bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid–rock interactions during continuous diagenesis of sandstone reservoirs and their effects on reservoir porosity
Authors: Yang Leilei , Xu Tianfu , Liu Keyu , Peng Bo , Yu Zhichao , Xu Xiaomeng
Published: December 2016

The Cretaceous sandstone reservoir in the Kuche Depression, Tarim Basin, western China, was investigated with reference to its reservoir property evolution during diagenesis. Six general diagenetic stages were recognized through petrographic, mineralogical and geochemical analyses. Fluid–rock interaction experiments were conducted under these six continuous diagenetic conditions, that is with a simulation sequence of compaction → early diagenesis → organic acid incursion I → elevated temperature/pressure → organic acid incursion II → late diagenesis. Corresponding to these six experimental stages, a total of six models were constructed. Finally, an extended model of fluid–rock interaction during diagenesis at a geological timescale (from 30 Ma to present) was constructed after various parameters had been validated. Results demonstrate that the diagenetic stages from both the experimental and numerical simulations generally matched findings obtained from the petrographic and geochemical analyses: (i) With compaction becoming weakened, cementation by various minerals was gradually increased. (ii) Quartz overgrowth occurred because the contemporaneous sedimentary water was alkaline. (iii) Most minerals (for example, calcite and feldspar minerals) displayed dissolution owing to the first organic acid incursion, resulting in the visual porosity increasing to 29·26%. (iv) Increases in temperature and pressure caused a minor fluctuation of the porosity change. (v) The cement that formed during earlier stages largely dissolved with the second organic acid incursion. (vi) During the last stage, the reservoir fluid was diluted by sedimentary alkaline water and most minerals precipitated under an alkalic environment. The present porosity simulated is about 11·4%, comparable with the actually measured data. This study demonstrates that the combination of petrographic observations, laboratory experiments and numerical simulations can not only reconstruct the diagenetic process, but also provide a quantitative evaluation and prediction of reservoir petrophysical properties.
Experimental characterization of meso‐scale deformation mechanisms and the RVE size in plastically deformed carbon steel
Authors: Ravindran Suraj , Koohbor Behrad , Kidane Addis
Published: December 2016

The local deformation response of low carbon steel subjected to uniaxial tensile loading is investigated, and the local strain field at sub‐grain scale is obtained using high‐spatial‐resolution digital image correlation. The implemented digital image correlation method enables the observation and study of inhomogeneous deformation response at microstructural levels. Detailed local deformation mechanisms including mesoscopic slip bands are captured. Furthermore, the local information is used for the determination of representative volume element size in polycrystalline low carbon steel. To obtain the representative volume element size, we proposed and successfully implemented a strain variation method. Further, the influence of global strain on the local deformation mechanisms and representative volume element size is discussed. The challenges associated with the local strain measurement using digital image correlation are also discussed.
AraQTL – workbench and archive for systems genetics in Arabidopsis thaliana
Authors: Nijveen Harm , Ligterink Wilco , Keurentjes Joost J. B. , Loudet Olivier , Long Jiao , Sterken Mark G. , Prins Pjotr , Hilhorst Henk W. , de Ridder Dick , Kammenga Jan E. , Snoek Basten L.
Published: December 2016

Genetical genomics studies uncover genome‐wide genetic interactions between genes and their transcriptional regulators. High‐throughput measurement of gene expression in recombinant inbred line populations has enabled investigation of the genetic architecture of variation in gene expression. This has the potential to enrich our understanding of the molecular mechanisms affected by and underlying natural variation. Moreover, it contributes to the systems biology of natural variation, as a substantial number of experiments have resulted in a valuable amount of interconnectable phenotypic, molecular and genotypic data. A number of genetical genomics studies have been published for Arabidopsis thaliana, uncovering many expression quantitative trait loci (eQTLs). However, these complex data are not easily accessible to the plant research community, leaving most of the valuable genetic interactions unexplored as cross‐analysis of these studies is a major effort. We address this problem with AraQTL (http://www.bioinformatics.nl/AraQTL/), an easily accessible workbench and database for comparative analysis and meta‐analysis of all published Arabidopsis eQTL datasets. AraQTL provides a workbench for comparing, re‐using and extending upon the results of these experiments. For example, one can easily screen a physical region for specific local eQTLs that could harbour candidate genes for phenotypic QTLs, or detect gene‐by‐environment interactions by comparing eQTLs under different conditions.
Global identification of alternative splicing via comparative analysis of SMRT‐ and Illumina‐based RNA‐seq in strawberry
Authors: Li Yongping , Dai Cheng , Hu Chungen , Liu Zhongchi , Kang Chunying
Published: December 2016

Alternative splicing (AS) is a key post‐transcriptional regulatory mechanism, yet little information is known about its roles in fruit crops. Here, AS was globally analyzed in the wild strawberry Fragaria vesca genome with RNA‐seq data derived from different stages of fruit development. The AS landscape was characterized and compared between the single‐molecule, real‐time (SMRT) and Illumina RNA‐seq platform. While SMRT has a lower sequencing depth, it identifies more genes undergoing AS (57.67% of detected multiexon genes) when it is compared with Illumina (33.48%), illustrating the efficacy of SMRT in AS identification. We investigated different modes of AS in the context of fruit development; the percentage of intron retention (IR) is markedly reduced whereas that of alternative acceptor sites (AA) is significantly increased post‐fertilization when compared with pre‐fertilization. When all the identified transcripts were combined, a total of 66.43% detected multiexon genes in strawberry undergo AS, some of which lead to a gain or loss of conserved domains in the gene products. The work demonstrates that SMRT sequencing is highly powerful in AS discovery and provides a rich data resource for later functional studies of different isoforms. Further, shifting AS modes may contribute to rapid changes of gene expression during fruit set.
Plant invasiveness and target plant density: high densities of native Schima wallichii seedlings reduce negative effects of invasive Ageratina adenophora
Authors: Thapa L B , Kaewchumnong K , Sinkkonen A , Sridith K
Published: December 2016

Economically feasible strategies to cope with invasive species are urgently needed. Plant density can be increased to reduce competitive effects on target plants. This study indicates that increasing native plant density can be used to reduce the effect of invasive Ageratina adenophora. Seedlings of an indigenous tree species, Schima wallichii, were grown in pots containing uninvaded or invaded soil, with or without A. adenophora leaf litter on the soil surface. Schima wallichii seedlings were also grown at four densities under four levels of A. adenophora leaf litter. Root and shoot biomass and length were measured as response parameters in both bioassays. Schima wallichii growth was inhibited by A. adenophora leaf litter and invaded soil. High litter levels reduced S. wallichii root length and dry weight at low plant densities. The inhibition disappeared at high S. wallichii plant densities. As A. adenophora did not inhibit S. wallichii growth at high plant densities, adjustments of seedling density should be studied as a possible management strategy for invasion by A. adenophora and potentially by other exotic plant species. As density‐dependent growth inhibition is the key characteristic of chemical interference, we propose that phytotoxins contribute to A. adenophora invasion particularly at low densities of native seedlings.
The role of allogenic keratin‐derived dressing in wound healing in a mouse model
Authors: Konop Marek , Sulejczak Dorota , Czuwara Joanna , Kosson Piotr , Misicka Aleksandra , Lipkowski Andrzej W. , Rudnicka Lidia
Published: December 2016

Keratin is an interesting protein needed for wound healing and tissue recovery. We have recently proposed a new, simple and inexpensive method to obtain fur and hair keratin‐derived biomaterials suitable for medical application. The aim of the study was to evaluate the role of the fur keratin‐derived protein (FKDP) dressing in the allogenic full‐thickness surgical skin wound model. The data obtained using scanning electron microscopy showed that employed processed biomaterial had higher surface porosity compared with control raw material. From the MTS test, it was found keratin biomaterial is not only toxic to the NIH/3T3 cell line (p < 0.05), but also enhances cell proliferation compared with the control. In vivo studies have shown keratin dressings are tissue biocompatible, accelerate wound closure and epithelialization to the statistically significant differences on day 5 (p < 0.05) in comparison to control wounds. Histological examination revealed, that in FKDP‐treated wounds the inflammatory response contained predominantly macrophages whilst their morphological untreated variants showed mixed cell infiltrates rich in neutrophils. Predominant macrophages based response creates more favorable environment for healing. In FKDP‐dressed wounds the number of microhemorrhages was also significantly decreased (p < 0.05) as compared with undressed wounds. Applied keratin dressing favors reconstruction of a more regular skin structure and assures better cosmetic effect in terms of scar formation and appearance. In conclusion, fur keratin‐derived protein dressings significantly accelerated wound healing in the mouse model. Further studies are needed to determine the molecular mechanisms involved in the multilayer wound healing process and to assess the possible use of these dressings for medical purposes.
Effects of Filtered Containment Venting on Fission Product Releases During CANDU Reactor Severe Accidents
Authors: Morreale A. C. , Lebel L. S. , Brown M. J.
Published: December 2016

Severe accidents are of increasing concern in the nuclear industry worldwide since the accidents at Fukushima Daiichi (March 2011). These events have significant consequences that must be mitigated to ensure public and employee safety. Filtered containment venting (FCV) systems are beneficial in this context as they would help to maintain containment integrity while also reducing radionuclide releases to the environment. This paper explores the degree to which filtered containment venting would reduce fission product releases during two Canada Deuterium Uranium (CANDU) 6 severe accident scenarios, namely a station blackout (SBO) and a large loss of coolant accident (LLOCA) (with limited emergency cooling). The effects on the progression of the severe accident and radionuclide releases to the environment are explored using the Modular Accident Analysis Program (MAAP)–CANDU integrated severe accident analysis code. The stylized filtered containment venting system model employed in this study avoids containment failure and significantly reduces radionuclide releases by 95–97% for non-noble gas fission products. Filtered containment venting is shown to be a suitable technology for the mitigation of severe accidents in CANDU, maintaining containment integrity and reducing radionuclide releases to the environment.
On the Structure of the Optimal Solution to a Periodic Drug-Delivery Problem
Authors: Ghanaatpishe Mohammad , Fathy Hosam K.
Published: December 2016

This paper examines the shaping of a drug's delivery—in this case, nicotine—to maximize its efficacy. Previous research: (i) furnishes a pharmacokinetic–pharmacodynamic (PKPD) model of this drug's metabolism; (ii) shows that the drug-delivery problem is proper, meaning that its optimal solution is periodic; (iii) shows that the underlying PKPD model is differentially flat; and (iv) exploits differential flatness to solve the problem by optimizing the coefficients of a truncated Fourier expansion of the flat output trajectory. In contrast, the work in this article provides insight into the structure of the theoretical solution to this optimal periodic control (OPC) problem. First, we argue for the existence of a bijection between feasible periodic input and state trajectories of the problem. Second, we exploit Pontryagin's maximum principle to show that the optimal periodic solution has a bang–singular–bang structure. Building on these insights, this article proposes two different numerical methods for solving this OPC problem. One method uses nonlinear programming (NLP) to optimize the states at which the optimal solution transitions between the different solution arcs. The second method approximates the control input trajectory as piecewise constant and optimizes the discrete values of the input sequence. The paper concludes by discussing the computational costs of these two algorithms as well as the importance of the associated insights into the structure of the optimal solution trajectory.
Rail Passenger Vehicle Crashworthiness Simulations Using Multibody Dynamics Approaches
Authors: Quan Sun Yan , Spiryagin Maksym , Cole Colin
Published: December 2016

Multibody dynamics approaches have nowadays been an essential part in examining train crashworthiness. A typical passenger train structure has been investigated on its crashworthiness using three-dimensional (3D) models of a single passenger car and multiple cars formulated using multibody dynamics approaches. The simulation results indicate that the crush length or crush force or both of the crush mechanisms in the high and low energy (HE and LE) crush zones of a passenger train have to be increased for the higher crash speeds. The results on multiple cars (up to ten cars) show that the design of HE and LE crush zones is significantly influenced by the number of cars. The energy absorbed by the HE zone is reasonably consistent for train models with more than four cars at the crash speed of 35 km/h. The comparison of simulations can identify the contribution of the number of cars to the head-on crash forces. The influence of train mass on the design of both HE and LE crush zones, and the influence of design of the crush zones on the wheel-rail contacts are examined.
Benchmarking of a Computational Fluid Dynamics-Based Numerical Wave Tank for Studying Wave Load Effects on Fixed and Floating Offshore Structures
Authors: Nematbakhsh Ali , Gao Zhen , Moan Torgeir
Published: December 2016

A computational fluid dynamics (CFD) based numerical wave tank (NWT) is developed and verified to study wave load effects on fixed and free floating offshore structures. The model is based on solving Navier–Stokes equations on a structured grid, level set method for tracking the free surface, and an immersed boundary method for studying wave–structure interaction. This paper deals with establishing and verifying a CFD-based NWT. Various concerns that arise during this establishment are discussed, namely effects of wave reflection which might affect the structure response, damping of waves in downstream, and three-dimensional (3D) effects of the waves. A method is described and verified to predict the time when incoming waves from wave generator are affected by reflecting waves from the structure which can help in better designing the dimensions of NWT. The model is then used to study sway, heave, and roll responses of a floating barge which is nonuniform in density and limited in sway direction by a spring and damper. Also, it is used to study wave loads on a fixed, large diameter, surface piercing circular cylinder. The numerical results are compared with the experimental and other numerical results, and in general very good agreement is observed in all range of studied wave frequencies. It is shown that for the studied fixed cylinder, the Morison equation leads to promising results for wavelength to diameter ratio larger than 2π (kD < 1), while for shorter wavelengths results in considerable over prediction of wave loads, due to simplification of wave diffraction effects.
Efficient Impedance Eductions for Liner Tests in Grazing Flow Incidence Tube
Authors: Jiang Hanbo , Huang Xun
Published: December 2016

This paper presents an efficient impedance eduction method for grazing flow incidence tube by using a surrogating model along with the Wiener–Hopf method, which enables rapid acoustic predictions and effective impedance eductions over a range of parametric values and working conditions. The proposed method is demonstrated by comparing to the theoretical results, numerical predictions, and experimental measurements, respectively. All the demonstrations clearly suggest the capability and the potential of the proposed solver for parametric studies and optimizations of the lining methods.
Material Modeling of Concrete for the Numerical Simulation of Steel Plate Reinforced Concrete Panels Subjected to Impacting Loading
Authors: Li Huiyun , Shi Guangyu
Published: December 2016

The steel plate reinforced concrete (SC) walls and roofs are effective protective structures in nuclear power plants against aircraft attacks. The mechanical behavior of the concrete in SC panels is very complicated when SC panels are under the action of impacting loading. This paper presents a dynamic material model for concrete subjected to high-velocity impact, in which pressure hardening, strain rate effect, plastic damage, and tensile failure are taken into account. The loading surface of the concrete undergoing plastic deformation is defined based on the extended Drucker–Prager strength criterion and the Johnson–Cook material model. The associated plastic flow rule is utilized to evaluate plastic strains. Two damage parameters are introduced to characterize, respectively, the plastic damage and tensile failure of concrete. The proposed concrete model is implemented into the transient nonlinear dynamic analysis code ls-dyna. The reliability and accuracy of the present concrete material model are verified by the numerical simulations of standard compression and tension tests with different confining pressures and strain rates. The numerical simulation of the impact test of a 1/7.5-scale model of an aircraft penetrating into a half steel plate reinforced concrete (HSC) panel is carried out by using ls-dyna with the present concrete model. The resulting damage pattern of concrete slab and the predicted deformation of steel plate in the HSC panel are in good agreement with the experimental results. The numerical results illustrate that the proposed concrete model is capable of properly charactering the tensile damage and failure of concrete.
Flow Stress and Damage Behavior of C45 Steel Over a Range of Temperatures and Loading Rates
Authors: Abed Farid H. , Saffarini Mohammad H. , Abdul-Latif Akrum , Voyiadjis George Z.
Published: December 2016

This research aims to describe the behavior of C45 steel and provide better understanding of the thermomechanical ductile failure that occurs due to accumulation of microcracks and voids along with plastic deformation to enable proper structural design, and hence provide better serviceability. A series of quasi-static tensile tests are conducted on C45 steel at a range of temperatures between 298 K and 923 K for strain rates up to 0.15 s−1. Drop hammer dynamic tests are also performed considering different masses and heights to study the material response at higher strain rates. Scanning electron microscopy (SEM) images are taken to quantify the density of microcracks and voids of each fractured specimens, which are needed to define the evolution of internal defects using an energy-based damage model. The coupling effect of damage and plasticity is incorporated to accurately define the constitutive relation that can simulate the different structural responses of this material. Good correlation was observed between the proposed model predictions and experiments particularly at regions where dynamic strain aging (DSA) is not present.
Synthesis and Characterization of Dielectric Elastomer Nanocomposites Filled With Multiwalled Carbon Nanotubes
Authors: Wang Yu , Sun L. Z.
Published: December 2016

Dielectric elastomers (DEs) have been attracting great attention in the field of electro-mechanical actuation and sensing. In this paper, we develop a new type of silicone-based DEs by incorporating multiwalled carbon nanotubes (MWNTs) to the DEs as fillers. The dispersion of MWNTs during the material processing plays a significant role in deciding the final properties of the nanocomposites. In this work, acetone and ultrasonication along with characterization tools such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are utilized to examine the MWNT dispersion quality within DE nanocomposites. Furthermore, microstructural MWNT dispersion and filler–matrix interfacial bonding as well as the overall dynamic mechanical responses are investigated to reveal the correlation between them. It is concluded that the processing of DE nanocomposites strongly affects the dynamic mechanical properties, which can inversely provide with microstructural information for the nanocomposites.
Deriving Humanlike Arm Hand System Poses
Authors: Liarokapis Minas , Bechlioulis Charalampos P. , Artemiadis Panagiotis K. , Kyriakopoulos Kostas J.
Published: December 2016

Robots are rapidly becoming part of our lives, coexisting, interacting, and collaborating with humans in dynamic and unstructured environments. Mapping of human to robot motion has become increasingly important, as human demonstrations are employed in order to “teach” robots how to execute tasks both efficiently and anthropomorphically. Previous mapping approaches utilized complex analytical or numerical methods for the computation of the robot inverse kinematics (IK), without considering the humanlikeness of robot motion. The scope of this work is to synthesize humanlike robot trajectories for robot arm-hand systems with arbitrary kinematics, formulating a constrained optimization scheme with minimal design complexity and specifications (only the robot forward kinematics (FK) are used). In so doing, we capture the actual human arm-hand kinematics, and we employ specific metrics of anthropomorphism, deriving humanlike poses and trajectories for various arm-hand systems (e.g., even for redundant or hyper-redundant robot arms and multifingered robot hands). The proposed mapping scheme exhibits the following characteristics: (1) it achieves an efficient execution of specific human-imposed goals in task-space, and (2) it optimizes anthropomorphism of robot poses, minimizing the structural dissimilarity/distance between the human and the robot arm-hand systems.
On Turbulence Measurements and Analyses in a Two-Stage Two-Spool Turbine Rig
Authors: Bauinger Sabine , Behre Stephan , Lengani Davide , Guendogdu Yavuz , Heitmeir Franz , Goettlich Emil
Published: December 2016

Since the experiment in turbulence research is of very high importance for evaluating turbulence hypothesis, turbulence measurements were carried out in a two-stage two-spool transonic turbine test rig at the Institute for Thermal Turbomachinery and Machine Dynamics in Graz in which the two rotors are counter-rotating with two different rotational speeds. For the current measurement campaign, triple hot-wire probes, which represent a very new measurement technique in this test rig, were used and their results validated with a fast response aerodynamic pressure probe (FRAPP). Based on the data measured with this device, turbulence intensities may be determined using a method called Fourier filtering. If the classical ensemble averaging procedure with only one trigger is applied, the periodic fluctuations of the other rotor will artificially increase the stochastic fluctuations. Therefore, the two trigger signals of the two rotors require a special analysis method, which was established at Graz University of Technology. The results from this method will be compared to the classical triple decomposition, which uses only one trigger signal. With this analysis tool, it is not only possible to evaluate unsteady signals triggered by one of the two rotors, but also the unsteady interactions of the rotors can be determined and investigated.
Scaling Criteria for Waterflooding and Immiscible CO2 Flooding in Heavy Oil Reservoirs
Authors: Zhou Deyue , Yang Daoyong
Published: December 2016

Scaling criteria have been developed and validated to evaluate performance of waterflooding and immiscible CO2 flooding in heavy oil reservoirs by using a three-dimensional (3D) sandpacked displacement model. Experimentally, the 3D physical model consisting of a pair of horizontal wells together with five vertical wells is used to conduct waterflooding and immiscible CO2 flooding processes, respectively. Theoretically, mathematical formulae have been developed for waterflooding and immiscible CO2 flooding by performing dimensional and inspectional analyses. The scaling group of the gravitational force to viscous force is found to be negligible when scaling up a model to its prototype. The relaxed scaling criteria are validated by comparing the simulation results of a synthetic reservoir with experimental measurements and then extended for a field application. There also exists a reasonably good agreement between the laboratory measurements and the field application with the determined scaling criteria.
Effects of Double-Leakage Tip Clearance Flow on the Performance of a Compressor Stage With a Large Rotor Tip Gap
Authors: Hah Chunill
Published: December 2016

Effects of a large rotor tip gap on the performance of a one and a half stage axial compressor are investigated in detail with a numerical simulation based on large eddy simulation (LES) and available particle image velocimetry (PIV) data. This paper studies the main flow physics, including why and how the loss generation is increased with the large rotor tip gap. The present study reveals that when the tip gap becomes large, tip clearance fluid goes over the tip clearance core vortex and enters into the next blade's tip gap, which is called double-leakage tip clearance flow. As the tip clearance flow enters into the adjacent blade's tip gap, a vortex rope with a lower pressure core is generated. This vortex rope breaks up the tip clearance core vortex of the adjacent blade, resulting in a large additional mixing. This double-leakage tip clearance flow occurs at all the operating conditions, from design flow to near stall condition, with the large tip gap for the current compressor stage. The double-leakage tip clearance flow, its interaction with the tip clearance core vortex of the adjacent blade, and the resulting large mixing loss are the main flow mechanism of the large rotor tip gap in the compressor. When the tip clearance is smaller, flow near the end wall follows more closely with the main passage flow and this double-leakage tip clearance flow does not happen near the design flow condition for the current compressor stage. When the compressor with a large tip gap operates at near stall operation, a strong vortex rope is generated near the leading edge due to the double-leakage flow. Part of this vortex separates from the path of the tip clearance core vortex and travels from the suction side of the blade toward the pressure side of the blade. This vortex is generated periodically at near stall operation with a large tip gap. As the vortex travels from the suction side to the pressure side of the blade, a large fluctuation of local pressure forces blade vibration. Nonsynchronous blade vibration occurs due to this vortex as the frequency of this vortex generation is not the same as the rotor. The present investigation confirms that this vortex is a part of separated tip clearance vortex, which is caused by the double-leakage tip clearance flow.
Hotspots of mite new species discovery: Parasitiformes (2013–2015)
Authors: Lam Wendy , Zhang Zhi-Qiang
Published: December 2016

A survey of type localities of new species of the Parasitiformes described in two journals (Systematic & Applied Acarology and Zootaxa) during the last three years (2013–2015) revealed interesting patterns of species discovery. Taxonomically, the 142 new species are unevenly distributed among 24 families with the top three families accounting for over 61% of the total. The economically important Phytoseiidae is the top-ranked family. Geographically, the 142 new species of the Parasitiformes are described from 29 countries in the world. The pattern of distribution of these new species among the countries is highly uneven—over half of the new species (52.8%) are from the top 3 countries (Brazil, Iran and Turkey), whereas most countries (65.5%) have only 1–3 new species each.
The Dolphin in the Mirror – A Familiar Face?
Authors: Dibble Dianna Samuelson , Van Alstyne Kaitlin (Katie) , Rohr Jim , Ridgway Sam
Published: December 2016

We suggest how a basic physics problem becomes much richer when researchers of various disciplines converse. Our discussion explores Snell’s window from the perspective of what a dolphin might see. An aperture, Snell’s window, allows light to travel through the air-water interface. Outside this window, there is total reflection from under the water-air interface. Dolphins see through the aperture to follow our movements above the water’s surface. When dolphins look outside the window, can they see their own reflections from under the water-air interface?
An Introduction to the New SI
Authors: Knotts Sandra , Mohr Peter J. , Phillips William D.
Published: December 2016

Plans are under way to redefine the International System of Units (SI) around 2018. The new SI specifies the values of certain physical constants to define units. This article explains the new SI in order to provide a resource for high school teachers as well as for advanced students already familiar with the pre-2018 SI.
Slow Down or Speed up? Lowering Periapsis Versus Escaping from a Circular Orbit
Authors: Blanco Philip
Published: December 2016

Paul Hewitt’s Figuring Physics in the Feb. 2016 issue asked whether it would take a larger velocity change to stop a satellite in a circular orbit or to cause it to escape. An extension of this problem asks: What minimum velocity change is required to crash a satellite into the planet, and how does that compare with the velocity change required for escape? The solution presented here, using conservation principles taught in a mechanics course, serves as an introduction to orbital maneuvers, and can be applied to questions regarding the removal of objects orbiting Earth, other planets, and the Sun.
Grading for Understanding – Standards-Based Grading
Authors: Zimmerman Todd
Published: December 2016

Standards-based grading (SBG), sometimes called learning objectives-based assessment (LOBA), is an assessment model that relies on students demonstrating mastery of learning objectives (sometimes referred to as standards). The goal of this grading system is to focus students on mastering learning objectives rather than on accumulating points. I have used SBG in an introductory physics course for the past five years and worked with several physics faculty members to implement SBG in the first and second semester of algebra-based and calculus-based introductory physics courses at a primarily undergraduate comprehensive public university with class sizes of 48 students. In this article I will discuss methods for implementing SBG in a physics class.
On the dimensionality of elastic wave scattering within heterogeneous media
Authors: Van Pamel Anton , Nagy Peter B. , Lowe Michael J. S.
Published: December 2016

Elastic waves scatter when the wavelength becomes comparable to random spatial fluctuations in the elastic properties of the propagation medium. It is postulated that within the long-wavelength Rayleigh regime, the scattering induced attenuation obeys a D = 1,2,3 dimensional dependence on wavenumber, kD+1, whilst within the shorter-wavelength stochastic regime, it becomes independent of the dimensions and thus varies as k2. These predictions are verified numerically with a recently developed finite element method in three dimensions (3D), two dimensions (2D), and one dimension (1D), for the example of ultrasonic waves propagating within polycrystalline materials. These findings are thought to be practically useful given the increasing uptake of numerical methods to study highly scattering environments which exhibit multiple scattering, but often remain limited to 2D given computational constraints. It is hoped that these results lay the groundwork for eventually producing computationally efficient 2D simulations that are representative of 3D.
Vowel and consonant confusions from spectrally manipulated stimuli designed to simulate poor cochlear implant electrode-neuron interfaces
Authors: DiNino Mishaela , Wright Richard A. , Winn Matthew B. , Bierer Julie Arenberg
Published: December 2016

Suboptimal interfaces between cochlear implant (CI) electrodes and auditory neurons result in a loss or distortion of spectral information in specific frequency regions, which likely decreases CI users' speech identification performance. This study exploited speech acoustics to model regions of distorted CI frequency transmission to determine the perceptual consequences of suboptimal electrode-neuron interfaces. Normal hearing adults identified naturally spoken vowels and consonants after spectral information was manipulated through a noiseband vocoder: either (1) low-, middle-, or high-frequency regions of information were removed by zeroing the corresponding channel outputs, or (2) the same regions were distorted by splitting filter outputs to neighboring filters. These conditions simulated the detrimental effects of suboptimal CI electrode-neuron interfaces on spectral transmission. Vowel and consonant confusion patterns were analyzed with sequential information transmission, perceptual distance, and perceptual vowel space analyses. Results indicated that both types of spectral manipulation were equally destructive. Loss or distortion of frequency information produced similar effects on phoneme identification performance and confusion patterns. Consonant error patterns were consistently based on place of articulation. Vowel confusions showed that perceptions gravitated away from the degraded frequency region in a predictable manner, indicating that vowels can probe frequency-specific regions of spectral degradations.
Perceptive and objective evaluation of calibrated room acoustic simulation auralizations
Authors: Postma Barteld N. J. , Katz Brian F. G.
Published: December 2016

Recently, auralizations have become more prevalent in architectural acoustics and virtual reality. However, there have been few studies examining the perceptual quality achievable by room acoustic simulations and auralizations. Such studies have highlighted potential problems in creating perceptually equivalent simulations when compared to measured auralizations in terms of parameter estimation. In order to accomplish realistic auralizations, calibration of the geometrical acoustics model can be considered a necessary step. In situations where the studied space exists, well-calibrated auralizations can be employed for multiple purposes, such as multi-modal virtual reality explorations, studies of the acoustical influence of renovations, and historic research. Using this case type as a base, a perceptual study evaluating state-of-the-art binaural auralizations has been carried out. Three test sites of different complexity and acoustics were selected: the abbey church Saint-Germain-des-Prés, the cathedral Notre-Dame de Paris, and the Théâtre de l'Athénée. Models were calibrated according to omni-directional source-receiver measurements for reverberation and clarity parameters. In the subjective listening test, measured and simulated binaural auralizations were compared according to eight acoustic perceptual attributes. Results showed that the methodical calibration procedure employed in combination with attention to control factors led to ecologically/perceptually valid auralizations.
Optimized single-number quantity for rating the airborne sound insulation of constructions: Living sounds
Authors: Virjonen Petra , Hongisto Valtteri , Oliva David
Published: December 2016

ISO 717-1 [(1996). International Organization for Standardization, Geneva, Switzerland] and ASTM 413 [(2010). American Society for Testing and Materials International] define various single-number quantities (SNQs) that are commonly used to rate objectively airborne sound insulation of constructions. Recent psychoacoustic evidence suggests that none of them is appropriate for a wide range of living sound stimuli. The purpose of the study was to develop an alternative compromising SNQ for the frequency range 50–5000 Hz that explains well the annoyance caused by various airborne living sounds transmitted from the neighboring dwelling. Optimal reference spectra for different living sounds were found by mathematical optimization. Experimental data from a psychoacoustic laboratory study [Hongisto, Oliva, and Keränen (2014). Acta Acust. Acust. 100, 848–863] were utilized. The subjects (n = 59) had evaluated the disturbance of living sounds that were electrically filtered to mimic transmission through commonly used wall structures. To find a high-performing reference spectrum for living sounds in general, the optimized reference spectra were averaged over all sound types. The resulting SNQ was called Rw + Copt. The related reference spectrum deviates significantly from the reference spectrum for living activities, C50–5000, below 315 Hz. The suggested SNQ correlates better with the subjective disturbance caused by living sounds than any of the present standardized SNQs of ISO 717-1 or ASTM 413.
Categorical perception of lexical tones by English learners of Mandarin Chinese
Authors: Shen Guannan , Froud Karen
Published: December 2016

Whether native speakers of non-tonal languages can acquire categorical representations of lexical tones remains controversial. This study investigates the acquisition of lexical tone categories by native English speakers learning Mandarin Chinese as a foreign language by comparing the categorical perception (CP) of lexical tones between three groups of listeners: (1) native English speakers who had taken advanced Mandarin courses in colleges; (2) native English speakers with no knowledge of Mandarin Chinese; and (3) native Mandarin speakers. Two tonal continua derived from natural speech within carrier phrases were created through interpolation within two tonal contrasts (tone 1/tone 4, T1/T4; tone 2/tone 3, T2/T3). Results showed categorical-like perception of tones by native Mandarin speakers. The inexperienced English speakers performed near chance on discrimination tasks and showed significantly broader identification boundaries than the other two groups. The learners of Mandarin showed similar pattern of CP to native Mandarin speakers, but with higher overall discrimination scores. Findings suggest that CP of lexical tone may be available to advanced second language learners.
Effect of Exercise Intensity on Neurotrophic Factors and Blood–Brain Barrier Permeability Induced by Oxidative–Nitrosative Stress in Male College Students
Authors: Roh Hee-Tae , Cho Su-Youn , Yoon Hyung-Gi , So Wi-Young
Published: December 2016

We investigated the effects of aerobic exercise intensity on oxidative–nitrosative stress, neurotrophic factor expression, and blood–brain barrier (BBB) permeability. Fifteen healthy men performed treadmill running under low-intensity (LI), moderate-intensity (MI), and high-intensity (HI) conditions. Blood samples were collected immediately before exercise (IBE), immediately after exercise (IAE), and 60 min after exercise (60MAE) to examine oxidative–nitrosative stress (reactive oxygen species [ROS]; nitric oxide [NO]), neurotrophic factors (brain-derived neurotrophic factor [BDNF]; nerve growth factor [NGF]), and blood-brain barrier (BBB) permeability (S-100β; neuron-specific enolase). ROS concentration significantly increased IAE and following HI (4.9 ± 1.7 mM) compared with that after LI (2.8 ± 1.4 mM) exercise (p < .05). At 60MAE, ROS concentration was higher following HI (2.5 ± 1.2 mM) than after LI (1.5 ± 0.5 mM) and MI (1.4 ± 0.3 mM) conditions (p < .05). Plasma NO IAE increased significantly after MI and HI exercise (p < .05). Serum BDNF, NGF, and S-100b levels were significantly higher IAE following MI and HI exercise (p < .05). BDNF and S-100b were higher IAE following MI (29.6 ± 3.4 ng/mL and 87.1 ± 22.8 ng/L, respectively) and HI (31.4 ± 3.8 ng/mL and 100.6 ± 21.2 ng/L, respectively) than following LI (26.5 ± 3.0 ng/mL and 64.8 ± 19.2 ng/L, respectively) exercise (p < .05). 60MAE, S-100b was higher following HI (71.1 ± 14.5 ng/L) than LI (56.2 ± 14.7 ng/L) exercise (p < .05). NSE levels were not significantly different among all intensity conditions and time points (p > .05). Moderate- and/or high-intensity exercise may induce higher oxidative-nitrosative stress than may low-intensity exercise, which can increase peripheral neurotrophic factor levels by increasing BBB permeability.
Dietary Nitrate Fails to Improve 1 and 4 km Cycling Performance in Highly Trained Cyclists
Authors: McQuillan Joseph A. , Dulson Deborah K. , Laursen Paul B. , Kilding Andrew E.
Published: December 2016

We aimed to compare the effects of two different dosing durations of dietary nitrate (NO3-) supplementation on 1 and 4 km cycling time-trial performance in highly trained cyclists. In a double-blind crossover-design, nine highly trained cyclists ingested 140ml of NO3--rich beetroot juice containing ~8.0mmol [NO3-], or placebo, for seven days. Participants completed a range of laboratory-based trials to quantify physiological and perceptual responses and cycling performance: time-trials on day 3 and 6 (4km) and on day 4 and 7 (1km) of the supplementation period. Relative to placebo, effects following 3- and 4-days of NO3- supplementation were unclear for 4 (-0.8; 95% CL, ± 2.8%, p = .54) and likely harmful for 1km (-1.9; ± 2.5% CL, p = .17) time-trial mean power. Effects following 6- and 7-days of NO3- supplementation resulted in unclear effects for 4 (0.1; ± 2.2% CL, p = .93) and 1km (-0.9; ± 2.6%CL, p = .51) time-trial mean power. Relative to placebo, effects for 40, 50, and 60% peak power output were unclear for economy at days 3 and 6 of NO3- supplementation (p > .05). Dietary NO3- supplementation appears to be detrimental to 1km time-trial performance in highly trained cyclists after 4-days. While, extending NO3- dosing to ≥ 6-days reduced the magnitude of harm in both distances, overall performance in short duration cycling time-trials did not improve relative to placebo.
Decrease in Ionized and Total Magnesium Blood Concentrations in Endurance Athletes Following an Exercise Bout Restores within Hours—Potential Consequences for Monitoring and Supplementation
Authors: Terink Rieneke , Balvers Michiel G.J. , Hopman Maria T. , Witkamp Renger F. , Mensink Marco , Gunnewiek Jacqueline M.T. Klein
Published: December 2016

Magnesium is essential for optimal sport performance, generating an interest to monitor its status in athletes. However, before measuring magnesium status in blood could become routine, more insight into its diurnal fluctuations and effects of exercise itself is necessary. Therefore, we measured the effect of an acute bout of exercise on ionized (iMg) and total plasma magnesium (tMg) in blood obtained from 18 healthy well-trained endurance athletes (age, 31.1 ± 8.1 yr.; VO2max, 50.9 ± 7.5 ml/kg/min) at multiple time points, and compared this with a resting situation. At both days, 7 blood samples were taken at set time points (8:30 fasted, 11:00, 12:30, 13:30, 15:00, 16:00, 18:30). The control day was included to correct for a putative diurnal fluctuation of magnesium. During the exercise day, athletes performed a 90 min bicycle ergometer test (70% VO2max) between 11:00 and 12:30. Whole blood samples were analyzed for iMg and plasma for tMg concentrations. Both concentrations decreased significantly after exercise (0.52 ± 0.04–0.45 ± 0.03 mmol/L and 0.81 ± 0.07–0.73 ± 0.06 mmol/L, respectively, p < .001) while no significant decline was observed during that time-interval on control days. Both, iMg and tMg, returned to baseline, on average, 2.5 hr after exercise. These findings suggest that timing of blood sampling to analyze Mg status is important. Additional research is needed to establish the recovery time after different types of exercise to come to a general advice regarding the timing of magnesium status assessment in practice.
One-year Stability of Objectively Measured Physical Activity in Young Brazilian Adults
Authors: Martins Rafaela Costa , Reichert Felipe Fossati , Bielemann Renata Moraes , Hallal Pedro C.
Published: December 2016

Background:

To evaluate the 1-year stability of objectively measured physical activity among young adults living in South Brazil, as well as assessing the influences of temperature, humidity and precipitation on physical activity.

Methods:

A longitudinal study was conducted over 12 consecutive months (October 2012 to September 2013). Sixteen participants (8 men) used GT3X+ accelerometers 1 week per month for the entire year. Climate variables were obtained from an official climate information provider.

Results:

Physical activity was remarkably stable over the year—the proportion of the day spent in moderate-to-vigorous intensity physical activity (MVPA) was around 5% in every month. Average temperature (ρ = –0.64; P = .007), humidity (ρ = –0.68; P = .004) and rain (ρ = –0.67; P = .004) were inversely correlated to MVPA in the Summer. Rain was also inversely correlated to MVPA in the Spring (ρ = –0.54; P = .03).

Conclusions:

Objectively measured physical activity was stable over a 1-year period. Climate variables consistently influenced physical activity practice in the Summer, but not in the other seasons.
Improvement in Physical Activity in Persons With Obstructive Sleep Apnea Treated With Continuous Positive Airway Pressure
Authors: Jean Raymonde E. , Duttuluri Manideep , Gibson Charlisa D. , Mir Sadaf , Fuhrmann Katherine , Eden Edward , Supariwala Azhar
Published: December 2016

Background:

Exercise improves sleep quality, yet people with untreated obstructive sleep apnea (OSA) may engage in less physical activity (PA) due to fatigue and daytime sleepiness. We examined changes in PA and sleep quality before and after treatment with continuous positive airway pressure (CPAP) in OSA patients.

Methods:

In this prospective longitudinal study, persons with a primary diagnosis of OSA were enrolled at a community-based hospital in New York City. At 3 time intervals pre- and post-CPAP (3–8 months), we measured sleep quality using validated questionnaires, perceived PA using the International Physical Activity Questionnaire (IPAQ), and actual PA using pedometer steps per day. We sought to investigate how CPAP use and changes in sleep quality impacted the number of steps taken, as recorded in pedometer steps.

Results:

In total, 62 patients were enrolled in the study from March 2012 to July 2014. In all, patients averaged 53 years of age, and 26 patients (42%) were female. Among all participants, 86% of persons had moderate to severe sleep apnea (AHI ≥15). Approximately 73% of participants were compliant with CPAP use. Poor sleep quality correlated with lower actual PA (P = .004) at baseline. At 3 and 7 months, there was significant improvement in sleep quality (Δ –2.63 ± 3.4 and Δ –3.5 ± 3.8; P < .001) and actual PA (Δ 840 ± 1313 and Δ 1431 ± 1419 steps/day, P < .001) compared with baseline. On multivariate analyses, participants with a higher waist circumference had a significantly greater increase in actual PA (P = .018).

Conclusion:

Treatment of OSA with CPAP had a progressive incremental improvement in sleep quality and actual PA.