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At least 145 records · Page 8

What’s That Supposed to Mean? Capturing Micro-Behaviors in Teams

Future long-duration space exploration (LDSE) crews will require extensive coordination, cooperation, and team functioning as they face a myriad of challenges rooted in both taskwork and teamwork (Bell et al., 2015; Landon et al., 2018). While exposed to extreme conditions, crew members must navigate living and working together in prolonged confinement. Moreover, astronaut teams are becoming increasingly diverse, introducing significant variability in team composition. This increasing diversity, alongside traditional constraints of LDSE, introduces additional challenges into effective team functioning. To date, most methods for capturing team functioning rely on self-report measures. Such measures are prone to several limitations, including but not limited to social desirability bias, halo effect, and leniency effects (Trull & Ebner-Priemer, 2013), which skew data and limit nuanced understandings of phenomena at play. Self-report measures broadly capture team functioning, lending the nature of such methods to identifying underlying “macro”-behaviors (i.e., behaviors that are long-standing and last over time). However, team functioning is far more complex than a series of macro-behaviors, rendering reliance on self-report data deficient for accurate measurement. Recent research demonstrates the potential of alternative methods for capturing team functioning, such as speech and physiological data (Chaffin et al., 2017; Murray & Oertel, 2018). Consequently, these methods are more suitable for capturing micro-behaviors: brief, often unconscious expressions that affect the extent to which an individual feels included by others around them (Paletz et al., 2013). Micro-behaviors can be further classified into micro-aggressions (i.e., subtle, negative exchanges; Keller & Galgay, 2010) or micro-affirmations (i.e., subtle, positive exchanges; Kyte et al. 2020), both of which influence team functioning. Due to the subtle nature of micro-behaviors, contextual factors have a significant impact when determining if it is aggressive or affirmative. Additionally, several iterations of micro-behaviors can have lingering effects on team interactions. For example, the use of “mm-hmm” by a crew member can function as both a micro-affirmation and micro-aggression. Specifically, it can be indication of active listening (i.e., micro-affirmation) or as an expression of annoyance (i.e., aggression) depending on the context in which it occurs. Auditory features (e.g., tone, frequency) can help delineate between the two forms; however, the contextual factors (e.g., previous interactions between team members, crew demographics) add a layer of complexity that render auditory features alone as insufficient to capture micro-behaviors. Consequently, this paper seeks to provide a novel approach in which multi-modal data (i.e., auditory features and contextual features) are used in a random-forest model to better identify distinguishing characteristics between micro-affirmations and micro-aggressions. In turn, detected micro-behaviors are used to predict team performance, thereby demonstrating the value of capturing micro-behaviors as supplemental data to macro-behaviors.

Sydney Begerowski↗

Method and apparatus for virtualizing the micro-op cache

Systems, apparatuses, and methods for virtualizing a micro-operation cache are disclosed. A processor includes at least a micro-operation cache, a conventional cache subsystem, a decode unit, and control logic. The decode unit decodes instructions into micro-operations which are then stored in the micro-operation cache. The micro-operation cache has limited capacity for storing micro-operations. When new micro-operations are decoded from pending instructions, existing micro-operations are evicted from the micro-operation cache to make room for the new micro-operations. Rather than being discarded, micro-operations evicted from the micro-operation cache are stored in the conventional cache subsystem. This prevents the original instruction from having to be decoded again on subsequent executions. When the control logic determines that micro-operations for one or more fetched instructions are stored in either the micro-operation cache or the conventional cache subsystem, the control logic causes the decode unit to transition to a reduced-power state.

Kalamatianos, John↗

Method and apparatus for virtualizing the micro-op cache

Systems, apparatuses, and methods for virtualizing a micro-operation cache are disclosed. A processor includes at least a micro-operation cache, a conventional cache subsystem, a decode unit, and control logic. The decode unit decodes instructions into micro-operations which are then stored in the micro-operation cache. The micro-operation cache has limited capacity for storing micro-operations. When new micro-operations are decoded from pending instructions, existing micro-operations are evicted from the micro-operation cache to make room for the new micro-operations. Rather than being discarded, micro-operations evicted from the micro-operation cache are stored in the conventional cache subsystem. This prevents the original instruction from having to be decoded again on subsequent executions. When the control logic determines that micro-operations for one or more fetched instructions are stored in either the micro-operation cache or the conventional cache subsystem, the control logic causes the decode unit to transition to a reduced-power state.

Kalamatianos, John↗

A magnetic micro-manipulator for application of three dimensional forces

Magnetic manipulation finds diverse applications in actuation, characterization, and manipulation of micro- and nano-scale samples. This paper presents the design and development of a novel magnetic micro-manipulator for application of three-dimensional forces on a magnetic micro-bead. A simple analytical model is proposed to obtain the forces of interaction between the magnetic micro-manipulator and a magnetic micro-bead. Subsequently, guidelines are proposed to perform systematic design and analysis of the micro-manipulator. The designed micro-manipulator is fabricated and evaluated. The manipulator is experimentally demonstrated to possess an electrical bandwidth of about 1 MHz. The ability of the micro-manipulator to apply both in-plane and out-of-plane forces is demonstrated by actuating permanent-magnet micro-beads attached to micro-cantilever beams. The deformations of the micro-cantilevers are also employed to calibrate the dependence of in-plane and out-of-plane forces on the position of the micro-bead relative to the micro-manipulator. The experimentally obtained dependences are found to agree well with theory.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

What’s That Supposed to Mean? Capturing Micro-Behaviors in Teams

Future long-duration space exploration (LDSE) crews will require extensive coordination, cooperation, and team functioning as they face a myriad of challenges rooted in both taskwork and teamwork (Bell et al., 2015; Landon et al., 2018). While exposed to extreme conditions, crew members must navigate living and working together in prolonged confinement. Moreover, astronaut teams are becoming increasingly diverse, introducing significant variability in team composition. This increasing diversity, alongside traditional constraints of LDSE, introduces additional challenges into effective team functioning. To date, most methods for capturing team functioning rely on self-report measures. Such measures are prone to several limitations, including but not limited to social desirability bias, halo effect, and leniency effects (Trull & Ebner-Priemer, 2013), which skew data and limit nuanced understandings of phenomena at play. Self-report measures broadly capture team functioning, lending the nature of such methods to identifying underlying “macro”-behaviors (i.e., behaviors that are long-standing and last over time). However, team functioning is far more complex than a series of macro-behaviors, rendering reliance on self-report data deficient for accurate measurement. Recent research demonstrates the potential of alternative methods for capturing team functioning, such as speech and physiological data (Chaffin et al., 2017; Murray & Oertel, 2018). Consequently, these methods are more suitable for capturing micro-behaviors: brief, often unconscious expressions that affect the extent to which an individual feels included by others around them (Paletz et al., 2013). Micro-behaviors can be further classified into microaggressions (i.e., subtle, negative exchanges; Keller & Galgay, 2010) or micro-affirmations (i.e., subtle, positive exchanges; Kyte et al. 2020), both of which influence team functioning. Due to the subtle nature of micro-behaviors, contextual factors have a significant impact when determining if it is aggressive or affirmative. Additionally, several iterations of microbehaviors can have lingering effects on team interactions. For example, the use of “mm-hmm” by a crew member can function as both a micro-affirmation and micro-aggression. Specifically, it can be indication of active listening (i.e., micro-affirmation) or as an expression of annoyance (i.e., aggression) depending on the context in which it occurs. Auditory features (e.g., tone, frequency) can help delineate between the two forms; however, the contextual factors (e.g., previous interactions between team members, crew demographics) add a layer of complexity that render auditory features alone as insufficient to capture micro-behaviors. Consequently, this paper seeks to provide a novel approach in which multi-modal data (i.e., auditory features and contextual features) are used in a random-forest model to better identify distinguishing characteristics between micro-affirmations and micro-aggressions. In turn, detected micro-behaviors are used to predict team performance, thereby demonstrating the value of capturing micro-behaviors as supplemental data to macro-behaviors.

Sydney R. Begerowski↗

A hetero-micro-seeding strategy for readily crystallizing closely related protein variants

Protein crystallization remains difficult to rationalize and screening for optimal crystallization conditions is a tedious and time consuming procedure. Here, we report a hetero-micro-seeding strategy for producing high resolution crystals of closely related protein variants, where micro crystals from a readily crystallized variant are used as seeds to develop crystals of other variants less amenable to crystallization. We applied this strategy to Bovine Pancreatic Trypsin Inhibitor (BPTI) variants, which would not crystallize using standard crystallization practice. Out of six variants in our analysis, only one called BPTI-[5,55]A14G formed well behaving crystals; and the remaining five (A14GA38G, A14GA38V, A14GA38L, A14GA38I, and A14GA38K) could be crystallized only using micro-seeds from the BPTI-[5,55]A14G crystal. All hetero-seeded crystals diffracted at high resolution with minimum mosaicity, retaining the same space group and cell dimension. Moreover, hetero-micro-seeding did not introduce any biases into the mutant’s structure toward the seed structure, as demonstrated by A14GA38I structures solved using micro-seeds from A14GA38G, A14GA38L and A14GA38I. Though hetero-micro-seeding is a simple and almost naïve strategy, this is the first direct demonstration of its workability. We believe that hetero-micro-seeding, which is contrasting with the popular idea that crystallization requires highly purified proteins, could contribute a new tool for rapidly solving protein structures in mutational analysis studies. - Highlights: • In hetero-micro-seeding, hard-to-crystalize mutants are crystallized using micro-seeds from a readily crystalized variant. • Hetero-micro-seeding did not introduce any biases of the mutant structure toward the seed structure. • Though hetero-micro-seeding is a simple strategy, this is the first direct demonstration of its workability at atomic level.

36 MATERIALS SCIENCE↗

Green micromachining of ceramics using tungsten carbide micro-endmills

This paper presents an experimental analysis on micromachining of green-state silicon carbide (SiC) and aluminum nitride (AlN) using uncoated tungsten carbide (WC) micro-endmills. Although the unique properties of ceramics make them ideal materials for many applications involving micro-scale features, the industrial adaptation of ceramics at the micro-scale has been hindered due to the lack of viable ceramic micro-manufacturing techniques. Green micromachining (GMM), where micro-scale features are created by micromachining green-state ceramics that contain ceramic particles and a polymer binder, offers a potential solution for this problem by affording tremendous improvements in micromachinability with respect to sintered ceramics. After the completion of GMM, the green parts are debound and sintered to obtain the final component with the desired microscale features. In this work, we evaluated GMM characteristics of powder-injection molded green-state SiC and AlN to correlate process conditions and green-material compositions with the micromachining forces, quality, and tool wear. An experimental study that involves full immersion micromilling tests with 254 μm diameter micro-endmills at different cutting speeds and feed rates is conducted. For each of the two materials, two binder states (with and without wax) and two powder states (with micro particles only, or with both micro- and nanoparticles) are investigated. Green micromachining forces, specific energies and the resulting surface roughness are analyzed quantitatively. A qualitative analysis of burr formation and channel quality, as well as a preliminary study on micro-tool wear are also performed. Both the machining conditions and the material compositions are seen to have a strong effect on micro-machinability of green-state ceramics. Overall, we conclude that GMM can be a viable ceramic micro-manufacturing strategy if favorable (or optimal) micromachining and material parameters are identified through the presented (or a similar) micromachinability study.

36 MATERIALS SCIENCE↗

Micro-grid for Future Planetary Surface Needs

Under the current Artemis Program, the National Aeronautics and Space Administration (NASA) will send its next set of astronauts (first woman and next man) to the Moon by 2024 and establish a sustainable presence on the lunar surface by 2028. The challenge of creating a sustained lunar surface presence is significantly different than previous efforts. Lunar surface operations will require access to continuous and highly reliable power to support mission needs, such as to support ISRU operations. Adding to this challenge, the lunar surface operations are not going to be established over a single effort, rather the system and operations will evolve and grow over time (years). The first initial loads that arrive on the lunar surface will be integrated to their own dedicated power sources. As the lunar surface operations grow, so will the demand for power and at some point these individual loads will require more power than can be generated with any single power device. This power demand drives the need for inter-connecting the loads and power devices to share power between them, resulting in a micro-grid. One of the advantages of developing a lunar surface micro-grid is that allows lunar surface operations to resemble electrical utility operations on Earth; it allows power to be generated where it is convenient and allows power to be consumed where it is convenient, rather than negotiating between generation and consumption. The micro-grid concept also provides another benefit of affording the ability to increase overall system reliability by integrating dissimilar power generation and energy storage devices together, for example modifying the power generation strategy to include both solar arrays and nuclear. Creating a lunar surface micro-grid has its advantages, however there are significant challenges associated with an evolvable micro-grid concept. The challenges include how to efficiently transmit large amounts of power (10kW+) long distances (1kW+), how to effectively integrate dissimilar power generation and energy storage devices to maximize power consumption and minimize downtime, and how to physically connect these devices together with a connector that can survive the lunar environment (dust, extreme cold temperatures) and is capable of both astronaut and robotic operation. The basic components of the micro-grid have to be designed to ensure the system is sustainable, modular, and reconfigurable. An interface to the micro-grid has to be designed that allows for additional technologies, some of which may not yet be fully designed, to easily integrate into the micro-grid concept. This presentation discusses these lunar challenges in some more depth and offers a path forward in designing an evolvable micro-grid to meet the needs of the lunar surface operations and proposes a Universal Micro-grid Interface Converter to connect these dissimilar power sources and mission loads to the micro-grid.

Jeffrey Csank↗

Implementing a micro-operation cache with compaction

Systems, apparatuses, and methods for compacting multiple groups of micro-operations into individual cache lines of a micro-operation cache are disclosed. A processor includes at least a decode unit and a micro-operation cache. When a new group of micro-operations is decoded and ready to be written to the micro-operation cache, the micro-operation cache determines which set is targeted by the new group of micro-operations. If there is a way in this set that can store the new group without evicting any existing group already stored in the way, then the new group is stored into the way with the existing group(s) of micro-operations. Metadata is then updated to indicate that the new group of micro-operations has been written to the way. Additionally, the micro-operation cache manages eviction and replacement policy at the granularity of micro-operation groups rather than at the granularity of cache lines.

Kotra, Jagadish B.↗

Influence of the secondary phase on micro galvanic corrosion of low carbon bainitic steel in NaCl solution

Highlights: • Micro galvanic couple forms between steel matrix and secondary phase for LCB steel. • Micro galvanic couple causes non-uniform corrosion on micro area surface of steel. • The ω secondary phase acts as the micro anode in lath bainitic steel. • The M secondary phase acts as the micro cathode in granular bainitic steel. • Galvanic accelerated corrosion is obvious initially and weakened for long term. - Abstract: The corrosion behavior of lath bainitic and granular bainitic steels in 0.01 mol/L NaCl solution was studied by SEM and TEM observation, electrochemical monitoring and weight loss test. The results indicate that the micro galvanic couple forms between the steel matrix and the secondary phase, which causes non-uniform micro corrosion on surfaces of two steels. In lath bainitic steel, the secondary phase ω acts as the micro anode. While in granular bainitic steel, the secondary phase M acts as the micro cathode. Moreover, the corrosion acceleration caused by micro galvanic couple is obvious in the initial immersion stage, and then it becomes weak during the long term corrosion.

36 MATERIALS SCIENCE↗

Optimal Control of Shock Wave Turbulent Boundary Layer Interactions Using Micro-Array Actuation

The intent of this study on micro-array flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to determine optimal designs of micro-array actuation for controlling the shock wave turbulent boundary layer interactions within supersonic inlets and compare these concepts to conventional bleed performance. The term micro-array refers to micro-actuator arrays which have heights of 25 to 40 percent of the undisturbed supersonic boundary layer thickness. This study covers optimal control of shock wave turbulent boundary layer interactions using standard micro-vane, tapered micro-vane, and standard micro-ramp arrays at a free stream Mach number of 2.0. The effectiveness of the three micro-array devices was tested using a shock pressure rise induced by the 10 shock generator, which was sufficiently strong as to separate the turbulent supersonic boundary layer. The overall design purpose of the micro-arrays was to alter the properties of the supersonic boundary layer by introducing a cascade of counter-rotating micro-vortices in the near wall region. In this manner, the impact of the shock wave boundary layer (SWBL) interaction on the main flow field was minimized without boundary bleed.

Anderson, Bernhard H.↗

Towards time-resolved MicroED grid preparation using mix-and-inject gas dynamic virtual nozzles

Recent progress in gas dynamic virtual nozzle (GDVN) technologies in combination with high-brilliance synchrotron and X-ray free-electron lasers (XFELs) has allowed the visualization of protein dynamics in crystallo by mixing macromolecular protein crystals with a substrate using tunable mixing times on the order of milliseconds to seconds prior to serial X-ray diffraction data collection. This has become the method of choice for high-resolution structure determination of intermediate states. However, such experiments require large counts of crystals of proper sizes for high-resolution data collection, and premium beam times for screening efforts. Cryogenic microcrystal electron diffraction (MicroED) represents a complementary technique that may be a more accessible avenue for time-resolved nanocrystallography compared with serial X-ray diffraction experiments. MicroED can produce full diffraction datasets from just a few submicrometre-thick crystals, and the approach is more readily accessible, requiring standard cryogenic transmission electron microscopy (TEM) equipment available at many universities and institutes. Cryogenic MicroED, like other forms of cryo-EM, begins with rapidly freezing biological material on electron microscopy grids. In the case of MicroED, micro- to nano-crystals (<500 nm thick) are deposited onto electron microscopy grids and plunge-frozen for subsequent electron diffraction data collection. Here, we have incorporated GDVN technology developed originally for XFEL experiments into the freezing process as a first step towards time-resolved studies. We describe the limited deposition efficiency of the model MicroED protein proteinase K on TEM grids using GDVNs, preceding sample vitrification and successful MicroED data collection. We discuss both the initial results from such experiments and the methodological challenges in developing this approach into a reliable workflow for millisecond-to-second time-resolved structural studies of macromolecules. Our results promise a strategy to deposit crystals on grids using GDVNs and determine high-resolution structures by MicroED, constituting a first step towards development of time-resolved MicroED experiments.

MicroED↗

Tariff Considerations for Micro-Grids in Sub-Saharan Africa

This report examines some of the key drivers and considerations policymakers and decision makers face when deciding if and how to regulate electricity tariffs for micro-grids. Presenting a range of tariff options, from mandating some variety of national (uniform) tariff to allowing micro-grid developers and operators to set fully cost-reflective tariffs, it examines various benefits and drawbacks of each. In addition, the report and explores various types of cross-subsidies and other transitional forms of regulation that may offer a regulatory middle ground that can help balance the often competing goals of providing price control on electricity service in the name of social good while still providing a means for investors to ensure high enough returns on their investment to attract the necessary capital financing to the market. Using the REopt tool developed by the U.S. Department of Energy's National Renewable Energy Laboratory to inform their study, the authors modeled a few representative micro-grid systems and the resultant levelized cost of electricity, lending context and scale to the consideration of these tariff questions. This simple analysis provides an estimate of the gap between current tariff regimes and the tariffs that would be necessary for developers to recover costs and attract investment, offering further insight into the potential scale of subsidies or other grants that may be required to enable micro-grid development under current regulatory structures. It explores potential options for addressing this gap while trying to balance This report examines some of the key drivers and considerations policymakers and decision makers face when deciding if and how to regulate electricity tariffs for micro-grids. Presenting a range of tariff options, from mandating some variety of national (uniform) tariff to allowing micro-grid developers and operators to set fully cost-reflective tariffs, it examines various benefits and drawbacks of each. In addition, the report and explores various types of cross-subsidies and other transitional forms of regulation that may offer a regulatory middle ground that can help balance the often competing goals of providing price control on electricity service in the name of social good while still providing a means for investors to ensure high enough returns on their investment to attract the necessary capital financing to the market. Using the REopt tool developed by the U.S. Department of Energy's National Renewable Energy Laboratory to inform their study, the authors modeled a few representative micro-grid systems and the resultant levelized cost of electricity, lending context and scale to the consideration of these tariff questions. This simple analysis provides an estimate of the gap between current tariff regimes and the tariffs that would be necessary for developers to recover costs and attract investment, offering further insight into the potential scale of subsidies or other grants that may be required to enable micro-grid development under current regulatory structures. It explores potential options for addressing this gap while trying to balance stakeholder needs, from subsidized national tariffs to lightly regulated cost-reflective tariffs to more of a compromise approach, such as different standards of regulation based on the size of a micro-grid.takeholder needs, from subsidized national tariffs to lightly regulated cost-reflective tariffs to more of a compromise approach, such as different standards of regulation based on the size of a micro-grid.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Nematic Colloidal Micro‐Robots as Physically Intelligent Systems

Abstract Physically intelligent micro‐robotic systems exploit information embedded in micro‐robots, their colloidal cargo, and their milieu to interact, assemble, and form functional structures. Nonlinear anisotropic fluids such as nematic liquid crystals (NLCs) provide untapped opportunities to embed interactions via their topological defects, complex elastic responses, and ability to dramatically restructure in dynamic settings. Here a four‐armed ferromagnetic micro‐robot is designed and fabricated to embed and dynamically reconfigure information in the nematic director field, generating a suite of physical interactions for cargo manipulation. The micro‐robot shape and surface chemistry are designed to generate a nemato‐elastic energy landscape in the domain that defines multiple modes of emergent, bottom‐up interactions with passive colloids. Micro‐robot rotation expands the ability to sculpt interactions; the energy landscape around a rotating micro‐robot is dynamically reconfigured by complex far‐from‐equilibrium dynamics of the micro‐robot's companion topological defect. These defect dynamics allow transient information to be programmed into the domain and exploited. Robust micro‐robotic manipulation strategies are demonstrated that exploit these diverse modes of nemato‐elastic interaction to achieve cargo docking, transport, release, and assembly of complex reconfigurable structures at multi‐stable sites. Such structures are of great interest to future developments of LC‐based advanced optical device and micro‐manufacturing in anisotropic environments.

Yao, Tianyi↗

Buckling analysis of planar compression micro-springs

Large compression deformation causes micro-springs buckling and loss of load capacity. We analyzed the impact of structural parameters and boundary conditions for planar micro-springs, and obtained the change rules for the two factors that affect buckling. A formula for critical buckling deformation of micro-springs under compressive load was derived based on elastic thin plate theory. Results from this formula were compared with finite element analysis results but these did not always correlate. Therefore, finite element analysis is necessary for micro-spring buckling analysis. We studied the variation of micro-spring critical buckling deformation caused by four structural parameters using ANSYS software under two constraint conditions. The simulation results show that when an x-direction constraint is added, the critical buckling deformation increases by 32.3-297.9%. The critical buckling deformation decreases with increase in micro-spring arc radius or section width and increases with increase in micro-spring thickness or straight beam width. We conducted experiments to confirm the simulation results, and the experimental and simulation trends were found to agree. Buckling analysis of the micro-spring establishes a theoretical foundation for optimizing micro-spring structural parameters and constraint conditions to maximize the critical buckling load.

36 MATERIALS SCIENCE↗

Non-linear macro evolution of a dc driven micro atmospheric glow discharge

We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Formation and Growth of Micro and Macro Bubbles on Copper-Graphite Composite Surfaces

Micro scale boiling behavior in the vicinity of graphite micro-fiber tips on the coppergraphite composite boiling surfaces is investigated. It is discovered that a large number of micro bubbles are formed first at the micro scratches and cavities on the copper matrix in pool boiling. In virtue of the non-wetting property of graphite, once the growing micro bubbles touch the graphite tips, the micro bubbles are sucked by the tips and merged into larger micro bubbles sitting on the tips. The micro bubbles grow rapidly and coalesce to form macro bubbles, each of which sitting on several tips. The growth processes of the micro and macro bubbles are analyzed and formulated followed by an analysis of bubble departure on the composite surfaces. Based on these analyses, the enhancement mechanism of the pool boiling heat transfer on the composite surfaces is clearly revealed. Experimental results of pool boiling heat transfer both for water and Freon-113 on the composite surfaces convincingly demonstrate the enhancement effects of the unique structure of Cu-Gr composite surfaces on boiling heat transfer.

Chao, David F.↗

Analysis of Membrane Lipids of Airborne Micro-Organisms

A method of characterization of airborne micro-organisms in a given location involves (1) large-volume filtration of air onto glass-fiber filters; (2) accelerated extraction of membrane lipids of the collected micro-organisms by use of pressurized hot liquid; and (3) identification and quantitation of the lipids by use of gas chromatography and mass spectrometry. This method is suitable for use in both outdoor and indoor environments; for example, it can be used to measure airborne microbial contamination in buildings ("sick-building syndrome"). The classical approach to analysis of airborne micro-organisms is based on the growth of cultureable micro-organisms and does not provide an account of viable but noncultureable micro-organisms, which typically amount to more than 90 percent of the micro-organisms present. In contrast, the present method provides an account of all micro-organisms, including cultureable, noncultureable, aerobic, and anaerobic ones. The analysis of lipids according to this method makes it possible to estimate the number of viable airborne micro-organisms present in the sampled air and to obtain a quantitative profile of the general types of micro-organisms present along with some information about their physiological statuses.

MacNaughton, Sarah↗