Local Voids as the Origin of Large-angle Cosmic Microwave Background Anomalies: The Effect of a Cosmological Constant

We explore the large angular scale temperature anisotropies in the cosmic microwave background (CMB) due to homogeneous local dust-filled voids in a flat Friedmann-Robertson-Walker universe with a cosmological constant. In comparison with the equivalent dust-filled void model in the Einstein-de Sitter background, we find that the anisotropy for compensated asymptotically expanding local voids can be larger because second-order effects enhance the linear integrated Sachs-Wolfe (ISW) effect. However, for local voids that expand sufficiently faster than the asymptotic velocity of the wall, the second-order effect can suppress the fluctuation due to the linear ISW effect. A pair of quasi-linear compensated asymptotic local voids with radius (2-3)*10^2 ~h^{-1} Mpc and a matter density contrast ~-0.3 can be observed as cold spots with a temperature anisotropy Delta T/T~O(10^{-5}) that might help explain the observed large-angle CMB anomalies. We predict that the associated anisotropy in the local Hubble constant in the direction of the voids could be as large as a few percent.Comment: 23 pages, 5 figures, version accepted for publication in ApJ with minor revisio

Comparison of stray-light and diffraction-caused crosstalk in free-space optical interconnects

In this paper we investigate for the first time the effect of the crosstalk introduced due to laser beam imaging in a free-space optical interconnect (FSOI) system. Due to the overfill of the transmitter microlens array by the vertical cavity surface emitting laser (VCSEL) beam, one part of the signal is imaged by the adjacent microlens to another channel, possibly far from the intended one. Even though this causes increase in interchannel and intersymbol interference, to our knowledge this issue has been neglected so far. The numerical simulation has been performed using a combination of exact ray tracing and the beam propagation methods. The results show that some characteristics of stray-light crosstalk are similar to that of diffraction-caused crosstalk, where it is strongly dependent on the fill factor of the microlens, array pitch, and the channel density of the system. Despite the similarities, the stray-light crosstalk does not affect by an increase in the interconnection distance. As simulation models for optical crosstalk are numerically intensive, we propose here a crosstalk behavioural model as a useful tool for optimisation and design of FSOIs. We show that this simple model compares favourably with the numerical simulation models

A simple rule for axon outgrowth and synaptic competition generates realistic connection lengths and filling fractions

Neural connectivity at the cellular and mesoscopic level appears very specific and is presumed to arise from highly specific developmental mechanisms. However, there are general shared features of connectivity in systems as different as the networks formed by individual neurons in Caenorhabditis elegans or in rat visual cortex and the mesoscopic circuitry of cortical areas in the mouse, macaque, and human brain. In all these systems, connection length distributions have very similar shapes, with an initial large peak and a long flat tail representing the admixture of long-distance connections to mostly short-distance connections. Furthermore, not all potentially possible synapses are formed, and only a fraction of axons (called filling fraction) establish synapses with spatially neighboring neurons. We explored what aspects of these connectivity patterns can be explained simply by random axonal outgrowth. We found that random axonal growth away from the soma can already reproduce the known distance distribution of connections. We also observed that experimentally observed filling fractions can be generated by competition for available space at the target neurons--a model markedly different from previous explanations. These findings may serve as a baseline model for the development of connectivity that can be further refined by more specific mechanisms.Comment: 31 pages (incl. supplementary information); Cerebral Cortex Advance Access published online on May 12, 200

Angular dependence of the emission wavelength in microactivity organic light-emitting diodes

In this work, we have calculated the emission wavelength dependence on the viewing angle for different combinations of metallic mirrors. The dispersion of the optical functions of ten different metals is fully taken into account using Lorentz oscillator model. The metals have been assigned to a function of top (cathode) or bottom (anode) mirror based on their work function. Refractive index dispersion of organic layers, N,N'-disphenyl-N,N'-bis(3-methylphenyl)-1,1'-disphenyl-4,4'-diamine (TPD) and tris (8-hydroxyquinoline) aluminum (emitting layer) is taken into account via Cauchy model. The change of the emission wavelength with angle has been calculated iteratively-to fully take into account wavelength dependence of indices of refraction and phase change. Calculations have been performed for different hole transport materials and different thickness of the emitting layer

The role of the lateral prefrontal cortex and anterior cingulate in stimulus–response association reversals

Many complex tasks require us to flexibly switch between behavioral rules, associations, and strategies. The prefrontal cerebral cortex is thought to be critical to the performance of such behaviors, although the relative contribution of different components of this structure and associated subcortical regions are not fully understood. We used functional magnetic resonance imaging to measure brain activity during a simple task which required repeated reversals of a rule linking a colored cue and a left/right motor response. Each trial comprised three discrete events separated by variable delay periods. A colored cue instructed which response was to be executed, followed by a go signal which told the subject to execute the response and a feedback instruction which indicated whether to ‘‘hold’’ or ‘‘f lip’’ the rule linking the colored cue and response. The design allowed us to determine which brain regions were recruited by the specific demands of preparing a rule contingent motor response, executing such a response, evaluating the significance of the feedback, and reconfiguring stimulus–response (SR) associations. The results indicate that an increase in neural activity occurs within the anterior cingulate gyrus under conditions in which SR associations are labile. In contrast, lateral frontal regions are activated by unlikely/unexpected perceptual events regardless of their significance for behavior. A network of subcortical structures, including the mediodorsal nucleus of the thalamus and striatum were the only regions showing activity that was exclusively correlated with the neurocognitive demands of reversing SR associations. We conclude that lateral frontal regions act to evaluate the behavioral significance of perceptual events, whereas medial frontal–thalamic circuits are involved in monitoring and reconfiguring SR associations when necessary

A Comparison of Small Signal Modulation Parameter Extraction Techniques for Vertical-Cavity, Surface-Emitting Lasers

The small signal modulation characteristics of a vertical-cavity, surface-emitting laser (VCSEL) are determined using three different measurements: relative intensity noise, frequency response, and high resolution optical spectra. The resonant and damping frequencies were measured, and related rate equation parameters were extracted; excellent agreement was found both between experiment and theory, and amongst the different measurement techniques. The results and procedures are compared, and the findings are presented below

Digital Servitization and Firm Performance: Technology Intensity Approach

Digital servitization provides radical changes in the offer of products from manufacturing firms. The purpose of this paper is to investigate the impact of digital servitization on manufacturing firm performance and demonstrate the role of technology intensity, product-related services, and digital solutions in different industry sectors. This research collected data from 240 manufacturing firms from the Republic of Serbia under the European manufacturing survey from 2018. Multivariate regression analysis was used to test the impact of product-related services and digital solutions on manufacturing firm performance according to technology intensity. The findings show that the impact of digital servitization is more significant with the higher technology intensity level of the industry sector. Furthermore, the results show that Data-based services based on Big Data Analysis have the highest impact on manufacturing firm performance in all categories of technology intensity. Moreover, results from the fixed panel regression show production managers which combination of product-related services along with digital solutions make the highest financial performance according to the technology intensity of the firm

Digital twin control of multi-axis wood CNC machining center based on LinuxCNC

Abstrack: This paper presents an application of an open architecture control system implemented on a multi-axis wood computer numerical control milling machining center, as a digital twin control. The development of the digital twin control system was motivated by research and educational requirements, especially in the field of configuring a new control system by “virtual commissioning”, enabling the validation of the developed controls, program verification, and analysis of the machining process and monitoring. The considered wood computer numerical control (CNC) machining system is supported by an equivalent virtual machine in a computer-aided design and computer-aided manufacturing (CAD/CAM) environment, as well as in the control system, as a digital twin. The configured virtual machines are used for the verification of the machining program and programming system via machining simulation, which is extremely important in multi-axis machining. Several test wood workpieces were machined to validate the effectiveness of the developed control system based on LinuxCNC