Predicting Powder-Polymer Mixture Properties for PIM Design

Powder injection molding (PIM) is a high-volume manufacturing technique for fabricating ceramic and metal components that have complex shapes. In PIM design, it is important to know the injection molding behavior at different powder-polymer compositions so as to understand the trade-offs between ease-of-fabrication, process throughput, and part quality at the design stage. A limited database of materials properties at different powder-polymer compositions is a significant challenge that needs to be addressed in order to conduct accurate computer simulations that aid part and mold design in PIM. However, accurate material property measurements are expensive and time-consuming. In order to resolve these conflicting challenges it is hypothesized that experimental measurements of material properties of a filled polymer at a specific filler content combined with similar measurements of unfilled polymer will be adequate to estimate the dependence of properties on filler content using rule-of-mixture models. To this end, this article focuses on a literature review of experimental data obtained from measurements of rheological, thermal, and mechanical properties for a wide range of powder-polymer mixtures at various filler volume fractions. The experimental data were compared to property estimates using various predictive models. It is expected that the current review will be valuable in selecting appropriate predictive models for estimating properties based on the input data requirements for commercially available mold-filling simulation platforms such as Moldflow® and PIMSolver®. The combined protocol will be useful to design new materials and component geometries as well as optimize process parameters while eliminating expensive and time-consuming trial-and-error practices prevalent in PIM.     

Ambient Bistable Single Dipole Switching in a Molecular Monolayer

Reported here is a molecular dipole that self‐assembles into highly ordered patterns at the liquid‐solid interface, and it can be switched at room temperature between a bright and a dark state at the single‐molecule level. Using a scanning tunneling microscope (STM) under suitable bias conditions, binary information can be written at a density of up to 41 Tb cm^?2 (256 Tb/in²). The written information is stable during reading at room temperature, but it can also be erased at will, instantly, by proper choice of tunneling conditions. DFT calculations indicate that the contrast and switching mechanism originate from the stacking sequence of the molecular dipole, which is reoriented by the electric field between the tip and substrate.     

A Fluorogenic Assay: Analysis of Chemical Modification of Lysine and Arginine to Control Proteolytic Activity of Trypsin

The chemical modification of amino acids plays an important role in the modulation of proteins or peptides and has useful applications in the activation and stabilization of enzymes, chemical biology, shotgun proteomics, and the production of peptide-based drugs. Although chemoselective modification of amino acids such as lysine and arginine via the insertion of respective chemical moieties as citraconic anhydride and phenyl glyoxal is important for achieving desired application objectives and has been extensively reported, the extent and chemoselectivity of the chemical modification of specific amino acids using specific chemical agents (blocking or modifying agents) has yet to be sufficiently clarified owing to a lack of suitable assay methodologies. In this study, we examined the utility of a fluorogenic assay method, based on a fluorogenic tripeptide substrate (FP-AA1-AA2-AA3) and the proteolytic enzyme trypsin, in determinations of the extent and chemoselectivity of the chemical modification of lysine or arginine. As substrates, we used two fluorogenic tripeptide probes, MeRho-Lys-Gly-Leu(Ac) (lysine-specific substrate) and MeRho-Arg-Gly-Leu(Ac) (arginine-specific substrate), which were designed, synthesized, and evaluated for chemoselective modification of specific amino acids (lysine and arginine) using the fluorogenic assay. The results are summarized in terms of half-maximal inhibitory concentrations (IC₅₀) for the extent of modification and ratios of IC₅₀ values (IC₅₀arginine/IC₅₀lysine and IC₅₀lysine/IC₅₀arginine) as a measure of the chemoselectivity of chemical modification for amino acids lysine and arginine. This novel fluorogenic assay was found to be rapid, precise, and reproducible for determinations of the extent and chemoselectivity of chemical modification.     

Thermal–electrical–structural performances of hot heat exchanger with different internal fins of thermoelectric generator for low power generation application

Journal of Thermal Analysis and Calorimetry - In this study, an electro-thermo-structural coupled numerical analysis is conducted to evaluate the thermal, electrical, and structural performances of...     

High Yielding Synthesis of Carboranes Under Mild Reaction Conditions Using a Homogeneous Silver(I) Catalyst: Direct Evidence of a Bimetallic Intermediate

Methods used to prepare functionalized carboranes generally require heating to high temperatures, and thus limits the range of derivatives which can be prepared directly from alkynes. We show here that by using a homogeneous silver(I) catalyst it is now possible to prepare carboranes in good to excellent yield at temperatures below 40 °C, including at room temperature. The process is general and provides an important new synthetic strategy for the preparation of functionalized boron clusters.     

One‐Pot Decarboxylative Acylation of N‐, O‐, S‐Nucleophiles and Peptides with 2,2‐Disubstituted Malonic Acids

Monocarbonyl activation of 2,2‐disubstituted malonic acids with benzotriazole leads to decarboxylation of one of the carboxy groups and formation of a C?H bond. Intermediate carbonyl benzotriazoles then readily acylate nucleophilic reagents and peptides resulting in libraries of conjugates and peptidomimetics.