Measuring eye aberrations with Hartmann-Shack wave-front sensors: should the irradiance distribution across the eye pupil be taken into account?

A usual approximation in Hartmann-Shack aberrometry is that the centroid displacements are proportional to the spatial averages of the wave-front slopes at the sampling subapertures. However, these spatial averages are actually weighted by the local irradiance distribution across each microlens. The irradiance across the eye pupil is not uniform in usual reflectometric aberrometers, which is due to several factors including retinal scattering and cone waveguiding directionality. It is shown that neglecting this fact in usual least-squares reconstruction procedures gives rise to a biased estimation of the aberration coefficients. The magnitude of this bias depends on the actual irradiance distribution across the eye pupil, the mode being estimated, the detailed modal composition of the aberrated wave front, and the geometry of the wave-front sampling array. Order-of-magnitude calculations suggest that this bias may well be in the range 5%-10% for relatively smooth irradiance distributions. The systematic nature of this error makes it advisable to check for its presence and, if required, to compensate for it by an adequate choice of the least-squares reconstruction matrix.     

The mathematical review system: does reviewer status play a role in the citation process?

This paper revisits an aspect of citation theory (i.e., citer motivation) with respect to the Mathematical Review system and the reviewer’s role in mathematics. We focus on a set of journal articles (369) published in Singularity Theory (1974–2003), the mathematicians who wrote editorial reviews for these articles, and the number of citations each reviewed article received within a 5 year period. Our research hypothesis is that the cognitive authority of a high status reviewer plays a positive role in how well a new article is received and cited by others. Bibliometric evidence points to the contrary: Singularity Theorists of lower status (junior researchers) have reviewed slightly more well-cited articles (2–5 citations, excluding author self-citations) than their higher status counterparts (senior researchers). One explanation for this result is that lower status researchers may have been asked to review ‘trendy’ or more accessible parts of mathematics, which are easier to use and cite. We offer further explanations and discuss a number of implications for a theory of citation in mathematics. This research opens the door for comparisons to other editorial review systems, such as book reviews written in the social sciences or humanities.     

Does p-glycoprotein play a role in gastrointestinal absorption and cellular transport of dietary cholesterol?

This commentary discusses the potential role of p-glycoprotein (Pgp) on the gastrointestinal absorption and cellular transport of dietary cholesterol. This is currently a controversial issue due to the conflicting evidence about the role of this ABC transporter in cholesterol transport. During the preparation of this commentary, several key publications on this topic arguing for and against this mechanism have been published. If true, this mechanism of Pgp could represent a novel role for Pgp and provide a potentially new molecular target for drug design and development.     

Does China's higher education investment play a role in industrial growth?

The first sentence in the abstract needs to be changed from:This research divides the process through which China’s higher education investment turned into industrial economic growth between 2014 and 2017 into higher education investment transformation division, knowledge innovation division, and innovation commercialization division, then applies a Network Slacks-Based Measure (SBM) model to evaluate the efficiency of the process, and finally uses the individual fixed effect model to analyze its influencing factors. ToThis research divides the process through which China’s higher education investment turned into industrial economic growth between 2014 and 2017. The process is broken down into higher education investment transformation division, knowledge innovation division, and innovation commercialization division. This study then applies a Network Slacks-Based Measure (SBM) model to evaluate the efficiency of the process, and finally uses the individual fixed effect model to analyze its influencing factors.     

Antisemitism and Islamophobia: what does a bibliometric study reveal?

Although Islamophobia and Antisemitism are two phenomena different in their nature, both represent a form of Otherness that entails a complicated inclusion into multi-ethnic societies of modern Europe and the United States. The purpose of the present study is to show how the research literature has portrayed both phenomena in terms of bibliometric data retrieved from the SCIE Clarivate Analytics database. In addition, we were interested to find out if there is a literature that connects Islamophobia and Antisemitism, its direction and influence. Our findings show that because publications and citations on Islamophobia are relatively new, the research in terms of publications draws the attention of academic society in the direction of research of Antisemitism, but the citations count of the literature on Islamophobia exceeds by far that of the literature on Antisemitism. Moreover, we found that although Antisemitism and Islamophobia are distinct trends, there is an interaction between the literatures that discuss both, and the research that combines the analysis of both phenomena gains more influence than research dedicated to each phenomenon separately.     

Carbon nanotube-metal cluster composites: a new road to chemical sensors?

Novel carbon nanotube-metal cluster structures are proposed as prototype systems for molecular recognition at the nanoscale. Ab initio calculations show that already the bare nanotube cluster system displays some specificity because the adsorption of ammonia on a carbon nanotube-Al cluster system is easily detected electrically, while diborane adsorption does not provide an electrical signature. Since there are well-established procedures for attaching molecular receptors to metal clusters, these results provide a "proof-of-principle" for the development of novel, high-specificity molecular sensors.     

Where, and how, does a nanowire break?

Using molecular dynamics (MD) simulation, we studied the structural transformation and breaking mechanism of a single crystalline copper nanowire under continuous strain. At a certain strain rate, an ensemble of relaxed initial states of the nanowire can preferentially go through one or more paths of deformation. In each deformation path, disordered atoms can be generated at the specific positions of the nanowire, where necking and breaking take place afterward. Such a breaking position is not predetermined; multiple initial states lead to a strain-rate-dependent, statistical distribution of breaking positions.     

Vortex Dynamics in a Superconducting Film with a Kagome and?a?Honeycomb Pinning Landscape

The vortex dynamics in a superconducting thin Al film with a periodic Honeycomb or Kagome array of antidots has been investigated by electrical transport measurements. The large values of the superconducting coherence length and penetration depth of the Al films guarantee a maximum of one flux quantum trapped per pinning site. This allows us to directly compare the experimental results with previous theoretical investigations based on molecular dynamics simulations. For the Kagome lattice, two submatching features not anticipated theoretically at H/H ₁=1/3 and 2/3, where H ₁ is the field at which the number of vortices coincides with the number of pinning sites, are observed. Possible corresponding stable vortex patterns are suggested. For the Honeycomb pinning landscape, the commensurability effects are in agreement with the theoretical expectations. A preliminary analysis of the vortex mobility in this lattice shows the presence of a weak vortex guidance.     

Wavefront-guided correction of ocular aberrations: are phase plate and refractive surgery solutions equal?

Wavefront-guided laser eye surgery has been recently introduced and holds the promise of correcting not only defocus and astigmatism in patients but also higher-order aberrations. Research is just beginning on the implementation of wavefront-guided methods in optical solutions, such as phase-plate-based spectacles, as alternatives to surgery. We investigate the theoretical differences between the implementation of wavefront-guided surgical and phase plate corrections. The residual aberrations of 43 model eyes are calculated after simulated refractive surgery and also after a phase plate is placed in front of the untreated eye. In each case, the current wavefront-guided paradigm that applies a direct map of the ocular aberrations to the correction zone is used. The simulation results demonstrate that an ablation map that is a Zernike fit of a direct transform of the ocular wavefront phase error is not as efficient in correcting refractive errors of sphere, cylinder, spherical aberration, and coma as when the same Zernike coefficients are applied to a phase plate, with statistically significant improvements from 2% to 6%.     

Emergency management: does it have a sufficiently comprehensive understanding of decision-making, process and context?

It is widely recognised in the social and management sciences that the effective support of decision-making requires a multidisciplinary perspective. This trend is also clear in nuclear emergency management (EM). However, communication between disciplines is not easy to maintain in EM contexts when the decision makers (DMs) are likely to be highly stressed. Such circumstances can lead them to revert to the instinctive patterns of perception of their core disciplines, making communication between disciplines difficult and, perhaps, obscuring complex interactions that have not been rehearsed in practice exercises. This paper explores decision making in EM and the nature of the socio-technical issues that will arise, suggesting that despite the lessons of past accidents the research EM community is still not taking a broad enough view of what future incidents may entail.     

Distance between speed humps and pedestrian crossings: does it matter?

Speed humps are a common physical measure installed at pedestrian crossings to reduce vehicle speeds therefore improve the safety and mobility of pedestrians at the crossing.The aim of this study was to determine whether variations in distance between speed humps and pedestrian crossings contribute differently to the safety and mobility of pedestrians and cyclists, especially children and the elderly, and if so, how. Three sites in Sweden were studied, where vehicle speed measurements and video filming at the site resulted in manually coded, road user behaviour of 1972 pedestrians and cyclists.Road user behaviour at three test sites and two comparison sites equipped with speed cushion at distances of about 5 m and 10 m from the pedestrian crossing, i.e. about one or two car lengths, were studied. As vehicle speeds were somewhat lower at the pedestrian crossing when the distance between the speed cushion to the pedestrian crossing was greater, and there were positive aspects regarding the mobility of the pedestrians and cyclists, a greater distance of about 10 m or two car lengths between the hump and the pedestrian crossing is suggested. The present study only covers speed cushions, but the same distance is also regarded as important when installing other types of physical measures to reduce vehicle speed.     

Selective vapor sorption by polymers and cavitands on acoustic wave sensors: is this molecular recognition?

Selectivity patterns for the sorption of organic vapors from the gas phase into cavitand monolayers on acoustic wave sensors are very similar to those seen for sorption of the same vapors by amorphous polymers, demonstrating that the vapor/cavitand selectivity patterns are determined primarily by solubility interactions. The amorphous polymers serve as controls demonstrating that the three-dimensional structure of a cavitand layer is not primarily responsible for the selectivity observed. Binding and selectivity in the examples cited are governed primarily by general dispersion interactions and not by specific oriented interactions that could lead to molecular recognition.     

Information metrics (iMetrics): a research specialty with a socio-cognitive identity?

“Bibliometrics”, “scientometrics”, “informetrics”, and “webometrics” can all be considered as manifestations of a single research area with similar objectives and methods, which we call “information metrics” or iMetrics. This study explores the cognitive and social distinctness of iMetrics with respect to the general information science (IS), focusing on a core of researchers, shared vocabulary and literature/knowledge base. Our analysis investigates the similarities and differences between four document sets. The document sets are drawn from three core journals for iMetrics research (Scientometrics, Journal of the American Society for Information Science and Technology, and Journal of Informetrics). We split JASIST into document sets containing iMetrics and general IS articles. The volume of publications in this representation of the specialty has increased rapidly during the last decade. A core of researchers that predominantly focus on iMetrics topics can thus be identified. This core group has developed a shared vocabulary as exhibited in high similarity of title words and one that shares a knowledge base. The research front of this field moves faster than the research front of information science in general, bringing it closer to Price’s dream.     

Electronic and optical moi? Interference with microchannel plates: artifacts and benefits

The spatial resolution of position-sensitive detectors that use stacks of microchannel plates (MCP's) with high-resolution anodes can be better than 20-mum FWHM [Proc. SPIE 3114, 283-294 (1997)]. At this level of accuracy, channel misalignments of the MCP's in the stack can cause observable moiré interference patterns. We show that the flat-field detector response can have moiré beat pattern modulations of as great as ~27% with periods from as small as a few channel diameters to as great as the size of a MCP multifiber. These modulations, however, may be essentially eliminated by rotation of the MCP's or by a mismatch of the channel sizes. We also discuss how the modulation phenomena can be a useful tool for mapping the metric nonlinearities of MCP detector readout systems. Employing the optical moiré effect, we demonstrate a simple, but effective, technique for evaluation of geometrical deformations simultaneously over a large MCP area. For a typical MCP, with a 60-channel-wide multifiber, we can obtain accuracies of 1.2 mrad for multifiber rotations and twists and 35/(L/p) mrad for channel-long axis distortions (where L/p is MCP thickness to interchannel distance ratio). This technique may be used for the development of MCP x-ray optics, which impose tight limitations on geometrical distortions, which in turn are not otherwise easily measurable with high accuracy.     

Theory of constraints: is it a theory and a good one?

In this study, we attempted to advance the academic dialogue towards establishing TOC as a formal operations management theory, so it can continue improving practice. We link the component parts of the TOC and map the theoretical arrangement to the consensual definitional components and properties of a theory. Also, we examine whether TOC satisfy the virtues of a good theory (uniqueness, parsimony, conservation, generalisability, fecundity, internal consistency, empirical riskiness, and abstraction). Consequently, a practical outcome of our study stems from demonstrating the utility of the goodness criteria as a useful instrument for examining future theories in the field of operations. From a practitioner's standpoint, by establishing a strong theoretical foundation for TOC, we assist managers deploying it to gain better understanding of TOC elements and ultimately avoid implementation failures. Also, we increase the credibility of TOC in the eyes of senior executives. The study concludes by sketching new avenues for future research that have industrial relevance for successful TOC implementation efforts.     

Strength size effects and fracture mechanics: What does the physical evidence say?

Being able to predict the strength of geometrically-similar cracked specimens of different sizes or scales is a fundamental requirement for success for linear elastic fracture mechanics (LEFM). The prediction contained in LEFM is that the strength reduces as the inverse square-root of the scale factor in the plane of the crack: here we review how well this prediction actually agrees with the physical evidence. In particular we examine agreement for materials and configurations exhibiting brittle responses—the situations complying best with the underlying linear elastic assumptions in the theory. The data show that the agreement is not good, even in the most brittle of instances.     

Why does library holding format really matter for book impact assessment?: Modelling the relationship between citations and altmetrics with print and electronic holdings

Scientometrics - Scholarly books are important outputs in some fields and their many publishing formats seem to introduce opportunities to scrutinize their impact. As there is a growing interest in...     

Phase transition in space: how far does a symmetry bend before it breaks?

We extend the theory of symmetry-breaking dynamics in non-equilibrium second-order phase transitions known as the Kibble-Zurek mechanism (KZM) to transitions where the change of phase occurs not in time but in space. This can be due to a time-independent spatial variation of a field that imposes a phase with one symmetry to the left of where it attains critical value, while allowing spontaneous symmetry breaking to the right of that critical borderline. Topological defects need not form in such a situation. We show, however, that the size, in space, of the 'scar' over which the order parameter adjusts as it 'bends' interpolating between the phases with different symmetries follows from a KZM-like approach. As we illustrate on the example of a transverse quantum Ising model, in quantum phase transitions this spatial scale--the size of the scar--is directly reflected in the energy spectrum of the system: in particular, it determines the size of the energy gap.