bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization sounding of the pulsar magnetosphere
Authors: Ulyanov O. M. , Shevtsova A. I. , Seredkina A. A.
Published: March 2013

The possibility of a polarization sounding of the pulsar magnetosphere is examined, using intrinsic pulsar emission as a probe signal, for modern radio telescopes operating in the meter and decameter wavelength range. Different models of the pulsar magnetosphere at altitudes higher than a radius of critical polarization are used. The propagation medium besides magnetosphere is described by the stratified model, in which each layer has its own density of free electrons and vector of magnetic induction, as well as the spatial and temporal fluctuation scales of these parameters.

The frequency dependence of the polarization parameters of the pulsar radio emission, obtained in the broad band for a selected pulse phase, will enable a sounding deep into the pulsar magnetosphere.
Quadrupole moments of rotating compact stars
Authors: Urbanec Martin , Miller John , Stuchlik Zdenek
Published: March 2013

We present quadrupole moments of rotating neutron and strange stars calculated using standard Hartle Thorne approach. We demonstrate differences between neutron and strange star parameters connected with quadrupole moments and how this parameters could be, in the case of neutron stars, approximated almost independently on neutron star equation of state.
Particle simulation for an axisymmetric pulsar magnetosphere
Authors: Wada Tomohide
Published: March 2013

We developed a new particle simulation code which includes pair creation (magnetic pair creation and photon collision process), propagation of gamma-ray, inertia of particle, interaction of plasma and multi-pole stellar field for steady axisymmetric pulsar magnetosphere. The photon path is solved stochastically by an analytical solution of the mean free path of pair creation processes at the photon position. The superimposed quadrupole magnetic field forms asymmetric electrostatic clouds on tje poloidal plane and the accelerating region is different from the dipole case. Here, we demonstrate some results of a test run for our simulation. We will adopt the code for more complicated cases, such that all above-mentioned effects will be considered together in future work.
Wave propagation in pulsar magnetospheres
Authors: Wang Chen , Lai Dong , Han Jinlin
Published: March 2013

We study the propagation effects of radio waves in a pulsar magnetosphere, composed of relativistic electron-positron pair plasmas streaming along the magnetic field lines and corotating with the pulsar. We critically examine the various physical effects that can potentially influence the observed wave intensity and polarization. We numerically integrate the transfer equations for wave polarization in the rotating magnetosphere, taking account of all the propagation effects in a self-consistent manner. For typical magnetospheric plasma parameters produced by pair cascade, we find that the observed radio intensity and polarization profiles can be strongly modified by the propagation effects. Some applications of our results are discussed.
On the origin of the low-frequency QPO in GRS 1915+105 ρ state
Authors: Yan Shu-Ping , Wang Na , Ding Guo-Qiang
Published: March 2013

We performed a phase-resolved timing analysis of GRS 1915+105 in its ρ state and identify detailed ρ cycle evolution of frequency, amplitude and coherence of the low-frequency quasi-periodic oscillation (LFQPO). We combined our timing results with the spectral study by Neilsen et al. (2011) to do an elaborate contrast analysis. The results are naturally explained by tying the LFQPO to the corona.
Glitches detected in southern radio pulsars
Authors: Yu Meng
Published: March 2013

Parkes pulse arrival-time data for 165 radio pulsars spanning from 1990 to 2011 have been searched for period glitches. Forty-six events out of the detected 107 glitches were found to be new contributions to the entire glitch population which currently contains approximately 400 events.
Mutual influence of magnetic field decay and thermal evolution of rotational neutron stars
Authors: Zhou Xia , Kang Miao , Wang Na
Published: March 2013

The effect of magnetic field decay on the chemical heating and thermal evolution of neutron stars is discussed. Our main goal is to study how chemical heating mechanisms and thermal evolution are changed by field decay and how magnetic field decay is modified by the thermal evolution. We show that the effect of chemical heating is suppressed by the star spin-down through decaying magnetic field at a later stage; magnetic field decay is delayed significantly relative to stars cooling without heating mechanisms; compared to typical chemical heating, the decay of the magnetic field can even cause the temperature to turn down at a later stage.
Reliabilität und Validität des MoMo-Aktivitätsfragebogens für Jugendliche (MoMo-AFB)
Authors: Jekauc Darko , Wagner Matthias O. , Kahlert Daniela , Woll Alexander
Published: March 2013

Der vorliegende Beitrag beschreibt die psychometrischen Eigenschaften des Aktivitätsfragebogens des Motorikmoduls (MoMo-AFB; Bös, Worth, Opper, Oberger & Woll, 2009 ), einer Skala zur Messung körperlicher Aktivität bei Kindern und Jugendlichen. Der Fragebogen besteht aus 28 Items, die Alltagsaktivität, Sport in und außerhalb von organisierten Vereinen, Schulsport und die Erfüllung von Aktivitätsguidelines erfassen. Untersucht wurden 109 Schüler und 87 Schülerinnen im Alter zwischen 9 und 17 Jahren. Zur Überprüfung der Reliabilität wurde der Fragebogen zweimal in einem Abstand von sieben Tagen ausgefüllt. Zur Untersuchung der kriteriumsbezogenen Validität wurden die Fragebogendaten mit Accelerometerdaten (ActiGraph GT1X) verglichen. Der durchschnittliche (gewichtete) Kappa-Koeffizient und die Intraklassenkorrelation (ICC) für den Gesamtindex betrugen .66 bzw .68. Der mittels MoMo-AFB und Accelerometer ermittelte Gesamtumfang der Zeit mit moderater bis hoher Intensität der KA zeigte eine signifikante Spearman-Korrelation von r = .29. Der MoMo-AFB ist bezüglich der Reliabilität und Validität vergleichbar mit anderen international publizierten Aktivitätsfragebögen für Jugendliche.
Diagnostische Herausforderungen bei der Auswahl von Frühstudierenden
Authors: Stumpf Eva , Schneider Wolfgang
Published: March 2013

Bislang werden die Auswahlentscheidungen für das Frühstudium üblicherweise auf Basis des Notendurchschnitts getroffen. In vorliegender Studie wird überprüft, ob dieser einen validen Prädiktor für den Erfolg im Frühstudium darstellt und inwiefern sich einzelne Fachnoten bzw. intellektuelle Fähigkeitsmaße besser zur Erfolgsprognose eignen. Regressionsanalytische Ergebnisse verdeutlichen die Abhängigkeit der Ergebnismuster vom Studienfach: Für die Fächergruppe Mathematik, Physik und Informatik ist die Erfolgsprognose anhand der Noten- und Intelligenzprädiktoren nicht gelungen, in den übrigen Studienfächern wird sie durch den Studienabschnitt moderiert. Hier erwies sich die Zeugnisdurchschnittsnote als bester Einzelprädiktor für den kurzfristigen Erfolg, die Kombination der Deutschnote mit den verbalen intellektuellen Fähigkeiten eignete sich am besten zur Prognose des langfristigen Erfolgs.
Photoinduced dynamics in a molecule metal nanoparticle complex: Mean–field approximation versus exact treatment of the interaction
Authors: Zelinskyy Yaroslav , Zhang Yuan , May Volkhard
Published: March 2013

Photoexcitation of a molecule placed in the proximity of a metal nanoparticle (MNP) is described theoretically. For a sufficient small spatial extension of the whole system the molecule–MNP coupling is given by the instantaneous Coulomb–interaction. The coupling can also be considered in terms of a local field to which an external field has been transferred due to the presence of the MNP. It is known that such an approach can explain a number of observations. However, it fails to describe molecular excited state quenching. By considering the exact molecule-MNP Coulomb–coupling and a related mean field approximation which directly leads to a local field description we investigate this disappearance of excited state quenching in detail. Laser pulse induced dynamics in the molecule-MNP system are studied and the importance of higher multipole excitations in a spherical MNP is underlined. The equivalence of the mean field approximation with the exact approach when calculating spectra of linear absorption is also demonstrated.
Electrorotation of a viscous droplet in a uniform direct current electric field
Authors: He Hui , Salipante Paul F. , Vlahovska Petia M.
Published: March 2013

We present a small-deformation theory which explains the experimentally observed nonaxisymmetric droplet deformation and orientation in a uniform DC electric field. The model shows that above a threshold electric field a rotational flow is induced about the droplet. As a result, drop shape becomes a general ellipsoid with major axis obliquely oriented to the applied field direction. The theory is in excellent agreement with the experimental data for high viscosity drops.
Spin-torque nano-oscillator based on a synthetic antiferromagnet free layer and perpendicular to plane polarizer
Authors: Firastrau I. , Buda-Prejbeanu L. D. , Dieny B. , Ebels U.
Published: March 2013

Coupled free layers systems used as active elements in spin-transfer nano-oscillators (STNOs) can have improved microwave performances in terms of linewidth or tunability. Here, we report a numerical study on the magnetization dynamics of a synthetic antiferromagnet (SAF) driven by a perpendicularly spin-polarized current and an in-plane applied magnetic field. Compared to the single free layer STNO, the current-field state diagrams, derived for strong and weak RKKY exchange coupling strength inside the SAF, show a more complex structure, with new static or dynamic states (chaotic dynamics), and also a larger zone of out-of-plane precession state (OPP) oscillations. The OPP frequency behaviour is generally similar to that of the single free layer STNO except for the zone near the chaotic dynamics and for fields larger than the spin-flop field of the SAF, where several frequency jumps have been observed.
Spectroscopic study of the 22Σ+ and the 42Σ+ excited states of LiCa
Authors: Stein Alexander , Ivanova Milena , Pashov Asen , Knöckel Horst , Tiemann Eberhard
Published: March 2013

The 22Σ+ and 42Σ+ excited states of 7Li40Ca have been studied by high resolution Fourier-transform spectroscopy. The data on the lower state, 22Σ+, were obtained by analyzing the rotationally resolved spectra of the thermal emission of LiCa in the 22Σ+ → X2Σ+ band around 9500 cm−1. These data contained transitions mainly from v′ = 0 and 1 for N′ up to 92 and allowed us to derive molecular parameters describing the potential curve of the state close to its minimum. The dataset on the second state, 42Σ+, is much larger and comes from a laser-induced fluorescence experiment. The levels were excited by a single mode dye laser and the 42Σ+ → X2Σ+ fluorescence was recorded through a Fourier-transform spectrometer. For both states potential energy curves and Dunham coefficients were derived and the spin-rotation structure was evaluated. The results are compared with theoretical and experimental data from the literature.
Transition from Newtonian to non-Newtonian surface shear viscosity of phospholipid monolayers
Authors: Sadoughi A. H. , Lopez J. M. , Hirsa A. H.
Published: March 2013

The surface shear viscosity of DPPC (dipalmitoylphosphatidylcholine) monolayers on the air/water interface was determined over a wide range of surface concentrations in an annular channel. DPPC is studied widely because it is ubiquitous in biological systems. Brewster angle microscopy (BAM) was found to be capable of measuring the monolayer velocity field, even in the absence of co-existing phase domains. Interfacial velocimetry via cross correlations of BAM images provides accurate and non-invasive measurements, useful for both macro and microrheology. The measured velocity profiles are compared with computed profiles obtained over a range of surface shear conditions using the Boussinesq-Scriven surface model, from which the surface shear viscosity was determined. For monolayers in the liquid expanded (LE) and liquid expanded/liquid condensed (LE/LC) co-existing phases, we observe Newtonian behavior. We also show how the flow departs from the Newtonian regime for monolayers with larger surface concentration, corresponding to LC phase transition to solid phase.
The effect of fluctuations, thermal and otherwise, on the temperature dependence of thermopower in aromatic chain single-molecule junctions
Authors: Dubi Yonatan
Published: March 2013

We report a theoretical study of the thermopower of single-molecule junctions with focus on phenyl-based molecular junctions. In contrast to prior studies, thermal fluctuations of the torsional angle between the phenyl rings and variations in the position of the molecular level alignment with respect to the electrode Fermi energy were taken into account. Full thermopower histograms were obtained, and their dependence on the magnitude of the fluctuations was studied. We found that at large molecular orbital variations, the thermopower becomes strongly dependent on the torsion angle and can even change sign. This results in a marked effect of fluctuations on the thermopower distribution, yielding an average thermopower at high temperatures that differs (smaller or larger) from the fluctuation-free value, depending on the strength of fluctuations. We therefore conclude that fluctuations should be taken into account both when extracting single-molecule parameters, such as the molecular level-Fermi level offset, and in predictions of the thermopower of molecular junctions.
Room temperature ferromagnetism in non-magnetic doped TiO2 nanoparticles
Authors: Gómez-Polo C. , Larumbe S. , Pastor J. M.
Published: March 2013

Room-temperature ferromagnetism in non-magnetic doped TiO2 semiconductor nanoparticles is analyzed in the present work. Undoped and N-doped TiO2 nanoparticles were obtained employing sol-gel procedure using urea as the nitrogen source. The obtained gels were first dried at 70 °C and afterwards calcined in air at 300 °C. A residual carbon concentration was retained in the samples as a consequence of the organic decomposition process. Post-annealing treatments at 300 °C under air and vacuum conditions were also performed. The crystallographic structure of nanoparticles was analyzed by X-ray diffraction, obtaining a single anatase crystalline phase after the calcinations (mean nanoparticle diameters around 5–8 nm). SQUID magnetometry was employed to analyze the magnetic response of the samples. Whereas for the undoped samples synthesized with hydrolysis rate h = 6, paramagnetic like behavior is observed at room temperature, the N-doped nanoparticles (h = 3) show a weak ferromagnetic response (saturation magnetization ≈10−3 emu/g). Moreover, a clear reinforcement of the room-temperature ferromagnetism response is found with the post-annealing treatments, in particular that performed in vacuum. Thus, the results indicate the dominant role of the oxygen stoichiometry and the oxygen vacancies in the room temperature ferromagnetic response of these TiO2 nanoparticles.
Tailoring of domain wall dynamics in amorphous microwires by annealing
Authors: Chichay K. , Zhukova V. , Rodionova V. , Ipatov M. , Talaat A. , Blanco J. M. , Gonzalez J. , Zhukov A.
Published: March 2013

We studied the effect of annealing on the magnetic properties and domain wall (DW) dynamics of magnetically bistable, Fe-based, glass-covered microwires with two different compositions, and different diameters. We observed the correlation of the domain wall dynamics with the distribution of the nucleation fields, measured in as-prepared samples, and after annealing for up to 150 min at temperatures of 250 and 300 °C. We found that both DW velocity and the range of the field limiting the single DW dynamics changed after annealing.
Low pressure characterization of dielectric barrier discharge actuators
Authors: Soni Jignesh , Roy Subrata
Published: March 2013

Dielectric barrier discharge actuators tested for thrust inducement between 13 and 101 kPa ambient air pressure show that as the pressure decreases, the thrust increases to a maximum, then drops steadily approaching zero while the power consumption monotonically increases. The amplification in induced thrust at the peak ranges from a few percent to several folds of the thrust measured at atmospheric condition. The effect is more pronounced for thinner dielectrics at lower operating voltages than thicker dielectrics at higher operating voltages and is fairly independent of the ground electrode width. Results identify several optimal control parameters for high-altitude operations.
Metamorphic InAsSb/AlInAsSb heterostructures for optoelectronic applications
Authors: Belenky Gregory , Wang Ding , Lin Youxi , Donetsky Dmitry , Kipshidze Gela , Shterengas Leon , Westerfeld David , Sarney Wendy L. , Svensson Stefan P.
Published: March 2013

Metamorphic heterostructures containing bulk InAs1−xSbx layers and AlInAsSb barriers were grown on GaSb substrates. The lattice mismatch (up to 2.1%) between the GaSb substrates and the InAsSb layers was accommodated by the growth of GaInSb linearly graded buffers. The 1 μm thick InAsSb0.44 layer with an absorption edge above 9 μm exhibited an in-plane residual strain of about 0.08%. InAs1−xSbx structures with x = 0.2 and x = 0.44 operated as light emitting diodes at 80 K demonstrated output powers of 90 μW and 8 μW at 5 μm and 8 μm, respectively.
Peculiarities of spin polarization inversion at a thiophene/cobalt interface
Authors: Wang Xuhui , Zhu Zhiyong , Manchon Aurelien , Schwingenschlögl Udo
Published: March 2013

We perform ab initio calculations to investigate the spin polarization at the interface between a thiophene molecule and cobalt substrate. We find that the reduced symmetry in the presence of a sulfur atom (in the thiophene molecule) leads to a strong spatial dependence of the spin polarization of the molecule. The two carbon atoms far from the sulfur acquire a polarization opposite to that of the substrate, while the carbon atoms bonded directly to sulfur possess the same polarization as the substrate. We determine the origin of this peculiar spin interface property as well as its impact on the spin transport.
Mini-stop bands in single heterojunction photonic crystal waveguides
Authors: Shahid N. , Amin M. , Naureen S. , Anand S.
Published: March 2013

Spectral characteristics of mini-stop bands (MSB) in line-defect photonic crystal (PhC) waveguides and in heterostructure PhC waveguides having one abrupt interface are investigated. Tunability of the MSB position by air-fill factor heterostructure PhC waveguides is utilized to demonstrate different filter functions, at optical communication wavelengths, ranging from resonance-like to wide band pass filters with high transmission. The narrowest filter realized has a resonance-like transmission peak with a full width at half maximum of 3.4 nm. These devices could be attractive for coarse wavelength selection (pass and drop) and for sensing applications.
Visualization-Based Decision Tool for Urban Meteorological Modeling
Authors: Aliaga Daniel G , Vanegas Carlo , Lei Ming , Niyogi Dev
Published: March 2013

We present a visualization-based decision tool that enables exploring the link between urban land use and urban weather, in particular predicting and visualizing changes in urban temperature, precipitation, and humidity. Our work combines recent work from urban planning, weather and climate studies, and visualization and computer graphics. Our approach uses an interactive tool to produce quickly and automatically plausible detailed 3D city models by means of a hybrid computational simulation of urban behavior and procedural urban geometry. From the city model, urban morphology parameters are efficiently computed and used by our custom meteorological simulator which considers the influence of the urban landscape. The result is a compelling visualization ability for understanding the complex feedback between urban land use and the regional meteorology of current cities and of potential future cities with desired greening patterns. Our work includes a case-study example spanning a 1600 km2 area.
Assessing Smart Phones for Generating Life-Space Indicators
Authors: Wan Neng , Qu Wenyu , Whittington Jackie , Witbrodt Bradley C , Henderson Mary Pearl , Goulding Evan H , Schenk A Katrin , Bonasera Stephen J , Lin Ge
Published: March 2013

Life-space is a promising method for estimating older adults' functional status. However, traditional life-space measures are costly and time consuming because they often rely on active subject participation. This study assesses the feasibility of using the global positioning system (GPS) function of smart phones to generate life-space indicators. We first evaluated the location accuracy of smart-phone-collected GPS points versus those acquired by a commercial GPS unit. We then assessed the specificity of the smart-phone-processed life-space information against the traditional diary method. Our results suggested comparable location accuracy between the smart phone and the standard GPS unit in most outdoor situations. In addition, the smart-phone method revealed more comprehensive life-space information than the diary method, which leads to higher and more consistent life-space scores. We conclude that the smart-phone method is more reliable than traditional methods for measuring life-space. Further improvements will be required to develop a robust application of this method that is suitable for health-related practices.
Thiazolidinediones are acute, specific inhibitors of the mitochondrial pyruvate carrier
Authors: Divakaruni Ajit S. , Wiley Sandra E. , Rogers George W. , Andreyev Alexander Y. , Petrosyan Susanna , Loviscach Mattias , Wall Estelle A. , Yadava Nagendra , Heuck Alejandro P. , Ferrick David A. , Henry Robert R. , McDonald William G. , Colca Jerry R. , Simon Melvin I. , Ciaraldi Theodore P. , Murphy Anne N.
Published: March 2013

Facilitated pyruvate transport across the mitochondrial inner membrane is a critical step in carbohydrate, amino acid, and lipid metabolism. We report that clinically relevant concentrations of thiazolidinediones (TZDs), a widely used class of insulin sensitizers, acutely and specifically inhibit mitochondrial pyruvate carrier (MPC) activity in a variety of cell types. Respiratory inhibition was overcome with methyl pyruvate, localizing the effect to facilitated pyruvate transport, and knockdown of either paralog, MPC1 or MPC2, decreased the EC
50
for respiratory inhibition by TZDs. Acute MPC inhibition significantly enhanced glucose uptake in human skeletal muscle myocytes after 2 h. These data (
i
) report that clinically used TZDs inhibit the MPC, (
ii
) validate that MPC1 and MPC2 are obligatory components of facilitated pyruvate transport in mammalian cells, (
iii
) indicate that the acute effect of TZDs may be related to insulin sensitization, and (
iv
) establish mitochondrial pyruvate uptake as a potential therapeutic target for diseases rooted in metabolic dysfunction.
Quotients of Fourier algebras, and representations which are not completely bounded
Authors: Choi Yemon , Samei Ebrahim
Published: March 2013

We observe that for a large class of non-amenable groups

G
G

, one can find bounded representations of

A

(
G
)

{\operatorname {A}}(G)

on a Hilbert space which are not completely bounded. We also consider restriction algebras obtained from

A

(
G
)

{\operatorname {A}}(G)

, equipped with the natural operator space structure, and ask whether such algebras can be completely isomorphic to operator algebras. Partial results are obtained using a modified notion of the Helson set which takes into account operator space structure. In particular, we show that when

G
G

is virtually abelian and

E
E

is a closed subset, the restriction algebra

A

G

(
E
)

{\operatorname {A}} _G(E)

is completely isomorphic to an operator algebra if and only if

E
E

is finite.
When will the Stanley depth increase?
Authors: Shen Yi-Huang
Published: March 2013

Let

I
⊂
S
=

K

,
[

x
1

,
…
,

x
n

]

I\subset S=\mathbb {K},[x_1,\dots ,x_n]

be an ideal generated by squarefree monomials of degree

≥
d

\ge d

. If the number of degree

d
d

minimal generating monomials is
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="mu Subscript d Baseline left-parenthesis upper I right-parenthesis less-than-or-equal-to min left-parenthesis StartBinomialOrMatrix n Choose d plus 1 EndBinomialOrMatrix comma sigma-summation Underscript j equals 1 Overscript n minus d Endscripts StartBinomialOrMatrix 2 j minus 1 Choose j EndBinomialOrMatrix right-parenthesis">

μ
d

(
I
)
≤
min
(

(

n

d
+
1

)

,

∑

j
=
1

n
−
d

(

2
j
−
1

j

)

)

\mu _d(I)\le \min (\binom {n}{d+1},\sum _{j=1}^{n-d}\binom {2j-1}{j})

, then the Stanley depth

sdepth
S

⁡
(
I
)
≥
d
+
1

\operatorname {sdepth}_S(I)\ge d+1

.
Constraining the initial conditions of globular clusters using their radius distribution
Authors: Alexander Poul E. R. , Gieles Mark
Published: March 2013

Studies of extragalactic globular clusters (GCs) have shown that the peak size of the GC radius distribution (RD) depends only weakly on galactic environment. We model RDs of GC populations using a simple prescription for a Hubble time of relaxation-driven evolution of cluster mass and radius. We consider a power-law cluster initial mass function (CIMF) with and without an exponential truncation, and focus in particular on a flat and a steep CIMF (power-law indices of 0 and −2, respectively). For the initial half-mass radii at birth, we adopt either Roche volume (RV) filling conditions (‘filling’, meaning that the ratio of half-mass to Jacobi radius is approximately rh/rJ ≃ 0.15) or strongly RV under-filling conditions (‘under-filling’, implying that initially rh/rJ ≪ 0.15). Assuming a constant orbital velocity about the galaxy centre, we find for a steep CIMF that the typical half-light radius scales with the galactocentric radius RG as R${^{1/3}_{\rm G}}$. This weak scaling is consistent with observations, but this scenario has the (well-known) problem that too many low-mass clusters survive. A flat CIMF with ‘filling’ initial conditions results in the correct MF at old ages, but with too many large (massive) clusters at large RG. An ‘under-filling’ GC population with a flat CIMF also results in the correct MF, and can also successfully reproduce the shape of the RD, with a peak size that is (almost) independent of RG. In this case, the peak size depends (almost) only on the peak mass of the GC MF. The (near) universality of the GC RD is therefore because of the (near) universality of the CIMF. There are some extended GCs in the outer halo of the Milky Way that cannot be explained by this model.
A constructive method for an approximate solution to scalar Wiener–Hopf equations
Authors: Kisil Anastasia V.
Published: March 2013

This paper presents a novel method of approximating the scalar Wiener–Hopf equation, and therefore constructing an approximate solution. The advantages of this method over the existing methods are reliability and explicit error bounds. Additionally, the degrees of the polynomials in the rational approximation are considerably smaller than in other approaches. The need for a numerical solution is motivated by difficulties in computation of the exact solution. The approximation developed in this paper is with a view of generalization to matrix Wiener–Hopf problems for which the exact solution, in general, is not known. The first part of the paper develops error bounds in
L

p

for

. These indicate how accurately the solution is approximated in terms of how accurately the equation is approximated. The second part of the paper describes the approach of approximately solving the Wiener–Hopf equation that employs the rational Carathéodory–Fejér approximation. The method is adapted by constructing a mapping of the real line to the unit interval. Numerical examples to demonstrate the use of the proposed technique are included (performed on C
hebfun
), yielding errors as small as 10
−12
on the whole real line.
A mathematical model for mechanotransduction at the early steps of suture formation
Authors: Khonsari R. H. , Olivier J. , Vigneaux P. , Sanchez S. , Tafforeau P. , Ahlberg P. E. , Di Rocco F. , Bresch D. , Corre P. , Ohazama A. , Sharpe P. T. , Calvez V.
Published: March 2013

Growth and patterning of craniofacial sutures is subjected to the effects of mechanical stress. Mechanotransduction processes occurring at the margins of the sutures are not precisely understood. Here, we propose a simple theoretical model based on the orientation of collagen fibres within the suture in response to local stress. We demonstrate that fibre alignment generates an instability leading to the emergence of interdigitations. We confirm the appearance of this instability both analytically and numerically. To support our model, we use histology and synchrotron X-ray microtomography and reveal the fine structure of fibres within the sutural mesenchyme and their insertion into the bone. Furthermore, using a mouse model with impaired mechanotransduction, we show that the architecture of sutures is disturbed when forces are not interpreted properly. Finally, by studying the structure of sutures in the mouse, the rat, an actinopterygian (Polypterus bichir) and a placoderm (Compagopiscis croucheri), we show that bone deposition patterns during dermal bone growth are conserved within jawed vertebrates. In total, these results support the role of mechanical constraints in the growth and patterning of craniofacial sutures, a process that was probably effective at the emergence of gnathostomes, and provide new directions for the understanding of normal and pathological suture fusion.
The collective action problem in primate territory economics
Authors: Willems Erik P. , Hellriegel Barbara , van Schaik Carel P.
Published: March 2013

Group-living animals often do not maintain territories, but instead have highly overlapping ranges, even though in principle these are economically defendable. We investigate whether this absence of range defence reflects a collective action problem, since a territory can be considered a public good. In a comparative analysis comprising 135 primate species, we find a positive association between range overlap and group size, controlling for economic defendability and phylogenetic non-independence. We subsequently demonstrate that groups with multiple adults of both sexes suffer levels of range overlap twice as high as groups with only a single adult representative of either sex, consistent with the presence of a collective action problem. Finally, we reveal that this collective action problem can be overcome through philopatry of the larger sex. These results suggest that a social complication of group living is a stronger determinant of between-group relations among social animals than ecological factors, but also that collective defence is still achieved where the dominant sex is philopatric and effective defence is critical to reproductive success and survival. In addition, our findings support the idea that human-like warfare, defined as escalated collective territorial conflict, has an evolutionary basis reflected by cases of convergent evolution among non-human primates.
Mhc
supertypes confer both qualitative and quantitative resistance to avian malaria infections in a wild bird population
Authors: Sepil Irem , Lachish Shelly , Hinks Amy E. , Sheldon Ben C.
Published: March 2013

Major histocompatibility complex (
Mhc
) genes are believed to play a key role in the genetic basis of disease control. Although numerous studies have sought links between
Mhc
and disease prevalence, many have ignored the ecological and epidemiological aspects of the host–parasite interaction. Consequently, interpreting associations between prevalence and
Mhc
has been difficult, whereas discriminating alleles for qualitative resistance, quantitative resistance and susceptibility remains challenging. Moreover, most studies to date have quantified associations between genotypes and disease status, overlooking the complex relationship between genotype and the properties of the
Mhc
molecule that interacts with parasites. Here, we address these problems and demonstrate avian malaria (
Plasmodium
) parasite species-specific associations with functional properties of
Mhc
molecules (
Mhc
supertypes) in a wild great tit (
Parus major
) population. We further show that correctly interpreting these associations depends crucially on understanding the spatial variation in risk of infection and the fitness effects of infection. We report that a single
Mhc
supertype confers qualitative resistance to
Plasmodium relictum
, whereas a different
Mhc
supertype confers quantitative resistance to
Plasmodium circumflexum
infections. Furthermore, we demonstrate common functional properties of
Plasmodium-
resistance alleles in passerine birds, suggesting this is a model system for parasite–
Mhc
associations in the wild.
Deep sequencing reveals complex mechanisms of diapause preparation in the invasive mosquito,
Aedes albopictus
Authors: Poelchau Monica F. , Reynolds Julie A. , Elsik Christine G. , Denlinger David L. , Armbruster Peter A.
Published: March 2013

Seasonal environments present fundamental physiological challenges to a wide range of insects. Many temperate insects surmount the exigencies of winter by undergoing photoperiodic diapause, in which photoperiod provides a token cue that initiates an alternative developmental programme leading to dormancy. Pre-diapause is a crucial preparatory phase of this process, preceding developmental arrest. However, the regulatory and physiological mechanisms of diapause preparation are largely unknown. Using high-throughput gene expression profiling in the Asian tiger mosquito,
Aedes albopictus
, we reveal major shifts in endocrine signalling, cell proliferation, metabolism, energy production and cellular structure across pre-diapause development. While some hallmarks of diapause, such as insulin signalling and stress response, were not important at the transcriptional level, two genes,
Pepck
and
PCNA,
appear to show diapause-induced transcriptional changes across insect taxa. These processes demonstrate physiological commonalities between
Ae. albopictus
pre-diapause and diapause strategies across insects, and support the idea of a genetic ‘toolkit’ for diapause. Observations of gene expression trends from a comparative developmental perspective suggest that individual physiological processes are delayed against a background of a fixed morphological ontogeny. Our results demonstrate how deep sequencing can provide new insights into elusive molecular bases of complex ecological adaptations.
Neural correlates of appetitive–aversive interactions in Pavlovian fear conditioning
Authors: Nasser Helen M. , McNally Gavan P.
Published: March 2013

We used Pavlovian counterconditioning in rats to identify the neural mechanisms for appetitive–aversive motivational interactions. In Stage I, rats were trained on conditioned stimulus (CS)–food (unconditioned stimulus [US]) pairings. In Stage II, this appetitive CS was transformed into a fear CS via pairings with footshock. The development of fear responses was retarded in rats that had received Stage I appetitive training. This counterconditioning was associated with increased levels of phosphorylated mitogen activated protein kinase immunoreactivity (pMAPK-IR) in several brain regions, including midline thalamus, rostral agranular insular cortex (RAIC), lateral amygdala, and nucleus accumbens core and shell, but decreased expression in the ventrolateral quadrant of the midbrain periaqueductal gray. These brain regions showing differential pMAPK-IR have previously been identified as part of the fear prediction error circuit. We then examined the causal role of RAIC MAPK in fear learning and showed that Stage II fear learning was prevented by RAIC infusions of the MEK inhibitor PD098059 (0.5 µg/hemisphere). Taken together, these results show that there are opponent interactions between the appetitive and aversive motivational systems during fear learning and that the transformation of a reward CS into a fear CS is linked to heightened activity in the fear prediction error circuit.
EGFR signaling in the brain is necessary for olfactory learning in Drosophila larvae
Authors: Rahn Tasja , Leippe Matthias , Roeder Thomas , Fedders Henning
Published: March 2013

Signaling via the epidermal growth factor receptor (EGFR) pathway has emerged as one of the key mechanisms in the development of the central nervous system in Drosophila melanogaster. By contrast, little is known about the functions of EGFR signaling in the differentiated larval brain. Here, promoter-reporter lines of EGFR and its most prominent activating ligands, Spitz, Keren, and Vein, were used to identify the brain structures relevant for the EGFR pathway. Unexpectedly, promoter activity of all these pathway components was found in the mushroom bodies, which are known to be a higher brain center required for olfactory learning. We investigated the role of the EGFR pathway in this process by using different mutant larvae with reduced pan-neuronal EGFR signaling and those with reduced EGFR signaling in mushroom bodies only. Expression of a dominant-negative form of EGFR as well as silencing of the ligands via RNA interference was applied and resulted in significantly impaired olfactory learning performances. General defects in the ability to taste or smell as well as impaired EGFR signaling during embryonic development could be excluded as major reasons for this learning phenotype. In addition, targeted expression of a constitutively active form of the ligand Spitz also led to a significantly reduced learning ability. Thus, very low levels as well as very high levels of EGFR signaling are deleterious for olfactory learning and memory formation. We hypothesize that EGFR signaling in a certain range maintains a homeostatic situation in the mushroom bodies that is necessary for proper learning and memory.
A review of virtual reality and haptics for product assembly: from rigid parts to soft cables
Authors: Xia Pingjun , Mendes Lopes António , Restivo Maria Teresa
Published: March 2013

Purpose

The use of virtual reality for product assembly has been studied for more than 20 years; however its practical application in industry is still very much in its infancy. Haptics is a new and important interaction method for virtual reality, and currently constitutes a strong and growing research area; however despite this, its application in industry still remains virtually unknown. This paper seeks to address this issue.

Design/methodology/approach

This paper presents a comprehensive survey of the topics of virtual reality and haptics for product assembly, from rigid parts to soft cables, and investigates some new ideas and recent advances in the area. The survey work has been divided into two parts: addressing rigid parts and soft cables. The main focus of part two, the present work, concentrates on virtual reality and haptics for soft cable design and assembly.

Findings

In the first instance, the main research groups and typical systems are investigated, followed by extensive exploration of the major research issues. The latter can be reviewed from three perspectives: geometry modelling, physical modelling and haptics interaction. Finally, the barriers that prevent successful application of virtual assembly are also discussed, and the future research directions are summarized.

Originality/value

This paper presents a comprehensive survey of the topics of virtual reality and haptics for product assembly, from rigid parts to soft cables, and investigates some new ideas and recent advances in the area.
AI tools for use in assembly automation and some examples of recent applications
Authors: Sanders David , Gegov Alexander
Published: March 2013

Purpose

This paper aims to review seven artificial intelligence tools that are useful in assembly automation: knowledge‐based systems, fuzzy logic, automatic knowledge acquisition, neural networks, genetic algorithms, case‐based reasoning and ambient‐intelligence.

Design/methodology/approach

Each artificial intelligence tool is outlined, together with some examples of their use in assembly automation.

Findings

Artificial intelligence has produced a number of useful and powerful tools. This paper reviews some of those tools. Applications of these tools in assembly automation have become more widespread due to the power and affordability of present‐day computers.

Research limitations/implications

Many new assembly automation applications may emerge and greater use may be made of hybrid tools that combine the strengths of two or more of the tools reviewed in the paper. The tools and methods reviewed in this paper have minimal computation complexity and can be implemented on small assembly lines, single robots or systems with low‐capability microcontrollers.

Practical implications

It may take another decade for engineers to recognize the benefits given the current lack of familiarity and the technical barriers associated with using these tools and it may take a long time for direct digital manufacturing to be considered commonplace… but it is expanding. The appropriate deployment of the new AI tools will contribute to the creation of more competitive assembly automation systems.

Social implications

Other technological developments in AI that will impact on assembly automation include data mining, multi‐agent systems and distributed self‐organising systems.

Originality/value

The novel approaches proposed use ambient intelligence and the mixing of different AI tools in an effort to use the best of each technology. The concepts are generically applicable across all industrial assembly processes and this research is intended to prove that the concepts work in manufacturing.
Review and analysis of the residential building certification process in south east Queensland
Authors: Smith Jim , Smith Ben , Mitchell Geoff
Published: March 2013

Purpose

The purpose of this paper is to review the four stages of approval and describe the process of building certification. It reviews a sample of the inspection and certification records of 109 houses in south‐east Queensland and analyses their progress through each of the stages. The incidence of minor faults and failures is examined, together with requests for further information. Trends in these incidents are enumerated, described and analysed with a view to improving the process.

Design/methodology/approach

Access to a private certifier’s inspection data base was given and 109 houses were randomly selected. All the houses were built in 2010 in south‐east Queensland from the Gold Coast, Brisbane and stretching up to the Sunshine Coast. The full range of inspections was conducted to completion. The records of each house inspection at each of the stages were examined, with the detailed notes of each inspection reviewed and analysed. The inspector’s notes were often extensive and detailed and the authors condensed these down into the main causes of problems in approval for that stage.

Findings

The results provide an insight into the process of building approval with documentation required to ensure its integrity and satisfactory completion. A summary of the results provides an insight into this performance.

Practical implications

The building control and certification system is working well and the regulations, codes and trained personnel are maintaining high standards of construction and safety.

Social implications

Safer and better quality house construction should lead to greater consumer satisfaction and confidence in the community.

Originality/value

This is the first time that such a study of the private certification process has been undertaken in Australia.
The impact of design decisions on post occupancy processes in school buildings
Authors: Adeyeye Kemi , Piroozfar Poorang , Rosenkind Micah , Winstanley Graham , Pegg Ian
Published: March 2013

Purpose

This paper aims to review the impact of design and specification decisions for major works during post‐occupancy processes; the routine maintenance and management of school premises. It also seeks to explore the relationship between the main stakeholders and how this impacts decision‐making and the post‐occupancy operation of school buildings.

Design/methodology/approach

In addition to a literature review, qualitative data were also obtained through a focus group; a steering group. The steering group consisted of stakeholders tasked with delivering and managing school premises in the Sussex County.

Findings

The findings contribute to understanding the impact of design decisions on post‐occupancy processes in schools. A basic model is also presented as a guide for requirements and decision mapping in post‐occupancy design decision processes in schools.

Research limitations/implications

The study was conducted with the participation of a representative sample of stakeholders. There may be the need to investigate the issues further in a localised context before detailed solutions are proposed.

Practical implications

The paper reports findings based on the needs, requirements, and preferences of the stakeholders as well as the opportunities and constraints to improving the quality of design processes which in turn will improve post occupancy processes.

Originality/value

The paper highlights the complexity of design decision‐making in schools, presents the viewpoint of stakeholders, and proposes a basic model to ensure performance for post‐occupancy processes to inform the next stage of the research.
Construction of property price indices
Authors: Owusu‐Ansah Anthony
Published: March 2013

Purpose

The purpose of this paper is to examine if temporal aggregation matters in the construction of house price indices and to test the accuracy of alternative index construction methods.

Design/methodology/approach

Five index construction models based on the hedonic, repeat‐sales and hybrid methods are examined. The accuracy of the alternative index construction methods are examined using the mean squared error and out‐of‐sample technique. Monthly, quarterly, semi‐yearly and yearly indices are constructed for each of the methods and six null hypotheses are tested to examine the temporal aggregation effect.

Findings

Overall, the hedonic is the best method to use. While running separate regressions to estimate the index is best at the broader level of time aggregation like the annual, pooling data together and including time dummies to estimate the index is the best at the lower level of time aggregation. The repeat‐sales method is the least preferred method. The results also show that it is important to limit time to the lowest level of temporal aggregation when construction property price indices.

Practical implications

This paper provides alternative method, the mean squared error method based on an out‐of‐sample technique to evaluate the accuracy of alternative index construction methods.

Originality/value

The introduction of financial products like the property derivatives and home equity insurances to the financial market calls for accurate and robust property price indices. However, the index method and level of temporal aggregation to use still remain unresolved in the index construction literature. This paper contributes to fill these gaps.