scholarly journals Effect of Magnesium Addition and High Energy Processing on the Degradation Behavior of Iron Powder in Modified Hanks’ Solution for Bioabsorbable Implant Applications

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 78
Author(s):  
Rafael G. Estrada ◽  
Marta Multigner ◽  
Marcela Lieblich ◽  
Santiago Fajardo ◽  
Joaquín Rams
Keyword(s):  
Degradation Rate ◽  
Degradation Products ◽  
High Energy ◽  
Structural Features ◽  
Degradation Behavior ◽  
Medical Implants ◽  
Fe Powder ◽  
Energy Processing ◽  
Powder Particles ◽  
Phase Quantification

This paper shows the results of applying a combination of high energy processing and magnesium (Mg) as an alloying element in a strategy for enhancing the degradation rate of iron (Fe) for applications in the field of non-permanent medical implants. For this purpose, Fe powder was milled with 5 wt% of Mg (Fe5Mg) and its microstructure and characterized degradation behavior. As-received Fe powder was also milled in order to distinguish between the effects due to high energy processing from those due to the presence of Mg. The powders were prepared by high energy planetary ball milling for 16 h. The results show that the initial crystallite size diminishes from >150 nm to 16 nm for Fe and 46 nm for Fe5Mg. Static degradation tests of loose powder particles were performed in Hanks’ solution. Visual inspection of the immersed powders and the X-ray diffraction (XRD) phase quantification indicate that Fe5Mg exhibited the highest degradation rate followed by milled Fe and as received Fe, in this order. The analysis of degradation products of Fe5Mg showed that they consist on magnesium ferrite and pyroaurite, which are known to present good biocompatibility and low toxicity. Differences in structural features and degradation behaviors of milled Fe and milled Fe5Mg suggest the effective dissolution of Mg in the Fe lattice. Based on the obtained results, it can be said that Fe5Mg powder would be a suitable candidate for non-permanent medical implants with a higher degradation rate than Fe.

scholarly journals Structural features of the exocellular polysaccharides of Mycobacterium tuberculosis

1994 ◽  
Vol 297 (2) ◽  
pp. 351-357 ◽  
Author(s):  
A Lemassu ◽  
M Daffé
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Molecular Mimicry ◽  
Degradation Products ◽  
Cell Envelope ◽  
Gel Filtration ◽  
Structural Features ◽  
Two Dimensional ◽  
Phagocytic Cells ◽  
Molecular Masses ◽  
Branched Structure

The cell envelope which surrounds pathogenic mycobacteria is postulated to be a defence barrier against phagocytic cells and its outermost constituents have a tendency to accumulate in the culture medium. The present work demonstrates that the exocellular material of Mycobacterium tuberculosis contains large amounts of polysaccharides with only traces, if any at all, of lipids. Three types of polysaccharides were purified by anion-exchange and gel-filtration chromatography; all were found to be neutral compounds devoid of acyl substituents. They consisted of D-glucan, D-arabino-D-mannan and D-mannan, which were eluted from gel-filtration columns in positions corresponding to molecular masses of 123, 13 and 4 kDa respectively. Their predominant structural features were determined by the characterization of the per-O-methyl derivatives of enzymic, acetolysis and Smith-degradation products and by 1H- and 13C-n.m.r. spectroscopy of the purified polysaccharides, using mono- and two-dimensional homonuclear chemical-shift correlated spectroscopy and two-dimensional heteronuclear (1H/13C) spectroscopy. The glucan which represented up to 90% of the polysaccharides was composed of repeating units of five or six-->4-alpha-D-Glcp-1--> residues and a -->4-alpha-D-Glcp substituted at position 6 with an alpha-D-Glcp, indicating a glycogen-like highly branched structure not related to the so-called polysaccharide-II previously identified in tuberculin. The arabinomannan consisted of a mannan segment composed of a -->6-alpha-D-Man-1--> core substituted at some positions 2 with an alpha-D-Manp. The arabinan termini of the arabinomannan were found to be extensively capped with mannosyl residues. The possibility that these polysaccharides contribute to the persistence of the tubercle bacillus in the macrophage by molecular mimicry is discussed.

Effect of Composition on the Morphology and Hardness of Nanostructured Cu Based Composite and Alloy Powders/Granules Produced by High Energy Mechanical Milling

2007 ◽  
Vol 29-30 ◽  
pp. 143-146 ◽  
Author(s):  
Aamir Mukhtar ◽  
De Liang Zhang ◽  
C. Kong ◽  
P. R. Munroe
Keyword(s):  
Grain Size ◽  
Mechanical Milling ◽  
Alloy Powder ◽  
High Energy ◽  
Al2o3 Nanoparticles ◽  
X Ray ◽  
Fine Powders ◽  
Average Grain Size ◽  
Powder Particles

Cu-(2.5 or 5.0vol.%)Al2O3 nanocomposite balls and granules and Cu-(2.5vol.% or 5.0vol.%)Pb alloy powder were prepared by high energy mechanical milling (HEMM) of mixtures of Cu and either Al2O3 or Pb powders. It was observed that with the increase of the content of Al2O3 nanoparticles from 2.5vol.% to 5vol.% in the powder mixture, the product of HEMM changed from hollow balls into granules and the average grain size and microhardness changed from approximately 130nm and 185HV to 100nm and 224HV, respectively. On the other hand, HEMM of Cu–(2.5 or 5.0vol.%) Pb powder mixtures under the same milling conditions failed to consolidate the powder in-situ. Instead, it led to formation of nanostructured fine powders with an average grain size of less than 50nm. Energy dispersive X-ray mapping showed homogenous distribution of Pb in the powder particles in Cu–5vol.%Pb alloy powder produced after 12 hours of milling. With the increase of the Pb content from 2.5 to 5.0 vol.%, the average microhardness of the Cu-Pb alloy powder particles increases from 270 to 285 HV. The mechanisms of the effects are briefly discussed.

Correlation Between the V-I Characteristics of (0001) 4H-SiC PN Junctions Having Different Structural Features and Synchrotron X-ray Topography

2008 ◽  
Vol 1069 ◽  
Author(s):  
Ryoji Kosugi ◽  
Toyokazu Sakata ◽  
Yuuki Sakuma ◽  
Tsutomu Yatsuo ◽  
Hirofumi Matsuhata ◽  
...  
Keyword(s):  
High Energy ◽  
Structural Features ◽  
Incidence Geometry ◽  
Voltage Source ◽  
Large Area ◽  
Chip Area ◽  
Power Mosfets ◽  
X Ray ◽  
Pn Junctions ◽  
The Difference

ABSTRACTIn practical use of the SiC power MOSFETs, further reduction of the channel resistance, high stability under harsh environments, and also, high product yield of large area devices are indispensable. Pn diodes with large chip area have been already reported with high fabrication yield, however, there is few reports in terms of the power MOSFETs. To clarify the difference between the simple pn diodes and power MOSFETs, we have fabricated four pn-type junction TEGs having the different structural features. Those pn junctions are close to the similar structure of DIMOS (Double-implanted MOS) step-by-step from the simple pn diodes. We have surveyed the V-I characteristics dependence on each structural features over the 2inch wafer. Before their fabrication, we formed grid patterns with numbering over the 2inch wafer, then performed the synchrotron x-ray topography observation. This enables the direct comparison the electrical and spectrographic characteristics of each pn junctions with the fingerprints of defects.Four structural features from TypeA to TypeD are as follows. TypeA is the most simple structure as same as the standard pn diodes formed by Al+ ion implantation (I/I), except that the Al+ I/I condition conforms to that of the p-well I/I in the DIMOS. The JTE structure was used for the edge termination on all junctions. While the TypeA consists of one p-type region, TypeB and TypeC consists of a lot of p-wells. The difference of Type B and C is a difference of the oxide between the adjacent p-wells. The oxide of TypeB consists of the thick field oxide, while that of TypeC consists of the thermal oxide corresponding to the gate oxide in the DIMOS. In the TypeD structure, n+ region corresponding to the source in the DIMOS was added by the P+ I/I. The TypeD is the same structure of the DIMOS, except that the gate and source contacts are shorted. The V-I measurements of the pn junctions are performed using the KEITHLEY 237 voltage source meters with semi-auto probe machine. An active area of the fabricated pn junctions TEGs are 150um2 and 1mm2. Concentration and thickness of the drift layer are 1e16cm−3 and 10um, respectively.In order to compare the V-I characteristics of fabricated pn junctions with their defects information that obtained from x-ray topography measurements directly, the grid patterns are formed before the fabrication. The grid patterns were formed over the 2inch wafer by the SiC etching. The synchrotron x-ray topography measurements are carried out at the Beam-Line 15C in Photon-Factory in High-Energy-Accelerator-Research-Organization. Three diffraction conditions, g=11-28, -1-128, and 1-108, are chosen in grazing-incidence geometry (improved Berg-Barrett method).In the presentation, the V-I characteristics mapping on the 2inch wafer for each pn junctions, and the comparison of V-I characteristics with x-ray topography will be reported.

Electrochemical processes during plating Fe powder particles by Ni and Ni/Cu coating in the fluidized bed

2001 ◽  
Vol 5 (7-8) ◽  
pp. 502-506 ◽  
Author(s):  
Andrea Turonová ◽  
Miriam Gálová ◽  
Ladislav Lux ◽  
Miroslav Gál
Keyword(s):  
Fluidized Bed ◽  
Electrochemical Processes ◽  
Fe Powder ◽  
Powder Particles

scholarly journals Research on the Defrosting System of Refrigerated Containers Combining Air and Electro-Thermal Energy and the Controlling Strategy

2021 ◽  
Vol 248 ◽  
pp. 02058
Author(s):  
Kaitai Hua
Keyword(s):  
Energy Consumption ◽  
Thermal Energy ◽  
Pressure Change ◽  
High Energy ◽  
Structural Features ◽  
Low Energy ◽  
Wind Pressure ◽  
Long Duration ◽  
Low Energy Consumption ◽  
High Energy Consumption

Considering the problems such as long duration of defrosting, low working reliability and high energy consumption of refrigerated containers, this paper put forward a new defrosting method combining air and electro-thermal energy, and designed a new defrosting structure system based on the structural features of refrigeration modules of refrigerated containers. The two-variable method of wind pressure change and temperature difference change on both sides of the evaporator was used to detect frosting, and the specific controlling strategy supporting the new defrosting system was provided to realize the effect of intelligent defrosting. It can provide references for fast defrosting, intelligent defrosting and low energy consumption defrosting of refrigerated containers.

scholarly journals Preparation of RGO/TiO2/Ag Aerogel and Its Photodegradation Performance in Gas Phase Formaldehyde

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Haiwang Wang ◽  
Guanqi Wang ◽  
Yukai Zhang ◽  
Yuan Ma ◽  
Zhengjie Wu ◽  
...  
Keyword(s):  
Particle Size ◽  
Gas Phase ◽  
Degradation Rate ◽  
Catalytic Efficiency ◽  
Formaldehyde Solution ◽  
Degradation Behavior ◽  
Photocatalytic Effect ◽  
Utilization Ratio ◽  
20 Nm ◽  
Degradation Effect

Abstract To increase the utilization ratio and catalytic efficiency of the nano TiO2, The RGO/TiO2/(Ag) powders and RGO/TiO2/Ag aerogel photocatalyst were designed and prepared. The composition and microstructure of RGO/TiO2/(Ag) powders and RGO/TiO2/Ag aerogel were studied, in addition, the photocatalytic activity of RGO/TiO2/(Ag) powders and RGO/TiO2/Ag aerogel was researched by the photocatalytic degradation behavior of formaldehyde solution and formaldehyde gas respectively. The result indicate that TiO2 is uniformly loaded on the surface of RGO with a particle size of 10 nm to 20 nm. When the amount of graphene oxide added is 1 wt%, RGO/TiO2 powder has the highest degradation effect on formaldehyde solution, in addition, the introduction of Ag can greatly improve the photocatalytic effect of the sample. The results also show that the pore size of RGO/TiO2/Ag aerogel is between 7.6 nm and 12.1 nm, and the degradation rate of formaldehyde gas is 77.08% within 2 hours.

Modeling Strategies for the Degradation Behavior of Porous Polyester Materials Based on Their Key Structural Features

2020 ◽  
Vol 59 (33) ◽  
pp. 14806-14816
Author(s):  
Chaobo Song ◽  
Jiapeng Zhang ◽  
Lian Cen ◽  
Zhenhao Xi ◽  
Ling Zhao ◽  
...  
Keyword(s):  
Structural Features ◽  
Degradation Behavior

Closed Cellular Materials for Smart Materials

2010 ◽  
Vol 638-642 ◽  
pp. 2074-2079
Author(s):  
Satoshi Kishimoto
Keyword(s):  
Internal Friction ◽  
Smart Materials ◽  
Metal Layer ◽  
Pure Aluminum ◽  
Physical And Mechanical Properties ◽  
High Energy ◽  
Cellular Materials ◽  
Plasma Sintering ◽  
Powder Particles ◽  
High Energy Absorption

New methods to fabricate a metallic closed cellular material for smart materials using an isostatic pressing and penetrating method are introduced. Powder particles of polymer or ceramics coated with a metal layer using electro-less plating were pressed into pellets and sintered at high temperature. These powder particles were sintered by spark plasma sintering (SPS) method. Closed cellular materials including polymer were fabricated by penetrating polymer into metallic foams. Many kinds of metallic closed cellular materials including different materials from that of cell walls were tried to fabricate. The physical and mechanical properties of these materials were measured. The results of the compressive tests show that this material has high-energy absorption and the result of measuring the internal friction show that the internal friction of these materials is larger than that of pure aluminum.

scholarly journals Comprehensive Assessment of Degradation Behavior of Simvastatin by UHPLC/MS Method, Employing Experimental Design Methodology

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Maja Hadzieva Gigovska ◽  
Ana Petkovska ◽  
Jelena Acevska ◽  
Natalija Nakov ◽  
Packa Antovska ◽  
...  
Keyword(s):  
Experimental Design ◽  
Design Methodology ◽  
Method Development ◽  
Ion Trap ◽  
Degradation Products ◽  
Forced Degradation ◽  
Degradation Behavior ◽  
Liquid Chromatograph ◽  
Photolytic Degradation ◽  
Experimental Design Methodology

This manuscript describes comprehensive approach for assessment of degradation behavior of simvastatin employing experimental design methodology as scientific multifactorial strategy. Experimental design methodology was used for sample preparation and UHPLC method development and optimization. Simvastatin was subjected to stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Using2nfull factorial design degradation conditions were optimized to obtain targeted level of degradation. Screening for optimal chromatographic condition was made by Plackett–Burman design and optimization chromatographic experiments were conducted according to Box-Behnken design. Successful separation of simvastatin from the impurities and degradation products was achieved on Poroshell 120 EC C18 50 × 3.0 mm 2.7μm, using solutions of 20 mM ammonium formate pH 4.0 and acetonitrile as the mobile phase in gradient mode. The proposed method was validated according to International Conference on Harmonization (ICH) guidelines. Validation results have shown that the proposed method is selective, linear, sensitive, accurate, and robust and it is suitable for quantitative determination of simvastatin and its impurities. Afterwards, the degradation products were confirmed by a direct hyphenation of liquid chromatograph to ion-trap mass spectrometer with heated electrospray ionization interface. This study highlights the multiple benefits of implementing experimental design, which provides a better understanding of significant factors responsible for degradation and ensures successful way to achieve degradation and can replace the trial and error approach used in conventional forced degradation studies.

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