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1

A comparative study of three glass ionomer base materials.  

PubMed

This study compared the compressive and diametral tensile strength, compressive modulus, shear bond strength to dentin and resin composite, marginal gap between the base and tooth in Class V cavity preparation, and fluoride release of three glass ionomer base materials. In general, visible light-cured (VLC) base materials outperform the autopolymerizing glass ionomer base Ketac-Bond. The compressive modulus is significantly less for the VLC glass ionomer materials Vitrebond and Fuji LC compared to Ketac-Bond. The Fuji LC had greater diametral tensile strength, compressive strength, bond to dentin and bond to resin composite than Vitrebond or Ketac-Bond. The fluoride release of Vitrebond was greater than Ketac-Bond or Fuji LC. The marginal gap at the tooth/base interface was significantly less with the Fuji LC compared to the other two materials. PMID:8240775

Burgess, J O; Barghi, N; Chan, D C; Hummert, T

1993-06-01

2

An in vitro investigation of a poly (vinyl phosphonic acid) based cement with four conventional glass-ionomer cements  

Microsoft Academic Search

Objective: To investigate the surface hardness of four conventional glass-ionomer cements: Ketac-Molar (KM), HiFi (HF), Vivaglass Fil (VF), Ketac-Fil (KF) and a newly developed glass polyphosphonate based cement, Diamond Carve (DC) at different maturation times in water and to investigate the effects of early water exposure on their surface hardness.Method: Disc specimens (10mm diameter, 1mm thick) were prepared and mould

V. H. W Khouw-Liu; H. M Anstice; G. J Pearson

1999-01-01

3

Leaching from glass ionomer cements.  

PubMed

This study compared the electrical conductivities, pH and leached ion (F-, Ca, Al, Si) concentrations in supernatant liquids obtained from four glassionomer cements, a buffered ionomer cement, a polycarboxylate cement and a zinc phosphate cement, at three different levels of settings. The result indicated that the measured parameters are highest for the unset condition of cements and decreases as the set condition is approached, except for pH, which shows the opposite trend. Two pulp sensitive glassionomer cements, Chem Bond and Ketac Cem showed high Ca:F ratios as well as high Ca and F concentrations. Further, it is suggested that the cytotoxicity of leached F-, Si, Al and Zn at high concentration and at low pH may induce sensitivity in tooth structure. PMID:7996341

Bapna, M S; Mueller, H J

1994-09-01

4

Shear bond strengths of glass-ionomer cements to sound and to prepared carious dentine  

Microsoft Academic Search

Summary  The aim of this study was determine whether bonding of glass-ionomer cements to non-carious dentine differed from that to\\u000a carious dentine. Five commercial cements were used, namely Fuji IX GP, Fuji IX capsulated, Fuji IX Fast capsulated (all GC,\\u000a Japan), Ketac-Molar and Ketac-Molar Aplicap (both 3M-ESPE, Germany). Following conditioning of the substrate with 10% poly\\u000a (acrylic acid) for 10 s, sets

Beata Czarnecka; Patricia Der?gowska-Nosowicz; Honorata Limanowska-Shaw; John W. Nicholson

2007-01-01

5

Mechanical performance of encapsulated restorative glass-ionomer cements for use with Atraumatic Restorative Treatment (ART)  

PubMed Central

The Atraumatic Restorative Treatment (ART) approach was suggested to be a suitable method to treat enamel and dentine carious lesions in patients with disabilities. The use of a restorative glass-ionomer with optimal mechanical properties is, therefore, very important. Objective: To test the null-hypotheses that no difference in diametral tensile, compressive and flexural strengths exists between: (1) The EQUIA system and (2) The Chemfil Rock (encapsulated glass-ionomers; test materials) and the Fuji 9 Gold Label and the Ketac Molar Easymix (hand-mixed conventional glass-ionomers; control materials); (3) The EQUIA system and Chemfil Rock. Material and Methods: Specimens for testing flexural (n=240) and diametral tensile (n=80) strengths were prepared according to standardized specifications; the compressive strength (n=80) was measured using a tooth-model of a class II ART restoration. ANOVA and Tukey B tests were used to test for significant differences between dependent and independent variables. Results: The EQUIA system and Chemfil Rock had significantly higher mean scores for all the three strength variables than the Fuji 9 Gold Label and Ketac Molar Easymix (?=0.05). The EQUIA system had significant higher mean scores for diametral tensile and flexural strengths than the Chemfil Rock (?=0.05). Conclusion: The two encapsulated high-viscosity glass-ionomers had significantly higher test values for diametral tensile, flexural and compressive strengths than the commonly used hand-mixed high-viscosity glass-ionomers. PMID:23857657

MOLINA, Gustavo Fabián; CABRAL, Ricardo Juan; MAZZOLA, Ignacio; BRAIN LASCANO, Laura; FRENCKEN, Jo. E.

2013-01-01

6

Availability of fluoride from glass-ionomer luting cements in human saliva.  

PubMed

Fluoride availability from two glass-ionomer luting agents, Ketac-Cement and Aqua-Cement, was monitored after a 1-h treatment in distilled water at pH 7. The recorded results were then compared to the ones obtained from those same cements, after 1 h, in saliva, in water pretreated with saliva (pH 7 and 4.5), and in albumen and phosphate buffer solutions (pH 7). The Mann-Whitney two-sample rank test was utilized in order to identify the differences. The presence of proteins and phosphate reduced fluoride availability. A reduction in the pH from 7 to 4.5 resulted in an increased rate of fluoride release, in water, from glass-ionomers pretreated with saliva. The present study indicates that fluoride availability from glass-ionomers, in vivo, is pH controlled. The rate controlling factors appear to be phosphate and proteins. PMID:2047755

Rezk-Lega, F; Ogaard, B; Rölla, G

1991-02-01

7

Push-out bond strength of fiber posts to root dentin using glass ionomer and resin modified glass ionomer cements  

PubMed Central

Objective The purpose of this study was to assess the push-out bond strength of glass fiber posts to root dentin after cementation with glass ionomer (GICs) and resin-modified glass ionomer cements (RMGICs). Material and Methods Fifty human maxillary canines were transversally sectioned at 15 mm from the apex. Canals were prepared with a step back technique until the application of a #55 K-file and filled. Post spaces were prepared and specimens were divided into five groups according to the cement used for post cementation: Luting & Lining Cement; Fuji II LC Improved; RelyX Luting; Ketac Cem; and Ionoseal. After cementation of the glass fiber posts, all roots were stored at 100% humidity until testing. For push-out test, 1-mm thick slices were produced. The push-out test was performed in a universal testing machine at a crosshead speed of 0.5 mm/minute and the values (MPa) were analyzed by Kolmogorov-Smirnov and Levene's tests and by two-way ANOVA and Tukey's post hoc test at a significance level of 5%. Results Fiber posts cemented using Luting & Lining Cement, Fuji II LC Improved, and Ketac Cem presented the highest bond strength to root dentin, followed by RelyX Luting. Ionoseal presented the lowest bond strength values (P>0.05). The post level did not influence the bond strength of fiber posts to root dentin (P=0.148). The major cause of failure was cohesive at the cement for all GICs and RMGICs. Conclusions Except for Ionoseal, all cements provided satisfactory bond strength values. PMID:25004052

PEREIRA, Jefferson Ricardo; da ROSA, Ricardo Abreu; SÓ, Marcus Vinícius Reis; AFONSO, Daniele; KUGA, Milton Carlos; HONÓRIO, Heitor Marques; do VALLE, Accácio Lins; VIDOTTI, Hugo Alberto

2014-01-01

8

A review of glass-ionomers: From conventional glass-ionomer to bioactive glass-ionomer  

PubMed Central

Materials used in the body, especially the materials used in various oral cavity regions should be stable and passive without any interactions with the body tissues or fluids. Dental amalgam, composite resins and dental cements are the materials of choice with such properties. The first attempts to produce active materials, which could interact with the human body tissues and fluids were prompted by the concept that fluoride-releasing materials exert useful effects in the body. The concept of using the “smart” materials in dentistry has attracted a lot of attention in recent years. Conventional glass-ionomer (GI) cements have a large number of applications in dentistry. They are biocompatible with the dental pulp to some extent. GI is predominantly used as cements in dentistry; however, they have some disadvantages, the most important of which is lack of adequate strength and toughness. In an attempt to improve the mechanical properties of the conventional GI, resin-modified glass-ionomers have been marketed, with hydrophilic monomers, such as hydroxyethyl methacrylated (HEMA). Some recent studies have evaluated GI with bioactive glass in its structure to validate the claims that such a combination will improve tooth bioactivity, regeneration capacity and restoration. There is ever-increasing interest in the application of bioactive materials in the dental field in an attempt to remineralize affected dentin. The aim of this review article is to evaluate these materials and their characteristics and applications. PMID:24130573

Khoroushi, Maryam; Keshani, Fateme

2013-01-01

9

Long-term F Release from Glass Ionomer Cements  

Microsoft Academic Search

Fluoride release from three commercial glass ionomer filling cements and three glass ionomer luting cements was measured in the laboratory over a 12-month period. Fluoride release from these glass ionomer cements was compared with that released from a silicate, silicophosphate, and a fluoride-containing polycarboxylate cement. The fluoride released from the glass ionomer cements throughout the one-year period was similar, both

M. L. Swartz; R. W. Phillips; H. E. Clark

1984-01-01

10

Glass-ionomer cements as adhesives  

Microsoft Academic Search

The literature on the clinical use of glass-ionomer cements is reviewed, and this shows that these materials are successful partly because of the good adhesion they exhibit towards a variety of substrates encountered in dentistry. The reasons for this good adhesion are identified as the good initial wetting of the surfaces met in clinical dentistry, the development of strong chemical

A. O. Akinmade; J. W. Nicholson

1993-01-01

11

Glass-ionomer cements in restorative dentistry.  

PubMed

This article reviews the current status and future prospects for glass-ionomer materials. These materials are of two chemical types: the older, self-hardening cements, which set by an acid-base neutralization reaction to give relatively brittle materials; and the newer, resin-modified cements, which set partly by polymerization and partly by neutralization. Compared with the self-hardening cements, the latter materials have improved esthetics, improved resistance to moisture, and greater toughness. Both types of glass-ionomer cement bond well to enamel and dentin and release a clinically useful amount of fluoride. They have been used in a variety of applications: as liners or bases, for luting of stainless steel crowns, for Class V restorations in permanent teeth, and for Class II and Class III restorations in primary teeth. The resin-modified glass-ionomers are particularly promising for these latter uses, although it is too early to be sure whether their long-term durability is sufficient. Self-hardening glass-ionomer materials are likely to retain specific niches of clinical application, including in their metal-reinforced and cermet-containing forms. PMID:9573860

Nicholson, J W; Croll, T P

1997-11-01

12

A comparison of the in vitro cytotoxicity of conventional and resin modified glass ionomer cements  

PubMed Central

To evaluate cytotoxicity of experimental conventional and resin modified glass-ionomer cements on UMR-106 osteoblast cell cultures and cell cultures of NIH3T3 mouse fibroblasts specimens were prepared for every experimental material and divided into: group 1. Conventional glass-ionomer cements: GC Fuji IX GP Fast, GC Fuji Triage and Ketac Silver; group 2. Resin modified glass-ionomer cements: GC Fuji II LC, GC Fuji Plus and Vitrebond; group 3. Positive control was presented by specimens of composite Vit-l-ecence® and negative control-group 4. was presented by ?-minimum essential medium for UMR-106 – osteoblast-like cells and Dulbecco’s Modified Eagle’s Medium for NIH3T3 mouse fibroblast cells. Both cell cultures were exposed to 10% of eluate of each single specimen of each experimental material. Experimental dishes were incubated for 24 h. Cell metabolism was evaluated using methyltetrazolium assay. Kruskal-Wallis test and Tukey-Kramer post hoc test for the materials evaluated on NIH3T3 mouse fibroblast cells, as well as UMR-106 osteoblast-like cells showed significantly more cytotoxicity of RMGICs, predominantly Vitrebond to both GICs and composite-Vit-l-ecence®. The lowest influence on cell’s metabolism on UMR-106 osteoblas-like cells was shown by Ketac Silver and the lowest influence on cell’s metabolism on NIH3T3 mouse fibroblast cells was shown by Fuji IX GP Fast. Statistical evaluation of sensitivity of cell lines UMR-106 osteoblast-like cells and NIH3T3 mouse fibroblast cells, using Mann-Whitney test, showed that NIH3T3 mouse fibroblast cells were more sensitive for the evaluation of cytotoxicity of dental materials. PMID:23198945

Selimovi?-Dragaš, Mediha; Huseinbegovi?, Amina; Kobašlija, Sedin; Hatibovi?-Kofman, Šahza

2012-01-01

13

Biaxial flexural strength of high-viscosity glass-ionomer cements heat-cured with an LED lamp during setting.  

PubMed

Adding heat to glass ionomers during setting might improve mechanical properties. The aim was to compare the biaxial flexural strength (BFS) between and within four glass ionomers, by time of exposure to a high-intensity LED light-curing unit. Materials and methods. Samples of Fuji 9 Gold Label, Ketac Molar Easymix, ChemFil Rock, and the EQUIA system were divided into three treatment groups (n = 30): without heating (Group 1), heated with LED lamp of 1400?mW/cm(2) for 30?s while setting (Group 2), and heated with LED lamp of 1400?mW/cm(2) for 60?s while setting (Group 3). Samples were stored for 48 hours in distilled water at 37°C until tested. BFS was tested, using a universal testing machine at a crosshead speed of 1?mm/min. Data were analyzed, using ANOVA test with the Bonferroni correction (? = 0.05). Heating the glass-ionomer cements with an LED curing light of 1400?mW/cm(2) during setting for 30?s increased the BFS value of all GICs. No statistically significant difference in mean BFS scores was found between the EQUIA system and ChemFil Rock at 30?s and 60?s. The mean BFS value was statistically significantly higher for the EQUIA system and ChemFil Rock than for Fuji 9 Gold Label and Ketac Molar Easymix at all exposure times. PMID:23841095

Fabián Molina, Gustavo; Cabral, Ricardo Juan; Mazzola, Ignacio; Brain Lascano, Laura; Frencken, Jo E

2013-01-01

14

Comparative evaluation of microleakage of nano-filled resin-modified glass ionomer: An in vitro study  

PubMed Central

Objective: This in vitro study evaluated the microleakage of a nano-filled resin-modified glass ionomer and a high viscosity glass-ionomer restorations in class V cavities. Materials and Methods: Thirty-two class V cavities prepared on the buccal and lingual surfaces of 16 sound, third molar teeth were randomly assigned into two groups and restored by one of the glass ionomer material; Group A: A high viscosity (Ketac Molar, 3M ESPE) Group B: A nano-filled resin-modified (Ketac N100, 3M ESPE) glass ionomer. One clinician prepared all the cavities. The materials were used according to the manufacturers’ recommendations. The restored teeth were then stored in distilled water at 37°C for 24 h, thermocycled at 5-55°C for 1000 cycles. The specimens were immersed in aqueous solution of Indian ink dye for 48 h at room temperature. They were embedded in resin polyester and sectioned longitudinally in a buccolingual direction. Microleakage was assessed according to the depth of dye penetration along the restoration. The extent of dye penetration at the occlusal and gingival margins was assessed using a stereo microscope. Randomly selected samples from each group were prepared for scanning electron microscope evaluation. The data were statistically analyzed with Friedman and Wilcoxon signed ranks tests. Results: There were statistically significant differences between the microleakage scores of the two groups for both occlusal and gingival scores (P = 0.001). Occlusal and gingival scores for high viscosity glass ionomer (P = 0.024) and nanoionomer (P = 0.021) using Wilcoxon signed ranks tests showed statistically significant differences. High viscosity glass ionomer showed significantly less microleakage compared to the nano-filled resin-modified glass-ionomer (RMGIs) at occlusal margin (P = 0.001). No significant differences were found between the groups at gingival margin (P = 0.0317). Conclusion: Within the limitations of this in vitro study, nano-filled RMGIs restorations did not perform better than high viscosity glass ionomer in class V cavities in terms of microleakage assessment. PMID:25512723

Eronat, Nesrin; Yilmaz, Emir; Kara, Nazan; Topaloglu, Ak Asli

2014-01-01

15

Evaluation of Adhesive and Compressive Strength of Glass Ionomer Cements  

Microsoft Academic Search

The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands\\u000a of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex\\u000a (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal\\u000a alloy (Ni–Cr:

Ramashanker; Raghuwar D. Singh; Pooran Chand; Sunit Km. Jurel; Shuchi Tripathi

16

Germicide effect of several glass ionomer cements.  

PubMed

One the most significant characteristics of glass ionomer cements is their ability to release fluoride compounds. This study was carried out to try establish relationships between this property and the possible effect on the growth of microorganisms that are found in carious lesions, Agar BHI medium containing Petri dishes were flooded with strains of Actinomyces naeslundii, Actinomyces israelii and Actinomyces odontolyticus. Cavities were then prepared in the agar and filled with mixtures of several glass ionomer cements. Some of them were polymerizable resin containing products. A zinc phosphate and a zinc oxide-eugenol cement were used as controls. After a seven day incubation at 37 degrees C under anaerobic conditions the inhibition halos around the specimens were measured in a way similar to that used for antibiograms. The statistical analysis of the results showed no significant differences among Actinomyces strains but a significant difference one among cements. Even when no definitive conclusions could be drawn it is worth taking into consideration the effect of glass ionomer cements on microorganisms such as the Actinomyces and continuing studies to establish more clearly what is required from the material to produce a clinically significant outcome. PMID:11885259

Molgatini, S L; Bertacchini, S M; Abate, P F; Macchi, R L; Negroni, M B

1996-01-01

17

Ion processes in glass ionomer cements.  

PubMed

Ion processes are involved in many aspects of glass-ionomer cements. The ions released from the glass take part in the formation of the cement matrix. Although this process has been investigated, particularly using model cement systems, no study provides a complete matrix composition. Combining results from different studies enables an approximate composition to be derived. The importance of Phosphorous in controlling ion release from the glass surface has been identified in a number of studies. The release of ions from the set cement into water (and other aqueous liquids) has been much reported, particularly for fluoride. Over most of the release periods studied (i.e. from >7 days up to 3 years), release of F ion is related to t1/2 indicating a diffusion-controlled process. Other ions, except possibly Na+ also show this relationship. The amount of cumulative F release whilst maintaining this relationship indicates that more F than is in the matrix is involved. Ion chromatography would probably elucidate the precise form of the ionic species released. Glass-ionomer cements take up ions from solutions in which they are immersed. The levels are much higher than required to produce as internal/external equilibrium. Studies using dynamic SIMS and XPS give some information on ion location and elemental association. It is suggested that ToF SIMS would elucidate these further. Re-release of uptaken ions can vary considerably for different cements and ion species. Surface disruption of glass ionomers is caused by both F ion and monofluorophosphate ion and occurs much more readily in F containing cements than in F free ones. The mechanism of this process has not been elucidated. Analysis of the ions released from the cement as disruption occurs should provide an indication of the site of attack. PMID:16574301

Billington, R W; Williams, J A; Pearson, G J

2006-09-01

18

Wear and superficial roughness of glass ionomer cements used as sealants, after simulated toothbrushing.  

PubMed

The purpose of this study was to evaluate, in vitro, the properties (wear and roughness) of glass ionomer cements that could influence their indication as pit and fissure sealants. The utilized materials were Fuji Plus, Ketac-Molar and Vitremer (in two different proportions: 1:1 and :1). The resin-based sealant Delton was used as control. By means of an electronic balance (precision of 10-4 g), wear was measured in function of weight loss after simulated toothbrushing. Superficial roughness was determined by means of a surface roughness-measuring apparatus. The results revealed that diluted Vitremer and Fuji Plus were less resistant to toothbrushing abrasion and had the greatest increase in superficial roughness. Although in clinical situations luting or diluted ionomer cements are often utilized as alternatives to resin-based sealants, the resultsof this study revealed that the properties of those cements are worse than those of restorative ionomers, whichpresented results similar to those of the evaluated resin sealant. PMID:12612774

Rios, Daniela; Honôrio, Heitor Marques; de Araújo, Paulo Amarante; Machado, Maria Aparecida de Andrade Moreira

2002-01-01

19

Clinical performance of glass-ionomers.  

PubMed

Glass-ionomers were introduced to the profession 20 years ago and have been shown to be a very useful adjunct to restorative dentistry. Their major advantages include the ion exchange adhesion to both enamel and dentine and a continuing fluoride release throughout the life of the restoration. The chemistry of the setting reaction is essentially an acid/base reaction but recent research has introduced variations in an effort to improve clinical handling. Small additions of resin increase the physical properties to a degree and allow for a light-initiated setting mechanism. However, it is essential that the acid/base reaction remains dominant if the full advantages of the glass-ionomer are to be retained. The material has multiple uses in dentistry and it shows a high degree of biocompatibility to the pulp and surrounding soft tissues. The main limitation at this time is a relatively low fracture resistance but it is possible to protect it through lamination with stronger materials if the need arises. This paper examines the essential parameters for successful clinical placement and comments on its longevity. PMID:9645565

Mount, G J

1998-03-01

20

Effect of green propolis addition to physical-mechanical properties of glass ionomer cements  

PubMed Central

Objective This study investigated the mechanical properties of glass ionomer cements (GICs) combined with propolis as a natural antimicrobial substance Material and Methods Typified green propolis, as an ethanolic extract (EEP) or in the lyophilized form (powder), was incorporated to specimens of Ketac Fil Plus, ChemFlex and Ketac Molar Easymix GICs. For each test, 8 specimens of each material were prepared. For water sorption and solubility tests, specimens were subjected to dehydration, hydration and re-dehydration cycles until a constant mass was obtained for each step. Measurements were recorded using a digital balance of 10-4 g precision. For the diametral tensile strength test, specimens were tested in a universal test machine at 0.5 mm/min crosshead speed after 24 h storage in deionized water. Data were evaluated by one-way ANOVA and Tukey’s tests (p<0.05). Results The addition of propolis to GIC clearly increased water sorption compared to pure material. Solubility was material-dependent and was not clearly evident. For the diametral tensile strength test, association with propolis altered negatively only Chemflex. Conclusion It may be concluded that incorporation of propolis to GICs alters some properties in a material-dependent condition. PMID:21552709

TROCA, Valéria Barros Pereira Barbosa; FERNANDES, Karen Barros Parron; TERRILE, Amélia Elena; MARCUCCI, Maria Cristina; de ANDRADE, Flaviana Bombarda; WANG, Linda

2011-01-01

21

A Comparative Evaluation of Microleakage of Glass Ionomer Cement and Chitosan-modified Glass Ionomer Cement: An in vitro Study  

PubMed Central

ABSTRACT Objective: To do a comparative study of microleakage of glass ionomer cement (GIC) and chitosan modified glass ionomer cement and evaluate which exhibited lesser microleakage. Materials and methods: Sixty freshly extracted sound primary molar teeth were obtained. Two groups of samples were created for the study which comprised of group I (glass ionomer cement—GIC) and group II (Chitosan modified glass ionomer cement). Class V cavities were prepared on the buccal surfaces. All the tooth surfaces except the restoration and a 1 mm zone adjacent to its margins were covered with two coats of varnish. The specimens were then immersed in 2% basic fuschin dye solution for 24 hours. The teeth were sectioned into two halves buccolingually in an occlusoapical direction. Sections were viewed under stereomicroscope and the degree of microleakage was evaluated using specific scoring criteria. For comparative evaluation of microleakage scores between glass ionomer cement and chitosan modified cement, a nonparametric Mann-Whitney statistical analysis was done. Results: Statistical analysis showed no significant differences between groups I and II with the p-value at >0.05. Conclusion: Chitosan modified GIC holds great promise for general dentistry as a future restorative material with microleakage properties similar to or better than GIC. How to cite this article: Abraham D, Thomas AM, Chopra S, Koshy S. A Comparative Evaluation of Microleakage of Glass Ionomer Cement and Chitosan-modified Glass Ionomer Cement: An in vitro Study. Int J Clin Pediatr Dent 2014;7(1):6-10. PMID:25206230

Thomas, Abi Mathew; Chopra, Saroj; Koshy, Stephen

2014-01-01

22

Physicomechanical properties of a zinc-reinforced glass ionomer restorative material.  

PubMed

We compared a zinc-reinforced glass ionomer restorative material (ChemFil Rock) with three commercially available glass ionomer cements (GICs), namely, Fuji IX GP Extra, Ketac Molar Quick Aplicap, and EQUIA Fil, with respect to fracture toughness, microhardness, roughness, and abrasive wear. Fracture toughness (KIC) was tested according to ISO 13586 (n = 10). Hardness, roughness, and abrasive wear were also tested (n = 9). Data were analyzed using the Wilcoxon rank-sum test with adjustment for multiple comparisons (? = 0.05). As compared with the other GICs ChemFil Rock exhibited a greater increase in surface roughness (P < 0.05) and lower microhardness (P < 0.01). The wear resistance of ChemFil Rock was comparable to that of the other GICs (P > 0.05). ChemFil Rock had significantly lower fracture toughness as compared with EQUIA Fil (P = 0.01) and significantly higher fracture toughness as compared with the other GICs (P < 0.02). In conclusion, as compared with the three other commercially available GICs, ChemFil Rock had intermediate fracture toughness, the lowest microhardness, and the greatest change in surface roughness. PMID:24739702

Al-Angari, Sarah S; Hara, Anderson T; Chu, Tien-Min; Platt, Jeffrey; Eckert, George; Cook, N Blaine

2014-01-01

23

Comparative evaluation of microleakage of three restorative glass ionomer cements: An in vitro study  

PubMed Central

Purpose: The aim of this study was to compare the microleakage of glass ionomers (conventional and resin modified) with that of recently introduced nanoionomers. Materials and Methods: Standardized class I and class V cavities were prepared on 120 young permanent teeth. Samples were equally divided into group I (class I restorations) and group II (class V restorations), and further divided into subgroups. The subgroups were restored with Fuji IX, Fuji II LC, and newly introduced Ketac™ N 100 (KN 100). Samples were thermocycled and submerged in Acridine dye for 24 h. Samples were sectioned to view under fluorescent microscope and marginal leakage was evaluated by Chi-square and Kruskal — Wallis test. Results: Fuji IX showed the maximum leakage, followed by LC II and the least was observed in KN 100. In class I restorations, there was significant difference while comparing Fuji IX with Fuji LC II and KN 100 and nonsignificant difference between LC II and KN100. In class V restorations, Fuji IX and KN100, KN 100 and LC II showed significant difference. Fuji IX and LC II showed nonsignificant difference. Conclusion: Within the limitations of this study, Fuji IX showed the maximum microleakage. KN 100 showed minimum leakage, better sealing ability, and was more consistent. PMID:25097418

Diwanji, Amish; Dhar, Vineet; Arora, Ruchi; Madhusudan, A.; Rathore, Ambika Singh

2014-01-01

24

Removal of amalgam, glass-ionomer cement and compomer restorations: changes in cavity dimensions and duration of the procedure.  

PubMed

This study investigated changes in the dimensions of Class II cavities following the removal of amalgam, glass ionomer and compomer restorations. In 30 extracted caries-free human molars, preparation for 60 mesio-occlusal and occluso-distal cavities (two cavities per tooth) occurred. With a CEREC 3 laser triangulation sensor and software-based construction analysis, the dimensions of the cavities at seven defined sites were measured. The cavities were randomized into four groups. Group 1 was restored with Ketac-Fil glass-ionomer cement, Group 2 with amalgam and Group 3 with Compoglass F compomer. In Group 4, Compoglass F was used in combination with photochromic Tetric Flow Chroma as a cavity liner. The completed restorations were then removed using 2x magnification and the cavities were once again controlled using the laser system. The duration of the removal procedure was also recorded. Changes in cavity dimensions (depth, height and width) following removal of the restorations were significantly smaller in Groups 1 and 2. Groups 3 and 4 were characterized by a significant overextension of the cavities compared to Groups 1 and 2 in all three dimensions. Group 4, with Tetric Flow Chroma as a cavity liner, showed better results than Group 3, but this improvement was not statistically significant. The duration of the removal procedure was significantly shorter in Group 2 than in the other groups. PMID:12413228

Szep, Susanne; Baum, C; Alamouti, C; Schmidt, D; Gerhardt, T; Heidemann, D

2002-01-01

25

Evaluation on Shear Bond Strength of Different Glass Ionomer and Hydroxy Apatite Cements Used in Ossiculoplasty  

PubMed Central

Background: Glass ionomer cements (GIC) have been widely used in dentistry for many years. In recent years, GIC have also been used for ossiculoplasty. The bond strength of GIC used in ossiculoplasty and the way they may change over the years in the cementation area are being questioned. The bonding strength of the substance may be of importance for long-term outcomes. Aims: The aim of this study was to investigate the bond strength of different GIC on ossicles. Study Design: In vitro study. Methods: Twenty ossicles were obtained from patients who had undergone ear surgery. All specimens were randomly divided into four subgroups. All specimens were inserted into a specially designed apparatus for shear bond strength (SBS) testing. The tested materials [Aqua Meron (AM), Aqua Cem (AC), Ketac Cem (KC), and Otomimix CPB (OH)] were prepared and applied according to the manufacturer’s instructions. The SBS was tested using a universal testing machine at a crosshead speed of 0.5 mm/min. Results: The mean SBSs were found to be 13.28 MPa, 23.43 MPa, 8.51MPa, and 1.78 MPa for AM, AC, KC, and OH, respectively. AC had the highest SBS, which was statistically significantly different from that of KC and OH (p<0.05). Both AM and KC had higher SBS than OH (p<0.05). Conclusion: The results obtained in this study by investigating the bone-bonding strength of cements widely used in ossiculoplasty demonstrate that some of these substances have a greater ability to bond to ossicles compared to others. Further clinical investigations are needed to test different parameters.

Kalc?o?lu, M. Tayyar; Uzun, ?smail Hakk?; Yalç?n, Muhammet; Malkoç, Meral Arslan; Ö?reten, Ay?e Tuba; Hanege, Fatih Mehmet

2015-01-01

26

Ionomics  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ionomics is the study of elemental accumulation (e.g., Ca, K, P, and metal ions) in living systems using high-throughput elemental profiling. This approach has been applied extensively in plants for forward and reverse genetics, screening diversity panels and modeling of physiological states. In thi...

27

Glass-ionomer cements as restorative and preventive materials.  

PubMed

This article focuses on glass-ionomer cement (GIC) and its role in the clinical management of caries. It begins with a brief description of GIC, the mechanism of fluoride release and ion exchange, the interaction between GIC and the external environment, and finally the ion exchange between GIC and the tooth at the internal interface. The importance of GIC, as a tool, in caries management, in minimal intervention dentistry (MI), and Caries Management by Risk Assessment (CAMBRA) also will be highlighted. PMID:20630196

Ngo, Hien

2010-07-01

28

Adhesive properties of modified glass-ionomer cements.  

PubMed

The incorporation of water-soluble polymers and/or vinyl monomers into glass-ionomer cements can yield toughened "hybrid cement-composites". This study compared a commercial water-hardening glass-ionomer cement and seven experimental hybrids in their bonding to both dentin and Silar composite. The cements were sanded and phosphoric-acid-etched or left with an unaltered matrix-formed surface when adhesion to composite was tested. The seven hybrids included: 15% 2-hydroxyethyl methacrylate (HEMA) with appropriate initiators/activators, 29% HEMA, 27% HEMA + 0.5% polyacrylic acid (PAA), 0.5% PAA, 1.5% PAA, 2.5% polyvinyl alcohol, and 2.5% gelatin. Acceptable bond strengths to applied composite and to dentin were observed for most of the modified hybrid cements. There were higher bond strengths with composite when the hybrids were left unetched. Bonding of some unetched, HEMA-containing cements achieved bond strengths (29% HEMA, 10.09 MPa) significantly higher than those of the unmodified cement (4.92 MPa). Resin-modified cements may promote better bonding by improved interaction and compatibility with the resin component of the composite. PMID:1387853

Rusz, J E; Antonucci, J M; Eichmiller, F; Anderson, M H

1992-01-01

29

Residual HEMA and TEGDMA Release and Cytotoxicity Evaluation of Resin-Modified Glass Ionomer Cement and Compomers Cured with Different Light Sources  

PubMed Central

The purpose of this study was first to evaluate the elution of 2-hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) monomers from resin-modified glass ionomer cement (RMGIC) and compomers cured with halogen and light-emitting diode (LED) light-curing units (LCUs). The effect of cured materials on the viability of L929 fibroblast cells was also evaluated. One RMGIC (Ketac N100) and two compomers (Dyract Extra and Twinkystar) were tested. Materials were prepared in teflon disks and light-cured with LED or halogen LCUs. The residual monomers of resin materials in solution were identified using high-performance liquid chromatography. The fibroblast cells' viability was analyzed using MTT assay. The type of LCU did not have a significant effect on the elution of HEMA and TEGDMA. A greater amount of HEMA than TEGMDA was eluted. The amount of TEGDMA eluted from Twinkystar was greater than Dyract Extra (P < 0.05) when cured with a halogen LCU. All material-LCU combinations decreased the fibroblast cells' viability more than the control group (P < 0.01), except for Dyract Extra cured with a halogen LCU (P > 0.05). Curing with the LED LCU decreased the cells' viability more than curing with the halogen LCU for compomers. For Ketac N100, the halogen LCU decreased the cells' viability more than the LED LCU. PMID:24592149

Botsali, Murat Selim; Ku?göz, Adem; Altinta?, Subutay Han; Ülker, Hayriye Esra; Kiliç, Serdar; Ba?ak, Feridun; Ülker, Mustafa

2014-01-01

30

Fluoride release and bioactivity evaluation of glass ionomer: Forsterite nanocomposite  

PubMed Central

Background: The most important limitation of glass ionomer cements (GICs) is the weak mechanical properties. Our previous research showed that higher mechanical properties could be achieved by addition of forsterite (Mg2SiO4) nanoparticles to ceramic part of GIC. The objective of the present study was to fabricate a glass ionomer- Mg2SiO4 nanocomposite and to evaluate the effect of addition of Mg2SiO4 nanoparticles on bioactivity and fluoride release behavior of prepared nanocomposite. Materials and Methods: Forsterite nanoparticles were made by sol-gel process. X-ray diffraction (XRD) technique was used in order to phase structure characterization and determination of grain size of Mg2SiO4 nanopowder. Nanocomposite was fabricated via adding 3wt.% of Mg2SiO4 nanoparticles to ceramic part of commercial GIC (Fuji II GC). Fluoride ion release and bioactivity of nanocomposite were measured using the artificial saliva and simulated body fluid (SBF), respectively. Bioactivity of specimens was investigated by Fourier transitioned-infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and registration of the changes in pH of soaking solution at the soaking period. Statistical analysis was carried out by one Way analysis of variance and differences were considered significant if P < 0.05. Results: The results of XRD analysis confirmed that nanocrystalline and pure Mg2SiO4 powder was obtained. Fluoride ion release evaluation showed that the values of released fluoride ions from nanocomposite are somewhat less than Fuji II GC. SEM images, pH changes of the SBF and results of the ICP-OES and FTIR tests confirmed the bioactivity of the nanocomposite. Statistical analysis showed that the differences between the results of all groups were significant (P < 0.05). Conclusion: Glass ionomer- Mg2SiO4 nanocomposite could be a good candidate for dentistry and orthopedic applications, through of desirable fluoride ion release and bioactivity. PMID:24130579

Sayyedan, Fatemeh Sadat; Fathi, Mohammadhossein; Edris, Hossein; Doostmohammadi, Ali; Mortazavi, Vajihesadat; Shirani, Farzaneh

2013-01-01

31

Improvement of enamel bond strengths for conventional and resin-modified glass ionomers: acid-etching vs. conditioning*  

PubMed Central

Objective: This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths (?TBSs) of conventional and resin-modified glass ionomer cements (GICs/RMGICs). Methods: Forty-eight bovine incisors were prepared into rectangular blocks. Highly-polished labial enamel surfaces were either acid-etched, conditioned with liquids of cements, or not further treated (control). Subsequently, two matching pre-treated enamel surfaces were cemented together with one of four cements [two GICs: Fuji I (GC), Ketac Cem Easymix (3M ESPE); two RMGICs: Fuji Plus (GC), RelyX Luting (3M ESPE)] in preparation for ?TBS tests. Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy (SEM). Results: Phosphoric acid etching significantly increased the enamel ?TBS of GICs/RMGICs. Conditioning with the liquids of the cements produced significantly weaker or equivalent enamel ?TBS compared to the control. Regardless of etching, RMGICs yielded stronger enamel ?TBS than GICs. A visible hybrid layer was found at certain enamel-cement interfaces of the etched enamels. Conclusions: Phosphoric acid etching significantly increased the enamel ?TBSs of GICs/RMGICs. Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays, using GICs/RMGICs to improve the bond strengths. RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength. PMID:24190447

Zhang, Ling; Tang, Tian; Zhang, Zhen-liang; Liang, Bing; Wang, Xiao-miao; Fu, Bai-ping

2013-01-01

32

Post cementation sensitivity evaluation of glass Ionomer, zinc phosphate and resin modified glass Ionomer luting cements under class II inlays: An in vivo comparative study  

PubMed Central

Objective: This study aims to compare the patient-perceived post-cementation sensitivity of class II metal restorations preoperatively, immediately after cementation, one week after cementation and one month after cementation with (1) Glass Ionomer luting cement (2) Zinc Phosphate cement and (3) Resin-modified Glass Ionomer luting cement. Materials and Methods: A total of 60 patients, irrespective of sex, in the age group of 15-50 years were selected and the teeth were randomly divided into three groups of 20 each. Twenty inlay cast restorations were cemented with three different luting cements. The criteria adapted to measure tooth sensitivity in the present study were objective examination for sensitivity. (1) Cold water test (2) Compressed air test and (3) Biting pressure test. Results: The patients with restorations cemented with Resin-modified Glass ionomer demonstrated the least postoperative sensitivity when compared with Glass Ionomer and zinc phosphate cement at all different intervals of time evaluated by different tests. Conclusion: The patients with restorations cemented with resin-modified Glass ionomer demonstrated the least postoperative sensitivity. PMID:20582215

Chandrasekhar, V

2010-01-01

33

Influence of enamel conditioning on bond strength of resin-modified glass ionomer restorative materials and polyacid-modified composites  

Microsoft Academic Search

This study evaluated enamel bond strength of restorative materials containing both glass ionomer and composite components. Three resin-modified glass ionomer restorative materials (Fuji II LC, Vitremer, Photac-Fil), three polyacid-modified composites (VariGlass VLC, Dyract, Ionosit Fil), a hybrid composite (blend-a-lux) and a chemical-cured glass-ionomer cement (ChemFil Superior) were tested for enamel tensile bond strength with and without conditioning of the tooth

Thomas Attin; Wolfgang Buchalla; Elmar Hellwig

1996-01-01

34

Adhesion of glass-ionomer cement in the clinical environment.  

PubMed

This paper discusses the literature concerning the development of an ion-enriched layer between the glass-ionomer cement and tooth structure. Two restorations that had been in the oral cavity for considerable periods of time were used to confirm the existence of this layer. It is suggested that development of the layer is dependent on careful adherence to the recommendations for clinical placement, and recognition of the need to clean the surface of the cavity and to maintain the water balance of the cement. Having developed the ion-exchange layer, failure will be cohesive in the cement itself. Thus the strength of the union is dependent on the tensile strength of the cement. PMID:1805183

Mount, G J

1991-01-01

35

In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers  

Microsoft Academic Search

Objectives. This study was conducted to compare the rate of abrasive wear and change in surface roughness of resin-modified and conventional acid-base glass ionomers when subjected to toothbrush-dentifrice abrasion.Methods. Two resin-modified and two conventional glass ionomers were used. Samples of a high-copper amalgam and a hybrid resin composite were used as reference materials. Specimens of each material were prepared and

Yasuko Momoi; Kunitsugu Hirosaki; Atsushi Kohno; John F. McCabe

1997-01-01

36

In-vitro study of resin-modified glass ionomer cements for cementation of orthodontic bands. Isolation, surplus removal and humidity as factors influencing the bond strength between enamel, cement and metal.  

PubMed

The aim of this in vitro study was to investigate different light-cured and chemically cured resin-modified glass ionomer cements used for the cementation of orthodontic bands and to analyze various factors influencing the adhesive strength between enamel, cement and stainless steel. Four resin-modified glass ionomers (Fuji Ortho LC/GC, Fuji Duet/GC, Unitek Multi-Cure Glass Ionomer Orthodontic Band Cement/3M Unitek, Vitremer/3M) and 1 compomer (Band-Lok/Reliance) were examined. Flattened and polished bovine teeth embedded in polyurethane resin were used as enamel specimens. Before cementation, 50% of the specimens were moistened with the aerosol of an inhalation device, while the rest were dried with compressed air. Stainless steel cylinders (CrNi 18 10) were perpendicularly bonded onto the polished enamel using a custom-made cementation device and immediately topped with a pressure of 0.25 MPa. The cement was isolated with either Ketac Glaze/ESPE, Fuji Coat/GC, Cacao Butter/GC, Dryfoil/Jalenko or Final Varnish/VOCO, or was left uncoated. Eight minutes after the beginning of mixing, either the surplus cement was removed with a scalpel or surplus removal was simulated with ultrasound. After 24 hours storage in a water bath at 37 degrees C and 1,000 thermocycles the shear bond strength was determined. Significant differences with respect to the shear bond strength were found among the following cements, ranking from highest to lowest: Fuji Duet, Unitek cement > Fuji Ortho LC > Vitremer > Band-Lok. The application of a barrier coating significantly increased the shear bond strength of all cements except Fuji Ortho LC. The light-cured resin Ketac Glaze proved to be the most effective barrier coating. A dry enamel surface increased the bond strength of all investigated cements except Unitek cement. The use of ultrasound led to no significant reduction in shear bond strength in comparison with surplus removal with a scalpel. PMID:10546417

Liebmann, S M; Jost-Brinkmann, P G

1999-01-01

37

Microleakage and marginal gap formation of glass ionomer resin restorations.  

PubMed

The purpose of this in vitro study was to compare microleakage and marginal gap formation of three light-cured glass ionomer cements (LCGI). Thirty non-carious human premolar teeth were used in this study. A Class V cavity was prepared in the buccal surface of each tooth. The teeth were randomly divided into three experimental groups of 10 teeth each and restored with three LCGI materials. The teeth in each group were processed for microleakage study using 5% methylene blue. Subsequently, each tooth was embedded in acrylic resin and sectioned longitudinally in a buccolingual direction. Examination of the specimens for dye penetration was done. Later, evaluation of marginal gap formation and analysis of adhesion mechanism were done using SEM. The results indicated that LCGI restorations placed in vitro without thermocycling did not consistently prevent microleakage. Vari Glass VLC showed the least leakage. There was no significant difference in the microleakage between the occlusal and gingival margins. Marginal gap formation was found only in one LCGI material. Generally, the presence of a clearly identified ion-exchange layer was not found. PMID:8634192

Salama, F S; Riad, M I; Abdel Megid, F Y

1995-01-01

38

Interaction of glass-ionomer cements with moist dentin.  

PubMed

Glass-ionomer cements (GICs) are regarded as aqueous gels made up of polyalkenoic acid salts containing ion-leachable glass fillers. The consequence of water permeation across the GIC-dentin interface is unknown. This study used SEM, field-emission/environmental SEM (FE-ESEM), and TEM to examine the ultrastructure of GIC-bonded moist dentin. Dentin surfaces bonded with 6 auto-cured GICs were examined along the fractured GIC-dentin interfaces. Additional specimens fractured 3 mm away from the interfaces were used as controls. SEM revealed spherical bodies along GIC-dentin interfaces that resembled hollow eggshells. FE-SEM depicted similar bodies with additional solid cores. Energy-dispersive x-ray analysis and TEM showed that the spherical bodies consisted of a silicon-rich GIC phase that was absent from the air-voids in the controls. The GIC inclusions near dentin surfaces result from a continuation of the GI reaction, within air-voids of the original polyalkenoate matrix, that occurred upon water diffusion from moist dentin. PMID:15044500

Yiu, C K Y; Tay, F R; King, N M; Pashley, D H; Sidhu, S K; Neo, J C L; Toledano, M; Wong, S L

2004-04-01

39

Effect of Vital Bleaching on Disintegration Tendency of Glass Ionomer Restorations  

PubMed Central

Introduction: This study was designed to assess the effect of two bleaching agents on the disintegration tendency of three types of glass ionomers. Materials and Methods: A total of 90 specimens were prepared by using a split Teflon ring with an internal diameter of 5 mm and a thickness of 2 mm. The tested materials were applied and bleached according to manufacturer’s instructions. Dissolution measurements were made by calculating weight loss through different periods of the test; (one week, one month and three months) and they were analyzed by using one-way analysis of variance (ANOVA), followed by Tukey’s post-hoc test. Results: All glass ionomer materials exhibited a degree of dissolution. Opalescence Xtra increased the dissolution of Photac Fil and F2000 significantly, while Opalescence Quick had no effect on dissolution of glass ionomer restoratives. Conclusion: Bleaching effect on dissolution of glass ionomers is material and time dependant. Care should be taken by clinicians When bleaching teeth that are restored by glass ionomer, because this dissolution may affect the physical properties of these restorations. PMID:24701538

Baroudi, Kusai; Mahmoud, Rasha Said; Tarakji, Bassel; Altamimi, Mohammed Alsakran

2014-01-01

40

Fluoride uptake in human dentine from glass-ionomer cement in vivo.  

PubMed

The purpose was to examine F uptake and distribution in dentine from a F-containing glass-ionomer cement in vivo. Nine volunteers were selected from dental students who were scheduled for extraction of their third molars. Two cavities were prepared on the same occlusal surface of the third molars for each subject; one was restored with glass-ionomer cement (Virtabond), the other with zinc phosphate cement as a control. After 3 months the teeth were extracted. F profiles in the dentine from the cavity floor to the pulpal surface were determined in tissue immediately adjacent to the restorations. An abrasive micro-sampling technique was used. The F concentration of the dentine was highest immediately beneath glass-ionomer cement filling, decreasing towards the pulpal surface. Overall F concentrations were greater in the dentine beneath the glass-ionomer cement than in that beneath the zinc phosphate cement. It was concluded that the glass-ionomer cement markedly enhanced fluoride uptake by underlying dentine in vivo. PMID:8141671

Mukai, M; Ikeda, M; Yanagihara, T; Hara, G; Kato, K; Nakagaki, H; Robinson, C

1993-12-01

41

A new light-cured glass ionomer cement that bonds brackets to teeth without etching in the presence of saliva  

Microsoft Academic Search

Previous studies stress certain advantages of glass ionomer cements, for use in bonding orthodontic brackets to teeth. Failure rate, however, had been higher than with conventional procedures. A new light-cured glass ionomer cement exhibited all the necessary qualities needed to bond brackets, without any etching and in the presence of saliva. The tensile strength of this cement exhibited enough resistance

Elliott Silverman; Morton Cohen; Richard S. Demke; Mitchell Silverman

1995-01-01

42

Studies on the adhesion of glass-ionomer cements to dentin.  

PubMed

This study investigated the bonding mechanisms of glass-ionomer cement to dentin. The approaches included mechanical determination of bond strengths, analysis of surface morphology by means of scanning electron microscopy (SEM) and confocal microscopy, and measurement of chemical changes of fracture bond sites by means of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The highest bond strengths were obtained with light-cured glass-ionomer cement. SEM and confocal images showed evidence of mechanical interlocking of cement in dentinal tubules. SIMS depth profiles confirmed the ion-exchange process between the light-cured glass-ionomer cement and the dentin surface. From corresponding XPS results, it was clear that the adhesion characteristics were significantly affected by light-curing and the chemical structure of the polymer. PMID:1401448

Lin, A; McIntyre, N S; Davidson, R D

1992-11-01

43

An in vitro evaluation of bond strength of three glass ionomer cements.  

PubMed

The purpose of this study was to determine the bond strength of three commercially available glass ionomer cements when used to bond mesh-backed medium twin (0.130 inch) brackets to enamel surface. Three different enamel surface conditions, which included use of pumice, pumice and polyacrylic acid, and pumice followed by acidulated phosphate fluoride, were also tested to determine their effect on the bond strength. In addition, bond strength of one composite resin was compared with those of glass ionomer cements. The teeth were bonded with all the materials according to manufacturers' instructions. Each specimen was embedded in Super-Die with the bonded facial surface exposed. A surveyor was used to align the teeth in the stone uniformly for all specimens. A special bracket holder was used to hold the brackets precisely under the wings during debonding. An Instron universal testing machine was used to measure the force required for bond failure. To stimulate oral conditions, the direction of pull was so designed that it included an element of torsional stress along with tensile force. The findings indicate that a large variation existed between the bond strengths of all materials tested. The bond strength of glass ionomer cements was significantly less than that composite resin. However, the bond strength of at least one glass ionomer cement appears to be adequate for clinical use. The different surface preparation before bonding did not significantly affect the bond strengths of glass ionomer cements. Further investigation is required to test the bond strengths of glass ionomer cements clinically. PMID:2181867

Fajen, V B; Duncanson, M G; Nanda, R S; Currier, G F; Angolkar, P V

1990-04-01

44

Caries protection after orthodontic band cementation with glass ionomer.  

PubMed

This study evaluated the resistance of the enamel to an artificial caries challenge after removing orthodontic bands cemented with a glass ionomer cement (GIC). Ten extracted caries-free molars were cleaned with a slurry of pumice and randomly divided into 2 groups of 5 teeth each: Group 1: Cementation with GIC (Fuji) and Group 2: Cementation with a zinc phosphate cement (Mizzy). Both cements were handled according to manufacturer's instructions. Before cementing the bands, an area of S x S mm was masked with adhesive tape on the lingual surfaces of all teeth. The orthodontic bands were cemented over this adhesive tape. After band cementation, the occlusal and gingival margins of the band were delineated with a bur on the tooth surface. The teeth were thermocycled (200 cycles, 5-55 degrees C, 30-second dwell time) and stored in distilled water for 24 hours. Then, the bands and adhesive tape were removed and the teeth again stored in distilled water for a week, changing the water daily. The teeth were then varnished with the exception of a 5 x 5 mm window (including previously exposed and covered areas) on the buccal and lingual surfaces. All teeth were then placed in an acidified gel (pH 4.5) for 5 weeks to produce artificial caries. At least three sections from the exposed and covered areas were made from the buccal and lingual challenged areas. Sections were ground to approximately 100 microns. Polarized microscopy and image analysis were used to analyze the results.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8258573

Marcushamer, M; Garcia-Godoy, F; Chan, D C

1993-01-01

45

A novel acrylic copolymer for a poly(alkenoate) glass-ionomer cement.  

PubMed

The interest in the clinical use of polyalkenoate cements stems mainly from their behavior as bioactive adhesive materials with therapeutic action. Glass-ionomer cements set by an acid-base reaction between a degradable glass and a poly(alkenoic acid) and the therapeutic action is related to the release of fluoride ions which are present in the hardened cement that show a sustained release over years, responsible for caries inhibition in teeth. Conventional glass-ionomers, however, suffer from some disadvantages such as short working time, initial moisture sensitivity and prone to desiccation after setting and are generally brittle. In the present study, a poly(alkenoic acid) copolymer was synthesized based on acrylic acid and 2-hydroxyethylmethacrylate (HEMA) using azobisisobutyronitrile as the initiator and characterized. The acid-base reaction was carried out by reacting aqueous solutions of the new copolymer (40 and 60%) with a commercial aluminofluorosilicate glasses as used in conventional glass-ionomer cements. The results showed that the copolymer of HEMA and acrylic acid was a viable poly(alkenoic) acid for formation of glass-ionomer cements. PMID:15348418

Deb, S; Shah, P; Vazquez, B; San Roman, J

2003-07-01

46

Glass ionomer as an expander of allograft in revision arthroplasty of the hip.  

PubMed

The use of glass ionomer as a bone graft expander was investigated in an in vivo model of revision hip arthroplasty. Bone grafts of pure allograft and allograft + glass ionomer particles in a 50:50 by weight mixture were implanted in an ovine hemi-arthroplasty model. Post-operative assessments of locomotor function, radiographic appearance and quantitative changes in mineralisation around the graft were made at 2, 4 and 6 months. Post-mortem assessments of radiographic and histologic appearance of the grafts were made at 6 months. No significant differences were noted in any of the measured or assessed parameters between the two graft types. The glass ionomer particles seemed to be well tolerated within the matrix of new bone, smaller sized particles appearing to be better incorporated than larger ones. The use of particles of glass ionomer as a bone graft expander, in this in vivo model of revision hip arthroplasty, would therefore appear to offer no detriment in performance over pure allograft in the short to medium term. PMID:12423605

Eldridge, J D J; Cunningham, J L; Samuels, A; Blunn, G W; Lawes, T J; Learmonth, I D; Goodship, A E

2003-02-01

47

Studies on the Adhesion of Glass-ionomer Cements to Dentin  

Microsoft Academic Search

This study investigated the bonding mechanisms of glass-ionomer cement to dentin. The approaches included mechanical determination of bond strengths, analysis of surface morphology by means of scanning electron microscopy (SEM) and confocal microscopy, and measurement of chemical changes of fracture bond sites by means of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The highest bond strengths were

A. Lin; N. S. McIntyre; R. D. Davidson

1992-01-01

48

Effects of incorporation of hydroxyapatite and fluoroapatite nanobioceramics into conventional glass ionomer cements (GIC).  

PubMed

Hydroxyapatite (HA) has excellent biological behavior, and its composition and crystal structure are similar to the apatite in the human dental structure and skeletal system; a number of researchers have attempted to evaluate the effect of the addition of HA powders to restorative dental materials. In this study, nanohydroxy and fluoroapatite were synthesized using an ethanol based sol-gel technique. The synthesized nanoceramic particles were incorporated into commercial glass ionomer powder (Fuji II GC) and were characterized using Fourier transform infrared and Raman spectroscopy, X-ray diffraction and scanning electron microscopy. Compressive, diametral tensile and biaxial flexural strengths of the modified glass ionomer cements were evaluated. The effect of nanohydroxyapatite and fluoroapatite on the bond strength of glass ionomer cement to dentin was also investigated. Results showed that after 1 and 7 days of setting, the nanohydroxyapatite/fluoroapatite added cements exhibited higher compressive strength (177-179MPa), higher diametral tensile strength (19-20MPa) and higher biaxial flexural strength (26-28MPa) as compared with the control group (160MPa in CS, 14MPa in DTS and 18MPa in biaxial flexural strength). The experimental cements also exhibited higher bond strength to dentin after 7 and 30 days of storage in distilled water. It was concluded that glass ionomer cements containing nanobioceramics are promising restorative dental materials with both improved mechanical properties and improved bond strength to dentin. PMID:17921077

Moshaverinia, Alireza; Ansari, Sahar; Moshaverinia, Maryam; Roohpour, Nima; Darr, Jawwad A; Rehman, Ihtesham

2008-03-01

49

Management of a Large Internal Resorption Lesion with Metal Reinforced Glass Ionomer Cement  

PubMed Central

Mineral trioxide aggregate is the mainstay of treatment of large internal resorption defects. But its cost may be a deterrent to its use in some patients. The present case report describes the successful endodontic management of an extensive internal resorptive lesion in a mandibular molar with metal reinforced glass ionomer cement. PMID:25436156

Bhuyan, Atool Chandra; Arora, Suraj; Sethi, Kunal; Kalra, Tarun

2014-01-01

50

Effects of dentin surface treatments on shear bond strength of glass-ionomer cements  

PubMed Central

Summary Aim The aim of this in vitro study was to evaluate the effect of different surface treatments on shear bond strength of a conventional glass-ionomer cement (GIC) and a resin-modified glass-ionomer cement (RMGIC) to dentin. Materials and methods 80 bovine permanent incisors were used. 40 cylindrical specimens of a GIC (Fuji IX GP Extra) and 40 cylindrical specimens of a RMGIC (Fuji II LC) were attached to the dentin. The teeth were then randomly assigned to 8 groups of equal size (n=10), 4 for every type of glass-ionomer cement, corresponding to type of dentin surface treatments. Group 1: GC Cavity Conditioner; Group 2: 37% phosphoric acid gel; Group 3: Clearfil SE Bond; Group 4: no dentin conditioning (control). The specimens were placed in a universal testing machine (Model 3343, Instron Corp., Canton, Mass., USA) and subsequently tested for shear bond strength (MPa). Results ANOVA showed the presence of significant differences among the various groups. Post hoc Tukey test showed different values of shear bond strength for Fuji IX GP Extra and for Fuji II LC. The different conditioners variably influence the adhesion of the glass-ionomer cements tested. Conclusions. RMGIC shear bond to dentin was higher than GIC. The use of a Self-etch adhesive system improved the shear bond strength values of RMGIC and lowered the shear bond strength values of GIC significantly. PMID:24753797

Poggio, Claudio; Beltrami, Riccardo; Scribante, Andrea; Colombo, Marco; Lombardini, Marco

2014-01-01

51

In vitro enamel remineralization at orthodontic band margins cemented with glass ionomer cement.  

PubMed

Demineralization adjacent to orthodontic bands remains a clinical concern. The release of fluoride from glass ionomer cement has been shown to inhibit demineralization. The purpose of this study was to examine the remineralization effects of a glass ionomer cement adjacent to orthodontic bands. Forty extracted molars were painted with an acid-protective varnish, excluding a 2 x 6 mm window on the buccal surfaces. Artificial caries-like lesions were created in the exposed enamel with an acidified gel. Half the lesion on each tooth was then painted with an acid-protective varnish. An orthodontic band was cemented with a glass ionomer cement or zinc phosphate cement, the gingival margin of the band located at the level of the artificial carious lesion. The teeth were placed in separate closed environments of a nonfluoridated artificial saliva for 3 months. The teeth were then sectioned and photographed with polarized light microscopy in imbibition medias of water and Thoulet's (R.I.: 1.41, 1.47), representing a minimum of 5%, 10%, and 25% pore volume, respectively. With a sonic digitizer, the area of the body of the lesion was measured in each imbibition media, comparing the maintained varnished out lesions to the lesions exposed to the cement. Results demonstrated a statistically significant reduction in the body of the lesions (p < 0.005) for those exposed to the glass ionomer cement. PMID:7733054

Donly, K J; Istre, S; Istre, T

1995-05-01

52

Histological assessment of pulpal responses to resin modified glass ionomer cements in human teeth  

PubMed Central

Background: The biocompatibility of resin-modified glass ionomers (RMGIs) as a lining material is still under question. The present study evaluated the response of the pulp-dentin complex following application of resin-modified glass-ionomer cement, calcium hydroxide and conventional glass-ionomer in deep cavities prepared in human teeth. Materials and Methods: In this controlled clinical trial, 30 deep class V buccal cavities (3 mm × 2 mm × 2 mm) were prepared in human premolars treatment planned to be extracted for orthodontic reasons and divided into 3 groups. Groups were lined by a RMGI (Vivaglass), conventional glass Ionomer (Ionocid) and calcium hydroxide respectively. The cavities were subsequently filled with amalgam. Each group was then divided into two sub-groups according to time intervals 5 and 30 days. The patients were referred to Kerman Dental School and in accordance with orthodontic treatment plan; premolars were extracted and then prepared for histological assessment. The sections were stained with hematoxylin and eosin and periodic acid Schiff techniques. All of the samples were examined using a number of criteria including odontoblastic changes, inflammatory cells response, reactionary dentin formation and presence of microorganisms. The data were analyzed by Kruskal-Wallis and Mann-Whitney tests. P < 0.05 was considered as significant. Results: There was no significant difference among odontoblastic changes, reactionary dentin, presence of bacteria and inflammatory cells response of the groups (P > 0.05). Conclusion: Ionocid and Vivaglass resin-modified glass ionomers can be used as lining materials in human teeth. PMID:25878679

Eskandarizadeh, Ali; Parizi, Molook Torabi; Goroohi, Hossein; Badrian, Hamid; Asadi, Abbas; Khalighinejad, Navid

2015-01-01

53

Inhibitory effect on S. mutans by fluoride-treated conventional and resin-reinforced glass ionomer cements.  

PubMed

The aim of the present study was to study the effect of fluoride gel treatment on fluoride release and inhibition of acid production of Streptococcus mutans by different glass ionomer cements. Test slabs of four glass ionomer materials were fitted into the bottom of a test tube. A layer of S. mutans cells was centrifuged onto the test slabs, and the specimens were incubated for 4 h in 1.7% sucrose solution. Incubations were made using fresh, aged (29 d), aged and F-treated (1.25% F-gel), and aged, F-treated and aged samples (n = 15 per group). After each incubation, pH and F contents of the fluid phase were determined. The freshly mixed glass ionomer samples released large amounts of fluoride, and the pH fall in the fluid phase was significantly inhibited. For aged samples, the fluoride release decreased strongly and no inhibitory effect on acid production by S. mutans was seen. After application of fluoride gel, fluoride release and inhibitory effect were significantly higher than initially for all glass ionomer cements. In conclusion, all glass ionomer cements were able to take up fluoride and subsequently release it, which resulted in reestablishment of their antibacterial effect. The patterns of fluoride release and antibacterial action were virtually the same for conventional and resin-reinforced glass ionomer cements. PMID:7634135

Seppä, L; Korhonen, A; Nuutinen, A

1995-06-01

54

GLASS IONOMER CEMENTS AND THEIR ROLE IN THE RESTORATION OF NON-CARIOUS CERVICAL LESIONS  

PubMed Central

Glass ionomer based materials are clinically popular in several areas of restorative dentistry, but restoration of cervical lesions has proven particularly successful. Various etiologies, conformations, locations and structural characteristics make non-carious cervical lesions more challenging to adhesive restorative procedures and marginal seal in the long run. Due to their characteristics, glass ionomer cements (GICs) have precise indication for these cases. Moreover, the use of a GIC base underneath composite resin, the so-called "sandwich" or mixed technique, allows associating the good characteristics of composite resins and GICs, and has been considered quite useful in the restoration of non-carious cervical defects. The aim of this paper is to critically review the literature and discuss peculiar features of GICs regarding their role in the restoration of non-carious cervical lesions. PMID:19936509

Francisconi, Luciana Fávaro; Scaffa, Polliana Mendes Candia; de Barros, Vivian Rosa dos Santos Paes; Coutinho, Margareth; Francisconi, Paulo Afonso Silveira

2009-01-01

55

How mobile are protons in the structure of dental glass ionomer cements?  

NASA Astrophysics Data System (ADS)

The development of dental materials with improved properties and increased longevity can save costs and minimize discomfort for patients. Due to their good biocompatibility, glass ionomer cements are an interesting restorative option. However, these cements have limited mechanical strength to survive in the challenging oral environment. Therefore, a better understanding of the structure and hydration process of these cements can bring the necessary understanding to further developments. Neutrons and X-rays have been used to investigate the highly complex pore structure, as well as to assess the hydrogen mobility within these cements. Our findings suggest that the lower mechanical strength in glass ionomer cements results not only from the presence of pores, but also from the increased hydrogen mobility within the material. The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements.

Benetti, Ana R.; Jacobsen, Johan; Lehnhoff, Benedict; Momsen, Niels C. R.; Okhrimenko, Denis V.; Telling, Mark T. F.; Kardjilov, Nikolay; Strobl, Markus; Seydel, Tilo; Manke, Ingo; Bordallo, Heloisa N.

2015-03-01

56

How mobile are protons in the structure of dental glass ionomer cements?  

PubMed Central

The development of dental materials with improved properties and increased longevity can save costs and minimize discomfort for patients. Due to their good biocompatibility, glass ionomer cements are an interesting restorative option. However, these cements have limited mechanical strength to survive in the challenging oral environment. Therefore, a better understanding of the structure and hydration process of these cements can bring the necessary understanding to further developments. Neutrons and X-rays have been used to investigate the highly complex pore structure, as well as to assess the hydrogen mobility within these cements. Our findings suggest that the lower mechanical strength in glass ionomer cements results not only from the presence of pores, but also from the increased hydrogen mobility within the material. The relationship between microstructure, hydrogen mobility and strength brings insights into the material's durability, also demonstrating the need and opening the possibility for further research in these dental cements. PMID:25754555

Benetti, Ana R.; Jacobsen, Johan; Lehnhoff, Benedict; Momsen, Niels C. R.; Okhrimenko, Denis V.; Telling, Mark T. F.; Kardjilov, Nikolay; Strobl, Markus; Seydel, Tilo; Manke, Ingo; Bordallo, Heloisa N.

2015-01-01

57

Immediate implantation of glass-ionomer cement granules increases osteogenesis during rat alveolar wound healing.  

PubMed

A study was conducted to determine whether granules of type III glass-ionomer cement (currently used as a fast-setting lining material and fissure sealant) implanted immediately after tooth extraction interfere with the time course of alveolar wound healing. Histologic examination of the entire socket showed normal progression of the healing process. Progressive bone neoformation in parallel with a decrease in the volume fraction of connective tissue was quantified by a histometric method up to 6 weeks after tooth extraction. The presence of glass-ionomer granules in the cervical third led to a small delay in bone formation by the first week but not thereafter, as also observed in the remaining regions of the alveolus (middle and apical thirds) which tended, in contrast, to show a larger amount of trabecular bone from the third week onwards. These results show that the material does not hinder the wound healing process, and in fact favors bone neoformation. PMID:9058996

Brentegani, L G; Bombonato, K F; Carvalho, T L

1996-12-01

58

In-vitro Comparison of the Antimicrobial Properties of Glass Ionomer Cements with Zinc Phosphate Cements  

PubMed Central

White spot lesions are observed in nearly 50% of patients undergoing orthodontic treatment. Long-lasting antibacterial properties of orthodontic cements can reduce this phenomenon. The aim of this research was to compare antimicrobial activity of three commercial glass ionomer cements with three commercial zinc phosphate cements, over time, against streptococcus mutans and candida albicans. Direct contact test (DCT) was used to evaluate the antibacterial and antifungal activity of products after 48 h and 7 days of incubation. The results demonstrated that all the cements presented antibacterial activity but the antibacterial activity of glass ionomer cements was more than that of zinc phosphate cements. Counts of C. albicans after 48 h were lower and statistically different in the GIC group in relation to the control groups. But no differences were observed between GIC and control groups at 7 days. Based on the results of this study, the antimicrobial and mainly antifungal effects of all the cements were so short. PMID:25317187

Vahid Dastjerdie, Elaheh; Oskoui, Mahvash; Sayanjali, Elham; Tabatabaei, Fahimeh Sadat

2012-01-01

59

No evidence to support use of glass ionomer as a fissure sealant in primary molars  

Microsoft Academic Search

DesignRandomised controlled trial in primary care setting.Intervention508 children aged 18–30 months from high caries areas of South Wales with caries-free first primary molars were recruited to the trial after informed consent. All children (n=508) received a standard package of dental health education. Children in the test group (n=241) had their first primary molars sealed with glass ionomer. All the children

Sergio Uribe

2005-01-01

60

Antimicrobial Effects of Dental Luting Glass Ionomer Cements on Streptococcus mutans  

PubMed Central

Objective. To reduce secondary caries, glass ionomer luting cements are often used for cementing of indirect restorations. This is because of their well-known antimicrobial potential through the release of fluoride ions. The aim of this in vitro study was to investigate the antimicrobial effect of five dental luting cements which were based on glass ionomer cement technology. Methods. Five different glass ionomer based luting cements were tested for their antimicrobial effects on Streptococcus mutans in two different experimental setups: (i) determination of colony-forming units (CFUs) in a plate-counting assay; (ii) live/dead staining (LDS) and fluorescence microscopy. All experiments were conducted with or without prior treatment of the materials using sterilized human saliva. Antimicrobial effects were evaluated for adherent and planktonic bacteria. Bovine enamel slabs (BES) were used as negative control. BES covered with 0.2% chlorhexidine (CHX) served as positive control. Results. Each of the tested materials significantly reduced the number of initially adhered CFUs; this reduction was even more pronounced after prior incubation in saliva. Antimicrobial effects on adherent bacteria were confirmed by live-dead staining. Conclusion. All five luting cements showed an antimicrobial potential which was increased by prior incubation with human saliva, suggesting an enhanced effect in vivo. PMID:24795539

Altenburger, Markus; Spitzmüller, Bettina; Anderson, Annette; Hellwig, Elmar

2014-01-01

61

Histological evaluation of the biocompatibility of a glass-ionomer cement in rat alveolus.  

PubMed

A type III glass-ionomer cement (Vidrion F), currently used as fast-setting lining material and fissure sealant, was implanted into rat dental alveolus immediately after tooth extraction and its biocompatibility was analysed in terms of incorporation into alveolar bone in the wound healing process. Histological and histometric evaluation of trial areas adjacent to the implants showed that by week 1 the glass-ionomer granules were encircled by a conspicuous capsule surrounded by immature connective tissue. By week 3 the implants were surrounded by a less prominent fibrous capsule and most of the tested area was occupied by mature trabecular bone. By week 6 the fibrous capsule was thinner and the tested area was almost totally covered by bone, which was in close contact with the implanted material in several places. Quantitative data confirmed progressive new bone formation in parallel with a decrease in the percentage fraction of connective tissue in the trial areas around the implants. The results revealed that the tested material is biologically compatible, being progressively incorporated into alveolar bone in the wound healing process. The quantitative evaluation of alveolar wound healing around a glass-ionomer implant may provide an experimental model for future comparative studies carried out with other biomaterials. PMID:9022960

Brentegani, L G; Bombonato, K F; Carvalho, T L

1997-01-01

62

Composition-structure-property relationships for non-classical ionomer cements formulated with zinc-boron germanium-based glasses.  

PubMed

Non-classical ionomer glasses like those based on zinc-boron-germanium glasses are of special interest in a variety of medical applications owning to their unique combination of properties and potential therapeutic efficacy. These features may be of particular benefit with respect to the utilization of glass ionomer cements for minimally invasive dental applications such as the atruamatic restorative treatment, but also for expanded clinical applications in orthopedics and oral-maxillofacial surgery. A unique system of zinc-boron-germanium-based glasses (10 compositions in total) has been designed using a Design of Mixtures methodology. In the first instance, ionomer glasses were examined via differential thermal analysis, X-ray diffraction, and (11)B MAS NMR spectroscopy to establish fundamental composition - structure-property relationships for the unique system. Secondly, cements were synthesized based on each glass and handling characteristics (working time, Wt, and setting time, St) and compression strength were quantified to facilitate the development of both experimental and mathematical composition-structure-property relationships for the new ionomer cements. The novel glass ionomer cements were found to provide Wt, St, and compression strength in the range of 48-132?s, 206-602?s, and 16-36?MPa, respectively, depending on the ZnO/GeO2 mol fraction of the glass phase. A lower ZnO mol fraction in the glass phase provides higher glass transition temperature, higher N4 rate, and in combination with careful modulation of GeO2 mol fraction in the glass phase provides a unique approach to extending the Wt and St of glass ionomer cement without compromising (in fact enhancing) compression strength. The data presented in this work provide valuable information for the formulation of alternative glass ionomer cements for applications within and beyond the dental clinic, especially where conventional approaches to modulating working time and strength exhibit co-dependencies (i.e. the enhancement of one property comes at the expense of the other) and therefore limit development strategies. PMID:25391445

Zhang, Xiaofang; Werner-Zwanziger, Ulrike; Boyd, Daniel

2015-04-01

63

Buonocore Memorial Lecture. Glass-ionomer cements: past, present and future.  

PubMed

It was Michael Buonocore who focused the attention of the profession on adhesion in the oral cavity. He expanded the concept of adhesion of resins to enamel and investigated adhesion to dentin. The problem has been solved through the glass-ionomer cements rather than with resins, but sadly, he did not live to see them achieve maturity. The glass-ionomer cements were introduced to the profession in 1976, and they provide adhesion to both enamel and dentin through an ion exchange with the additional benefit of a continuing fluoride release throughout the life of the restoration. Solubility is low, abrasion resistance is high, and biocompatability is excellent. As a water-based material, they have an excellent chance of survival in the hostile environment of the oral cavity. Acceptance of the early versions was slow because of perceived problems with water exchange, a poor color range, and a lack of translucency. Considerable research has been carried out over the last 20 years by members of the profession and the manufacturers; at this point, the glass-ionomer cements make a very valuable contribution to everyday practice. They are now available as both an autocure and a dual-cure cement, and the color range and translucency are excellent. Problems of clinical placement have been overcome, and it is now a simple matter to take advantage of the adhesion and the fluoride release and place a restoration that is esthetic, resistant to microleakage, long lasting, and a deterent to recurrent caries. Their only limitation lies in the fact that they lack the fracture strength to rebuild marginal ridges and incisal corners. In spite of this limitation, they have opened the way for the introduction of a new range of microcavity designs that allow for conservation of remaining tooth structure to an extent never before available. In the near future physical properties will be improved still further, and the use of these cements will expand considerably. PMID:9028245

Mount, G J

1994-01-01

64

Effect of Self-etching Adhesives on the Bond Strength of Glass-Ionomer Cements  

PubMed Central

Objective: Statement of Problem: Adequate bond strength between glass ionomer cements and composite resin is necessary for the success of the sandwich technique. Purpose of Study: This study assessed the micro-shear bond strength of composite resin to glass-ionomer cements (GIC) using self-etch adhesives with different pH values. Materials and Methods: One hundred specimens (6×4×2 mm) were made using Fuji II and Fuji II LC GICs and treated with different adhesives as follows: Group 1:Fuji II+ Adper Prompt L-Pop, Group-2: Fuji II+SE bond, Group-3: Fuji II + AdheSE, Group-4:Fuji II+ Protect bond, Group-5: Fuji II + Single bond, Group-6:Fuji II LC+ Adper Prompt LPop, Group-7: Fuji II LC+SE bond, Group-8:Fuji II LC+ AdheSE, Group-9: Fuji II LC+ Protect bond, and Group-10: Fuji II LC+ Single bond. Each group consisted of 10 specimens. A cylinder of Z100 composite resin was placed on each sample and light cured. After 24 hours of water storage (37°C), the specimens were subjected to micro-shear bond strength tests (0.5 mm/min). Data were analyzed using two-way ANOVA and Tukey’s test. Results: The mean micro-shear bond strength of groups 1–10 was 11.66±1.79, 16.50±1.85, 18.47±1.77, 13.95±1.77, 15.27±1.49, 15.14±0.90, 20.03±1.19, 17.48±3.00, 16.24±1.98 and 16.03±1.49 MPa, respectively. There were significant differences between groups 1 and 7 (P<0.05). No significant difference was observed between other groups (P>0.05). Fuji II LC showed higher bond strength than Fuji II (P<0.05). Conclusion: Type of self-etch adhesive had no significant effect on micro-shear bond strength of glass-ionomer to composite resin. Resin modified glass ionomer cement (RMGIC) exhibited higher bond strength than the conventional GIC. PMID:25628698

Jaberi Ansari, Zahra; Panahandeh, Narges; Tabatabaei Shafiei, Zahra Sadat; Akbarzadeh Baghban, Alireza

2014-01-01

65

Effect of hygroscopic expansion on the push-out resistance of glass ionomer-based cements used for the luting of glass fiber posts.  

PubMed

This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice push-out tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention. PMID:16728245

Cury, Alvaro H; Goracci, Cecilia; de Lima Navarro, Maria Fidela; Carvalho, Ricardo M; Sadek, Fernanda T; Tay, Franklin R; Ferrari, Marco

2006-06-01

66

Use of Raman spectroscopy in the characterisation of the acid–base reaction in glass-ionomer cements  

Microsoft Academic Search

Raman spectra of various combinations of glass-ionomer cement components have been compared with those of the reactants and the salts of polyacrylic and tartaric acids. The components consisted of a fast-setting acid-degradable dental glass (containing, inter alia, oxides of Si, Al, Ca, Ba and Na), polyacrylic acid (PAA) and\\/or tartaric acid (TA). On the addition of water to the glass

A. M Young; A Sherpa; G Pearson; B Schottlander; D. N Waters

2000-01-01

67

Longevity in glass-ionomer restorations: review of a successful technique.  

PubMed

It is just 20 years since glass-ionomer cements were introduced to the profession as a restorative material capable of an ion exchange adhesion to tooth structure as well as a continuing fluoride release. At the time of presentation there was considerable publicity, but, in retrospect, it is likely that the materials were marketed prematurely, before there had been a great deal of clinical investigation. The clinical short-term results were rather disappointing, particularly in relation to esthetics, because the original version lacked translucency. In the next few years, some manufacturers worked to refine the product and improve the properties and achieved reasonable results. In the early 1980s, it was shown that the main problem with both esthetics and physical properties was the need to maintain a proper water balance in the material during the early setting phase. Once this problem was identified and overcome, it became possible to achieve excellent results, but these have not been reported frequently. This article discusses a method of placement that will lead to acceptable glass-ionomer restorations and shows a series of restorations that are up to 15 years old. PMID:9477884

Mount, G J

1997-10-01

68

Enamel fluoride levels after orthodontic band cementation with glass ionomer cement.  

PubMed

The aim of this investigation was to examine the fluoride uptake by enamel after application of glass ionomer cement for orthodontic band cementation compared with zinc phosphate cement. The study was conducted on 21 children whose mean age was 14 years. All the children were reared in the Middle Anatolian cities where the water fluoride concentration was below the level of 0.50 ppm. The subjects were randomly divided into three groups. The first experimental group, had seven subjects whose teeth were topically fluoridated with 2 per cent NaF solution, before orthodontic band cementation with zinc phosphate cement. The second experimental group also had seven subjects whose orthodontic bands were cemented with glass ionomer cement. The third group, consisted of seven control subjects and no dental procedures were performed in this group. All the participants were followed for 3 months and at the end of this period maxillary first premolars, which were in the ninth developmental stage according to Nolla (1960), were extracted for orthodontic purposes. The enamel fluoride concentrations were determined on the left maxillary first premolars at three successive etch depths by means of a fluor ion electrode, whereas the calcium concentrations were determined with an atomic absorption spectrophotometer. The results of this investigation showed that in both cementation groups enamel fluoride concentrations at three successive etch depths were highly increased compared with the control group. However, the difference between the cementation groups was not statistically significant. PMID:8746180

Akkaya, S; Uner, O; Alaçam, A; De?im, T

1996-02-01

69

Comparative Evaluation of Voids Present in Conventional and Capsulated Glass Ionomer Cements Using Two Different Conditioners: An In Vitro Study  

PubMed Central

This in vitro study evaluated the presence of voids in powder-liquid and capsulated glass ionomer cement. 40 cavities were prepared on root surfaces of maxillary incisors and divided into four groups. Cavities were conditioned with glass ionomer cement liquid (GC Corporation, Tokyo, Japan) in Groups 1 and 3 and with dentin conditioner (GC Corporation, Tokyo, Japan) in Groups 2 and 4. Conventional powder-liquid glass ionomer cement (GC Fuji II, GC Corporation, Tokyo, Japan) was used as a restorative material in Groups 1 and 2. Capsulated glass ionomer cement (GC Fuji II, GC Corporation, Tokyo, Japan) was used in Groups 3 and 4. Samples were sectioned and viewed under stereomicroscope to check for the presence of voids within the cement and at the cement-tooth junction. Data was analyzed using one-way ANOVA and Tukey's post hoc tests. Group 4 showed statistically significant results (P < 0.05) when compared to Groups 1 and 2 for voids within the cement. However, for voids at the margins, the results were statistically insignificant. PMID:25544842

Sharma, Roshni; Reddy, Pallavi; Udameshi, Pooja; Vallakuruchi Jayabal, Narmatha

2014-01-01

70

Effect of Ultrasonic Excitation on the Microtensile Bond Strength of Glass Ionomer Cements to Dentin after Different Water Storage Times  

Microsoft Academic Search

The application of ultrasound waves on glass ionomer cement (GIC) surface can accelerate the early setting reaction and improve the mechanical properties of the material, resulting in higher resistance to masticatory forces within a short period of time and thus increasing the clinical longevity of the GIC restoration. In this study, the microtensile bond strength (?TBS) of two high-viscosity GICs (Fuji

Elcilaine Rizzato Azevedo; Cármen Regina Coldebella; Ângela Cristina Cilense Zuanon

71

Comparative evaluation of voids present in conventional and capsulated glass ionomer cements using two different conditioners: an in vitro study.  

PubMed

This in vitro study evaluated the presence of voids in powder-liquid and capsulated glass ionomer cement. 40 cavities were prepared on root surfaces of maxillary incisors and divided into four groups. Cavities were conditioned with glass ionomer cement liquid (GC Corporation, Tokyo, Japan) in Groups 1 and 3 and with dentin conditioner (GC Corporation, Tokyo, Japan) in Groups 2 and 4. Conventional powder-liquid glass ionomer cement (GC Fuji II, GC Corporation, Tokyo, Japan) was used as a restorative material in Groups 1 and 2. Capsulated glass ionomer cement (GC Fuji II, GC Corporation, Tokyo, Japan) was used in Groups 3 and 4. Samples were sectioned and viewed under stereomicroscope to check for the presence of voids within the cement and at the cement-tooth junction. Data was analyzed using one-way ANOVA and Tukey's post hoc tests. Group 4 showed statistically significant results (P < 0.05) when compared to Groups 1 and 2 for voids within the cement. However, for voids at the margins, the results were statistically insignificant. PMID:25544842

Kaushik, Mamta; Sharma, Roshni; Reddy, Pallavi; Pathak, Pallavi; Udameshi, Pooja; Vallakuruchi Jayabal, Narmatha

2014-01-01

72

Effects of porous-hydroxyapatite incorporated into glass-ionomer sealants.  

PubMed

The purpose of the present study was to evaluate the mechanical and chemical properties of a novel glass ionomer cement for use as a pit and fissure sealant containing a porous hydroxyapatite, namely, apatite ionomer cement (AIC). Control sealant samples were used Fuji III (GIC-S). The experiment sealant samples (AIC-S) consisted of porous spherical hydroxyapatite (HApS) particles added at 28 wt% to GIC-S powder. The GIC-S and AIC-S samples were evaluated through mechanical strength measurements, scanning electron microscopy observations, energy dispersive X-ray spectroscopy analysis, fluoride ion release tests, and antibacterial tests. The flexural strength of the AIC-S was significantly higher than that of GIC-S for each period, 1 h, 24 h and 1 year. The fluoride release dose for AIC-S was consistently higher than that for GIC-S. In addition, the antibacterial properties of AIC-S were superior to those of GIC-S. The novel AIC-S may be a more suitable sealant material for pits and fissures with intact and/or infected enamel. PMID:25740161

Shinonaga, Yukari; Arita, Kenji; Nishimura, Takako; Chiu, Szu-Yu; Chiu, Hsiu-Hui; Abe, Yoko; Sonomoto, Mie; Harada, Kyoko; Nagaoka, Noriyuki

2015-04-01

73

A Comparative Study of Color Stability and Fluoride Release from Glass Ionomer Cements Combined with Chlorhexidine  

PubMed Central

ABSTRACT Background: Restoring carious teeth is one of the major treatment needs of young children. Glass ionomer cement (GIC) systems had become the most important dental restorative and luting materials for use in preschoolers, children and teenagers. Several attempts in developing GIC with antibacterial effects by addition of bactericides, such as chlorhexidine, have been reported. Aim: Aim of the study was to evaluate and compare the color and fluoride ion release of conventional and resin-modified GICs in combination with 1.25 and 2.5% chlorhexidine diacetate. Materials and methods: The control groups consisted of conventional GIC and resin-modified GIC. The experimental groups consisted of conventional and resin-modified GIC groups, consisting of 1.25 and 2.5% chlorhexidine. A total of six groups were included with each group being allotted 20 specimens for the evaluation of color stability and 10 specimens each were allotted for the evaluation of fluoride release. Color and fluoride release were recorded using spectrophoto-meter and fluoride selective electrode respectively at 24 hours 7 days and 1 month. Results: Resin-modified GIC groups showed less color stability and better fluoride release at the end of the study compared to conventional GIC groups. Conclusion: There was no significant change in color and fluoride release between 1.25 and 2.5% conventional GIC and also between 1.25 and 2.5% resin-modified GIC combined with chlorhexidine diacetate at the end of the study. Conventional GIC showed better color stability and less fluoride release compared to resin-modified GIC. How to cite this article: Prabhakar AR, Pattanshetti K, Sugandhan S. A Comparative Study of Color Stability and Fluoride Release from Glass Ionomer Cements Combined with Chlorhexidine. Int J Clin Pediatr Dent 2013;6(1):26-29. PMID:25206183

Pattanshetti, Kirti; Sugandhan, S

2013-01-01

74

Effect of Nanoclay Dispersion on the Properties of a Commercial Glass Ionomer Cement  

PubMed Central

Objective. The reinforcement effect of polymer-grade montmorillonite (PGV and PGN nanoclay) on Fuji-IX glass ionomer cement was investigated. Materials and Method. PGV and PGV nanoclays (2.0?wt%) were dispersed in the liquid portion of Fuji-IX. Fourier-transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) were used to quantify acid-base reaction and the liquid portion of GIC. The mechanical properties (CS, DTS, FS, and Ef) of cements (n = 20) were measured at 1 hour, 1 day, and 1 month. The microstructure was examined by cryo-SEM and TEM. Results. FTIR shows that the setting reaction involves the neutralisation of PAA by the glass powder which was linked with the formation of calcium and aluminium salt-complexes. The experimental GICs (C-V and C-N) exhibited mechanical properties in compliance to ISO standard requirement have higher values than Fuji-IX cement. There was no significant correlation of mechanical properties was found between C-V and C-N. The average Mw of Fuji-IX was 15,700 and the refractive index chromatogram peak area was 33,800. TEM observation confirmed that nanoclays were mostly exfoliated and dispersed in the matrix of GIC. Conclusion. The reinforcement of nanoclays in GICs may potentially produce cements with better mechanical properties without compromising the nature of polyacid neutralisation. PMID:25210518

Fareed, Muhammad A.; Stamboulis, Artemis

2014-01-01

75

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment  

PubMed Central

Summary Background Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. Aim The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Materials and methods Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. Results No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. Conclusions When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs. PMID:24611090

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

76

Identification of organic extractables from commercial resin-modified glass-ionomers using HPLC-MS.  

PubMed

Elution of organic compounds from resin-based dental fillings during their application in the human mouth environment may have a potential impact on the human health. Ethanol, water and other solvents very often present in the human mouth have the ability to penetrate dental fillings placed in the human tooth. Penetration of liquids into the tooth may lead to the liberation of unreacted dental filling ingredients or their degradation products. Determination of these compounds is necessary for better knowledge from possible harmful effects caused by dental fillings. The aim of this study was the isolation and identification of compounds released from resin-modified glass-ionomer cements (RMGICs), resin-based dental materials applied in dentistry. Compounds were extracted from fillings by using four solvents (40% ethanol, water, 1% acetic acid and artificial saliva). Liquid samples containing eluted compounds were then extracted, evaporated and analyzed by using of HPLC-MS (high-performance liquid chromatography-mass spectrometry) and HPLC-DAD (high-performance liquid chromatography-diode array detection) techniques. Almost thirty components (monomers and additives) of RMGICs were identified. The main identified extractables were: Bis-GMA (bisphenol A glycidyl dimethacrylate), Bis-EMA (ethoxylated bisphenol A dimethacrylate), UDMA (urethane dimethacrylate), TEGDMA (triethylene glycol dimethacrylate), HEMA (2-hydroxyethyl methacrylate) as monomers and diphenyliodonium chloride, camphorquinone (initiators), BHA (inhibitor), 4-(dimethylamino) ethyl benzoate (co-initiator) as additives. PMID:16826288

Rogalewicz, Rafal; Batko, Kalina; Voelkel, Adam

2006-07-01

77

Fluoride release from three glass ionomers after exposure to sodium fluoride and acidulated phosphate fluoride gels  

PubMed Central

Background: Glass ionomer (GI) restorations exposed to fluoride have the ability to slowly release fluoride. Therefore, the aim of this study was to investigate fluoride release from three GIs before and after exposure to sodium fluoride (NaF) and acidulated phosphate fluoride (APF). Materials and Methods: Fifteen disc-shaped samples (6 mm in diameter and 2 mm in thickness) from three GIs (Fuji II, Fuji IX, Chem Flex) were made and suspended in a polypropylene recipient containing 10 mL distilled water and stored at 37°C. At the 13th day, the samples of each GI were randomly divided into 3 groups. Groups 1 and 2 were exposed to NaF and APF gels for 4 min and group 3 served as control in distilled water. The fluoride released was measured at day 1, 4, 10, 13, 14, 17, 20 and 23 by potentiometer. Data were analyzed by one-way ANOVA and Tukey test. P < 0.05 was considered as significant. Results: Fluoride release was highest after 24 h for the tested GIs, but Fuji II demonstrated the least amount. Fuji IX showed the highest fluoride release followed by Chem Flex. Exposure to fluoride gels significantly increased fluoride release for all materials (P < 0.05). The amount of fluoride release for the three GIs was significantly higher in APF groups during the test period. Conclusion: Highly viscous conventional GIs (Fuji IX and Chem Flex) released higher quantity of fluoride. PMID:25426154

Ghajari, Masoud Fallahinejad; Torabzadeh, Hassan; Safavi, Nassim; Sohrabi, Azin; Ardakani, Faezeh Fotouhi

2014-01-01

78

Effectiveness of a resin-modified glass ionomer liner in reducing hypersensitivity in posterior restorations  

PubMed Central

Background The objectives of this randomized comparative effectiveness study conducted by members of the Practitioners Engaged in Applied Research and Learning (PEARL) Network were to determine whether using a resin-modified glass ionomer (RMGI) liner reduces postoperative hypersensitivity (POH) in dentin-bonded Class I and Class II resin-based composite (RBC) restorations, as well as to identify other factors (putative risk factors) associated with increased POH. Methods PEARL Network practitioner-investigators (P-Is) (n = 28) were trained to assess sensitivity determination, enamel and dentin caries activity rankings, evaluation for sleep bruxism, and materials and techniques used. The P-Is enrolled 341 participants who had hypersensitive posterior lesions. Participants were randomly assigned to receive an RBC restoration with or without an RMGI liner before P-Is applied a one-step, self-etching bonding agent. P-Is conducted sensitivity evaluations at baseline, at one and four weeks after treatment, and at all visits according to patient-reported outcomes. Results P-Is collected complete data regarding 347 restorations (339 participants) at baseline, with 341 (98 percent) (333 participants) recalled at four weeks. Treatment groups were balanced across baseline characteristics and measures. RBC restorations with or without an RMGI liner had the same one-week and four-week POH outcomes, as measured clinically (by means of cold or air stimulation) and according to patient-reported outcomes. Conclusions Use of an RMGI liner did not reduce clinically measured or patient-reported POH in moderate-depth Class I and Class II restorations. Cold and air clinical stimulation findings were similar between groups. Practical Implications The time, effort and expense involved in placing an RMGI liner in these moderate-depth RBC restorations may be unnecessary, as the representative liner used did not improve hypersensitivity outcomes. PMID:23904575

Strober, Brad; Veitz-Keenan, Analia; Barna, Julie Ann; Matthews, Abigail G.; Vena, Donald; Craig, Ronald G.; Curro, Frederick A.; Thompson, Van P.

2014-01-01

79

Nanoclay addition to a conventional glass ionomer cements: Influence on physical properties  

PubMed Central

Objective: The objective of the present study is to investigate the reinforcement effect of polymer-grade montmorillonite (PGN nanoclay) on physical properties of glass ionomer cement (GIC). Materials and Methods: The PGN nanoclay was dispersed in the liquid portion of GIC (HiFi, Advanced Healthcare, Kent, UK) at 1%, 2% and 4% (w/w). Fourier-transform infrared (FTIR) spectroscopy was used to quantify the polymer liquid of GICs after dispersion of nanoclay. The molecular weight (Mw) of HiFi liquid was determined by gel permeation chromatography. The compressive strength (CS), diametral-tensile strength, flexural strength (FS) and flexural modulus (Ef) of cements (n = 20) were measured after storage for 1 day, 1 week and 1 month. Fractured surface was analyzed by scanning electron microscopy. The working and setting time (WT and ST) of cements was measured by a modified Wilson's rheometer. Results: The FTIR results showed a new peak at 1041 cm?1 which increased in intensity with an increase in the nanoclay content and was related to the Si-O stretching mode in PGN nanoclay. The Mw of poly (acrylic acid) used to form cement was in the range of 53,000 g/mol. The nanoclay reinforced GICs containing <2% nanoclays exhibited higher CS and FS. The Ef cement with 1% nanoclays was significantly higher. The WT and ST of 1% nanoclay reinforced cement were similar to the control cement but were reduced with 2% and 4% nanoclay addition. Conclusion: The dispersion of nanoclays in GICs was achieved, and GIC containing 2 wt% nanoclay is a promising restorative materials with improved physical properties. PMID:25512724

Fareed, Muhammad A.; Stamboulis, Artemis

2014-01-01

80

Development of a novel antimicrobial-releasing glass ionomer cement functionalized with chlorhexidine hexametaphosphate nanoparticles  

PubMed Central

Background Glass ionomer cements (GICs) are a class of dental biomaterials. They have a wide range of uses including permanent restorations (fillings), cavity linings, fissure sealants and adhesives. One of the most common reasons for replacing a dental restoration is recurrent bacterial tooth decay around the margins of the biomaterial. Therefore, a dental biomaterial which creates a sustained antimicrobial environment around the restoration would be of considerable clinical benefit. In this manuscript, the formulation of a GIC containing novel antimicrobial nanoparticles composed of chlorhexidine hexametaphosphate at 1, 2, 5, 10 and 20% powder substitution by mass is reported. The aim is to create GICs which contain chlorhexidine-hexametaphosphate nanoparticles and characterize the nanoparticle size, morphology and charge and the release of chlorhexidine and fluoride, tensile strength and morphology of the GICs. Results The GICs released chlorhexidine, which is a broad spectrum antimicrobial agent effective against a wide range of oral bacteria, over the duration of the experiment in a dose-dependent manner. This was not at the expense of other properties; fluoride release was not significantly affected by the substitution of antimicrobial nanoparticles in most formulations and internal structure appeared unaffected up to and including 10% substitution. Diametral tensile strength decreased numerically with substitutions of 10 and 20% nanoparticles but this difference was not statistically significant. Conclusion A series of GICs functionalized with chlorhexidine-hexametaphosphate nanoparticles were created for the first time. These released chlorhexidine in a dose-dependent manner. These materials may find application in the development of a new generation of antimicrobial dental nanomaterials. PMID:24456793

2014-01-01

81

Tensile and shear bond strength of resin-reinforced glass ionomer cement to glazed porcelain.  

PubMed

The purpose of this study was to measure the tensile and shear bond strength of resin-reinforced glass ionomer cement (RGIC) to glazed porcelain, to evaluate the durability of RGIC by thermal cycling, and to examine the RGIC remaining on the surface of the porcelain after the bond strength test to evaluate bonding conditions. Three adhesives were used in this study: Concise (CO) as a chemically cured composite resin, Fuji ORTHO (FO) as a chemically cured RGIC, and Fuji ORTHO LC (FOLC) as a light-cured RGIC. Tensile and shear bond strengths were measured 24 hours after bonding orthodontic brackets and also after thermal cycling. Tensile bond strength after 24 hours was 6.6 +/- 3.2 MPa in CO, 7.3 +/- 1.4 MPa in FO, and 8.6 +/- 1.9 MPa in FOLC, and the strength significantly decreased after the thermal cycling test. Shear bond strength after 24 hours was 32.5 +/- 8.9 MPa in CO, 23.3 +/- 6.8 MPa in FO, and 24.7 +/- 6.5 MPa in FOLC, and in contrast to tensile bond strength, no decreases in the strength were detected after the thermal cycling test. CO showed significantly higher shear bond strength than did FO and FOLC. When using the shear bond strength test and CO, destruction of porcelain surfaces frequently occurred after 24 hours and was observed in every specimen after the thermal cycling. RGIC was found to be an advantageous alternative to resin adhesive for bracket bonding to porcelain and to enamel. PMID:12940567

Kitayama, Yoshitaka; Komori, Akira; Nakahara, Rizako

2003-08-01

82

EFFECT OF LIGHT CURING UNIT ON RESIN-MODIFIED GLASS-IONOMER CEMENTS: A MICROHARDNESS ASSESSMENT  

PubMed Central

Objective: To evaluate the microhardness of resin-modified glass-ionomer cements (RMGICs) photoactivated with a blue light-emitting diode (LED) curing light. Material and Methods: Thirty specimens were distributed in 3 groups: Fuji II LC Improved/GC (RM1), Vitremer/3M ESPE (RM2) and Filtek Z250/ 3M ESPE (RM3). Two commercial light-curing units were used to polymerize the materials: LED/Ultrablue IS and a halogen light/XL3000 (QTH). After 24 h, Knoop microhardness test was performed. Data were submitted to three-way ANOVA and Tukey's test at a pre-set alpha of 0.05. Results: At the top surface, no statistically significant difference (p>0.05) in the microhardness was seen when the LED and QTH lights were used for all materials. At the bottom surface, microhardness mean value of RM2 was significantly higher when the QTH light was used (p<0.05). For RM1, statistically significant higher values (p<0.05) were seen when the LED light was used. No statistically significant difference (p>0.05) was seen at the bottom surface for RM3, irrespective of the light used. Top-to-bottom surface comparison showed no statistically significant difference (p>0.05) for both RMGICs, regardless of the light used. For RM3, microhardness mean value at the top was significantly higher (p<0.05) than bottom microhardness when both curing units were used. Conclusion: The microhardness values seen when a LED light was used varied depending on the restorative material tested. PMID:19466242

Cefaly, Daniela Francisca Gigo; de Mello, Liliam Lucia Carrara Paes; Wang, Linda; Lauris, José Roberto Pereira; D'Alpino, Paulo Henrique Perlatti

2009-01-01

83

A novel high-wear-resistant glass-ionomer cement for class I and class II restorations.  

PubMed

This study reports the results of an evaluation on the in vitro wear of a newly developed experimental light-cured glass-ionomer cement composed of the synthesized six-arm star-shape poly(acrylic acid) and Fuji II LC glass fillers. The resin composite P-60, as well as glass-ionomer cements Fuji II and Fuji II LC, were used for comparison. All specimens were conditioned in distilled water at 37 degrees C for 1 d prior to testing. The experimental cement exhibited statistically the same wear-resistance to abrasion as P-60, but the wear-resistance was 14 times higher for the experimental cement than for Fuji II and Fuji II LC. Furthermore, the experimental cement showed a degree of wear-resistance to attrition that was 1.4 times higher than both Fuji II and Fuji II LC but six times lower than that of P-60. Impressively, after 1 month of aging the experimental cement was able to compete with P-60 in wear-resistance to attrition, showing a degree of wear depth that was only 1.3 times more than that of P-60. It appears that this novel cement is a clinically attractive dental restorative that can be potentially used for high-wear sites such as class I and class II restorations. PMID:19196323

Zhao, Jun; Weng, Yiming; Xie, Dong

2009-02-01

84

Retention of a resin-based sealant and a glass ionomer used as a fissure sealant in children with special needs  

PubMed Central

Objectives: The aim of this research is to evaluate the retention of sealants of resin and resin-modified ionomeric glass pits and fissures, on first permanent molars of special patients. Material and Methods: The sample was comprised by 32 children. The ages were between 7 and 18 years. The sealing procedure was made with the relative isolation of the molars to be sealed, through the use of cotton rolls. Two molars were sealed with Clinpro Sealant 3M Dental and the others with Vitremer. Checking of the sealants was made after 3 and 6 months of their placement, evaluating with 3 values: TR: Totally Restrained; PR: Partially Restrained; and CL: Completely Lost. Results: 67.18% of the resinous sealants, and 70.31% of the glass ionomer sealants were successful after three months. After six months, 57.81% of the resin-based sealants and 51.56% of the glass ionomer sealants were successful. When performing the Chi-square statistical analysis (P<0.05) no statistical significance was observed after 6 months. Conclusions: The retention of the resin sealant was similar to that of the glass ionomer cement at the end of six months and the retention of sealants on maxillary teeth was higher than on mandibular teeth. Key words:Sealant, glass ionomer, retention, caries, special needs. PMID:25674325

Nualart-Grollmus, Zacy-Carola

2014-01-01

85

In Vitro Comparison of Coronal Microleakage between Resilon Alone and Gutta-Percha with a Glass-ionomer Intraorifice Barrier Using a Fluid Filtration Model  

Microsoft Academic Search

The prevention and control of coronal microleakage is critical for successful endodontic outcomes. The purpose of this study was to compare coronal microleakage between Resilon alone and gutta-percha with a glass ionomer intraorifice barrier using a fluid filtration model. Thirty-four extracted human teeth were decoronated, prepared to a standardized length of 16 mm, and instrumented to a .06 taper ISO

Ryan M. Jack; Gary G. Goodell

2008-01-01

86

Glass ionomer cement: evidence pointing to fluorine release in the form of monofluorophosphate in addition to fluoride ion.  

PubMed

The fluoride ion released from glass ionomer cements into water is reportedly, in part, complexed with other elements present in the cement. When measured using ion selective electrode potentiometry (ISE) a decomplexant TISAB IV (T) is used to convert all fluoride to F- ion which the ISE can detect. In this study, an additional decomplexing procedure (H) designed to hydrolyse fluorine covalently bonded to phosphorus in the monofluorophosphate (MFP) ion into F- was also used. The soluble products from three glass ionomers were analysed by both techniques (H & T). Five 1 x 10 mm discs were each immersed in 10 ml of de-ionised water. This was changed and 4 ml analysed by T and 4 ml by H at 1, 2, 3, 6, 10, 13, 17, 21, 24, 28, and 31 days. H was greater than T for 161 of the 165 pairs ( chi2=74.7, p=<0.001 ). The total cumulative F release H (in micromol/g cement) at 31 days for AH2 was 122.3, s.d. 30.8; LG26 44.0, s.d. 1.55; LG30 10.0, s.d. 3.15 as compared T results of 100.1, s.d. 31.1; 30.3, s.d. 1.92; 3.7, s.d. 1.36, respectively. In all three cases the H was significantly greater than T (matched pair 't' test with p=0.01 or less). H-T was show to have a very strong associative relationship with t1/2 (R2=0.98 or greater p<0.001 ). Evaluating the ratio of P:F in the cements in comparison with the ratio of additional F measured by H to that measured by T produced a relationship log[(H-T)/T]=0.28 x log[P/F]-0.45 with R2=0.999. It is concluded that glass ionomers release more fluorine than is detected by ISE using TISAB IV. If this F is in the form of MFP this may be released more completely into saliva than F as F-, release of which is substantially reduced by Ca2+, since calcium monofluorophosphate is more soluble than CaF2. PMID:15020112

Billington, R W; Williams, J A; Dorban, A; Pearson, G J

2004-08-01

87

Histological analysis of biocompatibility of ionomer cements with an acid-base reaction.  

PubMed

The purpose of this study was to evaluate the inflammatory and cure events of acid-based reactions using glass ionomer cement used for cementation of crowns, bridges, onlays and orthodontic bands implanted in subcutaneous tissue, at different time intervals. A total of 48 male Wistar rats were used, distributed into 4 groups (n = 12), as follows: Group C (control, polyethylene), Group ME (Meron), Group KC (Ketac Cem) and Group PR (Precedent). The animals were sacrificed after time intervals of 7, 15 and 30 days, and their tissues were analyzed under an optical microscope for such events as inflammatory infiltrate, edema, necrosis, granulation tissue, multinucleated giant cells, young fibroblasts and collagen. The results was assessed using Kruskal-Wallis and Dunn's tests (p < 0.05). In the initial period, intense inflammatory infiltrate was observed for all the materials with no significant difference among them (p = 0.104). Groups PR and KC showed significant difference in relation to Group C, at 7 days (p = 0.025) and 15 days (p = 0.006). Edema and giant cells were more expressive in Group ME, differing significantly from Groups C (p = 0.023) and KC (p = 0.039), respectively, at 7 days. Group ME showed a statistically significant difference in relation to Groups PR and KC for the presence of young fibroblasts (p = 0.009) and for collagen (p = 0.002), at 7 days. Within the limits of this in vivo study, Precedent and Ketac Cem glass ionomer cements showed better tissue healing with a greater number of fibroblasts and collagen, as compared to Meron. PMID:25006620

Santos, Rogério Lacerda dos; Moura, Mirella de Fátima Liberato de; Carvalho, Fabiola Galbiatti de; Guênes, Gymenna Maria Tenório; Alves, Polliana Muniz; Pithon, Matheus Melo

2014-01-01

88

Effect of Marginal Sealant on Shear Bond Strength of Glass Ionomer Cement: Used as A Luting Agent  

PubMed Central

Background: Moisture sensitivity and dissolution has been a known drawback of glass ionomer cement (GIC). When used as a luting agent for cementation of casted indirect restoration, the exposed cement at the margins is often a primary factor for marginal leakage and consequent failure of the restoration. The following in vitro study was planned to evaluate the effect of a marginal sealant on GIC used as luting agent. Materials and Methods: Sixty healthy extracted premolars were selected and prepared to receive metal-ceramic prosthesis. The prepared restorations were cemented using GIC and were divided randomly into two groups. The specimens in Group A were directly immersed in artificial saliva solution without any protection at the margins, while the exposed cement for Group B specimens was protected using a marginal sealant before immersing it in the artificial saliva solution. The specimens were tested after 24 h using a crown pull test on the universal testing machine to measure the shear bond strength of the cement. Result: The specimens in Group B showed statistically significant difference from the specimens in Group A with the mean shear bond strength of 6.60 Mpa and 5.32 respectively. Conclusion: Protection of GIC exposed at the margins of indirect cast restorations with a marginal sealant can significantly increase the longevity of the prosthesis by reducing the marginal leakage and perlocation of fluids. How to cite the article: Nazirkar G, Singh S, Badgujar M, Gaikwad B, Bhanushali S, Nalawade S. Effect of marginal sealant on shear bond strength of glass ionomer cement: Used as a luting agent. J Int Oral Health 2014;6(3):65-9 PMID:25083035

Nazirkar, Girish; Singh, Shailendra; Badgujar, Mayura; Gaikwad, Bhushan; Bhanushali, Shilpa; Nalawade, Sumit

2014-01-01

89

A preliminary study of the effect of glass-ionomer and related dental cements on the pH of lactic acid storage solutions.  

PubMed

Glass-ionomer cements, both self-hardening and resin-modified, have been shown to increase the pH of lactic acid solutions in which they are stored. Similar results have been obtained for a zinc phosphate and a zinc polycarboxylate cement. The pH was increased over a period of 7 days by between 1.54 and 2.65 pH units from an initial value of pH of 2.60, depending on the cement. It is concluded that, as a result of this ability to neutralize surrounding aqueous solutions, these materials may have the beneficial effect in vivo of inhibiting caries development. In the case of glass-ionomers, this mechanism might complement that of fluoride release. PMID:10022784

Nicholson, J W; Czarnecka, B; Limanowska-Shaw, H

1999-01-01

90

Effects of conventional and high-intensity light-curing on enamel shear bond strength of composite resin and resin-modified glass-ionomer  

Microsoft Academic Search

The purpose of this study was to evaluate the shear bond strengths of a composite resin (Transbond XT; 3M\\/Unitek, Monrovia, Calif) and a resin-modified glass ionomer (Fuji Ortho LC; GC America Inc, Alsip, Ill) cured with 2 different light-curing units: a conventional visible light unit (Ortholux XT; 3M Dental Products, St Paul, Minn) and a xenon arc light unit (Plasma

Maria Francesca Sfondrini; Vittorio Cacciafesta; Angela Pistorio; Giuseppe Sfondrini

2001-01-01

91

Effect of different light curing systems on the shear bond strength of resin-modified glass ionomer cement and polyacid-modified composite resin  

Microsoft Academic Search

The aim of this study was to determine in vitro shear bond strength of resin-modified glass ionomer cement (RMGIC) and polyacid-modified composite resin (PMCR) polymerized with conventional halogen light curing unit (LCU) or light emitting diode (LED). Twenty-four mandibular molar teeth were used. Enamel was removed from buccal and lingual surfaces of the teeth to expose superficial dentin. Teeth were

Oya Bala; Hacer Deniz Arisu; Bagdagul Helvacioglu Kivanc; Sara Samur

92

An in vitro study of fluoride release from a resin-modified glass ionomer cement after exposure to toothpaste slurries of different pH  

Microsoft Academic Search

. The aim of the study was to evaluate the fluoride release from an aged resin-modified glass ionomer (Vitremer) after exposure\\u000a to five toothpaste slurries with different pH values. Cylindrical specimens of the material were leached in de-ionized water\\u000a for 3 months and then exposed for 30 min daily for 10 days to three dentifrice slurries (20 specimens\\/group) containing 0.05%

C. Olsson; C. G. Emilson; D. Birkhed

2000-01-01

93

Three-Year Survival of One-Surface ART Restorations and Glass-Ionomer Sealants in a School Oral Health Programme in Zimbabwe  

Microsoft Academic Search

An oral health care programme in secondary schools using the atraumatic restorative treatment (ART) approach for dental caries was started in 1993. Glass ionomer (restorative type II, 1) was used as the restorative and sealant material. Sealants were placed using the ‘press-finger’ technique. Results after 3 years revealed a survival percentage for one-surface ART restorations of 85.3 (95% CL: 89.7–80.9%),

J. E. Frencken; F. Makoni; W. D. Sithole; E. Hackenitz

1998-01-01

94

Comparative Assessment of ActiV GP\\/Glass Ionomer Sealer, Resilon\\/Epiphany, and Gutta-Percha\\/AH Plus Obturation: A Bacterial Leakage Study  

Microsoft Academic Search

The objective of this study was to compare the sealing ability of ActiV GP\\/glass ionomer (GI) sealer (Brasseler USA, Savannah, GA), Resilon\\/Epiphany (Pentron Clinical Technologies, Wallingford, CT), and gutta-percha (GP)\\/AH Plus (Dentsply Maillefer, Tulsa, OK). Seventy-three human single-rooted teeth were randomly divided into three test groups (20 canals each) and two control groups (5 positive and 8 negative). Using Enterococcus

Joel N. Fransen; Jianing He; Gerald N. Glickman; Alejandro Rios; Jay D. Shulman; Allen Honeyman

2008-01-01

95

Morphological Changes Of The Root Surface And Fracture Resistance After Treatment Of Root Fracture By CO2 Laser And Glass Ionomer Or Mineral Trioxide Aggregates  

NASA Astrophysics Data System (ADS)

This in vitro study evaluates the morphological changes of the root surface and fracture resistance after treatment of root cracks by CO2 laser and glass Ionomer or mineral trioxide aggregates (MTA). Fifty freshly extracted human maxillary central incisor teeth with similar dimension were selected. Crowns were sectioned at the cemento-enamel junction, and the lengths of the roots were adjusted to 13 mm. A longitudinal groove with a dimension of 1×5 mm2 and a depth of 1.5 mm was prepared by a high speed fissure bur on the labial surface of the root. The roots were divided into 5 groups: the 10 root grooves in group 1 were remained unfilled and were used as a control group. The 10 root grooves in group 2 were filled with glass Ionomer, 10 root grooves in group 3 were filled with MTA, the 10 root grooves in group 4 were filled with glass Ionomer and irradiated by CO2 laser and the 10 root grooves in group 5 were filled with MTA and irradiated with CO2 laser. Scanning electron microscopy was performed for two samples in each group. Tests for fracture strength were performed using a universal testing machine and a round tip of a diameter of 4 mm. The force was applied vertically with a constant speed of 1 mm min 1. For each root, the force at the time of fracture was recorded in Newtons. Results were evaluated statistically with ANOVA and Turkey's Honestly Significant Difference (HSD) tests. SEM micrographs revealed that the melted masses and the plate-like crystals formed a tight Chemical bond between the cementum and glass Ionomer and melted masses and globular like structure between cementum and MTA. The mean fracture resistance was the maximum fracture resistance in group 5 (810.8 N). Glass Ionomer and MTA with the help of CO2 laser can be an alternative to the treatment of tooth crack or fracture. CO2 laser increase the resistance of the teeth to fracture.

Badr, Y. A.; Abd El-Gawad, L. M.; Ghaith, M. E.

2009-09-01

96

A novel star-shaped poly(carboxylic acid) for resin-modified glass-ionomer restoratives.  

PubMed

We have developed a novel glass-ionomer cement (GIC) system composed of photo-curable star-shaped poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer radical polymerization using a newly synthesized multi-arm chain-transfer agent. The star-shaped polyacids showed significantly lower viscosities in water as compared to the linear polyacids. Due to the lower viscosities, the molecular weight (MW) of the polyacids can be significantly increased for enhancing the mechanical strengths while keeping the ease of mixing and handling. The effects of MW, GM-tethering ratio, P/L ratio, and aging on the compressive properties of the experimental cements were significant. The light-cured experimental cements showed significantly improved mechanical strengths i.e. 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS, and 36% in FS, higher than commercial Fuji II LC. After aging in water for 1 month, the compressive strength of the novel light-cured experimental cement reached 343?MPa, which was 34% and 42% higher than Fuji II and Fuji II LC, respectively. This one-month aged experimental cement was also 23% higher than itself after one day aging, indicating that aging in water can significantly enhance salt-bridge formation for this novel star-shaped polyacid-comprised GIC. PMID:24865692

Weng, Y; Howard, L; Xie, D

2014-07-01

97

Evaluation of antibacterial and antifungal activity of new calcium-based cement (Biodentine) compared to MTA and glass ionomer cement  

PubMed Central

Objective: To evaluate the antibacterial and antifungal properties of calcium-based cement, Biodentine (Ca3SiO2), compared to commercial glass ionomer cements (GICs) and mineral trioxide aggregate (MTA). Materials and Methods: Pellets of GICs, ProRoot MTA, and Biodentine were prepared to test the influence of these cements on the growth of four oral microbial strains: Streptococcus mutans, Enterococcus faecalis, Escherichia coli, and Candida albicans; using agar diffusion method. Wells were formed by removing the agar and the manipulated materials were immediately placed in the wells. The pellets were lodged in seeded plates and the growth inhibition diameter around the material was measured after 24-72 h incubation at 37°C. The data were analyzed using analysis of variance (ANOVA) test to compare the differences among the three cements at different concentrations. Results: Test indicates that the antimicrobial activity of Biodentine, on all the microorganisms tested, was very strong, showing a mean inhibition zone of 3.2 mm, which extends over time towards all the strains. For Biodentine, GIC, and MTA, the diameters of the inhibition zones for S. mutans were significantly larger than for E. faecalis, Candida, and E. coli (P < 0.05). Conclusion: All materials showed antimicrobial activity against the tested strains except for GIC on Candida. Largest inhibition zone was observed for Streptococcus group. Biodentine created larger inhibition zones than MTA and GIC. PMID:25657526

Bhavana, Vankayala; Chaitanya, Krishna Popuri; Gandi, Padma; Patil, Jayaprakash; Dola, Binoy; Reddy, Rahul B.

2015-01-01

98

Predicting composition-property relationships for glass ionomer cements: A multifactor central composite approach to material optimization.  

PubMed

Adjusting powder-liquid ratio (P/L) and polyacrylic acid concentration (AC) has been documented as a means of tailoring the handling and mechanical properties of glass ionomer cements (GICs). This work implemented a novel approach in which the interactive effects of these two factors on three key GIC properties (working time, setting time, and compressive strength) were investigated using a central composite design of experiments. Using nonlinear regression analysis, formulation-property relationships were derived for each property, which enabled prediction of an optimal formulation (P/L and AC) through application of the desirability approach. A novel aluminum free GIC was investigated, as this material may present the first clinically viable GIC for use in injectable spinal applications, such as vertebroplasty. Ultimately, this study presents the first series of predictive regression models that explain the formulation-dependence of a GIC, and the first statistical method for optimizing both P/L and AC depending on user-defined inputs. PMID:25828159

Kiri, Lauren; Boyd, Daniel

2015-06-01

99

Effect of dietary solvents on the strength of nanocomposite, compomer, glass ionomer cement: An in-vitro study  

PubMed Central

Background: Intraoral degradation of resin restorative materials involves both mechanical and chemical factors. Thus, an in vitro study was conducted to compare the strength of nanocomposite to commonly used esthetic restorative materials in simulated in vivo conditions. Aim: The aim of this study was to determine the influence of dietary solvents on the strength of nanocomposite and other esthetic restorative materials. Materials and Methods: Three test groups (nanocomposite, compomer and glass ionomer cement) each containing 60 pre-conditioned samples, divided into four subgroups of 15 samples each and conditioned in different dietary solvents, were subjected to shear punch test in custom designed shear punch apparatus in Instron Universal Testing Machine. Statistical Analysis: Descriptive statistics, one way analysis of variance (ANOVA), paired t-test were implied. Results: One-way ANOVA revealed nanocomposite to bear most shear punch strength post-conditioning, as compared with the other two test materials. Conclusion: Nanocomposite yielded better strength than the other two test materials, indicating its universal application as a restorative material. PMID:24347887

Kaur, Harsimran; Nandlal, B

2013-01-01

100

Evaluation of micro-shear bond strength of resin modified glass-ionomer to composite resins using various bonding systems  

PubMed Central

Aim: The aim was to compare the micro-shear bond strength between composite and resin-modified glass-ionomer (RMGI) by different adhesive systems. Materials and Methods: A total of 16 discs of RMGI with a diameter of 15 mm and a thickness of 2 mm were randomly divided into four groups (n = 4). Four cylinders of composite resin (z250) were bonded to the RMGI discs with Single Bond, Clearfil SE Bond and Clearfil S3 Bond in Groups 1-3, respectively. The fourth group was the control. Samples were tested by a mechanical testing machine with a strain rate of 0.5 mm/min. Failure mode was assessed under a stereo-microscope. Results: The means of micro-shear bond strength values for Groups 1-4 were 14.45, 23.49, 16.23 and 5.46 MPa, respectively. Using a bonding agent significantly increased micro-shear bond strength (P = 0.0001). Conclusion: Micro-shear bond strength of RMGI to composite increased significantly with the use of adhesive resin. The bond strength of RMGI to composite resin could vary depending upon the type of adhesive system used. PMID:24347892

Kasraie, Shahin; Shokripour, Mohadese; Safari, Mahin

2013-01-01

101

Interfacial characteristics of resin-modified glass-ionomer materials: a study on fluid permeability using confocal fluorescence microscopy.  

PubMed

The tooth interface with resin-modified glass-ionomer cements (RM GICs) is poorly understood. This study examined the interface, especially with dentin. Cervical cavities in extracted teeth were restored with Fuji II LC, Vitremer, Photac-Fil, or a conventional GIC, Fuji Cap II. Fluorescent dye was placed in the pulp chambers for 3 hrs before the specimens were sectioned. Examination of the tooth/material interface with a confocal microscope showed that dye uptake by the restoration varied among materials. A "structureless", non-particulate, highly-stained layer of GIC was observed next to dentin in Fuji II LC. This layer varied in width, was prominent where the dentin tubules were cut "end-on" and in areas closer to the pulp, and was not seen adjacent to enamel. Vitremer showed minimal dye uptake, and the "structureless" layer was barely discernible. Photac-Fil showed more uniform uptake and absence of this layer. Cracking of enamel was also noted with these materials. The conventional GIC did not show any dye uptake, presence of a "structureless" layer, or enamel cracking. We elucidated the potential mechanisms involved in the formation of a "structureless" interfacial layer in Fuji II LC by studying the variables of cavity design, surface pre-treatment, water content of the tooth, time for it to develop, early finishing, and coating of the restoration. This layer, the "absorption layer", is probably related to water flux within the maturing cement, depending on environmental moisture changes and communication with the pulp in a wet tooth. The "micropermeability model" was useful in this study of the interfacial characteristics of RM GICs. PMID:9759672

Sidhu, S K; Watson, T F

1998-09-01

102

Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements.  

PubMed

This in vitro study evaluated the marginal gap, cement thickness, and microleakage of glass-ionomer cement (GIC) and phosphate monomer-containing resin cement (MDP-RC) under 2 zirconia crown systems (Cercon and DC-Zirkon). Forty human premolars were prepared for all-ceramic zirconia crowns with a 1 mm circumferential finish line and a 1.5 mm occlusal reduction. The crowns (n = 10 per group) from each zirconia system were randomly divided into 2 groups and cemented either with GIC (Vivaglass CEM) or MDP-RC (Panavia F 2.0) cement. The cemented crowns were thermocycled 5000 times (5°-55°C). The crowns were immersed in 0.5% basic fuchsine dye solution for 24 hours and sectioned buccolingually and mesiodistally. Specimens were examined under optical microscope (100X). Data were analyzed using Student t-test and chi-square tests (? = 0.05). Mean marginal gap values for Cercon (85 ± 11.4 ?m) were significantly higher than for DC-Zircon (75.3 ± 13.2 ?m) (P = 0.018). The mean cement thickness values of GIC (81.7 ± 13.9 ?m) and MDP-RC (78.5 ± 12.5 ?m) were not significantly different (P = 0.447). Microleakage scores did not demonstrate significant difference between GIC (P = 0.385) and MDP-RC (P = 0.631) under Cercon or DC-Zircon. Considering the cement thickness values and microleakage scores obtained, both zirconia crown systems could be cemented in combination with either GIC or MDP-RC. PMID:24598500

Sener, Isil; Turker, Begum; Valandro, Luiz Felipe; Ozcan, Mutlu

2014-01-01

103

Nanoclays reinforced glass ionomer cements: dispersion and interaction of polymer grade (PG) montmorillonite with poly(acrylic acid).  

PubMed

Montmorillonite nanoclays (PGV and PGN) were dispersed in poly(acrylic acid) (PAA) for utilization as reinforcing filler in glass ionomer cements (GICs). Chemical and physical interaction of PAA and nanoclay (PGV and PGN) was studied. PAA–PGV and PAA–PGN solutions were prepared in different weight percent loadings of PGV and PGN nanoclay (0.5-8.0 wt%) via exfoliation-adsorption method. Characterization was carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared (FTIR) spectroscopy. XRD results of PAA–PGN demonstrated that the interlayer space expanded from 12.83 to 16.03 Å indicating intercalation whereas the absence of the peak at d(001) in PAA–PGV indicated exfoliation. XPS scans of PGV and PGN nanoclays depicted the main peak of O 1s photoelectron due to Si–O–M (M = Mg, Al, Fe) whereas, Si–O–Al linkages were identified by Si 2p or Si 2s and Al 2p or Al 2s peaks. The disappearance of the Na peak confirmed that PAA molecules exchanged sodium ions present on surface of silicate layers and significantly reduced the electrostatic van-der-Waals forces between silicate plates resulting in intercalation or exfoliation. FTIR spectra of PAA–nanoclay suspensions demonstrated the presence of a new peak at 1,019 cm(-1) associated with Si–O– stretching vibrations which increased with increasing nanoclays concentration. Information concerning the dispersion of nanoclay in PAA aqueous solutions, chemical reaction and increase interlayer space in montmorillonite nanoclay is particularly useful regarding dispersion and reinforcement of nanoclay in PAA. PMID:24077996

Fareed, Muhammad A; Stamboulis, Artemis

2014-01-01

104

An in vitro study on the maturation of conventional glass ionomer cements and their interface to dentin.  

PubMed

The objective of the study was to investigate the influence of long-term storage (up to 1 year) and coating on the variation of micro-mechanical properties of four conventional restorative glass ionomer cements (GICs) within 3.5 mm deep class I cavities. Four commercially available GICs (Riva Self Cure (SDI), ChemFil Rock (Dentsply), Fuji IX Fast and Fuji IX GP Extra/Equia (GC)) were applied to 100 teeth. In each tooth, two similar 3.5 mm deep class I cavities were prepared and filled with the GICs, with and without resin coating. The samples were stored in artificial saliva at 37 °C for 1 week, 1 month, 3 months, 6 months and 1 year. The variation in mechanical properties (indentation modulus (E) and Vickers hardness (HV)) were determined in 100 ?m steps starting from the filling surface, through the intermediate layer in between dentine and GIC, and ending 100 ?m in dentin. HV and E were strongly influenced by the material (P<0.05, partial eta-squared ?P(2) = 0.31 and 0.23) but less by aging duration (P<0.05, ?P(2) = 0.02 and 0.12) and resin coating (P<0.05, ?P(2) = 0.02 and 0.03). The depth of measurement (0-2 mm) has no influence on HV (P = 0.789). HV shows a gentle increase over the 1 year storage period (P = 0.002). A ?300 ?m GIC zone at the areas close to dentin with weaker properties as those measured in dentin or GIC was identified in all fillings, irrespective of the presence of coating, and at all storage periods. The thickness of this zone is more strongly influenced by storage (P<0.05, ?P(2) = 0.081) than by material type (P<0.05, ?P(2) = 0.056), while coating showed no influence (P = 0.869). Filler morphology and dimension were similar to upper parts of the GIC filling; however, the amount of low cations was higher. We concluded that the development of an intermediate layer in between dentine and GIC with lower mechanical properties might be responsible for the bond quality of GIC to dentine. Moreover, class I GIC restorations are unlikely to feature constant mechanical properties throughout the cavity, regardless of conditions such as aging and coating. PMID:23954325

Zoergiebel, Julius; Ilie, Nicoleta

2013-12-01

105

Dielectric properties of conductive ionomers  

NASA Astrophysics Data System (ADS)

Ion and polymer dynamics of ion-containing polymers were investigated, with the majority of results obtained from application of a physical model of electrode polarization (EP) to dielectric spectroscopy data. The physical model of MacDonald, further developed by Coelho, was extended for application to tan delta (the ratio of dielectric loss to dielectric constant) as a function of frequency. The validity of this approach was confirmed by plotting the characteristic EP time as a function of thickness and comparing the actual and predicted unrelaxed dielectric constant for a poly(ethylene oxide) (PEO)-based ionomer neutralized by lithium, sodium, and cesium. Results were obtained for ion mobility and mobile ion concentration for a neat PEO-based ionomer, two (methoxyethoxy-ethoxy phosphazene) (MEEP) -based ionomers, two MEEP-based salt-doped polymers, sulfonated polystyrene (SPS) neutralized by sodium with a high sulfonation fraction, and SPS neutralized by zinc with a low sulfonation fraction. Additionally, the conductivity parameters of six plasticized forms of a neat PEO-based ionomer were characterized, but the method apparently failed to correctly evaluate bulk ionic behavior. In all cases except the SPS ionomers ion mobility follows a Vogel-Fulcher-Tammann (VFT) temperature dependence. In all cases, mobile ion concentration follows an Arrhenius temperature dependence. Fitting parameters from these two relationships yielded direct information about the state of ionic diffusion and ion pairing in each system. Combination of these two functionalities predicts a relationship for conductivity that is significantly different than the VFT relation typically used in the literature to fit conductivity. The most outstanding result was the extremely small fraction of ions found to be mobile. For ionomers it can be concluded that the primary reason for low conductivities arises from the low fraction of mobile ions. The local and segmental dynamics of the neat and plasticized PEO-based ionomer were also studied in comparison to conductivity, with the conclusion that the glass transition temperature (a manifestation of the segmental segments) is the primary property governing conduction behavior in single-phase ionomers. Consideration of the solvent quality parameters yielded a similar result, that the plasticization effect on the glass transition is far stronger than the dielectric constant, donor number, or viscosity of the solvents.

Klein, Robert James

106

Fracture frequency and longevity of fractured resin composite, polyacid-modified resin composite, and resin-modified glass ionomer cement class IV restorations: an up to 14 years of follow-up  

Microsoft Academic Search

The aim of this study was to evaluate the fracture frequency and longevity of fractured class IV resin composite (RC), polyacid-modified\\u000a resin composite (compomer; PMRC), and resin-modified glass ionomer cement (RMGIC) restorations in a longitudinal long-term\\u000a follow-up. Eighty-five class IV RC (43: Pekafil), PMRC (24: Dyract (D), Hytac (H)), and RMGIC (18: Fuji II LC (F), Photac\\u000a Fil (P)) restorations

Jan W. V. van Dijken; Ulla Pallesen

2010-01-01

107

Methods and preliminary findings of a cost-effectiveness study of glass-ionomer-based and composite resin sealant materials after 2 yr.  

PubMed

The cost-effectiveness of glass-carbomer, conventional high-viscosity glass-ionomer cement (HVGIC) [without or with heat (light-emitting diode (LED) thermocuring) application], and composite resin sealants were compared after 2 yr in function. Estimated net costs per sealant were obtained from data on personnel time (measured with activity sampling), transportation, materials, instruments and equipment, and restoration costs for replacing failed sealants from a community trial involving 7- to 9-yr-old Chinese children. Cost data were standardized to reflect the placement of 1,000 sealants per group. Outcomes were the differences in the number of dentine caries lesions that developed between groups. The average sealant application time ranged from 5.40 min (for composite resin) to 8.09 min (for LED thermocured HVGIC), and the average cost per sealant for 1,000 performed per group (simulation sample) ranged from $US3.73 (for composite resin) to $US7.50 (for glass-carbomer). The incremental cost-effectiveness of LED thermocured HVGIC to prevent one additional caries lesion per 1,000 sealants performed was $US1,106 compared with composite resin. Sensitivity analyses showed that differences in the cost of materials across groups had minimal impact on the overall cost. Cost and effectiveness data enhance policymakers' ability to address issues of availability, access, and compliance associated with poor oral-health outcomes, particularly when large numbers of children are excluded from care, in economies where oral health services are still developing. PMID:24799118

Goldman, Ann S; Chen, Xi; Fan, Mingwen; Frencken, Jo E

2014-06-01

108

Calcium silicate cement-induced remineralisation of totally demineralised dentine in comparison with glass ionomer cement: tetracycline labelling and two-photon fluorescence microscopy.  

PubMed

Two-photon fluorescence microscopy, in combination with tetracycline labelling, was used to observe the remineralising potentials of a calcium silicate-based restorative material (Biodentine(TM) ) and a glass ionomer cement (GIC:?Fuji?IX) on totally demineralised dentine. Forty demineralised dentine discs were stored with either cement in three different solutions: phosphate buffered saline (PBS) with tetracycline, phosphate-free tetracycline, and tetracycline-free PBS. Additional samples of demineralised dentine were stored alone in the first solution. After 8-week storage at 37 °C, dentine samples were imaged using two-photon fluorescence microscopy and Raman spectroscopy. Samples were later embedded in PMMA and polished block surfaces studied by 20 kV BSE imaging in an SEM to study variations in mineral concentration. The highest fluorescence intensity was exhibited by the dentine stored with Biodentine(TM) in the PBS/tetracycline solution. These samples also showed microscopic features of matrix remineralisation including a mineralisation front and intra- and intertubular mineralisation. In the other solutions, dentine exhibited much weaker fluorescence with none of these features detectable. Raman spectra confirmed the formation of calcium phosphate mineral with Raman peaks similar to apatite, while no mineral formation was detected in the dentine stored in cement-free or PBS-free media, or with GIC. It could therefore be concluded that Biodentine(TM) induced calcium phosphate mineral formation within the dentine matrix when stored in phosphate-rich media, which was selectively detectable using the tetracycline labelling. PMID:25421432

Atmeh, A R; Chong, E Z; Richard, G; Boyde, A; Festy, F; Watson, T F

2015-02-01

109

Influence of air-abrasion executed with polyacrylic acid-Bioglass 45S5 on the bonding performance of a resin-modified glass ionomer cement.  

PubMed

The aim of this study was to test the microtensile bond strength (?TBS), after 6 months of storage in PBS, of a resin-modified glass ionomer cement (RMGIC) bonded to dentine pretreated with Bioglass 45S5 (BAG) using various etching and air-abrasion techniques. The RMGIC (GC Fuji II LC) was applied onto differently treated dentine surfaces followed by light curing for 30 s. The specimens were cut into matchsticks with cross-sectional areas of 0.9 mm(2). The ?TBS of the specimens was measured after 24 h or 6 months of storage in PBS and the results were statistically analysed using two-way anova and the Student-Newman-Keuls test (? = 0.05). Further RMCGIC-bonded dentine specimens were used for interfacial characterization, micropermeability, and nanoleakage analyses by confocal microscopy. The RMGIC-dentine interface layer showed no water absorption after 6 months of storage in PBS except for the interdiffusion layer of the silicon carbide (SiC)-abraded/polyacrylic acid (PAA)-etched bonded dentine. The RMGIC applied onto dentine air-abraded with BAG/H(2)O only or with BAG/PAA-fluid followed by etching procedures (10% PAA gel) showed no statistically significant reduction in ?TBS after 6 months of storage in PBS. The abrasion procedures performed using BAG in combination with PAA might be a suitable strategy to enhance the bonding durability and the healing ability of RMGIC bonded to dentine. PMID:22409224

Sauro, Salvatore; Watson, Timothy F; Thompson, Ian; Toledano, Manuel; Nucci, Cesare; Banerjee, Avijit

2012-04-01

110

Comparison of Marginal Microleakage of Glass Ionomer Restorations in Primary Molars Prepared by Chemo-mechanical Caries Removal (CMCR), Erbium: Yttrium Aluminum-Garnet (Er:YAG) Laser and Atraumatic Restorative Technique (ART)  

PubMed Central

ABSTRACT Background: It is important to emphasize that the aspects of pretreatment techniques, as well as the composition and mechanism of adhesion, may decisively influence the effectiveness of the restorative materials in sealing cavity margins and preventing marginal leakage. Aims: This study assessed the in vitro influence of surface preparation techniques on the microleakage of glass ionomer restorations in primary teeth. Materials and methods: The study groups were divided into three different techniques: (1) The chemomechanical caries removal (CMCR) method using the Apacaries gel, (2) the erbium:yttrium aluminum-garnet (Er:YAG) laser method and (3) the atraumatic restorative technique (ART). The teeth restored with a glass ionomer restorative material (Fuji IX GP capsule, GC Corporation, Tokyo, Japan). The dye penetration was measured in micrometers using a polarized light microscope and specific computer software. Results: The results showed that the mean microleakage level after was lowest with the CMCR method using Apacaries gel and highest with the Er:YAG laser. There was a statistically significant difference regarding the mean microleakage level between the group with the CMCR method using Apacaries gel and the Er:YAG laser. Conclusion: Marginal leakage was significantly higher with preparations made using the Er:YAG laser than with the CMCR method using Apacaries gel and spoon excavator (p < 0.05). How to cite this article: Juntavee A, Juntavee N, Peerapattana J, Nualkaew N, Sutthisawat S. Comparison of Marginal Microleakage of Glass Ionomer Restorations in Primary Molars Prepared by Chemomechanical Caries Removal (CMCR), Erbium: Yttrium Aluminum-Garnet (Er:YAG) Laser and Atraumatic Restorative Technique (ART). Int J Clin Pediatr Dent 2013;6(2):75-79. PMID:25206196

Juntavee, Niwut; Peerapattana, Jomjai; Nualkaew, Nartsajee; Sutthisawat, Sitikorn

2013-01-01

111

Effect of Ascorbic Acid on Shear Bond Strength of Orthodontic Brackets Bonded with Resin-modified Glass-ionomer Cement to Bleached Teeth  

PubMed Central

Background and aims Bleaching can considerably reduce shear bond strength (SBS) of orthodontic brackets bonded with composite adhesives. Application of antioxidants is a method to reverse the negative effect of bleaching on composite-to-enamel bond. However, the efficacy of antioxidants in increasing the SBS of brackets bonded using resin-modified glass-ionomer cement (RMGIC) has not been studied, which was the aim of this study. Materials and methods Fifty freshly extracted human maxillary first premolars were bleached with 35% hydrogen peroxide (Pola Office Bleaching, SDI). Sodium ascorbate 10% was applied to the experimental specimens (n=25). All the specimens were etched with 37% phosphoric acid (Ivoclar/Vivadent) and bonded using RMGIC (Fuji Ortho LC, GC). The specimens were subjected to incubation (37°C, 24h) and thermocycling (1000 cycles, 5-55°C, dwell time = 1 min). The SBS was measured at 0.5 mm/min debonding crosshead speed. The adhesive remnant index (ARI) was scored under ×10 magni-fication. Data were analyzed using Mann-Whitney U test, one- and independent-samples t-test, and Fisher’sexact test (?=0.05). Results The mean SBS of experimental and control groups were 11.97 ± 4.49 and 7.7 ± 3.19 MPa, respectively. The dif-ference was statistically significant (P=0.000 by t-test). SBS of both control (P=0.014) and experimental (P=0.000) groups were significantly higher than the minimum acceptable SBS of 6 MPa, according to one-sample t-test. Conclusion Application of ascorbic acid can guarantee a strong bond when RMGIC is to be used. However, RMGIC might tolerate the negative effect of bleaching with minimum SA treatments (or perhaps without treatments), which de-serves further studies. PMID:22991638

Khosravanifard, Behnam; Rakhshan, Vahid; Araghi, Solmaz; Parhiz, Hadi

2012-01-01

112

The effects of ambient temperature and mixing time of glass ionomer cement material on the survival rate of proximal ART restorations in primary molars  

PubMed Central

Objective: Temperature fluctuations and material mixing times are likely to affect the consistency and integrity of the material mixture, and hence the restoration made out of it. The purpose of the present study was to determine the influence of the ambient temperature and the mixing time of glass ionomer cement (GIC) restorative material on the survival rate of proximal atraumatic restorative treatment (ART) restorations placed in primary molars. Materials and Methods: A total of 804 restorations were placed in the primary molars of 6-8-year-olds using the ART approach. The restorations were then followed for a period of 2 years and evaluated at given intervals. The data collected were analyzed using SPSS computer statistical program, and the results tested and compared using the Chi-square, Kaplan Meier survival analysis and Cox Proportional hazard statistical tests. Results: The cumulative survival rate of the restorations dropped from the initial 94.4% to 30.8% at the end of 2 years. The higher survival rate of the restorations was associated with the experienced operators and assistants when using the rubber dam isolation method. However, there was no statistically significant difference in the survival rate of the restorations when related to the room temperature and the mixing time of the GIC materials used in spite of the variations in the temperature recoded and the methods used in mixing the materials. Conclusion: The ambient temperature and mixing time of GIC did not have a significant effect on the survival of the proximal ART restorations. PMID:24808692

Kemoli, Arthur M

2014-01-01

113

Effect of acid pre-conditioning and/or delayed light irradiation on enamel bond strength of three resin-modified glass ionomers  

PubMed Central

Background: Polymerization of resin-modified glass-ionomers (RMGIs) is mediated through two competing mechanisms: An acid-base reaction and a light-dependent resin polymerization. Furthermore, pre-conditioning with acid has resulted in an increase in enamel bond strength of some RMGIs. This in vitro study evaluated the effect of pre-conditioning and/or delayed irradiation on bond strength of three RMGIs to enamel. Materials and Methods: In this in vitro study, 144 flat enamel surfaces of human molars were ground using consecutively finer abrasives up to 600-grit silicon carbide paper. Each surface was rinsed and gently air-dried (n =12). The RMGIs (Fuji II LC Improved; Ionolux and Vitremer) were bonded to enamel surfaces using the following protocols: Groups 1: Based on manufacturers’ instructions; Groups 2: Pre-conditioning with phosphoric acid for 30 s; groups 3: A 2-min delay in irradiation; groups 4: Pre-conditioning with acid for 30 s plus a 2-min delay in light activation. After 24-h storage at 37°C and 500 rounds of thermocycling, the samples underwent shear bond strength (SBS) test. Data was analyzed with 3-way ANOVA and Tukey HSD test (? =0.05). Results: There were significant differences between the study groups (P < 0.001). Acid-pre-conditioning increased Fuji II LC SBS values; it significantly decreased SBS values of Vitremer but had no effect on SBS values of Ionolux. Ionolux and Vitremer exhibited decreased enamel bond strength after a delay in light activation (P < 0.05). A 2-min delay in light activation combined with acid pre-conditioning increased RMGI SBS values only for Fuji II LC. Conclusion: Within the limitations of the present study, the effect of acid pre-conditioning, delaying irradiation and both on enamel bond strength of RMGIs was material-dependent. Further investigations are recommended. PMID:24019800

Khoroushi, Maryam; Hosseini-Shirazi, Moeen; Soleimani, Hojatolah

2013-01-01

114

Remineralizing efficacy of silver diamine fluoride and glass ionomer type VII for their proposed use as indirect pulp capping materials – Part II (A clinical study)  

PubMed Central

Aim: To evaluate in vivo the remineralizing efficacy of silver diamine fluoride (SDF), glass ionomer Type VII (GC VII) and calcium hydroxide (Dycal). Materials and Methods: 60 subjects in the age group of 18-35 years, matching the inclusion criteria and having deep carious lesions in the permanent first and second molars were selected. The teeth were aseptically opened under rubber dam and after gross caries removal, approximately 0.4mg of soft discolored dentin was removed with a sharp spoon excavator from the mesial or distal aspect of the cavity. The test material was randomly selected and applied in a thickness of 1.5-2mm and the cavity sealed with cavit. The patients were followed up at regular intervals with radiographic evaluation at 12 weeks. At 3 months the temporary restoration was removed and dentin samples were collected from the other half of the cavity which was left in the first appointment. Atomic absorption spectrophotometry, Colorimetric test using UV-vis spectrometer and potentiometric titration were used for determining calcium, phosphorous and fluoride respectively. Results: Almost equivalent rise in the percentage of calcium level was seen in GC VII and Ca(OH)2 groups, followed by SDF group. Highest percentage rise in phosphate ions was seen in GC VII group followed by SDF group and Ca(OH)2 group. Highest percentage of fluoride rise was seen in GC VII group followed by SDF group and Ca(OH)2 group. Conclusions: The results indicated that both GC VII and SDF can be potential indirect pulp capping materials. PMID:22025824

Sinha, N; Gupta, A; Logani, A; Shah, N

2011-01-01

115

Nafion Perfluorosulfonate Ionomer Membranes  

NSDL National Science Digital Library

This document provides some information on Nafion perfluorosulfonate ionomer membranes. This particular ionomer is used in several applications including liquid and gas separations, fuel cells, and the chlor-alkali industries. The structure of the material and its chemical makeup is discussed here in depth. This document may be downloaded in PDF file format.

116

Can Seedling Ionomics Predict Rice Grain Ionomics?  

Technology Transfer Automated Retrieval System (TEKTRAN)

The study investigated the possibility of using the mineral (ionomic) composition of rice (Oryza sativa L.) seedling leaves to predict cultivars that accumulate large amounts of certain minerals in their grains. This information will be used for genetically improving the nutritional value of rice gr...

117

An in vitro study of apical and coronal microleakage of laterally condensed gutta percha with Ketac-Endo and AH-26.  

PubMed

The purpose of this in vitro study was to compare both apical and coronal dye penetration when Ketac-Endo and AH-26 sealers were used with laterally condensed gutta percha. Crowns were removed from 28 teeth and the root canals were biomechanically prepared. The teeth were divided into two groups of 12-teeth each and a control group of 4 teeth. Root canals in the two experimental groups were filled with laterally condensed gutta percha and either Ketac-Endo or AH-26 sealer. The Ketac-Endo group had the coronal 3 mm of gutta percha and sealer removed and the resultant cavity was filled with Ketac-Endo alone. After the sealers had set, the root surfaces were coated with nail varnish except at the apex and at the coronal end. Positive controls had no root fillings and were coated with nail varnish in the same manner while the negative controls were sealed apically and coronally with Cavit prior to sealing the entire external root surface with nail varnish. Specimens were placed in 2% methylene blue dye in a vacuum of 660 mm of mercury for five minutes and then left immersed for a further two days. The roots were vertically sectioned to determine the following mean levels of dye penetration: Ketac-Endo, 1.08 mm apically and 6.29 mm coronally; AH-26, 0.75 mm apically and 6.67 mm coronally. Positive controls had total leakage and negative controls had no leakage. This study demonstrated that the apical and coronal seals obtained with Ketac-Endo and AH-26 were not significantly different although the apical seal obtained with each material was significantly better than the corresponding coronal seal. PMID:9775474

Oliver, C M; Abbott, P V

1998-08-01

118

Effect of cement type and water storage time on the push-out bond strength of a glass fiber post.  

PubMed

This study investigated the effects of the cement type and the water storage time on the push-out bond strength of a glass fiber post. Glass fiber posts (Fibrekor, Jeneric Pentron) were luted to post spaces using a self-cured resin cement (C&B Cement [CB]), a glass ionomer cement (Ketac Cem [KC]) or a resin-modified glass ionomer cement (GC FujiCEM [FC]) according to the manufacturers' instructions. For each luting agent, the specimens were exposed to one of the following water storage times (n=5): 1 day (T1), 7 days (T7), 90 days (T90) and 180 days (T180). Push-out tests were performed after the storage times. Control specimens were not exposed to water storage, but subjected to the push-out test 10 min after post cementation. Data (in MPa) were analyzed by Kruskal-Wallis and Dunn`s test (?=0.05). Cement type and water storage time had a significant effect (p<0.05) on the push-out bond strength. CB showed significantly higher values of retention (p<0.05) than KC and FC, irrespective of the water storage time. Water storage increased significantly the push-out bond strength in T7 and T90, regardless of the cement type (p<0.05). The results showed that fiber posts luted to post spaces with the self-cured resin cement exhibited the best bonding performance throughout the 180-day water storage period. All cements exhibited a tendency to increase the bond strength after 7 and 90 days of water storage, decreasing thereafter. PMID:22011889

Reis, Kátia Rodrigues; Spyrides, George Miguel; Oliveira, Jonas Alves de; Jnoub, Alexandre Abrão; Dias, Kátia Regina Hostilio Cervantes; Bonfantes, Gerson

2011-01-01

119

Comparison of marginal adaptation of mineral trioxide aggregate, glass ionomer cement and intermediate restorative material as root-end filling materials, using scanning electron microscope: An in vitro study  

PubMed Central

Aim: The present study compares the marginal adaption of Mineral Trioxide Aggregate (MTA), Glass Ionomer Cement (GIC) and Intermediate Restorative Material (IRM) as root-end filling materials in extracted human teeth using Scanning Electron Microscope (SEM). Materials and Methods: Thirty single rooted human teeth were obturated with Gutta-percha after cleaning and shaping. Apical 3 mm of roots were resected and retrofilled with MTA, GIC and IRM. One millimeter transverse section of the retrofilled area was used to study the marginal adaptation of the restorative material with the dentin. Mounted specimens were examined using SEM at approximately 15 Kv and 10-6 Torr under high vacuum condition. At 2000 X magnification, the gap size at the material-tooth interface was recorded at 2 points in microns. Statistical Analysis: One way ANOVA Analysis of the data from the experimental group was carried out with gap size as the dependent variable, and material as independent variable. Results: The lowest mean value of gap size was recorded in MTA group (0.722 ± 0.438 ?m) and the largest mean gap in GIC group (1.778 ± 0.697 ?m). Conclusion: MTA showed least gap size when compared to IRM and GIC suggesting a better marginal adaptation. PMID:25506146

Gundam, Sirisha; Patil, Jayaprakash; Venigalla, Bhuvan Shome; Yadanaparti, Sravanthi; Maddu, Radhika; Gurram, Sindhura Reddy

2014-01-01

120

An ex vivo study to evaluate the remineralizing and antimicrobial efficacy of silver diamine fluoride and glass ionomer cement type VII for their proposed use as indirect pulp capping materials – Part I  

PubMed Central

Aim: Indirect pulp capping (IPC) preserves the pulp vitality by disinfecting and remineralizing remaining carious dentin. In the present study, glass ionomer (GC, FUJI VII) and silver diamine fluoride (SDF) were tested and compared to calcium hydroxide for their antimicrobial efficacy and remineralizing potential. Materials and Methods: Dentin disks prepared from 45 freshly extracted first premolars were divided into three groups (n = 15). Each disk was cut into two equal parts, in which one half formed the control. Thirty dentin samples were used for ion estimation and the other 15 for microhardness testing. Atomic absorption spectrophotometry, colorimetric and potentiometric titration analyses were performed for calcium, phosphate and fluoride ion detection, respectively. The antimicrobial efficacy was analyzed using pure culture of Streptococcus mutans and mixed flora. Results: Increase in the levels of calcium and phosphate ions was the highest in calcium hydroxide group. Both SDF and GC VII groups showed significant increase in fluoride ion levels. Samples treated with GC VII showed maximum increase in micro hardness. The highest zone of bacterial inhibition was found with SDF group. Conclusions: This in vitro study documented the remineralizing, re-hardening and antimicrobial efficacy of both SDF and GC VII and hence can act as effective IPC materials. PMID:21814348

Gupta, A; Sinha, N; Logani, A; Shah, N

2011-01-01

121

Rheological Behavior of Oligomeric Ionomers  

SciTech Connect

The rheological behavior of the alkali metal salts of oligomeric sulfonated polystyrene (PS) ionomers was characterized using dynamic and steady shear measurements. The starting PS had a weight average molecular weight of 4000 g/mol and a narrow molecular weight distribution (1.06). Two sulfonation levels were examined, 2.5 and 4.8 mol %, which corresponded, respectively, to one and two sulfonate groups per chain on average. The ionomers exhibited nanophase separation of an ion-rich phase, and as a consequence, time-temperature superposition failed for all samples. Sulfonation increased the melt viscosity of the ionomers, as much as seven orders of magnitude. The zero shear viscosity scaled as cq/a, where c was the concentration of the ionic groups, q was the charge of the cation, and a was the cation radius, and although the molecular weight of the parent polystyrene was much lower than the entanglement molecular weight, the ionomer melts exhibited strong elastic behavior. The flow activation energy of the ionomers was similar to that of high molecular weight PS and the calculated molecular weight between 'entanglements' of the ionomers was the same as for PS.

Weiss, R.; Zhao, H

2009-01-01

122

Anion Conduction in PEO-Functionalized Polyphosphazene Ionomers  

NASA Astrophysics Data System (ADS)

A series of novel polyphosphazene ionomers with short chain poly(ethylene oxide) (PEO) moieties, bound ammonium cations, and free iodide anions were previously synthesized. Ion dynamics during anion conduction of the ionomers were studied by dielectric relaxation spectroscopy (DRS). These polyphosphazenes provide interesting conductive materials to study because of their low glass transition temperature, high segmental mobility, and high ion content. Analysis of DRS results provides static dielectric constant, conducting ion mobility, and conducting ion content for the materials. An increase in the length of the alkyl group extending from the polymer-bound ammonium cation increases conductivity and conducting ion concentration due to new steric interactions weakening ion-ion associations that restrict segmental mobility. By placing ether oxygens in the short alkyl group a large increase in conductivity and a decrease in the glass transition temperature is observed due to strong associations between the cation and ether oxygen lone pairs.

Bartels, Joshua; Hess, Andrew; Allcock, Harry; Colby, Ralph; Runt, James

2013-03-01

123

Glass ionomer cements: chemistry of erosion.  

PubMed

A three-month study of the chemistry of the water erosion of two forms of ASPA cement has been made. The effect of varying cement consistency and cure time was investigated. The results are discussed in terms of the known chemistry and structure of the cement. The erosion behavior is compared to that of silicate, silicophosphate, and zinc polycarboxylate dental cements. The state of absorbed water and the mechanism of erosion is discussed. PMID:187630

Crisp, S; Lewis, B G; Wilson, A D

1976-01-01

124

Encapsulant Material For Solar Cell Module And Laminated Glass Applications  

DOEpatents

An encapsulant material includes a layer of metallocene polyethylene disposed between two layers of ionomer. More specifically, the layer of metallocene polyethylene is disposed adjacent a rear surface of the first ionomer layer, and a second layer of ionomer is disposed adjacent a rear surface of the layer of metallocene polyethylene. The encapsulant material can be used in solar cell module and laminated glass applications.

Hanoka, Jack I. (Brookline, MA)

2000-09-05

125

Comparative evaluation of microleakage in conventional glass ionomer cements and triclosan incorporated glass ionomer cements  

PubMed Central

Aim and Objective: The aim of the following study is to comparatively evaluate the microleakage of triclosan incorporated GIC with conventional restorative GIC. Materials and Methods: Triclosan in powder form was added to conventional GIC to formulate a concentration of 2.5%. Class five cavities were prepared in non-carious extracted molars and were respectively restored with conventional restorative GIC and triclosan incorporated GIC. Samples were kept in 10% methylene blue dye. Ground sections were obtained and were observed under a binocular microscope for dye penetration. Result: No significant difference was found in the microleakage of two groups. Conclusion: Triclosan incorporated GIC can be considered as an alternative to GIC with enhanced antibacterial property. PMID:24808702

Somani, Rani; Jaidka, Shipra; Jawa, Deepti; Mishra, Shreya

2014-01-01

126

Ionic Association States in Polyester Copolymer Ionomers  

NASA Astrophysics Data System (ADS)

A series of random copolyester ionomers were previously synthesized from poly(ethylene oxide) (PEO600) and poly(tetramethylene oxide) (PTMO650) oligomers, separated by the lithium or sodium salt of a sulfonated phthalate. PEO exhibits better solvating ability, while PTMO based ionomers have somewhat lower Tg. By changing the ratio of PEO/PTMO, the polymer's ability to solvate ions at the same ion content was varied, in order to explore the trade-off between ion solvation and lower Tg. Ionomers with different PEO/PTMO ratios were investigated by FTIR spectroscopy. The results show a systematic change in the ion association states and ion aggregation geometries with PEO/PTMO ratio and temperature. Ionomers with sodium cations have more ion pairs compared to the Lithium ionomers at the same PEO/PTMO ratio, which correspond to the higher dielectric constants in the sodium ionomers. These findings agree with previous X-ray scattering and dielectric relaxation spectroscopy results that the system microphase separates into PEO-rich and a PTMO-rich microphases and the majority of the cations reside in the PEO-rich microphase.

Masser, Hanqing; Dou, Shichen; Colby, Ralph; Painter, Paul; Runt, James

2013-03-01

127

Oxygen reduction at platimun/ionomer interface: effects of phase separation of ionomer  

SciTech Connect

Oxygen reduction reaction (ORR) at the interface between platinum and recast ionomers (Nafion EW 1100 and 950 and 6F-40) was studied at different temperatures (20--80{sup o}C) and humidities (10--100%) employing smooth Pt and Pt-black-covered ultramicroelectrodes. ORR was strongly inhibited on smooth electrodes. The inhibition increased with the reduction time, temperature and humidity, but was absent for Nafion EW 1100 in contact with liquid water. It was attributed to the hydrophobic component of ionomer blocking both active sites and oxygen transport. It was postulated that the dynamic changes in interfacial phase separation of ionomer are facilitated by the attractive interactions between the hydrophobic component of ionomer and bare platinum and between oxide-covered Pt and the hydrophilic component of ionomer. These interactions were also proposed to be responsible for the differences in ORR voltammetry for films prepared and equilibrated under different conditions. The decrease in ORR inhibition, Nafion EW 950> Nafion EW 1100> 6F-40, was correlated with physical and molecular properties of the ionomers. The lack of inhibition for Pt-black-covered electrodes was attributed to the more random distribution of ionomer chains and the high activation barriers for the ionomer restructuring at rough interfaces.

Chlistunoff, Jerzy [Los Alamos National Laboratory

2008-01-01

128

Thermal analytical study of polyamide copolymer/Surlyn Ionomers Blends  

SciTech Connect

Thermal analytical technique was used as a screening method to study polyamide(Nylon)/ethylene-co-methacrylic acid copolymer-based ionomer(Surlyn)blends. The retardation of crystallization process from molten state of Nylon-12 by the existence of the ionomer was observed, but the crystallization of Nylon-12 can not be thwarted even at high concentration of ionomers. Zinc ionomers shows stronger effect than sodium ionomers. A Nylon copolymer, polyamide-6,6-co-polyamide-6,10, was used to blend with different ionomers and the crystallization process from molten state of Nylon copolymer could be thwarted at high concentration of zinc ionomer even at very cooling rate. Interesting cold crystallization behavior of polyamide copolymer was observed during second DSC heating cycle in the temperature range of the melting process of ionomer.

Qin, C.; Ding, Y.P. [Baxter Healthcare Corp., Round Lake, IL (United States)

1993-12-31

129

Molecular mobility, morphology, and ion conduction in ionomers for electroactive devices  

NASA Astrophysics Data System (ADS)

A sequential study of ion-containing polymers capable of ion solvation with varied ion content, dielectric constant, and counterions is presented in this dissertation in order to compare ion transport properties in ionomers with various ionic interactions. Structure-property relationships in these ion containing polymers are defined using x-ray scattering, rheology and dielectric spectroscopy, enabling the quantification of ion transport dynamics. Poly(ethylene oxide), (PEO) based ionomers are investigated in order to probe the relation between ion conduction and segmental relaxation, and copolymers of PEO and Poly(tetramethylene oxide), (PTMO) further develop an understanding of the trade-off between ion solvation and segmental dynamics. Ionomers with ionic liquid counterions probe diffuse charge interactions and steric effects on ion transport, and incorporation of ionic liquids into ionomer membranes such as Nafion provides desirable thermal and ion conducting properties which extend the use of such membranes for electroactive devices. PEO ionomers exhibit a strong relation between ionic conductivity and segmental dynamics, providing insight that the glass transition temperature, Tg, dominates the ion conduction mechanism. Increasing temperature induces aggregation of ionic groups as evidenced by the static dielectric constant and X-ray scattering as a function of temperature, revealing the contribution of ionic dipoles in the measured dielectric constant. The trade-off between ion solvation and fast polymer segmental dynamics are quantified in copolymer ionomers of PEO and lower Tg PTMO. While conducting ion content remains nearly unchanged, conductivity is lowered upon incorporation of PTMO, because the vast majority of the PTMO microphase separates from the PEO-rich microdomain that remains continuous and contributes most of the ion conduction. Dielectric constants and X-ray scattering show consistent changes with temperature that suggest a cascading aggregation process in Na ionomers as ionic dipoles thermally randomize and lower the measured dielectric constant of the medium, leading to further aggregation. We observe amplified microphase-separation through ionic groups preferentially solvated by PEO chains, as seen in block copolymers with added salt. Even at 25%PEO / 75%PTMO the ionomers have VFT temperature dependence of conducting ion mobility, meaning that the 25% PEO/ion microphase is still continuous A model is developed to describe the frequency dependent storage and loss modulus and the delay in Rouse motion due to ion association lifetime, as functions of ion content and molecular weight for our low molecular weight ionomers. The ion rearrangement relaxation in dielectric spectroscopy is clearly the ion association lifetime that controls terminal dynamics in linear viscoelasticity, allowing a simple sticky Rouse model, using the most-probable distribution based on NMR Mn, to fully describe master curves of the frequency dependent storage and loss modulus. Using insight from ionic interaction strength, ionic liquids are used as counterions, effectively plasticizing the ionomers without added solvent. Ionic interactions were weakened with increasing counterion size, and with modification of cations using ether-oxygen, promoting self-solvation, which increases conducting ion density by an order of magnitude. Room temperature ionic liquids were subsequently used in combination with NafionRTM membranes as electroactive substrates to correlate ion transport to morphology as a function of volume fraction of ionic liquid. This study illuminated the critical volume uptake of ionic liquid in Nafion, identifying percolation of ionic pathways and a significant increase in dielectric constant at low frequencies, indicating an increase in the number density of ions capable of polarizing at the electrode surface. Consequently, the fundamental information obtained about the structure-property relations of ionomers can be used to predict and design advanced ion-containing polymers to be used in battery membranes and a v

Tudryn, Gregory J.

130

Comparative ionomes of rice leaves and seeds  

Technology Transfer Automated Retrieval System (TEKTRAN)

The project is investigating the possibility of using the mineral (ionomics) composition of rice (Oryza sativa L.) seedling leaves to predict varieties that accumulate large amounts of certain minerals in their seeds. This information will be used for improving our understanding of the mineral physi...

131

In vitro fracture strengths of six core materials supported with a prefabricated metal post  

Microsoft Academic Search

Results: The fracture strength of Clearfil group, except Coremax group, was significantly higher than the other groups (p<0.05). Empress 2 group followed them and there was no significant difference between Empress 2 and coremax groups. Empress showed significantly lower fracture resistance than these three groups but higher than Ionofil and Ketac-silver groups. Glass- ionomer and Ketac silver groups were statistically

Mustafa KALKAN; Filiz AYKENT; Münir Tolga YÜCEL; Serhan AKMAN

132

An impedance spectroscopy study in poly(butylene adipate) ionomers  

NASA Astrophysics Data System (ADS)

Poly(butylenes adipate) ionomers (PBAi) were synthesized using dimethyl 5-sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. We have investigated electrical and dielectric properties of the ionomers to evaluate alternating current (AC) parameters such as impedance, conductance, dielectric constant, admittance, susceptance, dielectric loss, and resistance by an impedance spectroscopy. It is seen that the ionic conductances of the ionomers increase with increasing content of DMSI. The AC conductance for the ionomers was found to vary as s with the index s 1. A decrease in the relative dielectric constant of the ionomers is observed with the increase in the ionic content. The electrical relaxation in the dielectric spectra of the ionomers was not observed due to the orientation polarization of the dipoles. It is also observed that the tangent loss increases with the increase in the ionic content.

Yakuphanoglu, F.; Yoo, Y. T.; Okutan, M.

2004-10-01

133

Isobutylene-based ionomer composites: siliceous filler reinforcement  

Microsoft Academic Search

The morphology, mechanical, and barrier properties of composites derived from phosphonium bromide ionomer derivatives of an isobutylene-based elastomer (IIR-PPh3Br) are compared with analogous non-ionic composites. Improved adhesion between the ionomer and onium ion-exchanged montmorillonite clay (NR4+-MM) allowed standard polymer compounding techniques to yield highly reinforced elastomer nanocomposites. Similar increases in the strength of interactions between ionomer and precipitated silica resulted

J. Scott Parent; Andrea Liskova; Rui Resendes

2004-01-01

134

Size-exclusion chromatography of perfluorosulfonated ionomers  

Microsoft Academic Search

A size-exclusion chromatography (SEC) method in N,N-dimethylformamide containing 0.1M LiNO3 is shown to be suitable for the determination of molar mass distributions of three classes of perfluorosulfonated ionomers, including Nafion®. Autoclaving sample preparation is optimized to prepare molecular solutions free of aggregates, and a solvent exchange method concentrates the autoclaved samples to enable the use of molar-mass-sensitive detection. Calibration curves

T. H. Mourey; L. A. Slater; R. C. Galipo; R. J. Koestner

2011-01-01

135

Ionomer Degradation in Electrodes of PEM Fuel Cell  

SciTech Connect

Although PEMFC Membrane Electrode Assembly (MEA) durability related studies have increased dramatically since 2004, studies on ionomer degradation of the composite electrodes has received far less attention than that of the proton exchange membranes, electrocatalysts, and catalyst supports. The catalyst layer ionomer unavoidably gets involved in other components degradation processes since it is subjected to exposure to different operating effects, including the presence of the catalyst, catalyst support, and the porous nature of the electrode layer which includes 2-phase flow. PEMFC durability issues cannot be fully resolved without understanding the contribution of ionomer degradation in electrode to the performance decay in life time. However, addressing the impact of changes to the catalyst layer ionomer during durability tests is experimentally difficult mainly because of the need to separate the ionomer in the electrode from other components during chemical, electrical and materials characterization. The catalyst layer ionomer is essentially chemically identical to the membrane ionomeric material, and is composed of low atomic number elements, making characterization difficult. In the present work, MEAs with different Nafion ionomer types: stabilized and non-stablized ionomer in the electrode layer (Type I) and mixed membrane/ionomer MEAs (Type II) were designed to separate ionomer degradation from membrane degradation, as shown in Figure (1a) and (b) respectively. Stabilized and non stabilized ionomers were 5% Nafion{reg_sign} solutions (Ion Power, New Castle, Delaware). The non-stabilized version is the typical Nafion chemical structure with carboxylic acid (-COOH) end groups; these end groups are thought to be a susceptible point of degradative peroxide attack. The stabilized version replaces the -COOH end groups with -CF{sub 3} end groups to prevent peroxide attack at the end groups. Type I MEAs were designed to compare ionomer degradation and its effect on performance decay. Since F{sup -} ions are released only from PFSA based membranes, and not from non-PFSA based membranes, Type II MEAs use a hydrocarbon membrane with no fluorine with a PFSA (Nafion{reg_sign}) ionomer in the catalyst layer for FER measurements. Any F{sup -} ions measured will then have come only for the catalyst layer ionomer during degradation experiments. Type II MEAs allow more detailed chemical characterization exclusively of the catalyst layer ionomer to better understand its degradation.

Borup, Rodney L. [Los Alamos National Laboratory

2011-01-01

136

Microleakage of newly developed glass carbomer cement in primary teeth  

PubMed Central

Objective: Glass carbomer cement represents a new generation of dental material, which mineralizes gradually into fluorapatite. The aim of this study was to evaluate the microleakage and marginal integrity of newly developed glass carbomer cement with and without protective surface coating (SC) in primary molars. Methods: Standardized cavities were prepared on extracted human primary molars, and the teeth were randomly assigned into the following groups (n = 10/each): (1) conventional glass ionomer cement (GIC) without SC; (2) GIC with SC; (3) glass carbomer cement without SC; (4) glass carbomer cement with SC; and (5) compomer without SC. Following thermocycling (5 ± 2°C–55 ± 2°C, dwell time 15 s, 2000×), the specimens were immersed in 0.5% basic fuchsin solution, sectioned, and digitally photographed. Microleakage was evaluated quantitatively by using open-source image analysis toolkit (ImageJ), and the data were analyzed statistically by using Kruskal-Wallis and Conover’s Multiple Comparison tests (P=.05). Results: The greatest amount of dye leakage was observed in the uncoated glass carbomer specimens, followed by the uncoated glass ionomer group (P<.05). There was no significant difference between the microleakage values of coated glass ionomer, coated glass carbomer, and the compomer (P>.05). The following statistical ranking was observed among microleakage of the test materials: uncoated glass carbomer > uncoated glass ionomer > coated glass ionomer ? coated glass carbomer ? compomer. Uncoated glass carbomer exhibited severe internal ice crack-like lines. Conclusion: The use of the new glass carbomer cement without SC results in severe microleakage and catastrophic internal cracks. PMID:23408469

Cehreli, Sevi Burcak; Tirali, R. Ebru; Yalcinkaya, Zeynep; Cehreli, Zafer C.

2013-01-01

137

Influence of the polymer backbone structure on the properties of aromatic ionomers with pendant sulfobenzoyl side chains for use as proton-exchange membranes.  

PubMed

Six different ionomers having various aromatic polymer backbones with pendant 2-sulfobenzoyl side chains were prepared by nucleophilic aromatic substitution reactions of lithium 2,6-difluoro-2'-sulfobenzophenone with 4,4-biphenol, 2,7-dihydroxynaphthalene, 4,4-isopropylidenediphenol, 4,4-dihydroxydiphenyl ether, 4,4'-thiodiphenol, and 4,4'-thiobisbenzenethiol, respectively, to produce four poly(arylene ether)s, one poly(arylene ether sulfide), and one poly(arylene sulfide). Mechanically tough proton-exchange membranes with ion-exchange capacities in the narrow range from 1.9 to 2.3 mequiv/g were cast from the high-molecular-weight ionomers, and subsequently investigated with respect to their structure-property relationships. Glass transitions were only detected for ionomers in the sodium salt form, and increasing glass-transition temperatures (Tg) were found to give higher thermal decomposition temperatures. Analysis by small-angle X-ray scattering indicated that the ionic clustering was promoted for ionomers with flexible polymer backbones and low Tg values. The proton conductivity of the membranes at 80 °C under fully humidified conditions was found between 0.02 and 0.2 S/cm and appeared to depend primarily on the Tg. PMID:21138250

Jutemar, Elin Persson; Jannasch, Patric

2010-12-01

138

Glass transition and ionic conduction in plasticized and doped ionomers  

E-print Network

electrolytes for lith- ium-ion batteries and other electrochemical applications [1­4]. Although physical(ethylene glycol) (PEG) and dimethyl 5-sul- foisophthalate sodium salt. The sodium can be ex- changed to lithium

Colby, Ralph H.

139

Comparison of a SiO(2)-CaO-ZnO-SrO glass polyalkenoate cement to commercial dental materials: glass structure and physical properties.  

PubMed

Glass polyalkenoate cements (GPCs) have previously been considered for orthopedic applications. A Zn-GPC (BT 101) was compared to commercial GPCs (Fuji IX and Ketac Molar) which have a setting chemistry analogous to BT 101. Handling properties (working, T (w) and setting, T (s) times) for BT 101 were shorter than the commercial GPCs. BT 101 also had a higher setting exotherm (S (x) -34 °C) than the commercial GPCs (29 °C). The maximum strengths for BT 101, Fuji IX, and Ketac Molar were 75, 238, and 216 MPa (compressive, ? (c)), and 34, 54, and 62 MPa (biaxial flexural strengths, ? (f)), respectively. The strengths of BT 101 are more suitable for spinal applications than commercial GPCs. PMID:23179999

Wren, A W; Coughlan, A; Laffir, F R; Towler, M R

2013-02-01

140

Effect of loading and distributions of Nafion ionomer in the catalyst layer for PEMFCs  

Microsoft Academic Search

The electrode with various contents of Nafion ionomer for inside and\\/or on the surface in the catalyst layer, respectively, was designed for proton exchange membrane fuel cell (PEMFC) electrode to investigate the effect of Nafion ionomer distribution in the catalyst layer on cell performance and improve electrode performance. The effect of Nafion ionomer on the electrode of each design was

Dokyol Lee; Siwoo Hwang

2008-01-01

141

Chemical interactions in ionomers and ionomer membranes containing metal particles and ions  

SciTech Connect

Ionomer membranes are employed in PEM fuel cells as the proton conducting element, but they also hold potential for catalytic applications in both hydrogen based and other low temperature fuel cells. In these applications the reactions of H{sub 2}, CO, O{sub 2}, H{sub 2}O and other small molecules with metal-based catalysts are important to consider. Reactions of these species with perfluorocarbonsulfonic acid based ionomers (PFSA), of which Nafions{reg_sign} are prototypical, containing Rh, Ru, Pt and other metal ions and particles are shown. Metal carbonyls form with metal ions that have been reduced in situ to reduced valence ions or to metal particles, by the combination of CO and H{sub 2}O or with H{sub 2} directly. Metal nitrogen complexes also can be formed. In addition, the interactions of dissimilar metal ions leads to distinct species with NO or CO, for example, that are different from the products with either ion separately.

Risen, W.M. Jr.

2000-07-01

142

Preparation and properties of ionomers of bisphenol A polycarbonate  

SciTech Connect

The preparation and properties of bisphenol A polycarbonate with a small percentage (0.5-10 mol%) of sulfonate groups attached randomly along the backbone are described. This small modification has a dramatic influence on the polymer properties, particularly the rheology. The melt viscosity at low shear rates is comparable to a branched polycarbonate, and the ionomers have improved flame and solvent resistance. Water absorption is increased, but the increase is not large. These ionomers can be prepared inexpensively using a reactive blending process starting with commercial bisphenol A polycarbonate and a diphenyl ester of sulfoisophthalic acid, a monomer used for PET fiber.

Drumright, R.E.; Stevens, C.; Mullins, M.J. [Dow Chemical Co., Freeport, TX (United States)

1996-12-31

143

The assessment of surface roughness and microleakage of eroded tooth-colored dental restorative materials  

PubMed Central

Objectives: To investigate the effect of acidic solution on surface roughness and microleakage of tooth-colored restorative materials. Materials and Methods: A 160 box-shaped cavities were prepared on the buccal surfaces of 160 human molars, and assigned to four groups: Group A restored with Ketac™ Molar Easymix, Group B with Fuji II™ LC, Group C with Ketac™ N100, and Group D with Filtek™ Z250, and subdivided into study and control groups (n = 20). Study groups were immersed in lemon juice (pH = 2.79) for 24 h, whilst controlgroups in deionized distilled water. All samples were immersed in 2% methylene blue dye, sectioned into two equal halves for surface roughness, and microleakage tests. Data were analyzed using Mann–Whitney and Kruskal–Wallis tests at P < 0.05. Results: There was a significant difference in surface roughness of Ketac™ Molar, Fuji II™ LC, and Ketac™ N100. No significant difference was found in microleakage of Ketac™ Molar and Fuji II™ LC; however, there were significant differences in the gingival margin of Ketac™ N100, and the occlusal margin of Filtek™ Z250. Conclusions: All glass ionomer cements were eroded after exposure to the acidic drink. Filtek™ Z250 and Ketac™ Molar Easymix showed more microleakage. All materials showed more microleakage at the gingival margins. PMID:25506139

Hussein, Thulfiqar Ali; Bakar, Wan Zaripah Wan; Ghani, Zuryati Ab; Mohamad, Dasmawati

2014-01-01

144

Confinement-driven increase in ionomer thin-film modulus.  

PubMed

Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex heterogeneous structures in which they occur, there is a need to elucidate the governing structure-property relationships, especially at nanoscale dimensions where interfacial interactions dominate the overall materials response due to confinement effects. It is widely acknowledged that polymer physical behavior can be drastically altered from the bulk when under confinement and the literature is replete with examples thereof. However, there is a deficit in the understanding of ionomers when confined to the nanoscale, although it is apparent from literature that confinement can influence ionomer properties. Herein we show that as one particular ionomer, Nafion, is confined to thin films, there is a drastic increase in the modulus over the bulk value, and we demonstrate that this stiffening can explain previously observed deviations in materials properties such as water transport and uptake upon confinement. Moreover, we provide insight into the underlying confinement-induced stiffening through the application of a simple theoretical framework based on self-consistent micromechanics. This framework can be applied to other polymer systems and assumes that as the polymer is confined the mechanical response becomes dominated by the modulus of individual polymer chains. PMID:24773397

Page, Kirt A; Kusoglu, Ahmet; Stafford, Christopher M; Kim, Sangcheol; Kline, R Joseph; Weber, Adam Z

2014-05-14

145

The Plant Ionome Revisited by the Nutrient Balance Concept  

PubMed Central

Tissue analysis is commonly used in ecology and agronomy to portray plant nutrient signatures. Nutrient concentration data, or ionomes, belong to the compositional data class, i.e., multivariate data that are proportions of some whole, hence carrying important numerical properties. Statistics computed across raw or ordinary log-transformed nutrient data are intrinsically biased, hence possibly leading to wrong inferences. Our objective was to present a sound and robust approach based on a novel nutrient balance concept to classify plant ionomes. We analyzed leaf N, P, K, Ca, and Mg of two wild and six domesticated fruit species from Canada, Brazil, and New Zealand sampled during reproductive stages. Nutrient concentrations were (1) analyzed without transformation, (2) ordinary log-transformed as commonly but incorrectly applied in practice, (3) additive log-ratio (alr) transformed as surrogate to stoichiometric rules, and (4) converted to isometric log-ratios (ilr) arranged as sound nutrient balance variables. Raw concentration and ordinary log transformation both led to biased multivariate analysis due to redundancy between interacting nutrients. The alr- and ilr-transformed data provided unbiased discriminant analyses of plant ionomes, where wild and domesticated species formed distinct groups and the ionomes of species and cultivars were differentiated without numerical bias. The ilr nutrient balance concept is preferable to alr, because the ilr technique projects the most important interactions between nutrients into a convenient Euclidean space. This novel numerical approach allows rectifying historical biases and supervising phenotypic plasticity in plant nutrition studies. PMID:23526060

Parent, Serge-Étienne; Parent, Léon Etienne; Egozcue, Juan José; Rozane, Danilo-Eduardo; Hernandes, Amanda; Lapointe, Line; Hébert-Gentile, Valérie; Naess, Kristine; Marchand, Sébastien; Lafond, Jean; Mattos, Dirceu; Barlow, Philip; Natale, William

2013-01-01

146

Polymer Communication The swelling behaviour of perfluorinated ionomer membranes in  

E-print Network

and bulk swelling of "Nafion " perfluorinated ionomer membranes in mixtures of ethanol and water alone. The conclusion is that the ethanol plasticises the fluorocarbon matrix in Nafion, allowing with water alone. 2000 Elsevier Science Ltd. All rights reserved. Keywords: Nafion; Small angle X

Elliott, James

147

Simulation of Ionic Aggregation and Ion Dynamics in Model Ionomers  

NASA Astrophysics Data System (ADS)

Ionomers, polymers containing a small fraction of covalently bound ionic groups, are of interest as possible electrolytes in batteries. A single-ion conducting polymer electrolyte would be safer and have higher efficiency than the currently-used liquid electrolytes. However, to date ionomeric materials do not have sufficiently high conductivities for practical application. This is most likely because the ions tend to form aggregates, leading to slow ion transport. A key question is therefore how molecular structure affects the ionic aggregation and ion dynamics. To probe these structure-property relationships, we have performed molecular simulations of a set of recently synthesized poly(ethylene-co-acrylic acid) copolymers and ionomers, with a focus on the morphology of the ionic aggregates. The ionomers have a precise, constant spacing of charged groups, making them ideal for direct comparisons with simulations. Ab initio calculations give insight into the expected coordination of cations with fragments of the ionomers. All-atom molecular dynamics (MD) simulations of the ionomer melt show aggregation of the ionic groups into extended string-like clusters. An extensive set of coarse-grained molecular dynamics simulations extend the results to longer times and larger length scales. The structure factors calculated from the MD simulations compare favorably with x-ray scattering data. Furthermore, the simulations give a detailed picture of the sizes, shapes, and composition of the ionic aggregates, and how they depend on polymer architecture. Implications for ion transport will be discussed. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Frischknecht, Amalie L.

2012-02-01

148

Self-Healing Behavior of Ethylene-Based Ionomers  

NASA Technical Reports Server (NTRS)

The self-healing behavior of poly(ethylene-co-methacrylic acid) (EMAA)-based ionomers holds tremendous potential for use in a wide variety of unique applications. However, to effectively utilize this self-healing behavior and to design novel materials which possess this ability, the mechanism by which they heal must first be understood ionomers are a class of polymers that can be described as copolymers containing less than 15 mol% ionic content whereby the bulk properties are governed by ionic interactions within the polymer. These ionic groups aggregate into discrete regions known as multiplets which overlap forming clusters that act as physical cross-links profoundly influencing the bulk physical properties. These clusters possess an order-disorder transition (T(sub i)) where the clustered regions may rearrange themselves given time and stimuli. Recognizing the strong influence of these ionic regions on other well understood ionomer properties, their role in self-heating behavior will be assessed. The self-healing behavior is observed following projectile puncture. It has been suggested that during impact energy is passed to the ionomer material, heating it to the melt state. After penetration, it is proposed that the ionic regions maintain their attractions and flow together patching the hole. Thus, the importance of this ionic character and is unique interaction must be established. This will be accomplished through examination of materials with varying ionic content and through the analysis of the T(sub i). The specific ionomer systems examined include a number of ethylene-based materials. Materials of varying ionic content, including the non-ionic base copolymers, will be examined by peel tests, projectile impact and DSC analysis. The information will also be compared with some basic data on LDPE material.

Kalista, Stephen J., Jr.; Ward, Thomas C.; Oyetunji, Zainab

2004-01-01

149

Low equivalent weight short-side-chain perfluorosulfonic acid ionomers in fuel cell cathode catalyst layers  

Microsoft Academic Search

The morphology and fuel cell performance of cathode catalyst layers (CCLs) using low equivalent weight (EW) short-side-chain (SSC) perfluorosulfonic acid ionomers have been investigated in this work. The results were compared with those for a baseline CCL containing 30wt% of the conventional ionomer 1100 EW Nafion®. The CCLs fabricated with 10–20wt% of the Aquivion™ ionomer displayed a similar morphology to

Chao Lei; Dmitri Bessarabov; Siyu Ye; Zhong Xie; Steven Holdcroft; Titichai Navessin

2011-01-01

150

Blends of polyester ionomers with polar polymers: Interactions, reactions, and compatibilization  

NASA Astrophysics Data System (ADS)

The compatibility of amorphous and semicrystalline polyester ionomers with various polar polymers (i.e., polyesters and polyamides) has been investigated for their potential use as minor component compatibilizers. The degree of compatibility (i.e., ranging from incompatible to miscible) between the polyester ionomers and the polar polymers was determined by evaluating the effect of blend composition on the melting behavior and phase behavior of binary blends. In addition, the origin of compatibility and/or incompatibility for each of the binary blends (i.e., polyamide/ionomer and polyester/ionomer) was determined by evaluating blends prepared by both solution and melt mixed methods. Subsequent to investigation of the binary blends, the effect of polyester ionomer addition on the compatibility of polyamide/polyester blends was investigated by evaluating the mechanical properties and phase morphology of ionomer compatibilized polyamide/polyester blends. Polyester ionomers (amorphous and semicrystalline) were shown to exhibit a high degree of compatibility (even miscibility) with polyamides, such as nylon 6,6 (N66). Compatibility was attributed to specific interactions between the metal counterion of the polyester ionomer and the amide groups of N66. The degree of compatibility (or miscibility) was shown to be dependent on the counterion type of the ionomer, with the highest degree exhibited by blends containing the divalent form of the polyester ionomers. Although polyester ionomers were shown to exhibit incompatibility with both poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), increasing the time of melt processing significantly enhanced the compatibility of the polyester ionomers with both PET and PBT. The observed enhancement in compatibility was attributed to ester-ester interchange between the polyester blend components, which was confirmed by NMR spectroscopy. The addition of polyester ionomers as a minor component compatibilizer (i.e., 2 to 5 wt%) resulted in significant enhancement in the impact strength and a dramatic improvement in the tensile properties compared to uncompatibilized blends of nylon 6,6 (N66) with poly(butylene terephthalate) (PBT). This behavior was attributed to an increase in the interfacial adhesion between the phase-separated domains due to strong interactions between the polyester ionomer and N66. The placement of the ionomer compatibilizer at the N66/PBT interface was facilitated by pre-extrusion of the polyester ionomer with PBT, prior to extrusion with N66.

Boykin, Timothy Lamar

151

Counterion Effects on Ion Mobility and Mobile Ion Concentration of Doped Polyphosphazenes and Polyphosphazene Ionomers  

NASA Astrophysics Data System (ADS)

Previous investigations have shed some light on the ion conduction process in polymer electrolytes, yet ion transport is still not well understood. Here, upon the application of a physical model of electrode polarization to two systems with nearly identical chemical structure, one composed of an ionomer (MI) with a single mobile cation, and the other a salt-doped polymer (M+S) with mobile cation and mobile anion, quantitative comparison of the conductivity parameters is achieved. The polymer electrolyte chemistries of both MI and M+S are based on poly(methoxyethoxy-ethoxy phosphazene) (MEEP). The glass transition was found to be an important factor governing the conductivity and ion mobility. However, even accounting for the glass transition, the mobility of ions in the M+S system is 10 times larger than that in the MI system, which must arise from faster diffusion of the anion than the cation. Values for mobile ion concentration are also approximately 10 times higher in M+S than MI. These differences originate from free volume available for diffusion and local environment surrounding the ion pairs, demonstrating that the location of the ion pairs in the polymer matrix has a crucial effect on both conductivity parameters. Research supported by NSF Polymers Program.

Runt, Jim; Klein, Robert

2007-03-01

152

Double-layer ionomer membrane for improving fuel cell performance.  

PubMed

A double-layer ionomer membrane, thin-layer Nafion (perfluorinated sulfonic acid polymer) on a sulfonated aromatic block copolymer (SPK-bl-1), was prepared for improving fuel cell performance. Each component of the double-layer membrane showed similar phase-separated morphologies to those of the original membranes. A fuel cell with the double-layer membrane exhibited lower ohmic resistance and higher cathode performance than those with the original SPK-bl-1 membrane despite their comparable water uptake and proton conductivity. Detailed electrochemical analyses of fuel cell data suggested that the thin Nafion interlayer contributed to improving the interfacial contact between the SPK-bl-1 membrane and the cathode catalyst layer and to mitigating excessive drying of the membrane. The results provide new insight on designing high-performance fuel cells with nonfluorinated ionomer membranes such as sulfonated aromatic polymers. PMID:24988282

Mochizuki, Takashi; Uchida, Makoto; Uchida, Hiroyuki; Watanabe, Masahiro; Miyatake, Kenji

2014-08-27

153

Associations between Ionomic Profile and Metabolic Abnormalities in Human Population  

Microsoft Academic Search

BackgroundFew studies assessed effects of individual and multiple ions simultaneously on metabolic outcomes, due to methodological limitation.Methodology\\/Principal FindingsBy combining advanced ionomics and mutual information, a quantifying measurement for mutual dependence between two random variables, we investigated associations of ion modules\\/networks with overweight\\/obesity, metabolic syndrome (MetS) and type 2 diabetes (T2DM) in 976 middle-aged Chinese men and women. Fasting plasma ions

Liang Sun; Yu Yu; Tao Huang; Peng An; Danxia Yu; Zhijie Yu; Huaixing Li; Hongguang Sheng; Lu Cai; Jun Xue; Miao Jing; Yixue Li; Xu Lin; Fudi Wang

2012-01-01

154

The retention of gold crowns on human dentine preparations--a comparison of eight cements.  

PubMed

Experiments were carried out to compare the retentive properties of eight dental luting cements, using gold crowns cemented onto human dentine. The order of retention of the cements was: 1 Composite (Panavia-Ex, J & S Davis); 2 Glass-ionomer. (AquaCem, DeTrey); Glass-ionomer (Ketac-Bond, Cottrell); and Polycarboxylate (Bondalcap, Vivadent); 3 Polycarboxylate (Poly F Plus, DeTrey); Zinc phosphate (DeTrey); and Zinc phosphate (Phosphacap, Vivadent); and 4 Zinc oxide/eugenol, alumina, EBA (Opotow, Teledyne Getz). PMID:2697038

Black, S M; Charlton, G

1989-05-01

155

Tensile bond strength of glass fiber posts luted with different cements.  

PubMed

Proper selection of the luting agent is fundamental to avoid failure due to lack of retention in post-retained crowns. The objective of this study was to investigate the tensile bond strength and failure mode of glass fiber posts luted with different cements. Glass fiber posts were luted in 40 mandibular premolars, divided into 4 groups (n = 10): Group 1--resin-modified glass ionomer RelyX Luting; Group 2--resin-modified glass ionomer Fuji Plus; Group 3--resin cement RelyX ARC; Group 4--resin cement Enforce. Specimens were assessed by tensile strength testing and light microscopy analysis for observation of failure mode. The tensile bond strength values of each group were compared by ANOVA and Tukey test. The significance level was set at 5%. The failure modes were described as percentages. The following tensile strength values were obtained: Group 1--247.6 N; Group 2--256.7 N; Group 3--502.1 N; Group 4--477.3 N. There was no statistically significant difference between Groups 1 and 2 or between Groups 3 and 4, yet the resin cements presented significantly higher tensile bond strength values than those presented by the glass ionomer cements. Group 1 displayed 70% of cohesive failures, whereas Groups 2, 3 and 4 exhibited 70% to 80% of adhesive failures at the dentin-cement interface. We concluded that resin cements and glass ionomer cements are able to provide clinically sufficient retention of glass fiber posts, and that glass ionomer cements may be especially indicated when the application of adhesive techniques is difficult. PMID:17589652

Bonfante, Gerson; Kaizer, Osvaldo Bazzan; Pegoraro, Luiz Fernando; do Valle, Accácio Lins

2007-01-01

156

High mineral affinity of polyphosphoester ionomer-phospholipid vesicles.  

PubMed

Bone-specific drug delivery is important for the treatment of osteoporosis and osseous metastases. However, there have been limitations in the design of drug carriers having bone affinity. We synthesized amphiphilic polyphosphoester ionomers (CH-PHE) and modified them to 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) vesicles. The ?-potential of the vesicles was decreased by immobilization of CH-PHE; the amount was influenced by the structure and fraction of CH-PHE. The release rate of 5-carboxyfluorescein from the vesicles could be controlled by changing the fraction of DOPC and CH-PHE. In particular, the release of CF from DOPC vesicles containing 3% CH-PHE was most reduced. In addition, the enzymatic degradation of DOPC was reduced by immobilization with polyphosphoester ionomers; enzyme tolerance was increased with an increase in the molar fraction of polyphosphoester ionomers. Hemolytic activity of the phospholipid vesicles bearing CH-PHE was infrequently observed and was similar to that of the DOPC vesicles. Although a decrease in the viability of mouse osteoblastic cells (MC3T3-E1) in contact with the vesicles bearing CH-PHE was observed when the DOPC concentration of the vesicles bearing 20 mol % CH-PHE with highly ionized units was greater than 200 ?M, the cytotoxicity was diminished by sodium salt formation of the CH-PHE. The affinity of the vesicles to calcium deposits generated by MC3T3-E1 cells was significantly improved by the immobilization polyphosphoesters. PMID:22829566

Ikeuchi, Ryota; Iwasaki, Yasuhiko

2013-02-01

157

Compatibilization of PP\\/Vectra B “in situ” composites by means of an ionomer  

Microsoft Academic Search

Ionomer addition has been investigated as a compatibilizer for the immiscible polypropylene (PP)\\/Vectra B 950 (VB). Both modified and unmodified blends as a reference, with VB contents up to 30% were obtained by direct injection moulding. The crystallinity of PP\\/VB was barely influenced by the presence of the ionomer. The compatibilization leads to the presence of thinner fibres that broke

F. J Vallejo; J. I Eguiazábal; J Nazábal

2000-01-01

158

An Overview of the Viscous and Viscoelastic Behavior of Ionomers in Bulk and Solution  

Microsoft Academic Search

The subject of the viscous and viscoelastic behavior of ionomer systems is addressed from a general point of view. Following some introductory material concerning terminology and characteristics of ionomers that are pertinent for later discussion, the format will be to first briefly consider the glassy state followed with a more complete discussion of the rubbery and viscous flow (melt) states.

Martin R. Tant; Garth L. Wilkes

1988-01-01

159

Imaging and microanalysis of thin ionomer layers by scanning transmission electron microscopy  

SciTech Connect

Improved conditions for imaging and spectroscopic mapping of thin perfluorosulfonic acid (PFSA) ionomer layers in fuel cell electrodes by scanning transmission electron microscopy (STEM) have been investigated. These conditions are first identified on model systems of Nafion ionomer-coated nanostructured thin films and nanoporous Si. The optimized conditions are then applied in a quantitative study of the ionomer through-layer loading for two typical electrode catalyst coatings using electron energy loss and energy dispersive X-ray spectroscopy in the transmission electron microscope. The e-beam induced damage to the perfluorosulfonic acid (PFSA) ionomer is quantified by following the fluorine mass loss with electron exposure and is then mitigated by a few orders of magnitude using cryogenic specimen cooling and a higher incident electron voltage. Multivariate statistical analysis is also applied to the analysis of spectrum images for data denoising and unbiased separation of independent components related to the catalyst, ionomer, and support.

Cullen, David A [ORNL; Koestner, Roland [General Motors Corporation; Kukreja, Ratan [General Motors Corporation; Minko, Sergiy [Clarkson University, Potsdam, NY; Trotsenko, Oleksandr [Clarkson University, Potsdam, NY; Tokarev, Alexander V [ORNL; Guetaz, Laure [French Atomic Energy Commission (CEA), Grenoble; Meyer III, Harry M [ORNL; Parish, Chad M [ORNL; More, Karren Leslie [ORNL

2014-01-01

160

S Sppeeccttrroopphhoottoommeettrriicc A Annaallyyssiiss o off A Allll-c ceerraammiicc MMaatteerriiaallss a anndd T Thheeiirr IInntteerraaccttiioonn w wiitthh LLuuttiinngg A Aggeennttss a anndd D Diiffffeerreenntt B Baacckkggrroouunnddss  

Microsoft Academic Search

In this study, two All-Ceramic (AC) materials— Empress 2 (EMP) (Ivoclar Vivadent AG, Schaan, Liechtenstein) and In-Ceram ALUMINA (ICA) (Vita Zahnfabrik, Bad Säckingen, Germany)—were analyzed, along with the effects of 3 luting agents—viz. Zinc Phosphate cement (ZNPO, PhospaCEM PL, Ivoclar Vivadent AG, Schaan, Liechtenstein), Glass Ionomer Cement (GIC, Ketac-Cem Radiopaque, ESPE Dental AG, Seefeld, Germany), and Compolute (COMP, ESPE Dental

V. S. Barath; F.-J. Faber; S. Westland; W. Niedermeier

161

Counterion Dynamics in Polyester-Sulfonate Ionomers with Ionic Liquid Counterions  

SciTech Connect

Conventional sodium cations (Na{sup +}) in sulfonated polyester ionomers were replaced with ammonium-based ionic liquid counterions. Counterion dynamics were measured by dielectric spectroscopy and linear viscoelastic response via oscillatory shear. Ion exchange from sodium counterions to ionic liquid counterions such as tetramethylammonium and tetrabutylammonium showed an order of 10{sup 4} increase in conductivity compared with sodium counterions, primarily attributed to weaker ionic interactions that lower the glass transition temperature. Electrode polarization was used in conjunction with the 1953 Macdonald model to determine the number density of conducting counterions and their mobility. Conductivity and mobility exhibit Vogel-Fulcher-Tammann (VFT) temperature dependences and both increased with counterion size. Conducting counterion concentrations showed Arrhenius temperature dependences, with activation energy reduced as counterion size increased. When ether-oxygen was incorporated into the mobile cation structure, self-solvating ability notably increased the conducting ion concentration. Weakened ion pairing interactions prove favorable for fundamental design of single-ion conductors for actuators, as ionic liquid counterions can provide both larger and faster strains, required by such electro-active devices.

Tudryn, Gregory J.; Liu, Wenjuan; Wang, Shih-Wa; Colby, Ralph H. (Penn)

2012-04-02

162

Addition of mechanically processed cellulosic fibers to ionomer cement: mechanical properties.  

PubMed

In this study, conventional restorative glass ionomer cement (GIC) was modified by embedding it with mechanically processed cellulose fibers. Two concentrations of fibers were weighed and agglutinated into the GIC during manipulation, yielding Experimental Groups 2 (G2; 3.62 wt% of fibers) and 3 (G3; 7.24 wt% of fibers), which were compared against a control group containing no fibers (G1). The compressive strengths and elastic modulus of the three groups, and their diametral tensile strengths and stiffness, were evaluated on a universal test machine. The compressive and diametral tensile strengths were significantly higher in G3 than in G1. Statistically significant differences in elastic modulus were also found between G2 and G1 and between G2 and G3, whereas the stiffness significantly differed between G1 and G2. The materials were then characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Heterogeneously shaped particles were found on the G2 and G3 surfaces, and the cement matrices were randomly interspersed with long intermingled fibers. The EDS spectra of the composites revealed the elemental compositions of the precursor materials. The physically processed cellulosic fibers (especially at the higher concentration) increased the compressive and diametral tensile strengths of the GIC, and demonstrated acceptable elastic modulus and stiffness. PMID:25627882

Silva, Rafael Menezes; Carvalho, Vinícius Xavier Mattar de; Dumont, Vitor César; Santos, Maria Helena; Carvalho, Ana Márcia Macedo Ladeira

2015-01-01

163

The effect of pressure changes during simulated diving on the pull out strength of glass fiber posts  

PubMed Central

Background: Scuba diving is one of the fastest growing sports in the world. The objective of this study was to evaluate the effect of pressure variations to which divers are exposed on the pull out strength of glass fiber post luted with different cements. Materials and Methods: In this in vitro study, 120 extracted, single-rooted lower premolars were endodontically treated. They were randomly divided into six groups and restored using the glass fiber post (Ivoclar Vivadent AG) and the following luting agents: Zinc phosphate, conventional glass ionomer, resin reinforced glass ionomer, resin cement with etch-and-rinse adhesive, resin cement with self-etching adhesive, and self-adhesive resin cement. Each group was randomly divided into two equal subgroups, one as a control, and the other to be used experimentally. After 7 days of storage, experimental groups were pressure cycled. The force required to dislodge each post was recorded in Newton (N) on Universal testing machine (Star Testing System) at a crosshead speed of 1 mm/min. Data were statistically analyzed using the ANOVA and Student's t-test (P < 0.001). Results: The pull out strength of posts cemented with zinc phosphate and conventional glass ionomer in pressure cycle group was significantly less than their control group. Although, no significant difference was found between pressure cycle and control group using resin reinforced glass ionomer cement and resin cements. Conclusion: Dentist should consider using resin reinforced glass ionomer or resin cement, for the cementation of glass fiber post, for the patients such as divers, who are likely to be exposed to pressure cycling. PMID:24379861

Gulve, Meenal Nitin; Gulve, Nitin Dilip

2013-01-01

164

Radiopacity Evaluation of Contemporary Luting Cements by Digitization of Images  

PubMed Central

Objective. The aim of this study was to evaluate the radiopacity of two conventional cements (Zinc Cement and Ketac Cem Easymix), one resin-modified glass ionomer cement (RelyX Luting 2) and six resin cements (Multilink, Bistite II DC, RelyX ARC, Fill Magic Dual Cement, Enforce and Panavia F) by digitization of images. Methods. Five disc-shaped specimens (10 × 1.0?mm) were made for each material, according to ISO 4049. After setting of the cements, radiographs were made using occlusal films and a graduated aluminum stepwedge varying from 1.0 to 16?mm in thickness. The radiographs were digitized, and the radiopacity of the cements was compared with the aluminum stepwedge using the software VIXWIN-2000. Data (mmAl) were submitted to one-way ANOVA and Tukey's test (? = 0.05). Results. The Zinc Cement was the most radiopaque material tested (P < 0.05). The resin cements presented higher radiopacity (P < 0.05) than the conventional (Ketac Cem Easymix) or resin-modified glass ionomer (RelyX Luting 2) cements, except for the Fill Magic Dual Cement and Enforce. The Multilink presented the highest radiopacity (P < 0.05) among the resin cements. Conclusion. The glass ionomer-based cements (Ketac Cem Easymix and RelyX Luting 2) and the resin cements (Fill Magic Dual Cement and Enforce) showed lower radiopacity values than the minimum recommended by the ISO standard. PMID:23008777

Reis, José Maurício dos Santos Nunes; Jorge, Érica Gouveia; Ribeiro, João Gustavo Rabelo; Pinelli, Ligia Antunes Pereira; Abi-Rached, Filipe de Oliveira; Tanomaru-Filho, Mário

2012-01-01

165

Radically coarse-grained approach to the modeling of chemical degradation in fuel cell ionomers.  

PubMed

We present a kinetic model of chemical degradation in perfluorosulfonic acid ionomer membranes. It accounts for pathways of radical formation along with mechanisms of ionomer degradation through radical attack. Simplifications in the set of model equations leads to analytical expressions for the concentration of hydroxyl radicals as a function of initial concentrations of iron ions and hydrogen peroxide. The coarse-grained ionomer degradation model distinguishes units that correspond to ionomer head groups, trunk segments of ionomer side chains, and backbone segments between two side chains. A set of differential equations is formulated to describe changes in concentrations of these units. The model is used to study the impact of different degradation mechanisms and ionomer chemistries on fluorine loss and change in ion exchange capacity. Comparison of the model with experimental degradation data for Nafion and Aquivion membranes allows rate constants of degradation processes to be determined. Results of these analyses are discussed in view of strategies to mitigate chemical degradation of ionomer membranes. PMID:25164106

Ghelichi, Mahdi; Melchy, Pierre-Éric Alix; Eikerling, Michael H

2014-09-25

166

Associations between Ionomic Profile and Metabolic Abnormalities in Human Population  

PubMed Central

Background Few studies assessed effects of individual and multiple ions simultaneously on metabolic outcomes, due to methodological limitation. Methodology/Principal Findings By combining advanced ionomics and mutual information, a quantifying measurement for mutual dependence between two random variables, we investigated associations of ion modules/networks with overweight/obesity, metabolic syndrome (MetS) and type 2 diabetes (T2DM) in 976 middle-aged Chinese men and women. Fasting plasma ions were measured by inductively coupled plasma mass spectroscopy. Significant ion modules were selected by mutual information to construct disease related ion networks. Plasma copper and phosphorus always ranked the first two among three specific ion networks associated with overweight/obesity, MetS and T2DM. Comparing the ranking of ion individually and in networks, three patterns were observed (1) “Individual ion,” such as potassium and chrome, which tends to work alone; (2) “Module ion,” such as iron in T2DM, which tends to act in modules/network; and (3) “Module-individual ion,” such as copper in overweight/obesity, which seems to work equivalently in either way. Conclusions In conclusion, by using the novel approach of the ionomics strategy and the information theory, we observed potential associations of ions individually or as modules/networks with metabolic disorders. Certainly, these findings need to be confirmed in future biological studies. PMID:22719963

An, Peng; Yu, Danxia; Yu, Zhijie; Li, Huaixing; Sheng, Hongguang; Cai, Lu; Xue, Jun; Jing, Miao; Li, Yixue; Lin, Xu; Wang, Fudi

2012-01-01

167

[Phase transition in polymer blends and structure of ionomers and copolymers  

SciTech Connect

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Not Available

1993-01-01

168

Electrochemical degradation of Nafion ionomer to functionalize carbon support for methanol electro-oxidation  

Microsoft Academic Search

An effective electrochemical route to produce functional groups on carbon surface is demonstrated. Cyclic voltammetric (CV) sweeps are performed in 0.5M H2SO4 electrolyte on electrodes containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient oxygen, the generation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that leads to

Yu-Chi Hsieh; Jing-Yu Chen; Pu-Wei Wu

169

Synthesis of indium sulphide quantum dots in perfluoronated ionomer membrane  

SciTech Connect

In this paper, we demonstrate a simple and efficient method for synthesis of ?-indium sulphide (In{sub 2}S{sub 3}) nanoparticles embedded in an ionomer matrix (nafion membrane). The influence of reaction temperature on structural, compositional and optical properties of these films were analysed using X-Ray Diffraction, EDAX, UV-Vis absorption spectroscopy and photoluminescence studies. Average particle diameter was estimated using modified effective mass approximation method. Absorption spectra of In{sub 2}S{sub 3} nanoparticles show blue shift compared to bulk In{sub 2}S{sub 3}, indicating strong quantum size confinement effects. PL emission in the wavelength range 530–600 nm was recorded using a 488 nm line from an Ar{sup +} laser as the excitation source.

Sumi, R. [Centre for Nanotechnology Research, VIT University, Vellore (India); Warrier, Anita R.; Vijayan, C. [Department of Physics, Indian Institute of Technology, Chennai (India)

2014-01-28

170

Effect of Equivalent Weight on Water Sorption, PTFE-Like Crystallinity, and Ionic Conductivity in Bis((Perfluoroalkyl)Sulfonyl) Imide Perfluorinated Ionomers  

Microsoft Academic Search

Measurements of water absorption and ionic conductivity as a function of relative humidity (RH) were carried out on membranes comprised of bis((perfluoroalkyl)sulfonyl) imide ionomers of equivalent weights 1470, 1200, and 1075 g equiv-1, and on a sample of the perfluorosulfonic ionomer Nafion™ ionomer of equivalent weight 1100 g equiv-1 for comparison. All of the ionomers exhibited decreased water absorption and

J. R. Atkins; C. R. Sides; S. E. Creager; J. L. Harris; W. T. Pennington; B. H. Thomas; D. D. DesMarteau

171

Puncture-Healing Properties of Carbon Nanotube-Filled Ionomers  

NASA Technical Reports Server (NTRS)

Ionomers are polymers that contain ionic groups in relatively low concentrations along the polymer backbone. These ionic groups, in the presence of oppositely charged ions, form aggregates that lead to novel physical properties of the polymer. React-A-Seal(trademark) and Surlyn(trademark) are poly(ethylene-co-methacrylic acid) (EMAA) ionomer-based materials and Nucrel(trademark) is the EMAA acid copolymer neutralized to produce Surlyn(trademark). React-A-Seal(trademark), Surlyn(trademark), and Nucrel(trademark) recover into their original shapes following a high impact puncture at velocities ranging from 300 to 1200 ft/s ('self-healing'). This self-healing process may be of great benefit in space applications where structures are exposed to matter impacts. A thermal IR camera indicated a temperature increase to 98 C for Nucrel(trademark) 925, Surlyn(trademark) 8940, React-A-Seal(trademark), and Surlyn(trademark) 8920 after initial penetration. To understand and generalize the observed phenomena, questions concerning the mechanism of the puncture resealing must be answered. One suggestion is that the elastic character of the melt created by the puncture drives the self-healing. This inference is based on the observed temperature rise of approx. 3 C above the melting temperature of the samples (approx. 95 C) during the impact. With the expectation of gaining additional insight into the self-healing phenomenon, a thermodynamic and viscoelastic investigation was conducted using primarily DSC and DMA. Surlyn(trademark) and React-A-Seal(trademark) showed the characteristic order-disorder transition at approx. 52 C that has been reported in literature. Master curves were constructed from the creep isotherms for the four EMAA samples. An aging study was performed to investigate the irreproducibility and "tailing effect" observed in the creep data. The aging study indicated that, with increased aging time and temperature, changes in the polyethylene matrix lead to complexities in morphology resulting in changes in the magnitude and shape of the creep curves.

Ward, Thomas C.

2003-01-01

172

Water sorption and expansion of an ionomer membrane constrained by fuel cell electrodes  

NASA Astrophysics Data System (ADS)

This article reveals that catalyst coated membranes (CCM) and membrane electrode assemblies (MEA) expand and contract differently than pure ionomer membranes during hydration and dehydration. Pure membranes are shown to generate twice as much longitudinal peak and residual stress during dehydration than CCMs, reflecting the higher modulus of the pure ionomer material. Moreover, the stronger confinement imposed by the lamination of relatively stiff gas diffusion layers to the CCM prevents the ionomer membrane from expanding in the in-plane direction. This is shown to lead to a significant increase in the through-plane stress and strain during hydration of MEAs versus CCMs and pure ionomer membranes. Supplementary measurements indicate that the water sorption properties of the ionomer (at equilibrium) are not altered by the lamination of catalyst layers and gas diffusion layers; hence, the changes in expansion behavior in the MEA are attributed to the mechanical confinement provided by the other layers. These features should be captured by finite element modeling of fuel cell stacks for accurate cell design and may have important implications for fuel cell durability.

Goulet, Marc-Antoni; Arbour, Spencer; Lauritzen, Michael; Kjeang, Erik

2015-01-01

173

Ionome changes in Xylella fastidiosa-infected Nicotiana tabacum correlate with virulence and discriminate between subspecies of bacterial isolates.  

PubMed

Characterization of ionomes has been used to uncover the basis of nutrient utilization and environmental adaptation of plants. Here, ionomic profiles were used to understand the phenotypic response of a plant to infection by genetically diverse isolates of Xylella fastidiosa, a gram-negative, xylem-limited bacterial plant pathogen. In this study, X. fastidiosa isolates were used to infect a common model host (Nicotiana tabacum 'SR1'), and leaf and sap concentrations of eleven elements together with plant colonization and symptoms were assessed. Multivariate statistical analysis revealed that changes in the ionome were significantly correlated with symptom severity and bacterial populations in host petioles. Moreover, plant ionome modification by infection could be used to differentiate the X. fastidiosa subspecies with which the plant was infected. This report establishes host ionome modification as a phenotypic response to infection. PMID:24983508

Oliver, J E; Sefick, S A; Parker, J K; Arnold, T; Cobine, P A; De La Fuente, L

2014-10-01

174

In Silico Ionomics Segregates Parasitic from Free-Living Eukaryotes  

PubMed Central

Ion transporters are fundamental to life. Due to their ancient origin and conservation in sequence, ion transporters are also particularly well suited for comparative genomics of distantly related species. Here, we perform genome-wide ion transporter profiling as a basis for comparative genomics of eukaryotes. From a given predicted proteome, we identify all bona fide ion channels, ion porters, and ion pumps. Concentrating on unicellular eukaryotes (n = 37), we demonstrate that clustering of species according to their repertoire of ion transporters segregates obligate endoparasites (n = 23) on the one hand, from free-living species and facultative parasites (n = 14) on the other hand. This surprising finding indicates strong convergent evolution of the parasites regarding the acquisition and homeostasis of inorganic ions. Random forest classification identifies transporters of ammonia, plus transporters of iron and other transition metals, as the most informative for distinguishing the obligate parasites. Thus, in silico ionomics further underscores the importance of iron in infection biology and suggests access to host sources of nitrogen and transition metals to be selective forces in the evolution of parasitism. This finding is in agreement with the phenomenon of iron withholding as a primordial antimicrobial strategy of infected mammals. PMID:24048281

Greganova, Eva; Steinmann, Michael; Mäser, Pascal; Fankhauser, Niklaus

2013-01-01

175

Mixed hydrocarbon/fluoropolymer membrane/ionomer MEAs for durability studies  

SciTech Connect

The durability of polymer electrolyte membrane (PEM) fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Commercial viability depends on improving the durability of the fuel cell components to increase the system reliability. The aim of this work is to separate ionomer degradation from membrane degradation via mixed membrane/ionomer MEA experiments. The challenges of mixed MEA fabrication due to the incompatibility of the membrane and the electrode are addressed. OCV accelerated testing experiment (AST) were performed. Development of in situ diagnostics and unique experiments to characterize the performance and properties of the ionomer in the electrode as a function of time is reported. These measurements, along with extensive ex situ and post-mortem characterization, can delineate the degradation mechanisms in order to develop more durable fuel cells and fuel cell components.

Li, Bo [Los Alamos National Laboratory; Kim, Yu Seung [Los Alamos National Laboratory; Mukundan, Rangachary [Los Alamos National Laboratory; Borup, Rodney L [Los Alamos National Laboratory; Wilson, Mahlon S [Los Alamos National Laboratory; Welch, Cynthia [Los Alamos National Laboratory; Fenton, James [FLORIDA SOLAR ENERGY CENTER

2010-01-01

176

Effects of short-side-chain perfluorosulfonic acid ionomers as binders on the performance of low Pt loading fuel cell cathodes  

NASA Astrophysics Data System (ADS)

We investigated the effects of short-side-chain (SSC) perfluorosulfonic acid ionomers on the electrochemical properties, fuel cell performance and ionomer distribution of a highly dispersed Pt/GCB catalyst with a low Pt loading, 0.05 mg cm-2. The SSC ionomers in the cathode catalyst layers (CLs) resulted in an improvement of the Pt utilization (UPt) and Pt effectiveness (EfPt) values compared with those for the conventional long-side-chain (LSC) ionomer. Furthermore, the SSC ionomers with high ion exchange capacity (IEC), e.g., SSC-1.43 and SSC-1.80 ionomers, exhibited significantly enhanced cell performance under low to medium relative humidity (RH) conditions. This result is ascribed to the higher proton conductivity of the SSC ionomers and more effective trapping of water that is produced during the oxygen reduction reaction (ORR) than those of the LSC ionomer. It was also found that the SSC ionomers showed better continuity and uniformity on the Pt and carbon particles than the LSC ionomer, which might have led to improvement of both the mass transport and the proton-conducting network in the CLs. The application of the SSC ionomers as binders demonstrated an increase of the performance at the low Pt loading fuel cell cathode over a wide range of humidity.

Park, Young-Chul; Kakinuma, Katsuyoshi; Uchida, Hiroyuki; Watanabe, Masahiro; Uchida, Makoto

2015-02-01

177

Nuclear magnetic resonance investigation of dynamics in poly(ethylene oxide)-based lithium polyether-ester-sulfonate ionomers  

DOE PAGESBeta

Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.

Roach, David J. [Pennsylvania State University, University Park, PA (United States); Dou, Shichen [Pennsylvania State University, University Park, PA (United States); Colby, Ralph H. [Pennsylvania State University, University Park, PA (United States); Mueller, Karl T. [Pacific Northwest Lab., Richland, WA (United States)

2012-01-06

178

Nuclear Magnetic Resonance Investigation of Dynamics in Poly(Ethylene Oxide) Based Lithium Polyether-ester-sulfonate Ionomers  

SciTech Connect

Nuclear magnetic resonance (NMR) spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. 1H and 7Li spin-lattice relaxation times (T1) of the bulk polymer and lithium ions, respectively, were analyzed in samples with a range of ion contents. The temperature dependence of T1 values along with the presence of minima in T1 enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies of both the polymer and lithium ions in the lower ion content samples indicate that the polymer segmental motion and lithium ion hopping motion are correlated even though their respective correlation times differ significantly. A divergent trend is observed for correlation times and activation energies of the highest ion content sample due to the presence of ionic aggregation. Details about the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and Quasi Elastic Neutron Scattering experiments.

Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

2012-01-07

179

Mineral content of ionomer cements and preventive effect of these cements against white spot lesions around restorations.  

PubMed

This study evaluated the ion exchange at the material/enamel interface and the preventive effect of restorative materials submitted to cariogenic challenge against white spot. Restorations in enamel/dentin of bovine teeth were performed with composite resin (Filtek™ Z250 - control group) and glass-ionomers cements - GICs (Ionomaster R™ and Fuji IX™ - experimental groups). Samples were grouped and submitted to neutral saliva (n = 15) or pH-cycling regimen (n = 15). After eight days of pH cycling, material/enamel interfaces were analyzed by EDX in order to determine the differences (p < 0.05) in ionic exchange (Ca, P, F, Al, Sr, and Si) between restorative materials and teeth. In addition, enamel white spot lesion formation was evaluated macroscopically (p < 0.05). Sr content was higher in the enamel of the control group (p > 0.05) versus the experimental groups. Ca and P content were higher in enamel than in restorative materials. After pH cycling, the GIC enamel bulk showed a significantly higher Sr content compared with the composite resin (p < 0.05). Filtek™ Z250 was not able to prevent white spot formation around restorations in comparison with Ionomaster R™ (p < 0.001) and Fuji IX™ (p = 0.004). GICs reduced white spot formation and presented a preventive effect (p = 0.051). GICs presented a greater percentage of fluoride, aluminum, and strontium, and proved effective in white spot lesion prevention around restorations. PMID:25184496

Paiva, Lilian Fernanda Santos; Fidalgo, Tatiana Kelly da Silva; Maia, Lucianne Cople

2014-01-01

180

Poly(vinylidene fluoride) based anion conductive ionomer as a catalyst binder for application in anion exchange membrane fuel cell  

NASA Astrophysics Data System (ADS)

An anion conductive polymeric ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) can help to enhance anion transport in the catalyst layer of electrode, and thus improve the catalyst efficiency and performance of AEMFC. In this work, we report the synthesis and properties of a new type of anion conductive ionomer, which is synthesized by grafting of poly(vinylidene fluoride), or PVDF with poly(vinylbenzyltrimethylammonium chloride) via atom transfer radical polymerization. The ionomer obtained shows improved hydrophilicity relative to pristine PVDF, and exhibits an ion exchange capacity of 1.59 mmol g-1. When used in a direct hydrazine hydrate fuel cell (DHFC) as a catalyst binder, the synthesized ionomer imparts the DHFC a significantly improved power density, which is 5-10 fold as much as that of the cells without using such ionomer. The method developed here for anion exchange ionomer synthesis is facile, green and does not involve the use of carcinogenic chemicals such as chloromethylmethylether and trimethylamine, which are often used for conventional anion exchange membrane or ionomer synthesis.

Zhang, Fengxiang; Zhang, Huamin; Qu, Chao; Ren, Junxia

2011-03-01

181

Surface characteristics and in vitro biofilm formation on glass ionomer and composite resin  

Microsoft Academic Search

In the initial stages of dental plaque formation, early colonizing bacteria bind to receptor structures in the pellicle, a proteinaceous film formed instantly after cleaning of the tooth surface. Dental restorative materials with surface characteristics different from the tooth might affect pellicle formation and the ability of bacteria to colonize the oral cavity. In this study (i) roughness and chemical

A. Carlén; K. Nikdel; A. Wennerberg; K. Holmberg; J. Olsson

2001-01-01

182

The effect of adding hydroxyapatite on the flexural strength of glass ionomer cement.  

PubMed

This present study investigated the effects of the addition of hydroxyapatite (HA) on the flexural strength and microstructure of conventional GIC, and its effect on the cement's initial flexural strength at different storage conditions. Specimens were fabricated by mixing HA in whisker or granule form into commercially prepared GIC, and these were subjected to a three-point bending test and SEM observations. Some specimens were stored in different conditions from dry to wet for 15 minutes to an hour prior to testing. When compared to the control, specimens with 16-25% HA whiskers added at P/L 1.75 showed a significant increase in the flexural strength (p < 0.05), and as well with 19% HA whiskers at P/L 1.75 (p < 0.001) and 2.33 (p < 0.05). A significant increase was also noted for those with 8-25% HA granules added at P/L's 1.75 (p < 0.05), 2.5 (p < 0.05) and 3.60 (p < 0.01). The addition of HA hastens the development of early (15 min, 1 hour) flexural strength of GIC in moist or wet conditions. These results indicate that the addition of HA, regardless of form, improve the flexural and microstructural properties of GIC. PMID:12873116

Arita, Kenji; Lucas, Milanita E; Nishino, Mizuho

2003-06-01

183

Elimination of Orientation in Perfluorinated Ionomer J.A. Elliott, S. Hanna  

E-print Network

Elimination of Orientation in Perfluorinated Ionomer Membranes J.A. Elliott, S. Hanna H. H. Wills.M.S. Elliott Regenesys Technology Ventures Limited, Harwell International Business Centre, Harwell, Didcot, OX.A. Elliott is Department of Materials Science and Metallurgy, University of Cambridge, CB2 3QZ, United

Elliott, James

184

An efficient Ag-ionomer interface for hydroxide exchange membrane fuel cells.  

PubMed

An efficient Ag-phosphonium ionomer interface is discovered in HEMFCs, helping enhance oxygen reduction and improve mass transports simultaneously. As a result, a completely-precious-metal-free HEMFC has been fabricated, which shows a cost-normalized power much higher than that of a Pt-based PEMFC benchmark (117 vs. 7.7 W US$(-1)). PMID:23019567

Gu, Shuang; Sheng, Wenchao; Cai, Rui; Alia, Shaun M; Song, Shuqin; Jensen, Kurt O; Yan, Yushan

2013-01-01

185

The effects of relative humidity on the performances of PEMFC MEAs with various Nafion ® ionomer contents  

Microsoft Academic Search

For PEMFC operation, water management is very important to provide both sufficient proton conductivity and mass transport. Therefore, in this study, the effect of the relative humidity (38–87%) on cell performance is examined for PEMFC MEAs with various Nafion® ionomer contents. The MEAs were fabricated using a CCM (catalyst-coated membrane) spraying method. As the relative humidity of the cathodes (RHC)

Kun-Ho Kim; Kwan-Young Lee; Sang-Yeop Lee; EunAe Cho; Tae-Hoon Lim; Hyoung-Juhn Kim; Sung Pil Yoon; Sae Hoon Kim; Tae Won Lim; Jong Hyun Jang

2010-01-01

186

Predicted electric-field-induced hexatic structure in an ionomer membrane Elshad Allahyarov  

E-print Network

changes induced in a Nafion®-like ionomer by the imposition of a strong electric field. We observe­3 . For perfluorosulfonated iono- mer membranes such as Nafion® 4 the structure is charac- terized by a long, hydrophobic changes in poled Nafion. In order to increase mobility, poling fields were applied to solvent-cast Nafion

Taylor, Philip L.

187

Solid state nuclear magnetic resonance investigation of polymer backbone dynamics in poly(ethylene oxide) based lithium and sodium polyether-ester-sulfonate ionomers  

NASA Astrophysics Data System (ADS)

Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (Tg) have been investigated using solid-state nuclear magnetic resonance. Experiments detecting 13C with 1H decoupling under magic angle spinning (MAS) conditions identified the different components of the polymer backbone (PEO spacer and isophthalate groups) and their relative mobilities for a suite of lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) 1H-13C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of cation content and identity. Each of the main backbone components exhibit distinct motions, following the trends expected for motional characteristics based on earlier Quasi Elastic Neutron Scattering and 1H spin-lattice relaxation rate measurements. Previous 1H and 7Li spin-lattice relaxation measurements focused on both the polymer backbone and cation motion on the nanosecond timescale. The studies presented here assess the slower timescale motion of the polymer backbone allowing for a more comprehensive understanding of the polymer dynamics. The temperature dependences of 13C linewidths were used to both qualitatively and quantitatively examine the effects of cation content and identity on PEO spacer mobility. Variable contact time 1H-13C CP-MAS experiments were used to further assess the motions of the polymer backbone on the microsecond timescale. The motion of the PEO spacer, reported via the rate of magnetization transfer from 1H to 13C nuclei, becomes similar for T ˜x 1{.1} Tg in all ionic samples, indicating that at similar elevated reduced temperatures the motions of the polymer backbones on the microsecond timescale become insensitive to ion interactions. These results present an improved picture, beyond those of previous findings, for the dependence of backbone dynamics on cation density (and here, cation identity as well) in these amorphous PEO-based ionomer systems.

Roach, David J.; Dou, Shichen; Colby, Ralph H.; Mueller, Karl T.

2013-05-01

188

Solid State Nuclear Magnetic Resonance Investigation of Polymer Backbone Dynamics in Poly(Ethylene Oxide) Based Lithium and Sodium Polyether-ester-sulfonate Ionomers  

SciTech Connect

Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (Tg) have been investigated using solid-state nuclear magnetic resonance (NMR). Experiments detecting 13C with 1H decoupling under magic angle spinning (MAS) conditions identified the different components of the polymer backbone (PEO spacer and isophthalate groups) and their relative mobilities for a suite of lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) 1H-13C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of cation content and identity. Each of the main backbone components exhibit distinct motions, following the trends expected for motional characteristics based on earlier Quasi Elastic Neutron Scattering and 1H spin-lattice relaxation rate measurements. Previous 1H and 7Li spin-lattice relaxation measurements focused on both the polymer backbone and cation motion on the nanosecond timescale. The studies presented here assess the slower timescale motion of the polymer backbone allowing for a more comprehensive understanding of the polymer dynamics. The temperature dependences of 13C linewidths were used to both qualitatively and quantitatively examine the effects of cation content and identity on PEO spacer mobility. Variable contact time 1H-13C CP-MAS experiments were used to further assess the motions of the polymer backbone on the microsecond timescale. The motion of the PEO spacer, reported via the rate of magnetization transfer from 1H to 13C nuclei, becomes similar for T ? 1.1 Tg in all ionic samples, indicating that at similar elevated reduced temperatures the motions of the polymer backbones on the microsecond timescale become insensitive to ion interactions. These results present an improved picture, beyond those of previous findings, for the dependence of backbone dynamics on cation density (and here, cation identity as well) in these amorphous PEO-based ionomer systems.

Roach, David J. [Penn State Univ., State College, PA (United States). Dept. of Chemistry; Dou, Shichen [Penn State Univ., State College, PA (United States). Dept. of Materials Science and Engineering; Colby, Ralph H. [Penn State Univ., State College, PA (United States). Dept. of Materials Science and Engineering; Mueller, Karl T. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Penn State Univ., State College, PA (United States). Dept. of Chemistry

2013-05-21

189

[Phase transition in polymer blends and structure of ionomers and copolymers]. [Annual report, April 1, 1989--June 30, 1993  

SciTech Connect

The main thrust of the program in the past 3 years are summarized: SAXS instrumentation development; structure and dynamics of macro- and supra-molecules, phase transitions in polymer blends and solutions, structure of ionomers, and fractals and anisotropic systems.

Not Available

1993-07-01

190

Effect of sealers on fracture resistance of endodontically treated teeth with and without smear layer removal: An in vitro study  

PubMed Central

Aim: The present study involved the in vitro comparison of root reinforcing abilities of two sealers, i.e., Ketac-Endo and Acroseal, in endodontically treated teeth in the presence and absence of smear layer. Materials and Methods: Fifty teeth were taken and sectioned at the cementoenamel junction. The teeth with faults were discarded and a total of 36 teeth were used for study. The samples were biomechanically prepared using step-back technique. In 10 teeth, the smear layer was preserved using sodium hypochlorite. Smear layers were removed from 10 teeth using 17% EDTA, and in another 10 samples, the smear layers were eliminated using 17% EGTA. The remaining samples served as controls. Samples were obturated with sealers using the lateral condensation technique. Ketac-Endo (3M) is a glass ionomer based root canal sealer, and Acroseal (Septodont) sealers were used. The teeth were then tested by using an Instron testing machine. Results: Ketac-Endo shows higher fracture resistance values in comparison to Acroseal. Other factors as the amount of tooth structure remaining, the agents used for the removal of smear layer and instrumentation techniques may alter the tooth resistance to fracture. Conclusion: Ketac-Endo shows higher fracture resistance values in comparison to Acroseal. PMID:20543918

Jhamb, Swaty; Nikhil, Vineeta; Singh, Vijay

2009-01-01

191

[The marginal sealing of composite inlays with different cavity liners].  

PubMed

In this in-vitro study we investigated the sealing properties of composite inlays (EOS system) dependent on 8 different base materials. Using a dye-penetration test, the sealing was determined after mechanical and thermal cycling. A partially massive dye-penetration was detected in most cases when one of the following materials was used: a calciumsalicylate cement (Dycal), a combination of calciumsalicylate cement and a resin (Basic), a calcium hydroxide filled resin (Prisma VLC-Dycal), or a zinc phosphate cement (Harvard Cement). In contrast to this, we discovered a complete or almost complete sealing in most cases after application of chemically-cured glass ionomer cements (Ketac-Bond, Ketac-Bond Aplicap, Base-Line) or a light-cured glass ionomer cement (XR-Ionomer) as base materials. From these results it can be concluded that the choice of base materials has an influence on the marginal sealing of composite inlays after thermal and mechanical cycling. However, it is not possible to make a definitive statement on the suitability of these base materials under clinical conditions, because the results of dye-penetration tests have only limited clinical validity. PMID:1439695

Staehle, H J; Emmerich, M; Scharbeth, C

1992-01-01

192

Developments in Metal?Containing Polyurethanes, Co?polyurethanes and Polyurethane Ionomers  

Microsoft Academic Search

The growth of science and technology of polyurethanes leads to the development of new materials with more desirable properties. Such kinds of materials include metal?containing polyurethanes, poly(urethane?urea)s, poly(urethane?ether)s, poly(urethane?ester)s, poly(urethane?ether?ester)s, poly(urethane?imide)s, and polyurethane ionomers with isocyanate structural units combining the properties of enhanced thermal stability, fire retardancy, flexibility, and solubility. Ionic diols containing metal salts are used as important starting

R. Jayakumar; S. Nanjundan; M. Prabaharan

2005-01-01

193

Low platinum loading electrodes for polymer electrolyte fuel cells fabricated using thermoplastic ionomers  

Microsoft Academic Search

Low platinum loading catalyst layers for polymer electrolyte fuel cells (PEFCs) consist of a thin film of highly inter-mixed ionomer and catalyst that is applied to the electrolyte membrane. High performances are achieved with loadings as low as 0.12 mg Pt cm?2 at the cathode and even lower loadings are required at the anode. However, the long-term performance of these

Mahlon S. Wilson; Judith A. Valerio; Shimshon Gottesfeld

1995-01-01

194

Synthesis and Characterization of Isobutylene-Based Ammonium and Phosphonium Bromide Ionomers  

Microsoft Academic Search

The preparation of isobutylene-based ionomers through displacement of halide from brominated poly(isobutylene-co-isoprene) (BIIR) by triphenylphosphine (PPh3) and N,N-dimethyloctyl- amine (DMOA) is demonstrated. While the resulting phosphonium and ammonium bromide salts (IIR- PPh3Br and IIR-NR3Br, respectively) possess dynamic mechanical properties that are comparable to thermoset vulcanizates, the elastomeric network is the result of ion-pair aggregation. Evidence of intra- and intermolecular aggregation

J. Scott Parent; Anca Penciu; Sergio A. Guillen-Castellanos; Andrea Liskova; Ralph A. Whitney

2004-01-01

195

Electrochemical degradation of Nafion ionomer to functionalize carbon support for methanol electro-oxidation  

NASA Astrophysics Data System (ADS)

An effective electrochemical route to produce functional groups on carbon surface is demonstrated. Cyclic voltammetric (CV) sweeps are performed in 0.5 M H2SO4 electrolyte on electrodes containing carbon cloth, Vulcan XC72R, and Nafion ionomer. With supply of ambient oxygen, the generation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that leads to formation of oxygenated functional groups on the carbon surface. Ion chromatography confirms the dissolution of sulfate anions upon CV scans. Raman analysis suggests a minor alteration for the carbon structure. However, X-ray photoelectron spectroscopy indicates a significant increase of oxygenated functional groups in conjunction with notable reduction in the fluorine content. The amount of the oxygenated functional groups is determined by curve fitting of C 1s spectra with known constituents. These functional groups can also be found by immersing the as-prepared electrode in a solution containing concentrated residues from Nafion ionomer decomposition. The functionalized electrode allows a 170% increment of Pt ion adsorption as compared to the reference sample. After electrochemical reductions, the functionalized electrode reveals significant improvements in electrocatalytic abilities for methanol oxidation, which is attributed to the oxygenated functional groups that facilitates the oxidation of CO on Pt.

Hsieh, Yu-Chi; Chen, Jing-Yu; Wu, Pu-Wei

2011-10-01

196

Dynamics and partitioning of the ionome in seeds and germinating seedlings of winter oilseed rape.  

PubMed

Germination and seedling establishment are among the most critical phases in the development of plants, and seed vigour has become an important trait for the selection of robust crop cultivars. Little is known about the potentially limiting role of mineral nutrients in early metabolic and developmental processes during germination. Therefore, we assessed the ionome and relative distribution of mineral elements in different seed and seedling tissues of oilseed rape (Brassica napus L.) and monitored the internal allocation of nutrients during germination. In seeds, cotyledons harboured the main pool of K, P, S, Mg, Fe, Mn and Zn, whereas the seed coat contained most of the Ca, Na, B, Cu and Mo. Although the early root and hypocotyl tissue expanded first, concentrations of most elements were initially low. Re-allocation of elements to the root/hypocotyl tissue from other pools set in two days after seed imbibition and was most rapid for K. Relative to the critical deficiency levels of vegetative tissues, seed tissues were particularly low in B, K and Fe. Further analyses of the ionome of seeds and seedlings, grouped according to their germination efficiency, indicated that in particular low S, Mg and Ca coincided with germination failure. This study documents highly dynamic changes in the ionome of seed and seedling tissues and provides evidence for potentially limiting elements during early germination and seedling establishment in rapeseed. PMID:23939714

Eggert, Kai; von Wirén, Nicolaus

2013-09-01

197

Influence of ionomer content on the structure and performance of PEFC membrane electrode assemblies  

SciTech Connect

Nafion ionomer content of the cathode catalyst-layer of a polymer electrolyte fuel cell (PEFC), made by the decal hot pressing method, has been investigated for its effect on performance and structure of the membrane electrode assembly (MEA). Varying Nafion content was shown to have an effect on performance within the entire range of polarization curves (i.e. kinetic, ohmic, and mass-transport regions) as well as on the structure. AFM analysis shows the effect of Nafion on the dispersion of carbon aggregates. Further analysis using TEM demonstrates the effect of Nafion on both the dispersion of carbon aggregates and the distribution and thickness of the Nafion ionomer films surrounding the catalyst/carbon aggregates. The MEA structure change correlates well with the MEA performance on both kinetics and mass-transport region. The determining factors on the performance of MEA are the interfacial zone (between the ionomer and catalyst particle), the dispersion of catalyst/carbon aggregates and the distribution/thickness of Nafion films. An optimized Nafion content in the range of 27 6 wt.% for the cathode was determined for an E-TEK 20% Pt3Cr/C catalyst at a loading of 0.20mg Pt/cm2.

Xie, Jian [Indiana University and Purdue University; Xu, Fan [Indiana University and Purdue University; WoodIII, David L [Los Alamos National Laboratory (LANL); More, Karren Leslie [ORNL; Zawodzinski, Thomas [Case Western Reserve University; Smith, Wayne H [Los Alamos National Laboratory (LANL)

2010-01-01

198

The bacterial pathogen Xylella fastidiosa affects the leaf ionome of plant hosts during infection.  

PubMed

Xylella fastidiosa is a plant pathogenic bacterium that lives inside the host xylem vessels, where it forms biofilm believed to be responsible for disrupting the passage of water and nutrients. Here, Nicotiana tabacum was infected with X. fastidiosa, and the spatial and temporal changes in the whole-leaf ionome (i.e. the mineral and trace element composition) were measured as the host plant transitioned from healthy to diseased physiological status. The elemental composition of leaves was used as an indicator of the physiological changes in the host at a specific time and relative position during plant development. Bacterial infection was found to cause significant increases in concentrations of calcium prior to the appearance of symptoms and decreases in concentrations of phosphorous after symptoms appeared. Field-collected leaves from multiple varieties of grape, blueberry, and pecan plants grown in different locations over a four-year period in the Southeastern US showed the same alterations in Ca and P. This descriptive ionomics approach characterizes the existence of a mineral element-based response to X. fastidiosa using a model system suitable for further manipulation to uncover additional details of the role of mineral elements during plant-pathogen interactions. This is the first report on the dynamics of changes in the ionome of the host plant throughout the process of infection by a pathogen. PMID:23667547

De La Fuente, Leonardo; Parker, Jennifer K; Oliver, Jonathan E; Granger, Shea; Brannen, Phillip M; van Santen, Edzard; Cobine, Paul A

2013-01-01

199

Small-angle x-ray scattering investigation of temperature influences on microstructures of an ionomer  

SciTech Connect

Ionomer morphology has received extensive studies due to its interesting characteristics in the molecular aggregation of ionic groups. The strong scattering peak in the small-angle X-ray scattering (SAXS) profile has been accounted for by several models. From the multiphase relaxation point of view, Eisenberg et al. proposed that the ionic multiplets were the basic unit of aggregation. The ionic aggregates were surrounded by a spherical region of polymer backbones of restricted mobility. Some overlap of the restricted regions of the ionic phases could be characterized by a high-temperature relaxation relative to the one for the surrounding matrix. The electron density inhomogeneity in a length scale comparable to the average distance between two adjacent multiplets leads to an ionic peak in the SAXS profile. The SAXS profiles of ionomers at different temperatures depended on the counterions and the method of sample preparation. In this paper the authors report SAXS measurements of an ionomer which has undergone different thermal treatment. Extra care was taken in correcting the thermal expansion which was responsible for the primary change in the SAXS profile at different temperatures. The authors used an approach developed by Fischer and Gehrke et al. The modified Porod law and the inverse Fourier transform were used to evaluate the microstructure parameters.

Wang, Jian; Li, Yingjie; Chu, B. (State Univ. of New York, Stony Brook (United States)); Peiffer, D.G. (Exxon Research And Engineering Co., Linden, NJ (United States))

1993-05-10

200

Glass Works  

NSDL National Science Digital Library

This website is about glass and glass-making in Canada and it is presented by the Canadian Museum of Civilization. The site teaches visitors about natural glass, Canadian glass, practical glass, industrial glass, and inspirational glass. Before delving into the different ways glass is used in society, the website provides a thorough answer to the question "What is glass?" It is a mixture of sand, soda, and lime which is heated to extremely high temperatures, then cooled. Visitors will learn the benefits of glass, such as the fact that it is recyclable, inexpensive to produce from common materials, non-corrosive, and it also possesses the ability to be rolled, molded, blown, or cast. The "Making Glass" link shows visitors images of a glassworks furnace, an early 1900s automatic bottle-blowing machine, and a recipe for 2,000 pounds of amber-colored glass from the Dominion Glass Company. The "Practical Glass" link has photos of several objects such as a canning jar, goblet, flytrap, all of which are quite beautiful.

201

The role of acrylonitrile in controlling the structure and properties of nanostructured ionomer films.  

PubMed

Ionomers are polymers which contain ionic groups that are covalently bound to the main chain. The presence of a small percentage of ionic groups strongly affects the polymer's mechanical properties. Here, we examine a new family of nanostructured ionomer films prepared from core-shell polymer nanoparticles containing acrylonitrile (AN), 1,3-butadiene (Bd) and methacrylic acid (MAA). Three new AN-containing dispersions were investigated in this study. The core-shell nanoparticles contained a PBd core. The shells contained copolymerised Bd, AN and MAA, i.e., PBd-AN-MAA. Three types of crosslinking were present in these films: covalent crosslinks (from Bd); strong physical crosslinks (involving ionic bonding of RCOO(-) and Zn(2+)) and weaker physical crosslinks (from AN). We examined and compared the roles of AN and ionic crosslinking (from added Zn(2+)) on the structure and mechanical properties of the films. The FTIR spectroscopy data showed evidence for RCOOH-nitrile hydrogen bonding with tetrahedral geometry. DMTA studies showed that AN copolymerised within the PBd-AN-MAA phase uniformly. Tensile stress-strain data showed that inclusion of AN increased elasticity and toughness. Analysis showed that about 33 AN groups were required to provide an elastically-effective chain. However, only 1.5 to 2 ionically bonded RCOO(-) groups were required to generate an elastically-effective chain. By contrast to ionic bonding, AN inclusion increased the modulus without compromising ductility. Our results show that AN is an attractive, versatile, monomer for increasing the toughness of nanostructured ionomers and this should also be the case for other nanostructured polymer elastomers. PMID:24852137

Tungchaiwattana, Somjit; Musa, Muhamad Sharan; Yan, Junfeng; Lovell, Peter A; Shaw, Peter; Saunders, Brian R

2014-07-14

202

Purdue Ionomics Information Management System. An Integrated Functional Genomics Platform1[C][W][OA  

PubMed Central

The advent of high-throughput phenotyping technologies has created a deluge of information that is difficult to deal with without the appropriate data management tools. These data management tools should integrate defined workflow controls for genomic-scale data acquisition and validation, data storage and retrieval, and data analysis, indexed around the genomic information of the organism of interest. To maximize the impact of these large datasets, it is critical that they are rapidly disseminated to the broader research community, allowing open access for data mining and discovery. We describe here a system that incorporates such functionalities developed around the Purdue University high-throughput ionomics phenotyping platform. The Purdue Ionomics Information Management System (PiiMS) provides integrated workflow control, data storage, and analysis to facilitate high-throughput data acquisition, along with integrated tools for data search, retrieval, and visualization for hypothesis development. PiiMS is deployed as a World Wide Web-enabled system, allowing for integration of distributed workflow processes and open access to raw data for analysis by numerous laboratories. PiiMS currently contains data on shoot concentrations of P, Ca, K, Mg, Cu, Fe, Zn, Mn, Co, Ni, B, Se, Mo, Na, As, and Cd in over 60,000 shoot tissue samples of Arabidopsis (Arabidopsis thaliana), including ethyl methanesulfonate, fast-neutron and defined T-DNA mutants, and natural accession and populations of recombinant inbred lines from over 800 separate experiments, representing over 1,000,000 fully quantitative elemental concentrations. PiiMS is accessible at www.purdue.edu/dp/ionomics. PMID:17189337

Baxter, Ivan; Ouzzani, Mourad; Orcun, Seza; Kennedy, Brad; Jandhyala, Shrinivas S.; Salt, David E.

2007-01-01

203

Glass Artworks  

NASA Technical Reports Server (NTRS)

Several NASA technologies have played part in growth and cost containment of studio glass art, among them a foam type insulation developed to meet a need for lightweight material that would reduce flame spread in aircraft fire. Foam comes in several forms and is widely used by glass artists, chiefly as an insulator for the various types of ovens used in glass working. Another Spinoff is alumina crucibles to contain molten glass. Before alumina crucibles were used, glass tanks were made of firebrick which tended to erode under high temperatures and cause impurities; this not only improved quality but made the process more cost effective. One more NASA technology that found its way into glass art working is a material known as graphite board, a special form of graphite originally developed for rocket motor applications. This graphite is used to exact compound angles and creates molds for poured glass artworks of dramatic design.

1988-01-01

204

Ionomers of intrinsic microporosity: in silico development of ionic-functionalized gas-separation membranes.  

PubMed

This work presents the predictive molecular simulations of a functionalized polymer of intrinsic microporosity (PIM) with an ionic backbone (carboxylate) and extra-framework counterions (Na(+)) for CO2 gas storage and separation applications. The CO2-philic carboxylate-functionalized polymers are predicted to contain similar degrees of free volume to PIM-1, with Brunauer-Emmett-Teller (BET) surface areas from 510 to 890 m(2)/g, depending on concentration of ionic groups from 100% to 17%. As a result of ionic groups enhancing the CO2 enthalpy of adsorption (to 42-50 kJ/mol), the uptake of the proposed polymers at 293 K exceeded 1.7 mmol/g at 10 kPa and 3.3 mmol/g at 100 kPa for the polymers containing 100% and 50% ionic functional groups, respectively. In addition, CO2/CH4 and CO2/N2 mixed-gas separation performance was evaluated under several industrially relevant conditions, where the IonomIMs are shown to increase both the working capacity and selection performance in certain pressure swing applications (e.g., natural gas separations). These simulations reveal that intrinsically microporous ionomers show great potential as the future of energy-efficient gas-separation polymeric materials. PMID:25272236

Hart, Kyle E; Colina, Coray M

2014-10-14

205

Sphingolipids in the root play an important role in regulating the leaf ionome in Arabidopsis thaliana.  

PubMed

Sphingolipid synthesis is initiated by condensation of Ser with palmitoyl-CoA producing 3-ketodihydrosphinganine (3-KDS), which is reduced by a 3-KDS reductase to dihydrosphinganine. Ser palmitoyltransferase is essential for plant viability. Arabidopsis thaliana contains two genes (At3g06060/TSC10A and At5g19200/TSC10B) encoding proteins with significant similarity to the yeast 3-KDS reductase, Tsc10p. Heterologous expression in yeast of either Arabidopsis gene restored 3-KDS reductase activity to the yeast tsc10? mutant, confirming both as bona fide 3-KDS reductase genes. Consistent with sphingolipids having essential functions in plants, double mutant progeny lacking both genes were not recovered from crosses of single tsc10A and tsc10B mutants. Although the 3-KDS reductase genes are functionally redundant and ubiquitously expressed in Arabidopsis, 3-KDS reductase activity was reduced to 10% of wild-type levels in the loss-of-function tsc10a mutant, leading to an altered sphingolipid profile. This perturbation of sphingolipid biosynthesis in the Arabidopsis tsc10a mutant leads an altered leaf ionome, including increases in Na, K, and Rb and decreases in Mg, Ca, Fe, and Mo. Reciprocal grafting revealed that these changes in the leaf ionome are driven by the root and are associated with increases in root suberin and alterations in Fe homeostasis. PMID:21421810

Chao, Dai-Yin; Gable, Kenneth; Chen, Ming; Baxter, Ivan; Dietrich, Charles R; Cahoon, Edgar B; Guerinot, Mary Lou; Lahner, Brett; Lü, Shiyou; Markham, Jonathan E; Morrissey, Joe; Han, Gongshe; Gupta, Sita D; Harmon, Jeffrey M; Jaworski, Jan G; Dunn, Teresa M; Salt, David E

2011-03-01

206

Graphene-supported platinum catalyst prepared with ionomer as surfactant for anion exchange membrane fuel cells  

NASA Astrophysics Data System (ADS)

In this work, we have synthesized an ionomer-coated graphene-supported platinum catalyst for anion exchange membrane fuel cells. Unlike the common surfactant stabilized colloidal method, we employ a home-made anion exchange ionomer (AEI), namely quaternary ammonia poly (2, 6-dimethyl-1, 4-phenylene oxide) (QAPPO), as the surfactant. The AEI coated on reduced graphene oxide (rGO) surfaces serves as a stabilizer to anchor the platinum precursor on rGO surfaces due to electrostatic interactions. As a result, platinum nanoparticles (Pt NPs) can be easily deposited onto rGO surfaces with a uniform distribution. The remarkable feature of the present synthesis method is that the surfactant, the coated AEI, does not need to be removed from the catalyst, but serves as hydroxide-conductive paths in the catalyst layer, leading to enhanced triple phase boundaries. It is demonstrated that the use of the catalyst obtained with the present method enables a H2/O2 AEMFC to yield a peak power density of 264.8 mW cm-2 at 60 °C, which is 30% higher than that produced from the same fuel cell but with the use of the catalyst synthesized by the conventional synthesis method.

Zeng, L.; Zhao, T. S.; An, L.; Zhao, G.; Yan, X. H.; Jung, C. Y.

2015-02-01

207

High-resolution genome-wide scan of genes, gene-networks and cellular systems impacting the yeast ionome  

Technology Transfer Automated Retrieval System (TEKTRAN)

To balance the demand for uptake of essential elements with their potential toxicity living cells have complex regulatory mechanisms. Here, we describe a genome-wide screen to identify genes that impact the elemental composition (‘ionome’) of yeast Saccharomyces cerevisiae. Using inductively coupled...

208

Cluster-continuum quantum mechanical models to guide the choice of anions for Li+-conducting ionomers  

NASA Astrophysics Data System (ADS)

A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li+-anion pair, triple ion, and quadrupole was used to represent the states of Li+ within the ionomer in the CCM. The relative energy of each state was calculated for Li+ with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li+ ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li+-conducting states (free Li+ and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li+-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

Shiau, Huai-Suen; Liu, Wenjuan; Colby, Ralph H.; Janik, Michael J.

2013-11-01

209

Elemental-composition and plant-trait patterns in an ionomically and genetically diverse set of rice germplasm  

Technology Transfer Automated Retrieval System (TEKTRAN)

With about half of the worlds people dependent on rice as their main food source, improving the nutritional value of rice could have major impact on human health. The first step toward breeding rice cultivars with enhanced element composition (ionomics) is to understand the genetic diversity availab...

210

Comparative experimental study of ionic polymer-metal composites with different backbone ionomers and in various cation forms  

Microsoft Academic Search

An ionic polymer-metal composite (IPMC) consisting of a thin perfluorinated ionomer (usually, Nafion or Flemion) strip, platinum, and\\/or gold plated on both faces and neutralized by a certain amount of appropriate cations undergoes large bending motion when, in a hydrated state, a small electric field is applied across its thickness. When the same membrane is suddenly bent, a small voltage

Sia Nemat-Nasser; Yongxian Wu

2003-01-01

211

Cluster-continuum quantum mechanical models to guide the choice of anions for Li{sup +}-conducting ionomers  

SciTech Connect

A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li{sup +}-anion pair, triple ion, and quadrupole was used to represent the states of Li{sup +} within the ionomer in the CCM. The relative energy of each state was calculated for Li{sup +} with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li{sup +} ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li{sup +}-conducting states (free Li{sup +} and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li{sup +}-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

Shiau, Huai-Suen; Janik, Michael J. [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Liu, Wenjuan; Colby, Ralph H. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2013-11-28

212

Interpretation of the Small-Angle X-ray Scattering from Swollen and Oriented Perfluorinated Ionomer Membranes  

E-print Network

on the perfluorinated ionomer membrane "Nafion". The swelling experiments were conducted using controlled environments model for Nafion is an ion clustered morphology with a hierarchical scale of structure. The smallest Nemours and Company, under the trade name "Nafion". The structural formula of Nafion is shown in Figure 1

Elliott, James

213

glass ceramic  

NASA Astrophysics Data System (ADS)

Glass sample with a composition of Li1.3Nb0.3Fe1.7(PO4)3, prepared by a conventional melt-quenching method, was heat treated to obtain glass ceramics of NASICON type. Glass transition ( T g) and crystallization ( T c) temperatures of as-quenched glass sample were determined by differential thermal analysis (DTA). X-ray diffraction (XRD) patterns also confirmed the formation of glass sample. After heat treatment above T c, precipitation of crystalline particles with NASICON-type structure was confirmed by XRD. Valency and local structure of Fe atoms were investigated by Mössbauer spectroscopy at room temperature. DC-conductivity and impedance measurements of the glass ceramics proved the increased electrical conduction caused by heat treatment.

Hassaan, M. Y.; Salem, S. M.; Moustafa, M. G.; Kubuki, S.; Matsuda, K.; Nishida, T.

2014-04-01

214

Lithium Polymer Electrolytes Based On PMMA / PEG And Penetrant Diffusion In Kraton Penta-Block Ionomer  

NASA Astrophysics Data System (ADS)

The study of diffusion in polymeric material is critical to many research fields and applications, such as polymer morphology, protective coatings (paints and varnishes), separation membranes, transport phenomena, polymer electrolytes, polymer melt, and controlled release of drugs from polymer carriers [1-9]. However, it is still a challenge to understand, predict and control the diffusion of molecules and ions of different sizes in polymers [2]. This work studied the medium to long range diffusion of species (i.e., ions and molecules) in solid polymer electrolytes based on poly(ethylene glycol)/poly(methyl methacrylate) (PEG/PMMA) for Li-based batteries, and polymeric permselective membranes via pulsed-field gradient NMR and a.c. impedance. Over the past decades polymer electrolytes have attracted much attention because of their promising technological application as an ion-conducting medium in solid-state batteries, fuel cells, electrochromic displays, and chemical sensors [10, 11]. However, despite numerous studies related to ionic transport in these electrolytes the understanding of the migration mechanism is still far from being complete, and progress in the field remains largely empirical [10, 12-15]. Among various candidates for solid polymer electrolyte (SPE) material, the miscible polymer pair, poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA), is an attractive one, because there is a huge difference in mobility between PEO and PMMA in their blends, and PEO chains remain exceptionally mobile in the blend even at temperature below the glass transition temperature of the blend [ 16]. Thus the mechanical strength and dimensional stability is maintained by PMMA component, while the chain motions or rearrangements of the PEO component virtually contribute to the ion transport [17]. The current work prepared two types of SPE based on poly(ethylene glycol) (PEG) /PMMA (40/60 by weight) for Li-based batteries: lithium bis(trifluoromethylsulfonylimide) (LiN(SO2CF3)2, LiTFSI) doped SPE and single-ion SPE. PEG, which is the very low molecular weight version of PEO, was used instead of PLO due to PEG's advantages of being noncrystalline, higher mobility, and having relatively high ionic conductivity when doped with alkali metal salts [18]. The medium to long range diffusion of species (i.e., ions and molecules) were studied via pulsed-field gradient NMR and a.c. impedance, along with other properties. For the LiTFSI doped system, the samples are named with their F0 to Li ratios. The order of diffusivity of ions is 16:1> 24:1> 8:1, while the order of a.c. conductivity is 24:1 > 16:1> 8:1. The largest diffusion 7Li coefficient is 1.4 x 108 cm 2/s in 16:1 at 77°C , and the largest a.c. conductivity is 1.43x 10-5S/cm for 24:1 at 68°C. The discrepancy between the diffusivity order and conductivity order is attributed to the formation of neutral contact ion pairs by a substantial fraction of ions in 16:1 . As the salt concentration is increased as 24:1?16:1?8:1, there is the transition of mostly free ions (i.e., 24:1)?free ions+contact ion pairs (i.e.. 16:1)?free ions+contact ion pairs+higher aggregates (i.e., 8:1). For the single-ion system, ion pairing of lithium PMMA ionomer is a serious problem due to the relatively low acidity of its corresponding acid and the low dielectric constant of the solvent (i.e. PEG). The Li+ diffusivity is fair (on the order of 10-8 cm2/s at 65°C, 77°C, and 89°C), but the fraction of free Li+ is only 1-2%. This severely limits the resulting a.c. conductivity, which is 2.72x 10-7 S/cm for 40P600 at 81°C. The second project involves studying the transport properties of a sulfonated pentablock copolymer, poly(para-methylstyrene)--b-hydrogenated polybutadiene-b-polystyrene-bhydrogenated polybutadiene - b-poly(para-methylstyrene) with polystyrene sulfonated in the midblock(PMS-HPB-sS-HPB-PMS), as pemrselective membranes for protective clothing, with high permeability to water and low permeability to hazardous organic chemicals. In addition, this work also contribute

Meng, Yan

215

Rainbow Glasses  

NSDL National Science Digital Library

In this activity, learners explore light, color and rainbows by making their own rainbow glasses. Learners glue "rainbow optics paper" onto the glasses cutout, add decorations and attach pipe cleaner earpieces. Learners name the different colors they observe and notice that the colors always appear in the same order. This activity guide includes open-ended questions to help learners explore these topics further.

OMSI

2004-01-01

216

Antibacterial Properties of Dental Luting Agents: Potential to Hinder the Development of Secondary Caries  

PubMed Central

A modified direct contact test was used to evaluate the antibacterial properties of four commercially available dental luting agents (RelyX Unicem, Ketac Cem, Ceramir Crown & Bridge and Harvard Cement) and two reference materials (glass-ionomer cement and calcium aluminate cement) compared to a negative-control material (PMMA). Streptococcus mutans bacteria were placed in direct contact with specimens that had been aged for 10?min, 1?day, and 7?days, in order to test the antibacterial properties of the materials. A metabolic assay containing resazurin was used to quantify the amount of viable bacteria remaining after the direct contact tests. The effects of pH and fluoride on bacteria proliferation were also evaluated. Strongest antibacterial properties were found for calcium aluminate cement, followed by Ceramir Crown & Bridge and RelyX Unicem. Ketac Cem, Harvard Cement, and the reference glass-ionomer cement showed bacteria content either higher than or not significantly different from the PMMA control in all instances. pH levels below 6.3 and above 9.0 were found to have negative effects on bacterial proliferation. No correlation between either acidic materials or fluoride release and antibacterial properties could be seen; rather, basic materials showed stronger antibacterial properties. PMID:22505901

Unosson, Erik; Cai, Yanling; Jiang, Xiyuan; Lööf, Jesper; Welch, Ken; Engqvist, Håkan

2012-01-01

217

One-year clinical evaluation of a Glass Carbomer fissure sealant, a preliminary study.  

PubMed

Glass Carbomer is a new generation of restorative material developed from glass-ionomer cements with possibility of gradual mineralization into fluorapatite. The aim of this clinical trial was to investigate the retention of Glass Carbomer fissure sealant after 12 months, in comparison to a commonly used conventional resin-based sealant. Forty-eight teeth in 24 patients [mean (SD) = 8 (2.3) years] with well-delineated fissure morphology were randomly divided into two equal groups and sealed with Bis-GMA resin-based Helioseal F (group A, Ivoclar Vivadent, Liechtenstein) and Glass Carbomer (group B, Glass Carbomer Sealant, Glass Carbomer Products, Leiden, Netherlands) using the split mouth design. Materials were placed and set according to the manufacturer's instructions using a polymerization unit Bluephase 16i (Vivadent, Liechtenstein). Complete sealant retentions in both groups were 100% and 75% after 6 and 12 months of clinical service, respectively. There were there were no secondary caries lesions in both groups after 6 months; two new carious lesions were detected in both groups after 12 months. The Mann-Whitney U test revealed no significant difference between the two groups at both evaluations points (P > 0.05). Glass Carbomer material showed a similar retention rate when compared with a resin-based sealant. Future studies are required to examine the long-term performance of Glass Carbomer sealants. PMID:25134364

Gorseta, K; Glavina, D; Borzabadi-Farahani, A; Van Duinen, R N; Skrinjaric, I; Hill, R G; Lynch, E

2014-06-01

218

Morphological investigation of midblock-sulfonated block ionomers prepared from solvents differing in polarity.  

PubMed

Recent developments regarding charged multiblock copolymers that can form physical networks and exhibit robust mechanical properties herald new and exciting opportunities for contemporary technologies requiring amphiphilic attributes. Due to the presence of strong interactions, however, control over the phase behavior of such materials remains challenging, especially since their morphologies can be solvent-templated. In this study, transmission electron microscopy and microtomography are employed to examine the morphological characteristics of midblock-sulfonated pentablock ionomers prepared from solvents differing in polarity. Resultant images confirm that discrete, spherical ion-rich microdomains form in films cast from a relatively nonpolar solvent, whereas an apparently mixed morphology with a continuous ion-rich pathway is generated when the casting solvent is more highly polar. Detailed 3D analysis of the morphological characteristics confirms the coexistence of hexagonally-packed nonpolar cylinders and lamellae, which facilitates the diffusion of ions and/or other polar species through the nanostructured medium. PMID:25537368

Mineart, Kenneth P; Jiang, Xi; Jinnai, Hiroshi; Takahara, Atsushi; Spontak, Richard J

2015-03-01

219

Simulation of a small molecule analogue of a lithium ionomer in an external electric field  

SciTech Connect

We have investigated the ion dynamics in lithium-neutralized 2-pentylheptanoic acid, a small molecule analogue of a precise poly(ethylene-co-acrylic acid) lithium ionomer. Atomistic molecular dynamics simulations were performed in an external electric field. The electric field causes alignment of the ionic aggregates along the field direction. The energetic response of the system to an imposed oscillating electric field for a wide range of frequencies was tracked by monitoring the coulombic contribution to the energy. The susceptibility found in this manner is a component of the dielectric susceptibility typically measured experimentally. A dynamic transition is found and the frequency associated with this transition varies with temperature in an Arrhenius manner. The transition is observed to be associated with rearrangements of the ionic aggregates.

Waters, Sara M.; McCoy, John D., E-mail: mccoy@nmt.edu; Brown, Jonathan R. [Department of Materials Engineering, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 (United States)] [Department of Materials Engineering, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801 (United States); Frischknecht, Amalie L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2014-01-07

220

Micro direct methanol fuel cell with perforated silicon-plate integrated ionomer membrane  

NASA Astrophysics Data System (ADS)

This article describes the fabrication and characterization of a silicon based micro direct methanol fuel cell using a Nafion ionomer membrane integrated into a perforated silicon plate. The focus of this work is to provide a platform for micro- and nanostructuring of a combined current collector and catalytic electrode. AC impedance spectroscopy is utilized alongside IV characterization to determine the influence of the plate perforation geometries on the cell performance. It is found that higher ratios of perforation increases peak power density, with the highest achieved being 2.5 mW cm-2 at a perforation ratio of 40.3%. The presented fuel cells also show a high volumetric peak power density of 2  mW cm-3 in light of the small system volume of 480  ?L, while being fully self contained and passively feed.

Larsen, J. V.; Dalslet, B. T.; Johansson, A.-C.; Kallesøe, C.; Thomsen, E. V.

2014-07-01

221

Edible Glass  

NSDL National Science Digital Library

In this activity, learners discover the principles of edible glass by making a supersaturated sugar solution. The goal of this activity is to provide an interesting experiment which learners of many different levels can perform. The write-up for this activity provides explanatory information that presents the experiment from several different perspectives. This activity includes an introduction to common sugars, as well as some discussion of temperature and thermometry, basic thermodynamics, and the experimental procedure to make the candy glass.

Josh Pomeroy

2012-01-01

222

Pulp response after application of two resin modified glass ionomer cements (RMGICs) in deep cavities of prepared human teeth  

Microsoft Academic Search

Objectives: This study evaluated the human pulp response to the application of two RMGICs in deep cavities in vivo. Methods: The cavity floor prepared on the buccal surface of 34 premolars was lined with VBP (VBP), Vitrebond (VB) or Dycal® (DY), and restored with composite resin. Additional teeth were used as an intact control group. After 7 or 30–60 days,

Carlos A. de Souza Costa; Ana Paula D. Ribeiro; Elisa M. Aparecida Giro; Ros C. Randall; Josimeri Hebling

2011-01-01

223

The effects of Nafion ® ionomer content in PEMFC MEAs prepared by a catalyst-coated membrane (CCM) spraying method  

Microsoft Academic Search

We analyzed the effects of ionomer content on the proton exchange membrane fuel cell (PEMFC) performance of membrane electrode assemblies (MEAs) fabricated by a catalyst-coated membrane (CCM) spraying method in partially humidified atmospheric air and hydrogen. When high loading Pt\\/C catalysts (45.5 wt.%) were used, we observed that catalytic activity was not directly proportional to electrochemical active surface area (EAS). This

Kun-Ho Kim; Kwan-Young Lee; Hyoung-Juhn Kim; EunAe Cho; Sang-Yeop Lee; Tae-Hoon Lim; Sung Pil Yoon; In Chul Hwang; Jong Hyun Jang

2010-01-01

224

Using decomposed Nafion ionomers to anchor Pt nanoparticles and improve their durability during methanol electro-oxidation  

NASA Astrophysics Data System (ADS)

Nafion ionomers were partially decomposed to produce oxygenated functional groups on Vulcan XC72R (XC72R) that enabled increased Pt ion adsorption when the functionalized XC72R was immersed in a 5 mM aqueous H2PtCl6 solution. X-ray absorption spectroscopy spectra indicated that the oxidation state for the Pt ions remained unchanged upon adsorption on the functionalized XC72R whereas a notable reduction in the oxidation state was recorded when the Pt ions were adsorbed onto untreated XC72R. After a hydrogen reduction treatment, the Pt nanoparticles on the functionalized XC72R demonstrated impressive mass activities and durability retention during the methanol electro-oxidation reaction (MOR), compared to those of commercial E-TEK Pt/C samples. After the durability test, transmission electron microscope images showed that the Pt nanoparticles on the functionalized XC72R exhibited significantly reduced agglomeration, and X-ray photoelectron spectra confirmed that the functional groups from the decomposed Nafion ionomers were still present. We attributed the notable durability improvement to the anchoring effect of decomposed Nafion ionomers that prevented the Pt nanoparticles from contacting XC72R directly, thus minimizing the undesirable migration and detachment of Pt nanoparticles during repeated MOR cycles.

Hsieh, Yu-Chi; Chang, Li-Chung; Chen, Yong-Min; Wu, Pu-Wei; Lee, Jyh-Fu

2014-01-01

225

Mapping of Ionomic Traits in Mimulus guttatus Reveals Mo and Cd QTLs That Colocalize with MOT1 Homologues  

PubMed Central

Natural variation in the regulation of the accumulation of mineral nutrients and trace elements in plant tissues is crucial to plant metabolism, development, and survival across different habitats. Studies of the genetic basis of natural variation in nutrient metabolism have been facilitated by the development of ionomics. Ionomics is a functional genomic approach for the identification of the genes and gene networks that regulate the elemental composition, or ionome, of an organism. In this study, we evaluated the genetic basis of divergence in elemental composition between an inland annual and a coastal perennial accession of Mimulus guttatus using a recombinant inbred line (RIL) mapping population. Out of 20 elements evaluated, Mo and Cd were the most divergent in accumulation between the two accessions and were highly genetically correlated in the RILs across two replicated experiments. We discovered two major quantitative trait loci (QTL) for Mo accumulation, the largest of which consistently colocalized with a QTL for Cd accumulation. Interestingly, both Mo QTLs also colocalized with the two M. guttatus homologues of MOT1, the only known plant transporter to be involved in natural variation in molybdate uptake. PMID:22292026

Lowry, David B.; Sheng, Calvin C.; Zhu, Zhirui; Juenger, Thomas E.; Lahner, Brett; Salt, David E.; Willis, John H.

2012-01-01

226

Species- and genome-wide dissection of the shoot ionome in Brassica napus and its relationship to seedling development  

PubMed Central

Knowing the genetic basis of the plant ionome is essential for understanding the control of nutrient transport and accumulation. The aim of this research was to (i) study mineral nutrient concentrations in a large and diverse set of Brassica napus, (ii) describe the relationships between the shoot ionome and seedling development, and (iii) identify genetic regions associated with variation of the shoot ionome. The plant material under study was a germplasm set consisting of 509 inbred lines that was genotyped by a 6K single nucleotide polymorphism (SNP) array and phenotyped by analyzing the concentrations of eleven mineral nutrients in the shoots of 30 days old seedlings. Among mineral concentrations, positive correlations were found, whereas mineral concentrations were mainly negatively correlated with seedling development traits from earlier studies. In a genome-wide association mapping approach, altogether 29 significantly associated loci were identified across seven traits after correcting for multiple testing. The associations included a locus with effects on the concentrations of Cu, Mn, and Zn on chromosome C3, and a genetic region with multiple associations for Na concentration on chromosome A9. This region was situated within an association hotspot close to SOS1, a key gene for Na tolerance in plants. PMID:25324847

Bus, Anja; Körber, Niklas; Parkin, Isobel A. P.; Samans, Birgit; Snowdon, Rod J.; Li, Jinquan; Stich, Benjamin

2014-01-01

227

Comparison of self-healing ionomer to aluminium-alloy bumpers for protecting spacecraft equipment from space debris impacts  

NASA Astrophysics Data System (ADS)

This paper discusses the impact behavior of a self-healing ionomeric polymer and compares its protection capability against space debris impacts to that of simple aluminium-alloy bumpers. To this end, 14 impact experiments on both ionomer and Al-7075-T6 thin plates with similar surface density were made with 1.5 mm aluminium spheres at velocity between 1 and 4 km/s.First, the perforation extent in both materials was evaluated vis-à-vis the prediction of well known hole-size equations; then, attention was given to the damage potential of the cloud of fragments ejected from the rear side of the target by analysing the craters pattern and the momentum transferred to witness plates mounted on a ballistic pendulum behind the bumpers.Self-healing was completely successful in all but one ionomer samples and the primary damage on ionomeric polymers was found to be significantly lower than that on aluminium. On the other hand, aluminium plates exhibited slightly better debris fragmentation abilities, even though the protecting performance of ionomers seemed to improve at increasing impact speed.

Francesconi, A.; Giacomuzzo, C.; Grande, A. M.; Mudric, T.; Zaccariotto, M.; Etemadi, E.; Di Landro, L.; Galvanetto, U.

2013-03-01

228

From a Molecule to a Micelle: Small Angle Neutron Scattering Study of a Perfluoro Ionomer in Polar Solvents  

NASA Astrophysics Data System (ADS)

The solution structure of perfluorosulfonimide ionomer has been investigated using small angle neutron scattering (SANS). The significance of this ionomer lies in its high potential as proton Exchange membrane for fuel cells. In polar solvents, the hydrophobicity of the fluorinated backbone drives aggregation. SANS measurements have been carried out as a function of the concentration of the ionomer, temperature as well as ionic strength. With increasing concentration, a clear transition from a molecular form factor to micellar one has been observed. Above the critical micelle concentration (CMC), SANS data revealed cylindrical aggregates. Bellow the CMC, it corresponds to a Gaussian chain. This expended configuration is intriguing since the density of the polar groups is rather low and in poor solvent one would expect a collapsed chain. The micelles were found to be extremely stable and did not brake up with increasing temperature. The radius of the micelle did not change much as a function of temperature or ionic strength. Increasing the salt concentration resulted in a significant increase in the length of the micelle. Further studies are currently underway way to discern the factors, which affect the shape and stability of these micelles.

Jiao, Xuesong; Thomas, Brian; Desmartaue, Darryl D.; Perahia, Dvora; Lal, Jyotsna

2001-03-01

229

Pinhole Glasses  

NASA Astrophysics Data System (ADS)

Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole glasses really give better vision? Some ways to use this question for motivation in teaching optics have been discussed. For this column we include a series of experiments that students can complete using a model of the eye and demonstrate issues related to pinhole vision correction.

Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

2008-01-01

230

Ionizing radiation-induced copolymerization of 2-ethylhexyl acrylate and acrylic acid and ionomer formation  

NASA Astrophysics Data System (ADS)

The ionizing radiation-induced polymerization of acrylate esters is a technique employed for the curing of such materials for a variety of adhesive, coating, ink, and lithographic applications. The work presented in this dissertation involves the synthesis of a copolymer composed of 2-ethylhexyl acrylate (2-EHA) and acrylic acid (AA) using pulsed electron beam and gamma irradiation. The structure and synthesis kinetics of this copolymer were investigated by 1H nuclear magnetic resonance (NMR), electron pulse radiolysis with kinetic spectroscopic detection (PR-KSD), and Fourier transform infrared spectroscopy (FTIR). The effects of total dose, dose rate, and acrylic acid content on the polymerization reaction were studied. The conversion of 2-EHA monomer into polymer at a given total dose was found to be enhanced at lower dose rates and higher concentrations of acrylic acid. The pulse radiolysis investigation of the polymerization of 2-EHA and AA was performed through studies of four different types of systems: (i) neat 2-EHA, (ii) 2-EHA/methanol (MeOH) solutions, (iii) mixtures of 2-EHA and AA, and (iv) 2-EHA/AA/MeOH solutions. The build-up of carbon-centered neutral 2-EHA free radicals in neat 2-EHA was found to obey a second order rate law with a rate coefficient of ((7 +/- 3) x 108)epsilon EHA·, whereas in 2-EHA/AA mixtures it was found to obey a pseudo-first order rate law with a rate coefficient of (1.5 +/- 0.3) x 10 10 mol-1 dm3 s-1. This phenomenon is suggested to originate in the increased H+ ion concentration in the presence of acrylic acid, which leads to a faster neutralization step of 2-EHA radical anions as they are transformed into neutral free radicals during the initiation step of the reaction. An investigation of the formation of ion-containing copolymers (known as ionomers) was performed using the radiation-synthesized poly(2-EHA-co-AA) and iron cations. Verification of successful incorporation of iron into the copolymer was identified by an asymmetric carboxylate stretch at 1600 cm -1 of the FTIR spectrum. TEM analysis of poly(2-EHA-co-AA)/Fe 2+ ionomers formed from formulated compositions involving a 2:1 mole ratio of ferrous acetate to acrylic acid exhibited ionic clusters of approximately 100 nm in diameter, which may include up to 350 ferrous cations.

Weaver, Alia

231

Dental glass-reinforced composite for caries inhibition: Calcium phosphate ion release and mechanical properties  

PubMed Central

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker-reinforced Ca-PO4 composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle-reinforced, photo-cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO4 release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength (p < 0.05). Flexural strength (mean ± sd; n = 6) at 30% glass was (99 ± 18) MPa, higher than (54 ± 20) MPa at 0% glass (p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 d, the released Ca ion concentration was (4.61 ± 0.18) mmol/L at pH of 4, much higher than (1.14 ± 0.07) at pH of 5.5, and (0.27 ± 0.01) at pH of 7 (p < 0.05). PO4 release was also dramatically increased at cariogenic, acidic pH. The TTCP-glass composite had strength 2-3 fold that of a resin-modified glass ionomer control. In conclusion, the photo-cured TTCP-glass composite was “smart” and substantially increased the Ca and PO4 release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO4 and fluoride releasing restoratives. Hence, the photo-cured TTCP-glass composite may have potential to provide the necessary combination of load-bearing and caries-inhibiting capabilities. PMID:19810118

Xu, Hockin H. K.; Moreau, Jennifer L.

2010-01-01

232

Dental glass-reinforced composite for caries inhibition: calcium phosphate ion release and mechanical properties.  

PubMed

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker-reinforced Ca-PO(4) composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle-reinforced, photo-cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO(4) release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength (p < 0.05). Flexural strength (Mean +/- SD; n = 6) at 30% glass was 99 +/- 18 MPa, higher than 54 +/- 20 MPa at 0% glass (p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 days, the released Ca ion concentration was 4.61 +/- 0.18 mmol/L at pH of 4, much higher than 1.14 +/- 0.07 at pH of 5.5, and 0.27 +/- 0.01 at pH of 7 (p < 0.05). PO(4) release was also dramatically increased at cariogenic, acidic pH. The TTCP-glass composite had strength 2-3 fold that of a resin-modified glass ionomer control. In conclusion, the photo-cured TTCP-glass composite was "smart" and substantially increased the Ca and PO(4) release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO(4), and fluoride releasing restoratives. Hence, the photo-cured TTCP-glass composite may have potential to provide the necessary combination of load-bearing and caries-inhibiting capabilities. PMID:19810118

Xu, Hockin H K; Moreau, Jennifer L

2010-02-01

233

Single-Kernel Ionomic Profiles Are Highly Heritable Indicators of Genetic and Environmental Influences on Elemental Accumulation in Maize Grain (Zea mays)  

PubMed Central

The ionome, or elemental profile, of a maize kernel can be viewed in at least two distinct ways. First, the collection of elements within the kernel are food and feed for people and animals. Second, the ionome of the kernel represents a developmental end point that can summarize the life history of a plant, combining genetic programs and environmental interactions. We assert that single-kernel-based phenotyping of the ionome is an effective method of analysis, as it represents a reasonable compromise between precision, efficiency, and power. Here, we evaluate potential pitfalls of this sampling strategy using several field-grown maize sample sets. We demonstrate that there is enough genetically determined diversity in accumulation of many of the elements assayed to overcome potential artifacts. Further, we demonstrate that environmental signals are detectable through their influence on the kernel ionome. We conclude that using single kernels as the sampling unit is a valid approach for understanding genetic and environmental effects on the maize kernel ionome. PMID:24489944

Baxter, Ivan R.; Ziegler, Gregory; Lahner, Brett; Mickelbart, Michael V.; Foley, Rachel; Danku, John; Armstrong, Paul; Salt, David E.; Hoekenga, Owen A.

2014-01-01

234

Pinhole Glasses  

ERIC Educational Resources Information Center

Eye aberrations are commonly corrected by lenses that restore vision by altering rays before they pass through the cornea. Some modern promoters claim that pinhole glasses are better than conventional lenses in correcting all kinds of refractive defects such as myopia (nearsighted), hyperopia (farsighted), astigmatisms, and presbyopia. Do pinhole…

Colicchia, Giuseppe; Hopf, Martin; Wiesner, Hartmut; Zollman, Dean

2008-01-01

235

Setting reaction of polyacid modified composite resins or compomers.  

PubMed

The hardening of modified polyacid composite resins (compomers) and glass-ionomers have been studied using infrared spectroscopy. The acid-base reaction in Ketac-fil, a glass ionomer, was followed by the ratio between the COOH band located around 1715 cm?¹ and that corresponding to COO? located around 1570 cm?¹. The combination of infrared analysis and band narrowing treatments enable us to propose in the glass-ionomer two maturation steps. First, a very rapid equilibrium acid-base related, and second the cross-linking of polycarboxylate with the metal ions present in the cement. In compomers, a new reaction has been described involving polymerization induced by free radicals besides the two steps associated with the acid-base reaction. Using infrared spectroscopy and band narrowing techniques, it is shown that water is essential to complete the hardening process but no acid-base reaction is produced since the COO? band does not appear. The reaction associated with free radicals could be described as a polymerization of methacrylate monomers together with an aqueous dilution of the filling particles releasing different metal cations that would chelate with the polymer molecules to form a macromolecular structure. PMID:19834564

Arrondo, J L R; Collado, M I; I, Soler; Triana, R; Ellacuria, J

2009-01-01

236

Modulation of fibroblast inflammatory response by surface modification of a perfluorinated ionomer.  

PubMed

An ideal surface for implantable glucose sensors would be able to evade the events leading to chronic inflammation and fibrosis, thereby extending its utility in an in vivo environment. Nafion™, a perfluorinated ionomer, is the membrane material preferred for in situ glucose sensors. Unfortunately, the surface properties of Nafion™ promote random protein adsorption and eventual foreign body encapsulation, thus leading to loss of glucose signal over time. Details of the techniques to render Nafion™ nonprotein fouling are given in a previous article [T. I. Valdes et al., Biomaterials 29, 1356 (2008)]. Once random protein adsorption is prevented, a biologically active peptide can be covalently bonded to the treated Nafion™ to induce cellular adhesion. Cellular responses to these novel decorated Nafion™ surfaces are detailed here, including cell viability, cell spreading, and type I collagen synthesis. Normal human dermal fibroblasts (NHDFs) were cultured on control and modified Nafion™ surfaces. Findings indicate that Nafion™ modified with 10% 2-hydroxyethyl methacrylate and 90% tetraglyme created a nonfouling surface that was subsequently decorated with the YRGDS peptide. NHDFs were shown to have exhibited decreased type I collagen production in comparison to NHDF cells on unmodified Nafion™ surfaces. Here, the authors report evidence that proves that optimizing conditions to prevent protein adsorption and enhance cellular adhesion may eliminate fibrous encapsulation of an implant. PMID:21721839

Valdes, Thelma I; Ciridon, Winston; Ratner, Buddy D; Bryers, James D

2011-06-01

237

Modulation of fibroblast inflammatory response by surface modification of a perfluorinated ionomer  

PubMed Central

An ideal surface for implantable glucose sensors would be able to evade the events leading to chronic inflammation and fibrosis, thereby extending its utility in an in vivo environment. Nafion™, a perfluorinated ionomer, is the membrane material preferred for in situ glucose sensors. Unfortunately, the surface properties of Nafion™ promote random protein adsorption and eventual foreign body encapsulation, thus leading to loss of glucose signal over time. Details of the techniques to render Nafion™ nonprotein fouling are given in a previous article [T. I. Valdes et al., Biomaterials 29, 1356 (2008)]. Once random protein adsorption is prevented, a biologically active peptide can be covalently bonded to the treated Nafion™ to induce cellular adhesion. Cellular responses to these novel decorated Nafion™ surfaces are detailed here, including cell viability, cell spreading, and type I collagen synthesis. Normal human dermal fibroblasts NHDFs) were cultured on control and modified Nafion™ surfaces. Findings indicate that Nafion™ modified with 10% 2-hydroxyethyl methacrylate and 90% tetraglyme created a nonfouling surface that was subsequently decorated with the YRGDS peptide. NHDFs were shown to have exhibited decreased type I collagen production in comparison to NHDF cells on unmodified Nafion™ surfaces. Here, the authors report evidence that proves that optimizing conditions to prevent protein adsorption and enhance cellular adhesion may eliminate fibrous encapsulation of an implant. PMID:21721839

Valdes, Thelma I.; Ciridon, Winston; Ratner, Buddy D.; Bryers, James D.

2011-01-01

238

Methanol Diffusion into Thin Ionomer Films: An in situ Study Using Neutron Reflectometry .  

NASA Astrophysics Data System (ADS)

THUSITHA, N. ETAMPAWALA DVORA, PERAHIA ^ Department of Chemistry, Clemson University, Clemson, SC 29634 JAROSLAW MAJEWSKI, Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM 87545 CHRISTOPHER J. CORNELIUS^ Sandia National Laboratories, MS 0886, Albuquerque, New Mexico 87185-0886 The penetration of solvent into a polymer that consists of incompatable groups is determined by the specific interactions with the guest molecule, where interfacial structure and dynamics of the polymer affect the onset of the process. The current work presents a neutron reflectometry study of the penetration of methanol into sulfonated polyphenlylene thin films. The ionomer films were exposed to saturated deuterated methanol vapor and reflectometry patterns were recorded until equilibrium was reached. The process incorporates two stages where the vapors first wet the surface and then penetrate into the film. Significant swelling takes place as soon as the film is exposed to the vapors. Similar to previous studied in water, the onset diffusion is Fickian followed by an anomalous diffusion process. The entire process however is faster than that observed for water.

He, Lilin

2008-03-01

239

Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes  

SciTech Connect

Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.

J Park; J Li; G Divoux; L Madsen; R Moore

2011-12-31

240

A Study of the Effect of Heat-Treatment on the Morphology of Nafion Ionomer Dispersion for Use in the Passive Direct Methanol Fuel Cell (DMFC)  

PubMed Central

Aggregation in heat-treated Nafion ionomer dispersion and 117 membrane are investigated by 1H and 19F Nuclear Magnetic Resonance (NMR) spectra, spin-lattice relaxation time, and self-diffusion coefficient measurements. Results demonstrate that heat-treatment affects the average Nafion particle size in aqueous dispersions. Measurements on heat-treated Nafion 117 membrane show changes in the 1H isotropic chemical shift and no significant changes in ionic conductivity. Scanning electron microscopy (SEM) analysis of prepared cathode catalyst layer containing the heat-treated dispersions reveals that the surface of the electrode with the catalyst ink that has been pretreated at ca. 80 °C exhibits a compact and uniform morphology. The decrease of Nafion ionomer’s size results in better contact between catalyst particles and electrolyte, higher electrochemically active surface area, as well as significant improvement in the DMFC’s performance, as verified by electrochemical analysis and single cell evaluation. PMID:24958431

Yuan, Ting; Zhang, Haifeng; Zou, Zhiqing; Khatun, Sufia; Akins, Daniel; Adam, Yara; Suarez, Sophia

2012-01-01

241

Formation of Nanoparticles during Melt mixing a Thermotropic Liquid Crystalline Polyester and Sulfonated Polystyrene Ionomers: Morphology and Origin of Formation  

SciTech Connect

The formation of nanoparticles and the mechanism of their formation in a blend of a thermotropic liquid crystalline polyester (LCP) and the zinc salt of a lightly sulfonated polystyrene ionomer (Zn-SPS) were investigated using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and gas chromatography-mass spectroscopy (GC-MS). Transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) were used to study the morphology of the blends and structure of nanoparticles. The origin of nanoparticle formation appeared to be related to the development of phenyl acetate chain ends on the LCP that arose due to a chemical reaction between the LCP and residual catalytic amounts of zinc acetate and/or acetic acid that were present from the neutralization step in the preparation of the ionomer. Two-dimensional X-ray diffraction patterns for the blends revealed that chain-packing within nanoparticles was different than that of the LCP or the homopolymers prepared from the LCP co-monomers. The crystals formed in the nanoparticles were also stable to much higher temperature (>350 C) than the parent LCP crystallites that melted at {approx}280 C.

Lee,H.; Zhu, L.; Weiss, R.

2005-01-01

242

Zinc Detoxification Is Required for Full Virulence and Modification of the Host Leaf Ionome by Xylella fastidiosa.  

PubMed

Zinc (Zn) is an essential element for all forms of life because it is a structural or catalytic cofactor of many proteins, but it can have toxic effects at high concentrations; thus, microorganisms must tightly regulate its levels. Here, we evaluated the role of Zn homeostasis proteins in the virulence of the xylem-limited bacterium Xylella fastidiosa, causal agent of Pierce's disease of grapevine, among other diseases. Two mutants of X. fastidiosa 'Temecula' affected in genes which regulate Zn homeostasis (zur) and Zn detoxification (czcD) were constructed. Both knockouts showed increased sensitivity to Zn at physiologically relevant concentrations and increased intracellular accumulation of this metal compared with the wild type. Increased Zn sensitivity was correlated with decreased growth in grapevine xylem sap, reduced twitching motility, and downregulation of exopolysaccharide biosynthetic genes. Tobacco plants inoculated with either knockout mutant showed reduced foliar symptoms and a much reduced (czcD) or absent (zur) modification of the leaf ionome (i.e., the mineral nutrient and trace element composition), as well as reduced bacterial populations. The results show that detoxification of Zn is crucial for the virulence of X. fastidiosa and verifies our previous findings that modification of the host leaf ionome correlates with bacterial virulence. PMID:25561271

Navarrete, Fernando; De La Fuente, Leonardo

2015-04-01

243

Sphingolipids in the Root Play an Important Role in Regulating the Leaf Ionome in Arabidopsis thaliana[W][OA  

PubMed Central

Sphingolipid synthesis is initiated by condensation of Ser with palmitoyl-CoA producing 3-ketodihydrosphinganine (3-KDS), which is reduced by a 3-KDS reductase to dihydrosphinganine. Ser palmitoyltransferase is essential for plant viability. Arabidopsis thaliana contains two genes (At3g06060/TSC10A and At5g19200/TSC10B) encoding proteins with significant similarity to the yeast 3-KDS reductase, Tsc10p. Heterologous expression in yeast of either Arabidopsis gene restored 3-KDS reductase activity to the yeast tsc10? mutant, confirming both as bona fide 3-KDS reductase genes. Consistent with sphingolipids having essential functions in plants, double mutant progeny lacking both genes were not recovered from crosses of single tsc10A and tsc10B mutants. Although the 3-KDS reductase genes are functionally redundant and ubiquitously expressed in Arabidopsis, 3-KDS reductase activity was reduced to 10% of wild-type levels in the loss-of-function tsc10a mutant, leading to an altered sphingolipid profile. This perturbation of sphingolipid biosynthesis in the Arabidopsis tsc10a mutant leads an altered leaf ionome, including increases in Na, K, and Rb and decreases in Mg, Ca, Fe, and Mo. Reciprocal grafting revealed that these changes in the leaf ionome are driven by the root and are associated with increases in root suberin and alterations in Fe homeostasis. PMID:21421810

Chao, Dai-Yin; Gable, Kenneth; Chen, Ming; Baxter, Ivan; Dietrich, Charles R.; Cahoon, Edgar B.; Guerinot, Mary Lou; Lahner, Brett; Lü, Shiyou; Markham, Jonathan E.; Morrissey, Joe; Han, Gongshe; Gupta, Sita D.; Harmon, Jeffrey M.; Jaworski, Jan G.; Dunn, Teresa M.; Salt, David E.

2011-01-01

244

Methodological approaches for using synchrotron X-ray fluorescence (SXRF) imaging as a tool in ionomics: Examples from Arabidopsis thaliana  

PubMed Central

Here we present approaches for using multi-elemental imaging (specifically synchrotron X-ray fluorescence microscopy, SXRF) in ionomics, with examples using the model plant Arabidopsis thaliana. The complexity of each approach depends on the amount of a priori information available for the gene and/or phenotype being studied. Three approaches are outlined, which apply to experimental situations where a gene of interest has been identified but has an unknown phenotype (Phenotyping), an unidentified gene is associated with a known phenotype (Gene Cloning) and finally, a Screening approach, where both gene and phenotype are unknown. These approaches make use of open-access, online databases with which plant molecular genetics researchers working in the model plant Arabidopsis will be familiar, in particular the Ionomics Hub and online transcriptomic databases such as the Arabidopsis eFP browser. The approaches and examples we describe are based on the assumption that altering the expression of ion transporters can result in changes in elemental distribution. We provide methodological details on using elemental imaging to aid or accelerate gene functional characterization by narrowing down the search for candidate genes to the tissues in which elemental distributions are altered. We use synchrotron X-ray microprobes as a technique of choice, which can now be used to image all parts of an Arabidopsis plant in a hydrated state. We present elemental images of leaves, stem, root, siliques and germinating hypocotyls. PMID:23912758

Hindt, Maria; Socha, Amanda L.; Zuber, Hélène

2013-01-01

245

Thin graphite bipolar plate with associated gaskets and carbon cloth flow-field for use in an ionomer membrane fuel cell  

DOEpatents

The present invention comprises a thin graphite plate with associated gaskets and pieces of carbon cloth that comprise a flow-field. The plate, gaskets and flow-field comprise a "plate and gasket assembly" for use in an ionomer membrane fuel cell, fuel cell stack or battery.

Marchetti, George A. (Western Springs, IL)

2003-01-03

246

Investigation of the microstructure in the catalyst layer and effects of both perfluorosulfonate ionomer and PTFE-loaded carbon on the catalyst layer of polymer electrolyte fuel cells  

Microsoft Academic Search

Effects of a perfluorosulfonate ionomer (PFSI) and of a polytetrafluoroethylene (PTFE) loaded carbon (PTFE-C) on the catalyst layer in the electrode of a polymer electrolyte fuel cell (PEFC) prepared by a new method based on the process of PFSI-colloid formation were investigated by electrochemical techniques and a mercury pore sizer. The microstructure of the catalyst layer and its effect on

Makoto Uchida; Yuko Aoyama; Nobuo Eda; Akira Ohta

1995-01-01

247

CRYSTALLIZATION IN MULTICOMPONENT GLASSES  

SciTech Connect

In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

KRUGER AA; HRMA PR

2009-10-08

248

IMPACT STRENGTH OF GLASS AND GLASS CERAMIC  

SciTech Connect

Strength of glass and glass ceramic was measured with a bar impact technique. High-speed movies show regions of tensile and compressive failure. The borosilicate glass had a compressive strength of at least 2.2 GPa, and the glass ceramic at least 4 GPa. However, the BSG was much stronger in tension than GC. In ballistic tests, the BSG was the superior armor.

Bless, S.; Tolman, J. [Institute for Advanced Technology, University of Texas at Austin, Austin, TX 78759 (United States)

2009-12-28

249

NEWS & VIEWS Glass dynamics  

E-print Network

NEWS & VIEWS Glass dynamics Diverging views on glass transition Gregory B. mc.mckenna@ttu.edu T he glass transition is one of the most intriguing phenomena in the world of soft condensed matter. Despite decades of study, many aspects of the behaviour of glass-forming liquids remain elusive

Weeks, Eric R.

250

Glass-silicon column  

DOEpatents

A glass-silicon column that can operate in temperature variations between room temperature and about 450.degree. C. The glass-silicon column includes large area glass, such as a thin Corning 7740 boron-silicate glass bonded to a silicon wafer, with an electrode embedded in or mounted on glass of the column, and with a self alignment silicon post/glass hole structure. The glass/silicon components are bonded, for example be anodic bonding. In one embodiment, the column includes two outer layers of silicon each bonded to an inner layer of glass, with an electrode imbedded between the layers of glass, and with at least one self alignment hole and post arrangement. The electrode functions as a column heater, and one glass/silicon component is provided with a number of flow channels adjacent the bonded surfaces.

Yu, Conrad M.

2003-12-30

251

Chemical modification of Nafion membranes by protic ionic liquids: the key role of ionomer-cation interactions.  

PubMed

Chemically modified Nafion composite membranes were successfully fabricated using five kinds of protic ionic liquids (PILs) with different cations, 1-butylammonium methanesulfonate (BA-MS), tributylammonium methanesulfonate (TBA-MS), 2,4,6-trimethylphenylammonium methanesulfonate (TMA-MS), butane-1,4-diammonium methanesulfonate (BDA-MS), and N-(2-aminoethyl)ethane-1,2-diammonium methanesulfonate (DETA-MS). The PIL incorporated Nafion composite membranes were characterized by impedance spectroscopy, small-angle X-ray scattering (SAXS), dynamic-mechanical analysis (DMA) and thermogravimetric analysis (TGA). In general, the Nafion/PIL composite membranes exhibit a significant increase in the ionic conductivities than Nafion under anhydrous conditions. The interactions between the Nafion ionomer and different geometric cations of PILs were also discussed by the comparison of nanostructures, dynamic-mechanical properties and thermal stabilities of the Nafion/PIL composite membranes. PMID:25148206

Lu, Fei; Gao, Xinpei; Xie, Shuting; Sun, Nan; Zheng, Liqiang

2014-10-21

252

Picture Wall (Glass Structures)  

NASA Technical Reports Server (NTRS)

Photo shows a subway station in Toronto, Ontario, which is entirely glass-enclosed. The all-glass structure was made possible by a unique glazing concept developed by PPG Industries, Pittsburgh, Pennsylvania, one of the largest U.S. manufacturers of flat glass. In the TVS glazing system, transparent glass "fins" replace conventional vertical support members used to provide support for wind load resistance. For stiffening, silicone sealant bonds the fins to adjacent glass panels. At its glass research center near Pittsburgh, PPG Industries uses the NASTRAN computer program to analyze the stability of enclosures made entirely of glass. The company also uses NASTRAN to simulate stresses on large containers of molten glass and to analyze stress effects of solar heating on flat glass.

1978-01-01

253

Reaction cured glass and glass coatings  

NASA Technical Reports Server (NTRS)

The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF).

Goldstein, H. E.; Leiser, D. B.; Katvala, V. W. (inventors)

1978-01-01

254

6. Looking glass aircraft in the project looking glass historic ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. Looking glass aircraft in the project looking glass historic district. View to north. - Offutt Air Force Base, Looking Glass Airborne Command Post, Looking Glass Avenue between Comstat Drive & Nightwatch Avenue, Offutt Air Force Base, Bellevue, Sarpy County, NE

255

A proof of principle experiment: Structural transitions in self-healing poly (ethylene co-methacrylic acid) ionomers using acoustic and ultrasonic time dependent resonant spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate a method for assessing structural transitions in self-healing poly (ethylene co-methacrylic acid) ionomers as a function of time, by observing the evolution of their acoustic and ultrasonic resonant spectra and associated quality factors during the post-damage healing phase. Two samples composed of EMAA-0.6Na and EMAA-0.3Na were scanned from 1 kHz to 2 MHz before and after a damage event. After damage, time varying resonances were discovered using time dependent resonant spectroscopy (TDRS), and several of these resonances continued to evolve after visible changes in the samples ceased. These time dependent resonances enable characterization of energy dissipation, relaxation and structural ordering in self-healing ionomers. In addition, TDRS may provide a method for isolating material properties that affect the healing process, such as ion content and their associated structures as well as the effect of sample aging, which may lead to improved structural models.

Pestka, K. A.; Kalista, S. J.; Ricci, A.

2013-08-01

256

Oxynitride glass fibers  

NASA Technical Reports Server (NTRS)

Research at the Army Materials Technology Laboratory (AMTL) and elsewhere has shown that many glass properties including elastic modulus, hardness, and corrosion resistance are improved markedly by the substitution of nitrogen for oxygen in the glass structure. Oxynitride glasses, therefore, offer exciting opportunities for making high modulus, high strength fibers. Processes for making oxynitride glasses and fibers of glass compositions similar to commercial oxide glasses, but with considerable enhanced properties, are discussed. We have made glasses with elastic moduli as high as 140 GPa and fibers with moduli of 120 GPa and tensile strengths up to 2900 MPa. AMTL holds a U.S. patent on oxynitride glass fibers, and this presentation discusses a unique process for drawing small diameter oxynitride glass fibers at high drawing rates. Fibers are drawn through a nozzle from molten glass in a molybdenum crucible at 1550 C. The crucible is situated in a furnace chamber in flowing nitrogen, and the fiber is wound in air outside of the chamber, making the process straightforward and commercially feasible. Strengths were considerably improved by improving glass quality to minimize internal defects. Though the fiber strengths were comparable with oxide fibers, work is currently in progress to further improve the elastic modulus and strength of fibers. The high elastic modulus of oxynitride glasses indicate their potential for making fibers with tensile strengths surpassing any oxide glass fibers, and we hope to realize that potential in the near future.

Patel, Parimal J.; Messier, Donald R.; Rich, R. E.

1991-01-01

257

Influence of different conditioning methods on the shear bond strength of novel light-curing nano-ionomer restorative to enamel and dentin  

Microsoft Academic Search

The purpose of this study was to investigate shear bond strength (SBS) between a light-curing nano-ionomer restorative and\\u000a enamel or dentin after acid etching, after erbium:yttrium–aluminum–garnet (Er:YAG) laser etching, or after combined treatment.\\u000a Forty third molars were selected, the crowns were sectioned, and 80 tooth slabs were obtained. The specimens were assigned\\u000a to two groups, which were divided into four

Yonca Korkmaz; Emre Ozel; Nuray Attar; Ceren Ozge Bicer

2010-01-01

258

A Simple and Efficient Synthesis of an Acid-labile Polyphosphoramidate by Organobase-catalyzed Ring-Opening Polymerization and Transformation to Polyphosphoester Ionomers by Acid Treatment  

PubMed Central

The direct synthesis of an acid-labile polyphosphoramidate by organobase-catalyzed ring-opening polymerization and an overall two-step preparation of polyphosphodiester ionomers (PPEI) by acid-assisted cleavage of the phosphoramidate bonds along the backbone of the polyphosphoramidate were developed in this study. The ultrafast organobase-catalyzed ring-opening polymerization of a cyclic phospholane methoxyethyl amidate monomer initiated by benzyl alcohol allowed for the preparation of well-defined polyphosphoramidates (PPA) with predictable molecular weights, narrow molecular weight distributions (PDI<1.10), and well-defined chain ends. Cleavage of the acid-labile phosphoramidate bonds on the polyphosphoramidate repeat units was evaluated under acidic conditions over a pH range of 1–5, and the complete hydrolysis produced polyphosphodiesters. The thermal properties of the resulting polyphosphoester ionomer acid and polyphosphoester ionomer sodium salt exhibited significant thermal stability. The parent PPA and both forms of the PPEIs showed low cytotoxicities toward HeLa cells and RAW 264.7 mouse macrophage cells. The synthetic methodology developed here has enriched the family of water-soluble polymers prepared by rapid and convenient organobase-catalyzed ring-opening polymerizations and straightforward chemical medication reactions, which are designed to be hydrolytically degradable and have promise for numerous biomedical and other applications. PMID:23997276

Zhang, Shiyi; Wang, Hai; Shen, Yuefei; Zhang, Fuwu; Seetho, Kellie; Zou, Jiong; Taylor, John-Stephen A.; Dove, Andrew P.; Wooley, Karen L.

2013-01-01

259

Glass in Class  

ERIC Educational Resources Information Center

Glass is reviewed from fabrication to application, laying emphasis on the wide-ranging physics involved. This begins with liquids and solids and the way in which glasses are defined and can be demonstrated in the classroom. At the atomic level the regular structure of crystals and their irregular counterparts in glasses are explained through…

Greaves, Neville

2005-01-01

260

Nanoparticle Stained Glass  

NSDL National Science Digital Library

In this activity/demo, learners are introduced to the connection between medieval stained glass artisans and nanotechnology. Learners discover that the red and yellow colors in stained glass windows come from nanoparticles of gold and silver embedded in the glass. This activity/demo consists of two hands-on activities: making a collaborative stained glass window with pre-made nanoparticle solutions containing silver or gold and making a take-away card that contains a small piece of nanoparticle stained “glass."

2014-06-18

261

Radiation coloration resistant glass  

DOEpatents

A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10.sup.7 rad, the coloration resistant glass does not lose transparency.

Tomozawa, Minoru (Troy, NY); Watson, E. Bruce (Troy, NY); Acocella, John (Troy, NY)

1986-01-01

262

Radiation coloration resistant glass  

DOEpatents

A radiation coloration resistant glass is disclosed which is used in a radiation environment sufficient to cause coloration in most forms of glass. The coloration resistant glass includes higher proportions by weight of water and has been found to be extremely resistant to color change when exposed to such radiation levels. The coloration resistant glass is free of cerium oxide and has more than about 0.5% by weight water content. Even when exposed to gamma radiation of more than 10[sup 7] rad, the coloration resistant glass does not lose transparency. 3 figs.

Tomozawa, M.; Watson, E.B.; Acocella, J.

1986-11-04

263

High-temperature glass and glass coatings  

NASA Technical Reports Server (NTRS)

Reaction-cured glasses resist thermal shock and maintain properties over range of -100 degrees Centrigrade to +1,480 degrees Centigrade. Stability makes these excellent materials for high-temperature glassware and tubing or as coatings for porous materials.

Goldstein, H. E.; Katvala, V. E.; Leiser, D. B.

1977-01-01

264

Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition  

PubMed Central

Mineral malnutrition stemming from undiversified plant-based diets is a top global challenge. In C3 plants (e.g., rice, wheat), elevated concentrations of atmospheric carbon dioxide (eCO2) reduce protein and nitrogen concentrations, and can increase the total non-structural carbohydrates (TNC; mainly starch, sugars). However, contradictory findings have obscured the effect of eCO2 on the ionome—the mineral and trace-element composition—of plants. Consequently, CO2-induced shifts in plant quality have been ignored in the estimation of the impact of global change on humans. This study shows that eCO2 reduces the overall mineral concentrations (?8%, 95% confidence interval: ?9.1 to ?6.9, p<0.00001) and increases TNC:minerals > carbon:minerals in C3 plants. The meta-analysis of 7761 observations, including 2264 observations at state of the art FACE centers, covers 130 species/cultivars. The attained statistical power reveals that the shift is systemic and global. Its potential to exacerbate the prevalence of ‘hidden hunger’ and obesity is discussed. DOI: http://dx.doi.org/10.7554/eLife.02245.001 PMID:24867639

Loladze, Irakli

2014-01-01

265

A macroscopic model of proton transport through the membrane-ionomer interface of a polymer electrolyte membrane fuel cell.  

PubMed

The membrane-ionomer interface is the critical interlink of the electrodes and catalyst to the polymer electrolyte membrane (PEM); together forming the membrane electrode assembly in current state-of-the-art PEM fuel cells. In this paper, proton conduction through the interface is investigated to understand its effect on the performance of a PEM fuel cell. The water containing domains at this interface were modeled as cylindrical pores/channels with the anionic groups (i.e., -SO(3)(-)) assumed to be fixed on the pore wall. The interactions of each species with all other species and an applied external field were examined. Molecular-based interaction potential energies were computed in a small test element of the pore and were scaled up in terms of macroscopic variables. Evolution equations of the density and momentum of the species (water molecules and hydronium ions) were derived within a framework of nonequilibrium thermodynamics. The resulting evolution equations for the species were solved analytically using an order-of-magnitude analysis to obtain an expression for the proton conductivity. Results show that the conductivity increases with increasing water content and pore radius, and strongly depends on the separation distance between the sulfonate groups and their distribution on the pore wall. It was also determined that the conductivity of two similar pores of different radii in series is limited by the pore with the smaller radius. PMID:23425489

Kumar, Milan; Edwards, Brian J; Paddison, Stephen J

2013-02-14

266

Diamond turning of glass  

SciTech Connect

A new research initiative will be undertaken to investigate the critical cutting depth concepts for single point diamond turning of brittle, amorphous materials. Inorganic glasses and a brittle, thermoset polymer (organic glass) are the principal candidate materials. Interrupted cutting tests similar to those done in earlier research are Ge and Si crystals will be made to obtain critical depth values as a function of machining parameters. The results will provide systematic data with which to assess machining performance on glasses and amorphous materials

Blackley, W.S.; Scattergood, R.O.

1988-12-01

267

Topical fluoride application is able to reduce acid susceptibility of restorative materials.  

PubMed

This study aimed to investigate the effect of topical fluoride application on the acid susceptibility of restorative materials. Four restorative materials were investigated in this study: 2 composite resins (Tetric EvoCeram and Filtek Silorane), a polyacid-modified resin composite (Dyract Extra), and a conventional glass-ionomer cement (Ketac Fil Plus). The samples were treated once with 1 of 8 different fluoride solutions (TiF4, NaF, AmF, and SnF2, each at native pH or pH 4) for 3 min or remained untreated (control). The samples were then eroded by citric acid (pH 2.6) for 5 days (6×1 min daily). Erosive substance loss, surface topographic and compositional changes were investigated using surface profilometry, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), respectively, after fluoride pretreatment and after erosion. The results indicate high-concentrated AmF solution at native pH was effective in inhibiting erosion in the conventional glass-ionomer cement and polyacid-modified resin composite. PMID:22673456

Yu, Hao; Buchalla, Wolfgang; Cheng, Hui; Wiegand, Annette; Attin, Thomas

2012-01-01

268

A method for producing controlled fluoride release from an orthodontic bracket.  

PubMed

The aim of this study was to manufacture and test, in vitro, a novel modification to provide fluoride-releasing orthodontic brackets. Thirty-two orthodontic brackets were drilled to produce a recess (approximately 1.3 mm in diameter and 0.7 mm in depth) at the centre of the bracket base. Four materials, with and without the addition of sodium fluoride, a glass ionomer cement (Ketac Cem micro), a resin-modified glass ionomer cement (RMGIC; GC Fuji Ortho LC), a zinc phosphate (Zinc Cement Improved), and a resin (Transbond XT) were used to fill the recess in the bracket base. Fluoride release was measured daily during the first week and then weekly for 10 weeks. An ion chromatograph with suppressed conductivity was used for free fluoride ion determination. Statistical analysis to determine the amount of flouride release was undertaken using analysis of variance and Tukey's test. During the first 2 weeks, the resin group, with the addition of 38 per cent sodium fluoride added, released significantly more free fluoride (P < 0.05), but after 2 weeks the fluoride release markedly decreased. After 5 weeks, the RMGIC group, with 15 per cent added sodium fluoride, had significantly higher (P < 0.05) daily fluoride release than the other groups. The findings demonstrated that an appropriate fluoridated material can be used as a fluoride-releasing reservoir in a modified orthodontic bracket to enable it to release fluoride over the period of fixed appliance treatment. PMID:17804428

Li, Song; Hobson, Ross S; Bai, Yuxing; Yan, Zhuoqun; Carrick, Thomas E; McCabe, John F

2007-12-01

269

Chalcogenide glass microsphere laser.  

PubMed

Laser action has been demonstrated in chalcogenide glass microsphere. A sub millimeter neodymium-doped gallium lanthanum sulphide glass sphere was pumped at 808 nm with a laser diode and single and multimode laser action demonstrated at wavelengths between 1075 and 1086 nm. The gallium lanthanum sulphide family of glass offer higher thermal stability compared to other chalcogenide glasses, and this, along with an optimized Q-factor for the microcavity allowed laser action to be achieved. When varying the pump power, changes in the output spectrum suggest nonlinear and/or thermal effects have a strong effect on laser action. PMID:21165022

Elliott, Gregor R; Murugan, G Senthil; Wilkinson, James S; Zervas, Michalis N; Hewak, Daniel W

2010-12-01

270

Containerless processing of glass  

NASA Technical Reports Server (NTRS)

Ground-based research on the containerless melting of glass and experiments performed during a flight on the SPAR 6 are described. Experiments leading to selection of the flight sample composition, a silica-modified gallia/calcia glass, and the preparation of a one quarter inch diameter flight sample are described. During the flight experiment, a sample of the glass was containerless melted and cooled to a clear glass in a single axis acoustic positioning apparatus. The functioning of the flight experimental hardware was evaluated. The evaluation of the sample is presented.

Happe, R. A.

1981-01-01

271

Drugstore Reading Glasses  

NASA Astrophysics Data System (ADS)

The occasion for this paper was my reading of a paper in the February 2005 issue of TPT. As one gets older the near point of the eye begins to recede.2 This is called presbyopia.3 An alternative to purchasing glasses from an optometrist is to purchase an inexpensive pair of reading glasses in a pharmacy. The pharmacy has these glasses ordered by diopters corresponding to the strength of the lens needed for a particular presbyopic eye. The glasses are, of course, not available for myopic eyes.

Erlichson, Herman

2006-03-01

272

Apollo 15 green glasses.  

NASA Technical Reports Server (NTRS)

The samples analyzed include 28 spheres, portions of spheres, and angular fragments from soil 15101. Emerald green glasses from other soils are identical to those from 15101. The composition of the green glass is unlike that of any other major lunar glass group. The Fe content is comparable to that in mare basalts, but Ti is much lower. The Mg content is much higher than in most lunar materials analyzed to date, and the Cr content is also high. The low Al content is comparable to that of mare basalt glasses.

Ridley, W. I.; Reid, A. M.; Warner, J. L.; Brown, R. W.

1973-01-01

273

Glass--Sand + Imagination  

NASA Astrophysics Data System (ADS)

Glass is older than recorded history, and yet it is as new as tomorrow! How, when, or where man first learned to make glass is not known, but we do know that the ancient Egyptians were making glass articles as early as 2,600 B.C.E. (The making of glass beads may have begun as much as 3000 years earlier.) They used it to make jewelry and luxury items, such as decorative bowls and perfume bottles, available only to the wealthy.

Kolb, Kenneth E.; Kolb, Doris K.

2000-07-01

274

Poly(styrene- b-isobutylene- b-styrene) block copolymers and ionomers therefrom: morphology as determined by small-angle X-ray scattering and transmission electron microscopy  

Microsoft Academic Search

Solvent-cast films of poly(styrene-b-isobutylene-b-styrene) (PS–PIB–PS) block copolymers and block ionomers were analyzed using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Four block copolymer samples with center block molecular weights of 52,000gmol?1 and PS volume fractions (?PS) ranging from 0.17 to 0.31 were studied. Block ionomers were produced by lightly sulfonating the PS outer blocks of the PS–PIB–PS block

R. F Storey; D. W Baugh

2000-01-01

275

The effect of mechanical load cycling and polishing time on microleakage of class V glass-ionomer and composite restorations: A scanning electron microscopy evaluation  

PubMed Central

Background: Microleakage is one of the challenging concerns in direct filling restorations. Understanding of its related factors is important in clinical practice. The aim of this study was scanning electron microscopy (SEM) evaluation of marginal integrity in three types of tooth-colored restorative materials in class V cavity preparations and the effect of load cycling and polishing time on the microleakage. Materials and Methods: In this in vitro experimental study, class V cavity preparations were prepared on the buccal and lingual surfaces of 60 bovine incisors. The specimens were divided into three groups each containing 20 teeth: group 1: Filtek Z350, Group 2: Fuji IX/G Coat Plus, Group 3: Fuji II LC/GC varnish. In each group, 2 subgroups (n = 20) were established based on finishing time (immediate or delayed by 24 h). All specimens were thermocycled (×2,000, 5-50°C). In each sub groups, half of the teeth were load cycled. Epoxy resin replicas of 24 specimens were evaluated under field emission-SEM and interfacial gaps were measured. All teeth were then immersed in 0.5% basic fuchsin dye for 24 h, sectioned and observed under stereomicroscope. Data were analyzed with Kruskal-Wallis’ test and Mann-Whitney U test and a comparison between incisal and cervical microleakage was made with Wilcoxon test. P < 0.05 was considered as significant. Results: Load cycling and filling material had a significant effect on microleakage, but polishing time did not. Cervical microleakage in Z350/load cycle/immediate polish and Fuji IX/load cycle/immediate or delayed polish and Fuji IX/no load cycle/immediate polish were significantly higher than incisal microleakage. Conclusion: It was concluded that the cervical sealing ability of Fuji IX under load cycling was better than Fuji II LC. Under load cycling and immediate polishing Z350 showed better marginal integrity than both Fuji II LC and Fuji IX. The immediate polishing didn’t cause a statistically significant increase in microleakage of evaluated tooth-colored class V restorations. PMID:24688568

Mirzaie, Mansoreh; Yasini, Esmail; Kermanshah, Hamid; Omidi, Baharan Ranjbar

2014-01-01

276

Evaluation and Comparison of the Effect of Different Surface Preparations on Bond Strength of Glass Ionomer Cement with Nickel–Chrome Metal–Ceramic Alloy: A Laboratory Study  

Microsoft Academic Search

Retention of fixed partial dentures is mostly dependent upon the bond between metal and cement as well as cement and tooth\\u000a structure. However, most of the time clinical failure of bond has been observed at metal and cement interface. The treatment\\u000a of metal surface, prior to luting, plays a crucial role in bonding cement with the metal. This study is

Kalpana Hasti; H. G. Jagadeesh; Narendra P. Patil

2011-01-01

277

Clinical evaluation of giomer- and resin-modified glass ionomer cement in class V noncarious cervical lesions: An in vivo study  

PubMed Central

Objectives: To evaluate and compare the clinical performance of Giomer (Beautifil II) and RMGIC (Fuji II LC) in noncarious cervical lesions. Materials and Methods: Thirty-two subjects with one or two pairs of noncarious cervical lesions were included in the study. Each pair of lesion was restored with either giomer or RMGIC assigned randomly. Clinical evaluation of restorations was done using USPHS criteria. Data was formulated in a predesigned format and subjected to statistical analysis using the chi square test. Results: Statistically significant difference was found between RMGIC and Giomer with respect to surface roughness with P value <0.001. Conclusion: Giomer showed superior surface finish compared to RMGIC. Both Giomer and RMGIC showed equal retention ability. PMID:22144814

Jyothi, KN; Annapurna, S; Kumar, Anil S; Venugopal, P; Jayashankara, CM

2011-01-01

278

Pressure dependence of glass transition temperature of elastomeric glasses  

Microsoft Academic Search

The pressure dependence of the glass transition temperature Tg of two elastomers, Solithane 113 and 3,3-bis(azidomethyl)oxetane\\/tetrahydrofuran (BAMO\\/THF) has been determined, employing high-pressure differential thermal analysis (HP-DTA) and dielectric techniques, up to 8.5 kbar. The glasses of the elastomers were named the specific (or Pi glass) or the general glass depending on how the glasses were formed. A Pi glass was

K. D. Pae; C.-L. Tang; E.-S. Shin

1984-01-01

279

Fracture resistance of endodontically treated maxillary premolars restored by silorane-based composite with or without fiber or nano-ionomer  

PubMed Central

PURPOSE This in vitro study investigated the fracture resistance of endodontically treated premolars restored using silorane- or methacrylate-based composite along with or without fiber or nano-ionomer base. MATERIALS AND METHODS Ninety-six intact maxillary premolars were randomly divided into eight groups (n = 12). G1 (negative control) was the intact teeth. In Groups 2-8, root canal treatment with mesio-occlusodistal preparation was performed. G2 (positive control) was kept unrestored. The other groups were restored using composite resin as follows: G3, methacrylate-based composite (Z250); G4, methacrylate composite (Z250) with polyethylene fiber; G5 and G6, silorane-based composite (Filtek P90) without and with the fiber, respectively; G7 and G8, methacrylate- and silorane-based composite with nano-ionomer base, respectively. After aging period and thermocycling for 1000 cycles, fracture strength was tested and fracture patterns were inspected. The results were analyzed using ANOVA and Tukey HSD tests (?=0.05). RESULTS Mean fracture resistance for the eight groups (in Newton) were G1: 1200 ± 169a, G2: 360 ± 93b, G3: 632 ± 196c, G4: 692 ± 195c, G5: 917 ± 159d, G6: 1013 ± 125ad, G7: 959 ± 148d, G8: 947 ± 105d (different superscript letters revealed significant difference among groups). Most of the fractures in all the groups were restorable, except Group 3. CONCLUSION Silorane-based composite revealed significantly higher strength of the restored premolars compared to that of methacrylate one. Fiber insertion demonstrated no additional effect on the strength of both composite restorations; however, it increased the prevalence of restorable fracture of methacrylate-based composite restored teeth. Using nano-ionomer base under methacrylate-based composite had a positive effect on fracture resistance and pattern. Only fiber-reinforced silorane composite restoration resulted in a strength similar to that of the intact teeth. PMID:25006384

Shafiei, Fereshteh; Ghahramani, Yasamin; Fattah, Zahra

2014-01-01

280

Rare Earth Phosphate Glass and Glass-Ceramic Proton Conductors  

SciTech Connect

The structure and conductivity of cerium and lanthanum phosphate glasses and glass-ceramics were investigated. The effects of varying the metal to phosphate ratio in the glasses, doping LaP3O9 glasses with Ce, and recrystallization of CeP3O9 glasses, on the glasses' microstructure and total conductivity were investigated using XRD, SEM, and AC impedance techniques. Strong increases in conductivity occurred when the glasses were recrystallized: the conductivity of a cerium metaphosphate glass increased conductivity after recrystallization from 10-7.5 S/cm to 10-6 S/cm at 400oC.

De Jonghe, Lutgard C.; Ray, Hannah L.; Wang, Ruigang

2008-12-03

281

Poly(styrene- b-isobutylene- b-styrene) block copolymer ionomers (BCPI) and BCPI\\/silicate nanocomposites. 2. Na +BCPI sol–gel polymerization templates  

Microsoft Academic Search

Polystyrene (PS) blocks in poly(styrene-b-isobutylene-b-styrene) (PS–PIB–PS) block copolymers were partially sulfonated and the acid groups converted to Na+SO3? groups to create ionomers. Then, dimethylacetamide was used to selectively swell the ionic PS domains and the swollen films were exposed to sol–gel reactive tetraethylorthosilicate solutions. (EtO)4?xSi(OH)x monomers then permeated films so that sol–gel reactions occurred within\\/around the ionic PS domains. Environmental

Kenneth A. Mauritz; Robson F. Storey; David A. Reuschle; Nora Beck Tan

2002-01-01

282

Glasses for Children  

MedlinePLUS

... is a need for glasses, or whether the condition can be monitored. What are the different types of refractive errors (need for glasses) that can affect children? There are 4 basic types of refractive errors: • Myopia (near-sighted) – This is a condition where the distance vision is blurred, but a ...

283

Stained Glass Glue  

NSDL National Science Digital Library

In this activity on page 6 of the PDF, learners use glue instead of glass to create artwork that can be hung in a window. Discover how the chemicals in various materials mix together to make a colorful, translucent "stained glass" creation.

American Chemical Society

2001-01-01

284

Getting Started with Glass  

ERIC Educational Resources Information Center

The metamorphosis of glass when heated is a magical process to students, yet teachers are often reluctant to try it in class. The biggest challenge in working with glass in the classroom is to simplify procedures just enough to ensure student success while maintaining strict safety practices so no students are injured. Project concepts and safety…

White, Heather

2007-01-01

285

Disappearing Glass Rods  

NSDL National Science Digital Library

In this optics activity, learners discover how they can make glass objects "disappear." Learners submerge glass objects like stirring rods into a beaker of Wesson™ oil to explore how the principles of reflection and refraction affect what we see. Use this activity as a demonstration or allow learners to experiment on their own.

2011-12-05

286

Corning Museum of Glass  

NSDL National Science Digital Library

The Corning Museum has a website that contains images from part of their 45,000 item historical and art glass collection. The collection spans 3,500 years, and includes "The Origins of Glassmaking", "Asian Glass", "Glass in America", and "Glass After 1960". Visitors can search or browse the collection by the name of the artist or maker, the date made, location made, or the name of the object. One of the "Current Exhibitions" that has some fantastic images of glass objects is the "Medieval Glass for Popes, Princes, and Peasants" exhibit that can be found via their homepage. Visitors interested in seeing images and reading about the history behind medieval glass, should click on the "Medieval Glass Story". The first image, of a cage cup, is a stunning piece from the early fourth century. The last image of the exhibit, entitled "Nef", is Venetian and looks like an elaborate ship with a spout on top of a conical base. Visitors who would like to hear an audio tour of the exhibit should click on "Audio Tour" to listen to any of the 20 short segments explaining the exhibit.

287

Surface Conductive Glass.  

ERIC Educational Resources Information Center

Discusses the properties of surface-conducting glass and the chemical nature of surface-conducting stannic (tin) oxide. Also provides the procedures necessary for the preparation of surface-conducting stannic oxide films on glass substrates. The experiment is suitable for the advanced inorganic chemistry laboratory. (JN)

Tanaka, John; Suib, Steven L.

1984-01-01

288

Defense HLW Glass Degradation Model  

SciTech Connect

The purpose of this report is to document the development of a model for calculating the release rate for radionuclides and other key elements from high-level radioactive waste (HLW) glasses under exposure conditions relevant to the performance of the repository. Several glass compositions are planned for the repository, some of which have yet to be identified (i.e., glasses from Hanford and Idaho National Engineering and Environmental Laboratory). The mechanism for glass dissolution is the same for these glasses and the glasses yet to be developed for the disposal of DOE wastes. All of these glasses will be of a quality consistent with the glasses used to develop this report.

D. Strachan

2004-10-20

289

Profiling the ionome of rice and its use in discriminating geographical origins at the regional scale, China.  

PubMed

Element profile was investigated for their use to trace the geographical origin of rice (Oryza sativa L.) samples. The concentrations of 13 elements (calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), boron (B), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), arsenic (As), selenium (Se), molybdenum (Mo), and cadmium (Cd)) were determined in the rice samples by inductively coupled plasma optical emission and mass spectrometry. Most of the essential elements for human health in rice were within normal ranges except for Mo and Se. Mo concentrations were twice as high as those in rice from Vietnam and Spain. Meanwhile, Se concentrations were three times lower in the whole province compared to the Chinese average level of 0.088 mg/kg. About 12% of the rice samples failed the Chinese national food safety standard of 0.2 mg/kg for Cd. Combined with the multi-elemental profile in rice, the principal component analysis (PCA), discriminant function analysis (DFA) and Fibonacci index analysis (FIA) were applied to discriminate geographical origins of the samples. Results indicated that the FIA method could achieve a more effective geographical origin classification compared with PCA and DFA, due to its efficiency in making the grouping even when the elemental variability was so high that PCA and DFA showed little discriminatory power. Furthermore, some elements were identified as the most powerful indicators of geographical origin: Ca, Ni, Fe and Cd. This suggests that the newly established methodology of FIA based on the ionome profile can be applied to determine the geographical origin of rice. PMID:23586309

Li, Gang; Nunes, Luis; Wang, Yijie; Williams, Paul N; Zheng, Maozhong; Zhang, Qiufang; Zhu, Yongguan

2013-01-01

290

Sequential optimization of methotrexate encapsulation in micellar nano-networks of polyethyleneimine ionomer containing redox-sensitive cross-links  

PubMed Central

A functional polycation nanonetwork was developed for delivery of water soluble chemotherapeutic agents. The complexes of polyethyleneimine grafted methoxy polyethylene glycol (PEI-g-mPEG) and Zn2+ were utilized as the micellar template for cross-linking with dithiodipropionic acid, followed by an acidic pH dialysis to remove the metal ion from the micellar template. The synthesis method was optimized according to pH, the molar ratio of Zn2+, and the cross-link ratio. The atomic force microscopy showed soft, discrete, and uniform nano-networks. They were sensitive to the simulated reductive environment as determined by Ellman’s assay. They showed few positive ? potential and an average hydrodynamic diameter of 162±10 nm, which decreased to 49±11 nm upon dehydration. The ionic character of the nano-networks allowed the achievement of a higher-loading capacity of methotrexate (MTX), approximately 57% weight per weight, depending on the cross-link and the drug feed ratios. The nano-networks actively loaded with MTX presented some suitable properties, such as the hydrodynamic size of 117±16 nm, polydispersity index of 0.22, and a prolonged swelling-controlled release profile over 24 hours that boosted following reductive activation of the nanonetwork biodegradation. Unlike the PEI ionomer, the nano-networks provided an acceptable cytotoxicity profile. The drug-loaded nano-networks exhibited more specific cytotoxicity against human hepatocellular carcinoma cells if compared to free MTX at concentrations above 1 ?M. The enhanced antitumor activity in vitro might be attributed to endocytic entry of MTX-loaded nano-networks that was found in the epifluorescence microscopy experiment for the fluorophore-labeled nano-networks. PMID:24944513

Abolmaali, Samira Sadat; Tamaddon, Ali; Yousefi, Gholamhossein; Javidnia, Katayoun; Dinarvand, Rasoul

2014-01-01

291

Sequence and Ionomic Analysis of Divergent Strains of Maize Inbred Line B73 with an Altered Growth Phenotype  

PubMed Central

Maize (Zea mays) is the most widely grown crop species in the world and a classical model organism for plant research. The completion of a high-quality reference genome sequence and the advent of high-throughput sequencing have greatly empowered re-sequencing studies in maize. In this study, plants of maize inbred line B73 descended from two different sets of seed material grown for several generations either in the field or in the greenhouse were found to show a different growth phenotype and ionome under phosphate starvation conditions and moreover a different responsiveness towards mycorrhizal fungi of the species Glomus intraradices (syn: Rhizophagus irregularis). Whole genome re-sequencing of individuals from both sets and comparison to the B73 reference sequence revealed three cryptic introgressions on chromosomes 1, 5 and 10 in the line grown in the greenhouse summing up to a total of 5,257 single-nucleotide polymorphisms (SNPs). Transcriptome sequencing of three individuals from each set lent further support to the location of the introgression intervals and confirmed them to be fixed in all sequenced individuals. Moreover, we identified >120 genes differentially expressed between the two B73 lines. We thus have found a nearly-isogenic line (NIL) of maize inbred line B73 that is characterized by an altered growth phenotype under phosphate starvation conditions and an improved responsiveness towards symbiosis with mycorrhizal fungi. Through next-generation sequencing of the genomes and transcriptomes we were able to delineate exact introgression intervals. Putative de novo mutations appeared approximately uniformly distributed along the ten maize chromosomes mainly representing G:C -> A:T transitions. The plant material described in this study will be a valuable tool both for functional studies of genes differentially expressed in both B73 lines and for research on growth behavior especially in response to symbiosis between maize and mycorrhizal fungi. PMID:24804793

Gahrtz, Manfred; Bucher, Marcel; Scholz, Uwe; Dresselhaus, Thomas

2014-01-01

292

Comparative experimental study of ionic polymer-metal composites with different backbone ionomers and in various cation forms  

NASA Astrophysics Data System (ADS)

An ionic polymer-metal composite (IPMC) consisting of a thin perfluorinated ionomer (usually, Nafion or Flemion) strip, platinum, and/or gold plated on both faces and neutralized by a certain amount of appropriate cations undergoes large bending motion when, in a hydrated state, a small electric field is applied across its thickness. When the same membrane is suddenly bent, a small voltage of the order of millivolts is produced across its surfaces. Hence IPMCs can serve as soft bending actuators and sensors. This coupled electrical-chemical-mechanical response of IPMCs depends on the structure of the backbone ionic polymer, the morphology and conductivity of the metal electrodes, the nature of the cations, and the level of hydration (or other solvent uptake). We have carried out extensive experimental studies on both Nafion- and Flemion-based IPMCs in various cation forms, seeking to understand the fundamental properties of these composites, to explore the mechanism of their actuation, and finally, to optimize their performance for various potential applications. The results of some of these tests on both Nafion- and Flemion-based IPMCs with alkali-metal or alkyl-ammonium cations are reported here. Compared with Nafion-based IPMCs, Flemion-based IPMCs with fine dendritic gold electrodes have higher ion-exchange capacity, better surface conductivity, higher hydration capacity, and higher longitudinal stiffness. They also display greater bending actuation under the same applied voltage. In addition, they do not display a reverse relaxation under a sustained dc voltage, which is typical of Nafion-based IPMCs in alkali-metal form. Flemion IPMCs thus are promising composites for application as bending actuators.

Nemat-Nasser, Sia; Wu, Yongxian

2003-05-01

293

Glass leaching performance  

SciTech Connect

Current understanding of the leaching performance of high-level nuclear waste (HLW) glass is summarized. The empirical model of waste glass leaching behavior developed shows that at high water flow rates the glass leach rate is kinetically limited to a maximum value. At intermediate water flow rates, leaching is limited by the solution concentration of silica and decreases with decreasing water flow rates. Release of soluble elements is controlled by silica dissolution because silica forms the binding network of the glass. At low water flow rates, mass loss rates reach values controlled by formation rates of alteration minerals, or by diffusion of dissolution products through essentially stagnant water. The parameters reviewed with respect to their quantifiable influence on leaching behavior include temperature, pH, leachant composition, glass composition, thermal history, and radiation. Of these, temperature is most important since the rate of mass loss approximately doubles with each 10/sup 0/C increase in dilute solutions. The pH has small effects within the 4 to 10 range. The chemical composition of the leachant is most important with regard to its influence on alteration product formation. Glass composition exhibits the largest effects at high flow rates where improved glasses leach from ten to thirty times slower than glass 76 to 68. The effects of the thermal history (devitrification) of the glass are not likely to be significant. Radiation effects are important primarily in that radiolysis can potentially drive pH values to less than 4. Radiation damage to the glass causes insignificant changes in leaching performance.

Chick, L.A.; Turcotte, R.P.

1983-05-01

294

CCMR: Study of Mixed Glass Former Phenomena in Glasses  

NSDL National Science Digital Library

Water concentration in varying compositions of sodium borosilicate glass was studied by Fourier Transform Infrared Spectroscopy. This is to further explore the Mixed Glass Former Effect (MGFE) in glasses with two or more network formers. Previous data shows that the water concentration increases with time.1 Thick and thin sample analysis was carried out on the glass to validate this data.

Clark, Braeden

2009-08-15

295

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University Making, The University of Texas at Austin #12;Glass, Brian 2 Duties include: Designing and constructing, constructing, and running experiments, statistical analysis. JOURNAL PUBLICATIONS Glass, B. D., Chotibut, T

Maddox, W. Todd

296

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University of Categorization and Decision Making, The University of Texas at Austin #12;Glass, Brian 2 Duties include: Programming, constructing, and running experiments, statistical analysis. JOURNAL PUBLICATIONS Glass, B. D

Maddox, W. Todd

297

Glass, Brian 1 BRIAN DANIEL GLASS, M.A.  

E-print Network

Glass, Brian 1 BRIAN DANIEL GLASS, M.A. University Department of Psychology, A8000 The University of Texas at Austin Austin, TX 78712 (512) 232-2883 e-mail: glass@mail.utexas.edu EDUCATION 2006 ­ Cognitive include: Designing and constructing experiments, statistical #12;Glass, Brian 2 analysis, manuscript

Maddox, W. Todd

298

Effect of different glasses in glass bonded zeolite  

SciTech Connect

A mineral waste form has been developed for chloride waste salt generated during the pyrochemical treatment of spent nuclear fuel. The waste form consists of salt-occluded zeolite powders bound within a glass matrix. The zeolite contains the salt and immobilizes the fission products. The zeolite powders are hot pressed to form a mechanically stable, durable glass bonded zeolite. Further development of glass bonded zeolite as a waste form requires an understanding of the interaction between the glass and the zeolite. Properties of the glass that enhance binding and durability of the glass bonded zeolite need to be identified. Three types of glass, boroaluminosilicate, soda-lime silicate, and high silica glasses, have a range of properties and are now being investigated. Each glass was hot pressed by itself and with an equal amount of zeolite. MCC-1 leach tests were run on both. Soda-lime silicate and high silica glasses did not give a durable glass bonded zeolite. Boroaluminosilicate glasses rich in alkaline earths did bind the zeolite and gave a durable glass bonded zeolite. Scanning electron micrographs suggest that the boroaluminosilicate glasses wetted the zeolite powders better than the other glasses. Development of the glass bonded zeolite as a waste form for chloride waste salt is continuing.

Lewis, M.A.; Ackerman, J.P. [Argonne National Lab., IL (United States); Verma, S. [Univ. of Illinois, Chicago, IL (United States)

1995-05-01

299

The glass transition diagram in model metallic glasses  

E-print Network

We report a strain rate (equivalent to experimental observation time) induced glass transition in model SrCaYbMg(Li)Zn(Cu) metallic glasses at room temperature. A critical strain rate, equivalent to glass transition temperature, is found for the strain rate induced a glassy state to liquid-like viscoplastic state translation. The results show that the observation time, equivalent to temperature and stress, is a key parameter for the glass transition. A three-dimension glass transition phase diagram involved in time, temperature and stress in metallic glasses is established for understanding the nature of the metallic glasses.

X. Q. Gao; W. H. Wang; K. Zhao; H. Y. Bai

2013-05-22

300

Glass Ceiling Commission  

NSDL National Science Digital Library

Existing from 1991-1996, the Glass Ceiling Commission was a federally funded commission which considered the "invisible, artificial barriers that prevent qualified individuals from advancing within their organization and reaching full potential." While the term "Glass Ceiling" originally referred to women, it was expanded to also include minorities. The Catherwood Library at the School of Industrial and Labor Relations at Cornell University has electronically archived the reports and findings of the commission, as well as a host of papers written on the Glass Ceiling Commission. The Commission summaries, reports, and findings are annotated, as are the accompanying papers.

United States. Federal Glass Ceiling Commission.

301

Relaxations in spin glasses: similarities and differences from ordinary glasses  

SciTech Connect

Relaxation phenomena have become a major concern in the physics of spin glasses. There are certain resemblances of these relaxation properties to those of ordinary glasses. In this work, we compare the relaxation properties of spin glasses near the freezing temperature with those of glasses near the glass transition temperature. There are remarkable similarities between them and they both are in conformity with two coupled universality relations predicted by a recent model of relaxations in condensed matter.

Ngai, K.L.; Rajagopal, A.K.; Huang, C.Y.

1983-01-01

302

Molecular Mobility in Sugar Glasses  

Microsoft Academic Search

Glasses are liquids that exhibit solid state behavior as a result of their extremely high viscosity. Regarding their application to foods, glasses play a role in the preservation of foods, due to their high viscosity and the concomitant low molecular mobility. This thesis focuses on sugar glasses. Sugar glasses are relevant as model systems for foods that contain sugars and

Dries van den I. J

2000-01-01

303

Pressure dependence of glass transition temperature of elastomeric glasses  

NASA Astrophysics Data System (ADS)

The pressure dependence of the glass transition temperature Tg of two elastomers, Solithane 113 and 3,3-bis(azidomethyl)oxetane/tetrahydrofuran (BAMO/THF) has been determined, employing high-pressure differential thermal analysis (HP-DTA) and dielectric techniques, up to 8.5 kbar. The glasses of the elastomers were named the specific (or Pi glass) or the general glass depending on how the glasses were formed. A Pi glass was formed by lowering temperature under a constant pressure (Pi) and the pressure dependency of the Pi glass was determined after changing pressure only in the glassy state. The general glass consists of a series of specific glasses but the Tg is determined only at pressures under which the glass is formed. The Tg for both glasses increased with increasing pressure. However, the Tg for the Pi glass appears to level off at very high pressures while the Tg does not level off for the general glass. Thermodynamic analysis was made to show that for many general glasses dTg/dP=??/(1+n)?? holds, in which n=1 for Solithane and many other glasses. It is also shown that a modified Gibbs and DiMarzio theory can be used effectively to predict the observed experimental results.

Pae, K. D.; Tang, C.-L.; Shin, E.-S.

1984-11-01

304

Baseline LAW Glass Formulation Testing  

SciTech Connect

The major objective of the baseline glass formulation work was to develop and select glass formulations that are compliant with contractual and processing requirements for each of the LAW waste streams. Other objectives of the work included preparation and characterization of glasses with respect to the properties of interest, optimization of sulfate loading in the glasses, evaluation of ability to achieve waste loading limits, testing to demonstrate compatibility of glass melts with melter materials of construction, development of glass formulations to support ILAW qualification activities, and identification of glass formulation issues with respect to contract specifications and processing requirements.

Kruger, Albert A. [USDOE Office of River Protection, Richland, WA (United States); Mooers, Cavin [The Catholic University of America, Washington, DC (United States). Vitreous State Lab.; Bazemore, Gina [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Pegg, Ian L. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Hight, Kenneth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Lai, Shan Tao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Buechele, Andrew [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Rielley, Elizabeth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Gan, Hao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Muller, Isabelle S. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Cecil, Richard [The Catholic University of America, Washington, DC (United States). Vitreous State Lab

2013-06-13

305

Seeing Glass Contractors Clearly.  

ERIC Educational Resources Information Center

Offers seven tips for finding and working with an effective glass contractor. For example, schools should consider the company's reputation and longevity of service, and whether it has in-house engineering capabilities. (EV)

Deliberato, Jerry

2003-01-01

306

CCMR: Water in Glass  

NSDL National Science Digital Library

Water uptake for various compositions of the model glass (Fe2O3)0.01(B2O3)0.048(Na2O)0.142(SiO2)0.8x(Al2O3)0.8(1?x) under fixed annealing conditions was studied via FTIR. Glasses of this formulation were found to take up water at both 300 and 380 °C. The time dependence of their water uptake entails that the governing kinetics are determined by the diffusion of water molecules in the glass network. The experimental approach used was validated by confirming previous water concentration results regarding glasses of the composition (Na2O)0.2[(BO1.5)x(SiO2)1?x]0.8.

Harrell, Stuart

2010-08-15

307

Whisker reinforced glass ceramic  

SciTech Connect

The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

Hirschfeld, D.A.; Brown, J.J. Jr.

1996-06-03

308

Glasses and Contact Lenses  

MedlinePLUS

... together the way they should. But eyeglasses or contact lenses, also called corrective lenses, can help most ... trouble, it's often a refractive problem. Glasses or contact lenses work so well because they can correct ...

309

THE COLOR GLASS CONDENSATE.  

SciTech Connect

The Color Glass Condensate is a state of high density gluonic matter which controls the high energy limit of hadronic interactions. Its properties are important for the initial conditions for matter produced at RHIC.

MCLERRAN,L.

2001-08-26

310

Waste glass weathering  

SciTech Connect

The weathering of glass is reviewed by examining processes that affect the reaction of commercial, historical, natural, and nuclear waste glass under conditions of contact with humid air and slowly dripping water, which may lead to immersion in nearly static solution. Radionuclide release data from weathered glass under conditions that may exist in an unsaturated environment are presented and compared to release under standard leaching conditions. While the comparison between the release under weathering and leaching conditions is not exact, due to variability of reaction in humid air, evidence is presented of radionuclide release under a variety of conditions. These results suggest that both the amount and form of radionuclide release can be affected by the weathering of glass.

Bates, J.K.; Buck, E.C.

1993-12-31

311

Glass formation in microgravity  

NASA Technical Reports Server (NTRS)

An account is given of containerless glass-forming experiments conducted aboard the Space Shuttle in 1985, using a single-axis acoustic levitator furnace apparatus. An attempt was made to obtain quantitative evidence for the suppression of heterogeneous nucleation/crystallization in containerless melts under microgravity conditions, as well as to study melt homogenization in the absence of gravity-driven convection and assess the feasibility of laser fusion target glass microsphere preparation with a microgravity apparatus of the present type. A ternary calcia-gallia-silica glass thus obtained indicated a 2-3-fold increase in glass-formation tendency for this material composition in microgravity, by comparison with 1g.

Ray, C. S.; Day, D. E.

1987-01-01

312

Microstructuring of Photosensitive Glass  

NASA Astrophysics Data System (ADS)

Femtosecond laser direct writing followed by thermal treatment and successive wet etching can form three-dimensional (3D) hollow microstructures inside photosensitive glass. The principles and procedures of this process are explained. Next, the fabrication of 3D microfluidic structures and optical microcomponents is reviewed. Finally, the manufacture of functional microchip devices such as a microfluidic dye laser, optofluidics, and a nano-aquarium by integrating the microcomponents in a single glass chip is demonstrated.

Sugioka, Koji

313

Metallic glass composition  

DOEpatents

A metallic glass alloy that is either iron-based or nickel-based or based on a mixture of iron and nickel, containing lesser amounts of elements selected from the group boron, silicon carbon and phosphorous to which is added an amount of a ductility enhancing element selected from the group cerium, lanthanum, praseodymium and neodymium sufficient to increase ductility of the metallic glass upon annealing.

Kroeger, Donald M. (Knoxville, TN); Koch, Carl C. (Raleigh, NC)

1986-01-01

314

Containerless synthesis of interesting glasses  

NASA Technical Reports Server (NTRS)

One aspect of containerless glass experimentation was thoroughly examined: glass forming ability. It is argued that although containerless processing will abet glass formation, other ground-based methods can do the job better. However, these methods have limitations, such as sample dimensions and concomitant ability to make property measurements. Most importantly, perhaps, is the observation that glass properties are a function of preparation procedure. Thus, it seems as though there still is an argument for use of containerless processing for glass forming.

Weinberg, Michael C.

1990-01-01

315

Glasses with ferroelectric phases  

NASA Astrophysics Data System (ADS)

Glasses ceramics, with ferroelectric phases embedded in the glass matrix, were prepared by the melt- quenching through heat-treatments (HT) of silicate, borate and phosphate glasses. Some glasses were heat-treated with the application of an external electric field (TET). The structure and morphology of the samples were studied by X-ray powder diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). The dielectric properties, in function of frequency and temperature, were studied and discussed through a three serial of a resistance in parallel with a constant phase element (CPE), two related with the sample surfaces and one with the bulk material, showing that the bulk has the major contribution for the dielectrical characteristics. The temperature dependence of the dc electrical conductivity (?dc), the thermally stimulated depolarization current (TSDC), and the ac conductivity (?ac), measured at 1 kHz, were used to characterize the samples. The structure, the dielectric properties and the electrical conductivity reflect the important role carried out by the base glass the heat-treatment and the electric field during the HT and the ferroelectric phases in the properties of glass-ceramics.

Valente, M. A.; Graça, M. P. F.

2009-07-01

316

Volcanic Glasses: Construction Materials  

NASA Astrophysics Data System (ADS)

Natural glass is the product of rapidly cooled molten rock. Two natural sources of the melt are volcanic eruption and meteoritic impact. Pure glass is an amorphous aggregate. Volcanic glass is a material that could be utilized in the construction of extraterrestrial outposts. Pumice and perlite are volcanic glasses currently used in the building industry. Samples of natural volcanic glass found in the lunar regolith were returned to Earth as part of the Apollo and Luna programs. An alpha proton X-ray spectrometer onboard the Pathfinder recently examined martian rocks located in the vicinity of the lander craft. Preliminary results of chemical composition by weight of SiO2 50-55%, Al203 11-13%, K20 1-2%, Na20 2-5%, CaO 4-6%, MgO 3-7%, FeO 12-14%, S03 2-5%, and MnO <1% were given for two rocks. Parenthetically, the values for K and Mn were perhaps too high, and the analysis was based on X-ray data only. The appreciable amount of silica already found on Mars and empirical evidence to support the hypothesis that the planet once had water sufficient to rapidly cool magma imply the possibility of discovering natural glass of volcanic origin in subsequent missions.

Moskowitz, Samuel E.

1998-01-01

317

DWPF GLASS BEADS AND GLASS FRIT TRANSPORT DEMONSTRATION  

SciTech Connect

DWPF is considering replacing irregularly shaped glass frit with spherical glass beads in the Slurry Mix Evaporator (SME) process to decrease the yield stress of the melter feed (a non-Newtonian Bingham Plastic). Pilot-scale testing was conducted on spherical glass beads and glass frit to determine how well the glass beads would transfer when compared to the glass frit. Process Engineering Development designed and constructed the test apparatus to aid in the understanding and impacts that spherical glass beads may have on the existing DWPF Frit Transfer System. Testing was conducted to determine if the lines would plug with the glass beads and the glass frit slurry and what is required to unplug the lines. The flow loop consisted of vertical and horizontal runs of clear PVC piping, similar in geometry to the existing system. Two different batches of glass slurry were tested: a batch of 50 wt% spherical glass beads and a batch of 50 wt% glass frit in process water. No chemicals such as formic acid was used in slurry, only water and glass formers. The glass beads used for this testing were commercially available borosilicate glass of mesh size -100+200. The glass frit was Frit 418 obtained from DWPF and is nominally -45+200 mesh. The spherical glass beads did not have a negative impact on the frit transfer system. The transferring of the spherical glass beads was much easier than the glass frit. It was difficult to create a plug with glass bead slurry in the pilot transfer system. When a small plug occurred from setting overnight with the spherical glass beads, the plug was easy to displace using only the pump. In the case of creating a man made plug in a vertical line, by filling the line with spherical glass beads and allowing the slurry to settle for days, the plug was easy to remove by using flush water. The glass frit proved to be much more difficult to transfer when compared to the spherical glass beads. The glass frit impacted the transfer system to the point that the test apparatus had to be disassembled to dislodge the plugs created in the system.

Adamson, D; Bradley Pickenheim, B

2008-11-24

318

Glass microsphere lubrication  

NASA Technical Reports Server (NTRS)

The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the manufacturing of the microspheres, while sorting entails deciphering the good microspheres from the bad ones. Each process is discussed in detail.

Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

1991-01-01

319

Electrical properties of phosphate glasses  

NASA Astrophysics Data System (ADS)

Investigation of the electrical properties of phosphate glasses where transition metal oxide such as iron oxide is the network former and network modifier is presented. Phosphate glasses containing iron are electronically conducting glasses where the polaronic conduction is due to the electron hopping from low to high iron valence state. The identification of structural defects caused by ion/polaron migration, the analysis of dipolar states and electrical conductivity in iron phosphate glasses containing various alkali and mixed alkali ions was performed on the basis of the impedance spectroscopy (IS). The changes in electrical conductivity from as-quenched phosphate glass to fully crystallized glass (glass-ceramics) by IS are analyzed. A change in the characteristic features of IS follows the changes in glass and crystallized glass network. Using IS, the contribution of glass matrix, crystallized grains and grain boundary to the total electrical conductivity for iron phosphate glasses was analyzed. It was shown that decrease in conductivity is caused by discontinuities in the conduction pathways as a result of the disruption of crystalline network where two or more crystalline phases are formed. Also, phosphate-based glasses offer a unique range of biomaterials, as they form direct chemical bonding with hard/soft tissue. The surface charges of bioactive glasses are recognized to be the most important factors in determining biological responses. The improved bioactivity of the bioactive glasses as a result of the effects of the surface charges generated by electrical polarization is discussed.

Mogus-Milankovic, A.; Santic, A.; Reis, S. T.; Day, D. E.

2009-07-01

320

Fibrous glass and cancer.  

PubMed

Some argue that fibrous glass (glass wool) should not be considered as a likely human carcinogen and hence should not be listed in the Seventh Annual Report on Carcinogens (ARC) prepared by the National Toxicology Program (NTP) and mandated by the U.S. Congress. In examining this issue, data from both laboratory experiments (animal studies) and epidemiologic studies (human data) are reviewed with the results evaluated according to the criteria established by the International Agency for Research on Cancer (IARC) and adopted in slightly modified form by the NTP for classifying substances as human carcinogens or likely human carcinogens. From our comprehensive review of the available information, we conclude that fibrous glass materials are carcinogenic, and in view of the NTP and IARC definitions should be listed in the ARC. Our review then examines the carcinogenic potency of glass fibers to humans in comparison with asbestos fibers and concludes that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos. The implications of these findings are then presented for regulatory purposes in the occupational setting. PMID:7810554

Infante, P F; Schuman, L D; Dement, J; Huff, J

1994-10-01

321

Museum of Glass  

NSDL National Science Digital Library

The Museum of Glass in Tacoma, Washington maintains a well crafted website for their spectacular museum. Founded in part by the famous glass artist Dale Chihuly, a Tacoma native, this museum highlights glass artists from the Pacific Northwest. Visitors won't want to miss any of the breathtaking online exhibits on this website, but one of the most spectacular is the "Chihuly Bridge of Glass" under the "Exhibitions & Collections" tab, in the "Outdoor Art" link. The slideshow of five photos shows a 500-foot pedestrian bridge that connects the Museum to downtown Tacoma. The bridge is composed of three distinct sections, one of which allows visitors to "experience a seemingly underwater world of glass shapes and forms a few feet above their heads." Also found under the "Exhibitions & Collections" tab, in the "Current Exhibitions" link, visitors will enjoy a multimedia treatment of the work "Glimmering Gone". Visitors can listen to poems by university students inspired by the exhibit, watch a "Residency" video of the artist who created the work, and view a video tour of the catalog for the exhibit.

322

Connecting supramolecular bond lifetime and network mobility for scratch healing in poly(butyl acrylate) ionomers containing sodium, zinc and cobalt.  

PubMed

In this work, we correlate network dynamics, supramolecular reversibility and the macroscopic surface scratch healing behavior for a series of elastomeric ionomers based on an amorphous backbone with varying fractions of carboxylate pendant groups completely neutralized by Na(+), Zn(2+) or Co(2+) as the counter ions. Our results based on temperature dependent dynamic rheology with simultaneous FTIR analysis clearly indicate that the effective supramolecular bond lifetime (?(b)) is an important parameter to ascertain the ideal range of viscoelasticity for good macroscopic healing. The reversible coordination increased with higher valence metal ions and ionic content. Both rheological and spectroscopic analyses show a decrease in supramolecular assembly with temperature. The temperature dependent ?(b) was used to calculate the activation energy (Ea) of dissociation for the ionic clusters. According to self-healing experiments based on macroscale surface scratching, a supramolecular bond lifetime between 10 and 100 s results in samples with complete surface scratch healing and good mechanical robustness. PMID:25463031

Bose, Ranjita K; Hohlbein, Nico; Garcia, Santiago J; Schmidt, Annette M; van der Zwaag, Sybrand

2015-01-21

323

Transient nucleation in glasses  

NASA Technical Reports Server (NTRS)

Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

Kelton, K. F.

1991-01-01

324

Nuclear waste glass interfaces after one year burial in STRIPA part 1: Glass/glass  

NASA Astrophysics Data System (ADS)

Two simulated nuclear waste glasses were corroded in an in-situ experiment in the STRIPA mine up to one year at 90°C. Changes in compositional in-depth profiles for glass/glass interfaces were measured using SIMS. Both glasses showed a depletion of Na, Cs, and B, but for the more corrosion resistant glass, the lower depletion depth is ascribed to the formation of a thin (2.0 m) coherent and dense outer layer, enriched in Mg, Ca, Sr, Ba, Zn-Al, Fe, and Si, which impedes both the ion exchange and network attack of the bulk glass underneath.

Hench, Larry L.; Lodding, Alexander; Werme, Lars

1984-08-01

325

Glass enamel and glass-ceramic coatings for chemical apparatus  

Microsoft Academic Search

Among the known anticorrosion coatings used in chemical engineering, glass enamel base coatings are distinguished by such advantages as a high degree of continuity and chemical resistance. The paper describes basic principles for the creation of acid and alkali resistant glass enamel and ceramic coatings for chemical apparatus. As the result of investgations, glass enamel coatings with increased electrical conductivity

A. S. Eskov; M. I. Oleinik; E. A. Shabrova

1984-01-01

326

Glass and ceramics. [lunar resources  

NASA Technical Reports Server (NTRS)

A variety of glasses and ceramics can be produced from bulk lunar materials or from separated components. Glassy products include sintered regolith, quenched molten basalt, and transparent glass formed from fused plagioclase. No research has been carried out on lunar material or close simulants, so properties are not known in detail; however, common glass technologies such as molding and spinning seem feasible. Possible methods for producing glass and ceramic materials are discussed along with some potential uses of the resulting products.

Haskin, Larry A.

1992-01-01

327

Enthalpy of diaplectic labradorite glass  

Microsoft Academic Search

Enthalpies of solution in molten 2PbO·B2O3 at ~988 K have been measured for diaplectic labradorite glass from the Manicouagan impact crater and a fused glass formed from the same material. The enthalpies of solution of the diaplectic and fusion-formed glasses are 4,347 and 2,023 cal mol-1, respectively. The more endothermic enthalpy of solution of the diaplectic glass indicates a greater

K. L. Geisinger; A. Navrotsky; J. Arndt

1986-01-01

328

Spectroscopic studies of glass structure  

SciTech Connect

Today`s understanding of the molecular-level structure of inorganic glasses has been transformed by the availability of a wide range of sensitive spectroscopic probes. Today we can relate glass composition to quantitative distributions of glass-forming cations and to changes in oxygen bonding and modifying cation geometries. Future spectroscopic studies will result in improved descriptions of anion and cation geometries and should provide glass scientists with the capability to optimize atomic arrangements for specific optical, electrical, and thermal properties.

Brow, R.K.

1994-08-01

329

Strength of glass (a review)  

Microsoft Academic Search

After defining the termglass, brief consideration is given to the theories of glass structure which have been propounded. That glass, in practice, is very much weaker than its theoretical strength predicts is established, and the prime factor for this is shown to be the surface condition of the glass. Surface defects which are accentuated by heat treatment or other processes

B. Sugarman

1967-01-01

330

Physics of glass manufacturing processes  

Microsoft Academic Search

After briefly describing some general features of continuous glass manufacturing processes, the article reviews advances in the theoretical understanding of these processes with particular emphasis on those aspects which involve an interaction between heat transfer and fluid flow. The following topics are included: radiation heat transfer in the large thicknesses of glass encountered in glass melting furnaces, heat transfer in

H. Rawson

1974-01-01

331

Barstow heliostat mirror glass characterization  

SciTech Connect

The technical analysis performed on the special run of low iron float glass procured from the Ford Glass Division for the ten megawatt solar thermal/electric pilot power plant to be constructed at Barstow, California is discussed. The topics that are addressed include the optical properties and the relative durability of the glass. Two optical parameters, solar transmittance and optical flatness, were measured as referenced in the specification and found to be better than the stated tolerances. The average solar transmittance exceeded 0.890 transmittance units. The glass also exhibited optical angular flatness deviations less than +-1.0 mrad as required. Both qualitative and quantitative accelerated weathering tests were performed on the glass in order to compare its durability to other soda lime float glass and alternate composition glasses of interest to the solar community. In both the quantitative leaching experiments and the more qualitative room temperature and elevated temperature water vapor exposure experiments the heliostat glass exhibited the same characteristics as the other soda-lime silicate float glasses. As a final test for mirroring compatability, selected samples of the production run of the glass were sent to four different commercial manufacturers for mirror coating. None of the manufacturers reported any difficulty silvering the glass. Based on the tests performed, the glass meets or exceeds all optical specifications for the Barstow heliostat field.

Lind, M.A.; Buckwalter, C.Q.

1980-09-01

332

Yesterday's Trash Makes Tomorrow's "Glass"  

ERIC Educational Resources Information Center

In this article, the author describes a glass art project inspired by Dale Chihuly. This project uses two-liter plastic soda bottles which are cut apart and trimmed. Applying heat using a hair dryer, the plastic curls and takes an uneven blown-glass quality. The "glass" is then painted using acrylic paint. (Contains 2 resources and 1 online…

Wayne, Dale

2010-01-01

333

Stained-Glass Pastels  

ERIC Educational Resources Information Center

The author has always liked the look of stained-glass windows. Usually the designs are simplified and the shapes are easier for younger students to draw. This technique seemed to be the perfect place for her fifth-graders to try their hand at color mixing. The smaller spaces and simple shapes were just what she needed for this group. Her students…

Laird, Shirley

2009-01-01

334

The Color Glass Condensate  

E-print Network

We provide a broad overview of the theoretical status and phenomenological applications of the Color Glass Condensate effective field theory describing universal properties of saturated gluons in hadron wavefunctions that are extracted from deeply inelastic scattering and hadron-hadron collision experiments at high energies.

F. Gelis; E. Iancu; J. Jalilian-Marian; R. Venugopalan

2010-02-01

335

"Stained Glass" Landscape Windows  

ERIC Educational Resources Information Center

Both adults and children alike marvel at the grand vivid stained-glass windows created by American artist Louis Comfort Tiffany. Today he is commonly recognized as one of America's most influential designers and artists throughout the last nineteenth and early twentieth century. In the lesson described in this article, students created their own…

Vannata, Janine

2008-01-01

336

Volcanic glass as a natural analog for borosilicate waste glass  

SciTech Connect

Obsidian and basaltic glass are opposite end-members of natural volcanic glass compositions. Syngenetic and diagenetic tensile failure in basaltic glass (low silica glass) is pervasive and provides abundant alteration fronts deep into the glass structure. Perlitic fracturing in obsidian (high silica glass) limits the alteration zones to an {open_quotes}onion skin{close_quotes} geometry. Borosilicate waste glass behaves similarly to the natural analog of basaltic glass (sideromelane). During geologic time, established and tensile fracture networks form glass cells (a three-dimensional reticulated pattern) where the production of new fracture surfaces increases through time by geometric progression. This suggests that borosilicate glass monoliths will eventually become rubble. Rates of reaction appear to double for every 12C{degrees} of temperature increase. Published leach rates suggest that the entire inventory of certain radionuclides may be released during the 10,000 year regulatory time period. Steam alteration prior to liquid attack combined with pervasive deep tensile failure behavior may suggest that the glass waste form is not license defensible without a metallic- and/or ceramic-type composite barrier as an overpack.

Morgenstein, M.E.; Shettel, D.L. [Geosciences Management Institute, Inc., Boulder City, NV (United States)

1994-12-31

337

Bioactive calcium pyrophosphate glasses and glass-ceramics.  

PubMed

Calcium phosphate glass-based materials in the pyrophosphate region are briefly reviewed. Calcium pyrophosphate glasses can be prepared by including a small amount of TiO(2) (glasses in simulated body fluid. By heating powder-compacts of the glasses, they are crystallized and subsequently are sintered, resulting in fabrication of high-strength glass-ceramics with machinability; they are easier to be machined using conventional tools in comparison with conventional calcium phosphate ceramics. beta-Ca(2)P(2)O(7) crystal formed in the glass-ceramics plays an important role in the machinability. Their apatite-forming ability in simulated body fluid is drastically enhanced after autoclaving in distilled water. The glass-ceramics can be easily coated on a new beta-type titanium alloy using a conventional glazing technique. PMID:16701780

Kasuga, Toshihiro

2005-01-01

338

Apollo 12 ropy glasses revisited  

NASA Technical Reports Server (NTRS)

We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have potassium rare earth elements phosphorous (KREEP)-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma. Measurements of 39-Ar-40-Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact. Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.

Wentworth, S. J.; Mckay, D. S.; Lindstrom, D. J.; Basu, A.; Martinez, R. R.; Bogard, D. D.; Garrison, D. H.

1994-01-01

339

Numerical study of XY spin glass and gauge glass models  

NASA Astrophysics Data System (ADS)

We study the +/- J XY spin glass and gauge glass models by a zero temperature domain wall renormalization group method, which enables us to investigate the possibility of an ordered phase at small but finite temperature, that is, to determine the lower critical dimension of the models. The domain wall energy of the system is computed by using the Hamiltonian in the Coulomb gas representation instead of the usual phase representation, since the former is more convenient for our numerical study as it eliminates spin wave contributions to the energy. We reconfirm the earlier prediction in gauge glass that there is no ordered phase in 2d but an ordered phase can exist in 3d at low temperature. However, our simulation yield the stiffness exponents q? --0.35 in 2d and q? +0.30 in 3d, which are considerably larger than the previous estimates but reconcile with the recent finite temperature Monte Carlo study, and strongly suggests that the lower critical dimension, dl, is less than three. In +/- J XY spin glass, there can exist two different glass orders, spin glass and chiral glass orders. It has been numerically suggested the decoupling of the spin and chiral degrees of freedom in both 2 d and 3d, and dl = 4 for spin glass order and 2 < dl < 3 for chiral glass order. We obtain the same stiffness exponents for spin glass and chiral glass in 2d, which suggests that the decoupling does not occur in 2d, which is consistent with the non-rigorous but plausible conjecture. In 3d, our study yields a positive stiffness exponents qs? +0.10 for spin glass. This strongly suggests the lower critical dimension for spin glass order is 2 < dl < 3 as well as a chiral glass order.

Akino, Nobuhiko

340

Production of glass or glass-ceramic to metal seals with the application of pressure  

DOEpatents

In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

Kelly, M.D.; Kramer, D.P.

1985-01-04

341

Production of glass or glass-ceramic to metal seals with the application of pressure  

DOEpatents

In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

Kelly, Michael D. (West Alexandria, OH); Kramer, Daniel P. (Dayton, OH)

1987-11-10

342

Profiles in garbage glass containers  

SciTech Connect

Glass containers are made from sand, limestone, soda ash, cullet (crushed bottles), and various additives, including those used to color brown, green, or blue bottles. Sixty percent of the glass used in the US is clear (flint) and one-fourth is brown (amber). Almost half of the green bottles are imported wind and beer bottles. Other glass products include flat glass such as windows; fiberglass insulation; and glassware. These products use different manufacturing processes and different additives than container glass. This profile covers only container glass. Glass bottles are commonly collected in curb-side programs. Losses due to breakage and the abrasiveness of glass during collection and processing offset their low collection and processing costs. Breakage solutions include installation of interior baffles or nets in the collection trucks, special glass-only truck compartments, and limiting the number of times glass is transferred after collection before final processing. Ten states require deposits on glass bottles for beer and soft drinks and related items.

Miller, C. [Environmental Industry Associations, Washington, DC (United States)

1997-09-01

343

The performance of Glass GEM  

NASA Astrophysics Data System (ADS)

Here we report the performance of Glass gas electron multipliers (Glass GEMs), which were fabricated with photo-etchable glass. The photo-etchable glass used for substrate is called PEG3 (Hoya Corporation). With this material, we succeeded in fabricating a Glass GEM that was 680 ? m-thick with a hole diameter of 170 ? m and Cr and Cu layer electrodes. A Glass GEM has advantages such as good uniformity, high gain, a flat surface without stretching, cylindrical holes, and the absence of outgassing from the material. We successfully operated a Glass GEM having 100 × 100 m 2 effective area with various gas mixtures. The energy resolution for 5.9 keV X-rays was 18%, obtained by uniform irradiation of the entire effective area. The gas gain of the Glass GEM reached up to 90,000 with a gas mixture of Ne/C 4 (90:10). The Glass GEM was also operated with Ar/C 4 and Ar/C 4 gas. The gain stability measured for Glass GEM showed no significant increase or decrease as a function of elapsed time from applying high voltage. The gain stability over 15 hours of operation was about 10% in high-count-rate irradiation. Gain mapping across the Glass GEM showed good uniformity with a standard deviation of about 10%.

Fujiwara, T.; Mitsuya, Y.; Takahashi, H.; Fushie, T.; Kishimito, S.; Guèrard, B.; Uesaka, M.

2014-11-01

344

Nanostructure of glasses: experimental evidence  

NASA Astrophysics Data System (ADS)

Inorganic glass is material having nanoscaled physical and chemical inhomogeneities ad initio because glass inherits thermodynamic fluctuations of concentration, density and anisotropy of a glass forming melt. Combining light scattering and high temperature acoustics data allows to use the effect of internal immersion for designing multicomponent glasses with Rayleigh scattering losses lower than those of the silica glass. Non-random spatial distribution of dopants including rare-earth (RE) ions in a glass host (doped ion segregation) causes excessive Rayleigh scattering losses and enhancement of RE ion-ion interaction. Therefore, it opens the way to optimize operation parameters of laser and up-converting glasses by the proper choice of glass host composition. Results of Raman scattering spectra processing and characterization of electrooptical (EO) sensitivity of niobate glasses showed the existence of groups with stoichiometry of the well-known EO crystals and crystal-like orderliness (crystal motifs) in the glasses as the necessary condition of high EO sensitivity. It was found that EO sensitivity of glasses could be essentially increased by thermal treatment.

Maksimov, Leonid V.; Anan'ev, Anatolii V.; Bogdanov, Victor N.; Lipovskii, Andrey A.; Tagantsev, Dmitri K.; Yanush, Oleg V.

2008-09-01

345

Fluoride glass: Crystallization, surface tension  

NASA Technical Reports Server (NTRS)

Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.

Doremus, R. H.

1988-01-01

346

CCMR: Water in Glass  

NSDL National Science Digital Library

Water uptake for various compositions of the model glass (CaO·Al2O3)x (2 SiO2)1-x under fixed annealing conditions was studied via FTIR. The water saturation concentration increased with time for certain sample sets, suggesting slow equilibration of the surface with the annealing atmosphere, while the water diffusion coefficient exhibited no appreciable time dependence. The saturation concentration and diffusion coefficient were not found to vary significantly with composition.

Uspal, William

2005-08-17

347

Cluster-assembled metallic glasses  

PubMed Central

A bottom-up approach to nanofabricate metallic glasses from metal clusters as building blocks is presented. Considering metallic glasses as a subclass of cluster-assembled materials, the relation between the two lively fields of metal clusters and metallic glasses is pointed out. Deposition of selected clusters or collections of them, generated by state-of-the-art cluster beam sources, could lead to the production of a well-defined amorphous material. In contrast to rapidly quenched glasses where only the composition of the glass can be controlled, in cluster-assembled glasses, one can precisely control the structural building blocks. Comparing properties of glasses with similar compositions but differing in building blocks and therefore different in structure will facilitate the study of structure–property correlation in metallic glasses. This bottom-up method provides a novel alternative path to the synthesis of glassy alloys and will contribute to improving fundamental understanding in the field of metallic glasses. It may even permit the production of glassy materials for alloys that cannot be quenched rapidly enough to circumvent crystallization. Additionally, gaining deeper insight into the parameters governing the structure–property relation in metallic glasses can have a great impact on understanding and design of other cluster-assembled materials. PMID:23899019

2013-01-01

348

Enthalpy of diaplectic labradorite glass  

NASA Astrophysics Data System (ADS)

Enthalpies of solution in molten 2PbO·B2O3 at ˜988 K have been measured for diaplectic labradorite glass from the Manicouagan impact crater and a fused glass formed from the same material. The enthalpies of solution of the diaplectic and fusion-formed glasses are 4,347 and 2,023 cal mol-1, respectively. The more endothermic enthalpy of solution of the diaplectic glass indicates a greater relative energetic stability of about 2.3 kcal mol-1. The data are consistent with Diemann and Arndt's (1984) structural model that suggests the diaplectic glass is more ordered than fusion-formed glass and with the presence of crystallites. Comparison of data to enthalpies of solution of crystalline labradorite (Carpenter et al. 1985) indicates a maximum percentage of crystalline relics of ˜15 18%, also consistent with Diemann and Arndt's (1984) estimate of <17%. Thus the diaplectic glass is intermediate in thermochemical properties between normal glass and crystal (much closer to glass) and does not represent any state more unstable than normal fusion-formed glass.

Geisinger, K. L.; Navrotsky, A.; Arndt, J.

1986-11-01

349

Analytical Plan for Roman Glasses  

SciTech Connect

Roman glasses that have been in the sea or underground for about 1800 years can serve as the independent “experiment” that is needed for validation of codes and models that are used in performance assessment. Two sets of Roman-era glasses have been obtained for this purpose. One set comes from the sunken vessel the Iulia Felix; the second from recently excavated glasses from a Roman villa in Aquileia, Italy. The specimens contain glass artifacts and attached sediment or soil. In the case of the Iulia Felix glasses quite a lot of analytical work has been completed at the University of Padova, but from an archaeological perspective. The glasses from Aquileia have not been so carefully analyzed, but they are similar to other Roman glasses. Both glass and sediment or soil need to be analyzed and are the subject of this analytical plan. The glasses need to be analyzed with the goal of validating the model used to describe glass dissolution. The sediment and soil need to be analyzed to determine the profile of elements released from the glass. This latter need represents a significant analytical challenge because of the trace quantities that need to be analyzed. Both pieces of information will yield important information useful in the validation of the glass dissolution model and the chemical transport code(s) used to determine the migration of elements once released from the glass. In this plan, we outline the analytical techniques that should be useful in obtaining the needed information and suggest a useful starting point for this analytical effort.

Strachan, Denis M.; Buck, Edgar C.; Mueller, Karl T.; Schwantes, Jon M.; Olszta, Matthew J.; Thevuthasan, Suntharampillai; Heeren, Ronald M.

2011-01-01

350

Bioactive glass in tissue engineering  

PubMed Central

This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth. In addition to the new bioactive glasses, recent advances in biomaterials processing have resulted in the creation of scaffold architectures with a range of mechanical properties suitable for the substitution of loaded as well as non-loaded bone. While bioactive glass has been extensively investigated for bone repair, there has been relatively little research on the application of bioactive glass to the repair of soft tissues. However, recent work has shown the ability of bioactive glass to promote angiogenesis, which is critical to numerous applications in tissue regeneration, such as neovascularization for bone regeneration and the healing of soft tissue wounds. Bioactive glass has also been shown to enhance neocartilage formation during in vitro culture of chondrocyte-seeded hydrogels, and to serve as a subchondral substrate for tissue-engineered osteochondral constructs. Methods used to manipulate the structure and performance of bioactive glass in these tissue engineering applications are analyzed. PMID:21421084

Rahaman, Mohamed N.; Day, Delbert E.; Bal, B. Sonny; Fu, Qiang; Jung, Steven B.; Bonewald, Lynda F.; Tomsia, Antoni P.

2011-01-01

351

Non-platinum group metal oxgyen reduction catalysts and their mechanism in both acid and alkaline media: The effect of the catalyst precursor and the ionomer on oxygen reduction  

NASA Astrophysics Data System (ADS)

Non-platinum catalysts are an attractive strategy for lowering the cost of fuel cells, but much more development is needed in order to replace platinum, especially at the cathode where oxygen is reduced. Research groups worldwide have donated material for a study in which precursor structure to catalyst activity correlations are made. The donated samples have been divided into three classes based on their precursor; macrocyclic chelates, small molecule, and polymeric precursors. The precursor is one activity-dictating factor among many, but it is one of the most influential. It was found that macrocyclic chelates on average produced the most active catalysts, having the highest limiting, diffusion-limited, kinetic, and exchange current densities, as well as the lowest overpotentials and H2O2 production. This suggests that the M-N4 atomic structure of the precursor remains largely static throughout heat treatment, as the M-Nx motif is the accepted active site conformation. The other classes were somewhat less active, but the breadth of precursor materials that range in structure and functionality, as well as low associated costs, make them attractive precursor materials. Careful precursor selection based on this analysis was applied to a new generation of catalyst derived from iron salt and 4-aminoantipyrine. An extensive investigation of the reduction of oxygen on the material performed in both acid and alkaline media, and it was found that reduction follows a two-step pathway. While the peroxide reducing step is also very fast, the first step is so rapid that, even at low active site density, the material is almost as active as platinum if all diffusion limitations are removed. In addition to bottom-up catalyst design, the catalyst:ionomer complex, by which catalyst is incorporated into the membrane electrode assembly, also affects reductive kinetics. A series of novel anionically conductive ionomers have been evaluated using a well-described cyanamide derived catalyst, and the ionomeric influence on activity was mechanistically evaluated. It was found that the water-uptake percentage of the ionomer and the ion exchange capacity has a major role in catalyzing the reaction. The ionomer content of the complex must balance ionic and electrical charge transfer, as well as manage a certain degree of hydration at the active site. In order for a catalyst to perform optimally in an operational fuel cell, design considerations must be addressed at the precursor, support, synthesis, morphological, and ionomer-complexing levels. If any level of design is neglected, catalytic performance will be sacrificed.

Robson, Michael H.

352

Mixed Glass Former Effect In Silver Molybdophosphate and Borophosphate Glasses  

NASA Astrophysics Data System (ADS)

We report the study of electrical properties of some silver ion conducting molybdophosphate and borophosphate mixed network former glasses in a wide frequency and temperature range. The dc conductivity of the mixed network former glasses is higher than that of the single network former glasses. The ac conductivity spectra show a power law type dependence on frequency. The frequency exponent obtained from ac conductivity is observed to be independent of both temperature and composition.

Deb, B.; Kabi, S.; Ghosh, A.

2011-07-01

353

Mixed polyanion glass cathodes: Iron phosphate vanadate glasses  

SciTech Connect

Mixed polyanion (MP) glasses have been investigated for use as cathodes in lithium ion batteries. MP glass cathodes are similar in composition to theoretically promising crystalline polyanionic (CP) cathodes (e.g., lithium cobalt phosphate, lithium manganese silicate), but with proper polyanion substitution, they can be designed to overcome the key shortcomings of CP cathodes, such as poor electrical conductivity and irreversible phase changes. Iron phosphate/vanadate glasses were chosen as a first demonstration of the MP glass concept. Polyanion substitution with vanadate was shown to improve the intercalation capacity of an iron phosphate glass from almost zero to full theoretical capacity. In addition, the MP glass cathodes also exhibited an unexpected second high-capacity electrochemical reaction. X-ray absorption near-edge structure (XANES) and x-ray diffraction (XRD) of cathodes from cells having different states of charge suggested that this second electrochemical reaction is a glass-state conversion reaction. With a first demonstration established, MP glass materials utilizing an intercalation and/or glass-state conversion reaction are promising candidates for future high-energy cathode research.

Kercher, Andrew K [ORNL; Ramey, Joanne Oxendine [ORNL; Carroll, Kyler J [Massachusetts Institute of Technology (MIT); Kiggans Jr, James O [ORNL; Veith, Gabriel M [ORNL; Meisner, Roberta [Oak Ridge National Laboratory (ORNL); Boatner, Lynn A [ORNL; Dudney, Nancy J [ORNL

2014-01-01

354

46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Sighting ports, tubular gauge glasses, and flat plate type gauge glasses. 154.1320 Section 154.1320 Shipping...154.1320 Sighting ports, tubular gauge glasses, and flat plate type gauge glasses....

2013-10-01

355

46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 false Sighting ports, tubular gauge glasses, and flat plate type gauge glasses. 154.1320 Section 154.1320 Shipping...154.1320 Sighting ports, tubular gauge glasses, and flat plate type gauge glasses....

2014-10-01

356

46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Sighting ports, tubular gauge glasses, and flat plate type gauge glasses. 154.1320 Section 154.1320 Shipping...154.1320 Sighting ports, tubular gauge glasses, and flat plate type gauge glasses....

2011-10-01

357

46 CFR 154.1320 - Sighting ports, tubular gauge glasses, and flat plate type gauge glasses.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Sighting ports, tubular gauge glasses, and flat plate type gauge glasses. 154.1320 Section 154.1320 Shipping...154.1320 Sighting ports, tubular gauge glasses, and flat plate type gauge glasses....

2012-10-01

358

Space processing of chalcogenide glass  

NASA Technical Reports Server (NTRS)

The manner in which the weightless, containerless nature of in-space processing can be successfully utilized to improve the quality of infrared transmitting chalcogenide glasses is determined. The technique of space processing chalcogenide glass was developed, and the process and equipment necessary to do so was defined. Earthbound processing experiments with As2S3 and G28Sb12Se60 glasses were experimented with. Incorporated into these experiments is the use of an acoustic levitation device.

Larsen, D. C.; Ali, M. I.

1977-01-01

359

Compositional threshold for Nuclear Waste Glass Durability  

SciTech Connect

Within the composition space of glasses, a distinct threshold appears to exist that separates "good" glasses, i.e., those which are sufficiently durable, from "bad" glasses of a low durability. The objective of our research is to clarify the origin of this threshold by exploring the relationship between glass composition, glass structure and chemical durability around the threshold region.

Kruger, Albert A. [Pacific Northwest National Lab., Richland, WA (United States); Farooqi, Rahmatullah [Pohang Univ. of Science and Technology, (Korea, Republic of); Hrma, Pavel R. [Pacific Northwest National Lab., Richland, WA (United States), Pohang Univ. of Science and Technology, (Korea, Republic of)

2013-04-24

360

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.

Boaz, P.T.

1998-07-21

361

Terahertz transmission spectroscopy of chalcogenide glasses  

Microsoft Academic Search

Terahertz transmission of a chalcogenide family of glasses is reported. The glasses were processed using established methods for non-oxide glasses. Transmission through the samples was measured using a THz spectrometer. The transmission and optical properties of the glasses are summarized. The results show promise of these glasses for application as THz windows.

S. K. Sundaram; B. J. Riley; J. V. Crum

2008-01-01

362

Power laser application for security glass production  

Microsoft Academic Search

Modern glass application needs to move from traditional tempering with only average controlled fragmentation of security glass to computerized controlled fragmentation by developing engineered stress profiles in glass article. The new treatment methods of soda-lime float glass using irradiation by power Nd:YAG laser which is moved by robot will be discussed. The transparency of glass for laser wavelength is one

Vladimir Abashkin; Elena Achimova

2009-01-01

363

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.

Boaz, Premakaran Tucker (Livonia, MI)

1998-01-01

364

Fabrication of glass microspheres with conducting surfaces  

Microsoft Academic Search

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming

Elsholz

1984-01-01

365

Fabrication of glass microspheres with conducting surfaces  

Microsoft Academic Search

A method for making hollow glass microspheres with conducting surfaces by adding a conducting vapor to a region of the glass fabrication furnace. As droplets or particles of glass forming material pass through multiple zones of different temperature in a glass fabrication furnace, and are transformed into hollow glass microspheres, the microspheres pass through a region of conducting vapor, forming

Elsholz

1982-01-01

366

Glass corrosion in natural environments  

NASA Technical Reports Server (NTRS)

Experiments carried out during the progress period are summarized. Experiments carried out involving glass samples exposed to solutions of Tris have shown the appearance of 'spikes' upon monitoring glass dissolution as a function of time. The periodic 'spikes' observed in Tris-based media were interpreted in terms of cracking due to excessive stress in the surface region of the glass. Studies of the interactions of silicate glasses with metal ions in buffered media were extended to systems containing Al. Caps buffer was used to establish the pH. The procedures used are described and the results are given. Preliminary studies were initiated as to the feasibility of adding a slowly dissolving solid compound of the additive to the glass-water system to maintain a supply of dissolved additive. It appears that several magnesium compounds have a suitable combination of solubility and affinity towards silicate glass surfaces to have a pronounced retarding effect on the extraction of uranium from the glass. These preliminary findings raise the possibility that introducing a magnesium source into geologic repositories for nuclear waste glass in the form of a sparingly soluble Mg-based backfill material may cause a substantial reduction in the extent of long-term glass corrosion. The studies described also provide mechanistic understanding of the roles of various metal solutes in the leachant. Such understanding forms the basis for developing long-term predictions of nuclear waste glass durability under repository conditions. From what is known about natural highly reduced glasses such as tektites, it is clear that iron is dissolved as ferrous iron with little or no ferric iron. The reducing conditions were high enough to cause metallic iron to exsolve out of the glass in the form of submicroscopic spherules. As the nuclear waste glass is much less reduced, a study was initiated on other natural glasses in addition to the nuclear waste glass. Extensive measurements were carried out on these glasses in order to characterize their magnetic properties. Results of these studies are described.

Thorpe, Arthur N.; Barkatt, Aaron

1992-01-01

367

Crystallization of copper metaphosphate glass  

NASA Technical Reports Server (NTRS)

The effect of the valence state of copper in copper metaphosphate glass on the crystallization behavior and glass transition temperature has been investigated. The crystallization of copper metaphosphate is initiated from the surface and its main crystalline phase is copper metaphosphate (Cu(PO)3),independent of the (Cu sup 2+)/(Cu(total)). However, the crystal morphology, the relative crystallization rates, and their temperature dependences are affected by the (Cu sup 2+)/(Cu (total)) ratio in the glass. On the other hand, the totally oxidized glass crystallizes from all over the surface. The relative crystallization rate of the reduced glass to the totally oxidized glass is large at low temperature, but small at high temperature. The glass transition temperature of the glass increases as the (Cu sup 2+)/(Cu(total)) ratio is raised. It is also found that the atmosphere used during heat treatment does not influence the crystallization of the reduced glass, except for the formation of a very thin CuO surface layer when heated in air.

Bae, Byeong-Soo; Weinberg, Michael C.

1993-01-01

368

Glass corrosion in natural environment  

NASA Technical Reports Server (NTRS)

A series of studies of the effects of solutes which appear in natural aqueous environments, specifically Mg and Al, under controlled conditions, permit characterization of the retardation of silicate glass leaching in water containing such solutes. In the case of Mg the interaction with the glass appears to consist of exchange with alkali ions present in the glass to a depth of several microns. The effect of Al can be observed at much lower levels, indicating that the mechanism in the case of Al involves irreversible formation of aluminosilicate species at the glass surface.

Thorpe, Arthur N.

1989-01-01

369

Examination of glass-silicon and glass-glass bonding techniques for microfluidic systems  

SciTech Connect

We report here on the results of experiments concerning particular bonding processes potentially useful for ultimate miniaturization of microfluidic systems. Direct anodic bonding of continuous thin pyrex glass of 250 {mu}m thickness to silicon substrates gives multiple, large voids in the glass. Etchback of thick glass of 1200 {mu}m thickness bonded to silicon substrates gives thin continuous glass layers of 189 {mu}m thickness without voids over areas of 5 cm {times} 12 cm. Glass was also successfully bonded to glass by thermal bonding at 800{degrees}C over a 5 cm {times} 7 cm area. Anticipated applications include microfabricated DNA sequencing, flow injection analysis, and liquid and gas chromatography microinstruments.

Raley, N.F.; Davidson, J.C.; Balch, J.W.

1995-10-23

370

7.G Stained Glass  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The students in Mr. Rivera's art class are designing a stained-glass window to hang in the school entryway. The window will be 2 feet tall and 5 feet w...

371

Halide laser glasses  

SciTech Connect

Energy storage and energy extraction are of prime importance for efficient laser action and are affected by the line strengths and linewidths of optical transitions, excited-state lifetimes, nonradiative decay processes, spectroscopic inhomogeneities, nonlinear refractive index, and damage threshold. These properties are all host dependent. To illustrate this, the spectroscopic properties of Nd/sup 3 +/ have been measured in numerous oxide, oxyhalide, and halide glasses. A table summarizes the reported ranges of stimulated emission cross sections, peak wavelengths, linewidths, and radiative lifetimes associated with the /sup 4/F/sub 3/2/ ..-->.. /sup 4/I/sub 11/2/ lasing transition.

Weber, M.J.

1982-01-14

372

Glasses on the seabed: surface study of chemical corrosion in sunken Roman glasses  

Microsoft Academic Search

The current work aims to describe surface weathering of ancient glasses in marine environment. All data are collected using different techniques: optical microscopy, RGA, surface techniques (XPS, SEM and SIMS). Three types of glass weathering have been observed: white glass, glossy glass and glass showing growth rings. A compact structure characterizes white glasses, while a porous structure with flaked layers

Barbara Dal Bianco; Renzo Bertoncello; Laura Milanese; Simona Barison

2004-01-01

373

POROUS WALL, HOLLOW GLASS MICROSPHERES  

SciTech Connect

Hollow Glass Microspheres (HGM) is not a new technology. All one has to do is go to the internet and Google{trademark} HGM. Anyone can buy HGM and they have a wide variety of uses. HGM are usually between 1 to 100 microns in diameter, although their size can range from 100 nanometers to 5 millimeters in diameter. HGM are used as lightweight filler in composite materials such as syntactic foam and lightweight concrete. In 1968 a patent was issued to W. Beck of the 3M{trademark} Company for 'Glass Bubbles Prepared by Reheating Solid Glass Particles'. In 1983 P. Howell was issued a patent for 'Glass Bubbles of Increased Collapse Strength' and in 1988 H. Marshall was issued a patent for 'Glass Microbubbles'. Now Google{trademark}, Porous Wall, Hollow Glass Microspheres (PW-HGMs), the key words here are Porous Wall. Almost every article has its beginning with the research done at the Savannah River National Laboratory (SRNL). The Savannah River Site (SRS) where SRNL is located has a long and successful history of working with hydrogen and its isotopes for national security, energy, waste management and environmental remediation applications. This includes more than 30 years of experience developing, processing, and implementing special ceramics, including glasses for a variety of Department of Energy (DOE) missions. In the case of glasses, SRS and SRNL have been involved in both the science and engineering of vitreous or glass based systems. As a part of this glass experience and expertise, SRNL has developed a number of niches in the glass arena, one of which is the development of porous glass systems for a variety of applications. These porous glass systems include sol gel glasses, which include both xerogels and aerogels, as well as phase separated glass compositions, that can be subsequently treated to produce another unique type of porosity within the glass forms. The porous glasses can increase the surface area compared to 'normal glasses of a 1 to 2 order of magnitude, which can result in unique properties in areas such as hydrogen storage, gas transport, gas separations and purifications, sensors, global warming applications, new drug delivery systems and so on. One of the most interesting porous glass products that SRNL has developed and patented is Porous Wall, Hollow Glass Microspheres (PW-HGMs) that are being studied for many different applications. The European Patent Office (EPO) just recently notified SRS that the continuation-in-part patent application for the PW-HGMs has been accepted. The original patent, which was granted by the EPO on June 2, 2010, was validated in France, Germany and the United Kingdom. The microspheres produced are generally in the range of 2 to 100 microns, with a 1 to 2 micron wall. What makes the SRNL microspheres unique from all others is that the team in Figure 1 has found a way to induce and control porosity through the thin walls on a scale of 100 to 3000 {angstrom}. This is what makes the SRNL HW-HGMs one-of-a-kind, and is responsible for many of their unique properties and potential for various applications, including those in tritium storage, gas separations, H-storage for vehicles, and even a variety of new medical applications in the areas of drug delivery and MRI contrast agents. SRNL Hollow Glass Microspheres, and subsequent, Porous Wall, Hollow Glass Microspheres are fabricated using a flame former apparatus. Figure 2 is a schematic of the apparatus.

Sexton, W.

2012-06-30

374

Understanding the fingerprint region in the infra-red spectra of perfluorinated ionomer membranes and corresponding model compounds: Experiments and theoretical calculations  

NASA Astrophysics Data System (ADS)

We present an ATR-FTIR study of three major perfluorinated ionomers that are used as proton exchange membranes in fuel cells (FCs) and that differ in their side chains: Nafion, Aquivion and 3M membrane. The choice of the following low-molecular-weight model compounds (MCs) that mimic the membrane side chains was essential for FTIR band assignment: perfluoro(3-methyl-2,4-dioxahexane)sulfonic acid for Nafion, perfluoro(2-ethoxyethane)sulfonic acid for Aquivion, and perfluoro(2-ethoxybutane)sulfonic acid for the 3M membrane. The major goal was to identify spectral bands that can be used for recognizing bonds involved in membrane fragmentation. A major focus was on the signals from the C-O-C bonds, which were assigned in some papers for Nafion and Aquivion membranes. Our ATR-FTIR results for 3M membranes did not conform to these assignments, and DFT calculations of the vibrational frequencies for the MCs were used to resolve this conundrum. The ATR-FTIR spectra of membranes and MCs and the DFT calculations led to an understanding of the fingerprint region of all membranes, and to a re-examination and re-assignment of results for Nafion and Aquivion membranes. The low intensity of the spectral bands for the ether link connected to the backbone (for all membranes) and also in the side chain (for Nafion) suggests that these bands cannot be used for the determination of the extent of degradation.

Danilczuk, Marek; Lin, Lu; Schlick, Shulamith; Hamrock, Steven J.; Schaberg, Mark S.

2011-10-01

375

The fate of arsenic, cadmium and lead in Typha latifolia: a case study on the applicability of micro-PIXE in plant ionomics.  

PubMed

Understanding the uptake, accumulation and distribution of toxic elements in plants is crucial to the design of effective phytoremediation strategies, especially in the case of complex multi-element pollution. Using micro-proton induced X-ray emission, the spatial distribution of Na, Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Zn, As, Br, Rb, Sr, Cd and Pb have been quantitatively resolved in roots and rhizomes of an obligate wetland plant species, Typha latifolia, treated with a mixture of 100 ?M each of As, Cd and Pb, together. The highest concentrations of As, Cd and Pb were found in the roots of the T. latifolia, with tissue-specific distributions. The As was detected in the root rhizodermis, and in the rhizome the majority of the As was within the vascular tissues, which indicates the high mobility of As within T. latifolia. The Cd was detected in the root exodermis, and in the vascular bundle and epidermis of the rhizome. The highest Pb concentrations were detected in the root rhizodermis and exodermis, and in the epidermis of the rhizome. These data represent an essential step in the resolution of fundamental questions in plant ionomics. PMID:23416480

Lyubenova, Lyudmila; Pongrac, Paula; Vogel-Mikuš, Katarina; Mezek, Gašper Kukec; Vavpeti?, Primož; Grlj, Nataša; Regvar, Marjana; Pelicon, Primož; Schröder, Peter

2013-03-15

376

Visual evaluation of in vitro cariostatic effect of restorative materials associated with dentifrices.  

PubMed

This study evaluated in vitro the cariostatic effect of 6 restorative materials with and without fluoride release (Fuji II LC, F-2000, Degufil Mineral, Sure Fil and Z-250) associated with a fluoridated and a non-fluoridated dentifrice (Sensodyne Original Formula and Sensodyne Sodium Bicarbonate), on human enamel. Class V-like cavities were prepared on 240 enamel slabs, assigned to 12 groups (6 materials and 2 dentifrices). After cavity restoration, the slabs were submitted to a thermocycling regimen of 1000 thermal cycles and demineralization/remineralization cycles. During pH cycles, slurries of fluoridated and non-fluoridated dentifrices were applied for 5 min. Formation of artificial caries-like lesions was scored independently and blindly by 5 calibrated examiners according to an ordinal scale ranked 0 to 3 by visual examination. The results were analyzed statistically by the Kruskal-Wallis test and pair-wise comparisons (alpha=0.05). There were no significant differences (p>0.05) among the restorative materials associated with the fluoridated dentifrice. When used in association with the non-fluoridated dentifrice, Ketac-Fil showed the highest cariostatic effect followed by Fuji II LC and the other materials. Ketac-Fil was the only material that did not differ statistically when combined with either the fluoridated or the non-fluoridated dentifrice. In conclusion, under the tested experimental conditions, the association of restorative materials and fluoridated dentifrice yielded higher cariostatic effect, except for the conventional glass ionomer cement, whose cariostatic effect was not influenced by the type of dentifrice. PMID:16475604

Rodrigues, José Augusto; Marchi, Giselle Maria; Serra, Mônica Campos; Hara, Anderson Takeo

2005-01-01

377

7 CFR 3201.30 - Glass cleaners.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Glass cleaners. 3201.30 Section 3201...PROCUREMENT Designated Items § 3201.30 Glass cleaners. (a) Definition. Cleaning...designed specifically for use in cleaning glass surfaces, such as windows,...

2012-01-01

378

7 CFR 2902.30 - Glass cleaners.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Glass cleaners. 2902.30 Section 2902...PROCUREMENT Designated Items § 2902.30 Glass cleaners. (a) Definition. Cleaning...designed specifically for use in cleaning glass surfaces, such as windows,...

2010-01-01

379

7 CFR 3201.30 - Glass cleaners.  

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Glass cleaners. 3201.30 Section 3201...PROCUREMENT Designated Items § 3201.30 Glass cleaners. (a) Definition. Cleaning...designed specifically for use in cleaning glass surfaces, such as windows,...

2014-01-01

380

7 CFR 3201.30 - Glass cleaners.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Glass cleaners. 3201.30 Section 3201...PROCUREMENT Designated Items § 3201.30 Glass cleaners. (a) Definition. Cleaning...designed specifically for use in cleaning glass surfaces, such as windows,...

2013-01-01

381

ConcepTest: Glass-Rock Analogy  

NSDL National Science Digital Library

Glass is made by melting silica-rich sand. The molten glass is then formed into shapes as it cools. Glass making could be seen as an analog for the formation of a. igneous rock b. metamorphic rock c. sedimentary ...

382

Aspects of the mechanics of metallic glasses  

E-print Network

Metallic glasses are amorphous materials that possess unique mechanical properties, such as high tensile strengths and good fracture toughnesses. Also, since they are amorphous, metallic glasses exhibit a glass transition, ...

Henann, David Lee

2011-01-01

383

Quinary metallic glass alloys  

DOEpatents

At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

Lin, X.; Johnson, W.L.

1998-04-07

384

Quinary metallic glass alloys  

DOEpatents

At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

Lin, Xianghong (Pasadena, CA); Johnson, William L. (Pasadena, CA)

1998-01-01

385

From Christmas Ornament to Glass Electrode  

NASA Astrophysics Data System (ADS)

In potentiometric techniques, pH measurements require a costly and fragile accessory: the glass electrode. A glass electrode is difficult to make because the wall of the sensing glass bulb must be very thin, and glass of special composition is required. Although the glass bulb may be made by a skilled glazier, we choose a more impressive and simple way. The glass bulb can be made from a Christmas-tree ornamental ball.

da Rocha, Rogério T.; Gutz, Ivano G. R.; Do Lago, Claudimir L.

1995-12-01

386

Space processing of chalcogenide glass  

NASA Technical Reports Server (NTRS)

A program was conducted to develop the technique of space processing for chalcogenide glass, and to define the process and equipment necessary. In the course of this program, successful long term levitation of objects in a 1-g environment was achieved. Glass beads 4 mm diameter were containerless melted and fused together.

Firestone, R. F.; Schramm, S. W.

1978-01-01

387

Refractory Glass Seals for SOFC  

SciTech Connect

One of the critical challenges facing planar solid oxide fuel cell (SOFC) technology is the need for reliable sealing technology. Seals must exhibit long-term stability and mechanical integrity in the high temperature SOFC environment during normal and transient operation. Several different approaches for sealing SOFC stacks are under development, including glass or glass-ceramic seals, metallic brazes, and compressive seals. Among glass seals, rigid glass-ceramics, self-healing glass, and composite glass approaches have been investigated under the SECA Core Technology Program. The U.S. Department of Energy's Pacific Northwest National Laboratory (PNNL) has developed the refractory glass approach in light of the fact that higher sealing temperatures (e.g., 930-1000 degrees C) may enhance the ultimate in-service bulk strength and electrical conductivity of contact materials, as well as the bonding strength between contact materials and adjacent SOFC components, such as interconnect coatings and electrodes. This report summarizes the thermal, chemical, mechanical, and electrical properties of the refractory sealing glass.

Chou, Y. S.; Stevenson, Jeffry W.

2011-07-01

388

A novel borophosphosilicate glass process  

Microsoft Academic Search

A novel low cost borophosphosilicate glass (BPSG) technology suitable for one micron processing is presented here. This technique allows glass to be flowed consistently and reproducibly at temperatures as low as 750°C. Flow angles are independent of device linewidths from 1 to 10 microns. The flow angle can be adjusted by changing the deposition time. The simplicity of the process

C. Y. Fu

1985-01-01

389

Method of determining glass durability  

DOEpatents

A process for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, .DELTA.G.sub.p, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, .DELTA.G.sub.a, based upon the free energy associated with weak acid dissociation, .DELTA.G.sub.a.sup.WA, and accelerated matrix dissolution at high pH, .DELTA.G.sub.a.sup.SB associated with solution strong base formation, and determining a final hydration free energy, .DELTA.G.sub.f. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log.sub.10 (N C.sub.i (g/L))=a.sub.i +b.sub.i .DELTA.G.sub.f. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained.

Jantzen, Carol Maryanne (Aiken, SC); Pickett, John Butler (Aiken, SC); Brown, Kevin George (Augusta, GA); Edwards, Thomas Barry (Aiken, SC)

1998-01-01

390

Method of determining glass durability  

DOEpatents

A process is described for determining one or more leachate concentrations of one or more components of a glass composition in an aqueous solution of the glass composition by identifying the components of the glass composition, including associated oxides, determining a preliminary glass dissolution estimator, {Delta}G{sub p}, based upon the free energies of hydration for the component reactant species, determining an accelerated glass dissolution function, {Delta}G{sub a}, based upon the free energy associated with weak acid dissociation, {Delta}G{sub a}{sup WA}, and accelerated matrix dissolution at high pH, {Delta}G{sub a}{sup SB} associated with solution strong base formation, and determining a final hydration free energy, {Delta}G{sub f}. This final hydration free energy is then used to determine leachate concentrations for elements of interest using a regression analysis and the formula log{sub 10}(N C{sub i}(g/L))=a{sub i} + b{sub i}{Delta}G{sub f}. The present invention also includes a method to determine whether a particular glass to be produced will be homogeneous or phase separated. The present invention is also directed to methods of monitoring and controlling processes for making glass using these determinations to modify the feedstock materials until a desired glass durability and homogeneity is obtained. 4 figs.

Jantzen, C.M.; Pickett, J.B.; Brown, K.G.; Edwards, T.B.

1998-12-08

391

HEAT TRANSFER DURING GLASS FORMING  

Microsoft Academic Search

An important step in the optimization of a glass container production cycle is the determination of the glass temperature distribution during heat treatment. The ideal approach to this problem is to formulate a theoretical model for comparison against experimental data measured in a well-determined system. Discrepancies between theory and experiment may then give further direction for model improvement. This approach,

IHAB H. FARAG; MICHAEL J. BELIVEAU; RICHARD L. CURRAN

1987-01-01

392

SRNL POROUS WALL GLASS MICROSPHERES  

Microsoft Academic Search

The Savannah River National Laboratory (SRNL) has developed a new medium for storage of hydrogen and other gases. This involves fabrication of thin, Porous Walled, Hollow Glass Microspheres (PW-HGMs), with diameters generally in the range of 1 to several hundred microns. What is unique about the glass microballons is that porosity has been induced and controlled within the thin, one

G Wicks; L Leung Heung; R Ray Schumacher

2008-01-01

393

Glass-An Environmental Protector  

SciTech Connect

From asbestos abatement to lead paint removal to nuclear waste stabilization and even to heavy metal removal using microorganisms, glass has great potential as a solution to many environmental problems. The ability to accommodate an array of chemical elements within the glass structure has facilitated the use of glass as a medium for the stabilization of numerous hazardous substances. The resulting glasses have proven to be durable enough for direct land disposal. In many cases, the stabilized forms have been deemed suitable for re-use in other applications. As recycling and hazardous material treatment become even more important in the global materials cycle, it is a certainty that glass will assume a prominent role.

MARRA, JAMES

2004-11-01

394

Glass science tutorial: Lecture No. 7, Waste glass technology for Hanford  

SciTech Connect

This paper presents the details of the waste glass tutorial session that was held to promote knowledge of waste glass technology and how this can be used at the Hanford Reservation. Topics discussed include: glass properties; statistical approach to glass development; processing properties of nuclear waste glass; glass composition and the effects of composition on durability; model comparisons of free energy of hydration; LLW glass structure; glass crystallization; amorphous phase separation; corrosion of refractories and electrodes in waste glass melters; and glass formulation for maximum waste loading.

Kruger, A.A.

1995-07-01

395

Glass Ceramic Formulation Data Package  

SciTech Connect

A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the waste form.

Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

2012-06-17

396

Database and Interim Glass Property Models for Hanford HLW Glasses  

SciTech Connect

The purpose of this report is to provide a methodology for an increase in the efficiency and a decrease in the cost of vitrifying high-level waste (HLW) by optimizing HLW glass formulation. This methodology consists in collecting and generating a database of glass properties that determine HLW glass processability and acceptability and relating these properties to glass composition. The report explains how the property-composition models are developed, fitted to data, used for glass formulation optimization, and continuously updated in response to changes in HLW composition estimates and changes in glass processing technology. Further, the report reviews the glass property-composition literature data and presents their preliminary critical evaluation and screening. Finally the report provides interim property-composition models for melt viscosity, for liquidus temperature (with spinel and zircon primary crystalline phases), and for the product consistency test normalized releases of B, Na, and Li. Models were fitted to a subset of the screened database deemed most relevant for the current HLW composition region.

Hrma, Pavel R.; Piepel, Gregory F.; Vienna, John D.; Cooley, Scott K.; Kim, Dong-Sang; Russell, Renee L.

2001-07-24

397

Controlled morphology of Nafion^ perflourinated ionomer membrane and poly(vinylidene-co-trifluoroethylene) blends for swelling suppression.  

NASA Astrophysics Data System (ADS)

The major objective of the present study is concerned with the swelling suppression of Nafion^ membrane upon hydration through blending with poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) copolymer. The phase diagram of the Nafion/PVDF-TrFE blend was established by differential scanning calorimetry, cloud point measurement, and optical microscopy. A theoretical phase diagram was calculated by self-consistently solving the combined Flory-Huggins free energy for liquid-liquid demixing and the phase field free energy for crystal solidification. The resulting phase diagram is the combined LCST-UCST and/or an hour glass type. Guided by the phase diagram, the phase separated domain morphology can be controlled to exhibit bicontinuous or dispersed domains via phase separation by solvent casting or thermal quenching. The blends thus prepared not only afford suppression of water uptake, but also render dimensional stability. Fourier transform infrared spectroscopy studies and water uptake measurement showed infallible evidence that modification of Nafion^ with PVDF-TrFE reduces swelling upon hydration.

Nazir, Nadzrinahamin Ahmad; Kyu, Thein

2009-03-01

398

A Topological Glass  

E-print Network

We propose and study a model with glassy behavior. The state space of the model is given by all triangulations of a sphere with $n$ nodes, half of which are red and half are blue. Red nodes want to have 5 neighbors while blue ones want 7. Energies of nodes with different numbers of neighbors are supposed to be positive. The dynamics is that of flipping the diagonal of two adjacent triangles, with a temperature dependent probability. We show that this system has an approach to a steady state which is exponentially slow, and show that the stationary state is unordered. We also study the local energy landscape and show that it has the hierarchical structure known from spin glasses. Finally, we show that the evolution can be described as that of a rarefied gas with spontaneous generation of particles and annihilating collisions.

Jean-Pierre Eckmann

2007-04-07

399

Containerless glass fiber processing  

NASA Technical Reports Server (NTRS)

An acoustic levitation furnace system is described that was developed for testing the feasibility of containerless fiber pulling experiments. It is possible to levitate very dense materials such as platinum at room temperature. Levitation at elevated temperatures is much more difficult. Samples of dense heavy metal fluoride glass were levitated at 300 C. It is therefore possible that containerless fiber pulling experiments could be performed. Fiber pulling from the melt at 650 C is not possible at unit gravity but could be possible at reduced gravities. The Acoustic Levitation Furnace is described, including engineering parameters and processing information. It is illustrated that a shaped reflector greatly increases the levitation force aiding the levitation of more dense materials.

Ethridge, E. C.; Naumann, R. J.

1986-01-01

400

Raman study of glass transition in iron phosphate glasses  

NASA Astrophysics Data System (ADS)

Iron phosphate (Fe2O3: P2O5) glass with 40: 60 mol% composition having glass transition temperature, Tg at 782 K, was investigated between 81-873 K using Raman spectroscopy. The spectra were corrected for thermal population factor and the Raman mode frequencies were obtained from Lorentzian peak fits. Three characteristic modes of iron phosphate glass, corresponding to asymmetric stretching of Q0, Q1 and Q2 tetrahedral units, were analyzed for temperature dependences of the mode frequencies. All the modes are found to exhibit typical anharmonic behavior below Tg, while discontinuous changes are found near Tg, thereby suggesting structural relaxations.

Chakraborty, S.; Arora, A. K.

2012-06-01

401

Glass ceramic seals to inconel  

DOEpatents

A glass ceramic composition prepared by subjecting a glass composition comprising, by weight, 65-80% SiO.sub.2, 8-16%, Li.sub.2 O, 2-8% , Al.sub.2 O.sub.3, 1-8% K.sub.2 O, 1-5% P.sub.2 O.sub.5 and 1.5-7% B.sub.2 O.sub.3, to the following processing steps of heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein, holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii, cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein, and thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient and products containing said composition.

McCollister, Howard L. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

1983-11-08

402

Tensile bond strength of gold and porcelain inlays to extracted teeth using three cements.  

PubMed

This in vitro study compared the tensile bond strength of gold and porcelain inlays to extracted molars in standardized cavities. Three cements were used: zinc phosphate, glass-ionomer, and a resin composite cement. The gold inlays were cemented using zinc phosphate or glass-ionomer cement, and the porcelain inlays were luted using resin composite or glass-ionomer cement. Surface treatments included, for gold inlays, either no treatment (zinc phosphate cement) or airborne particle abraded and tinplated (glass-ionomer cement); and for porcelain inlays, either no treatment (glass-ionomer cement) or etched and silane-treated (resin composite cement). Statistical analysis was performed using the Weibull distribution. Results showed no significant differences between gold inlays cemented using zinc phosphate or glass-ionomer cements and porcelain inlays luted using glass-ionomer cements. The bonded porcelain inlays (resin composite cement) showed tensile bond strengths two to three times higher than those obtained for cemented gold inlays. PMID:7575974

Michelini, F S; Belser, U C; Scherrer, S S; De Rijk, W G

1995-01-01

403

Space processing of chalcogenide glasses  

NASA Technical Reports Server (NTRS)

Manufacture of chalcogenide glasses in space will eliminate many of the causes of optical non-homogeneity and contamination that are inherent in earth-bound manufacture. A program is outlined to demonstrate the feasibility of various techniques and processes that will be utilized to manufacture chalcogenide glasses in space. Amorphous character, purity, and homogeneity parameters are being investigated at various stages of the glass forming process. These parameters in merit index form will serve to provide guidelines for the design of the actual melting experiment in space, and for the optimization of the exact chalcogenide composition to be included in the space experiments.

Larsen, D. C.; Ali, M. A.; Crandall, W. B.

1974-01-01

404

Glass microspheres for medical applications  

NASA Astrophysics Data System (ADS)

Radioactive dysprosium lithium borate glass microspheres have been developed as biodegradable radiation delivery vehicles for the radiation synovectomy treatment of rheumatoid arthritis. Once injected into a diseased joint, the microspheres deliver a potent dose of radiation to the diseased tissue, while a non-uniform chemical reaction converts the glass into an amorphous, porous, hydrated dysprosium phosphate reaction product. The non-radioactive, lithium-borate component is dissolved from the glass (up to 94% weight loss), while the radioactive 165Dy reacts with phosphate anions in the body fluids, and becomes "chemically" trapped in a solid, dysprosium phosphate reaction product that has the same size as the un-reacted glass microsphere. Ethylene diamine tetraacetate (EDTA) chelation therapy can be used to dissolve the dysprosium phosphate reaction product after the radiation delivery has subsided. The dysprosium phosphate reaction product, which formed in vivo in the joint of a Sprague-Dawley rat, was dissolved by EDTA chelation therapy in <1 week, without causing any detectable joint damage. The combination of dysprosium lithium borate glass microspheres and EDTA chelation therapy provides an unique "tool" for the medical community, which can deliver a large dose (>100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability. The non-uniform reaction process is a desirable characteristic for a biodegradable radiation delivery vehicle, but it is also a novel material synthesis technique that can convert a glass to a highly porous materials with widely varying chemical composition by simple, low-temperature, glass/solution reaction. The reaction product formed by nonuniform reaction occupies the same volume as the un-reacted glass, and after drying for 1 h at 300°C, has a specific surface area of ?200 m2/g, a pore size of ?30 nm, and a nominal crushing strength of ?10 MPa. Finally, rhenium glass microspheres, composed of micron-sized, metallic rhenium particles dispersed within a magnesium alumino borate glass matrix were produced by sintering ReO2 powder and glass frit at 1050°C. A 50 mg injection of radioactive rhenium glass microspheres containing 3.7 GBq of 186Re and 8.5 GBq of 188Re could be used to deliver a 100 Gy dose to a cancerous tumor, while limiting the total body dose caused by rhenium dissolution to approximately 1 mGy.

Conzone, Samuel David

405

Continuous Fibre Reinforced Glass and Glass-Ceramic Matrix Composites  

Microsoft Academic Search

Glass and glass-ceramic matrix composites with continuous fibre reinforcement are considered in this Chapter, covering aspects\\u000a of their fabrication, microstructural characterisation, properties and applications. The great variety of composite systems\\u000a developed during the last 30 years is discussed and their outstanding thermomechanical properties and high technological potential\\u000a are highlighted. These composites constitute a new family of high-temperature capability, lightweight structural

Aldo R. Boccaccini

406

Spin glasses and fragile glasses: Statics, dynamics, and complexity  

PubMed Central

In this paper I will briefly review some theoretical results that have been obtained in recent years for spin glasses and fragile glasses. I will concentrate my attention on the predictions coming from the so called broken replica symmetry approach and on their experimental verifications. I will also mention the relevance or these results for other fields, and in general for complex systems. PMID:16690744

Parisi, Giorgio

2006-01-01

407

Turning geothermal waste into glasses and glass ceramics  

SciTech Connect

Researchers investigating the waste on the pipes at the Cerro Prieto geothermal plant in Mexico found that it contained high amounts of silica. Initial tests showed that this waste silica had a high specific surface area, contained salts that could easily be eliminated, and resisted high temperatures effectively. Further research was done to see if this waste material could be used as silica sand in the production of glass. Testing of the waste material included the following: X-ray diffraction with nickel filters; EDX spectroscopy with ultrathin window; Differential thermal analysis; IR spectroscopy analysis; Electron microscope analysis. The tests were done on the raw material itself and on four sets of glass formulated from the raw material. Two sets of glass were formulated from untreated waste material, and two sets were formulated from treated waste material. The raw material was tested for purity, and the glass was tested for hardness, toughness, and transparency. As the tests show, the silica material from the Cerro Prieto plant steam pipes is not merely useless industrial waste. It is a reproducible source of silica sand that producers can use in ceramic and glass production. The initial tests show that the properties of the raw material, and those of the glass formulated from the raw material, will meet industry requirements.

Diaz, C. (Univ. Autonoma de Baja California, Tijuana, NM (United States)); Torres-Martinez, L.M.; Garza, L. (Univ. Autonoma de Nuevo Leon, Monterrey, NM (United States)); Avalos-Borja, M. (Univ. Autonoma de Mexico, Eusenada, Baja, NM (United States)); Rincon, J.M. (Instituto de Ceramica y Vidrio, Madrid (Spain))

1993-10-01

408

Glass-glass transition during aging of a colloidal clay.  

PubMed

Colloidal suspensions are characterized by a variety of microscopic interactions, which generate unconventional phase diagrams encompassing fluid, gel and glassy states and offer the possibility to study new phase and/or state transitions. Among these, glass-glass transitions are rare to be found, especially at ambient conditions. Here, through a combination of dilution experiments, X-ray photon correlation spectroscopy, small angle X-ray scattering, rheological measurements and Monte Carlo simulations, we provide evidence of a spontaneous glass-glass transition in a colloidal clay. Two different glassy states are distinguished with evolving waiting time: a first one, dominated by long-range screened Coulombic repulsion (Wigner glass) and a second one, stabilized by orientational attractions (Disconnected House of Cards glass), occurring after a much longer time. These findings may have implications for heterogeneously charged systems out-of-equilibrium and for applications where a fine control of the local order and/or long term stability of the amorphous materials are required. PMID:24887086

Angelini, Roberta; Zaccarelli, Emanuela; de Melo Marques, Flavio Augusto; Sztucki, Michael; Fluerasu, Andrei; Ruocco, Giancarlo; Ruzicka, Barbara

2014-01-01

409

Glass-glass transition during aging of a colloidal clay  

NASA Astrophysics Data System (ADS)

Colloidal suspensions are characterized by a variety of microscopic interactions, which generate unconventional phase diagrams encompassing fluid, gel and glassy states and offer the possibility to study new phase and/or state transitions. Among these, glass-glass transitions are rare to be found, especially at ambient conditions. Here, through a combination of dilution experiments, X-ray photon correlation spectroscopy, small angle X-ray scattering, rheological measurements and Monte Carlo simulations, we provide evidence of a spontaneous glass-glass transition in a colloidal clay. Two different glassy states are distinguished with evolving waiting time: a first one, dominated by long-range screened Coulombic repulsion (Wigner glass) and a second one, stabilized by orientational attractions (Disconnected House of Cards glass), occurring after a much longer time. These findings may have implications for heterogeneously charged systems out-of-equilibrium and for applications where a fine control of the local order and/or long term stability of the amorphous materials are required.

Angelini, Roberta; Zaccarelli, Emanuela; de Melo Marques, Flavio Augusto; Sztucki, Michael; Fluerasu, Andrei; Ruocco, Giancarlo; Ruzicka, Barbara

2014-06-01

410

Properties Of Soda/Yttria/Silica Glasses  

NASA Technical Reports Server (NTRS)

Experimental study of glass-formation compositional region of soda/ yttria/silicate system and of selected physical properties of glasses within compositional region part of continuing effort to identify glasses with high coefficients of thermal expansion and high softening temperatures, for use as coatings on superalloys and as glass-to-metal seals.

Angel, Paul W.; Hann, Raiford E.

1994-01-01

411

Initial stages of float glass corrosion  

Microsoft Academic Search

The differences between the corrosion process of the bath and the top side of float glass and the dependence on the corrosion process on the thickness of the glass could be demonstrated by ellipsometric measurements of defined corroded float glasses. The effectiveness of different cleaning procedures on corroded float glass surfaces is discussed. Ellipsometry can help determine suitable separating agent

M. Feldmann; R. Wei?mann

1997-01-01

412

Oxygen and silver diffusion into float glass  

Microsoft Academic Search

In the float glass process, molten glass is floated on a molten metallic tin bath, such that tin penetrates the glass surface. Consequently, the glass has distinctly two different faces; the tin-penetrated face (bottom face) and the opposite face (top face). In this paper, the effects of tin on oxygen and silver diffusion into the top and bottom faces of

Satoshi Takeda

2006-01-01

413

Supercooled Liquids and Glasses M. D. Ediger*  

E-print Network

. As described below, cooling a supercooled liquid below the glass transition temperature Tg produces a glassSupercooled Liquids and Glasses M. D. Ediger* Department of Chemistry, UniVersity of Wisconsin of recent progress in the study of supercooled liquids and glasses are presented in this review

Weeks, Eric R.

414

A simple window glass design chart  

Microsoft Academic Search

A recently published ASTM standard outlines procedures for determining the strength of glass products used in buildings as windows and cladding. The new standard uses structural mechanics relationships to define the strength of a wide range of products, including monolithic glass, laminated glass and insulating glass. While the new standard is thorough and accurate, it is also complex. The authors

Joseph E. Minor; H. Scott Norville

1998-01-01

415

EVA-glass interface bond stability  

NASA Technical Reports Server (NTRS)

The ethylene vinyl acetate/glass interface bond stability was investigated. Special methods to determine the structure of polymer/glass interface were developed. Structural changes related to hydrothermal degradation of polymer/glass interface are examined. Methods to inhibit the degradation reaction which occur at polymer/glass interface are developed.

Koenig, J. L.

1984-01-01

416

Galactic Hearts of Glass  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on image for larger graph

This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

Spitzer detected the same crystals in 20 additional galaxies, all belonging to a class called ultraluminous infrared galaxies. These extremely bright and dusty galaxies usually consist of two galaxies in the process of smashing into each other. Astronomers believe massive stars at the hearts of the galaxies are churning out clouds of silicate crystals. This phenomenon may represent a short-lived phase in the evolution of galactic mergers.

2006-01-01

417

Reinforced glass beamsReinforced glass beamsg Auteur Dr. Christian LOUTER 1  

E-print Network

Reinforced glass beamsReinforced glass beamsg EDCE Auteur Dr. Christian LOUTER 1 ENAC/EDCE 2011In contemporary architecture glass is increasinglyIn contemporary architecture glass is increasingly applied for structural components such as beamsapplied for structural components such as beams. However glass

418

Study of glass transition of metallic glasses by temperature-modulated differential scanning calorimetry (MDSC)  

Microsoft Academic Search

The glass transition behavior of several Zr- and Mg-based metallic glasses has been studied by temperature-modulated differential scanning calorimetry (MDSC). It is clearly demonstrated that the glass transition can be separated from crystallization for these glasses by MDSC. Some glass transitions that could not be observed by a conventional differential scanning calorimetry (DSC) have been detected. Furthermore, the complex change

Z. P Lu; Y Li; S. C Ng; Y. P Feng

2000-01-01

419

Crystallization during processing of nuclear waste glass  

SciTech Connect

In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glassmaking are reviewed.

Hrma, Pavel R.

2010-12-01

420

Ion implantation in silicate glasses  

SciTech Connect

This review examines the effects of ion implantation on the physical properties of silicate glasses, the compositional modifications that can be brought about, and the use of metal implants to form colloidal nanosize particles for increasing the nonlinear refractive index.

Arnold, G.W.

1993-12-01

421

Dispersion of barium gallogermanate glass.  

PubMed

Gallogermanate glasses are the subject of intense study as a result of their unique combination of physical and optical properties, including transmission from 0.4 to beyond 5.0 microm. These glasses can be easily made into large optics with high-index homogeneity for numerous U.S. Department of Defense and commercial visible-IR window applications such as reconnaissance, missile domes, IR countermeasures, avionics, and collision avoidance on automobiles. These applications require a knowledge of the refractive index of glass throughout the region of transmission. Consequently, we have measured the refractive index of BaO-Ga2O3-GeO2 glass from 0.4 to 5.0 microm and calculated the Sellmeier coefficients required for optical device design. PMID:11900015

Zelmon, David E; Bayya, Shyam S; Sanghera, Jasbinder S; Aggarwal, Ishwar D

2002-03-01

422

Fiber glass pulling. [in space  

NASA Technical Reports Server (NTRS)

Experiments were conducted to determine the viability of performing containerless glass fiber pulling in space. The optical transmission properties and glass-forming capabilities of the heavy metal fluorides are reviewed and the acoustic characteristics required for a molten glass levitation system are examined. The design limitations of, and necessary modifications to the acoustic levitation furnace used in the experiments are discussed in detail. Acoustic levitator force measurements were performed and a thermal map of the furnace was generated from thermocouple data. It was determined that the thermal capability of the furnace was inadequate to melt a glass sample in the center. The substitution of a 10 KW carbon monoxide laser for the original furnace heating elements resulted in improved melt heating.

Workman, Gary L.

1987-01-01

423

Formation of zirconium metallic glass.  

PubMed

Bulk metallic glasses are commonly produced by the rapid cooling of liquid alloys. They have emerged over the past decade as a novel class of materials, with attractive properties and technological promise. The bulk metallic glasses so far produced contain three or more component elements. These complex compositions are necessary to frustrate the crystallization of the liquid melt on cooling, but can also lead to phase separation, which is detrimental to the thermal and mechanical properties of metallic glasses. Here we report, using X-ray diffraction measurements, the formation of a bulk metallic glass from elemental zirconium at high static pressures and low temperatures (relative to its melting temperature at atmospheric pressure). Amorphous zirconium can be recovered at ambient conditions and demonstrates a superior thermal stability compared to amorphous alloys, which could lead to new high-temperature applications of amorphous metals. PMID:15254533

Zhang, Jianzhong; Zhao, Yusheng

2004-07-15

424

Fast Crystals and Strong Glasses  

SciTech Connect

This talk describes new results on model colloid systems that provide insight into the behavior of fundamental problems in colloid physics, and more generally, for other materials as well. By visualizing the nucleation and growth of colloid crystals, we find that the incipient crystallites are much more disordered than expected, leading to a larger diversity of crystal morphologies. When the entropic contribution of these diverse morphologies is included in the free energy, we are able to describe the behavior very well, and can predict the nucleation rate surprisingly accurately. The talk also describes the glass transition in deformable colloidal particles, and will show that when the internal elasticity of the particles is included, the colloidal glass transition mimics that of molecular glass formers much more completely. These results also suggest that the elasticity at the scale of the fundamental unit, either colloid particle or molecule, determines the nature of the glass transition, as described by the "fragility."

Weitz, David (Harvard) [Harvard

2009-11-04

425

Comparison of Macedon and Darwin glass  

USGS Publications Warehouse

Chemical analyses are presented for major and minor elements in two specimens of natural glass reported from Macedon, Victoria, and are compared with new analyses of glass from Mt. Darwin, Tasmania. One specimen of Macedon glass is dark, the other light; both are spongy with relatively large cavities of size uncommon in Darwin glass. Some of the new analyses of Darwin glass extend considerably the compositional range previously reported for Mg, Ni and Co. The chemical composition of Macedon glass cannot be distinguished from that of Darwin glass for any of twenty-five elements investigated. It appears possible that the two specimens of glass reported from Macedon may represent either two mislabelled pieces of Darwin glass, or else a separate natural occurrence of Darwin glass 560 km north of Mt. Darwin. ?? 1967.

Chapman, D.R.; Keil, K.; Annell, C.

1967-01-01

426

Glass Transitions: Opportunities and Challenges  

Microsoft Academic Search

\\u000a Glass transition is a time-dependent change in the state of a noncrystalline material. It often explains solid–liquid transformations\\u000a in foods and it may control changes in food structure and texture as well as chemical reactions. At temperatures around the\\u000a glass transition, an amorphous solid transforms to a supercooled liquid (rubber) which contributes to changes in molecular\\u000a mobility and flow properties

Yrjö H. Roos; Nattiga Silalai

427

Luminescence of powdered uranium glasses  

NASA Technical Reports Server (NTRS)

Measurement of cathodoluminescence and photoluminescence efficiencies in powdered borosilicate glasses having different particle size and different uranium content. Excitation with 100 to 350 keV electrons and with 253.7 nm light was found to produce identical absolute radiant exitance spectra in powdered samples. The most efficient glass was one containing 29.4 wt% B2O3, 58.8 wt% SiO2, 9.8 wt% Na2O and 2.0 wt% UO2.

Eubanks, A. G.; Mcgarrity, J. M.; Silverman, J.

1974-01-01

428

Driving bubbles out of glass  

NASA Technical Reports Server (NTRS)

Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

Mattox, D. M.

1981-01-01

429

The following document is the Dental Board of California's Dental Materials Fact Sheet. The Department of Consumer Affairs has no position with respect to the language of this Dental  

E-print Network

are amalgam, composite resin, glass ionomer cement, resin-ionomer cement, porcelain (ceramic), porcelain are compared in the attached matrix titled "Comparisons of Restorative Dental Materials." A Glossary of Terms

Klein, Ophir

430

Durability of simulated DWPF annealed glasses  

SciTech Connect

Simulated high-level waste glass samples of the DWPF projected compositions were annealed at various times and temperatures in order to develop time-temperature-transformation diagrams. These heat treated glasses were subjected to the Product Consistency Test (PCT) to evaluate glass durability. The B, Li, and Na concentrations in the leachate (the PCT results) were compared to the PCT results of the Environmental Assessment benchmark glass. Durability as a function of glass composition and crystallinity was also examined.

Andrews, M.K.; Cicero, C.A.; Marra, S.L.; Beam, D.C.

1993-01-01

431

Durability of simulated DWPF annealed glasses  

SciTech Connect

Simulated high-level waste glass samples of the DWPF projected compositions were annealed