A comparative study of the mechanical performance of Glass and Glass/Carbon hybrid polymer composites at different temperature environments

NASA Astrophysics Data System (ADS)

Shukla, M. J.; Kumar, D. S.; Mahato, K. K.; Rathore, D. K.; Prusty, R. K.; Ray, B. C.

2015-02-01

Glass Fiber Reinforced Polymer (GFRP) composites have been widely accepted as high strength, low weight structural material as compared to their metallic counterparts. Some specific advanced high performance applications such as aerospace components still require superior specific strength and specific modulus. Carbon Fiber Reinforced Polymer (CFRP) composites exhibit superior specific strength and modulus but have a lower failure strain and high cost. Hence, the combination of both glass and carbon fiber in polymer composite may yield optimized mechanical properties. Further the in-service environment has a significant role on the mechanical performance of this class of materials. Present study aims to investigate the mechanical property of GFRP and Glass/Carbon (G/C hybrid) composites at room temperature, in-situ and ex-situ temperature conditions. In-situ testing at +70°C and +100°C results in significant loss in inter-laminar shear strength (ILSS) for both the composites as compared to room temperature. The ILSS was nearly equal for both the composite systems tested in-situ at +100°C and effect of fiber hybridisation was completely diminished there. At low temperature ex-situ conditioning significant reduction in ILSS was observed for both the systems. Further at -60°C G/C hybrid exhibited 32.4 % higher ILSS than GFRP. Hence this makes G/C hybrid a better choice of material in low temperature environmental applications.

Comparative life cycle studies on poly(3-hydroxybutyrate)-based composites as potential replacement for conventional petrochemical plastics.

PubMed

Pietrini, Matteo; Roes, Lex; Patel, Martin K; Chiellini, Emo

2007-07-01

A cradle-to-grave environmental life cycle assessment (LCA) of a few poly(3-hydroxybutyrate) (PHB) based composites has been performed and was compared to commodity petrochemical polymers. The end products studied are a cathode ray tube (CRT) monitor housing (conventionally produced from high-impact polystyrene, HIPS) and the internal panels of an average car (conventionally produced from glass-fibers-filled polypropylene, PP-GF). The environmental impact is evaluated on the basis of nonrenewable energy use (NREU) and global warming potential over a 100 years time horizon (GWP100). Sugar cane bagasse (SCB) and nanoscaled organophilic montmorillonite (OMMT) are used as PHB fillers. The results obtained show that, despite the unsatisfying mechanical properties of PHB composites, depending on the type of filler and on the product, it is possible to reach lower environmental impacts than by use of conventional petrochemical polymers. These savings are mainly related to the PHB production process, while there are no improvements related to composites preparation. SCB-based composites seem to be environmentally superior to clay-based ones.

[Comparative study of chemical composition of pomegranate peel pomegranates inside and pomegranate seeds].

PubMed

Zhou, Qian; Sun, Li-Li; Dai, Yan-Peng; Wang, Liang; Su, Ben-Zheng

2013-07-01

An HPLC fingerprint of pomegranate peel was established. Using chromatographic conditions, we compared the chemical composition of pomegranate peel, inside and seeds, and simultaneously determined the contents of gallic acid and ellagic acid. By comparison, we found that there were no significant differences between pomegranate peel and inside, but there was a big difference between pomegranate seeds and another two. The contents of gallic acid and ellagic acid of pomegranate peel respectively were 0.33%, 0.59%, while in pomegranate inside the result respectively were 0.52%, 0.38%. Content of ellagic acid from pomegranate seeds was only 0.01%. By study, we thought that when pomegranate peel was processed, pomegranate seeds should be removed, while pomegranate inside could be retained on the premise of full drying.

Comparative study of the nutritional composition and toxic elements of farmed and wild Chanodichthys mongolicus

NASA Astrophysics Data System (ADS)

Jiang, Haifeng; Cheng, Xiaofei; Geng, Longwu; Tang, Shizhan; Tong, Guangxiang; Xu, Wei

2017-07-01

Information of the difference in quality between farmed and wild fish is central to better ensuring fish products produced in aquaculture meet regulatory and consumer requirements. Proximate composition, amino acid and fatty acid profiles, and toxic elements contents of farmed and wild Chanodichthys mongolicus were established and compared. Significantly higher crude protein content while lower moisture content in farmed fish compared to wild fish were observed ( P<0.05). The percentages of total amino acids (TAA), total essential amino acids (TEAA), total non-essential amino acids (TNEAA) and total delicious amino acids (TDAA) in farmed fish were all significantly higher than those in the wild equivalent ( P<0.05). Compared to the FAO/WHO recommended reference values, the ratios of TEAA/TAA (39.84%-40.33%) were comparable to 40% and TEAA / TNEAA (66.22%-67.60%) were above 60%. Fatty acid profiles in both farmed and wild C. mongolicus were dominated by monounsaturated fatty acid (MUFA), with farmed fish contained much more MUFA content compared to wild counterpart ( P<0.05). Notably, wild fish exhibited significantly higher levels of total polyunsaturated fatty acid (PUFA) including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) than farmed fish ( P<0.05). The EPA (C20:5n3) and linoleic acid (C18:2n6) were the predominant PUFA in wild and farmed C. mongolicus, respectively. Moreover, farmed fish displayed an overall lower toxic element levels (As, Cd, Pb and Hg) in comparison with wild fish, and both were far lower than the established limit standard. In conclusion, our results suggest that the nutritional quality of farmed C. mongolicus was inferior to their wild counterpart with respect to fatty acids nutrition, and therefore further studies should focus on the improving C. mongolicus diet in order to enhance the overall nutritional composition.

Comparative Evaluation of Fracture Strength of Different Types of Composite Core Build-up Materials: An in vitro Study.

PubMed

Gowda, Srinivasa; Quadras, Dilip D; Sesappa, Shetty R; Maiya, G R Ramakrishna; Kumar, Lalit; Kulkarni, Dinraj; Mishra, Nitu

2018-05-01

The aim of the study was to evaluate the fracture strength of three types of composite core build-up materials. The objectives were to study and evaluate the fracture strength and type of fracture in composite core build-up in restoration of endodonti-cally treated teeth with or without a prefabricated metallic post. A total of 60 freshly extracted mandibular premolars free of caries, cracks, or fractures were end-odontically treated and restored with composite core build-up with prefabricated metallic posts cemented with resin luting cement (group I) and without a post (group II). This was followed by a core build-up of 10 teeth each with three different types of composite materials: Hybrid composite, nanocomposite, and ormocer respectively. The samples were mounted on polyvinyl chloride block and then loaded in the universal load frame at 90° to the long axis of tooth. The fracture strength of the samples was directly obtained from the load indicator attached to the universal load frame. Analysis of variance (ANOVA) test revealed that teeth restored with post exhibited highest fracture strength (1552.32 N) and teeth restored without post exhibited lowest fracture strength (232.20 N). Bonferroni's test revealed that values for hybrid composite (Z-100, 3M ESPE) with post, nanocomposite (Z-350, 3M ESPE) with post, ormocer composite (Admira-VOCO) with post, and nanocomposite (Z-350, 3M ESPE) without post were not significantly different from each other. Teeth restored with post and core using hybrid composite yielded the highest values for fracture strength. Teeth restored with ormocer core without post exhibited the lowest values. Teeth restored with nanocomposite core without post exhibited strength that was comparable with hybrid composite core but higher than that of ormocer. Mutilated endodontically treated teeth can be prosthetically rehabilitated successfully by using adhesive composite core build-up along with post to meet anatomical, functional, and

Comparing and improving reconstruction methods for proxies based on compositional data

NASA Astrophysics Data System (ADS)

Nolan, C.; Tipton, J.; Booth, R.; Jackson, S. T.; Hooten, M.

2017-12-01

Many types of studies in paleoclimatology and paleoecology involve compositional data. Often, these studies aim to use compositional data to reconstruct an environmental variable of interest; the reconstruction is usually done via the development of a transfer function. Transfer functions have been developed using many different methods. Existing methods tend to relate the compositional data and the reconstruction target in very simple ways. Additionally, the results from different methods are rarely compared. Here we seek to address these two issues. First, we introduce a new hierarchical Bayesian multivariate gaussian process model; this model allows for the relationship between each species in the compositional dataset and the environmental variable to be modeled in a way that captures the underlying complexities. Then, we compare this new method to machine learning techniques and commonly used existing methods. The comparisons are based on reconstructing the water table depth history of Caribou Bog (an ombrotrophic Sphagnum peat bog in Old Town, Maine, USA) from a new 7500 year long record of testate amoebae assemblages. The resulting reconstructions from different methods diverge in both their resulting means and uncertainties. In particular, uncertainty tends to be drastically underestimated by some common methods. These results will help to improve inference of water table depth from testate amoebae. Furthermore, this approach can be applied to test and improve inferences of past environmental conditions from a broad array of paleo-proxies based on compositional data

Curriculum time compared to clinical procedures in amalgam and composite posterior restorations in U.S. dental schools: a preliminary study.

PubMed

Rey, Rosalia; Nimmo, Susan; Childs, Gail S; Behar-Horenstein, Linda S

2015-03-01

Dental clinicians have an expanding range of biomaterial choices for restoring tooth structure. Scientific developments in cariology, advances in dental biomaterials, and patients' esthetic concerns have led to a reduction in amalgam restorations and an increase in composite restorations. The aim of this study was to compare teaching time with students' clinical procedures in amalgam and composite posterior restorations in dental schools across the United States. Academic deans in 60 schools were invited to complete a survey that asked for the amount of instructional time for amalgam and composite posterior restorations and the number of clinical restorations performed by their Classes of 2009, 2010, and 2011. Of these 60, 12 returned surveys with complete data, for a 20% response rate. Responses from these schools showed little change in lecture and preclinical laboratory instruction from 2009 to 2011. There was a slight increase in two-surface restorations for both amalgam and composites; however, the total number of reported composite and amalgam restorations remained the same. Of 204,864 restorations reported, 53% were composite, and 47% were amalgam. There were twice as many multisurface large or complex amalgam restorations as composites. One-surface composite restorations exceeded amalgams. Among the participating schools, there was little to no change between curriculum time and clinical procedures. Findings from this preliminary study reflect a modest increase in two-surface resin-based restorations placed by dental students from 2009 to 2011 and little change in curricular time devoted to teaching amalgam restorations. The total number of posterior composite restorations placed by students in these schools was slightly higher than amalgams.

COMPARATIVE ANALYSIS OF THE SHRINKAGE STRESS OF COMPOSITE RESINS

PubMed Central

Pereira, Rosana Aparecida; de Araujo, Paulo Amarante; Castañeda-Espinosa, Juan Carlos; Mondelli, Rafael Francisco Lia

2008-01-01

The aim of this study was to compare the shrinkage stress of composite resins by three methods. In the first method, composites were inserted between two stainless steel plates. One of the plates was connected to a 20 kgf load cell of a universal testing machine (EMIC-DL-500). In the second method, disk-shaped cavities were prepared in 2-mm-thick Teflon molds and filled with the different composites. Gaps between the composites and molds formed after polymerization were evaluated microscopically. In the third method, the wall-to-wall shrinkage stress of the resins that were placed in bovine dentin cavities was evaluated. The gaps were measured microscopically. Data were analyzed by one-way ANOVA and Tukey's test (α=0.05). The obtained contraction forces were: Grandio = 12.18 ± 0.428N; Filtek Z 250 = 11.80 ± 0.760N; Filtek Supreme = 11.80 ± 0.707 N; and Admira = 11.89 ± 0.647 N. The gaps obtained between composites and Teflon molds were: Filtek Z 250 = 0.51 ± 0.0357%; Filtek Supreme = 0.36 ± 0.0438%; Admira = 0.25 ± 0.0346% and Grandio = 0.16 ± 0.008%. The gaps obtained in wall-to-wall contraction were: Filtek Z 250 = 11.33 ± 2.160 μm; Filtek Supreme = 10.66 ± 1.211μm; Admira = 11.16 ± 2.041 μm and Grandio = 10.50 ± 1.224 μm. There were no significant differences among the composite resins obtained with the first (shrinkage stress generated during polymerization) and third method (wall-to-wall shrinkage). The composite resins obtained with the second method (Teflon method) differed significantly regarding gap formation. PMID:19089286

Less favorable body composition and adipokines in South Asians compared with other US ethnic groups: results from the MASALA and MESA studies.

PubMed

Shah, A D; Kandula, N R; Lin, F; Allison, M A; Carr, J; Herrington, D; Liu, K; Kanaya, A M

2016-04-01

Small studies have shown that South Asians (SAs) have more total body, subcutaneous, visceral and hepatic fat and abnormal adipokine levels compared with Whites. However, comprehensive studies of body composition and adipokines in SAs compared with other ethnic groups are lacking. Using harmonized data, we performed a cross-sectional analysis of two community-based cohorts: Mediators of Atherosclerosis of South Asians Living in America (MASALA, n=906) and Multi-Ethnic Study of Atherosclerosis (MESA which included 2622 Whites, 803 Chinese Americans, 1893 African Americans and 1496 Latinos). General linear models were developed to assess the ethnic differences in ectopic fat (visceral, intermuscular and pericardial fat; and hepatic attenuation), lean muscle mass and adipokines (adiponectin and resistin). Models were adjusted for age, sex, site, alcohol use, smoking, exercise, education, household income and body mass index. Ectopic fat models were additionally adjusted for hypertension, diabetes, high-density lipoprotein and triglycerides. Adipokine models were adjusted for subcutaneous, visceral, intermuscular and pericardial fat; and hepatic attenuation. Compared with all ethnic groups in MESA (Whites, Chinese Americans, African Americans and Latinos), SAs had greater intermuscular fat (pairwise comparisons with each MESA group, P<0.01), lower hepatic attenuation (P<0.001) and less lean mass (P<0.001). SAs had greater visceral fat compared with Chinese Americans, African Americans and Latinos (P<0.05) and greater pericardial fat compared with African Americans (P<0.001). SAs had lower adiponectin levels compared with other ethnic groups (P<0.01; except Chinese Americans) and higher resistin levels than all groups (P<0.001), even after adjusting for differences in body composition. There are significant ethnic differences in ectopic fat, lean mass and adipokines. A less favorable body composition and adipokine profile in SAs may partially explain the increased

Body composition phenotypes in systemic lupus erythematosus and rheumatoid arthritis: a comparative study of Caucasian female patients.

PubMed

Santos, M J; Vinagre, F; Canas da Silva, J; Gil, V; Fonseca, J E

2011-01-01

The amount and distribution of fat and lean mass have important implications for health and systemic inflammation may represent a risk for altered body composition. The aim of this study was to analyse whether changes in body composition are similarly associated with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), two inflammatory conditions of different pathogenesis. Body mass index (BMI), waist circumference, fat mass (FM) and fat-free mass (FFM) were measured in 92 women with SLE, 89 with RA and 107 controls. Results were compared among the 3 groups and correlations of FM percentage were explored within SLE and RA. Abnormal body composition was more frequent in women with SLE and RA than in non-inflammatory controls, despite having a similar BMI. RA diagnosis was significantly associated with overfat (OR=2.782, 95%CI 1.470-5.264; p=0.002) and central obesity (OR=2.998, 95%CI 1.016-8.841; p=0.04), while sarcopenia was more common among SLE (OR=3.003; 95%CI 1.178-7.676; p=0.01). Sarcopenic obesity, i.e. the coexistence of overfat with sarcopenia, was present in 6.5% of SLE and 5.6% of RA women, but no controls. Independent correlations of FM percentage in women with SLE included smoking, disease activity and CRP. In RA, education, disease activity and cumulative corticosteroid dose were identified as independent predictors of FM percentage. Women with SLE or RA diagnosis are more likely to have abnormal body composition phenotype, with some differences existing between these two conditions. Changes in body composition are partly explained by the inflammatory burden of disease and its treatment.

A Comparative Study of the Adsorption of Methylene Blue onto Synthesized Nanoscale Zero-Valent Iron-Bamboo and Manganese-Bamboo Composites

PubMed Central

Shaibu, Solomon E.; Adekola, Folahan A.; Adegoke, Halimat I.; Ayanda, Olushola S.

2014-01-01

In this study, bamboo impregnated with nanoscale zero-valent iron (nZVI) and nanoscale manganese (nMn) were prepared by the aqueous phase borohydride reduction method and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and PIXE analysis. The synthesized nMn-bamboo and nZVI-bamboo composites were subsequently applied to the sorption of methylene blue (MB) dye from aqueous solution. The adsorption of MB dye was investigated under various experimental conditions such as pH, contact time, initial concentration of MB dye and adsorbent dosage. The results showed that the synthesized nZVI-bamboo composite was more effective than nMn-bamboo composite in terms of higher MB dye adsorption capacity of 322.5 mg/g compared to 263.5 mg/g of nMn-bamboo composite. At a concentration of 140 mg/L MB dye, 0.02 g of nZVI-bamboo and nMn-bamboo composites resulted in 79.6% and 78.3% removal, respectively, at 165 rpm, contact time of 120 min and at a solution pH of 7.6. The equilibrium data was best represented by Freundlich isotherm model and the pseudo-second order kinetic model better explained the kinetic data for both nZVI-bamboo and nMn-bamboo composites. PMID:28788688

Comparative Studies on Al-Based Composite Powder Reinforced with Nano Garnet and Multi-wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Basariya, M. Raviathul; Srivastava, V. C.; Mukhopadhyay, N. K.

2015-11-01

Effect of mechanical alloying/milling on microstructural evolution and hardness variations of garnet and multi-walled carbon nanotubes (MWCNTs)-reinforced Al-Mg-Si alloy (EN AW6082) composites are investigated. Structural and morphological studies revealed that the composite powders prepared by milling display a more homogenous distribution of the reinforcing particles. Improved nanoindentation hardness viz., 4.24 and 5.90 GPa are achieved for EN AW6082/Garnet and EN AW6082/MWCNTs composites, respectively, and it is attributed to severe deformation of the aluminum alloy powders and embedding of the harder reinforcement particles uniformly into the aluminum alloy matrix. However, enhancement in case of MWCNTs-reinforced composite makes apparent the effect of its nanosized uniform dispersion in the matrix, thereby resisting the plastic deformation at lower stress and increased dislocation density evolved during high-energy ball milling. The results of the present study indicate that carbon nanotubes and garnet can be effectively used as reinforcements for Al-based composites.

Comparative study on proximate, functional, mineral, and antinutrient composition of fermented, defatted, and protein isolate of Parkia biglobosa seed.

PubMed

Ogunyinka, Bolajoko I; Oyinloye, Babatunji E; Osunsanmi, Foluso O; Kappo, Abidemi P; Opoku, Andrew R

2017-01-01

The use of plant-derived foods in the prevention, treatment, and management of metabolic diseases especially diabetes has gained prominence; this has been associated with their physicochemical properties. This study was conducted to compare the proximate, functional, mineral, and antinutrient composition of the fermented seeds, the defatted seeds, and the protein isolate from Parkia biglobosa seeds. The results showed that the fermented, defatted, and protein isolate varied in composition within the parameters studied. The proximate analysis revealed that the protein isolate had the highest ash (6.0%) and protein (59.4%) as well as the lowest fat (5.7%) and moisture (5.1%) content when compared to the fermented and defatted samples. In like manner, the functional properties of the protein isolate were relatively better than those of the fermented and defatted samples, with oil absorption capacity of 4.2% and emulsion capacity of 82%. The magnesium and zinc content of the protein isolate were significantly higher when compared with the fermented and defatted samples, while a negligible amount of antinutrient was present in all the samples, with the protein isolate having the lowest quantity. The overall data suggest that the protein isolate had better proximate, mineral, functional, and antinutrient properties when compared to the fermented and defatted samples. Therefore, the synergistic effect of all these components present in the protein isolate from P. biglobosa seed in association with its low carbohydrate and high protein/ash contents could play a vital role in the management of diabetes and its associated complications.

Comparative study of tow buckling defect during preforming of structural composites based on vegetable fibers

NASA Astrophysics Data System (ADS)

Salem, Mohamed; Fazzini, Marina; Ouagne, Pierre

2018-02-01

During the complex shape forming of composite fibrous reinforcement, the planar bending of roving tows results in an out-of-plane deflection, along with a rotation on its central axis. The need to accurately follow and quantify the mechanism of formation of such defect has led us to consider two 3D imaging techniques, of which, have been tested and compared in this work.

A comparative study on biodegradation and mechanical properties of pressureless infiltrated Ti/Ti6Al4V-Mg composites.

PubMed

Esen, Ziya; Bütev, Ezgi; Karakaş, M Serdar

2016-10-01

The mechanical response and biodegradation behavior of pressureless Mg-infiltrated Ti-Mg and Ti6Al4V-Mg composites were investigated by compression and simulated body fluid immersion tests, respectively. Prior porous preforms were surrounded uniformly with magnesium as a result of infiltration and the resultant composites were free of secondary phases and intermetallics. Although the composites' compressive strengths were superior compared to bone, both displayed elastic moduli similar to that of cortical bone and had higher ductility with respect to their starting porous forms. However, Ti-Mg composites were unable to preserve their mechanical stabilities during in-vitro tests such that they fractured in multiple locations within 15 days of immersion. The pressure generated by H2 due to rapid corrosion of magnesium caused failure of the Ti-Mg composites through sintering necks. On the other hand, the galvanic effect seen in Ti6Al4V-Mg was less severe compared to that of Ti-Mg. The degradation rate of magnesium in Ti6Al4V-Mg was slower, and the composites were observed to be mechanically stable and preserved their integrities over the entire 25-day immersion test. Both composites showed bioinert and biodegradable characteristics during immersion tests and magnesium preferentially corroded leaving porosity behind while Ti/Ti6Al4V remained as a permanent scaffold. The porosity created by degradation of magnesium was refilled by new globular agglomerates. Mg(OH)2 and CaHPO4 phases were encountered during immersion tests while MgCl2 was detected during only the first 5 days. Both composites were classified as bioactive since the precipitation of CaHPO4 phase is known to be precursor of hydroxyapatite formation, an essential requirement for an artificial material to bond to living bone. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Experimental study of PVPP/silicone composite automatic expanded material as implants].

PubMed

Yin, Wei-min; Gao, Jian-hua; Yang, Qing-fang; Lu, Feng; Ye, Jia-jia

2009-03-01

To study the feasibility of Polyvinylpolypyrrolidone (PVPP)/silicone composite automatic expanded material as implants. The PVPP hydrogel was mixed with silicone through the location at the high temperature. Implants with different ratio of PVPP to silicone were placed under the back and nose skin in 24 New Zealand rabbits. The surrounding tissue reaction, material and skin expansion were observed and compared with those with pure silicone implants. The study lasted for 200 days. Compared with pure silicone implants, the composite material could expand automatically and stop expanding at about 2 weeks after implantation. Histological study showed similar inflectional and foreign body reaction around the composite material and the pure silicone. Compared with pure silicone, the PVPP/silicone composite implant has the advantage of automatic expansion, so as to expand the soft tissue.

Comparative study between the radiopacity levels of high viscosity and of flowable composite resins, using digital imaging.

PubMed

Arita, Emiko S; Silveira, Gilson P; Cortes, Arthur R; Brucoli, Henrique C

2012-01-01

The development of countless types and trends of high viscosite and flowable composite resins, with different physical and chemical properties applicable to their broad use in dental clinics calls for further studies regarding their radiopacity level. The aim of this study was to evaluate the radiopacity levels of high viscosity and the flowable composite resins, using digital imaging. 96 composite resin discs 5 mm in diameter and 3 mm thick were radiographed and analyzed. The image acquisition system used was the Digora® Phosphor Storage System and the images were analyzed with the Digora software for Windows. The exposure conditions were: 70 kVp, 8 mA, and 0.2 s. The focal distance was 40 cm. The image densities were obtained with the pixel values of the materials in the digital image. Most of the high viscosity composite resins presented higher radiopacity levels than the flowable composite resins, with statistically significant differences between the trends and groups analyzed (P < 0.05). Among the high viscosity composite resins, Tetric®Ceram presented the highest radiopacity levels and Glacier® presented the lowest. Among the flowable composite resins, Tetric®Flow presented the highest radiopacity levels and Wave® presented the lowest.

A comparative study of Ni-Mn layered double hydroxide/carbon composites with different morphologies for supercapacitors.

PubMed

Li, M; Liu, F; Zhang, X B; Cheng, J P

2016-11-02

A variety of carbon materials varying from 0D to 2D, i.e. 0D nanoparticles, 1D carbon nanotubes (CNTs) and 2D reduced graphene oxide (rGO) are selected to in situ combine with Ni-Mn layered double hydroxide (LDH) to prepare electrode materials for supercapacitors. Through a simple solution method, hierarchical Ni-Mn LDH/carbon composites can be easily fabricated. A comparative study is carried out on the sandwich-like LDH/rGO, flower-like LDH/carbon black, turbostratic-structured LDH/CNTs and ternary LDH/CNTs/rGO for their structure, morphology, porous properties and electrochemical performances. The results show that the ternary Ni-Mn LDH/CNTs/rGO composite yields the highest specific capacitance of 1268 F g -1 in 2 M KOH electrolyte and a long lifespan, exhibiting great potential for supercapacitor applications. Meanwhile, investigation on the influence of the cation species of MOH (M = Li + , Na + or K + ) and the alkali concentration of the KOH electrolyte illustrates that increasing the concentration of the KOH electrolyte can benefit the capacitive performance of the electrode and that NaOH shows great advantages as an electrolyte for the Ni-Mn LDH/CNTs/rGO electrode due to its high capacitance and small resistance.

Comparative study of new autologous material, bone-cartilage composite graft, for ossiculoplasty with Polycel® and Titanium.

PubMed

Kong, J S; Jeong, C Y; Shim, M J; Kim, W J; Yeo, S W; Park, S N

2018-04-01

Ossiculoplasty is a surgical procedure that recreates sound transmission of the middle ear in conductive hearing loss. Various materials have been used for ossicular reconstruction, but the most ideal material for ossiculoplasty remains controversial. The purpose of this study was to introduce a novel method of autologous ossiculoplasty, bone-cartilage composite graft (BCCG) and to compare its surgical results with different types of ossiculoplastic prostheses. A retrospective study was performed in a tertiary referral centre. Data of 275 patients who received ossiculoplasty using the three different materials of BCCG, Polycel ® and titanium were analysed according to type of ossiculoplasty: partial or total ossicular replacement prosthesis (PORP or TORP). Hearing results, complication rates and clinical parameters including age, sex, past history, preoperative diagnosis and surgery type were compared among different groups. Ossiculoplasty with BCCG showed satisfactory hearing outcomes and the lowest complication rate among the three different materials. In particular, its extrusion rate was 0%. We propose that the BCCG technique is a useful alternative method for ossiculoplasty, with proper patient selection. © 2017 John Wiley & Sons Ltd.

Comparative Study of Chemical Composition and Biological Activity of Yellow, Green, Brown, and Red Brazilian Propolis

PubMed Central

Machado, Christiane Schineider; Mokochinski, João Benhur; de Lira, Tatiana Onofre; de Oliveira, Fátima de Cassia Evangelista; Cardoso, Magda Vieira; Ferreira, Roseane Guimarães; Sawaya, Alexandra Christine Helena Frankland; Ferreira, Antonio Gilberto; Pessoa, Cláudia; Cuesta-Rubio, Osmany; Monteiro, Marta Chagas; de Campos, Mônica Soares

2016-01-01

The chemical composition and biological activity of a sample of yellow propolis from Mato Grosso do Sul, Brazil (EEP-Y MS), were investigated for the first time and compared with green, brown, and red types of Brazilian propolis and with a sample of yellow propolis from Cuba. Overall, EEP-Y MS had different qualitative chemical profiles, as well as different cytotoxic and antimicrobial activities when compared to the other types of propolis assessed in this study and it is a different chemotype of Brazilian propolis. Absence of phenolic compounds and the presence of mixtures of aliphatic compounds in yellow propolis were determined by analysing 1H-NMR spectra and fifteen terpenes were identified by GC-MS. EEP-Y MS showed cytotoxic activity against human tumour strain OVCAR-8 but was not active against Gram-negative or Gram-positive bacteria. Our results confirm the difficulty of establishing a uniform quality standard for propolis from diverse geographical origins. The most appropriate pharmacological applications of yellow types of propolis must be further investigated. PMID:27525023

Passive damping of composite blades using embedded piezoelectric modules or shape memory alloy wires: a comparative study

NASA Astrophysics Data System (ADS)

Bachmann, F.; de Oliveira, R.; Sigg, A.; Schnyder, V.; Delpero, T.; Jaehne, R.; Bergamini, A.; Michaud, V.; Ermanni, P.

2012-07-01

Emission reduction from civil aviation has been intensively addressed in the scientific community in recent years. The combined use of novel aircraft engine architectures such as open rotor engines and lightweight materials offer the potential for fuel savings, which could contribute significantly in reaching gas emissions targets, but suffer from vibration and noise issues. We investigated the potential improvement of mechanical damping of open rotor composite fan blades by comparing two integrated passive damping systems: shape memory alloy wires and piezoelectric shunt circuits. Passive damping concepts were first validated on carbon fibre reinforced epoxy composite plates and then implemented in a 1:5 model of an open rotor blade manufactured by resin transfer moulding (RTM). A two-step process was proposed for the structural integration of the damping devices into a full composite fan blade. Forced vibration measurements of the plates and blade prototypes quantified the efficiency of both approaches, and their related weight penalty.

Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

PubMed

Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

2016-02-01

This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

Composite scores in comparative effectiveness research: counterbalancing parsimony and dimensionality in patient-reported outcomes.

PubMed

Schwartz, Carolyn E; Patrick, Donald L

2014-07-01

When planning a comparative effectiveness study comparing disease-modifying treatments, competing demands influence choice of outcomes. Current practice emphasizes parsimony, although understanding multidimensional treatment impact can help to personalize medical decision-making. We discuss both sides of this 'tug of war'. We discuss the assumptions, advantages and drawbacks of composite scores and multidimensional outcomes. We describe possible solutions to the multiple comparison problem, including conceptual hierarchy distinctions, statistical approaches, 'real-world' benchmarks of effectiveness and subgroup analysis. We conclude that comparative effectiveness research should consider multiple outcome dimensions and compare different approaches that fit the individual context of study objectives.

Comparative studies on structures, mechanical properties, sensitivity, stabilities and detonation performance of CL-20/TNT cocrystal and composite explosives by molecular dynamics simulation.

PubMed

Hang, Gui-Yun; Yu, Wen-Li; Wang, Tao; Wang, Jin-Tao; Li, Zhen

2017-09-19

To investigate and compare the differences of structures and properties of CL-20/TNT cocrystal and composite explosives, the CL-20/TNT cocrystal and composite models were established. Molecular dynamics simulations were performed to investigate the structures, mechanical properties, sensitivity, stabilities and detonation performance of cocrystal and composite models with COMPASS force field in NPT ensemble. The lattice parameters, mechanical properties, binding energies, interaction energy of trigger bond, cohesive energy density and detonation parameters were determined and compared. The results show that, compared with pure CL-20, the rigidity and stiffness of cocrystal and composite models decreased, while plastic properties and ductility increased, so mechanical properties can be effectively improved by adding TNT into CL-20 and the cocrystal model has better mechanical properties. The interaction energy of the trigger bond and the cohesive energy density is in the order of CL-20/TNT cocrystal > CL-20/TNT composite > pure CL-20, i.e., cocrystal model is less sensitive than CL-20 and the composite model, and has the best safety parameters. Binding energies show that the cocrystal model has higher intermolecular interaction energy values than the composite model, thus illustrating the better stability of the cocrystal model. Detonation parameters vary as CL-20 > cocrystal > composite, namely, the energy density and power of cocrystal and composite model are weakened; however, the CL-20/TNT cocrystal explosive still has desirable energy density and detonation performance. This results presented in this paper help offer some helpful guidance to better understand the mechanism of CL-20/TNT cocrystal explosives and provide some theoretical assistance for cocrystal explosive design.

Comparative activity of silver based antimicrobial composites for urinary catheters.

PubMed

Thokala, Nikhil; Kealey, Carmel; Kennedy, James; Brady, Damien B; Farrell, Joseph

2018-04-04

Biomedical polymers are an integral component in a wide range of medical device designs due to their range of desirable properties. However, extensive use of polymer materials in medical devices have also been associated with an increasing incidence of patient infections. Efforts to address this issue have included the incorporation of antimicrobial additives for developing novel antimicrobial polymeric materials. Silver with its high toxicity towards bacteria, oligodynamic effect and good thermal stability has been employed as an additive for polymeric medical devices. In the present study, commercially available elemental (Biogate) and ionic (Ultrafresh 16) silver additives were incorporated into a Polyamide 11 (PA 11) matrix using a compression press. These polymer composites were evaluated for their antimicrobial and ion release properties. Elemental silver composites were determined to retain their antimicrobial properties for extended periods and actively release silver ions for 84 days; whereas the ionic silver composites lost their ion release activity and therefore antibacterial activity after 56 days. Bacterial log reduction units of 3.87 for ionic silver and 2.41 for elemental silver was identified within 24 hr, when tested in accordance with ISO 22196 test standard; indicating that ionic silver is more efficient for short-term applications compared to elemental silver. Copyright © 2018 Elsevier Ltd. All rights reserved.

Algal and Invertebrate Community Composition along Agricultural Gradients: A Comparative Study from Two Regions of the Eastern United States

USGS Publications Warehouse

Calhoun, Daniel L.; Gregory, M. Brian; Weyers, Holly S.

2008-01-01

Benthic algal and invertebrate communities in two Coastal Plain regions of the Eastern United States?the Delmarva Peninsula (27 sites) and Georgia Upper Coastal Plain (29 sites)?were assessed to determine if aspects of agricultural land use and nutrient conditions (dissolved and whole-water nitrogen and phosphorus) could be linked to biological community compositions. Extensive effort was made to compile land-use data describing the basin and riparian conditions at multiple scales to determine if scale played a role in these relations. Large differences in nutrient condition were found between the two study areas, wherein on average, the Delmarva sites had three times the total phosphorus and total nitrogen as did the sites in the Georgia Upper Coastal Plain. A statistical approach was undertaken that included multivariate correlations between Bray-Curtis similarity matrices of the biological communities and Euclidean similarity matrices of instream nutrients and land-use categories. Invertebrate assemblage composition was most associated with land use near the sampled reach, and algal diatom assemblage composition was most associated with land use farther from the streams and into the watersheds. Link tree analyses were conducted to isolate portions of nonmetric multidimensional scaling ordinations of community compositions that could be explained by break points in abiotic datasets. Invertebrate communities were better defined by factors such as agricultural land use near streams and geographic position. Algal communities were better defined by agricultural land use at the basin scale and instream nutrient chemistry. Algal autecological indices were more correlated with gradients of nutrient condition than were typically employed invertebrate metrics and may hold more promise in indicating nutrient impairment in these regions. Nutrient conditions in the respective study areas are compared to draft nutrient criteria established by the U.S. Environmental Protection

Amino acid and proximate composition of fish bone gelatin from different warm-water species: A comparative study

NASA Astrophysics Data System (ADS)

Atma, Y.

2017-03-01

Research on fish bone gelatin has been increased in the last decade. The quality of gelatin depends on its physicochemical properties. Fish bone gelatin from warm-water fishes has a superior amino acid composition than cold-water fishes. The composition of amino acid can determine the strength and stability of gelatin. Thus, it is important to analyze the composition of amino acid as well as proximate composition for potential gelatin material. The warm water fish species used in this study were Grass carp, Pangasius catfish, Catfish, Lizard fish, Tiger-toothed croaker, Pink perch, Red snapper, Brown spotted grouper, and King weakfish. There werre five dominant amino acid in fish bone gelatin including glycine (21.2-36.7%), proline (8.7-11.7%), hydroxyproline (5.3-9.6%), alanine (8.48-12.9%), and glutamic acid (7.23-10.15%). Different warm-water species has some differences in amino acid composition. The proximate composition showed that fishbone gelatin from Pangasius catfish has the highest protein content. The water composition of all fishbone gelatin was well suited to the standard. Meanwhile, based on ash content, only gelatin from gelatin Pangasius catfish met the standard for food industries.

Experimental Study on Welded Headed Studs Used In Steel Plate-Concrete Composite Structures Compared with Contactless Method of Measuring Displacement

NASA Astrophysics Data System (ADS)

Kisała, Dawid; Tekieli, Marcin

2017-10-01

Steel plate-concrete composite structures are a new innovative design concept in which a thin steel plate is attached to the reinforced concrete beam by means of welded headed studs. The comparison between experimental studies and theoretical analysis of this type of structures shows that their behaviour is dependent on the load-slip relationship of the shear connectors used to ensure sufficient bond between the concrete and steel parts of the structure. The aim of this paper is to describe an experimental study on headed studs used in steel plate-concrete composite structures. Push-out tests were carried out to investigate the behaviour of shear connectors. The test specimens were prepared according to standard push-out tests, however, instead of I-beam, a steel plate 16 mm thick was used to better reflect the conditions in the real structure. The test specimens were produced in two batches using concrete with significantly different compressive strength. The experimental study was carried out on twelve specimens. Besides the traditional measurements based on LVDT sensors, optical measurements based on the digital image correlation method (DIC) and pattern tracking methods were used. DIC is a full-field contactless optical method for measuring displacements in experimental testing, based on the correlation of the digital images taken during test execution. With respect to conventional methods, optical measurements offer a wider scope of results and can give more information about the material or construction behaviour during the test. The ultimate load capacity and load-slip curves obtained from the experiments were compared with the values calculated based on Eurocodes, American and Chinese design specifications. It was observed that the use of the relationships developed for the traditional steel-concrete composite structures is justified in the case of ultimate load capacity of shear connectors in steel plate-concrete composite structures.

PMMA-hydroxyapatite composite material retards fatigue failure of augmented bone compared to augmentation with plain PMMA: in vivo study using a sheep model.

PubMed

Arabmotlagh, Mohammad; Bachmaier, Samuel; Geiger, Florian; Rauschmann, Michael

2014-11-01

Polymethylmethacrylate (PMMA) is the most commonly used void filler for augmentation of osteoporotic vertebral fracture, but the differing mechanical features of PMMA and osteoporotic bone result in overload and failure of adjacent bone. The aim of this study was to compare fatigue failure of bone after augmentation with PMMA-nanocrystalline hydroxyapatite (HA) composite material or with plain PMMA in a sheep model. After characterization of the mechanical properties of a composite material consisting of PMMA and defined amounts (10, 20, and 30% volume fraction) of HA, the composite material with 30% volume fraction HA was implanted in one distal femur of sheep; plain PMMA was implanted in the other femur. Native non-augmented bone served as control. Three and 6 months after implantation, the augmented bone samples were exposed to cyclic loading and the evolution of damage was investigated. The fatigue life was highest for the ovine native bone and lowest for bone-PMMA specimens. Bone-composite specimens showed significantly higher fatigue life than the respective bone-PMMA specimens in both 3- and 6-month follow-up groups. These results suggest that modification of mechanical properties of PMMA by addition of HA to approximate those of cancellous bone retards fatigue failure of the surrounding bone compared to augmented bone with plain PMMA. © 2014 Wiley Periodicals, Inc.

Comparative study of solvation parameter models accounting the effects of mobile phase composition in reversed-phase liquid chromatography.

PubMed

Torres-Lapasió, J R; Ruiz-Angel, M J; García-Alvarez-Coque, M C

2007-09-28

Solvation parameter models relate linearly compound properties with five fundamental solute descriptors (excess molar refraction, dipolarity/polarizability, effective hydrogen-bond acidity and basicity, and McGowan volume). These models are widely used, due to the availability of protocols to obtain the descriptors, good performance, and general applicability. Several approaches to predict retention in reversed-phase liquid chromatography (RPLC) as a function of these descriptors and mobile phase composition are compared, assaying the performance with a set of 146 organic compounds of diverse nature, eluted with acetonitrile and methanol. The approaches are classified in two groups: those that only allow predictions of retention for the mobile phases used to build the models, and those valid at any other mobile phase composition. The first group includes the use of ratios between the regressed coefficients of the solvation models that are assumed to be characteristic for a column/solvent system, and the application of offsets to transfer the retention from a reference mobile phase to any other. Maximal accuracy in predictions corresponded, however, to the approaches in the second group, which were based on models that describe the retention as a function of mobile phase composition (expressed as the solvent volume fraction or a normalised polarity measurement), where the coefficients were made dependent on the solvent descriptors. The study revealed the properties that influence the retention and distinguish the particular behaviour of acetonitrile and methanol in RPLC.

Impact of weighted composite compared to traditional composite endpoints for the design of randomized controlled trials.

PubMed

Bakal, Jeffrey A; Westerhout, Cynthia M; Armstrong, Paul W

2015-12-01

Composite endpoints are commonly used in cardiovascular clinical trials. When using a composite endpoint a subject is considered to have an event when the first component endpoint has occurred. The use of composite endpoints offers the ability to incorporate several clinically important endpoint events thereby augmenting the event rate and increasing statistical power for a given sample size. One assumption of the composite is that all component events are of equal clinical importance. This assumption is rarely achieved given the diversity of component endpoints included. One means of adjusting for this diversity is to adjust the outcomes using severity weights determined a priori. The use of a weighted endpoint also allows for the incorporation of multiple endpoints per patient. Although weighting the outcomes lowers the effective number of events, it offers additional information that reduces the variance of the estimate. We created a series of simulation studies to examine the effect on power as the individual components of a typical composite were changed. In one study, we noted that the weighted composite was able to offer discriminative power when the component outcomes were altered, while the traditional method was not. In the other study, we noted that the weighted composite offered a similar level of power to the traditional composite when the change was driven by the more severe endpoints. © The Author(s) 2011.

Mapping of compositional properties of coal using isometric log-ratio transformation and sequential Gaussian simulation - A comparative study for spatial ultimate analyses data.

PubMed

Karacan, C Özgen; Olea, Ricardo A

2018-03-01

Chemical properties of coal largely determine coal handling, processing, beneficiation methods, and design of coal-fired power plants. Furthermore, these properties impact coal strength, coal blending during mining, as well as coal's gas content, which is important for mining safety. In order for these processes and quantitative predictions to be successful, safer, and economically feasible, it is important to determine and map chemical properties of coals accurately in order to infer these properties prior to mining. Ultimate analysis quantifies principal chemical elements in coal. These elements are C, H, N, S, O, and, depending on the basis, ash, and/or moisture. The basis for the data is determined by the condition of the sample at the time of analysis, with an "as-received" basis being the closest to sampling conditions and thus to the in-situ conditions of the coal. The parts determined or calculated as the result of ultimate analyses are compositions, reported in weight percent, and pose the challenges of statistical analyses of compositional data. The treatment of parts using proper compositional methods may be even more important in mapping them, as most mapping methods carry uncertainty due to partial sampling as well. In this work, we map the ultimate analyses parts of the Springfield coal from an Indiana section of the Illinois basin, USA, using sequential Gaussian simulation of isometric log-ratio transformed compositions. We compare the results with those of direct simulations of compositional parts. We also compare the implications of these approaches in calculating other properties using correlations to identify the differences and consequences. Although the study here is for coal, the methods described in the paper are applicable to any situation involving compositional data and its mapping.

Autologous Cartilage Chip Transplantation Improves Repair Tissue Composition Compared With Marrow Stimulation.

PubMed

Christensen, Bjørn Borsøe; Olesen, Morten Lykke; Lind, Martin; Foldager, Casper Bindzus

2017-06-01

Repair of chondral injuries by use of cartilage chips has recently demonstrated clinical feasibility. To investigate in vivo cartilage repair outcome of autologous cartilage chips compared with marrow stimulation in full-thickness cartilage defects in a minipig model. Controlled laboratory study. Six Göttingen minipigs received two 6-mm chondral defects in the medial and lateral trochlea of each knee. The two treatment groups were (1) autologous cartilage chips embedded in fibrin glue (ACC) (n = 12) and (2) marrow stimulation (MST) (n = 12). The animals were euthanized after 6 months, and the composition of repair tissue was quantitatively determined using histomorphometry. Semiquantitative evaluation was performed by means of the International Cartilage Repair Society (ICRS) II score. Collagen type II staining was used to further evaluate the repair tissue composition. Significantly more hyaline cartilage was found in the ACC (17.1%) compared with MST (2.9%) group ( P < .01). Furthermore, the ACC group had significantly less fibrous tissue (23.8%) compared with the MST group (41.1%) ( P < .01). No significant difference in fibrocartilage content was found (54.7% for ACC vs 50.8% for MST). The ACC group had significantly higher ICRS II scores for tissue morphological characteristics, matrix staining, cell morphological characteristics, surface assessment, mid/deep assessment, and overall assessment ( P < .05). The ACC-treated defects had significantly more collagen type II staining (54.5%) compared with the MST-treated defects (28.1%) ( P < .05). ACC transplant resulted in improved quality of cartilage repair tissue compared with MST at 6 months postoperatively. Further studies are needed to investigate ACC as a possible alternative first-line treatment for focal cartilage injuries in the knee.

Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant.

PubMed

Petersen, Richard C

2011-05-03

Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8 mm, P < 10 -4 , and 19.3% to 77.7% at 0.1 mm, P < 10 -8 . Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential.

[Comparative study of polymerization shrinkage and related properties of flowable composites and an unfilled resin].

PubMed

Bukovinszky, Katalin; Molnár, Lilla; Bakó, József; Szalóki, Melinda; Hegedus, Csaba

2014-03-01

The polymerization shrinkage and shrinkage stress of dental composites are in the center of the interest of researchers and manufacturers. It is a great challenge to minimize this important property as low as possible. Many factors are related and are in complicated correlation with each other affecting the polymerization shrinkage. Polymerization shrinkage stress degree of conversion and elasticity has high importance from this aspect. Our aim was to study the polymerization shrinkage and related properties (modulus of elasticity, degree of conversion, shrinkage stress) of three flowable composite (Charisma Opal Flow, SDR, Filtek Ultimate) and an unfilled composite resin. Modulus of elasticity was measured using three point flexure tests on universal testing machine. The polymerization shrinkage stress was determined using bonded-disc technique. The degree of conversion measurements were performed by FT-IR spectroscopy. And the volumetric shrinkage was investigated using Archimedes principle and was measured on analytical balance with special additional equipment. The unfilled resin generally showed higher shrinkage (8,26%), shrinkage stress (0,8 MPa) and degree of conversion (38%), and presented the lowest modulus of elasticity (3047,02MPa). Highest values of unfilled resin correspond to the literature. The lack of fillers enlarges the shrinkage, and the shrinkage stress, but gives the higher flexibility and higher degree of conversion. Further investigations needs to be done to understand and reveal the differences between the composites.

Studies on thermo-mechanical properties of chemically treated jute-polyester composite

NASA Astrophysics Data System (ADS)

Chaudhari, Vikas; Chandekar, Harichandra; Saboo, Jayesh; Mascarenhas, Adlete

2018-03-01

The effect of chemical treatments on jute-polyester composites is studied in this paper. The jute fabrics are chemically treated with NaOH and benzoyl chloride and its tensile and visco-elastic properties are compared with untreated jute composite. The NaOH treated jute-polyester composite show superior tensile strength and modulus compared to other jute-polyester composites. The glass transition temperature obtained from DMA shift to higher temperature for composites in comparison to polyester resin, this is due to restriction of mobility in chains due to introduction of jute reinforcement. The DMA results also show favourable results towards NaOH treatment i.e. higher storage modulus and lower tan δ values relative to untreated jute-polyester composite. The benzoyl treated jute-polyester composite however do not show promising results which may be attributed to the fact that the adhesion properties associated with similar ester functional groups in the benzoyl treated jute fabric and polyester resin were not obtained.

Grinding, Machining Morphological Studies on C/SiC Composites

NASA Astrophysics Data System (ADS)

Xiao, Chun-fang; Han, Bing

2018-05-01

C/SiC composite is a typical material difficult to machine. It is hard and brittle. In machining, the cutting force is large, the material removal rate is low, the edge is prone to collapse, and the tool wear is serious. In this paper, the grinding of C/Si composites material along the direction of fiber distribution is studied respectively. The surface microstructure and mechanical properties of C/SiC composites processed by ultrasonic machining were evaluated. The change of surface quality with the change of processing parameters has also been studied. By comparing the performances of conventional grinding and ultrasonic grinding, the surface roughness and functional characteristics of the material can be improved by optimizing the processing parameters.

Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant

PubMed Central

Petersen, Richard C.

2014-01-01

Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8 mm, P < 10−4, and 19.3% to 77.7% at 0.1 mm, P < 10−8. Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential. PMID:25553057

Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic.

PubMed

He, Fupo; Ren, Weiwei; Tian, Xiumei; Liu, Wei; Wu, Shanghua; Chen, Xiaoming

2016-07-01

In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones. Copyright © 2016 Elsevier B.V. All rights reserved.

A comparative study on the tensile and impact properties of Kevlar, carbon, and S-glass/epoxy composites reinforced with SiC particles

NASA Astrophysics Data System (ADS)

Bulut, Mehmet; Alsaadi, Mohamad; Erkliğ, Ahmet

2018-02-01

Present study compares the tensile and impact characteristics of Kevlar, carbon and glass fiber reinforced composites with addition of microscale silicon carbide (SiC) within the common matrix of epoxy. The variation of tensile and impact strength values was explored for different content of SiC in the epoxy resin by weight (0, 5, 10, 15 and 20 wt%). Resulting failure characteristics were identified by assisting Charpy impact tests. The influence of interfacial adhesion between particle and fiber/matrix on failure and tensile properties was discussed from obtained results and scanning electron microscopy (SEM) figures. It is concluded from results that the content of SiC particles, and fiber types used as reinforcement are major parameters those effecting on tensile and impact resistance of composites as a result of different interface strength properties between particle-matrix and particle-fiber.

International collaborative project to compare and monitor the nutritional composition of processed foods.

PubMed

Dunford, Elizabeth; Webster, Jacqui; Metzler, Adriana Blanco; Czernichow, Sebastien; Ni Mhurchu, Cliona; Wolmarans, Petro; Snowdon, Wendy; L'Abbe, Mary; Li, Nicole; Maulik, Pallab K; Barquera, Simon; Schoj, Verónica; Allemandi, Lorena; Samman, Norma; de Menezes, Elizabete Wenzel; Hassell, Trevor; Ortiz, Johana; Salazar de Ariza, Julieta; Rahman, A Rashid; de Núñez, Leticia; Garcia, Maria Reyes; van Rossum, Caroline; Westenbrink, Susanne; Thiam, Lim Meng; MacGregor, Graham; Neal, Bruce

2012-12-01

Chronic diseases are the leading cause of premature death and disability in the world with overnutrition a primary cause of diet-related ill health. Excess energy intake, saturated fat, sugar, and salt derived from processed foods are a major cause of disease burden. Our objective is to compare the nutritional composition of processed foods between countries, between food companies, and over time. Surveys of processed foods will be done in each participating country using a standardized methodology. Information on the nutrient composition for each product will be sought either through direct chemical analysis, from the product label, or from the manufacturer. Foods will be categorized into 14 groups and 45 categories for the primary analyses which will compare mean levels of nutrients at baseline and over time. Initial commitments to collaboration have been obtained from 21 countries. This collaborative approach to the collation and sharing of data will enable objective and transparent tracking of processed food composition around the world. The information collected will support government and food industry efforts to improve the nutrient composition of processed foods around the world.

Comparative evaluation of self-etching primers and phosphoric acid effectiveness on composite to enamel bond: an in vitro study.

PubMed

Patil, Basanagouda S; Rao, Bk Raghavendra; Sharathchandra, Sm; Hegde, Reshma; Kumar, G Vinay

2013-09-01

The aim of the present study was to investigate the effectiveness of the one total-etch self-priming adhesive, one two-step self-etching primer adhesive, and one 'all-in-one' self-etching adhesive system on the adhesion of a resin composite to enamel. Thirty-six freshly extracted human mandibular molars were selected for this study. A fat area about 5 mm in diameter was created on the exposed mesial surface of enamel of each tooth by moist grinding with 320, 420 and 600 grit silicon carbide paper. Twelve teeth were randomly assigned into three groups. In group 1, Adper Easy One (3M ESPE), a one step self-etching primer adhesive was applied and light curing unit for 10 seconds. In group 2, Adper SE Plus, a two-step self-etching primer with bottle A containing the aqueous primer and bottle B containing the acidic adhesive was applied and light cured for 10 seconds. Group 3 (control)-etchant 37% phosphoric acid is applied to the surface for 15 seconds and rinsed with water and air dried and adhesive (single bond 2) is applied to the surface and tube is placed and light cured for 20 seconds. Composite material (Z350) was placed in the tube and light cured for 40 seconds in all the groups. Bond strength testing was done using universal testing machine at the enamel-composite interface. The debonded enamel surface was evaluated in stereomicroscope to assess the cohesive, adhesive or mixed fracture. Data was statistically analyzed by one way analysis of variance (ANOVA). Group 1 performed least among all groups with a mean score of 19.46 MPa. Group 2 had a mean score of 25.67 MPa. Group 3 had a mean score of 27.16 MPa. Under the conditions of this in vitro study, the bond strength values of the two-step self-etching primer systems tested were similar to the total-etch. And, one step self-etching primers have lower bond strength compared to the total-etch.

Comparative study of anthocyanin composition, antimicrobial and antioxidant activity in bilberry (Vaccinium myrtillus L.) and blueberry (Vaccinium corymbosum L.) fruits.

PubMed

Burdulis, Deividas; Sarkinas, Antanas; Jasutiené, Ina; Stackevicené, Elicija; Nikolajevas, Laurynas; Janulis, Valdimaras

2009-01-01

Simultaneous comparison of bilberry (Vaccinium myrtillus L.) and blueberry (Vaccinium corymbosum L) fruits for their anthocyanin composition, antimicrobial and antioxidant activity is reported. The aim of this study was to investigate and to compare anthocyanin composition, antimicrobial and antioxidant activity in bilberry and blueberry fruits and their skins. The investigations revealed that the highest amount of total anthocyanins was observed in fruits skins of blueberry cultivars. The results, obtained by chromatographic analysis, indicated that cyanidin is a dominant anthocyanidin in bilberry and malvidin in blueberry samples. Extracts of "Herbert", "Coville", "Toro" blueberry cultivars and bilberry fruits revealed antimicrobial properties. Citrobacter freundii (ATCC 8090) and Enterococcus faecalis (ATCC29212) were the most sensitive among eight tested Gram-negative and Gram-positive bacteria. Significant differences between berry and skin extracts were not established. Studies with fruits showed that the strongest antioxidant activity possesses blueberry cultivar "Berkeley" (82.13 +/- 0.51%). Meanwhile, the amount of quenched free radicals in bilberry samples was 63.72 +/- 1.11%, respectively. The lowest antioxidant activity was estimated in blueberry cultivar "Coville". Accordingly, the strongest antiradical properties were estimated in blueberry cultivar "Ama" fruit skins. Bilberry fruit skin samples possess strong antiradical activity as well (82.69 +/- 0.37%).

Estimating means and variances: The comparative efficiency of composite and grab samples.

PubMed

Brumelle, S; Nemetz, P; Casey, D

1984-03-01

This paper compares the efficiencies of two sampling techniques for estimating a population mean and variance. One procedure, called grab sampling, consists of collecting and analyzing one sample per period. The second procedure, called composite sampling, collectsn samples per period which are then pooled and analyzed as a single sample. We review the well known fact that composite sampling provides a superior estimate of the mean. However, it is somewhat surprising that composite sampling does not always generate a more efficient estimate of the variance. For populations with platykurtic distributions, grab sampling gives a more efficient estimate of the variance, whereas composite sampling is better for leptokurtic distributions. These conditions on kurtosis can be related to peakedness and skewness. For example, a necessary condition for composite sampling to provide a more efficient estimate of the variance is that the population density function evaluated at the mean (i.e.f(μ)) be greater than[Formula: see text]. If[Formula: see text], then a grab sample is more efficient. In spite of this result, however, composite sampling does provide a smaller estimate of standard error than does grab sampling in the context of estimating population means.

Study on erosion behaviour of hybrid aluminium composite

NASA Astrophysics Data System (ADS)

Vishwas, D. K.; Chandrappa, C. N.; Venkatesh, Shreyas

2018-04-01

The origin of the light metals, as compared to other metals in this century, is noticeable and an exciting area of expansion for innovation. Light metals, are need of the day in engineering, among them application of aluminium and its alloys is enormous. we observe that these metals tend to have a progressive loss of metal from having contact surface with other metals. Erosion is one such wear process, where damage occurs by the repeated application of high localised stresses. Erosion due to impact of solid particle, is a significant problem. In the present work, the erosion behaviour of hybrid aluminium composite is studied. AL 6061 is used as the base alloy. AL 6061 alloy has excellent corrosion resistance but poor wear resistance. So, in order to have improved properties, it is reinforced with Tungsten Chromium Nickel powder in varied proportions by the method of stir casting. The results are compared with the as-cast Al-alloy to determine the improvement in mechanical properties. The tests were conducted in ASTM G76 setup, to determine solid particle erosion behaviour and the results of the hybrid composite were compared with that of as-cast AL 6061 alloy. It was evident that mass loss was maximum at 300 inclinations, which is a characteristic of ductile materials. It was observed that upon increasing the percentages of reinforcement (wt.%), the wear resistance of the hybrid composite increased significantly. It was also observed that the inclusion of tungsten-chromium-nickel powder increased the hardness of the hybrid composite significantly.

U.S. GASOLINE COMPOSITION STUDY

EPA Science Inventory

This presentation presents results from a 2004/2005 study of U.S. gasoline composition. Differences in composition are driven by regulation, octane requirements, refining methods, and performance needs. Major differences in composition were traced to a few compounds: benzene, MTB...

Study of Selected Composites Copper Concentrate-Plastic Waste Using Thermal Analysis

NASA Astrophysics Data System (ADS)

Szyszka, Danuta

2017-12-01

The paper presents thermal analysis of selected composites (copper concentrate, plastic waste) in two stages. The first stage consisted in thermogravimetric analysis and differential thermal analysis on the applied plastic waste and copper concentrate, and subsequently, a comparative study has been carried out on products obtained, constituting composites of those materials. As a result of analyses, it was found that up to ca. 400 °C composites show high thermal stability, whereas above that temperature, a thermal decomposition of the composite occurs, resulting in emissions of organic compounds, i.e. hydrocarbon compounds and organic oxygenate derivatives.

Comparative evaluation between glass and polyethylene fiber reinforced composites: A review of the current literature

PubMed Central

Mangoush, Enas; Säilynoja, Eija; Prinssi, Roosa; Lassila, Lippo; Vallittu, Pekka K.

2017-01-01

Background Fiber reinforced composite (FRC) is a promising class of material that gives clinicians alternative treatment options. There are many FRC products available in the market based on either glass or polyethylene fiber type. The aim of this study was to present a comparison between glass and polyethylene fiber reinforced composites based on available literature review. Material and Methods A thorough literature search, with no limitation, was done up to June 2017. The range of relevant publications was surveyed using PubMed and Google Scholar. From the search results, articles related to our search terms were only considered. An assessment of these articles was done by two individuals in order to include only articles directly compare between glass and polyethylene FRCs. The search terms used were “fiber reinforced dental composites” and “glass and polyethylene fibers in dentistry”. Results The search provided 276 titles. Full-text analysis was performed for 29 articles that met the inclusion criteria. Most were laboratory-based research with various test specimen designs prepared according to ISO standard or with extracted teeth and only three articles were clinical studies. Most of studies (n=23) found superior characteristics of glass FRCs over polyethylene FRCs. Conclusions Significant reinforcement differences between commercial glass and polyethylene fiber reinforced composites were found. Key words:Fiber reinforced composite, glass fiber, polyethylene fiber. PMID:29410756

Holistic Facial Composite Construction and Subsequent Lineup Identification Accuracy: Comparing Adults and Children.

PubMed

Davis, Josh P; Thorniley, Sarah; Gibson, Stuart; Solomon, Chris

2016-01-01

When the police have no suspect, they may ask an eyewitness to construct a facial composite of that suspect from memory. Faces are primarily processed holistically, and recently developed computerized holistic facial composite systems (e.g., EFIT-V) have been designed to match these processes. The reported research compared children aged 6-11 years with adults on their ability to construct a recognizable EFIT-V composite. Adult constructor's EFIT-Vs received significantly higher composite-suspect likeness ratings from assessors than children's, although there were some notable exceptions. In comparison to adults, the child constructors also overestimated the composite-suspect likeness of their own EFIT-Vs. In a second phase, there were no differences between adult controls and constructors in correct identification rates from video lineups. However, correct suspect identification rates by child constructors were lower than those of child controls, suggesting that a child's memory for the suspect can be adversely influenced by composite construction. Nevertheless, all child constructors coped with the demands of the EFIT-V system, and the implications for research, theory, and the criminal justice system practice are discussed.

Comparative Study of Phenolic Profile, Antioxidant Capacity, and Color-composition Relation of Roselle Cultivars with Contrasting Pigmentation.

PubMed

Camelo-Méndez, Gustavo A; Jara-Palacios, M José; Escudero-Gilete, M Luisa; Gordillo, Belén; Hernanz, Dolores; Paredes-López, Octavio; Vanegas-Espinoza, Pablo E; Del Villar-Martínez, Alma A; Heredia, Francisco J

2016-03-01

Roselle is a plant that accumulates anthocyanins significantly, hence its importance as food coloring and as a source of antioxidant compounds for human health. This study was aimed to determine phenolic composition and antioxidant capacity of methanolic extracts, and beverages obtained from native roselle cultivars in Mexico (Negra, Sudan, Rosa and Blanca) with different degrees of pigmentation, and to establish the color-composition relationship. Chromatographic methods were used to determine phenolic compounds: flavanols, flavonols, benzoic, hibiscus and phenolic acids as well as two main anthocyanins (cyanidin 3-sambubioside and delphinidin 3-sambubioside). The antioxidant capacity was evaluated by ABTS and FRAP assays. Tristimulus colorimetry showed to be a useful technique to determine the color-composition relationship, leading to equations that allowed to predict anthocyanin content of roselle (R > 0.84). Also, a stepwise linear discriminant analysis (SLDA) was developed in order to classify roselle cultivars. The obtained mathematical model could be an important tool to be used in colorimetric characterization of functional compounds used in food processing.

Antibacterial Properties of Calcium Fluoride-Based Composite Materials: In Vitro Study

PubMed Central

Zarzycka, Beata; Grzegorczyk, Janina; Sokołowski, Krzysztof; Półtorak, Konrad; Sokołowski, Jerzy

2016-01-01

The aim of the study was to evaluate antibacterial activity of composite materials modified with calcium fluoride against cariogenic bacteria S. mutans and L. acidophilus. One commercially available conventional light-curing composite material containing fluoride ions (F2) and two commercially available flowable light-curing composite materials (Flow Art and X-Flow) modified with 1.5, 2.5, and 5.0 wt% anhydrous calcium fluoride addition were used in the study. Composite material samples were incubated in 0.95% NaCl at 35°C for 3 days; then dilution series of S. mutans and L. acidophilus strains were made from the eluates. Bacteria dilutions were cultivated on media afterwards. Colony-forming unit per 1 mL of solution (CFU/mL) was calculated. Composite materials modified with calcium fluoride highly reduced (p < 0.001) bacteria growth compared to commercially available composite materials containing fluoride compounds. The greatest reduction in bacteria growth was observed for composite materials modified with 1.5% wt. CaF2. All three tested composite materials showed statistically greater antibacterial activity against L. acidophilus than against S. mutans. PMID:28053976

A comparative study on nutritional status and body composition of urban and rural schoolchildren from Brandsen district (Argentina).

PubMed

Cesani, Maria Florencia; Garraza, Mariela; Bergel Sanchís, María Laura; Luis, María Antonia; Torres, María Fernanda; Quintero, Fabián Aníbal; Oyhenart, Evelia Edith

2013-01-01

The purpose of this study was to analyze whether nutritional status and body composition varies according to the environment of residence (urban or rural) of children in the Brandsen district (Argentina). Weight, height, arm circumference and tricipital and subscapular skinfolds were performed in 1368 schoolchildren aged 3 to 14. NHANES III reference was used to estimate nutritional status -underweight, stunting, wasting, overweight, and obesity- and to evaluate body composition -deficit and excess of adipose (DA, EA) and muscular (DM, EM) tissues of the arm-. Central fat distribution (CFD) was estimated using the subscapular-tricipital index. A structured questionnaire was implemented to evaluate socio-environmental characteristics. Nutritional categories based on body size and body composition were compared between urban and rural areas of residence using Chi-squared tests (χ2). The results indicated for the total sample: 1.1% underweight, 6.9% stunting, 0.4% wasting, 12.1% overweight, 9.7% obesity, 22.0% DM, 2.5% EM, 0.1% DA, 17.6% EA, and 8.5% CFD. Significant differences between urban and rural areas were found only for CFD. The socio-environmental analysis showed that while access to public services and housing quality was significantly better in the urban area, a considerable number of city households lived under deficient conditions, lacked health insurance and had low socioeconomic level. Fifty-three percent of the undernourished children had DM without urban-rural significant differences, and none of them showed DA. In the overweight plus obesity group, 62.8% presented EA, 6.4% EM, 4.7% DM, and 22.8% CFD. The highest percentages of DM and CFD were recorded in rural areas (p = 0.00). We conclude that the child population shows the "double burden" of malnutrition. The environment of residence does not promote any differentiation in the nutritional status. Nevertheless, the increment of central adiposity and, in some cases of muscle deficit in rural

A Comparative Study on Nutritional Status and Body Composition of Urban and Rural Schoolchildren from Brandsen District (Argentina)

PubMed Central

Cesani, Maria Florencia; Garraza, Mariela; Bergel Sanchís, María Laura; Luis, María Antonia; Torres, María Fernanda; Quintero, Fabián Aníbal; Oyhenart, Evelia Edith

2013-01-01

The purpose of this study was to analyze whether nutritional status and body composition varies according to the environment of residence (urban or rural) of children in the Brandsen district (Argentina). Weight, height, arm circumference and tricipital and subscapular skinfolds were performed in 1368 schoolchildren aged 3 to 14. NHANES III reference was used to estimate nutritional status -underweight, stunting, wasting, overweight, and obesity- and to evaluate body composition -deficit and excess of adipose (DA, EA) and muscular (DM, EM) tissues of the arm-. Central fat distribution (CFD) was estimated using the subscapular-tricipital index. A structured questionnaire was implemented to evaluate socio-environmental characteristics. Nutritional categories based on body size and body composition were compared between urban and rural areas of residence using Chi-squared tests (χ2). The results indicated for the total sample: 1.1% underweight, 6.9% stunting, 0.4% wasting, 12.1% overweight, 9.7% obesity, 22.0% DM, 2.5% EM, 0.1% DA, 17.6% EA, and 8.5% CFD. Significant differences between urban and rural areas were found only for CFD. The socio-environmental analysis showed that while access to public services and housing quality was significantly better in the urban area, a considerable number of city households lived under deficient conditions, lacked health insurance and had low socioeconomic level. Fifty-three percent of the undernourished children had DM without urban-rural significant differences, and none of them showed DA. In the overweight plus obesity group, 62.8% presented EA, 6.4% EM, 4.7% DM, and 22.8% CFD. The highest percentages of DM and CFD were recorded in rural areas (p = 0.00). We conclude that the child population shows the “double burden” of malnutrition. The environment of residence does not promote any differentiation in the nutritional status. Nevertheless, the increment of central adiposity and, in some cases of muscle deficit in rural

Hybrid Composite Material and Solid Particle Erosion Studies

NASA Astrophysics Data System (ADS)

Chellaganesh, D.; Khan, M. Adam; Ashif, A. Mohamed; Ragul Selvan, T.; Nachiappan, S.; Winowlin Jappes, J. T.

2018-04-01

Composite is one of the predominant material for most challenging engineering components. Most of the components are in the place of automobile structure, aircraft structures, and wind turbine blade and so on. At the same all the components are indulged to mechanical loading. Recent research on composite material are machinability, wear, tear and corrosion studies. One of the major issue on recent research was solid particle air jet erosion. In this paper hybrid composite material with and without filler. The fibre are in the combination of hemp – kevlar (60:40 wt.%) as reinforcement using epoxy as a matrix. The natural material palm and coconut shell are used as filler materials in the form of crushed powder. The process parameter involved are air jet velocity, volume of erodent and angle of impingement. Experiment performed are in eight different combinations followed from 2k (k = 3) factorial design. From the investigation surface morphology was studied using electron microscope. Mass change with respect to time are used to calculate wear rate and the influence of the process parameters. While solid particle erosion the hard particle impregnates in soft matrix material. Influence of filler material has reduced the wear and compared to plain natural composite material.

Comparative evaluation of microleakage of lingual retainer wires bonded with three different lingual retainer composites: an in vitro study.

PubMed

Nimbalkar-Patil, Smita; Vaz, Anna; Patil, Pravinkumar G

2014-11-01

To evaluate microleakage when two types of retainer wires were bonded with two light cured and a self cured lingual retainer composites. Total 120 freshly extracted human mandibular incisor teeth were collected and separated into six subgroups of 20 teeth each. Two different wires, a 0.036 inch hard round stainless steel (HRSS) wire sandblasted at the ends and 0.0175 inch multistranded wire bonded onto the lingual surfaces of the incisors with three different types of composite resins of 3M company; Concise Orthodontic (self-cure), Transbond XT (light-cure) and Transbond LR (light-cure). Specimens were further sealed with a nail varnish, stained with 0.5% basic fuchsine for 24 hours, sectioned and examined under a stereomicroscope, and scored for microleakage for the enamel-composite and wire-composite interfaces. Statistical analysis was performed by Kruskal-Wallis and Mann-Whitney U-tests. For HRSS wire, at the enamel-composite interface, the microleakage was least with Transbond LR followed by Concise Orthodontic and greatest for Transbond XT (p<0.05). At the wire composite interface too, the microleakage was in order of Transbond LRcomposite interface, the microleakage was least with Transbond LR followed by Concise Orthodontic and Transbond XT (p<0.05). At the wire composite interface too, it was seen that microleakage was the least with Transbond LR followed by Concise Orthodontic and Transbond XT. Transbond LR in combination with 0.0175 inch multistranded wire showed least microleakage amongst the groups studied.

Reconstruction of a composite comparative map composed of ten legume genomes.

PubMed

Lee, Chaeyoung; Yu, Dongwoon; Choi, Hong-Kyu; Kim, Ryan W

2017-01-01

The Fabaceae (legume family) is the third largest and the second of agricultural importance among flowering plant groups. In this study, we report the reconstruction of a composite comparative map composed of ten legume genomes, including seven species from the galegoid clade ( Medicago truncatula , Medicago sativa , Lens culinaris, Pisum sativum , Lotus japonicus , Cicer arietinum , Vicia faba ) and three species from the phaseoloid clade ( Vigna radiata , Phaseolus vulgaris , Glycine max ). To accomplish this comparison, a total of 209 cross-species gene-derived markers were employed. The comparative analysis resulted in a single extensive genetic/genomic network composed of 93 chromosomes or linkage groups, from which 110 synteny blocks and other evolutionary events (e.g., 13 inversions) were identified. This comparative map also allowed us to deduce several large scale evolutionary events, such as chromosome fusion/fission, with which might explain differences in chromosome numbers among compared species or between the two clades. As a result, useful properties of cross-species genic markers were re-verified as an efficient tool for cross-species translation of genomic information, and similar approaches, combined with a high throughput bioinformatic marker design program, should be effective for applying the knowledge of trait-associated genes to other important crop species for breeding purposes. Here, we provide a basic comparative framework for the ten legume species, and expect to be usefully applied towards the crop improvement in legume breeding.

Thermoplastic composites for veneering posterior teeth-a feasibility study.

PubMed

Gegauff, Anthony G; Garcia, Jose L; Koelling, Kurt W; Seghi, Robert R

2002-09-01

This pilot study was conducted to explore selected commercially-available thermoplastic composites that potentially had physical properties superior to currently available dental systems for restoring esthetic posterior crowns. Polyurethane, polycarbonate, and poly(ethylene/tetrafluoroethylene) (ETFE) composites and unfilled polyurethane specimens were injection molded to produce shapes adaptive to five standardized mechanical tests. The mechanical testing included abrasive wear rate, yield strength, apparent fracture toughness (strength ratio), flexural strength, and compressive strength. Compared to commercially available dental composites, abrasion wear rates were lower for all materials tested, yield strength was greater for the filled polycarbonates and filled polyurethane resins, fracture toughness testing was invalid (strength ratios were calculated for comparison of the pilot test materials), flexural strength was roughly similar except for the filled ETFE which was significantly greater, and compressive strength was lower. Commercially available thermoplastic resin composites, such as polyurethane, demonstrate the potential for development of an artificial crown material which exceeds the mechanical properties of currently available esthetic systems, if compressive strength can be improved.

Bioactive nanoparticle-gelatin composite scaffold with mechanical performance comparable to cancellous bones.

PubMed

Wang, Chen; Shen, Hong; Tian, Ye; Xie, Yue; Li, Ailing; Ji, Lijun; Niu, Zhongwei; Wu, Decheng; Qiu, Dong

2014-08-13

Mechanical properties are among the most concerned issues for artificial bone grafting materials. The scaffolds used for bone grafts are either too brittle (glass) or too weak (polymer), and therefore composite scaffolds are naturally expected as the solution. However, despite the intensive studies on composite bone grafting materials, there still lacks a material that could be matched to the natural cancellous bones. In this study, nanosized bioactive particles (BP) with controllable size and good colloidal stability were used to composite with gelatin, forming macroporous scaffolds. It was found that the mechanical properties of obtained composite scaffolds, in terms of elastic modulus, compressive strength, and strain at failure, could match to that of natural cancellous bones. This is ascribed to the good distribution of particle in matrix and strong interaction between particle and gelatin. Furthermore, the incorporation of BPs endues the composite scaffolds with bioactivity, forming HA upon reacting with simulated body fluid (SBF) within days, thus stimulating preosteoblasts attachment, growth, and proliferation in these scaffolds. Together with their good mechanical properties, these composite scaffolds are promising artificial bone grating materials.

A comparative study of shear bond strength between metal and ceramic brackets and artificially aged composite restorations using different surface treatments.

PubMed

Eslamian, Ladan; Borzabadi-Farahani, Ali; Mousavi, Nasim; Ghasemi, Amir

2012-10-01

This in vitro study evaluated the shear bond strength (SBS) between ceramic brackets (CBs) and resin composite restorations (RCRs) prepared using different surface treatments. The findings were also compared with a similar study that used stainless steel brackets (SSBs). Forty-five premolars were restored with a nano-hybrid composite resin (Tetric EvoCeram) and randomly assigned to three surface treatment groups: group 1, 5 per cent hydrofluoric acid (HF); group 2, air abrasion (50 μm alumina particles); and group 3, diamond bur. Specimens were bonded with CBs (Fascination) and exposed to thermo-cycling (500 cycles). The shear force at a crosshead speed of 1 mm/minute was transmitted to brackets. The adhesive remnant index (ARIs) scores were recorded after bracket failure. The analysis of SBS variance (P < 0.01) and chi-square test of ARIs scores (P < 0.01) revealed significant differences among three groups tested. The SBS in group 3 (mean: 26.34 ± 4.76 MPa) and group 2 (mean: 26.68 ± 5.93 MPa) was significantly higher than group 1 (mean: 16.25 ± 5.42 MPa). The SBS was significantly higher in CBs (mean: 23.09 ± 7.19 MPa) compared to SSBs (mean: 15.56 ± 5.13 MPa). High ARIs (100 per cent) occurred in SSBs treated with a diamond bur, whereas CBs primarily failed at the resin-adhesive interface (P < 0.01). In two-thirds of the specimens (SSBs or CBs), no adhesive was left on the restoration after HF conditioning. The ARIs profile of CBs and SSBs that received surface treatments with air abrasion were similar (P > 0.05) and bond failure occurred mainly in adhesive-bracket base and resin-adhesive interfaces. The diamond bur surface treatment is recommended as a safe and cost-effective method of bonding CBs to RCRs.

Tribological study of non-asbestos fiber reinforced phenolic composites for braking applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopal, P.; Dharani, L.R.; Blum, F.D.

A cashew modified phenolic resin was used as the binder to prepare several different nonasbestos fiber reinforced composite friction materials. Friction-wear tests were conducted at various loads, speeds and temperatures on a Chase friction testing machine. The fade and wear characteristics of glass and carbon fiber reinforced friction materials were studied. The wear rates of hybrid composites containing Kevlar{reg_sign} (registered trademark of E.I. duPont de Nemours) pulp were compared to those of control composites without Kevlar{reg_sign} pulp.

Comparative study of biogenic and abiotic iron-containing materials

NASA Astrophysics Data System (ADS)

Cherkezova-Zheleva, Z.; Shopska, M.; Paneva, D.; Kovacheva, D.; Kadinov, G.; Mitov, I.

2016-12-01

Series of iron-based biogenic materials prepared by cultivation of Leptothrix group of bacteria in different feeding media ( Sphaerotilus-Leptothrix group of bacteria isolation medium, Adler, Lieske and silicon-iron-glucose-peptone) were studied. Control samples were obtained in the same conditions and procedures but the nutrition media were not infected with bacteria, i.e. they were sterile. Room and low temperature Mössbauer spectroscopy, powder X-ray diffraction (XRD), and infrared spectroscopy (IRS) were used to reveal the composition and physicochemical properties of biomass and respective control samples. Comparative analysis showed differences in their composition and dispersity of present phases. Sample composition included different ratio of nanodimensional iron oxyhydroxide and oxide phases. Relaxation phenomena such as superparamagnetism or collective magnetic excitation behaviour were registered for some of them. The experimental data showed that the biogenic materials were enriched in oxyhydroxides of high dispersion. Catalytic behaviour of a selected biomass and abiotic material were studied in the reaction of CO oxidation. In situ diffuse-reflectance (DR) IRS was used to monitor the phase transformations in the biomass and CO conversion.

Comparative study of fungal deterioration in Liquidambar orientalis mill heartwood extractives

Treesearch

Roderquita K Moore; Doreen Mann; Nural Yilgor

2017-01-01

A comparative study was done on Liquidambar Orientalis Mill heartwood extractive samples. These extractives were collected from wood decay specimens. The objective of the study was to determine the chemical composition of the extractives remaining after exposure to brown rot fungi Tyromyces Palustris and white rot fungi Trametes Vericolor...

Silicate and borate glasses as composite fillers: a bioactivity and biocompatibility study.

PubMed

Lopes, P P; Ferreira, B J M Leite; Gomes, P S; Correia, R N; Fernandes, M H; Fernandes, M H V

2011-06-01

Composites filled with a silicate glass (CSi) and a new borate glass (CB) were developed and compared in terms of their in vitro behaviour both in acellular and cellular media. Acellular tests were carried out in SBF and the composites were characterized by SEM-EDS, XRD and ICP. Biocompatibility studies were investigated by in vitro cell culture with MG-63 osteoblast-like and human bone marrow cells. The growth of spherical calcium phosphate aggregates was observed in acellular medium on all composite surfaces indicating that these materials became potentially bioactive. The biological assessment resulted in a dissimilar behavior of the composites. The CSi demonstrated an inductive effect on the proliferation of cells. The cells showed a normal morphology and high growth rate when compared to standard culture plates. Contrarily, inhibition of cell proliferation occurred in the CB probably due to its high degradation rate, leading to high B and Mg ionic concentration in the cell culture medium.

Fatty acid composition of freshwater wild fish in subalpine lakes: a comparative study.

PubMed

Vasconi, Mauro; Caprino, Fabio; Bellagamba, Federica; Busetto, Maria Letizia; Bernardi, Cristian; Puzzi, Cesare; Moretti, Vittorio Maria

2015-03-01

In this study, the proximate and fatty acid compositions of the muscle tissue of 186 samples of fish belonging to fifteen species of freshwater fish harvested in subalpine lakes (bleak, shad, crucian carp, whitefish, common carp, pike, black bullhead, burbot, perch, Italian roach, roach, rudd, wels catfish, chub and tench) were investigated. Most of the fish demonstrated a lipid content in the fillet lower than 2.0 g 100 g(-1) wet weight (range 0.6-9.7). A strong relationship between feeding behavior and fatty acid composition of the muscle lipids was observed. Planktivorous fish showed the lowest amounts of n-3 fatty acids (p < 0.05), but the highest monounsaturated fatty acid (MUFA) contents, in particular 18:1n-9. Conversely, carnivorous fish showed the highest amounts of saturated fatty acids and n-3 fatty acids (p < 0.05), but the lowest MUFA contents. Omnivorous fish showed substantial proportions of n-3 fatty acids and the highest contents of n-6 fatty acids. Principal component analysis showed a distinct separation between fish species according to their feeding habits and demonstrated that the most contributing trophic markers were 18:1n-9, 18:3n-3, 22:6n-3 and 20:4n-6. The quantitative amounts n-3 polyunsaturated fatty acid in muscle tissues varied depending on the fish species, the lipid content and the feeding habits. Some species were very lean, and therefore would be poor choices for human consumption to meet dietary n-3 fatty acid requirements. Nevertheless, the more frequently consumed and appreciated fish, shad and whitefish, had EPA and DHA contents in the range 900-1,000 mg 100 g(-1) fresh fillet.

Impacts of Changing Racial Composition upon Commercial Land Use Succession and Commercial Structure: A Comparative Neighborhood Analysis.

ERIC Educational Resources Information Center

Schmidt, Charles G.; Lee, Yuk

1978-01-01

Three Denver neighborhoods are used in this comparative analysis to investigate the extent to which racial composition, population, or income influence commercial land use succession patterns and total business composition. (EB)

Hydrothermal Liquefaction Biocrude Compositions Compared to Petroleum Crude and Shale Oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarvis, Jacqueline M.; Billing, Justin M.; Hallen, Richard T.

We provide a direct and detailed comparison of the chemical composition of petroleum crude oil (from the Gulf of Mexico), shale oil, and three biocrudes (i.e., clean pine, microalgae Chlorella sp., and sewage sludge feedstocks) generated by hydrothermal liquefaction (HTL). Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) reveals that HTL biocrudes are compositionally more similar to shale oil than petroleum crude oil and that only a few heteroatom classes (e.g., N1, N2, N1O1, and O1) are common to organic sediment- and biomass-derived oils. All HTL biocrudes contain a diverse range of oxygen-containing compounds when compared tomore » either petroleum crude or shale oil. Overall, petroleum crude and shale oil are compositionally dissimilar to HTL oils, and >85% of the elemental compositions identified within the positive-ion electrospray (ESI) mass spectra of the HTL biocrudes were not present in either the petroleum crude or shale oil (>43% for negative-ion ESI). Direct comparison of the heteroatom classes that are common to both organic sedimentand biomass-derived oils shows that HTL biocrudes generally contain species with both smaller core structures and a lower degree of alkylation relative to either the petroleum crude or the shale oil. Three-dimensional plots of carbon number versus molecular double bond equivalents (with observed abundance as the third dimension) for abundant molecular classes reveal the specific relationship of the composition of HTL biocrudes to petroleum and shale oils to inform the possible incorporation of these oils into refinery operations as a partial amendment to conventional petroleum feeds.« less

Waiting for Answerability: Bakhtin and Composition Studies.

ERIC Educational Resources Information Center

Ewald, Helen Rothschild

1993-01-01

Discusses Mikhail Bakhtin's interest in ethical action and response, or "answerability," and its relevance for composition studies. Examines how Bakhtin has been used to authorize various research in composition studies. Shows how composition instruction might be undertaken as influenced by answerability. (HB)

Assessment of Dry Powder Inhaler Carrier Targeted Design: A Comparative Case Study of Diverse Anomeric Compositions and Physical Properties of Lactose.

PubMed

Pinto, Joana T; Zellnitz, Sarah; Guidi, Tomaso; Roblegg, Eva; Paudel, Amrit

2018-06-19

The pulmonary administration landscape has rapidly advanced in recent years. Targeted design of particles by spray-drying for dry powder inhaler development offers an invaluable tool for engineering of new carriers. In this work, different formulation and process aspects of spray-drying were exploited to produce new lactose carriers. Using an integrated approach, lactose was spray-dried in the presence of polyethylene glycol 200 (PEG 200), and the in vitro performance of the resulting particles was compared with other grades of lactose with varying anomeric compositions and/or physical properties. The anomeric composition of lactose in lactose-PEG 200 feed solutions of variable compositions was analyzed via polarimetry at different temperatures. These results were correlated with the solid-state and anomeric composition of the resulting spray-dried particles using modulated differential scanning calorimetry and wide-angle X-ray scattering. The distinct selected grades of lactose were characterized in terms of their micromeritic properties using laser diffraction, helium pycnometry, and gas adsorption, and their particle surface morphologies were evaluated via scanning electron microscopy. Adhesive mixtures of the different lactose carriers with inhalable-sized salbutamol sulfate, as a model drug, were prepared in low doses and evaluated for their blend homogeneity and aerodynamic performance using a Next Generation Impactor. Characterization of the spray-dried particles revealed that predominantly crystalline (in an anomeric ratio 0.8:1 of α to β) spherical particles with a mean size of 50.9 ± 0.4 μm could be produced. Finally, it was apparent that micromeritic, in particular, the shape, and surface properties (inherent to solid-state and anomeric composition) of carrier particles dominantly control DPI delivery. This provided an insight into the relatively inferior performance of the adhesive blends containing the spherical spray-dried lactose-PEG 200

Histological Evaluation to Study the Effects of Dental Amalgam and Composite Restoration on Human Dental Pulp: An in vivo Study

PubMed Central

Chandwani, Neelam D.; Pawar, Mansing G.; Tupkari, Jagdish V.; Yuwanati, Monal

2013-01-01

Objective To study and compare the effects of dental amalgam and composite restorations on human dental pulp. Materials and Methods One hundred sound premolars scheduled for orthodontic extraction were divided equally into two groups: group A, teeth restored with silver amalgam, and group B, teeth restored with composite resin. Each group was equally subdivided into two subgroups [extracted after 24 h (A-1 and B-1) or 7 days (A−2 and B−2)], and the histological changes in the pulp related to the two different materials at the two different intervals were studied. Results It was found that after 24 h, the inflammatory response of the pulp in teeth restored with amalgam and composite was similar (p = 1.00). However, after 7 days, the severity of the inflammatory response of the pulp in teeth restored with amalgam was less compared to that in teeth restored with composite (p = 0.045). Conclusion This study confirmed that amalgam continues to be the mechanically as well as biologically more competent restorative material. Composite could be a promising restorative material to satisfy esthetic needs for a considerable period of time. However, its biological acceptance is still in doubt. PMID:24217468

Discussion on the methodology for determining food waste in household waste composition studies.

PubMed

Lebersorger, S; Schneider, F

2011-01-01

Food waste has become an increasingly discussed topic in recent years. However, there is little authoritative data on food waste quantities and composition and systematic and comparable data are missing. Household waste composition analyses, which are often carried out routinely at regular or irregular intervals, provide an opportunity for obtaining data about food waste at both local and regional levels. The results of prior waste composition studies are not really comparable due to the different classifications, definitions and methods used; in addition, these are mostly insufficiently described and not reproducible by a third party. The aim of this paper is to discuss a methodology for determining the proportion of food waste in household waste composition studies, by analysing specific problems and possible solutions. For that purpose, findings from the literature are analysed and the approach and results of a composition analysis of residual waste of a stratified sample (urban, rural area) are presented. The study suggests that in order to avoid a significant loss of information, waste should not be sieved before sorting and packed food waste should be classified into the relevant food waste category together with its packaging. The case study showed that the overall influence of the proportion of food packaging included in the food waste category, which amounted to only 8%, did not significantly influence the results and can therefore be disregarded. Copyright © 2011 Elsevier Ltd. All rights reserved.

Composition Studies/English Education Connections

ERIC Educational Resources Information Center

Baker, W. Douglas; Brockman, Elizabeth; Bush, Jonathan; Richmond, Kia Jane

2007-01-01

This roundtable explores several different composition-related questions and topics. It raises two questions: (1) What theory from composition studies do you believe is important to include in classes for future elementary and/or secondary writing teachers? (2) What are the knowledge, background, traits, and abilities of a successful writing…

Effects of breast-feeding compared with formula-feeding on preterm infant body composition: a systematic review and meta-analysis.

PubMed

Huang, Pan; Zhou, Jianghua; Yin, Yanan; Jing, Wenjuan; Luo, Biru; Wang, Jiang

2016-07-01

We conducted a systematic review and meta-analysis to compare the effect of breast-feeding and formula-feeding on body composition of preterm infants. We searched the literature using PubMed, Cochrane Central Library Issue, Ovid (Medline), Embase and other resources such as Google Scholar, electronic databases and bibliographies of relevant articles; two reviewers collected and extracted data independently. All the authors assessed risk of bias independently using the Newcastle-Ottawa Scale (NOS). A fixed-effects meta-analysis was undertaken with RevMan 5 software (The Cochrane Collaboration) using the inverse variance method (P≥0·05; χ 2 test). In contrast, a random-effects meta-analysis was carried out. Altogether, 630 articles were identified using search strategy, and the references within retrieved articles were also assessed. A total of six studies were included in this systematic review. In formula-fed infants, fat mass was higher at term (mean difference 0·24 (95 % CI 0·17, 0·31) kg), fat-free mass was higher at 36 weeks of gestational (mean difference 0·12 (95 % CI 0·04, 0·21) kg) and the percentage of fat mass was higher at 36 weeks of gestation (mean difference 3·70 (95 % CI 1·81, 5·59) kg) compared with breast-fed infants. Compared with breast-feeding, formula-feeding is associated with altered body composition from birth to term in preterm infants. The effects of formula-feeding on preterm infant body composition from term to 12-month corrected age are inconclusive in our study. Well-designed studies are required in the future to explore the effects of formula-feeding compared with breast-feeding.

Study on influence of vibration behavior of composite material damage by holography

NASA Astrophysics Data System (ADS)

Guo, Linfeng; Zhao, Zhimin; Gao, Mingjuan; Zhuang, Xianzhong

2006-01-01

Composite material has been applied widely in aeronautics, astronautics and some other fields due to their high strength, light weight and antifatigue and etc. But in the application, composite material may be destroyed or damaged, which may have impact on its further applications. Therefore, study on the influence of behavior of composite material damage becomes a hot research. In this paper, the common composite material for aircraft is used as the test object, and a study is conducted to investigate the influence of vibration behavior of composite material damage. The authors adopt the method of light-carrier wave and time-average holography. Compared the interference fringes of composite materials before and after damage, the width of the interference fringes of hologram of the damaged composite material is narrower than that of the fringes before. It means that the off-plane displacement of each point on the test object is larger than before. Based on the elastic mechanics theory, the off-plane displacement is inverse to the bending stiffness, and the bending stiffness of the test object will decrease after it is damaged. In other words, the vibration property of the composite material changes after damages occur. The research results of the paper show that the results accord with the analysis of theory.

Longitudinal study of body composition in spinal cord injury patients.

PubMed

Singh, Roop; Rohilla, Rajesh K; Saini, Gaurav; Kaur, Kiranpreet

2014-03-01

Bone mass loss and muscle atrophy are the frequent complications occurring after spinal cord injury (SCI). The potential risks involved with these changes in the body composition have implications for the health of the SCI individual. Thus, there is a need to quantitate and monitor body composition changes accurately in an individual with SCI. Very few longitudinal studies have been reported in the literature to assess body composition and most include relatively small number of patients. The present prospective study aimed to evaluate the body composition changes longitudinally by DEXA in patients with acute SCI. Ninety five patients with acute SCI with neurological deficits were evaluated for bone mineral content (BMC), body composition [lean body mass (LBM) and fat mass] by dual-energy X-ray absorptiometry during the first year of SCI. There was a significant decrease in BMC (P < 0.05) and LBM (P < 0.05) and increase in total body fat mass (TBFM) and percentage fat at infra-lesional sites. The average decrease was 14.5% in BMC in lower extremities, 20.5% loss of LBM in legs and 15.1% loss of LBM in trunk, and increase of 0.2% in fat mass in legs and 17.3% increased fat in the lower limbs at 1 year. The tetraplegic patients had significant decrease in arm BMC (P < 0.001), arm LBM (P < 0.01) and fat percentage (P < 0.01) compared to paraplegics. Patients with complete motor injury had higher values of TBFM and fat percentage, but comparable values of BMC and LBM to patients with incomplete motor injury. Our findings suggest that there is a marked decrease in BMC and LBM with increase in adiposity during the first year of SCI. Although these changes depend on the level and initial severity of lesions, they are also influenced by the neurological recovery after SCI.

International collaborative project to compare and track the nutritional composition of fast foods.

PubMed

2012-07-27

Chronic diseases are the leading cause of premature death and disability in the world with over-nutrition a primary cause of diet-related ill health. Excess quantities of energy, saturated fat, sugar and salt derived from fast foods contribute importantly to this disease burden. Our objective is to collate and compare nutrient composition data for fast foods as a means of supporting improvements in product formulation. Surveys of fast foods will be done in each participating country each year. Information on the nutrient composition for each product will be sought either through direct chemical analysis, from fast food companies, in-store materials or from company websites. Foods will be categorized into major groups for the primary analyses which will compare mean levels of saturated fat, sugar, sodium, energy and serving size at baseline and over time. Countries currently involved include Australia, New Zealand, France, UK, USA, India, Spain, China and Canada, with more anticipated to follow. This collaborative approach to the collation and sharing of data will enable low-cost tracking of fast food composition around the world. This project represents a significant step forward in the objective and transparent monitoring of industry and government commitments to improve the quality of fast foods.

Feasibility Study for Casting of High Temperature Refractory Superalloy Composites

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

1998-01-01

Abstract This study investigated the feasibility of using conventional casting technique to fabricate refractory wires reinforced superalloy composites. These composites were being developed for advanced rocket engine turbine blades and other high temperature applications operating up to 2000 F. Several types of refractory metal wires such as W- Th, W-Re, Mo-Hf-C and W-HF-C reinforced waspaloy were experimentally cast and heat treated at 2000 F up to 48 hrs. Scanning electron microscope analysis was conducted in regions adjacent to the wire-matrix interface to determine the reaction zone and chemical compatibility resulting from material interdiffusion. It was concluded that fabrication using conventional casting may be feasible because the wire-matrix reaction zone thickness was comparable to similar composites produced by arc-sprayed monotape with hot isostatic pressing technique, Moreover, it was also found that the chemical compatibility could be improved significantly through a slight modification of the superalloy matrix compositions.

Studies on the electrical transport properties of carbon nanotube composites

NASA Astrophysics Data System (ADS)

Tarlton, Taylor Warren

This work presents a probabilistic approach to model the electrical transport properties of carbon nanotube composite materials. A pseudo-random generation method is presented with the ability to generate 3-D samples with a variety of different configurations. Periodic boundary conditions are employed in the directions perpendicular to transport to minimize edge effects. Simulations produce values for drift velocity, carrier mobility, and conductivity in samples that account for geometrical features resembling those found in the lab. All results show an excellent agreement to the well-known power law characteristic of percolation processes, which is used to compare across simulations. The effect of sample morphology, like nanotube waviness and aspect ratio, and agglomeration on charge transport within CNT composites is evaluated within this model. This study determines the optimum simulation box-sizes that lead to minimize size-effects without rendering the simulation unaffordable. In addition, physical parameters within the model are characterized, involving various density functional theory calculations within Atomistix Toolkit. Finite element calculations have been performed to solve Maxwell's Equations for static fields in the COMSOL Multiphysics software package in order to better understand the behavior of the electric field within the composite material to further improve the model within this work. The types of composites studied within this work are often studied for use in electromagnetic shielding, electrostatic reduction, or even monitoring structural changes due to compression, stretching, or damage through their effect on the conductivity. However, experimental works have shown that based on various processing techniques the electrical properties of specific composites can vary widely. Therefore, the goal of this work has been to form a model with the ability to accurately predict the conductive properties as a function physical characteristics of the

Comparative studies of the composition of bacterial microbiota associated with the ruminal content, ruminal epithelium and in the faeces of lactating dairy cows.

PubMed

Liu, Jun-hua; Zhang, Meng-ling; Zhang, Rui-yang; Zhu, Wei-yun; Mao, Sheng-yong

2016-03-01

The objective of this research was to compare the composition of bacterial microbiota associated with the ruminal content (RC), ruminal epithelium (RE) and faeces of Holstein dairy cows. The RC, RE and faecal samples were collected from six Holstein dairy cows when the animals were slaughtered. Community compositions of bacterial 16S rRNA genes from RC, RE and faeces were determined using a MiSeq sequencing platform with bacterial-targeting universal primers 338F and 806R. UniFrac analysis revealed that the bacterial communities of RC, RE and faeces were clearly separated from each other. Statistically significant dissimilarities were observed between RC and faeces (P = 0.002), between RC and RE (P = 0.003), and between RE and faeces (P = 0.001). A assignment of sequences to taxa showed that the abundance of the predominant phyla Bacteroidetes was lower in RE than in RC, while a significant higher (P < 0.01) abundance of Proteobacteria was present in RE than in RC. When compared with the RC, the abundance of Firmicutes and Verrucomicrobia was higher in faeces, and RC contained a greater abundance of Bacteroidetes and Tenericutes. A higher proportions of Butyrivibrio and Campylobacter dominated RE as compared to RC. The faecal microbiota was less diverse than RC and dominated by genera Turicibacter and Clostridium. In general, these findings clearly demonstrated the striking compositional differences among RC, RE and faeces, indicating that bacterial communities are specific and adapted to the harbouring environment. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Multiple sclerosis and nephrolithiasis: a matched-case comparative study.

PubMed

Ganesan, Vishnu; Chen, Wen Min; Jain, Rajat; De, Shubha; Monga, Manoj

2017-06-01

To compare stone composition and serum/urine biochemistries in stone formers with multiple sclerosis (MS) against stone formers without MS and to examine the association between mobility, methods of bladder emptying, and stone formation. In this retrospective case-control study, we identified patients diagnosed with MS and kidney stone disease who were seen at our institution between 2001 and 2016. For the first part of the study, up to two controls (stone formers without a history of MS) were identified for each case and matched on age, body mass index, and sex. For the second part of this study, matched controls (MS patients without a history of stones) were identified in a 1:1 ratio in a similar fashion. Results of 24-h urine biochemistry studies, stone compositions, serum laboratory measures, medications, history of stone surgeries, mobility, and method of bladder emptying were collected. In all, 587 patients were identified who had both MS and a history of stone disease. Of these, 118 patients had a stone composition available. When compared to matched controls, patients with MS were significantly more likely to have calcium phosphate stones (42% vs 15%, P < 0.001) and struvite stones (8% vs 3%, P = 0.03) and less likely to have calcium oxalate monohydrate stones (39% vs 64%, P < 0.001). Among those patients with a composition available, those with MS were more likely to have undergone a percutaneous nephrolithotomy (PCNL; 25% vs 12%, P = 0.005) or a cystolithopaxy (16% vs 3%, P < 0.001) compared to their matched controls. In all, 61 patients had a complete 24-h urinary stone panel. There were no significant differences in urinary pH, volume, creatinine, calcium, citrate, oxalate, sodium, and uric acid as well as rates of hypocitraturia, hyperoxaluria, hypercalciuria, and hyperuricosuria among patients with MS. Use of intermittent straight catheterisation [ISC; odds ratio (OR) 3.50, 95% confidence interval (CI) 1.89-6.47]; P < 0.001] or an indwelling catheter

Comparative study on composition, physicochemical and antioxidant characteristics of different varieties of kiwifruit seed oil in China.

PubMed

Deng, Jianjun; Liu, Qingqing; Zhang, Qi; Zhang, Chao; Liu, Dan; Fan, Daidi; Yang, Haixia

2018-10-30

In this study, fatty acid compositions, physiochemical properties, and antioxidant activities of eight varieties of kiwifruit seed oil (KSO) in China were comparatively investigated. All varieties of KSO were rich in unsaturated fatty acid (UFA), especially linolenic acid. Different varieties of KSO showed subtle differences in physico-chemical characteristics; e.g., density (0.88-0.091 mg/mL), refractive index (1.4803-1.4823), acid value (3.21-3.99 mg KOH/g oil), iodine value (177.22-202.75 g I/100 g oil), and peroxide value (7.23-14.75 mM/kg oil). Different varieties of KSO demonstrated different radical scavenging capacities for DPPH (IC 50  = 25.7-35.1 mg/mL), HO (IC 50 =0.93-1.26 mg/mL), ORAC (1.26-1.99 mM Trolox/kg), and FRAP (3.30-132.30 mg Trolox/kg). Principal component analysis indicated the variety "Hongyang" to have a higher content of UFA and better antioxidant capacity than other varieties. Furthermore, comet assay verified that KSO can protect mice lymphocytes against oxidative DNA damage. Taken together, our findings provide evidence for the bioactivity of KSO as a potential dietary supplement. Copyright © 2018 Elsevier Ltd. All rights reserved.

A study on the crushing behavior of basalt fiber reinforced composite structures

NASA Astrophysics Data System (ADS)

Pandian, A.; Veerasimman, A. P.; Vairavan, M.; Francisco, C.; Sultan, M. T. H.

2016-10-01

The crushing behavior and energy absorption capacity of basalt fiber reinforced hollow square structure composites are studied under axial compression. Using the hand layup technique, basalt fiber reinforced composites were fabricated using general purpose (GP) polyester resin with the help of wooden square shaped mould of varying height (100 mm, 150 mm and 200 mm). For comparison, similar specimens of glass fiber reinforced polymer composites were also fabricated and tested. Axial compression load is applied over the top end of the specimen with cross head speed as 2 mm/min using Universal Testing Machine (UTM). From the experimental results, the load-deformation characteristics of both glass fiber and basalt fiber composites were investigated. Crashworthiness and mode of collapse for the composites were determined from load-deformation curve, and they were then compared to each other in terms of their crushing behaviors.

Study of Natural Fiber Breakage during Composite Processing

NASA Astrophysics Data System (ADS)

Quijano-Solis, Carlos Jafet

Biofiber-thermoplastic composites have gained considerable importance in the last century. To provide mechanical reinforcement to the polymer, fibers must be larger than a critical aspect ratio (length-to-width ratio). However, biofibers undergo breakage in length or width during processing, affecting their final aspect ratio in the composites. In this study, influence on biofiber breakage by factors related to processing conditions, fiber morphology and the flow type was investigated through: a) experiments using an internal mixer, a twin-screw extruder (TSE) or a capillary rheometer; and b) a Monte Carlo computer simulation. Composites of thermomechanical fibers of aspen or wheat straw mixed with polypropylene were studied. Internal mixer experiments analyzed wheat straw and two batches of aspen fibers, named AL and AS. AL fibers had longer average length. Processing variables included the temperature, rotors speed and fiber concentration. TSE experiments studied AL and AS fiber composites under various screws speeds, temperatures and feeding rates of the polymer and fibers. Capillary rheometers experiments determined AL fiber breakage in shear and elongational flows for composites processed at different concentrations, temperatures, and strain rates. Finally, the internal mixer experimental results where compared to Monte Carlo simulation predictions. The simulation focused on fiber length breakage due to fiber-polymer interactions. Internal mixer results showed that final fiber average length depended almost solely on processing conditions while final fiber average width depended on both processing conditions and initial fiber morphology. In the TSE, processing conditions as well as initial fiber length influenced final average length. TSE results showed that the fiber concentration regime seems to influence the effect of processing variables on fiber breakage. Capillary rheometer experiments demonstrated that biofiber breakage happens in both elongational and

The comparative biomechanics of the reinforced interdental crossover and the Stout loop composite splints for mandibular fracture repair in dogs.

PubMed

Kitshoff, A M; de Rooster, H; Ferreira, S M; Burger, D; Steenkamp, G

2013-01-01

To describe a new technique, the reinforced interdental crossover composite splint (RIC), for transverse mandibular fracture repair in dogs. This technique was compared biomechanically with the established reinforced interdental Stout loop composite splint (RIS) technique. Six pairs of mandibles from young adult small breed dogs were used for the study. Osteotomies were created in a standardized fashion and fixed with either RIC or RIS. All composite splint constructs were tested biomechanically with a cantilever bending force, using a single column testing machine at a rate of 2 mm/min. The time of application, amount of composite used, ultimate force, stiffness, total displacement, and total energy absorbed during displacement of the rostral mandibular segment were calculated and compared between the two groups. No significant difference was found when comparing the time of application of the RIC and the RIS techniques. All implants failed by either composite resin fracture over the region of the osteotomy or by fracture between the first and second molar followed by detachment of the resin from the lingual enamel surface of the first molar. Differences between the RIC and RIS in force (80.5 N ± 40.3 and 51.8 N ± 27.4. respectively) and stiffness (16.2 N/mm ± 4.4 and 10.1 N/mm ± 4.1 respectively) were significant (p = 0.03). However differences between the two techniques in displacement and total energy absorbed were not significant. In experimentally fractured mandibles of young adult dogs there is evidence that RIC is biomechanically similar to RIS.

Comparative Experimental Study on Ionic Polymer Mental Composite based on Nafion and Aquivion Membrane as Actuators

NASA Astrophysics Data System (ADS)

Luo, B.; Chen, Z.

2017-11-01

Most ionic polymer mental composites employ Nafion as the polymer matrix, Aquivion can also manufactured as ionic polymer mental composite while research was little. This paper researched on two kinds of ionic polymer mental composite based on Aquivion and Nafion matrix with palladium electrode called Aquivion-IPMC and Nafion-IPMC. The samples were fabricated by the same preparation process. The current and deformation responses of the samples were measured at voltage to characterize the mechano-electrical properties. The experimental observations revealed that shorter flexible side chains in Aquivion-IPMC provide a larger force than Nafion-IPMC, while the displacement properties were similar in two different samples. The results also showed that Aquivion membrane can also replace Nafion to reproduce IPMC application in soft robots, MEMS, and so on.

Feasibility of generating quantitative composition images in dual energy mammography: a simulation study

NASA Astrophysics Data System (ADS)

Lee, Donghoon; Kim, Ye-seul; Choi, Sunghoon; Lee, Haenghwa; Choi, Seungyeon; Kim, Hee-Joung

2016-03-01

Breast cancer is one of the most common malignancies in women. For years, mammography has been used as the gold standard for localizing breast cancer, despite its limitation in determining cancer composition. Therefore, the purpose of this simulation study is to confirm the feasibility of obtaining tumor composition using dual energy digital mammography. To generate X-ray sources for dual energy mammography, 26 kVp and 39 kVp voltages were generated for low and high energy beams, respectively. Additionally, the energy subtraction and inverse mapping functions were applied to provide compositional images. The resultant images showed that the breast composition obtained by the inverse mapping function with cubic fitting achieved the highest accuracy and least noise. Furthermore, breast density analysis with cubic fitting showed less than 10% error compare to true values. In conclusion, this study demonstrated the feasibility of creating individual compositional images and capability of analyzing breast density effectively.

Comparative analysis of essential oil composition of Iranian and Indian Nigella sativa L. extracted using supercritical fluid extraction and solvent extraction

PubMed Central

Ghahramanloo, Kourosh Hasanzadeh; Kamalidehghan, Behnam; Akbari Javar, Hamid; Teguh Widodo, Riyanto; Majidzadeh, Keivan; Noordin, Mohamed Ibrahim

2017-01-01

The objective of this study was to compare the oil extraction yield and essential oil composition of Indian and Iranian Nigella sativa L. extracted by using Supercritical Fluid Extraction (SFE) and solvent extraction methods. In this study, a gas chromatography equipped with a mass spectrophotometer detector was employed for qualitative analysis of the essential oil composition of Indian and Iranian N. sativa L. The results indicated that the main fatty acid composition identified in the essential oils extracted by using SFE and solvent extraction were linoleic acid (22.4%–61.85%) and oleic acid (1.64%–18.97%). Thymoquinone (0.72%–21.03%) was found to be the major volatile compound in the extracted N. sativa oil. It was observed that the oil extraction efficiency obtained from SFE was significantly (P<0.05) higher than that achieved by the solvent extraction technique. The present study showed that SFE can be used as a more efficient technique for extraction of N. Sativa L. essential oil, which is composed of higher linoleic acid and thymoquinone contents compared to the essential oil obtained by the solvent extraction technique. PMID:28814830

Comparative analysis of essential oil composition of Iranian and Indian Nigella sativa L. extracted using supercritical fluid extraction and solvent extraction.

PubMed

Ghahramanloo, Kourosh Hasanzadeh; Kamalidehghan, Behnam; Akbari Javar, Hamid; Teguh Widodo, Riyanto; Majidzadeh, Keivan; Noordin, Mohamed Ibrahim

2017-01-01

The objective of this study was to compare the oil extraction yield and essential oil composition of Indian and Iranian Nigella sativa L. extracted by using Supercritical Fluid Extraction (SFE) and solvent extraction methods. In this study, a gas chromatography equipped with a mass spectrophotometer detector was employed for qualitative analysis of the essential oil composition of Indian and Iranian N. sativa L. The results indicated that the main fatty acid composition identified in the essential oils extracted by using SFE and solvent extraction were linoleic acid (22.4%-61.85%) and oleic acid (1.64%-18.97%). Thymoquinone (0.72%-21.03%) was found to be the major volatile compound in the extracted N. sativa oil. It was observed that the oil extraction efficiency obtained from SFE was significantly ( P <0.05) higher than that achieved by the solvent extraction technique. The present study showed that SFE can be used as a more efficient technique for extraction of N. Sativa L. essential oil, which is composed of higher linoleic acid and thymoquinone contents compared to the essential oil obtained by the solvent extraction technique.

Study Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James; Workman,Gary

1998-01-01

The purpose of this work will be to develop techniques for monitoring the acoustic emissions from carbon epoxy composite structures at cryogenic temperatures. Performance of transducers at temperatures ranging from ambient to cryogenic and the characteristics of acoustic emission from composite structures will be studied and documented. This entire effort is directed towards characterization of structures used in NASA propulsion programs such as the X-33.

Written Composition Process, Evaluation Difficulties and Modalities: An Experimental Study

ERIC Educational Resources Information Center

Rodriguez, Celestino; Garci, Jesus Nicasio; Gonzalez-Castro, Paloma; Alvarez, David; Cerezo, Rebeca; Bernardo, Ana

2011-01-01

The underlying processes used in written compositions are currently a very interesting subject. Participants in this study were 326 people between 10 and 16 years of age, divided into two groups and compared by means of a "writing log". One group was provided assistance in the writing task by means of a graphic organiser, whilst the other was not…

Comparative analysis of bioactive phenolic compounds composition from 26 medicinal plants.

PubMed

Sytar, Oksana; Hemmerich, Irene; Zivcak, Marek; Rauh, Cornelia; Brestic, Marian

2018-05-01

Bioactive phenolic compounds are powerful antioxidants in traditionally used medicinal and industrial crop plants and have attracted increased interest in the last years in their application and role in non-destructive methodology for pre-screening analysis of some stress factors. In this study the qualitative target was linked with future possible applications of received data for improving non-destructive methodology as well as for improving existing knowledge regarding antioxidant content in some plant species. Comparative analysis of total phenolics, flavonoid contents, phenolic acid composition, and antioxidant activity in known east central Europe medicinal and industrial crop plants of 26 species of families Asteraceae , Rosaceae and Lamiaceae was done. Among the investigated leaf extracts the highest total phenolic, total flavonoid contents and antioxidant activity have been seen for Stachys byzantine L. ( Lamiaceae ), Calendula officinalis L. ( Asteraceae ) and for Potentilla recta L. ( Rosaceae ). The highest syringic acid content has been found in the leaf extracts of plant family Asteraceae - in the range from 0.782 to 5.078 mg g -1  DW. The representative's family Rosaceae has a higher content of p-anisic acid in the range 0.334-3.442 mg g -1 DW compared to the leaf extracts of families Lamiaceae and Asteraceae . The comparative study showed significant differences of content of phenolic acids in the leaf extracts of different representative's families Rosaceae , Asteraceae and Lamiaceae . We suggest that the presence of some phenolic acids can be used as a possible marker for family botanical specifications of representative families Asteraceae and Rosaceae . It was supposed that some pharmacological effects can be connected with the analyzed data.

[Comparative studies on the bacteriostatic effect of "Grisaldon" and "Cholinesalicylate gel"].

PubMed

Fröhlich, M; Wichmann, G

1977-07-01

The authors present a choline salicylate gel at present on trial and compare it, by means of microbiologic studies, with Grisaldon as to composition, consistency and bacteriostatic properties. Choline salicylate showed a good bacteriostatic effect. As to Grisaldon, the conditions are considerably less favorable due to the poor solubility of acetylsalicylic acid.

A comparative evaluation of microleakage of three different newer direct composite resins using a self etching primer in class V cavities: An in vitro study

PubMed Central

Hegde, Mithra N; Vyapaka, Pallavi; Shetty, Shishir

2009-01-01

Aims/Objectives: The aim of this in vitro study is to study, measure and compare the microleakage in three different newer direct composite resins using a self-etch adhesive bonding system in class V cavities by fluorescent dye penetration technique. Materials and Methods: Class V cavities were prepared on 45 human maxillary premolar teeth. On all specimens, one coat of G-Bond (GC Japan) applied and light cured. Teeth are then equally divided into 3 groups of 15 samples each. Filtek Z350 (3M ESPE), Ceram X duo (Dentsply Asia) and Synergy D6 (Coltene/Whaledent) resin composites were placed on samples of Groups I, II and III, respectively, in increments and light cured. After polishing the restorations, the specimens were suspended in Rhodamine 6G fluorescent dye for 48 h. The teeth were then sectioned longitudinally and observed for the extent of microleakage under the florescent microscope. Statistical Analysis Used: The results were subjected to statistical analysis using Kruskal Wallis and Mann–Whitney U Test. Results: Results showed no statistically significant difference among three groups tested. Conclusions: None of the materials tested was able to completely eliminate the microleakage in class V cavities. PMID:20543926

A comparative study of gelatin and starch-based nano-composite films modified by nano-cellulose and chitosan for food packaging applications.

PubMed

Noorbakhsh-Soltani, S M; Zerafat, M M; Sabbaghi, S

2018-06-01

Environmental concerns have led to extensive research for replacing polymer-based food packaging with bio-nano-composites. In this study, incorporation of nano-cellulose into gelatin and starch matrices is investigated for this purpose. Chitosan is used to improve mechanical, anti-fungal and waterproof properties. Experiments are designed and analyzed using response surface methodology. Nano-Cellulose is synthesized via acid hydrolysis and incorporated in base matrices through wet processing. Also, tensile strength test, food preservation, transparency in visible and UV and water contact angle are performed on the nano-composite films. DSC/TGA and air permeability tests are also performed on the optimal films. The results show that increasing nano-cellulose composition to 10% leads to increase the tensile strength at break to 8121 MN/m 2 and decrease the elongation at break. Also, increasing chitosan composition from 5% to 30% can enhance food preservation up to 15 days. Copyright © 2018 Elsevier Ltd. All rights reserved.

A comprehensive study of woven carbon fiber-reinforced nylon 6 composites

NASA Astrophysics Data System (ADS)

Pillay, Selvum

Liquid molding of thermoset composites has become very popular in all industry sectors, including aerospace, automotive, mass transit, and sporting goods, but the cost of materials and processing has limited the use to high-end applications. Thermoplastic composites are relatively cheap; however, the use has been limited to components with short fiber reinforcing. The high melt viscosity and short processing window precludes their use in the liquid molding of large structures and applications with continuous fiber reinforcement. The current research addresses the processing parameters, methodology, and limitations of vacuum assisted resin transfer molding (VARTM) of carbon fabric-reinforced, thermoplastic polyamide 6 (PA6). The material used is casting grade PA6. The process developed for using VARTM to produce carbon fabric-reinforced PA6 composites is explained in detail. The effects of infusion temperature and flow distance on the fiber weight fraction and crystallinity of the PA6 resin are presented. The degree of conversion from monomer to polymer was determined. Microscopic studies to show the wet-out of the fibers at the filament level are also presented. Tensile, flexural, short beam shear strength (SBSS), and low-velocity impact test results are presented and compared to a equivalent thermoset matrix composite. The rubber toughened epoxy system (SC-15) was chosen for the comparative study because the system has been especially developed to overcome the brittle nature of epoxy composites. The environmental effects of moisture and ultraviolet (UV) radiation on the carbon/nylon 6 composite were investigated. The samples were immersed in boiling water for 100 hr, and mechanical tests were conducted. Results showed that moisture causes plasticization of the matrix and attacks the fiber matrix interface. This leads to deterioration of the mechanical properties. The samples were also exposed to UV for up to 600 hr, and post exposure tests were conducted. The

Chemical composition and strength of dolomite geopolymer composites

NASA Astrophysics Data System (ADS)

Aizat, E. A.; Al Bakri, A. M. M.; Liew, Y. M.; Heah, C. Y.

2017-09-01

The chemical composition of dolomite and the compressive strength of dolomite geopolymer composites were studied. The both composites prepared with mechanical mixer manufactured by with rotor speed of 350 rpm and curing in the oven for 24 hours at 80˚C. XRF analysis showThe dolomite raw materials contain fewer amounts of Si and Al but high Ca in its composition. Dolomite geopolymer composites with 20M of NaOH shows greater and optimum compressive strength compared to dolomite geopolymer with other NaOH molarity. This indicated better interaction of dolomite raw material and alkaline activator need high molarity of NaOH in order to increase the reactivity of dolomite.

Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels

PubMed Central

Jiang, Nan; Ma, Shaochun

2015-01-01

In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel and proposed a feasible technical solution to simplified calculation. In conformity with mechanical rules, a typical panel element was selected and divided into two homogenous composite sub-elements and a secondary homogenous element, respectively for solution, thus establishing an equivalence of the composite panel to a simple homogenous panel and obtaining the effective formulas for calculating the various elastic constants. Finally, the calculation results and the experimental results were compared, which revealed that the calculation method was correct and reliable and could meet the calculation needs of practical engineering and provide a theoretical basis for simplified calculation for studies on composite panel elements and structures as well as a reference for calculations of other panels. PMID:28793631

Simplified Calculation Model and Experimental Study of Latticed Concrete-Gypsum Composite Panels.

PubMed

Jiang, Nan; Ma, Shaochun

2015-10-27

In order to address the performance complexity of the various constituent materials of (dense-column) latticed concrete-gypsum composite panels and the difficulty in the determination of the various elastic constants, this paper presented a detailed structural analysis of the (dense-column) latticed concrete-gypsum composite panel and proposed a feasible technical solution to simplified calculation. In conformity with mechanical rules, a typical panel element was selected and divided into two homogenous composite sub-elements and a secondary homogenous element, respectively for solution, thus establishing an equivalence of the composite panel to a simple homogenous panel and obtaining the effective formulas for calculating the various elastic constants. Finally, the calculation results and the experimental results were compared, which revealed that the calculation method was correct and reliable and could meet the calculation needs of practical engineering and provide a theoretical basis for simplified calculation for studies on composite panel elements and structures as well as a reference for calculations of other panels.

Single agglutinates: A comparative study of compositions of agglutinitic glass, whole-grain, bulk soil, and FMR

NASA Technical Reports Server (NTRS)

Basu, A.; Robinson, R.; Mckay, D. S.; Blanchard, D. P.; Morris, R. V.; Wentworth, Susan J.

1994-01-01

Previous workers on single agglutinates have variously interpreted the composition of agglutinitic glass to represent impact melts of (1) bulk soil, (2) mixed components in finer sizes, and (3) microtargets. Separately, Papike has argued in favor of fusion of the finest fraction of bulk soils. Thirty-four single agglutinates were hand-picked from the mature Apollo 16 soil 61181 (I(sub s)/FeO = 82) and the FMR and chemical composition (INAA for Fe, Sc, Sm, Co, Ni, and Cr) of each agglutinate particle were measured. Thirteen of these single agglutinates were selected for electron beam microanalysis and imaging. Less than 1 micron spots were analyzed (for Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Ni, and Ba) on pure glassy areas (approximately ten in each particle) selected on the basis of optical and BSE images (avoiding all clasts and inclusions) with an electron microprobe to obtain average glass compositions of each single agglutinate.

Disability Studies in the Composition Classroom

ERIC Educational Resources Information Center

Browning, Ella R.

2014-01-01

Although attention to disability is becoming more apparent in first-year composition curricula, too often disability is simply "tacked on" to existing courses. Scholars have argued that composition instructors interested in fully integrating a disability studies perspective into their curriculum would do well, instead, to think…

Comparative study on nutrient composition, phytochemical, and functional characteristics of raw, germinated, and fermented Moringa oleifera seed flour

PubMed Central

Ijarotimi, Oluwole S; Adeoti, Oluwole A; Ariyo, Oluwaseun

2013-01-01

Moringa oleifera seeds were processed as raw M. oleifera (RMO), germinated M. oleifera (GMO), and fermented M. oleifera (FMO), and were evaluated for proximate, minerals, amino acids, fatty acids, phytochemicals/antinutrients, and functional properties. Protein content of GMO (23.69 ± 0.11 g/100 g) was higher than FMO (21.15 ± 0.08 g/100 g) and that of RMO (18.86 ± 0.09 g/100 g) (P < 0.05), respectively. Energy value of FMO (465.32 ± 0.48 kcal) was higher than GMO (438.62 ± 0.12 kcal) and that of RMO (409.04 ± 1.61 kcal), respectively. Mineral contents in GMO were significantly higher in iron, sodium, potassium, magnesium, and copper, while FMO were higher in calcium, phosphorus, and magnesium, and both were significantly lower than those in RMO (P < 0.05). Total essential amino acids (TEAAs) in FMO (31.07 mg/g crude protein) were higher than in GMO (26.52 mg/g crude protein), and were higher than that in RMO (23.56 mg/g crude protein). Linoleic acid (58.79 ± 0.02–62.05 ± 0.01 g/100 g) and behenic acid (0.13 ± 0.00–0.20 ± 0.06 g/100 g) were the predominant and least fatty acids, respectively. Phytochemical/antinutrient compositions in FMO samples were significantly lower than GMO, and both were significantly lower when compared with RMO samples (P < 0.05). The bulk density (pack and loose), foaming capacity, swelling capacity, and water absorption capacity (WAC) of FMO were significantly higher than those of GMO, and there was no significant difference between GMO and RMO samples. The study established that fermentation processing methods increased the protein content, essential amino acid, and polyunsaturated fatty acid profiles, and reduced antinutrient compositions of M. oleifera seed than germination processing techniques; hence, fermentation techniques should be encouraged in processing moringa seeds in food processing. PMID:24804056

The Uses of Toulmin in Composition Studies

ERIC Educational Resources Information Center

Bizup, Joseph

2009-01-01

This article examines the various uses to which Stephen Toulmin has been put in composition studies. It presents data on citations of Toulmin in nine journals, considers appeals to Toulmin in several strains of composition scholarship, and argues that composition scholars ought to attend more carefully to Toulmin's later works. (Contains 4 tables…

A Study of Flexible Composites for Expandable Space Structures

NASA Technical Reports Server (NTRS)

Scotti, Stephen J.

2016-01-01

Payload volume for launch vehicles is a critical constraint that impacts spacecraft design. Deployment mechanisms, such as those used for solar arrays and antennas, are approaches that have successfully accommodated this constraint, however, providing pressurized volumes that can be packaged compactly at launch and expanded in space is still a challenge. One approach that has been under development for many years is to utilize softgoods - woven fabric for straps, cloth, and with appropriate coatings, bladders - to provide this expandable pressure vessel capability. The mechanics of woven structure is complicated by a response that is nonlinear and often nonrepeatable due to the discrete nature of the woven fiber architecture. This complexity reduces engineering confidence to reliably design and certify these structures, which increases costs due to increased requirements for system testing. The present study explores flexible composite materials systems as an alternative to the heritage softgoods approach. Materials were obtained from vendors who utilize flexible composites for non-aerospace products to determine some initial physical and mechanical properties of the materials. Uniaxial mechanical testing was performed to obtain the stress-strain response of the flexible composites and the failure behavior. A failure criterion was developed from the data, and a space habitat application was used to provide an estimate of the relative performance of flexible composites compared to the heritage softgoods approach. Initial results are promising with a 25% mass savings estimated for the flexible composite solution.

Analytical and experimental study of structurally efficient composite hat-stiffened panels loaded in axial compression

NASA Technical Reports Server (NTRS)

Williams, J. G.; Mikulus, M. M., Jr.

1976-01-01

Structural efficiency studies were made to determine the weight saving potential of graphite/epoxy composite structures for compression panel applications. Minimum weight hat-stiffened and open corrugation configurations were synthesized using a nonlinear mathematical programming technique. Selected configurations were built and tested to study local and Euler buckling characteristics. Test results for 23 panels critical in local buckling and six panels critical in Euler buckling are compared with analytical results obtained using the BUCLASP-2 branched plate buckling program. A weight efficiency comparison is made between composite and aluminum compression panels using metal test data generated by the NACA. Theoretical studies indicate that potential weight savings of up to 50% are possible for composite hat-stiffened panels when compared with similar aluminum designs. Weight savings of 32% to 42% were experimentally achieved. Experience suggests that most of the theoretical weight saving potential is available if design deficiencies are eliminated and strict fabrication control is exercised.

A study on the performance of piezoelectric composite materials for designing embedded transducers for concrete assessment

NASA Astrophysics Data System (ADS)

Dumoulin, Cédric; Deraemaeker, Arnaud

2018-03-01

Ultrasonic measurements of concrete can provide crucial information about its state of health. The most common practice in the construction industry consists in using external probes which strongly limits the use of the method since large parts of the in-service structures are difficult to access. It is also possible to assess in real time the setting process of the concrete using ultrasonic measurements. In practice, the field measurement of the concrete hardening is limited by the formworks. As an alternative, some research teams have studied the possibility to directly embed the transducers into the concrete structures. The current embedded ultrasonic transducers are of two categories: bulk piezoelectric elements surrounded by several coating and matching layers and composites piezoelectric elements. Both technologies aim at optimizing the wave energy transmitted to the tested medium. The performances of the transducers of the first kind have been studied in a previous study. A fair amount of recent research has been focused on the development of novel cement-based piezoelectric composites. In this study, we first compare the effective properties of such cement-based materials with more widespread composites made with matrices of epoxy resins or polyurethane. The study only concerns the 1-3 fiber arrangement composites. The effective properties are computed using both an analytical mixing rule method and a finite element based homogenization method using representative volume elements (RVEs) which allows for considering more realistic fiber arrangements, leading yet to very similar results. The effective piezoelectric properties of cement-based composites appear to be very low compared to composites made of epoxy or polyurethane. This result is underlined by looking at the acoustic response and the electric input impedance of different piezoelectric disks where we compare performances of such transducers with a low-cost bulk piezoelectric disc element. The first

Updating and testing of a Finnish method for mixed municipal solid waste composition studies.

PubMed

Liikanen, M; Sahimaa, O; Hupponen, M; Havukainen, J; Sorvari, J; Horttanainen, M

2016-06-01

More efficient recycling of municipal solid waste (MSW) is an essential precondition for turning Europe into a circular economy. Thus, the recycling of MSW must increase significantly in several member states, including Finland. This has increased the interest in the composition of mixed MSW. Due to increased information needs, a method for mixed MSW composition studies was introduced in Finland in order to improve the national comparability of composition study results. The aim of this study was to further develop the method so that it corresponds to the information needed about the composition of mixed MSW and still works in practice. A survey and two mixed MSW composition studies were carried out in the study. According to the responses of the survey, the intensification of recycling, the landfill ban on organic waste and the producer responsibility for packaging waste have particularly influenced the need for information about the composition of mixed MSW. The share of biowaste in mixed MSW interested the respondents most. Additionally, biowaste proved to be the largest waste fraction in mixed MSW in the composition studies. It constituted over 40% of mixed MSW in both composition studies. For these reasons, the classification system of the method was updated by further defining the classifications of biowaste. The classifications of paper as well as paperboard and cardboard were also updated. The updated classification system provides more information on the share of avoidable food waste and waste materials suitable for recycling in mixed MSW. The updated method and the information gained from the composition studies are important in ensuring that the method will be adopted by municipal waste management companies and thus used widely in Finland. Copyright © 2016 Elsevier Ltd. All rights reserved.

Failure Study of Composite Materials by the Yeh-Stratton Criterion

NASA Technical Reports Server (NTRS)

Yeh, Hsien-Yang; Richards, W. Lance

1997-01-01

The newly developed Yeh-Stratton (Y-S) Strength Criterion was used to study the failure of composite materials with central holes and normal cracks. To evaluate the interaction parameters for the Y-S failure theory, it is necessary to perform several biaxial loading tests. However, it is indisputable that the inhomogeneous and anisotropic nature of composite materials have made their own contribution to the complication of the biaxial testing problem. To avoid the difficulties of performing many biaxial tests and still consider the effects of the interaction term in the Y-S Criterion, a simple modification of the Y-S Criterion was developed. The preliminary predictions by the modified Y-S Criterion were relatively conservative compared to the testing data. Thus, the modified Y-S Criterion could be used as a design tool. To further understand the composite failure problem, an investigation of the damage zone in front of the crack tip coupled with the Y-S Criterion is imperative.

Body composition in Pan paniscus compared with Homo sapiens has implications for changes during human evolution.

PubMed

Zihlman, Adrienne L; Bolter, Debra R

2015-06-16

The human body has been shaped by natural selection during the past 4-5 million years. Fossils preserve bones and teeth but lack muscle, skin, fat, and organs. To understand the evolution of the human form, information about both soft and hard tissues of our ancestors is needed. Our closest living relatives of the genus Pan provide the best comparative model to those ancestors. Here, we present data on the body composition of 13 bonobos (Pan paniscus) measured during anatomical dissections and compare the data with Homo sapiens. These comparative data suggest that both females and males (i) increased body fat, (ii) decreased relative muscle mass, (iii) redistributed muscle mass to lower limbs, and (iv) decreased relative mass of skin during human evolution. Comparison of soft tissues between Pan and Homo provides new insights into the function and evolution of body composition.

In vitro study of transverse strength of fiber reinforced composites.

PubMed

Mosharraf, R; Hashemi, Z; Torkan, S

2011-01-01

Reinforcement with fiber is an effective method for considerable improvement in flexural properties of indirect composite resin restorations. The aim of this in-vitro study was to compare the transverse strength of composite resin bars reinforced with pre-impregnated and non-impregnated fibers. Thirty six bar type composite resin specimens (3×2×25 mm) were constructed in three groups. The first group was the control group (C) without any fiber reinforcement. The specimens in the second group (P) were reinforced with pre-impregnated fibers and the third group (N) with non-impregnated fibers. These specimens were tested by the three-point bending method to measure primary transverse strength. Data were statistically analyzed with one way ANOVA and Tukey's tests. There was a significant difference among the mean primary transverse strength in the three groups (P<0.001). The post-hoc (Tukey) test showed that there was a significant difference between the pre-impregnated and control groups in their primary transverse strength (P<0.001). Regarding deflection, there was also a significant difference among the three groups (P=0.001). There were significant differences among the mean deflection of the control group and two other groups (P(C&N)<.001 and P(C&P)=.004), but there was no significant difference between the non-and pre-impregnated groups (P(N&P)=.813). Within the limitations of this study, it was concluded that reinforcement with fiber considerably increased the transverse strength of composite resin specimens, but impregnation of the fiber used implemented no significant difference in the transverse strength of composite resin samples.

Comparative Efficacies of Collagen-Based 3D Printed PCL/PLGA/β-TCP Composite Block Bone Grafts and Biphasic Calcium Phosphate Bone Substitute for Bone Regeneration.

PubMed

Hwang, Kyoung-Sub; Choi, Jae-Won; Kim, Jae-Hun; Chung, Ho Yun; Jin, Songwan; Shim, Jin-Hyung; Yun, Won-Soo; Jeong, Chang-Mo; Huh, Jung-Bo

2017-04-17

The purpose of this study was to compare bone regeneration and space maintaining ability of three-dimensional (3D) printed bone grafts with conventional biphasic calcium phosphate (BCP). After mixing polycaprolactone (PCL), poly (lactic-co-glycolic acid) (PLGA), and β-tricalcium phosphate (β-TCP) in a 4:4:2 ratio, PCL/PLGA/β-TCP particulate bone grafts were fabricated using 3D printing technology. Fabricated particulate bone grafts were mixed with atelocollagen to produce collagen-based PCL/PLGA/β-TCP composite block bone grafts. After formation of calvarial defects 8 mm in diameter, PCL/PLGA/β-TCP composite block bone grafts and BCP were implanted into bone defects of 32 rats. Although PCL/PLGA/β-TCP composite block bone grafts were not superior in bone regeneration ability compared to BCP, the results showed relatively similar performance. Furthermore, PCL/PLGA/β-TCP composite block bone grafts showed better ability to maintain bone defects and to support barrier membranes than BCP. Therefore, within the limitations of this study, PCL/PLGA/β-TCP composite block bone grafts could be considered as an alternative to synthetic bone grafts available for clinical use.

Comparative study of the chemical composition and mineral element content of Artocarpus heterophyllus and Treculia africana seeds and seed oils.

PubMed

Ajayi, Ibironke Adetolu

2008-07-01

A comparative study of Artocarpus heterophyllus and Treculia africana seeds, both of Moraceae family, was carried out to establish their chemical compositions and evaluate their mineral element content in order to investigate the possibility of using them for human and or animal consumption and also to examine if there is a relationship between the properties of these seeds. A. heterophyllus and T. africana are rich in protein; their protein contents are higher than those from high protein animal sources such as beef and marine fishes. Both seeds have high carbohydrate content and could act as source of energy for animals if included in their diets. The oil contents of the seeds are 11.39% and 18.54% for A. heterophyllus and T. africana, respectively. The oils are consistently liquid at room temperature. The results of the physicochemical properties of the two seeds are comparable to those of conventional oil seeds such as groundnut and palm kernel oils and could be useful for nutritional and industrial purposes. The seeds were found to be good sources of mineral elements. The result revealed potassium to be the prevalent mineral elements which are 2470.00 ppm and 1680.00 ppm for A. heterophyllus and T. africana, respectively followed by sodium, magnesium and then calcium. They also contain reasonable quantity of iron, in particular A. heterophyllus 148.50 ppm.

Preparation and crystalline studies of PVDF hybrid composites

NASA Astrophysics Data System (ADS)

Chethan P., B.; Renukappa, N. M.; Sanjeev, Ganesh

2018-04-01

The conducting polymer composites have become increasingly important for electrical and electronic applications due to their flexibility, easy of processing, high strength and low cost. A flexible conducting polymer hybrid composite was prepared by melt mixing of nickel coated multi-walled carbon nanotubes (Ni-MWNT) and graphitized carbon nanofibres (GCNF) in Polyvinylidene fluoride (PVDF) matrix. The crystalline structures of the nano composites were studied by X-ray diffraction (XRD) method and showed characteristic peaks at 17.7°, 18.5°, 20° and 26.7° of 2θ. The β phase crystalline nature of the composite films, degree of crystallinity, melting temperature and crystallization behavior of the hybrid composites were studied using appropriate characterization techniques. The filler in the insulating polymer matrix plays crucial role to improve the crystallinity of the composites.

Study Of Nondestructive Techniques For Testing Composites

NASA Technical Reports Server (NTRS)

Roth, D.; Kautz, H.; Draper, S.; Bansal, N.; Bowles, K.; Bashyam, M.; Bishop, C.

1995-01-01

Study evaluates some nondestructive methods for characterizing ceramic-, metal-, and polymer-matrix composite materials. Results demonstrated utility of two ultrasonic methods for obtaining quantitative data on microstructural anomalies in composite materials.

A prospective, randomized, comparative clinical study of resin composite and glass ionomer cement for retrograde root filling.

PubMed

Jensen, S S; Nattestad, A; Egdø, P; Sewerin, I; Munksgaard, E C; Schou, S

2002-12-01

To compare the clinical and radiographic treatment outcome of retrograde root filling with either dentin-bonded resin composite (Retroplast, RP) or glass ionomer cement (Chelon-Silver, CS). A prospective, randomized clinical study of 134 consecutive patients with indication of retrograde root filling of an incisor, canine, premolar, or first molar. Either RP or CS was chosen at random as retrograde filling material. Either material was applied onto the entire resection surface after prepared slightly concave. This preparation technique makes a sealing of the entire resection surface possible and prevents marginal contraction gaps during polymerization. A total of 122 patients were available for 1-year follow-up. After 1 year the proportion of successful cases was significantly higher in the RP group (73%) than in the CS group (31%) (p<0.001). Doubtful healing with a need for a longer observation period was seen in 17% of the RP cases and 19% of the CS cases. The proportion of failures in the RP group (10%) was significantly lower than that in the CS group (50%) (p<0.001). Most of the unsuccessful CS cases failed due to loosening of the retrograde filling. Dentin-bonded RP applied onto the entire, slightly concave resection surface is a predictable apical sealant characterized by a high success rate. In contrast, retrograde root filling with CS results in an unacceptably high failure rate due to insufficient bonding strength to the concave resection surface.

Comparative carcass and tissue nutrient composition of transgenic Yorkshire pigs expressing phytase in the saliva and conventional Yorkshire pigs.

PubMed

Forsberg, C W; Meidinger, R G; Ajakaiye, A; Murray, D; Fan, M Z; Mandell, I B; Phillips, J P

2014-10-01

A transgenic line of Yorkshire (YK) pigs named the Cassie (CA) line was produced with a low copy number phytase transgene inserted in the genome. The transgenic line efficiently digests P, Ca, and other major minerals of plant dietary origin. The objectives of this study were to 1) compare carcass and tissue nutrient composition and meat quality traits for third generation hemizygous CA line market BW finisher pigs (n = 24) with age-matched conventional YK finisher pigs (n = 24) and 2) examine effects of outbreeding with high-index conventional YK boars on modifying carcass leanness from the third to sixth generations in CA line finisher boars (n = 73) and gilts (n = 103). Cassie boars (n = 12) and CA gilts (n = 12) were fed diets without supplemental P and comparable numbers of age-matched YK boars and gilts fed diets containing supplement P were raised throughout the finisher phase. The pigs were slaughtered and then fabricated into commercial pork primals before meat composition and quality evaluation. Proximate and major micronutrient composition was determined on tissues including fat, kidney, lean, liver, and skin. The main difference observed was greater (P = 0.033) crude fat content in CA boar carcasses and increased (P < 0.04) leaf lard in both CA boars and gilts but no differences were observed (P = 0.895 and P = 0.223, respectively) in carcass backfat thickness as compared with YK pigs. There were no substantive differences in tissue composition, except for CA boar kidneys. Numerous changes in the mineral, fatty acid, and indispensable AA composition for CA boar kidneys were not apparent in CA gilts. These changes may point to adaptive physiological changes in the boar kidney necessary for homeostatic regulation of mineral retention related to phytase action rather than to insertion of the transgene. However, from a meat composition perspective, transgenic expression of phytase in the CA line of YK pigs had little overall effect on meat composition

One year comparative clinical evaluation of EQUIA with resin-modified glass ionomer and a nanohybrid composite in noncarious cervical lesions

PubMed Central

Vaid, Deepa Sunil; Shah, Nimisha Chinmay; Bilgi, Priyanka Shripad

2015-01-01

Aims: Comparative evaluation of EQUIA with a resin-modified glass ionomer cement (RMGIC; GC Gold Label glass ionomer light cured universal restorative cement) and a nanohybrid composite (Tetric N-Ceram) in noncarious cervical lesions (NCCLs). Background: To establish the most suitable material for the restoration of NCCLs. Settings and Design: In vivo study. Materials and Methods: Eighty-seven NCCLs were randomly restored with EQUIA, a RMGIC, and a nanohybrid composite. Clinical evaluation of the restorations was done following the Unites States Public Health criteria by a single-blinded investigator. Data were formulated, and statistical analysis was done by Chi-square test. Statistical Analysis Used: Chi-square test. Results: No significant difference was found between EQUIA, RMGIC, and nanohybrid composite at 1-month, at 6 months, and at 1-year (P > 0.05). Conclusions: EQUIA, resin-modified glass ionomer, and nanohybrid composite performed equally at 1-month, 6 months, and 1-year follow-up periods. PMID:26752837

The study of fix composite panel and steel plates on testing stand

NASA Astrophysics Data System (ADS)

Wróbel, A.; Płaczek, M.; Wachna, M.

2016-08-01

In this paper the practical possibilities of strength verification analysis of composite materials used in the manufacture of selected components of railway wagons are presented. Real laboratory stand for measurements in a scale controlled by PLC controller were made. The study of different types of connections of composite materials with sheet metal is presented. In one of the chapter of this paper principles construction of testing stand with pneumatic cylinder were presented. Mainly checking of displacements and stresses generated on the sheet as a result of pneumatic actuators load for composite boards was carried out. The use of the controller with operating panel allows to easy programming testing cycle. The user can define the force generated by the actuator by change of air pressure in cylinder. Additionally the location of acting cylinders and their jump can be changed by operator. The examination of the volume displacements was done by displacement sensor, and the tensile strain gauge. All parameters are written in CatmanEasy - data acquisition software. This article presents the study of stresses and displacements in the composite plates joined with sheet metal, in summary of this article, the authors compare the obtained results with the computer simulation results in the article: "Simulation of stresses in an innovative combination of composite with sheet".

Alternating current response studies on nickel ferrite-niobium composite at room temperature

NASA Astrophysics Data System (ADS)

Reddy, L. P. Babu; Rajprakash, H. G.; Chethan, B.; Vijayakumari, S. C.; Ravikiran, Y. T.

2018-05-01

In the present research NDNF -Niobium Pentaxide doped Nickel Ferrite [NiFe2O4-Nb2O5-50%] composite was prepared by Mechano-Chemical mixing of NiFe2O4 [NF] with Nb2O5. NF and the NDNF were structurally characterized by four transform infrared spectroscopy [FTIR] and X-ray diffraction [XRD] techniques. The presence of characteristic absorption bands of NF and Nb2O5 in the FTIR spectrum of NDNF with small shift confirmed interfacial interaction of NF with Nb2O5. XRD studies also confirm interfacial interaction between NF and Nb2O5 in the composite and crystalline nature with an average crystallite size of 30nm. The Alternating Current (AC) response parameters of NF and the NDNF were comparatively studied in the frequency range 100Hz-1MHz at room temperature. Increase in AC conductivity of the NDNF has compared to NF was observed and discussed based on the electron hole exchange mechanism.

Comparative Study of the Shear Bond Strength of Flowable Composite in Permanent Teeth Treated with Conventional Bur and Contact or Non-Contact Er:YAG Laser

PubMed Central

Parhami, Parisa; Pourhashemi, Seyed Jalal; Ghandehari, Mehdi; Mighani, Ghasem; Chiniforush, Nasim

2014-01-01

Introduction: The aim of this study was to evaluate and compare the in vitro effect of the Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser with different radiation distances and high-speed rotary treatment on the shear bond strength of flowable composite to enamel of human permanent posterior teeth. Methods: freshly extracted human molar teeth with no caries or other surface defects were used in this study (n=45). The teeth were randomly divided into 3 groups. Group 1: treated with non-contact Er:YAG Laser and etched with Er:YAG laser, Group 2: treated with contact Er:YAG Laser and etched with Er:YAG laser, Group 3 (control): treated with diamond fissure bur and etched with acid phosphoric 37%. Then the adhesive was applied on the surafces of the teeth and polymerized using a curing light appliance. Resin cylinders were fabricated from flowable composite. Shear bond strength was tested at a crosshead speed of 0.5 mm/min. Results: The amount of Shear Bond Strength (SBS) in the 3 treatment groups was not the same (P<0.05).The group in which enamel surfaces were treated with diamond fissure bur and etched with acid (conrtol group) had the highest mean shear bond strength (19.92±4.76) and the group in which the enamel surfaces were treated with contact Er:YAG laser and etched with Er:YAG laser had the lowest mean shear bond strength (10.89±2.89). Mann-whitney test with adjusted P-value detected significant difference in shear bond strength between the control group and the other 2 groups (P < 0.05). Conclusion: It was concluded that both contact and non-contact Er:YAG laser treatment reduced shear bond strength of flowable resin composite to enamel in comparison with conventional treatment with high speed rotary. Different Er:YAG laser distance irradiations did not influence the shear bond strength of flowable composite to enamel. PMID:25653813

Development of chitosan-pullulan composite nanoparticles for nasal delivery of vaccines: in vivo studies.

PubMed

Cevher, Erdal; Salomon, Stefan K; Somavarapu, Satyanarayana; Brocchini, Steve; Alpar, H Oya

2015-01-01

Here, we aimed at developing chitosan/pullulan composite nanoparticles and testing their potential as novel systems for the nasal delivery of diphtheria toxoid (DT). All the chitosan derivatives [N-trimethyl (TMC), chloride and glutamate] and carboxymethyl pullulan (CMP) were synthesised and antigen-loaded composites were prepared by polyion complexation of chitosan and pullulan derivatives (particle size: 239-405 nm; surface charge: +18 and +27 mV). Their immunological effects after intranasal administration to mice were compared to intramuscular route. Composite nanoparticles induced higher levels of IgG responses than particles formed with chitosan derivative and antigen. Nasally administered TMC-pullulan composites showed higher DT serum IgG titre when compared with the other composites. Co-encapsulation of CpG ODN within TMC-CMP-DT nanoparticles resulted in a balanced Th1/Th2 response. TMC/pullulan composite nanoparticles also induced highest cytokine levels compared to those of chitosan salts. These findings demonstrated that TMC-CMP-DT composite nanoparticles are promising delivery system for nasal vaccination.

Body composition in Pan paniscus compared with Homo sapiens has implications for changes during human evolution

PubMed Central

Zihlman, Adrienne L.; Bolter, Debra R.

2015-01-01

The human body has been shaped by natural selection during the past 4–5 million years. Fossils preserve bones and teeth but lack muscle, skin, fat, and organs. To understand the evolution of the human form, information about both soft and hard tissues of our ancestors is needed. Our closest living relatives of the genus Pan provide the best comparative model to those ancestors. Here, we present data on the body composition of 13 bonobos (Pan paniscus) measured during anatomical dissections and compare the data with Homo sapiens. These comparative data suggest that both females and males (i) increased body fat, (ii) decreased relative muscle mass, (iii) redistributed muscle mass to lower limbs, and (iv) decreased relative mass of skin during human evolution. Comparison of soft tissues between Pan and Homo provides new insights into the function and evolution of body composition. PMID:26034269

Synthesis of Carbon-Coated ZnO Composite and Varistor Properties Study

NASA Astrophysics Data System (ADS)

Sun, Wei-Jie; Liu, Jin-Ran; Yao, Da-Chuan; Chen, Yong; Wang, Mao-Hua

2017-03-01

In this article, monodisperse ZnO composite nanoparticles were successfully prepared by sol-gel mixed precursor method. Subsequently, carbon as the shell was homogeneously coated on the surface of the ZnO composite nanoparticles via a simple adsorption and calcination process. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy with energy dispersive x-ray spectroscopy, and Fourier transform infrared spectroscopy. The results show that the pink ZnO composite powders were fully coated by carbon. Based on the results, the effect of glucose content on the microstructure of the synthesized composites and the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h were also fully studied. As the amount of glucose increased, the thickness of carbon can be increased from 2.5 nm to 5 nm. In particular, the ZnO varistor fabricated with the appropriate thickness of the carbon coating (5 nm) leads to the superior electrical performance, with present high breakdown voltage ( V b = 420 V/mm) and excellent nonlinear coefficient ( α = 61.7), compared with the varistors obtained without carbon coating.

Investigation on mechanical properties of basalt composite fabrics (experiment study)

NASA Astrophysics Data System (ADS)

Talebi Mazraehshahi, H.; Zamani, H.

2010-06-01

To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with

Comparative study of metallic silicide-germanide orthorhombic MnP systems.

PubMed

Connétable, Damien; Thomas, Olivier

2013-09-04

We present a comparative study of the structural, energetic, electronic and elastic properties of MX type MnP systems (where X=Si or Ge, and M=Pt, Pd or Ni) using first-principles calculations. The optimized ground state properties of these systems are in excellent agreement with the experimental values. A detailed comparative study of the elastic properties of polycrystalline structures is also presented. We analyze the relationship between the composition and the properties of the systems. Finally, we present the properties of NiSi1-xGex alloys. We show that these properties depend linearly on the Ge content of the alloy. This work has important consequences for semiconductor devices in which silicides, germanides and alloys thereof are used as contact materials.

Comparative efficacy of Er,Cr:YSGG and Er:YAG lasers for etching of composite for orthodontic bracket bonding.

PubMed

Mirhashemi, Amir Hossein; Chiniforush, Nasim; Sharifi, Nastaran; Hosseini, Amir Mehdi

2018-05-01

Several techniques have been proposed to obtain a durable bond, and the efficacy of these techniques is assessed by measuring parameters such as bond strength. Laser has provided a bond strength as high as that of acid etching in vitro and has simpler use with shorter clinical time compared to acid etching. This study aimed to compare the efficacy of Er:YAG and Er,Cr:YSGG lasers for etching and bonding of composite to orthodontic brackets. No previous study has evaluated the effect of these particular types of laser. A total of 70 composite blocks were randomly divided into five groups (n = 14): group 1, etching with phosphoric acid for 20 s; group 2, Er:YAG laser irradiation with 2 W power for 10 s; group 3, Er:YAG laser with 3 W power for 10 s; group 4, Er,Cr:YSGG laser with 2 W power for 10 s; group 5, Er,Cr:YSGG laser with 3 W power for 10 s. Metal brackets were then bonded to composites, and after 5000 thermal cycles, they were subjected to shear bond strength test in a universal testing machine after 24 h of water storage. One sample of each group was evaluated under a scanning electron microscope (SEM) to assess changes in composite surface after etching. The adhesive remnant index (ARI) was calculated under a stereomicroscope. Data were statistically analyzed. The mean and standard deviation of shear bond strength were 18.65 ± 3.36, 19.68 ± 5.34, 21.31 ± 4.03, 17.38 ± 6.94, and 16.45 ± 4.26 MPa in groups 1-5, respectively. The ARI scores showed that the bond failure mode in all groups was mainly mixed. The groups were not significantly different in terms of shear bond strength. Er:YAG and Er,Cr:YSGG lasers with the mentioned parameters yield optimal shear bond strength and can be used as an alternative to acid etching for bracket bond to composite.

Study of high resistance inorganic coatings on graphite fibers. [for graphite-epoxy composite materials

NASA Technical Reports Server (NTRS)

Galasso, F. S.; Veltri, R. D.; Scola, D. A.

1979-01-01

Coatings made of boron, silicon carbide, silica, and silica-like materials were studied to determine their ability to increase resistance of graphite fibers. The most promising results were attained by chemical vapor depositing silicon carbide on graphite fiber followed by oxidation, and drawing graphite fiber through ethyl silicate followed by appropriate heat treatments. In the silicon carbide coating studies, no degradation of the graphite fibers was observed and resistance values as high as three orders of magnitude higher than that of the uncoated fiber was attained. The strength of a composite fabricated from the coated fiber had a strength which compared favorably with those of composites prepared from uncoated fiber. For the silica-like coated fiber prepared by drawing the graphite fiber through an ethyl silicate solution followed by heating, coated fiber resistances about an order of magnitude greater than that of the uncoated fiber were attained. Composites prepared using these fibers had flexural strengths comparable with those prepared using uncoated fibers, but the shear strengths were lower.

Parametric Study of Single Bolted Composite Bolted Joint Subjected to Static Tensile Loading

NASA Astrophysics Data System (ADS)

Awadhani, L. V.; Bewoor, Anand, Dr.

2017-08-01

The use of composites is increasing in the engineering applications in order to reduce the weight, building energy efficient systems, designing a suitable material according to the requirements of the application. But at the same time, building a structure is possible only by bonding or bolting or combination of them. There are limitations for the bonding methods and problems with the bolting such as stress concentration near the neighborhood of the bolt hole, tensile or shear failure, delamination etc. Hence the design of a composite bolted structure needs a special attention. This paper focuses on the performance of the composite bolted joint under static tensile loading and the effect of variation in the parameters such as the bolt pitch, plate width, thickness, bolt tightening torque, composite material, coefficient of friction between the bolt and plate etc. A simple spring mass model is used to study the single bolted composite bolted joint. The influencing parameters are identified through the developed model and compared with the results from the literature. The best geometric parameters for the applied load are identified for the composite bolted joints.

A comparative study of monosaccharide composition analysis as a carbohydrate test for biopharmaceuticals.

PubMed

Harazono, Akira; Kobayashi, Tetsu; Kawasaki, Nana; Itoh, Satsuki; Tada, Minoru; Hashii, Noritaka; Ishii, Akiko; Arato, Teruyo; Yanagihara, Shigehiro; Yagi, Yuki; Koga, Akiko; Tsuda, Yuriko; Kimura, Mikiko; Sakita, Masashi; Kitamura, Satoshi; Yamaguchi, Hideto; Mimura, Hisashi; Murata, Yoshimi; Hamazume, Yasuki; Sato, Takayuki; Natsuka, Shunji; Kakehi, Kazuaki; Kinoshita, Mitsuhiro; Watanabe, Sakie; Yamaguchi, Teruhide

2011-05-01

The various monosaccharide composition analysis methods were evaluated as monosaccharide test for glycoprotein-based pharmaceuticals. Neutral and amino sugars were released by hydrolysis with 4-7N trifluoroacetic acid. The monosaccharides were N-acetylated if necessary, and analyzed by high-performance liquid chromatography (HPLC) with fluorometric or UV detection after derivatization with 2-aminopyridine, ethyl 4-aminobenzoate, 2-aminobenzoic acid or 1-phenyl-3-methyl-5-pyrazolone, or high pH anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Sialic acids were released by mild acid hydrolysis or sialidase digestion, and analyzed by HPLC with fluorometric detection after derivatization with 1,2-diamino-4,5-methylenedioxybenzene, or HPAEC-PAD. These methods were verified for resolution, linearity, repeatability, and accuracy using a monosaccharide standard solution, a mixture of epoetin alfa and beta, and alteplase as models. It was confirmed that those methods were useful for ensuring the consistency of glycosylation. It is considered essential that the analytical conditions including desalting, selection of internal standards, release of monosaccharides, and gradient time course should be determined carefully to eliminate interference of sample matrix. Various HPLC-based monosaccharide analysis methods were evaluated as a carbohydrate test for glycoprotein pharmaceuticals by an inter-laboratory study. Copyright © 2011 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

Comparative study on inorganic composition and crystallographic properties of cortical and cancellous bone.

PubMed

Wang, Xiao-Yan; Zuo, Yi; Huang, Di; Hou, Xian-Deng; Li, Yu-Bao

2010-12-01

To comparatively investigate the inorganic composition and crystallographic properties of cortical and cancellous bone via thermal treatment under 700 °C. Thermogravimetric measurement, infrared spectrometer, X-ray diffraction, chemical analysis and X-ray photo-electron spectrometer were used to test the physical and chemical properties of cortical and cancellous bone at room temperature 250 °C, 450 °C, and 650 °C, respectively. The process of heat treatment induced an extension in the a-lattice parameter and changes of the c-lattice parameter, and an increase in the crystallinity reflecting lattice rearrangement after release of lattice carbonate and possible lattice water. The mineral content in cortical and cancellous bone was 73.2wt% and 71.5wt%, respectively. For cortical bone, the weight loss was 6.7% at the temperature from 60 °C to 250 °C, 17.4% from 250 °C to 450 °C, and 2.7% from 450 °C to 700 °C. While the weight loss for the cancellous bone was 5.8%, 19.9%, and 2.8 % at each temperature range, the Ca/P ratio of cortical bone was 1.69 which is higher than the 1.67 of stoichiometric HA due to the B-type CO₃²⁻ substitution in apatite lattice. The Ca/P ratio of cancellous bone was lower than 1.67, suggesting the presence of more calcium deficient apatite. The collagen fibers of cortical bone were arrayed more orderly than those of cancellous bone, while their mineralized fibers ollkded similar. The minerals in both cortical and cancellous bone are composed of poorly crystallized nano-size apatite crystals with lattice carbonate and possible lattice water. The process of heat treatment induces a change of the lattice parameter, resulting in lattice rearrangement after the release of lattice carbonate and lattice water and causing an increase in crystal size and crystallinity. This finding is helpful for future biomaterial design, preparation and application. Copyright © 2010 The Editorial Board of Biomedical and Environmental Sciences

Comparative physico-mechanical characterization of new hybrid restorative materials with conventional glass-ionomer and resin composite restorative materials.

PubMed

Gladys, S; Van Meerbeek, B; Braem, M; Lambrechts, P; Vanherle, G

1997-04-01

The recently developed hybrid restorative materials contain the essential components of conventional glass ionomers and light-cured resins. The objective of this study was to determine several physical and mechanical properties of eight such materials in comparison with two conventional glass ionomers, one micro-filled, and one ultrafine compact-filled resin composite. The two resin composites and two of the three polyacid-modified resin composites could be polished to a higher gloss than the conventional as well as the resin-modified glass ionomers. After abrasion, surface roughness increased for all materials, but not at the same extent, being the least for the conventional resin composites and one polyacid-modified resin composite, Dyract. In contrast to the later resin composites, of which the surface roughness is principally determined by the presence of protruding filler particles above the resin matrix, roughness of conventional and resin-modified glass ionomers results from both protruding filler particles and intruding porosities. The mean particle size of the hybrid restorative materials fell between the smaller mean particle size of the resin composites and the larger one of the conventional glass ionomers. The micro-hardness and Young's modulus values varied substantially among all eight hybrid restorative materials. For all the resin-modified glass-ionomer restorative materials, the Young's modulus reached a maximum value one month after mixing and remained relatively stable thereafter. The Young's modulus of the conventional and the polyacid-modified resin composites decreased slightly after one month. The conventional glass-ionomer materials undoubtedly set the slowest, since their Young's modulus took six months to reach its maximum. The flexural fatigue limit of the hybrid restorative materials is comparable with that of the micro-filled composite. From this investigation, it can be concluded that the physico-mechanical properties vary widely among

Hybrid-Wing-Body Vehicle Composite Fuselage Analysis and Case Study

NASA Technical Reports Server (NTRS)

Mukhopadhyay, Vivek

2014-01-01

Recent progress in the structural analysis of a Hybrid Wing-Body (HWB) fuselage concept is presented with the objective of structural weight reduction under a set of critical design loads. This pressurized efficient HWB fuselage design is presently being investigated by the NASA Environmentally Responsible Aviation (ERA) project in collaboration with the Boeing Company, Huntington Beach. The Pultruded Rod-Stiffened Efficient Unitized Structure (PRSEUS) composite concept, developed at the Boeing Company, is approximately modeled for an analytical study and finite element analysis. Stiffened plate linear theories are employed for a parametric case study. Maximum deflection and stress levels are obtained with appropriate assumptions for a set of feasible stiffened panel configurations. An analytical parametric case study is presented to examine the effects of discrete stiffener spacing and skin thickness on structural weight, deflection and stress. A finite-element model (FEM) of an integrated fuselage section with bulkhead is developed for an independent assessment. Stress analysis and scenario based case studies are conducted for design improvement. The FEM model specific weight of the improved fuselage concept is computed and compared to previous studies, in order to assess the relative weight/strength advantages of this advanced composite airframe technology

A Comprehensive Study on Dielectric Properties of Volcanic Rock/PANI Composites

NASA Astrophysics Data System (ADS)

Kiliç, M.; Karabul, Y.; Okutan, M.; İçelli, O.

2016-05-01

Basalt is a very well-known volcanic rock that is dark colored and relatively rich in iron and magnesium, almost located each country in the world. These rocks have been used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and fibers of basalt rocks are widely used of radiation shielding, thermal stability, heat and sound insulation. This study examined three different basalt samples (coded CM-1, KYZ-13 and KYZ-24) collected from different regions of Van province in Turkey. Polyaniline (PANI) is one of the representative conductive polymers due to its fine environmental stability, huge electrical conductivity, as well as a comparatively low cost. Also, the electrical and thermal properties of polymer composites containing PANI have been widely studied. The dielectric properties of Basalt/Polyaniline composites in different concentrations (10, 25, 50 wt.% PANI) have been investigated by dielectric spectroscopy method at the room temperature. The dielectric parameters (dielectric constants, loss and strength) were measured in the frequency range of 102 Hz-106 Hz at room temperature. The electrical mechanism change with PANI dopant. A detailed dielectrically analysis of these composites will be presented.

Adjusting for geographic variation in observational comparative effectiveness studies: a case study of antipsychotics using state Medicaid data.

PubMed

Root, Elisabeth Dowling; Thomas, Deborah S K; Campagna, Elizabeth J; Morrato, Elaine H

2014-08-27

Area-level variation in treatment and outcomes may be a potential source of confounding bias in observational comparative effectiveness studies. This paper demonstrates how to use exploratory spatial data analysis (ESDA) and spatial statistical methods to investigate and control for these potential biases. The case presented compares the effectiveness of two antipsychotic treatment strategies: oral second-generation antipsychotics (SGAs) vs. long-acting paliperiodone palmitate (PP). A new-start cohort study was conducted analyzing patient-level administrative claims data (8/1/2008-4/30/2011) from Missouri Medicaid. ESDA techniques were used to examine spatial patterns of antipsychotic prescriptions and outcomes (hospitalization and emergency department (ED) visits). Likelihood of mental health-related outcomes were compared between patients starting PP (N = 295) and oral SGAs (N = 8,626) using multilevel logistic regression models adjusting for patient composition (demographic and clinical factors) and geographic region. ESDA indicated significant spatial variation in antipsychotic prescription patterns and moderate variation in hospitalization and ED visits thereby indicating possible confounding by geography. In the multilevel models for this antipsychotic case example, patient composition represented a stronger source of confounding than geographic context. Because geographic variation in health care delivery is ubiquitous, it could be a comparative effectiveness research (CER) best practice to test for possible geographic confounding in observational data. Though the magnitude of the area-level geography effects were small in this case, they were still statistically significant and should therefore be examined as part of this observational CER study. More research is needed to better estimate the range of confounding due to geography across different types of observational comparative effectiveness studies and healthcare utilization outcomes.

Molecular Simulation Study of Gas Solubility and Diffusion in a Polymer-Boron Nitride Nanotube Composite.

PubMed

Wang, Congyue; Jagirdar, Preeti; Naserifar, Saber; Sahimi, Muhammad

2016-02-25

We study the possibility of using polymer composites made of a polymer and boron nitride nanotubes (BNNTs) as a new type of membranes for gas separation. The polymer used is amorphous poly(ether imide) (PEI), and zigzag BNNTs are used to generate the composites with the PEI. The solubilities and self-diffusivities of CO2 and CH4 in the PEI and its composites with the BNNTs are calculated by molecular dynamics (MD) simulations. The molecular models of the PEI and its composites with the BNNTs are generated using energy minimization and MD simulation, and the Universal Force Field is used to represent the interactions between all the atoms. The morhology of the composites are characterized and are compared with that of PEI. The accuracy of the computations is tested by calculating the gases' solubilities and self-diffsivities in the pure PEI and comparing them with the experimental data. Good agreement is obtained with the data. The computed diffusivities and solubilities in the polymer-BNNTs composites are much larger than those in the pure polymer, which are attributed to the changes that the BNNTs induce in the polymer composite's free-volume distribution. As the mechanical properties of the polymer-BNNTs composites are superior over those of the pure PEI, their use as a membrane for gas separation offers distinct advantages over the pure polymer. We also demonstrate that, calculating the diffusion coefficients with MD simulations in the NPT ensemble, as opposed to the common practice of utilizing the NVT ensemble, leads to much more accurate results.

Comparative study about the tensile strength and yielding mechanism of pacing lead among major manufacturers.

PubMed

Chi-Wo, Chan; Lip-Kiong, Chan; Tongny, Lam; Kin-Keung, Tsang; Kin-Wing, Chan

2018-05-14

With extraction of cardiovascular implantable electronic devices (CIED) increasingly necessitated, various studies have contemplated to investigate clinical predictors for its success and complications. Intrinsic parameters of CIED leads have been studied less extensively and are the foci of this study. Three major pacemaker manufacturers accepted invitation. Leads then underwent tensile test in-vitro with their composite tensile strength (TS) compared. Mechanism of yielding, under tensile stress, was also observed among them. All pacing leads, participated in this study, surpassed requirement of European Standard EN 45502-2-1. Boston Scientific's FINELINE II STENOX 4456/52 cm and Medtronic's CAPSURE SENSE 4074/52 cm showed similar composite TS and both were stronger compared with St. Jude Medical's ISOFLEX OPTIM 1948/52 cm (P < 0.001). Despite a difference in the exact site, the Medtronic 4074 and St. Jude Medical 1948 yielded similarly in that their distal tip electrode remained connected with a flimsy inner coil to proximal portion of the lead after their composite TS was exceeded. Boston Scientific 4456's insulation tubing and coil wire broke almost simultaneously and separated completely from the tip electrode when it yielded. FINELINE II STENOX 4456/52 cm and CAPSURE SENSE 4074/52 cm showed stronger composite tensile strength than ISOFLEX OPTIM 1948/52 cm. FINELINE II STENOX 4456 was found more prone to complete severance. Limitations and precautions to translate these differences directly into real-life scenario are discussed. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Compositional analysis of biomass reference materials: Results from an interlaboratory study

DOE PAGES

Templeton, David W.; Wolfrum, Edward J.; Yen, James H.; ...

2015-10-29

Biomass compositional methods are used to compare different lignocellulosic feedstocks, to measure component balances around unit operations and to determine process yields and therefore the economic viability of biomass-to-biofuel processes. Four biomass reference materials (RMs NIST 8491–8494) were prepared and characterized, via an interlaboratory comparison exercise in the early 1990s to evaluate biomass summative compositional methods, analysts, and laboratories. Having common, uniform, and stable biomass reference materials gives the opportunity to assess compositional data compared to other analysts, to other labs, and to a known compositional value. The expiration date for the original characterization of these RMs was reached andmore » an effort to assess their stability and recharacterize the reference values for the remaining material using more current methods of analysis was initiated. We sent samples of the four biomass RMs to 11 academic, industrial, and government laboratories, familiar with sulfuric acid compositional methods, for recharacterization of the component reference values. In this work, we have used an expanded suite of analytical methods that are more appropriate for herbaceous feedstocks, to recharacterize the RMs’ compositions. We report the median values and the expanded uncertainty values for the four RMs on a dry-mass, whole-biomass basis. The original characterization data has been recalculated using median statistics to facilitate comparisons with this data. We found improved total component closures for three out of the four RMs compared to the original characterization, and the total component closures were near 100 %, which suggests that most components were accurately measured and little double counting occurred. Here, the major components were not statistically different in the recharacterization which suggests that the biomass materials are stable during storage and that additional components, not seen in the original

Pyronin Y (basic xanthene dye)-bentonite composite: A spectroscopic study

NASA Astrophysics Data System (ADS)

Tabak, A.; Kaya, M.; Yilmaz, N.; Meral, K.; Onganer, Y.; Caglar, B.; Sungur, O.

2014-02-01

The expansion by 1.43 Angstrom of basal spacing and the shift to higher frequencies of in-plane ring vibrations of the Pyronin Y molecule at 1603 and 1527 cm-1 on the formation of Pyronin Y-bentonite composite exhibited that the dye cations might be oriented as a monolayer form in the interlamellar spacing with aromatic rings parallel to clay layers. Thermal analysis results of this composite compared to those of raw bentonite signified the different outer sphere water entities associated with the replacement of inorganic cations with organic dye cations and the gradual decomposition of the organic molecule in the interlamellar spacing. Thermo-Infrared spectra of Pyronin Y-bentonite sample up to high temperatures showed the thermal stability of the dye-clay composite as a result of the presence of π interactions. The pore structure characteristics of Pyronin Y-bentonite composite exhibited the increase in the number of mesopores during formation of the composite.

A comparative evaluation of the staining capacity of microhybrid and nanohybrid resin-based composite to indian spices and food colorants: An In vitro study.

PubMed

Usha, Carounanidy; Rao, Sathyanarayanan Rama; George, Geena Mary

2018-01-01

Resin composite restorative materials can mimic the natural color and shade of the tooth. However, exogenous colorants from food and drinks can stain them due to adsorption. The influence of Indian food colorants and spices on resin composite restorations has not been evaluated extensively. This study aims to evaluate the staining capacity of microhybrid and nanohybrid resin-based composites, to saffron extract, tandoori powder, and turmeric powder. Forty samples of microhybrid (Kulzer Charisma) and nanohybrid (3M Filtek Z350) resin composites were prepared using an acrylic template of dimension 5 mm × 3 mm. They were randomly divided into four groups and immersed into solutions of saffron extract, tandoori powder, and turmeric powder. Distilled water was used as the control group. Color values (LFNx01, aFNx01, bFNx01) were measured by colorimeter using the CIE LFNx01aFNx01bFNx01 system before and after 72 h of immersion. Color differences ΔEFNx01ab were statistically analyzed. Two-way ANOVA and post-hoc Tukey (honest significant difference) test were done using IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY: IBM Corp. : All the immersion media changed the color of the resin composites to varying degrees. However, turmeric solution showed the maximum mean color variation ΔEFNx01ab of 14.8 ± 2.57 in microhybrid resin composites and 16.8 ± 3.50 in nanohybrid resin composites. Microhybrid and nanohybrid resin composites tend to stain to Indian food colorants, especially to turmeric powder.

Comparative Ultrastructure and Carbohydrate Composition of Gastroliths from Astacidae, Cambaridae and Parastacidae Freshwater Crayfish (Crustacea, Decapoda)

PubMed Central

Luquet, Gilles; Fernández, María S.; Badou, Aïcha; Guichard, Nathalie; Roy, Nathalie Le; Corneillat, Marion; Alcaraz, Gérard; Arias, José L.

2012-01-01

Crustaceans have to cyclically replace their rigid exoskeleton in order to grow.Most of them harden this skeleton by a calcification process. Some decapods (land crabs, lobsters and crayfish) elaborate calcium storage structures as a reservoir of calcium ions in their stomach wall, as so-called gastroliths. For a better understanding of the cyclic elaboration of these calcium deposits, we studied the ultrastructure of gastroliths from freshwater crayfish by using a combination of microscopic and physical techniques. Because sugars are also molecules putatively involved in the elaboration process of these biomineralizations, we also determined their carbohydrate composition. This study was performed in a comparative perspective on crayfish species belonging to the infra-order Astacidea (Decapoda, Malacostraca): three species from the Astacoidea superfamily and one species from the Parastacoidea superfamily. We observed that all the gastroliths exhibit a similar dense network of protein-chitin fibers, from macro- to nanoscale, within which calcium is precipitated as amorphous calcium carbonate. Nevertheless, they are not very similar at the molecular level, notably as regards their carbohydrate composition. Besides glucosamine, the basic carbohydrate component of chitin, we evidenced the presence of other sugars, some of which are species-specific like rhamnose and galacturonic acid whereas xylose and mannose could be linked to proteoglycan components. PMID:24970155

Women's Experience Studying Rhetoric and Composition, 1890-1910.

ERIC Educational Resources Information Center

Bacon, Nora

Those who wish to learn about the experience of women studying rhetoric and composition at American colleges 100 years ago can draw upon two sorts of histories. The story of women's entry into higher education is told by such historians as Mabel Newcomer and Barbara Solomon, but such historians seldom focus on composition studies specifically.…

Hydrogen kinetics studies of MgH2-FeTi composites

NASA Astrophysics Data System (ADS)

Meena, Priyanka; Jangir, Mukesh; Singh, Ramvir; Sharma, V. K.; Jain, I. P.

2018-05-01

MgH2 + x wt% FeTi (x=10, 25, 50) nano composites were ball milled to get nano structured material and characterized for structural, morphological and thermal properties. XRD of the milled samples revealed the formation of MgH2, FeTi, Fe2Ti and H0.06FeTi phases. Morphological studies by SEM were undertaken to investigate the effect of hydrogenation of nanostructure alloy. EDX confirmed elemental composition of the as-prepared alloy. TGA studies showed higher desorption temperature for milled MgH2 compared to x wt% FeTi added MgH2. Activation energy for hydrogen desorption was found to be -177.90, -215.69, -162.46 and -87.93 kJ/mol for milled MgH2 and Mg2+x wt% FeTi (10, 25, 50), showing 89.97 kJ/ mol reduction in activation energy for 50 wt% alloy additives resulting in improved hydrogen storage capacity. DSC investigations were carried out to investigate the effect of alloy on hydrogen absorption behavior of MgH2.

A parametric study of fracture toughness of fibrous composite materials

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1987-01-01

Impacts to fibrous composite laminates by objects with low velocities can break fibers giving crack-like damage. The damage may not extend completely through a thick laminate. The tension strength of these damage laminates is reduced much like that of cracked metals. The fracture toughness depends on fiber and matrix properties, fiber orientations, and stacking sequence. Accordingly, a parametric study was made to determine how fiber and matrix properties and fiber orientations affect fracture toughness and notch sensitivity. The values of fracture toughness were predicted from the elastic constants of the laminate and the failing strain of the fibers using a general fracture toughness parameter developed previously. For a variety of laminates, values of fracture toughness from tests of center-cracked specimens and values of residual strength from tests of thick laminates with surface cracks were compared to the predictions to give credibility to the study. In contrast to the usual behavior of metals, it is shown that both ultimate tensile strength and fracture toughness of composites can be increased without increasing notch sensitivity.

Nutritional composition of the commonly consumed composite dishes for the Barbados National Cancer Study.

PubMed

Sharma, Sangita; Harris, Rachel; Cao, Xia; Hennis, Anselm J M; Leske, M Cristina; Wu, Suh-Yuh

2007-09-01

To provide, for the first time, the calculated nutritional composition of 32 composite dishes commonly consumed in Barbados to enable dietary intake to be calculated from a Quantitative Food Frequency Questionnaire developed specifically for this population to determine associations between diet and risk of prostate and breast cancer. Weighed recipes were collected in up to six different households for each of the 32 composite dishes. The average nutritional composition for these composite dishes was calculated using the US Department of Agriculture National Nutrient Database. One hundred and fifty-two weighed recipes were collected for 32 composite dishes: five were fish based, two were ground beef dishes, two were chicken based, two were offal based, two were lamb dishes, one was pork based, three were rice based, three were commonly consumed home-made drinks, and the remaining were miscellaneous items. A total of 152 weighed recipes were collected and we provide, for the first time, nutritional composition data for 32 commonly consumed food and drink items in Barbados. Such data are essential for assessing nutrient intake and determining associations between diet and prostate and breast cancer in the Barbados National Cancer Study.

Comparative Study of Composition, Antioxidant, and Antimicrobial Activities of Essential Oils of Selected Aromatic Plants from Balkan Peninsula.

PubMed

Stanković, Nemanja; Mihajilov-Krstev, Tatjana; Zlatković, Bojan; Matejić, Jelena; Stankov Jovanović, Vesna; Kocić, Branislava; Čomić, Ljiljana

2016-05-01

The objective of the present study to perform a comparative analysis of the chemical composition, antioxidant, and antimicrobial activities of the essential oils of plant species Hyssopus officinalis, Achillea grandifolia, Achillea crithmifolia, Tanacetum parthenium, Laserpitium latifolium, and Artemisia absinthium from Balkan Peninsula. The chemical analysis of essential oils was performed by using gas chromatography and gas chromatography-mass spectrometry. Monoterpenes were dominant among the recorded components, with camphor in T. parthenium, A. grandifolia, and A. crithmifolia (51.4, 45.4, and 25.4 %, respectively), 1,8-cineole in H. officinalis, A. grandifolia, and A. crithmifolia (49.1, 16.4, and 14.8 %, respectively), and sabinene in L. latifolium and A. absinthium (47.8 and 21.5 %). The antiradical and antioxidant activities were determined by using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and 2,2-diphenyl-1-picrylhydrazyl radical scavenging methods. The essential oil of A. grandifolia has shown the highest antioxidant activity [IC50 of 33.575 ± 0.069 mg/mL for 2,2-diphenyl-1-picrylhydrazyl and 2.510 ± 0.036 mg vitamin C/g for the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assay]. The antimicrobial activity against 16 multiresistant pathogenic bacteria isolated from human source material was tested by the broth microdilution assay. The resulting minimum inhibitory concentration/minimum bactericidal concentration values ranged from 4.72 to 93.2 mg/mL. Therefore, the essential oils of the plant species included in this study may be considered to be prospective natural sources of antimicrobial substances, and may contribute as effective agents in the battle against bacterial multiresistance. Georg Thieme Verlag KG Stuttgart · New York.

A study of the electrical properties of carbon nanofiber polymer composites

NASA Astrophysics Data System (ADS)

Cardoso, Paulo Jorge Magalhaes

electromechanical studies were performed in epoxy resin composites with vapor-grown carbon nanofibers (VGCNF). First, the electrical properties of VGCNF/epoxy resin composites produced with a simple method were studied. Then, it was investigated the relation between the electrical properties and the dispersion level of VGCNF/epoxy composites produced with different methods, which were selected to provide different levels of dispersion.The level of nanofiber dispersion of the composites produced with the different methods and filler contents was analyzed by transmission optical microscopy (TOM) and greyscale analysis (GSA) and then compared to the electrical conductivity measurements. After this study, the influence of different methods of VGCNF dispersion on the electrical conduction mechanism of the composites was investigated. Then, these composites were submitted to electromechanical tests in order to apply them as piezoresistive sensors. The last study of this work was dedicated to an initial comparison between the epoxy composites with VGCNG and multi-walled carbon nanotubes (MWCNT), in terms of electrical and morphological properties. As the main outcomes of the present work, it can be concluded that a better cluster dispersion seems to be more suitable than good filler dispersion for achieving larger electrical conductivities and lower percolation thresholds. It is also concluded that hopping conductivity is a relevant mechanism for determining the overall conductivity of the composites and that the CNF/epoxy composites are appropriate materials for piezoresistive sensors in particular at concentrations close to the percolation threshold.

A Study of Damage Tolerance in Curved Composite Panels.

DTIC Science & Technology

1988-03-01

A198 617 A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS 1/2 I CNO O NGNERN BLNuE Hl(U) Ala FORCE INST OF TECH &IRIGHT-PATTERSON APR ON...OAL B PEAU OF STANOARDS- -T - % r . P.4 .% FILE CC R CDV OF DTIC MAR3 11988 *grr A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS THESIS...AFIT/GA/AA/88-.3 0 A STUDY OF DAMAGE TOLERANCE IN CURVED COMPOSITE PANELS THESIS - Brendan L. Wilder Captain, USAF S*2822 $$$*fltf$$*2*f$1fltf

Body Composition, Sarcopenia, and Suicidal Ideation in Elderly Koreans: Hallym Aging Study.

PubMed

Kim, Jeong-Hyeon; Kim, Dong-Hyun; Park, Yong Soon

2016-04-01

This study was conducted to assess the relationship between body composition and suicidal ideation among the Korean elderly population (n = 302; ≥ 65 years) who participated in the Hallym Aging Study in 2010. Body composition was measured using dual-energy X-ray absorptiometry, and obesity was measured by the indices of body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and body fat percentage. Sarcopenia was defined as presence of both low muscle mass and low muscle function. Suicidal ideation was assessed using the Beck Scale for Suicide Ideation. We found no differences in body composition measures between subjects with suicidal ideation and those without. In the logistic regression analyses, there were no significant relationships for suicidal ideation according to body composition measures, including BMI, WC, WHR, WHtR, and body fat percentage in both sexes. After adjusting for age, smoking status, alcohol drinking, regular exercise, medical comorbidities, monthly income, education level, and presence of depressive symptoms, the odds ratio (OR) of suicidal ideation was higher in elderly men with sarcopenia compared to those without, whereas no significant relationships were observed in elderly women (OR 8.28, 95% confidence interval [CI] 1.20-61.34 in men; OR 0.79, 95% CI 0.07-8.43 in women). Sarcopenia is closely associated with an increased risk of suicidal ideation in elderly men.

Household composition and psychological health: Results of the Second Diabetes Attitudes, Wishes and Needs (DAWN2) study.

PubMed

Joensen, Lene E; Willaing, Ingrid; Holt, Richard I G; Wens, Johan; Skovlund, Søren; Peyrot, Mark

2017-02-01

1) To explore the effect of household composition on the psychological health of adults with diabetes by comparing those living with other adult(s) including a partner with those living with neither partner nor other adult(s); 2) to examine potential mediation of social support in the association between household composition and psychological health. The study is part of the DAWN2 study conducted in 17 countries. The population comprised 8596 people with diabetes (PWD). Multiple regression models (linear and binary) were applied. People living with 'other adult(s) but no partner' experienced significantly lower well-being, higher diabetes distress and worried more frequently about hypoglycaemic events than those with a partner or those not co-habiting with another adult. However, participants living with 'other adult(s) but no partner' were more empowered compared to the other household composition groups. The association between household composition and psychological health was not mediated by diabetes-specific social support. The study indicates the psychological vulnerability of respondents living without a partner but with other adult(s). Appropriate support interventions must be developed and tested in order to enhance psychological health in people with diabetes living with other adults such as adult children, but with no partner. Copyright © 2017 Elsevier Inc. All rights reserved.

Chemical composition studies of flint with different origins

NASA Astrophysics Data System (ADS)

Zarina, Liga; Seglins, Valdis; Kostjukovs, Juris; Burlakovs, Juris

2015-04-01

Flint is a widely used material in the Stone Age because of its physical characteristics, which makes the material suitable for obtaining tools with sharp working edges. Chert, flint, chalcedony, agate and jasper in composition and several other physical characteristics are very similar. Therefore in archaeology most often they are determined simplified and are not distinguished, but described as flint or chert, denoting only the material in a general sense. However, in-depth studies it is necessary accurately identify the rock type and, in addition, to determine the origin of the flint and the conditions of the formation for the various archaeological research needs. As a typical example can be noted the localization problems in determining whether flint is local, or have emerged in the region through the exchange or by transportation. Flint consists mainly from quartz and mostly it has cryptocrystalline or amorphous structure. In nature it occurs as nodules and interbedded inclusions in sedimentary deposits as a result of digenesis processes when calcium carbonate is replaced with silicia. Bedded chert primarily is accumulations originated from excess alkalinity in the sediments. Flint can also be formed in the crystallization processes of the chemically unstable amorphous silicia. In this context, it should be noted that flint is naturally heterogeneous and very varied material by the physical properties and therefore problematic in many contemporary studies. In the study different origin flint samples from England, Denmark and Latvia were compared after their chemical composition. Flint nodules from Northern Europe chalk cliffs formed as inclusions in interbedded deposits or results of the digenesis and samples of chalcedony saturated dolomite from Latvia formed in hydrothermal processes were analysed using XRD and XRF methods. The obtained data were statistically analysed, identifying major, minor and trace elements and subsequently assessing the chemical

Thermal Performance Study of Composite Phase Change Material with Polyacrylicand Conformal Coating.

PubMed

Kee, Shin Yiing; Munusamy, Yamuna; Ong, Kok Seng; Cornelis Metselaar, Hendrik Simon; Chee, Swee Yong; Lai, Koon Chun

2017-07-28

The composite PCM was prepared by blending polymethyl methacrylate (PMMA) and myristic acid (MA) in different weight percentages. The MA and PMMA were selected as PCM and supporting material, respectively. As liquid MA may leak out during the phase transition, this study proposes the use of two coatings, namely a polyacrylic coating and a conformal coating to overcome the leakage problem. Both coatings were studied in terms of the leakage test, chemical compatibility, thermal stability, morphology, and reliability. No leakage was found in the PCMs with coatings compared to those without under the same proportions of MA/PMMA, thus justifying the use of coatings in the present study. The chemically compatibility was confirmed by FTIR spectra: the functional groups of PCMs were in accordance with those of coatings. DSC showed that the coatings did not significantly change the melting and freezing temperatures, however, they improved the thermal stability of composite PCMs as seen in TGA analysis. Furthermore, the composite PCMs demonstrated good thermal reliability after 1000 times thermal cycling. The latent heat of melting reduced by only 0.16% and 1.02% for the PCMs coated with conformal coating and polyacrylic coating, respectively. Therefore, the proposed coatings can be considered in preparing fatty acid/PMMA blends attributed to the good stability, compatibility and leakage prevention.

V/STOL tilt rotor aircraft study. Volume 6: Preliminary design of a composite wing for tilt rotor research aircraft

NASA Technical Reports Server (NTRS)

Soule, V. A.; Badri-Nath, Y.

1973-01-01

The results of a study of the use of composite materials in the wing of a tilt rotor aircraft are presented. An all-metal tilt rotor aircraft was first defined to provide a basis for comparing composite with metal structure. A configuration study was then done in which the wing of the metal aircraft was replaced with composite wings of varying chord and thickness ratio. The results of this study defined the design and performance benefits obtainable with composite materials. Based on these results the aircraft was resized with a composite wing to extend the weight savings to other parts of the aircraft. A wing design was then selected for detailed structural analysis. A development plan including costs and schedules to develop this wing and incorporate it into a proposed flight research tilt rotor vehicle has been devised.

Decomposing the trade-environment nexus for Malaysia: what do the technique, scale, composition, and comparative advantage effect indicate?

PubMed

Ling, Chong Hui; Ahmed, Khalid; Binti Muhamad, Rusnah; Shahbaz, Muhammad

2015-12-01

This paper investigates the impact of trade openness on CO2 emissions using time series data over the period of 1970QI-2011QIV for Malaysia. We disintegrate the trade effect into scale, technique, composition, and comparative advantage effects to check the environmental consequence of trade at four different transition points. To achieve the purpose, we have employed augmented Dickey-Fuller (ADF) and Phillips-Perron (PP) unit root tests in order to examine the stationary properties of the variables. Later, the long-run association among the variables is examined by applying autoregressive distributed lag (ARDL) bounds testing approach to cointegration. Our results confirm the presence of cointegration. Further, we find that scale effect has positive and technique effect has negative impact on CO2 emissions after threshold income level and form inverted U-shaped relationship-hence validates the environmental Kuznets curve hypothesis. Energy consumption adds in CO2 emissions. Trade openness and composite effect improve environmental quality by lowering CO2 emissions. The comparative advantage effect increases CO2 emissions and impairs environmental quality. The results provide the innovative approach to see the impact of trade openness in four sub-dimensions of trade liberalization. Hence, this study attributes more comprehensive policy tool for trade economists to better design environmentally sustainable trade rules and agreements.

COMPARATIVE ASSESSMENT OF THE COMPOSITION AND CHARGE STATE OF NITROGENASE FeMo-COFACTOR

PubMed Central

Harris, Travis V.; Szilagyi, Robert K.

2011-01-01

A significant limitation in our understanding of the molecular mechanism of biological nitrogen fixation is the uncertain composition of the FeMo-cofactor (FeMo-co) of nitrogenase. In this study we present a systematic, density functional theory-based evaluation of spin coupling schemes, iron oxidation states, ligand protonation states, and interstitial ligand composition using a wide range of experimental criteria. The employed functionals and basis sets were validated with molecular orbital information from X-ray absorption spectroscopic data of relevant iron-sulfur clusters. Independently from the employed level of theory, the electronic structure with the greatest number of antiferromagnetic interactions corresponds to the lowest energy state for a given charge and oxidation state distribution of the iron ions. The relative spin state energies of resting and oxidized FeMo-co already allowed the exclusion of certain iron oxidation state distributions and interstitial ligand compositions. Geometry optimized FeMo-co structures of several models further eliminated additional states and compositions, while reduction potentials indicated a strong preference for the most likely charge state of FeMo-co. Mössbauer and ENDOR parameter calculations were found to be remarkably dependent on the employed training set, density functional and basis set. Overall, we found that a more oxidized [MoIV-2FeII-5FeIII-9S2−-C4−] composition with a hydroxyl-protonated homocitrate ligand satisfies all of the available experimental criteria, and is thus favored over the currently preferred composition of [MoIV-4FeII-3FeIII-9S2−-N3−] from the literature. PMID:21545160

Colour stainability of indirect CAD-CAM processed composites vs. conventionally laboratory processed composites after immersion in staining solutions.

PubMed

Arocha, Mariana A; Basilio, Juan; Llopis, Jaume; Di Bella, Enrico; Roig, Miguel; Ardu, Stefano; Mayoral, Juan R

2014-07-01

The aim of this study was to determine, by using a spectrophotometer device, the colour stainability of two indirect CAD/CAM processed composites in comparison with two conventionally laboratory-processed composites after being immersed 4 weeks in staining solutions such as coffee, black tea and red wine, using distilled water as control group. Two indirect CAD/CAM composites (Lava Ultimate and Paradigm MZ100) and two conventionally laboratory-processed composites (SR Adoro and Premise Indirect) of shade A2 were selected (160 disc samples). Colour stainability was measured after 4 weeks of immersion in three staining solutions (black tea, coffee, red wine) and distilled water. Specimen's colour was measured each week by means of a spectrophotometer (CIE L*a*b* system). Statistical analysis was carried out performing repeated ANOVA measurements and Tukey's HSD test to evaluate differences in ΔE00 measurements between groups; the interactions among composites, staining solutions and time duration were also evaluated. All materials showed significant discoloration (p<0.01) when compared to control group. The highest ΔE00 observed was with red wine, whereas black tea showed the lowest one. Indirect laboratory-processed resin composites showed the highest colour stability compared with CAD/CAM resin blocks. CAD/CAM processed composites immersed in staining solutions showed lower colour stability when compared to conventionally laboratory-processed resin composites. The demand for CAD/CAM restorations has been increasing; however, colour stainability for such material has been insufficiently studied. Moreover, this has not been performed comparing CAD/CAM processed composites versus laboratory-processed indirect composites by immersing in staining solutions for long immersion periods. Copyright © 2014 Elsevier Ltd. All rights reserved.

Design of pilot studies to inform the construction of composite outcome measures.

PubMed

Edland, Steven D; Ard, M Colin; Li, Weiwei; Jiang, Lingjing

2017-06-01

Composite scales have recently been proposed as outcome measures for clinical trials. For example, the Prodromal Alzheimer's Cognitive Composite (PACC) is the sum of z-score normed component measures assessing episodic memory, timed executive function, and global cognition. Alternative methods of calculating composite total scores using the weighted sum of the component measures that maximize signal-to-noise of the resulting composite score have been proposed. Optimal weights can be estimated from pilot data, but it is an open question how large a pilot trial is required to calculate reliably optimal weights. In this manuscript, we describe the calculation of optimal weights, and use large-scale computer simulations to investigate the question of how large a pilot study sample is required to inform the calculation of optimal weights. The simulations are informed by the pattern of decline observed in cognitively normal subjects enrolled in the Alzheimer's Disease Cooperative Study (ADCS) Prevention Instrument cohort study, restricting to n=75 subjects age 75 and over with an ApoE E4 risk allele and therefore likely to have an underlying Alzheimer neurodegenerative process. In the context of secondary prevention trials in Alzheimer's disease, and using the components of the PACC, we found that pilot studies as small as 100 are sufficient to meaningfully inform weighting parameters. Regardless of the pilot study sample size used to inform weights, the optimally weighted PACC consistently outperformed the standard PACC in terms of statistical power to detect treatment effects in a clinical trial. Pilot studies of size 300 produced weights that achieved near-optimal statistical power, and reduced required sample size relative to the standard PACC by more than half. These simulations suggest that modestly sized pilot studies, comparable to that of a phase 2 clinical trial, are sufficient to inform the construction of composite outcome measures. Although these findings

Pyridine-type alkaloid composition affects bacterial community composition of floral nectar

PubMed Central

Aizenberg-Gershtein, Yana; Izhaki, Ido; Santhanam, Rakesh; Kumar, Pavan; Baldwin, Ian T.; Halpern, Malka

2015-01-01

Pyridine-type alkaloids are most common in Nicotiana species. To study the effect of alkaloid composition on bacterial community composition in floral nectar, we compared the nicotine-rich wild type (WT) N. attenuata, the nicotine biosynthesis-silenced N. attenuata that was rich in anatabine and the anabasine-rich WT N. glauca plants. We found that the composition of these secondary metabolites in the floral nectar drastically affected the bacterial community richness, diversity and composition. Significant differences were found between the bacterial community compositions in the nectar of the three plants with a much greater species richness and diversity in the nectar from the transgenic plant. The highest community composition similarity index was detected between the two wild type plants. The different microbiome composition and diversity, caused by the different pyridine-type alkaloid composition, could modify the nutritional content of the nectar and consequently, may contribute to the change in the nectar consumption and visitation. These may indirectly have an effect on plant fitness. PMID:26122961

Pyridine-type alkaloid composition affects bacterial community composition of floral nectar.

PubMed

Aizenberg-Gershtein, Yana; Izhaki, Ido; Santhanam, Rakesh; Kumar, Pavan; Baldwin, Ian T; Halpern, Malka

2015-06-30

Pyridine-type alkaloids are most common in Nicotiana species. To study the effect of alkaloid composition on bacterial community composition in floral nectar, we compared the nicotine-rich wild type (WT) N. attenuata, the nicotine biosynthesis-silenced N. attenuata that was rich in anatabine and the anabasine-rich WT N. glauca plants. We found that the composition of these secondary metabolites in the floral nectar drastically affected the bacterial community richness, diversity and composition. Significant differences were found between the bacterial community compositions in the nectar of the three plants with a much greater species richness and diversity in the nectar from the transgenic plant. The highest community composition similarity index was detected between the two wild type plants. The different microbiome composition and diversity, caused by the different pyridine-type alkaloid composition, could modify the nutritional content of the nectar and consequently, may contribute to the change in the nectar consumption and visitation. These may indirectly have an effect on plant fitness.

Comparative sulfur analysis using thermal combustion or inductively coupled plasma methodology and mineral composition of common livestock feedstuffs.

PubMed

Kerr, B J; Ziemer, C J; Weber, T E; Trabue, S L; Bearson, B L; Shurson, G C; Whitney, M H

2008-09-01

The objective of this study was to compare the use of thermal combustion (CNS) and inductively coupled plasma (ICP) to measure the total S content in plant-, animal-, and mineral-based feedstuffs, and to provide concentrations of other macro- and micro-minerals contained in these feedstuffs. Forty-five feedstuffs (464 total samples) were obtained from suppliers as well as swine feed and pet food manufacturers throughout the United States. Mineral data from IPC analysis were summarized on a DM basis using sample mean and SD, whereas the comparison of total S content between CNS and ICP was examined by bivariate plot and correspondence correlation. Analyses of a wide range of feedstuffs by CNS and ICP for total S were comparable for all but a few feedstuffs. For potassium iodide and tribasic copper chloride, ICP estimated total S to be lower than when analyzed by CNS (bias = 2.51 +/- 0.15 SE, P < 0.01). In contrast, for defluorinated phosphate and limestone, ICP estimated total S to be greater than when analyzed by CNS (bias = -1.46 +/- 0.51 SE, P < 0.01). All other samples had similar estimates of total S, whether analyzed by CNS or ICP. As expected, S composition varied greatly among feedstuffs. For total S, plant-based feedstuffs generally had lower total S compared with animal-based feedstuffs, whereas minerals supplied in sulfate form had the greatest concentration of total S. In addition to total S, mineral composition data are provided for all feedstuffs as obtained by ICP analysis. Within specific feedstuffs, mineral composition was quite variable, potentially due to low concentrations in the feed-stuff causing high mathematical variation or due to the source of feedstock obtained. In general, analyzed values of P were similar to previous tabular values. These data provide feed formulators a database from which modifications in dietary minerals can be accomplished and from which mineral requirements can be met more precisely to reduce losses of minerals into

Wear of human enamel opposing monolithic zirconia, glass ceramic, and composite resin: an in vitro study.

PubMed

Sripetchdanond, Jeerapa; Leevailoj, Chalermpol

2014-11-01

Demand is increasing for ceramic and composite resin posterior restorations. However, ceramics are recognized for their high abrasiveness to opposing dental structure. The purpose of this study was to investigate the wear of enamel as opposed to dental ceramics and composite resin. Twenty-four test specimens (antagonists), 6 each of monolithic zirconia, glass ceramic, composite resin, and enamel, were prepared into cylindrical rods. Enamel specimens were prepared from 24 extracted human permanent molar teeth. Enamel specimens were abraded against each type of antagonist with a pin-on-disk wear tester under a constant load of 25 N at 20 rpm for 4800 cycles. The maximum depth of wear (Dmax), mean depth of wear (Da), and mean surface roughness (Ra) of the enamel specimens were measured with a profilometer. All data were statistically analyzed by 1-way ANOVA, followed by the Tukey test (α=.05). A paired t test was used to compare the Ra of enamel at baseline and after testing. The wear of both the enamel and antagonists was evaluated qualitatively with scanning electron microscopic images. No significant differences were found in enamel wear depth (Dmax, Da) between monolithic zirconia (2.17 ±0.80, 1.83 ±0.75 μm) and composite resin (1.70 ±0.92, 1.37 ±0.81 μm) or between glass ceramic (8.54 ±2.31, 7.32 ±2.06 μm) and enamel (10.72 ±6.31, 8.81 ±5.16 μm). Significant differences were found when the enamel wear depth caused by monolithic zirconia and composite resin was compared with that of glass ceramic and enamel (P<.001). The Ra of enamel specimens increased significantly after wear tests with monolithic zirconia, glass ceramic, and enamel (P<.05); however, no difference was found among these materials. Within the limitations of this in vitro study, monolithic zirconia and composite resin resulted in less wear depth to human enamel compared with glass ceramic and enamel. All test materials except composite resin similarly increased the enamel

Theoretical studies of radiation effects in composite materials for space use. [graphite-epoxy composites

NASA Technical Reports Server (NTRS)

Chang, C. K.; Kamaratos, E.

1982-01-01

Tetraglycidyl 4,4'-diamino diphenyl methane epoxy cured with diamino diphenyl sulfone was used as a model compound. Computer programs were developed to calculate (1) energy deposition coefficients of protons and electrons of various energies at different depths of the material; (2) ranges of protons and electrons of various energies in the material; and (3) cumulative doses received by the composite in different geometric shapes placed in orbits of various altitudes and inclination. A preliminary study on accelerated testing was conducted and it was found that an elliptical equitorial orbit of 300 km perigee by 2750 km apogee can accumulate, in 2 years or less, enough radiation dose comparable to geosynchronous environment for 30 years. The local plasma model calculated the mean excitation energies for covalent and ionic compounds. Longitudinal and lateral distributions of excited species by electron and proton impact as well as the probability of overlapping of two tracks due to two charged particles within various time intervals were studied.

Effect of electrospun nanofibers on flexural properties of fiberglass composites

NASA Astrophysics Data System (ADS)

White, Fatima T.

In the present study, sintered electrospun TEOS nanofibers were interleaved in S2 fiberglass woven fabric layers, and composite panels were fabricated using the heated vacuum assisted resin transfer molding (H-VARTM) process. Cured panels were water jet cut to obtain the flexural test coupons. Flexural coupons were then tested using ASTM D7264 standard. The mechanical properties such as flexural strength, ultimate flexural failure strains, flexural modulus, and fiber volume fraction were measured. The S-2 fiberglass composite with the sintered TEOS electrospun nanofibers displayed lower flexural stiffness and strength as compared to the composites that were fabricated using S-2 fiberglass composite without the TEOS electrospun nanofibers. The present study also indicated that the composites fabricated with sintered TEOS electrospun nanofibers have larger failure strains as compared to the ones that were fabricated without the presence of electrospun nanofibers. The study indicates that the nanoengineered composites have better energy absorbing mechanism under flexural loading as compared to conventional fiberglass composites without presence of nanofibers.

Permeability studies on 3D Ni foam/graphene composites

NASA Astrophysics Data System (ADS)

Yang, Zhuxian; Chen, Hongmei; Wang, Nannan; Xia, Yongde; Zhu, Yanqiu

2017-09-01

This study investigates the permeability of new 3D Ni foam/graphene composites (Ni foam covered with graphene) using compressed air, Ar and N2 as the probe gases. The results show that the introduction of graphene on the surface of Ni foam via in situ chemical vapour deposition is not detrimental to the permeability of the composites; on the contrary, in some cases it improves permeability. A modified Ergun-type correlation has been proposed, which represents very well the permeability of the Ni foam/graphene composites, especially at flow rates higher than 0.3 m s-1. Further studies show that graphene also helps to improve the thermal conductivity of the composite. These results suggest that the graphene involvement will make the Ni foam/graphene composite a good candidate for potential applications such as filters or heat exchangers suitable for working under harsh conditions such as at high temperatures, in corrosive environments, etc.

A comparative evaluation of in-plane shear test methods for laminated graphite-epoxy composites

NASA Technical Reports Server (NTRS)

Morton, John; Ho, Henjen

1992-01-01

The objectives were to evaluate popular shear test methods for various forms of graphite-epoxy composite materials and to determine the shear response of graphite-epoxy composites with various forms of fiber architecture. Numerical and full-field experimental stress analyses were performed on four shear test configurations for unidirectional and bidirectional graphite-epoxy laminates to assess the uniformity and purity of the shear stress (strain) fields produced in the specimen test section and to determine the material in-plane shear modulus and shear response. The test methods were the 10 deg off-axis, the +/- 45 deg tension, the Iosipescu V-notch, and a compact U-notch specimen. Specimens were prepared from AS4/3501-6 graphite-epoxy panels, instrumented with conventional strain gage rosettes and with a cross-line moire grating, and loaded in a convenient testing machine. The shear responses obtained for each test method and the two methods of specimen instrumentation were compared. In a second phase of the program the shear responses obtained from Iosipescu V-notch beam specimens were determined for woven fabric geometries of different weave and fiber architectures. Again the responses of specimens obtained from strain gage rosettes and moire interferometry were compared. Additional experiments were performed on a bidirectional cruciform specimen which was also instrumented with strain gages and a moire grating.

Dielectric studies on PEG-LTMS based polymer composites

NASA Astrophysics Data System (ADS)

Patil, Ravikumar V.; Praveen, D.; Damle, R.

2018-02-01

PEG LTMS based polymer composites were prepared and studied for dielectric constant variation with frequency and temperature as a potential candidate with better dielectric properties. Solution cast technique is used for the preparation of polymer composite with five different compositions. Samples show variation in dielectric constant with frequency and temperature. Dielectric constant is large at low frequencies and higher temperatures. Samples with larger space charges have shown larger dielectric constant. The highest dielectric constant observed was about 29244 for PEG25LTMS sample at 100Hz and 312 K.

Evaluation of Microleakage and Marginal Ridge Fracture Resistance of Primary Molars Restored with Three Restorative Materials: A Comparative in vitro Study

PubMed Central

Yeolekar, Tapan Satish; Mukunda, KS; Kiran, NK

2015-01-01

ABSTRACT Composite restorations are popular because of their superior esthetics and acceptable clinical performance. But shrinkage is still a drawback. Polymerization shrinkage results in volumetric contraction, leading to deformation of the cusps, microleakage, decrease of marginal adaptation, enamel micro-cracks and postoperative sensitivity. A new class of ring opening resin composite based on silorane chemistry has been introduced with claims of less than 1% shrinkage during polymerization. The present study was conducted to evaluate and compare the ability of low shrink silorane based material, a packable composite and a compomer to resist microleakage in class II restorations on primary molars and evaluate marginal ridge fracture resistance of these materials. Sixty human primary molars were selected. Class II cavities were prepared and the teeth were divided into three groups of twenty each. Groups were as follows group I: low shrink composite resin (Filtek P90). Group II: packable composite (Filtek P60) and Group III: compomer (Compoglass F). Half of the teeth were used for microleakage and the rest for marginal ridge fracture resistance. For microleakage testing, dye penetration method was used with 1% methylene blue dye. Followed by evaluation and grading under stereomicroscope at 10* magnification. Fracture resistance was tested with universal testing machine. It was concluded that low shrink silorane based composite resin showed the least amount of microleakage, whereas compomer showed the highest microleakage. Packable composite resisted fracture of marginal ridge better than other composite resins. Marginal ridge fracture resistance of packable composite was comparable to the intact side. How to cite this article: Yeolekar TS, Chowdhary NR, Mukunda KS, Kiran NK. Evaluation of Microleakage and Marginal Ridge Fracture Resistance of Primary Molars Restored with Three Restorative Materials: A Comparative in vitro Study. Int J Clin Pediatr Dent 2015

The study about the use of the natural fibres in composite materials

NASA Astrophysics Data System (ADS)

Hristian, L.; Ostafe, M. M.; Manea, L. R.; Leon, A. L.

2016-08-01

The current technological development, the crises of raw materials and energy, the increased aggression towards the environment have led to the development of the new materials and unconventional technologies. The composite materials have both many important advantages compared to the traditional materials and provide many functional advantages: low weight, mechanical resistance, low maintenance costs. The main advantage of the composites lies in their ability to combine the physical properties of components to achieve new structural functionalities, so the modulation of the properties and finally, to obtain a wide variety of materials which may be used in all areas of activities. Some biodegradable fibers, flax, hemp, may provide the specific mechanical properties compared to those of the glass fiber, due to their high strength and low density of their volume. To make the right choice, even if the natural fibers have very low power consumption compared with the synthetic fibers, such as glass or carbon, it should be considered a careful assessment of the environmental impact. The present study shows that the validity of the replacement of the synthetic fibers with natural fibers, depends on the reinforcement type and the complexity of the problems due to the processing of natural fibers.

Comparative study on fatty acid composition of olive (Olea europaea L.), with emphasis on phytosterol contents.

PubMed

Ozkan, Ali; Aboul-Enein, Hassan Y; Kulak, Muhittin; Bindak, Recep

2017-08-01

The present study was designed to determine the fatty acid composition and phytosterol contents of Turkish native olive cultivars, namely Kilis Yağlık and Nizip Yağlık cv. In this context, olive fruits from 34 locations were sampled and then screened for their components in comparison. Fifteen different fatty acids were found in both olive oils. In the order of abundance, the most important ones were oleic acid (18:1) > palmitic acid (16:0) > linoleic acid (18:2) > stearic acid (18:0). Significant differences were observed in the contents of oleic acid (18:1), palmitic acid (16:0), linoleic acid (18:2) but not for stearic acid content in comparison both oils (p < 0.01). There were significant differences in terms of unsaturated fatty acids, saturated fatty acids and polyunsaturated fatty acids (p < 0.01). The seven phytosterols - cholesterol, campesterol, stigmasterol, β-sitosterol, Δ-5-avenasterol, Δ-7-stigmastenol and Δ-7-avenasterol - were studied in both oil sources. The predominant sterols were β-sitosterol, Δ5-avenasterol and campesterol in the samples analysed. However, no significant differences were found in the levels of the phytosterols between the two olive cultivars. Copyright © 2017 John Wiley & Sons, Ltd.

Body composition in men with anorexia nervosa: Longitudinal study.

PubMed

El Ghoch, Marwan; Calugi, Simona; Milanese, Chiara; Bazzani, Paola Vittoria; Dalle Grave, Riccardo

2017-07-01

To compare body composition patterns before and after complete weight restoration in men with anorexia nervosa. Dual-energy X-ray absorptiometry (DXA) was used to measure body composition patterns in 10 men with anorexia nervosa before and after complete weight restoration, and in 10 healthy men matched to age and patients' post-treatment body mass index (BMI). Before weight restoration, men with anorexia nervosa displayed lower total body fat mass (FM) and lean mass (LBM) than those in the healthy comparison group, with a greater FM loss from the extremity than the trunk region. After short-term weight restoration, patients displayed complete normalization in total LBM and FM, but greater deposition of FM in the trunk region. Short-term weight restoration can normalize body composition patterns in men with anorexia nervosa, but results in a central adiposity phenotype. The clinical implication of this finding is unknown, but should be explored given the high levels of concern about central adiposity in anorexia nervosa. © 2017 Wiley Periodicals, Inc.

[Study on the antibacterial activity of four kinds of nano-hydroxyapatite composites against Enterococcus faecalis].

PubMed

Liu, Yi; Zhou, Rongjing; Wu, Hongkun

2015-06-01

This study aims to compare and determine a kind of nano-hydroxyapatite composite material with good antibacterial efficacy on Enterococcusfaecalis (E. faecalis) in vitro. We investigated the antimicrobial activity of four kinds of nano-hydroxyapatite composites, namely, silver/hydroxyapatite composite nanoparticles (Ag/nHA), yttrium/hydroxyapatite composite nanoparticles (Yi/nHA), cerium/hydroxyapatite composite nanoparticles (Ce/nHA), and hydroxyapatite nanoparticles (nHA), against E. faecalis in vitro using the agar diffusion and broth dilution method by measuring the growth inhibition zone and the minimum inhibitory concentration (MIC), respectively. The agar diffusion test results showed that Ag/nHA displayed an obvious growth inhibition zone, whereas Yi/nHA, Ce/nHA, and nHA showed no influence on E. faecalis. The MIC value of Ag/nHA was 1.0 g.L-1, and the three other materials had no effect on E.faecalis even at the high concentration of 32.0 g.L-1. Ag/nHA display a potential antimicrobial efficacy to planktonic E.faecalis. Whereas, the three other kinds of nano-hydroxyapatite composites (Yi/nHA, Ce/nHA, nHA) show no influence.

Study of morphology, chemical, and amino acid composition of red deer meat.

PubMed

Okuskhanova, Eleonora; Assenova, Bahytkul; Rebezov, Maksim; Amirkhanov, Kumarbek; Yessimbekov, Zhanibek; Smolnikova, Farida; Nurgazezova, Almagul; Nurymkhan, Gulnur; Stuart, Marilyne

2017-06-01

The aim of this study was to evaluate red deer (maral) meat quality based on chemical composition, pH, water-binding capacity (WBC), and amino acid content. Maral meat surface morphology measurements were obtained by scanning electron microscopy. Active acidity (pH) was determined by potentiometry. Samples were analyzed for WBC by exudation of moisture to a filter paper by the application of pressure. Chemical composition (moisture, protein, fat, and ash fractions) was obtained by drying at 150°C and by extraction, using ethylic ether, and ashing at 500-600°C. The amino acid composition was obtained by liquid chromatography. Maral meat, with a pH of 5.85 and an average moisture content of 76.82%, was found to be low in fat (2.26%). Its protein content was 18.71% while its ash content was 2.21%. The amino acid composition showed that lysine (9.85 g/100 g), threonine (5.38 g/100 g), and valine (5.84 g/100 g) predominated in maral meat, while phenylalanine (4.08 g/100 g), methionine (3.29 g/100 g), and tryptophan (0.94 g/100 g) were relatively low in maral meat compared to other meats. The average WBC was found to be 65.82% and WBC was found to inversely correlate with moisture content. Low-fat content, high mineral content, and balanced amino-acid composition qualify maral meat as a worthy dietary and functional food.

Differences in the Density of Fungiform Papillae and Composition of Saliva in Patients With Taste Disorders Compared to Healthy Controls.

PubMed

Walliczek-Dworschak, Ute; Schöps, Franz; Feron, Gilles; Brignot, Helene; Hähner, Antje; Hummel, Thomas

2017-10-01

This study investigated the relation of the fungiform taste papillae density and saliva composition with the taste perception of patients suffering from diagnosed taste disorders. For this purpose, 81 patients and 40 healthy subjects were included. Taste was measured by means of regional and whole mouth chemosensory tests, and electrogustometry. Olfaction was assessed using the Sniffin Sticks. Fungiform papillae were quantified using the "Denver Papillae Protocol for Objective Analysis of Fungiform Papillae". In addition, salivary parameters [flow rate, total proteins, catalase, total anti-oxidative capacity (TAC), carbonic anhydrase VI (caVI), and pH] were determined and the Beck Depression Inventory was administered. Patients showed less taste papillae compared to healthy subjects. The number of papillae correlated with total taste strip score and salivary flow rate. Regarding salivary parameters, the flow rate, protein concentration, and TAC of patients were higher compared to controls. In addition, salivary flow rate, protease, caVI, and catalase values correlated with the summed taste strip score. Regarding various taste disorders, salty-dysgeusia patients showed the lowest taste test scores compared to those with bitter or metal-dysgeusia. Olfactory function of patients was significantly worse compared to healthy controls. This difference was most pronounced for ageusia patients. Compared to controls, patients also exhibited higher depressive symptoms. The density of fungiform papillae seemed to be positively associated with taste perception. Furthermore, patients exhibited changes in saliva composition (higher salivary flow rate, increased protein concentration, proteolysis, and TAC) compared to controls indicating that assessment of saliva may be critical for the diagnostic procedure in taste disorders. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparative nutrient composition of selected wild edible mushrooms from two agro-ecological zones, Uganda.

PubMed

Nakalembe, Immaculate; Kabasa, John David; Olila, Deogratias

2015-01-01

In Uganda, wild mushrooms are mainly collected during the rainy season and valued as a traditionally nutritious food by the rural poor. However, their nutritional attributes have not been adequately studied and documented. Comparative nutrient composition of five wild edible mushroom species was determined, namely: P. tenucuilus, T. tyleranus, T. clypeatus, V. speciosa and T. microcarpus of sub-humid and humid agro-ecological zones. Standard analytical techniques following the AOAC were used for proximate and mineral contents determinations. Vitamins determination followed the established standard protocols of the laboratories where the analyses were conducted. Combined use of nutrient concentration and scores were used to compare the level of the contents in the mushroom species. Significant differences (p < 0.05) in nutrient values were demonstrated between and among the mushroom species obtained from the two agro-ecological zones. On dry weight basis, all proximate compositions were high in mushroom species obtained from the humid zone with exception of the total carbohydrates and energy values. Irrespective of the source of the mushrooms, significant amounts were demonstrated in protein, dry matter, ash and total carbohydrates ranging between 11.56-27.42%, 82.34-99.76%, 10.79-16.87%, and 37.12-61.05%, respectively. In comparison with recommended dietary daily intakes, the K, P, Se, Mn, Cu and Fe contents were relatively high with low Ca, Mg, Zn and Na. Thiamin, folic acid, vitamin C, and niacin levels were high but below the recommended FAO references. Considering mushrooms from different agro-ecological zones, significant differences (p < 0.05) were observed in all mushroom species in P except in T. clypeatus, T. tyleranus, T. microcarpus and T. clypeatus in potassium, T. clypeatus and T. microcarpus in Mg. Mushrooms from humid agro-ecological zones had relatively high overall mineral and vitamin supply potential. In conclusion, consumption of these

Study of Swift Heavy Ion Modified Conducting Polymer Composites for Application as Gas Sensor

PubMed Central

Srivastava, Alok; Singh, Virendra; Dhand, Chetna; Kaur, Manindar; Singh, Tejvir; Witte, Karin; Scherer, Ulrich W.

2006-01-01

A polyaniline-based conducting composite was prepared by oxidative polymerisation of aniline in a polyvinylchloride (PVC) matrix. The coherent free standing thin films of the composite were prepared by a solution casting method. The polyvinyl chloride-polyaniline composites exposed to 120 MeV ions of silicon with total ion fluence ranging from 1011 to 1013 ions/cm2, were observed to be more sensitive towards ammonia gas than the unirradiated composite. The response time of the irradiated composites was observed to be comparably shorter. We report for the first time the application of swift heavy ion modified insulating polymer conducting polymer (IPCP) composites for sensing of ammonia gas.

Evaluation of a reproduction technique for the study of the enamel composite/bracket base area.

PubMed

Wilner, F J; Oliver, R G

2000-09-01

The objective of the study was to evaluate a reproduction method that would enable the study of the enamel/ bracket/composite interface in vivo, and consisted of in vitro assessment of two different impression materials to compare reproduction of brackets bonded to extracted teeth followed by in vivo assessment of the superior material. In vitro standard edgewise brackets were bonded to two extracted teeth and impressions were taken using two different types of low viscosity silicone-based impression materials. A medium viscosity silicone impression material was used to support the original impression. Three impressions of both the gingival and occlusal aspect of the bracket base region were obtained using each of the impression materials. Replicas were then prepared for SEM viewing and these compared to SEMs of the real teeth for reproduction of detail. A 3-point Reproducibility Index was used to compare the SEM photographs of the comparable replicas. One impression material was clearly superior to the other and produced an acceptably accurate representation of the true clinical situation in three out of four samples. This material also performed well in the in vivo situation. The technique described is satisfactory for the production and analysis of SEM pictures of the enamel/composite/ bracket base interface in vivo.

Comparative in vitro encrustation studies of biomaterials in human urine.

PubMed

Gleeson, M J; Glueck, J A; Feldman, L; Griffith, D P; Noon, G P

1989-01-01

A new dynamic in vitro human urine model was developed to compare biomaterial encrustation. The model incorporates a capacity to study seven biomaterials, a daily urine inflow of 500 ml, a reservoir capacity of 700 ml, and a turnover rate of four days. Encrustation studies performed for 2 weeks in sterile and infected (Proteus Vulgaris) urine on segmented polyether polyurethane, polyester polyurethane, silicone (Mitsui), silicone (Dow Corning), biothane, biolor 1 and biolor 11 demonstrated that biolor 11 (silicone-carbon composite) caused the least encrustation. Encrustation analysis showed brushite in the sterile model and struvite and ammonium acid urate in the infected mode I. Biolor II should have beneficial applications in catheters, stents and prosthetics which come in contact with urine.

Comparative carotenoid compositions during maturation and their antioxidative capacities of three citrus varieties.

PubMed

Yoo, Kyung-Mi; Moon, BoKyung

2016-04-01

This study investigated total carotenoid content, comparative carotenoid composition, vitamin C content, and total antioxidant capacity of three citrus varieties which are Yuza (Citrus junos Sieb ex Tabaka), Kjool (Citrus unshiu Marcow), and Dangyooja (Citrus grandis Osbeck). Seven carotenoids were identified, with β-cryptoxanthin, astaxanthin, and zeaxanthin being predominant in citrus varieties. Ripening increased the total carotenoid in three citrus varieties. Individual carotenoid of canthaxanthin, astaxanthin, and α-carotene in citrus varieties decreased with maturation, whereas the others increased with ripening. Yuza exhibited the highest total antioxidant capacity in 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, with VCEAC values of 582.9 mg/100 g and 451.5 mg/100g, respectively. The relative VCEAC values were vitamin C (1.00)>lycopene (0.375), α-carotene (0.304), β-carotene (0.289), β-cryptoxanthin (0.242), and zeaxanthin (0.099). These results indicate that Yuza contains higher amounts of total carotenoids, individual carotenoids, and vitamin C than other Korean citrus varieties. Copyright © 2015 Elsevier Ltd. All rights reserved.

Atomic-level study on mechanical properties and strengthening mechanisms of Al/SiC nano-composites

NASA Astrophysics Data System (ADS)

Huo, Shiyan; Xie, Lijing; Xiang, Junfeng; Pang, Siqin; Hu, Fang; Umer, Usama

2018-02-01

Molecular dynamics (MD) models for the study on the mechanical properties of β-SiC particles-reinforced aluminum matrix nano-composites (Al/SiC nano-composites) are established. The nano-composites in the model are fabricated by a powder metallurgy (P/M) process, followed by a hot isostatic pressing and then annealing to room temperature. The fabricated nano-composites have dense and even distributions of reinforced particles. Then representative volume elements (RVEs) of the fabricated nano-composites are built by adding periodic boundary conditions (PBCs). In this way, RVEs with different volume fractions and particle sizes of SiC are produced and put into the simulation of tension tests. The elasticity and strength in single axial tension obtained from MD analysis are in good agreement with those calculated according to the rule of mixture. It is found that the dispersion of SiC particles into the Al matrix leads to a significant enhancement in the strength of nano-composites compared to pure Al, which is also dramatically affected by both the volume fraction and particle size. Additionally, the Al/SiC nano-composites with finer SiC particles get greater enhancement in the mechanical behavior than those with coarser ones. MD analysis clearly shows the contributions of load-transfer effect, thermal mismatch strengthening and Orowan strengthening to the strengthening of Al/SiC nano-composites.

Study Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1997-01-01

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires, light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

Comparing molecular composition of dissolved organic matter in soil and stream water: Influence of land use and chemical characteristics.

PubMed

Seifert, Anne-Gret; Roth, Vanessa-Nina; Dittmar, Thorsten; Gleixner, Gerd; Breuer, Lutz; Houska, Tobias; Marxsen, Jürgen

2016-11-15

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) was used to examine the molecular composition of dissolved organic matter (DOM) from soils under different land use regimes and how the DOM composition in the catchment is reflected in adjacent streams. The study was carried out in a small area of the Schwingbach catchment, an anthropogenic-influenced landscape in central Germany. We investigated 30 different soil water samples from 4 sites and different depths (managed meadow (0-5cm, 40-50cm), deciduous forest (0-5cm), mixed-coniferous forest (0-5cm) and agricultural land (0-5cm, 40-50cm)) and 8 stream samples. 6194 molecular formulae and their magnitude-weighted parameters ((O/C)w, (H/C)w, (N/C)w, (AI-mod)w, (DBE/C)w, (DBE/O)w, (DBE-O)w, (C#)w, (MW)w) were used to describe the molecular composition of the samples. The samples can be roughly divided in three groups. Group 1 contains samples from managed meadow 40-50cm and stream water, which are characterized by high saturation compared to samples from group 2 including agricultural samples and samples from the surface meadow (0-5cm), which held more nitrogen containing and aromatic compounds. Samples from both forested sites (group 3) are characterized by higher molecular weight and O/C ratio. Environmental parameters vary between sites and among these parameters pH and nitrate significantly affect chemical composition of DOM. Results indicate that most DOM in streams is of terrestrial origin. However, 120 molecular formulae were detected only in streams and not in any of the soil samples. These compounds share molecular formulae with peptides, unsaturated aliphatics and saturated FA-CHO/FA-CHOX. Compounds only found in soil samples are much more aromatic, have more double bonds and a much lower H/C ratio but higher oxygen content, which indicates the availability of fresh plant material and less microbial processed material compared to stream samples. Copyright �

Structure and Composition of Vegetation of Longleaf Pine Plantations Compared to Natural Stands Occurring Along an Environmental Gradient at the Savannah River Site

Treesearch

Gregory P. Smith; Victor B. Shelburne; Joan L. Walker

2002-01-01

Fifty-four plots in 33-43 year old longleaf pine plantations were compared to 30 remnant plots in longleaf stands on the Savannah River Site in South Carolina. Within these stands, the structure and composition of primarily the herb layer relative to a presumed soil moisture or soil texture gradient was studied using the North Carolina Vegetation Survey methodology....

A comparative evaluation of piezoelectric sensors for acoustic emission-based impact location estimation and damage classification in composite structures

NASA Astrophysics Data System (ADS)

Uprety, Bibhisha; Kim, Sungwon; Mathews, V. John; Adams, Daniel O.

2015-03-01

Acoustic Emission (AE) based Structural Health Monitoring (SHM) is of great interest for detecting impact damage in composite structures. Within the aerospace industry the need to detect and locate these events, even when no visible damage is present, is important both from the maintenance and design perspectives. In this investigation, four commercially available piezoelectric sensors were evaluated for usage in an AE-based SHM system. Of particular interest was comparing the acoustic response of the candidate piezoelectric sensors for impact location estimations as well as damage classification resulting from the impact in fiber-reinforced composite structures. Sensor assessment was performed based on response signal characterization and performance for active testing at 300 kHz and steel-ball drop testing using both aluminum and carbon/epoxy composite plates. Wave mode velocities calculated from the measured arrival times were found to be in good agreement with predictions obtained using both the Disperse code and finite element analysis. Differences in the relative strength of the received wave modes, the overall signal strengths and signal-to-noise ratios were observed through the use of both active testing as well as passive steel-ball drop testing. Further comparative is focusing on assessing AE sensor performance for use in impact location estimation algorithms as well as detecting and classifying damage produced in composite structures due to impact events.

Impact behaviour of auxetic Kevlar®/ epoxy composites

NASA Astrophysics Data System (ADS)

Yang, S.; Chalivendra, V. B.; Kim, Y. K.

2017-10-01

Experimental study was performed to investigate fracture and impact properties of novel Auxetic Kevlar® laminated composites. For comparison, standard Kevlar® woven composites with and without polyurethane surface treatment were also considered in this study. For these three composites, short nylon fibers of two different fiber lengths and three different fiber densities were flocked between laminates. Vacuum infusion process along with optimized compaction was employed to fabricate composites. The double cantilever beam configuration was used to investigate the fracture properties. The Auxetic Kevlar® composites showed a significant improvement of 225% in fracture toughness compared to regular woven Kevlar® composites. Furthermore, the initiation toughness was increased by 577% with the application of flocking in Auxetic Kevlar®. During impact testing, the Auxetic Kevlar® reinforced composites showed a significant reduction in damaged area compared to woven counterpart. On the other hand, the reduction in damaged area influenced the reduction in impact energy absorption.

Prey specificity, comparative lethality and compositional differences of coral snake venoms.

PubMed

Jorge da Silva, N; Aird, S D

2001-03-01

Toxicities of crude venoms from 49 coral snake (Micrurus sp.) populations, representing 15 nominal taxa, were examined in both laboratory mice and in native prey animals and compared with data gathered from two non-micrurine elapids and a crotalid, which served as outgroups. These venoms were further compared on the basis of 23 enzymatic activities. Both toxicities and enzymatic activities were analyzed with respect to natural prey preferences, as determined from stomach content analyses and literature reports. Venoms of nearly all Micrurus for which prey preferences are known, are more toxic to natural prey than to non-prey species. Except for amphisbaenians, prey are more susceptible to venoms of Micrurus that feed upon them, than to venoms of those that eat other organisms. All venoms were more toxic i.v.>i.p.>i.m. Route-specific differences in toxicity are generally greatest for preferred prey species. Cluster analyses of venom enzymatic activities resulted in five clusters, with the fish-eating M. surinamensis more distant from other Micrurus than even the crotalid, Bothrops moojeni. Ophiophagous and amphisbaenian-eating Micrurus formed two close subclusters, one allied to the outgroup species Naja naja and the other to the fossorial, ophiophagous Bungarus multicinctus. Prey preference is shown to be the most important determinant of venom composition in Micrurus.

Thermographic imaging for high-temperature composite materials: A defect detection study

NASA Technical Reports Server (NTRS)

Roth, Don J.; Bodis, James R.; Bishop, Chip

1995-01-01

The ability of a thermographic imaging technique for detecting flat-bottom hole defects of various diameters and depths was evaluated in four composite systems (two types of ceramic matrix composites, one metal matrix composite, and one polymer matrix composite) of interest as high-temperature structural materials. The holes ranged from 1 to 13 mm in diameter and 0.1 to 2.5 mm in depth in samples approximately 2-3 mm thick. The thermographic imaging system utilized a scanning mirror optical system and infrared (IR) focusing lens in conjunction with a mercury cadmium telluride infrared detector element to obtain high resolution infrared images. High intensity flash lamps located on the same side as the infrared camera were used to heat the samples. After heating, up to 30 images were sequentially acquired at 70-150 msec intervals. Limits of detectability based on depth and diameter of the flat-bottom holes were defined for each composite material. Ultrasonic and radiographic images of the samples were obtained and compared with the thermographic images.

Effect of gamma radiation on the mechanical properties of natural silk fiber and synthetic E-glass fiber reinforced polypropylene composites: A comparative study

NASA Astrophysics Data System (ADS)

Shubhra, Quazi T. H.; Alam, A. K. M. M.

2011-11-01

Silk is a strong natural proteinous fiber and E-glass is a very strong synthetic fiber. Compression molding method was used to fabricate B. mori silk fiber reinforced polypropylene (PP) matrix composites. The tensile strength (TS), tensile modulus (TM), bending strength (BS), bending modulus (BM) and impact strength (IS) of prepared composites were 55.1 MPa, 780 MPa, 56.3 MPa, 3450 MPa and 17 kJ/m 2, respectively. Synthetic E-glass fiber reinforced PP based composites were fabricated in the same way and TS, TM, BS, BM, IS of E-glass fiber reinforced polypropylene composites were found to be 128.7 MPa, 4350 MPa, 141.6 MPa, 6300 MPa and 19 kJ/m 2, respectively. Gamma radiation is high energy ionizing radiation and was applied to increase the mechanical properties of the composites. Application of gamma ray increases the mechanical properties of silk/PP composites to a greater extent than that of E-glass/PP composites.

Nitrile crosslinked polyphenyl-quinoxaline/graphite fiber composites

NASA Technical Reports Server (NTRS)

Alston, W. B.

1976-01-01

Studies were performed to reduce the 600 F thermoplasticity of polyphenylquinoxaline (PPQ) matrix resins by introducing crosslinking by the reaction of terminal nitrile groups. Seven solvents and solvent mixtures were studied as the crosslinking catalysts and used to fabricate crosslinked PPQ/HMS graphite fiber composites. The room temperature and 600 F composite mechanical properties after short time and prolonged 600 F air exposure and the 600 F composite weight loss were determined and compared to those properties of high molecular weight, linear PPQ/HMS graphite fiber composites.

Do Nanofilled/Nanohybrid Composites Allow for Better Clinical Performance of Direct Restorations Than Traditional Microhybrid Composites? A Systematic Review.

PubMed

Angerame, D; De Biasi, M

2018-03-23

This systematic review was carried out to assess the clinical effectiveness of nanofilled and nanohybrid composites used for direct restorations in comparison with microhybrid composites. The guidelines for the preferred reporting items for systematic reviews and meta-analyses were followed. A search of articles published from July 1996 to February 2017 was performed in PubMed, SciVerse Scopus, Latin American and Caribbean Health Sciences, the Scientific Electronic Library Online, and the Cochrane Library. The present review selected only randomized controlled trials comparing the clinical performance of a nanofilled or nanohybrid composite for direct restorations with that of a microhybrid composite. The research found 201 studies. Twenty-one articles fulfilled the criteria of the present review. However, the included studies were characterized by great methodological diversities. As a general trend, nanofilled and nanohybrid composites were found to be capable of clinical performance, marginal quality, and resistance to wear similar to that of traditional composites without showing improved surface characteristics. The risk of bias of included studies was judged unclear or high. The clinical performance of nanofilled/nanohybrid composites was found to be comparable to that of traditional composites in the posterior area. The data concerning anterior and cervical restorations were insufficient. With regard to the esthetic properties, there is a compelling need for studies on anterior teeth in which the operators are kept unaware of the restorative material. Nanofilled/nanohybrid composites seem to be a valid alternative to traditional microhybrid composites, and at the moment, there is low-level evidence attesting a lack of their superiority.

Adhesive restorations: comparative evaluation between the adhesion of the glass-ceramics to the composite cement and the adhesion of the ceromer to the composite cement.

PubMed

Ceruti, P; Erovigni, F; Casella, F; Lombardo, S

2005-10-01

The aim of this work is to compare the adhesion of the glass-ceramic (empress II) to the composite cement and the adhesion of the ceromer to the composite cement. From each of the above materials, 10 little blocks, of 8 x 6 x 2 mm size, have been prepared. All the surface treatments suggested by the manufacturing industry have been performed: sandblasting and acid-etching of the ceramic, ceromer surface roughening with diamond bur and silanization and bonding application on both materials. A homogeneous layer of cement has been placed between couples of blocks of the same material and photopolymerised. Every sample, consisting of 2 bonded blocks, has been submitted to a traction force on a universal test machine connected with a computerized measure system (SINTEC D/10). Samples have been anchored to the machine binding devices by a bicomponent epoxy glue. Data on the breaking charge have been recorded and an analysis of the broken surfaces has been performed in order to classify the breaking modalities. The results ontained showed that the composite-glass-ceramic adhesion force (mean value 64 Mpa) was remarkably higher than the composite-ceromer adhesion (mean value 37.21 Mpa). The analysis of the broken surfaces by SEM showed that a mixed fracture occurred in all samples (both partly adhesive and cohesive).

A Study of Failure Criteria of Fibrous Composite Materials

NASA Technical Reports Server (NTRS)

Paris, Federico; Jackson, Karen E. (Technical Monitor)

2001-01-01

The research described in this paper is focused on two areas: (1) evaluation of existing composite failure criteria in the nonlinear, explicit transient dynamic finite element code, MSC.Dytran, and (2) exploration of the possibilities for modification of material and failure models to account for large deformations, progressive failure, and interaction of damage accumulation with stress/strain response of laminated composites. Following a review of the MSC.Dytran user manual, a bibliographical review of existing failure criteria of composites was performed. The papers considered most interesting for the objective of this report are discussed in section 2. The failure criteria included in the code under consideration are discussed in section 3. A critical summary of the present procedures to perform analysis and design of composites is presented in section 4. A study of the most important historical failure criteria for fibrous composite materials and some of the more recent modifications proposed were studied. The result of this analysis highlighted inadequacies in the existing failure criteria and the need to perform some numerical analyses to elucidate the answer to questions on which some of the proposed criteria are based. A summary of these ideas, which is a proposal of studies to be developed, is presented in section 5. Finally, some ideas for future developments are summarized in section 6.

Study of morphology, chemical, and amino acid composition of red deer meat

PubMed Central

Okuskhanova, Eleonora; Assenova, Bahytkul; Rebezov, Maksim; Amirkhanov, Kumarbek; Yessimbekov, Zhanibek; Smolnikova, Farida; Nurgazezova, Almagul; Nurymkhan, Gulnur; Stuart, Marilyne

2017-01-01

Aim: The aim of this study was to evaluate red deer (maral) meat quality based on chemical composition, pH, water-binding capacity (WBC), and amino acid content. Materials and Methods: Maral meat surface morphology measurements were obtained by scanning electron microscopy. Active acidity (pH) was determined by potentiometry. Samples were analyzed for WBC by exudation of moisture to a filter paper by the application of pressure. Chemical composition (moisture, protein, fat, and ash fractions) was obtained by drying at 150°C and by extraction, using ethylic ether, and ashing at 500-600°C. The amino acid composition was obtained by liquid chromatography. Results: Maral meat, with a pH of 5.85 and an average moisture content of 76.82%, was found to be low in fat (2.26%). Its protein content was 18.71% while its ash content was 2.21%. The amino acid composition showed that lysine (9.85 g/100 g), threonine (5.38 g/100 g), and valine (5.84 g/100 g) predominated in maral meat, while phenylalanine (4.08 g/100 g), methionine (3.29 g/100 g), and tryptophan (0.94 g/100 g) were relatively low in maral meat compared to other meats. The average WBC was found to be 65.82% and WBC was found to inversely correlate with moisture content. Conclusion: Low-fat content, high mineral content, and balanced amino-acid composition qualify maral meat as a worthy dietary and functional food. PMID:28717313

In vitro study of biocompatibility of a graphene composite with gold nanoparticles and hydroxyapatite on human osteoblasts.

PubMed

Crisan, Liana; Crisan, Bogdan; Soritau, Olga; Baciut, Mihaela; Biris, Alexandru Radu; Baciut, Grigore; Lucaciu, Ondine

2015-10-01

The purpose of this study was to evaluate the biocompatibility of some composites consisting of different proportions of graphene in combination with gold nanoparticles (AuNPs) and nanostructured hydroxyapatite (HA) on osteoblast viability, proliferation and differentiation. Au/HA@graphene composites synthesized by the catalytic chemical vapor deposition induction heating method with acetylene as the carbon source and over an Au/HA catalyst, were characterized by transmission electron microscopy, thermogravimetric analysis and Raman spectroscopy and showed that the few-layer graphene was grown over the Au/HA catalyst. The cytocompatibility study was performed using the fluorescein diacetate assay for assessment of the viability and proliferation of osteoblasts cultivated in the presence of HA, Au/HA and Au/HA@graphene composites as colloidal suspensions or as substrates. The most favorable composites for cell adhesion and proliferation were HA, Au/HA and Au/HA composites with 1.6% and 3.15% concentration of graphenes. Immunocytochemical staining performed after 19 days of osteoblasts cultivation on substrates showed that the graphene composites induced low expression of alkaline phosphatase compared to the control group and HA and Au/HA substrates. The presence of graphene in the substrate composition also induced an increased level of intracellular osteopontin and cytoskeleton reorganization (actin-F) depending on graphene concentration, suggesting cell activation, increased cellular adhesion and acquisition of a mechanosensorial osteocyte phenotype. Copyright © 2015 John Wiley & Sons, Ltd.

Characterizing the variability in chemical composition of flowback and produced waters - results from lab and field studies

NASA Astrophysics Data System (ADS)

Vieth-Hillebrand, Andrea; Wilke, Franziska D. H.; Schmid, Franziska E.; Zhu, Yaling; Lipińska, Olga; Konieczyńska, Monika

2017-04-01

The huge volumes and unknown composition of flowback and produced waters cause major public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of gas from unconventional reservoirs. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the target shales themselves. Shales are a heterogeneous mixture of minerals, organic matter, and formation water and little is actually understood about the fluid-rock interactions occurring during hydraulic fracturing of the shales and their effects on the chemical composition of flowback and produced water. To overcome this knowledge gap, interactions of different shales with different artificial stimulation fluids were studied in lab experiments under ambient and elevated temperature and pressure conditions. These lab experiments showed clearly that fluid-rock interactions change the chemical composition of the initial stimulation fluid and that geochemistry of the fractured shale is relevant for understanding flowback water composition. In addition, flowback water samples were taken after hydraulic fracturing of one horizontal well in Pomeranian region, Poland and investigated for their chemical composition. With this presentation, results from lab and field studies will be presented and compared to decipher possible controls on chemical compositions of flowback and produced water.

Shaped fiber composites

DOEpatents

Kinnan, Mark K.; Roach, Dennis P.

2017-12-05

A composite article is disclosed that has non-circular fibers embedded in a polymer matrix. The composite article has improved damage tolerance, toughness, bending, and impact resistance compared to composites having traditional round fibers.

Comparative study of mechanical properties of direct core build-up materials

PubMed Central

Kumar, Girish; Shivrayan, Amit

2015-01-01

Background and Objectives: The strength greatly influences the selection of core material because core must withstand forces due to mastication and para-function for many years. This study was conducted to evaluate certain mechanical properties of commonly used materials for direct core build-up, including visible light cured composite, polyacid modified composite, resin modified glass ionomer, high copper amalgam, and silver cermet cement. Materials and Methods: All the materials were manipulated according to the manufacturer's recommendations and standard test specimens were prepared. A universal testing machine at different cross-head speed was used to determine all the four mechanical properties. Mean compressive strength, diametral tensile strength, flexural strength, and elastic modulus with standard deviations were calculated. Multiple comparisons of the materials were also done. Results: Considerable differences in compressive strength, diametral tensile strength, and flexural strength were observed. Visible light cured composite showed relatively high compressive strength, diametral tensile strength, and flexural strength compared with the other tested materials. Amalgam showed the highest value for elastic modulus. Silver cermet showed less value for all the properties except for elastic modulus. Conclusions: Strength is one of the most important criteria for selection of a core material. Stronger materials better resist deformation and fracture provide more equitable stress distribution, greater stability, and greater probability of clinical success. PMID:25684905

Study on the electrical behavior of MWCNTs in GF/Epoxy composites.

PubMed

Yan, Zhao; Lu, Yuan; Yuexin, Duan

2010-08-01

The multi-wall nanotubes (MWCNTs) were divisionalized equably by the fabric of glass in composites. Then the electrical properties such as permittivity, conductance and electromagnetic interference (EMI) shielding effectiveness (SE) of MWCNTs in GF/EP composite were studied. The effect of the content and dispersion of MWCNTs were researched in this work. Firstly the permittivity of MWCNTs/GF/EP composites were studied respectively by keeping layers of glass fabric and increasing content of MWCNTs or keeping content of MWCNTs and changing layers of glass fabric in electromagnetic wave band (5.85-18 GHz). Then the conductance of MWCNTs/GF/EP composites with different MWCNTs contents was tested. Furthermore, the EMI SE of composites with different MWCNTs contents in electromagnetic wave band (5.85-18 GHz) were studied. In addition, the morphologies of MWCNTs/GF/EP composites with the different MWCNTs weight percent were observed. The results show that the real part of permittivity of composites can be improved highest up to 75 and the imaginary part increase maximum up to 80. However there is no disciplinarian about effect of layers of glass fabric on dielectric property. The MWCNTs/GF/EP composite can be changed from the insulator to the semiconductor along with increasing the weight percent of MWCNTs. In electromagnetic wave band 5.85-18 GHz, the values of SE are increasing with increasing content of the MWCNTs.

Synthesis and Study of Optical Properties of Graphene/TiO2 Composites Using UV-VIS Spectroscopy

NASA Astrophysics Data System (ADS)

Rathod, P. B.; Waghuley, S. A.

2016-09-01

Graphene and TiO2 were synthesized using electrochemical exfoliation and co-precipitation methods, respectively. An ex situ approach was adopted for the graphene/TiO2 composites. The conformation of graphene in the TiO2 samples was examined through X-ray diffraction. Optical properties of the as-synthesised composites such as optical absorption, extinction coefficient, refractive index, real dielectric constant, imaginary dielectric constant, dissipation factor, and optical conductivity were measured using UV-Vis spectroscopy. The varying concentration of graphene in TiO2 affects the optical properties which appear different for 10 wt.% as compared to 5 wt.% graphene/ TiO2 composite. The composites exhibit an absorption peak at 300 nm with a decrease in band gap for 10 wt.% as compared to 5 wt.% graphene/TiO2 composite. The maximum optical conductivity for the graphene/TiO2 composite of 10 wt.% was found to be 1.86·10-2 Ω-1·m-1 at 300 nm.

Mechanical characterization of scalable cellulose nano-fiber based composites made using liquid composite molding process

Treesearch

Bamdad Barari; Thomas K. Ellingham; Issam I. Ghamhia; Krishna M. Pillai; Rani El-Hajjar; Lih-Sheng Turng; Ronald Sabo

2016-01-01

Plant derived cellulose nano-fibers (CNF) are a material with remarkable mechanical properties compared to other natural fibers. However, efforts to produce nano-composites on a large scale using CNF have yet to be investigated. In this study, scalable CNF nano-composites were made from isotropically porous CNF preforms using a freeze drying process. An improvised...

Restrictive vs. non-restrictive composition: a magnetoencephalography study

PubMed Central

Leffel, Timothy; Lauter, Miriam; Westerlund, Masha; Pylkkänen, Liina

2014-01-01

Recent research on the brain mechanisms underlying language processing has implicated the left anterior temporal lobe (LATL) as a central region for the composition of simple phrases. Because these studies typically present their critical stimuli without contextual information, the sensitivity of LATL responses to contextual factors is unknown. In this magnetoencephalography (MEG) study, we employed a simple question-answer paradigm to manipulate whether a prenominal adjective or determiner is interpreted restrictively, i.e., as limiting the set of entities under discussion. Our results show that the LATL is sensitive to restriction, with restrictive composition eliciting higher responses than non-restrictive composition. However, this effect was only observed when the restricting element was a determiner, adjectival stimuli showing the opposite pattern, which we hypothesise to be driven by the special pragmatic properties of non-restrictive adjectives. Overall, our results demonstrate a robust sensitivity of the LATL to high level contextual and potentially also pragmatic factors. PMID:25379512

Optical spectroscopy to study confined and semi-closed explosions of homogeneous and composite charges

NASA Astrophysics Data System (ADS)

Maiz, Lotfi; Trzciński, Waldemar A.; Paszula, Józef

2017-01-01

Confined and semi-closed explosions of new class of energetic composites as well as TNT and RDX charges were investigated using optical spectroscopy. These composites are considered as thermobarics when used in layered charges or enhanced blast explosives when pressed. Two methods to estimate fireball temperature histories of both homogeneous and metallized explosives from the spectroscopic data are also presented, compared and analyzed. Fireball temperature results of the charges detonated in a small explosion chamber under air and argon atmospheres, and detonated in a semi-closed bunker are presented and compared with theoretical ones calculated by a thermochemical code. Important conclusions about the fireball temperatures and the physical and chemical phenomena occurring after the detonation of homogeneous explosives and composite formulations are deduced.

Advanced composites wing study program, volume 2

NASA Technical Reports Server (NTRS)

Harvey, S. T.; Michaelson, G. L.

1978-01-01

The study on utilization of advanced composites in commercial aircraft wing structures was conducted as a part of the NASA Aircraft Energy Efficiency Program to establish, by the mid-1980s, the technology for the design of a subsonic commercial transport aircraft leading to a 40% fuel savings. The study objective was to develop a plan to define the effort needed to support a production commitment for the extensive use of composite materials in wings of new generation aircraft that will enter service in the 1985-1990 time period. Identification and analysis of what was needed to meet the above plan requirements resulted in a program plan consisting of three key development areas: (1) technology development; (2) production capability development; and (3) integration and validation by designing, building, and testing major development hardware.

Chemical diversity in the genus Alpinia (Zingiberaceae): comparative composition of four Alpinia species grown in Northern India.

PubMed

Padalia, Rajendra C; Verma, Ram S; Sundaresan, Velusamy; Chanotiya, Chandan S

2010-08-01

The essential-oil compositions of leaves, flowers, and rhizomes of Alpinia galanga (L.) Willd., Alpinia calcarata Rosc., Alpinia speciosa K. Schum., and Alpinia allughas Rosc. were examined and compared by capillary GC and GC/MS. Monoterpenoids were the major oil constituents identified. 1,8-Cineole, alpha-terpineol, (E)-methyl cinnamate, camphor, terpinen-4-ol, and alpha- and beta-pinenes were the major constituents commonly distributed in leaf and flower essential oils. The presence of endo-fenchyl acetate, exo-fenchyl acetate, and endo-fenchol was the unique feature of rhizome essential oils of A. galanga, A. calcarata, and A. speciosa. On contrary, the rhizome oil of A. allughas was dominated by beta-pinene. Significant qualitative and quantitative variations were observed in essential-oil compositions of different parts of Alpinia species growing in subtemperate and subtropical regions of Northern India. Cluster analysis was performed to find similarities and differences in essential-oil compositions based on representative molecular skeletons. Monoterpenoids, viz., 1,8-cineole, terpinen-4-ol, camphor, pinenes, (E)-methyl cinnamate, and fenchyl derivatives, were used as chemotaxonomic markers.

Study on voids of epoxy matrix composites sandwich structure parts

NASA Astrophysics Data System (ADS)

He, Simin; Wen, Youyi; Yu, Wenjun; Liu, Hong; Yue, Cheng; Bao, Jing

2017-03-01

Void is the most common tiny defect of composite materials. Porosity is closely related to composite structure property. The voids forming behaviour in the composites sandwich structural parts with the carbon fiber reinforced epoxy resin skins was researched by adjusting the manufacturing process parameters. The composites laminate with different porosities were prepared with the different process parameter. The ultrasonic non-destructive measurement method for the porosity was developed and verified through microscopic examination. The analysis results show that compaction pressure during the manufacturing process had influence on the porosity in the laminate area. Increasing the compaction pressure and compaction time will reduce the porosity of the laminates. The bond-line between honeycomb core and carbon fiber reinforced epoxy resin skins were also analyzed through microscopic examination. The mechanical properties of sandwich structure composites were studied. The optimization process parameters and porosity ultrasonic measurement method for composites sandwich structure have been applied to the production of the composite parts.

Table of Phenylalanine Content of Foods: Comparative Analysis of Data Compiled in Food Composition Tables.

PubMed

Araújo, Ana Claudia Marquim F; Araújo, Wilma M C; Marquez, Ursula M Lanfer; Akutsu, Rita; Nakano, Eduardo Y

2017-01-01

Knowing the phenylalanine (Phe) content of foods is essential for managing the diet of patients with phenylketonuria. Data on the Phe content of foods are scarce and sometimes vary between different Food Composition Tables (FCT). Brazil created its own table of the Phe contents of fruits and vegetables based exclusively on the chemical analysis of protein content, considering that proteins contain 3-4% Phe (TCFA/ANVISA). This study compared the protein and Phe contents of vegetables and fruits provided by the TCFA/ANVISA with those listed in international food composition tables. The Phe content of 71 fruits and vegetables listed in TCFA/ANVISA was classified into four subgroups, and the Wilcoxon nonparametric test compared the Phe and mean protein contents provided by the FCTs. All tests considered the bilateral hypothesis, and the level of significance was set at 5%. The Spearman's correlation coefficient measured the statistical dependence between Phe and protein contents. The mean Phe content was <50 mg Phe/100 g for 15 fruits; >50 mg/100 g for 11 type-A vegetables; <50 mg/100 g for 8 type-B vegetables; ≤50 mg/100 g for 7 type-C vegetables. The percentage of Phe in protein varied from 3.13 ± 1.03% to 3.74 ± 2.55% in fruits; 3.33 ± 1.41 to 4.82 ± 1.17 in type-A vegetables; 3.46 ± 1.25% to 4.83 ± 2.46 in type-B vegetables; and 3.14% ± 1.49 to 4.62% ± 2.26 in type-C vegetables. The Phe and protein contents provided by most FCTs were positively correlated, suggesting that it is possible to estimate the Phe content of fruits by multiplying its protein content by 3%. For type-A, -B, and -C vegetables, 4% may be used.

Cellulose Nanocrystals vs. Cellulose Nanofibrils: A Comparative study on Their Microstructures and Effects as Polymer Reinforcing Agents

Treesearch

Xuezhu Xu; Fei Liu; Long Jiang; J.Y. Zhu; Darrin Haagenson; Dennis P. Wiesenborn

2013-01-01

Both cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are nanoscale cellulose fibers that have shown reinforcing effects in polymer nanocomposites. CNCs and CNFs are different in shape, size and composition. This study systematically compared their morphologies, crystalline structure, dispersion properties in polyethylene oxide (PEO) matrix, interactions...

Composite-composite repair bond strength: effect of different adhesion primers.

PubMed

Tezvergil, A; Lassila, L V J; Vallittu, P K

2003-11-01

Recently, new products have been introduced to repair composite restorations that may be used as 'one-step' primers or monomers and silane compounds which are used separately as 'multi-step' primers. The aim of this study was to compare the shear bond strength of the new composite resin to aged composite, by using different adhesion primers. The substrates were particulate filler composite (Z250, 3M-ESPE), which was aged by boiling for 8 h and storing at 37 degrees C in water for 3 weeks. The aged substrate surfaces were wet-ground flat with 320-grit silicon carbide paper and subjected randomly (n=8) to either one-step adhesion primer: Compoconnect (CC) (Heraus Kulzer), or multi-step: Clearfil Repair (CF) (Kuraray) or an intermediate resin: Scothchbond Multi-purpose adhesive resin (3M-ESPE) according to the manufacturers' recommendations. Specimens with no surface treatment were used as control (C). New composite resin (Z250) was added to the substrate using 2 mm layer increments and light cured. The specimens were either water stored for 48 h or water stored for 24 h and then thermocycled for 6000 cycles. The shear bond strengths were measured with a crosshead speed of 1.0 mm/min using a universal testing machine. Data were analysed by two-way ANOVA and Tukey's post-hoc tests (p=0.05). All surface treatment methods showed significant difference compared to control (p<0.05). CF showed higher bond strength than CC and MP (p<0.05). Storage condition did not show a significant difference (p>0.05) in bond strength values. It was concluded that multi-step adhesion primer yielded higher bond strength compared to one-step primer or intermediate resin.

CO2 adsorption using TiO2 composite polymeric membranes: A kinetic study.

PubMed

Hafeez, Sarah; Fan, X; Hussain, Arshad; Martín, C F

2015-09-01

CO2 is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas separation by composite membranes. The separation of CO2 by a membrane is not just a process to physically sieve out of CO2 through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO2. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO2 in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO2 through membranes. Pure cellulose acetate (CA) and cellulose acetate-titania nanoparticle (CA-TiO2) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO2 membrane adsorbed more quantity of CO2 gas as compared to pure CA membrane. The high CO2 adsorption capacity may enhance the diffusion and solubility of CO2 in the CA-TiO2 composite membrane, which results in a better CO2 separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models. According to correlation factor R(2), the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion. Copyright © 2015. Published by Elsevier B.V.

Opinion: Composition Studies Saves the World!

ERIC Educational Resources Information Center

Bizzell, Patricia

2009-01-01

Stanley Fish in his new book ["Save the World on Your Own Time" (New York: Oxford UP,2008)] says that composition studies presents "the clearest example" of what is desperately wrong in the academy, because in writing classrooms, he says, "more often than not anthologies of provocative readings take center stage and the actual teaching of writing…

Study on preparation and mechanical performance of TPU/nonwoven composites

NASA Astrophysics Data System (ADS)

Sun, X. C.; Xi, B. J.

2016-07-01

In order to study the influence of resin content and layer sequence parameters on the mechanical properties of TPU/non-woven composite materials synthesized by moulding pressing technology. The effects of the resin content and layer sequence on composites were discussed. Through experiments and theoretical analysis, it was revealed how resin content, layer sequence impact on mechanical properties of composite. The mechanics properties of TPU/non-woven composite materials are improved. The process is pressure 0.5 MPa, temperature 110 °C and time 120s min. The melting of the TPU infiltrated into the fabric and filled the space between the fibers.

Optical properties study of nano-composite filled D shape photonic crystal fibre

NASA Astrophysics Data System (ADS)

Udaiyakumar, R.; Mohamed Junaid, K. A.; Janani, T.; Maheswar, R.; Yupapin, P.; Amiri, I. S.

2018-06-01

With the nano-composite materials gaining momentum in the optical field, a new nano-composite filled D shape Photonic Crystal Fiber (PCF) is designed and the various optical properties are investigated with help of Finite Element Method. In the proposed structure the D-shape PCF is made up of silica with embedded silver nanoparticles and air holes are distributed along the fibre. The designed fibre shows various optical properties such as dispersion, birefringence, beat length and loss with respect to wavelength and compared with different filling factor like 0.1, 0.3 and 0.5. From our estimation and comparative analysis, it has been proved that the fibre loss has been decreased with increasing filling factor. Further this also showed flat dispersion at maximum filling factor.

Removal of phenol from synthetic wastewater using carbon-mineral composite: Batch mechanisms and composition study

NASA Astrophysics Data System (ADS)

Kamaruddin, Mohamad Anuar; Alrozi, Rasyidah; Aziz, Hamidi Abdul; Han, Tan Yong; Yusoff, Mohd Suffian

2017-09-01

This study investigates the treatability of composite adsorbent made from waste materials and minerals which is widely available in Malaysia. The composite adsorbent was prepared based on wet attrition method which focuses on the determination of optimum dosage of each of raw materials amount by conventional design of experiment work. Zeolite, activated carbon, rice husk and limestone were ground to obtained particle size of 150 µm. 45.94% zeolite, 15.31% limestone, 4.38% activated carbon, 4.38% rice husk carbon and 30% of ordinary Portland cement (OPC). The mixture was mixed together under pre-determined mixing time. About 60% (by weight) of water was added and the mixture paste was allowed to harden for 24 hours and then submersed in water for three days for curing. Batch experimental study was performed on synthetic dissolving a known amount of solid crystal phenol with distilled water into the volumetric flasks. From the batch experimental study, it was revealed that the optimum shaking speed for removal of phenol was 200 rpm. The removal efficiency was 65%. The optimum shaking time for removing phenol was 60 minutes; the percentage achieved was 55%. The removal efficiency increased with the increased of the amount of composite adsorbent. The removal efficiency for optimum adsorbent dosage achieved 86%. Furthermore, the influence of pH solution was studied. The optimum pH for removing phenol was pH 6, with the removal percentage of 95%. The results implies that carbon-mineral based composite adsorbent is promising replacement for commercial adsorbent that provides alternative source for industrial adsorption application in various types of effluent treatment system.

The comparison study of bioactivity between composites containing synthetic non-substituted and carbonate-substituted hydroxyapatite.

PubMed

Borkowski, Leszek; Sroka-Bartnicka, Anna; Drączkowski, Piotr; Ptak, Agnieszka; Zięba, Emil; Ślósarczyk, Anna; Ginalska, Grażyna

2016-05-01

Apatite forming ability of hydroxyapatite (HAP) and carbonate hydroxyapatite (CHAP) containing composites was compared. Two composite materials, intended for filling bone defects, were made of polysaccharide polymer and one of two types of hydroxyapatite. The bioactivity of the composites was evaluated in vitro by soaking in a simulated body fluid (SBF), and the formation of the apatite layer was determined by scanning electron microscopy with energy-dispersive spectrometer and Raman spectroscopy. The results showed that both the composites induced the formation of apatite layer on their surface after soaking in SBF. In addition, the sample weight changes and the ion concentration of the SBF were scrutinized. The results showed the weight increase for both materials after SBF treatment, higher weight gain and higher uptake of calcium ions by HAP containing scaffolds. SBF solution analysis indicated loss of calcium and phosphorus ions during experiment. All these results indicate apatite forming ability of both biomaterials and suggest comparable bioactive properties of composite containing pure hydroxyapatite and carbonate-substituted one. Copyright © 2016 Elsevier B.V. All rights reserved.

Leaves, flowers, immature fruits and leafy flowered stems of Malva sylvestris: a comparative study of the nutraceutical potential and composition.

PubMed

Barros, Lillian; Carvalho, Ana Maria; Ferreira, Isabel C F R

2010-06-01

Malva sylvestris is widely used in Mediterranean and European traditional medicine and ethnoveterinary for the treatment of external and internal inflammation, as well as injuries. Moreover, its use is not only limited to therapeutic purposes; but also the species is locally regarded as a food wild herb. Considering that antioxidants and free radical scavengers can exert also an anti-inflammatory effect, the extracts of different parts of the medicinal/edible plant M. sylvestris (leaves, flowers, immature fruits and leafy flowered stems) were compared for their nutraceutical potential (antioxidant properties) and chemical composition. Particularly, mallow leaves revealed very strong antioxidant properties including radical-scavenging activity (EC(50)=0.43 mg/mL), reducing power (0.07 mg/mL) and lipid peroxidation inhibition in lipossomes (0.04 mg/mL) and brain cells homogenates (0.09 mg/mL). This part of the plant is also the richest in nutraceuticals such as powerful antioxidants (phenols, flavonoids, carotenoids, and tocopherols), unsaturated fatty acids (e.g. alpha-linolenic acid), and minerals measured in ash content. Copyright 2010 Elsevier Ltd. All rights reserved.

Valve-Sparing Root Replacement Compared With Composite Valve Graft Procedures in Patients With Aortic Root Dilation.

PubMed

Ouzounian, Maral; Rao, Vivek; Manlhiot, Cedric; Abraham, Nachum; David, Carolyn; Feindel, Christopher M; David, Tirone E

2016-10-25

Although aortic valve-sparing (AVS) operations are established alternatives to composite valve graft (CVG) procedures for patients with aortic root aneurysms, comparative long-term outcomes are lacking. This study sought to compare the results of patients undergoing AVS procedures with those undergoing CVG operations. From 1990 to 2010, a total of 616 patients age <70 years and without aortic stenosis underwent elective aortic root surgery (AVS, n = 253; CVG with a bioprosthesis [bio-CVG], n = 180; CVG with a mechanical prosthesis [m-CVG], n = 183). A propensity score was used as a covariate to adjust for unbalanced variables in group comparisons. Mean age was 46 ± 14 years, 83.3% were male, and mean follow-up was 9.8 ± 5.3 years. Patients undergoing AVS had higher rates of Marfan syndrome and lower rates of bicuspid aortic valve than those undergoing bio-CVG or m-CVG procedures. In-hospital mortality (0.3%) and stroke rate (1.3%) were similar among groups. After adjusting for clinical covariates, both bio-CVG and m-CVG procedures were associated with increased long-term major adverse valve-related events compared with patients undergoing AVS (hazard ratio [HR]: 3.4, p = 0.005; and HR: 5.2, p < 0.001, respectively). They were also associated with increased cardiac mortality (HR: 7.0, p = 0.001; and HR: 6.4, p = 0.003). Furthermore, bio-CVG procedures were associated with increased risk of reoperations (HR: 6.9; p = 0.003), and m-CVG procedures were associated with increased risk of anticoagulant-related hemorrhage (HR: 5.6; p = 0.008) compared with AVS procedures. This comparative study showed that AVS procedures were associated with reduced cardiac mortality and valve-related complications when compared with bio-CVG and m-CVG. AVS is the treatment of choice for young patients with aortic root aneurysm and normal or near-normal aortic cusps. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

[Experimental Study of PMI Foam Composite Properties in Terahertz].

PubMed

Xing, Li-yun; Cui, Hong-liang; Shi, Chang-cheng; Han, Xiao-hui; Zhang, Zi-yin; Li, Wei; Ma, Yu-ting; Zheng, Yan; Zhang, Song-nian

2015-12-01

Polymethacrylimide (PMI) foam composite has many excellent properties. Currently, PMI is heat-resistant foam, with the highest strength and stiffness. It is suitable as a high-performance sandwich structure core material. It can replace the honeycomb structure. It is widely used in aerospace, aviation, military, marine, automotive and high-speed trains, etc. But as new sandwich materials, PMI performance testing in the THz band is not yet visible. Based on the Terahertz (THz) time-domain spectroscopy technique, we conducted the transmission and reflection experiments, got the time domain waveforms and power density spectrum. And then we analyzed and compared the signals. The MATALB and Origin 8. 0 was used to calculate and obtain the transmittance (transfer function), absorptivity Coefficient, reflectance and the refractive index of the different thickness Degussa PMI (Model: Rohacell WF71), which were based on the application of the time-domain and frequency-domain analysis methods. We used the data to compared with the THz refractive index and absorption spectra of a domestic PMI, Baoding Meiwo Technology Development Co. , Ltd. (Model: SP1D80-P-30). The result shows that the impact of humidity on the measurement results is obvious. The refractive index of PMI is about 1. 05. The attenuation of power spectrum is due to the signal of the test platform is weak, the sample is thick and the internal scattering of PMI foam microstructure. This conclusion provides a theoretical basis for the THz band applications in the composite PMI. It also made a good groundwork for THz NDT (Non-Destructive Testing, NDT) technology in terms of PMI foam composites.

Composite chronicles: A study of the lessons learned in the development, production, and service of composite structures

NASA Technical Reports Server (NTRS)

Vosteen, Louis F.; Hadcock, Richard N.

1994-01-01

A study of past composite aircraft structures programs was conducted to determine the lessons learned during the programs. The study focused on finding major underlying principles and practices that experience showed have significant effects on the development process and should be recognized and understood by those responsible for using of composites. Published information on programs was reviewed and interviews were conducted with personnel associated with current and past major development programs. In all, interviews were conducted with about 56 people representing 32 organizations. Most of the people interviewed have been involved in the engineering and manufacturing development of composites for the past 20 to 25 years. Although composites technology has made great advances over the past 30 years, the effective application of composites to aircraft is still a complex problem that requires experienced personnel with special knowledge. All disciplines involved in the development process must work together in real time to minimize risk and assure total product quality and performance at acceptable costs. The most successful programs have made effective use of integrated, collocated, concurrent engineering teams, and most often used well-planned, systematic development efforts wherein the design and manufacturing processes are validated in a step-by-step or 'building block' approach. Such approaches reduce program risk and are cost effective.

Evolving and Combining Facial Composites: Between-Witness and Within-Witness Morphs Compared

ERIC Educational Resources Information Center

Valentine, Tim; Davis, Josh P.; Thorner, Kate; Solomon, Chris; Gibson, Stuart

2010-01-01

Student participant-witnesses produced 4 composites of unfamiliar faces with a system that uses a genetic algorithm to evolve appearance of artificial faces. Morphs of 4 composites produced by different witnesses (between-witness morphs) were judged better likenesses (Experiment 1) and were more frequently named (Experiment 2) by participants who…

Proximate Composition and Antioxidant Potential of Leaves from Three Varieties of Mulberry (Morus sp.): A Comparative Study

PubMed Central

Iqbal, Shahid; Younas, Umer; Sirajuddin; Chan, Kim Wei; Sarfraz, Raja Adil; Uddin, Kamal

2012-01-01

In this study, leaves of three indigenous varieties of Mulberry namely, Morus alba L., Morus nigra L. and Morus rubra L. were investigated for their antioxidant potential and their proximate composition was determined. The yields of 80% methanolic extracts ranged between 8.28–13.89%. The contents of total phenolics (TPC), total flavonoids (TFC) and ascorbic acid (AA) ranged between 16.21–24.37 mg gallic acid equivalent (GAE)/g, 26.41–31.28 mg rutin equivalent (RE)/g and 0.97–1.49 mg/g, respectively. The antioxidant activity of leaf extracts was evaluated by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical scavenging actity, 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid (ABTS•+) radical cation scavenging capacity and ferric ion reducing power and values ranged between 1.89–2.12, 6.12–9.89 and 0.56–0.97 mM Trolox equivalent/g of dried leaves, respectively. The investigated features reveal good nutritive and antioxidant attributes of all the varieties with mutually significant differences. PMID:22837655

Evaluation of Mechanical Properties and Morphological Studies of Rice Husk (Treated/Untreated)-CaCO3 Reinforced Epoxy Hybrid Composites

NASA Astrophysics Data System (ADS)

Verma, Deepak; Joshi, Garvit; Gupta, Ayush

2016-10-01

Natural fiber reinforced composites are a very popular area of research because of the easy availability and biodegradability of these fibers. The manufacturing of natural fiber composite is done by reinforcing fibers in the particulate form, fiber form or in woven mat form. Natural fiber composites also utilize industrial wastes as a secondary reinforcements like fly ash, sludge etc. By keeping all these point of views in the present investigation the effect of rice husk flour (chemically treated/untreated) and micro sized calcium carbonate with epoxy resin have been evaluated. The diameter of rice husk flour was maintained at 600 µm through mechanical sieving machine. The husk flour was chemically treated with NaOH (5 % w/v). Mechanical properties like hardness, flexural impact and compression strength were evaluated and found to be superior in modified or chemically treated flour as compared to unmodified or untreated flour reinforced composites. Scanning electron microscopy (SEM) study was also undertaken for the developed composites. SEM study shows the distribution of the rice husk flour and calcium carbonate over the matrix.

Soft Tissue Phantoms for Realistic Needle Insertion: A Comparative Study.

PubMed

Leibinger, Alexander; Forte, Antonio E; Tan, Zhengchu; Oldfield, Matthew J; Beyrau, Frank; Dini, Daniele; Rodriguez Y Baena, Ferdinando

2016-08-01

Phantoms are common substitutes for soft tissues in biomechanical research and are usually tuned to match tissue properties using standard testing protocols at small strains. However, the response due to complex tool-tissue interactions can differ depending on the phantom and no comprehensive comparative study has been published to date, which could aid researchers to select suitable materials. In this work, gelatin, a common phantom in literature, and a composite hydrogel developed at Imperial College, were matched for mechanical stiffness to porcine brain, and the interactions during needle insertions within them were analyzed. Specifically, we examined insertion forces for brain and the phantoms; we also measured displacements and strains within the phantoms via a laser-based image correlation technique in combination with fluorescent beads. It is shown that the insertion forces for gelatin and brain agree closely, but that the composite hydrogel better mimics the viscous nature of soft tissue. Both materials match different characteristics of brain, but neither of them is a perfect substitute. Thus, when selecting a phantom material, both the soft tissue properties and the complex tool-tissue interactions arising during tissue manipulation should be taken into consideration. These conclusions are presented in tabular form to aid future selection.

Compositional analysis of genetically modified corn events (NK603, MON88017×MON810 and MON89034×MON88017) compared to conventional corn.

PubMed

Rayan, Ahmed M; Abbott, Louise C

2015-06-01

Compositional analysis of genetically modified (GM) crops continues to be an important part of the overall evaluation in the safety assessment for these materials. The present study was designed to detect the genetic modifications and investigate the compositional analysis of GM corn containing traits of multiple genes (NK603, MON88017×MON810 and MON89034×MON88017) compared with non-GM corn. Values for most biochemical components assessed for the GM corn samples were similar to those of the non-GM control or were within the literature range. Significant increases were observed in protein, fat, fiber and fatty acids of the GM corn samples. The observed increases may be due to the synergistic effect of new traits introduced into corn varieties. Furthermore, SDS-PAGE analysis showed high similarity among the protein fractions of the investigated corn samples. These data indicate that GM corn samples were compositionally equivalent to, and as nutritious as, non-GM corn. Copyright © 2014 Elsevier Ltd. All rights reserved.

Urogenital function in robotic vs laparoscopic rectal cancer surgery: a comparative study.

PubMed

Panteleimonitis, Sofoklis; Ahmed, Jamil; Ramachandra, Meghana; Farooq, Muhammad; Harper, Mick; Parvaiz, Amjad

2017-02-01

Urological and sexual dysfunction are recognised risks of rectal cancer surgery; however, there is limited evidence regarding urogenital function comparing robotic to laparoscopic techniques. The aim of this study was to assess the urogenital functional outcomes of patients undergoing laparoscopic and robotic rectal cancer surgery. Urological and sexual functions were assessed using gender-specific validated standardised questionnaires. Questionnaires were sent a minimum of 6 months after surgery, and patients were asked to report their urogenital function pre- and post-operatively, allowing changes in urogenital function to be identified. Questionnaires were sent to 158 patients (89 laparoscopy, 69 robotic) of whom 126 (80 %) responded. Seventy-eight (49 male, 29 female) of the responders underwent laparoscopic and 48 (35 male, 13 female) robotic surgery. Male patients in the robotic group deteriorated less across all components of sexual function and in five components of urological function. Composite male urological and sexual function score changes from baseline were better in the robotic cohort (p < 0.001). In females, there was no difference between the two groups in any of the components of urological or sexual function. However, composite female urological function score change from baseline was better in the robotic group (p = 0.003). Robotic rectal cancer surgery might offer better post-operative urological and sexual outcomes compared to laparoscopic surgery in male patients and better urological outcomes in females. Larger scale, prospective randomised control studies including urodynamic assessment of urogenital function are required to validate these results.

Design feasibility study of a divertor component reinforced with fibrous metal matrix composite laminate

NASA Astrophysics Data System (ADS)

You, Jeong-Ha

2005-01-01

Fibrous metal matrix composites possess advanced mechanical properties compared to conventional alloys. It is expected that the application of these composites to a divertor component will enhance the structural reliability. A possible design concept would be a system consisting of tungsten armour, copper composite interlayer and copper heat sink where the composite interlayer is locally inserted into the highly stressed domain near the bond interface. For assessment of the design feasibility of the composite divertor concept, a non-linear multi-scale finite element analysis was performed. To this end, a micro-mechanics algorithm was implemented into a finite element code. A reactor-relevant heat flux load was assumed. Focus was placed on the evolution of stress state, plastic deformation and ductile damage on both macro- and microscopic scales. The structural response of the component and the micro-scale stress evolution of the composite laminate were investigated.

Comparative study of sex pheromone composition and biosynthesis in Helicoverpa armigera, H. assulta and their hybrid.

PubMed

Wang, Hong-Lei; Zhao, Cheng-Hua; Wang, Chen-Zhu

2005-06-01

Two Helicoverpa species, H. armigera and H. assulta use (Z)-11-hexadecenal and (Z)-9-hexadecenal as their sex attractant pheromone components but in opposite ratios. Since both female and male interspecific hybrids produced by female H. assulta and male H. armigera have been obtained in our laboratory, we can make a comparative study of sex pheromone composition and biosynthesis in the two species and their hybrid. With GC and GC-MS analyses using single gland extracts, the ratio of (Z)-9-hexadecenal to (Z)-11-hexadecenal was determined as 2.1:100 in H. armigera, and 1739:100 in H. assulta. The hybrid has a ratio of 4.0: 100, which is closer to that of H. armigera, but significantly different from H. armigera. We investigated pheromone biosynthesis with labeling experiments, using various fatty acid precursors in H. armigera, H. assulta and the hybrid. In H. armigera, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation; (Z)-9-hexadecenal results from delta11 desaturation of stearic acid, followed by one cycle of chain shortening, reduction and terminal oxidation. delta11 desaturase is the unique desaturase for the production of the two pheromone components. In our Chinese strain of H. assulta, palmitic acid is used as the substrate to form both the major pheromone component, (Z)-9-hexadecenal and the minor one, (Z)-11-hexadecenal. Our data suggest that delta9 desaturase is the major desaturase, and delta11 desaturase is responsible for the minor component in H. assulta, which is consistent with previous work. However, the weak chain shortening acting on (Z)-9 and (Z)-11-octadecenoic acid, which is present in the pheromone glands, does occur in this species to produce (Z)-7 and (Z)-9-hexadecenoic acid. In the hybrid, the major pheromone component, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation. The direct fatty acid precursor of

Morphological and compositional study of 238U thin film targets for nuclear experiments

NASA Astrophysics Data System (ADS)

Sibbens, Goedele; Ernstberger, Markus; Gouder, Thomas; Marouli, Maria; Moens, André; Seibert, Alice; Vanleeuw, David; Zúñiga, Martin Vargas; Wiss, Thierry; Zampella, Mariavittoria; Zuleger, Evelyn

2018-05-01

The uncertainty in neutron cross section values strongly depends on the quality and characteristics of the deposited actinide films which are used as "targets" in the nuclear experiments. Until recently, at the Joint Research Centre in Geel (JRC-Geel), mass and areal densities of actinide layers were determined by measuring activity (using alpha-particle counting), isotopic composition (using thermal ionisation mass spectrometry) and diameter. In this study a series of 238U deposits, prepared by molecular plating and vacuum deposition on different substrates, were characterized with additional non-destructive and destructive analysis techniques. The quality of the deposits was investigated by autoradiography, high-resolution alpha-particle spectrometry, and scanning electron microscopy. The elemental composition was determined by x-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry. The latter technique was also applied on the U3O8 starting material and the converted UF4 powder. This paper compares the quality and morphology of deposited 238U films prepared by molecular plating and vacuum deposition on various backings, including their elemental composition determined by different characterization techniques. Also discussed are problems in target preparation and characterization.

Study of Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1997-01-01

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

Subclinical Hypothyroidism, Weight Change, and Body Composition in the Elderly: The Cardiovascular Health Study

PubMed Central

Garin, Margaret C.; Arnold, Alice M.; Lee, Jennifer S.; Tracy, Russell P.

2014-01-01

Background: Subclinical hypothyroidism is common in the elderly, yet its relationship with weight and body composition is unclear. Objective: We examined the relationship between subclinical hypothyroidism and weight change and body composition in older adults. Methods: A total of 427 subclinically hypothyroid and 2864 euthyroid U.S. individuals ≥65 years old enrolled in the Cardiovascular Health Study and not taking thyroid preparations were included. Analyses of 6-year weight change were performed, compared by thyroid status. A cross-sectional analysis of thyroid status and body composition was performed in a subset of 1276 participants who had dual-energy x-ray absorptiometry scans. Models were risk factor-adjusted and stratified by sex. Results: Overall, participants lost weight during follow-up (−0.38 kg/y in men, −0.37 kg/y in women). Subclinical hypothyroidism, when assessed at a single time point or persisting over 2 years, was not associated with a difference in weight change compared with euthyroidism. Subclinical hypothyroidism was also not associated with differences in lean mass, fat mass, or percent fat compared with euthyroidism. A TSH level 1 mU/L higher within the euthyroid or subclinical hypothyroid range was associated with a 0.51-kg higher baseline weight in women only (P < .001) but not with weight change in either sex. A 1 ng/dL higher free T4 level was associated with lower baseline weight and 0.32 kg/y greater weight loss in women only (P = .003). Baseline weight and weight change did not differ by T3 levels. Conclusions: Our data do not support a clinically significant impact of subclinical hypothyroidism on weight status in the elderly. PMID:24432998

Subclinical hypothyroidism, weight change, and body composition in the elderly: the Cardiovascular Health Study.

PubMed

Garin, Margaret C; Arnold, Alice M; Lee, Jennifer S; Tracy, Russell P; Cappola, Anne R

2014-04-01

Subclinical hypothyroidism is common in the elderly, yet its relationship with weight and body composition is unclear. We examined the relationship between subclinical hypothyroidism and weight change and body composition in older adults. A total of 427 subclinically hypothyroid and 2864 euthyroid U.S. individuals ≥65 years old enrolled in the Cardiovascular Health Study and not taking thyroid preparations were included. Analyses of 6-year weight change were performed, compared by thyroid status. A cross-sectional analysis of thyroid status and body composition was performed in a subset of 1276 participants who had dual-energy x-ray absorptiometry scans. Models were risk factor-adjusted and stratified by sex. Overall, participants lost weight during follow-up (-0.38 kg/y in men, -0.37 kg/y in women). Subclinical hypothyroidism, when assessed at a single time point or persisting over 2 years, was not associated with a difference in weight change compared with euthyroidism. Subclinical hypothyroidism was also not associated with differences in lean mass, fat mass, or percent fat compared with euthyroidism. A TSH level 1 mU/L higher within the euthyroid or subclinical hypothyroid range was associated with a 0.51-kg higher baseline weight in women only (P < .001) but not with weight change in either sex. A 1 ng/dL higher free T4 level was associated with lower baseline weight and 0.32 kg/y greater weight loss in women only (P = .003). Baseline weight and weight change did not differ by T3 levels. Our data do not support a clinically significant impact of subclinical hypothyroidism on weight status in the elderly.

Study on the PTC/NTC effect of carbon black-filled polymer composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Hao; Chen, Xinfang; Luo, Yunxia

1995-12-01

In this work, the effect of processing condition and radiation-crosslinking on the electrical and dynamic behaviors of carbon black filled low density polyethylene (LDPE) composites were investigated. Compared with the solution counterpart, the mechanical composites have a strong PTC effect and a great dynamic elastic mold, which results from the strong interaction between carbon black and LDPE. The experiment result shows that the NTC effect is caused by the decrease of elastic mold of LDPE at high temperature, and it can be declined significantly by radiation-crosslinking. We conclude that the strong interaction between polymer and carbon black is essentially importantmore » for composites to have a great PTC intensity good electrical reproducibility and high dynamic elastic sold.« less

Conceptual design study of advanced acoustic-composite nacelles

NASA Technical Reports Server (NTRS)

Nordstrom, K. E.; Marsh, A. H.; Sargisson, D. F.

1975-01-01

Conceptual studies were conducted to assess the impact of incorporating advanced technologies in the nacelles of a current wide-bodied transport and an advanced technology transport. The improvement possible in the areas of fuel consumption, flyover noise levels, airplane weight, manufacturing costs, and airplane operating cost were evaluated for short and long-duct nacelles. Use of composite structures for acoustic duct linings in the fan inlet and exhaust ducts was considered as well as for other nacelle components. For the wide-bodied transport, the use of a long-duct nacelle with an internal mixer nozzle in the primary exhaust showed significant improvement in installed specific fuel consumption and airplane direct operating costs compared to the current short-duct nacelle. The long-duct mixed-flow nacelle is expected to achieve significant reductions in jet noise during takeoff and in turbo-machinery noise during landing approach. Recommendations were made of the technology development needed to achieve the potential fuel conservation and noise reduction benefits.

A Comparative Study of the Microstructure, Mechanical Properties and Corrosion Resistance of Ni- or Fe- Based Composite Coatings by Laser Cladding

NASA Astrophysics Data System (ADS)

Wan, M. Q.; Shi, J.; Lei, L.; Cui, Z. Y.; Wang, H. L.; Wang, X.

2018-04-01

Ni- and Fe-based composite coatings were laser cladded on 40Cr steel to improve the surface mechanical property and corrosion resistance, respectively. The microstructure and phase composition were analyzed by x-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectrometer (EDS). The micro-hardness, tribological properties and electrochemical corrosion behavior of the coatings were evaluated. The results show that the thickness of both the coatings is around 0.7 mm, the Ni-based coating is mainly composed of γ-(Ni, Fe), FeNi3, Ni31Si12, Ni3B, CrB and Cr7C3, and the Fe-based coating is mainly composed of austenite and (Fe, Cr)7C3. Micro-hardness of the Ni-based composite coating is about 960 HV0.3, much higher than that of Fe-based coating (357.4 HV0.3) and the 40Cr substrate (251 HV0.3). Meanwhile, the Ni-based composite coating possesses better wear resistance than the Fe-based coating validated by the worn appearance and the wear loss. Electrochemical results suggested that Ni-based coating exhibited better corrosion resistance than the Fe-based coating. The 40Cr substrate could be well protected by the Ni-based coating.

Fiber reinforced PMR polyimide composites

NASA Technical Reports Server (NTRS)

Cavano, P. J.; Winters, W. E.

1978-01-01

Commercially obtained PMR-15 polyimide prepregs with S-glass and graphite fiber reinforcements were evaluated along with in-house prepared glass and graphite cloth PMR 2 materials. A novel autoclave approach was conceived and used to demonstrate that both the PMR systems respond to 1.4 MPa (200 psi) autoclave pressures to produce void free composites equivalent to die molded laminates. Isothermal gravimetric analysis and subsequent mechanical property tests indicated that the PMR 2 system was significantly superior in thermo-oxidative stability, and that S-glass reinforcements may contribute to the accelerated degradation of composites at 316 C (600 F) when compared to graphite fiber reinforced composites. Fully reversed bending fatigue experiments were conducted with a type of fixture unused for organic matrix composites. These studies indicated that the graphite fiber composites were clearly superior in fatigue resistance to the glass fiber reinforced material and that PMR matrix composite systems yield performance of the same order as composite materials employing other families of matrices.

Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

NASA Astrophysics Data System (ADS)

Sikarwar, Rahul S.; Velmurugan, Raman; Madhu, Velmuri

2012-12-01

In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

Study on preferred crystal orientations of Mg-Zr-O composite protective layer in AC-PDP

NASA Astrophysics Data System (ADS)

Bingang, G.; Chunliang, L.; Zhongxiao, S.; Liu, L.; Yufeng, F.; Xing, X.; Duowang, F.

2006-11-01

In order to study the preferred crystal orientations of Mg-Zr-O composite protective layers in PDP, Mg-Zr-O composite protective layers were deposited by Electron-beam Evaporator using (MgO+ZrO{2}) powder mixture as evaporation source material. X-ray diffractometer (XRD) was used to determine preferred crystal orientations of Mg-Zr-O composite protective layers, surface morphologies of films were analyzed by FESEM and voltage characteristics were examined in a testing macroscopic discharge cell of AC-PDP. On the basis of experimental analysis, the influence of oxide addition and deposition conditions on preferred orientations of Mg-Zr-O composite protective layers were investigated. The results showed that the preferred orientations of Mg-Zr-O films were determined by lattice distortion of MgO crystal. The deposition conditions have great effects on the preferred orientations of Mg-Zr-O films. The preferred orientations affect voltage characteristics through affecting surface morphology of Mg-Zr-O films. A small amount of Zr solution in MgO can decrease firing voltage compared with using pure MgO film. Firing voltage is closely related with the [ ZrO{2}/(MgO+ZrO{2})] ratio of evaporation source materials.

5-year results comparing mineral trioxide aggregate and adhesive resin composite for root-end sealing in apical surgery.

PubMed

von Arx, Thomas; Hänni, Stefan; Jensen, Simon Storgård

2014-08-01

Recent meta-analyses of the outcome of apical surgery using modern techniques including microsurgical principles and high-power magnification have yielded higher rates of healing. However, the information is mainly based on 1- to 2-year follow-up data. The present prospective study was designed to re-examine a large sample of teeth treated with apical surgery after 5 years. Patients were recalled 5 years after apical surgery, and treated teeth were classified as healed or not healed based on clinical and radiographic examination. (The latter was performed independently by 3 observers). Two different methods of root-end preparation and filling (primary study parameters) were to be compared (mineral trioxide aggregate [MTA] vs adhesive resin composite [COMP]) without randomization. A total of 271 patients and teeth from a 1-year follow-up sample of 339 could be re-examined after 5 years (dropout rate = 20.1%). The overall rate of healed cases was 84.5% with a significant difference (P = .0003) when comparing MTA (92.5%) and COMP (76.6%). The evaluation of secondary study parameters yielded no significant difference for healing outcome when comparing subcategories (ie, sex, age, type of tooth treated, post/screw, type of surgery). The results from this prospective nonrandomized clinical study with a 5-year follow-up of 271 teeth indicate that MTA exhibited a higher healing rate than COMP in the longitudinal prognosis of root-end sealing. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Surface morphology and electrochemical studies on polyaniline/CuO nano composites

NASA Astrophysics Data System (ADS)

Ashokkumar, S. P.; Vijeth, H.; Yesappa, L.; Niranjana, M.; Vandana, M.; Basappa, M.; Devendrappa, H.

2018-05-01

An electrochemically synthesized Polyaniline (PANI) and Polyaniline/copper oxide (PCN) nano composite have studied the morphology and electrochemical properties. The composite is characterized by X-ray diffraction (XRD) and surface morphology was studied using FESEM and electrochemical behavior is studied using cyclic voltammetry (CV) technique. The CV curves shows rectangular shaped curve and they have contribution to electrical double layer capacitance (EDCL).

Tribology Study of High-Technological Composite Coatings Applied Using High Velocity Oxy-Fuel

NASA Astrophysics Data System (ADS)

Kandeva, M.; Grozdanova, T.; Karastoyanov, D.; Ivanov, Pl; Kalichin, Zh

2018-01-01

In the work are studied the differential parameters of wear and wear resistance of high-tech composite coatings of powder superalloys with nickel matrix, WC-12Co and mixed compositions. Coatings were created and applied to a substrate of steel with a different flame velocity - 700 m/s and 1000 m/s without preheating the substrate and with preheating the substrate to 650° C. The wear is carried out with a "thumb-disk" tribotester under dry surface friction with fixed black corundum abrasive particles. Comparative results were obtained for the microstructure and texture of the pre- and post- friction coating, the porosity, roughness, hardness, the dependence of mass wear, the speed and wear intensity and the wear resistance of the coatings on the number of friction cycles. Influence of the flame rate and substrate temperature on wear resistance and differential wear parameters has been determined.

Part I. Corrosion studies of continuous alumina fiber reinforced aluminum-matrix composites. Part II. Galvanic corrosion between continuous alumina fiber reinforced aluminum-matrix composites and 4340 steel

NASA Astrophysics Data System (ADS)

Zhu, Jun

Part I. The corrosion performance of continuous alumina fiber reinforced aluminum-matrix composites (CF-AMCs) was investigated in both the laboratory and field environments by comparing them with their respective monolithic matrix alloys, i.e., pure Al, A1-2wt%Cu T6, and Al 6061 T6. The corrosion initiation sites were identified by monitoring the changes in the surface morphology. Corrosion current densities and pH profiles at localized corrosion sites were measured using the scanning-vibrating electrode technique and the scanning ion-selective electrode technique, respectively. The corrosion damage of the materials immersed in various electrolytes, as well as those exposed in a humidity chamber and outdoor environments, was evaluated. Potentiodynamic polarization behavior was also studied. The corrosion initiation for the composites in 3.15 wt% NaCl occurred primarily around the Fe-rich intermetallic particles, which preferentially existed around the fiber/matrix interface on the composites. The corrosion initiation sites were also caused by physical damage (e.g., localized deformation) to the composite surface. At localized corrosion sites, the buildup of acidity was enhanced by the formation of micro-crevices resulting from fibers left in relief as the matrix corroded. The composites that were tested in exposure experiments exhibited higher corrosion rates than their monolithic alloys. The composites and their monolithic alloys were subjected to pitting corrosion when anodically polarized in the 3.15 wt% NaCl, while they passivated when anodically polarized in 0.5 M Na2SO4. The experimental results indicated that the composites exhibited inferior corrosion resistance compared to their monolithic matrix alloys. Part II. Galvanic corrosion studies were conducted on CF-AMCs coupled to 4340 steel since CF-AMCs have low density and excellent mechanical properties and are being considered as potential jacketing materials for reinforcing steel gun barrels. Coupled and

Parametric Study Of A Ceramic-Fiber/Metal-Matrix Composite

NASA Technical Reports Server (NTRS)

Murthy, P. L. N.; Hopkins, D. A.; Chamis, C. C.

1992-01-01

Report describes computer-model parametric study of effects of degradation of constituent materials upon mechanical properties of ceramic-fiber/metal-matrix composite material. Contributes to understanding of weakening effects of large changes in temperature and mechanical stresses in fabrication and use. Concerned mainly with influences of in situ fiber and matrix properties upon behavior of composite. Particular attention given to influence of in situ matrix strength and influence of interphase degradation.

[Comparative study on alkaloids of tissue-culture seedling and wild plant of Dendrobium huoshanense ].

PubMed

Chen, Nai-dong; Gao, Feng; Lin, Xin; Jin, Hui

2014-06-01

To compare the composition and content of alkaloid of Dendrobium huoshanense tissue-culture seedling and wild plant. A comparative evaluation on the quality was carried out by HPLC and TLC methods including the composition and the content of alkaloids. Remarkable variation existed in the two kinds of Dendrobium huoshanense. For the tissue-culture plant, only two alkaloids were checked out by both HPLC and TLC while four alkaloids were observed in the wild plant. The alkaloid content of tissue-culture seedling and wild plant was(0. 29 ± 0. 11)%o and(0. 43 ± 0. 15) %o,respectively. Distinguished difference is observed in both composition and content of alkaloids from the annual shoots of different provenances of Dendrobium huoshanense. It suggested that the quality of tissue-culture seedling of Dendrobium huoshanense might be inconsistent with the wild plant. Furthermore, the established alkaloids-knock-out HPLC method would provide a new research tool on quality control of Chinese medicinal materials which contain unknown alkaloids.

Design of unique composites based on aromatic thermosetting copolyesters

NASA Astrophysics Data System (ADS)

Parkar, Zeba

Aromatic thermosetting copolyester (ATSP) has promise in high-temperature applications. It can be employed as a bulk polymer, as a coating and as a matrix for carbon fiber composites (ATSP/C composites). This work focuses on the applications of high performance ATSP/C composites. The morphology of the ATSP matrix in the presence of carbon fiber was studied. The effect of liquid crystalline character of starting oligomers used to prepare ATSP on the final crystal structure of the ATSP/C composite was evaluated. Matrices obtained by crosslinking of both liquid crystalline oligomers (ATSP2) and non-liquid crystalline oligomers (ATSP1) tend to crystallize in presence of carbon fibers. The crystallite size of ATSP2 is 4 times that of ATSP1. Composites made from ATSP2 yield tougher matrices compared to those made from ATSP1. Thus toughened matrices could be achieved without incorporating any additives by just changing the morphology of the final polymer. The flammability characteristics of ATSP were also studied. The limiting oxygen index (LOI) of bulk ATSP was found to be 40% whereas that of ATSP/C composites is estimated to be 85%. Thus, ATSP shows potential to be used as a flame resistant material, and also as an aerospace reentry shield. Mechanical properties of the ATSP/C composite were characterized. ATSP was observed to bond strongly with reinforcing carbon fibers. The tensile strength, modulus and shear modulus were comparable to those of conventionally used high temperature epoxy resins. ATSP shows a unique capability for healing of interlaminar cracks on application of heat and pressure, via the Interchain Transesterification Reaction (ITR). ITR can also be used for reduction in void volume and healing of microcracks. Thus, ATSP resin systems provide a unique intrinsic repair mechanism compared to any other thermosetting systems in use today. Preliminary studies on measurement of residual stresses for ATSP/C composites indicate that the stresses induced are

Ultrasonic Resonance Spectroscopy of Composite Rims for Flywheel Rotors

NASA Technical Reports Server (NTRS)

Harmon, Laura M.; Baaklini, George Y.

2002-01-01

Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The ultrasonic system employs a continuous swept-sine waveform and performs a fast Fourier transform (FFT) on the frequency response spectrum. In addition, the system is capable of equalizing the amount of energy at each frequency. Equalization of the frequency spectrum, along with interpretation of the second FFT, aids in the evaluation of the fundamental frequency. The frequency responses from multilayered material samples, with and without known defects, were analyzed to assess the capabilities and limitations of this nondestructive evaluation technique for material characterization and defect detection. Amplitude and frequency changes were studied from ultrasonic responses of thick composite rings and a multiring composite rim. A composite ring varying in thickness was evaluated to investigate the full thickness resonance. The frequency response characteristics from naturally occurring voids in a composite ring were investigated. Ultrasonic responses were compared from regions with and without machined voids in a composite ring and a multiring composite rim. Finally, ultrasonic responses from the multiring composite rim were compared before and after proof spin testing to 63,000 rpm.

A comparative study of conventionally sintered and microwave sintered nickel zinc ferrite

NASA Astrophysics Data System (ADS)

Rani, Rekha; Juneja, J. K.; Raina, K. K.; Kotnala, R. K.; Prakash, Chandra

2014-04-01

For the present work, nickel zinc ferrite having compositional formula Ni0.8Zn0.2Fe2O4 was synthesized by conventional solid state method and sintered in conventional and microwave furnaces. Pellets were sintered with very short soaking time of 10 min at 1150 °C in microwave furnace whereas 4 hrs of soaking time was selected for conventional sintering at 1200 °C. Phase formation was confirmed by X-ray diffraction analysis technique. Scanning electron micrographs were taken for microstructural study. Dielectric properties were studied as a function of temperature. To study magnetic behavior, M-H hysteresis loops were recorded for both samples. It is observed that microwave sintered sample could obtain comparable properties to the conventionally sintered one in lesser soaking time at lower sintering temperature.

Assessing compositional variability through graphical analysis and Bayesian statistical approaches: case studies on transgenic crops.

PubMed

Harrigan, George G; Harrison, Jay M

2012-01-01

New transgenic (GM) crops are subjected to extensive safety assessments that include compositional comparisons with conventional counterparts as a cornerstone of the process. The influence of germplasm, location, environment, and agronomic treatments on compositional variability is, however, often obscured in these pair-wise comparisons. Furthermore, classical statistical significance testing can often provide an incomplete and over-simplified summary of highly responsive variables such as crop composition. In order to more clearly describe the influence of the numerous sources of compositional variation we present an introduction to two alternative but complementary approaches to data analysis and interpretation. These include i) exploratory data analysis (EDA) with its emphasis on visualization and graphics-based approaches and ii) Bayesian statistical methodology that provides easily interpretable and meaningful evaluations of data in terms of probability distributions. The EDA case-studies include analyses of herbicide-tolerant GM soybean and insect-protected GM maize and soybean. Bayesian approaches are presented in an analysis of herbicide-tolerant GM soybean. Advantages of these approaches over classical frequentist significance testing include the more direct interpretation of results in terms of probabilities pertaining to quantities of interest and no confusion over the application of corrections for multiple comparisons. It is concluded that a standardized framework for these methodologies could provide specific advantages through enhanced clarity of presentation and interpretation in comparative assessments of crop composition.

A 15-year randomized controlled study of a reduced shrinkage stress resin composite.

PubMed

van Dijken, Jan W V; Lindberg, Anders

2015-09-01

The aim of this randomized controlled study was to evaluate the long term effectiveness of a reduced shrinkage stress resin composite in Class II restorations. The material was compared intra-individually with a microhybrid resin composite. Each of 50 patients with at least one pair of two similar sized Class II cavities participated (22 female, 28 male, mean age 43 years, range 18-64). Each participant received in each pair, in a randomized way, one Class II restoration performed with a reduced shrinkage stress resin composite (InTen-S) and the other restoration with a microhybrid resin composite restoration (Point 4). Both restorations were placed with an etch-and-rinse bonding system and an oblique layering technique. A total of 106 restorations, 33 premolar and 73 molars, were placed. The restorations were evaluated blindly each year using modified USPHS criteria. The overall performance of the experimental restorations was tested after intra-individual comparison using the Friedmańs two-way analysis of variance test. The hypothesis was rejected at the 5% level. At 15 years, 91 restorations were evaluated. The drop out frequency was 15 restorations (5 male, 3 female participants; 2 premolar and 13 molar restorations). Except for 2 participants, who reported slight symptoms during a few weeks after placement, no post-operative sensitivity was observed at the recalls. The overall success rate at 15 years was 77%. Twenty-one non acceptable restorations were observed during the 15 years follow up, 10 InTen-S (21.7%) and 11 Point 4 (24.4%) restorations (p>0.05). Annual failure rates for the resin composites were 1.5% and 1.6%, respectively. The main reasons for failure were secondary caries (8) and resin composite fracture (7). The differences between premolar vs. molar restorations and between restorations in male vs. female participants were not significant. Significant differences were observed between 2-surface vs. 3-surface restorations. During the 15-year

Composition Instruction and Cognitive Performance: Results of a Pilot Study

ERIC Educational Resources Information Center

Bugos, Jennifer; Jacobs, Edward

2012-01-01

The purpose of this study was to evaluate the effects of a composition program, Composers in Public Schools (CiPS), on cognitive skills essential for academic success. The underlying hypothesis is that composition instruction will promote creative expression and increase performance on music-specific skills such as music reading, as well as foster…

Study to determine and analyze the strength of high modulus glass in epoxy-matrix composites

NASA Technical Reports Server (NTRS)

Bacon, J. F.

1974-01-01

Glass composition research was conducted to produce a high modulus, high strength beryllium-free glass fiber. This program was built on the previous research for developing high modulus, high strength glass fibers which had a 5 weight percent beryllia content. The fibers resulting from the composition program were then used to produce fiber reinforced-epoxy resin composites which were compared with composites reinforced by commercial high modulus glass fibers, Thornel S graphite fiber, and hybrids where the external quarters were reinforced with Thornel S graphite fiber and the interior half with glass fiber as well as the reverse hybrid. The composites were given tensile strength, compressive strength, short-beam shear strength, creep and fatigue tests. Comments are included on the significance of the test data.

THE BALLISTICS OF A RIBBON COMPOSITE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Larcombe, J.; Morley, M.; Earp, S.

2009-12-28

The impact behaviour of composites is of great importance in the field of aerospace and vehicle protection. The combination of formability, lightness and strength make composite systems attractive compared to equivalent monolithic systems. However, their use as optical components has been hampered by their lack of transparency. Transparency is strongly affected by refractive index differences in the materials that form the composite. In this study a number of ribbon-based composites were produced. The impact velocity, sample deformation during the impact process and residual impactor velocity were measured. This allowed comparison between the materials ballistic efficiency. The materials are then comparedmore » to other transparent systems.« less

Fusion processing of itraconazole solid dispersions by kinetisol dispersing: a comparative study to hot melt extrusion.

PubMed

DiNunzio, James C; Brough, Chris; Miller, Dave A; Williams, Robert O; McGinity, James W

2010-03-01

KinetiSol Dispersing (KSD) is a novel high energy manufacturing process investigated here for the production of pharmaceutical solid dispersions. Solid dispersions of itraconazole (ITZ) and hypromellose were produced by KSD and compared to identical formulations produced by hot melt extrusion (HME). Materials were characterized for solid state properties by modulated differential scanning calorimetry and X-ray diffraction. Dissolution behavior was studied under supersaturated conditions. Oral bioavailability was determined using a Sprague-Dawley rat model. Results showed that KSD was able to produce amorphous solid dispersions in under 15 s while production by HME required over 300 s. Dispersions produced by KSD exhibited single phase solid state behavior indicated by a single glass transition temperature (T(g)) whereas compositions produced by HME exhibited two T(g)s. Increased dissolution rates for compositions manufactured by KSD were also observed compared to HME processed material. Near complete supersaturation was observed for solid dispersions produced by either manufacturing processes. Oral bioavailability from both processes showed enhanced AUC compared to crystalline ITZ. Based on the results presented from this study, KSD was shown to be a viable manufacturing process for the production of pharmaceutical solid dispersions, providing benefits over conventional techniques including: enhanced mixing for improved homogeneity and reduced processing times. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

Comparative Analysis of Lipid Content and Fatty Acid Composition of Commercially Important Fish and Shellfish from Sri Lanka and Japan.

PubMed

Devadason, Chandravathany; Jayasinghe, Chamila; Sivakanesan, Ramiah; Senarath, Samanthika; Beppu, Fumiaki; Gotoh, Naohiro

2016-01-01

Sri Lanka is surrounded by the Indian Ocean, allowing plenty of fishes to be caught. Moreover, these fishes represent one of the undocumented fish resources in the world and their detailed lipid profiles have not been previously examined. In this study, the lipid content and fatty acid composition of 50 commercially important fishes from the Indian Ocean (Sri Lanka) and the Pacific Ocean (Japan) were compared. The total lipid content and fatty acid composition, including eicosapentaenoic acid (C20:5n-3, EPA) and docosahexaenoic acid (C22:6n-3, DHA), differed significantly among species. Fish from the Pacific Ocean had higher proportions of fatty acids, including EPA and DHA. Herrings and mackerels from both oceanic areas demonstrated high levels of EPA and DHA, and n-3/n-6 ratio. Brackish and freshwater fishes from both groups showed low levels of PUFAs. Fish from the Indian Ocean were high in n-6 fatty acids. Monounsaturated fatty acid levels were high in omnivorous fish from the Pacific Ocean, and saturated fatty acid levels were high in fish from the Indian Ocean. The results of this study will be of value in determining the dietary usefulness of fish caught in Sri Lanka.

Studying impact damage on carbon-fiber reinforced aircraft composite panels with sonicir

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han Xiaoyan; Zhang Ding; He Qi

2011-06-23

Composites are becoming more important materials in commercial aircraft structures such as the fuselage and wings with the new B787 Dreamliner from Boeing which has the target to utilize 50% by weight of composite materials. Carbon-fiber reinforced composites are the material of choice in aircraft structures. This is due to their light weight and high strength (high strength-to-weight ratio), high specific stiffness, tailorability of properties, design flexibility etc. Especially, by reducing the aircraft's body weight by using such lighter structures, the cost of fuel can be greatly reduced with the high jet fuel price for commercial airlines. However, these compositesmore » are prone to impact damage and the damage may occur without any observable sign on the surface, yet resulting in delaminations and disbonds that may occur well within the layers. We are studying the impact problem with carbon-fiber reinforced composite panels and developing SonicIR for this application as a fast and wide-area NDE technology. In this paper, we present our results in studying composite structures including carbon-fiber reinforced composite materials, and preliminary quantitative studies on delamination type defect depth identification in the panels.« less

Focus: Composition and Language Study, K-6.

ERIC Educational Resources Information Center

Stewart, Donald, Ed.

1974-01-01

This issue of "Kansas English" focus on composition and language study, kindergarten through grade six. The articles and authors are "Evaluating Process and Product in Children's Writing" by Robert L. Hillerich, "Written Language Development and Instruction of Elementary School Children" by Lester S. Golub, "From a Reading Desk" by Myrline…

Embracing Wicked Problems: The Turn to Design in Composition Studies

ERIC Educational Resources Information Center

Marback, Richard

2009-01-01

Recent appeal to the concept of design in composition studies benefits teaching writing in digital media. Yet the concept of design has not been developed enough to fully benefit composition instruction. This article develops an understanding of design as a matter of resolving wicked problems and makes a case for the advantages of this…

Histamine-binding capacities of different natural zeolites: a comparative study.

PubMed

Selvam, Thangaraj; Schwieger, Wilhelm; Dathe, Wilfried

2018-06-07

Two different natural zeolites from Cuba and Mexico, which are already being used as contemporaneous drugs or dietary supplements in Germany and Mexico, respectively, are applied in a comparative study of their histamine-binding capacities as a function of their particle sizes. The zeolites are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and N 2 -sorption measurements (BET surface areas). The Cuban zeolite contains clinoptilolite and mordenite as major phases (78% zeolite), whereas the Mexican one contains only clinoptilolite (65% zeolite). Both zeolites are apparently free from fibrous materials according to SEM. Both zeolites adsorb significant amount of histamine under the experimental conditions. Nevertheless, the results showed that the histamine-binding capacity of the Cuban zeolite is higher than the Mexican one and the smaller the particle size of zeolite, the higher the histamine-binding capacity. This difference could be due to the variation in their mineralogical compositions resulting in varied BET surface areas. Thus, the high histamine-binding capacities of Cuban zeolites seem to be due at least partly to the presence of the large-pore zeolite mordenite, providing high total pore volumes, which will be discussed in detail. For the first time, we have shown that the mineralogical compositions of natural zeolites and their particle sizes play a key role in binding histamine, which is one of the most important regulators in human physiology.

In vitro studies of degradation and bioactivity of aliphatic polyester composites

NASA Astrophysics Data System (ADS)

Chouzouri, Georgia

In spite of numerous publications on the potential use of combinations of aliphatic polyester composites containing bioactive fillers for bone regeneration, little information exists on the combined in vitro mechanisms involving simultaneously diffusion for polymer degradation and bioactivity through nucleation and growth of apatite in simulated body fluid (SBF) solution. The objective of this study is to contribute to the understanding of the fundamentals in designing non-porous, solid materials for bone regeneration, from experimental data along with their engineering interpretation. Bioactivity, in terms of apatite growth, was assessed through several experimental methods such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray-diffraction (XRD) and changes in ion concentration. In the case of the six neat fillers evaluated, the filler shape, form and chemical structure showed significant differences in bioactivity response. Bioglass and calcium silicate fillers showed faster nucleation and growth rates in the screening experiments. Composites at 30% by weight filler were prepared by solution and/or melt mixing. Polycaprolactone (PCL) composites containing five different fillers were evaluated. Solution processed PCL/calcium silicate (CS) samples showed faster bioactivity, as determined by apatite growth, compared to melt mixed samples. The onset time for bioactivity was different for all PCL composites. The limited bioactivity in the PCL composites over longer periods of time could be attributed to the PCL hydrophobicity leading to a slow polymer degradation rate, and also to the lack of SBF replenishment. For both polylactic acid (PLA) composites containing CS and bioglass, significant growth was observed after one week and in the case of CS was still evident after four weeks immersion. However, at prolonged time periods no further bioactivity was observed, although ion release results indicated a faster release rate that would

Does type of feeding affect body composition in very low birth weight infants? - A prospective cohort study.

PubMed

Nina, Mól; Magdalena, Zasada; Przemko, Kwinta

2018-05-04

The aim of the study was to analyse body composition of preterm infants fed with either breast milk or formula compared to a control group of full-term newborns. Fifty-three newborns were enrolled: a group of 34 very low birth weight (VLBW) preterm newborns subdivided into a formula-fed (n = 23; group A) and breast milk-fed (n = 11; group B) group, and a control group of 19 full-term infants (group C). Their body composition was assessed by a bioelectrical impedance analysis (BIA) either at the estimated time of birth in the VLBW group or during the 1st week of life in the full-term group. There was no difference in body weight or length between any of the three studied groups. However, we discovered that fat free mass (% FFM) was lower (83.5% vs. 85.5%; p < 0.01), while fat mass (% FM) was higher (16.4% vs.14.5%; p < 0.01) in group A compared to full-term newborns. There were no such differences in FFM (84.3% vs. 85.5%; p = 0.13) or FM (15.7% vs. 14.5%; p = 0.13) between group B and control. To sum up, the VLBW infants fed with breast milk shared similar body composition with the full-term infants, while the formula-fed VLBW developed higher amounts of adipose tissue and lower amounts of fat-free mass. This is the first study to expose differences in fat tissue content attributed to type of provided nutrition, which has become significant as early as estimated time of birth despite the comparable weight. Copyright © 2018. Published by Elsevier B.V.

Application study of filamentary composites in a commercial jet aircraft fuselage

NASA Technical Reports Server (NTRS)

Johnson, R. W.; June, R. R.

1972-01-01

A study of applications of filamentary composite materials to aircraft fuselage structure was performed. General design criteria were established and material studies conducted using the 727-200 forebody as the primary structural component. Three design approaches to the use of composites were investigated: uniaxial reinforcement of metal structure, uniaxial and biaxial reinforcement of metal structure, and an all-composite design. Materials application studies for all three concepts were conducted on fuselage shell panels, keel beam, floor beams, floor panels, body frames, fail-safe straps, and window frames. Cost benefit studies were conducted and developmental program costs estimated. On the basis of weight savings, cost effectiveness, developmental program costs, and potential for early application on commercial aircraft, the unaxial design is recommended for a 5-year flight service evaluation program.

Hot forming of composite prepreg : Experimental study

NASA Astrophysics Data System (ADS)

Tardif, Xavier; Duthille, Bertrand; Bechtel, Stephane; le Pinru, Louis; Campagne, Benjamin; Destombes, Gautier; Deshors, Antoine; Marchand, Christophe; Azzouzi, Khalid El; Moro, Tanguy

2017-10-01

The hot forming of thermoset prepreg consists in bending an uncured composite part by applying a mechanical constrain on the hot laminate. Most of the time, the mold is inserted in a vacuum box and the mechanical constrain is applied on the composite laminate by a single membrane or a double-membrane. But the performance improvement products resulted in forming increasingly complex parts with advanced materials having a less formability. These new complex parts require a finer comprehension of the process and an optimization of the key parameters to get acceptable quality. In this work, an experimental study has been carried out to identify the process conditions that do not lead to unacceptable defaults: undulations of fibers. In the present study, downward-bending has been evaluated with an original light mechanical forming concept, for a given stacking sequence. The influence of the part's temperature and the part's bending speed are investigated. To carry this study out, a hot forming test bench has been designed and manufactured to have a precise supervision of the process conditions. It is able to bend parts of 1500 mm length x 600 mm width x 20 mm thick.

Precursor composites for oxygen dispersion hardened silver sheathed superconductor composites

DOEpatents

Podtburg, E.R.

1999-06-22

An oxide superconductor composite having improved texture and durability is disclosed. The oxide superconductor composite includes an oxide superconductor phase substantially surrounded with/by a noble metal matrix, the noble metal matrix comprising a metal oxide in an amount effective to form metal oxide domains that increase hardness of the composite. The composite is characterized by a degree of texture at least 10% greater than a comparable oxide superconductor composite lacking metal oxide domains. An oxide superconducting composite may be prepared by oxidizing the precursor composite under conditions effective to form solute metal oxide domains within the silver matrix and to form a precursor oxide in the precursor alloy phase; subjecting the oxidized composite to a softening anneal under conditions effective to relieve stress within the noble metal phase; and converting the oxide precursor into an oxide superconductor. 1 fig.

Precursor composites for oxygen dispersion hardened silver sheathed superconductor composites

DOEpatents

Podtburg, Eric R.

1999-01-01

An oxide superconductor composite having improved texture and durability. The oxide superconductor composite includes an oxide superconductor phase substantially surrounded with/by a noble metal matrix, the noble metal matrix comprising a metal oxide in an amount effective to form metal oxide domains that increase hardness of the composite. The composite is characterized by a degree of texture at least 10% greater than a comparable oxide superconductor composite lacking metal oxide domains. An oxide superconducting composite may be prepared by oxidizing the precursor composite under conditions effective to form solute metal oxide domains within the silver matrix and to form a precursor oxide in the precursor alloy phase; subjecting the oxidized composite to a softening anneal under conditions effective to relieve stress within the noble metal phase; and converting the oxide precursor into an oxide superconductor.

A Holistic Landscape Description Reveals That Landscape Configuration Changes More over Time than Composition: Implications for Landscape Ecology Studies.

PubMed

Mimet, Anne; Pellissier, Vincent; Houet, Thomas; Julliard, Romain; Simon, Laurent

2016-01-01

Space-for-time substitution-that is, the assumption that spatial variations of a system can explain and predict the effect of temporal variations-is widely used in ecology. However, it is questionable whether it can validly be used to explain changes in biodiversity over time in response to land-cover changes. Here, we hypothesize that different temporal vs spatial trajectories of landscape composition and configuration may limit space-for-time substitution in landscape ecology. Land-cover conversion changes not just the surface areas given over to particular types of land cover, but also affects isolation, patch size and heterogeneity. This means that a small change in land cover over time may have only minor repercussions on landscape composition but potentially major consequences for landscape configuration. Using land-cover maps of the Paris region for 1982 and 2003, we made a holistic description of the landscape disentangling landscape composition from configuration. After controlling for spatial variations, we analyzed and compared the amplitudes of changes in landscape composition and configuration over time. For comparable spatial variations, landscape configuration varied more than twice as much as composition over time. Temporal changes in composition and configuration were not always spatially matched. The fact that landscape composition and configuration do not vary equally in space and time calls into question the use of space-for-time substitution in landscape ecology studies. The instability of landscapes over time appears to be attributable to configurational changes in the main. This may go some way to explaining why the landscape variables that account for changes over time in biodiversity are not the same ones that account for the spatial distribution of biodiversity.

Superficial roughness on composite surface, composite-enamel and composite-dentin junctions after different finishing and polishing procedures. Part II: roughness with diamond finishing and differences between enamel composite vs body composite.

PubMed

Ferraris, Federico; Conti, Alessandro

2014-01-01

The following study asks three principle questions relative to composite finishing and composite polishing: 1) Will the superficial roughness of different restoration surfaces have different values, utilizing the same polishing system (multistep), after finishing with the tungsten carbide or diamond bur? 2) Under the same conditions of finishing and polishing sequences, will the composite surfaces (C), the composite-enamel (CE) and composite-dentin (CD) interfaces show different roughness values? 3) Will the surface roughness of composites of different translucency in the various phases of finishing and polishing, and on different interfaces, have different results? The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations when polishing, after finishing with tungsten carbide or diamond burs. Furthermore, the null hypothesis is that there are no significant differences on roughness between polishing on composite surface, composite-enamel and composite-dentin interfaces, and finally there are no differences on roughness after finishing and polishing of two composite with different translucency. For the study, 56 class V cavities were prepared on extracted teeth. Restorations were done in nanofilled composite Filtek XTE (3M Espe) in a standard fashion, and then finished and polished. The 28 buccal cavities were restored on the surface with composite enamel and the 28 palatals with composite body. Finishing was done with fine toothing burs in tungsten carbide (16 blades) or fine grit diamond burs (46 μm), and made by the same manufacturer (Komet). The second phase of finishing was done with burs (with the same form as already mentioned) ultrafine toothing tungsten carbide (30 blades) or with extra and ultrafine grit diamond (25 and 8 μm). The polishing phase for both of the earlier sequences was done with the application of three rubber tips with decreasing abrasiveness and an application with a

A Comparative Analysis of Disaster Risk, Vulnerability and Resilience Composite Indicators.

PubMed

Beccari, Benjamin

2016-03-14

In the past decade significant attention has been given to the development of tools that attempt to measure the vulnerability, risk or resilience of communities to disasters. Particular attention has been given to the development of composite indices to quantify these concepts mirroring their deployment in other fields such as sustainable development. Whilst some authors have published reviews of disaster vulnerability, risk and resilience composite indicator methodologies, these have been of a limited nature. This paper seeks to dramatically expand these efforts by analysing 106 composite indicator methodologies to understand the breadth and depth of practice. An extensive search of the academic and grey literature was undertaken for composite indicator and scorecard methodologies that addressed multiple/all hazards; included social and economic aspects of risk, vulnerability or resilience; were sub-national in scope; explained the method and variables used; focussed on the present-day; and, had been tested or implemented. Information on the index construction, geographic areas of application, variables used and other relevant data was collected and analysed. Substantial variety in construction practices of composite indicators of risk, vulnerability and resilience were found. Five key approaches were identified in the literature, with the use of hierarchical or deductive indices being the most common. Typically variables were chosen by experts, came from existing statistical datasets and were combined by simple addition with equal weights. A minimum of 2 variables and a maximum of 235 were used, although approximately two thirds of methodologies used less than 40 variables. The 106 methodologies used 2298 unique variables, the most frequently used being common statistical variables such as population density and unemployment rate. Classification of variables found that on average 34% of the variables used in each methodology related to the social environment, 25

A Comparative Analysis of Disaster Risk, Vulnerability and Resilience Composite Indicators

PubMed Central

Beccari, Benjamin

2016-01-01

Introduction: In the past decade significant attention has been given to the development of tools that attempt to measure the vulnerability, risk or resilience of communities to disasters. Particular attention has been given to the development of composite indices to quantify these concepts mirroring their deployment in other fields such as sustainable development. Whilst some authors have published reviews of disaster vulnerability, risk and resilience composite indicator methodologies, these have been of a limited nature. This paper seeks to dramatically expand these efforts by analysing 106 composite indicator methodologies to understand the breadth and depth of practice. Methods: An extensive search of the academic and grey literature was undertaken for composite indicator and scorecard methodologies that addressed multiple/all hazards; included social and economic aspects of risk, vulnerability or resilience; were sub-national in scope; explained the method and variables used; focussed on the present-day; and, had been tested or implemented. Information on the index construction, geographic areas of application, variables used and other relevant data was collected and analysed. Results: Substantial variety in construction practices of composite indicators of risk, vulnerability and resilience were found. Five key approaches were identified in the literature, with the use of hierarchical or deductive indices being the most common. Typically variables were chosen by experts, came from existing statistical datasets and were combined by simple addition with equal weights. A minimum of 2 variables and a maximum of 235 were used, although approximately two thirds of methodologies used less than 40 variables. The 106 methodologies used 2298 unique variables, the most frequently used being common statistical variables such as population density and unemployment rate. Classification of variables found that on average 34% of the variables used in each methodology

Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity.

PubMed

Xu, Yonggang; Yang, Chi; Li, Jun; Mao, Xiaojian; Zhang, Hailong; Hu, Song; Wang, Shiwei

2017-12-18

AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity.

Development of AlN/Epoxy Composites with Enhanced Thermal Conductivity

PubMed Central

Xu, Yonggang; Yang, Chi; Li, Jun; Zhang, Hailong; Hu, Song; Wang, Shiwei

2017-01-01

AlN/epoxy composites with high thermal conductivity were successfully prepared by infiltrating epoxy into AlN porous ceramics which were fabricated by gelcasting of foaming method. The microstructure, mechanical, and thermal properties of the resulting composites were investigated. The compressive strengths of the AlN/epoxy composites were enhanced compared with the pure epoxy. The AlN/epoxy composites demonstrate much higher thermal conductivity, up to 19.0 W/(m·K), compared with those by the traditional particles filling method, because of continuous thermal channels formed by the walls and struts of AlN porous ceramics. This study demonstrates a potential route to manufacture epoxy-based composites with extremely high thermal conductivity. PMID:29258277

Mesoporous silica fillers and resin composition effect on dental composites cytocompatibility.

PubMed

Attik, Nina; Hallay, Franck; Bois, Laurence; Brioude, Arnaud; Grosgogeat, Brigitte; Colon, Pierre

2017-02-01

Many new dental composites containing mesoporous silica fillers have been developed to improve rheological properties and enhance the resin-filler interface. To investigate the correlation between the cytocompatibility of several dental composites and their composition; two aspects have been considered: presence of bisphenol A (BPA)-glycidyl methacrylate (Bis-GMA) or triethyleneglycol-dimethacrylate (TEGDMA) among the resin monomers and presence of porous particles among the filler blends. Five commercial composites with different resin matrices and mineral fillers were compared to four experimental composites designed without any BPA-based monomers or TEGDMA. Porous fillers, with or without silanation, were added in some of the experimental composites. Two reference resin matrices were also selected. Cytocompatibility with cultured primary human gingival fibroblasts was assessed by confocal laser scanning microscopy with time-lapse imaging. Fourier transform infrared spectroscopy was used to control monomer conversion rate. Conversion rates of the experimental composites ranged from 57% to 71%, a comparable ratio for dental composites. Experimental samples were better tolerated than tested commercial samples not containing TEGDMA and significantly better than those containing TEGDMA. Experimental composites with porous fillers exhibited good cytocompatibility, especially when surfaces were silanated. Cytotoxicity was associated with resin amount and especially resin nature. Composites containing porous fillers might behave as if the resin trapped into pores has no effect on toxicity. The cytotoxicity of composites with and without BPA derivatives was mainly attributed to the release of residual TEGDMA rather than the BPA derivatives. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The effects of embedded piezoelectric fiber composite sensors on the structural integrity of glass-fiber-epoxy composite laminate

NASA Astrophysics Data System (ADS)

Konka, Hari P.; Wahab, M. A.; Lian, K.

2012-01-01

Piezoelectric fiber composite sensors (PFCSs) made from micro-sized lead zirconate titanate (PZT) fibers have many advantages over the traditional bulk PZT sensors for embedded sensor applications. PFCSs as embedded sensors will be an ideal choice to continuously monitor the stress/strain levels and health conditions of composite structures. PFCSs are highly flexible, easily embeddable, have high compatibility with composite structures, and also provides manufacturing flexibility. This research is focused on examining the effects of embedding PFCS sensors (macro-fiber composite (MFC) and piezoelectric fiber composite (PFC)) on the structural integrity of glass-fiber-epoxy composite laminates. The strengths of composite materials with embedded PFCSs and conventional PZT sensors were compared, and the advantages of PFCS sensors over PZTs were demonstrated. Initially a numerical simulation study is performed to understand the local stress/strain field near the embedded sensor region inside a composite specimen. High stress concentration regions were observed near the embedded sensor corner edge. Using PFCS leads to a reduction of 56% in longitudinal stress concentration and 38% in transverse stress concentration, when compared to using the conventional PZTs as embedded sensors. In-plane tensile, in-plane tension-tension fatigue, and short beam strength tests are performed to evaluate the strengths/behavior of the composite specimens containing embedded PFCS. From the tensile test it is observed that embedding PFCS and PZT sensors in the composite structures leads to a reduction in ultimate strength by 3 and 6% respectively. From the fatigue test results it is concluded that both embedded PFCS and PZT sensors do not have a significant effect on the fatigue behavior of the composite specimens. From the short beam strength test it is found that embedding PFCS and PZT sensors leads to a reduction in shear strength by 7 and 15% respectively. Overall the pure PZT sensors

A comparative study on the effects of ultrathin luminescent graphene oxide quantum dot (GOQD) and graphene oxide (GO) nanosheets on the interfacial interactions and mechanical properties of an epoxy composite.

PubMed

Karimi, B; Ramezanzadeh, B

2017-05-01

The reinforcement effect of graphene oxide nanosheets on the mechanical properties of an epoxy coating has been extensively studied. However, the effect of graphene oxide quantum dot (GOQD) as a new unique carbon based nanomaterial (with lateral dimension of 5-6nm and thickness of one carbon atom) on the mechanical properties of epoxy coating has not been reported and compared with GO yet. So this study aims at fabrication of a high-performance polymer composite with unique mechanical properties using GOQD nanosheets. GO and GOQD were obtained through two different strategies of "top-down" synthesis from an expandable graphite by a modified Hummers' method and an easy "bottom-up" method by carbonizing citric acid, respectively. The morphology, size distribution, microstructure and chemistry of the GO and GOQD were compared by utilizing X-ray diffraction (XRD) analysis, atomic force microscopy (AFM), high resolution-transmission electron microscopy (HR-TEM), high resolution field-emission scanning electron microscopy (FE-SEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). Results obtained from these analyses confirmed successful synthesize of GOQD and GO nanosheets. The reinforcement effect of GO and GOQD nanosheets on the mechanical properties of the epoxy coating was studied by dynamic mechanical thermal analysis (DMTA) and tensile test. It was found that the GOQD could remarkably enhance the energy of break, Young's modulus, tensile stress and interfacial interactions compared to the neat epoxy and the one reinforced with GO nanosheets. GOQD improved the fracture toughness by factor of 175% and 700% compared to the GO/Epoxy and neat epoxy, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

Study of x CNFO + (1-x) PLZT magnetoelectric composites

NASA Astrophysics Data System (ADS)

Dipti, Singh, Sangeeta; Juneja, J. K.; Pant, R. P.; Raina, K. K.; Prakash, Chandra

2014-04-01

In the present paper, we are reporting the studies on structural, dielectric, ferroelectric and magnetic properties of Lanthanum (La) substituted Lead Zirconate Titanate (PZT) and Cobalt Nickel ferrite (CNFO) composites with compositional formula x(Co0.80Ni0.20Fe2O4)+(1-x)(Pb1.01625La0.0025Zr0.55Ti0.45O3) (x = 0.00,0.10). The materials were synthesized by solid state reaction route. XRD analysis confirms the presence of both ferrite and ferroelectric phases. Dielectric properties were studied as a function of frequency and temperature. Ferroelectric P-E and Magnetic M-H hysteresis loops were measured at room temperature.

Comparative Packaging Study

NASA Technical Reports Server (NTRS)

Perchonok, Michele; Antonini, David

2008-01-01

This viewgraph presentation describes a comparative packaging study for use on long duration space missions. The topics include: 1) Purpose; 2) Deliverables; 3) Food Sample Selection; 4) Experimental Design Matrix; 5) Permeation Rate Comparison; and 6) Packaging Material Information.

Natural ageing of EPDM composite insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlastos, A.E.; Sherif, E.

1990-01-01

Long-rod composite insulators, with weather sheds (sheds) made of ethylene propylene rubbers (EPDM), were exposed for many years to HVAC and HVDC under realistic conditions and natural pollution. The change of their properties with time and their aging was studied. The results show that the insulator shed material undergoes a slow degradation process and loses successively its water repelling properties which initially make the EPDM composite insulators superior to inorganic glass and porcelain insulator. The outdoor degradation of the shed material depends on the electric stress, in the environmental factors (such as pollution, rain, salt-laden fog, and UV-radiation from sun)more » and on the materials and fillers used in the construction of the composite insulators. A thorough macro- and microscopic study of the EPDM composite insulator sheds illustrates the differences of the surface state of EPDM insulators of different makes in which different basic material compositions and fillers are used. The poor performance of aged EPDM composite insulators compared to inorganic insulators depends on the design and on environmental factors.« less

Relationships between cognitive function and body composition among community-dwelling older adults: a cross-sectional study.

PubMed

Noh, Hye-Mi; Oh, Sohee; Song, Hong Ji; Lee, Eun Young; Jeong, Jin-Young; Ryu, Ohk-Hyun; Hong, Kyung-Soon; Kim, Dong-Hyun

2017-11-02

Previous studies reported mixed results regarding the association between cognition and body weight in late life. We evaluated the relationships between cognitive function and body composition among community-dwelling older adults. Three hundred twenty subjects (≥65 years, women 53%) with available data of cognitive function and body composition from 2010 Hallym Aging Study. Cognitive function was assessed using Korean Mini-Mental State Examination (K-MMSE). Dual-energy X-ray absorptiometry (DEXA) was used for measuring body composition including body fat and lean body mass. Anthropometric measurements and laboratory data were collected in clinical examination. Body composition variables were divided into sex-specific tertiles, and examined by multivariable logistic regression. Among female, the highest tertile group of fat mass and second tertile group of total lean body mass were associated with lower risk for cognitive impairment compared to the respective first tertile groups (odds ratios, 0.23 and 0.09, respectively; 95% confidence intervals, 0.04-0.88 and 0.01-0.44, respectively) after adjusting for confounding factors. In male, higher arm bone mineral content was associated with lower risk for cognitive impairment, but significance was lost after adjusting for adiponectin, age, and education. Higher fat mass and lean body mass were associated with lower risk of cognitive impairment in older women. These observations suggest that body fat and lean mass later in life might be beneficial for cognition.

Design, Static Analysis And Fabrication Of Composite Joints

NASA Astrophysics Data System (ADS)

Mathiselvan, G.; Gobinath, R.; Yuvaraja, S.; Raja, T.

2017-05-01

The Bonded joints will be having one of the important issues in the composite technology is the repairing of aging in aircraft applications. In these applications and also for joining various composite material parts together, the composite materials fastened together either using adhesives or mechanical fasteners. In this paper, we have carried out design, static analysis of 3-D models and fabrication of the composite joints (bonded, riveted and hybrid). The 3-D model of the composite structure will be fabricated by using the materials such as epoxy resin, glass fibre material and aluminium rivet for preparing the joints. The static analysis was carried out with different joint by using ANSYS software. After fabrication, parametric study was also conducted to compare the performance of the hybrid joint with varying adherent width, adhesive thickness and overlap length. Different joint and its materials tensile test result have compared.

Esthetics and Biocompatibility of Composite Dental Laminates.

PubMed

D'Souza, Dsj; Kumar, M

2010-07-01

Advances in modern dental materials provide patients with a choice of natural looking veneers to provide esthetic restorations. These may be directly fabricated composite resin veneers or indirectly fabricated veneers. This study was carried out to evaluate the clinical effect of new generation indirect veneering composites and to compare them with veneers fabricated from direct composite restorations. The present study was carried out in the Prosthodontics department of a medical college. A total of forty patients requiring restoration of the anterior teeth using composite veneers were selected and either of the two materials was used to fabricate the veneers. Clinical evaluation was done for esthetics and periodontal health. Statistical analysis showed that there were no significant changes to the periodontal health during the period of the study. The evidence obtained from this study indicates that both direct as well as indirect composite materials had clinically acceptable outcomes in terms of restoration of esthetics. Biocompatibility with the periodontal tissues of both materials was also evident by the improvement in oral health indices used in the study.

Comparing MCDA Aggregation Methods in Constructing Composite Indicators Using the Shannon-Spearman Measure

ERIC Educational Resources Information Center

Zhou, P.; Ang, B. W.

2009-01-01

Composite indicators have been increasingly recognized as a useful tool for performance monitoring, benchmarking comparisons and public communication in a wide range of fields. The usefulness of a composite indicator depends heavily on the underlying data aggregation scheme where multiple criteria decision analysis (MCDA) is commonly used. A…

Effect of Salivary pH on Color Stability of Different Flowable Composites - A Prospective In-vitro Study.

PubMed

Batra, Renu; Kataria, Pratik; Kapoor, Sonali

2016-10-01

Scientifically and clinically there has been lot of development in the field of aesthetic dentistry. However, there is limited or restricted information regarding the color stability of flowable composite materials. The aim of this study was to evaluate the spectrophotometric color stability of three different flowable composite materials with respect to three different pH of saliva. The study included 90 different samples. Thirty samples in each composite group; (Group A: G-aenial universal flo; Group B: Z 350 XT flowable; Group C: Esthet x flow). All samples from each group were immersed in distilled water for 24 hours. Total color difference (ΔE) was recorded for each sample. After this 10 samples from each group were respectively immersed in 6.5, 7 and 7.5 pH of artificial saliva. All samples were kept in dark room for seven days and then ΔE for each sample was recorded and was compared to previous recorded ΔE for the same sample. Maximum color change was seen irrespective of material in 6.5 pH of saliva. G-aenial universal flo showed least change irrespective of pH of saliva. Thus, the present study reveals that acidic pH level affects the coloration of composite resins by affecting the surface integrity and as reported in previous studies, various coloring agents in beverages and other dietary components assists the process due to absorption of these coloring substances into the resin matrix.

A field study on the effects of dietary monensin on milk production and milk composition in dairy cows

PubMed Central

Dubuc, Jocelyn; DuTremblay, Denis; Baril, Jean; Bagg, Randy; Brodeur, Marcel; Duffield, Todd; DesCôteaux, Luc

2010-01-01

The objectives of this study were to quantify the effect of 16 ppm of dietary monensin on milk production and composition of dairy cows, and to investigate factors having a potential impact on this effect. Data were generated from a total of 3577 Holstein dairy cows (47 herds) in Quebec enrolled in a herd-level, randomized clinical trial investigating the effects of monensin supplementation. Milk production and composition data were collected from monthly dairy herd improvement (DHI) testing. Monensin increased milk production by 0.9 kg/cow/d in cows under 150 days in milk (DIM) (P < 0.05). Monensin decreased milk fat percentage by 0.18 percentage points during the whole lactation (P < 0.05). This decreasing effect was larger for component-fed cows (P < 0.05) and for cows being fed low levels of dietary physically effective particles (P < 0.05) when compared respectively to cows fed total mixed ration and cows fed high levels of dietary physically effective particles. The results of this study suggest that monensin influences milk production and milk composition of dairy cows, and that diet composition and feeding system influence those effects. PMID:20592825

A comparative study of electrochemical machining process parameters by using GA and Taguchi method

NASA Astrophysics Data System (ADS)

Soni, S. K.; Thomas, B.

2017-11-01

In electrochemical machining quality of machined surface strongly depend on the selection of optimal parameter settings. This work deals with the application of Taguchi method and genetic algorithm using MATLAB to maximize the metal removal rate and minimize the surface roughness and overcut. In this paper a comparative study is presented for drilling of LM6 AL/B4C composites by comparing the significant impact of numerous machining process parameters such as, electrolyte concentration (g/l),machining voltage (v),frequency (hz) on the response parameters (surface roughness, material removal rate and over cut). Taguchi L27 orthogonal array was chosen in Minitab 17 software, for the investigation of experimental results and also multiobjective optimization done by genetic algorithm is employed by using MATLAB. After obtaining optimized results from Taguchi method and genetic algorithm, a comparative results are presented.

Synchronized manufacture of composites knowledge study (SMACKS)

NASA Astrophysics Data System (ADS)

Strickland, B.; Oliver, M.

1990-06-01

The need for a competitive manufacturing knowledge base for the composites industry, encompasses a change from a 'functionally' organized factory to a product-based organization, and has led to major reductions in inventories, manufacturing costs and cycle times. The net effect was that products became more price- and delivery-competitive. It is believed that composite manufacturers have an equal need to improve their competitive edge, particularly as the demand for composite products grows and more manufacturers enter the marketplace. 'SMACKS' has begun to establish these needs and market trends, with a view to establishing the advantages offered to composite manufacturers by synchronized manufacturing methods.

Experimental study of optical fibers influence on composite

NASA Astrophysics Data System (ADS)

Liu, Rong-Mei; Liang, Da-Kai

2010-03-01

Bending strength and elasticity modulus of composite, with and without embedded optical fibers, were experimentally studied. Two kinds of laminates, which were denoted as group 1 and group 2, were fabricated from an orthogonal woven glass/epoxy prepreg. Since the normal stress value becomes the biggest at the surface of a beam, the optical fibers were embedded at the outmost layer and were all along the loading direction. Four types of materials, using each kind of laminated prepreg respectively, were manufactured. The embedded optical fibers for the 4 material types were 0, 10, 30 and 50 respectively. Three-point bending tests were carried out on the produced specimens to study the influence of embedded optical fiber on host composite. The experimental results indicated that the materials in group 2 were more sensitive to the embedded optical fibers.

Composite risers for deep-water offshore technology: Problems and prospects. 1. Metal-composite riser

NASA Astrophysics Data System (ADS)

Beyle, A. I.; Gustafson, C. G.; Kulakov, V. L.; Tarnopol'skii, Yu. M.

1997-09-01

Prospects for the application of advanced composites in the offshore technology of oil production are considered. The use of composites in vertical pipelines-risers seems to be the most efficient. The operating loads are studied and the attendant problems are formulated. A comparative analysis of the characteristics of metal, composite, and metal-composite deep-water risers is presented. A technique is developed for designing multilayered risers, taking into account the action of internal and external pressures, gravity, and the axial tensile force created by tensioners, as well as the residual technological stresses due to the difference in coefficients of thermal expansion, physical-chemical shrinkage, and force winding. Numerical estimations are given for a two-layered riser with an inner metal layer of steel, titanium, or aluminum alloys and a composite layer of glass- or carbon-fiber plastics formed by circumferential winding. It is shown that the technological stresses substantially affect the characteristics of the riser.

Effect of organic solvents compared to sandblasting on the repair bond strength of nanohybrid and nanofilled composite resins.

PubMed

Brum, Rafael Torres; Vieira, Sergio; Freire, Andrea; Mazur, Rui Fernando; De Souza, Evelise Machado; Rached, Rodrigo Nunes

2017-01-01

This study evaluated the effect of different surface treatments on the repair bond strength of nanohybrid (Empress Direct) and nanofilled (Filtek Z350 XT) composite resins. A total of 120 specimens of each material (7.5 x 4.5 x 3 mm) were prepared and polished with SiC paper. Half of the specimens were kept in water for seven days and the other half for six months; they were then divided into six groups according to the type of surface treatment: negative control (no treatment), Al2O3sandblasted, liquid acetone, acetone gel, liquid alcohol and alcohol gel. Following application of the silane coupling agent and the adhesive system, composite resin cylinders were fabricated on the specimens and light cured (20 seconds). The same composite resins were used for the repair. Additionally, ten intact specimens of each composite resin (without repair) were prepared (positive control). The specimens were then loaded to failure in the microshear mode. Three additional specimens were fabricated in each group, and the surface treatments were analyzed by atomic force microscopy, energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The nanofilled composite resin showed higher cohesive strength and repair bond strength than the nanohybrid composite resin. The aging process affected the repair bond strength of the nanofilled composite resin. Al2O3sandblasting was more efficient for the nanofilled composite resin and promoted greater surface roughness in both materials. The solvents demonstrated higher efficacy for the nanohybrid composite resin. The strengths resulting from the solvents were material dependent, and Al2O3sandblasting resulted in superior repair bond strength in both materials.

Comparative studies on cervical and colonic malignancies using FTIR microspectroscopy

NASA Astrophysics Data System (ADS)

Mordechai, Shaul; Mark, Shlomo; Podshyvalov, A.; Kantarovich, Keren; Bernshtain, Y.; Salman, Ahmad; Erukhimovitch, Vitaly; Guterman, Hugo; Goldstein, Jed; Argov, Shmuel; Jagannathan, R.

2003-07-01

IR spectroscopy provides a new diagnostic tool due to its sensitivity to molecular composition and structure in cells, which accompany transformation from healthy to diseased state. The IR spectrum of a sample is, therefore, a biochemical fingerprint. It has been found that the most significant changes occur in the mid-IR spectral range 3-25 mm. Encouraging results have been reported in the literature on various types of cancers, such as human breast, lung, colon, cervical, and leukemia using FT-IR microspectroscopy. Much progress has also been made by several groups on IR spectral maps and IR imaging with good agreement between the data and the histopathological information. In an attempt to characterize healthy and diseased tissues, infrared microspectroscopy of cervical and colon human tissues was studied using an infrared microscopy. The comparative qualitative and quantitative changes detected using FTIR microspectroscopy are discussed.

Changes in urinary stone composition in the Tunisian population: a retrospective study of 1,301 cases.

PubMed

Alaya, Akram; Nouri, Abdellatif; Belgith, Mohsen; Saad, Hammadi; Jouini, Riadh; Najjar, Mohamed Fadhel

2012-05-01

Studies that evaluate the effect of age on stone composition are scarce. The aim of this study was to highlight the changes in epidemiological characteristics (stone composition and location) of urolithiasis according to patients' age. We studied 1,301 urolithiasis patients with age ranging from 6 months to 92 yr (781 males and 520 females). Stone analysis was performed using a stereomicroscope and infrared spectroscopy to determine the morphological type and molecular composition of each stone. The annual average incidence of new stone formation was 31.7 per 100,000 persons. In 71.8% of cases, calculi were located in the upper urinary tract. Compared to other age groups, children and old men were more affected by bladder stones. Calcium oxalate monohydrate was the most frequent stone component, even though its frequency decreased with age (59.5% in young adults and 43.7% in the elderly, P<0.05) in favor of an increase in uric acid stones (11.5% in young adults and 36.4% in the elderly, P<0.05). Struvite stones were rare (3.8%) and more frequent in children than in adults. The analysis of these data showed that urinary stones in Tunisian patients are tending to evolve in the same direction as the stones in patients from industrialized countries.

[Experimental study on loading naringin composite scaffolds for repairing rabbit osteochondral defects].

PubMed

Huang, Junbo; Wang, Shiyong; Zhang, Xiaomin; Li, Gen; Ji, Puzhong; Zhao, Hongbin

2017-04-01

To investigate the performance of loading naringin composite scaffolds and its effects on repair of osteochondral defects. The loading naringin and unloading naringin sustained release microspheres were prepared by W/O/W method; with the materials of the attpulgite and the collagen type I, the loading naringin, unloading naringin, and loading transforming growth factor β 1 (TGF-β 1 ) osteochondral composite scaffolds were constructed respectively by "3 layers sandwich method". The effect of sustained-release of loading naringin microspheres, the morphology of the composite scaffolds, and the biocompatibility were evaluated respectively by releasing in vitro , scanning electron microscope, and cell counting kit 8. Forty Japanese white rabbits were randomly divided into groups A, B, C, and D, 10 rabbits each group. After a osteochondral defect of 4.5 mm in diameter and 4 mm in depth was made in the intercondylar fossa of two femurs. Defect was not repaired in group A (blank control), and defect was repaired with unloading naringin composite scaffolds (negative control group), loading naringin composite scaffolds (experimental group), and loading TGF-β 1 composite scaffolds (positive control group) in groups B, C, and D respectively. At 3 and 6 months after repair, the intercondylar fossa was harvested for the general, HE staining, and toluidine blue staining to observe the repair effect. Western blot was used to detect the expression of collagen type II in the new cartilage. Loading naringin microspheres had good effect of sustained-release; the osteochondral composite scaffolds had good porosity; the cell proliferation rate on loading naringin composite scaffold was increased significantly when compared with unloading naringin scaffold ( P <0.05). General observation revealed that defect range of groups C and D was reduced significantly when compared with groups A and B at 3 months after repair; at 6 months after repair, defects of group C were covered by new

Study of thermal and fire behavior of wood fiber/thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Oladipo, Adedejo Bukola

The fire safety characteristics of wood fiber/thermoplastic composite materials were investigated in this study. Composites comprising wood fiber fillers and polymeric binders are known to offer many advantages such as good strength to weight ratio, ease of manufacture, low cost, and the possibility for recycling. In spite of these advantages however, the fire safety question of plastic-based materials is an important one since they can, under certain conditions, drip or run, under fire, thereby potentially spreading fire from one location to the other. It is important therefore to understand the fire behavior of such a composite if the advantages it offers are to be fully utilized. To this end, numerical and experimental studies of opposed flow flame spread over the composite were conducted with emphasis on the influences of gravity, material thermal property variations, and finite-rate chemistry on the rate of spread. The thermal properties of the composite material, needed for opposed flame spread computations, were first determined using a combination of inverse heat conduction and non-linear parameter estimation procedures. The influences of wood fiber mass fraction and temperature on the effective thermal properties of the composite were established. The means for predicting the effective properties from those of the individual constituents were also examined and the results showed that the composite is close to being isotropic. The experimental and numerical methods used to determine the thermal properties of the composite were also adapted for the investigation of various proprietary automobile sound blanket materials to assess their effectiveness as thermal barriers separating the engine compartment from the passenger cabin. The results of opposed flame spread study over the composite suggests that, for opposed flow velocities lower than about 245 cm/s, finite rate chemistry will dominate the spread process when the oxygen mass fraction is 70% or less

ICAN/PART: Particulate composite analyzer, user's manual and verification studies

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Murthy, Pappu L. N.; Mital, Subodh K.

1996-01-01

A methodology for predicting the equivalent properties and constituent microstresses for particulate matrix composites, based on the micromechanics approach, is developed. These equations are integrated into a computer code developed to predict the equivalent properties and microstresses of fiber reinforced polymer matrix composites to form a new computer code, ICAN/PART. Details of the flowchart, input and output for ICAN/PART are described, along with examples of the input and output. Only the differences between ICAN/PART and the original ICAN code are described in detail, and the user is assumed to be familiar with the structure and usage of the original ICAN code. Detailed verification studies, utilizing dim dimensional finite element and boundary element analyses, are conducted in order to verify that the micromechanics methodology accurately models the mechanics of particulate matrix composites. ne equivalent properties computed by ICAN/PART fall within bounds established by the finite element and boundary element results. Furthermore, constituent microstresses computed by ICAN/PART agree in average sense with results computed using the finite element method. The verification studies indicate that the micromechanics programmed into ICAN/PART do indeed accurately model the mechanics of particulate matrix composites.

Two-year clinical comparison of a flowable-type nano-hybrid composite and a paste-type composite in posterior restoration.

PubMed

Hirata-Tsuchiya, Shizu; Yoshii, Shinji; Ichimaru-Suematsu, Miki; Washio, Ayako; Saito, Noriko; Urata, Mariko; Hanada, Kaori; Morotomi, Takahiko; Kitamura, Chiaki

2017-08-01

The purpose of the present study was to compare the clinical efficacy between a flowable-type nano-hybrid composite and a paste-type composite for posterior restoration. Of 62 posterior teeth in 33 patients (mean age: 34.1 years), 31 were filled with a paste-type composite (Heliomolar [HM] group), and another 31 with a flowable nano-hybrid composite (MI FIL [MI] group). Clinical efficacy was evaluated at 2 years after the restoration. There were no differences for retention, surface texture deterioration, anatomical form change, deterioration of marginal adaptation, and secondary caries, while a statistical difference was found for marginal discoloration, which was significantly greater in the HM group (P < 0.05). Furthermore, color matching in the MI group was superior to that in the HM group immediately after the restoration throughout the study period. The present 2-year clinical evaluation of different composites showed that the flowable nano-hybrid composite could be an effective esthetic material for posterior restoration. © 2016 John Wiley & Sons Australia, Ltd.

A composite study of onset of the Australian summer monsoon

NASA Technical Reports Server (NTRS)

Hendon, Harry H.; Liebmann, Brant

1990-01-01

The circulation changes that accompany an onset (defined as the first occurrence of wet 850-mb westerly winds at Darwin, Australia) of the Australian summer monsoon are documented by a composite study for the years 1957-1987. Composites of atmospheric fields at stations in and about the Australian tropics are constructed relative to the onset data at Darwin. It is shown that the composite onset is dominated by a slow eastward migration of a deep-baroclinic convective circulation displaced south of the equator. This propagating anomaly exhibited many features of the so-called 40-50 day oscillation, including an upper level anticyclone that accompanies the convective anomaly.

Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades

NASA Technical Reports Server (NTRS)

Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

2012-01-01

Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin.

PubMed

Shori, Deepa; Pandey, Swapnil; Kubde, Rajesh; Rathod, Yogesh; Atara, Rahul; Rathi, Shravan

2013-10-01

Fiber posts are widely used for restoration of mutilated teeth that lack adequate coronal tooth structure to retain a core for definitive restoration, bond between the fiber post and composite material depends upon the chemical reaction between the post surface and the resin material used for building up the core. In attempt to maximize the resin bonding with fiber post, different post surface conditioning is advocated. Therefore the purpose of the study is to examine the interfacial strength between fiber post and composite, as core build-up material after different surface treatments of fiber posts. Twenty fiber posts were split into four groups off five each according to different surface treatments viz. Group I-(Negative Control), Group II-Silanization (Positive control), Group III-(37% Phosphoric Acid & Silanization) ,Group IV- (10% Hydrogen Peroxide and Silanization). With the preformed plastic mould, a core of dual cure composite resin around the fiber post having the uniform thickness was created. Tensile bond strength of each specimen was measured under Universal Testing Machine (UTM) at the cross head speed of 3mm/min. The results achieved with 10% Hydrogen peroxide had a marked effect on micro tensile bond strength values between the tested materials. Immense enhancement in the silanization efficiency of quartz fiber phase was observed with different surface chemical treatment of the resin phase of fiber posts with the marked increase in the micro-tensile bond strength between fiber post and composite core. Shori D, Pandey S, Kubde R, Rathod Y, Atara R, Rathi S. To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin. J Int Oral Health 2013; 5(5):27-32.

Structural arrangement trade study. Volume 3: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Addendum

NASA Astrophysics Data System (ADS)

1995-03-01

This volume is the third of a 3 volume set that addresses the structural trade study plan that will identify the most suitable structural configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The most suitable Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Tank System (GCPS) composite materials for intertank, wing and thrust structures are identified. Vehicle resizing charts, selection criteria and back-up charts, parametric costing approach and the finite element method analysis are discussed.

Structural arrangement trade study. Volume 3: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Addendum

NASA Technical Reports Server (NTRS)

1995-01-01

This volume is the third of a 3 volume set that addresses the structural trade study plan that will identify the most suitable structural configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The most suitable Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Tank System (GCPS) composite materials for intertank, wing and thrust structures are identified. Vehicle resizing charts, selection criteria and back-up charts, parametric costing approach and the finite element method analysis are discussed.

Study on the mechanical properties of Cu/LDPE composite IUDs.

PubMed

Tang, Ying; Xia, Xianping; Wang, Yun; Xie, Changsheng

2011-03-01

The copper/low-density polyethylene composite (Cu/LDPE composite) intrauterine devices (IUDs), which can eliminate or lessen the side effects of existing IUDs, have been developed in our laboratory. As a novel type of copper-containing IUDs, it is not clear whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. Therefore, the mechanical properties of the Cu/LDPE composite IUDs have been studied in the present article. The influence of copper particle content and size on the mechanical properties of the Cu/LDPE composite IUDs was analyzed firstly to provide guidance for the material composition design of the Cu/LDPE composite IUDs, and then the BaSO(4)/LDPE composite, which has been applied as a framework of the existing copper-containing IUDs in clinical use for decades, has been used as reference to judge whether the mechanical properties of the Cu/LDPE composite IUDs can meet the need of clinical use or not. However, the mechanical properties of IUDs cannot be characterized directly. Therefore, the mechanical properties of both the Cu/LDPE composite IUDs and the framework of the existing copper-containing IUDs were investigated by means of tensile test using standard tensile samples, and the fracture surface morphology of the tensile samples was characterized by scanning electron microscopy (SEM). Both the elongation at break and the tensile strength decrease with increasing of copper particle content and increase with increasing of the copper particle size, while the elastic modulus shows an opposite tendency. The tensile strength and elastic modulus of both the Cu/LDPE microcomposite IUDs and the Cu/LDPE nanocomposite IUDs with 25 wt.% of copper particles are higher than those of existing copper-containing IUDs (TCu220C; its framework is made of the BaSO(4)/LDPE composite with 20 wt.% of BaSO(4)). The content and size of the copper particles have significant effect on the mechanical properties of Cu

Comparative Evaluation of Impact Strength of Fragment Bonded Teeth and Intact Teeth: An In Vitro Study

PubMed Central

Venugopal, L; Lakshmi, M Narasimha; Babu, Devatha Ashok; Kiran, V Ravi

2014-01-01

Background: To test and compare the impact strength of fragment bonded teeth with that of intact teeth by using impact testing machine (pendulum type) as a mode of load. Materials and Methods: Forty extracted, maxillary, central incisors selected for this study (20 control group and 20 experimental group). In experimental group, teeth crowns were fractured with a microtome at 2.5 mm from mesioincisal angle cervically, fractured portion is attached to original crown portion with 3 M single bond dentin bonding agent and 3 M Z ‘100’, composite resin. Impact strength of fragment bonded teeth and intact teeth tested with impact testing machine and compared. Results: Mean impact strength of fragment bonded teeth (30.76 KJ/M2 ) is not statistically significant deferent from mean impact strength of intact teeth (31.11 KJ/M2 ). Conclusion: Mean impact strength of fragment bonded teeth is not statistically different with that of intact teeth. Hence, after fracture of teeth if it is restored with fragment reattachment by using 3 M single bond dentin bonding agent and 3 M Z ‘100’ composite resin is having impact strength like that of intact teeth. How to cite the article: Venugopal L, Lakshmi MN, Babu DA, Kiran VR. Comparative evaluation of impact strength of fragment bonded teeth and intact teeth: An in vitro study. J Int Oral Health 2014;6(3):73-6. PMID:25083037

Polylactic acid composites incorporating casein functionalized cellulose nanowhiskers

PubMed Central

2013-01-01

Background Polylactic acid (PLA) is considered to be a sustainable alternative to petroleum-based polymers for many applications. Using cellulose fiber to reinforce PLA is of great interest recently due to its complete biodegradability and potential improvement of the mechanical performance. However, the dispersion of hydrophilic cellulose fibers in the hydrophobic polymer matrix is usually poor without using hazardous surfactants. The goal of this study was to develop homogenously dispersed cellulose nanowhisker (CNW) reinforced PLA composites using whole milk casein protein, which is an environmentally compatible dispersant. Results In this study, whole milk casein was chosen as a dispersant in the PLA-CNW system because of its potential to interact with the PLA matrix and cellulose. The affinity of casein to PLA was studied by surface plasmon resonance (SPR) imaging. CNWs were functionalized with casein and used as reinforcements to make PLA composites. Fluorescent staining of CNWs in the PLA matrix was implemented as a novel and simple way to analyze the dispersion of the reinforcements. The dispersion of CNWs in PLA was improved when casein was present. The mechanical properties of the composites were studied experimentally. Compared to pure PLA, the PLA composites had higher Young’s modulus. Casein (CS) functionalized CNW reinforced PLA (PLA-CS-CNW) at 2 wt% filler content maintained higher strain at break compared to normal CNW reinforced PLA (PLA-CNW). The Young’s modulus of PLA-CS-CNW composites was also higher than that of PLA-CNW composites at higher filler content. However, all composites exhibited lower strain at break and tensile strength at high filler content. Conclusions The presence of whole milk casein improved the dispersion of CNWs in the PLA matrix. The improved dispersion of CNWs provided higher modulus of the PLA composites at higher reinforcement loading and maintained the strain and stress at break of the composites at relatively low

Cellular Magnesium Matrix Foam Composites for Mechanical Damping Applications

NASA Astrophysics Data System (ADS)

Shunmugasamy, Vasanth Chakravarthy; Mansoor, Bilal; Gupta, Nikhil

2016-01-01

The damping characteristics of metal alloys and metal matrix composites are relevant to the automotive, aerospace, and marine structures. Use of lightweight materials can help in increasing payload capacity and in decreasing fuel consumption. Lightweight composite materials possessing high damping capabilities that can be designed as structural members can greatly benefit in addressing these needs. In this context, the damping properties of lightweight metals such as aluminum and magnesium and their respective composites have been studied in the existing literature. This review focuses on analyzing the damping properties of aluminum and magnesium alloys and their cellular composites. The damping properties of various lightweight alloys and composites are compared on the basis of their density to understand the potential for weight saving in structural applications. Magnesium alloys are observed to possess better damping properties in comparison to aluminum. However, aluminum matrix syntactic foams reinforced with silicon carbide hollow particles possess a damping capacity and density comparable to magnesium alloy. By using the data presented in the study, composites with specific compositions and properties can be selected for a given application. In addition, the comparison of the results helps in identifying the areas where attention needs to be focused to address the future needs.

A Holistic Landscape Description Reveals That Landscape Configuration Changes More over Time than Composition: Implications for Landscape Ecology Studies

PubMed Central

Mimet, Anne; Pellissier, Vincent; Houet, Thomas; Julliard, Romain; Simon, Laurent

2016-01-01

Background Space-for-time substitution—that is, the assumption that spatial variations of a system can explain and predict the effect of temporal variations—is widely used in ecology. However, it is questionable whether it can validly be used to explain changes in biodiversity over time in response to land-cover changes. Hypothesis Here, we hypothesize that different temporal vs spatial trajectories of landscape composition and configuration may limit space-for-time substitution in landscape ecology. Land-cover conversion changes not just the surface areas given over to particular types of land cover, but also affects isolation, patch size and heterogeneity. This means that a small change in land cover over time may have only minor repercussions on landscape composition but potentially major consequences for landscape configuration. Methods Using land-cover maps of the Paris region for 1982 and 2003, we made a holistic description of the landscape disentangling landscape composition from configuration. After controlling for spatial variations, we analyzed and compared the amplitudes of changes in landscape composition and configuration over time. Results For comparable spatial variations, landscape configuration varied more than twice as much as composition over time. Temporal changes in composition and configuration were not always spatially matched. Significance The fact that landscape composition and configuration do not vary equally in space and time calls into question the use of space-for-time substitution in landscape ecology studies. The instability of landscapes over time appears to be attributable to configurational changes in the main. This may go some way to explaining why the landscape variables that account for changes over time in biodiversity are not the same ones that account for the spatial distribution of biodiversity. PMID:26959363

A comparative study of the metabolic response in rainbow trout and Nile tilapia to changes in dietary macronutrient composition.

PubMed

Figueiredo-Silva, A Cláudia; Saravanan, Subramanian; Schrama, Johan W; Panserat, Stéphane; Kaushik, Sadasivam; Geurden, Inge

2013-03-14

Metabolic mechanisms underlying the divergent response of rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus) to changes in dietary macronutrient composition were assessed. Fish were fed one of four isoenergetic diets having a digestible protein-to-digestible energy (DP:DE) ratio above or below the optimal DP:DE ratio for both species. At each DP:DE ratio, fat was substituted by an isoenergetic amount of digestible starch as the non-protein energy source (NPE). Dietary DP:DE ratio did not affect growth and only slightly lowered protein gains in tilapia. In rainbow trout fed diets with low DP:DE ratios, particularly with starch as the major NPE source, growth and protein utilisation were highly reduced, underlining the importance of NPE source in this species. We also observed species-specific responses of enzymes involved in amino acid catabolism, lipogenesis and gluconeogenesis to dietary factors. Amino acid transdeamination enzyme activities were reduced by a low dietary DP:DE ratio in both species and in tilapia also by the substitution of fat by starch as the NPE source. Such decreased amino acid catabolism at high starch intakes, however, did not lead to improved protein retention. Our data further suggest that a combination of increased lipogenic and decreased gluconeogenic enzyme activities accounts for the better use of carbohydrates and to the improved glycaemia control in tilapia compared with rainbow tront fed starch-enriched diets with low DP:DE ratio.

A Comparative Study on Permanent Mold Cast and Powder Thixoforming 6061 Aluminum Alloy and Sicp/6061Al Composite: Microstructures and Mechanical Properties.

PubMed

Zhang, Xuezheng; Chen, Tijun; Qin, He; Wang, Chong

2016-05-24

Microstructural and mechanical characterization of 10 vol% SiC particles (SiC p ) reinforced 6061 Al-based composite fabricated by powder thixoforming (PTF) was investigated in comparison with the PTF and permanent mold cast (PMC) 6061 monolithic alloys. The results reveal that the microstructure of the PMC alloy consists of coarse and equiaxed α dendrites and interdendritic net-like eutectic phases. However, the microstructure of the PTF composite, similar to that of the PTF alloy, consists of near-spheroidal primary particles and intergranular secondarily solidified structures except SiC p , which are distributed in the secondarily solidified structures. The eutectics amount in the PTF materials is distinctly lower than that in the PMC alloy, and the microstructures of the former materials are quite compact while that of the latter alloy is porous. Therefore, the PTF alloy shows better tensile properties than the PMC alloy. Owing to the existence of the SiC reinforcing particles, the PTF composite attains an ultimate tensile strength and yield strength of 230 MPa and 128 MPa, representing an enhancement of 27.8% and 29.3% than those (180 MPa and 99 MPa) of the PTF alloy. A modified model based on three strengthening mechanisms was proposed to calculate the yield strength of the PTF composite. The obtained theoretical results were quite consistent with the experimental data.

Physical properties of a new sonically placed composite resin restorative material.

PubMed

Ibarra, Emily T; Lien, Wen; Casey, Jeffery; Dixon, Sara A; Vandewalle, Kraig S

2015-01-01

A new nanohybrid composite activated by sonic energy has been recently introduced as a single-step, bulk-fill restorative material. The purpose of this study was to compare the physical properties of this new composite to various other composite restorative materials marketed for posterior or bulk-fill placement. The following physical properties were examined: depth of cure, volumetric shrinkage, flexural strength, flexural modulus, fracture toughness, and percent porosity. A mean and standard deviation were determined per group. One-way ANOVA and Tukey's post hoc tests were performed per property (α = 0.05). Percent porosity was evaluated with a Kruskal-Wallis/Mann-Whitney test (α = 0.005). Significant differences were found between groups (P < 0.001) per test type. Compared to the other composite restorative materials, the new nanohybrid composite showed low shrinkage and percent porosity, moderate fracture toughness and flexural modulus, and high flexural strength. However, it also demonstrated a relatively reduced depth of cure compared to the other composites.

Conceptual Design Studies of Composite AMST

DTIC Science & Technology

1974-10-01

WEIGHT OF THE AIRFRAME THE PROPERTIES OF HIGH -STRENGTH GRAPHITE-EPOXY COMPOSITES (REPRESENTATIVE OF THORNEL 300 FIBERS) WERE USED IN THE APPLICATION...The primary advanced composite material selected was a high -strength graphite-epoxy (Thornel 300/Narmco 5208). Boron-infiltrated aluminum extrusions...Figure Page 25 Trimming Irregular Cutouts in Wing Box Attach Angles ...... 71 26 Hydroforming W-Truss Web Beaded Panels ................ 72 27 Exploded

Multifunctional carbon nano-paper composite

NASA Astrophysics Data System (ADS)

Zhang, Zhichun; Chu, Hetao; Wang, Kuiwen; Liu, Yanjv; Leng, Jinsong

2013-08-01

Carbon Nanotube (CNT), for its excellent mechanical, electrical properties and nano size, large special surface physical property, become the most promising material. But carbon nanotube can still fabricated in micro dimension, and can't be made into macro size, so to the carbon nanotube filled composite can't explore the properties of the CNT. Carbon nano-paper is made of pure CNT, with micro pore, and it turn micro sized CNT into macro shaped membrane. Based on the piezo-resistivity and electrical conductivity of the carbon nano-paper, we used the carbon nano-paper as functional layers fabricate functional composite, and studies its strain sensing, composite material deicing and shape memory polymer (SMP) material electric actuation performance. The results shown that the resin can pregnant the nano paper, and there was good bond for nano paper and composite. The functional composite can monitoring the strain with high sensitivity comparing to foil strain gauge. The functional composite can be heated via the carbon nano paper with low power supply and high heating rate. The composite has good deicing and heat actuation performance to composite material. For the good strain sensing, electric conductivity and self-heating character of the carbon nano-paper composite, it can be used for self sensing, anti lightning strike and deicing of composite materials in aircrafts and wind turbine blades.

Comparative evaluation of microleakage of various retrograde filling materials: An in vitro study.

PubMed

Galhotra, Virat; Sofat, Anjali; Pandit, Inder K; Gambhir, Ramandeep Singh; Srivastava, Nikhil; Gugnani, Neeraj

2013-07-01

The present study is envisaged to evaluate and compare the microleakage of mineral trioxide aggregate (MTA) with commonly used retrograde filling materials, like light-cured composite with dentin-bonding agents, light-cured glass ionomer cement (LC GIC) and resin-modified zinc oxide eugenol. Ninety freshly extracted non-carious single-rooted human anterior teeth were used in the study. They were randomly divided into four experimental groups and two control groups of 15 each. Following the biomechanical preparation, all teeth were obturated and then the apices of the obturated teeth were resected by removing 3 mm of each apex at 90° to the long axis of the tooth with a straight fissure bur in a high-speed air-rotor handpiece with water coolant. A 3-mm-deep root end cavity was prepared and the root end fillings were placed as per the manufacturer's instructions and according to the groups divided. The samples were then immersed in 1% methylene blue at room temperature for 72 h, 96 h and 1 week and the dye penetration was measured. All the four materials used in the study showed some microleakage throughout the experimental period. The sealing ability in terms of microleakage can be summarized as: MTA > Composite resin with dentin bonding agent > LC GIC > Resin modified zinc oxide eugenol.

The Write Stuff: On the Relation between Composition Studies and Psychology.

ERIC Educational Resources Information Center

Vipond, Douglas

Composition studies is a plausible choice for a "potentially liberating influence" for psychology, because it offers a useful place from which to think about and critique the writing practices of the psychology discipline. One area in which psychology can learn from composition is audience. Writing guides for psychologists tend to speak…

Advanced Design Composite Aircraft (ADCA) Study. Volume I

DTIC Science & Technology

1976-11-01

Aluminum Machined Paits 008 ’— Aluminum Honeycomb 001 - - Steel Machined Parts 0.08 - Titanium 0 66 Fiberglass 1 18 _ Boron Composite 0...Honeycomb 001 ~ Steel Machined Parti 0 09 | Titanium 056 Fi bei glass 037 r i Boron Composite 0 Graphite Composite 6 36 Total 81 2 31 7 42 1...1 Aluminum Machined Parts 006 - 2 1 Aluminum Honeycomb 001 Steel Machined Parts 007 - Trtamum 001 1 Frberglass 029 - Boron Composite 0

Study of nano mechanical properties polydimethylsiloxane (PDMS)/MWCNT composites

NASA Astrophysics Data System (ADS)

Murudkar, Vrishali; Gaonkar, Amita; Deshpande, V. D.; Mhaske, S. T.

2018-05-01

Polydimethylsiloxane (PDMS), a clear elastomer, is a common material used in many applications; but has poor mechanical properties. Carbon nano tubes (CNT) exhibit excellent mechanical properties & hence are used as filler in PDMS. It was found that the elastic modulus and strength of the PDMS/MWCNT nano composites were enhanced by adding MWCNT [1]. Through the nano indentation experiment, the hardness (H), the elastic modulus (E), and other mechanical properties can be determined from very small volumes of materials [2]; hence nano indentation is widely used to study mechanical properties. PDMS/MWCNT composites have enhanced mechanical properties over neat PDMS. FTIR analysis shows bonding between MWCNT and PDMS; which affects the mechanical properties. From AFM study it shows decreasing roughness for increasing MWCNT concentration. Surface morphology (SEM) study shows well dispersion of MWCNT into PDMS matrix.

Comparative study of the physical properties of core materials.

PubMed

Saygili, Gülbin; Mahmali, Sevil M

2002-08-01

This study was undertaken to measure physical properties of materials used for direct core buildups, including high-copper amalgam, visible light-cured resin composite, autocured titanium-containing composite, polyacid-modified composite, resin-modified glass-ionomer, and silver cermet cement. Compressive strength, diametral tensile strength, and flexural strength of six core materials of various material classes were measured for each material as a function of time up to 3 months at different storage conditions, using a standard specification test designed for the materials. Three different storage conditions (dry, humid, wet) at 37 degrees C were chosen. Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive, diametral tensile, and flexural strengths with associated standard deviations were calculated for each material. Multiple comparison and Newman-Keuls tests discerned many differences among materials. All materials were found to meet the minimum specification requirements, except in terms of flexural strength for amalgam after 1 hour and the silver cermet at all time intervals.

Development of Novel Warfarin-Silica Composite for Controlled Drug Release.

PubMed

Parfenyuk, Elena V; Dolinina, Ekaterina S

2017-04-01

The work is devoted to synthesis and study of warfarin composites with unmodified, methyl and phenyl modified silica in order to develop controlled release formulation of the anticoagulant. The composites were prepared by two routes, adsorption and sol-gel, and characterized with FTIR spectroscopy, dynamic light scattering and DSC methods. The drug release behavior from the composites in media with pH 1.6, 6.8 and 7.4 was analyzed in vitro. The release kinetics of the warfarin - silica composites prepared by the two routes was compared among each other and with analogous silica composites with water soluble drug molsidomine. The comparative analysis showed that in general the kinetic regularities and mechanisms of release for both drugs are similar and determined by nonuniform distribution of the drugs over the silica matrixes and stability of the matrixes in the studied media for the adsorbed composites and uniformly distributed drug and more brittle structure for the sol-gel composites. The sol-gel composite of warfarin - phenyl modified silica is perspective for further development of novel warfarin formulation with controlled release because it releases warfarin according to zero-order kinetic law with approximately equal rate in the media imitating different segments of gastrointestinal tract.

Comparative analytical study of the selected wine varieties grown in Montenegro.

PubMed

Đorđević, Neda O; Novaković, Miroslav M; Pejin, Boris; Mutić, Jelena J; Vajs, Vlatka E; Pajović, Snežana B; Tešević, Vele V

2017-08-01

Samples of the selected red wine varieties grown in Montenegro (Merlot, Cabernet Sauvignon and Vranac; vintages 2010-2012) were compared according to total phenolic content, anti-DPPH radical activity, phenolic profile and elemental composition. All the samples showed profound anti-DPPH radical activity, due to high content of total phenolic compounds (R = 0.92). The most abundant phenolics were catechin and gallic acid with the highest values recorded for Merlot 2012 (43.22 and 28.65 mg/L, respectively). In addition to this, the content of essential elements including the potentially toxic ones was within healthy (safe) level for all the samples analysed. This study has actually pointed out Merlot wine variety as the best quality one, though all three varieties may be used as safe and health-promoting nutritional products.

Epigenome-wide association studies without the need for cell-type composition.

PubMed

Zou, James; Lippert, Christoph; Heckerman, David; Aryee, Martin; Listgarten, Jennifer

2014-03-01

In epigenome-wide association studies, cell-type composition often differs between cases and controls, yielding associations that simply tag cell type rather than reveal fundamental biology. Current solutions require actual or estimated cell-type composition--information not easily obtainable for many samples of interest. We propose a method, FaST-LMM-EWASher, that automatically corrects for cell-type composition without the need for explicit knowledge of it, and then validate our method by comparison with the state-of-the-art approach. Corresponding software is available from http://www.microsoft.com/science/.

Numerical Study on Density Gradient Carbon-Carbon Composite for Vertical Launching System

NASA Astrophysics Data System (ADS)

Yoon, Jin-Young; Kim, Chun-Gon; Lim, Juhwan

2018-04-01

This study presents new carbon-carbon (C/C) composite that has a density gradient within single material, and estimates its heat conduction performance by a numerical method. To address the high heat conduction of a high-density C/C, which can cause adhesion separation in the steel structures of vertical launching systems, density gradient carbon-carbon (DGCC) composite is proposed due to its exhibiting low thermal conductivity as well as excellent ablative resistance. DGCC is manufactured by hybridizing two different carbonization processes into a single carbon preform. One part exhibits a low density using phenolic resin carbonization to reduce heat conduction, and the other exhibits a high density using thermal gradient-chemical vapor infiltration for excellent ablative resistance. Numerical analysis for DGCC is performed with a heat conduction problem, and internal temperature distributions are estimated by the forward finite difference method. Material properties of the transition density layer, which is inevitably formed during DGCC manufacturing, are assumed to a combination of two density layers for numerical analysis. By comparing numerical results with experimental data, we validate that DGCC exhibits a low thermal conductivity, and it can serve as highly effective ablative material for vertical launching systems.

Study of Near-Stall Flow Behavior in a Modern Transonic Fan with Composite Sweep

NASA Technical Reports Server (NTRS)

Hah, Chunill; Shin, Hyoun-Woo

2011-01-01

Detailed flow behavior in a modern transonic fan with a composite sweep is investigated in this paper. Both unsteady Reynolds-averaged Navier-Stokes (URANS) and Large Eddy Simulation (LES) methods are applied to investigate the flow field over a wide operating range. The calculated flow fields are compared with the data from an array of high-frequency response pressure transducers embedded in the fan casing. The current study shows that a relatively fine computational grid is required to resolve the flow field adequately and to calculate the pressure rise across the fan correctly. The calculated flow field shows detailed flow structure near the fan rotor tip region. Due to the introduction of composite sweep toward the rotor tip, the flow structure at the rotor tip is much more stable compared to that of the conventional blade design. The passage shock stays very close to the leading edge at the rotor tip even at the throttle limit. On the other hand, the passage shock becomes stronger and detaches earlier from the blade passage at the radius where the blade sweep is in the opposite direction. The interaction between the tip clearance vortex and the passage shock becomes intense as the fan operates toward the stall limit, and tip clearance vortex breakdown occurs at near-stall operation. URANS calculates the time-averaged flow field fairly well. Details of measured RMS static pressure are not calculated with sufficient accuracy with URANS. On the other hand, LES calculates details of the measured unsteady flow features in the current transonic fan with composite sweep fairly well and reveals the flow mechanism behind the measured unsteady flow field.

Comparative study of particle structure evolution during water sorption: skim and whole milk powders.

PubMed

Murrieta-Pazos, I; Gaiani, C; Galet, L; Cuq, B; Desobry, S; Scher, J

2011-10-01

Surface composition of dairy powders influences significantly a quantity of functional properties such as rehydration, caking, agglomeration. Nevertheless, the kinetic of water uptake by the powders was never directly related to the structure and the composition of the surface. In this work, the effect of relative humidity on the structural reorganization of two types of dairy powder was studied. The water-powder interaction for industrial whole milk powder, and skim milk powder was studied using dynamic vapor sorption. The water sorption isotherms were fitted with a Brunner-Emmet-Teller model and each stage of the sorption curve was analyzed with a Fickian diffusion. The water content in the monolayer predicted for each powder and the moisture diffusivity calculated were discussed and compared. Concurrently, powders microstructure and powders surface under variable relative humidity were assessed by X-ray photoelectron spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray and atomic force microscopy. A correlation between the data obtained from the sorption isotherms and the modifications of structure allowed us to conclude that powder microstructure and chemical state of the components could play an important role in determining the water diffusivity. Copyright © 2011 Elsevier B.V. All rights reserved.

Water Absorption Behavior of Hemp Hurds Composites

PubMed Central

Stevulova, Nadezda; Cigasova, Julia; Purcz, Pavol; Schwarzova, Ivana; Kacik, Frantisek; Geffert, Anton

2015-01-01

In this paper, water sorption behavior of 28 days hardened composites based on hemp hurds and inorganic binder was studied. Two kinds of absorption tests on dried cube specimens in deionized water bath at laboratory temperature were performed. Short-term (after one hour water immersion) and long-term (up to 180 days) water absorption tests were carried out to study their durability. Short-term water sorption behavior of original hemp hurds composites depends on mean particle length of hemp and on binder nature. The comparative study of long-term water sorption behavior of composites reinforced with original and chemically modified hemp hurds in three reagents confirmed that surface treatment of filler influences sorption process. Based on evaluation of sorption curves using a model for composites based on natural fibers, diffusion of water molecules in composite reinforced with original and chemically modified hemp hurds is anomalous in terms of the Fickian behavior. The most significant decrease in hydrophility of hemp hurds was found in case of hemp hurds modified by NaOH and it relates to change in the chemical composition of hemp hurds, especially to a decrease in average degree of cellulose polymerization as well as hemicellulose content.

Carbon/PEEK composite materials as an alternative for stainless steel/titanium hip prosthesis: a finite element study.

PubMed

Rezaei, Farshid; Hassani, Kamran; Solhjoei, Nosratollah; Karimi, Alireza

2015-12-01

Total hip replacement (THR) has been ranked within the most typical surgical processes in the world. The durability of the prosthesis and loosening of prosthesis are the main concerns that mostly reported after THR surgeries. In THR, the femoral prosthesis can be fixed by either cement or cementless methods in the patient's bones. In both procedures, the stability of the prosthesis in the hosted bone has a key asset in its long-term durability and performance. This study aimed to execute a comparative finite element simulation to assess the load transfer between the prosthesis, which is made of carbon/PEEK composite and stainless steel/titanium, and the femur bone. The mechanical behavior of the cortical bone was assumed as a linear transverse isotropic while the spongy bone was modeled like a linear isotropic material. The implants were made of stainless steel (316L) and titanium alloy as they are common materials for implants. The results showed that the carbon/PEEK composites provide a flatter load transfer from the upper body to the leg compared to the stainless steel/titanium prosthesis. Furthermore, the results showed that the von Mises stress, principal stress, and the strain in the carbon/PEEK composites prosthesis were significantly lower than that made of the stainless steel/titanium. The results also imply that the carbon/PEEK composites can be applied to introduce a new optimum design for femoral prosthesis with adjustable stiffness, which can decrease the stress shielding and interface stress. These findings will help clinicians and biomedical experts to increase their knowledge about the hip replacement.

Comparative study of the synthesis of layered transition metal molybdates

NASA Astrophysics Data System (ADS)

Mitchell, S.; Gómez-Avilés, A.; Gardner, C.; Jones, W.

2010-01-01

Mixed metal oxides (MMOs) prepared by the mild thermal decomposition of layered double hydroxides (LDHs) differ in their reactivity on exposure to aqueous molybdate containing solutions. In this study, we investigate the reactivity of some T-Al containing MMOs ( T=Co, Ni, Cu or Zn) towards the formation of layered transition metal molybdates (LTMs) possessing the general formula AT2(OH)(MoO 4) 2·H 2O, where A=NH 4+, Na + or K +. The phase selectivity of the reaction was studied with respect to the source of molybdate, the ratio of T to Mo and the reaction pH. LTMs were obtained on reaction of Cu-Al and Zn-Al containing MMOs with aqueous solutions of ammonium heptamolybdate. Rehydration of these oxides in the presence of sodium or potassium molybdate yielded a rehydrated LDH phase as the only crystalline product. The LTM products obtained by the rehydration of MMO precursors were compared with LTMs prepared by direct precipitation from the metal salts in order to study the influence of preparative route on their chemical and physical properties. Differences were noted in the composition, morphology and thermal properties of the resulting products.

Defluoridation using biomimetically synthesized nano zirconium chitosan composite: kinetic and equilibrium studies.

PubMed

Prasad, Kumar Suranjit; Amin, Yesha; Selvaraj, Kaliaperumal

2014-07-15

The present study reports a novel approach for synthesis of Zr nanoparticles using aqueous extract of Aloe vera. Resulting nanoparticles were embedded into chitosan biopolymer and termed as CNZr composite. The composite was subjected to detailed adsorption studies for removal of fluoride from aqueous solution. The synthesized Zr nanoparticles showed UV-vis absorption peak at 420nm. TEM result showed the formation of polydispersed, nanoparticles ranging from 18nm to 42nm. SAED and XRD analysis suggested an fcc (face centered cubic) Zr crystallites. EDAX analysis suggested that Zr was an integral component of synthesized nanoparticles. FT-IR study indicated that functional group like NH, CO, CN and CC were involved in particle formation. The adsorption of fluoride on to CNZr composite worked well at pH 7.0, where ∼99% of fluoride was found to be adsorbed on adsorbent. Langmuir isotherm model best fitted the equilibrium data since it presented higher R(2) value than Freundlich model. In comparison to pseudo-first order kinetic model, the pseudo-second order model could explain adsorption kinetic behavior of F(-) onto CNZr composite satisfactorily with a good correlation coefficient. The present study revealed that CNZr composite may work as an effective tool for removal of fluoride from contaminated water. Copyright © 2014 Elsevier B.V. All rights reserved.

Ultrasonic Studies of Composites Undergoing Thermal and Fatigue Loading

NASA Technical Reports Server (NTRS)

Madaras, Eric I.; Winfree, William P.; Johnston, Patrick H.

1997-01-01

New composite materials possess attractive properties for use in advanced aircraft. A necessary requirement for their introduction into aeronautic use is an accurate understanding of their long term aging processes so that proper design criteria can be established. In order to understand those properties, these composites must be exposed to thermal and load cycles that are characteristic of flight conditions. Additionally, airline companies will require nondestructive evaluation (NDE) methods that can be used in the field to assess the condition of these new materials as they age. As part of an effort to obtain the required information about new composites for aviation use, we are performing ultrasonic measurements both in the NDE laboratory and in the materials testing laboratory at NASA. The materials testing laboratory is equipped with environmental chambers mounted on load frames so that composite samples can be exposed to thermal and loading cycles representative of flight protocols. Applying both temperature and load simultaneously will help to highlight temperature and load interactions during the aging of these composite materials. This study reports on our initial ultrasonic attenuation results from thermoset and thermoplastic composite samples. Ultrasonic attenuation measurements have been used reliably to assess the effects of material degradation. For example, recently, researchers have shown that by using frequencies of ultrasound on the order of 24 MHz, they could obtain adequate contrast in the evaluation of thermal degradation in these composites. This paper will present data that shows results at a lower frequency range. In addition, we report results on the frequency dependence of attenuation as the slope of attenuation with respect to frequency, beta = delta alpha (f) / delta f. The slope of attenuation is an attractive parameter since it is quantitative, yet does not require interface corrections like conventional quantitative attenuation

Characterization of human kidney stones using micro-PIXE and RBS: a comparative study between two different populations.

PubMed

Pineda-Vargas, C A; Eisa, M E M; Rodgers, A L

2009-03-01

The micro-PIXE and RBS techniques are used to investigate the matrix as well as the trace elemental composition of calcium-rich human tissues on a microscopic scale. This paper deals with the spatial distribution of trace metals in hard human tissues such as kidney stone concretions, undertaken at the nuclear microprobe (NMP) facility. Relevant information about ion beam techniques used for material characterization will be discussed. Mapping correlation between different trace metals to extract information related to micro-regions composition will be illustrated with an application using proton energies of 1.5 and 3.0 MeV and applied to a comparative study for human kidney stone concretions nucleation region analysis from two different population groups (Sudan and South Africa).

Comparative fatty acid composition of four Sargassum species (Fucales, Phaeophyta)

NASA Astrophysics Data System (ADS)

Wu, Xiang-Chun; Lu, Bao-Ren; Tseng, C. K.

1995-12-01

Fatty acid composition of four Sargassum species from Qingdao and Shidao, Shandong Province was investigated. 16:0 (palmitic acid) was the major saturated fatty acid. C18 and C20 were the main polyunsaturated fatty acids (PUFAs). Arachidonic acid and eicosapentaenoic acid predominated among polyenoic acids in all the algal species examined, except for Sargassum sp. which had low concentration of eicosapentaenoic acid.

[Effect of thermal cycling on the composite- composite repair bond strength].

PubMed

Liu, Chang; Lin, Fei; Yue, Lin

2015-08-01

To evaluate the effect of aging of the composite and the adhesive interface on composite-composite repair bond strength. Methacrylate-based composite resin (Clearfil AP-X, composite A) and silorane-based composite resin (Filtek P90, composite B) and their corresponding adhesive, Clearfil SE Bond (adhesive a) and Filtek P90 System Adhesive (adhesive b), were selected in this study. Twenty-four substrates were prepared from composite A or B separately and divided into three groups, each group had 8 substrates: group one, new composites were adhered to the substrates with the use of adhesive a or b, followed by cutting the blocks into sticks; group two, new composites were adhered to the substrates using adhesive a or b, followed by cutting into sticks and thermal cycling; group three, substrates were thermocycled, then polished and adhered new composites using adhesive a or b, followed by cutting into sticks. Each group had 8 combinations of substrate(A, B)-adhesive(a, b)-repair composite (A, B). Fifteen sticks without flaws in each combination of 3 groups were selected utilizing stereomicroscope. The data were analyzed by independent samples t test. In group two, the microtensile strength(MS) of combinations using adhesive a and composite A or B to repair [A-a-A: (45.0 ± 3.2) MPa, B-a-A: (41.7 ± 3.3) MPa, A-a-B: (28.6 ± 3.9) MPa, B-a-B: (47.7 ± 6.6) MPa], and using adhesive b and composite A to repair [A-b-A: (44.2 ± 4.7) MPa, B-b-A: (38.0 ± 3.2) MPa] decreased significantly compared with corresponding combinations in group 1[A-a-A: (70.7 ± 5.5) MPa, B-a-A: (60.3 ± 5.1) MPa, A-a-B: (44.2 ± 1.6) MPa, B-a-B: (54.1 ± 3.2) MPa, A-b-A: (65.6 ± 7.2) MPa, B-b-A: (59.1 ± 4.1) MPa] (P<0.05). However, there was no significant difference between the MS of combinations using adhesive b and composite B to repair in group one and the MS of combinations in group two (P>0.05). The MS of all combinations in group three decreased significantly (P<0.05). Aging of the

Composite measures for profiling hospitals on bariatric surgery performance

PubMed Central

Dimick, Justin B.; Birkmeyer, Nancy J.; Finks, Jonathan F.; Share, David A.; English, Wayne J.; Carlin, Arthur M.; Birkmeyer, John D.

2014-01-01

Objective We sought to develop a novel composite measure for profiling hospital performance with bariatric surgery. Design, Setting, and Patients Using clinical registry data from the Michigan Bariatric Surgery Collaborative (MBSC), we studied all patients undergoing bariatric surgery from 2008 to 2010. For gastric bypass surgery, we used empirical Bayes techniques to create a composite measure by combining several measures, including serious complications, reoperations, and readmissions; hospital and surgeon volume; and outcomes with other, related procedures. Hospitals were ranked based on 2008-09 and placed in one of 3 groups: 3-star (top third), 2-star (middle third), and 1-star (bottom third). We assessed how well these ratings predicted outcomes in the next year (2010), compared to other widely used measures. Main Outcome Measures Risk-adjusted serious complications. Results Composite measures explained a larger proportion of hospital-level variation in serious complication rates with gastric bypass than other measures. For example, the composite measure explained 89% of the variation compared to only 28% for risk-adjusted complication rates alone. Composite measures also appeared better at predicting future performance compared to individual measures. When ranked on the composite measure, 1-star hospitals (bottom 20%), had 2-fold higher serious complication rates (4.6% vs. 2.4%; OR 2.0; 95% CI, 1.1 to 3.5) compared to 3-star (top 20%) hospitals. Differences in serious complications rates between 1-star and 3-star hospitals were much smaller when hospitals were ranked using serious complications (4.0% vs. 2.7%; OR 1.6; 95% CI, 0.8-2.9) and hospital volume (3.3% vs. 3.2%; OR 0.85; 95% CI, 0.4 to 1.7) Conclusions Composite measures are much better at explaining hospital-level variation in serious complications and predicting future performance than other approaches. In this preliminary study, it appears that such composite measures may be better than existing

Finite element analyses of wood laminated composite poles

Treesearch

Cheng Piao; Todd F. Shupe; R.C. Tang; Chung Y. Hse

2005-01-01

Finite element analyses using ANSYS were conducted on orthotropic, polygonal, wood laminated composite poles subjected to a body force and a concentrated load at the free end. Deflections and stress distributions of small-scale and full-size composite poles were analyzed and compared to the results obtained in an experimental study. The predicted deflection for both...

Study of the proximate and mineral composition of different Nigerian yam chips, flakes and flours.

PubMed

Omohimi, C I; Piccirillo, C; Roriz, M; Ferraro, V; Vasconcelos, M W; Sanni, L O; Tomlins, K; Pintado, M M; Abayomi, L A

2018-01-01

Yam ( Dioscorea spp) is an essential tuber crop for hundreds of millions of people in many African, Asian and South American countries. Considering in particular Southwest Nigeria, chips, flakes and flours are amongst the most common shelf-stable traditionally-processed yam products. This paper reports a systematic study on the proximate (moisture, protein, carbohydrate, fibre, fat, ash and gross energy) and mineral composition of these three food commodities sold in Nigerian markets. Results showed no significant differences in the moisture, crude protein and fibre content of all samples (10.0-12.3, 2.7-4.3 and 1.3-2.0 wt%, respectively). Gross energy was also comparable for all yam derived food items (between 3300 and 3507 kcal/kg), contradicting the common belief that yam flakes have lower nutritional value than chips and flours. Considering the mineral composition, Ca, Mg, P and K were the predominant macronutrients. Micronutrients such as Zn, Co, Mn and Cu were also detected. Significant differences existed between products, and their various sources (markets). Principal component analysis showed a direct correlation between ash content of the samples and the assessed macronutrients, irrespective of the market, or the seller of the commodities. This study confirmed that yam derived food stuffs have an adequate nutritional composition, irrespective of their form and/or origin.

Alternative Smoothing and Scaling Strategies for Weighted Composite Scores

ERIC Educational Resources Information Center

Moses, Tim

2014-01-01

In this study, smoothing and scaling approaches are compared for estimating subscore-to-composite scaling results involving composites computed as rounded and weighted combinations of subscores. The considered smoothing and scaling approaches included those based on raw data, on smoothing the bivariate distribution of the subscores, on smoothing…

Body Composition Measurements of 161-km Ultramarathon Participants

USDA-ARS?s Scientific Manuscript database

This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. Height, mass, and percent body fat from bioimpedence spectroscopy were measured on 72 starters. Correlation analyses were used to compare body characteristics with finish time, ...

Exploring the variability of aerosol particle composition in the Arctic: a study from the springtime ACCACIA campaign

NASA Astrophysics Data System (ADS)

Young, G.; Jones, H. M.; Darbyshire, E.; Baustian, K. J.; McQuaid, J. B.; Bower, K. N.; Connolly, P. J.; Gallagher, M. W.; Choularton, T. W.

2015-10-01

Single-particle compositional analysis of filter samples collected on-board the FAAM BAe-146 aircraft is presented for six flights during the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign (March-April 2013). Scanning electron microscopy was utilised to derive size distributions and size-segregated particle compositions. These data were compared to corresponding data from wing-mounted optical particle counters and reasonable agreement between the calculated number size distributions was found. Significant variability in composition was observed, with differing external and internal mixing identified, between air mass trajectory cases based on HYSPLIT analyses. Dominant particle classes were silicate-based dusts and sea salts, with particles notably rich in K and Ca detected in one case. Source regions varied from the Arctic Ocean and Greenland through to northern Russia and the European continent. Good agreement between the back trajectories was mirrored by comparable compositional trends between samples. Silicate dusts were identified in all cases, and the elemental composition of the dust was consistent for all samples except one. It is hypothesised that long-range, high-altitude transport was primarily responsible for this dust, with likely sources including the Asian arid regions.

Comparative study on polyvinyl chloride film as flexible substrate for preparing free-standing polyaniline-based composite electrodes for supercapacitors.

PubMed

Wang, Hongxing; Liu, Dong; Du, Pengcheng; Wei, Wenli; Wang, Qi; Liu, Peng

2017-11-15

The free-standing polyaniline (PANI)-based composite film electrodes were prepared with polyvinyl chloride (PVC) and the aniline modified PVC (PVC-An) films as flexible substrates for supercapacitors, via facile in-situ chemical oxidative polymerization of aniline, with conventional chemical oxidative polymerization or rapid-mixing chemical oxidative polymerization technique. Owing to the grafting of PANI from the PVC-An film as substrate and the suppression of the secondary growth of the primary PANI particles in the rapid-mixing chemical oxidative polymerization, the PVC-g-PANI-2 composite film with loose surface possessed better comprehensive performance, accompanying the high specific capacitance (645.3F/g at a current density of 1A/g), good rate capacitance (retaining 63.2% of original value at a current density of 10A/g and 52.0% at a scan rate of 100mV/s), good cycle stability (retaining 83.1% after 1000 cycles) and the improved internal resistance. Besides its excellent flexibility, it could retain 61.2% of its original specific capacitance under the stress of 8.66MPa for 1h, demonstrating a good tensile-resistance. Copyright © 2017 Elsevier Inc. All rights reserved.

An effective approach to study the biocompatibility of Fe3O4 nanoparticles, graphene and their nanohybrid composite

NASA Astrophysics Data System (ADS)

Singh, Ashwani Kumar; Singh, Pallavi; Verma, Rajiv Kumar; Yadav, Suresh; Singh, Kedar; Srivastava, Amit

2018-02-01

The present manuscript describes a simple, facile and effective solvothermal route to synthesize Fe3O4 nanoparticles (Fe3O4 NPs), reduced graphene oxide nanosheets (rGO NSs) and Fe3O4/reduced graphene oxide nanohybrid composite (Fe3O4/rGO nanohybrid composite) and subsequently examines their comparative biocompatibilities. The as-obtained Fe3O4 NPs, rGO NSs and Fe3O4/rGO nanohybrid composite have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The XRD studies and scanning electron microscope confirmed the proper phase formation and the surface morphology of the as-synthesized products, respectively. The Raman spectra of Fe3O4 NPs show the strongest peak at 673 cm-1 which can be assigned to A1g peak of bare Fe3O4 NPs and it complements the XRD studies. Furthermore, the increment in the I D/I G ratio in the Fe3O4/rGO nanohybrid composite suggests the creation of defects in graphene sheets due to strain caused by Fe3O4 NPs. The biocompatibility of these samples has been tested using Lung cancer cell line H1299 through MTT assay. The MTT assay reveals that the nanohybrid composite endows more biocompatible and effectiveness than rGO NSs and Fe3O4 NPs individually, as anti-proliferative agent for cancer treatment.

An analytical and experimental study of crack extension in center-notched composites

NASA Technical Reports Server (NTRS)

Beuth, Jack L., Jr.; Herakovich, Carl T.

1987-01-01

The normal stress ratio theory for crack extension in anisotropic materials is studied analytically and experimentally. The theory is applied within a microscopic-level analysis of a single center notch of arbitrary orientation in a unidirectional composite material. The bulk of the analytical work of this study applies an elasticity solution for an infinite plate with a center line to obtain critical stress and crack growth direction predictions. An elasticity solution for an infinite plate with a center elliptical flaw is also used to obtain qualitative predictions of the location of crack initiation on the border of a rounded notch tip. The analytical portion of the study includes the formulation of a new crack growth theory that includes local shear stress. Normal stress ratio theory predictions are obtained for notched unidirectional tensile coupons and unidirectional Iosipescu shear specimens. These predictions are subsequently compared to experimental results.

Surface roughness of composite resins subjected to hydrochloric acid.

PubMed

Roque, Ana Carolina Cabral; Bohner, Lauren Oliveira Lima; de Godoi, Ana Paula Terossi; Colucci, Vivian; Corona, Silmara Aparecida Milori; Catirse, Alma Blásida Concepción Elizaur Benitez

2015-01-01

The purpose of this study was to determine the influence of hydrochloric acid on surface roughness of composite resins subjected to brushing. Sixty samples measuring 2 mm thick x 6 mm diameter were prepared and used as experimental units. The study presented a 3x2 factorial design, in which the factors were composite resin (n=20), at 3 levels: microhybrid composite (Z100), nanofilled composite (FiltekTM Supreme), nanohybrid composite (Ice), and acid challenge (n=10) at 2 levels: absence and presence. Acid challenge was performed by immersion of specimens in hydrochloric acid (pH 1.2) for 1 min, 4 times per day for 7 days. The specimens not subjected to acid challenge were stored in 15 mL of artificial saliva at 37 oC. Afterwards, all specimens were submitted to abrasive challenge by a brushing cycle performed with a 200 g weight at a speed of 356 rpm, totaling 17.8 cycles. Surface roughness measurements (Ra) were performed and analyzed by ANOVA and Tukey test (p≤0.05). Surface roughness values were higher in the presence (1.07±0.24) as compared with the absence of hydrochloric acid (0.72±0.04). Surface roughness values were higher for microhybrid (1.01±0.27) compared with nanofilled (0.68 ±0.09) and nanohybrid (0.48±0.15) composites when the specimens were not subjects to acid challenge. In the presence of hydrochloric acid, microhybrid (1.26±0.28) and nanofilled (1.18±0,30) composites presents higher surface roughness values compared with nanohybrid (0.77±0.15). The hydrochloric acid affected the surface roughness of composite resin subjected to brushing.

Material and structural studies of metal and polymer matrix composites

NASA Technical Reports Server (NTRS)

Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

1972-01-01

The application of fiber composites to aeronautical and space vehicle systems indicates the following: It appears quite probable that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

Experimental Fatigue Study of Composite Patch Repaired Steel Plates with Cracks

NASA Astrophysics Data System (ADS)

Karatzas, Vasileios A.; Kotsidis, Elias A.; Tsouvalis, Nicholas G.

2015-10-01

Cracks are among the most commonly encountered defects in metallic structures operating at sea. Composite patch repairing is a repair method which is gaining popularity as it counters most of the problems faced by conventional renewal repairs. Extensive studies can be found in the literature addressing the efficiency of this novel repair method using techniques which meet higher performance and monitoring standards than these commonly found in naval applications. In this work the efficiency of practices widely used in the ship repair industry for the implementation of composite patch repairing is addressed. To this end, steel plates repaired with composite patches were tested under fatigue loading. The composite patches consisted of carbon fibers in epoxy matrix and were directly laminated to the steel surface using the vacuum infusion method. Two different surface preparation methods, namely grit-blasting and mechanical treatment with the use of a needle gun were studied. In addition, in order to account for the harsh environmental conditions during the operating life of the structure and to study its effect on the repair, two different aging scenarios were considered. Non-destructive evaluation of the patches was performed so as to assess the quality of the repair, and the evolution of debonding during testing.

Osteoinductive composite coatings for flexible intramedullary nails.

PubMed

Bolbasov, E N; Popkov, A V; Popkov, D A; Gorbach, E N; Khlusov, I A; Golovkin, A S; Sinev, A; Bouznik, V M; Tverdokhlebov, S I; Anissimov, Y G

2017-06-01

This work presents composite coatings based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and hydroxyapatite (HA) for flexible intramedullary nails (FIN). The effect of the proportion of VDF-TeFE (100-25% wt.) on physicochemical and biological properties of the composite coatings was investigated. It was shown that a decrease of VDF-TeFE in the coating hinders its crystallization in β and γ forms which have piezoelectric properties. The decrease also reduces an adhesive strength to 9.9±2.4MPa and a relative elongation to 5.9±1.2%, but results in increased osteogenesis. It was demonstrated that the composite coatings with 35% VDF-TeFE has the required combination of physicochemical properties and osteogenic activity. Comparative studies of composite coatings (35% VDF-TeFE) and calcium phosphate coatings produced using micro-arc oxidation, demonstrated comparable results for strength of bonding of these FINs with trabecular bones (~530MPa). It was hypothesized that the high osteoinductive properties of the composite coatings are due to their piezoelectric properties. Copyright © 2017 Elsevier B.V. All rights reserved.

The fixation effect of a silk fibroin-bacterial cellulose composite plate in segmental defects of the zygomatic arch: an experimental study.

PubMed

Lee, Jung Min; Kim, Ji Heui; Lee, Ok Joo; Park, Chan Hum

2013-06-01

Bioresorbable fixation systems have been popular for the treatment of facial fractures. However, their mechanical properties are uncertain and complications have been reported. To overcome these problems, we developed a bioresorbable fixation plate using a composite of silk fibroin and bacterial cellulose (SF-BC) with biodegradability and increased biocompatibility. To investigate the regenerative effect of the bioresorbable SF-BC fixation plate on zygomatic arch defects in rats. In vivo animal study. The SF-BC composite plate had a tensile strength similar to that of a polylactic acid plate and a tight, pore-free microstructure. Bilateral segmental bone defects (2 mm in length) were created in the zygomatic arches of adult rats. One side was fixed with the SF-BC composite plate, and the other side was left without fixation. Academic research laboratory. Fifteen adult Sprague-Dawley rats. Fixation of the zygomatic arch defect with the SF-BC composite plate. Micro-computed tomography and histological evaluation of bone samples. Gross inspection revealed no specific complication. At 1, 2, 4, and 8 postoperative weeks, the zygomatic arches were explored by micro-computed tomography and histological examination. Control sides did not heal completely and showed bony degeneration and necrosis during the 8-week follow-up. However, we observed new bone formation in sides treated with the SF-BC composite plate, and bony defects were completely healed within 8 weeks. The SF-BC composite plate is a potential candidate for a new bioresorbable fixation system. Our composite material could considerably shorten bone regeneration time. Additional study of the control of biodegradability and mechanical properties of SF-BC composite plates and a comparative study with the resorbable plates currently in use should be undertaken.

Food composition database development for between country comparisons.

PubMed

Merchant, Anwar T; Dehghan, Mahshid

2006-01-19

Nutritional assessment by diet analysis is a two-stepped process consisting of evaluation of food consumption, and conversion of food into nutrient intake by using a food composition database, which lists the mean nutritional values for a given food portion. Most reports in the literature focus on minimizing errors in estimation of food consumption but the selection of a specific food composition table used in nutrient estimation is also a source of errors. We are conducting a large prospective study internationally and need to compare diet, assessed by food frequency questionnaires, in a comparable manner between different countries. We have prepared a multi-country food composition database for nutrient estimation in all the countries participating in our study. The nutrient database is primarily based on the USDA food composition database, modified appropriately with reference to local food composition tables, and supplemented with recipes of locally eaten mixed dishes. By doing so we have ensured that the units of measurement, method of selection of foods for testing, and assays used for nutrient estimation are consistent and as current as possible, and yet have taken into account some local variations. Using this common metric for nutrient assessment will reduce differential errors in nutrient estimation and improve the validity of between-country comparisons.

Study on interfacial and mechanical improvement of carbon fiber/epoxy composites by depositing multi-walled carbon nanotubes on fibers

NASA Astrophysics Data System (ADS)

Xiao, Chufan; Tan, Yefa; Wang, Xiaolong; Gao, Li; Wang, Lulu; Qi, Zehao

2018-07-01

To improve the interfacial properties between carbon fiber (CF) and epoxy resin (EP), T300 carbon fibers were coated with multi-walled carbon nanotubes (MWCNTs) using aqueous suspension deposition method. The carbon fiber/epoxy laminated composites were prepared by molding process. The wettability and interfacial properties between MWCNTs deposited carbon fibers (MWCNTs-T300) and EP were studied. The mechanical properties of carbon fiber/epoxy laminated composites were tested, and the mechanism of the interface strengthening was discussed. The results show that the surface energy of T300 carbon fiber is obviously increased after MWCNT deposition. The contact angle between MWCNTs-T300 and EP is reduced, and the interfacial energy and adhesion work are greatly improved. The MWCNTs-T300/EP laminated composites have excellent mechanical properties, the flexural strength is 822 MPa, the tensile strength is 841 MPa, and the interlaminar shear strength (ILSS) is 25.68 MPa, which are increased by 15.1%, 17.6% and 12.6% compared with those of the original carbon fiber/EP laminated composites (original T300/EP) respectively. The MWCNTs-T300/EP composites have good interface bonding performance, low porosity and uniform fiber distribution. Interfacial friction and resin toughening are the main mechanisms for the interface enhancement of MWCNTs-T300/EP composites.

Modulus, strength and thermal exposure studies of FP-Al2O3/aluminum and FP-Al2O3/magnesium composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1981-01-01

The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.

Study of samarium modified lead zirconate titanate and nickel zinc ferrite composite system

NASA Astrophysics Data System (ADS)

Rani, Rekha; Juneja, J. K.; Singh, Sangeeta; Raina, K. K.; Prakash, Chandra

2015-03-01

In the present work, composites of samarium substituted lead zirconate titanate and nickel zinc ferrite with compositional formula 0.95Pb1-3x/2 SmxZr0.65Ti0.35O3-0.05Ni0.8Zn0.2Fe2O4 (x=0, 0.01, 0.02 and 0.03) were prepared by the conventional solid state route. X-ray diffraction analysis was carried out to confirm the coexistence of individual phases. Microstructural study was done by using scanning electron microscope. Dielectric constant and loss were studied as a function of temperature and frequency. To study ferroelectric and magnetic properties of the composite samples, corresponding P-E and M-H hysteresis loops were recorded. Change in magnetic properties of electrically poled composite sample (x=0.02) was studied to confirm the magnetoelectric (ME) coupling. ME coefficient (dE/dH) of the samples (x=0 and 0.02) was measured as a function of DC magnetic field.

Composite resins in 2013: an update on their progress.

PubMed

Radz, Gary M

2013-01-01

Having steadily evolved and improved over the past several decades, composite resins are providing clinicians with an increased array of options for successfully restoring teeth in a minimally invasive manner. Numerous advances compared to early composite resin systems, such as increased shade availability, reduced polymerization shrinkage, and the development of nanoparticles, have enabled composite resins to offer long-term esthetic solutions for patients. This article summarizes the changes that have occurred, discusses popular applications for the use of composite materials, and presents brief case studies demonstrating their capabilities.

Exploring the piezoelectric performance of PZT particulate-epoxy composites loaded in shear

NASA Astrophysics Data System (ADS)

Van Loock, F.; Deutz, D. B.; van der Zwaag, S.; Groen, W. A.

2016-08-01

The active and passive piezoelectric response of lead zirconium titanate (PZT)-epoxy particulate composites loaded in shear is studied using analytical models, a finite element model and by experiments. The response is compared to that of the same composites when loaded in simple tension. Analogously to bulk PZT, particulate PZT-polymer composites loaded in shear show higher piezoelectric charge coefficient (d 15) and energy density figure of merit (FOM15) values compared to simple tension (d 33) and (FOM33). This outcome demonstrates the as-yet barely explored potential of piezoelectric particulate composites for optimal strain energy harvesting when activated in shear.

Sorption Studies and Characterization of As (III) Adsorption over Developed Iron-Biochar Composites from Water.

NASA Astrophysics Data System (ADS)

Singh, P.; Mohan, D.

2016-12-01

Problem related to arsenic occurrence in groundwater has caused severe threat to human health in worldwide. Thus there is an increasing demand to find the chemistry and plausible mechanism of arsenic adsorption while remediating it from water. In present study iron-biochar composites are synthesised using agricultural waste materials. The rice husk iron-biochar composite (RIBC) and wheat husk iron-biochar composite (WIBC) were characterised and utilised for As (III) remediation from aqueous solution. The rice husk (RIBC) and wheat husk (WIBC) iron biochar composites were characterised. XPS, FT-IR, and XRD, were studied to analyse their elemental composition and functional group identification. While SEM, TEM, SEM-EDX were conducted to study their surface chemistry, mineralogy, porosity and crystallinity etc. Batch sorption studies were conducted for both rice husk (RIBC) and wheat husk (WIBC) iron-biochar composites to find sorption efficiency. Maximum As (III) adsorption was achieved in pH range 6-8 for both iron-biochar composites. Kinetic studies were conducted to establish the mechanism of As (III) adsorption at different dose and time. Optimum dose of 2g/L and 1g/L were reported for rice husk (RIBC) and wheat husk (WIBC) iron-biochar composites respectively. Electrostatic forces developed between arsenites and iron hydroxyl surface developed over the surface may have caused the removal of As (III). Significant amount of oxygen containing groups have been revealed through studies. Higher As (III) adsorption capacities were obtained for both iron-biochar composites to measure the amount of surface sites. Furthermore, various adsorption models are used to find the monolayer adsorption capacity. These findings suggest that developed iron-biochar composites may be used to remediate As (III) from contaminated water.

A comparative study of AMF diversity in annual and perennial plant species from semiarid gypsum soils.

NASA Astrophysics Data System (ADS)

Alguacil, M. M.; Torrecillas, E.; Roldán, A.; Díaz, G.; Torres, P.

2012-04-01

The arbuscular mycorrhizal fungi (AMF) communities composition regulate plant interactions and determine the structure of plant communities. In this study we analysed the diversity of AMF in the roots of two perennial gypsophyte plant species, Herniaria fruticosa and Senecio auricula, and an annual herbaceous species, Bromus rubens, growing in a gypsum soil from a semiarid area. The objective was to determine whether perennial and annual host plants support different AMF communities in their roots and whether there are AMF species that might be indicators of specific functional plant roles in these ecosystems. The roots were analysed by nested PCR, cloning, sequencing of the ribosomal DNA small subunit region and phylogenetic analysis. Twenty AMF sequence types, belonging to the Glomus group A, Glomus group B, Diversisporaceae, Acaulosporaceae, Archaeosporaceae and Paraglomeraceae, were identified. Both gypsophyte perennial species had differing compositions of the AMF community and higher diversity when compared with the annual species, showing preferential selection by specific AMF sequences types. B. rubens did not show host specificity, sharing the full composition of its AMF community with both perennial plant species. Seasonal variations in the competitiveness of AM fungi could explain the observed differences in AMF community composition, but this is still a working hypothesis that requires the analysis of further data obtained from a higher number of both annual and perennial plant species in order to be fully tested.

Comparative Studies on Phenolic Composition, Antioxidant, Wound Healing and Cytotoxic Activities of Selected Achillea L. Species Growing in Turkey.

PubMed

Agar, Osman Tuncay; Dikmen, Miris; Ozturk, Nilgun; Yilmaz, Mustafa Abdullah; Temel, Hamdi; Turkmenoglu, Fatma Pinar

2015-09-30

Turkey is one of the most important centers of diversity for the genus Achillea L. in the world. Keeping in mind the immense medicinal importance of phenols, in this study, three species growing in Turkey, A. coarctata Poir. (AC), A. kotschyi Boiss. subsp. kotschyi (AK) and A. lycaonica Boiss. & Heldr. (AL) were evaluated for their phenolic compositions, total phenolic contents (TPC), antioxidant properties, wound healing potencies on NIH-3T3 fibroblasts and cytotoxic effects on MCF-7 human breast cancer cells. Comprehensive LC-MS/MS analysis revealed that AK was distinctively rich in chlorogenic acid, hyperoside, apigenin, hesperidin, rutin, kaempferol and luteolin (2890.6, 987.3, 797.0, 422.5, 188.1, 159.4 and 121.2 µg analyte/g extract, respectively). The findings exhibited a strong correlation between TPC and both free radical scavenging activity and total antioxidant capacity (TAC). Among studied species, the highest TPC (148.00 mg GAE/g extract) and TAC (2.080 UAE), the strongest radical scavenging (EC50 = 32.63 μg/mL), the most prominent wound healing and most abundant cytotoxic activities were observed with AK. The results suggested that AK is a valuable source of flavonoids and chlorogenic acid with important antioxidant, wound healing and cytotoxic activities. These findings warrant further studies to assess the potential of AK as a bioactive source that could be exploited in pharmaceutical, cosmetics and food industries.

Quantification of breast lesion compositions using low-dose spectral mammography: A feasibility study

PubMed Central

Ding, Huanjun; Sennung, David; Cho, Hyo-Min; Molloi, Sabee

2016-01-01

Purpose: The positive predictive power for malignancy can potentially be improved, if the chemical compositions of suspicious breast lesions can be reliably measured in screening mammography. The purpose of this study is to investigate the feasibility of quantifying breast lesion composition, in terms of water and lipid contents, with spectral mammography. Methods: Phantom and tissue samples were imaged with a spectral mammography system based on silicon-strip photon-counting detectors. Dual-energy calibration was performed for material decomposition, using plastic water and adipose-equivalent phantoms as the basis materials. The step wedge calibration phantom consisted of 20 calibration configurations, which ranged from 2 to 8 cm in thickness and from 0% to 100% in plastic water density. A nonlinear rational fitting function was used in dual-energy calibration of the imaging system. Breast lesion phantoms, made from various combinations of plastic water and adipose-equivalent disks, were embedded in a breast mammography phantom with a heterogeneous background pattern. Lesion phantoms with water densities ranging from 0% to 100% were placed at different locations of the heterogeneous background phantom. The water density in the lesion phantoms was measured using dual-energy material decomposition. The thickness and density of the background phantom were varied to test the accuracy of the decomposition technique in different configurations. In addition, an in vitro study was also performed using mixtures of lean and fat bovine tissue of 25%, 50%, and 80% lean weight percentages as the background. Lesions were simulated by using breast lesion phantoms, as well as small bovine tissue samples, composed of carefully weighed lean and fat bovine tissues. The water densities in tissue samples were measured using spectral mammography and compared to measurement using chemical decomposition of the tissue. Results: The thickness of measured and known water contents was

Polylactide-based renewable green composites from agricultural residues and their hybrids.

PubMed

Nyambo, Calistor; Mohanty, Amar K; Misra, Manjusri

2010-06-14

Agricultural natural fibers like jute, kenaf, sisal, flax, and industrial hemp have been extensively studied in green composites. The continuous supply of biofibers in high volumes to automotive part makers has raised concerns. Because extrusion followed by injection molding drastically reduces the aspect ratio of biofibers, the mechanical performance of injection molded agricultural residue and agricultural fiber-based composites are comparable. Here, the use of inexpensive agricultural residues and their hybrids that are 8-10 times cheaper than agricultural fibers is demonstrated to be a better way of getting sustainable materials with better performance. Green renewable composites from polylactide (PLA), agricultural residues (wheat straw, corn stover, soy stalks, and their hybrids) were successfully prepared through twin-screw extrusion, followed by injection molding. The effect on mechanical properties of varying the wheat straw amount from 10 to 40 wt % in PLA-wheat straw composites was studied. Tensile moduli were compared with theoretical calculations from the rule of mixture (ROM). Combination of agricultural residues as hybrids is proved to reduce the supply chain concerns for injection molded green composites. Densities of the green composites were found to be lower than those of conventional glass fiber composites.

Progressive Failure Studies of Composite Panels with and without Cutouts

NASA Technical Reports Server (NTRS)

Jaunky, Navin; Ambur, Damodar R.; Davila, Carlos G.; Hilburger, Mark; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

Progressive failure analyses results are presented for composite panels with and without a cutout and subjected to in-plane shear loading and compression loading well into their postbuckling regime. Ply damage modes such as matrix cracking, fiber-matrix shear, and fiber failure are modeled by degrading the material properties. Results from finite element analyses are compared with experimental data. Good agreement between experimental data and numerical results are observed for most structural configurations when initial geometric imperfections are appropriately modeled.

Progressive Failure Studies of Composite Panels With and Without Cutouts

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Jaunky, Navin; Davila, Carlos G.; Hilburger, Mark

2001-01-01

Progressive failure analyses results are presented for composite panels with and without a cutout and are subjected to in-plane shear loading and compression loading well into their post-buckling regime. Ply damage modes such as matrix cracking, fiber-matrix shear, and fiber failure are modeled by degrading the material properties. Results from finite element analyses are compared with experimental data. Good agreement between experimental data and numerical results are observed for most structural configurations when initial geometric imperfections are appropriately modeled.

A composite system approach to aircraft cabin fire safety

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A.; Gilwee, W. J., Jr.; Lerner, N. R.; Hilado, C. J.; Labossiere, L. A.; Hsu, M.-T.

1976-01-01

The thermochemical and flammability characteristics of two polymeric composites currently in use and seven others being considered for use as aircraft interior panels are described. The properties studied included: (1) limiting oxygen index of the composite constituents; (2) fire containment capability of the composite; (3) smoke evolution from the composite; (4) thermogravimetric analysis; (5) composition of the volatile products of thermal degradation; and (6) relative toxicity of the volatile products of pyrolysis. The performance of high-temperature laminating resins such as bismaleimides is compared with the performance of phenolics and epoxies. The relationship of increased fire safety with the use of polymers with high anaerobic char yield is shown. Processing parameters of one of the bismaleimide composites is detailed.

A composite system approach to aircraft cabin fire safety

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A.; Gilwee, W. J., Jr.; Lerner, N. R.; Hilado, C. J.; Labossiere, L. A.; Hsu, M. T. S.

1976-01-01

The thermochemical and flammability characteristics of two polymeric composites currently in use and seven others being considered for use as aircraft interior panels are described. The properties studied included: (1) limiting oxygen index of the composite constituents; (2) fire containment capability of the composite; (3) smoke evolution from the composite; (4) thermogravimetric analysis; (5) composition of the volatile products of thermal degradation; and (6) relative toxicity of the volatile products of pyrolysis. The performance of high temperature laminating resins such as bismaleimides is compared with the performance of phenolics and epoxies. The relationship of increased fire safety with the use of polymers with high anaerobic char yield is shown. Processing parameters of one of the baremaleimide composites are detailed.

Changes in Composition of the Mixed Mesophytic Forest: Effects of Succession and Disturbance

Treesearch

Jim Steinman

1999-01-01

This study investigated the hypothesis that air pollution is causing mortality of the larger overstory trees, which results in a shift in species composition. To determine if the theorized shifts in species composition have occurred, this study compared historical changes in forest composition as described by Braun (1940) with more recent changes as quantified by the...

Isotopic composition of atmospheric moisture from pan water evaporation measurements.

PubMed

Devi, Pooja; Jain, Ashok Kumar; Rao, M Someshwer; Kumar, Bhishm

2015-01-01

A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability.

Comparative study of the chemical composition of essential oils of five Tagetes species collected in Venezuela.

PubMed

Armas, Kaylin; Rojas, Janne; Rojas, Luis; Morales, Antonio

2012-09-01

The leaves and inflorescences of five species of Tagetes, family Asteraceae, were collected from different locations in Mérida state, Venezuela, and their essential oils analyzed by GC and GC/MS. Several differences were observed in the composition of these oils, mainly regarding the major components, which for T. caracasana were trans-ocimenone (64.3%) and cis-tagetone (13.7%), and for T. erecta, piperitone (35.9%) and terpinolene (22.2%). High amounts of trans-anethole (87.5%) and estragole (10.7%) were observed in T. filifolia, while T. subulata essential oil contained terpinolene (26.0%), piperitenone (13.1%) and limonene (10.8%). For T. patula, two different oil samples were analyzed, leaves (TPL) and inflorescences (TPI). The TPL oil showed terpinolene (20.9%) and piperitenone (14.0%) as main components, while the TPI sample was composed mainly of beta-caryophyllene (23.7%), terpinolene (15.6%) and cis-beta-ocimene (15.5%).

Study on the electromagnetic properties of mwcnts/gf/epoxy composites

NASA Astrophysics Data System (ADS)

Yan, Zhao; Lu, Yuan; Duan, Yuexin

2007-07-01

In this paper, multiwalled carbon nanotubes (MWCNTs)/GF/epoxy composites were prepared by utilizing fabric of fiberglass to divisionalize the MWCNTs because MWCNTs are very difficult to disperse. Then the electromagnetic properties of MWCNTs/GF/epoxy composites with different contents of MWCNTs and the same layers of fiberglass or with same content of MWCNTs and different layers of fiberglass were studied respectively in electromagnetic wave band (8.2~12.4GHz). The results show that the dielectric property of MWCNTs/GF/epoxy composites can be improved along with increasing the content of MWCNTs while the magnetic conductivity is stay around the level of one (μ=1). Although the dielectric property is affected by the layers of fiberglass, it is not monotonic increasing or decreasing. Moreover, the number of ply does not impact the magnetic conductivity. Actually the real part value of the magnetic conductivity of MWCNTs/GF/epoxy composites is close to one (μ'=1) while the imaginary part is close to zero (μ"=0), and the value of them is unvariable in the whole electromagnetic wave band (8.2~12.4GHz).

Comparative Proteomic and Nutritional Composition Analysis of Independent Transgenic Pigeon Pea Seeds Harboring cry1AcF and cry2Aa Genes and Their Nontransgenic Counterparts.

PubMed

Mishra, Pragya; Singh, Shweta; Rathinam, Maniraj; Nandiganti, Muralimohan; Ram Kumar, Nikhil; Thangaraj, Arulprakash; Thimmegowda, Vinutha; Krishnan, Veda; Mishra, Vagish; Jain, Neha; Rai, Vandna; Pattanayak, Debasis; Sreevathsa, Rohini

2017-02-22

Safety assessment of genetically modified plants is an important aspect prior to deregulation. Demonstration of substantial equivalence of the transgenics compared to their nontransgenic counterparts can be performed using different techniques at various molecular levels. The present study is a first-ever comprehensive evaluation of pigeon pea transgenics harboring two independent cry genes, cry2Aa and cry1AcF. The absence of unintended effects in the transgenic seed components was demonstrated by proteome and nutritional composition profiling. Analysis revealed that no significant differences were found in the various nutritional compositional analyses performed. Additionally, 2-DGE-based proteome analysis of the transgenic and nontransgenic seed protein revealed that there were no major changes in the protein profile, although a minor fold change in the expression of a few proteins was observed. Furthermore, the study also demonstrated that neither the integration of T-DNA nor the expression of the cry genes resulted in the production of unintended effects in the form of new toxins or allergens.

In vivo experimental study on bone regeneration in critical bone defects using PIB nanogels/boron-containing mesoporous bioactive glass composite scaffold

PubMed Central

Chen, Xiaohui; Zhao, Yanbing; Geng, Shinan; Miron, Richard J; Zhang, Qiao; Wu, Chengtie; Zhang, Yufeng

2015-01-01

Purpose In the present study, the fabrication of novel p(N-isopropylacrylamide-co-butyl methylacrylate) (PIB) nanogels was combined with boron-containing mesoporous bioactive glass (B-MBG) scaffolds in order to improve the mechanical properties of PIB nanogels alone. Scaffolds were tested for mechanical strength and the ability to promote new bone formation in vivo. Patients and methods To evaluate the potential of each scaffold in bone regeneration, ovariectomized rats were chosen as a study model to determine the ability of PIB nanogels to stimulate bone formation in a complicated anatomical bone defect. PIB nanogels and PIB nanogels/B-MBG composites were respectively implanted into ovariectomized rats with critical-sized femur defects following treatment periods of 2, 4, and 8 weeks post-implantation. Results Results from the present study demonstrate that PIB nanogels/B-MBG composites showed greater improvement in mechanical strength when compared to PIB nanogels alone. In vivo, hematoxylin and eosin staining revealed significantly more newly formed bone in defects containing PIB nanogels/B-MBG composite scaffolds when compared to PIB nanogels alone. Tartrate-resistant acid phosphatase-positive staining demonstrated that both scaffolds were degraded over time and bone remodeling occurred in the surrounding bone defect as early as 4 weeks post-implantation. Conclusion The results from the present study indicate that PIB nanogels are a potential bone tissue engineering biomaterial able to treat defects of irregular shapes and deformities as an injectable, thermoresponsive, biocompatible hydrogel which undergoes rapid thermal gelation once body temperature is reached. Furthermore, its combination with B-MBG scaffolds improves the mechanical properties and ability to promote new bone formation when compared to PIB nanogels alone. PMID:25653525

In vivo experimental study on bone regeneration in critical bone defects using PIB nanogels/boron-containing mesoporous bioactive glass composite scaffold.

PubMed

Chen, Xiaohui; Zhao, Yanbing; Geng, Shinan; Miron, Richard J; Zhang, Qiao; Wu, Chengtie; Zhang, Yufeng

2015-01-01

In the present study, the fabrication of novel p(N-isopropylacrylamide-co-butyl methylacrylate) (PIB) nanogels was combined with boron-containing mesoporous bioactive glass (B-MBG) scaffolds in order to improve the mechanical properties of PIB nanogels alone. Scaffolds were tested for mechanical strength and the ability to promote new bone formation in vivo. To evaluate the potential of each scaffold in bone regeneration, ovariectomized rats were chosen as a study model to determine the ability of PIB nanogels to stimulate bone formation in a complicated anatomical bone defect. PIB nanogels and PIB nanogels/B-MBG composites were respectively implanted into ovariectomized rats with critical-sized femur defects following treatment periods of 2, 4, and 8 weeks post-implantation. Results from the present study demonstrate that PIB nanogels/B-MBG composites showed greater improvement in mechanical strength when compared to PIB nanogels alone. In vivo, hematoxylin and eosin staining revealed significantly more newly formed bone in defects containing PIB nanogels/B-MBG composite scaffolds when compared to PIB nanogels alone. Tartrate-resistant acid phosphatase-positive staining demonstrated that both scaffolds were degraded over time and bone remodeling occurred in the surrounding bone defect as early as 4 weeks post-implantation. The results from the present study indicate that PIB nanogels are a potential bone tissue engineering biomaterial able to treat defects of irregular shapes and deformities as an injectable, thermoresponsive, biocompatible hydrogel which undergoes rapid thermal gelation once body temperature is reached. Furthermore, its combination with B-MBG scaffolds improves the mechanical properties and ability to promote new bone formation when compared to PIB nanogels alone.

Permeability and flammability study of composite sandwich structures for cryogenic applications

NASA Astrophysics Data System (ADS)

Bubacz, Monika

Fiber reinforced plastics offer advantageous specific strength and stiffness compared to metals and has been identified as candidates for the reusable space transportation systems primary structures including cryogenic tanks. A number of carbon and aramid fiber reinforced plastics have been considered for the liquid hydrogen tanks. Materials selection is based upon mechanical properties and containment performance (long and short term) and upon manufacturing considerations. The liquid hydrogen tank carries shear, torque, end load, and bending moment due to gusts, maneuver, take-off, landing, lift, drag, and fuel sloshing. The tank is pressurized to about 1.5 atmosphere (14.6psi or 0.1 MPa) differential pressure and on ascent maintains the liquid hydrogen at a temperature of 20K. The objective of the research effort into lay the foundation for developing the technology required for reliable prediction of the effects of various design, manufacturing, and service parameters on the susceptibility of composite tanks to develop excessive permeability to cryogenic fuels. Efforts will be expended on developing the materials and structural concepts for the cryogenic tanks that can meet the functional requirements. This will include consideration for double wall composite sandwich structures, with inner wall to meet the cryogenic requirements. The structure will incorporate nanoparticles for properties modifications and developing barriers. The main effort will be extended to tank wall's internal skin design. The main requirements for internal composite stack are: (1) introduction of barrier film (e.g. honeycomb material paper sheet) to reduce the wall permeability to hydrogen, (2) introduction of nanoparticles into laminate resin to prevent micro-cracking or crack propagation. There is a need to characterize and analyze composite sandwich structural damage due to burning and explosion. Better understanding of the flammability and blast resistance of the composite structures

The Role of Edited Collections in Composition Studies.

ERIC Educational Resources Information Center

Micciche, Laura

2001-01-01

Describes general characteristics of edited collections and then offers a brief history of the genre in composition studies based in part on the existing data in CompPile, an online and ongoing bibliography. Explores several explanations for the proliferation of edited collections in the field. Makes note of what these explanations can say about…

The Underdog Disciplines: Comics Studies and Composition and Rhetoric

ERIC Educational Resources Information Center

Kirtley, Susan

2015-01-01

This report discusses the answer to the question: What might comic studies learn from the slightly older field of composition and rhetoric? The author asks the question as a member of both fields. It is clear that both disciplines struggle for legitimacy within the academy. While comics studies strives for respectability given the popular nature…

The Impact of Simulated Nature on Patient Outcomes: A Study of Photographic Sky Compositions.

PubMed

Pati, Debajyoti; Freier, Patricia; O'Boyle, Michael; Amor, Cherif; Valipoor, Shabboo

2016-01-01

To examine whether incorporation of simulated nature, in the form of ceiling mounted photographic sky compositions, influences patient outcomes. Previous studies have shown that most forms of nature exposure have a positive influence on patients. However, earlier studies have mostly focused on wall-hung nature representations. The emergence of simulated nature products has raised the question regarding the effects of the new product on patient outcomes. A between-subject experimental design was adopted, where outcomes from five inpatient rooms with sky composition ceiling fixture were compared to corresponding outcomes in five identical rooms without the intervention. Data were collected from a total of 181 subjects on 11 outcomes. Independent sample tests were performed to identify differences in mean outcomes. Significant positive outcomes were observed in environmental satisfaction and diastolic blood pressure (BP). Environmental satisfaction in the experimental group was 12.4% higher than the control group. Direction of association for diastolic BP, nausea/indigestion medication, acute stress, anxiety, pain, and environmental satisfaction were consistent with a priori hypothesis. A post hoc exploratory assessment involving patients who did not self-request additional pain and sleep medication demonstrated confirmatory directions for all outcomes except Systolic BP, and statistically significant outcomes for Acute Stress and Anxiety-Acute Stress and Anxiety levels of the experimental group subjects was 53.4% and 34.79% lower, respectively, than that of the control group subjects. Salutogenic benefits of photographic sky compositions render them better than traditional ceiling tiles and offer an alternative to other nature interventions. © The Author(s) 2015.

Study on Fatigue Performance of Composite Bolted Joints with Bolt-Hole Delamination

NASA Astrophysics Data System (ADS)

Liu, M. J.; Yu, S.; Zhao, Q. Y.

2018-03-01

Fatigue performance of composite structure with imperfections is a challenging subject at present. Based on cohesive zone method and multi-continuum theory, delamination evolution response and fatigue life prediction of a 3D composite single-lap joint with a bolt-hole have been investigated through computer codes Abaqus and Fe-safe. Results from the comparison of a perfect composite bolted joint with another defect one indicates that a relatively small delamination damage around the bolt hole brings about significant degradation of local material performance. More notably, fatigue life of stress concentration region of composite bolted joints is highly sensitive to external loads, as an increase of 67% cyclic load amplitude leads to an decrease of 99.5% local fatigue life in this study. However, the numerical strategy for solving composite fatigue problems is meaningful to engineering works.

Mechanical and Morphological Study of Synthesized PMMA/CaCO3 Nano composites

NASA Astrophysics Data System (ADS)

Alam Md., Azad; Arif, Sajjad; Ansari, Akhter H.

2017-08-01

In this study, Nano-composites have been synthesized in which PMMA is the matrix material and calcium carbonate nanoparticles as the filler by In-situ polymerization reaction. Nano-CaCO3 added during polymerization and the quantity of nano-CaCO3 varied as 0.2, 0.4 and 0.6 wt. % of monomer quantity. The Nano-composites were prepared at three distinct stirring speeds 600, 800, 1000 rpm in order to observe the property with respect to stirring speeds. XRD gram depicts that the presence of nano-CaCO3 has given crystalline nature to Nano-composites. The effects of different concentrations of nano-CaCO3 loading on PMMA morphology were studied by using scanning electron microscope (SEM). The mechanical property is increasing with the stirring speed and concentration. Relative to neat PMMA a 62% increase in impact strength were observed in PMMA based Nano-composites using 0.6 wt.% nano-CaCO3.

Functional Cementitious Composites for Pyroelectric Applications

NASA Astrophysics Data System (ADS)

Srikanth, K. S.; Patel, Satyanarayan; Vaish, Rahul

2018-04-01

We have synthesized Ba0.85Ca0.15Zr0.10Ti0.88Sn0.02O3 (BCZT-Sn)-cement composites. They were prepared as BCZT-Sn to cement ratios of 90-10% and 85-15% by weight. The larger fraction of BCZT-Sn ceramic was used to minimize the losses in the composites. The open circuit voltage was found to be 0.75 V, 0.56 V and 0.4 V for pure, 10% and 15% cement composites, respectively. The voltage and current were also measured across resistances of 1 and 3 MΩ, and the obtained voltages were lower for composites compared to pure BCZT-Sn. Nonetheless, they remain promising candidates over traditional pyroelectric materials for device applications owing to their advantages, such as (1) these composites can be made without any sintering process and (2) they can be made in any shape and size. We also studied relative permittivity, which influences performance of pyroelectric devices.

Impact damage in filament wound composite bottles

NASA Technical Reports Server (NTRS)

Highsmith, Alton L.

1993-01-01

Increasingly, composite materials are being used in advanced structural applications because of the significant weight savings they offer when compared to more traditional engineering materials. The higher cost of composites must be offset by the increased performance that results from reduced structural weight if these new materials are to be used effectively. At present, there is considerable interest in fabricating solid rocket motor cases out of composite materials, and capitalizing on the reduced structural weight to increase rocket performance. However, one of the difficulties that arises when composite materials are used is that composites can develop significant amounts of internal damage during low velocity impacts. Such low velocity impacts may be encountered in routine handling of a structural component like a rocket motor case. The ability to assess the reduction in structural integrity of composite motor cases that experience accidental impacts is essential if composite rocket motor cases are to be certified for manned flight. While experimental studies of the post-impact performance of filament wound composite motor cases haven been proven performed (2,3), scaling impact data from small specimens to full scale structures has proven difficult. If such a scaling methodology is to be achieved, an increased understanding of the damage processes which influence residual strength is required. The study described herein was part of an ongoing investigation of damage development and reduction of tensile strength in filament wound composites subjected to low velocity impacts. The present study, which focused on documenting the damage that develops in filament wound composites as a result of such impacts, included two distinct tasks. The first task was to experimentally assess impact damage in small, filament wound pressure bottles using x-ray radiography. The second task was to study the feasibility of using digital image processing techniques to assist in

A study on effect of ATH on Euphorbia coagulum modified polyester banana fiber composite

NASA Astrophysics Data System (ADS)

Kumari, Sanju; Rai, Bhuvneshwar; Kumar, Gulshan

2018-02-01

Fiber reinforced polymer composites are used for building and structural applications due to their high strength. In conventional composites both the binder and the reinforcing fibers are synthetic or either one of the material is natural. In the present study coagulum of Euphorbia royleana has been used for replacing polyester resinas binder in polyester banana composite. Euphorbia coagulum (driedlatex) is rich in resinous mass (60-80%), which are terpenes and polyisoprene (10-20%). Effect of varying percentage of coagulum content on various physico-mechanical properties of polyester-banana composites has been studied. Since banana fiber is sensitive to water due to presence of polar group, banana composite undergoes delamination and deterioration under humid condition. Alkali treated banana fiber along with coagulum content has improved overall mechanical properties and reduction in water absorption. The best physico-mechanical properties have been achieved on replacing 40% of polyester resin by coagulum. An increase of 50% in bending strength, 30% bending modulus and 45% impact strength as well as 68% decrease in water absorption was observed. Incorporation of 20% ATH as flame retardant in coagulum modified banana polyester composite enhanced limiting oxygen index from 20.6 to 26.8% and smoke density reduced up to 40%. This study presents the possibility of utilization of renewable materials for environmental friendly composite development as well as to find out alternative feedstock for petroleum products. Developed Euphorbia latex modified banana polyester composites can have potential utility in hardboard, partition panel, plywood and automotive etc.

Parametric studies to determine the effect of compliant layers on metal matrix composite systems

NASA Technical Reports Server (NTRS)

Caruso, J. J.; Chamis, C. C.; Brown, H. C.

1990-01-01

Computational simulation studies are conducted to identify compliant layers to reduce matrix stresses which result from the coefficient of thermal expansion mismatch and the large temperature range over which the current metal matrix composites will be used. The present study includes variations of compliant layers and their properties to determine their influence on unidirectional composite and constituent response. Two simulation methods are used for these studies. The first approach is based on a three-dimensional linear finite element analysis of a 9 fiber unidirectional composite system. The second approach is a micromechanics based nonlinear computer code developed to determine the behavior of metal matrix composite system for thermal and mechanical loads. The results show that an effective compliant layer for the SCS 6 (SiC)/Ti-24Al-11Nb (Ti3Al + Nb) and SCS 6 (SiC)/Ti-15V-3Cr-3Sn-3Al (Ti-15-3) composite systems should have modulus 15 percent that of the matrix and a coefficient of thermal expansion of the compliant layer roughly equal to that of the composite system without the CL. The matrix stress in the longitudinal and the transverse tangent (loop) direction are tensile for the Ti3Al + Nb and Ti-15-3 composite systems upon cool down from fabrication. The fiber longitudinal stress is compressive from fabrication cool down. Addition of a recommended compliant layer will result in a reduction in the composite modulus.

Effect of composition ratio on the thermal and physical properties of semicrystalline PLA/PHB-HHx composites.

PubMed

Lim, Jung Seop; Park, Ku-il; Chung, Gun Soo; Kim, Jong Hoon

2013-05-01

In this study, composites of semicrystalline, biodegradable polylactide (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) were prepared by direct melt compounding. The physical and thermal properties of the composites were investigated as a function of the composition ratio. Differential scanning calorimetry analysis indicated that PLA and PHB-HHx formed immiscible composites over the observed range of composition. The crystallization of PLA was gradually suppressed by increasing proportions of PHB-HHx. Dynamic mechanical analysis results confirmed that the innate ductility of PHB-HHX and its inhibiting effect on PLA crystallization improved the stiffness of the composite compared to those of neat PLA. The infrared spectra of the immiscible PLA/PHB-HHx composites at two crystallization temperatures (30 °C, 130 °C) were obtained and presented. At 30 °C, PHB-HHx existed as crystalline domains in the PLA matrix, while, amorphous phase of molten PHB-HHx was diffused within the crystalline phase of PLA at 130 °C. The interaction between PHB-HHX and PLA could not be elucidated from the temperature data. Mechanical tests showed that the addition of PHB-HHx improves ductility of PLA/PHB-HHx composite. Morphological analysis revealed that small proportions of PHB-HHx exhibited less tendency to aggregate, which resulted in greater plastic deformation and improved toughness. From this study, PLA blended with small portions of PHB-HHx may further expand the use of bio-friendly resources in a variety of applications such as flexible films, food packaging and something like that. Copyright © 2013 Elsevier B.V. All rights reserved.

Bioactive composite for keratoprosthesis skirt.

PubMed

Laattala, Kaisa; Huhtinen, Reeta; Puska, Mervi; Arstila, Hanna; Hupa, Leena; Kellomäki, Minna; Vallittu, Pekka K

2011-11-01

In this study, the fabrication and properties of a synthetic keratoprosthesis skirt for use in osteo-odonto-keratoprosthesis (OOKP) surgery are discussed. In the search for a new material concept, bioactive glass and polymethyl methacrylate (PMMA)-based composites were prepared. Three different bioactive glasses (i.e. 45S5, S53P4 and 1-98) and one slowly resorbing glass, FL107, with two different forms (i.e. particles and porous glass structures) were employed in the fabrication of specimens. In in vitro studies, the dissolution behaviour in simulated aqueous humour, compressive properties, and pore formation of the composites were investigated. According to the results, FL107 dissolved very slowly (2.4% of the initial glass content in three weeks); thus, the pore formation of the FL107 composite was also observed to be restricted. The dissolution rates of the bioactive glass-PMMA composites were greater (12%-17%). These faster dissolving bioactive glass particles caused some porosity on the outermost surfaces of the composite. The slight surface porosity was also confirmed by a decrease in compressive properties. During six weeks' in vitro dissolution, the compressive strength of the test specimens containing particles decreased by 22% compared to values in dry conditions (90-107 MPa). These results indicate that the bioactive composites could be stable synthetic candidates for a keratoprosthesis skirt in the treatment of severely damaged or diseased cornea. Copyright © 2011 Elsevier Ltd. All rights reserved.

Thermo-hydroforming of a fiber-reinforced thermoplastic composites considering fiber orientations

NASA Astrophysics Data System (ADS)

Ahn, Hyunchul; Kuuttila, Nicholas Eric; Pourboghrat, Farhang

2018-05-01

The Thermoplastic woven composites were formed using a composite thermal hydroforming process, utilizing heated and pressurized fluid, similar to sheet metal forming. This study focuses on the modification of 300-ton pressure formation and predicts its behavior. Spectra Shield SR-3136 is used in this study and material properties are measured by experiments. The behavior of fiber-reinforced thermoplastic polymer composites (FRTP) was modeled using the Preferred Fiber Orientation (PFO) model and validated by comparing numerical analysis with experimental results. The thermo-hydroforming process has shown good results in the ability to form deep drawn parts with reduced wrinkles. Numerical analysis was performed using the PFO model and implemented as commercial finite element software ABAQUS / Explicit. The user subroutine (VUMAT) was used for the material properties of the thermoplastic composite layer. This model is suitable for working with multiple layers of composite laminates. Model parameters have been updated to work with cohesive zone model to calculate the interfacial properties between each composite layer. The results of the numerical modeling showed a good correlation with the molding experiment on the forming shape. Numerical results were also compared with experimental results on punch force-displacement curves for deformed geometry and forming processes of the composite layer. Overall, the shape of the deformed FRTP, including the distribution of wrinkles, was accurately predicted as shown in this study.

Study on shape recovery speed of SMP, SMP composite, and SMP foam

NASA Astrophysics Data System (ADS)

Wu, Xuelian; Liu, Yanju; Leng, Jinsong

2008-03-01

Shape memory polymer (SMP) receives increasing attention along with its derivants - SMP composite and SMP foam in recent years. In this paper, after fabricating thermoset styrene-based SMP, SMP/carbon black (CB) composite and SMP foam, we studied their shape recovery speed in bending. Different from those reported in the literature, we propose a new approach, i.e., using infrared light, for actuating SMP materials for shape recovery. The results show that SMP, SMP/CB composite and SMP foam can recover to their original shape perfectly in a wide temperature range. Shape recovery speed of SMP composite is not uniform during the overall recovery process, and it is the same trend with SMP but not prominent with SMP foam. Repeatability of shape recovery speed for styrene-based SMP and SMP/CB composite are similarly stable and the former is the better, but it is so worse for SMP foam. Temperature-dependent of shape recovery speed test for styrene-based SMP and SMP/CB composite reveal that higher temperature increases their shape recovery speed.

Out-of-Autoclave Cure Composites

NASA Technical Reports Server (NTRS)

Hayes, Brian S.

2015-01-01

As the size of aerospace composite parts exceeds that of even the largest autoclaves, the development of new out-of-autoclave processes and materials is necessary to ensure quality and performance. Many out-of-autoclave prepreg systems can produce high-quality composites initially; however, due to long layup times, the resin advancement commonly causes high void content and variations in fiber volume. Applied Poleramic, Inc. (API), developed an aerospace-grade benzoxazine matrix composite prepreg material that offers more than a year out-time at ambient conditions and provides exceptionally low void content when out-of-autoclave cured. When compared with aerospace epoxy prepreg systems, API's innovation offers significant improvements in terms of out-time at ambient temperature and the corresponding tack retention. The carbon fiber composites developed with the optimized matrix technology have significantly better mechanical performance in terms of hot-wet retention and compression when compared with aerospace epoxy matrices. These composites also offer an excellent overall balance of properties. This matrix system imparts very low cure shrinkage, low coefficient of thermal expansion, and low density when compared with most aerospace epoxy prepreg materials.

Chemical studies of H chondrites. 6: Antarctic/non-Antarctic compositional differences revisited

NASA Astrophysics Data System (ADS)

Wolf, Stephen F.; Lipschutz, Michael E.

1995-02-01

We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, T1, and In (ordered by putative volatility during nebular condensation and accretion) determined by radiochemical neutron activation analysis of 14 additional H5 and H6 chondrite falls. Data for the 10 most volatile elements (Rb to In) treated by the multivariate techniques of linear discriminant analysis and logistic regression in these and 44 other falls are compared with those of 59 H4-6 chondrites from Antarctica. Various populations are tested by the multivariate techniques, using the previously developed method of randomization-simulation to assess significance levels. An earlier conclusion, based on fewer examples, that H4-6 chondrite falls are compositionally distinguishable from the Antarctic suite is verified by the additional data. This distinctiveness is highly significant because of the presence of samples from Victoria Land in the Antarctic population, which differ compositionally from falls beyond any reasonable doubt. However, it cannot be proven unequivocally that falls and Antarctic samples from Queen Maud Land are compositionally distinguishable. Trivial causes (e.g., analyst bias, weathering) cannot explain the Victoria Land (Antarctic)/non-Antarctic compositional difference for paradigmatic H4-6 chondrites. This seems to reflect a time-dependent variation of near-Earth meteoroid source regions differing in average thermal history.

Chemical studies of H chondrites. 6: Antarctic/non-Antarctic compositional differences revisited

NASA Technical Reports Server (NTRS)

Wolf, Stephen F.; Lipschutz, Michael E.

1995-01-01

We report data for the trace elements Au, Co, Sb, Ga, Rb, Ag, Se, Cs, Te, Zn, Cd, Bi, T1, and In (ordered by putative volatility during nebular condensation and accretion) determined by radiochemical neutron activation analysis of 14 additional H5 and H6 chondrite falls. Data for the 10 most volatile elements (Rb to In) treated by the multivariate techniques of linear discriminant analysis and logistic regression in these and 44 other falls are compared with those of 59 H4-6 chondrites from Antarctica. Various populations are tested by the multivariate techniques, using the previously developed method of randomization-simulation to assess significance levels. An earlier conclusion, based on fewer examples, that H4-6 chondrite falls are compositionally distinguishable from the Antarctic suite is verified by the additional data. This distinctiveness is highly significant because of the presence of samples from Victoria Land in the Antarctic population, which differ compositionally from falls beyond any reasonable doubt. However, it cannot be proven unequivocally that falls and Antarctic samples from Queen Maud Land are compositionally distinguishable. Trivial causes (e.g., analyst bias, weathering) cannot explain the Victoria Land (Antarctic)/non-Antarctic compositional difference for paradigmatic H4-6 chondrites. This seems to reflect a time-dependent variation of near-Earth meteoroid source regions differing in average thermal history.

Compression-induced structural and mechanical changes of fibrin-collagen composites.

PubMed

Kim, O V; Litvinov, R I; Chen, J; Chen, D Z; Weisel, J W; Alber, M S

2017-07-01

Fibrin and collagen as well as their combinations play an important biological role in tissue regeneration and are widely employed in surgery as fleeces or sealants and in bioengineering as tissue scaffolds. Earlier studies demonstrated that fibrin-collagen composite networks displayed improved tensile mechanical properties compared to the isolated protein matrices. Unlike previous studies, here unconfined compression was applied to a fibrin-collagen filamentous polymer composite matrix to study its structural and mechanical responses to compressive deformation. Combining collagen with fibrin resulted in formation of a composite hydrogel exhibiting synergistic mechanical properties compared to the isolated fibrin and collagen matrices. Specifically, the composite matrix revealed a one order of magnitude increase in the shear storage modulus at compressive strains>0.8 in response to compression compared to the mechanical features of individual components. These material enhancements were attributed to the observed structural alterations, such as network density changes, an increase in connectivity along with criss-crossing, and bundling of fibers. In addition, the compressed composite collagen/fibrin networks revealed a non-linear transformation of their viscoelastic properties with softening and stiffening regimes. These transitions were shown to depend on protein concentrations. Namely, a decrease in protein content drastically affected the mechanical response of the networks to compression by shifting the onset of stiffening to higher degrees of compression. Since both natural and artificially composed extracellular matrices experience compression in various (patho)physiological conditions, our results provide new insights into the structural biomechanics of the polymeric composite matrix that can help to create fibrin-collagen sealants, sponges, and tissue scaffolds with tunable and predictable mechanical properties. Copyright © 2016 Elsevier B.V. All rights

A study on the utilization of advanced composites in commercial aircraft wing structure

NASA Technical Reports Server (NTRS)

Watts, D. J.

1978-01-01

A study was conducted to define the technology and data needed to support the introduction of advanced composite materials in the wing structure of future production aircraft. The study accomplished the following: (1) definition of acceptance factors, (2) identification of technology issues, (3) evaluation of six candidate wing structures, (4) evaluation of five program options, (5) definition of a composite wing technology development plan, (6) identification of full-scale tests, (7) estimation of program costs for the total development plan, (8) forecast of future utilization of composites in commercial transport aircraft and (9) identification of critical technologies for timely program planning.

Design of a unidirectional composite momentum wheel rim

NASA Astrophysics Data System (ADS)

Shogrin, Bradley; Jones, William R., Jr.; Prahl, Joseph M.

1995-05-01

A preliminary study comparing twelve unidirectional-fiber composite systems to five metal materials conventionally used in momentum wheels is presented. Six different fibers are considered in the study: E-Glass, S-Glass, Boron, AS, T300, and Kevlar. Because of the possibility of high momentum requirements, and thus high stresses, only two matrix materials are considered: a high-modulus (HM) and a intermediate-modulus-high-strength (IMHS) matrix. Each of the six fibers are coupled with each of the two matrix materials. In an effort to optimize the composite system, each composite is considered while varying the fiber volume ratio from 0.0 to 0.7 in increments of 0.1. For fiber volume ratios above 0.2, all twelve unidirectional-fiber composite systems meet the study's requirements with higher factors of safety and less mass than the five conventional isotropic (metal) materials. For example, at a fiber volume ratio of 0.6, the Kevlar/IMHS composite system has a safety factor 4.5 times greater than that of a steel (maraging) system and an approximately 10 percent reduction in weight.

Study of the mechanical properties of Ziziphus nummularia (ber) fibers for formation of fiber reinforced composites

NASA Astrophysics Data System (ADS)

Joshi, Akshay; Mangal, R.; Bhojak, N.

2018-05-01

Ziziphus is the one of the most abundant plant of arid region of Rajasthan and rest part of desert land in world. There are a lots of research work going on and has been done on medical applications of this plant and it is playing very important role in economy of desert areas. In this paper our discussion will bring the attention its physical properties so that we can find the possibility of its applications in the various field of fiber reinforced composites which either can be used in such as interior & exterior part of automotive so it can reduce their overall weight, cost and improve its fuel efficiency without compromising in strength or can be used in flywheel technology for energy saving in automobiles or in building materials and so on. In this paper our approach is to extract the fiber from this plant, analyze the mechanical properties of the fiber and then discuss the various possibility of its application in appropriate field of composites. To find the possibility in FRC for Ziziphus fiber our next step is to compare it with other fibers whose composites have already been formed and studied.

Impact of the material composition on proton range variation - A Monte Carlo study

NASA Astrophysics Data System (ADS)

Wu, S. W.; Tung, C. J.; Lee, C. C.; Fan, K. H.; Huang, H. C.; Chao, T. C.

2015-11-01

In this study, we used the Geant4 toolkit to demonstrate the impacts of the material composition of tissues on proton range variation. Bragg curves of different materials subjected to a 250 MeV mono-energy proton beam were simulated and compared. These simulated materials included adipose, heart, brain, cartilage, cortical bone and water. The results showed that there was significant proton range deviation between Bragg curves, especially for cortical bone. The R50 values for a 250 MeV proton beam were approximately 39.55 cm, 35.52 cm, 37.00 cm, 36.51 cm, 36.72 cm, 22.53 cm, and 38.52 cm in the phantoms that were composed completely of adipose, cartilage, tissue, heart, brain, cortical bone, and water, respectively. Mass density and electron density were used to scale the proton range for each material; electron density provided better range scaling. In addition, a similar comparison was performed by artificially setting all material density to 1.0 g/cm3 to evaluate the range deviation due to chemical components alone. Tissue heterogeneity effects due to density variation were more significant, and less significant for chemical composition variation unless the Z/A was very different.

A regional study of the seasonal variation in the molecular composition of rainwater

NASA Astrophysics Data System (ADS)

Cottrell, Barbara A.; Gonsior, Michael; Isabelle, Lorne M.; Luo, W.; Perraud, Véronique; McIntire, Theresa M.; Pankow, James F.; Schmitt-Kopplin, Philippe; Cooper, William J.; Simpson, André J.