Perceived object motion variance across optical contexts

Visual motion computation is challenging under real-world conditions due to continuous contextual changes such as varying lighting conditions and a large range of optical material properties. Due to these changes the retinal optical flow can drastically vary while the physical motion of an object remains constant. Especially materials with high reflective and refractive interactions can cause complex motion patterns. Here we investigate object motion constancy across various optical contexts and if the human visual system compensates for other causal sources in motion.We performed two experiments. In the first experiment observers had to estimate which of two stimuli was rotating faster around the vertical axis. The stimuli were displayed for 500 ms in a 2-IFC staircase design. For the Match stimulus the illumination, material properties and shape were constant. The stimulus was rendered at a high temporal resolution allowing for small rotational speed changes for the staircase design. The Test stimuli varied in ten optical properties (e.g., matte, glossy, anisotropic, translucent), three illumination maps (sunny, cloudy, indoor), and three shapes (knot, cubic, blobby), the rotational speed remained constant. There were three different conditions in the second experiment: 1. unmasked Match and Test stimulus (same as experiment one); 2. masked Test stimulus (circular gaussian mask, masking outer shape contours); 3. masked Test stimulus and masked Match stimulus where the Match stimulus was replaced by horizontally moving 2D pink noise. In this experiment a subset of the optical conditions was used.Expanding on our previously presented work [1], we applied three image-based motion capturing models (Figure 1) to gain deeper insights on motion cues that are predictive of human judgements. The models are Lucas-Kanade (optical flow), RAFT (optical flow DNN), FFV1MT (motion energy). First, we found that there are clear illusory differences of perceived rotational speed with even bigger effects when the circular mask was applied. The transparent material with the refractive index of water is systematically perceived to be rotating faster than other materials across all conditions. We performed an RSA (representational similarity analysis) to compare a range of different metrics across conditions and flow models. We find that the gradient of the optical flow is a particularly good predictor of human performance. The gradient emphasizes local speed changes in the optical flow, for example with moving highlights. Another observation is that Lucas-Kanade is most predictive of human performance under most conditions while RAFT is most stable across materials and closest to the ground truth. Our results further suggest that the human visual system does partially compensate for motion flow effects across optical contexts in object motion.[1] Van Assen, J. J. R., Kawabe, T., & Nishida, S. Y. (2020). Object motion and flow variance across optical contexts. Journal of Vision, 20(11), 458-458.This work has been supported by a Marie-Skłodowska-Curie Actions Individual Fellowship (H2020-MSCA-IF-2019-FLOW) and by JSPS Kakenhi JP20H05957

Outcome of a questionnaire within European pharmaceutical aerosol group (EPAG) companies concerning the implementation of the abbreviated impactor measurement (AIM) concept for the assessment of orally inhaled product (OIP) aerosol aerodynamic particle size properties

The AIM Concept as an augmentation of full resolution cascade impactor (CI) measurements of the aerodynamic properties of aerosols emitted by OIPs has been in existence for about ten years. A previous EPAG-based survey undertaken five years ago indicated significant interest in the approach, particularly for the screening of candidate products in early stage product development. We report the outcome of a further questionnaire with the goals of establishing: (a) the types of AIM-based equipment currently in use; and (b) insight into perceived hurdles towards full implementation within the product lifecycle. Responses were received in October 2016 from 17 out of 22 organizations from people involved directly with the in vitro testing of pressurized metered dose inhaler (pMDI) and dry powder inhaler (DPI) products. The survey has shown that the AIM concept has sufficient popularity within the EPAG respondent organizations to be considered a viable augmentation to existing full resolution CI methodology. The main conclusions are: (1) The Fast Screening Andersen (FSA), reduced Next Generation Impactor (rNGI) and Fast Screening Impactor (FSI) are all used as AIM-based impactor configurations for both dry powder inhaler (DPI) and pressurized metered dose inhaler (pMDI) applications; (2) AIM-based methods are used almost entirely for the early development phase of the OIP life cycle; (3) Organizations in general do not have confidence to use the AIM concept more widely in the product life cycle whilst no compendial/regulatory guidance is available to provide standard procedures and precautions/regulatory acceptance respectively

A European Pharmaceutical Aerosol Group (EPAG)-led cross-industry assessment of inlet flow rate profiles of compendial DPI test systems: Part 1 – experimental data

We report outcomes from an EPAG-led cross-industry study, characterizing flow rate/elapsed-time profiles of equipment used for testing dry powder inhalers (DPIs). A thermal mass flow sensor was used by nine organizations in a round-robin approach to record inlet flow rate-time profiles of individual participant compendial test systems (TS) including either sample collection tubes (SCT) or a cascade impactor (either the Andersen 8-stage non-viable impactor, ACI, or the Next Generation Impactor, NGI) equipped with USP/PhEur induction port and pre-separator. An inlet orifice generated a 4-kPa pressure drop at each of the target flow rates (30, 60 and 90 L/min), simulating a pressure drop typical for high-, medium- and low-resistance DPIs respectively. Rise times to 90% of these target flow rates (t90) were longest with largest internal dead volume and followed the order NGI>ACI >SCT>TS. When the surrogate DPI (4-kPa orifice) was absent, t90 values generally lengthened with increasing target flow rate. In contrast, the opposite behaviour was observed when the surrogate DPI was present. A flow acceleration parameter was also calculated, expressed as the slope between the 20% and 80% flow rates of each final steady flow value (slopet20/t80). Greater flow acceleration occurred at higher final flow rates, irrespective of apparatus, but the presence of the surrogate DPI was associated with slower flow acceleration. These flow rate-rise time profiles will be useful for those involved in evaluating equipment for characterizing both existing and new DPIs

Numerical study of jets produced by conical wire arrays on the Magpie pulsed power generator

The aim of this work is to model the jets produced by conical wire arrays on the MAGPIE generator, and to design and test new setups to strengthen the link between laboratory and astrophysical jets. We performed the modelling with direct three-dimensional magneto-hydro-dynamic numerical simulations using the code GORGON. We applied our code to the typical MAGPIE setup and we successfully reproduced the experiments. We found that a minimum resolution of approximately 100 is required to retrieve the unstable character of the jet. We investigated the effect of changing the number of wires and found that arrays with less wires produce more unstable jets, and that this effect has magnetic origin. Finally, we studied the behaviour of the conical array together with a conical shield on top of it to reduce the presence of unwanted low density plasma flows. The resulting jet is shorter and less dense.Comment: Accepted for publication in Astrophysics & Space Science. HEDLA 2010 conference procedings. Final pubblication will be available on Springe

High Pressure Thermoelasticity of Body-centered Cubic Tantalum

We have investigated the thermoelasticity of body-centered cubic (bcc) tantalum from first principles by using the linearized augmented plane wave (LAPW) and mixed--basis pseudopotential methods for pressures up to 400 GPa and temperatures up to 10000 K. Electronic excitation contributions to the free energy were included from the band structures, and phonon contributions were included using the particle-in-a-cell (PIC) model. The computed elastic constants agree well with available ultrasonic and diamond anvil cell data at low pressures, and shock data at high pressures. The shear modulus $c_{44}$ and the anisotropy change behavior with increasing pressure around 150 GPa because of an electronic topological transition. We find that the main contribution of temperature to the elastic constants is from the thermal expansivity. The PIC model in conjunction with fast self-consistent techniques is shown to be a tractable approach to studying thermoelasticity.Comment: To be appear in Physical Review

On the algebraic K-theory of the complex K-theory spectrum

Let p>3 be a prime, let ku be the connective complex K-theory spectrum, and let K(ku) be the algebraic K-theory spectrum of ku. We study the p-primary homotopy type of the spectrum K(ku) by computing its mod (p,v_1) homotopy groups. We show that up to a finite summand, these groups form a finitely generated free module over a polynomial algebra F_p[b], where b is a class of degree 2p+2 defined as a higher Bott element.Comment: Revised and expanded version, 42 pages

Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure

Ab initio total-energy density-functional methods with supercell models have been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and Au(100) surfaces. The atomic geometries of the surfaces and the preferred bonding sites of the bromine have been determined. The bonding character of bromine with the substrates has also been studied by analyzing the electronic density of states and the charge transfer. The calculations show that while the four-fold hollow-site configuration is more stable than the two-fold bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on the Au(100) surface. The one-fold on-top configuration is the least stable configuration on both surfaces. It is also observed that the second layer of the Ag substrate undergoes a small buckling as a consequence of the adsorption of Br. Our results provide a theoretical explanation for the experimental observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres

Thermal and Hadrochemical Equilibration in Nucleus-Nucleus Collisions at the SPS

The currently available set of hadron abundances at the SPS for central S+Au(W,Pb) collisions is compared to predictions from a scenario assuming local thermal and hadrochemical equilibrium. The data are consistent with a freeze-out temperature T = 160-170 MeV. Spectra are consistent with this temperature range and a moderate transverse expansion. The freeze-out points at the AGS and SPS are found to be close to the phase boundary between a hadron gas and an ideal quark-gluon phase.Comment: 14 pages + 3 figures. Paper replaced with version accepted for publication in Phys. Lett.