Science.gov

Sample records for polyvinyl siloxane impression

  1. Comparison of the effect of different medicaments on surface reproduction of two commercially available Polyvinyl Siloxane impression materials - An Invitro Study

    PubMed Central

    Singh, Rina; Singh, Jagjit; Singh, Ramanpreet; Nanda, Sonia

    2013-01-01

    Objective:To determine the effect of different retraction cord medicaments on surface detail reproduction of polyvinyl siloxane impression materials and compare this effect on any two brands of commercially available polyvinyl siloxane impression materials. Material and methods: Four stainless steel dies were made according to ADA specification no.19. Three dies were treated with aluminium chloride (5%), ferric sulphate (13.3%) and epinephrine (0.1%) while the fourth one was left untreated to serve as control. Two impression materials (Dentsply and 3M ESPE) were used. Results: All the three medicaments adversely affected the surface detail reproduction of both the brands of the polyvinyl siloxane impression materials. These effects were statistically significant as compared to untreated control. The impressions of 3M ESPE brand have shown better surface detail reproduction as compared to Dentsply impression material. Conclusion: Surface detail reproduction of the polyvinyl siloxane impression materials is adversely affected by the retraction cord medicaments. The presence of moisture or any traces of the medicaments should be removed from the tooth surface to provide a dry field for the correct reproduction of the surface detail of these materials. Key words:Polyvinyl Siloxane, retraction cord medicaments, surface detail reproduction. PMID:24455069

  2. Effect of impression tray design and impression technique upon the accuracy of stone casts produced from a putty-wash polyvinyl siloxane impression material.

    PubMed

    Saunders, W P; Sharkey, S W; Smith, G M; Taylor, W G

    1991-10-01

    This study examined the accuracy of stone casts produced from impressions taken in stock polycarbonate trays, some of which had been strengthened with autopolymerizing polymethyl methacrylate resin. Three techniques were used to make the impression of an acrylic master model of the mandibular arch on which two extracoronal preparations for bridgework and one intracoronal inlay preparation had been carried out. Each preparation had been indented with a reference point for later measurement. The impression material was a putty-wash polyvinyl siloxane material. Five impressions were taken for each type of tray for each impression technique and these were cast in die-stone after 24 h. The distances between the points were measured with a reflex microscope and the means determined for each design of tray. The mean difference between casts produced from the various tray designs and the acrylic master model were determined for each of the distances between the three measuring points for the various impression techniques. Statistical analysis showed that, with the polycarbonate stock trays, there were significant differences between some of the modifications and between them and the acrylic model, for the three distances (P less than 0.05). These differences were limited to one measurement for one design of tray for each of the two-stage impression methods. With the one-stage technique the unreinforced tray and those reinforced with acrylic, over the heels and anteriorly, and the barred design were statistically significantly different from the acrylic model for measurement A-B.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1806594

  3. Comparative evaluation of dimensional accuracy of different polyvinyl siloxane putty-wash impression techniques-in vitro study.

    PubMed Central

    Dugal, Ramandeep; Railkar, Bhargavi; Musani, Smita

    2013-01-01

    Background: Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. The purpose of this in vitro study was to compare the dimensional accuracy of the casts obtained from one step double mix, two step double mix polyvinyl siloxane putty- wash impression techniques using three different spacer thicknesses (0.5mm, 1mm and 1.5mm), in order to determine the impression technique that displays the maximum linear dimensional accuracy. Materials & Methods: A Mild steel model with 2 abutment preparations was fabricated, and impressions were made 15 times with each technique. All impressions were made with an addition-reaction silicone impression material (Express, 3M ESPE) and customarily made perforated metal trays. The 1-step putty/light-body impressions were made with simultaneous use of putty and light-body materials. The 2-step putty/light-body impressions were made with 0.5-mm, 1mm and 1.5mm-thick metal-prefabricated spacer caps. The accuracy of the 4 different impression techniques was assessed by measuring 7 dimensions (intra- and inter abutment) (20-?m accuracy) on stone casts poured from the impressions of the mild steel model. The data were analyzed by one samplet test. Results: The stone dies obtained with all the techniques had significantly larger or smaller dimensions as compared to those of the mild steel model (P<0.05). The order for highest to lowest deviation from the mild steel model was: single step putty/light body, 2-step putty/light body with 0.5mm spacer thickness, 2-step putty/light body1.5mm spacer thickness, and 2-step putty/light body with 1mm spacer thickness. Significant differences among all of the groups for both absolute dimensions of the stone dies, and their standard deviations from the master model (P<0.05), were noted. Conclusions: The 2-step putty/light-body impression technique with 1mm spacer thickness was most dimensionally accurate impression methods in terms of resultant casts. How to cite this article: Dugal R, Railkar B, Musani S. Dimensional accuracy when making impressions is crucial to the quality of fixed prosthodontic treatment, and the impression technique is a critical factor affecting this accuracy. J Int Oral Health 2013;5(5):85-94. PMID:24324310

  4. Effect of reactive adhesives on the tensile bond strength of polyvinyl siloxane impression materials to methyl methacrylate tray material.

    PubMed

    Ona, Masahiro; Takahashi, Hidekazu; Sato, Masayuki; Igarashi, Yoshimasa; Wakabayashi, Noriyuki

    2010-05-01

    The effect of new adhesives on the bond strength of elastomeric impression materials to acrylic trays was evaluated. Two polyvinyl siloxane impression materials (Fusion and Imprinsis) with reactive adhesives and one (Examix) with a conventional adhesive were tested. Flat, double-sided plates of auto-polymerizing methyl methacrylate (10 x 10 x 2.5 mm) were prepared with one of the adhesives. Five specimens were prepared by injecting each impression material into a 2-mm gap between the two plates. Tensile tests were conducted until separation failure occurred. The mean bond strengths of Fusion (1.0 MPa) and Imprinsis (0.8 MPa) were significantly greater than that of Examix (0.2 MPa). On the contrary, one of five Fusion showed adhesive failure mode while all the Imprinsis exhibited mixed failure. The conflicting results were presumably attributed to the mean tear strength of Fusion (0.8 N/mm) being higher than that of Imprinsis (0.5 N/mm). PMID:20484844

  5. The accuracy of polyvinyl siloxane impressions made with standard and reinforced stock trays.

    PubMed

    Wassell, R W; Ibbetson, R J

    1991-06-01

    A laboratory investigation was done to assess the influence of proprietary stock trays on the accuracy of impressions recorded with heavy light-body (HL) and putty light-body (PL) wash impression techniques. Two brands of trays were tested and the same trays were reinforced with acrylic resin. Individual die accuracy and overall distortion of the resultant casts were assessed. PL impressions in both stock trays gave undersized buccolingual dimensions at the preparation finishing lines whereas reinforcing the trays reduced this distortion. Significant inaccuracy at the second molar was found for all trays when PL impressions were made. These distortions would have resulted in clinically unacceptable dies. HL impressions, regardless of tray type, produced highly accurate dies at this critical site. Resultant overall cast distortion was reduced, but not eliminated, by using reinforced trays with either PL or HL techniques. PMID:2072315

  6. Effect of impression tray design upon the accuracy of stone casts produced from a single-phase medium-bodied polyvinyl siloxane impression material.

    PubMed

    Saunders, W P; Sharkey, S W; Smith, G M; Taylor, W G

    1992-06-01

    The study examined the accuracy of stone casts produced from impressions taken in stock polycarbonate trays, some of which had been strengthened with autopolymerizing polymethyl methacrylate resin and four designs of custom-made trays. Impressions of an acrylic master model of the mandibular arch on which two extracoronal crown preparations and one intracoronal inlay preparation had been carried out were taken using a medium-bodied polyvinyl siloxane material. Each preparation had been intended with a reference point for later measurement. Five impressions were taken for each type of tray and these were cast in die-stone after 24 h. The distances between the points were measured with a reflex microscope and the means determined for each design of tray. The mean difference between casts produced from the various tray designs and the acrylic master model were determined for each of the distances between the three measuring points. Statistical analysis showed that, with the stock trays, there were no significant differences between any of the modifications, or between them and the acrylic model, for any of the three distances (P greater than 0.1). When the results from the custom-made trays were analysed there were statistical differences between the acrylic model and the casts from the unperforated tray with no stops (P = 0.02), and between the unperforated tray with no stops and the perforated with stops for the distance A-B (P less than 0.01). There were no other significant differences.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1624625

  7. Effect of five brands of latex gloves on the setting time of polyvinyl siloxane putty impression materials.

    PubMed

    Ravikumar, C M; Sangur, Rajashekar

    2012-01-01

    Addition silicone impression materials have been used as impression material for more than 20 years. Although they are among the most expensive impression materials, they became popular during the past decade as they have excellent physical properties. Prevention of infection is an important aspect in dental treatment since dental professionals are routinely exposed to the wide variety of microorganisms present in saliva. Gloves are the most common protective measure used during dental treatment. The gloves are mostly made of latex. In this study, we examine how the setting time of three types polyvinyl putty materials were affected by the use of five different brands of latex gloves and one brand of vinyl gloves. Each material was first mixed without wearing gloves according to the manufacturer's instructions. After the stipulated mixing time, the setting time was measured using the Vicat needle. The setting time is measured from the time of mixing till the time that the needle does not produce any indentation on the surface of the material. The putty material was then mixed with gloved hands (using the five different brands of latex gloves in turn) and the setting time was measured. Then the material was mixed with washed gloved hands, and the setting time was measured again. Finally, the material was mixed with vinyl gloved hands and the setting time was measured. The following conclusions were drawn from the study: Reprosil and Express showed significant variation in the setting time with the latex gloved hands.There was no significant variation in the setting time when material was mixed with unwashed vs washed gloved hands.Vinyl gloves did not significantly affect the setting time of any of the putty impression materials. PMID:22945711

  8. Effects of sulfur-based hemostatic agents and gingival retraction cords handled with latex gloves on the polymerization of polyvinyl siloxane impression materials

    PubMed Central

    MACHADO, Carlos Eduardo Palhares; GUEDES, Carlos Gramani

    2011-01-01

    Objectives This study investigated the possible interactions between three addition silicone materials (Express, Aquasil Ultra and Adsil), three hemostatic agents (ferric sulfate, StatGel FS; aluminum sulfate, GelCord; and aluminum chloride, Hemostop) and gingival retraction cords previously handled with latex gloves to determine whether direct contact with medicaments or indirect contamination by latex in conditions similar to those found in clinical practice inhibit or affect the setting of the impression materials. Material and Methods A portable device for the simultaneous test of several specimens was specifically developed for this study. Polymerization inhibition was analyzed by examination of the impressions and the molded surface. Ten trials were performed for each addition silicone material used in the study, at a total of 240 study samples. Results All the samples tested (N=240) were nonreactive regardless of the type of combination used. Conclusions Aluminum sulfate, ferric sulfate and aluminum chloride hemostatic solutions did not show any inhibitory potential on the addition silicone samples under study, and there were no changes in polymerization as a result of contact between addition silicone and retraction cords handled with latex gloves. PMID:22230998

  9. Polyvinyl siloxane: novel material for external nasal splinting.

    PubMed

    Jayakumar, N K; Rathnaprabhu, V; Ramesh, S; Parameswaran, A

    2016-01-01

    External nasal splinting is performed routinely after nasal bone fracture reductions, osteotomies, and rhinoplasties. Materials commonly used include plaster of Paris (POP), thermoplastic splints, self-adhesive padded aluminium splints, and Orthoplast, among many others. The disadvantages of these materials are described in this paper, and polyvinyl siloxane is recommended as an effective and more readily available alternative material to counter these pitfalls. PMID:26454773

  10. Evaluation of the Effect of Ultraviolet Disinfection on Dimensional Stability of the Polyvinyl Silioxane Impressions. an in-Vitro Study

    PubMed Central

    Godbole, Surekha R; Dahane, Trupti M; Nimonkar, Sharayu V

    2014-01-01

    Introduction: Infection control is an important concept in the present day practice of dentistry. The prosthodontists are at an added risk of transmission because of the infection spreading through the contaminated lab equipments while working in the lab. The purpose of this study is to evaluate the effect of UV light disinfection on dimensional stability of polyvinyl siloxane impressions. Materials and Methods : Impressions were made in perforated custom tray. After polymerization of impression, half the samples were disinfected in UV light and remaining samples were not subjected to disinfection and poured in die stone which served as control group. Linear dimensions were measured on the cast with travelling microscope of 0.001accuracy. Result : The result showed that UV light disinfectant showed no significant dimensional changes on impressions. Conclusion: Hence, it can be safely used to disinfect impressions in clinical prosthodontic procedures. PMID:25386528

  11. Thiol-Ene functionalized siloxanes for use as elastomeric dental impression materials

    PubMed Central

    Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

    2014-01-01

    Objectives Thiol- and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies. Methods Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The Tg, storage modulus, and creep behavior are determined by DMA. Results Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy. Significance Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and click nature. PMID:24553250

  12. Effects of implant angulation, material selection, and impression technique on impression accuracy: a preliminary laboratory study.

    PubMed

    Rutkunas, Vygandas; Sveikata, Kestutis; Savickas, Raimondas

    2012-01-01

    The aim of this preliminary laboratory study was to evaluate the effects of 5- and 25-degree implant angulations in simulated clinical casts on an impression's accuracy when using different impression materials and tray selections. A convenience sample of each implant angulation group was selected for both open and closed trays in combination with one polyether and two polyvinyl siloxane impression materials. The influence of material and technique appeared to be significant for both 5- and 25-degree angulations (P < .05), and increased angulation tended to decrease impression accuracy. The open-tray technique was more accurate with highly nonaxially oriented implants for the small sample size investigated. PMID:22930776

  13. Pressure produced on the residual maxillary alveolar ridge by different impression materials and tray design: an in vivo study.

    PubMed

    Reddy, Subash M; Mohan, Chenthil Arun; Vijitha, D; Balasubramanian, R; Satish, A; Kumar, Mahendira

    2013-12-01

    Increased ridge resorption may occur due to inappropriate pressure applied during final impression making phase of complete denture fabrication. This study was done to evaluate the pressure applied on the residual ridge while making impressions with two tray designs (with and without spacer) using, zinc oxide eugenol and light body polyvinyl siloxane impression material. Five edentulous subjects were randomly selected. For each of the five subjects four maxillary final impressions were made and were labelled as, Group A-Impression made with tray without spacer using zinc oxide eugenol impression, Group B-Impression made with tray with spacer using zinc oxide eugenol impression material, Group C-Impression made with tray without spacer using light body polyvinyl siloxane impression material, Group D-Impression made with tray with spacer using light body polyvinyl siloxane impression material. During the impression procedure a closed hydraulic system was used to remotely measure the pressures produced in three areas. The pressure produced were calibrated according to the micro strain record. Statistical comparisons of readings were done using t test and ANOVA. The acquired data revealed that ZOE produced an average pressures value of 26.534 and 72.05 microstrain, while light body PVS produced 11.430 and 37.584 microstrain value with and without spacer respectively. Significantly high values were recorded on the vault of the palate when using trays without spacer. The use of light body polyvinyl siloxane and zinc oxide eugenol impression material showed insignificant difference. Within the limitations of this study, tray design has a significantly effected on the pressures produced, while the impression materials does not have any significant difference. PMID:24431783

  14. An innovative impression technique for fabrication of a custom made ocular prosthesis

    PubMed Central

    Tripuraneni, Sunil Chandra; Vadapalli, Sriharsha Babu; Ravikiran, P; Nirupama, N

    2015-01-01

    Various impression and fitting techniques have been described in the past for restoring ocular defects. The present article describes a new direct impression technique for recording and rehabilitating ocular defects, by custom-made ocular prosthesis. All the techniques described in the history, mainly concentrated in recording the tissue surface of the defect, which made it difficult to contour the palpebral surface resulting in the poor esthetics of the prosthesis. The present impression technique uses heavy bodied polyvinyl siloxane impression material, which facilitates accurate recording of the tissue surface and the palpebral surface of the defect, resulting in the fabrication of functionally and esthetically acceptable prosthesis. PMID:26265651

  15. Two-piece impression procedure for implant-retained orbital prostheses.

    PubMed

    Ozcelik, Tuncer Burak; Yilmaz, Burak

    2012-01-01

    Obtaining an accurate impression of facial tissues with undercuts and extraoral implants has always been a challenge for both clinicians and patients. This report describes a three-step, two-piece technique that enables an accurate and comfortable impression of undercut tissues and extraoral implants in an orbital defect. An impression of the basal tissue surface of the defect area was made using a medium-body polyether impression material followed by an impression of the entire face of the patient made with a polyvinyl siloxane (PVS) impression material. First, the PVS impression material was removed; second, the impression posts were removed from the magnets; and third, the polyether impression was removed from the defect. The impression posts were attached to the implant analogs and placed in the negative spaces in the polyether impression. The polyether impression, which carries the implant analogs and impression posts, was placed in the PVS impression through the negative spaces. This technique minimizes trauma to the soft tissues and implants during impression making and also does not require additional materials. PMID:23057049

  16. Hydrophilicity of unset and set elastomeric impression materials.

    PubMed

    Rupp, Frank; Geis-Gerstorfer, Jurgen

    2010-01-01

    The aim of this study was to compare the initial hydrophilicity of unset and set elastomeric impression materials. Initial water contact angles were studied on thin unset and set films of one polyether and six polyvinyl siloxane (PVS) impression materials using high-resolution drop shape analysis at drop ages of 1 and 3 seconds. All unset PVS materials were very hydrophobic initially but showed different kinetics of hydrophilization. In contrast, the unset polyether was more hydrophilic initially but lacked distinct hydrophilization. All impression materials showed statistically significant contact angle differences between unset and set surfaces (P < .05). Dependent on the drop age, two PVS materials reached or exceeded the hydrophilicity of the polyether (P < .05). It can be concluded that studies on the wetting behavior of elastomeric impression materials should consider both the experimental drop age and set and unset material surfaces. PMID:21209992

  17. Wettability of impression materials treated with disinfectants.

    PubMed

    DeWald, J P; Nakajima, H; Schniederman, E; Okabe, T

    1992-04-01

    The purpose of this investigation was to comprehensively compare various combinations of impression materials, die stones and disinfectants so as to provide clinical guidelines for selection of materials. The effect of immersion disinfection on the wettability of five types of impression materials, polyether, light-cured polyether urethane dimethacrylate, polysulfide, hydrophilic and hydrophobic polyvinyl siloxanes, was evaluated. This evaluation was determined by contact angle measurement of two die stones on the impression materials and also by bubble formation in casts made from the same materials after disinfection. The disinfectants utilized were 0.5% sodium hypochlorite and 0.13% glutaraldehyde-phenate. There were significant interactive effects (P less than 0.02) on contact angle between stone and disinfectant, impression and disinfectant, and impression and stone. The effect of disinfection was found to vary among impression materials. Although there was a significant correlation found between contact angle and bubble formation, contact angle was not found to be a strong predictor of bubble formation in this study. For these findings, it is recommended to evaluate each disinfectant and impression material combination individually. PMID:1524745

  18. The persistence of microorganisms on impression materials following disinfection.

    PubMed

    Jennings, K J; Samaranayake, L P

    1991-01-01

    Following in vitro inoculation with C albicans or P aeruginosa, three impression materials--polysulfide rubber, irreversible hydrocolloid, and poly(vinyl siloxane)--were disinfected with either 0.1% or 0.02% chlorhexidine gluconate and a quantitative assessment of the microorganisms was made. Very few microorganisms were retained on the poly(vinyl siloxane) material immediately after microbial inoculation. The numbers of microorganisms on polysulfide impression materials diminished rapidly with time even without disinfection, and a 30-minute disinfection procedure resulted in total microbe elimination. With irreversible hydrocolloid, microorganisms persisted and disinfection procedures were considerably less effective. When the disinfection efficacy of three commercially available agents was compared using irreversible hydrocolloid impression material, chlorhexidine gluconate (0.2%) was found to be less effective than either glutaraldehyde (2%) or sodium hypochlorite (0.0125%); the latter two agents were comparable in their antimicrobial effect. Thus, a simple disinfection regime of 30 minutes with commonly available disinfectants may be effective in eliminating cross-contamination from impression materials. PMID:1811634

  19. Effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts

    PubMed Central

    Ebadian, Behnaz; Rismanchian, Mansor; Dastgheib, Badrosadat; Bajoghli, Farshad

    2015-01-01

    Background: Different factors such as impression techniques and materials can affect the passive fit between the superstructure and implant. The aim of this study was to determine the effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts. Materials and Methods: Four internal hex implants (Biohorizons 4 mm) were placed on a metal maxillary model perpendicular to the horizontal plane in maxillary lateral incisors, right canine and left first premolar areas. Three impression techniques including open tray, closed tray using ball top screw abutments and closed tray using short impression copings and two impression materials (polyether and polyvinyl siloxane) were evaluated (n = 60). The changes in distances between implant analogues in mediolateral (x) and anteroposterior (y) directions and analogue angles in x/z and y/z directions in the horizontal plane on the definitive casts were measured by coordinate measuring machine. The data were analyzed by multivariate two-way analysis of variance and one sample t-test (? = 0.05). Results: No statistical significant differences were observed between different impression techniques and materials. However, deviation and distortion of definitive casts had a significant difference with the master model when short impression copings and polyvinyl siloxane impression material were used (P < 0.05). In open tray technique, there was a significant difference in the rotation of analogs compared with the master model with both impression materials (P < 0.05). Conclusion: There was no difference between open and closed tray impression techniques; however, less distortion and deviation were observed in the open tray technique. In the closed tray impression technique, ball top screw was more accurate than short impression copings. PMID:25878678

  20. Effect of disinfection of custom tray materials on adhesive properties of several impression material systems.

    PubMed

    Thompson, G A; Vermilyea, S G; Agar, J R

    1994-12-01

    The effects of impression tray disinfection procedures on the bond strength of impression-material adhesives to two types of resin trays were evaluated with a tensile test. Autopolymerizing acrylic resin and a visible light-curing resin were formed into one-half inch cubes. A screw eye was attached to each cube before polymerization. Perforated trays were fabricated with stops to maintain an even one-eighth inch of impression material over the resin block. Hooks on the opposite side permitted attachment of the metal plate to a mechanical testing machine. Before adhesive was applied, one third of the resin specimens were immersed in a 1:213 iodophor solution; one third in a 10% sodium hypochlorite solution, and one third were kept in the "as fabricated" condition. Polysulfide, polyether, and polyvinyl siloxane impression material-adhesive systems were evaluated. The resin-impression material-metal plate couples were attached to a mechanical testing machine and tensile forces were applied at a separation rate of 5 inches per minute. Mean values for adhesive strength ranged from 3.49 kg/cm2 for the autopolymerizing acrylic resin/iodophor/polyether combination to 10.55 kg/cm2 for the autopolymerizing acrylic resin/untreated/polyvinyl siloxane combination. Differences were detected among materials and disinfecting procedure. Clinically, disinfection of resin trays may adversely affect retention of the impression material to the tray. PMID:7853264

  1. An Investigation into the Accuracy of Two Currently Available Dental Impression Materials in the Construction of Cobalt-Chromium Frameworks for Removable Partial Dentures.

    PubMed

    Dubal, Rajesh Kumar; Friel, Tim; Taylor, Philip D

    2015-03-01

    This study investigated the suitability of irreversible hydrocolloid as an impression material for cobalt-chromium framework construction. Scans of casts derived from (1) alginate and (2) addition-cured polyvinylsiloxane impressions were superposed on to a control. The differences within and between groups were compared at fixed landmarks. The investigation revealed a high degree of scan coincidence within and between groups. However, certain features, such as undercuts, resulted in a lower degree of scan coincidence. Irreversible hydrocolloid appears to be a viable alternative to addition-cured polyvinyl-siloxane as an impression material for cobalt-chromium framework construction. PMID:26415334

  2. Effect of splinting in accuracy of two implant impression techniques.

    PubMed

    de Avila, Erica Dorigatti; de Matos Moraes, Fernanda; Castanharo, Sabrina Maria; Del'Acqua, Marcelo Antonialli; de Assis Mollo, Francisco

    2014-12-01

    Because there is no consensus in the literature about the need for a splint between copings, the aim of this study was to evaluate, in vitro, the accuracy of 2 impression techniques for implant-supported prostheses. A master cast was fabricated with four parallel implant abutment analogs and a passive framework. Two groups with 5 casts each were formed: Group 1 (squared impression copings with no splint: S) and Group 2 (splinted squared impression copings, using metal drill burs and Pattern resin: SS). The impression material used was polyvinyl siloxane with open trays for standard preparation of the casts. For each cast, the framework was positioned, and a titanium screw was tightened with 10 Ncm torque in analog A, after which measurements of the abutment-framework interface gaps were performed at analogs C and D. This process was repeated for analog D. These measurements were analyzed using software. A one-way analysis of variance (ANOVA) with a confidence interval of 95% was used to analyze the data. Significant differences were detected between S and SS in relation to the master cast (P ? 0.05). The median values of the abutment-framework interface gaps were as follows: master cast: 39.64 ?m; squared impression copings with no splint: 205.86 ?m; splinted squared impression copings: 99.19 ?m. Under the limitations of this study, the technique presented for Group 2 produces better results compared with the technique used for Group 1. PMID:25506658

  3. Accuracy of different impression materials in parallel and nonparallel implants

    PubMed Central

    Vojdani, Mahroo; Torabi, Kianoosh; Ansarifard, Elham

    2015-01-01

    Background: A precise impression is mandatory to obtain passive fit in implant-supported prostheses. The aim of this study was to compare the accuracy of three impression materials in both parallel and nonparallel implant positions. Materials and Methods: In this experimental study, two partial dentate maxillary acrylic models with four implant analogues in canines and lateral incisors areas were used. One model was simulating the parallel condition and the other nonparallel one, in which implants were tilted 30° bucally and 20° in either mesial or distal directions. Thirty stone casts were made from each model using polyether (Impregum), additional silicone (Monopren) and vinyl siloxanether (Identium), with open tray technique. The distortion values in three-dimensions (X, Y and Z-axis) were measured by coordinate measuring machine. Two-way analysis of variance (ANOVA), one-way ANOVA and Tukey tests were used for data analysis (α = 0.05). Results: Under parallel condition, all the materials showed comparable, accurate casts (P = 0.74). In the presence of angulated implants, while Monopren showed more accurate results compared to Impregum (P = 0.01), Identium yielded almost similar results to those produced by Impregum (P = 0.27) and Monopren (P = 0.26). Conclusion: Within the limitations of this study, in parallel conditions, the type of impression material cannot affect the accuracy of the implant impressions; however, in nonparallel conditions, polyvinyl siloxane is shown to be a better choice, followed by vinyl siloxanether and polyether respectively. PMID:26288620

  4. Effect of Splinting in Accuracy of Two Implant Impression Techniques.

    PubMed

    Avila, Erica Dorigatti; Moraes, Fernanda de Matos; Castanharo, Sabrina Maria; Del Acqua, Marcelo Antonialli; Mollo Junior, Francisco Assis

    2012-10-26

    Abstract Purpose: Because there is no consensus in the literature about the need for a splint between copings, the aim of this study was to evaluate, in vitro, the accuracy of two impression techniques for implant-supported prostheses. Methods: A master cast was fabricated with four parallel implant abutment analogs and a passive framework. Two groups with five casts each were formed: Group 1 (squared impression copings with no splint - S) and Group 2 (splinted squared impression copings, using metal drill burs and Pattern resin - SS). The impression material used was polyvinyl siloxane with open trays, for standard preparation of the casts. For each cast, the framework was positioned, and a titanium screw was tightened with 10 N*cm torque in analog A, after which measurements of the abutment-framework interface gaps were performed at analogs C and D. This process was repeated for analog D. These measurements were analyzed using software (Leica QWin, Leica Imaging Systems). A one-way analysis of variance (ANOVA) with a confidence interval of 95% was used to analyze the data. Results: Significant differences were detected between S and SS in relation to the master cast (P ? 0,05). The median values of the abutment/framework interface gaps were as follows: master cast: 39,64?m; squared impression copings with no splint: 205, 86?m; splinted squared impression copings: 99,19?m. Conclusion: Under the limitations of this study, the technique presented for Group 2 produces better results compared with the technique used for group 1. PMID:23101476

  5. Three-dimensional accuracy of different impression techniques for dental implants

    PubMed Central

    Nakhaei, Mohammadreza; Madani, Azam S; Moraditalab, Azizollah; Haghi, Hamidreza Rajati

    2015-01-01

    Background: Accurate impression making is an essential prerequisite for achieving a passive fit between the implant and the superstructure. The aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques. Materials and Methods: Three acrylic resin mandibular master models with four parallel implants were used: Biohorizons (BIO), Straumann tissue-level (STL), and Straumann bone-level (SBL). Forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. Closed-tray impressions were made using snap-on (STL model), transfer coping (TC) (BIO model) and TC plus plastic cap (TC-Cap) (SBL model). The impressions were poured with type IV stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (?R) were evaluated using a coordinate measuring machine. Data were analyzed using ANOVA and post-hoc Tukey tests (? = 0.05). Results: The ?R values of the snap-on technique were significantly lower than those of TC and TC-Cap techniques (P < 0.001). No significant differences were found between closed and open impression techniques for STL in ?x, ?y, ?z and ?R values (P = 0.444, P = 0.181, P = 0.835 and P = 0.911, respectively). Conclusion: Considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than TC and TC-Cap, but it was similar to the open-tray technique. PMID:26604956

  6. Polyimides containing pendent siloxane groups

    NASA Technical Reports Server (NTRS)

    Connell, John W. (inventor); St.clair, Terry L. (inventor); Hergenrother, Paul M. (inventor)

    1994-01-01

    Novel polyimides containing pendent siloxane groups (PISOX) were prepared by the reaction of functionalized siloxane compounds with hydroxy containing polyimides (PIOH). The pendent siloxane groups on the polyimide backbone offer distinct advantages such as lowering the dielectric constant and moisture resistance and enhanced atomic oxygen resistance. The siloxane containing polyimides are potentially useful as protective silicon oxide coatings and are useful for a variety of applications where atomic oxygen resistance is needed.

  7. Acetylene-Terminated Polyimide Siloxanes

    NASA Technical Reports Server (NTRS)

    St. Clair, Terry L.; Maudgal, Shubba

    1987-01-01

    Siloxane-containing addition polyimides yield toughened high-temperature adhesives and matrix resins. Addition polyimide made by reaction of aromatic tetracarboxylic acid dianhydride with aromatic diamine in presence of ethynyl-substituted aromatic monoamine. Acetylene-terminated siloxane imide cured by heating to yield acetylene-terminated polyimide siloxane.

  8. Siloxane-grafted membranes

    DOEpatents

    Friesen, D.T.; Obligin, A.S.

    1989-10-31

    Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional group. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

  9. Siloxane-grafted membranes

    DOEpatents

    Friesen, Dwayne T. (Bend, OR); Obligin, Alan S. (Catonville, MD)

    1989-01-01

    Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional groups. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

  10. Comparison of dimensional accuracy of digital dental models produced from scanned impressions and scanned stone casts

    NASA Astrophysics Data System (ADS)

    Subeihi, Haitham

    Introduction: Digital models of dental arches play a more and more important role in dentistry. A digital dental model can be generated by directly scanning intraoral structures, by scanning a conventional impression of oral structures or by scanning a stone cast poured from the conventional impression. An accurate digital scan model is a fundamental part for the fabrication of dental restorations. Aims: 1. To compare the dimensional accuracy of digital dental models produced by scanning of impressions versus scanning of stone casts. 2. To compare the dimensional accuracy of digital dental models produced by scanning of impressions made of three different materials (polyvinyl siloxane, polyether or vinyl polyether silicone). Methods and Materials: This laboratory study included taking addition silicone, polyether and vinyl polyether silicone impressions from an epoxy reference model that was created from an original typodont. Teeth number 28 and 30 on the typodont with a missing tooth number 29 were prepared for a metal-ceramic three-unit fixed dental prosthesis with tooth #29 being a pontic. After tooth preparation, an epoxy resin reference model was fabricated by duplicating the typodont quadrant that included the tooth preparations. From this reference model 12 polyvinyl siloxane impressions, 12 polyether impressions and 12 vinyl polyether silicone impressions were made. All 36 impressions were scanned before pouring them with dental stone. The 36 dental stone casts were, in turn, scanned to produce digital models. A reference digital model was made by scanning the reference model. Six groups of digital models were produced. Three groups were made by scanning of the impressions obtained with the three different materials, the other three groups involved the scanning of the dental casts that resulted from pouring the impressions made with the three different materials. Groups of digital models were compared using Root Mean Squares (RMS) in terms of their dimensional accuracy, which is defined as the absolute value of deviation in micrometers from the reference model. A two-way analysis of analysis of variance (ANOVA) was applied to calculate if the measurements for the six test groups were statistically significantly different from the original reference model as well as between test groups (p <.05). Tukey's HSD was also applied to characterize the differences. Results: The mean (± SD) RMS was 29.42 ± 5.80 microns for digital models produced from polyether impression scans, 27.58 ± 5.85 microns for digital models from PVS impressions scans, and 24.08 ± 4.89 microns for digital models produced from VPES impressions scans. 26.08 ± 6.58 microns for digital models produced by scanning stone casts poured from PE, 31.67 ± 9.95 microns for digital models produced by scanning stone casts poured from PVS and 22.58 ± 2.84 microns for digital models produced by scanning stone casts poured from VPES. In the Two-Way ANOVA, the p-value for the material factor was 0.004, reflecting a statistically significant difference between the accuracy of the three impression materials, with VPES showing the highest accuracy (mean RMS = 23.33 ± 3.99 microns) followed by PE (mean RMS = 27.75 ± 6.3 microns) and PVS (mean RMS = 29.63 ± 8.25 microns). For the technique factor, the p-value was 0.870 reflecting no statistically significant difference between the accuracy of the two techniques (impression scan and stone cast scan). The mean RMS values were 27.03 ± 5.82 microns and 26.78 ± 7.85 microns, respectively. In the post-hoc tests for the material factor, a significant difference was found between the accuracy of VPES and PVS (p-value = 0.004) with VPES having the higher accuracy (lower mean RMS). No significant difference was found between the accuracies of PE and PVS (p-value = 0.576), and between the accuracies of PE and VPES (p-value = 0.054). Conclusions: Within the limitations of this in vitro study, it can be concluded that: 1. There is no statistically significant difference in dimensional accuracy between digital models produced by scanning dental impressions and those produced by scanning stone casts. 2. Digital models produced from the scans of VPES impressions are dimensionally more accurate than those produced from PVS impressions scans. No significant difference in accuracy was observed between PE and PVS impression scans, or between PE and VPES impression scans.

  11. First Impressions.

    ERIC Educational Resources Information Center

    Coen, Frank

    1969-01-01

    The unreliability of first impressions and subjective judgments is the subject of both Jane Austen's "Pride and Prejudice" and Lionel Trilling's "Of This Time, Of That Place"; consequently, the works are worthwhile parallel studies for high school students. Austen, by means of irony and subtle characterization, dramatizes the need for constant…

  12. Dinosaur Impressions

    NASA Astrophysics Data System (ADS)

    Taquet, Philippe

    1998-09-01

    Perhaps you are a paleontologist or have always wondered what it is like to be one. Or you are fascinated by fossils and like to read about the origins and natural history of dinosaurs. Or maybe you are an avid traveler and reader of travelogues. If you are any of these things, then this book is for you. Originally published in 1994 in French, Dinosaur Impressions is the engaging account of thirty years of travel and paleontological exploration by Philippe Taquet, one of the world's most noted paleontologists. Dr. Taquet takes the reader on a surprisingly far-flung tour ranging from the Provence countryside to the Niger desert, from the Brazilian bush to the Mongolian Steppes, and from the Laos jungle to the Moroccan mountains in search of dinosaur bones and what they have to tell us about a vanished world. With wry humor and lively anecdotes, Dr. Taquet retraces the history of paleontological research, along the way discussing the latest theories of dinosaur existence and extinction. Elegantly translated by Kevin Padian, Dinosaur Impressions provides a unique, thoughtful perspective not often encountered in American- and English-language works. This insightful, first-hand account of an exceptional career is also a travelogue par excellence that will enthrall enthusiasts and general readers alike. Philippe Taquet is the Director of the National Museum of Natural History in Paris and is a member of the French Academy of Sciences. Kevin Padian is a professor in the Department of Integrative Biology and Curator of the Museum of Paleontology at the University of California, Berkeley. He is also the editor of The Beginning of the Age of Dinosaurs (Cambridge, 1986) and The Encyclopedia of Dinosaurs (1997).

  13. Dual-arch impressions.

    PubMed

    Bass, E V; Kafalias, M C

    1992-02-01

    All dual-arch impression techniques utilize special stock impression trays of various designs. These trays are made of flexible plastic with fabric or mesh material placed across the occlusal surfaces of the teeth connecting their buccal and lingual flanges. The presence of this material will result in errors by (1) not allowing complete intercuspation during impression-taking; (2) producing incorrect recording of centric occlusion; and (3) because of the elastic memory of the tray/fabric, creating distortion of the elastic impression material. An impression technique is presented which provides a simple and effective method of obtaining dual-arch impressions for single restorations, post and cores, and small bridges. This technique obivates the need for impression trays thus eliminating the errors outlined. PMID:1567288

  14. TOWARD MINIMALLY ADHESIVE SURFACES UTILIZING SILOXANES

    EPA Science Inventory

    Three types of siloxane-based network polymers have been investigated for their surface properties towards potential applications as minimally adhesive coatings. A filled poly(dimethylsiloxane) (PDMS) elastomer, RTV it, has been studied to determine surface weldability and stabil...

  15. Synthesis, Characterization, Topographical Modification, and Surface Properties of Copoly(Imide Siloxane)s

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Atkins, Brad M.; Belcher, Marcus A.; Connell, John W.

    2012-01-01

    Novel copoly(imide siloxane)s were synthesized from commercially available aminopropyl terminated siloxane oligomers, aromatic dianhydrides, and diamines. This synthetic approach produced copolymers with well-defined siloxane blocks linked with imide units in a random fashion. The copoly(amide acid)s were characterized by solution viscosity and subsequently used to cast thin films followed by thermal imidization in an inert atmosphere. Thin films were characterized using contact angle goniometry, attenuated total reflection Fourier transform infrared spectroscopy, confocal and optical microscopy, and tensile testing. Adhesion of micronsized particles was determined quantitatively using a sonication device. The polydimethylsiloxane (PDMS) moieties lowered the copolymer surface energy due to migration of siloxane moieties to the film s surface, resulting in a notable reduction in particle adhesion. A further reduction in particle adhesion was achieved by introducing topographical features on a scale of several to tens of microns by a laser ablation technique.

  16. ETI: Our first impressions

    NASA Astrophysics Data System (ADS)

    Harrison, Albert A.; Johnson, Joel T.

    2000-06-01

    Despite scant or ambiguous information, people are capable of developing comprehensive and detailed impressions. Consequently, if the detection of an electromagnetically-active civilization is announced, many people will rapidly form impressions of what the extraterrestrials and their civilization are "like". First impressions are crucial, not only because of their immediate psychological, social, and political consequences on Earth, but because they can influence the future of interstellar communication. Initial impressions will rest less on hard data than on the nature and tone of the "evidence" that is gleaned from the transmission; the interpretation and dissemination of this evidence; and the hard wiring, psychological programming, cultural conditioning, and social influence processes that shape human perception. We consider how dispositional inferences, implicit theories of personality, negatively toned or adverse information, physical appearance, prior expectations, the confirmation bias, and thinking and unthinking approaches to attitude formation are likely to affect human impressions of ETI.

  17. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  18. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  19. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  20. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  1. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  2. Impression block with orientator

    NASA Astrophysics Data System (ADS)

    Brilin, V. I.; Ulyanova, O. S.

    2015-02-01

    Tool review, namely the impression block, applied to check the shape and size of the top of fish as well as to determine the appropriate tool for fishing operation was realized. For multiple application and obtaining of the impress depth of 3 cm and more, the standard volumetric impression blocks with fix rods are used. However, the registered impress of fish is not oriented in space and the rods during fishing are in the extended position. This leads to rods deformation and sinking due to accidental impacts of impression block over the borehole irregularity and finally results in faulty detection of the top end of fishing object in hole. The impression blocks with copy rods and fixed magnetic needle allow estimating the object configuration and fix the position of magnetic needle determining the position of the top end of object in hole. However, the magnetic needle fixation is realized in staged and the rods are in extended position during fishing operations as well as it is in standard design. The most efficient tool is the impression block with copy rods which directs the examined object in the borehole during readings of magnetic needles data from azimuth plate and averaging of readings. This significantly increases the accuracy of fishing toll direction. The rods during fishing are located in the body and extended only when they reach the top of fishing object.

  3. Self-assembling particle-siloxane coatings for superhydrophobic concrete.

    PubMed

    Flores-Vivian, Ismael; Hejazi, Vahid; Kozhukhova, Marina I; Nosonovsky, Michael; Sobolev, Konstantin

    2013-12-26

    We report here, for the first time in the literature, a method to synthesize hydrophobic and superhydrophobic concrete. Concrete is normally a hydrophilic material, which significantly reduces the durability of concrete structures and pavements. To synthesize water-repellent concrete, hydrophobic emulsions were fabricated and applied on portland cement mortar tiles. The emulsion was enriched with the polymethyl-hydrogen siloxane oil hydrophobic agent as well as metakaolin (MK) or silica fume (SF) to induce the microroughness and polyvinyl alcohol (PVA) fibers to create hierarchical surfaces. Various emulsion types were investigated by using different mixing procedures, and single- and double-layer hydrophobic coatings were applied. The emulsions and coatings were characterized with optical microscope and scanning electron microscope (SEM), and their wetting properties, including the water contact angle (CA) and roll-off angle, were measured. A theoretical model for coated and non-coated concrete, which can be generalized for other types of materials, was developed to predict the effect of surface roughness and composition on the CA. An optimized distance between the aggregates was found where the CA has the highest value. The maximal CA measured was 156 for the specimen with PVA fibers treated with MK based emulsion. Since water penetration is the main factor leading to concrete deterioration, hydrophobic water-repellent concretes have much longer durability then regular concretes and can have a broad range of applications in civil and materials engineering. PMID:24245777

  4. Evidence for a sedimentary siloxane horizon

    SciTech Connect

    Pellenbarg, R.E.; Tevault, D.E.

    1986-07-01

    Selected samples from two Puget Sound sediment cores have been analyzed for poly(organo)siloxanes(silicones). One core was 60 years old at 30-cm depth (ages by lead-210 dating) and showed no evidence for silicones there. The second, 15 years old at depth, exhibited silicones at depth. Clearly shown is evidence for a siloxane horizon in theses two cores, with the presence of the horizon directly related to the fact that silicones have been in widespread use only since World War II. All samples were analyzed by solvent extraction and diffuse reflectance Fourier transform infrared spectrometry. 10 references, 2 figures, 1 table.

  5. Impression materials and virus.

    PubMed

    Gerhardt, D E; Sydiskis, R J

    1991-05-01

    Results of this study indicate that impression materials vary in their ability to absorb and retain virus. Disinfection procedures specific for each material or groups of materials should be developed. PMID:2045601

  6. Copoly(Imide Siloxane) Abhesive Materials with Varied Siloxane Oligomer Length

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Atkins, Brad M.; Belcher, Marcus A.; Connell, John W.

    2010-01-01

    Incorporation of PDMS moieties into a polyimide matrix lowered the surface energy resulting in enhanced adhesive interactions. Polyimide siloxane materials were generated using amine-terminated PDMS oligomers of different lengths to study changes in surface migration behavior, phase segregation, mechanical, thermal, and optical properties. These materials were characterized using contact angle goniometry, tensile testing, and differential scanning calorimetry. The surface migration behavior of the PDMS component depended upon the siloxane molecular weight as indicated by distinct relationships between PDMS chain length and advancing water contact angles. Similar correlations were observed for percent elongation values obtained from tensile testing, while the addition of PDMS reduced the modulus. High fidelity topographical modification via laser ablation patterning further reduced the polyimide siloxane surface energy. Initial particulate adhesion testing experiments demonstrated that polyimide siloxane materials exhibited greater abhesive interactions relative to their respective homopolyimides.

  7. [Elastomeric impression materials].

    PubMed

    Levartovsky, S; Folkman, M; Alter, E; Pilo, R

    2011-04-01

    Elastomeric impression materials are in common use. The impression taken should be highly precise, thus, requiring specific care when manipulatingthese materials. There are 4 groups of elastomers; polysulfide, condensation silicone, addition silicone and polyether; each differ in their setting mechanism and their physical and chemical properties. This review elaborates the major properties of elastomers and its implications on their use. The impression material is inserted into the patient's mouth in a viscous state and transforms into viscoelastic state, upon withdrawal, influencing the residual deformation. The requirements are minimal residual deformation or maximal elastic recovery. As the mouth is a wet environment a major consideration is hydrophilicity. The wettability which is estimated by measuring either the contact angle of a droplet of water and the substrate post setting or the contact angle of a droplet of impression material and the wet tooth pre setting, determines the interaction of the material with both mouth fluids and gypsum. As the primary end target is to obtain a model depicting accurately the oral details, an attention to the impressions' compatibility with gypsum should also be given. Many studies were conducted to get a thorough understanding of the hydrophilic properties of each material, and the mechanism utilized, such as surfactants in hydrophilic PVS. Polyether is the only material that is truly hydrophilic; it exhibits the lowest contact angle, during and after setting. Recent studies show that during setting the Polyether hydrophilicity is increased compared to the condition after setting. Dimensional stability, a crucial property of the impression, is affected by the physical and chemical attributes of the material, such as its tear strength. Polysulfide has the highest tear strength. Tear Strength is affected by two major parameters, viscosity, a built-in property, and how fast the impression is pulled out of the mouth, the faster the impression is loaded and pulled out, the higher the tear strength is. The clinical use is dictated from the properties of each impression material, and the understanding of those enables the practitioner to minimize failures. PMID:21848031

  8. Alginate impressions: A practical perspective

    PubMed Central

    Nandini, V Vidyashree; Venkatesh, K Vijay; Nair, K Chandrasekharan

    2008-01-01

    The choice of an impression material for a particular situation depends on the treatment being provided, operator preference, and so on. Even with the introduction of more advanced and more accurate rubber base impression materials, irreversible hydrocolloid impression materials have stood the test of time. This article gives a detailed perspective of how best to make alginate impressions. PMID:20142882

  9. Copoly(imide siloxane) Abhesive Materials with Varied Siloxane Oligomer Length

    NASA Technical Reports Server (NTRS)

    Wohl, Christoper J.; Atkins, Brad M.; Lin, Yi; Belcher, Marcus A.; Connell, John W.

    2010-01-01

    In this work, low surface energy copoly(imide siloxane)s were synthesized with various siloxane segment lengths. Characterization of these materials revealed that domain formation of the low surface energy component within the matrix was more prevalent for longer siloxane segments as indicated by increased opacity, decreased mechanical properties, and variation of the Tg. Incorporation of siloxanes lowered the polymer s surface energy as indicated by water contact angle values. Topographical modification of these materials by laser ablation patterning further reduced the surface energy, even generating superhydrophobic surfaces. Combined, the contact angle data and particle adhesion testing indicated that copoly(imide siloxane) materials may provide greater mitigation to particulate adhesion than polyimide materials alone. These enhanced surface properties for abhesive applications did result in a reduction of the tensile moduli of the copolymers. It is possible that lower siloxane loading levels would result in retention of the mechanical properties of the polyimide while still affording abhesive surface properties. This hypothesis is currently being investigated. Laser ablation patterning offers further reduction in particle retention as the available surface area for particle adhesion is reduced. Pattern variation and size dependencies are currently being evaluated. For the purposes of lunar dust adhesion mitigation, it is likely that this approach, termed passive due to the lack of input from an external energy source, would not be sufficient to mitigate surface contamination or clean contaminated surfaces for some lunar applications. It is feasible to combine these materials with active mitigation strategies - methods that utilize input from external energy sources - would broaden the applicability of such materials for abhesive purposes. Collaborative efforts along these lines have been initiated with researchers at NASA Kennedy Space Center where experiments are being conducted involving a series of embedded electrodes within polymeric matrices.

  10. Siloxane treatment by adsorption into porous materials.

    PubMed

    Ricaurte Ortega, D; Subrenat, A

    2009-09-01

    Siloxanes are widely used in different applications: health care, dry cleaning, household products, paints and coatings, paper, personal care, for example. This explains their prevalence in the environment. Because of their volatile nature, most of the time they are dispersed in the atmosphere, but they can also be present in the slurry from landfills. During anaerobic digestion, when the temperature goes up to 60 degrees C, siloxanes are volatilized, forming part of the biogas. Operational problems using biogas to produce energy, heat and hydrogen have been identified. At high temperatures the siloxanes are transformed into silicate dioxide (commonly called sand transmission). These white deposits may adhere to metal or catalytic substrate surfaces, seriously reducing equipment efficiency, and this can be a reason for changing equipment warranties. Consequently, elimination of siloxanes has become very important. Unfortunately, relatively little information can be found on this subject. Nevertheless some authors have described different analytical methods for siloxane quantification, and recent studies have looked at the presence of siloxanes in landfills and the restriction on the energy recovery equipment using the biogas produced. The growing consumption of siloxanes and silicones in industrial processes consequently increase their prevalence in the environment, hampering the use of biogas as a source of 'green energy'. Therefore, the principal focus of this study is the treatment of siloxanes. Their elimination was carried out using an adsorption process with four different porous materials: activated carbon cloths (ACC), granular activated carbon (GAC), zeolite and silica gel. Two representative siloxane compounds were used in this study, hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4). Adsorption kinetics and isotherms in batch reactors were performed. It was observed that the mass transfer into the porous material was more rapid for the activated carbon than for the zeolite and silica gel, congruent with the porous structure of the material. Moreover, it was found that D4 is more adsorbable than L2, due to possible interactions between the solid surface and the physical structure of the cyclic compound (D4). The influence of humidity and temperature were also studied. The increase in the temperature reduced the adsorption capacities. The influence of humidity on the adsorption was investigated under dry air and humid air at 70%. No significant difference in the adsorption capacities was found for the activated carbon and for the zeolite, but for the silica gel the mass transfer decreased considerably. For the adsorption isotherms, the maximal capacity of elimination was obtained with the activated carbon materials and was directly related to the porous structure. Thus activated carbon cloth was chosen to design the adsorption-desorption processes in a dynamic system. Thermal heating was used to achieve the regeneration process. Initial cycles have been accomplished and show the stability of the process. PMID:19886432

  11. Complete denture impressioning technique.

    PubMed

    Kois, J C; Fan, P P

    1997-07-01

    This article describes a technique that simplifies the making of an edentulous arch impression before the fabrication of a complete denture. Making an impression of an edentulous arch requires a unique combination of managing movable soft tissue commensurate with integrating different materials and a technique for accurate reproduction. The technique described requires a two-phase approach using a syringeable addition silicone during the border molding process and a condensation silicone wash material to capture the soft tissue while the functional border molding is repeated. These more recently developed products allow us to achieve similar results and are easier, faster, and more predictable than those products used previously. PMID:9533331

  12. Virtual First Impressions

    ERIC Educational Resources Information Center

    Bergren, Martha Dewey

    2005-01-01

    Frequently, a nurse's first and only contact with a graduate school, legislator, public health official, professional organization, or school nursing colleague is made through e-mail. The format, the content, and the appearance of the e-mail create a virtual first impression. Nurses can manage their image and the image of the profession by

  13. Airbag Impressions in Soil

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken by the Mars Exploration Rover Opportunity's panoramic camera shows where the rover's airbags left impressions in the martian soil. The drag marks were made after the rover successfully landed at Meridiani Planum and its airbags were retracted. The rover can be seen in the foreground.

  14. Relevance of an organic solvent for absorption of siloxanes.

    PubMed

    Ghorbel, Leila; Tatin, Romuald; Couvert, Annabelle

    2014-01-01

    A wide range of siloxanes exist but the most abundant in biogas are Hexamethyldisiloxane (L2) and Octamethyltrisiloxane (L3) as linear siloxanes and Octamethylcyclotetrasiloxane (D4) as a cyclic siloxane. In order to remove volatile organic compound from biogas, different processes can be used. A promising process for siloxane removal is their absorption in an organic solvent. In this work, three oils were tested to absorb the selected siloxanes: silicone oil 47V20, Seriola 1510 and Polyalphaolefin. Initially, the characterization of these oils was realized by measuring their viscosities and densities, depending on temperature. The second time, the absorption capacity of the siloxanes by selected oils was characterized through the determination of their Henry's constants, but also owing to the implementation of a wet-wall column. Both Henry's constants and removal efficiencies in continuous regime revealed that silicone oil (47V20) can be considered as the most efficient oil among the three selected siloxanes. Moreover, the cyclic siloxane (D4) showed more affinity with oils than linear siloxanes. Silicone oil 47V20 appeared to be the best oil (intermediate price 14 euro/L, low viscosity, low volatility, chemical inertness (no corrosion) and resistance to high and low temperatures). PMID:24600877

  15. Waxes for functional impressions.

    PubMed

    Kotsiomiti, E; McCabe, J F

    1996-02-01

    The aim of this study was to develop a wax suitable to serve as a functional impression material. Several binary mixtures of paraffin, beeswax and rosin were prepared. They were characterized by differential thermal analysis (DTA), and tested for plastic deformation, thermal expansion, detail reproduction and mechanical properties. It was found that the combinations of paraffin with rosin can function well as impression materials, as they combine a high value of plastic deformation at 37 degrees C with relatively low values at room temperature. Concentrations of rosin as small as 1% or 2% are adequate to produce this result. The flow of paraffin was significantly reduced by the addition of beeswax. A linear relationship was found between the 37 degrees C flow values of paraffin-beeswax mixtures and the proportions of the ingredients. PMID:8850062

  16. Tool for Taking Clay Impressions

    NASA Technical Reports Server (NTRS)

    Duncan, R. S.

    1984-01-01

    Clay impression of small parts taken with tool consisting of hollow tube closed at one end. Slots at other end admit part short distance into tube. Impression used to make silicone rubber mold for examination.

  17. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  18. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  19. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  20. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  1. 40 CFR 721.10120 - Siloxane modified alumina nanoparticles (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... nanoparticles (generic). 721.10120 Section 721.10120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances 721.10120 Siloxane modified alumina nanoparticles (generic). (a) Chemical... as siloxane modified alumina nanoparticles (PMN P-05-687) is subject to reporting under this...

  2. Drug and dental impression materials

    PubMed Central

    Maller, Sudhakara V.; Karthik, K. S.; Maller, Udita S.; Abraham, Mathew C.; Kumar, Rachuri Narendra; Manikandan, R.

    2012-01-01

    Guidelines to prevent cross contamination with infectious agents have been instituted for dental clinical and laboratory procedures. However, compliance by dental offices and clinics in disinfecting impression material has not been universal. Techniques for disinfecting impression materials are spraying or immersing impression materials. These techniques can reduce the surface detail and dimensional accuracy of impressions; most disinfectants are irritants. This study reviewed whether antimicrobial activity can be achieved by mixing certain drugs with the impression material and their effects on the disinfection are achieved through such additions. PMID:23066280

  3. SOURCE ASSESSMENT: POLYVINYL CHLORIDE

    EPA Science Inventory

    This report summarizes data on air emissions from the polyvinyl chloride (PVC) industry. PVC is manufactured by 20 companies at 35 plants. Each plant uses one or more of four possible polymerization processes: (1) suspension polymerization, (2) emulsion polymerization, (3) bulk p...

  4. Synthesis and characterization of thiol-ene functionalized siloxanes and evaluation of their polymerization kinetics, network properties, and dental applications

    NASA Astrophysics Data System (ADS)

    Cole, Megan A.

    We explored formation-structure-property relationships in thiol-ene functionalized oligosiloxanes to create crosslinked networks. Specifically, nine oligomers were synthesized, three with thiol-functional silane repeats and three with allyl-functional silane repeats. Structural variations in each oligomer were systematically induced through the incorporation of non-reactive repeats bearing either diphenyl or di-n-octyl moieties, and the oligomer molecular weight was limited by the presence of monofunctional silane condensation species. The molecular weights and chain compositions of all oligomers were ascertained and subsequently used in the evaluation of network properties formed upon photopolymerization of thiol- and ene-functional reactants. Polymerization kinetics of the thiol-ene functionalized siloxanes were also investigated using photoinitiation owing to the spatial and temporal control afforded by this technique. In particular, the effects of the viscosity of the ene-functionalized oligomer and the degree of thiol functionalization on the observed polymerization rate were determined. Results showed that the speed of polymerization varied with changes to the rate-limiting step, which was heavily influenced by neighboring non-reactive functionalities. Moreover, the thiol-ene reaction was found to exhibity unimolecular termination exclusively in siloxane-based systems. Proposed use of the thiol-ene functionalized siloxane system as a dental impression material necessitated the development of a redox initiation scheme. Evaluation of the benzoylperoxide/dimethyl-p-toluidine redox pair in traditional systems showed bulk thiol-ene polymerizations comparable to photoinitiation with the added advantage of uninhibited depth control, as also demonstrated in small molecule thiol-ene coupling reactions initiated by this same redox system. Application of the redox pair to the siloxane system allowed for the viscoelastic properties as well as the feature replication abilities to be compared against commercial impression materials. The siloxane system was found to match the commercial material for strain recovery and stress relaxation and exceed its replication properties though it would require greater overall strength to function adequately in the clinical setting.

  5. Reproducibility of sterilized rubber impressions.

    PubMed

    Abdelaziz, Khalid M; Hassan, Ahmed M; Hodges, J S

    2004-01-01

    Impressions, dentures and other dental appliances may be contaminated with oral micro-flora or other organisms of varying pathogenicity from patient's saliva and blood. Several approaches have been tried to control the transmission of infectious organisms via dental impressions and because disinfection is less effective and has several drawbacks for impression characterization, several sterilization methods have been suggested. This study evaluated the reproducibility of rubber impressions after sterilization by different methods. Dimensional accuracy and wettability of two rubber impression materials (vinyl polysiloxane and polyether) were evaluated after sterilization by each of three well-known methods (immersion in 2% glutaraldehyde for 10 h, autoclaving and microwave radiation). Non-sterilized impressions served as control. The effect of the tray material on impression accuracy and the effect of topical surfactant on the wettability were also evaluated. One-way ANOVA with Dunnett's method was used for statistical analysis. All sterilizing methods reduced the reproducibility of rubber impressions, although not always significantly. Microwave sterilization had a small effect on both accuracy and wettability. The greater effects of the other methods could usually be overcome by using ceramic trays and by spraying impression surfaces with surfactant before pouring the gypsum mix. There was one exception: glutaraldehyde still degraded dimensional accuracy even with ceramic trays and surfactant. We conclude that a) sterilization of rubber impressions made on acrylic trays was usually associated with a degree of dimensional change; b) microwave energy seems to be a suitable technique for sterilizing rubber impressions; c) topical surfactant application helped restore wettability of sterilized impressions. PMID:15798825

  6. Ultrahigh molecular weight aromatic siloxane polymers

    NASA Technical Reports Server (NTRS)

    Ludwick, L. M.

    1982-01-01

    The condensation of a diol with a silane in toluene yields a silphenylene-siloxane polymer. The reaction of stiochiometric amounts of the diol and silane produced products with molecular weights in the range 2.0 - 6.0 x 10 to the 5th power. The molecular weight of the product was greatly increased by a multistep technique. The methodology for synthesis of high molecular weight polymers using a two step procedure was refined. Polymers with weight average molecular weights in excess of 1.0 x 10 to the 6th power produced by this method. Two more reactive silanes, bis(pyrrolidinyl)dimethylsilane and bis(gamma butyrolactam)dimethylsilane, are compared with the dimethyleminodimethylsilane in ability to advance the molecular weight of the prepolymer. The polymers produced are characterized by intrinsic viscosity in tetrahydrofuran. Weight and number average molecular weights and polydispersity are determined by gel permeation chromatography.

  7. Modified chemistry of siloxanes under tensile stress: interaction with environment.

    PubMed

    Lupton, Elizabeth M; Achenbach, Frank; Weis, Johann; Bräuchle, Christoph; Frank, Irmgard

    2006-08-01

    We present first principles molecular dynamics simulations of stretched siloxane oligomers in an environment representative of that present in single molecule atomic force microscopy experiments. We determine that the solvent used (hexamethyldisiloxane) does not influence the stretching of the siloxane in the high force regime or the rupture process, but trace amounts of water can induce rupture before the maximum siloxane extension has been attained. This would result in a significantly lower rupture force. The simulations show that the rupture of a covalent bond through a reaction with a molecule from the environment, which would not normally occur between the species when the polymer is not stressed, is possible, opening a route to mechanically induced chemical reactions. The attack of the normally hydrophobic siloxane by water when it is stretched has wider implications for the material failure under tensile stress, where trace amounts of water could induce tearing of the material. PMID:16869555

  8. Preliminary impression in patients with microstomia.

    PubMed

    Moghadam, B K

    1992-01-01

    This article describes a preliminary impression technique for edentulous patients with microstomia. Stock impression trays are modified to make sectional impressions of the left and right sides of the maxillary arch. The cast poured into the first impression is positioned in the second impression, which is then poured to make the diagnostic cast. PMID:1548600

  9. Issues in handling impression materials.

    PubMed

    Giordano, R

    2000-01-01

    Implant restorations require extreme accuracy since the implants are rigidly fixed. Although impression materials can be highly accurate, small inaccuracies are acceptable because the periodontal ligament allows for tooth movement. This luxury is not available with implants. A problem is the rotation of direct impression copings and distortion of interabutment positions in the master cast. Wee investigated the amount of torque required to displace a coping in eight impression material groups and the positional accuracy of the materials. The initial examination of torque narrowed the acceptable materials to a medium viscosity polyether, a high viscosity addition silicone, and a medium viscosity polysulfide-condensation silicones were eliminated. The results showed that the polyether and addition silicone produced casts with minimal distortion. Finally, it always is prudent to read the manufacturer's recommendations for use of impression materials. Catalyst-to-base ratios vary, as do working and setting times, depending on exact compositions. Impression materials also have various degrees of compatibility with stone, particularly the hydrocolloids, and it is advisable to use the recommended stone. Adhesives should be applied at least 15 minutes prior to loading the impression material. If at all possible, use of a rigid tray is recommended and impressions should be poured in the dental office; this minimizes the error produced at the beginning of the fabrication process. Elimination of errors early in fabrication of a prosthesis help prevent their magnification and result in a better-fitting restoration, requiring minimal adjustment in the end. PMID:12004656

  10. 40 CFR 721.9502 - Siloxanes and silicones, aminoalkyl, fluorooctyl, hydroxy-terminated salt (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxanes and silicones, aminoalkyl... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9502 Siloxanes and silicones... subject to reporting. (1) The chemical substance identified generically as siloxanes and...

  11. 40 CFR 721.9502 - Siloxanes and silicones, aminoalkyl, fluorooctyl, hydroxy-terminated salt (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxanes and silicones, aminoalkyl... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9502 Siloxanes and silicones... subject to reporting. (1) The chemical substance identified generically as siloxanes and...

  12. 40 CFR 721.9502 - Siloxanes and silicones, aminoalkyl, fluorooctyl, hydroxy-terminated salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxanes and silicones, aminoalkyl... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9502 Siloxanes and silicones... subject to reporting. (1) The chemical substance identified generically as siloxanes and...

  13. 40 CFR 721.9502 - Siloxanes and silicones, aminoalkyl, fluorooctyl, hydroxy-terminated salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxanes and silicones, aminoalkyl... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9502 Siloxanes and silicones... subject to reporting. (1) The chemical substance identified generically as siloxanes and...

  14. 40 CFR 721.9502 - Siloxanes and silicones, aminoalkyl, fluorooctyl, hydroxy-terminated salt (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxanes and silicones, aminoalkyl... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9502 Siloxanes and silicones... subject to reporting. (1) The chemical substance identified generically as siloxanes and...

  15. [Characteristics of domestically produced siloxane elastomer for making elastic gingival prosthetic device].

    PubMed

    Riakhovski?, A N; Poiurovskaia, I Ia; Kirillova, E V

    2006-01-01

    Gingival prosthetics effectively eliminates esthetic and phonetic disturbances in cases of pronounced gingival recession. Technology for making elastic gingival prosthetic devices of domestically produced siloxane elastomer composition with microwave siloxane vulcanization is described as well as the technique for making combined gingival prosthetics of siloxane composition and colorless plastic. PMID:16482030

  16. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  17. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  18. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impression tube. 872.6570 Section 872.6570 Food... DEVICES DENTAL DEVICES Miscellaneous Devices 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single...

  19. Ecotoxicity of siloxane D5 in soil.

    PubMed

    Velicogna, Jessica; Ritchie, Ellyn; Princz, Juliska; Lessard, Marie-Eve; Scroggins, Rick

    2012-03-01

    Decamethylcyclopentasiloxane (D5) is a cyclic volatile methyl siloxane (cVMS) commonly found in commercially available products. D5 is expected to enter the terrestrial environment through the deposit of biosolids from sewage treatment plants onto agricultural fields for nutrient enrichment. Little to no information currently exists as to the risks of D5 to the terrestrial environment. In order to evaluate the potential risk to terrestrial organisms, the toxicity of a D5 contaminated biosolid in an agricultural soil was assessed with a battery of standardized soil toxicity tests. D5 was spiked into a surrogate biosolid and then mixed with a sandy loam soil to create test concentrations ranging from 0 to 4074 mg kg(-1). Plant (Hordeum vulgare (barley) and Trifolium pratense (red clover)) and soil invertebrates (Eisenia andrei (earthworm) and Folsomia candida (springtail)) toxicity tests were completed to assess for lethal and sub-lethal effects. Plant testing evaluated the effects on seedling emergence, shoot and root length, and shoot and root dry mass. Invertebrate test endpoints included adult lethality, juvenile production, and individual juvenile dry mass (earthworms only). Soil samples were collected over time to confirm test concentrations and evaluate the loss of chemical over the duration of a test. The toxicity of the D5 was species and endpoint dependent, such that no significant adverse effects were observed for T. pratense or E. andrei test endpoints, however, toxicity was observed for H. vulgare plant growth and F. candida survival and reproduction. Chemical losses of up to 50% were observed throughout the tests, most significantly at high concentrations. PMID:22197313

  20. Structural Characterization of New Ferroelectric Liquid-Crystalline Siloxanes

    NASA Astrophysics Data System (ADS)

    Ibn-Elhaj, Mohammed; Skoulios, Antoine; Guillon, Daniel; Newton, Joanna; Hodge, Philip; Coles, Harry J.

    1996-02-01

    In a previous paper [1] we reported the structural study of new smectogenic molecules containing three distinct parts, an aromatic core, a central paraffin chain and a siloxane endgroup. In the present paper we report the structural characterization of new ferroelectric liquid crystalline siloxanes containing, in addition to these three parts, a branched aliphatic tail. These low molar mass chiral organosiloxane mesognes and their racemic analogs have been characterized using X-ray diffraction both on powder and oriented samples. The chiral (and achiral) compounds exhibit enantiotropic ferroelectric smectic C^* (or smectic C) mesophases with high tilt angles at low temperatures and over a broad temperatrue range.

  1. Surface Activity and Aggregation Behavior of Siloxane-Based Ionic Liquids in Aqueous Solution.

    PubMed

    Wang, Guoyong; Li, Ping; Du, Zhiping; Wang, Wanxu; Li, Guojin

    2015-08-01

    Six novel siloxane-based surface-active ionic liquids (SAILs)--siloxane ammonium carboxylate [Si(n)N(2)-CA(1), (n = 3, 4)]--were designed and synthesized. Their melting points, surface activities, and self-aggregation behavior in aqueous solution were studied. The results showed that because of the bulky hydrophobic siloxane chains at the end of the tail, all six siloxane-based SAILs are room-temperature ionic liquids (RT-SAILs). The introduction of the siloxane group can reduce the melting point of ionic liquids to below room temperature and can promote the micellization and aggregation behavior more efficiently. These siloxane-based SAILs can greatly reduce the surface tension of water, as shown by the critical aggregation concentration (?CAC) values of 20 mNm(-1); all six siloxane RT-SAILs can form a vesicle spontaneously in aqueous solution, indicating potential uses as model systems for biomembranes and vehicles for drug delivery. PMID:26172585

  2. Acetylene (ethynyl) terminated polyimide siloxane and process for preparation thereof

    NASA Technical Reports Server (NTRS)

    Stclair, T. L.; ASI primers applied over ste (inventors)

    1986-01-01

    Siloxane containing addition polyimides having improved physical property characteristics of flexibility, drape, tack, and toughness and the process for preparing and utilizing the same are disclosed. The novelty of this invention appears to reside in the composition and process of preparing addition type polyimides useful as structural adhesives as well as composite matrix materials and the process of preparing the same.

  3. Safe human exposure limits for airborne linear siloxanes during spaceflight

    PubMed Central

    García, Hector D.; McMullin, Tami S.; Tobin, Joseph M.; James, John T.

    2013-01-01

    Background Low molecular weight siloxanes are used in industrial processes and consumer products, and their vapors have been detected in the atmospheres of the Space Shuttle and International Space Station. Therefore, the National Aeronautics and Space Administration (NASA) developed spacecraft maximum allowable concentrations (SMACs) for siloxane vapors to protect astronaut health. Since publication of these original SMACs, new studies and new risk assessment approaches have been published that warrant re-examination of the SMACs. Objective To reevaluate SMACs published for octamethyltrisiloxane (L3) for exposures ranging from 1 hour to 180 days, to develop a 1000-day SMAC, and to expand the applicability of those values to the family of linear siloxanes. Methods A literature review was conducted to identify studies conducted since the SMACs for L3 were set in 1994. The updated data were reviewed to determine the sensitive toxicity endpoints, and current risk assessment approaches and methods for dosimetric adjustments were evaluated. Results Recent data were used to update the original 1-hour, 24-hour, 30-day, and 180-day SMACs for L3, and a 1000-day SMAC was developed to protect crewmembers during future exploration beyond Earth orbit. Group SMACs for the linear siloxane family, including hexamethyldisiloxane (L2), L3, decamethyltetrasiloxane (L4), and dodecamethylpentasiloxane (L5), were set for exposures of 1-hour to 1000 days. Conclusion New SMACs, based on acute pulmonary and neurotoxicity at high doses only achievable with L2 and potential liver effects following longer-term exposures to L2 and L3, were established to protect crewmembers from the adverse effects of exposure to linear siloxanes. PMID:24255951

  4. 76 FR 13660 - Polyvinyl Alcohol From Taiwan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-14

    ... COMMISSION Polyvinyl Alcohol From Taiwan Determination On the basis of the record \\1\\ developed in the... United States is materially injured by reason of imports from Taiwan of polyvinyl alcohol, provided for... of a preliminary determination by Commerce that imports of polyvinyl alcohol from Taiwan were...

  5. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... tube is a device consisting of a hollow copper tube intended to take an impression of a single tooth... material, such as wax, the remaining end is slipped over the tooth to make the impression....

  6. 21 CFR 872.6570 - Impression tube.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... tube is a device consisting of a hollow copper tube intended to take an impression of a single tooth... material, such as wax, the remaining end is slipped over the tooth to make the impression....

  7. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impression material. 872.3660 Section 872.3660...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be...

  8. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impression material. 872.3660 Section 872.3660...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3660 Impression material. (a) Identification. Impression material is a device composed of materials such as alginate or polysulfide intended to be...

  9. Recyclable polystyrene-supported siloxane-transfer agent for palladium-catalyzed cross-coupling reactions.

    PubMed

    Nguyen, Minh H; Smith, Amos B

    2014-04-01

    The rational design, synthesis, and validation of a significantly improved insoluble polymer-supported siloxane-transfer agent has been achieved that permits efficient palladium-catalyzed cross-coupling reactions. The cross-linked polystyrene support facilitates product purification with excellent siloxane recycling. Drawbacks of a previous polymer-supported siloxane-transfer agent, relating to reaction efficiency and polymer stability after repeated cycles, have been addressed. PMID:24661113

  10. Ultra-high molecular weight silphenylene-siloxane polymers

    NASA Technical Reports Server (NTRS)

    Patterson, W. J.; Hundley, N. H.; Ludwick, L. M.

    1984-01-01

    Silphenylene-siloxane copolymers with molecular weights above one million were prepared using a two stage polymerization technique. The technique was successfully scaled up to produce 50 grams of this high polymer in a single run. The reactive monomer approach was also investigated using the following aminosilanes: bis(dimethylamino)dimethylsilane, N,N-bis(pyrrolidinyl)dimethylsilane and N,N-bis(gamma-butyrolactam)dimethylsilane). Thermal analyses were performed in both air and nitrogen. The experimental polymers decomposed at 540 to 562 C, as opposed to 408 to 426 C for commercial silicones. Differential scanning calorimetry showed a glass transition (Tg) at -50 to -55 C for the silphenylene-siloxane copolymer while the commercial silicones had Tg's at -96 to -112 C.

  11. Siloxanes removal from biogas by high surface area adsorbents.

    PubMed

    Gislon, P; Galli, S; Monteleone, G

    2013-12-01

    Biogas utilized for energy production needs to be free from organic silicon compounds, as their burning has damaging effects on turbines and engines; organic silicon compounds in the form of siloxanes can be found in biogas produced from urban wastes, due to their massive industrial use in synthetic product, such as cosmetics, detergents and paints. Siloxanes removal from biogas can be carried out by various methods (Mona, 2009; Ajhar et al., 2010 May; Schweigkofler and Niessner, 2001); aim of the present work is to find a single practical and economic way to drastically and simultaneously reduce both the hydrogen sulphide and the siloxanes concentration to less than 1 ppm. Some commercial activated carbons previously selected (Monteleone et al., 2011) as being effective in hydrogen sulfide up taking have been tested in an adsorption measurement apparatus, by flowing the most volatile siloxane (hexamethyldisiloxane or L2) in a nitrogen stream, typically 100-200 ppm L2 over N2, through an activated carbon powder bed; the adsorption process was analyzed by varying some experimental parameters (concentration, grain size, bed height). The best activated carbon shows an adsorption capacity of 0.1g L2 per gram of carbon. The next thermogravimetric analysis (TGA) confirms the capacity data obtained experimentally by the breakthrough curve tests. The capacity results depend on L2 concentration. A regenerative carbon process is then carried out by heating the carbon bed up to 200 °C and flushing out the adsorbed L2 samples in a nitrogen stream in a three step heating procedure up to 200 °C. The adsorption capacity is observed to degrade after cycling the samples through several adsorption-desorption cycles. PMID:24075968

  12. Ultra-High-Molecular-Weight Silphenylene/Siloxane Elastomers

    NASA Technical Reports Server (NTRS)

    Hundley, N. H.; Patterson, W. J.

    1989-01-01

    Elastomers enhance thermal and mechancial properties. Capable of performing in extreme thermal/oxidative environments and having molecular weights above 10 to the sixth power prepared and analyzed in laboratory experiments. Made of methylvinylsilphenylene-siloxane terpolymers, new materials amenable to conventional silicone-processing technology. Similarly formulated commercial methyl-vinyl silicones, vulcanized elastomers exhibit enhance thermal/oxidative stability and equivalent or superior mechanical properties.

  13. Novel Low-Temperature Poss-Containing Siloxane Elastomers

    NASA Technical Reports Server (NTRS)

    Belcher, Marcus A.; Hinkley, Jeffrey A.; Kiri, Neha N.; Lillehei, Peter T.

    2008-01-01

    One route to increased aircraft performance is through the use of flexible, shape-changeable aerodynamics effectors. However, state of the art materials are not flexible or durable enough over the required broad temperature range. Mixed siloxanes were crosslinked by polyhedral oligomeric silsesquioxanes (POSS) producing novel materials that remained flexible and elastic from -55 to 94 C. POSS molecules were chemically modified to generate homogeneous distributions within the siloxane matrix. High resolution scanning electron microscope (HRSEM) images indicated homogenous POSS distribution up to 0.8 wt %. Above the solubility limit, POSS aggregates could be seen both macroscopically and via SEM (approx.60-120 nm). Tensile tests were performed to determine Young s modulus, tensile strength, and elongation at break over the range of temperatures associated with transonic aircraft use (-55 to 94 C; -65 to 200 F). The siloxane materials developed here maintained flexibility at -55 C, where previous candidate materials failed. At room temperature, films could be elongated up to 250 % before rupturing. At -55 and 94 C, however, films could be elongated up to 400 % and 125 %, respectively.

  14. From hydrophobic to superhydrophobic and superhydrophilic siloxanes by thermal treatment.

    PubMed

    Karapanagiotis, Ioannis; Manoudis, Panagiotis N; Zurba, Andreea; Lampakis, Dimitrios

    2014-11-11

    The cross-influence effects of treatment temperature and time on the wettability of a siloxane elastomer is investigated in detail, through static and tilt contact angle measurements. The material is heated at 400, 500, 600, 650, 700, and 800 °C for various periods, ranging from 1 to 300 s. The siloxane surface is subjected to multiple wettability transitions with treatment time: from intrinsic hydrophobicity to superhydrophobicity (and water repellency) and then through intermediate stages (hydrophobicity and hydrophilicity) to superhydrophilicity. For the time scale used herein (1-300 s), this scenario is recorded for treatment at 650, 700, and 800 °C. For treatment at lower temperatures (400, 500, and 600 °C) only the first transition, from intrinsic hydrophobicity to superhydrophobicity, is recorded. Scanning electron microscopy, micro-Fourier transform infrared (micro-FTIR), and micro-Raman spectroscopies are employed to correlate the aforementioned wettability transitions with structural and chemical changes of the siloxane surface, developed during thermal treatment. It is shown that the first transition from intrinsic hydrophobicity to superhydrophobicity is accompanied by a severe surface-structure evolution that increases surface roughness. Once superhydrophobicity is achieved, the surface structure reaches a saturation point and it is not subjected to any other change with further thermal treatment. FTIR spectroscopy shows that the intensity of the O-H/C-H peaks increases/decreases with treatment time, and Raman measurements show that the C-Si-C vibrations gradually disappear with treatment time. The evaporation of a droplet resting on a superhydrophobic, water-repellent siloxane surface, which was produced after appropriate thermal treatment, is monitored. It is shown that droplet evaporation initially follows the constant contact area mode. At later evaporation stages, a transition to the constant contact angle mode is recorded. Finally, it is demonstrated that the superhydrophobic and water-repellent siloxane surfaces exhibit self-cleaning properties, good durability, and furthermore do not practically affect the optical transparency of glass substrates. PMID:25313653

  15. Impressions for complete dentures using new silicone impression materials.

    PubMed

    Hayakawa, Iwao; Watanabe, Ikki

    2003-03-01

    This article describes a convenient technique for making impressions of complete dentures using two newly developed silicone materials. One of these materials, a heavy-bodied silicone material, is used for simultaneous molding of all borders. The material is available in automatic mixing systems, so it can be easily and evenly applied on the tray borders. The material is designed to have a low elasticity after setting so that excess material can be carved or deficient sites corrected with a small mix. The other newly developed material, a light-bodied silicone material, possesses better flow than the usual light-bodied silicones. In addition, since viscosity is controlled and adequate flow is maintained during seating in the mouth, mucosal detail is superior. PMID:12731598

  16. Determination of siloxanes in silicone products and potential migration to milk, formula and liquid simulants.

    PubMed

    Zhang, Kai; Wong, Jon W; Begley, Timothy H; Hayward, Douglas G; Limm, William

    2012-08-01

    A pressurised solvent extraction procedure coupled with a gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM) method was developed to determine three cyclic siloxanes, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and three linear siloxanes, octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), in silicone products. Additionally, two different extraction methods were developed to measure these siloxanes migrating into milk, infant formula and liquid simulants (50 and 95% ethanol in water). The limits of quantification (LOQs) of the six siloxanes ranged from 6?ng/g (L3) to 15?ng/g (D6). Silicone nipples and silicone bakewares were extracted using pressurised solvent extraction (PSE) and analysed using the GC-MS-SIM method. No linear siloxanes were detected in the silicone nipple samples analysed. The three cyclic siloxanes (D4, D5 and D6) were detected in all silicone nipple samples with concentrations ranging from 0.5 to 269?g/g. In the bakeware samples, except for L3, the other five siloxanes were detected with concentrations ranging from 0.2?g/g (L4) to 7030?g/g (D6). To investigate the potential migration of the six siloxanes from silicone nipples to milk and infant formula, a liquid extraction and dispersive clean-up procedure was developed for the two matrices. The procedure used a mix of hexane and ethyl acetate (1?:?1, v/v) as extraction solvent and C?? powder as the dispersive clean-up sorbent. For the liquid simulants, extraction of the siloxanes was achieved using hexane without any salting out or clean-up procedures. The recoveries of the six siloxanes from the milk, infant formula and simulants fortified at 50, 100, 200, 500 and 1000?g/l ranged from 70 to 120% with a relative standard derivation (RSD) of less than 15% (n?=?4). Migration tests were performed by exposing milk, infant formula and the liquid simulants to silicone baking sheets with known concentrations of the six siloxanes at 40C. No siloxanes were detected in milk or infant formula after 6?h of direct contact with the silicone baking sheet plaques, indicating insignificant migration of the siloxanes to milk or infant formula. Migration tests in the two simulants lasted up to 72?h and the three cyclic siloxanes were detected in 50% ethanol after an 8-h exposure and after 2?h in 95% ethanol. The highest detected concentrations of D4, D5 and D6 were 42, 36 and 155?ng/ml, respectively, indicating very limited migration of D4, D5 or D6 into the two simulants. PMID:22575024

  17. Siloxane-based hybrid semiconducting polymers prepared by fluoride-mediated suzuki polymerization.

    PubMed

    Lee, Junghoon; Han, A-Reum; Lee, Sang Myeon; Yoo, Dohyuk; Oh, Joon Hak; Yang, Changduk

    2015-04-01

    Siloxane-containing materials are a large and important class of organic-inorganic hybrids. In this report, a practical variation of the Suzuki polymerization to generate semiconducting polymeric hybrids based on siloxane units, which proceeds under essentially nonbasic conditions, is presented. This method generates solution-processable poly(diketopyrrolopyrrole-alt-benzothiadiazole) (PDPPBT-Si) consisting of the hybrid siloxane substituents, which could not be made using conventional methods. PDPPBT-Si exhibits excellent ambipolar transistor performance with well-balanced hole and electron FET mobilities. The siloxane-containing DPP-thiophene polymer classes (PDPP3T-Si and PDPP4T-Si), synthesized by this method, exhibit high hole mobility of up to 1.29 cm(2)  V(-1)  s(-1) . This synthetic approach should provide access to a variety of novel siloxane-containing conjugated semiconductor classes by using a variety of aryldihalides and aryldiboronic acids/esters. PMID:25677803

  18. A nationwide survey and emission estimates of cyclic and linear siloxanes through sludge from wastewater treatment plants in Korea.

    PubMed

    Lee, Sunggyu; Moon, Hyo-Bang; Song, Geum-Ju; Ra, Kongtae; Lee, Won-Chan; Kannan, Kurunthachalam

    2014-11-01

    Siloxanes are widely used in various industrial applications as well as in personal care products. Despite their widespread use and potential toxic effects, few studies have reported on the occurrence of siloxanes in the environment. In this study, we determined the concentrations of 5 cyclic and 15 linear siloxanes in sludge collected from 40 representative wastewater treatment plants (WWTPs) in Korea. Total concentrations of 20 siloxanessiloxane) in sludge ranged from 0.05 to 142 (mean: 45.7) μg/g dry weight, similar to the concentrations reported in European countries but higher than those reported in China. The concentrations of siloxanes in sludge from domestic WWTPs were significantly (p<0.01) higher than those from industrial WWTPs, indicating higher consumption of siloxanes in various personal care products (e.g. shampoos and conditioners). The major siloxane compounds found in sludge were decamethylcyclopentasilane (D5), docosamethyldecasiloxane (L10) and dodecamethylcyclohexasilane (D6), which collectively accounted for, on average, 62% of the Σsiloxane concentrations. Non-parametric multidimensional scaling ordination of the profiles of siloxanes indicated the existence of different usage patterns of siloxanes between industrial and household activities. Multiple linear regression analysis of siloxane concentrations and WWTP characteristics suggested that D5, D6 and linear siloxane concentrations in sludge were positively correlated with population served by a WWTP. Environmental emission fluxes of cyclic and linear siloxanes through sludge disposal in Korea were 14,800 and 18,500 kg/year, respectively. This is the first report describing occurrence and environmental emission of siloxanes through sludge in Korea. PMID:25127445

  19. A Comparative Evaluation of the Linear Dimensional Accuracy of Four Impression Techniques using Polyether Impression Material.

    PubMed

    Manoj, Smita Sara; Cherian, K P; Chitre, Vidya; Aras, Meena

    2013-12-01

    There is much discussion in the dental literature regarding the superiority of one impression technique over the other using addition silicone impression material. However, there is inadequate information available on the accuracy of different impression techniques using polyether. The purpose of this study was to assess the linear dimensional accuracy of four impression techniques using polyether on a laboratory model that simulates clinical practice. The impression material used was Impregum Soft™, 3 M ESPE and the four impression techniques used were (1) Monophase impression technique using medium body impression material. (2) One step double mix impression technique using heavy body and light body impression materials simultaneously. (3) Two step double mix impression technique using a cellophane spacer (heavy body material used as a preliminary impression to create a wash space with a cellophane spacer, followed by the use of light body material). (4) Matrix impression using a matrix of polyether occlusal registration material. The matrix is loaded with heavy body material followed by a pick-up impression in medium body material. For each technique, thirty impressions were made of a stainless steel master model that contained three complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring eight dimensions (mesiodistal, faciolingual and inter-abutment) on stone dies poured from impressions of the master model. A two-tailed t test was carried out to test the significance in difference of the distances between the master model and the stone models. One way analysis of variance (ANOVA) was used for multiple group comparison followed by the Bonferroni's test for pair wise comparison. The accuracy was tested at α = 0.05. In general, polyether impression material produced stone dies that were smaller except for the dies produced from the one step double mix impression technique. The ANOVA revealed a highly significant difference for each dimension measured (except for the inter-abutment distance between the first and the second die) between any two groups of stone models obtained from the four impression techniques. Pair wise comparison for each measurement did not reveal any significant difference (except for the faciolingual distance of the third die) between the casts produced using the two step double mix impression technique and the matrix impression system. The two step double mix impression technique produced stone dies that showed the least dimensional variation. During fabrication of a cast restoration, laboratory procedures should not only compensate for the cement thickness, but also for the increase or decrease in die dimensions. PMID:24431772

  20. Development of novel cycloaliphatic siloxanes for thermal and UV-curable applications

    NASA Astrophysics Data System (ADS)

    Chakraborty, Ruby

    Siloxanes have been extensively used as additives to modulate surface properties such as surface tension, hydrophobicity/hydrophobicity, and adhesion, etc. Although, polydimethyl -siloxane and polydiphenylsiloxane are the most commonly used siloxanes, the properties are at extremes in terms of glass transition temperature and flexibility. It is proposed that the ability to control the properties in between the these extremes can be provided by cycloaliphatic substitutions at the siloxane backbone. It is expected that this substitution might work due to the intermediate backbone rigidity. In order to achieve the above objectives, a synthetic route was developed to prepare cycloaliphatic (cyclopentane and cyclohexane) silane monomers followed by subsequent polymerization and functionalizations to obtain glycidyl epoxy, aliphatic amine and methacrylate telechelic siloxanes. The siloxanes were either thermally or UV-cured depending on end functionalizations. Chemical characterization of monomers, oligomers and polymers were performed using 1H, 13C, 29Si-NMR, FT-IR and GPC. The curing kinetics of photo-induced reactions were investigated through photo-differential scanning calorimetry (PDSC). The oxygen permeability, mechanical, coatings, and release properties of siloxanes were studied as a function of the backbone substitutions. The mechanical, coatings and released properties of cycloaliphatic siloxanes improved with respect to polydimethylsiloxanes. The thermal analysis of the cured films were carried out using differential scanning calorimetry (DSC). Viscoelastic properties of the cured siloxanes due to the variation of substitution at the siloxane backbone were measured using dynamic mechanical thermal analysis (DMTA). The cycloaliphatic substituted siloxanes showed an increased glass transition temperature and permeability but reduced crosslink density, conversion, and rate of curing with respect to polydimethylsiloxanes. Hybrids of siloxanes were prepared with linseed oil based alkyds to study the effect of variation of alkyd oil lengths and cycloaliphatic substitutions on siloxane backbone. The oil length of an alkyd resin is defined as the number of grams of oil used to produce 100 grams of resin. Three linseed oil based alkyds representing long, medium, and short oil lengths were grafted with siloxanes substituted with methyl, cyclopentyl, and cyclohexyl groups. The reaction was monitored through FTIR and 1H-NMR. The hybrids were formulated with standard drier package and thermally cured for detailed film characterization. Improvement in crosslink density, flexibility, and reverse impact resistance were found as function of oil length. However, tensile modulus, elongation, glass transition temperature, drying time and fracture toughness decreased with increase in oil length. For hybrids, the cycloaliphatic substituents at the siloxane backbone showed enhanced mechanical and coating properties as compared to hybrids with polydimethylsiloxanes. Random and block copolymer of polydimethylsiloxanes with polydicycloaliphatic-siloxanes were synthesized and compared with homopolymers of polydicycloaliphatic siloxanes. The chemical characterization of the copolymers and homopolymers were carried out through 1H, 13C, 29Si-NMR, and FT-IR. The glass transition temperatures (Tg) of the synthesized polymers were obtained through DSC and advanced rheometric expansion system (ARES). The Tg of random copolymers were found to be higher than the corresponding block copolymers. There was very small difference in T g between cycloaliphaticsiloxanes homopolymers and corresponding random copolymers. From the above results, it can be inferred that the cycloaliphatic substitutions at the siloxane backbone can be used as a means to obtain properties intermediate to polydimethyl- and polydiphenyl siloxanes.

  1. 21 CFR 872.3660 - Impression material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impression material. 872.3660 Section 872.3660 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices 872.3660 Impression material. (a)...

  2. Fogging in Polyvinyl Toluene Scintillators

    SciTech Connect

    Cameron, Richard J.; Fritz, Brad G.; Hurlbut, Charles; Kouzes, Richard T.; Ramey, Ashley; Smola, Richard

    2015-02-01

    It has been observed that large polyvinyl toluene (PVT)-based gamma ray detectors can suffer internal “fogging” when exposed to outdoor environmental conditions over long periods of time. When observed, this change results in reduced light collection by photomultiplier tubes connected to the PVT. Investigation of the physical cause of these changes has been explored, and a root cause identified. Water penetration into the PVT from hot, high-humidity conditions results in reversible internal water condensation at room temperature, and permanent micro-fracturing of the PVT at very low environmental temperatures. Mitigation procedures and methods are being investigated.

  3. Computational benchmark for calculation of silane and siloxane thermochemistry.

    PubMed

    Cypryk, Marek; Gosty?ski, Bart?omiej

    2016-01-01

    Geometries of model chlorosilanes, R3SiCl, silanols, R3SiOH, and disiloxanes, (R3Si)2O, R?=?H, Me, as well as the thermochemistry of the reactions involving these species were modeled using 11 common density functionals in combination with five basis sets to examine the accuracy and applicability of various theoretical methods in organosilicon chemistry. As the model reactions, the proton affinities of silanols and siloxanes, hydrolysis of chlorosilanes and condensation of silanols to siloxanes were considered. As the reference values, experimental bonding parameters and reaction enthalpies were used wherever available. Where there are no experimental data, W1 and CBS-QB3 values were used instead. For the gas phase conditions, excellent agreement between theoretical CBS-QB3 and W1 and experimental thermochemical values was observed. All DFT methods also give acceptable values and the precision of various functionals used was comparable. No significant advantage of newer more advanced functionals over 'classical' B3LYP and PBEPBE ones was noted. The accuracy of the results was improved significantly when triple-zeta basis sets were used for energy calculations, instead of double-zeta ones. The accuracy of calculations for the reactions in water solution within the SCRF model was inferior compared to the gas phase. However, by careful estimation of corrections to the ?Hsolv and ?Gsolv of H(+) and HCl, reasonable values of thermodynamic quantities for the discussed reactions can be obtained. PMID:26781663

  4. Dimensional accuracy of 2-stage putty-wash impressions: influence of impression trays and viscosity.

    PubMed

    Balkenhol, Markus; Ferger, Paul; Wstmann, Bernd

    2007-01-01

    The aim of this in vitro study was to evaluate the influence of the impression tray and viscosity of the wash material on the dimensional accuracy of impressions taken using a 2-stage putty-wash technique. Identically shaped metal stock trays (MeTs) and disposable plastic stock trays (DiTs) were used for taking impressions (n = 10) of a mandibular cast (4 abutments) with 2 different impression materials. Dies were poured and the relative diameter deviation was calculated after measurement. Zero viscosity of the materials was determined. Dimensional accuracy was significantly affected when DiTs were used. Lower-viscosity wash materials led to more precise impressions. PMID:18069363

  5. Polyvinyl alcohol hydrogels for iontohporesis

    NASA Astrophysics Data System (ADS)

    Bera, Prasanta; Alam, Asif Ali; Arora, Neha; Tibarewala, Dewaki Nandan; Basak, Piyali

    2013-06-01

    Transdermal therapeutic systems propound controlled release of active ingredients through the skin into the systemic circulation in a predictive manner. Drugs administered through these systems escape first-pass metabolism and maintain a steady state scenario similar to a continuous intravenous infusion for up to several days. The iontophoresis deal with the systemic delivery of the bioactive agents (drug) by applying an electric current. It is basically an injection without the needle. The iontophoretic system requires a gel-based matrix to accommodate the bioactive agent. Hydrogels have been used by many investigators in controlled-release drug delivery systems because of their good tissue compatibility and easy manipulation of swelling level and, thereby, solute permeability. In this work we have prepared polyvinyl alcohol (PVA) hydrogel. We have cross linked polyvinyl alcohol chemically with Glutaraldehyde with different wt%. FTIR study reveals the chemical changes during cross linking. Swelling in water, is done to have an idea about drug loading and drug release from the membrane. After drug loading to the hydrogels, we have studied the drug release property of the hydrogels using salicylic acid as a model drug.

  6. Concentrations and assessment of exposure to siloxanes and synthetic musks in personal care products from China.

    PubMed

    Lu, Yan; Yuan, Tao; Wang, Wenhua; Kannan, Kurunthachalam

    2011-12-01

    We investigated the concentrations and profiles of 15 siloxanes (four cyclic siloxanes, D(4)-D(7); 11 linear siloxanes, L(4)-L(14)), four synthetic musks (two polycyclic musks, HHCB and AHTN; two nitro musks, MX and MK), and HHCB-lactone, in 158 personal care products marketed in China. Siloxanes were detected in 88% of the samples analyzed, at concentrations as high as 52.6 mg g(-1); Linear siloxanes were the predominant compounds. Among synthetic musks, more than 80% of the samples contained at least one of these compounds, and their total concentrations were as high as 1.02 mg g(-1). HHCB was the predominant musk in all of the samples analyzed, on average, accounting for 52% of the total musk concentrations. Based on the median concentrations of siloxanes and musks and the average daily usage amounts of consumer products, dermal exposure rates in adults were calculated to be 3.69 and 3.38 mg d(-1) for siloxanes and musks, respectively. PMID:21899935

  7. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  8. The O-ring universal impression technique.

    PubMed

    Hussaini, Souheil

    2008-10-01

    Recording the implant position for master cast fabrication for multiple implant systems may require a large inventory of impression copings. A technique is described whereby implant impression-making procedures can be modified to be more universal to all implant systems. This makes the procedure more cost-effective by simply incorporating the use of a rubber O-ring on the abutment or fixture mount, which then eliminates the use of a transfer coping. This technique can be applied at the time of surgery for indexing as well as during the final impression appointment. PMID:18761567

  9. Technique for making flexible impression trays for the microstomic patient.

    PubMed

    Whitsitt, J A; Battle, L W

    1984-10-01

    This impression technique can be used for patients in whom routine use of stock impression trays is hindered by microstomia. Putty wash material can be manipulated with minimal effort and time. Placing the completed preliminary impression in a free-flowing mix of dental stone stabilizes the impression material and facilitates boxing and pouring of the impression. The resultant preliminary casts can then be used for diagnostic purposes and for making rigid sectional trays for final impressions. PMID:6389845

  10. Impression success using the dual arch technique.

    PubMed

    Small, Bruce W

    2005-01-01

    Taking an accurate impression and pouring a model that duplicates the clinical situation is the goal of every restorative dentist. The chance of having a restoration that fits the tooth properly increases as more care, skill, and judgment are applied to these early steps in restoration construction. When used as described above with any of the trays mentioned, the dual arch impression technique can be of great value in restorative dentistry. PMID:16366044

  11. Preparation and characterization of a siloxane containing bismaleimide

    NASA Technical Reports Server (NTRS)

    Maudgal, S.; St. Clair, T. L.

    1984-01-01

    A novel siloxane containing bismaleimide has been prepared by reacting maleic anhydride, benzophenonetetracarboxylic dianhydride and bis(gamma-aminopropyl)tetramethyldisiloxane. Characterization of this monomer was done by comparing its nuclear magnetic resonance spectrum (NMR) to those of model compounds. Solubility of the prepolymer was tested in amide, chlorinated and ether solvents. Films were cast from solution as well as by melt processing and a cure cycle was determined. Infrared spectrum (IR) of the resulting film was obtained. Thermal polymerization was investigated by differential scanning calorimetry (DSC). Thermal properties of the cured resin were followed by means of thermogravimetric analysis (TGA), torsional braid analysis (TBA) and dynamic mechanical analysis (DMA). Thermomechanical analysis (TMA) was used to study the effect of postcure on the glass transition temperature (Tg) of the resin. Adhesive strength of the resin was obtained at ambient temperature.

  12. Vinyl polysiloxane impression material in removable prosthodontics. Part 1: Edentulous impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2009-02-01

    Recent advances in impression materials and stock edentulous impression trays have resulted in simplified approaches to impression making in removable prosthodontics. Once considered an absolute necessity, it is now possible to avoid the need for custom impression trays. In an effort to achieve reliable master casts in a single appointment, new and innovative procedures are now available. This article, the first in a 3-part series, will review historical information, basic concepts, materials considerations, and philosophic approaches to impression making in complete-denture therapy. A modern technique using readily available impression materials will be described and illustrated so readers can consider the benefits of incorporation into their daily management of edentulous patients. PMID:19331063

  13. Vinyl polysiloxane impression material in removable prosthodontics. Part 1: edentulous impressions.

    PubMed

    Massad, Joseph J; Cagna, David R

    2007-08-01

    Recent advances in impression materials and stock edentulous impression trays have resulted in simplified approaches to impression making in removable prosthodontics. Once considered an absolute necessity, it is now possible to avoid the need for custom impression trays. In an effort to achieve reliable master casts in a single appointment, new and innovative procedures are now available. This article, the first in a 3-part series, will review historical information, basic concepts, materials considerations, and philosophic approaches to impression making in complete-denture therapy. A modem technique using readily available impression materials will be described and illustrated so readers can consider the benefits of incorporation into their daily management of edentulous patients. PMID:18578103

  14. The influence of impression trays on the accuracy of stone casts poured from irreversible hydrocolloid impressions.

    PubMed

    Mendez, A J

    1985-09-01

    An investigation was conducted to determine which of four commonly used impression trays yields the best results when making irreversible hydrocolloid impressions. This objective was achieved by evaluating the comparative accuracy of stone casts obtained from irreversible hydrocolloid impressions made with trays of different characteristics. The following conclusions are drawn from this study. Some kind of distortion can be expected in irreversible hydrocolloid impressions with the use of any of the tested impression trays. The perforated trays (B and D) reproduce more accurately the distances along the length and the width of the arch than the nonperforated trays (A and C). The depth of the palatal vault (distance f-g) is reproduced most accurately by the Rim-lock nonperforated tray (A) followed closely by the stock perforated (B) and the custom nonperforated (C) trays. Under the conditions of this study, all the impressions had a tendency to be oversized except the impressions made with the stock perforated tray (B). Those impressions were slightly undersized for all but two measured distances. Clinically significant inaccuracies produced by any of the four tested impression trays were not found in this study. PMID:3906093

  15. Impression formation: the role of expressive behavior.

    PubMed

    Riggio, R E; Friedman, H S

    1986-02-01

    This research examined the effects of personality/social skills and individual differences in expressive style on impression formation. Particular attention was given to the role of nonverbal behaviors in the formation of initial impressions. Sixty-two subjects were measured on self-report personality and communication skill scales, on posed emotional sending ability, and on physical attractiveness. Subjects were then videotaped while giving a spontaneous "explanation." Trained coders measured five separate nonverbal cue factors displayed by the subjects in the videotapes. Groups of untrained judges viewed the tapes and rated their impressions of the subjects on scales of likability, speaking effectiveness, and expressivity-confidence. Male subjects who were nonverbally skilled and extraverted tended to display more outwardly focused and fluid expressive behaviors, and made more favorable impressions on judges, than did males who scored low on the measures of nonverbal skills and extraversion. Females who were nonverbally skilled displayed more facial expressiveness, which led to more favorable initial impressions. Sex differences may reflect basic differences in the acquisition and use of expressive nonverbal cues by males and females. PMID:3517289

  16. Giving the wrong impression: food and beverage brand impressions delivered to youth through popular movies

    PubMed Central

    Skatrud-Mickelson, Monica; Adachi-Mejia, Anna M.; MacKenzie, Todd A.; Sutherland, Lisa A.

    2012-01-01

    Background Marketing on television showcases less-healthful options, with emerging research suggesting movies promote similar products. Given the obesity epidemic, understanding advertising to youth should be a public health imperative. The objective of this study was to estimate youth impressions to food and beverages delivered through movies. Methods Impressions were calculated by dividing US receipts annually into average movie ticket prices, then multiplying this by the number of brand appearances. Examination by ratings, product types and ages were conducted by Spearman rank correlation coefficient tests. Results Youth in the USA saw over 3 billion food, beverage or foodretail establishment (FRE) impressions on average, annually from 1996 to 2005. Those aged 1218 viewed over half of all impressions, with PG-13-rated movies containing 61.5% of impressions. There were no significant trends in brand appearances by food, beverage or FRE impressions over the decade, although there was a decreasing trend in R-rated impressions for both foods (P< 0.01) and beverages (P< 0.01), but not FREs (P= 0.08). Conclusions Movies promote billions of food and beverage impressions annually to youth. Given the public health crisis of obesity, future research should further investigate these trends, as well as the potential association of these unhealthy exposures in youth. PMID:22076600

  17. A predictable and accurate technique with elastomeric impression materials.

    PubMed

    Barghi, N; Ontiveros, J C

    1999-08-01

    A method for obtaining more predictable and accurate final impressions with polyvinylsiloxane impression materials in conjunction with stock trays is proposed and tested. Heavy impression material is used in advance for construction of a modified custom tray, while extra-light material is used for obtaining a more accurate final impression. PMID:10649919

  18. How To Achieve Better Impressions in Computer-Mediated Communication?

    ERIC Educational Resources Information Center

    Liu, Yuliang; Ginther, Dean

    This paper presents a review of the literature on impression formation in face-to-face (FtF) and computer-mediated communication (CMC) and provides impression management recommendations for CMC users in a variety of environments. The first section provides an introduction to impression formation. Factors affecting impression formation in FtF and

  19. Comparative study of dimensional accuracy of different impression techniques using addition silicone impression material.

    PubMed

    Penaflor, C F; Semacio, R C; De Las Alas, L T; Uy, H G

    1998-01-01

    This study compared dimensional accuracy of the single, double with spacer, double with cut-out and double mix impression technique using addition silicone impression material. A typhodont containing Ivorine teeth model with six (6) full-crown tooth preparations were used as the positive control. Two stone replication models for each impression technique were made as test materials. Accuracy of the techniques were assessed by measuring four dimensions on the stone dies poured from the impression of the Ivorine teeth model. Results indicated that most of the measurements for the height, width and diameter slightly decreased and a few increased compared with the Ivorine teeth model. The double with cut-out and double mix technique presents the least difference from the master model as compared to the two latter impression techniques. PMID:10202524

  20. Accuracy of three implant impression techniques with different impression materials and stones.

    PubMed

    Chang, Won-Gun; Vahidi, Farhad; Bae, Kwang-Hak; Lim, Bum-Soon

    2012-01-01

    The purpose of this study was to compare the accuracy of casts made using three different impression techniques to obtain an accurate definitive cast for fabrication of multiple-implant prostheses. Twelve experimental groups were formed combining the following conditions: three impression techniques, two impression materials, and two cast materials. The main effects of the three factors were analyzed by three-way analysis of variance using the full factorial general linear model between factors. The results showed that there were no significant differences in mean values for the transferred dimensions between the control and experimental groups. None of the measurements in the horizontal plane of the definitive casts demonstrated significant differences among the impression techniques with different impression and cast materials (P > .01). PMID:22259795

  1. Linear dimensional changes in elastic impression materials.

    PubMed

    Marcinak, C F; Young, F A; Draughn, R A; Flemming, W R

    1980-07-01

    Four classes of elastomeric impression materials (polysulfide, polyether, silicone, and agar-agar) were evaluated on the basis of linear dimensional stability as a function of time between taking and pouring an impression of mounted teeth. Four polysulfide materials produced dies which were larger than the teeth and generally increased in size with impression storage time. One silicone material produced dies slightly smaller than the teeth, and the dies from another silicone were dramatically smaller with increasing storage times. A polyether material produced slightly smaller dies for up to four hours' storage time, then increasingly larger dies up to 24 h. The dies from a reversible hydrocolloid were larger than the teeth for storage times up to 30 min, and then decreased rapidly at longer times. PMID:6929810

  2. Modified functional impression technique for complete dentures.

    PubMed

    Malachias, Alexandre; Paranhos, Helena de Freitas Oliveira; da Silva, Cludia Helena Lovato; Muglia, Valdir Antnio; Moreto, Carla

    2005-01-01

    This report describes the use of a removable acrylic resin tray handle that can be easily attached to custom impression trays to produce an improved peripheral sealing zone. This device can be indicated to develop functional impressions for complete dentures using the patient-conducted muscular motion technique. In upper trays, the handle is fixed in the midline with acrylic resin, while in lower trays the centrally positioned handle is removed before border molding. This removable handle allows patient's suction and free tongue movements. Final impression is carried out in two stages: peripheral sealing (low fusion compound) and recording of the main supporting region of the denture (zinc oxide and eugenol paste). All border records are obtained from the patient's own movements (handle suction and tongue motion). The removable handle is simple to use, is reusable, can be adapted to any individual acrylic resin trays and allows accurate registration of the peripheral sealing zone (border tissues). PMID:16475608

  3. Impression Testing of Self-Healing Polymers

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Huber, Amy

    2005-01-01

    As part of the BIOSANT program (biologically-inspired smart nanotechnology), scientists at NASA-Langley have identified a "self-healing" plastic that spontaneously closes the hole left by the passage of a bullet. To understand and generalize the phenomenon in question, the mechanical properties responsible for this ability are being explored. Low-rate impression testing was chosen to characterize post-yield material properties, and it turned out that materials that heal following ballistic puncture also show up to 80% healing of the low-rate impression. Preliminary results on the effects of temperature and rate of puncture are presented.

  4. Revisiting impressions using dual-arch trays.

    PubMed

    Small, Bruce W

    2012-01-01

    Making routine perfect impressions is the goal of any restorative dentist. Using dual-arch trays is an easy, repeatable way to accomplish that goal, as long as each step is done before the next and each step is performed perfectly. This column reviewed several articles that support the metal dual-arch concept and provided some clinical tips that might help restorative dentists. The dual-arch technique does have its limits and is meant for one or two teeth in a quadrant when there are other teeth to occlude with. Also, if the case involves anterior guidance, a full-arch impression maybe advisable. PMID:23032223

  5. Pressures involved in making upper edentulous impressions.

    PubMed

    Rihani, A

    1981-12-01

    A study was made of the pressures exerted on the upper denture-bearing area in three patients each with a different type of palatal vault. A method of measuring the relative pressures in different regions of the upper denture bearing area was devised. These pressures were registered with the use of manometers while making an impression in close fitting acrylic resin special trays. The results indicated that the main pressure regions during impression making were near the center of the palate and these pressures diminished toward the buccal borders. PMID:7028974

  6. Food web accumulation of cyclic siloxanes in Lake Mjsa, Norway.

    PubMed

    Borg, Katrine; Fjeld, Eirik; Kierkegaard, Amelie; McLachlan, Michael S

    2012-06-01

    The biomagnification of the cyclic volatile methyl siloxanes octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexatetrasiloxane (D6) was analyzed in the Lake Mjsa food web in Norway from zooplankton and Mysis to planktivorous and piscivorous fish. The trophic magnification factor (TMF) for D5 was determined and compared with TMFs of several legacy contaminants: polychlorinated biphenyl (PCB) congeners 153 and 180, polybrominated diphenyl ether (PBDE) congeners 47 and 99, and p,p'-DDE. D5 showed TMF significantly greater than 1, implying food web biomagnification (TMF = 2.28, CI: 1.22-4.29). This contrasts with two studies that reported TMF < 1, which may reflect variability in TMF between food webs. The Lake Mjsa D5 TMF was sensitive to the species included at the higher trophic level; whole food web TMF differed from TMF excluding smelt (Osmerus eperlanus) or brown trout (Salmo trutta) (TMF(-SMELT) = 1.62, CI: 0.96-2.72; TMF(-TROUT) = 3.58, CI: 1.82-7.03). For legacy contaminants (e.g., PCB-153 and PCB-180), the TMFs were less sensitive to the food web composition, and a better model fit was obtained compared to D5. The differences in biomagnification behavior between D5 and the legacy contaminants suggest that the biomagnification of D5 is being governed by species-specific properties such as biotransformation rate or tissue distribution that differ from those of legacy contaminants. PMID:22571757

  7. Junge relationships in measurement data for cyclic siloxanes in air.

    PubMed

    MacLeod, Matthew; Kierkegaard, Amelie; Genualdi, Susie; Harner, Tom; Scheringer, Martin

    2013-10-01

    In 1974, Junge postulated a relationship between variability of concentrations of gases in air at remote locations and their atmospheric residence time, and this Junge relationship has subsequently been observed empirically for a range of trace gases. Here, we analyze two previously-published datasets of concentrations of cyclic volatile methyl siloxanes (cVMS) in air and find Junge relationships in both. The first dataset is a time series of concentrations of decamethylcyclopentasiloxane (D5) measured between January and June, 2009 at a rural site in southern Sweden that shows a Junge relationship in the temporal variability of the measurements. The second dataset consists of measurements of hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and D5 made simultaneously at 12 sites in the Global Atmospheric Passive Sampling (GAPS) network that shows a Junge relationship in the spatial variability of the three cVMS congeners. We use the Junge relationship for the GAPS dataset to estimate atmospheric lifetimes of dodecamethylcyclohexasiloxane (D6), 8:2-fluorotelomer alcohol and trichlorinated biphenyls that are within a factor of 3 of estimates based on degradation rate constants for reaction with hydroxyl radical determined in laboratory studies. PMID:23177712

  8. Patterns of Vocalization and Impression Formation

    ERIC Educational Resources Information Center

    Hayes, Donald P.; Bouma, Gary D.

    1975-01-01

    This article discusses the interactive behavior that accompanies verbal exchange. It specifically describes a set of experiments designed to isolate an important subset of interactive behavior, the vocal (as opposed to the verbal) and to relate this information to a wide range of social impressions resulting from verbal exchange. (Available from…

  9. Patterns of Vocalization and Impression Formation

    ERIC Educational Resources Information Center

    Hayes, Donald P.; Bouma, Gary D.

    1975-01-01

    This article discusses the interactive behavior that accompanies verbal exchange. It specifically describes a set of experiments designed to isolate an important subset of interactive behavior, the vocal (as opposed to the verbal) and to relate this information to a wide range of social impressions resulting from verbal exchange. (Available from

  10. Neurological Impress--Good News or Bad?

    ERIC Educational Resources Information Center

    Arnold, Richard D.

    In the Neurological Impress Method (NIM) for helping children with reading problems, the teacher and student read aloud together while the child points with an index finger to the words that are being spoken. The system thus provides visual, auditory, and kinesthetic-tactile input for learners. A review of the scant information on NIM reported in

  11. Additivity of Clothing Cues in First Impressions.

    ERIC Educational Resources Information Center

    Lennon, Sharron J.

    1986-01-01

    The theory of information integration was used to predict that in first impression situations, clothing/physical appearance cues have differential importance depending upon the type of judgment elicited. Female college students (N=104) viewed and responded to slides of colored line drawings of female stimulus persons. Multiple regression of data

  12. Impressive Subcutaneous Calcifications in Systemic Lupus Erythematosus

    PubMed Central

    DIMA, Alina; BERZEA, Ioana; BAICUS, Cristian

    2015-01-01

    Dystrophic calcinosis cutis was commonly described in long-term dermatomyositis or systemic sclerosis, being rarely reported in other connective tissue diseases. We report the case of a 65-years old woman with an only 5-years history of systemic lupus erythematosus, who presents with multiple, impressive subcutaneous calcified masses and biological normal serum calcium and phosphate levels. PMID:26225152

  13. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test.

    PubMed

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-01

    Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane. PMID:23684695

  14. Formation mechanism of photo-induced nested wrinkles on siloxane-photomonomer hybrid film

    NASA Astrophysics Data System (ADS)

    Suzuki, Kazumasa; Tokudome, Yasuaki; Takahashi, Masahide

    2014-10-01

    Nested wrinkle structures, hierarchical surface wrinkles of different periodicities of sub-?m and tens-?m, have been fabricated on a siloxane-photomonomer hybrid film via a photo-induced surface polymerization of acrylamide. The formation mechanism of the nested wrinkle structures is examined based on a time-dependent structure observation and chemical composition analyses. In-situ observation of the evolving surface structure showed that sub-?m scale wrinkles first formed, subsequently the tens-?m scale ones did. In-situ FT-IR analysis indicated that the nested wrinkles formation took place along with the development of siloxane network of under layer. A cross sectional observation of the film revealed that the film was composed of three layers. FT-IR spectra of the film revealed that the surface and interior layers were polyacrylamide rich layer and siloxane-polymer rich layer, respectively. The intermediate layer formed as a diffusion layer by migration of acrylamide from interior to the surface. These three layers have different chemical compositions and therefore different mechanical characteristics, which allows the wrinkle formation. Shrinkage of siloxane-polymer interior layers, as a result of polycondensation of siloxane network, induced mechanical instabilities at interlayers, to form the nested wrinkle structures.

  15. Formation mechanism of photo-induced nested wrinkles on siloxane-photomonomer hybrid film

    SciTech Connect

    Suzuki, Kazumasa; Tokudome, Yasuaki Takahashi, Masahide

    2014-10-21

    Nested wrinkle structures, hierarchical surface wrinkles of different periodicities of sub-μm and tens-μm, have been fabricated on a siloxane-photomonomer hybrid film via a photo-induced surface polymerization of acrylamide. The formation mechanism of the nested wrinkle structures is examined based on a time-dependent structure observation and chemical composition analyses. In-situ observation of the evolving surface structure showed that sub-μm scale wrinkles first formed, subsequently the tens-μm scale ones did. In-situ FT-IR analysis indicated that the nested wrinkles formation took place along with the development of siloxane network of under layer. A cross sectional observation of the film revealed that the film was composed of three layers. FT-IR spectra of the film revealed that the surface and interior layers were polyacrylamide rich layer and siloxane-polymer rich layer, respectively. The intermediate layer formed as a diffusion layer by migration of acrylamide from interior to the surface. These three layers have different chemical compositions and therefore different mechanical characteristics, which allows the wrinkle formation. Shrinkage of siloxane-polymer interior layers, as a result of polycondensation of siloxane network, induced mechanical instabilities at interlayers, to form the nested wrinkle structures.

  16. 40 CFR 721.9517 - Siloxanes and silicones, de-Me, 3-[4-[[[3-(dimethyl amino) propyl] amino]carbonyl]-2-oxo-1...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxanes and silicones, de-Me, 3... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9517 Siloxanes and silicones, de-Me, 3... to reporting. (1) The chemical substance identified as siloxanes and silicones, de-Me, 3-...

  17. 40 CFR 721.6170 - Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxanes and silicones, Me hydrogen... Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy)piperdine... identified as siloxanes and silicones, Me hydrogen, reaction products with...

  18. 40 CFR 721.6170 - Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxanes and silicones, Me hydrogen... Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy)piperdine... identified as siloxanes and silicones, Me hydrogen, reaction products with...

  19. 40 CFR 721.6170 - Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxanes and silicones, Me hydrogen... Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy)piperdine... identified as siloxanes and silicones, Me hydrogen, reaction products with...

  20. 40 CFR 721.6170 - Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxanes and silicones, Me hydrogen... Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy)piperdine... identified as siloxanes and silicones, Me hydrogen, reaction products with...

  1. 40 CFR 721.6170 - Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxanes and silicones, Me hydrogen... Siloxanes and silicones, Me hydrogen, reaction products with 2,2,6,6-tetramethyl-4-(2-propenyloxy)piperdine... identified as siloxanes and silicones, Me hydrogen, reaction products with...

  2. 40 CFR 721.9517 - Siloxanes and silicones, de-Me, 3-[4-[[[3-(dimethyl amino) propyl] amino]carbonyl]-2-oxo-1...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxanes and silicones, de-Me, 3... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9517 Siloxanes and silicones, de-Me, 3... to reporting. (1) The chemical substance identified as siloxanes and silicones, de-Me, 3-...

  3. 40 CFR 721.9517 - Siloxanes and silicones, de-Me, 3-[4-[[[3-(dimethyl amino) propyl] amino]carbonyl]-2-oxo-1...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxanes and silicones, de-Me, 3... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9517 Siloxanes and silicones, de-Me, 3... to reporting. (1) The chemical substance identified as siloxanes and silicones, de-Me, 3-...

  4. 40 CFR 721.9517 - Siloxanes and silicones, de-Me, 3-[4-[[[3-(dimethyl amino) propyl] amino]carbonyl]-2-oxo-1...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxanes and silicones, de-Me, 3... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9517 Siloxanes and silicones, de-Me, 3... to reporting. (1) The chemical substance identified as siloxanes and silicones, de-Me, 3-...

  5. 40 CFR 721.9517 - Siloxanes and silicones, de-Me, 3-[4-[[[3-(dimethyl amino) propyl] amino]carbonyl]-2-oxo-1...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxanes and silicones, de-Me, 3... SUBSTANCES Significant New Uses for Specific Chemical Substances 721.9517 Siloxanes and silicones, de-Me, 3... to reporting. (1) The chemical substance identified as siloxanes and silicones, de-Me, 3-...

  6. Radiolysis of tetrazolium salts in polyvinyl alcohol

    SciTech Connect

    Kriminskaya, Z.K.; Ginzburg, S.F.; Molin, A.A.

    1992-01-01

    The radiation chemical yields of formazans were measured in binary systems containing polyvinyl alcohol and tetrazolium salts as additives; it was established that they are more than half of the yields of radicals in pure polyvinyl alcohol. The ESR spectra of the indicated systems were measured at various temperatures, and the relative changes in the radical concentrations were determined. It was suggested that the increase in the concentration of single radicals at T > 400 K is due to the participation of radical pairs in the reaction. 15 refs., 4 figs., 1 tab.

  7. Disinfection of irreversible hydrocolloid impressions: a comparative study.

    PubMed

    McNeill, M R; Coulter, W A; Hussey, D L

    1992-01-01

    This paper demonstrates the potential for cross contamination with bacteria and viruses from impression materials and evaluates the efficacy of four disinfection systems on irreversible hydrocolloid impressions contaminated with Streptococcus sanguis or poliovirus. An irreversible hydrocolloid impression was made of a contaminated acrylic resin template. The impression was disinfected and residual microorganisms were harvested by sonication, cultured, and counted. The results showed that the impression material could act as a vehicle for the transfer of both bacteria and viruses. Further, the virus was shown to be present in the body of the impression and under certain conditions may evade decontamination. PMID:1339136

  8. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in 176.170(c) of...

  9. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in 176.170(c) of...

  10. 75 FR 15726 - Polyvinyl Alcohol From Taiwan; Determination

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-30

    ... COMMISSION Polyvinyl Alcohol From Taiwan; Determination On the basis of the record \\1\\ developed in the... Taiwan of polyvinyl alcohol provided for in subheading 3905.30.00 of the Harmonized Tariff Schedule of... threatened with material injury by reason of allegedly LTFV imports of polyvinyl alcohol from...

  11. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in § 176.170(c) of...

  12. Concentrations and distribution of synthetic musks and siloxanes in sewage sludge of wastewater treatment plants in China.

    PubMed

    Liu, Nannan; Shi, Yali; Li, Wenhui; Xu, Lin; Cai, Yaqi

    2014-04-01

    In this study, we assessed the occurrence and distribution patterns of seven synthetic musks (SMs) and 17 siloxanes in anaerobic digested sludge samples collected at the dewatering process from 42 wastewater treatment plants (WWTPs) in China. SMs in sludge from different WWTPs exhibited similar composition profiles, and their total concentrations ranged from 47.3 ng/g to 68.2 ?g/g dry weight (dw). On average, galaxolide (HHCB, 63.8%) and tonalide (AHTN, 31.7%) accounted for 95.5% of ?SMs. The total concentrations of cyclic siloxanes ranged from siloxanes. On average, cyclic siloxanes accounted for 68% of the total siloxanes. High concentrations and detection frequencies of SMs and siloxanes in sewage sludge indicated that both of them were widely used in China. Among the sludge samples from 42 WWTPs, the concentrations of both ?SMs and ?siloxanes had considerable variations. We investigated the influence of potential factors (wastewater and sludge characteristics, the treatment capacity, serving population, and the treatment techniques of WWTPs) on the levels of target compounds in sludge, and found that SMs were significantly (p<0.05) correlated with the total organic carbon (TOC) of the sludge and the serving population of WWTP. There were also strong correlations (p<0.05) between the treatment capacity of WWTPs and cyclic siloxanes, as well as between the TOC of the sludge and linear siloxanes. In addition, the ecological risks of SMs and siloxanes in sewage sludge addressed to land application were assessed, which suggested that there was a low risk to the soil environment. PMID:24463026

  13. Bonded Interactions in Silica Polymorphs, Silicates and Siloxane Molecules

    SciTech Connect

    Gibbs, Gerald V.; Wallace, Adam F.; Cox, David F.; Downs, R. T.; Ross, Nancy L.; Rosso, Kevin M.

    2009-08-01

    Experimental model electron density distributions recorded for the silica polymorphs coesite and stishovite are comparable with electron density distributions calculated for a variety of silicates and siloxane molecules. The Si-O bond lengths and Si-O-Si angles calculated with first principles density functional theory methods as a function of pressure are also comparable with the bond lengths and angles observed for coesite and quartz within the experimental error. The similarity of the topological properties of the Si-O bonded interactions and the experimental and the geometry optimized structures for the silica polymorphs provides a basis for understanding the properties and crystal chemistry in terms of a molecular-based model. The agreement supports the argument that the bulk of the structural, physical and thermodynamic properties of the silica polymorphs are intrinsic properties of the molecular-like coordinated polyhedra such that the silica polymorphs can be pictured as supermolecules of silica bound by the virtually same forces that bind the Si and O atoms in simple siloxane molecules. The topology of the electron density distribution is consistent with the assertion that the Si-O bonded interaction arises from the net electrostatic attraction exerted on the nuclei by the electron density accumulated between the Si and O atoms. The correlation between the Si-O bond length and Si-O-Si angle is ascribed to the progressive local concentration of the electron density in the nonbonded region of the O atom as the bond length increases and angle decreases rather then to bonded interactions involving the d-orbitals on Si. On the basis of the proximity of the bond critical point, rc, to the nodal surface of the Laplacian, ?2?(rc), and the values of ?(rc) and G(rc)/?(rc), the Si-O bond qualifies as an intermediate bonded interaction. For bonded interactions of intermediate character, ?2?(rc) increases linearly as ?(rc) increases, the greater the shared character, the larger the value of ?2?(rc). In addition, a mapping of ?2?(r) serves to highlight those Lewis base domains that are susceptible to electrophilic attack by H like the O atom in coesite involved in bent Si-O-Si angles, the narrower the angle, the greater the affinity for H . On the basis of the net charges conferred on the Si and O atoms and the bonded radii of the two atoms, the Si-O bond of stishovite with six-coordinated Si and three-coordinated O is indicated to be more ionic in character than that in quartz with four-coordinated Si and two coordinated O. Unlike the conclusion reached for ionic and crystal radii (quantum mechanical unobservables), it is the bonded radius of the O atom that increases with the increasing coordination number of Si, not the radius of the Si atom. The modeling of the electron density distributions for quartz, coesite and beryl as a function of pressure indicates that the shared character of the bonded interactions in these minerals increases slightly with increasing pressure. The insight provided by the calculations and the modeling of the electron density distributions and the structures of the silica polymorphs bodes well for future Earth materials studies that are expected to improve and clarify our understanding of the connection between properties and structure within the framework of quantum mechanical observables, to find new and improved uses and to predict new properties for materials and to enhance our understanding of crystal chemistry and chemical reactions of materials in their natural environment at the atomic level

  14. Covalent immobilisation of protease and laccase substrates onto siloxanes.

    PubMed

    Rollett, Alexandra; Schroeder, Marc; Schneider, Konstantin P; Fischer, Roland; Kaufmann, Franz; Schftner, Rainer; Guebitz, Georg M

    2010-08-01

    Immobilisation of enzyme substrates is a powerful tool in the detection of enzymes in the chemosphere and the environment. A siloxane based strategy for the covalent immobilisation of oxidoreductase and protease substrates was developed involving activation of silica gel and polyethylene terephthalate (PET) as model carriers with (3-aminopropyl)-triethoxysilane or (3-mercaptopropyl)-trimethoxysilane (APTS, MPTS). Ferulic acid and L-Leucine-p-nitroanilide, Gly-Phe p-nitroanilide (GPpNA) and N-Succinyl-Ala-Ala-Pro-Leu p-nitroanilide (SAAPLpNA) as laccase and protein substrates, respectively, were covalently attached using glutaraldehyde or carbodiimide based cross-linking strategies. In contrast to conversion in solution, immobilised SAAPLpNA was hydrolysed much faster by protease than immobilised GPpNA indicating steric hindrance with decreasing chain length between point of attachment and site of enzyme attack. Immobilised ferulic acid was oxidised by laccase both in case of MPTS and APTS-modified silica gel giving clearly visible colour changes with Delta E values of 7.2 and 2.3, respectively after 24h of incubation, where Delta E describes the distance between two colours. Similarly, clearly visible colour changes with a Delta E value of 8.6 were seen after laccase treatment of ferulic acid immobilised on APTS activated PET as carrier. Limited surface hydrolysis of PET with a cutinase enhanced coupling of APTS and ferulic acid due to a larger number of hydroxyl groups available on the surface and consequently led to a higher colour difference of Delta E=12.2 after laccase oxidation. The covalent coupling product between ferulic acid and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was identified by LC-MS (M+1m/z601) and successfully oxidised with laccase. PMID:20547407

  15. ANIMAL ANALOGIES IN FIRST IMPRESSIONS OF FACES

    PubMed Central

    Zebrowitz, Leslie A.; Wadlinger, Heather A.; Luevano, Victor X.; White, Benjamin M.; Xing, Cai; Zhang, Yi

    2013-01-01

    Analogies between humans and animals based on facial resemblance have a long history. We report evidence for reverse anthropomorphism and the extension of facial stereotypes to lions, foxes, and dogs. In the stereotype extension, more positive traits were attributed to animals judged more attractive than con-specifics; more childlike traits were attributed to those judged more babyfaced. In the reverse anthropomorphism, human faces with more resemblance to lions, ascertained by connectionist modeling of facial metrics, were judged more dominant, cold, and shrewd, controlling attractiveness, babyfaceness, and sex. Faces with more resemblance to Labradors were judged warmer and less shrewd. Resemblance to foxes did not predict impressions. Results for lions and dogs were consistent with trait impressions of these animals and support the species overgeneralization hypothesis that evolutionarily adaptive reactions to particular animals are overgeneralized, with people perceived to have traits associated with animals their faces resemble. Other possible explanations are discussed. PMID:25339791

  16. [Complications Resulting from Taking Ear Impressions].

    PubMed

    Sugiuchi, Tomoko; Kodera, Kazuoki; Zusho, Hiroyuki; Asano, Yoshikazu; Kanesada, Keiko; Hayashida, Mitsuhiro; Kanaya, Koichiro; Tokumaru, Takeshi

    2015-08-01

    In 2012, we carried out a study in a large sample to understand the secondary injuries caused during the taking ear impressions for hearing aids. This study is a follow-up of previous research conducted in 1986 (285 medical institutions) and 1999 (98 medical institutions). We posted a questionnaire survey to the otolaryngology departments of 3,257 medical institutions. The response rate to the questionnaire was 62.9% (2,050 of the 3,257 institutions), and the results indicated that 301 of the 2050 institutions (14.7%) had experience with secondary injuries, with a total of 460 cases reported. In 342 of the 460 cases (74.3%), the secondary injuries occurred at hearing-aid dealerships, followed by 67 cases (14.6%) at affiliated medical institutions, and 51 cases (11.1%) in other locations, including other medical institutions, rehabilitation counseling centers, and educational institutions. The most common type of secondary injury (298 cases, 64.8%) was caused by the presence of foreign bodies in the ear, which in turn was a result of complications occurring during the removal of residual ear impression material. Of these 298 cases, 32 required excision of the foreign bodies and surgical intervention under general anesthesia. The remaining 10 cases exhibited isolated tympanic membrane perforation without foreign body-related complications. Furthermore, 146 cases (31.7%) developed bleeding and otitis externa following removal of the ear impression, and there were reports of cases with bleeding that required long-term outpatient care and treatment. Therefore, since retention of a foreign body in the ear and tympanic membrane perforation can occur even in patients without a history of surgery or prior otologic history, adjustment of hearing aids requires prior otorhinolaryngological examination. Furthermore, because of the risk of secondary injury when taking ear impressions, this procedure must be performed with caution under the guidance of an otolaryngologist. PMID:26548100

  17. First results of ESA's IMPRESS Project

    NASA Astrophysics Data System (ADS)

    Heppener, Marc; Minster, Olivier; Jarvis, David John

    2008-07-01

    IMPRESS is an acronym for Intermetallic Materials Processing in Relation to Earth and Space Solidification. This 5-year project was selected by the European Commission in 2004 and is being coordinated by the European Space Agency. The main scientific objective of IMPRESS is to gain a better understanding of the links between materials processing routes, structure and final properties of novel intermetallic alloys. From a technical standpoint, the project aims to develop and test two distinct prototypes based on intermetallic materials; namely (i) gas turbine blades and (ii) Raney-type catalytic powders. Numerous material processing routes are being investigated within the project with a strong emphasis on solidification. For turbine blade manufacturing the main processes under study are casting and heat treatment. For catalytic powder production the focus is placed on gas atomisation and vapour condensation processes. IMPRESS combines a wide range of fundamental studies of solidification both on ground and in space, as well as industrial process development. This paper will describe some of the different facets related to solidification and the benchmark space experiments.

  18. Burger or yogurt? Indulgent consumption in impression management contexts.

    PubMed

    Cheng, Yin-Hui; Huang, Molly C-J; Chuang, Shih-Chieh; Ju, Ying Rung

    2015-10-01

    We conducted three studies to investigate indulgent choice in settings with and without impression management by public-private manipulation with evaluation. Study 1 showed that the participants were less indulgent under public scrutiny due to the employment of impression management. Study 2 focused on the impression management context to test the moderate effect of self-consciousness in two impression managed contexts. Study 3 focused on context without impression management to test the moderate effects of self-awareness on choices. We found that depending on differences in primed personality, individuals tended to make choices other than those they favoured privately when anticipating that others might form impressions of them based on the decisions made. The findings of all three studies support our basic prediction that people are less indulgent under impression management and suggest that people tend to manage their impression by eating healthier (less indulgently) in public. PMID:25287306

  19. Dimensional accuracy of stone casts made from silicone-based impression materials and three impression techniques.

    PubMed

    Vitti, Rafael Pino; da Silva, Marcos Aurélio Bomfim; Consani, Rafael Leonardo Xediek; Sinhoreti, Mário Alexandre Coelho

    2013-01-01

    The aim of this study was to measure and compare the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two condensation silicones, two addition silicones and three impression techniques (1-step putty/light-body, 2-step putty/light-body and monophase technique). A partially edentulous standard stainless steel mandibular arch cast was obtained with reference points on the permanent mandibular right and left canines, and permanent mandibular right and left second molars. The anteroposterior distances (between the mandibular left canine and second molar and between the mandibular right canine and second molar) and transverse distances (between the mandibular left and right canines and between the mandibular left and right second molars) of stainless steel cast were measured by a microscope at 30× magnification and 0.5 µm accuracy. All impressions were made with condensation or addition silicones. The 1- and 2-step putty/light-body impressions were accomplished with putty and light-body materials and the monophase impressions with light-body material only. After the impression procedures, accuracy of each material and technique was assessed measuring the stone casts poured (n=5) from the impressions, by the same microscope. The differences between the values of stone cast and stainless steel cast were calculated, presented as percentages and analyzed statistically by two-way ANOVA and the means compared by Tukey's test (α=0.05). All distances measured on stone casts showed altered dimensions with significantly negative linear changes (shrinkage) as compared to those of the stainless steel cast. The stone casts made from the addition silicones were dimensionally more accurate. No differences were found among the impression techniques. PMID:24474292

  20. [Problems in disinfection of dental impression materials].

    PubMed

    Borneff, M; Fuhr, K; Behneke, N

    1989-04-01

    In view of the risk of infection of the dentist and his staff in the dental surgery and dental laboratory and also of the patient with regard to hepatitis B and potentially also of AIDS, interruption of possible chains of infection by means of specific disinfection measures is to be demanded. Whereas appropriate hygiene concepts exist for disinfection of instruments, surfaces of equipment and furniture with regard to selection and application of various methods which may be considered, there are still extensive deficits for the domain of impression materials and their possible decontamination. In this regard, dentists frequently lack information with an adequate scientific basis that is understandable and oriented to practical requirements. Owing to the diversity of materials and their different behavior (cf. Tab. 1), appropriate recommendations can only be made on the basis of extensive studies. We assume that a practically relevant procedure must meet the following requirements: 1) sufficiently high rates of bacterial reduction in accordance with the guidelines of the DGHM, 2) lack of alterations in the dimensions or surfaces of the materials, 3) universal applicability, 4) practicability within a time period which is acceptable for smooth operation of the practice, 5) can be employed without problems for the staff. The object of the report are bacteriological results and materials testing data for the application of various methods of disinfection to selected impression materials. To summarize, it can be stated with regard to the bacteriological results that disinfection of impression materials is possible with fulfillment of the criteria specified above, but that there is a pronounced dependence of the results on the product formulation of the disinfectant and also of the impression material (cf. Fig. 4 and 5). Investigations of the material-related effects of the disinfection measures showed that extrapolation of the findings from one group of materials to another is also not possible in this connection, and that moreover the materials used to produce the model must also be included besides the impression materials used (cf. Fig. 9). Accordingly, statements on the suitability of a disinfection procedure are present admissible at most for the respective combination of materials tested, which makes practical introduction problematical. PMID:2500803

  1. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resin impression tray material. 872.3670 Section 872.3670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices 872.3670 Resin impression tray material. (a) Identification. Resin impression tray...

  2. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resin impression tray material. 872.3670 Section 872.3670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices 872.3670 Resin impression tray material. (a) Identification. Resin impression tray...

  3. Hydrogen-Bond Basic Siloxane Phosphonate Polymers for Surface Acoustic Wave (Saw) Sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A surface acoustic wave (SAW) sensor coated with a novel hydrogen-bond basic siloxane phosphonate SAW polymer gave excellent initial response and long-term performance when tested against phenol vapor and compared with polyethyleneimine (PEI), a conventional hydrogent-bond basic SAW polymer....

  4. Cyclic siloxanes in air, including identification of high levels in Chicago and distinct diurnal variation

    PubMed Central

    Yucuis, Rachel A.; Stanier, Charles O.; Hornbuckle, Keri C.

    2014-01-01

    The organosilicon compounds octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) are high production volume chemicals that are widely used in household goods and personal care products. Due to their prevalence and chemical characteristics, cyclic siloxanes are being assessed as possible persistent organic pollutants. D4, D5, and D6 were measured in indoor and outdoor air to quantify and compare siloxane concentrations and compound ratios depending on location type. Indoor air samples had a median concentration of 2200 ng m−3 for the sum of D4, D5, and D6. Outdoor sampling locations included downtown Chicago, Cedar Rapids, IA, and West Branch, IA, and had median sum siloxane levels of 280, 73, and 29 ng m−3 respectively. A diurnal trend is apparent in the samples taken in downtown Chicago. Nighttime samples had a median 2.7 times higher on average than daytime samples, which is due, in part, to the fluctuations of the planetary boundary layer. D5 was the dominant siloxane in both indoor and outdoor air. Ratios of D5 to D4 averaged 91 and 3.2 for indoor and outdoor air respectively. PMID:23541357

  5. Adsorptive characteristics of the siloxane surfaces of reduced-charge bentonites saturated with tetramethylammonium cation.

    PubMed

    Ruan, Xiuxiu; Zhu, Lizhong; Chen, Baoliang

    2008-11-01

    To elucidate interactions of neutral organic contaminants (NOCs) with siloxane surfaces (often referred to hydrophobic nanosites)found between cations in 2:1 phyllosilicates, adsorption of aliphatic and aromatic compounds onto both internal and external siloxane surfaces oftetramethylammonium-intercalated bentonite with a cation exchange capacity (CEC) of 108 cmol/kg (108TMA) and its reduced-charge bentonite (CEC = 65 cmol/ kg, 65TMA) were investigated. Reduction of the layer charge and saturation of bentonite interlayers with TMA+ modify the interlayer microenvironments, which dramatically promote adsorption of NOCs. Specific mechanisms (i.e., steric restriction and phenyl-effect) control the adsorption of NOCs onto internal siloxane surfaces of TMA+ -bentonites from water. The adsorption sites of 108TMA can not provide sufficient space to accommodate NOCs, hence hindering adsorption. Adsorption mechanism on 65TMA varies with solute-loadings, from polarity-selective at low loadings to aromaticity-preferable at high loadings. Significant contribution of phenyl-effect between adsorbed-solutes to aromatics adsorption on 65TMA is found. Solvent polarity effect on the aggregation of TMA+ -bentonites and aniline adsorption demonstrated that the contribution of external siloxane surfaces to favor adsorption in n-hexane are actually exploited but generally omitted. These observations provide significant insights into distinguishing different uptake mechanisms as well as the potential means for the rational design of better organic sorbents. PMID:19031880

  6. 40 CFR 721.10484 - Siloxanes and Silicones, Me vinyl, hydroxy-terminated, reaction products with...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10484 Siloxanes and Silicones, Me vinyl, hydroxy-terminated, reaction products with -modified silica. (a) Chemical substance and..., hydroxy-terminated, reaction products with -modified silica. 721.10484 Section 721.10484 Protection...

  7. 40 CFR 721.10484 - Siloxanes and Silicones, Me vinyl, hydroxy-terminated, reaction products with...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10484 Siloxanes and Silicones, Me vinyl, hydroxy-terminated, reaction products with -modified silica. (a) Chemical substance and..., hydroxy-terminated, reaction products with -modified silica. 721.10484 Section 721.10484 Protection...

  8. Bioactive and degradable hybridized nanofibers of gelatin-siloxane for bone regeneration.

    PubMed

    Song, Ju-Ha; Yoon, Byung-Ho; Kim, Hyoun-Ee; Kim, Hae-Won

    2008-03-15

    Organic-inorganic hybridized nanofibers constituted of gelatin and siloxane were generated by the electrospinning technique for use as bone regeneration matrices. The composition of the nanofibers selected was to be both degradable and bioactive. Precursors of gelatin and siloxane were dissolved in a modified acidic solvent composed of acetic acid, ethyl acetate, and distilled water. The hybridized nanofibers with various compositions (gelatin/siloxane = 1/2, 1, and 2 by weight fraction) were successfully electrospun under the adjusted processing conditions. Compared to the pure gelatin nanofiber, the hybridized nanofibers showed improved chemical stability in a saline solution. This was attributed to the cross-linking effect of the siloxane with the gelatin chains. Osteoblastic cells were observed to attach, spread, and populate actively on the hybridized nanofiber matrices. In particular, the cells on the hybridized nanofibers were recruited to elicit better osteoblastic activity (alkaline phosphatase) with respect to those on the pure gelatin. The newly-developed hybridized nanofiber is considered to be useful as a bone regeneration matrix, due to its nanofibrous structural trait as well as its degradability and bone cell activity. PMID:17647222

  9. A multiphase analysis of partitioning and hazard index characteristics of siloxanes in biosolids.

    PubMed

    Surita, Sharon C; Tansel, Berrin

    2014-04-01

    Siloxanes are widely used in personal care and industrial products due to their soft texture, low surface tension, thermal stability, antimicrobial and hydrophobic properties, among other characteristics. As a result, they are released to gas phase during waste decompositions and found in biogas at landfills and digester gas at wastewater treatment facilities. The objectives of this study were to investigate the release of siloxanes in aqueous and gaseous phase as well as in biosolids in a local wastewater treatment facility. The formation reactions were estimated using first order kinetics for commonly found siloxanes (L3, D3, D4, D5 and D6) during waste decomposition. Expected concentrations and the risk factors of exposure to siloxanes were evaluated based on the initial concentrations, partitioning characteristics and persistence parameter. D4 and D5 presented the highest initial gaseous phase concentrations of 5000 and 1800 ?g/m(3) respectively. Based on first order kinetics, partition coefficients and initial concentrations, the hazards potentials were largest for D4 in both liquid phase and biosolids while D6 poses the highest risk in gaseous phase. PMID:24580825

  10. Occurrence of cyclic and linear siloxanes in indoor air from Albany, New York, USA, and its implications for inhalation exposure.

    PubMed

    Tran, Tri Manh; Kannan, Kurunthachalam

    2015-04-01

    Cyclic and linear siloxanes are used in a wide variety of household and consumer products. Nevertheless, very few studies have reported the occurrence of these compounds in indoor air or inhalation exposure to these compounds. In this study, five cyclic (D3-D7) and nine linear siloxanes (L3-L11) were determined in 60 indoor air samples collected in Albany, New York, USA. The mean concentrations of individual siloxanes in particulate and vapor phases ranged from <12 ?g g(-1) (for octamethyltrisiloxane [L3], decamethyltetrasiloxane [L4]) to 2420 ?g g(-1) (for decamethylcyclopentasiloxane [D5]) and from 1.05 ng m(-3) to 543 ng m(-3), respectively. The mean concentrations of individual siloxanes in combined particulate and vapor phases of bulk indoor air ranged from 1.41 ng m(-3) (for L4) to 721 ng m(-3) (for D5). Cyclic siloxanes hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), D5, dodecamethylcyclohexasiloxane (D6), and octadecamethylcycloheptasiloxane (D7) were found in all indoor air samples. The mean concentrations of total siloxanes (i.e., sum of cyclic and linear siloxanes) ranged from 249 ng m(-3) in laboratories to 6210 ng m(-3) in salons, with an overall mean concentration of 1470 ng m(-3) in bulk indoor air samples. The calculated mean daily inhalation exposure doses of total siloxanes (sum of 14 siloxanes) for infants, toddlers, children, teenagers, and adults were 3.18, 1.59, 0.76, 0.34, and 0.27 ?g/kg-bw/day, respectively. PMID:25540848

  11. Chemical enhancement of footwear impressions in urine on fabric.

    PubMed

    Farrugia, Kevin J; Bandey, Helen; Bleay, Steve; NicDaid, Niamh

    2012-01-10

    A range of chemical techniques were utilised for the enhancement of footwear impressions deposited on a variety of fabric types of different colours with urine as a contaminant. A semi-automated stamping device was used to deliver test impressions at a set force to minimise the variability between impressions; multiple impressions were produced and enhanced by each reagent to determine the repeatability of the enhancement. Urine samples from different donors were analysed using a spectrofluorophotometer revealing differences between individuals. Results indicated that the enhancement of footwear impressions in urine was possible using amino acid staining techniques whereas protein stains failed to achieve successful enhancement. PMID:21813253

  12. Fabrication of a custom-made impression tray for making preliminary impressions of edentulous mandibles.

    PubMed

    Sofou, A M; Diakoyianni-Mordohai, I; Pissiotis, A L; Emmanuel, I

    1998-08-01

    Severe mandibular alveolar ridge resorption is usually observed in patients with long-term edentulism and/or ill-fitting dentures. In some of these patients, the genial tubercles project into the floor of the mouth as a high point in the anterior area of the mandibular residual ridge. The lingual flanges of mandibular stock impression trays usually impinge on the most prominent areas of the resorbed mandibular edentulous ridge (i.e., internal oblique lines and genial tubercles). It is suggested that a preliminary custom tray be made in such cases to pour an initial impression so that individual custom trays can be fabricated. An efficient method for constructing such a custom impression tray from readily available materials is described. PMID:9807132

  13. Reliability of the impression replica technique.

    PubMed

    Falk, Anders; Vult von Steyern, Per; Fransson, Hkan; Thorn, Margareta Molin

    2015-01-01

    The aim of this study was to evaluate the reliability of the impression replica technique with a four-unit zirconia fixed dental prosthesis (FDP). Marginal and internal fit were measured by repeatedly placing the FDP on an epoxy cast using light-body silicone material corresponding to cement. All measured marginal and internal fit points showed varying values. The greatest variations were seen at the most distal margin (33 ?m) and at the distal abutment of the FDP (77 ?m). The results showed that the technique gives moderate variations and is a useful method to evaluate marginal and internal fit. PMID:25822305

  14. Destruction of polyvinyl chloride under extrusion

    NASA Astrophysics Data System (ADS)

    Dmitriev, M. T.; Serebriakova, R. V.; Serebriakov, V. N.; Zimin, P. N.; Nastenko, A. V.; Derevianchenko, L. G.; Antsifirova, N. P.; Visloukh, V. V.

    1982-08-01

    An common industrial application of polyvinyl chloride (PVC) is the extrusive insulation of electric wires and cables. Experimental results are presented on the thermal and mechanical destruction of PVC under extrusion. Under extrusion conditions (at temperatures higher than 150 C), the evolution of hydrogen chloride determines practically the entire process of PVC destruction. The use of the present data to establish hygienic standards regarding safe concentrations of PVC destruction products in the work environment is discussed.

  15. Electrospun polyvinyl alcohol-polyvinyl pyrrolidone nanofibrous membranes for interactive wound dressing application.

    PubMed

    Shankhwar, Nisha; Kumar, Manishekhar; Mandal, Biman B; Robi, P S; Srinivasan, A

    2016-02-01

    Cross-linked polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) composite nanofibrous membranes have been prepared by electrospinning. Mechanical properties of the membranes improved significantly with PVP addition. PVP improved hydrophilicity and sustainable degradation of the membranes. Biocompatibility of the membranes was assessed by in vitro culture of native skin cells (L929 fibroblast and HaCaT keratinocytes). Tests showed sustained release of the antibiotic ciprofloxacin hydrochloride monohydrate by the membranes. Further, zone of inhibition study against Staphylococcus aureus growth demonstrated protective action against external pathogenic microbes. These studies show these simple PVA-PVP nanofibrous membranes are promising interactive antibiotic-eluting wound dressing materials. PMID:26573740

  16. Affective impressions and memorability of color-form combinations.

    PubMed

    Sakuta, Yuiko; Gyoba, Jiro

    2006-04-01

    In this study the authors investigate how various impressions affect the recognition of color-form pairs. They performed a preliminary study, a main study of impression rating using the semantic differential method, and a recognition experiment. On the basis of the preliminary study, the authors chose 14 appropriate pairs of adjectives and 48 color and form stimuli and used them for the main study. Factor analysis of the main study extracted three factors: Activity, Potency, and Evaluation. In the recognition test, the authors found that color-form pairs with congruent impressions in Activity or Potency were more easily recognized than pairs with incongruent impressions. In contrast, pairs with incongruent impressions in Evaluation were recognized more easily than congruent pairs. These results are discussed in relation to the assumed network representations of affective impressions that have different characteristics depending on the three factors. PMID:16705912

  17. Dimensional stability ofautoclave sterilised addition cured impressions and trays.

    PubMed

    Deb, S; Etemad-Shahidi, S; Millar, B J

    2014-03-01

    The aim of this study was to investigate the dimensional accuracy of impressions following sterilisation by autoclaving. Dental impressions (75) were of a dentoform containing 6 reference points. The impressions were split into 5 groups of 15, each group used a different impression technique. Groups were divided into 3 subgroups with 5 impressions as control, 5 for disinfection by Perform-ID and 5 being autoclaved. Measurements were made using a travelling light microscope. A minimal significant dimensional difference (0.01impression method. No significant dimensional differences were observed for all other groups (P>0.05). The trays and materials tested were suitable for the autoclave sterilisation. PMID:24922998

  18. Contribution of siloxanes to COD loading at wastewater treatment plants: phase transfer, removal, and fate at different treatment units.

    PubMed

    Surita, Sharon C; Tansel, Berrin

    2015-03-01

    Cyclic volatile methylsiloxanes (cVMSs) are entering to waste stream in increasing quantities due to their increasing use in personal care products (i.e., shampoos, creams). The cVMSs have high vapor pressures and low solubilities and are mostly transferred into the gaseous phase via volatilization; however, some are sorbed onto biosolids. The purpose of this study was to track and estimate the phase transfer (water, solids, gas), fate, and contribution to COD loading of selected siloxanes (D4, D5 and D6) which are the most commonly found cVMSs in the wastewater systems. Removal efficiencies of the wastewater treatment units were evaluated based on the partitioning characteristics of the cVMSs in gas, liquid, and biosolids phases. The contributions of the siloxanes present in the influent and effluent were estimated in terms of COD levels based on the theoretical oxygen demand (ThOD) of the siloxanes. Siloxanes constitute approximately 39 and 0.001mgL(-1) of the COD in the influents and effluent. Oxidation systems showed higher removal efficiencies based COD loading in comparison to the removal efficiencies achieved aeration tanks and filtration systems. Treatment systems effectively remove the siloxanes from the aqueous phase with over 94% efficiency. About 50% of the siloxanes entering to the wastewater treatment plant accumulate in biosolids. PMID:25528947

  19. Characterization of full-scale carbon contactors for siloxane removal from biogas using online Fourier transform infrared spectroscopy.

    PubMed

    Hepburn, C A; Martin, B D; Simms, N; McAdam, E J

    2015-01-01

    In this study, online Fourier transform infrared (FTIR) spectroscopy has been used to generate the first comprehensive characterization of full-scale carbon contactors for siloxane removal from biogas. Using FTIR, two clear operational regions within the exhaustion cycle were evidenced: an initial period of pseudo-steady state where the outlet siloxane concentration was consistently below the proposed siloxane limits; and a second period characterized by a progressive rise in outlet siloxane concentration during and after breakthrough. Due to the sharp breakthrough front identified, existing detection methods (which comprise field sampling coupled with laboratory-based chromatographic determination) are insufficiently responsive to define breakthrough, thus carbon contactors currently remain in service while providing limited protection to the combined heat and power engine. Integration of the exhaustion cycle to breakthrough identified average specific media capacities of 8.5-21.5 gsiloxane kg(-1)GAC, which are lower than that has been reported for vapour phase granular activated carbon (GAC). Further speciation of the biogas phase identified co-separation of organic compounds (alkanes and aromatics), which will inevitably reduce siloxane capacity. However, comparison of the five full-scale contactors identified that greater media capacity was accessible through operating contactors at velocities sufficient to diminish axial dispersion effects. In addition to enabling significant insight into gas phase GAC contactors, the use of FTIR for online control of GAC for siloxane removal is also presented. PMID:25413112

  20. Impression Management in Survey Responding: Easier for Collectivists or Individualists?

    PubMed Central

    Riemer, Hila; Shavitt, Sharon

    2012-01-01

    Three experiments indicate that when individualists and collectivists engage in impression management on self-reports, they do so through different psychological mechanism s. Collectivists do so through a relatively automatic process. Thus, they can impression manage even when cognitively busy. Individualists impression manage through a more effortful process. Therefore, they can do so only when the situation permits effortful processing. These findings highlight distinct conditions under which social norms may influence consumer self-reports across cultures. PMID:23175618

  1. Comparing the accuracy of reversible hydrocolloid and elastomeric impression materials.

    PubMed

    Federick, D R; Caputo, A

    1997-02-01

    This in vitro investigation evaluated the accuracy of reversible hydrocolloid, vinyl polysiloxane and polyether elastic impression materials used in conjunction with two die stones. The authors made impressions in an experimental environment that approximated clinical conditions in regard to temperature and moisture. Analysis of variance and t-tests were used to compare corresponding measurements on experimental casts made from the various impression materials. PMID:9037971

  2. A new simplified beading and boxing procedure for elastic impression.

    PubMed

    Vyas, Anup; Maru, Kavita; Bali, Sandeep Kaur; Jain, Sumet; Shukla, Jyotsna; Kataria, Neene

    2011-03-01

    Beading and Boxing of impression is taught in most dental colleges. The boxing procedure is crucial step to preserve the details of the final impression especially of the vestibular area. This article describes an alternative beading-boxing procedure that is compatible with all impression materials, is efficient, simple, inexpensive, and practicable. Use of commercially available instant adhesive around the border to act as a joining agent between elastic impressions and beading wax or bead made up of base plate wax is advocated in this technique. PMID:22379306

  3. The fungicidal effect of ultraviolet light on impression materials

    SciTech Connect

    Ishida, H.; Nahara, Y.; Tamamoto, M.; Hamada, T. )

    1991-04-01

    The effects of ultraviolet (UV) light on fungi and impression materials were tested. UV light (250 microW/cm2) killed most Candida organisms (10(3) cells/ml) within 5 minutes. UV light (8000 microW/cm2) killed most C. albicans (10(7) cells/ml) within 2 minutes of exposure. The effect of UV light on dimensional change and surface roughness of impression materials (irreversible hydrocolloid, agar, and silicone rubber) was tested. The results showed that neither dimensional change nor surface roughness of the impression materials were affected. The results of this study indicate that UV light disinfects impression materials that are contaminated with Candida organisms.

  4. Insights into siloxane removal from biogas in biotrickling filters via process mapping-based analysis.

    PubMed

    Soreanu, Gabriela

    2016-03-01

    Data process mapping using response surface methodology (RSM)-based computational techniques is performed in this study for the diagnosis of a laboratory-scale biotrickling filter applied for siloxane (i.e. octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5)) removal from biogas. A mathematical model describing the process performance (i.e. Si removal efficiency, %) was obtained as a function of key operating parameters (e.g biogas flowrate, D4 and D5 concentration). The contour plots and the response surfaces generated for the obtained objective function indicate a minimization trend in siloxane removal performance, however a maximum performance of approximately 60% Si removal efficiency was recorded. Analysis of the process mapping results provides indicators of improvement to biological system performance. PMID:26745382

  5. Phthalide Cardo Chain Extended Siloxane Core Skeletal Modified Polyimide/Multi-Walled Carbon Nanotube Nanocomposites.

    PubMed

    Priya, R Padhma; Gunasekaran, S G; Dharmendirakumar, M

    2015-09-01

    A new type of siloxane core modified phthalide cardo chain based polyimide (PI) was successfully prepared from siloxane core dianhydride and ether linked phenolphthalein diamine moiety. This PI was further modified with different weight percentages of multi-walled carbon nanotubes (MWCNTs) to obtain MWCNT reinforced PI nanocomposites. The enhancement in the glass transition temperature and improved thermal stability could be afforded by the restrained motion of polymeric chain, caused from nanoreinforcement effect of MWCNTs. The successive increment in the concentration of MWCNTs resulted in augmented dielectric constant because of interfacial polarization of MWCNTs. This PI shows better solubility and low water uptake percentage of 0.42-0.58%. The morphological studies ascertain the molecular level dispersion of MWCNT throughout the PI matrix. PMID:26716238

  6. Non-toxic liquid scintillators with high light output based on phenyl-substituted siloxanes

    NASA Astrophysics Data System (ADS)

    Dalla Palma, M.; Carturan, S. M.; Degerlier, M.; Marchi, T.; Cinausero, M.; Gramegna, F.; Quaranta, A.

    2015-04-01

    The work describes the development of a new class of liquid scintillators based on polysiloxane liquid compounds. These materials are characterized by low toxicity, chemical inertness, very low volatility and low flammability, allowing their use without concerns even at high temperatures in vacuum. In this view different polysiloxane based liquids have been tested, with variable content and distribution of phenyl lateral substituents and added with suitable dyes, namely 2,5-diphenyloxazole (PPO) and Lumogen Violet (LV). Absorption and fluorescence spectroscopy have been used in order to study the emission feature of the various compounds and to investigate the spectral matching between siloxane solvents and dissolved primary dyes. Scintillation efficiency towards 60Co and 137Cs gamma rays, relative to commercial liquid scintillator (EJ-309), has been measured and the results have been related to the energy transfer and energy migration mechanism from monomer and excimer forming sites in liquid siloxanes.

  7. Mitigating the effect of siloxanes on internal combustion engines using landfill gasses

    SciTech Connect

    Besmann, Theodore M

    2015-01-06

    A waste gas combustion method that includes providing a combustible fuel source, in which the combustible fuel source is composed of at least methane and siloxane gas. A sodium source or magnesium source is mixed with the combustible fuel source. Combustion of the siloxane gas of the combustible fuel source produces a silicon containing product. The sodium source or magnesium source reacts with the silicon containing product to provide a sodium containing glass or sodium containing silicate, or a magnesium containing silicate. By producing the sodium containing glass or sodium containing silicate, or the magnesium containing silicate, or magnesium source for precipitating particulate silica instead of hard coating, the method may reduce or eliminate the formation of silica deposits within the combustion chamber and the exhaust components of the internal combustion engine.

  8. Mitigating the effect of siloxanes on internal combustion engines using landfill gasses

    SciTech Connect

    Besmann, Theodore M

    2014-01-21

    A waste gas combustion method that includes providing a combustible fuel source, in which the combustible fuel source is composed of at least methane and siloxane gas. A sodium source or magnesium source is mixed with the combustible fuel source. Combustion of the siloxane gas of the combustible fuel source produces a silicon containing product. The sodium source or magnesium source reacts with the silicon containing product to provide a sodium containing glass or sodium containing silicate, or a magnesium containing silicate. By producing the sodium containing glass or sodium containing silicate, or the magnesium containing silicate, or magnesium source for precipitating particulate silica instead of hard coating, the method may reduce or eliminate the formation of silica deposits within the combustion chamber and the exhaust components of the internal combustion engine.

  9. Polyvinyl alcohol as photoluminescent conductive polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Wetzel, G. B. J.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Toxqui-López, S.; Fuentes-Tapia, I.

    2007-02-01

    We synthesized a photoluminescent conductor polymer composed of polyvinyl alcohol, which was doped with nickel chloride to decrease its resistivity (300 Ωcm) and benzalkonium chloride to obtain photoluminescence properties, when it is radiated with a green laser beam (532 nm). We compared its absorbance curve and its energy emitted curve to observe the amount energy that is taken advantage of this process. Besides we research the photoluminescence behavior when an electric currant is applied in our conductor polymer, obtaining a modulation capacity.

  10. Synthesis and properties of dicationic ionic liquids containing a siloxane structural moiety

    NASA Astrophysics Data System (ADS)

    Glukhov, L. M.; Krasovskiy, V. G.; Chernikova, E. A.; Kapustin, G. I.; Kustov, L. M.; Koroteev, A. A.

    2015-12-01

    Five new ionic liquids formed by doubly charged cations containing a siloxane moiety and bis(trifluoromethylsulfonyl) imide anion are synthesized and characterized. Their thermal stability is studied by means of TGA; melting points (glass transition temperatures) and densities are measured. The temperature dependences of kinematic viscosity of the obtained ionic liquids are presented along with their approximations by the Vogel-Tammann-Fulcher equation.

  11. Dynamic surface tension and adsorption kinetics of a siloxane dicephalic surfactant

    NASA Astrophysics Data System (ADS)

    Zhang, Dianlong; Qu, Wenshan; Li, Zhe

    2015-02-01

    The dynamic surface tension (DST) of a siloxane dicephalic surfactant was measured by using the maximum bubble pressure method. By using the classical Ward and Tordai equation, the diffusion coefficient for each bulk surfactant concentration was calculated. The results show that at the initial adsorption stage and at the end of the adsorption process, the dynamic surface tension data were all consistent with this diffusion-controlled mechanism. Their diffusion coefficient was slightly lower than that for conventional hydrocarbon surfactants.

  12. Effect of siloxane spacer length on organosilicon bi-quaternary ammonium amphiphiles.

    PubMed

    Hao, Chuanming; Cui, Yuezhi; Yang, Pengfei; Zhang, Huayong; Mao, Dejiang; Cui, Xiao; Li, Junying

    2015-04-01

    A series of organosilicon Bola-form bi-quaternary ammonium amphiphiles, [OH5C3(C2H5)2N+-(CH2)3-Si(CH2)3-O-(Si(CH3)2O)n-Si(CH2)3⋯(CH2)3-N+(C2H5)2C3H5O]Cl2- (SinN2Cl2, n=0, 4, 6, 8), with the same headgroups and different length of hydrophobic linkage has been synthesized. The critical micelle concentration (CMC) of each amphiphiles was determined by equilibrium surface tension. With the increased length of hydrophobic siloxane spacer, the CMC values follow the order of Si8N2Cl2siloxane spacer and its internal oxygen atom, which make the molecular stretch free. The antimicrobial property of Si4N2Cl2 is more effective than others below the concentration of CMC, while the antimicrobial property of Si8N2Cl2 is more effective above the concentration of CMC, which indicated that both the adsorbability in formation of micellar and the hydrophobicity arising from the different length of siloxane spacer are important to inhibit microbe. Moreover, their wetting ability has been characterized by contact angles on various material surfaces. It shows that the higher weight of lipophilic siloxane spacer leads to lower contact angels. PMID:25794442

  13. The effect of amphiphilic siloxane oligomers on fibroblast and keratinocyte proliferation and apoptosis.

    PubMed

    Lynam, Emily C; Xie, Yan; Loli, Bree; Dargaville, Tim R; Leavesley, David I; George, Graeme A; Upton, Zee

    2010-11-01

    The formation of hypertrophic scars (HSF) is a frequent medical outcome of wound repair and often requires further therapy with treatments such as silicone gel sheets (SGS) or apoptosis-inducing agents, including bleomycin. Although widely used, knowledge regarding SGS and their mode of action is limited. Preliminary research has shown that small amounts of amphiphilic silicone present in SGS have the ability to move into skin during treatment. We demonstrate herein that a commercially available analogue of these amphiphilic siloxane species, the rake copolymer GP226, decreases collagen synthesis on exposure to cultures of fibroblasts derived from HSF. By size exclusion chromatography, GP226 was found to be a mixture of siloxane species, containing five fractions of different molecular weight. By studies of collagen production, cell viability and proliferation, it was revealed that a low molecular weight fraction (fraction IV) was the most active, reducing the number of viable cells present after treatment and thereby reducing collagen production as a result. On exposure of fraction IV to human keratinocytes, viability and proliferation were also significantly affected. HSF undergoing apoptosis after application of fraction IV were also detected via real-time microscopy and by using the TUNEL assay. Taken together, these data suggests that these amphiphilic siloxanes could be potential non-invasive substitutes to apoptotic-inducing chemical agents that are currently used as scar treatments. PMID:20725963

  14. Occurrence and fate of volatile siloxanes in a municipal wastewater treatment plant of Beijing, China.

    PubMed

    Xu, Lin; Shi, Yali; Cai, Yaqi

    2013-02-01

    The occurrence and fate of four cyclic and two linear volatile siloxanes were studied in a municipal Wastewater Treatment Plant (WWTP), Beijing City, China. Aqueous and sludge samples were analyzed by solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). In the studied WWTP, four cyclic analogs (D3-D6) had significantly higher concentrations and frequencies than the two linear analogs [Octamethyltrisiloxane (L3) and Decamethyltetrasiloxane (L4)], with inputs into the WWTP ranging from 78.2 to 387.7 kg/year. Removal efficiencies of volatile cyclic siloxanes in two parallel secondary treatment processes ranged from 59.3 to 92.7%. For volatile cyclic siloxanes, relative fractions of mass loss by adsorption to sludge ranged from 8.3 to 53.0%, and their adsorption capacities were significantly affected by the dissolved organic matter. Besides adsorption, they were eliminated mainly in anaerobic units (44.4-84.3%). Through in vitro biodegradation experiments, we concluded that in the anaerobic compartments, Hexamethylcyclotrisiloxane (D3) and Dodecamethylcyclohexasiloxane (D6) were eliminated mostly by volatilization, while Octamethylcyclotetrasiloxane (D4) and Decamethylcyclopentasiloxane (D5) may be eliminated by both volatilization and degradation. Furthermore, microbe catalysis hydrolysis was identified as one of the main degradation pathways for D4 and D5 in anaerobic compartments. PMID:23182664

  15. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces 177.1670 Polyvinyl...

  16. Evaluation of accuracy of direct transfer snapon impression coping closed tray impression technique and direct transfer open tray impression technique: an in vitro study.

    PubMed

    Balamurugan, T; Manimaran, P

    2013-09-01

    Accuracy of the implant impression technique is one of the key factor determining the strain free fit of the prosthesis fabricated which influences the treatment success. Two implant impression techniques namely the closed tray technique with transfer coping and open tray technique were evaluated for accuracy with stone casts obtained from them. Casts were evaluated using a custom constructed bar on strain gage (SYSCOM) and abutment coordinates using Coordinate Measuring Machine (TESA micro-HITE). The statistical analysis with one way ANOVA and Mann-Whitney tests show that the casts obtained with open tray technique were accurate than the casts of closed tray technique (significance P < 0.001). Direct transfer impression technique with less number of components ensures the high accuracy of transfer of implant positions from master cast to the laboratory cast compared to the indirect transfer impression technique. PMID:24431738

  17. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... fabrication of crowns, bridges, or full dentures. A preliminary plaster or stone model of the patient's teeth... form a custom tray. This tray is then filled with impression material and inserted into the patient's mouth to make an impression, from which a final, more precise, model of the patient's mouth is cast....

  18. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... fabrication of crowns, bridges, or full dentures. A preliminary plaster or stone model of the patient's teeth... form a custom tray. This tray is then filled with impression material and inserted into the patient's mouth to make an impression, from which a final, more precise, model of the patient's mouth is cast....

  19. Impressions of College Intructors: Stability and Change in Student Ratings

    ERIC Educational Resources Information Center

    Dudley, Kari L.

    2013-01-01

    Although the topic of stability and change in classroom impressions research is not new, there remain unanswered questions about what impressions are stable, when they are likely to change, and for whom they are likely to change over the course of a semester. My research will begin to answer those questions. My research took place in four college

  20. 21 CFR 872.3670 - Resin impression tray material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Resin impression tray material. 872.3670 Section 872.3670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices 872.3670 Resin impression tray material....

  1. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Preformed impression tray. 872.6880 Section 872.6880 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED..., such as alginate, to make an impression of a patient's teeth or alveolar process (bony tooth...

  2. Dimensional stability of alginate impressions immersed in disinfecting solutions.

    PubMed

    Durr, D P; Novak, E V

    1987-01-01

    The stability of full-arch alginate impressions that had been immersed in one of two disinfecting solutions was assessed by measuring stone casts poured from the alginate impressions. Statistically significant dimensional changes occurred, when compared with master casts, but only by 1 mm or less, a clinically insignificant amount. PMID:3100593

  3. A Study of Peer Tutors Using the Neurological Impress Method.

    ERIC Educational Resources Information Center

    McAllister, Elizabeth A.

    A study investigated the efficacy of using the neurological impress method in peer tutoring during reading instruction. The neurological impress reading method is a unison reading procedure in which the student and teacher or tutor read aloud simultaneously and quickly, with the student placed slightly in front of the teacher so that the teacher's

  4. Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations

    SciTech Connect

    Tansel, Berrin Surita, Sharon C.

    2014-11-15

    Highlights: • In the digester gas, D4 and D5 comprised the 62% and 27% if siloxanes, respectively. • In landfill gas, the bulk of siloxanes were TMSOH (58%) followed by D4 (17%). • Methane utilization may be a possible mechanism for TMSOH formation in the landfills. • The geometric configurations of D4 and D5 molecules make them very stable. - Abstract: The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si–O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si–O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups.

  5. Using double-poured alginate impressions to fabricate bleaching trays.

    PubMed

    Haywood, V B; Powe, A

    1998-01-01

    Esthetic and diagnostic treatment often requires two casts of one arch, one for baseline and one for alterations (diagnostic wax-up, bleaching tray, occlusal analysis). The purpose of this study was to compare the accuracy of stone casts generated from a second pour of a properly handled alginate impression with first-poured casts. A maxillary dentoform was indexed with six reference spaces (#8-15, 9-2, 2-15, and incisal-to-gingival of #3, 9, 14). Irreversible hydrocolloid (Jeltrate) impressions were made in perforated steel trays by a single investigator. Impression material was spatulated for 1 minute. The seated impression and dentoform were wrapped in a damp paper towel to simulate intraoral conditions, and allowed to set for 2 minutes. Upon separation, the impression was stored in a damp towel for 5 minutes. The impression was poured in cast stone (Microstone) according to the manufacturer's instructions. The stone-filled impression was immediately rewrapped in a damp paper towel and allowed to set for 45 minutes at room temperature. Upon removal of the stone, the impression was rinsed with cold water, shaken dry, and repoured in the same manner. Ten impressions were made: the first five impressions were poured to make casts for Group A, then repoured as described above for casts for Group B. The remaining five impressions were poured once to make casts for Group C. The six spaces of each cast were measured three times in random order using a dial caliper and the space average calculated for the cast. At each space, analysis of variance showed no significant difference among Groups A, B, or C (P < 0.05). When alginate impressions that have been poured with cast stone are kept moist during stone setting and repoured within 45 minutes, two casts can be generated from one impression with the same degree of accuracy as two casts made from taking two separate impressions, providing the alginate does not tear during first cast removal. PMID:9656923

  6. MECHANICAL PROPERTIES OF BLENDS OF PAMAM DENDRIMERS WITH POLY(VINYL CHLORIDE) AND POLY(VINYL ACETATE)

    EPA Science Inventory

    Hybrid blends of poly(amidoamine) PAMAM dendrimers with two linear high polymers, poly(vinyl chloride), PVC, and poly(vinyl acetate), PVAc, are reported. The interaction between the blend components was studied using dynamic mechanical analysis, xenon nuclear magnetic resonacne ...

  7. Process for the extrusion of compositions comprising polypropylene, polyvinyl alcohol and a polypropylene-polyvinyl alcohol adhesive

    SciTech Connect

    Derrick, W.E.

    1989-04-18

    This patent describes a process for extruding a composition comprising polyvinyl alcohol, a polypropylene-polyvinyl alcohol adhesive and a plypropylene prepared with a high activity polymerization catalyst. The improvement consists of utilizing polypropylene having from about 50 to about 5000 ppm by weight of hydrotalcite incorporated therein to substantially eliminate gel formation.

  8. An alternative impression technique for individuals with special care needs.

    PubMed

    Topouzelis, Nikolaos; Kotsiomiti, Eleni; Arhakis, Aristidis

    2010-01-01

    Impression making may be complicated in individuals with limited ability to cooperate with caregivers. An alternative technique for obtaining full-arch casts from sectional preliminary impressions is described. The technique is a modification of the procedure advocated for impression making in subjects with limited mouth opening. A pair of partial stock trays is selected to fit the right and left side of the arch. Two sectional irreversible hydrocolloid impressions are made separately. The first cast is placed into the second impression prior to pouring, to obtain a cast of the complete arch. The procedure was used during the treatment of an uncooperative young patient with Lesch-Nyhan Syndrome and provided a simple and reliable means to obtain the diagnostic cast of the mandibular teeth. It is recommended not only for uncooperative patients, but also for patients with special needs; such as those with anatomical restrictions, functional impairment, and movement disorders. PMID:21044108

  9. A Paradigm shift in the concept for making dental impressions

    PubMed Central

    Nayar, Sanjna; Mahadevan, R.

    2015-01-01

    Digital dental impression is a revolutionary technological advancement that so surpasses the accuracy and efficiency of former techniques for obtaining replicas of prepared teeth for the purpose of fabricating restorations that its adoption by dentists is rapidly eclipsing the use of elastomeric impression materials. The ultimate goals of dentists dedicated to quality restorative dentistry are to make their treatment of patients as accurate, stressless, and efficient as possible. By elimination of the everyday problems described above, there is no question that the significant advantages of digital impressions will make intraoral digital scanning standard procedure in most dental offices within the next several years. Furthermore, digital impressions have proven to reduce remakes and returns, as well as increase overall efficiency. The patient also benefits by being provided a far more positive experience. Finally, through the use of digital impression making, it has been determined that laboratory products become more consistent and require less chair time at insertion. PMID:26015714

  10. Critical Finding Capture in the Impression Section of Radiology Reports

    PubMed Central

    Gershanik, Esteban F.; Lacson, Ronilda; Khorasani, Ramin

    2011-01-01

    Introduction Radiology reports communicate imaging findings to ordering physicians. The substantial information in these reports often causes physicians to focus on the summarized impression section. This study evaluated how often a critical finding is documented in the reports impression section and describes how an automated application can improve documentation. Methods A retrospective review of all chest CT scan reports finalized between October, 2009 and September, 2010 at an academic institution was performed. A natural language processing application was utilized to evaluate the frequency of reporting a pulmonary nodule in the impression section, versus the findings section of a report. Results Results showed 3,401 reports with documented pulmonary nodules in the findings section, compared to 2,162 in the impression section a 36.4% difference. Conclusion The study revealed significant discrepant documentation in the findings versus impression sections. Automated systems could improve such critical findings documentation and communication between ordering physicians and radiologists. PMID:22195100

  11. Personality impressions associated with four distinct humor styles.

    PubMed

    Kuiper, Nicholas A; Leite, Catherine

    2010-04-01

    This study examined how personality impressions about another person are influenced by the style of humor that person displays. Four distinct styles were examined, with two of these being adaptive (affiliative and self-enhancing humor), and two being maladaptive (aggressive and self-defeating humor). Participants read descriptions of an individual displaying each humor style, and then rated that individual on several other personality attributes (e.g., friendly, complaining). The adaptive humor styles enhanced personality impressions of another individual, whereas the maladaptive styles had strong detrimental effects. Furthermore, participants provided clearly differentiated personality impressions within both the adaptive and maladaptive humor categories. Affiliative humor led to more positive impressions of another than self-enhancing humor; whereas aggressive humor resulted in more negative personality impressions than self-defeating humor. These findings were discussed in terms of approaches to humor that acknowledge the multifaceted nature of this construct and the resulting impact on social relationships. PMID:19674401

  12. Synthesis and characterization of novel polysiloxanes. I. Telechelic cyanate esters. II. Hindered alkyl siloxanes

    NASA Astrophysics Data System (ADS)

    Fu, Zhidong

    Two aspects of novel polysiloxane chemistry have been explored in this work: (1) the synthesis and characterization of polysiloxanes functionalized with terminal cyanate ester groups for use as low flammability impact modifiers for commercial phenolic cyanate ester resins (CERs) and (2) the synthesis and characterization of polydiethylsiloxane and polycyclotetramethylenesiloxane. CERs have been proposed as a potentially useful matrix material for commercial aircraft manufacture. However, commercial CERs do not currently have the appropriate fracture toughness for practical applications. Prior studies have shown that siloxanes offer excellent flame suppression and can improve the CERs impact properties. In this work, a series of new siloxanes terminated with cyanate-reactive groups, including bis[1,3-(4--cyanatophenyl)]-1,1,3,3-tetramethyldisiloxane (11), alpha,o-(4-cyanatophenyl) oligodimethylsiloxane (12), and alpha,o-(4-cyanatophenyl) oligo(dimethyl- co-diphenylsiloxane) (13), have been synthesized from corresponding diphenols. The intermediates and products were characterized by 1H NMR, 13C NMR, FTIR, GC-MS, and GPC. To synthesize the diphenols, a new route to synthesize disiloxane terminated with THP protected diphenols (dimer) was established. The synthesized dimer was used to equilibrate with D4 and/or D4'' to make desired siloxane oligomers. The mechanism of the equilibration of the dimer with D4 were studied. The synthesized CER monomers were polymerized by a cyclotrimerization reaction. The cured compound 11 is a brittle solid with Tg of 274C. The cured 12 (oligodimethyl-siloxane) and 13 (oligodimethylsiloxane- co-diphenylsiloxane) are elastomers with Tg of -110C and -8C, respectively. The curing processes and intermediates were studied by dynamic and isothermal differential scanning calorimetry, GPC, IR and 13C NMR. The synthesized CER monomers were used as impact modifiers to blend and co-cure with the commercial CERs, Primaset PT-30. SEM shows that the cured blends of 12 and 13 with PT-30 are multiphase while the cured blend of 11 with PT-30 has no phase separation. In the second part of this work, the synthetic methods for preparing polydiethylsiloxane (PDES) and polycyclotetramethylenesiloxane were explored by both anionic and cationic ring-opening polymerization and by condensation of hydroxyl end-groups in alpha,o-dihydroxy terminated siloxanes. The intermediates and products were characterized by GPC, IR GC-MS and 1H NMR. The process of polycondensation of PDES was followed by GPC and IR.

  13. Development of on-line FTIR spectroscopy for siloxane detection in biogas to enhance carbon contactor management.

    PubMed

    Hepburn, C A; Vale, P; Brown, A S; Simms, N J; McAdam, E J

    2015-08-15

    Activated carbon filters are used to limit engine damage by siloxanes when biogas is utilised to provide electricity. However, carbon filter siloxane removal performance is poorly understood as until recently, it had not been possible to measure siloxanes on-line. In this study, on-line Fourier Transform Infrared (FTIR) spectroscopy was developed to measure siloxane concentration in real biogas both upstream (86.1-157.5mg m(-3)) and downstream (2.2-4.3mg m(-3)) of activated carbon filters. The FTIR provided reasonable precision upstream of the carbon vessel with a root mean square error of 10% using partial least squares analysis. However, positive interference from volatile organic carbons was observed in downstream gas measurements limiting precision at the outlet to an RMSE of 1.5mg m(-3) (47.8%). Importantly, a limit of detection of 3.2mg m(-3) was identified which is below the recommended siloxane limit and evidences the applicability of on-line FTIR for this application. PMID:25966392

  14. Complete denture impression techniques practiced by private dental practitioners: a survey.

    PubMed

    Kakatkar, Vinay R

    2013-09-01

    Impression making is an important step in fabricating complete dentures. A survey to know the materials used and techniques practiced while recording complete denture impressions was conducted. It is disheartening to know that 33% practitioners still use base plate custom trays to record final impressions. 8% still use alginate for making final impressions. An acceptable technique for recording CD impressions is suggested. PMID:24431739

  15. Contamination level of alginate impressions arriving at a dental laboratory.

    PubMed

    Sofou, A; Larsen, T; Fiehn, N-E; Owall, B

    2002-09-01

    The contamination level of alginate impressions delivered to a large dental laboratory in Sweden was determined. One hundred and seven consecutive alginate impressions were included during 7 days. Samples were taken and transferred into sterile physiological saline and analysed microbiologically for colony-forming units (cfu) as well as nonhemolytic, alpha-hemolytic, and beta-hemolytic colonies. After sampling, the clinics were contacted and asked to fill in simple questionnaires about their routines of disinfecting impressions. The questionnaire study revealed that about half of the clinics had some kind of disinfection routine, while the others rinsed in running water only. Seventy-two percent of the impressions yielded growth of bacteria, with a median number of 1.3x10(2) cfu. Thirteen per cent of the samples yielded >10(3) cfu, with a maximum number of 3.4x10(4) cfu. The majority of isolates were non- and alpha-hemolytic bacteria. Growth was recorded in 61.3% of disinfected impressions, and the numbers of bacteria in disinfected and nondisinfected impressions were similar. These findings raise the question of whether impressions need to be disinfected or if proper handling and hygienic procedures are sufficient to block the possible route of infection. PMID:12271349

  16. Accuracy of stone casts obtained by different impression materials.

    PubMed

    Faria, Adriana Cludia Lapria; Rodrigues, Renata Cristina Silveira; Macedo, Ana Paula; Mattos, Maria da Gloria Chiarello de; Ribeiro, Ricardo Faria

    2008-01-01

    Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p < or = .05), presenting smaller discrepancies. However, condensation silicone was similar (p > or = .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials. PMID:19148382

  17. A Randomised Controlled Trial of complete denture impression materials

    PubMed Central

    Hyde, T.P.; Craddock, H.L.; Gray, J.C.; Pavitt, S.H.; Hulme, C.; Godfrey, M.; Fernandez, C.; Navarro-Coy, N.; Dillon, S.; Wright, J.; Brown, S.; Dukanovic, G.; Brunton, P.A.

    2014-01-01

    Objectives There is continuing demand for non-implant prosthodontic treatment and yet there is a paucity of high quality Randomised Controlled Trial (RCT) evidence for best practice. The aim of this research was to provide evidence for best practice in prosthodontic impressions by comparing two impression materials in a double-blind, randomised, crossover, controlled, clinical trial. Methods Eighty-five patients were recruited, using published eligibility criteria, to the trial at Leeds Dental Institute, UK. Each patient received two sets of dentures; made using either alginate or silicone impressions. Randomisations determined the order of assessment and order of impressions. The primary outcome was patient blinded preference for unadjusted dentures. Secondary outcomes were patient preference for the adjusted dentures, rating of comfort, stability and chewing efficiency, experience of each impression, and an OHIP-EDENT questionnaire. Results Seventy-eight (91.8%) patients completed the primary assessment. 53(67.9%) patients preferred dentures made from silicone impressions while 14(17.9%) preferred alginate impressions. 4(5.1%) patients found both dentures equally satisfactory and 7 (9.0%) found both equally unsatisfactory. There was a 50% difference in preference rates (in favour of silicone) (95%CI 32.767.3%, p<0.0001). Conclusion There is significant evidence that dentures made from silicone impressions were preferred by patients. Clinical significance Given the strength of the clinical findings within this paper, dentists should consider choosing silicone rather than alginate as their material of choice for secondary impressions for complete dentures. Trial Registration: ISRCTN 01528038.?? This article forms part of a project for which the author (TPH) won the Senior Clinical Unilever Hatton Award of the International Assocation for Dental Research, Capetown, South Africa, June 2014. PMID:24995473

  18. A rare allergy to a polyether dental impression material.

    PubMed

    Mittermller, Pauline; Szeimies, Rolf-Markus; Landthaler, Michael; Schmalz, Gottfried

    2012-08-01

    Polyether impression materials have been used in dentistry for more than 40 years. Allergic reactions to these materials such as reported in the 1970s ceased after replacement of a catalyst. Very recently, however, patients have started to report symptoms that suggest a new allergic reaction from polyether impression materials. Here, we report on the results of allergy testing with polyether impression materials as well as with its components. Eight patients with clinical symptoms of a contact allergy (swelling, redness or blisters) after exposure to a polyether impression material were subjected to patch tests, two of them additionally to a prick test. A further patient with atypical symptoms of an allergy (nausea and vomiting after contact with a polyether impression material in the oral cavity) but with a history of other allergic reaction was also patch tested. The prick tests showed no immediate reactions in the two patients tested. In the patch tests, all eight patients with typical clinical symptoms showed positive reactions to the mixed polyether impression materials, to the base paste or to a base paste component. The patient with the atypical clinical symptoms did not show any positive patch test reactions. Polyether impression materials may evoke type IV allergic reactions. The causative agent was a component of the base paste. In consideration of the widespread use of this impression material (millions of applications per year) and in comparison to the number of adverse reactions from other dental materials, the number of such allergic reactions is very low. In very scarce cases, positive allergic reactions to polyether impression materials are possible. PMID:21947905

  19. Fabrication of polyvinyl alcohol coated polystyrene shells

    SciTech Connect

    Burnham, A.K.; Grens, J.Z.; Lilley, E.M.

    1987-11-01

    Glass shells have been used traditionally as the deuterium--tritium fuel container for direct-drive laser fusion experiments because of their convenience and availability, but lower-Z fuel containers have superior implosion characteristics and diagnostic possibilities. Unfortunately, polymers such as polystyrene (PS) that produce shells easily have very high permeabilities so require cryogenics to retain fuel, and impermeable polymers such as polyvinyl alcohol (PVA) are difficult to make into high-quality shells. We have developed improved methods of making PS shells with diameters from 0.2 to 0.7 mm and coating them with a 3-..mu..m layer of PVA to obtain the advantages of both. Both the PS shells and the PVA coating are made in drop towers using gas-stripped nozzles. Details of the procedures and product quality are discussed.

  20. Polyvinyl alcohol membranes as alkaline battery separators

    SciTech Connect

    Sheibley, D.W.; Gonzalez-Sanabria, O.; Manzo, M.

    1982-01-01

    Polyvinyl alcohol (PVA) cross-linked with aldehyde reagents yields membranes that demonstrate properties that make them suitable for use as alkaline battery separators. Film properties can be controlled by the choice of cross-linker, cross-link density and the method of cross-linking. Three methods of cross-linking and their effects on film properties are discussed. Film properties can also be modified by using a copolymer of vinyl alcohol and acrylic acid as the base for the separator and cross-linking it similarly to the PVA. Fillers can be incorporated into the films to further modify film properties. Results of separator screening tests and cell tests for several variations of PBA films are discussed.

  1. Effects of polyvinyl chloride ingestion by dogs.

    PubMed

    Johnson, W S; Schmidt, R E

    1977-11-01

    Polyvinyl chloride (PVC) acrylic thermoplastic sheeting was fed to 6 dogs to determine whether ingestion during periods of normal transit of military working dogs would be toxic and thus affect the safety of this material for construction of shipping containers. The test dogs were fed PVC acrylic (0.125 g/kg of body weight; by gelatin capsule) twice each day for 5 days: for 2 dogs, the test material was in a shredded form; for 2 dogs, the material was diced; and for 2 dogs, it was powdered. Two other dogs were used as controls. Dogs were observed for clinical signs, and feed consumption and body weights were recorded. Blood and urine samples were examined. All animals were necropsied approximately 10 days after the feeding was stopped. Clinical or pathologic indication of a toxic effect of PVC was not seen within the time limits of the study. PMID:931170

  2. Poly(vinyl chloride) processes and products.

    PubMed Central

    Wheeler, R N

    1981-01-01

    Poly(vinyl chloride) resins are produced by four basic processes: suspension, emulsion, bulk and solution polymerization. PVC suspensions resins are usually relatively dust-free and granular with varying degrees of particle porosity. PVC emulsion resins are small particle powders containing very little free monomer. Bulk PVC resins are similar to suspension PVC resins, though the particles tend to be more porous. Solution PVC resins are smaller in particle size than suspension PVC with high porosity particles containing essentially no free monomer. The variety of PVC resin products does not lend itself to broad generalizations concerning health hazards. In studying occupational hazards the particular PVC process and the product must be considered and identified in the study. PMID:7333230

  3. Fatal anaphylactic shock due to a dental impression material.

    PubMed

    Gangemi, Sebastiano; Spagnolo, Elvira Ventura; Cardia, Giulio; Minciullo, Paola L

    2009-01-01

    Materials used for dental impressions are usually safe. This study describes a case of fatal anaphylaxis that appeared immediately after the oral mucosa came into contact with an alginate paste used for dental impressions. The cadaveric examination and the postmortem toxicology report confirmed that the cause of death was anaphylactic shock. The patient was affected by both cardiovascular and lung diseases that worsened the condition and forbade the use of epinephrine. To the authors' knowledge, dental impression materials, and alginate in particular, have not been reported previously as being a cause of anaphylaxis. PMID:19260424

  4. Using air, soil and vegetation to assess the environmental behaviour of siloxanes.

    PubMed

    Ratola, N; Ramos, S; Homem, V; Silva, J A; Jiménez-Guerrero, P; Amigo, J M; Santos, L; Alves, A

    2016-02-01

    This study aimed to contribute to the enhancement of the knowledge of levels, trends and behaviour of eight siloxanes (four linear and four cyclic) in the environment. Adding to the prioritised scrutiny of the incidence in the atmosphere through passive samplers (sorbent-impregnated polyurethane foam disks-SIPs), the sampling of pine needles and soil was also performed, thus closing the circle of atmospheric exposure in the areas of study. Two sampling campaigns (one in summer and one in winter) were done in a total of eight sampling points in the Portuguese territory, which covered a wide range of human presence and land uses (urban, industrial, remote and beach areas). By adopting a "green" approach in terms of analytical methods, namely reducing the clean-up steps for the passive air samples and using the quick, easy, cheap, effective, rugged and safe (QuEChERS) technology for soils and pine needles, the results showed total concentration of siloxanes between 5 and 70 ng g(-1) (dry weight) for soils and from 2 to 118 ng g(-1) (dry weight (dw)) for pine needles, with no clear seasonal trend. For SIPs, the levels varied from 0.6 to 7.8 ng m(-3) and were higher in summer than in winter in all sites. Overall, the cyclic siloxanes were found in much higher concentrations, with D5 and D6 being the most predominant in a great majority of cases. Also, the urban and industrial areas had the highest incidence, suggesting a strong anthropogenic fingerprint, in line with their main uses. PMID:26490903

  5. Electronic evaluation for video commercials by impression index.

    PubMed

    Kong, Wanzeng; Zhao, Xinxin; Hu, Sanqing; Vecchiato, Giovanni; Babiloni, Fabio

    2013-12-01

    How to evaluate the effect of commercials is significantly important in neuromarketing. In this paper, we proposed an electronic way to evaluate the influence of video commercials on consumers by impression index. The impression index combines both the memorization and attention index during consumers observing video commercials by tracking the EEG activity. It extracts features from scalp EEG to evaluate the effectiveness of video commercials in terms of time-frequency-space domain. And, the general global field power was used as an impression index for evaluation of video commercial scenes as time series. Results of experiment demonstrate that the proposed approach is able to track variations of the cerebral activity related to cognitive task such as observing video commercials, and help to judge whether the scene in video commercials is impressive or not by EEG signals. PMID:24427225

  6. [Effects of different tray types on the resulting impression].

    PubMed

    Biffar, R; Bittner, B

    1989-08-01

    In addition to the impression material the type of the used impression tray influences the accurat dimensional transfer of the teeth position to the master cast. In total 80 impressions were taken from models of the upper- and lower jaw by using condensation silicone, hydrocolloid, solid and perforated stock trays and acrylic custom trays. After that the casts were measured. The highest conformity with the original could be achieved with a hydrocolloid stock tray. The custom tray for the upper jaw showed short differences to the original model. By using a custom tray for the lower jaw higher dimensional changes occurred. Besides the different impression material thickness, distorsions of the trays should be discussed. PMID:2700730

  7. Synthetic casting tape as a facial impression tray material.

    PubMed

    Saunders, T R; Hansen, N A

    1995-08-01

    A procedure is described that uses thermoplastic synthetic casting tape for fabrication of facial impression trays. Once used, these trays can be disinfected without degradation of the tray material, which allows for storage and later use. PMID:8537924

  8. Use of casting tape for support of an extraoral impression.

    PubMed

    Siadat, Hakimeh; Mirfazaelian, Ali

    2003-12-01

    This article describes a technique for using casting tape to support irreversible hydrocolloid material when making extraoral impressions to increase patient comfort, save time, and produce less tissue distortion. PMID:14668762

  9. Accuracy of impressions obtained with dual-arch trays.

    PubMed

    Wstmann, Bernd; Rehmann, Peter; Balkenhol, Markus

    2009-01-01

    This study aimed to analyze the accuracy resulting from dual-arch impressions when compared to conventional impressions in complex preparations (ie, inlay and partial crown). One hundred eighty impressions were made using two different dual-arch trays; conventional trays served as the control. The accuracy of the dies obtained (Fuji-Rock EP, GC Europe) was assessed indirectly from the change of 59 transversal dimensions. Statistical analysis (t test, analysis of variance) revealed that less rigid dual-arch trays performed better than rigid ones. Though the inlay preparation was more difficult to reproduce with dual-arch trays, it can be concluded that the accuracy obtainable with nonrigid dual-arch trays is comparable to impressions taken from full-arch trays. PMID:19418862

  10. Impression management and food intake. Current directions in research.

    PubMed

    Vartanian, Lenny R

    2015-03-01

    This paper reviews recent research on consumption stereotypes (judgments of others based on what they eat) and impression management (modifying one's eating behavior in order to create a particular impression). A major recent focus in the literature has been on masculinity and meat eating, with research showing that meat is strongly associated with masculinity, and that individuals who follow a meat-based diet are perceived as more masculine than are individuals who follow a vegetarian diet. Although direct evidence for impression management through food intake remains sparse, a number of methodological approaches (including priming techniques and ecological valid assessments) are described that could be used in future research to identify the motives underlying people's eating behavior. Consumption stereotypes and impression management may be important influences on people's eating behavior, but the complexities of how, when, and for whom these factors influence food intake are still not well understood. PMID:25149198

  11. Persons who most impress gifted youth: a replication.

    PubMed

    Karnes, F A; McGinnis, J C

    1994-06-01

    A replication of a study of the persons who most impressed gifted youth was conducted with 95 students enrolled in a summer residential program for the gifted. Students were asked to indicate the person who most impressed them and to include the reason(s) for choosing that person. The most frequently chosen category of individuals was family members (61.1%), then a tie between persons in the world of arts and culture and persons doing a specific job (8.4%), another tie between comrades and sports stars (6.3%), followed by political or historical figures (4.2%), themselves (3.2%), and moral and religious personalities (2.1%). Consistent with the 1982 study by Karnes and Lee, most impressive to these students were family members and least impressive moral and religious personalities. PMID:8058865

  12. Impression Formation and Role Fulfillment: A "Holistic Reference" Approach

    ERIC Educational Resources Information Center

    Higgins, E. Tory; Rholes, William S.

    1976-01-01

    Previous approaches to impression formation from verbal information are discussed. A "holistic reference" approach is presented which proposes that a person first calls to mind the reference of the verbal description as a whole, and then evaluates that reference. (Editor)

  13. Polyvinyl alcohol cross-linked with two aldehydes

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Rieker, L. L.; Hsu, L. C.; Manzo, M. A. (Inventor)

    1982-01-01

    A film forming polyvinyl alcohol resin is admixed, in aqueous solution, with a dialdehyde crosslinking agent which is capable of crosslinking the polyvinyl alcohol resin and a water soluble acid aldehyde containing a reactive aldehyde group capable of reacting with hydroxyl groups in the polyvinyl alcohol resin and an ionizable acid hydrogen atom. The dialdehyde is present in an amount sufficient to react with from 1 to 20% by weight of the theoretical amount required to react with all of the hydroxyl groups of the polyvinyl alcohol. The amount of acid aldehyde is from 1 to 50% by weight, same basis, and is sufficient to reduce the pH of the aqueous admixture to 5 or less. The admixture is then formed into a desired physical shape, such as by casting a sheet or film, and the shaped material is then heated to simultaneously dry and crosslink the article.

  14. Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

    NASA Technical Reports Server (NTRS)

    Hundley, N. H.; Patterson, W. J.

    1985-01-01

    Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

  15. Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

    DOEpatents

    Babcock, Walter C. (Bend, OR); Friesen, Dwayne T. (Bend, OR)

    1988-01-01

    Novel semiperimeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

  16. Sensitivity of the asymmetric siloxane region in the infrared to silane structure

    SciTech Connect

    Ishida, H.; Gorecki J. )

    1990-04-01

    In the past, the asymmetric siloxane region (1200-1000cm{sup {minus}1}) has been used to assign silane structure. Fourier transform infrared spectroscopy and {sup 29}Si nuclear magnetic resonance have been used to investigate silane structure. Gel permeation chromatography has been used to identify silane species present. It was found that a number of silane structures could produce the same infrared band within this region. Also, this region was insensitive to molecular weight of silane until a high degree of condensation of the silane species was reached.

  17. Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

    DOEpatents

    Babcock, W.C.; Friesen, D.T.

    1988-11-01

    Novel semipermeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

  18. [Technological aspects of agar-hydrocolloid impression materials].

    PubMed

    Davidson, C L; Bekke-Hoekstra, I S

    1979-01-01

    Physical properties with clinical relevance has been tested on a number of agar hydrocolloid impression materials For 1 hour an almost perfect dimensional stability can be maintained when the impression is stored in water. Elasticity and strength are poor. Only the use of much bulk material may prevent damage during manipulation of the gel. The detail reproduceability meets all standards. A good compatibility with dental stone subsequently allows sharp details in the model. PMID:293792

  19. A survey of cyclic and linear siloxanes in indoor dust and their implications for human exposures in twelve countries.

    PubMed

    Tran, Tri Manh; Abualnaja, Khalid O; Asimakopoulos, Alexandros G; Covaci, Adrian; Gevao, Bondi; Johnson-Restrepo, Boris; Kumosani, Taha A; Malarvannan, Govindan; Minh, Tu Binh; Moon, Hyo-Bang; Nakata, Haruhiko; Sinha, Ravindra K; Kannan, Kurunthachalam

    2015-05-01

    Siloxanes are used widely in a variety of consumer products, including cosmetics, personal care products, medical and electrical devices, cookware, and building materials. Nevertheless, little is known on the occurrence of siloxanes in indoor dust. In this survey, five cyclic (D3-D7) and 11 linear (L4-L14) siloxanes were determined in 310 indoor dust samples collected from 12 countries. Dust samples collected from Greece contained the highest concentrations of total cyclic siloxanes (TCSi), ranging from 118 to 25,100ng/g (median: 1380), and total linear siloxanes (TLSi), ranging from 129 to 4990ng/g (median: 772). The median total siloxane (TSi) concentrations in dust samples from 12 countries were in the following decreasing order: Greece (2970ng/g), Kuwait (2400), South Korea (1810), Japan (1500), the USA (1220), China (1070), Romania (538), Colombia (230), Vietnam (206), Saudi Arabia (132), India (116), and Pakistan (68.3). TLSi concentrations as high as 42,800ng/g (Kuwait) and TCSi concentrations as high as 25,000ng/g (Greece) were found in indoor dust samples. Among the 16 siloxanes determined, decamethylcyclopentasiloxane (D5) was found at the highest concentration in dust samples from all countries, except for Japan and South Korea, with a predominance of L11; Kuwait, with L10; and Pakistan and Romania, with L12. The composition profiles of 16 siloxanes in dust samples varied by country. TCSi accounted for a major proportion of TSi concentrations in dust collected from Colombia (90%), India (80%) and Saudi Arabia (70%), whereas TLSi predominated in samples collected from Japan (89%), Kuwait (85%), and South Korea (78%). Based on the measured median TSi concentrations in indoor dust, we estimated human exposure doses through indoor dust ingestion for various age groups. The exposure doses ranged from 0.27 to 11.9ng/kg-bw/d for toddlers and 0.06 to 2.48ng/kg-bw/d for adults. PMID:25749636

  20. Comparison of two impression techniques for auricular prosthesis: pilot study.

    PubMed

    Mohamed, Kasim; Mani, U M; Seenivasan, M K; Vaidhyanathan, A K; Veeravalli, P T

    2013-01-01

    The purpose of this article was to compare the accuracy of a new impression technique, the triple-layer impression technique (TLIT), with the conventional impression technique (CIT) to fabricate an auricular prosthesis. Fifteen male subjects (aged 22-45 yr) were selected. Ten markings were made on the subject's ear (super aurale [sa], sub aurale [sba], pre aurale [pra], post aurale [poa], A, A1, B, B1, C, and C1) and five measurements (sa-sba, pra-poa, A-A1, B-B1, and C-C1) were made. Custom-made trays were used to record impression in CIT and TLIT. Impressions were made using alginate, and models were cast with type IV gypsum product. Markings were transferred on the cast. Measurements were rechecked on the models. Distribution analysis of difference in measurements between the two impression techniques and the subject's actual values was evaluated. Sign test was used to analyze the statistical significance. Statistically significant differences were found in measurements A-A1, B-B1, and C-C1 between the two techniques when compared with the subject's actual dimensions (p < 0.01). TLIT was found to produce accurate models when compared with CIT. The TLIT used in the study was cost effective, less technique sensitive, and tailor made to reduce chairside orientation time during wax try-in appointments for rehabilitating patients, especially those with unilateral auricular defects. PMID:24458893

  1. In Situ Cross-Linking of Polyvinyl Alcohol Films

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Shu, L. C.; May, C. E.

    1984-01-01

    Films or impregnated matrices readily made from aqueous polyvinyl alcohol solution. Controlled thickness films made by casting precise quantities of aqueous polymer solution on smooth surface, allowing water to evaporate and then removing film. Composite separators formed in similar fashion by impregnating cloth matrix with polyvinyl alcohol solution and drying composite. Insoluble thin hydrophilic membranes made from aqueous systems, and use of undesirable organic solvents not required.

  2. Solid oxide fuel cell anode degradation by the effect of siloxanes

    NASA Astrophysics Data System (ADS)

    Madi, Hossein; Lanzini, Andrea; Diethelm, Stefan; Papurello, Davide; Van herle, Jan; Lualdi, Matteo; Gutzon Larsen, Jørgen; Santarelli, Massimo

    2015-04-01

    Lifetime and durability issues connected with Solid Oxide Fuel Cell (SOFC) technology are strongly related to the amount of contaminants that reach the stack. In this study the focus is on organic silicon compounds (siloxanes) and their highly detrimental effects on the performance of SOFC Ni-YSZ anodes. The involved mechanism of degradation is clarified and quantified through several test runs and subsequent post-mortem analysis on tested samples. In particular, experiments on both Ni anode-supported single cells and 11-cell- stacks are performed, co-feeding D4-siloxane (octamethylcyclotetrasiloxane, C8H24O4Si4) as model compound for the organic silicon species which are generally found in sewage biogas. High degradation rates are observed already at ppb(v) level of contaminant in the fuel stream. Post-test analysis revealed that Si (as silica) is mostly deposited at the inlet of the fuel channel on both the interconnect and the anode side of the cell suggesting a relatively fast condensation-type process. Deposition of the Si was found on the interconnect and on the anode contact layer, throughout the anode support and the three phase boundary in the anode, correlating with the observed increase of polarization losses from the EIS analysis of tested cells.

  3. Triblock siloxane copolymer surfactant: template for spherical mesoporous silica with a hexagonal pore ordering.

    PubMed

    Stb, M J; Emo, M; Forny-Le Follotec, A; Metlas-Komunjer, L; Pezron, I; Blin, J L

    2013-02-01

    Ordered mesoporous silica materials with a spherical morphology have been prepared for the first time through the cooperative templating mechanism (CTM) by using a silicone triblock copolymer as template. The behavior of the pure siloxane copolymer amphiphile in water was first investigated. A direct micellar phase (L(1)) and a hexagonal (H(1)) liquid crystal were found. The determination of the structural parameters by SAXS measurements leads us to conclude that in the hexagonal liquid crystal phase a part of the ethylene oxide group is not hydrated as observed for the micelles. Mesoporous materials were then synthesized from the cooperative templating mechanism. The recovered materials were characterized by SAXS measurements, nitrogen adsorption-desorption analysis, and transmission and scanning electron microscopy. The results clearly evidence that one can control the morphology and the nanostructuring of the resulting material by modifying the synthesis parameters. Actually, highly ordered mesoporous materials with a spherical morphology have been obtained with a siloxane copolymer/tetramethoxysilane molar ratio of 0.10 after hydrothermal treatment at 100 C. Our study also supports the fact that the interactions between micelles and the hydrolyzed precursor are one of the key parameters governing the formation of ordered mesostructures through the cooperative templating mechanism. Indeed, we have demonstrated that when the interactions between micelles are important, only wormhole-like structures are recovered. PMID:23305163

  4. Solvent effects on silica domain growth in silica/siloxane composite materials

    SciTech Connect

    Ulibarri, T.A.; Bates, S.E.; Black, E.P.; Schaefer, D.W.; Beaucage, W.G.; Lee, M.K.; Moore, P.A.; Burns, G.T.

    1995-07-01

    The effect of solvent addition on the phase separation, mechanical Properties and thermal stability of silica/siloxane composite materials prepared by in situ reinforcement was examined. The addition of a solvent enhances the miscibility of the reinforcement precursor, a partial hydrolyzate of tetraethoxysilane (TEOS-PH), with the polydimethylsiloxane (PDMS) polymer. As a result, the phase separation at the micron level, termed the large-scale structure, diminished in size. This decrease in particle size resulting from the addition of moderate amounts of solvent was accompanied by an improvement in the mechanical properties. However, solvent addition in the excess of 50 weight percent led to a decrease in mechanical properties even though the large-scale structure continued to diminish in size. Small Angle X-Ray Scattering (SAXS) was used to examine the Angstrom level or small-scale structure. This small-scale structure was only affected by the presence of solvent, not the amount. The silica/siloxane composite materials showed the same thermal transition temperatures as the original PDMS material.

  5. Hydrothermal carbonization of poly(vinyl chloride).

    PubMed

    Poerschmann, J; Weiner, B; Woszidlo, S; Koehler, R; Kopinke, F-D

    2015-01-01

    Poly(vinyl chloride) (PVC) was subjected to hydrothermal carbonization in subcritical water at 180-260 C. Dehydrochlorination increased with increasing reaction temperature. The release of chlorine was almost quantitative above ?235 C. The fraction of organic carbon (OC) recovered in the hydrochar decreased with increasing operating temperature from 93% at 180 C to 75% at 250 C. A wide array of polycyclic aromatic hydrocarbons (PAHs) could be detected in the aqueous phase, but their combined concentration amounted to only ?140 ?g g(-1) PVC-substrate at 240 C. A pathway for the formation of cyclic hydrocarbons and O-functionalized organics was proposed. Chlorinated hydrocarbons including chlorophenols could only be identified at trace levels (low ppb). Polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) could not be detected. The sorption potential of the hydrochar turned out to be very low, in particular for polar organic pollutants. Our results provide strong evidence that hydrothermal carbonization of household organic wastes which can be tied to co-discarded PVC-plastic residues is environmentally sound regarding the formation of toxic organic products. Following these findings, hydrothermal treatment of PVC-waste beyond operating temperatures of ?235 C to allow complete release of organic chlorine should be further pursued. PMID:25150971

  6. Biochemistry of microbial polyvinyl alcohol degradation.

    PubMed

    Kawai, Fusako; Hu, Xiaoping

    2009-08-01

    Effect of minor chemical structures such as 1,2-diol content, ethylene content, tacticity, a degree of polymerization, and a degree of saponification of the main chain on biodegradability of polyvinyl alcohol (PVA) is summarized. Most PVA-degraders are Gram-negative bacteria belonging to the Pseudomonads and Sphingomonads, but Gram-positive bacteria also have PVA-degrading abilities. Several examples show symbiotic degradation of PVA by different mechanisms. Penicillium sp. is the only reported eukaryotic degrader. A vinyl alcohol oligomer-utilizing fungus, Geotrichum fermentans WF9101, has also been reported. Lignolytic fungi have displayed non-specific degradation of PVA. Extensive published studies have established a two-step process for the biodegradation of PVA. Some bacteria excrete extracellular PVA oxidase to yield oxidized PVA, which is partly under spontaneous depolymerization and is further metabolized by the second step enzyme (hydrolase). On the other hand, PVA (whole and depolymerized to some extent) must be taken up into the periplasmic space of some Gram-negative bacteria, where PVA is oxidized by PVA dehydrogenase, coupled to a respiratory chain. The complete pva operon was identified in Sphingopyxis sp. 113P3. Anaerobic biodegradability of PVA has also been suggested. PMID:19590867

  7. Preparation and properties of polyvinyl alcohol microspheres

    SciTech Connect

    Campbell, J.H.; Grens, J.Z.; Poco, J.F.; Ives, B.H.

    1986-06-01

    Polyvinyl alcohol (PVA) microspheres, having a size range of approx.150- to 250-..mu..m diameter with 1- to 5-..mu..m wall thickness, have been fabricated using a solution droplet technique. The spheres were developed for possible use on the Lawrence Livermore National Laboratory (LLNL) Inertial Confinement Fusion (ICF) Program. PVA, a polymer chosen based on earlier survey work carried out at KMS Fusion, Inc., has good strength, low hydrogen permeability, is optically transparent, and water soluble. The latter property makes it safe and easy to use in our droplet generator system. A unique dual-orifice droplet generator was used to prepare the spheres. The droplet generator operating conditions and the column processing parameters were chosen using results from our 1-D model calculations as a guide. The polymer microsphere model is an extension of the model we developed to support the glass sphere production. After preparation, the spheres were physically characterized for surface quality, sphericity, wall thickness (and uniformity), and size. We also determined the buckling pressure for both uncoated and CH-coated spheres. Radiation stability to beta decay (from tritium) was evaluated by exposing the spheres to a 7-keV electron beam. The results from these and other physical property measurements are presented in this report.

  8. Piezoresistive Properties of Polyvinyl Chloride Composites

    NASA Astrophysics Data System (ADS)

    Toprakci, Hatice Aylin Karahan

    Textile based sensors provide an interface between the user and the electronic system by converting any type of physiological or environmental signal into electrical signals. Common applications include health monitoring, rehabilitation, multimedia, and surveillance. In this research we demonstrate fabrication of piezoresistive sensors on textile fabrics through application of a screen-printed conductive nanocomposite layer of plasticized poly(vinyl chloride) (PVC), and carbon nanofiber (CNF). In order to understand the behavior of conductive plastisol, morphological, mechanical and electrical properties of composite films were investigated for different molecular weights of PVC. Homogeneous filler dispersion and good filler/polymer interphase were observed without any dominant filler orientation. Mechanical and electrical properties were found to be affected by CNF, plasticizer content and matrix molecular weight. CNFs were found to provide substantial bridging in the matrix and enhance strength. These nanostructured composite sensors were found to be sensitive under different levels of strain which can be monitored by change in electrical resistance. Finally, we demonstrate the fabrication of piezoresistive sensors on textile fabrics through application of a screen-printed conductive nanocomposite layer of conductive plastisol. Conductive plastisol was found to show good adhesion to fabric with homogeneous CNF distribution. As in composite films, samples were found to show negative piezoresistance at different levels of strain. Strain level and filler concentration were found to affect the piezoresistive behavior and sensitivity of the printed sensors.

  9. Heat resistance poly(vinyl alcohol) hydrogel

    NASA Astrophysics Data System (ADS)

    Yoshii, F.; Makuuchi, K.; Darwis, D.; Iriawan, T.; Razzak, M. T.; Rosiak, Janusz M.

    1995-08-01

    Six methods were used to evaluate the heat resistance of poly(vinyl alcohol) (PVA) hydrogel prepared by a combination of electron beam irradiation and acetalization of PVA. The physical properties of the hydrogel depended on the degree of acetilization which was affected by content of water in PVA sheet of acetalization in formaldehyde solution at 60C. It was found that the optimum water content was 20-30%. The acetalized PVA sheet gave maximum tensile strength in electron beams irradiation at 100 kGy. The tensile strength of the hydrogel film increased to 20 MPa from 14 MPa by the irradiation. Heat resistance of the hydrogel was evaluated by measuring the mechanical properties after sterilization in a steam autoclave at 121C for 90 min. The tensile strength decreased to 10 MPa whereas the elongation at break increased to 300%. The tackiness of the hydrogel was improved by radiation grafting of acrylic acid. Wholesomeness of the hydrogel as a wound dressing was evaluated by attaching to a burn or wound of the back skin of marmots. Advantages of the hydrogel over a gauze dressing were homogeneous adhesion to the affected parts, easy removal without damage to renewed skin and slightly faster rate of reconstruction of the injured skin.

  10. 40 CFR 721.10483 - Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... vinyl, hydroxy-terminated, reaction products with -modified silica. 721.10483 Section 721.10483... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10483 Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with -modified silica....

  11. 40 CFR 721.10482 - Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with silica.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10482 Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with silica. (a) Chemical substance and... vinyl, hydroxy-terminated, reaction products with silica. 721.10482 Section 721.10482 Protection...

  12. 40 CFR 721.10482 - Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with silica.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10482 Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with silica. (a) Chemical substance and... vinyl, hydroxy-terminated, reaction products with silica. 721.10482 Section 721.10482 Protection...

  13. 40 CFR 721.10483 - Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... vinyl, hydroxy-terminated, reaction products with -modified silica. 721.10483 Section 721.10483... SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10483 Siloxanes and Silicones, di-Me, Me vinyl, hydroxy-terminated, reaction products with -modified silica....

  14. Evaluation of a Full-Scale Water-Based Scrubber for Removing Siloxanes from Digester Gas: A Case Study.

    PubMed

    Surita, Sharon C; Tansel, Berrin

    2015-05-01

    Siloxanes are becoming more prominent in digester gas at water resource recovery facilities because of their wide use in personal care products. This study evaluates a full-scale water-based scrubber operating in a water resource recovery facility (Miami, FL). The digester gas is used for energy generation due to its high methane content. During energy generation, siloxanes are converted to silicates and Silicon Dioxide (SiO2), which leave deposits on engine components. Trimethylsilanol (TMSOH), Octamethyltrisiloxane (L3), Hexamethylcyclotrisiloxane (D3), Octamethylcyclotetrasiloxane (D4), Decamethylcyclopentasiloxane (D5), and Dodecamethylcyclohexasiloxane (D6) were detected in the digester gas. D4 and D5 were present at the highest concentrations, 5000 and 1800 μg/ m3, respectively. Sampling results have indicated that scrubbers employed for hydrogen sulfide (H2S) removal at the facility do not provide effective removal of siloxanes due to their high Henry's Constant. Post scrubber treatment is needed to remove siloxanes from the digester gas prior to combustion. PMID:26460464

  15. Polyvinylidene fluoride/siloxane nanofibrous membranes for long-term continuous CO2 -capture with large absorption-flux enhancement.

    PubMed

    Lin, Yi-Feng; Wang, Chi-Sen; Ko, Chia-Chieh; Chen, Chien-Hua; Chang, Kai-Shiun; Tung, Kuo-Lun; Lee, Kueir-Rarn

    2014-02-01

    In a CO2 membrane contactor system, CO2 passes through a hydrophobic porous membrane in the gas phase to contact the amine absorbent in the liquid phase. Consequently, additional CO2 gas is absorbed by amine absorbents. This study examines highly porous polyvinylidene fluoride (PVDF)/siloxane nanofibrous layers that are modified with hydrophobic fluoroalkylsilane (FAS) functional groups and successfully coated onto a macroporous Al2 O3 membrane. The performance of these materials in a membrane contactor system for CO2 absorption is also investigated. Compared with pristine PVDF nanofibrous membranes, the PVDF/siloxane nanofibrous membranes exhibit greater solvent resistance and mechanical strength, making them more suitable for use in CO2 capture by the membrane contactor. The PVDF/siloxane nanofibrous layer in highly porous FAS-modified membranes can prevent the wetting of the membrane by the amine absorbent; this extends the periods of continuous CO2 absorption and results in a high CO2 absorption flux with a minimum of 500 % enhancement over that of the uncoated membranes. This study suggests the potential use of an FAS-modified PVDF/siloxane nanofibrous membrane in a membrane contactor system for CO2 absorption. The resulting hydrophobic membrane contactor also demonstrates the potential for large-scale CO2 absorption during post-combustion processes in power plants. PMID:24194500

  16. Similarity to the self influences cortical recruitment during impression formation.

    PubMed

    Leshikar, Eric D; Cassidy, Brittany S; Gutchess, Angela H

    2016-04-01

    Prior work has shown that whether or not someone is similar to the self influences person memory-a type of self-reference effect for others. In this study, we were interested in understanding the neural regions supporting the generation of impressions and subsequent memory for targets who vary in similarity to the self. Participants underwent fMRI scanning while forming positive or negative impressions of face-behavior pairs. We tested participants' memory for their generated impressions and then back-sorted the impression trials (encoding) into different levels of self-similarity (high, medium, low) using a self-similarity posttest that came after recognition. Extending prior behavioral work, our data confirmed our hypothesis that memory would be highest for self-similar others and lowest for self-dissimilar others. Dorsal anterior cingulate cortex (dACC) activity increased with self-similarity (high > medium > low) to targets, regardless of later memory for them. An analysis of regions supporting impression memory revealed a double dissociation within medial temporal lobe regions: for similar others, amygdala recruitment supported memory, whereas for dissimilar others, hippocampal activation supported memory. These results suggest that self-similarity influences evaluation and memory for targets but also affects the underlying neural resources engaged when thinking about others who vary in self-similarity. PMID:26558615

  17. Enhancing the authenticity of assessments through grounding in first impressions.

    PubMed

    Hum?, Bogdana

    2015-09-01

    This article examines first impressions through a discursive and interactional lens. Until now, social psychologists have studied first impressions in laboratory conditions, in isolation from their natural environment, thus overseeing their discursive roles as devices for managing situated interactional concerns. I examine fragments of text and talk in which individuals spontaneously invoke first impressions of other persons as part of assessment activities in settings where the authenticity of speakers' stances might be threatened: (1) in activities with inbuilt evaluative components and (2) in sequential contexts where recipients have been withholding affiliation to speakers' actions. I discuss the relationship between authenticity, as a type of credibility issue related to intersubjective trouble, and the characteristics of first impression assessments, which render them useful for dealing with this specific credibility concern. I identify four features of first impression assessments which make them effective in enhancing authenticity: witness positioning (Potter, 1996, Representing reality: Discourse, rhetoric and social construction, Sage, London), (dis)location in time and space, automaticity, and extreme formulations (Edwards, 2003, Analyzing race talk: Multidisciplinary perspectives on the research interview, Cambridge University Press, New York). PMID:25346466

  18. Prefabricated stock trays for impression of auricular region.

    PubMed

    Vibha, Shetty; Anandkrishna, G N; Anupam, Purwar; Namratha, N

    2010-06-01

    The conventional methods of impression making for maxillofacial defects are cumbersome and time consuming for both patient and operator. This study focuses upon standardizing and simplifying the impression making methodology for auricular prosthesis with the help of prefabricated stock trays for auricular region. The stock trays were designed on positive replicas of anatomical structures, broadly divided into long and narrow, short and broad and long and broad ear. For each stock tray, impressions of auricle, of patients of different morphology were made with plastic funnels of different shape and size ensuring at least 6mm of space between the anatomical part and inner surface of funnel and master cast was obtained. Subsequent adaptation of wax was done and fabrications of stock stainless steel trays were done. A standardized stock tray for making of auricular impressions was developed. From this innovative technical procedure it is possible to get an accurate impression of auricular defects now by the use of prefabricated stock trays rather than the cumbersome conventional method. PMID:21629455

  19. Impression material thickness in stock and custom trays.

    PubMed

    Bomberg, T J; Hatch, R A; Hoffman, W

    1985-08-01

    This study did not examine the accuracy of the resultant impressions. Rather, the impression material thickness in impressions made using both the highly advocated custom acrylic resin tray and in the highly used manufactured stock tray was examined. Comparison between the material thickness at the prepared tooth area revealed a mean difference in material thickness of less than 1 mm. The question of the significance of this difference remains to be answered. If the difference is not significant in the success of the impression and the resultant casting, then there are several advantages in using the manufactured stock tray; the first is economy. The average cost of a custom acrylic full arch impression tray is $3.65, compared with an average cost of slightly over $0.30 for the stock tray. The second advantage is the convenience factor. Making a custom tray requires planning, study models, laboratory time, curing interval, and finishing time. In contrast, the stock tray can be selected, adapted, and used in a single visit for both anticipated and unanticipated situations. If the difference in material thickness is significant, the custom tray is indicated. However, attention to detail in making and inserting the tray in the mouth must be observed to maximize the benefits of the custom tray. PMID:3903109

  20. Outcome dependency alters the neural substrates of impression formation

    PubMed Central

    Ames, Daniel L.; Fiske, Susan T.

    2015-01-01

    How do people maintain consistent impressions of other people when other people are often inconsistent? The present research addresses this question by combining recent neuroscientific insights with ecologically meaningful behavioral methods. Participants formed impressions of real people whom they met in a personally involving situation. fMRI and supporting behavioral data revealed that outcome dependency (i.e., depending on another person for a desired outcome) alters previously identified neural dynamics of impression formation. Consistent with past research, a functional localizer identified a region of dorsomedial PFC previously linked to social impression formation. In the main task, this ROI revealed the predicted patterns of activity across outcome dependency conditions: greater BOLD response when information confirmed (vs. violated) social expectations if participants were outcome-independent and the reverse pattern if participants were outcome-dependent. We suggest that, although social perceivers often discount expectancy-disconfirming information as noise, being dependent on another person for a desired outcome focuses impression-formation processing on the most diagnostic information, rather than on the most tractable information. PMID:23850465

  1. Determining the accuracy of stock and custom tray impression/casts.

    PubMed

    Millstein, P; Maya, A; Segura, C

    1998-08-01

    A study was conducted to evaluate the accuracy of casts made from stock tray and custom tray impressions using polysiloxane impression material. The results indicate that all casts distort but that impressions made from custom trays were more accurate and consistent in reproduction than were stock tray impressions. PMID:9781870

  2. Custom sectional impression trays with interlocking type handle for microstomia patients.

    PubMed

    Fernandes, Aquaviva S; Mascarenhas, Kennedy; Aras, Meena A

    2009-01-01

    Making impressions in microstomia patients is often cumbersome. A modification of standard impression procedure is often necessary while treating such patients. This article describes the fabrication of a custom sectional impression tray with interlocking type of a handle for definitive impression procedures in a microstomia patient. PMID:19884726

  3. Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations.

    PubMed

    Tansel, Berrin; Surita, Sharon C

    2014-11-01

    The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si-O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si-O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups. PMID:25160660

  4. Sodium hypochlorite disinfection of irreversible hydrocolloid impression material.

    PubMed

    Rueggeberg, F A; Beall, F E; Kelly, M T; Schuster, G S

    1992-05-01

    Alginate impression material is one of the most frequently used in dentistry. However, this material is susceptible to dimensional distortion during disinfection because of its hydrophilic nature. This study examined the effects of alginate disinfection using a sodium hypochlorite spray or impression immersion. Spray disinfection of an alginate impression did not cause dimensional differences of the poured stone casts when compared with casts from water-rinsed controls. Immersion disinfection created dimensional distortion of the anterior, posterior, and interarch model segments. Both the spray and immersion treatments equally decreased the surface detail reproducibility. The antimicrobial effects of the spray treatment were similar to those of the immersion treatment, while mere water rinsing resulted in inadequate disinfection. PMID:1527745

  5. Coping with stereotype threat: denial as an impression management strategy.

    PubMed

    von Hippel, William; von Hippel, Courtney; Conway, Leanne; Preacher, Kristopher J; Schooler, Jonathan W; Radvansky, Gabriel A

    2005-07-01

    Four experiments tested the hypothesis that people who are concerned with impression management cope with stereotype threat through denial. Consistent with this hypothesis, temporary employees threatened by a stereotype of incompetence (Study 1) and hostel-dwelling older adults (Study 2) were more likely to deny incompetence if they were high in impression management. African Americans (Study 3) showed a similar pattern of denying cognitive incompetence, which emerged primarily when they were interviewed by a White experimenter and had attended a predominantly Black high school. In Study 4, White students who expected to take an IQ test and were threatened by a stereotype of being less intelligent than Asians were more likely to deny that intelligence is important if they were high in impression management. PMID:16060740

  6. A Sensitive Measurement for Estimating Impressions of Image-Contents

    NASA Astrophysics Data System (ADS)

    Sato, Mie; Matouge, Shingo; Mori, Toshifumi; Suzuki, Noboru; Kasuga, Masao

    We have investigated Kansei Content that appeals maker's intention to viewer's kansei. An SD method is a very good way to evaluate subjective impression of image-contents. However, because the SD method is performed after subjects view the image-contents, it is difficult to examine impression of detailed scenes of the image-contents in real time. To measure viewer's impression of the image-contents in real time, we have developed a Taikan sensor. With the Taikan sensor, we investigate relations among the image-contents, the grip strength and the body temperature. We also explore the interface of the Taikan sensor to use it easily. In our experiment, a horror movie is used that largely affects emotion of the subjects. Our results show that there is a possibility that the grip strength increases when the subjects view a strained scene and that it is easy to use the Taikan sensor without its circle base that is originally installed.

  7. Impression formation and revision in social anxiety disorder.

    PubMed

    Haker, Ayala; Aderka, Idan M; Marom, Sofi; Hermesh, Haggai; Gilboa-Schechtman, Eva

    2014-03-01

    Interpersonal relations are markedly impaired in social anxiety. Yet, little is known about the ways social anxiety affects social cognition. We examined impression formation and impression revision among individuals with social anxiety disorder (SAD, n = 26) and non-anxious individuals (n = 29). Participants read initial descriptions of protagonists depicted as dominant, neutral or submissive and rated them on social rank and affiliation dimensions. Next, participants were presented with behavioral acts that were either congruent, incongruent or irrelevant to the initial descriptions, and re-rated the protagonists. Individuals with SAD (a) rated others as more extreme on social rank dimension, (b) rated others as lower on the affiliation dimension, and (c) revised their impressions of others to a greater extent than did the non-anxious individuals. Understanding the ways social anxiety affects the formation and revision of perceptions of others can improve our understanding of maintaining processes in SAD. PMID:23774009

  8. Cytotoxicity associated with electrospun polyvinyl alcohol.

    PubMed

    Pathan, Saif G; Fitzgerald, Lisa M; Ali, Syed M; Damrauer, Scott M; Bide, Martin J; Nelson, David W; Ferran, Christiane; Phaneuf, Tina M; Phaneuf, Matthew D

    2015-11-01

    Polyvinyl alcohol (PVA) is a synthetic, water-soluble polymer, with applications in industries ranging from textiles to biomedical devices. Research on electrospinning of PVA has been targeted toward optimizing or finding novel applications in the biomedical field. However, the effects of electrospinning on PVA biocompatibility have not been thoroughly evaluated. In this study, the cytotoxicity of electrospun PVA (nPVA) which was not crosslinked after electrospinning was assessed. PVA polymers of several molecular weights were dissolved in distilled water and electrospun using the same parameters. Electrospun PVA materials with varying molecular weights were then dissolved in tissue culture medium and directly compared against solutions of nonelectrospun PVA polymer in human coronary artery smooth muscle cells and human coronary artery endothelial cells cultures. All nPVA solutions were cytotoxic at a threshold molar concentration that correlated with the molecular weight of the starting PVA polymer. In contrast, none of the nonelectrospun PVA solutions caused any cytotoxicity, regardless of their concentration in the cell culture. Evaluation of the nPVA material by differential scanning calorimetry confirmed that polymer degradation had occurred after electrospinning. To elucidate the identity of the nPVA component that caused cytotoxicity, nPVA materials were dissolved, fractionated using size exclusion columns, and the different fractions were added to HCASMC and human coronary artery endothelial cells cultures. These studies indicated that the cytotoxic component of the different nPVA solutions were present in the low-molecular-weight fraction. Additionally, the amount of PVA present in the 3-10 kg/mol fraction was approximately sixfold greater than that in the nonelectrospun samples. In conclusion, electrospinning of PVA resulted in small-molecular-weight fractions that were cytotoxic to cells. This result demonstrates that biocompatibility of electrospun biodegradable polymers should not be assumed on the basis of success of their nonelectrospun predecessors. PMID:25573200

  9. EFFECT OF STORAGE PERIOD ON THE ACCURACY OF ELASTOMERIC IMPRESSIONS

    PubMed Central

    Franco, Eduardo Batista; da Cunha, Leonardo Fernandes; Benetti, Ana Raquel

    2007-01-01

    Aims: To investigate the effect of the storage period on the accuracy of recently developed elastomeric materials. Methods: Simultaneous impressions of a steel die were taken using a polyether (I: Impregum Soft Heavy and Light body, 3M ESPE) and vinyl polysiloxane (P: Perfectim Blue Velvet and Flexi-Velvet, J.Morita). The trays were loaded with the heavy-bodied impression materials while the light-bodied impression materials were simultaneously spread on the steel die. The impressions were poured after 2 hours, 24 hours, and 7 days. Impressions were stored at approximately 55% relative humidity and room temperature. Ten replicas were produced for each experimental condition (n=60). Accuracy of the stone dies was assessed with a depth-measuring microscope. The difference in height between the surface of the stone die and a standard metallic ring was recorded in micrometers at four demarcated points, by two independent examiners. Dxata were submitted to two-way ANOVA and Tukey test (α = 0.05). Results: Significant differences were found among the groups. Smaller discrepancies were observed when pouring was performed up to 24 hours (I-2h= 65.0 ± 15.68 μm; I-24h= 81.6 ± 11.13 μm) for the polyether, and up to 7 days for the vinyl polysiloxane (P-2h= 79.1 ± 13.82 μm; P-24h= 96.8 ± 6.02 μm; P-7d= 81.4 ± 4.3 μm). Significant dimensional discrepancies, however, were observed when polyether was stored for 7 days (I-7d= 295.3 ± 17.4 μm). Conclusion: Storage may significantly affect the dimensional accuracy of impressions and, thus, a maximum period and storage condition should be specified for the recently developed materials. PMID:19089129

  10. Does immediate dentin sealing influence the polymerization of impression materials?

    PubMed Central

    Ghiggi, Paula Cristine; Steiger, Arno Kieling; Marcondes, Maurem Leitão; Mota, Eduardo Gonçalves; Burnett, Luiz Henrique; Spohr, Ana Maria

    2014-01-01

    Objectives: The objective of the following study is to evaluate the interaction between the resin materials used in immediate dentin sealing (IDS) techniques and impression materials with two different techniques to eliminate the oxygen-inhibition layer. Materials and Methods: The occlusal dentin surface of 35 human molars was exposed. The teeth were used in two Groups: Group 1 – Impression with Express XT; Group 2 – Impression with Impregum. Groups 1 and 2 were divided into 14 subgroups: Groups 1a and 2a – Control groups; 1b and 2b – IDS with Clearfil SE Bond (CSE); 1c and 2c – IDS with CSE + additional polymerization with glycerin jelly; 1d and 2d – IDS with CSE + alcohol; 1e and 2e – IDS with CSE and Protect Liner F (PLF); 1f and 2f – IDS with CSE and PLF + additional polymerization with glycerin jelly; and 1g and 2g – IDS with CSE and PLF + alcohol. Five teeth were used in each experimental group, and the tooth surface was photographed using a digital camera. Results: Small quantity of unpolymerized impression material remained attached to the CSE or to the PLF in Groups 1b and 1e. Groups 1c and 1d prevented the interaction. Small quantity of polymerized impression material remained attached to the CSE or to the PLF for Groups 2b and 2e. The same interaction was observed for Groups 2c and 2d. For Groups 2c and 2f, no interactions were observed. Conclusion: Resin materials interacted with impression materials. The application of glycerin jelly and alcohol prevented the interaction of CSE with Express XT and PLF with Impregum; however, these treatments were not completely effective in preventing the interaction of CSE with Impregum and PLF with Express XT. PMID:25202218

  11. The fit of crowns produced using digital impression systems.

    PubMed

    Vennerstrom, Micael; Fakhary, Mobin; Von Steyern, Per Vult

    2014-01-01

    Compare the marginal and internal fit of crowns manufactured using four different digital impression systems with crowns manufactured using conventional impression technique, that served as a control group. Fifty all-ceramic crowns were fabricated using 50 standardized dies divided into five groups, each group representing one impression system. Each crown was cemented onto its respective model and sectioned into four segments.The marginal and internal fit were measured at 8 predefined points. A total of 1567 measurements were made, statistically analyzed and compared with crowns fabricated using the five systems. The following was found: (1) No significant difference was found with regard to mar ginal gap when comparing the control group to any of the digital systems. (2) Lava had smaller marginal gaps than CEREC and iTero, (3) CEREC and Lava had smaller gaps in the chamfer compared to iTero and the control, (4) E4D showed smaller gaps than CEREC at measuring points 4-8 and CEREC a smaller gap at point 2, (5) Lava showed smaller gaps than CEREC at measuring points 1,3 and 5-8. (6) Lava had smaller gaps than iTero at measuring points 1-4,7 and 8. All differences presented were significant. In conclusions, crowns manufactured using digital impressions present a marginal and internal fit equal to, or better than, crowns made using a conventional impression method.The marginal and internal fit of reconstructions made using digital impression techniques could improve with a lower initial setting of the spacer. PMID:25796804

  12. Trophic transfer of methyl siloxanes in the marine food web from coastal area of Northern China.

    PubMed

    Jia, Hongliang; Zhang, Zifeng; Wang, Chaoqun; Hong, Wen-Jun; Sun, Yeqing; Li, Yi-Fan

    2015-03-01

    Methyl siloxanes, which belong to organic silicon compounds and have linear and cyclic structures, are of particular concern because of their potential characteristic of persistent, bioaccumulated, toxic, and ecological harm. This study investigated the trophic transfer of four cyclic methyl siloxanes (octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), and tetradecamethylcycloheptasiloxane (D7)) in a marine food web from coastal area of Northern China. Trophic magnification of D4, D5, D6, and D7 were assessed as the slope of lipid equivalent concentrations regressed against trophic levels of marine food web configurations. A significant positive correlation (R = 0.44, p < 0.0001) was found between lipid normalized D5 concentrations and trophic levels in organisms, showing the trophic magnification potential of this chemical in the marine food web. The trophic magnification factor (TMF) of D5 was estimated to be 1.77 (95% confidence interval (CI): 1.41-2.24, 99.8% probability of the observing TMF > 1). Such a significant link, however, was not found for D4 (R = 0.14 and p = 0.16), D6 (R = 0.01 and p = 0.92), and D7 (R = -0.15 and p = 0.12); and the estimated values of TMFs (95% CI, probability of the observing TMF > 1) were 1.16 (0.94-1.44, 94.7%), 1.01 (0.84-1.22, 66.9%) and 0.85 (0.69-1.04, 48.6%) for D4, D6, and D7, respectively. The TMF value for the legacy contaminant BDE-99 was also estimated as a benchmark, and a significant positive correlation (R = 0.65, p < 0.0001) was found between lipid normalized concentrations and trophic levels in organisms. The TMF value of BDE-99 was 3.27 (95% CI: 2.49-4.30, 99.7% probability of the observing TMF > 1), showing the strong magnification in marine food webs. To the best of our knowledge, this is the first report on the trophic magnification of methyl siloxanes in China, which provided important information for trophic transformation of these compounds in marine food webs. PMID:25625298

  13. Setting properties of alginate impression materials in dynamic viscoelasticity.

    PubMed

    Shigeto, N; Yamada, Y; Iwanaga, H; Subianto, A; Hamada, T

    1997-10-01

    The viscoelastic properties of three alginate impression materials were investigated. A landmark of working time was calculated using a raw phase-time curve. A landmark of setting time was calculated from an inflection point of the divided difference of the first order in the share modulus-time curve. As a result, the working time was common at the point of delta = 45 degrees in variable frequencies. The mean value was obtained with less deviation. The setting times obtained were similar for variable frequencies. The mean values showed a distinct difference for each impression material. PMID:9372467

  14. Disinfection of dental impressions and occlusal records by ultraviolet radiation.

    PubMed

    Larsen, T; Fiehn, N E; Peutzfeldt, A; Owall, B

    2000-06-01

    As chemical disinfection of dental impressions may cause adverse effects on materials and the dental personnel this study examined disinfection by ultraviolet radiation. Alginate, addition silicone rubber and red wax contaminated by Streptococcus salivarius, Fusobacterium nucleatum and five other bacteria in different suspension media were radiated for up to 18 min, and the number of colony forming units was compared to non-radiated controls. The effect of ultraviolet radiation differed among bacterial species and depended on the organic content in the suspension. Generally, the bacterial reduction after ultraviolet radiation was below 4 log steps and thus insufficient for disinfection of dental impressions. PMID:11307403

  15. Evaluation of a rubber-base impression material.

    PubMed

    Gunther, G; Welsh, S I

    1978-01-01

    A laboratory experiment has been described that utilized materials found in most dental offices and that was designed to evaluate a distinctly different polysulfide impression material. In this experiment the largest duplicating errors were produced with use of the stock tray and single-mix technique recommended by the manufacturer. This study therefore supports the use of the custom tray and double-mix technique for dental duplication procedures utilizing Neo-Plex impression material. Further investigation is necessary before stock trays and single-mix techniques can be recommended for routine use in fixed prosthodontics. PMID:340664

  16. Transparent and robust siloxane-based hybrid lamella film as a water vapor barrier coating.

    PubMed

    Tokudome, Yasuaki; Hara, Takaaki; Abe, Risa; Takahashi, Masahide

    2014-11-12

    Water vapor barriers are important in various application fields, such as food packaging and sealants in electronic devices. Polymer/clay composites are well-studied water vapor barrier materials, but their transparency and mechanical strength degrade with increasing clay loading. Herein, we demonstrate films with good water vapor barrier properties, high transparency, and mechanical/thermal stability. Water vapor barrier films were prepared by the solution crystallization of siloxane hybrid lamellae. The films consist of highly crystallized organic/inorganic hybrid lamellae, which provide high transparency, hardness, and thermal stability and inhibit the permeation of water vapor. The water permeability of a 6 ?m thick hybrid film is comparable to that of a 200 ?m thick silicon rubber film. PMID:25296395

  17. Thermal neutron detection by entrapping 6LiF nanocrystals in siloxane scintillators

    NASA Astrophysics Data System (ADS)

    Carturan, S. M.; Marchi, T.; Maggioni, G.; Gramegna, F.; Degerlier, M.; Cinausero, M.; Dalla Palma, M.; Quaranta, A.

    2015-06-01

    Exploiting the long experience in design and production of scintillating mixtures based on siloxane matrices with combinations of primary dye and waveshifter, a first set of 6LiF loaded scintillator disks has been produced. The synthesis is herein described and reported, as well as preliminary results on their light response towards thermal neutrons. The preservation of transparency and mechanical integrity of the scintillator material is challenging when introducing the inorganic salt LiF which is a "foreign body" to the organic polysiloxane host matrix Different strategies such as synthesis of nanoparticles and surface functionalization have been pursued to succeed in the entrapment of the neutron converter whilst maintaining moderate light output, optical transparency and flexibility of the base scintillator.

  18. The effect of temperature on the electric conductivity of poly(dimethyl siloxane) ferromagnetic gel

    NASA Astrophysics Data System (ADS)

    Kubisz, L.; Skumiel, A.; Hornowski, T.; Szlaferek, A.; Pankowski, E.

    2008-05-01

    In this paper the influence of temperature on the electrical conductivity of a ferromagnetic gel is investigated. The material used was poly(dimethyl siloxane) (PDMS) gel which contained randomly distributed magnetite nanosized particles. The electrical conductivity was measured by means of the two-point dc method. During the heating of the PDMS in the temperature range of 295-460 K the electrical conductivity increased from about 2 10-12 to 2 10-8 S m-1. A study of the current-temperature dependence obtained during subsequent heating runs revealed two subranges of temperature characterized by different activation energies. The presence of these subranges could be explained either by the liberation of two different types of charge carrier or by the increase in the degree of polymer cross-linking. In the upper temperature subrange (420-460 K) both types of charge carrier probably contribute to the electrical conductivity of PDMS ferromagnetic gel.

  19. The effect of temperature on the electric conductivity of poly(dimethyl siloxane) ferromagnetic gel.

    PubMed

    Kubisz, L; Skumiel, A; Hornowski, T; Szlaferek, A; Pankowski, E

    2008-05-21

    In this paper the influence of temperature on the electrical conductivity of a ferromagnetic gel is investigated. The material used was poly(dimethyl siloxane) (PDMS) gel which contained randomly distributed magnetite nanosized particles. The electrical conductivity was measured by means of the two-point dc method. During the heating of the PDMS in the temperature range of 295-460K the electrical conductivity increased from about 2 10(-12) to 2 10(-8)Sm(-1). Astudy of the current-temperature dependence obtained during subsequent heating runs revealed two subranges of temperature characterized by different activation energies. The presence of these subranges could be explained either by the liberation of two different types of charge carrier or by the increase in the degree of polymer cross-linking. In the upper temperature subrange (420-460K) both types of charge carrier probably contribute to the electrical conductivity of PDMS ferromagnetic gel. PMID:21694247

  20. Liquid-phase-deposited siloxane-based capping layers for silicon solar cells

    SciTech Connect

    Veith-Wolf, Boris; Wang, Jianhui; Hannu-Kuure, Milja; Chen, Ning; Hadzic, Admir; Williams, Paul; Leivo, Jarkko; Karkkainen, Ari; Schmidt, Jan

    2015-02-02

    We apply non-vacuum processing to deposit dielectric capping layers on top of ultrathin atomic-layer-deposited aluminum oxide (AlO{sub x}) films, used for the rear surface passivation of high-efficiency crystalline silicon solar cells. We examine various siloxane-based liquid-phase-deposited (LPD) materials. Our optimized AlO{sub x}/LPD stacks show an excellent thermal and chemical stability against aluminum metal paste, as demonstrated by measured surface recombination velocities below 10 cm/s on 1.3 Ωcm p-type silicon wafers after firing in a belt-line furnace with screen-printed aluminum paste on top. Implementation of the optimized LPD layers into an industrial-type screen-printing solar cell process results in energy conversion efficiencies of up to 19.8% on p-type Czochralski silicon.

  1. Interfacial enhancement of polypropylene composites modified with sorbitol derivatives and siloxane-silsesquioxane resin

    NASA Astrophysics Data System (ADS)

    Dobrzyńska-Mizera, Monika; Dutkiewicz, Michał; Sterzyński, Tomasz; Di Lorenzo, Maria Laura

    2015-12-01

    Composites based on polypropylene (iPP) modified with a sorbitol derivative (NX8000) and siloxane-silsesquioxane resin (SiOPh) containing maleated polypropylene (MAPP) as compatibilizer were prepared by melt extrusion. Calorimetric investigations were carried out using differential scanning calorimetry (DSC), whereas the morphological and mechanical properties were investigated by scanning electron microscopy (SEM) and static tensile tests. DSC measurements revealed no influence of SiOPh and a slight effect of MAPP addition on the crystallization kinetics of polypropylene. Additionally, the introduction of MAPP into the iPP+NX8000+SiOPh composites increased plastic properties of the samples. All the above was attributed to the compatibilizing effect of MAPP which improved interfacial adhesion between iPP, NX8000 and SiOPh. This phenomenon was also confirmed by the SEM images illustrating more homogenous distribution of the filler in the compatibilized samples.

  2. Improved resolution of natural diacylglycerols by gas-liquid chromatography on polar siloxanes.

    PubMed

    Myher, J J; Kuksis, A

    1975-03-01

    A new cyanoalkylphenylsiloxane (SILAR 5CP) liquid phase is shown to possess sufficient polarity to permit improved GC separations of natural diacylglycerols based on unsaturation and positional placement of fatty acids as well as on molecular weight, which was previously possible only on ethylene glycol succinate polyesters. Unlike the polyesters, the polar siloxane polymer has moderate thermal stability and provides GC columns which can be used for several months without replacing the packing. The GC analyses were made with conventional columns containing 3% SILAR 5CP on Gas Chrom Q at 270 degrees C isothermally. The diacylglycerols were chromatographed as the TMS ethers. Excellent seperations were obtained for the 1,2(2,3)- and 1,3-diacyglycerols derived from corn, linseed, peanut and cod liver oils and for the 1,2-diacyl-sn-glycerols from hepatic glycerophospholipids. PMID:1150850

  3. An Investigation of Siloxane Cross-linked Hydroxyapatite-Gelatin/Copolymer Composites for Potential Orthopedic Applications†

    PubMed Central

    Dyke, Jason Christopher; Knight, Kelly Jane; Zhou, Huaxing; Chiu, Chi-Kai; Ko, Ching-Chang; You, Wei

    2012-01-01

    Causes of bone deficiency are numerous, but biomimetic alloplastic grafts provide an alternative to repair tissue naturally. Previously, a hydroxyapatite-gelatin modified siloxane (HAp-Gemosil) composite was prepared by cross-linking (N, N′-bis[(3-trimethoxysilyl)propyl]ethylene diamine (enTMOS) around the HAp-Gel nanocomposite particles, to mimic the natural composition and properties of bone. However, the tensile strength remained too low for many orthopedic applications. It was hypothesized that incorporating a polymer chain into the composite could help improve long range interaction. Furthermore, designing this polymer to interact with the enTMOS siloxane cross-linked matrix would provide improved adhesion between the polymer and the ceramic composite, and improve mechanical properties. To this end, copolymers of L-Lactide (LLA), and a novel alkyne derivatized trimethylene carbonate, propargyl carbonate (PC), were synthesized. Incorporation of PC during copolymerization affects properties of copolymers such as molecular weight, Tg, and % PC incorporation. More importantly, PC monomers bear a synthetic handle, allowing copolymers to undergo post-polymerization functionalization with graft monomers to specifically tailor the properties of the final composite. For our investigation, P(LLA-co-PC) copolymers were functionalized by an azido-silane (AS) via copper catalyzed azide-alkyne cycloaddition (CuAAC) through terminal alkyne on PC monomers. The new functionalized polymer, P(LLA-co-PC)(AS) was blended with HAp-Gemosil, with the azido-silane linking the copolymer to the silsesquioxane matrix within the final composite. These HAp-Gemosil/P(LLA-co-PC)(AS) composites were subjected to mechanical and biological testing, and the results were compared with those from the HAp-Gemosil composites. This study revealed that incorporating a cross-linkable polymer served to increase the flexural strength of the composite by 50%, while maintaining the biocompatibility of HAp-Gemosil ceramics. PMID:23139457

  4. Preparation of poly(lactic acid)/siloxane/calcium carbonate composite membranes with antibacterial activity.

    PubMed

    Tokuda, Shingo; Obata, Akiko; Kasuga, Toshihiro

    2009-05-01

    A poly(lactic acid) (PLA)/siloxane/calcium carbonate composite membrane containing mercapto groups (PSC-SH) with antibacterial ability and excellent bone-forming ability was prepared using 3-mercaptopropyltrimethoxysilane for application in guided bone regeneration. Mercapto groups were reported to adsorb silver ions, which are well known to show antibacterial activity. Ionic silicon species were reported to stimulate the proliferation of osteoblasts. A PSC-SH membrane with a thickness of about 10 microm shows high flexibility. The PLA in PSC-SH was converted from the crystalline phase to the amorphous phase due to dispersion of condensed siloxane clusters. The amount of mercapto group on PSC-SH surface was estimated to be about 55 nmol mm(-2) by quantitative analysis using the thiol-disulfide exchange reaction. PSC-SH adsorbed silver ions on its surface after being soaked in 6 microM silver acetate aqueous solution for 1 min. The adsorbed silver ions were seen by X-ray photoelectron spectroscopy to form SAg and SO3Ag bonds. A trace amount of ionic silicon species was released from the membrane after soaking in culture medium. PSC-SH with adsorbed silver ions showed good antibacterial activity and cellular compatibility in tests conducted with Staphylococcus aureus and mouse osteoblast-like cells, respectively. Antibacterial activity is expected to occur during the implantation operation by the silver ions but not to remain in the body for a long period, as the ions were present on the surface of the membrane but not inside the structure. The membrane should be useful as a biodegradable material with antibacterial activity and bone-forming ability. PMID:18996778

  5. System constants of synthesized poly(methyl-3,3,3-trifluoropropyl) siloxanes.

    PubMed

    Lebrn-Aguilar, R; Quintanilla-Lpez, J E; Tello, A M; Prez-Parajn, J M; Santiuste, J M

    2005-12-30

    The method of solvation model has been applied to five poly (methyl-trifluoropropyl) siloxanes (TFPSXX) prepared in our laboratories, at five trifluoropropyl (TFP) group contents, XX = 0, 11.5, 26.3, 35.5 and 50.0%, at 80, 100, 120 and 140 degrees C. Previously, specific retention volumes of 60-odd solutes of varied polarities were measured upon each of these stationary phases within the above temperature range. Constant s prevails over all other constants, TFPSXX stationary phases showing strong dipole/induced dipole forces with the solutes, moderate acidity and no basicity at all. Constant e is zero in the stationary phase without TFP groups, but has negative low-medium values for the other fluorine contents, XX from 11.5 to 50.0%, hinting at repulsive forces, as expected. Normal values for constant l, decreasing from the less cohesive TFPS00 to the more cohesive TFPS50, were found. For each TFP content constants s, a and l show a negative temperature dependence, while constant e increases as temperature increases. Constant c also decreases with increasing temperature. At each temperature, constants s and a increase with increasing %TFP (or increasing stationary phase polarity), whereas constants e and l show the opposite trend, diminishing with increasing polarity of the stationary phase. Principal component analysis shows that the five stationary phases presented in this work conform a group with other earlier synthesized trifluoropropyl siloxanes and other fluorinated stationary phases taken from literature: VB-210, QF-1, DB-200, DB-210 and PFS6, showing the same selectivity which only the fluorine atom confers. A dendrogram of 38 stationary phases supports these results. PMID:16236288

  6. Complexes of polyvinyl alcohol with insoluble inorganic compounds

    NASA Astrophysics Data System (ADS)

    Prosanov, I. Yu.; Bulina, N. V.; Gerasimov, K. B.

    2013-10-01

    Hybrid materials of polyvinyl alcohol-hydroxides/oxides of Be, Mg, Zn, Cd, B, Al, Cr, and Fe have been obtained. The studies have been carried out by the methods of optical spectroscopy, X-ray diffraction, and synchronous thermal analysis. Interpretation of experimental data is presented, presuming that, in systems with zinc, boron, aluminum, chromium, and iron hydroxides/oxides, interpolymeric complexes of polyvinyl alcohol with corresponding polymeric inorganic compounds are formed. They belong to a new class of materials with unusual structure containing chains of inorganic polymers isolated in the organic matrix.

  7. Polyvinyl alcohol battery separator containing inert filler. [alkaline batteries

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Hsu, L. C.; Manzo, M. A. (Inventor)

    1981-01-01

    A cross-linked polyvinyl alcohol battery separator is disclosed. A particulate filler, inert to alkaline electrolyte of an alkaline battery, is incorporated in the separator in an amount of 1-20% by weight, based on the weight of the polyvinyl alcohol, and is dispersed throughout the product. Incorporation of the filler enhances performance and increases cycle life of alkaline batteries when compared with batteries containing a similar separator not containing filler. Suitable fillers include titanates, silicates, zirconates, aluminates, wood floor, lignin, and titania. Particle size is not greater than about 50 microns.

  8. [Pulmonary manifestations of polyvinyl chloride exposure].

    PubMed

    Syr, Hseyin; Bayram, Nazan; Ayd?n, Neriman; Uyar, Meral; Gndo?du, Nevhiz; Elbek, Osman

    2011-01-01

    There is currently no national data on the effects of polyvinyl chloride (PVC) exposure on pulmonary function. In this study we recruited workers and administrative staff from two PVC plants between July 2008 and July 2009. A questionnaire, pulmonary function tests, carbon monoxide diffusion capacity, and peak flows were recorded. Particulate matter analyses were performed by the Adana Central Laboratory of the Directorate of Occupational Health and Safety. Data were analyzed with SPSS 13.0 software. Nine of the 147 subjects were female. The incidence of a cough was more common in the administrative group. Of the study population, 59.1% were smokers. Tobacco addiction significantly increased cough and dyspnea [OR= 1.10 (1.00-1.20, 95% CI) p= 0.007 and OR= 1.08 (1.02-1.14, 95% CI), p= 0.008, respectively]. Dust exposure was correlated with the incidence of a cough [OR= 0.20 (0.04-0.80, 95% CI) p= 0.008]. The period of work correlated with sputum production [OR= 1.00 (1.00-1.02, 95% CI) p= 0.044]. The FVC% was significantly higher in the administrative group, and FEV1/FVC and DLCO were higher in the exposed group. Tobacco addiction increased the risk of airflow limitation, as evaluated by FEV1/FVC < 70% and FEF25-75 < 50% [OR= 1.15 (1.06-1.25, 95% CI) p= 0.001 and OR= 1.09 (1.02-1.17, 95% CI) p= 0.010, respectively]. Tobacco addiction and increasing duration of work had a negative influence on DLCO in the exposed group (r= -0.270, p= 0.025 and r= -0.210, p= 0.037). In the exposed group PEF variability was significantly greater on workdays, compared with rest days. This study shows that tobacco consumption has a greater affect on the airways than PVC dust exposure. A median of 36 months exposure to PVC dust had no significant impact on pulmonary function parameters, except for DLCO and PEF variability. PMID:21554225

  9. First Impressions: Gait Cues Drive Reliable Trait Judgements

    ERIC Educational Resources Information Center

    Thoresen, John C.; Vuong, Quoc C.; Atkinson, Anthony P.

    2012-01-01

    Personality trait attribution can underpin important social decisions and yet requires little effort; even a brief exposure to a photograph can generate lasting impressions. Body movement is a channel readily available to observers and allows judgements to be made when facial and body appearances are less visible; e.g., from great distances.

  10. Method for creating stomatal impressions directly onto archivable microscope slides

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stomatal density has been shown to be a primary determinant of water use efficiency, limitation to CO2 assimilation rate and yield. Widely used methods of stomatal impressioning sample small regions of the leaf, are labor intensive, or do not yield stable archivable samples for potentially revisitin...

  11. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., such as alginate, to make an impression of a patient's teeth or alveolar process (bony tooth sockets) to reproduce the structure of a patient's teeth and gums. (b) Classification. Class I (general... regulation in part 820 of this chapter, with the exception of 820.180, with respect to general...

  12. 21 CFR 872.6880 - Preformed impression tray.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., such as alginate, to make an impression of a patient's teeth or alveolar process (bony tooth sockets) to reproduce the structure of a patient's teeth and gums. (b) Classification. Class I (general... regulation in part 820 of this chapter, with the exception of 820.180, with respect to general...

  13. DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE ...

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

    DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE SOUTH END OF THE ABOVE-GROUND PORTION. NOTE STEP DOWN TO THE STEEL PLATE IN BACKGROUND. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  14. Making an Impression: YA Authors and Their Influential Teachers

    ERIC Educational Resources Information Center

    Eisenbach, Brooke; Kaywell, Joan F.

    2013-01-01

    This article recounts significant moments from online interviews these authors conducted with Young Adult (YA) authors concerning the teachers who left a lasting impression on them and assisted them in finding their voice and unique writing abilities. S. E. Hinton, Walter Dean Myers, Erin Gruwell, Chris Crutcher, and other popular YA authors…

  15. Reaching Readers: Assessing Readers' Impressions of Science News.

    ERIC Educational Resources Information Center

    Steinke, Jocelyn

    1995-01-01

    This study used think-aloud protocols to examine the responses of readers to two newspaper science articles. When readers encountered information they could not understand, they used reading strategies; responses illustrate how individual predispositions, social affiliations, and information processing can influence impressions of science news.

  16. A Survey of Sophomore Students' Impressions of Academic Advising Services.

    ERIC Educational Resources Information Center

    Gross, Ronald Dale

    1998-01-01

    A study investigated 463 East Tennessee State University sophomores' perceived academic advising needs, levels of satisfaction with advising sessions, and impressions of the advisor. Results revealed dissatisfaction with advisors' assistance, and suggested areas for improvement. Several institutional and programmatic strategies are outlined.

  17. Impressions of Counselors as a Function of Counselor Physical Attractiveness

    ERIC Educational Resources Information Center

    Carter, Jean A.

    1978-01-01

    Research assessed the effects of counselor physical attractiveness and inter-actions between attractiveness and counselor subject sex. It is suggested that sex of counselor and client may play a more important role independently and in conjunction with attractiveness than does attractiveness alone in influencing impressions and expectations.

  18. The impact of motivation on race-based impression formation.

    PubMed

    Li, Tianyi; Cardenas-Iniguez, Carlos; Correll, Joshua; Cloutier, Jasmin

    2016-01-01

    Affective biases toward racial out-group members, characterized by White perceivers' negative evaluations of Black individuals, prevail in U.S. culture. Such affective associations have been found to guide race-based impression formation. Accordingly, individuals may strive to resolve inconsistencies when perceiving targets violating their expectations. The current study focuses on the impact of evaluative incongruence on the activity of the dorsomedial prefrontal cortex (dmPFC) - a brain region previously shown to support impression formation. When asking participants to form impressions of positively and negatively evaluated Black and White individuals, we found preferential dmPFC activity in response to individuals paired with information that violates race-based affective associations. Importantly, individual differences in internal motivation to respond without prejudice (IMS) were found to shape the extent to which dmPFC activity indexes the interactive effects of race and affective associations during impression formation. Specifically, preferential dmPFC activity in response to evaluatively incongruent targets (i.e., Black-positive & White-negative) was present among participants with lower, but not those with higher, levels of IMS. Implications and future directions are discussed in the context of dmPFC involvement in social cognition. PMID:26302673

  19. Curriculum Challenge from the Religious Right: The "Impressions" Reading Series.

    ERIC Educational Resources Information Center

    Adler, Louise; Tellez, Kip

    1992-01-01

    Studies curriculum challenges by religious conservatives to the "Impressions" reading series in California. Many parents thought the series promoted satanism, witchcraft, and disrespect toward parents. Data from 22 school districts, 4 of which dropped the series, illustrate the complex nature of such challenges and highlight school district…

  20. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

    PubMed Central

    De Angelis, Francesco; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

  1. Microbiological evaluation of ultrasonic nebulization for disinfecting dental impressions.

    PubMed

    Mendonca, Marcio Jose; Rafael, Renata Santos; Camilotti, Veridiana; Menolli, Rafael Andrade; Sicoli, Eliseu Augusto; Teixeira, Nancielli; Sinhoreti, Mario Alexandre Coelho

    2013-07-01

    Disinfecting dental impressions is necessary to decrease the risk of cross-contamination in dental offices. Ultrasonic nebulization has been mentioned as a microbicidal technique that can be used to disinfect contaminated dental impressions. This study compared the microbicidal effect of 2% glutaraldehyde and 0.2% peracetic acid for the disinfection of dental impressions made with vinyl polysiloxane, using 2 disinfection methods: immersion and ultrasonic nebulization. Bactericial efficacy was examined using Staphylococcus aureus and Bacillus atrophaeus as indicators. Thirty impressions were obtained and distributed randomly in 5 groups (n = 6). Group 1 was immersed in 2% glutaraldehyde immersion for 10 minutes, Group 2 was immersed in 0.2% peracetic acid for 10 minutes, Group 3 underwent ultrasonic nebulization for 10 minutes in 2% glutaraldehyde solution, Group 4 underwent ultrasonic nebulization for 10 minutes in 0.2% peracetic acid solution, and Group 5 was a control group that received no disinfectant. Both solutions experienced a 100% reduction in microorganisms following ultrasonic nebulization, as did peracetic acid following immersion; however, immersion in glutaraldehyde demonstrated lower values of reduction in B atrophaeus group, with a statistically significant difference compared with the other experimental groups. PMID:23823336

  2. Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison.

    PubMed

    Re, Dino; De Angelis, Francesco; Augusti, Gabriele; Augusti, Davide; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

    2015-01-01

    Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (? = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70?MPa). Polyethers showed the lowest tensile (1.44?MPa) and yield (0.94?MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

  3. Cross-Cultural Impression Management: A Cultural Knowledge Audit Model

    ERIC Educational Resources Information Center

    Spong, Abigail; Kamau, Caroline

    2012-01-01

    Purpose: Many people moving into a new culture for work or study do so without prior cross-cultural training, yet successful cultural adaptation has important ramifications. The purpose of this paper is to focus on cross-cultural impression management as an element of cultural adaptation. Does cultural adaptation begin by paying strong attention

  4. Cross-Cultural Impression Management: A Cultural Knowledge Audit Model

    ERIC Educational Resources Information Center

    Spong, Abigail; Kamau, Caroline

    2012-01-01

    Purpose: Many people moving into a new culture for work or study do so without prior cross-cultural training, yet successful cultural adaptation has important ramifications. The purpose of this paper is to focus on cross-cultural impression management as an element of cultural adaptation. Does cultural adaptation begin by paying strong attention…

  5. 75 FR 38079 - Postponement of Preliminary Determination of Antidumping Duty Investigation: Polyvinyl Alcohol...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-01

    ...) initiated the antidumping duty investigation on polyvinyl alcohol from Taiwan. See Initiation of Anti-Dumping Duty Investigation: Polyvinyl Alcohol From Taiwan, 69 FR 59204 (October 4, 2004). On October 22...: Polyvinyl Alcohol From Taiwan AGENCY: Import Administration, International Trade Administration,...

  6. 78 FR 20890 - Polyvinyl Alcohol From Taiwan: Preliminary Results of Antidumping Duty Administrative Review...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-08

    ... established in the Antidumping Duty Order: Polyvinyl Alcohol From Taiwan, 76 FR 13982 (March 15, 2011). These... International Trade Administration Polyvinyl Alcohol From Taiwan: Preliminary Results of Antidumping Duty... the antidumping duty order on polyvinyl alcohol (PVA) from Taiwan. The period of review (POR)...

  7. Potential estrogenic and antiestrogenic activity of the cyclic siloxane octamethylcyclotetrasiloxane (D4) and the linear siloxane hexamethyldisiloxane (HMDS) in immature rats using the uterotrophic assay.

    PubMed

    McKim, J M; Wilga, P C; Breslin, W J; Plotzke, K P; Gallavan, R H; Meeks, R G

    2001-09-01

    The cyclic siloxane octamethylcyclotetrasiloxane (D4) and the linear siloxane hexamethyldisiloxane (HMDS) have numerous industrial and consumer applications and thus have the potential for human exposure. The present study was undertaken to examine potential estrogenic and antiestrogenic activities of D4 and HMDS. To address potential differences in sensitivity between rat strains the study used both Sprague-Dawley (SD) and Fischer 344 (F-344) rats. Estrogenicity of the test compounds was determined by measuring absolute and relative uterine weights in immature rats and by monitoring uterine epithelial cell height. In order to place the data obtained for D4 into perspective relative to strong and weak estrogenic compounds, the response produced by D4 at 0, 10, 50, 100, 250, 500, and 1000 mg/kg/day was compared to responses produced by ethinyl estradiol (EE) (1, 3, 10, or 30 microg/kg/day), diethylstilbestrol dipropionate (DES-DP) (0.5, 1.5, 5, 15 microg/kg/day), and coumestrol (CE) (10, 35, 75, 150 mg/kg/day). Antiestrogenic effects were evaluated by co-administering D4 (500 mg/kg/day) with EE at 1, 3, 10, and 30 microg /kg/day. All compounds were administered in sesame oil at a volume of 5 mL/kg by oral gavage. Beginning on postnatal day 18 (SD) or 21 (F-344) each pup (12 per group) received a single dose of test compound once a day for 4 consecutive days. The pups were euthanized the morning after the last treatment and their uteri removed, weighed, and processed for histological examination. EE and DES-DP produced a significant dose-dependent increase in absolute and relative uterine weights and uterine cell height. The maximum increase in uterine weight following EE exposure was approximately 350% relative to controls in both strains. The weak phytoestrogen CE also produced a dose-related increase in absolute and relative uterine weight and epithelial cell height, but the response occurred over a much higher range of doses. At the highest dose of CE, uterine weight was increased approximately 230% relative to controls. Following exposure to D4, absolute and relative uterine weights and uterine epithelial cell height were statistically significantly increased in both strains of rats at doses above 100 mg/kg/day. In terms of uterine weight, D4 was approximately 0.6 million times less potent than EE or DES-DP in SD pups and 3.8 million times less potent than EE or DES-DP in F-344 pups. The maximal increase in uterine weight, relative to controls, produced by D4 at 1000 mg/kg/day was approximately 160% in SD rats, while the maximum increase produced by D4 in F-344 rats was 86%. D4 co-administered over a wide range of EE doses, resulted in a significant reduction in uterine weight compared to EE alone. HMDS was evaluated in SD rats only. The response produced by HMDS (600 and 1200 mg/kg/day) was compared to EE (3 microg/kg/day). Antiestrogenic effects were evaluated by co-administering HMDS (1200 mg/kg/day) with EE at 3 microg/kg/day. HMDS had no measurable effect on uterine weight under the experimental conditions described here. However, HMDS coadministered with EE did produce a small, but statistically significant reduction in uterine weight compared to EE alone. In conclusion, D4 showed weak estrogenic and antiestrogenic activity that was several orders of magnitude less potent than EE, and many times less potent than the weak phytoestrogen CE. PMID:11509742

  8. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers, which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers, which is incorporated by reference; see paragraph (b)...

  9. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers, which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers, which is incorporated by reference; see paragraph (b)...

  10. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  11. 21 CFR 175.270 - Poly(vinyl fluoride) resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... polymerization of vinyl fluoride. (b) The poly(vinyl fluoride) basic resins have an intrinsic viscosity of not... Dilute Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference. Copies may be... Solution Viscosity of Vinyl Chloride Polymers,” which is incorporated by reference; see paragraph (b)...

  12. EXPOSURE TO CHEMICAL ADDITIVES FROM POLYVINYL CHLORIDE POLYMER EXTRUSION PROCESSING

    EPA Science Inventory

    This report presents a model to predict worker inhalation exposure due to off-gassing of additives during polyvinyl chloride (PVC) extrusion processing. ata on off-gassing of additives were reviewed in the literature, the off-gassing at normal PVC processing temperatures was stud...

  13. Anammox sludge immobilized in polyvinyl alcohol (PVA) cryogel carriers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluated the use of polyvinyl alcohol (PVA) cryogels to encapsulate slow-growing anammox bacteria for deammonification treatment of wastewater. The cryogel pellets were prepared by a freezing-thawing procedure at -8 oC. On average, pellets contained 11.8 mg TSS/g-pellet of enriched anamm...

  14. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyvinyl alcohol film. 177.1670 Section 177.1670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food...

  15. Analytical methodology for sampling and analysing eight siloxanes and trimethylsilanol in biogas from different wastewater treatment plants in Europe.

    PubMed

    Raich-Montiu, J; Ribas-Font, C; de Arespacochaga, N; Roig-Torres, E; Broto-Puig, F; Crest, M; Bouchy, L; Cortina, J L

    2014-02-17

    Siloxanes and trimethylsilanol belong to a family of organic silicone compounds that are currently used extensively in industry. Those that are prone to volatilisation become minor compounds in biogas adversely affecting energetic applications. However, non-standard analytical methodologies are available to analyse biogas-based gaseous matrixes. To this end, different sampling techniques (adsorbent tubes, impingers and tedlar bags) were compared using two different configurations: sampling directly from the biogas source or from a 200 L tedlar bag filled with biogas and homogenised. No significant differences were apparent between the two sampling configurations. The adsorbent tubes performed better than the tedlar bags and impingers, particularly for quantifying low concentrations. A method for the speciation of silicon compounds in biogas was developed using gas chromatography coupled with mass spectrometry working in dual scan/single ion monitoring mode. The optimised conditions could separate and quantify eight siloxane compounds (L2, L3, L4, L5, D3, D4, D5 and D6) and trimethylsilanol within fourteen minutes. Biogas from five waste water treatment plants located in Spain, France and England was sampled and analysed using the developed methodology. The siloxane concentrations in the biogas samples were influenced by the anaerobic digestion temperature, as well as the nature and composition of the sewage inlet. Siloxanes D4 and D5 were the most abundant, ranging in concentration from 1.5 to 10.1 and 10.8 to 124.0 mg Nm(-3), respectively, and exceeding the tolerance limit of most energy conversion systems. PMID:24491768

  16. Oxidation of siloxanes during biogas combustion and nanotoxicity of Si-based particles released to the atmosphere.

    PubMed

    Tansel, Berrin; Surita, Sharon C

    2014-01-01

    Siloxanes have been detected in the biogas produced at municipal solid waste landfills and wastewater treatment plants. When oxidized, siloxanes are converted to silicon oxides. The objectives of this study were to evaluate the transformation of siloxanes and potential nanotoxicity of Si-based particles released to the atmosphere from the gas engines which utilize biogas. Data available from nanotoxicity studies were used to assess the potential health risks associated with the inhalation exposure to Si-based nanoparticles. Silicon dioxide formed from siloxanes can range from 5 nm to about 100 nm in diameter depending on the combustion temperature and particle clustering characteristics. In general, silicon dioxide particles formed during from combustion process are typically 40-70 nm in diameter and can be described as fibrous dusts and as carcinogenic, mutagenic, astmagenic or reproductive toxic (CMAR) nanoparticles. Nanoparticles deposit in the upper respiratory system, conducting airways, and the alveoli. Size ranges between 5 and 50 nm show effective deposition in the alveoli where toxic effects are higher. In this study the quantities for the SiO? formed and release during combustion of biogas were estimated based on biogas utilization characteristics (gas compositions, temperature). The exposure to Si-based particles and potential effects in humans were analyzed in relation to their particle size, release rates and availability in the atmosphere. The analyses showed that about 54.5 and 73 kg/yr of SiO? can be released during combustion of biogas containing D4 and D5 at 14.1 mg/m(3) (1 ppm) and 15.1 mg/m(3) (1ppm), respectively, per MW energy yield. PMID:24355797

  17. Determination of siloxanes and VOC in landfill gas and sewage gas by canister sampling and GC-MS/AES analysis

    SciTech Connect

    Schweigkofler, M.; Niessner, R.

    1999-10-15

    Biogases such as landfill gas and sewage gas undergo a combustion process which is generating electric energy. Since several trace compounds such as siloxanes (also halogenated and sulfur compounds) are known to cause severe problems to these gas combustion engines, they are of particular interest. In this work, a new technique for sampling, identification, and quantification of siloxanes and volatile organic carbon (VOC) in landfill gas and sewage gas is presented. After sample collection using evacuated stainless steel canisters biogas was analyzed by gas chromatography-mass spectrometry/atomic emission spectroscopy (GC-MS/AES). Using gas canisters, the sampling process was simplified (no vacuum pump needed), and multiple analysis was possible. The simultaneous application of MSD and AED allowed a rapid screening of silicon compounds in the complex biogases. Individual substances were identified independently both by MSD analysis and by determination of their elemental constitution. Quantification of trace compounds was achieved using a 30 component external standard containing siloxanes, organochlorine and organosulfur compounds, alkanes, terpenes, and aromatic compounds. Precision, linearity, and detection limits have been studied. In real samples, concentrations of silicon containing compounds (trimethylsilanol, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasilioxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane) in the mg/m{sub 3} range have been observed.

  18. First impressions: towards becoming a health-literate health service.

    PubMed

    Johnson, Anne

    2014-05-01

    A 'health-literate organisation' recognises that miscommunication is very common and can negatively affect consumer care and outcomes, and makes it easier for people to navigate, understand, and use health information and services. This paper reports on the First Impressions Activities conducted by consumers to assess aspects of the literacy environment of a rural health service. The First Impressions Activities consists of three tools to assist health services to begin to consider some of the characteristics of their organisation that help and hinder a consumer's ability to physically navigate their way to and about the health service. The results show that navigation to and within the rural health service was made more complex due to lack of information, difficulty finding information, inconsistent terminology used in signage, missing signage, signage obscured by foliage, and incorrect signage. PMID:24670250

  19. First impressions: gait cues drive reliable trait judgements.

    PubMed

    Thoresen, John C; Vuong, Quoc C; Atkinson, Anthony P

    2012-09-01

    Personality trait attribution can underpin important social decisions and yet requires little effort; even a brief exposure to a photograph can generate lasting impressions. Body movement is a channel readily available to observers and allows judgements to be made when facial and body appearances are less visible; e.g., from great distances. Across three studies, we assessed the reliability of trait judgements of point-light walkers and identified motion-related visual cues driving observers' judgements. The findings confirm that observers make reliable, albeit inaccurate, trait judgements, and these were linked to a small number of motion components derived from a Principal Component Analysis of the motion data. Parametric manipulation of the motion components linearly affected trait ratings, providing strong evidence that the visual cues captured by these components drive observers' trait judgements. Subsequent analyses suggest that reliability of trait ratings was driven by impressions of emotion, attractiveness and masculinity. PMID:22717166

  20. Finite Element Analysis of Plastic Deformation During Impression Creep

    NASA Astrophysics Data System (ADS)

    Naveena; Ganesh Kumar, J.; Mathew, M. D.

    2015-04-01

    Finite element (FE) analysis of plastic deformation associated with impression creep deformation of 316LN stainless steel was carried out. An axisymmetric FE model of 10 10 10 mm specimen with 1-mm-diameter rigid cylindrical flat punch was developed. FE simulation of impression creep deformation was performed by assuming elastic-plastic-power-law creep deformation behavior. Evolution of the stress with time under the punch during elastic, plastic, and creep processes was analyzed. The onset of plastic deformation was found to occur at a nominal stress about 1.12 times the yield stress of the material. The size of the developed plastic zone was predicted to be about three times the radius of the punch. The material flow behavior and the pile-up on specimen surface have been modeled.

  1. Impression Material Mass Retained in the Mucobuccal Fold

    PubMed Central

    Karam Genno, N.; Assaf, A.

    2014-01-01

    Trapped foreign bodies and tissue reactions to foreign materials are commonly encountered in the oral cavity. Traumatically introduced dental materials, instruments, or needles are the most common materials referred to in the dental literature. This paper describes an iatrogenic foreign body encapsulation in the oral mucosa, clinically appearing as 5 10?mm tumor-like swelling with an intact overlying epithelium and diagnosed as a polymeric impression material. Detailed case history and, clinical and radiographic examinations including CBCT and spectrometric analysis of the retrieved sample were necessary to determine accurately the nature, size, and location of the foreign body. It is suggested that the origin of the material relates to an impression made 2 years ago, leaving a mass trapped in a traumatized mucosal tissue. PMID:25061529

  2. [The viscosity of Thiokol impression material during gelation (author's transl)].

    PubMed

    Araki, Y; Kawakami, M

    1976-09-01

    Viscosity behavior of the impression materials is important property which determines the pressure and its distribution to be exerted on oral soft tissues in relation to the tray design and impression technique. The impression material, however, react to gel so fast to measure the viscosity during the reaction that it is still not completely elucidated. It would be able to seize the viscosity behavior of Thiokol impression material during the gelation unequivocally by retarding the oxidative condensation reaction using weak oxidative, lead monoxide. Based on the equal reactivity of SH groups of Thiokol liquid polymer there is no difference in statistic molecular weight distribution at any degree of the reaction between with lead monoxide and with the other oxidatives now in practical use. The viscosity measurement of the mixture of Thiokol LP-2, lead monoxide, and di-butyl phthalate was performed at the rates of shear ranged from 10(1.5) to 10(3.9) sec-1 at 20 degrees C. The viscosity of the mixture progressively increases after spatulation of the materials but yield value does not appear for the time being before setting, that is, the infinite network forming via the pendant SH groups could not take place until the most of SH groups were consumed, attributed to low concentration of poly-functional prepolymer in the liquid polymer. At early stages of the reaciton the viscosity behavior is approximately Newtonian at lower rates of shear and pseudplastic at higher rates of shear. As the reaction proceeds it becomes pseudplastic even at lower rates of shear. PMID:1069036

  3. [Dimensional stability of alginate impressions after immersion disinfection with Impresept].

    PubMed

    Biffar, R; Bitschnau, U

    1991-11-01

    With an experimental design near clinical conditions the alginates Alginoplast, Blend-a-print, Blue-print, Palgaflex and Xantalgin were examined under the influence of the disinfection with Impresept (Espe). The absolute means of the differences between models from disinfected or nondisinfected impressions reached from 0.05%lin to 0.19%lin. In comparison to the specific tolerances of the materials the influence of Impresept on the dimension stability is not important. PMID:1818441

  4. [A Polish physician's impressions from the Viennese Clinic of Winternitz].

    PubMed

    Kierzek, A

    1999-01-01

    The achievements of Vincenz Priestnitz, Sebastian Kneipp and Wilhelm Winternitz for the development of hydrotherapy are presented at the beginning. The professional and scientific activities of Winternitz are strongly pointed out. Eugeniusz Piasecki (1872-1947), the Polish physician and theorist of physical education impressions from Vieneese Clinic of Winternitz are depicted widely. The role of Winternitz in formation of modern hydrotherapy in Polish territories is presented finally. PMID:10695389

  5. Evaluation of transfer impressions for osseointegrated implants at various angulations.

    PubMed

    Assuncao, Wirley Gonçalves; Filho, Humberto Gennari; Zaniquelli, Osvaldo

    2004-12-01

    The accuracy of impressions that transfer the relationship of the implant to the metal framework of the prosthesis continues to be a problem. This study was designed to evaluate the accuracy of the transfer process under variable conditions with regard to implant analog angulations, impression materials, and techniques. Replicas (n = 60) of a metal matrix (control) containing four implants at 90 degrees , 80 degrees , 75 degrees , and 65 degrees in relation to the horizontal surface were obtained by using three impression techniques: T1-indirect technique with conical copings in closed trays; T2-direct technique with square copings in open trays; and T3-square copings splinted with autopolymerizing acrylic resin; and four elastomers: "P"-polysulfide; "I"-polyether; "A"-addition silicone; and "Z"-condensation silicone. The values of the implant analog angulations were assessed by a profilometer to the nearest 0.017 degrees , then submitted to analysis of variance for comparisons at significance of 5% (P < .05). For implant analog at 90 degrees , the material "A" associated with T2 and material "Z" with T3 behaved differently (P < .05) from all groups. At 80 degrees , all materials behaved differently (P < .01) with T1. At 75 degrees , when T1 was associated, materials "P" and "A" showed similar behavior, as well as materials "I" and "Z"; however, "P" and "A" were different from "I" and "Z" (P < .01). When T3 was associated, all experimental groups behaved differently among them (P < .01). At 65 degrees , the materials "P" and "Z" behaved differently (P < .01) from the control group with T1, T2, and T3; the materials "I" and "A" behaved differently from the control group (P < .01) when T1 and T2, respectively, were associated. The more perpendicular the implant analog angulation is in relation to the horizontal surface, the more accurate the impression. The best materials were material "I" and "A" and the most satisfactory technique was technique 3. PMID:15591998

  6. High-rate thermomechanical behavior of poly(vinyl chloride) and plasticized poly(vinyl chloride)

    NASA Astrophysics Data System (ADS)

    Mulliken, A. D.; Soong, S. Y.; Boyce, M. C.; Cohen, R. E.

    2006-08-01

    A combined experimental and analytical investigation was carried out in order to develop predictive capabilities for the rate-dependent behavior of poly(vinyl chloride) (PVC) and a dioctyl phthalate (DOP)-plasticized PVC, with focus on predicting the thermo-mechanically coupled behavior under high rates of deformation. The two materials were studied experimentally using both dynamic mechanical analysis (DMA) and compression testing over a wide range of strain rates (10 - 4 s - 1 to 2000 s - 1). DMA testing revealed both an ? -transition and a low-temperature ? -transition (-56circC) in the neat PVC; the incorporation of 20wt% DOP in PVC reduced the ? -transition temperature by 54circC, and also suppressed the ? -transition peak. In compression testing, rate-sensitivity transitions were observed in both the neat PVC and the PVC-20wt% DOP compound. The transition in PVC is attributed to the shift of the ? -transition, whereas the transition in the 20wt% DOP blend is due to the rubbery-to-glassy transition as the deformation rate goes from low to high. A constitutive model for the finite strain deformation of amorphous polymers, introduced elsewhere [1,2] and tailored here for the two material systems of interest, is shown to capture the large deformation stress-strain behavior at all rates tested.

  7. Effect of Time on Gypsum-Impression Material Compatibility

    NASA Astrophysics Data System (ADS)

    Won, John Boram

    The purpose of this study was to evaluate the compatibility of dental gypsum with three recently introduced irreversible hydrocolloid (alginate) alternatives. The test materials were Alginot® (Kerr™), Position Penta Quick® (3M ESPE™) and Silgimix ® (Sultan Dental™). The irreversible hydrocolloid impression material, Jeltrate Plus antimicrobial® (Dentsply Caulk™) served as the control. Materials and Methods: Testing of materials was conducted in accordance with ANSI/ADA Specification No. 18 for Alginate Impression Materials. Statistical Analysis: The 3-Way ANOVA test was used to analyze measurements between different time points at a significance level of (p < 0.05). Outcome: It was found that there was greater compatibility between gypsum and the alternative materials over time than the traditional irreversible hydrocolloid material that was tested. A statistically significant amount of surface change/incompatibility was found over time with the combination of the dental gypsum products and the control impression material (Jeltrate Plus antimicrobial®).

  8. Duplication of interim speech aid for definitive impression tray fabrication.

    PubMed

    Jacob, R F

    1992-09-01

    A wax tray is stable and easily relieved if overextended. Unusual tray undercuts or angles needed for the partial resection patient need not be eliminated before the impression procedure. Relief of these undercuts is necessary with acrylic resin trays to ensure separation from the final stone cast. Because the wax tray is separated easily from the prosthesis during the boil-out, it is not necessary to "burn" or grind acrylic resin from the framework. The tray shape is duplicated from the existing interim prosthesis on the nasopharyngeal and oropharyngeal side. An arbitrarily shaped acrylic resin tray may be grossly overextended and require time-consuming clinical adjustments. An underextended tray on the nasopharyngeal side will not carry or support the impression material around or through the residual soft palate remnant. A tray that closely approximates the final prosthesis will allow use of a tissue conditioner final impression without need for border molding (Fig. 2). Duplicating the oropharyngeal side of the interim speech aid duplicates the previously established plane that is compatible with the tongue. The author has used this technique successfully for eight total and five partial soft palate resections. A cleft palate speech aid prosthesis has also been made with this technique. PMID:1432786

  9. Face value: amygdala response reflects the validity of first impressions.

    PubMed

    Rule, Nicholas O; Moran, Joseph M; Freeman, Jonathan B; Whitfield-Gabrieli, Susan; Gabrieli, John D E; Ambady, Nalini

    2011-01-01

    The human amygdala responds to first impressions of people as judged from their faces, such as normative judgments about the trustworthiness of strangers. It is unknown, however, whether amygdala responses to first impressions can be validated by objective criteria. Here, we examined amygdala responses to faces of Chief Executive Officers (CEOs) where real-world outcomes could be measured objectively by the amounts of profits made by each CEO's company. During fMRI scanning, participants made incidental judgments about the symmetry of each CEO's face. After scanning, participants rated each CEO's face on leadership ability. Parametric analyses showed that greater left amygdala response to the CEOs' faces was associated with higher post-scan ratings of the CEOs' leadership ability. In addition, greater left amygdala response was also associated with greater profits made by the CEOs' companies and this relationship was statistically mediated by external raters' perceptions of arousal. Thus, amygdala response reflected both subjective judgments and objective measures of leadership ability based on first impressions. PMID:20633663

  10. Emotion in the Neutral Face: A Mechanism for Impression Formation?

    PubMed Central

    Adams, Reginald B.; Nelson, Anthony J.; Soto, Jos A.; Hess, Ursula; Kleck, Robert E.

    2012-01-01

    The current work examined contributions of emotion-resembling facial cues to impression formation. There exist common facial cues that make people look male or female, emotional, and from which we derive personality inferences. We first conducted a Pilot study to assess these effects. We found that neutral female versus neutral male faces were rated as more submissive, affiliative, nave, honest, cooperative, babyish, fearful, happy, and less angry than neutral male faces. In our Primary Study, we then warped these same neutral faces over their corresponding anger and fear displays so the resultant facial appearance cues now structurally resembled emotion while retaining a neutral visage (e.g., no wrinkles, furrows, creases etc.). The gender effects found in the Pilot Study were replicated in the Primary Study, suggesting clear stereotype driven impressions. Critically, ratings of the neutral-over-fear warps versus neutral-over-anger warps also revealed a profile similar to the gender-based ratings, revealing perceptually driven impressions directly attributable to emotion overgeneralization. PMID:22471850

  11. Effects of disinfection of combined agar/alginate impressions on the dimensional accuracy of stone casts.

    PubMed

    Hiraguchi, Hisako; Nakagawa, Hisami; Kaketani, Masahiro; Hirose, Hideharu; Nishiyama, Minoru

    2007-05-01

    This study investigated the effects of disinfection of combined agar/alginate impressions on the dimensional accuracy of resultant stone casts. Impressions of a master cast designed to simulate an abutment tooth were prepared by combining each of two brands of cartridge-form agar impression materials with an alginate impression material. The impressions were immersed in 1% sodium hypochlorite for 10 minutes or 2% glutaraldehyde for 30 minutes. The remaining impressions were sprayed with these two disinfectants and then stored in sealed bags for 10, 30, 60, and 120 minutes. Stone casts obtained from the non-disinfected impressions were also prepared as control. Changes in diameter of the stone casts were then measured. Results indicated that storage for 10 minutes after spraying with 1% sodium hypochlorite was an appropriate disinfection method for combined agar/alginate impressions, as well as immersion in 1% sodium hypochlorite for 10 minutes. PMID:17694758

  12. The Role of Profanity and Sex Variables in Interpersonal Impression Formation

    ERIC Educational Resources Information Center

    Cohen, Marshall M.; Saine, Thomas J.

    1977-01-01

    Discusses a study designed to identify areas of research which may increase under standing of the relationship between speaker profanity and impression formation. Provides an experimental test of the predicted interrelationships between profanity, sex variables, and impression formation. (MH)

  13. Characterization and impression creep testing of silicon aluminum oxynitride ceramics

    NASA Astrophysics Data System (ADS)

    Fox, Kevin M.

    2005-11-01

    Three Yb-containing SiAlON materials were studied for potential use as hot section components in advanced microturbine engines. Two of the materials consisted of equiaxed alpha-SiAlON grains, elongated beta-SiAlON grains, and an amorphous intergranular phase containing a relatively large amount of Yb. The third material consisted of alpha- and beta-SiAlON grains with equiaxed morphologies and virtually no intergranular phase. An instrument was designed and constructed for impression creep testing of the YbSiAlON materials. Uniaxial compression creep experiments were also performed for comparison. In compression creep, the SiAlON materials exhibited activation energies that were similar to those of other SiAlONs reports in the literature, and stress exponents that were approximately 1. In impression creep, the SiAlONs tested exhibited activation energies similar to those reported in the literature for SiAlONs tested in uniaxial compression and tension. However, the SiAlON composition with equiaxed beta-SiAlON grains showed an exaggerated activation energy due to a change in creep mechanism above 1340C. The measured stress exponents in impression creep were approximately 2. The stress state present below the punch in impression creep caused dilation to occur in the grain structure. The dilation results in an increase in the volume of the multi-grain junctions, and an increased dependence of strain rate on stress. The enlarged multi-grain junctions can become filled with the intergranular glassy phase. These large pockets of the glassy phase can enable an additional creep mechanism whereby the equiaxed grains slide past each other viscously. All of the SiAlONs developed an additional volume of the intergranular glassy phase during creep testing. A microstructure containing elongated beta-SiAlON grains is most effective in enhancing creep performance of the Yb-SiAlON materials tested. The impression creep data for the Yb-SiAlON materials can be related to the compression creep data by using a stress correction factor of 1.6 and an effective gauge length of 1.2 times the punch diameter when the creep testing conditions are the same.

  14. Computer-Mediated Impression Formation: A Test of the Sticky Cues Model Using Facebook

    ERIC Educational Resources Information Center

    Van Der Heide, Brandon Lee

    2009-01-01

    This research offers a model of online impression formation that explains how different impression-bearing cues may carry more or less informational value. This research considers the possibility that impression-bearing cues have greater informational value when those cues are distinctive and are task-relevant. This research refers to such cues as

  15. Exploring the Ways that Adolescents Form and Perpetuate Impressions of Their Teachers

    ERIC Educational Resources Information Center

    Kucinski, Steven Jon

    2010-01-01

    This study used qualitative methodology including observations and interviews to attempt to discover how secondary students form impressions of their teachers and how those impressions are perpetuated among students, leading to teacher reputation. The findings from the study indicate that students form impressions of their teachers by assessing

  16. Simplifying and improving soft-tissue management for fixed-prosthodontic impressions.

    PubMed

    Christensen, Gordon J

    2013-10-01

    It is apparent that conventional impressions, usually made in vinyl polysiloxane or polyether material, could be better. One of the significant reasons for impressions' inadequacy is incomplete inclusion of the tooth preparation margins in the impression. There are numerous reasons for this challenge, some of which could be overcome by implementing the technique changes I have described in this column. PMID:24354169

  17. Study of the interocclusal distortion in impressions taken with different types of closed-mouth trays and two types of impression materials.

    PubMed

    Mañes-Ferrer, José-Félix; Selva-Otaolaurruchi, Eduardo-José; Parra-Arenós, Carmina; Selfa-Bas, Isabel

    2010-01-01

    The aim of this study was to compare different types of impression trays for the closed-mouth impression technique, using two different types of impression material. For this study, five different types of impression trays were used with two different types of impression materials, one of addition silicone and the other of polyether. We designed a model used for taking the impressions and for measuring interocclusal distortion. The results obtained show that the impression trays COE (GC (R) GC America INC. Alsip) and Premier (Premier (R), Premier Dental Products Co. Canada) show a lesser degree of interocclusal distortion when taking closed-mouth impressions. In terms of impression materials, the polyether was the one that produced the best results. From a clinical point of view, our study shows that the use of these types of trays is absolutely recommendable when used according to the clinical indications for which they have been designed; that said, we must not fail to consider that selecting the proper type of tray is also important. PMID:19680183

  18. Optical and mechanical behaviors of glassy silicone networks derived from linear siloxane precursors

    NASA Astrophysics Data System (ADS)

    Jang, Heejun; Seo, Wooram; Kim, Hyungsun; Lee, Yoonjoo; Kim, Younghee

    2016-01-01

    Silicon-based inorganic polymers are promising materials as matrix materials for glass fiber composites because of their good process ability, transparency, and thermal property. In this study, for utilization as a matrix precursor for a glass-fiber-reinforced composite, glassy silicone networks were prepared via hydrosilylation of linear/pendant Si-H polysiloxanes and the C=C bonds of viny-lterminated linear/cyclic polysiloxanes. 13C nuclear magnetic resonance spectroscopy was used to determine the structure of the cross-linked states, and a thermal analysis was performed. To assess the mechanical properties of the glassy silicone networks, we performed nanoindentation and 4-point bending tests. Cross-linked networks derived from siloxane polymers are thermally and optically more stable at high temperatures. Different cross-linking agents led to final networks with different properties due to differences in the molecular weights and structures. After stepped postcuring, the Young's modulus and the hardness of the glassy silicone networks increased; however, the brittleness also increased. The characteristics of the cross-linking agent played an important role in the functional glassy silicone networks.

  19. Novel gelatin siloxane nanoparticles decorated by Tat peptide as vectors for gene therapy

    NASA Astrophysics Data System (ADS)

    Wang, Zu-yong; Zhao, Yang; Ren, Lei; Jin, Li-hua; Sun, Li-ping; Yin, Pei; Zhang, Ya-fei; Zhang, Qi-Qing

    2008-11-01

    In principle, the technique of gene delivery involves taking complete or parts of genes that can code specific messages and delivering them to selected cells in the body. Such a transfer of plasmid DNA into mammalian cells has posed major challenges for gene therapy. A series of gelatin-siloxane nanoparticles (GS NPs) with controlled size and surface charge were synthesized through a two-step sol-gel process. In order to increase the efficiency of cellular uptake, HIV-derived Tat peptide was further grafted to GS NPs. In vitro co-location and endocytosis inhibition experiments suggested that the as-synthesized TG NPs may enter HeLa cells via a combined pathway of lipid-raft- and receptor-dependent endocytosis, and only cause little cell damage. Moreover, this study shows the encapsulation of a plasmid DNA in TG NPs to be obtained as a non-viral gene vector. This kind of encapsulation provides complete protection to the plasmid DNA from the external DNase and serum environment, and generates the hope that the resulting formulation can be developed into a potential vector for effective gene delivery. In order to check this potential, the reporter gene pSVβ-gal was encapsulated, and in vitro transfection efficiency of this system was found to be nearly 130% compared to the commercially available transfection reagent Lipofectamine™.

  20. Some possibilities to reduce the biofilm formation on transparent siloxane coatings.

    PubMed

    Akuzov, D; Brmmer, F; Vladkova, T

    2013-04-01

    Presence of biofilms is a significant problem to a variety of industrial areas, underwater sensors, shipping, etc. Therefore solutions are sought to inhibit biofilm formation and to permit biofilm removal. Surface modification by suitable coating could be one of them. The present study reports the potential of new transparent biocides-free siloxane antifouling coatings, containing low toxic additives, such as TiO(2) nanoparticles, surfactants and antioxidants, to reduce biofilm formation in mimicking marine environment, laboratory conditions. As evaluated with several parameters: chlorophyll content, carotenoids content, total protein and total dry mass, the biofilm formation was most sharply reduced by the composition coatings containing non-ionic surfactant, super spreader Y17112, followed by those containing antioxidant, ?-tocopherol. Depending on the amount of the super spreader (0.1-1.0 wt.%) and the tested parameter, approximately 3-8-fold reduction was observed in the biofilm formation. It is supposed, that the effect of the studied additives, both surfactant and antioxidant, is due to some inhibition of the adhesive extra cellular substances cross-linking with impact onto the biofilm cohesion strength and its adhesion. PMID:23333915

  1. Poly (dimethyl siloxane) micro/nanostructure replication using proton beam written masters

    NASA Astrophysics Data System (ADS)

    Shao, P. G.; van Kan, J. A.; Ansari, K.; Bettiol, A. A.; Watt, F.

    2007-07-01

    Proton beam writing (PBW) has been proven to be a powerful tool for fabricating micro and nanostructures with high aspect ratio. However, being a direct-write technique, and therefore, a serial process, PBW is not economic for low cost multiple component production. Techniques for replicating PBW structures with low cost are necessary for applications in for example nanofluidics, tissue engineering and optical devices. We have investigated casting poly (dimethyl siloxane) (PDMS Sylgard 184, Dow Corning Corp.) with PBW structures as masters. First, a 2 MeV focused H2+ beam was written into a 2 ?m thick PMMA layer spin coated onto 50 ?m thick Kapton film substrate. Next, these PMMA structures, with details down to 700 nm, were replicated with PDMS. Without any release coating treatment, PDMS circular pillars, 700 nm in diameter were successfully replicated. We also fabricated a nickel master with nanofeature dimensions and 2 ?m depth using proton beam writing and sulfamate electroplating. The nickel master was used to successfully replicate a prototype DNA separation chip using PDMS.

  2. The effectiveness of silane and siloxane treatments on the superhydrophobicity and icephobicity of concrete surfaces

    NASA Astrophysics Data System (ADS)

    Rao, Sunil M.

    Icy roads lead to treacherous driving conditions in regions of the U.S., leading to over 450 fatalities per year. De-icing chemicals, such as road salt, leave much to be desired. In this report, commercially available silane, siloxane, and related materials were evaluated as solutions, simple emulsions, and complex emulsions with incorporated particulates, for their effectiveness as superhydrophobic treatments. Through the development and use of a basic impact test, the ease of ice removal (icephobicity) was examined as an application of the targeted superhydrophobicity. A general correlation was found between icephobicity and hydrophobicity, with the amount of ice removed on impact increasing with increasing contact angle. However, the correlation was poor in the high performance region (high contact angle and high ice removal.) Polymethylhydrogensiloxane was a top performer and was more effective when used as a "shell" type emulsion with silica fume particulates. An aqueous sodium methyl siliconate solution showed good performance for ice loss and contact angle, as did a commercial proprietary emulsion using a diethoxyoctylsilyl trimethylsilyl ester of silicic acid. These materials have sterically available functional groups that can react or associate with the concrete surface and are potentially film-forming. Materials with less reactive functional groups and a lower propensity to film-form did not perform as well.

  3. Controllable photophysical properties and self-assembly of siloxane-poly(amidoamine) dendrimers.

    PubMed

    Lu, Hang; Zhang, Jie; Feng, Shengyu

    2015-10-28

    Poly(amidoamine) dendrimers are typical luminescent polymers containing unconventional chromophores. A series of novel siloxane-poly(amidoamine) (Si-PAMAM) dendrimers were synthesized and investigated in this study. Their structures and properties were determined by NMR, XPS, LC/MS, and fluorescence spectroscopy. The introduction of Si-O-Si units in Si-PAMAM changed the photophysical properties of the dendrimers. The luminescence of Si-PAMAM was associated with the aggregation of its carbonyl groups, which was caused by N ? Si coordination bonds. The strong blue luminescence of Si-PAMAM was also studied in detail, and it was found to be quite different from the ethanediamine-based poly(amidoamine). Results indicated that the luminescence of Si-PAMAM could be controlled by solvents, acids, metal ions, temperature, or degree of aggregation of the carbonyl groups. Moreover, micron-sized tubes composed of Si-PAMAM molecules were generated and found in water/methanol solution. PMID:26395084

  4. Volatile siloxanes in the European arctic: assessment of sources and spatial distribution.

    PubMed

    Warner, Nicholas A; Evenset, Anita; Christensen, Guttorm; Gabrielsen, Geir W; Borgå, Katrine; Leknes, Henriette

    2010-10-01

    The purpose of this study was to investigate presence and potential accumulation of cyclic volatile methyl siloxanes (cVMS) in the Arctic environment. Octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were analyzed in sediment, zooplankton, Atlantic cod (Gadus morhua), shorthorn sculpin (Myxocephalus scorpius), and bearded seal (Erignathus barbatus) collected from the Svalbard archipelago within the European Arctic in July 2009. Highest levels were found for D5 in fish collected from Adventfjorden, with average concentrations of 176 and 531 ng/g lipid in Atlantic cod and shorthorn sculpin, respectively. Decreasing concentration of D5 in sediment collected away from waste water outlet in Adventfjorden indicates that the local settlement of Longyearbyen is a point source to the local aquatic environment. Median biota sediment accumulation factors (BSAFs) calculated for D5 in Adventfjorden were 2.1 and 1.5 for Atlantic cod and shorthorn sculpin, respectively. Biota concentrations of D5 were lower or below detection limits in remote and sparsely populated regions (Kongsfjorden and Liefdefjorden) compared to Adventfjorden. The levels of cVMS were found to be low or below detection limits in bearded seal blubber and indicate a low risk for cVMS accumulation within mammals. Accumulation of cVMS in fish appears to be influenced by local exposure from human settlements within the Arctic. PMID:20836489

  5. Synthesis of a novel multi N-halamines siloxane precursor and its antimicrobial activity on cotton

    NASA Astrophysics Data System (ADS)

    Wu, Lin; Xu, Yan; Cai, Lu; Zang, Xiong; Li, Zhanxiong

    2014-09-01

    A novel N-halamine siloxane antibacterial precursor N-(3-triethoxysilylpropyl)-N‧- (N″‧-heptylcarbamido-N″-ethyl)-butanediamide (TSHCEB) was synthesized and characterized in this study. The compound was then tethered to the surface of cotton fabrics through covalent ether linkages, followed by exposure to dilute sodium hypochlorite solutions to confer the cotton fabrics antibacterial property. The chemical structure of the monomer was confirmed by FTIR, 1H NMR and MS, and the surface of the treated cotton fabrics was characterized by FTIR, TGA, SEM, and XPS analysis. The antimicrobial cotton materials were then challenged with Gram-negative Escherichia coli O157:H7 (ATCC 43895) and Gram-positive Staphylococcus aureus (ATCC 6538). Results showed that it provided excellent antimicrobial properties against E. coli O157:H7 and S. aureus via direct contacting for 2-15 min. The controlled release of diverse chlorines was proved by inhibition zone. The chlorine bonded to the coating was stable under standard washing test and routine storage, stability toward UVA irradiation was also investigated, and the lost chlorine could be regenerated by rechlorination. The new N-halamine antibacterial precursor can provide superior antibacterial property within a short contact time.

  6. Electric-field alignment of chitin nanorod-siloxane oligomer reactive suspensions.

    PubMed

    Boltoeva, Maria Yu; Dozov, Ivan; Davidson, Patrick; Antonova, Krassa; Cardoso, Laura; Alonso, Bruno; Belamie, Emmanuel

    2013-07-01

    Uniaxially anisotropic chitin-silica nanocomposite solids have been obtained thanks to the electric field-induced macroscopic alignment of liquid-crystalline reactive cosuspensions. We demonstrate how chitin nanorods (260 nm long, 23 nm thick) can be aligned upon the application of an alternating current (ac) electric field, and within water-ethanol suspensions containing reactive siloxane oligomers (D(h) ∼ 3 nm). The alignment at the millimeter length scale is monitored by in situ small-angle X-ray scattering (SAXS) and polarized light optical microscopy. The composition and state (isotropic, chiral nematic) of the cosuspensions are proven to be determining factors. For nematic phases, the alignment is preserved when the electric field is switched off. Further solvent evaporation induces sol-gel transition, and uniaxially anisotropic chitin-silica nanocomposites are formed after complete drying of the aligned nematic suspensions. Here, the collective response of colloidal mesophases to external electric fields and the subsequent formation of ordered nanocomposite solids would represent a new opportunity for materials design. PMID:23777221

  7. Occurrence and seasonality of cyclic volatile methyl siloxanes in Arctic air.

    PubMed

    Krogseth, Ingjerd S; Kierkegaard, Amelie; McLachlan, Michael S; Breivik, Knut; Hansen, Kaj M; Schlabach, Martin

    2013-01-01

    Cyclic volatile methyl siloxanes (cVMS) are present in technical applications and personal care products. They are predicted to undergo long-range atmospheric transport, but measurements of cVMS in remote areas remain scarce. An active air sampling method for decamethylcyclopentasiloxane (D5) was further evaluated to include hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and dodecamethylcyclohexasiloxane (D6). Air samples were collected at the Zeppelin observatory in the remote Arctic (79 N, 12 E) with an average sampling time of 81 23 h in late summer (August-October) and 25 10 h in early winter (November-December) 2011. The average concentrations of D5 and D6 in late summer were 0.73 0.31 and 0.23 0.17 ng/m(3), respectively, and 2.94 0.46 and 0.45 0.18 ng/m(3) in early winter, respectively. Detection of D5 and D6 in the Arctic atmosphere confirms their long-range atmospheric transport. The D5 measurements agreed well with predictions from a Eulerian atmospheric chemistry-transport model, and seasonal variability was explained by the seasonality in the OH radical concentrations. These results extend our understanding of the atmospheric fate of D5 to high latitudes, but question the levels of D3 and D4 that have previously been measured at Zeppelin with passive air samplers. PMID:23194257

  8. Structural characterization of sol-gel derived siloxane-oxide materials

    SciTech Connect

    Babonneau, F.; Dire, S.

    1993-12-31

    Sol-gel processing of hybrid siloxane-oxide materials is currently widely investigated due to a large amount of potential applications for these systems. They are usually based on silicon alkoxides and derivatives. Various new materials have been prepared combining a modified silicon alkoxide, diethoxydimethylsilane (DEDMS) and a transition metal alkoxide, M(OR){sub n} with M=Ti and Zr. Transparent monolithic pieces or thick films can be obtained over a wide range of compositions. The hydrolysis process of various preparations was followed by {sup 29}Si liquid NMR, and indicates the formation of Si-O-M bonds. The structure of the final gels was essentially characterized by solid state NMR ({sup 1}H, {sup 13}C and {sup 29}Si) and X-ray absorption spectroscopies (Ti K-edge), and leads to propose structural models for these gels. This study points out that titanium and zirconium alkoxides does not only act as cross linking agents, such as silicon alkoxides, but behave as catalysts for the formation of polydimethylsiloxane chains within the materials.

  9. Nonfunctionalized Polydimethyl Siloxane Superhydrophobic Surfaces Based on Hydrophobic-Hydrophilic Interactions

    SciTech Connect

    Polizos, Georgios; Tuncer, Enis; Qiu, Xiaofeng; Aytug, Tolga; Kidder, Michelle; Messman, Jamie M; Sauers, Isidor

    2011-01-01

    Superhydrophobic surfaces based on polydimethyl siloxane (PDMS) were fabricated using a 50:50 PDM-poly(ethylene glycol) (PEG) blend. PDMS was mixed with PEG, and incomplete phase separation yielded a hierarchic structure. The phase-separated mixture was annealed at a temperature close to the crystallization temperature of the PEG. The PEG crystals were formed isothermally at the PDMS/PEG interface, leading to an engineered surface with PDMS spherulites. The resulting roughness of the surface was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The PDMS spherulites, a few micrometers in diameter observed from SEM images, were found to have an undulated (rippled) surface with nanometer-sized features. The combination of micrometer- and nanometer-sized surface features created a fractal surface and increased the water contact angle (WCA) of PDMS more than 60, resulting in a superhydrophobic PDMS surface with WCA of >160 degrees. The active surface layer for the superhydrophobicity was approximately 100 mu m thick, illustrating that the material had bulk superhydrophobicity compared to conventional fluorocarbon or fluorinated coated rough surfaces. Theoretical analysis of the fractal surface indicates that the constructed surface has a fractal dimension of 2.5, which corresponds to the Apollonian sphere packing.

  10. Cross-linked polyvinyl alcohol and method of making same

    NASA Technical Reports Server (NTRS)

    Hsu, L. C.; Sheibley, D. W.; Philipp, W. H. (Inventor)

    1981-01-01

    A film-forming polyvinyl alcohol polymer is mixed with a polyaldehyde-polysaccharide cross-linking agent having at least two monosaccharide units and a plurality of aldehyde groups per molecule, perferably an average of at least one aldehyde group per monosaccharide units. The cross-linking agent, such as a polydialdehyde starch, is used in an amount of about 2.5 to 20% of the theoretical amount required to cross-link all of the available hydroxyl groups of the polyvinyl alcohol polymer. Reaction between the polymer and cross-linking agent is effected in aqueous acidic solution to produce the cross-linked polymer. The polymer product has low electrical resistivity and other properties rendering it suitable for making separators for alkaline batteries.

  11. Nanocomposites of ZnS and poly-(dimethyl)-block-(phenyl)siloxane as a new high-refractive-index polymer media

    PubMed Central

    2012-01-01

    In the present paper, we describe a new and original method to obtain transparent, siloxane-based composites, with high refractive index (up to 1.68). The method is based on the decomposition of Zn-siloxane, mixed with a poly-(dimethyl)-block-(phenyl)siloxane matrix in different ratios. It was found that after treatment of such mixed metal-containing polymer blend with H2S, the nanoparticles of ZnS are formed, with the size in a 1- to 5-nm range, which allow effective increase of the refractive index of the nanocomposite mixture with poly-(dimethyl)-block-(phenyl)siloxane without loss of film transparency. We succeded to increase the refractive index from 1.54 (pure matrix) up to 1.68 (composite with a ZnS content of 4.6 vol.%). The siloxane-based compositions are optically transparent, which makes it possible to use them as light-emitting diodes or solar cell sealants or adhesives. PMID:22401650

  12. Hybrid material polyvinyl alcohol-stannic acid/stannic oxide

    NASA Astrophysics Data System (ADS)

    Prosanov, I. Yu.; Chesalov, Yu. A.; Gerasimov, K. B.; Bulina, N. V.

    2013-07-01

    Hybrid materials polyvinyl alcohol (PVA)-stannic acid and PVA-SnO2 were produced in the form of transparent films. Their investigations by means of optical spectroscopy, X-ray analysis, thermo-gravimetry, and mass-spectrometry were carried out as well as electrical measurements. The model is discussed where the polymeric chains of inorganic constituent are linked by coordinative bonds with carbon polymeric chains. Photoconductivity of PVA-SnO2 was discovered.

  13. A technique for using short term soft liners as complete dentures final impression material

    PubMed Central

    Baslas, Varun; Singh, Saumyendra V.; Aggarwal, Himanshi; Kaur, Simranjeet; Singh, Kamleshwar; Agarwal, Kaushal K.

    2014-01-01

    Tissue conditioners can be used to condition abused tissues, record functional impressions, make temporary relining for surgical splints and obturators, and for other clinical applications, mainly because of their specific viscoelasticity. Their function in complete denture fabrication is debatable but their use as a functional impression material has been proved. The present article describes a technique for using tissue conditioners as functional impression materials. Correct method of usage, manipulation, specific properties as impression materials and precautions in different situations for obtaining accurate impressions has been highlightened. PMID:25737945

  14. Wettability changes in polyether impression materials subjected to immersion disinfection

    PubMed Central

    Shetty, Shweta; Kamat, Giridhar; Shetty, Rajesh

    2013-01-01

    Background: Disinfection of impression materials prevents cross-contamination; however, the disinfectants may alter the wettability property. The purpose of this investigation was to evaluate the wettability changes of polyether impression material after immersing in four different chemical disinfectant solutions for a period of 10 min and 30 min, respectively. Materials and Methods: A total of 45 samples of polyether dental impression material (Impregum soft, 3MESPE, St. Paul, MN, USA) were randomly divided into nine groups with five specimens each. Each specimen was disc shaped, flat of 32 mm diameter and 3 mm thickness. The samples were immersed in four disinfectant solutions: 2% Glutaraldehyde, 5% sodium hypochlorite, 0.05% iodophor, and 5.25% phenol for 10 min and 30 min, respectively. The control was without disinfection. Wettability of the samples was assessed by measuring the contact angle by using the Telescopic Goniometer. Data were subjected to analysis of variance (Fisher's test) and Tukey's post hoc test for multiple comparisons at 5% level of significance. Results: The contact angle of 20.21 0.22 were recorded in the control samples. After 10 min, the samples that were immersed in 5% sodium hypochlorite and 5.25% phenol showed significant statistical increase in the contact angle as compared to the control (P < 0.001). After 30 min of disinfection, only the samples immersed in 0.05% iodophor showed there were no significant changes in the contact angle, whereas the other disinfectants significantly increased the contact angle and decreased the wettability of the polyether material. Conclusion: Within the limitations of the study, 2% glutaraldehyde proved safe for 10 min of immersion disinfection while 0.05% iodophor holds promise as an effective disinfectant without affecting the wettability of the material. PMID:24130593

  15. Dimensional stability of elastomeric impression materials in custom-made and stock trays.

    PubMed

    Valderhaug, J; Flystrand, F

    1984-10-01

    Elastomeric impression materials for fixed prosthodontics are considered most stable when they have an even thickness of 2 to 4 mm. To obtain this, a custom-made impression tray is recommended. The purpose of the present study was to compare the stability of impressions made in custom trays and trays made of chromium-plated brass. The impression materials chosen were polyether and silicone. Two master models of the upper jaw were made of metal. The canines and first molars represented abutment teeth with flat occlusal surfaces. An engraved cross on each surface made it possible to measure in a microscope the distances between the abutment teeth on the models and in the impressions. The accuracy of the method was within +/- 8 micron. Twelve standardized impressions were made with each impression material in the two types of trays. The distances between the abutment teeth were measured immediately on removal of the impression, and after 1 and 24 hours. Although ample amount of impression material (2 to 9 mm) was allowed, the linear dimensional stability of the impressions made in stock trays was not inferior to the stability of impressions made in custom-made trays. PMID:6389833

  16. Impression Procedures for Metal Frame Removable Partial Dentures as Applied by General Dental Practitioners.

    PubMed

    Fokkinga, Wietske A; van Uchelen, Judith; Witter, Dick J; Mulder, Jan; Creugers, Nico H

    2016-01-01

    This pilot study analyzed impression procedures for conventional metal frame removable partial dentures (RPDs). Heads of RPD departments of three dental laboratories were asked to record features of all incoming impressions for RPDs during a 2-month period. Records included: (1) impression procedure, tray type (stock/custom), impression material (elastomer/alginate), use of border-molding material (yes/no); and (2) RPD type requested (distal-extension/tooth-bounded/combination). Of the 132 total RPD impressions, 111 (84%) involved custom trays, of which 73 (55%) were combined with an elastomer. Impression border-molding material was used in 4% of the cases. Associations between impression procedure and RPD type or dentists' year/university of graduation were not found. PMID:26929957

  17. A comparison of dimensional accuracy between three different addition cured silicone impression materials.

    PubMed

    Forrester-Baker, L; Seymour, K G; Samarawickrama, D; Zou, L; Cherukara, G; Patel, M

    2005-06-01

    Ten impressions of a metal implant abutment were made with each of three addition-cured silicone impression materials. Using the technique of co-ordinate metrology, the shoulder region of the abutment and corresponding regions of both impressions and dies made from these impressions were scanned and measured. Comparison of these measurements indicated that the mean dimension measured from the shoulder region for each group of impression materials was significantly different from those taken from the original metal implant abutment. However, when these impressions were cast in a gypsum based die material, none of the measured dimensions taken from the casts were significantly different from those taken from the original metal implant abutment. Thus, any change in measured dimensions occurring during impression making, was compensated for in some way by the casting process. PMID:16011234

  18. Preliminary impressions in microstomia patients: an innovative technique.

    PubMed

    Aswini Kumar, K; Bhat, Vinaya; Nandini, V Vidyashree; Chandrasekharan Nair, K

    2013-03-01

    Microstomia has been defined as an abnormally small oral orifice associated with various etiopathologic factors. Management of these patients poses extreme difficulties in every procedure during prosthesis fabrication. Restricted mouth opening of the patient makes the insertion and the removal of the tray extremely difficult. So sectioning of the existing stock tray is necessary, so that the trays can be inserted and removed in sections. The main problem encountered during this procedure is the reorientation of the tray back in position. This article presents an innovative technique for the easy handling of the sectioned stock impression trays. PMID:24431708

  19. DIELECTRIC PROPERTIES OF POLYVINYL ALCOHOL, POLY(METHYL METHACRYLATE), POLYVINYL BUTYRAL RESIN AND POLYIMIDE AT LOW TEMPERATURES

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R

    2008-01-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI--Kapton\\textregistered). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45K to 350K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and \\pmma\\ dissolved in toluene have the lowest dielectric losses for temperatures lower than $100\\ \\kelvin$. \\Blx\\ and PI have the smallest spread in their breakdown strength data.

  20. Accuracy of five implant impression technique: effect of splinting materials and methods

    PubMed Central

    Cho, Sung-Bum

    2011-01-01

    PURPOSE The aim of this study was to evaluate the effect of dimensional stability of splinting material on the accuracy of master casts. MATERIALS AND METHODS A stainless steel metal model with 6 implants embedded was used as a master model. Implant level impressions were made after square impression copings were splinted using 5 different techniques as follows. (1) Splinted with autopolymerizing resin and sectioned, reconnected to compensate polymerization shrinkage before the impression procedure. (2) Splinted with autopolymerizing resin just before impression procedure. (3) Primary impression made with impression plaster and secondary impression were made over with polyether impression material. (4) Splinted with impression plaster. (5) Splinted with VPS bite registration material. From master model, 5 impressions and 5 experimental casts, total 25 casts were made for each of 5 splinting methods. The distortion values of each splinting methods were measured using coordinate measuring machine, capable of recordings in the x-, y-, z-axes. A one-way analysis of variance (ANOVA) at a confidence level of 95% was used to evaluate the data and Tukey's studentized range test was used to determine significant differences between the groups. RESULTS Group 1 showed best accuracy followed by Group 3 & 4. Group 2 and 5 showed relatively larger distortion value than other groups. No significant difference was found between group 3, 4, 5 in x-axis, group 2, 3, 4 in y-axis and group 1, 3, 4, 5 in z-axis (P<.0001). CONCLUSION Both Splinting impression copings with autopolymerizing resin following compensation of polymerization shrinkage and splinting method with impression plaster can enhance the accuracy of master cast and impression plaster can be used simple and effective splinting material for implant impression procedure. PMID:22259700

  1. Use of Clinical UV Chamber to Disinfect Dental Impressions: A Comparative Study

    PubMed Central

    Sharma, Sakshi; Kumar, Varun; Gupta, Neelu

    2015-01-01

    Introduction Dental impressions are potential source of infection in a prosthodontic practice. Risk of transmission of infection through saliva, blood etc is considered as hazard for both dentist as well as dental auxiliary staff. A number of methods are currently employed for disinfecting the impressions which are technique sensitive and time consuming. This study focuses on disinfecting impression using dental UV chamber which is commonly employed for storing sterilized instruments. Aim The aim of this invitro study was to evaluate the use of clinical UV chamber to disinfect various impression materials at different time intervals and its comparison with 2% glutaraldehyde using standard immersion technique. Materials and Methods Total sample size of 180 specimens was taken from three different impression materials. The impressions were made from 30 dentulous subjects. A total of ten impressions were made for each impression material i.e. alginate, addition silicone and polyether impression material. Six punch samples were taken from each impression. Out of 6 punch sample, one was kept as control, second was disinfected by immersing in freshly prepared 2% glutaraldehyde solution for 10 minutes and remaining four were exposed to UV rays for 3 minutes, 6 minutes, 10 minutes and 15 minutes using dental UV chamber. Amount of disinfection achieved was evaluated by counting the colonies over the culture plates with the help of digital colony. Results The results showed that the mean CFUs for alginate were found to be i.e. 11797.40 ± 5989.73 (mean ± SD). The mean CFUs for addition silicone impression material was found 7095.40 with a standard deviation of 4268.83 and the mean CFUs for polyether impression material was found to be 2168.92 ± 1676 (mean ± SD). Conclusion For alginate and addition silicone impression material, disinfection was achieved on exposure to UV rays for a period of 10 minutes. However, for polyether impression material 3 minutes of exposure to UV rays was sufficient to cause complete disinfection. PMID:26436051

  2. Formation of Linear Polyenes in Thermal Dehydration of Polyvinyl Alcohol, Catalyzed by Phosphotungstic Acid

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.

    2015-01-01

    In order to obtain linear polyenes in polyvinyl alcohol films via acid-catalyzed thermal dehydration of the polyvinyl alcohol, we used phosphotungstic acid as the catalyst: a safe and heat-stable solid chemical compound. We established that phosphotungstic acid, introduced as solid nanoparticles into polyvinyl alcohol films, is a more effective dehydration catalyst than hydrochloric acid, since in contrast to HCl it does not evaporate from the film during heat treatment.

  3. Lateral Orbitofrontal Cortex Involvement in Initial Negative Aesthetic Impression Formation

    PubMed Central

    Munar, Enric; Nadal, Marcos; Rossell, Jaume; Flexas, Albert; Moratti, Stephan; Maest, Fernando; Marty, Gisle; Cela-Conde, Camilo J.

    2012-01-01

    It is well established that aesthetic appreciation is related with activity in several different brain regions. The identification of the neural correlates of beauty or liking ratings has been the focus of most prior studies. Not much attention has been directed towards the fact that humans are surrounded by objects that lead them to experience aesthetic indifference or leave them with a negative aesthetic impression. Here we explore the neural substrate of such experiences. Given the neuroimaging techniques that have been used, little is known about the temporal features of such brain activity. By means of magnetoencephalography we registered the moment at which brain activity differed while participants viewed images they considered to be beautiful or not. Results show that the first differential activity appears between 300 and 400 ms after stimulus onset. During this period activity in right lateral orbitofrontal cortex (lOFC) was greater while participants rated visual stimuli as not beautiful than when they rated them as beautiful. We argue that this activity is associated with an initial negative aesthetic impression formation, driven by the relative hedonic value of stimuli regarded as not beautiful. Additionally, our results contribute to the understanding of the nature of the functional roles of the lOFC. PMID:22675517

  4. Chemical enhancement of soil based footwear impressions on fabric.

    PubMed

    Farrugia, Kevin J; Bandey, Helen; Dawson, Lorna; Daid, Niamh Nic

    2012-06-10

    This study investigates the enhancement of footwear impressions prepared with soils from different locations on a variety of fabric surfaces with different morphology. Preliminary experiments using seventeen techniques were carried out and the best responding reagents were evaluated further. Results indicated that the soils investigated (a cross-section of soils from Scotland) are more likely to respond to reagents that target iron ions rather than calcium, aluminium or phosphorus ions. Furthermore, the concentration of iron and soil pH did not appear to have an effect on the performance of the enhancement techniques. For the techniques tested, colour enhancement was observed on all light coloured substrates while enhancement on dark coloured fabrics, denim and leatherette was limited due to poor contrast with the background. Of the chemical enhancement reagents tested, 2,2'-dipyridil was a suitable replacement for the more common enhancement technique using potassium thiocyanate. The main advantages are the use of less toxic and flammable solvents and improved clarity and sharpness of the enhanced impression. The surface morphology of the fabrics did not have a significant effect on the enhancement ability of the reagents apart from a slight tendency for diffusion to occur on less porous fabrics such as polyester and nylon/lycra blends. PMID:22153620

  5. Effect of Siloxane Ring Strain and Cation Charge Density on the Formation of Coordinately Unsaturated Metal Sites on Silica: Insights from DFT Studies

    SciTech Connect

    Das, Ujjal; Zhang, Guanghui; Hu, Bo; Hock, Adam S.; Redfern, Paul C.; Miller, Jeffrey T.; Curtiss, Larry A.

    2015-12-01

    Amorphous silica (SiO2) is commonly used as a support in heterogeneous catalysis. However, due to the structural disorder and temperature induced change of surface morphology, the structures of silica supported metal catalysts are difficult to determine. Most studies are primarily focused on understanding the interactions of different types of surface hydroxyl groups with metal ions. In comparison, the effect of siloxane ring size on the structure of silica supported metal catalysts and how it affects catalytic activity is poorly understood. Here, we have used density functional theory calculations to understand the effect of siloxane ring strain on structure and activity of different monomeric Lewis acid metal sites on silica. In particular, we have found that large siloxane rings favor strong dative bonding interaction between metal ion and surface hydroxyls, leading to the formation of high-coordinate metal sites. In comparison, metal-silanol interaction is weak in small siloxane rings, resulting in low-coordinate metal sites. The physical origin of this size dependence is associated with siloxane ring strain, and, a correlation between metal-silanol interaction energy and ring strain energy has been observed. In addition to ring strain, the strength of the metal-silanol interaction also depends on the positive charge density of the cations. In fact, a correlation also exists between metal-silanol interaction energy and charge density of several first-row transition and post-transition metals. The theoretical results are compared with the EXAFS data of monomeric Zn(II) and Ga(III) ions grafted on silica. The molecular level insights of how metal ion coordination on silica depends on siloxane ring strain and cation charge density will be useful in the synthesis of new catalysts.

  6. Influence of Variations in Liquid-Crystalline Content upon the Self-Assembly Behavior of Siloxane-Based Block Copolymers

    SciTech Connect

    Verploegen,E.; Zhang, T.; Murlo, N.; Hammond, P.

    2008-01-01

    A series of well-defined smectic side chain liquid-crystalline (LC) block copolymers with a low glass transition (Tg) siloxane block has been synthesized via anionic polymerization; these systems consist of a glassy polystyrene block and a unique low glass transition temperature LC block based on poly(vinylmethylsiloxane) to which six different LCs have been synthesized and attached. The synthesis techniques used provide systematic control over covalent LC side chain content, allowing for a range of morphologies to be obtained from a single block copolymer backbone during a one-step LC attachment reaction. Variations in the LC structure and content significantly affect the morphology of the LC mesophase, allowing the smectic-to-isotropic transition temperature to be tuned from room temperature up to 150 C. There are two key driving forces in the self-assembly behavior of these materials that are significantly affected by the LC content. The first is the segmental interaction parameter (?) between the blocks, which is a function of the amount of LC attached to the siloxane block. The attachment percent of the LCs to the siloxane block determines the packing density, which affects the stability of the LC mesophase and its interactions with the inter-material dividing surface. The self-assembled morphologies are characterized as a function of LC content and the mechanisms for the observed behavior are detailed. Additional insights into the interactions between the LC and block copolymer mesophases are gained by investigating the morphologies in response to mechanical deformation. The elastic modulus of this system can be tailored over several orders of magnitude by controlling the LC content, and the thermo-mechanical behavior is also highly dependent. The ability to precisely control the degree of LC functionalization enables the custom design and tailoring of material properties for specific applications such as electro-mechanical, damping, and mechano-optical devices.

  7. Proton imaging of siloxanes to map tissue oxygenation levels (PISTOL): a tool for quantitative tissue oximetry.

    PubMed

    Kodibagkar, Vikram D; Wang, Xianghui; Pacheco-Torres, Jesús; Gulaka, Praveen; Mason, Ralph P

    2008-10-01

    Hexamethyldisiloxane (HMDSO) has been identified as a sensitive proton NMR indicator of tissue oxygenation (pO(2)) based on spectroscopic spin-lattice relaxometry. A rapid MRI approach has now been designed, implemented, and tested. The technique, proton imaging of siloxanes to map tissue oxygenation levels (PISTOL), utilizes frequency-selective excitation of the HMDSO resonance and chemical-shift selective suppression of residual water signal to effectively eliminate water and fat signals and pulse-burst saturation recovery (1)H echo planar imaging to map T(1) of HMDSO and hence pO(2). PISTOL was used here to obtain maps of pO(2) in rat thigh muscle and Dunning prostate R3327 MAT-Lu tumor-implanted rats. Measurements were repeated to assess baseline stability and response to breathing of hyperoxic gas. Each pO(2) map was obtained in 3(1/2) min, facilitating dynamic measurements of response to oxygen intervention. Altering the inhaled gas to oxygen produced a significant increase in mean pO(2) from 55 Torr to 238 Torr in thigh muscle and a smaller, but significant, increase in mean pO(2) from 17 Torr to 78 Torr in MAT-Lu tumors. Thus, PISTOL enabled mapping of tissue pO(2) at multiple locations and dynamic changes in pO(2) in response to intervention. This new method offers a potentially valuable new tool to image pO(2) in vivo for any healthy or diseased state by (1)H MRI. PMID:18574806

  8. Development of Magnesium and Siloxane-Containing Vaterite and Its Composite Materials for Bone Regeneration.

    PubMed

    Yamada, Shinya; Obata, Akiko; Maeda, Hirotaka; Ota, Yoshio; Kasuga, Toshihiro

    2015-01-01

    Development of novel biomaterials with Mg(2+), Ca(2+), and silicate ions releasability for bone regeneration is now in progress. Several inorganic ions have been reported to stimulate bone-forming cells. We featured Ca(2+), silicate, and especially, Mg(2+) ions as growth factors for osteoblasts. Various biomaterials, such as ceramic powders and organic-inorganic composites, that release the ions, have been developed and investigated for their cytocompatibilities in our previous work. Through the investigation, providing the three ions was found to be effective to activate osteogenic cells. Magnesium and siloxane--containing vaterite was prepared by a carbonation process as an inorganic particle that can has the ability to simultaneously release Ca(2+), silicate, and Mg(2+) ions to biodegradable polymers. Poly (l-lactic acid) (PLLA)- and bioactive PLLA-based composites containing vaterite coatings were discussed regarding their degradability and cytocompatibility using a metallic Mg substrate as Mg(2+) ion source. PLLA/SiV composite film, which has a releasability of silicate ions besides Ca(2+) ion, was coated on a pure Mg substrate to be compared with the PLLA/V coating. The degradability and releasability of inorganic ions were morphologically and quantitatively monitored in a cell culture medium. The bonding strength between the coatings and Mg substrates was one of the key factors to control Mg(2+) ion release from the substrates. The cell culture tests were conducted using mouse osteoblast-like cells (MC3T3-E1 cells); cellular morphology, proliferation, and differentiation on the materials were evaluated. The PLLA/V and PLLA/SiV coatings on Mg substrates were found to enhance the proliferation, especially the PLLA/SiV coating possessed a higher ability to induce the osteogenic differentiation of the cells. PMID:26697421

  9. Development of Magnesium and Siloxane-Containing Vaterite and Its Composite Materials for Bone Regeneration

    PubMed Central

    Yamada, Shinya; Obata, Akiko; Maeda, Hirotaka; Ota, Yoshio; Kasuga, Toshihiro

    2015-01-01

    Development of novel biomaterials with Mg2+, Ca2+, and silicate ions releasability for bone regeneration is now in progress. Several inorganic ions have been reported to stimulate bone-forming cells. We featured Ca2+, silicate, and especially, Mg2+ ions as growth factors for osteoblasts. Various biomaterials, such as ceramic powders and organic–inorganic composites, that release the ions, have been developed and investigated for their cytocompatibilities in our previous work. Through the investigation, providing the three ions was found to be effective to activate osteogenic cells. Magnesium and siloxane-­containing vaterite was prepared by a carbonation process as an inorganic particle that can has the ability to simultaneously release Ca2+, silicate, and Mg2+ ions to biodegradable polymers. Poly (l-lactic acid) (PLLA)- and bioactive PLLA-based composites containing vaterite coatings were discussed regarding their degradability and cytocompatibility using a metallic Mg substrate as Mg2+ ion source. PLLA/SiV composite film, which has a releasability of silicate ions besides Ca2+ ion, was coated on a pure Mg substrate to be compared with the PLLA/V coating. The degradability and releasability of inorganic ions were morphologically and quantitatively monitored in a cell culture medium. The bonding strength between the coatings and Mg substrates was one of the key factors to control Mg2+ ion release from the substrates. The cell culture tests were conducted using mouse osteoblast-like cells (MC3T3-E1 cells); cellular morphology, proliferation, and differentiation on the materials were evaluated. The PLLA/V and PLLA/SiV coatings on Mg substrates were found to enhance the proliferation, especially the PLLA/SiV coating possessed a higher ability to induce the osteogenic differentiation of the cells. PMID:26697421

  10. Synthesis and characterization of high-performance polymeric materials: Part I. Silphenylene-siloxanes. Part II. Biodegradable films from gelatins

    NASA Astrophysics Data System (ADS)

    Zhang, Ruzhi

    Poly(tetramethyl-m-silphenylene-siloxane) (PTMMS) has been successfully synthesized from m-bis(dimethylhydroxysilyl)benzene in a step-growth polymerization using n-hexylamine 2-ethylhexoate as the catalyst. The glass transition temperature of PTMMS is -52 C, but no melting temperature was detected by DSC. TGA measurements revealed excellent high-temperature properties under nitrogen or air. Random copolymers of tetramethyl-p-silphenylene-siloxane and tetramethyl-m-silphenylene-siloxane were synthesized through condensation copolymerization. Alternating copolymers were prepared through dehydrogenation polymerization. The physical properties can be adjusted from those of a crystalline polymer to those of an amorphous, elastomeric polymer by increasing the amount of the meta comonomer. Thermal studies revealed that these copolymers possess excellent thermal stability. PTMMS has been successfully cross-linked by UV irradiation under air or argon in the presence of benzophenone. Mechanical properties of PTMMS networks were studied by equilibrium stress-strain measurements, and the cross-link density was estimated by means of the Mooney-Rivlin equation. TGA studies revealed that PTMMS elastomers have excellent thermal and thermo-oxidative stabilities. Dehydrogenation polymerization of bis-silanes and disilanols to silphenylenesiloxane polymers through the formation of Si-O-Si bonds as mediated by a rhodium complex was successfully developed. Coordination polymerization using Wilkinson's catalyst provided high molecular weight polymers in high yield at room temperature in an open system. Octamethylcyclo-di(meta-silphenylenesiloxane) (cyclic meta-dimer) was synthesized as the dominant cyclic oligomer product from 1,3--bis(dimethylhydroxysilyl)benzene using 4-dimethylaminopyridine as the catalyst in a dilute THF solution. The X-ray structure of the cyclic meta-dimer was obtained and the Si-O-Si bond angle is 142.1. The attempted ring-opening polymerization of cyclic meta-dimer to silphenylene-siloxane polymer resulted in a low yield due to the unstrained ring of cyclic meta-dimer. Oligomers of poly(diisopropylsiloxane) with repeating units of up to five have been synthesized. The synthesis of poly(diisopropylsiloxane) is feasible, especially for the heterofunctional polycondensation between silanediols and bisureidosilanes. Cross-linking of gelatin by liquid smoke (dialdehyde) and diisocyanate was successfully carried out. The coagulation technique can be successfully incorporated into the cross-linking and orientation processes to provide a unique method for developing high-performance materials. The resulting films showed excellent tensile strengths in the dry state (as high as 78 MPa) but low tensile strengths when wet.

  11. Polydimethyl siloxane wet etching for three dimensional fabrication of microneedle array and high-aspect-ratio micropillars

    PubMed Central

    Deng, Yu-Luen; Juang, Yi-Je

    2014-01-01

    Among various transdermal drug delivery (TDD) approaches, utilizing the microneedles (MNs) not only can penetrate the skin but also deliver the drug with reduced tissue damage, reduced pain, and no bleeding. However, the MNs with larger height are required to overcome the skin barrier for effective TDD. Unlike 2D patterning, etching polydimethyl siloxane (PDMS) micropillars for fabrication of 3D microstructures is presented. The PDMS micropillars were first constructed by casting PDMS on the computer numerical control-machined cylindrical microwells, which then went through etching process to obtain the MNs for subsequent fabrication of polymer MNs or high aspect ratio micropillars. PMID:24803970

  12. A laboratory study of dimensional changes for three elastomeric impression materials using custom and stock trays.

    PubMed

    Boulton, J L; Gage, J P; Vincent, P F; Basford, K E

    1996-12-01

    Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. Three elastomeric impression materials were used in custom and stock trays to determine the accuracy of impressions taken from an experimental stainless steel model representing premolar and molar bridge abutment preparations. Horizontal and vertical individual abutment and interabutment dimensions were measured on die stone replicas, and the measurements compared with those obtained from stainless steel master models. The results of this study demonstrate polysulphide is the least accurate impression material for both vertical and horizontal individual abutment dimensions. However, for interabutment horizontal dimensions, no statistical differences were noted between impression material types when using a custom tray. Stock trays produced unreliable results for all the materials tested. PMID:9008997

  13. Managing and creating an image in the interview: the role of interviewee initial impressions.

    PubMed

    Swider, Brian W; Barrick, Murray R; Harris, T Brad; Stoverink, Adam C

    2011-11-01

    In employment interviews, individuals use impression management tactics to present themselves as suitable candidates to interviewers. However, not all impression management tactics, or the interviewees who employ them, are effective at positively influencing interview scores. Results of this study indicate that the relationship between impression management tactic usage and interview success is contingent on the type of tactic employed. Specifically, self-promotion was found to have a positive relationship (r = .20) and slight (r = -.11) and extensive (r = -.19) image creation were found to have negative relationships with end-of-interview scores. Further, the relationships between these 3 impression management tactics were moderated by interviewees' initial impressions of the interview (ΔR² ranged from .04 to .10). Interviewees who perceived they were seen as less suitable during rapport building were more effective when using any of the 3 impression management tactics. PMID:21639599

  14. [Application study of optical method in measuring wall thickness of dental impression].

    PubMed

    Mi, Honglin; Wu, Yan; Zheng, Gang

    2014-12-01

    Dental impressions are widely used in the field of oral restoration. The materials are used for making impression in oral cavity. In order to measure the thickness of impression for reference in clinic, the real impressions are taken as the object for studying. Through optical method, charge-coupled device (CCD) is used for collecting the grey image of cutting section of the impressions which are located in the same plane with steel dividing ruler. According to convert relationship between dividing ruler and pixels collecting grey image, the thickness of impression specimens can be obtained. The results show that the optical method used for measuring thickness is feasible to the task and the precision can reach micro dimension. The experiment method and technique can also be provided for measuring thickness of similar tissue engineering materials. PMID:25868235

  15. Evaluation of oral scanning in comparison to impression using three-dimensional registration

    NASA Astrophysics Data System (ADS)

    Brogle-Kim, Yur-Chung; Deyhle, Hans; Mller, Bert; Schulz, Georg; Bormann, Therese; Beckmann, Felix; Jger, Kurt

    2012-10-01

    Crown and bridge restorations are one of the main treatment methods in fixed prosthodontics. The fabrication requires data on the patient's denture shape. This information is generally obtained as a hard copy from an impression mold. Alternatively, one can acquire the data electronically using oral optical three-dimensional (3D) imaging techniques, which determine the surface of the denture. The aim of the study was to quantitatively compare the accuracy of three dimensional scanning with that of conventional impressions and give a statement how far the scanner provides a clinical alternative with equal or better precision. Data from 10 teeth were acquired in the dental office with a polyether impression material and an oral scanner. Data from the impressions were digitalized by means of micro computed tomography. The data were then 3D registered to identify the potential differences between impression and optical scan. We could demonstrate that the oral scanner's data and the conventional impressions are comparable.

  16. Interpretation of Appearance: The Effect of Facial Features on First Impressions and Personality

    PubMed Central

    Wolffhechel, Karin; Fagertun, Jens; Jacobsen, Ulrik Plesner; Majewski, Wiktor; Hemmingsen, Astrid Sofie; Larsen, Catrine Lohmann; Lorentzen, Sofie Katrine; Jarmer, Hanne

    2014-01-01

    Appearance is known to influence social interactions, which in turn could potentially influence personality development. In this study we focus on discovering the relationship between self-reported personality traits, first impressions and facial characteristics. The results reveal that several personality traits can be read above chance from a face, and that facial features influence first impressions. Despite the former, our prediction model fails to reliably infer personality traits from either facial features or first impressions. First impressions, however, could be inferred more reliably from facial features. We have generated artificial, extreme faces visualising the characteristics having an effect on first impressions for several traits. Conclusively, we find a relationship between first impressions, some personality traits and facial features and consolidate that people on average assess a given face in a highly similar manner. PMID:25233221

  17. Effects of Exposure to Advertisements on Audience Impressions

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hiroshi; Sato, Mie; Kasuga, Masao; Nagao, Yoshihide; Shono, Toru; Norose, Yuka; Oku, Ritsuya; Nogami, Akira; Miyazawa, Yoshitaka

    This study investigated effects of listening and/or watching commercial-messages (CMs) on audience impressions. We carried out experiments of TV advertisements presentation in conditions of audio only, video only, and audio-video. As results, we confirmed the following two effects: image-multiple effect, that is, the audience brings to mind various images that are not directly expressed in the content, and marking-up effect, that is, the audience concentrates on some images that are directly expressed in the content. The image-multiple effect, in particular, strongly appeared under the audio only condition. Next, we investigated changes in the following seven subjective responses; usage image, experience, familiarity, exclusiveness, feeling at home, affection, and willingness to buy, after exposure to advertisements under conditions of audio only and audio-video. As a result, noting that the image-multiple effect became stronger as the evaluation scores of the responses increased.

  18. The complex interplay between semantics and grammar in impression formation.

    PubMed

    Shreves, Wyley B; Hart, William; Adams, John M; Guadagno, Rosanna E; Eno, Cassie A

    2014-09-01

    We sought to bridge findings showing that (a) describing a person's behavior with the perfective verb aspect (did), compared to the imperfective aspect (was doing), increases processing of semantic knowledge unrelated to the target's action such as stereotypes and (b) an increased recognition of stereotypical thoughts often promotes a judgment correction for the stereotypes. We hypothesized an interplay between grammar (verb conjugation) and semantic information (gender) in impression-formation. Participants read a resume, attributed to a male or female, for a traditionally masculine job. When the resume was written in the imperfective, people rated a male (vs. female) more positively. When the resume was in the perfective, this pattern reversed. Only these latter effects of gender were influenced by cognitive load. Further, people more quickly indicated the applicant's gender in the perfective condition, suggesting an enhanced focus on gender during processing. PMID:24950389

  19. Neuro-impressions: interpreting the nature of human creativity

    PubMed Central

    Siler, Todd Lael

    2012-01-01

    Understanding the creative process is essential for realizing human potential. Over the past four decades, the author has explored this subject through his brain-inspired drawings, paintings, symbolic sculptures, and experimental art installations that present myriad impressions of human creativity. These impressionistic artworks interpret rather than illustrate the complexities of the creative process. They draw insights from empirical studies that correlate how human beings create, learn, remember, innovate, and communicate. In addition to offering fresh aesthetic experiences, this metaphorical art raises fundamental questions concerning the deep connections between the brain and its creations. The author describes his artworks as embodiments of everyday observations about the neuropsychology of creativity, and its all-purpose applications for stimulating and accelerating innovation. PMID:23091455

  20. Optical impression systems for CAD-CAM restorations.

    PubMed

    Galhano, Graziela vila Prado; Pellizzer, Eduardo Piza; Mazaro, Jos Vitor Quinelli

    2012-11-01

    Computer-aided design/computer-aided manufacturing images can be taken through either direct or indirect imaging. For the indirect systems, the digitalization is obtained from the impression material or cast, and for the direct ones the image is taken directly from the mouth using intraoral scanners.The direct acquisition systems have been constantly improved because these are less invasive, quicker, and more precise than the conventional method. Besides, the digital images can be easily stored for a long time. Therefore, the aim of this paper was to describe and discuss based on the literature the main direct image acquisition systems available on the market: CEREC Bluecam (Sirona), Lava C.O.S. System (3M ESPE), iTero System (Cadent/Straumann), and E4D System (D4D Technologies). PMID:23172483

  1. Salaried general practice in Czechoslovakia: personal observations and impressions.

    PubMed Central

    Gibbons, B

    1993-01-01

    In 1991, a visit was undertaken, to the former Czechoslovakia, during which discussions were held with general practitioners. Some personal observations and impressions from the visit are presented. For four decades, salaried general practice was a feature of the Czechoslovakian health care system. Primary health care comprised three strands: paediatric services, an occupational health service and community general practitioner care. The main point of service delivery was the polyclinic which, although being large and impersonal, provided easy access to other primary and secondary services. General practitioners, over half of whom were women, had regular leave entitlement and predictable hours of work, out of hours work being provided through separate contracts based on primary care emergency centres. However, doctors were poorly paid compared with industrial workers. Following the 'velvet revolution' in 1989, all aspects of the health service have been subject to major review, and salaried general practice is likely to give way to a more entrepreneurial system. PMID:8251221

  2. Nanodielectric system for cryogenic applications: Barium titanate filled polyvinyl alcohol

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R; Duckworth, Robert C

    2008-01-01

    In the current study the focus is on dielectric properties (as a function of frequency and temperature) of a polymeric composite system composed of polyvinyl alcohol and barium titanate nano powder. In the investigations, the temperature range is between 50-295 K, and the frequency range is between $20\\ \\hertz-1\\ \\mega\\hertz$. Polarization and conduction processes are investigated in the linear regime. Dielectric breakdown strengths of samples are also reported. The materials presented have potential to be implemented in cryogenic capacitor or field grading applications.

  3. Starch-polyvinyl alcohol cast film-performance and biodegradation

    SciTech Connect

    Chen, Liang; Imam, S.H.; Stein, T.M.

    1996-10-01

    Starch-polyvinyl alcohol (PVOH) cast films were prepared in the absence of plasticizer. Their physical and biodegradable properties were examined. Moisture absorption by the films was similar to that of PVOH at low humidity and increased linearly as the relative humidity increased. The tensile strength of the films decreased with increased humidity and did not display significant improvement with increased PVOH content. Higher PVOH content improved elongation when the relative humidity was 80% or higher. Biodegradation studies revealed that the presence of PVOH in the films slowed the rate of degradation.

  4. Electrical and Thermal Properties of Polyvinyl Acetal Based Nanocomposites

    SciTech Connect

    Sauers, Isidor; James, David Randy; Ellis, Alvin R; Tuncer, Enis; Polyzos, Georgios; Pace, Marshall O

    2009-10-01

    A water chemistry procedure is used to synthesize titanium dioxide nanoparticles which can later be blended with a polymer to form a nanodielectric. The synthesized nanoparticles are dispersed in two grades of polyvinyl acetal (commercially available under the trade names BX-L and KS-10, manufactured by SEKISUI Chemicals). Nanocomposite materials were prepared with 15 and 33 wt% titanium dioxide. The variation of the glass transition temperature with increasing filler weight fraction is presented. The dielectric breakdown strengths of the nanodielectric samples are reported. The presented results can be employed to optimize the dielectric properties of the studied nanocomposites for potential use in cryogenic high voltage applications.

  5. Computational studies of polyvinyl alcohol encapsulated tetrahedral cadmium sulphide cluster

    NASA Astrophysics Data System (ADS)

    Bala, Vaneeta; Tripathi, S. K.; Kumar, Ranjan

    2013-06-01

    In the present work theoretical encapsulation of tetrahedral cluster of cadmium sulphide within polyvinyl alcohol (PVA) chains has been studied. Density of states, binding energy and optical properties are calculated using density functional theory (DFT) as implemented in SIESTA code with local density approximation (LDA) functionals. We observe that PVA chains strongly interact with [Cd4(SH)10]2- cluster through-OH groups and results in broadening of the band gap. Absorption spectrum of hybrid structure is also computed which is comparable to experimental results.

  6. Catalytic dehydrochlorination of polyvinyl chloride in two-phase systems

    SciTech Connect

    Leplyanin, G.V.; Salimgareeva, V.N.; Sannikova, N.S.

    1994-11-01

    The catalytic activity of quaternary ammonium salts (QAS), whose cation and anion structures are different, and the mechanism of catalytic two-phase dehydrochlorination of polyvinyl chloride (PVC) are studied. Under phase-transfer conditions, dehydrochlorination of PVC is shown to proceed at the interface via an ionic mechanism in the presence of quaternary ammonium salts. The catalytic activity of QAS is governed by both the cation lipophilicity and the anion nature and increases as alcohols are introduced into the reaction mixture. The alcohol nature does not influence the extent of the reaction completion, but it does effect the supermolecular structure of the polyacetylene synthesized.

  7. Polyvinyl alcohol doped with nickel chloride hexahydrate as conductor polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limon, B.; Olivares-Perez, Arturo; Silva-Andrade, F.; Fuentes-Tapia, I.; Ibarra-Torres, Juan Carlos

    2004-06-01

    Polyvinyl alcohol is a viscous solution, with blue clear appearance, not has odor, when is deposited, as a film dry the appearance is clear transparent and has high flexibility. This polymer no has double link and don not has p orbital that permit the conductivity. However, can be doped with salts as ammonium dichromate and nickel chloride hexahydrate NiCl26H2O constructing a good conductor polymer with a resistivity around 300 ohms cm. Conserving the high flexibility opened new possibilities and applications.

  8. Memristive learning and memory functions in polyvinyl alcohol polymer memristors

    NASA Astrophysics Data System (ADS)

    Lei, Yan; Liu, Yi; Xia, Yidong; Gao, Xu; Xu, Bo; Wang, Suidong; Yin, Jiang; Liu, Zhiguo

    2014-07-01

    Polymer based memristive devices can offer simplicity in fabrication and at the same time promise functionalities for artificial neural applications. In this work, inherent learning and memory functions have been achieved in polymer memristive devices employing Polyvinyl Alcohol. The change in conduction in such polymer devices strongly depends on the pulse amplitude, duration and time interval. Through repetitive stimuli training, temporary short-term memory can transfer into consolidated long-term memory. These behaviors bear remarkable similarities to certain learning and memory functions of biological systems.

  9. Impression Creep Behavior of a Cast AZ91 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Kabirian, F.; Mahmudi, R.

    2009-01-01

    The creep behavior of the cast AZ91 magnesium alloy was investigated by impression testing. The tests were carried out under constant punching stress in the range 100 to 650 MPa, corresponding to 0.007 ? ? imp/ G ? 0.044, at temperatures in the range 425 to 570 K. Assuming a power-law relationship between the impression velocity and stress, depending on the testing temperature, stress exponents of 4.2 to 6.0 were obtained. When the experimental creep rates were normalized to the grain size and effective diffusion coefficient, a stress exponent of approximately 5 was obtained, which is in complete agreement with stress exponents determined by the conventional creep testing of the same material reported in the literature. Calculation of the activation energy showed a slight decrease in the activation energy with increasing stress such that the creep-activation energy of 122.9 kJ/mol at ? imp/ G = 0.020 decreases to 94.0 kJ/mol at ? imp/ G = 0.040. Based on the obtained stress exponents and activation energy data, it is proposed that dislocation climb is the controlling creep mechanism. However, due to the decreasing trend of creep-activation energy with stress, it is suggested that two parallel mechanisms of lattice and pipe-diffusion-controlled dislocation climb are competing. To elucidate the contribution of each mechanism to the overall creep deformation, the creep rates were calculated based on the effective activation energy. This yielded a criterion that showed that, in the high-stress regimes, the experimental activation energies fall in the range in which the operative creep mechanism is dislocation climb controlled by dislocation pipe diffusion. In the low-stress regime, however, the lattice-diffusion dislocation climb is dominant.

  10. A Single Step Impression Technique of Flabby Ridges Using Monophase Polyvinylsiloxane Material: A Case Report

    PubMed Central

    Pai, Umesh Y.; Reddy, Vikram Simha; Hosi, Rushad Nariman

    2014-01-01

    Complete denture fabrication in clinically compromised situations such as flabby ridges is a challenging task for the clinician. Accurate impressioning of these tissues plays a major role in ensuring a well-fitting prosthesis. In this paper, the authors have proposed a newer technique of impression making of the flabby tissues using a combination of readily available newer and older materials to ensure an accurate and easy impression of these tissues. PMID:24872897

  11. [Effect of impression contamination on the accuracy of plaster model surface].

    PubMed

    Pasiek, S

    1990-01-01

    Macroscopic and microscopic examination of plaster models obtained from impressions with alginate mass Kromopan Super and silicone mass Dentaflex Pasta confirmed that leaving of saliva and blood on the surface of impressions causes uneven surface of plaster models. For ensuring sufficiently even surface of the model the impression should be cleaned immediately after its obtaining with water and a brush, or later on by immersion in 2% Na2SO4 solution. PMID:2103030

  12. Comparison of intraoral scanning and conventional impression techniques using 3-dimensional superimposition

    PubMed Central

    Rhee, Ye-Kyu

    2015-01-01

    PURPOSE The aim of this study is to evaluate the appropriate impression technique by analyzing the superimposition of 3D digital model for evaluating accuracy of conventional impression technique and digital impression. MATERIALS AND METHODS Twenty-four patients who had no periodontitis or temporomandibular joint disease were selected for analysis. As a reference model, digital impressions with a digital impression system were performed. As a test models, for conventional impression dual-arch and full-arch, impression techniques utilizing addition type polyvinylsiloxane for fabrication of cast were applied. 3D laser scanner is used for scanning the cast. Each 3 pairs for 25 STL datasets were imported into the inspection software. The three-dimensional differences were illustrated in a color-coded map. For three-dimensional quantitative analysis, 4 specified contact locations(buccal and lingual cusps of second premolar and molar) were established. For twodimensional quantitative analysis, the sectioning from buccal cusp to lingual cusp of second premolar and molar were acquired depending on the tooth axis. RESULTS In color-coded map, the biggest difference between intraoral scanning and dual-arch impression was seen (P<.05). In three-dimensional analysis, the biggest difference was seen between intraoral scanning and dual-arch impression and the smallest difference was seen between dual-arch and full-arch impression. CONCLUSION The two- and three-dimensional deviations between intraoral scanner and dual-arch impression was bigger than full-arch and dual-arch impression (P<.05). The second premolar showed significantly bigger three-dimensional deviations than the second molar in the three-dimensional deviations (P>.05). PMID:26816576

  13. Comparison of epoxy- and siloxane-based single-mode optical waveguides defined by direct-write lithography

    NASA Astrophysics Data System (ADS)

    Elmogi, Ahmed; Bosman, Erwin; Missinne, Jeroen; Van Steenberge, Geert

    2016-02-01

    This paper reports on the fabrication and characterization of single-mode polymer optical waveguides at telecom and SOI compatible wavelengths; by making a comparison between an epoxy and a siloxane polymer waveguide material system (both commercially-available). The proposed waveguides can be used in short-reach optical interconnects targeting chip-to-chip communication on the interposer level or providing a coupling interface between single-mode optical fibers and photonic integrated circuits (PICs). This technology enables the integration of optoelectronic chips for photonic packaging purposes. First, the single-mode dimensions (4 × 4 μm2 and 5 × 5 μm2) for both materials at selected wavelengths (1.31 μm and 1.55 μm) were determined based on the refractive index measurements. Then, the waveguides were patterned by a direct-write lithography method. The fabricated waveguides show a high-quality surface with smooth sidewalls. The optical propagation losses were measured using the cut-back method. For the siloxane-based waveguides, the propagation losses were found to be 0.34 dB/cm and 1.36 dB/cm at 1.31 μm and 1.55 μm respectively while for the epoxy-based waveguides the losses were 0.49 dB/cm and 2.23 dB/cm at 1.31 μm and 1.55 μm respectively.

  14. Absorption of a linear (L2) and a cyclic (D4) siloxane using different oils: application to biogas treatment.

    PubMed

    Rojas Devia, Carolina; Subrenat, Albert

    2013-01-01

    Hydrophobic volatile methyl siloxanes (VMS), such as hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4), present a low solubility in water. An alternative treatment by absorption into hydrophobic absorbents was therefore studied. For this purpose, three different absorbents, motor oil, cutting oil and a water-cutting oil mixture, were selected with the aim of re-using a waste product. The set of experiments was carried out in a bubble column, where parameters such as inlet concentration, residence time and temperature were studied. The best performance for the removal of both siloxanes, in terms of absorption capacity, was observed for motor oil, particularly for D4. In fact, motor oil removal efficiency for D 4 was 80%, whereas for L2 it was 60%, indicating that D 4 is more easily absorbed than L2. In the case of water-cutting oil, this showed a mass transfer enhancement from the gas phase to the liquid phase compared with water alone. Furthermore, a removal efficiency of 70% was observed for D 4, showing that the addition of an oil fraction to a water system improves the absorption of VMS. These results show that VMS absorption into oils could be a promising way to achieve their abatement. PMID:24617070

  15. Theoretical studies of the molecular structures of dinitrotoluenes and their interactions with siloxane site surface of clays

    NASA Astrophysics Data System (ADS)

    Ramos, Carmen M.; Alzate, Liliana F.; Colon, Yleana M.; Santana, Alberto; Hernandez-Rivera, Samuel P.; Castro, Miguel E.; Briano, Julio G.; Mina, Nairmen

    2004-09-01

    Among the many different signature compounds emitted from a landmine in the vapor phase, 2,4-dinitrotoluene (2,4-DNT) is the most common nitroaromatic compound in terms of detecting buried landmines, although it is a byproduct in the synthesis of TNT. 2,4-DNT is used as an ingredient in mining explosives and also prevalent on the soil surface but is somewhat seasonally dependent. The B3LYP hybrid functional was used to obtain the lowest-energy structure of both 2,4 and 2,6-DNT. Increasing basis sets from the 3-21G up to the 6-31++G (d, p) are used to predict structural parameters, vibrational frequencies, IR intensities and Raman activities for the explosives molecules. The calculated energies show that the 2,4-dinitrotoluene isomer is more stable than 2,6-dinitrotoluene isomer due to the lesser levels of steric effects between the nitro groups and the methyl group. The optimized structures were interacted with the siloxane site of clay minerals, using the density functional level of theory and the basis sets used to optimize the geometry of the DNT molecules. The binding energy (Eb) between the optimized molecules and the basal siloxane site surface of clay minerals was calculated at distances in a range between 2.5 to 8.5 .

  16. 40 CFR 61.64 - Emission standard for polyvinyl chloride plants.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., excluding latex resins, with the product determined on a dry solids basis; (ii) 0.4 g/kg (0.8 lb/ton) product from the strippers for all other polyvinyl chloride resins, including latex resins, with the... dispersion polyvinyl chloride resins, excluding latex resins, with the product determined on a dry...

  17. 40 CFR 61.64 - Emission standard for polyvinyl chloride plants.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., may not exceed: (i) 2000 ppm for polyvinyl chloride dispersion resins, excluding latex resins; (ii) 400 ppm for all other polyvinyl chloride resins, including latex resins, averaged separately for each..., excluding latex resins, with the product determined on a dry solids basis; (ii) 0.4 g/kg (0.8...

  18. 40 CFR 61.64 - Emission standard for polyvinyl chloride plants.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., may not exceed: (i) 2000 ppm for polyvinyl chloride dispersion resins, excluding latex resins; (ii) 400 ppm for all other polyvinyl chloride resins, including latex resins, averaged separately for each..., excluding latex resins, with the product determined on a dry solids basis; (ii) 0.4 g/kg (0.8...

  19. 40 CFR 61.64 - Emission standard for polyvinyl chloride plants.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., may not exceed: (i) 2000 ppm for polyvinyl chloride dispersion resins, excluding latex resins; (ii) 400 ppm for all other polyvinyl chloride resins, including latex resins, averaged separately for each..., excluding latex resins, with the product determined on a dry solids basis; (ii) 0.4 g/kg (0.8...

  20. 40 CFR 61.64 - Emission standard for polyvinyl chloride plants.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., may not exceed: (i) 2000 ppm for polyvinyl chloride dispersion resins, excluding latex resins; (ii) 400 ppm for all other polyvinyl chloride resins, including latex resins, averaged separately for each..., excluding latex resins, with the product determined on a dry solids basis; (ii) 0.4 g/kg (0.8...

  1. Polymeric sulfides CdS, CuS, and NiS in polyvinyl alcohol matrix

    NASA Astrophysics Data System (ADS)

    Prosanov, I. Yu.; Bulina, N. V.

    2014-06-01

    Cadmium, copper, and nickel sulfides have been synthesized in a polyvinyl alcohol matrix. The specimens have been investigated by means of vibration spectroscopy and X-ray diffraction analysis. The obtained data have confirmed the formation of cadmium sulfide with a polymeric chain structure in polyvinyl alcohol. The possibility of producing similar materials based on copper and nickel sulfides has been discussed.

  2. 78 FR 39256 - Polyvinyl Alcohol From Taiwan: Rescission of Antidumping Duty Administrative Review; 2012-2013

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-01

    ... International Trade Administration Polyvinyl Alcohol From Taiwan: Rescission of Antidumping Duty Administrative... the antidumping duty order on polyvinyl alcohol (PVA) from Taiwan for the period March 1, 2012... FR 13858 (March 1, 2013). \\2\\ See Initiation of Antidumping and Countervailing Duty...

  3. 77 FR 14342 - Polyvinyl Alcohol From Taiwan: Correction to Notice of Opportunity To Request Administrative Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-09

    ... International Trade Administration Polyvinyl Alcohol From Taiwan: Correction to Notice of Opportunity To Request... antidumping duty order on polyvinyl alcohol from Taiwan. See Antidumping or Countervailing Duty Order, Finding, or Suspended Investigation; Opportunity To Request Administrative Review, 77 FR 12559 (March 1,...

  4. Establishing versus preserving impressions: Predicting success in the multiple audience problem.

    PubMed

    Nichols, Austin Lee; Cottrell, Catherine A

    2015-12-01

    People sometimes seek to convey discrepant impressions of themselves to different audiences simultaneously. Research suggests people are generally successful in this "multiple audience problem." Adding to previous research, the current research sought to examine factors that may limit this success by measuring social anxiety and placing participants into situations requiring them to either establish or preserve multiple impressions simultaneously. In general, participants were more successful when preserving previously conveyed impressions than when establishing impressions for the first time. In contrast, social anxiety did not affect multiple audience success. In all, this research offers valuable insight into potential challenges that people face in many social situations. PMID:25581114

  5. Insular and hippocampal contributions to remembering people with an impression of bad personality

    PubMed Central

    Shigemune, Yayoi; Nouchi, Rui; Kambara, Toshimune; Kawashima, Ryuta

    2013-01-01

    Our impressions of other people are formed mainly from the two possible factors of facial attractiveness and trustworthiness. Previous studies have shown the importance of orbitofrontalhippocampal interactions in the better remembering of attractive faces, and psychological data have indicated that faces giving an impression of untrustworthiness are remembered more accurately than those giving an impression of trustworthiness. However, the neural mechanisms of the latter effect are largely unknown. To investigate this issue, we investigated neural activities with event-related fMRI while the female participants rated their impressions of the personalities of men in terms of trustworthiness. After the rating, memory for faces was tested to identify successful encoding activity. As expected, faces that gave bad impressions were remembered better than those that gave neutral or good impressions. In fMRI data, right insular activity reflected an increasing function of bad impressions, and bilateral hippocampal activities predicted subsequent memory success. Additionally, correlation between these insular and hippocampal regions was significant only in the encoding of faces associated with a bad impression. Better memory for faces associated with an impression of bad personality could reflect greater interaction between the avoidance-related insular region and the encoding-related hippocampal region. PMID:22349799

  6. Accuracy and stability of impression materials subjected to chemical disinfection - a literature review.

    PubMed

    Kotsiomiti, E; Tzialla, A; Hatjivasiliou, K

    2008-04-01

    Disinfection of impressions by immersion or spraying with disinfecting solutions is considered nowadays mandatory for effective infection control. The purpose of this review was to examine existing evidence on the effects that chemical disinfection may have on critical qualities of impressions, namely dimensional accuracy and stability over time. A PubMed search was conducted to include original laboratory research articles written in English, published between 1980 and 2005 in peer-reviewed journals and investigating the effect of chemical disinfection, by immersion or spraying, on the dimensional changes that the impression materials experience after setting. Studies were also sought manually, by tracing the references cited in the retrieved articles. The reports on dimensional changes of disinfected impression materials, although rather numerous, are difficult to compare and analyze because of variations of the experimental design. The investigations broadly agree that the disinfection process does not generally affect the dimensional integrity of the impressions, in spite of the statistically significant differences occasionally found. However, the immersion in the disinfecting solution encourages water absorption phenomena in the case of the so-called hydrophilic impression materials, especially after the long-term immersion. Chemical interactions between impressions and disinfectants may occur, but they do not appear to influence the dimensional behaviour of the former. The overall effect of the disinfection is influenced not only by the changes experienced by the impression per se, but also by the alterations of the acrylic tray containing the impression and of the gypsum product poured in it. PMID:18321265

  7. Quality of master impressions and related materials for fabrication of complete dentures in the UK.

    PubMed

    Al-Ahmar, A O; Lynch, C D; Locke, M; Youngson, C C

    2008-02-01

    The aim of this study was to examine the quality of master impressions and related materials for fabricating complete dentures in the UK. One hundred and fifty pre-piloted questionnaires were distributed to a number of dental laboratories in the UK with large catchment areas. Information requested related to the quality and choice of techniques for the master impression stage of fabricating complete dentures, as well as prescription of materials for occlusal registration, amongst others. All information was recorded anonymously. One hundred and forty-four completed questionnaires were returned. All items were provided on a private basis. Eighty-three per cent (n=119) of master impressions were made using a custom tray, the remainder were made using a plastic stock tray. The most commonly used impression material was zinc oxide-eugenol (42%, n=60), followed by polyvinylsiloxane (39%, n=56) and irreversible hydrocolloid (19%, n=28). Master casts were poured after a minimum of 4 days. Eleven per cent of impressions examined (n=16) were judged to have errors. It was reported that 64% of master impressions (n=92) examined had been disinfected adequately. While this study revealed evidence of good clinical practice, particularly in relation to the selection of impression trays and quality of master impressions for complete dentures, there were some areas of concern, particularly in relation to the disinfection of the impressions examined. Dental practitioners should aim to provide their patients with high-quality prostheses by observing best clinical practice at all times. PMID:18053059

  8. The effect of tray selection on the accuracy of elastomeric impression materials.

    PubMed

    Gordon, G E; Johnson, G H; Drennon, D G

    1990-01-01

    This study evaluated the accuracy of reproduction of stone casts made from impressions using different tray and impression materials. The tray materials used were an acrylic resin, a thermoplastic, and a plastic. The impression materials used were an additional silicone, a polyether, and a polysulfide. Impressions were made of a stainless steel master die that simulated crown preparations for a fixed partial denture and an acrylic resin model with cross-arch and anteroposterior landmarks in stainless steel that typify clinical intra-arch distances. Impressions of the fixed partial denture simulation were made with all three impression materials and all three tray types. Impressions of the cross-arch and anteroposterior landmarks were made by using all three tray types with only the addition reaction silicone impression material. Impressions were poured at 1 hour with a type IV dental stone. Data were analyzed by using ANOVA with a sample size of five. Results indicated that custom-made trays of acrylic resin and the thermoplastic material performed similarly regarding die accuracy and produced clinically acceptable casts. The stock plastic tray consistently produced casts with greater dimensional change than the two custom trays. PMID:2404101

  9. Chemical enhancement of footwear impressions in blood on fabric - part 2: peroxidase reagents.

    PubMed

    Farrugia, Kevin J; Savage, Kathleen A; Bandey, Helen; Ciuksza, Tomasz; Nic Daid, Niamh

    2011-09-01

    This study investigates the optimisation of peroxidase based enhancement techniques for footwear impressions made in blood on various fabric surfaces. Four different haem reagents: leuco crystal violet (LCV), leuco malachite green (LMG), fluorescein and luminol were used to enhance the blood contaminated impressions. The enhancement techniques in this study were used successfully to enhance the impressions in blood on light coloured surfaces, however, only fluorescent and/or chemiluminescent techniques allowed visualisation on dark coloured fabrics, denim and leather. Luminol was the only technique to enhance footwear impressions made in blood on all the fabrics investigated in this study. PMID:21889107

  10. A novel technique of impression procedure in a hemimaxillectomy patient with microstomia.

    PubMed

    Deogade, Suryakant C

    2012-01-01

    A restricted mouth opening in hemimaxillectomy patient can create a significant problem with the insertion and the removal of the obturator prosthesis. Even it poses a problem in impression making due to small oral opening. A modification of the standard impression procedure is often necessary to accomplish an acceptable impression in the fabrication of a successful prosthesis. Sectional trays are a good option for such patients. This paper describes a novel technique of impression procedure and a method of fabricating a sectional tray with the anterior and the posterior locking mechanism for a hemimaxillectomy patient with limited oral opening. PMID:23316395

  11. Carriage of oral flora on irreversible hydrocolloid and elastomeric impression materials.

    PubMed

    Samaranayake, L P; Hunjan, M; Jennings, K J

    1991-02-01

    This study assessed the carriage and persistence of oral flora on irreversible hydrocolloid and elastomeric impression materials. In the first part of the study, a single isolate each of Streptococcus mutans, Escherichia coli, Staphylococcus aureus, and Candida albicans were inoculated onto each of two elastomeric and two irreversible hydrocolloid impression surfaces artificially created in vitro. Then the inoculum was discarded, samples of impression material (13 mm in diameter) were removed over a 5-hour period, and the remainder of viable organisms were estimated. In the second part of the study, impressions were made from 21 dentate and eight edentulous patients, and bacterial counts were estimated as described. The results showed twofold to fivefold retention of bacteria on the irreversible hydrocolloids compared with the elastomeric impression surfaces. With all impression materials, the number of viable bacteria retained within 5 hours decreased 65% to 98% except for the "disinfectant" irreversible hydrocolloid Blueprint Asept, which totally destroyed the organisms in less than 3 minutes. It is concluded that the total bacterial "load" on impression surfaces is relatively low and decreases rapidly after impression making. However, disinfection of impression surfaces should be mandatory to prevent cross-infection. PMID:2051359

  12. The effect of a range of disinfectants on the dimensional accuracy of some impression materials.

    PubMed

    Jagger, D C; Al Jabra, O; Harrison, A; Vowles, R W; McNally, L

    2004-12-01

    In this study the dimensional accuracy of two model materials; dental stone and plaster of Paris, reproduced from three commonly used impression materials; alginate, polyether and addition-cured silicone, retained by their adhesives in acrylic resin trays and exposed to four disinfectant solutions was evaluated. Ninety casts were used to investigate the effect of the four disinfectants on the dimensional accuracy of alginate, polyether and addition-cured silicone impression material. For each impression material 30 impressions were taken, half were poured in dental stone and half in plaster of Paris. The disinfectants used were Dimenol, Perform-ID, MD-520, and Haz-tabs. Measurements were carried out using a High Precision Reflex Microscope. For the alginate impressions only those disinfected by 5-minute immersion in Haz-tabs solution and in full-strength MD 520 were not adversely affected by the disinfection treatment. All polyether impressions subjected to immersion disinfection exhibited a clinically acceptable expansion. Disinfected addition-cured silicone impressions produced very accurate stone casts. Those disinfected by spraying with fill-strength Dimenol produced casts that were very similar to those left as controls, but those treated by immersion disinfection exhibited negligible and clinically acceptable expansion. The results of the studied demonstrated that the various disinfection treatments had different effects on the impression materials. It is important that an appropriate disinfectant is used for each type of impression material. PMID:15691188

  13. Preparation and application of low molecular weight poly(vinyl chloride). III mechanical properties of blended poly(vinyl chloride)

    SciTech Connect

    Yamamoto, Kikuo; Maehala, Takashi; Mitani, Katsuo; Mizutani, Yukio )

    1993-11-05

    The blending effect of poly(vinyl chloride) with relatively higher molecular weight (HMW-PVC) and relatively lower molecular weight (LMW-PVC) has been investigated by measuring various mechanical properties: melt properties, tensile strength, tensile modulus, and impact strength. The blended PVC has slightly improved melt properties in comparison with the HMW-PVC used. The tensile strength of the blended PVC is related to the weight-average polymerization degree (Pw) of LMW-PVC and the LMW-PVC content. At the LMW-PVC content of 20%, the tensile strength of blended PVC is a maximum: approximately 58 MPa.

  14. Li(+)- and Eu(+)-doped poly(?-caprolactone)/siloxane biohybrid electrolytes for electrochromic devices.

    PubMed

    Fernandes, M; Nobre, S S; Rodrigues, L C; Gonalves, A; Rego, R; Oliveira, M C; Ferreira, R A S; Fortunato, E; Silva, M M; Carlos, L D; Bermudez, V de Zea

    2011-08-01

    The sol-gel process has been successfully combined with the "mixed cation" effect to produce novel luminescent and ion conducting biohybrids composed of a diurethane cross-linked poly(?-caprolactone) (PCL530)/siloxane hybrid network (PCL stands for the poly(?-caprolactone) biopolymer and 530 is the average molecular weight in gmol(-1)) doped with a wide range of concentrations of lithium and europium triflates (LiCF(3)SO(3) and Eu(CF(3)SO(3))(3), respectively) (molar ratio of ca. 50:50). The hybrid samples are all semicrystalline: whereas at n = 52.6 and 27.0 (n, composition, corresponds to the number of (C(?O)(CH(2))(5)O) repeat units of PCL(530) per mixture of Li(+) and Eu(3+) ions) a minor proportion of crystalline PCL(530) chains is present, at n = 6.1, a new crystalline phase emerges. The latter electrolyte is thermally stable up to 220 C and exhibits the highest conductivity over the entire range of temperatures studied (3.7 10(-7) and 1.71 10(-4) S cm(-1) at 20 and 102 C, respectively). According to infrared spectroscopic data, major modifications occur in terms of hydrogen bonding interactions at this composition. The electrochemical stability domain of the biohybrid sample with n = 27 spans more than 7 V versus Li/Li(+). This sample is a room temperature white light emitter. Its emission color can be easily tuned across the Commission Internationale d'E?clairage (CIE) chromaticity diagram upon simply changing the excitation wavelength. Preliminary tests performed with a prototype electrochromic device (ECD) comprising the sample with n = 6.1 as electrolyte and WO(3) as cathodically coloring layer are extremely encouraging. The device exhibits switching time around 50 s, an optical density change of 0.15, good open circuit memory under atmospheric conditions (ca. 1 month) and high coloration efficiency (577 cm(2) C(-1) in the second cycle). PMID:21774498

  15. 40 CFR 721.9516 - Siloxanes and silicones, 3-[(2-aminoethyl) amino]propyl Me, di-Me, reaction products with...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., di-Me, reaction products with polyethylene-polypropylene glycol Bu glycidal ether. 721.9516 Section... Substances § 721.9516 Siloxanes and silicones, 3- propyl Me, di-Me, reaction products with polyethylene..., reaction products with polyethylene-polypropylene glycol Bu glycidyl ether (PMN P-97-740; CAS No....

  16. 40 CFR 721.9516 - Siloxanes and silicones, 3-[(2-aminoethyl) amino]propyl Me, di-Me, reaction products with...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., di-Me, reaction products with polyethylene-polypropylene glycol Bu glycidal ether. 721.9516 Section... Substances § 721.9516 Siloxanes and silicones, 3- propyl Me, di-Me, reaction products with polyethylene..., reaction products with polyethylene-polypropylene glycol Bu glycidyl ether (PMN P-97-740; CAS No....

  17. 40 CFR 721.9516 - Siloxanes and silicones, 3-[(2-aminoethyl) amino]propyl Me, di-Me, reaction products with...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., di-Me, reaction products with polyethylene-polypropylene glycol Bu glycidal ether. 721.9516 Section... Substances § 721.9516 Siloxanes and silicones, 3- propyl Me, di-Me, reaction products with polyethylene..., reaction products with polyethylene-polypropylene glycol Bu glycidyl ether (PMN P-97-740; CAS No....

  18. 40 CFR 721.9516 - Siloxanes and silicones, 3-[(2-aminoethyl) amino]propyl Me, di-Me, reaction products with...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., di-Me, reaction products with polyethylene-polypropylene glycol Bu glycidal ether. 721.9516 Section... Substances § 721.9516 Siloxanes and silicones, 3- propyl Me, di-Me, reaction products with polyethylene..., reaction products with polyethylene-polypropylene glycol Bu glycidyl ether (PMN P-97-740; CAS No....

  19. 40 CFR 721.9516 - Siloxanes and silicones, 3-[(2-aminoethyl) amino]propyl Me, di-Me, reaction products with...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., di-Me, reaction products with polyethylene-polypropylene glycol Bu glycidal ether. 721.9516 Section... Substances § 721.9516 Siloxanes and silicones, 3- propyl Me, di-Me, reaction products with polyethylene..., reaction products with polyethylene-polypropylene glycol Bu glycidyl ether (PMN P-97-740; CAS No....

  20. Cross-linked polyvinyl alcohol and method of making same

    SciTech Connect

    Hsu, L.; Philipp, W.H.; Sheibley, D.W.

    1981-06-09

    A film-forming polyvinyl alcohol polymer is mixed with a polyaldehyde-polysaccharide cross-linking agent having at least two monosaccharide units and a plurality of aldehyde groups per molecule, preferably an average of at least one aldehyde group per monosaccharide units. The cross-linking agent, such as a polydialdehyde starch, is used in an amount of about 2.5 to 20% of the theoretical amount required to cross-link all of the available hydroxyl groups of the polyvinyl alcohol polymer. Reaction between the polymer and cross-linking agent is effected in aqueous acidic solution to produce the cross-linked polymer. The polymer product has low electrical resistivity and other properties rendering it suitable for making separators for alkaline batteries. In that event, the mixture of polymer and cross-linking agent is formed into a sheet or film or the like and the film is cut to size and otherwise fabricated into a configuration suitable for a particular end use. The crosslinking reaction is then carried out to produce the final product.

  1. The effect of disinfecting alginate and addition cured silicone rubber impression materials on the physical properties of impressions and resultant casts.

    PubMed

    al-Omari, W M; Jones, J C; Wood, D J

    1998-09-01

    Four commercially available disinfectants were tested and the dimensional stability and detail reproduction of impressions and their resultant casts were measured according to ANSI/ISO specifications. Results showed that alginate impressions immersed in chlorhexidine exhibited considerable dimensional change if not poured immediately. Moreover, alginate impressions soaked in a paraldehyde agent (Virkon) for more than 2 minutes produced casts of inferior surface quality whilst those sprayed and left in contact with phenol derivatives (C&J Spray) for 30 minutes resulted in casts which demonstrated statistically and clinically significant dimensional changes. Addition cured silicone impressions exhibited minimal dimensional change regardless of the disinfection regime employed and the resultant casts were accurate with acceptable surface quality. PMID:10218014

  2. The use of a scannable impression coping and digital impression technique to fabricate a customized anatomic abutment and zirconia restoration in the esthetic zone.

    PubMed

    Lin, Wei-Shao; Harris, Bryan T; Morton, Dean

    2013-03-01

    This report described the fabrication of a customized anatomic abutment and zirconia restoration in the esthetic zone with a digital pathway. The implant level impression was made with a scannable impression coping and intraoral digital scanner. The milled definitive polyurethane cast with corresponding implant analog, customized anatomic abutment, and definitive zirconia restoration were made with a computer-aided design and computer-aided manufacturing (CAD/CAM) process. PMID:23522368

  3. Clinical Evaluation of Different Pre-impression Preparation Procedures of Dental Arch

    PubMed Central

    Arora, Nitin; Arora, Monika; Gupta, Naveen; Agarwal, Manisha; Verma, Rohit; Rathod, Pankaj

    2015-01-01

    Background: Bubbles and voids on the occlusal surface impede the actual intercuspation and pre-impression preparation aims to reduce the incidence of air bubbles and voids as well as influences the quality of occlusal reproduction and actual clinical intercuspation in the articulator. The study was undertaken to determine the influence of different pre-impression preparation procedures of antagonistic dental arch on the quality of the occlusal reproduction of the teeth in irreversible hydrocolloid impressions and to determine most reliable pre-impression preparation method to reduce the incidence of air bubbles. Materials and Methods: A total of 20 subjects were selected having full complement of mandibular teeth from second molar to second molar with well demarcated cusp height. 200 impressions were made with irreversible hydrocolloid material. The impressions were divided into five groups of 40 impressions each and each group had one specific type of pre-impression preparation. All the impressions were poured in die stone. A stereomicroscope with graduated eyepiece was used to count the number of bubbles on the occlusal surface of premolars and molars. The mean and standard deviations were calculated for each group. Mann–Whitney U-test was applied to find the significant difference between different groups. Results: Least bubbles were found in the group in which oral cavity was dried by saliva ejector and fluid hydrocolloid was finger painted onto the occlusal surfaces immediately before the placement of impression tray in the mouth. Conclusion: It was found that finger painting the tooth surfaces with fluid hydrocolloid immediately before the placement of loaded impression tray in the mouth was the most reliable method. The oral cavity can be cleared more easily of excess saliva by vacuum suction rather than by use of an astringent solution. PMID:26229376

  4. 21 CFR 872.3661 - Optical Impression Systems for CAD/CAM.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CAD/CAM) is a device used to record the topographical characteristics of teeth, dental impressions, or... Design and Manufacturing (CAD/CAM) of Dental Restorations; Guidance for Industry and FDA.” For the... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Optical Impression Systems for CAD/CAM....

  5. 21 CFR 872.3661 - Optical Impression Systems for CAD/CAM.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CAD/CAM) is a device used to record the topographical characteristics of teeth, dental impressions, or... Design and Manufacturing (CAD/CAM) of Dental Restorations; Guidance for Industry and FDA.” For the... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Optical Impression Systems for CAD/CAM....

  6. The Effect of Clothing Variation on First Impressions of Female Job Applicants: What to Wear When.

    ERIC Educational Resources Information Center

    Rucker, M.; And Others

    1981-01-01

    Male and female subjects rated a standardized, professionally drawn female in 12 outfits as to impressions they would make in job interviews. The 12 jobs represented combinations of high- and low-status and male-dominated and female-dominated occupations. Discusses outfits and suggests women made better impressions when applying for

  7. "Leer-ics" or Lyrics: Teenage Impressions of Rock 'n' Roll.

    ERIC Educational Resources Information Center

    Prinsky, Lorraine E.; Rosenbaum, Jill L.

    1987-01-01

    This study compared adults' impressions of rock music with those of teenagers and found vast differences. Youths reported hearing subjects relating to their lives such as "growing up" while adults heard more references to sex and violence. Perhaps the differing impressions reflect differences in learning, experience, and literary abilities. (VM)

  8. Managing and Creating an Image in the Interview: The Role of Interviewee Initial Impressions

    ERIC Educational Resources Information Center

    Swider, Brian W.; Barrick, Murray R.; Harris, T. Brad; Stoverink, Adam C.

    2011-01-01

    In employment interviews, individuals use impression management tactics to present themselves as suitable candidates to interviewers. However, not all impression management tactics, or the interviewees who employ them, are effective at positively influencing interview scores. Results of this study indicate that the relationship between impression…

  9. Instructional Strategies for Achieving a Positive Impression in Computer-Mediated Communication (CMC) Distance Education Courses.

    ERIC Educational Resources Information Center

    Liu, Yuliang; Ginther, Dean W.

    With the rapid development of computer technology in recent years, distance education, and especially computer-mediated communication (CMC), has expanded very quickly. The application of computer technology in education presents many unanswered questions, including issues related to impression formation and impression management in

  10. Older and Younger Adults First Impressions From Faces: Similar in Agreement but Different in Positivity

    PubMed Central

    Zebrowitz, Leslie A.; Franklin, Robert G.; Hillman, Suzanne; Boc, Henry

    2014-01-01

    People readily form first impressions from faces, with consensual judgments that have significant social consequences. Similar impressions are shown by children, young adults (YA), and people from diverse cultures. However, this is the first study to systematically investigate older adults (OA) impressions. OA and YA showed similar levels of within-age agreement in their impressions of competence, health, hostility, and trustworthiness. Both groups also showed stronger within- than between age agreement. Consistent with other evidence for age-related increases in positivity, OA showed more positive impressions of the health, hostility, and trustworthiness of faces. These effects tended to be strongest for the most negatively valenced faces, suggesting that they derive from OA lesser processing of negative cues rather than greater processing of positive cues. An own-age bias in impressions was limited to greater OA positivity in impressions of the hostility of older faces, but not younger ones. Although OA and YA differed in vision and executive function, only OA slower processing speed contributed to age differences in impression positivity. Positivity effects in OA have not been previously linked to processing speed, and research investigating possible explanations for this effect would be worthwhile. PMID:23276216

  11. Personality and workplace impression management: correlates and implications.

    PubMed

    Bourdage, Joshua S; Wiltshire, Jocelyn; Lee, Kibeom

    2015-03-01

    In the present study, we investigated the role of personality in understanding impression management (IM) behaviors. We hypothesized that the HEXACO model of personality could provide an intricate understanding of the dispositional bases of IM behaviors, as well as coworkers' ability to accurately perceive the IM of those they work with. Using 2 samples (N = 176 and N = 366), we found that the common core underlying 5 IM behaviors possesses a strong negative relationship with the personality trait of Honesty-Humility, such that individuals low in this trait were more likely to report using all IM behaviors. Furthermore, we found that the unique variance associated with specific IM behaviors can be understood using other traits included in the HEXACO personality model, including Emotionality, Extraversion, Agreeableness, and Conscientiousness. In a subset of the data (N = 100), we examined self-coworker convergence in IM and personality. We found that while coworkers are adequate at judging traditional personality traits, the self-coworker convergence for all 5 IM behaviors, as well as the personality trait of Honesty-Humility, were not significant. This adds to a growing body of evidence that coworkers may not be good at accurately perceiving IM or Honesty-Humility in the workplace. PMID:25243995

  12. Lateral orbitofrontal cortex links social impressions to political choices.

    PubMed

    Xia, Chenjie; Stolle, Dietlind; Gidengil, Elisabeth; Fellows, Lesley K

    2015-06-01

    Recent studies of political behavior suggest that voting decisions can be influenced substantially by "first-impression" social attributions based on physical appearance. Separate lines of research have implicated the orbitofrontal cortex (OFC) in the judgment of social traits on the one hand and economic decision-making on the other, making this region a plausible candidate for linking social attributions to voting decisions. Here, we asked whether OFC lesions in humans disrupted the ability to judge traits of political candidates or affected how these judgments influenced voting decisions. Seven patients with lateral OFC damage, 18 patients with frontal damage sparing the lateral OFC, and 53 matched healthy participants took part in a simulated election paradigm, in which they voted for real-life (but unknown) candidates based only on photographs of their faces. Consistent with previous work, attributions of "competence" and "attractiveness" based on candidate appearance predicted voting behavior in the healthy control group. Frontal damage did not affect substantially the ability to make competence or attractiveness judgments, but patients with damage to the lateral OFC differed from other groups in how they applied this information when voting. Only attractiveness ratings had any predictive power for voting choices after lateral OFC damage, whereas other frontal patients and healthy controls relied on information about both competence and attractiveness in making their choice. An intact lateral OFC may not be necessary for judgment of social traits based on physical appearance, but it seems to be crucial in applying this information in political decision-making. PMID:26041918

  13. Measuring turbulent gust impressions in a forested canopy

    NASA Astrophysics Data System (ADS)

    Hiscox, A.; Ertell, K.

    2014-12-01

    The temporal and spatial characteristics of tree-sway motions and their aerodynamic interactions with coherent turbulence wind fields in a forest (Howland Forest, ME) are examined. Year round measurements of turbulence where taken at heights, above, below, and in the live crown. Additionally measurements of tree bole motion were taken simultaneously for 150 trees surrounding the main meteorological tower. To identify the gust impressions and further understand the timing, spacing and intensity of momentum flux, a a multi-resolution decomposition (MRD) technique was used to find the dominant eddy size. Fourier analysis was applied to each tree for the corresponding time and changes in dominant tree frequency were mapped over time. Results indicate that the most coherency in stand-scale motion occurs when frequency changes are mapped at the same time resolution of the dominant eddy size. Through a mapping-displacement comparison, the sub-mesoscale motions of a canopy atmosphere and their effect on the tree's movement as well as fluxes of energy will be better understood.

  14. Dimensional stability of newer alginate impression materials over seven days.

    PubMed

    Wandrekar, Siddharth; Juszczyk, Andrzej S; Clark, Robert K F; Radford, David R

    2010-12-01

    The aim of this study was to determine the dimensional stability of the so called '5 day stable' alginates. Ten specimens each of three alginate materials were prepared using a standardised impression technique and a typodont model. Travelling microscope measurements were recorded for six distances at 24 hour intervals. SEM and EDX analysis was undertaken. Changes in dimension over time and differences between materials were tested using analysis of variance. 95% confidence intervals were calculated for the percentage change for comparison with a target of 1.5% based on the ISO Standard. Statistically significant dimensional changes were observed in some measured distances for all materials, but only six out of fifty four distances measured at 1, 5 and 7 days in three materials showed 95% confidence intervals that included the 1.5% ISO standard. There were no statistically significant differences in the proportional change between the three materials. The three materials showed similar appearance under SEM and similar composition by EDX analysis. It is concluded that all materials demonstrated good dimensional stability over the recommended maximum of 5 days. PMID:21265435

  15. A video Clinical Global Impression (CGI) in obsessive compulsive disorder.

    PubMed

    Bourredjem, Abderrahmane; Pelissolo, Antoine; Rotge, Jean-Yves; Jaafari, Nematollah; Machefaux, Sebastien; Quentin, Solene; Bui, Eric; Bruno, Nicolas; Pochon, Jean-Baptiste; Polosan, Mircea; Baup, Nicolas; Papetti, Franois; Chreau, Isabelle; Arbus, Christophe; Mallet, Luc; du Montcel, Sophie Tezenas

    2011-03-30

    The Clinical Global Impression scale (CGI) is frequently used in clinical research because of its face validity and ease of use but data on its reliability are scarce. Our goal was to estimate the reliability of the scale and compare reliability between face-to-face and video scoring. We analyzed 50 different video interviews recorded during 5 visits of a crossover trial to study the effect of subthalamic nucleus stimulation. Six specialized clinicians rated the CGI using these videos, providing 300 different ratings. The intraclass correlation was lower at inclusion (0.30 [0.13-0.50]) than at later visits (0.68 [0.61-0.80]). Reliability was not influenced by the patients' stimulation status. The mean of at least two independent evaluations of the video is needed to achieve an ICC greater than 0.8. The video CGI is a valid clinical outcome measure suitable for clinical trials (ClinicalTrials.gov number, NCT00169377). PMID:20621362

  16. Try to find me: social anxiety and peer first impressions.

    PubMed

    Aiken, Audrey; Human, Lauren J; Alden, Lynn E; Biesanz, Jeremy C

    2014-11-01

    Following initial interactions, some people are less willing to pursue ongoing contact with socially anxious individuals than with those who are not socially anxious. To better understand this process, we conducted two studies that examined peers' first impressions of target individuals. Unacquainted individuals (N=104 and 114) participated in round robin, unstructured interactions in groups of 3 to 10 and then rated each partner and themselves on items reflecting the Big Five personality dimensions. The ratings were analyzed according to Biesanz's (2010) social accuracy model of interpersonal perception, which distinguishes the positivity from the accuracy of social judgments. Study 1 revealed that perceivers did not view socially anxious targets more negatively or as less likable than non-socially anxious targets but were less able to recognize their unique personality features. Study 2 replicated those findings and indicated that perceivers' difficulties recognizing socially anxious targets' unique features were not due to negative biases in the socially anxious targets' self-ratings or to general psychological maladjustment. The findings are consistent with cognitive models, which underscore the role of self-concealment in social anxiety disorder. PMID:25311293

  17. Chemical enhancement of footwear impressions in blood on fabric - part 1: protein stains.

    PubMed

    Farrugia, Kevin J; Savage, Kathleen A; Bandey, Helen; Nic Daéid, Niamh

    2011-09-01

    A range of protein stains were utilised for the enhancement of footwear impressions on a variety of fabric types of different colours with blood as a contaminant. A semi-automated stamping device was used to deliver test impressions at a set force to minimise the variability between impressions; multiple impressions were produced and enhanced by each reagent to determine the repeatability of the enhancement. Results indicated that while most protein stains used in this study successfully enhanced impressions in blood on light coloured fabrics, background staining caused interference on natural fabrics. Enhancement on dark coloured fabrics was only achieved using fluorescent protein stains, as non-fluorescent protein stains provided poor contrast. A further comparison was performed with commercially available protein staining solutions and solutions prepared within the laboratory from the appropriate chemicals. Both solutions performed equally well, though it is recommended to use freshly prepared solutions whenever possible. PMID:21889106

  18. A novel method for the photographic recovery of fingermark impressions from ammunition cases using digital imaging.

    PubMed

    Porter, Glenn; Ebeyan, Robert; Crumlish, Charles; Renshaw, Adrian

    2015-03-01

    The photographic preservation of fingermark impression evidence found on ammunition cases remains problematic due to the cylindrical shape of the deposition substrate preventing complete capture of the impression in a single image. A novel method was developed for the photographic recovery of fingermarks from curved surfaces using digital imaging. The process involves the digital construction of a complete impression image made from several different images captured from multiple camera perspectives. Fingermark impressions deposited onto 9-mm and 0.22-caliber brass cartridge cases and a plastic 12-gauge shotgun shell were tested using various image parameters, including digital stitching method, number of images per 360° rotation of shell, image cropping, and overlap. The results suggest that this method may be successfully used to recover fingermark impression evidence from the surfaces of ammunition cases or other similar cylindrical surfaces. PMID:25537854

  19. Capturing finger and palm impressions using a hand cream and thermochromatic paper.

    PubMed

    Bond, John W

    2013-09-01

    An inkless set of finger and palm impressions has been obtained on thermochromatic paper by incorporating the protic solvent butylene glycol into a base hand cream mixture, which is rubbed into the hands for 30sec before donation. This requires no washing of the hands before or after donation, removing many of the difficulties associated with inked impressions. In a random trial of 50 male and 50 female participants (mean age 41years), 96 found the hand cream pleasant and easy to use and all produced identifiable finger and palm impressions. Following donation, participants continued to rub the hand cream into their hands. Impressions were visible immediately after donation and have not exhibited fading 2years after being taken. 10% of participants produced impressions that captured third-level detail, the variation between participants being thought to be associated with the amount of pressure applied during donation. PMID:23865966

  20. Fertilizing ROSES through the STEM: Interdisciplinary Modules as Pre-service Research Experiences for Secondary STEM Educators (IMPRESS-Ed)

    NASA Astrophysics Data System (ADS)

    Magee, N. B.; Kavic, M.; Benoit, M. H.; Wiita, P.

    2011-12-01

    IMPRESS-Ed is a program designed to provide authentic summer research experiences in the space, earth, and atmospheric sciences for pre-service K-12 educators at The College of New Jersey (TCNJ). In 2011, the program involved five students and took place over eight weeks with recruitment occurring during the preceding academic year. The program was divided into two modules: A common core module and an individual mentored research experience. The common module consisted of three units focusing on data-driven pedagogical approaches in astrophysics, tectonophysics, and atmospheric science, respectively. The common module also featured training sessions in observational astronomy, and use of a 3D geowall and state of the art planetarium. Participants in the program are also offered the opportunity to utilize the available TCNJ facilities with their future students. Given that a large number of graduates from the TCNJ take positions in local New Jersey schools, the opportunity to make use of these facilities at a future time would be of great significance to them and their future students. The individual mentored research module matched student interests with potential projects. Research led by M.H. Benoit analyzed gravity data from the NASA-GRACE mission to find lithospheric density contrasts beneath the eastern US. A student working with N.B. Magee used data from NASA satellites CALIPSO, CloudSat, and AQUA-MODIS to study the dynamics of convective cloud tops. Research projects led by M. Kavic performed simulations to investigate the possibility of detecting superconducting cosmic strings using radio observations and also designed and constructed a radio interferometer based on the NASA's Radio-Jove program. P. Wiita supervised a research project studying star-forming regions of active galaxies through analysis of images from NASA's Hubble Space Telescope and GALEX. The research program was also incorporated into the framework of the TCNJ Mentored Undergraduate Summer Experience (MUSE), which provided weekly seminars and community-building activities for approximately 85 undergraduate summer researchers. This program concludes with a large research symposium in which all participants present the results of their research efforts. Initial evaluation of the program was highly positive. All five students demonstrated strong gains in earth and space science literacy compared to a baseline measurement. Each student also reported gaining confidence to incorporate data and research-driven instruction in the space and earth sciences into the K-12 STEM classroom setting. All five research projects were also quite successful: several of the students plan to continue research during the academic year and two students are presenting research findings as first authors here at AGU. Other research results are likely to be presented at this year's American Astronomical Society meeting.

  1. An evaluation of dimensional accuracy of one-step and two-step impression technique using addition silicone impression material: an in vitro study.

    PubMed

    Pande, Neelam A; Parkhedkar, R D

    2013-09-01

    The study is aimed to evaluate the dimensional accuracy, the effect of undercut of two different configurations and the elastic recovery of addition silicone impression material assessed indirectly, by measuring the dimensions on stone models recorded from the impression of the master model, using one-step and two-step impression technique, for addition silicone impression materials. Measurements are taken to evaluate horizontal or linear and vertical dimensional changes, of the abutment V and abutment C from the stainless steel model. Heavy body/light body material is used for making one-step impression technique in a custom tray. Putty/light body is used for taking two-step technique in a stock metal tray. Improved die stone is used for pouring the impression. The different 11 locations on the dies produced by two different techniques are measured microscopically on image analyzer and compared with those of stainless steel model. Anova test was applied to test the differences of mean values of inter and intra abutment measurements, to calculate p value. Unpaired t test was applied to calculate t value. Results showed less deviation of stone models produced by one-step technique from stainless steel model, whereas the deviation of stone models produced by two-step is comparatively more. (p < 0.01). This difference of deviation is significantly less in one-step as compared to two-step technique. One-step is sufficiently dimensionally accurate than two-step technique in conjunction with addition silicone impression material. They have the best elastic recovery from the two undercut configurations. PMID:24431743

  2. Vitrification of Polyvinyl Chloride Waste from Korean Nuclear Power Plants

    SciTech Connect

    Sheng, Jiawei; Choi, Kwansik; Yang, Kyung-Hwa; Lee, Myung-Chan; Song, Myung-Jae

    2000-02-15

    Vitrification is considered as an economical and safe treatment technology for low-level radioactive waste (LLW) generated from nuclear power plants (NPPs). Korea is in the process of preparing for its first ever vitrification plant to handle LLW from its NPPs. Polyvinyl chloride (PVC) has the largest volume of dry active wastes and is the main waste stream to treat. Glass formulation development for PVC waste is the focus of study. The minimum additive waste stabilization approach has been utilized in vitrification. It was found that glasses can incorporate a high content of PVC ash (up to 50 wt%), which results in a large volume reduction. A glass frit, KEP-A, was developed to vitrify PVC waste after the optimization of waste loading, melt viscosity, melting temperature, and chemical durability. The KEP-A could satisfactorily vitrify PVC with a waste loading of 30 to 50 wt%. The PVC-frit was tolerant of variations in waste composition.

  3. Friction loss in straight pipes of unplasticized polyvinyl chloride.

    PubMed

    Iwasaki, T; Ojima, J

    1996-01-01

    In order to design proper ductwork for a local exhaust system, airflow characteristics were investigated in straight pipes of unplasticized polyvinyl chloride (PVC). A linear decrease in static pressure was observed downstream at points from the opening of the VU pipes (JIS K 6741) located at distances greater than 10 times the pipe diameter, for velocities ranging between 10.18-36.91 m/s. Roughness inside pipes with small diameters was found to be 0.0042-0.0056 mm and the friction factor was calculated on the basis of Colebrook's equation for an airflow transition zone. An extended friction chart was then constructed on the basis of the roughness value and the friction factor. This chart can be applied when designing a local exhaust system with the ducts of diameters ranging from 40 to 900 mm. The friction loss of the PVC pipe was found to be approximately 2/3 of that of a galvanized steel pipe. PMID:8768669

  4. Evaluation of a Polyvinyl Toluene Neutron Counter Array

    SciTech Connect

    Robert Hayes

    2008-03-01

    The purpose of this article is to simulate the performance of a neutron detector array for empirical configuration optimization and preliminary algorithm evaluation. Utilizing a compact array of borated Polyvinyl Toluene light pipes and Photomultiplier Tubes, pulse shape analysis, standard spectral histogramming, and multiplicity counting can enable neutron measurements for multiple applications. Results demonstrate that analysis with Monte Carlo N-Particle (MCNP) can be used to obtain a better understanding of field measurement results and aid in algorithm development for unfolding in conjunction with detector optimization. Use of a handheld neutron spectrometer has promise of widespread applicability. By correlating MCNP results with empirical measurements, substantial confidence can be placed on predicting detector response to sufficiently similar spectral sources under alternate experimental configurations. In addition, use of the detector has substantial promise for operational health physics applications.

  5. Evaluation of vascular grafts based on polyvinyl alcohol cryogels.

    PubMed

    Conconi, Maria Teresa; Borgio, Luca; Di Liddo, Rosa; Sartore, Leonardo; Dalzoppo, Daniele; Amist, Pietro; Lora, Silvano; Parnigotto, Pier Paolo; Grandi, Claudio

    2014-09-01

    The present study designed and developed blood vessel substitutes (BVSs) composed of polyvinyl alcohol (PVA) cryogels. The in vitro results demonstrated that the coating of the polymer with lyophilized decellularized vascular matrix (DVM) greatly enhanced the adhesion of human umbilical vein endothelial cells (HUVECs). However, when PVA?DVM BVSs were implanted into the abdominal aorta of Sprague?Dawley rats, DVM was identified as a highly thrombogenic surface resulting in the mortality of all animals 3?4 days after surgery. By contrast, all rats implanted with PVA survived and were sacrificed after 12 months. The luminal surface of the explanted grafts was completely covered by endothelial cells and the inner diameter was similar to that of the original vessel. In conclusion, the present study indicated that PVA may be considered as a promising biomaterial for the fabrication of artificial vessels. PMID:24969541

  6. Silver Nanoparticle Fabrication by Laser Ablation in Polyvinyl Alcohol Solutions

    NASA Astrophysics Data System (ADS)

    Halimah Mohamed., K.; Mahmoud Goodarz, Naseri; Amir, Reza Sadrolhosseini; Arash, Dehzangi; Ahmad, Kamalianfar; Elias, B. Saion; Reza, Zamiri; Hossein Abastabar, Ahangar; Burhanuddin, Y. Majlis

    2014-07-01

    A laser ablation technique is applied for synthesis of silver nanoparticles in different concentrations of polyvinyl alcohol (PVA) aqueous solution. The ablation of high pure silver plate in the solution is carried out by a nanosecond Q-switched Nd:YAG pulsed laser. X-ray diffraction and transmission electron microscopy are implemented to explore the particles sizes. The effects of PVA concentrations on the absorbance of the silver nanoparticles are studied as well, by using a UV-vis spectrophotometer. The preparation process is carried out for deionized water as a reference sample. The comparison of the obtained results with the reference sample shows that the formation efficiency of nanoparticles in PVA is much higher and the sizes of particles are also smaller.

  7. Cross-linked polyvinyl alcohol films as alkaline battery separators

    SciTech Connect

    Sheibley, D.W.; Gonzalez-Sanabria, O.D.; Manzo, M.A.

    1983-02-01

    Cross-linking methods have been investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: PVA-dialdehyde blends post-treated with an acid or acid periodate solution and PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality. Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. Then pilotplant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide-zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  8. Cross-linked polyvinyl alcohol films as alkaline battery separators

    SciTech Connect

    Sheibley, D.W.; Manzo, M.A.; Gonzalez-Sanabria, O.D.

    1982-03-01

    Cross-linking methods were investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. The pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide - zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  9. Preparation and characterization of bioglass/polyvinyl alcohol composite hydrogel.

    PubMed

    Xu, Hong; Wang, Yingjun; Zheng, Yudong; Chen, Xiaofeng; Ren, Li; Wu, Gang; Huang, Xiaoshan

    2007-06-01

    In order to form firm active fixation with the adjacent bone, a new kind of bioactive composite hydrogel was prepared with polyvinyl alcohol (PVA) and bioglass (BG) through ultrasonic dispersion, heat-high-pressure and freeze/thawed technique. A digital speckle correlation method (DSCM) was utilized to characterize the mechanical properties of the series of BG/PVA composites. Results showed that at different load pressures, the composite hydrogel displayed different displacement and deformation in the V field. Results also showed that an increase of PVA percentage (15-30 wt%) or of bioglass percentage (2-10 wt%) in composite hydrogel could lead to an increase in the elastic compression modulus. Scanning electron microscope results indicated that bioglass was uniformly dispersed in the BG/PVA composite hydrogel. The BG/PVA composite hydrogel shows a promising prospect as a new bionic cartilage implantation material. PMID:18458437

  10. Surface Sulfonation of Polyvinyl Chloride by Plasma for Antithrombogenicity

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Chen, Yashao

    2004-06-01

    To enhance the blood compatibility of Polyvinyl Chloride (PVC) film, the film was modified by SO2/O2 gas plasma treatment. The effect of surface sulfonation of PVC treated by various SO2/O2 gas plasma depended on the volume ratio O2/(SO2 + O2). When the volume ratio was 0.5, the effect of sulfonation was the best. Sulfonic acid groups were specifically and efficiently introduced onto the PVC surface, which was proved by x-ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR-FTIR) spectroscopy. The surface microstructure of modified PVC film was studied with scanning electron microscopy (SEM). The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and plasma recalcification time (PRT) tests and platelet adhesion experiment. The results indicated that the antithrombogenicity of modified PVC was improved remarkably.

  11. Hemocompatibility study of a bacterial cellulose/polyvinyl alcohol nanocomposite.

    PubMed

    Leito, Alexandre F; Gupta, Swati; Silva, Joo Pedro; Reviakine, Ilya; Gama, Miguel

    2013-11-01

    Bacterial cellulose (BC) has been suggested to be a suitable biomaterial for the development of cardiovascular grafts. The combination of BC with polyvinyl alcohol (PVA) results in nanocomposites with improved properties. Surprisingly, there are very few studies on the BC-blood interaction. This is the focus of this paper. We present the first thorough assessment of the hemocompatibility of the BC/PVA nanocomposite. Whole blood clotting time, plasma recalcification, Factor XII activation, platelet adhesion and activation, hemolytic index and complement activation are all determined. The platelet activation profiles on BC and BC/PVA surfaces are comprehensively characterized. BC and BC/PVA outperformed ePTFE--used as a point of comparison--thus evidencing their suitability for cardiovascular applications. PMID:23880088

  12. Immobilization of enzyme into poly(vinyl alcohol) membrane

    SciTech Connect

    Imai, K.; Shiomi, T.; Uchida, K.; Miya, M.

    1986-11-01

    Glucoamylase, invertase, and cellulase were entrapped within poly(vinyl alcohol) (PVA) membrane cross-linked by means of irradiation of ultraviolet light. The conditions for immobilization of glucoamylase were examined with respect to enzyme concentration in PVA, sensitizer (sodium benzoate) concentration in PVA, irradiation time, and membrane thickness. Various characteristics of immobilized glucoamylase were evaluated. Among them, the pH activity curve for the immobilized enzyme was superior to that for the native one, and thermal stability was improved by immobilization with bovine albumin. The apparent Km was larger for immobilized glucoamylase than for the native one, while Vmax was smaller for the immobilized enzyme. Also, the apparent Km appeared to be affected by the molecular size of the substrate. Further, immobilized invertase and cellulase showed good stabilities in repeating usage. 9 references.

  13. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1982-01-01

    Cross-linking methods were investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. The pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide - zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  14. Polyvinyl alcohol coating of polystyrene inertial confinement fusion targets

    NASA Technical Reports Server (NTRS)

    Annamalai, P.; Lee, M. C.; Crawley, R. L.; Downs, R. L.

    1985-01-01

    An inertial confinement fusion (ICF) target made of polystyrene is first levitated in an acoustic field. The surface of the target is then etched using an appropriate solution (e.g., cyclohexane) to enhance the wetting characteristics. A specially prepared polyvinyl alcohol solution is atomized using an acoustic atomizer and deposited on the surface of the target. The solution is air dried to form a thin coating (2 microns) on the target (outside diameter of about 350-850 microns). Thicker coatings are obtained by repeated applications of the coating solutions. Preliminary results indicate that uniform coatings may be achievable on the targets with a background surface smoothness in the order of 1000 A.

  15. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1983-01-01

    Cross-linking methods have been investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. Then pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide-zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  16. Behaviour of polymer (poly(vinyl chloride)) membrane systems

    NASA Astrophysics Data System (ADS)

    Moody, G. J.; Thomas, J. D. R.

    Radiotracer studies are discussed for alkaline earth metal ion-permeation through poly(vinyl chloride) matrix membranes containing sensors based on organophosphates and on the tetraphenylborates of the complex of barium with a polyethoxylate. There is selective permeation of calcium ions, from among alkaline earth cations, through the phosphate-based membranes, but the polyethoxylate membranes do not permeate ions to any significant extent. The phosphate-based membranes maintain stable current flows over prolonged periods under conditions of applied potential and are not affected by polarity reversals. For example, current flows of 5 - 6 ?A are maintained for 2 V applied potential. Current flows fall rapidly for the polyethoxylate membranes and do not recover on repeated polarity reversal of the applied potential. The possibility of the permeation of metal ions of the first transition series through the phosphate-based membranes is discussed briefly.

  17. Estimation of mechanochemical dechlorination rate of poly(vinyl chlorde).

    PubMed

    Mio, Hiroshi; Saeki, Shu; Kano, Junya; Saito, Fumio

    2002-03-15

    Poly(vinyl chloride) (PVC) was ground in air with CaO in the presence of quartz powder as a grinding aid by a small-scale planetary ball mill to investigate the relation of the dechlorination rate of PVC with the impact energy of the balls calculated from a computer simulation based on the Discrete Element Method under various conditions. Mechanochemical dechlorination proceeds as the grinding progresses and is improved with an increase in both the mill speed and the amount of balls introduced into the mill. The same trend can be seen in the relation between the specific normal impact energy of the balls and the rotational speed. The relationship between the observed dechlorination rate and the computed normal impact energy of the balls is linear, with a correlation coefficient of 0.965. This relationship can be used to estimate the dechlorination rate of PVC in a large-scale planetary ball mill. PMID:11944691

  18. Surface alignment, anchoring transitions, optical properties, and topological defects in the thermotropic nematic phase of organo-siloxane tetrapodes.

    PubMed

    Kim, Young-Ki; Senyuk, Bohdan; Shin, Sung-Tae; Kohlmeier, Alexandra; Mehl, Georg H; Lavrentovich, Oleg D

    2014-01-21

    We perform optical, surface anchoring, and textural studies of an organo-siloxane "tetrapode" material in the broad temperature range of the nematic phase. The optical, structural, and topological features are compatible with the uniaxial nematic order rather than with the biaxial nematic order, in the entire nematic temperature range -25 C < T < 46 C studied. For homeotropic alignment, the material experiences surface anchoring transition, but the director can be realigned into an optically uniaxial texture by applying a sufficiently strong electric field. The topological features of textures in cylindrical capillaries, in spherical droplets and around colloidal inclusions are consistent with the uniaxial character of the long-range nematic order. In particular, we observe isolated surface point defects - boojums and bulk point defects - hedgehogs that can exist only in the uniaxial nematic liquid crystal. PMID:24651889

  19. Preparation, characterization, and evaluation of a heparin-benzalkonium chloride-graphite oxide/polymethylvinyl siloxane nanocomposite.

    PubMed

    Zhou, Ninglin; Xu, Dong; Zhang, Jun; Ma, Yinchen; Yuan, Jiang; Shen, Jian

    2012-06-01

    A heparin (Hep)-benzalkonium chloride (C12)-graphite oxide (GO)/polymethylvinyl siloxane (PMVS) nancomposite was prepared via melting intercalation at different temperatures. Scanning electron microscopy images showed the Hep-C12-GO was well dispersed into PMVS processed at 100C. Mechanical properties measurement demonstrated that the addition of Hep-C12-GO maintained its strength. XRD data indicated that Hep-C12-GO lost its layer structure completely. FTIR results suggested that Hep-C12-GO interacted with PMVS strongly. Antibacterial activity of resulting nanocomposite was evaluated using zone of inhibition and bacteria adhesion methods. The results demonstrated that Hep-C12-GO/PMVS had a good capability against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Antithrombogenic properties were assessed using platelet adhesion experiment and the results showed that Hep-C12-GO/PMVS was blood-compatible. PMID:22447679

  20. Growth characteristics of selected fungi on polyvinyl film

    SciTech Connect

    Roberts, W.T.; Davidson, P.M.

    1986-04-01

    The objective of this study was to determine if plasticized polyvinyl chloride film would support the growth of any of nine species of fungi. The film was suspended in distilled water with no nutrients or with glucose or ammonium sulfate. Spores of each of the test species were inoculated into the suspension medium, and the mixture was incubated at 30/sup 0/C for up to 18 weeks. Most species were found to be capable of utilizing the film for carbon or nitrogen when the other nutrient was supplied. Only two species, Aspergillus fischeri and Paecilomyces sp., were found to be capable of utilizing components of the film without added nutrients. Components of the polyvinyl chloride film were then incorporated into mineral salts medium to determine if these components could serve as carbon sources in the presence of ammonium nitrate. The only component found to be utilized by all the fungi as a carbon source was epoxidized oil, a plasticizer-stabilizer. Calcium-zinc stearate was an available carbon source for all except the Penicillium and Verticillium strains. The only other component utilized was a stearamide, which was metabolized solely by the Aspergillus sp. Only the stearamide contained enough nitrogen to serve as a primary source in the film. The compound, however, did not support growth of fungi in the presence of glucose. It was theorized that either the nitrogen of the stearamide was more readily available to the fungi in the whole film due to the presence of trace nutrients or the nitrogen was supplied by exogenous sources.

  1. In situ self cross-linking of polyvinyl alcohol battery separators

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Hsu, L. C.; Sheibley, D. W. (Inventor)

    1979-01-01

    A battery separator was produced from a polyvinyl alcohol sheet structure which was subjected to an in situ, self crosslinking process by selective oxidation of the 1,2 diol units present in the polyvinyl alcohol sheet structure. The 1,2 diol units were cleaved to form aldehyde end groups which subsequently crosslink through acetalization of the 1,3 diol units of the polyvinyl alcohol. Selective oxidation was achieved using a solution of a suitable oxidizing agent such as periodic acid or lead tetraacetate.

  2. A technique to ensure the reproducibility of a cast post and core.

    PubMed

    Naas, Haitem M M; Dashti, Mohammad Hossein; Hashemian, Roxana; Hifeda, Nedda Y

    2014-12-01

    The post-and-core pattern duplication technique is a simple, cost-effective, and accurate method of ensuring the reproducibility of a cast post and core. An acrylic resin pattern is fabricated for an endodontically treated tooth. The post portion of the pattern is duplicated with a polyvinyl siloxane impression material in the lower compartment of a container. The core portion is then duplicated with a polyether impression material in the upper compartment. After the original pattern has been retrieved, the duplicate resin pattern is fabricated in the provided space. This technique will improve efficiency if damage or loss of the pattern or the actual cast post and core occurs. PMID:25156094

  3. The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing qualities of impressions that may lead to occlusal discrepancies with indirect restorations.

    PubMed

    Storey, D; Coward, T J

    2014-03-01

    There are few published studies that directly assess the quality of impressions for crowns and bridges in the UK. This paper considers aspects of impression quality with particular attention to factors causing potential occlusal discrepancies in the final restoration. To this end three dental laboratories were visited over a 3-month period. All impressions for conventional crown and bridgework that arrived on the days of the visits were examined and assessed against criteria defined on a custom-designed assessment form. A total of 206 impression cases were considered in this study. Flexible impression trays were used for 65% of working impressions. Their use was more common for NHS work than for private work. 31.9% of all alginate impressions examined were not adequately fixed to the tray. Visible contamination of impressions was not uncommon. PMID:24922994

  4. Cost of Impressed Current Cathodic Protection for Coastal Oregon Bridges

    SciTech Connect

    Holcomb, Gordon R.; Cryer, Curtis B.

    1998-07-01

    The State of Oregon is using arc-sprayed zinc coatings for anodes in impressed current cathodic protection (ICCP) systems on reinforced concrete coastal bridges. The two lowest bids for four ICCP projects were averaged and converted to 1997 dollars. The total average cost for the ICCP projects was $51.63/ft2 ($555.51/m2) of protected concrete. The cathodic protection part of the ICCP projects average $14.08/ft2 ($151.47/m2), while zinc anode installation cost an average of $7.13/ft2 ($76.67/m2). Oregon's rugged and beautiful coastline is graced with a series of historical arched bridges designed by Conde B. McCullough. McCullough is the internationally recognized architect who designed many of the Oregon Coast Highway (U.S. 101) bridges in the 1920s and 1930s. Many are listed on the National Historic Register. After the expense ($45m) and public outcry associated with the replacement of the historic Alsea Bay Bridge in Waldport, Oregon, the Oregon Department of Transportation began using impressed current cathodic protection (ICCP) to extend the service life of reinforced concrete bridges. Figure 1 visually illustrates the need for such remediation. It shows exposed rebar from underneath the Brush Creek Bridge, which is very representative of the conditions found underneath many coastal Oregon bridges. Four ICCP projects have been funded, put out for bid, and completed. The four projects, their bid closing dates, and their completion dates are the Cape Creek Bridge (1990- 1992), the Yaquina Bay Bridge south arches (1991-1995), the Depoe Bay Bridge (1993-1997), and the Yaquina Bay Bridge south approach (1995-1997). The Cape Creek, Yaquina Bay, and Depoe Bay Bridges are shown in Figs. 2-4. Other ICCP projects are underway on the Oregon coast. In the ICCP systems, arc-sprayed zinc coatings on the concrete surface are anodes that protect the steel rebar. Accelerated laboratory studies at the Albany Research Center have predicted zinc anode service lives of approximately 27 years based on long-term bond strength measurements.1-3 Experience in California4 has documented zinc anode service lives of over 11 years. Both indicate a substantial savings in project costs compared to bridge replacement. For example, the replacement cost of the arc-sprayed sections of the three Oregon bridges is estimated to be $57m, while the four ICCP projects on those bridges have cost $20m. (The $45m to replace the Alsea Bay Bridge was more than simply the replacement cost--it included expanding the bridge to four lanes and making the bridge ''ICCP ready'' by ensuring electrically continuous rebar).

  5. The First Impression of Data Sent by Two Martian Rovers

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    ``Spirit'' at the Gusev crater near the dichotomy boundary sent a panoramic view, an image of the near ground and a very close view of a small spot analyzed by X-ray. The first impression of chaotic disposition of big and small rocks and sandy fragments is wrong. All scales images display striations in 4 directions probably due to intersecting undulations, besides, rock fragments are rather evenly distributed. This is not of surprise because many MOLA images show very regular patterns described earlier for intersecting wave processes on planetary surfaces [1]. The middle scale image shows angular rock fragments of various sizes protruding soil. There is an impression that the protruding blocks represent uplifted parts of a wave-woven surface of volcanic infilling , subsided parts being covered with sandy soil mainly of eolian origin. Such an interpretation is supported by the THEMIS image (released 23 Sept., 2003 in Internet) of a 22 km-diameter crater on Sirenum Fossae where wave structurized (volcanic?) material is gradually covered by eolian sediments leaving protruding high standing blocks (antinodes). The soil X-ray analysis shows high Si an Fe, some Al, Ca, Mg, K, Na, Cl, S, minor Cu, Ni, Zn that should be expected for a mixed material at low/highland contact contaminated by an eolian stuff. ``Opportunity'' is the first highland landing and in this is its highest importance. It seems that long awaited light (in color and density) rock type without Fe [2, 3 & others] is in front of us. The leveled out white outcrops probably represent this kind of rocks (albitites, syenites). Eleveted K, Na, CL, S, Si and H20 (!) detected by gamma and neutron spectra can be explained by sodalite (hydrosodalite) and cancrinite group minerals present in nepheline syenites -- albitites and always accompanied by zeolites containing water. The high chemical dichotomy (and mantle fractionation) between lowlands and highlands is an important part of the wave planetology (Theorem 4 [3]). References: [1] Kochemasov G.G. (1991) Periodic system of multi-ring planetary structures as result of interference of variously oriented lithospheric waves // Astronom. Tsirkular RAS, # 1550, 35-36 (in Russian); [2] Kochemasov G.G. (1995) Possibility of highly contrasting rock types at martian highland/lowland contact // In: Golombek M.P., Edgett K.S., and Rice J.W.Jr., eds. Mars Pathfinder Landing Site Workshop II: Characteristics of the Ares Vallis Region and Field Trips to the Channeled Scabland, Washington. LPI Tech. Rpt. 95-01, Pt. 1, LPI, Houston, 63 pp.; [3] Kochemasov G.G. (1999) On a successful prediction of martian crust fractionation based on comparative wave planetology // The Fifth International Conference on Mars, July 18-23, 1999, Pasadena, California, Abstr. # 6034, (CD-ROM).

  6. Appearance-based first impressions and person memory.

    PubMed

    Bell, Raoul; Mieth, Laura; Buchner, Axel

    2015-03-01

    Previous research has demonstrated that people preferentially remember reputational information that is emotionally incongruent to their expectations, but it has left open the question of the generality of this effect. Three conflicting hypotheses were proposed: (a) The effect is restricted to information relevant to reciprocal social exchange. (b) The effect is most pronounced for emotional (approach-and-avoidance-relevant) information. (c) The effect is due to a general tendency of the cognitive system to attend to unexpected and novel information regardless of its (emotional) content. Here, we varied the type of to-be-remembered person information across experiments. To stimulate expectations, we selected faces whose facial appearance was rated as pleasant or disgusting (Experiments 1 and 2), as intelligent or unintelligent (Experiment 3), or as being that of a lawyer or a farmer (Experiment 4). These faces were paired with behavior descriptions that violated or confirmed these appearance-based 1st impressions. Source memory for the association between the faces and the descriptions was assessed with surprise memory tests. The results show that people are willing to form various social expectations based on facial appearance alone, and they support the hypothesis that the classification of the faces in the memory test is biased by schema-congruent guessing. Source memory was generally enhanced for information violating appearance-based social expectations. In sum, the results show that person memory is consistently affected by different kinds of social expectations, supporting the idea that the mechanisms determining memory performance generalize beyond exchange-relevant reputational and emotional information. PMID:24999709

  7. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness

    PubMed Central

    Arora, Aman; Singh, Vijay Pratap

    2012-01-01

    ABSTRACT One of the most important steps is accurate impression making for fabrication of fixed partial denture. The two different putty-wash techniques that are commonly used are: (1) Putty-wash one-step technique, (2) putty-wash two-step technique. A uniform wash space is needed for an accurate impression. Nissan et al recommended the use of two-step technique for accurate impression making as there is uniform wash space for the light body material to polymerize. The aim of the present study was to compare the accuracy of stone casts obtained from different putty-wash impression techniques using various spacer thickness. The critical factor that influences the accuracy of putty-wash impression techniques is the controlled wash bulk which is absent in one-step putty-wash impression technique and with polyethylene spacer was used. How to cite this article: Chugh A, Arora A, Singh VP. Accuracy of Different Putty-Wash Impression Techniques with Various Spacer Thickness. Int J Clin Pediatr Dent 2012;5(1):33-38. PMID:25206132

  8. In Vitro Evaluation of Dimensional Stability of Alginate Impressions after Disinfection by Spray and Immersion Methods

    PubMed Central

    Hamedi Rad, Fahimeh; Ghaffari, Tahereh; Safavi, Sayed Hamed

    2010-01-01

    Background and aims The most common method for alginate impression disinfection is spraying it with disinfecting agents, but some studies have shown that these impressions can be immersed, too. The aim of this study was to evaluate the dimensional stability of alginate impressions following disinfecting by spray and immersion methods. Materials and methods Four common disinfecting agents (Sodium Hypochlorite, Micro 10, Glutaraldehyde and De-conex) were selected and the impressions (n=108) were divided into four groups (n=24) and eight subgroups (n=12) for disinfecting by any of the four above-mentioned agents by spray or immersion methods. The control group (n=12) was not disinfected. Then the impressions were poured by type III Dental Stone Plaster in a standard method. The results were ana-lyzed by descriptive methods (mean and standard deviation), t-test, two-way analysis of variance (ANOVA) and Duncan test, using SPSS 14.0 software for windows. Results The mean changes of length and height were significant between the various groups and disinfecting methods. Regarding the length, the greatest and the least amounts were related to Deconex and Micro 10 in the immersion method, respectively. Regarding height, the greatest and the least amounts were related to Glutaraldehyde and Deconex in the im-mersion method, respectively. Conclusion Disinfecting alginate impressions by Sodium Hypochlorite, Deconex and Glutaraldehyde by immersion method is not recommended and it is better to disinfect alginate impressions by spraying of Micro 10, Sodium Hypochlorite, Glutaraldehyde and immersion in Micro 10. PMID:23346340

  9. Evaluation of properties of irreversible hydrocolloid impression materials mixed with disinfectant liquids

    PubMed Central

    Amalan, Arul; Ginjupalli, Kishore; Upadhya, Nagaraja

    2013-01-01

    Background: Addition of disinfectant to irreversible hydrocolloid impression materials can eliminate the disinfection step to avoid dimensional changes associated with it. The aim of the present study was to evaluate the effect of various disinfectant mixing liquids on the properties of commercially available irreversible hydrocolloid impression materials. Materials and Methods: Four commercially available irreversible hydrocolloid impression materials (Zelgan, Vignette, Tropicalgin, and Algitex) were mixed with disinfectant liquid containing chlorhexidine (0.1 and 0.2%) and sodium hypochlorite (0.1 and 0.5%). After mixing with disinfectant liquids, materials were evaluated for pH changes during gelation, gelation time, flow, gel strength, permanent deformation and detail reproduction. Results: Significant changes in gelation time were observed in irreversible hydrocolloid impression materials upon mixing with disinfectant liquids. In general, chlorhexidine increased the gelation time, whereas sodium hypochlorite reduced it. However, no significant changes in the flow were observed both with chlorhexidine and sodium hypochlorite. Gel strength was found to decrease when mixed with chlorhexidine, whereas an increase in gel strength was observed upon mixing with sodium hypochlorite. Permanent deformation of the most irreversible hydrocolloid impression materials was below the specification limit even after mixing with disinfectant liquids. Sodium hypochlorite significantly reduced the surface detail reproduction, whereas no change in detail reproduction was observed with chlorhexidine. Conclusion: Chlorhexidine solution can be used to mix irreversible hydrocolloid impression materials in regular dental practice as it did not significantly alter the properties. This may ensure effective disinfection of impressions. PMID:23878566

  10. Dimensional Changes of Alginate Dental Impression Materials-An Invitro Study

    PubMed Central

    Thombare, Ram U

    2015-01-01

    Background Dentists are always looking ahead for more dimensionally stable material for accurate and successful fabrication of prosthesis in this competitive world. Arrival of newer materials and increased material market puts dentists in dilemma for selection of material. Aim The study evaluated the effect of variations in time of pour and temperature on dimensional stability of three brands of commercially available alginates. Materials and Methods Velplast, Marieflex & Zelgan alginate impression materials were evaluated by measuring dimensional accuracy of the master cast. A die was prepared and mounted on the apparatus for the ease of impression making. The prepared casts were categorized into five groups and made up of three brands of alginate impression material with variation in time of pour viz: immediate, 20&40 minutes interval and with varying temperature of 250C, 300C & 400C. Results Impressions showed least distortion at varying degrees of temperature for 20 minutes, but the values obtained by storing of alginate impressions for 20 minutes at 300C were found to be nearly accurate than the values obtained by storing of impression at 400C. However, storing showed shrinkage of impressions. Conclusion Marieflex showed better accuracy in comparison with other two materials. Maintenance of temperature and humidity play key role during storage & transport to prevent distortion. But the study suggests immediate pouring which will minimize the distortion. The manipulation instructions, temperature of mixing water, environment & water powder ratio also plays key role in minimizing the distortion. PMID:26436059

  11. Influence of retentive areas associated to onlay preparations on the dimensional stability of silicone impression materials.

    PubMed

    Yatsuda, Regis A; Lima, Adriano F; Yatsuda, Regiane; Cavalcanti, Andrea N; Capp, Cláudia I; Novelli, Moacyr D; de Cara, Antonio A

    2010-01-01

    This study evaluated the effect of retentive areas on onlay preparations on the dimensional alterations in condensation and addition silicone materials. A standard model with an onlay preparation was made. Each impression material was used through the double or simultaneous impression technique (n=25), resulting in a hundred impressions of the same model. Impressions were poured with type IV dental stone. Digital images were taken with a light microscope and the distances between the reference points created on the plaster dies were compared with the ones on the standard model. In the occlusal, mesial-medium and mesial-cervical segments, the double impression (DI) with condensation silicone presented similar values compared to the standard model. The values of the addition silicone with DI were similar to the standard model only in the mesial-occlusal segment. In the other segments (distal-cervical, distal-medium and distal-occlusal), all groups were statistically different from the control. It could be concluded that addition and condensation silicone impressions provided plaster dies with significant dimensional alterations in most of the evaluated areas when compared to the standard model. The retentive areas related to the onlay preparation influenced the dimensional stability of the addition and condensation silicone impressions. PMID:21053692

  12. Chlorhexidine gluconate mouthwashes as a surfactant for addition-reaction silicone impressions.

    PubMed

    Reshad, Mamaly; Nesbit, Michael; Petrie, Aviva; Setchell, Derrick

    2009-03-01

    Addition-reaction silicone impression (PVS) materials are hydrophobic. Hydrophobicity of the impression material may interfere with the wetting of the tooth, resulting in void formation. The study investigates whether conditioning teeth with Chlorhexidine-gluconate based mouthwashes can reduce the hydrophobicity and the number of voids on PVS impressions. Impression material contact angle specimens on bovine tooth surfaces were measured using a Reflex Microscope. PVS impressions (President) were made of untreated bovine teeth in three groups (1, 2 and 3) and fourth group used Impregum polyether impression material: Group I was used as a control group, and original and mint flavoured Corsodyl (Chlorhexidine) mouthwashes were used as clinical surfactants in Groups 2 and 3, respectively. Contact angle readings were recorded on each side of every impression in each of the four groups and compared by an analysis of variance. In the second part of the study, the numbers of air voids on impression surfaces were visually recorded. The proportions of air voids in the groups were compared using a Chi-squared test. The mean angle for Group 3 with mint flavoured Corsodyl mouthwash was significantly smaller than that of any of the other groups (P < 0.05). The only statistically significant (P < 0.01) comparisons of the proportions of air voids were between Group 4 and each of the other experimental groups, with the percentage of voids being significantly greater in Group 4. Although Corsodyl mint significantly reduced the mean contact angle it did not significantly reduce the percentage of voids on impression surfaces. PMID:19378615

  13. Three-dimensional accuracy of implant and abutment level impression techniques: effect on marginal discrepancy.

    PubMed

    Alikhasi, Marzieh; Siadat, Hakimeh; Monzavi, Abbas; Momen-Heravi, Fatemeh

    2011-12-01

    Impression techniques should precisely represent the 3-dimensional status of implants to allow for the fabrication of passively fitting prostheses and subsequently the elimination of strain on supporting implant components and surrounding bone. The aim of this study was to compare the accuracy of an abutment level impression method with that of an implant level (direct and indirect) impression method using polyether impression material to obtain precise definitive casts and prostheses. A reference acrylic resin dentoform with 2 internal connection implants (Implantium) was made. A total of 21 medium-consistency polyether impressions of the dentoform, including 7 direct implant level, 7 indirect implant level, and 7 abutment level (after 2 straight abutments were secured), were made. Impressions were poured with American Dental Association (ADA) type IV stone, and the positional accuracy of the implant replica heads and abutment analogs in each dimension of x-, y-, and z-axes, as well as angular displacement (??), was evaluated using a coordinate measuring machine. Noble alloy 3-unit castings were fabricated and seated on the abutments in 3 groups; marginal discrepancies were measured at 4 points between prostheses and abutments. Data were analyzed using Mann-Whitney U test, 1-way analysis of variance (ANOVA), and Kruskal-Wallis tests. In comparisons of different impression techniques, only significant statistical ?? differences were noted between the abutment level method and other techniques (P < .001). Results of this study reveal that although the implant level impression method could better transfer the angular position of the implants (??), the impression method could not affect ?y, ?x, and ?z coordinates of the implants or marginal discrepancy of the 3-unit fixed partial dentures (FPD). PMID:20594060

  14. Spectroscopic investigation of the thermal conversion of catalytically dehydrated polyvinyl alcohol

    SciTech Connect

    Gavrilov, M.Z.

    1986-09-01

    The authors examine the structural conversion of dehydrated polyvinyl alcohol thermally treated at temperatures exceeding the temperature of the catalytic dehydration. The authors used electron and infrared spectroscopy to study the thermal conversion of catalytically dehydrated polyvinyl alcohol in an inert atmosphere and in air. Aluminum chloride and hydrogen chloride were used as catalysts of the dehydration. Spectra are shown which were obtained in the visible part from ALCL/sub 3/-containing polyvinyl alcohol films after their thermal treatment in an inert gas flow. It is shown that optimal temperatures must be selected to obtain high-quality recordings of optical information when the dehydration of polyvinyl alcohol is to be used to advantage.

  15. The elastomers for complete denture impression: A review of the literature

    PubMed Central

    Daou, Elie E.

    2010-01-01

    This article reviews the current trends in materials used for complete denture impression. Peer-reviewed articles, published in English and in French between 1954 and 2007, were identified through a MEDLINE search (Pubmed and Elsevier) and a hand search of relevant textbooks and annual publications. Emphasis was made on the characteristics of the elastomers, their manipulation, the different techniques used, and the quality of the impression obtained. The combination of excellent physical properties, handling characteristics, and unlimited dimensional stability assures the popularity of these impression materials. PMID:24151408

  16. Agar impression materials, dimensional stability and surface detail sharpness following treatment with disinfectant solutions.

    PubMed

    Olsson, S; Bergman, B; Bergman, M

    1987-01-01

    The influence of seven dissimilar disinfectants on the dimensional stability and the surface detail sharpness of two agar impression materials was studied. Two methods for treatment with disinfectant solutions were tested--immersion for 1 hour and spraying. In contrast to immersion the spraying method had no obvious influence on the agar material. It is concluded that if the disinfection method necessitates immersion of the impression in a solution for 1 hour or more the use of agar impression materials should be avoided. PMID:3480616

  17. [The dimensional stability of hydrophilic impression materials after application of a disinfectant].

    PubMed

    Stoll, R; Segschneider, F; Stachniss, V; Jrgensen, R

    1991-11-01

    The influence of a disinfectant solution containing glutaraldehyde on the dimensional stability of 2 alginate and 4 elastomeric impression materials has been investigated. Die models were measured using a computer-controlled method and compared to the master die to assess the three-dimensional change in the impression material. After an immersion time of 10 min, a dimensional change did not occur. When using immersion times longer than 10 min, the accuracy of the alginate materials was generally more affected by the disinfecting solution than that of the elastomeric impression materials. PMID:1817870

  18. [The need and possibility for disinfecting impressions in orthodontics (a review of the literature)].

    PubMed

    Shcherbakov, A S; Iushmanova, T N; Mokrenko, E V

    1992-01-01

    Reviews the data on a high risk of viral and bacterial infection of dentists in connection with the high prevalence of AIDS and viral hepatitis B and on the possibility of infection of dental patients and the staff by microorganisms transfer on the impressions. Presents the present-day methods and means for disinfection of the impression material. Emphasizes inadequate knowledge of the dentists about the virucidal efficacy and the possibility of the impressions changing their properties in disinfection, which fact results in inaccuracy of the ready articles. PMID:1307161

  19. Dental impression material: a rare cause of small-bowel obstruction.

    PubMed

    Dent, Lemuel; Peterson, Analeta; Pruett, Danica; Beech, Derrick

    2009-12-01

    Small-bowel obstruction due to foreign bodies is unusual in adults. Intestinal obstruction is occasionally caused by pits, bezoars, endoscopy capsules, and gastrostomy tube buttons. We report a rare case of distal small-bowel obstruction due to dental impression material. Avoidance of this potentially life-threatening complication may be achieved by increased vigilance in accounting for all impression material when dental impression trays are removed. Early detection of swallowed dental material may afford endoscopic removal from the stomach, thus preventing intestinal obstruction. PMID:20070020

  20. Comparison of Different Final Impression Techniques for Management of Resorbed Mandibular Ridge: A Case Report

    PubMed Central

    Yadav, Bhupender; Jayna, Manisha; Yadav, Harish; Suri, Shrey; Phogat, Shefali; Madan, Reshu

    2014-01-01

    The history of complete denture impression procedures has been influenced largely by the development of impression materials from which new techniques and ideas arose. The purpose of this study was to compare the retention of complete dentures made by using different impression techniques like conventional, admixed, all green, and functional techniques. The results showed that there was significant difference in retention between the six techniques where functional technique showed the highest mean value of retention followed by elastomeric, all green, and admixed, while cocktail and green stick compound showed the lowest mean value. However, on clinical examination, the retention produced by the six techniques was satisfactory. PMID:25180105

  1. Examining the Moderating Effect of Appearance Impression Motivation on the Relationship between Perceived Physical Appearance and Social Physique Anxiety

    ERIC Educational Resources Information Center

    Amorose, Anthony J.; Hollembeak, Jill

    2005-01-01

    Despite the conceptual importance of impression motivation in predicting social anxiety (Leary & Kowalski, 1995; Schlenker & Leary, 1982), no research has tested the link between impression motivation specifically regarding one's physical appearance (appearance impression motivation, or AIM) and social physique anxiety (SPA). The purpose of this

  2. Comparison of digital and conventional impression techniques: evaluation of patients perception, treatment comfort, effectiveness and clinical outcomes

    PubMed Central

    2014-01-01

    Background The purpose of this study was to compare two impression techniques from the perspective of patient preferences and treatment comfort. Methods Twenty-four (12 male, 12 female) subjects who had no previous experience with either conventional or digital impression participated in this study. Conventional impressions of maxillary and mandibular dental arches were taken with a polyether impression material (Impregum, 3M ESPE), and bite registrations were made with polysiloxane bite registration material (Futar D, Kettenbach). Two weeks later, digital impressions and bite scans were performed using an intra-oral scanner (CEREC Omnicam, Sirona). Immediately after the impressions were made, the subjects attitudes, preferences and perceptions towards impression techniques were evaluated using a standardized questionnaire. The perceived source of stress was evaluated using the State-Trait Anxiety Scale. Processing steps of the impression techniques (tray selection, working time etc.) were recorded in seconds. Statistical analyses were performed with the Wilcoxon Rank test, and p?impressions were more comfortable than conventional techniques. Conclusions Digital impressions resulted in a more time-efficient technique than conventional impressions. Patients preferred the digital impression technique rather than conventional techniques. PMID:24479892

  3. Impression materials and techniques for crown and bridgework: a survey of undergraduate teaching in the UK.

    PubMed

    Randall, R C; Wilson, M A; Setcos, J C; Wilson, N H

    1998-06-01

    The aim of this study was to document the teaching of impression materials and techniques for crown and bridgework in the undergraduate curriculum in UK dental schools. A questionnaire sent to each school during the 1993/1994 academic year elicited fourteen replies (100% response). Addition-cured silicones were found to predominate; 71% of schools taught and used clinically a one-stage, full arch impression technique involving stock trays, and 57% of schools a full-arch custom tray technique. Routine disinfection of impressions was taught and practised in 43% of schools. The results demonstrated variation between UK dental schools in their teaching of impression materials and techniques for crown and bridgework in the undergraduate curriculum. PMID:9927922

  4. Effect of two different disinfectants on dimensional stability of newer alginate impression materials over five days.

    PubMed

    Ambrose, Prem Kumar; Juszczyk, Andrzej S; Clark, Robert K F; Radford, David R

    2011-12-01

    The effect of two different disinfectants on the dimensional stability of two alginate impression materials over five days was investigated. 60 impressions were made under standardised conditions, 30 with each alginate, of which ten were disinfected in each disinfectant and ten were controls. Impressions were stored over a period of five days in a container with 100% humidity. Measurements were made between four points. Two-way analysis of variance indicated no differences in the change from baseline to day 5 between any of the combinations of alginate and disinfectant. Only two of the changes between baseline and day 5 reached statistical significance at the p < 0.01 level. Therefore it can be concluded that within the limitations of this study when newer alginate impression materials are disinfected they remain stable over 5 days. PMID:22645797

  5. Factors affecting dimensional instability of alginate impressions during immersion in the fixing and disinfectant solutions.

    PubMed

    Saito, S; Ichimaru, T; Araki, Y

    1998-12-01

    To clarify the factors determining the dimensional stability of alginate impressions during immersion in disinfectant and fixing solution, the weight change of impressions in solutions of glutaraldehyde (GA), NaClO, Na2SO4, K2SO4, CaCl2, and ZnSO4 was measured. In the nonelectrolytic solution, GA, the weight decreased in proportion to concentration, possibly due to the gradient of osmotic pressure between the impression and solution. In monovalent metallic salt solutions the weight change decreased with increased concentration. Especially at lower concentrations the rate of weight loss was high. A chemical action of the solution might also be involved, in addition to the osmotic pressure difference. The weight loss in divalent metallic salt solutions was greater than in monovalent solutions, implicating crosslinking reactions between the impression and solution. PMID:10219143

  6. On First Impression of the Teaching Materials which used Haptic Display

    NASA Astrophysics Data System (ADS)

    Ishihara, Manabu

    The virtual reality (VR) is one in the intelligence information communications technologies. As the application to the education field of VR, we construct a support system for the penmanship using the haptic display. We evaluated the first impression.

  7. Surficial Siloxane-to-Silanol Interconversion during Room-Temperature Hydration/Dehydration of Amorphous Silica Films Observed by ATR-IR and TIR-Raman Spectroscopy.

    PubMed

    Warring, Suzanne L; Beattie, David A; McQuillan, A James

    2016-02-16

    Silica has been frequently studied using infrared and Raman spectroscopy due to its importance in many practical contexts where its surface chemistry plays a vital role. The majority of these studies have utilized chemical-vapor-deposited films in vacuo after high-temperature calcination. However, room-temperature hydration and dehydration of thin silica particle films has not been well characterized in spite of the importance of such films as substrates for polymer and surfactant adsorption. The present study has utilized ATR-IR spectroscopy and thin silica particle films exposed to varying humidity to clearly show reversible conversion between surface siloxanes and hydrogen-bonded silanols without the need for semiempirical peak deconvolution. The IR spectra from corresponding hydration experiments on deuterated silica films has confirmed the vibrational mode assignments. The variation of humidity over silica films formed from silica suspensions of differing pH gave IR spectra consistent with the change in the relative populations of siloxide to silanol surface groups. In addition, total internal reflection Raman spectroscopy has been used to provide further evidence of room-temperature dehydroxylation, with spectral evidence for the presence of three-membered siloxane rings when films are dehydrated under argon. The confirmation of room-temperature siloxane-to-silanol interconversion is expected to benefit understanding in many silica surface chemical contexts. PMID:26804934

  8. Stabilization of the bicontinuous cubic phase in siloxane-terminated mesogens, 1,2-bis[4'-(n-(oligodimethylsiloxyl)alkoxy)benzoyl]hydrazine.

    PubMed

    Kutsumizu, Shoichi; Tokiwa, Issei; Kawafuchi, Akane; Miwa, Yohei; Yamamura, Yasuhisa; Saito, Kazuya

    2016-03-23

    The introduction of oligodimethyl siloxane segments at the termini of the alkyl tails has been employed to stabilize the bicontinuous cubic (Cubbi) phase of a chain-core-chain type molecule having a 1,2-bis(benzoyl)hydrazine central core with two chains attached at the 4' position of each benzoyl moiety. In this study, three silylated molecules, , , and , were synthesized, where "CnSim" represents the number of carbon and silicon atoms in the chain and "bis" indicates the two chains being the same, whereas the last one is asymmetric with respect to the core. The phase behaviors were examined by using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction techniques. All three compounds form Cubbi phases and their syntheses were compared including their parent compound . It was clearly revealed that the introduction of oligodimethyl siloxane segments effectively suppresses the crystallization at low temperatures, and as a result stabilizes the Cubbi phases, in an extreme case down to room temperature. The semi-quantitative analyses in terms of lattice constant and three-dimensional electron density map help us to better understand the self-assembly process in the Cubbi phases. The study also revealed that the introduction of oligodimethyl siloxane segments is not only an alternative for the hydrocarbon segment but also is able to provide a versatile design strategy for obtaining stable Cubbi phases. PMID:26965052

  9. Synthesis and properties of a novel UV-cured fluorinated siloxane graft copolymer for improved surface, dielectric and tribological properties of epoxy acrylate coating

    NASA Astrophysics Data System (ADS)

    Yan, Zhenlong; Liu, Weiqu; Gao, Nan; Wang, Honglei; Su, Kui

    2013-11-01

    A novel functional fluorinated siloxane graft copolymer bearing with vinyl end-groups was synthesized from dihydroxypropyl-terminated poly(dimethylsiloxane) (PDMS), dicarboxyl terminated poly(2,2,3,4,4,4-hexafluorobutyl acrylate) oligomer (CTHFA), 2,4-toluene diissocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA). The chemical structure was characterized by FT-IR and GPC. The effect of concentration of the vinyl-capped fluorosilicone graft copolymer (Vi-PFSi) on the surface, thermal properties, dielectric and tribological properties of UV-cured films was investigated. Contact angles and surface energies showed that the high hydrophobic and oleophobic surfaces were obtained by incorporation of Vi-PFSi at very low amount (0.5 wt%). X-ray photoelectron spectroscopy (XPS) evidenced that the fluorinated and siloxane moiety selectively migrated to the outermost surface of UV-cured film, thus reduced its surface energy from 45.42 to 15.40 mN/m2 without affecting its bulk properties. The morphology of fracture surface of modified film exhibited rough fracture surface only at the outermost surface, revealing fluorinated and siloxane groups migrated toward air-side surface. The dielectric constants decreased from 5.32 (1 MHz) for bisphenol-A epoxy methacrylate (EMA) to 2.82 (1 MHz) for modified film when the Vi-PFSi copolymer concentration increased from 0 to 0.8 wt%. Tribological results from abrasion tester suggested that the Vi-PFSi could obviously reduce the abrasion weight loss of modified films.

  10. Corrosion resistance of siloxane-poly(methyl methacrylate) hybrid films modified with acetic acid on tin plate substrates: Influence of tetraethoxysilane addition

    NASA Astrophysics Data System (ADS)

    Kunst, S. R.; Cardoso, H. R. P.; Oliveira, C. T.; Santana, J. A.; Sarmento, V. H. V.; Muller, I. L.; Malfatti, C. F.

    2014-04-01

    The aim of this paper is to study the corrosion resistance of hybrid films. Tin plate was coated with a siloxane-poly (methyl methacrylate) (PMMA) hybrid film prepared by sol-gel route with covalent bonds between the organic (PMMA) and inorganic (siloxane) phases obtained by hydrolysis and polycondensation of 3-(trimethoxysilylpropyl) methacrylate (TMSM) and polymerization of methyl methacrylate (MMA) using benzoyl peroxide (BPO) as a thermic initiator. Hydrolysis reactions were catalyzed by acetic acid solution avoiding the use of chlorine or stronger acids in the film preparation. The effect of the addition of tetraethoxysilane (TEOS) on the protective properties of the film was evaluated. The hydrophobicity of the film was determined by contact angle measurements, and the morphology was evaluated by scanning electron microscopy (SEM) and profilometry. The local nanostructure was investigated by Fourier transform infrared spectroscopy (FT-IR). The electrochemical behavior of the films was assessed by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements in a 0.05 M NaCl solution. The mechanical behavior was evaluated by tribology. The results highlighted that the siloxane-PMMA hybrid films modified with acetic acid are promising anti-corrosive coatings that acts as an efficient diffusion barrier, protecting tin plates against corrosion. However, the coating properties were affected by the TEOS addition, which contributed for the thickness increase and irregular surface coverage.

  11. Impression technique for monitoring and virtual treatment planning in nasoalveolar moulding.

    PubMed

    Loeffelbein, Denys J; Rau, Andrea; Wolff, Klaus-Dietrich

    2013-12-01

    We describe our experience with various silicone materials for making one-step and two-step impressions of the cleft-lip-palate-nose complex during nasoalveolar moulding. Our technique is superior to common alginate-based impression techniques, as it provides precise reproduction of the complex anatomy of the cleft, and is compatible with the latest available methods of planning treatment with nasoalveolar moulding, such as computer-aided reverse engineering and rapid prototyping. PMID:23414909

  12. Impressions in cleft lip and palate--a novel two stage technique.

    PubMed

    Pani, Sharat Chandra; Hedge, Amitha M

    2008-01-01

    Though the field of presurgical orthopedics for the management of children with cleft Lip and Palate (CLAP) has made great advances over the past few decades, little is found in literature regarding the imressions required to fabricate these appliances. The purpose of this paper is to describe a novel two stage technique utilizing greenstick compound and addition silicone impression material to provide a safe, economical and accurate method for recording impressions in children with cleft lip and palate. PMID:19358372

  13. Development and Psychometric Evaluation of a Clinical Global Impression for Schizoaffective Disorder Scale

    PubMed Central

    Daniel, David G; Revicki, Dennis A; Canuso, Carla M; Turkoz, Ibrahim; Fu, Dong-Jing; Alphs, Larry; Ishak, K. Jack; Bartko, John J; Lindenmayer, Jean-Pierre

    2012-01-01

    Objective: The Clinical Global Impression for Schizoaffective Disorder scale is a new rating scale adapted from the Clinical Global Impression scale for use in patients with schizoaffective disorder. The psychometric characteristics of the Clinical Global Impression for Schizoaffective Disorder are described. Design: Content validity was assessed using an investigator questionnaire. Inter-rater reliability was determined with 12 sets of videotaped interviews rated independently by two trained individuals. Test-retest reliability was assessed using 30 randomly selected raters from clinical trials who evaluated the same videos on separate occasions two weeks apart. Convergent and divergent validity and effect size were evaluated by comparing scores between the Clinical Global Impression for Schizoaffective Disorder and the Positive and Negative Syndrome Scale, 21-item Hamilton Rating Scale for Depression, and Young Mania Rating Scale scales using pooled patient data from two clinical trials. Clinical Global Impression for Schizoaffective Disorder scores were then linked to corresponding Positive and Negative Syndrome Scale scores. Results: Content validity was strong. Inter-rater agreement was good to excellent for most scales and subscales (intra-class correlation coefficient ?0.50). Test-retest showed good reproducibility, with intraclass correlation coefficients ranging from 0.444 to 0.898. Spearman correlations between Clinical Global Impression for Schizoaffective Disorder domains and corresponding symptom scales were 0.60 or greater, and effect sizes for Clinical Global Impression for Schizoaffective Disorder overall and domain scores were similar to Positive and Negative Syndrome Scale Young Mania Rating Scale, and 21-item Hamilton Rating Scale for Depression scores. Raters anticipated that the scale might be less effective in distinguishing negative from depressive symptoms, and, in fact, the results here may reflect that clinical reality. Conclusion: Multiple lines of evidence support the reliability and validity of the Clinical Global Impression for Schizoaffective Disorder for studies in schizoaffective disorder. PMID:22347687

  14. In vitro and clinical examination of the effect of an antimicrobial impression material on the oral microflora.

    PubMed

    Brauner, A W

    1990-07-01

    The bacterial colonization of impression materials by the oral microflora is an indication that impressions need disinfection. Till now, particularly where alginate materials are concerned, the disinfection of impressions has had a negative influence on the working properties of the material. The addition of an antimicrobial substance to alginate Blueprint asept is meant to disinfect the impression after removal from the oral cavity. Using both test cultures as well as clinically examining 30 patients, I verified the claims of the manufacturer. Electromicroscopic examinations showed no reduction in accuracy of impressions taken with Blueprint asept as compared with current alginate materials. PMID:2086295

  15. Production of a calcium silicate cement material from alginate impression material.

    PubMed

    Washizawa, Norimasa; Narusawa, Hideaki; Tamaki, Yukimichi; Miyazaki, Takashi

    2012-01-01

    The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified investment materials at 1,200°C produced calcium silicates, firing the set alginate impression material did not. However, we succeeded when firing the set blend of pre-fired set alginate impression material and gypsum at 1,200°C. SEM observations of the powder revealed that the featured porous structures of diatomite as an alginate impression material component appeared useful for synthesizing calcium silicates. Experimentally fabricated calcium silicate powder was successfully mixed with phosphoric acid solution and set by depositing the brushite. Therefore, we conclude that the production of calcium silicate cement material is possible from waste alginate impression material. PMID:22864217

  16. Resistance to disinfection of a polymicrobial association contaminating the surface of elastomeric dental impressions.

    PubMed

    Giammanco, Giovanni M; Melilli, Dario; Rallo, Antonio; Pecorella, Sonia; Mammina, Caterina; Pizzo, Giuseppe

    2009-04-01

    The aim of this study was to evaluate the ability to resist disinfection of a polymicrobial association contaminating the surface of dental impressions obtained with two different elastomers: a polyether (Impregum) and an addition-polymerized silicone (Elite). Impressions were contaminated with a mixture of three biofilm-forming microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans) and disinfected immediately after contamination, or after microbial layers were allowed to develop during a six-hour storage. Two commercial disinfectants were tested: MD 520 containing 0.5% glutaraldehyde and Sterigum Powder without glutaraldehyde. Residual contamination was recovered by mechanical rinsing immediately after disinfection and after a six-hour storage of disinfected impressions, and assessed by colony counting. Both disinfectants tested were shown to be effective in reducing the microbial presence on the impression materials, achieving at least a 102 reduction of microbial counts compared to water rinsing. However, Sterigum was generally less effective on the Elite elastomer and could not grant disinfection on six-hour aged P. aeruginosa and C. albicans microbial layers. The results of this study suggest that the materials used for the impressions influence the efficacy of disinfection. Disinfectants should be tested according to conditions encountered in everyday clinical practice and the need for immediate disinfection of impressions should be clearly indicated by manufacturers. PMID:19579694

  17. The Effect of Disinfection by Spray Atomization on Dimensional Accuracy of Condensation Silicone Impressions

    PubMed Central

    Saleh Saber, Fariba; Abolfazli, Nader; Kohsoltani, Maryam

    2010-01-01

    Background and aims The condensation silicone impression materials are available, but there is little knowledge of their accuracy after disinfection. The objective of this study was to evaluate the effect of the disinfection by spray atomization on dimensional accuracy of condensation silicone impressions. Materials and methods Impressions were made on a stainless steel master model containing a simulated two complete crown preparation with an edentulous space interposed using Spidex and Rapid impression materials. 44 impressions were made with each material, of which 16 were disinfected with 5.25% sodium hypochlorite, 16 were disinfected with 10% iodophor and 12 were not disinfected. Three dimensional measurements of working casts, including interpreparation distance, height, and diameter, were calculated using a measuring microscope graduated at 0.001 mm. Dimensional changes (mm) between the disinfected and non-disinfected working casts were compared. One-way analysis of variance (ANOVA) was employed to analyze the data (?=0.05). Results Disinfection of each condensation silicone material by spraying atomization with two different disinfectant material resulted in significant change in interpreparation distance (p<0.05). Changes in height and diameter were only significant in Spidex impressions (p<0.05). Conclusion Significant changes in the mean dimensions were seen as a result of disinfection by spraying; however, the dimensional changes do not seem great enough to cause critical positional distortion of teeth when fixed partial denture restorations are made. PMID:23346339

  18. Single Stage Silicone Border Molded Closed Mouth Impression Technique-Part II.

    PubMed

    Solomon, E G R

    2011-09-01

    Functioning of a complete denture depends to a great extent on the impression technique. Several impression techniques have been described in the literature since the turn of this century when Greene [Clinical courses in dental prothesis, 1916] brothers introduced the first scientific system of recording dental impression. Advocates of each technique have their own claim of superiority over the other. The introduction of elastomeric impression materials [Skinner and Cooper, J Am Dent Assoc 51:523-536, 1955] has made possible new techniques of recording impression for complete denture construction. These rubber like materials are of two types; one has a polysulfide base and is popularily known as polysulfide rubber (Thiokol and Mercaptan). The other variety has a silicone base known as silicone rubber or silicone elastomer. Silicone elastomers are available in four different consistencies; a thin easy flowing light bodied material,a creamy medium bodied material, a highly viscous heavy bodied material and a kneadable putty material. This paper describes an active closed mouth impression technique with one stage border molding using putty silicone material as a substitute for low fusing compound. PMID:22942578

  19. Effect of temperature changes on the dimensional stability of elastomeric impression materials

    PubMed Central

    Kambhampati, Sujan; Subhash, Vaddavalli; Vijay, Chellagulla; Das, Aruna

    2014-01-01

    Background: The purpose of this study was to evaluate the changed dimensions of dies obtained from impressions made with different combinations of addition sillicones which were subjected to variations in storage temperature. Materials & Methods: 45 die stone models were obtained of 45 impressions of which 15 each were stored at three different storage temperatures(25C, 37C and 42C). 15 impressions each were made using one impression technique. The measurements of the dies made from the impressions were measured with the help of Profile Projector with a accuracy of 0.001mm. Results: The results were statistically analyzed. The results indicated the significant decrease in dimensions when the storage temperature reduced from the mouth temperature. As compared to this there was a marginal increase in overall dimensions of all variables when storage temperature increased. Conclusion: More changes were seen in putty/light body combination followed by monophase and least in heavy/light body combination. How to cite the article: Kambhampati S, Subhash V, Vijay C, Das A. Effect of temperature changes on the dimensional stability of elastomeric impression materials. J Int Oral Health 2014;6(1):12-9. PMID:24653597

  20. Effect of mixing techniques on bacterial attachment and disinfection time of polyether impression material

    PubMed Central

    Guler, Umut; Budak, Yasemin; Ruh, Emrah; Ocal, Yesim; Canay, Senay; Akyon, Yakut

    2013-01-01

    Objective: The aim of this study was 2-fold. The first aim was to evaluate the effects of mixing technique (hand-mixing or auto-mixing) on bacterial attachment to polyether impression materials. The second aim was to determine whether bacterial attachment to these materials was affected by length of exposure to disinfection solutions. Materials and Methods: Polyether impression material samples (n = 144) were prepared by hand-mixing or auto-mixing. Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were used in testing. After incubation, the bacterial colonies were counted and then disinfectant solution was applied. The effect of disinfection solution was evaluated just after the polymerization of impression material and 30 min after polymerization. Differences in adherence of bacteria to the samples prepared by hand-mixing and to those prepared by auto-mixing were assessed by Kruskal-Wallis and Mann-Whitney U-tests. For evaluating the efficiency of the disinfectant, Kruskal-Wallis multiple comparisons test was used. Results: E. coli counts were higher in hand-mixed materials (P < 0.05); no other statistically significant differences were found between hand- and auto-mixed materials. According to the Kruskal-Wallis test, significant differences were found between the disinfection procedures (Z > 2.394). Conclusion: The methods used for mixing polyether impression material did not affect bacterial attachment to impression surfaces. In contrast, the disinfection procedure greatly affects decontamination of the impression surface. PMID:24966729