Electrodynamic Concentration of Non-ferrous Metallic Particles in the Moving Gas-powder Stream: Mathematical Modeling and Analysis

This paper presents theory, modeling, and analysis of a novel electrodynamic concentration approach for submillimeter-sized conductive metal particles focusing in moving gas-powder stream. Such method is of particular interest in blown-powder feeding fabrication industry (e.g., powder-fed additive manufacturing) to generate a tightly focused powder stream. Conceptual design of a concentration generator is proposed with two different configurations: The doublet Halbach permanent magnet quadrupoles (doublet-Halbach-PMQs) and the doublet electromagnet quadrupoles (doublet-EMQs). Analytical models for magnetic forces and concentration angles were built. Numerical calculations were conducted for pure aluminum particles with a radius of 50 150 μm. The particles with a radius of R_{p} = 300 μm can be concentrated with more than 15∘ angle at the frequency of 600 kHz. Therefore, the proposed doublet-EMQs configuration has a great potential to generate a narrowed and finely focused powder stream in the blown-powder feeding fabrication process

HVOF and laser cladded Fe-Cr-B coating in simulated biomass combustion: microstructure and fireside corrosion

Biomass is often considered as a low carbon alternative to fossil fuels in the power industry. However the heat exchangers in biomass plants can suffer from chloride based aggressive fireside corrosion. A commercially available amorphous Fe-Cr-B alloy was deposited onto a stainless steel substrate by HVOF thermal spray and laser cladding. The controlled environment corrosion tests were conducted in a HCl rich environment at 700°C for 250 h with and without KCl deposits. The samples were examined with XRD, SEM and EDX mapping to understand the corrosion mechanisms. In the absence of any deposits, the amorphous HVOF coating performed very well with a thin oxide growth whereas the crystalline laser cladding suffered from ~350 μm metal loss. The scales were composed of MnWO₄, Fe₂O₃, Fe₃O₄ and Cr₂O₃. When a KCl deposit was present, the HVOF sprayed coating delaminated from the substrate and MnCl₂ was found in the scale

An Analytical Model to Predict and Minimize the Residual Stress of Laser Cladding Process

Laser Cladding is one of the advanced thermal techniques used to repair or modify the surface properties of high value components such as tools, military and aerospace parts. Tensile residual stresses are formed in the thermally treated area of this process. This work focuses on to find out key factors of formation and minimization of tensile residual stresses in dissimilar materials. In order to predict the tensile residual stress, one dimensional analytical model has been adopted. Four cladding materials (Al2O3, TiC, TiO2, ZrO2) on the H13 tool steel substrate and a range of preheating temperature of the substrate, from 300K to 1200K, have been investigated. The thermal strain and Young’s modulus are found as key factors of formation and minimization of residual stresses. Additionally, the investigation of preheating temperature of the substrate showed the reduction of residual stress with increasing the preheating temperature of the substrate

Microstructure and Phase Formation in a Rapidly Solidified Laser-Deposited Ni-Cr-B-Si-C Hardfacing Alloy

In this study, microstructural evolutions and phase selection phenomena during laser deposition of a hardfacing Ni-Cr-B-Si-C alloy at different processing conditions are experimentally investigated. The results show that even minor variations in the thermal conditions during solidification can modify the type and morphology of the phases. Higher undercoolings obtained at faster cooling rates suppressed the primary borides and encouraged floret-shape mixtures of Ni and Cr5B3 via a metastable reaction. Variations in the boride phases are discussed in terms of nucleation-and growth-controlled phase selection mechanisms. These selection processes also influenced the nature and proportion of the Ni-B-Si eutectics by changing the amount of the boron available for the final eutectic reactions. The results of this work emphasize the importance of controlling the cooling rate during deposition of these industrially important alloys using laser beam or other rapid solidification techniques. (C) The Minerals, Metals & Materials Society and ASM International 201

Inhaled calcilytics: effects on airway inflammation and remodeling

Chronic obstructive pulmonary disease (COPD) is a major cause of mortality and there is a lack of available drugs that reduce the decline in lung function seen with disease progression. Therefore, there is clearly an unmet need for new therapeutics. Previously, we have shown that calcium sensing receptor (CaSR) activation elicits airways hyper-responsiveness and inflammation in pre-clinical in vivo murine models of asthma. However, the role of CaSR in the progression of COPD is currently unknown. In this article, a role for CaSR and topical calcilytic therapies will be proposed and discussed to reduce COPD pathogenesis and disease progression. The proposal is supported by new data on the anti-inflammatory effects of the inhaled negative allosteric CaSR modulator or calcilytic, NPS89636. The effects of NPS89636 were studied in an in vivo model of COPD induced in guinea pigs by inhalation of lipopolysaccharide (LPS); as in human subjects with COPD, pulmonary inflammation in the guinea pig lungs were shown to be insensitive to inhaled corticosteroids. Here, we show that treatment with NPS89636 reduced inflammation, specifically leukocyte and neutrophil infiltration, in the airways of LPS-treated animals. In addition, calcilytic treatment reduced lung interstitial wall thickening. These effects were unlikely attributable to off-target calcilytic actions on the parathyroid glands, as free ionized blood calcium levels were not altered for up to 24 hours after calcilytic inhalation. Together, these observations suggested that topically delivered calcilytics may represent a novel treatment strategy for COPD

The role and uses of antibodies in COVID-19 infections: a living review

Coronavirus disease 2019 has generated a rapidly evolving field of research, with the global scientific community striving for solutions to the current pandemic. Characterizing humoral responses towards SARS-CoV-2, as well as closely related strains, will help determine whether antibodies are central to infection control, and aid the design of therapeutics and vaccine candidates. This review outlines the major aspects of SARS-CoV-2-specific antibody research to date, with a focus on the various prophylactic and therapeutic uses of antibodies to alleviate disease in addition to the potential of cross-reactive therapies and the implications of long-term immunity

Selective laser sintering of calcium polyphosphate - Polyvinyl alcohol for biomedical applications

It is widely recognized that layered manufacturing techniques have the potential to make an important contribution in medicine. One of the most exciting areas of their application is the production of the bone-interfacing implants currently used in orthopaedics and dentistry. This article studies the laser sintering of a mixture of Calcium Polyphosphate (CPP) and Polyvinyl Alcohol (PVA) to make structures with possible applications in such areas. An experimental study of the creation of the green part is performed to identify the effects of different process parameters such as laser power and scanning speed. The work indicated that the CPP-PVA sintered layer thickness can be adjusted by controlling the laser sintering process parameters. The fabricated samples can be either utilized as composite bio-structures or considered as green parts for post-densification through conventional sintering