filler to improve the mechanical properties of dental resin and dental composite.

Few layered vanadyl phosphate nano sheets-MWCNT hybrid as an electrode material for supercapacitor application

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; De, Sukanta

2016-05-01

It have been already seen that 2-dimensional nano materials are the suitable choice for the supercapacitor application due to their large specific surface area, electrochemical active sites, micromechanical flexibility, expedite ion migration channel properties. Free standing hybrid films of functionalized MWCNT (- COOH group) and α-Vanadyl phosphates (VOPO42H2O) are prepared by vacuum filtering. The surface morphology and microstructure of the samples are studied by transmission electron microscope, field emission scanning electron microscope, XRD, Electrochemical properties of hybrid films have been investigated systematically in 1M Na2SO4 aqueous electrolyte. The hybrid material exhibits a high specific capacitance 236 F/g with high energy density of 65.6 Wh/Kg and a power density of 1476 W/Kg.

In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

2011-01-01

To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

Applications of a global nuclear-structure model to studies of the heaviest elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moeller, P.; Nix, J.R.

1993-10-01

We present some new results on heavy-element nuclear-structure properties calculated on the basis of the finite-range droplet model and folded-Yukawa single-particle potential. Specifically, we discuss calculations of nuclear ground-state masses and microscopic corrections, {alpha}-decay properties, {beta}-decay properties, fission potential-energy surfaces, and spontaneous-fission half-lives. These results, obtained in a global nuclear-structure approach, are particularly reliable for describing the stability properties of the heaviest elements.

Anisotropy analysis of thermoelectric properties of Bi{sub 2}Te{sub 2.9}Se{sub 0.1} prepared by SPS method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zybala, Rafal; Wojciechowski, Krzysztof T.

2012-06-26

The n-type Bi{sub 2}Te{sub 2.9}Se{sub 0.1} materials were synthesized by the direct fusion technique. The polycrystalline samples were fabricated by the uniaxial pressing of powders in spark plasma sintering (SPS) apparatus. The materials were subjected to the heat treatment in H{sub 2}-Ar atmosphere at 470 K for 24 h. The influence of preparation conditions on the anisotropy of electrical and thermal properties was thoroughly studied for the direction perpendicular and parallel to the pressing force. The microstructure and the chemical composition of both types of samples were examined using a scanning microscope (SEM) equipped with an X-ray energy dispersion detectormore » (EDX). The XRD method was applied for the phase analysis of materials, as well as, for determination of preferred orientation of Bi{sub 2}Te{sub 2.9}Se{sub 0.1} grains. The Seebeck coefficient distribution was studied by the scanning thermoelectric microprobe (STM). Temperature dependences of thermoelectric properties (thermal and electrical conductivities, Seebeck coefficient) were measured in the temperature from 300 K to 550 K. The statistical analysis of results has shown strong influence of pressing force direction both on structural and transport properties. The applied heat treatment of materials significantly improves their thermoelectric figure of merit. Particularly, it was found that annealing in H2-Ar atmosphere leads to enhancement of the ZT three times up to {approx}0.7 at 370 K in perpendicular direction to the pressing force.« less

Morphology-controllable of Sn doped ZnO nanorods prepared by spray pyrolysis for transparent electrode application

NASA Astrophysics Data System (ADS)

Hameed, M. Shahul; Princice, J. Joseph; Babu, N. Ramesh; Zahirullah, S. Syed; Deshmukh, Sampat G.; Arunachalam, A.

2018-05-01

Transparent conductive Sn doped ZnO nanorods have been deposited at various doping level by spray pyrolysis technique on glass substrate. The structural, surface morphological and optical properties of these films have been investigated with the help of X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-Vis spectrophotometer respectively. XRD patterns revealed a successful high quality growth of single crystal ZnO nanorods with hexagonal wurtzite structure having (002) preferred orientation. The scanning electron microscope (SEM) image of the prepared films exposed the uniform distribution of Sn doped ZnO nanorod shaped grains. All these films were highly transparent in the visible region with average transmittance of 90%.

Installation of Multiple Application X-ray Imaging Undulator Microscope (MAXIMUM) at ALS: Final report, 8/15/95-8/15/96

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-12-31

MAXIMUM is short for Multiple Application X-ray IMaging Undulator Microscope, a project started in 1988 by our group at the Synchrotron Radiation Center of the University of Wisconsin-Madison. It is a scanning x-ray photoemission microscope that uses a multilayer-coated Schwarzschild objective as the focusing element. It was designed primarily for materials science studies of lateral variations in surface chemistry. Suitable problems include: lateral inhomogeneities in Schottky barrier formation, heterojunction formation, patterned samples and devices, insulating samples. Any system which has interesting properties that are not uniform as a function of spatial dimension can potentially be studied with MAXIMUM. 6 figs.,more » 3 tabs.« less

Commissioning of the PRIOR proton microscope

DOE PAGES

Varentsov, D.; Antonov, O.; Bakhmutova, A.; ...

2016-02-18

Recently, a new high energy proton microscopy facility PRIOR (Proton Microscope for FAIR Facility for Anti-proton and Ion Research) has been designed, constructed, and successfully commissioned at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany). As a result of the experiments with 3.5–4.5 GeV proton beams delivered by the heavy ion synchrotron SIS-18 of GSI, 30 μm spatial and 10 ns temporal resolutions of the proton microscope have been demonstrated. A new pulsed power setup for studying properties of matter under extremes has been developed for the dynamic commissioning of the PRIOR facility. This study describes the PRIOR setup as well asmore » the results of the first static and dynamic protonradiography experiments performed at GSI.« less

Review on Microstructure Analysis of Metals and Alloys Using Image Analysis Techniques

NASA Astrophysics Data System (ADS)

Rekha, Suganthini; Bupesh Raja, V. K.

2017-05-01

The metals and alloys find vast application in engineering and domestic sectors. The mechanical properties of the metals and alloys are influenced by their microstructure. Hence the microstructural investigation is very critical. Traditionally the microstructure is studied using optical microscope with suitable metallurgical preparation. The past few decades the computers are applied in the capture and analysis of the optical micrographs. The advent of computer softwares like digital image processing and computer vision technologies are a boon to the analysis of the microstructure. In this paper the literature study of the various developments in the microstructural analysis, is done. The conventional optical microscope is complemented by the use of Scanning Electron Microscope (SEM) and other high end equipments.

Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

PubMed

Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

2015-05-01

Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface.

Commissioning of the PRIOR proton microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varentsov, D.; Antonov, O.; Bakhmutova, A.

Recently, a new high energy proton microscopy facility PRIOR (Proton Microscope for FAIR Facility for Anti-proton and Ion Research) has been designed, constructed, and successfully commissioned at GSI Helmholtzzentrum für Schwerionenforschung (Darmstadt, Germany). As a result of the experiments with 3.5–4.5 GeV proton beams delivered by the heavy ion synchrotron SIS-18 of GSI, 30 μm spatial and 10 ns temporal resolutions of the proton microscope have been demonstrated. A new pulsed power setup for studying properties of matter under extremes has been developed for the dynamic commissioning of the PRIOR facility. This study describes the PRIOR setup as well asmore » the results of the first static and dynamic protonradiography experiments performed at GSI.« less

A candidate gene based approach validates Md-PG1 as the main responsible for a QTL impacting fruit texture in apple (Malus x domestica Borkh).

PubMed

Longhi, Sara; Hamblin, Martha T; Trainotti, Livio; Peace, Cameron P; Velasco, Riccardo; Costa, Fabrizio

2013-03-04

Apple is a widely cultivated fruit crop for its quality properties and extended storability. Among the several quality factors, texture is the most important and appreciated, and within the apple variety panorama the cortex texture shows a broad range of variability. Anatomically these variations depend on degradation events occurring in both fruit primary cell wall and middle lamella. This physiological process is regulated by an enzymatic network generally encoded by large gene families, among which polygalacturonase is devoted to the depolymerization of pectin. In apple, Md-PG1, a key gene belonging to the polygalacturonase gene family, was mapped on chromosome 10 and co-localized within the statistical interval of a major hot spot QTL associated to several fruit texture sub-phenotypes. In this work, a QTL corresponding to the position of Md-PG1 was validated and new functional alleles associated to the fruit texture properties in 77 apple cultivars were discovered. 38 SNPs genotyped by gene full length resequencing and 2 SSR markers ad hoc targeted in the gene metacontig were employed. Out of this SNP set, eleven were used to define three significant haplotypes statistically associated to several texture components. The impact of Md-PG1 in the fruit cell wall disassembly was further confirmed by the cortex structure electron microscope scanning in two apple varieties characterized by opposite texture performance, such as 'Golden Delicious' and 'Granny Smith'. The results here presented step forward into the genetic dissection of fruit texture in apple. This new set of haplotypes, and microsatellite alleles, can represent a valuable toolbox for a more efficient parental selection as well as the identification of new apple accessions distinguished by superior fruit quality features.

Effect of different storage conditions on the physical properties of bleached enamel: An in vitro vs. in situ study.

PubMed

Zeczkowski, Marília; Tenuta, Livia Maria Andaló; Ambrosano, Gláucia Maria Bovi; Aguiar, Flávio Henrique Baggio; Lima, Débora Alves Nunes Leite

2015-09-01

Evaluate the effect of different storage conditions on bleached enamel using Knoop microhardness (KHN) and colour variation. Forty-eight tooth blocks were divided into four groups (n=12), based on storage media (SM): purified water (PW), artificial saliva (AS), natural saliva (NS), in situ (IS). Three whitening sessions were carried out using 35% hydrogen peroxide, with a week interval. Colour and KHN measurements were taken before the samples were placed in the SM (t1), after 24h in the SM (t2), and after 24h at the end of the bleaching treatment (t3). Two extra samples from each group were analysed using a scanning electron microscope (SEM). KHN results were analysed by PROC-MIXED and Tukey-Kramer test (α=0.05), and colour changes were evaluated using ΔL, Δa, Δb, ΔE between the different times Δ1(t1-t2), Δ2(t2-t3) using the Kruskal-Wallis test and Dunn's test (α=0.05). Significant statistical difference was noted in KHN at t3, with the lowest values found for PW. As for colour analysis in ΔE2 and Δb2, IS showed values that were statistically lower when compared to AS. Likewise, there were differences between PW and AS in relation to IS when evaluating ΔL2. In addition, NS showed similar values to IS. The storage conditions had different effects on the physical properties of bleached enamel. NS was the only SM that showed similar behaviour to IS. NS proved an effective SM in the protection and recovery of damage caused by bleaching and is a viable SM for in vitro studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Hybrid MD-Nernst Planck Model of Alpha-hemolysin Conductance Properties

NASA Technical Reports Server (NTRS)

Cozmuta, Ioana; O'Keefer, James T.; Bose, Deepak; Stolc, Viktor

2006-01-01

Motivated by experiments in which an applied electric field translocates polynucleotides through an alpha-hemolysin protein channel causing ionic current transient blockade, a hybrid simulation model is proposed to predict the conductance properties of the open channel. Time scales corresponding to ion permeation processes are reached using the Poisson-Nemst-Planck (PNP) electro-diffusion model in which both solvent and local ion concentrations are represented as a continuum. The diffusion coefficients of the ions (K(+) and Cl(-)) input in the PNP model are, however, calculated from all-atom molecular dynamics (MD). In the MD simulations, a reduced representation of the channel is used. The channel is solvated in a 1 M KCI solution, and an external electric field is applied. The pore specific diffusion coefficients for both ionic species are reduced 5-7 times in comparison to bulk values. Significant statistical variations (17-45%) of the pore-ions diffusivities are observed. Within the statistics, the ionic diffusivities remain invariable for a range of external applied voltages between 30 and 240mV. In the 2D-PNP calculations, the pore stem is approximated by a smooth cylinder of radius approx. 9A with two constriction blocks where the radius is reduced to approx. 6A. The electrostatic potential includes the contribution from the atomistic charges. The MD-PNP model shows that the atomic charges are responsible for the rectifying behaviour and for the slight anion selectivity of the a-hemolysin pore. Independent of the hierarchy between the anion and cation diffusivities, the anionic contribution to the total ionic current will dominate. The predictions of the MD-PNP model are in good agreement with experimental data and give confidence in the present approach of bridging time scales by combining a microscopic and macroscopic model.

Study on stabilities, thermophysical properties and natural convective heat transfer characteristics of TiO2-water nanofluids

NASA Astrophysics Data System (ADS)

Qi, Cong; Wan, Yong Liang; Wang, Gui Qing; Han, Dong Tai

2018-04-01

TiO2-water nanofluids with different mass fractions ( ω = 0.1 wt%, ω = 0.3 wt% and ω = 0.5 wt%) are prepared respectively, and the stabilities are studied by scanning electron microscope, transmission electron microscope, dynamic analysis method and settlement observation method. Additionally, thermophysical properties of nanofluids are discussed, and models of thermophysical properties are deduced. Then, an experimental installation and a two-phase lattice Boltzmann model for natural convection heat transfer are established in this paper and the effects of cavity ratio, heating power and nanoparticle mass fraction on heat transfer are discussed respectively. It can be obtained that the thermal conductivities of TiO2-water nanofluids can be improved by 5.23% to the utmost extent. However, the heat transfer can be enhanced by 34.2% in the maximum with the increase of nanoparticle mass fraction at the lowest heating power and the largest cavity ratio.

Microstructures and tribological properties of GLC coated 100Cr6 bearing steels

NASA Astrophysics Data System (ADS)

Kong, Yonghua; Chen, Qiao; Wang, Long

2017-11-01

Low friction and hard amorphous carbon films were fabricated on 100Cr6 bearing steels via the unbalanced magnetron sputtering method. This paper studied the effect of graphite-like carbon (GLC) coatings on the wear resistance of 100Cr6, which are widely used in textile rings. The microstructures of the GLC coatings were investigated using scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive Spectrometer (EDS) and Raman. A comparative analysis using a ball-on-disc tribometer was carried out on 100Cr6 bearing steels with GLC coatings and those that had chromium-electroplated coatings. It was demonstrated that the GLC films on 100Cr6 presented better tribological properties, and the corresponding wear mechanisms were investigated. The tribological properties of GLC films under cryogenic treatment (-196 °C), annealing at temperatures of 300 °C and 350 °C were characterized. It was revealed that the friction coefficients decreased after using three kinds of treatments above.

Structure and physico-mechanical properties of low temperature plasma treated electrospun nanofibrous scaffolds examined with atomic force microscopy.

PubMed

Chlanda, Adrian; Kijeńska, Ewa; Rinoldi, Chiara; Tarnowski, Michał; Wierzchoń, Tadeusz; Swieszkowski, Wojciech

2018-04-01

Electrospun nanofibrous scaffolds are willingly used in tissue engineering applications due to their tunable mechanical, chemical and physical properties. Additionally, their complex openworked architecture is similar to the native extracellular matrix of living tissue. After implantation such scaffolds should provide sufficient mechanical support for cells. Moreover, it is of crucial importance to ensure sterility and hydrophilicity of the scaffold. For this purpose, a low temperature surface plasma treatment can be applied. In this paper, we report physico-mechanical evaluation of stiffness and adhesive properties of electrospun mats after their exposition to low temperature plasma. Complex morphological and mechanical studies performed with an atomic force microscope were followed by scanning electron microscope imaging and a wettability assessment. The results suggest that plasma treatment can be a useful method for the modification of the surface of polymeric scaffolds in a desirable manner. Plasma treatment improves wettability of the polymeric mats without changing their morphology. Copyright © 2018 Elsevier Ltd. All rights reserved.

Site-specific acid-base properties of pholcodine and related compounds.

PubMed

Kovács, Z; Hosztafi, S; Noszál, B

2006-11-01

The acid-base properties of pholcodine, a cough-depressant agent, and related compounds including metabolites were studied by 1H NMR-pH titrations, and are characterised in terms of macroscopic and microscopic protonation constants. New N-methylated derivatives were also synthesized in order to quantitate site- and nucleus-specific protonation shifts and to unravel microscopic acid-base equilibria. The piperidine nitrogen was found to be 38 and 400 times more basic than its morpholine counterpart in pholcodine and norpholcodine, respectively. The protonation data show that the molecule of pholcodine bears an average of positive charge of 1.07 at physiological pH, preventing it from entering the central nervous system, a plausible reason for its lack of analgesic or addictive properties. The protonation constants of pholcodine and its derivatives are interpreted by comparing with related molecules of pharmaceutical interest. The pH-dependent relative concentrations of the variously protonated forms of pholcodine and morphine are depicted in distribution diagrams.

The Effects of Fluid Absorption on the Mechanical Properties of Joint Prostheses Components

NASA Astrophysics Data System (ADS)

Yarbrough, David; Viano, Ann

2010-02-01

Ultra-high-molecular-weight polyethylene (UHMWPE) is the material playing the role of cartilage in human prosthetic joints. Wear debris from UHMWPE is a common reason for joint arthroplasty failure, and the exact mechanism responsible for wear remains an area of investigation. In this study, the microstructure of UHMWPE was examined as a function of fluid absorption. Samples with varying exposure to e-beam radiation (as part of the manufacturing process) were soaked for forty days in saline or artificial synovial fluid, under zero or 100 lbs load. Samples were then tensile-tested according to ASTM D-3895. The post-stressed material was then examined by transmission electron microscopy to evaluate the molecular response to stress, which correlates with macroscopic mechanical properties. Three parameters of the crystalline lamellae were measured: thickness, stacking ratio, and alignment to stress direction. Results indicate that fluid absorption does affect the mechanical properties of UHMWPE at both the microscopic and microscopic levels. )

Laser-assisted manufacturing of super-insulation materials

NASA Astrophysics Data System (ADS)

Wang, Zhen; Zhang, Tao; Park, Byung Kyu; Lee, Woo Il; Hwang, David

2017-02-01

Being lightweight materials with good mechanical and thermal properties, hollow glass micro-particles (HGMPs) have been widely studied for multiple applications. In this study, it is shown that by using reduced binder fraction diluted in solvent, enables minimal contacts among the HGMPs assisted by a natural capillary trend, as confirmed by optical and electron microscope imaging. Such material architecture fabricated in a composite level proves to have enhanced thermal insulation performance through quantitative thermal conductivity measurement. Mechanical strength has also been evaluated in terms of particle-binder bonding by tensile test via in-situ microscope inspection. Effect of laser treatment was examined for further improvement of thermal and mechanical properties by selective binder removal and efficient redistribution of remaining binder components. The fabricated composite materials have potential applications to building insulation materials for their scalable manufacturing nature, improved thermal insulation performance and reasonable mechanical strength. Further studies are needed to understand mechanical and thermal properties of the resulting composites, and key fabrication mechanisms involved with laser treatment of complex multi-component and multi-phase systems.

Multiparametric, Longitudinal Optical Coherence Tomography Imaging Reveals Acute Injury and Chronic Recovery in Experimental Ischemic Stroke

PubMed Central

Srinivasan, Vivek J.; Mandeville, Emiri T.; Can, Anil; Blasi, Francesco; Climov, Mihail; Daneshmand, Ali; Lee, Jeong Hyun; Yu, Esther; Radhakrishnan, Harsha; Lo, Eng H.; Sakadžić, Sava; Eikermann-Haerter, Katharina; Ayata, Cenk

2013-01-01

Progress in experimental stroke and translational medicine could be accelerated by high-resolution in vivo imaging of disease progression in the mouse cortex. Here, we introduce optical microscopic methods that monitor brain injury progression using intrinsic optical scattering properties of cortical tissue. A multi-parametric Optical Coherence Tomography (OCT) platform for longitudinal imaging of ischemic stroke in mice, through thinned-skull, reinforced cranial window surgical preparations, is described. In the acute stages, the spatiotemporal interplay between hemodynamics and cell viability, a key determinant of pathogenesis, was imaged. In acute stroke, microscopic biomarkers for eventual infarction, including capillary non-perfusion, cerebral blood flow deficiency, altered cellular scattering, and impaired autoregulation of cerebral blood flow, were quantified and correlated with histology. Additionally, longitudinal microscopy revealed remodeling and flow recovery after one week of chronic stroke. Intrinsic scattering properties serve as reporters of acute cellular and vascular injury and recovery in experimental stroke. Multi-parametric OCT represents a robust in vivo imaging platform to comprehensively investigate these properties. PMID:23940761

Microwave absorption properties of a wave-absorbing coating employing carbonyl-iron powder and carbon black

NASA Astrophysics Data System (ADS)

Liu, Lidong; Duan, Yuping; Ma, Lixin; Liu, Shunhua; Yu, Zhen

2010-11-01

To prevent serious electromagnetic interference, a single-layer wave-absorbing coating employing complex absorbents composed of carbonyl-iron powder (CIP) and carbon black (CB) with epoxy resin as matrix was prepared. The morphologies of CIP and CB were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The electromagnetic parameters of CIP and CB were measured in the frequency range of 2-18 GHz by transmission/reflection technology, and the electromagnetic loss mechanisms of the two particles were discussed, respectively. The microwave absorption properties of the coatings were investigated by measuring reflection loss (RL) using arch method. The effects of CIP ratio, CB content and thickness on the microwave absorption properties were discussed, respectively. The results showed that the higher thickness, CIP or CB content could make the absorption band shift towards the lower frequency range. Significantly, the wave-absorbing coating could be applied in different frequency ranges according to actual demand by controlling the content of CIP or CB in composites.

Increasing Student Understanding of Microscope Optics by Building and Testing the Limits of Simple, Hand-Made Model Microscopes†

PubMed Central

Drace, Kevin; Couch, Brett; Keeling, Patrick J.

2012-01-01

The ability to effectively use a microscope to observe microorganisms is a crucial skill required for many disciplines within biology, especially general microbiology and cell biology. A basic understanding of the optical properties of light microscopes is required for students to use microscopes effectively, but this subject can also be a challenge to make personally interesting to students. To explore basic optical principles of magnification and resolving power in a more engaging and hands-on fashion, students constructed handmade lenses and microscopes based on Antony van Leeuwenhoek’s design using simple materials—paper, staples, glass, and adhesive putty. Students determined the power of their lenses using a green laser pointer to magnify a copper grid of known size, which also allowed students to examine variables affecting the power and resolution of a lens such as diameter, working distance, and wavelength of light. To assess the effectiveness of the laboratory’s learning objectives, four sections of a general microbiology course were given a brief pre-activity assessment quiz to determine their background knowledge on the subject. One week after the laboratory activity, students were given the same quiz (unannounced) under similar conditions. Students showed significant gains in their understanding of microscope optics. PMID:23653781

Inferring the background traffic arrival process in the Internet.

PubMed

Hága, Péter; Csabai, István; Vattay, Gábor

2009-12-01

Phase transition has been found in many complex interactivity systems. Complex networks are not exception either but there are quite few real systems where we can directly understand the emergence of this nontrivial behavior from the microscopic view. In this paper, we present the emergence of the phase transition between the congested and uncongested phases of a network link. We demonstrate a method to infer the background traffic arrival process, which is one of the key state parameters of the Internet traffic. The traffic arrival process in the Internet has been investigated in several studies, since the recognition of its self-similar nature. The statistical properties of the traffic arrival process are very important since they are fundamental in modeling the dynamical behavior. Here, we demonstrate how the widely used packet train technique can be used to determine the main properties of the traffic arrival process. We show that the packet train dispersion is sensitive to the congestion on the network path. We introduce the packet train stretch as an order parameter to describe the phase transition between the congested and uncongested phases of the bottleneck link in the path. We find that the distribution of the background traffic arrival process can be determined from the average packet train dispersion at the critical point of the system.

Comparison of cyclic fatigue resistance and bending properties of two reciprocating nickel-titanium glide path files.

PubMed

Özyürek, T; Uslu, G; Gündoğar, M; Yılmaz, K; Grande, N M; Plotino, G

2018-02-25

To compare the cyclic fatigue resistance and bending properties of R-Pilot and WaveOne Gold (WOG) Glider files, at intracanal temperature (35°C). Forty R-Pilot and 40 WOG Glider files were subjected to a cyclic fatigue resistance test (n = 20), calculating the time to fracture (TTF) in an artificial stainless steel canal. The length of the fractured file tips (FL) was also measured. The fracture surface of fragments was examined with a scanning electron microscope, and the cross-sectional area of the fractured surfaces was measured. Flexibility of the tested files (n = 20) was determined using 45° bending test. Data were analysed statistically using the Mann-Whitney U-test at 5% significance level. Time to fracture was significantly higher in the R-Pilot group compared to the WOG Glider (P < 0.05). There was no significant difference between groups for fracture length. The bending resistance of R-Pilot files was significantly greater than WOG Glider files (P < 0.05). A significant greater cyclic fatigue resistance was observed for R-Pilot files compared to WOG Glider instruments, although the bending resistance of WOG Glider files was lower. © 2018 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Cell Model Of A Disordered Solid

NASA Technical Reports Server (NTRS)

Peng, Steven T. J.; Landel, Robert F.; Moacanin, Jovan; Simha, Robert; Papazoglou, Elizabeth

1990-01-01

Elastic properties predicted from first principles. Paper discusses generalization of cell theory of disordered (non-crystaline) solid to include anisotropic stresses. Study part of continuing effort to understand macroscopic stress-and-strain properties of solid materials in terms of microscopic physical phenomena. Emphasis on derivation, from first principles, of bulk, shear, and Young's moduli of glassy material at zero absolute temperature.

Effect of endodontic irrigation with 1% sodium hypochlorite and 17% EDTA on primary teeth: a scanning electron microscope analysis.

PubMed

Ximenes, Marcos; Triches, Thaisa C; Beltrame, Ana Paula C A; Hilgert, Leandro A; Cardoso, Mariane

2013-01-01

This study evaluated the efficacy of 2 final irrigation solutions for removal of the smear layer (SL) from root canals of primary teeth, using scanning electron microscope (SEM) analysis. Thirty primary molars were selected and a single operator instrumented the canals. The initial irrigation was done with a 1% sodium hypochlorite (NaOCl) solution. After the preparation, the roots were randomly divided into 3 groups for final irrigation: Group 1, 1% NaOCl (n = 10); Group 2, 17% EDTA + 1% NaOCl (n = 10); and Group 3, 17% EDTA + saline solution (n = 10). The roots were prepared for SEM analysis (magnification 1000X). The photomicrographs were independently analyzed by 2 investigators with SEM experience, attributing scores to each root third in terms of SL removal. Kruskal-Wallis and Mann-Whitney tests revealed that there was no statistical difference between the groups (P = 0.489). However, a statistical difference was found (P < 0.05) in a comparison of root thirds, with the apical third having the worst results. Comparing the thirds within the same group, all canals showed statistical differences between the cervical and apical thirds (P < 0.05). The authors determined that no substance or association of substances were able to completely remove SL.

Index of A/T's in Science.

ERIC Educational Resources Information Center

Bonney, Catherine

This monograph presents an annotated index of auto-tutorial materials in science education available to middle and secondary schools in the Newark School District. Materials relevant to the study of the biological sciences enable the students to become more familiar with Biology Statistics, Cytology, Marine Field Trips, Use of Microscopes,…

Statistical and Microscopic Approach to Gas Phase Chemical Kinetics.

ERIC Educational Resources Information Center

Perez, J. M.; Quereda, R.

1983-01-01

Describes advanced undergraduate laboratory exercise examining the dependence of the rate constants and the instantaneous concentrations with the nature and energy content in a gas-phase complex reaction. Computer program (with instructions and computation flow charts) used with the exercise is available from the author. (Author/JN)

Mechanical characterization of metallic nanowires by using a customized atomic microscope

NASA Astrophysics Data System (ADS)

Celik, Emrah

A new experimental method to characterize the mechanical properties of metallic nanowires is introduced. An accurate and fast mechanical characterization of nanowires requires simultaneous imaging and testing of nanowires. However, there exists no practical experimental procedure in the literature that provides a quantitative mechanical analysis and imaging of the nanowire specimens during mechanical testing. In this study, a customized atomic force microscope (AFM) is placed inside a scanning electron microscope (SEM) in order to locate the position of the nanowires. The tip of the atomic force microscope cantilever is utilized to bend and break the nanowires. The nanowires are prepared by electroplating of nickel ions into the nanoscale pores of the alumina membranes. Force versus bending displacement responses of these nanowires are measured experimentally and then compared against those of the finite element analysis and peridynamic simulations to extract their mechanical properties through an inverse approach. The average elastic modulus of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, varies between 220 GPa and 225 GPa. The elastic modulus of bulk nickel published in the literature is comparable to that of nickel nanowires. This observation agrees well with the previous findings on nanowires stating that the elastic modulus of nanowires with diameters over 100nm is similar to that of bulk counterparts. The average yield stress of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, is found to be between 3.6 GPa to 4.1 GPa. The average value of yield stress of nickel nanowires with 250nm diameter is significantly higher than that of bulk nickel. Higher yield stress of nickel nanowires observed in this study can be explained by the lower defect density of nickel nanowires when compared to their bulk counterparts. Deviation in the extracted mechanical properties is investigated by analyzing the major sources of uncertainty in the experimental procedure. The effects of the nanowire orientation, the loading position and the nanowire diameter on the mechanical test results are quantified using ANSYS simulations. Among all of these three sources of uncertainty investigated, the nanowire diameter has been found to have the most significant effect on the extracted mechanical properties.

Understanding gas-surface interactions from direct force measurements using a specialized torsion balance

NASA Technical Reports Server (NTRS)

Cook, S. R.; Hoffbauer, M. A.

1996-01-01

The first comprehensive measurements of the magnitude and direction of the forces exerted on surfaces by molecular beams are discussed and used to obtain information about the microscopic properties of the gas-surface interactions. This unique approach is not based on microscopic measurements of the scattered molecules. The reduced force coefficients are introduced as a new set of parameters that completely describe the macroscopic average momentum transfer to a surface by an incident molecular beam. By using a specialized torsion balance and molecular beams of N2, CO, CO2, and H2, the reduced force coefficients are determined from direct measurements of the force components exerted on surface of a solar panel array material, Kapton, SiO2-coated Kapton, and Z-93 as a function of the angle of incidence ranging from 0 degrees to 85 degrees. The absolute flux densities of the molecular beams were measured using a different torsion balance with a beam-stop that nullified the force of the scattered molecules. Standard time-of-flight techniques were used to determine the flux-weighted average velocities of the various molecular beams ranging from 1600 m/s to 4600 m/s. The reduced force coefficients can be used to directly obtain macroscopic average properties of the scattered molecules, such as the flux-weighted average velocity and translational energy, that can then be used to determine microscopic details concerning gas-surface interactions without the complications associated with averaging microscopic measurements.

Effect of Nickel Contents on the Microstructure and Mechanical Properties for Low-Carbon Bainitic Weld Metals

NASA Astrophysics Data System (ADS)

Mao, Gaojun; Cao, Rui; Yang, Jun; Jiang, Yong; Wang, Shuai; Guo, Xili; Yuan, Junjun; Zhang, Xiaobo; Chen, Jianhong

2017-05-01

Multi-pass weld metals were deposited on Q345 base steel using metal powder-flux-cored wire with various Ni contents to investigate the effects of the Ni content on the weld microstructure and property. The types of the microstructures were identified by optical microscope, scanning electron microscope, transmission electron microscope, and micro-hardness tests. As a focusing point, the lath bainite and lath martensite were distinguished by their compositions, morphologies, and hardness. In particular, a number of black plane facets appearing between lath bainite or lath martensite packets were characterized by laser scanning confocal microscope. The results indicated that with the increase in Ni contents in the range of 0, 2, 4, and 6%, the microstructures in the weld-deposited metal were changed from the domination of the granular bainite to the majority of the lath bainite and/or the lath martensite and the micro-hardness of the weld-deposited metal increased. Meanwhile, the average width of columnar grain displays a decreasing trend and prior austenite grain size decreases while increases with higher Ni content above 4%. Yield strength and ultimate tensile strength decrease, while the reduction in fracture area increases with the decreasing Ni mass fraction and the increasing test temperature, respectively. And poor yield strength in Ni6 specimen can be attributed to elements segregation caused by weld defect. Finally, micro-hardness distribution in correspondence with specimens presents as a style of cloud-map.

Photonic Microhand with Autonomous Action.

PubMed

Martella, Daniele; Nocentini, Sara; Nuzhdin, Dmitry; Parmeggiani, Camilla; Wiersma, Diederik S

2017-11-01

Grabbing and holding objects at the microscale is a complex function, even for microscopic living animals. Inspired by the hominid-type hand, a microscopic equivalent able to catch microelements is engineered. This microhand is light sensitive and can be either remotely controlled by optical illumination or can act autonomously and grab small particles on the basis of their optical properties. Since the energy is delivered optically, without the need for wires or batteries, the artificial hand can be shrunk down to the micrometer scale. Soft material is used, in particular, a custom-made liquid-crystal network that is patterned by a photolithographic technique. The elastic reshaping properties of this material allow finger movement, using environmental light as the only energy source. The hand can be either controlled externally (via the light field), or else the conditions in which it autonomously grabs a particle in its vicinity can be created. This microrobot has the unique feature that it can distinguish between particles of different colors and gray levels. The realization of this autonomous hand constitutes a crucial element in the development of microscopic creatures that can perform tasks without human intervention and self-organized automation at the micrometer scale. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

NASA Astrophysics Data System (ADS)

Yui, Hiroharu; Banno, Motohiro

2018-01-01

In this article, we review the development of scientific instruments for obtaining information on the evolution of physical properties and chemical species of solution plasma (SP). When a pulsed high voltage is applied between electrodes immersed in an aqueous solution, SP is formed in water vapor bubbles transiently generated in the solution under atmospheric pressure. To clarify how SP emerges in water vapor bubbles and is sustained in solutions, an instrument with micrometer spatial resolution and nanosecond temporal resolution is required. To meet these requirements, a microscopic system with a custom-made optical discharge cell was newly developed, where the working distance between the SP and the microscopic objective lens was minimized. A hollow electrode equipped in the discharge cell also enabled us to control the chemical composition in water vapor bubbles. To study the spatial and temporal evolutions of chemical species in micrometer and nano- to microsecond regions, a streak camera with a spectrometer and a CCD detector with a time-gated electronic device were combined with the microscope system. The developed instrument is expected to contribute to providing a new means of developing new schemes for chemical reactions and material syntheses.

Microscopic structure of liquid 1-1-1-2-tetrafluoroethane (R134a) from Monte Carlo simulation.

PubMed

Do, Hainam; Wheatley, Richard J; Hirst, Jonathan D

2010-10-28

1-1-1-2-tetrafluoroethane (R134a) is one of the most commonly used refrigerants. Its thermophysical properties are important for evaluating the performance of refrigeration cycles. These can be obtained via computer simulation, with an insight into the microscopic structure of the liquid, which is not accessible to experiment. In this paper, vapour-liquid equilibrium properties of R134a and its liquid microscopic structure are investigated using coupled-decoupled configurational-bias Monte Carlo simulation in the Gibbs ensemble, with a recent potential [J. Phys. Chem. B 2009, 113, 178]. We find that the simulations agree well with the experimental data, except at the vicinity of the critical region. Liquid R134a packs like liquid argon, with a coordination number in the first solvation shell of 12 at 260 K. The nearest neighbours prefer to be localized in three different spaces around the central molecule, in such a manner that the dipole moments are in a parallel alignment. Analysis of the pair interaction energy shows clear association of R134a molecules, but no evidence for C-HF type hydrogen bonding is found. The above findings should be of relevance to a broad range of fluoroalkanes.

On the application of accelerated molecular dynamics to liquid water simulations.

PubMed

de Oliveira, César Augusto F; Hamelberg, Donald; McCammon, J Andrew

2006-11-16

Our group recently proposed a robust bias potential function that can be used in an efficient all-atom accelerated molecular dynamics (MD) approach to simulate the transition of high energy barriers without any advance knowledge of the potential-energy landscape. The main idea is to modify the potential-energy surface by adding a bias, or boost, potential in regions close to the local minima, such that all transitions rates are increased. By applying the accelerated MD simulation method to liquid water, we observed that this new simulation technique accelerates the molecular motion without losing its microscopic structure and equilibrium properties. Our results showed that the application of a small boost energy on the potential-energy surface significantly reduces the statistical inefficiency of the simulation while keeping all the other calculated properties unchanged. On the other hand, although aggressive acceleration of the dynamics simulation increases the self-diffusion coefficient of water molecules greatly and dramatically reduces the correlation time of the simulation, configurations representative of the true structure of liquid water are poorly sampled. Our results also showed the strength and robustness of this simulation technique, which confirm this approach as a very useful and promising tool to extend the time scale of the all-atom simulations of biological system with explicit solvent models. However, we should keep in mind that there is a compromise between the strength of the boost applied in the simulation and the reproduction of the ensemble average properties.

Living Matter Observations with a Novel Hyperspectral Supercontinuum Confocal Microscope for VIS to Near-IR Reflectance Spectroscopy

PubMed Central

Bertani, Francesca R.; Ferrari, Luisa; Mussi, Valentina; Botti, Elisabetta; Costanzo, Antonio; Selci, Stefano

2013-01-01

A broad range hyper-spectroscopic microscope fed by a supercontinuum laser source and equipped with an almost achromatic optical layout is illustrated with detailed explanations of the design, implementation and data. The real novelty of this instrument, a confocal spectroscopic microscope capable of recording high resolution reflectance data in the VIS-IR spectral range from about 500 nm to 2.5 μm wavelengths, is the possibility of acquiring spectral data at every physical point as defined by lateral coordinates, X and Y, as well as at a depth coordinate, Z, as obtained by the confocal optical sectioning advantage. With this apparatus we collect each single scanning point as a whole spectrum by combining two linear spectral detector arrays, one CCD for the visible range, and one InGaAs infrared array, simultaneously available at the sensor output channel of the home made instrument. This microscope has been developed for biomedical analysis of human skin and other similar applications. Results are shown illustrating the technical performances of the instrument and the capability in extracting information about the composition and the structure of different parts or compartments in biological samples as well as in solid statematter. A complete spectroscopic fingerprinting of samples at microscopic level is shown possible by using statistical analysis on raw data or analytical reflectance models based on Abelés matrix transfer methods. PMID:24233077

Zoom microscope objective using electrowetting lenses.

PubMed

Li, Lei; Wang, Di; Liu, Chao; Wang, Qiong-Hua

2016-02-08

We report a zoom microscope objective which can achieve continuous zoom change and correct the aberrations dynamically. The objective consists of three electrowetting liquid lenses and two glass lenses. The magnification is changed by applying voltages on the three electrowetting lenses. Besides, the three electrowetting liquid lenses can play a role to correct the aberrations. A digital microscope based on the proposed objective is demonstrated. We analyzed the properties of the proposed objective. In contrast to the conventional objectives, the proposed objective can be tuned from ~7.8 × to ~13.2 × continuously. For our objective, the working distance is fixed, which means no movement parts are needed to refocus or change its magnification. Moreover, the zoom objective can be dynamically optimized for a wide range of wavelength. Using such an objective, the fabrication tolerance of the optical system is larger than that of a conventional system, which can decrease the fabrication cost. The proposed zoom microscope objective cannot only take place of the conventional objective, but also has potential application in the 3D microscopy.

Towards native-state imaging in biological context in the electron microscope

PubMed Central

Weston, Anne E.; Armer, Hannah E. J.

2009-01-01

Modern cell biology is reliant on light and fluorescence microscopy for analysis of cells, tissues and protein localisation. However, these powerful techniques are ultimately limited in resolution by the wavelength of light. Electron microscopes offer much greater resolution due to the shorter effective wavelength of electrons, allowing direct imaging of sub-cellular architecture. The harsh environment of the electron microscope chamber and the properties of the electron beam have led to complex chemical and mechanical preparation techniques, which distance biological samples from their native state and complicate data interpretation. Here we describe recent advances in sample preparation and instrumentation, which push the boundaries of high-resolution imaging. Cryopreparation, cryoelectron microscopy and environmental scanning electron microscopy strive to image samples in near native state. Advances in correlative microscopy and markers enable high-resolution localisation of proteins. Innovation in microscope design has pushed the boundaries of resolution to atomic scale, whilst automatic acquisition of high-resolution electron microscopy data through large volumes is finally able to place ultrastructure in biological context. PMID:19916039

Apparatus and methods for controlling electron microscope stages

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duden, Thomas

Methods and apparatus for generating an image of a specimen with a microscope (e.g., TEM) are disclosed. In one aspect, the microscope may generally include a beam generator, a stage, a detector, and an image generator. A plurality of crystal parameters, which describe a plurality of properties of a crystal sample, are received. In a display associated with the microscope, an interactive control sphere based at least in part on the received crystal parameters and that is rotatable by a user to different sphere orientations is presented. The sphere includes a plurality of stage coordinates that correspond to a pluralitymore » of positions of the stage and a plurality of crystallographic pole coordinates that correspond to a plurality of polar orientations of the crystal sample. Movement of the sphere causes movement of the stage, wherein the stage coordinates move in conjunction with the crystallographic coordinates represented by pole positions so as to show a relationship between stage positions and the pole positions.« less

Cleft Lip and Palate Repair Using a Surgical Microscope.

PubMed

Kato, Motoi; Watanabe, Azusa; Watanabe, Shoji; Utsunomiya, Hiroki; Yokoyama, Takayuki; Ogishima, Shinya

2017-11-01

Cleft lip and palate repair requires a deep and small surgical field and is usually performed by surgeons wearing surgical loupes. Surgeons with loupes can obtain a wider surgical view, although headlights are required for the deepest procedures. Surgical microscopes offer comfort and a clear and magnification-adjustable surgical site that can be shared with the whole team, including observers, and easily recorded to further the education of junior surgeons. Magnification adjustments are convenient for precise procedures such as muscle dissection of the soft palate. We performed a comparative investigation of 18 cleft operations that utilized either surgical loupes or microscopy. Paper-based questionnaires were completed by staff nurses to evaluate what went well and what could be improved in each procedure. The operating time, complication rate, and scores of the questionnaire responses were statistically analyzed. The operating time when microscopy was used was not significantly longer than when surgical loupes were utilized. The surgical field was clearly shared with surgical assistants, nurses, anesthesiologists, and students via microscope-linked monitors. Passing surgical equipment was easier when sharing the surgical view, and preoperative microscope preparation did not interfere with the duties of the staff nurses. Surgical microscopy was demonstrated to be useful during cleft operations.

Mineral Trioxide Aggregate and Portland Cement for Direct Pulp Capping in Dog: A Histopathological Evaluation

PubMed Central

Bidar, Maryam; Naghavi, Neda; Mohtasham, Nooshin; Sheik-Nezami, Mahshid; Fallahrastegar, Amir; Afkhami, Farzaneh; Attaran Mashhadi, Negin; Nargesi, Iman

2014-01-01

Background and aims. Mineral trioxide aggregate and calcium hydroxide are considered the gold standard pulp-capping materials. Recently, Portland cement has been introduced with properties similar to those of mineral trioxide aggregate. Histopathological effects of direct pulp capping using mineral trioxide aggregate and Portland cements on dog dental pulp tissue were evaluated in the present study. Materials and methods. This histopatological study was carried out on 64 dog premolars. First, the pulp was exposed with a sterile bur. Then, the exposed pulp was capped with white or gray mineral trioxide aggregates and white or gray Portland cements in each quadrant and sealed with glass-ionomer. The specimens were evaluated under a light microscope after 6 months. Statistical analysis was carried out using Kruskal-Wallis test. Statistical significance was defined at α=5%. Results. There was no acute inflammation in any of the specimens. Chronic inflammation in white and gray mineral trioxide aggregates and white and gray Portland cements was reported to be 45.5%, 27.3%, 57.1% and 34.1%, respectively. Although the differences were not statistically significant, severe inflammation was observed mostly adjacent to white mineral trioxide aggregate. The largest extent of increased vascularization (45%) and the least increase in fibrous tissue were observed adjacent to white mineral trioxide aggregate, with no significant differences. In addition, the least calcified tissue formed adjacent to white mineral trioxide aggregate, although the difference was not significant. Conclusion. The materials used in this study were equally effective as pulp protection materials following direct pulp capping in dog teeth. PMID:25346831

Study on mechanical properties and damage behaviors of Kevlar fiber reinforced epoxy composites by digital image correlation technique under optical microscope

NASA Astrophysics Data System (ADS)

Gao, Xiang; Shao, Wenquan; Ji, Hongwei

2010-10-01

Kevlar fiber-reinforced epoxy (KFRE) composites are widely used in the fields of aerospace, weapon, shipping, and civil industry, due to their outstanding capabilities. In this paper, mechanical properties and damage behaviors of KFRE laminate (02/902) were tested and studied under tension condition. To precisely measure the tensile mechanical properties of the material and investigate its micro-scale damage evolution, a micro-image measuring system with in-situ tensile device was designed. The measuring system, by which the in-situ tensile test can be carried out and surface morphology evolution of the tensile specimen can be visually monitored and recorded during the process of loading, includes an ultra-long working distance zoom microscope and a in-situ tensile loading device. In this study, a digital image correlation method (DICM) was used to calculate the deformation of the tensile specimen under different load levels according to the temporal series images captured by an optical microscope and CCD camera. Then, the elastic modulus and Poisson's ratio of the KFRE was obtained accordingly. The damage progresses of the KFRE laminates were analyzed. Experimental results indicated that: (1) the KFRE laminate (02/902) is almost elastic, its failure mode is brittle tensile fracture.(2) Mechanical properties parameters of the material are as follows: elastic modulus is 14- 16GPa, and tensile ultimate stress is 450-480 Mpa respectively. (3) The damage evolution of the material is that cracks appear in epoxy matrix firstly, then, with the increasing of the tensile loading, matrix cracks add up and extend along a 45° angle direction with tensile load. Furthermore, decohesion between matrix and fibers as well as delamination occurs. Eventually, fibers break and the material is damaged.

Microscopic, Macroscopic, and Megascopic Melts: a simple model to synthesize simulation, spectroscopy, shock, and sink/float constraints on silicate melts and magma oceans

NASA Astrophysics Data System (ADS)

Asimow, P. D.; Thomas, C.; Wolf, A. S.

2012-12-01

Silicate melts are the essential agents of planetary differentiation and evolution. Their phase relations, element partitioning preferences, density, and transport properties determine the fates of heat and mass flow in the high-temperature interior of active planets. In the early Earth and in extrasolar super-Earth-mass terrestrial planets it is these properties at very high pressure (> 100 GPa) that control the evolution from possible magma oceans to solid-state convecting mantles. Yet these melts are complex, dynamic materials that present many challenges to experimental, theoretical, and computational understanding or prediction of their properties. There has been encouraging convergence among various approaches to understanding the structure and dynamics of silicate melts at multiple scales: nearest- and next-nearest neighbor structural information is derived from spectroscopic techniques such as high-resolution multinuclear NMR; first-principles molecular dynamics probe structure and dynamics at scales up to hundreds of atoms; Archimedean, ultrasonic, sink/float, and shock wave methods probe macroscopic properties (and occasionally dynamics); and deformation and diffusion experiments probe dynamics at macroscopic scale and various time scales. One challenge that remains to integrating all this information is a predictive model of silicate liquid structure that agrees with experiments and simulation both at microscopic and macroscopic scale. In addition to our efforts to collect macroscopic equation of state data using shock wave methods across ever-wider ranges of temperature, pressure, and composition space, we have introduced a simple model of coordination statistics around cations that can form the basis of a conceptual and predictive link across scales and methods. This idea is explored in this presentation specifically with regard to the temperature dependence of sound speed in ultramafic liquids. This is a highly uncertain quantity and yet it is key, in many models, to extrapolating the equation of state up or down temperature to geophysically relevant conditions. Ultrasonic data on felsic to basaltic melts, across a fairly narrow temperature range from their liquidi to ≤1650 °C, suggest either no temperature dependence or sound speeds that increase with temperature. Simulations, conducted at much higher temperature to obtain relaxation, suggest a strong decrease in sound speed with temperature. Our shock wave data on Mg2SiO4 liquid at 2000 °C yield a sound speed significantly lower than that predicted from data on less mafic liquids collected at lower temperatures where Mg2SiO4 liquid is not stable. The same shock method applied to melt compositions that are stable at 1300-1550 °C, however, yields sound speeds comparable to the ultrasonic results. Although each of these methods has its shortcomings, we show that considerable insight can be obtained in the context of a predictive model of Mg2+ and Si4+ coordination statistics as functions of temperature and pressure. We suggest that this can explain the difference between results obtained at ordinary upper mantle magmatic temperatures and those expected for magma oceans.

Investigation of the structural, surface, optical and electrical properties of the Indium doped CuxO thin films deposited by a thermionic vacuum arc

NASA Astrophysics Data System (ADS)

Musaoğlu, Caner; Pat, Suat; Özen, Soner; Korkmaz, Şadan; Mohammadigharehbagh, Reza

2018-03-01

In this study, investigation of some physical properties of In-doped CuxO thin films onto amorphous glass substrates were done. The thin films were depsoied by thermionic vacuum arc technique (TVA). TVA technique gives a thin film with lower precursor impurity according to the other chemical and physical depsoition methods. The microstructural properties of the produced thin films was determined by x-ray diffraction device (XRD). The thickness values were measured as to be 30 nm and 60 nm, respectively. The miller indices of the thin films’ crystalline planes were determined as to be Cu (111), CuO (\\bar{1} 12), CuInO2 (107) and Cu2O (200), Cu (111), CuO (\\bar{1} 12), CuO (\\bar{2} 02), CuInO2 (015) for sample C1 and C2, respectively. The produced In-doped CuO thin films are in polycrystalline structure. The surface properties of produced In doped CuO thin films were determined by using an atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) tools. The optical properties of the In doped CuO thin films were determined by UV–vis spectrophotometer, interferometer, and photoluminescence devices. p-type semiconductor thin film was obtained by TVA depsoition.

Large scale ZnTe nanostructures on polymer micro patterns via capillary force photolithography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florence, S. Sasi, E-mail: sshanmugaraj@jazanu.edu.sa; Can, N.; Adam, H.

2016-06-10

A novel approach to prepare micro patterns ZnTe nanostructures on Si (100) substrate using thermal evaporation is proposed by capillary Force Lithography (CFL) technique on a self-assembled sacrificial Polystyrene mask. Polystyrene thin films on Si substrates are used to fabricate surface micro-relief patterns. ZnTe nanoparticles have been deposited by thermal evaporation method. The deposited ZnTe nanoparticles properties were assessed by Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM). SEM studies indicated that the particles are uniform in size and shape, well dispersed and spherical in shape. This study reports the micro-arrays of ZnTe nanoparticles on a self-assembled sacrificial PS maskmore » using a capillary flow photolithography process which showed excellent, morphological properties which can be used in photovoltaic devices for anti-reflection applications.« less

Few layered vanadyl phosphate nano sheets-MWCNT hybrid as an electrode material for supercapacitor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, Shibsankar; De, Sukanta, E-mail: sukanta.physics@presiuniv.ac.in

It have been already seen that 2-dimensional nano materials are the suitable choice for the supercapacitor application due to their large specific surface area, electrochemical active sites, micromechanical flexibility, expedite ion migration channel properties. Free standing hybrid films of functionalized MWCNT (– COOH group) and α-Vanadyl phosphates (VOPO{sub 4}2H{sub 2}O) are prepared by vacuum filtering. The surface morphology and microstructure of the samples are studied by transmission electron microscope, field emission scanning electron microscope, XRD, Electrochemical properties of hybrid films have been investigated systematically in 1M Na{sub 2}SO{sub 4} aqueous electrolyte. The hybrid material exhibits a high specific capacitance 236more » F/g with high energy density of 65.6 Wh/Kg and a power density of 1476 W/Kg.« less

Light Microscopy Module: An On-Orbit Microscope Planned for the Fluids and Combustion Facility on the International Space Station

NASA Technical Reports Server (NTRS)

Doherty, Michael P.; Motil, Susan M.; Snead, John H.; Griffin, DeVon W.

2001-01-01

The Light Microscopy Module (LMM) is planned as a fully remotely controllable on-orbit microscope subrack facility, allowing flexible scheduling and control of fluids and biology experiments within NASA Glenn Research Center's Fluids and Combustion Facility on the International Space Station. Within the Fluids and Combustion Facility, four fluids physics experiments will utilize an instrument built around a light microscope. These experiments are the Constrained Vapor Bubble experiment (Peter C. Wayner of Rensselaer Polytechnic Institute), the Physics of Hard Spheres Experiment-2 (Paul M. Chaikin of Princeton University), the Physics of Colloids in Space-2 experiment (David A. Weitz of Harvard University), and the Low Volume Fraction Colloidal Assembly experiment (Arjun G. Yodh of the University of Pennsylvania). The first experiment investigates heat conductance in microgravity as a function of liquid volume and heat flow rate to determine, in detail, the transport process characteristics in a curved liquid film. The other three experiments investigate various complementary aspects of the nucleation, growth, structure, and properties of colloidal crystals in microgravity and the effects of micromanipulation upon their properties. Key diagnostic capabilities for meeting the science requirements of the four experiments include video microscopy to observe sample features including basic structures and dynamics, interferometry to measure vapor bubble thin film thickness, laser tweezers for colloidal particle manipulation and patterning, confocal microscopy to provide enhanced three-dimensional visualization of colloidal structures, and spectrophotometry to measure colloidal crystal photonic properties.

The statistical average of optical properties for alumina particle cluster in aircraft plume

NASA Astrophysics Data System (ADS)

Li, Jingying; Bai, Lu; Wu, Zhensen; Guo, Lixin

2018-04-01

We establish a model for lognormal distribution of monomer radius and number of alumina particle clusters in plume. According to the Multi-Sphere T Matrix (MSTM) theory, we provide a method for finding the statistical average of optical properties for alumina particle clusters in plume, analyze the effect of different distributions and different detection wavelengths on the statistical average of optical properties for alumina particle cluster, and compare the statistical average optical properties under the alumina particle cluster model established in this study and those under three simplified alumina particle models. The calculation results show that the monomer number of alumina particle cluster and its size distribution have a considerable effect on its statistical average optical properties. The statistical average of optical properties for alumina particle cluster at common detection wavelengths exhibit obvious differences, whose differences have a great effect on modeling IR and UV radiation properties of plume. Compared with the three simplified models, the alumina particle cluster model herein features both higher extinction and scattering efficiencies. Therefore, we may find that an accurate description of the scattering properties of alumina particles in aircraft plume is of great significance in the study of plume radiation properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naulleau, Patrick; Mochi, Iacopo; Goldberg, Kenneth A.

Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modelingmore » software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes rou tinely used in the synchrotron community.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naulleau, Patrick P.; Mochi, Iacopo; Goldberg, Kenneth A.

Defect free masks remain one of the most significant challenges facing the commercialization of extreme ultraviolet (EUV) lithography. Progress on this front requires high-performance wavelength-specific metrology of EUV masks, including high-resolution and aerial-image microscopy performed near the 13.5 nm wavelength. Arguably the most cost-effective and rapid path to proliferating this capability is through the development of Fresnel zoneplate-based microscopes. Given the relative obscurity of such systems, however, modeling tools are not necessarily optimized to deal with them and their imaging properties are poorly understood. Here we present a modeling methodology to analyze zoneplate microscopes based on commercially available optical modelingmore » software and use the technique to investigate the imaging performance of an off-axis EUV microscope design. The modeling predicts that superior performance can be achieved by tilting the zoneplate, making it perpendicular to the chief ray at the center of the field, while designing the zoneplate to explicitly work in that tilted plane. Although the examples presented here are in the realm of EUV mask inspection, the methods described and analysis results are broadly applicable to zoneplate microscopes in general, including full-field soft-x-ray microscopes routinely used in the synchrotron community.« less

Impact of Microscope-Integrated OCT on Ophthalmology Resident Performance of Anterior Segment Surgical Maneuvers in Model Eyes.

PubMed

Todorich, Bozho; Shieh, Christine; DeSouza, Philip J; Carrasco-Zevallos, Oscar M; Cunefare, David L; Stinnett, Sandra S; Izatt, Joseph A; Farsiu, Sina; Mruthyunjaya, Privthi; Kuo, Anthony N; Toth, Cynthia A

2016-07-01

The integration of swept-source optical coherence tomography (SS-OCT) into the operating microscope enables real-time, tissue-level three-dimensional (3D) imaging to aid in ophthalmic microsurgery. In this prospective randomized controlled study, we evaluated the impact of SS microscope-integrated OCT (MI-OCT) on ophthalmology residents' performance of ophthalmic microsurgical maneuvers. Fourteen ophthalmology residents from a single institution were stratified by year of training and randomized to perform four anterior segment surgical maneuvers on porcine eyes with (MI-OCT+) or without (MI-OCT-) direct intraoperative OCT guidance. Subsequently, both groups repeated the same maneuvers without MI-OCT feedback to test whether initial MI-OCT experience affected subsequent surgical performance. Finally, the MI-OCT- group was crossed over and allowed to repeat the same maneuvers with direct MI-OCT guidance. Each resident completed a survey at the completion of the study. With direct MI-OCT feedback, residents demonstrated enhanced performance in depth-based anterior segment maneuvers (corneal suture passes at 50% and 90% depth and corneal laceration repair) compared with the residents operating without MI-OCT. Microscope-integrated OCT+ residents continued to outperform the controls when both groups subsequently operated without MI-OCT. For clear corneal wound geometry, there was no statistically significant effect of MI-OCT as applied in this study. Overall, the resident surgeons rated their subjective experience of using MI-OCT very favorably. Microscope-integrated OCT feedback enhances performance of ophthalmology residents in select anterior segment surgical maneuvers. Microscope-integrated OCT represents a valuable tool in the surgical education of ophthalmology residents.

Model of cohesive properties and structural phase transitions in non-metallic solids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Majewski, J.A.; Vogl, P.

1986-01-01

We have developed a simple, yet microscopic and universal model for cohesive properties of solids. This model explains the physical mechanisms determining the chemical and predicts semiquantitatively static and dynamic cohesive properties. It predicts a substantial softening of the long-wavelength transverse optical phonons across the pressure induced phase transition from the zincblenda to rocksalt structure in II-VI compounds. The origin of this softening is shown to be closely related to ferroelectricity.

Transport Properties of Complex Oxides: New Ideas and Insights from Theory and Simulation

NASA Astrophysics Data System (ADS)

Benedek, Nicole

Complex oxides are one of the largest and most technologically important materials families. The ABO3 perovskite oxides in particular display an unparalleled variety of physical properties. The microscopic origin of these properties (how they arise from the structure of the material) is often complicated, but in many systems previous research has identified simple guidelines or `rules of thumb' that link structure and chemistry to the physics of interest. For example, the tolerance factor is a simple empirical measure that relates the composition of a perovskite to its tendency to adopt a distorted structure. First-principles calculations have shown that the tendency towards ferroelectricity increases systematically as the tolerance factor of the perovskite decreases. Can we uncover a similar set of simple guidelines to yield new insights into the ionic and thermal transport properties of perovskites? I will discuss recent research from my group on the link between crystal structure and chemistry, soft phonons and ionic transport in a family of layered perovskite oxides, the Ln2NiO4+δ Ruddlesden-Popper phases. In particular, we show how the lattice dynamical properties of these materials (their tendency to undergo certain structural distortions) can be correlated with oxide ion transport properties. Ultimately, we seek new ways to understand the microscopic origins of complex transport processes and to develop first-principles-based design rules for new materials based on our understanding.

Comparative analysis of endodontic smear layer removal efficacy of 17% ethylenediaminetetraacetic acid, 7% maleic acid, and 2% chlorhexidine using scanning electron microscope: An in vitro study.

PubMed

Attur, Kailash; Joy, Mathew T; Karim, Riyas; Anil Kumar, V J; Deepika, C; Ahmed, Haseena

2016-08-01

The aim of the present study was to evaluate the efficiency of different endodontic irrigants in the removal of smear layer through scanning electron microscopic image analysis. The present in vitro study was carried out on 45 single-rooted extracted human mandibular premolar teeth with single canal and complete root formation. Teeth were randomly assigned to three groups with 15 teeth in each group. Group I samples were irrigated with 17% ethylenediaminetetraacetic (EDTA) irrigation, Group II with 7% maleic acid irrigation, and Group III with 2% chlorhexidine irrigation. Scanning electron microscope evaluation was done for the assessment of smear layer removal in the coronal, middle, and apical thirds. Comparison of the smear layer removal between the three different groups was done by Kruskal-Wallis test, followed by Mann-Whitney U test for comparing individual groups. A P value less than 0.05 was considered to be statistically significant. Statistically significant difference was seen between the two test groups (17% EDTA vs. 7% maleic acid and 17% EDTA vs. 2% chlorhexidine) in smear layer removal at coronal, middle, and apical thirds of the root canal. The most efficient smear layer removal was seen in Group I with 17% EDTA irrigation compared with other groups (P < 0.05) and the least by 2% chlorhexidine. The present study shows that 17% EDTA efficiently removes the smear layer from root canal walls.

A scanning electron microscopic study to evaluate the efficacy of NaviTip FX in removing the canal debris during root canal preparation: an in vitro study.

PubMed

Chandra, Vinay; Gandi, Padma; Shivanna, Anil Kumar; Srinivas, Siva; Himgiri, S; Nischith, K G

2013-07-01

To evaluate the efficacy of NaviTip FX in removing the canal debris during root canal preparation using scanning electron microscopic study. Thirty single rooted teeth with completely formed apices were used in this study. Standard endodontic access cavity preparations were performed. Then the teeth were randomly divided into two groups: groups 1 and 2 of 15 teeth each group. For group 1, NaviTip FX (brush covered needle) was used to irrigate the canal with 5.25% sodium hypochlorite after each instrument use. For group 2, NaviTip (brushless needle) was used for irrigation following each instrument use. ProTaper rotary files were used for the canal preparation. The teeth were then cleaned and dried before splitting them into two halves. The half with most visible part of the apex was used for scanning electron microscopic evaluation. The results were statistically analyzed using the Mann-Whitney U-test at significance level p < 0.005. The mean values for coronal and middle third of group 1 showed lower debris scores than group 2 and this difference was statistically significant at a p-value 0.01 and 0.05 respectively, but no significance difference between them at the apical third at a p-value of < 0.05. The NaviTip FX (brush covered needle) showed effectively better canal wall debris removal than the NaviTip (brushless needle).

A comparative evaluation of smear layer removal by using edta, etidronic acid, and maleic acid as root canal irrigants: An in vitro scanning electron microscopic study

PubMed Central

Kuruvilla, Aby; Jaganath, Bharath Makonahalli; Krishnegowda, Sahadev Chickmagaravalli; Ramachandra, Praveen Kumar Makonahalli; Johns, Dexton Antony; Abraham, Aby

2015-01-01

Aim: The purpose of this study is to evaluate and compare the efficacy of 17% EDTA, 18% etidronic acid, and 7% maleic acid in smear layer removal using scanning electron microscopic image analysis. Materials and Methods: Thirty, freshly extracted mandibular premolars were used. The teeth were decoronated to obtain working length of 17mm and instrumentation up to 40 size (K file) with 2.5% NaOCl irrigation between each file. The samples were divided into Groups I (17% ethylenediaminetetraacetic acid (EDTA)), II (18% etidronic acid), and III (7% maleic acid) containing 10 samples each. Longitudinal sectioning of the samples was done. Then the samples were observed under scanning electron microscope (SEM) at apical, middle, and coronal levels. The images were scored according to the criteria: 1. No smear layer, 2. moderate smear layer, and 3 heavy smear layer. Statistical Analysis: Data was analyzed statistically using Kruskal–Wallis analysis of variance (ANOVA) followed by Mann-Whitney U test for individual comparisons. The level for significance was set at 0.05. Results: The present study showed that all the three experimental irrigants removed the smear layer from different tooth levels (coronal, middle, and apical). Final irrigation with 7% maleic acid is more efficient than 17% EDTA and 18% etidronic acid in the removal of smear layer from the apical third of root canal. PMID:26069414

Reconstruction of explicit structural properties at the nanoscale via spectroscopic microscopy

NASA Astrophysics Data System (ADS)

Cherkezyan, Lusik; Zhang, Di; Subramanian, Hariharan; Taflove, Allen; Backman, Vadim

2016-02-01

The spectrum registered by a reflected-light bright-field spectroscopic microscope (SM) can quantify the microscopically indiscernible, deeply subdiffractional length scales within samples such as biological cells and tissues. Nevertheless, quantification of biological specimens via any optical measures most often reveals ambiguous information about the specific structural properties within the studied samples. Thus, optical quantification remains nonintuitive to users from the diverse fields of technique application. In this work, we demonstrate that the SM signal can be analyzed to reconstruct explicit physical measures of internal structure within label-free, weakly scattering samples: characteristic length scale and the amplitude of spatial refractive-index (RI) fluctuations. We present and validate the reconstruction algorithm via finite-difference time-domain solutions of Maxwell's equations on an example of exponential spatial correlation of RI. We apply the validated algorithm to experimentally measure structural properties within isolated cells from two genetic variants of HT29 colon cancer cell line as well as within a prostate tissue biopsy section. The presented methodology can lead to the development of novel biophotonics techniques that create two-dimensional maps of explicit structural properties within biomaterials: the characteristic size of macromolecular complexes and the variance of local mass density.

Partitioning a macroscopic system into independent subsystems

NASA Astrophysics Data System (ADS)

Delle Site, Luigi; Ciccotti, Giovanni; Hartmann, Carsten

2017-08-01

We discuss the problem of partitioning a macroscopic system into a collection of independent subsystems. The partitioning of a system into replica-like subsystems is nowadays a subject of major interest in several fields of theoretical and applied physics. The thermodynamic approach currently favoured by practitioners is based on a phenomenological definition of an interface energy associated with the partition, due to a lack of easily computable expressions for a microscopic (i.e. particle-based) interface energy. In this article, we outline a general approach to derive sharp and computable bounds for the interface free energy in terms of microscopic statistical quantities. We discuss potential applications in nanothermodynamics and outline possible future directions.

Rheological Analysis of Live and Dead Microalgae Suspensions

NASA Astrophysics Data System (ADS)

Song, Young Seok; Kang, Chul; Jeong, Jiwon; Kim, Kyu-Oh; Lim, Eunju

2018-04-01

We investigate the rheological properties of microalgae suspensions that are currently being used in various applications. Two kinds of microalgae, chlorella and Synechococcus, were used for preparation of the suspensions, and their rheological characteristics were analyzed experimentally. In order to evaluate the viability of algae, we performed live and dead tests using trypan blue staining assays. Morphological analyses for the algae were conducted using a scanning electron microscope (SEM) and an optical microscope (OP). We examined the viscoelastic behavior of the live and the dead algae suspensions by performing dynamic oscillatory shear tests.

Studying aerosol light scattering based on aspect ratio distribution observed by fluorescence microscope.

PubMed

Li, Li; Zheng, Xu; Li, Zhengqiang; Li, Zhanhua; Dubovik, Oleg; Chen, Xingfeng; Wendisch, Manfred

2017-08-07

Particle shape is crucial to the properties of light scattered by atmospheric aerosol particles. A method of fluorescence microscopy direct observation was introduced to determine the aspect ratio distribution of aerosol particles. The result is comparable with that of the electron microscopic analysis. The measured aspect ratio distribution has been successfully applied in modeling light scattering and further in simulation of polarization measurements of the sun/sky radiometer. These efforts are expected to improve shape retrieval from skylight polarization by using directly measured aspect ratio distribution.

Studies on the annealing and antibacterial properties of the silver-embedded aluminum/silica nanospheres

PubMed Central

2014-01-01

Substantial silver-embedded aluminum/silica nanospheres with uniform diameter and morphology were successfully synthesized by sol-gel technique. After various annealing temperatures, the surface mechanisms of each sample were analyzed using scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy. The chemical durability examinations and antibacterial tests of each sample were also carried out for the confirmation of its practical usage. Based on the result of the above analyses, the silver-embedded aluminum/silica nanospheres are eligible for fabricating antibacterial utensils. PMID:25136275

An ultrafast electron microscope gun driven by two-photon photoemission from a nanotip cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bormann, Reiner; Strauch, Stefanie; Schäfer, Sascha, E-mail: schaefer@ph4.physik.uni-goettingen.de

We experimentally and numerically investigate the performance of an advanced ultrafast electron source, based on two-photon photoemission from a tungsten needle cathode incorporated in an electron microscope gun geometry. Emission properties are characterized as a function of the electrostatic gun settings, and operating conditions leading to laser-triggered electron beams of very low emittance (below 20 nm mrad) are identified. The results highlight the excellent suitability of optically driven nano-cathodes for the further development of ultrafast transmission electron microscopy.

Energy-gap spectroscopy of superconductors using a tunneling microscope

NASA Technical Reports Server (NTRS)

Le Duc, H. G.; Kaiser, W. J.; Stern, J. A.

1987-01-01

A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.

Microscopic analysis of Hopper flow with ellipsoidal particles

NASA Astrophysics Data System (ADS)

Liu, Sida; Zhou, Zongyan; Zou, Ruiping; Pinson, David; Yu, Aibing

2013-06-01

Hoppers are widely used in process industries. With such widespread application, difficulties in achieving desired operational behaviors have led to extensive experimental and mathematical studies in the past decades. Particularly, the discrete element method has become one of the most important simulation tools for design and analysis. So far, most studies are on spherical particles for computational convenience. In this work, ellipsoidal particles are used as they can represent a large variation of particle shapes. Hopper flow with ellipsoidal particles is presented highlighting the effect of particle shape on the microscopic properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jae Sung; Lee, Shinbuhm; Noh, Tae Won

Here we report that resistive switching (RS) phenomena are reversible changes in the metastable resistance state induced by external electric fields. After discovery ~50 years ago, RS phenomena have attracted great attention due to their potential application in next-generation electrical devices. Considerable research has been performed to understand the physical mechanisms of RS and explore the feasibility and limits of such devices. There have also been several reviews on RS that attempt to explain the microscopic origins of how regions that were originally insulators can change into conductors. However, little attention has been paid to the most important factor inmore » determining resistance: how conducting local regions are interconnected. Here, we provide an overview of the underlying physics behind connectivity changes in highly conductive regions under an electric field. We first classify RS phenomena according to their characteristic current–voltage curves: unipolar, bipolar, and threshold switchings. Second, we outline the microscopic origins of RS in oxides, focusing on the roles of oxygen vacancies: the effect of concentration, the mechanisms of channel formation and rupture, and the driving forces of oxygen vacancies. Third, we review RS studies from the perspective of statistical physics to understand connectivity change in RS phenomena. We discuss percolation model approaches and the theory for the scaling behaviors of numerous transport properties observed in RS. Fourth, we review various switching-type conversion phenomena in RS: bipolar-unipolar, memory-threshold, figure-of-eight, and counter-figure-of-eight conversions. Finally, we review several related technological issues, such as improvement in high resistance fluctuations, sneak-path problems, and multilevel switching problems.« less

Toward a Parastatistics in Quantum Nonextensive Statistical Mechanics

NASA Astrophysics Data System (ADS)

Zaripov, R. G.

2018-05-01

On the basis of Bose quantum states in parastatistics the equations for the equilibrium distribution of quantum additive and nonextensive systems are determined. The fluctuations and variances of physical quantities for the equilibrium system are found. The Abelian group of microscopic entropies is determined for the composition law with a quadratic nonlinearity.

Efficacy of sodium hypochlorite, ethylenediaminetetraacetic acid, citric acid and phosphoric acid in calcium hydroxide removal from the root canal: a microscopic cleanliness evaluation.

PubMed

da Silva, Juliana Melo; Silveira, Amanda; Santos, Elizandra; Prado, Laiìs; Pessoa, Oscar F

2011-12-01

Rooted molars were subjected to standardized canal instrumentation to a master apical file (MAF). The samples were dressed with Ca(OH)(2), and after 7 days, teeth were reopened and Ca(OH)(2) medication was removed by 1 of 4 different experimental procedures: 2.5% sodium hypochlorite (NaOCl) (n = 10); 17% EDTA-T (n = 10); 10% citric acid (n = 10); or 37% phosphoric acid (n = 10). This was followed by reinstrumentation with MAF plus 15 mL saline solution. The roots were prepared for scanning electron microscopic analysis of the cervical, middle, and apical thirds. Statistical analysis was performed with the Kruskal-Wallis test. EDTA-T and phosphoric acid gave the best results in the apical third, with significant statistical differences compared with other groups. NaOCl gave the worst results. Irrigation with 17% EDTA-T and 37% phosphoric acid is more effective than sodium hypochlorite and citric acid in the removal of calcium hydroxide from the apical third. Copyright © 2011 Mosby, Inc. All rights reserved.

Microscopic Examination of Gallbladder Stones Improves Rate of Detection of Clonorchis sinensis Infection

PubMed Central

Ma, Rui-hong; Luo, Xiao-bing; Zheng, Pei-ming; Luo, Zhen-liang; Yang, Liu-qing

2013-01-01

To improve the rate of detection of Clonorchis sinensis infection, we compared different specimens from patients with cholecystolithiasis. Feces, gallbladder bile, and gallbladder stones collected from 179 consecutive patients with cholecystolithiasis underwent microscopic examination, and according to the results, 30 egg-positive and 30 egg-negative fecal, gallbladder bile, and gallbladder stone specimens, respectively, underwent real-time fluorescent PCR. The detection rates of eggs in feces, bile, and gallbladder stones were 30.7%, 44.7%, and 69.8%, respectively, and the differences were statistically significant (P < 0.01). The PCR results confirmed that the eggs in the specimens were C. sinensis eggs. Eggs in the feces were “fresh” and in the gallbladder stones were “old.” Microscopic examination of gallbladder stones may improve the detection rates of C. sinensis infection, which is important for developing individualized treatments to prevent the recurrence of gallbladder stones and to prevent the occurrence of severe liver damage and cholangiocarcinoma. PMID:23698535

Microscopic anthropogenic litter in terrestrial birds from Shanghai, China: Not only plastics but also natural fibers.

PubMed

Zhao, Shiye; Zhu, Lixin; Li, Daoji

2016-04-15

The level of contamination by microscopic anthropogenic litter (0.5-5mm) in terrestrial ecosystems is not well understood. After chemical digestion in 10% KOH, microscopic anthropogenic litter from the gastrointestinal tracts of 17 terrestrial birds was identified and categorized under a stereomicroscope based on its physical properties and melting tests. In total, 364 items from 16 birds were identified as microscopic anthropogenic litter, ranging in size from 0.5 to 8.5mm. No relationship between plastic load and body condition was found. Natural fibers, plastic fibers and fragmented plastics represented, respectively, 37.4% (136 items), 54.9% (200 items) and 7.7% (28 items) of total litter items. Small sample sizes limited our ability to draw strong conclusions about the metabolism of natural fibers, but the decline in the proportion of natural fibers from the esophagus to stomach to intestine suggested that they may be digestible. Particles smaller than 5mm represented more than 90% of the total number of pollutant items. Particles with colors in the mid-tones and fibrous shapes were overwhelmingly common particles. The results reflect pollution by microscopic anthropogenic litter in the terrestrial ecosystem of the study area. Microscopic natural fibers, which may disperse and adsorb chemical pollutants differently from microplastic and may pose an even greater risk, are in urgent need of further research. Copyright © 2016 Elsevier B.V. All rights reserved.

Universality of emergent states in diverse physical systems

NASA Astrophysics Data System (ADS)

Guidry, Mike

2017-12-01

Our physics textbooks are dominated by examples of simple weakly-interacting microscopic states, but most of the real world around us is most effectively described in terms of emergent states that have no clear connection to simple textbook states. Emergent states are strongly-correlated and dominated by properties that emerge as a consequence of interactions and are not part of the description of the corresponding weakly-interacting system. This paper proposes a connection of weakly-interacting textbook states and realistic emergent states through fermion dynamical symmetries having fully-microscopic generators of the emergent states. These imply unique truncation of the Hilbert space for the weakly-interacting system to a collective subspace where the emergent states live. Universality arises because the possible symmetries under commutation of generators, which transcend the microscopic structure of the generators, are highly restricted in character and determine the basic structure of the emergent state, with the microscopic structure of the generators influencing emergent state only parametrically. In support of this idea we show explicit evidence that high-temperature superconductors, collective states in heavy atomic nuclei, and graphene quantum Hall states in strong magnetic fields exhibit a near-universal emergent behavior in their microscopically-computed total energy surfaces, even though these systems share essentially nothing in common at the microscopic level and their emergent states are characterized by fundamentally different order parameters.

Third law of thermodynamics as a key test of generalized entropies.

PubMed

Bento, E P; Viswanathan, G M; da Luz, M G E; Silva, R

2015-02-01

The laws of thermodynamics constrain the formulation of statistical mechanics at the microscopic level. The third law of thermodynamics states that the entropy must vanish at absolute zero temperature for systems with nondegenerate ground states in equilibrium. Conversely, the entropy can vanish only at absolute zero temperature. Here we ask whether or not generalized entropies satisfy this fundamental property. We propose a direct analytical procedure to test if a generalized entropy satisfies the third law, assuming only very general assumptions for the entropy S and energy U of an arbitrary N-level classical system. Mathematically, the method relies on exact calculation of β=dS/dU in terms of the microstate probabilities p(i). To illustrate this approach, we present exact results for the two best known generalizations of statistical mechanics. Specifically, we study the Kaniadakis entropy S(κ), which is additive, and the Tsallis entropy S(q), which is nonadditive. We show that the Kaniadakis entropy correctly satisfies the third law only for -1<κ<+1, thereby shedding light on why κ is conventionally restricted to this interval. Surprisingly, however, the Tsallis entropy violates the third law for q<1. Finally, we give a concrete example of the power of our proposed method by applying it to a paradigmatic system: the one-dimensional ferromagnetic Ising model with nearest-neighbor interactions.

ENVIRONMENTALLY FRIENDLY LEATHER TANNING USING ENZYMES

EPA Science Inventory

The effectiveness of the leather tanning will be evaluated by measuring shrinkage temperature, and analyzing leather structure using Scan Electron Microscope (SEM). The team will also measure leather physical/mechanical properties, including softness, tensile strength, elon...

Three-dimensional mapping of soil chemical characteristics at micrometric scale: Statistical prediction by combining 2D SEM-EDX data and 3D X-ray computed micro-tomographic images

NASA Astrophysics Data System (ADS)

Hapca, Simona

2015-04-01

Many soil properties and functions emerge from interactions of physical, chemical and biological processes at microscopic scales, which can be understood only by integrating techniques that traditionally are developed within separate disciplines. While recent advances in imaging techniques, such as X-ray computed tomography (X-ray CT), offer the possibility to reconstruct the 3D physical structure at fine resolutions, for the distribution of chemicals in soil, existing methods, based on scanning electron microscope (SEM) and energy dispersive X-ray detection (EDX), allow for characterization of the chemical composition only on 2D surfaces. At present, direct 3D measurement techniques are still lacking, sequential sectioning of soils, followed by 2D mapping of chemical elements and interpolation to 3D, being an alternative which is explored in this study. Specifically, we develop an integrated experimental and theoretical framework which combines 3D X-ray CT imaging technique with 2D SEM-EDX and use spatial statistics methods to map the chemical composition of soil in 3D. The procedure involves three stages 1) scanning a resin impregnated soil cube by X-ray CT, followed by precision cutting to produce parallel thin slices, the surfaces of which are scanned by SEM-EDX, 2) alignment of the 2D chemical maps within the internal 3D structure of the soil cube, and 3) development, of spatial statistics methods to predict the chemical composition of 3D soil based on the observed 2D chemical and 3D physical data. Specifically, three statistical models consisting of a regression tree, a regression tree kriging and cokriging model were used to predict the 3D spatial distribution of carbon, silicon, iron and oxygen in soil, these chemical elements showing a good spatial agreement between the X-ray grayscale intensities and the corresponding 2D SEM-EDX data. Due to the spatial correlation between the physical and chemical data, the regression-tree model showed a great potential in predicting chemical composition in particular for iron, which is generally sparsely distributed in soil. For carbon, silicon and oxygen, which are more densely distributed, the additional kriging of the regression tree residuals improved significantly the prediction, whereas prediction based on co-kriging was less consistent across replicates, underperforming regression-tree kriging. The present study shows a great potential in integrating geo-statistical methods with imaging techniques to unveil the 3D chemical structure of soil at very fine scales, the framework being suitable to be further applied to other types of imaging data such as images of biological thin sections for characterization of microbial distribution. Key words: X-ray CT, SEM-EDX, segmentation techniques, spatial correlation, 3D soil images, 2D chemical maps.

iSBatch: a batch-processing platform for data analysis and exploration of live-cell single-molecule microscopy images and other hierarchical datasets.

PubMed

Caldas, Victor E A; Punter, Christiaan M; Ghodke, Harshad; Robinson, Andrew; van Oijen, Antoine M

2015-10-01

Recent technical advances have made it possible to visualize single molecules inside live cells. Microscopes with single-molecule sensitivity enable the imaging of low-abundance proteins, allowing for a quantitative characterization of molecular properties. Such data sets contain information on a wide spectrum of important molecular properties, with different aspects highlighted in different imaging strategies. The time-lapsed acquisition of images provides information on protein dynamics over long time scales, giving insight into expression dynamics and localization properties. Rapid burst imaging reveals properties of individual molecules in real-time, informing on their diffusion characteristics, binding dynamics and stoichiometries within complexes. This richness of information, however, adds significant complexity to analysis protocols. In general, large datasets of images must be collected and processed in order to produce statistically robust results and identify rare events. More importantly, as live-cell single-molecule measurements remain on the cutting edge of imaging, few protocols for analysis have been established and thus analysis strategies often need to be explored for each individual scenario. Existing analysis packages are geared towards either single-cell imaging data or in vitro single-molecule data and typically operate with highly specific algorithms developed for particular situations. Our tool, iSBatch, instead allows users to exploit the inherent flexibility of the popular open-source package ImageJ, providing a hierarchical framework in which existing plugins or custom macros may be executed over entire datasets or portions thereof. This strategy affords users freedom to explore new analysis protocols within large imaging datasets, while maintaining hierarchical relationships between experiments, samples, fields of view, cells, and individual molecules.

Implementation of PSF engineering in high-resolution 3D microscopy imaging with a LCoS (reflective) SLM

NASA Astrophysics Data System (ADS)

King, Sharon V.; Doblas, Ana; Patwary, Nurmohammed; Saavedra, Genaro; Martínez-Corral, Manuel; Preza, Chrysanthe

2014-03-01

Wavefront coding techniques are currently used to engineer unique point spread functions (PSFs) that enhance existing microscope modalities or create new ones. Previous work in this field demonstrated that simulated intensity PSFs encoded with a generalized cubic phase mask (GCPM) are invariant to spherical aberration or misfocus; dependent on parameter selection. Additional work demonstrated that simulated PSFs encoded with a squared cubic phase mask (SQUBIC) produce a depth invariant focal spot for application in confocal scanning microscopy. Implementation of PSF engineering theory with a liquid crystal on silicon (LCoS) spatial light modulator (SLM) enables validation of WFC phase mask designs and parameters by manipulating optical wavefront properties with a programmable diffractive element. To validate and investigate parameters of the GCPM and SQUBIC WFC masks, we implemented PSF engineering in an upright microscope modified with a dual camera port and a LCoS SLM. We present measured WFC PSFs and compare them to simulated PSFs through analysis of their effect on the microscope imaging system properties. Experimentally acquired PSFs show the same intensity distribution as simulation for the GCPM phase mask, the SQUBIC-mask and the well-known and characterized cubic-phase mask (CPM), first applied to high NA microscopy by Arnison et al.10, for extending depth of field. These measurements provide experimental validation of new WFC masks and demonstrate the use of the LCoS SLM as a WFC design tool. Although efficiency improvements are needed, this application of LCoS technology renders the microscope capable of switching among multiple WFC modes.

Micro Structural, Optical and Magnetic Properties of Co-SiO2 Nanocomposite Synthesized by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Saha, Mrinal; Mukherjee, Soumya; Gayen, Arup; Mukherjee, Siddhartha

2017-04-01

Co-SiO2 nano composite has been synthesized via sol-gel technique using dextrose [C6H12O6] as a reducer and tetraethyl orthosilicate [Si(OCH2CH3)4] as oxide forming agent, respectively. The dried gel has been subsequently calcined at different temperature (850 and 900 °C) for 30 min in an inert atmosphere by N2 purging. The synthesized materials have been characterized by X-ray diffraction, high resolution transmission microscope, Fourier transform infrared spectroscopy, UV-Vis spectroscopy, scanning electron microscope, field emission microscope, atomic force microscope and physical property measurement system. The crystallite sizes of the face centered cubic cobalt nano composite materials have been found to be in the range of 14-28 nm. The crystallite size of the material found to be increased at higher calcination temperature due to the grain growth. The surface morphology of the obtained material has been found to be agglomerated but spherical in nature. This agglomeration tendency could be attributed to magnetic interaction between particles, large surface area as well as high surface energy. The band gap value of the obtained material has been determined to be 1.92 eV. The saturation magnetization (Ms) and the coercivity (Hc) of the composite material were found to be 29.45 emu g-1and 23.2 Oe, respectively. This technique has thus been found to be a convenient and effective method to prepare pure metallic cobalt nanoparticles with uniform size and homogeneous distribution throughout the matrix.

A versatile LabVIEW and field-programmable gate array-based scanning probe microscope for in operando electronic device characterization.

PubMed

Berger, Andrew J; Page, Michael R; Jacob, Jan; Young, Justin R; Lewis, Jim; Wenzel, Lothar; Bhallamudi, Vidya P; Johnston-Halperin, Ezekiel; Pelekhov, Denis V; Hammel, P Chris

2014-12-01

Understanding the complex properties of electronic and spintronic devices at the micro- and nano-scale is a topic of intense current interest as it becomes increasingly important for scientific progress and technological applications. In operando characterization of such devices by scanning probe techniques is particularly well-suited for the microscopic study of these properties. We have developed a scanning probe microscope (SPM) which is capable of both standard force imaging (atomic, magnetic, electrostatic) and simultaneous electrical transport measurements. We utilize flexible and inexpensive FPGA (field-programmable gate array) hardware and a custom software framework developed in National Instrument's LabVIEW environment to perform the various aspects of microscope operation and device measurement. The FPGA-based approach enables sensitive, real-time cantilever frequency-shift detection. Using this system, we demonstrate electrostatic force microscopy of an electrically biased graphene field-effect transistor device. The combination of SPM and electrical transport also enables imaging of the transport response to a localized perturbation provided by the scanned cantilever tip. Facilitated by the broad presence of LabVIEW in the experimental sciences and the openness of our software solution, our system permits a wide variety of combined scanning and transport measurements by providing standardized interfaces and flexible access to all aspects of a measurement (input and output signals, and processed data). Our system also enables precise control of timing (synchronization of scanning and transport operations) and implementation of sophisticated feedback protocols, and thus should be broadly interesting and useful to practitioners in the field.

A versatile LabVIEW and field-programmable gate array-based scanning probe microscope for in operando electronic device characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, Andrew J., E-mail: berger.156@osu.edu; Page, Michael R.; Young, Justin R.

Understanding the complex properties of electronic and spintronic devices at the micro- and nano-scale is a topic of intense current interest as it becomes increasingly important for scientific progress and technological applications. In operando characterization of such devices by scanning probe techniques is particularly well-suited for the microscopic study of these properties. We have developed a scanning probe microscope (SPM) which is capable of both standard force imaging (atomic, magnetic, electrostatic) and simultaneous electrical transport measurements. We utilize flexible and inexpensive FPGA (field-programmable gate array) hardware and a custom software framework developed in National Instrument's LabVIEW environment to perform themore » various aspects of microscope operation and device measurement. The FPGA-based approach enables sensitive, real-time cantilever frequency-shift detection. Using this system, we demonstrate electrostatic force microscopy of an electrically biased graphene field-effect transistor device. The combination of SPM and electrical transport also enables imaging of the transport response to a localized perturbation provided by the scanned cantilever tip. Facilitated by the broad presence of LabVIEW in the experimental sciences and the openness of our software solution, our system permits a wide variety of combined scanning and transport measurements by providing standardized interfaces and flexible access to all aspects of a measurement (input and output signals, and processed data). Our system also enables precise control of timing (synchronization of scanning and transport operations) and implementation of sophisticated feedback protocols, and thus should be broadly interesting and useful to practitioners in the field.« less

Characterization of articular cartilage by combining microscopic analysis with a fibril-reinforced finite-element model.

PubMed

Julkunen, Petro; Kiviranta, Panu; Wilson, Wouter; Jurvelin, Jukka S; Korhonen, Rami K

2007-01-01

Load-bearing characteristics of articular cartilage are impaired during tissue degeneration. Quantitative microscopy enables in vitro investigation of cartilage structure but determination of tissue functional properties necessitates experimental mechanical testing. The fibril-reinforced poroviscoelastic (FRPVE) model has been used successfully for estimation of cartilage mechanical properties. The model includes realistic collagen network architecture, as shown by microscopic imaging techniques. The aim of the present study was to investigate the relationships between the cartilage proteoglycan (PG) and collagen content as assessed by quantitative microscopic findings, and model-based mechanical parameters of the tissue. Site-specific variation of the collagen network moduli, PG matrix modulus and permeability was analyzed. Cylindrical cartilage samples (n=22) were harvested from various sites of the bovine knee and shoulder joints. Collagen orientation, as quantitated by polarized light microscopy, was incorporated into the finite-element model. Stepwise stress-relaxation experiments in unconfined compression were conducted for the samples, and sample-specific models were fitted to the experimental data in order to determine values of the model parameters. For comparison, Fourier transform infrared imaging and digital densitometry were used for the determination of collagen and PG content in the same samples, respectively. The initial and strain-dependent fibril network moduli as well as the initial permeability correlated significantly with the tissue collagen content. The equilibrium Young's modulus of the nonfibrillar matrix and the strain dependency of permeability were significantly associated with the tissue PG content. The present study demonstrates that modern quantitative microscopic methods in combination with the FRPVE model are feasible methods to characterize the structure-function relationships of articular cartilage.

A model of cell wall expansion based on thermodynamics of polymer networks

NASA Technical Reports Server (NTRS)

Veytsman, B. A.; Cosgrove, D. J.

1998-01-01

A theory of cell wall extension is proposed. It is shown that macroscopic properties of cell walls can be explained through the microscopic properties of interpenetrating networks of cellulose and hemicellulose. The qualitative conclusions of the theory agree with the existing experimental data. The dependence of the cell wall yield threshold on the secretion of the wall components is discussed.

Investigation of phase transition properties of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

This paper presents the synthesis of transparent thin films of zirconium oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Synthesized films were characterized for different annealing time and withdrawal speed. Change in crystallographic properties of thin films was investigated by using X-ray diffraction. Surface morphology of transparent thin films was estimated by using scanning electron microscope.

ZnO/TiO2 nanocomposite rods synthesized by microwave-assisted method for humidity sensor application

NASA Astrophysics Data System (ADS)

Ashok, CH.; Venkateswara Rao, K.

2014-12-01

The nanocomposite rods shows well known properties compared with nano structured materials for various applications like light-emitting diodes, electron field emitters, solar cells, optoelectronics, sensors, transparent conductors and fabrication of nano devices. Present paper investigates the properties of ZnO/TiO2 nanocomposite rods. The bi component of ZnO/TiO2 nanocomposite rods was synthesized by microwave-assisted method which is very simple, rapid and uniform in heating. The frequency of microwaves 2.45 GHz was used and temperature maintained 180 °C. Zinc acetate and titanium isopropoxide precursors were used in the preparation. The obtained ZnO/TiO2 nanocomposite rods were annealed at 500 °C and 600 °C. ZnO/TiO2 nanocomposite rods have been characterized by X-ray Diffraction (XRD) for average crystallite size and phase of the composite material, Particle Size Analyser (PSA) for average particle size, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) for morphology study, Energy Dispersive X-ray Spectrometry (EDX) for elemental analysis, and Thermal Gravimetric and Differential Thermal Analysis (TG-DTA) for thermal property.

Nitrogen-Doped Carbon Fiber Paper by Active Screen Plasma Nitriding and Its Microwave Heating Properties.

PubMed

Zhu, Naishu; Ma, Shining; Sun, Xiaofeng

2016-12-28

In this paper, active screen plasma nitriding (ASPN) treatment was performed on polyacrylonitrile carbon fiber papers. Electric resistivity and microwave loss factor of carbon fiber were described to establish the relationship between processing parameters and fiber's ability to absorb microwaves. The surface processing effect of carbon fiber could be characterized by dynamic thermal mechanical analyzer testing on composites made of carbon fiber. When the process temperature was at 175 °C, it was conducive to obtaining good performance of dynamical mechanical properties. The treatment provided a way to change microwave heating properties of carbon fiber paper by performing different treatment conditions, such as temperature and time parameters. Atomic force microscope, scanning electron microscope, and X-ray photoelectron spectroscopy analysis showed that, during the course of ASPN treatment on carbon fiber paper, nitrogen group was introduced and silicon group was removed. The treatment of nitrogen-doped carbon fiber paper represented an alternative promising candidate for microwave curing materials used in repairing and heating technology, furthermore, an efficient dielectric layer material for radar-absorbing structure composite in metamaterial technology.

Direct Visualization of Conformation and Dense Packing of DNA-Based Soft Colloids

NASA Astrophysics Data System (ADS)

Zhang, Jing; Lettinga, Paul M.; Dhont, Jan K. G.; Stiakakis, Emmanuel

2014-12-01

Soft colloids—such as polymer-coated particles, star polymers, block-copolymer micelles, microgels—constitute a broad class of materials where microscopic properties such as deformability and penetrability of the particle play a key role in tailoring their macroscopic properties which is of interest in many technological areas. The ability to access these microscopic properties is not yet demonstrated despite its great importance. Here we introduce novel DNA-coated colloids with star-shaped architecture that allows accessing the above local structural information by directly visualizing their intramolecular monomer density profile and arm's free-end locations with confocal fluorescent microscopy. Compression experiments on a two-dimensional hexagonal lattice formed by these macromolecular assemblies reveal an exceptional resistance to mutual interpenetration of their charged corona at pressures approaching the MPa range. Furthermore, we find that this lattice, in a close packing configuration, is surprisingly tolerant to particle size variation. We anticipate that these stimuli-responsive materials could aid to get deeper insight in a wide range of problems in soft matter, including the study and design of biomimetic lubricated surfaces.

Effect of citric acid, tetracycline, and doxycycline on instrumented periodontally involved root surfaces: A SEM study

PubMed Central

Chahal, Gurparkash Singh; Chhina, Kamalpreet; Chhabra, Vipin; Bhatnagar, Rakhi; Chahal, Amna

2014-01-01

Background: A surface smear layer consisting of organic and inorganic material is formed on the root surface following mechanical instrumentation and may inhibit the formation of new connective tissue attachment to the root surface. Modification of the tooth surface by root conditioning has resulted in improved connective tissue attachment and has advanced the goal of reconstructive periodontal treatment. Aim: The aim of this study was to compare the effects of citric acid, tetracycline, and doxycycline on the instrumented periodontally involved root surfaces in vitro using a scanning electron microscope. Settings and Design: A total of 45 dentin samples obtained from 15 extracted, scaled, and root planed teeth were divided into three groups. Materials and Methods: The root conditioning agents were applied with cotton pellets using the Passive burnishing technique for 5 minutes. The samples were then examined by the scanning electron microscope. Statistical Analysis Used: The statistical analysis was carried out using Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, version 15.0 for Windows). For all quantitative variables means and standard deviations were calculated and compared. For more than two groups ANOVA was applied. For multiple comparisons post hoc tests with Bonferroni correction was used. Results: Upon statistical analysis the root conditioning agents used in this study were found to be effective in removing the smear layer, uncovering and widening the dentin tubules and unmasking the dentin collagen matrix. Conclusion: Tetracycline HCl was found to be the best root conditioner among the three agents used. PMID:24744541

Augmented microscopy with near-infrared fluorescence detection

NASA Astrophysics Data System (ADS)

Watson, Jeffrey R.; Martirosyan, Nikolay; Skoch, Jesse; Lemole, G. Michael; Anton, Rein; Romanowski, Marek

2015-03-01

Near-infrared (NIR) fluorescence has become a frequently used intraoperative technique for image-guided surgical interventions. In procedures such as cerebral angiography, surgeons use the optical surgical microscope for the color view of the surgical field, and then switch to an electronic display for the NIR fluorescence images. However, the lack of stereoscopic, real-time, and on-site coregistration adds time and uncertainty to image-guided surgical procedures. To address these limitations, we developed the augmented microscope, whereby the electronically processed NIR fluorescence image is overlaid with the anatomical optical image in real-time within the optical path of the microscope. In vitro, the augmented microscope can detect and display indocyanine green (ICG) concentrations down to 94.5 nM, overlaid with the anatomical color image. We prepared polyacrylamide tissue phantoms with embedded polystyrene beads, yielding scattering properties similar to brain matter. In this model, 194 μM solution of ICG was detectable up to depths of 5 mm. ICG angiography was then performed in anesthetized rats. A dynamic process of ICG distribution in the vascular system overlaid with anatomical color images was observed and recorded. In summary, the augmented microscope demonstrates NIR fluorescence detection with superior real-time coregistration displayed within the ocular of the stereomicroscope. In comparison to other techniques, the augmented microscope retains full stereoscopic vision and optical controls including magnification and focus, camera capture, and multiuser access. Augmented microscopy may find application in surgeries where the use of traditional microscopes can be enhanced by contrast agents and image guided delivery of therapeutics, including oncology, neurosurgery, and ophthalmology.

Morphometric analysis of root canal cleaning after rotary instrumentation with or without laser irradiation

NASA Astrophysics Data System (ADS)

Marchesan, Melissa A.; Geurisoli, Danilo M. Z.; Brugnera, Aldo, Jr.; Barbin, Eduardo L.; Pecora, Jesus D.

2002-06-01

The present study examined root canal cleaning, using the optic microscope, after rotary instrumentation with ProFile.04 with or without laser application with different output energies. Cleaning and shaping can be accomplished manually, with ultra-sonic and sub-sonic devices, with rotary instruments and recently, increasing development in laser radiation has shown promising results for disinfection and smear layer removal. In this study, 30 palatal maxillary molar roots were examined using an optic microscope after rotary instrumentation with ProFile .04 with or without Er:YAG laser application (KaVo KeyLaser II, Germany) with different output energies (2940 nm, 15 Hz, 300 pulses, 500 milli-sec duration, 42 J, 140 mJ showed on the display- input, 61 mJ at fiberoptic tip-output and 140 mJ showed on the display-input and 51 mJ at fiberoptic tip-output). Statistical analysis showed no statistical differences between the tested treatments (ANOVA, p>0.05). ANOVA also showed a statistically significant difference (p<0.01) between the root canal thirds, indicating that the middle third had less debris than the apical third. We conclude that: 1) none of the tested treatments led to totally cleaned root canals; 2) all treatments removed debris similarly, 3) the middle third had less debris than the apical third; 4) variation in output energy did not increase cleaning.

A microscopic study investigating the structure of SnSe surfaces

NASA Astrophysics Data System (ADS)

Kim, Sang-ui; Duong, Anh-Tuan; Cho, Sunglae; Rhim, S. H.; Kim, Jungdae

2016-09-01

SnSe has been widely studied due to its many potential applications that take advantage of its excellent thermoelectric, photovoltaic, and optoelectronic properties. However, experimental investigations into the microscopic structure of SnSe remain largely unexplored. Herein, for the first time, the atomic and electronic structures of SnSe surfaces are studied by a home-built low temperature scanning tunneling microscope (STM) and density functional theory (DFT) calculations. The cleaved surface of SnSe is comprised of covalently bonded Se and Sn atoms in zigzag patterns. However, rectangular periodicity was observed in the atomic images of SnSe surfaces for filled and empty state probing. Detailed atomic structures are analyzed by DFT calculations, indicating that the bright extrusions of both filled and empty state images are mostly located at the positions of Sn atoms.

Microstructures and electrochemical behaviors of the friction stir welding dissimilar weld.

PubMed

Shen, Changbin; Zhang, Jiayan; Ge, Jiping

2011-06-01

By using optical microscope, the microstructures of 5083/6082 friction stir welding (FSW) weld and parent materials were analyzed. Meanwhile, at ambient temperature and in 0.2 mol/L NaHS03 and 0.6 mol/L NaCl solutionby gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, the electrochemical behavior of 5083/6082 friction stir welding weld and parent materials were comparatively investigated by gravimetric test, potentiodynamic polarization curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation. The results indicated that at given processing parameters, the anti-corrosion property of the dissimilar weld was superior to those of the 5083 and 6082 parent materials. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Imaging of current density distributions with a Nb weak-link scanning nano-SQUID microscope

PubMed Central

Shibata, Yusuke; Nomura, Shintaro; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Ishiguro, Ryosuke; Takayanagi, Hideaki

2015-01-01

Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field. PMID:26459874

Imaging of current density distributions with a Nb weak-link scanning nano-SQUID microscope

NASA Astrophysics Data System (ADS)

Shibata, Yusuke; Nomura, Shintaro; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Ishiguro, Ryosuke; Takayanagi, Hideaki

2015-10-01

Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field.

Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope

NASA Astrophysics Data System (ADS)

Burgess, Jacob A. J.; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

2015-09-01

Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface.

The effect of mechanical drawing on optical and structural properties of nylon 6 fibres

NASA Astrophysics Data System (ADS)

El-Bakary, M. A.

2007-09-01

The Pluta polarizing double-refracting interference microscope was attached to a mechanical drawing device to study the effect of cold drawing on the optical and structural properties of nylon 6 fibres. The microscope was used in its two positions for determining the refractive indices and birefringence of fibres. Different applied stresses and strain rates were obtained using the mechanical-drawing device. The effect of the applied stresses on the optical and physical parameters was investigated. The resulting optical parameters were utilized to investigate the polarizability per unit volume, the optical orientation factor, the orientation angle and the average work per chain. The refractive index and birefringence profiles were measured. Relationships between the average work per chain and optical parameters at different strains rates were determined. An empirical formula was deduced for these fibres. Micro-interferograms are given for illustration.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Rabindar K., E-mail: rkrksharma6@gmail.com; Reddy, G. B., E-mail: rkrksharma6@gmail.com

In this report, we synthesize vertically aligned molybdenum trioxide (α−MoO{sub 3}) nanoflakes (NFs) with high aspect ratio (height/thickness >15) on the cobalt coated glass substrates by the plasma assisted sublimation process, employing Mo metal strip as a sublimation source. The effect of substrate temperature, nature of substrate as well as the geometry of the sublimation source (Mo-strip) have been investigated on the morphological, structural and optical properties of the grown NFs, keeping plasma parameters as fixed. The surface morphology, crystalline structure and optical properties of MoO{sub 3} NFs have been studied systematically by using scanning electron microscope (SEM), transmission electronmore » microscope (TEM) with selected area electron diffraction (SAED), X-ray diffractometer, and IR- spectroscopy. The experimental observations endorse that the characteristics of MoO{sub 3} NFs are strongly depend on substrate temperature, substrate nature as well as geometry of Mo-strip. All the observed results are well in consonance with each other.« less

Modeling the microscopic electrical properties of thrombin binding aptamer (TBA) for label-free biosensors.

PubMed

Alfinito, Eleonora; Reggiani, Lino; Cataldo, Rosella; De Nunzio, Giorgio; Giotta, Livia; Guascito, Maria Rachele

2017-02-10

Aptamers are chemically produced oligonucleotides, able to bind a variety of targets such as drugs, proteins and pathogens with high sensitivity and selectivity. Therefore, aptamers are largely employed for producing label-free biosensors (aptasensors), with significant applications in diagnostics and drug delivery. In particular, the anti-thrombin aptamers are biomolecules of high interest for clinical use, because of their ability to recognize and bind the thrombin enzyme. Among them, the DNA 15-mer aptamer (TBA), has been widely explored around the possibility of using it in aptasensors. This paper proposes a microscopic model of the electrical properties of TBA and of the aptamer-thrombin complex, combining information from both structure and function, following the issues addressed in an emerging branch of electronics known as proteotronics. The theoretical results are compared and validated with measurements reported in the literature. Finally, the model suggests resistance measurements as a novel tool for testing aptamer-target affinity.

Research on Microstructure and Properties of Welded Joint of High Strength Steel

NASA Astrophysics Data System (ADS)

Zhu, Pengxiao; Li, Yi; Chen, Bo; Ma, Xuejiao; Zhang, Dongya; Tang, Cai

2018-01-01

BS960 steel plates were welded by Laser-MAG and MAG. The microstructure and properties of the welded joints were investigated by optical microscope, micro-hardness tester, universal tensile testing machine, impact tester, scanning electron microscope (SEM) and fatigue tester. By a series of experiments, the following results were obtained: The grain size of the coarse grain zone with Laser-MAG welded joint is 20μm, and that with MAG welded joint is about 32μm, both of the fine grain region are composed of fine lath martensite and granular bainite; the width of the heat affected region with Laser-MAG is lower than that with MAG. The strength and impact energy of welded joints with Laser-MAG is higher than that with MAG. The conditioned fatigue limit of welded joint with Laser-MAG is 280MPa; however, the conditioned fatigue limit of welded joint with MAG is 250MPa.

Toolkit for the Automated Characterization of Optical Trapping Forces on Microscopic Particles

NASA Astrophysics Data System (ADS)

Glaser, Joseph; Hoeprich, David; Resnick, Andrew

2014-03-01

Optical traps have been in use in microbiological studies for the past 40 years to obtain noninvasive control of microscopic particles. However, the magnitude of the applied forces is often unknown. Therefore, we have developed an automated data acquisition and processing system which characterizes trap properties for known particle geometries. Extensive experiments and measurements utilizing well-characterized objects were performed and compared to literature to confirm the system's performance. This system will enable the future analysis of a trapped primary cilium, a slender rod-shaped organelle with aspect ratio L/R >30, where `L' is the cilium length and `R' the cilium diameter. The trapping of cilia is of primary importance, as it will lead to the precise measurements of mechanical properties of the organelle and its significance to the epithelial cell. Support from the National Institutes of Health, 1R15DK092716 is gratefully acknowledged.

Molecular engineering of chiral colloidal liquid crystals using DNA origami

NASA Astrophysics Data System (ADS)

Siavashpouri, Mahsa; Wachauf, Christian H.; Zakhary, Mark J.; Praetorius, Florian; Dietz, Hendrik; Dogic, Zvonimir

2017-08-01

Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials.

Molecular engineering of chiral colloidal liquid crystals using DNA origami.

PubMed

Siavashpouri, Mahsa; Wachauf, Christian H; Zakhary, Mark J; Praetorius, Florian; Dietz, Hendrik; Dogic, Zvonimir

2017-08-01

Establishing precise control over the shape and the interactions of the microscopic building blocks is essential for design of macroscopic soft materials with novel structural, optical and mechanical properties. Here, we demonstrate robust assembly of DNA origami filaments into cholesteric liquid crystals, one-dimensional supramolecular twisted ribbons and two-dimensional colloidal membranes. The exquisite control afforded by the DNA origami technology establishes a quantitative relationship between the microscopic filament structure and the macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of one-dimensional twisted ribbons, which behave as effective supramolecular polymers whose structure and elastic properties can be precisely tuned by controlling the geometry of the elemental building blocks. Our results demonstrate the potential synergy between DNA origami technology and colloidal science, in which the former allows for rapid and robust synthesis of complex particles, and the latter can be used to assemble such particles into bulk materials.

Sensitivity of Dielectric Properties to Wear Process on Carbon Nanofiber/High-Density Polyethylene Composites.

PubMed

Liu, Tian; Wood, Weston; Zhong, Wei-Hong

2011-12-01

We examined the correlation of wear effects with dielectric properties of carbon nanofibers (CNFs; untreated and organosilane-treated)-reinforced high-density polyethylene (HDPE) composites. Wear testing for the nanocomposites over up to 120 h was carried out, and then, dielectric permittivity and dielectric loss factor of the polymer composites with the increased wear time were studied. Scanning electron microscope and optical microscope observations were made to analyze the microstructure features of the nanocomposites. The results reveal that there exist approximate linear relationships of permittivity with wear coefficient for the nanocomposites. Composites containing silanized CNFs with the sufficiently thick coating exhibited high wear resistance. The change in permittivity was more sensitive to the increased wear coefficient for the nanocomposites with lower wear resistance. This work provides potential for further research on the application of dielectric signals to detect the effects of wear process on lifetime of polymeric materials.

Modeling the microscopic electrical properties of thrombin binding aptamer (TBA) for label-free biosensors

NASA Astrophysics Data System (ADS)

Alfinito, Eleonora; Reggiani, Lino; Cataldo, Rosella; De Nunzio, Giorgio; Giotta, Livia; Guascito, Maria Rachele

2017-02-01

Aptamers are chemically produced oligonucleotides, able to bind a variety of targets such as drugs, proteins and pathogens with high sensitivity and selectivity. Therefore, aptamers are largely employed for producing label-free biosensors (aptasensors), with significant applications in diagnostics and drug delivery. In particular, the anti-thrombin aptamers are biomolecules of high interest for clinical use, because of their ability to recognize and bind the thrombin enzyme. Among them, the DNA 15-mer aptamer (TBA), has been widely explored around the possibility of using it in aptasensors. This paper proposes a microscopic model of the electrical properties of TBA and of the aptamer-thrombin complex, combining information from both structure and function, following the issues addressed in an emerging branch of electronics known as proteotronics. The theoretical results are compared and validated with measurements reported in the literature. Finally, the model suggests resistance measurements as a novel tool for testing aptamer-target affinity.

Color-tunable properties of Eu3+- and Dy3+-codoped Y2O3 phosphor particles

PubMed Central

2012-01-01

Rare-earth phosphors are commonly used in display panels, security printing, and fluorescent lamps, and have potential applications in lasers and bioimaging. In the present study, Eu3+- and Dy3+-codoped uniform-shaped Y2O3 submicron particles were prepared using the urea homogeneous precipitation method. The structure and morphology of the resulting particles were characterized by X-ray diffraction, field emission scanning electron microscope, and field emission transmission electron microscope, whereas their optical properties were monitored by photoluminescence spectroscopy. The room-temperature luminescence color emission of the synthesized particles can be tuned from red to yellow by switching the excitation wavelength from 254 to 350 nm. The luminescence intensities of red and yellow emissions could be altered by varying the dopant concentration. Strong quenching was observed at high Eu3+ and Dy3+ concentrations in the Y2O3 host lattice. PMID:23043645

Microstructure-related properties of magnesium fluoride films at 193nm by oblique-angle deposition.

PubMed

Guo, Chun; Kong, Mingdong; Lin, Dawei; Liu, Cunding; Li, Bincheng

2013-01-14

Magnesium fluoride (MgF2) films deposited by resistive heating evaporation with oblique-angle deposition have been investigated in details. The optical and micro-structural properties of single-layer MgF2 films were characterized by UV-VIS and FTIR spectrophotometers, scanning electron microscope (SEM), atomic force microscope (AFM), and x-ray diffraction (XRD), respectively. The dependences of the optical and micro-structural parameters of the thin films on the deposition angle were analyzed. It was found that the MgF2 film in a columnar microstructure was negatively inhomogeneous of refractive index and polycrystalline. As the deposition angle increased, the optical loss, extinction coefficient, root-mean-square (rms) roughness, dislocation density and columnar angle of the MgF2 films increased, while the refractive index, packing density and grain size decreased. Furthermore, IR absorption of the MgF2 films depended on the columnar structured growth.

Structural Investigation of Biological and Semiconductor Nanostructures with Nonlinear Multicontrast Microscopy

NASA Astrophysics Data System (ADS)

Cisek, Richard

Physical and functional properties of advanced nano-composite materials and biological structures are determined by self-organized atoms and molecules into nanostructures and in turn by microscopic organization of the nanostructures into assemblies of higher structural complexity. Therefore, microscopes are indispensable tools for structural investigations at various levels of organization. In this work, novel nonlinear optical microscopy methods were developed to non-invasively study structural organization at the nanoscopic and microscopic levels. Atomic organization of semiconductor nanowires, molecular organization of amylose biocrystallites in starch granules, and microscopic organization of several photosynthetic organisms was elucidated. The structure of ZnSe nanowires, key components in many modern nanodevices, was investigated using polarization harmonic generation microscopy. Based on nonlinear optical properties of the different crystal lattices, zinc blende and wurtzite nanowires were differentiated, and the three-dimensional orientation of the zinc blende nanowires could be found. The structure of starch granules, a model biocrystal, important in food as well as health sciences, was also investigated using polarization harmonic microscopy. The study was combined with ab initio calculations using the crystal structures of amylose A and B, revealing that second harmonic signals originate from the hydroxide and hydrogen bonds in the starch granules. Visualization of several photosynthetic organisms including the green algae, Chlamydomonas reinhardtii, two species of cyanobacteria, Leptolyngbya sp. and Anabaena sp., aggregates of light-harvesting pigment-protein complexes as well as chloroplasts from green plants were also explored, revealing that future nonlinear microscopy applications could include structural studies of cell walls, the Chlamydomonas eyespot, and photosynthetic membranes. In this study, several nonlinear optical microscopy modalities were developed for quantitative structural investigations of nano and micro-sized architectures. Non-invasive extraction of crystallographic information in microscopic samples will have a number of potential benefits, for example, in clinical applications, allowing observations of disease states inside tissues without the need for biopsy. Industrial nanotechnology will benefit from fast determination of nanostructures with nonlinear microscopy that will improve quality of nanodevices.

Impact of Microscope-Integrated OCT on Ophthalmology Resident Performance of Anterior Segment Surgical Maneuvers in Model Eyes

PubMed Central

Todorich, Bozho; Shieh, Christine; DeSouza, Philip J.; Carrasco-Zevallos, Oscar M.; Cunefare, David L.; Stinnett, Sandra S.; Izatt, Joseph A.; Farsiu, Sina; Mruthyunjaya, Privthi; Kuo, Anthony N.; Toth, Cynthia A.

2016-01-01

Purpose The integration of swept-source optical coherence tomography (SS-OCT) into the operating microscope enables real-time, tissue-level three-dimensional (3D) imaging to aid in ophthalmic microsurgery. In this prospective randomized controlled study, we evaluated the impact of SS microscope-integrated OCT (MI-OCT) on ophthalmology residents' performance of ophthalmic microsurgical maneuvers. Methods Fourteen ophthalmology residents from a single institution were stratified by year of training and randomized to perform four anterior segment surgical maneuvers on porcine eyes with (MI-OCT+) or without (MI-OCT−) direct intraoperative OCT guidance. Subsequently, both groups repeated the same maneuvers without MI-OCT feedback to test whether initial MI-OCT experience affected subsequent surgical performance. Finally, the MI-OCT− group was crossed over and allowed to repeat the same maneuvers with direct MI-OCT guidance. Each resident completed a survey at the completion of the study. Results With direct MI-OCT feedback, residents demonstrated enhanced performance in depth-based anterior segment maneuvers (corneal suture passes at 50% and 90% depth and corneal laceration repair) compared with the residents operating without MI-OCT. Microscope-integrated OCT+ residents continued to outperform the controls when both groups subsequently operated without MI-OCT. For clear corneal wound geometry, there was no statistically significant effect of MI-OCT as applied in this study. Overall, the resident surgeons rated their subjective experience of using MI-OCT very favorably. Conclusions Microscope-integrated OCT feedback enhances performance of ophthalmology residents in select anterior segment surgical maneuvers. Microscope-integrated OCT represents a valuable tool in the surgical education of ophthalmology residents. PMID:27409466

Endoscopic Versus Microscopic Transsphenoidal Surgery in the Treatment of Pituitary Adenoma: A Systematic Review and Meta-Analysis.

PubMed

Li, Aijun; Liu, Weisheng; Cao, Peicheng; Zheng, Yuehua; Bu, Zhenfu; Zhou, Tao

2017-05-01

Inconsistent findings have been reported regarding the efficacy and safety of endoscopic and microscopic transsphenoidal surgery for pituitary adenoma. This study aimed to assess the benefits and shortcomings of these surgical methods in patients with pituitary adenoma. The electronic databases PubMed, Embase, and the Cochrane Library were systematically searched, as well as proceedings of major meetings. Eligible studies with a retrospective or prospective design that evaluated endoscopic versus microscopic methods in patients with pituitary adenoma were included. Primary outcomes included gross tumor removal, cerebrospinal fluid leak, diabetes insipidus, and other complications. Overall, 23 studies (4 prospective and 19 retrospective) assessing 2272 patients with pituitary adenoma were included in the final analysis. Endoscopic transsphenoidal surgery was associated with a higher incidence of gross tumor removal (odds ratio, 1.52; 95% confidence interval, 1.11-2.08; P = 0.009) than those with microscopic transsphenoidal surgery. In addition, endoscopic transsphenoidal surgery had no significant effect on the risk of cerebrospinal fluid leak, compared with microscopic transsphenoidal surgery. Furthermore, endoscopic transsphenoidal surgery was associated with a 22% reduction in risk of diabetes insipidus compared with microscopic transsphenoidal surgery, but the difference was not statistically significant. Endoscopic transsphenoidal surgery significantly reduced the risk of septal perforation (odds ratio, 0.29; 95% confidence interval, 0.11-0.78; P = 0.014) and was not associated with the risk of meningitis, epistaxis, hematoma, hypopituitarism, hypothyroidism, hypocortisolism, total mortality, and recurrence. Endoscopic transsphenoidal surgery is associated with higher gross tumor removal and lower incidence of septal perforation in patients with pituitary adenoma. Future large-scale prospective randomized controlled trials are needed to verify these findings. Copyright © 2017 Elsevier Inc. All rights reserved.

Direct construction of mesoscopic models from microscopic simulations

NASA Astrophysics Data System (ADS)

Lei, Huan; Caswell, Bruce; Karniadakis, George Em

2010-02-01

Starting from microscopic molecular-dynamics (MD) simulations of constrained Lennard-Jones (LJ) clusters (with constant radius of gyration Rg ), we construct two mesoscopic models [Langevin dynamics and dissipative particle dynamics (DPD)] by coarse graining the LJ clusters into single particles. Both static and dynamic properties of the coarse-grained models are investigated and compared with the MD results. The effective mean force field is computed as a function of the intercluster distance, and the corresponding potential scales linearly with the number of particles per cluster and the temperature. We verify that the mean force field can reproduce the equation of state of the atomistic systems within a wide density range but the radial distribution function only within the dilute and the semidilute regime. The friction force coefficients for both models are computed directly from the time-correlation function of the random force field of the microscopic system. For high density or a large cluster size the friction force is overestimated and the diffusivity underestimated due to the omission of many-body effects as a result of the assumed pairwise form of the coarse-grained force field. When the many-body effect is not as pronounced (e.g., smaller Rg or semidilute system), the DPD model can reproduce the dynamic properties of the MD system.

Variable-focus microscopy and UV surface dissolution imaging as complementary techniques in intrinsic dissolution rate determination.

PubMed

Ward, Adam; Walton, Karl; Box, Karl; Østergaard, Jesper; Gillie, Lisa J; Conway, Barbara R; Asare-Addo, Kofi

2017-09-15

This work reports a novel approach to the assessment of the surface properties of compacts used in Surface Dissolution Imaging (SDI). SDI is useful for determining intrinsic dissolution rate (IDR), an important parameter in early stage drug development. Surface topography, post-compaction and post-SDI run, have been measured using a non-contact, optical, three-dimensional microscope based on focus variation, the Alicona Infinite Focus Microscope, with the aim of correlating the IDRs to the surface properties. Ibuprofen (IBU) was used as a model poorly-soluble drug. DSC and XRD were used to monitor possible polymorphic changes that may have occurred post-compaction and post-SDI run. IBUs IDR decreased from 0.033mg/min/cm 2 to 0.022mg/min/cm 2 from 10 to 20min, respectively, during the experiment. XRD and DSC showed no form changes during the SDI run. The surface topography images showed that a distinct imprint was embossed on the surfaces of some compacts which could affect IDRs. Surface parameter values were associated with the SDI experiments which showed strong correlations with the IDR values. The variable-focus microscope can be used as a complimentary tool in the determination of IDR values from the SDI. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

Gold Nanomaterials in Consumer Cosmetics Nanoproducts: Analyses, Characterization, and Dermal Safety Assessment.

PubMed

Cao, Mingjing; Li, Jiayang; Tang, Jinglong; Chen, Chunying; Zhao, Yuliang

2016-10-01

Establishment of analytical methods of engineered nanomaterials in consumer products for their human and environmental risk assessment becomes urgent for both academic and industrial needs. Owing to the difficulties and challenges around nanomaterials in complex media, proper chemical separation and biological assays of nanomaterials from nanoproducts needs to be firstly developed. Herein, a facile and rapid method to separate and analyze gold nanomaterials in cosmetics is reported. Gold nanomaterials are successfully separated from different facial or eye creams and their physiochemical properties are analyzed by quantitative and qualitative state-of-the art techniques with high sensitivity or high spatial resolution. In turn, a protocol including quantification of gold by inductively coupled plasma mass spectrometry and thorough characterization of morphology, size distribution, and surface property by electron microscopes, atomic force microscope, and X-ray photoelectron spectroscope is developed. Subsequently, the preliminary toxicity assessment indicates that gold nanomaterials in cosmetic creams have no observable toxicity to human keratinocytes even after 24 h exposure up to a concentration of 200 μg mL -1 . The environmental scanning electron microscope reveals that gold nanomaterials are mostly attached on the cell membrane. Thus, the present study provides a full analysis protocol for toxicity assessment of gold nanomaterials in consumer products (cosmetic creams). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timmermans, F. J.; Otto, C.

New developments in the field of microscopy enable to acquire increasing amounts of information from large sample areas and at an increased resolution. Depending on the nature of the technique, the information may reveal morphological, structural, chemical, and still other sample characteristics. In research fields, such as cell biology and materials science, there is an increasing demand to correlate these individual levels of information and in this way to obtain a better understanding of sample preparation and specific sample properties. To address this need, integrated systems were developed that combine nanometer resolution electron microscopes with optical microscopes, which produce chemicallymore » or label specific information through spectroscopy. The complementary information from electron microscopy and light microscopy presents an opportunity to investigate a broad range of sample properties in a correlated fashion. An important part of correlating the differences in information lies in bridging the different resolution and image contrast features. The trend to analyse samples using multiple correlated microscopes has resulted in a new research field. Current research is focused, for instance, on (a) the investigation of samples with nanometer scale distribution of inorganic and organic materials, (b) live cell analysis combined with electron microscopy, and (c) in situ spectroscopic and electron microscopy analysis of catalytic materials, but more areas will benefit from integrated correlative microscopy.« less

Effect of Yttrium Addition on the Microstructure and Mechanical Properties of Cu-Rich Nano-phase Strengthened Ferritic Steel

NASA Astrophysics Data System (ADS)

Liu, Hongyu; He, Jibai; Luan, Guoqing; Ke, Mingpeng; Fang, Haoyan; Lu, Jianduo

2018-03-01

Due to the brittle problem of Cu-rich nano-phase strengthened ferritic steel (CNSFS) after air aging, the effect of Y addition in CNSFS was systemically investigated in the present work. The microstructure, tensile fracture morphology and oxide layer of the steels were surveyed by optical microscope and scanning electron microscope. Transmission electron microscope with the combination of energy-dispersive x-ray spectroscopy and selected area electron diffraction was used to analyze the morphology, size, number density, chemical compositions and crystal structure for nano-crystalline precipitates. Microstructural examinations of the nano-crystalline precipitates show that Cu-rich precipitates and Y compounds in the range of 2-10 and 50-100 nm, respectively, form in the Y-containing steel; meanwhile, the average size of nano-crystalline precipitates in Y-containing steel is larger, but the number density is lower, and the ferritic grains are refined. Furthermore, the tensile strength and ductility of Y-containing steel after air aging are improved, whereas the tensile strength is enhanced and the ductility decreased after vacuum aging. The drag effect of Y makes the oxide layer thinner and be compacted. Tensile properties of CNSFS after air aging are improved due to the refined grains, antioxidation and purification by the addition of Y.

A Multiscale Material Testing System for In Situ Optical and Electron Microscopes and Its Application

PubMed Central

Ye, Xuan; Cui, Zhiguo; Fang, Huajun; Li, Xide

2017-01-01

We report a novel material testing system (MTS) that uses hierarchical designs for in-situ mechanical characterization of multiscale materials. This MTS is adaptable for use in optical microscopes (OMs) and scanning electron microscopes (SEMs). The system consists of a microscale material testing module (m-MTM) and a nanoscale material testing module (n-MTM). The MTS can measure mechanical properties of materials with characteristic lengths ranging from millimeters to tens of nanometers, while load capacity can vary from several hundred micronewtons to several nanonewtons. The m-MTM is integrated using piezoelectric motors and piezoelectric stacks/tubes to form coarse and fine testing modules, with specimen length from millimeters to several micrometers, and displacement distances of 12 mm with 0.2 µm resolution for coarse level and 8 µm with 1 nm resolution for fine level. The n-MTM is fabricated using microelectromechanical system technology to form active and passive components and realizes material testing for specimen lengths ranging from several hundred micrometers to tens of nanometers. The system’s capabilities are demonstrated by in-situ OM and SEM testing of the system’s performance and mechanical properties measurements of carbon fibers and metallic microwires. In-situ multiscale deformation tests of Bacillus subtilis filaments are also presented. PMID:28777341

Contributed review: Review of integrated correlative light and electron microscopy.

PubMed

Timmermans, F J; Otto, C

2015-01-01

New developments in the field of microscopy enable to acquire increasing amounts of information from large sample areas and at an increased resolution. Depending on the nature of the technique, the information may reveal morphological, structural, chemical, and still other sample characteristics. In research fields, such as cell biology and materials science, there is an increasing demand to correlate these individual levels of information and in this way to obtain a better understanding of sample preparation and specific sample properties. To address this need, integrated systems were developed that combine nanometer resolution electron microscopes with optical microscopes, which produce chemically or label specific information through spectroscopy. The complementary information from electron microscopy and light microscopy presents an opportunity to investigate a broad range of sample properties in a correlated fashion. An important part of correlating the differences in information lies in bridging the different resolution and image contrast features. The trend to analyse samples using multiple correlated microscopes has resulted in a new research field. Current research is focused, for instance, on (a) the investigation of samples with nanometer scale distribution of inorganic and organic materials, (b) live cell analysis combined with electron microscopy, and (c) in situ spectroscopic and electron microscopy analysis of catalytic materials, but more areas will benefit from integrated correlative microscopy.

Microstructural evolution and micromechanical properties of gamma-irradiated Au ball bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yusoff, Wan Yusmawati Wan, E-mail: yusmawati@upnm.edu.my; Ismail, Roslina, E-mail: roslina.ismail@ukm.my; Jalar, Azman, E-mail: azmn@ukm.my

2014-07-01

The effect of gamma radiation on the mechanical and structural properties of gold ball bonds was investigated. Gold wires from thermosonic wire bonding were exposed to gamma rays from a Cobalt-60 source at a low dose (5 Gy). The load–depth curve of nanoindentation for the irradiated gold wire bond has an apparent staircase shape during loading compared to the as-received sample. The hardness of the specimens calculated from the nanoindentation shows an increase in value from 0.91 to 1.09 GPa for specimens after exposure. The reduced elastic modulus for irradiated specimens significantly increased as well, with values from 75.18 tomore » 98.55 GPa. The change in intrinsic properties due to gamma radiation was investigated using dual-focused ion beam and high-resolution transmission electron microscope analysis. The dual-focused ion beam and high-resolution transmission electron microscope images confirmed the changes in grain structure and the presence of dislocations. The scanning electron microscope micrographs of focused ion beam cross sections showed that the grain structure of the gold became elongated and smaller after exposure to gamma rays. Meanwhile, high-resolution transmission electron microscopy provided evidence that gamma radiation induced dislocation of the atomic arrangement. - Highlights: • Nanoindentation technique provides a detailed characterisation of Au ball bond. • P–h curve of irradiated Au ball bond shows an apparent pop-in event. • Hardness and reduced modulus increased after exposure. • Elongated and smaller grain structure in irradiated specimens • Prevalent presence of dislocations in the atomic arrangement.« less

Watching fat digestion: a microscopic method assessing intraluminal lipolysis.

PubMed

Alliet, P; Eggermont, E

1990-01-01

We investigated the utility of a microscopic method assessing lipolytic activity of duodenal fluid. The method is based on evaluating microscopically physicochemical changes along time when olive oil is mixed with duodenal fluid in the presence of excess bile salts (13 mM) and calcium ions (8 mM) at pH 6.5. Data are analyzed on duodenal aspirations from 155 children referred for failure to thrive or gastrointestinal disorders. The "fat digestion index" (FDI) is the percentage of intact olive oil droplets that underwent complete hydrolysis or are transformed into amorphous reticular bodies (ARB) at steady state. In all patients with proven exocrine pancreatic disorder, a FDI less than 25% was found. This value was thus considered as a cut-off value. When no microscopic lipolysis (FDI = 0) was observed, exocrine pancreatic enzyme assays are suggestive for a total exocrine pancreatic insufficiency. In the group of children with FDI ranging 5-25%, however, no statistical difference in exocrine pancreatic enzymes could be found, as compared to control values. Our tests thus evaluate fat digestion in a dynamic way. It further seems to give additional information on intraluminal lipolysis as compared to exocrine pancreatic enzyme concentrations, since it gives an idea about the integrated action of (co)lipase and bile salts.

Segmentation of White Blood Cells From Microscopic Images Using a Novel Combination of K-Means Clustering and Modified Watershed Algorithm.

PubMed

Ghane, Narjes; Vard, Alireza; Talebi, Ardeshir; Nematollahy, Pardis

2017-01-01

Recognition of white blood cells (WBCs) is the first step to diagnose some particular diseases such as acquired immune deficiency syndrome, leukemia, and other blood-related diseases that are usually done by pathologists using an optical microscope. This process is time-consuming, extremely tedious, and expensive and needs experienced experts in this field. Thus, a computer-aided diagnosis system that assists pathologists in the diagnostic process can be so effective. Segmentation of WBCs is usually a first step in developing a computer-aided diagnosis system. The main purpose of this paper is to segment WBCs from microscopic images. For this purpose, we present a novel combination of thresholding, k-means clustering, and modified watershed algorithms in three stages including (1) segmentation of WBCs from a microscopic image, (2) extraction of nuclei from cell's image, and (3) separation of overlapping cells and nuclei. The evaluation results of the proposed method show that similarity measures, precision, and sensitivity respectively were 92.07, 96.07, and 94.30% for nucleus segmentation and 92.93, 97.41, and 93.78% for cell segmentation. In addition, statistical analysis presents high similarity between manual segmentation and the results obtained by the proposed method.

Color digital lensless holographic microscopy: laser versus LED illumination.

PubMed

Garcia-Sucerquia, Jorge

2016-08-20

A comparison of the performance of color digital lensless holographic microscopy (CDLHM) as utilized for illumination of RGB lasers or a super-bright white-light LED with a set of spectral filters is presented. As the use of lasers in CDLHM conceals the possibility of having a compact, lightweight, portable, and low cost microscope, and additionally the limited available laser radiation wavelengths limit a real multispectral imaging microscope, here we present the use of super-bright white-light LED and spectral filters for illuminating the sample. The performance of RGB laser-CDLHM and LED-CDLHM is evaluated on imaging a section of the head of a Drosophila melanogaster fly. This comparison shows that there is trade-off between the spatial resolution of the microscope and the light sources utilized, which can be understood with regard to the coherence properties of the illuminating light. Despite the smaller spatial coherence features of LED-CDLHM in comparison with laser-CDLHM, the former shows promise as a portable RGB digital lensless holographic microscope that could be extended to other wavelengths by the use of different spectral filters.

Observation instrument of dynamic frictional interface of gel engineering materials with polarized optical microscopic

NASA Astrophysics Data System (ADS)

Yamada, Naoya; Wada, Masato; Kabir, M. Hasnat; Gong, Jin; Furukawa, Hidemitsu

2013-03-01

Gels are soft and wet materials that differ from hard and dry materials like metals, plastics and ceramics. These have some unique characteristic such as low frictional properties, high water content and materials permeability. A decade earlier, DN gels having a mechanical strength of 30MPa of the maximum breaking stress in compression was developed and it is a prospective material as the biomaterial of the human body. Indeed it frictional coefficient and mechanical strength are comparable to our cartilages. In this study, we focus on the dynamic frictional interface of hydrogels and aim to develop a new apparatus with a polarization microscope for observation. The dynamical interface is observed by the friction of gel and glass with hudroxypropylcellulose (HPC) polymer solution sandwiching. At the beginning, we rubbed hydrogel and glass with HPC solution sandwiching on stage of polarization microscope. Second step, we designed a new system which combined microscope with friction measuring machine. The comparison between direct observation with this instrument and measurement of friction coefficient will become a foothold to elucidate distinctive frictional phenomena that can be seen in soft and wet materials.

Visualizing chemical functionality in plant cell walls

DOE PAGES

Zeng, Yining; Himmel, Michael E.; Ding, Shi-You

2017-11-30

Understanding plant cell wall cross-linking chemistry and polymeric architecture is key to the efficient utilization of biomass in all prospects from rational genetic modification to downstream chemical and biological conversion to produce fuels and value chemicals. In fact, the bulk properties of cell wall recalcitrance are collectively determined by its chemical features over a wide range of length scales from tissue, cellular to polymeric architectures. Microscopic visualization of cell walls from the nanometer to the micrometer scale offers an in situ approach to study their chemical functionality considering its spatial and chemical complexity, particularly the capabilities of characterizing biomass non-destructivelymore » and in real-time during conversion processes. Microscopic characterization has revealed heterogeneity in the distribution of chemical features, which would otherwise be hidden in bulk analysis. Key microscopic features include cell wall type, wall layering, and wall composition - especially cellulose and lignin distributions. Microscopic tools, such as atomic force microscopy, stimulated Raman scattering microscopy, and fluorescence microscopy, have been applied to investigations of cell wall structure and chemistry from the native wall to wall treated by thermal chemical pretreatment and enzymatic hydrolysis. While advancing our current understanding of plant cell wall recalcitrance and deconstruction, microscopic tools with improved spatial resolution will steadily enhance our fundamental understanding of cell wall function.« less

Visualizing chemical functionality in plant cell walls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Yining; Himmel, Michael E.; Ding, Shi-You

Understanding plant cell wall cross-linking chemistry and polymeric architecture is key to the efficient utilization of biomass in all prospects from rational genetic modification to downstream chemical and biological conversion to produce fuels and value chemicals. In fact, the bulk properties of cell wall recalcitrance are collectively determined by its chemical features over a wide range of length scales from tissue, cellular to polymeric architectures. Microscopic visualization of cell walls from the nanometer to the micrometer scale offers an in situ approach to study their chemical functionality considering its spatial and chemical complexity, particularly the capabilities of characterizing biomass non-destructivelymore » and in real-time during conversion processes. Microscopic characterization has revealed heterogeneity in the distribution of chemical features, which would otherwise be hidden in bulk analysis. Key microscopic features include cell wall type, wall layering, and wall composition - especially cellulose and lignin distributions. Microscopic tools, such as atomic force microscopy, stimulated Raman scattering microscopy, and fluorescence microscopy, have been applied to investigations of cell wall structure and chemistry from the native wall to wall treated by thermal chemical pretreatment and enzymatic hydrolysis. While advancing our current understanding of plant cell wall recalcitrance and deconstruction, microscopic tools with improved spatial resolution will steadily enhance our fundamental understanding of cell wall function.« less

Visualizing chemical functionality in plant cell walls.

PubMed

Zeng, Yining; Himmel, Michael E; Ding, Shi-You

2017-01-01

Understanding plant cell wall cross-linking chemistry and polymeric architecture is key to the efficient utilization of biomass in all prospects from rational genetic modification to downstream chemical and biological conversion to produce fuels and value chemicals. In fact, the bulk properties of cell wall recalcitrance are collectively determined by its chemical features over a wide range of length scales from tissue, cellular to polymeric architectures. Microscopic visualization of cell walls from the nanometer to the micrometer scale offers an in situ approach to study their chemical functionality considering its spatial and chemical complexity, particularly the capabilities of characterizing biomass non-destructively and in real-time during conversion processes. Microscopic characterization has revealed heterogeneity in the distribution of chemical features, which would otherwise be hidden in bulk analysis. Key microscopic features include cell wall type, wall layering, and wall composition-especially cellulose and lignin distributions. Microscopic tools, such as atomic force microscopy, stimulated Raman scattering microscopy, and fluorescence microscopy, have been applied to investigations of cell wall structure and chemistry from the native wall to wall treated by thermal chemical pretreatment and enzymatic hydrolysis. While advancing our current understanding of plant cell wall recalcitrance and deconstruction, microscopic tools with improved spatial resolution will steadily enhance our fundamental understanding of cell wall function.

Fabrication and mechanical evaluation of hydroxyapatite/oxide nano-composite materials.

PubMed

Mohamed, Khaled R; Beherei, Hanan H; El Bassyouni, Gehan T; El Mahallawy, Nahed

2013-10-01

In the current study, the semiconducting metal oxides such as nano-ZnO and SiO2 powders were prepared via sol-gel technique and conducted on nano-hydroxyapatite (nHA) which was synthesized by chemical precipitation. The properties of fabricated nano-structured composites containing different ratios of HA, ZnO and SiO2 were examined using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The effect of the variation of ratios between the three components on mechanical, microstructure and in-vitro properties was assessed to explore the possibility of enhancing these properties. The results proved that the mechanical properties exhibited an increment with increasing the ZnO content at the extent of HA. In-vitro study proved the formation and nucleation of apatite onto the surface of the fabricated composites after one week of immersion. It is concluded that HA composites containing SiO2 or SiO2/ZnO content had a suitable mechanical properties and ability to form apatite particles onto the composite surface. Based on bioactivity behavior, Si-HA is more bioactive than pure hydroxyapatite and nano-arrangements will provide an interface for better bone formation. Therefore, these nano-composites will be promising as bone substitutes especially in load bearing sites. Copyright © 2013 Elsevier B.V. All rights reserved.

Effectiveness of Dry Cell Microscopic Simulation (DCMS) to Promote Conceptual Understanding about Battery

NASA Astrophysics Data System (ADS)

Catur Wibowo, Firmanul; Suhandi, Andi; Rusdiana, Dadi; Samsudin, Achmad; Rahmi Darman, Dina; Faizin, M. Noor; Wiyanto; Supriyatman; Permanasari, Anna; Kaniawati, Ida; Setiawan, Wawan; Karyanto, Yudi; Linuwih, Suharto; Fatah, Abdul; Subali, Bambang; Hasani, Aceng; Hidayat, Sholeh

2017-07-01

Electricity is a concept that is abstract and difficult to see by eye directly, one example electric shock, but cannot see the movement of electric current so that students have difficulty by students. A computer simulation designed to improve the understanding of the concept of the workings of the dry cell (battery). This study was conducted to 82 students (aged 18-20 years) in the experimental group by learning to use the Dry Cell Microscopic Simulation (DCMS). The result shows the improving of students’ conceptual understanding scores from post test were statistically significantly of the workings of batteries. The implication using computer simulations designed to overcome the difficulties of conceptual understanding, can effectively help students in facilitating conceptual change.

MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle.

PubMed

Touboul, Pierre; Métris, Gilles; Rodrigues, Manuel; André, Yves; Baghi, Quentin; Bergé, Joël; Boulanger, Damien; Bremer, Stefanie; Carle, Patrice; Chhun, Ratana; Christophe, Bruno; Cipolla, Valerio; Damour, Thibault; Danto, Pascale; Dittus, Hansjoerg; Fayet, Pierre; Foulon, Bernard; Gageant, Claude; Guidotti, Pierre-Yves; Hagedorn, Daniel; Hardy, Emilie; Huynh, Phuong-Anh; Inchauspe, Henri; Kayser, Patrick; Lala, Stéphanie; Lämmerzahl, Claus; Lebat, Vincent; Leseur, Pierre; Liorzou, Françoise; List, Meike; Löffler, Frank; Panet, Isabelle; Pouilloux, Benjamin; Prieur, Pascal; Rebray, Alexandre; Reynaud, Serge; Rievers, Benny; Robert, Alain; Selig, Hanns; Serron, Laura; Sumner, Timothy; Tanguy, Nicolas; Visser, Pieter

2017-12-08

According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10^{-15} precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ(Ti,Pt)=[-1±9(stat)±9(syst)]×10^{-15} (1σ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations.

Fundamental quantum noise mapping with tunnelling microscopes tested at surface structures of subatomic lateral size.

PubMed

Herz, Markus; Bouvron, Samuel; Ćavar, Elizabeta; Fonin, Mikhail; Belzig, Wolfgang; Scheer, Elke

2013-10-21

We present a measurement scheme that enables quantitative detection of the shot noise in a scanning tunnelling microscope while scanning the sample. As test objects we study defect structures produced on an iridium single crystal at low temperatures. The defect structures appear in the constant current images as protrusions with curvature radii well below the atomic diameter. The measured power spectral density of the noise is very near to the quantum limit with Fano factor F = 1. While the constant current images show detailed structures expected for tunnelling involving d-atomic orbitals of Ir, we find the current noise to be without pronounced spatial variation as expected for shot noise arising from statistically independent events.

On-line transmission electron microscopic image analysis of chromatin texture for differentiation of thyroid gland tumors.

PubMed

Kriete, A; Schäffer, R; Harms, H; Aus, H M

1987-06-01

Nuclei of the cells from the thyroid gland were analyzed in a transmission electron microscope by direct TV scanning and on-line image processing. The method uses the advantages of a visual-perception model to detect structures in noisy and low-contrast images. The features analyzed include area, a form factor and texture parameters from the second derivative stage. Three tumor-free thyroid tissues, three follicular adenomas, three follicular carcinomas and three papillary carcinomas were studied. The computer-aided cytophotometric method showed that the most significant differences were the statistics of the chromatin texture features of homogeneity and regularity. These findings document the possibility of an automated differentiation of tumors at the ultrastructural level.

MICROSCOPE Mission: First Results of a Space Test of the Equivalence Principle

NASA Astrophysics Data System (ADS)

Touboul, Pierre; Métris, Gilles; Rodrigues, Manuel; André, Yves; Baghi, Quentin; Bergé, Joël; Boulanger, Damien; Bremer, Stefanie; Carle, Patrice; Chhun, Ratana; Christophe, Bruno; Cipolla, Valerio; Damour, Thibault; Danto, Pascale; Dittus, Hansjoerg; Fayet, Pierre; Foulon, Bernard; Gageant, Claude; Guidotti, Pierre-Yves; Hagedorn, Daniel; Hardy, Emilie; Huynh, Phuong-Anh; Inchauspe, Henri; Kayser, Patrick; Lala, Stéphanie; Lämmerzahl, Claus; Lebat, Vincent; Leseur, Pierre; Liorzou, Françoise; List, Meike; Löffler, Frank; Panet, Isabelle; Pouilloux, Benjamin; Prieur, Pascal; Rebray, Alexandre; Reynaud, Serge; Rievers, Benny; Robert, Alain; Selig, Hanns; Serron, Laura; Sumner, Timothy; Tanguy, Nicolas; Visser, Pieter

2017-12-01

According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10-15 precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ (Ti ,Pt )=[-1 ±9 (stat)±9 (syst)]×10-15 (1 σ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations.

Enhancement of Spartium junceum L. fibres properties

NASA Astrophysics Data System (ADS)

Kovačević, Z.; Bischof, S.; Antonović, A.

2017-10-01

Properties of lignocellulosic Spartium junceum L. (SJL) fibres were investigated in order to use them as reinforcement in composite material production. The fibres were obtained by microwave maceration process and additionally modified with NaOH, nanoclay and citric acid with the aim to improve their mechanical, thermal and other physical-chemical properties. Tensile and thermal properties of these natural fibres were enhanced by the different modification treatment which is investigated by the Vibrodyn/Vibroskop method and thermogravimetric analysis (TGA), whilst determination of chemical composition and fibre’s surface properties were explored using scanning electron microscope (SEM), electron dispersive spectroscopy (EDS) and elektrokinetic analyser. All the results show great improvement of nanoclay/citric acid modified SJL properties.

Manipulating, Reacting, and Constructing Single Molecules with a Scanning Tunneling Microscope Tip

NASA Astrophysics Data System (ADS)

Hla, S.-W.

The fascinating advances in atom and molecule manipulation with the scanning tunneling microscope (STM) tip allow scientists to fabricate artificial atomic scale structures, to study local quantum phenomena, or to probe physical and chemical properties of single atoms and molecules on surfaces. Recent achievements in individual synthesis of single molecules with the STM tip further open up an entirely new opportunities in nanoscience and technology. The STM manipulation techniques usef ul in the molecular construction are reviewed and prospects for future opportunities of single molecule chemical engineering and their possible implications to nano-scale science and technology are discussed.

Fourier plane imaging microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dominguez, Daniel, E-mail: daniel.dominguez@ttu.edu; Peralta, Luis Grave de; Nano Tech Center, Texas Tech University, Lubbock, Texas 79409

We show how the image of an unresolved photonic crystal can be reconstructed using a single Fourier plane (FP) image obtained with a second camera that was added to a traditional compound microscope. We discuss how Fourier plane imaging microscopy is an application of a remarkable property of the obtained FP images: they contain more information about the photonic crystals than the images recorded by the camera commonly placed at the real plane of the microscope. We argue that the experimental results support the hypothesis that surface waves, contributing to enhanced resolution abilities, were optically excited in the studied photonicmore » crystals.« less

Deciphering the physics and chemistry of perovskites with transmission electron microscopy.

PubMed

Polking, Mark J

2016-03-28

Perovskite oxides exhibit rich structural complexity and a broad range of functional properties, including ferroelectricity, ferromagnetism, and superconductivity. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, electron holography, and other techniques has fueled rapid progress in the understanding of the physics and chemistry of these materials. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, chemistry, electrostatics, and dynamics of perovskite oxides are then explored in detail, with a particular focus on ferroelectric materials.

Development of Nomarski microscopy for quantitative determination of surface topography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartman, J. S.; Gordon, R. L.; Lessor, D. L.

1979-01-01

The use of Nomarski differential interference contrast (DIC) microscopy has been extended to provide nondestructive, quantitative analysis of a sample's surface topography. Theoretical modeling has determined the dependence of the image intensity on the microscope's optical components, the sample's optical properties, and the sample's surface orientation relative to the microscope. Results include expressions to allow the inversion of image intensity data to determine sample surface slopes. A commercial Nomarski system has been modified and characterized to allow the evaluation of the optical model. Data have been recorded with smooth, planar samples that verify the theoretical predictions.

The petrographic microscope: Evolution of a mineralogical research instrument

USGS Publications Warehouse

Kile, D.E.

2003-01-01

The petrographic microscope, designed to observe and measure the optical properties of minerals as a means of identifying them, has provided a foundation for mineralogical and petrological research for more than 120 years. Much of what is known today in these fields is attributable to this instrument, the development of which paralleled an evolution of fundamental optical theory and its correlation with mineral structure and composition. This instrument and its related accessories have evolved through a range of models and designs, which are in themselves distinctive for their scientific function and elegant construction, and are today prized by collectors of scientific instruments.

Statistical analysis of polarization interference images of biological fluids polycrystalline films in the tasks of optical anisotropy weak changes differentiation

NASA Astrophysics Data System (ADS)

Ushenko, Yu. O.; Dubolazov, O. V.; Ushenko, V. O.; Zhytaryuk, V. G.; Prydiy, O. G.; Pavlyukovich, N.; Pavlyukovich, O.

2018-01-01

In this paper, we present the results of a statistical analysis of polarization-interference images of optically thin histological sections of biological tissues and polycrystalline films of biological fluids of human organs. A new analytical parameter is introduced-the local contrast of the interference pattern in the plane of a polarizationinhomogeneous microscopic image of a biological preparation. The coordinate distributions of the given parameter and the sets of statistical moments of the first-fourth order that characterize these distributions are determined. On this basis, the differentiation of degenerative-dystrophic changes in the myocardium and the polycrystalline structure of the synovial fluid of the human knee with different pathologies is realized.

Alternative Derivations of the Statistical Mechanical Distribution Laws

PubMed Central

Wall, Frederick T.

1971-01-01

A new approach is presented for the derivation of statistical mechanical distribution laws. The derivations are accomplished by minimizing the Helmholtz free energy under constant temperature and volume, instead of maximizing the entropy under constant energy and volume. An alternative method involves stipulating equality of chemical potential, or equality of activity, for particles in different energy levels. This approach leads to a general statement of distribution laws applicable to all systems for which thermodynamic probabilities can be written. The methods also avoid use of the calculus of variations, Lagrangian multipliers, and Stirling's approximation for the factorial. The results are applied specifically to Boltzmann, Fermi-Dirac, and Bose-Einstein statistics. The special significance of chemical potential and activity is discussed for microscopic systems. PMID:16578712

Alternative derivations of the statistical mechanical distribution laws.

PubMed

Wall, F T

1971-08-01

A new approach is presented for the derivation of statistical mechanical distribution laws. The derivations are accomplished by minimizing the Helmholtz free energy under constant temperature and volume, instead of maximizing the entropy under constant energy and volume. An alternative method involves stipulating equality of chemical potential, or equality of activity, for particles in different energy levels. This approach leads to a general statement of distribution laws applicable to all systems for which thermodynamic probabilities can be written. The methods also avoid use of the calculus of variations, Lagrangian multipliers, and Stirling's approximation for the factorial. The results are applied specifically to Boltzmann, Fermi-Dirac, and Bose-Einstein statistics. The special significance of chemical potential and activity is discussed for microscopic systems.

Biostatistical analysis of quantitative immunofluorescence microscopy images.

PubMed

Giles, C; Albrecht, M A; Lam, V; Takechi, R; Mamo, J C

2016-12-01

Semiquantitative immunofluorescence microscopy has become a key methodology in biomedical research. Typical statistical workflows are considered in the context of avoiding pseudo-replication and marginalising experimental error. However, immunofluorescence microscopy naturally generates hierarchically structured data that can be leveraged to improve statistical power and enrich biological interpretation. Herein, we describe a robust distribution fitting procedure and compare several statistical tests, outlining their potential advantages/disadvantages in the context of biological interpretation. Further, we describe tractable procedures for power analysis that incorporates the underlying distribution, sample size and number of images captured per sample. The procedures outlined have significant potential for increasing understanding of biological processes and decreasing both ethical and financial burden through experimental optimization. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

New statistical scission-point model to predict fission fragment observables

NASA Astrophysics Data System (ADS)

Lemaître, Jean-François; Panebianco, Stefano; Sida, Jean-Luc; Hilaire, Stéphane; Heinrich, Sophie

2015-09-01

The development of high performance computing facilities makes possible a massive production of nuclear data in a full microscopic framework. Taking advantage of the individual potential calculations of more than 7000 nuclei, a new statistical scission-point model, called SPY, has been developed. It gives access to the absolute available energy at the scission point, which allows the use of a parameter-free microcanonical statistical description to calculate the distributions and the mean values of all fission observables. SPY uses the richness of microscopy in a rather simple theoretical framework, without any parameter except the scission-point definition, to draw clear answers based on perfect knowledge of the ingredients involved in the model, with very limited computing cost.

Image Statistics and the Representation of Material Properties in the Visual Cortex

PubMed Central

Baumgartner, Elisabeth; Gegenfurtner, Karl R.

2016-01-01

We explored perceived material properties (roughness, texturedness, and hardness) with a novel approach that compares perception, image statistics and brain activation, as measured with fMRI. We initially asked participants to rate 84 material images with respect to the above mentioned properties, and then scanned 15 of the participants with fMRI while they viewed the material images. The images were analyzed with a set of image statistics capturing their spatial frequency and texture properties. Linear classifiers were then applied to the image statistics as well as the voxel patterns of visually responsive voxels and early visual areas to discriminate between images with high and low perceptual ratings. Roughness and texturedness could be classified above chance level based on image statistics. Roughness and texturedness could also be classified based on the brain activation patterns in visual cortex, whereas hardness could not. Importantly, the agreement in classification based on image statistics and brain activation was also above chance level. Our results show that information about visual material properties is to a large degree contained in low-level image statistics, and that these image statistics are also partially reflected in brain activity patterns induced by the perception of material images. PMID:27582714

Image Statistics and the Representation of Material Properties in the Visual Cortex.

PubMed

Baumgartner, Elisabeth; Gegenfurtner, Karl R

2016-01-01

We explored perceived material properties (roughness, texturedness, and hardness) with a novel approach that compares perception, image statistics and brain activation, as measured with fMRI. We initially asked participants to rate 84 material images with respect to the above mentioned properties, and then scanned 15 of the participants with fMRI while they viewed the material images. The images were analyzed with a set of image statistics capturing their spatial frequency and texture properties. Linear classifiers were then applied to the image statistics as well as the voxel patterns of visually responsive voxels and early visual areas to discriminate between images with high and low perceptual ratings. Roughness and texturedness could be classified above chance level based on image statistics. Roughness and texturedness could also be classified based on the brain activation patterns in visual cortex, whereas hardness could not. Importantly, the agreement in classification based on image statistics and brain activation was also above chance level. Our results show that information about visual material properties is to a large degree contained in low-level image statistics, and that these image statistics are also partially reflected in brain activity patterns induced by the perception of material images.

[Histopathological changes in human placentas related to hypertensive disorders].

PubMed

Artico, Luciano Guimarães; Madi, José Mauro; Godoy, Alessandra Eifler Guerra; Coelho, Celso Piccoli; Rombaldi, Renato Luís; Artico, Graziela Rech

2009-01-01

to determine the prevalence of histopathological changes, in human placentas, related to hypertensive syndromes. a transversal study that compares histopathological changes identified in 43 placentae from hypertensive pregnant women (HypPr), with the ones from 33 placentae from normotensive pregnant women (NorPr). The weight, volume and macroscopic and microscopic occurrence of infarctions, clots, hematomas, atherosis (partial obliteration, thickness of layers and presence of blood vessels hyalinization) and Tenney-Parker changes (absent, discreet and prominent), as well as the locating of infarctions and clots (central, peripheral or the association of both) have been analyzed. The chi2 and t Student tests have been used for the statistical analysis, as well as medians, standard deviations and ratios. It has been considered as significant, p<0.05. the macroscopic study of HypPr placentae have presented lower weight (461.1 versus 572.1 g) and volume (437.4 versus 542.0 cm(3)), higher infarction (51.2 versus 45.5%; p<0.05: OR=1.15) and clots (51.2 versus 15.1%; p<0.05; OR=5.4) ratios, as compared to the NorPr's. In the HypPr and NorPr, microscopic clots have occurred in 83.7 versus 45.5% (p<0.05; OR=4.3), respectively. Atherosis and Tenney-Parker changes have been statistically associated to the hypertensive syndromes (p<0.05). the obtained data allow us to associate lower placentary weight and volume, higher ratio of macro and microscopic infarction, clots, atherosis and Tenney-Parker changes to placentae of gestations occurring with hypertensive syndromes.

Do NiTi instruments show defects before separation? Defects caused by torsional fatigue in hand and rotary nickel-titanium (NiTi) instruments which lead to failure during clinical use.

PubMed

Chakka, N V Murali Krishna; Ratnakar, P; Das, Sanjib; Bagchi, Anandamy; Sudhir, Sudhir; Anumula, Lavanya

2012-11-01

Visual and microscopic evaluation of defects caused by torsional fatigue in hand and rotary nickel titanium (NiTi) instruments. Ninety-six NiTi greater taper instruments which were routinely used for root canal treatment only in anterior teeth were selected for the study. The files taken include ProTaper for hand use, ProTaper Rotary files and Endowave rotary files. After every use, the files were observed visually and microscopically (Stereomicroscope at 10×) to evaluate the defects caused by torsional fatigue. Scoring was given according to a new classification formulated which gives an indication of the severity of the defect or damage. Data was statistically analyzed using KruskallWallis and Mann-Whitney U test. Number of files showing defects were more under stereomicroscope than visual examination. But, the difference in the evaluation methods was not statistically significant. The different types of defects observed were bent instrument, straightening/stretching of twist contour and partial reverse twisting. Endowave files showed maximum number of defects followed by ProTaper for hand use and least in ProTaper Rotary. Visible defects due to torsional fatigue do occur in NiTi instruments after clinical use. Both visual and microscopic examinations were efficient in detecting defects caused due to torsional fatigue. This study emphasizes that all files should be observed for any visible defects before and after every instrumentation cycle to minimize the risk of instrument separation and failure of endodontic therapy.

Application of microscopy technique and high-performance liquid chromatography for quality assessment of the flower bud of Tussilago farfara L. (Kuandonghua)

PubMed Central

Li, Da; Liang, Li; Zhang, Jing; Kang, Tingguo

2015-01-01

Background: Quality control is one of the bottleneck problems limiting the application and development of traditional Chinese medicine (TCM). In recent years, microscopy and high-performance liquid chromatography (HPLC) techniques have been frequently applied in the quality control of TCM. However, studies combining conventional microscopy and HPLC techniques for the quality control of the flower bud of Tussilago farfara L. (Kuandonghua) have not been reported. Objective: This study was undertaken to evaluate the quality of the flower bud of T. farfara L. and to establish the relationships between the quantity of pollen grains and four main bioactive constituents: tussilagone, chlorogenic acid, rutin and isoquercitrin. Materials and Methods: In this study, microscopic examination was used to quantify microscopic characteristics of the flower bud of T. farfara L., and the chemical components were determined by HPLC. The data were analyzed by Statistical Package for the Social Sciences statistics software. Results: The results of the analysis showed that tussilagone, chlorogenic acid, rutin and isoquercitrin were significantly correlated with the quantity of pollen grains in the flower bud of T. farfara L. There is a positive correlation between them. From these results, it can be deduced that the flower bud of T. farfara L. with a greater quantity of pollen grains should be of better quality. Conclusion: The study showed that the established method can be helpful for evaluating the quality of the flower bud of T. farfara L. based on microscopic characteristic constants and chemical quantitation. PMID:26246737

Multiplexed single-molecule force spectroscopy using a centrifuge.

PubMed

Yang, Darren; Ward, Andrew; Halvorsen, Ken; Wong, Wesley P

2016-03-17

We present a miniature centrifuge force microscope (CFM) that repurposes a benchtop centrifuge for high-throughput single-molecule experiments with high-resolution particle tracking, a large force range, temperature control and simple push-button operation. Incorporating DNA nanoswitches to enable repeated interrogation by force of single molecular pairs, we demonstrate increased throughput, reliability and the ability to characterize population heterogeneity. We perform spatiotemporally multiplexed experiments to collect 1,863 bond rupture statistics from 538 traceable molecular pairs in a single experiment, and show that 2 populations of DNA zippers can be distinguished using per-molecule statistics to reduce noise.

Multiplexed single-molecule force spectroscopy using a centrifuge

PubMed Central

Yang, Darren; Ward, Andrew; Halvorsen, Ken; Wong, Wesley P.

2016-01-01

We present a miniature centrifuge force microscope (CFM) that repurposes a benchtop centrifuge for high-throughput single-molecule experiments with high-resolution particle tracking, a large force range, temperature control and simple push-button operation. Incorporating DNA nanoswitches to enable repeated interrogation by force of single molecular pairs, we demonstrate increased throughput, reliability and the ability to characterize population heterogeneity. We perform spatiotemporally multiplexed experiments to collect 1,863 bond rupture statistics from 538 traceable molecular pairs in a single experiment, and show that 2 populations of DNA zippers can be distinguished using per-molecule statistics to reduce noise. PMID:26984516

Vibrational microspectroscopic identification of powdered traditional medicines: Chemical micromorphology of Poria observed by infrared and Raman microspectroscopy

NASA Astrophysics Data System (ADS)

Chen, Jian-bo; Sun, Su-qin; Ma, Fang; Zhou, Qun

2014-07-01

Microscopic identification using optical microscopes is a simple and effective method to identify powdered traditional medicines made from plants, animals and fungi. Sometimes, the criteria based on physical properties of the microscopic characteristics of drug powder may be ambiguous, which makes the microscopic identification method subjective and empirical to some extent. In this research, the vibrational microspectroscopic identification method is proposed for more explicit discrimination of powdered traditional medicines. The chemical micromorphology, i.e., chemical compositions and related physical morphologies, of the drug powder can be profiled objectively and quantitatively by infrared and Raman microspectroscopy, leading to better understanding about the formation mechanisms of microscopic characteristics and more accurate identification criteria. As an example, the powder of Poria, which is one of the most used traditional Chinese medicines, is studied in this research. Three types of hyphae are classified according to their infrared spectral features in the region from 1200 to 900 cm-1. Different kinds of polysaccharides indicate that these hyphae may be in different stages of the growth. The granular and branched clumps observed by the optical microscope may be formed from the aggregation of the mature hyphae with β-D-glucan reserves. The newfound spherical particles may originate from the exuded droplets in the fresh Poria because they are both composed of α-D-glucan. The results are helpful to understand the development of the hyphae and the formation of active polysaccharides in Poria and to establish accurate microspectroscopic identification criteria.

Atomic kinetic energy, momentum distribution, and structure of solid neon at zero temperature

NASA Astrophysics Data System (ADS)

Cazorla, C.; Boronat, J.

2008-01-01

We report on the calculation of the ground-state atomic kinetic energy Ek and momentum distribution of solid Ne by means of the diffusion Monte Carlo method and Aziz HFD-B pair potential. This approach is shown to perform notably for this crystal since we obtain very good agreement with respect to experimental thermodynamic data. Additionally, we study the structural properties of solid Ne at densities near the equilibrium by estimating the radial pair-distribution function, Lindemann’s ratio, and atomic density profile around the positions of the perfect crystalline lattice. Our value for Ek at the equilibrium density is 41.51(6)K , which agrees perfectly with the recent prediction made by Timms , 41(2)K , based on their deep-inelastic neutron scattering experiments carried out over the temperature range 4-20K , and also with previous path integral Monte Carlo results obtained with the Lennard-Jones and Aziz HFD-C2 atomic pairwise interactions. The one-body density function of solid Ne is calculated accurately and found to fit perfectly, within statistical uncertainty, to a Gaussian curve. Furthermore, we analyze the degree of anharmonicity of solid Ne by calculating some of its microscopic ground-state properties within traditional harmonic approaches. We provide insightful comparison to solid He4 in terms of the Debye model in order to assess the relevance of anharmonic effects in Ne.

The system spatial-frequency filtering of birefringence images of human blood layers

NASA Astrophysics Data System (ADS)

Ushenko, A. G.; Boychuk, T. M.; Mincer, O. P.; Angelsky, P. O.; Bodnar, N. B.; Oleinichenko, B. P.; Bizer, L. I.

2013-09-01

Among various opticophysical methods [1 - 3] of diagnosing the structure and properties of the optical anisotropic component of various biological objects a specific trend has been singled out - multidimensional laser polarimetry of microscopic images of the biological tissues with the following statistic, correlative and fractal analysis of the coordinate distributions of the azimuths and ellipticity of polarization in approximating of linear birefringence polycrystalline protein networks [4 - 10]. At the same time, in most cases, experimental obtaining of tissue sample is a traumatic biopsy operation. In addition, the mechanisms of transformation of the state of polarization of laser radiation by means of the opticoanisotropic biological structures are more varied (optical dichroism, circular birefringence). Hereat, real polycrystalline networks can be formed by different types, both in size and optical properties of biological crystals. Finally, much more accessible for an experimental investigation are biological fluids such as blood, bile, urine, and others. Thus, further progress of laser polarimetry can be associated with the development of new methods of analysis and processing (selection) of polarization- heterogeneous images of biological tissues and fluids, taking into account a wider set of mechanisms anisotropic mechanisms. Our research is aimed at developing experimental method of the Fourier polarimetry and a spatialfrequency selection for distributions of the azimuth and the ellipticity polarization of blood plasma laser images with a view of diagnosing prostate cancer.

Mechanical, morphological and structural properties of cellulose nanofibers reinforced epoxy composites.

PubMed

Saba, N; Mohammad, F; Pervaiz, M; Jawaid, M; Alothman, O Y; Sain, M

2017-04-01

Present study, deals about isolation and characterization of cellulose nanofibers (CNFs) from the Northern Bleached Softwood Kraft (NBSK) pulp, fabrication by hand lay-up technique and characterization of fabricated epoxy nanocomposites at different filler loadings (0.5%, 0.75%, 1% by wt.). The effect of CNFs loading on mechanical (tensile, impact and flexural), morphological (scanning electron microscope and transmission electron microscope) and structural (XRD and FTIR) properties of epoxy composites were investigated. FTIR analysis confirms the introduction of CNFs into the epoxy matrix while no considerable change in the crystallinity and diffraction peaks of epoxy composites were observed by the XRD patterns. Additions of CNFs considerably enhance the mechanical properties of epoxy composites but a remarkable improvement is observed for 0.75% CNFs as compared to the rest epoxy nanocomposites. In addition, the electron micrographs revealed the perfect distribution and dispersion of CNFs in the epoxy matrix for the 0.75% CNFs/epoxy nanocomposites, while the existence of voids and agglomerations were observed beyond 0.75% CNFs filler loadings. Overall results analysis clearly revealed that the 0.75% CNFs filler loading is best and effective with respect to rest to enhance the mechanical and structural properties of the epoxy composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of Thickness and Amount of Carbon Nanofiber Coated Carbon Fiber on Improving the Mechanical Properties of Nanocomposites

PubMed Central

Ghaemi, Ferial; Ahmadian, Ali; Yunus, Robiah; Ismail, Fudziah; Rahmanian, Saeed

2016-01-01

In the current study, carbon nanofibers (CNFs) were grown on a carbon fiber (CF) surface by using the chemical vapor deposition method (CVD) and the influences of some parameters of the CVD method on improving the mechanical properties of a polypropylene (PP) composite were investigated. To obtain an optimum surface area, thickness, and yield of the CNFs, the parameters of the chemical vapor deposition (CVD) method, such as catalyst concentration, reaction temperature, reaction time, and hydrocarbon flow rate, were optimized. It was observed that the optimal surface area, thickness, and yield of the CNFs caused more adhesion of the fibers with the PP matrix, which enhanced the composite properties. Besides this, the effectiveness of reinforcement of fillers was fitted with a mathematical model obtaining good agreement between the experimental result and the theoretical prediction. By applying scanning electronic microscope (SEM), transmission electron microscope (TEM), and Raman spectroscopy, the surface morphology and structural information of the resultant CF-CNF were analyzed. Additionally, SEM images and a mechanical test of the composite with a proper layer of CNFs on the CF revealed not only a compactness effect but also the thickness and surface area roles of the CNF layers in improving the mechanical properties of the composites. PMID:28344263

Optimizing adsorption of fluoride from water by modified banana peel dust using response surface modelling approach

NASA Astrophysics Data System (ADS)

Bhaumik, Ria; Mondal, Naba Kumar

2016-06-01

The present work highlighted the effective application of banana peel dust (BPD) for removal of fluoride (F-) from aqueous solution. The effects of operating parameters such as pH, initial concentration, adsorbent dose, contact time, agitation speed and temperature were analysed using response surface methodology. The significance of independent variables and their interactions were tested by the analysis of variance and t test statistics. Experimental results revealed that BPD has higher F- adsorption capacity (17.43, 26.31 and 39.5 mg/g). Fluoride adsorption kinetics followed pseudo-second-order model with high correlation of coefficient value (0.998). On the other hand, thermodynamic data suggest that adsorption is favoured at lower temperature, exothermic in nature and enthalpy driven. The adsorbents were characterised through scanning electron microscope, Fourier transform infrared spectroscopy and point of zero charges (pHZPC) ranges from pH 6.2-8.2. Finally, error analysis clearly demonstrates that all three adsorbents are well fitted with Langmuir isotherm compared to the other isotherm models. The reusable properties of the material support further development for commercial application purpose.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition.

PubMed

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D; Renevier, Hubert; Consonni, Vincent

2017-03-03

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 10 7 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

NASA Astrophysics Data System (ADS)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph; Cantelli, Valentina; Albertini, David; Gautier, Brice; Brémond, Georges; Fong, Dillon D.; Renevier, Hubert; Consonni, Vincent

2017-03-01

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscale-engineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol-gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on the macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscale-engineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.

Quantitative and simultaneous analysis of the polarity of polycrystalline ZnO seed layers and related nanowires grown by wet chemical deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillemin, Sophie; Parize, Romain; Carabetta, Joseph

The polarity in ZnO nanowires is an important issue since it strongly affects surface configuration and reactivity, nucleation and growth, electro-optical properties, and nanoscaleengineering device performances. However, measuring statistically the polarity of ZnO nanowire arrays grown by chemical bath deposition and elucidating its correlation with the polarity of the underneath polycrystalline ZnO seed layer grown by the sol–gel process represents a major difficulty. To address that issue, we combine resonant x-ray diffraction (XRD) at Zn K-edge using synchrotron radiation with piezoelectric force microscopy and polarity-sensitive chemical etching to statistically investigate the polarity of more than 107 nano-objects both on themore » macroscopic and local microscopic scales, respectively. By using high temperature annealing under an argon atmosphere, it is shown that the compact, highly c-axis oriented ZnO seed layer is more than 92% Zn-polar and that only a few small O-polar ZnO grains with an amount less than 8% are formed. Correlatively, the resulting ZnO nanowires are also found to be Zn-polar, indicating that their polarity is transferred from the c-axis oriented ZnO grains acting as nucleation sites in the seed layer. These findings pave the way for the development of new strategies to form unipolar ZnO nanowire arrays as a requirement for a number of nanoscaleengineering devices like piezoelectric nanogenerators. They also highlight the great advantage of resonant XRD as a macroscopic, non-destructive method to simultaneously and statistically measure the polarity of ZnO nanowire arrays and of the underneath ZnO seed layer.« less

Corrosion resistance assessment of Co-Cr alloy frameworks fabricated by CAD/CAM milling, laser sintering, and casting methods.

PubMed

Tuna, Süleyman Hakan; Özçiçek Pekmez, Nuran; Kürkçüoğlu, Işin

2015-11-01

The effects of fabrication methods on the corrosion resistance of frameworks produced with Co-Cr alloys are not clear. The purpose of this in vitro study was to evaluate the electrochemical corrosion resistance of Co-Cr alloy specimens that were fabricated by conventional casting, milling, and laser sintering. The specimens fabricated with 3 different methods were investigated by potentiodynamic tests and electrochemical impedance spectroscopy in an artificial saliva. Ions released into the artificial saliva were estimated with inductively coupled plasma-mass spectrometry, and the results were statistically analyzed. The specimen surfaces were investigated with scanning electron microscopy before and after the tests. In terms of corrosion current and Rct properties, statistically significant differences were found both among the means of the methods and among the means of the material groups (P<.05). With regard to ions released, a statistically significant difference was found among the material groups (P<.05); however, no difference was found among the methods. Scanning electron microscopic imaging revealed that the specimens produced by conventional casting were affected to a greater extent by etching and electrochemical corrosion than those produced by milling and laser sintering. The corrosion resistance of a Co-Cr alloy specimens fabricated by milling or laser sintering was greater than that of the conventionally cast alloy specimens. The Co-Cr specimens produced by the same method also differed from one another in terms of corrosion resistance. These differences may be related to the variations in the alloy compositions. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Corrosive and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy.

PubMed

Ristic, Ljubisa; Vucevic, Dragana; Radovic, Ljubica; Djordjevic, Snezana; Nikacevic, Milutin; Colic, Miodrag

2014-04-01

Nickel-chromium (Ni-Cr) dental alloys have been widely used in prosthodontic practice, but there is a permanent concern about their biocompatibility due to the release of metal ions. This is especially important when Ni-Cr metal microparticles are incorporated into gingival tissue during prosthodontic procedures. Therefore, the aim of this study was to examine and compare the corrosion and cytotoxic properties of compact specimens and microparticles of Ni-Cr dental alloy. Ni-Cr alloy, Remanium CSe bars (4 mm diameter), were made by the standard casting method and then cut into 0.5-mm-thick disks. Metal particles were obtained by scraping the bars using a diamond instrument for crown preparation. The microstructure was observed by an optical microscope. Quantitative determination and morphological and dimensional characterization of metal particles were carried out by a scanning electron microscope and Leica Application Suite software for image analysis. Corrosion was studied by conditioning the alloy specimens in the RPMI 1640 medium, containing 10% fetal calf serum in an incubator with 5% CO2 for 72 hours at 37°C. Inductively coupled plasma-optical emission spectrometry was used to assess metal ion release. The cytotoxity of conditioning medium (CM) was investigated on L929 cells using an MTT test. One-way ANOVA was used for statistical analysis. After casting, the microstructure of the Remanium CSe compact specimen composed of Ni, Cr, Mo, Si, Fe, Al, and Co had a typical dendritic structure. Alloy microparticles had an irregular shape with a wide size range: from less than 1 μm to more than 100 μm. The release of metal ions, especially Ni and Mo from microparticles, was significantly higher, compared to the compact alloy specimen. The CM prepared from compact alloy was not cytotoxic at any tested dilutions, whereas CM from alloy microparticles showed dose-dependent cytotoxicity (90% CM and 45% CM versus control; p < 0.005). Ni-Cr microparticles showed less corrosion resistance and lower biocompatibility than compact alloy. This could affect health on long-term exposure, especially in sensitized individuals. © 2013 by the American College of Prosthodontists.

Scanned gate microscopy of inter-edge channel scattering in the quantum Hall regime

NASA Astrophysics Data System (ADS)

Woodside, Michael T.; Vale, Chris; McEuen, Paul L.; Kadow, C.; Maranowski, K. D.; Gossard, A. C.

2000-03-01

Novel scanned probe techniques have recently been used to study in detail the microscopic properties of 2D electron gases in the quantum Hall regime [1]. We report local measurements of the scattering between edge states in a quantum Hall conductor with non-equilibrium edge state populations. Using an atomic force microscope (AFM) tip as a local gate to perturb the edge states, we find that the scattering is dominated by individual, microscopic scattering sites, which we directly image and characterise. The dependence of the scattering on the AFM tip voltage reveals that it involves tunneling both through quasi-bound impurity states and through disorder-induced weak links between the edge states. [1] S. H. Tessmer et al., Nature 392, 51 (1998); K. L. McCormick et al., Phys. Rev. B 59, 4654 (1999); A. Yacoby et al., Solid State Comm. 111, 1 (1999).

Spectroscopy of reflection-asymmetric nuclei with relativistic energy density functionals

NASA Astrophysics Data System (ADS)

Xia, S. Y.; Tao, H.; Lu, Y.; Li, Z. P.; Nikšić, T.; Vretenar, D.

2017-11-01

Quadrupole and octupole deformation energy surfaces, low-energy excitation spectra, and transition rates in 14 isotopic chains: Xe, Ba, Ce, Nd, Sm, Gd, Rn, Ra, Th, U, Pu, Cm, Cf, and Fm, are systematically analyzed using a theoretical framework based on a quadrupole-octupole collective Hamiltonian (QOCH), with parameters determined by constrained reflection-asymmetric and axially symmetric relativistic mean-field calculations. The microscopic QOCH model based on the PC-PK1 energy density functional and δ -interaction pairing is shown to accurately describe the empirical trend of low-energy quadrupole and octupole collective states, and predicted spectroscopic properties are consistent with recent microscopic calculations based on both relativistic and nonrelativistic energy density functionals. Low-energy negative-parity bands, average octupole deformations, and transition rates show evidence for octupole collectivity in both mass regions, for which a microscopic mechanism is discussed in terms of evolution of single-nucleon orbitals with deformation.

A novel 3D deformation measurement method under optical microscope for micro-scale bulge-test

NASA Astrophysics Data System (ADS)

Wu, Dan; Xie, Huimin

2017-11-01

A micro-scale 3D deformation measurement method combined with optical microscope is proposed in this paper. The method is based on gratings and phase shifting algorithm. By recording the grating images before and after deformation from two symmetrical angles and calculating the phases of the grating patterns, the 3D deformation field of the specimen can be extracted from the phases of the grating patterns. The proposed method was applied to the micro-scale bulge test. A micro-scale thermal/mechanical coupling bulge-test apparatus matched with the super-depth microscope was exploited. With the gratings fabricated onto the film, the deformed morphology of the bulged film was measured reliably. The experimental results show that the proposed method and the exploited bulge-test apparatus can be used to characterize the thermal/mechanical properties of the films at micro-scale successfully.

PHOTONICS AND NANOTECHNOLOGY Microscopic theory of optical properties of composite media with chaotically distributed nanoparticles

NASA Astrophysics Data System (ADS)

Shalin, A. S.

2010-12-01

The boundary problem of light reflection and transmission by a film with chaotically distributed nanoinclusions is considered. Based on the proposed microscopic approach, analytic expressions are derived for distributions inside and outside the nanocomposite medium. Good agreement of the results with exact calculations and (at low concentrations of nanoparticles) with the integral Maxwell-Garnett effective-medium theory is demonstrated. It is shown that at high nanoparticle concentrations, averaging the dielectric constant in volume as is done within the framework of the effective-medium theory yields overestimated values of the optical film density compared to the values yielded by the proposed microscopic approach. We also studied the dependence of the reflectivity of a system of gold nanoparticles on their size, the size dependence of the plasmon resonance position along the wavelength scale, and demonstrated a good agreement with experimental data.

Design and properties of a cryogenic dip-stick scanning tunneling microscope with capacitive coarse approach control.

PubMed

Schlegel, R; Hänke, T; Baumann, D; Kaiser, M; Nag, P K; Voigtländer, R; Lindackers, D; Büchner, B; Hess, C

2014-01-01

We present the design, setup, and operation of a new dip-stick scanning tunneling microscope. Its special design allows measurements in the temperature range from 4.7 K up to room temperature, where cryogenic vacuum conditions are maintained during the measurement. The system fits into every (4)He vessel with a bore of 50 mm, e.g., a transport dewar or a magnet bath cryostat. The microscope is equipped with a cleaving mechanism for cleaving single crystals in the whole temperature range and under cryogenic vacuum conditions. For the tip approach, a capacitive automated coarse approach is implemented. We present test measurements on the charge density wave system 2H-NbSe2 and the superconductor LiFeAs which demonstrate scanning tunneling microscopy and spectroscopy data acquisition with high stability, high spatial resolution at variable temperatures and in high magnetic fields.

Emperical Laws in Economics Uncovered Using Methods in Statistical Mechanics

NASA Astrophysics Data System (ADS)

Stanley, H. Eugene

2001-06-01

In recent years, statistical physicists and computational physicists have determined that physical systems which consist of a large number of interacting particles obey universal "scaling laws" that serve to demonstrate an intrinsic self-similarity operating in such systems. Further, the parameters appearing in these scaling laws appear to be largely independent of the microscopic details. Since economic systems also consist of a large number of interacting units, it is plausible that scaling theory can be usefully applied to economics. To test this possibility using realistic data sets, a number of scientists have begun analyzing economic data using methods of statistical physics [1]. We have found evidence for scaling (and data collapse), as well as universality, in various quantities, and these recent results will be reviewed in this talk--starting with the most recent study [2]. We also propose models that may lead to some insight into these phenomena. These results will be discussed, as well as the overall rationale for why one might expect scaling principles to hold for complex economic systems. This work on which this talk is based is supported by BP, and was carried out in collaboration with L. A. N. Amaral S. V. Buldyrev, D. Canning, P. Cizeau, X. Gabaix, P. Gopikrishnan, S. Havlin, Y. Lee, Y. Liu, R. N. Mantegna, K. Matia, M. Meyer, C.-K. Peng, V. Plerou, M. A. Salinger, and M. H. R. Stanley. [1.] See, e.g., R. N. Mantegna and H. E. Stanley, Introduction to Econophysics: Correlations & Complexity in Finance (Cambridge University Press, Cambridge, 1999). [2.] P. Gopikrishnan, B. Rosenow, V. Plerou, and H. E. Stanley, "Identifying Business Sectors from Stock Price Fluctuations," e-print cond-mat/0011145; V. Plerou, P. Gopikrishnan, L. A. N. Amaral, X. Gabaix, and H. E. Stanley, "Diffusion and Economic Fluctuations," Phys. Rev. E (Rapid Communications) 62, 3023-3026 (2000); P. Gopikrishnan, V. Plerou, X. Gabaix, and H. E. Stanley, "Statistical Properties of Share Volume Traded in Financial Markets," Phys. Rev. E (Rapid Communications) 62, 4493-4496 (2000).

Optimization of mechanical properties, biocorrosion properties and antibacterial properties of as-cast Ti-Cu alloys.

PubMed

Zhang, Erlin; Ren, Jing; Li, Shengyi; Yang, Lei; Qin, Gaowu

2016-10-21

Ti-Cu sintered alloys have shown good antibacterial abilities. However, the sintered method (powder metallurgy) is not convenient to produce devices with a complex structure. In this paper, Ti-Cu alloys with 2.0, 3.0 and 4.0 wt.% Cu were prepared in an arc melting furnace and subjected to different heat treatments: solid solution and ageing, to explore the possibility of preparing an antibacterial Ti-Cu alloy by a casting method and to examine the effect of Cu content. Phase identification was conducted on an XRD diffraction meter, and the microstructure was observed by a metallographic microscope, a scanning electron microscope (SEM) with energy disperse spectroscopy (EDS) and transmission electron microscopy (TEM). Microhardness and the compressive property of Ti-Cu alloys were tested, and the corrosion resistance and antibacterial activity were assessed in order to investigate the effect of the Cu content. Results showed that the as-cast Ti-Cu alloys exhibited a very low antibacterial rate against Staphylococcus aureus (S. aureus). Heat treatment improved the antibacterial rate significantly, especially after a solid and ageing treatment (T6). Antibacterial rates as high as 90.33% and 92.57% were observed on Ti-3Cu alloy and Ti-4Cu alloy, respectively. The hardness, the compressive yield strength, the anticorrosion resistance and the antibacterial rate of Ti-Cu alloys increased with an increase of Cu content in all conditions. It was demonstrated that homogeneous distribution and a fine Ti 2 Cu phase played a very important role in the mechanical property, anticorrosion and antibacterial properties. Furthermore, it should be pointed out that the Cu content should be at least 3 wt.% to obtain good antibacterial properties (>90% antibacterial rate) as well as satisfactory mechanical properties.

Surface chemistry and tribology of MEMS.

PubMed

Maboudian, Roya; Carraro, Carlo

2004-01-01

The microscopic length scale and high surface-to-volume ratio, characteristic of microelectro-mechanical systems (MEMS), dictate that surface properties are of paramount importance. This review deals with the effects of surface chemical treatments on tribological properties (adhesion, friction, and wear) of MEMS devices. After a brief review of materials and processes that are utilized in MEMS technology, the relevant tribological and chemical issues are discussed. Various MEMS microinstruments are discussed, which are commonly employed to perform adhesion, friction, and wear measurements. The effects of different surface treatments on the reported tribological properties are discussed.

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.

Silylene-diethynyl-arylene polymers having liquid crystalline properties

DOEpatents

Barton, Thomas J.; Ding, Yiwei

1993-09-07

The present invention provides linear organosilicon polymers including diethynyl-(substituted)arylene units, and a process for their preparation. These novel polymers possess useful properties including electrical conductivity, liquid crystallinity, and/or photoluminescence. These polymers possess good solubility in organic solvents. A preferred example is produced according to the following reaction scheme. ##STR1## These polymers can be solvent-cast to yield excellent films and can also be pulled into fibers from concentrated solutions. All possess substantial crystallinity as revealed by DSC analysis and observation through a polarizing microscope, and possess liquid crystalline properties.

Tuning donut profile for spatial resolution in stimulated emission depletion microscopy.

PubMed

Neupane, Bhanu; Chen, Fang; Sun, Wei; Chiu, Daniel T; Wang, Gufeng

2013-04-01

In stimulated emission depletion (STED)-based or up-conversion depletion-based super-resolution optical microscopy, the donut-shaped depletion beam profile is of critical importance to its resolution. In this study, we investigate the transformation of the donut-shaped depletion beam focused by a high numerical aperture (NA) microscope objective, and model STED point spread function (PSF) as a function of donut beam profile. We show experimentally that the intensity profile of the dark kernel of the donut can be approximated as a parabolic function, whose slope is determined by the donut beam size before the objective back aperture, or the effective NA. Based on this, we derive the mathematical expression for continuous wave (CW) STED PSF as a function of focal plane donut and excitation beam profiles, as well as dye properties. We find that the effective NA and the residual intensity at the center are critical factors for STED imaging quality and the resolution. The effective NA is critical for STED resolution in that it not only determines the donut shape but also the area the depletion laser power is dispersed. An improperly expanded depletion beam will have negligible improvement in resolution. The polarization of the depletion beam also plays an important role as it affects the residual intensity in the center of the donut. Finally, we construct a CW STED microscope operating at 488 nm excitation and 592 nm depletion with a resolution of 70 nm. Our study provides detailed insight to the property of donut beam, and parameters that are important for the optimal performance of STED microscopes. This paper will provide a useful guide for the construction and future development of STED microscopes.

Assessing the Penetrating Abilities of Experimental Preparation with Dental Infiltrant Features Using Optical Microscope: Preliminary Study.

PubMed

Skucha-Nowak, Małgorzata; Machorowska-Pieniążek, Agnieszka; Tanasiewicz, Marta

2016-01-01

The aim of the infiltration technique is to penetrate demineralized enamel with a low viscosity resin. Icon® (DMG) is the first ever and so far the only dental infiltrant. Bacteriostaticity is one of the properties that should be inherent in dental infiltrants, but Icon lacks this feature. The aim of the preliminary study was to properly choose a dye which would allow us to assess the penetrating abilities of our own, experimental preparation with features of a dental infiltrant with bacteriostatic properties and to compare using an optical microscope the depth of infiltration of the designed experimental preparation with the infiltrant available on the market. The preparation is supposed to infiltrate decalcified human enamel and be assessed with an optical microscope. Eosin, neutral fuchsine and methylene blue were added to experimental preparation with dental infiltrant features and to Icon® (DMG) in order to assess the depth of penetration of the experimental solution into the decalcified layers of enamel. The experimental solution mixes well with eosin, neutral fuchsine, and methylene blue. During the preliminary study, the authors concluded that the experimental solution mixes well with methylene blue, neutral fuchsine, and eosin. An addition of eosin to a preparation which infiltrates inner, demineralized enamel layers, facilitates the assessment of such a preparation with an optical microscope. A designed experimental solution with the main ingredients, i.e., 2-hydroxyethyl methacrylate (HEMA) and tetraethylene glycol dimethacrylate (TEGDMA) with a ratio of 75% to 25% penetrates the demineralized (decalcified) inner parts of the enamel and polymerizes when exposed to light. In order to assess the infiltration of the experimental solution into the demineralized enamel layers, it is required to improve the measurement techniques that utilize optical microscopy.

Correlation between inflammatory infiltrate and epithelial lining in 214 cases of periapical cysts.

PubMed

Alcantara, Bárbara Albertini Roquim; Carli, Marina Lara de; Beijo, Luiz Alberto; Pereira, Alessandro Antônio Costa; Hanemann, João Adolfo Costa

2013-01-01

The aim of this study was to evaluate the prevalence of periapical cysts, identify their clinical and microscopic features and correlate their microscopic features with the inflammatory infiltrate present in the lesion site. A total of 214 cases were collected over a 10-year period. Clinical data, including gender, age, race, symptoms and location of the lesion, were recorded. Two independent examiners with no prior knowledge of the patients' clinical data conducted the microscopic evaluations. Statistical analyses were performed using Fisher's or chi-square tests at a 5% level of significance. The results showed that periapical cysts were more prevalent in white women, with a mean age of 35 years, and in the anterosuperior region. The majority of the lesions were lined by atrophic cystic epithelium, which was associated with moderate inflammatory infiltrate in the cystic capsule (p < 0.01), with a diffuse localization pattern (p = 0.03) and absence of neutrophils (p = 0.01). Our findings suggest that periapical cysts lined by atrophic epithelium are related to the presence of moderate mononuclear inflammatory infiltrate.

Design of order statistics filters using feedforward neural networks

NASA Astrophysics Data System (ADS)

Maslennikova, Yu. S.; Bochkarev, V. V.

2016-08-01

In recent years significant progress have been made in the development of nonlinear data processing techniques. Such techniques are widely used in digital data filtering and image enhancement. Many of the most effective nonlinear filters based on order statistics. The widely used median filter is the best known order statistic filter. Generalized form of these filters could be presented based on Lloyd's statistics. Filters based on order statistics have excellent robustness properties in the presence of impulsive noise. In this paper, we present special approach for synthesis of order statistics filters using artificial neural networks. Optimal Lloyd's statistics are used for selecting of initial weights for the neural network. Adaptive properties of neural networks provide opportunities to optimize order statistics filters for data with asymmetric distribution function. Different examples demonstrate the properties and performance of presented approach.

Surface topography study of prepared 3D printed moulds via 3D printer for silicone elastomer based nasal prosthesis

NASA Astrophysics Data System (ADS)

Abdullah, Abdul Manaf; Din, Tengku Noor Daimah Tengku; Mohamad, Dasmawati; Rahim, Tuan Noraihan Azila Tuan; Akil, Hazizan Md; Rajion, Zainul Ahmad

2016-12-01

Conventional prosthesis fabrication is highly depends on the hand creativity of laboratory technologist. The development in 3D printing technology offers a great help in fabricating affordable and fast yet esthetically acceptable prostheses. This study was conducted to discover the potential of 3D printed moulds for indirect silicone elastomer based nasal prosthesis fabrication. Moulds were designed using computer aided design (CAD) software (Solidworks, USA) and converted into the standard tessellation language (STL) file. Three moulds with layer thickness of 0.1, 0.2 and 0.3mm were printed utilizing polymer filament based 3D printer (Makerbot Replicator 2X, Makerbot, USA). Another one mould was printed utilizing liquid resin based 3D printer (Objet 30 Scholar, Stratasys, USA) as control. The printed moulds were then used to fabricate maxillofacial silicone specimens (n=10)/mould. Surface profilometer (Surfcom Flex, Accretech, Japan), digital microscope (KH77000, Hirox, USA) and scanning electron microscope (Quanta FEG 450, Fei, USA) were used to measure the surface roughness as well as the topological properties of fabricated silicone. Statistical analysis of One-Way ANOVA was employed to compare the surface roughness of the fabricated silicone elastomer. Result obtained demonstrated significant differences in surface roughness of the fabricated silicone (p<0.01). Further post hoc analysis also revealed significant differences in silicone fabricated using different 3D printed moulds (p<0.01). A 3D printed mould was successfully prepared and characterized. With surface topography that could be enhanced, inexpensive and rapid mould fabrication techniques, polymer filament based 3D printer is potential for indirect silicone elastomer based nasal prosthesis fabrication.

Plantar fascia anatomy and its relationship with Achilles tendon and paratenon

PubMed Central

Stecco, Carla; Corradin, Marco; Macchi, Veronica; Morra, Aldo; Porzionato, Andrea; Biz, Carlo; De Caro, Raffaele

2013-01-01

Although the plantar fascia (PF) has been studied quite well from a biomechanical viewpoint, its microscopic properties have been overlooked: nothing is known about its content of elastic fibers, the features of the extracellular matrix or the extent of innervation. From a functional and clinical standpoint, the PF is often correlated with the triceps surae muscle, but the anatomical grounds for this link are not clear. The aim of this work was to focus on the PF macroscopic and microscopic properties and study how Achilles tendon diseases might affect it. Twelve feet from unembalmed human cadavers were dissected to isolate the PF. Specimens from each PF were tested with various histological and immunohistochemical stains. In a second stage, 52 magnetic resonance images (MRI) obtained from patients complaining of aspecific ankle or foot pain were analyzed, dividing the cases into two groups based on the presence or absence of signs of degeneration and/or inflammation of the Achilles tendon. The thickness of PF and paratenon was assessed in the two groups and statistical analyses were conducted. The PF is a tissue firmly joined to plantar muscles and skin. Analyzing its possible connections to the sural structures showed that this fascia is more closely connected to the paratenon of Achilles tendon than to the Achilles tendon, through the periosteum of the heel. The PF extended medially and laterally, continuing into the deep fasciae enveloping the abductor hallucis and abductor digiti minimi muscles, respectively. The PF was rich in hyaluronan, probably produced by fibroblastic-like cells described as ‘fasciacytes’. Nerve endings and Pacini and Ruffini corpuscles were present, particularly in the medial and lateral portions, and on the surface of the muscles, suggesting a role for the PF in the proprioception of foot. In the radiological study, 27 of the 52 MRI showed signs of Achilles tendon inflammation and/or degeneration, and the PF was 3.43 ± 0.48 mm thick (99%CI and SD = 0.95), as opposed to 2.09 ± 0.24 mm (99%CI, SD = 0.47) in the patients in which the MRI revealed no Achilles tendon diseases; this difference in thickness of 1.29 ± 0.57 mm (99%CI) was statistically significant (P < 0.001). In the group of 27/52 patients with tendinopathies, the PF was more than 4.5 mm thick in 5, i.e. they exceeded the threshold for a diagnosis of plantar fasciitis. None of the other 25/52 paitents had a PF more than 4 mm thick. There was a statistically significant correlation between the thicknesses of the PF and the paratenon. These findings suggest that the plantar fascia has a role not only in supporting the longitudinal arch of the foot, but also in its proprioception and peripheral motor coordination. Its relationship with the paratenon of the Achilles tendon is consistent with the idea of triceps surae structures being involved in the PF pathology, so their rehabilitation can be considered appropriate. Finally, the high concentration of hyaluronan in the PF points to the feasibility of using hyaluronan injections in the fascia to treat plantar fasciitis. PMID:24028383

Photon event distribution sampling: an image formation technique for scanning microscopes that permits tracking of sub-diffraction particles with high spatial and temporal resolutions.

PubMed

Larkin, J D; Publicover, N G; Sutko, J L

2011-01-01

In photon event distribution sampling, an image formation technique for scanning microscopes, the maximum likelihood position of origin of each detected photon is acquired as a data set rather than binning photons in pixels. Subsequently, an intensity-related probability density function describing the uncertainty associated with the photon position measurement is applied to each position and individual photon intensity distributions are summed to form an image. Compared to pixel-based images, photon event distribution sampling images exhibit increased signal-to-noise and comparable spatial resolution. Photon event distribution sampling is superior to pixel-based image formation in recognizing the presence of structured (non-random) photon distributions at low photon counts and permits use of non-raster scanning patterns. A photon event distribution sampling based method for localizing single particles derived from a multi-variate normal distribution is more precise than statistical (Gaussian) fitting to pixel-based images. Using the multi-variate normal distribution method, non-raster scanning and a typical confocal microscope, localizations with 8 nm precision were achieved at 10 ms sampling rates with acquisition of ~200 photons per frame. Single nanometre precision was obtained with a greater number of photons per frame. In summary, photon event distribution sampling provides an efficient way to form images when low numbers of photons are involved and permits particle tracking with confocal point-scanning microscopes with nanometre precision deep within specimens. © 2010 The Authors Journal of Microscopy © 2010 The Royal Microscopical Society.

Micrometer-resolved film dosimetry using a microscope in microbeam radiation therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartzsch, Stefan, E-mail: stefan.bartzsch@icr.ac.uk; Oelfke, Uwe; Lott, Johanna

2015-07-15

Purpose: Microbeam radiation therapy (MRT) is a still preclinical tumor therapy approach that uses arrays of a few tens of micrometer wide parallel beams separated by a few 100 μm. The production, measurement, and planning of such radiation fields are a challenge up to now. Here, the authors investigate the feasibility of radiochromic film dosimetry in combination with a microscopic readout as a tool to validate peak and valley doses in MRT, which is an important requirement for a future clinical application of the therapy. Methods: Gafchromic{sup ®} HD-810 and HD-V2 films are exposed to MRT fields at the biomedicalmore » beamline ID17 of the European Synchrotron Radiation Facility (ESRF) and are afterward scanned with a microscope. The measured dose is compared with Monte Carlo calculations. Image analysis tools and film handling protocols are developed that allow accurate and reproducible dosimetry. The performance of HD-810 and HD-V2 films is compared and a detailed analysis of the resolution, noise, and energy dependence is carried out. Measurement uncertainties are identified and analyzed. Results: The dose was measured with a resolution of 5 × 1000 μm{sup 2} and an accuracy of 5% in the peak and between 10% and 15% in the valley region. As main causes for dosimetry uncertainties, statistical noise, film inhomogeneities, and calibration errors were identified. Calibration errors strongly increase at low doses and exceeded 3% for doses below 50 and 70 Gy for HD-V2 and HD-810 films, respectively. While the grain size of both film types is approximately 2 μm, the statistical noise in HD-V2 is much higher than in HD-810 films. However, HD-810 films show a higher energy dependence at low photon energies. Conclusions: Both film types are appropriate for dosimetry in MRT and the microscope is superior to the microdensitometer used before at the ESRF with respect to resolution and reproducibility. However, a very careful analysis of the image data is required. Dosimetry at low photon energies should be performed with great caution due to the energy sensitivity of the films. In this respect, HD-V2 films showed to have an advantage over HD-810 films. However, HD-810 films have a lower statistical noise level. When a higher resolution is required, e.g., for the dosimetry of pencil beam irradiations, noise may render HD-V2 films inapplicable.« less

Structure models: From shell model to ab initio methods. A brief introduction to microscopic theories for exotic nuclei

NASA Astrophysics Data System (ADS)

Bacca, Sonia

2016-04-01

A brief review of models to describe nuclear structure and reactions properties is presented, starting from the historical shell model picture and encompassing modern ab initio approaches. A selection of recent theoretical results on observables for exotic light and medium-mass nuclei is shown. Emphasis is given to the comparison with experiment and to what can be learned about three-body forces and continuum properties.

Electric Conduction in Solids: a Pedagogical Approach Supported by Laboratory Measurements and Computer Modelling Environments

NASA Astrophysics Data System (ADS)

Bonura, A.; Capizzo, M. C.; Fazio, C.; Guastella, I.

2008-05-01

In this paper we present a pedagogic approach aimed at modeling electric conduction in semiconductors, built by using NetLogo, a programmable modeling environment for building and exploring multi-agent systems. `Virtual experiments' are implemented to confront predictions of different microscopic models with real measurements of electric properties of matter, such as resistivity. The relations between these electric properties and other physical variables, like temperature, are, then, analyzed.

Microscopic Electronic and Mechanical Properties of Ultra-Thin Layered Materials

DTIC Science & Technology

2016-07-25

Graphene single layers grown by chemical vapor deposition on single crystal Cu substrates are subject to nonuniform physisorption strains that...the observed highly nonuniform strains. 4. Connecting dopant bond type with electronic structure in N-doped graphene (reference [4]) Robust methods

Viscoelastic properties of dendrimers in the melt from nonequlibrium molecular dynamics

NASA Astrophysics Data System (ADS)

Bosko, Jaroslaw T.; Todd, B. D.; Sadus, Richard J.

2004-12-01

The viscoelastic properties of dendrimers of generation 1-4 are studied using nonequilibrium molecular dynamics. Flow properties of dendrimer melts under shear are compared to systems composed of linear chain polymers of the same molecular weight, and the influence of molecular architecture is discussed. Rheological material properties, such as the shear viscosity and normal stress coefficients, are calculated and compared for both systems. We also calculate and compare the microscopic properties of both linear chain and dendrimer molecules, such as their molecular alignment, order parameters and rotational velocities. We find that the highly symmetric shape of dendrimers and their highly constrained geometry allows for substantial differences in their material properties compared to traditional linear polymers of equivalent molecular weight.

Evaluation of penetration depth of 2% chlorhexidine digluconate into root dentinal tubules using confocal laser scanning microscope.

PubMed

Vadhana, Sekar; Latha, Jothi; Velmurugan, Natanasabapathy

2015-05-01

This study evaluated the penetration depth of 2% chlorhexidine digluconate (CHX) into root dentinal tubules and the influence of passive ultrasonic irrigation (PUI) using a confocal laser scanning microscope (CLSM). Twenty freshly extracted anterior teeth were decoronated and instrumented using Mtwo rotary files up to size 40, 4% taper. The samples were randomly divided into two groups (n = 10), that is, conventional syringe irrigation (CSI) and PUI. CHX was mixed with Rhodamine B dye and was used as the final irrigant. The teeth were sectioned at coronal, middle and apical levels and viewed under CLSM to record the penetration depth of CHX. The data were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests. The mean penetration depths of 2% CHX in coronal, middle and apical thirds were 138 µm, 80 µm and 44 µm in CSI group, respectively, whereas the mean penetration depths were 209 µm, 138 µm and 72 µm respectively in PUI group. Statistically significant difference was present between CSI group and PUI group at all three levels (p < 0.01 for coronal third and p < 0.001 for middle and apical thirds). On intragroup analysis, both groups showed statistically significant difference among three levels (p < 0.001). Penetration depth of 2% CHX into root dentinal tubules is deeper in coronal third when compared to middle and apical third. PUI aided in deeper penetration of 2% CHX into dentinal tubules when compared to conventional syringe irrigation at all three levels.