Monte-Carlo Simulation of Pulsed Laser Deposition

Using the Monte Carlo method, we have studied the pulsed laser deposition process at the sub-monolayer regime. In our simulations, dissociation of an atom from a cluster is incorporated. Our results indicate that the pulsed laser deposition resembles molecular beam epitaxy at very low intensity, and that it is characteristically different from molecular beam epitaxy at higher intensity. We have also obtained the island size distributions. The scaling function for the island size distribution for pulsed laser deposition is different from that of molecular beam epitaxy.Comment: 15 pages, 8 figure

Grand challenges for aerosol science and technology

The Grand Challenges Workshop for Aerosol Science and Technology was organized for the International Aerosol Conference (IAC), in St Louis, September 2–7, 2018. The purpose of the workshop was to identify “Grand Challenges” for aerosol science and technology in the next decade and thereby indicate a viable research road map for the aerosol community

Explicit expressions for the minimum efficiency and most penetrating particle size of Nuclepore filters

Nuclepore filters are capillary pore membrane filters with an array of microscopic cylindrical holes of uniform diameters. Their structure is suitable for particle collection and ensuing offline analyses, therefore they are being widely used for exposure assessment of engineered nanoparticles, ambient PM2.5, virus, bacteria, asbestos, etc., as well as in powder manufacturing industries. However, there exists a particle size range in which all the filtration capture mechanisms are not effective. This size is the most penetrating particle size (MPPS), which corresponds to the minimum efficiency (ME) of the filter. Both MPPS and ME are important parameters for a user to select an adequate Nuclepore filter and preferred operating conditions. For rapid estimation of the MPPS and ME, we derived their explicit expressions by simplifying the formulas for the impaction, diffusion and interception deposition and differentiating the combined efficiency with respect to the particle size. The comparison between the experimental data and the prediction from the explicit expressions shows the explicit expressions can provide MPPS for a wide range of filter properties (pore radius, porosity and length) and filtration conditions (particle density, face velocity and temperature). The ME can also be estimated satisfactorily when a simplified term of filter surface diffusion deposition is further considered. By the explicit expressions of MPPS and ME, a quick screening for selecting a Nuclepore filter with the proper properties and suitable filtration conditions can be easily achieved. From the theoretical point of view, the explicit expressions facilitate better understanding of the effects of filter properties and conditions on the filtration characteristic

Interlaboratory comparison to evaluate the methodology for determination of the media filtration efficiency against nanoparticles

Current international standards dealing with efficiency test for filters and filter media focus on measurement of the minimum efficiency at the most penetrating particle size. The available knowledge and instruments provide a solid base for development of test methods to determine the effectiveness of filtration media against airborne nanoparticles down to single-digit nanometer range. An interlaboratory evaluation was performed in the framework of the European Mandate M/461 activities, within the Technical Committee 195 of European Committee for Standardization (CEN/TC195). The purpose was to develop a methodology to determine effectiveness of filtration media against air-borne particles in the 3 – 500 nm range. Five different laboratories (Camfil, ETH/Empa, Politecnico di Torino, University of Minnesota, Unifil) participate in the round robin test in order to verify the repeatability and reproducibility of the test method. The qualification of test rig and apparatus was performed prior of the filtration efficiency and air flow resistance measurement tests.Twilled dutch weave wire mesh was chosen to perform the validation filtration efficiency tests so as to ensure high uniformity of the samples being tested by each different laboratory. We present the experimental data with the discussion about their validity

Interatomic exchange coupling of BCC iron

We performed first-principle calculations on the exchange interaction (EI) between atoms in BCC-Fe strained volumetrically. Our results show that the volume-dependence of the EI deviates considerably from the Bethe-Slater curve. This behavior is discussed in terms of the on-site and/or inter-site direct exchange interactions between electrons.Comment: 22 pages, 7 figure

Resistance of MLL–AFF1-positive acute lymphoblastic leukemia to tumor necrosis factor-alpha is mediated by S100A6 upregulation

Mixed-lineage leukemia (MLL)–AFF1 (MLL–AF4)-positive acute lymphoblastic leukemia (ALL) is associated with poor prognosis, even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The resistance to graft-versus-leukemia (GVL) effects may be responsible for the poor effect of allo-HSCT on MLL–AFF1-positive ALL. Cytotoxic effector mechanisms mediated by tumor necrosis factor-alpha (TNF-α) was reported to contribute to the GVL effect. We showed that MLL–AFF1-positive ALL cell lines are resistant to TNF-α. To examine the mechanism of resistance to TNF-α of MLL–AFF1-positive leukemia, we focused on S100A6 as a possible factor. Upregulation of S100A6 expression and inhibition of the p53–caspase 8–caspase 3 pathway were observed only in MLL–AFF1-positive ALL cell lines in the presence of TNF-α. The effect of S100A6 on resistance to TNF-α by inhibition of the p53–caspase 8–caspase 3 pathway of MLL–AFF1-positive ALL cell lines were also confirmed by analysis using small interfering RNA against S100A6. This pathway was also confirmed in previously established MLL–AFF1 transgenic mice. These results suggest that MLL–AFF1-positive ALL escapes from TNF-α-mediated apoptosis by upregulation of S100A6 expression, followed by interfering with p53–caspase 8–caspase 3 pathway. These results suggest that S100A6 may be a promising therapeutic target for MLL–AFF1-positive ALL in combination with allo-HSCT

Streaming 3D Meshes Using Spectral Geometry Images

National Research Foundation (NRF) Singapor