No abstract available.
Molecular Weight*

OBJECTIVE: Rod-screw fixation systems are widely used for spinal instrumentation. Although many biomechanical studies on rod-screw systems have been carried out, but the effects of rod contouring on the construct strength is still not very well defined in the literature. This work examines the mechanical impact of straight, 20° kyphotic, and 20° lordotic rod contouring on rod-screw fixation systems, by forming a corpectomy model. METHODS: The corpectomy groups were prepared using ultra-high molecular weight polyethylene samples. Non-destructive loads were applied during flexion/extension and torsion testing. Spine-loading conditions were simulated by load subjections of 100 N with a velocity of 5 mm min⁻¹, to ensure 8.4-Nm moment. For torsional loading, the corpectomy models were subjected to rotational displacement of 0.5° s⁻¹ to an end point of 5.0°, in a torsion testing machine. RESULTS: Under both flexion and extension loading conditions the stiffness values for the lordotic rod-screw system were the highest. Under torsional loading conditions, the lordotic rod-screw system exhibited the highest torsional rigidity. CONCLUSION: We concluded that the lordotic rod-screw system was the most rigid among the systems tested and the risk of rod and screw failure is much higher in the kyphotic rod-screw systems. Further biomechanical studies should be attempted to compare between different rod kyphotic angles to minimize the kyphotic rod failure rate and to offer a more stable and rigid rod-screw construct models for surgical application in the kyphotic vertebrae.
Molecular Weight ; Polyethylene ; Spine*

This study aimed to extract and type the plasmids of S. typhi strains and antibiogram. 2 S. typhi strains were selected. One multi-antibiotic resistant strain carried only R-plasmid and the other sensitive strain carried 2 smaller plasmids. Both of them were cultured and extracted DNA plasmid. Then 20 different enzymes were analysed to choose proper enzymes. There were 7 enzymes met the requirements. For DNA of larger plasmid, Kpn 1 and Sca 1 cut to 11 fractions. All of them had lower molecular weight than standard DNA. For DNA of smaller plasmid, Kpn 1 enzyme cut to 16 fractions, BamH 1 cut to 10 fractions, Mlu cut to 9 fractions, Cla cut to 11 fractions, and Bgl II cut to 7 fractions. All these fractions had lower weight than standard DNA. Molecular weight of larger plasmid is 188 206bp X 660D = 124 215 960D (124MD). That of smaller plasmid is 99 731bp X 660D = 65 822 460D.
Plasmids ; Molecular Weight

Dissolving pulp consists of high purity cellulose and is widely used to as raw materials for the production of regenerated cellulose fiber, cellulose ester and cellulose ether. The characteristic of dissolving pulp affects greatly the production and processing performance of subsequent products. The α-cellulose content, hemicellulose content, pulp viscosity, ash, transition metal ion content, fiber morphology, molecular weight distribution of cellulose and the reactivity are the important properties. Because of its green, mild and high efficiency, the application of enzymes in improving the properties of dissolving pulp has a promising application prospect and has been researched significantly. In this review, the main properties of dissolving pulp are presented first, followed by a recommendation of the enzymes to improve these properties. The application and current research of cellulase and xylanase in improving the properties of dissolving pulp are emphasized. The main problems and the future research areas in improving the properties of dissolving pulp by enzymes are revealed. Finally, the technology prospects in this field are proposed.
Cellulase ; Molecular Weight ; Viscosity ; Wood

PURPOSE: To evaluate the NMR relaxation properties and imaging characteristics of tissue-specificity for a newly developed macromolecular MR agent. MATERIALS AND METHODS: Phthalocyanine (PC) was chelated with paramagnetic ion, Mn. 2.01g(5.2 mmol) of Phthalocyanine was mixed with 0.37g (1.4 mmol) of Mn chloride at 310 degrees C for 36 hours and then purified by chromatography (CHC13/CH3OH 98/2 v/v, Rf, 0.76) to obtain 1.04g (46%) of MnPC (molecular weight = 2000d), The T1/T2 relaxivity of MnPC was measured in 1.5T(64 MHz) MR using 0.1 mM MnPC. The MR image characteristics of MnPC was evaluated using spin-echo (TR/TE = 500/14 msec) and gradient-echo (FLASH) (TR/TE = 80/4 msec, flip angle = 60) techniques in 1.5T MR scanner. The images of rabbit liver were obtained every 10 minutes up to 4 hours. To study the effect of concentration on image, 20 mM, 50 mM, 100 mM of MnPC were tested. RESULTS: The relaxivities of MnPC at 1.5T (64MHz) were R1 = 7.28 mM-1S-1, R2 = 55.56 mM-1S-1. Compared to the values of Gd-DTPA (R1[= 4.8 mM-1S-1), R2[= 5.2 mM-1S-1]), both T1/T2 relaxivities of MnPC were higher than those of Gd-DTPA. For both of SE and FLASH techniques, the contrast enhancement reached maximum at 10 minutes after bolus injection and the enhancement continued for more than 2 hours. When compared with small molecular weight liver agents such as Gd-EOB-DTPA, Gd-BOPTA and MnDPDP, MnPC was characterized by more prolonged enhancement time. The time course of MR images also revealed biliary excretion of MnPC. CONCLUSION: We developed a new macromolecular MR agent, MnPC. The relaxivities of MnPC were higher than those of small molecular weight Gd-chelate. Hepatic uptake and biliary excretion of MnPC suggests that this agent is a new liver-specific MR agent.
Chromatography ; Gadolinium DTPA ; Liver ; Molecular Weight ; Relaxation

Dextranase can degrade dextran polymer into low molecular weight polysaccharide. Dextranase and its hydrolysates are widely used in food, medicine and chemical industries. Studies on dextranase progresses rapidly in recent years. We reviewed literature reports combined with our study about the progress of dextranase and its potential applications in industry. In addition, we addressed hot topics and emphasized on the current research about dextranase, existing problems in domesticstudies and the future research needs needs.
Dextranase ; chemistry ; Dextrans ; chemistry ; Molecular Weight ; Polymers

Intracranial venous infarction and drainage alteration are rare clinical events developing after intracranial operation. Immediate anticoagulation has been recommended to restore the alteration of the intracranial venous drainage. However, for the venous drainage alteration or infarction developed just after intracranial operation, the bleeding tendency induced by the anticoagulation should be considered. We report a case of successfully managed cortical venous infarctions developed immediately after intracranial operation using low molecular weight heparin.
Drainage* ; Hemorrhage ; Heparin, Low-Molecular-Weight* ; Infarction

Based on the nanofiltration mass transfer model, the enhanced separation behavior of ephedrine in organic solution was studied. In the experiment, the sensitive region of ethanol concentration and pH on the rejection of ephedrine was screened out by Box-Behnken central composite experiment design. Furthermore, to analyze the separation regularity of ephedrine and organic solution, the correlation between mass transfer coefficient and concentration of organic solvent was fitted with the changed organic solution by nanofiltration mass transfer mathematical model. Experiments showed the enhanced separation behavior, the decrease in the mass transfer coefficient while the increase in ethanol concentration from 20% to 40%, MWCO at 450 and pH 6.0. Under the same conditions, the enhanced separation behavior was appeared as the solvent changed into methanol and acetonitrile, the enhanced effect was positively correlated with the concentration of the three common organic solvents, and the effect order was acetonitrile>ethanol>methanol. This study took ephedrine as an example, and explored the mechanism of nanofiltration separation in the environment of organic solution, so as to provide references for nanofiltration separation for heat-sensitive traditional Chinese medicine of alkaloid.
Ephedrine ; chemistry ; Ethanol ; Methanol ; Molecular Weight ; Solvents

The purpose of this study is to see the value of transsectional morphology of polyethylene for evaluation of wear and characteristics of ultra-high molecular weight polyethylene. Retrieved nineteen polyeth- ylene tibial components were examined for this study. Ten components were the directly molded 1900 Himont polyethylene, and 9 components were the machined GUR 415 polyethylene. Transsection of polyethylene(thickness: 60 - 150 micron) was obtained by microtome and was examined microscopical- ly for the fusion defects, subsurface white bands, and delamination as a mode of wear. Significant differ- ences between two groups of polyethylene were found. Fusion defects greater than 100 micron were observed in 5 among 9 GUR 415 polyethylene. Subsurface white band were observed in 7 among 9 GUR 415 polyethylene. Delamination was found in 6 arnong 9 GUR 415 polyethylene. Neither fusion defects greater than 100 micron, nor delamination were observed in 1900 Himont polyethylene. Morphological examination of polyethylene section is an efficient way to differentiate the polyethylene and to evaluate the wear behavior of retrieved polyethylene. This study suggests that delamination of polyethylene tibial components is influenced by resin type and / or manufacturing method.
Arthroplasty* ; Fungi ; Knee* ; Molecular Weight ; Polyethylene*

Warfarin-induced skin necrosis is a rare complication caused by transient hypercoagulable state. This state is a result of rapid decline of the protein C activity relative to that of coagulation factor II, IX, and X during initiation of oral anticoagulant therapy. We experienced a case of warfarin-induced skin necrosis involving both breasts in a patient who underwent double valve replacement 1 month before. Warfarin was replaced to a low- molecular weight heparin and the necrotic breast lesion was healed spontaneously. Low-dose warfarin was restarted and gradually increased, after which a low molecular weight heparin discontinued.
Breast ; Heparin ; Heparin, Low-Molecular-Weight ; Humans ; Molecular Weight ; Necrosis* ; Protein C ; Prothrombin ; Skin* ; Warfarin