Shortages in the availability of personal protective face masks during the COVID-19 pandemic required many to fabricate masks and filter inserts from available materials. While the base filtration efficiency of a material is of primary importance when a perfect seal is possible, ideal fit is not likely to be achieved by the average person preparing to enter a public space or even a healthcare worker without fit-testing before each shift. Our findings suggest that parameters including permeability and pliability can play a strong role in the filtration efficiency of a mask fabricated with various filter media, and that the filtration efficiency of loosely fitting masks/respirators against ultrafine particulates can drop by more than 60% when worn compared to the ideal filtration efficiency of the base material. Further, a test method using SARS-CoV-2 virion-sized silica nanoaerosols is demonstrated to assess the filtration efficiency against nanoparticulates that follow air currents associated with mask leakage.

Novel materials with unique or enhanced properties relative to conventional materials are being developed at an increasing rate. These materials are often referred to as advanced materials (AdMs) and they enable technological innovations that can benefit society. Despite their benefits, however, the unique characteristics of many AdMs, including many nanomaterials, are poorly understood and may pose environmental safety and occupational health (ESOH) risks that are not readily determined by traditional risk assessment methods. To assess these risks while keeping up with the pace of development, technology developers and risk assessors frequently employ risk-screening methods that depend on a clear definition for the materials that are to be assessed (e.g., engineered nanomaterial) as well as a method for binning materials into categories for ESOH risk prioritization. The term advanced material lacks a consensus definition and associated categorization or grouping system for risk screening. In this study, we aim to establish a practitioner-driven definition for AdMs and a practitioner-validated framework for categorizing AdMs into conceptual groupings based on material characteristics. Results from multiple workshops and interviews with practitioners provide consistent differentiation between AdMs and conventional materials, offer functional nomenclature for application science, and provide utility for future ESOH risk assessment prioritization. The definition and categorization framework established here serve as a first step in determining if and when there is a need for specific ESOH and regulatory screening for an AdM as well as the type and extent of risk-related information that should be collected or generated for AdMs and AdM-enabled technologies.

We investigate the phase diagram of a system with two layers of an Ising lattice gas at half filling. In addition to the usual intralayer nearest neighbor attractive interaction, there is an interlayer potential J. Under equilibrium conditions, the phase diagram is symmetric under J ! 2J, though the ground states are different. The effects of imposing a uniform external drive, studied by simulation techniques, are dramatic. The mechanisms responsible for such behavior are discussed. [S0031-9007(96)00614-X] PACS numbers: 64.60.Cn, 05.70.Fh, 82.20.Mj Over a decade ago, motivated by the physics of fast ionic conductors, Katz et al. [1] introduced a simple modification to the well known Ising lattice gas [2], so that nonequilibrium steady states may be studied. The dynamics of this model consists of particle hopping, or Kawasaki exchange [3], controlled by the usual Ising Hamiltonian and a thermal bath at temperature T, as well as a bias in one direction so as to describe the effect of a uniform, dc "electric" field E, acting on the "charged" particles. In the ensuing years, many unexpected properties have been discovered in the prototype model and numerous of its variants, and, by now, some are well understood [4]. On the other hand, a few of the surprising results observed in Ref.[1] remain unexplained. An example is the basic question: Why should the critical temperature, T c ͑E͒, increase with E, saturating at about 40% above the Onsager temperature as E ![ 5]? Indeed, one might have predicted a lowering of T c , since large fields should overwhelm the nearest neighbor coupling whenever hops along the field are attempted, so that the system is effectively subjected to an extra noise. Given simulation data and a better understanding of other phenomena displayed by this system, simple arguments in favor of an increased T c emerged. However, to date, there is still no intuitive picture which guides us to the correct behavior. One motivation of our study is to explore similar systems, in order to test which type of argument is successful in "predicting" the qualitative behavior of the novel phase diagram.At an entirely different level, this work is motivated by interesting properties in driven multilayered structures, observed in both physical systems [6] and Monte Carlo simulations [7,8]. In the former, the process of intercalation, where foreign atoms or molecules diffuse into a layered host material, is well suited for modeling by driven, layered lattice gases [8]. On the simulation front, the effects of particle transfer between two decoupled Ising systems, subject to a global conservation law, turn out to be quite intriguing: two transitions were found [7]. As T is lowered, the disordered (D) phase transforms into a state with strips in both layers, reminiscent of two entirely unrelated, yet aligned, single-layer driven systems. We will

We present, for the first time to our knowledge, a sapphire-fiber-based distributed high-temperature sensing system based on a Raman distributed sensing technique. High peak power laser pulses at 532 nm were coupled into the sapphire fiber to generate the Raman signal. The returned Raman Stokes and anti-Stokes signals were measured in the time domain to determine the temperature distribution along the fiber. The sensor was demonstrated from room temperature up to 1200°C in which the average standard deviation is about 3.7°C and a spatial resolution of about 14 cm was achieved.

In this study, we fabricated a p-n junction in a fiber with a phosphorous doped silicon core and fused silica cladding. The fibers were fabricated via a hybrid process of the core-suction and melt-draw techniques and maintained overall diameters ranging from 200 to 900 μm and core diameters of 20–800 μm. The p-n junction was formed by doping the fiber with boron and confirmed via the current-voltage characteristic. The demonstration of a p-n junction in a melt-drawn silicon core fiber paves the way for the seamless integration of optical and electronic devices in fibers.