bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Unsteady Pressure Measurement Uncertainty—Part I: Single Sensor Probe
Authors: Dell'Era Giulia , Mersinligil Mehmet , Brouckaert Jean-François
Published: August 2015

With the advancements in miniaturization and temperature capabilities of piezoresistive pressure sensors, pneumatic probes—which are the long established standard for flow-path pressure measurements in gas turbine environments—are being replaced with unsteady pressure probes. Any measured quantity is by definition inherently different from the “true” value, requiring the estimation of the associated errors for determining the validity of the results and establishing respective confidence intervals. In the context of pressure measurements, the calibration uncertainty values, which differ from measurement uncertainties, are typically provided. Even then, the lack of a standard methodology is evident as uncertainties are often reported without appropriate confidence intervals. Moreover, no time-resolved measurement uncertainty analysis has come to the attention of the authors. The objective of this paper is to present a standard method for the estimation of the uncertainties related to measurements performed using single sensor unsteady pressure probes, with the help of measurements obtained in a one and a half stage low pressure (LP) high speed axial compressor test rig as an example. The methodology presented is also valid for similar applications involving the use of steady or unsteady sensors and instruments. The static calibration uncertainty, steady measurement uncertainties, and unsteady measurement uncertainties based on phase-locked average (PLA) and ensemble average are presented in this contribution. Depending on the number of points used for the averaging, different values for uncertainty have been observed, underlining the importance of having greater number of samples. For unsteady flows, higher uncertainties have been observed at regions of higher unsteadiness such as tip leakage vortices, hub corner vortices, and blade wakes. Unfortunately, the state of the art in single sensor miniature unsteady pressure probes is comparable to multihole pneumatic probes in size, preventing the use of multihole unsteady probes in turbomachinery environments. However, the angular calibration properties of a single sensor probe obtained via an aerodynamic calibration may further be exploited as if a three-hole directional probe is employed, yielding corrected total pressure, unsteady yaw angle, static pressure, and Mach number distributions based on the PLAs with the expense of losing the time-correlation between the virtual ports. The aerodynamic calibration and derivation process are presented together with the assessment of the uncertainties associated to these derived quantities by the authors in Dell'Era et al. (2016, “Assessment of Unsteady Pressure Measurement Uncertainty—Part II: Virtual Three Hole Probe,” ASME J. Eng. Gas Turbines Power, 138(4), p. 041602). In the virtual three-hole mode, similar to that of a single sensor probe, higher uncertainty values are observed at regions of higher unsteadiness.
Experimental and Numerical Investigation of Shock Wave Attenuation by Dynamic Barriers
Authors: Berger Shahar , Ben-Dor Gabi , Sadot Oren
Published: August 2015

An explosion at the entrance of an underground bunker and a suicide bomber inside an airplane are examples of scenarios in which blast waves propagate in tunnels and corridor-type structures. The need to attenuate the shock/blast wave propagating downstream a corridor and mitigate the developed loads inside the structure is essential. The interaction of a shock/blast wave with an obstacle inside a tunnel can dramatically reduce its strength. Earlier researches revealed that the dominant parameter in attenuating a shock wave by rigid barriers is the barrier opening ratio (i.e., the cross section that is open to the flow divided by the total cross section of the tunnel). Decreasing the opening ratio from 0.6 to 0.2 increased the attenuation by about 40%. Based on strong dependence of the attenuation on the opening ratio, a barrier designed to adjust its opening ratio to the loads exerted upon it is essential. In our previous study, we found that the effect of the rigid barrier geometry becomes more significant when the barrier inclination angle is larger, i.e., the barriers inclined toward the oncoming shock wave were found to be more effective in reducing the transmitted shock wave intensity than those inclined in the opposite direction. The pressure difference between both sides of the barrier exerts massive loads on the barrier. In the present ongoing research, based on a numerical approach using a commercial solver (msc.dytran), we focus on the geometry of a dynamic barrier, which changes its orientation as a response to the loads exerted on it. As a result, the barrier opening ratio, which as mentioned earlier strongly affects the shock wave attenuation, changes too. In this study, the feasibility of a dynamic barrier and the complex flow regime around it are investigated. The rapid pressure drop downstream of the barrier depends both on the shock wave strength and the barrier material and geometrical properties. Barriers with various geometries and properties are used to investigate the concept of a deflecting/rotating barrier as a response to the shock wave loads exerted upon it. For the first time, a new and exciting proven concept of a dynamic barrier, which reacts to the loads exerted upon it from a passing shock wave, and dramatically reduces the shock-induced pressure jump downstream of the barrier, is demonstrated.
Segmentation Effects on Brush Seal Leakage and Rotordynamic Coefficients
Authors: Pugachev Alexander O. , Gaszner Manuel , Georgakis Christos , Cooper Paul
Published: August 2015

This paper studies the effect of brush seal segmentation on the seal performance characteristics. A brush–labyrinth sealing configuration arranged of one brush seal downstream and two labyrinth fins upstream is studied experimentally and theoretically. The studied brush seal is of welded design installed with zero cold radial clearance. The brush seal front and back rings as well as the bristle pack are segmented radially in a single plane using the electrical discharge machining (EDM) technique. The segmentation procedure results in loss of bristles at the site of the cuts altering the leakage flow structure in the seal and its performance characteristics. Two test rigs are used to obtain leakage, as well as rotordynamic stiffness and damping coefficients of the seal at different pressure ratios. The computational fluid dynamics (CFD)-based model is used to predict the seal performance and to study in detail local changes in the flow field due to the segmentation. A back-to-back comparison of the performance of nonsegmented and segmented brush seals as well as baseline labyrinth seal is provided. The obtained results demonstrate that the segmentation in general negatively affects the performance of the studied brush–labyrinth sealing configuration. However, the segmented brush seal shows increased direct damping coefficients.
Coupled Aerothermal Modeling of a Rotating Cavity With Radial Inflow
Authors: Sun Zixiang , Amirante Dario , Chew John W. , Hills Nicholas J.
Published: August 2015

Flow and heat transfer in an aero-engine compressor disk cavity with radial inflow has been studied using computational fluid dynamics (CFD), large eddy simulation (LES), and coupled fluid/solid modeling. Standalone CFD investigations were conducted using a set of popular turbulence models along with 0.2 deg axisymmetric and a 22.5 deg discrete sector CFD models. The overall agreement between the CFD predictions is good, and solutions are comparable to an established integral method solution in the major part of the cavity. The LES simulation demonstrates that flow unsteadiness in the cavity due to the unstable thermal stratification is largely suppressed by the radial inflow. Steady flow CFD modeling using the axisymmetric sector model and the Spalart–Allmaras turbulence model was coupled with a finite element (FE) thermal model of the rotating cavity. Good agreement was obtained between the coupled solution and rig test data in terms of metal temperature. Analysis confirms that using a small radial bleed flow in compressor cavities is effective in reducing thermal response times for the compressor disks and that this could be applied in management of compressor blade clearance.
A Comparison of Modeling Techniques for Polydispersed Droplet Spectra in Steam Turbines
Authors: Hughes Fiona R. , Starzmann Jörg , White Alexander J. , Young John B.
Published: August 2015

Within steam turbine flows, condensation phenomena give rise to complex droplet spectra that can span more than two orders of magnitude in size. To predict the behavior of the two-phase flow and the resulting losses, the interactions between the vapor phase and droplets of all sizes must be accurately calculated. The estimation of thermodynamic losses and droplet deposition rates, in particular, depends on the size range and shape of the droplet spectrum. These calculations become computationally burdensome when a large number of droplet groups are present, and it is therefore advantageous to capture the complete droplet spectrum in a compressed form. This paper compares several methods for reducing the complexity of the droplet spectrum: a single representative droplet size (equivalent monodispersion), the moment method (including various growth rate approximations), the quadrature method of moments (QMOM), and spectrum pruning. In spectrum pruning, droplet groups are individually nucleated, but their number is subsequently reduced by combining groups together in a manner that preserves droplet number, wetness fraction, and the shape of the initial spectrum. The various techniques are compared within a Lagrangian framework by tracking the two-phase behavior along predefined pressure–time trajectories. Primary and secondary nucleation, droplet evaporation, and a representative turbomachinery case are modeled. The calculations are compared in terms of speed, accuracy, and robustness. It is shown that both the moment methods and spectrum pruning provide an appreciable improvement in accuracy over the use of an “equivalent” monodispersion without compromising calculation speed. Although all the examined methods are adequate for primary nucleation and droplet growth calculations, spectrum pruning and the QMOM are most accurate over the range of conditions considered.
Multiresponse Optimization of a Hydraulic Oil Formulation by Mixture Design and Response Surface Methods
Authors: Khalilian H. , Semnani A. , Haddadi H. , Nekoeinia M.
Published: August 2015

The field performance of hydraulic oils depends on factors such as the viscosity index (VI), flash point (FP), pour point (PP), and demulsibility. A hydraulic oil formulation was performed by applying a multiresponse optimization, for which the PP was minimized, the FP, demulsibility, and VI were maximized. The range of viscosities at 40 and 100 °C was selected according to the International Organization for Standardization (ISO) viscosity grade for hydraulic oil. The experiments were accomplished according to an extreme vertices mixture design using solvent neutral-100 (SN-100) and SN-500 as major components and polyisobutene (PIB) as minor component. The results shows that the optimum formulation consisted of 37.5% SN-100, 60% SN-500, and 2.5% PIB, and the values of FP, PP, VI, demulsibility at 30 mins and viscosities at 40 and 100 °C were equal to 227 °C, −6 °C, 107.5, 28/2012/40, 67.3 cS, and 9 cS, respectively.
Wear and Friction of AA5052-Al3Zr In Situ Composites Synthesized by Direct Melt Reaction
Authors: Gautam Gaurav , Mohan Anita
Published: August 2015

Particulate aluminum matrix composites (PAMCs) with different volume percent of Al3Zr particles have been developed by direct melt reaction (DMR). Wear and friction have been studied in detail for all compositions under dry sliding conditions. Results indicate that the wear rate, normalized wear rate, and wear coefficient of PAMCs decrease continuously with increase in volume percent of Al3Zr particles, however, with applied load and sliding distance, wear continuously increases. Wear rate and wear coefficient with sliding velocity initially decrease for all compositions, attains minima, and then increase sharply. However, coefficient of friction shows increasing trend with composition and sliding velocity but with load it shows a decreasing trend and with distance slid it fluctuates within a value of ±0.025. At low load and sliding velocity three-dimensional (3D)-profilometer, scanning electron microscope (SEM), and debris studies show low Ra values and mild wear dominated by oxidative nature, whereas at high loads and sliding velocities high Ra values and wear nature change to severe wear with mixed mode (oxidative–metallic) and surface with deep grooves is observed. Further, it is also important to note from morphological studies that refinement of matrix phase takes place with in situ formation of Al3Zr particles, which helps to improve hardness and tensile properties finally contributing to low wear rate.
Intermittency Route to Combustion Instability in a Laboratory Spray Combustor
Authors: Pawar Samadhan A. , Vishnu R. , Vadivukkarasan M. , Panchagnula M. V. , Sujith R. I.
Published: August 2015

In the present study, we investigate the phenomenon of transition of a thermoacoustic system involving two-phase flow, from aperiodic oscillations to limit cycle oscillations. Experiments were performed in a laboratory scale model of a spray combustor. A needle spray injector is used to generate a droplet spray having one-dimensional velocity field. This simplified design of the injector helps in keeping away the geometric complexities involved in the real spray atomizers. We investigate the stability of the spray combustor in response to the variation of the flame location inside the combustor. Equivalence ratio is maintained constant throughout the experiment. The dynamics of the system is captured by measuring the unsteady pressure fluctuations present in the system. As the flame location is gradually varied, self-excited high-amplitude acoustic oscillations are observed in the combustor. We observe the transition of the system behavior from low-amplitude aperiodic oscillations to large amplitude limit cycle oscillations occurring through intermittency. This intermittent state mainly consists of a sequence of high-amplitude bursts of periodic oscillations separated by low-amplitude aperiodic regions. Moreover, the experimental results highlight that during intermittency, the maximum amplitude of bursts, near to the onset of intermittency, is as much as three times higher than the maximum amplitude of the limit cycle oscillations. These high-amplitude intermittent loads can have stronger adverse effects on the structural properties of the engine than the low-amplitude cyclic loading caused by the sustained limit cycle oscillations. Evolution of the three different dynamical states of the spray combustion system (viz., stable, intermittency, and limit cycle) is studied in three-dimensional phase space by using a phase space reconstruction tool from the dynamical system theory. We report the first experimental observation of type-II intermittency in a spray combustion system. The statistical distributions of the length of aperiodic (turbulent) phase with respect to the control parameter, first return map and recurrence plot (RP) techniques are employed to confirm the type of intermittency.
Realistic respiratory motion margins for external beam partial breast irradiation
Authors: Conroy Leigh , Quirk Sarah , Smith Wendy L.
Published: August 2015

Purpose:

Respiratory margins for partial breast irradiation (PBI) have been largely based on geometric observations, which may overestimate the margin required for dosimetric coverage. In this study, dosimetric population‐based respiratory margins and margin formulas for external beam partial breast irradiation are determined.

Methods:

Volunteer respiratory data and anterior–posterior (AP) dose profiles from clinical treatment plans of 28 3D conformal radiotherapy (3DCRT) PBI patient plans were used to determine population‐based respiratory margins. The peak‐to‐peak amplitudes (A) of realistic respiratory motion data from healthy volunteers were scaled from A = 1 to 10 mm to create respiratory motion probability density functions. Dose profiles were convolved with the respiratory probability density functions to produce blurred dose profiles accounting for respiratory motion. The required margins were found by measuring the distance between the simulated treatment and original dose profiles at the 95% isodose level.

Results:

The symmetric dosimetric respiratory margins to cover 90%, 95%, and 100% of the simulated treatment population were 1.5, 2, and 4 mm, respectively. With patient set up at end exhale, the required margins were larger in the anterior direction than the posterior. For respiratory amplitudes less than 5 mm, the population‐based margins can be expressed as a fraction of the extent of respiratory motion. The derived formulas in the anterior/posterior directions for 90%, 95%, and 100% simulated population coverage were 0.45A/0.25A, 0.50A/0.30A, and 0.70A/0.40A. The differences in formulas for different population coverage criteria demonstrate that respiratory trace shape and baseline drift characteristics affect individual respiratory margins even for the same average peak‐to‐peak amplitude.

Conclusions:

A methodology for determining population‐based respiratory margins using real respiratory motion patterns and dose profiles in the AP direction was described. It was found that the currently used respiratory margin of 5 mm in partial breast irradiation may be overly conservative for many 3DCRT PBI patients. Amplitude alone was found to be insufficient to determine patient‐specific margins: individual respiratory trace shape and baseline drift both contributed to the dosimetric target coverage. With respiratory coaching, individualized respiratory margins smaller than the full extent of motion could reduce planning target volumes while ensuring adequate coverage under respiratory motion.
Coverage‐based treatment planning to accommodate delineation uncertainties in prostate cancer treatment
Authors: Xu Huijun , Gordon J. James , Siebers Jeffrey V.
Published: August 2015

Purpose:

To compare two coverage‐based planning (CP) techniques with fixed margin‐based (FM) planning for high‐risk prostate cancer treatments, with the exclusive consideration of the dosimetric impact of delineation uncertainties of target structures and normal tissues.

Methods:

In this work, 19‐patient data sets were involved. To estimate structure dose for each delineated contour under the influence of interobserver contour variability and CT image quality limitations, 1000 alternative structures were simulated by an average‐surface‐of‐standard‐deviation model, which utilized the patient‐specific information of delineated structure and CT image contrast. An IMRT plan with zero planning‐target‐volume (PTV) margin on the delineated prostate and seminal vesicles [clinical‐target‐volume (CTVprostate) and CTVSV] was created and dose degradation due to contour variability was quantified by the dosimetric consequences of 1000 alternative structures. When D98 failed to achieve a 95% coverage probability objective D98,95 ≥ 78 Gy (CTVprostate) or D98,95 ≥ 66 Gy (CTVSV), replanning was performed using three planning techniques: (1) FM (PTVprostate margin = 4,5,6 mm and PTVSV margin = 4,5,7 mm for RL, PA, and SI directions, respectively), (2) CPOM which optimized uniform PTV margins for CTVprostate and CTVSV to meet the D98,95 objectives, and (3) CPCOP which directly optimized coverage‐based objectives for all the structures. These plans were intercompared by computing percentile dose‐volume histograms and tumor‐control probability/normal tissue complication probability (TCP/NTCP) distributions.

Results:

Inherent contour variability resulted in unacceptable CTV coverage for the zero‐PTV‐margin plans for all patients. For plans designed to accommodate contour variability, 18/19 CP plans were most favored by achieving desirable D98,95 and TCP/NTCP values. The average improvement of probability of complication free control was 9.3% for CPCOP plans and 3.4% for CPOM plans.

Conclusions:

When the delineation uncertainties need to be considered for prostate patients, CP techniques can produce more desirable plans than FM plans for most patients. The relative advantages between CPCOP and CPOM techniques are patient specific.
The Enigmatic Neutrino
Authors: Lincoln Don , Miceli Tia
Published: August 2015

Through a century of work, physicists have refined a model to describe all fundamental particles, the forces they share, and their interactions on a microscopic scale. This masterpiece of science is called the Standard Model. While this theory is incredibly powerful, we know of at least one particle that exhibits behaviors that are outside of its scope and remain unexplained. These particles are called neutrinos and they are the enigmatic ghosts of the quantum world. Interacting only via the weak nuclear force, literally billions of them pass through you undetected every second. While we understand that particular spooky behavior, we do not understand in any fundamental way how it is that neutrinos can literally change their identity, much as if a house cat could turn into a lion and then a tiger before transitioning back into a house cat again.
Rosetta Mission's “7 Hours of Terror” and Philae's Descent
Authors: Blanco Philip
Published: August 2015

In November 2014 the Rosetta mission to Comet 67P/Churyumov-Gerasimenko made the headlines when its Philae lander completed a successful unpowered descent onto the surface of the comet nucleus after “7 hours of terror” for the mission scientists. 67P's irregular shape and rotation made this task even more challenging. Philae fell almost radially towards 67P, as shown in an animation produced by the European Space Agency (ESA) prior to the event. Below, we investigate whether it is possible to model the spacecraft's descent time and impact speed using concepts taught in an introductory physics course.
Treb-Bot: Development and Use of a Trebuchet Simulator
Authors: Constans Eric , Constans Aileen
Published: August 2015

The trebuchet has quickly become a favorite project for physics and engineering teachers seeking to provide students with a simple, but spectacular, hands-on design project that can be applied to the study of projectile motion, rotational motion, and the law of conservation of energy. While there have been free trebuchet simulators and range calculators available online for several years, these have been limited to simple designs. Other simulators are available for a fee, precluding practical use in introductory courses. With this in mind, one of the authors developed a free web-based trebuchet simulation that can be found at http://www.benchtophybrid.com/TB_index.html. This simulation, named Treb-Bot, is designed to be visually appealing to high school students and includes simulations of trebuchet designs that are unavailable elsewhere on the web. The website was successfully field-tested by a group of Advanced Placement Physics 1 students.
Quantitative Comparisons to Promote Inquiry in the Introductory Physics Lab
Authors: Holmes N. G. , Bonn D. A.
Published: August 2015

In a recent report, the American Association of Physics Teachers has developed an updated set of recommendations for curriculum of undergraduate physics labs. This document focuses on six major themes: constructing knowledge, modeling, designing experiments, developing technical and practical laboratory skills, analyzing and visualizing data, and communicating physics. These themes all tie together as a set of practical skills in scientific measurement, analysis, and experimentation. In addition to teaching students how to use these skills, it is important for students to know when to use them so that they can use them autonomously. This requires, especially in the case of analytical skills, high levels of inquiry behaviors to reflect on data and iterate measurements, which students rarely do in lab experiments. Often, they perform lab experiments in a plug-and-chug frame, procedurally completing each activity with little to no sensemaking. An emphasis on obtaining true theoretical values or agreement on individual measurements also reinforces inauthentic behaviors such as retroactively inflating measurement uncertainties. This paper aims to offer a relatively simple pedagogical framework for engaging students authentically in experimentation and inquiry in physics labs.
Use of Bratwurst Sausage as a Model Cadaver in Introductory Physics for the Life Sciences Lab Experiments
Authors: Sidebottom David
Published: August 2015

The general physics course that is taught in most departments as a service course for pre-med or pre-health students is undergoing a large shift in course content to better appeal to this group of learners. This revision also extends to the laboratory component, where more emphasis is being placed on teaching physics through biological examples. Here, two undergraduate-level lab experiments, one dealing with buoyancy and the other with heat transfer, are described. The two labs were designed specifically to appeal to pre-med students taking introductory physics, and their novelty arises from the use of a bratwurst sausage as a miniature model cadaver. Results suggest that the sausage provides a suitable approximation to the mass density and thermal properties of the human body.
The Atwood machine revisited using smartphones
Authors: Monteiro Martín , Stari Cecilia , Cabeza Cecilia , Marti Arturo C.
Published: August 2015

The Atwood machine is a simple device used for centuries to demonstrate Newton's second law. It consists of two supports containing different masses joined by a string. Here we propose an experiment in which a smartphone is fixed to one support. With the aid of the built-in accelerometer of the smartphone, the vertical acceleration is registered. By redistributing the masses of the supports, a linear relationship between the mass difference and the vertical acceleration is obtained. In this experiment, the use of a smartphone contributes to enhance a classical demonstration.
Design of robust differential microphone arrays with orthogonal polynomials
Authors: Pan Chao , Benesty Jacob , Chen Jingdong
Published: August 2015

Differential microphone arrays have the potential to be widely deployed in hands-free communication systems thanks to their frequency-invariant beampatterns, high directivity factors, and small apertures. Traditionally, they are designed and implemented in a multistage way with uniform linear geometries. This paper presents an approach to the design of differential microphone arrays with orthogonal polynomials, more specifically with Jacobi polynomials. It first shows how to express the beampatterns as a function of orthogonal polynomials. Then several differential beamformers are derived and their performance depends on the parameters of the Jacobi polynomials. Simulations show the great flexibility of the proposed method in terms of designing any order differential microphone arrays with different beampatterns and controlling white noise gain.
Should Western Arkansas University Move to a Football Bowl Subdivision Conference?
Authors: Barnhill Chris , Palmero Mauro
Published: August 2015

Mary Graham is the athletic director at Western Arkansas University (WAU), a successful Football Championship Subdivision (FCS) school that is about to receive an invitation to join a Football Bowl Subdivision (FBS) conference. WAU’s Board of Regents has put the decision to join in her hands, but WAU’s president is pushing her to recommend accepting the invitation. Using details from a recently completed feasibility study and information from a professor in the sport management program, Graham must decide the future of her athletic program and university.
Gender Differences on Attitudes and Participation in an Extracurricular Gymnastics Course Among Greek University Students
Authors: Milosis Dimitrios C. , Papaioannou Athanasios G. , Siatras Theophanis A. , Proios Miltiadis , Proios Michael
Published: August 2015

The aims of the study were (a) to test the effectiveness of the theory of planned behavior (TPB) to predict Greek university students’ voluntary participation in an extracurricular gymnastics course, and (b) to evaluate gender differences. Two hundred sixty-three (127 female, 136 male) students participated in the study. Students’ attitudes, intention, and PBC were measured with a questionnaire and their attendance in the course was recorded by the teacher. Results from the MANOVA conducted showed that females had higher scores compared with males in all observed variables. Results from the structural equation modeling (SEM) employed supported the usefulness of TPB to explain students’ attitudes and behavior toward extracurricular physical activities (PA). Differences also emerged on path structure of the relationships among the variables.
Effects of Vigorous Intensity Physical Activity on Mathematics Test Performance
Authors: Phillips David , Hannon James C. , Castelli Darla M.
Published: August 2015

The effect of an acute bout of physical activity on academic performance in school-based settings is under researched. The purpose of this study was to examine associations between a single, vigorous (70–85%) bout of physical activity completed during physical education on standardized mathematics test performance among 72, eighth grade students at a school in the Southwestern United States. Students received both a physical activity and nonactive condition, in a repeated measures design. Academic performance measures were collected at 30 and 45-minutes post condition. It was hypothesized that students would have greater gains in mathematics test scores post physical activity condition compared with post nonactive condition. Results reported students achieved 11–22% higher math scores at 30 minutes post physical activity condition compared with other time points (45 minutes post PA, 30 and 45 minutes post sedentary) (F(1, 68) = 14.42, p < .001, d = .90). Findings suggest that physical activity may facilitate academic performance in math.
Effects of Physical Education on Objectively Determined Physical Activity in Primary School Children—Which Proportioning Is Best?
Authors: Kobel Susanne , Kettner Sarah , Erkelenz Nanette , Kesztyüs Dorothea , Steinacker Jürgen M.
Published: August 2015

Physical Education (PE) can foster regular physical activity (PA) in children. However, children engage in insufficient moderate to vigorous PA (MVPA) during PE. This study objectively investigated MVPA of children during a single, compared with double PE-period. In 294 children (7.1 ± 0.7 years) PA was objectively assessed. PE periods were determined and PA was individually calculated. Children spent 8.5 ± 7.3 minutes of each 45 minutes PE lesson in MVPA. Boys were significantly more active than girls (p ≤ .01). All children participated in 135 minutes PE/week, 32.7% were scheduled one double and one single PE-period. Children, with a double PE-period and one single lesson engaged in significantly less MVPA than children, who had three single periods of PE (6.7 ± 6.9 minutes/45 minutes vs. 9.4 ± 7.4 minutes/45 minutes, respectively; p ≤ .01) In conclusion, single periods of PE seem to be more effective in getting primary school children to engage in more MVPA than one double period per week.
Crystal structure of the metazoan Nup62•Nup58•Nup54 nucleoporin complex
Authors: Chug Hema , Trakhanov Sergei , Hülsmann Bastian B. , Pleiner Tino , Görlich Dirk
Published: August 2015

Building a gate to the nucleus

Nuclear pore complexes form a gateway between the cytoplasm and the nucleus (see the Perspective by Ullman and Powers). Stuwe
et al.
combined structural, biochemical, and functional analyses to elucidate the architecture of a six-protein complex that makes up the inner ring of the fungal nuclear pore. This includes a central trimeric complex homologous to the Nup62 complex found in metazoans that is incorporated into the nuclear pore inner-ring complex. Chug
et al.
report the structure of the metazoan trimeric Nup62 complex. Neither study supports a model in which the pore can dilate and constrict. Instead they suggest a rigid pore in which flexible domains called FG repeats fill the channel and form a barrier that can be traversed by receptors that carry cargos across.

Science
, this issue pp.
56
and
106
; see also p.
33
Structural basis of pre-mRNA splicing
Authors: Hang Jing , Wan Ruixue , Yan Chuangye , Shi Yigong
Published: August 2015

Structure and function of the spliceosome

When RNA is transcribed from DNA in the eukaryotic cell nucleus, the initial transcript includes noncoding introns that must be spliced out. This splicing is done by a complex macromolecular machine, the spliceosome, which comprises five small nuclear RNAs and more than 100 associated proteins. Now, two papers reveal insights into the structure and function of the yeast spliceosome. Yan
et al.
describe a high-resolution structure determined by electron microscopy of a spliceosome complex comprising four RNAs and 37 proteins. Hang
et al.
focus on the catalytic site and show how protein components anchor the transcribed RNA and allow sufficient flexibility to deliver RNA components involved in catalyzing the splicing reaction.

Science
, this issue pp.
1182
and
1191
Covalent organic frameworks comprising cobalt porphyrins for catalytic CO
2
reduction in water
Authors: Lin Song , Diercks Christian S. , Zhang Yue-Biao , Kornienko Nikolay , Nichols Eva M. , Zhao Yingbo , Paris Aubrey R. , Kim Dohyung , Yang Peidong , Yaghi Omar M. , Chang Christopher J.
Published: August 2015

Improving cobalt catalysts

Tethering molecular catalysts together is a tried and trusted method for making them easier to purify and reuse. Lin
et al.
now show that the assembly of a covalent organic framework (COF) structure can also improve fundamental catalytic performance. They used cobalt porphyrin complexes as building blocks for a COF. The resulting material showed greatly enhanced activity for the aqueous electrochemical reduction of CO
2
to CO.

Science
, this issue p.
1208
Gorlin-Goltz syndrome in twin brothers: an unusual occurrence with review of the literature
Authors: Anchlia Sonal , Vyas Siddharth , Bahl Sumit , Nagavadiya Vipul
Published: August 2015

Gorlin-Goltz syndrome, also known as nevoid basal cell carcinoma syndrome, is caused by genetic alteration produced by a mutation in the ‘patched’ tumour suppressor gene, and is inherited in a dominant autosomal way. Although sporadic cases have been found, this syndrome has rarely been reported in twin patients. The syndrome is characterised by a wide range of developmental abnormalities and has a predisposition to neoplasms such as multiple pigmented basal cell carcinomas and keratocysts in jaws; it also has other features such as palmar and/or plantar pits and calcification of falx cerebri. Owing to the critical oral and maxillofacial manifestations of this syndrome, it is important to recognise its characteristics in order to make a diagnosis, and to plot early preventive treatment and establish the right genetic evidence. Based on a combination of imaging, clinical and histopathological findings, we present a diagnosed case of Gorlin-Goltz syndrome in 18-year-old twin brothers. All cystic lesions were enucleated and 1 year follow-up showed no recurrence.
Widening inequalities in self-rated health by material deprivation? A trend analysis between 2001 and 2011 in Germany
Authors: Pförtner Timo-Kolja , Elgar Frank J
Published: August 2015

Background

Research on inequalities in health has shown a strong association between the lack of standard of living (defined as material deprivation) and self-rated health (SRH). In this study, we sought to further examine this association in a trend analysis of relative and absolute inequalities in SRH as defined by material deprivation in Germany.

Methods

Data were obtained from the German Socio-Economic Panel (GSOEP) between 2001 and 2011. Material deprivation was measured on the basis of 11 living standard items missing due to financial reasons. We used the relative index of inequality (RII) and slope index of inequality (SII) to measure inequalities in SRH by material deprivation, calculating pooled interval logistic regression with robust SEs. Stepwise models were estimated, including demographic and socioeconomic variables, to assess their inter-relation with inequalities in SRH by material deprivation.

Results

The results showed a steady increase in poor SRH over the 10-year duration of the study. A quadratic (inverted U-shaped) trend was observed in material deprivation in the standards of living, which rose from 2001 to 2005, and then declined in 2011. A similar but non-significant trend was found in relative and absolute inequalities in SRH by material deprivation, which increased from 2001 to 2005 and then declined.

Conclusions

Inequality in SRH by material deprivation was relatively stable; however, an observed quadratic trend coincided with active and passive labour market reforms in Germany in early 2005.
Analysis of removability and stability of rock blocks by considering the rock bridge effect
Authors: Zheng Yinhe , Xia Lu , Yu Qingchun
Published: August 2015

In traditional block theory, the removability and stability of rock blocks are analyzed independently; that is, the stability of a removable block is analyzed in detail, and nonremovable blocks are regarded as stable. However, in practical situations, nonremovable blocks may pose more danger than removable blocks. This paper presents a unified method for analyzing the removability and stability of rock blocks. In this method, the cracking of rock bridges is considered and nonremovable blocks are not assumed to be stable. First, possible cracking rock bridges are identified by extending finite-sized fractures and comparing the boundary surfaces of the resulting blocks with those of the original blocks. Then, the sliding direction associated with each possible moving block is determined by solving an optimization problem. The normal force acting on each sliding surface is determined, and the resisting force on each rock bridge is calculated and integrated into the total resisting force when calculating the safety factor of a possible moving block. Procedures to determine all possible moving blocks are introduced, and the possible moving block with the minimum safety factor is regarded as the actual moving block. The corresponding minimum safety factor is defined as the actual safety factor of the block. The proposed method is verified by considering a few examples. The results show that nonremovable blocks may be unstable if the cracking of rock bridges is considered.
The energy level structure of a variety of one-dimensional confining potentials and the effects of a local singular perturbation
Authors: Glasser M.L. , Nieto L.M.
Published: August 2015

Motivated by current interest in quantum confinement potentials, especially with respect to the Stark spectroscopy of new types of quantum wells, we examine several novel one-dimensional singular oscillators. A Green function method is applied, the construction of the necessary resolvents is reviewed and several new ones are introduced. In addition, previous work on the singular harmonic oscillator model, introduced by Avakian et al. (Phys. Lett. A, 124, 233 (1987). doi:10.1016/0375-9601(87)90627-X0) is reproduced to verify the method and results. A novel feature is the determination of the spectra of asymmetric hybrid linear and quadratic potentials. As in previous work, the singular perturbations are modeled by delta functions.
Epoch-based Entropy for Early Screening of Alzheimer’s Disease
Authors: Houmani N. , Dreyfus G. , Vialatte F. B.
Published: August 2015

In this paper, we introduce a novel entropy measure, termed epoch-based entropy. This measure quantifies disorder of EEG signals both at the time level and spatial level, using local density estimation by a Hidden Markov Model on inter-channel stationary epochs. The investigation is led on a multi-centric EEG database recorded from patients at an early stage of Alzheimer’s disease (AD) and age-matched healthy subjects. We investigate the classification performances of this method, its robustness to noise, and its sensitivity to sampling frequency and to variations of hyperparameters. The measure is compared to two alternative complexity measures, Shannon’s entropy and correlation dimension. The classification accuracies for the discrimination of AD patients from healthy subjects were estimated using a linear classifier designed on a development dataset, and subsequently tested on an independent test set. Epoch-based entropy reached a classification accuracy of 83% on the test dataset (specificity = 83.3%, sensitivity = 82.3%), outperforming the two other complexity measures. Furthermore, it was shown to be more stable to hyperparameter variations, and less sensitive to noise and sampling frequency disturbances than the other two complexity measures.
Social opinion dynamics is not chaotic
Authors: Lim Chjan , Zhang Weituo
Published: August 2015

Motivated by the research on social opinion dynamics over large and dense networks, a general framework for verifying the monotonicity property of multi-agent dynamics is introduced. This allows a derivation of sociologically meaningful sufficient conditions for monotonicity that are tailor-made for social opinion dynamics, which typically have high nonlinearity. A direct consequence of monotonicity is that social opinion dynamics is nonchaotic. A key part of this framework is the definition of a partial order relation that is suitable for a large class of social opinion dynamics such as the generalized naming games. Comparisons are made to previous techniques to verify monotonicity. Using the results obtained, we extend many of the consequences of monotonicity to this class of social dynamics, including several corollaries on their asymptotic behavior, such as global convergence to consensus and tipping points of a minority fraction of zealots or leaders.
Coupling Dynamic Programming with Machine Learning for Horizon Line Detection
Authors: Ahmad Touqeer , Bebis George , Regentova Emma , Nefian Ara , Fong Terry
Published: August 2015

In this paper, we consider the problem of segmenting an image into sky and non-sky regions, typically referred to as horizon line detection or skyline extraction. Specifically, we present a new approach to horizon line detection by coupling machine learning with dynamic programming. Given an image, the Canny edge detector is applied first and keeping only those edges which survive over a wide range of thresholds. We refer to the surviving edges as Maximally Stable Extremal Edges (MSEEs). The number of edges is further reduced by classifying MSEEs into horizon and non-horizon edges using a Support Vector Machine (SVM) classifier. Dynamic programming is then applied on the horizon classified edges to extract the horizon line. Various local texture features and their combinations have been investigated in training the horizon edge classifier including SIFT, LBP, HOG, SIFT-LBP, SIFT-HOG, LBP-HOG and SIFT-LBP-HOG. We have also investigated various nodal costs in the context of dynamic programming including binary edge scores, normalized edge classification scores, gradient magnitude and their combinations. The proposed approach has been evaluated and compared with a competitive approach on two challenging data sets, illustrating superior performance.
2-Adjacency between knots
Authors: Tao Zhi-Xiong
Published: August 2015

We study the properties of a knot K to be 2-adjacent to another knot W by analyzing their Conway polynomials, Jones polynomials and Homfly polynomials and give some very useful conditions. We discuss whether each pair of knots can be 2-adjacent to each other, i.e. whether 2-adjacency is a symmetric relation. We discuss also whether the trivial knot, the trefoil knot and the figure-eight knot can be 2-adjacent to any knot in Rolfsen's table and the opposite cases, except for 934 it is not decided whether it is 2-adjacent to 41. Finally, we give some examples to answer I. Torisu's problem partly and etc.
Coherent adequate forcing and preserving CH
Authors: Krueger John , Mota Miguel Angel
Published: August 2015

We develop a general framework for forcing with coherent adequate sets on [Formula: see text] as side conditions, where [Formula: see text] is a cardinal of uncountable cofinality. We describe a class of forcing posets which we call coherent adequate type forcings. The main theorem of the paper is that any coherent adequate type forcing preserves CH. We show that there exists a forcing poset for adding a club subset of [Formula: see text] with finite conditions while preserving CH, solving a problem of Friedman [Forcing with finite conditions, in Set Theory: Centre de Recerca Matemática, Barcelona, 2003–2004, Trends in Mathematics (Birkhäuser-Verlag, 2006), pp. 285–295.].
Designing and exploring risk matrices with MACBETH
Authors: Oliveira Mónica D. , Bana e Costa Carlos A. , Lopes Diana F.
Published: August 2015

Risk matrices are adopted and recommended by many organizations, but the way they are usually constructed violates some basic theoretical principles, giving rise to inconsistent risk ratings. This paper studies ways in which multiple criteria and portfolio decision analyses can improve the design and deployment of risk matrices, using MACBETH (the “Measuring Attractiveness by a Categorical Based Evaluation TecHnique”). Firstly, it introduces ‘value risk-matrices’, built with MACBETH in the following modeling steps: (1) building a value measurement scale on each impact dimension and constructing a subjective probability scale, (2) additive aggregation of the value scales into a cumulative value scale, and (3) design of the value risk-matrix. The value and probability scores of risks are plotted in the matrix and its analysis informs the identification of mitigation actions, which can then be prioritized making use of the recent portfolio module of the MACBETH decision support system. Taken all together, the paper sketches a new modeling approach for Improving Risk Matrice s (IRIS).