Measurement of particle adhesion force and effective contact radius via centrifuge equipped with horizontal and vertical substrates

A centrifugal method was used to analyze and evaluate particle–surface interactions. Particles with count median diameters of 9.7, 14.5, and 32.8 μm were removed from horizontally and vertically mounted metal substrates. A point-mass model is conventionally used to analyze the forces exerted on particles during centrifugation. Conversely, in this study, a rigid-body model was employed considering the particle diameter and effective contact radius between a particle and substrate. As the moments of force exerted on the particles on the horizontal and vertical substrates were simultaneously formulated, the adhesion force and contact radius could be determined based on the particle diameter and angular velocities obtained at a given removal fraction. It was quantitatively demonstrated that as the particle diameter, relative humidity, and/or initial load increase and surface roughness decreases, the adhesion force increases. Furthermore, the contact radius increased as the particle diameter and/or surface roughness increased

Evaluation of mechanical properties of nanoparticles using a constant-volume shear tester

Nanoparticles have advantageous small-size and surface effects that impart them with unique mechanical properties. To evaluate these properties, a constant-volume shear tester that can precisely measure stresses on the shear plane was used. Six samples, namely, hydrophilic and hydrophobic silica, alumina, and titania nanoparticles, were prepared for the shear tests. For each sample, a single shear test provided the void fraction, stress relaxation ratio, stress transmission ratio, powder yield locus, consolidation yield locus, critical state line, shear cohesion, and flow function. All the tests were conducted under ambient conditions using powder beds, in which the void fractions were in the range of 0.89–0.96. A series of analyses demonstrated that the hydrophilic nanoparticles have lower flowability than the hydrophobic nanoparticles, indicating that moisture on the surface increases the cohesion and inhibits the flow

Detailed analysis of particle–substrate interaction based on a centrifugal method

The interaction between particles and inclined substrates in a centrifuge was investigated theoretically and experimentally. First, the balance of the force acting on a particle adhering to the substrate, with an inclination angle from 0 to 90° to the horizontal, was formulated separately in the normal and tangential directions. The adhesion force was then derived based on the point-mass model as a function of the angular velocity. Next, the balance of the moments of the forces acting on a particle adhering to the substrate was formulated; theoretical equations for the adhesion force and the effective contact radius were then derived from the angular velocities, obtained at any two inclination angles, based on the rigid-body model. Finally, the removal fraction curves of spherical/nonspherical particles with median diameters of less than 10 µm were experimentally obtained by increasing the angular velocity at each inclination angle. The experimentally obtained angular velocities were substituted into the theoretical equations to compare the point-mass and rigid-body models. The effects of the particle shape on the adhesion force and effective contact radius and that of the inclination angle on the removal fraction curves based on the theoretical equation were also investigated

Inhibition-excitation balance in the parietal cortex modulates volitional control for auditory and visual multistability

International audiencePerceptual organisation must select one interpretation from several alternatives to guide behaviour. Computational models suggest that this could be achieved through an interplay between inhibition and excitation across competing types of neural population coding for each interpretation. Here, to test for such models, we used magnetic resonance spectroscopy to measure non-invasively the concentrations of inhibitory γ-aminobutyric acid (GABA) and excitatory glutamate-glutamine (Glx) in several brain regions. Human participants first performed auditory and visual multistability tasks that produced spontaneous switching between percepts. Then, we observed that longer percept durations during behaviour were associated with higher GABA/Glx ratios in the sensory area coding for each modality. When participants were asked to voluntarily modulate their perception, a common factor across modalities emerged: the GABA/Glx ratio in the posterior parietal cortex tended to be positively correlated with the amount of effective volitional control. Our results provide direct evidence implicating that the balance between neural inhibition and excitation within sensory regions resolves perceptual competition. This powerful computational principle appears to be leveraged by both audition and vision, implemented independently across modalities, but modulated by an integrated control process. Perceptual multistability describes an intriguing situation, whereby an observer reports random changes in conscious perception for a physically unchanging stimulus 1,2. Multistability is a powerful tool with which to probe perceptual organisation, as it highlights perhaps the most fundamental issue faced by perception for any reasonably complex natural scene. And because the information encoded by sensory receptors is never sufficient to fully specify the state of the outside world 3 , at each instant perception must always choose between a number of competing alternatives. In realistic situations, the process produces a stable and useful representation of the world. In situations with intrinsically ambiguous information, the same process is revealed as multistable perception. A number of theoretical models have converged to pinpoint the generic computational principles likely to be required to explain multistability, and hence perceptual organisation 4-9. All of these models consider three core ingredients: inhibition between competing neural populations, adaptation within these populations, and neuronal noise. The precise role of each ingredient and their respective importance is still being debated. Noise is introduced to induce fluctuations in each population and initiate the stochastic perceptual switching in some models 7-9 , whereas switching dynamics are solely determined by inhibition in others 5,6. Functional brain imaging in humans has provided results qualitatively compatible with those computational principles at several levels of the visual processing hierarchy 10. But, for most functional imaging techniques in humans such as fMRI or MEG/EEG, change

Development of a New Measurement Method to Evaluate the Physical Properties of Granules for Dry Powder Inhalation Produced by New Spouted Bed Type Binderless Granulator

The spouted bed type of binderless granulator is one of the most appropriate methods available for producing granules of dry powder inhalation (DPI) from cohesive fine powder. However the compressive strength of produced granule is too small to be measure by conventional method. In this work a new apparatus was developed to evaluate the strength of such a soft granule. Load and displacement curve of the granule were measured by new method of compressive strength measurement. To observe the compression process of the granule, photographs were taken with a microscopic camera. It was clarified that this measurement method was remarkably useful to evaluate the compressive strength of soft granule

Comparison of FDTD and Ray-Tracing Method for Site Attenuation Analysis of Compact Anechoic Chamber

In this paper, the FDTD method and the ray tracing method have been applied to analyze the site attenuation of a compact anechoic chamber in the frequency range from 30 MHz to 200 MHz. For FDTD analysis, half-wave dipole antenna, shortened dipole antenna and EM absorber were modeled by using large-cells, which were larger than the diameter of antenna element and the thickness of EM absorber. For verification, the site attenuation of a compact anechoic chamber was measured and compared with the calculated values through the FDTD method and the ray tracing method. As the results, the calculated values through the FDTD method agreed well with the measured ones within 2 dB and the calculated values through the ray tracing method have larger deviation in the frequency range less than 180 MHz.2004 International Symposium on Electromagnetic Compatibility (EMC\u2704/Sendai), June 1-4, 2004, Sendai International Center, Sendai, Japa

Cognitive clustering in schizophrenia patients, their first-degree relatives and healthy subjects is associated with anterior cingulate cortex volume

Cognitive impairments are a core feature in schizophrenia patients (SCZ) and are also observed in first-degree relatives (FR) of SCZ. However, substantial variability in the impairments exists within and among SCZ, FR and healthy controls (HC). A cluster-analytic approach can group individuals based on profiles of traits and create more homogeneous groupings than predefined categories. Here, we investigated differences in the Brief Assessment of Cognition in Schizophrenia (BACS) neuropsychological battery (six subscales) among SCZ, unaffected FR and HC. To identify three homogeneous and meaningful cognitive groups regardless of categorical diagnoses (SCZ, FR and HC), cognitive clustering was performed, and differences in the BACS subscales among the cognitive cluster groups were investigated. Finally, the effects of diagnosis and cognition on brain volumes were examined. As expected, there were significant differences in the five BACS subscales among the diagnostic groups. The cluster-analytic approach generated three meaningful subgroups: (i) neuropsychologically normal, (ii) intermediate impaired and (iii) widespread impaired. The cognitive subgroups were mainly affected by the clinical diagnosis, and significant differences in all BACS subscales among clusters were found. The effects of the diagnosis and cognitive clusters on brain volumes overlapped in the frontal, temporal and limbic regions. Frontal and temporal volumes were mainly affected by the diagnosis, whereas the anterior cingulate cortex (ACC) volumes were affected by the additive effects of diagnosis and cognition. Our findings demonstrate a cognitive continuum among SCZ, FR and HC and support the concept of cognitive impairment and the related ACC volumes as intermediate phenotypes in SCZ

Construction of possible integrated predictive index based on EGFR and ANXA3 polymorphisms for chemotherapy response in fluoropyrimidine-treated Japanese gastric cancer patients using a bioinformatic method

Selected genetic and clinical parameters of gastric cancer patients. (XLS 33 kb