bluuebunny/crossref_metadata_2025 huggingface dataset:
Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence
Authors: Katahara John K. , Hillhouse Hugh W.
Published: November 2014

A unified model for the direct gap absorption coefficient (band-edge and sub-bandgap) is developed that encompasses the functional forms of the Urbach, Thomas-Fermi, screened Thomas-Fermi, and Franz-Keldysh models of sub-bandgap absorption as specific cases. We combine this model of absorption with an occupation-corrected non-equilibrium Planck law for the spontaneous emission of photons to yield a model of photoluminescence (PL) with broad applicability to band-band photoluminescence from intrinsic, heavily doped, and strongly compensated semiconductors. The utility of the model is that it is amenable to full-spectrum fitting of absolute intensity PL data and yields: (1) the quasi-Fermi level splitting, (2) the local lattice temperature, (3) the direct bandgap, (4) the functional form of the sub-bandgap absorption, and (5) the energy broadening parameter (Urbach energy, magnitude of potential fluctuations, etc.). The accuracy of the model is demonstrated by fitting the room temperature PL spectrum of GaAs. It is then applied to Cu(In,Ga)(S,Se)2 (CIGSSe) and Cu2ZnSn(S,Se)4 (CZTSSe) to reveal the nature of their tail states. For GaAs, the model fit is excellent, and fitted parameters match literature values for the bandgap (1.42 eV), functional form of the sub-bandgap states (purely Urbach in nature), and energy broadening parameter (Urbach energy of 9.4 meV). For CIGSSe and CZTSSe, the model fits yield quasi-Fermi leveling splittings that match well with the open circuit voltages measured on devices made from the same materials and bandgaps that match well with those extracted from EQE measurements on the devices. The power of the exponential decay of the absorption coefficient into the bandgap is found to be in the range of 1.2 to 1.6, suggesting that tunneling in the presence of local electrostatic potential fluctuations is a dominant factor contributing to the sub-bandgap absorption by either purely electrostatic (screened Thomas-Fermi) or a photon-assisted tunneling mechanism (Franz-Keldysh). A Gaussian distribution of bandgaps (local Eg fluctuation) is found to be inconsistent with the data. The sub-bandgap absorption of the CZTSSe absorber is found to be larger than that for CIGSSe for materials that yield roughly equivalent photovoltaic devices (8% efficient). Further, it is shown that fitting only portions of the PL spectrum (e.g., low energy for energy broadening parameter and high energy for quasi-Fermi level splitting) may lead to significant errors for materials with substantial sub-bandgap absorption and emission.
Self-consistent elastic continuum theory of degenerate, equilibrium aperiodic solids
Authors: Bevzenko Dmytro , Lubchenko Vassiliy
Published: November 2014

We show that the vibrational response of a glassy liquid at finite frequencies can be described by continuum mechanics despite the vast degeneracy of the vibrational ground state; standard continuum elasticity assumes a unique ground state. The effective elastic constants are determined by the bare elastic constants of individual free energy minima of the liquid, the magnitude of built-in stress, and temperature, analogously to how the dielectric response of a polar liquid is determined by the dipole moment of the constituent molecules and temperature. In contrast with the dielectric constant—which is enhanced by adding polar molecules to the system—the elastic constants are down-renormalized by the relaxation of the built-in stress. The renormalization flow of the elastic constants has three fixed points, two of which are trivial and correspond to the uniform liquid state and an infinitely compressible solid, respectively. There is also a nontrivial fixed point at the Poisson ratio equal to 1/5, which corresponds to an isospin-like degeneracy between shear and uniform deformation. The present description predicts a discontinuous jump in the (finite frequency) shear modulus at the crossover from collisional to activated transport, consistent with the random first order transition theory.
Free-energy calculations for semi-flexible macromolecules: Applications to DNA knotting and looping
Authors: Giovan Stefan M. , Scharein Robert G. , Hanke Andreas , Levene Stephen D.
Published: November 2014

We present a method to obtain numerically accurate values of configurational free energies of semiflexible macromolecular systems, based on the technique of thermodynamic integration combined with normal-mode analysis of a reference system subject to harmonic constraints. Compared with previous free-energy calculations that depend on a reference state, our approach introduces two innovations, namely, the use of internal coordinates to constrain the reference states and the ability to freely select these reference states. As a consequence, it is possible to explore systems that undergo substantially larger fluctuations than those considered in previous calculations, including semiflexible biopolymers having arbitrary ratios of contour length L to persistence length P. To validate the method, high accuracy is demonstrated for free energies of prime DNA knots with L/P = 20 and L/P = 40, corresponding to DNA lengths of 3000 and 6000 base pairs, respectively. We then apply the method to study the free-energy landscape for a model of a synaptic nucleoprotein complex containing a pair of looped domains, revealing a bifurcation in the location of optimal synapse (crossover) sites. This transition is relevant to target-site selection by DNA-binding proteins that occupy multiple DNA sites separated by large linear distances along the genome, a problem that arises naturally in gene regulation, DNA recombination, and the action of type-II topoisomerases.
Tunneling splitting in double-proton transfer: Direct diagonalization results for porphycene
Authors: Smedarchina Zorka , Siebrand Willem , Fernández-Ramos Antonio
Published: November 2014

Zero-point and excited level splittings due to double-proton tunneling are calculated for porphycene and the results are compared with experiment. The calculation makes use of a multidimensional imaginary-mode Hamiltonian, diagonalized directly by an effective reduction of its dimensionality. Porphycene has a complex potential energy surface with nine stationary configurations that allow a variety of tunneling paths, many of which include classically accessible regions. A symmetry-based approach is used to show that the zero-point level, although located above the cis minimum, corresponds to concerted tunneling along a direct trans − trans path; a corresponding cis − cis path is predicted at higher energy. This supports the conclusion of a previous paper [Z. Smedarchina, W. Siebrand, and A. Fernández-Ramos, J. Chem. Phys. 127, 174513 (2007)] based on the instanton approach to a model Hamiltonian of correlated double-proton transfer. A multidimensional tunneling Hamiltonian is then generated, based on a double-minimum potential along the coordinate of concerted proton motion, which is newly evaluated at the RI-CC2/cc-pVTZ level of theory. To make it suitable for diagonalization, its dimensionality is reduced by treating fast weakly coupled modes in the adiabatic approximation. This results in a coordinate-dependent mass of tunneling, which is included in a unique Hermitian form into the kinetic energy operator. The reduced Hamiltonian contains three symmetric and one antisymmetric mode coupled to the tunneling mode and is diagonalized by a modified Jacobi-Davidson algorithm implemented in the Jadamilu software for sparse matrices. The results are in satisfactory agreement with the observed splitting of the zero-point level and several vibrational fundamentals after a partial reassignment, imposed by recently derived selection rules. They also agree well with instanton calculations based on the same Hamiltonian.
Radiation and bias switch-induced charge dynamics in Al2O3-based metal-oxide-semiconductor structures
Authors: Sambuco Salomone L. , Kasulin A. , Lipovetzky J. , Carbonetto S. H. , Garcia-Inza M. A. , Redin E. G. , Berbeglia F. , Campabadal F. , Faigón A.
Published: November 2014

Charge trapping dynamics induced by exposition to γ-ray (60Co) radiation and bias switching in MOS capacitors with atomic layer deposited Al2O3 as insulating layer was studied. Electrical characterization prior to irradiation showed voltage instabilities due to electron tunneling between the substrate and preexisting defects inside the dielectric layer. Real-time capacitance-voltage (C-V) measurements during irradiation showed two distinct regimes: For short times, the response is strongly bias dependent and linear with log(t), consistent with electron trapping/detrapping; for long times, the voltage shift is dominated by the radiation-induced hole capture being always negative and linear with dose. A simple model that takes into account these two phenomena can successfully reproduce the observed results.
Application of Proper Orthogonal Decomposition to the morphological analysis of confined co-axial jets of immiscible liquids with comparable densities
Authors: Charalampous Georgios , Hardalupas Yannis
Published: November 2014

The development of a round liquid jet under the influence of a confined coaxial flow of an immiscible liquid of comparable density (central to annular flow density ratio of 8:10) was investigated in the vicinity of the nozzle exit. Two flow regimes were considered; one where the annular flow is faster than the central jet, so the central liquid jet is accelerated and one where the annular flow is slower, so the central liquid jet is decelerated. The central jet was visualised by high speed photography. Three modes of jet development were identified and classified in terms of the Reynolds number, Re, of the central jet which was in the range of 525 < Re < 2725, a modified definition of the Weber number, We, which allows the distinction between accelerating and deceleration flows and was in the range of −22 < We < 67 and the annular to central Momentum Ratio, MR, of the two streams which was in the range of 3.6 < MR < 91. By processing the time resolved jet images using Proper Orthogonal Decomposition (POD), it was possible to reduce the description of jet morphology to a small number of spatial modes, which isolated the most significant morphologies of the jet development. In this way, the temporal and spatial characteristics of the instabilities on the interface were clearly identified which highlights the advantages of POD over direct observation of the images. Relationships between the flow parameters and the interfacial waves were established. The wavelength of the interfacial instability was found to depend on the velocity of the fastest moving stream, which is contrary to findings for fluids with large density differences.
Enhancement of 1.5 μm emission in Ce3+/Li+-codoped YPO4:Yb3+, Er3+ phosphor
Authors: Gao Xuejun , Liu Xiaohai , Wen Qin , Yang Xiaoliang , Xiao Siguo
Published: November 2014

YPO4:Yb3+, Er3+ near infrared luminescent materials have been prepared with a co-precipitation method. It is found that Ce3+, Li+ ions co-doped into the Y0.59Yb0.4Er0.01PO4 can result in the 1530 nm emission a 20 times of enhancement as compared with the Y0.58Yb0.4Er0.01Ce0.01PO4 counterpart, meaning it a promising phosphor of wide application prospects. The mechanism of the near infrared emission enhancement is ascribed to the high efficiency energy transfer from Er3+ to Ce3+ and the modification of the crystal field around Er3+ and Yb3+ ions caused by the doped Li+ ions.
A compact quantum correction model for symmetric double gate metal-oxide-semiconductor field-effect transistor
Authors: Cho Edward Namkyu , Shin Yong Hyeon , Yun Ilgu
Published: November 2014

A compact quantum correction model for a symmetric double gate (DG) metal-oxide-semiconductor field-effect transistor (MOSFET) is investigated. The compact quantum correction model is proposed from the concepts of the threshold voltage shift (ΔVTHQM) and the gate capacitance (Cg) degradation. First of all, ΔVTHQM induced by quantum mechanical (QM) effects is modeled. The Cg degradation is then modeled by introducing the inversion layer centroid. With ΔVTHQM and the Cg degradation, the QM effects are implemented in previously reported classical model and a comparison between the proposed quantum correction model and numerical simulation results is presented. Based on the results, the proposed quantum correction model can be applicable to the compact model of DG MOSFET.
Measurement of electron-spin transports in GaAs quantum wells using a transmission-grating-sampled circular dichroism absorption spectroscopy
Authors: Yu Hua-Liang , Fang Shaoyin , Wen Jinhui , Lai Tianshu
Published: November 2014

A transmission-grating-sampled circular dichroism absorption spectroscopy (TGS-CDAS) and its theoretical model are developed sensitively to measure decay dynamics of a transient spin grating (TSG). A binary transmission grating with the same period as TSG is set behind TSG. It allows only a same small part of each period in TSG measured by circular dichroism absorption effect of a probe. In this way, the zero average of spin-dependent effects measured over a whole period in TSG is avoided so that TGS-CDAS has a high sensitivity to spin evolution in TSG. Spin transport experiments are performed on GaAs/AlGaAs quantum wells. Experimental results prove the feasibility and reliability of TGS-CDAS.
Control of emitted light polarization in a 1310 nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection
Authors: Alharthi S. S. , Hurtado A. , Al Seyab R. K. , Korpijarvi V.-M. , Guina M. , Henning I. D. , Adams M. J.
Published: November 2014

We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.
Charge state hysteresis in semiconductor quantum dots
Authors: Yang C. H. , Rossi A. , Lai N. S. , Leon R. , Lim W. H. , Dzurak A. S.
Published: November 2014

Semiconductor quantum dots provide a two-dimensional analogy for real atoms and show promise for the implementation of scalable quantum computers. Here, we investigate the charge configurations in a silicon metal-oxide-semiconductor double quantum dot tunnel coupled to a single reservoir of electrons. By operating the system in the few-electron regime, the stability diagram shows hysteretic tunnelling events that depend on the history of the dots charge occupancy. We present a model which accounts for the observed hysteretic behaviour by extending the established description for transport in double dots coupled to two reservoirs. We demonstrate that this type of device operates like a single-electron memory latch.
Zwitterionic CS2 Adducts of Bis(dialkylphosphino)amines: Syntheses, Spectroscopy, and Structures
Authors: Dickie Diane A. , Ulibarri-Sanchez Raymond P. , Kemp Richard A.
Published: November 2014

Both bis(diisopropylphosphino)amine and bis(di-t-butylphosphino)amine react with CS2 to give bright red zwitterionic adducts of the form R2P(CS2)NP(R2)H (R = iPr or tBu). The P–H tautomer is the exclusive species present in solution, and there is no evidence of CS2 lability. The tautomeric hydrogen can undergo exchange with deuterium in protic solvents such as CD3OD. The products were characterized by single-crystal X-ray diffraction, IR and multinuclear (1H, 2H, 13C, 31P) NMR spectroscopies.
Attitudes toward sex and relationships: the Second Australian Study of Health and Relationships
Authors: de Visser Richard O. , Badcock Paul B. , Simpson Judy M. , Grulich Andrew E. , Smith Anthony M. A. , Richters Juliet , Rissel Chris
Published: November 2014

Background
Attitudes towards sex and relationships influence laws about what is and is not permissible and social sanctions against behaviours considered unacceptable. They are an important focus for research given their links to sexual behaviour. The aim of the present study was to describe attitudes towards sex and relationships, to identify correlates of scores on a scale of sexual liberalism and to examine responses to jealousy-evoking scenarios among Australian adults. Methods: Computer-assisted landline and mobile telephone interviews were completed by a population-representative sample of 20 094 men and women aged 16–69 years. The overall participation rate among eligible people was 66.2%. Respondents expressed their agreement with 11 attitude statements, five of which formed a valid scale of liberalism, and also responded to a jealousy-evoking scenario. Results: There was general agreement that premarital sex was acceptable (87%), that sex was important for wellbeing (83%) and that sex outside a committed relationship was unacceptable (83%). Respondents were accepting of homosexual behaviour and abortion and few believed that sex education encouraged earlier sexual activity. More liberal attitudes were associated with: being female; speaking English at home; homosexual or bisexual identity; not being religious; greater education; and higher incomes. Respondents who expressed more liberal attitudes had more diverse patterns of sexual experience. Predicted sex differences were found in response to the jealousy-evoking scenario — men were more jealous of a partner having sex with someone else and women were more jealous of a partner forming an emotional attachment — but responses varied with age. Conclusion: Sexual attitudes of Australians largely support a permissive but monogamous paradigm. Since 2002, there has been a shift to less tolerance of sex outside a committed relationship, but greater acceptance of homosexual behaviour.
Sexual identity, sexual attraction and sexual experience: the Second Australian Study of Health and Relationships
Authors: Richters Juliet , Altman Dennis , Badcock Paul B. , Smith Anthony M. A. , de Visser Richard O. , Grulich Andrew E. , Rissel Chris , Simpson Judy M.
Published: November 2014

Background
Behavioural and other aspects of sexuality are not always consistent. This study describes the prevalence and overlap of same-sex and other-sex attraction and experience and of different sexual identities in Australia. Methods: Computer-assisted telephone interviews were completed by a representative sample of 20 094 men and women aged 16–69 years recruited by landline and mobile phone random-digit dialling with a response rate (participation rate among eligible people) of 66.2%. Respondents were asked about their sexual identity (‘Do you think of yourself as’ heterosexual/straight, homosexual/gay, bisexual, etc.) and the sex of people with whom they had ever had sexual contact and to whom they had felt sexually attracted. Results: Men and women had different patterns of sexual identity. Although the majority of people identified as heterosexual (97% men, 96% women), women were more likely than men to identify as bisexual. Women were less likely than men to report exclusively other-sex or same-sex attraction and experience; 9% of men and 19% of women had some history of same-sex attraction and/or experience. Sexual attraction and experience did not necessarily correspond. Homosexual/gay identity was more common among men with tertiary education and living in cities and less common among men with blue-collar jobs. Many gay men (53%) and lesbians (76%) had some experience with an other-sex partner. More women identified as lesbian or bisexual than in 2001–02. Similarly, more women reported same-sex experience and same-sex attraction. Conclusion: In Australia, men are more likely than women to report exclusive same-sex attraction and experience, although women are more likely than men to report any non-heterosexual identity, experience and attraction. Whether this is a feature of the plasticity of female sexuality or due to lesser stigma than for men is unknown.
Space, innovation and the locus of knowledge: an ontological response to Rutten
Authors: Bahlmann Marc D.
Published: November 2014

Marc Bahlmann is assistant professor at VU University Amsterdam. He received his Ph.D. from the Faculty of Social Sciences (VU University) for a study on knowledge dynamics among IT entrepreneurs located in the Amsterdam IT and new media cluster. His current research interests include alliance portfolios, organizational and regional innovation.
Learning in socio-spatial context: an individual perspective
Authors: Rutten Roel
Published: November 2014

Roel Rutten is assistant professor at the School of Social and Behavioural Sciences of Tilburg University and has worked as a consultant of regional innovation policy. His research interests include innovation and organization and the geography of innovation and learning. He is a founding member of the Social Dynamics of Innovation Networks research community and an active member of the Regional Studies Association. He frequently engages with practitioners in the field of innovation and regional development.
Cholesterol-lowering effect of rice bran protein containing bile acid-binding proteins
Authors: Wang Jilite , Shimada Masaya , Kato Yukina , Kusada Mio , Nagaoka Satoshi
Published: November 2014

Dietary plant protein is well known to reduce serum cholesterol levels. Rice bran is a by-product of rice milling and is a good source of protein. The present study examined whether feeding rats a high-cholesterol diet containing 10% rice bran protein (RBP) for 10 d affected cholesterol metabolism. Rats fed dietary RBP had lower serum total cholesterol levels and increased excretion of fecal steroids, such as cholesterol and bile acids, than those fed dietary casein. In vitro assays showed that RBP strongly bound to taurocholate, and inhibited the micellar solubility of cholesterol, compared with casein. Moreover, the bile acid-binding proteins of the RBP were eluted by a chromatographic column conjugated with cholic acid, and one of them was identified as hypothetical protein OsJ_13801 (NCBI accession No. EAZ29742) using MALDI-TOF mass spectrometry analysis. These results suggest that the hypocholesterolemic action of the RBP may be caused by the bile acid-binding proteins.
A Prolegomenon to Clinical Psychology
Authors: Barlow David H.
Published: November 2014

In 1969, David Shakow, generally acknowledged as the founding father of modern-day clinical psychology, recounted his 40-year odyssey in the field. He focused on advances in training, diagnosis and assessment, and treatment, and projected trends in these areas in the years to come. The author recounts his own 40-year odyssey, beginning in 1969, and reflects on the remarkable growth of clinical psychology, progress that has occurred in the areas of training, diagnosis and assessment, and treatment, and the extent to which Shakow’s vision has been realized.
Disorders of Development
Authors: Durand V. Mark
Published: November 2014

Disorders of development include a range of disorders first evidenced in childhood. Although most disorders have their origins in childhood, a few fully express themselves before early adulthood. This chapter describes the nature, assessment, and treatment of the more common disorders that are revealed in a clinically significant way during a child’s developing years. The disorders of development affect a range of functioning from single skills deficits to more pervasive problems that negatively impact a child’s ability to function. Included is coverage of several disorders usually diagnosed first in infancy, childhood, or adolescence, including the neurodevelopmental disorders (e.g., attention-deficit/ hyperactivity disorder, autism spectrum disorder, communication disorders, intellectual disability, and specific learning disorder) and the disruptive, impulse control, and conduct disorders (e.g., oppositional defiant disorder, conduct disorder). Recommendations for future research on the potential for advancing knowledge regarding spectrums within some of these disorders as well as recommendations for treatment are outlined.
Interventions for Mental Health Problems in Later Life
Authors: Holland Jason M. , Gallagher-Thompson Dolores
Published: November 2014

Older adults are increasingly making up a larger segment of the worldwide population, which presents both challenges and opportunities for the clinical psychologist in the 21st century. In this chapter, we address some of the unique aspects of working with this population, focusing on general guidelines for tailoring interventions for older adults, specific treatments for particular problems commonly faced in later life, as well as issues of diversity and how they might impact psychotherapy with older clients. We also outline several areas in geropsychology that are in need of further investigation, namely the use of technology, post-traumatic stress, and family therapy, and offer some recommendations for future directions in this field of study.
The Future of Clinical Psychology
Authors: Barlow David H. , Carl Jenna R.
Published: November 2014

In this chapter, we speculate on near to immediate future trends in clinical psychology and make ten predictions in the broad areas of training, diagnosis and assessment, and treatment. These include: (1) an increased focus on competencies in training; (2) the implications of evidence-based practice as a new major focus of training; (3) changes in the accreditation of training programs; (4) a move to dimensional conceptions of diagnosis; (5) clinical outcomes assessment as an integral part of practice, as well as a more individual focus in clinical research; (6) the increasing recognition and dissemination of psychological treatments; (7) the end of single-diagnosis psychological treatment manuals; (8) the development of drugs that specifically enhance the mechanisms of action of psychological treatments; (9) an expanded role for technology in service delivery; and (10) a clearer delineation of the terms “psychological treatments,” referring to interventions directed at psychopathology and pathophysiology in the context of our health-care delivery system, and, “psychotherapy,” increasingly based on data from positive psychology, but directed at enhancing personal adjustment and growth.
The Spectrum of Personality Disorders
Authors: South Susan C. , Oltmanns Thomas F. , Krueger Robert F.
Published: November 2014

The concept of personality disorder has existed throughout the history of psychology and psychiatry. The ten current personality disorders (PDs) listed in the DSM-IV are conceived of as distinct syndromes. Nevertheless, DSM-IV PDs overlap extensively with each other, with normal personality traits, and with Axis I psychopathology. Thus, many investigators suggest that, in DSM-5, the classification system for PDs should be revised to better reflect the closeness of the links between personality and psychopathology, perhaps by linking both constructs within broader spectrums of psychopathological variation. The most common and well-accepted suggestion is that the categorical diagnoses of DSM-IV should be replaced with a dimensional model of pathological personality traits, and the links between personality traits and more syndromal forms of psychopathology (Axis I disorders) should also be explicitly articulated. In this chapter, we review current research on how PDs are linked with broad spectrums of personality and psychopathology. Specifically, we examine (1) evidence relevant to the etiology and course of PDs, (2) how these disorders can best be assessed, and (3) evidence regarding the most effective practices in the treatment of PDs, with the aim of articulating how etiology, course, assessment, and treatment of PDs might be conceptualized in a spectrum-based classification system.
Behavioral Economics and Tort Law
Authors: Halbersberg Yoed , Guttel Ehud
Published: November 2014

The chapter discusses the contributions of cognitive psychology and behavioral studies to the research of tort law. These contributions, we show, relate to a wide range of issues in torts: from the basic decision to impose tort liability, through the choice between liability rules, to specific rules and remedies. Accordingly, behavioral studies are of particular significance for the analysis of the tort system. The literature review focuses on contributions made to three key elements of tort law: the choice between liability regimes; the choice between tort liability and regulation (including the choice between harm-based and risk-based liability); and damages (in particular, punitive damages and damages for pain and suffering). The chapter also offers two new avenues for future research: vicarious liability and people’s perceptions of the variability among large groups of tort victims.
Unexpectedly low UV-sensitivity in a bird, the budgerigar
Authors: Chavez Johanna , Kelber Almut , Vorobyev Misha , Lind Olle
Published: November 2014

Photoreceptor adaptation ensures appropriate visual responses during changing light conditions and contributes to colour constancy. We used behavioural tests to compare UV-sensitivity of budgerigars after adaptation to UV-rich and UV-poor backgrounds. In the latter case, we found lower UV-sensitivity than expected, which could be the result of photon-shot noise corrupting cone signal robustness or nonlinear background adaptation. We suggest that nonlinear adaptation may be necessary for allowing cones to discriminate UV-rich signals, such as bird plumage colours, against UV-poor natural backgrounds.
Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs
Authors: Boonstra Rudy , Mo Kaiguo , Monks Douglas Ashley
Published: November 2014

Androgens have benefits, such as promoting muscle growth, but also significant costs, including suppression of immune function. In many species, these trade-offs in androgen action are reflected in regulated androgen production, which is typically highest only in reproductive males. However, all non-reproductive Arctic ground squirrels, irrespective of age and sex, have high levels of androgens prior to hibernating at sub-zero temperatures. Androgens appear to be required to make muscle in summer, which, together with lipid, is then catabolized during overwinter. By contrast, most hibernating mammals catabolize only lipid. We tested the hypothesis that androgen action is selectively enhanced in Arctic ground squirrel muscle because of an upregulation of androgen receptors (ARs). Using Western blot analysis, we found that Arctic ground squirrels have AR in skeletal muscle more than four times that of Columbian ground squirrels, a related southern species that overwinters at approximately 0°C and has low pre-hibernation androgen levels. By contrast, AR in lymph nodes was equivalent in both species. Brain AR was also modestly but significantly increased in Arctic ground squirrel relative to Columbian ground squirrel. These results are consistent with the hypothesis that tissue-specific AR regulation prior to hibernation provides a mechanism whereby Arctic ground squirrels obtain the life-history benefits and mitigate the costs associated with high androgen production.
Are empidine dance flies major flower visitors in alpine environments? A case study in the Alps, France
Authors: Lefebvre Vincent , Fontaine Colin , Villemant Claire , Daugeron Christophe
Published: November 2014

Pollination is one of the most important ecosystem services and bees the most important pollinators. As a population decline of bees has been documented in numerous regions of the world, it is crucial to develop understanding on other possible pollinators. Here, we study the potential pollination impact of Diptera, and among them Empidinae, in an alpine environment, where the abundance of bees is naturally lower. Interactions between 19 entomophilous plants and their flower visitors were recorded in a subalpine meadow in the French Alps during six weeks. Visitation frequencies were used to build the flower–visitor network. Our results show that interactions between flies and plants are dominant; flies represent more than 60% of all visitors, with 54% of them being Empidinae. We especially found that flies, Empidinae and bees are the main visitors of 11, three and one plants, respectively. When considering both bees and Syrphidae together, six plants were more visited by Empidinae; when considering bees and Syrphidae separately, 10 plants were more visited by Empidinae than by bees or Syrphidae. The results support the idea that flies widely replace bees as main flower visitors at altitude, and among them the Empidinae might play a key role in pollination.
Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey
Authors: Zurek Daniel B. , Perkins Madeleine Q. , Gilbert Cole
Published: November 2014

In dynamic locomotory contexts, visual cues often trigger adaptive behaviour by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. Here, we describe a dynamic situation of visually guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviours in the pursuer, a predatory beetle. We investigated which visual cues may independently control opening and closing of the beetle's jaws during chases of prey dummies. Jaw opening and closing typically occur when prey is within the 60° binocular field, but not at specific distances, angular sizes or time-to-collision. We show that a sign change in the expansion rate of the target image precedes jaw opening (16 ms) and closing (35 ms), signalling to the beetle that it is gaining on the target or that the target is getting away. We discuss the ‘sloppiness' of such variation in the lag of the behavioural response, especially jaw closing, as an adaptation to uncertainty about target position due to degradation of the target image by motion blur from the fast-running beetle.
Recent divergences and size decreases of eastern gorilla populations
Authors: Roy Justin , Arandjelovic Mimi , Bradley Brenda J. , Guschanski Katerina , Stephens Colleen R. , Bucknell Dan , Cirhuza Henry , Kusamba Chifundera , Kyungu Jean Claude , Smith Vince , Robbins Martha M. , Vigilant Linda
Published: November 2014

Compared with other African apes, eastern gorillas (
Gorilla beringei
) have been little studied genetically. We used analysis of autosomal DNA genotypes obtained from non-invasively collected faecal samples to estimate the evolutionary histories of the two extant mountain gorilla populations and the closely related eastern lowland gorillas. Our results suggest that eastern lowland gorillas and mountain gorillas split beginning some 10 000 years ago, followed 5000 years ago by the split of the two mountain gorilla populations of Bwindi Impenetrable National Park and the Virungas Massif. All three populations have decreased in effective population size, with particularly substantial 10-fold decreases for the mountain gorillas. These dynamics probably reflect responses to habitat changes resulting from climate fluctuations over the past 20 000 years as well as increasing human influence in this densely populated region in the last several thousand years.
Sisters' curse: sexually antagonistic effects constrain the spread of a mitochondrial haplogroup superior in sperm competition
Authors: Padua Michael V. , Zeh David W. , Bonilla Melvin M. , Zeh Jeanne A.
Published: November 2014

Maternal inheritance of mitochondria creates a sex-specific selective sieve with implications for male longevity, disease susceptibility and infertility. Because males are an evolutionary dead end for mitochondria, mitochondrial mutations that are harmful or beneficial to males but not females cannot respond directly to selection. Although the importance of this male/female asymmetry in evolutionary response depends on the extent to which mitochondrial mutations exert antagonistic effects on male and female fitness, few studies have documented sex-specific selection acting on mitochondria. Here, we exploited the discovery of two highly divergent mitochondrial haplogroups (A and B2) in central Panamanian populations of the pseudoscorpion
Cordylochernes scorpioides
. Next-generation sequencing and phylogenetic analyses suggest that selection on the
ND4
and
ND4L
mitochondrial genes may partially explain sexually antagonistic mitochondrial effects on reproduction. Males carrying the rare B2 mitochondrial haplogroup enjoy a marked advantage in sperm competition, but B2 females are significantly less sexually receptive at second mating than A females. This reduced propensity for polyandry is likely to significantly reduce female lifetime reproductive success, thereby limiting the spread of the male beneficial B2 haplogroup
.
Our findings suggest that maternal inheritance of mitochondria and sexually antagonistic selection can constrain male adaptation and sexual selection in nature.
Spectral tuning by opsin coexpression in retinal regions that view different parts of the visual field
Authors: Dalton Brian E. , Loew Ellis R. , Cronin Thomas W. , Carleton Karen L.
Published: November 2014

Vision frequently mediates critical behaviours, and photoreceptors must respond to the light available to accomplish these tasks. Most photoreceptors are thought to contain a single visual pigment, an opsin protein bound to a chromophore, which together determine spectral sensitivity. Mechanisms of spectral tuning include altering the opsin, changing the chromophore and incorporating pre-receptor filtering. A few exceptions to the use of a single visual pigment have been documented in which a single mature photoreceptor coexpresses opsins that form spectrally distinct visual pigments, and in these exceptions the functional significance of coexpression is unclear. Here we document for the first time photoreceptors coexpressing spectrally distinct opsin genes in a manner that tunes sensitivity to the light environment. Photoreceptors of the cichlid fish,Metriaclima zebra, mix different pairs of opsins in retinal regions that view distinct backgrounds. The mixing of visual pigments increases absorbance of the corresponding background, potentially aiding the detection of dark objects. Thus, opsin coexpression may be a novel mechanism of spectral tuning that could be useful for detecting prey, predators and mates. However, our calculations show that coexpression of some opsins can hinder colour discrimination, creating a trade-off between visual functions.
A classification approach based on variable precision rough sets and cluster validity index function
Authors: Lin Hongkang
Published: November 2014

Purpose

– The clustering/classification method proposed in this study, designated as the PFV-index method, provides the means to solve the following problems for a data set characterized by imprecision and uncertainty: first, discretizing the continuous values of all the individual attributes within a data set; second, evaluating the optimality of the discretization results; third, determining the optimal number of clusters per attribute; and fourth, improving the classification accuracy (CA) of data sets characterized by uncertainty. The paper aims to discuss these issues.

Design/methodology/approach

– The proposed method for the solution of the clustering/classifying problem, designated as PFV-index method, combines a particle swarm optimization algorithm, fuzzy C-means method, variable precision rough sets theory, and a new cluster validity index function.

Findings

– This method could cluster the values of the individual attributes within the data set and achieves both the optimal number of clusters and the optimal CA.

Originality/value

– The validity of the proposed approach is investigated by comparing the classification results obtained for UCI data sets with those obtained by supervised classification BPNN, decision-tree methods.
Lean transformation in a high mix low volume electronics assembly environment
Authors: Arasanipalai Raghavan Venkatesh , Yoon Sangwon , Srihari Krishnaswami
Published: November 2014

Purpose

– This paper aims to focus on integrating a lean framework in a high-mix-low-volume (HMLV) printed circuit board assembly (PCBA) environment to enhance current assembly processes and facility layouts. An HMLV PCBA environment is characterized by stochastic demands, a variety of products in terms of shapes and sizes and different sequences of assembly and test operations, in addition to long cycle times and high fall-out rates.

Design/methodology/approach

– Preliminary analysis indicates that the push inventory control system led to the longer cycle times, such that various lean methodologies have been applied to enhance the assembly operations. In this research, Kanban sizes for different assembly lines are also estimated to integrate and implement a “pull-system” into the lean framework. In addition, material movement and facility layout have been studied to minimize work-in-process travel time. An “iterative-MAIC” approach has been applied to implement lean principles.

Findings

– As a result, a lean manufacturing pilot line has been implemented to evaluate the effectiveness of the lean principles before rolling them out across the manufacturing floor. It has been shown that the cycle times of the pilot line products are decreased by 40 per cent and the number of defects decreased by 10-30 per cent, depending on different assembly processes, after the lean implementation.

Originality/value

– There is limited literature that addresses lean transformation in an HMLV electronics manufacturing service provider handling several product types with different testing methodologies, frequent product revision changes and higher fall-out rates. Hence, in this research, lean manufacturing has been implemented in an HMLV PCBA environment, which has the challenges of varying demand with a mix of assembly and test operations for different product families.
Vacancy chains and the business cycle. Stringing together job-to-job transitions in micro data
Authors: Gianelle Carlo , Tattara Giuseppe
Published: November 2014

Purpose

– The purpose of this paper is to examine the dynamics of labour market flows over the business cycle through a vacancy chain model. It provides a direct computation of vacancy chains using micro data, empirically investigates the relationship between chain length and the characteristics of jobs and workers initiating the chain, and finally assesses the wage progression of workers moving along the chain.

Design/methodology/approach

– The paper draws on a longitudinal matched employer-employee database covering all employees in manufacturing in a large region of Italy. A transparent algorithm for vacancy chain computation is developed and standard econometric techniques are employed to analyze job-to-job transitions within identified chains.

Findings

– Vacancy chains account on average for more than one-third of total hires, and both the number and the length of chains are clearly pro-cyclical. Chains set in motion by women workers, young, old, blue collars, or employed by small firms tend to be shorter. There is a well-defined wage progression from the tail to the head of the chain, revealing that workers are sorted along chains according to skill and/or bargaining power.

Research limitations/implications

– There is a limited possibility of identifying separately individual ability and bargaining power.

Practical implications

– The vacancy chain methodology can increase the ability of policy makers to produce detailed maps of the labour market and identify worker profiles associated with poor outcomes and hence deserving special attention.

Originality/value

– For the first time, this paper operationalizes the vacancy chain approach on a large scale, at a very high level of detail, and over a long-time span.
A review on structural integrity assessment procedures
Authors: Ajay Shah Utkarsh
Published: November 2014

Purpose

– The purpose of this paper is to compare different existing assessment procedures for their limitations and applicable areas.

Design/methodology/approach

– Procedures have been studied in-depth along with their criterion for applications.

Findings

– The study shows applicability of different procedures along with their limitations and future scope.

Originality/value

– The paper provides starting point for performing damage assessment based on relevant procedures.
Buckling analysis of a delaminated panel by using a kinematic global-local coupling approach
Authors: Sellitto A. , Borrelli R. , Caputo F. , Riccio A. , Scaramuzzino F.
Published: November 2014

Purpose

– The purpose of this paper is to investigate on the behaviour of a delaminated stiffened panel; the delamination growth is simulated via fracture elements implemented in B2000++® code based on the Modified Virtual Crack Closure Technique (MVCCT), matrix cracking and fibre failure have been also taken into account.

Design/methodology/approach

– In order to correctly apply the MVCCT on the delamination front a very fine three-dimensional (3D) mesh is required very close to the delaminated area, while a 2D-shell model has been employed for the areas of minor interest. In order to couple the shell domain to the solid one, shell-to-solid coupling elements based on kinematic constraints have been used.

Findings

– Results obtained with the global/local approach are in good correlation with those obtained with experimental results.

Originality/value

– The global/local approach based on kinematic coupling elements in conjunction with fracture elements allows to investigate and predict the behaviour of a stiffened delaminated composite panel in an efficient and effective way.
Experimental and numerical investigation of fatigue crack growth in aluminum plates repaired by FML composite patch
Authors: Rahmani Kalestan M. , Moayeri Kashani H. , Pourkamali Anaraki A. , Ashena Ghasemi F.
Published: November 2014

Purpose

– The purpose of this paper is to use the fiber metal laminates (FML) composites as a patch for repairing a single notched specimen made of AL1035 aluminum alloy. The FML composite patch was bonded on one side of the cracked specimens by adhesive Araldite 2015. Then the fatigue crack growth tests were conducted on the specimens and the effects of both FML patch lay-up sequence and pre-crack angle on the fatigue life were investigated. Finally, the effect of repairing on the fracture parameters (SIF and crack propagation direction) at the crack front has also been calculated using three-dimensional finite element analysis.

Design/methodology/approach

– The fatigue crack growth tests were conducted on the specimens and the effects of both FML patch lay-up sequence and pre-crack angle on the fatigue life were investigated.

Findings

– The results show that the fatigue life of the patched specimens with inclined crack increased approximately 2-6.02 times compared to the un-patched specimens. In addition, the fatigue crack growth rate decreased significantly when the patch was used. Generally, the FML patch with Plate-Fiber-Fiber-AL lay-up has more efficiency than other lay-up sequences.

Originality/value

– Recently, composite patches are used in the structure repair processes to increase the service life of cracked components. The bonded patch method is one of the efficient methods among repairing methods. Today, the FMLs are used in the aircraft structures as a replacement of high-strength aluminum alloys due to their lightweight and high-strength properties. Many researches have been performed on single and double side repaired panels using composite patches. In this study, the FML composites have been used as a patch for repairing a single notched specimen made of AL1035 aluminum alloy.