bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Phenomenon of Pressure Pulses Reflecting Between Blades of Adjacent Blade Rows of Turbomachines
Authors: Owczarek Jerzy A.
Published: October 2010

The recently revived interest in “acoustic resonances,” whose details are still not well defined or understood, points to a realization that a new look at some previously unrecognized findings is needed to explain problems encountered in operation of compressors and turbines. The purpose of this paper is to call the attention of the turbomachinery community to an important physical phenomenon of pressure waves in form of pulses, which reflect between blades of adjacent blade rows of turbomachines discovered more than 40 years ago, about whose existence and consequences there is little awareness today. The turbine test results which led the author in 1957 to hypothesize the existence of the phenomenon of reflecting pressure pulses are described. Subsequently, his 1966 ASME paper is discussed. In it, the author reported on the photographed observations of pressure pulses reflecting between stationary nozzles and moving blades of a water-table turbine at Lehigh University, on the description of the various types of such waves, and on an explanation of some of the resonant blade excitation frequencies observed by National Advisory Committee for Aeronautics (NACA) in a turbine of turbojet engine. This is followed by a description of his 1984 ASME paper, in which more general formulae were derived for the blade excitation frequencies caused by the reflections of pressure pulses between the rotor blades, and both upstream and downstream stator vanes. These equations were subsequently used to explain the blade excitation frequencies measured in an axial compressor stage. Finally, his 1992 AIAA paper is discussed, in which additional formulae relating to the reflecting pressure pulses were derived, and the process of formation of a pressure pulse was explained. To put this work in perspective, the author provided, in mostly chronological order, excerpts from reports on operational problems encountered with turbomachines in service and brief descriptions, from selected publications, of pertinent research work.
Blade Excitation in Pulse-Charged Mixed-Flow Turbocharger Turbines
Authors: Senn Stephan M. , Seiler Martin , Schaefer Ottmar
Published: October 2010

In this article, a fully three-dimensional computational modeling approach in the time and frequency domain is presented, which allows to accurately predicting fluid-structure interactions in pulse-charged mixed-flow turbocharger turbines. As part of the approach, a transient computational fluid mechanics analysis is performed based on the compressible inviscid Euler equations covering an entire engine cycle. The resulting harmonic orders of aerodynamic excitation are imposed in a forced response analysis of the respective eigenvector to determine effective stress amplitudes. The modeling approach is validated with experimental results based on various mixed-flow turbine designs. It is shown that the numerical results accurately predict the measured stress levels. The numerical approach can be used in the turbine design and optimization process. Aerodynamic excitation forces are the main reason for high cycle fatigue in turbocharger turbines and therefore a fundamental understanding is of key importance.
A Method for Identifying and Visualizing Foreign Particle Motion Using Time-Resolved Particle Tracking Velocimetry
Authors: Cardwell N. D. , Vlachos P. P. , Thole K. A.
Published: October 2010

Gas turbines for aircraft are designed for operation with a clean inlet air flow. This ideal operational condition is often violated during take-off and landing, where the probability of particle ingestion is high, with sand and dirt being the most commonly observed foreign particles. Current research on particle ingestion has identified several mechanisms that contribute to performance degradation in the turbine: erosion of internal and external surfaces, and flow blockages of film-cooling holes and internal cooling passages. The focus of the study given in this paper is to present a method that identifies the motion of foreign particles within an internal ribbed passage. The method uses a high-resolution, flow field interrogation method known as time-resolved digital particle image velocimetry (TRDPIV). Observations from the two-phase flows showed that particle collisions occurred more frequently on the upstream surface of the ribs, especially in the inlet region. Results from these collisions included substantial particle breakup, and a particle rebounding phenomenon between the upper and lower walls. Comparisons are made to large eddy simulation predicted particle trajectories indicating some agreement, as well as phenomena that are not predicted due to the inherent assumption of the modeling.
Effect of Radial Location of Nozzles on Heat Transfer in Preswirl Cooling Systems
Authors: Kakade V. U. , Lock G. D. , Wilson M. , Owen J. M. , Mayhew J. E.
Published: October 2010

This paper investigates heat transfer in a rotating disk system using preswirled cooling air from nozzles at high and low radius. The experiments were conducted over a range of rotational speeds, flow rates, and preswirl ratios. Narrow-band thermochromic liquid crystal (TLC) was specifically calibrated for application to experiments on a disk, rotating at ∼5000 rpm and subsequently used to measure surface temperature in a transient experiment. The TLC was viewed through the transparent polycarbonate disk using a digital video camera and strobe light synchronized to the disk frequency. The convective heat transfer coefficient h was subsequently calculated from the one-dimensional solution of Fourier's conduction equation for a semi-infinite wall. The analysis was accounted for the exponential rise in the air temperature driving the heat transfer, and for the experimental uncertainties in the measured values of h. The experimental data was supported by “flow visualization,” determined from CFD. Two heat transfer regimes were revealed for the low-radius preswirl system: a viscous regime at relatively low coolant flow rates, and an inertial regime at higher flow rates. Both regimes featured regions of high heat transfer where thin, boundary layers replaced air exiting through receiver holes at high radius on the rotating disk. The heat transfer in the high-radius preswirl system was shown to be dominated by impingement under the flow conditions tested.
Advanced Nonaxisymmetric Endwall Contouring for Axial Compressors by Generating an Aerodynamic Separator—Part I: Principal Cascade Design and Compressor Application
Authors: Dorfner Christian , Hergt Alexander , Nicke Eberhard , Moenig Reinhard
Published: October 2010

Modern methods for axial compressor design are capable of shaping the blade surfaces in a three-dimensional way. Linking these methods with automated optimization techniques provides a major benefit to the design process. The application of nonaxisymmetric contoured endwalls is considered to be very successful in turbine rotors and vanes. Concerning axial compressors, nonaxisymmetric endwalls are still a field of research. This two-part paper presents the recent development of a novel endwall design. An aerodynamic separator, generated by a nonaxisymmetric endwall groove, interacts with the passage vortex. This major impact on the secondary flow results in a significant loss reduction because of load redistribution, reduction in recirculation areas, and suppressed corner separation. The first paper deals with the development of the initial endwall design using a linear compressor cascade application. A brief introduction of the design methods is provided, including the automated optimization and the 3D process chain with a focus on the endwall contouring tool. Hereafter, the resulting flow phenomena and physics due to the modified endwall surface are described and analyzed in detail. Additionally, the endwall design principal is transferred to an axial compressor stage. The endwall groove is applied to the hub and casing endwalls of the stator, and the initial numerical investigation is presented. For highly loaded operating points, the flow behavior at the hub region can be improved in accord with the cascade results. Obviously, the casing region is dominated by the incoming tip vortex generated by the rotor and still remains an area for further investigations concerning nonaxisymmetric endwall contouring.
Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip
Authors: O’Dowd D. O. , Zhang Q. , He L. , Ligrani P. M. , Friedrichs S.
Published: October 2010

The present study considers spatially resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Five different measurement and processing techniques using infrared thermography are considered and compared. Three transient methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. These three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two of these methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1D nonsteady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. The fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady-state condition using a thin-foil heater on the tip surface. Finally, the fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady-state condition is present. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the impulse method is the most accurate, computationally efficient, and reliable method to obtain detailed, spatially resolved heat transfer coefficients and adiabatic wall temperatures on a transonic turbine blade tip in a linear cascade.
The Instability of Webs in Transport
Authors: Beisel J. A. , Good J. K.
Published: October 2010

A method is presented for determining the two levels of instability that are associated with thin web materials traveling through process machinery. The first level of instability involves the out-of-plane buckling of expanses of web supported only by rollers at opposing ends. A method is developed using linear plate theory, which is verified by tests that show that this first level of instability can be predicted. The second level of instability involves the buckling of the web when it has taken the form of a cylindrical shell as it transits a roller. A nonlinear finite element method with strain dependent constitutive relations is developed and verified by tests to predict this second level of instability.
Singular Stress Fields at the Intersection of a Grain Boundary and a Stress-Free Edge in a Columnar Polycrystal
Authors: Reedy E. D.
Published: October 2010

The singular stress field generated at the intersection of a grain boundary and a stress-free edge is investigated for a columnar polycrystal. An idealized, plane strain geometry that embeds four columnar cubic crystals within an effective isotropic media is analyzed. This idealized problem permits a detailed finite element analysis that can resolve the nature of stress singularities. Particular emphasis is placed on characterizing the magnitude of the stress fields and defining the size of the region dominated by the singularity. The effects of crystal and grain boundary orientation combinations and crystal properties are examined.
An Analysis of Higher Order Effects in the Half Power Method for Calculating Damping
Authors: Wang Ivan
Published: October 2010

The half power method is a technique commonly used for calculating the system damping using frequency response curves. Past derivations typically assume a small damping ratio but do not keep track of the order of magnitude when simplifying results and focus mainly on displacement frequency response curves. This paper provides two separate and rigorous derivations of the half power bandwidth for displacement and acceleration frequency response functions. The exact expressions are simplified systematically using binomial expansions to include third order effects. The third order and classical approximations are compared with the exact expressions, and the truncation errors are presented for both displacement and acceleration cases. The high order effects are more apparent and the truncation errors are greater for the acceleration case. The classical method is sufficiently accurate for many practical cases where the damping ratio is less than 0.1 but higher order corrections may be used to reduce truncation error for systems where the damping ratio is higher.
The Shear Response of a Thin Aluminum Layer
Authors: Tagarielli V. L. , Fleck N. A.
Published: October 2010

Aluminum layers, 10–50 μm thick, have been diffusion bonded to alumina blocks and subjected to simple shear in order to determine the sensitivity of shear stress versus strain response to layer thickness. No significant thickness effect on strength is observed and reversed loading tests indicate isotropic hardening. Final failure in shear is by microvoid coalescence within the sandwich layer with a void spacing comparable to the layer thickness. The significance of the results for strain gradient plasticity theory is discussed.
Surface and Interface Effects on Torsion of Eccentrically Two-Phase fcc Circular Nanorods: Determination of the Surface/Interface Elastic Properties via an Atomistic Approach
Authors: Pahlevani Ladan , Shodja Hossein M.
Published: October 2010

The effect of surface and interface elasticity in the analysis of the Saint–Venant torsion problem of an eccentrically two-phase fcc circular nanorod is considered; description of the behavior of such a small structure via usual classical theories cease to hold. In this work, the problem is formulated in the context of the surface/interface elasticity. For a rigorous solution of the proposed problem, conformal mapping with a Laurent series expansion are employed together. The numerical results well illustrate that the torsional rigidity and stress distribution corresponding to such nanosized structural elements are significantly affected by the size. In order to employ surface and interface elasticity, several key properties such as surface energy, surface stresses, and surface elastic constants of several fcc materials as well as interface properties of the noncoherent fcc bicrystals are derived in terms of Rafii-Tabar and Sutton interatomic potential function. For determination of the surface/interface parameters a molecular dynamics program, which uses the above-mentioned potential function, is developed. The calculated surface and interface properties are in reasonable agreement with the corresponding results in literature. Some applications of the given results can be contemplated in the design of micro-/nano-electromechanical systems.
Investigation of Thermal Stress Variability Due to Microstructure in Thin Aluminum Films
Authors: Maniatty Antoinette M. , Cargill G. S. , Moyer Laura E. , Yang Chia-Ju
Published: October 2010

An X-ray microbeam study and a polycrystal finite element model of a 10×10 μm2 section of a 1 μm thick polycrystalline aluminum film on a silicon substrate are used to investigate the effect of microstructure on thermal stress variability. In the X-ray microbeam study, the grain orientations and deviatoric elastic strain field are measured at the subgrain level in the film during and after two thermal cycles. A finite element model of the observed grain structure is created and modeled with an elastoviscoplastic crystal constitutive model that incorporates film thickness and grain size effects as well as dislocation entanglement hardening. The experimental and simulation results are compared at both the film and subgrain scales. While the experiment and model agree fairly well at the film level, the experimental results show much greater elastic strain variability than the simulations. In considering the grain size effect, the experiment and model both predict a similar Hall–Petch coefficient, which is consistent with literature data on free standing aluminum thin films.
On Crack-Tip Stresses as Crack-Tip Radii Decrease
Authors: Sinclair G. B. , Meda G. , Smallwood B. S.
Published: October 2010

In classical elasticity, when cracks are modeled with stress-free elliptical holes, stress singularities occur as crack-tip root radii go to zero. This raises the question of when crack-tip stresses first start to depart from physical reality as radii go to zero. To address this question, here, cohesive stress action is taken into account as radii go to zero. To obtain sufficient resolution of the key crack-tip fields, two highly focused numerical approaches are employed: finite elements with successive submodeling concentrated on the crack-tip and numerical analysis of a companion integral equation with considerable discretization refinement at the crack-tip. Both numerical approaches are verified with convergence checks and test problems. Results show that for visible cracks, classical elasticity analysis leads to physically sensible stresses, provided that crack-tip radii are accounted for properly. For microcracks with smaller crack-tip radii, however, cohesive stress action also needs to be included if accurate crack-tip stresses are to be obtained. For cracks with yet smaller crack-tip radii, cracks close and stresses throughout the crack plane become uniform.
Higher-Order Terms for the Mode-III Stationary Crack-Tip Fields in a Functionally Graded Material
Authors: Zhang Linhui , Kim Jeong-Ho
Published: October 2010

This paper provides full asymptotic crack-tip field solutions for an antiplane (mode-III) stationary crack in a functionally graded material. We use the complex variable approach and an asymptotic scaling factor to provide an efficient procedure for solving standard and perturbed Laplace equations associated with antiplane fracture in a graded material. We present the out-of-plane displacement and the shear stress solutions for a crack in exponentially and linearly graded materials by considering the gradation of the shear modulus either parallel or perpendicular to the crack. We discuss the characteristics of the asymptotic solutions for a graded material in comparison with the homogeneous solutions. We address the effects of the mode-III stress intensity factor and the antiplane T-stress onto crack-tip field solutions. Finally, engineering significance of the present work is discussed.
Modeling Nanowire Indentation Test With Adhesion Effect
Authors: Zhang Yin , Zhao Ya-pu
Published: October 2010

Because of the large aspect ratio of its length to radius and the large surface area to volume ratio, the nanowire is highly flexural and susceptible to the adhesion influence. The bending deflection of nanowire and its adhesion effect make the previous indentation models inappropriate for the nanowire indentation test. In this paper, a new model incorporating the nanowire bending deflection, loading symmetry/asymmetry, and adhesion effect is presented and compared with the previous models. Because of the bending deflection of the flexural nanowire, the nanowire may lift-off/separate from its contacting elastic medium and the localized contact effects may thus be induced. The localized contact effects as predicted by this new model can cause the relatively large deflection difference of the nanowire in test as compared with those obtained by the previous models, which impacts directly and significantly on the interpretation of the indentation experimental data. The nanowire is modeled as a cylinder/beam and the indentation force is modeled as a concentrated force. The elastic medium is modeled as an elastic foundation. The elastic foundation behaves as a linear spring in nonadhesive Hertz contact and as a nonlinear softening spring in adhesive contact. In the Hertz contact, due to lift-off, the contact length is independent of the load. However, in adhesive contact, larger load results in smaller contact length. Unlike the Hertz contact in which lift-off always occurs when adhesion force is too large for bending cylinder to overcome, there is no lift-off for cylinder and the full contact scenario is thus formed.
Analytical and 3D Finite Element Study of the Deflection of an Elastic Cantilever Bilayer Plate
Authors: Chekchaki M. , Lazarus V. , Frelat J.
Published: October 2010

The mechanical system considered is a bilayer cantilever plate. The substrate and the film are linear elastic. The film is subjected to isotropic uniform prestresses due for instance to volume variation associated with cooling, heating, or drying. This loading yields deflection of the plate. We recall Stoney’s analytical formula linking the total mechanical stresses to this deflection. We also derive a relationship between the prestresses and the deflection. We relax Stoney’s assumption of very thin films. The analytical formulas are derived by assuming that the stress and curvature states are uniform and biaxial. To quantify the validity of these assumptions, finite element calculations of the three-dimensional elasticity problem are performed for a wide range of plate geometries, Young’s and Poisson’s moduli. One purpose is to help any user of the formulas to estimate their accuracy. In particular, we show that for very thin films, both formulas written either on the total mechanical stresses or on the prestresses, are equivalent and accurate. The error associated with the misfit between our theorical study and numerical results are also presented. For thicker films, the observed deflection is satisfactorily reproduced by the expression involving the prestresses and not the total mechanical stresses.
Study of Thin Sandwich Beams With Steel Faces and Perforated Polymer Core in Bending Loading: Experiments and Simulations
Authors: Lhuissier P. , Masse J.-P. , Salvo L. , Brechet Y.
Published: October 2010

The mechanical behavior of thin sandwich beams with steel faces and porous polymer core have been investigated using quasistatic four-points bending. Classic sandwich models predicting the behavior and the failure modes are improved to fit the particular configuration of the structure. Numerical simulations were set up in order to investigate damage at large strain. Macroscopic results are compared with analytical models and numerical simulations. Two numerical models of the core allowed confrontation of local behavior with experiments. Criteria for localization and damaging depending on core architecture are proposed.
A Nonlinear Thermomechanical Model of Spinel Ceramics Applied to Aluminum Oxynitride (AlON)
Authors: Clayton J. D.
Published: October 2010

A continuum model is developed for describing deformation and failure mechanisms in crystalline solids (ceramics and minerals) with the cubic spinel structure. The constitutive model describes the response under conditions pertinent to impact loading: high pressures, high strain rates, and, possibly, high temperatures. Nonlinear elasticity, anisotropy, thermoelastic coupling, dislocation glide, twinning, shear-induced fracture, and pressure-induced pore collapse are addressed. The model is applied to enable an improved understanding of transparent ceramic aluminum oxynitride (AlON). Calculations demonstrate an accurate depiction of hydrostatic and shear stresses observed experimentally in shock-loaded polycrystalline AlON. Various choices of initial resistances to slip, twinning, or shear fracture that result in similar predictions for average stresses in polycrystals but different predictions for defect densities (accumulated dislocations and twin volume fractions) are investigated. Predictions for single crystals provide insight into grain orientation effects not available from previous experimental investigations.
Some Further Remarks on Hamilton’s Principle
Authors: Udwadia Firdaus E. , Leitmann George , Cho Hancheol
Published: October 2010

This paper deals with the inverse problem of finding a suitable integrand so that upon the use of the calculus of variations, one obtains the equations of motion for systems in which the forces are nonpotential. New extensions and generalizations of previous results are obtained.
Pyrolysis of two-dimensional and three-dimensional interferometrically patterned resist structures
Authors: Burckel D. B. , Washburn C. M. , Koleske D. D. , Polsky R.
Published: October 2010

Interferometric lithography was used to create a wide variety of two-dimensional and three-dimensional patterns in standard photoresist. The patterns were then converted to amorphous carbon structures through pyrolysis in a reducing atmosphere. The structures maintain their fundamental in-plane morphology despite undergoing significant shrinkage. As an indication of their functionality, the authors highlight their use in two diverse applications: (1) as a defect reduction mask in metal-organic chemical vapor deposition growth of gallium nitride (GaN) on sapphire and (2) as a nanoparticle decorated electrode for catalytic oxidation of methanol.
Direct synthesis of vertical α-Fe2O3 nanowires from sputtered Fe thin film
Authors: Nagato Keisuke , Furubayashi Masaki , Hamaguchi Tetsuya , Nakao Masayuki
Published: October 2010

α -Fe 2 O 3 (hematite) nanowires were synthesized from Fe thin films. The bladelike nanowires were synthesized by the simple annealing of a sputtered Fe thin film in a furnace with the annealing time varied between 0 and 100 min. The length of the nanowires was proportional to the logarithm of the annealing time. The number density of nanowires was saturated within an annealing time of 0–1 min. The Fe thin film may have been oxidized during annealing and the iron oxide molecules may have diffused to the roots of nanowires in accordance with the solid-phase growth model or they may have vaporized and then have been deposited on the surface of nanowires in accordance with the vapor-liquid-solid model. The authors characterized the nanowires by Raman spectroscopy and transmission electron microscopy (TEM). The Raman shift and the results of TEM indicated that the nanowires consisted of trigonal α-Fe2O3.
Nonlinearities in depth profiling nanometer layers
Authors: Seah M. P. , Mulcahy C. P. A. , Biswas S.
Published: October 2010

An analysis is made of the sputter depth profiling of ultrathin silicon dioxide layers on silicon to evaluate the variation in the sputtering rate in the first few nanometers. Such changes in sputtering rate are important for the development of the analysis of nanoparticles. Cs+ ions are chosen as an example of a metal ion popular in secondary ion mass spectrometry (SIMS) studies that provide excellent depth resolution. It is found that, if it is assumed that the signal is linear with oxygen content, the sputtering rate falls rapidly by a factor of 4.8, with an exponential decay near 1.2 nm when using 600 eV Cs+ ions at 60° incidence angle. The interface may be described by the integral of the response function of Dowsett et al. developed for SIMS depth profiling of delta layers with λu=0.5 nm, λd=0.7 nm, and σ=0.4 nm, showing the excellent depth resolution. However, if published data for the nonlinearity of the signal with oxygen content are used, the rapid change is still seen but with an initial sputtering rate that is reduced from the above 4.8 to 3.5 times that at equilibrium.
Physical Phenomena in Real Time
Authors: Brookes David , Etkina Eugenia
Published: October 2010

The use of videos allows teachers to tame the vagaries of experimentation while engaging students in the process of physics.
Cognitive Illusions of Authorship Reveal Hierarchical Error Detection in Skilled Typists
Authors: Logan Gordon D. , Crump Matthew J. C.
Published: October 2010

Touchy Typing

Even the most able typist makes errors, and
Logan and Crump
(p.
683
) have used this real-world task to probe for the existence of two error-detection mechanisms. They inserted errors into words that had been typed correctly by the subjects, and they corrected errors that had been made. By measuring implicit error detection as the slowing of movement just after an error had been committed and by eliciting explicit monitoring of errors by the output shown on the screen, they uncovered a double dissociation. Inserted errors did not lengthen the interval until the next letter was typed, but they were reported by the typist as errors; on the other hand, corrected errors did increase the interval, but were nevertheless claimed by the subjects as having been typed correctly.
Paramutation’s Properties and Puzzles
Authors: Chandler Vicki L.
Published: October 2010

Paramutation refers to the process by which homologous DNA sequences communicate in trans to establish meiotically heritable expression states. Although mechanisms are unknown, current data are consistent with the hypothesis that the establishment and heritable transmission of specific chromatin states underlies paramutation. Transcribed, noncoding tandem repeats and proteins implicated in RNA-directed transcriptional silencing in plants and yeast are required for paramutation, yet the specific molecules mediating heritable silencing remain to be determined.
Molecular Signals of Epigenetic States
Authors: Bonasio Roberto , Tu Shengjiang , Reinberg Danny
Published: October 2010

Epigenetic signals are responsible for the establishment, maintenance, and reversal of metastable transcriptional states that are fundamental for the cell’s ability to “remember” past events, such as changes in the external environment or developmental cues. Complex epigenetic states are orchestrated by several converging and reinforcing signals, including transcription factors, noncoding RNAs, DNA methylation, and histone modifications. Although all of these pathways modulate transcription from chromatin in vivo, the mechanisms by which epigenetic information is transmitted through cell division remain unclear. Because epigenetic states are metastable and change in response to the appropriate signals, a deeper understanding of their molecular framework will allow us to tackle the dysregulation of epigenetics in disease.
Sustaining the Data and Bioresource Commons
Authors: Schofield Paul N. , Eppig Janan , Huala Eva , de Angelis Martin Hrabe , Harvey Mark , Davidson Duncan , Weaver Tom , Brown Steve , Smedley Damian , Rosenthal Nadia , Schughart Klaus , Aidinis Vassilis , Tocchini-Valentini Glauco , Hancock John M.
Published: October 2010

Globalization of biomedical research requires sustained investment for databases and biorepositories.
A Little Chemistry Helps the Big Get Bigger
Authors: Evans James W. , Thiel Patricia A.
Published: October 2010

The coarsening of small metal particles can be enhanced when metal atoms are transported between particles as part of larger complexes.
Visualizing Ribosome Biogenesis: Parallel Assembly Pathways for the 30
S
Subunit
Authors: Mulder Anke M. , Yoshioka Craig , Beck Andrea H. , Bunner Anne E. , Milligan Ronald A. , Potter Clinton S. , Carragher Bridget , Williamson James R.
Published: October 2010

Ribosome Assembly Pathway

The bacterial ribosome is made up of two subunits (50
S
and 30
S
) that together comprise 55 proteins and three large ribosomal RNAs. Both subunits self-assemble from their components in vitro, and hence,

Mulder
et al.

(p.
673
) were able to use a derivation of time-resolved electron microscopy to monitor assembly of the 30
S
subunit. This approach identified 14 distinct assembly intermediates and allowed characterization of the population, conformation, and protein composition of the intermediates along the assembly pathway.
Large δ
13
C Gradients in the Preindustrial North Atlantic Revealed
Authors: Olsen Are , Ninnemann Ulysses
Published: October 2010

Lost Details

Changes in ocean circulation are commonly inferred by differences between the distribution of carbon isotopes in the past and now, but making such comparisons neglects the fact that modern fossil fuel burning has modified the carbon isotopic composition of the ocean. This in turn obscures details about recent mass movement of water.
Olsen and Ninnemann
(p.
658
) correct for this effect in the North Atlantic and show that the natural distribution of carbon isotopes has more detail and is clearly related to water mass distributions. The results change some important ideas about glacial-interglacial ocean variations within the context of modern climate variability.
A Small-RNA Perspective on Gametogenesis, Fertilization, and Early Zygotic Development
Authors: Bourc’his Déborah , Voinnet Olivier
Published: October 2010

Transient populations of cis- and trans-acting small RNAs have recently emerged as key regulators of extensive epigenetic changes taking place during periconception, which encompasses gametogenesis, fertilization, and early zygotic development. These small RNAs are not only important to maintain genome integrity in the gametes and zygote, but they also actively contribute to assessing the compatibility of parental genomes at fertilization and to promoting long-term memory of the zygotic epigenetic landscape by affecting chromatin. Striking parallels exist in the biogenesis and modus operandi of these molecules among diverse taxa, unraveling universal themes of small-RNA–mediated epigenetic reprogramming during sexual reproduction.
The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
Authors: Howard Andrew W. , Marcy Geoffrey W. , Johnson John Asher , Fischer Debra A. , Wright Jason T. , Isaacson Howard , Valenti Jeff A. , Anderson Jay , Lin Doug N. C. , Ida Shigeru
Published: October 2010

Closing in on Extraterrestrial Earths

With close to 500 extrasolar planets discovered to date, researchers are starting to estimate the occurrence of low-mass planets to help our understanding of how planets form and evolve. Based on observations of 166 nearby stars with the Keck Telescope,

Howard
et al.

(p.
653
) report the occurrence of short-period planets around Sun-like stars as a function of planet mass. Planet formation models predicted that planet occurrence would increase with decreasing mass, such that satellites with masses similar to that of Neptune, and less, would be more common than gas-giant planets like Jupiter. Contrary to predictions, there is no dearth of planets with masses 5 to 30 times that of Earth, implying that the models may need revision. Nevertheless, observations suggest that 23% of Sun-like stars may be orbited by a close-in, terrestrial mass planet.
Fitness Correlates of Heritable Variation in Antibody Responsiveness in a Wild Mammal
Authors: Graham Andrea L. , Hayward Adam D. , Watt Kathryn A. , Pilkington Jill G. , Pemberton Josephine M. , Nussey Daniel H.
Published: October 2010

Self-Recognition and Survival

Soay sheep are a remnant of an ancient breed of sheep that, although intensively studied for many years, live unmanaged on the remote Scottish island of St. Kilda. Life is harsh on the island, and the numbers of sheep show cycles of winter population crashes and high exposure to infection.

Graham
et al.

(p.
662
; see the Perspective by

Martin and Coon

) measured levels of self-reactive antibodies in the sheep called antinuclear antibodies (ANA). Having high ANA levels was a heritable trait that reflected generally high levels of immunoglobulin in individuals and of specific antibodies to parasitic worms. Female sheep with high levels of ANAs survived better during crash years, but had fewer births. If these sheep did reproduce, although the lambs tended to be small, they tended to have higher rates of early survival. Thus, maintaining high antibody levels apparently reflected investment in immunity and greater survival, but doing so was also associated with reduced reproductive success.
Transferable GaN Layers Grown on ZnO-Coated Graphene Layers for Optoelectronic Devices
Authors: Chung Kunook , Lee Chul-Ho , Yi Gyu-Chul
Published: October 2010

Gallium Nitride Grown on Graphene

Nitride semiconductor materials used in light-emitting diodes and lasers are usually grown on single-crystal sapphire substrates with intermediate buffer layers. Instead,

Chung
et al.

(p.
655
) used graphene as a substrate for gallium nitride growth and found that nucleation of the gallium nitride layers was enhanced by first depositing zinc oxide, which grew as vertical nanowalls on the graphene. The gallium nitride layers displayed strong photo- and electroluminescence and, even better, the layers could be transferred to flexible substrates such as plastic.
Early Use of Pressure Flaking on Lithic Artifacts at Blombos Cave, South Africa
Authors: Mourre Vincent , Villa Paola , Henshilwood Christopher S.
Published: October 2010

Ancient Innovations

Pressure flaking is a method of forming points, grooves, and notches on stone tools in which a tool is pressed up against another stone, instead of striking it. It has been thought to be a fairly recent innovation, arising in the Upper Paleolithic 20,000 or so years ago.

Mourre
et al.

(p.
659
), show that tools from Blombos Cave, dating to about 75,000 years ago, have grooves and patterns resembling production by heat treatment followed by pressure flaking. Replication experiments were performed using similar source material followed by microscopic study of the tools. Despite the evidence for an early innovation, it seems that pressure flaking was not used widely elsewhere until much later; thus, such early innovations may have been sporadic ephemeral.
Diversity of Human Copy Number Variation and Multicopy Genes
Authors: Sudmant Peter H. , Kitzman Jacob O. , Antonacci Francesca , Alkan Can , Malig Maika , Tsalenko Anya , Sampas Nick , Bruhn Laurakay , Shendure Jay ,   1000 Genomes Project, Eichler Evan E.
Published: October 2010

Evolution, Gene Number, and Disease

Slight variations in the numbers of copies of genes influence human disease and other characters. Variants can be hard to detect when they lie in heavily duplicated and widely similar regions of sequence known as “dark matter.”

Sudmant
et al.

(p.
641
) have methods to tease apart the duplicated regions to reveal singly unique nucleotide identifiers. These have turned out to be among the most variable seen in different human population groups—most notably among genes for neurodevelopment and neurological diseases. Such polymorphisms can be genotyped with specificity and may help us understand how variation in copy number may affect human evolution and disease.
Unbounding the Mind

The Extended Mind
Richard Menary, Ed.

MIT Press, Cambridge, MA, 2010. 390 pp. $40, £29.95. ISBN 9780262014038.
Authors: Myin Erik
Published: October 2010

The contributors examine Clark and Chalmers's claim that the mind is not confined to the head but extends into the world and discuss its implications.
A Size Threshold Limits Prion Transmission and Establishes Phenotypic Diversity
Authors: Derdowski Aaron , Sindi Suzanne S. , Klaips Courtney L. , DiSalvo Susanne , Serio Tricia R.
Published: October 2010

Processing Prion Phenotype

How misfolding of a prion protein translates into transmissible changes in cellular physiology is unclear.

Derdowski
et al.

(p.
680
) integrated a computational model of prion aggregate dynamics with an empirical analysis of the physical and functional dynamics of prion protein in yeast cells. Remarkably, they found that prion phenotypes resulted from fluctuations in the accumulation of aggregates and suggested that it is the process rather than the product of protein misfolding that is crucial in establishing the severity or stability of the resulting phenotype.
Caging Carbon Dioxide
Authors: Lastoskie Christian
Published: October 2010

A better understanding of amine-CO
2
interactions may be pivotal in functionalizing novel adsorbents for carbon capture.
Innate Lymphoid Cell Relations
Authors: Veldhoen Marc , Withers David R.
Published: October 2010

A common progenitor cell gives rise to distinct lineages of innate lymphoid cells in the gastrointestinal tract.
Infection Protection and Natural Selection
Authors: Martin Lynn B. , Coon Courtney A. C.
Published: October 2010

On an island off Scotland, variation in sheep immune response imposes fitness costs and benefits.
Epigenome Disruptors
Authors: Hemberger Myriam , Pedersen Roger
Published: October 2010

What can stem cells tell us about epigenetic perturbations?
Campaign for U.K. Science Helps Deflect Budget Ax
Authors: Clery Daniel
Published: October 2010

Despite warnings to expect funding cuts of 20%, 30%, or even 40%, the U.K. science budget has been fixed for the next 4 years at this year's amount, £4.6 billion ($7.2 billion).
Liquid Water Found on Mars, But It's Still a Hard Road for Life
Authors: Kerr Richard A.
Published: October 2010

Researchers appear to have finally achieved one of the Phoenix lander's primary goals. After digging through piles of data left from the mission to Mars more than 2 years ago, they've discovered signs that liquid water has lately flowed on the frigid planet.
Leaked Documents Provide Bonanza for Researchers
Authors: Bohannon John
Published: October 2010

The Pentagon is fuming after last week's release of a huge cache of classified Iraq War data by the organization WikiLeaks. But researchers struggling to build an accurate picture of the death toll in post-invasion Iraq are thrilled.
Epigenetic Drugs Take On Cancer
Authors: Kaiser Jocelyn
Published: October 2010

Armed with nearly $10 million raised by telethons, a research “dream team” hopes to prove that a new approach to cancer therapy can halt solid tumors.
Genes Link Epigenetics and Cancer
Authors: Kaiser Jocelyn
Published: October 2010

Recent reports that genes affecting chromatin structure are mutated in several types of solid tumors could help resolve the conundrum of whether so-called epigenetic changes are a cause or a consequence of disease.
Gene Variants Affect Hepatitis C Treatment, But Link Is Elusive
Authors: Wapner Jessica
Published: October 2010

Genome scans have turned up single nucleotide polymorphisms associated with different responses to treatment, but efforts to uncover the mechanism have drawn a blank.
Going Back to the Future To Understand Climate Change
Authors: Gibbons Ann
Published: October 2010

Several speakers at the meeting used paleontological data to predict the future, drawing on species' behavior during past episodes of climate change to predict how they will fare—and how to help them—as greenhouse gases warm the planet.
When Rodents Marched Into Paris
Authors: Gibbons Ann
Published: October 2010

At the meeting, researchers announced the discovery of some of the world's oldest rodents, an important clue to the mystery of how the first modern mammals spread around the globe, replacing archaic animals and ushering in the age of modern mammals.
Correlation of Immune Activation during Late Pregnancy and Early Postpartum with Increases in Plasma HIV RNA, CD4/CD8 T Cells, and Serum Activation Markers
Authors: Truong Hong-Ha M. , Sim Myung S. , Dillon Maryanne , Uittenbogaart Christel H. , Dickover Ruth , Plaeger Susan F. , Bryson Yvonne J.
Published: October 2010

A previously observed rise in the plasma viral load postpartum in both treated and untreated HIV-positive women remains unexplained. Virological and immunological markers were evaluated in HIV-negative controls and HIV-positive pregnant women with and without antiretroviral treatment. Plasma HIV RNA, CD4/CD8 T cells, and serum activation markers were sequentially measured during the third trimester, at delivery, and 2 to 8 weeks postpartum in a cohort of HIV-positive pregnant women (n= 96) enrolled in a maternal-fetal HIV transmission study and a control group of HIV-negative pregnant women (n= 28). Mean plasma HIV RNA (P= 0.003) increased from delivery to postpartum, and mean CD4 T cells (P= 0.002) and serum β2-microglobulin (P< 0.0001) increased from the third trimester through postpartum among the HIV-positive women. Mean CD8 T cells increased from the third trimester through postpartum in women receiving zidovudine (ZDV) and in those not treated (P< 0.05) but remained stable in those on highly active antiretroviral therapy (HAART) and the HIV-negative controls. Increases in serum β2-microglobulin were correlated with increases in HIV RNA (P= 0.01). HIV-positive pregnant women showed postpartum increases in plasma HIV RNA, CD4 T cells, and serum β2-microglobulin regardless of the treatment regimen. The rise in CD4 T cells and β2-microglobulin was also observed in HIV-negative pregnant women, suggesting hormonal changes and/or labor-induced cytokines may contribute to immune activation. Immune activation correlated with increased plasma HIV RNA in postpartum women despite treatment, although HAART appeared to blunt the effect. The observed rise in plasma HIV RNA postpartum, which correlated with markers of immune activation, may have implications for enhanced transmission to infants through early breast-feeding and to sexual partners.
Escherichia coliK88ac Fimbriae Expressing Heat-Labile and Heat-Stable (STa) Toxin Epitopes Elicit Antibodies That Neutralize Cholera Toxin and STa Toxin and Inhibit Adherence of K88ac FimbrialE. coli
Authors: Zhang Chengxian , Zhang Weiping
Published: October 2010

EnterotoxigenicEscherichia coli(ETEC) strains are a major cause of diarrheal disease in humans and animals. Bacterial adhesins and heat-labile (LT) and heat-stable (ST) enterotoxins are the virulence determinants in ETEC diarrhea. It is believed that vaccines inducing anti-adhesin immunity to inhibit bacterial adherence and anti-toxin immunity to eliminate toxin activity would provide broad-spectrum protection against ETEC. In this study, an ETEC fimbrial adhesin was used as a platform to express LT and STa for adhesin-toxin fusion antigens to induce anti-toxin and anti-adhesin immunity. An epitope from the B subunit of LT toxin (LTP1,8LCSEYRNTQIYTIN21) and an STa toxoid epitope (5CCELCCNPQCAGCY18) were embedded in the FaeG major subunit ofE. coliK88ac fimbriae. Constructed K88ac-toxin chimeric fimbriae were harvested and used for rabbit immunization. Immunized rabbits developed anti-K88ac, anti-LT, and anti-STa antibodies. Moreover, induced antibodies not only inhibited adherence of K88ac fimbrialE. colito porcine small intestinal enterocytes but also neutralized cholera toxin and STa toxin. Data from this study demonstrated that K88ac fimbriae expressing LT and STa epitope antigens elicited neutralizing anti-toxin antibodies and anti-adhesin antibodies and suggested thatE. colifimbriae could serve as a platform for the development of broad-spectrum vaccines against ETEC.