Anisotropic random resistor networks: a model for piezoresistive response of thick-film resistors

A number of evidences suggests that thick-film resistors are close to a metal-insulator transition and that tunneling processes between metallic grains are the main source of resistance. We consider as a minimal model for description of transport properties in thick-film resistors a percolative resistor network, with conducting elements governed by tunneling. For both oriented and randomly oriented networks, we show that the piezoresistive response to an applied strain is model dependent when the system is far away from the percolation thresold, while in the critical region it acquires universal properties. In particular close to the metal-insulator transition, the piezoresistive anisotropy show a power law behavior. Within this region, there exists a simple and universal relation between the conductance and the piezoresistive anisotropy, which could be experimentally tested by common cantilever bar measurements of thick-film resistors.Comment: 7 pages, 2 eps figure

Taxonomic resolution of different 16S rRNA variable regions varies strongly across plant-associated bacteria

Plant-microbiome research plays a pivotal role in understanding the relationships between plants and their associated microbial communities, with implications for agriculture and ecosystem dynamics. Metabarcoding analysis on variable regions of the 16S ribosomal RNA (rRNA) gene remains the dominant technology to study microbiome diversity in this field. However, the choice of the targeted variable region might affect the outcome of the microbiome studies. In our in silico analysis, we have evaluated whether the targeted variable region has an impact on taxonomic resolution in 16 plant-related microbial genera. Through a comparison of 16S rRNA gene variable regions with whole-genome data, our findings suggest that the V1–V3 region is generally a more suitable option than the widely used V3–V4 region for targeting microbiome analysis in plant-related genera. However, sole reliance on one region could introduce detection biases for specific genera. Thus, we are suggesting that while transitioning to full-length 16S rRNA gene and whole-genome sequencing for plant-microbiome analysis, the usage of genus-specific variable regions can achieve more precise taxonomic assignments. More broadly, our approach provides a blueprint to identify the most discriminating variable regions of the 16S rRNA gene for genera of interest

Open-Access, Low-Magnetic-Field MRI System for Lung Research

An open-access magnetic resonance imaging (MRI) system is being developed for use in research on orientational/gravitational effects on lung physiology and function. The open-access geometry enables study of human subjects in diverse orientations. This system operates at a magnetic flux density, considerably smaller than the flux densities of typical other MRI systems, that can be generated by resistive electromagnet coils (instead of the more-expensive superconducting coils of the other systems). The human subject inhales air containing He-3 or Xe-129 atoms, the nuclear spins of which have been polarized by use of a laser beam to obtain a magnetic resonance that enables high-resolution gas space imaging at the low applied magnetic field. The system includes a bi-planar, constant-current, four-coil electromagnet assembly and associated electronic circuitry to apply a static magnetic field of 6.5 mT throughout the lung volume; planar coils and associated circuitry to apply a pulsed magnetic-field-gradient for each spatial dimension; a single, detachable radio-frequency coil and associated circuitry for inducing and detecting MRI signals; a table for supporting a horizontal subject; and electromagnetic shielding surrounding the electromagnet coils

Channel Capacities for Different Antenna Arrays with Various Transmitting Angles in Tunnels

[[abstract]]This paper focuses on the research of channel capacity of multiple-input multipleoutput (MIMO) system with different transmitting angles in straight and curvy tunnels.Araytracing technique is developed to calculate channel frequency responses for tunnels, and the channel frequency response is further used to calculate corresponding channel capacity. The channel capacities are calculated based on the realistic environment. The channel capacities of MIMO long term evolution system using spatial and polar antenna arrays by different transmitting angles are computed. Numerical results show that, The channel capacity for transmitting angle at 15◦ is largest compared to the other angles in the tunnels. Moreover, the channel capacity of polar array is better than that of spatial array both in the straight and curvy tunnels. Besides, the channel capacity for the tunnels with traffic is larger than that without traffic. Finally, it isworth noting that in these cases the presentwork provides not only comparative information but also quantitative information on the performance reduction.[[notice]]補正完畢[[incitationindex]]SC

Segregated tunneling-percolation model for transport nonuniversality

We propose a theory of the origin of transport nonuniversality in disordered insulating-conducting compounds based on the interplay between microstructure and tunneling processes between metallic grains dispersed in the insulating host. We show that if the metallic phase is arranged in quasi-one dimensional chains of conducting grains, then the distribution function of the chain conductivities g has a power-law divergence for g -> 0 leading to nonuniversal values of the transport critical exponent t. We evaluate the critical exponent t by Monte Carlo calculations on a cubic lattice and show that our model can describe universal as well nonuniversal behavior of transport depending on the value of few microstructural parameters. Such segregated tunneling-percolation model can describe the microstructure of a quite vast class of materials known as thick-film resistors which display universal or nonuniversal values of t depending on the composition.Comment: 8 pages, 5 figures (Phys. Rev. B - 1 August 2003)(fig1 replaced

Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels

An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments

NLRP1 variant M1184V decreases inflammasome activation in the context of DPP9 inhibition and asthma severity.

BackgroundNLRP1 is an innate immune sensor that can form cytoplasmic inflammasome complexes. Polymorphisms in NLRP1 are linked to asthma; however, there is currently no functional or mechanistic explanation for this.ObjectiveWe sought to clarify the role of NLRP1 in asthma pathogenesis.MethodsResults from the GALA II cohort study were used to identify a link between NLRP1 and asthma in Mexican Americans. In vitro and in vivo models for NLRP1 activation were applied to investigate the role of this inflammasome in asthma at the molecular level.ResultsWe document the association of an NLRP1 haplotype with asthma for which the single nucleotide polymorphism rs11651270 (M1184V) individually is the most significant. Surprisingly, M1184V increases NLRP1 activation in the context of N-terminal destabilization, but decreases NLRP1 activation on dipeptidyl peptidase 9 inhibition. In vitro studies demonstrate that M1184V increases binding to dipeptidyl peptidase 9, which can account for its inhibitory role in this context. In addition, in vivo data from a mouse model of airway inflammation reveal a protective role for NLRP1 inflammasome activation reducing eosinophilia in this setting.ConclusionsLinking our in vitro and in vivo results, we found that the NLRP1 variant M1184V reduces inflammasome activation in the context of dipeptidyl peptidase 9 inhibition and could thereby increase asthma severity. Our studies may have implications for the treatment of asthma in patients carrying this variant of NLRP1

Piezoresistivity and conductance anisotropy of tunneling-percolating systems

Percolating networks based on interparticle tunneling conduction are shown to yield a logarithmic divergent piezoresistive response close to the critical point as long as the electrical conductivity becomes nonuniversal. At the same time, the piezoresistivity or, equivalently, the conductivity anisotropy exponent $\lambda$ remains universal also when the conductive exponent is not, suggesting a purely geometric origin of $\lambda$. We discuss our results in relation to the nature of transport for a variety of materials such as carbon-black--polymer composites and RuO_2-glass systems which show nonuniversal transport properties and coexistence between tunneling and percolating behaviors.Comment: 6 pages, 3 figures, Added discussion on experiment