Creating Cycling-Friendly Environments for Children: Which Micro-Scale Factors Are Most Important? An Experimental Study Using Manipulated Photographs.

PubMed

Ghekiere, Ariane; Deforche, Benedicte; Mertens, Lieze; De Bourdeaudhuij, Ilse; Clarys, Peter; de Geus, Bas; Cardon, Greet; Nasar, Jack; Salmon, Jo; Van Cauwenberg, Jelle

2015-01-01

Increasing participation in transportation cycling represents a useful strategy for increasing children's physical activity levels. Knowledge on how to design environments to encourage adoption and maintenance of transportation cycling is limited and relies mainly on observational studies. The current study experimentally investigates the relative importance of micro-scale environmental factors for children's transportation cycling, as these micro-scale factors are easier to change within an existing neighborhood compared to macro-scale environmental factors (i.e. connectivity, land-use mix, …). Researchers recruited children and their parents (n = 1232) via 45 randomly selected schools across Flanders and completed an online questionnaire which consisted of 1) demographic questions; and 2) a choice-based conjoint (CBC) task. During this task, participants chose between two photographs which we had experimentally manipulated in seven micro-scale environmental factors: type of cycle path; evenness of cycle path; traffic speed; traffic density; presence of speed bumps; environmental maintenance; and vegetation. Participants indicated which route they preferred to (let their child) cycle along. To find the relative importance of these micro-scale environmental factors, we conducted Hierarchical Bayes analyses. Type of cycle path emerged as the most important factor by far among both children and their parents, followed by traffic density and maintenance, and evenness of the cycle path among children. Among parents, speed limits and maintenance emerged as second most important, followed by evenness of the cycle path, and traffic density. Findings indicate that improvements in micro-scale environmental factors might be effective for increasing children's transportation cycling, since they increase the perceived supportiveness of the physical environment for transportation cycling. Investments in creating a clearly designated space for the young cyclist, separated from motorized traffic, appears to be the most effective way to increase perceived supportiveness. Future research should confirm our laboratory findings with experimental on-site research.

Microscale Group Test for Carbonyl Compounds.

ERIC Educational Resources Information Center

Horak, V.; Klein, R. F. X.

1985-01-01

Procedures are provided for a test that (1) demonstrates principles of derivatization with 2,4-dinitrophenylhydrazine; (2) is a thin layer chromatography experiment that visually demonstrates separation of colored compounds of different polarities; and (3) introduces microscale experimentation to students in sophomore organic chemistry…

Photothermal fabrication of microscale patterned DNA hydrogels

NASA Astrophysics Data System (ADS)

Shimomura, Suguru; Nishimura, Takahiro; Ogura, Yusuke; Tanida, Jun

2018-02-01

This paper introduces a method for fabricating microscale DNA hydrogels using irradiation with patterned light. Optical fabrication allows for the flexible and tunable formation of DNA hydrogels without changing the environmental conditions. Our scheme is based on local heat generation via the photothermal effect, which is induced by light irradiation on a quenching species. We demonstrate experimentally that, depending on the power and irradiation time, light irradiation enables the creation of local microscale DNA hydrogels, while the shapes of the DNA hydrogels are controlled by the irradiation patterns.

Microscale Organic Lab Course Has Many Assets.

ERIC Educational Resources Information Center

Rawls, Rebecca

1984-01-01

Describes a microscale laboratory course in which students perform many classic organic reactions using only one-hundredth to one-thousandth the amount of starting material usual in student experiments. Reduction of toxic chemicals concentration in laboratory air and savings in chemical costs and experimental time are benefits of the novel course.…

Cyber integrated MEMS microhand for biological applications

NASA Astrophysics Data System (ADS)

Weissman, Adam; Frazier, Athena; Pepen, Michael; Lu, Yen-Wen; Yang, Shanchieh Jay

2009-05-01

Anthropomorphous robotic hands at microscales have been developed to receive information and perform tasks for biological applications. To emulate a human hand's dexterity, the microhand requires a master-slave interface with a wearable controller, force sensors, and perception displays for tele-manipulation. Recognizing the constraints and complexity imposed in developing feedback interface during miniaturization, this project address the need by creating an integrated cyber environment incorporating sensors with a microhand, haptic/visual display, and object model, to emulates human hands' psychophysical perception at microscale.

Self-assembly kinetics of microscale components: A parametric evaluation

NASA Astrophysics Data System (ADS)

Carballo, Jose M.

The goal of the present work is to develop, and evaluate a parametric model of a basic microscale Self-Assembly (SA) interaction that provides scaling predictions of process rates as a function of key process variables. At the microscale, assembly by "grasp and release" is generally challenging. Recent research efforts have proposed adapting nanoscale self-assembly (SA) processes to the microscale. SA offers the potential for reduced equipment cost and increased throughput by harnessing attractive forces (most commonly, capillary) to spontaneously assemble components. However, there are challenges for implementing microscale SA as a commercial process. The existing lack of design tools prevents simple process optimization. Previous efforts have characterized a specific aspect of the SA process. However, the existing microscale SA models do not characterize the inter-component interactions. All existing models have simplified the outcome of SA interactions as an experimentally-derived value specific to a particular configuration, instead of evaluating it outcome as a function of component level parameters (such as speed, geometry, bonding energy and direction). The present study parameterizes the outcome of interactions, and evaluates the effect of key parameters. The present work closes the gap between existing microscale SA models to add a key piece towards a complete design tool for general microscale SA process modeling. First, this work proposes a simple model for defining the probability of assembly of basic SA interactions. A basic SA interaction is defined as the event where a single part arrives on an assembly site. The model describes the probability of assembly as a function of kinetic energy, binding energy, orientation and incidence angle for the component and the assembly site. Secondly, an experimental SA system was designed, and implemented to create individual SA interactions while controlling process parameters independently. SA experiments measured the outcome of SA interactions, while studying the independent effects of each parameter. As a first step towards a complete scaling model, experiments were performed to evaluate the effects of part geometry and part travel direction under low kinetic energy conditions. Experimental results show minimal dependence of assembly yield on the incidence angle of the parts, and significant effects induced by changes in part geometry. The results from this work indicate that SA could be modeled as an energy-based process due to the small path dependence effects. Assembly probability is linearly related to the orientation probability. The proportionality constant is based on the area fraction of the sites with an amplification factor. This amplification factor accounts for the ability of capillary forces to align parts with only very small areas of contact when they have a low kinetic energy. Results provide unprecedented insight about SA interactions. The present study is a key step towards completing a basic model of a general SA process. Moreover, the outcome from this work can complement existing SA process models, in order to create a complete design tool for microscale SA systems. In addition to SA experiments, Monte Carlo simulations of experimental part-site interactions were conducted. This study confirmed that a major contributor to experimental variation is the stochastic nature of experimental SA interactions and the limited sample size of the experiments. Furthermore, the simulations serve as a tool for defining an optimum sampling strategy to minimize the uncertainty in future SA experiments.

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.

The Effect of Microscale Chemistry Experimentation on Students' Attitude and Motivation towards Chemistry Practical Work

ERIC Educational Resources Information Center

Abdullah, Mashita; Mohamed, Norita; Ismail, Zurida Hj

2007-01-01

Microscale chemistry is an approach to conducting chemistry practicals which can help overcome increased concerns about environmental pollution problems as well as rising laboratory costs. It is accomplished by using miniature labware and significantly reduced amounts of chemicals. This paper reports on students' attitudes and motivation towards…

Capillary hydrodynamics and transport processes during phase change in microscale systems

NASA Astrophysics Data System (ADS)

Kuznetsov, V. V.

2017-09-01

The characteristics of two-phase gas-liquid flow and heat transfer during flow boiling and condensing in micro-scale heat exchangers are discussed in this paper. The results of numerical simulation of the evaporating liquid film flowing downward in rectangular minichannel of the two-phase compact heat exchanger are presented and the peculiarities of microscale heat transport in annular flow with phase changes are discussed. Presented model accounts the capillarity induced transverse flow of liquid and predicts the microscale heat transport processes when the nucleate boiling becomes suppressed. The simultaneous influence of the forced convection, nucleate boiling and liquid film evaporation during flow boiling in plate-fin heat exchangers is considered. The equation for prediction of the flow boiling heat transfer at low flux conditions is presented and verified using experimental data.

Microscale vortex laser with controlled topological charge

NASA Astrophysics Data System (ADS)

Wang, Xing-Yuan; Chen, Hua-Zhou; Li, Ying; Li, Bo; Ma, Ren-Min

2016-12-01

A microscale vortex laser is a new type of coherent light source with small footprint that can directly generate vector vortex beams. However, a microscale laser with controlled topological charge, which is crucial for virtually any of its application, is still unrevealed. Here we present a microscale vortex laser with controlled topological charge. The vortex laser eigenmode was synthesized in a metamaterial engineered non-Hermitian micro-ring cavity system at exceptional point. We also show that the vortex laser cavity can operate at exceptional point stably to lase under optical pumping. The microscale vortex laser with controlled topological charge can serve as a unique and general building block for next-generation photonic integrated circuits and coherent vortex beam sources. The method we used here can be employed to generate lasing eigenmode with other complex functionalities. Project supported by the “Youth 1000 Talent Plan” Fund, Ministry of Education of China (Grant No. 201421) and the National Natural Science Foundation of China (Grant Nos. 11574012 and 61521004).

A Novel Multiscale Physics Based Progressive Failure Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Pineda, Evan J.; Waas, Anthony M.; Bednarcyk, Brett A.; Collier, Craig S.; Yarrington, Phillip W.

2008-01-01

A variable fidelity, multiscale, physics based finite element procedure for predicting progressive damage and failure of laminated continuous fiber reinforced composites is introduced. At every integration point in a finite element model, progressive damage is accounted for at the lamina-level using thermodynamically based Schapery Theory. Separate failure criteria are applied at either the global-scale or the microscale in two different FEM models. A micromechanics model, the Generalized Method of Cells, is used to evaluate failure criteria at the micro-level. The stress-strain behavior and observed failure mechanisms are compared with experimental results for both models.

The Effect of an Individualized Laboratory Approach through Microscale Chemistry Experimentation on Students' Understanding of Chemistry Concepts, Motivation and Attitudes

ERIC Educational Resources Information Center

Abdullah, Mashita; Mohamed, Norita; Ismail, Zurida Hj

2009-01-01

The main goal of this study was to investigate whether the use of an individualized approach through microscale chemistry experiments in secondary schools can increase students' understanding of chemistry concepts, improve attitude towards chemistry practical work and motivation. Two comparable groups of Form Four students (16 years old)…

Microscale autonomous sensor and communications module

DOEpatents

Okandan, Murat; Nielson, Gregory N

2014-03-25

Various technologies pertaining to a microscale autonomous sensor and communications module are described herein. Such a module includes a sensor that generates a sensor signal that is indicative of an environmental parameter. An integrated circuit receives the sensor signal and generates an output signal based at least in part upon the sensor signal. An optical emitter receives the output signal and generates an optical signal as a function of the output signal. An energy storage device is configured to provide power to at least the integrated circuit and the optical emitter, and wherein the module has a relatively small diameter and thickness.

Experimental far-field imaging properties of a ~5-μm diameter spherical lens.

PubMed

Ye, Ran; Ye, Yong-Hong; Ma, Hui Feng; Ma, Jun; Wang, Bin; Yao, Jie; Liu, Shuai; Cao, Lingling; Xu, Huanhuan; Zhang, Jia-Yu

2013-06-01

Microscale lenses are mostly used as near-sighted lenses. The far-field imaging properties of a microscale spherical lens, where the lens is spatially separated from the object, are experimentally studied. Our experimental results show that, for a blu-ray disc (an object) whose spacing is 300 nm, the lens can magnify the stripe patterns of the disc when the lens is spatially separated from the object. In the experimentally tested range (0-14 μm), all the magnified images are virtual images. When the distance is increased from 0 to 14 μm the magnification decreases from 1.47× to 1.20× and the field of view increases from 3.8 to 12.2 μm. The image magnification cannot be described by standard geometrical optics.

Advances in microscale separations towards nanoproteomics applications

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

Yi, Lian; Piehowski, Paul D.; Shi, Tujin

Microscale separations (e.g., liquid chromatography or capillary electrophoresis) coupled with mass spectrometry (MS) has become the primary tool for advanced proteomics, an indispensable technology for gaining understanding of complex biological processes. While significant advances have been achieved in MS-based proteomics, the current platforms still face a significant challenge in overall sensitivity towards nanoproteomics (i.e., with less than 1 g total amount of proteins available) applications such as cellular heterogeneity in tissue pathologies. Herein, we review recent advances in microscale separation techniques and integrated sample processing systems that improve the overall sensitivity and coverage of the proteomics workflow, and their contributionsmore » towards nanoproteomics applications.« less

Micro-scale finite element modeling of ultrasound propagation in aluminum trabecular bone-mimicking phantoms: A comparison between numerical simulation and experimental results.

PubMed

Vafaeian, B; Le, L H; Tran, T N H T; El-Rich, M; El-Bialy, T; Adeeb, S

2016-05-01

The present study investigated the accuracy of micro-scale finite element modeling for simulating broadband ultrasound propagation in water-saturated trabecular bone-mimicking phantoms. To this end, five commercially manufactured aluminum foam samples as trabecular bone-mimicking phantoms were utilized for ultrasonic immersion through-transmission experiments. Based on micro-computed tomography images of the same physical samples, three-dimensional high-resolution computational samples were generated to be implemented in the micro-scale finite element models. The finite element models employed the standard Galerkin finite element method (FEM) in time domain to simulate the ultrasonic experiments. The numerical simulations did not include energy dissipative mechanisms of ultrasonic attenuation; however, they expectedly simulated reflection, refraction, scattering, and wave mode conversion. The accuracy of the finite element simulations were evaluated by comparing the simulated ultrasonic attenuation and velocity with the experimental data. The maximum and the average relative errors between the experimental and simulated attenuation coefficients in the frequency range of 0.6-1.4 MHz were 17% and 6% respectively. Moreover, the simulations closely predicted the time-of-flight based velocities and the phase velocities of ultrasound with maximum relative errors of 20 m/s and 11 m/s respectively. The results of this study strongly suggest that micro-scale finite element modeling can effectively simulate broadband ultrasound propagation in water-saturated trabecular bone-mimicking structures. Copyright © 2016 Elsevier B.V. All rights reserved.

Integrative Systems Models of Cardiac Excitation Contraction Coupling

PubMed Central

Greenstein, Joseph L.; Winslow, Raimond L.

2010-01-01

Excitation-contraction coupling in the cardiac myocyte is mediated by a number of highly integrated mechanisms of intracellular Ca2+ transport. The complexity and integrative nature of heart cell electrophysiology and Ca2+-cycling has led to an evolution of computational models that have played a crucial role in shaping our understanding of heart function. An important emerging theme in systems biology is that the detailed nature of local signaling events, such as those that occur in the cardiac dyad, have important consequences at higher biological scales. Multi-scale modeling techniques have revealed many mechanistic links between micro-scale events, such as Ca2+ binding to a channel protein, and macro-scale phenomena, such as excitation-contraction coupling gain. Here we review experimentally based multi-scale computational models of excitation-contraction coupling and the insights that have been gained through their application. PMID:21212390

Microscale surface modifications for heat transfer enhancement.

PubMed

Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

2013-10-09

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 μm for the reference smooth surface to 19.5 μm for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.

Evaluation of a micro-scale wind model's performance over realistic building clusters using wind tunnel experiments

NASA Astrophysics Data System (ADS)

Zhang, Ning; Du, Yunsong; Miao, Shiguang; Fang, Xiaoyi

2016-08-01

The simulation performance over complex building clusters of a wind simulation model (Wind Information Field Fast Analysis model, WIFFA) in a micro-scale air pollutant dispersion model system (Urban Microscale Air Pollution dispersion Simulation model, UMAPS) is evaluated using various wind tunnel experimental data including the CEDVAL (Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models) wind tunnel experiment data and the NJU-FZ experiment data (Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data). The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier-Stokes equations, and can produce very high-resolution (1-5 m) wind fields of a complex neighborhood scale urban building canopy (~ 1 km ×1 km) in less than 3 min when run on a personal computer.

Advances in microscale separations towards nanoproteomics applications

DOE PAGES

Yi, Lian; Piehowski, Paul D.; Shi, Tujin; ...

2017-07-21

Microscale separation (e.g., liquid chromatography or capillary electrophoresis) coupled with mass spectrometry (MS) has become the primary tool for advanced proteomics, an indispensable technology for gaining understanding of complex biological processes. In recent decades significant advances have been achieved in MS-based proteomics. But, the current proteomics platforms still face an analytical challenge in overall sensitivity towards nanoproteomics applications for starting materials of less than 1 μg total proteins (e.g., cellular heterogeneity in tissue pathologies). We review recent advances in microscale separation techniques and integrated sample processing strategies that improve the overall sensitivity and proteome coverage of the proteomics workflow, andmore » their contributions towards nanoproteomics applications.« less

Advances in microscale separations towards nanoproteomics applications

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

Yi, Lian; Piehowski, Paul D.; Shi, Tujin

Microscale separation (e.g., liquid chromatography or capillary electrophoresis) coupled with mass spectrometry (MS) has become the primary tool for advanced proteomics, an indispensable technology for gaining understanding of complex biological processes. In recent decades significant advances have been achieved in MS-based proteomics. But, the current proteomics platforms still face an analytical challenge in overall sensitivity towards nanoproteomics applications for starting materials of less than 1 μg total proteins (e.g., cellular heterogeneity in tissue pathologies). We review recent advances in microscale separation techniques and integrated sample processing strategies that improve the overall sensitivity and proteome coverage of the proteomics workflow, andmore » their contributions towards nanoproteomics applications.« less

Microfabricated ion trap array

DOEpatents

Blain, Matthew G [Albuquerque, NM; Fleming, James G [Albuquerque, NM

2006-12-26

A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

Microscale Electromagnetic Heating in Heterogeneous Energetic Materials Based on X-ray Computed Tomography

NASA Astrophysics Data System (ADS)

Kort-Kamp, W. J. M.; Cordes, N. L.; Ionita, A.; Glover, B. B.; Duque, A. L. Higginbotham; Perry, W. L.; Patterson, B. M.; Dalvit, D. A. R.; Moore, D. S.

2016-04-01

Electromagnetic stimulation of energetic materials provides a noninvasive and nondestructive tool for detecting and identifying explosives. We combine structural information based on x-ray computed tomography, experimental dielectric data, and electromagnetic full-wave simulations to study microscale electromagnetic heating of realistic three-dimensional heterogeneous explosives. We analyze the formation of electromagnetic hot spots and thermal gradients in the explosive-binder mesostructures and compare the heating rate for various binder systems.

Can Integrated Micro-Optical Concentrator Technology Revolutionize Flat-Plate Photovoltaic Solar Energy Harvesting?

NASA Astrophysics Data System (ADS)

Haney, Michael W.

2015-12-01

The economies-of-scale and enhanced performance of integrated micro-technologies have repeatedly delivered disruptive market impact. Examples range from microelectronics to displays to lighting. However, integrated micro-scale technologies have yet to be applied in a transformational way to solar photovoltaic panels. The recently announced Micro-scale Optimized Solar-cell Arrays with Integrated Concentration (MOSAIC) program aims to create a new paradigm in solar photovoltaic panel technology based on the incorporation of micro-concentrating photo-voltaic (μ-CPV) cells. As depicted in Figure 1, MOSAIC will integrate arrays of micro-optical concentrating elements and micro-scale PV elements to achieve the same aggregated collection area and high conversion efficiency of a conventional (i.e., macro-scale) CPV approach, but with the low profile and mass, and hopefully cost, of a conventional non-concentrated PV panel. The reduced size and weight, and enhanced wiring complexity, of the MOSAIC approach provide the opportunity to access the high-performance/low-cost region between the conventional CPV and flat-plate (1-sun) PV domains shown in Figure 2. Accessing this portion of the graph in Figure 2 will expand the geographic and market reach of flat-plate PV. This talk reviews the motivation and goals for the MOSAIC program. The diversity of the technical approaches to micro-concentration, embedded solar tracking, and hybrid direct/diffuse solar resource collection found in the MOSAIC portfolio of projects will also be highlighted.

Biological Response of Human Bone Marrow-Derived Mesenchymal Stem Cells to Commercial Tantalum Coatings with Microscale and Nanoscale Surface Topographies

NASA Astrophysics Data System (ADS)

Skoog, Shelby A.; Kumar, Girish; Goering, Peter L.; Williams, Brian; Stiglich, Jack; Narayan, Roger J.

2016-06-01

Tantalum is a promising orthopaedic implant coating material due to its robust mechanical properties, corrosion resistance, and excellent biocompatibility. Previous studies have demonstrated improved biocompatibility and tissue integration of surface-treated tantalum coatings compared to untreated tantalum. Surface modification of tantalum coatings with biologically inspired microscale and nanoscale features may be used to evoke optimal tissue responses. The goal of this study was to evaluate commercial tantalum coatings with nanoscale, sub-microscale, and microscale surface topographies for orthopaedic and dental applications using human bone marrow-derived mesenchymal stem cells (hBMSCs). Tantalum coatings with different microscale and nanoscale surface topographies were fabricated using a diffusion process or chemical vapor deposition. Biological evaluation of the tantalum coatings using hBMSCs showed that tantalum coatings promote cellular adhesion and growth. Furthermore, hBMSC adhesion to the tantalum coatings was dependent on surface feature characteristics, with enhanced cell adhesion on sub-micrometer- and micrometer-sized surface topographies compared to hybrid nano-/microstructures. Nanostructured and microstructured tantalum coatings should be further evaluated to optimize the surface coating features to promote osteogenesis and enhance osseointegration of tantalum-based orthopaedic implants.

Microscale electromagnetic heating in heterogeneous energetic materials based on x-ray computed tomography

DOE PAGES

Kort-Kamp, W. J. M.; Cordes, N. L.; Ionita, A.; ...

2016-04-01

Electromagnetic stimulation of energetic materials provides a noninvasive and nondestructive tool for detecting and identifying explosives. We combine structural information based on x-ray computed tomography, experimental dielectric data, and electromagnetic full-wave simulations to study microscale electromagnetic heating of realistic three-dimensional heterogeneous explosives. In conclusion, we analyze the formation of electromagnetic hot spots and thermal gradients in the explosive-binder mesostructures and compare the heating rate for various binder systems.

Microscale electromagnetic heating in heterogeneous energetic materials based on x-ray computed tomography

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

Kort-Kamp, W. J. M.; Cordes, N. L.; Ionita, A.

Electromagnetic stimulation of energetic materials provides a noninvasive and nondestructive tool for detecting and identifying explosives. We combine structural information based on x-ray computed tomography, experimental dielectric data, and electromagnetic full-wave simulations to study microscale electromagnetic heating of realistic three-dimensional heterogeneous explosives. In conclusion, we analyze the formation of electromagnetic hot spots and thermal gradients in the explosive-binder mesostructures and compare the heating rate for various binder systems.

Anomalous resonance in a nanomechanical biosensor

PubMed Central

Gupta, Amit K.; Nair, Pradeep R.; Akin, Demir; Ladisch, Michael R.; Broyles, Steve; Alam, Muhammad A.; Bashir, Rashid

2006-01-01

The decrease in resonant frequency (−Δωr) of a classical cantilever provides a sensitive measure of the mass of entities attached on its surface. This elementary phenomenon has been the basis of a new class of bio-nanomechanical devices as sensing components of integrated microsystems that can perform rapid, sensitive, and selective detection of biological and biochemical entities. Based on classical analysis, there is a widespread perception that smaller sensors are more sensitive (sensitivity ≈ −0.5ωr/mC, where mC is the mass of the cantilever), and this notion has motivated scaling of biosensors to nanoscale dimensions. In this work, we show that the response of a nanomechanical biosensor is far more complex than previously anticipated. Indeed, in contrast to classical microscale sensors, the resonant frequencies of the nanosensor may actually decrease or increase after attachment of protein molecules. We demonstrate theoretically and experimentally that the direction of the frequency change arises from a size-specific modification of diffusion and attachment kinetics of biomolecules on the cantilevers. This work may have broad impact on microscale and nanoscale biosensor design, especially when predicting the characteristics of bio-nanoelectromechanical sensors functionalized with biological capture molecules. PMID:16938886

Micro-scale heat-exchangers for Joule-Thomson cooling.

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

Gross, Andrew John

2014-01-01

This project focused on developing a micro-scale counter flow heat exchangers for Joule-Thomson cooling with the potential for both chip and wafer scale integration. This project is differentiated from previous work by focusing on planar, thin film micromachining instead of bulk materials. A process will be developed for fabricating all the devices mentioned above, allowing for highly integrated micro heat exchangers. The use of thin film dielectrics provides thermal isolation, increasing efficiency of the coolers compared to designs based on bulk materials, and it will allow for wafer-scale fabrication and integration. The process is intended to implement a CFHX asmore » part of a Joule-Thomson cooling system for applications with heat loads less than 1mW. This report presents simulation results and investigation of a fabrication process for such devices.« less

Sample extraction and injection with a microscale preconcentrator.

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

Robinson, Alex Lockwood; Chan, Helena Kai Lun

2007-09-01

This report details the development of a microfabricated preconcentrator that functions as a fully integrated chemical extractor-injector for a microscale gas chromatograph (GC). The device enables parts-per-billion detection and quantitative analysis of volatile organic compounds (VOCs) in indoor air with size and power advantages over macro-scale systems. The 44 mm{sup 3} preconcentrator extracts VOCs using highly adsorptive, granular forms of graphitized carbon black and carbon molecular sieves. The micron-sized silicon cavities have integrated heating and temperature sensing allowing low power, yet rapid heating to thermally desorb the collected VOCs (GC injection). The keys to device construction are a new adsorbent-solventmore » filling technique and solvent-tolerant wafer-level silicon-gold eutectic bonding technology. The product is the first granular adsorbent preconcentrator integrated at the wafer level. Other advantages include exhaustive VOC extraction and injection peak widths an order of magnitude narrower than predecessor prototypes. A mass transfer model, the first for any microscale preconcentrator, is developed to describe both adsorption and desorption behaviors. The physically intuitive model uses implicit and explicit finite differences to numerically solve the required partial differential equations. The model is applied to the adsorption and desorption of decane at various concentrations to extract Langmuir adsorption isotherm parameters from effluent curve measurements where properties are unknown a priori.« less

Microassembly of Heterogeneous Materials using Transfer Printing and Thermal Processing

PubMed Central

Keum, Hohyun; Yang, Zining; Han, Kewen; Handler, Drew E.; Nguyen, Thong Nhu; Schutt-Aine, Jose; Bahl, Gaurav; Kim, Seok

2016-01-01

Enabling unique architectures and functionalities of microsystems for numerous applications in electronics, photonics and other areas often requires microassembly of separately prepared heterogeneous materials instead of monolithic microfabrication. However, microassembly of dissimilar materials while ensuring high structural integrity has been challenging in the context of deterministic transferring and joining of materials at the microscale where surface adhesion is far more dominant than body weight. Here we present an approach to assembling microsystems with microscale building blocks of four disparate classes of device-grade materials including semiconductors, metals, dielectrics, and polymers. This approach uniquely utilizes reversible adhesion-based transfer printing for material transferring and thermal processing for material joining at the microscale. The interfacial joining characteristics between materials assembled by this approach are systematically investigated upon different joining mechanisms using blister tests. The device level capabilities of this approach are further demonstrated through assembling and testing of a microtoroid resonator and a radio frequency (RF) microelectromechanical systems (MEMS) switch that involve optical and electrical functionalities with mechanical motion. This work opens up a unique route towards 3D heterogeneous material integration to fabricate microsystems. PMID:27427243

Efficient designs for powering microscale devices with nanoscale biomolecular motors.

PubMed

Lin, Chih-Ting; Kao, Ming-Tse; Kurabayashi, Katsuo; Meyhöfer, Edgar

2006-02-01

Current MEMS and microfluidic designs require external power sources and actuators, which principally limit such technology. To overcome these limitations, we have developed a number of microfluidic systems into which we can seamlessly integrate a biomolecular motor, kinesin, that transports microtubules by extracting chemical energy from its aqueous working environment. Here we establish that our microfabricated structures, the self-assembly of the bio-derived transducer, and guided, unidirectional transport of microtubules are ideally suited to create engineered arrays for efficiently powering nano- and microscale devices.

Producing fluid flow using 3D carbon electrodes

NASA Astrophysics Data System (ADS)

Rouabah, H. A.; Park, B. Y.; Zaouk, R. B.; Madou, M. J.; Green, Nicolas G.

2008-12-01

Moving and manipulating bio-particles and fluids on the microscale is central to many lab-on-a-chip applications. Techniques for pumping fluids which use electric fields have shown promise using both DC and AC voltages. AC techniques, however, require the use of integrated metal electrodes which have a low resistance but can suffer from unwanted chemical reactions even at low potentials. In this paper we introduce the use of carbon MEMS technology (C-MEMS), a fabrication method which produces 3D conductive polymeric structures. Results are presented of the fabrication of an innovative design of 3D AC-electroosmotic micropump and preliminary experimental measurements which demonstrate the potential of both the technology and the design.

Multi-scale modelling of elastic moduli of trabecular bone

PubMed Central

Hamed, Elham; Jasiuk, Iwona; Yoo, Andrew; Lee, YikHan; Liszka, Tadeusz

2012-01-01

We model trabecular bone as a nanocomposite material with hierarchical structure and predict its elastic properties at different structural scales. The analysis involves a bottom-up multi-scale approach, starting with nanoscale (mineralized collagen fibril) and moving up the scales to sub-microscale (single lamella), microscale (single trabecula) and mesoscale (trabecular bone) levels. Continuum micromechanics methods, composite materials laminate theory and finite-element methods are used in the analysis. Good agreement is found between theoretical and experimental results. PMID:22279160

New dynamic silicon photonic components enabled by MEMS technology

NASA Astrophysics Data System (ADS)

Errando-Herranz, Carlos; Edinger, Pierre; Colangelo, Marco; Björk, Joel; Ahmed, Samy; Stemme, Göran; Niklaus, Frank; Gylfason, Kristinn B.

2018-02-01

Silicon photonics is the study and application of integrated optical systems which use silicon as an optical medium, usually by confining light in optical waveguides etched into the surface of silicon-on-insulator (SOI) wafers. The term microelectromechanical systems (MEMS) refers to the technology of mechanics on the microscale actuated by electrostatic actuators. Due to the low power requirements of electrostatic actuation, MEMS components are very power efficient, making them well suited for dense integration and mobile operation. MEMS components are conventionally also implemented in silicon, and MEMS sensors such as accelerometers, gyros, and microphones are now standard in every smartphone. By combining these two successful technologies, new active photonic components with extremely low power consumption can be made. We discuss our recent experimental work on tunable filters, tunable fiber-to-chip couplers, and dynamic waveguide dispersion tuning, enabled by the marriage of silicon MEMS and silicon photonics.

The Integrated WRF/Urban Modeling System: Development, Evaluation, and Applications to Urban Environmental Problems

EPA Science Inventory

To bridge the gaps between traditional mesoscale modelling and microscale modelling, the National Center for Atmospheric Research, in collaboration with other agencies and research groups, has developed an integrated urban modelling system coupled to the weather research and fore...

Comparing Macroscale and Microscale Simulations of Porous Battery Electrodes

DOE PAGES

Higa, Kenneth; Wu, Shao-Ling; Parkinson, Dilworth Y.; ...

2017-06-22

This article describes a vertically-integrated exploration of NMC electrode rate limitations, combining experiments with corresponding macroscale (macro-homogeneous) and microscale models. Parameters common to both models were obtained from experiments or based on published results. Positive electrode tortuosity was the sole fitting parameter used in the macroscale model, while the microscale model used no fitting parameters, instead relying on microstructural domains generated from X-ray microtomography of pristine electrode material held under compression while immersed in electrolyte solution (additionally providing novel observations of electrode wetting). Macroscale simulations showed that the capacity decrease observed at higher rates resulted primarily from solution-phase diffusion resistance.more » This ability to provide such qualitative insights at low computational costs is a strength of macroscale models, made possible by neglecting electrode spatial details. To explore the consequences of such simplification, the corresponding, computationally-expensive microscale model was constructed. This was found to have limitations preventing quantitatively accurate predictions, for reasons that are discussed in the hope of guiding future work. Nevertheless, the microscale simulation results complement those of the macroscale model by providing a reality-check based on microstructural information; in particular, this novel comparison of the two approaches suggests a reexamination of salt diffusivity measurements.« less

Integrated Micro-scale Power Conversion

DTIC Science & Technology

2012-08-01

Micro Power Converters (μPC) Loads: Sources: μ-Power Converter (μPC) Thin-film battery Solar Cell Micro- fuel Cell Vibration Harvester...passive size • Hybrid integration with MEMS passives, particularly inductors Hybrid integration ARL focus Bubble Size = Volume [mm3] Industry Focus...Power converters survey Compiled by Bedair, Bashirullah Switched inductor (SI) Switched capacitor (SC) Resonant Resonat piezo Hybrid - SI / SC

Electrochemical detection for microscale analytical systems: a review.

PubMed

Wang, Joseph

2002-02-11

As the field of chip-based microscale systems continues its rapid growth, there are urgent needs for developing compatible detection modes. Electrochemistry detection offers considerable promise for such microfluidic systems, with features that include remarkable sensitivity, inherent miniaturization and portability, independence of optical path length or sample turbidity, low cost, low-power requirements and high compatibility with advanced micromachining and microfabrication technologies. This paper highlights recent advances, directions and key strategies in controlled-potential electrochemical detectors for miniaturized analytical systems. Subjects covered include the design and integration of the electrochemical detection system, its requirements and operational principles, common electrode materials, derivatization reactions, electrical-field decouplers, typical applications and future prospects. It is expected that electrochemical detection will become a powerful tool for microscale analytical systems and will facilitate the creation of truly portable (and possibly disposable) devices.

Microscale optical cryptography using a subdiffraction-limit optical key

NASA Astrophysics Data System (ADS)

Ogura, Yusuke; Aino, Masahiko; Tanida, Jun

2018-04-01

We present microscale optical cryptography using a subdiffraction-limit optical pattern, which is finer than the diffraction-limit size of the decrypting optical system, as a key and a substrate with a reflectance distribution as an encrypted image. Because of the subdiffraction-limit spatial coding, this method enables us to construct a secret image with the diffraction-limit resolution. Simulation and experimental results demonstrate, both qualitatively and quantitatively, that the secret image becomes recognizable when and only when the substrate is illuminated with the designed key pattern.

Microscale bioprocess optimisation.

PubMed

Micheletti, Martina; Lye, Gary J

2006-12-01

Microscale processing techniques offer the potential to speed up the delivery of new drugs to the market, reducing development costs and increasing patient benefit. These techniques have application across both the chemical and biopharmaceutical sectors. The approach involves the study of individual bioprocess operations at the microlitre scale using either microwell or microfluidic formats. In both cases the aim is to generate quantitative bioprocess information early on, so as to inform bioprocess design and speed translation to the manufacturing scale. Automation can enhance experimental throughput and will facilitate the parallel evaluation of competing biocatalyst and process options.

Understanding the scaling of electron kinetics in the transition from collisional to collisionless conditions in microscale gas discharges

NASA Astrophysics Data System (ADS)

Tan, Xi; Go, David B.

2018-02-01

When gas discharge and plasma devices shrink to the microscale, the electrode distance in the device approaches the mean free path of electrons and they experience few collisions. As microscale gas discharge and plasma devices become more prevalent, the behavior of discharges at these collisionless and near-collisionless conditions need to be understood. In conditions where the characteristic length d is much greater than the mean free path λ (i.e., macroscopic conditions), electron energy distributions (EEDs) and rate coefficients scale with the reduced electric field E/p. However, when d is comparable with or much lower than λ, this E/p scaling breaks. In this work, particle-in-cell/Monte Carlo collision simulations are used to explore the behavior of the EED and subsequent reaction rate coefficients in microscale field emission-driven Townsend discharges for both an atomic (argon) and a molecular (hydrogen) gas. To understand the behavior, a pseudo-analytical model is developed for the spatially integrated EED and rate coefficients in the collisional to collisionless transition regime based on the weighted sum of a fully collisional, two-temperature Maxwellian EED and the ballistic EED. The theory helps clarify the relative contribution of ballistic electrons in these extreme conditions and can be used to more accurately predict when macroscopic E/p scaling fails at the microscale.

Applications of Microscale Technologies for Regenerative Dentistry

PubMed Central

Hacking, S.A.; Khademhosseini, A.

2009-01-01

While widespread advances in tissue engineering have occurred over the past decade, many challenges remain in the context of tissue engineering and regeneration of the tooth. For example, although tooth development is the result of repeated temporal and spatial interactions between cells of ectoderm and mesoderm origin, most current tooth engineering systems cannot recreate such developmental processes. In this regard, microscale approaches that spatially pattern and support the development of different cell types in close proximity can be used to regulate the cellular microenvironment and, as such, are promising approaches for tooth development. Microscale technologies also present alternatives to conventional tissue engineering approaches in terms of scaffolds and the ability to direct stem cells. Furthermore, microscale techniques can be used to miniaturize many in vitro techniques and to facilitate high-throughput experimentation. In this review, we discuss the emerging microscale technologies for the in vitro evaluation of dental cells, dental tissue engineering, and tooth regeneration. Abbreviations: AS, adult stem cell; BMP, bone morphogenic protein; ECM, extracellular matrix; ES, embryonic stem cell; HA, hydroxyapatite; FGF-2, fibroblast growth factor; iPS, inducible pleuripotent stem cell; IGF-1, insulin-like growth factor; PDGF, platelet-derived growth factor; PDMS, poly(dimethylsiloxane); PGA, polyglycolate; PGS, polyglycerol sebacate; PLGA, poly-L-lactate-co-glycolate; PLL, poly-L-lactate; RGD, Arg-Gly-Asp attachment site; TCP, tricalcium phosphate; TGF-β, transforming growth factor beta; and VEGF, vascular endothelial growth factor. PMID:19493883

Deterministic Integration of Biological and Soft Materials onto 3D Microscale Cellular Frameworks

PubMed Central

McCracken, Joselle M.; Xu, Sheng; Badea, Adina; Jang, Kyung-In; Yan, Zheng; Wetzel, David J.; Nan, Kewang; Lin, Qing; Han, Mengdi; Anderson, Mikayla A.; Lee, Jung Woo; Wei, Zijun; Pharr, Matt; Wang, Renhan; Su, Jessica; Rubakhin, Stanislav S.; Sweedler, Jonathan V.

2018-01-01

Complex 3D organizations of materials represent ubiquitous structural motifs found in the most sophisticated forms of matter, the most notable of which are in life-sustaining hierarchical structures found in biology, but where simpler examples also exist as dense multilayered constructs in high-performance electronics. Each class of system evinces specific enabling forms of assembly to establish their functional organization at length scales not dissimilar to tissue-level constructs. This study describes materials and means of assembly that extend and join these disparate systems—schemes for the functional integration of soft and biological materials with synthetic 3D microscale, open frameworks that can leverage the most advanced forms of multilayer electronic technologies, including device-grade semiconductors such as monocrystalline silicon. Cellular migration behaviors, temporal dependencies of their growth, and contact guidance cues provided by the nonplanarity of these frameworks illustrate design criteria useful for their functional integration with living matter (e.g., NIH 3T3 fibroblast and primary rat dorsal root ganglion cell cultures). PMID:29552634

Hybrid integration of III-V semiconductor lasers on silicon waveguides using optofluidic microbubble manipulation

PubMed Central

Jung, Youngho; Shim, Jaeho; Kwon, Kyungmook; You, Jong-Bum; Choi, Kyunghan; Yu, Kyoungsik

2016-01-01

Optofluidic manipulation mechanisms have been successfully applied to micro/nano-scale assembly and handling applications in biophysics, electronics, and photonics. Here, we extend the laser-based optofluidic microbubble manipulation technique to achieve hybrid integration of compound semiconductor microdisk lasers on the silicon photonic circuit platform. The microscale compound semiconductor block trapped on the microbubble surface can be precisely assembled on a desired position using photothermocapillary convective flows induced by focused laser beam illumination. Strong light absorption within the micro-scale compound semiconductor object allows real-time and on-demand microbubble generation. After the assembly process, we verify that electromagnetic radiation from the optically-pumped InGaAsP microdisk laser can be efficiently coupled to the single-mode silicon waveguide through vertical evanescent coupling. Our simple and accurate microbubble-based manipulation technique may provide a new pathway for realizing high precision fluidic assembly schemes for heterogeneously integrated photonic/electronic platforms as well as microelectromechanical systems. PMID:27431769

An Integrated Computational Materials Engineering Method for Woven Carbon Fiber Composites Preforming Process

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

Zhang, Weizhao; Ren, Huaqing; Wang, Zequn

2016-10-19

An integrated computational materials engineering method is proposed in this paper for analyzing the design and preforming process of woven carbon fiber composites. The goal is to reduce the cost and time needed for the mass production of structural composites. It integrates the simulation methods from the micro-scale to the macro-scale to capture the behavior of the composite material in the preforming process. In this way, the time consuming and high cost physical experiments and prototypes in the development of the manufacturing process can be circumvented. This method contains three parts: the micro-scale representative volume element (RVE) simulation to characterizemore » the material; the metamodeling algorithm to generate the constitutive equations; and the macro-scale preforming simulation to predict the behavior of the composite material during forming. The results show the potential of this approach as a guidance to the design of composite materials and its manufacturing process.« less

Nucleophilic Aromatic Substitution.

ERIC Educational Resources Information Center

Avila, Walter B.; And Others

1990-01-01

Described is a microscale organic chemistry experiment which demonstrates one feasible route in preparing ortho-substituted benzoic acids and provides an example of nucleophilic aromatic substitution chemistry. Experimental procedures and instructor notes for this activity are provided. (CW)

Corrigendum to “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [Compos Struct 134 (2015) 132–141

DOE PAGES

Bai, Xiaoming; Bessa, Miguel A.; Melro, Antonio R.; ...

2016-10-01

The authors would like to inform that one of the modifications proposed in the article “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [1] was found to be unnecessary: the paraboloid yield criterion is sufficient to describe the shear behavior of the epoxy matrix considered (Epoxy 3501-6). The authors recently noted that the experimental work [2] used to validate the pure matrix response considered engineering shear strain instead of its tensorial counter-part, which caused the apparent inconsistency with the paraboloid yield criterion. A recently proposed temperature dependency law for glassy polymers is evaluated herein, thusmore » better agreement with the experimental results for this epoxy is observed.« less

Corrigendum to “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [Compos Struct 134 (2015) 132–141

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

Bai, Xiaoming; Bessa, Miguel A.; Melro, Antonio R.

The authors would like to inform that one of the modifications proposed in the article “High-fidelity micro-scale modeling of the thermo-visco-plastic behavior of carbon fiber polymer matrix composites” [1] was found to be unnecessary: the paraboloid yield criterion is sufficient to describe the shear behavior of the epoxy matrix considered (Epoxy 3501-6). The authors recently noted that the experimental work [2] used to validate the pure matrix response considered engineering shear strain instead of its tensorial counter-part, which caused the apparent inconsistency with the paraboloid yield criterion. A recently proposed temperature dependency law for glassy polymers is evaluated herein, thusmore » better agreement with the experimental results for this epoxy is observed.« less

Experimental Investigations And Numerical Modelling of 210CR12 Steel in Semi-Solid State

NASA Astrophysics Data System (ADS)

Macioł, Piotr; Zalecki, Władysław; Kuziak, Roman; Jakubowicz, Aleksandra; Weglarczyk, Stanisław

2011-05-01

Experimental investigation, including hot compression and simple closed die filling was performed. Temperature range of tests was between 1225 °C and 1320 °C. Temperature selection was adequate with liquid fraction between 20 and 60%, which is typical for thixoforming processes. In the die filling test, steel dies with ceramic layer was used (highly refractory air-setting mortar JM 3300 manufactured by Thermal Ceramics). Experiments were carried out on the Gleeble 3800 physical simulator with MCU unit. In the paper, methodology of experimental investigation is described. Dependency of forming forces on temperature and forming velocities is analysed. Obtained results are discussed. The second part of the paper concerns numerical modelling of semi-solid forming. Numerical models for both sets of test were developed. Structural and Computational Fluid Dynamics models are compared. Initial works in microstructural modelling of 210CR12 steel behaviour are described. Lattice Boltzman Method model for thixotropic flows is introduced. Microscale and macroscale models were integrated into multiscale simulation of semi-solid forming. Some fundamental issues related to multiscale modelling of thixoforming are discussed.

Analytical and Computational Modeling of Mechanical Waves in Microscale Granular Crystals: Nonlinearity and Rotational Dynamics

NASA Astrophysics Data System (ADS)

Wallen, Samuel P.

Granular media are one of the most common, yet least understood forms of matter on earth. The difficulties in understanding the physics of granular media stem from the fact that they are typically heterogeneous and highly disordered, and the grains interact via nonlinear contact forces. Historically, one approach to reducing these complexities and gaining new insight has been the study of granular crystals, which are ordered arrays of similarly-shaped particles (typically spheres) in Hertzian contact. Using this setting, past works explored the rich nonlinear dynamics stemming from contact forces, and proposed avenues where such granular crystals could form designer, dynamically responsive materials, which yield beneficial functionality in dynamic regimes. In recent years, the combination of self-assembly fabrication methods and laser ultrasonic experimental characterization have enabled the study of granular crystals at microscale. While our intuition may suggest that these microscale granular crystals are simply scaled-down versions of their macroscale counterparts, in fact, the relevant physics change drastically; for example, short-range adhesive forces between particles, which are negligible at macroscale, are several orders of magnitude stronger than gravity at microscale. In this thesis, we present recent advances in analytical and computational modeling of microscale granular crystals, in particular concerning the interplay of nonlinearity, shear interactions, and particle rotations, which have previously been either absent, or included separately at macroscale. Drawing inspiration from past works on phononic crystals and nonlinear lattices, we explore problems involving locally-resonant metamaterials, nonlinear localized modes, amplitude-dependent energy partition, and other rich dynamical phenomena. This work enhances our understanding of microscale granular media, which may find applicability in fields such as ultrasonic wave tailoring, signal processing, shock and vibration mitigation, and powder processing.

Microscale Digital Vacuum Electronic Gates

NASA Technical Reports Server (NTRS)

Manohara, Harish (Inventor); Mojarradi, Mohammed M. (Inventor)

2014-01-01

Systems and methods in accordance with embodiments of the invention implement microscale digital vacuum electronic gates. In one embodiment, a microscale digital vacuum electronic gate includes: a microscale field emitter that can emit electrons and that is a microscale cathode; and a microscale anode; where the microscale field emitter and the microscale anode are disposed within at least a partial vacuum; where the microscale field emitter and the microscale anode are separated by a gap; and where the potential difference between the microscale field emitter and the microscale anode is controllable such that the flow of electrons between the microscale field emitter and the microscale anode is thereby controllable; where when the microscale anode receives a flow of electrons, a first logic state is defined; and where when the microscale anode does not receive a flow of electrons, a second logic state is defined.

Microstructure actuation and gas sensing by the Knudsen thermal force

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

Strongrich, Andrew; Alexeenko, Alina, E-mail: alexeenk@purdue.edu

2015-11-09

The generation of forces and moments on structures immersed in rarefied non-isothermal gas flows has received limited practical implementation since first being discovered over a century ago. The formation of significant thermal stresses requires both large thermal gradients and characteristic dimensions which are comparable to the gas molecular mean free path. For macroscopic geometries, this necessitates impractically high temperatures and very low pressures. At the microscale, however, these conditions are easily achieved, allowing the effects to be exploited, namely, for gas-property sensing and microstructure actuation. In this letter, we introduce and experimentally evaluate performance of a microelectromechanical in-plane Knudsen radiometricmore » actuator, a self-contained device having Knudsen thermal force generation, sensing, and tuning mechanisms integrated onto the same platform. Sensitivity to ambient pressure, temperature gradient, as well as gas composition is demonstrated. Results are presented in terms of a non-dimensional force coefficient, allowing measurements to be directly compared to the previous experimental and computational data on out-of-plane cantilevered configurations.« less

Experimental investigation into vortex structure and pressure drop across microcavities in 3D integrated electronics

NASA Astrophysics Data System (ADS)

Renfer, Adrian; Tiwari, Manish K.; Brunschwiler, Thomas; Michel, Bruno; Poulikakos, Dimos

2011-09-01

Hydrodynamics in microcavities with cylindrical micropin fin arrays simulating a single layer of a water-cooled electronic chip stack is investigated experimentally. Both inline and staggered pin arrangements are investigated using pressure drop and microparticle image velocimetry (μPIV) measurements. The pressure drop across the cavity shows a flow transition at pin diameter-based Reynolds numbers ( Re d ) ~200. Instantaneous μPIV, performed using a pH-controlled high seeding density of tracer microspheres, helps visualize vortex structure unreported till date in microscale geometries. The post-transition flow field shows vortex shedding and flow impingement onto the pins explaining the pressure drop increase. The flow fluctuations start at the chip outlet and shift upstream with increasing Re d . No fluctuations are observed for a cavity with pin height-to-diameter ratio h/ d = 1 up to Re d ~330; however, its pressure drop was higher than for a cavity with h/d = 2 due to pronounced influence of cavity walls.

Modeling of Density-Dependent Flow based on the Thermodynamically Constrained Averaging Theory

NASA Astrophysics Data System (ADS)

Weigand, T. M.; Schultz, P. B.; Kelley, C. T.; Miller, C. T.; Gray, W. G.

2016-12-01

The thermodynamically constrained averaging theory (TCAT) has been used to formulate general classes of porous medium models, including new models for density-dependent flow. The TCAT approach provides advantages that include a firm connection between the microscale, or pore scale, and the macroscale; a thermodynamically consistent basis; explicit inclusion of factors such as a diffusion that arises from gradients associated with pressure and activity and the ability to describe both high and low concentration displacement. The TCAT model is presented and closure relations for the TCAT model are postulated based on microscale averages and a parameter estimation is performed on a subset of the experimental data. Due to the sharpness of the fronts, an adaptive moving mesh technique was used to ensure grid independent solutions within the run time constraints. The optimized parameters are then used for forward simulations and compared to the set of experimental data not used for the parameter estimation.

Microarc oxidation coating covered Ti implants with micro-scale gouges formed by a multi-step treatment for improving osseointegration.

PubMed

Bai, Yixin; Zhou, Rui; Cao, Jianyun; Wei, Daqing; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2017-07-01

The sub-microporous microarc oxidation (MAO) coating covered Ti implant with micro-scale gouges has been fabricated via a multi-step MAO process to overcome the compromised bone-implant integration. The as-prepared implant has been further mediated by post-heat treatment to compare the effects of -OH functional group and the nano-scale orange peel-like morphology on osseointegration. The bone regeneration, bone-implant contact interface, and biomechanical push-out force of the modified Ti implant have been discussed thoroughly in this work. The greatly improved push-out force for the MAO coated Ti implants with micro-scale gouges could be attributed to the excellent mechanical interlocking effect between implants and biologically meshed bone tissues. Attributed to the -OH functional group which promotes synostosis between the biologically meshed bone and the gouge surface of implant, the multi-step MAO process could be an effective strategy to improve the osseointegration of Ti implant. Copyright © 2017 Elsevier B.V. All rights reserved.

A coral-on-a-chip microfluidic platform enabling live-imaging microscopy of reef-building corals

PubMed Central

Shapiro, Orr H.; Kramarsky-Winter, Esti; Gavish, Assaf R.; Stocker, Roman; Vardi, Assaf

2016-01-01

Coral reefs, and the unique ecosystems they support, are facing severe threats by human activities and climate change. Our understanding of these threats is hampered by the lack of robust approaches for studying the micro-scale interactions between corals and their environment. Here we present an experimental platform, coral-on-a-chip, combining micropropagation and microfluidics to allow direct microscopic study of live coral polyps. The small and transparent coral micropropagates are ideally suited for live-imaging microscopy, while the microfluidic platform facilitates long-term visualization under controlled environmental conditions. We demonstrate the usefulness of this approach by imaging coral micropropagates at previously unattainable spatio-temporal resolutions, providing new insights into several micro-scale processes including coral calcification, coral–pathogen interaction and the loss of algal symbionts (coral bleaching). Coral-on-a-chip thus provides a powerful method for studying coral physiology in vivo at the micro-scale, opening new vistas in coral biology. PMID:26940983

A coral-on-a-chip microfluidic platform enabling live-imaging microscopy of reef-building corals.

PubMed

Shapiro, Orr H; Kramarsky-Winter, Esti; Gavish, Assaf R; Stocker, Roman; Vardi, Assaf

2016-03-04

Coral reefs, and the unique ecosystems they support, are facing severe threats by human activities and climate change. Our understanding of these threats is hampered by the lack of robust approaches for studying the micro-scale interactions between corals and their environment. Here we present an experimental platform, coral-on-a-chip, combining micropropagation and microfluidics to allow direct microscopic study of live coral polyps. The small and transparent coral micropropagates are ideally suited for live-imaging microscopy, while the microfluidic platform facilitates long-term visualization under controlled environmental conditions. We demonstrate the usefulness of this approach by imaging coral micropropagates at previously unattainable spatio-temporal resolutions, providing new insights into several micro-scale processes including coral calcification, coral-pathogen interaction and the loss of algal symbionts (coral bleaching). Coral-on-a-chip thus provides a powerful method for studying coral physiology in vivo at the micro-scale, opening new vistas in coral biology.

Enhanced flow boiling in microchannels through integrating multiple micro-nozzles and reentry microcavities

NASA Astrophysics Data System (ADS)

Li, Wenming; Qu, Xiaopeng; Alam, Tamanna; Yang, Fanghao; Chang, Wei; Khan, Jamil; Li, Chen

2017-01-01

In a microchannel system, a higher mass velocity can lead to enhanced flow boiling performances, but at a cost of two-phase pressure drop. It is highly desirable to achieve a high heat transfer rate and critical heat flux (CHF) exceeding 1 kW/cm2 without elevating the pressure drop, particularly, at a reduced mass velocity. In this study, we developed a microchannel configuration that enables more efficient utilization of the coolant through integrating multiple microscale nozzles connected to auxiliary channels as well as microscale reentry cavities on sidewalls of main microchannels. We achieved a CHF of 1016 W/cm2 with a 50% less mass velocity, i.e., 680 kg/m2s, compared to the two-nozzle configuration developed in our previous studies. Two primary enhancement mechanisms are: (a) the enhanced global liquid supply by four evenly distributed micronozzles, particularly near the outlet region and (b) the effective management of local dryout by the capillary flow-induced sustainable thin liquid film resulting from an array of microscale cavities. A significantly improved heat transfer coefficient of 131 kW/m2 K at a mass velocity of 680 kg/m2s is attributed to the enhanced nucleate boiling, the established capillary/thin film evaporation, and the induced advection from the present microchannel configuration. All these significant enhancements have been achieved with a ˜55% lower two-phase pressure drop.

Computerized microfluidic cell culture using elastomeric channels and Braille displays.

PubMed

Gu, Wei; Zhu, Xiaoyue; Futai, Nobuyuki; Cho, Brenda S; Takayama, Shuichi

2004-11-09

Computer-controlled microfluidics would advance many types of cellular assays and microscale tissue engineering studies wherever spatiotemporal changes in fluidics need to be defined. However, this goal has been elusive because of the limited availability of integrated, programmable pumps and valves. This paper demonstrates how a refreshable Braille display, with its grid of 320 vertically moving pins, can power integrated pumps and valves through localized deformations of channel networks within elastic silicone rubber. The resulting computerized fluidic control is able to switch among: (i) rapid and efficient mixing between streams, (ii) multiple laminar flows with minimal mixing between streams, and (iii) segmented plug-flow of immiscible fluids within the same channel architecture. The same control method is used to precisely seed cells, compartmentalize them into distinct subpopulations through channel reconfiguration, and culture each cell subpopulation for up to 3 weeks under perfusion. These reliable microscale cell cultures showed gradients of cellular behavior from C2C12 myoblasts along channel lengths, as well as differences in cell density of undifferentiated myoblasts and differentiation patterns, both programmable through different flow rates of serum-containing media. This technology will allow future microscale tissue or cell studies to be more accessible, especially for high-throughput, complex, and long-term experiments. The microfluidic actuation method described is versatile and computer programmable, yet simple, well packaged, and portable enough for personal use.

Computerized microfluidic cell culture using elastomeric channels and Braille displays

PubMed Central

Gu, Wei; Zhu, Xiaoyue; Futai, Nobuyuki; Cho, Brenda S.; Takayama, Shuichi

2004-01-01

Computer-controlled microfluidics would advance many types of cellular assays and microscale tissue engineering studies wherever spatiotemporal changes in fluidics need to be defined. However, this goal has been elusive because of the limited availability of integrated, programmable pumps and valves. This paper demonstrates how a refreshable Braille display, with its grid of 320 vertically moving pins, can power integrated pumps and valves through localized deformations of channel networks within elastic silicone rubber. The resulting computerized fluidic control is able to switch among: (i) rapid and efficient mixing between streams, (ii) multiple laminar flows with minimal mixing between streams, and (iii) segmented plug-flow of immiscible fluids within the same channel architecture. The same control method is used to precisely seed cells, compartmentalize them into distinct subpopulations through channel reconfiguration, and culture each cell subpopulation for up to 3 weeks under perfusion. These reliable microscale cell cultures showed gradients of cellular behavior from C2C12 myoblasts along channel lengths, as well as differences in cell density of undifferentiated myoblasts and differentiation patterns, both programmable through different flow rates of serum-containing media. This technology will allow future microscale tissue or cell studies to be more accessible, especially for high-throughput, complex, and long-term experiments. The microfluidic actuation method described is versatile and computer programmable, yet simple, well packaged, and portable enough for personal use. PMID:15514025

In situ SEM observation of microscale strain fields around a crack tip in polycrystalline molybdenum

NASA Astrophysics Data System (ADS)

Li, J. J.; Li, W. C.; Jin, Y. J.; Wang, L. F.; Zhao, C. W.; Xing, Y. M.; Lang, F. C.; Yan, L.; Yang, S. T.

2016-06-01

In situ scanning electron microscopy was employed to investigate the crack initiation and propagation in polycrystalline molybdenum under uniaxial tensile load at room temperature. The microscale grid pattern was fabricated using the sputtering deposition technology on the specimen surface covered with a fine square mesh copper grid. The microscale strain fields around the crack tip were measured by geometric phase analysis technique and compared with the theoretical solutions based on the linear elastic fracture mechanics theory. The results showed that as the displacement increases, the crack propagated mainly perpendicular to the tensile direction during the fracture process of molybdenum. The normal strain ɛ xx and shear strain ɛ xy are relatively small, and the normal strain ɛ yy holds a dominant position in the deformation fields and plays a key role in the whole fracture process of molybdenum. With the increase in displacement, the ɛ yy increases rapidly and the two lobes grow significantly but maintain the same shape and orientation. The experimental ɛ yy is in agreement with the theoretical solution. Along the x-axis in front of the crack tip, there is minor discrepancy between the experimental ɛ yy and theoretical ɛ yy within 25 μm from the crack tip, but the agreement between them is very good far from the crack tip (>25 μm).

Multiscale Modeling of Carbon Fiber Reinforced Polymer (CFRP) for Integrated Computational Materials Engineering Process

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

Gao, Jiaying; Liang, Biao; Zhang, Weizhao

In this work, a multiscale modeling framework for CFRP is introduced to study hierarchical structure of CFRP. Four distinct scales are defined: nanoscale, microscale, mesoscale, and macroscale. Information at lower scales can be passed to higher scale, which is beneficial for studying effect of constituents on macroscale part’s mechanical property. This bottom-up modeling approach enables better understanding of CFRP from finest details. Current study focuses on microscale and mesoscale. Representative volume element is used at microscale and mesoscale to model material’s properties. At microscale, unidirection CFRP (UD) RVE is used to study properties of UD. The UD RVE can bemore » modeled with different volumetric fraction to encounter non-uniform fiber distribution in CFRP part. Such consideration is important in modeling uncertainties at microscale level. Currently, we identified volumetric fraction as the only uncertainty parameters in UD RVE. To measure effective material properties of UD RVE, periodic boundary conditions (PBC) are applied to UD RVE to ensure convergence of obtained properties. Properties of UD is directly used at mesoscale woven RVE modeling, where each yarn is assumed to have same properties as UD. Within woven RVE, there can be many potential uncertainties parameters to consider for a physical modeling of CFRP. Currently, we will consider fiber misalignment within yarn and angle between wrap and weft yarns. PBC is applied to woven RVE to calculate its effective material properties. The effect of uncertainties are investigated quantitatively by Gaussian process. Preliminary results of UD and Woven study are analyzed for efficacy of the RVE modeling. This work is considered as the foundation for future multiscale modeling framework development for ICME project.« less

Macro- and microscale fluid flow systems for endothelial cell biology.

PubMed

Young, Edmond W K; Simmons, Craig A

2010-01-21

Recent advances in microfluidics have brought forth new tools for studying flow-induced effects on mammalian cells, with important applications in cardiovascular, bone and cancer biology. The plethora of microscale systems developed to date demonstrate the flexibility of microfluidic designs, and showcase advantages of the microscale that are simply not available at the macroscale. However, the majority of these systems will likely not achieve widespread use in the biological laboratory due to their complexity and lack of user-friendliness. To gain widespread acceptance in the biological research community, microfluidics engineers must understand the needs of cell biologists, while biologists must be made aware of available technology. This review provides a critical evaluation of cell culture flow (CCF) systems used to study the effects of mechanical forces on endothelial cells (ECs) in vitro. To help understand the need for various designs of CCF systems, we first briefly summarize main properties of ECs and their native environments. Basic principles of various macro- and microscale systems are described and evaluated. New opportunities are uncovered for developing technologies that have potential to both improve efficiency of experimentation as well as answer important biological questions that otherwise cannot be tackled with existing systems. Finally, we discuss some of the unresolved issues related to microfluidic cell culture, suggest possible avenues of investigation that could resolve these issues, and provide an outlook for the future of microfluidics in biological research.

Thermo-Oxidative Induced Damage in Polymer Composites: Microstructure Image-Based Multi-Scale Modeling and Experimental Validation

NASA Astrophysics Data System (ADS)

Hussein, Rafid M.; Chandrashekhara, K.

2017-11-01

A multi-scale modeling approach is presented to simulate and validate thermo-oxidation shrinkage and cracking damage of a high temperature polymer composite. The multi-scale approach investigates coupled transient diffusion-reaction and static structural at macro- to micro-scale. The micro-scale shrinkage deformation and cracking damage are simulated and validated using 2D and 3D simulations. Localized shrinkage displacement boundary conditions for the micro-scale simulations are determined from the respective meso- and macro-scale simulations, conducted for a cross-ply laminate. The meso-scale geometrical domain and the micro-scale geometry and mesh are developed using the object oriented finite element (OOF). The macro-scale shrinkage and weight loss are measured using unidirectional coupons and used to build the macro-shrinkage model. The cross-ply coupons are used to validate the macro-shrinkage model by the shrinkage profiles acquired using scanning electron images at the cracked surface. The macro-shrinkage model deformation shows a discrepancy when the micro-scale image-based cracking is computed. The local maximum shrinkage strain is assumed to be 13 times the maximum macro-shrinkage strain of 2.5 × 10-5, upon which the discrepancy is minimized. The microcrack damage of the composite is modeled using a static elastic analysis with extended finite element and cohesive surfaces by considering the modulus spatial evolution. The 3D shrinkage displacements are fed to the model using node-wise boundary/domain conditions of the respective oxidized region. Microcrack simulation results: length, meander, and opening are closely matched to the crack in the area of interest for the scanning electron images.

Instability of nano- and microscale liquid metal filaments: Transition from single droplet collapse to multidroplet breakup

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

Hartnett, Chris A.; Mahady, Kyle; Fowlkes, Jason Davidson

We carry out experimental and numerical studies to investigate the collapse and breakup of finite size, nano- and microscale, liquid metal filaments supported on a substrate. We find the critical dimensions below which filaments do not break up but rather collapse to a single droplet. The transition from collapse to breakup can be described as a competition between two fluid dynamic phenomena: the capillary driven end retraction and the Rayleigh–Plateau type instability mechanism that drives the breakup. We focus on the unique spatial and temporal transition region between these two phenomena using patterned metallic thin film strips and pulsed-laser-induced dewetting.more » The experimental results are compared to an analytical model proposed by Driessen et al. and modified to include substrate interactions. Additionally, we report the results of numerical simulations based on a volume-of-fluid method to provide additional insight and highlight the importance of liquid metal resolidification, which reduces inertial effects.« less

Instability of nano- and microscale liquid metal filaments: Transition from single droplet collapse to multidroplet breakup

DOE PAGES

Hartnett, Chris A.; Mahady, Kyle; Fowlkes, Jason Davidson; ...

2015-11-23

We carry out experimental and numerical studies to investigate the collapse and breakup of finite size, nano- and microscale, liquid metal filaments supported on a substrate. We find the critical dimensions below which filaments do not break up but rather collapse to a single droplet. The transition from collapse to breakup can be described as a competition between two fluid dynamic phenomena: the capillary driven end retraction and the Rayleigh–Plateau type instability mechanism that drives the breakup. We focus on the unique spatial and temporal transition region between these two phenomena using patterned metallic thin film strips and pulsed-laser-induced dewetting.more » The experimental results are compared to an analytical model proposed by Driessen et al. and modified to include substrate interactions. Additionally, we report the results of numerical simulations based on a volume-of-fluid method to provide additional insight and highlight the importance of liquid metal resolidification, which reduces inertial effects.« less

Mechanical response of common millet (Panicum miliaceum) seeds under quasi-static compression: Experiments and modeling.

PubMed

Hasseldine, Benjamin P J; Gao, Chao; Collins, Joseph M; Jung, Hyun-Do; Jang, Tae-Sik; Song, Juha; Li, Yaning

2017-09-01

The common millet (Panicum miliaceum) seedcoat has a fascinating complex microstructure, with jigsaw puzzle-like epidermis cells articulated via wavy intercellular sutures to form a compact layer to protect the kernel inside. However, little research has been conducted on linking the microstructure details with the overall mechanical response of this interesting biological composite. To this end, an integrated experimental-numerical-analytical investigation was conducted to both characterize the microstructure and ascertain the microscale mechanical properties and to test the overall response of kernels and full seeds under macroscale quasi-static compression. Scanning electron microscopy (SEM) was utilized to examine the microstructure of the outer seedcoat and nanoindentation was performed to obtain the material properties of the seedcoat hard phase material. A multiscale computational strategy was applied to link the microstructure to the macroscale response of the seed. First, the effective anisotropic mechanical properties of the seedcoat were obtained from finite element (FE) simulations of a microscale representative volume element (RVE), which were further verified from sophisticated analytical models. Then, macroscale FE models of the individual kernel and full seed were developed. Good agreement between the compression experiments and FE simulations were obtained for both the kernel and the full seed. The results revealed the anisotropic property and the protective function of the seedcoat, and showed that the sutures of the seedcoat play an important role in transmitting and distributing loads in responding to external compression. Copyright © 2017 Elsevier Ltd. All rights reserved.

Education: DNA replication using microscale natural convection.

PubMed

Priye, Aashish; Hassan, Yassin A; Ugaz, Victor M

2012-12-07

There is a need for innovative educational experiences that unify and reinforce fundamental principles at the interface between the physical, chemical, and life sciences. These experiences empower and excite students by helping them recognize how interdisciplinary knowledge can be applied to develop new products and technologies that benefit society. Microfluidics offers an incredibly versatile tool to address this need. Here we describe our efforts to create innovative hands-on activities that introduce chemical engineering students to molecular biology by challenging them to harness microscale natural convection phenomena to perform DNA replication via the polymerase chain reaction (PCR). Experimentally, we have constructed convective PCR stations incorporating a simple design for loading and mounting cylindrical microfluidic reactors between independently controlled thermal plates. A portable motion analysis microscope enables flow patterns inside the convective reactors to be directly visualized using fluorescent bead tracers. We have also developed a hands-on computational fluid dynamics (CFD) exercise based on modeling microscale thermal convection to identify optimal geometries for DNA replication. A cognitive assessment reveals that these activities strongly impact student learning in a positive way.

Cruise control for segmented flow.

PubMed

Abolhasani, Milad; Singh, Mayank; Kumacheva, Eugenia; Günther, Axel

2012-11-21

Capitalizing on the benefits of microscale segmented flows, e.g., enhanced mixing and reduced sample dispersion, so far requires specialist training and accommodating a few experimental inconveniences. For instance, microscale gas-liquid flows in many current setups take at least 10 min to stabilize and iterative manual adjustments are needed to achieve or maintain desired mixing or residence times. Here, we report a cruise control strategy that overcomes these limitations and allows microscale gas-liquid (bubble) and liquid-liquid (droplet) flow conditions to be rapidly "adjusted" and maintained. Using this strategy we consistently establish bubble and droplet flows with dispersed phase (plug) velocities of 5-300 mm s(-1), plug lengths of 0.6-5 mm and continuous phase (slug) lengths of 0.5-3 mm. The mixing times (1-5 s), mass transfer times (33-250 ms) and residence times (3-300 s) can therefore be directly imposed by dynamically controlling the supply of the dispersed and the continuous liquids either from external pumps or from local pressurized reservoirs. In the latter case, no chip-external pumps, liquid-perfused tubes or valves are necessary while unwanted dead volumes are significantly reduced.

A tension-torsional fatigue testing apparatus for micro-scale components.

PubMed

Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

2016-01-01

Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results.

A tension-torsional fatigue testing apparatus for micro-scale components

NASA Astrophysics Data System (ADS)

Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

2016-01-01

Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results.

A Causal Relation between Bioluminescence and Oxygen to Quantify the Cell Niche

PubMed Central

Lambrechts, Dennis; Roeffaers, Maarten; Goossens, Karel; Hofkens, Johan; Van de Putte, Tom; Schrooten, Jan; Van Oosterwyck, Hans

2014-01-01

Bioluminescence imaging assays have become a widely integrated technique to quantify effectiveness of cell-based therapies by monitoring fate and survival of transplanted cells. To date these assays are still largely qualitative and often erroneous due to the complexity and dynamics of local micro-environments (niches) in which the cells reside. Here, we report, using a combined experimental and computational approach, on oxygen that besides being a critical niche component responsible for cellular energy metabolism and cell-fate commitment, also serves a primary role in regulating bioluminescent light kinetics. We demonstrate the potential of an oxygen dependent Michaelis-Menten relation in quantifying intrinsic bioluminescence intensities by resolving cell-associated oxygen gradients from bioluminescent light that is emitted from three-dimensional (3D) cell-seeded hydrogels. Furthermore, the experimental and computational data indicate a strong causal relation of oxygen concentration with emitted bioluminescence intensities. Altogether our approach demonstrates the importance of oxygen to evolve towards quantitative bioluminescence and holds great potential for future microscale measurement of oxygen tension in an easily accessible manner. PMID:24840204

Fast and high resolution thermal detector based on an aluminum nitride piezoelectric microelectromechanical resonator with an integrated suspended heat absorbing element

NASA Astrophysics Data System (ADS)

Hui, Yu; Rinaldi, Matteo

2013-03-01

This letter presents a miniaturized, fast, and high resolution thermal detector, in which a heat absorbing element and a temperature sensitive microelectromechanical system (MEMS) resonator are perfectly overlapped but separated by a microscale air gap. This unique design guarantees efficient and fast (˜10s μs) heat transfer from the absorbing element to the temperature sensitive device and enables high resolution thermal power detection (˜nW), thanks to the low noise performance of the high quality factor (Q = 2305) MEMS resonant thermal detector. A device prototype was fabricated, and its detection capabilities were experimentally characterized. A thermal power as low as 150 nW was experimentally measured, and a noise equivalent power of 6.5 nW/Hz1/2 was extracted. A device thermal time constant of only 350 μs was measured (smallest ever reported for MEMS resonant thermal detectors), indicating the great potential of the proposed technology for the implementation of ultra-fast and high resolution un-cooled resonant thermal detectors.

A causal relation between bioluminescence and oxygen to quantify the cell niche.

PubMed

Lambrechts, Dennis; Roeffaers, Maarten; Goossens, Karel; Hofkens, Johan; Vande Velde, Greetje; Van de Putte, Tom; Schrooten, Jan; Van Oosterwyck, Hans

2014-01-01

Bioluminescence imaging assays have become a widely integrated technique to quantify effectiveness of cell-based therapies by monitoring fate and survival of transplanted cells. To date these assays are still largely qualitative and often erroneous due to the complexity and dynamics of local micro-environments (niches) in which the cells reside. Here, we report, using a combined experimental and computational approach, on oxygen that besides being a critical niche component responsible for cellular energy metabolism and cell-fate commitment, also serves a primary role in regulating bioluminescent light kinetics. We demonstrate the potential of an oxygen dependent Michaelis-Menten relation in quantifying intrinsic bioluminescence intensities by resolving cell-associated oxygen gradients from bioluminescent light that is emitted from three-dimensional (3D) cell-seeded hydrogels. Furthermore, the experimental and computational data indicate a strong causal relation of oxygen concentration with emitted bioluminescence intensities. Altogether our approach demonstrates the importance of oxygen to evolve towards quantitative bioluminescence and holds great potential for future microscale measurement of oxygen tension in an easily accessible manner.

A Kinematically Consistent Two-Point Correlation Function

NASA Technical Reports Server (NTRS)

Ristorcelli, J. R.

1998-01-01

A simple kinematically consistent expression for the longitudinal two-point correlation function related to both the integral length scale and the Taylor microscale is obtained. On the inner scale, in a region of width inversely proportional to the turbulent Reynolds number, the function has the appropriate curvature at the origin. The expression for two-point correlation is related to the nonlinear cascade rate, or dissipation epsilon, a quantity that is carried as part of a typical single-point turbulence closure simulation. Constructing an expression for the two-point correlation whose curvature at the origin is the Taylor microscale incorporates one of the fundamental quantities characterizing turbulence, epsilon, into a model for the two-point correlation function. The integral of the function also gives, as is required, an outer integral length scale of the turbulence independent of viscosity. The proposed expression is obtained by kinematic arguments; the intention is to produce a practically applicable expression in terms of simple elementary functions that allow an analytical evaluation, by asymptotic methods, of diverse functionals relevant to single-point turbulence closures. Using the expression devised an example of the asymptotic method by which functionals of the two-point correlation can be evaluated is given.

EXPERIMENTAL INVESTIGATION OF RELATIVE PERMEABILITY UPSCALING FROM THE MICRO-SCALE TO THE MACRO-SCALE

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

Laura J. Pyrak-Nolte; Ping Yu; JiangTao Cheng

2002-12-01

The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements ofmore » interfacial area per volume. During this reporting period, we have shown experimentally that the coherence detection can be performed in a borescope. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures has shown the existence of a unique relationship among these hydraulic parameters for different pore geometry. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, is essentially completed for imbibition conditions.« less

Microscale Soft Patterning for Solution Processable Metal Oxide Thin Film Transistors.

PubMed

Jung, Sang Wook; Chae, Soo Sang; Park, Jee Ho; Oh, Jin Young; Bhang, Suk Ho; Baik, Hong Koo; Lee, Tae Il

2016-03-23

We introduce a microscale soft pattering (MSP) route utilizing contact printing of chemically inert sub-nanometer thick low molecular weight (LMW) poly(dimethylsiloxane) (PDMS) layers. These PDMS layers serve as a release agent layer between the n-type Ohmic metal and metal oxide semiconductors (MOSs) and provide a layer that protects the MOS from water in the surrounding environment. The feasibility of our MSP route was experimentally demonstrated by fabricating solution processable In2O3, IZO, and IGZO TFTs with aluminum (Al), a typical n-type Ohmic metal. We have demonstrated patterning gaps as small as 13 μm. The TFTs fabricated using MSP showed higher field-effect-mobility and lower hysteresis in comparison with those made using conventional photolithography.

Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels.

PubMed

Kargol, Armin; Malkinski, Leszek; Eskandari, Rahmatollah; Carter, Maya; Livingston, Daniel

2015-09-01

We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus.

Synthesis micro-scale boron nitride nanotubes at low substrate temperature

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

Sajjad, Muhammad, E-mail: msajjadd@gmail.com; Makarov, Vladimir; Morell, Gerardo

2016-07-15

High temperature synthesis methods produce defects in 1D nanomaterials, which ultimately limit their applications. We report here the synthesis of micro-scale boron nitride nanotubes (BNNT) at low substrate temperature (300 {sup o}C) using a pulsed CO{sub 2} laser deposition technique in the presence of catalyst. The electron microscopic analyses have shown the nanotubes distributed randomly on the surface of the substrate. The average diameter (∼0.25 μm) of a nanotube, which is the highest reported value to date, is estimated by SEM data and confirmed by TEM measurements. These nanotubes are promising for high response deep-UV photo-luminescent devices. A detailed synthesismore » mechanism is presented and correlated with the experimental results.« less

Toward a Micro-Scale Acoustic Direction-Finding Sensor with Integrated Electronic Readout

DTIC Science & Technology

2013-06-01

measurements with curve fits . . . . . . . . . . . . . . . 20 Figure 2.10 Failure testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22...2.1 Sensor parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 2.2 Curve fit parameters...elastic, the quantity of interest is the elastic stiffness. In a typical nanoindentation test, the loading curve is nonlinear due to combined plastic

An Integrated Ignition and Combustion System for Liquid Propellant Micro Propulsion

DTIC Science & Technology

2008-06-26

using a microfin electrode array. They demonstrated successful gasification and ignition of the liquid propellant using this concept. The concept has...Transition to Detonation of Stoichiometric Ethylene/Oxygen in Microscale Tubes (with M-H. Wu, M.P. Burke, and S.F. Son) Proceedings of the

An experimental investigation of a three dimensional wall jet. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Catalano, G. D.

1977-01-01

One and two point statistical properties are measured in the flow fields of a coflowing turbulent jet. Two different confining surfaces (one flat, one with large curvature) are placed adjacent to the lip of the circular nozzle; and the resultant effects on the flow field are determined. The one point quantities measured include mean velocities, turbulent intensities, velocity and concentration autocorrelations and power spectral densities, and intermittencies. From the autocorrelation curves, the Taylor microscale and the integral length scale are calculated. Two point quantities measured include velocity and concentration space-time correlations and pressure velocity correlations. From the velocity space-time correlations, iso-correlation contours are constructed along with the lines of maximum maximorum. These lines allow a picture of the flow pattern to be determined. The pressures monitored in the pressure velocity correlations are measured both in the flow field and at the surface of the confining wall(s).

Phloem-sap-dynamics sensor device for monitoring photosynthates transportation in plant shoots

NASA Astrophysics Data System (ADS)

Yano, Yuya; Ono, Akihito; Terao, Kyohei; Suzuki, Takaaki; Takao, Hidekuni; Kobayashi, Tsuyoshi; Kataoka, Ikuo; Shimokawa, Fusao

2018-06-01

We propose a microscale phloem-sap-dynamics sensor device to obtain the index of an internal plant condition regarding the transportation of primary photosynthates in phloem, which is an essential indicator of stable crop production under controlled-growth environments. In detail, we integrated a conventional Granier sensor with a thermal-flow sensor and devised an improved sensor device to quantify such index, including the information on velocity and direction of the phloem-sap flow using the microelectromechanical systems (MEMS) technology. The experimental results showed that although the proposed sensor device was approximately only 1/10 the size of the conventional Granier sensor, it could generate an output nearly equal to that of the conventional sensor. Furthermore, experiments using mimicked plants demonstrated that the proposed device could measure minute flow velocities in the range of 0–200 µm/s, which are generally known as the phloem-sap flow velocity, and simultaneously detect the flow direction.

Thermal Conductivity Measurement of Low-k Dielectric Films: Effect of Porosity and Density

NASA Astrophysics Data System (ADS)

Alam, M. T.; Pulavarthy, R. A.; Bielefeld, J.; King, S. W.; Haque, M. A.

2014-03-01

The thermal conductivity of low-dielectric-constant (low-k) SiOC:H and SiC:H thin films has been measured as a function of porosity using a heat transfer model based on a microfin geometry and infrared thermometry. Microscale specimens were patterned from blanket films, released from the substrate, and subsequently integrated with the experimental setup. Results show that the thermal conductivity of a dense specimen, 0.7 W/mK, can be reduced to as low as 0.1 W/mK by introducing 30% porosity into it. The measured thermal conductivity shows a nonlinear decrease with increasing porosity that approximately follows the porosity-weighted simple medium model for porous materials. Neither the differential effective medium nor the coherent potential model could predict the density dependence of the thermal conductivity. These results suggest that more careful consideration is required for application of generic porous materials modeling to low-k dielectrics.

Preparation and Characterization of Colloidal Silica Particles under Mild Conditions

ERIC Educational Resources Information Center

Neville, Frances; Zin, Azrinawati Mohd.; Jameson, Graeme J.; Wanless, Erica J.

2012-01-01

A microscale laboratory experiment for the preparation and characterization of silica particles at neutral pH and ambient temperature conditions is described. Students first employ experimental fabrication methods to make spherical submicrometer silica particles via the condensation of an alkoxysilane and polyethyleneimine, which act to catalyze…

High-throughput micro-scale cultivations and chromatography modeling: Powerful tools for integrated process development.

PubMed

Baumann, Pascal; Hahn, Tobias; Hubbuch, Jürgen

2015-10-01

Upstream processes are rather complex to design and the productivity of cells under suitable cultivation conditions is hard to predict. The method of choice for examining the design space is to execute high-throughput cultivation screenings in micro-scale format. Various predictive in silico models have been developed for many downstream processes, leading to a reduction of time and material costs. This paper presents a combined optimization approach based on high-throughput micro-scale cultivation experiments and chromatography modeling. The overall optimized system must not necessarily be the one with highest product titers, but the one resulting in an overall superior process performance in up- and downstream. The methodology is presented in a case study for the Cherry-tagged enzyme Glutathione-S-Transferase from Escherichia coli SE1. The Cherry-Tag™ (Delphi Genetics, Belgium) which can be fused to any target protein allows for direct product analytics by simple VIS absorption measurements. High-throughput cultivations were carried out in a 48-well format in a BioLector micro-scale cultivation system (m2p-Labs, Germany). The downstream process optimization for a set of randomly picked upstream conditions producing high yields was performed in silico using a chromatography modeling software developed in-house (ChromX). The suggested in silico-optimized operational modes for product capturing were validated subsequently. The overall best system was chosen based on a combination of excellent up- and downstream performance. © 2015 Wiley Periodicals, Inc.

Integrated detection of fractures and caves in carbonate fractured-vuggy reservoirs based on seismic data and well data

NASA Astrophysics Data System (ADS)

Cao, Zhanning; Li, Xiangyang; Sun, Shaohan; Liu, Qun; Deng, Guangxiao

2018-04-01

Aiming at the prediction of carbonate fractured-vuggy reservoirs, we put forward an integrated approach based on seismic and well data. We divide a carbonate fracture-cave system into four scales for study: micro-scale fracture, meso-scale fracture, macro-scale fracture and cave. Firstly, we analyze anisotropic attributes of prestack azimuth gathers based on multi-scale rock physics forward modeling. We select the frequency attenuation gradient attribute to calculate azimuth anisotropy intensity, and we constrain the result with Formation MicroScanner image data and trial production data to predict the distribution of both micro-scale and meso-scale fracture sets. Then, poststack seismic attributes, variance, curvature and ant algorithms are used to predict the distribution of macro-scale fractures. We also constrain the results with trial production data for accuracy. Next, the distribution of caves is predicted by the amplitude corresponding to the instantaneous peak frequency of the seismic imaging data. Finally, the meso-scale fracture sets, macro-scale fractures and caves are combined to obtain an integrated result. This integrated approach is applied to a real field in Tarim Basin in western China for the prediction of fracture-cave reservoirs. The results indicate that this approach can well explain the spatial distribution of carbonate reservoirs. It can solve the problem of non-uniqueness and improve fracture prediction accuracy.

Optical fiber loops and helices: tools for integrated photonic device characterization and microfluidic trapping

NASA Astrophysics Data System (ADS)

Ren, Yundong; Zhang, Rui; Ti, Chaoyang; Liu, Yuxiang

2016-09-01

Tapered optical fibers can deliver guided light into and carry light out of micro/nanoscale systems with low loss and high spatial resolution, which makes them ideal tools in integrated photonics and microfluidics. Special geometries of tapered fibers are desired for probing monolithic devices in plane as well as optical manipulation of micro particles in fluids. However, for many specially shaped tapered fibers, it remains a challenge to fabricate them in a straightforward, controllable, and repeatable way. In this work, we fabricated and characterized two special geometries of tapered optical fibers, namely fiber loops and helices, that could be switched between one and the other. The fiber loops in this work are distinct from previous ones in terms of their superior mechanical stability and high optical quality factors in air, thanks to a post-annealing process. We experimentally measured an intrinsic optical quality factor of 32,500 and a finesse of 137 from a fiber loop. A fiber helix was used to characterize a monolithic cavity optomechanical device. Moreover, a microfluidic "roller coaster" was demonstrated, where microscale particles in water were optically trapped and transported by a fiber helix. Tapered fiber loops and helices can find various applications ranging from on-the-fly characterization of integrated photonic devices to particle manipulation and sorting in microfluidics.

Microscale Laminar Vortices for High-Purity Extraction and Release of Circulating Tumor Cells.

PubMed

Hur, Soojung Claire; Che, James; Di Carlo, Dino

2017-01-01

Circulating tumor cells (CTCs) are disseminated tumor cells that reflect the tumors of origin and can provide a liquid biopsy that would potentially enable noninvasive tumor profiling, treatment monitoring, and identification of targeted treatments. Accurate and rapid purification of CTCs holds great potential to improve cancer care but the task remains technically challenging. Microfluidic isolation of CTCs within microscale vortices enables high-throughput and size-based purification of rare CTCs from bodily fluids. Collected cells are highly pure, viable, and easily accessible, allowing seamless integration with various downstream applications. Here, we describe how to fabricate the High-Throughput Vortex Chip (Vortex-HT) and to process diluted whole blood for CTC collection. Lastly, immunostaining and imaging protocols for CTC classification and corresponding CTC image galleries are reported.

Mechanical characterization of poly-SiGe layers for CMOS-MEMS integrated application

NASA Astrophysics Data System (ADS)

Modlinski, Robert; Witvrouw, Ann; Verbist, Agnes; Puers, Robert; De Wolf, Ingrid

2010-01-01

Measuring mechanical properties at the microscale is essential to understand and to fabricate reliable MEMS. In this paper a tensile testing system and matching microscale test samples are presented. The test samples have a dog-bone-like structure. They are designed to mimic standard macro-tensile test samples. The micro-tensile tests are used to characterize 0.9 µm thick polycrystalline silicon germanium (poly-SiGe) films. The poly-SiGe film, that can be considered as a close equivalent to polycrystalline silicon (poly-Si), is studied as a very promising material for use in CMOS/MEMS integration in a single chip due to its low-temperature LPCVD deposition (T < 450 °C). The fabrication process of the poly-SiGe micro-tensile test structure is explained in detail: the design, the processing and post-processing, the testing and finally the results' discussion. The poly-SiGe micro-tensile results are also compared with nanoindentation data obtained on the same poly-SiGe films as well as with results obtained by other research groups.

Bio-hybrid cell-based actuators for microsystems.

PubMed

Carlsen, Rika Wright; Sitti, Metin

2014-10-15

As we move towards the miniaturization of devices to perform tasks at the nano and microscale, it has become increasingly important to develop new methods for actuation, sensing, and control. Over the past decade, bio-hybrid methods have been investigated as a promising new approach to overcome the challenges of scaling down robotic and other functional devices. These methods integrate biological cells with artificial components and therefore, can take advantage of the intrinsic actuation and sensing functionalities of biological cells. Here, the recent advancements in bio-hybrid actuation are reviewed, and the challenges associated with the design, fabrication, and control of bio-hybrid microsystems are discussed. As a case study, focus is put on the development of bacteria-driven microswimmers, which has been investigated as a targeted drug delivery carrier. Finally, a future outlook for the development of these systems is provided. The continued integration of biological and artificial components is envisioned to enable the performance of tasks at a smaller and smaller scale in the future, leading to the parallel and distributed operation of functional systems at the microscale. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reaction-diffusion processes at the nano- and microscales

NASA Astrophysics Data System (ADS)

Epstein, Irving R.; Xu, Bing

2016-04-01

The bottom-up fabrication of nano- and microscale structures from primary building blocks (molecules, colloidal particles) has made remarkable progress over the past two decades, but most research has focused on structural aspects, leaving our understanding of the dynamic and spatiotemporal aspects at a relatively primitive stage. In this Review, we draw inspiration from living cells to argue that it is now time to move beyond the generation of structures and explore dynamic processes at the nanoscale. We first introduce nanoscale self-assembly, self-organization and reaction-diffusion processes as essential features of cells. Then, we highlight recent progress towards designing and controlling these fundamental features of life in abiological systems. Specifically, we discuss examples of reaction-diffusion processes that lead to such outcomes as self-assembly, self-organization, unique nanostructures, chemical waves and dynamic order to illustrate their ubiquity within a unifying context of dynamic oscillations and energy dissipation. Finally, we suggest future directions for research on reaction-diffusion processes at the nano- and microscales that we find hold particular promise for a new understanding of science at the nanoscale and the development of new kinds of nanotechnologies for chemical transport, chemical communication and integration with living systems.

Development of a microimpedance pump for pulsatile flow transport - Part : Flow characteristics of the microimpedance pump. Part 2: A systematic study of steady and pulsatile transport in microscale cavities

NASA Astrophysics Data System (ADS)

Rinderknecht, Derek

Microfluidics offers an effective means to carry out a wide range of transport processes within a controlled microenvironment by drawing on the benefits imparted by increasing surface area to volume ratio at the microscale. Critical to the impact of microfluidics on integrated devices in the fields of bioengineering and biomedicine is the ability to transport fluids and biomolecules effectively particularly at the size scales involved. In this context a bio-inspired pumping mechanism, the valveless impedance pump, was explored for applications in microfluidics ranging from micro total analysis systems to microchannel cooling. Adhering to the basic principles of the impedance pump mechanism, pumps have been constructed at a variety of size scales from a few centimeters to a few hundred microns. The micro impedance pump is valveless, bidirectional, and can be constructed simply from a wide range of materials. Depending on the size of the pump flow rates range from nL/min to mL/min and pressures can be generated that exceed 20 kPa. Another benefit of the impedance pump is the pulsatile flow output which can be used in the context of microfluidic applications to enhance transport at low Reynolds numbers as well as metering in drug delivery. Pulsatile flow was therefore investigated as a method of augmenting transport in microfluidic systems. Micro PIV was used to study the affect of both steady and pulsatile flows on transport at low Reynolds number was examined in microscale rectangular cavities. Ventilation of the cavity contents was examined in terms of the residence time or average time a particle remains in the cavity region. Lagrangian coherent structures (LCS) were applied to empirical velocity fields to determine the impact of unsteadiness on time dependent boundaries to fluid transport present in the flow. Experimental results show that there are both frequencies which are beneficial and detrimental to cavity ventilation as well as certain frequencies which more evenly distribute particles originating in the cavity throughout the freestream.

Micromechanical characterization of shales through nanoindentation and energy dispersive x-ray spectrometry

DOE PAGES

Veytskin, Yuriy B.; Tammina, Vamsi K.; Bobko, Christopher P.; ...

2017-03-01

Shales are heterogeneous sedimentary rocks which typically comprise a variable mineralogy (including compacted clay particles sub-micrometer in size), silt grains, and nanometer sized pores collectively arranged with transversely isotropic symmetry. Moreover, a detailed understanding of the micro- and sub-microscale geomechanics of these minerals is required to improve models of shale strength and stiffness properties. In this paper, we propose a linked experimental–computational approach and validate a combination of grid nanoindentation and Scanning Electron Microscopy (SEM) with Energy and Wavelength Dispersive X-ray Spectrometry (EDS/WDS) at the same spatial locations to identify both the nano-mechanical morphology and local mineralogy of these nanocomposites.more » The experimental parameters of each method are chosen to assess a similar volume of material. By considering three different shales of varying mineralogy and mechanical diversity, we show through the EMMIX statistical iterative technique that the constituent phases, including highly compacted plate- or sheet-like clay particles, carbonates, silicates, and sulfides, have distinct nano-mechanical morphologies and associated indentation moduli and hardness. Nanoindentation-based strength homogenization analysis determines an average clay packing density, friction coefficient, and solid cohesion for each tested shale sample. Comparison of bulk to microscale geomechanical properties, through bulk porosimetry measurements, reveals a close correspondence between bulk and microscale clay packing densities. Determining the mechanical microstructure and material properties is useful for predictive microporomechanical models of the stiffness and strength properties of shale. Furthermore, the experimental and computational approaches presented here also apply to other chemically and mechanically complex materials exhibiting nanogranular, composite behavior.« less

Mesoscale Computational Investigation of Shocked Heterogeneous Materials with Application to Large Impact Craters

NASA Technical Reports Server (NTRS)

Crawford, D. A.; Barnouin-Jha, O. S.; Cintala, M. J.

2003-01-01

The propagation of shock waves through target materials is strongly influenced by the presence of small-scale structure, fractures, physical and chemical heterogeneities. Pre-existing fractures often create craters that appear square in outline (e.g. Meteor Crater). Reverberations behind the shock from the presence of physical heterogeneity have been proposed as a mechanism for transient weakening of target materials. Pre-existing fractures can also affect melt generation. In this study, we are attempting to bridge the gap in numerical modeling between the micro-scale and the continuum, the so-called meso-scale. To accomplish this, we are developing a methodology to be used in the shock physics hydrocode (CTH) using Monte-Carlo-type methods to investigate the shock properties of heterogeneous materials. By comparing the results of numerical experiments at the micro-scale with experimental results and by using statistical techniques to evaluate the performance of simple constitutive models, we hope to embed the effect of physical heterogeneity into the field variables (pressure, stress, density, velocity) allowing us to directly imprint the effects of micro-scale heterogeneity at the continuum level without incurring high computational cost.

Macro- and microscale variables regulate stent haemodynamics, fibrin deposition and thrombomodulin expression

PubMed Central

Jiménez, Juan M.; Prasad, Varesh; Yu, Michael D.; Kampmeyer, Christopher P.; Kaakour, Abdul-Hadi; Wang, Pei-Jiang; Maloney, Sean F.; Wright, Nathan; Johnston, Ian; Jiang, Yi-Zhou; Davies, Peter F.

2014-01-01

Drug eluting stents are associated with late stent thrombosis (LST), delayed healing and prolonged exposure of stent struts to blood flow. Using macroscale disturbed and undisturbed fluid flow waveforms, we numerically and experimentally determined the effects of microscale model strut geometries upon the generation of prothrombotic conditions that are mediated by flow perturbations. Rectangular cross-sectional stent strut geometries of varying heights and corresponding streamlined versions were studied in the presence of disturbed and undisturbed bulk fluid flow. Numerical simulations and particle flow visualization experiments demonstrated that the interaction of bulk fluid flow and stent struts regulated the generation, size and dynamics of the peristrut flow recirculation zones. In the absence of endothelial cells, deposition of thrombin-generated fibrin occurred primarily in the recirculation zones. When endothelium was present, peristrut expression of anticoagulant thrombomodulin (TM) was dependent on strut height and geometry. Thinner and streamlined strut geometries reduced peristrut flow recirculation zones decreasing prothrombotic fibrin deposition and increasing endothelial anticoagulant TM expression. The studies define physical and functional consequences of macro- and microscale variables that relate to thrombogenicity associated with the most current stent designs, and particularly to LST. PMID:24554575

Characterization of an Aerosol Microconcentrator for Analysis Using Microscale Optical Spectroscopies

PubMed Central

Zheng, Lina; Kulkarni, Pramod; Zavvos, Konstantinos; Liang, Huayan; Birch, M. Eileen; Dionysiou, Dionysios D.

2017-01-01

Efficient microconcentration of aerosols to a substrate is essential for effectively coupling the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma, or micro-Raman or infrared spectroscopies. In this study, we present detailed characterization of a corona-based aerosol microconcentration technique developed previously (Diwakar and Kulkarni, 2012). The method involves two coaxial electrodes separated by a few millimeters, one held at a high electrical potential and the other grounded. The particles are collected on the collection (i.e., ground) electrode from a coaxial aerosol flow in a one-step charge-and-collect scheme using corona discharge and electrical precipitation between the two electrodes. Performance of the corona microconcentration method was determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity was experimentally determined for the aerosol microconcentrator. Using this sensitivity, we show that corona-based microconcentration is much superior to alternative methods, including filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. The method offers unique advantages for compact, hand-held aerosol analytical instrumentation. PMID:28626243

A strong integrated strength and toughness artificial nacre based on dopamine cross-linked graphene oxide.

PubMed

Cui, Wei; Li, Mingzhu; Liu, Jiyang; Wang, Ben; Zhang, Chuck; Jiang, Lei; Cheng, Qunfeng

2014-09-23

Demands of the strong integrated materials have substantially increased across various industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, we have developed a strategy for fabricating the strong integrated artificial nacre based on graphene oxide (GO) sheets by dopamine cross-linking via evaporation-induced assembly process. The tensile strength and toughness simultaneously show 1.5 and 2 times higher than that of natural nacre. Meanwhile, the artificial nacre shows high electrical conductivity. This type of strong integrated artificial nacre has great potential applications in aerospace, flexible supercapacitor electrodes, artificial muscle, and tissue engineering.

A High-Performance Deformable Mirror with Integrated Driver ASIC for Space Based Active Optics

NASA Astrophysics Data System (ADS)

Shelton, Chris

Direct imaging of exoplanets is key to fully understanding these systems through spectroscopy and astrometry. The primary impediment to direct imaging of exoplanets is the extremely high brightness ratio between the planet and its parent star. Direct imaging requires a technique for contrast suppression, which include coronagraphs, and nulling interferometers. Deformable mirrors (DMs) are essential to both of these techniques. With space missions in mind, Microscale is developing a novel DM with direct integration of DM and its electronic control functions in a single small envelope. The Application Specific Integrated Circuit (ASIC) is key to the shrinking of the electronic control functions to a size compatible with direct integration with the DM. Through a NASA SBIR project, Microscale, with JPL oversight, has successfully demonstrated a unique deformable mirror (DM) driver ASIC prototype based on an ultra-low power switch architecture. Microscale calls this the Switch-Mode ASIC, or SM-ASIC, and has characterized it for a key set of performance parameters, and has tested its operation with a variety of actuator loads, such as piezo stack and unimorph, and over a wide temperature range. These tests show the SM-ASIC's capability of supporting active optics in correcting aberrations of a telescope in space. Microscale has also developed DMs to go with the SM-ASIC driver. The latest DM version produced uses small piezo stack elements in an 8x8 array, bonded to a novel silicon facesheet structure fabricated monolithically into a polished mirror on one side and mechanical linkage posts that connect to the piezoelectric stack actuators on the other. In this Supporting Technology proposal we propose to further develop the ASIC-DM and have assembled a very capable team to do so. It will be led by JPL, which has considerable expertise with DMs used in Adaptive Optics systems, with high-contrast imaging systems for exoplanet missions, and with designing DM driver electronics. On its part Microscale will continue its design and fabrication of the ASIC-DM combination. Both the SM-ASIC and the DM are currently at a Technology Readiness Level (TRL) of 3; the major goal of the proposed effort is to raise the TRL of the combined system to 4 by scaling up the array formats and by testing, characterizing, and operating multiple generations of the integrated DM-ASIC systems in a laboratory environment. We propose a three year effort, with these tasks: Year 1: Optimize the influence function of an 8x8 DM for active / adaptive optics, by modeling and fabricating different geometric parameters of the facesheet, with its mechanical linkage posts. Fabricate an SM-ASIC and an 8x8 piezo stack DM, and evaluate their performance. Characterize and optimize the integration processes to achieve a driver/DM combination that can support high contrast imaging of exoplanets. Test the control resolution of the ASIC in driving actuators using a commercial interferometer, to ensure the ASIC can command the piezo stack actuator to nanometer levels. The goal, by year three, is control to a small number of picometers; 10-20 pm (surface) may be a practical goal, while 5 pm is the ultimate goal. Year 2: Fabricate 16x16 piezo stack DMs and matching driver ASICS, and repeat Year 1 tasks with the larger format devices. Year 3: Fabricate 32x32 DMs and SM-ASICs, and repeat Year 1 tasks with the larger format devices. Fabricate versions of the 32x32 devices that can be formed into a 2x2 array, to make a composite 64x64 DM/driver. Fabricate such a composite 64x64 DM/ASIC and evaluate its performance.

EXPERIMENTAL INVESTIGATION OF RELATIVE PERMEABILITY UPSCALING FROM THE MICRO-SCALE TO THE MACRO-SCALE

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

JiangTao Cheng; Ping Yu; William Headley

2001-12-01

The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements ofmore » interfacial area per volume. During this reporting period, we have shown experimentally and theoretically that the optical coherence imaging system is optimized for sandstone. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures that are statistically similar to real porous media has shown the existence of a unique relationship among these hydraulic parameters. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, has the same length-scale as the values of IAV determined for the two-dimensional micro-models.« less

Cryogenic Calcite: A Morphologic and Isotopic Analog to the ALH84001 Carbonates

NASA Technical Reports Server (NTRS)

Niles, P. B.; Leshin, L. A.; Socki, R. A.; Guan, Y.; Ming, D. W.; Gibson, E. K.

2004-01-01

Martian meteorite ALH84001 carbonates preserve large and variable microscale isotopic compositions, which in some way reflect their formation environment. These measurements show large variations (>20%) in the carbon and oxygen isotopic compositions of the carbonates on a 10-20 micron scale that are correlated with chemical composition. However, the utilization of these data sets for interpreting the formation conditions of the carbonates is complex due to lack of suitable terrestrial analogs and the difficulty of modeling under non-equilibrium conditions. Thus, the mechanisms and processes are largely unknown that create and preserve large microscale isotopic variations in carbonate minerals. Experimental tests of the possible environments and mechanisms that lead to large microscale isotopic variations can help address these concerns. One possible mechanism for creating large carbon isotopic variations in carbonates involves the freezing of water. Carbonates precipitate during extensive CO2 degassing that occurs during the freezing process as the fluid s decreasing volume drives CO2 out. This rapid CO2 degassing results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing an enrichment of 13C in the remaining dissolved bicarbonate. This study seeks to determine the suitability of cryogenically formed carbonates as analogs to ALH84001 carbonates. Specifically, our objective is to determine how accurately models using equilibrium fractionation factors approximate the isotopic compositions of cryogenically precipitated carbonates. This includes determining the accuracy of applying equilibrium fractionation factors during a kinetic process, and determining how isotopic variations in the fluid are preserved in microscale variations in the precipitated carbonates.

Implementation of Gas Chromatography and Microscale Distillation into the General Chemistry Laboratory Curriculum as Vehicles for Examining Intermolecular Forces

ERIC Educational Resources Information Center

Csizmar, Clifford M.; Force, Dee Ann; Warner, Don L.

2011-01-01

As part of an NSF-funded Course Curriculum and Laboratory Improvement (CCLI) project that seeks, in part, to increase student exposure to scientific instrumentation, a gas chromatography experiment has been integrated into the second-semester general chemistry laboratory curriculum. The experiment uses affordable, commercially available equipment…

Micro-scale characterization of a CMOS-based neutron detector for in-phantom measurements in radiation therapy

NASA Astrophysics Data System (ADS)

Arbor, Nicolas; Higueret, Stephane; Husson, Daniel

2018-04-01

The CMOS sensor AlphaRad has been designed at the IPHC Strasbourg for real-time monitoring of fast and thermal neutrons over a full energy spectrum. Completely integrated, highly transparent to photons and optimized for low power consumption, this sensor offers very interesting characteristics for the study of internal neutrons in radiation therapy with anthropomorphic phantoms. However, specific effects related to the CMOS metal substructure and to the charge collection process of low energy particles must be carefully estimated before being used for medical applications. We present a detailed characterization of the AlphaRad chip in the MeV energy range using proton and alpha micro-beam experiments performed at the AIFIRA facility (CENBG, Bordeaux). Two-dimensional maps of the charge collection were carried out on a micro-metric scale to be integrated into a Geant4 Monte Carlo simulation of the system. The gamma rejection, as well as the fast and thermal neutrons separation, were studied using both simulation and experimental data. The results highlight the potential of a future system based on CMOS sensor for in-phantom neutron detection in radiation therapies.

Unusual strategies for using indium gallium nitride grown on silicon (111) for solid-state lighting

PubMed Central

Kim, Hoon-sik; Brueckner, Eric; Song, Jizhou; Li, Yuhang; Kim, Seok; Lu, Chaofeng; Sulkin, Joshua; Choquette, Kent; Huang, Yonggang; Nuzzo, Ralph G.; Rogers, John A.

2011-01-01

Properties that can now be achieved with advanced, blue indium gallium nitride light emitting diodes (LEDs) lead to their potential as replacements for existing infrastructure in general illumination, with important implications for efficient use of energy. Further advances in this technology will benefit from reexamination of the modes for incorporating this materials technology into lighting modules that manage light conversion, extraction, and distribution, in ways that minimize adverse thermal effects associated with operation, with packages that exploit the unique aspects of these light sources. We present here ideas in anisotropic etching, microscale device assembly/integration, and module configuration that address these challenges in unconventional ways. Various device demonstrations provide examples of the capabilities, including thin, flexible lighting “tapes” based on patterned phosphors and large collections of small light emitters on plastic substrates. Quantitative modeling and experimental evaluation of heat flow in such structures illustrates one particular, important aspect of their operation: small, distributed LEDs can be passively cooled simply by direct thermal transport through thin-film metallization used for electrical interconnect, providing an enhanced and scalable means to integrate these devices in modules for white light generation. PMID:21666096

An Intelligent Automation Platform for Rapid Bioprocess Design.

PubMed

Wu, Tianyi; Zhou, Yuhong

2014-08-01

Bioprocess development is very labor intensive, requiring many experiments to characterize each unit operation in the process sequence to achieve product safety and process efficiency. Recent advances in microscale biochemical engineering have led to automated experimentation. A process design workflow is implemented sequentially in which (1) a liquid-handling system performs high-throughput wet lab experiments, (2) standalone analysis devices detect the data, and (3) specific software is used for data analysis and experiment design given the user's inputs. We report an intelligent automation platform that integrates these three activities to enhance the efficiency of such a workflow. A multiagent intelligent architecture has been developed incorporating agent communication to perform the tasks automatically. The key contribution of this work is the automation of data analysis and experiment design and also the ability to generate scripts to run the experiments automatically, allowing the elimination of human involvement. A first-generation prototype has been established and demonstrated through lysozyme precipitation process design. All procedures in the case study have been fully automated through an intelligent automation platform. The realization of automated data analysis and experiment design, and automated script programming for experimental procedures has the potential to increase lab productivity. © 2013 Society for Laboratory Automation and Screening.

Building an experimental model of the human body with non-physiological parameters.

PubMed

Labuz, Joseph M; Moraes, Christopher; Mertz, David R; Leung, Brendan M; Takayama, Shuichi

2017-03-01

New advances in engineering and biomedical technology have enabled recent efforts to capture essential aspects of human physiology in microscale, in-vitro systems. The application of these advances to experimentally model complex processes in an integrated platform - commonly called a 'human-on-a-chip (HOC)' - requires that relevant compartments and parameters be sized correctly relative to each other and to the system as a whole. Empirical observation, theoretical treatments of resource distribution systems and natural experiments can all be used to inform rational design of such a system, but technical and fundamental challenges (e.g. small system blood volumes and context-dependent cell metabolism, respectively) pose substantial, unaddressed obstacles. Here, we put forth two fundamental principles for HOC design: inducing in-vivo -like cellular metabolic rates is necessary and may be accomplished in-vitro by limiting O 2 availability and that the effects of increased blood volumes on drug concentration can be mitigated through pharmacokinetics-based treatments of solute distribution. Combining these principles with natural observation and engineering workarounds, we derive a complete set of design criteria for a practically realizable, physiologically faithful, five-organ millionth-scale (× 10 -6 ) microfluidic model of the human body.

An Intelligent Automation Platform for Rapid Bioprocess Design

PubMed Central

Wu, Tianyi

2014-01-01

Bioprocess development is very labor intensive, requiring many experiments to characterize each unit operation in the process sequence to achieve product safety and process efficiency. Recent advances in microscale biochemical engineering have led to automated experimentation. A process design workflow is implemented sequentially in which (1) a liquid-handling system performs high-throughput wet lab experiments, (2) standalone analysis devices detect the data, and (3) specific software is used for data analysis and experiment design given the user’s inputs. We report an intelligent automation platform that integrates these three activities to enhance the efficiency of such a workflow. A multiagent intelligent architecture has been developed incorporating agent communication to perform the tasks automatically. The key contribution of this work is the automation of data analysis and experiment design and also the ability to generate scripts to run the experiments automatically, allowing the elimination of human involvement. A first-generation prototype has been established and demonstrated through lysozyme precipitation process design. All procedures in the case study have been fully automated through an intelligent automation platform. The realization of automated data analysis and experiment design, and automated script programming for experimental procedures has the potential to increase lab productivity. PMID:24088579

Building an experimental model of the human body with non-physiological parameters

PubMed Central

Labuz, Joseph M.; Moraes, Christopher; Mertz, David R.; Leung, Brendan M.; Takayama, Shuichi

2017-01-01

New advances in engineering and biomedical technology have enabled recent efforts to capture essential aspects of human physiology in microscale, in-vitro systems. The application of these advances to experimentally model complex processes in an integrated platform — commonly called a ‘human-on-a-chip (HOC)’ — requires that relevant compartments and parameters be sized correctly relative to each other and to the system as a whole. Empirical observation, theoretical treatments of resource distribution systems and natural experiments can all be used to inform rational design of such a system, but technical and fundamental challenges (e.g. small system blood volumes and context-dependent cell metabolism, respectively) pose substantial, unaddressed obstacles. Here, we put forth two fundamental principles for HOC design: inducing in-vivo-like cellular metabolic rates is necessary and may be accomplished in-vitro by limiting O2 availability and that the effects of increased blood volumes on drug concentration can be mitigated through pharmacokinetics-based treatments of solute distribution. Combining these principles with natural observation and engineering workarounds, we derive a complete set of design criteria for a practically realizable, physiologically faithful, five-organ millionth-scale (× 10−6) microfluidic model of the human body. PMID:28713851

Innovative Tools and Technology for Analysis of Single Cells and Cell-Cell Interaction.

PubMed

Konry, Tania; Sarkar, Saheli; Sabhachandani, Pooja; Cohen, Noa

2016-07-11

Heterogeneity in single-cell responses and intercellular interactions results from complex regulation of cell-intrinsic and environmental factors. Single-cell analysis allows not only detection of individual cellular characteristics but also correlation of genetic content with phenotypic traits in the same cell. Technological advances in micro- and nanofabrication have benefited single-cell analysis by allowing precise control of the localized microenvironment, cell manipulation, and sensitive detection capabilities. Additionally, microscale techniques permit rapid, high-throughput, multiparametric screening that has become essential for -omics research. This review highlights innovative applications of microscale platforms in genetic, proteomic, and metabolic detection in single cells; cell sorting strategies; and heterotypic cell-cell interaction. We discuss key design aspects of single-cell localization and isolation in microfluidic systems, dynamic and endpoint analyses, and approaches that integrate highly multiplexed detection of various intracellular species.

Power management circuits for self-powered systems based on micro-scale solar energy harvesting

NASA Astrophysics Data System (ADS)

Yoon, Eun-Jung; Yu, Chong-Gun

2016-03-01

In this paper, two types of power management circuits for self-powered systems based on micro-scale solar energy harvesting are proposed. First, if a solar cell outputs a very low voltage, less than 0.5 V, as in miniature solar cells or monolithic integrated solar cells, such that it cannot directly power the load, a voltage booster is employed to step up the solar cell's output voltage, and then a power management unit (PMU) delivers the boosted voltage to the load. Second, if the output voltage of a solar cell is enough to drive the load, the PMU directly supplies the load with solar energy. The proposed power management systems are designed and fabricated in a 0.18-μm complementary metal-oxide-semiconductor process, and their performances are compared and analysed through measurements.

Apparatus and method for determining microscale interactions based on compressive sensors such as crystal structures

DOEpatents

McAdams, Harley; AlQuraishi, Mohammed

2015-04-21

Techniques for determining values for a metric of microscale interactions include determining a mesoscale metric for a plurality of mesoscale interaction types, wherein a value of the mesoscale metric for each mesoscale interaction type is based on a corresponding function of values of the microscale metric for the plurality of the microscale interaction types. A plurality of observations that indicate the values of the mesoscale metric are determined for the plurality of mesoscale interaction types. Values of the microscale metric are determined for the plurality of microscale interaction types based on the plurality of observations and the corresponding functions and compressed sensing.

Localized Scale Coupling and New Educational Paradigms in Multiscale Mathematics and Science

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

Ingber, Marc; Vorobieff, Peter

2014-03-14

We have experimentally demonstrated how microscale phenomena affect suspended particle behavior on the mesoscale, and how particle group behavior on the mesoscale influences the macroscale suspension behavior. Semi-analytical and numerical methods to treat flows on different scales have been developed, and a framework to combine these scale-dependent treatment has been described.

An Experimental Study of Momentum and Thermal Transport in Flow through Smooth- and Rough-Wall Microchannels

ERIC Educational Resources Information Center

Natrajan, Vinay Kumar

2009-01-01

The impact of surface roughness on momentum and thermal transport in microscale flow passages of hydraulic diameter D[subscript h] = 600 micrometer is investigated in the laminar, transitional and turbulent flow regimes using microscopic PIV, two-color LIF thermometry and pressure-drop measurements. In addition to smooth-wall flow, two different…

A new class of boron nitride fibers with tunable properties by combining an electrospinning process and the polymer-derived ceramics route

NASA Astrophysics Data System (ADS)

Salles, Vincent; Bernard, Samuel; Brioude, Arnaud; Cornu, David; Miele, Philippe

2010-02-01

Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments.Novel boron nitride (BN) fibers have been developed with diameters ranging from the nano- to microscale by thermal conversion of as-electrospun fibers from polyacrylonitrile and poly[B-(methylamino)borazine] blend solutions. Such a new class of ceramic fibers is seen as potential candidate for thermal management applications and filtration systems in harsh environments. Electronic supplementary information (ESI) available: Experimental details and EDX results. See DOI: 10.1039/b9nr00185a

Predicting the structure of screw dislocations in nanoporous materials

NASA Astrophysics Data System (ADS)

Walker, Andrew M.; Slater, Ben; Gale, Julian D.; Wright, Kate

2004-10-01

Extended microscale crystal defects, including dislocations and stacking faults, can radically alter the properties of technologically important materials. Determining the atomic structure and the influence of defects on properties remains a major experimental and computational challenge. Using a newly developed simulation technique, the structure of the 1/2a <100> screw dislocation in nanoporous zeolite A has been modelled. The predicted channel structure has a spiral form that resembles a nanoscale corkscrew. Our findings suggest that the dislocation will enhance the transport of molecules from the surface to the interior of the crystal while retarding transport parallel to the surface. Crucially, the dislocation creates an activated, locally chiral environment that may have enantioselective applications. These predictions highlight the influence that microscale defects have on the properties of structurally complex materials, in addition to their pivotal role in crystal growth.

Prediction of water loss and viscoelastic deformation of apple tissue using a multiscale model.

PubMed

Aregawi, Wondwosen A; Abera, Metadel K; Fanta, Solomon W; Verboven, Pieter; Nicolai, Bart

2014-11-19

A two-dimensional multiscale water transport and mechanical model was developed to predict the water loss and deformation of apple tissue (Malus × domestica Borkh. cv. 'Jonagold') during dehydration. At the macroscopic level, a continuum approach was used to construct a coupled water transport and mechanical model. Water transport in the tissue was simulated using a phenomenological approach using Fick's second law of diffusion. Mechanical deformation due to shrinkage was based on a structural mechanics model consisting of two parts: Yeoh strain energy functions to account for non-linearity and Maxwell's rheological model of visco-elasticity. Apparent parameters of the macroscale model were computed from a microscale model. The latter accounted for water exchange between different microscopic structures of the tissue (intercellular space, the cell wall network and cytoplasm) using transport laws with the water potential as the driving force for water exchange between different compartments of tissue. The microscale deformation mechanics were computed using a model where the cells were represented as a closed thin walled structure. The predicted apparent water transport properties of apple cortex tissue from the microscale model showed good agreement with the experimentally measured values. Deviations between calculated and measured mechanical properties of apple tissue were observed at strains larger than 3%, and were attributed to differences in water transport behavior between the experimental compression tests and the simulated dehydration-deformation behavior. Tissue dehydration and deformation in the high relative humidity range ( > 97% RH) could, however, be accurately predicted by the multiscale model. The multiscale model helped to understand the dynamics of the dehydration process and the importance of the different microstructural compartments (intercellular space, cell wall, membrane and cytoplasm) for water transport and mechanical deformation.

The Microscale Synthesis and Electrochemistry of Low-Valent Mononuclear Complexes (h3-C3H5)Fe(CO)3 X (X = I, Br, Cl)

NASA Astrophysics Data System (ADS)

Mocellin, Enrico; Russell, Richard; Ravera, Mauro

1998-06-01

The experimental content of this paper will appeal to pedagogues and students who might be looking for new ideas that have an element of challenge. By combining experimental procedures which place microscale, chemical synthesis, and an inclusive, unified, product characterization in perspective, we have afforded the student the scope to obtain progressive, disciplined results and the opportunity to discuss these in the subsequent reporting. By this process, it is our experience that the students often identify with the practical work that is being undertaken, and they develop considerable empathy during their contribution to the "discovery" process that this laboratory program offers. The experimental work can be abbreviated to a single compound, subdivided into synthesis or electrochemistry, or extended to macroscale and other instrumental techniques of characterization, thus offering opportunities to accommodate time constraints, class results combination and discussion, and individual student enthusiasm. We believe that having to accept and/or constructively criticize sequential experimental results, collected by fellow students, mimics more realistically the practice of chemistry at the workplace and can build enthusiasm and elicit contagious fellowship from the class. All of these aspects can simply be achieved by utilizing the listed journals and references therein. Most importantly, it affords the students the opportunity to extricate themselves as innocent bystanders from the conventional "single experiment" practical laboratory to a path of practice and achievement in the scientific method.

Integrated process development-a robust, rapid method for inclusion body harvesting and processing at the microscale level.

PubMed

Walther, Cornelia; Kellner, Martin; Berkemeyer, Matthias; Brocard, Cécile; Dürauer, Astrid

2017-10-21

Escherichia coli stores large amounts of highly pure product within inclusion bodies (IBs). To take advantage of this beneficial feature, after cell disintegration, the first step to optimal product recovery is efficient IB preparation. This step is also important in evaluating upstream optimization and process development, due to the potential impact of bioprocessing conditions on product quality and on the nanoscale properties of IBs. Proper IB preparation is often neglected, due to laboratory-scale methods requiring large amounts of materials and labor. Miniaturization and parallelization can accelerate analyses of individual processing steps and provide a deeper understanding of up- and downstream processing interdependencies. Consequently, reproducible, predictive microscale methods are in demand. In the present study, we complemented a recently established high-throughput cell disruption method with a microscale method for preparing purified IBs. This preparation provided results comparable to laboratory-scale IB processing, regarding impurity depletion, and product loss. Furthermore, with this method, we performed a "design of experiments" study to demonstrate the influence of fermentation conditions on the performance of subsequent downstream steps and product quality. We showed that this approach provided a 300-fold reduction in material consumption for each fermentation condition and a 24-fold reduction in processing time for 24 samples.

MEMS Stirling Cooler Development Update

NASA Technical Reports Server (NTRS)

Moran, Matthew E.; Wesolek, Danielle

2003-01-01

This presentation provides an update on the effort to build and test a prototype unit of the patented MEMS Stirling cooler concept. A micro-scale regenerator has been fabricated by Polar Thermal Technologies and is currently being integrated into a Stirling cycle simulator at Johns Hopkins University Applied Physics Laboratory. A discussion of the analysis, design, assembly, and test plans for the prototype will be presented.

Mesoscale characterization of local property distributions in heterogeneous electrodes

NASA Astrophysics Data System (ADS)

Hsu, Tim; Epting, William K.; Mahbub, Rubayyat; Nuhfer, Noel T.; Bhattacharya, Sudip; Lei, Yinkai; Miller, Herbert M.; Ohodnicki, Paul R.; Gerdes, Kirk R.; Abernathy, Harry W.; Hackett, Gregory A.; Rollett, Anthony D.; De Graef, Marc; Litster, Shawn; Salvador, Paul A.

2018-05-01

The performance of electrochemical devices depends on the three-dimensional (3D) distributions of microstructural features in their electrodes. Several mature methods exist to characterize 3D microstructures over the microscale (tens of microns), which are useful in understanding homogeneous electrodes. However, methods that capture mesoscale (hundreds of microns) volumes at appropriate resolution (tens of nm) are lacking, though they are needed to understand more common, less ideal electrodes. Using serial sectioning with a Xe plasma focused ion beam combined with scanning electron microscopy (Xe PFIB-SEM), two commercial solid oxide fuel cell (SOFC) electrodes are reconstructed over volumes of 126 × 73 × 12.5 and 124 × 110 × 8 μm3 with a resolution on the order of ≈ 503 nm3. The mesoscale distributions of microscale structural features are quantified and both microscale and mesoscale inhomogeneities are found. We analyze the origin of inhomogeneity over different length scales by comparing experimental and synthetic microstructures, generated with different particle size distributions, with such synthetic microstructures capturing well the high-frequency heterogeneity. Effective medium theory models indicate that significant mesoscale variations in local electrochemical activity are expected throughout such electrodes. These methods offer improved understanding of the performance of complex electrodes in energy conversion devices.

Cavitation in flow through a micro-orifice inside a silicon microchannel

NASA Astrophysics Data System (ADS)

Mishra, Chandan; Peles, Yoav

2005-01-01

Hydrodynamic cavitation in flows through a micro-orifice entrenched in a microchannel has been detected and experimentally investigated. Microfabrication techniques have been employed to design and develop a microfluidic device containing an 11.5μm wide micro-orifice inside a 100.2μm wide and 101.3μm deep microchannel. The flow of de-ionized water through the micro-orifice reveals the presence of multifarious cavitating flow regimes. This investigation divulges both similarities and differences between cavitation in micro-orifices and cavitation in their macroscale counterparts. The low incipient cavitation number obtained from the current experiments suggests a dominant size scale effect. Choking cavitation is observed to be independent of any pressure or velocity scale effects. However, choking is significantly influenced by the small stream nuclei residence time at such scales. Flow rate choking leads to the establishment of a stationary cavity. Large flow and cavitation hysteresis have been detected at the microscale leading to very high desinent cavitation numbers. The rapid transition from incipient bubbles to choking cavitation and subsequent supercavitation suggests the presence of radically different flow patterns at the microscale. Supercavitation results in a thick cavity, which extends throughout the microchannel, and is encompassed by the liquid. Cavitation at the microscale is expected to considerably influence the design of innovative high-speed microfluidic systems.

The finite element method for micro-scale modeling of ultrasound propagation in cancellous bone.

PubMed

Vafaeian, B; El-Rich, M; El-Bialy, T; Adeeb, S

2014-08-01

Quantitative ultrasound for bone assessment is based on the correlations between ultrasonic parameters and the properties (mechanical and physical) of cancellous bone. To elucidate the correlations, understanding the physics of ultrasound in cancellous bone is demanded. Micro-scale modeling of ultrasound propagation in cancellous bone using the finite-difference time-domain (FDTD) method has been so far utilized as one of the approaches in this regard. However, the FDTD method accompanies two disadvantages: staircase sampling of cancellous bone by finite difference grids leads to generation of wave artifacts at the solid-fluid interface inside the bone; additionally, this method cannot explicitly satisfy the needed perfect-slip conditions at the interface. To overcome these disadvantages, the finite element method (FEM) is proposed in this study. Three-dimensional finite element models of six water-saturated cancellous bone samples with different bone volume were created. The values of speed of sound (SOS) and broadband ultrasound attenuation (BUA) were calculated through the finite element simulations of ultrasound propagation in each sample. Comparing the results with other experimental and simulation studies demonstrated the capabilities of the FEM for micro-scale modeling of ultrasound in water-saturated cancellous bone. Copyright © 2014 Elsevier B.V. All rights reserved.

Integration of 3D Printed and Micropatterned Polycaprolactone Scaffolds for Guidance of Oriented Collagenous Tissue Formation In Vivo.

PubMed

Pilipchuk, Sophia P; Monje, Alberto; Jiao, Yizu; Hao, Jie; Kruger, Laura; Flanagan, Colleen L; Hollister, Scott J; Giannobile, William V

2016-03-01

Scaffold design incorporating multiscale cues for clinically relevant, aligned tissue regeneration has potential to improve structural and functional integrity of multitissue interfaces. The objective of this preclinical study is to develop poly(ε-caprolactone) (PCL) scaffolds with mesoscale and microscale architectural cues specific to human ligament progenitor cells and assess their ability to form aligned bone-ligament-cementum complexes in vivo. PCL scaffolds are designed to integrate a 3D printed bone region with a micropatterned PCL thin film consisting of grooved pillars. The patterned film region is seeded with human ligament cells, fibroblasts transduced with bone morphogenetic protein-7 genes seeded within the bone region, and a tooth dentin segment positioned on the ligament region prior to subcutaneous implantation into a murine model. Results indicate increased tissue alignment in vivo using micropatterned PCL films, compared to random-porous PCL. At week 6, 30 μm groove depth significantly enhances oriented collagen fiber thickness, overall cell alignment, and nuclear elongation relative to 10 μm groove depth. This study demonstrates for the first time that scaffolds with combined hierarchical mesoscale and microscale features can align cells in vivo for oral tissue repair with potential for improving the regenerative response of other bone-ligament complexes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reaction Scale and Green Chemistry: Microscale or Macroscale, Which is Greener?

ERIC Educational Resources Information Center

Duarte, Rita C. C.; Ribeiro, M. Gabriela T. C.; Machado, Adelio A. S. C.

2017-01-01

The different ways microscale and green chemistry allow reducing the deleterious impacts of chemistry on human health and the environment are discussed in terms of their different basic paradigms: green chemistry follows the ecologic paradigm and microscale the risk paradigm. A study of the synthesis of 1-bromobutane at macro- ? microscale (109.3…

Method and apparatus for actively controlling a micro-scale flexural plate wave device

DOEpatents

Dohner, Jeffrey L.

2001-01-01

An actively controlled flexural plate wave device provides a micro-scale pump. A method of actively controlling a flexural plate wave device produces traveling waves in the device by coordinating the interaction of a magnetic field with actively controlled currents. An actively-controlled flexural plate wave device can be placed in a fluid channel and adapted for use as a micro-scale fluid pump to cool or drive micro-scale systems, for example, micro-chips, micro-electrical-mechanical devices, micro-fluid circuits, or micro-scale chemical analysis devices.

Hybrid micro-scale photovoltaics for enhanced energy conversion across all irradiation conditions

NASA Astrophysics Data System (ADS)

Agrawal, Gautam

A novel hybrid photovoltaics (HPV) architecture is presented that integrates high-performance micro-optics-based concentrator photovoltaics (CPV) array technology with a 1-sun photovoltaic (PV) cell within a low-profile panel structure. The approach simultaneously captures the direct solar radiation components with arrayed high-efficiency CPV cells and the diffuse solar components with an underlying wide-area PV cell. Performance analyses predict that the hybrid approach will significantly enhance the average energy produced per unit area for the full range of diffuse/direct radiation patterns across the USA. Furthermore, cost analyses indicate that the hybrid concept may be financially attractive for a wide range of locations. Indoor and outdoor experimental evaluation of a micro-optical system designed for use in a hybrid architecture verified that a large proportion of the direct radiation component was concentrated onto emulated micro-cell regions while most of the diffuse radiation and the remaining direct radiation was collected in the 1-sun cell area.

Integrated optical sensors for 2D spatial chemical mapping (Conference Presentation)

NASA Astrophysics Data System (ADS)

Flores, Raquel; Janeiro, Ricardo; Viegas, Jaime

2017-02-01

Sensors based on optical waveguides for chemical sensing have attracted increasing interest over the last two decades, fueled by potential applications in commercial lab-on-a-chip devices for medical and food safety industries. Even though the early studies were oriented for single-point detection, progress in device size reduction and device yield afforded by photonics foundries have opened the opportunity for distributed dynamic chemical sensing at the microscale. This will allow researchers to follow the dynamics of chemical species in field of microbiology, and microchemistry, with a complementary method to current technologies based on microfluorescence and hyperspectral imaging. The study of the chemical dynamics at the surface of photoelectrodes in water splitting cells are a good candidate to benefit from such optochemical sensing devices that includes a photonic integrated circuit (PIC) with multiple sensors for real-time detection and spatial mapping of chemical species. In this project, we present experimental results on a prototype integrated optical system for chemical mapping based on the interaction of cascaded resonant optical devices, spatially covered with chemically sensitive polymers and plasmon-enhanced nanostructured metal/metal-oxide claddings offering chemical selectivity in a pixelated surface. In order to achieve a compact footprint, the prototype is based in a silicon photonics platform. A discussion on the relative merits of a photonic platform based on large bandgap metal oxides and nitrides which have higher chemical resistance than silicon is also presented.

Microscale and nanoscale strain mapping techniques applied to creep of rocks

NASA Astrophysics Data System (ADS)

Quintanilla-Terminel, Alejandra; Zimmerman, Mark E.; Evans, Brian; Kohlstedt, David L.

2017-07-01

Usually several deformation mechanisms interact to accommodate plastic deformation. Quantifying the contribution of each to the total strain is necessary to bridge the gaps from observations of microstructures, to geomechanical descriptions, to extrapolating from laboratory data to field observations. Here, we describe the experimental and computational techniques involved in microscale strain mapping (MSSM), which allows strain produced during high-pressure, high-temperature deformation experiments to be tracked with high resolution. MSSM relies on the analysis of the relative displacement of initially regularly spaced markers after deformation. We present two lithography techniques used to pattern rock substrates at different scales: photolithography and electron-beam lithography. Further, we discuss the challenges of applying the MSSM technique to samples used in high-temperature and high-pressure experiments. We applied the MSSM technique to a study of strain partitioning during creep of Carrara marble and grain boundary sliding in San Carlos olivine, synthetic forsterite, and Solnhofen limestone at a confining pressure, Pc, of 300 MPa and homologous temperatures, T/Tm, of 0.3 to 0.6. The MSSM technique works very well up to temperatures of 700 °C. The experimental developments described here show promising results for higher-temperature applications.

Effects of electric field on micro-scale flame properties of biobutanol fuel

PubMed Central

Xu, Tao; Chen, Qinglin; Zhang, Bingjian; Lu, Shushen; Mo, Dongchuan; Zhang, Zhengguo; Gao, Xuenong

2016-01-01

With the increasing need of smaller power sources for satellites, energy systems and engine equipment, microcombustion pose a potential as alternative power source to conventional batteries. As the substitute fuel source for gasoline, biobutanol shows more promising characteristics than ethanol. In this study, the diffusion microflame of liquid biobutanol under electric field have been examined through in-lab experiment and numerical simulation. It is found that traditional gas jet diffusion flame theory shows significant inconsistency with the experimental results of micro scale flame in electric field. The results suggest that with the increase of electric field intensity, the quenching flow rate decrease first and increase after it reach its minimum, while the flame height and highest flame temperature increase first and drop after its peak value. In addition, it was also observed that the flame height and highest temperature for smaller tube can reach its maximum faster. Therefore, the interaction between microscale effect and electric field plays a significant role on understanding the microcombustion of liquid fuel. Therefore, FLUENT simulation was adopted to understand and measure the impacts of microflame characteristic parameters. The final numerical results are consistent with the experimental data and show a high reliability. PMID:27609428

Comparison of competing segmentation standards for X-ray computed topographic imaging using Lattice Boltzmann techniques

NASA Astrophysics Data System (ADS)

Larsen, J. D.; Schaap, M. G.

2013-12-01

Recent advances in computing technology and experimental techniques have made it possible to observe and characterize fluid dynamics at the micro-scale. Many computational methods exist that can adequately simulate fluid flow in porous media. Lattice Boltzmann methods provide the distinct advantage of tracking particles at the microscopic level and returning macroscopic observations. While experimental methods can accurately measure macroscopic fluid dynamics, computational efforts can be used to predict and gain insight into fluid dynamics by utilizing thin sections or computed micro-tomography (CMT) images of core sections. Although substantial effort have been made to advance non-invasive imaging methods such as CMT, fluid dynamics simulations, and microscale analysis, a true three dimensional image segmentation technique has not been developed until recently. Many competing segmentation techniques are utilized in industry and research settings with varying results. In this study lattice Boltzmann method is used to simulate stokes flow in a macroporous soil column. Two dimensional CMT images were used to reconstruct a three dimensional representation of the original sample. Six competing segmentation standards were used to binarize the CMT volumes which provide distinction between solid phase and pore space. The permeability of the reconstructed samples was calculated, with Darcy's Law, from lattice Boltzmann simulations of fluid flow in the samples. We compare simulated permeability from differing segmentation algorithms to experimental findings.

Results of the GABLS3 diurnal-cycle benchmark for wind energy applications

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

Rodrigo, J. Sanz; Allaerts, D.; Avila, M.

We present results of the GABLS3 model intercomparison benchmark revisited for wind energy applications. The case consists of a diurnal cycle, measured at the 200-m tall Cabauw tower in the Netherlands, including a nocturnal low-level jet. The benchmark includes a sensitivity analysis of WRF simulations using two input meteorological databases and five planetary boundary-layer schemes. A reference set of mesoscale tendencies is used to drive microscale simulations using RANS k-ϵ and LES turbulence models. The validation is based on rotor-based quantities of interest. Cycle-integrated mean absolute errors are used to quantify model performance. The results of the benchmark are usedmore » to discuss input uncertainties from mesoscale modelling, different meso-micro coupling strategies (online vs offline) and consistency between RANS and LES codes when dealing with boundary-layer mean flow quantities. Altogether, all the microscale simulations produce a consistent coupling with mesoscale forcings.« less

Results of the GABLS3 diurnal-cycle benchmark for wind energy applications

DOE PAGES

Rodrigo, J. Sanz; Allaerts, D.; Avila, M.; ...

2017-06-13

We present results of the GABLS3 model intercomparison benchmark revisited for wind energy applications. The case consists of a diurnal cycle, measured at the 200-m tall Cabauw tower in the Netherlands, including a nocturnal low-level jet. The benchmark includes a sensitivity analysis of WRF simulations using two input meteorological databases and five planetary boundary-layer schemes. A reference set of mesoscale tendencies is used to drive microscale simulations using RANS k-ϵ and LES turbulence models. The validation is based on rotor-based quantities of interest. Cycle-integrated mean absolute errors are used to quantify model performance. The results of the benchmark are usedmore » to discuss input uncertainties from mesoscale modelling, different meso-micro coupling strategies (online vs offline) and consistency between RANS and LES codes when dealing with boundary-layer mean flow quantities. Altogether, all the microscale simulations produce a consistent coupling with mesoscale forcings.« less

Development of a 3D printer using scanning projection stereolithography

PubMed Central

Lee, Michael P.; Cooper, Geoffrey J. T.; Hinkley, Trevor; Gibson, Graham M.; Padgett, Miles J.; Cronin, Leroy

2015-01-01

We have developed a system for the rapid fabrication of low cost 3D devices and systems in the laboratory with micro-scale features yet cm-scale objects. Our system is inspired by maskless lithography, where a digital micromirror device (DMD) is used to project patterns with resolution up to 10 µm onto a layer of photoresist. Large area objects can be fabricated by stitching projected images over a 5cm2 area. The addition of a z-stage allows multiple layers to be stacked to create 3D objects, removing the need for any developing or etching steps but at the same time leading to true 3D devices which are robust, configurable and scalable. We demonstrate the applications of the system by printing a range of micro-scale objects as well as a fully functioning microfluidic droplet device and test its integrity by pumping dye through the channels. PMID:25906401

Suzuki-Miyaura Cross-Coupling Reactions of Primary Alkyltrifluoroborates with Aryl Chlorides

PubMed Central

Dreher, Spencer D.; Lim, Siang-Ee; Sandrock, Deidre L.; Molander, Gary A.

2009-01-01

Parallel microscale experimentation was used to develop general conditions for the Suzuki-Miyaura cross-coupling of diversely functionalized primary alkyltrifluoroborates with a variety of aryl chlorides. These conditions were found to be amenable to coupling with aryl bromides, iodides, and triflates as well. The conditions that were previously identified through similar techniques to promote the cross-coupling of secondary alkyltrifluoroborates with aryl chlorides were not optimal for the primary alkyltrifluoroborates, thus demonstrating the value of parallel experimentation to develop novel, substrate specific results. PMID:19271726

Denitrification in Agricultural Soils: Integrated control and Modelling at various scales (DASIM)

NASA Astrophysics Data System (ADS)

Müller, Christoph; Well, Reinhard; Böttcher, Jürgen; Butterbach-Bahl, Klaus; Dannenmann, Michael; Deppe, Marianna; Dittert, Klaus; Dörsch, Peter; Horn, Marcus; Ippisch, Olaf; Mikutta, Robert; Senbayram, Mehmet; Vogel, Hans-Jörg; Wrage-Mönnig, Nicole; Müller, Carsten

2016-04-01

The new research unit DASIM brings together the expertise of 11 working groups to study the process of denitrification at unprecedented spatial and temporal resolution. Based on state-of-the art analytical techniques our aim is to develop improved denitrification models ranging from the microscale to the field/plot scale. Denitrification, the process of nitrate reduction allowing microbes to sustain respiration under anaerobic conditions, is the key process returning reactive nitrogen as N2to the atmosphere. Actively denitrifying communities in soil show distinct regulatory phenotypes (DRP) with characteristic controls on the single reaction steps and end-products. It is unresolved whether DRPs are anchored in the taxonomic composition of denitrifier communities and how environmental conditions shape them. Despite being intensively studied for more than 100 years, denitrification rates and emissions of its gaseous products can still not be satisfactorily predicted. While the impact of single environmental parameters is well understood, the complexity of the process itself with its intricate cellular regulation in response to highly variable factors in the soil matrix prevents robust prediction of gaseous emissions. Key parameters in soil are pO2, organic matter content and quality, pH and the microbial community structure, which in turn are affected by the soil structure, chemistry and soil-plant interactions. In the DASIM research unit, we aim at the quantitative prediction of denitrification rates as a function of microscale soil structure, organic matter quality, DRPs and atmospheric boundary conditions via a combination of state-of-the-art experimental and analytical tools (X-ray μCT, 15N tracing, NanoSIMS, microsensors, advanced flux detection, NMR spectroscopy, and molecular methods including next generation sequencing of functional gene transcripts). We actively seek collaboration with researchers working in the field of denitrification.

Microscale Titration in Schools Titration Competition.

ERIC Educational Resources Information Center

Clark, Michael J.

1998-01-01

Reviews the requirements of the National Titration Competition and describes how a team in a local competition used the technique. Compares microscale titration to conventional titration. Outlines the benefits of employing microscale techniques. (DDR)

The dynamical integrity concept for interpreting/ predicting experimental behaviour: from macro- to nano-mechanics.

PubMed

Lenci, Stefano; Rega, Giuseppe; Ruzziconi, Laura

2013-06-28

The dynamical integrity, a new concept proposed by J.M.T. Thompson, and developed by the authors, is used to interpret experimental results. After reviewing the main issues involved in this analysis, including the proposal of a new integrity measure able to capture in an easy way the safe part of basins, attention is dedicated to two experiments, a rotating pendulum and a micro-electro-mechanical system, where the theoretical predictions are not fulfilled. These mechanical systems, the former at the macro-scale and the latter at the micro-scale, permit a comparative analysis of different mechanical and dynamical behaviours. The fact that in both cases the dynamical integrity permits one to justify the difference between experimental and theoretical results, which is the main achievement of this paper, shows the effectiveness of this new approach and suggests its use in practical situations. The men of experiment are like the ant, they only collect and use; the reasoners resemble spiders, who make cobwebs out of their own substance. But the bee takes the middle course: it gathers its material from the flowers of the garden and field, but transforms and digests it by a power of its own. Not unlike this is the true business of philosophy (science); for it neither relies solely or chiefly on the powers of the mind, nor does it take the matter which it gathers from natural history and mechanical experiments and lay up in the memory whole, as it finds it, but lays it up in the understanding altered and digested. Therefore, from a closer and purer league between these two faculties, the experimental and the rational (such as has never been made), much may be hoped. (Francis Bacon 1561-1626) But are we sure of our observational facts? Scientific men are rather fond of saying pontifically that one ought to be quite sure of one's observational facts before embarking on theory. Fortunately those who give this advice do not practice what they preach. Observation and theory get on best when they are mixed together, both helping one another in the pursuit of truth. It is a good rule not to put overmuch confidence in a theory until it has been confirmed by observation. I hope I shall not shock the experimental physicists too much if I add that it is also a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory. (Arthur Stanley Eddington 1882-1944).

Hybrid soft-lithography/laser machined microchips for the parallel generation of droplets†

PubMed Central

Muluneh, M.

2015-01-01

Microfluidic chips have been developed to generate droplets and microparticles with control over size, shape, and composition not possible using conventional methods. However, it has remained a challenge to scale-up production for practical applications due to the inherently limited throughput of micro-scale devices. To address this problem, we have developed a self-contained microchip that integrates many (N = 512) micro-scale droplet makers. This 3 × 3 cm2 PDMS microchip consists of a two-dimensional array of 32 × 16 flow-focusing droplet makers, a network of flow channels that connect them, and only two inputs and one output. The key innovation of this technology is the hybrid use of both soft-lithography and direct laser-micromachining. The microscale resolution of soft lithography is used to fabricate flow-focusing droplet makers that can produce small and precisely defined droplets. Deeply engraved (h ≈ 500 μm) laser-machined channels are utilized to supply each of the droplet makers with its oil phase, aqueous phase, and access to an output channel. The engraved channels' low hydrodynamic resistance ensures that each droplet maker is driven with the same flow rates for highly uniform droplet formation.To demonstrate the utility of this approach, water droplets (d ≈ 80 μm) were generated in hexadecane on both 8 × 1 and 32 × 16 geometries. PMID:24166156

Superimpose methods for uncooled infrared camera applied to the micro-scale thermal characterization of composite materials

NASA Astrophysics Data System (ADS)

Morikawa, Junko

2015-05-01

The mobile type apparatus for a quantitative micro-scale thermography using a micro-bolometer was developed based on our original techniques such as an achromatic lens design to capture a micro-scale image in long-wave infrared, a video signal superimposing for the real time emissivity correction, and a pseudo acceleration of a timeframe. The total size of the instrument was designed as it was put in the 17 cm x 28 cm x 26 cm size carrying box. The video signal synthesizer enabled to record a direct digital signal of monitoring temperature or positioning data. The encoded digital signal data embedded in each image was decoded to read out. The protocol to encode/decode the measured data was originally defined. The mixed signals of IR camera and the imposed data were applied to the pixel by pixel emissivity corrections and the pseudo-acceleration of the periodical thermal phenomena. Because the emissivity of industrial materials and biological tissues were usually inhomogeneous, it has the different temperature dependence on each pixel. The time-scale resolution for the periodic thermal event was improved with the algorithm for "pseudoacceleration". It contributes to reduce the noise by integrating the multiple image data, keeping a time resolution. The anisotropic thermal properties of some composite materials such as thermal insulating materials of cellular plastics and the biometric composite materials were analyzed using these techniques.

A practical guide to microfluidic perfusion culture of adherent mammalian cells.

PubMed

Kim, Lily; Toh, Yi-Chin; Voldman, Joel; Yu, Hanry

2007-06-01

Culturing cells at microscales allows control over microenvironmental cues, such as cell-cell and cell-matrix interactions; the potential to scale experiments; the use of small culture volumes; and the ability to integrate with microsystem technologies for on-chip experimentation. Microfluidic perfusion culture in particular allows controlled delivery and removal of soluble biochemical molecules in the extracellular microenvironment, and controlled application of mechanical forces exerted via fluid flow. There are many challenges to designing and operating a robust microfluidic perfusion culture system for routine culture of adherent mammalian cells. The current literature on microfluidic perfusion culture treats microfluidic design, device fabrication, cell culture, and micro-assays independently. Here we systematically present and discuss important design considerations in the context of the entire microfluidic perfusion culture system. These design considerations include the choice of materials, culture configurations, microfluidic network fabrication and micro-assays. We also present technical issues such as sterilization; seeding cells in both 2D and 3D configurations; and operating the system under optimized mass transport and shear stress conditions, free of air-bubbles. The integrative and systematic treatment of the microfluidic system design and fabrication, cell culture, and micro-assays provides novices with an effective starting point to build and operate a robust microfludic perfusion culture system for various applications.

Uncertainty prediction for PUB

NASA Astrophysics Data System (ADS)

Mendiondo, E. M.; Tucci, C. M.; Clarke, R. T.; Castro, N. M.; Goldenfum, J. A.; Chevallier, P.

2003-04-01

IAHS’ initiative of Prediction in Ungaged Basins (PUB) attempts to integrate monitoring needs and uncertainty prediction for river basins. This paper outlines alternative ways of uncertainty prediction which could be linked with new blueprints for PUB, thereby showing how equifinality-based models should be grasped using practical strategies of gauging like the Nested Catchment Experiment (NCE). Uncertainty prediction is discussed from observations of Potiribu Project, which is a NCE layout at representative basins of a suptropical biome of 300,000 km2 in South America. Uncertainty prediction is assessed at the microscale (1 m2 plots), at the hillslope (0,125 km2) and at the mesoscale (0,125 - 560 km2). At the microscale, uncertainty-based models are constrained by temporal variations of state variables with changing likelihood surfaces of experiments using Green-Ampt model. Two new blueprints emerged from this NCE for PUB: (1) the Scale Transferability Scheme (STS) at the hillslope scale and the Integrating Process Hypothesis (IPH) at the mesoscale. The STS integrates a multi-dimensional scaling with similarity thresholds, as a generalization of the Representative Elementary Area (REA), using spatial correlation from point (distributed) to area (lumped) process. In this way, STS addresses uncertainty-bounds of model parameters, into an upscaling process at the hillslope. In the other hand, the IPH approach regionalizes synthetic hydrographs, thereby interpreting the uncertainty bounds of streamflow variables. Multiscale evidences from Potiribu NCE layout show novel pathways of uncertainty prediction under a PUB perspective in representative basins of world biomes.

Big whorls carry little whorls

NASA Technical Reports Server (NTRS)

Hunt, J. C. R.; Buell, J. C.; Wray, A. A.

1987-01-01

The aim of the research was to explore the space-time structure of homogeneous turbulence by computing and then interpreting the two-point spectra and correlations of the velocity and pressure fields. Many of these statistics are of considerable practical importance. In particular, it is of interest to compare the different time and length integral scales and microscales for Eulerian and Lagrangian qualities, and to compare the space and time spectra.

Manufacturing at the Nanoscale. Report of the National Nanotechnology Initiative Workshops, 2002-2004

DTIC Science & Technology

2007-01-01

positioning and assembling? • Do nanoscale properties remain once the nanostructures are integrated up to the microscale? • How do we measure...viii Manufacturing at the Nanoscale 1 1. VISION Employing the novel properties and processes that are associated with the nanoscale—in the...Theory, modeling, and simulation software are being developed to investigate nanoscale material properties and synthesis of macromolecular systems with

Low loss fusion splicing of micron scale silica fibers.

PubMed

Pal, Parama; Knox, Wayne H

2008-07-21

Tapered micron-sized optical fibers may be important in the future for development of microscale integrated photonic devices. Complex photonic circuits require many devices and a robust technique for interconnection. We demonstrate splicing of four micron diameter step-index air-clad silica microfibers using a CO2 laser. We obtain splice losses lower than 0.3%. Compared with evanescent coupling of microfibers, our splices are more mechanically stable and efficient.

Chemical Reactions of Portland Cement with Aqueous CO2 and Their Impacts on Cement's Mechanical Properties under Geologic CO2 Sequestration Conditions.

PubMed

Li, Qingyun; Lim, Yun Mook; Flores, Katharine M; Kranjc, Kelly; Jun, Young-Shin

2015-05-19

To provide information on wellbore cement integrity in the application of geologic CO2 sequestration (GCS), chemical and mechanical alterations were analyzed for cement paste samples reacted for 10 days under GCS conditions. The reactions were at 95 °C and had 100 bar of either N2 (control condition) or CO2 contacting the reaction brine solution with an ionic strength of 0.5 M adjusted by NaCl. Chemical analyses showed that the 3.0 cm × 1.1 cm × 0.3 cm samples were significantly attacked by aqueous CO2 and developed layer structures with a total attacked depth of 1220 μm. Microscale mechanical property analyses showed that the hardness and indentation modulus of the carbonated layer were 2-3 times greater than for the intact cement, but those in the portlandite-dissolved region decreased by ∼50%. The strength and elastic modulus of the bulk cement samples were reduced by 93% and 84%, respectively. The properties of the microscale regions, layer structure, microcracks, and swelling of the outer layers combined to affect the overall mechanical properties. These findings improve understanding of wellbore integrity from both chemical and mechanical viewpoints and can be utilized to improve the safety and efficiency of CO2 storage.

Multiscale mechanical integrity of human supraspinatus tendon in shear after elastin depletion.

PubMed

Fang, Fei; Lake, Spencer P

2016-10-01

Human supraspinatus tendon (SST) exhibits region-specific nonlinear mechanical properties under tension, which have been attributed to its complex multiaxial physiological loading environment. However, the mechanical response and underlying multiscale mechanism regulating SST behavior under other loading scenarios are poorly understood. Furthermore, little is known about the contribution of elastin to tendon mechanics. We hypothesized that (1) SST exhibits region-specific shear mechanical properties, (2) fiber sliding is the predominant mode of local matrix deformation in SST in shear, and (3) elastin helps maintain SST mechanical integrity by facilitating force transfer among collagen fibers. Through the use of biomechanical testing and multiphoton microscopy, we measured the multiscale mechanical behavior of human SST in shear before and after elastase treatment. Three distinct SST regions showed similar stresses and microscale deformation. Collagen fiber reorganization and sliding were physical mechanisms observed as the SST response to shear loading. Measures of microscale deformation were highly variable, likely due to a high degree of extracellular matrix heterogeneity. After elastase treatment, tendon exhibited significantly decreased stresses under shear loading, particularly at low strains. These results show that elastin contributes to tendon mechanics in shear, further complementing our understanding of multiscale tendon structure-function relationships. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stress enhanced calcium kinetics in a neuron.

PubMed

Kant, Aayush; Bhandakkar, Tanmay K; Medhekar, Nikhil V

2018-02-01

Accurate modeling of the mechanobiological response of a Traumatic Brain Injury is beneficial toward its effective clinical examination, treatment and prevention. Here, we present a stress history-dependent non-spatial kinetic model to predict the microscale phenomena of secondary insults due to accumulation of excess calcium ions (Ca[Formula: see text]) induced by the macroscale primary injuries. The model is able to capture the experimentally observed increase and subsequent partial recovery of intracellular Ca[Formula: see text] concentration in response to various types of mechanical impulses. We further establish the accuracy of the model by comparing our predictions with key experimental observations.

Detection of Brownian Torque in a Magnetically-Driven Rotating Microsystem

PubMed Central

Romodina, Maria N.; Lyubin, Evgeny V.; Fedyanin, Andrey A.

2016-01-01

Thermal fluctuations significantly affect the behavior of microscale systems rotating in shear flow, such as microvortexes, microbubbles, rotating micromotors, microactuators and other elements of lab-on-a-chip devices. The influence of Brownian torque on the motion of individual magnetic microparticles in a rotating magnetic field is experimentally determined using optical tweezers. Rotational Brownian motion induces the flattening of the breakdown transition between the synchronous and asynchronous modes of microparticle rotation. The experimental findings regarding microparticle rotation in the presence of Brownian torque are compared with the results of numerical Brownian dynamics simulations. PMID:26876334

Microscale photo interpretation of forest and nonforest land classes

NASA Technical Reports Server (NTRS)

Aldrich, R. C.; Greentree, W. J.

1972-01-01

Remote sensing of forest and nonforest land classes are discussed, using microscale photointerpretation. Results include: (1.) Microscale IR color photography can be interpreted within reasonable limits of error to estimate forest area. (2.) Forest interpretation is best on winter photography with 97 percent or better accuracy. (3.) Broad forest types can be classified on microscale photography. (4.) Active agricultural land is classified most accurately on early summer photography. (5.) Six percent of all nonforest observations were misclassified as forest.

Multi-peaks scattering of light in glasses

NASA Astrophysics Data System (ADS)

Smirnov, V. A.; Vostrikova, L. I.

2018-04-01

Investigations of the multi-peaks scattering of the laser light on the micro-scale susceptibility gratings with small periodicities photo-induced in the various glass materials are presented. The observed pictures of the multi-peaks scattering of light in oxide samples show that the efficiencies of the processes of scattering can vary for the different chemical compositions. Experimental results are in agreement with the proposed theory of light scattering.

Summer 2017 Microfluidics Research Report

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

Mcculloch, Quinn

Liquid-liquid Extraction (LLE), also known as solvent extraction, represents a large subset of chemistry where one or more solutes are transferred across an interface between two immiscible liquids. This type of chemistry is used in industrial scale processes to purify solvents, refine ore, process petroleum, treat wastewater, and much more. Although LLE has been successfully employed at the macroscale, where many liters/kgs of species are processed at large flow rates, LLE stands to benefit from lab-on-a-chip technology, where reactions take place quickly and efficiently at the microscale. A device, called a screen contactor, has been invented at Los Alamos Nationalmore » Laboratory (LANL) to perform solvent extraction at the microscale. This invention has been submitted to LANL’s Feynman Center for Innovation, and has been filed for provisional patent under U.S. Patent Application No. 62/483,107 1. The screen contactor consists of a housing that contains two different screen materials, flametreated stainless steel and polyether ether ketone (PEEK) thermoplastic, that are uniquely wetted by either an aqueous or an organic liquid phase, respectively. Liquids in this device flow longitudinally through the screens. The fine pore size of the screens (tens of microns) provide large capillary/adhesional forces while maintaining small hydraulic pressure drops. These physical characteristics are paramount to efficient microscale liquid phase separation. To demonstrate mass transfer using the screen contactor, a well-known chemical system 2 consisting of water and n-decane as solvents and trimethylamine (TEA) as a solute was selected. TEA is basic in water so its concentration can easily be quantified using a digital pH meter and an experimentally determined base dissociation constant. Characterization of this solvent system and its behavior in the screen contactor have been the focus of my research activities this summer. In the following sections, I have detailed experimental results that have been gathered.« less

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

Roehm, Dominic; Pavel, Robert S.; Barros, Kipton

We present an adaptive sampling method supplemented by a distributed database and a prediction method for multiscale simulations using the Heterogeneous Multiscale Method. A finite-volume scheme integrates the macro-scale conservation laws for elastodynamics, which are closed by momentum and energy fluxes evaluated at the micro-scale. In the original approach, molecular dynamics (MD) simulations are launched for every macro-scale volume element. Our adaptive sampling scheme replaces a large fraction of costly micro-scale MD simulations with fast table lookup and prediction. The cloud database Redis provides the plain table lookup, and with locality aware hashing we gather input data for our predictionmore » scheme. For the latter we use kriging, which estimates an unknown value and its uncertainty (error) at a specific location in parameter space by using weighted averages of the neighboring points. We find that our adaptive scheme significantly improves simulation performance by a factor of 2.5 to 25, while retaining high accuracy for various choices of the algorithm parameters.« less

Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage

NASA Astrophysics Data System (ADS)

El-Kady, Maher F.; Kaner, Richard B.

2013-02-01

The rapid development of miniaturized electronic devices has increased the demand for compact on-chip energy storage. Microscale supercapacitors have great potential to complement or replace batteries and electrolytic capacitors in a variety of applications. However, conventional micro-fabrication techniques have proven to be cumbersome in building cost-effective micro-devices, thus limiting their widespread application. Here we demonstrate a scalable fabrication of graphene micro-supercapacitors over large areas by direct laser writing on graphite oxide films using a standard LightScribe DVD burner. More than 100 micro-supercapacitors can be produced on a single disc in 30 min or less. The devices are built on flexible substrates for flexible electronics and on-chip uses that can be integrated with MEMS or CMOS in a single chip. Remarkably, miniaturizing the devices to the microscale results in enhanced charge-storage capacity and rate capability. These micro-supercapacitors demonstrate a power density of ~200 W cm-3, which is among the highest values achieved for any supercapacitor.

Distributed database kriging for adaptive sampling (D²KAS)

DOE PAGES

Roehm, Dominic; Pavel, Robert S.; Barros, Kipton; ...

2015-03-18

We present an adaptive sampling method supplemented by a distributed database and a prediction method for multiscale simulations using the Heterogeneous Multiscale Method. A finite-volume scheme integrates the macro-scale conservation laws for elastodynamics, which are closed by momentum and energy fluxes evaluated at the micro-scale. In the original approach, molecular dynamics (MD) simulations are launched for every macro-scale volume element. Our adaptive sampling scheme replaces a large fraction of costly micro-scale MD simulations with fast table lookup and prediction. The cloud database Redis provides the plain table lookup, and with locality aware hashing we gather input data for our predictionmore » scheme. For the latter we use kriging, which estimates an unknown value and its uncertainty (error) at a specific location in parameter space by using weighted averages of the neighboring points. We find that our adaptive scheme significantly improves simulation performance by a factor of 2.5 to 25, while retaining high accuracy for various choices of the algorithm parameters.« less

Microscale transport and sorting by kinesin molecular motors.

PubMed

Jia, Lili; Moorjani, Samira G; Jackson, Thomas N; Hancock, William O

2004-03-01

As biomolecular detection systems shrink in size, there is an increasing demand for systems that transport and position materials at micron- and nanoscale dimensions. Our goal is to combine cellular transport machinery-kinesin molecular motors and microtubules-with integrated optoelectronics into a hybrid biological/engineered microdevice that will bind, transport, and detect specific proteins, DNA/RNA molecules, viruses, or cells. For microscale transport, 1.5 microm deep channels were created with SU-8 photoresist on glass, kinesin motors adsorbed to the bottom of the channels, and the channel walls used to bend and redirect microtubules moving over the immobilized motors. Novel channel geometries were investigated as a means to redirect and sort microtubules moving in these channels. We show that DC and AC electric fields are sufficient to transport microtubules in solution, establishing an approach for redirecting microtubules moving in channels. Finally, we inverted the geometry to demonstrate that kinesins can transport gold nanowires along surface immobilized microtubules, providing a model for nanoscale directed assembly.

Continuous separation of colloidal particles using dielectrophoresis.

PubMed

Yunus, Nurul Amziah Md; Nili, Hossein; Green, Nicolas G

2013-04-01

Dielectrophoresis is the movement of particles in nonuniform electric fields and has been of interest for application to manipulation and separation at and below the microscale. This technique has the advantages of being noninvasive, nondestructive, and noncontact, with the movement of particle achieved by means of electric fields generated by miniaturized electrodes and microfluidic systems. Although the majority of applications have been above the microscale, there is increasing interest in application to colloidal particles around a micron and smaller. This paper begins with a review of colloidal and nanoscale dielectrophoresis with specific attention paid to separation applications. An innovative design of integrated microelectrode array and its application to flow-through, continuous separation of colloidal particles is then presented. The details of the angled chevron microelectrode array and the test microfluidic system are then discussed. The variation in device operation with applied signal voltage is presented and discussed in terms of separation efficiency, demonstrating 99.9% separation of a mixture of colloidal latex spheres. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New microscale constitutive model of human trabecular bone based on depth sensing indentation technique.

PubMed

Pawlikowski, Marek; Jankowski, Krzysztof; Skalski, Konstanty

2018-05-30

A new constitutive model for human trabecular bone is presented in the present study. As the model is based on indentation tests performed on single trabeculae it is formulated in a microscale. The constitutive law takes into account non-linear viscoelasticity of the tissue. The elastic response is described by the hyperelastic Mooney-Rivlin model while the viscoelastic effects are considered by means of the hereditary integral in which stress depends on both time and strain. The material constants in the constitutive equation are identified on the basis of the stress relaxation tests and the indentation tests using curve-fitting procedure. The constitutive model is implemented into finite element package Abaqus ® by means of UMAT subroutine. The curve-fitting error is low and the viscoelastic behaviour of the tissue predicted by the proposed constitutive model corresponds well to the realistic response of the trabecular bone. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

EXPERIMENTAL INVESTIGATION OF RELATIVE PERMEABILITY UPSCALING FROM THE MICRO-SCALE TO THE MACRO-SCALE

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

Laura J. Pyrak-Nolte; Nicholas J. Giordano; David D. Nolte

2004-03-01

The principal challenge of upscaling techniques for multi-phase fluid dynamics in porous media is to determine which properties on the micro-scale can be used to predict macroscopic flow and spatial distribution of phases at core- and field-scales. The most notable outcome of recent theories is the identification of interfacial areas per volume for multiple phases as a fundamental parameter that determines much of the multi-phase properties of the porous medium. A formal program of experimental research was begun to directly test upscaling theories in fluid flow through porous media by comparing measurements of relative permeability and capillary-saturation with measurements ofmore » interfacial area per volume. This project on the experimental investigation of relative permeability upscaling has produced a unique combination of three quite different technical approaches to the upscaling problem of obtaining pore-related microscopic properties and using them to predict macroscopic behavior. Several important ''firsts'' have been achieved during the course of the project. (1) Optical coherence imaging, a laser-based ranging and imaging technique, has produced the first images of grain and pore structure up to 1 mm beneath the surface of the sandstone and in a laboratory borehole. (2) Woods metal injection has connected for the first time microscopic pore-scale geometric measurements with macroscopic saturation in real sandstone cores. (3) The micro-model technique has produced the first invertible relationship between saturation and capillary pressure--showing that interfacial area per volume (IAV) provides the linking parameter. IAV is a key element in upscaling theories, so this experimental finding may represent the most important result of this project, with wide ramifications for predictions of fluid behavior in porous media.« less

Microstructural Influence on Deformation and Fatigue Life of Composites Using the Generalized Method of Cells

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Murthy, P.; Bednarcyk, B. A.; Pineda, E. J.

2015-01-01

A fully coupled deformation and damage approach to modeling the response of composite materials and composite laminates is presented. It is based on the semi-­-analytical generalized method of cells (GMC) micromechanics model as well as its higher fidelity counterpart, HFGMC, both of which provide closed-form constitutive equations for composite materials as well as the micro scale stress and strain fields in the composite phases. The provided constitutive equations allow GMC and HFGMC to function within a higher scale structural analysis (e.g., finite element analysis or lamination theory) to represent a composite material point, while the availability of the micro fields allow the incorporation of lower scale sub­-models to represent local phenomena in the fiber and matrix. Further, GMC's formulation performs averaging when applying certain governing equations such that some degree of microscale field accuracy is surrendered in favor of extreme computational efficiency, rendering the method quite attractive as the centerpiece in a integrated computational material engineering (ICME) structural analysis; whereas HFGMC retains this microscale field accuracy, but at the price of significantly slower computational speed. Herein, the sensitivity of deformation and the fatigue life of graphite/epoxy PMC composites, with both ordered and disordered microstructures, has been investigated using this coupled deformation and damage micromechanics based approach. The local effects of fiber breakage and fatigue damage are included as sub-models that operate on the microscale for the individual composite phases. For analysis of laminates, classical lamination theory is employed as the global or structural scale model, while GMC/HFGMC is embedded to operate on the microscale to simulate the behavior of the composite material within each laminate layer. A key outcome of this study is the statistical influence of microstructure and micromechanics idealization (GMC or HFGMC) on the overall accuracy of unidirectional and laminated composite deformation and fatigue response.

SENSITIVITY ANALYSIS AND EVALUATION OF MICROFACPM: A MICROSCALE MOTOR VEHICLE EMISSION FACTOR MODEL FOR PARTICULATE MATTER EMISSIONS

EPA Science Inventory

A microscale emission factor model (MicroFacPM) for predicting real-time site-specific motor vehicle particulate matter emissions was presented in the companion paper entitled "Development of a Microscale Emission Factor Model for Particulate Matter (MicroFacPM) for Predicting Re...

A Novel W-Tube for Microscale Experiments in Chemistry

ERIC Educational Resources Information Center

Gupta, H. O.

2007-01-01

A simple W-shaped apparatus was developed by bending glass tubing to contain all of the chemicals involved and to limit the quantities to microscale. The W-tubes were tested by the teachers and students from a few schools to demonstrate its great utility and convenience in microscale chemistry laboratory.

Coupling a Mesoscale Numerical Weather Prediction Model with Large-Eddy Simulation for Realistic Wind Plant Aerodynamics Simulations (Poster)

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

Draxl, C.; Churchfield, M.; Mirocha, J.

Wind plant aerodynamics are influenced by a combination of microscale and mesoscale phenomena. Incorporating mesoscale atmospheric forcing (e.g., diurnal cycles and frontal passages) into wind plant simulations can lead to a more accurate representation of microscale flows, aerodynamics, and wind turbine/plant performance. Our goal is to couple a numerical weather prediction model that can represent mesoscale flow [specifically the Weather Research and Forecasting model] with a microscale LES model (OpenFOAM) that can predict microscale turbulence and wake losses.

Micro- and macroscale coefficients of friction of cementitious materials

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

Lomboy, Gilson; Sundararajan, Sriram, E-mail: srirams@iastate.edu; Wang, Kejin

2013-12-15

Millions of metric tons of cementitious materials are produced, transported and used in construction each year. The ease or difficulty of handling cementitious materials is greatly influenced by the material friction properties. In the present study, the coefficients of friction of cementitious materials were measured at the microscale and macroscale. The materials tested were commercially-available Portland cement, Class C fly ash, and ground granulated blast furnace slag. At the microscale, the coefficient of friction was determined from the interaction forces between cementitious particles using an Atomic Force Microscope. At the macroscale, the coefficient of friction was determined from stresses onmore » bulk cementitious materials under direct shear. The study indicated that the microscale coefficient of friction ranged from 0.020 to 0.059, and the macroscale coefficient of friction ranged from 0.56 to 0.75. The fly ash studied had the highest microscale coefficient of friction and the lowest macroscale coefficient of friction. -- Highlights: •Microscale (interparticle) coefficient of friction (COF) was determined with AFM. •Macroscale (bulk) COF was measured under direct shear. •Fly ash had the highest microscale COF and the lowest macroscale COF. •Portland cement against GGBFS had the lowest microscale COF. •Portland cement against Portland cement had the highest macroscale COF.« less

Using Mesoscale Weather Model Output as Boundary Conditions for Atmospheric Large-Eddy Simulations and Wind-Plant Aerodynamic Simulations (Presentation)

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

Churchfield, M. J.; Michalakes, J.; Vanderwende, B.

Wind plant aerodynamics are directly affected by the microscale weather, which is directly influenced by the mesoscale weather. Microscale weather refers to processes that occur within the atmospheric boundary layer with the largest scales being a few hundred meters to a few kilometers depending on the atmospheric stability of the boundary layer. Mesoscale weather refers to large weather patterns, such as weather fronts, with the largest scales being hundreds of kilometers wide. Sometimes microscale simulations that capture mesoscale-driven variations (changes in wind speed and direction over time or across the spatial extent of a wind plant) are important in windmore » plant analysis. In this paper, we present our preliminary work in coupling a mesoscale weather model with a microscale atmospheric large-eddy simulation model. The coupling is one-way beginning with the weather model and ending with a computational fluid dynamics solver using the weather model in coarse large-eddy simulation mode as an intermediary. We simulate one hour of daytime moderately convective microscale development driven by the mesoscale data, which are applied as initial and boundary conditions to the microscale domain, at a site in Iowa. We analyze the time and distance necessary for the smallest resolvable microscales to develop.« less

Biofuel Cell Based on Microscale Nanostructured Electrodes with Inductive Coupling to Rat Brain Neurons

NASA Astrophysics Data System (ADS)

Andoralov, Viktor; Falk, Magnus; Suyatin, Dmitry B.; Granmo, Marcus; Sotres, Javier; Ludwig, Roland; Popov, Vladimir O.; Schouenborg, Jens; Blum, Zoltan; Shleev, Sergey

2013-11-01

Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm-2 in vitro and 2 μW cm-2 in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons.

Microscale oxygraphy reveals OXPHOS impairment in MRC mutant cells

PubMed Central

Invernizzi, F.; D'Amato, I.; Jensen, P.B.; Ravaglia, S.; Zeviani, M.; Tiranti, V.

2012-01-01

Given the complexity of the respiratory chain structure, assembly and regulation, the diagnostic workout for the identification of defects of oxidative phosphorylation (OXPHOS) is a major challenge. Spectrophotometric assays, that measure the activity of individual respiratory complexes in tissue and cell homogenates or isolated mitochondria, are highly specific, but their utilization is limited by the availability of sufficient biological material and intrinsic sensitivity. A further limitation is tissue specificity, which usually determines attenuation, or disappearance, in cultured fibroblasts, of defects detected in muscle or liver. We used numerous fibroblast cell lines derived from patients with OXPHOS deficiencies to set up experimental protocols required for the direct readout of cellular respiration using the Seahorse XF96 apparatus, which measures oxygen consumption rate (OCR) and extra-cellular acidification rate (ECAR) in 96 well plates. Results demonstrate that first level screening based on microscale oxygraphy is more sensitive, cheaper and rapid than spectrophotometry for the biochemical evaluation of cells from patients with suspected mitochondrial disorders. PMID:22310368

On the Link Between Kolmogorov Microscales and Friction in Wall-Bounded Flow of Viscoplastic Fluids

NASA Astrophysics Data System (ADS)

Ramos, Fabio; Anbarlooei, Hamid; Cruz, Daniel; Silva Freire, Atila; Santos, Cecilia M.

2017-11-01

Most discussions in literature on the friction coefficient of turbulent flows of fluids with complex rheology are empirical. As a rule, theoretical frameworks are not available even for some relatively simple constitutive models. In this work, we present a new family of formulas for the evaluation of the friction coefficient of turbulent flows of a large family of viscoplastic fluids. The developments combine an unified analysis for the description of the Kolmogorov's micro-scales and the phenomenological turbulence model of Gioia and Chakraborty. The resulting Blasius-type friction equation has only Blasius' constant as a parameter, and tests against experimental data show excellent agreement over a significant range of Hedstrom and Reynolds numbers. The limits of the proposed model are also discussed. We also comment on the role of the new formula as a possible benchmark test for the convergence of DNS simulations of viscoplastic flows. The friction formula also provides limits for the Maximum Drag Reduction (MDR) for viscoplastic flows, which resembles MDR asymptote for viscoelastic flows.

Hot emission model for mobile sources: application to the metropolitan region of the city of Santiago, Chile.

PubMed

Corvalán, Roberto M; Osses, Mauricio; Urrutia, Cristian M

2002-02-01

Depending on the final application, several methodologies for traffic emission estimation have been developed. Emission estimation based on total miles traveled or other average factors is a sufficient approach only for extended areas such as national or worldwide areas. For road emission control and strategies design, microscale analysis based on real-world emission estimations is often required. This involves actual driving behavior and emission factors of the local vehicle fleet under study. This paper reports on a microscale model for hot road emissions and its application to the metropolitan region of the city of Santiago, Chile. The methodology considers the street-by-street hot emission estimation with its temporal and spatial distribution. The input data come from experimental emission factors based on local driving patterns and traffic surveys of traffic flows for different vehicle categories. The methodology developed is able to estimate hourly hot road CO, total unburned hydrocarbons (THCs), particulate matter (PM), and NO(x) emissions for predefined day types and vehicle categories.

Hardening mechanisms in olivine single crystal deformed at 1090 °C: an electron tomography study

NASA Astrophysics Data System (ADS)

Mussi, Alexandre; Cordier, Patrick; Demouchy, Sylvie; Hue, Benoit

2017-11-01

The dislocation microstructures in a single crystal of olivine deformed experimentally in uniaxial compression at 1090 °C and under a confining pressure of 300 MPa, have been investigated by transmission electron tomography in order to better understand deformation mechanisms at the microscale relevant for lithospheric mantle deformations. Investigation by electron tomography reveals microstructures, which are more complex than previously described, composed of ? and ? dislocations commonly exhibiting 3D configurations. Numerous mechanisms such as climb, cross-slip, double cross-slip as well as interactions like junction formations and collinear annihilations are the source of this complexity. The diversity observed advocates for microscale deformation of olivine significantly less simple than classic dislocation creep reported in metals or ice close to melting temperature. Deciphering mechanism of hardening in olivine at temperatures where ionic diffusion is slow and is then expected to play very little role is crucial to better understand and thus model deformation at larger scale and at temperatures (900-1100 °C) highly relevant for the lithospheric mantle.

Modeling and Characterization of Damage Processes in Metallic Materials

NASA Technical Reports Server (NTRS)

Glaessgen, E. H.; Saether, E.; Smith, S. W.; Hochhalter, J. D.; Yamakov, V. I.; Gupta, V.

2011-01-01

This paper describes a broad effort that is aimed at understanding the fundamental mechanisms of crack growth and using that understanding as a basis for designing materials and enabling predictions of fracture in materials and structures that have small characteristic dimensions. This area of research, herein referred to as Damage Science, emphasizes the length scale regimes of the nanoscale and the microscale for which analysis and characterization tools are being developed to predict the formation, propagation, and interaction of fundamental damage mechanisms. Examination of nanoscale processes requires atomistic and discrete dislocation plasticity simulations, while microscale processes can be examined using strain gradient plasticity, crystal plasticity and microstructure modeling methods. Concurrent and sequential multiscale modeling methods are being developed to analytically bridge between these length scales. Experimental methods for characterization and quantification of near-crack tip damage are also being developed. This paper focuses on several new methodologies in these areas and their application to understanding damage processes in polycrystalline metals. On-going and potential applications are also discussed.

A two-scale model of radio-frequency electrosurgical tissue ablation

NASA Astrophysics Data System (ADS)

Karaki, Wafaa; Rahul; Lopez, Carlos A.; Borca-Tasciuc, Diana-Andra; De, Suvranu

2017-12-01

Radio-frequency electrosurgical procedures are widely used to simultaneously dissect and coagulate tissue. Experiments suggest that evaporation of cellular and intra-cellular water plays a significant role in the evolution of the temperature field at the tissue level, which is not adequately captured in a single scale energy balance equation. Here, we propose a two-scale model to study the effects of microscale phase change and heat dissipation in response to radiofrequency heating on the tissue level in electrosurgical ablation procedures. At the microscale, the conservation of mass along with thermodynamic and mechanical equilibrium is applied to obtain an equation-of-state relating vapor mass fraction to temperature and pressure. The evaporation losses are incorporated in the macro-level energy conservation and results are validated with mean experimental temperature distributions measured from electrosurgical ablation testing on ex vivo porcine liver at different power settings of the electrosurgical instrument. Model prediction of water loss and its effect on the temperature along with the effect of the mechanical properties on results are evaluated and discussed.

Modeling Microscale Electro-thermally Induced Vortex Flows

NASA Astrophysics Data System (ADS)

Paul, Rajorshi; Tang, Tian; Kumar, Aloke

2017-11-01

In presence of a high frequency alternating electric field and a laser induced heat source, vortex flows are generated inside micro-channels. Such electro-thermally influenced micro-vortices can be used for manipulating nano-particles, programming colloidal assemblies, trapping biological cells as well as for fabricating designed bacterial biofilms. In this study, a theoretical model is developed for microscale electro-thermally induced vortex flows with multiple heat sources. Semi-analytical solutions are obtained, using Hankel transformation and linear superposition, for the temperature, pressure and velocity fields. The effect of material properties such as electrical and thermal conductivities, as well as experimental parameters such as the frequency and strength of the alternating electric field, and the intensity and heating profile of the laser source, are systematically investigated. Resolution for a pair of laser sources is determined by analyzing the strength of the micro-vortices under the influence of two heating sources. Results from this work will provide useful insights into the design of efficient optical tweezers and Rapid Electrokinetic Patterning techniques.

Biofuel cell based on microscale nanostructured electrodes with inductive coupling to rat brain neurons.

PubMed

Andoralov, Viktor; Falk, Magnus; Suyatin, Dmitry B; Granmo, Marcus; Sotres, Javier; Ludwig, Roland; Popov, Vladimir O; Schouenborg, Jens; Blum, Zoltan; Shleev, Sergey

2013-11-20

Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm(-2) in vitro and 2 μW cm(-2) in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons.

Microscale cavitation as a mechanism for nucleating earthquakes at the base of the seismogenic zone.

PubMed

Verberne, Berend A; Chen, Jianye; Niemeijer, André R; de Bresser, Johannes H P; Pennock, Gillian M; Drury, Martyn R; Spiers, Christopher J

2017-11-21

Major earthquakes frequently nucleate near the base of the seismogenic zone, close to the brittle-ductile transition. Fault zone rupture at greater depths is inhibited by ductile flow of rock. However, the microphysical mechanisms responsible for the transition from ductile flow to seismogenic brittle/frictional behaviour at shallower depths remain unclear. Here we show that the flow-to-friction transition in experimentally simulated calcite faults is characterized by a transition from dislocation and diffusion creep to dilatant deformation, involving incompletely accommodated grain boundary sliding. With increasing shear rate or decreasing temperature, dislocation and diffusion creep become too slow to accommodate the imposed shear strain rate, leading to intergranular cavitation, weakening, strain localization, and a switch from stable flow to runaway fault rupture. The observed shear instability, triggered by the onset of microscale cavitation, provides a key mechanism for bringing about the brittle-ductile transition and for nucleating earthquakes at the base of the seismogenic zone.

DURIP: A Confocal Imaging System for Ultra-Fast Three-Dimensional Transport Studies in Thermal Management Applications

DTIC Science & Technology

2011-12-01

Transport Phenomena and Thermal Management Applications,” Proceedings of the XXVIII UIT Heat Transfer Conference, Brescia, Italy, June 21-23, 2010...measurements in microscale systems. The integrated confocal microscope system is a critical component to obtain understanding of fluid- heat ...objective of this work was to develop a high speed three-dimensional (3D) confocal imaging system to study coupled fluidic and heat transport

Excitation of Terahertz Charge Transfer Plasmons in Metallic Fractal Structures

NASA Astrophysics Data System (ADS)

Ahmadivand, Arash; Gerislioglu, Burak; Sinha, Raju; Vabbina, Phani Kiran; Karabiyik, Mustafa; Pala, Nezih

2017-08-01

There have been extensive researches on terahertz (THz) plasmonic structures supporting resonant modes to demonstrate nano and microscale devices with high efficiency and responsivity as well as frequency selectivity. Here, using antisymmetric plasmonic fractal Y-shaped (FYS) structures as building blocks, we introduce a highly tunable four-member fractal assembly to support charge transfer plasmons (CTPs) and classical dipolar resonant modes with significant absorption cross section in the THz domain. We first present that the unique geometrical nature of the FYS system and corresponding spectral response allow for supporting intensified dipolar plasmonic modes under polarised light exposure in a standalone structure. In addition to classical dipolar mode, for the very first time, we demonstrated CTPs in the THz domain due to the direct shuttling of the charges across the metallic fractal microantenna which led to sharp resonant absorption peaks. Using both numerical and experimental studies, we have investigated and confirmed the excitation of the CTP modes and highly tunable spectral response of the proposed plasmonic fractal structure. This understanding opens new and promising horizons for tightly integrated THz devices with high efficiency and functionality.

Modelling approaches for evaluating multiscale tendon mechanics

PubMed Central

Fang, Fei; Lake, Spencer P.

2016-01-01

Tendon exhibits anisotropic, inhomogeneous and viscoelastic mechanical properties that are determined by its complicated hierarchical structure and varying amounts/organization of different tissue constituents. Although extensive research has been conducted to use modelling approaches to interpret tendon structure–function relationships in combination with experimental data, many issues remain unclear (i.e. the role of minor components such as decorin, aggrecan and elastin), and the integration of mechanical analysis across different length scales has not been well applied to explore stress or strain transfer from macro- to microscale. This review outlines mathematical and computational models that have been used to understand tendon mechanics at different scales of the hierarchical organization. Model representations at the molecular, fibril and tissue levels are discussed, including formulations that follow phenomenological and microstructural approaches (which include evaluations of crimp, helical structure and the interaction between collagen fibrils and proteoglycans). Multiscale modelling approaches incorporating tendon features are suggested to be an advantageous methodology to understand further the physiological mechanical response of tendon and corresponding adaptation of properties owing to unique in vivo loading environments. PMID:26855747

Microscale High-Throughput Experimentation as an Enabling Technology in Drug Discovery: Application in the Discovery of (Piperidinyl)pyridinyl-1H-benzimidazole Diacylglycerol Acyltransferase 1 Inhibitors.

PubMed

Cernak, Tim; Gesmundo, Nathan J; Dykstra, Kevin; Yu, Yang; Wu, Zhicai; Shi, Zhi-Cai; Vachal, Petr; Sperbeck, Donald; He, Shuwen; Murphy, Beth Ann; Sonatore, Lisa; Williams, Steven; Madeira, Maria; Verras, Andreas; Reiter, Maud; Lee, Claire Heechoon; Cuff, James; Sherer, Edward C; Kuethe, Jeffrey; Goble, Stephen; Perrotto, Nicholas; Pinto, Shirly; Shen, Dong-Ming; Nargund, Ravi; Balkovec, James; DeVita, Robert J; Dreher, Spencer D

2017-05-11

Miniaturization and parallel processing play an important role in the evolution of many technologies. We demonstrate the application of miniaturized high-throughput experimentation methods to resolve synthetic chemistry challenges on the frontlines of a lead optimization effort to develop diacylglycerol acyltransferase (DGAT1) inhibitors. Reactions were performed on ∼1 mg scale using glass microvials providing a miniaturized high-throughput experimentation capability that was used to study a challenging S N Ar reaction. The availability of robust synthetic chemistry conditions discovered in these miniaturized investigations enabled the development of structure-activity relationships that ultimately led to the discovery of soluble, selective, and potent inhibitors of DGAT1.

Characterization of low-mass deformable mirrors and ASIC drivers for high-contrast imaging

NASA Astrophysics Data System (ADS)

Mejia Prada, Camilo; Yao, Li; Wu, Yuqian; Roberts, Lewis C.; Shelton, Chris; Wu, Xingtao

2017-09-01

The development of compact, high performance Deformable Mirrors (DMs) is one of the most important technological challenges for high-contrast imaging on space missions. Microscale Inc. has fabricated and characterized piezoelectric stack actuator deformable mirrors (PZT-DMs) and Application-Specific Integrated Circuit (ASIC) drivers for direct integration. The DM-ASIC system is designed to eliminate almost all cables, enabling a very compact optical system with low mass and low power consumption. We report on the optical tests used to evaluate the performance of the DM and ASIC units. We also compare the results to the requirements for space-based high-contrast imaging of exoplanets.

Liquid Tunable Microlenses based on MEMS techniques

PubMed Central

Zeng, Xuefeng; Jiang, Hongrui

2013-01-01

The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven, and those integrated within microfluidic systems. PMID:24163480

A New Scheme for the Simulation of Microscale Flow and Dispersion in Urban Areas by Coupling Large-Eddy Simulation with Mesoscale Models

NASA Astrophysics Data System (ADS)

Li, Haifeng; Cui, Guixiang; Zhang, Zhaoshun

2018-04-01

A coupling scheme is proposed for the simulation of microscale flow and dispersion in which both the mesoscale field and small-scale turbulence are specified at the boundary of a microscale model. The small-scale turbulence is obtained individually in the inner and outer layers by the transformation of pre-computed databases, and then combined in a weighted sum. Validation of the results of a flow over a cluster of model buildings shows that the inner- and outer-layer transition height should be located in the roughness sublayer. Both the new scheme and the previous scheme are applied in the simulation of the flow over the central business district of Oklahoma City (a point source during intensive observation period 3 of the Joint Urban 2003 experimental campaign), with results showing that the wind speed is well predicted in the canopy layer. Compared with the previous scheme, the new scheme improves the prediction of the wind direction and turbulent kinetic energy (TKE) in the canopy layer. The flow field influences the scalar plume in two ways, i.e. the averaged flow field determines the advective flux and the TKE field determines the turbulent flux. Thus, the mean, root-mean-square and maximum of the concentration agree better with the observations with the new scheme. These results indicate that the new scheme is an effective means of simulating the complex flow and dispersion in urban canopies.

Small swimmers and sinkers structure the microenvironment by deforming ambient chemical gradients

NASA Astrophysics Data System (ADS)

Inman, B.; Franks, P. J. S.; Torres, C.

2016-02-01

Chemical gradients in the microscale environment determine the rates of fundamental planktonic processes such as signaling and sensing, grazing, predation, mating, infection, nutrient uptake, and primary production. We show that bodies swimming or sinking at low Reynolds number can deform and intensify ambient scalar gradients on the order of 10-1000 times. Over time, this restructuring of the microenvironment in the wake of a moving particle results in elevated diffusive fluxes of ecologically relevant tracers. We use diffusive Stokes flow to model the time evolution of planes of tracer particles that represent a gradient being deformed by a sinking sphere. Ultimately, the degree of gradient intensification and the corresponding diffusive flux enhancement depend on how far a moving body deforms a plane of tracer before it punches through. We derive a scaling for this distance, Ldef, as a function of the Péclet number and describe its importance in the microscale planktonic environment. We then test the modeled gradient deformation, diffusive flux enhancement, and Ldef using an experimental tank apparatus in which the marine copepod, Calanus pacificus, is induced to swim through a layer of tracer dye. We show that the gradient deformation due to the copepod swimming can enhance the apparent tracer diffusivity by 500% over 10 minutes, drawing the tracer out into centimeters-long tendrils. These swimming-induced gradient deformations may be an important source of structure in the microscale environment of the plankton.

Studies of interactions of a propagating shock wave with decaying grid turbulence: velocity and vorticity fields

NASA Astrophysics Data System (ADS)

Agui, Juan H.; Briassulis, George; Andreopoulos, Yiannis

2005-02-01

The unsteady interaction of a moving shock wave with nearly homogeneous and isotropic decaying compressible turbulence has been studied experimentally in a large-scale shock tube facility. Rectangular grids of various mesh sizes were used to generate turbulence with Reynolds numbers based on Taylor's microscale ranging from 260 to 1300. The interaction has been investigated by measuring the three-dimensional velocity and vorticity vectors, the full velocity gradient and rate-of-strain tensors with instrumentation of high temporal and spatial resolution. This allowed estimates of dilatation, compressible dissipation and dilatational stretching to be obtained. The time-dependent signals of enstrophy, vortex stretching/tilting vector and dilatational stretching vector were found to exhibit a rather strong intermittent behaviour which is characterized by high-amplitude bursts with values up to 8 times their r.m.s. within periods of less violent and longer lived events. Several of these bursts are evident in all the signals, suggesting the existence of a dynamical flow phenomenon as a common cause. Fluctuations of all velocity gradients in the longitudinal direction are amplified significantly downstream of the interaction. Fluctuations of the velocity gradients in the lateral directions show no change or a minor reduction through the interaction. Root mean square values of the lateral vorticity components indicate a 25% amplification on average, which appears to be very weakly dependent on the shock strength. The transmission of the longitudinal vorticity fluctuations through the shock appears to be less affected by the interaction than the fluctuations of the lateral components. Non-dissipative vortex tubes and irrotational dissipative motions are more intense in the region downstream of the shock. There is also a significant increase in the number of events with intense rotational and dissipative motions. Integral length scales and Taylor's microscales were reduced after the interaction with the shock in all investigated flow cases. The integral length scales in the lateral direction increase at low Mach numbers and decrease during strong interactions. It appears that in the weakest of the present interactions, turbulent eddies are compressed drastically in the longitudinal direction while their extent in the normal direction remains relatively the same. As the shock strength increases the lateral integral length scales increase while the longitudinal ones decrease. At the strongest interaction of the present flow cases turbulent eddies are compressed in both directions. However, even at the highest Mach number the issue is more complicated since amplification of the lateral scales has been observed in flows with fine grids. Thus the outcome of the interaction strongly depends on the initial conditions.

The US DOE A2e Mesoscale to Microscale Coupling Project: Nonstationary Modeling Techniques and Assessment

NASA Astrophysics Data System (ADS)

Haupt, Sue Ellen; Kosovic, Branko; Shaw, William

2017-04-01

The purpose of the US DOE's Mesoscale-Microscale Coupling (MMC) Project is to develop, verify, and validate physical models and modeling techniques that bridge the most important atmospheric scales that determine wind plant performance and reliability. As part of DOE's Atmosphere to Electrons (A2e) program, the MMC project seeks to create a new predictive numerical simulation capability that is able to represent the full range of atmospheric flow conditions impacting wind plant performance. The recent focus of MMC has been on nonstationary conditions over flat terrain. These nonstationary cases are critical for wind energy and represent a primary need for mesoscale meteorological forcing of the microscale models. The MMC team modeled two types of non-stationary cases: 1) diurnal cycles in which the daytime convective boundary layer collapses with the setting of the sun when the surface heat flux changes from positive to negative, passing through a brief period of neutral stability before becoming stable, with smaller scale turbulence and the potential for low level jet (LLJ) formation; and 2) frontal passage as an example of a synoptic weather event that may cause relatively rapid changes in wind speed and direction. The team compared and contrasted two primary techniques for non-stationary forcing of the microscale by the mesoscale model. The first is to use the tendencies from the mesoscale model to directly force the microscale mode. The second method is to couple not only the microscale domain's internal forcing parameters, but also its lateral boundaries, to a mesoscale simulation. While the boundary coupled approach provides the greatest generality, since the mesoscale flow information providing the lateral boundary information for the microscale domain contains no explicit turbulence information, the approach requires methods to accelerate turbulence production at the microscale domain's inflow boundaries. Forefront assessment strategies, including comparing spectra and cospectra, were used to assess the techniques. Testing methods to initialize turbulence at the microscale was also accomplished.

Experimental Investigation of Relative Permeability Upscaling from the Micro-Scale to the Macro-Scale

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

Pyrak-Nolte, Laura J.; Cheng, JiangTao; Yu, Ping

2003-01-29

During this reporting period, shown experimentally that the optical coherence imaging system can acquire information on grain interfaces and void shape for a maximum depth of half a millimeter into sandstone. The measurement of interfacial area per volume (IAV), capillary pressure and saturation in two dimensional micro-models structures has shown the existence of a unique relationship among these hydraulic parameters for different pore geometry. The measurement of interfacial area per volume on a three-dimensional natural sample, i.e., sandstone, has shown the homogeneity of IAV with depth in a sample when the fluids are in equilibrium.

Effective, Safe, and Inexpensive Microscale Ultrasonic Setup for Teaching and Research Laboratories.

ERIC Educational Resources Information Center

Montana, Angel M.; Grima, Pedro M.

2000-01-01

Presents a homemade, safe, effective, and inexpensive reactor vessel for ultrasonic horns with applications in microscale experiments in teaching and research laboratories. The reactor vessel is designed for an ultrasonic probe that allows reactions to be run at the microscale level at a wide range of temperatures and under inert atmosphere.…

Microscale Heat Transfer Enhancement using Spinodal Decomposition of Binary Liquid Mixtures: A Collaborative Modeling/Experimental Approach

DTIC Science & Technology

2013-09-01

heat transfer coefficients due to the high heat of vapor- ization. Many authors ([ Mudawar (2001)], [ Mudawar and Bowers (1999)] and [Kandlikar (2005...Letters, 95, (2005), 1. [Rosales and Meneveau (2006)] C. Rosales and C. Meneveau. Physics of Fluids, 18, (2006), 075104. [ Mudawar and Bowers (1999)] I... Mudawar and M.B. Bowers, Ultra-high crit- ical heat flux (CHF) for subcooled water flow boiling-I: CHF data and parametric effects for small

Palladium-Catalyzed Nitromethylation of Aryl Halides: An Orthogonal Formylation Equivalent

PubMed Central

Walvoord, Ryan R.; Berritt, Simon; Kozlowski, Marisa C.

2012-01-01

An efficient cross-coupling reaction of aryl halides and nitromethane was developed with the use of parallel microscale experimentation. The arylnitromethane products are precursors for numerous useful synthetic products. An efficient method for their direct conversion to the corresponding oximes and aldehydes in a one-pot operation has been discovered. The process exploits inexpensive nitromethane as a carbonyl equivalent, providing a mild and convenient formylation method that is compatible with many functional groups. PMID:22839593

LES of flow in the street canyon

NASA Astrophysics Data System (ADS)

Fuka, Vladimír; Brechler, Josef

2012-04-01

Results of computer simulation of flow over a series of street canyons are presented in this paper. The setup is adapted from an experimental study by [4] with two different shapes of buildings. The problem is simulated by an LES model CLMM (Charles University Large Eddy Microscale Model) and results are analysed using proper orthogonal decomposition and spectral analysis. The results in the channel (layout from the experiment) are compared with results with a free top boundary.

Technical Description of Urban Microscale Modeling System: Component 1 of CRTI Project 02-0093RD

DTIC Science & Technology

2007-03-01

0093RD which involved (1) development and implementation of a com- putational fluid dynamics model for the simulation of urban flow in an arbitrary...resource will serve as a nation-wide general problem- solving tool for first-responders involved with CBR incidents in the urban environment and...predictions with experimental data obtained from a comprehensive full-scale urban field experiment conducted in Oklahoma City, Oklahoma in July 2003 (Joint

Magnetic Microhelix Coil Structures

NASA Astrophysics Data System (ADS)

Smith, Elliot J.; Makarov, Denys; Sanchez, Samuel; Fomin, Vladimir M.; Schmidt, Oliver G.

2011-08-01

Together with the well-known ferro- and antiferromagnetic ordering, nature has created a variety of complex helical magnetic configurations. Here, we design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials.

Drosophila learn efficient paths to a food source.

PubMed

Navawongse, Rapeechai; Choudhury, Deepak; Raczkowska, Marlena; Stewart, James Charles; Lim, Terrence; Rahman, Mashiur; Toh, Alicia Guek Geok; Wang, Zhiping; Claridge-Chang, Adam

2016-05-01

Elucidating the genetic, and neuronal bases for learned behavior is a central problem in neuroscience. A leading system for neurogenetic discovery is the vinegar fly Drosophila melanogaster; fly memory research has identified genes and circuits that mediate aversive and appetitive learning. However, methods to study adaptive food-seeking behavior in this animal have lagged decades behind rodent feeding analysis, largely due to the challenges presented by their small scale. There is currently no method to dynamically control flies' access to food. In rodents, protocols that use dynamic food delivery are a central element of experimental paradigms that date back to the influential work of Skinner. This method is still commonly used in the analysis of learning, memory, addiction, feeding, and many other subjects in experimental psychology. The difficulty of microscale food delivery means this is not a technique used in fly behavior. In the present manuscript we describe a microfluidic chip integrated with machine vision and automation to dynamically control defined liquid food presentations and sensory stimuli. Strikingly, repeated presentations of food at a fixed location produced improvements in path efficiency during food approach. This shows that improved path choice is a learned behavior. Active control of food availability using this microfluidic system is a valuable addition to the methods currently available for the analysis of learned feeding behavior in flies. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Computational and experimental studies of microvascular void features for passive-adaptation of structural panel dynamic properties

NASA Astrophysics Data System (ADS)

Sears, Nicholas C.; Harne, Ryan L.

2018-01-01

The performance, integrity, and safety of built-up structural systems are critical to their effective employment in diverse engineering applications. In conflict with these goals, harmonic or random excitations of structural panels may promote large amplitude oscillations that are particularly harmful when excitation energies are concentrated around natural frequencies. This contributes to fatigue concerns, performance degradation, and failure. While studies have considered active or passive damping treatments that adapt material characteristics and configurations for structural control, it remains to be understood how vibration properties of structural panels may be tailored via internal material transitions. Motivated to fill this knowledge gap, this research explores an idea of adapting the static and dynamic material distribution of panels through embedded microvascular channels and strategically placed voids that permit the internal movement of fluids within the panels for structural dynamic control. Finite element model and experimental investigations probe how redistributing material in the form of microscale voids influences the global vibration modes and natural frequencies of structural panels. Through parameter studies, the relationships among void shape, number, size, and location are quantified towards their contribution to the changing structural dynamics. For the panel composition and boundary conditions considered in this report, the findings reveal that transferring material between strategically placed voids may result in eigenfrequency changes as great as 10.0, 5.0, and 7.4% for the first, second, and third modes, respectively.

Microscale Concentration Measurements Using Laser Light Scattering Methods

NASA Technical Reports Server (NTRS)

Niederhaus, Charles; Miller, Fletcher

2004-01-01

The development of lab-on-a-chip devices for microscale biochemical assays has led to the need for microscale concentration measurements of specific analyses. While fluorescence methods are the current choice, this method requires developing fluorophore-tagged conjugates for each analyte of interest. In addition, fluorescent imaging is also a volume-based method, and can be limiting as smaller detection regions are required.

Three-Dimensional Mapping of Soil Chemical Characteristics at Micrometric Scale by Combining 2D SEM-EDX Data and 3D X-Ray CT Images.

PubMed

Hapca, Simona; Baveye, Philippe C; Wilson, Clare; Lark, Richard Murray; Otten, Wilfred

2015-01-01

There is currently a significant need to improve our understanding of the factors that control a number of critical soil processes by integrating physical, chemical and biological measurements on soils at microscopic scales to help produce 3D maps of the related properties. Because of technological limitations, most chemical and biological measurements can be carried out only on exposed soil surfaces or 2-dimensional cuts through soil samples. Methods need to be developed to produce 3D maps of soil properties based on spatial sequences of 2D maps. In this general context, the objective of the research described here was to develop a method to generate 3D maps of soil chemical properties at the microscale by combining 2D SEM-EDX data with 3D X-ray computed tomography images. A statistical approach using the regression tree method and ordinary kriging applied to the residuals was developed and applied to predict the 3D spatial distribution of carbon, silicon, iron, and oxygen at the microscale. The spatial correlation between the X-ray grayscale intensities and the chemical maps made it possible to use a regression-tree model as an initial step to predict the 3D chemical composition. For chemical elements, e.g., iron, that are sparsely distributed in a soil sample, the regression-tree model provides a good prediction, explaining as much as 90% of the variability in some of the data. However, for chemical elements that are more homogenously distributed, such as carbon, silicon, or oxygen, the additional kriging of the regression tree residuals improved significantly the prediction with an increase in the R2 value from 0.221 to 0.324 for carbon, 0.312 to 0.423 for silicon, and 0.218 to 0.374 for oxygen, respectively. The present research develops for the first time an integrated experimental and theoretical framework, which combines geostatistical methods with imaging techniques to unveil the 3-D chemical structure of soil at very fine scales. The methodology presented in this study can be easily adapted and applied to other types of data such as bacterial or fungal population densities for the 3D characterization of microbial distribution.

Three-Dimensional Mapping of Soil Chemical Characteristics at Micrometric Scale by Combining 2D SEM-EDX Data and 3D X-Ray CT Images

PubMed Central

Hapca, Simona; Baveye, Philippe C.; Wilson, Clare; Lark, Richard Murray; Otten, Wilfred

2015-01-01

There is currently a significant need to improve our understanding of the factors that control a number of critical soil processes by integrating physical, chemical and biological measurements on soils at microscopic scales to help produce 3D maps of the related properties. Because of technological limitations, most chemical and biological measurements can be carried out only on exposed soil surfaces or 2-dimensional cuts through soil samples. Methods need to be developed to produce 3D maps of soil properties based on spatial sequences of 2D maps. In this general context, the objective of the research described here was to develop a method to generate 3D maps of soil chemical properties at the microscale by combining 2D SEM-EDX data with 3D X-ray computed tomography images. A statistical approach using the regression tree method and ordinary kriging applied to the residuals was developed and applied to predict the 3D spatial distribution of carbon, silicon, iron, and oxygen at the microscale. The spatial correlation between the X-ray grayscale intensities and the chemical maps made it possible to use a regression-tree model as an initial step to predict the 3D chemical composition. For chemical elements, e.g., iron, that are sparsely distributed in a soil sample, the regression-tree model provides a good prediction, explaining as much as 90% of the variability in some of the data. However, for chemical elements that are more homogenously distributed, such as carbon, silicon, or oxygen, the additional kriging of the regression tree residuals improved significantly the prediction with an increase in the R2 value from 0.221 to 0.324 for carbon, 0.312 to 0.423 for silicon, and 0.218 to 0.374 for oxygen, respectively. The present research develops for the first time an integrated experimental and theoretical framework, which combines geostatistical methods with imaging techniques to unveil the 3-D chemical structure of soil at very fine scales. The methodology presented in this study can be easily adapted and applied to other types of data such as bacterial or fungal population densities for the 3D characterization of microbial distribution. PMID:26372473

The effect of deformation on two-phase flow through proppant-packed fractured shale samples: A micro-scale experimental investigation

NASA Astrophysics Data System (ADS)

Arshadi, Maziar; Zolfaghari, Arsalan; Piri, Mohammad; Al-Muntasheri, Ghaithan A.; Sayed, Mohammed

2017-07-01

We present the results of an extensive micro-scale experimental investigation of two-phase flow through miniature, fractured reservoir shale samples that contained different packings of proppant grains. We investigated permeability reduction in the samples by conducting experiments under a wide range of net confining pressures. Three different proppant grain distributions in three individual fractured shale samples were studied: i) multi-layer, ii) uniform mono-layer, and iii) non-uniform mono-layer. We performed oil-displacing-brine (drainage) and brine-displacing-oil (imbibition) flow experiments in the proppant packs under net confining pressures ranging from 200 to 6000 psi. The flow experiments were performed using a state-of-the-art miniature core-flooding apparatus integrated with a high-resolution, X-ray microtomography system. We visualized fluid occupancies, proppant embedment, and shale deformation under different flow and stress conditions. We examined deformation of pore space within the proppant packs and its impact on permeability and residual trapping, proppant embedment due to changes in net confining stress, shale surface deformation, and disintegration of proppant grains at high stress conditions. In particular, geometrical deformation and two-phase flow effects within the proppant pack impacting hydraulic conductivity of the medium were probed. A significant reduction in effective oil permeability at irreducible water saturation was observed due to increase in confining pressure. We propose different mechanisms responsible for the observed permeability reduction in different fracture packings. Samples with dissimilar proppant grain distributions showed significantly different proppant embedment behavior. Thinner proppant layer increased embedment significantly and lowered the onset confining pressure of embedment. As confining stress was increased, small embedments caused the surface of the shale to fracture. The produced shale fragments were then entrained by the flow and partially blocked pore-throat connections within the proppant pack. Deformation of proppant packs resulted in significant changes in waterflood residual oil saturation. In-situ contact angles measured using micro-CT images showed that proppant grains had experienced a drastic alteration of wettability (from strong water-wet to weakly oil-wet) after the medium had been subjected to flow of oil and brine for multiple weeks. Nanometer resolution SEM images captured nano-fractures induced in the shale surfaces during the experiments with mono-layer proppant packing. These fractures improved the effective permeability of the medium and shale/fracture interactions.

A Finite Element Model to Predict the Effect of Porosity on Elastic Modulus in Low-Porosity Materials

NASA Astrophysics Data System (ADS)

Morrissey, Liam S.; Nakhla, Sam

2018-07-01

The effect of porosity on elastic modulus in low-porosity materials is investigated. First, several models used to predict the reduction in elastic modulus due to porosity are compared with a compilation of experimental data to determine their ranges of validity and accuracy. The overlapping solid spheres model is found to be most accurate with the experimental data and valid between 3 and 10 pct porosity. Next, a FEM is developed with the objective of demonstrating that a macroscale plate with a center hole can be used to model the effect of microscale porosity on elastic modulus. The FEM agrees best with the overlapping solid spheres model and shows higher accuracy with experimental data than the overlapping solid spheres model.

Collection, Measurement and Treatment of Microorganism Using Dielectrophoretic Micro Devices

NASA Astrophysics Data System (ADS)

Uchida, Satoshi

Constant monitoring of manufacturing processes has been essential in food industry because of global expansion of microbial infection. Micro-scale dielectrophoretic method is an attractive technique for direct operation and quantitative detection of bioparticles. The electrical system is capable of rapid and simple treatments corresponding to severe legal control for food safety. In this paper, newly developed techniques are reviewed for bacterial concentration, detection and sterilization using dielectrophoresis in a micro reactor. The perspective to an integrated micro device of those components is also discussed.

A micro-scale plasma spectrometer for space and plasma edge applications (invited)

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

Scime, E. E., E-mail: escime@wvu.edu; Keesee, A. M.; Elliott, D.

2016-11-15

A plasma spectrometer design based on advances in lithography and microchip stacking technologies is described. A series of curved plate energy analyzers, with an integrated collimator, is etched into a silicon wafer. Tests of spectrometer elements, the energy analyzer and collimator, were performed with a 5 keV electron beam. The measured collimator transmission and energy selectivity were in good agreement with design targets. A single wafer element could be used as a plasma processing or fusion first wall diagnostic.

Compliant heterogeneous assemblies of micro-VCSELs as a new materials platform for integrated optoelectronics

NASA Astrophysics Data System (ADS)

Kang, Dongseok; Lee, Sung-Min; Kwong, Anthony; Yoon, Jongseung

2015-03-01

Despite many unique advantages, vertical cavity surface emitting lasers (VCSELs) have been available mostly on rigid, planar wafers over restricted areas, thereby limiting their usage for applications that can benefit from large-scale, programmable assemblies, hybrid integration with dissimilar materials and devices, or mechanically flexible constructions. Here, materials design and fabrication strategies that address these limitations of conventional VCSELs are presented. Specialized design of epitaxial materials and etching processes, together with printing-based deterministic assemblies and substrate thermal engineering, enabled defect-free release of microscale VCSELs and their device- and circuit-level implementation on non-native, flexible substrates with performance comparable to devices on the growth substrate.

Micromechanics-Based Structural Analysis (FEAMAC) and Multiscale Visualization within Abaqus/CAE Environment

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Bednarcyk, Brett A.; Hussain, Aquila; Katiyar, Vivek

2010-01-01

A unified framework is presented that enables coupled multiscale analysis of composite structures and associated graphical pre- and postprocessing within the Abaqus/CAE environment. The recently developed, free, Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software couples NASA's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with Abaqus/Standard and Abaqus/Explicit to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. The Graphical User Interfaces (FEAMAC-Pre and FEAMAC-Post), developed through collaboration between SIMULIA Erie and the NASA Glenn Research Center, enable users to employ a new FEAMAC module within Abaqus/CAE that provides access to the composite microscale. FEA IAC-Pre is used to define and store constituent material properties, set-up and store composite repeating unit cells, and assign composite materials as sections with all data being stored within the CAE database. Likewise FEAMAC-Post enables multiscale field quantity visualization (contour plots, X-Y plots), with point and click access to the microscale i.e., fiber and matrix fields).

Emerging Technologies for Assembly of Microscale Hydrogels

PubMed Central

Kavaz, Doga; Demirel, Melik C.; Demirci, Utkan

2013-01-01

Assembly of cell encapsulating building blocks (i.e., microscale hydrogels) has significant applications in areas including regenerative medicine, tissue engineering, and cell-based in vitro assays for pharmaceutical research and drug discovery. Inspired by the repeating functional units observed in native tissues and biological systems (e.g., the lobule in liver, the nephron in kidney), assembly technologies aim to generate complex tissue structures by organizing microscale building blocks. Novel assembly technologies enable fabrication of engineered tissue constructs with controlled properties including tunable microarchitectural and predefined compositional features. Recent advances in micro- and nano-scale technologies have enabled engineering of microgel based three dimensional (3D) constructs. There is a need for high-throughput and scalable methods to assemble microscale units with a complex 3D micro-architecture. Emerging assembly methods include novel technologies based on microfluidics, acoustic and magnetic fields, nanotextured surfaces, and surface tension. In this review, we survey emerging microscale hydrogel assembly methods offering rapid, scalable microgel assembly in 3D, and provide future perspectives and discuss potential applications. PMID:23184717

A Three-Dimensional Multiscale Model for Gas Exchange in Fruit1[C][W][OA

PubMed Central

Ho, Quang Tri; Verboven, Pieter; Verlinden, Bert E.; Herremans, Els; Wevers, Martine; Carmeliet, Jan; Nicolaï, Bart M.

2011-01-01

Respiration of bulky plant organs such as roots, tubers, stems, seeds, and fruit depends very much on oxygen (O2) availability and often follows a Michaelis-Menten-like response. A multiscale model is presented to calculate gas exchange in plants using the microscale geometry of the tissue, or vice versa, local concentrations in the cells from macroscopic gas concentration profiles. This approach provides a computationally feasible and accurate analysis of cell metabolism in any plant organ during hypoxia and anoxia. The predicted O2 and carbon dioxide (CO2) partial pressure profiles compared very well with experimental data, thereby validating the multiscale model. The important microscale geometrical features are the shape, size, and three-dimensional connectivity of cells and air spaces. It was demonstrated that the gas-exchange properties of the cell wall and cell membrane have little effect on the cellular gas exchange of apple (Malus × domestica) parenchyma tissue. The analysis clearly confirmed that cells are an additional route for CO2 transport, while for O2 the intercellular spaces are the main diffusion route. The simulation results also showed that the local gas concentration gradients were steeper in the cells than in the surrounding air spaces. Therefore, to analyze the cellular metabolism under hypoxic and anoxic conditions, the microscale model is required to calculate the correct intracellular concentrations. Understanding the O2 response of plants and plant organs thus not only requires knowledge of external conditions, dimensions, gas-exchange properties of the tissues, and cellular respiration kinetics but also of microstructure. PMID:21224337

Numerical modeling of immiscible two-phase flow in micro-models using a commercial CFD code

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

Crandall, Dustin; Ahmadia, Goodarz; Smith, Duane H.

2009-01-01

Off-the-shelf CFD software is being used to analyze everything from flow over airplanes to lab-on-a-chip designs. So, how accurately can two-phase immiscible flow be modeled flowing through some small-scale models of porous media? We evaluate the capability of the CFD code FLUENT{trademark} to model immiscible flow in micro-scale, bench-top stereolithography models. By comparing the flow results to experimental models we show that accurate 3D modeling is possible.

Laser etching of groove structures with micro-optical fiber-enhanced irradiation

PubMed Central

2012-01-01

A microfiber is used as a laser-focusing unit to fabricate a groove structure on TiAlSiN surfaces. After one laser pulse etching, a groove with the minimum width of 265 nm is manufactured at the area. This technique of microfabricating the groove in microscale is studied. Based on the near-field intensity enhancement at the contact area between the fiber and the surface during the laser irradiation, simulation results are also presented, which agree well with the experimental results. PMID:22713521

Palladium-Catalyzed α-Arylation of Aryl Nitromethanes

PubMed Central

2015-01-01

Catalytic conditions for the α-arylation of aryl nitromethanes have been discovered using parallel microscale experimentation, despite two prior reports of the lack of reactivity of these aryl nitromethane precursors. The method efficiently provides a variety of substituted, isolable diaryl nitromethanes. In addition, it is possible to sequentially append two different aryl groups to nitromethane. Mild oxidation conditions were identified to afford the corresponding benzophenones via the Nef reaction, and reduction conditions were optimized to afford several diaryl methylamines. PMID:26584680

Good coupling for the multiscale patch scheme on systems with microscale heterogeneity

NASA Astrophysics Data System (ADS)

Bunder, J. E.; Roberts, A. J.; Kevrekidis, I. G.

2017-05-01

Computational simulation of microscale detailed systems is frequently only feasible over spatial domains much smaller than the macroscale of interest. The 'equation-free' methodology couples many small patches of microscale computations across space to empower efficient computational simulation over macroscale domains of interest. Motivated by molecular or agent simulations, we analyse the performance of various coupling schemes for patches when the microscale is inherently 'rough'. As a canonical problem in this universality class, we systematically analyse the case of heterogeneous diffusion on a lattice. Computer algebra explores how the dynamics of coupled patches predict the large scale emergent macroscale dynamics of the computational scheme. We determine good design for the coupling of patches by comparing the macroscale predictions from patch dynamics with the emergent macroscale on the entire domain, thus minimising the computational error of the multiscale modelling. The minimal error on the macroscale is obtained when the coupling utilises averaging regions which are between a third and a half of the patch. Moreover, when the symmetry of the inter-patch coupling matches that of the underlying microscale structure, patch dynamics predicts the desired macroscale dynamics to any specified order of error. The results confirm that the patch scheme is useful for macroscale computational simulation of a range of systems with microscale heterogeneity.

Verifying detailed fluctuation relations for discrete feedback-controlled quantum dynamics

NASA Astrophysics Data System (ADS)

Camati, Patrice A.; Serra, Roberto M.

2018-04-01

Discrete quantum feedback control consists of a managed dynamics according to the information acquired by a previous measurement. Energy fluctuations along such dynamics satisfy generalized fluctuation relations, which are useful tools to study the thermodynamics of systems far away from equilibrium. Due to the practical challenge to assess energy fluctuations in the quantum scenario, the experimental verification of detailed fluctuation relations in the presence of feedback control remains elusive. We present a feasible method to experimentally verify detailed fluctuation relations for discrete feedback control quantum dynamics. Two detailed fluctuation relations are developed and employed. The method is based on a quantum interferometric strategy that allows the verification of fluctuation relations in the presence of feedback control. An analytical example to illustrate the applicability of the method is discussed. The comprehensive technique introduced here can be experimentally implemented at a microscale with the current technology in a variety of experimental platforms.

Discharge characteristics of a needle-to-plate electrode at a micro-scale gap

NASA Astrophysics Data System (ADS)

Ronggang, WANG; Qizheng, JI; Tongkai, ZHANG; Qing, XIA; Yu, ZHANG; Jiting, OUYANG

2018-05-01

To understand the discharge characteristics under a gap of micrometers, the breakdown voltage and current–voltage curve are measured experimentally in a needle-to-plate electrode at a micro-scale gap of 3–50 μm in air. The effect of the needle radius and the gas pressure on the discharge characteristics are tested. The results show that when the gap is larger than 10 μm, the relation between the breakdown voltage and the gap looks like the Paschen curve; while below 10 μm, the breakdown voltage is nearly constant in the range of the tested gap. However, at the same gap distance, the breakdown voltage is still affected by the pressure and shows a trend similar to Paschen’s law. The current–voltage characteristic in all the gaps is similar and follows the trend of a typical Townsend-to-glow discharge. A simple model is used to explain the non-normality of breakdown in the micro-gaps. The Townsend mechanism is suggested to control the breakdown process in this configuration before the gap reduces much smaller in air.

Environmental Stress-mediated EPS Production Shape Microbial Activity on Various Hydrated Rough Surfaces

NASA Astrophysics Data System (ADS)

Wang, G.; Liu, L.; Chen, G.

2016-12-01

The complex environmental physical and chemical processes and interplay with the associating biological responses are keys to understanding the environmental microbiology ensconced in environmental remediation, water quality control, food safety, nutrient cycling, and etc., yet remain poorly understood. Using experimental micromodels, we study how environmental conditions (e.g., hydration fluctuation, nutrient limitation, pH variation, etc.) affect microbial extracellular polymeric substances (EPS) production and their configuration within various hydrated surfaces, and impacts on microbial motility, surface attachment, aggregation, and other bioremediation activities. To elucidate the potential mechanisms underlying the complex bio-physicochemical processes, we developed an individual-based and spatio-temporally resolved modeling platform that explicitly considers microscale aqueous-phase configuration and nutrient transport/diffusion and associated biophysical processes affecting individual microbial cell life history. We quantitatively explore the effects of the above microscale environmental processes on bio-physicochemical interactions affecting microbial growth, motility, surface attachment and aggregation, and shaping population interactions and functions. Simulation scenarios of microbial induced pollutant (e.g., roxarsone) biotransformation on various hydrated rough surfaces will also be present.

Engineering of microscale three-dimensional pancreatic islet models in vitro and their biomedical applications.

PubMed

Gao, Bin; Wang, Lin; Han, Shuang; Pingguan-Murphy, Belinda; Zhang, Xiaohui; Xu, Feng

2016-08-01

Diabetes now is the most common chronic disease in the world inducing heavy burden for the people's health. Based on this, diabetes research such as islet function has become a hot topic in medical institutes of the world. Today, in medical institutes, the conventional experiment platform in vitro is monolayer cell culture. However, with the development of micro- and nano-technologies, several microengineering methods have been developed to fabricate three-dimensional (3D) islet models in vitro which can better mimic the islet of pancreases in vivo. These in vitro islet models have shown better cell function than monolayer cells, indicating their great potential as better experimental platforms to elucidate islet behaviors under both physiological and pathological conditions, such as the molecular mechanisms of diabetes and clinical islet transplantation. In this review, we present the state-of-the-art advances in the microengineering methods for fabricating microscale islet models in vitro. We hope this will help researchers to better understand the progress in the engineering 3D islet models and their biomedical applications such as drug screening and islet transplantation.

Modeling the impact of scaffold architecture and mechanical loading on collagen turnover in engineered cardiovascular tissues.

PubMed

Argento, G; de Jonge, N; Söntjens, S H M; Oomens, C W J; Bouten, C V C; Baaijens, F P T

2015-06-01

The anisotropic collagen architecture of an engineered cardiovascular tissue has a major impact on its in vivo mechanical performance. This evolving collagen architecture is determined by initial scaffold microstructure and mechanical loading. Here, we developed and validated a theoretical and computational microscale model to quantitatively understand the interplay between scaffold architecture and mechanical loading on collagen synthesis and degradation. Using input from experimental studies, we hypothesize that both the microstructure of the scaffold and the loading conditions influence collagen turnover. The evaluation of the mechanical and topological properties of in vitro engineered constructs reveals that the formation of extracellular matrix layers on top of the scaffold surface influences the mechanical anisotropy on the construct. Results show that the microscale model can successfully capture the collagen arrangement between the fibers of an electrospun scaffold under static and cyclic loading conditions. Contact guidance by the scaffold, and not applied load, dominates the collagen architecture. Therefore, when the collagen grows inside the pores of the scaffold, pronounced scaffold anisotropy guarantees the development of a construct that mimics the mechanical anisotropy of the native cardiovascular tissue.

Laboratory Study of Homogeneous and Isotropic Turbulence at High Reynolds Number

NASA Astrophysics Data System (ADS)

Pecenak, Zachary; Dou, Zhongwang; Yang, Fan; Cao, Lujie; Liang, Zach; Meng, Hui

2013-11-01

To study particle dynamics modified by isotropic turbulence at high Reynolds numbers and provide experimental data for DNS validation, we have developed a soccer-ball-shaped truncated icosahedron turbulence chamber with 20 adjoining hexagon surfaces, 12 pentagon surfaces and twenty symettrically displaced fans, which form an enclosed chamber of 1m diameter. We use Particle Image Velocimetry (PIV) technique to characterize the base turbulent flow, using different PIV set ups to capture various characteristic scales of turbulence. Results show that the stationary isotropic turbulence field is a spherical domain with diameter of 40 mm with quasi-zero mean velocities. The maximum rms velocity is ~1.5 m/s, corresponding to a Taylor microscale Re of 450. We extract from the PIV velocity field the whole set of turbulent flow parameters including: turbulent kinetic energy, turbulent intensity, kinetic energy dissipation rate, large eddy length and time scales, the Kolmogorov length, time and velocity scales, Taylor microscale and Re, which are critical to the study of inter-particle statistics modified by turbulence. This research is funded by an NSF grant CBET-0967407.

Photogrammetric measurement of 3D freeform millimetre-sized objects with micro features: an experimental validation of the close-range camera calibration model for narrow angles of view

NASA Astrophysics Data System (ADS)

Percoco, Gianluca; Sánchez Salmerón, Antonio J.

2015-09-01

The measurement of millimetre and micro-scale features is performed by high-cost systems based on technologies with narrow working ranges to accurately control the position of the sensors. Photogrammetry would lower the costs of 3D inspection of micro-features and would be applicable to the inspection of non-removable micro parts of large objects too. Unfortunately, the behaviour of photogrammetry is not known when photogrammetry is applied to micro-features. In this paper, the authors address these issues towards the application of digital close-range photogrammetry (DCRP) to the micro-scale, taking into account that in literature there are research papers stating that an angle of view (AOV) around 10° is the lower limit to the application of the traditional pinhole close-range calibration model (CRCM), which is the basis of DCRP. At first a general calibration procedure is introduced, with the aid of an open-source software library, to calibrate narrow AOV cameras with the CRCM. Subsequently the procedure is validated using a reflex camera with a 60 mm macro lens, equipped with extension tubes (20 and 32 mm) achieving magnification of up to 2 times approximately, to verify literature findings with experimental photogrammetric 3D measurements of millimetre-sized objects with micro-features. The limitation experienced by the laser printing technology, used to produce the bi-dimensional pattern on common paper, has been overcome using an accurate pattern manufactured with a photolithographic process. The results of the experimental activity prove that the CRCM is valid for AOVs down to 3.4° and that DCRP results are comparable with the results of existing and more expensive commercial techniques.

Fundamentals of microfluidic cell culture in controlled microenvironments†

PubMed Central

Young, Edmond W. K.; Beebe, David J.

2010-01-01

Microfluidics has the potential to revolutionize the way we approach cell biology research. The dimensions of microfluidic channels are well suited to the physical scale of biological cells, and the many advantages of microfluidics make it an attractive platform for new techniques in biology. One of the key benefits of microfluidics for basic biology is the ability to control parameters of the cell microenvironment at relevant length and time scales. Considerable progress has been made in the design and use of novel microfluidic devices for culturing cells and for subsequent treatment and analysis. With the recent pace of scientific discovery, it is becoming increasingly important to evaluate existing tools and techniques, and to synthesize fundamental concepts that would further improve the efficiency of biological research at the microscale. This tutorial review integrates fundamental principles from cell biology and local microenvironments with cell culture techniques and concepts in microfluidics. Culturing cells in microscale environments requires knowledge of multiple disciplines including physics, biochemistry, and engineering. We discuss basic concepts related to the physical and biochemical microenvironments of the cell, physicochemical properties of that microenvironment, cell culture techniques, and practical knowledge of microfluidic device design and operation. We also discuss the most recent advances in microfluidic cell culture and their implications on the future of the field. The goal is to guide new and interested researchers to the important areas and challenges facing the scientific community as we strive toward full integration of microfluidics with biology. PMID:20179823

Implementation of thermoelectric module for cooling process of microscale experimental room

NASA Astrophysics Data System (ADS)

Gołebiowska, Justyna; Żelazna, Agnieszka; Zioło, Paweł

2017-08-01

Thermoelectric modules, also known as Peltier modules, are used for cooling small devices and also, according to literature, in refrigeration. They can be an alternative to conventional refrigeration systems based on the use of compressors chillers powered by AC power. Peltier modules are powered by direct current (DC), which allows to power them directly supply by photovoltaic modules. In this paper operation of thermoelectric module used for cooling experimental room of cubature 0.125 m3 is presented. The study involves investigation of temperatures achieved on the cold and hot sides of module and inside the experimental room depending on the values of module supplying current. These studies provide an introduction to the assessment of the influence of different methods of heat removal on the hot side of thermoelectric module on cooling efficiency of whole system.

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

NASA Astrophysics Data System (ADS)

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

2017-04-01

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H+/OH- transport) and electric field-driven migration on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Overall, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.

The Microscale Inorganic Laboratory: Safety, Economy and Versatility.

ERIC Educational Resources Information Center

Szafran, Zvi; And Others

1989-01-01

Discussed are four major advantages to the use of microscale laboratories for teaching chemistry. Included are effects on waste generation, laboratory safety, reagent variety, and laboratory efficiency. (CW)

Geckoprinting: assembly of microelectronic devices on unconventional surfaces by transfer printing with isolated gecko setal arrays

PubMed Central

Jeong, Jaeyoung; Kim, Juho; Song, Kwangsun; Autumn, Kellar; Lee, Jongho

2014-01-01

Developing electronics in unconventional forms provides opportunities to expand the use of electronics in diverse applications including bio-integrated or implanted electronics. One of the key challenges lies in integrating semiconductor microdevices onto unconventional substrates without glue, high pressure or temperature that may cause damage to microdevices, substrates or interfaces. This paper describes a solution based on natural gecko setal arrays that switch adhesion mechanically on and off, enabling pick and place manipulation of thin microscale semiconductor materials onto diverse surfaces including plants and insects whose surfaces are usually rough and irregular. A demonstration of functional ‘geckoprinted’ microelectronic devices provides a proof of concept of our results in practical applications. PMID:25056216

Influence of the Martensitic Transformation on the Microscale Plastic Strain Heterogeneities in a Duplex Stainless Steel

NASA Astrophysics Data System (ADS)

Lechartier, Audrey; Martin, Guilhem; Comby, Solène; Roussel-Dherbey, Francine; Deschamps, Alexis; Mantel, Marc; Meyer, Nicolas; Verdier, Marc; Veron, Muriel

2017-01-01

The influence of the martensitic transformation on microscale plastic strain heterogeneity of a duplex stainless steel has been investigated. Microscale strain heterogeneities were measured by digital image correlation during an in situ tensile test within the SEM. The martensitic transformation was monitored in situ during tensile testing by high-energy synchrotron X-ray diffraction. A clear correlation is shown between the plasticity-induced transformation of austenite to martensite and the development of plastic strain heterogeneities at the phase level.

Experimental design and modeling of a microscale differential thermal calorimeter for the purposes of cryopreservation

NASA Astrophysics Data System (ADS)

Armes, James L.

In order to develop successful cryopreservation protocols for various biological materials, it is necessary to determine the thermodynamic properties of nanoliter- scale biological samples: ranging from heat capacity to heat of fusion. Differential thermal analysis is a calorimetric technique which is efficacious at determining these thermodynamic properties and will help lend insight into the formation of intracellular ice which depends heavily on the rate at which the sample is cooled. If too much intracellular ice is formed during the cooling process, the biological material can be destroyed. To investigate the effects of a range of cooling and warming rates on a cell, a control system and data acquisition software has been developed for use with a custom microfabricated differential thermal analyzer (muDTA). Utilizing either an a-priori prediction of the muDTA's thermal response or an integrated software-based PID control system, the program developed allows for precise control over the cooling and warming rate of the muDTA. In order to enhance the accuracy of the a-priori predicted current profile, a 2D numeric model was developed of the muDTA. This model also has allowed for geometric optimization to be performed on the next generation prototype of the muDTA. The muDTA has been shown to accurately measure the freezing point and heat of fusion of deionized water samples, with sample volumes on the order of nanoliters. The heat capacity of dimethyl sulfoxide (DMSO) has also been experimentally determined.

Geomorphology and the Law of Unintended Consequences (Locke, 1691): Lessons from coastal weathering and erosion at Prawle (UK) and Kaikoura (NZ)

NASA Astrophysics Data System (ADS)

Mottershead, Derek N.; Stephenson, Wayne J.; Hemmingsen, Maree A.

2016-07-01

The sites of two field experiments based on micro-erosion metering, one in UK the other in New Zealand, were independently revisited respectively 33 and 17 years after installation. At both sites natural weathering and erosion processes had been inadvertently interrupted by the experimental works, leading to the development of new microscale landforms. These are interpreted in the context of modifications of the controls on weathering processes, leading to enhanced understanding of the processes themselves. This has lessons for the geomorphologist in maintaining a long-term watching brief over former experimental sites, lest some unintended and potentially beneficial outcome has ensued. This theme is embraced by the Law of Unintended Consequences.

Operation of a gated field emitter using an individual carbon nanofiber cathode

NASA Astrophysics Data System (ADS)

Guillorn, M. A.; Melechko, A. V.; Merkulov, V. I.; Ellis, E. D.; Britton, C. L.; Simpson, M. L.; Lowndes, D. H.; Baylor, L. R.

2001-11-01

We report on the operation of an integrated gated cathode device using a single vertically aligned carbon nanofiber as the field emission element. This device is capable of operation in a moderate vacuum for extended periods of time without experiencing a degradation of performance. Less than 1% of the total emitted current is collected by the gate electrode, indicating that the emitted electron beam is highly collimated. As a consequence, this device is ideal for applications that require well-focused electron emission from a microscale structure.

Film-Evaporation MEMS Tunable Array for Picosat Propulsion and Thermal Control

NASA Technical Reports Server (NTRS)

Alexeenko, Alina; Cardiff, Eric; Martinez, Andres; Petro, Andrew

2015-01-01

The Film-Evaporation MEMS Tunable Array (FEMTA) concept for propulsion and thermal control of picosats exploits microscale surface tension effect in conjunction with temperature- dependent vapor pressure to realize compact, tunable and low-power thermal valving system. The FEMTA is intended to be a self-contained propulsion unit requiring only a low-voltage DC power source to operate. The microfabricated thermal valving and very-high-integration level enables fast high-capacity cooling and high-resolution, low-power micropropulsion for picosats that is superior to existing smallsat micropropulsion and thermal management alternatives.

3D MEMS in Standard Processes: Fabrication, Quality Assurance, and Novel Measurement Microstructures

NASA Technical Reports Server (NTRS)

Lin, Gisela; Lawton, Russell A.

2000-01-01

Three-dimensional MEMS microsystems that are commercially fabricated require minimal post-processing and are easily integrated with CMOS signal processing electronics. Measurements to evaluate the fabrication process (such as cross-sectional imaging and device performance characterization) provide much needed feedback in terms of reliability and quality assurance. MEMS technology is bringing a new class of microscale measurements to fruition. The relatively small size of MEMS microsystems offers the potential for higher fidelity recordings compared to macrosize counterparts, as illustrated in the measurement of muscle cell forces.

Multi-scale finite element model of growth plate damage during the development of slipped capital femoral epiphysis.

PubMed

Farzaneh, S; Paseta, O; Gómez-Benito, M J

2015-04-01

Slipped capital femoral epiphysis (SCFE) is one of the most common disorders of adolescent hips. A number of works have related the development of SCFE to mechanical factors. Due to the difficulty of diagnosing SCFE in its early stages, the disorder often progresses over time, resulting in serious side effects. Therefore, the development of a tool to predict the initiation of damage in the growth plate is needed. Because the growth plate is a heterogeneous structure, to develop a precise and reliable model, it is necessary to consider this structure from both macro- and microscale perspectives. Thus, the main objective of this work is to develop a numerical multi-scale model that links damage occurring at the microscale to damage occurring at the macroscale. The use of this model enables us to predict which regions of the growth plate are at high risk of damage. First, we have independently analyzed the microscale to simulate the microstructure under shear and tensile tests to calibrate the damage model. Second, we have employed the model to simulate damage occurring in standardized healthy and affected femurs during the heel-strike stage of stair climbing. Our results indicate that on the macroscale, damage is concentrated in the medial region of the growth plate in both healthy and affected femurs. Furthermore, damage to the affected femur is greater than damage to the healthy femur from both the micro- and macrostandpoints. Maximal damage is observed in territorial matrices. Furthermore, simulations illustrate that little damage occurs in the reserve zone. These findings are consistent with previous findings reported in well-known experimental works.

Experimental investigation of the microscale rotor-stator cavity flow with rotating superhydrophobic surface

NASA Astrophysics Data System (ADS)

Wang, Chunze; Tang, Fei; Li, Qi; Wang, Xiaohao

2018-03-01

The flow characteristics of microscale rotor-stator cavity flow and the drag reduction mechanism of the superhydrophobic surface with high shearing stress were investigated. A microscale rotating flow testing system was established based on micro particle image velocimetry (micro-PIV), and the flow distribution under different Reynolds numbers (7.02 × 103 ≤ Re ≤ 3.51 × 104) and cavity aspect ratios (0.013 ≤ G ≤ 0.04) was measured. Experiments show that, for circumferential velocity, the flow field distributes linearly in rotating Couette flow in the case of low Reynolds number along the z-axis, while the boundary layer separates and forms Batchelor flow as the Reynolds number increases. The separation of the boundary layer is accelerated with the increase of cavity aspect ratio. The radial velocities distribute in an S-shape along the z-axis. As the Reynolds number and cavity aspect ratio increase, the maximum value of radial velocity increases, but the extremum position at rotating boundary remains at Z* = 0.85 with no obvious change, while the extremum position at the stationary boundary changes along the z-axis. The model for the generation of flow disturbance and the transmission process from the stationary to the rotating boundary was given by perturbation analysis. Under the action of superhydrophobic surface, velocity slip occurs near the rotating boundary and the shearing stress reduces, which leads to a maximum drag reduction over 51.4%. The contours of vortex swirling strength suggest that the superhydrophobic surface can suppress the vortex swirling strength and repel the vortex structures, resulting in the decrease of shearing Reynolds stress and then drag reduction.

Identifying stereotypic evolving micro-scale seizures (SEMS) in the hypoxic-ischemic EEG of the pre-term fetal sheep with a wavelet type-II fuzzy classifier.

PubMed

Abbasi, Hamid; Bennet, Laura; Gunn, Alistair J; Unsworth, Charles P

2016-08-01

Perinatal hypoxic-ischemic encephalopathy (HIE) around the time of birth due to lack of oxygen can lead to debilitating neurological conditions such as epilepsy and cerebral palsy. Experimental data have shown that brain injury evolves over time, but during the first 6-8 hours after HIE the brain has recovered oxidative metabolism in a latent phase, and brain injury is reversible. Treatments such as therapeutic cerebral hypothermia (brain cooling) are effective when started during the latent phase, and continued for several days. Effectiveness of hypothermia is lost if started after the latent phase. Post occlusion monitoring of particular micro-scale transients in the hypoxic-ischemic (HI) Electroencephalogram (EEG), from an asphyxiated fetal sheep model in utero, could provide precursory evidence to identify potential biomarkers of injury when brain damage is still treatable. In our studies, we have reported how it is possible to automatically detect HI EEG transients in the form of spikes and sharp waves during the latent phase of the HI EEG of the preterm fetal sheep. This paper describes how to identify stereotypic evolving micro-scale seizures (SEMS) which have a relatively abrupt onset and termination in a frequency range of 1.8-3Hz (Delta waves) superimposed on a suppressed EEG amplitude background post occlusion. This research demonstrates how a Wavelet Type-II Fuzzy Logic System (WT-Type-II-FLS) can be used to automatically identify subtle abnormal SEMS that occur during the latent phase with a preliminary average validation overall performance of 78.71%±6.63 over the 390 minutes of the latent phase, post insult, using in utero pre-term hypoxic fetal sheep models.

Towards microscale electrohydrodynamic three-dimensional printing

NASA Astrophysics Data System (ADS)

He, Jiankang; Xu, Fangyuan; Cao, Yi; Liu, Yaxiong; Li, Dichen

2016-02-01

It is challenging for the existing three-dimensional (3D) printing techniques to fabricate high-resolution 3D microstructures with low costs and high efficiency. In this work we present a solvent-based electrohydrodynamic 3D printing technique that allows fabrication of microscale structures like single walls, crossed walls, lattice and concentric circles. Process parameters were optimized to deposit tiny 3D patterns with a wall width smaller than 10 μm and a high aspect ratio of about 60. Tight bonding among neighbour layers could be achieved with a smooth lateral surface. In comparison with the existing microscale 3D printing techniques, the presented method is low-cost, highly efficient and applicable to multiple polymers. It is envisioned that this simple microscale 3D printing strategy might provide an alternative and innovative way for application in MEMS, biosensor and flexible electronics.

Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

2015-09-01

The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area.

Toughening Effect of Microscale Particles on the Tensile and Vibration Properties of S-Glass-Fiber-Reinforced Epoxy Composites

NASA Astrophysics Data System (ADS)

Erkliğ, A.; Bulut, M.; Fayzulla, B.

2018-03-01

The effect of borax, sewage sludge ash, silicon carbide, and perlite microparticles on the tensile, damping, and vibration characteristics of S-glass/epoxy composite laminates was examined Their damping and vibration properties were evaluated experimentally by using the dynamic modal analysis, identifying the response of the fundamental natural frequency to the type and weight content of the particulates. The results obtained showed that the introduction of specific amounts of such particulates into the matrix of S-glass/epoxy composite noticeably improved its mechanical properties.

On Laboratory Work

NASA Astrophysics Data System (ADS)

Olney, Dave

1997-11-01

This paper offers some suggestions on making lab work for high school chemistry students more productive, with students taking an active role. They include (1) rewriting labs from manuals to better suit one's purpose, (2) the questionable use of canned data tables, (3) designing microscale labs that utilize its unique features, such as safety and ease of repetition, (4) having students actually carry out experimental design on occasion, using a model from PRACTICE IN THINKING, and (5) using comuters/calculators in the lab in meaningful ways. Many examples feature discovery-type labs the author has developed over the years.

Immobilized enzyme studies in a microscale bioreactor.

PubMed

Jones, Francis; Forrest, Scott; Palmer, Jim; Lu, Zonghuan; Elmore, John; Elmore, Bill B

2004-01-01

Novel microreactors with immobilized enzymes were fabricated using both silicon and polymer-based microfabrication techniques. The effectiveness of these reactors was examined along with their behavior over time. Urease enzyme was successfully incorporated into microchannels of a polymeric matrix of polydimethylsiloxane and through layer-bylayer self-assembly techniques onto silicon. The fabricated microchannels had cross-sectional dimensions ranging from tens to hundreds of micrometers in width and height. The experimental results for continuous-flow microreactors are reported for the conversion of urea to ammonia by urease enzyme. Urea conversions of >90% were observed.

From micro-scale 3D simulations to macro-scale model of periodic porous media

NASA Astrophysics Data System (ADS)

Crevacore, Eleonora; Tosco, Tiziana; Marchisio, Daniele; Sethi, Rajandrea; Messina, Francesca

2015-04-01

In environmental engineering, the transport of colloidal suspensions in porous media is studied to understand the fate of potentially harmful nano-particles and to design new remediation technologies. In this perspective, averaging techniques applied to micro-scale numerical simulations are a powerful tool to extrapolate accurate macro-scale models. Choosing two simplified packing configurations of soil grains and starting from a single elementary cell (module), it is possible to take advantage of the periodicity of the structures to reduce the computation costs of full 3D simulations. Steady-state flow simulations for incompressible fluid in laminar regime are implemented. Transport simulations are based on the pore-scale advection-diffusion equation, that can be enriched introducing also the Stokes velocity (to consider the gravity effect) and the interception mechanism. Simulations are carried on a domain composed of several elementary modules, that serve as control volumes in a finite volume method for the macro-scale method. The periodicity of the medium involves the periodicity of the flow field and this will be of great importance during the up-scaling procedure, allowing relevant simplifications. Micro-scale numerical data are treated in order to compute the mean concentration (volume and area averages) and fluxes on each module. The simulation results are used to compare the micro-scale averaged equation to the integral form of the macroscopic one, making a distinction between those terms that could be computed exactly and those for which a closure in needed. Of particular interest it is the investigation of the origin of macro-scale terms such as the dispersion and tortuosity, trying to describe them with micro-scale known quantities. Traditionally, to study the colloidal transport many simplifications are introduced, such those concerning ultra-simplified geometry that usually account for a single collector. Gradual removal of such hypothesis leads to a detailed description of colloidal transport mechanisms. Starting from nearly realistic 3D geometries, the ultimate purpose of this work is that of develop an improved understanding of the fate of colloidal particles through, for example, an accurate description of the deposition efficiency, in order design efficient remediation techniques. G. Boccardo, D.L. Marchisio, R.Sethi, Journal of colloid and interface science, Vol 417C, pp 227-237, 2014 M. Icardi, G. Boccardo, D.L. Marchisio, T. Tosco, R.Sethi, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 2014 S. Torkzaban, S.S. Tazehkand, S.L. Walker, S.A. Bradford, Water resources research, Vol 44, 2008 S.M. Hassanizadeh, Adv in Water Resources, Vol. 2, pp 131-144, 1979 S. Whitaker, AIChE Journal, Vol. 13 No. 3, pp 420-428, May 1967

Miniature Fuel Processors for Portable Fuel Cell Power Supplies

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

Holladay, Jamie D.; Jones, Evan O.; Palo, Daniel R.

2003-06-02

Miniature and micro-scale fuel processors are discussed. The enabling technologies for these devices are the novel catalysts and the micro-technology-based designs. The novel catalyst allows for methanol reforming at high gas hourly space velocities of 50,000 hr-1 or higher, while maintaining a carbon monoxide levels at 1% or less. The micro-technology-based designs enable the devices to be extremely compact and lightweight. The miniature fuel processors can nominally provide between 25-50 watts equivalent of hydrogen which is ample for soldier or personal portable power supplies. The integrated processors have a volume less than 50 cm3, a mass less than 150 grams,more » and thermal efficiencies of up to 83%. With reasonable assumptions on fuel cell efficiencies, anode gas and water management, parasitic power loss, etc., the energy density was estimated at 1700 Whr/kg. The miniature processors have been demonstrated with a carbon monoxide clean-up method and a fuel cell stack. The micro-scale fuel processors have been designed to provide up to 0.3 watt equivalent of power with efficiencies over 20%. They have a volume of less than 0.25 cm3 and a mass of less than 1 gram.« less

Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study

NASA Astrophysics Data System (ADS)

Szarf, Krzysztof; Combe, Gael; Villard, Pascal

2015-02-01

The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods. Moreover, Discrete Element approach is able to provide information about the grain-grain and grain-structure interactions at the microscale. This paper presents numerical and experimental investigations of flexible buried pipe behaviour with focus placed on load transfer above the buried structure. Numerical modeling was able to reproduce the experimental results. Load repartition was observed, being affected by a number of factors such as particle shape, pipe friction and pipe stiffness.

A statistical nanomechanism of biomolecular patterning actuated by surface potential

NASA Astrophysics Data System (ADS)

Lin, Chih-Ting; Lin, Chih-Hao

2011-02-01

Biomolecular patterning on a nanoscale/microscale on chip surfaces is one of the most important techniques used in vitro biochip technologies. Here, we report upon a stochastic mechanics model we have developed for biomolecular patterning controlled by surface potential. The probabilistic biomolecular surface adsorption behavior can be modeled by considering the potential difference between the binding and nonbinding states. To verify our model, we experimentally implemented a method of electroactivated biomolecular patterning technology and the resulting fluorescence intensity matched the prediction of the developed model quite well. Based on this result, we also experimentally demonstrated the creation of a bovine serum albumin pattern with a width of 200 nm in 5 min operations. This submicron noncovalent-binding biomolecular pattern can be maintained for hours after removing the applied electrical voltage. These stochastic understandings and experimental results not only prove the feasibility of submicron biomolecular patterns on chips but also pave the way for nanoscale interfacial-bioelectrical engineering.

In situ nonlinear ultrasonic technique for monitoring microcracking in concrete subjected to creep and cyclic loading.

PubMed

Kim, Gun; Loreto, Giovanni; Kim, Jin-Yeon; Kurtis, Kimberly E; Wall, James J; Jacobs, Laurence J

2018-08-01

This research conducts in situ nonlinear ultrasonic (NLU) measurements for real time monitoring of load-induced damage in concrete. For the in situ measurements on a cylindrical specimen under sustained load, a previously developed second harmonic generation (SHG) technique with non-contact detection is adapted to a cylindrical specimen geometry. This new setup is validated by demonstrating that the measured nonlinear Rayleigh wave signals are equivalent to those in a flat half space, and thus the acoustic nonlinearity parameter, β can be defined and interpreted in the same way. Both the acoustic nonlinearity parameter and strain are measured to quantitatively assess the early-age damage in a set of concrete specimens subjected to either 25 days of creep, or 11 cycles of cyclic loading at room temperature. The experimental results show that the acoustic nonlinearity parameter is sensitive to early-stage microcrack formation under both loading conditions - the measured β can be directly linked to the accumulated microscale damage. This paper demonstrates the potential of NLU for the in situ monitoring of mechanical load-induced microscale damage in concrete components. Copyright © 2018 Elsevier B.V. All rights reserved.

Electrical percolation threshold of cementitious composites possessing self-sensing functionality incorporating different carbon-based materials

NASA Astrophysics Data System (ADS)

Al-Dahawi, Ali; Haroon Sarwary, Mohammad; Öztürk, Oğuzhan; Yıldırım, Gürkan; Akın, Arife; Şahmaran, Mustafa; Lachemi, Mohamed

2016-10-01

An experimental study was carried out to understand the electrical percolation thresholds of different carbon-based nano- and micro-scale materials in cementitious composites. Multi-walled carbon nanotubes (CNTs), graphene nanoplatelets (GNPs) and carbon black (CB) were selected as the nano-scale materials, while 6 and 12 mm long carbon fibers (CF6 and CF12) were used as the micro-scale carbon-based materials. After determining the percolation thresholds of different electrical conductive materials, mechanical properties and piezoresistive properties of specimens produced with the abovementioned conductive materials at percolation threshold were investigated under uniaxial compressive loading. Results demonstrate that regardless of initial curing age, the percolation thresholds of CNT, GNP, CB and CFs in ECC mortar specimens were around 0.55%, 2.00%, 2.00% and 1.00%, respectively. Including different carbon-based conductive materials did not harm compressive strength results; on the contrary, it improved overall values. All cementitious composites produced with carbon-based materials, with the exception of the control mixtures, exhibited piezoresistive behavior under compression, which is crucial for sensing capability. It is believed that incorporating the sensing attribute into cementitious composites will enhance benefits for sustainable civil infrastructures.

Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet

NASA Astrophysics Data System (ADS)

Reddemann, Manuel A.; Mathieu, Florian; Kneer, Reinhold

2013-11-01

Aiming at a maximum spatial resolution and a minimum motion blur, a new simple double-imaging transmitted light microscopy technique is developed in this work enabling a fundamental investigation of primary breakup of a microscale liquid jet. Contrary to conventional far-field visualization techniques, the working distance is minimized to increase the numerical aperture. The resulting images provide information about shapes, length scales and velocities of primary liquid structures. The method is applied to an optically dense spray leaving a 109-μm diesel nozzle at various injection pressures under atmospheric conditions. A phenomenological study on the temporal spray evolution is done with focus on droplet and ligament formation. Different breakup processes are identified and described. It is found that the jet is characterized by long ligaments parallel or angular to the inner jet region. These ligaments result from collapsing films developing at the spray edge. A significant influence of outlet velocity variation on shape and velocity of these ligaments is observed. The experimental results prove that a transmitted light microscopy technique with reduced working distance is an appropriate tool for a better understanding of primary breakup for small-scaled diesel nozzles and a valuable complement to highly complex measurement techniques.

Measuring contact area in a sliding human finger-pad contact.

PubMed

Liu, X; Carré, M J; Zhang, Q; Lu, Z; Matcher, S J; Lewis, R

2018-02-01

The work outlined in this paper was aimed at achieving further understanding of skin frictional behaviour by investigating the contact area between human finger-pads and flat surfaces. Both the static and the dynamic contact areas (in macro- and micro-scales) were measured using various techniques, including ink printing, optical coherence tomography (OCT) and Digital Image Correlation (DIC). In the studies of the static measurements using ink printing, the experimental results showed that the apparent and the real contact area increased with load following a piecewise linear correlation function for a finger-pad in contact with paper sheets. Comparisons indicated that the OCT method is a reliable and effective method to investigate the real contact area of a finger-pad and allow micro-scale analysis. The apparent contact area (from the DIC measurements) was found to reduce with time in the transition from the static phase to the dynamic phase while the real area of contact (from OCT) increased. The results from this study enable the interaction between finger-pads and contact object surface to be better analysed, and hence improve the understanding of skin friction. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The role of the substrate in micro-scale scratching of epoxy-polyester films

NASA Astrophysics Data System (ADS)

Barletta, M.; Gisario, A.

2011-02-01

The present investigation analyzes the deformation response of electrostatically sprayed epoxy-polyester powder coatings by 'in situ' micro-mechanical tests. The characterization of the performance of the coatings was carried out by micro-scale scratching, by varying the indenter type, the applied load and the sliding speed. The tests were carried out on polymeric coatings deposited on as-received, micro and macro-corrugated AISI 304 stainless steel substrates and 'rigidly adhered' to them. Further tests were performed on 'free-standing' coatings, that is, on the as-received metal substrates pre-coated with an intermediate layer of silicon-based heat curable release coating. Experimental data allow us to evaluate the influence of the contact conditions between substrate and indenter and the role of the loading conditions on the scratch and penetration resistance of the epoxy-polyester coatings. The different responses of the polymeric coatings when deposited on untreated or pre-treated substrates as well as on an intermediate layer of release coating, contribute to a better understanding of the intrinsic roles of the polymeric material and substrate as well as the influence of the interfacial adhesion between coating and substrate.

Evaporation-induced cavitation in nanofluidic channels

PubMed Central

Duan, Chuanhua; Karnik, Rohit; Lu, Ming-Chang; Majumdar, Arun

2012-01-01

Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7 MPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale. PMID:22343530

Statistical Thermodynamics and Microscale Thermophysics

NASA Astrophysics Data System (ADS)

Carey, Van P.

1999-08-01

Many exciting new developments in microscale engineering are based on the application of traditional principles of statistical thermodynamics. In this text Van Carey offers a modern view of thermodynamics, interweaving classical and statistical thermodynamic principles and applying them to current engineering systems. He begins with coverage of microscale energy storage mechanisms from a quantum mechanics perspective and then develops the fundamental elements of classical and statistical thermodynamics. Subsequent chapters discuss applications of equilibrium statistical thermodynamics to solid, liquid, and gas phase systems. The remainder of the book is devoted to nonequilibrium thermodynamics of transport phenomena and to nonequilibrium effects and noncontinuum behavior at the microscale. Although the text emphasizes mathematical development, Carey includes many examples and exercises to illustrate how the theoretical concepts are applied to systems of scientific and engineering interest. In the process he offers a fresh view of statistical thermodynamics for advanced undergraduate and graduate students, as well as practitioners, in mechanical, chemical, and materials engineering.

Investigation on Convergence – Divergence Nozzle Shape for Microscale Channel in Harvesting Kinetic Energy

NASA Astrophysics Data System (ADS)

Zakaria, M. S.; Zairi, S.; Misbah, M. N.; Saifizi, M.; Rakawi, Izzudin

2018-03-01

This paper presents performance evaluation of nozzle shapes on microscale channel by employing different types of NACA airfoils profile and conventional profile. The deploying nozzle used are NACA 0012, NACA 0021 and NACA 0024 airfoils while for conventional convergence-divergence nozzle diameter ratio (d2 / d1) in the range from 1/4 to 3/4 are applied. These nozzles are assembled on rectangular cross sectional microscale channel which has designated constant fluid flow velocity at the channel inlet. This study revealed reduction on diameter ratio increased dramatically fluid velocity but further reduction on diameter ratio exposed fluid flow to fluctuate which slightly slowing down the fluid velocity. Nevertheless, curved NACA profiles are favourable for convergence – divergence nozzle in microscale channel as it significantly improved flow characteristics by enhancing fluid velocity and resultant kinetic energy as compared to conventional profile.

An Efficient Procedure for Microscale Synthesis of Semicarbazones

ERIC Educational Resources Information Center

Pandita, Sangeeta; Goyal, Samta; Passey, Sarita

2004-01-01

A successful microscale fusion of semicarbazones, or transformation of carbonyl compounds into semicarbazones is performed through an effective grinding system. The donning of protective attire is advised to avoid the hazardous effects of semicarbazide hydrochloride during the fusion process.

Interfacial separation of a mature biofilm from a glass surface - A combined experimental and cohesive zone modelling approach.

PubMed

Safari, Ashkan; Tukovic, Zeljko; Cardiff, Philip; Walter, Maik; Casey, Eoin; Ivankovic, Alojz

2016-02-01

A good understanding of the mechanical stability of biofilms is essential for biofouling management, particularly when mechanical forces are used. Previous biofilm studies lack a damage-based theoretical model to describe the biofilm separation from a surface. The purpose of the current study was to investigate the interfacial separation of a mature biofilm from a rigid glass substrate using a combined experimental and numerical modelling approach. In the current work, the biofilm-glass interfacial separation process was investigated under tensile and shear stresses at the macroscale level, known as modes I and II failure mechanisms respectively. The numerical simulations were performed using a Finite Volume (FV)-based simulation package (OpenFOAM®) to predict the separation initiation using the cohesive zone model (CZM). Atomic force microscopy (AFM)-based retraction curve was used to obtain the separation properties between the biofilm and glass colloid at microscale level, where the CZM parameters were estimated using the Johnson-Kendall-Roberts (JKR) model. In this study CZM is introduced as a reliable method for the investigation of interfacial separation between a biofilm and rigid substrate, in which a high local stress at the interface edge acts as an ultimate stress at the crack tip.This study demonstrated that the total interfacial failure energy measured at the macroscale, was significantly higher than the pure interfacial separation energy obtained by AFM at the microscale, indicating a highly ductile deformation behaviour within the bulk biofilm matrix. The results of this study can significantly contribute to the understanding of biofilm detachments. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dynamics of motile phytoplankton in turbulence: Laboratory investigation of microscale patchiness

NASA Astrophysics Data System (ADS)

Crimaldi, J. P.; True, A.; Stocker, R.

2016-02-01

Phytoplankton represent the basis of oceanic life and play a critical role in biogeochemical cycles. While phytoplankton are traditionally studied in bulk, their collective impact stems from cell-level processes and interactions at the microscale. A fundamental element that determines these interactions is the small-scale spatial distribution of individual cells: this directly determines the local cell concentration and the probability that two cells contact or interact with each other. The traditional, bulk perspective on phytoplankton distributions is that turbulence acts to smear out patchiness and locally homogenizes the distributions. However, recent numerical simulations suggest that the action of turbulence on motile phytoplankton may be precisely the opposite: by biasing the swimming direction of cells through the action of viscous torques, turbulence is predicted to generate strong patchiness at small scales. Flow-mediated patch formation has been demonstrated experimentally in simple laminar flows, but has never been tested experimentally in turbulence. In this talk we report on preliminary laboratory experiments performed in a purpose-built flow facility that uses a pair of computer-controlled oscillating grids to generate approximately homogenous isotropic 3D turbulence. Turbulent flow characteristics and dissipation rates are first quantified using particle image velocimetry (PIV). Then, 2D distributions of the motile dinoflagellate Heterosigma akashiwo are imaged using planar laser-induced fluorescence (PLIF). Analysis of imaged phytoplankton distributions for patchiness is performed using a Voronoi tessellation approach. Results suggest that motile phytoplankton distributions differ from those of passive particles. Furthermore, computed values for the patch enhancement factor are shown to be roughly consistent with those of previous DNS predictions.

Self-consistent clustering analysis: an efficient multiscale scheme for inelastic heterogeneous materials

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

Liu, Z.; Bessa, M. A.; Liu, W.K.

A predictive computational theory is shown for modeling complex, hierarchical materials ranging from metal alloys to polymer nanocomposites. The theory can capture complex mechanisms such as plasticity and failure that span across multiple length scales. This general multiscale material modeling theory relies on sound principles of mathematics and mechanics, and a cutting-edge reduced order modeling method named self-consistent clustering analysis (SCA) [Zeliang Liu, M.A. Bessa, Wing Kam Liu, “Self-consistent clustering analysis: An efficient multi-scale scheme for inelastic heterogeneous materials,” Comput. Methods Appl. Mech. Engrg. 306 (2016) 319–341]. SCA reduces by several orders of magnitude the computational cost of micromechanical andmore » concurrent multiscale simulations, while retaining the microstructure information. This remarkable increase in efficiency is achieved with a data-driven clustering method. Computationally expensive operations are performed in the so-called offline stage, where degrees of freedom (DOFs) are agglomerated into clusters. The interaction tensor of these clusters is computed. In the online or predictive stage, the Lippmann-Schwinger integral equation is solved cluster-wise using a self-consistent scheme to ensure solution accuracy and avoid path dependence. To construct a concurrent multiscale model, this scheme is applied at each material point in a macroscale structure, replacing a conventional constitutive model with the average response computed from the microscale model using just the SCA online stage. A regularized damage theory is incorporated in the microscale that avoids the mesh and RVE size dependence that commonly plagues microscale damage calculations. The SCA method is illustrated with two cases: a carbon fiber reinforced polymer (CFRP) structure with the concurrent multiscale model and an application to fatigue prediction for additively manufactured metals. For the CFRP problem, a speed up estimated to be about 43,000 is achieved by using the SCA method, as opposed to FE2, enabling the solution of an otherwise computationally intractable problem. The second example uses a crystal plasticity constitutive law and computes the fatigue potency of extrinsic microscale features such as voids. This shows that local stress and strain are capture sufficiently well by SCA. This model has been incorporated in a process-structure-properties prediction framework for process design in additive manufacturing.« less

Microscale Demonstration of the Paramagnetism of Liquid Oxygen with a Neodymium Magnet

ERIC Educational Resources Information Center

Mattson, Bruce

2007-01-01

A microscale classroom demonstration of the paramagnetic behavior of various samples of liquid oxygen with neodymium magnet is being presented. The experiment should be done with extreme caution, as liquid oxygen reacts violently with organic matters.

Multiscale Mechanical Characterization of Biomimetic Physically Associating Gels

DTIC Science & Technology

2006-09-01

work, a ballistic gelatin and two styrene- isoprene triblock copolymer gels are tested and compared using both macroscale and microscale measurements... isoprene triblock copolymer gels are tested and compared using both macroscale and microscale measurements. A methodology is presented to conduct

Boiling Heat Transfer Measurements on Highly Conductive Surfaces Using Microscale Heater and Temperature Arrays

NASA Technical Reports Server (NTRS)

Kim, J.; Bae, S. W.; Whitten, M. W.; Mullen, J. D.; Quine, R. W.; Kalkur, T. S.

1999-01-01

Two systems have been developed to study boiling heat transfer on the microscale. The first system utilizes a 32 x 32 array of diodes to measure the local temperature fluctuations during boiling on a silicon wafer heated from below. The second system utilizes an array of 96 microscale heaters each maintained at constant surface temperature using electronic feedback loops. The power required to keep each heater at constant temperature is measured, enabling the local heat transfer coefficient to be determined. Both of these systems as well as some preliminary results are discussed.

Effect of microscale ZVI/magnetite on methane production and bioavailability of heavy metals during anaerobic digestion of diluted pig manure.

PubMed

Liang, Yue-Gan; Li, Xiu-Juan; Zhang, Jin; Zhang, Li-Gan; Cheng, Beijiu

2017-05-01

Low methane production and high levels of heavy metal in pig slurries limit the feasibility of anaerobic digestion of pig manure. In this study, changes in the methane production and bioavailability of heavy metals in the anaerobic digestion of diluted pig manure were evaluated using single and combined action of microscale zero-valence iron (ZVI) and magnetite. After 30 days of anaerobic digestion, the methane yield ranged from 246.9 to 334.5 mL/g VS added, which increased by 20-26% in the group added with microscale ZVI and/or magnetite relative to that in the control group. Results of the first-order kinetic model revealed that addition of microscale ZVI and/or magnetite increased the biogas production potential, rather than the biogas production rate constant. These treatments also changed the distribution of chemical fractions for heavy metal. The addition of ZVI decreased the bioavailability of Cu and Zn in the solid digested residues. Moreover, a better performance was observed in the combined action of microscale ZVI and magnetite, and the ZVI anaerobic corrosion end-product, magnetite, might help enhance methane production through direct interspecies electron transfer in ZVI-anaerobic digestion process.

The potential for microtechnology applications in energy systems: Results of an experts workshop

NASA Astrophysics Data System (ADS)

1995-02-01

Microscale technologies, or microelectromechanical systems (MEMS), are currently under development in the United States and abroad. Examples include microsensors, microactuators (including micromotors), and microscale heat exchangers. Typically, microscale devices have features ranging in size from a few microns to several millimeters, with fabrication methods adapted from those developed for the semiconductor industry. Microtechnologies are already being commercialized; initial markets include the biomedical and transportation industries. Applications are being developed in other industries as well. Researchers at the Pacific Northwest Laboratory (PNL) hypothesize that a significant number of energy applications are possible. These applications range from environmental sensors that support enhanced control of building (or room) temperature and ventilation to microscale heat pumps and microscale heat engines that could collectively provide for kilowatt quantities of energy conversion. If efficient versions of these devices are developed, they could significantly advance the commercialization of distributed energy conversion systems, thereby reducing the energy losses associated with energy distribution. Based upon the potential for energy savings, the U.S. Department of Energy (DOE) Office of Building Technologies (OBT) has proposed a new initiative in energy systems miniaturization. The program would focus on the development of microtechnologies for the manufactured housing sector and would begin in either FY 1997 or FY 1998, ramping up to $5 million per year investment by FY 2001.

The Importance of Parameter Variances, Correlations Lengths, and Cross-Correlations in Reactive Transport Models: Key Considerations for Assessing the Need for Microscale Information (Invited)

NASA Astrophysics Data System (ADS)

Reimus, P. W.

2010-12-01

A process-oriented modeling approach is implemented to examine the importance of parameter variances, correlation lengths, and especially cross-correlations in contaminant transport predictions over large scales. It is shown that the most important consideration is the correlation between flow rates and retardation processes (e.g., sorption, matrix diffusion) in the system. If flow rates are negatively correlated with retardation factors in systems containing multiple flow pathways, then characterizing these negative correlation(s) may have more impact on reactive transport modeling than microscale information. Such negative correlations are expected in porous-media systems where permeability is negatively correlated with clay content and rock alteration (which are usually associated with increased sorption). Likewise, negative correlations are expected in fractured rocks where permeability is positively correlated with fracture apertures, which in turn are negatively correlated with sorption and matrix diffusion. Parameter variances and correlation lengths are also shown to have important effects on reactive transport predictions, but they are less important than parameter cross-correlations. Microscale information pertaining to contaminant transport has become more readily available as characterization methods and spectroscopic instrumentation have achieved lower detection limits, greater resolution, and better precision. Obtaining detailed mechanistic insights into contaminant-rock-water interactions is becoming a routine practice in characterizing reactive transport processes in groundwater systems (almost necessary for high-profile publications). Unfortunately, a quantitative link between microscale information and flow and transport parameter distributions or cross-correlations has not yet been established. One reason for this is that quantitative microscale information is difficult to obtain in complex, heterogeneous systems, so simple systems that lack the complexity and heterogeneity of real aquifer materials are often studied. Another is that instrumentation used to obtain microscale information often probes only one variable or family of variables at a time, so linkages to other variables must be inferred by indirect means from other lines of evidence. Despite these limitations, microscale information can be useful in the development and validation of reactive transport models. For example, knowledge of mineral phases that have strong affinities for contaminants can help in the development of cross-correlations between flow and sorption parameters via characterization of permeability and mineral distributions in aquifers. Likewise, microscale information on pore structures in low-permeability zones and contaminant penetration distances into these zones from higher-permeability zones (e.g., fractures) can provide valuable constraints on the representation of diffusive mass transfer processes between flowing porosity and secondary porosity. The prioritization of obtaining microscale information in any groundwater system can be informed by modeling exercises such as those conducted for this study.

Micro-Bubble Experiments at the Van de Graaff Accelerator

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

Sun, Z. J.; Wardle, Kent E.; Quigley, K. J.

In order to test and verify the experimental designs at the linear accelerator (LINAC), several micro-scale bubble ("micro-bubble") experiments were conducted with the 3-MeV Van de Graaff (VDG) electron accelerator. The experimental setups included a square quartz tube, sodium bisulfate solution with different concentrations, cooling coils, gas chromatography (GC) system, raster magnets, and two high-resolution cameras that were controlled by a LabVIEW program. Different beam currents were applied in the VDG irradiation. Bubble generation (radiolysis), thermal expansion, thermal convection, and radiation damage were observed in the experiments. Photographs, videos, and gas formation (O 2 + H 2) data were collected.more » The micro-bubble experiments at VDG indicate that the design of the full-scale bubble experiments at the LINAC is reasonable.« less

Integrated Hydro-geomorphological Monitoring System of the Upper Bussento river basin (Cilento and Vallo Diano Geopark, S-Italy)

NASA Astrophysics Data System (ADS)

Guida, D.; Cuomo, A.; Longobardi, A.; Villani, P.; Guida, M.; Guadagnuolo, D.; Cestari, A.; Siervo, V.; Benevento, G.; Sorvino, S.; Doto, R.; Verrone, M.; De Vita, A.; Aloia, A.; Positano, P.

2012-04-01

The Mediterranean river ecosystem functionings are supported by river-aquifer interactions. The assessment of their ecological services requires interdisciplinary scientific approaches, integrate monitoring systems and inter-institutional planning and management. This poster illustrates the Hydro-geomorphological Monitoring System build-up in the Upper Bussento river basin by the University of Salerno, in agreement with the local Basin Autorities and in extension to the other river basins located in the Cilento and Vallo Diano National Park (southern Italy), recently accepted in the European Geopark Network. The Monitoring System is based on a hierarchical Hydro-geomorphological Model (HGM), improved in a multiscale, nested and object-oriented Hydro-geomorphological Informative System (HGIS, Figure 1). Hydro-objects are topologically linked and functionally bounded by Hydro-elements at various levels of homogeneity (Table 1). Spatial Hydro-geomorpho-system, HG-complex and HG-unit support respectively areal Hydro-objects, as basin, sector and catchment and linear Hydro-objects, as river, segment, reach and section. Runoff initiation points, springs, disappearing points, junctions, gaining and water losing points complete the Hydro-systems. An automatic procedure use the Pfafstetter coding to hierarchically divide a terrain into arbitrarily small hydro-geomorphological units (basin, interfluve, headwater and no-contribution areas, each with a unique label with hierarchical topological properties. To obtain a hierarchy of hydro-geomorphological units, the method is then applied recursively on each basin and interbasin, and labels of the subdivided regions are appended to the existing label of the original region. The monitoring stations are ranked consequently in main, secondary, temporary and random and located progressively at the points or sections representative for the hydro-geomorphological responses by validation control and modeling calibration. The datasets are organized into a relational geodatabase supporting tracer testings, space-time analysis and hydrological modeling. At the moment, three main station for hourly streamflow measurements are located at the terminal sections of the main basin and the two main sub-basin; secondary stations for weekly discharge measurements are located along the Upper Bussento river segment, upstream and downstream of each river reach or tributary catchments or karst spring inflow. Temporary stations are located in the representative sections of the catchments to detect stream flow losses into alluvial beds or experimental parcels in the bare karst and forested sandstone headwaters. Streamflow measurements are combined with geochemical survey and water sampling for Radon activity concentration measurements. Results of measurement campains in Radon space-time distribution within the basin are given in other contribution of same EGU session. Monitoring results confirm the hourly, daily, weekly and monthly hydrological data and validate outcomes of semi-distributed hydrological models based on previously time series, allowing both academic consultants and institutional subject to extend the Integrated Hydro-geomorphological Monitoring System to the surrounding drainage areas of the Cilento and Vallo di Diano Geopark. Keywords: River-aquifer interaction, Upper Bussento river basin, monitoring system, hydro-geomorphology, semi-distributed hydrological model. Table 1: Comparative, hierarchical Hydro-morpho-climate entities Hierarchy levelArea (Km2) Scale Orography Entity Climate Entity Morfological Entity Areal Drainage Entity Linear Drainage Entity VIII 106 1:15E6 Orogen Macroscale α Morphological Region Hydrological Region VII 105 1:10E6 Chain Sistem Macroscale β Morphological Province Hydrological Province VI 104 1:5E5 Chain Mesoscale α Morphological Sistem Basin River V 103 1:2,5E5Chain Segment Mesoscale β Morphological Sub-systemSub-Basin Torrent IV 100 1:1,0E5Orographic Group Mesoscale γ Morphological Complex Basin Sector Mid Order Channel/ Segment III 10 1: 5E4 Orographic System Microscale αMorphological Unit Watershed Low Order Channel/ Reach II 1 1:2,5E3Orographic ComplexMicroscale βMorphological ComponentCatchment Transient Channel/ Pool I 10-2 1:5E3 Orographic Unit Microscale γMorphological Element Hollow Zero Order Channel PIC

A review on microscale polymerase chain reaction based methods in molecular diagnosis, and future prospects for the fabrication of fully integrated portable biomedical devices.

PubMed

Lee, Nae Yoon

2018-05-08

Since the advent of microfabrication technology and soft lithography, the lab-on-a-chip concept has emerged as a state-of-the-art miniaturized tool for conducting the multiple functions associated with micro total analyses of nucleic acids, in series, in a seamless manner with a miniscule volume of sample. The enhanced surface-to-volume ratio inside a microchannel enables fast reactions owing to increased heat dissipation, allowing rapid amplification. For this reason, PCR has been one of the first applications to be miniaturized in a portable format. However, the nature of the basic working principle for microscale PCR, such as the complicated temperature controls and use of a thermal cycler, has hindered its total integration with other components into a micro total analyses systems (μTAS). This review (with 179 references) surveys the diverse forms of PCR microdevices constructed on the basis of different working principles and evaluates their performances. The first two main sections cover the state-of-the-art in chamber-type PCR microdevices and in continuous-flow PCR microdevices. Methods are then discussed that lead to microdevices with upstream sample purification and downstream detection schemes, with a particular focus on rapid on-site detection of foodborne pathogens. Next, the potential for miniaturizing and automating heaters and pumps is examined. The review concludes with sections on aspects of complete functional integration in conjunction with nanomaterial based sensing, a discussion on future prospects, and with conclusions. Graphical abstract In recent years, thermocycler-based PCR systems have been miniaturized to palm-sized, disposable polymer platforms. In addition, operational accessories such as heaters and mechanical pumps have been simplified to realize semi-automatted stand-alone portable biomedical diagnostic microdevices that are directly applicable in the field. This review summarizes the progress made and the current state of this field.

Method for producing electrodes using microscale or nanoscale materials obtained from hydrogendriven metallurgical reactions

DOEpatents

Reilly, James J.; Adzic, Gordana D.; Johnson, John R.; Vogt, Thomas; McBreen, James

2003-09-02

A method is provided for producing electrodes using microscale and nanoscale metal materials formed from hydrogen driven metallurgical processes; such a the HD (hydriding, dehydriding) process, the HDDR (hydriding, dehydriding, disproportionation, and recombination) process, and variants thereof.

Micro and Macroscale Drivers of Nutrient Concentrations in Urban Streams in South, Central and North America.

PubMed

Loiselle, Steven A; Gasparini Fernandes Cunha, Davi; Shupe, Scott; Valiente, Elsa; Rocha, Luciana; Heasley, Eleanore; Belmont, Patricia Pérez; Baruch, Avinoam

Global metrics of land cover and land use provide a fundamental basis to examine the spatial variability of human-induced impacts on freshwater ecosystems. However, microscale processes and site specific conditions related to bank vegetation, pollution sources, adjacent land use and water uses can have important influences on ecosystem conditions, in particular in smaller tributary rivers. Compared to larger order rivers, these low-order streams and rivers are more numerous, yet often under-monitored. The present study explored the relationship of nutrient concentrations in 150 streams in 57 hydrological basins in South, Central and North America (Buenos Aires, Curitiba, São Paulo, Rio de Janeiro, Mexico City and Vancouver) with macroscale information available from global datasets and microscale data acquired by trained citizen scientists. Average sub-basin phosphate (P-PO4) concentrations were found to be well correlated with sub-basin attributes on both macro and microscales, while the relationships between sub-basin attributes and nitrate (N-NO3) concentrations were limited. A phosphate threshold for eutrophic conditions (>0.1 mg L-1 P-PO4) was exceeded in basins where microscale point source discharge points (eg. residential, industrial, urban/road) were identified in more than 86% of stream reaches monitored by citizen scientists. The presence of bankside vegetation covaried (rho = -0.53) with lower phosphate concentrations in the ecosystems studied. Macroscale information on nutrient loading allowed for a strong separation between basins with and without eutrophic conditions. Most importantly, the combination of macroscale and microscale information acquired increased our ability to explain sub-basin variability of P-PO4 concentrations. The identification of microscale point sources and bank vegetation conditions by citizen scientists provided important information that local authorities could use to improve their management of lower order river ecosystems.

Micro and Macroscale Drivers of Nutrient Concentrations in Urban Streams in South, Central and North America

PubMed Central

Loiselle, Steven A.; Gasparini Fernandes Cunha, Davi; Shupe, Scott; Valiente, Elsa; Rocha, Luciana; Heasley, Eleanore; Belmont, Patricia Pérez; Baruch, Avinoam

2016-01-01

Global metrics of land cover and land use provide a fundamental basis to examine the spatial variability of human-induced impacts on freshwater ecosystems. However, microscale processes and site specific conditions related to bank vegetation, pollution sources, adjacent land use and water uses can have important influences on ecosystem conditions, in particular in smaller tributary rivers. Compared to larger order rivers, these low-order streams and rivers are more numerous, yet often under-monitored. The present study explored the relationship of nutrient concentrations in 150 streams in 57 hydrological basins in South, Central and North America (Buenos Aires, Curitiba, São Paulo, Rio de Janeiro, Mexico City and Vancouver) with macroscale information available from global datasets and microscale data acquired by trained citizen scientists. Average sub-basin phosphate (P-PO4) concentrations were found to be well correlated with sub-basin attributes on both macro and microscales, while the relationships between sub-basin attributes and nitrate (N-NO3) concentrations were limited. A phosphate threshold for eutrophic conditions (>0.1 mg L-1 P-PO4) was exceeded in basins where microscale point source discharge points (eg. residential, industrial, urban/road) were identified in more than 86% of stream reaches monitored by citizen scientists. The presence of bankside vegetation covaried (rho = –0.53) with lower phosphate concentrations in the ecosystems studied. Macroscale information on nutrient loading allowed for a strong separation between basins with and without eutrophic conditions. Most importantly, the combination of macroscale and microscale information acquired increased our ability to explain sub-basin variability of P-PO4 concentrations. The identification of microscale point sources and bank vegetation conditions by citizen scientists provided important information that local authorities could use to improve their management of lower order river ecosystems. PMID:27662192

Mechanical property characterization of polymeric composites reinforced by continuous microfibers

NASA Astrophysics Data System (ADS)

Zubayar, Ali

Innumerable experimental works have been conducted to study the effect of polymerization on the potential properties of the composites. Experimental techniques are employed to understand the effects of various fibers, their volume fractions and matrix properties in polymer composites. However, these experiments require fabrication of various composites which are time consuming and cost prohibitive. Advances in computational micromechanics allow us to study the various polymer based composites by using finite element simulations. The mechanical properties of continuous fiber composite strands are directional. In traditional continuous fiber laminated composites, all fibers lie in the same plane. This provides very desirable increases in the in-plane mechanical properties, but little in the transverse mechanical properties. The effect of different fiber/matrix combinations with various orientations is also available. Overall mechanical properties of different micro continuous fiber reinforced composites with orthogonal geometry are still unavailable in the contemporary research field. In this research, the mechanical properties of advanced polymeric composite reinforced by continuous micro fiber will be characterized based on analytical investigation and FE computational modeling. Initially, we have chosen IM7/PEEK, Carbon Fiber/Nylon 6, and Carbon Fiber/Epoxy as three different case study materials for analysis. To obtain the equivalent properties of the micro-hetero structures, a concept of micro-scale representative volume elements (RVEs) is introduced. Five types of micro scale RVEs (3 square and 2 hexagonal) containing a continuous micro fiber in the polymer matrix were designed. Uniaxial tensile, lateral expansion and transverse shear tests on each RVE were designed and conducted by the finite element computer modeling software ANSYS. The formulae based on elasticity theory were derived for extracting the equivalent mechanical properties (Young's moduli, shear moduli, and Poisson's ratios) from the numerical solutions of the RVEs undergone these three load tests. Validation of the obtained micro-scale mechanical properties will be performed using rule of mixture (ROM), 1st, and 2nd order of the mathematical model and experimental data.

Upscaling mixing in porous media from an experimental quantification of pore scale Lagrangian deformation statistics

NASA Astrophysics Data System (ADS)

Turuban, R.; Jimenez-Martinez, J.; De Anna, P.; Tabuteau, H.; Meheust, Y.; Le Borgne, T.

2014-12-01

As dissolved chemical elements are transported in the subsurface, their mixing with other compounds and potential reactivity depends on the creation of local scale chemical gradients, which ultimately drive diffusive mass transfer and reaction. The distribution of concentration gradients is in turn shaped by the spatial gradients of flow velocity arising from the random distribution of solid grains. We present an experimental investigation of the relationship between the microscale flow stretching properties and the effective large scale mixing dynamics in porous media. We use a flow cell that models a horizontal quasi two-dimensional (2D) porous medium, the grains of which are cylinders randomly positioned between two glass plates [de Anna et al. 2013]. In this setup, we perform both non diffusive and diffusive transport tests, by injecting respectively microsphere solid tracers and a fluorescent dye. While the dye front propagates through the medium, it undergoes in time a kinematic stretching that is controlled by the flow heterogeneity, as it encounters stagnation zones and high velocity channels between the grains. The spatial distribution of the dye can then be described as a set of stretched lamellae whose rate of diffusive smoothing is locally enhanced by kinematic stretching [Le Borgne et al., 2013]. We show that this representation allows predicting the temporal evolution of the mixing rate and the probability distribution of concentration gradients for a range of Peclet numbers. This upscaling framework hence provides a quantification of the dynamics of effective mixing from the microscale Lagrangian velocity statistics. References:[1] P. de Anna, J. Jimenez-Martinez, H. Tabuteau, R. Turuban, T. Le Borgne, M. Derrien,and Yves Méheust, Mixing and reaction kinetics in porous media : an experimental pore scale quantification, Environ. Sci. Technol. 48, 508-516, 2014. [2] Le Borgne, T., M. Dentz, E. Villermaux, Stretching, coalescence and mixing in porous media, Phys. Rev. Lett., 110, 204501 (2013)

Microscale Experiments in the Organic Chemistry Laboratory.

ERIC Educational Resources Information Center

Williamson, Kenneth L.

1991-01-01

Discusses the advent of microscale experiments within undergraduate organic chemistry laboratories mainly resulting from environmental safety concerns involving waste disposal. Considers the cost savings in purchasing less reagents and chemicals, the typical glassware and apparatus, the reduced hazards from elimination of open flames, and other…

Micro-scale thermal imaging of advanced organic and polymeric materials

NASA Astrophysics Data System (ADS)

Morikawa, Junko

2012-10-01

Recent topics of micro-scale thermal imaging on advanced organic and polymeric materials are presented, the originally developed IR camera systems equipped with a real time direct impose-signal capturing device and a laser drive generating a modulated spot heating with a diode laser, controlled by the x-y positioning actuator, has been applied to measure the micro-scale thermal phenomena. The advanced organic and polymeric materials are now actively developed especially for the purpose of the effective heat dissipation in the new energy system, including, LED, Lithium battery, Solar cell, etc. The micro-scale thermal imaging in the heat dissipation process has become important in view of the effective power saving. In our system, the imposed temperature data are applied to the pixel emissivity corrections and visualizes the anisotropic thermal properties of the composite materials at the same time. The anisotropic thermal diffusion in the ultra-drawn high-thermal conductive metal-filler composite polymer film and the carbon-cloth for the battery systems are visualized.

Effects of microscale inertia on dynamic ductile crack growth

NASA Astrophysics Data System (ADS)

Jacques, N.; Mercier, S.; Molinari, A.

2012-04-01

The aim of this paper is to investigate the role of microscale inertia in dynamic ductile crack growth. A constitutive model for porous solids that accounts for dynamic effects due to void growth is proposed. The model has been implemented in a finite element code and simulations of crack growth in a notched bar and in an edge cracked specimen have been performed. Results are compared to predictions obtained via the Gurson-Tvergaard-Needleman (GTN) model where micro-inertia effects are not accounted for. It is found that microscale inertia has a significant influence on the crack growth. In particular, it is shown that micro-inertia plays an important role during the strain localisation process by impeding void growth. Therefore, the resulting damage accumulation occurs in a more progressive manner. For this reason, simulations based on the proposed modelling exhibit much less mesh sensitivity than those based on the viscoplastic GTN model. Microscale inertia is also found to lead to lower crack speeds. Effects of micro-inertia on fracture toughness are evaluated.

Phase transformations in steels: Processing, microstructure, and performance

DOE PAGES

Gibbs, Paul J.

2014-04-03

In this study, contemporary steel research is revealing new processing avenues to tailor microstructure and properties that, until recently, were only imaginable. Much of the technological versatility facilitating this development is provided by the understanding and utilization of the complex phase transformation sequences available in ferrous alloys. Today we have the opportunity to explore the diverse phenomena displayed by steels with specialized analytical and experimental tools. Advances in multi-scale characterization techniques provide a fresh perspective into microstructural relationships at the macro- and micro-scale, enabling a fundamental understanding of the role of phase transformations during processing and subsequent deformation.

Catalytic micromotor generating self-propelled regular motion through random fluctuation.

PubMed

Yamamoto, Daigo; Mukai, Atsushi; Okita, Naoaki; Yoshikawa, Kenichi; Shioi, Akihisa

2013-07-21

Most of the current studies on nano∕microscale motors to generate regular motion have adapted the strategy to fabricate a composite with different materials. In this paper, we report that a simple object solely made of platinum generates regular motion driven by a catalytic chemical reaction with hydrogen peroxide. Depending on the morphological symmetry of the catalytic particles, a rich variety of random and regular motions are observed. The experimental trend is well reproduced by a simple theoretical model by taking into account of the anisotropic viscous effect on the self-propelled active Brownian fluctuation.

Catalytic micromotor generating self-propelled regular motion through random fluctuation

NASA Astrophysics Data System (ADS)

Yamamoto, Daigo; Mukai, Atsushi; Okita, Naoaki; Yoshikawa, Kenichi; Shioi, Akihisa

2013-07-01

Most of the current studies on nano/microscale motors to generate regular motion have adapted the strategy to fabricate a composite with different materials. In this paper, we report that a simple object solely made of platinum generates regular motion driven by a catalytic chemical reaction with hydrogen peroxide. Depending on the morphological symmetry of the catalytic particles, a rich variety of random and regular motions are observed. The experimental trend is well reproduced by a simple theoretical model by taking into account of the anisotropic viscous effect on the self-propelled active Brownian fluctuation.

Crystal growth of device quality GaAs in space

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Lagowski, J.

1984-01-01

The crystal growth, device processing and device related properties and phenomena of GaAs are investigated. Our GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor materials (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; (3) investigation of electronic properties and phenomena controlling device applications and device performance. The ground based program is developed which would insure successful experimentation with and eventually processing of GaAs in a near zero gravity environment.

Micro-scale environment and mental health in later life: Results from the Cognitive Function and Ageing Study II (CFAS II).

PubMed

Wu, Yu-Tzu; Prina, A Matthew; Jones, Andy; Barnes, Linda E; Matthews, Fiona E; Brayne, Carol

2017-08-15

Poor micro-scale environmental features, such as graffiti and broken windows, have been associated with crime and signs of social disorder with a potential impact on mental health. The aim of this study is to investigate the association between micro-scale environment and mental health problems in later life, including cognitive (cognitive impairment and dementia) and common mental disorders (depressive and anxiety symptoms). The method of visual image audits was used to collect micro-scale environmental data for 3590 participants in the Cognitive Function and Ageing Study II, a population-based multicentre cohort of people aged 65 or above in England. Multilevel logistic regression was used to examine the associations between the quality of micro-scale environment and mental health problems taking into account urban/rural difference. Poor quality of micro-scale environment was associated with nearly 20% increased odds of depressive (OR: 1.19; 95% CI: 0.99, 1.44) and anxiety symptoms (OR: 1.17; 95% CI: 0.99, 1.38) while the direction of association for cognitive disorders differed across urban and rural settings. Although higher odds of cognitive disorders were found in rural settings, living in a poor quality environment was associated with nearly twice higher odds of cognitive impairment (OR: 1.88; 95% CI: 1.18, 2.97) in urban conurbations but 20% lower odds in rural areas (OR: 0.80; 95% CI: 0.57, 1.11). The causal direction could not be fully determined due to the cross-sectional nature of the data. The visual nature of the environmental assessment tool means it likely does not fully capture features related to the availability of local support services, or opportunities for social participation and interaction. The quality of micro-scale environment appears to be important to mental health in older people. Interventions may incorporate the environmental aspect to reduce cognitive and common mental disorders. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Investigation of microscale dielectric barrier discharge plasma devices

NASA Astrophysics Data System (ADS)

Zito, Justin C.

This dissertation presents research performed on reduced-scale dielectric barrier discharge (DBD) plasma actuators. A first generation of microscale DBD actuators are designed and manufactured using polymeric dielectric layers, and successfully demonstrate operation at reduced scales. The actuators are 1 cm long and vary in width from tens of microns to several millimeters. A thin-film polymer or ceramic material is used as the dielectric barrier with thicknesses from 5 to 20 microns. The devices are characterized for their electrical, fluidic and mechanical performance. With electrical input of 5 kVpp, 1 kHz, the microscale DBD actuators induce a wall jet with velocity reaching up to 2 m/s and produce 3.5 mN/m of thrust, while consuming an average power of 20 W/m. A 5 mN/m plasma body force was observed, acting on the surrounding air. Failure of the microscale DBD actuators is investigated using thermal measurements of the dielectric surface in addition to both optical and scanning electron microscopy. The cause of device failure is identified as erosion of the dielectric surface due to collisions with ions from the discharge. A second generation of microscale actuators is then designed and manufactured using a more reliable dielectric material, namely silicon dioxide. These actuators demonstrate a significant improvement in device lifetime compared with first-generation microscale DBD actuators. The increase in actuator lifetime allowed the electrical, fluidic and mechanical characterization to be repeated over several input voltages and frequencies. At 7 kVpp, 1 kHz, the actuators with SiO2 dielectric induced velocities up to 1.5 m/s and demonstrated 1.4 mN/m of thrust while consuming an average power of 41 W/m. The plasma body force reached up to 2.5 mN/m. Depending on electrical input, the induced velocity and thrust span an order of magnitude in range. Comparisons are made with macroscale DBD actuators which relate the actuator's output performance and power consumption with the mass and volume of the actuator design. The small size and of microscale DBD actuators reduces its weight and power requirements, making them attractive for portable or battery-powered applications (e.g., on UAVs).

Quantitative Investigation of the Role of Intra-/Intercellular Dynamics in Bacterial Quorum Sensing.

PubMed

Leaman, Eric J; Geuther, Brian Q; Behkam, Bahareh

2018-04-20

Bacteria utilize diffusible signals to regulate population density-dependent coordinated gene expression in a process called quorum sensing (QS). While the intracellular regulatory mechanisms of QS are well-understood, the effect of spatiotemporal changes in the population configuration on the sensitivity and robustness of the QS response remains largely unexplored. Using a microfluidic device, we quantitatively characterized the emergent behavior of a population of swimming E. coli bacteria engineered with the lux QS system and a GFP reporter. We show that the QS activation time follows a power law with respect to bacterial population density, but this trend is disrupted significantly by microscale variations in population configuration and genetic circuit noise. We then developed a computational model that integrates population dynamics with genetic circuit dynamics to enable accurate (less than 7% error) quantitation of the bacterial QS activation time. Through modeling and experimental analyses, we show that changes in spatial configuration of swimming bacteria can drastically alter the QS activation time, by up to 22%. The integrative model developed herein also enables examination of the performance robustness of synthetic circuits with respect to growth rate, circuit sensitivity, and the population's initial size and spatial structure. Our framework facilitates quantitative tuning of microbial systems performance through rational engineering of synthetic ribosomal binding sites. We have demonstrated this through modulation of QS activation time over an order of magnitude. Altogether, we conclude that predictive engineering of QS-based bacterial systems requires not only the precise temporal modulation of gene expression (intracellular dynamics) but also accounting for the spatiotemporal changes in population configuration (intercellular dynamics).

Flow topologies and turbulence scales in a jet-in-cross-flow

DOE PAGES

Oefelein, Joseph C.; Ruiz, Anthony M.; Lacaze, Guilhem

2015-04-03

This study presents a detailed analysis of the flow topologies and turbulence scales in the jet-in-cross-flow experiment of [Su and Mungal JFM 2004]. The analysis is performed using the Large Eddy Simulation (LES) technique with a highly resolved grid and time-step and well controlled boundary conditions. This enables quantitative agreement with the first and second moments of turbulence statistics measured in the experiment. LES is used to perform the analysis since experimental measurements of time-resolved 3D fields are still in their infancy and because sampling periods are generally limited with direct numerical simulation. A major focal point is the comprehensivemore » characterization of the turbulence scales and their evolution. Time-resolved probes are used with long sampling periods to obtain maps of the integral scales, Taylor microscales, and turbulent kinetic energy spectra. Scalar-fluctuation scales are also quantified. In the near-field, coherent structures are clearly identified, both in physical and spectral space. Along the jet centerline, turbulence scales grow according to a classical one-third power law. However, the derived maps of turbulence scales reveal strong inhomogeneities in the flow. From the modeling perspective, these insights are useful to design optimized grids and improve numerical predictions in similar configurations.« less

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

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

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H +/OH – transport) and electric field-driven migrationmore » on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Altogether, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.« less

All-optical control of light on a graphene-on-silicon nitride chip using thermo-optic effect.

PubMed

Qiu, Ciyuan; Yang, Yuxing; Li, Chao; Wang, Yifang; Wu, Kan; Chen, Jianping

2017-12-06

All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si 3 N 4 ) provides a possibility to realize all-optical large-scale integrated circuits due to its insulator nature without TPA and FCA. In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si 3 N 4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.

ON THE BIOMECHANICAL FUNCTION OF SCAFFOLDS FOR ENGINEERING LOAD BEARING SOFT TISSUES

PubMed Central

Stella, John A.; D’Amore, Antonio; Wagner, William R.; Sacks, Michael S.

2010-01-01

Replacement or regeneration of load bearing soft tissues has long been the impetus for the development bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors. PMID:20060509

Full cell simulation and the evaluation of the buffer system on air-cathode microbial fuel cell

DOE PAGES

Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; ...

2017-02-23

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H +/OH – transport) and electric field-driven migrationmore » on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Altogether, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system.« less

Acoustofluidic waveguides for localized control of acoustic wavefront in microfluidics

PubMed Central

Bian, Yusheng; Guo, Feng; Yang, Shujie; Mao, Zhangming; Bachman, Hunter; Tang, Shi-Yang; Ren, Liqiang; Zhang, Bin; Gong, Jianying; Guo, Xiasheng

2017-01-01

The precise manipulation of acoustic fields in microfluidics is of critical importance for the realization of many biomedical applications. Despite the tremendous efforts devoted to the field of acoustofluidics during recent years, dexterous control, with an arbitrary and complex acoustic wavefront, in a prescribed, microscale region is still out of reach. Here, we introduce the concept of acoustofluidic waveguide, a three-dimensional compact configuration that is capable of locally guiding acoustic waves into a fluidic environment. Through comprehensive numerical simulations, we revealed the possibility of forming complex field patterns with defined pressure nodes within a highly localized, pre-determined region inside the microfluidic chamber. We also demonstrated the tunability of the acoustic field profile through controlling the size and shape of the waveguide geometry, as well as the operational frequency of the acoustic wave. The feasibility of the waveguide concept was experimentally verified via microparticle trapping and patterning. Our acoustofluidic waveguiding structures can be readily integrated with other microfluidic configurations and can be further designed into more complex types of passive acoustofluidic devices. The waveguide platform provides a promising alternative to current acoustic manipulation techniques and is useful in many applications such as single-cell analysis, point-of-care diagnostics, and studies of cell–cell interactions. PMID:29358901

Dynamic properties of micro-particles in ultrasonic transportation using phase-controllable standing waves

NASA Astrophysics Data System (ADS)

Jia, Kun; Mei, Deqing; Meng, Jianxin; Yang, Keji

2014-10-01

Ultrasonic manipulation has become an attractive method for surface-sensitive objects in micro-technology. Related phenomena, such as radiation force, multiple scattering, and acoustic streaming, have been widely studied. However, in current studies, the behavior of micro-particles in potential force fields is always analyzed in a quasi-static manner. We developed a dynamic model of a dilute micro-particle in the commonly used two-dimensional ultrasonic manipulation system to provide a systemic and quantitative analysis of the transient properties of particle movement. In this model, the acoustic streaming and hydrodynamic forces, omitted in previous work, were both considered. The trajectory of a spherical silica particle with different initial conditions was derived by numerically solving the established nonlinear differential integral equation system, which was then validated experimentally. The envelope of the experimental data on the x-axis showed good agreement with the theoretical calculation, and the greater influence on the y-axis of the deviation between the actual sound field and the ideal distribution employed in our dynamic model could account for the differences in displacement in that direction. Finally, the influence of particle size on its movement and the effect of acoustic streaming on calculating the hydrodynamic forces for an isolated particle with motion relative to the fluid were analyzed theoretically. It was found that the ultrasonic manipulation system will translate from an under-damped system to an over-damped system with a decrease in particle size and the micro-scale acoustic streaming velocity was negligible when calculating the hydrodynamic forces on the particle in the ultrasonic manipulation system.

On the influence of microscale inertia on dynamic ductile crack extension

NASA Astrophysics Data System (ADS)

Jacques, N.; Mercier, S.; Molinari, A.

2012-08-01

The present paper is devoted to the modelling of damage by micro-voiding in ductile solids under dynamic loading conditions. Using a dynamic homogenization procedure, a constitutive damage model accounting for inertial effects due to void growth (microscale inertia or micro-inertia) has been developed. The role played by microscale inertia in dynamic ductile crack growth is investigated with the use of the proposed micromechanical modelling. It is found that micro-inertia has a significant influence on the fracture behaviour. Micro-inertia limits the velocity at which cracks propagate. It also contributes to increase the apparent dynamic toughness of the material.

Accelerated design of bioconversion processes using automated microscale processing techniques.

PubMed

Lye, Gary J; Ayazi-Shamlou, Parviz; Baganz, Frank; Dalby, Paul A; Woodley, John M

2003-01-01

Microscale processing techniques are rapidly emerging as a means to increase the speed of bioprocess design and reduce material requirements. Automation of these techniques can reduce labour intensity and enable a wider range of process variables to be examined. This article examines recent research on various individual microscale unit operations including microbial fermentation, bioconversion and product recovery techniques. It also explores the potential of automated whole process sequences operated in microwell formats. The power of the whole process approach is illustrated by reference to a particular bioconversion, namely the Baeyer-Villiger oxidation of bicyclo[3.2.0]hept-2-en-6-one for the production of optically pure lactones.

Using a Microscale Approach to Rapidly Separate and Characterize Three Photosynthetic Pigment Species from Fern

ERIC Educational Resources Information Center

Ayudhya, Theppawut Israsena Na; Posey, Frederick T.; Tyus, Jessica C.; Dingra, Nin N.

2015-01-01

A rapid separation of three photosynthetic pigments (chlorophyll "a" and "b" and xanthophyll) from fern ("Polystichum acrostichoides") is described using microscale solvent extraction and traditional thin layer chromatography that minimizes use of harmful chemicals and lengthy procedures. The experiment introduces…

Microwave-Assisted Esterification: A Discovery-Based Microscale Laboratory Experiment

ERIC Educational Resources Information Center

Reilly, Maureen K.; King, Ryan P.; Wagner, Alexander J.; King, Susan M.

2014-01-01

An undergraduate organic chemistry laboratory experiment has been developed that features a discovery-based microscale Fischer esterification utilizing a microwave reactor. Students individually synthesize a unique ester from known sets of alcohols and carboxylic acids. Each student identifies the best reaction conditions given their particular…

Zebrafish Embryo Toxicity Microscale Model for Ichthyotoxicity Evaluation of Marine Natural Products.

PubMed

Bai, Hong; Kong, Wen-Wen; Shao, Chang-Lun; Li, Yun; Liu, Yun-Zhang; Liu, Min; Guan, Fei-Fei; Wang, Chang-Yun

2016-04-01

Marine organisms often protect themselves against their predators by chemical defensive strategy. The second metabolites isolated from marine organisms and their symbiotic microbes have been proven to play a vital role in marine chemical ecology, such as ichthyotoxicity, allelopathy, and antifouling. It is well known that the microscale models for marine chemoecology assessment are urgently needed for trace quantity of marine natural products. Zebrafish model has been widely used as a microscale model in the fields of environment ecological evaluation and drug safety evaluation, but seldom reported for marine chemoecology assessment. In this work, zebrafish embryo toxicity microscale model was established for ichthyotoxicity evaluation of marine natural products by using 24-well microplate based on zebrafish embryo. Ichthyotoxicity was evaluated by observation of multiple toxicological endpoints, including coagulation egg, death, abnormal heartbeat, no spontaneous movement, delayed hatch, and malformation of the different organs during zebrafish embryogenesis periods at 24, 48, and 72 h post-fertilization (hpf). 3,4-Dichloroaniline was used as the positive control for method validation. Subsequently, the established model was applied to test the ichthyotoxic activity of the compounds isolated from corals and their symbiotic microbes and to isolate the bioactive secondary metabolites from the gorgonian Subergorgia mollis under bioassay guidance. It was suggested that zebrafish embryo toxicity microscale model is suitable for bioassay-guided isolation and preliminary bioactivity screening of marine natural products.

Microscale architecture in biomaterial scaffolds for spatial control of neural cell behavior

NASA Astrophysics Data System (ADS)

Meco, Edi; Lampe, Kyle J.

2018-02-01

Biomaterial scaffolds mimic aspects of the native central nervous system (CNS) extracellular matrix (ECM) and have been extensively utilized to influence neural cell (NC) behavior in in vitro and in vivo settings. These biomimetic scaffolds support NC cultures, can direct the differentiation of NCs, and have recapitulated some native NC behavior in an in vitro setting. However, NC transplant therapies and treatments used in animal models of CNS disease and injury have not fully restored functionality. The observed lack of functional recovery occurs despite improvements in transplanted NC viability when incorporating biomaterial scaffolds and the potential of NC to replace damaged native cells. The behavior of NCs within biomaterial scaffolds must be directed in order to improve the efficacy of transplant therapies and treatments. Biomaterial scaffold topography and imbedded bioactive cues, designed at the microscale level, can alter NC phenotype, direct migration, and differentiation. Microscale patterning in biomaterial scaffolds for spatial control of NC behavior has enhanced the capabilities of in vitro models to capture properties of the native CNS tissue ECM. Patterning techniques such as lithography, electrospinning and 3D bioprinting can be employed to design the microscale architecture of biomaterial scaffolds. Here, the progress and challenges of the prevalent biomaterial patterning techniques of lithography, electrospinning, and 3D bioprinting are reported. This review analyzes NC behavioral response to specific microscale topographical patterns and spatially organized bioactive cues.

Diameter-tailored telecom-band luminescence in InP/InAs heterostructure nanowires grown on InP (111)B substrate with continuously-modulated diameter from microscale to nanoscale

NASA Astrophysics Data System (ADS)

Zhang, Guoqiang; Tateno, Kouta; Sogawa, Tetsuomi; Gotoh, Hideki

2018-04-01

We report diameter-tailored luminescence in telecom band of InP/InAs multi-heterostructure nanowires with continuously-modulated diameter from microscale to nanoscale. By using the self-catalyzed vapor-solid-liquid approach, we tune the indium particle size, and consequently the InP/InAs nanowire diameter, during growth by modulating the flow rate of the indium source material. This technique allows a high degree of continuous tuning in a wide scale from microscale to nanoscale. Hence it offers an original way to bridge the gap between microscale-featured photolithographic and nanoscale-featured nanolithographic processes and to incorporate InAs quantum disks with tunable diameters into a single InP/InAs quantum heterostructure nanowire. We realized site-defined nanowires with nanoscale diameters initiated from site-defined microscale-diameter particles made with a conventional photolithographic process. The luminescence wavelength from InAs quantum disks is directly connected to the nanowire diameter, by which the strain in the InAs quantum disks is tailored. This work provides new opportunities in the fabrication and design of nanowire devices that extends beyond what is achievable with the current technologies and enables the nanowire shape to be engineered thus offering the potential to broaden the application range of nanowire devices.

Diameter-tailored telecom-band luminescence in InP/InAs heterostructure nanowires grown on InP (111)B substrate with continuously-modulated diameter from microscale to nanoscale.

PubMed

Zhang, Guoqiang; Tateno, Kouta; Sogawa, Tetsuomi; Gotoh, Hideki

2018-04-02

We report diameter-tailored luminescence in telecom band of InP/InAs multi-heterostructure nanowires with continuously-modulated diameter from microscale to nanoscale. By using the self-catalyzed vapor-solid-liquid approach, we tune the indium particle size, and consequently the InP/InAs nanowire diameter, during growth by modulating the flow rate of the indium source material. This technique allows a high degree of continuous tuning in a wide scale from microscale to nanoscale. Hence it offers an original way to bridge the gap between microscale-featured photolithographic and nanoscale-featured nanolithographic processes and to incorporate InAs quantum disks with tunable diameters into a single InP/InAs quantum heterostructure nanowire. We realized site-defined nanowires with nanoscale diameters initiated from site-defined microscale-diameter particles made with a conventional photolithographic process. The luminescence wavelength from InAs quantum disks is directly connected to the nanowire diameter, by which the strain in the InAs quantum disks is tailored. This work provides new opportunities in the fabrication and design of nanowire devices that extends beyond what is achievable with the current technologies and enables the nanowire shape to be engineered thus offering the potential to broaden the application range of nanowire devices.

Direct Prototyping of Patterned Nanoporous Carbon: A Route from Materials to On-chip Devices

PubMed Central

Shen, Caiwei; Wang, Xiaohong; Zhang, Wenfeng; Kang, Feiyu

2013-01-01

Prototyping of nanoporous carbon membranes with three-dimensional microscale patterns is significant for integration of such multifunctional materials into various miniaturized systems. Incorporating nano material synthesis into microelectronics technology, we present a novel approach to direct prototyping of carbon membranes with highly nanoporous structures inside. Membranes with significant thicknesses (1 ~ 40 μm) are rapidly prototyped at wafer level by combining nano templating method with readily available microfabrication techniques, which include photolithography, high-temperature annealing and etching. In particular, the high-surface-area membranes are specified as three-dimensional electrodes for micro supercapacitors and show high performance compared to reported ones. Improvements in scalability, compatibility and cost make the general strategy promising for batch fabrication of operational on-chip devices or full integration of three-dimensional nanoporous membranes with existing micro systems. PMID:23887486

Optogenetic activation of neocortical neurons in vivo with a sapphire-based micro-scale LED probe.

PubMed

McAlinden, Niall; Gu, Erdan; Dawson, Martin D; Sakata, Shuzo; Mathieson, Keith

2015-01-01

Optogenetics has proven to be a revolutionary technology in neuroscience and has advanced continuously over the past decade. However, optical stimulation technologies for in vivo need to be developed to match the advances in genetics and biochemistry that have driven this field. In particular, conventional approaches for in vivo optical illumination have a limitation on the achievable spatio-temporal resolution. Here we utilize a sapphire-based microscale gallium nitride light-emitting diode (μLED) probe to activate neocortical neurons in vivo. The probes were designed to contain independently controllable multiple μLEDs, emitting at 450 nm wavelength with an irradiance of up to 2 W/mm(2). Monte-Carlo stimulations predicted that optical stimulation using a μLED can modulate neural activity within a localized region. To validate this prediction, we tested this probe in the mouse neocortex that expressed channelrhodopsin-2 (ChR2) and compared the results with optical stimulation through a fiber at the cortical surface. We confirmed that both approaches reliably induced action potentials in cortical neurons and that the μLED probe evoked strong responses in deep neurons. Due to the possibility to integrate many optical stimulation sites onto a single shank, the μLED probe is thus a promising approach to control neurons locally in vivo.

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications.

PubMed

Farahani, Rouhollah D; Dubé, Martine; Therriault, Daniel

2016-07-01

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effective Light Directed Assembly of Building Blocks with Microscale Control.

PubMed

Dinh, Ngoc-Duy; Luo, Rongcong; Christine, Maria Tankeh Asuncion; Lin, Weikang Nicholas; Shih, Wei-Chuan; Goh, James Cho-Hong; Chen, Chia-Hung

2017-06-01

Light-directed forces have been widely used to pattern micro/nanoscale objects with precise control, forming functional assemblies. However, a substantial laser intensity is required to generate sufficient optical gradient forces to move a small object in a certain direction, causing limited throughput for applications. A high-throughput light-directed assembly is demonstrated as a printing technology by introducing gold nanorods to induce thermal convection flows that move microparticles (diameter = 40 µm to several hundreds of micrometers) to specific light-guided locations, forming desired patterns. With the advantage of effective light-directed assembly, the microfluidic-fabricated monodispersed biocompatible microparticles are used as building blocks to construct a structured assembly (≈10 cm scale) in ≈2 min. The control with microscale precision is approached by changing the size of the laser light spot. After crosslinking assembly of building blocks, a novel soft material with wanted pattern is approached. To demonstrate its application, the mesenchymal stem-cell-seeded hydrogel microparticles are prepared as functional building blocks to construct scaffold-free tissues with desired structures. This light-directed fabrication method can be applied to integrate different building units, enabling the bottom-up formation of materials with precise control over their internal structure for bioprinting, tissue engineering, and advanced manufacturing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microscale force response and morphology of tunable co-polymerized cytoskeleton networks

NASA Astrophysics Data System (ADS)

Ricketts, Shea; Yadav, Vikrant; Ross, Jennifer L.; Robertson-Anderson, Rae M.

The cytoskeleton is largely comprised of actin and microtubules that entangle and crosslink to form complex networks and structures, giving rise to nonlinear multifunctional mechanics in cells. The relative concentrations of semiflexible actin filaments and rigid microtubules tune cytoskeleton function, allowing cells to move and divide while maintaining rigidity and resilience. To elucidate this complex tunability, we create in vitro composites of co-polymerized actin and microtubules with actin:microtubule molar ratios of 0:1-1:0. We use optical tweezers and confocal microscopy to characterize the nonlinear microscale force response and morphology of the composites. We optically drag a microsphere 30 μm through varying actin-microtubule networks at 10 μm/s and 20 μm/s, and measure the force the networks exerts to resist the strain and the force relaxation following strain. We use dual-color confocal microscopy to image distinctly-labeled filaments in the networks, and characterize the integration of actin and microtubules, network connectivity, and filament rigidity. We find that increasing the fraction of microtubules in networks non-monotonically increases elasticity and stiffness, and hinders force relaxation by suppressing network mobility and fluctuations. NSF CAREER Award (DMR-1255446), Scialog Collaborative Innovation Award funded by Research Corporation for Scientific Advancement (Grant No. 24192).

Laser vaporization/ionization interface for coupling microscale separation techniques with mass spectrometry

DOEpatents

Yeung, Edward S.; Chang, Yu-chen

1999-06-29

The present invention provides a laser-induced vaporization and ionization interface for directly coupling microscale separation processes to a mass spectrometer. Vaporization and ionization of the separated analytes are facilitated by the addition of a light-absorbing component to the separation buffer or solvent.

Microscale Synthesis of 1-Bromo-3-Chloro-5-Iodobenzene: An Improved Deamination of 4-Bromo-2-Chloro-6-Iodoaniline

ERIC Educational Resources Information Center

Pelter, Michael W.; Pelter, Libbie S. W.; Colovic, Dusanka; Strug, Regina

2004-01-01

The sequence of microscale mixing of 1-bromo-3-chloro-5-iodobenzene along with reductive deamination of 4-bromo-2-chloro-6-iodoaniline is described. This novel deamination approach is beneficial in final product separation and higher product output.

Thermal Equilibrium in Plastic and Glass Microscale Containers

ERIC Educational Resources Information Center

Curbelo, Estela; Cerda, Maria F.; Mendez, Eduardo

2007-01-01

The study describes the various thermal equilibrium conditions, which should be taken care for while designing or selecting the plastic and glass microscale containers for physical chemistry experiments. The results show that the thermal equilibrium completely depends on the material of the container for the same volume and thickness.

Laser vaporization/ionization interface for coupling microscale separation techniques with mass spectrometry

DOEpatents

Yeung, E.S.; Chang, Y.C.

1999-06-29

The present invention provides a laser-induced vaporization and ionization interface for directly coupling microscale separation processes to a mass spectrometer. Vaporization and ionization of the separated analytes are facilitated by the addition of a light-absorbing component to the separation buffer or solvent. 8 figs.

Microscale and Compact Scale Chemistry in South Africa

ERIC Educational Resources Information Center

Taylor, Warwick

2011-01-01

Reduced costs and greater time efficiency are often quoted among the main benefits of microscale chemistry. Do these benefits outweigh some of the limitations and difficulties faced in terms of students needing to develop new manipulation skills, and teachers requiring training in terms of implementation and management? This article describes a…

Convenient Microscale Synthesis of a Coumarin Laser Dye Analog

ERIC Educational Resources Information Center

Aktoudianakis, Evangelos; Dicks, Andrew P.

2006-01-01

Coumarin (2H-1-benzopyran-2-one) and its derivatives constitute a fascinating class of organic substances that are utilized industrially in areas such as cosmetics, food preservatives, insecticides and fluorescent laser dyes. The product can be synthesized, purified, and characterized within two hours with benefits of microscale reactivity being…

A reversibly sealed, easy access, modular (SEAM) microfluidic architecture to establish in vitro tissue interfaces

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

Abhyankar, Vinay V.; Wu, Meiye; Koh, Chung -Yan

Microfluidic barrier tissue models have emerged as advanced in vitro tools to explore interactions with external stimuli such as drug candidates, pathogens, or toxins. However, the procedures required to establish and maintain these systems can be challenging to implement for end users, particularly those without significant in-house engineering expertise. Here we present a module-based approach that provides an easy-to-use workflow to establish, maintain, and analyze microscale tissue constructs. Our approach begins with a removable culture insert that is magnetically coupled, decoupled, and transferred between standalone, prefabricated microfluidic modules for simplified cell seeding, culture, and downstream analysis. The modular approach allowsmore » several options for perfusion including standard syringe pumps or integration with a self-contained gravity-fed module for simple cell maintenance. As proof of concept, we establish a culture of primary human microvascular endothelial cells (HMVEC) and report combined surface protein imaging and gene expression after controlled apical stimulation with the bacterial endotoxin lipopolysaccharide (LPS). We also demonstrate the feasibility of incorporating hydrated biomaterial interfaces into the microfluidic architecture by integrating an ultra-thin (< 1 μm), self-assembled hyaluronic acid/peptide amphiphile culture membrane with brain-specific Young’s modulus (~ 1kPa). To highlight the importance of including biomimetic interfaces into microscale models we report multi-tiered readouts from primary rat cortical cells cultured on the self-assembled membrane and compare a panel of mRNA targets with primary brain tissue signatures. As a result, we anticipate that the modular approach and simplified operational workflows presented here will enable a wide range of research groups to incorporate microfluidic barrier tissue models into their work.« less

A reversibly sealed, easy access, modular (SEAM) microfluidic architecture to establish in vitro tissue interfaces

DOE PAGES

Abhyankar, Vinay V.; Wu, Meiye; Koh, Chung -Yan; ...

2016-05-26

Microfluidic barrier tissue models have emerged as advanced in vitro tools to explore interactions with external stimuli such as drug candidates, pathogens, or toxins. However, the procedures required to establish and maintain these systems can be challenging to implement for end users, particularly those without significant in-house engineering expertise. Here we present a module-based approach that provides an easy-to-use workflow to establish, maintain, and analyze microscale tissue constructs. Our approach begins with a removable culture insert that is magnetically coupled, decoupled, and transferred between standalone, prefabricated microfluidic modules for simplified cell seeding, culture, and downstream analysis. The modular approach allowsmore » several options for perfusion including standard syringe pumps or integration with a self-contained gravity-fed module for simple cell maintenance. As proof of concept, we establish a culture of primary human microvascular endothelial cells (HMVEC) and report combined surface protein imaging and gene expression after controlled apical stimulation with the bacterial endotoxin lipopolysaccharide (LPS). We also demonstrate the feasibility of incorporating hydrated biomaterial interfaces into the microfluidic architecture by integrating an ultra-thin (< 1 μm), self-assembled hyaluronic acid/peptide amphiphile culture membrane with brain-specific Young’s modulus (~ 1kPa). To highlight the importance of including biomimetic interfaces into microscale models we report multi-tiered readouts from primary rat cortical cells cultured on the self-assembled membrane and compare a panel of mRNA targets with primary brain tissue signatures. As a result, we anticipate that the modular approach and simplified operational workflows presented here will enable a wide range of research groups to incorporate microfluidic barrier tissue models into their work.« less

TOPICAL REVIEW: Integrated genetic analysis microsystems

NASA Astrophysics Data System (ADS)

Lagally, Eric T.; Mathies, Richard A.

2004-12-01

With the completion of the Human Genome Project and the ongoing DNA sequencing of the genomes of other animals, bacteria, plants and others, a wealth of new information about the genetic composition of organisms has become available. However, as the demand for sequence information grows, so does the workload required both to generate this sequence and to use it for targeted genetic analysis. Microfabricated genetic analysis systems are well poised to assist in the collection and use of these data through increased analysis speed, lower analysis cost and higher parallelism leading to increased assay throughput. In addition, such integrated microsystems may point the way to targeted genetic experiments on single cells and in other areas that are otherwise very difficult. Concomitant with these advantages, such systems, when fully integrated, should be capable of forming portable systems for high-speed in situ analyses, enabling a new standard in disciplines such as clinical chemistry, forensics, biowarfare detection and epidemiology. This review will discuss the various technologies available for genetic analysis on the microscale, and efforts to integrate them to form fully functional robust analysis devices.

Design, fabrication, and packaging of an integrated, wirelessly-powered optrode array for optogenetics application

PubMed Central

Kwon, Ki Yong; Lee, Hyung-Min; Ghovanloo, Maysam; Weber, Arthur; Li, Wen

2015-01-01

The recent development of optogenetics has created an increased demand for advancing engineering tools for optical modulation of neural circuitry. This paper details the design, fabrication, integration, and packaging procedures of a wirelessly-powered, light emitting diode (LED) coupled optrode neural interface for optogenetic studies. The LED-coupled optrode array employs microscale LED (μLED) chips and polymer-based microwaveguides to deliver light into multi-level cortical networks, coupled with microelectrodes to record spontaneous changes in neural activity. An integrated, implantable, switched-capacitor based stimulator (SCS) system provides high instantaneous power to the μLEDs through an inductive link to emit sufficient light and evoke neural activities. The presented system is mechanically flexible, biocompatible, miniaturized, and lightweight, suitable for chronic implantation in small freely behaving animals. The design of this system is scalable and its manufacturing is cost effective through batch fabrication using microelectromechanical systems (MEMS) technology. It can be adopted by other groups and customized for specific needs of individual experiments. PMID:25999823

Bio-Based Artificial Nacre with Excellent Mechanical and Barrier Properties Realized by a Facile In Situ Reduction and Cross-Linking Reaction.

PubMed

Shahzadi, Kiran; Mohsin, Imran; Wu, Lin; Ge, Xuesong; Jiang, Yijun; Li, Hui; Mu, Xindong

2017-01-24

Demands for high strength integrated materials have substantially increased across various kinds of industries. Inspired by the relationship of excellent integration of mechanical properties and hierarchical nano/microscale structure of the natural nacre, a simple and facile method to fabricate high strength integrated artificial nacre based on sodium carboxymethylcellulose (CMC) and borate cross-linked graphene oxide (GO) sheets has been developed. The tensile strength and toughness of cellulose-based hybrid material reached 480.5 ± 13.1 MPa and 11.8 ± 0.4 MJm -3 by a facile in situ reduction and cross-linking reaction between CMC and GO (0.7%), which are 3.55 and 6.55 times that of natural nacre. This hybrid film exhibits better thermal stability and flame retardancy. More interestingly, the hybrid material showed good water stability compared to that in the original water-soluble CMC. This type of hybrid has great potential applications in aerospace, artificial muscle, and tissue engineering.

Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell

PubMed Central

Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

2015-01-01

The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area. PMID:26412619

Transfection in perfused microfluidic cell culture devices: A case study.

PubMed

Raimes, William; Rubi, Mathieu; Super, Alexandre; Marques, Marco P C; Veraitch, Farlan; Szita, Nicolas

2017-08-01

Automated microfluidic devices are a promising route towards a point-of-care autologous cell therapy. The initial steps of induced pluripotent stem cell (iPSC) derivation involve transfection and long term cell culture. Integration of these steps would help reduce the cost and footprint of micro-scale devices with applications in cell reprogramming or gene correction. Current examples of transfection integration focus on maximising efficiency rather than viable long-term culture. Here we look for whole process compatibility by integrating automated transfection with a perfused microfluidic device designed for homogeneous culture conditions. The injection process was characterised using fluorescein to establish a LabVIEW-based routine for user-defined automation. Proof-of-concept is demonstrated by chemically transfecting a GFP plasmid into mouse embryonic stem cells (mESCs). Cells transfected in the device showed an improvement in efficiency (34%, n = 3) compared with standard protocols (17.2%, n = 3). This represents a first step towards microfluidic processing systems for cell reprogramming or gene therapy.

Half-Heusler Alloys as Promising Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Page, Alexander A.

This thesis describes Ph.D. research on the half-Heusler class of thermoelectric materials. Half-Heusler alloys are a versatile class of materials that have been studied for use in photovoltaics, phase change memory, and thermoelectric power generation. With respect to thermoelectric power generation, new approaches were recently developed in order to improve the thermoelectric figure of merit, ZT, of half-Heusler alloys. Two of the strategies discussed in this work are adding excess Ni within MNiSn (M = Ti, Zr, or Hf) compounds to form full-Heusler nanostructures and using isoelectronic substitution of Ti, Zr, and Hf in MNiSn compounds to create microscale grain boundaries. This work uses computational simulations based on density functional theory, combined with the cluster expansion method, to predict the stable phases of pseudo-binary and pseudo-ternary composition systems. Statistical mechanics methods were used to calculate temperature-composition phase diagrams that relate the equilibrium phases. It is shown that full-Heusler nanostructures are predicted to remain stable even at high temperatures, and the microscale grain boundaries observed in (Ti,Zr,Hf)NiSn materials are found to be thermodynamically unstable at equilibrium. A new strategy of combining MNiSn materials with ZrNiPb has also recently emerged, and theoretical and experimental work show that a solid solution of the two materials is stable.

A predictive parameter estimation approach for the thermodynamically constrained averaging theory applied to diffusion in porous media

NASA Astrophysics Data System (ADS)

Valdes-Parada, F. J.; Ostvar, S.; Wood, B. D.; Miller, C. T.

2017-12-01

Modeling of hierarchical systems such as porous media can be performed by different approaches that bridge microscale physics to the macroscale. Among the several alternatives available in the literature, the thermodynamically constrained averaging theory (TCAT) has emerged as a robust modeling approach that provides macroscale models that are consistent across scales. For specific closure relation forms, TCAT models are expressed in terms of parameters that depend upon the physical system under study. These parameters are usually obtained from inverse modeling based upon either experimental data or direct numerical simulation at the pore scale. Other upscaling approaches, such as the method of volume averaging, involve an a priori scheme for parameter estimation for certain microscale and transport conditions. In this work, we show how such a predictive scheme can be implemented in TCAT by studying the simple problem of single-phase passive diffusion in rigid and homogeneous porous media. The components of the effective diffusivity tensor are predicted for several porous media by solving ancillary boundary-value problems in periodic unit cells. The results are validated through a comparison with data from direct numerical simulation. This extension of TCAT constitutes a useful advance for certain classes of problems amenable to this estimation approach.

Ultrahigh throughput microfluidic platform for in-air production of microscale droplets

NASA Astrophysics Data System (ADS)

Tirandazi, Pooyan; Healy, John; Hidrovo, Carlos H.

2017-11-01

In-air droplet formation inside microfluidic networks is an alternative technique to the conventional in-liquid systems for creating uniform, microscale droplets. Recent works have highlighted and quantified the use of a gaseous continuous phase for controlled generation of droplets in the Dripping regime in planar structures. Here we demonstrate a new class of non-planar droplet-based systems which rely on controlled breakup of a liquid microjet within a high speed flow of air inside a confined microfluidic flow-focusing PDMS channel. We investigate the physics of confined gas-liquid flows and the effect of geometry on the behavior of a liquid water jet in a gaseous flow. Droplet breakup in the Jetting regime is studied both numerically and experimentally and the results are compared. We show droplet production capability at rates higher than 100 KHz with droplets ranging from 15-30 μm in diameter and a polydispersity index of less than 15%. This work represents an important investigation into the Jetting regime in confined microchannels. The ability to control jet behavior, generation rate, and droplet size in gas-liquid microflows will further expand the potential applications of this system for high throughput operations in material synthesis and biochemical analysis. We acknowledge funding support from NSF CAREER Award Grant CBET-1522841.

A micrometre-sized heat engine operating between bacterial reservoirs

NASA Astrophysics Data System (ADS)

Krishnamurthy, Sudeesh; Ghosh, Subho; Chatterji, Dipankar; Ganapathy, Rajesh; Sood, A. K.

2016-12-01

Artificial microscale heat engines are prototypical models to explore the mechanisms of energy transduction in a fluctuation-dominated regime. The heat engines realized so far on this scale have operated between thermal reservoirs, such that stochastic thermodynamics provides a precise framework for quantifying their performance. It remains to be seen whether these concepts readily carry over to situations where the reservoirs are out of equilibrium, a scenario of particular importance to the functioning of synthetic and biological microscale engines and motors. Here, we experimentally realize a micrometre-sized active Stirling engine by periodically cycling a colloidal particle in a time-varying optical potential across bacterial baths characterized by different degrees of activity. We find that the displacement statistics of the trapped particle becomes increasingly non-Gaussian with activity and contributes substantially to the overall power output and the efficiency. Remarkably, even for engines with the same energy input, differences in non-Gaussianity of reservoir noise results in distinct performances. At high activities, the efficiency of our engines surpasses the equilibrium saturation limit of Stirling efficiency, the maximum efficiency of a Stirling engine where the ratio of cold to hot reservoir temperatures is vanishingly small. Our experiments provide fundamental insights into the functioning of micromotors and engines operating out of equilibrium.

Isotropic microscale mechanical properties of coral skeletons

PubMed Central

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

2015-01-01

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

MICRO-SCALE CFD MODELING OF OSCILLATING FLOW IN A REGENERATOR

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

Cheadle, M. J.; Nellis, G. F.; Klein, S. A.

2010-04-09

Regenerator models used by designers are macro-scale models that do not explicitly consider interactions between the fluid and the solid matrix. Rather, the heat transfer coefficient and pressure drop are calculated using correlations for Nusselt number and friction factor. These correlations are typically based on steady flow data. The error associated with using steady flow correlations to characterize the oscillatory flow that is actually present in the regenerator is not well understood. Oscillating flow correlations based on experimental data do exist in the literature; however, these results are often conflicting. This paper uses a micro-scale computational fluid dynamic (CFD) modelmore » of a unit-cell of a regenerator matrix to determine the conditions for which oscillating flow affects friction factor. These conditions are compared to those found in typical pulse tube regenerators to determine whether oscillatory flow is of practical importance. CFD results clearly show a transition Valensi number beyond which oscillating flow significantly increases the friction factor. This transition Valensi number increases with Reynolds number. Most practical pulse tube regenerators will operate below this Valensi transition number and therefore this study suggests that the effect of flow oscillation on pressure drop can be neglected in macro-scale regenerator models.« less

Characterisation of an Al-BN nanocomposite prepared by ball milling and hot extrusion

NASA Astrophysics Data System (ADS)

Arlic, U.; Drozd, Z.; Trojanová, Z.; Molnárová, O.; Kasakewitsch, A.

2017-07-01

Aluminium-matrix-nanocomposites were manufactured by ball milling of microscale aluminium powder with BN nanoparticles in air, followed by subsequent consolidation by hot extrusion. The microstructure of the samples was studied using scanning electron microscopy. Vickers microhardness measurements were used to probe the mechanical properties of the samples. The amplitude dependent damping of the nanocomposites was measured at room temperature after thermal treatment of samples, and the linear thermal expansion was measured over a wide temperature range from room temperature up to 670K in the as-extruded state. The experimental results give a comprehensive picture of the behaviour of this nanocomposite system over the range of thermomechanical treatment conditions examined in this study. Based on these experimental data some possible influences of BN nanoparticles on the anelastic, plastic and thermal properties of microcrystalline aluminium are discussed.

Study on Manipulations of Fluids in Micro-scale and Their Applications in Physical, Bio/chemistry

NASA Astrophysics Data System (ADS)

Zhou, Bingpu

Microfluidics is a highly interdisciplinary research field which manipulates, controls and analyzes fluids in micro-scale for physical and bio/chemical applications. In this thesis, several aspects of fluid manipulations in micro-scale were studied, discussed and employed for demonstrations of practical utilizations. To begin with, mixing in continuous flow microfluidic was raised and investigated. A simple method for mixing actuation based on magnetism was proposed and realized via integration of magnetically functionalized micropillar arrays inside the microfluidic channel.With such technique, microfluidic mixing could be swiftly switched on and off via simple application or retraction of the magnetic field. Thereafter, in Chapter 3 we mainly focused on how to establish stable while tunable concentration gradients inside microfluidic network using a simple design. The proposed scheme could also be modified with on-chip pneumatic actuated valve to realize pulsatile/temporal concentration gradients simultaneously in ten microfluidic branches. We further applied such methodology to obtain roughness gradients onPolydimethylsiloxane (PDMS) surface via combinations of the microfluidic network andphoto-polymerizations. The obtained materials were utilized in parallel cell culture to figure out the relationship between substrate morphologies and the cell behaviors. In the second part of this work, we emphasized on manipulations on microdroplets insidethe microfluidic channel and explored related applications in bio/chemical aspects. Firstly, microdroplet-based microfluidic universal logic gates were successfully demonstrated vialiquid-electronic hybrid divider. For application based on such novel scheme of control lable droplet generation, on-demand chemical reaction within paired microdroplets was presented using IF logic gate. Followed by this, another important operation of microdroplet - splitting -was investigated. Addition lateral continuous flow was applied at the bifurcation as a mediumto controllably divide microdroplets with highly tunable splitting ratios. Related physical mechanism was proposed and such approach was adopted further for rapid synthesis of multi-scale microspheres.

The case for applying tissue engineering methodologies to instruct human organoid morphogenesis.

PubMed

Marti-Figueroa, Carlos R; Ashton, Randolph S

2017-05-01

Three-dimensional organoids derived from human pluripotent stem cell (hPSC) derivatives have become widely used in vitro models for studying development and disease. Their ability to recapitulate facets of normal human development during in vitro morphogenesis produces tissue structures with unprecedented biomimicry. Current organoid derivation protocols primarily rely on spontaneous morphogenesis processes to occur within 3-D spherical cell aggregates with minimal to no exogenous control. This yields organoids containing microscale regions of biomimetic tissues, but at the macroscale (i.e. 100's of microns to millimeters), the organoids' morphology, cytoarchitecture, and cellular composition are non-biomimetic and variable. The current lack of control over in vitro organoid morphogenesis at the microscale induces aberrations at the macroscale, which impedes realization of the technology's potential to reproducibly form anatomically correct human tissue units that could serve as optimal human in vitro models and even transplants. Here, we review tissue engineering methodologies that could be used to develop powerful approaches for instructing multiscale, 3-D human organoid morphogenesis. Such technological mergers are critically needed to harness organoid morphogenesis as a tool for engineering functional human tissues with biomimetic anatomy and physiology. Human PSC-derived 3-D organoids are revolutionizing the biomedical sciences. They enable the study of development and disease within patient-specific genetic backgrounds and unprecedented biomimetic tissue microenvironments. However, their uncontrolled, spontaneous morphogenesis at the microscale yields inconsistences in macroscale organoid morphology, cytoarchitecture, and cellular composition that limits their standardization and application. Integration of tissue engineering methods with organoid derivation protocols could allow us to harness their potential by instructing standardized in vitro morphogenesis to generate organoids with biomimicry at all scales. Such advancements would enable the use of organoids as a basis for 'next-generation' tissue engineering of functional, anatomically mimetic human tissues and potentially novel organ transplants. Here, we discuss critical aspects of organoid morphogenesis where application of innovative tissue engineering methodologies would yield significant advancement towards this goal. Copyright © 2017. Published by Elsevier Ltd.

Material Properties of the Posterior Human Sclera☆

PubMed Central

Grytz, Rafael; Fazio, Massimo A.; Girard, Michael J.A.; Libertiaux, Vincent; Bruno, Luigi; Gardiner, Stuart; Girkin, Christopher A.; Downs, J. Crawford

2013-01-01

To characterize the material properties of posterior and peripapillary sclera from human donors, and to investigate the macro- and micro-scale strains as potential control mechanisms governing mechanical homeostasis. Posterior scleral shells from 9 human donors aged 57–90 years were subjected to IOP elevations from 5 to 45 mmHg and the resulting full-field displacements were recorded using laser speckle interferometry. Eye-specific finite element models were generated based on experimentally measured scleral shell surface geometry and thickness. Inverse numerical analyses were performed to identify material parameters for each eye by matching experimental deformation measurements to model predictions using a microstructure-based constitutive formulation that incorporates the crimp response and anisotropic architecture of scleral collagen fibrils. The material property fitting produced models that fit both the overall and local deformation responses of posterior scleral shells very well. The nonlinear stiffening of the sclera with increasing IOP was well reproduced by the uncrimping of scleral collagen fibrils, and a circumferentially-aligned ring of collagen fibrils around the scleral canal was predicted in all eyes. Macroscopic in-plane strains were significantly higher in peripapillary region then in the mid-periphery. In contrast, the meso- and micro-scale strains at the collagen network and collagen fibril level were not significantly different between regions. The elastic response of the posterior human sclera can be characterized by the anisotropic architecture and crimp response of scleral collagen fibrils. The similar collagen fibril strains in the peripapillary and mid-peripheral regions support the notion that the scleral collagen architecture including the circumpapillary ring of collagen fibrils evolved to establish optimal load bearing conditions at the collagen fibril level. PMID:23684352

Micro-scale experimental study of Microbial-Induced Carbonate Precipitation (MICP) by using microfluidic devices

NASA Astrophysics Data System (ADS)

Wang, Y.; Soga, K.; DeJong, J. T.; Kabla, A.

2017-12-01

Microbial-induced carbonate precipitation (MICP), one of the bio-mineralization processes, is an innovative subsurface improvement technique for enhancing the strength and stiffness of soils, and controlling their hydraulic conductivity. These macro-scale engineering properties of MICP treated soils controlled by micro-scale factors of the precipitated carbonate, such as its content, amount and distribution in the soil matrix. The precipitation process itself is affected by bacteria amount, reaction kinetics, porous medium geometry and flow distribution in the soils. Accordingly, to better understand the MICP process at the pore scale a new experimental technique that can observe the entire process of MICP at the pore-scale was developed. In this study, a 2-D transparent microfluidic chip made of Polydimethylsiloxane (PDMS) representing the soil matrix was designed and fabricated. A staged-injection MICP treatment procedure was simulated inside the microfluidic chip while continuously monitored using microscopic techniques. The staged-injection MICP treatment procedure started with the injection of bacteria suspension, followed with the bacteria setting for attachment, and then ended with the multiple injections of cementation liquid. The main MICP processes visualized during this procedure included the bacteria transport and attachment during the bacteria injection, the bacteria attachment and growth during the bacteria settling, the bacteria detachment during the cementation liquid injection, the cementation development during the cementation liquid injection, and the cementation development after the completion of cementation liquid injection. It is suggested that the visualization of the main MICP processes using the microfluidic technique can improve understating of the fundamental mechanisms of MICP and consequently help improve the treatment technique for in situ implementation of MICP.

Micro-scale dynamic simulation of erythrocyte-platelet interaction in blood flow.

PubMed

AlMomani, T; Udaykumar, H S; Marshall, J S; Chandran, K B

2008-06-01

Platelet activation, adhesion, and aggregation on the blood vessel and implants result in the formation of mural thrombi. Platelet dynamics in blood flow is influenced by the far more numerous erythrocytes (RBCs). This is particularly the case in the smaller blood vessels (arterioles) and in constricted regions of blood flow (such as in valve leakage and hinge regions) where the dimensions of formed elements of blood become comparable with that of the flow geometry. In such regions, models to predict platelet motion, activation, aggregation and adhesion must account for platelet-RBC interactions. This paper studies platelet-RBC interactions in shear flows by performing simulations of micro-scale dynamics using a computational fluid dynamics (CFD) model. A level-set sharp-interface immersed boundary method is employed in the computations in which RBC and platelet boundaries are tracked on a two-dimensional Cartesian grid. The RBCs are assumed to have an elliptical shape and to deform elastically under fluid forces while the platelets are assumed to behave as rigid particles of circular shape. Forces and torques between colliding blood cells are modeled using an extension of the soft-sphere model for elliptical particles. RBCs and platelets are transported under the forces and torques induced by fluid flow and cell-cell and cell-platelet collisions. The simulations show that platelet migration toward the wall is enhanced with increasing hematocrit, in agreement with past experimental observations. This margination is seen to occur due to hydrodynamic forces rather than collisional forces or volumetric exclusion effects. The effect of fluid shear forces on the platelets increases exponentially as a function of hematocrit for the range of parameters covered in this study. The micro-scale analysis can be potentially employed to obtain a deterministic relationship between fluid forces and platelet activation and aggregation in blood flow past cardiovascular implants.

Assessment of microscale spatio-temporal variation of air pollution at an urban hotspot in Madrid (Spain) through an extensive field campaign

NASA Astrophysics Data System (ADS)

Borge, Rafael; Narros, Adolfo; Artíñano, Begoña; Yagüe, Carlos; Gómez-Moreno, Francisco Javier; de la Paz, David; Román-Cascón, Carlos; Díaz, Elías; Maqueda, Gregorio; Sastre, Mariano; Quaassdorff, Christina; Dimitroulopoulou, Chrysanthi; Vardoulakis, Sotiris

2016-09-01

Poor urban air quality is one of the main environmental concerns worldwide due to its implications for population exposure and health-related issues. However, the development of effective abatement strategies in cities requires a consistent and holistic assessment of air pollution processes, taking into account all the relevant scales within a city. This contribution presents the methodology and main results of an intensive experimental campaign carried out in a complex pollution hotspot in Madrid (Spain) under the TECNAIRE-CM research project, which aimed at understanding the microscale spatio-temporal variation of ambient concentration levels in areas where high pollution values are recorded. A variety of instruments were deployed during a three-week field campaign to provide detailed information on meteorological and micrometeorological parameters and spatio-temporal variations of the most relevant pollutants (NO2 and PM) along with relevant information needed to simulate pedestrian fluxes. The results show the strong dependence of ambient concentrations on local emissions and meteorology that turns out in strong spatial and temporal variations, with gradients up to 2 μg m-3 m-1 for NO2 and 55 μg m-3 min-1 for PM10. Pedestrian exposure to these pollutants also presents strong variations temporally and spatially but it concentrates on pedestrian crossings and bus stops. The analysis of the results show that the high concentration levels found in urban hotspots depend on extremely complex dynamic processes that cannot be captured by routinely measurements made by air quality monitoring stations used for regulatory compliance assessment. The large influence from local traffic in the concentration fields highlights the need for a detailed description of specific variables that determine emissions and dispersion at microscale level. This also indicates that city-scale interventions may be complemented with local control measures and exposure management, to improve air quality and reduce air pollution health effects more effectively.

Electric field enhancement due to a saw-tooth asperity in a channel and implications on microscale gas breakdown

NASA Astrophysics Data System (ADS)

Venkattraman, Ayyaswamy

2014-10-01

The electric field enhancement due to an isolated saw-tooth asperity in an infinite channel is considered with the goal of providing some inputs to the choice of field enhancement factors used to describe microscale gas breakdown. The Schwarz-Christoffel transformation is used to map the interior of the channel to the upper half of the transformed plane. The expression for the electric field in the transformed plane is then used to determine the electric field distribution in the channel as well as field enhancement near the asperity. The effective field enhancement factor is determined and its dependence on operating and geometrical parameters is studied. While the effective field enhancement factor depends only weakly on the height of the asperity in comparison to the channel, it is influenced significantly by the base angles of the asperity. Due to the strong dependence of field emission current density on electric field, the effective field enhancement factor (βeff) is shown to vary rapidly with the applied electric field irrespective of the geometrical parameters. This variation is included in the analysis of microscale gas breakdown and compared with results obtained using a constant βeff as is done traditionally. Even though results for a varying βeff may be approximately reproduced using an equivalent constant βeff independent of E-field, it might be important for a range of operating conditions. This is confirmed by extracting βeff from experimental data for breakdown in argon microgaps with plane-parallel cathodes and comparing its dependence on the E-field. While the use of two-dimensional asperities is shown to be a minor disadvantage of the proposed approach in its current form, it can potentially help in developing predictive capabilities as opposed to treating βeff as a curve-fitting parameter.

Stochastic Models of Macroscale Quantities for the Prediction of the REV Scale for Multiphase Flow through Porous Media

NASA Astrophysics Data System (ADS)

Talbot, C.; McClure, J. E.; Armstrong, R. T.; Mostaghimi, P.; Hu, Y.; Miller, C. T.

2017-12-01

Microscale experimental and computational methods can be used to evaluate fundamental microscale mechanisms and deduce macroscale constitutive relationships and parameter values. The link between the microscale and the macroscale is especially demanding, because technical issues arise regarding the necessary scale of the system needed for a meaningful set of macroscale measures to be insensitive to the size of the system, which is known as a representative elementary volume (REV). While the REV scale is routinely determined for single-phase flow in porous media, no systematic study of the scale of a REV for the comprehensive set of macroscale measures considered here has been reported in the literature. A comprehensive set of measures of the macroscale state is developed. We further develop and apply methods to predict the REV scale and quantify the uncertainty of the estimate for this set of macroscale quantities. We model the system state in terms of standard errors of macroscale quantities as a multivariate Gaussian process dependent on the size of the domain simulated. We determine predictive distributions of function values and a posterior distributions of weights using standard kernels, as well as a kernel constructed using relationships between physical quantities. For each kernel, we discuss the decay of the mean and covariance with increasing domain size, and use cross-validation to facilitate model selection. The procedure yields a model of the domain size needed to achieve a REV with quantifiable uncertainty. We present results in the context of multiphase fluid flow through a highly resolved realization of sandstone imaged using micro-CT. A 1440x1440x4320 section of the full 2520x2520x5280 imaged medium is simulated using the lattice-Boltzmann method. We compare the fidelity of the predictive model with results obtained by an analogous approach using polynomial regression.

Scaling of normalized mean energy and scalar dissipation rates in a turbulent channel flow

NASA Astrophysics Data System (ADS)

Abe, Hiroyuki; Antonia, Robert Anthony

2011-05-01

Non-dimensional parameters for the mean energy and scalar dissipation rates Cɛ and Cɛθ are examined using direct numerical simulation (DNS) data obtained in a fully developed turbulent channel flow with a passive scalar (Pr = 0.71) at several values of the Kármán (Reynolds) number h+. It is shown that Cɛ and Cɛθ are approximately equal in the near-equilibrium region (viz., y+ = 100 to y/h = 0.7) where the production and dissipation rates of either the turbulent kinetic energy or scalar variance are approximately equal and the magnitudes of the diffusion terms are negligibly small. The magnitudes of Cɛ and Cɛθ are about 2 and 1 in the logarithmic and outer regions, respectively, when h+ is sufficiently large. The former value is about the same for the channel, pipe, and turbulent boundary layer, reflecting the similarity between the mean velocity and temperature distributions among these three canonical flows. The latter value is, on the other hand, about twice as large as in homogeneous isotropic turbulence due to the existence of the large-scale u structures in the channel. The behaviour of Cɛ and Cɛθ impacts on turbulence modeling. In particular, the similarity between Cɛ and Cɛθ leads to a simple relation for the scalar variance to turbulent kinetic energy time-scale ratio, an important ingredient in the eddy diffusivity model. This similarity also yields a relation between the Taylor and Corrsin microscales and analogous relations, in terms of h+, for the Taylor microscale Reynolds number and Corrsin microscale Peclet number. This dependence is reasonably well supported by both the DNS data at small to moderate h+ and the experimental data of Comte-Bellot [Ph. D. thesis (University of Grenoble, 1963)] at larger h+. It does not however apply to a turbulent boundary layer where the mean energy dissipation rate, normalized on either wall or outer variables, is about 30% larger than for the channel flow.

Enhanced reactivity of microscale Fe/Cu bimetallic particles (mFe/Cu) with persulfate (PS) for p-nitrophenol (PNP) removal in aqueous solution.

PubMed

Ji, Qingqing; Li, Jun; Xiong, Zhaokun; Lai, Bo

2017-04-01

In this study, batch experiments were conducted to examine the enhanced reactivity of microscale Fe/Cu bimetallic particles (mFe/Cu) with persulfate (PS) for p-nitrophenol (PNP) removal in aqueous solution. The key operating parameters (i.e., theoretical Cu mass loadings (TML Cu ), mFe/Cu dosage, PS dose, initial pH and temperature) were optimized by the batch experiments, respectively. The experimental data were followed well the pseudo-first-order kinetic model. Result reveals that refractory PNP (500 mg L -1 ) was effectively degraded by mFe/Cu-PS system with removal of 98.4% and k obs of 1.91 min -1 after only 3 min treatment under the optimal operating conditions. Moreover, compared with control experiments (i.e., mFe/Cu, microscale Fe 0 with PS (mFe 0 -PS), and PS alone), mFe/Cu-PS system exerted better performance for PNP removal due to the strong synergistic effect between PS and mFe/Cu. According to the analysis results of degradation kinetics of PNP, COD (chemical oxygen demand) removal, UV-vis absorption spectra and the intermediates formed, the results reveal that the PNP removal by mFe/Cu-PS system was mainly attributed to reduction accompanied slight oxidation. And based on the analysis of surface characteristics of mFe/Cu particles, it is further demonstrated that PS could enhance the reactivity of mFe/Cu through rapid corrosion of iron surface and decrease of surface passivation of mFe/Cu surface when the low molar ratio of PS to mFe/Cu (i.e., 1:43) was used in this study. These results also illustrates mFe/Cu-PS can be as a high efficient pretreatment technology for the removal of toxic refractory PNP from wastewater. Copyright © 2016 Elsevier Ltd. All rights reserved.

Silica Nanowires: Growth, Integration, and Sensing Applications

PubMed Central

Kaushik, Ajeet; Kumar, Rajesh; Huey, Eric; Bhansali, Shekhar; Nair, Narayana; Nanir, Madhavan

2014-01-01

This review (with 129 refs.) gives an overview on how the integration of silica nanowires (NWs) into micro-scale devices has resulted, in recent years, in simple yet robust nano-instrumentation with improved performance in targeted application areas such as sensing. This has been achieved by the use of appropriate techniques such as di-electrophoresis and direct vapor-liquid-growth phenomena, to restrict the growth of NWs to site-specific locations. This also has eliminated the need for post-growth processing and enables nanostructures to be placed on pre-patterned substrates. Various kinds of NWs have been investigated to determine how their physical and chemical properties can be tuned for integration into sensing structures. NWs integrated onto interdigitated micro-electrodes have been applied to the determination of gases and biomarkers. The technique of directly growing NWs eliminates the need for their physical transfer and thus preserves their structure and performance, and further reduces the costs of fabrication. The biocompatibility of NWs also has been studied with respect to possible biological applications. This review addresses the challenges in growth and integration of NWs to understand related mechanism on biological contact or gas exposure and sensing performance for personalized health and environmental monitoring. PMID:25382871

Washington's "free" 300-station microscale weather network

Treesearch

Thomas Blackburn

1977-01-01

This article is intended to encourage those planning to conduct meso- or microscale weather studies to supplement their sophisticated observing techniques and equipment- with low-cost observations taken by volunteers. Such observations can often show high benefits per unit costs in expanding the geographical area of study, increasing the density of observations, or in...

Laboratory Experiments on the Electrochemical Remediation of the Environment. Part 8. Microscale Simultaneous Photocatalysis

ERIC Educational Resources Information Center

Ibanez, Jorge G.; Mena-Brito, Rodrigo; Fregoso-Infante, Arturo

2005-01-01

A microscale experiment in which the simultaneous oxidation of an organic compound and the reduction of a metal ion are photocatalytically performed in an aqueous slurry containing TiO[subscript 2] irradiated with UV light. This experiment can be performed in the laboratory session with simple chemicals and equipments.

Development of a gastrointestinal tract microscale cell culture analog to predict drug transport

USDA-ARS?s Scientific Manuscript database

Microscale cell culture analogs (uCCAs) are used to study the metabolism and toxicity of a chemical or drug. These in vitro devices are physical replicas of physiologically based pharmacokinetic models that combine microfabrication and cell culture. The goal of this project is to add an independent ...

The Petasis Reaction: Microscale Synthesis of a Tertiary Amine Antifungal Analog

ERIC Educational Resources Information Center

Koroluk, Katherine J.; Jackson, Derek A.; Dicks, Andrew P.

2012-01-01

Students prepare a tertiary amine antifungal analog in an upper-level undergraduate organic laboratory. A microscale Petasis reaction is performed to generate a liquid compound readily characterized via IR and proton NMR spectroscopy. The biological relevance of the product is highlighted, with the tertiary amine scaffold being an important…

Evaluating Mechanisms of Dihydroxylation by Thin-Layer Chromatography: A Microscale Experiment for Organic Chemistry

ERIC Educational Resources Information Center

Burlingham, Benjamin T.; Rettig, Joseph C.

2008-01-01

A microscale experiment is presented in which cyclohexene is dihydroxylated under three sets of conditions: epoxidation-hydrolysis, permanganate oxidation, and the Woodward dihydroxylation. The products of the reactions are determined by the use of thin-layer chromatography. Teams of students are presented with proposed mechanisms for each…

Evaluation of three flame retardant (FR) grey cotton blend nonwoven fabrics using micro-scale combustion calorimetry

USDA-ARS?s Scientific Manuscript database

Unbleached (grey or greige) cotton nonwoven (NW) fabrics (with 12.5% polypropylene scrim) were treated with three phosphate-nitrogen based FR formulations and evaluated with micro-scale combustion calorimetry (MCC). Heat release rate (HRR), Peak heat rate (PHRR), temperature at peak heat release ra...

Demonstrating Microscale Gas Reactions Using Disposable Plastic Syringes

ERIC Educational Resources Information Center

Goodwin, Alan

2011-01-01

This article provides an example of a teacher's learning, since the author only became aware of the microscale technique described very late in his professional career. The technique provides a convenient method of preparing and manipulating gases on a very small scale and a relatively safe means of demonstrating reactions that would be very…

Organ-On-A-Chip Platforms: A Convergence of Advanced Materials, Cells, and Microscale Technologies.

PubMed

Ahadian, Samad; Civitarese, Robert; Bannerman, Dawn; Mohammadi, Mohammad Hossein; Lu, Rick; Wang, Erika; Davenport-Huyer, Locke; Lai, Ben; Zhang, Boyang; Zhao, Yimu; Mandla, Serena; Korolj, Anastasia; Radisic, Milica

2018-01-01

Significant advances in biomaterials, stem cell biology, and microscale technologies have enabled the fabrication of biologically relevant tissues and organs. Such tissues and organs, referred to as organ-on-a-chip (OOC) platforms, have emerged as a powerful tool in tissue analysis and disease modeling for biological and pharmacological applications. A variety of biomaterials are used in tissue fabrication providing multiple biological, structural, and mechanical cues in the regulation of cell behavior and tissue morphogenesis. Cells derived from humans enable the fabrication of personalized OOC platforms. Microscale technologies are specifically helpful in providing physiological microenvironments for tissues and organs. In this review, biomaterials, cells, and microscale technologies are described as essential components to construct OOC platforms. The latest developments in OOC platforms (e.g., liver, skeletal muscle, cardiac, cancer, lung, skin, bone, and brain) are then discussed as functional tools in simulating human physiology and metabolism. Future perspectives and major challenges in the development of OOC platforms toward accelerating clinical studies of drug discovery are finally highlighted. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano- and Micro-Scale Oxidative Patterning of Titanium Implant Surfaces for Improved Surface Wettability.

PubMed

Kim, In-hye; Son, Jun Sik; Choi, Seok Hwa; Kim, Kyo-han; Kwon, Tae-yub

2016-02-01

A simple and scalable surface modification treatment is demonstrated, in which nano- and microscale features are introduced into the surface of titanium (Ti) substrates by means of a novel and eco-friendly oxidative aqueous solution composed of hydrogen peroxide (H202) and sodium bicarbonate (NaHCO3). By immersing mirror-polished Ti discs in an aqueous mixture of 30 wt% H2O2/5 wt% NaHCO3 at 23 +/- 3 degrees C for 4 h, it was confirmed that this mixture is capable of generating microscale topographies on Ti surfaces. It also simultaneously formed nanochannels that were regularly arranged in a comb-like pattern on the Ti surface, thus forming a hierarchical surface structure. Further, these nano/micro-textured Ti surfaces showed great surface roughness and excellent wettability when compared with control Ti surfaces. This study demonstrates that a H2O2/NaHCO3 mixture can be effectively utilized to create reproducible nano/microscale topographies on Ti implant surfaces, thus providing an economical new oxidative solution that may be used effectively and safely as a Ti surface modification treatment.

Improving device performance of perovskite solar cells by micro-nanoscale composite mesoporous TiO2

NASA Astrophysics Data System (ADS)

Ting, Hungkit; Zhang, Danfei; He, Yihao; Wei, Shiyuan; Li, Tieyi; Sun, Weihai; Wu, Cuncun; Chen, Zhijian; Wang, Qi; Zhang, Guoyi; Xiao, Lixin

2018-02-01

In perovskite solar cells, the morphology of the porous TiO2 electron transport layer (ETL) largely determines the quality of the perovskites. Here, we chose micro-scale TiO2 (0.2 µm) and compared it with the conventional nanoscale TiO2 (20 nm) in relation to the crystallinity of perovskites. The results show that the micro-scale TiO2 is favorable for increasing the grain size of the perovskites and enhancing the light scattering. However, the oversized TiO2 results in an uneven surface. The evenness of the perovskites can be improved by nanoscale TiO2, while the crystallinity and compactness are not as good as those of the films based on micro-scale TiO2. To combine the advantages of both micro-scale and nanoscale TiO2, by mixing 0.2 µm/20 nm TiO2 with a ratio of 1:2 as the composite ETL, the device average power conversion efficiency was increased to 11.2% from 9.9% in the case of only 20 nm TiO2.

Maintaining the pluripotency of mouse embryonic stem cells on gold nanoparticle layers with nanoscale but not microscale surface roughness.

PubMed

Lyu, Zhonglin; Wang, Hongwei; Wang, Yanyun; Ding, Kaiguo; Liu, Huan; Yuan, Lin; Shi, Xiujuan; Wang, Mengmeng; Wang, Yanwei; Chen, Hong

2014-06-21

Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction.

Contribution of streetscape audits to explanation of physical activity in four age groups based on the Microscale Audit of Pedestrian Streetscapes (MAPS).

PubMed

Cain, Kelli L; Millstein, Rachel A; Sallis, James F; Conway, Terry L; Gavand, Kavita A; Frank, Lawrence D; Saelens, Brian E; Geremia, Carrie M; Chapman, James; Adams, Marc A; Glanz, Karen; King, Abby C

2014-09-01

Ecological models of physical activity emphasize the effects of environmental influences. "Microscale" streetscape features that may affect pedestrian experience have received less research attention than macroscale walkability (e.g., residential density). The Microscale Audit of Pedestrian Streetscapes (MAPS) measures street design, transit stops, sidewalk qualities, street crossing amenities, and features impacting aesthetics. The present study examined associations of microscale attributes with multiple physical activity (PA) measures across four age groups. Areas in the San Diego, Seattle, and the Baltimore metropolitan areas, USA, were selected that varied on macro-level walkability and neighborhood income. Participants (n = 3677) represented four age groups (children, adolescents, adults, older adults). MAPS audits were conducted along a 0.25 mile route along the street network from participant residences toward the nearest non-residential destination. MAPS data were collected in 2009-2010. Subscale and overall summary scores were created. Walking/biking for transportation and leisure/neighborhood PA were measured with age-appropriate surveys. Objective PA was measured with accelerometers. Mixed linear regression analyses were adjusted for macro-level walkability. Across all age groups 51.2%, 22.1%, and 15.7% of all MAPS scores were significantly associated with walking/biking for transport, leisure/neighborhood PA, and objectively-measured PA, respectively. Supporting the ecological model principle of behavioral specificity, destinations and land use, streetscape, street segment, and intersection variables were more related to transport walking/biking, while aesthetic variables were related to leisure/neighborhood PA. The overall score was related to objective PA in children and older adults. Present findings provide strong evidence that microscale environment attributes are related to PA across the lifespan. Improving microscale features may be a feasible approach to creating activity-friendly environments. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Micro-scale abrasive wear behavior of medical implant material Ti-25Nb-3Mo-3Zr-2Sn alloy on various friction pairs.

PubMed

Wang, Zhenguo; Huang, Weijiu; Ma, Yanlong

2014-09-01

The micro-scale abrasion behaviors of surgical implant materials have often been reported in the literature. However, little work has been reported on the micro-scale abrasive wear behavior of Ti-25Nb-3Mo-3Zr-2Sn (TLM) titanium alloy in simulated body fluids, especially with respect to friction pairs. Therefore, a TE66 Micro-Scale Abrasion Tester was used to study the micro-scale abrasive wear behavior of the TLM alloy. This study covers the friction coefficient and wear loss of the TLM alloy induced by various friction pairs. Different friction pairs comprised of ZrO2, Si3N4 and Al2O3 ceramic balls with 25.4mm diameters were employed. The micro-scale abrasive wear mechanisms and synergistic effect between corrosion and micro-abrasion of the TLM alloy were investigated under various wear-corrosion conditions employing an abrasive, comprised of SiC (3.5 ± 0.5 μm), in two test solutions, Hanks' solution and distilled water. Before the test, the specimens were heat treated at 760°C/1.0/AC+550°C/6.0/AC. It was discovered that the friction coefficient values of the TLM alloy are larger than those in distilled water regardless of friction pairs used, because of the corrosive Hanks' solution. It was also found that the value of the friction coefficient was volatile at the beginning of wear testing, and it became more stable with further experiments. Because the ceramic balls have different properties, especially with respect to the Vickers hardness (Hv), the wear loss of the TLM alloy increased as the ball hardness increased. In addition, the wear loss of the TLM alloy in Hanks' solution was greater than that in distilled water, and this was due to the synergistic effect of micro-abrasion and corrosion, and this micro-abrasion played a leading role in the wear process. The micro-scale abrasive wear mechanism of the TLM alloy gradually changed from two-body to mixed abrasion and then to three-body abrasion as the Vickers hardness of the balls increased. Copyright © 2014 Elsevier B.V. All rights reserved.

Recent advances in micro-scale and nano-scale high-performance liquid-phase chromatography for proteome research.

PubMed

Tao, Dingyin; Zhang, Lihua; Shan, Yichu; Liang, Zhen; Zhang, Yukui

2011-01-01

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS-MS) is regarded as one of the most powerful techniques for separation and identification of proteins. Recently, much effort has been made to improve the separation capacity, detection sensitivity, and analysis throughput of micro- and nano-HPLC, by increasing column length, reducing column internal diameter, and using integrated techniques. Development of HPLC columns has also been rapid, as a result of the use of submicrometer packing materials and monolithic columns. All these innovations result in clearly improved performance of micro- and nano-HPLC for proteome research.

Experimental study on the flow/ heat transfer performance of micro-scale pin fin coating with super-hydrophobic surface adding Nano particle

NASA Astrophysics Data System (ADS)

Hua, Junye; Duan, Yuanyuan; Li, Gui; Xu, Qiong; Li, Dong; Wu, Wei; Zhao, Xiaobao; Qiu, Delai

2018-02-01

The experimental studies on heat transfer and flow resistance characteristics of ellipse-shape micro pin fin have been conducted which is drafted with hydrophobic material, holding the various contact angles fulfilled by adjusting the amount of Nano particle. The results show that with the increases of contact angle(83°,99.5°, 119.5°and 151.5°), the bottom wall temperature rises under the same flow rate. Under a certain heating condition with heating power as 100 W, the average convective heat transfer coefficient decreases with the increase of contact angle with the same Re. The value of Nu for ellipse-shape micro pin fin increases with a higher Re, with the maximum value under experimental condition of Nu as 25. Besides, the friction coefficient of micro pin fin experimental section drafted hydrophobicity treatment significantly decreases, compared with the smooth micro pin fin experimental section (θ = 83°). While the higher contact angle has obvious positive influences on friction coefficient under the same Re. Generally, the flow resistance performance of ellipse-shape micro pin fin drafted with hydrophobic material is better than that without any treatment.

Maintaining the pluripotency of mouse embryonic stem cells on gold nanoparticle layers with nanoscale but not microscale surface roughness

NASA Astrophysics Data System (ADS)

Lyu, Zhonglin; Wang, Hongwei; Wang, Yanyun; Ding, Kaiguo; Liu, Huan; Yuan, Lin; Shi, Xiujuan; Wang, Mengmeng; Wang, Yanwei; Chen, Hong

2014-05-01

Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction.Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01540a

Measuring the light scattering and orientation of a spheroidal particle using in-line holography.

PubMed

Seo, Kyung Won; Byeon, Hyeok Jun; Lee, Sang Joon

2014-07-01

The light scattering properties of a horizontally and vertically oriented spheroidal particle under laser illumination are experimentally investigated using digital in-line holography. The reconstructed wave field shows the bright singular points as a result of the condensed beam formed by a transparent spheroidal particle acting as a lens. The in-plane (θ) and out-of-plane (ϕ) rotating angles of an arbitrarily oriented spheroidal particle are measured by using these scattering properties. As a feasibility test, the 3D orientation of a transparent spheroidal particle suspended in a microscale pipe flow is successfully reconstructed by adapting the proposed method.

Computational Thermomechanical Modelling of Early-Age Silicate Composites

NASA Astrophysics Data System (ADS)

Vala, J.; Št'astník, S.; Kozák, V.

2009-09-01

Strains and stresses in early-age silicate composites, widely used in civil engineering, especially in fresh concrete mixtures, in addition to those caused by exterior mechanical loads, are results of complicated non-deterministic physical and chemical processes. Their numerical prediction at the macro-scale level requires the non-trivial physical analysis based on the thermodynamic principles, making use of micro-structural information from both theoretical and experimental research. The paper introduces a computational model, based on a nonlinear system of macroscopic equations of evolution, supplied with certain effective material characteristics, coming from the micro-scale analysis, and sketches the algorithm for its numerical analysis.

Active mixing of complex fluids at the microscale

DOE PAGES

Ober, Thomas J.; Foresti, Daniele; Lewis, Jennifer A.

2015-09-22

Mixing of complex fluids at low Reynolds number is fundamental for a broad range of applications, including materials assembly, microfluidics, and biomedical devices. Of these materials, yield stress fluids (and gels) pose the most significant challenges, especially when they must be mixed in low volumes over short timescales. New scaling relationships between mixer dimensions and operating conditions are derived and experimentally verified to create a framework for designing active microfluidic mixers that can efficiently homogenize a wide range of complex fluids. As a result, active mixing printheads are then designed and implemented for multimaterial 3D printing of viscoelastic inks withmore » programmable control of local composition.« less

Hydrodynamic modeling of laser interaction with micro-structured targets

DOE PAGES

Velechovsky, Jan; Limpouch, Jiri; Liska, Richard; ...

2016-08-03

A model is developed for numerical simulations of laser absorption in plasmas made of porous materials, with particular interest in low-density foams. Laser absorption is treated on two spatial scales simultaneously. At the microscale, the expansion of a thin solid pore wall is modeled in one dimension and the information obtained is used in the macroscale fluid simulations for the description of the plasma homogenization behind the ionization front. This two-scale laser absorption model is implemented in the arbitrary Lagrangian–Eulerian hydrocode PALE. In conclusion, the numerical simulations of laser penetration into low-density foams compare favorably with published experimental data.

Microfluidic proportional flow controller

PubMed Central

Prentice-Mott, Harrison; Toner, Mehmet; Irimia, Daniel

2011-01-01

Precise flow control in microfluidic chips is important for many biochemical assays and experiments at microscale. While several technologies for controlling fluid flow have been implemented either on- or off-chip, these can provide either high-speed or high-precision control, but seldom could accomplish both at the same time. Here we describe a new on-chip, pneumatically activated flow controller that allows for fast and precise control of the flow rate through a microfluidic channel. Experimental results show that the new proportional flow controllers exhibited a response time of approximately 250 ms, while our numerical simulations suggest that faster actuation down to approximately 50 ms could be achieved with alternative actuation schemes. PMID:21874096

Toward microscale flow control using non-uniform electro-osmotic flow

NASA Astrophysics Data System (ADS)

Paratore, Federico; Boyko, Evgeniy; Gat, Amir D.; Kaigala, Govind V.; Bercovici, Moran

2018-02-01

We present a novel method that allows establishing desired flow patterns in a Hele-Shaw cell, solely by controlling the surface chemistry, without the use of physical walls. Using weak electrolytes, we locally pattern the chamber's ceiling and/or floor, thus defining a spatial distribution of surface charge. This translates to a non-uniform electric double layer which when subjected to an external electric field applied along the chamber, gives rise to non-uniform electroosmotic flow (EOF). We present the theory that allows prediction and design of such flows fields, as well as experimental demonstrations opening the door to configurable microfluidic devices.

Active mixing of complex fluids at the microscale

PubMed Central

Ober, Thomas J.; Foresti, Daniele; Lewis, Jennifer A.

2015-01-01

Mixing of complex fluids at low Reynolds number is fundamental for a broad range of applications, including materials assembly, microfluidics, and biomedical devices. Of these materials, yield stress fluids (and gels) pose the most significant challenges, especially when they must be mixed in low volumes over short timescales. New scaling relationships between mixer dimensions and operating conditions are derived and experimentally verified to create a framework for designing active microfluidic mixers that can efficiently homogenize a wide range of complex fluids. Active mixing printheads are then designed and implemented for multimaterial 3D printing of viscoelastic inks with programmable control of local composition. PMID:26396254

Microscale out-of-plane anemometer

NASA Technical Reports Server (NTRS)

Liu, Chang (Inventor); Chen, Jack (Inventor)

2005-01-01

A microscale out-of-plane thermal sensor. A resistive heater is suspended over a substrate by supports raised with respect to the substrate to provide a clearance underneath the resistive heater for fluid flow. A preferred fabrication process for the thermal sensor uses surface micromachining and a three-dimensional assembly to raise the supports and lift the resistive heater over the substrate.

Projection-viewer for microscale aerial photography

Treesearch

Robert C. Aldrich; James von Mosch; Wallace Greentree

1972-01-01

A low-cost projection-viewer has been developed to enlarge portions of microscale aerial photographs. These pictures can be used for interpretation or mapping, or for comparison with existing photographs, maps, and overlays to monitor environmental changes. The projection-viewer can enlarge from 2.5 to 20 times, and can be calibrated so that maps may be drawn with a...

Organic Materials in the Undergraduate Laboratory: Microscale Synthesis and Investigation of a Donor-Acceptor Molecule

ERIC Educational Resources Information Center

Pappenfus, Ted M.; Schliep, Karl B.; Dissanayake, Anudaththa; Ludden, Trevor; Nieto-Ortega, Belen; Lopez Navarrete, Juan T.; Ruiz Delgado, M. Carmen; Casado, Juan

2012-01-01

A series of experiments for undergraduate courses (e.g., organic, physical) have been developed in the area of small molecule organic materials. These experiments focus on understanding the electronic and redox properties of a donor-acceptor molecule that is prepared in a convenient one-step microscale reaction. The resulting intensely colored…

Microscale pH Titrations Using an Automatic Pipet.

ERIC Educational Resources Information Center

Flint, Edward B.; Kortz, Carrie L.; Taylor, Max A.

2002-01-01

Presents a microscale pH titration technique that utilizes an automatic pipet. A small aliquot (1-5 mL) of the analyte solution is titrated with repeated additions of titrant, and the pH is determined after each delivery. The equivalence point is determined graphically by either the second derivative method or a Gran plot. The pipet can be…

Two-photon excited microscale colour centre patterns in Ag-activated phosphate glass written using a focused proton beam

NASA Astrophysics Data System (ADS)

Kurobori, Toshio; Kada, Wataru; Shirao, Taichi; Satoh, Takahiro

2018-02-01

We report a demonstration of microscale patterns in Ag-activated phosphate glass fabricated using a focused proton beam with an energy range of 1-3 MeV. Various microscale patterns are based on blue and orange radiophotoluminescent (RPL) centres. Two- and three-dimensional (2D and 3D) microstructures are visualised by combining two-photon confocal microscopy with femtosecond (fs) laser pulses generated from a mode-locked Ti:sapphire laser operating at 700 nm. The reconstructed images are analytically evaluated using lateral/axial dose mapping and RPL spectra. In addition, the advantages of two-photon excitation applied to Ag-activated phosphate glass are discussed, and this method is compared with single-photon excitation.

Modular microfluidics for point-of-care protein purifications

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

Millet, L. J.; Lucheon, J. D.; Standaert, R. F.

Biochemical separations are the heart of diagnostic assays and purification methods for biologics. On-chip miniaturization and modularization of separation procedures will enable the development of customized, portable devices for personalized health-care diagnostics and point-of-use production of treatments. In this report, we describe the design and fabrication of miniature ion exchange, size exclusion and affinity chromatography modules for on-chip clean-up of recombinantly-produced proteins. Our results demonstrate that these common separations techniques can be implemented in microfluidic modules with performance comparable to conventional approaches. We introduce embedded 3-D microfluidic interconnects for integrating micro-scale separation modules that can be arranged and reconfigured tomore » suit a variety of fluidic operations or biochemical processes. In conclusion, we demonstrate the utility of the modular approach with a platform for the enrichment of enhanced green fluorescent protein (eGFP) from Escherichia coli lysate through integrated affinity and size-exclusion chromatography modules.« less

Printing Highly Controlled Suspended Carbon Nanotube Network on Micro-patterned Superhydrophobic Flexible Surface

PubMed Central

Li, Bo; Wang, Xin; Jung, Hyun Young; Kim, Young Lae; Robinson, Jeremy T.; Zalalutdinov, Maxim; Hong, Sanghyun; Hao, Ji; Ajayan, Pulickel M.; Wan, Kai-Tak; Jung, Yung Joon

2015-01-01

Suspended single-walled carbon nanotubes (SWCNTs) offer unique functionalities for electronic and electromechanical systems. Due to their outstanding flexible nature, suspended SWCNT architectures have great potential for integration into flexible electronic systems. However, current techniques for integrating SWCNT architectures with flexible substrates are largely absent, especially in a manner that is both scalable and well controlled. Here, we present a new nanostructured transfer paradigm to print scalable and well-defined suspended nano/microscale SWCNT networks on 3D patterned flexible substrates with micro- to nanoscale precision. The underlying printing/transfer mechanism, as well as the mechanical, electromechanical, and mechanical resonance properties of the suspended SWCNTs are characterized, including identifying metrics relevant for reliable and sensitive device structures. Our approach represents a fast, scalable and general method for building suspended nano/micro SWCNT architectures suitable for flexible sensing and actuation systems. PMID:26511284

Printing Highly Controlled Suspended Carbon Nanotube Network on Micro-patterned Superhydrophobic Flexible Surface.

PubMed

Li, Bo; Wang, Xin; Jung, Hyun Young; Kim, Young Lae; Robinson, Jeremy T; Zalalutdinov, Maxim; Hong, Sanghyun; Hao, Ji; Ajayan, Pulickel M; Wan, Kai-Tak; Jung, Yung Joon

2015-10-29

Suspended single-walled carbon nanotubes (SWCNTs) offer unique functionalities for electronic and electromechanical systems. Due to their outstanding flexible nature, suspended SWCNT architectures have great potential for integration into flexible electronic systems. However, current techniques for integrating SWCNT architectures with flexible substrates are largely absent, especially in a manner that is both scalable and well controlled. Here, we present a new nanostructured transfer paradigm to print scalable and well-defined suspended nano/microscale SWCNT networks on 3D patterned flexible substrates with micro- to nanoscale precision. The underlying printing/transfer mechanism, as well as the mechanical, electromechanical, and mechanical resonance properties of the suspended SWCNTs are characterized, including identifying metrics relevant for reliable and sensitive device structures. Our approach represents a fast, scalable and general method for building suspended nano/micro SWCNT architectures suitable for flexible sensing and actuation systems.

Modular microfluidics for point-of-care protein purifications.

PubMed

Millet, L J; Lucheon, J D; Standaert, R F; Retterer, S T; Doktycz, M J

2015-04-21

Biochemical separations are the heart of diagnostic assays and purification methods for biologics. On-chip miniaturization and modularization of separation procedures will enable the development of customized, portable devices for personalized health-care diagnostics and point-of-use production of treatments. In this report, we describe the design and fabrication of miniature ion exchange, size exclusion and affinity chromatography modules for on-chip clean-up of recombinantly-produced proteins. Our results demonstrate that these common separations techniques can be implemented in microfluidic modules with performance comparable to conventional approaches. We introduce embedded 3-D microfluidic interconnects for integrating micro-scale separation modules that can be arranged and reconfigured to suit a variety of fluidic operations or biochemical processes. We demonstrate the utility of the modular approach with a platform for the enrichment of enhanced green fluorescent protein (eGFP) from Escherichia coli lysate through integrated affinity and size-exclusion chromatography modules.

Modular microfluidics for point-of-care protein purifications

DOE PAGES

Millet, L. J.; Lucheon, J. D.; Standaert, R. F.; ...

2015-01-01

Biochemical separations are the heart of diagnostic assays and purification methods for biologics. On-chip miniaturization and modularization of separation procedures will enable the development of customized, portable devices for personalized health-care diagnostics and point-of-use production of treatments. In this report, we describe the design and fabrication of miniature ion exchange, size exclusion and affinity chromatography modules for on-chip clean-up of recombinantly-produced proteins. Our results demonstrate that these common separations techniques can be implemented in microfluidic modules with performance comparable to conventional approaches. We introduce embedded 3-D microfluidic interconnects for integrating micro-scale separation modules that can be arranged and reconfigured tomore » suit a variety of fluidic operations or biochemical processes. In conclusion, we demonstrate the utility of the modular approach with a platform for the enrichment of enhanced green fluorescent protein (eGFP) from Escherichia coli lysate through integrated affinity and size-exclusion chromatography modules.« less

Field-programmable lab-on-a-chip based on microelectrode dot array architecture.

PubMed

Wang, Gary; Teng, Daniel; Lai, Yi-Tse; Lu, Yi-Wen; Ho, Yingchieh; Lee, Chen-Yi

2014-09-01

The fundamentals of electrowetting-on-dielectric (EWOD) digital microfluidics are very strong: advantageous capability in the manipulation of fluids, small test volumes, precise dynamic control and detection, and microscale systems. These advantages are very important for future biochip developments, but the development of EWOD microfluidics has been hindered by the absence of: integrated detector technology, standard commercial components, on-chip sample preparation, standard manufacturing technology and end-to-end system integration. A field-programmable lab-on-a-chip (FPLOC) system based on microelectrode dot array (MEDA) architecture is presented in this research. The MEDA architecture proposes a standard EWOD microfluidic component called 'microelectrode cell', which can be dynamically configured into microfluidic components to perform microfluidic operations of the biochip. A proof-of-concept prototype FPLOC, containing a 30 × 30 MEDA, was developed by using generic integrated circuits computer aided design tools, and it was manufactured with standard low-voltage complementary metal-oxide-semiconductor technology, which allows smooth on-chip integration of microfluidics and microelectronics. By integrating 900 droplet detection circuits into microelectrode cells, the FPLOC has achieved large-scale integration of microfluidics and microelectronics. Compared to the full-custom and bottom-up design methods, the FPLOC provides hierarchical top-down design approach, field-programmability and dynamic manipulations of droplets for advanced microfluidic operations.

Evaluation of Micro- and Macro-Scale Petrophysical Characteristics of Lower Cretaceous Sandstone with Flow Modeling in µ-CT Imaged Geometry

NASA Astrophysics Data System (ADS)

Katsman, R.; Haruzi, P.; Waldmann, N.; Halisch, M.

2017-12-01

In this study petrophysical characteristics of rock samples from 3 successive outcrop layers of Hatira Formation Lower Cretaceous Sandstone in northen Israel were evaluated at micro- and macro-scales. The study was carried out by two complementary methods: using conventional experimental measurements of porosity, pore size distribution and permeability; and using a 3D µCT imaging and modeling of signle-phase flow in the real micro-scale sample geometry. The workfow included µ-CT scanning, image processing, image segmentation, and image analyses of pore network, followed by fluid flow simulations at a pore-scale. Upscaling the results of the micro-scale flow simulations yielded a macroscopic permeabilty tensor. Comparison of the upscaled and the experimentally measured rock properties demonstrated a reasonable agreement. In addition, geometrical (pore size distribution, surface area and tortuosity) and topological (Euler characteristic) characteristics of the grains and of the pore network were evaluated at a micro-scale. Statistical analyses of the samples for estimation of anisotropy and inhomogeneity of the porous media were conducted and the results agree with anisotropy and inhomogeneity of the upscaled permeabilty tensor. Isotropic pore orientation of the primary inter-granular porosity was identified in all three samples, whereas the characteristics of the secondary porosity were affected by precipitated cement and clay matrix within the primary pore network. Results of this study provide micro- and macro-scale characteristics of the Lower Cretaceous sandstone that is used in different places over the world as a reservoir for petroleum production and sequestration.

Auditory Mechanics of the Tectorial Membrane and the Cochlear Spiral

PubMed Central

Gavara, Núria; Manoussaki, Daphne; Chadwick, Richard S.

2012-01-01

Purpose of review This review is timely and relevant since new experimental and theoretical findings suggest that cochlear mechanics from the nanoscale to the macroscale are affected by mechanical properties of the tectorial membrane and the spiral shape. Recent findings Main tectorial membrane themes covered are i) composition and morphology, ii) nanoscale mechanical interactions with the outer hair cell bundle, iii) macroscale longitudinal coupling, iv) fluid interaction with inner hair cell bundles, v) macroscale dynamics and waves. Main cochlear spiral themes are macroscale low-frequency energy focusing and microscale organ of Corti shear gain. Implications Findings from new experimental and theoretical models reveal exquisite sensitivity of cochlear mechanical performance to tectorial membrane structural organization, mechanics, and its positioning with respect to hair bundles. The cochlear spiral geometry is a major determinant of low frequency hearing. Suggestions are made for future research directions. PMID:21785353

Confining standing waves in optical corrals.

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

Babayan, Y.; McMahon, J. M.; Li, S.

2009-03-01

Near-field scanning optical microscopy images of solid wall, circular, and elliptical microscale corrals show standing wave patterns confined inside the structures with a wavelength close to that of the incident light. The patterns inside the corrals can be tuned by changing the size and material of the walls, the wavelength of incident light, and polarization direction for elliptical corrals. Finite-difference time-domain calculations of the corral structures agree with the experimental observations and reveal that the electric and magnetic field intensities are out of phase inside the corral. A theoretical modal analysis indicates that the fields inside the corrals can bemore » attributed to p- and s-polarized waveguide modes, and that the superposition of the propagating and evanescent modes can explain the phase differences between the fields. These experimental and theoretical results demonstrate that electromagnetic fields on a dielectric surface can be controlled in a predictable manner.« less

Fabrication of flexible, multimodal light-emitting devices for wireless optogenetics

PubMed Central

Huang, Xian; Jung, Yei Hwan; Al-Hasani, Ream; Omenetto, Fiorenzo G.

2014-01-01

Summary The rise of optogenetics provides unique opportunities to advance materials and biomedical engineering as well as fundamental understanding in neuroscience. This protocol describes the fabrication of optoelectronic devices for studying intact neural systems. Unlike optogenetic approaches that rely on rigid fiber optics tethered to external light sources, these novel devices utilize flexible substrates to carry wirelessly powered microscale, inorganic light-emitting diodes (μ-ILEDs) and multimodal sensors inside the brain. We describe the technical procedures for construction of these devices, their corresponding radiofrequency power scavengers, and their implementation in vivo for experimental application. In total, the timeline of the procedure, including device fabrication, implantation, and preparation to begin in vivo experimentation, can be completed in approximately 3–8 weeks. Implementation of these devices allows for chronic (tested up to six months), wireless optogenetic manipulation of neural circuitry in animals experiencing behaviors such as social interaction, home cage, and other complex natural environments. PMID:24202555

Conformal piezoelectric systems for clinical and experimental characterization of soft tissue biomechanics

NASA Astrophysics Data System (ADS)

Dagdeviren, Canan; Shi, Yan; Joe, Pauline; Ghaffari, Roozbeh; Balooch, Guive; Usgaonkar, Karan; Gur, Onur; Tran, Phat L.; Crosby, Jessi R.; Meyer, Marcin; Su, Yewang; Chad Webb, R.; Tedesco, Andrew S.; Slepian, Marvin J.; Huang, Yonggang; Rogers, John A.

2015-07-01

Mechanical assessment of soft biological tissues and organs has broad relevance in clinical diagnosis and treatment of disease. Existing characterization methods are invasive, lack microscale spatial resolution, and are tailored only for specific regions of the body under quasi-static conditions. Here, we develop conformal and piezoelectric devices that enable in vivo measurements of soft tissue viscoelasticity in the near-surface regions of the epidermis. These systems achieve conformal contact with the underlying complex topography and texture of the targeted skin, as well as other organ surfaces, under both quasi-static and dynamic conditions. Experimental and theoretical characterization of the responses of piezoelectric actuator-sensor pairs laminated on a variety of soft biological tissues and organ systems in animal models provide information on the operation of the devices. Studies on human subjects establish the clinical significance of these devices for rapid and non-invasive characterization of skin mechanical properties.

A universal theory for gas breakdown from microscale to the classical Paschen law

NASA Astrophysics Data System (ADS)

Loveless, Amanda M.; Garner, Allen L.

2017-11-01

While well established for larger gaps, Paschen's law (PL) fails to accurately predict breakdown for microscale gaps, where field emission becomes important. This deviation from PL is characterized by the absence of a minimum breakdown voltage as a function of the product of pressure and gap distance, which has been demonstrated analytically for microscale and smaller gaps with no secondary emission at atmospheric pressure [A. M. Loveless and A. L. Garner, IEEE Trans. Plasma Sci. 45, 574-583 (2017)]. We extend these previous results by deriving analytic expressions that incorporate the nonzero secondary emission coefficient, γS E, that are valid for gap distances larger than those at which quantum effects become important (˜100 nm) while remaining below those at which streamers arise. We demonstrate the validity of this model by benchmarking to particle-in-cell simulations with γSE = 0 and comparing numerical results to an experiment with argon, while additionally predicting a minimum voltage that was masked by fixing the gap pressure in previous analyses. Incorporating γSE demonstrates the smooth transition from field emission dominated breakdown to the classical PL once the combination of electric field, pressure, and gap distance satisfies the conventional criterion for the Townsend avalanche; however, such a condition generally requires supra-atmospheric pressures for breakdown at the microscale. Therefore, this study provides a single universal breakdown theory for any gas at any pressure dominated by field emission or Townsend avalanche to guide engineers in avoiding breakdown when designing microscale and larger devices, or inducing breakdown for generating microplasmas.

The measurement of the synoptic scale wind over the ocean

NASA Technical Reports Server (NTRS)

Pierson, W. J.

1982-01-01

Mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic scale winds in terms of published spectral forms for the microscale, a mesoscale valley and published values of U*, VAR u', VAR v' and z/L, as defined in the text and as obtained for moderate to gale force winds. The frequencies involved correspond to periods longer than 1 hour and extend to the microscale, which starts at a period near 2 minutes, or so, and continues to the Kolmogorov inertial range. Nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u, f(= n z/u) and z/L, where z is 10 meters, L is the Monin Obukov stability length and u is evaluated at 10 meters. For the same u, different values of z/L produce a range of values of u which in turn result in variations of the eddy structure of the mesoscale and microscale spectra. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differnces and not errors when winds are compared, and quantitative values for these differences are given. Ways to improve the measurement of the synoptic scale wind by transient ships, data buoys and scatterometers on future spacecraft are described. These ways are loner averaging times for ships and data buoys, depending on the synoptic conditions, and pooling spacecraft to form super observations. Design considerations for future remote sensing systems are given.

Application of in-plant control measures in some Egyptian micro-scale dairy enterprises and its impact on heavy metal contents of their products.

PubMed

Abd El-Salam, Magda Magdy; Farahat, Mohamed F; Abu-Zuid, Gaber I; Saad, Samia G

2017-09-05

Egypt is encouraging micro-scale enterprises as proved to be one of the most important reasons of economic growth. Most of the annual milk production is processed in micro-scale dairy enterprises located in squatter areas with high health risks and negative environmental impact. The aim of this study was to assess the effectiveness of in-plant control measures in controlling lead and cadmium levels in dairy products from nine Egyptian micro-scale enterprises. The results revealed that white cheese enterprises had the highest mean lead and cadmium contents; both in their raw milk (0.712 and 0.134 mg/L, respectively) and final products (0.419 and 0.061 mg/kg). Higher compliance percentages were found with cadmium levels specified in the Egyptian standards than with lead levels and ranged from 59.4% in raw milk to 100% in dry milk for cadmium levels and from 8.3% in white cheese to 66.7% in ice cream for lead; moreover, none of the collected raw milk samples were complying with the lead levels. After implementation of in-plant control measures, lower lead levels were found in all samples with reduction percentages ranging from 35.2% in raw milk from the ice cream enterprises to 73.2% in yoghurt; moreover, higher percentages of samples complied with cadmium levels. This study highlights the urgent need for applying in-plant control measures to the Egyptian micro-scale dairy enterprises to improve both safety and quality of their products.

Changes in divergence-free grid turbulence interacting with a weak spherical shock wave

NASA Astrophysics Data System (ADS)

Kitamura, T.; Nagata, K.; Sakai, Y.; Sasoh, A.; Ito, Y.

2017-06-01

The characteristics of divergence-free grid turbulence interacting with a weak spherical shock wave with a Mach number of 1.05 are experimentally investigated. Turbulence-generating grids are used to generate nearly isotropic, divergence-free turbulence. The turbulent Reynolds number based on the Taylor microscale R eλ and the turbulent Mach number Mt are 49 ≤R eλ≤159 and 0.709 × 1 0-3≤Mt≤2.803 ×1 0-3, respectively. A spherical shock wave is generated by a diaphragmless shock tube. The instantaneous streamwise velocity before and after the interaction is measured by a hot wire probe. The results show that the root-mean-square value of streamwise velocity fluctuations (r.m.s velocity) increases and the streamwise integral length scale decreases after the interaction. The changes in the r.m.s velocity become small with the increase in R eλ and Mt for the same strength of the shock wave. This tendency is similar to that of the streamwise integral length scale. The continuous wavelet analysis shows that high intensity appears mainly in the low-frequency region and positive and negative wavelet coefficients appear periodically in time before the interaction, whereas such high intensity appears in both the low- and high-frequency regions after the interaction. The spectral analysis reveals that the energy at high wavenumbers increases after the interaction. The change in turbulence after the interaction is explained from the viewpoint of the initial turbulent Mach number. It is suggested that the change is more significant for initial divergence-free turbulence than for curl-free turbulence.

Park design and children’s active play a micro-scale spatial analysis of intensity of play in Olmsted’s Delaware Park

USDA-ARS?s Scientific Manuscript database

This paper offers a micro-scale exploration of the role of park design on intensity of physical activity among youth. The actual, unstructured use of a park - specifically, Delaware Park, an Olmsted-designed park in Buffalo, New York - by 94 children was objectively observed and analyzed using Geog...

Nondestructive chemical imaging of wood at the micro-scale: advanced technology to complement macro-scale evaluations

Treesearch

Barbara L. Illman; Julia Sedlmair; Miriam Unger; Carol Hirschmugl

2013-01-01

Chemical images help understanding of wood properties, durability, and cell wall deconstruction for conversion of lignocellulose to biofuels, nanocellulose and other value added chemicals in forest biorefineries. We describe here a new method for nondestructive chemical imaging of wood and wood-based materials at the micro-scale to complement macro-scale methods based...

How Does CIGS Performance Depend on Temperature at the Microscale?

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

Stuckelberger, Michael E.; Nietzold, Tara; West, Bradley M.

Unveiling the correlation among electrical performance, elemental distribution, and defects at the microscale is crucial for the understanding and improvement of the overall solar cell performance. While this is true in general for solar cells with polycrystalline absorber layers, it is particularly critical for defect engineering of the complex quaternary CuIn xGa 1-xSe 2 (CIGS) material system. Studying these relationships under standard ambient conditions can provide important insights but does not provide input on the behavior of the cell under real operating conditions. In this contribution, we take a close look at the complex temperature dependence of defects and voltagemore » in CIGS at the microscale. We have developed correlative X-raymicroscopymethods and adapted them for temperature-dependent measurements of the locally generated voltage and elemental compositions at the microscale. We have applied these techniques to industrial CIGS solar cells covering temperatures from room temperature up to 100 degrees C. Finally, we find underperforming areas spanning multiple grains that do not correlate with the elemental distribution of major absorber constituents. However, we demonstrate that low-performing areas perform better at higher temperatures relative to the high-performing areas.« less

How Does CIGS Performance Depend on Temperature at the Microscale?

DOE PAGES

Stuckelberger, Michael E.; Nietzold, Tara; West, Bradley M.; ...

2017-11-03

Unveiling the correlation among electrical performance, elemental distribution, and defects at the microscale is crucial for the understanding and improvement of the overall solar cell performance. While this is true in general for solar cells with polycrystalline absorber layers, it is particularly critical for defect engineering of the complex quaternary CuIn xGa 1-xSe 2 (CIGS) material system. Studying these relationships under standard ambient conditions can provide important insights but does not provide input on the behavior of the cell under real operating conditions. In this contribution, we take a close look at the complex temperature dependence of defects and voltagemore » in CIGS at the microscale. We have developed correlative X-raymicroscopymethods and adapted them for temperature-dependent measurements of the locally generated voltage and elemental compositions at the microscale. We have applied these techniques to industrial CIGS solar cells covering temperatures from room temperature up to 100 degrees C. Finally, we find underperforming areas spanning multiple grains that do not correlate with the elemental distribution of major absorber constituents. However, we demonstrate that low-performing areas perform better at higher temperatures relative to the high-performing areas.« less

MICROSCALE METABOLIC, REDOX AND ABIOTIC REACTIONS IN HANFORD 300 AREA SUBSURFACE SEDIMENTS

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

Beyenal, Haluk; McLEan, Jeff; Majors, Paul

2013-11-14

The Hanford 300 Area is a unique site due to periodic hydrologic influence of river water resulting in changes in groundwater elevation and flow direction. This area is also highly subject to uranium remobilization, the source of which is currently believed to be the region at the base of the vadose zone that is subject to period saturation due to the changes in the water levels in the Columbia River. We found that microbial processes and redox and abiotic reactions which operate at the microscale were critical to understanding factors controlling the macroscopic fate and transport of contaminants in themore » subsurface. The combined laboratory and field research showed how microscale conditions control uranium mobility and how biotic, abiotic and redox reactions relate to each other. Our findings extended the current knowledge to examine U(VI) reduction and immobilization using natural 300 Area communities as well as selected model organisms on redox-sensitive and redox-insensitive minerals. Using innovative techniques developed specifically to probe biogeochemical processes at the microscale, our research expanded our current understanding of the roles played by mineral surfaces, bacterial competition, and local biotic, abiotic and redox reaction rates on the reduction and immobilization of uranium.« less

The influence of micro-scale dimples and nano-sized grains on the fretting characteristics generated by laser pulses.

PubMed

Amanov, Auezhan; Watabe, Tsukasa; Sasaki, Shinya

2013-12-01

The tribological characteristics of micro-scale dimpled Cu-based alloy specimen generated using a laser surface texturing (LST) were assessed and compared with that of the untextured specimen. The objective of this study is to improve the tribological characteristics of internal combustion engine (ICE) bearings and bushings made of Cu-based alloy by generating micro-scale dimples using an LST. Fretting wear tests were performed by sliding a hardened SAE52100 steel ball against the untextured and LSTed specimens at a normal load of 5 N under oil-lubricated conditions. The friction force and relative movement between the specimens were measured simultaneously during the fretting tests. The test results showed that the LSTed specimens showed a reduction in friction coefficient and an enhancement in fretting wear resistance compared to that of the untextured specimen. The friction coefficient and fretting wear volume increased with increasing frequency for both untextured and LSTed specimens. The improved tribological properties of the LSTed specimen may be attributed to the micro-scale dimples, refined grain size and high lattice strain. In addition, a model for the nanocrystallization mechanism of the LSTed specimen was proposed.

A mixture theory model of fluid and solute transport in the microvasculature of normal and malignant tissues. II: Factor sensitivity analysis, calibration, and validation.

PubMed

Schuff, M M; Gore, J P; Nauman, E A

2013-12-01

The treatment of cancerous tumors is dependent upon the delivery of therapeutics through the blood by means of the microcirculation. Differences in the vasculature of normal and malignant tissues have been recognized, but it is not fully understood how these differences affect transport and the applicability of existing mathematical models has been questioned at the microscale due to the complex rheology of blood and fluid exchange with the tissue. In addition to determining an appropriate set of governing equations it is necessary to specify appropriate model parameters based on physiological data. To this end, a two stage sensitivity analysis is described which makes it possible to determine the set of parameters most important to the model's calibration. In the first stage, the fluid flow equations are examined and a sensitivity analysis is used to evaluate the importance of 11 different model parameters. Of these, only four substantially influence the intravascular axial flow providing a tractable set that could be calibrated using red blood cell velocity data from the literature. The second stage also utilizes a sensitivity analysis to evaluate the importance of 14 model parameters on extravascular flux. Of these, six exhibit high sensitivity and are integrated into the model calibration using a response surface methodology and experimental intra- and extravascular accumulation data from the literature (Dreher et al. in J Natl Cancer Inst 98(5):335-344, 2006). The model exhibits good agreement with the experimental results for both the mean extravascular concentration and the penetration depth as a function of time for inert dextran over a wide range of molecular weights.

Knowledge exchange and integrated services: experiences from an integrated community intellectual (learning) disability service for adults.

PubMed

Farrington, C; Clare, I C H; Holland, A J; Barrett, M; Oborn, E

2015-03-01

This paper examines knowledge exchange dynamics in a specialist integrated intellectual (learning) disability service, comprising specialist healthcare provision with social care commissioning and management, and considers their significance in terms of integrated service delivery. A qualitative study focusing on knowledge exchange and integrated services. Semi-structured interviews (n = 25) were conducted with members of an integrated intellectual disability service in England regarding their perceptions of knowledge exchange within the service and the way in which knowledge exchange impinges on the operation of the integrated service. Exchange of 'explicit' (codifiable) knowledge between health and care management components of the service is problematic because of a lack of integrated clinical governance and related factors such as IT and care record systems and office arrangements. Team meetings and workplace interactions allowed for informal exchange of explicit and 'tacit' (non-codifiable) knowledge, but presented challenges in terms of knowledge exchange completeness and sustainability. Knowledge exchange processes play an important role in the functioning of integrated services incorporating health and care management components. Managers need to ensure that knowledge exchange processes facilitate both explicit and tacit knowledge exchange and do not rely excessively on informal, 'ad hoc' interactions. Research on integrated services should take account of micro-scale knowledge exchange dynamics and relationships between social dynamics and physical factors. © 2014 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.

Mucin gel assembly is controlled by a collective action of non-mucin proteins, disulfide bridges, Ca2+-mediated links, and hydrogen bonding.

PubMed

Meldrum, Oliver W; Yakubov, Gleb E; Bonilla, Mauricio R; Deshmukh, Omkar; McGuckin, Michael A; Gidley, Michael J

2018-04-11

Mucus is characterized by multiple levels of assembly at different length scales which result in a unique set of rheological (flow) and mechanical properties. These physical properties determine its biological function as a highly selective barrier for transport of water and nutrients, while blocking penetration of pathogens and foreign particles. Altered integrity of the mucus layer in the small intestine has been associated with a number of gastrointestinal tract pathologies such as Crohn's disease and cystic fibrosis. In this work, we uncover an intricate hierarchy of intestinal mucin (Muc2) assembly and show how complex rheological properties emerge from synergistic interactions between mucin glycoproteins, non-mucin proteins, and Ca 2+ . Using a novel method of mucus purification, we demonstrate the mechanism of assembly of Muc2 oligomers into viscoelastic microscale domains formed via hydrogen bonding and Ca 2+ -mediated links, which require the joint presence of Ca 2+ ions and non-mucin proteins. These microscale domains aggregate to form a heterogeneous yield stress gel-like fluid, the macroscopic rheological properties of which are virtually identical to that of native intestinal mucus. Through proteomic analysis, we short-list potential protein candidates implicated in mucin assembly, thus paving the way for identifying the molecules responsible for the physiologically critical biophysical properties of mucus.

Mesoscopic Model — Advanced Simulation of Microforming Processes

NASA Astrophysics Data System (ADS)

Geißdörfer, Stefan; Engel, Ulf; Geiger, Manfred

2007-04-01

Continued miniaturization in many fields of forming technology implies the need for a better understanding of the effects occurring while scaling down from conventional macroscopic scale to microscale. At microscale, the material can no longer be regarded as a homogeneous continuum because of the presence of only a few grains in the deformation zone. This leads to a change in the material behaviour resulting among others in a large scatter of forming results. A correlation between the integral flow stress of the workpiece and the scatter of the process factors on the one hand and the mean grain size and its standard deviation on the other hand has been observed in experiments. The conventional FE-simulation of scaled down processes is not able to consider the size-effects observed such as the actual reduction of the flow stress, the increasing scatter of the process factors and a local material flow being different to that obtained in the case of macroparts. For that reason, a new simulation model has been developed taking into account all the size-effects. The present paper deals with the theoretical background of the new mesoscopic model, its characteristics like synthetic grain structure generation and the calculation of micro material properties — based on conventional material properties. The verification of the simulation model is done by carrying out various experiments with different mean grain sizes and grain structures but the same geometrical dimensions of the workpiece.

Analysis of CAD Model-based Visual Tracking for Microassembly using a New Block Set for MATLAB/Simulink

NASA Astrophysics Data System (ADS)

Kudryavtsev, Andrey V.; Laurent, Guillaume J.; Clévy, Cédric; Tamadazte, Brahim; Lutz, Philippe

2015-10-01

Microassembly is an innovative alternative to the microfabrication process of MOEMS, which is quite complex. It usually implies the use of microrobots controlled by an operator. The reliability of this approach has been already confirmed for micro-optical technologies. However, the characterization of assemblies has shown that the operator is the main source of inaccuracies in the teleoperated microassembly. Therefore, there is great interest in automating the microassembly process. One of the constraints of automation in microscale is the lack of high precision sensors capable to provide the full information about the object position. Thus, the usage of visual-based feedback represents a very promising approach allowing to automate the microassembly process. The purpose of this article is to characterize the techniques of object position estimation based on the visual data, i.e., visual tracking techniques from the ViSP library. These algorithms enables a 3-D object pose using a single view of the scene and the CAD model of the object. The performance of three main types of model-based trackers is analyzed and quantified: edge-based, texture-based and hybrid tracker. The problems of visual tracking in microscale are discussed. The control of the micromanipulation station used in the framework of our project is performed using a new Simulink block set. Experimental results are shown and demonstrate the possibility to obtain the repeatability below 1 µm.

Controlled propulsion and separation of helical particles at the nanoscale.

PubMed

Alcanzare, Maria Michiko T; Thakore, Vaibhav; Ollila, Santtu T T; Karttunen, Mikko; Ala-Nissila, Tapio

2017-03-15

Controlling the motion of nano and microscale objects in a fluid environment is a key factor in designing optimized tiny machines that perform mechanical tasks such as transport of drugs or genetic material in cells, fluid mixing to accelerate chemical reactions, and cargo transport in microfluidic chips. Directed motion is made possible by the coupled translational and rotational motion of asymmetric particles. A current challenge in achieving directed and controlled motion at the nanoscale lies in overcoming random Brownian motion due to thermal fluctuations in the fluid. We use a hybrid lattice-Boltzmann molecular dynamics method with full hydrodynamic interactions and thermal fluctuations to demonstrate that controlled propulsion of individual nanohelices in an aqueous environment is possible. We optimize the propulsion velocity and the efficiency of externally driven nanohelices. We quantify the importance of the thermal effects on the directed motion by calculating the Péclet number for various shapes, number of turns and pitch lengths of the helices. Consistent with the experimental microscale separation of chiral objects, our results indicate that in the presence of thermal fluctuations at Péclet numbers >10, chiral particles follow the direction of propagation according to its handedness and the direction of the applied torque making separation of chiral particles possible at the nanoscale. Our results provide criteria for the design and control of helical machines at the nanoscale.

Mechanism insights into enhanced trichloroethylene removal using xanthan gum-modified microscale zero-valent iron particles.

PubMed

Xin, Jia; Han, Jun; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf

2015-03-01

This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe(2+) concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the in-situ remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Experimental Investigations on Microshock Waves and Contact Surfaces

NASA Astrophysics Data System (ADS)

Kai, Yun; Garen, Walter; Teubner, Ulrich

2018-02-01

The present work reports on progress in the research of a microshock wave. Because of the lack of a good understanding of the propagation mechanism of the microshock flow system (shock wave, contact surface, and boundary layer), the current work concentrates on measuring microshock flows with special attention paid to the contact surface. A novel setup involving a glass capillary (with a 200 or 300 μ m hydraulic diameter D ) and a high-speed magnetic valve is applied to generate a shock wave with a maximum initial Mach number of 1.3. The current work applies a laser differential interferometer to perform noncontact measurements of the microshock flow's trajectory, velocity, and density. The current work presents microscale measurements of the shock-contact distance L that solves the problem of calculating the scaling factor Sc =Re ×D /(4 L ) (introduced by Brouillette), which is a parameter characterizing the scaling effects of shock waves. The results show that in contrast to macroscopic shock waves, shock waves at the microscale have a different propagation or attenuation mechanism (key issue of this Letter) which cannot be described by the conventional "leaky piston" model. The main attenuation mechanism of microshock flow may be the ever slower moving contact surface, which drives the shock wave. Different from other measurements using pressure transducers, the current setup for density measurements resolves the whole microshock flow system.

A simple and high-resolution stereolithography-based 3D bioprinting system using visible light crosslinkable bioinks.

PubMed

Wang, Zongjie; Abdulla, Raafa; Parker, Benjamin; Samanipour, Roya; Ghosh, Sanjoy; Kim, Keekyoung

2015-12-22

Bioprinting is a rapidly developing technique for biofabrication. Because of its high resolution and the ability to print living cells, bioprinting has been widely used in artificial tissue and organ generation as well as microscale living cell deposition. In this paper, we present a low-cost stereolithography-based bioprinting system that uses visible light crosslinkable bioinks. This low-cost stereolithography system was built around a commercial projector with a simple water filter to prevent harmful infrared radiation from the projector. The visible light crosslinking was achieved by using a mixture of polyethylene glycol diacrylate (PEGDA) and gelatin methacrylate (GelMA) hydrogel with eosin Y based photoinitiator. Three different concentrations of hydrogel mixtures (10% PEG, 5% PEG + 5% GelMA, and 2.5% PEG + 7.5% GelMA, all w/v) were studied with the presented systems. The mechanical properties and microstructure of the developed bioink were measured and discussed in detail. Several cell-free hydrogel patterns were generated to demonstrate the resolution of the solution. Experimental results with NIH 3T3 fibroblast cells show that this system can produce a highly vertical 3D structure with 50 μm resolution and 85% cell viability for at least five days. The developed system provides a low-cost visible light stereolithography solution and has the potential to be widely used in tissue engineering and bioengineering for microscale cell patterning.

Development of a high-throughput microscale cell disruption platform for Pichia pastoris in rapid bioprocess design.

PubMed

Bláha, Benjamin A F; Morris, Stephen A; Ogonah, Olotu W; Maucourant, Sophie; Crescente, Vincenzo; Rosenberg, William; Mukhopadhyay, Tarit K

2018-01-01

The time and cost benefits of miniaturized fermentation platforms can only be gained by employing complementary techniques facilitating high-throughput at small sample volumes. Microbial cell disruption is a major bottleneck in experimental throughput and is often restricted to large processing volumes. Moreover, for rigid yeast species, such as Pichia pastoris, no effective high-throughput disruption methods exist. The development of an automated, miniaturized, high-throughput, noncontact, scalable platform based on adaptive focused acoustics (AFA) to disrupt P. pastoris and recover intracellular heterologous protein is described. Augmented modes of AFA were established by investigating vessel designs and a novel enzymatic pretreatment step. Three different modes of AFA were studied and compared to the performance high-pressure homogenization. For each of these modes of cell disruption, response models were developed to account for five different performance criteria. Using multiple responses not only demonstrated that different operating parameters are required for different response optima, with highest product purity requiring suboptimal values for other criteria, but also allowed for AFA-based methods to mimic large-scale homogenization processes. These results demonstrate that AFA-mediated cell disruption can be used for a wide range of applications including buffer development, strain selection, fermentation process development, and whole bioprocess integration. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:130-140, 2018. © 2017 American Institute of Chemical Engineers.

On the biomechanical function of scaffolds for engineering load-bearing soft tissues.

PubMed

Stella, John A; D'Amore, Antonio; Wagner, William R; Sacks, Michael S

2010-07-01

Replacement or regeneration of load-bearing soft tissues has long been the impetus for the development of bioactive materials. While maturing, current efforts continue to be confounded by our lack of understanding of the intricate multi-scale hierarchical arrangements and interactions typically found in native tissues. The current state of the art in biomaterial processing enables a degree of controllable microstructure that can be used for the development of model systems to deduce fundamental biological implications of matrix morphologies on cell function. Furthermore, the development of computational frameworks which allow for the simulation of experimentally derived observations represents a positive departure from what has mostly been an empirically driven field, enabling a deeper understanding of the highly complex biological mechanisms we wish to ultimately emulate. Ongoing research is actively pursuing new materials and processing methods to control material structure down to the micro-scale to sustain or improve cell viability, guide tissue growth, and provide mechanical integrity, all while exhibiting the capacity to degrade in a controlled manner. The purpose of this review is not to focus solely on material processing but to assess the ability of these techniques to produce mechanically sound tissue surrogates, highlight the unique structural characteristics produced in these materials, and discuss how this translates to distinct macroscopic biomechanical behaviors. Copyright 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hierarchical analysis of the degradation of fibre-reinforced polymers under the presence of void imperfections

PubMed Central

2016-01-01

The subject of this work is the investigation of the influence of voids on the mechanical properties of fibre-reinforced polymers (FRPs) under compression loading. To specify the damage accumulation of FRPs in the presence of voids, the complex three-dimensional structure of the composite including voids was analysed and a reduced mechanical model composite was derived. The hierarchical analysis of the model composite on a micro-scale level implies the description of the stress and strain behaviour of the matrix using the photoelasticity technique and digital image correlation technology. These studies are presented along with an analytical examination of the stability of a single fibre. As a result of the experimental and analytical studies, the stiffness of the matrix and fibre as well as their bonding, the initial fibre orientation and the fibre diameter have the highest impact on the failure initiation. All these facts lead to a premature fibre–matrix debonding with ongoing loss of stability of the fibre and followed by kink-band formation. Additional studies on the meso-scale of transparent glass FRPs including a unique void showed that the experiments carried out on the model composites could be transferred to real composites. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242296

Modular microfluidic systems using reversibly attached PDMS fluid control modules

NASA Astrophysics Data System (ADS)

Skafte-Pedersen, Peder; Sip, Christopher G.; Folch, Albert; Dufva, Martin

2013-05-01

The use of soft lithography-based poly(dimethylsiloxane) (PDMS) valve systems is the dominating approach for high-density microscale fluidic control. Integrated systems enable complex flow control and large-scale integration, but lack modularity. In contrast, modular systems are attractive alternatives to integration because they can be tailored for different applications piecewise and without redesigning every element of the system. We present a method for reversibly coupling hard materials to soft lithography defined systems through self-aligning O-ring features thereby enabling easy interfacing of complex-valve-based systems with simpler detachable units. Using this scheme, we demonstrate the seamless interfacing of a PDMS-based fluid control module with hard polymer chips. In our system, 32 self-aligning O-ring features protruding from the PDMS fluid control module form chip-to-control module interconnections which are sealed by tightening four screws. The interconnection method is robust and supports complex fluidic operations in the reversibly attached passive chip. In addition, we developed a double-sided molding method for fabricating PDMS devices with integrated through-holes. The versatile system facilitates a wide range of applications due to the modular approach, where application specific passive chips can be readily attached to the flow control module.

Noise is the new signal: Moving beyond zeroth-order geomorphology (Invited)

NASA Astrophysics Data System (ADS)

Jerolmack, D. J.

2010-12-01

The last several decades have witnessed a rapid growth in our understanding of landscape evolution, led by the development of geomorphic transport laws - time- and space-averaged equations relating mass flux to some physical process(es). In statistical mechanics this approach is called mean field theory (MFT), in which complex many-body interactions are replaced with an external field that represents the average effect of those interactions. Because MFT neglects all fluctuations around the mean, it has been described as a zeroth-order fluctuation model. The mean field approach to geomorphology has enabled the development of landscape evolution models, and led to a fundamental understanding of many landform patterns. Recent research, however, has highlighted two limitations of MFT: (1) The integral (averaging) time and space scales in geomorphic systems are sometimes poorly defined and often quite large, placing the mean field approximation on uncertain footing, and; (2) In systems exhibiting fractal behavior, an integral scale does not exist - e.g., properties like mass flux are scale-dependent. In both cases, fluctuations in sediment transport are non-negligible over the scales of interest. In this talk I will synthesize recent experimental and theoretical work that confronts these limitations. Discrete element models of fluid and grain interactions show promise for elucidating transport mechanics and pattern-forming instabilities, but require detailed knowledge of micro-scale processes and are computationally expensive. An alternative approach is to begin with a reasonable MFT, and then add higher-order terms that capture the statistical dynamics of fluctuations. In either case, moving beyond zeroth-order geomorphology requires a careful examination of the origins and structure of transport “noise”. I will attempt to show how studying the signal in noise can both reveal interesting new physics, and also help to formalize the applicability of geomorphic transport laws. Flooding on an experimental alluvial fan. Intensity is related to the cumulative amount of time flow has visited an area of the fan over the experiment. Dark areas represent an emergent channel network resulting from stochastic migration of river channels.

PUBLISHER'S ANNOUNCEMENT: A revised scope for Journal of Micromechanics and Microengineering A revised scope for Journal of Micromechanics and Microengineering

NASA Astrophysics Data System (ADS)

Forbes, Ian

2010-05-01

Journal of Micromechanics and Microengineering is well known for publishing excellent work in highly competitive timescales. The journal's coverage has consistently evolved to reflect the current state of the field, and from May 2010 it will revisit its scope once again. The aims of the journal remain unchanged, however: to be the first choice of authors and readers in MEMS and micro-scale research. The new scope continues to focus on highlighting the link between fabrication technologies and their capacity to create novel devices. This link will be considered paramount in the journal, and both prospective authors and readers should let it serve as an inspiration to them. The burgeoning fields of NEMS and nano-scale engineering are more explicitly supported in the new scope. Research which ten years ago would have been considered science fiction has, through the tireless efforts of the community, become reality. The Editorial Board feel it is important to reflect the growing significance of this work in the scope. The new scope, drafted by Editor-in-Chief Professor Mark Allen, and approved by the Editorial Board, is as follows: Journal of Micromechanics and Microengineering covers all aspects of microelectromechanical structures, devices, and systems, as well as micromechanics and micromechatronics. The journal focuses on original work in fabrication and integration technologies, on the micro- and nano-scale. The journal aims to highlight the link between new fabrication technologies and their capacity to create novel devices. Original work in microengineering and nanoengineering is also reported. Such work is defined as applications of these fabrication and integration technologies to structures in which key attributes of the devices or systems depend on specific micro- or nano-scale features. Such applications span the physical, chemical, electrical and biological realms. New fabrication and integration techniques for both silicon and non-silicon materials are reported. Relevant modelling papers in micro- and nanoengineering are reported where supported by experimental data. The journal also covers integration of interface electronics with micro- and nanoengineered systems, as well as vacuum microelectronics, microfabricated electrically passive elements, and other micro- or nanoengineering-enabled electrical devices.

Microscale Synthesis, Reactions, and (Super 1)H NMR Spectroscopic Investigations of Square Planar Macrocyclic, Tetramido-N Co(III) Complexes Relevant to Green Chemistry

ERIC Educational Resources Information Center

Watson, Tanya T.; Uffelman, Erich S.; Lee, Daniel W., III; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen, R.

2004-01-01

The microscale preparation, characterization, and reactivity of a square planar Co(III) complex that has grown out of a program to introduce experiments of relevance to green chemistry into the undergraduate curriculum is presented. The given experiments illustrate the remarkable redox and aqueous acid-base stability that make the macrocycles very…

Microscale Syntheses, Reactions, and 1H NMR Spectroscopic Investigations of Square Planar Macrocyclic Tetraamido-N Cu(III) Complexes Relevant to Green Chemistry

ERIC Educational Resources Information Center

Uffelman, Erich S.; Doherty, Jonathan R.; Schulze, Carl; Burke, Amy L.; Bonnema, Kristen R.; Watson, Tanya T.; Lee, Daniel W., III

2004-01-01

Microscale fusions, description, and spectroscopic analysis of the reactivity of a square planar Cu(III) complex significant to green chemistry, are presented. The experiment also includes nine focal points on which pre-lab and post-lab questions are based, and the final exams reflect the students' comprehension of these and other features of…

Microscale assembly directed by liquid-based template.

PubMed

Chen, Pu; Luo, Zhengyuan; Güven, Sinan; Tasoglu, Savas; Ganesan, Adarsh Venkataraman; Weng, Andrew; Demirci, Utkan

2014-09-10

A liquid surface established by standing waves is used as a dynamically reconfigurable template to assemble microscale materials into ordered, symmetric structures in a scalable and parallel manner. The broad applicability of this technology is illustrated by assembling diverse materials from soft matter, rigid bodies, individual cells, cell spheroids and cell-seeded microcarrier beads. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A fully integrated oven controlled microelectromechanical oscillator – Part II. Characterization and measurement

DOE PAGES

Wojciechowski, Kenneth E.; Olsson, Roy H.

2015-06-24

Our paper reports the measurement and characterization of a fully integrated oven controlled microelectromechanical oscillator (OCMO). The OCMO takes advantage of high thermal isolation and monolithic integration of both aluminum nitride (AlN) micromechanical resonators and electronic circuitry to thermally stabilize or ovenize all the components that comprise an oscillator. Operation at microscale sizes allows implementation of high thermal resistance platform supports that enable thermal stabilization at very low-power levels when compared with the state-of-the-art oven controlled crystal oscillators. A prototype OCMO has been demonstrated with a measured temperature stability of -1.2 ppb/°C, over the commercial temperature range while using tensmore » of milliwatts of supply power and with a volume of 2.3 mm 3 (not including the printed circuit board-based thermal control loop). Additionally, due to its small thermal time constant, the thermal compensation loop can maintain stability during fast thermal transients (>10 °C/min). This new technology has resulted in a new paradigm in terms of power, size, and warm up time for high thermal stability oscillators.« less

A Cross-Course Investigation of Integrative Cases for Evolution Education.

PubMed

White, Peter John Thomas; Heidemann, Merle K; Smith, James J

2015-12-01

Evolution is a cornerstone theory in biology, yet many undergraduate students have difficulty understanding it. One reason for this is that evolution is often taught in a macro-scale context without explicit links to micro-scale processes. To address this, we developed a series of integrative evolution cases that present the evolution of various traits from their origin in genetic mutation, to the synthesis of modified proteins, to how these proteins produce novel phenotypes, to the related macro-scale impacts that the novel phenotypes have on populations in ecological communities. We postulated that students would develop a fuller understanding of evolution when learning biology in a context where these integrative evolution cases are used. We used a previously developed assessment tool, the ATEEK (Assessment Tool for Evaluating Evolution Knowledge), within a pre-course/post-course assessment framework. Students who learned biology in courses using the integrative cases performed significantly better on the evolution assessment than did students in courses that did not use the cases. We also found that student understanding of evolution increased with increased exposure to the integrative evolution cases. These findings support the general hypothesis that students acquire a more complete understanding of evolution when they learn about its genetic and molecular mechanisms along with macro-scale explanations.

A Cross-Course Investigation of Integrative Cases for Evolution Education †

PubMed Central

White, Peter John Thomas; Heidemann, Merle K.; Smith, James J.

2015-01-01

Evolution is a cornerstone theory in biology, yet many undergraduate students have difficulty understanding it. One reason for this is that evolution is often taught in a macro-scale context without explicit links to micro-scale processes. To address this, we developed a series of integrative evolution cases that present the evolution of various traits from their origin in genetic mutation, to the synthesis of modified proteins, to how these proteins produce novel phenotypes, to the related macro-scale impacts that the novel phenotypes have on populations in ecological communities. We postulated that students would develop a fuller understanding of evolution when learning biology in a context where these integrative evolution cases are used. We used a previously developed assessment tool, the ATEEK (Assessment Tool for Evaluating Evolution Knowledge), within a pre-course/post-course assessment framework. Students who learned biology in courses using the integrative cases performed significantly better on the evolution assessment than did students in courses that did not use the cases. We also found that student understanding of evolution increased with increased exposure to the integrative evolution cases. These findings support the general hypothesis that students acquire a more complete understanding of evolution when they learn about its genetic and molecular mechanisms along with macro-scale explanations. PMID:26753023

An integrated microfludic device for culturing and screening of Giardia lamblia.

PubMed

Zheng, Guo-Xia; Zhang, Xue-Mei; Yang, Yu-Suo; Zeng, Shu-Rui; Wei, Jun-Feng; Wang, Yun-Hua; Li, Ya-Jie

2014-02-01

In vitro culturing of trophozoites was important for research of Giardia lamblia (G. lamblia), especially in discovery of anti-Giardia agents. The current culture methods mainly suffer from lab-intension or the obstacle in standardizing the gas condition. Thus, it could benefit from a more streamlined and integrated approach. Microfluidics offers a way to accomplish this goal. Here we presented an integrated microfluidic device for culturing and screening of G. lamblia. The device consisted of a polydimethylsiloxane (PDMS) microchip with an aerobic culture system. In the microchip, the functionality of integrated concentration gradient generator (CGG) with micro-scale cell culture enables dose-response experiment to be performed in a simple and reagent-saving way. The diffusion-based culture chambers allowed growing G. lamblia at the in vivo like environment. It notable that the highly air permeable material of parallel chambers maintain uniform anaerobic environment in different chambers easily. Using this device, G. lamblia were successfully cultured and stressed on-chip. In all cases, a dose-related inhibitory response was detected. The application of this device for these purposes represents the first step in developing a completely integrated microfluidic platform for high-throughput screening and might be expanded to other assays based on in vitro culture of G. lamblia with further tests. Copyright © 2013 Elsevier Inc. All rights reserved.

Perspectives and Challenges of Microbial Application for Crop Improvement

PubMed Central

Timmusk, Salme; Behers, Lawrence; Muthoni, Julia; Muraya, Anthony; Aronsson, Anne-Charlotte

2017-01-01

Global population increases and climate change pose a challenge to worldwide crop production. There is a need to intensify agricultural production in a sustainable manner and to find solutions to combat abiotic stress, pathogens, and pests. Plants are associated with complex microbiomes, which have an ability to promote plant growth and stress tolerance, support plant nutrition, and antagonize plant pathogens. The integration of beneficial plant-microbe and microbiome interactions may represent a promising sustainable solution to improve agricultural production. The widespread commercial use of the plant beneficial microorganisms will require a number of issues addressed. Systems approach using microscale information technology for microbiome metabolic reconstruction has potential to advance the microbial reproducible application under natural conditions. PMID:28232839

Contribution of Streetscape Audits to Explanation of Physical Activity in Four Age Groups Based on the Microscale Audit of Pedestrian Streetscapes (MAPS)

PubMed Central

Cain, Kelli L.; Millstein, Rachel A.; Sallis, James F.; Conway, Terry L.; Gavand, Kavita A.; Frank, Lawrence D.; Saelens, Brian E.; Geremia, Carrie M.; Chapman, James; Adams, Marc A.; Glanz, Karen; King, Abby C.

2014-01-01

Ecological models of physical activity emphasize the effects of environmental influences. “Microscale” streetscape features that may affect pedestrian experience have received less research attention than macroscale walkability (e.g., residential density). The Microscale Audit of Pedestrian Streetscapes (MAPS) measures street design, transit stops, sidewalk qualities, street crossing amenities, and features impacting aesthetics. The present study examined associations of microscale attributes with multiple physical activity (PA) measures across four age groups. Areas in the San Diego, Seattle, and the Baltimore metropolitan areas, USA, were selected that varied on macro-level walkability and neighborhood income. Participants (n=3677) represented four age groups (children, adolescents, adults, older adults). MAPS audits were conducted along a 0.25 mile route along the street network from participant residences toward the nearest non-residential destination. MAPS data were collected in 2009–2010. Subscale and overall summary scores were created. Walking/biking for transportation and leisure/neighborhood PA were measured with age-appropriate surveys. Objective PA was measured with accelerometers. Mixed linear regression analyses were adjusted for macro-level walkability. Across all age groups 51.2%, 22.1%, and 15.7% of all MAPS scores were significantly associated with walking/biking for transport, leisure/neighborhood PA, and objectively-measured PA, respectively. Supporting the ecological model principle of behavioral specificity, destinations and land use, streetscape, street segment, and intersection variables were more related to transport walking/biking, while aesthetic variables were related to leisure/neighborhood PA. The overall score was related to objective PA in children and older adults. Present findings provide strong evidence that microscale environment attributes are related to PA across the lifespan. Improving microscale features may be a feasible approach to creating activity-friendly environments. PMID:24983701

Viscoplastic Creep Response and Microstructure of As-Fabricated Microscale Sn-3.0Ag-0.5Cu Solder Interconnects

NASA Astrophysics Data System (ADS)

Cuddalorepatta, Gayatri; Williams, Maureen; Dasgupta, Abhijit

2010-10-01

The viscoplastic behavior of as-fabricated, undamaged, microscale Sn-3.0 Ag-0.5Cu (SAC305) Pb-free solder is investigated and compared with that of eutectic Sn-37Pb solder and near-eutectic Sn-3.8Ag-0.7Cu (SAC387) solder from prior studies. Creep measurements of microscale SAC305 solder shear specimens show significant piece-to-piece variability under identical loading. Orientation imaging microscopy reveals that these specimens contain only a few, highly anisotropic Sn grains across the entire joint. For the studied loads, the coarse-grained Sn microstructure has a more significant impact on the scatter in primary creep compared to that in the secondary creep. The observed lack of statistical homogeneity (microstructure) and joint-dependent mechanical behavior of microscale SAC305 joints are consistent with those observed for functional microelectronics interconnects. Compared with SAC305 joints, microscale Sn-37Pb shear specimens exhibit more homogenous behavior and microstructure with a large number of small Sn (and Pb) grains. Creep damage in the Pb-free joint is predominantly concentrated at highly misoriented Sn grain boundaries. The coarse-grained Sn microstructure recrystallizes into new grains with high misorientation angles under creep loading. In spite of the observed joint-dependent behavior, as-fabricated SAC305 is significantly more creep resistant than Sn-37Pb solder and slightly less creep resistant than near-eutectic SAC387 solder. Average model constants for primary and secondary creep of SAC305 are presented. Since the viscoplastic measurements are averaged over a wide range of grain configurations, the creep model constants represent the effective continuum behavior in an average sense. The average secondary creep behavior suggests that the dominant creep mechanism is dislocation climb assisted by dislocation pipe diffusion.

Study on film resistivity of Energy Conversion Components for MEMS Initiating Explosive Device

NASA Astrophysics Data System (ADS)

Ren, Wei; Zhang, Bin; Zhao, Yulong; Chu, Enyi; Yin, Ming; Li, Hui; Wang, Kexuan

2018-03-01

Resistivity of Plane-film Energy Conversion Components is a key parameter to influence its resistance and explosive performance, and also it has important relations with the preparation of thin film technology, scale, structure and etc. In order to improve the design of Energy Conversion Components for MEMS Initiating Explosive Device, and reduce the design deviation of Energy Conversion Components in microscale, guarantee the design resistance and ignition performance of MEMS Initiating Explosive Device, this paper theoretically analyzed the influence factors of film resistivity in microscale, through the preparation of Al film and Ni-Cr film at different thickness with micro/nano, then obtain the film resistivity parameter of the typical metal under different thickness, and reveals the effect rule of the scale to the resistivity in microscale, at the same time we obtain the corresponding inflection point data.

Textured micrometer scale templates as light managing fabrication platform for organic solar cells

DOEpatents

Chaudhary, Sumit; Ho, Kai-Ming; Park, Joong-Mok; Nalwa, Kanwar Singh; Leung, Wai Y.

2016-07-26

A three-dimensional, microscale-textured, grating-shaped organic solar cell geometry. The solar cells are fabricated on gratings to give them a three-dimensional texture that provides enhanced light absorption. Introduction of microscale texturing has a positive effect on the overall power conversion efficiency of the devices. This grating-based solar cell having a grating of pre-determined pitch and height has shown improved power-conversion efficiency over a conventional flat solar cell. The improvement in efficiency is accomplished by homogeneous coverage of the grating with uniform thickness of the active layer, which is attributed to a sufficiently high pitch and low height of the underlying gratings. Also the microscale texturing leads to suppressed reflection of incident light due to the efficient coupling of the incident light into modes that are guided in the active layer.

Droplet impact on regular micro-grooved surfaces

NASA Astrophysics Data System (ADS)

Hu, Hai-Bao; Huang, Su-He; Chen, Li-Bin

2013-08-01

We have investigated experimentally the process of a droplet impact on a regular micro-grooved surface. The target surfaces are patterned such that micro-scale spokes radiate from the center, concentric circles, and parallel lines on the polishing copper plate, using Quasi-LIGA molding technology. The dynamic behavior of water droplets impacting on these structured surfaces is examined using a high-speed camera, including the drop impact processes, the maximum spreading diameters, and the lengths and numbers of fingers at different values of Weber number. Experimental results validate that the spreading processes are arrested on all target surfaces at low velocity. Also, the experimental results at higher impact velocity demonstrate that the spreading process is conducted on the surface parallel to the micro-grooves, but is arrested in the direction perpendicular to the micro-grooves. Besides, the lengths of fingers increase observably, even when they are ejected out as tiny droplets along the groove direction, at the same time the drop recoil velocity is reduced by micro-grooves which are parallel to the spreading direction, but not by micro-grooves which are vertical to the spreading direction.

A Method for Combining Experimentation and Molecular Dynamics Simulation to Improve Cohesive Zone Models for Metallic Microstructures

NASA Technical Reports Server (NTRS)

Hochhalter, J. D.; Glaessgen, E. H.; Ingraffea, A. R.; Aquino, W. A.

2009-01-01

Fracture processes within a material begin at the nanometer length scale at which the formation, propagation, and interaction of fundamental damage mechanisms occur. Physics-based modeling of these atomic processes quickly becomes computationally intractable as the system size increases. Thus, a multiscale modeling method, based on the aggregation of fundamental damage processes occurring at the nanoscale within a cohesive zone model, is under development and will enable computationally feasible and physically meaningful microscale fracture simulation in polycrystalline metals. This method employs atomistic simulation to provide an optimization loop with an initial prediction of a cohesive zone model (CZM). This initial CZM is then applied at the crack front region within a finite element model. The optimization procedure iterates upon the CZM until the finite element model acceptably reproduces the near-crack-front displacement fields obtained from experimental observation. With this approach, a comparison can be made between the original CZM predicted by atomistic simulation and the converged CZM that is based on experimental observation. Comparison of the two CZMs gives insight into how atomistic simulation scales.

Transformation-Induced, Geometrically Necessary, Dislocation-Based Flow Curve Modeling of Dual-Phase Steels: Effect of Grain Size

NASA Astrophysics Data System (ADS)

Ramazani, Ali; Mukherjee, Krishnendu; Prahl, Ulrich; Bleck, Wolfgang

2012-10-01

The flow behavior of dual-phase (DP) steels is modeled on the finite-element method (FEM) framework on the microscale, considering the effect of the microstructure through the representative volume element (RVE) approach. Two-dimensional RVEs were created from microstructures of experimentally obtained DP steels with various ferrite grain sizes. The flow behavior of single phases was modeled through the dislocation-based work-hardening approach. The volume change during austenite-to-martensite transformation was modeled, and the resultant prestrained areas in the ferrite were considered to be the storage place of transformation-induced, geometrically necessary dislocations (GNDs). The flow curves of DP steels with varying ferrite grain sizes, but constant martensite fractions, were obtained from the literature. The flow curves of simulations that take into account the GND are in better agreement with those of experimental flow curves compared with those of predictions without consideration of the GND. The experimental results obeyed the Hall-Petch relationship between yield stress and flow stress and the simulations predicted this as well.

Localization and stability in damageable amorphous solids

NASA Astrophysics Data System (ADS)

de Tommasi, D.; Marzano, S.; Puglisi, G.; Saccomandi, G.

2010-01-01

In the present article, based on a recently proposed model (De Tommasi et al. in J Rheol 50:495-512, 2006; Phys Rev Lett 100:085502, 2008), we analyze the influence of the microstructure properties on the damage behavior of amorphous materials. In accordance with the experimental observations, different scenarios of damage nucleation and evolution are associated to different material distributions at the microscale. In particular, we observe the possibilities of uniform or localized damage and strain geometries with a macroscopic behavior that may range from brittle to ductile or rubber-like. To describe the possibility of extending our stability analysis to three-dimensional damageable amorphous bodies we consider a simple boundary value problem of engineering interest.

An algorithm to predict the connectome of neural microcircuits

PubMed Central

Reimann, Michael W.; King, James G.; Muller, Eilif B.; Ramaswamy, Srikanth; Markram, Henry

2015-01-01

Experimentally mapping synaptic connections, in terms of the numbers and locations of their synapses and estimating connection probabilities, is still not a tractable task, even for small volumes of tissue. In fact, the six layers of the neocortex contain thousands of unique types of synaptic connections between the many different types of neurons, of which only a handful have been characterized experimentally. Here we present a theoretical framework and a data-driven algorithmic strategy to digitally reconstruct the complete synaptic connectivity between the different types of neurons in a small well-defined volume of tissue—the micro-scale connectome of a neural microcircuit. By enforcing a set of established principles of synaptic connectivity, and leveraging interdependencies between fundamental properties of neural microcircuits to constrain the reconstructed connectivity, the algorithm yields three parameters per connection type that predict the anatomy of all types of biologically viable synaptic connections. The predictions reproduce a spectrum of experimental data on synaptic connectivity not used by the algorithm. We conclude that an algorithmic approach to the connectome can serve as a tool to accelerate experimental mapping, indicating the minimal dataset required to make useful predictions, identifying the datasets required to improve their accuracy, testing the feasibility of experimental measurements, and making it possible to test hypotheses of synaptic connectivity. PMID:26500529

The Discovery-Oriented Approach to Organic Chemistry. 7. Rearrangement of "trans"-Stilbene Oxide with Bismuth Trifluoromethanesulfonate and Other Metal Triflates: A Microscale Green Organic Chemistry Laboratory Experiment

ERIC Educational Resources Information Center

Christensen, James E.; Huddle, Matthew G.; Rogers, Jamie L.; Yung, Herbie; Mohan, Ram S.

2008-01-01

Although green chemistry principles are increasingly stressed in the undergraduate curriculum, there are only a few lab experiments wherein the toxicity of reagents is taken into consideration in the design of the experiment. We report a microscale green organic chemistry laboratory experiment that illustrates the utility of metal triflates,…

A Microscale Approach to Chemical Kinetics in the General Chemistry Laboratory: The Potassium Iodide Hydrogen Peroxide Iodine-Clock Reaction

ERIC Educational Resources Information Center

Sattsangi, Prem D.

2011-01-01

A microscale laboratory for teaching chemical kinetics utilizing the iodine clock reaction is described. Plastic pipets, 3 mL volume, are used to store and deliver precise drops of reagents and the reaction is run in a 24 well plastic tray using a total 60 drops of reagents. With this procedure, students determine the rate of reaction and the…

Microscale simulations of shock interaction with large assembly of particles for developing point-particle models

NASA Astrophysics Data System (ADS)

Thakur, Siddharth; Neal, Chris; Mehta, Yash; Sridharan, Prasanth; Jackson, Thomas; Balachandar, S.

2017-01-01

Micrsoscale simulations are being conducted for developing point-particle and other related models that are needed for the mesoscale and macroscale simulations of explosive dispersal of particles. These particle models are required to compute (a) instantaneous aerodynamic force on the particle and (b) instantaneous net heat transfer between the particle and the surrounding. A strategy for a sequence of microscale simulations has been devised that allows systematic development of the hybrid surrogate models that are applicable at conditions representative of the explosive dispersal application. The ongoing microscale simulations seek to examine particle force dependence on: (a) Mach number, (b) Reynolds number, and (c) volume fraction (different particle arrangements such as cubic, face-centered cubic (FCC), body-centered cubic (BCC) and random). Future plans include investigation of sequences of fully-resolved microscale simulations consisting of an array of particles subjected to more realistic time-dependent flows that progressively better approximate the actual problem of explosive dispersal. Additionally, effects of particle shape, size, and number in simulation as well as the transient particle deformation dependence on various parameters including: (a) particle material, (b) medium material, (c) multiple particles, (d) incoming shock pressure and speed, (e) medium to particle impedance ratio, (f) particle shape and orientation to shock, etc. are being investigated.

Micro-scale environmental variation amplifies physiological variation among individual mussels.

PubMed

Jimenez, Ana Gabriela; Jayawardene, Sarah; Alves, Shaina; Dallmer, Jeremiah; Dowd, W Wesley

2015-12-07

The contributions of temporal and spatial environmental variation to physiological variation remain poorly resolved. Rocky intertidal zone populations are subjected to thermal variation over the tidal cycle, superimposed with micro-scale variation in individuals' body temperatures. Using the sea mussel (Mytilus californianus), we assessed the consequences of this micro-scale environmental variation for physiological variation among individuals, first by examining the latter in field-acclimatized animals, second by abolishing micro-scale environmental variation via common garden acclimation, and third by restoring this variation using a reciprocal outplant approach. Common garden acclimation reduced the magnitude of variation in tissue-level antioxidant capacities by approximately 30% among mussels from a wave-protected (warm) site, but it had no effect on antioxidant variation among mussels from a wave-exposed (cool) site. The field-acclimatized level of antioxidant variation was restored only when protected-site mussels were outplanted to a high, thermally stressful site. Variation in organismal oxygen consumption rates reflected antioxidant patterns, decreasing dramatically among protected-site mussels after common gardening. These results suggest a highly plastic relationship between individuals' genotypes and their physiological phenotypes that depends on recent environmental experience. Corresponding context-dependent changes in the physiological mean-variance relationships within populations complicate prediction of responses to shifts in environmental variability that are anticipated with global change. © 2015 The Author(s).

Study of Gas Flow Characteristics in Tight Porous Media with a Microscale Lattice Boltzmann Model

PubMed Central

Zhao, Jianlin; Yao, Jun; Zhang, Min; Zhang, Lei; Yang, Yongfei; Sun, Hai; An, Senyou; Li, Aifen

2016-01-01

To investigate the gas flow characteristics in tight porous media, a microscale lattice Boltzmann (LB) model with the regularization procedure is firstly adopted to simulate gas flow in three-dimensional (3D) digital rocks. A shale digital rock and a sandstone digital rock are reconstructed to study the effects of pressure, temperature and pore size on microscale gas flow. The simulation results show that because of the microscale effect in tight porous media, the apparent permeability is always higher than the intrinsic permeability, and with the decrease of pressure or pore size, or with the increase of temperature, the difference between apparent permeability and intrinsic permeability increases. In addition, the Knudsen numbers under different conditions are calculated and the results show that gas flow characteristics in the digital rocks under different Knudsen numbers are quite different. With the increase of Knudsen number, gas flow in the digital rocks becomes more uniform and the effect of heterogeneity of the porous media on gas flow decreases. Finally, two commonly used apparent permeability calculation models are evaluated by the simulation results and the Klinkenberg model shows better accuracy. In addition, a better proportionality factor in Klinkenberg model is proposed according to the simulation results. PMID:27587293

On the Grand Challenges in Physical Petrology: the Multiphase Crossroads

NASA Astrophysics Data System (ADS)

Bergantz, G. W.

2014-12-01

Rapid progress in experimental, micro-analytical and textural analysis at the crystal scale has produced an unprecedented record of magmatic processes. However an obstacle to further progress is the lack of understanding of how mass, energy and momentum flux associated with crystal-rich, open-system events produces identifiable outcomes. Hence developing a physically-based understanding of magmatic systems linking micro-scale petrological observations with a physical template operating at the macro-scale presents a so-called "Grand Challenge." The essence of this challenge is that magmatic systems have characteristic length and feedback scales between those accessible by classical continuum and discrete methods. It has become increasingly obvious that the old-school continuum methods have limited resolution and power of explanation for multiphase (real) magma dynamics. This is, in part, because in crystal-rich systems the deformation is non-affine, and so the concept of constitutive behavior is less applicable and likely not even relevant, especially if one is interested in the emergent character of micro-scale processes. One expression of this is the cottage industry of proposing viscosity laws for magmas, which serves as "blunt force" de facto corrections for what is intrinsically multiphase behavior. Even in more fluid-rich systems many of these laws are not suitable for use in the very transport theories they aim to support. The alternative approach is the discrete method, where multiphase interactions are explicitly resolved. This is a daunting prospect given the numbers of crystals in magmas. But perhaps all crystals don't need to be modeled. I will demonstrate how discrete methods can recover critical state behavior, resolve crystal migration, the onset of visco-elastic behavior such as melt-present shear bands which sets the large-scale mixing volumes, some of the general morpho-dynamics that underlies purported rheological models, and transient controls on the emergence and dissipation of distinct thermodynamic states. As simulations with 106 - 107 crystals are now possible both the local, micro-scale crystal processes as well as the larger scale processes controlled by particle-particle-fluid interactions, can be simultaneously resolved.

Renewable Energy Development in Hermosa Beach, California

NASA Astrophysics Data System (ADS)

Morris, K.

2016-12-01

The City of Hermosa Beach, California, with the support of the AGU's TEX program, is exploring the potential for renewable energy generation inside the City, as part of the implementation of the City's 2015 Municipal Carbon Neutral Plan. Task 1: Estimate the technical potential of existing and future technologies Given the City's characteristics, this task will identify feasible technologies: wind, solar, tidal/wave, wastewater biogas, landfill biogas, microscale anaerobic digestion (AD), and complementary energy storage. Some options may be open to the City acting alone, but others will require working with municipal partners and private entities that provide services to Hermosa Beach (e.g., wastewater treatment). Energy storage is a means to integrate intermittent renewable energy output. Task 2: Review transaction types and pathways In this task, feasible technologies will be further examined in terms of municipal ordinances and contractual paths: (a) power purchase agreements (PPAs) with developers, under which the City would purchase energy or storage services directly; (b) leases with developers, under which the City would rent sites (e.g., municipal rooftops) to developers; (c) ordinances related to permitting, under which the City would reduce regulatory barriers to entry for developers; (d) pilot projects, under which the City would engage with developers to test new technologies such as wind/wave/microscale AD (pursuant to PPAs and/or leases); and (e) existing projects, under which the City would work with current wastewater and landfill contractors to understand (i) current plans to develop renewable energy, and (ii) opportunities for the City to work with such contractors to promote renewable energy. Task 3: Estimate costs by technology Finally, the last task will gather existing information about the costs, both current and projected, of the feasible technologies, including (i) overnight construction cost (capital); (ii) integration costs (e.g., charges from Edison and energy storage); (iii) costs that may be avoided due to promotion of renewable energy; and (iv) comparisons of projected annual nominal costs (in $/MWh and net present values).

Filling in the blanks. An estimation of illicit cannabis growers' profits in Belgium.

PubMed

Vanhove, Wouter; Surmont, Tim; Van Damme, Patrick; De Ruyver, Brice

2014-05-01

As a result of increased pressure on cannabis cultivation in The Netherlands, the number of confiscated indoor cannabis plantations in Belgium is rising. Although increases are reported for all plantations sizes, half of the seized plantations contain less than 50 plants. In this study, factors and variables that influence costs and benefits of indoor cannabis cultivation are investigated as well as how these costs and benefits vary between different cannabis grower types. Real-situation data of four growers were used to perform financial analyses. Costs included fixed and variable material costs, as well as opportunity costs. Gross revenue per grow cycle was calculated based on most recent forensic findings for illicit Belgian cannabis plantations and was adjusted for the risk of getting caught. Finally, gross revenues and return on costs (ROC) were calculated over 1 year (4 cycles). Financial analysis shows that in all cases gross revenues as well as ROC are considerable, even after a single growth cycle. Highest profitability was found for large-scale (600 plants, ROC=6.8) and mid-scale plantations (150 plants, ROC=6.0). However, industrial plantations (23,000 plants, ROC=1.4) and micro-scale plantations (5 plants, ROC=2.8) are also highly remunerative. Shift of police focus away from micro-scale growers, least likely to be involved in criminal gangs, to large-scale and industrial scale plantations would influence costs as a result of changing risks of getting caught. However, sensitivity analysis shows that this does not significantly influence the conclusions on profitability of different types of indoor cannabis growers. Seizure and confiscation of profits are important elements in the integral and integrated policy approach required for tackling illicit indoor cannabis plantations. The large return of costs evidenced in the present study, underpin the policy relevance of confiscating those illicit profits as part of enforcement. Copyright © 2014 Elsevier B.V. All rights reserved.

Localized synthesis, assembly and integration of silicon nanowires

NASA Astrophysics Data System (ADS)

Englander, Ongi

Localized synthesis, assembly and integration of one-dimensional silicon nanowires with MEMS structures is demonstrated and characterized in terms of local synthesis processes, electric-field assisted self-assembly, and a proof-of-concept nanoelectromechanical system (HEMS) demonstration. Emphasis is placed on the ease of integration, process control strategies, characterization techniques and the pursuit of integrated devices. A top-down followed by a bottom-up integration approach is utilized. Simple MEMS heater structures are utilized as the microscale platforms for the localized, bottom-up synthesis of one-dimensional nanostructures. Localized heating confines the high temperature region permitting only localized nanostructure synthesis and allowing the surroundings to remain at room temperature thus enabling CMOS compatible post-processing. The vapor-liquid-solid (VLS) process in the presence of a catalytic nanoparticle, a vapor phase reactant, and a specific temperature environment is successfully employed locally. Experimentally, a 5nm thick gold-palladium layer is used as the catalyst while silane is the vapor phase reactant. The current-voltage behavior of the MEMS structures can be correlated to the approximate temperature range required for the VLS reaction to take place. Silicon nanowires averaging 45nm in diameter and up to 29mum in length synthesized at growth rates of up to 1.5mum/min result. By placing two MEMS structures in close proximity, 4--10mum apart, localized silicon nanowire growth can be used to link together MEMS structures to yield a two-terminal, self-assembled micro-to-nano system. Here, one MEMS structure is designated as the hot growth structure while a nearby structure is designated as the cold secondary structure, whose role is to provide a natural stopping point for the VLS reaction. The application of a localized electric-field, 5 to 13V/mum in strength, during the synthesis process, has been shown to improve nanowire organization, alignment, and assembly. The integrated nanoelectrormechanical system was found to be mechanically resilient as it proved to successfully withstand a wide variety of post-processing steps, including manipulations and examinations under scanning and transmission electron microscopes and aqueous processing, although a super critical drying step is necessary to preserve the integrated system during the drying process. Electrical characterization of the system proved challenging due to low carrier concentration and possible transport issues at the nano-micro interface. Nonetheless, in a proof-of-concept demonstration, the system was functionalized and tested for a hydrogen sensing application.

Nano- and micro-scale Bi-substituted iron garnet films for photonics and magneto-optic eddy current defectoscopy

NASA Astrophysics Data System (ADS)

Berzhansky, V. N.; Karavainikov, A. V.; Mikhailova, T. V.; Prokopov, A. R.; Shaposhnikov, A. N.; Shumilov, A. G.; Lugovskoy, N. V.; Semuk, E. Yu.; Kharchenko, M. F.; Lukienko, I. M.; Kharchenko, Yu. M.; Belotelov, V. I.

2017-10-01

Synthesis technology of nano-scale Bi-substituted iron garnets films with high magneto-optic activity for photonics and plasmonics applications were proposed. The micro-scale single-crystal garnet films with different types of magnetic anisotropy as a magneto-optic sensors were synthesized. It was shown that easy-axis anisotropy films demonstrated the best results for visualization of redistribution eddy current magnetic field near defects.

Surface-enabled propulsion and control of colloidal microwheels.

PubMed

Tasci, T O; Herson, P S; Neeves, K B; Marr, D W M

2016-01-04

Propulsion at the microscale requires unique strategies such as the undulating or rotating filaments that microorganisms have evolved to swim. These features however can be difficult to artificially replicate and control, limiting the ability to actuate and direct engineered microdevices to targeted locations within practical timeframes. An alternative propulsion strategy to swimming is rolling. Here we report that low-strength magnetic fields can reversibly assemble wheel-shaped devices in situ from individual colloidal building blocks and also drive, rotate and direct them along surfaces at velocities faster than most other microscale propulsion schemes. By varying spin frequency and angle relative to the surface, we demonstrate that microwheels can be directed rapidly and precisely along user-defined paths. Such in situ assembly of readily modified colloidal devices capable of targeted movements provides a practical transport and delivery tool for microscale applications, especially those in complex or tortuous geometries.

Initial investigations of microscale cellular convection in an equatorial marine atmospheric boundary layer revealed by lidar

NASA Astrophysics Data System (ADS)

Cooper, D. I.; Eichinger, W. E.; Ecke, R. E.; Kao, J. C. Y.; Reisner, J. M.; Tellier, L. L.

During the Combined Sensor Program (CSP) in March of 1996, the Los Alamos National Laboratory (LANL) fielded an advanced scanning Raman lidar. The lidar was part of a larger suite of micrometeorological sensors to quantify processes associated with the ocean-atmosphere interface, including intermittency and coherent atmospheric features in the “warm pool” of the Tropical Western Pacific (TWP) near Manus Island (2° S. lat, 147° E. long). Initial inspection of the data has revealed excellent information on the microscale vertical and horizontal spatial and temporal structure of the equatorial Marine Atmospheric Boundary Layer (MABL). The data from this experiment have added to the increasing body of measurements on surface layer convection and intermittency including, for the first time, the observation of microscale cellular convective structures such as hexagonal patterns associated with Rayleigh-Bénard cells.

A Micromechanics-Based Method for Multiscale Fatigue Prediction

NASA Astrophysics Data System (ADS)

Moore, John Allan

An estimated 80% of all structural failures are due to mechanical fatigue, often resulting in catastrophic, dangerous and costly failure events. However, an accurate model to predict fatigue remains an elusive goal. One of the major challenges is that fatigue is intrinsically a multiscale process, which is dependent on a structure's geometric design as well as its material's microscale morphology. The following work begins with a microscale study of fatigue nucleation around non- metallic inclusions. Based on this analysis, a novel multiscale method for fatigue predictions is developed. This method simulates macroscale geometries explicitly while concurrently calculating the simplified response of microscale inclusions. Thus, providing adequate detail on multiple scales for accurate fatigue life predictions. The methods herein provide insight into the multiscale nature of fatigue, while also developing a tool to aid in geometric design and material optimization for fatigue critical devices such as biomedical stents and artificial heart valves.

Micro-Organ Device

NASA Technical Reports Server (NTRS)

Sun, Wei (Inventor); Chang, Robert C. (Inventor); Starly, Binil (Inventor); Holtorf, Heidi L. (Inventor); Leslie, Julia (Inventor); Culbertson, Christopher (Inventor); Gonda, Steve R. (Inventor)

2013-01-01

A method for fabricating a micro-organ device comprises providing a microscale support having one or more microfluidic channels and one or more micro-chambers for housing a micro-organ and printing a micro-organ on the microscale support using a cell suspension in a syringe controlled by a computer-aided tissue engineering system, wherein the cell suspension comprises cells suspended in a solution containing a material that functions as a three-dimensional scaffold. The printing is performed with the computer-aided tissue engineering system according to a particular pattern. The micro-organ device comprises at least one micro-chamber each housing a micro-organ; and at least one microfluidic channel connected to the micro-chamber, wherein the micro-organ comprises cells arranged in a configuration that includes microscale spacing between portions of the cells to facilitate diffusion exchange between the cells and a medium supplied from the at least one microfluidic channel.

Micro-organ device

NASA Technical Reports Server (NTRS)

von Gustedt-Gonda, legal representative, Iris (Inventor); Holtorf, Heidi L. (Inventor); Gonda, Steve R. (Inventor); Leslie, Julia (Inventor); Chang, Robert C. (Inventor); Sun, Wei (Inventor); Starly, Binil (Inventor); Culbertson, Christopher (Inventor)

2013-01-01

A method for fabricating a micro-organ device comprises providing a microscale support having one or more microfluidic channels and one or more micro-chambers for housing a micro-organ and printing a micro-organ on the microscale support using a cell suspension in a syringe controlled by a computer-aided tissue engineering system, wherein the cell suspension comprises cells suspended in a solution containing a material that functions as a three-dimensional scaffold. The printing is performed with the computer-aided tissue engineering system according to a particular pattern. The micro-organ device comprises at least one micro-chamber each housing a micro-organ; and at least one microfluidic channel connected to the micro-chamber, wherein the micro-organ comprises cells arranged in a configuration that includes microscale spacing between portions of the cells to facilitate diffusion exchange between the cells and a medium supplied from the at least one microfluidic channel.

Microscale immobilized enzyme reactors in proteomics: latest developments.

PubMed

Safdar, Muhammad; Spross, Jens; Jänis, Janne

2014-01-10

Enzymatic digestion of proteins is one of the key steps in proteomic analyses. There has been a steady progress in the applied digestion protocols in the past, starting from conventional time-consuming in-solution or in-gel digestion protocols to rapid and efficient methods utilizing different types of microscale enzyme reactors. Application of such microreactors has been proven beneficial due to lower sample consumption, higher sensitivity and straightforward coupling with LC-MS set-ups. Novel stationary phases, immobilization techniques and device formats are being constantly developed and tested to optimize digestion efficiency of proteolytic enzymes. This review focuses on the latest developments associated with the preparation and application of microscale enzyme reactors for proteomics applications since 2008 onwards. A special attention has been paid to the discussion of different stationary phases applied for immobilization purposes. Copyright © 2013 Elsevier B.V. All rights reserved.

Surface-enabled propulsion and control of colloidal microwheels

PubMed Central

Tasci, T. O.; Herson, P. S.; Neeves, K. B.; Marr, D. W. M.

2016-01-01

Propulsion at the microscale requires unique strategies such as the undulating or rotating filaments that microorganisms have evolved to swim. These features however can be difficult to artificially replicate and control, limiting the ability to actuate and direct engineered microdevices to targeted locations within practical timeframes. An alternative propulsion strategy to swimming is rolling. Here we report that low-strength magnetic fields can reversibly assemble wheel-shaped devices in situ from individual colloidal building blocks and also drive, rotate and direct them along surfaces at velocities faster than most other microscale propulsion schemes. By varying spin frequency and angle relative to the surface, we demonstrate that microwheels can be directed rapidly and precisely along user-defined paths. Such in situ assembly of readily modified colloidal devices capable of targeted movements provides a practical transport and delivery tool for microscale applications, especially those in complex or tortuous geometries. PMID:26725747

Microstructure, crystallization and shape memory behavior of titania and yttria co-doped zirconia

DOE PAGES

Zeng, Xiao Mei; Du, Zehui; Schuh, Christopher A.; ...

2015-12-17

Small volume zirconia ceramics with few or no grain boundaries have been demonstrated recently to exhibit the shape memory effect. To explore the shape memory properties of yttria doped zirconia (YDZ), it is desirable to develop large, microscale grains, instead of submicron grains that result from typical processing of YDZ. In this paper, we have successfully produced single crystal micro-pillars from microscale grains encouraged by the addition of titania during processing. Titania has been doped into YDZ ceramics and its effect on the grain growth, crystallization and microscale elemental distribution of the ceramics have been systematically studied. With 5 mol%more » titania doping, the grain size can be increased up to ~4 μm, while retaining a large quantity of the desired tetragonal phase of zirconia. Finally, micro-pillars machined from tetragonal grains exhibit the expected shape memory effects where pillars made from titania-free YDZ would not.« less

Granular materials flow like complex fluids

NASA Astrophysics Data System (ADS)

Kou, Binquan; Cao, Yixin; Li, Jindong; Xia, Chengjie; Li, Zhifeng; Dong, Haipeng; Zhang, Ang; Zhang, Jie; Kob, Walter; Wang, Yujie

2017-11-01

Granular materials such as sand, powders and foams are ubiquitous in daily life and in industrial and geotechnical applications. These disordered systems form stable structures when unperturbed, but in the presence of external influences such as tapping or shear they `relax', becoming fluid in nature. It is often assumed that the relaxation dynamics of granular systems is similar to that of thermal glass-forming systems. However, so far it has not been possible to determine experimentally the dynamic properties of three-dimensional granular systems at the particle level. This lack of experimental data, combined with the fact that the motion of granular particles involves friction (whereas the motion of particles in thermal glass-forming systems does not), means that an accurate description of the relaxation dynamics of granular materials is lacking. Here we use X-ray tomography to determine the microscale relaxation dynamics of hard granular ellipsoids subject to an oscillatory shear. We find that the distribution of the displacements of the ellipsoids is well described by a Gumbel law (which is similar to a Gaussian distribution for small displacements but has a heavier tail for larger displacements), with a shape parameter that is independent of the amplitude of the shear strain and of the time. Despite this universality, the mean squared displacement of an individual ellipsoid follows a power law as a function of time, with an exponent that does depend on the strain amplitude and time. We argue that these results are related to microscale relaxation mechanisms that involve friction and memory effects (whereby the motion of an ellipsoid at a given point in time depends on its previous motion). Our observations demonstrate that, at the particle level, the dynamic behaviour of granular systems is qualitatively different from that of thermal glass-forming systems, and is instead more similar to that of complex fluids. We conclude that granular materials can relax even when the driving strain is weak.

Reinforcement of cement-based matrices with graphite nanomaterials

NASA Astrophysics Data System (ADS)

Sadiq, Muhammad Maqbool

Cement-based materials offer a desirable balance of compressive strength, moisture resistance, durability, economy and energy-efficiency; their tensile strength, fracture energy and durability in aggressive environments, however, could benefit from further improvements. An option for realizing some of these improvements involves introduction of discrete fibers into concrete. When compared with today's micro-scale (steel, polypropylene, glass, etc.) fibers, graphite nanomaterials (carbon nanotube, nanofiber and graphite nanoplatelet) offer superior geometric, mechanical and physical characteristics. Graphite nanomaterials would realize their reinforcement potential as far as they are thoroughly dispersed within cement-based matrices, and effectively bond to cement hydrates. The research reported herein developed non-covalent and covalent surface modification techniques to improve the dispersion and interfacial interactions of graphite nanomaterials in cement-based matrices with a dense and well graded micro-structure. The most successful approach involved polymer wrapping of nanomaterials for increasing the density of hydrophilic groups on the nanomaterial surface without causing any damage to the their structure. The nanomaterials were characterized using various spectrometry techniques, and SEM (Scanning Electron Microscopy). The graphite nanomaterials were dispersed via selected sonication procedures in the mixing water of the cement-based matrix; conventional mixing and sample preparation techniques were then employed to prepare the cement-based nanocomposite samples, which were subjected to steam curing. Comprehensive engineering and durability characteristics of cement-based nanocomposites were determined and their chemical composition, microstructure and failure mechanisms were also assessed through various spectrometry, thermogravimetry, electron microscopy and elemental analyses. Both functionalized and non-functionalized nanomaterials as well as different micro-scale fibers were used for comparison purposes at different volume fractions. Replicated mixes and tests were considered to provide the basis for statistically reliable inferences. Theoretical studies were conducted in order to develop insight into the reinforcement mechanisms of properly functionalized graphite nanomaterials. The results suggested that modified graphite nanomaterials improve the mechanical performance of cement-based matrices primarily through control of microcrack size and propagation, relying on their close spacing within matrix and dissipation of substantial energy by debonding and frictional pullout over their enormous surface areas. The gains in barrier qualities of cement-based materials with introduction of modified graphite nanomaterials could be attributed to the increased tortuosity of diffusion paths in the presence of closely spaced nanomaterials. Experimental investigations were designed and implemented towards identification of the optimum (nano- and micro-scale) reinforcement systems for high-performance concrete through RSA (Response Surface Analysis). A comprehensive experimental data base was developed on the mechanical, physical and durability characteristics as well as the structure and composition of high-performance cementitious nanocomposites reinforced with modified graphite nanomaterials and/ or different micro-fibers.

Inkjet-Print Micromagnet Array on Glass Slides for Immunomagnetic Enrichment of Circulating Tumor Cells

PubMed Central

Chen, Peng; Huang, Yu-Yen; Bhave, Gauri; Hoshino, Kazunori; Zhang, Xiaojing

2015-01-01

We report an inkjet-printed microscale magnetic structure that can be integrated on regular glass slides for the immunomagnetic screening of rare Circulating Tumor Cells (CTCs). CTCs detach from the primary tumor site, circulate with the bloodstream, and initiate the cancer metastasis process. Therefore, a liquid biopsy in the form of capturing and analyzing CTCs may provide key information for cancer prognosis and diagnosis. Inkjet printing technology provides a non-contact, layer-by-layer and mask-less approach to deposit defined magnetic patterns on an arbitrary substrate. Such thin film patterns, when placed in an external magnetic field, significantly enhance the attractive force in the near-field close to the CTCs to facilitate the separation. We demonstrated the efficacy of the inkjet-print micromagnet array integrated immunomagnetic assay in separating COLO205 (human colorectal cancer cell line) from whole blood samples. The micromagnets increased the capture efficiency by 26% compared with using plain glass slide as the substrate. PMID:26289942

Systemic characterization and evaluation of particle packings as initial sets for discrete element simulations

NASA Astrophysics Data System (ADS)

Morfa, Carlos Recarey; Cortés, Lucía Argüelles; Farias, Márcio Muniz de; Morales, Irvin Pablo Pérez; Valera, Roberto Roselló; Oñate, Eugenio

2018-07-01

A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension and shape of particles, space occupation, homogeneity, connectivity and isotropy, among others. This classification and integration of several properties allows to carry out a characterization process to systemically evaluate the particle packings in order to guarantee the quality of the initial meshes in discrete element simulations, in both the micro- and the macroscales. Several new properties were created, and improvements in existing ones are presented. Properties from other disciplines were adapted to be used in the evaluation of particle systems. The methodology allows to easily characterize media at the level of the microscale (continuous geometries—steels, rocks microstructures, etc., and discrete geometries) and the macroscale. A global, systemic and integral system for characterizing and evaluating particle sets, based on fuzzy logic, is presented. Such system allows researchers to have a unique evaluation criterion based on the aim of their research. Examples of applications are shown.

Portable Cytometry Using Microscale Electronic Sensing

PubMed Central

Emaminejad, Sam; Paik, Kee-Hyun; Tabard-Cossa, Vincent; Javanmard, Mehdi

2015-01-01

In this manuscript, we present three different micro-impedance sensing architectures for electronic counting of cells and beads. The first method of sensing is based on using an open circuit sensing electrode integrated in a micro-pore, which measures the shift in potential as a micron-sized particle passes through. Our micro-pore, based on a funnel shaped microchannel, was fabricated in PDMS and was bound covalently to a glass substrate patterned with a gold open circuit electrode. The amplification circuitry was integrated onto a battery-powered custom printed circuit board. The second method is based on a three electrode differential measurement, which opens up the potential of using signal processing techniques to increase signal to noise ratio post measurement. The third architecture uses a contactless sensing approach, which significantly minimizes the cost of the consumable component of the impedance cytometer. We demonstrated proof of concept for the three sensing architectures by measuring the detected signal due to the passage of micron sized beads through the pore. PMID:27647950

On-chip cooling by superlattice-based thin-film thermoelectrics.

PubMed

Chowdhury, Ihtesham; Prasher, Ravi; Lofgreen, Kelly; Chrysler, Gregory; Narasimhan, Sridhar; Mahajan, Ravi; Koester, David; Alley, Randall; Venkatasubramanian, Rama

2009-04-01

There is a significant need for site-specific and on-demand cooling in electronic, optoelectronic and bioanalytical devices, where cooling is currently achieved by the use of bulky and/or over-designed system-level solutions. Thermoelectric devices can address these limitations while also enabling energy-efficient solutions, and significant progress has been made in the development of nanostructured thermoelectric materials with enhanced figures-of-merit. However, fully functional practical thermoelectric coolers have not been made from these nanomaterials due to the enormous difficulties in integrating nanoscale materials into microscale devices and packaged macroscale systems. Here, we show the integration of thermoelectric coolers fabricated from nanostructured Bi2Te3-based thin-film superlattices into state-of-the-art electronic packages. We report cooling of as much as 15 degrees C at the targeted region on a silicon chip with a high ( approximately 1,300 W cm-2) heat flux. This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.

Toward a biophotonic MEMS cell sensor

NASA Astrophysics Data System (ADS)

Powers, Michael A.; Koev, Stephan T.; Schleunitz, Arne; Yi, Hyunmin; Hodzic, Vildana; Bentley, William E.; Payne, Gregory F.; Rubloff, Gary W.; Ghodssi, Reza

2005-06-01

We present a new platform for the optical analysis of biomolecules based upon the polysaccharide chitosan. The versatile, stable, and compatible nature of chitosan makes it an ideal material for integrating biological materials in microfabricated systems. Chitosan"s pH-responsive solubility allows electrochemical deposition, while its chemical reactivity enables facile coupling of proteins, oligonucleotides, and other biomolecules by covalent bonds. This work demonstrates the spatially selective assembly of a fluorescent molecule on chitosan and its applicability to microscale optical transducers. We define multimode waveguides and fluidic channels on a Pyrex wafer using a single layer of SU-8. Our implementation of sidewall patterning of transparent electrodes (indium tin oxide) on SU-8 structures is demonstrated and can be highly beneficial to fluorescent signal transduction. In this optical configuration, normally incident excitation light illuminates a chitosan surface on the vertical face of a collector waveguide intersected by a microfluidic channel. We demonstrate the collection of the optical signal in the integrated waveguide and analyze the signal by coupling the waveguide to a grating spectrometer.

Directed assembly of bio-inspired hierarchical materials with controlled nanofibrillar architectures

NASA Astrophysics Data System (ADS)

Tseng, Peter; Napier, Bradley; Zhao, Siwei; Mitropoulos, Alexander N.; Applegate, Matthew B.; Marelli, Benedetto; Kaplan, David L.; Omenetto, Fiorenzo G.

2017-05-01

In natural systems, directed self-assembly of structural proteins produces complex, hierarchical materials that exhibit a unique combination of mechanical, chemical and transport properties. This controlled process covers dimensions ranging from the nano- to the macroscale. Such materials are desirable to synthesize integrated and adaptive materials and systems. We describe a bio-inspired process to generate hierarchically defined structures with multiscale morphology by using regenerated silk fibroin. The combination of protein self-assembly and microscale mechanical constraints is used to form oriented, porous nanofibrillar networks within predesigned macroscopic structures. This approach allows us to predefine the mechanical and physical properties of these materials, achieved by the definition of gradients in nano- to macroscale order. We fabricate centimetre-scale material geometries including anchors, cables, lattices and webs, as well as functional materials with structure-dependent strength and anisotropic thermal transport. Finally, multiple three-dimensional geometries and doped nanofibrillar constructs are presented to illustrate the facile integration of synthetic and natural additives to form functional, interactive, hierarchical networks.

Systemic characterization and evaluation of particle packings as initial sets for discrete element simulations

NASA Astrophysics Data System (ADS)

Morfa, Carlos Recarey; Cortés, Lucía Argüelles; Farias, Márcio Muniz de; Morales, Irvin Pablo Pérez; Valera, Roberto Roselló; Oñate, Eugenio

2017-10-01

A methodology that comprises several characterization properties for particle packings is proposed in this paper. The methodology takes into account factors such as dimension and shape of particles, space occupation, homogeneity, connectivity and isotropy, among others. This classification and integration of several properties allows to carry out a characterization process to systemically evaluate the particle packings in order to guarantee the quality of the initial meshes in discrete element simulations, in both the micro- and the macroscales. Several new properties were created, and improvements in existing ones are presented. Properties from other disciplines were adapted to be used in the evaluation of particle systems. The methodology allows to easily characterize media at the level of the microscale (continuous geometries—steels, rocks microstructures, etc., and discrete geometries) and the macroscale. A global, systemic and integral system for characterizing and evaluating particle sets, based on fuzzy logic, is presented. Such system allows researchers to have a unique evaluation criterion based on the aim of their research. Examples of applications are shown.

Energy Spectra of Higher Reynolds Number Turbulence by the DNS with up to 122883 Grid Points

NASA Astrophysics Data System (ADS)

Ishihara, Takashi; Kaneda, Yukio; Morishita, Koji; Yokokawa, Mitsuo; Uno, Atsuya

2014-11-01

Large-scale direct numerical simulations (DNS) of forced incompressible turbulence in a periodic box with up to 122883 grid points have been performed using K computer. The maximum Taylor-microscale Reynolds number Rλ, and the maximum Reynolds number Re based on the integral length scale are over 2000 and 105, respectively. Our previous DNS with Rλ up to 1100 showed that the energy spectrum has a slope steeper than - 5 / 3 (the Kolmogorov scaling law) by factor 0 . 1 at the wavenumber range (kη < 0 . 03). Here η is the Kolmogorov length scale. Our present DNS at higher resolutions show that the energy spectra with different Reynolds numbers (Rλ > 1000) are well normalized not by the integral length-scale but by the Kolmogorov length scale, at the wavenumber range of the steeper slope. This result indicates that the steeper slope is not inherent character in the inertial subrange, and is affected by viscosity.

Microscale anthropogenic pollution modelling in a small tropical island during weak trade winds: Lagrangian particle dispersion simulations using real nested LES meteorological fields

NASA Astrophysics Data System (ADS)

Cécé, Raphaël; Bernard, Didier; Brioude, Jérome; Zahibo, Narcisse

2016-08-01

Tropical islands are characterized by thermal and orographical forcings which may generate microscale air mass circulations. The Lesser Antilles Arc includes small tropical islands (width lower than 50 km) where a total of one-and-a-half million people live. Air quality over this region is affected by anthropogenic and volcanic emissions, or saharan dust. To reduce risks for the population health, the atmospheric dispersion of emitted pollutants must be predicted. In this study, the dispersion of anthropogenic nitrogen oxides (NOx) is numerically modelled over the densely populated area of the Guadeloupe archipelago under weak trade winds, during a typical case of severe pollution. The main goal is to analyze how microscale resolutions affect air pollution in a small tropical island. Three resolutions of domain grid are selected: 1 km, 333 m and 111 m. The Weather Research and Forecasting model (WRF) is used to produce real nested microscale meteorological fields. Then the weather outputs initialize the Lagrangian Particle Dispersion Model (FLEXPART). The forward simulations of a power plant plume showed good ability to reproduce nocturnal peaks recorded by an urban air quality station. The increase in resolution resulted in an improvement of model sensitivity. The nesting to subkilometer grids helped to reduce an overestimation bias mainly because the LES domains better simulate the turbulent motions governing nocturnal flows. For peaks observed at two air quality stations, the backward sensitivity outputs identified realistic sources of NOx in the area. The increase in resolution produced a sharper inverse plume with a more accurate source area. This study showed the first application of the FLEXPART-WRF model to microscale resolutions. Overall, the coupling model WRF-LES-FLEXPART is useful to simulate the pollutant dispersion during a real case of calm wind regime over a complex terrain area. The forward and backward simulation results showed clearly that the subkilometer resolution of 333 m is necessary to reproduce realistic air pollution patterns in this case of short-range transport over a complex terrain area. Globally, this work contributes to enrich the sparsely documented domain of real nested microscale air pollution modelling. This study dealing with the determination of the proper resolution grid and proper turbulence scheme, is of significant interest to the near-source and complex terrain air quality research community.

Chip-based comparison of the osteogenesis of human bone marrow- and adipose tissue-derived mesenchymal stem cells under mechanical stimulation.

PubMed

Park, Sang-Hyug; Sim, Woo Young; Min, Byoung-Hyun; Yang, Sang Sik; Khademhosseini, Ali; Kaplan, David L

2012-01-01

Adipose tissue-derived stem cells (ASCs) are considered as an attractive stem cell source for tissue engineering and regenerative medicine. We compared human bone marrow-derived mesenchymal stem cells (hMSCs) and hASCs under dynamic hydraulic compression to evaluate and compare osteogenic abilities. A novel micro cell chip integrated with microvalves and microscale cell culture chambers separated from an air-pressure chamber was developed using microfabrication technology. The microscale chip enables the culture of two types of stem cells concurrently, where each is loaded into cell culture chambers and dynamic compressive stimulation is applied to the cells uniformly. Dynamic hydraulic compression (1 Hz, 1 psi) increased the production of osteogenic matrix components (bone sialoprotein, oateopontin, type I collagen) and integrin (CD11b and CD31) expression from both stem cell sources. Alkaline phosphatase and Alrizarin red staining were evident in the stimulated hMSCs, while the stimulated hASCs did not show significant increases in staining under the same stimulation conditions. Upon application of mechanical stimulus to the two types of stem cells, integrin (β1) and osteogenic gene markers were upregulated from both cell types. In conclusion, stimulated hMSCs and hASCs showed increased osteogenic gene expression compared to non-stimulated groups. The hMSCs were more sensitive to mechanical stimulation and more effective towards osteogenic differentiation than the hASCs under these modes of mechanical stimulation.

A deep etching mechanism for trench-bridging silicon nanowires

NASA Astrophysics Data System (ADS)

Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Erdem Alaca, B.

2016-03-01

Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping.

High-precision robotic microcontact printing (R-μCP) utilizing a vision guided selectively compliant articulated robotic arm.

PubMed

McNulty, Jason D; Klann, Tyler; Sha, Jin; Salick, Max; Knight, Gavin T; Turng, Lih-Sheng; Ashton, Randolph S

2014-06-07

Increased realization of the spatial heterogeneity found within in vivo tissue microenvironments has prompted the desire to engineer similar complexities into in vitro culture substrates. Microcontact printing (μCP) is a versatile technique for engineering such complexities onto cell culture substrates because it permits microscale control of the relative positioning of molecules and cells over large surface areas. However, challenges associated with precisely aligning and superimposing multiple μCP steps severely limits the extent of substrate modification that can be achieved using this method. Thus, we investigated the feasibility of using a vision guided selectively compliant articulated robotic arm (SCARA) for μCP applications. SCARAs are routinely used to perform high precision, repetitive tasks in manufacturing, and even low-end models are capable of achieving microscale precision. Here, we present customization of a SCARA to execute robotic-μCP (R-μCP) onto gold-coated microscope coverslips. The system not only possesses the ability to align multiple polydimethylsiloxane (PDMS) stamps but also has the capability to do so even after the substrates have been removed, reacted to graft polymer brushes, and replaced back into the system. Plus, non-biased computerized analysis shows that the system performs such sequential patterning with <10 μm precision and accuracy, which is equivalent to the repeatability specifications of the employed SCARA model. R-μCP should facilitate the engineering of complex in vivo-like complexities onto culture substrates and their integration with microfluidic devices.

Flow-through PCR on a 3D qiandu-shaped polydimethylsiloxane (PDMS) microdevice employing a single heater: toward microscale multiplex PCR.

PubMed

Wu, Wenming; Loan, Kieu The Loan; Lee, Nae Yoon

2012-05-07

Consistent temperature control in an on-chip flow-through polymerase chain reaction (PCR) employing two or more heaters is one of the main obstacles for device miniaturization and integration when realizing micro total analysis systems (μTAS), and also leads to operational complexity. In this study, we propose a qiandu (right triangular prism)-shaped polydimethylsiloxane (PDMS) microdevice with serpentine microchannels fabricated on its slanted plane, and apply the device for an on-chip flow-through PCR employing a single heater. The inclined nature of the qiandu-shaped microdevice enables the formation of a surface temperature gradient along the slanted plane of the microdevice in a height-dependent manner by the use of a single heater, and enables liquid to traverse over wide ranges of temperatures, including the three temperature zones--denaturation, annealing, and extension temperatures--required in a typical PCR. The feasibility of the qiandu-shaped PDMS microdevice as a versatile platform for performing a flow-through PCR was examined by employing multiple templates and varying the inclination angle of the device. In addition, the potential of performing a multiplex PCR using a single qiandu-shaped PDMS microdevice was explored. A 409 bp long gene fragment effective as a marker for diagnosing lung cancer and a 230 bp long gene fragment from a plasmid vector were simultaneously amplified in less than 25 min on a single microdevice, paving the way for a microscale, multiplex PCR on a single device employing a single heater.

Chip-Based Comparison of the Osteogenesis of Human Bone Marrow- and Adipose Tissue-Derived Mesenchymal Stem Cells under Mechanical Stimulation

PubMed Central

Min, Byoung-Hyun; Yang, Sang Sik; Khademhosseini, Ali; Kaplan, David L.

2012-01-01

Adipose tissue-derived stem cells (ASCs) are considered as an attractive stem cell source for tissue engineering and regenerative medicine. We compared human bone marrow-derived mesenchymal stem cells (hMSCs) and hASCs under dynamic hydraulic compression to evaluate and compare osteogenic abilities. A novel micro cell chip integrated with microvalves and microscale cell culture chambers separated from an air-pressure chamber was developed using microfabrication technology. The microscale chip enables the culture of two types of stem cells concurrently, where each is loaded into cell culture chambers and dynamic compressive stimulation is applied to the cells uniformly. Dynamic hydraulic compression (1 Hz, 1 psi) increased the production of osteogenic matrix components (bone sialoprotein, oateopontin, type I collagen) and integrin (CD11b and CD31) expression from both stem cell sources. Alkaline phosphatase and Alrizarin red staining were evident in the stimulated hMSCs, while the stimulated hASCs did not show significant increases in staining under the same stimulation conditions. Upon application of mechanical stimulus to the two types of stem cells, integrin (β1) and osteogenic gene markers were upregulated from both cell types. In conclusion, stimulated hMSCs and hASCs showed increased osteogenic gene expression compared to non-stimulated groups. The hMSCs were more sensitive to mechanical stimulation and more effective towards osteogenic differentiation than the hASCs under these modes of mechanical stimulation. PMID:23029565

Strain partitioning in shales during elastic and creep deformation observed by synchrotron X-ray micro-tomography.

NASA Astrophysics Data System (ADS)

Sone, H.; Cheung, C.; Rivers, M. L.; Wang, Y.; Yu, T.

2016-12-01

Knowledge about the ductile time-dependent constitutive behavior of geological materials is essential when evaluating the long-term integrity of subsurface structures and predicting the long-term geomechanical response of the surrounding formations. To this end, it is not only important to measure the bulk time-dependent behavior but also essential to understand the microscale mechanism by which rocks exhibit time-dependence, because laboratory data needs to be extrapolated to time-scales much beyond laboratory experiments. We conducted long-term creep experiments using Green River shale samples and obtained synchrotron X-ray images during the tests in an attempt to capture the microscale strain-partitioning that occurs within the sample. Shale samples of few millimeter dimensions were stressed up to several tens of MPa by a spring-loaded device within an X-ray transparent load frame, and the load was held constant for up to several months to allow creep deformation. Tomographic images of about 5 micron resolution were reconstructed from images collected at different timings of the experiment, which allows us to investigate where and how much strain localized during elastic and creep deformation. Tracking the position of some outstanding features in the rock texture (e.g. pyrite grains, organic material patches) indicate that strain magnitudes expected from the sample elastic and relaxation modulus can be successfully recovered from the tomographic images. We also attempt to use digital volume correlation to track sub-voxel displacements and to characterize the spatial heterogeneity of the deformation.

A deep etching mechanism for trench-bridging silicon nanowires.

PubMed

Tasdemir, Zuhal; Wollschläger, Nicole; Österle, Werner; Leblebici, Yusuf; Alaca, B Erdem

2016-03-04

Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with the surrounding microscale features up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 μm. Nanowire cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. The adoption of the technology in the fabrication of micro and nanosystems can potentially lead to a significant reduction in process complexity by facilitating direct access to the nanowire during surface processes such as contact formation and doping.

Microscale sulfur cycling in the phototrophic pink berry consortia of the Sippewissett Salt Marsh

PubMed Central

Wilbanks, Elizabeth G; Jaekel, Ulrike; Salman, Verena; Humphrey, Parris T; Eisen, Jonathan A; Facciotti, Marc T; Buckley, Daniel H; Zinder, Stephen H; Druschel, Gregory K; Fike, David A; Orphan, Victoria J

2014-01-01

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the ‘pink berry’ consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and 34S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0–500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ34S-sulfide decreased from 6‰ to −31‰ from the exterior to interior of the berry. These values correspond to sulfate–sulfide isotopic fractionations (15–53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria. PMID:24428801

The Development of a Full Field Three-Dimensional Microscale Flow Measurement Technique for Application to Near Contact Line Flows

NASA Technical Reports Server (NTRS)

He, Qun; Hallinan, Kevin

1996-01-01

The goal of this paper is to present details of the development of a new three-dimensional velocity field measurement technique which can be used to provide more insight into the dynamics of thin evaporating liquid films (not limited to just low heat inputs for the heat transfer) and which also could prove useful for the study of spreading and wetting phenomena and other microscale flows.

Two-scale modeling of joining of the aluminum alloys by a cohesive zone element technique

NASA Astrophysics Data System (ADS)

Zuo, Yinan; Wulfinghoff, Stephan; Reese, Stefanie

2016-10-01

The roll bonding of aluminum sheets is numerically investigated. In the first part of the paper, a cohesive zone element formulation in the framework of zero-thickness interface elements is developed. Based on a traction-separation law, this enables the modeling of bonding and debonding on both macroscale and microscale. Simulations on microscale are done to show the mechanism of bonding and the influence of different factors on the bonding strength.

The Production of Turbulence in Boundary Layers -- The Role of Microscale Coherent Motions.

DTIC Science & Technology

1987-06-01

unstable and it breaks up as it moves away from the wall. The wall layer must be thin and vortex stretching, due to inviscid image effects, dominate...how a Typical eddy ultimately creates the long streaks is not clear. It is entirely possible that the viscous image of the rolled up vorticity forms...clarified, especially the formation of the long streaky structure, and secondary hairpin vorticity. It appears that the outer region microscale coherent

Micro-scale heterogeneity of soil phosphorus depends on soil substrate and depth

DOE PAGES

Werner, Florian; Mueller, Carsten W.; Thieme, Jurgen; ...

2017-06-09

Soils comprise various heterogeneously distributed pools of lithogenic, free organic, occluded, adsorbed, and precipitated phosphorus (P) forms, which differ depending on soil forming factors. Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated the micro-scale distribution of total P and different specific P binding forms in aggregates taken from a high-P clay-rich soil and a low-P sandy soil by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils. Here we show that soil substrate and soilmore » depth determine micro-scale P heterogeneity in soil aggregates. In P-rich areas of all investigated soil aggregates, P was predominantly co-located with aluminium and iron oxides and hydroxides, which are known to strongly adsorb P. Clay minerals were co-located with P only to a lesser extent. In the low-P topsoil aggregate, the majority of the P was bound organically. Aluminium and iron phosphate predominated in the quartz-rich low-P subsoil aggregate. Sorbed and mineral P phases determined P speciation in the high-P top- and subsoil, and apatite was only detected in the high-P subsoil aggregate. Lastly, our results indicate that micro-scale spatial and chemical heterogeneity of P influences P accessibility and bioavailability.« less

Micro-scale heterogeneity of soil phosphorus depends on soil substrate and depth

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

Werner, Florian; Mueller, Carsten W.; Thieme, Jurgen

Soils comprise various heterogeneously distributed pools of lithogenic, free organic, occluded, adsorbed, and precipitated phosphorus (P) forms, which differ depending on soil forming factors. Small-scale heterogeneity of element distributions recently has received increased attention in soil science due to its influence on soil functions and soil fertility. We investigated the micro-scale distribution of total P and different specific P binding forms in aggregates taken from a high-P clay-rich soil and a low-P sandy soil by combining advanced spectrometric and spectroscopic techniques to introduce new insights on P accessibility and availability in soils. Here we show that soil substrate and soilmore » depth determine micro-scale P heterogeneity in soil aggregates. In P-rich areas of all investigated soil aggregates, P was predominantly co-located with aluminium and iron oxides and hydroxides, which are known to strongly adsorb P. Clay minerals were co-located with P only to a lesser extent. In the low-P topsoil aggregate, the majority of the P was bound organically. Aluminium and iron phosphate predominated in the quartz-rich low-P subsoil aggregate. Sorbed and mineral P phases determined P speciation in the high-P top- and subsoil, and apatite was only detected in the high-P subsoil aggregate. Lastly, our results indicate that micro-scale spatial and chemical heterogeneity of P influences P accessibility and bioavailability.« less

Micro-Scalable Thermal Control Device

NASA Technical Reports Server (NTRS)

Moran, Matthew E. (Inventor)

2002-01-01

A microscalable thermal control module consists of a Stirling cycle cooler that can be manipulated to operate at a selected temperature within the heating and cooling range of the module. The microscalable thermal control module is particularly suited for controlling the temperature of devices that must be maintained at precise temperatures. It is particularly suited for controlling the temperature of devices that need to be alternately heated or cooled. The module contains upper and lower opposing diaphragms, with a regenerator region containing a plurality of regenerators interposed between the diaphragms. Gaps exist on each side of each diaphragm to permit it to oscillate freely. The gap on the interior side one diaphragm is in fluid connection with the gap on the interior side of the other diaphragm through regenerators. As the diaphragms oscillate working gas is forced through the regenerators. The surface area of each regenerator is sufficiently large to effectively transfer thermal energy to and from the working gas as it is passed through them. The phase and amplitude of the oscillations can be manipulated electronically to control the steady state temperature of the active thermal control surface, and to switch the operation of the module from cooling to heating, or vice versa. The ability of the microscalable thermal control module to heat and cool may be enhanced by operating a plurality of modules in series, in parallel, or in connection through a shared bottom layer.

Light-Output Enhancement of GaN-Based Light-Emitting Diodes with Three-Dimensional Backside Reflectors Patterned by Microscale Cone Array

PubMed Central

Hu, Jinyong; Wang, Hong

2014-01-01

Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE. PMID:25133262

Validation of picogram- and femtogram-input DNA libraries for microscale metagenomics

DOE PAGES

Rinke, Christian; Low, Serene; Woodcroft, Ben J.; ...

2016-09-22

High-throughput sequencing libraries are typically limited by the requirement for nanograms to micrograms of input DNA. This bottleneck impedes the microscale analysis of ecosystems and the exploration of low biomass samples. Current methods for amplifying environmental DNA to bypass this bottleneck introduce considerable bias into metagenomic profiles. For this study, we describe and validate a simple modification of the Illumina Nextera XT DNA library preparation kit which allows creation of shotgun libraries from sub-nanogram amounts of input DNA. Community composition was reproducible down to 100 fg of input DNA based on analysis of a mock community comprising 54 phylogenetically diversemore » Bacteria and Archaea. The main technical issues with the low input libraries were a greater potential for contamination, limited DNA complexity which has a direct effect on assembly and binning, and an associated higher percentage of read duplicates. We recommend a lower limit of 1 pg (~100–1,000 microbial cells) to ensure community composition fidelity, and the inclusion of negative controls to identify reagent-specific contaminants. Applying the approach to marine surface water, pronounced differences were observed between bacterial community profiles of microliter volume samples, which we attribute to biological variation. This result is consistent with expected microscale patchiness in marine communities. We thus envision that our benchmarked, slightly modified low input DNA protocol will be beneficial for microscale and low biomass metagenomics.« less

Validation of picogram- and femtogram-input DNA libraries for microscale metagenomics

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

Rinke, Christian; Low, Serene; Woodcroft, Ben J.

High-throughput sequencing libraries are typically limited by the requirement for nanograms to micrograms of input DNA. This bottleneck impedes the microscale analysis of ecosystems and the exploration of low biomass samples. Current methods for amplifying environmental DNA to bypass this bottleneck introduce considerable bias into metagenomic profiles. For this study, we describe and validate a simple modification of the Illumina Nextera XT DNA library preparation kit which allows creation of shotgun libraries from sub-nanogram amounts of input DNA. Community composition was reproducible down to 100 fg of input DNA based on analysis of a mock community comprising 54 phylogenetically diversemore » Bacteria and Archaea. The main technical issues with the low input libraries were a greater potential for contamination, limited DNA complexity which has a direct effect on assembly and binning, and an associated higher percentage of read duplicates. We recommend a lower limit of 1 pg (~100–1,000 microbial cells) to ensure community composition fidelity, and the inclusion of negative controls to identify reagent-specific contaminants. Applying the approach to marine surface water, pronounced differences were observed between bacterial community profiles of microliter volume samples, which we attribute to biological variation. This result is consistent with expected microscale patchiness in marine communities. We thus envision that our benchmarked, slightly modified low input DNA protocol will be beneficial for microscale and low biomass metagenomics.« less

Validation of picogram- and femtogram-input DNA libraries for microscale metagenomics

PubMed Central

Low, Serene; Raina, Jean-Baptiste; Skarshewski, Adam; Le, Xuyen H.; Butler, Margaret K.; Stocker, Roman; Seymour, Justin; Tyson, Gene W.

2016-01-01

High-throughput sequencing libraries are typically limited by the requirement for nanograms to micrograms of input DNA. This bottleneck impedes the microscale analysis of ecosystems and the exploration of low biomass samples. Current methods for amplifying environmental DNA to bypass this bottleneck introduce considerable bias into metagenomic profiles. Here we describe and validate a simple modification of the Illumina Nextera XT DNA library preparation kit which allows creation of shotgun libraries from sub-nanogram amounts of input DNA. Community composition was reproducible down to 100 fg of input DNA based on analysis of a mock community comprising 54 phylogenetically diverse Bacteria and Archaea. The main technical issues with the low input libraries were a greater potential for contamination, limited DNA complexity which has a direct effect on assembly and binning, and an associated higher percentage of read duplicates. We recommend a lower limit of 1 pg (∼100–1,000 microbial cells) to ensure community composition fidelity, and the inclusion of negative controls to identify reagent-specific contaminants. Applying the approach to marine surface water, pronounced differences were observed between bacterial community profiles of microliter volume samples, which we attribute to biological variation. This result is consistent with expected microscale patchiness in marine communities. We thus envision that our benchmarked, slightly modified low input DNA protocol will be beneficial for microscale and low biomass metagenomics. PMID:27688978

Measurement of liquid film flow on nuclear rod bundle in micro-scale by using very high speed camera system

NASA Astrophysics Data System (ADS)

Pham, Son; Kawara, Zensaku; Yokomine, Takehiko; Kunugi, Tomoaki

2012-11-01

Playing important roles in the mass and heat transfer as well as the safety of boiling water reactor, the liquid film flow on nuclear fuel rods has been studied by different measurement techniques such as ultrasonic transmission, conductivity probe, etc. Obtained experimental data of this annular two-phase flow, however, are still not enough to construct the physical model for critical heat flux analysis especially at the micro-scale. Remain problems are mainly caused by complicated geometry of fuel rod bundles, high velocity and very unstable interface behavior of liquid and gas flow. To get over these difficulties, a new approach using a very high speed digital camera system has been introduced in this work. The test section simulating a 3×3 rectangular rod bundle was made of acrylic to allow a full optical observation of the camera. Image data were taken through Cassegrain optical system to maintain the spatiotemporal resolution up to 7 μm and 20 μs. The results included not only the real-time visual information of flow patterns, but also the quantitative data such as liquid film thickness, the droplets' size and speed distributions, and the tilt angle of wavy surfaces. These databases could contribute to the development of a new model for the annular two-phase flow. Partly supported by the Global Center of Excellence (G-COE) program (J-051) of MEXT, Japan.

Sandy beaches: state of the art of nematode ecology.

PubMed

Maria, Tatiana F; Vanaverbeke, Jan; Vanreusel, Ann; Esteves, André M

2016-01-01

In this review, we summarize existing knowledge of the ecology of sandy-beach nematodes, in relation to spatial distribution, food webs, pollution and climate change. We attempt to discuss spatial scale patterns (macro-, meso- and microscale) according to their degree of importance in structuring sandy-beach nematode assemblages. This review will provide a substantial background on current knowledge of sandy-beach nematodes, and can be used as a starting point to delineate further investigations in this field. Over decades, sandy beaches have been the scene of studies focusing on community and population ecology, both related to morphodynamic models. The combination of physical factors (e.g. grain size, tidal exposure) and biological interactions (e.g. trophic relationships) is responsible for the spatial distribution of nematodes. In other words, the physical factors are more important in structuring nematodes communities over large scale of distribution while biological interactions are largely important in finer-scale distributions. It has been accepted that biological interactions are assumed to be of minor importance because physical factors overshadow the biological interactions in sandy beach sediments; however, the most recent results from in-situ and ex-situ experimental investigations on behavior and biological factors on a microscale have shown promise for understanding the mechanisms underlying larger-scale patterns and processes. Besides nematodes are very promising organisms used to understand the effects of pollution and climate changes although these subjects are less studied in sandy beaches than distribution patterns.

Using high thermal stability flexible thin film thermoelectric generator at moderate temperature

NASA Astrophysics Data System (ADS)

Zheng, Zhuang-Hao; Luo, Jing-Ting; Chen, Tian-Bao; Zhang, Xiang-Hua; Liang, Guang-Xing; Fan, Ping

2018-04-01

Flexible thin film thermoelectric devices are extensively used in the microscale industry for powering wearable electronics. In this study, comprehensive optimization was conducted in materials and connection design for fabricating a high thermal stability flexible thin film thermoelectric generator. First, the thin films in the generator, including the electrodes, were prepared by magnetron sputtering deposition. The "NiCu-Cu-NiCu" multilayer electrode structure was applied to ensure the thermal stability of the device used at moderate temperature in an air atmosphere. A design with metal layer bonding and series accordant connection was then employed. The maximum efficiency of a single PN thermocouple generator is >11%, and the output power loss of the generator is <10% after integration.

Single-cell isolation using a DVD optical pickup

PubMed Central

Kasukurti, A.; Potcoava, M.; Desai, S.A.; Eggleton, C.; Marr, D. W. M.

2011-01-01

A low-cost single-cell isolation system incorporating a digital versatile disc burner (DVD RW) optical pickup has been developed. We show that these readily available modules have the required laser power and focusing optics to provide a steady Gaussian beam capable of optically trapping micron-sized colloids and red blood cells. Utility of the pickup is demonstrated through the non-destructive isolation of such particles in a laminar-flow based microfluidic device that captures and translates single microscale objects across streamlines into designated channel exits. In this, the integrated objective lens focusing coils are used to steer the optical trap across the channel, resulting in the isolation of colloids and red blood cells using a very inexpensive off-the-shelf optical component. PMID:21643294

Delivery of Functionality in Complex Food Systems: Physically Inspired Approaches from Nanoscale to Microscale, Wageningen 18–21 October 2009

PubMed Central

Ubbink, Job; Duchateau, Guus

2010-01-01

The Wageningen Delivery of Functionality symposium covered all aspects involved with food structural design to arrive at high-quality foods which meet demanding customer expectations and regulatory requirements. The symposium integrated aspects from the structural organization of foods at molecular and supramolecular scales to dedicated techniques required to describe and visualize such structures, the gastro-intestinal events and how to model these in a laboratory setting, and finally the impact those food structures and ingredients have on the consumer’s physiology and on the human perception. As an interdisciplinary platform, bringing together more than 160 researchers from academia and industry, the symposium meanwhile fulfills an important role in the food science community. PMID:21125000

3D printing of optical materials: an investigation of the microscopic properties

NASA Astrophysics Data System (ADS)

Persano, Luana; Cardarelli, Francesco; Arinstein, Arkadii; Uttiya, Sureeporn; Zussman, Eyal; Pisignano, Dario; Camposeo, Andrea

2018-02-01

3D printing technologies are currently enabling the fabrication of objects with complex architectures and tailored properties. In such framework, the production of 3D optical structures, which are typically based on optical transparent matrices, optionally doped with active molecular compounds and nanoparticles, is still limited by the poor uniformity of the printed structures. Both bulk inhomogeneities and surface roughness of the printed structures can negatively affect the propagation of light in 3D printed optical components. Here we investigate photopolymerization-based printing processes by laser confocal microscopy. The experimental method we developed allows the printing process to be investigated in-situ, with microscale spatial resolution, and in real-time. The modelling of the photo-polymerization kinetics allows the different polymerization regimes to be investigated and the influence of process variables to be rationalized. In addition, the origin of the factors limiting light propagation in printed materials are rationalized, with the aim of envisaging effective experimental strategies to improve optical properties of printed materials.

Micromechanical Fatigue Visco-Damage Model for Short Glass Fiber Reinforced Polyamide-66

NASA Astrophysics Data System (ADS)

Despringre, N.; Chemisky, Y.; Robert, G.; Meraghni, F.

This work presents a micromechanical fatigue damage model developed for short glass fiber reinforced PA66. It has been developed to predict the high cycle fatigue behavior of PA66/GF30. The model is based on an extended Mori-Tanaka method which includes coated inclusions, matrix viscoelasticity and the evolution of micro-scale damage. The developed model accounts for the nonlinear matrix viscoelasticity and the reinforcement orientation. The description of the damage processes is based on the experimental investigation of damage mechanisms previously performed through in-situ SEM tests and X-ray micro-computed tomography observations. Damage chronologies have been proposed involving three different processes: interface debonding/coating, matrix micro-cracking and fiber breakages. Their occurrence strongly depends on the microstructure and the relative humidity. Each damage mechanism is introduced through an evolution law coupled to local stress fields. The developed model is implemented using a UMAT subroutine. Its experimental validation is achieved under stress or strain controlled fatigue tests.

Tuning the Ignition Performance of a Microchip Initiator by Integrating Various Al/MoO3 Reactive Multilayer Films on a Semiconductor Bridge.

PubMed

Xu, Jianbing; Tai, Yu; Ru, Chengbo; Dai, Ji; Ye, Yinghua; Shen, Ruiqi; Zhu, Peng

2017-02-15

Reactive multilayer films (RMFs) can be integrated into semiconducting electronic structures with the use of microelectromechanical systems (MEMS) technology and represent potential applications in the advancement of microscale energy-demanding systems. In this study, aluminum/molybdenum trioxide (Al/MoO 3 )-based RMFs with different modulation periods were integrated on a semiconductor bridge (SCB) using a combination of an image reversal lift-off process and magnetron sputtering technology. This produced an energetic semiconductor bridge (ESCB)-chip initiator with controlled ignition performance. The effects of the Al/MoO 3 RMFs with different modulation periods on ignition properties of the ESCB initiator were then systematically investigated in terms of flame duration, maximum flame area, and the reaction ratio of the RMFs. These microchip initiators achieved flame durations of 60-600 μs, maximum flame areas of 2.85-17.61 mm 2 , and reaction ratios of ∼14-100% (discharged with 47 μF/30 V) by simply changing the modulation periods of the Al/MoO 3 RMFs. This behavior was also consistent with a one-dimensional diffusion reaction model. The microchip initiator exhibited a high level of integration and proved to have tuned ignition performance, which can potentially be used in civilian and military applications.

Fiber optical tweezers for microscale and nanoscale particle manipulation and force sensing

NASA Astrophysics Data System (ADS)

Liu, Yuxiang

2011-12-01

Optical tweezers have been an important tool in biology and physics for studying single molecules and colloidal systems. Most of current optical tweezers are built with microscope objectives, which are: i) expensive, ii) bulky and hard to integrate, iii) sensitive to environmental fluctuations, iv) limited in terms of working distances from the substrate, and v) rigid with the requirements on the substrate (transparent substrate made with glass and with a fixed thickness). These limitations of objective-based optical tweezers prevent them from being miniaturized. Fiber optical tweezers can provide a solution for cost reduction and miniaturization, and these optical tweezers can be potentially used in microfluidic systems. However, the existing fiber optical tweezers have the following limitations: i) low trapping efficiency due to weakly focused beams, ii) lack of the ability to control the positions of multiple particles simultaneously, and iii) limited functionalities. The overall objective of this dissertation work is to further the fundamental understanding of fiber optical tweezers through experimental study and modeling, and to develop novel fiber optical tweezers systems to enhance the capability and functionalities of fiber optical tweezers as microscale and nanoscale manipulators/sensors. The contributions of this dissertation work are summarized as follows. i) An enhanced understanding of the inclined dual-fiber optical tweezers (DFOTs) system has been achieved. Stable three dimensional (3D) optical trapping of a single micron-sized particle has been experimentally demonstrated. This is the first time that the trapping efficiency has been calibrated and the stiffness of the trap has been obtained in the experiments, which has been carried out by using two methods: the drag force method and power spectrum analysis. Such calibration enables the system to be used as a picoNewton-level force sensor in addition to a particle manipulator. The influence of system parameters on the trapping performance has been carefully investigated through both experimental and numerical studies. ii) Multiple traps have been created and carefully studied with the inclined DFOTs for the first time. Three traps, one 3D trap and two 2D traps, have been experimentally created at different vertical levels with adjustable separations and positions. iii) Multiple functionalities have been achieved and studied for the first time with the inclined DFOTs. Particle separation, grouping, stacking, rod alignment, rod rotation, and optical binding have been experimentally demonstrated. The multiple functionalities allow the inclined DFOTs to find applications in the study of interaction forces in colloidal systems as well as parallel particle manipulation in drug delivery systems. iv) Far-field superfocusing effect has been investigated and successfully demonstrated with a fiber-based surface plasmonic (SP) lens for the first time. A planar SP lens with a set of concentric nanoscale rings on a fiber endface has been developed. For the first time, a focus size that is comparable to the smallest achievable focus size of high NA objective lenses has been achieved with the fiber-based SP lens. The fiber-based SP lens can bridge the nanoscale particles/systems and the macroscale power sources/detectors, which has been a long standing challenge for nanophotonics. In addition to optical trapping, the fiber-based SP lens will impact many applications including high-resolution lithography, high-resolution fluorescence detection, and sub-wavelength imaging. v) Trapping ability enhanced with the fiber-based SP lens has been successfully demonstrated. With the help of the fiber-based SP lens, the trapping efficiency of fiber optical tweezers has been significantly enhanced, which is comparable with that of objective-based optical tweezers. A submicron-sized bacterium has been successfully trapped in three dimensions for the first time with optical tweezers based on single fibers.

Global- to Micro-Scale Evolution of the Pinatubo Aerosol: Using Composite Data Sets to Build the Picture and Assess Consistency of Different Measurements

NASA Technical Reports Server (NTRS)

Russell, P. B.; Pueschel, R. F.; Livingston, J. M.; Bergstrom, R.; Lawless, James G. (Technical Monitor)

1994-01-01

This paper brings together experimental. evidence required to build realistic models of the global evolution of physical, chemical, and optical properties of the aerosol resulting from the 1991 Pinatubo volcanic eruption. Such models are needed to compute the effects of the aerosol on atmospheric chemistry, dynamics, radiation, and temperature. Whereas there is now a large and growing body of post-Pinatubo measurements by a variety of techniques, some results are in conflict, and a self-consistent, unified picture is needed, along with an assessment of remaining uncertainties. This paper examines data from photometers, radiometers, impactors, optical counters/sizers, and lidars operated on the ground, aircraft, balloons, and spacecraft.

Two-Scale Simulation of Drop-Induced Failure of Polysilicon MEMS Sensors

PubMed Central

Mariani, Stefano; Ghisi, Aldo; Corigliano, Alberto; Martini, Roberto; Simoni, Barbara

2011-01-01

In this paper, an industrially-oriented two-scale approach is provided to model the drop-induced brittle failure of polysilicon MEMS sensors. The two length-scales here investigated are the package (macroscopic) and the sensor (mesoscopic) ones. Issues related to the polysilicon morphology at the micro-scale are disregarded; an upscaled homogenized constitutive law, able to describe the brittle cracking of silicon, is instead adopted at the meso-scale. The two-scale approach is validated against full three-scale Monte-Carlo simulations, which allow for stochastic effects linked to the microstructural properties of polysilicon. Focusing on inertial MEMS sensors exposed to drops, it is shown that the offered approach matches well the experimentally observed failure mechanisms. PMID:22163885

Revealing the physical insight of a length-scale parameter in metamaterials by exploiting the variational formulation

NASA Astrophysics Data System (ADS)

Abali, B. Emek

2018-04-01

For micro-architectured materials with a substructure, called metamaterials, we can realize a direct numerical simulation in the microscale by using classical mechanics. This method is accurate, however, computationally costly. Instead, a solution of the same problem in the macroscale is possible by means of the generalized mechanics. In this case, no detailed modeling of the substructure is necessary; however, new parameters emerge. A physical interpretation of these metamaterial parameters is challenging leading to a lack of experimental strategies for their determination. In this work, we exploit the variational formulation based on action principles and obtain a direct relation between a parameter used in the kinetic energy and a metamaterial parameter in the case of a viscoelastic model.

Application of Contact Mode AFM to Manufacturing Processes

NASA Astrophysics Data System (ADS)

Giordano, Michael A.; Schmid, Steven R.

A review of the application of contact mode atomic force microscopy (AFM) to manufacturing processes is presented. A brief introduction to common experimental techniques including hardness, scratch, and wear testing is presented, with a discussion of challenges in the extension of manufacturing scale investigations to the AFM. Differences between the macro- and nanoscales tests are discussed, including indentation size effects and their importance in the simulation of processes such as grinding. The basics of lubrication theory are presented and friction force microscopy is introduced as a method of investigating metal forming lubrication on the nano- and microscales that directly simulates tooling/workpiece asperity interactions. These concepts are followed by a discussion of their application to macroscale industrial manufacturing processes and direct correlations are made.

Calcium Signaling enhancement during oocyte maturation

NASA Astrophysics Data System (ADS)

Jung, Peter; Ullah, Ghanim; Machaca, Khaled

2006-03-01

A Ca2+ signal with a special spatial and temporal characteristic universally removes cell-cycle arrest after fertilization of a mature egg cell. The Ca2+ signal is characterized by a fast rise of intracellular Ca2+ and a slow decay on the time scale of minutes. We use computational modeling of Ca2+ release on the microscale (Ca2+ puffs) and cell-scale in conjunction with experimental knowledge of the changes in the Ca2+ signaling apparatus during oocyte maturation and changing signaling patterns to explore the relationship between organization and sensitivity of IP3 receptors and SERCA pumps and the resulting signaling patterns. We hypothesize that potentiation of the IP3 receptors during oocyte maturation is the main cause for the differentiation in the signaling patterns.

Optimization of chiral structures for microscale propulsion.

PubMed

Keaveny, Eric E; Walker, Shawn W; Shelley, Michael J

2013-02-13

Recent advances in micro- and nanoscale fabrication techniques allow for the construction of rigid, helically shaped microswimmers that can be actuated using applied magnetic fields. These swimmers represent the first steps toward the development of microrobots for targeted drug delivery and minimally invasive surgical procedures. To assess the performance of these devices and improve on their design, we perform shape optimization computations to determine swimmer geometries that maximize speed in the direction of a given applied magnetic torque. We directly assess aspects of swimmer shapes that have been developed in previous experimental studies, including helical propellers with elongated cross sections and attached payloads. From these optimizations, we identify key improvements to existing designs that result in swimming speeds that are 70-470% of their original values.

High temperature x-ray micro-tomography

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

MacDowell, Alastair A., E-mail: aamacdowell@lbl.gov; Barnard, Harold; Parkinson, Dilworth Y.

2016-07-27

There is increasing demand for 3D micro-scale time-resolved imaging of samples in realistic - and in many cases extreme environments. The data is used to understand material response, validate and refine computational models which, in turn, can be used to reduce development time for new materials and processes. Here we present the results of high temperature experiments carried out at the x-ray micro-tomography beamline 8.3.2 at the Advanced Light Source. The themes involve material failure and processing at temperatures up to 1750°C. The experimental configurations required to achieve the requisite conditions for imaging are described, with examples of ceramic matrixmore » composites, spacecraft ablative heat shields and nuclear reactor core Gilsocarbon graphite.« less

Prediction of the blowout of jet diffusion flames in a coflowing stream of air

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

Karbasi, M.; Wierzba, I.

1995-12-31

The blowout limits of a lifted diffusion flame in a coflowing stream of air are estimated using a simple model for extinction, for a range of fuels, jet diameters and co-flowing stream velocities. The proposed model uses a parameter which relates to the ratio of a time associated with the mixing processes in a turbulent jet to a characteristic chemical time. The Kolmogorov microscale of time is used as time scale in this model. It is shown that turbulent diffusion flames are quenched by excessive turbulence for a critical value of this parameter. The predicted blowout velocity of diffusion flamesmore » obtained using this model is in good agreement with the available experimental data.« less

Brain Neuromodulation Techniques: A Review.

PubMed

Lewis, Philip M; Thomson, Richard H; Rosenfeld, Jeffrey V; Fitzgerald, Paul B

2016-08-01

The modulation of brain function via the application of weak direct current was first observed directly in the early 19th century. In the past 3 decades, transcranial magnetic stimulation and deep brain stimulation have undergone clinical translation, offering alternatives to pharmacological treatment of neurological and neuropsychiatric disorders. Further development of novel neuromodulation techniques employing ultrasound, micro-scale magnetic fields and optogenetics is being propelled by a rapidly improving understanding of the clinical and experimental applications of artificially stimulating or depressing brain activity in human health and disease. With the current rapid growth in neuromodulation technologies and applications, it is timely to review the genesis of the field and the current state of the art in this area. © The Author(s) 2016.

Crystal Growth of Device Quality Gaas in Space

NASA Technical Reports Server (NTRS)

Gatos, H. C.

1985-01-01

The GaAs research evolves about these key thrust areas. The overall program combines: (1) studies of crystal growth on novel approaches to engineering of semiconductor material (i.e., GaAs and related compounds); (2) investigation and correlation of materials properties and electronic characteristics on a macro- and microscale; and (3) investigation of electronic properties and phenomena controlling device applications and device performance. This effort is aimed at the essential ground-based program which would insure successful experimentation with and eventually processing of GaAs in near zero gravity environment. It is believed that this program addresses in a unique way materials engineering aspects which bear directly on the future exploitation of the potential of GaAs and related materials in device and systems applications.

A microstructural model of motion of macro-twin interfaces in Ni-Mn-Ga 10 M martensite

NASA Astrophysics Data System (ADS)

Seiner, Hanuš; Straka, Ladislav; Heczko, Oleg

2014-03-01

We present a continuum-based model of microstructures forming at the macro-twin interfaces in thermoelastic martensites and apply this model to highly mobile interfaces in 10 M modulated Ni-Mn-Ga martensite. The model is applied at three distinct spatial scales observed in the experiment: meso-scale (modulation twinning), micro-scale (compound a-b lamination), and nano-scale (nanotwining in the concept of adaptive martensite). We show that two mobile interfaces (Type I and Type II macro-twins) have different micromorphologies at all considered spatial scales, which can directly explain their different twinning stress observed in experiments. The results of the model are discussed with respect to various experimental observations at all three considered spatial scales.

Developing and Validating an Abbreviated Version of the Microscale Audit for Pedestrian Streetscapes (MAPS-Abbreviated).

PubMed

Cain, Kelli L; Gavand, Kavita A; Conway, Terry L; Geremia, Carrie M; Millstein, Rachel A; Frank, Lawrence D; Saelens, Brian E; Adams, Marc A; Glanz, Karen; King, Abby C; Sallis, James F

2017-06-01

Macroscale built environment factors (e.g., street connectivity) are correlated with physical activity. Less-studied but more modifiable microscale elements (e.g., sidewalks) may also influence physical activity, but shorter audit measures of microscale elements are needed to promote wider use. This study evaluated the relation of an abbreviated 54-item streetscape audit tool with multiple measures of physical activity in four age groups. We developed a 54-item version from the original 120-item Microscale Audit of Pedestrian Streetscapes (MAPS). Audits were conducted on 0.25-0.45 mile routes from participant residences toward the nearest nonresidential destination for children (N=758), adolescents (N=897), younger adults (N=1,655), and older adults (N=367). Active transport and leisure physical activity were measured with surveys, and objective physical activity was measured with accelerometers. Items to retain from original MAPS were selected primarily by correlations with physical activity. Mixed linear regression analyses were conducted for MAPS-Abbreviated summary scores, adjusting for demographics, participant clustering, and macroscale walkability. MAPS-Abbreviated and original MAPS total scores correlated r=.94 The MAPS-Abbreviated tool was related similarly to physical activity outcomes as the original MAPS. Destinations and land use, streetscape and walking path characteristics, and overall total scores were significantly related to active transport in all age groups. Street crossing characteristics were related to active transport in children and older adults. Aesthetics and social characteristics were related to leisure physical activity in children and younger adults, and cul-de-sacs were related with physical activity in youth. Total scores were related to accelerometer-measured physical activity in children and older adults. MAPS-Abbreviated is a validated observational measure for use in research. The length and related cost of implementation has been cited as a barrier to use of microscale instruments, so availability of this shorter validated measure could lead to more widespread use of streetscape audits in health research.

Superimpose signal processing method for micro-scale thermal imaging of solar salts at high temperature

NASA Astrophysics Data System (ADS)

Morikawa, Junko; Zamengo, Massimiliano; Kato, Yukitaka

2016-05-01

The global interest in energy applications activates the advanced study about the molten salts in the usage of fluids in the power cycle, such as for transport and heat storage in solar power facilities. However, the basic properties of molten salts show a general scattering in characterization especially in thermal properties. It is suggested that new studies are required on the measurement of thermal properties of solar salts using recent technologies. In this study, micro-scale heat transfer and phase change in molten salts are presented using our originally developed device: the micro-bolometer Infrared focal plane arrays (IR FPA) measuring system is a portable type instrument, which is re-designed to measure the thermal phenomena in high temperature up to 700 °C or higher. The superimpose system is newly setup adjusted to the signal processing in high temperature to realize the quantitative thermal imaging, simultaneously. The portable type apparatus for a quantitative micro-scale thermography using a micro-bolometer has been proposed based on an achromatic lens design to capture a micro-scale image in the long-wave infrared, a video signal superimposing for the real time emissivity correction, and a pseudo acceleration of a timeframe. Combined with the superimpose technique, the micro-scale thermal imaging in high temperature is achieved and the molten flows of the solar salts, sodium nitrate, and potassium nitrate are successfully observed. The solar salt, the mixture of sodium nitrate and potassium nitrate, shows a different shape of exothermic heat front morphology in the lower phase transition (solidification) temperature than the nitrates on cooling. The proposed measuring technique will be utilized to accelerate the screening step to determine the phase diagram and the eutectics of the multiple mixtures of candidate molten salts, which may be used as heat transport medium from the concentrated solar power to a processing plant for thermal energy storage.

Developing and Validating an Abbreviated Version of the Microscale Audit for Pedestrian Streetscapes (MAPS-Abbreviated)

PubMed Central

Cain, Kelli L.; Gavand, Kavita A.; Conway, Terry L.; Geremia, Carrie M.; Millstein, Rachel A.; Frank, Lawrence D.; Saelens, Brian E.; Adams, Marc A.; Glanz, Karen; King, Abby C.; Sallis, James F.

2017-01-01

Purpose Macroscale built environment factors (e.g., street connectivity) are correlated with physical activity. Less-studied but more modifiable microscale elements (e.g., sidewalks) may also influence physical activity, but shorter audit measures of microscale elements are needed to promote wider use. This study evaluated the relation of an abbreviated 54-item streetscape audit tool with multiple measures of physical activity in four age groups. Methods We developed a 54-item version from the original 120-item Microscale Audit of Pedestrian Streetscapes (MAPS). Audits were conducted on 0.25-0.45 mile routes from participant residences toward the nearest nonresidential destination for children (N=758), adolescents (N=897), younger adults (N=1,655), and older adults (N=367). Active transport and leisure physical activity were measured with surveys, and objective physical activity was measured with accelerometers. Items to retain from original MAPS were selected primarily by correlations with physical activity. Mixed linear regression analyses were conducted for MAPS-Abbreviated summary scores, adjusting for demographics, participant clustering, and macroscale walkability. Results MAPS-Abbreviated and original MAPS total scores correlated r=.94 The MAPS-Abbreviated tool was related similarly to physical activity outcomes as the original MAPS. Destinations and land use, streetscape and walking path characteristics, and overall total scores were significantly related to active transport in all age groups. Street crossing characteristics were related to active transport in children and older adults. Aesthetics and social characteristics were related to leisure physical activity in children and younger adults, and cul-de-sacs were related with physical activity in youth. Total scores were related to accelerometer-measured physical activity in children and older adults. Conclusion MAPS-Abbreviated is a validated observational measure for use in research. The length and related cost of implementation has been cited as a barrier to use of microscale instruments, so availability of this shorter validated measure could lead to more widespread use of streetscape audits in health research. PMID:29270361

μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble.

PubMed

Yamaguchi, Eiichiro; Smith, Bradford J; Gaver, Donald P

2009-08-01

Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method.

A Microscale Spectrophotometric Determination of Water Hardness

NASA Astrophysics Data System (ADS)

Gordon, James S.

2001-08-01

A spectrophotometric titration was performed to determine water hardness. The titration incorporated the traditional titration method employing EDTA as the titrant and calmagite as the indicator. The microscale experiment was carried out in a spectrometer cuvette and made use of a Texas Instruments (TI-83) calculator interfaced through a TI Calculator-Based Laboratory system to a Vernier colorimeter as the detector. Monitoring at 635 nm, one of the colorimeter's fixed wavelengths, was well suited for this analysis. Agreement was found with results from traditional titrations.

Dynamic microscale temperature gradient in a gold nanorod solution measured by diffraction-limited nanothermometry

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

Li, Chengmingyue; Gan, Xiaosong; Li, Xiangping

2015-09-21

We quantify the dynamic microscale temperature gradient in a gold nanorod solution using quantum-dot-based microscopic fluorescence nanothermometry. By incorporating CdSe quantum dots into the solution as a nanothermometer, precise temperature mapping with diffraction-limited spatial resolution and sub-degree temperature resolution is achieved. The acquired data on heat generation and dissipation show an excellent agreement with theoretical simulations. This work reveals an effective approach for noninvasive temperature regulation with localized nanoheaters in microfluidic environment.