Phase‐Field Simulation of Solidification and Solid‐State Transformations in Multicomponent Steels

Calculating microstructures for technical materials is an ambitious task which not only implies different length scales but also the complex thermodynamic properties of multicomponent and multiphase alloys. We report some of the recent progress in simulating microstructure evolution in multicomponent steels using the multiphase‐field software MICRESS®. Several applications are reviewed in order to demonstrate the current status of applied phase‐field techniques.     

Role of the plasminogen activator and matrix metalloproteinase systems in epidermal growth factor- and scatter factor-stimulated invasion of carcinoma cells

Normal as well as neoplastic cells traverse extracellular matrix barriers by mobilizing proteolytic enzymes in response to epidermal growth factor (EGF)-EGF receptor (EGFR) or hepatocyte growth factor/scatter factor (SF)-c-Met interactions. The plasminogen activator-plasminogen axis has been proposed to play a key role during cell invasion, but the normal development of plasminogen activator- as well as that of plasminogen-deficient mice supports the existence of alternate proteolytic systems that permit cells to traverse extracellular matrix barriers. To characterize the role that matrix-degrading proteinases play in EGF- or SF-stimulated invasion, a human squamous carcinoma cell line (UM-SCC-1) was triggered atop the matrices of type I collagen or human dermal explants in a three-dimensional culture system. During EGF- or SF-induced invasion, UM-SCC-1 cells expressed urokinase-type plasminogen activator (uPA) and uPA receptor as well as the matrix metalloproteinases (MMPs), membrane-type MMP-1, collagenase 1, stromelysin 1, and gelatinase B. Despite the presence of a positive correlation between uPA receptor-uPA expression and growth factor-stimulated invasion, UM-SCC-1 invasion was not affected by inhibitors directed against the plasminogen activator-plasminogen axis. In contrast, both recombinant and synthetic MMP inhibitors completely suppressed invasion by either EGF- or SF-stimulated cells without affecting either proteinase expression or cell motility across collagen-coated surfaces. These data demonstrate that MMPs, but not the plasminogen activator-plasmin system, can directly regulate the ability of either EGF- or SF-stimulated tumor cells to invade interstitial matrix barriers.     

The production of porous glassy carbon membranes from swift heavy ion irradiated Kapton

A porous glassy carbon membrane was obtained by first producing ion tracks in a polymeric Kapton film by irradiation with high energy krypton or xenon ions. Pores are formed by selective chemical etching along the ion tracks, and then the film was converted to glassy carbon by heat treatment at 1000 °C under an inert atmosphere. The process yields a self-supported glassy carbon thin membrane. The density of the pores in the membrane depends on the ion irradiation fluence, and the length, diameter and shape of the pores could be controlled by the ion energy and etching procedure.     

Introduction to a tough,strong and stable Ce-TZP/MgAl2O4 composite for biomedical applications

The processing of a new ceria-doped tetragonal zirconia polycrystal-based (Ce-TZP) composite and its microstructural and mechanical features are presented. Slip casting and die pressing were used to process commercially available Ce-TZP and MgAl₂O₄ powders into a dense ceramic composite. The absence of tetragonal to monoclinic transformation under hydrothermal conditions was assessed during accelerated aging tests. Biaxial flexural strength and fracture toughness values of more than 900 MPa and 15 MPa √m, respectively were measured, showing that phase transformation toughening of zirconia is maintained in the composite, while the inter/intragranular dispersion of nano-scaled magnesia spinel leads to strengthening of the Ce-TZP matrix. Flaw tolerance is attained, since the strength appears to be transformation dependent. These properties allow the composite to be used in the fabrication of various load-bearing components by employing conventional processing methods and sintering, for example for structural biomedical applications.     

Electronic properties of interacting quantum dots

The electronic properties of two interacting dots connected to leads are studied in the Kondo regime. The configuration is such that one dot is inserted into the lead while the other is side-connected to it. The situation, where both dots are in the Kondo regime is investigated. We find that the development of a Kondo state related to the connected dot is mediated by the inserted dot. In this case, an anti-resonance appears in the density of states of the inserted dot, at the Fermi level. The equation of motion method is used to calculate the Green's functions of the system.     

A compact, high-gain, 2-20-GHz MMIC amplifier

The authors describe an advanced MMIC amplifier providing a 20-dB gain block over the 2-20-GHz frequency range. The chip requires only three external bias capacitors and is well suited to automatic assembly. By simultaneously offering improved gain, power, and circuit density in the 2-20-GHz range, a significant advancement in single chip performance has been achieved     

Development of gas phase bioreactors for the removal of nitrogen oxides from synthetic flue gas streams

Thermophilic denitrifying bacteria indigenous to composts and soils are capable of converting NO_x to environmentally benign nitrogen via a dissimilatory reductive pathway. The present study compares the performance of three bioreactor packing materials (compost, perlite, and biofoam) for the removal of nitric oxide (NO) from a simulated wet-scrubbed combustion gas. Although all three materials performed well (>85% NO removal) at residence times of 70-80 s, the compost performed better than the other materials at shorter residence times (13-44 s). The feasibility of biological NO_x conversion processes will depend on the combined factors of NO_x removal ability and pressure drop. The results presented here suggest that the compost, perlite and biofoam systems, subject to further optimization, offer potential for the biological removal of NO_x from gas streams.     

Numerical investigation of droplet impact on the welding pool in gas metal arc welding

A transient three‐dimensional model that describes physical phenomena inside a welding pool during gas–metal arc welding process is presented. The model considers such phenomena as heat‐mass transfer, electromagnetics, hydrodynamic processes and deformation of the weld pool free surface. The fluid flow in the weld pool is induced due to the presence of the mechanical impact of the droplets, thermo‐capillary surface tension, thermal buoyancy and electromagnetic forces. The weld pool surface deformation is calculated by considering arc pressure and droplet impact force. A comparative analysis of the impact of the electric current of the welding arc and different force factors causing the motion of liquid metal in the weld pool on the shape of the welded seam was carried out and discussed.     

Drimane Derivatives as the First Examples of Covalent BH3 Mimetics that Target MCL-1

Drimane sesquiterpenoid dialdehydes are natural compounds with antiproliferative properties. Nevertheless, their mode of action has not yet been discovered. Herein, we demonstrate that various drimanes are potent inhibitors of MCL-1 and BCL-xL, two proteins of the BCL-2 family that are overexpressed in various cancers, including lymphoid malignancies. Subtle changes in their structure significantly modified their activity on the target proteins. The two most active compounds are MCL-1 selective and bind in the BH3 binding groove of the protein. Complementary studies by NMR spectroscopy and mass spectrometry analyses, but also synthesis, showed that they covalently inhibit MCL-1 though the formation of a pyrrole adduct. In addition, cytotoxic assays revealed that these two compounds show a cytotoxic selectivity for BL2, a MCL-1/BCL-xL-dependent cell line and induce apoptosis.