bluuebunny/crossref_metadata_2025 huggingface dataset:
From meso‐ to macroscale population dynamics: a new density‐structured approach
Authors: Queenborough Simon A. , Burnet Kirsty M. , Sutherland William J. , Watkinson Andrew R. , Freckleton Robert P.
Published: November 2010

1. To predict how plant populations may respond to changes in the environment or management, it is necessary to quantify the factors influencing their population dynamics and distributions over large spatial and/or temporal scales.

2. Most studies of plant population dynamics monitor demography at the sub‐metre scale. Extrapolation or prediction from these studies is difficult because the data are sparse, parameter error cannot be ascertained and the data may not cover the range of expected environmental conditions.

3. Here, we describe a survey method based on density‐structured models. These models use a discrete density state variable and model rates of transition between density states. Although analytically simple, these models are empirically useful as they may be parameterized using readily collected data. They also offer an empirical link between meso‐scale and macro‐scale population dynamics.

4. For a large‐scale study on annual weeds, we describe the rapid estimation of densities using relatively coarse density estimates using visual estimates of density. Using information from detailed surveys, we describe how we use the method to measure populations of annual plants to a scale of 20 × 20 m in areas of up to 4 ha per population within 500 different arable fields over 3 years.

5. We show that the approach taken is repeatable within and among observers, and we quantify the degree of measurement error. We give examples of the resultant data, and compare these with the data obtained from nested small‐scale plots. Finally, we show how the information from this type of survey can be incorporated into population models and used to measure within‐population and inter‐annual flux.
Structure–metabolism relationships for the glucuronidation of flavonoids by UGT1A3 and UGT1A9
Authors: Xie Shenggu , Chen Yakun , Chen Shuqing , Zeng Su
Published: November 2010

Objectives

This study tries to find structure–metabolism relationships between flavonoids and human UGT1A3 and UGT1A9.

Methods

The glucuronidation of flavonoids was studied with recombinant UGT1A3 and UGT1A9, and the glucuronidation activity was determined by HPLC.

Key findings

Of the flavonoids studied, it was shown for the first time that baicalein, quercetin-3-OCH2OCH3, quercetin-4′-CH3, quercetin-3′-OCH3 and quercetin-3′-Br are substrates of UGT1A3. Wogonin, baicalein, quercetin-4′-Cl, quercetin-3-OCH2OCH3, quercetin-3-O-arabinoside, quercetin-4′-CH3, quercetin-3′-OCH3 and quercetin-3′-Br are the newly reported substrates of UGT1A9. The preferred substrates for UGT1A3 and UGT1A9 contain the hydroxyl group at the C7-position. The glycon and the position of the B ring have conspicuous influences on the glucuronidation activity, and other chemical structures of flavonoids have minor effects.

Conclusions

From the quantitative study, UGT1A9 in general has higher glucuronidation efficiency than UGT1A3.
Calculation of High-Lift Cascades in Low Pressure Turbine Conditions Using a Three-Equation Model
Authors: Pacciani Roberto , Marconcini Michele , Fadai-Ghotbi Atabak , Lardeau Sylvain , Leschziner Michael A.
Published: November 2010

A three-equation model has been applied to the prediction of separation-induced transition in high-lift low-Reynolds-number cascade flows. Classical turbulence models fail to predict accurately laminar separation and turbulent reattachment, and usually overpredict the separation length, the main reason for this being the slow rise of the turbulent kinetic energy in the early stage of the separation process. The proposed approach is based on solving an additional transport equation for the so-called laminar kinetic energy, which allows the increase in the nonturbulent fluctuations in the pretransitional and transitional region to be taken into account. The model is derived from that of Lardeau et al. (2004, “Modelling Bypass Transition With Low-Reynolds-Number Non-Linear Eddy-Viscosity Closure,” Flow, Turbul. Combust., 73, pp. 49–76), which was originally formulated to predict bypass transition for attached flows, subject to a wide range of freestream turbulence intensity. A new production term is proposed, based on the mean shear and a laminar eddy-viscosity concept. After a validation of the model for a flat-plate boundary layer, subjected to an adverse pressure gradient, the T106 and T2 cascades, recently tested at the von Kármán Institute, are selected as test cases to assess the ability of the model to predict the flow around high-lift cascades in conditions representative of those in low-pressure turbines. Good agreement with experimental data, in terms of blade-load distributions, separation onset, reattachment locations, and losses, is found over a wide range of Reynolds-number values.
A Turbomachinery Design Tool for Teaching Design Concepts for Axial-Flow Fans, Compressors, and Turbines
Authors: Turner Mark G. , Merchant Ali , Bruna Dario
Published: November 2010

A new turbomachinery design system, T-AXI, is described and demonstrated. It is intended primarily for use by educators and students, although it is sophisticated enough for actual designs. The codes, example cases, and user’s manual are available through the authors’ websites. The design system can be used to design multistage compressors and turbines from a small number of physical design parameters. Students can understand the connection between these physical parameters such as the Mach number and flow angles to the cross sectional area and angular momentum. There is also a clear connection between the angular momentum, work, and blade loadings. Loss models are built-in and results are compared against tested geometries. The code also has a built-in blade geometry generator, and the geometry can be the output for running the MISES blade-to-blade solver on each section or visualizing the blades. A single stage compressor from the U.S. Air Force Stage Matching Investigation rig, the 10 stage NASA/GE EEE high pressure compressor, and the NASA/GE EEE 5 stage low pressure turbine have been used to validate T-AXI as a design tool.
Radial Migration of Shed Vortices in a Transonic Rotor Following a Wake Generator: A Comparison Between Time Accurate and Average Passage Approaches
Authors: Turner Mark G. , Gorrell Steven E. , Car David
Published: November 2010

This paper shows a comparison of an unsteady simulation using turbo and an average passage simulation for a two blade row configuration consisting of a wake generator followed by a transonic rotor. Two spacings were simulated, both close and far. The unsteady results compare well with experiment especially for the profile of efficiency difference between close and far. An analysis of results helps to explain the unusual profile seen experimentally that is due to the radial migration of wake generator shed vortices with negative radial velocities near the tip. In addition, different components of the average passage body forces (deterministic stresses) are explored that shows the main terms are the axial momentum and the metal blockage.
Heat Transfer and Pressure Drop Measurements for a Square Channel With 45 deg Round-Edged Ribs at High Reynolds Numbers
Authors: Rallabandi Akhilesh P. , Alkhamis Nawaf , Han Je-Chin
Published: November 2010

Experiments to determine heat transfer coefficients and friction factors are conducted on a stationary 45 deg parallel rib-roughened square channel, which simulates a turbine blade internal coolant passage. Copper plates fitted with silicone heaters and thermocouples are used to measure regionally averaged heat transfer coefficients. Reynolds numbers studied range from 30,000 to 400,000. The ribs studied have rounded (filleted) edges to account for manufacturing limitations of actual engine blades. The rib height (e) to hydraulic diameter (D) ratio (e/D) ranges from 0.1 to 0.2, while spacing (p) to height ratio (p/e) ranges from 5 to 10. Results indicate an increase in the heat transfer due to the ribs at the cost of a higher friction factor, especially at higher Reynolds numbers. Round-edged ribs experience a similar heat transfer coefficient and a lower friction factor compared with sharp-edged ribs, especially at higher values of the rib height. Correlations predicting Nu and f as a function of e/D, p/e, and Re are presented. Also presented are correlations for the heat transfer and friction roughness parameters (G and R, respectively).
Laminar Flow in Microchannels With Noncircular Cross Section
Authors: Tamayol Ali , Bahrami Majid
Published: November 2010

Analytical solutions are presented for laminar fully developed flow in micro-/minichannels of hyperelliptical and regular polygonal cross sections in the form of compact relationships. The considered geometries cover a wide range of common simply connected shapes including circle, ellipse, rectangle, rectangle-with-round-corners, rhombus, star-shape, equilateral triangle, square, pentagon, and hexagon. A point matching technique is used to calculate closed form solutions for the velocity distributions in the above-mentioned channel cross sections. The developed relationships for the velocity distribution and pressure drop are successfully compared with existing analytical solutions and experimental data collected from various sources for a variety of geometries, including polygonal, rectangular, circular, elliptical, and rhombic cross sections. The present compact solutions provide a convenient and power tool for performing hydrodynamic analyses in a variety of fundamental and engineering applications such as in microfluidics, transport phenomena, and porous media.
Parallel Flow Through Ordered Fibers: An Analytical Approach
Authors: Tamayol A. , Bahrami M.
Published: November 2010

In this study, fully developed flow parallel to ordered fibers is investigated analytically. The considered fibrous media are made up of in-line (square), staggered, and hexagonal arrays of cylinders. Starting from the general solution of Poisson’s equation, compact analytical solutions are proposed for both velocity distribution and permeability of the considered structures. In addition, independent numerical simulations are performed for the considered arrangements over the entire range of porosity and the results are compared with the proposed solutions. The developed solutions are successfully verified through comparison with experimental data, collected by others, and the present numerical results over a wide range of porosity. The results show that for the ordered arrangements with high porosity, the parallel permeability is independent of the microstructure geometrical arrangements; on the other hand, for lower porosities the hexagonal arrangement provides lower pressure drop, as expected.
Importance of Auxiliary Power Consumption for Combined Cycle Performance
Authors: Gülen S. Can
Published: November 2010

The key product of a combined cycle power plant is electric power generated for industrial, commercial, and residential customers. In that sense, the key performance metric that establishes the pecking order among thousands of existing, new, old, and planned power plants is the thermal efficiency. This is a ratio of net electric power generated by the plant to its rate of fuel consumption in the gas turbine combustors and, if applicable, heat recovery boiler duct burners. The term in the numerator of that simple ratio is subject to myriad ambiguities and/or misunderstandings resulting primarily from the lack of a standardized definition agreed upon by all major players. More precisely, it is the lack of a standardized definition of the plant auxiliary power consumption (or load) that must be subtracted from the generator output of all turbines in the plant, which then determines the net contribution of that power plant to the electric grid. For a combined cycle power plant, the key contributor to the plant’s auxiliary power load is the heat rejection system. In particular, any statement of combined cycle power plant thermal efficiency that does not specify the steam turbine exhaust pressure and the exhaust steam cooling system to achieve that pressure at the site ambient and loading conditions is subject to conjecture. Furthermore, for an assessment of the realism associated with the two in terms of economic and mechanical design feasibility, it is necessary to know the steam turbine exhaust end size and configuration. Using fundamental design principles, this paper provides a precise definition of the plant auxiliary load and quantifies its ramification on the plant’s net thermal efficiency. In addition, four standard auxiliary load levels are quantitatively defined based on a rigorous study of heat rejection system design considerations with a second-law perspective.
Remaining Technical Challenges and Future Plans for Oil-Free Turbomachinery
Authors: DellaCorte Christopher , Bruckner Robert J.
Published: November 2010

The application of oil-free technologies (foil gas bearings, solid lubricants, and advanced analysis and predictive modeling tools) to advanced turbomachinery has been underway for several decades. During that time, full commercialization has occurred in aircraft air cycle machines, turbocompressors, cryocoolers, and ever-larger microturbines. Emerging products in the automotive sector (turbochargers and superchargers) indicate that a high volume serial production of foil bearings is imminent. The demonstration of foil bearings in auxiliary power units and select locations in propulsion gas turbines illustrates that such technology also has a place in these future systems. Foil bearing designs, predictive tools, and advanced solid lubricants that can satisfy anticipated requirements have been reported, but a major question remains regarding the scalability of foil bearings to ever-larger sizes to support heavier rotors. In this paper, the technological history, primary physics, engineering practicalities, and existing experimental and experiential database for scaling foil bearings are reviewed, and the major remaining technical challenges are identified.
Effect of Initial Constant Acceleration on the Transition to Turbulence in Transient Circular Pipe Flow
Authors: Iguchi Manabu , Nishihara Kazuyoshi , Nakahata Yusuke , Knisely Charles W.
Published: November 2010

Experimental investigation is carried out on the transition to turbulence in a transient circular pipe flow. The flow is accelerated from rest at a constant acceleration until its cross-sectional mean velocity reaches a constant value. Accordingly, the history of the flow thus generated consists of the initial stage of constant acceleration and the following stage of constant cross-sectional mean velocity. The final Reynolds number based on the constant cross-sectional mean velocity and the pipe diameter is chosen to be much greater than the transition Reynolds number of a steady pipe flow of about 3000. The transition to turbulence is judged from the output signal of the axial velocity component and its root-mean-square value measured with a hot-wire anemometer. A turbulent slug appears after the cross-sectional mean velocity of the flow reaches the predetermined constant value under every experimental condition. Turbulence production therefore is suppressed, while the flow is accelerated. The time lag for the appearance of the turbulent slug after the cross-sectional mean velocity of the flow reaches the constant value decreases with an increase in the constant acceleration value. An empirical equation is proposed for estimating the time lag. The propagation velocity of the leading edge of the turbulent slug is independent of the constant acceleration value under the present experimental conditions.
Mass Transfer Coefficients for a Non-Newtonian Fluid and Water With and Without Antifoam Agents
Authors: Leishear Robert A. , Guerrero Hector N. , Restivo Michael L. , Sherwood David J.
Published: November 2010

Mass transfer rates were measured in a large scale system, which is consisted of an 8.4 m tall by 0.76 m diameter column, containing one of the three fluids: water with an antifoam agent, water without an antifoam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated and due to flammability concerns, oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from the solution as air bubbled up or sparged through the solution from the bottom of the column. Air sparging was supplied by a single tube, which was co-axial to the column; the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2 mm/s, 5mm/s, and 10 mm/s were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.
Pressure Fluctuation Characteristics of Complex Turbulent Flow in a Single Elbow With Small Curvature Radius for a Sodium-Cooled Fast Reactor
Authors: Ebara Shinji , Aoya Yuta , Sato Tsukasa , Hashizume Hidetoshi , Kazuhisa Yuki , Aizawa Kosuke , Yamano Hidemasa
Published: November 2010

A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study.
Comparison of Local Interfacial Structures Around 90 and 45-Degree Elbows in Horizontal Bubbly Flows
Authors: Yadav Mohan , Talley Justin D. , Kim Seungjin
Published: November 2010

This study presents a comparison of the geometric effects of 90 deg and 45 deg elbows in horizontal two-phase air-water bubbly flow. Two separate experiments were performed in the horizontal test section made out of 50.3 mm inner diameter glass tubes. The first set of data was collected with a 90 deg elbow installed, and then a 45 deg elbow was added to the existing facility to acquire the second set of data. A total of 15 different flow conditions, all within the bubbly flow regime, were identified for the 90 deg experiment, and very similar flow conditions were extended to the 45 deg experiment. A double-sensor conductivity probe was employed to acquire the local data at seven different axial positions along the test section, out of which four measurement locations are associated with the 90 deg experiment and three with the 45 deg experiment. The data show that the elbows have a significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of the two elbows. While the effect of the 45 deg elbow is evident immediately after the elbow, the 90 deg elbow effect tends to propagate further downstream of the elbow rather than immediately after the elbow. Moreover, it is shown that both elbows induce spatial oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillations differ. The effects of the elbows are also compared for the axial transport of the two-phase flow parameters.
Study on Aeration for Disengaged Wet Clutches Using a Two-Phase Flow Model
Authors: Yuan Shihua , Guo Kai , Hu Jibin , Peng Zengxiong
Published: November 2010

The existing computational models for disengaged wet clutches are deduced based on the single-phase flow theory. However, the complex gas-liquid two-phase flow is formed due to aeration at high rotational speeds. The objective of this study is to use a two-phase flow model to demonstrate the aeration process at different rotational speeds not only of the friction plate but also of the separator plate. A nongrooved, steady-state, two-phase flow computational fluid dynamics model is built using FLUENT, and it is validated by experimental data. The results reveal that air enters the clearance at a critical rotational speed, which causes the drag torque to sharply decrease. The aeration mode and flow pattern are obtained via simulations. The rotational speed of the separator plate has a significant effect on the aeration, including the speed magnitude and direction.
Thermodynamic Effect on a Cavitating Inducer in Liquid Hydrogen
Authors: Goncalvès Eric , Fortes Patella Regiane , Rolland Julien , Pouffary Benoit , Challier Guillaume
Published: November 2010

This study was led in collaboration with the French Space Agency (CNES) and the Rocket Engine Division of Snecma. The main aims were the simulations and the analyses of cavitating flows in the rocket engine turbopump inducers, where the operating fluids are LH2 and LOx under cryogenic conditions. A ρ(P,T) state law modeling the cavitation phenomenon was integrated by the laboratory LEGI in the commercial computational fluid dynamics (CFD) code FINE/TURBO™, developed by Numeca International. Various 3D numerical results are given for an inducer geometry and comparisons are made with experimental data (head drop curves) obtained by NASA.
Investigation of the Flow Field on a Transonic Turbine Nozzle Guide Vane With Rim Seal Cavity Flow Ejection
Authors: Pau M. , Paniagua G.
Published: November 2010

Ensuring an adequate life of high pressure turbines requires efficient cooling methods such as rim seal flow ejection from the stator-rotor wheel space cavity interface, which prevents hot gas ingress into the rotor disk. The present paper addresses the potential to improve the efficiency in transonic turbines at certain rim seal ejection rates. To understand this process, a numerical study was carried out, combining computational fluid dynamic (CFD) simulations and experiments on a single stage axial test turbine. The three dimensional steady CFD analysis was performed, modeling the purge cavity flow ejected downstream of the stator blade row at three flow regimes: subsonic M2=0.73, transonic M2=1.12, and supersonic M2=1.33. Experimental static pressure measurements were used to calibrate the computational model. The main flow field-purge flow interaction is found to be governed by the vane shock structures at the stator hub. The interaction between the vane shocks at the hub and the purge flow has been studied and quantitatively characterized as a function of the purge ejection rate. The ejection of 1% of the core flow from the rim seal cavity leads to an increase in the hub static pressure of approximately 7% at the vane trailing edge. This local reduction of the stator exit Mach number decreases the trailing edge losses in the transonic regime. Finally, a numerically predicted loss breakdown is presented, focusing on the relative importance of the trailing edge losses, boundary layer losses, shock losses, and mixing losses, as a function of the purge rate ejected. Contrary to the experience in subsonic turbines, results in a transonic model demonstrate that ejecting purge flow improves the vane efficiency due to the shock structure modification downstream of the stator.
Actinic imaging and evaluation of phase structures on extreme ultraviolet lithography masks
Authors: Mochi Iacopo , Goldberg Kenneth A. , Huh Sungmin
Published: November 2010

The authors describe the implementation of a phase-retrieval algorithm to reconstruct the phase and complex amplitude of structures on extreme ultraviolet (EUV) lithography masks. Many native defects commonly found on EUV reticles are difficult to detect and review accurately because they have a strong phase component. Understanding the complex amplitude of mask features is essential for predictive modeling of defect printability and defect repair. Besides printing in a stepper, the most accurate way to characterize such defects is with actinic inspection, performed at the design, EUV wavelength. Phase defect and phase structures show a distinct through-focus behavior that enables qualitative evaluation of the object phase from two or more high-resolution intensity measurements. For the first time, the phase of structures and defects on EUV masks were quantitatively reconstructed based on aerial image measurements, using a modified version of a phase-retrieval algorithm developed to test optical phase shifting reticles.
Electron field emission from well-aligned GaP nanotips
Authors: Lo Hung-Chun , Tsai Jeff T. H. , Leu Jih-Perng , Chen Chia-Fu
Published: November 2010

Field emission of electrons from single crystal gallium phosphide (GaP) nanotips has been investigated. GaP nanotip arrays were fabricated using silane-methane-argon-hydrogen based plasma using the self-masking dry etching technique in an electron-cyclotron-resonance microwave plasma enhanced chemical vapor deposition system. These nanotips have an average of 2 and 80 nm in apex and bottom diameters, respectively. They are 900 nm in height, which makes them the perfect electron emission source for their high aspect ratio topography. A nanosized silicon carbide (SiC) cap on each GaP nanotip in the array has been found. The SiC core has a heterointerface with GaP crystal that was observed using a high resolution transmission electron microscope. Field emission analysis shows low turn-on fields of 8.5–9 V/μm. Cold electron emissions in Fowler–Nordheim type current-voltage were observed from such GaP nanotip arrays.
More about the falling raindrop
Authors: Mungan Carl E.
Published: November 2010

A simple strategy is presented for solving the “inverse rocket” problem of a particle accumulating material from a medium through which it falls vertically. Some forms of drag can also be easily included, thereby changing the constant acceleration to a more realistic value.
The quantum Gaussian well
Authors: Nandi Saikat
Published: November 2010

Different features of a potential in the form of a Gaussian well have been discussed extensively. Although the details of the calculation are involved, the general approach uses a variational method and WKB approximation, techniques that should be familiar to advanced undergraduates. A numerical solution of the Schrödinger equation through diagonalization has been developed in a self-contained way, and physical applications of the potential are mentioned.
What Brown saw and you can too
Authors: Pearle Philip , Collett Brian , Bart Kenneth , Bilderback David , Newman Dara , Samuels Scott
Published: November 2010

A discussion of Robert Brown’s original observations of particles ejected by pollen of the plant Clarkia pulchella undergoing what is now called Brownian motion is given. We consider the nature of those particles and how he misinterpreted the Airy disk of the smallest particles to be universal organic building blocks. Relevant qualitative and quantitative investigations with a modern microscope and with a “homemade” single lens microscope similar to Brown’s are presented.
Energy conservation in collective coherent emission by dipole oscillators
Authors: Berman P. R.
Published: November 2010

Coherent emission from two or more classical damped oscillators leads to an apparent violation of conservation of energy if the oscillators are assumed to emit independently. To resolve this apparent paradox, it is necessary to include effects related to cooperative decay, wherein each oscillator modifies the damping rate of the other oscillators. We show how these effects are included for two radiating oscillators and for a line of N oscillators. The relation between cooperative decay, optical coherent transients, and superradiance is discussed.
Bringing science policy into the optics classroom: Solid state lighting and United States lighting standards
Authors: Mayer Shannon K.
Published: November 2010

The challenges associated with the development of innovative energy efficient technology require a new generation of skilled and creative scientists and engineers. Moreover, it is vital that they possess the ability to communicate their expertise to the general public and to serve as advisors and participants in the development of science policy. This paper describes a curriculum for a course in optics that investigates the physical principles and policy aspects of solid state lighting. Recent legislation places stringent efficiency and reliability requirements on lighting, promoting the development of new commercial lighting options. The physics of solid state lighting fits naturally into the undergraduate optics curriculum, and the policy aspects provide students with an engaging connection between science and society.
Apparent shape of a swimming pool
Authors: Mendelson Kenneth S.
Published: November 2010

The apparent depth of a pool depends on the angle between the normal to the pool surface and the ray that reaches the observer’s eye. For small angles, the ratio of apparent to actual depth is 1/n, where n is the index of refraction of the water. As the angle increases, the image of a point on the bottom becomes astigmatic giving rise to two principal images. For both images, the apparent depth becomes smaller as the angle becomes larger. I show that the appearance of a typical gymnasium pool is significantly different depending on whether the observer is standing at the shallow or the deep end of the pool. In either case, one of the principal astigmatic images will be much more apparent than the other.
Periodic lattices in Minkowski space
Authors: Boozer A. D.
Published: November 2010

We describe a set of periodic lattices in (1+1)-dimensional Minkowski space, where each lattice has an associated symmetry group consisting of inhomogeneous Lorentz transformations that map the lattice onto itself. Our results show how ideas of crystal structure in Euclidean space generalize to Minkowski space and provide an example that illustrates basic concepts of spacetime symmetry.
Isotropic scaling law of the electrical capacitance
Authors: García-Valenzuela A. , Guadarrama-Santana A.
Published: November 2010

We give a simple proof that the electrical capacitance is proportional to an isotropic scaling factor regardless of the shape of the electrodes and of the spatial distribution of electric permittivity around them.
Design principles for effective physics instruction: A case from physics and everyday thinking
Authors: Goldberg Fred , Otero Valerie , Robinson Stephen
Published: November 2010

Although several successful inquiry-based physics and physical science curricula have been developed, little has been published that describes the development of these curricula in terms of their basic design principles. We describe the research-based design principles used in the development of one such curriculum and how these principles are reflected in its pedagogical structure. A case study drawn from an early pilot implementation illustrates how the design principles play out in a practical classroom setting. Extensive evaluation has shown that this curriculum enhances students’ conceptual understanding and improves students’ attitudes about science.
Fixed volume versus fixed pressure liquid-vapor transition
Authors: Calecki D. , Lederer D. , Roulet B. , Diu B. , Guthmann C.
Published: November 2010

We consider the equilibrium conditions for nucleation at the liquid-vapor transition at fixed volume in contrast to the traditional fixed pressure treatment. Significant differences appear, particularly for the stability of the diphasic states, which strongly depends on the external conditions.
Quantum mechanics with uniform forces
Authors: Andrews Mark
Published: November 2010

For a nonrelativistic particle acted on by a spatially uniform but possibly time-dependent force, or for a harmonic oscillator also subject to such a uniform force, the wave function differs from that without the force only by a spatial displacement and a phase factor. The shifts in position and phase are simply derived from a solution of the classical equations of motion.
A low cost, modular, and physiologically inspired electronic neuron
Authors: Sitt J. D. , Campetella F. , Aliaga J.
Published: November 2010

We describe a low cost design of an electronic neuron, which is designed to represent the dynamical properties of the membrane potential of biological neurons by modeling the states of the membrane channels. This electronic neuron can be used to study the nonlinear properties of the membrane voltage dynamics and to develop and analyze small neuronal circuits using electronic neurons as building blocks.
Students’ difficulties with tension in massless strings
Authors: Flores-García S. , Alfaro-Avena L. L. , Chávez-Pierce J. E. , Luna-González J. , González-Quezada M. D.
Published: November 2010

Many students enrolled in introductory mechanics courses have difficulties with understanding the concept of static equilibrium. Some of these difficulties are related to the concept of force in the context of tension in massless strings. We identify three kinds of misconceptions: Students’ beliefs that the angle of the string and proximity to the object are related to the tension. Students also use incorrect compensation arguments to reason about situations where both the angle and proximity change simultaneously. These difficulties were identified during investigations conducted in laboratory and lecture sessions at three universities in the United States and Mexico.
Investigating thin film interference with a digital camera
Authors: Atkins Leslie J. , Elliott Richard C.
Published: November 2010

Thin film interference is discussed in most introductory physics courses as an intriguing example of wave interference. Although students may understand the interference mechanism that determines the colors of a film, they are likely to have difficulty understanding why soap bubbles and oil slicks have a distinctive set of colors—colors that are strikingly different from those present in the rainbow. This article describes a way to model these colors and a simple method for investigating them using a digital camera and a computer.
A simple experiment for measuring bar longitudinal and flexural vibration frequencies
Authors: Velasco S. , Román F. L. , White J. A.
Published: November 2010

The sound wave in a cylindrical steel bar, generated by a light tap on one of its ends, is recorded by a microphone located near the other end. A sound analysis software is used to obtain the resonance spectrum of the bar. Longitudinal and flexural vibration frequencies are obtained from the peaks of the spectrum. The speed of sound, Young’s modulus, and Poisson’s ratio of steel are obtained.
The Boltzmann probability as a unifying approach to different phenomena
Authors: Battaglia Onofrio Rosario , Guastella Ivan , Fazio Claudio
Published: November 2010

We discuss a pedagogical approach to the role of the Boltzmann probability in describing the temperature dependence of three simple experimental situations. The approach has been experimented in an introductory course on statistical mechanics for undergraduate engineering students at University of Palermo.
Response to Comments on “Single-Crystal X-ray Structure of 1,3-Dimethylcyclobutadiene by Confinement in a Crystalline Matrix”
Authors: Legrand Yves-Marie , van der Lee Arie , Barboiu Mihail
Published: November 2010

Scheschkewitz and Alabugin
et al
. suggest that photolysis under confinement in a crystalline matrix of 4,6-dimethyl-α-pyrone does not yield the crystal structure of 1,3-dimethylcyclobutadiene (Me
2
CBD) as we reported, but rather that of a 4,6-dimethyl-β-lactone intermediate. We provide arguments that the square-planar Me
2
CBD
S
/
CO
2
complex and the rectangular-bent Me
2
CBD
R
molecule are stabilized under confinement by the guanidinium-sulfonate-calixarene host matrix used in our study.
Genetically Modified Salmon and Full Impact Assessment
Authors: Smith Martin D. , Asche Frank , Guttormsen Atle G. , Wiener Jonathan B.
Published: November 2010

Health and environmental impacts of GM salmon hinge on aggregate market size, which current regulatory processes ignore.
Nanosilver Revisited Downstream
Authors: Nowack Bernd
Published: November 2010

Wastewater treatment converts potentially toxic nanosilver particles into more benign silver sulfide nanoparticles.
Magnetic Resonance and Microfluidics
Authors: Utz Marcel , Landers James
Published: November 2010

The inner workings of microscale “lab-on-a-chip” devices can be revealed by nuclear magnetic resonance measurements on their exiting fluid flows.
γ-Secretase and Human Disease
Authors: Kelleher Raymond J. , Shen Jie
Published: November 2010

The role of an enzyme in disease pathogenesis extends beyond Alzheimer's disease to a skin disorder.
Topping Off a Multiscale Balancing Act
Authors: Lerman Joshua , Palsson Bernhard O.
Published: November 2010

Quantitative predictions of the relationship between cell growth and gene expression have been made and validated in
Escherichia coli
.
Massive Cost Overrun to Webb Threatens Other NASA Missions
Authors: Lawler Andrew , Bhattacharjee Yudhijit
Published: November 2010

An independent panel reported last week that overruns on the James Webb Space Telescope could reach $1.7 billion, bringing its total cost to as much as $6.8 billion.
Handful of U.S. Schools Claim Larger Share of Output
Authors: Mervis Jeffrey
Published: November 2010

A new analysis of the U.S. research base by Thomson Reuters points to an increasing concentration of academic research. The report examines both the share of scientific papers written by researchers at a particular institution and the impact of those papers.
New Spin on Solid Helium Bolsters Case for Bizarre Flow
Authors: Cho Adrian
Published: November 2010

A team from South Korea and Japan
reports
online in
Science
this week on a new experiment that strongly supports the presence of a strange resistance-free flow in supersolid helium by literally putting a new spin on the original experiment.
A World of Changes Prepares Subra Suresh to Tackle Change at NSF
Authors: Mervis Jeffrey
Published: November 2010

Last week, in his first public interview since taking office, the new director of the U.S. National Science Foundation, Subra Suresh, discussed his plans for the agency in the current politically charged climate.
University Research Should Compete With Russian Academy, Science Minister Argues
Authors: Clery Daniel
Published: November 2010

Minister of Education and Science Andrei Fursenko met with
Science
at the ministry's imposing Tverskaya Street headquarters in September to discuss how Russia plans to reinvigorate its research base.
Immunogenicity and Reactivity of Novel
Mycobacterium avium
subsp.
paratuberculosis
PPE MAP1152 and Conserved MAP1156 Proteins with Sera from Experimentally and Naturally Infected Animals
Authors: Bannantine John P. , Paulson Avery L. , Chacon Ofelia , Fenton Robert J. , Zinniel Denise K. , McVey David S. , Smith David R. , Czuprynski Charles J. , Barletta Raúl G.
Published: November 2010

Mycobacterium avium
subsp.
paratuberculosis
causes Johne's disease (JD) in ruminants. Development of genetic tools and completion of the
M. avium
subsp.
paratuberculosis
genome sequencing project have expanded the opportunities for antigen discovery. In this study, we determined the seroreactivities of two proteins encoded at the 5′ and 3′ regions of the MAP1152-MAP1156 gene cluster. MAP1152 encodes a PPE protein, and MAP1156 encodes a diacylglycerol acyltransferase involved in triglyceride metabolism and classified in the uncharacterized protein family UPF0089. Recombinant MAP proteins were overproduced and purified from
Escherichia coli
as maltose-binding protein (MBP) fusions. Immunoblotting analysis indicated that both MAP1152 and MAP1156 displayed reactivity against sera of mice and rabbits immunized with live
M. avium
subsp.
paratuberculosis
cells and against samples from naturally infected cattle. In immunoblot assays, MAP1156 yielded a stronger positive signal than MAP1152 against sera from cattle with JD. An enzyme-linked immunosorbent assay for the recombinant proteins was developed and used to test preclassified positive and negative serum samples from naturally infected and noninfected cattle. Samples, with one exception, displayed no seroreactivity against the MBP-LacZ fusion protein (
P
> 0.05), the negative-control antigen. MAP1152 displayed seroreactivity against all positive sera but no seroreactivity to the negative sera (
P
< 0.01). MAP1156 displayed stronger and more variable reactivity than MAP1152, but significant differences were observed between noninfected and infected cattle (
P
< 0.05). Otherwise, degrees of reactivity followed the same trend as the positive reference antigen. In conclusion, both proteins are immunogenic in mice and rabbits, and
M. avium
subsp.
paratuberculosis
-infected cattle mount a humoral response to both MAP1152 and MAP1156 cross-reactive epitopes. These findings have potential applications to diagnostics, vaccine production, and elucidation of the immunopathogenesis of JD.
Increased Pulmonary Tumor Necrosis Factor Alpha, Interleukin-6 (IL-6), and IL-17A Responses Compensate for Decreased Gamma Interferon Production in Anti-IL-12 Autovaccine-Treated,Mycobacterium bovisBCG-Vaccinated Mice
Authors: Freches Danielle , Romano Marta , Korf Hannelie , Renauld Jean-Christophe , Van Snick Jacques , Uyttenhove Catherine , Huygen Kris
Published: November 2010

Interleukin-12 (IL-12) and IL-23 (which share a p40 subunit) are pivotal cytokines in the generation of protective Th1/Th17-type immune responses upon infection with the intracellular pathogenMycobacterium tuberculosis. The role of IL-12 and IL-23 in protection conferred by the tuberculosis vaccineMycobacterium bovisbacillus Calmette-Guérin (BCG) is, however, less well documented. By using an autovaccine approach, i.e., IL-12p70 cross-linked with ovalbumin and PADRE peptide formulated with the GSK proprietary adjuvant system AS02V, we could specifically neutralize IL-12 while leaving the IL-23 axis intact. Neutralization of IL-12 beforeM. tuberculosischallenge rendered C57BL/6 mice highly susceptible, resulting in 30-fold-higher CFU in spleen and lungs and accelerated mortality. In contrast, neutralization of IL-12 in BCG-vaccinated mice prior toM. tuberculosischallenge only marginally affected vaccine-mediated protection. Analysis of cytokine production in spleen and lungs 3 weeks post-TB challenge by enzyme-linked immunosorbent assay and functional and flow cytometric assays showed significantly reduced mycobacterium-specific gamma interferon (IFN-γ) responses inM. tuberculosis-infected and BCG-vaccinated mice that had been treated with the autovaccine. Purified protein derivative-induced tumor necrosis factor alpha (TNF-α), IL-6, and IL-17A levels, however, were highest in lungs from BCG-vaccinated/IL-12-neutralized animals, and even unstimulated lung cells from these mice produced significant levels of the three cytokines. Mycobacterium-specific IL-4 and IL-5 production levels were overall very low, but IL-12 neutralization resulted in increased concanavalin A-triggered polyclonal secretion of these Th2-type cytokines. These results suggest that TNF-α, IL-6, and IL-17A may be more important pulmonary effector molecules of BCG-mediated protection than IFN-γ in a context of IL-12 deficiency.
The Inverse Correlation between
Staphylococcus aureus
and
Streptococcus pneumoniae
Colonization in Infants Is Not Explained by Differences in Serum Antibody Levels in the Generation R Study
Authors: Lebon Ankie , Verkaik Nelianne J. , de Vogel Corné P. , Hooijkaas Herbert , Verbrugh Henri A. , van Wamel Willem J. B. , Jaddoe Vincent W. V. , Hofman Albert , Hermans Peter W. M. , Mitchell Tim J. , Moll Henriette A. , van Belkum Alex
Published: November 2010

Colonization rates of
Streptococcus pneumoniae
and
Staphylococcus aureus
are inversely correlated in infants. Several studies have searched for determinants of this negative association. We studied the association between antipneumococcal antibodies with
Staphylococcus aureus
colonization and the association between antistaphylococcal antibodies with pneumococcal colonization in healthy children in the pneumococcal vaccine era. In the first year of life, no association between maternal IgG levels and colonization was seen. In addition, no association between the IgG and IgA levels in the child versus colonization status was seen.
Association of High-Level Mupirocin Resistance and Multidrug-Resistant Methicillin-Resistant
Staphylococcus aureus
at an Academic Center in the Midwestern United States
Authors: Cadilla Adriana , David Michael Z. , Daum Robert S. , Boyle-Vavra Susan
Published: November 2010

Mupirocin is a topical antimicrobial used to eradicate methicillin-resistant
Staphylococcus aureus
(MRSA) colonization, usually in the absence of susceptibility testing. We hypothesized that high-level (HL) mupirocin resistance was associated with multidrug resistance (MDR). To this end, unique patient isolates identified at our institution during 2008 were stratified into those resistant to ≥3 non-β-lactam antimicrobial classes (MDR) and non-MDR MRSA. HL mupirocin resistance was screened by
mupA
PCR on all MDR isolates (
n
= 191) and a 20% random sample (
n
= 130) of non-MDR isolates; E-testing confirmed HL resistance. We found that among MDR isolates, 13 (6.8%) carried
mupA
, whereas none of the non-MDR isolates did (
P
= 0.001). Thus, although the overall prevalence of HL mupirocin resistance is low among MRSA isolates at our institution, an association exists between
mupA
carriage and MDR. Using genotyping and antimicrobial susceptibility profiling, we identified nine HL mupirocin-resistant clones. Whereas the majority of
mupA
-negative MDR isolates had a health care-associated MRSA (HA-MRSA) genotype (multilocus sequence type 5 [ST5] or SCC
mec
type II), the majority of
mupA
-positive MDR isolates had a community-associated MRSA (CA-MRSA) genotype (ST8 or SCC
mec
type IV). However, CA- and HA-MRSA genotypes were more evenly distributed among
mupA
-positive isolates compared to
mupA
-negative MDR isolates. Thus, in Chicago,
mupA
is circulating among both CA- and HA-MRSA backgrounds.