Dual Setting β-tricalcium Phosphate Composite Cement

Dual Setting ÃŽ ²-tricalcium Phosphate Composite Cement Dual Setting ÃŽ ²-tricalcium Phosphate Composite Cement Obtained by 3D Printing Abstract: Calcium phosphate cements (CPCs) could be employed as synthetic bone graft substitutes or in the manufacture of scaffolds for tissue engineering. The limitations of these systems are their low mechanical strength, which limits its use to places with small mechanical stresses; however, the use of polymeric additives such us acrylamide (AA) and ammonium polyacrylate (PA), reinforced the system through in situ polymerization and increase the mechanical properties of the final piece. Moreover, the fabrication of the cement scaffolds through rapid prototyping technologies at low temperatures such as 3D printing, will allows the fabrication of more complex forms and customization of implants. Thus, the objective of this work was the evaluation of the ÃŽ ±-tricalcium phosphate/AA/PA system in the fabrication of scaffolds by rapid prototyping technology. The results showed slight differences between the porosities of the printed pieces (61% for cylindrical test bodies and 59% for rectangular ); but water absorption was significantly different for each type of printed form. Mechanical strength (1.3MPa) and flexural stress (3.2MPa) were lower than expected due to the high porosity of the samples although the morphology of the final material showed the presence of homogeneous and interlinked network of hydroxyapatite crystals. Nevertheless, printed materials might be used as spongy graft substitutes or scaffolds for tissue engineering in low-mechanical solicitation. Calcium phosphate cements (CPCs) could be employed as synthetic bone graft substitutes or scaffolds for tissue engineering allowing the fabrication of more complex geometries and the customization of the implants mainly due to the possibility of be molded [1]. Moreover, the use of additive manufacturing technologies at low temperatures such as 3D printing permits the fabrication of pieces with enhanced performance over traditional techniques [2-3]. Usually, the obtained pieces have low mechanical strength, which limits its use to places with small mechanical stresses; however, the use of polymeric additives such as acrylamide (AA) and ammonium polyacrylate (PA), could reinforce the system through in situ polymerization and increase the mechanical properties of the final piece [4]. Some studies reports the use of calcium phosphate powders such as à ¯Ã‚ Ã‚ ¢-tricalcium phosphate, tetracalcium phosphate, and ÃŽ ²-tricalcium phosphate [ÃŽ ²-Ca3(PO4)2; ÃŽ ²-TCP] as row material in the manufacture of scaffolds by means of 3D printing technology [5-8]. However, none of the reported studies refer the use of dual setting ÃŽ ²-TCP-based cement hydraulic system as proposed by the authors. Thus, the aim of this work was the fabrication and characterization of a dual setting composite cement based on ÃŽ ²-tricalcium phosphate (ÃŽ ²-TCP)/AA/PA by 3D printing technology. A Z310 Plus Printer Prototyper was used to print the pieces. Previously shyntethized ÃŽ ²-TCP powder [9], was mixed with ammonium persulfate [(NH4)2S2O8] and placed in the printer chamber. Powder layer thickness was set to 0.0875mm and binder liquid/powder ratio was 0.31mL/g. The binder was composed by a solution of 5%wt Na2HPO4, 10%wt acrylamide (AA), 1% N,N methylenebisacrylamide and 0.5% N,N,N,N- tetramethylethylenediamide [4]. Pieces in the form of cylinders and rectangles for compressive and 4 point bending assays were prototyped. Phase composition of the samples was determined by X-Ray Diffraction (XRD) in a PHILLIPSà ¯Ã†â€™Ã¢â‚¬â„¢ diffractometer (X ´Pert MPD). Morphological differences were observed by Scanning Electron Microscopy (SEM) using a JEOL microscope (JSM-6060). Compressive strength (CS) and flexure stress (FS) were measured in servohydraulic Universal Testing Machine (Instron 3369) with a load measuring cell of 2kN and a loading rate of 1 mm/min. Figure 1 shows a photograph of the printed materials after removing powder excess. Minor differences were observed in relation to the original sample size. Figure 2 shows the XRD patterns of ÃŽ ²-TCP powder and prototyped cement after 7 days in water/37.5 °C. After setting and aging, some ÃŽ ²-TCP peaks (JCPDS 09-0348) could be identified in addition to the characteristics peaks of CDHA (JCPDS 46-0905). Mechanical properties, water absorption apparent porosity and density can be observed in Table 1. Values of both compressive strength, and flexure stress were very low. Slight differences between the values of apparent porosity of the samples were found as a function of the arraignment of prototyped piece; on the other hand, apparent density values were the same regardless of the format of the piece. Microstructural features of the prototyped material are shown in Figure 4. Typical petal-like plates distinctive of setting and hardening ÃŽ ±-TCP-based cements can be observed both on the surface and the fracture surface. However, the size of the crystals in the inside of the material is higher (à ¯Ã‚ Ã‚ ¾5à ¯Ã‚ Ã‚ ­) than those found in the surface and a greater homogeneity is observed. In addition, some unreacted ÃŽ ±-TCP grains and macropores from about 5 microns of diameter can be observed at the outward of materials. No evidence of the presence of the hydrogel formed during the in situ polymerization of acrylamide was observed. Usually, strength is difficult to reproduce for ÃŽ ²-TCP-based CPCs because of the variability of ÃŽ ²-TCP phosphate properties from different sources. Factors like mean particle size and distribution, specific surface area, wettability, and phase impurities markedly influence the properties of the resulting cement. Since the precipitation of CHDA is responsible for the adherence and interlocking of the crystalline grains, which results in hardening; the fall of the mechanical strength can be attributed to the low transformation of ÃŽ ²-TCP into CDHA (Eq 1) according to the results of XRD. The value of the apparent density was close to the theoretical density of ÃŽ ²-TCP (2.86g/cm3), confirming no transformation of this phase into CHDA. When polymerization is conducted in aqueous slurry of ceramic powder, the resulted crosslinked polyacrilamide hydrogel is able to bind the ceramic particles and provide strength to the resulting system [10]. However, the addition of acrylamide to the system apparently did not work as reinforcement of the ÃŽ ²-TCP-based cement as expected. Moreover, the presence of the hydrogel after polymerization could be prevented the solubilization of the ÃŽ ²-TCP particles and subsequently inhibited the precipitation of the CDHA; so the strength of materials decreases. Furthermore, the high porosity of the prototyped materials also negatively influences the mechanical strength obtained. Water absorption values were not significantly different from those found for samples of cement without additions hydrogel [11], which reinforces the idea that it could be possible that the in situ polymerization of the acrylamide have not occurred. SEM results showed the presence of large number of plate-like crystals of aged CDHA in both: surface and fracture surface. Differences in the sizes of the crystals are due to the mechanism of hydrolysis which is dependent on the diffusion of fluid through the layer formed and occurs from the inside to the outside of the material. However, even though the presence of this entanglement of CDHA is responsible for the mechanical strength, the existence of unreacted ÃŽ ²-tricalcium phosphate and the high porosity of the prototyped materials are critical factors in the final properties of the cement. In conclusion, it is possible to obtaining scaffolds of dual setting hydraulic cement by 3D printing. The mechanical properties thereof are low for applications where high mechanical stresses were required. Nevertheless, the obtained pieces were high porosity and could be used as scaffolds for cellular growth and cancellous bone replacement. Acknowledgment The authors acknowledge the financial support from CNPq-the National Science and Technology Development Council (Research Grant 190005/2013-0). 1

Com/156 Week: 5: Outline and Thesis Statement Guide

Appendix H: Outline and Thesis Statement Guide name COM/156 date instructor Associate Level Material Appendix H Outline and Thesis Statement Guide A smoker may breathe better, have a less chance of getting cancer, and live longer if a choice is made to quit early in life. The benefits on their health when they quit smoking at an early age are immediate and substantial. A smoker may breathe better, have a less chance of getting cancer, and live longer if a choice is made to quit early in life. There are more reasons to stop smoking than there are to continue.Smoking cessation is the most important step that smokers can take to enhance the length and quality of their lives. I. There are many causes which make people smoke and  the effect of smoking  to their health. Even though smoker claim to get a calming affect when smoking, the negative outweigh the positive. Scientists and experts have made their point about there are some very severe reasons of smoking but its critical conseq uences should also be taken into consideration. However, it can divide to two main causes which are physical and psychological. A.The main causes for smoking are physical and psychological. 1. The physical cause of smoking concerns the human body's need for nicotine. 2. Smoking is psychological and seems to be due to low self-esteem. B. Not only does smoking cause diseases and is a slow way to die because of the effect smoking has on the human body. They know smoking has effects on the human body such like to the eyes, mouth and throat; lung, heart, stomach; pancreas and it also can cause cancers to those targeted areas. 1. The effect of smoking on the eyes, mouth and throat 2.The effect of smoking on the lung and heart 3. The effect of smoking on the stomach and pancreas II. When they stop smoking, their body experiences some positive side effects that may lengthen their lifespan. These positive aspects come in a lengthy time frame but with the ability to refrain from smoking, they will soon feel healthier all throughout their body. A. 20 minutes after they decide to quit smoking their body already starts healing. 1. Blood pressure returns to normal. 2. Pulse becomes stable and normal again. B.The effects of smoking cessation after 8 hours. 1. Oxygen levels turn to normal. 2. Nicotine and carbon monoxide levels in the blood are reduce by half. C. The effects of smoking cessation after 12-24 hours. 1. Carbon monoxide levels in blood drop to normal. 2. Carbon monoxide will be eliminated from the body. 3. Lungs start to clear out mucous and other smoking debris. D. The effects of smoking cessation after 48-72 hours. 1. There is no nicotine left in the body. 2. Ability to taste and smell is improved. 3. Breathing becomes easier. 4.Bronchial tubes begin to relax and energy levels increase. E. The effects of smoking cessation after 2-12 weeks. 1. Circulation improves. 2. Lung function increases. F. The effects of smoking cessation after 3-0 months. 1. Lung function s are increased by up to 10% which reduces coughs, wheezing and breathing problems. 2. Exercise becomes easier without losing your breath. G. The effects of smoking cessation after 12 months. 1. Excess risk of heart disease is about half and declines gradually hereafter. 2. A healthier heart starts to emerge on medical records. III.After the first year, their body continues to heal up until 15 years after they have quit the habit of smoking. The risk for certain disease becomes less and the way that they feel improves even more. A. The risk of heart attacks and strokes become less. 1. Risk of heart attack falls to about half that of a smoker. 2. Risk of stroke returns to the level of people who have never smoked (5-15 years). I. The effects of smoking cessation after 10-15 years. 1. Risk of lung cancer falls to about half that of a smoker. 2. Risk of lung cancer is less than that observed in nonsmokers. . Risk of coronary heart disease is no different than that of someone who has ne ver smoked. 4. If you have quit smoking before age 50 you have halved the risk of dying in the next 15 years compared with continuing smokers. In conclusion the sooner they quit smoking the sooner their body can start to heal. The healing process takes 15 years to completely reach its full potential. With this being said, the sooner a person quits smoking, the more chance they have to breathe better, have a less chance of getting cancer, and live longer.It is said that if they quit smoking by the age of 50, they are giving themselves longer than 15 more years to die. Younger people heal faster than older people, this is a known fact. The younger a person is when they decide to quit smoking, the longer they will live according to their physical health. References Stop smoking programs. (2012). Retrieved from http://www. stop-smoking-programs. org/quit-smoking-benefits. html University Of Phoenix. (2012). Appendix H: Outline and Thesis Statement Guide. Retrieved from University Of Pho enix, COM156 Version 5 website.

Comparison of “AP” by John Updike and “Barn Burning” by...

William Faulkner and John Updike short stories share the same theme loyalty. The use of different literary elements to explore this similarity is what differs within the two stories. The authors take different approaches such as characters, settings, and point of views to communicate the theme to the reader. Throughout both short stories, the reader can receive a precise overview of loyalty. Even though the differences of literary elements are announced, one can still analyze the deeper meaning overall. In â€Å"AP† there is a young nineteen year old boy name Sammy. He is currently working and to the readers perspective is for his family. Mr. Lengal says, Sammy, you dont want to do this to your Mom and Dad† (Updike, â€Å"AP†). The main character Sammy has dreams beyond being the manager at AP grocery store. Within the story, he also hopes to win the three girls attention. In the short story â€Å"Barn Burning†, Sartoris is the main character that is going through poverty because of his father’s actions. He soon comes to realization that his father has to stop what he is doing because it is wrong and is hurting the family in the end. â€Å"What†¦What are you†¦Ã¢â‚¬  cried Sarty (Updike, â€Å"AP†). The quote shows that Sarty had begun questioning his father and then realized he was planning on burning another barn. â€Å"AP† takes place in a grocery store. The grocery store, AP, is five miles from a beach which explains why the three girls walked into the store with bathing suits on. â€Å"Barn Burning†

Sports At High School Sports - 1945 Words

Although sports may be a distraction I think it’ll make kids work harder and strive for the necessary GPA to play. I’m all for sports in secondary schools it’ll give kids motive to do better in school. Many schools require that kids have at least have 2.0 to play any sports. That will make kids who really have a passion for sports to strive for that GPA. I think a 2.0 is an acceptable standard because it is mid range. Also, sports have other benefits. Sports Boost School spirit and student productivity. Those students who play sports in high school are local and they want to aspire themselves to be elite athletes. There are many schools that offer a wide range of subjects that meet the need and interests students of different students.†¦show more content†¦Examples of this include having excessive protein and even doing steroids that can cause hormonal and sexual disorders, temporary infertility, high blood pressure, high cholesterol and several other physical changes. It is estimated that about 3.5 million Americans do steroids and about 3% of American teenagers have tried it at some point in their lives. There are many more drugs to be afraid of. Pain relievers are just as harmful as any other drug.They temporarily numb the athlete so they can finish the remaining game with what seems to be no pain. Then afterward the damage could be irreversible. There are also many more health risks involved with high school sports. Football causes more injuries than any other sport simply because there are the most football athletes. Since 2000, 145 high-school football players have died from football-related accidents. There were more than 2.6 million children ages 19 and under are seen in emergency departments for injuries related to sports and recreation each year. This includes sports, such as football and basketball. 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