Chain growth algorithms for HP-type lattice proteins

1987 ◽

Vol 45 ◽

pp. 242-243

Author(s):

J. C. Barry ◽

H. Alexander

Keyword(s):

Dislocation Core ◽

Preparation Technique ◽

Burgers Vector ◽

Vector Type ◽

Sample Preparation Technique ◽

Lattice Images ◽

Dislocation Core Structure ◽

Type Lattice ◽

Direct Inspection

Dislocations in silicon produced by plastic deformation are generally dissociated into partials. 60° dislocations (Burgers vector type 1/2[101]) are dissociated into 30°(Burgers vector type 1/6[211]) and 90°(Burgers vector type 1/6[112]) dislocations. The 30° partials may be either of “glide” or “shuffle” type. Lattice images of the 30° dislocation have been obtained with a JEM 100B, and with a JEM 200Cx. In the aforementioned experiments a reasonable but imperfect match was obtained with calculated images for the “glide” model. In the present experiment direct structure images of 30° dislocation cores have been obtained with a JEOL 4000EX. It is possible to deduce the 30° dislocation core structure by direct inspection of the images. Dislocations were produced by compression of single crystal Si (sample preparation technique described in Alexander et al.).

Download Full-text

Carbon Chain Growth by Sequential Reactions of CO and CO2 with a Transition Metal Carbonyl Complex

10.26434/chemrxiv.7064474 ◽

2018 ◽

Author(s):

Richard Kong ◽

Mark Crimmin

Keyword(s):

Transition Metal ◽

Metal Carbonyl ◽

Carbon Chain ◽

Chain Growth ◽

Carbonyl Complex ◽

Fischer Tropsch ◽

Carbon Chains ◽

Sequential Coupling ◽

Energy Economy ◽

Sequential Reactions

<i>The formation of carbon chains by the coupling of COx (X = 1 or 2) units on transition metals is a fundamental step relevant to Fischer-Tropsch catalysis. Fischer-Tropsch catalysis produces energy dense liquid hydrocarbons from synthesis gas (CO and H2) and has been a mainstay of the energy economy since its discovery nearly a century ago. Despite detailed studies aimed at elucidating the steps of catalysis, experimental evidence for chain growth (Cn to Cn+1 ; n > 2) from the reaction of CO with metal complexes is unprecedented. In this paper, we show that carbon chains can be grown from sequential reactions of CO or CO2 with a transition metal carbonyl complex. By exploiting the cooperative effect of transition and main group metals, we document the first example of chain propagation from sequential coupling of CO units (C1 to C3 to C4), along with the first example of incorporation of CO2 into the growing carbon chain.</i><br>

Download Full-text

Polymer Chemistry

10.1093/oso/9780198503095.001.0001 ◽

2004 ◽

Keyword(s):

Conducting Polymers ◽

Liquid Crystalline ◽

Polymer Chemistry ◽

Chain Growth ◽

Crystalline Polymers ◽

Wide Range ◽

Cyclic Oligomers ◽

Step Growth

Polymer Chemistry: A Practical Approach in Chemistry has been designed for both chemists working in and new to the area of polymer synthesis. It contains detailed instructions for preparation of a wide-range of polymers by a wide variety of different techniques, and describes how this synthetic methodology can be applied to the development of new materials. It includes details of well-established techniques, e.g. chain-growth or step-growth processes together with more up-to-date examples using methods such as atom-transfer radical polymerization. Less well-known procedures are also included, e.g. electrochemical synthesis of conducting polymers and the preparation of liquid crystalline elastomers with highly ordered structures. Other topics covered include general polymerization methodology, controlled/"living" polymerization methods, the formation of cyclic oligomers during step-growth polymerization, the synthesis of conducting polymers based on heterocyclic compounds, dendrimers, the preparation of imprinted polymers and liquid crystalline polymers. The main bulk of the text is preceded by an introductory chapter detailing some of the techniques available to the scientist for the characterization of polymers, both in terms of their chemical composition and in terms of their properties as materials. The book is intended not only for the specialist in polymer chemistry, but also for the organic chemist with little experience who requires a practical introduction to the field.

Download Full-text

Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Catalysts ◽

10.3390/catal11060735 ◽

2021 ◽

Vol 11 (6) ◽

pp. 735

Author(s):

Yuhao Zheng ◽

Chenghua Xu ◽

Xia Zhang ◽

Qiong Wu ◽

Jie Liu

Keyword(s):

Synergistic Effect ◽

Active Sites ◽

Intermediate Formation ◽

Active Phase ◽

Dissociative Adsorption ◽

Co2 Hydrogenation ◽

Chain Growth ◽

Co2 Conversion ◽

Light Hydrocarbons ◽

Active Centers

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

Download Full-text

Optimization Design of Lattice Structures in Internal Cooling Channel with Variable Aspect Ratio of Gas Turbine Blade

Energies ◽

10.3390/en14133954 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3954

Author(s):

Liang Xu ◽

Qicheng Ruan ◽

Qingyun Shen ◽

Lei Xi ◽

Jianmin Gao ◽

...

Keyword(s):

Heat Transfer ◽

Aspect Ratio ◽

Optimization Model ◽

Lattice Structure ◽

Turbine Blades ◽

Internal Cooling ◽

Cooling Channel ◽

Cooling Channels ◽

Mechanical Performances ◽

Type Lattice

Traditional cooling structures in gas turbines greatly improve the high temperature resistance of turbine blades; however, few cooling structures concern both heat transfer and mechanical performances. A lattice structure (LS) can solve this issue because of its advantages of being lightweight and having high porosity and strength. Although the topology of LS is complex, it can be manufactured with metal 3D printing technology in the future. In this study, an integral optimization model concerning both heat transfer and mechanical performances was presented to design the LS cooling channel with a variable aspect ratio in gas turbine blades. Firstly, some internal cooling channels with the thin walls were built up and a simple raw of five LS cores was taken as an insert or a turbulator in these cooling channels. Secondly, relations between geometric variables (height (H), diameter (D) and inclination angle(ω)) and objectives/functions of this research, including the first-order natural frequency (freq1), equivalent elastic modulus (E), relative density (ρ¯) and Nusselt number (Nu), were established for a pyramid-type lattice structure (PLS) and Kagome-type lattice structure (KLS). Finally, the ISIGHT platform was introduced to construct the frame of the integral optimization model. Two selected optimization problems (Op-I and Op-II) were solved based on the third-order response model with an accuracy of more than 0.97, and optimization results were analyzed. The results showed that the change of Nu and freq1 had the highest overall sensitivity Op-I and Op-II, respectively, and the change of D and H had the highest single sensitivity for Nu and freq1, respectively. Compared to the initial LS, the LS of Op-I increased Nu and E by 24.1% and 29.8%, respectively, and decreased ρ¯ by 71%; the LS of Op-II increased Nu and E by 30.8% and 45.2%, respectively, and slightly increased ρ¯; the LS of both Op-I and Op-II decreased freq1 by 27.9% and 19.3%, respectively. These results suggested that the heat transfer, load bearing and lightweight performances of the LS were greatly improved by the optimization model (except for the lightweight performance for the optimal LS of Op-II, which became slightly worse), while it failed to improve vibration performance of the optimal LS.

Download Full-text

Synthesis of well-defined poly(p-benzamide) from chain-growth polycondensation and its application to block copolymers

Macromolecular Symposia ◽

10.1002/masy.200350916 ◽

2003 ◽

Vol 199 (1) ◽

pp. 187-196 ◽

Cited By ~ 16

Author(s):

Tsutomu Yokozawa ◽

Miyuki Ogawa ◽

Atsushi Sekino ◽

Ryuji Sugi ◽

Akihiro Yokoyama

Keyword(s):

Block Copolymers ◽

Chain Growth

Download Full-text

Identification of C2–C5 products from CO2 hydrogenation over PdZn/TiO2–ZSM-5 hybrid catalysts

Faraday Discussions ◽

10.1039/d0fd00135j ◽

2021 ◽

Author(s):

Jonathan Ruiz Esquius ◽

Hasliza Bahruji ◽

Michael Bowker ◽

Graham J. Hutchings

Keyword(s):

High Temperature ◽

Co2 Hydrogenation ◽

Chain Growth ◽

Hybrid Catalysts

PdZn/TiO2 combined with ZSM-5 zeolites allowed for consecutive CO2 hydrogenation to CH3OH, CH3OH dehydration to DME, and MTH/DMTH in a one-pass single bed reactor. PdZn alloys, although stable at high temperature, hydrogenate olefins, limiting MTH/DMTH chain growth.

Download Full-text