-
Crystal Structure: Reciprocal Space Methods for Carry out the Structure Solution from Powder Data
Mbark Ait Mouha,
Dounia Tlamsamani,
Khalid Yamni
Issue:
Volume 10, Issue 2, March 2021
Pages:
25-29
Received:
22 February 2021
Accepted:
10 March 2021
Published:
1 April 2021
Abstract: It is a relatively easy task to the solution of the so-called phase problem in crystallography, by applying ab initio phasing methods for the efficiency of structure solution from single-crystal data. Their effective application to powder x-ray diffraction data is still a real challenge unless the size of the structure is moderate. The percentage of principal success hinges on a number of factors; included are the quality of the experimental pattern, the success of the pattern-decomposition programs, the quality of the extracted structure-factor from the experimental pattern via the Le Bail or Pawley methods, the normalization of structure-factor process, the experimental resolution and the straightforward of the phasing process. This paper aims at providing an overall overview of the reciprocal space RS methods (ab initio phasing methods of crystal structure) as well as the direct methods, Patterson function and maximum entropy methods. This paper will also describe the factors affecting phasing by reciprocal space methods and the limitation of reciprocal space methods. Those are available for carry out the structure solution, in order to provide a clear theoretical account, experimental practice and computing approaches regarding and describe an outline of the solution process of phase problem by powder X-ray diffraction, leads to the best structure solution using practical examples.
Abstract: It is a relatively easy task to the solution of the so-called phase problem in crystallography, by applying ab initio phasing methods for the efficiency of structure solution from single-crystal data. Their effective application to powder x-ray diffraction data is still a real challenge unless the size of the structure is moderate. The percentage o...
Show More
-
Analysis and Suggestions on the Use of Polymer Materials for Coal Mines
Issue:
Volume 10, Issue 2, March 2021
Pages:
30-34
Received:
1 March 2021
Accepted:
29 March 2021
Published:
7 April 2021
Abstract: In recent years, polymer materials used in coal mines have been widely used in coal rock reinforcement, grouting and plugging in coal mines, and have played an important role in coal mine disaster management. However, according to the relevant data, more than 100 accidents have occurred in the use of polymer materials in China ' s coal mines, and most of them are used to reinforce coal and rock mass polymer materials. The use and safety management of polymer materials need to be strengthened. This paper summarizes the characteristics of polymer materials used in underground coal mines, analyzes the problems that may arise in the use of polymer materials used in coal mines and the shortcomings of relevant existing standards, and points out that most of the safety accidents of polymer materials are spontaneous combustion of materials, coal seam combustion and poisoning caused by toxic and harmful gases. The main causes of combustion accidents are too high reaction temperature, insufficient flame retardancy, uncontrollable reaction process, imperfect standards and insufficient safety awareness of the material itself. Reasonable suggestions and measures for preventing similar accidents are put forward to provide technical guidance for the safe use of polymer materials for coal mines.
Abstract: In recent years, polymer materials used in coal mines have been widely used in coal rock reinforcement, grouting and plugging in coal mines, and have played an important role in coal mine disaster management. However, according to the relevant data, more than 100 accidents have occurred in the use of polymer materials in China ' s coal mines, and m...
Show More
-
Application and Manufacturing Method of Stent Material in Vascular Regeneration and Prevention of Vascular Restenosis
Issue:
Volume 10, Issue 2, March 2021
Pages:
35-45
Received:
29 March 2021
Accepted:
14 April 2021
Published:
23 April 2021
Abstract: With the development of biological tissue engineering, vascular stent materials have been greatly improved. Synthetic polyester polymers and bio-derived materials with excellent biocompatibility, biodegradability and mechanical strength have greatly improved. These are ideal tissue vascular scaffold materials. Vascular stents mainly play two roles in the body: vascular regeneration and prevention of vascular restenosis. In terms of vascular regeneration, the repair of common bone defects and the pulp regeneration require revascularization. This type of stent has production-promoting ability of adopting the multi-level microtubule structure. Different aperture induces different vascular behavior of making the adhered macrophages deforming correspondingly, promoting the infiltration of endothelial cells into the extracellular matrix and accelerating the formation of new blood vessels. In the treatment of atherosclerosis, stents can not only support blood vessels, but also prevent blood vessel from restenosis and keep blood vessels opening for a long time. To this aim, stents generally carry and controllable release of drugs of inhibiting the proliferation of smooth muscle cells. Such stents are called drug-eluting stents. Usual drugs are rapamycin and paclitaxel. This review intends to mix the nano-scale anticancer drug nanoenzymes with polymers on the surface of the stent and exert the sustained drug releasing function of the drug-eluting stent. This type of drug-eluting stent can not only prevent blood vessel restenosis, but also treat cancer by attacking tumor cells.
Abstract: With the development of biological tissue engineering, vascular stent materials have been greatly improved. Synthetic polyester polymers and bio-derived materials with excellent biocompatibility, biodegradability and mechanical strength have greatly improved. These are ideal tissue vascular scaffold materials. Vascular stents mainly play two roles ...
Show More
