High-performance wholly aromatic polyamide–hydrazides

The review summarizes the various methods of preparing wholly aromatic polyamide–hydrazides (PAHs). Polyhydrazides are a class of polymers that possess in their repeating units one amide (–NHOC–) and one hydrazide (–CONHNHOC–) linking bond between appropriate aromatic nuclei. The review provides several figures of different molecular structures of PAH and expounds the methods of polymerization, low, high temperature, and phosphorylation polycondensation methods. Polyhydrazides exhibit some unique and potentially useful properties such as outstanding thermal and thermo-oxidative resistance, very high mechanical strength, and ultrahigh moduli. PAHs undergo structural transformation into poly(amide-1,3,4-oxadiazole)s upon heating, which are also considered highly thermally stable polymers. The review presents a description of the structure–property relation of PAHs. The application of PAHs in reverse osmosis applications has been discussed, as well as the preparation of fibers and metallized PAHs films. Modification of the PAH with carbon nanotubes and graphene and the future prospects for PAHs were introduced with comprehensive references pertaining to this area of research.

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Electron Microscopy in Molecular Biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060027 ◽

1967 ◽

Vol 25 ◽

pp. 2-3

Author(s):

Cecil E. Hall

Keyword(s):

Electron Microscopy ◽

Molecular Biology ◽

Noise Level ◽

Molecular Structures ◽

Material Structure ◽

The Arts ◽

Shadow Casting ◽

Electron Image ◽

High Degree ◽

Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

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Exchange Spin Coupling from Gaussian Process Regression

10.26434/chemrxiv.12589541.v3 ◽

2020 ◽

Author(s):

Marc Philipp Bahlke ◽

Natnael Mogos ◽

Jonny Proppe ◽

Carmen Herrmann

Keyword(s):

Machine Learning ◽

Gaussian Process ◽

Gaussian Process Regression ◽

Molecular Magnets ◽

Molecular Structures ◽

Spin Coupling ◽

Structure Property ◽

Data Set ◽

Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

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KEMPER C688

Alloy Digest ◽

10.31399/asm.ad.cu0867 ◽

2017 ◽

Vol 66 (12) ◽

Keyword(s):

Corrosion Resistance ◽

Physical Properties ◽

Tensile Properties ◽

Copper Alloy ◽

High Performance ◽

High Conductivity ◽

Bend Strength ◽

Very High

Abstract Alloy C688 is a high-performance copper alloy with very high conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming and joining. Filing Code: Cu-867. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

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KEMPER KHP7025

Alloy Digest ◽

10.31399/asm.ad.cu0865 ◽

2017 ◽

Vol 66 (10) ◽

Keyword(s):

Corrosion Resistance ◽

Physical Properties ◽

Tensile Properties ◽

Copper Alloy ◽

High Performance ◽

High Conductivity ◽

Bend Strength ◽

Very High

Abstract Alloy KHP 7025 (UNS C70250) is a high-performance copper alloy with very high conductivity. Uses include connector springs, tabs, contact springs, switches, relays, and leadframes. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming, machining, and joining. Filing Code: Cu-865. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

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CROFER 22 H

Alloy Digest ◽

10.31399/asm.ad.ss1121 ◽

2012 ◽

Vol 61 (5) ◽

Keyword(s):

Corrosion Resistance ◽

Solid Oxide Fuel Cells ◽

High Performance ◽

Heat Treating ◽

Solid Oxide ◽

Oxide Fuel ◽

High Mechanical Strength ◽

Excellent Corrosion Resistance ◽

Niobium Titanium ◽

Processing Properties

Abstract Crofer 22 H is an improved high performance material for use in high-temperature solid oxide fuel cells (SOFCs). The alloy contains 20% to 24% chromium plus tungsten, niobium, titanium, and lanthanum. It has excellent corrosion resistance at temperatures to 900 C (1652 F), good electrical conductivity of the oxide layer, and high mechanical strength at service temperature. It also has good processing properties. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-1121. Producer or source: ThyssenKrupp VDM GmbH.

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Use of activated carbon to remove undesirable residual amylase from refinery streams

Sugar Industry ◽

10.36961/si18170 ◽

2017 ◽

pp. 96-103 ◽

Cited By ~ 1

Author(s):

Gillian Eggleston ◽

Isabel Lima ◽

Emmanuel Sarir ◽

Jack Thompson ◽

John Zatlokovicz ◽

...

Keyword(s):

Activated Carbon ◽

High Temperature ◽

High Performance ◽

Activated Carbons ◽

Amylase Activity ◽

Sugar Industry ◽

End User ◽

Customer Complaints ◽

Carry Over ◽

Very High

In recent years, there has been increased world-wide concern over residual (carry-over) activity of mostly high temperature (HT) and very high temperature (VHT) stable amylases in white, refined sugars from refineries to various food and end-user industries. HT and VHT stable amylases were developed for much larger markets than the sugar industry with harsher processing conditions. There is an urgent need in the sugar industry to be able to remove or inactivate residual, active amylases either in factory or refinery streams or both. A survey of refineries that used amylase and had activated carbon systems for decolorizing, revealed they did not have any customer complaints for residual amylase. The use of high performance activated carbons to remove residual amylase activity was investigated using a Phadebas® method created for the sugar industry to measure residual amylase in syrups. Ability to remove residual amylase protein was dependent on the surface area of the powdered activated carbons as well as mixing (retention) time. The activated carbon also had the additional benefit of removing color and insoluble starch.

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Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

Nature Communications ◽

10.1038/s41467-021-21678-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yingfeng Yang ◽

Hanze Ying ◽

Zhixia Li ◽

Jiang Wang ◽

Yingying Chen ◽

...

Keyword(s):

High Efficiency ◽

Molecular Structures ◽

High Yield ◽

Kinetic Control ◽

High Concentration ◽

Weak Association ◽

Quantitative Synthesis ◽

Thermodynamic Stabilization ◽

Discrete Structures ◽

Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

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Nacre-inspired composite films with high mechanical strength constructed from MXenes and wood-inspired hydrothermal cellulose-based nanofibers for high performance flexible supercapacitors

Nanoscale ◽

10.1039/d0nr08090j ◽

2021 ◽

Vol 13 (5) ◽

pp. 3079-3091

Author(s):

Libo Chang ◽

Zhiyuan Peng ◽

Tong Zhang ◽

Chuying Yu ◽

Wenbin Zhong

Keyword(s):

Mechanical Strength ◽

High Performance ◽

Composite Films ◽

High Mechanical Strength ◽

Flexible Supercapacitor ◽

Flexible Supercapacitors

Wood-inspired HCNF@Lig introduced into MXenes constructing a nacre-like material with high mechanical strength and excellent flexibility used as a flexible supercapacitor.

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Ab initio molecular dynamics and materials design for embedded phase-change memory

npj Computational Materials ◽

10.1038/s41524-021-00496-7 ◽

2021 ◽

Vol 7 (1) ◽

Cited By ~ 1

Author(s):

Liang Sun ◽

Yu-Xing Zhou ◽

Xu-Dong Wang ◽

Yu-Han Chen ◽

Volker L. Deringer ◽

...

Keyword(s):

Phase Change ◽

High Performance ◽

Materials Design ◽

Atomic Scale ◽

Ab Initio Molecular Dynamics ◽

Core Material ◽

Structure Property ◽

Switching Speed ◽

Atomic Structures ◽

Memory Applications

AbstractThe Ge2Sb2Te5 alloy has served as the core material in phase-change memories with high switching speed and persistent storage capability at room temperature. However widely used, this composition is not suitable for embedded memories—for example, for automotive applications, which require very high working temperatures above 300 °C. Ge–Sb–Te alloys with higher Ge content, most prominently Ge2Sb1Te2 (‘212’), have been studied as suitable alternatives, but their atomic structures and structure–property relationships have remained widely unexplored. Here, we report comprehensive first-principles simulations that give insight into those emerging materials, located on the compositional tie-line between Ge2Sb1Te2 and elemental Ge, allowing for a direct comparison with the established Ge2Sb2Te5 material. Electronic-structure computations and smooth overlap of atomic positions (SOAP) similarity analyses explain the role of excess Ge content in the amorphous phases. Together with energetic analyses, a compositional threshold is identified for the viability of a homogeneous amorphous phase (‘zero bit’), which is required for memory applications. Based on the acquired knowledge at the atomic scale, we provide a materials design strategy for high-performance embedded phase-change memories with balanced speed and stability, as well as potentially good cycling capability.

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