STUDIES OF THE MECHANISM OF ACTION OF URETHANE IN INITIATING PULMONARY ADENOMAS IN MICE

PubMed Central

Rogers, Stanfield

1957-01-01

The process of carcinogenesis following exposure of mice to urethane is demonstrated in the present work to be intimately related to nucleic acid synthesis. Injection of animals with a DNA hydrolysate immediately prior to a single exposure of the animals to urethane markedly reduced the number of pulmonary adenomas initiated. Aminopterin, known to interfere in nucleic acid synthesis (46), potentiated the carcinogenic action of urethane and this potentiation was blocked by injection of a DNA hydrolysate. Of the components and precursors of nucleic acids the pyrimidine series seemed especially concerned. Alterations in the utilization of oxaloacetate, ureidosuccinic acid, dihydro-orotic acid, orotic acid, cytidylic acid, and thymine appeared to be critical steps in the oncogenic process, following upon the primary disorder of cellular metabolism initiated by the carcinogen. All these substances except oxaloacetate profoundly reduced the number of tumors initiated by urethane. Oxaloacetate potentiated the carcinogenic effect. When these results are viewed together and in relation to known facts concerning nucleic acid synthesis they provide evidence suggesting that the point of action of the carcinogen is in the pathway of nucleic acid synthesis below orotic acid and perhaps at the level of ureidosuccinic acid. The potentiating influence of adenine, 4-amino-5-imidazole carboxamide, and aminopterin, the lack of effect of uracil, and the inhibitory influence of thymine together suggest that DNA rather than RNA is the nucleic acid critical to the oncogenic response of mice to urethane. PMID:13416469

Flame resistant elastic elastomeric fibers

NASA Technical Reports Server (NTRS)

Howarth, J. T.; Massucco, A. A.

1972-01-01

Development of materials to improve flame resistance of elastic elastomeric fibers is discussed. Two approaches, synthesis of polyether based urethanes and modification of synthesized urethanes with flame ratardant additives, are described. Specific applications of both techniques are presented.

Flexible Vinyl and Urethane Coating and Printing: New Source Performance Standards (NSPS)

EPA Pesticide Factsheets

Learn about the New Source Performance Standards (NSPS) for flexible vinyl and urethane coating and printing by reading the rule summary, the rule history, the code of federal regulations subpart and related rules

Allergic contact dermatitis due to urethane acrylate in ultraviolet cured inks.

PubMed Central

Nethercott, J R; Jakubovic, H R; Pilger, C; Smith, J W

1983-01-01

Seven workers exposed to ultraviolet printing inks developed contact dermatitis. Six cases were allergic and one irritant. A urethane acrylate resin accounted for five cases of sensitisation, one of which was also sensitive to pentaerythritol triacrylate and another also to an epoxy acrylate resin. One instance of allergy to trimethylpropane triacrylate accounted for the sixth case of contact dermatitis in this group of workers. An irritant reaction is presumed to account for the dermatitis in the individual not proved to have cutaneous allergy by patch tests. In this instance trimethylpropane triacrylate was thought to be the most likely irritating agent. Laboratory investigation proved urethane acrylate to be an allergen. The results of investigations of the sensitisation potentials of urethane acrylate, methylmethacrylate, epoxy acrylate resins, toluene-2,4-diisocyanate, and other multifunctional acrylic monomers in the albino guinea pig are presented. The interpretation of such predictive tests is discussed. Images PMID:6223656

Production development of organic nonflammable spacecraft potting encapsulating and conformal coating compounds. Volume 2: Tables

NASA Technical Reports Server (NTRS)

Lieberman, S. L.

1974-01-01

Tables are presented which include: material properties; elemental analysis; silicone RTV formulations; polyester systems and processing; epoxy preblends and processing; urethane materials and processing; epoxy-urethanes elemental analysis; flammability test results, and vacuum effects.

Cold recycle pavement using urea urethane dispersion agent and rubber : final report.

DOT National Transportation Integrated Search

1994-12-01

This research study was a joint venture of the Oregon Department of Transportation (ODOT), Evans, Loosely, Inc., and Roseburg Paving Company, to evaluate the use of Urea Urethane Dispersion (UUD) agent, with finely ground tire rubber, high float emul...

Evaluation of urethane and carbide-tipped blades on wheel-supported snow plows.

DOT National Transportation Integrated Search

1997-01-01

The objective of this study was to evaluate the performance of urethane and carbide-tipped snow plow blades on wheel supported plows. Their performance was compared to that of VDOT's standard blade arrangement: carbide-tipped blades on plows without ...

Evaluation of pressor and visceromotor reflex responses to bladder distension in urethane anesthetized rats.

PubMed

Blatt, Lauren K; Lashinger, Erin S R; Laping, Nicholas J; Su, Xin

2009-01-01

We tested cardiovascular and visceromotor reflex (VMR) responses to urinary bladder distension (UBD) in urethane anesthetized rats to see if it can replicate the response pattern and the inhibition of bladder nociceptive transmission by analgesics seen in isoflurane anesthetized animals. Female Sprague-Dawley rats under 3% isoflurane anesthesia were acutely instrumented with jugular venous, carotid arterial, and bladder cannulas for drug administration, blood pressure (BP) measurement, and bladder distension, respectively. Needle electrodes were placed directly into the abdominal musculature to measure myoelectrical activity subsequent to phasic UBD (30 sec in 3 min intervals). A cardiovascular response (pressor) and a VMR response (a contraction of abdominal and hind limb musculature) to UBD were evaluated in urethane (1.2 g/kg, i.v.) or isoflurane (1%) anesthetized rats. Pressor and VMR responses to noxious UBD (60 mmHg) were generated under both anesthesics. The thresholds of stimulus response functions for both pressor and VMR responses were not affected by either anesthesics. However, the magnitude of the maximal pressor response was significantly reduced in urethane anesthesia. The analgesics, morphine, and mexiletine, significantly inhibited the VMR response to noxious UBD under both anesthetics, but the intensities of the inhibition from both analgesics under urethane anesthesia were much lower than under isoflurane anesthesia (ID50: 2.07 mg/kg vs. 0.88 mg/kg for morphine, >10 mg/kg vs. 0.47 mg/kg for mexiletine). The rat urinary bladder distension model in urethane anesthetized rats demonstrates a blunted maximal pressor response and a reduced inhibition of visceral nociceptive transmission by analgesics. Neurourol. Urodynam. 28:442-446, 2009. (c) 2008 Wiley-Liss, Inc.

Spectroscopic, semiempirical studies and antibacterial activity of new urethane derivatives of natural polyether antibiotic - Monensin A

NASA Astrophysics Data System (ADS)

Huczyński, Adam; Stefańska, Joanna; Piśmienny, Mieszko; Brzezinski, Bogumil

2013-02-01

A series of new Monensin A dimers linked by diurethane moiety were synthesised and their molecular structures were studied using ESI-MS, FT-IR, 1H and 13C NMR and PM5 methods. The results showed that the compounds form a pseudo-cyclic structure stabilized by three intramolecular hydrogen bonds and the sodium cation was coordinated by five oxygen atoms of polyether skeleton of Monensin moiety. The NMR and FT-IR data of complexes of Monensin urethane sodium salts demonstrated that within the pseudo-cyclic structure the carbonyl oxygen atom of the urethane group did not coordinate the sodium cation. Monensin urethanes were tested in vitro for the activity against Gram-positive and Gram-negative bacteria and fungi as well as against a series of clinical isolates of Staphylococcus: methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). The most active compound against MRSA and MSSA was 1,4-phenylene diurethane of Monensin with MIC 10.4-41.4 μmol/L).

Resin cements formulated with thio-urethanes can strengthen porcelain and increase bond strength to ceramics.

PubMed

Bacchi, Atais; Spazzin, Aloisio Oro; de Oliveira, Gabriel Rodrigues; Pfeifer, Carmem; Cesar, Paulo Francisco

2018-06-01

The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20 wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60 wt%. The microshear bond strength (μSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σ bf ) and m were calculated in the tensile surfaces of porcelain and RC structures (Z = 0 and Z = -t 2 , respectively). The μSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σ bf had superior values at Z = 0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σ bf increased with all RCs composed by thio-urethanes at Z = -t 2 . Fractographic analysis revealed all fracture origins at Z = 0. The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the μSBS to LD and ZR. The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers. Copyright © 2018 Elsevier Ltd. All rights reserved.

Laboratory and test-site testing of moisture-cured urethanes on steel in salt-rich environment.

DOT National Transportation Integrated Search

2000-11-01

Three 3-coat moisture-cured (MC) urethane commercial products formulated for protecting new steel (SSPC-SP 10) and power : tool-cleaned steel (SSPC-SP 3) surfaces against corrosion were evaluated; the total coating film thickness was about 75 : micro...

Laboratory and test-site testing of moisture-cured urethanes on steel in salt-rich environment

DOT National Transportation Integrated Search

2000-12-01

Three 3-coat moisture-cured (MC) urethane commercial products formulated for protecting new steel (SSPC-SP 10) and power tool-cleaned steel (SSPC-SP 3) surfaces against corrosion were evaluated; the total coating film thickness was about 75 microns. ...

Evaluation of urethane snow plow blades as an alternative to rubber blades.

DOT National Transportation Integrated Search

1995-01-01

The purpose of this study was to determine if urethane blades are a suitable alternative to rubber blades for use on snow plows. The importance of finding a suitable alternative is due to the anticipated increased need to protect the new, longer last...

77 FR 50411 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-21

... environmental control system (ECS) wrapped with BMS 8-39 or Aeronautical Materials Specifications (AMS) 3570... were assembled with duct assemblies in the ECS wrapped with BMS 8-39 urethane foam insulation, a... ECS with burned BMS 8-39 urethane foam insulation. We issued these ADs to prevent a potential...

QUANTITATIVE ULTRAVIOLET SPECTROSCOPY IN WEATHERING OF A MODEL POLYESTER-URETHANE COATING. (R828081E01)

EPA Science Inventory

Spectroscopy was used to quantify the effects of ultraviolet light on a model polyester–urethane coating as it degraded in an accelerated exposure chamber. An explorative calculation of the effective dosage absorbed by the coatings was made and, depending on the quantum...

Solvent for urethane adhesives and coatings and method of use

DOEpatents

Simandl, Ronald F.; Brown, John D.; Holt, Jerrid S.

2010-08-03

A solvent for urethane adhesives and coatings, the solvent having a carbaldehyde and a cyclic amide as constituents. In some embodiments the solvent consists only of miscible constituents. In some embodiments the carbaldehyde is benzaldehyde and in some embodiments the cyclic amide is N-methylpyrrolidone (M-pyrole). An extender may be added to the solvent. In some embodiments the extender is miscible with the other ingredients, and in some embodiments the extender is non-aqueous. For example, the extender may include isopropanol, ethanol, tetrahydro furfuryl alcohol, benzyl alcohol, Gamma-butyrolactone or a caprolactone. In some embodiments a carbaldehyde and a cyclic amide are heated and used to separate a urethane bonded to a component.

Biodegradable gadolinium-chelated cationic poly(urethane amide) copolymers for gene transfection and magnetic resonance imaging.

PubMed

Gao, Xiaolong; Wang, Gangmin; Shi, Ting; Shao, Zhihong; Zhao, Peng; Shi, Donglu; Ren, Jie; Lin, Chao; Wang, Peijun

2016-08-01

Theranostic nano-polyplexes containing gene and imaging agents hold a great promise for tumor diagnosis and therapy. In this work, we develop a group of new gadolinium (Gd)-chelated cationic poly(urethane amide)s for gene delivery and T1-weighted magnetic resonance (MR) imaging. Cationic poly(urethane amide)s (denoted as CPUAs) having multiple disulfide bonds, urethane and amide linkages were synthesized by stepwise polycondensation reaction between 1,4-bis(3-aminopropyl)piperazine and a mixture of di(4-nitrophenyl)-2, 2'-dithiodiethanocarbonate (DTDE-PNC) and diethylenetriaminepentaacetic acid (DTPA) dianhydride at varied molar ratios. Then, Gd-chelated CPUAs (denoted as GdCPUAs) were produced by chelating Gd(III) ions with DTPA residues of CPUAs. These GdCPUAs could condense gene into nanosized and positively-charged polyplexes in a physiological condition and, however, liberated gene in an intracellular reductive environment. In vitro transfection experiments revealed that the GdCPUA at a DTDE-PNC/DTPA residue molar ratio of 85/15 induced the highest transfection efficiency in different cancer cells. This efficiency was higher than that yielded with 25kDa branched polyethylenimine as a positive control. GdCPUAs and their polyplexes exhibited low cytotoxicity when an optimal transfection activity was detected. Moreover, GdCPUAs may serve as contrast agents for T1-weighted magnetic resonance imaging. The results of this work indicate that biodegradable Gd-chelated cationic poly(urethane amide) copolymers have high potential for tumor theranostics. Copyright © 2016 Elsevier B.V. All rights reserved.

Adhesive retention of experimental fiber-reinforced composite, orthodontic acrylic resin, and aliphatic urethane acrylate to silicone elastomer for maxillofacial prostheses.

PubMed

Kosor, Begüm Yerci; Artunç, Celal; Şahan, Heval

2015-07-01

A key factor of an implant-retained facial prosthesis is the success of the bonding between the substructure and the silicone elastomer. Little has been reported on the bonding of fiber reinforced composite (FRC) to silicone elastomers. Experimental FRC could be a solution for facial prostheses supported by light-activated aliphatic urethane acrylate, orthodontic acrylic resin, or commercially available FRCs. The purpose of this study was to evaluate the bonding of the experimental FRC, orthodontic acrylic resin, and light-activated aliphatic urethane acrylate to a commercially available high-temperature vulcanizing silicone elastomer. Shear and 180-degree peel bond strengths of 3 different substructures (experimental FRC, orthodontic acrylic resin, light-activated aliphatic urethane acrylate) (n=15) to a high-temperature vulcanizing maxillofacial silicone elastomer (M511) with a primer (G611) were assessed after 200 hours of accelerated artificial light-aging. The specimens were tested in a universal testing machine at a cross-head speed of 10 mm/min. Data were collected and statistically analyzed by 1-way ANOVA, followed by the Bonferroni correction and the Dunnett post hoc test (α=.05). Modes of failure were visually determined and categorized as adhesive, cohesive, or mixed and were statistically analyzed with the chi-squared goodness-of-fit test (α=.05). As the mean shear bond strength values were evaluated statistically, no difference was found among the experimental FRC, aliphatic urethane acrylate, and orthodontic acrylic resin subgroups (P>.05). The mean peel bond strengths of experimental fiber reinforced composite and aliphatic urethane acrylate were not found to be statistically different (P>.05). The mean value of the orthodontic acrylic resin subgroup peel bond strength was found to be statistically lower (P<.05). Shear test failure types were found to be statistically different (P<.05), whereas 180-degree peel test failure types were not found to be statistically significant (P>.05). Shear forces predominantly exhibited cohesive failure (64.4%), whereas peel forces predominantly exhibited adhesive failure (93.3%). The mean shear bond strengths of the experimental FRC and aliphatic urethane acrylate groups were not found to be statistically different (P>.05). The mean value of the 180-degree peel strength of the orthodontic acrylic resin group was found to be lower (P<.05). Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Evaluation Selection of Encapsulating Plastics for Ordnance Electronic Assemblies

DTIC Science & Technology

1981-05-01

ISP-100 Dow Two-component urethane (>70D) 10 B635/1- 4BD Uniroyal Two-component urethane (ɟD) 68 4. CIRCUIT ENCAPSULATION 4.1 Introduction This phase...HARRY DIAs ’ND LABORATORIES 3975 MCMM RD ATTN CO/ TD /TSO/DIVISION DIRFXTORS ATTN JERRY KRAMR ATTN RECORD COPY, 81200 CINCINNATI, ON 45245 ATTN HDL LIBRARY

The effect of virtual cross linking on the oxidative stability and lipid uptake of aliphatic poly(urethane urea).

PubMed

Thomas, Vinoy; Jayabalan, Muthu

2002-01-01

In vitro oxidative degradation and lipid sorption of aliphatic, low elastic modulus and virtually cross-linked poly(urethane urea)s based on 4,4' methylene bis(cyclohexyl isocyanate), hydroxy terminated poly butadiene and hexamethylene diamine were evaluated. The aged samples revealed no weight loss in the oxidation medium. The IR spectral analyses revealed the stability of unsaturated double bonds at 964 cm(-1) (characteristic for polybutadiene soft segment) with no change in peak intensity. The poly(tetramethylene glycol) (PTMG)-added poly(ether urethane urea) polymer also revealed no disappearance of IR peaks for ether and unsaturated double bonds in samples aged in vitro oxidation medium. All the polymers have shown increase in weight due to lipid up take in lipid-rich medium (palm oil) but it was rather low in Dulbecco's modified eagle medium (DMEM) cholesterol. The slight change in mechanical properties of the present polymers in oxidation and DMEM is due to the rearrangement of molecular structure with virtual cross links of hydrogen bonding (physical cross linking) without degradation and plasticization effect of lipid. The influence of these media on the rearrangement of virtual cross links has been observed. Higher the virtual cross-link density, lesser is the loss of tensile properties of poly(urethane urea)s in the oxidation medium and vice versa. On the other hand, higher the virtual cross-link density of poly(urethane urea), higher is the loss of ultimate tensile strength and stress at 100% strain and vice versa in DMEM medium.

Acute effects of pentobarbital, thiopental and urethane on lung oedema induced by alpha-naphthythiourea (ANTU).

PubMed

Sipahi, Emine; Ustün, Hüseyin; Niyazi Ayoglu, Ferruh

2002-03-01

This study was designed to investigate the possible participation of urethane, pentobarbital sodium and thiopental sodium anaesthesia in the lung oedema induced by alpha-naphthylthiourea (ANTU), which is a well known noxious chemical agent in the lung. ANTU when injected intraperitoneally (i.p.) into rats (10 mg x kg (-1) i.p.) produced lung oedema as indicated by an increase in lung weight/body weight (LW/BW) ratio and pleural effusion (PE) reaching a maximum within 4 h. Administration of urethane prior to ANTU, at doses of 100 and 200mg(100g)(-1), elicited a significant and dose-dependent inhibition in LW/BW ratio and PE. Thiopental sodium at doses of 25, 50 mg x kg (-1), also produced a significant and dose-dependent inhibition of both parameters. Prior i.p. injection of pentobarbital sodium at a dose of 40 mg x kg (-1) elicited a significant inhibition in both parameters. These results suggest that i.p. urethane, thiopental sodium and pentobarbital sodium pretreatment have a prophylactic effect on ANTU-induced lung injury in rats. The possible role of the anaesthetics in lung oedema induced by ANTU and the possible underlying mechanisms are discussed. Copyright 2002 Elsevier Science Ltd.

Gaskets for low-energy houses

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

Harr, D.

1986-05-01

New materials and techniques make it easier to build today's tight, energy-efficient homes. One system that has won many converts recently is the airtight drywall approach (ADA). ADA relies heavily on the use of foam gasketing. In the ADA building system, nearly all joints--sill to foundation, band joist, wall plate to subfloor, and drywall to frame-are gasketed with foam tapes. The combination of gaskets, drywall, and caulk creates an airtight envelope. Foam gasketing tape is well suited from many of these joints because it is clean, economical, and easy to apply. The right gasket will maintain the seal even ifmore » the joint moves, and won't squeeze out of the joint under compression. Caulk, on the other hand, is messy, hard to apply, and squeezes out of the joint under compression. Saturated urethanes are elastic sealants that always recover, even after being completely compressed. Some saturated urethanes recover faster than others, depending on what saturant is used, but all exert a force to recover because they are urethanes. In the construction industry, where gaskets are likely to be buried permanently within the framework, saturated urethane foam gaskets really make sense.« less

The Effect of Different Doses of Cigarette Smoke in a Mouse Lung Tumor Model

PubMed Central

Santiago, Ludmilla Nadir; de Camargo Fenley, Juliana; Braga, Lúcia Campanario; Cordeiro, José Antônio; Cury, Patrícia M.

2009-01-01

Few studies have used Balb/c mice as an animal model for lung carcinogenesis. In this study, we investigated the effect of different doses of cigarette smoking in the urethane-induced Balb/c mouse lung cancer model. After injection of 3mg/kg urethane intraperitoneally, the mice were then exposed to tobacco smoke once or twice a day, five times a week, in a closed chamber. The animals were randomly divided into four groups. The control group (G0) received urethane only. The experimental groups (G1, G2 and G3) received urethane and exposure to the smoke of 3 cigarettes for 10 minutes once a day, 3 cigarettes for 10 minutes twice a day, and 6 cigarettes for 10 minutes twice a day, respectively. The mice were sacrificed after 16 weeks of exposure, and the number of nodules and hyperplasia in the lungs was counted. The results showed no statistically significant difference in the mean number of nodules and hyperplasia among the different groups, suggesting that the Balb/c mice are not suitable to study the pathogenesis of tobacco smoking-induced tumor progression in the lungs. PMID:19079653

Alternative Fuels Compatibility with Army Equipment Testing - Alternative Fuels Material Compatibility Analysis

DTIC Science & Technology

2012-02-21

Testing and Materials °C Celsius DiEGME Diethylene Glycol Monomethyl Ether EPDM Ethylene Propylene Diene Monomer FARE Forward Area Refueling...urethane class AU, polyether urethane class EU, EPDM , Viton®, fluorosilicone class FQ, polytetrafluoroethylene (PTFE), polyolefin and polyester...sleeve Material not provided AAFARS 4720-00-540-1368 Hose, nonmetallic Material not provided AAFARS 4720-01-218-6958 Hose, preformed Rubber

Air Quality Management Using Pollution Prevention: A Joint Service Approach

DTIC Science & Technology

1998-03-01

sites to promote polymerization. High solids coatings may be one or two component systems based on acrylic , alkyd , epoxy, polyester, or urethane...formulation to form high molecular weight polymers. Examples include acrylic , epoxy/polyester hybrid , functional epoxy, thin film epoxy, and urethane...Air Human System Center (HSC/OEBQ) Naval Facilities Engineering Service Center (NFESC) 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 9

Development of l-Tyrosine-Based Enzyme-Responsive Amphiphilic Poly(ester-urethane) Nanocarriers for Multiple Drug Delivery to Cancer Cells.

PubMed

Aluri, Rajendra; Jayakannan, Manickam

2017-01-09

New classes of enzymatic-biodegradable amphiphilic poly(ester-urethane)s were designed and developed from l-tyrosine amino acid resources and their self-assembled nanoparticles were employed as multiple drug delivery vehicles in cancer therapy. The amine and carboxylic acid functional groups in l-tyrosine were converted into dual functional ester-urethane monomers and they were subjected to solvent free melt polycondensation with hydrophilic polyethylene glycols to produce comb-type poly(ester-urethane)s. The phenolic unit in the l-tyrosine was anchored with hydrophobic alkyl side chain to bring appropriate amphiphilicity in the polymer geometry to self-assemble them as stable nanoscaffolds in aqueous medium. The topology of the polymer was found to play a major role on the glass transition, crystallinity, and viscoelastic rheological properties of l-tyrosine poly(ester-urethane)s. The amphiphilic polymers were self-assembled as 200 ± 10 nm nanoparticles and they exhibited excellent encapsulation capabilities for anticancer drugs such as doxorubicin (DOX) and camptothecin (CPT). In vitro drug release studies revealed that the drug-loaded l-tyrosine nanoparticles were stable at extracellular conditions and they underwent enzymatic-biodegradation exclusively at the intracellular level to release the drugs. Cytotoxicity studies in the cervical cancer (HeLa) and normal WT-MEFs cell lines revealed that the nascent l-tyrosine nanoparticles were nontoxic, whereas the CPT and DOX drug-loaded polymer nanoparticles exhibited excellent cell killing in cancer cells. Confocal microscopic imaging confirmed the cellular internalization of drug-loaded nanoparticles. The drugs were taken up by the cells much higher quantity while delivering them from l-tyrosine nanoparticle platform compared to their free state. Flow cytometry analysis showed that the DOX-loaded polymer nanoscaffolds internalized the drugs 8-10× higher compared to free DOX. Both the synthesis of new classes of poly(ester-urethane)s via melt polycondensation approach and the enzyme-responsive drug delivery concept were accomplished for the first time. Thus, the present investigation is expected to open up new opportunities for l-tyrosine polymeric materials in biomaterial and thermoplastic applications.

Preparation and properties of an internal mold release for rigid urethane foam

NASA Astrophysics Data System (ADS)

Paker, B. G.

1980-08-01

Most mold release agents used in the molding of rigid polyurethane foam are applied to the internal surfaces of the mold. These materials form a thin layer between the surface of the mold and the foam, allowing for easy release of the molded parts. This type of mold release must be applied prior to each molding operation; and, after repeated use, cleaning of the mold is required. Small amounts of this mold release are transferred to the molded part, resulting in a part with poor surface bondability characteristics. An internal release agent, which can be mixed in a urethane foam resin was investigated. The internal mold release provided good releasability and resulted in urethane foam that has excellent surface bondability. No compatibility problems are expected from the use of this type of release agent.

Degradation Mechanisms of Poly(ester urethane) Elastomer

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

Edgar, Alexander S.

This report describes literature regarding the degradation mechanisms associated with a poly(ester urethane) block copolymer, Estane® 5703 (Estane), used in conjunction with Nitroplasticizer (NP), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane, also known as high molecular weight explosive (HMX) to produce polymer bonded explosive PBX 9501. Two principal degradation mechanisms are reported: NO2 oxidative reaction with the urethane linkage resulting in crosslinking and chain scission events, and acid catalyzed hydrolysis of the ester linkage. This report details future work regarding this PBX support system, to be conducted in late 2017 and 2018 at Engineered Materials Group (MST-7), Materials Science and Technology Division, Los Alamos Nationalmore » Laboratory. This is the first of a series of three reports on the degradation processes and trends of the support materials of PBX 9501.« less

Poly(hydroxyl urethane) compositions and methods of making and using the same

DOEpatents

Luebke, David; Nulwala, Hunaid; Tang, Chau

2016-01-26

Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

Poly(hydroxyl urethane) compositions and methods of making and using the same

DOEpatents

Luebke, David; Nulwala, Hunaid; Tang, Chau

2014-12-16

Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

The Reactions of Nitrogen Peroxide with Possible Stabilisers for Propellants

DTIC Science & Technology

1957-03-01

ether Carbamite Phe nyl-be nzyl-ure thane (pure) Cyclohexanyl-urethane Cyclohexano ne Die thyl phthalate Di-isoamyl phthalate Dibutyl oxalate Glycollic...saponification" arises from the presence of phenyl urethane and diphenyl urea; differences in contents of these impurities and of benzyl aniline...nitrogen that is recovered from a product. 4.2.2 Ure are fairly reactive. Triphenylethylurea present with diphenyl - amine in 蠢 compound" leads to a

FOAM-IN-PLACE FORM FITTING HELMET LINERS

DTIC Science & Technology

A urethane foam formulation has been developed to produce foamed-in-place helmet liners for Air Force crash or flying helmets. High density urethane...foam helmet liners has been foamed-in-place directly on the flying crew member’s head, producing a perfectly fitting helmet liner with a minimum of...time, labor and inconvenience. These liners were produced at an extremely modest cost. Design and fabrication of a suitable mold in which the helmet

Storage, Preservation, and Recovery of Magnetic Recording Tape

NASA Technical Reports Server (NTRS)

Cuddihy, Edward F.

1994-01-01

During the 1970's, a commercial magnetic recording tape fabricated with magnetic oxide particles, and with oxide and backcoat binders made from polyester urethane was being used for spacecraft tape recorders, and which would periodically manifest operational problems such as layer-to-layer adhesion, stick-slip, and shedding of sticky organic materials. These problems were generally associated with periods of high humidity. An experimental study identified that these problems resulted from hydrolysis of the polyester urethane binders.

An Acoustic-Instrumented Mine for Studying Subsequent Burial

DTIC Science & Technology

2007-01-01

seawater . A strong reflection from the transducer face therefore indicates sediment flush with the mine surface (i.e., the mine surface is buried...variations in seawater sound speed and urethane sound speed that create a slight acoustic impedance mismatch at the water-urethane in- terface. The water...following was used: w. = \\//,„/2f/« TTH, U, T;Sinh( kh ) /„• = 0.237 0.52 /„, is the wave friction factor, Uw is the wave orbital velocity

Isolation and characterization of an ether-type polyurethane-degrading micro-organism and analysis of degradation mechanism by Alternaria sp.

PubMed

Matsumiya, Y; Murata, N; Tanabe, E; Kubota, K; Kubo, M

2010-06-01

To degrade ether-type polyurethane (ether-PUR), ether-PUR-degrading micro-organism was isolated. Moreover, ether-PUR-degrading mechanisms were analysed using model compounds of ether-PUR. A fungus designated as strain PURDK2, capable of changing the configuration of ether-PUR, has been isolated. This isolated fungus was identified as Alternaria sp. Using a scanning electron microscope, the grid structure of ether-PUR was shown to be melted and disrupted by the fungus. The degradation of ether-PUR by the fungus was analysed, and the ether-PUR was degraded by the fungus by about 27.5%. To analyse the urethane-bond degradation by the fungus, a degraded product of ethylphenylcarbamate was analysed using GC/MS. Aniline and ethanol were detected by degradation with the supernatant, indicating that the fungus secreted urethane-bond-degrading enzyme(s). PURDK2 also degraded urea bonds when diphenylmethane-4,4'-dibutylurea was used as a substrate. The enzyme(s) from PURDK2 degraded urethane and urea bonds to convert the high molecular weight structure of ether-PUR to small molecules; and then the fungus seems to use the small molecules as an energy source. Ether-PUR-degrading fungus, strain PURDK2, was isolated, and the urethane- and urea-bonds-degrading enzymes from strain PURDK2 could contribute to the material recycling of ether-PUR.

Depletion of serotonin synthesis with p-CPA pretreatment alters EEG in urethane anesthetized rats under whole body hyperthermia.

PubMed

Sinha, Rakesh Kumar; Aggarwal, Yogender

2007-01-01

Serotonin is believed as an important factor in brain function. The role of serotonin in cerebral psycho-patho-physiology has already been well established. However, the function of serotonin antagonist in anesthetized subjects under hyperthermia has not been studied properly. Experiments were performed in three groups of urethane-anesthetized rats, such as: (i) control group, (ii) whole body hyperthermia group and (iii) p-CPA (para-Chlorophenylalanine) pretreated hyperthermia group. Hyperthermia was produced by subjecting the rats to high ambient temperature of 38 +/- 1 degrees C (relative humidity 45-50%). Each group was divided for EEG (electroencephalogram) study and for determination of edematous swelling in the brain. Urethane anesthetized rats under hyperthermia show highly significant reduction in their survival time. The body temperature recorded during the hyperthermia was observed with significant and linear rise with marked increase in brain water content, which was analyzed just after the death of the subjects. The results of the electroencephalographic study in urethane-anesthetized rats recorded before death indicate that brain function varies in systematic manner during hyperthermia as sequential changes in EEG patterns were observed. However, a serotonin antagonist, p-CPA pretreatment increases the survival time with significant reduction in edematous swelling in brain but it does not affect the relationship between the core body temperature and the brain cortical potentials as observed in urethane anesthetized subjects exposed to whole body hyperthermia. The core body temperature in p-CPA pretreated rats show non-linear relationship with respect to the exposure time as it was observed in drug untreated subjects. The findings of the present study indicate that although pretreatment of p-CPA in rats has a marked correlation between the extravasations of the blood-brain barrier under hyperthermia but shows minimum effect on the EEG in a model of hyperthermia under irreversible anesthesia.

Flexible, Water-Resistant Urethane Coatings for Ferrous Surfaces on U.S. Army Corps of Engineers’ Dams.

DTIC Science & Technology

1982-07-01

of Opaque Specimens by, Broad-Band Filter Reflectometry , ASTM E 97 (1977). could be produced on a specialty basis by interested 3 TEST SPECIMEN...Aeronautics and Space Adminis- tration ( NASA ) study deals with the long-term hy- drolytic stability of urethane elastomers used with CONCLUSIONS AND...necessary for high hydrolytic stability-are not better than the polyether- solids coatings. The NASA study may be correct in based X series. The highest

Research of low cost wind generator rotors

NASA Technical Reports Server (NTRS)

Fertis, D. G.; Ross, R. S.

1978-01-01

A feasibility program determined that it would be possible to significantly reduce the cost of manufacturing wind generator rotors by making them of cast urethane. Several high modulus urethanes which were structurally tested were developed. A section of rotor was also cast and tested showing the excellent aerodynamic surface which results. A design analysis indicated that a cost reduction of almost ten to one can be achieved with a small weight increase to achieve the same structural integrity as expected of current rotor systems.

NAVFAC Ocean Thermal Energy Conversion (OTEC) Project; OTEC Technology Development Report

DTIC Science & Technology

2010-11-01

platform and CWP. It was a goal of this program to find a material that is high in abrasion resistance and low in friction for the guide layers. Figure...preferred material was a high density urethane. Urethane has very high abrasion resistance – it is often used for marine buoys, fenders, and coatings...design thread in the document. The following is a list of the top level sections in the report. EXECUTIVE SUMMARY  1  1.  INTRODUCTION  2  2

Simultaneous Improvement of Oxidative and Hydrolytic Resistance of Polycarbonate Urethanes Based on Polydimethylsiloxane/Poly(hexamethylene carbonate) Mixed Macrodiols.

PubMed

Li, Zhen; Yang, Jian; Ye, Heng; Ding, Mingming; Luo, Feng; Li, Jianshu; Li, Jiehua; Tan, Hong; Fu, Qiang

2018-06-11

The degradation behaviors including oxidation and hydrolysis of silicone modified polycarbonate urethanes were thoroughly investigated. These polyurethanes were based on polyhexamethylene carbonate (PHMC)/polydimethylsiloxane (PDMS) mixed macrodiols with molar ratio of PDMS ranging from 5% to 30%. It was proved that PDMS tended to migrate toward surface and even a small amount of PDMS could form a silicone-like surface. Macrophages-mediated oxidation process indicated that the PDMS surface layer was desirable to protect the fragile soft PHMC from the attack of degradative species. Hydrolysis process was probed in detail after immersing in boiling buffered water using combined analytical tools. Hydrolytically stable PDMS could act as protective shields for the bulk to hinder the chain scission of polycarbonate carbonyls whereas the hydrolysis of urethane linkages was less affected. Although the promoted phase separation at higher PDMS fractions lead to possible physical defects and mechanical compromise after degradation, simultaneously enhanced oxidation and hydrolysis resistance could be achieved for the polyurethanes with proper PDMS incorporation.

Multistimuli-Responsive Amphiphilic Poly(ester-urethane) Nanoassemblies Based on l-Tyrosine for Intracellular Drug Delivery to Cancer Cells.

PubMed

Aluri, Rajendra; Saxena, Sonashree; Joshi, Dheeraj Chandra; Jayakannan, Manickam

2018-06-11

Multistimuli-responsive l-tyrosine-based amphiphilic poly(ester-urethane) nanocarriers were designed and developed for the first time to administer anticancer drugs in cancer tissue environments via thermoresponsiveness and lysosomal enzymatic biodegradation from a single polymer platform. For this purpose, multifunctional l-tyrosine monomer was tailor-made with a PEGylated side chain at the phenolic position along with urethane and carboxylic ester functionalities. Under melt dual ester-urethane polycondensation, the tyrosine monomer reacted with diols to produce high molecular weight amphiphilic poly(ester-urethane)s. The polymers produced 100 ± 10 nm spherical nanoparticles in aqueous medium, and they exhibited thermoresponsiveness followed by phase transition from clear solution into a turbid solution in heating/cooling cycles. Variable temperature transmittance, dynamic light scattering, and 1 H NMR studies revealed that the polymer chains underwent reversible phase transition from coil-to-expanded chain conformation for exhibiting the thermoresponsive behavior. The lower critical solution temperature of the nanocarriers was found to correspond to cancer tissue temperature (at 42-44 °C), which was explored as an extracellular trigger (stimuli-1) for drug delivery through the disassembly process. The ester bond in the poly(ester-urethane) backbones readily underwent enzymatic biodegradation in the lysosomal compartments that served as intracellular stimuli (stimuli-2) to deliver drugs. Doxorubicin (DOX) and camptothecin (CPT) drug-loaded polymer nanocarriers were tested for cellular uptake and cytotoxicity studies in the normal WT-MEF cell line and cervical (HeLa) and breast (MCF7) cancer cell lines. In vitro drug release studies revealed that the polymer nanoparticles were stable under physiological conditions (37 °C, pH 7.4) and they exclusively underwent disassembly at cancer tissue temperature (at 42 °C) and biodegradation by lysosomal-esterase enzyme to deliver 90% of DOX and CPT. Drug-loaded polymer nanoparticles exhibited better cytotoxic effects than their corresponding free drugs. Live cell confocal microscopy imaging experiments with lysosomal tracker confirmed the endocytosis of the polymer nanoparticles and their biodegradation in the lysosomal compartments in cancer cells. The increment in the drug content in the cells incubated at 42 °C compared to 37 °C supported the enhanced drug uptake by the cancer cells under thermoresponsive stimuli. The present work creates a new platform for the l-amino acid multiple-responsive polymer nanocarrier platform for drug delivery, and the proof-of-concept was successfully demonstrated for l-tyrosine polymers in cervical and breast cancer cells.

Division of constricted and urethane-treated sand dollar eggs: a test of the polar stimulation hypothesis.

PubMed

Rappaport, R; Rappaport, B N

1984-07-01

In spherical cells with a central mitotic apparatus, the centers of the asters are closer to the poles than to the equator. This circumstance is basic to several hypothetical explanations of the way in which the mitotic apparatus establishes the division mechanism. This investigation was designed to determine whether that geometrical relationship is necessary for division. Fertilized, mechanically denuded sand dollar eggs were inserted into glass loops, which reduced the diameter in the constriction plane from the normal 142 to 78-80 microns and partly constricted the cell into equal parts. The mitotic apparatus straddled the constriction, and its length was not significantly changed. The manipulation increased the distance from the astral centers to the poles and decreased the distance from the astral centers to the equator to a degree that reversed the normal distance relations. These cells divided normally. Ethyl urethane (0.06 M) reduces the size of the mitotic apparatus and blocks cleavage in spherical cells. When treated cells are confined in 80-microns i.d. capillaries, they divide. Treated cells also divide when they are constricted by an 80-microns i.d. glass loop if the mitotic apparatus straddles the constriction. An equal degree of constriction in the subfurrow and subpolar areas did not reverse the effect of urethane. The results demonstrate that cleavage does not depend on the normal distance relation between the mitotic apparatus and the poles, and that the urethane effect can be remedied only by reducing the distance between the mitotic apparatus and the equatorial surface. Both findings are inconsistent with the polar stimulation hypothesis.

[Change of character of intersystemic interactions in newborn rat pups under conditions of a decrease of central influences (urethane anesthesia)].

PubMed

Kuznetsov, S V; Sizonov, V A; Dmitrieva, L E

2014-01-01

On newborn rat pups, for the first day after birth, there was studied the character of mutual influences between the slow-wave rhythmical components of the cardiac, respiratory, and motor activities reflecting interactions between the main functional systems of the developing organism. The study was carried out in norm and after pharmacological depression of the spontaneous periodical motor activity (SPMA) performed by narcotization of rat pups with urethane at low (0.5 g/kg, i/p) and maximal (1 g/kg, i/p) doses. Based on the complex of our obtained data, it is possible to conclude that after birth in rat pups the intersystemic interactions are realized mainly by the slow-wave oscillations of the near- and manyminute diapason. The correlational interactions mediated by rhythms of the decasecond diapason do not play essential role in integrative processes. Injection to the animals of urethane producing selective suppression of reaction of consciousness, but not affecting activating influences of reticular formation on cerebral cortex does not cause marked changes of autonomous parameters, but modulates structure and expression of spontaneous periodical motor activity. There occurs an essential decrease of mutual influences between motor and cardiovascular systems. In the case of preservation of motor activity bursts, a tendency for enhancement of correlational relations between the modulating rhythms of motor and somatomotor systems is observed. The cardiorespiratory interactions, more pronounced in intact rat pups in the near- and many-minute modulation diapason, under conditions of urethane, somewhat decrease, whereas the rhythmical components of the decasecond diapason--are weakly enhanced.

Nanoscale Structure of Urethane/Urea Elastomeric Films

NASA Astrophysics Data System (ADS)

Reis, Dennys; Trindade, Ana C.; Godinho, Maria Helena; Silva, Laura C.; do Carmo Gonçalves, Maria; Neto, Antônio M. Figueiredo

2017-02-01

The nanostructure of urethane/urea elastomeric membranes was investigated by small-angle X-ray scattering (SAXS) in order to establish relationships between their structure and mechanical properties. The networks were made up of polypropylene oxide (PPO) and polybutadiene (PB) segments. The structural differences were investigated in two types of membranes with the same composition but with different thermal treatment after casting. Type I was cured at 70-80 °C and type II at 20 °C. Both membranes showed similar phase separation by TEM, with nanodomains rich in PB or PPO and 25 nm dimensions. The main difference between type I and type II membranes was found by SAXS. The type I membrane spectra showed, besides a broad band at a 27-nm q value (modulus of the scattering vector), an extra band at 6 nm, which was not observed in the type II membrane. The SAXS spectra were interpreted in terms of PPO, PB soft segments, and urethane/urea links, as well as hard moiety segregation in the reaction medium. This additional segregation ( q = 7 nm), although subtle, results in diverse mechanical behavior of in both membranes.

MDI Exposure for Spray-On Truck Bed Lining.

PubMed

Lofgren, Don J; Walley, Terry L; Peters, Phillip M; Weis, Marty L

2003-10-01

Worker exposure to MDI (methylenediphenyl isocyanate) in the sprayed-on truck bed lining industry was assessed by examining Washington State OSHA inspection files and industrial insurance records. The industry uses MDI to form a protective urethane coating on pick-up truck beds. The lining is applied by a worker using a handheld spray gun with application equipment at temperatures and pressures specified by the urethane supplier. Inspections with MDI sampling were initially identified by searching the agency's laboratory database and were further screened for the targeted process. Data for 13 employers was found and extracted from the inspection records. All were small companies with only 1 to 2 workers exposed to MDI; 10 of the 13 employers had started the bed lining service within the last 4 years. The process was found in truck bed lining specialty shops as well as in other truck-related businesses. Six different urethane products were used with reported MDI monomer concentrations of up to 75 percent along with varying concentrations of MDI pre-polymers and other reactants and solvents. Sampling for MDI by inspectors found 7 worksites with worker exposure in excess of the state and OSHA ceiling limit of 0.200 mg/M(3). Deficiencies in respirator programs and engineering controls for MDI were cited. A review of the industrial insurance records found a total of five MDI-related claims at 4 inspected worksites, two for new-onset asthma. It was concluded that workers in the urethane sprayed-on truck bed lining industry are at an increased risk of developing illnesses associated with isocyanate exposure. Interventions are needed to further assess the hazard as well as motivate and assist franchisers, distributors, and retailers to implement effective engineering controls and respiratory protection programs in this nationally emerging small employer industry.

Lamb Wave Dispersion Ultrasound Vibrometry (LDUV) Method for Quantifying Mechanical Properties of Viscoelastic Solids

PubMed Central

Nenadic, Ivan Z.; Urban, Matthew W.; Mitchell, Scott A.; Greenleaf, James F.

2011-01-01

Diastolic dysfunction is the inability of the left ventricle to supply sufficient stroke volumes under normal physiological conditions and is often accompanied by stiffening of the left-ventricular myocardium. A noninvasive technique capable of quantifying viscoelasticity of the myocardium would be beneficial in clinical settings. Our group has been investigating the use of Shearwave Dispersion Ultrasound Vibrometry (SDUV), a noninvasive ultrasound based method for quantifying viscoelasticity of soft tissues. The primary motive of this study is the design and testing of viscoelastic materials suitable for validation of the Lamb wave Dispersion Ultrasound Vibrometry (LDUV), an SDUV-based technique for measuring viscoelasticity of tissues with plate-like geometry. We report the results of quantifying viscoelasticity of urethane rubber and gelatin samples using LDUV and an embedded sphere method. The LDUV method was used to excite antisymmetric Lamb waves and measure the dispersion in urethane rubber and gelatin plates. An antisymmetric Lamb wave model was fitted to the wave speed dispersion data to estimate elasticity and viscosity of the materials. A finite element model of a viscoelastic plate submerged in water was used to study the appropriateness of the Lamb wave dispersion equations. An embedded sphere method was used as an independent measurement of the viscoelasticity of the urethane rubber and gelatin. The FEM dispersion data were in excellent agreement with the theoretical predictions. Viscoelasticity of the urethane rubber and gelatin obtained using the LDUV and embedded sphere methods agreed within one standard deviation. LDUV studies on excised porcine myocardium sample were performed to investigate the feasibility of the approach in preparation for open-chest in vivo studies. The results suggest that the LDUV technique can be used to quantify mechanical properties of soft tissues with a plate-like geometry. PMID:21403186

Lamb wave dispersion ultrasound vibrometry (LDUV) method for quantifying mechanical properties of viscoelastic solids.

PubMed

Nenadic, Ivan Z; Urban, Matthew W; Mitchell, Scott A; Greenleaf, James F

2011-04-07

Diastolic dysfunction is the inability of the left ventricle to supply sufficient stroke volumes under normal physiological conditions and is often accompanied by stiffening of the left-ventricular myocardium. A noninvasive technique capable of quantifying viscoelasticity of the myocardium would be beneficial in clinical settings. Our group has been investigating the use of shear wave dispersion ultrasound vibrometry (SDUV), a noninvasive ultrasound-based method for quantifying viscoelasticity of soft tissues. The primary motive of this study is the design and testing of viscoelastic materials suitable for validation of the Lamb wave dispersion ultrasound vibrometry (LDUV), an SDUV-based technique for measuring viscoelasticity of tissues with plate-like geometry. We report the results of quantifying viscoelasticity of urethane rubber and gelatin samples using LDUV and an embedded sphere method. The LDUV method was used to excite antisymmetric Lamb waves and measure the dispersion in urethane rubber and gelatin plates. An antisymmetric Lamb wave model was fitted to the wave speed dispersion data to estimate elasticity and viscosity of the materials. A finite element model of a viscoelastic plate submerged in water was used to study the appropriateness of the Lamb wave dispersion equations. An embedded sphere method was used as an independent measurement of the viscoelasticity of the urethane rubber and gelatin. The FEM dispersion data were in excellent agreement with the theoretical predictions. Viscoelasticity of the urethane rubber and gelatin obtained using the LDUV and embedded sphere methods agreed within one standard deviation. LDUV studies on excised porcine myocardium sample were performed to investigate the feasibility of the approach in preparation for open-chest in vivo studies. The results suggest that the LDUV technique can be used to quantify the mechanical properties of soft tissues with a plate-like geometry.

Strength of titanium intramedullary implant versus miniplate fixation of mandibular condyle fractures.

PubMed

Frake, Paul C; Howell, Rebecca J; Joshi, Arjun S

2012-07-01

To test the strength of internal fixation of mandibular condyle fractures repaired with titanium miniplates versus titanium intramedullary implants. Prospective laboratory experimentation in urethane mandible models and human cadaveric mandibles. Materials testing laboratory at an academic medical center. Osteotomies of the mandibular condyle were created in 40 urethane hemimandible models and 24 human cadaveric specimens. Half of the samples in each group were repaired with traditional miniplates, and the other half were repaired with intramedullary titanium implants. Anteroposterior and mediolateral loads were applied to the samples, and the displacement was measured with reference to the applied force. Titanium intramedullary implants demonstrated statistically significant improved strength and stiffness versus miniplates in the urethane model experimental groups. Despite frequent plastic deformation and mechanical failures of the miniplates, a 1.6-mm-diameter titanium intramedullary pin did not mechanically fail in any of the cases. Intramedullary implantation failures were due to secondary fracture of the adjacent cortical bone or experimental design limitations including rotation of the smooth pin implant. Mechanical implant failures that were encountered with miniplate fixation were not seen with titanium intramedullary implants. These intramedullary implants provide stronger and more rigid fixation of mandibular condyle fractures than miniplates in this in vitro model.

Antitumor activity of intratracheal inhalation of temozolomide (TMZ) loaded into gold nanoparticles and/or liposomes against urethane-induced lung cancer in BALB/c mice.

PubMed

Hamzawy, Mohamed A; Abo-Youssef, Amira M; Salem, Heba F; Mohammed, Sameh A

2017-11-01

The current study aimed to develop gold nanoparticles (GNPs) and liposome-embedded gold nanoparticles (LGNPs) as drug carriers for temozolomide (TMZ) and investigate the possible therapeutic effects of intratracheal inhalation of nanoformulation of TMZ-loaded gold nanoparticles (TGNPs) and liposome-embedded TGNPs (LTGNPs) against urethane-induced lung cancer in BALB/c mice. Physicochemical characters and zeta potential studies for gold nanoparticles (GNPs) and liposome-embedded gold nanoparticles (LGNPs) were performed. The current study was conducted by inducing lung cancer chemically via repeated exposure to urethane in BALB/C mice. GNPs and LGNPs were exhibited in uniform spherical shape with adequate dispersion stability. GNPs and LGNPs showed no significant changes in comparison to control group with high safety profile, while TGNPs and LTGNPs succeed to improve all biochemical data and histological patterns. GNPs and LGNPs are promising drug carriers and succeeded in the delivery of small and efficient dose of temozolomide in treatment lung cancer. Antitumor activity was pronounced in animal-treated LTGNPs, these effects may be due to synergistic effects resulted from combination of temozolomide and gold nanoparticles and liposomes that may improve the drug distribution and penetration.

Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices.

PubMed

Mathew, Simi; Baudis, Stefan; Neffe, Axel T; Behl, Marc; Wischke, Christian; Lendlein, Andreas

2015-09-01

In this study, the effect of three aliphatic diisocyanate linkers, L-lysine diisocyanate ethyl ester (LDI), hexamethylene diisocyanate (HDI), and racemic 2,2,4-/2,4,4-trimethyl hexamethylene diisocyanate (TMDI), on the degradation of oligo[(rac-lactide)-co-glycolide] (64:36 mol%) based polyester urethanes (PEU) was examined. Samples were characterized for their molecular weight, mass loss, water uptake, sequence structure, and thermal and mechanical properties. Compared to non-segmented PLGA, the PEU showed higher water uptake and generally degraded faster. Interestingly, the rate of degradation was not directly correlating with the hydrophilicity of the diisocyanate moieties; instead, competing intra-/intermolecular hydrogen bonds in between urethane moieties appear to substantially decrease the rate of degradation for LDI-derived PEU. By comparing microparticles (μm) and films (mm) as matrices of different dimensions, it was shown that autocatalysis remains a contributor to degradation of the larger-sized PEU matrices as it is typical for non-segmented lactide/glycolide copolymers. The shown capacity of lactide/glycolide-based multiblock copolymers to degrade faster than PLGA and exhibit improved elastic properties could be of interest for medical implants and drug release systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Syntheses and properties of elastic copoly(ester-urethane)s containing a phospholipid moiety and the fabrication of nanosheets.

PubMed

Sirithep, Wariya; Morita, Kohei; Iwano, Atsushi; Komachi, Takuya; Okamura, Yosuke; Nagase, Yu

2014-01-01

In these years, we have investigated the syntheses of novel diamine and diol monomers containing phosphorylcholine (PC) group to obtain biocompatible polymers, the backbone components of which were thermally stable and mechanically strong. In this study, the preparations of elastic copoly(ester-urethane)s containing PC group and polycarbonate segment were carried out by polycondensation and polyaddition using a diol monomer containing PC group and polycarbonate diol. It was found that the obtained polymers exhibited the high-thermal stability up to 200 °C and the elasticity derived from the soft segment. The introduction of PC group was effective to improve the resistance to the adhesions of proteins and platelets on the polymer films, which was the result of surface properties derived from the PC moiety. In addition, we tried to prepare ultra-thin polymer films composed of copoly(ester-urethane)s, so-called nanosheets. As a result, the desired nanosheets were successfully fabricated and the obtained nanosheets exhibited the high adhesive strength, indicating that the nanosheets could conform closely to the desired surfaces due to their exquisite flexibility and low roughness.

Development of high strength siloxane poly(urethane-urea) elastomers based on linked macrodiols for heart valve application.

PubMed

Dandeniyage, Loshini S; Gunatillake, Pathiraja A; Adhikari, Raju; Bown, Mark; Shanks, Robert; Adhikari, Benu

2017-08-31

Mixed macrodiol based siloxane poly(urethane-urea)s (SiPUU) having number average molecular weights in the range 87-129 kDa/mol were synthesized to give elastomers with high tensile and tear strengths required to fabricate artificial heart valves. Polar functional groups were introduced into the soft segment to improve the poor segmental compatibility of siloxane polyurethanes. This was achieved by linking α,ω-bis(6-hydroxyethoxypropyl) poly(dimethylsiloxane) (PDMS) or poly(hexamethylene oxide) (PHMO) macrodiols with either 4,4'-methylenediphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI) prior to polyurethane synthesis. The hard segment was composed of MDI, and a 1:1 mixture of 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane and 1,2-ethylene diamine. We report the effect of urethane linkers in soft segments on properties of the SiPUU. PHMO linked with either MDI or IPDI produced SiPUU with the highest tensile and tear strengths. Linking PDMS hardly affected the tensile strength; however, the tear strength was improved. The stress-strain curves showed no plastic deformation region typically observed for conventional polyurethanes indicating good creep resistance. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

Physiological Effects of Touching Coated Wood.

PubMed

Ikei, Harumi; Song, Chorong; Miyazaki, Yoshifumi

2017-07-13

This study examined the physiological effects of touching wood with various coating with the palm of the hand on brain activity and autonomic nervous activity. Participants were 18 female university students (mean age, 21.7 ± 1.6 years). As an indicator of brain activity, oxyhemoglobin concentrations were measured in the left and right prefrontal cortices using near-infrared time-resolved spectroscopy. Heart rate variability (HRV) and heart rate were used as indicators of autonomic nervous activity. The high-frequency (HF) component of HRV, which reflects parasympathetic nervous activity, and the low-frequency (LF)/HF ratio, which reflects sympathetic nervous activity, were measured. Plates of uncoated, oil-finished, vitreous-finished, urethane-finished, and mirror-finished white oak wood were used as tactile stimuli. After sitting at rest with their eyes closed for 60 s, participants touched the stimuli with their palm for 90 s each. The results indicated that tactile stimulation with uncoated wood calmed prefrontal cortex activity (vs. urethane finish and mirror finish), increased parasympathetic nervous activity (vs. vitreous finish, urethane finish, and mirror finish), and decreased heart rate (vs. mirror finish), demonstrating a physiological relaxation effect. Further, tactile stimulation with oil- and vitreous-finished wood calmed left prefrontal cortex activity and decreased heart rate relative to mirror-finished wood.

Physiological Effects of Touching Coated Wood

PubMed Central

2017-01-01

This study examined the physiological effects of touching wood with various coating with the palm of the hand on brain activity and autonomic nervous activity. Participants were 18 female university students (mean age, 21.7 ± 1.6 years). As an indicator of brain activity, oxyhemoglobin concentrations were measured in the left and right prefrontal cortices using near-infrared time-resolved spectroscopy. Heart rate variability (HRV) and heart rate were used as indicators of autonomic nervous activity. The high-frequency (HF) component of HRV, which reflects parasympathetic nervous activity, and the low-frequency (LF)/HF ratio, which reflects sympathetic nervous activity, were measured. Plates of uncoated, oil-finished, vitreous-finished, urethane-finished, and mirror-finished white oak wood were used as tactile stimuli. After sitting at rest with their eyes closed for 60 s, participants touched the stimuli with their palm for 90 s each. The results indicated that tactile stimulation with uncoated wood calmed prefrontal cortex activity (vs. urethane finish and mirror finish), increased parasympathetic nervous activity (vs. vitreous finish, urethane finish, and mirror finish), and decreased heart rate (vs. mirror finish), demonstrating a physiological relaxation effect. Further, tactile stimulation with oil- and vitreous-finished wood calmed left prefrontal cortex activity and decreased heart rate relative to mirror-finished wood. PMID:28703777

Measurement of tritium penetration through concrete material covered by various paints coating

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

Edao, Y.; Kawamura, Y.; Kurata, R.

The present study aims at obtaining fundamental data on tritium migration in porous materials, which include soaking effect, interaction between tritium and cement paste coated with paints and transient tritium sorption in porous cement. The amounts of tritium penetrated into or released from cement paste with epoxy and urethane paint coatings were measured. The tritium penetration amounts were increased with the HTO (tritiated water) exposure time. Time to achieve a saturated value of tritium sorption was more than 60 days for cement paste coated with epoxy paint and with urethane paint, while that for cement paste without any paint coatingmore » took 2 days to achieve it. The effect of tritium permeation reduction by the epoxy paint was higher than that of the urethane. Although their paint coatings were effective for reduction of tritium penetration through the cement paste which was exposed to HTO for a short period, it was found that the amount of tritium trapped in the paints became large for a long period. Tritium penetration rates were estimated by an analysis of one-dimensional diffusion in the axial direction of a thickness of a sample. Obtained data were helpful for evaluation of tritium contamination and decontamination. (authors)« less

Nondegradable magnetic poly (carbonate urethane) microspheres with good shape memory as a proposed material for vascular embolization.

PubMed

Liu, Rongrong; Zhang, Qian; Zhou, Qian; Zhang, Ping; Dai, Honglian

2018-06-01

In this study, nondegradable poly (carbonate urethane) (PCU) and poly (carbonate urethane) incorporated variable Fe 3 O 4 content microspheres (PCU/Fe 3 O 4 ) were synthesized using pre-polymerization and suspension polymerization. Synthesis was confirmed through Fourier transform infrared spectroscopy (FTIR). The effect of Fe 3 O 4 incorporation was investigated on crystalline, thermal, shape memory and degradation properties by X-Ray diffraction (XRD), Differential scanning calorimetery (DSC), compression test and degradation in vitro, respectively. Otherwise, the assessment of magnetic characteristics by vibrational sample magnetometry (VSM) disclosed superparamagnetic behavior. The tunable superparamagnetic behavior depends on the amount of magnetic particles incorporated within the networks. The biological study results of as-synthesized polymers from the platelet adhesion test and the cell proliferation inhibition test indicated they were biocompatible in vitro. Fe 3 O 4 incorporation was conductive to reducing platelet adhesion in blood contacting test and promotion of rat vascular smooth muscle cell proliferation and growth. These nondegradable, superparamagnetic, biocompatible polymers, combined with their good shape memory properties may allow for their future exploitation in the biomedical field, such as, in cardiovascular implants, targeted tumor treatment, tissue engineering and artificial organ's engineering. Copyright © 2018. Published by Elsevier Ltd.

Anesthetic state modulates excitability but not spectral tuning or neural discrimination in single auditory midbrain neurons

PubMed Central

Schumacher, Joseph W.; Schneider, David M.

2011-01-01

The majority of sensory physiology experiments have used anesthesia to facilitate the recording of neural activity. Current techniques allow researchers to study sensory function in the context of varying behavioral states. To reconcile results across multiple behavioral and anesthetic states, it is important to consider how and to what extent anesthesia plays a role in shaping neural response properties. The role of anesthesia has been the subject of much debate, but the extent to which sensory coding properties are altered by anesthesia has yet to be fully defined. In this study we asked how urethane, an anesthetic commonly used for avian and mammalian sensory physiology, affects the coding of complex communication vocalizations (songs) and simple artificial stimuli in the songbird auditory midbrain. We measured spontaneous and song-driven spike rates, spectrotemporal receptive fields, and neural discriminability from responses to songs in single auditory midbrain neurons. In the same neurons, we recorded responses to pure tone stimuli ranging in frequency and intensity. Finally, we assessed the effect of urethane on population-level representations of birdsong. Results showed that intrinsic neural excitability is significantly depressed by urethane but that spectral tuning, single neuron discriminability, and population representations of song do not differ significantly between unanesthetized and anesthetized animals. PMID:21543752

Soy-based polyols

DOEpatents

Suppes, Galen; Lozada, Zueica; Lubguban, Arnold

2013-06-25

The invention provides processes for preparing soy-based oligomeric polyols or substituted oligomeric polyols, as well as urethane bioelasteromers comprising the oligomeric polyols or substituted oligomeric polyols.

Chemical control of the viscoelastic properties of vinylogous urethane vitrimers

PubMed Central

Denissen, Wim; Droesbeke, Martijn; Nicolaÿ, Renaud; Leibler, Ludwik; Winne, Johan M.; Du Prez, Filip E.

2017-01-01

Vinylogous urethane based vitrimers are polymer networks that have the intrinsic property to undergo network rearrangements, stress relaxation and viscoelastic flow, mediated by rapid addition/elimination reactions of free chain end amines. Here we show that the covalent exchange kinetics significantly can be influenced by combination with various simple additives. As anticipated, the exchange reactions on network level can be further accelerated using either Brønsted or Lewis acid additives. Remarkably, however, a strong inhibitory effect is observed when a base is added to the polymer matrix. These effects have been mechanistically rationalized, guided by low-molecular weight kinetic model experiments. Thus, vitrimer elastomer materials can be rationally designed to display a wide range of viscoelastic properties. PMID:28317893

Reconfigurable and Reprocessable Thermoset Shape Memory Polymer with Synergetic Triple Dynamic Covalent Bonds.

PubMed

Wang, Yongwei; Pan, Yi; Zheng, Zhaohui; Ding, Xiaobin

2018-04-20

Degradable shape memory polymers (SMPs), especially for polyurethane-based SMPs, have shown great potential for biomedical applications. How to reasonably fabricate SMPs with the ideal combination of degradability, shape reconfigurability, and reprocessability is a critical issue and remains a challenge for medical disposable materials. Herein, a shape memory poly(urethane-urea) with synergetic triple dynamic covalent bonds is reported via embedding polycaprolactone unit into poly(urethane-urea) with the hindered urea dynamic bond. The single polymer network is biodegradable, thermadapt, and reprocessable, without sacrificing the outstanding shape memory performance. Such a shape memory network with plasticity and reprocessability is expected to have significant and positive impact on the medical device industry. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Binder and Mold parameters on Collapsibility and Surface Finish of Gray Cast Iron No-bake Sand Molds

NASA Astrophysics Data System (ADS)

Srinivasulu Reddy, K.; Venkata Reddy, Vajrala; Mandava, Ravi Kumar

2017-08-01

Chemically bonded no-bake molds and cores have good mechanical properties and produce dimensionally accurate castings compared to green sand molds. Poor collapsibility property of CO2 hardened sodium silicate bonded sand mold and phenolic urethane no-bake (PUN) binder system, made the reclamation of the sands more important. In the present work fine silica sand is mixed with phenolic urethane no-bake binder and the sand sets in a very short time within few minutes. In this paper it is focused on optimizing the process parameters of PUN binder based sand castings for better collapsibility and surface finish of gray cast iron using Taguchi design. The findings were successfully verified through experiments.

Fire retardant polyisocyanurate foam

NASA Technical Reports Server (NTRS)

Riccitiello, S. R.; Parker, J. A.

1972-01-01

Fire retardant properties of low density polymer foam are increased. Foam has pendant nitrile groups which form thermally-stable heterocyclic structures at temperature below degradation temperature of urethane linkages.

Acrylate-endcapped polymer precursors: effect of chemical composition on the healing efficiency of active concrete cracks

NASA Astrophysics Data System (ADS)

Araújo, Maria; Van Tittelboom, Kim; Dubruel, Peter; Van Vlierberghe, Sandra; De Belie, Nele

2017-05-01

The repair of cracks in concrete is an unavoidable practice since these cracks endanger the durability of the structure. Inspired by nature, the self-healing concept has been widely investigated in concrete as a promising solution to solve the limitations of manual repair. This self-healing functionality may be realized by the incorporation of encapsulated healing agents in concrete. Depending on the nature of the cracks, different healing agents can be used. For structures subjected to repeated loads, elastic materials should be considered to cope with the crack opening and closing movement. In this study, various acrylate-endcapped polymer precursors were investigated for their suitability to heal active cracks. The strain capacity of the polymers was assessed by means of visual observation together with water flow tests after widening of the healed cracks in a stepwise manner. A strain of at least 50% could be sustained by epoxy- and siloxane-based healing agents. For polyester- and urethane/poly(propylene glycol)-based precursors, failure occurred at 50% elongation due to detachment of the polymer from the crack walls. However, for urethane/poly(propylene glycol)-based healing agent, debonding was limited to some local spots. The resistance of the polymerized healing agents against degradation in the strong alkaline environment characteristic for concrete has also been evaluated, with the urethane/poly(propylene glycol)-based precursor showing the best performance to withstand degradation.

Low loading of carbon nanotubes to enhance acoustical properties of poly(ether)urethane foams

NASA Astrophysics Data System (ADS)

Basirjafari, Sedigheh; Malekfar, Rasoul; Esmaielzadeh Khadem, Siamak

2012-11-01

The aim of this paper is to fabricate a sound absorber flexible semi-open cell polymeric foam based on polyether urethane (PEU) with carboxylic functionalized multi-walled carbon nanotubes (COOH-MWCNTs) as an energy decaying filler at low loadings up to 0.20 wt. %. This paper provides the relationship between the mentioned foam microstructure via field emission scanning electron microscopy and different acoustical and non-acoustical properties of PEU/COOH-MWCNT composites. Addition of just 0.05 wt. % COOH-MWCNTs enhanced the sound absorption coefficient of the mentioned nanocomposite foam over the entire frequency range. Raman spectra revealed the better dispersion of COOH-MWCNTs in the PEU matrix leading to more stress transfer between them to cause a significant dissipation of energy.

Evaluation of fit of cement-retained implant-supported 3-unit structures fabricated with direct metal laser sintering and vacuum casting techniques.

PubMed

Oyagüe, Raquel Castillo; Sánchez-Turrión, Andrés; López-Lozano, José Francisco; Montero, Javier; Albaladejo, Alberto; Suárez-García, María Jesús

2012-07-01

This study evaluated the vertical discrepancy of implant-fixed 3-unit structures. Frameworks were constructed with laser-sintered Co-Cr, and vacuum-cast Co-Cr, Ni-Cr-Ti, and Pd-Au. Samples of each alloy group were randomly luted in standard fashion using resin-modified glass-ionomer, self-adhesive, and acrylic/urethane-based cements (n = 12 each). Discrepancies were SEM analyzed. Three-way ANOVA and Student-Newman-Keuls tests were run (P < 0.05). Laser-sintered structures achieved the best fit per cement tested. Within each alloy group, resin-modified glass-ionomer and acrylic/urethane-based cements produced comparably lower discrepancies than the self-adhesive agent. The abutment position did not yield significant differences. All misfit values could be considered clinically acceptable.

MAK-4 and -5 supplemented diet inhibits liver carcinogenesis in mice

PubMed Central

Penza, Marialetizia; Montani, Claudia; Jeremic, Marija; Mazzoleni, Giovanna; Hsiao, WL Wendy; Marra, Maurizio; Sharma, Hari; Di Lorenzo, Diego

2007-01-01

Background Maharishi Amrit Kalash (MAK) is an herbal formulation composed of two herbal mixtures, MAK-4 and MAK-5. These preparations are part of a natural health care system from India, known as Maharishi Ayur-Veda. MAK-4 and MAK-5 are each composed of different herbs and are said to have maximum benefit when used in combination. This investigation evaluated the cancer inhibiting effects of MAK-4 and MAK-5, in vitro and in vivo. Methods In vitro assays: Aqueous extracts of MAK-4 and MAK-5 were tested for effects on ras induced cell transformation in the Rat 6 cell line assessed by focus formation assay. In vivo assays: Urethane-treated mice were put on a standard pellet diet or a diet supplemented with MAK-4, MAK-5 or both. At 36 weeks, livers were examined for tumors, sera for oxygen radical absorbance capacity (ORAC), and liver homogenates for enzyme activities of glutathione peroxidase (GPX), glutathione-S-transferase (GST), and NAD(P)H: quinone reductase (QR). Liver fragments of MAK-fed mice were analyzed for connexin (cx) protein expression. Results MAK-5 and a combination of MAK-5 plus MAK-4, inhibited ras-induced cell transformation. In MAK-4, MAK-5 and MAK4+5-treated mice we observed a 35%, 27% and 46% reduction in the development of urethane-induced liver nodules respectively. MAK-4 and MAK4+5-treated mice had a significantly higher ORAC value (P < 0.05) compared to controls (200.2 ± 33.7 and 191.6 ± 32.2 vs. 152.2 ± 15.7 ORAC units, respectively). The urethane-treated MAK-4, MAK-5 and MAK4+5-fed mice had significantly higher activities of liver cytosolic enzymes compared to the urethane-treated controls and to untreated mice: GPX(0.23 ± 0.08, 0.21 ± 0.05, 0.25 ± 0.04, 0.20 ± 0.05, 0.21 ± 0.03 U/mg protein, respectively), GST (2.0 ± 0.4, 2.0 ± 0.6, 2.1 ± 0.3, 1.7 ± 0.2, 1.7 ± 0.2 U/mg protein, respectively) and QR (0.13 ± 0.02, 0.12 ± 0.06, 0.15 ± 0.03, 0.1 ± 0.04, 0.11 ± 0.03 U/mg protein, respectively). Livers of MAK-treated mice showed a time-dependent increased expression of cx32. Conclusion Our results show that a MAK-supplemented diet inhibits liver carcinogenesis in urethane-treated mice. The prevention of excessive oxidative damage and the up-regulation of connexin expression are two of the possible effects of these products. PMID:17559639

Crack sealer fill characteristics.

DOT National Transportation Integrated Search

2010-06-01

Laboratory testing was conducted to determine the extent of crack fill for crack sealers composed of methyl methacrylate, : epoxy, urethane, and high molecular weight methacrylate. The test specimens consisted of eight-inch long concrete : cylinders ...

Presidential Green Chemistry Challenge: 2005 Greener Reaction Conditions Award

EPA Pesticide Factsheets

Presidential Green Chemistry Challenge 2005 award winner, BASF, invented a one-component, urethane acrylate oligomer primer system for automobile refinishing that is UV-curable, has VOCs, and is free of diisocyanates.

Stable polyurethane coatings for electronic circuits. NASA tech briefs, fall 1982, volume 7, no. 1

NASA Technical Reports Server (NTRS)

1982-01-01

One of the most severe deficiencies of polyurethanes as engineering materials for electrical applications has been their sensitivity to combined humidity and temperature environments. Gross failure by reversion of urethane connector potting materials has occurred under these conditions. This has resulted in both scrapping of expensive hardware and reduction in reliability in other instances. A basic objective of this study has been to gain a more complete understanding of the mechanisms and interactions of moisture in urethane systems to guide the development of reversion resistant materials for connector potting and conformal coating applications in high humidity environments. Basic polymer studies of molecular weight and distribution, polymer structure, and functionality were carried out to define those areas responsible for hydrolytic instability and to define polymer structural feature conducive to optimum hydrolytic stability.

Continuous N-alkylation reactions of amino alcohols using γ-Al2O3 and supercritical CO2: unexpected formation of cyclic ureas and urethanes by reaction with CO2.

PubMed

Streng, Emilia S; Lee, Darren S; George, Michael W; Poliakoff, Martyn

2017-01-01

The use of γ-Al 2 O 3 as a heterogeneous catalyst in scCO 2 has been successfully applied to the amination of alcohols for the synthesis of N -alkylated heterocycles. The optimal reaction conditions (temperature and substrate flow rate) were determined using an automated self-optimising reactor, resulting in moderate to high yields of the target products. Carrying out the reaction in scCO 2 was shown to be beneficial, as higher yields were obtained in the presence of CO 2 than in its absence. A surprising discovery is that, in addition to cyclic amines, cyclic ureas and urethanes could be synthesised by incorporation of CO 2 from the supercritical solvent into the product.

Identification and quantification of ethyl carbamate occurring in urea complexation processes commonly utilized for polyunsaturated fatty acid concentration.

PubMed

Vázquez, Luis; Prados, Isabel M; Reglero, Guillermo; Torres, Carlos F

2017-08-15

The concentration of polyunsaturated fatty acids by formation of urea adducts from three different sources was studied to elucidate the formation of ethyl carbamates in the course of these procedures. Two different methodologies were performed: with ethanol at high temperature and with hexane/ethanol mixtures at room temperature. It was proved that the amount of urethanes generated at high temperature was higher than at room temperature. Besides, subsequent washing steps of the PUFA fraction with water were efficient to remove the urethanes from the final products. The methodology at room temperature with 0.4mL ethanol and 3g urea provided good relationship between concentration and yield of the main bioactive PUFA, with the lowest formation of ethyl carbamates in the process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Method of making thermally removable polyurethanes

DOEpatents

Loy, Douglas A.; Wheeler, David R.; McElhanon, James R.; Saunders, Randall S.; Durbin-Voss, Marvie Lou

2002-01-01

A method of making a thermally-removable polyurethane material by heating a mixture of a maleimide compound and a furan compound, and introducing alcohol and isocyanate functional groups, where the alcohol group and the isocyanate group reacts to form the urethane linkages and the furan compound and the maleimide compound react to form the thermally weak Diels-Alder adducts that are incorporated into the backbone of the urethane linkages during the formation of the polyurethane material at temperatures from above room temperature to less than approximately 90.degree. C. The polyurethane material can be easily removed within approximately an hour by heating to temperatures greater than approximately 90.degree. C. in a polar solvent. The polyurethane material can be used in protecting electronic components that may require subsequent removal of the solid material for component repair, modification or quality control.

Modeling the microstructurally dependent mechanical properties of poly(ester-urethane-urea)s.

PubMed

Warren, P Daniel; Sycks, Dalton G; McGrath, Dominic V; Vande Geest, Jonathan P

2013-12-01

Poly(ester-urethane-urea) (PEUU) is one of many synthetic biodegradable elastomers under scrutiny for biomedical and soft tissue applications. The goal of this study was to investigate the effect of the experimental parameters on mechanical properties of PEUUs following exposure to different degrading environments, similar to that of the human body, using linear regression, producing one predictive model. The model utilizes two independent variables of poly(caprolactone) (PCL) type and copolymer crystallinity to predict the dependent variable of maximum tangential modulus (MTM). Results indicate that comparisons between PCLs at different degradation states are statistically different (p < 0.0003), while the difference between experimental and predicted average MTM is statistically negligible (p < 0.02). The linear correlation between experimental and predicted MTM values is R(2) = 0.75. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

Laboratory development and field testing of sentinel toys to assess environmental faecal exposure of young children in rural India.

PubMed

Torondel, Belen; Gyekye-Aboagye, Yaw; Routray, Parimita; Boisson, Sophie; Schimdt, Wolf; Clasen, Thomas

2015-06-01

Sentinel toys are increasingly used as a method of assessing young children's exposure to faecal pathogens in households in low-income settings. However, there is no consensus on the suitability of different approaches. We evaluated three types of toy balls with different surfaces (plastic, rubber, urethane) in the laboratory to compare the uptake of faecal indicator bacteria (Escherichia coli) on their surface. We performed bacteria survival analysis under different environmental conditions and tested laboratory methods for bacteria removal and recovery. In a field study we distributed sterile urethane balls to children <5 from 360 households in rural India. After 24 hours, we collected and rinsed the toys in sterile water, assayed for thermotolerant coliforms (TTC) and explored associations between the level of contamination and household characteristics. In the laboratory, urethane foam balls took up more indicator bacteria than the other balls. Bacteria recovery did not differ based on mechanic vs no agitation. Higher temperatures and moisture levels increased bacterial yield. In the field, the only factor associated with a decreased recovery of TTC from the balls was having a soil (unpaved) floor. Sentinel toys may be an effective tool for assessing young children's exposure to faecal pathogens. However, even using methods designed to increase bacterial recovery, limited sensitivity may require larger sample sizes. © The Author 2015. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Comparative Study of Structure-Property Relationships in Polymer Networks Based on Bis-GMA, TEGDMA and Various Urethane-Dimethacrylates

PubMed Central

Barszczewska-Rybarek, Izabela; Jurczyk, Sebastian

2015-01-01

The effect of various dimethacrylates on the structure and properties of homo- and copolymer networks was studied. The 2,2-bis-[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]-propane) (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and 1,6-bis-(methacryloyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane (HEMA/TMDI), all popular in dentistry, as well as five urethane-dimethacrylate (UDMA) alternatives of HEMA/TMDI were used as monomers. UDMAs were obtained from mono-, di- and tri(ethylene glycol) monomethacrylates and various commercial diisocyanates. The chemical structure, degree of conversion (DC) and scanning electron microscopy (SEM) fracture morphology were related to the mechanical properties of the polymers: flexural strength and modulus, hardness, as well as impact strength. Impact resistance was widely discussed, being lower than expected in the case of poly(UDMA)s. It was caused by the heterogeneous morphology of these polymers and only moderate strength of hydrogen bonds between urethane groups, which was not high enough to withstand high impact energy. Bis-GMA, despite having the highest polymer morphological heterogeneity, ensured fair impact resistance, due to having the strongest hydrogen bonds between hydroxyl groups. The TEGDMA homopolymer, despite being heterogeneous, produced the smoothest morphology, which resulted in the lowest brittleness. The UDMA monomer, having diethylene glycol monomethacrylate wings and the isophorone core, could be the most suitable HEMA/TMDI alternative. Its copolymer with Bis-GMA and TEGDMA had improved DC as well as all the mechanical properties. PMID:28787999

Molecular recognition in poly(epsilon-caprolactone)-based thermoplastic elastomers.

PubMed

Wisse, Eva; Spiering, A J H; van Leeuwen, Ellen N M; Renken, Raymond A E; Dankers, Patricia Y W; Brouwer, Linda A; van Luyn, Marja J A; Harmsen, Martin C; Sommerdijk, Nico A J M; Meijer, E W

2006-12-01

The molecular recognition properties of the hydrogen bonding segments in biodegradable thermoplastic elastomers were explored, aiming at the further functionalization of these potentially interesting biomaterials. A poly(epsilon-caprolactone)-based poly(urea) 2 was synthesized and characterized in terms of mechanical properties, processibility and histocompatibility. Comparison of the data with those obtained from the structurally related poly(urethane urea) 1 revealed that the difference in hard segment structure does not significantly affect the potency for application as a biomaterial. Nevertheless, the small differences in hard block composition had a strong effect on the molecular recognition properties of the hydrogen bonding segments. High selectivity was found for poly(urea) 2 in which bisureidobutylene-functionalized azobenzene dye 3 was selectively incorporated while bisureidopentylene-functionalized azobenzene dye 4 was completely released. In contrast, the incorporation of both dyes in poly(urethane urea) 1 led in both cases to their gradual release in time. Thermal analysis of the polymers in combination with variable temperature infrared experiments indicated that the hard blocks in 1 showed a sharp melting point, whereas those in 2 showed a very broad melting trajectory. This suggests a more precise organization of the hydrogen bonding segments in the hard blocks of poly(urea) 2 compared to poly(urethane urea) 1 and explains the results from the molecular recognition experiments. Preliminary results revealed that a bisureidobutylene-functionalized GRGDS peptide showed more supramolecular interaction with the PCL-based poly(urea), containing the bisureidobutylene recognition unit, as compared to HMW PCL, lacking this recognition unit.

Cooling vest

NASA Technical Reports Server (NTRS)

Kosmo, J.; Kane, J.; Coverdale, J.

1977-01-01

Inexpensive vest of heat-sealable urethane material, when strapped to person's body, presents significant uncomplicated cooling system for environments where heavy accumulation of metabolic heat exists. Garment is applicable to occupations where physical exertion is required under heavy protective clothing.

Poly(glycerol sebacate urethane)-cellulose nanocomposites with water-active shape-memory effects.

PubMed

Wu, Tongfei; Frydrych, Martin; O'Kelly, Kevin; Chen, Biqiong

2014-07-14

Biodegradable and biocompatible materials with shape-memory effects (SMEs) are attractive for use as minimally invasive medical devices. Nanocomposites with SMEs were prepared from biodegradable poly(glycerol sebacate urethane) (PGSU) and renewable cellulose nanocrystals (CNCs). The effects of CNC content on the structure, water absorption, and mechanical properties of the PGSU were studied. The water-responsive mechanically adaptive properties and shape-memory performance of PGSU-CNC nanocomposites were observed, which are dependent on the content of CNCs. The PGSU-CNC nanocomposite containing 23.2 vol % CNCs exhibited the best SMEs among the nanocomposites investigated, with the stable shape fixing and shape recovery ratios being 98 and 99%, respectively, attributable to the formation of a hydrophilic, yet strong, CNC network in the elastomeric matrix. In vitro degradation profiles of the nanocomposites were assessed with and without the presence of an enzyme.

Synthesis of palm-based polyurethane-LiClO{sub 4} via prepolymerization

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

Sien, Jason Wong Chee; School of Biosciences, Taylor’s University, Subang Jaya; Badri, Khairiah Haji

2015-09-25

Palm-based polyurethane (pPU) with varying lithium salt (LiClO{sub 4}) content was synthesized. Higher loading percentage of LiClO{sub 4} in the pPU led to the inhibition of prepolymerization process from taking place. Hydrogen bonded C=O was detected in the FTIR spectrum indicating the hydrogen bonding between the urethane bonds. Ordered complexed C=O was observed in the FTIR spectrum confirming the complex formation between urethane bond and Li{sup +} ion. DSC thermogram showed the increase in the LiClO{sub 4} content could increase the glass transition temperature. SEM micrographs exhibited that more bubbles were formed when the LiClO{sub 4} increased from 10 tomore » 30wt% indicating the reaction between free isocyanate groups with moisture presence in the salt due to the hygroscopic properties of LiClO{sub 4}.« less

Frequency-Dependent Activation of Glucose Utilization in the Superior Cervical Ganglion by Electrical Stimulation of Cervical Sympathetic Trunk

NASA Astrophysics Data System (ADS)

Yarowsky, Paul; Kadekaro, Massako; Sokoloff, Louis

1983-07-01

Electrical stimulation of the distal stump of the transected cervical sympathetic trunk produces a frequency-dependent activation of glucose utilization, measured by the deoxy[14C]glucose method, in the superior cervical ganglion of the urethane-anesthetized rat. The frequency dependence falls between 0-15 Hz; at 20 Hz the activation of glucose utilization is no greater than at 15 Hz. Deafferentation of the superior cervical ganglion by transection of the cervical sympathetic trunk does not diminish the rate of glucose utilization in the ganglion in the urethane-anesthetized rat. These results indicate that the rate of energy metabolism in an innervated neural structure is, at least in part, regulated by the impulse frequency of the electrical input to the structure, and this regulation may be an essential component of the mechanism of the coupling of metabolic activity to functional activity in the nervous system.

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane.

PubMed

Lukas, Karin; Stadtherr, Karin; Gessner, Andre; Wehner, Daniel; Schmid, Thomas; Wendel, Hans Peter; Schmid, Christof; Lehle, Karla

2017-03-24

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels-(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)-and immobilization of human antithrombin III (AT). Their biological impact was tested in vitro under static and dynamic conditions. Static test methods showed a significantly reduced adhesion of endothelial cells, platelets, and bacteria, compared to untreated PCU. Modified PCU grafts were circulated in a Chandler-Loop model for 90 min at 37 °C with human blood. Before and after circulation, parameters of the hemostatic system (coagulation, platelets, complement, and leukocyte activation) were analyzed. PEI-AT significantly inhibited the activation of both coagulation and platelets and prevented the activation of leukocytes and complement. In conclusion, both modifications significantly reduce coagulation activation, but only PEI-AT creates anti-bacterial and anti-thrombogenic functionality.

Production development of organic nonflammable spacecraft potting, encapsulating and conformal coating compounds. Volume 1: Discussion, figures, and references

NASA Technical Reports Server (NTRS)

Lieberman, S. L.

1974-01-01

Based upon extensive contacts with vendors, a broad array of non-flammable polymeric specie, and additives generally noted to have flame retarding properties, were considered. The following polymeric matrices were examined: modified silicone and fluorosilicone RTV's polyesters, epoxies, urethanes, and epoxy-urethanes. Optimization of formulations to obtain a suitable balance between the various properties and flammability resistance led to the final selection of a silicone RTV/additive-loaded compound which meets almost all program requirements. The very low valued properties found are within a realistic level of design toleration. Complete formulation, processing, and test data is provided for this compound, EPOCAST 87517-A/B, and the other formulations prepared by the project. Details of those test methods are presented along with procedures utilized in the program. In addition, a description of the special flammability facility previously designed and then modified for this program is also presented.

Light-curing reinforcement for denture base resin using a glass fiber cloth pre-impregnated with various urethane oligomers.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2004-09-01

The purpose of this study was to investigate the flexural properties of denture base resin reinforced using glass fiber cloth and a urethane oligomer. The five types of oligomer used in this study were S5, S9, S3, U4, and U6, which have varying functional groups and viscosities. The flexural properties of S9 with glass fiber cloth could not be measured because S9 is elastic. In the heat-cured resin reinforced with S9, the reinforcement peeled away from the resin. In the self- and light-cured resins reinforced with S9, the flexural properties increased significantly. When reinforced with the other four oligomers (S5, S3, U4, and U6), the flexural strength and flexural modulus of the self-, heat-, and light-cured resins increased significantly (p<0.01).

Assessment of the viscoelastic mechanical properties of polycarbonate urethane for medical devices.

PubMed

Beckmann, Agnes; Heider, Yousef; Stoffel, Marcus; Markert, Bernd

2018-06-01

The underlying research work introduces a study of the mechanical properties of polycarbonate urethane (PCU), used in the construction of various medical devices. This comprises the discussion of a suitable material model, the application of elemental experiments to identify the related parameters and the numerical simulation of the applied experiments in order to calibrate and validate the mathematical model. In particular, the model of choice for the simulation of PCU response is the non-linear viscoelastic Bergström-Boyce material model, applied in the finite-element (FE) package Abaqus®. For the parameter identification, uniaxial tension and unconfined compression tests under in-laboratory physiological conditions were carried out. The geometry of the samples together with the applied loadings were simulated in Abaqus®, to insure the suitability of the modelling approach. The obtained parameters show a very good agreement between the numerical and the experimental results. Copyright © 2018 Elsevier Ltd. All rights reserved.

Investigation of test methods, material properties, and processes for solar cell encapsulants. Fourteenth quarterly progress report, August 12, 1978-November 12, 1979. [EVA, EPDM, aliphatic urethane, PVC plastisol, and butyl acrylate

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

Willis, P. B.; Baum, B.; Schnitzer, H. S.

1979-12-01

Springborn Laboratories is engaged in a study of evaluating potentially useful encapsulating materials for Task 3 of the Low-Cost Silicon Solar Array project (LSA) funded by DOE. The goal of this program is to identify, evaluate, and recommend encapsulant materials and processes for the production of cost-effective, long-life solar cell modules. This report presents the results of a cost analysis of candidate potting compounds for long life solar module encapsulation. Additionally, the two major encapsulation processes, sheet lamination and liquid casting, are costed on the basis of a large scale production facility. Potting compounds studied include EVA, sheet, clear; EVA,more » sheet, pigmented; EPDM, sheet, clear; Aliphatic urethane, syrup; PVC Plastisol; Butyl acrylate, syrup; and Butyl acrylate, sheet.« less

Biocompatibility of Synthetic Poly(ester urethane)/Polyhedral Oligomeric Silsesquioxane Matrices with Embryonic Stem Cell Proliferation and Differentiation

PubMed Central

Guo, Yan-Lin; Wang, Wenshou; Otaigbe, Joshua U.

2010-01-01

Incorporation of polyhedral oligomeric silsesquioxanes (POSS) into poly (ester urethane)s (PEU) as a building block results in a PEU/POSS hybrid polymer with increased mechanical strength and thermostability. An attractive feature of the new polymer is that it forms a porous matrix when cast in the form of a thin film, making it potentially useful in tissue engineering. In this study, we present detailed microscopic analysis of the PEU/POSS matrix and demonstrate its biocompatibility with cell culture. The PEU/POSS polymer forms a continuous porous matrix with open pores and interconnected grooves. From SEM image analysis, it is calculated that there are about 950 pores per mm2 of the matrix area with pore size ranging from 1 to 15 μm in diameter. The area occupied by the pores represents approximately 7.6 % of matrix area. Using mouse embryonic stem cells (ESCs), we demonstrate that the PEU/POSS matrix provides excellent support for cell proliferation and differentiation. Under the cell culture condition optimized to maintain self-renewal, ESCs grown on a PEU/POSS matrix exhibit undifferentiated morphology, express pluripotency markers, and have similar growth rate to cells grown on gelatin. When induced for differentiation, ESCs underwent dramatic morphological change, characterized by the loss of clonogenecity and increased cell size with well-expanded cytoskeleton networks. Differentiated cells are able to form a continuous monolayer that is closely embedded on the matrix. The excellent compatibility between the PEU/POSS matrix and ESC proliferation/differentiation demonstrates the potential of using PEU/POSS polymers in future ESC-based tissue engineering. PMID:20213627

Evaluation of chemical-specific IgG antibodies in male workers from a urethane foam factory.

PubMed

Tsuji, Mayumi; Ishihara, Yasuhiro; Isse, Toyohi; Koriyama, Chihaya; Yamamoto, Megumi; Kakiuchi, Noriaki; Yu, Hsu-Sheng; Tanaka, Masayuki; Tsuchiya, Takuto; Ohta, Masanori; Tanaka, Rie; Kawamoto, Toshihiro

2018-06-19

Plastic resins are complex chemicals that contain toluene diisocyanate (TDI) and/or trimellitic anhydride (TMA), which cause occupational allergies (OA), including respiratory allergies. Serum IgGs against TDI and TMA have been suggested as potential markers of the exposure status and as exploring cause of OA. Although TDI-specific IgG has been examined for suspected OA, TMA-specific IgG is not commonly evaluated in a urethane foam factory. This study therefore investigated both TDI- and TMA-specific IgGs in suspected OA patients and to evaluate the usefulness of the measurement of multiple chemical-specific IgG measurement for practical monitoring. Blood samples were collected from two male workers who developed respiratory allergies supposedly caused by occupational exposure to TDI and/or TMA for the presence of TDI- and TMA-specific IgGs. In addition, blood samples from 75 male workers from a urethane foam factory, along with 87 male control subjects, were collected in 2014 and tested for the same IgGs in 2014. The presence and levels of TDI- and TMA-specific serum IgGs were measured using dot blot assays. We found that controls had mean concentrations of TDI- and TMA-specific IgGs of 0.98 and 2.10 μg/mL, respectively. In the two workers with respiratory allergies, the TDI-specific IgG concentrations were 15.6 and 9.51 μg/mL, and TMA-specific IgG concentrations were 4.56 and 14.4 μg/mL, which are clearly higher than those in controls. Mean concentrations of TDI- and TMA-specific IgGs in the factory workers were 1.89 and 2.41 μg/mL, respectively, and are significantly higher than those of the controls (P < 0.001 and P < 0.026 for TDI- and TMA-specific IgGs, respectively). The workers suspected of OA showed an evidently high level of TDI- and TMA-specific IgG, and these levels in workers at the urethane foam factory were also significantly higher than those in controls. In conclusion, the measurement of TDI- and TMA-specific IgG among workers using plastic resins is helpful to monitor their exposure status.

Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers.

PubMed

Ou, Wenfeng; Qiu, Handi; Chen, Zhifei; Xu, Kaitian

2011-04-01

A series of block poly(ester-urethane)s (abbreviated as PU3/4HB) based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent and stannous octanoate (Sn(Oct)(2)) as catalyst, with different 4HB contents and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H nuclear magnetic resonance spectrum (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). DSC curves revealed that the PU3/4HB polyurethanes have their T(g) from -25.6 °C to -4.3 °C, and crystallinity from 2.5% to 25.3%, being almost amorphous to semi-crystalline. The obtained PU3/4HBs are hydrophobic (water contact angle 77.4°-95.9°), and their surface free energy (SFE) were studied. The morphology of platelets adhered on the polyurethane film observed by scanning electron microscope (SEM) showed that platelets were activated on the PU3/4HB films which would lead to blood coagulation. The lactate dehydrogenase (LDH) assay revealed that the PU3/4HBs displayed higher platelet adhesion property than raw materials and biodegradable polymer polylactic acid (PLA) and would be potential hemostatic materials. Crystallinity degree, hydrophobicity, surface free energy and urethane linkage content play important roles in affecting the LDH activity and hence the platelet adhesion. CCK-8 assay showed that the PU3/4HB is non-toxic and well for cell growth and proliferation of mouse fibroblast L929. It showed that the hydrophobicity is an important factor for cell growth while 3HB content of the PU3/4HB is important for the cell proliferation. Through changing the composition and the chain-length of P3/4HB-diol prepolymers, the biocompatibility of the poly(ester-urethane)s can be tailored. Copyright © 2011 Elsevier Ltd. All rights reserved.

Viscoelastic foam cushion

NASA Technical Reports Server (NTRS)

Kubokawa, C. C.; Yost, C.

1977-01-01

Foam is viscous and elastic with unusual and useful temperature, humidity, and compression responses. Applied weight and pressure distributed equally along entire interface with foam eliminates any pressure points. Flexible urethane foam is ideal for orthopedic and prosthetic devices, sports equipment, furniture, and crash protection.

Biodegradation Of thermoplastic polyurethanes from vegetable oils

USDA-ARS?s Scientific Manuscript database

Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration were prepared. Soft segment concentration was varied fro, 40 to 70 wt %. Biodegradation was studied by respirometry. Segmented polyurethanes with soft segments based ...

Use of a Lysine-Derived Urethane Surgical Adhesive as an Alternative to Progressive Tension Sutures in Abdominoplasty Patients: A Cohort Study.

PubMed

Spring, Michelle A

2018-04-07

Fluid accumulation is a common complication after abdominoplasty procedures, and is typically managed by the placement of post-surgical drains. Progressive tension sutures (PTS) have been shown to be an effective approach to reduce the dead space by point-wise mechanical fixation, allowing for drain-free procedures. Lysine-derived urethane surgical adhesive provides an alternative approach for mechanical fixation and reduction of dead space, and may reduce surgery time compared to PTS. This prospective, controlled, single center clinical study compared progressive tension suture wound closure technique without drains (control) to tissue adhesive wound closure technique without drains (test) during abdominoplasty surgery. The objective was to determine if lysine-derived urethane surgical adhesive is an effective alternative to PTS for drain-free abdominoplasty procedures. Patients undergoing abdominoplasty who met the established inclusion/exclusion criteria were consented and enrolled in the study. Ten PTS (control) cases were performed, followed immediately by ten tissue adhesive (test) cases. Drains were not used in any procedures. Key outcome measures included all major and minor post-surgical complications requiring any intervention, the time to place progressive tension sutures versus time for tissue adhesive application, and number of PTS attachments versus number of adhesive drops applied. Surgeries were completed over an 8-month period. No statistical differences were identified between the two groups with regard to age, BMI, dissection surface area or flap weight. No clinical seroma formation was observed in either group. In the control (PTS) group, two patients developed small areas of dermal closure suture abscess requiring removal of suture material. One control patient developed drainage and fat necrosis thought to be related to PTS above the incision and later required a scar revision. One tissue adhesive patient developed hypertrophic scars of both her breast reduction and abdominoplasty scars requiring additional treatment. The average time to place PTS in the control group was 10.7 minutes (range, 7-18 minutes) and the average number of sutures placed was 16.6 (range, 12-22 sutures). In the test group, the average time to place the tissue adhesive and hold pressure was 5.9 minutes (range 5.5-8.0 minutes). The average number of tissue adhesive drops applied was 69.6 (range: 63-78 drops). In the tissue adhesive group, both the reduction in time for flap adhesion and the increased number of adhesive points were statistically significant when compared to PTS. Lysine-derived urethane surgical adhesive was applied in less time than progressive tension sutures, even after accounting for holding pressure for 5 minutes. The tissue adhesive provided four times the number of attachment points compared to PTS, although the significance of this is not clear. There were no postoperative clinical seromas detected in either group and there were no major complications in either group. Based on these results, the use of lysine-derived urethane surgical adhesive was found to be a safe and effective alternative to progressive tension sutures to reduce seroma formation in drain-free abdominoplasty procedures.

VIBRATION TESTING OF RESILIENT PACKAGE CUSHIONING MATERIALS

DTIC Science & Technology

government and industry. Testing equipment which meets tentative ASTM requirements was developed. Preliminary tests were conducted on a resilient expanded ... polystyrene foam (in 3 densities) and a polyether urethane foam (in one density). When vibrated under static loads known to provide optimum shock

Assessment of Uretek deep injection process.

DOT National Transportation Integrated Search

2015-03-01

This project assesses the capacity of an in-situ urethane stabilized soil mass to halt subsidence on an Interstate highway. : An area of subsidence is approximately 100 meters long in the southbound barrel of I- from mile marker 0.124 to 0.153 in : H...

Supraspinal and spinal effects of L-trans-PDC, an inhibitor of glutamate transporter, on the micturition reflex in rats.

PubMed

Honda, Masashi; Yoshimura, Naoki; Hikita, Katsuya; Hinata, Nobuyuki; Muraoka, Kuniyasu; Saito, Motoaki; Chancellor, Michael B; Takenaka, Atsushi

2013-09-01

Glutamate is a major excitatory transmitter in the central nervous system, controlling lower urinary tract function. Five types of glutamate transporters such as GLAST (EAAT1), GLT-1 (EAAT2), EAAC-1 (EAAT3), EAAT4, and EAAT5 have been cloned so far. In the current study we tested whether L-trans-pyrrolidine-2,4-dicarboxylic acid (L-trans-PDC), a non-selective inhibitor of glutamate transporters that increases endogenous glutamate concentration, can affect the micturition reflex in urethane anesthetized rats. Continuous cystometrograms (CMG, 0.04 ml/min infusion rate) were performed in two groups of urethane-anesthetized rats. A group of 18 rats was used for intrathecal administration of 1-10 µg of L-trans-PDC via an intrathecal catheter. In the second group of 18 rats, 1-10 µg of L-trans-PDC were administered intracerebroventricularly via a catheter inserted into the lateral ventricle. Micturition parameters were recorded and compared before and after drug administration. Intrathecal administration of L-trans-PDC at 1, 3, and 10 µg (n = 6 per dose) increased intercontraction intervals in dose dependent fashion, but did not affect postvoid residual or basal pressure at any doses tested. Intracerebroventricular administration of L-trans-PDC at 1, 3, and 10 µg (n = 6 per dose) also increased intercontraction intervals in dose dependent fashion, but did not affect postvoid residual or basal pressure at any doses tested. The current results show that, in urethane-anesthetized rats, suppression of glutamate transporters by L-trans-PDC has an inhibitory effect on the micturition reflex at supraspinal and spinal sites, possibly via activation of glutamate-mediated inhibitory pathways. Copyright © 2012 Wiley Periodicals, Inc.

Carcinogenesis of urethane: simulation versus experiment.

PubMed

Lajovic, Andrej; Nagy, Leslie D; Guengerich, F Peter; Bren, Urban

2015-04-20

The carcinogenesis of urethane (ethyl carbamate), a byproduct of fermentation that is consistently found in various food products, was investigated with a combination of kinetic experiments and quantum chemical calculations. The main objective of the study was to find ΔG(⧧), the activation free energy for the rate-limiting step of the SN2 reaction among the ultimate carcinogen of urethane, vinyl carbamate epoxide (VCE), and different nucleobases of the DNA. In the experimental part, the second-order reaction rate constants for the formation of the main 7-(2-oxoethyl)guanine adduct in aqueous solutions of deoxyguanosine and in DNA were determined. A series of ab initio, density functional theory (DFT), and semiempirical molecular orbital (MO) calculations was then performed to determine the activation barriers for the reaction between VCE and nucleobases methylguanine, methyladenine, and methylcytosine. Effects of hydration were incorporated with the use of the solvent reaction field method of Tomasi and co-workers and the Langevine dipoles model of Florian and Warshel. The computational results for the main adduct were found to be in good agreement with the experiment, thus presenting strong evidence for the validity of the proposed SN2 mechanism. This allowed us to predict the activation barriers of reactions leading to side products for which kinetic experiments have not yet been performed. Our calculations have shown that the main 7-(2-oxoethyl)deoxyguanosine adduct indeed forms preferentially because the emergence of other adducts either proceeds across a significantly higher activation barrier or the geometry of the reaction requires the Watson-Crick pairs of the DNA to be broken. The computational study also considered the questions of stereoselectivity, the ease of the elimination of the leaving group, and the relative contributions of the two possible reaction paths for the formation of the 1,N(2)-ethenodeoxyguanosine adduct.

In-vivo evaluation of the kinematic behavior of an artificial medial meniscus implant: A pilot study using open-MRI.

PubMed

De Coninck, Tineke; Elsner, Jonathan J; Linder-Ganz, Eran; Cromheecke, Michiel; Shemesh, Maoz; Huysse, Wouter; Verdonk, René; Verstraete, Koenraad; Verdonk, Peter

2014-09-01

In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant. Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior-posterior meniscal movement, radial displacement, and meniscal height. No difference (P>0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height (P>0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference (P ≤ 0.05) in anterior-posterior movement during flexion was observed between the two groups. In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior-posterior movement was slightly different between the implant and the normal meniscus. Copyright © 2014 Elsevier Ltd. All rights reserved.

Characterization of a resorbable poly(ester urethane) with biodegradable hard segments.

PubMed

Dempsey, David K; Robinson, Jennifer L; Iyer, Ananth V; Parakka, James P; Bezwada, Rao S; Cosgriff-Hernandez, Elizabeth M

2014-01-01

The rapid growth of regenerative medicine and drug delivery fields has generated a strong need for improved polymeric materials that degrade at a controlled rate into safe, non-cytotoxic by-products. Polyurethane thermoplastic elastomers offer several advantages over other polymeric materials including tunable mechanical properties, excellent fatigue strength, and versatile processing. The variable segmental chemistry in developing resorbable polyurethanes also enables fine control over the degradation profile as well as the mechanical properties. Linear aliphatic isocyanates are most commonly used in biodegradable polyurethane formulations; however, these aliphatic polyurethanes do not match the mechanical properties of their aromatic counterparts. In this study, a novel poly(ester urethane) (PEsU) synthesized with biodegradable aromatic isocyanates based on glycolic acid was characterized for potential use as a new resorbable material in medical devices. Infrared spectral analysis confirmed the aromatic and phase-separated nature of the PEsU. Uniaxial tensile testing displayed stress-strain behavior typical of a semi-crystalline polymer above its Tg, in agreement with calorimetric findings. PEsU outperformed aliphatic PCL-based polyurethanes likely due to the enhanced cohesion of the aromatic hard domains. Accelerated degradation of the PEsU using 0.1 M sodium hydroxide resulted in hydrolysis of the polyester soft segment on the surface, reduced molecular weight, surface cracking, and a 30% mass loss after four weeks. Calorimetric studies indicated a disruption of the soft segment crystallinity after incubation which corresponded with a drop in initial modulus of the PEsU. Finally, cytocompatibility testing with 3T3 mouse fibroblasts exhibited cell viability on PEsU films comparable to a commercial poly(ether urethane urea) after 24 h followed by 85% cell viability at 72 h. Overall, this new resorbable polyurethane shows strong potential for use in wide range of biomedical applications.

Vascularization and tissue infiltration of a biodegradable polyurethane matrix

PubMed Central

Ganta, Sudhakar R.; Piesco, Nicholas P.; Long, Ping; Gassner, Robert; Motta, Luis F.; Papworth, Glenn D.; Stolz, Donna B.; Watkins, Simon C.; Agarwal, Sudha

2016-01-01

Urethanes are frequently used in biomedical applications because of their excellent biocompatibility. However, their use has been limited to bioresistant polyurethanes. The aim of this study was to develop a nontoxic biodegradable polyurethane and to test its potential for tissue compatibility. A matrix was synthesized with pentane diisocyanate (PDI) as a hard segment and sucrose as a hydroxyl group donor to obtain a microtextured spongy urethane matrix. The matrix was biodegradable in an aqueous solution at 37°C in vitro as well as in vivo. The polymer was mechanically stable at body temperatures and exhibited a glass transition temperature (Tg) of 67°C. The porosity of the polymer network was between 10 and 2000 µm, with the majority of pores between 100 and 300 µm in diameter. This porosity was found to be adequate to support the adherence and proliferation of bone-marrow stromal cells (BMSC) and chondrocytes in vitro. The degradation products of the polymer were nontoxic to cells in vitro. Subdermal implants of the PDI–sucrose matrix did not exhibit toxicity in vivo and did not induce an acute inflammatory response in the host. However, some foreign-body giant cells did accumulate around the polymer and in its pores, suggesting its degradation is facilitated by hydrolysis as well as by giant cells. More important, subdermal implants of the polymer allowed marked infiltration of vascular and connective tissue, suggesting the free flow of fluids and nutrients in the implants. Because of the flexibility of the mechanical strength that can be obtained in urethanes and because of the ease with which a porous microtexture can be achieved, this matrix may be useful in many tissue-engineering applications. PMID:12522810

Metal-Filled Adhesives Amenable To X-Ray Inspection

NASA Technical Reports Server (NTRS)

Hermansen, Ralph D.; Sutherland, Thomas H.; Predmore, Roamer

1994-01-01

Adhesive joints between metal parts made amenable to nondestructive radiographic inspection by incorporating radiopaque fillers that increase x-ray contrasts of joints. Adhesives can be epoxies, urethanes, acrylics, phenolics, or silicones, with appropriate curing agents and with such modifiers as polysulfides, polyamides, or butadiene rubbers.

Novel aminobenzyl and imidobenzyl benzenes

NASA Technical Reports Server (NTRS)

Bell, V. L.; Pratt, J. R.; Stump, B. L.

1976-01-01

Compounds are useful as intermediates for several classes of polymers. Amines can function as cross-linking agents for epoxide and urethane polymers, as well as intermediates for synthesis of thermally-stable addition-type polyimides. Imide derivatives can be obtained by reacting amines with certain monoanhydrides containing olefinic unsaturation.

Roofing with Urethane: Pro and Con.

ERIC Educational Resources Information Center

Kinzer, Michael; Scott, Gerald P.E.

1981-01-01

Gerald Scott's favorable evaluation of the foamed polyurethane roofing system is based on experiences with 55 buildings at Texas A & M. Michael Kinzer, an architect at Colorado State University, disagrees and claims that the system is difficult to install and maintain, and the cost prohibitive. (MLF)

The Finish Line.

ERIC Educational Resources Information Center

Cohen, Andrew

1998-01-01

Details what is expected in a good floor finish for athletic facilities, and explores the different categories of finishes and their content within the context of environmental regulation and manufacturing standards. Also discusses urethane finishings, the debate over using waterbased finishes, and the influence of regulatory control that may…

Solar Space and Water Heating for Hospital --Charlottesville, Virginia

NASA Technical Reports Server (NTRS)

1982-01-01

Solar heating system described in an 86-page report consists of 88 single-glazed selectively-coated baseplate collector modules, hot-water coils in air ducts, domestic-hot-water preheat tank, 3,000 Gallon (11,350-1) concrete urethane-insulated storage tank and other components.

Comparison of Polyurethanes with Polyhydroxyurethanes: Effect of the Hydroxyl Group on Structure-Property Relationships

NASA Astrophysics Data System (ADS)

Leitsch, Emily K.; Lombardo, Vince M.; Scheidt, Karl A.; Torkelson, John M.

2014-03-01

Polyurethanes (PUs) are commonly synthesized by rapid step-growth polymerization through the reaction of a multifunctional alcohol with a polyisocyanate. PUs can be prepared at ambient conditions utilizing a variety of starting material molecular weights and backbones, resulting in highly tunable thermal and physical properties. The urethane linkages as well as the nanophase separated morphology attainable in PU materials lead to desirable properties including elastomeric character and adhesion. The isocyanate-based monomers used in the synthesis of traditional PUs have come under increasing regulatory pressure and thus inspired the investigation of alternative routes for the formation of PU materials. We examine an alternative route to synthesize PU- the reaction of five-membered cyclic carbonate with amines. This reaction results in the formation of a urethane linkage with an adjacent alcohol group. The effects of this hydroxyl group on the thermal and mechanical properties of the resulting polymer are investigated and compared with an analogous traditional PU system.

Turbidimetric and photometric determination of total tannins in tea using a micro-flow-batch analyzer.

PubMed

Lima, Marcelo B; Andrade, Stéfani I E; Harding, David P; Pistonesi, Marcelo F; Band, Beatriz S F; Araújo, Mário C U

2012-01-15

Both turbidimetric and photometric determinations of total tannins in samples of green and black tea, using a micro-flow-batch analyzer (μFBA) were studied. The miniaturized system was formed using photocurable urethane-acrylate resin and ultraviolet lithography technique. The turbidimetric method was based on the precipitation reaction of Cu (II) with tannins in acetate medium at a pH of 4.5. The photometric method was based on the complexation reaction of tannins with ferrous tartrate. The turbidimetric μFBA was able to test 200 samples per hour. The photometric μFBA allowed 300 analyses per hour, generating 136μL of residue per analysis. The paired t test, at a 95% confidence level, showed no statistically significant differences between results obtained by both methods and the reference method. The urethane-acrylate μFBA maintained satisfactory physical and chemical properties, and represents an improvement over conventional flow-batch analyzer. Copyright © 2011 Elsevier B.V. All rights reserved.

Isopropyl Myristate-Modified Polyether-Urethane Coatings as Protective Barriers for Implantable Medical Devices

PubMed Central

Roohpour, Nima; Wasikiewicz, Jaroslaw M.; Moshaverinia, Alireza; Paul, Deepen; Rehman, Ihtesham U.; Vadgama, Pankaj

2009-01-01

Polyurethane films have potential applications in medicine, especially for packaging implantable medical devices. Although polyether-urethanes have superior mechanical properties and are biocompatible, achieving water resistance is still a challenge. Polyether based polyurethanes with two different molecular weights (PTMO1000, PTMO2000) were prepared from 4,4’-diphenylmethane diisocyanate and poly(tetra-methylene oxide). Polymer films were introduced using different concentrations (0.5-10 wt %) of isopropyl myristate lipid (IPM) as a non-toxic modifying agent. The physical and mechanical properties of these polymers were characterised using physical and spectroscopy techniques (FTIR, Raman, DSC, DMA, tensile testing). Water contact angle and water uptake of the membranes as a function of IPM concentration was also determined accordingly. The FTIR and Raman data indicate that IPM is dispersed in polyurethane at ≤ 2wt% and thermal analysis confirmed this miscibility to be dependent on soft segment length. Modified polymers showed increased tensile strength and failure strain as well as reduced water uptake by up to 24% at 1-2 wt% IPM.

Full-scale flammability test data for validation of aircraft fire mathematical models

NASA Technical Reports Server (NTRS)

Kuminecz, J. F.; Bricker, R. W.

1982-01-01

Twenty-five large scale aircraft flammability tests were conducted in a Boeing 737 fuselage at the NASA Johnson Space Center (JSC). The objective of this test program was to provide a data base on the propagation of large scale aircraft fires to support the validation of aircraft fire mathematical models. Variables in the test program included cabin volume, amount of fuel, fuel pan area, fire location, airflow rate, and cabin materials. A number of tests were conducted with jet A-1 fuel only, while others were conducted with various Boeing 747 type cabin materials. These included urethane foam seats, passenger service units, stowage bins, and wall and ceiling panels. Two tests were also included using special urethane foam and polyimide foam seats. Tests were conducted with each cabin material individually, with various combinations of these materials, and finally, with all materials in the cabin. The data include information obtained from approximately 160 locations inside the fuselage.

In vivo evaluation of a fluorine-acryl-stylene-urethane-silicone antithrombogenic coating material copolymer for intravascular stents.

PubMed

Matsuhashi, T; Miyachi, H; Ishibashi, T; Sakamoto, K; Yamadera, A

1996-07-01

We evaluated the effectiveness of a fluorine-acryl-styrene-urethane-silicone (FASUS) copolymer as an antithrombogenic coating material for intravascular stents in dogs. FASUS copolymer-coated stents were placed in the right iliac veins, and uncoated 304 stainless steel stents were placed in the left iliac veins. We examined platelet deposition, microthrombus formation, and neointimal hyperplasia 4 weeks after stent placement by measuring the activity of 111In-labeled platelets, by using scanning electron microscopy, and by measuring neointimal thickness. Platelet deposition was significantly decreased on coated than on uncoated stents (p < .05). A less pronounced increase in red blood cell deposition was observed at the sites of the coated than uncoated stents (p < .05). Neointimal thickness 4 weeks after stent placement also was significantly less at the sites of the coated stents (0.27 +/- 0.08 mm versus 0.48 +/- 0.23 mm, p < .05). FASUS copolymer coating over the vascular stent is effective for preventing thrombus formation and neointimal hyperplasia.

Potential applications of three-dimensional structure of silk fibroin/poly(ester-urethane) urea nanofibrous scaffold in heart valve tissue engineering

NASA Astrophysics Data System (ADS)

Du, Juan; Zhu, Tonghe; Yu, Haiyan; Zhu, Jingjing; Sun, Changbing; Wang, Jincheng; Chen, Sihao; Wang, Jihu; Guo, Xuran

2018-07-01

Tissue engineering heart valves (TEHV) are thought to have many advantages in low immunogenicity, good histocompatibility, excellent mechanical properties. In this paper, we reported the fabrication and characterization of a novel composite nanofibrous scaffold consisting of silk fibroin (SF) and poly(ester-urethane) urea (LDI-PEUU) by using electrospinning. Chemical and physical properties of scaffolds were evaluated using scanning electron microscopy, attenuated total reflectance Fourier transform infrared, X-ray diffraction, contact angle measurement, thermogravimetric analysis, biodegradation test and tensile strength analysis. We determined that the composite scaffolds supported the growth of human umbilical vein endothelial cell (HUVEC). The results of cell proliferation and cell morphology indicate that SF/LDI-PEUU nanofibers promoted cell viability, which supporting the application in tissue engineering. All results clarified that SF/LDI-PEUU (40:60) nanofibrous scaffolds meet the required specifications for tissue engineering and could be used as a promising construct for heart valve tissue engineering.

Development of a flameproof elastic elastomeric fiber

NASA Technical Reports Server (NTRS)

Howarth, J. T.; Nilgrom, J.; Massucco, A.; Sheth, S. G.; Dawn, F. S.

1971-01-01

Various flexible polyurethane structures containing halogen were synthesized from polyesters derived from aliphatic or aromatic polyols and dibasic acids. Aliphatic halide structures could not be used because they are unstable at the required reaction temperatures, giving of hydrogen halide which hydrolyzes the ester linkages. In contract, halogen-containing aromatic polyols were stable and satisfactory products were made. The most promising composition, a brominated neopentyl glycol capped with toluene disocyanate, was used as a conventional diisocyanate, in conjunction with hydroxy-terminated polyethers or polyesters to form elastomeric urethanes containing about 10% bromine with weight. Products made in this manner will not burn in air, have an oxygen index value of about 25, and have tensile strength values of about 5,000 psi at 450% elongation. The most efficient additives for imparting flame retardancy to Spandex urethanes are aromatic halides and the most effective of these are the bromide compounds. Various levels of flame retardancy have been achieved depending on the levels of additives used.

Development of a collapsible reinforced cylindrical space observation window

NASA Technical Reports Server (NTRS)

Khan, A. Q.

1971-01-01

Existing material technology was applied to the development of a collapsible transparent window suitable for manned spacecraft structures. The effort reported encompasses the evaluation of flame retardants intended for use in the window matrix polymer, evaluation of reinforcement angle which would allow for a twisting pantographing motion as the cylindrical window is mechanically collapsed upon itself, and evaluation of several reinforcement embedment methods. A fabrication technique was developed to produce a reinforced cylindrical space window of 45.7 cm diameter and 61.0 cm length. The basic technique involved the application of a clear film on a male-section mold; winding axial and girth reinforcements and vacuum casting the outer layer. The high-strength transparent window composite consisted of a polyether urethane matrix reinforced with an orthogonal pattern of black-coated carbon steel wire cable. A thin film of RTV silicone rubber was applied to both surfaces of the urethane. The flexibility, retraction system, and installation system are described.

Effects of adding methacrylate monomers on viscosity and mechanical properties of experimental light-curing soft lining materials based on urethane (meth)acrylate oligomers.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2008-11-01

We investigated the viscosity and mechanical properties of experimental light-curing soft lining materials based on six commercially available urethane (meth)acrylate oligomers. The viscosities of the six oligomers were 1.9, 20.6, 26.8, 144.0, 185.3, and 8803.4 Pa*s at 25 degrees C. Two monomers (ethyl- and butyl-methacrylate) were added at 20 wt% to these oligomers to decrease the viscosity, resulting in viscosity reductions of 0.2 to 13.6 Pa*s for the six oligomers. The mechanical properties (compressive modulus, Shore A hardness, and tensile strength) were measured after two times light-polymerization for 3 min. The addition of the monomers to the oligomers only slightly changed the mechanical properties, in contrast to the large viscosity changes. Based on these results, it appears that the addition of ethyl- or butyl-methacrylate monomers is useful for decreasing the viscosity of experimental light-curing soft lining materials without changing their mechanical properties.

Nano-Aramid Fiber Reinforced Polyurethane Foam

NASA Technical Reports Server (NTRS)

Semmes, Edmund B.; Frances, Arnold

2008-01-01

Closed cell polyurethane and, particularly, polyisocyanurate foams are a large family of flexible and rigid products the result of a reactive two part process wherein a urethane based polyol is combined with a foaming or "blowing" agent to create a cellular solid at room temperature. The ratio of reactive components, the constituency of the base materials, temperature, humidity, molding, pouring, spraying and many other processing techniques vary greatly. However, there is no known process for incorporating reinforcing fibers small enough to be integrally dispersed within the cell walls resulting in superior final products. The key differentiating aspect from the current state of art resides in the many processing technologies to be fully developed from the novel concept of milled nano pulp aramid fibers and their enabling entanglement capability fully enclosed within the cell walls of these closed cell urethane foams. The authors present the results of research and development of reinforced foam processing, equipment development, strength characteristics and the evolution of its many applications.

Hollow multilayer microcapsules for pH-/thermally responsive drug delivery using aliphatic poly(urethane-amine) as smart component.

PubMed

Shi, Jun; Du, Chao; Shi, Jin; Wang, Yaming; Cao, Shaokui

2013-04-01

Hollow multilayer microcapsules made of aliphatic poly(urethane-amine) (PUA) and sodium poly(styrene sulfonate) (PSS), templated on PSS-doped CaCO3 particles, are prepared for pH-/thermally responsive drug delivery. The electrostatic interaction and hydrogen bonding under weak-acid conditions between aliphatic PUA and PSS contribute to the formation of multilayer microcapsules. Scanning electron microscopy (SEM) results demonstrate an obvious variation of the hollow multilayer microcapsules in response to changes in temperature and pH value. Drug-release behaviors using DOX as a model drug demonstrate that the drug release increases on decreasing the pH value because of the interaction weakness between aliphatic PUA and PSS in acidic conditions. Moreover, the drug release is higher at 55 °C than that at 37 °C for the sake of the shrinkage of aliphatic PUA above its lower critical solution temperature (LCST). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Composite materials and method of making

DOEpatents

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

A chromatographic analysis of the response of polymeric fire-detection devices to combustion products

NASA Technical Reports Server (NTRS)

Senturia, S. D.

1977-01-01

Polymer responses to a variety of smouldering sources, including cellulose, acrylic, urethane, polyvinyl chloride, and wool were investigated. A suitable trapping system for combustion products was developed and a charge flow transistor was fabricated to monitor the transverse or sheet resistance of a thin film.

New class of thermosetting plastics has improved strength, thermal and chemical stability

NASA Technical Reports Server (NTRS)

Burns, E. A.; Dubrow, B.; Lubowitz, H. R.

1967-01-01

New class of thermosetting plastics has high hydrocarbon content, high stiffness, thermal stability, humidity resistance, and workability in the precured state. It is designated cyclized polydiene urethane, and is applicable as matrices to prepare chemically stable ablative materials for rocket nose cones of nozzles.

INFLUENCE OF CHEMICAL AND PHYSICAL MUTAGENIC FACTORS ON THE VIRUS of tick-BORNE ENCEPHALITIS

DTIC Science & Technology

In experiments the chemicals azouridine, azouracil, 5-bromuracil, formaldehyde, urethan and proflavine were used as mutagenic agents. The influence of...with passaging (tests with proflavine ). Subject to further study is the problem of the reversibility of these properties, and also the fixing of

Grit blasting nozzle fabricated from mild tool steel proves satisfactory

NASA Technical Reports Server (NTRS)

Mc Farland, J. E.; Turbitt, B.

1966-01-01

Dry blasting with glass beads through a nozzle assembly descales both the outside and inside surfaces of tubes of Inconel 718 used for the distribution of gaseous oxygen. The inside of the nozzle is coated with polyurethane and the deflector with a commercially available liquid urethane rubber.

Viscoelastic cationic polymers containing the urethane linkage

NASA Technical Reports Server (NTRS)

Rembaum, A. (Inventor)

1972-01-01

A method for the synthesis and manufacturing of elastomeric compositions and articles containing quaternary nitrogen centers and condensation residues along the polymeric backbone of the centers is presented. Linear and cross-linked straight chain and block polymers having a wide damping temperature range were synthesized. Formulae for the viscoelastic cationic polymers are presented.

Strand Burner Results of AFP-001 Propellant with Inert Coating for Temperature Compensation

DTIC Science & Technology

2015-10-01

there were 4 different configurations: baseline, a C-100 coated, an SC-11 coated, and a urethane acrylate (UA) coated. C-100 is a polyurea based...phenomena associated with coated AFP-001 propellant. Three different coating polymers were chosen for the experiments: an epoxy (SC-11), polyurea (C-100

Erosion resistant coatings

NASA Technical Reports Server (NTRS)

Falco, L.; Cushini, A.

1981-01-01

Apparatus for measuring the resistance of materials to erosion is examined and a scheme for standardization of the test parameters is described. Current materials being used for protecting aircraft parts from erosion are surveyed, their chief characteristics being given. The superior properties of urethane coatings are pointed out. The complete cycle for painting areas subject to erosion is described.

78 FR 33193 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-04

.... In addition, BMS 8-39 fire retardant properties, which deteriorate over time, can provide a fuel... flight deck and cargo compartments), with seals made of BMS 8-39 urethane foam, a material with fire-retardant properties that deteriorate with age. This AD requires replacing certain seals made of BMS 8-39...

Arf Suppresses Hepatic Vascular Neoplasia in a Carcinogen-Exposed Murine Model

PubMed Central

Busch, Stephanie E; Gurley, Kay E; Moser, Russell D; Kemp, Christopher J

2013-01-01

Hepatic haemangiosarcoma is a deadly malignancy whose aetiology remains poorly understood. Inactivation of the CDKN2A locus, which houses the ARF and p16INK4a tumour suppressor genes, is a common event in haemangiosarcoma patients, but the precise role of ARF in vascular tumourigenesis is unknown. To determine the extent to which ARF suppresses vascular neoplasia, we examined the incidence of hepatic vascular lesions in Arf-deficient mice exposed to the carcinogen urethane (i.p. 1 mg/g). Loss of Arf resulted in elevated morbidity and increased the incidence of both haemangiomas and incipient haemangiosarcomas. Suppression of vascular lesion development by ARF was heavily dependent on both Arf gene-dosage and the genetic strain of the mouse. Trp53-deficient mice also developed hepatic vascular lesions after exposure to urethane, suggesting that ARF signals through a p53-dependent pathway to inhibit the development of hepatic haemangiosarcoma. Our findings provide strong evidence that inactivation of Arf is a causative event in vascular neoplasia and suggest that the ARF pathway may be a novel molecular target for therapeutic intervention in haemangiosarcoma patients. PMID:22430984

Enzyme-catalyzed hydrolysis of dentin adhesives containing a new urethane-based trimethacrylate monomer

PubMed Central

Park, Jong-Gu; Ye, Qiang; Topp, Elizabeth M.; Spencer, Paulette

2009-01-01

A new trimethacrylate monomer with urethane-linked groups, 1,1,1-tri-[4-(methacryloxyethylamino-carbonyloxy)-phenyl]ethane (MPE), was synthesized, characterized, and used as a co-monomer in dentin adhesives. Dentin adhesives containing 2-hydroxyethyl methacrylate (HEMA, 45% w/w) and 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA, 30% w/w) in addition to MPE (25% w/w) were formulated with H2O at 0 (MPE0), 8 (MPE8) and 16 wt % water (MPE16) to simulate the wet demineralized dentin matrix and compared with controls [HEMA/BisGMA, 45/55 w/w, at 0 (C0), 8 (C8) and 16 wt% water (C16)]. The new adhesive showed a degree of double bond conversion and mechanical properties comparable with control, with good penetration into the dentin surface and a uniform adhesive/dentin interface. On exposure to porcine liver esterase, the net cumulative methacrylic acid (MAA) release from the new adhesives was dramatically (P < 0.05) decreased relative to the control, suggesting that the new monomer improves esterase resistance. PMID:19582843

Water Diffusion through a Titanium Dioxide/Poly(Carbonate Urethane) Nanocomposite for Protecting Cultural Heritage: Interactions and Viscoelastic Behavior

PubMed Central

Abbate, Mario; D’Orazio, Loredana

2017-01-01

Water diffusion through a TiO2/poly (carbonate urethane) nanocomposite designed for the eco-sustainable protection of outdoor cultural heritage stonework was investigated. Water is recognized as a threat to heritage, hence the aim was to gather information on the amount of water uptake, as well as of species of water molecules absorbed within the polymer matrix. Gravimetric and vibrational spectroscopy measurements demonstrated that diffusion behavior of the nanocomposite/water system is Fickian, i.e., diffusivity is independent of concentration. The addition of only 1% of TiO2 nanoparticles strongly betters PU barrier properties and water-repellency requirement is imparted. Defensive action against penetration of water free from, and bonded through, H-bonding association arises from balance among TiO2 hydrophilicity, tortuosity effects and quality of nanoparticle dispersion and interfacial interactions. Further beneficial to antisoiling/antigraffiti action is that water-free fraction was found to be desorbed at a constant rate. In environmental conditions, under which weathering processes are most likely to occur, nanocomposite Tg values remain suitable for heritage treatments. PMID:28902179

The First Normal Stress Difference in Waterborne Paints Thickened by Hydrophobically Ethoxylated Urethane (HEUR) Rheology Modifier: A Simplified Phase Diagram

NASA Astrophysics Data System (ADS)

Chatterjee, Tirtha; van Dyk, Antony; Ginzburg, Valeriy; Nakatani, Alan

Since their invention in the 1970s, hydrophobically ethoxylated urethane (HEUR) associative thickeners are widely used to modify the rheology of waterborne paints. While their flow curves (viscosity vs. shear rate) and microstructure have been studied extensively in recent years, there is surprisingly little information on the paint normal stress under application conditions. However, understanding of normal stress behavior is critical for many applications such as brush drag and spatter. In this work we will demonstrate that in HEUR-based paints the first normal stress difference (N1) is controlled by two factors: (a) adsorption of HEUR molecules on latex particles and (b) ability of non-adsorbed HEUR to form transient bridges between particles with HEUR shells. By controlling these two effects, one can design a paint formulation with targeted N1 behavior (positive or negative N1 under high shear). Finally, a simplified phase diagram will be presented connecting formulation composition-microstructure- and N1 behavior. The results would serve as guidelines to formulate paints to meet the specific customer needs.

Cleaning without chlorinated solvents

NASA Technical Reports Server (NTRS)

Thompson, L. M.; Simandl, R. F.

1995-01-01

Because of health and environmental concerns, many regulations have been passed in recent years regarding the use of chlorinated solvents. The Oak Ridge Y-12 Plant has had an active program to find alternatives for these solvents used in cleaning applications for the past 7 years. During this time frame, the quantity of solvents purchased has been reduced by 92 percent. The program has been a twofold effort. Vapor degreasers used in batch cleaning operations have been replaced by ultrasonic cleaning with aqueous detergent, and other organic solvents have been identified for use in hand-wiping or specialty operations. In order to qualify these alternatives for use, experimentation was conducted on cleaning ability as well as effects on subsequent operations such as welding, painting, and bonding. Cleaning ability was determined using techniques such as x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) which are capable of examining monolayer levels of contamination on a surface. Solvents have been identified for removal of rust preventative oils, lapping oils, machining coolants, lubricants, greases, and mold releases. Solvents have also been evaluated for cleaning urethane foam spray guns, swelling of urethanes, and swelling of epoxies.

Characterization and biocompatibility studies of new degradable poly(urea)urethanes prepared with arginine, glycine or aspartic acid as chain extenders.

PubMed

Chan-Chan, L H; Tkaczyk, C; Vargas-Coronado, R F; Cervantes-Uc, J M; Tabrizian, M; Cauich-Rodriguez, J V

2013-07-01

Polyurethanes are very often used in the cardiovascular field due to their tunable physicochemical properties and acceptable hemocompatibility although they suffer from poor endothelialization. With this in mind, we proposed the synthesis of a family of degradable segmented poly(urea)urethanes (SPUUs) using amino acids (L-arginine, glycine and L-aspartic acid) as chain extenders. These polymers degraded slowly in PBS (pH 7.4) after 24 weeks via a gradual decrease in molecular weight. In contrast, accelerated degradation showed higher mass loss under acidic, alkaline and oxidative media. MTT tests on polyurethanes with L-arginine as chain extenders showed no adverse effect on the metabolism of human umbilical vein endothelial cells (HUVECs) indicating the leachables did not provoke any toxic responses. In addition, SPUUs containing L-arginine promoted higher levels of HUVECs adhesion, spreading and viability after 7 days compared to the commonly used Tecoflex(®) polyurethane. The biodegradability and HUVEC proliferation on L-arginine-based SPUUs suggests that they can be used in the design of vascular grafts for tissue engineering.

A radiation-sensitive monomer of 2,4-hexadiyn-1,6-bis(p-toluene sulphonyl urethane) in PVA as a radiochromic film dosimeter

NASA Astrophysics Data System (ADS)

Soliman, Yasser S.; Abdel-Fattah, A. A.; Hamed, A. A.; Bayomi, A. M. M.

2018-03-01

A conjugated monomer 2,4-hexadiyn-1,6-bis(p-toluene sulphonyl urethane) (HDTU) was synthesized. Thereafter, it was incorporated into polyvinyl alcohol (PVA), and coated on self-adhesive sheet, thus to prepare film dosimeters. The monomer and films were analyzed using X-ray diffraction (XRD), FTIR spectroscopy and specular reflectance colorimetry. This monomer polymerizes in the films by radiation and turns progressively blue in proportion to absorbed dose, indicating the formation of π-conjugated colored poly-HDTU. Color development was investigated at 480 nm and 610 nm for dose monitoring ranging from 10 Gy to 15 kGy. HDTU in PVA film is highly ordered and crystalline and, upon irradiation, it forms a semi-crystalline polymer with nearly the same interplanar distances as the monomer, indicating the occurrence of topochemical polymerization. During irradiation, polymerization of the monomer is nearly independent of humidity in the range of 0-53% and temperature in the range of 25-45 °C. The uncertainty of this system is 5.16% at 95% confidence level.

Beamformed nearfield imaging of a simulated coronary artery containing a stenosis.

PubMed

Owsley, N L; Hull, A J

1998-12-01

This paper is concerned with the potential for the detection and location of an artery containing a partial blockage by exploiting the space-time properties of the shear wave field in the surrounding elastic soft tissue. As a demonstration of feasibility, an array of piezoelectric film vibration sensors is placed on the free surface of a urethane mold that contains a surgical tube. Inside the surgical tube is a nylon constriction that inhibits the water flowing through the tube. A turbulent field develops in and downstream from the blockage, creating a randomly fluctuating pressure on the inner wall of the tube. This force produces shear and compressional wave energy in the urethane. After the array is used to sample the dominant shear wave space-time energy field at low frequencies, a nearfield (i.e., focused) beamforming process then images the energy distribution in the three-dimensional solid. Experiments and numerical simulations are included to demonstrate the potential of this noninvasive procedure for the early identification of vascular blockages-the typical precursor of serious arterial disease in the human heart.

Mechanical properties and cytotoxicity of experimental soft lining materials based on urethane acrylate oligomers.

PubMed

Kanie, Takahito; Tomita, Koichi; Tokuda, Masayuki; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2009-07-01

The purpose of this investigation was to determine whether experimental light-curing soft lining materials (ESLMs) based on commercially available urethane acrylate oligomers (UA-160TM, UV-3200B, UV-3500BA, and UV-3700B) are suitable for clinical use by measuring their viscosity, compressive modulus, Shore A hardness, tensile strength, adhesive strength, and cytotoxicity. The viscosities of the four ESLMs at 25 degrees C were 10.5 Pa.s, UV-3500BA; 144.0 Pa.s, UA-160TM; 328.8 Pa.s, UV-3700B; and 1079.7 Pa.s, UV-3200B. Polymerized UV-3700B was very soft, whereas the softness of the other ESLMs was similar to that of conventional soft lining materials. No significant difference in adhesive strength was observed between UV-3500BA and UV-3700B at 1 day and those at 12 months. Cytotoxicity was measured by a MTT-based assay using HeLa S3 and Ca9-22 cells. UV-3200B and UV-3700B oligomers and all four polymerized ESLMs showed cell viability over 95.2% (p < 0.05).

Polyurethane intravaginal ring for controlled delivery of dapivirine, a nonnucleoside reverse transcriptase inhibitor of HIV-1.

PubMed

Gupta, Kavita M; Pearce, Serena M; Poursaid, Azadeh E; Aliyar, Hyder A; Tresco, Patrick A; Mitchnik, Mark A; Kiser, Patrick F

2008-10-01

Women-controlled methods for prevention of male-to-female sexual transmission of HIV-1 are urgently needed. Providing inhibitory concentrations of HIV-1 reverse transcriptase inhibitors to impede the replication of the virus in the female genital tissue offers a mechanism for prophylaxis of HIV-1. To this end, an intravaginal ring device that can provide long duration delivery of dapivirine, a nonnucleoside reverse transcriptase inhibitor of HIV-1, was developed utilizing a medical-grade polyether urethane. Monolithic intravaginal rings were fabricated and sustained release with cumulative flux linear with time was demonstrated under sink conditions for a period of 30 days. The release rate was directly proportional to the amount of drug loaded. Another release study conducted for a week utilizing liposome dispersions as sink conditions, to mimic the partitioning of dapivirine into vaginal tissue, also demonstrated release rates constant with time. These results qualify polyether urethanes for development of intravaginal rings for sustained delivery of microbicidal agents. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

SU-D-BRC-04: Development of Proton Tissue Equivalent Materials for Calibration and Dosimetry Studies

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

Olguin, E; Flampouri, S; Lipnharski, I

Purpose: To develop new proton tissue equivalent materials (PTEM), urethane and fiberglass based, for proton therapy calibration and dosimetry studies. Existing tissue equivalent plastics are applicable only for x-rays because they focus on matching mass attenuation coefficients. This study aims to create new plastics that match mass stopping powers for proton therapy applications instead. Methods: New PTEMs were constructed using urethane and fiberglass resin materials for soft, fat, bone, and lung tissue. The stoichiometric analysis method was first used to determine the elemental composition of each unknown constituent. New initial formulae were then developed for each of the 4 PTEMsmore » using the new elemental compositions and various additives. Samples of each plastic were then created and exposed to a well defined proton beam at the UF Health Proton Therapy Institute (UFHPTI) to validate its mass stopping power. Results: The stoichiometric analysis method revealed the elemental composition of the 3 components used in creating the PTEMs. These urethane and fiberglass based resins were combined with additives such as calcium carbonate, aluminum hydroxide, and phenolic micro spheres to achieve the desired mass stopping powers and densities. Validation at the UFHPTI revealed adjustments had to be made to the formulae, but the plastics eventually had the desired properties after a few iterations. The mass stopping power, density, and Hounsfield Unit of each of the 4 PTEMs were within acceptable tolerances. Conclusion: Four proton tissue equivalent plastics were developed: soft, fat, bone, and lung tissue. These plastics match each of the corresponding tissue’s mass stopping power, density, and Hounsfield Unit, meaning they are truly tissue equivalent for proton therapy applications. They can now be used to calibrate proton therapy treatment planning systems, improve range uncertainties, validate proton therapy Monte Carlo simulations, and assess in-field and out-of-field organ doses.« less

Development of palm oil-based UV-curable epoxy acrylate and urethane acrylate resins for wood coating application

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

Tajau, Rida; Mahmood, Mohd Hilmi; Salleh, Mek Zah

The trend of using renewable sources such as palm oil as raw material in radiation curing is growing due to the demand from the market to produce a more environmental friendly product. In this study, the radiation curable process was done using epoxy acrylate and urethane acrylate resins which are known as epoxidised palm olein acrylate (EPOLA) and palm oil based urethane acrylate (POBUA), respectively. The purpose of the study was to investigate curing properties and the application of this UV-curable palm oil resins for wood coating. Furthermore, the properties of palm oil based coatings are compared with the petrochemical-basedmore » compound such as ebecryl (EB) i.e. EB264 and EB830. From the experiment done, the resins from petrochemical-based compounds resulted higher degree of crosslinking (up to 80%) than the palm oil based compounds (up to 70%), where the different is around 10-15%. The hardness property from this two type coatings can reached until 50% at the lower percentage of the oligomer. However, the coatings from petrochemical-based have a high scratch resistance as it can withstand at least up to 3.0 Newtons (N) compared to the palm oil-based compounds which are difficult to withstand the load up to 1.0 N. Finally, the test on the rubber wood substrate showed that the coatings containing benzophenone photoinitiator give higher adhesion property and their also showed a higher glosiness property on the glass substrate compared to the coatings containing irgacure-819 photoinitiator. This study showed that the palm oil coatings can be a suitable for the replacement of petrochemicals compound for wood coating. The palm oil coatings can be more competitive in the market if the problems of using high percentage palm oil oligomer can be overcome as the palm oil price is cheap enough.« less

Electrospun polyurethane as an alternative ventricular catheter and in vitro model of shunt obstruction

PubMed Central

Suresh, Supraja

2015-01-01

Intracranial pressure and volume vary considerably between hydrocephalic patients, and with age, health and haemodynamic status; if left untreated, intracranial pressure rises and the ventricular system expands to accommodate the excess cerebrospinal fluid, with significant morbidity and mortality. Cerebrospinal fluid shunts in use today have a high incidence of failure with shunt obstruction being the most serious. Conventional proximal shunt catheters are made from poly(dimethyl)siloxane, the walls of which are perforated with holes for the cerebrospinal fluid to pass through. The limited range of catheters, in terms of material selection and flow distribution, is responsible in large part for their poor performance. In this study, we present an alternative design of proximal catheter made of electrospun polyether urethane, and evaluate its performance in the presence of glial cells, which are responsible for shunt blockage. The viability and growth of cells on catheter materials such as poly(dimethyl)siloxane and polyurethane in the form of cast films, microfibrous mats and porous sponges were studied in the presence of proteins present in cerebrospinal fluid after 48 h and 96 h in culture. The numbers of viable cells on each substrate were comparable to untreated poly(dimethyl)siloxane, both in the presence and absence of serum proteins found in cerebrospinal fluid. A cell culture model of shunt obstruction was developed in which cells on electrospun polyether urethane catheters were subjected to flow during culture in vitro, and the degree of obstruction quantified in terms of hydraulic permeability after static and perfusion culture. The results indicate that a catheter made of electrospun polyether urethane would be able to maintain cerebrospinal fluid flow even with the presence of cells for the time period chosen for this study. These findings have implications for the design and deployment of microporous shunt catheter systems for the treatment of hydrocephalus. PMID:25245779

High Strength Wood-based Sandwich Panels reinforced with fiberglass and foam

Treesearch

Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

2014-01-01

Mechanical analysis is presented for new high-strengthsandwich panels made from wood-based phenolic impregnated laminated paper assembled with an interlocking tri-axial ribbed core. Four different panel configurations were tested, including panels with fiberglass fabric bonded to both outside faces with self-expanding urethane foam used to fill the ribbed core. The...

Site-selective modification of cellulose nanocrystals with isophorone diisocyanate and formation of polyurethane-CNC composites

Treesearch

Natalie M. Girouard; Shanhong Xu; Gregory T. Schueneman; Meisha L. Shofner; J. Carson Meredith

2016-01-01

The unequal reactivity of the two isocyanate groups in an isophorone diisocyante (IPDI) monomer was exploited to yield modified cellulose nanocrystals (CNCs) with both urethane and isocyanate functionality. The chemical functionality of the modified CNCs was verified with ATR-FTIR analysis and elemental analysis. The selectivity for the secondary isocyanate group using...

Coefficient of friction of dry slash pine and southern red oak on three tension-grip facings

Treesearch

T.J. Lemoine; P. Koch

1975-01-01

A urethane material proved to have nine times higher static friction coefficient (0.9) than smooth steel (0.1) on radial and tangential wood surfaces pulled parallel to the grain. It is probably superior to 22O-grit garnet paper or sand coatings for tension-grip facings in lumber testing machines.

Coefficient of friction of dry slash pine and southern red oak on three tension-grip facings

Treesearch

Truett J. Lemoine; Peter Koch

1974-01-01

A urethane material proved to have nine times higher static friction coefficient (0.9) than smooth steel (0.1) on radial and tangential wood surfaces pulled parallel to the grain. It is probably superior to 220-grit garnet paper or sand coatings for tension-grip facings in lumber testing machines.

Extrusion cast explosive

DOEpatents

Scribner, Kenneth J.

1985-01-01

Improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst are disclosed. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants.

INVESTIGATION OF THE USE OF ISOCYANATE ADDUCTS IN URETHANE FOAM

DTIC Science & Technology

The fea ibility of a one-can, delayed action foaming system was successfully d monstra e . A literary arch revealed that y co poun s po e ing...ctive ydrogens may react with organic isocyanates to produce heat-s nsitive adducts. T HESE D UCT YI LD BACK THE ORIGINAL ISOCY N TE AND THE

40 CFR Table 6 to Subpart Jj of... - VHAP of Potential Concern

Code of Federal Regulations, 2010 CFR

2010-07-01

... Formaldehyde 0.2 101144 4,4′-Methylene bis(2-chloroaniline) 0.02 107131 Acrylonitrile 0.03 106934 Ethylene... Chlorobenzilate 0.04 62737 Dichlorvos 0.02 75014 Vinyl chloride 0.02 75218 Ethylene oxide 0.09 96457 Ethylene... 51796 Ethyl carbamate (Urethane) 0.08 107062 Ethylene dichloride (1,2-Dichloroethane) 0.08 78875...

Environmental Assessment of Selected Cone Penetrometer Grouts and a Tracer

DTIC Science & Technology

1993-08-01

Bentonite Clay ............ ...................... A2 Attapulgite Clay ................................... A22 Microfine Portland Cement...and the tracer are a. Bentonite clay. b. Attapulgite clay. c. Microfine portland cement. d. Joosten grout (calcium silicate grout). e. Urethane grout. f...Inc., on an attapulgite clay product (trade name: Zeogel). " Microfine portland cement. Information was obtained for two micro- fine portland cements

Air-Inflated Fabric Structures

DTIC Science & Technology

2006-11-05

environmental exposure to ultraviolet rays, moisture, fire, chemicals, etc. Coating such as urethane, PVC (polyvinyl chloride), neoprene, EPDM (ethylene...tests on rubber -coated, plain-woven fabrics and established that the initial shear response was dominated by the coating and with increased shearing...Farboodmanesh, S., Chen, J., Mead, J. L., White, K., "Effect of Construction on Mechanical Behavior of Fabric Reinforced Rubber ," Rubber Division

Asphaltenes-based polymer nano-composites

DOEpatents

Bowen, III, Daniel E

2013-12-17

Inventive composite materials are provided. The composite is preferably a nano-composite, and comprises an asphaltene, or a mixture of asphaltenes, blended with a polymer. The polymer can be any polymer in need of altered properties, including those selected from the group consisting of epoxies, acrylics, urethanes, silicones, cyanoacrylates, vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, imides, esters, cyanate esters, allyl resins.

Synthesis and Physical Properties of Poly(Perfluoroalkylether)Urethanes

DTIC Science & Technology

1989-05-30

Differential scanning calorimetry and dynamic mechanical analysis showed that the incorporation of PFEG into the soft segment phase slightly enhanced...for all the polymers, using electron spectroscopy for chemical analysis (ESCA). The dynamic contact angle results indicate that the polymer surfaces...these polymers were evaluated by a variety of techniques. Differential scanning calorimetry and dynamic mechanical analysis showed that the

The Marcraft floor-leveling system for urban rehabilitation

Treesearch

David G. Martens; E. Paul Craft

1967-01-01

A speedy and efficient system has been developed for installing wooden screeds that can be used as a base for laying a level new floor over an old sagging floor. The screeds are held in position by means of a new leveling device, and rigid urethane foam is sprayed under the screeds to hold them permanently in a level position.

The Causes of Blistering in Boat Building Materials

DTIC Science & Technology

1986-08-01

acrylate units (MET) Ethylene glycol (MET) Propylene glycol (MET) Neopentyl glycol (NET) Maleic acid or anhydride (unsaturated) (NET) lumaric acid...PROPYLENE GLYCOL OPA ORTHOPHTHALIC ACID VINYL - URETHANE BASED POLYESTER IqPG NEOPENTYL GLYCOL RESIN EG - ETHYLENE GLYCOL TMPD - 22,, - TRiMETHY...IPA Isophthalic acid WSN Low molecular weight water soluble material NPG Neopentyl glycol OPA Orthophthalio acid PG Propylene glycol MEKP Hethyl

Extrusion cast explosive

DOEpatents

Scribner, K.J.

1985-01-29

Improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst are disclosed. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants. 1 fig.

Extrusion cast explosive

DOEpatents

Scribner, K.J.

1985-11-26

Disclosed is an improved, multiphase, high performance, high energy, extrusion cast explosive compositions, comprising, a crystalline explosive material; an energetic liquid plasticizer; a urethane prepolymer, comprising a blend of polyvinyl formal, and polycaprolactone; a polyfunctional isocyanate; and a catalyst. These new explosive compositions exhibit higher explosive content, a smooth detonation front, excellent stability over long periods of storage, and lower sensitivity to mechanical stimulants. 1 fig.

Poly(ester-urethane) scaffolds: effect of structure on properties and osteogenic activity of stem cells.

PubMed

Kiziltay, Aysel; Marcos-Fernandez, Angel; San Roman, Julio; Sousa, Rui A; Reis, Rui L; Hasirci, Vasif; Hasirci, Nesrin

2015-08-01

The present study aimed to investigate the effect of structure (design and porosity) on the matrix stiffness and osteogenic activity of stem cells cultured on poly(ester-urethane) (PEU) scaffolds. Different three-dimensional (3D) forms of scaffold were prepared from lysine-based PEU using traditional salt-leaching and advanced bioplotting techniques. The resulting scaffolds were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury porosimetry and mechanical testing. The scaffolds had various pore sizes with different designs, and all were thermally stable up to 300 °C. In vitro tests, carried out using rat bone marrow stem cells (BMSCs) for bone tissue engineering, demonstrated better viability and higher cell proliferation on bioplotted scaffolds compared to salt-leached ones, most probably due to their larger and interconnected pores and stiffer nature, as shown by higher compressive moduli, which were measured by compression testing. Similarly, SEM, von Kossa staining and EDX analyses indicated higher amounts of calcium deposition on bioplotted scaffolds during cell culture. It was concluded that the design with larger interconnected porosity and stiffness has an effect on the osteogenic activity of the stem cells. Copyright © 2013 John Wiley & Sons, Ltd.

In situ SHG monitoring of dipolar orientation and relaxation in Disperse Red type/derivative urethane-urea copolymer

NASA Astrophysics Data System (ADS)

Samoc, A.; Holland, A.; Tsuchimori, M.; Watanabe, O.; Samoc, M.; Luther-Davies, B.; Kolev, V. Z.

2005-09-01

We investigated linear optical and second-order nonlinear optical (NLO) properties of films of urethane-urea copolymer (UU2) functionalised with a high concentration of an azobenzene chromophore. The polymer films on ITO-coated substrate were corona poled to induce a noncentrosymmetric organization of chromophore dipoles and data on the second harmonic generated with the laser beam (the fundamental wavelength 1053 nm, 6 ps/pulse, 20 Hz repetition rate) was acquired as a function of time and temperature. Second harmonic generation (SHG) was used to monitor in situ the polar alignment and relaxation of orientation of the side-chain Disperse Red-like chromophore molecules in the films poled at room temperature and high above the glass transition temperature (Tg 140-150oC). The deff coefficient was determined from the Maker-fringe method and corrected for absorption. A strong second harmonic effect with a fast relaxation was observed in "cold" (room temperature) poling experiments. A large second-order resonantly enhanced optical nonlinearity (d33 of the order of 200 pm/V) was obtained in high temperature poling. A strong and stable nonlinearity has persisted for years after the films were high-temperature poled.

Development of modified poly(perfluoropropyleneoxide) urethane systems for use in liquid oxygen and in enriched 100 percent oxygen atmosphere

NASA Technical Reports Server (NTRS)

Harrison, E. S.

1973-01-01

This program consisted of two separate though related phases. The initial phase was directed toward improving the mechanical and adhesive properties of the very highly fluorinated-polyurethane resin system derived from the hydroxyl-terminated polyperfluoropropylene oxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate. Various new curing agents for this system were investigated, with the goal of providing a more thermally stable crosslink (cure) mechanism to provide wider applicability and fuller utilization of the outstanding oxygen resistance of the PFPO system. Complete resistance to liquid- and gaseous-oxygen impact at presures as high as 1035 N/sq cm were attained with the use of the PFPO resin castings. The second corollary phase was directed toward investigating the feasibility and optimization of the allophanate cured, urethane extended polymer derived from hydroxyl-terminated polyperfluoropropyleneoxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate, as the adhesive system for use in a weld-bond configuration for liquid oxygen tankage. The synthesis and application procedures of the adhesive system to insure liquid oxygen compatibility (under 10 kg-m loading), and the development of procedures and techniques to provide high quality weld-bonded joint configurations were studied.

Applicability of cranial models in urethane resin and foam as a substitute for bone: are synthetic materials reliable?

PubMed

Muccino, Enrico; Porta, Davide; Magli, Francesca; Cigada, Alfredo; Sala, Remo; Gibelli, Daniele; Cattaneo, Cristina

2013-09-01

As literature is poor in functional synthetic cranial models, in this study, synthetic handmade models of cranial vaults were produced in two different materials (a urethane resin and a self-hardening foam), from multiple bone specimens (eight original cranial vaults: four human and four swine), in order to test their resemblance to bone structure in behavior, during fracture formation. All the vaults were mechanically tested with a 2-kg impact weight and filmed with a high-speed camera. Fracture patterns were homogeneous in all swine vaults and heterogeneous in human vaults, with resin fractures more similar to bone fractures. Mean fracture latency time extrapolated by videos were of 0.75 msec (bone), 1.5 msec (resin), 5.12 msec (foam) for human vaults and of 0.625 msec (bone), 1.87 msec (resin), 3.75 msec (foam) for swine vaults. These data showed that resin models are more similar to bone than foam reproductions, but that synthetic material may behave quite differently from bone as concerns fracture latency times. © 2013 American Academy of Forensic Sciences.

Multiscale Molecular Dynamics Simulations of Model Hydrophobically Modified Ethylene Oxide Urethane Micelles.

PubMed

Yuan, Fang; Larson, Ronald G

2015-09-24

The flower-like micelles of various aggregation numbers of a model hydrophobically modified ethylene oxide urethane (HEUR) molecule, C16E45C16, and their corresponding starlike micelles, containing the surfactants C16E22 and C16E23, were studied by atomistic and coarse-grained molecular dynamic (MD) simulations. We used free energies from umbrella sampling to calculate the size distribution of micelle sizes and the average time for escape of a hydrophobic group from the micelle. Using the coarse-grained MARTINI force field, the most probable size of the model HEUR molecule was thereby determined to be about 80 hydrophobes per micelle and the average hydrophobe escape time to be about 0.1 s, both of which are consistent with previous experimental studies. Atomistic simulations reveal that hydrogen bond formation and the mean lifetime of hydration waters of the poly(ethylene oxide) (or PEO) groups are location-dependent in the HEUR micelle, with PEO groups immediately adjacent to the C16 groups forming the fewest hydrogen bonds with water and having hydration waters with longer lifetimes than those of the PEO groups located further away from the C16 groups.

Pyrazole amino acids: hydrogen bonding directed conformations of 3-amino-1H-pyrazole-5-carboxylic acid residue.

PubMed

Kusakiewicz-Dawid, Anna; Porada, Monika; Ochędzan-Siodłak, Wioletta; Broda, Małgorzata A; Bujak, Maciej; Siodłak, Dawid

2017-09-01

A series of model compounds containing 3-amino-1H-pyrazole-5-carboxylic acid residue with N-terminal amide/urethane and C-terminal amide/hydrazide/ester groups were investigated by using NMR, Fourier transform infrared, and single-crystal X-ray diffraction methods, additionally supported by theoretical calculations. The studies demonstrate that the most preferred is the extended conformation with torsion angles ϕ and ψ close to ±180°. The studied 1H-pyrazole with N-terminal amide/urethane and C-terminal amide/hydrazide groups solely adopts this energetically favored conformation confirming rigidity of that structural motif. However, when the C-terminal ester group is present, the second conformation with torsion angles ϕ and ψ close to ±180° and 0°, respectively, is accessible. The conformational equilibrium is observed in NMR and Fourier transform infrared studies in solution in polar environment as well as in the crystal structures of other related compounds. The observed conformational preferences are clearly related to the presence of intramolecular interactions formed within the studied residue. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Strong photoluminescence characteristics of sulforhodamine B attached on photonic crystal

NASA Astrophysics Data System (ADS)

Kim, Byoung-Ju; Kang, Kwang-Sun

2014-10-01

The optical properties of sulforhodamine B (SRH) impregnated in photonic crystal by two step synthetic processes including a urethane bond formation between a 3-isocyanatopropyl triethoxysilane (ICPTES, -N=C=O) and a SRH with elevated temperature in pyridine and hydrolysis-condensation reactions between synthesized ICPTES/SRH (ICPSRH) and tetraethoxyorthosilicate (TEOS) in NH4OH. The monodisperse silica spheres impregnated the ICPSRH (ICPSRHS) are fabricated. The reduction of the absorption peak at 2270 cm-1 representing asymmetric stretching vibration of -N=C=O indicates the progress of the reaction and new absorption peak at 1712 cm-1 characterizing -C=O stretching vibration indicates the formation of urethane bond. The UV-visible absorption spectra show the broadened spectral line width by intermolecular interaction. The photoluminescence (PL) peak of the SRH in methanol shows a hypsochromic shift with the increase the excitation wavelength. However, the PL peak for the ICPSRH exhibits a bathochromic shift as the excitation wavelength increases. The PL peak for the ICPSRH shows no hypsochromic or bathochromic shift. The PL peaks for SRH in methanol, ICPSRH and ICPSRHS are at 568, 598 and 572 nm, respectively. The main cause of the PL peak shift is due to the intermolecular interaction.

Effects of Eucommia leaf extracts on autonomic nerves, body temperature, lipolysis, food intake, and body weight.

PubMed

Horii, Yuko; Tanida, Mamoru; Shen, Jiao; Hirata, Tetsuya; Kawamura, Naomi; Wada, Atsunori; Nagai, Katsuya

2010-08-02

Eucommia ulmoides Oliver leaf extracts (ELE) have been shown to exert a hypolipidemic effect in hamsters. Therefore, it was hypothesized that ELE might affect lipid metabolism via changes in autonomic nerve activities and causes changes in thermogenesis and body weight. We examined this hypothesis, and found that intraduodenal (ID) injection of ELE elevated epididymal white adipose tissue sympathetic nerve activity (WAT-SNA) and interscapular brown adipose tissue sympathetic nerve activity (BAT-SNA) in urethane-anesthetized rats and elevated the plasma concentration of free fatty acids (FFA) (a marker of lipolysis) and body temperature (BT) (a marker of thermogenesis) in conscious rats. Furthermore, it was observed that ID administration of ELE decreased gastric vagal nerve activity (GVNA) in urethane-anesthetized rats, and that ELE given as food reduced food intake, body and abdominal adipose tissue weights and decreased plasma triglyceride level. These findings suggest that ELE stimulates lipolysis and thermogenesis through elevations in WAT-SNA and BAT-SNA, respectively, suppresses appetite by inhibiting the activities of the parasympathetic nerves innervating the gastrointestinal tract, including GVNA, and decreases the amount of abdominal fat and body weight via these changes. Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

Thermal performance of aircraft polyurethane seat cushions

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A.

1982-01-01

Measurements were conducted on 7.6 x 7.6 cm samples of polyurethane seat cushion material in a modified National Bureau of Standards smoke density chamber to simulate real life conditions for an onboard aircraft fire or post-crash fire. In this study, a non-flaming heat radiation condition was simulated. Two aluminized polymeric fabrics (Norfab 11HT-26-A and Preox 1100-4) and one neoprene type material in two thicknesses (Vonar 2 and 3) were tested as heat blocking layers to protect the urethane foam from rapid heat degradation. Thermogravimetric analysis and differential scanning calorimetry were performed to characterize thermally the materials tested. It was found that Vonar 2 or 3 provided approximately equal thermal protection to F.R. urethane as the aluminized fabrics, but at a significant weight penalty. The efficiency of the foams to absorb heat per unit mass loss when protected with the heat blocking layer decreases in the heating range of 2.5-5.0 W/sq cm, but remains unchanged or slightly increases in the range of 5.0-7.5 W/sq cm. The results show that at all heat flux ranges tested the usage of a heat blocking layer in aircraft seats significantly improves their thermal performance.

Fabrication of a biodegradable calcium polyphosphate/polyvinyl-urethane carbonate composite for high load bearing osteosynthesis applications.

PubMed

Ramsay, Scott D; Pilliar, Robert M; Santerre, J Paul

2010-07-01

The formation of biodegradable implants for use in osteosynthesis has been a major goal of biomaterials research for the past 2-3 decades. Self-reinforced polylactide systems represent the most significant success of this research to date, however, with elastic constants up to 12-15 GPa at best, they fail to provide the initial stiffness required of devices for stabilizing fractures of major load-bearing bones. Our research has investigated the use of calcium polyphosphate (CPP), an inorganic polymer in combination with polyvinyl-urethane carbonate (PVUC) organic polymers for such applications. Initial studies indicated that composite samples formed as interpenetrating phase composites (IPC) exhibited suitable as-made strength and stiffness, however, they displayed a rapid loss of properties when exposed to in vitro aging. An investigation to determine the mechanism of this accelerated in vitro degradation for the IPCs as well as to identify possible design changes to overcome this drawback was undertaken using a model IPC system. It was found that strong interfacial strength and minimal swelling of the PVUC are very important for obtaining and maintaining appropriate mechanical properties in vitro. (c) 2010 Wiley Periodicals, Inc.

Quality Assurance Assessment of the F-35 Lightning II Program

DTIC Science & Technology

2013-09-30

assurance personnel had not verified epoxy primer, urethane topcoat, and abrasion - resistant coating processes. In another case, there was no indication...other for electrical resistance . A review of drawing requirements and discussions Contractor Assessments DODIG-2013-140 │ 11 with personnel noted that...the operators were not required to perform the electrical resistance verification, even though it was later determined to be required. Finally, the

Polyimide-glass multilayer printed wiring boards

NASA Astrophysics Data System (ADS)

Lula, J. W.

1984-07-01

Multilayer printed wiring boards (PWBs) from a polyimide/glass reinforced copper clad laminate and prepreg were manufactured. A lamination cycle and innerlayer copper surface treatment that gave satisfactory delamination resistance at soldering temperatures were developed. When compared to similar epoxy/glass multilayer PWBs, the polyimide PWBs had higher thermal stability, greater resistance to raised lands, fewer plating voids, less outgassing, and adhesion that was equivalent to urethane foam encapsulants.

Manufacturing Methods and Technology Project Summary Reports

DTIC Science & Technology

1981-06-01

a tough urethane film. The basic principle is to pump two components to a spinning disc, mixing the components just prior to depositing in a well...and check out an electronic target scoring device using developed scientific principles without drastically modifying existing commercial...equipment. The scoring device selected and installed was an Accubar Model ATS-16D using the underlying physics principle of acoustic shock wave propagation

Synthesis of Energetic Materials

DTIC Science & Technology

1988-03-01

reacted with excess ethyl urethane, under boron trifluoride catalysis in trifluoroacetic acid, to give the 2,3-bisurethane derivative. This conversion... trifluoride catalysis, to give none of the imidazolidine (1), but only a low yield of the MEDINA derivative (5), via an obscure reaction pathway...trifluoroacetic acid under boron trifluoride catalysis. The major product, isolated in high yield, was the tricyclic ether (18). In fact, compound 18 was

Plate-Impact Measurements of a Select Model Poly(urethane urea) Elastomer

DTIC Science & Technology

2013-06-01

experiments, and data for polyurea (dashed line) are also included for comparison. .....................................8 List of Tables Table 1...6 1 1. Introduction High-performance polyurea elastomers have recently gained considerable interest throughout the U.S. Department of...studies on high-strain-rate mechanical deformation and modeling (3, 6–11), wherein most are focused on a commercial polyurea . The commercial polyureas

Synthesis of a novel biomedical poly(ester urethane) based on aliphatic uniform-size diisocyanate and the blood compatibility of PEG-grafted surfaces.

PubMed

Liu, Xiaolong; Xia, Yiran; Liu, Lulu; Zhang, Dongmei; Hou, Zhaosheng

2018-05-01

The purpose of this study is to offer a novel kind of polyurethane with improved surface blood compatibility for long-term implant biomaterials. In this work, the aliphatic poly(ester-urethane) (PEU) with uniform-size hard segments was prepared and the PEU surface was grafted with hydrophilic poly(ethylene glycol) (PEG). The PEU was obtained by chain-extension of poly(ɛ-caprolactone) (PCL) with isocyanate-terminated urethane triblock. Free amino groups were introduced onto the surface of PEU film via aminolysis with hexamethylenediamine, and then the NH 2 -grafted PEU surfaces (PEU-NH 2 ) were reacted with isocyanate-terminated monomethoxyl PEG (MPEG-NCO) to obtain the PEG-grafted PEU surfaces (PEU-PEG). Analysis by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were performed to confirm the chemical structures of the chain extender, PCL, PEU, and PEU-PEG. Additionally, the influence of aminolysis on the physical-mechanical properties of PEU films was investigated. Two glass transition temperatures and a broad endothermic peak were observed in the differential scanning calorimetry curves of PEU, which demonstrated a microphase-separated and semicrystalline structure, respectively. The PEU-PEG film exhibited excellent mechanical properties with an ultimate stress of ∼39 MPa and an elongation at break of ∼1190%, which was slightly lower than that of PEU, indicating that the aminolysis has little influence on the tensile properties. Evaluation of the blood compatibility of the films by bovine serum albumin adsorption and the platelet adhesion test revealed that the PEG-grafted surface had improved resistance to protein adsorption and excellent resistance to platelet adhesion. In vitro degradation tests showed that the PEU-PEG film could maintain its mechanical properties for more than six months and only lost ∼25% weight after 18 months. Due to the excellent mechanical properties, good blood compatibility and slow degradability, this novel kind of polyurethane hold significant promise for long-term implant biomaterials, especially soft tissue augmentation and regeneration.

Investigation of the effects of P2 purinoceptor ligands on the micturition reflex in female urethane-anaesthetized rats.

PubMed

King, Brian F; Knowles, Ian D; Burnstock, Geoffrey; Ramage, Andrew G

2004-06-01

1 The effects of purinoceptor ligands for P2X1 and/or P2X3 receptors (alpha,beta-meATP, IP(5)I, TNP-ATP, MRS 2179, PPADS, Phenol red and RO116-6446/008; i.v., n=4-5) and for P2Y1 receptors (PPADS, MRS 2179 and MRS 2269; i.v., n=3-5) were investigated on the distension-evoked 'micturition reflex' in the urethane-anaesthetized female rat. 2 Alpha,beta-meATP (180 nmol kg(-1) min(-1)), IP5I (10, 30 and 100 nmol kg(-1)), TNP-ATP (1 micromol kg(-1)), MRS 2179 (1 micromol kg(-1)) and PPADS (17 micromol kg(-1)) each caused maintained bladder contractions to occur during the infusion of saline into the bladder. PPADS (17 micromol kg(-1) min(-1)) had a similar effect when infused intravesicularly. Regular bladder contractions were not observed until the infusion of saline was halted. For IP5I, TNP-ATP, MRS 2179 and PPADS, the magnitude of postinfusion isovolumetric contractions was significantly reduced and, for IP5I, this action was also associated with a significant reduction in urethral relaxation. Additionally, TNP-ATP caused a significant increase in the pressure and volume thresholds required to initiate a reflex. 3 Phenol red (a P2X1/P2X3 antagonist; 0.1 and 1 micromol kg(-1)) caused a significant increase in the pressure and volume thresholds required to initiate a reflex and, at the higher dose, also caused a reduction in postinfusion isovolumetric contractions. 4 RO116-6446/008 (a P2X1-selective antagonist; 1 and 10 micromol kg(-1)) only caused a reduction in postinfusion isovolumetric contractions. 5 It is concluded that P2X1 and P2X3 receptors play a fundamental role in the micturition reflex in urethane-anesthetized female rats. P2X3 receptor blockade raised the pressure and volume thresholds for the reflex, whereas P2X1 receptor blockade diminished motor activity associated with voiding. P2Y1 receptors may be involved in inhibition of rat detrusor tone.

Using Diffusion Bonding in Making Piezoelectric Actuators

NASA Technical Reports Server (NTRS)

Sager, Frank E.

2003-01-01

A technique for the fabrication of piezoelectric actuators that generate acceptably large forces and deflections at relatively low applied voltages involves the stacking and diffusion bonding of multiple thin piezoelectric layers coated with film electrodes. The present technique stands in contrast to an older technique in which the layers are bonded chemically, by use of urethane or epoxy agents. The older chemical-bonding technique entails several disadvantages, including the following: It is difficult to apply the bonding agents to the piezoelectric layers. It is difficult to position the layers accurately and without making mistakes. There is a problem of disposal of hazardous urethane and epoxy wastes. The urethane and epoxy agents are nonpiezoelectric materials. As such, they contribute to the thickness of a piezoelectric laminate without contributing to its performance; conversely, for a given total thickness, the performance of the laminate is below that of a unitary piezoelectric plate of the same thickness. The figure depicts some aspects of the fabrication of a laminated piezoelectric actuator by the present diffusion- bonding technique. First, stock sheets of the piezoelectric material are inspected and tested. Next, the hole pattern shown in the figure is punched into the sheets. Alternatively, if the piezoelectric material is not a polymer, then the holes are punched in thermoplastic films. Then both faces of each punched piezoelectric sheet or thermoplastic film are coated with a silver-ink electrode material by use of a silkscreen printer. The electrode and hole patterns are designed for minimal complexity and minimal waste of material. After a final electrical test, all the coated piezoelectric layers (or piezoelectric layers and coated thermoplastic films) are stacked in an alignment jig, which, in turn, is placed in a curved press for the diffusion-bonding process. In this process, the stack is pressed and heated at a specified curing temperature and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

Picrotoxin antagonism of γ aminobutyric acid inhibitory responses and synaptic inhibition in the rat substantia nigra

PubMed Central

Crossman, A. R.; Walker, R. J.; Woodruff, G. N.

1973-01-01

Neurones in the substantia nigra of the rat, anaesthetized with urethane, are inhibited both by electrical stimulation of the ipsilateral caudate nucleus and by iontophoretically applied γ-aminobutyric acid (GABA). Iontophoretically applied picrotoxin reversibly blocks both of these inhibitory responses. These results are consistent with the hypothesis that GABA is the transmitter released by the inhibitory striato-nigral pathway. PMID:4362811

Roof plan, Combat Operations Center, Building No. 2605. (Also includes ...

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

Roof plan, Combat Operations Center, Building No. 2605. (Also includes a typical roof section, with new fiberglass and urethane insulation layers.) By Federal Builders, 575 Carreon Drive, Colton, California. Sheet 1 of 1, dated 18 May 1992. Scale one-eighth inch to one foot. 24x36 inches. ink on paper - March Air Force Base, Strategic Air Command, Combat Operations Center, 5220 Riverside Drive, Moreno Valley, Riverside County, CA

120 DEG C Cure, Durable, Corrosion Protection Powder Coatings for Temperature Sensitive Substrates

DTIC Science & Technology

2005-01-28

Extrudate was passed through water-cooled pinch-rolls and collected onto a stainless steel belt; from exit of the extruder, approximately 60 sec... stainless steel belt; from exit of the extruder, approximately 60 sec. was required to reach ambient temperature. Production scale processing at...inherently free from volatile organic compounds, chromates, and hazardous air pollutants. Relative to the incumbent solvent-borne urethane paint

Evaluation of Moisture-Cure Urethane Coatings for Compliance with Industry Specifications

DTIC Science & Technology

2011-12-01

Upon curing, RUST GRIP provides a protective coating of superior adhesion, flexibility, abrasion - and impact- resistance . It is resistant to most...THANE 2821 is an extremely hard abrasion resistant coating. It is ideally suited for usage such as bridges, tanks, locks and dams, marine structures...extremely hard abrasion resistant coating. It makes an excellent coating for concrete floors when used directly on concrete. CHEM-THANE 2822HS

Demonstration/Validation of Tertiary Butyl Acetate (TBAC) for Hand Wipe Cleaning Applications

DTIC Science & Technology

2010-10-01

Solvent-based coatings come in two basic forms, thermoplastic (lacquers) and thermosetting ( enamels ). Both forms contain solvents, resins...with a low water content. It can therefore be used to thin two-component urethane and epoxy CARC coatings as well as alkyds enamels . Isotron...identification of known cracks and the intensity of the cracks should be brighter or equal to the control using Secondary Secondary (CCAD

Influence of Microstructure on Micro-/Nano-Mechanical Measurements of Select Model Transparent Poly(urethane urea) Elastomers

DTIC Science & Technology

2012-12-17

results. Furthermore, instrumented impact indentation is also utilized for elucidation of dynamic damping characteristics in these PUUs. REPORT... characteristics in these PUUs. Published by Elsevier Ltd. 1. Introduction Elastomers are versatile materials that are vital to a broad range of...industrial, medical, and military applications, particularly in the areas of coating, adhesives, foams , and composite structures [1]. More specifically, high

Investigating the reactivity of pMDI with wood cell walls using high-resolution solution-state NMR spectroscopy

Treesearch

Daniel J. Yelle; John Ralph; Charles R. Frihart

2009-01-01

The objectives of this study are the following: (1) Use solution-state NMR to assign contours in HSQC spectra of the reaction products between pMDI model compounds and: (a) lignin model compounds, (b) milled-wood lignin, (c) ball-milled wood, (d) microtomed loblolly pine; (2) Determine where and to what degree urethane formation occurs with loblolly pine cell wall...

Electrostatic Hazards of Urethane Packed Fuel Tanks.

DTIC Science & Technology

1986-03-01

Monsanto concluded (Appendix D) that the foam was absorbing substances ( alkylphenols ) from the fuel and that the fuel was extracting chemicals (the most...experienced fuel impingement exhibited very strong absorption at 2.9 pm which is attributed to the alkylphenol type substances extracted by the foam...from the foam. - Absorption of alkylphenol type compounds by the foam. The latter of these compositional changes is believed to have a relatively

Synthesis and characterization of shape-memory poly carbonate urethane microspheres for future vascular embolization.

PubMed

Liu, Rongrong; Dai, Honglian; Zhou, Qian; Zhang, Qian; Zhang, Ping

2016-08-01

Two types of shape memory poly carbonate urethanes (PCUs) microspheres were synthesized by pre-polymerization and suspension polymerization, based on Polycarbonate diol (PCDL) as the soft segment, Isophorone diisocyanate (IPDI) and 1,6-hexamethylene diisocyanate (HDI) as the hard segments and 1,4-butanediol (BDO) as the chain expanding agent. The structure, crystallinity, and thermal property of the two synthesized PCUs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetery (DSC), respectively. The results showed that the two types of PCUs exhibited high thermal stability with phase separation and semi-crystallinity. Also, the results of the compression test displayed that the shape fixity and the shape recovery of two PCUs were more than 90% compared to the originals, indicating their similar bio-applicability and shape-memory properties. The tensile strength, elongation at break was enhanced by introducing and increasing content of HDI. The water contact angles of PCUs decreased and their surface tension increased by surface modified with Bovine serum albumin (BSA). Furthermore, the biological study results of two types of PCUs from the platelet adhesion test and the cell proliferation inhibition test indicated they had some biocompatibilites. Hence, the PCU microspheres might represent a smart and shape-memory embolic agent for vascular embolization.

Morphology and surface properties of high strength siloxane poly(urethane-urea)s developed for heart valve application.

PubMed

Dandeniyage, Loshini S; Adhikari, Raju; Bown, Mark; Shanks, Robert; Adhikari, Benu; Easton, Christopher D; Gengenbach, Thomas R; Cookson, David; Gunatillake, Pathiraja A

2018-03-04

A series of siloxane poly(urethane-urea) (SiPUU) were developed by incorporating a macrodiol linked with a diisocyanate to enhance mixing of hard and soft segments (SS). The effect of this modification on morphology, surface properties, surface elemental composition, and creep resistance was investigated. The linked macrodiol was prepared by reacting α,ω-bis(6-hydroxyethoxypropyl) poly(dimethylsiloxane)(PDMS) or poly(hexamethylene oxide) (PHMO) with either 4,4'-methylenediphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), or isophorone diisocyanate (IPDI). SiPUU with PHMO-MDI-PHMO and PHMO-IPDI-PHMO linked macrodiols showed enhanced creep resistance and recovery when compared with a commercial biostable polyurethane, Elast-Eon™ 2A. Small and wide-angle X-ray scattering data were consistent with significant increase of hydrogen bonding between hard and SS with linked-macrodiols, which improved SiPUU's tensile stress and tear strengths. These SiPUU were hydrophobic with contact angle higher than 101° and they had low water uptake (0.7%·w/w of dry mass). They also had much higher siloxane concentration on the surface compared to that in the bulk. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

Controllable degradation kinetics of POSS nanoparticle-integrated poly(ε-caprolactone urea)urethane elastomers for tissue engineering applications

PubMed Central

Yildirimer, Lara; Buanz, Asma; Gaisford, Simon; Malins, Edward L.; Remzi Becer, C.; Moiemen, Naiem; Reynolds, Gary M.; Seifalian, Alexander M.

2015-01-01

Biodegradable elastomers are a popular choice for tissue engineering scaffolds, particularly in mechanically challenging settings (e.g. the skin). As the optimal rate of scaffold degradation depends on the tissue type to be regenerated, next-generation scaffolds must demonstrate tuneable degradation patterns. Previous investigations mainly focussed on the integration of more or less hydrolysable components to modulate degradation rates. In this study, however, the objective was to develop and synthesize a family of novel biodegradable polyurethanes (PUs) based on a poly(ε-caprolactone urea)urethane backbone integrating polyhedral oligomeric silsesquioxane (POSS-PCLU) with varying amounts of hard segments (24%, 28% and 33% (w/v)) in order to investigate the influence of hard segment chemistry on the degradation rate and profile. PUs lacking POSS nanoparticles served to prove the important function of POSS in maintaining the mechanical structures of the PU scaffolds before, during and after degradation. Mechanical testing of degraded samples revealed hard segment-dependent modulation of the materials’ viscoelastic properties, which was attributable to (i) degradation-induced changes in the PU crystallinity and (ii) either the presence or absence of POSS. In conclusion, this study presents a facile method of controlling degradation profiles of PU scaffolds used in tissue engineering applications. PMID:26463421

Pressor responses to nasal stimulation are unaltered after disrupting the CPA.

PubMed

Panneton, W Michael; Sun, Wei; Gan, Qi

2008-12-15

Stimulation of either the caudal pressor area (CPA) in the most caudal ventrolateral medulla with glutamate, or the nasal mucosa with ammonia vapors, induces an increase in mean arterial blood pressure (MABP). In the present study, we determined if neurons in the CPA serve as a relay for the increase in MABP seen after nasal stimulation. Ammonia vapors stimulated the nasal mucosa of rats anesthetized with either urethane alone or ketamine/xylazine and urethane to induce an increase in MABP, a bradycardia, and an apnea. Bilateral injections (50 nl) of glycine (1 M) or muscimol (2 mM) were placed in the CPA and the nasal mucosa again stimulated. The increases in MABP, the bradycardia and the duration of apnea to nasal stimulation were unchanged after either injection. However, resting MABP and HR were decreased significantly after glycine injections and resting MABP and resting respiratory rate were decreased after muscimol injections. The increase in MABP seen with nasal stimulation also did not change after multiple bilateral injections (3x40 nl) of ibotenate (5 microg/microl) in the CPA, but the bradycardia was eliminated and the duration of apnea was significantly shorter. These results suggest that the increase in MABP induced by nasal stimulation is via routes that do not include neurons in the CPA.

Ameliorative effects of gallic acid, quercetin and limonene on urethane-induced genotoxicity and oxidative stress in Drosophila melanogaster.

PubMed

Nagpal, Isha; Abraham, Suresh K

2017-05-01

The main objective of our present work was to ascertain the efficacy of Drosophila melanogaster model for assessing antigenotoxic and antioxidant effects of dietary phytochemicals gallic acid (GA), quercetin (QC) and limonene (Lim) against urethane (URE), a genotoxic environmental carcinogen. Oregon-K (ORK) adult male flies were fed GA, QC and Lim in combination with URE (20 mM) in 10% sucrose for 72 h. Third instar larvae were fed instant medium containing the above phytochemicals and URE for 24 h. Sex-linked recessive lethal (SLRL) test and assays for estimating glutathione content (GSH), glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and lipid peroxidation (MDA content) were performed. Adult feeding experiments demonstrated that co-treatment of flies with URE and the test phytochemicals has significantly decreased the frequencies of SLRL mutations in all the germ cell stages when compared to that with URE alone. Larval feeding experiments also showed a similar pattern. The above results correlate well with antioxidative potentials of the test agents where we observed the elevated enzymatic levels with a significant reduction in MDA level in Drosophila larvae. The results further suggest that the dietary phytochemicals have an antioxidant and antimutagenic property which can be assessed using D. melanogaster.

Genotoxicity studies of organically grown broccoli (Brassica oleracea var. italica) and its interactions with urethane, methyl methanesulfonate and 4-nitroquinoline-1-oxide genotoxicity in the wing spot test of Drosophila melanogaster.

PubMed

Heres-Pulido, María Eugenia; Dueñas-García, Irma; Castañeda-Partida, Laura; Santos-Cruz, Luis Felipe; Vega-Contreras, Viridiana; Rebollar-Vega, Rosa; Gómez-Luna, Juan Carlos; Durán-Díaz, Angel

2010-01-01

Broccoli (Brassica oleracea var. italica) has been defined as a cancer preventive food. Nevertheless, broccoli contains potentially genotoxic compounds as well. We performed the wing spot test of Drosophila melanogaster in treatments with organically grown broccoli (OGB) and co-treatments with the promutagen urethane (URE), the direct alkylating agent methyl methanesulfonate (MMS) and the carcinogen 4-nitroquinoline-1-oxide (4-NQO) in the standard (ST) and high bioactivation (HB) crosses with inducible and high levels of cytochrome P450s (CYPs), respectively. Larvae of both crosses were chronically fed with OGB or fresh market broccoli (FMB) as a non-organically grown control, added with solvents or mutagens solutions. In both crosses, the OGB added with Tween-ethanol yielded the expected reduction in the genotoxicity spontaneous rate. OGB co-treatments did not affect the URE effect, MMS showed synergy and 4-NQO damage was modulated in both crosses. In contrast, FMB controls produced damage increase; co-treatments modulated URE genotoxicity, diminished MMS damage, and did not change the 4-NQO damage. The high dietary consumption of both types of broccoli and its protective effects in D. melanogaster are discussed. Copyright 2009 Elsevier Ltd. All rights reserved.

Effects of Different Anesthetics on Oscillations in the Rat Olfactory Bulb

PubMed Central

Li, Anan; Zhang, Lei; Liu, Min; Gong, Ling; Liu, Qing; Xu, Fuqiang

2012-01-01

Different types of oscillations in the olfactory bulb (OB), including θ (1 to 4 and 5 to 12 Hz), β (13 to 30 Hz), and γ oscillations (31 to 64 and 65 to 90 Hz), are important in olfactory information processing and olfactory-related functions and have been investigated extensively in recent decades. The awake and anesthetized states, 2 different brain conditions, are used widely in electrophysiologic studies of OB. Chloral hydrate, pentobarbital, and urethane are commonly used anesthetics in these studies. However, the influence of these anesthetics on the oscillations has not been reported. In the present study, we recorded the local field potential (LFP) in the OB of rats that were freely moving or anesthetized with these agents. Chloral hydrate and pentobarbital had similar effects: they slightly affected the power of θ oscillations; significantly increased the power of β oscillations; significantly decreased the power of γ oscillations, and showed similar recovery of γ oscillations. Urethane had very different effects: it significantly increased oscillations at 1 to 4 Hz but decreased those at 5 to 12 Hz, decreased β and γ oscillations, and showed no overt recovery in γ oscillations. These results provide experimental evidence of different effects of various anesthetics on OB oscillations and suggest that the choice of anesthetic should consider the experimental application. PMID:23043811

Reactive polymer fused deposition manufacturing

DOEpatents

Kunc, Vlastimil; Rios, Orlando; Love, Lonnie J.; Duty, Chad E.; Johs, Alexander

2017-05-16

Methods and compositions for additive manufacturing that include reactive or thermosetting polymers, such as urethanes and epoxies. The polymers are melted, partially cross-linked prior to the depositing, deposited to form a component object, solidified, and fully cross-linked. These polymers form networks of chemical bonds that span the deposited layers. Application of a directional electromagnetic field can be applied to aromatic polymers after deposition to align the polymers for improved bonding between the deposited layers.

Solar space and water heating system installed at Charlottesville, Virginia

NASA Technical Reports Server (NTRS)

1980-01-01

The solar energy system located at David C. Wilson Neuropsychiatric Hospital, Charlottesville, Virginia, is described. The solar energy system consists of 88 single glazed, Sunworks 'Solector' copper base plate collector modules, hot water coils in the hot air ducts, a Domestic Hot Water (DHW) preheat tank, a 3,000 gallon concrete urethane insulated storage tank and other miscellaneous components. Extracts from the site files, specifications, drawings, installation, operation and maintenance instructions are included.

SPECT/CT of lung nodules using 111In-DOTA-c(RGDfK) in a mouse lung carcinogenesis model.

PubMed

Hayakawa, Takuya; Mutoh, Michihiro; Imai, Toshio; Tsuta, Koji; Yanaka, Akinori; Fujii, Hirofumi; Yoshimoto, Mitsuyoshi

2013-08-01

Lung cancer is one of the leading causes of cancer-related deaths worldwide, including Japan. Although computed tomography (CT) can detect small lung lesions such as those appearing as ground glass opacity, it cannot differentiate between malignant and non-malignant lesions. Previously, we have shown that single photon emission computed tomography (SPECT) imaging using (111)In-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-cyclo-(Arg-Gly-Asp-D-Phe-Lys) (DOTA-c(RGDfK)), an imaging probe of αvβ3 integrin, is useful for the early detection of pancreatic cancer in a hamster pancreatic carcinogenesis model. In this study, we aimed to assess the usefulness of SPECT/CT with (111)In-DOTA-c(RGDfK) for the evaluation of the malignancy of lung cancer. Lung tumors were induced by a single intraperitoneal injection (250 mg/kg) of urethane in male A/J mice. Twenty-six weeks after the urethane treatment, SPECT was performed an hour after injection of (111)In-DOTA-c(RGDfK). Following this, the radioactivity ratios of tumor to normal lung tissue were measured by autoradiography (ARG) in the excised lung samples. We also examined the expression of αvβ3 integrin in mouse and human lung samples. Urethane treatment induced 5 hyperplasias, 41 adenomas and 12 adenocarcinomas in the lungs of 8 A/J mice. SPECT with (111)In-DOTA-c(RGDfK) could clearly visualize lung nodules, though we failed to detect small lung nodules like adenoma and hyperplasias (adenocarcinoma: 66.7%, adenoma: 33.6%, hyperplasia: 0.0%). ARG analysis revealed significant uptake of (111)In-DOTA-c(RGDfK) in all the lesions. Moreover, tumor to normal lung tissue ratios increased along with the progression of carcinogenesis. Histopathological examination using human lung tissue samples revealed clear up-regulation of αvβ3 integrin in well-differentiated adenocarcinoma (Noguchi type B and C) rather than atypical adenomatous hyperplasia. Although there are some limitations in evaluating the malignancy of small lung tumors using (111)In-DOTA-c(RGDfK), SPECT with (111)In-DOTA-c(RGDfK) might be a useful non-invasive imaging approach for evaluating the characteristics of lung tumors in mice, thus showing potential for use in humans.

Biodegradable hyperbranched amphiphilic polyurethane multiblock copolymers consisting of poly(propylene glycol), poly(ethylene glycol), and polycaprolactone as in situ thermogels.

PubMed

Li, Zibiao; Zhang, Zhongxing; Liu, Kerh Li; Ni, Xiping; Li, Jun

2012-12-10

This paper reports the synthesis and characterization of new hyperbranched amphiphilic polyurethane multiblock copolymers consisting of poly(propylene glycol) (PPG), poly(ethylene glycol) (PEG), and polycaprolactone (PCL) segments as in situ thermogels. The hyperbranched poly(PPG/PEG/PCL urethane)s, termed as HBPEC copolymers, were synthesized from PPG-diol, PEG-diol, and PCL-triol by using 1,6-hexamethylene diisocyanate (HMDI) as a coupling agent. The compositions and structures of HBPEC copolymers were determined by GPC and 1H NMR spectroscopy. We carried out comparative studies of the new hyperbranched copolymers with their linear counterparts, the linear poly(PPG/PEG/PCL urethane) (LPEC) copolymer and Pluronic F127 PEG-PPG-PEG block copolymer, in terms of their self-assembly and aggregation behaviors and thermoresponsive properties. HBPEC copolymers were found to show thermoresponsive micelle formation and aggregation behaviors. Particularly, the lower critical solution temperature (LCST) of the copolymers was significantly affected by the copolymer architecture. HBPEC copolymers showed much lower LCST than LPEC, the linear counterpart. Our studies revealed that the effect of hyperbranch architecture was more prominent in the gelation of the copolymers. The aqueous solutions of HBPEC copolymers exhibited thermogelling behaviors at critical gelation concentrations (CGCs) ranging from 4.3 to 7.4 wt %. These values are much lower than those reported on other PCL-contained linear thermogelling copolymers and Pluronic F127 copolymer. In addition, the CGC of HBPEC copolymers is much lower than the control LPEC copolymer. More interestingly, at high temperatures, while LPEC and other linear thermogelling copolymers formed turbid sol, HBPEC formed a dehydrated gel. Our data suggest that these phenomena are caused by the hyperbranched structure of HBPEC copolymers, which could increase the interaction of copolymer branches and enhance the chain association through synergetic hydrogen bonding effect. The thermogelling behavior of HBPEC block copolymers was further evidenced by the 1H NMR molecular dynamic study and rheological study, which further support the above hypothesis. The hydrolytic degradation study showed that the HBPEC copolymer hydrogels are biodegradable under physiological conditions. Together with the good cell biocompatibility demonstrated by the cytotoxicity study, the new thermogelling copolymers reported in this paper could potentially be used as in situ-forming hydrogels for biomedical applications.

The Role of High Pressure and Inert Gases in the Production and Reversal of the High Pressure Neurological Syndrome.

DTIC Science & Technology

1982-08-06

mine, and phenytoin . All except the latter and/3-chloralose caused marked decreases in order. The bilayer/buffer partition coefficients of...phenobarbital, phenytoin , and urethane were measured. The change-in-order parameter as a function of total anesthetic concen- tration varied widely but when the...BY GENERAL ANESTHETICS 85 to disorder egg phosphatidylcholine:cholesterol (2:1) bi- Partition coefficients of phenobarbital and phenytoin layers. This

Fire and Flammability Characteristics of Materials Used in Rail Passenger Cars. A Literature Survey.

DTIC Science & Technology

1980-04-01

Charac- teristics of Fiber -Reinforced Organic-Matrix Composites ," Report No. MAT-77-21, David W. Taylor Naval Ship R&D Center, Annapolis, MD 21402, June...were limited to poly- vinyl chloride, urethanes, wool, and Nomex fiber ;and gas analysis was limited to carbon monoxide, hydrogen cyanide, and...liberation, smoke emission, combustion products, toxicity, pyrolysis, plastics, polymers, synthetic fibers , flammability test methods. 20, A MT’NACT (mftM m

Optimization of aircraft seat cushion fire blocking layers

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A.; Ling, A. C.; Hovatter, W. R.

1983-01-01

This report describes work completed by the National Aeronautics and Space Administration - for the Federal Aviation Administration Technical Center. The purpose of this work was to examine the potential of fire blocking mechanisms for aircraft seat cushions in order to provide an optimized seat configuration with adequate fire protection and minimum weight. Aluminized thermally stable fabrics were found to provide adequate fire protection when used in conjunction with urethane foams, while maintaining minimum weight and cost penalty.

The Synthesis of Carborane-Oxetane Monomers and their Polymerization

DTIC Science & Technology

1988-07-11

polyether glycol was liter demonstrated.’ During this time, " modified cationic polymerization technique was developef’, which allowed the synthesis of...Migration of these chemicals in the propellant grain is a continuous and serious problem. We proposed that a urethane curable polyether glycol with a...Br CH3 g 3 Cl CH3 This scheme has the advantage that the leaving group is not on the oxetane. Oxetane is a neopentyl type system which is typically

Copying Machine Improvement

NASA Technical Reports Server (NTRS)

1981-01-01

Manufacturer of the Model 2210 copying machine was looking for a plastic valve bushing material that could be produced by a low-cost injection molding process to replace the unsuitable valve bushing they were using. NERAC conducted a computer search of the NASA database and was able to supply Nashua Corporation with several technical reports in their area of interest. Information aided the company's development of a urethane valve bushing which solved the problem and created a dramatic reduction in unit cost.

Exploratory Development of Coated Fabric for Fire Proximity Suits

DTIC Science & Technology

1978-06-01

burner flame impinged directly on the surface for 1 minute. The Solucote urethane was the only coating which incorporated a flame retardant , so all the...blistering or flashing in the above test, but only some charring. On the basis of all the above tests, it was decided to use the flame retardant treated...fch4- fabric Wa8 not flame retardant . Consequently this surface coat ignited after 10 seconds of exposure. If ignition had not occurred, this

Biodegradable Poly (Ester Urethane) Urea Biomaterials For Applications in Combat Casualty Care

DTIC Science & Technology

2006-11-01

hydroxyapatite (Irvine, CA), and tissue culture polystyrene were used as positive controls in the cell culture experiments. 3.2 Synthesis of PEUUR cast...was performed to detect biomineralization after 28 days of culture in osteogenic medium. 3.6 MicroFT- IR The composition of the materials and...biomineralization was assessed by micro FT- IR (Nicollet Coninuµm™). After 28 days of cell culture on the foams the sample with the cells was fixed

A Durable Airfield Marking System.

DTIC Science & Technology

1985-06-01

Resin is Mixed with the Black Curing Agent to Form the Epoxy Adhesive ..... ........... 17 14 The Gray Adhesive (White Resin Mixed with Black Curing...rubber 100 0 Polyester (peroxide-catalyzed) 100 0 Urethane 100 0 Epoxy polyamide 100 0 Acrylic latex (TT-P-1952) 100 0 Thermoplastic Tapes Type 1 100 0...suzmarrizes cost data co1parisons for traffic marking tapes, CAS tiles, fluorocarbon composites (Teflon ),and acrylic latex paint TT-P-1952. 8 -p °’. TABLE 2

The National Shipbuilding Research Program. Application of Industrial Engineering Techniques to Reduce Workers’ Compensation and Environmental Costs - Deliverable D

DTIC Science & Technology

1999-10-01

Electrostatic guns provide opportunities for exterior application of topcoats such as urethanes, acrylics , alkyds and epoxies. Most shipbuilding...A hybrid of airless spray and conventional air-atomized spray, this kind of gun uses fluid pressures higher than those used in conventional air...voltage) by simply flipping a switch. All essential controls are located right at the back of the gun. Other electrostatic systems require constant

Amphiphilic graft copolymers from end-functionalized starches: synthesis, characterization, thin film preparation, and small molecule loading.

PubMed

Ryno, Lisa M; Reese, Cassandra; Tolan, McKenzie; O'Brien, Jeffrey; Short, Gabriel; Sorriano, Gerardo; Nettleton, Jason; Fulton, Kayleen; Iovine, Peter M

2014-08-11

End-functionalized macromolecular starch reagents, prepared by reductive amination, were grafted onto a urethane-linked polyester-based backbone using copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry to produce novel amphiphilic hybrid graft copolymers. These copolymers represent the first examples of materials where the pendant chains derived from starch biopolymers have been incorporated into a host polymer by a grafting-to approach. The graft copolymers were prepared in good yields (63-90%) with high grafting efficiencies (66-98%). Rigorous quantitative spectroscopic analyses of both the macromolecular building blocks and the final graft copolymers provide a comprehensive analytical toolbox for deciphering the reaction chemistry. Due to the modular nature of both the urethane-linked polyester synthesis and the postpolymerization modification, the starch content of these novel hybrid graft copolymers was easily tuned from 28-53% (w/w). The uptake of two low molecular weight guest molecules into the hybrid polymer thin films was also studied. It was found that binding of 1-naphthol and pterostilbene correlated linearly with amount of starch present in the hybrid polymer. The newly synthesized graft copolymers were highly processable and thermally stable, therefore, opening up significant opportunities in film and coating applications. These results represent a proof-of-concept system for not only the construction of starch-containing copolymers, but also the loading of these novel polymeric materials with active agents.

End-Group Effects on the Properties of PEG-co-PGA Hydrogels

PubMed Central

Bencherif, Sidi A.; Srinivasan, Abiraman; Sheehan, Jeffrey A.; Walker, Lynn M.; Gayathri, Chakicherla; Gil, Roberto; Hollinger, Jeffrey O.; Matyjaszewski, Krzysztof; Washburn, Newell R.

2009-01-01

A series of resorbable poly(ethylene glycol)-co-poly(glycolic acid) macromonomers have been synthesized with the chemistries from three different photopolymerizable end-groups (acrylates, methacrylates, and urethane methacrylates). The aim of the study is to examine the effects of the chemistry of the cross-linker group on the properties of photocross-linkable hydrogels. PEG-co-PGA (4KG5) hydrogels were prepared by photopolymerization with high vinyl group conversion as confirmed by 1H NMR spectroscopy using DOSY 1D pulse sequence. Our study reveals that the nature of end-groups in a moderately amphiphilic polymer can adjust the distribution and size of the micellar configuration in water leading to changes in the macroscopic structure of hydrogels. By varying the chemistry of the cross-linker group (diacrylates; DA, dimethacrylates; DM, and urethane dimethacrylates; UDM), we determined that the hydrophobocity of a single core polymer consisting of poly(glycolic acid) could be fine-tuned leading to significant variations in the mechanical, swelling, and degradation properties of the gels. In addition, the effects of cross-linker chemistry on cytotoxicity and proliferation were examined. Cytotoxicity assays showed that all the three types of hydrogels (4KG5 DA, DM, and UDM) were biocompatible and the introduction of RGD ligand enhanced cell adhesion. However, differences in gel properties and stability differentially affected the spreading and proliferation of myoblast C2C12 cells. PMID:19328754

Surface modification of a polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer as a stent coating for enhanced capture of endothelial progenitor cells

PubMed Central

Tan, Aaron; Farhatnia, Yasmin; Goh, Debbie; G, Natasha; de Mel, Achala; Lim, Jing; Teoh, Swee-Hin; Malkovskiy, Andrey V; Chawla, Reema; Rajadas, Jayakumar; Cousins, Brian G; Hamblin, Michael R; Alavijeh, Mohammad S; Seifalian, Alexander M

2013-01-01

An unmet need exists for the development of next-generation multifunctional nanocomposite materials for biomedical applications, particularly in the field of cardiovascular regenerative biology. Herein, we describe the preparation and characterization of a novel polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer with covalently attached anti-CD34 antibodies to enhance capture of circulating endothelial progenitor cells (EPC). This material may be used as a new coating for bare metal stents used after balloon angioplasty to improve re-endothelialization. Biophysical characterization techniques were used to assess POSS-PCU and its subsequent functionalization with anti-CD34 antibodies. Results indicated successful covalent attachment of anti-CD34 antibodies on the surface of POSS-PCU leading to an increased propensity for EPC capture, whilst maintaining in vitro biocompatibility and hemocompatibility. POSS-PCU has already been used in 3 first-in-man studies, as a bypass graft, lacrimal duct and a bioartificial trachea. We therefore postulate that its superior biocompatibility and unique biophysical properties would render it an ideal candidate for coating medical devices, with stents as a prime example. Taken together, anti-CD34 functionalized POSS-PCU could form the basis of a nano-inspired polymer platform for the next generation stent coatings. PMID:24706135

Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry.

PubMed

Patel, Jasmine D; Ebert, Michael; Stokes, Ken; Ward, Robert; Anderson, James M

2003-01-01

Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to < or = 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of < or = 7 dyne/cm2. Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.

Durable Suit Bladder with Improved Water Permeability for Pressure and Environment Suits

NASA Technical Reports Server (NTRS)

Bue, Grant C.; Kuznetz, Larry; Orndoff, Evelyne; Tang, Henry; Aitchison, Lindsay; Ross, Amy

2009-01-01

Water vapor permeability is shown to be useful in rejecting heat and managing moisture accumulation in launch-and-entry pressure suits. Currently this is accomplished through a porous Gortex layer in the Advanced Crew and Escape Suit (ACES) and in the baseline design of the Constellation Suit System Element (CSSE) Suit 1. Non-porous dense monolithic membranes (DMM) that are available offer potential improvements for water vapor permeability with reduced gas leak. Accordingly, three different pressure bladder materials were investigated for water vapor permeability and oxygen leak: ElasthaneTM 80A (thermoplastic polyether urethane) provided from stock polymer material and two custom thermoplastic polyether urethanes. Water vapor, carbon dioxide and oxygen permeability of the DMM's was measured in a 0.13 mm thick stand-alone layer, a 0.08 mm and 0.05 mm thick layer each bonded to two different nylon and polyester woven reinforcing materials. Additional water vapor permeability and mechanical compression measurements were made with the reinforced 0.05 mm thick layers, further bonded with a polyester wicking and overlaid with moistened polyester fleece thermal underwear .This simulated the pressure from a supine crew person. The 0.05 mm thick nylon reinforced sample with polyester wicking layer was further mechanically tested for wear and abrasion. Concepts for incorporating these materials in launch/entry and Extravehicular Activity pressure suits are presented.

Biodegradable, elastomeric coatings with controlled anti-proliferative agent release for magnesium-based cardiovascular stents.

PubMed

Gu, Xinzhu; Mao, Zhongwei; Ye, Sang-Ho; Koo, Youngmi; Yun, Yeoheung; Tiasha, Tarannum R; Shanov, Vesselin; Wagner, William R

2016-08-01

Vascular stent design continues to evolve to further improve the efficacy and minimize the risks associated with these devices. Drug-eluting coatings have been widely adopted and, more recently, biodegradable stents have been the focus of extensive evaluation. In this report, biodegradable elastomeric polyurethanes were synthesized and applied as drug-eluting coatings for a relatively new class of degradable vascular stents based on Mg. The dynamic degradation behavior, hemocompatibility and drug release were investigated for poly(carbonate urethane) urea (PCUU) and poly(ester urethane) urea (PEUU) coated magnesium alloy (AZ31) stents. Poly(lactic-co-glycolic acid) (PLGA) coated and bare stents were employed as control groups. The PCUU coating effectively slowed the Mg alloy corrosion in dynamic degradation testing compared to PEUU-coated, PLGA-coated and bare Mg alloy stents. This was confirmed by electron microscopy, energy-dispersive x-ray spectroscopy and magnesium ion release experiments. PCUU-coating of AZ31 was also associated with significantly reduced platelet adhesion in acute blood contact testing. Rat vascular smooth muscle cell (rSMC) proliferation was successfully inhibited when paclitaxel was released from pre-loaded PCUU coatings. The corrosion retardation, low thrombogenicity, drug loading capacity, and high elasticity make PCUU an attractive option for drug eluting coating on biodegradable metallic cardiovascular stents. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of a poly (ether urethane) system for the controlled release of two novel anti-biofilm agents based on gallium or zinc and its efficacy to prevent bacterial biofilm formation

PubMed Central

Ma, Hongyan; Darmawan, Erica T.; Zhang, Min; Zhange, Lei; Bryers, James D.

2013-01-01

Traditional antibiotic therapy to control medical device-based infections typically fails to clear biofilm infections and may even promote the evolution of antibiotic resistant species. We report here the development of two novel antibiofilm agents; gallium (Ga) or zinc (Zn) complexed with protoporphyrin IX (PP) or mesoprotoporphyrin IX (MP) that are both highly effective in negating suspended bacterial growth and biofilm formation. These chelated gallium or zinc complexes act as iron siderophore analogs, surplanting the natural iron uptake of most bacteria. Poly (ether urethane) (PEU; Biospan®) polymer films were fabricated for the controlled sustained release of the Ga- or Zn-complexes, using an incorporated pore-forming agent, poly (ethylene glycol) (PEG). An optimum formulation containing 8% PEG (MW=1450) in the PEU polymer effectively sustained drug release for at least 3 months. All drug-loaded PEU films exhibited in vitro ≥ 90% reduction of Gram-positive (Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa) bacteria in both suspended and biofilm culture versus the negative control PEU films releasing nothing. Cytotoxicity and endotoxin evaluation demonstrated no adverse responses to the Ga- or Zn-complex releasing PEU films. Finally, in vivo studies further substantiate the anti-biofilm efficacy of the PEU films releasing Ga- or Zn- complexes. PMID:24140747

Development of a poly(ether urethane) system for the controlled release of two novel anti-biofilm agents based on gallium or zinc and its efficacy to prevent bacterial biofilm formation.

PubMed

Ma, Hongyan; Darmawan, Erica T; Zhang, Min; Zhang, Lei; Bryers, James D

2013-12-28

Traditional antibiotic therapy to control medical device-based infections typically fails to clear biofilm infections and may even promote the evolution of antibiotic resistant species. We report here the development of two novel antibiofilm agents; gallium (Ga) or zinc (Zn) complexed with protoporphyrin IX (PP) or mesoprotoporphyrin IX (MP) that are both highly effective in negating suspended bacterial growth and biofilm formation. These chelated gallium or zinc complexes act as iron siderophore analogs, supplanting the natural iron uptake of most bacteria. Poly (ether urethane) (PEU; Biospan®) polymer films were fabricated for the controlled sustained release of the Ga- or Zn-complexes, using an incorporated pore-forming agent, poly(ethylene glycol) (PEG). An optimum formulation containing 8% PEG (MW=1450) in the PEU polymer effectively sustained drug release for at least 3months. All drug-loaded PEU films exhibited in vitro ≥ 90% reduction of Gram-positive (Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa) bacteria in both suspended and biofilm culture versus the negative control PEU films releasing nothing. Cytotoxicity and endotoxin evaluation demonstrated no adverse responses to the Ga- or Zn-complex releasing PEU films. Finally, in vivo studies further substantiate the anti-biofilm efficacy of the PEU films releasing Ga- or Zn- complexes. © 2013.

Modeling study of a proposed field calibration source using K-40 and high-Z targets for sodium iodide detectors

DOE PAGES

Rogers, Jeremy; Marianno, Craig; Kallenbach, Gene; ...

2016-06-01

Calibration sources based on the primordial isotope potassium-40 ( 40K) have reduced controls on the source’s activity due to its terrestrial ubiquity and very low specific activity. Potassium–40’s beta emissions and 1,460.8 keV gamma ray can be used to induce K-shell fluorescence x rays in high-Z metals between 60 and 80 keV. A gamma ray calibration source that uses potassium chloride salt and a high-Z metal to create a two-point calibration for a sodium iodide field gamma spectroscopy instrument is thus proposed. The calibration source was designed in collaboration with the Sandia National Laboratory using the Monte Carlo N-Particle eXtendedmore » (MCNPX) transport code. Two methods of x-ray production were explored. First, a thin high-Z layer (HZL) was interposed between the detector and the potassium chloride-urethane source matrix. Second, bismuth metal powder was homogeneously mixed with a urethane binding agent to form a potassium chloride-bismuth matrix (KBM). The bismuth-based source was selected as the development model because it is inexpensive, nontoxic, and outperforms the high-Z layer method in simulation. As a result, based on the MCNPX studies, sealing a mixture of bismuth powder and potassium chloride into a thin plastic case could provide a light, inexpensive field calibration source.« less

Accelerated aging, natural aging, and small punch testing of gamma-air sterilized polycarbonate urethane acetabular components.

PubMed

Kurtz, S M; Siskey, R; Reitman, M

2010-05-01

The objectives of this study were three-fold: (1) to determine the applicability of the small punch test to characterize Bionate 80A polycarbonate urethane (PCU) acetabular implants; (2) to evaluate the susceptibility of PCU acetabular implants to exhibit degradation of mechanical behavior following gamma irradiation in air and accelerated aging; and (3) to compare the oxidation of gamma-air sterilized PCU following accelerated aging and 5 years of natural shelf aging. In addition to attenuated total reflectance-Fourier transform infrared spectroscopy, we also adapted a miniature specimen mechanical test, the small punch test, for the deformable PCU cups. Accelerated aging was performed using ASTM F2003, a standard test that represents a severe oxidative challenge. The results of this study suggest that the small punch test is sufficiently sensitive and reproducible to discriminate slight differences in the large-deformation mechanical behavior of Bionate 80A following accelerated aging. The gamma-air sterilized PCU had a reduction of 9% in ultimate load after aging. Five years of shelf aging had little effect on the mechanical properties of the PCU. Overall, our findings suggest that the Bionate 80A material has greater oxidative stability than ultra-high molecular weight polyethylene following gamma irradiation in air and exposure to a severe oxidative challenge. (c) 2010 Wiley Periodicals, Inc.

Fabrication and characterization of biomimetic multichanneled crosslinked-urethane-doped polyester tissue engineered nerve guides.

PubMed

Tran, Richard T; Choy, Wai Man; Cao, Hung; Qattan, Ibrahim; Chiao, Jung-Chih; Ip, Wing Yuk; Yeung, Kelvin Wai Kwok; Yang, Jian

2014-08-01

Biomimetic scaffolds that replicate the native architecture and mechanical properties of target tissues have been recently shown to be a very promising strategy to guide cellular growth and facilitate tissue regeneration. In this study, porous, soft, and elastic crosslinked urethane-doped polyester (CUPE) tissue engineered nerve guides were fabricated with multiple longitudinally oriented channels and an external non-porous sheath to mimic the native endoneurial microtubular and epineurium structure, respectively. The fabrication technique described herein is highly adaptable and allows for fine control over the resulting nerve guide architecture in terms of channel number, channel diameter, porosity, and mechanical properties. Biomimetic multichanneled CUPE guides were fabricated with various channel numbers and displayed an ultimate peak stress of 1.38 ± 0.22 MPa with a corresponding elongation at break of 122.76 ± 42.17%, which were comparable to that of native nerve tissue. The CUPE nerve guides were also evaluated in vivo for the repair of a 1 cm rat sciatic nerve defect. Although histological evaluations revealed collapse of the inner structure from CUPE TENGs, the CUPE nerve guides displayed fiber populations and densities comparable with nerve autograft controls after 8 weeks of implantation. These studies are the first report of a CUPE-based biomimetic multichanneled nerve guide and warrant future studies towards optimization of the channel geometry for use in neural tissue engineering. © 2013 Wiley Periodicals, Inc.

Sol-gel-graphene-based fabric-phase sorptive extraction for cow and human breast milk sample cleanup for screening bisphenol A and residual dental restorative material before analysis by HPLC with diode array detection.

PubMed

Samanidou, Victoria; Filippou, Olga; Marinou, Eirini; Kabir, Abuzar; Furton, Kenneth G

2017-06-01

Fabric-phase sorptive extraction has already been recognized as a simple and green alternative to the conventional sorbent-based sorptive microextraction techniques, using hybrid organic-inorganic sorbent coatings chemically bonded to a flexible fabric surface. Herein, we have investigated the synergistic combination of the advanced material properties offered by sol-gel graphene sorbent and the simplicity of Fabric phase sorptive extraction approach in selectively extracting bisphenol A and residual monomers including bisphenol A glycerolatedimethacrylate, urethane dimethacrylate, and triethylene glycol dimethacrylate derived dental restorative materials from cow and human breast milk samples. Different coatings were evaluated. Final method development employed sol-gel graphene coated media. The main experimental parameters influencing extraction of the compounds, such as sorbent chemistry used, sample loading conditions, elution solvent, sorption stirring time, elution time, impact of protein precipitation, amount of sample, and matrix effect, were investigated and optimized. Absolute recovery values from standard solutions were 50% for bisphenol A, 78% for T triethylene glycol dimethacrylate, 110% for urethane dimethacrylate, and 103% for bisphenol A glycerolatedimethacrylate, while respective absolute recovery values from milk were 30, 52, 104, and 42%. Method validation was performed according to European Decision 657/2002/EC in terms of selectivity, sensitivity, linearity, accuracy, and precision. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Photocrosslinkable Urethane-Doped Polyester Elastomers for Soft Tissue Engineering

PubMed Central

Zhang, Yi; Tran, Richard T.; Gyawali, Dipendra; Yang, Jian

2012-01-01

Finding an ideal biomaterial with the proper mechanical properties and biocompatibility has been of intense focus in the field of soft tissue engineering. This paper reports on the synthesis and characterization of a novel crosslinked urethane-doped polyester elastomer (CUPOMC), which was synthesized by reacting a previously developed photocrosslinkable poly (octamethylene maleate citrate) (POMC) prepolymers (pre-POMC) with 1,6-hexamethylene diisocyanate (HDI) followed by thermo- or photo-crosslinking polymerization. The mechanical properties of the CUPOMCs can be tuned by controlling the molar ratios of pre-POMC monomers, and the ratio between the prepolymer and HDI. CUPOMCs can be crosslinked into a 3D network through polycondensation or free radical polymerization reactions. The tensile strength and elongation at break of CUPOMC synthesized under the known conditions range from 0.73±0.12MPa to 10.91±0.64MPa and from 72.91±9.09% to 300.41±21.99% respectively. Preliminary biocompatibility tests demonstrated that CUPOMCs support cell adhesion and proliferation. Unlike the pre-polymers of other crosslinked elastomers, CUPOMC pre-polymers possess great processability demonstrated by scaffold fabrication via a thermally induced phase separation method. The dual crosslinking methods for CUPOMC pre-polymers should enhance the versatile processability of the CUPOMC used in various conditions. Development of CUPOMC should expand the choices of available biodegradable elastomers for various biomedical applications such as soft tissue engineering. PMID:23565318

A functionalizable reverse thermal gel based on a polyurethane/PEG block copolymer

PubMed Central

Park, Daewon; Wu, Wei; Wang, Yadong

2010-01-01

Injectable reverse thermal gels have great potentials as biomaterials for tissue engineering and drug delivery. However, most existing gels lack functional groups that can be modified with biomolecules that can guide cell/material interactions. We created an amine-functionalized ABA block copolymer, poly(ethylene glycol)-poly(serinol hexamethylene urethane), or ESHU. This reverse thermal gel consists of a hydrophobic block (B): poly(serinol hexamethylene urethane) and a hydrophilic block (A): poly(ethylene glycol). The polymer was characterized by GPC, FTIR and 1H FTNMR. Rheological study demonstrated that ESHU solution in phosphate-buffered saline initiated phase transition at 32°C and reached maximum elastic modulus at 37°C. The in vitro degradation tests performed in PBS and cholesterol esterase solutions revealed that the polymer was hydrolyzable and the presence of cholesterol esterase greatly accelerated the hydrolysis. The in vitro cytotoxicity tests carried out using baboon smooth muscle cells demonstrated that ESHU had good cytocompatibility with cell viability indistinguishable from tissue culture treated polystyrene. Subcutaneous implantation in rats revealed well tolerated accurate inflammatory response with moderate ED-1 positive macrophages in the early stages, which largely resolved 4 weeks post-implantation. We functionalized ESHU with a hexapeptide, Ile-Lys-Val-Ala-Val-Ser (IKVAVS), which gelled rapidly at body temperature. We expect this new platform of functionalizable reverse thermal gels to provide versatile biomaterials in tissue engineering and regenerative medicine. PMID:20937526

Assessment of Superstructure Ice Protection as Applied to Offshore Oil Operations Safety: Problems, Hazards, Needs, and Potential Transfer Technologies

DTIC Science & Technology

2008-09-01

thermostats, or materials such as carbon layers, which vary in thickness with location and are self - healing and self - regulating. Ships commonly use heating...aircraft today. Pneumatic deicing systems consist of rubber or other elastomeric boots placed on the leading edge of an aircraft wing or on any surface...by Kenney, two as- semblies consisting of neoprene rubber and urethane-coated Dacron fabric were hung from bulkheads where icing would occur. A timer

Fire blocking systems for aircraft seat cushions

NASA Technical Reports Server (NTRS)

Parker, J. A.; Kourtides, D. A. (Inventor)

1984-01-01

A configuration and method for reducing the flammability of bodies of organic materials that thermally decompose to give flammable gases comprises covering the body with a flexible matrix that catalytically cracks the flammable gases to less flammable species. Optionally, the matrix is covered with a gas impermeable outer layer. In a preferred embodiment, the invention takes the form of an aircraft seat in which the body is a poly(urethane) seat cushion, the matrix is an aramid fabric or felt and the outer layer is an aluminum film.

Proceedings of the Floating Tire Breakwater Workshop Held in Niagara Falls, New York on 8-9 November 1984.

DTIC Science & Technology

1985-11-01

report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. The contents of...New York AGENDA Wednesday, 7 November 7:30 p.m. Registration 8:00 Floating Tire Breakwater (FTB) Slides and Movies Thursday, 8 November 8:30 a.m...which urethanes to use with which rubber. Some of the variables are: the -k solvent used in the bonding agent, room temperature, air moisture content

Proceedings of Cabin Safety Conference and Workshop Held on December 11-14, 1984.

DTIC Science & Technology

1985-08-01

Department of Transportation in the interest of information exchange. The United States Govern- - ment assumes no liability for its contents or use ...presently used FR urethane foam. Tests were also performed to study and compare the behavior of FR cushions with various blocking layers. The tests were... guinea pigs in front of such a large audience. (Pause: As cast returns to seats) Now, let’s get back to the real world. The FAA’s recent staff study

Foam, Foam-resin composite and method of making a foam-resin composite

NASA Technical Reports Server (NTRS)

MacArthur, Doug E. (Inventor); Cranston, John A. (Inventor)

1995-01-01

This invention relates to a foam, a foam-resin composite and a method of making foam-resin composites. The foam set forth in this invention comprises a urethane modified polyisocyanurate derived from an aromatic amino polyol and a polyether polyol. In addition to the polyisocyanurate foam, the composite of this invention further contains a resin layer, wherein the resin may be epoxy, bismaleimide, or phenolic resin. Such resins generally require cure or post-cure temperatures of at least 350.degree. F.

Extreme toxicity from combustion products of a fire-retarded polyurethane foam.

PubMed

Petajan, J H; Voorhees, K J; Packham, S C; Baldwin, R C; Einhorn, I N; Grunnet, M L; Dinger, B G; Birky, M M

1975-02-28

The products from nonflaming combustion of wood and a trimethylol-propane-based rigid-urethane foam that was not fire-retarded produced elevated carboxyhemoglobin levels but no abnormal neurological effects. However, when this type of foam contained a reactive phosphate fire retardant, the combustion products caused grand mal seizures and death in rats. The toxic combustion product responsible for the seizures has been identified as 4-ethyl-1-phospha-2,6,7-trioxabicyclo(2.2.2.)octane-1-oxide.

The Use of Thermal Spraying to Enhance the Bonding Characteristics of a Urethane Coated Propeller

DTIC Science & Technology

1999-05-03

NAME(S) AND ADDRESS( ES ) 8. PERFORMING ORGANIZATION REPORT NUMBER U.S. Naval Academy USNA Trident Scholar project report Annapolis, MD no. 265 (1999...9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS( ES ) 10. SPONSORING/MONITORING AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES Accepted by the U.S...TEST: A 90-degree Peel Test was used to examine the bond strength of the specimens. A SATEC tensile test machine was used with a 2000 lb. load cell

Preparation of Novel Hydrolyzing Urethane Modified Thiol-Ene Networks

DTIC Science & Technology

2011-10-25

EtO EtO EtO Si EtO OEt OEt O OEt Si OEt OEt OEt HO HOEt H H O H H H Si OEt EtO EtO ... EtO H H SiO H H OEt OEt OEt H Polymers 2011, 3 1851 Thiol-ene “click” chemistry, as a means to form polymer networks...Table 3. Analysis of kinetic rates for fluorine modified systems. Sample name a Zero order k r2 First order k r2 Higuchi KH r2

Sound-absorbing slabs and structures based on granular materials (bound and unbound). [energy absorbing efficiency of porous material

NASA Technical Reports Server (NTRS)

Petre-Lazar, S.; Popeea, G.

1974-01-01

Sound absorbing slabs and structures made up of bound or unbound granular materials are considered and how to manufacture these elements at the building site. The raw material is a single grain powder (sand, expanded blast furnace slag, etc.) that imparts to the end products an apparent porosity of 25-45% and an energy dissipation within the structure leading to absorption coefficients that can be compared with those of mineral wool and urethane.

Lunar surface engineering properties experiment definition

NASA Technical Reports Server (NTRS)

Mitchell, J. K.; Goodman, R. E.; Hurlbut, F. C.; Houston, W. N.; Willis, D. R.; Witherspoon, P. A.; Hovland, H. J.

1971-01-01

Research on the mechanics of lunar soils and on developing probes to determine the properties of lunar surface materials is summarized. The areas of investigation include the following: soil simulation, soil property determination using an impact penetrometer, soil stabilization using urethane foam or phenolic resin, effects of rolling boulders down lunar slopes, design of borehole jack and its use in determining failure mechanisms and properties of rocks, and development of a permeability probe for measuring fluid flow through porous lunar surface materials.

Molecular Design of Novel Poly(urethane-urea) Hybrids as Helmet Pads for Ballistic and Blast Trauma Mitigation

DTIC Science & Technology

2009-03-01

triptycene-1,4 hydroquinone resulted in a 9 °C increase in the soft segment glass transition temperature compared to hydroquinone -containing PU. The 1,4...Acknowledgments v 1. Objective 1 2. Background and Approach 1 3. Experimental 2 4. Results 4 4.1 Influence of Triptycene-1,4 Hydroquinone in PUs...Figures Figure 1. Chemical structures of triptycene-1,4 hydroquinone and 1,4-diaminotriptycene. ..........2 Figure 2. Synthesis reaction of PTMO and

Evaluation of a press-fit osteochondral poly(ester-urethane) scaffold in a rabbit defect model.

PubMed

Dresing, Iska; Zeiter, Stephan; Auer, Jörg; Alini, Mauro; Eglin, David

2014-07-01

The purpose of this study was to evaluate the impact on osteochondral healing of press-fitted multiphasic osteochondral scaffolds consisting of poly(ester-urethane) (PUR) and hydroxyapatite into a cylindric osteochondral defect in the distal non-weight bearing femoral trochlear ridge of the rabbit. Two scaffolds were investigated, one with and one without an intermediate microporous membrane between the cartilage and the bone compartment of the scaffold. A control group without a scaffold placed into the defect was included. After 12 weeks macroscopic and histomorphological analyses were performed. The scaffold was easily press-fitted and provided a stable matrix for tissue repair. The membrane did not demonstrate a detrimental effect on tissue healing compared with the scaffold without membrane. However, the control group had statistically superior healing as reflected by histological differences in the cartilage and subchondral bone compartment between control group and each scaffold group. A more detailed analysis revealed that the difference was localized in the bone compartment healing. The present study demonstrates that an elastomeric PUR scaffold can easily be press-fitted into an osteochondral defect and provides a stable matrix for tissue repair. However, the multi-phasic scaffold did not provide a clear advantage for tissue healing. Future investigations should refine especially the bone phase of the implant to increase its stiffness, biocompatibility and osteoconductive activity. A more precise fabrication technique would be necessary for the matching of tissue organisation.

Sustained viral gene delivery from a micro-fibrous, elastomeric cardiac patch to the ischemic rat heart.

PubMed

Gu, Xinzhu; Matsumura, Yasumoto; Tang, Ying; Roy, Souvik; Hoff, Richard; Wang, Bing; Wagner, William R

2017-07-01

Biodegradable and elastomeric patches have been applied to the surface of infarcted hearts as temporary mechanical supports to effectively alter adverse left ventricular remodeling processes. In this report, recombinant adeno-associated virus (AAV), known for its persistent transgene expression and low pathogenicity, was incorporated into elastomeric polyester urethane urea (PEUU) and polyester ether urethane urea (PEEUU) and processed by electrospinning into two formats (solid fibers and core-sheath fibers) designed to influence the controlled release behavior. The extended release of AAV encoding green fluorescent protein (GFP) was assessed in vitro. Sustained and localized viral particle delivery was achieved over 2 months in vitro. The biodegradable cardiac patches with or without AAV-GFP were implanted over rat left ventricular lesions three days following myocardial infarction to evaluate the transduction effect of released viral vectors. AAV particles were directly injected into the infarcted hearts as a control. Cardiac function and remodeling were significantly improved for 12 weeks after patch implantation compared to AAV injection. More GFP genes was expressed in the AAV patch group than AAV injection group, with both α-SMA positive cells and cardiac troponin T positive cells transduced in the patch group. Overall, the extended release behavior, prolonged transgene expression, and elastomeric mechanical properties make the AAV-loaded scaffold an attractive option for cardiac tissue engineering where both gene delivery and appropriate mechanical support are desired. Copyright © 2017. Published by Elsevier Ltd.

Inflammation has a role in urethane‑induced lung cancer in C57BL/6J mice.

PubMed

Xu, Cai; Zhou, Lingyu; Lu, Lei; Chen, Ting; Wei, Siyu; Lin, Xiaojing; Lian, Xuemei

2016-10-01

Lung cancer is a common and highly frequent cause of cancer‑associated mortality worldwide. Several studies have indicated that chronic inflammation is associated with an increased risk of several types of human cancer. The lung is vulnerable to various chemical and biological insults, and persistent exposure to these factors may result in the release of several inflammatory cytokines from inflammatory cells, thus leading to chronic inflammation and a risk of lung cancer. Due to the extensive application of C57BL/6J mice in lipid metabolism‑related research, it appears important to establish a lung cancer model based on C57BL/6J mice. Therefore, the present study designed an experimental model, in which C57BL/6J mice received several injections of urethane. The study aimed to explore whether inflammation has a role in this model of lung cancer. The results demonstrated that 10 weekly intraperitoneal injections of urethane induced a 100% lung tumor incidence, and urethane‑treated mice possessed higher numbers of immune cells. In addition, the expression levels of cytokines and chemokines in bronchoalveolar lavage fluid were significantly different between the two groups. Activation of the transcription factor nuclear factor‑κB was increased in the lung tissues of urethane‑treated mice, and its expression was upregulated in a time‑dependent manner. These results suggested that the accumulation of lung inflammation may be associated with the occurrence of lung cancer in C57BL/6J mice.

Resting-state functional MRI as a tool for evaluating brain hemodynamic responsiveness to external stimuli in rats.

PubMed

Paasonen, Jaakko; Salo, Raimo A; Huttunen, Joanna K; Gröhn, Olli

2017-09-01

Anesthesia is a major confounding factor in functional MRI (fMRI) experiments attributed to its effects on brain function. Recent evidence suggests that parameters obtained with resting-state fMRI (rs-fMRI) are coupled with anesthetic depth. Therefore, we investigated whether parameters obtained with rs-fMRI, such as functional connectivity (FC), are also directly related to blood-oxygen-level-dependent (BOLD) responses. A simple rs-fMRI protocol was implemented in a pharmacological fMRI study to evaluate the coupling between hemodynamic responses and FC under five anesthetics (α-chloralose, isoflurane, medetomidine, thiobutabarbital, and urethane). Temporal change in the FC was evaluated at 1-hour interval. Supplementary forepaw stimulation experiments were also conducted. Under thiobutabarbital anesthesia, FC was clearly coupled with nicotine-induced BOLD responses. Good correlation values were also obtained under isoflurane and medetomidine anesthesia. The observations in the thiobutabarbital group were supported by forepaw stimulation experiments. Additionally, the rs-fMRI protocol revealed significant temporal changes in the FC in the α-chloralose, thiobutabarbital, and urethane groups. Our results suggest that FC can be used to estimate brain hemodynamic responsiveness to stimuli and evaluate the level and temporal changes of anesthesia. Therefore, analysis of the fMRI baseline signal may be highly valuable tool for controlling the outcome of preclinical fMRI experiments. Magn Reson Med 78:1136-1146, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

High Dynamic Range (Δn) Two-Stage Photopolymers via Enhanced Solubility of a High Refractive Index Acrylate Writing Monomer.

PubMed

Alim, Marvin D; Glugla, David J; Mavila, Sudheendran; Wang, Chen; Nystrom, Philip D; Sullivan, Amy C; McLeod, Robert R; Bowman, Christopher N

2018-01-10

Holographic photopolymers capable of high refractive index modulation (Δn) on the order of 10 -2 are integral for the fabrication of functional holographic optical elements that are useful in a myriad of optical applications. In particular, to address the deficiency of suitable high refractive index writing monomers for use in two-stage holographic formulations, here we report a novel high refractive index writing monomer, 1,3-bis(phenylthio)-2-propyl acrylate (BPTPA), simultaneously possessing enhanced solubility in a low refractive index (n = 1.47) urethane matrix. When examined in comparison to a widely used high refractive index monomer, 2,4,6-tribromophenyl acrylate, BPTPA exhibited superior solubility in a stage 1 urethane matrix of approximately 50% with a 20% higher refractive index increase per unit amount of the writing monomer for stage 2 polymerizations. Formulations with 60 wt % loading of BPTPA exhibit a peak-to-mean holographic Δn ≈ 0.029 without obvious deficiencies in transparency, color, or scatter. To the best of our knowledge, this value is the highest reported in the peer-reviewed literature for a transmission hologram. The capabilities and versatility of BPTPA-based formulations are demonstrated at varying length scales via demonstrative refractive index gradient structure examples including direct laser write, projection mask lithography of a 1″ diameter Fresnel lens, and ∼100% diffraction efficiency volume transmission holograms with a 1 μm fringe spacing in 11 μm thick samples.

Biodegradable Poly(ester urethane)urea Elastomers with Variable Amino Content for Subsequent Functionalization with Phosphorylcholine

PubMed Central

Fang, Jun; Ye, Sang-Ho; Shankarraman, Venkat; Huang, Yixian; Mo, Xiumei; Wagner, William R.

2015-01-01

While surface modification is well suited for imparting biomaterials with specific functionality for favorable cell interactions, the modification of degradable polymers would be expected to provide only temporary benefit. Bulk modification by incorporating pendant reactive groups for subsequent functionalization of biodegradable polymers would provide a more enduring approach. Towards this end, a series of biodegradable poly(ester urethane)urea elastomers with variable amino content (PEUU-NH2 polymers) were developed. Carboxylated phosphorycholine was synthesized and conjugated to the PEUU-NH2 polymers for subsequent bulk functionalization to generate PEUU-PC polymers. Synthesis was verified by 1H NMR, X-ray photoelectron spectroscopy and ATR-FTIR. The impact of amine incorporation and phosphorylcholine conjugation was shown on mechanical, thermal and degradation properties. Water absorption increased with increasing amine content, and further with PC conjugation. In wet conditions, tensile strength and initial modulus generally decreased with increasing hydrophilicity, but remained in the range of 5–30 MPa and 10–20 MPa respectively. PC conjugation was associated with significantly reduced platelet adhesion in blood contact testing and the inhibition of rat vascular smooth muscle cell proliferation. These biodegradable PEUU-PC elastomers offer attractive properties for applications as non-thrombogenic, biodegradable coatings and for blood-contacting scaffold applications. Further, the PEUU-NH2 base polymers offer the potential to have multiple types of biofunctional groups conjugated onto the backbone to address a variety of design objectives. PMID:25132273

Mechanical properties of an experimental soft lining material based on urethane oligomer.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2005-09-01

The purpose of this study was to investigate the apparent viscosities and mechanical properties of two experimental light-curing soft lining materials (SLM-1 and SLM-2) based on soft-type urethane oligomers, as well as the shear bond strength and dye penetration between the denture base resin and the polymerized SLMs after storage in water. The apparent viscosities of SLM-1 and SLM-2 were 144.0-146.9 and 1.9 Pa x s respectively. After storage in water for two prescribed periods (one day and three months), the mechanical properties of the SLMs on the overall were 10.6-20.6 MPa for elastic modulus, 69.3-72.1 for hardness, and 3.8-4.0 MPa for adhesive strength. Tensile strength was observed to decrease after three months' storage in water, when compared to that after one-day storage (p < 0.01). Water sorption rates also differed significantly (p < 0.05)--namely 3.0 and 2.8 mg/cm2 for SLM-1 after one day and three months respectively, and 2.0 and 2.2 mg/cm2 for SLM-2. As for dye penetration, no infiltration was observed at the denture base resin-SLM interface after three months' storage. Based on the results of this study, it seemed like the SLMs possess many suitable properties for use with a new technique that we recently developed for preparing denture base resin and soft lining material.

G-Protein-Coupled Estrogen Receptor Antagonist G15 Decreases Estrogen-Induced Development of Non-Small Cell Lung Cancer.

PubMed

Liu, Changyu; Liao, Yongde; Fan, Sheng; Fu, Xiangning; Xiong, Jing; Zhou, Sheng; Zou, Man; Wang, Jianmiao

2017-08-25

G-protein-coupled estrogen receptor (GPER) was found to promote Non-small cell lung cancer (NSCLC) by estrogen, indicating the potential necessity of inhibiting GPER by selective antagonist. This study was performed to elucidate the function of GPER selective inhibitor G15 in NSCLC development. Cytoplasmic GPER (cGPER) and nuclear GPER (nGPER) were detected by immunohistochemical analysis in NSCLC samples. The relation of GPER and estrogen receptor β (ERβ) expression and correlation between GPER, ERβ and clinical factors were analyzed. The effects of activating GPER and function of G15 were analyzed in proliferation of A549, H1793 cell lines and development of urethane-induced adenocarcinoma. Overexpression of cGPER and nGPER was detected in 80.49% (120/150) and 52.00% (78/150) of the NSCLC samples. High expression of GPER related with higher stages, poorer differentiation and high expression of ERβ. Protein level of GPER in A549 and H1793 cell lines increased by treatment of E2, G1 (GPER agonist) or Ful (fulvestrant, ERβ antagonist), and decreased by G15. Administration with G15 reversed the E2- or G1-induced cell growth by inhibiting GPER. In urethane-induced adenocarcinoma mice, number of tumor nodules and tumor index increased in E2 or G1 group and decreased by treatment of G15. These findings deomonstrate that using of G15 to block GPER signaling may be considered as a new therapeutic target in NSCLC.

Gas-chromatographic resolution of enantiomeric secondary alcohols. Stereoselective reductive metabolism of ketones in rabbit-liver cytosol.

PubMed

Gal, J; DeVito, D; Harper, T W

1981-01-01

Chiral secondary alcohols were treated with (S)-(-)-1-phenylethyl isocyanate. For each racemic alcohol, the resulting diastereomeric urethane derivatives were resolved on flexible fused-silica capillary GLC columns with retention times of 15 min or less. Derivatization of individual enantiomers showed that the urethane derivatives of (R)-(-)-2-octanol, (R)-(+)-1-phenylethyl alcohol, and (S)-(+)-2,2,2-trifluoro-1-phenylethanol are eluted before the corresponding diastereomers. The procedure is simple and rapid, and is suitable for the determination of the enantiomeric composition of chiral alcohols extracted from biological media. A series of aliphatic alcohols, aryl alkyl carbinols, and arylalkyl alkyl carbinols were resolved with the procedure, and the degree of resolution varied from good to excellent. Eight achiral ketones were incubated, individually, with rabbit-liver 90,000 g supernatant fractions, and the enantiomeric composition of the alcohol metabolites was determined with the GLC procedure. The reductions proceeded with high stereoselectivity to give alcohol products of 90% or greater enantiomeric purity. The reduction of 2-octanone and acetophenone gave predominant alcohols of (S)-configuration, in agreement with the Baumann-Prelog rule. The configuration of the predominant alcohols arising in the reduction of the remainder of the ketones could not be firmly established, but the evidence suggests that they are also of the (S)-configuration. Fluorine or methyl substitution in the ortho position of acetophenone produced an increase in the stereoselectivity, and the alcohol produced from ortho-methylacetophenone was enantiomerically greater than 99% pure.

Microinjection of procaine and electrolytic lesion in the ventral tegmental area suppresses hippocampal theta rhythm in urethane-anesthetized rats.

PubMed

Orzeł-Gryglewska, Jolanta; Jurkowlaniec, Edyta; Trojniar, Weronika

2006-01-30

The midbrain ventral tegmental area (VTA), a key structure of the mesocorticolimbic system is anatomically connected with the hippocampal formation. In addition mesocortical dopamine was found to influence hippocampus-related memory and hippocampal synaptic plasticity, both being linked to the theta rhythm. Therefore, the aim of the present study was to evaluate the possible role of the VTA in the regulation of the hippocampal theta activity. The study was performed on urethane-anesthetized male Wistar rats in which theta rhythm was evoked by tail pinch. It was found that unilateral, temporal inactivation of the VTA by means of direct procaine injection resulted in bilateral suppression of the hippocampal theta which manifested as a loss of synchronization of hippocampal EEG and respective reduction of the power and also the frequency of the 3-6 Hz theta band. Depression of the power of the 3-6 Hz component of the EEG signal was also seen in spontaneous hippocampal EEG after procaine. The permanent destruction of the VTA by means of unilateral electrocoagulation evoked a long-lasting, mainly ipsilateral depression of the power of the theta with some influence on its frequency. Simultaneously, there was a substantial increase of the power in higher frequency bands indicating decrease of a synchrony of the hippocampal EEG activity. On the basis of these results indicating impairment of synchronization of the hippocampal activity the VTA may be considered as another part of the brainstem theta synchroning system.

Synthesis and characterisation of coating polyurethane cationomers containing fluorine built-in hard urethane segments

PubMed Central

Król, Bożena; Pikus, Stanisław; Chmielarz, Paweł; Skrzypiec, Krzysztof

2010-01-01

Polyurethane cationomers were synthesised in the reaction of 4,4’-methylenebis(phenyl isocyanate) with polyoxyethylene glycol (M = 2,000) or poly(tetrafluoroethyleneoxide-co-difluoromethylene oxide) α,ω-diisocyanate and N-methyl diethanolamine. Amine segments were built-in to the urethane-isocyanate prepolymer in the reaction with 1-bromobutane or formic acid, and then they were converted to alkylammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium that yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. 1H, 13C NMR and IR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on 1H NMR and IR spectra, the factors κ and α were calculated, which represented the polarity level of the obtained cationomers. The DSC, wide angle X-ray scattering and atom force microscopy methods were employed for the microstructural assessment of the obtained materials. Changes were discussed in the surface free energy and its components, as calculated independently according to the method suggested by van Oss–Good, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Fluorine incorporated into cationomers (about 30%) contributed to lower surface free energy values, down to about 15 mJ/m2. That was caused by gradual weakening of long-range interactions within which the highest share is taken by dispersion interactions. PMID:20927181

Viscoelastic properties of a spinal posterior dynamic stabilisation device.

PubMed

Lawless, Bernard M; Barnes, Spencer C; Espino, Daniel M; Shepherd, Duncan E T

2016-06-01

The purpose of this study was to quantify the frequency dependent viscoelastic properties of two types of spinal posterior dynamic stabilisation devices. In air at 37°C, the viscoelastic properties of six BDyn 1 level, six BDyn 2 level posterior dynamic stabilisation devices (S14 Implants, Pessac, France) and its elastomeric components (polycarbonate urethane and silicone) were measured using Dynamic Mechanical Analysis. The viscoelastic properties were measured over the frequency range 0.01-30Hz. The BDyn devices and its components were viscoelastic throughout the frequency range tested. The mean storage stiffness and mean loss stiffness of the BDyn 1 level device, BDyn 2 level device, silicone component and polycarbonate urethane component all presented a logarithmic relationship with respect to frequency. The storage stiffness of the BDyn 1 level device ranged from 95.56N/mm to 119.29N/mm, while the BDyn 2 level storage stiffness ranged from 39.41N/mm to 42.82N/mm. BDyn 1 level device and BDyn 2 level device loss stiffness ranged from 10.72N/mm to 23.42N/mm and 4.26N/mm to 9.57N/mm, respectively. No resonant frequencies were recorded for the devices or its components. The elastic property of BDyn 1 level device is influenced by the PCU and silicone components, in the physiological frequency range. The viscoelastic properties calculated in this study may be compared to spinal devices and spinal structures. Copyright © 2016 Elsevier Ltd. All rights reserved.

Silver-Teflon coating improvement

NASA Technical Reports Server (NTRS)

Reed, M. W.

1976-01-01

Approximately forty adhesives were subjected to laboratory screening. Seven candidate adhesives were selected from the screening tests and evaluated in a thermal vacuum test on radiator panels similar to the anticipated flight hardware configuration. Several classes of adhesives based on epoxide, polyester, silicone, and urethane resin systems were tested. These included contact adhesives, heat cured adhesives, heat and pressure cured adhesives, pressure sensitive adhesives, and two part paint-on or spray-on adhesives. The panels were tested in a space environmental simulation laboratory chamber during the July 9-20, 1973 time span.

You can't eat moon rocks. [aerospace technology spinoffs assessment

NASA Technical Reports Server (NTRS)

Kubokawa, C. C.

1976-01-01

The effects produced by the aerospace program are investigated. The technology developed from aerospace-related research, development, and manufacturing has been made available to the public for its use through the NASA Technology Utilization Program. A description is presented of 'spinoffs' of NASA's aerospace programs which are used on a daily basis by the public. Attention is given to the liquid cooled garment technology, meal systems for the elderly, the zinc-rich coating, the emergency blanket, the flexible urethane foam Temper Foam, the 'Fog-Away Coating', and composite graphite equipment.

Thermal control structure and garment

DOEpatents

Klett, James W [Knoxville, TN; Cameron, Christopher Stan [Sanford, NC

2012-03-13

A flexible thermally conductive structure. The structure generally includes a plurality of thermally conductive yarns, at least some of which are at least partially disposed adjacent to an elastomeric material. Typically, at least a portion of the plurality of thermally conductive yarns is configured as a sheet. The yarns may be constructed from graphite, metal, or similar materials. The elastomeric material may be formed from urethane or silicone foam that is at least partially collapsed, or from a similar material. A thermal management garment is provided, the garment incorporating a flexible thermally conductive structure.

Experimental suprachoroidal plombage with a urethane based hydrophilic polymer.

PubMed Central

Foulds, W. S.; Aitken, D.; Lee, W. R.

1988-01-01

Small portions of dehydrated hydrophilic polymer (HPU 90, Smith and Nephew) have been inserted into the suprachoroidal space in rabbits to investigate the possible use of suprachoroidal plombage in retinal detachment surgery. As it hydrates, the material causes a pronounced elevation of choroid and retina, and the implants have been well tolerated for periods of up to one year in experimental animals. The implant slowly breaks down and stimulates a simple macrophagic reaction: fibrosis in the overlying choroid is associated with ischaemic gliosis and chorioretinal fusion. Images PMID:3378024

Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

PubMed Central

Buruiana, Tinca; Melinte, Violeta; Buruiana, Emil C

2017-01-01

Polymer nanocomposites containing titanium oxide nanoparticles (TiO2 NPs) combined with other inorganic components (Si–O–Si or/and γ-Fe2O3) were prepared by the dispersion of premade NPs (nanocrystalline TiO2, TiO2/SiO2, TiO2/Fe2O3, TiO2/SiO2/Fe2O3) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1–S4) was realized through XRD, TEM and FTIR analyses. The mean size (10–30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO2/Fe2O3 or TiO2/SiO2/Fe2O3 NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV–visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts. PMID:28243566

Incorporation of amoxicillin-loaded organic montmorillonite into poly(ester-urethane) urea nanofibers as a functional tissue engineering scaffold.

PubMed

Yu, Kui; Zhu, Tonghe; Wu, Yu; Zhou, Xiangxiang; Yang, Xingxing; Wang, Juan; Fang, Jun; El-Hamshary, Hany; Al-Deyab, Salem S; Mo, Xiumei

2017-03-01

A dual drug-loaded system is a promising alternative for the sustained drug release system and skin tissue engineering. In this study, a natural sodium montmorillonite (Na-MMT) modified by cetyl trimethyl ammonium bromide (CTAB) was prepared as a carrier to load a model drug - amoxicillin (AMX), the modified organic montmorillonite (CTAB-OMMT) loaded with AMX was marked as AMX@CTAB-OMMT and was subsequently incorporated into poly(ester-urethane) urea (PEUU) and gelatin hybrid nanofibers via electrospinning, resulting in a new drug-loaded nanofibrous scaffold (AMX@CTAB-OMMT-PU75). The scanning electron microscopy (SEM) result showed that the fiber morphology did not change after the embedding of AMX@CTAB-OMMT. Meanwhile, there was a significant increase of mechanical properties for PEUU/Gelatin hybrid nanofibers (PU75) after the incorporation of AMX@CTAB-OMMT and CTAB-OMMT. Importantly, AMX@CTAB-OMMT-PU75 nanofibers showed a kind of sustained drug release property which could be justified reasonably for the controlled release of AMX depending on the various application. The sustained release property could be identified roughly by the result of antibacterial test. The anaphylactic reaction test proved that there was no any anaphylactic reaction or inflammation on the back of rat for AMX@CTAB-OMMT-PU75 nanofibers. Consequently, the prepared drug-loaded AMX@CTAB-OMMT-PU75 nanofibrous scaffold is a promising candidate for application in the skin tissue engineering field and controlled drug release system. Copyright © 2016 Elsevier B.V. All rights reserved.

Spatial integration in mouse primary visual cortex.

PubMed

Vaiceliunaite, Agne; Erisken, Sinem; Franzen, Florian; Katzner, Steffen; Busse, Laura

2013-08-01

Responses of many neurons in primary visual cortex (V1) are suppressed by stimuli exceeding the classical receptive field (RF), an important property that might underlie the computation of visual saliency. Traditionally, it has proven difficult to disentangle the underlying neural circuits, including feedforward, horizontal intracortical, and feedback connectivity. Since circuit-level analysis is particularly feasible in the mouse, we asked whether neural signatures of spatial integration in mouse V1 are similar to those of higher-order mammals and investigated the role of parvalbumin-expressing (PV+) inhibitory interneurons. Analogous to what is known from primates and carnivores, we demonstrate that, in awake mice, surround suppression is present in the majority of V1 neurons and is strongest in superficial cortical layers. Anesthesia with isoflurane-urethane, however, profoundly affects spatial integration: it reduces the laminar dependency, decreases overall suppression strength, and alters the temporal dynamics of responses. We show that these effects of brain state can be parsimoniously explained by assuming that anesthesia affects contrast normalization. Hence, the full impact of suppressive influences in mouse V1 cannot be studied under anesthesia with isoflurane-urethane. To assess the neural circuits of spatial integration, we targeted PV+ interneurons using optogenetics. Optogenetic depolarization of PV+ interneurons was associated with increased RF size and decreased suppression in the recorded population, similar to effects of lowering stimulus contrast, suggesting that PV+ interneurons contribute to spatial integration by affecting overall stimulus drive. We conclude that the mouse is a promising model for circuit-level mechanisms of spatial integration, which relies on the combined activity of different types of inhibitory interneurons.

Delayed photo-activation and addition of thio-urethane: Impact on polymerization kinetics and stress of dual-cured resin cements.

PubMed

Faria-E-Silva, André L; Pfeifer, Carmem S

2017-10-01

1) to determine the moment during the redox polymerization reaction of dual cure cements at which to photo-activate the material in order to reduce the polymerization stress, and 2) to evaluate possible synergistic effects between adding chain transfer agents and delayed photo-activation. The two pastes of an experimental dual-cure material were mixed, and the polymerization kinetics of the redox phase was followed. The moment when the material reached its maximum rate of redox polymerization (MRRP) of cement was determined. The degree of conversion (DC) and maximum rates of polymerization (Rp max ) were assessed for materials where: the photoactivation immediately followed material mixing, at MRRP, 1min before and 1min after MRRP. Thio-urethane (TU) additives were synthesized and added to the cement (20% wt), which was then cured under the same conditions. The polymerization kinetics was evaluated for both cements photo-activated immediately or at MRRP, followed by measurements of polymerization stress, flexural strength (FS) and elastic modulus (EM). Knoop hardness was measured before and after ethanol storage. Photo-activating the cement at or after MRRP reduced the Rp max and the polymerization stress. Addition of TU promoted additional and more significant reduction, while not affecting the Rp max . Greater hardness loss was observed for cements with TU, but the final hardness was similar for all experimental conditions. Addition of TU slightly reduced the EM and did not affect the FS. Delayed photo-activation and addition of TU significantly reduce the polymerization stress of dual-cured cements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Enduring critical period plasticity visualized by transcranial flavoprotein imaging in mouse primary visual cortex.

PubMed

Tohmi, Manavu; Kitaura, Hiroki; Komagata, Seiji; Kudoh, Masaharu; Shibuki, Katsuei

2006-11-08

Experience-dependent plasticity in the visual cortex was investigated using transcranial flavoprotein fluorescence imaging in mice anesthetized with urethane. On- and off-responses in the primary visual cortex were elicited by visual stimuli. Fluorescence responses and field potentials elicited by grating patterns decreased similarly as contrasts of visual stimuli were reduced. Fluorescence responses also decreased as spatial frequency of grating stimuli increased. Compared with intrinsic signal imaging in the same mice, fluorescence imaging showed faster responses with approximately 10 times larger signal changes. Retinotopic maps in the primary visual cortex and area LM were constructed using fluorescence imaging. After monocular deprivation (MD) of 4 d starting from postnatal day 28 (P28), deprived eye responses were suppressed compared with nondeprived eye responses in the binocular zone but not in the monocular zone. Imaging faithfully recapitulated a critical period for plasticity with maximal effects of MD observed around P28 and not in adulthood even under urethane anesthesia. Visual responses were compared before and after MD in the same mice, in which the skull was covered with clear acrylic dental resin. Deprived eye responses decreased after MD, whereas nondeprived eye responses increased. Effects of MD during a critical period were tested 2 weeks after reopening of the deprived eye. Significant ocular dominance plasticity was observed in responses elicited by moving grating patterns, but no long-lasting effect was found in visual responses elicited by light-emitting diode light stimuli. The present results indicate that transcranial flavoprotein fluorescence imaging is a powerful tool for investigating experience-dependent plasticity in the mouse visual cortex.

How do neurons work together? Lessons from auditory cortex.

PubMed

Harris, Kenneth D; Bartho, Peter; Chadderton, Paul; Curto, Carina; de la Rocha, Jaime; Hollender, Liad; Itskov, Vladimir; Luczak, Artur; Marguet, Stephan L; Renart, Alfonso; Sakata, Shuzo

2011-01-01

Recordings of single neurons have yielded great insights into the way acoustic stimuli are represented in auditory cortex. However, any one neuron functions as part of a population whose combined activity underlies cortical information processing. Here we review some results obtained by recording simultaneously from auditory cortical populations and individual morphologically identified neurons, in urethane-anesthetized and unanesthetized passively listening rats. Auditory cortical populations produced structured activity patterns both in response to acoustic stimuli, and spontaneously without sensory input. Population spike time patterns were broadly conserved across multiple sensory stimuli and spontaneous events, exhibiting a generally conserved sequential organization lasting approximately 100 ms. Both spontaneous and evoked events exhibited sparse, spatially localized activity in layer 2/3 pyramidal cells, and densely distributed activity in larger layer 5 pyramidal cells and putative interneurons. Laminar propagation differed however, with spontaneous activity spreading upward from deep layers and slowly across columns, but sensory responses initiating in presumptive thalamorecipient layers, spreading rapidly across columns. In both unanesthetized and urethanized rats, global activity fluctuated between "desynchronized" state characterized by low amplitude, high-frequency local field potentials and a "synchronized" state of larger, lower-frequency waves. Computational studies suggested that responses could be predicted by a simple dynamical system model fitted to the spontaneous activity immediately preceding stimulus presentation. Fitting this model to the data yielded a nonlinear self-exciting system model in synchronized states and an approximately linear system in desynchronized states. We comment on the significance of these results for auditory cortical processing of acoustic and non-acoustic information. © 2010 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Microencapsulated Phase Change Materials with Poly(urea-urethane) Shells Containing Cellulose Nanocrystals.

PubMed

Yoo, Youngman; Martinez, Carlos; Youngblood, Jeffrey P

2017-09-20

The main objective of this study is to develop microencapsulation technology for thermal energy storage incorporating a phase change material (PCM) in a composite wall shell, which can be used to create a stable environment and allow the PCM to undergo phase change without any outside influence. Surface modification of cellulose nanocrystals (CNCs) was conducted by grafting poly(lactic acid) oligomers and oleic acid to improve the dispersion of nanoparticles in a polymeric shell. A microencapsulated phase change material (methyl laurate) with poly(urea-urethane) (PU) composite shells containing the hydrophobized cellulose nanocrystals (hCNCs) was fabricated using an in situ emulsion interfacial polymerization process. The encapsulation process of the PCMs with subsequent interfacial hCNC-PU to form composite microcapsules as well as their morphology, composition, thermal properties, and release rates was examined in this study. Oil soluble Sudan II dye solution in methyl laurate was used as a model hydrophobic fill, representing other latent fills with low partition coefficients, and their encapsulation efficiency as well as dye release rates were measured spectroscopically in a water medium. The influence of polyol content in the PU polymer matrix of microcapsules was investigated. An increase in polyol contents leads to an increase in the mean size of microcapsules but a decrease in the gel content (degree of cross-linking density) and permeability of their shell structure. The encapsulated PCMs for thermal energy storage demonstrated here exhibited promising performance for possible use in building or paving materials in terms of released heat, desired phase transformation temperature, chemical and physical stability, and concrete durability during placement.

Evaluation of HFC 245ca and HFC 236ea as foam blowing agents

NASA Technical Reports Server (NTRS)

Sharpe, Jon; Macarthur, Doug; Kollie, Tom; Graves, Ron; Liu, Matthew; Hendriks, Robert V.

1995-01-01

Hydrochlorofluorocarbon (HCFC) 141b has been selected as the interim blowing agent for use in urethane insulations on NASA's Space Shuttle External Tank. Due to the expected limited commercial lifetime of this material, research efforts at the NASA Thermal Protection Systems Materials Research Laboratory at the Marshall Space Flight Center are now being devoted to the identification and development of alternatives with zero ozone depletion potential. Physical blowing agents identified to date have included hydrocarbons, fluorocarbons, hydrofluoroethers, and more predominantly, hydrofluorocarbons (HFCs). The majority of the HFC evaluations in industry have focused on the more readily available, low boiling candidates such as HFC 134a. Higher boiling HFC candidates that could be handled at ambient conditions and use current processing equipment would be more desirable. This paper will describe results from a research program of two such candidate HFC's performed as a cooperative effort between Martin Marietta Manned Space Systems, the U.S. Environmental Protection Agency, and Oak Ridge National Laboratories. The purpose of this effort was to perform a cursory evaluation of the developmental HFC's 245ca and 236ea as blowing agents in urethane based insulations. These two materials were selected from screening tests of 37 C2, C3, and C4 isomers based on physical properties, atmospheric lifetime, flammability, estimated toxicity, difficulty of synthesis, suitability for dual use as a refrigerant, and other factors. Solubility of the two materials in typical foam components was tested, pour foaming trials were performed, and preliminary data were gathered regarding foam insulation performance.

Effects of sterilization treatments on bulk and surface properties of nanocomposite biomaterials

PubMed Central

Ahmed, Maqsood; Punshon, Geoffrey; Darbyshire, Arnold; Seifalian, Alexander M

2013-01-01

With the continuous and expanding use of implantable biomaterials in a clinical setting, this study aims to elucidate the influence of sterilization techniques on the material surface and bulk properties of two polyurethane nanocomposite biomaterials. Both solid samples and porous membranes of nondegradable polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) and a biodegradable poly(caprolactone-urea) urethane (POSS-PCL) were examined. Sterilization techniques included conventional steam sterilization (autoclaving), gamma irradiation, and disinfection via incubating with ethanol (EtOH) for 10 min or 24 h. After treatment, the samples were examined using gel permeation chromatography (GPC), attenuated total reflectance Fourier transform infrared spectroscopy, and tensiometry. Cytotoxicity was evaluated through the culture of endothelial progenitor cells and the efficacy of sterilization method was determined by incubating each sample in tryptone soya broth and fluid thioglycollate medium for cultivation of microorganisms. Although EtOH did not affect the material properties in any form, the samples were found to be nonsterile with microbial growth detected on each of the samples. Gamma irradiation was not only effective in sterilizing both POSS-PCU and POSS-PCL but also led to minor material degradation and displayed a cytotoxic effect on the cultured cells. Autoclaving was found to be the optimal sterilization technique for both solid and porous membranes of the nondegradable POSS-PCU samples as it was successful in sterilizing the samples, displayed no cytotoxic side effects and did not degrade the material. However, the biodegradable POSS-PCL was not able to withstand the harsh environment during autoclaving, resulting in it losing all structural integrity. PMID:24039066

Gingerol Reverses the Cancer-Promoting Effect of Capsaicin by Increased TRPV1 Level in a Urethane-Induced Lung Carcinogenic Model.

PubMed

Geng, Shengnan; Zheng, Yaqiu; Meng, Mingjing; Guo, Zhenzhen; Cao, Ning; Ma, Xiaofang; Du, Zhenhua; Li, Jiahuan; Duan, Yongjian; Du, Gangjun

2016-08-10

Both gingerol and capsaicin are agonists of TRPV1, which can negatively control tumor progression. This study observed the long-term effects of oral administration of 6-gingerol alone or in combination with capsaicin for 20 weeks in a urethane-induced lung carcinogenic model. We showed that lung carcinoma incidence and multiplicity were 70% and 21.2 ± 3.6, respectively, in the control versus 100% and 35.6 ± 5.2 in the capsaicin group (P < 0.01) and 50% and 10.8 ± 3.1 in the 6-gingerol group (P < 0.01). The combination of 6-gingerol and capsaicin reversed the cancer-promoting effect of capsaicin (carcinoma incidence of 100% versus 20% and multiplicity of 35.6 ± 5.2 versus 4.7 ± 2.3; P < 0.001). The cancer-promoting effect of capsaicin was due to increased epidermal growth-factor receptor (EGFR) level by decreased transient receptor potential vanilloid type-1 (TRPV1) level (P < 0.01) . The capsaicin-decreased EGFR level subsequently reduced levels of nuclear factor-κB (NF-κB) and cyclin D1 that favored enhanced lung epithelial proliferation and epithelial-mesenchymal transition (EMT) during lung carcinogenesis (P < 0.01). In contrast, 6-gingerol promoted TRPV1 level and drastically decreased the levels of EGFR, NF-κB, and cyclin D1 that favored reduced lung epithelial proliferation and EMT (P < 0.01). This study provides valuable information for the long-term consumption of chili-pepper-rich diets to decrease the risk of cancer development.

Shipping container for fissile material

DOEpatents

Crowder, H.E.

1984-12-17

The present invention is directed to a shipping container for the interstate transportation of enriched uranium materials. The shipping container is comprised of a rigid, high-strength, cylindrical-shaped outer vessel lined with thermal insulation. Disposed inside the thermal insulation and spaced apart from the inner walls of the outer vessel is a rigid, high-strength, cylindrical inner vessel impervious to liquid and gaseous substances and having the inner surfaces coated with a layer of cadmium to prevent nuclear criticality. The cadmium is, in turn, lined with a protective shield of high-density urethane for corrosion and wear protection. 2 figs.

Lightweight Towed Howitzer Demonstrator. Phase 1 and Partial Phase 2. Volume B. Technical Presentations - Part 1.

DTIC Science & Technology

1987-04-01

tray hsg assy 1 85 5 62360 . ..Frame 1 TRAD Ti 70 0.16 281 45 6 G2370 . ..Wrap 1 Kevlar/epoxy 70 0.05 700 35 6 62380 . ..Coating 1 Urethane 70 0.05...CL -4L- I-J .4cm=CLC ~LU LAJL~ I.-- LL== L6 0 - -JA z ~ LA =c = La z 4c > =w ZwI . z C/)-- oc W LA. 0z C 0 CI. CC Z u z LJ -6 C-.- -4 mAC. L6 w z 4c0

Strong composition dependence of adhesive properties of ultraviolet curing adhesives with modified acrylates

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Li, Yandong; Wang, Fupeng; Peng, Cheng; Xu, Zhichao; Hu, Jianbing

2018-05-01

Ultraviolet (UV) curable adhesives have been widely researched in fields of health care and electronic components. UV curing systems with modified acrylic ester prepolymers have been frequently employed. In order to clarify composition dependence of adhesive properties of adhesives containing modified acrylates, in this work, several UV curing adhesives bearing urethane and epoxy acrylates were designed and fabricated. The effects of prepolymer, diluent, feed ratio, initiator and assistant on adhesive performances were investigated. This work might offer a facile route to gain promising high-performance UV curable adhesives with desired adhesive traits through regulating their compositions.

Synthesis of collagenase-sensitive polyureas for ligament tissue engineering.

PubMed

Benhardt, Hugh; Sears, Nick; Touchet, Tyler; Cosgriff-Hernandez, Elizabeth

2011-08-11

Recently, poly(ester urethanes) were investigated for use as ligament grafts due to their exceptional mechanical properties and highly tunable structure; however, these grafts are susceptible to hydrolytic degradation that occurs independent of tissue regeneration. To address this limitation, polyureas containing collagen-derived peptides were synthesized which enable cellular release of proteases to dictate degradation rate. It is hypothesized that this cell-responsive design will facilitate load transfer from the biodegradable scaffold to neotissue at a rate that promotes proper tissue orientation and function while maintaining construct integrity. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermally stable surfactants and compositions and methods of use thereof

DOEpatents

Chaiko, David J [Woodridge, IL

2008-09-02

There are provided novel thermally stable surfactants for use with fillers in the preparation of polymer composites and nanocomposites. Typically, surfactants of the invention are urethanes, ureas or esters of thiocarbamic acid having a hydrocarbyl group of from 10 to 50 carbons and optionally including an ionizable or charged group (e.g., carboxyl group or quaternary amine). Thus, there are provided surfactants having Formula I: ##STR00001## wherein the variables are as defined herein. Further provided are methods of making thermally stable surfactants and compositions, including composites and nanocomposites, using fillers coated with the surfactants.

Effects of sterilization treatments on bulk and surface properties of nanocomposite biomaterials.

PubMed

Ahmed, Maqsood; Punshon, Geoffrey; Darbyshire, Arnold; Seifalian, Alexander M

2013-10-01

With the continuous and expanding use of implantable biomaterials in a clinical setting, this study aims to elucidate the influence of sterilization techniques on the material surface and bulk properties of two polyurethane nanocomposite biomaterials. Both solid samples and porous membranes of nondegradable polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) and a biodegradable poly(caprolactone-urea) urethane (POSS-PCL) were examined. Sterilization techniques included conventional steam sterilization (autoclaving), gamma irradiation, and disinfection via incubating with ethanol (EtOH) for 10 min or 24 h. After treatment, the samples were examined using gel permeation chromatography (GPC), attenuated total reflectance Fourier transform infrared spectroscopy, and tensiometry. Cytotoxicity was evaluated through the culture of endothelial progenitor cells and the efficacy of sterilization method was determined by incubating each sample in tryptone soya broth and fluid thioglycollate medium for cultivation of microorganisms. Although EtOH did not affect the material properties in any form, the samples were found to be nonsterile with microbial growth detected on each of the samples. Gamma irradiation was not only effective in sterilizing both POSS-PCU and POSS-PCL but also led to minor material degradation and displayed a cytotoxic effect on the cultured cells. Autoclaving was found to be the optimal sterilization technique for both solid and porous membranes of the nondegradable POSS-PCU samples as it was successful in sterilizing the samples, displayed no cytotoxic side effects and did not degrade the material. However, the biodegradable POSS-PCL was not able to withstand the harsh environment during autoclaving, resulting in it losing all structural integrity. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

Urodynamic function during sleep-like brain states in urethane anesthetized rats.

PubMed

Crook, J; Lovick, T

2016-01-28

The aim was to investigate urodynamic parameters and functional excitability of the periaqueductal gray matter (PAG) during changes in sleep-like brain states in urethane anesthetized rats. Simultaneous recordings of detrusor pressure, external urethral sphincter (EUS) electromyogram (EMG), cortical electroencephalogram (EEG), and single-unit activity in the PAG were made during repeated voiding induced by continuous infusion of saline into the bladder. The EEG cycled between synchronized, high-amplitude slow wave activity (SWA) and desynchronized low-amplitude fast activity similar to slow wave and 'activated' sleep-like brain states. During (SWA, 0.5-1.5 Hz synchronized oscillation of the EEG waveform) voiding became more irregular than in the 'activated' brain state (2-5 Hz low-amplitude desynchronized EEG waveform) and detrusor void pressure threshold, void volume threshold and the duration of bursting activity in the external urethral sphincter EMG were raised. The spontaneous firing rate of 23/52 neurons recorded within the caudal PAG and adjacent tegmentum was linked to the EEG state, with the majority of responsive cells (92%) firing more slowly during SWA. Almost a quarter of the cells recorded (12/52) showed phasic changes in firing rate that were linked to the occurrence of voids. Inhibition (n=6), excitation (n=4) or excitation/inhibition (n=2) was seen. The spontaneous firing rate of 83% of the micturition-responsive cells was sensitive to changes in EEG state. In nine of the 12 responsive cells (75%) the responses were reduced during SWA. We propose that during different sleep-like brain states changes in urodynamic properties occur which may be linked to changing excitability of the micturition circuitry in the periaqueductal gray. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Synthesis, characterization, shrinkage and curing kinetics of a new low-shrinkage urethane dimethacrylate monomer for dental applications.

PubMed

Atai, Mohammad; Ahmadi, Mehdi; Babanzadeh, Samal; Watts, David C

2007-08-01

The aim of the study was to synthesize and characterize an isophorone-based urethane dimethacrylate (IP-UDMA) resin-monomer and to investigate its shrinkage and curing kinetics. The IP-UDMA monomer was synthesized through the reaction of polyethylene glycol 400 and isophorone diisocyanate followed by reacting with HEMA to terminate it with methacrylate end groups. The reaction was followed using a standard back titration method and FTIR spectroscopy. The final product was purified and characterized using FTIR, (1)H NMR, elemental analysis and refractive index measurement. The shrinkage-strain of the specimens photopolymerized at circa 700mW/cm(2) was measured using the bonded-disk technique at 23, 35, and 45 degrees C. Initial shrinkage-strain-rates were obtained by numerical differentiation of shrinkage-strain data with respect to time. Degree-of-conversion of the specimens was measured using FTIR spectroscopy. The thermal curing kinetics of the monomer were also studied by differential scanning calorimetry (DSC). The characterization methods confirmed the suggested reaction route and the synthesized monomer. A low shrinkage-strain of about 4% was obtained for the new monomer. The results showed that the shrinkage-strain-rate of the monomer followed the autocatalytic model of Kamal and Sourour [Kamal MR, Sourour S. Kinetic and thermal characterization of thermoset cure. Polym Eng Sci 1973;13(1):59-64], which is used to describe the reaction kinetics of thermoset resins. The model parameters were calculated by linearization of the equation. The model prediction was in a good agreement with the experimental data. The properties of the new monomer compare favorably with properties of the commercially available resins.

Effects of cathodal trans-spinal direct current stimulation on lower urinary tract function in normal and spinal cord injury mice with overactive bladder

NASA Astrophysics Data System (ADS)

Ahmed, Zaghloul

2017-10-01

Objective. Lower urinary tract (LUT) dysfunction is a monumental problem affecting quality of life following neurotrauma, such as spinal cord injury (SCI). Proper function of the bladder and its associated structures depends on coordinated activity of the neuronal circuitry in the spinal cord and brain. Disconnection between the spinal and brain centers controlling the LUT causes fundamental changes in the mechanisms involved in the micturition and storage reflexes. We investigated the effects of cathodal trans-spinal direct current stimulation (c-tsDCS) of the lumbosacral spine on bladder and external urinary sphincter (EUS) functions. Approach. We used cystometry and electromyography (EMG), in mice with and without SCI. Main results. c-tsDCS caused initiation of the micturition reflex in urethane-anesthetized normal mice with depressed micturition reflexes. This effect was associated with normalized EUS-EMG activity. Moreover, in urethane-anesthetized normal mice with expressed micturition reflexes, c-tsDCS increased the firing frequency, amplitude, and duration of EUS-EMG activity. These effects were associated with increased maximum intravesical pressure (P max) and intercontraction interval (ICI). In conscious normal animals, c-tsDCS caused significant increases in P max, ICI, threshold pressure (P thres), baseline pressure (P base), and number and amplitude of non-voiding contractions (NVCnumb and P im, respectively). In conscious mice with severe contusive SCI and overactive bladder, c-tsDCS increased P max, ICI, and P thres, but decreased P base, NVCnumb, and P im. c-tsDCS reduced the detrusor-overactivity/cystometry ratio, which is a measure of bladder overactivity associated with renal deterioration. Significance. These results indicate that c-tsDCS induces robust modulation of the lumbosacral spinal-cord circuitry that controls the LUT.

The effect of pharmacological inactivation of the mammillary body and anterior thalamic nuclei on hippocampal theta rhythm in urethane-anesthetized rats.

PubMed

Żakowski, Witold; Zawistowski, Piotr; Braszka, Łukasz; Jurkowlaniec, Edyta

2017-10-24

The mammillary body (MB) and the anterior thalamic nuclei (ATN) are closely related structures, which take part in learning and memory processes. However, the exact role of these structures has remained unclear. In both structures neurons firing according to hippocampal theta rhythm have been found, mainly in the medial mammillary nucleus (MM) and anteroventral thalamic nucleus (AV). These neurons are driven by descending projections from the hippocampal formation and are thought to convey theta rhythm back to the hippocampus (HP). We argue that the MB-ATN axis not only relays theta signal, but may also modulate it. To examine it, we performed a pharmacological inactivation of the MM and AV by local infusion of procaine, and measured changes in theta activity in selected structures of the extended hippocampal system in urethane-anesthetized rats. The inactivation of the MM resulted in decrease in EEG power in the HP and AV, the most evidently in the lower theta frequency bands, i.e. 3-5Hz in the HP (down to 9.2% in 3- to 4-Hz band and 37.6% in 4- to 5-Hz band, in comparison to the power in the control conditions) and 3-4Hz in the AV (down to 24.9%). After the AV inactivation, hippocampal EEG power decreased in theta frequency bands of 3-8Hz (down to 61.6% in 6- to 7-Hz band and 69.4% in 7- to 8-Hz band). Our results suggest that the role of the MB-ATN axis in regulating theta rhythm signaling may be much more important than has been speculated so far. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Comparison of clinical explants and accelerated hydrolytic aging to improve biostability assessment of silicone-based polyurethanes.

PubMed

Cosgriff-Hernandez, Elizabeth; Tkatchouk, Ekaterina; Touchet, Tyler; Sears, Nick; Kishan, Alysha; Jenney, Christopher; Padsalgikar, Ajay D; Chen, Emily

2016-07-01

Although silicone-based polyurethanes have demonstrated increased oxidative stability, there have been conflicting reports of the long-term hydrolytic stability of Optim™ and PurSil(®) 35 based on recent temperature-accelerated hydrolysis studies. The goal of the current study was to identify in vitro-in vivo correlations to determine the relevance of this accelerated in vitro model for predicting clinical outcomes. Temperature-accelerated hydrolytic aging of three commonly used cardiac lead insulation materials, Optim™, Elasthane™ 55D, Elasthane™ 80A, and a related silicone-polyurethane, PurSil(®) 35, was performed. After 1 year at 85°C, similar losses in Mn and Mz were observed for the poly(ether urethanes), but an increase in Mz loss as compared to Mn loss was observed for the silicone-based polyurethanes. A similar trend of increased Mz loss as compared to Mn loss was observed in explanted Optim™ leads after 2-3 years; however, no statistically significant Mn loss was detected between 2-3 and 7-8 years of implantation. Given this preferential loss of high molecular weight chains, it was hypothesized that the observed differences between the polyurethanes were due to allophanate dissociation rather than backbone chain scission. Following full dissociation of the small percentage of allophanates in vivo, the observed molecular weight stability and proven clinical performance of Optim™ was attributed to the well-documented stability of the urethane bond under physiological conditions. This allophanate dissociation reaction is incompatible with the first order mechanism proposed in previous temperature-accelerated hydrolysis studies and may be the reason for the model's inaccurate prediction of significant and progressive molecular weight loss in vivo. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1805-1816, 2016. © 2016 Wiley Periodicals, Inc.

Poly(propylene glycol) and urethane dimethacrylates improve conversion of dental composites and reveal complexity of cytocompatibility testing.

PubMed

Walters, Nick J; Xia, Wendy; Salih, Vehid; Ashley, Paul F; Young, Anne M

2016-02-01

To determine the effects of various monomers on conversion and cytocompatibility of dental composites and to improve these properties without detrimentally affecting mechanical properties, depth of cure and shrinkage. Composites containing urethane dimethacrylate (UDMA) or bisphenol A glycidyl methacrylate (Bis-GMA) with poly(propylene glycol) dimethacrylate (PPGDMA) or triethylene glycol dimethacrylate (TEGDMA) were characterized using the following techniques: conversion (FTIR at 1 and 4mm depths), depth of cure (BS EN ISO 4049:2009 and FTIR), shrinkage (BS EN ISO 17304:2013 and FTIR), strength and modulus (biaxial flexural test) and water sorption. Cytocompatibility of composites and their liquid phase components was assessed using three assays (resazurin, WST-8 and MTS). UDMA significantly improved conversion, BFS and depth of cure compared to Bis-GMA, without increasing shrinkage. UDMA was cytotoxic at lower concentrations than Bis-GMA, but extracts of Bis-GMA-containing composites were less cytocompatible than of those containing UDMA. PPGDMA improved conversion and depth of cure compared to TEGDMA, without detrimentally affecting shrinkage. TEGDMA was shown by all assays to be highly toxic. Resazurin, but not WST-8 and MTS, suggested that PPGDMA exhibited improved cytocompatibility compared to TEGDMA. The use of UDMA and PPGDMA results in composites with excellent conversion, depth of cure and mechanical properties, without increasing shrinkage. Composites containing UDMA appear to be slightly more cytocompatible than those containing Bis-GMA. These monomers may therefore improve the material properties of dental restorations, particularly bulk fill materials. The effect of diluent monomer on cytocompatibility requires further investigation. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Optimal endothelialisation of a new compliant poly(carbonate-urea)urethane vascular graft with effect of physiological shear stress.

PubMed

Salacinski, H J; Tai, N R; Punshon, G; Giudiceandrea, A; Hamilton, G; Seifalian, A M

2000-10-01

to define the optimal seeding conditions of a new stress free poly(carbonate-urea)urethane (CPU) graft with compliance similar to that of human artery with honeycomb structure engineered during the manufacturing process to enhance adhesion and growth of endothelial cells. (111)Indium-oxine radiolabeled human umbilical vein endothelial cells (HUVEC) were seeded onto CPU grafts at (a) concentrations from 2-24x10(5)cells/cm(2)and (b) incubated for 0.5, 1, 2, 4 and 6 h. Following incubation, graft segments were subjected to three washing/gamma counting procedures and scanning electron microscopy (SEM). Cell viability was measured using a modified Alamar blue(TM)assay. To test physiological retention a pulsatile flow phantom was used to subject optimally seeded (16x10(5), 4 h) CPU grafts to arterial shear stress for 6 h with real time acquisition of scintigraphic images of seeded grafts using a nuclear medicine gamma camera system. the seeding efficiency of 54+/-13% post three washes was achieved using 16x10(5)cells/cm(2). Similarly in SEM micrographs a seeding density of 16x10(5)cells/cm(2)resulted in a confluent monolayer. Seeded CPU segments incubated for 4 h exhibited significantly higher resistance to wash-off than segments incubated for 30 min (p <0.05). Exposure of seeded grafts to pulsatile shear stress resulted in some cell loss with 67+/-3% of cells adherent following 6 h of perfusion with ongoing metabolic activity. Thus, optimal conditions were 16x10(5)cells/cm(2)at 4 h. the optimal seeding conditions have been defined for "tissue-engineered" vascular graft which allow complete endothelialisation and high cell-to-substrate strength that resists hydrodynamic stress. Copyright 2000 Harcourt Publishers Ltd.

Misfit and microleakage of implant-supported crown copings obtained by laser sintering and casting techniques, luted with glass-ionomer, resin cements and acrylic/urethane-based agents.

PubMed

Castillo-Oyagüe, Raquel; Lynch, Christopher D; Turrión, Andrés S; López-Lozano, José F; Torres-Lagares, Daniel; Suárez-García, María-Jesús

2013-01-01

This study evaluated the marginal misfit and microleakage of cement-retained implant-supported crown copings. Single crown structures were constructed with: (1) laser-sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC) and (3) vacuum-cast Ni-Cr-Ti (CN). Samples of each alloy group were randomly luted in standard fashion onto machined titanium abutments using: (1) GC Fuji PLUS (FP); (2) Clearfil Esthetic Cement (CEC); (3) RelyX Unicem 2 Automix (RXU) and (4) DentoTemp (DT) (n=15 each). After 60 days of water ageing, vertical discrepancy was SEM-measured and cement microleakage was scored using a digital microscope. Misfit data were subjected to two-way ANOVA and Student-Newman-Keuls multiple comparisons tests. Kruskal-Wallis and Dunn's tests were run for microleakage analysis (α=0.05). Regardless of the cement type, LS samples exhibited the best fit, whilst CC and CN performed equally well. Despite the framework alloy and manufacturing technique, FP and DT provide comparably better fit and greater microleakage scores than did CEC and RXU, which showed no differences. DMLS of Co-Cr may be a reliable alternative to the casting of base metal alloys to obtain well-fitted implant-supported crowns, although all the groups tested were within the clinically acceptable range of vertical discrepancy. No strong correlations were found between misfit and microleakage. Notwithstanding the framework alloy, definitive resin-modified glass-ionomer (FP) and temporary acrylic/urethane-based (DT) cements demonstrated comparably better marginal fit and greater microleakage scores than did 10-methacryloxydecyl-dihydrogen phosphate-based (CEC) and self-adhesive (RXU) dual-cure resin agents. Copyright © 2012 Elsevier Ltd. All rights reserved.

Inhibitory effects of retigabine, a Kv7 channel activator, on mechanosensitive primary bladder afferent activities and nociceptive behaviors in rats.

PubMed

Aizawa, Naoki; Wakamatsu, Daisuke; Kida, Jun; Otsuki, Takeya; Saito, Yasuho; Matsuya, Hidekazu; Homma, Yukio; Igawa, Yasuhiko

2017-02-01

Kv7 voltage-gated potassium channels have been suggested to modulate mechano-afferent transduction and nociception in the bladder. We investigated the effects of retigabine, a Kv7 channel activator, on rhythmic bladder contractions (RBCs), and single-unit afferent activities (SAAs) of the primary bladder mechanosensitive afferent nerve fibers in urethane-anesthetized rats. In addition, the effects of pretreatment with retigabine on the nociceptive behaviors provoked by an intravesical instillation of resiniferatoxin (RTX) were evaluated in the conscious condition. Female Sprague-Dawley rats were used. Under urethane anesthesia, saline was instilled into the bladder until RBCs were induced reproducibly. Then, the effects of intravenous, cumulative administrations of retigabine (0.1-3 mg/kg) or vehicle (saline) on RBCs were assessed. In separate animals, SAAs of Aδ- and C-fibers were identified by electrical stimulation of the pelvic nerve and by bladder distention with saline. After baseline recording, vehicle or retigabine (0.01-1 mg/kg) was administered intravenously and further recordings were performed. Under pretreatment with vehicle or retigabine (3 mg/kg intraperitoneally), the frequencies of lower abdominal licking and freezing were counted and scored as the bladder nociceptive behaviors induced by intravesical RTX instillation (3 µM, 0.3 ml). Retigabine dose-dependently decreased both the frequency and the amplitude of RBCs and SAAs of both Aδ- and C-fibers. The effect on RBCs was more potent on the frequency than the amplitude. Retigabine inhibited the RTX-induced abdominal licking, but not freezing. Kv7 channels are likely to be implicated in inhibition of bladder mechano- and nociceptive sensory transduction. Neurourol. Urodynam. 36:280-285, 2017. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Glial cell adhesion and protein adsorption on SAM coated semiconductor and glass surfaces of a microfluidic structure

NASA Astrophysics Data System (ADS)

Sasaki, Darryl Y.; Cox, Jimmy D.; Follstaedt, Susan C.; Curry, Mark S.; Skirboll, Steven K.; Gourley, Paul L.

2001-05-01

The development of microsystems that merge biological materials with microfabricated structures is highly dependent on the successful interfacial interactions between these innately incompatible materials. Surface passivation of semiconductor and glass surfaces with thin organic films can attenuate the adhesion of proteins and cells that lead to biofilm formation and biofouling of fluidic structures. We have examined the adhesion of glial cells and serum albumin proteins to microfabricated glass and semiconductor surfaces coated with self-assembled monolayers of octadecyltrimethoxysilane and N-(triethoxysilylpropyl)-O- polyethylene oxide urethane, to evaluate the biocompatibility and surface passivation those coatings provide.

NMDA receptor gating of information flow through the striatum in vivo.

PubMed

Pomata, Pablo E; Belluscio, Mariano A; Riquelme, Luis A; Murer, M Gustavo

2008-12-10

A role of NMDA receptors in corticostriatal synaptic plasticity is widely acknowledged. However, the conditions that allow NMDA receptor activation in the striatum in vivo remain obscure. Here we show that NMDA receptors contribute to sustain the membrane potential of striatal medium spiny projection neurons close to threshold during spontaneous UP states in vivo. Moreover, we found that the blockade of striatal NMDA receptors reduces markedly the spontaneous firing of ensembles of medium spiny neurons during slow waves in urethane-anesthetized rats. We speculate that recurrent activation of NMDA receptors during UP states allows off-line information flow through the striatum and system level consolidation during habit formation.

[Development of elastameric sealant designed for arterial field].

PubMed

Matsuda, Takehisa; Nakajima, Nobuyuki

2013-04-01

The development of a reliable surgical sealant specific for arterial tissues has been long awaited. In this article, first the "ideal" adhesion mechanism formulated from biomechanical concept is proposed for ensured hemostasis in dissected arteries with pulsatile flow. An urethane prepolymer prepared along the design criteria is viscous liquid. Due to its high water absorbility and high reactivity with water, the sealant applied to vascular tissues becomes an elastomer within several minutes. When the sealant was applied to dissected canine abdominal arteries with 3 stay sutures, followed by declamping 5 minutes, neither bleeding nor detrimental effect on tissue morphogenesis was observed. This sealant is being ready to the market.

Electrical Arc Ignition Testing of Spacesuit Materials

NASA Technical Reports Server (NTRS)

Smith, Sarah; Gallus, Tim; Tapia, Susana; Ball, Elizabeth; Beeson, Harold

2006-01-01

A viewgraph presentation on electrical arc ignition testing of spacesuit materials is shown. The topics include: 1) Background; 2) Test Objectives; 3) Test Sample Materials; 4) Test Methods; 5) Scratch Test Objectives; 6) Cotton Scratch Test Video; 7) Scratch Test Results; 8) Entire Date Plot; 9) Closeup Data Plot; 10) Scratch Test Problems; 11) Poke Test Objectives; 12) Poke Test Results; 13) Poke Test Problems; 14) Wire-break Test Objectives; 15) Cotton Wire-Break Test Video; 16) High Speed Cotton Wire-break Test Video; 17) Typical Data Plot; 18) Closeup Data Plot; 19) Wire-break Test Results; 20) Wire-break Tests vs. Scratch Tests; 21) Urethane-coated Nylon; and 22) Moleskin.

Fracture load of implant-supported zirconia all-ceramic crowns luted with various cements.

PubMed

Lim, Hyun-Pil; Yoo, Jeong-Min; Park, Sang-Won; Yang, Hong-So

2010-01-01

This study compared the fracture load and failure types of implant-supported zirconia all-ceramic crowns cemented with various luting agents. The ceramic frameworks were fabricated from a presintered yttria-stabilized zirconium dioxide block using computer-aided design/computer-assisted manufacturing technology, and were then veneered with feldspathic porcelain. Three luting agents were used. Composite resin cement (1,560.78 +/- 39.43 N) showed the highest mean fracture load, followed by acrylic/urethane cement (1,116.20 +/- 77.32 N) and zinc oxide eugenol cement (741.21 +/- 41.95 N) (P < .05). The types of failure varied between groups.

THE NATURE AND CONTROL OF REACTIONS IN BIOLUMINESCENCE

PubMed Central

Johnson, F. H.; Eyring, H.; Steblay, R.; Chaplin, H.; Huber, C.; Gherardi, G.

1945-01-01

On the basis of available data with regard to the chemical and physical properties of the "substrate" luciferin (LH2) and enzyme, luciferase (A), and of kinetic data derived both from the reaction in extracts of Cypridina, and from the luminescence of intact bacteria, the fundamental reactions involved in the phenomenon of bioluminescence have been schematized. These reactions provide a satisfactory basis for interpreting the known characteristics of the system, as well as the theoretical chemistry with regard to the control of its over-all velocity in relation to various factors. These factors, here studied experimentally wholly with bacteria, Photobacterium phosphoreum in particular, include pH, temperature, pressure, and the drugs sulfanilamide, urethane, and alcohol, separately and in relation to each other. Under steady state conditions of bacterial luminescence, with excess of oxidizable substrate and with oxygen not limiting, the data indicate that the chief effects of these agents center around the pace setting reactions, which may be designated by the equation: A + LH2 → ALH2 following which light emission is assumed proportional to the amount of the excited molecule, AL*. The relation between pH and luminescence intensity varies with (a), the buffer mixture and concentration, (b), the temperature, and (c), the hydrostatic pressure. At an optimum temperature for luminescence of about 22° C. in P. phosphoreum, the effects of increasing or decreasing the hydrogen ion concentration are largely reversible over the range between pH 3.6 and pH 8.8. The relation between luminescence intensity and pH, under the experimental conditions employed, is given by the following equation, in which I 1 represents the maximum intensity, occurring about pH 6.5; I 2 the intensity at any other given pH; K 5 the equilibrium constant between hydrogen ions and the AL-; and K 6 the corresponding constant with respect to hydroxyl ions: See PDF for Equation The value of K 5, as indicated by the data, amounts to 4.84 x 104, while that of K 6 amounts to 4.8 x 105. Beyond the range between approximately pH 3.8 and 8.8, destructive effects of the hydrogen and hydroxyl ions, respectively, were increasingly apparent. By raising the temperature above the optimum, the destructive effects were apparent at all pH, and the intensity of the luminescence diminished logarithmically with time. With respect to pH, the rate of destruction of the light-emitting system at temperatures above the optimum was slowest between pH 6.5 and 7.0, and increased rapidly with more acid or more alkaline reactions of the medium. The reversible effects of slightly acid pH vary with the temperature in the manner of an inhibitor (Type I) that acts independently of the normal, reversible denaturation equilibrium (K 1) of the enzyme. The per cent inhibition caused by a given acid pH in relation to the luminescence intensity at optimum pH, is much greater at low temperatures, and decreases as the temperature is raised towards the optimum temperature. The observed maximum intensity of luminescence is thus shifted to slightly higher temperatures by increase in (H+). The apparent activation energy of luminescence is increased by a decrease in pH. The value of ΔH‡ at pH 5.05 was calculated to be 40,900 calories, in comparison with 20,700 at a pH of 6.92. The difference of 20,200 is taken to represent an estimate of the heat of ionization of ALH in the activation process, and compares roughtly with the 14,000 calories estimated for the same process, by analyzing the data from the point of view of hydrogen ions as an inhibitor. The decreasing temperature coefficient for luminescence in proceeding from low temperatures towards the optimum is accounted for in part by the greater degree of ionization of ALH. At the optimum temperature and acid reactions, pressures up to about 500 atmospheres retard the velocity of the luminescent oxidation. At the same temperature, with decrease in hydrogen ion concentration, the pressure effect is much less, indicating a considerable volume increase in the process of ionization and activation. In the extremely alkaline range, beyond pH 9, luminescence is greatly reduced, as compared with the intensity at neutrality, and under these conditions pressure causes a pronounced increase in intensity, presumably by acting upon the reversible denaturation equilibrium of the protein enzyme, A. Sulfanilamide, in neutral solutions, acts on luminescence in a manner very much resembling that of hydrogen ions at acidities between pH 4.0 and pH 6.5. Like the hydrogen ion equilibrium, the sulfanilamide equilibrium involves a ratio of approximately one inhibitor molecule to one enzyme molecule. The heat of reaction amounts to about 11,600 calories or more in a reversible combination that evidently evolves heat. Like the action of H ions, sulfanilamide causes a slight shifting of maximum luminescence intensity in the direction of higher temperatures, and an increase in the energy of activation. The effect of sulfanilamide on the growth of broth cultures of eight species of luminous bacteria indicates that there is no regular relationship among the different organisms between the concentration of the drug that prevents growth, and that which prevents luminescence in the cells which develop in the presence of sulfanilamide. p-Aminobenzoic acid (PAB) antagonizes the sulfanilamide inhibition of growth in luminous bacteria, and the cultures that develop are luminous. When (PAB) is added to cells from fully developed cultures, it has no effect on luminescence, or causes a slight inhibition, depending on the concentration. With luminescence partly inhibited by sulfanilamide, the addition of PAB has no effect, or has an inhibitory effect which adds to that caused by sulfanilamide. Two different, though possibly related, enzyme systems thus appear to limit growth and luminescence, respectively. The possible mechanism through which both the inhibitions and the antagonism take place is discussed. The irreversible destruction of the luminescent system at temperatures above that of the maximum luminescence, in a medium of favorable pH to which no inhibitors have been added, proceeds logarithmically with time at both normal and increased hydrostatic pressures. Pressure retards the rate of the destruction, and the analysis of the data indicates that a volume increase of roughly 71 cc. per gm. molecule at 32° C. takes place in going from the normal to the activated state in this reaction. At normal pressure, the rate of destruction has a temperature coefficient of approximately 90,000 calories, or about 20,000 calories more than the heat of reaction in the reversible denaturation equilibrium. The data indicate that the equilibrium and the rate process are two distinct reactions. The equation for luminescence intensity, taking into account both the reversible and irreversible phases of the reaction is given below. In the equation b is a proportionality constant; k' the rate constant of the luminescent reaction; A0 the total luciferase; A0i the total initial luciferase at time t equals 0; kn the rate constant for the destruction of the native, active form of the enzyme; kd the rate constant for the destruction of the reversibly denatured, inactive form; t the time; and the other symbols are as indicated above: See PDF for Equation For reasons cited in the text, kn evidently equals kd. Urethane and alcohol, respectively, act in a manner (Type II) that promotes the breaking of the type of bonds broken in both the reversible and irreversible reactions and so promotes the irreversible denaturation. This result is in contrast to the effects of sulfanilamide, which at appropriate concentrations may give rise to the same initial inhibition as that caused by urethane, but remains constant with time. The inhibition caused by urethane and alcohol, respectively, increases as the temperature is raised. As a result, the apparent optimum is shifted to lower temperatures, and the activation energy for the over-all process of luminescence diminishes. An analysis for the approximate heat of reaction in the equilibrium between these drugs and the enzyme, indicates 65,000 calories for urethane, and 37,000 for alcohol. A similar analysis with respect to the effect of hydroxyl ions as the inhibitor gives 60,300 calories. The effects of alcohol and urethane are sensitive to hydrostatic pressure. Moderate inhibitions at optimum temperature and pH, caused by relatively small concentrations of either drug, are completely abolished by pressures of 3,000 to 4,000 pounds per square inch. At optimum temperature and pH, increasing concentrations of alcohol caused the apparent optimum pressure for luminescence to shift markedly in the direction of higher pressures. Analysis of the data with respect to concentration of alcohol at different pressures indicated that the ratio of alcohol to enzyme molecules amounted to approximately 4, at 7,000 pounds, but only about 2.8 at normal pressures. This phenomenon was taken to indicate that more than one equilibrium is established between the alcohol and the protein. A similar interpretation was suggested in connection with the fact that analysis of the relation between concentration of urethane and amount of inhibition at different temperatures also indicated a ratio of urethane to enzyme molecules that increased with temperature in the equilibria involved. Analysis of the data with respect to pressure and the inhibition caused by a given concentration of alcohol at different temperatures indicated that the volume change involved in the combination of alcohol with the enzyme must be very small, while the actual effect of pressure is apparently mediated through the reversible denaturation of the protein enzyme, which is promoted by alcohol, urethane, and drugs of similar type. PMID:19873433

A survey of levels of ethyl carbamate in alcoholic beverages in 2009-2012, Hebei Province, China.

PubMed

Liu, Yinping; Wang, Shuhui; Hu, Ping

2013-01-01

Results of a survey of levels of ethyl carbamate (EC) (urethane) in alcoholic beverages carried out in four successive years from 2009 to 2012 by gas chromatography-mass spectrometry (GC/MS) are presented. The beverages were purchased for sampling from Hebei Province of China, including eight main areas of production. The samples comprised wines (n = 212), grain spirits (n = 143) and wine sauces (n = 164). The data show that the average EC content in these kinds of alcoholic beverages remains nearly constant over the years. The results provide valuable data for food authorities to establish maximum limits for EC in China.

Demonstration of a sterilizable solid rocket motor system

NASA Technical Reports Server (NTRS)

Mastrolia, E. J.; Santerre, G. M.; Lambert, W. L.

1975-01-01

A solid propellant rocket motor containing 60.9 Kg (134-lb) of propellant was successfully static fired after being subjected to eight heat sterilization cycles (three 54-hour cycles plus five 40-hour cycles) at 125 C (257 F). The test motor, a modified SVM-3 chamber, incorporated a flexible grain retention system of EPR rubber to relieve thermal shrinkage stresses. The propellant used in the motor was ANB-3438, and 84 wt% solids system (18 wt% aluminum) containing 66 wt% stabilized ammonium perchlorate oxidizer and a saturated hydroxylterminated polybutadiene binder. Bonding of the propellant to the EPR insulation (GenGard V-4030) was provided by the use of SD-886, an epoxy urethane restriction.

Thermal performance evaluation of the Calmac (liquid) solar collector

NASA Technical Reports Server (NTRS)

Usher, H.

1978-01-01

The procedures used and the results obtained during the evaluation test program on the S. N. 1, (liquid) solar collector are presented. The flat plate collector uses water as the working fluid. The absorber plate is aluminum with plastic tubes coated with urethane black. The glazing consists of .040 in fiberglass reinforced polyester. The collector weight is 78.5 pounds with overall external dimensions of approximately 50.3in. x 98.3in. x 3.8in. The following information is given: thermal performance data under simulated conditions, structural behavior under static loading, and the effects of long term exposure to natural weathering. These tests were conducted using the MSFC Solar Simulator.

Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties of new epoxy and urethane adhesives

NASA Technical Reports Server (NTRS)

Glasgow, D. G.

1976-01-01

The effects of novel aromatic diamine structures on the adhesive properties of epoxy and polyurethane adhesives were studied. Aromatic diamines based on benzophenone and diphenyl-methane isomers were evaluated as curing agents for epoxy resins and benzophenone and diphenyl-methane based diamine isomers were evaluated as curing agents for polyurethane adhesives. Polyurethane adhesives were prepared based on m, m prime-diisocyanato-diphenyl-methane and m, m prime-diisocyanato-benzophenone. The m, m prime-diisocayanato-diphenyl-methane based adhesive had properties comparable to state-of-the-art adhesives. The m, m prime-diisocyanato-benzophenone based adhesive was extremely reactive.

Neural Mechanism by which Gravitational Stimuli and Stress Affect the Secretion of Renin and Other Hormones

NASA Technical Reports Server (NTRS)

Ganong, W. F.; Gotoh, E.; Alper, R. H.

1985-01-01

The serotonin-releasing drug p-chloroamphetamine (PCA), as well as L-propranolol and chloriasondamine were used in a study which established that the pathway from the hypothalamus to the kidneys is sympathetic. Which hypothalamic nuclei mediate the response to PCA is being investigated experiments are being conducted to determine a readily reproducible psychological stimulus to renin secretion that can be used in rats. The effects of equithesin, urethane, and inactin on plasma renin activity were examined in preparation for tilting experiments. The relation of vasopressin-secreting neurons in the brain sem to PCA response was explored in Brattleboro rats that are congenitally unable to produce vasopressin in their hypothalami.

Cooling Vest

NASA Technical Reports Server (NTRS)

1983-01-01

Because quadriplegics are unable to perspire below the level of spinal injury, they cannot tolerate heat stress. A cooling vest developed by Ames Research Center and Upjohn Company allows them to participate in outdoor activities. The vest is an adaptation of Ames technology for thermal control garments used to remove excess body heat of astronauts. The vest consists of a series of corrugated channels through which cooled water circulates. Its two outer layers are urethane coated nylon, and there is an inner layer which incorporates the corrugated channels. It can be worn as a backpack or affixed to a wheelchair. The unit includes a rechargeable battery, mini-pump, two quart reservoir and heat sink to cool the water.

Reconstitution of craniofacial osseous contour deformities, sequelae of trauma and post resection for tumors, with an alloplastic-autogenous graft.

PubMed

Leake, D L; Habal, M B

1977-04-01

Our experience using a new technique for reconstructing contour defects of facial bones has been presented. It employs particulate, cancellous bone and an implantable prosthesis accurately fabricated of polyether urethane and polyethylene terephthalate cloth mesh which can be produced in a variety of configurations. A mannequin made of these materials displaying the various parts of the craniofacial complex that have been restored or are currently under investigation is shown in Figure 10. Large cranial vault defects, orbital floors, mandibles including chin augmentation, and nasal bone deformities have been successfully restored in man. Restoration of the pinna of the ear is currently being evaluated in laboratory animals.

WE-E-213CD-01: Best in Physics (Joint Imaging-Therapy) - Evaluation of Deformation Algorithm Accuracy with a Two-Dimensional Anatomical Pelvic Phantom.

PubMed

Kirby, N; Chuang, C; Pouliot, J

2012-06-01

To objectively evaluate the accuracy of 11 different deformable registration techniques for bladder filling. The phantom represents an axial plane of the pelvic anatomy. Urethane plastic serves as the bony anatomy and urethane rubber with three levels of Hounsfield units (HU) is used to represent fat and organs, including the prostate. A plastic insert is placed into the phantom to simulate bladder filling. Nonradiopaque markers reside on the phantom surface. Optical camera images of these markers are used to measure the positions and determine the deformation from the bladder insert. Eleven different deformable registration techniques are applied to the full- and empty-bladder computed tomography images of the phantom to calculate the deformation. The applied algorithms include those from MIMVista Software and Velocity Medical Solutions and 9 different implementations from the Deformable Image Registration and Adaptive Radiotherapy Toolbox for Matlab. The distance to agreement between the measured and calculated deformations is used to evaluate algorithm error. Deformable registration warps one image to make it similar to another. The root-mean-square (RMS) difference between the HUs at the marker locations on the empty-bladder phantom and those at the calculated marker locations on the full-bladder phantom is used as a metric for image similarity. The percentage of the markers with an error larger than 3 mm ranges from 3.1% to 28.2% with the different registration techniques. This range is 1.1% to 3.7% for a 7 mm error. The least accurate algorithm at 3 mm is also the most accurate at 7 mm. Also, the least accurate algorithm at 7 mm produces the lowest RMS difference. Different deformation algorithms generate very different results and the outcome of any one algorithm can be misleading. Thus, these algorithms require quality assurance. The two-dimensional phantom is an objective tool for this purpose. © 2012 American Association of Physicists in Medicine.

α1- and α2-adrenergic receptors in the retrotrapezoid nucleus differentially regulate breathing in anesthetized adult rats.

PubMed

Oliveira, Luiz M; Moreira, Thiago S; Kuo, Fu-Shan; Mulkey, Daniel K; Takakura, Ana C

2016-09-01

Norepinephrine (NE) is a potent modulator of breathing that can increase/decrease respiratory activity by α1-/α2-adrenergic receptor (AR) activation, respectively. The retrotrapezoid nucleus (RTN) is known to contribute to central chemoreception, inspiration, and active expiration. Here we investigate the sources of catecholaminergic inputs to the RTN and identify respiratory effects produced by activation of ARs in this region. By injecting the retrograde tracer Fluoro-Gold into the RTN, we identified back-labeled catecholaminergic neurons in the A7 region. In urethane-anesthetized, vagotomized, and artificially ventilated male Wistar rats unilateral injection of NE or moxonidine (α2-AR agonist) blunted diaphragm muscle activity (DiaEMG) frequency and amplitude, without changing abdominal muscle activity. Those inhibitory effects were reduced by preapplication of yohimbine (α2-AR antagonist) into the RTN. Conversely, unilateral RTN injection of phenylephrine (α1-AR agonist) increased DiaEMG amplitude and frequency and facilitated active expiration. This response was blocked by prior RTN injection of prazosin (α1-AR antagonist). Interestingly, RTN injection of propranolol (β-AR antagonist) had no effect on respiratory inhibition elicited by applications of NE into the RTN; however, the combined blockade of α2- and β-ARs (coapplication of propranolol and yohimbine) revealed an α1-AR-dependent excitatory response to NE that resulted in increase in DiaEMG frequency and facilitation of active expiration. However, blockade of α1-, α2-, or β-ARs in the RTN had minimal effect on baseline respiratory activity, on central or peripheral chemoreflexes. These results suggest that NE signaling can modulate RTN chemoreceptor function; however, endogenous NE signaling does not contribute to baseline breathing or the ventilatory response to central or peripheral chemoreceptor activity in urethane-anesthetized rats. Copyright © 2016 the American Physiological Society.

Space environmental effects on LDEF composites: A leading edge coated graphite epoxy panel

NASA Technical Reports Server (NTRS)

George, Pete E.; Dursch, Harry W.; Hill, Sylvester G.

1993-01-01

The electronics module cover for the leading edge (Row D 9) experiment M0003-8 was fabricated from T300 graphite/934 epoxy unidirectional prepreg tape in a (O(sub 2), +/- 45, O(sub 2), +/- 45, 90, 0)(sub s) layup. This 11.75 in x 16.75 in panel was covered with thermal control coatings in three of the four quadrants with the fourth quadrant uncoated. The composite panel experienced different thermal cycling extremes in each quadrant due to the different optical properties of the coatings and bare composite. The panel also experienced ultraviolet (UV) and atomic oxygen (AO) attack as well as micrometeoroid and space debris impacts. An AO reactivity of 0.99 x 10(exp -24) cm(sup 3)/atom was calculated for the bare composite based on thickness loss. The white urethane thermal control coatings (A276 and BMS 1060) prevented AO attack of the composite substrate. However, the black urethane thermal control coating (Z306) was severely eroded by AO, allowing some AO attack of the composite substrate. An interesting banding pattern on the AO eroded bare composite surface was investigated and found to match the dimensions of the graphite fiber tow widths as prepregged. Also, erosion depths were greater in the darker bands. Five micrometeoroid/space debris impacts were cross sectioned to investigate possible structural damage as well as impact/AO interactions. Local crushing and delaminations were found to some extent in all of the impacts. No signs of coating undercutting were observed despite the extensive AO erosion patterns seen in the exposed composite material at the impact sites. An extensive microcrack study was performed on the panel along with modeling of the thermal environment to estimate temperature extremes and thermal shock. The white coated composite substrate displayed almost no microcracking while the black coated and bare composite showed extensive microcracking. Significant AO erosion was seen in many of the cracks in the bare composite.

TH-CD-207B-10: Effect of CT Reconstruction Filter On Measured Hounsfield Values in Lung Nodules

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

Little, K; Reiser, I; Sanchez, A

Purpose: Measured Hounsfield numbers in CT are used by radiologists to determine the presence of calcium or fat in lung nodules, either of which suggests a benign diagnosis. However, substantial variations in Hounsfield number may arise due to the use of different reconstruction parameters such as the filter/kernel, leading to measurement inaccuracies. This quality improvement project was developed to demonstrate measurement pitfalls and to identify acceptable conditions for incorporating Hounsfield values as a factor in lung nodule diagnosis. Methods: 12 mm-diameter spheres of polyurethane and urethane foam were placed into an anthropomorphic chest phantom, and 10 mm-diameter tubes with varyingmore » iodine concentrations were placed into a 16 cm PMMA cylindrical phantom. Additionally, 11 mm-diameter PMMA and HDPE spheres were placed in a 10 cm PMMA cylindrical phantom. Phantoms were scanned at 120 kVp using a Siemens Biograph mCT and on a Philips iCT and reconstructed using various reconstruction filters. Results: For the Siemens system, both sharp kernels and smooth kernels altered the Hounsfield numbers. Hounsfield numbers varied within a range of 8.9 HU for urethane foam and varied within 58.7 HU for polyurethane. The iodine measurements varied up to 37.9 HU for the lowest concentration. For the Philips system, Hounsfield numbers were relatively consistent but were higher for the “Detail” and “Lung Enhanced” filters, varying by 36.9 HU for PMMA and 15.9 HU for HDPE. Conclusion: Reconstruction filters can change the measured Hounsfield numbers of nodular objects, especially with detail-enhancing (sharpening) filters commonly used in lung imaging. Measured values should only be used for diagnostic decision support with filters that have demonstrated accuracy and consistency. While filter accuracy statements are available from manufacturers, radiologists are likely not aware of the extent of potential variations that can occur in a clinical setting.« less

Surface structural conformations of fibrinogen polypeptides for improved biocompatibility.

PubMed

Yaseen, Mohammed; Zhao, Xiubo; Freund, Amy; Seifalian, Alexander M; Lu, Jian R

2010-05-01

This work reports on how incorporation of silica nanocages into poly(urethane) copolymers (PU) affects conformational orientations of adsorbed fibrinogen and how different surfaces subsequently influenced HeLa cell attachment and proliferation. Incorporation of 2 wt% silica nanocages into poly(urethane) (PU4) substantially altered the surface topography of the films and some 50% of the surface was covered with the nanocages due to their preferential exposure. AFM studies revealed the deposition of a dense protein network on the soft polymeric domains of PU4 and much reduced fibrinogen adsorption on the hard nanocage domains. As on the bare SiO(2) control surface, fibrinogen molecules adsorbed on top of the hard nanocages mainly took the dominant trinodular structures in monomeric and dimeric forms. In addition, net positively charged long alpha chains were prone to being hidden beneath the D domains whilst gamma chains predominantly remained exposed. Dynamic interfacial adsorption as probed by spectroscopic ellipsometry revealed fast changes in interfacial conformation induced by electrostatic interactions between different segments of fibrinogen and the surface, consistent with the AFM imaging. On the PU surfaces without nanocage incorporation (PUA), however, adsorbed fibrinogen molecules formed beads-like chain networks, consistent with the structure featured on the soft PU4 domains, showing very different effects of surface chemical nature. Monoclonal antibodies specific to the alpha and gamma chains showed reduced alpha but increased gamma chain binding at the silicon oxide control and PU4 surfaces, whilst on the PUA, C18 and amine surfaces (organic surface controls) the opposite binding trend was detected with alpha chain binding dominant, showing different fibrinogen conformations. Cell attachment studies revealed differences in cell attachment and proliferation, consistent with the different polypeptide conformations on the two types of surfaces, showing a strong preference to the extent of exposure of gamma chains. Crown Copyright 2010. Published by Elsevier Ltd. All rights reserved.

Dental Composite Restorations and Psychosocial Function in Children

PubMed Central

Trachtenberg, Felicia L.; Hauser, Russ; McKinlay, Sonja; Shrader, Peter; Tavares, Mary; Bellinger, David C.

2012-01-01

BACKGROUND AND OBJECTIVE: Resin-based dental materials may intraorally release their chemical components and bisphenol A. The New England Children’s Amalgam Trial found that children randomized to amalgam had better psychosocial outcomes than those assigned to composites for posterior tooth restorations. The objective of this study was to examine whether greater exposure to dental composites is associated with psychosocial problems in children. METHODS: Analysis of treatment-level data from the New England Children’s Amalgam Trial, a 2-group randomized safety trial comparing amalgam with the treatment plan of bisphenol A-glycidyl methacrylate (bisGMA)-based composite and urethane dimethacrylate–based polyacid-modified composite (compomer), among 534 children aged 6 to 10 years at baseline. Psychosocial function at follow-up (n = 434) was measured by using the self-reported Behavior Assessment System for Children (BASC-SR) and parent-reported Child Behavior Checklist (CBCL). RESULTS: Children with higher cumulative exposure to bisGMA-based composite had poorer follow-up scores on 3 of 4 BASC-SR global scales: Emotional Symptoms (β = 0.8, SE = 0.3, P = .003), Clinical Maladjustment (β = 0.7, SE = 0.3, P = .02), and Personal Adjustment (β = –0.8, SE = 0.2, P = .002). Associations were stronger with posterior-occlusal (chewing) surfaces, where degradation of composite was more likely. For CBCL change, associations were not statistically significant. At-risk or clinically significant scores were more common among children with greater exposure for CBCL Total Problem Behaviors (16.3% vs 11.2%, P-trend = .01) and numerous BASC-SR syndromes (eg, ≥13 vs 0 surface-years, Interpersonal Relations 13.7% vs 4.8%, P-trend = .01). No associations were found with compomer, nor with amalgam exposure levels among children randomized to amalgam. CONCLUSIONS: Greater exposure to bisGMA-based dental composite restorations was associated with impaired psychosocial function in children, whereas no adverse psychosocial outcomes were observed with greater urethane dimethacrylate–based compomer or amalgam treatment levels. PMID:22802599

Biocompatibility of a polyether urethane, polypropylene oxide, and a polyether polyester copolymer. A qualitative and quantitative study of three alloplastic tympanic membrane materials in the rat middle ear.

PubMed

Bakker, D; van Blitterswijk, C A; Hesseling, S C; Koerten, H K; Kuijpers, W; Grote, J J

1990-04-01

The biocompatibility of porous implants made of Estane 5714 F1 polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer (HPOE/PBT copolymer), which were selected as candidates for an alloplastic tympanic membrane, was assessed after implantation in rat middle ears for periods of up to 1 year. Implantation of the materials led to tissue reactions initially associated with the wound-healing process, whereas after 1 month not only the presence of macrophages and foreign-body giant cells surrounding the implant materials but also implant degradation were characteristic for a foreign-body reaction. Macrophages and foreign-body giant cells dominated the picture of the tissue surrounding polypropylene oxide. The altered morphology of these cells, the persistent infiltration of the implantation sites by exudate cells, and the premature death of five rats in the 1-year group suggest that polypropylene oxide degradation was accompanied by the release of toxic substances. Estane and copolymer degradation did not induce tissue responses reflecting implant toxicity, and tympanic membranes given these alloplasts showed a normal healing pattern. Inclusions in the cytoplasm of macrophages associated with degradation and phagocytosis of all of the polymers under study were found to contain iron, silicon, titanium, and aluminum. Growth of fibrous tissue and bone, the latter into Estane and HPOE/PBT copolymer implants, indicated appropriate implant fixation by tissue, although macrophages and foreign-body giant cells were present as well. Especially the fixation of copolymer by ingrowth of bone seems promising in terms of the amount of bone in the pores and the electron-dense bone/copolymer interface. The latter is indicative for bonding osteogenesis. The HPOE/PBT copolymer is a better candidate for alloplastic tympanic membrane than Estane, and the use of polypropylene oxide cannot be recommended.

Male-mediated developmental toxicity

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

Anderson, Diana

2005-09-01

In recent years, the public has become more aware that exposure of males to certain agents can adversely affect their offspring and cause infertility and cancer. The hazards associated with exposure to ionising radiation have been recognised for nearly a century, but interest was aroused when a cluster of leukaemia cases was identified in young children living in Seascale, close to the nuclear processing plant at Sellafield in West Cumbria. There was a civil court case on behalf of two of the alleged victims of paternal irradiation at Seascale against British Nuclear Fuels. The case foundered on 'the balance ofmore » probabilities'. Nevertheless, there was support for paternal exposure from Japanese experimental X-ray studies in mice. The tumours were clearly heritable as shown by F2 transmission. Also, effects of a relatively non-toxic dose of radiation (1Gy) on cell proliferation transmitted to the embryo were manifested in the germ line of adult male mice even after two generations. In addition in humans, smoking fathers appear to give rise to tumours in the F{sub 1} generation. Using rodent models, developmental abnormalities/congenital malformations and tumours can be studied after exposure of males in an extended dominant lethal assay and congenital malformations can be determined which have similar manifestations in humans. The foetuses can also be investigated for skeletal malformations and litters can be allowed to develop to adulthood when tumours, if present, can be observed. Karyotype analysis can be performed on foetuses and adult offspring to determine if induced genetic damage can be transmitted. Using this study design, cyclophosphamide, 1,3-butadiene and urethane have been examined and each compound produced positive responses: cyclophosphamide in all endpoints examined, 1,3-butadiene in some and urethane only produced liver tumours in F{sub 1} male offspring. This suggests the endpoints are determined by independent genetic events. The results from heritable studies with 1,3-butadiene have been used in the parallelogram approach to determine a risk assessment for the germ cells in man.« less

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents.

PubMed

Castillo-de-Oyagüe, Raquel; Sánchez-Turrión, Andrés; López-Lozano, José-Francisco; Albaladejo, Alberto; Torres-Lagares, Daniel; Montero, Javier; Suárez-García, Maria-Jesús

2012-07-01

This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05. The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences. Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range.

Investigation of Test Methods, Material Properties and Processes for Solar Cell Encapsulants

NASA Technical Reports Server (NTRS)

Willis, P.; Baum, B.

1982-01-01

The evaluation of potentially useful low cost encapsulation materials is discussed. The goal is to identify, evaluate, test and recommend encapsulant materials and processes for the production of cost effective, long life solar cell modules. Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatment, and the results of an accelerated aging test program for the comparison of material stabilities. New compounds were evaluated for efficiency in curing both ethylene/vinyl acetate and ethylene/methyl acrylate pottants intended for vacuum bag lamination of solar cells. Two component aliphatic urethane casting syrups were evaluated for suitability as solar module pottants on the basis of optical, physical and fabrication characteristics.

Antibacterial Optimization of 4-Aminothiazolyl Analogues of the Natural Product GE2270 A: Identification of the Cycloalkylcarboxylic Acids

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

LaMarche, Matthew J.; Leeds, Jennifer A.; Amaral, Kerri

4-Aminothiazolyl analogues of the antibiotic natural product GE2270 A (1) were designed, synthesized, and optimized for their activity against Gram positive bacterial infections. Optimization efforts focused on improving the physicochemical properties (e.g., aqueous solubility and chemical stability) of the 4-aminothiazolyl natural product template while improving the in vitro and in vivo antibacterial activity. Structure-activity relationships were defined, and the solubility and efficacy profiles were improved over those of previous analogues and 1. These studies identified novel, potent, soluble, and efficacious elongation factor-Tu inhibitors, which bear cycloalkylcarboxylic acid side chains, and culminated in the selection of development candidates amide 48 andmore » urethane 58.« less

[Studies on organic protective coatings for anti-atomic oxygen effects by spectrum analysis].

PubMed

Zhang, Lei

2004-11-01

This paper describes organic protective coatings on space material for anti-AO effects and the experiments to assess properties of the coatings. Organic protection was analyzed after exposures to ground state fast atomic (AO) radiation in the atomic oxygen beam facility for ground simulation experiments. The tests results have been analyzed with advanced FTIR, XPS and SEM. The test indicated that epoxy, alkyd and urethane organic coatings were highly reactive to AO with a strong degradation and changed in morphology of the surface layer. It is evident that siloxane coatings have excellent properties for anti-AO effects. The erosion product has SiO2 left on the surface, thus providing protection from further attack by the energetic oxygen atoms.

Oriental mystery: ginseng

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

Yun, T.K.; Cho, H.O.; Yun, Y.S.

1985-01-01

As a mysterious cure-all medicine Korea ginseng has been, since four or five thousand years ago, used as a tonic in the orient. Ginseng has been known to have a tonic effect and it is the general opinion of many investigators that ginseng has the effect of normalization of physical conditions, that is; maintaining individual homeostasis. On the other hand, the authors have found that ginseng extract inhibits the incidence and also the proliferation of tumors induced by carcinogens such as urethane, DMBA and aflatoxin B. The anticarcinogenic effect of ginseng was due to its ability to enhance the naturalmore » killer activity of the host. Korea ginseng is highly effective in preventing or curing various disease such as diabetes, cancer, high blood pressure, etc.« less

Effects of harmane (1-methyl-beta-carboline) on neurons in the nucleus accumbens of the rat.

PubMed

Ergene, E; Schoener, E P

1993-04-01

Harmane, a beta-carboline alkaloid reported to exert locomotor and psychoactive effects, is found in certain plants and also has been shown to exist in the mammalian brain as an endogenous substance. In this study, the effects of locally perfused harmane were examined on spontaneous neuronal activity in the nucleus accumbens of urethane-anesthetized rats. Extracellular single-unit recording, coupled with push-pull perfusion, enabled the discrimination of specific, dose-related effects of harmane across a wide concentration range. At lower concentrations (10(-9)-10(-11) M), excitation prevailed, while at higher concentrations (10(-8)-10(-6) M) depression was most pronounced. These findings suggest a neuromodulatory role for harmane in the forebrain reward system.

Cool Vest

NASA Technical Reports Server (NTRS)

1982-01-01

ILC, Dover Division's lightweight cooling garment, called Cool Vest was designed to eliminate the harmful effects of heat stress; increases tolerance time in hot environments by almost 300 percent. Made of urethane-coated nylon used in Apollo, it works to keep the body cool, circulating chilled water throughout the lining by means of a small battery-powered pump. A pocket houses the pump, battery and the coolant which can be ice or a frozen gel, a valve control allows temperature regulation. One version is self-contained and portable for unrestrained movement, another has an umbilical line attached to an external source of coolant, such as standard tap water, when extended mobility is not required. It is reported from customers that the Cool Vest pays for itself in increased productivity in very high temperatures.

Temperature Effects on the Impact Behavior of Fiberglass and Fiberglass/Kevlar Sandwich Composites

NASA Astrophysics Data System (ADS)

Halvorsen, Aaron; Salehi-Khojn, Amin; Mahinfalah, Mohammad; Nakhaei-Jazar, Reza

2006-11-01

Impact tests were performed on sandwich composites with Fiberglass and Fiberglass/Kevlar face sheets subjected to varied temperatures. A number of specimens were tested at -50 to 120 °C temperature range and at 20, 30, and 45 J low velocity energy levels. Impact properties of the sandwich composites that were evaluated include maximum normal and shear stresses, maximum energy absorption, non-dimensional parameters (AEMP, PI, and RD), and compression after impact strength. Composite specimens tested have a urethane foam filled honeycomb center sandwiched between a variation of four layered Fiberglass and Kevlar/Fiberglass face sheets in a thermoset polymer epoxy matrix. Results showed that the impact performance of these sandwich composites changed over the range of temperature considered and with the addition of a Kevlar layer.

Waveguide transition with vacuum window for multiband dynamic nuclear polarization systems

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

Rybalko, Oleksandr; Bowen, Sean; Zhurbenko, Vitaliy

2016-05-15

A low loss waveguide transition section and oversized microwave vacuum window covering several frequency bands (94 GHz, 140 GHz, 188 GHz) is presented. The transition is compact and was optimized for multiband Dynamic Nuclear Polarization (DNP) systems in a full-wave simulator. The window is more broadband than commercially available windows, which are usually optimized for single band operation. It is demonstrated that high-density polyethylene with urethane adhesive can be used as a low loss microwave vacuum window in multiband DNP systems. The overall assembly performance and dimensions are found using full-wave simulations. The practical aspects of the window implementation inmore » the waveguide are discussed. To verify the design and simulation results, the window is tested experimentally at the three frequencies of interest.« less

Effects of hyperthyroidism and hypothyroidism on rat growth hormone release induced by thyrotropin-releasing hormone.

PubMed

Chihara, K; Kato, Y; Ohgo, S; Iwasaki, Y; Maeda, K

1976-06-01

The effect of synthetic thyrotropin-releasing hormone (TRH) on the release of growth hormone (GH) and thyroid-stimulating hormone (TSH) was investigated in euthyroid, hypothyroid, and hyperthyroid rats under urethane anesthesia. In euthyroid control rats, intravenous injection of TRH (200 ng/100 g BW) resulted in a significant increase in both plasma GH and TSH. In rats made hypothyroid by treatment with propylthiouracil or by thyroidectomy, basal GH and TSH levels were significantly elevated with exaggerated responses to TRH. In contrast, plasma GH and TSH responses to TRH were both significantly inhibited in rats made hyperthyroid by L-thyroxine (T4) treatment. These results suggest that altered thyroid status influences GH release as well as TSH secretion induced by TRH in rats.

Dynamics of supersonic microparticle impact on elastomers revealed by real–time multi–frame imaging

PubMed Central

Veysset, David; Hsieh, Alex J.; Kooi, Steven; Maznev, Alexei A.; Masser, Kevin A.; Nelson, Keith A.

2016-01-01

Understanding high–velocity microparticle impact is essential for many fields, from space exploration to medicine and biology. Investigations of microscale impact have hitherto been limited to post–mortem analysis of impacted specimens, which does not provide direct information on the impact dynamics. Here we report real–time multi–frame imaging studies of the impact of 7 μm diameter glass spheres traveling at 700–900 m/s on elastomer polymers. With a poly(urethane urea) (PUU) sample, we observe a hyperelastic impact phenomenon not seen on the macroscale: a microsphere undergoes a full conformal penetration into the specimen followed by a rebound which leaves the specimen unscathed. The results challenge the established interpretation of the behaviour of elastomers under high–velocity impact. PMID:27156501

Method for making field-structured memory materials

DOEpatents

Martin, James E.; Anderson, Robert A.; Tigges, Chris P.

2002-01-01

A method of forming a dual-level memory material using field structured materials. The field structured materials are formed from a dispersion of ferromagnetic particles in a polymerizable liquid medium, such as a urethane acrylate-based photopolymer, which are applied as a film to a support and then exposed in selected portions of the film to an applied magnetic or electric field. The field can be applied either uniaxially or biaxially at field strengths up to 150 G or higher to form the field structured materials. After polymerizing the field-structure materials, a magnetic field can be applied to selected portions of the polymerized field-structured material to yield a dual-level memory material on the support, wherein the dual-level memory material supports read-and-write binary data memory and write once, read many memory.

Effects of Temperature and Humidity on Wilethane 44 Cure

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

John C. Weigle

Wilethane 44 is a polyurethane adhesive developed by the Materials Team within ESA-MEE at Los Alamos National Laboratory as a replacement for Hexcel Corporation Urethane 7200. Urethane 7200 is used in numerous weapon systems, but it was withdrawn from the market in 1989. The weapons complex requires a replacement material for use in the W76-1 LEP and the W88, as well as for assembly of JTAs for other warheads. All polyurethane systems are susceptible to moisture reacting with unreacted isocyanate groups. This side reaction competes with the curing reaction and results in CO{sub 2} formation. Therefore, a polyurethane adhesive canmore » exhibit foaming if appropriate environmental controls are not in place while it cures. A designed experiment has been conducted at TA-16-304 to determine the effects of ambient conditions on the properties of cured Wilethane 44. Temperature was varied from 15 C to 30 C and relative humidity from 15% to 40%. The density, hardness at 24 hours, and butt tensile strength on aluminum substrates were measured and fitted to quadratic equations over the experimental space. Additionally, the loss and storage moduli during cure were monitored as a function of cure temperature. These experiments provide a stronger basis for establishing appropriate environmental conditions and cure times when using Wilethane 44. The current guidelines are a working time of 90 minutes, a cure time of 18 hours, and a relative humidity of less than 25%, regardless of ambient temperature. Viscosity measurements revealed that the working time is a strong function of temperature and can be as long as 130 minutes at 15 C or as short as 90 minutes at 30 C. The experiments also showed that the gel time is much longer than originally thought, as long as 13 hours at 15 C. Consequently, it may be necessary to extend the required cure time at temperatures below 20 C. Allowable humidity varies as a function of temperature from 34% at 15 C to 15% at 30 C.« less

Estrogen and insulin-like growth factor 1 synergistically promote the development of lung adenocarcinoma in mice.

PubMed

Tang, Hexiao; Liao, Yongde; Xu, Liqiang; Zhang, Chao; Liu, Zhaoguo; Deng, Yu; Jiang, Zhixiao; Fu, Shengling; Chen, Zhenguang; Zhou, Sheng

2013-11-15

Estrogen receptor (ER) and insulin-like growth factor-1 receptor (IGF-1R) signaling are implicated in lung cancer progression. Based on their previous findings, the authors sought to investigate whether estrogen and IGF-1 act synergistically to promote lung adenocarcinoma (LADE) development in mice. LADE was induced with urethane in ovariectomized Kunming mice. Tumor-bearing mice were divided into seven groups: 17β-estradiol (E2), E2+fulvestrant (Ful; estrogen inhibitor), IGF-1, IGF-1+AG1024 (IGF-1 inhibitor), E2+IGF-1, E2+IGF-1+Ful+AG1024 and control groups. After 14 weeks, the mice were sacrificed, and then the tumor growth was determined. The expression of ERα/ERβ, IGF-1, IGF-1R and Ki67 was examined using tissue-microarray-immunohistochemistry, and IGF-1, p-ERβ, p-IGF-1R, p-MAPK and p-AKT levels were determined based on Western blot analysis. Fluorescence-quantitative polymerase chain reaction was used to detect the mRNA expression of ERβ, ERβ2 and IGF-1R. Tumors were found in 93.88% (46/49) of urethane-treated mice, and pathologically proven LADE was noted in 75.51% (37/49). In the E2+IGF-1 group, tumor growth was significantly higher than in the E2 group (p < 0.05), the IGF-1 group (p < 0.05) and control group (p < 0.05). Similarly, the expression of ERβ, p-ERβ, ERβ2, IGF-1, IGF-1R, p-IGF-1R, p-MAPK, p-AKT and Ki67 at the protein and/or mRNA levels was markedly higher in the ligand group than in the ligand + inhibitor groups (all p < 0.05). This study demonstrated for the first time that estrogen and IGF-1 act to synergistically promote the development of LADE in mice, and this may be related to the activation of the MAPK and AKT signaling pathways in which ERβ1, ERβ2 and IGF-1R play important roles. Copyright © 2013 UICC.

Optimization of a novel large field of view distortion phantom for MR-only treatment planning.

PubMed

Price, Ryan G; Knight, Robert A; Hwang, Ken-Pin; Bayram, Ersin; Nejad-Davarani, Siamak P; Glide-Hurst, Carri K

2017-07-01

MR-only treatment planning requires images of high geometric fidelity, particularly for large fields of view (FOV). However, the availability of large FOV distortion phantoms with analysis software is currently limited. This work sought to optimize a modular distortion phantom to accommodate multiple bore configurations and implement distortion characterization in a widely implementable solution. To determine candidate materials, 1.0 T MR and CT images were acquired of twelve urethane foam samples of various densities and strengths. Samples were precision-machined to accommodate 6 mm diameter paintballs used as landmarks. Final material candidates were selected by balancing strength, machinability, weight, and cost. Bore sizes and minimum aperture width resulting from couch position were tabulated from the literature (14 systems, 5 vendors). Bore geometry and couch position were simulated using MATLAB to generate machine-specific models to optimize the phantom build. Previously developed software for distortion characterization was modified for several magnet geometries (1.0 T, 1.5 T, 3.0 T), compared against previously published 1.0 T results, and integrated into the 3D Slicer application platform. All foam samples provided sufficient MR image contrast with paintball landmarks. Urethane foam (compressive strength ∼1000 psi, density ~20 lb/ft 3 ) was selected for its accurate machinability and weight characteristics. For smaller bores, a phantom version with the following parameters was used: 15 foam plates, 55 × 55 × 37.5 cm 3 (L×W×H), 5,082 landmarks, and weight ~30 kg. To accommodate > 70 cm wide bores, an extended build used 20 plates spanning 55 × 55 × 50 cm 3 with 7,497 landmarks and weight ~44 kg. Distortion characterization software was implemented as an external module into 3D Slicer's plugin framework and results agreed with the literature. The design and implementation of a modular, extendable distortion phantom was optimized for several bore configurations. The phantom and analysis software will be available for multi-institutional collaborations and cross-validation trials to support MR-only planning. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Age-Related Differences in Postural Control and Attentional Cost During Tasks Performed in a One-Legged Standing Posture.

PubMed

Ihira, Hikaru; Makizako, Hyuma; Mizumoto, Atsushi; Makino, Keitarou; Matsuyama, Kiyoji; Furuna, Taketo

2016-01-01

In dual-task situations, postural control is closely associated with attentional cost. Previous studies have reported age-related differences between attentional cost and postural control, but little is known about the association in conditions with a one-legged standing posture. The purpose of this study was to determine age-related differences in postural control and attentional cost while performing tasks at various difficulty levels in a one-legged standing posture. In total, 29 healthy older adults aged 64 to 78 years [15 males, 14 females, mean (SD) = 71.0 (3.8) years] and 29 healthy young adults aged 20 to 26 years [14 males, 15 females, mean (SD) = 22.5 (1.5) years] participated in this study. We measured the reaction time, trunk accelerations, and lower limb muscle activity under 3 different one-legged standing conditions-on a firm surface, on a soft surface with a urethane mat, and on a softer more unstable surface with 2 piled urethane mats. Reaction time as an indication of attentional cost was measured by pressing a handheld button as quickly as possible in response to an auditory stimulus. A 2-way repeated-measures analysis of variance was performed to examine the differences between the 3 task conditions and the 2 age groups for each outcome. Trunk accelerations showed a statistically significant group-by-condition interaction in the anteroposterior (F = 9.1, P < .05), mediolateral (F = 9.9, P < .05), and vertical (F = 9.3, P < .05) directions. Muscle activity did not show a statistically significant group-by-condition interaction, but there was a significant main effect of condition in the tibialis anterior muscle (F = 33.1, P < .01) and medial gastrocnemius muscle (F = 14.7, P < .01) in young adults and the tibialis anterior muscle (F = 24.8, P < .01) and medial gastrocnemius muscle (F = 10.8, P < .01) in older adults. In addition, there was a statistically significant interaction in reaction time (F = 8.2, P < .05) for group-by-condition. The study results confirmed that reaction times in older adults are more prolonged than young adults in the same challenging postural control condition.

Vertical misfit of laser-sintered and vacuum-cast implant-supported crown copings luted with definitive and temporary luting agents

PubMed Central

Sánchez-Turrión, Andrés; López-Lozano, José F.; Albaladejo, Alberto; Torres-Lagares, Daniel; Montero, Javier; Suárez-García, Maria J.

2012-01-01

Objectives. This study aimed to evaluate the vertical discrepancy of implant-supported crown structures constructed with vacuum-casting and Direct Metal Laser Sintering (DMLS) technologies, and luted with different cement types. Study Design. Crown copings were fabricated using: (1) direct metal laser sintered Co-Cr (LS); (2) vacuum-cast Co-Cr (CC); and (3) vacuum-cast Ti (CT). Frameworks were luted onto machined implant abutments under constant seating pressure. Each alloy group was randomly divided into 5 subgroups (n = 10 each) according to the cement system utilized: Subgroup 1 (KC) used resin-modified glass-ionomer Ketac Cem Plus; Subgroup 2 (PF) used Panavia F 2.0 dual-cure resin cement; Subgroup 3 (RXU) used RelyX Unicem 2 Automix self-adhesive dual-cure resin cement; Subgroup 4 (PIC) used acrylic/urethane-based temporary Premier Implant Cement; and Subgroup 5 (DT) used acrylic/urethane-based temporary DentoTemp cement. Vertical misfit was measured by scanning electron microscopy (SEM). Two-way ANOVA and Student-Newman-Keuls tests were run to investigate the effect of alloy/fabrication technique, and cement type on vertical misfit. The statistical significance was set at α = 0.05. Results. The alloy/manufacturing technique and the luting cement affected the vertical discrepancy (p < 0.001). For each cement type, LS samples exhibited the best fit (p < 0.01) whereas CC and CT frames were statistically similar. Within each alloy group, PF and RXU provided comparably greater discrepancies than KC, PIC, and DT, which showed no differences. Conclusions. Laser sintering may be an alternative to vacuum-casting of base metals to obtain passive-fitting implant-supported crown copings. The best marginal adaptation corresponded to laser sintered structures luted with glass-ionomer KC, or temporary PIC or DT cements. The highest discrepancies were recorded for Co-Cr and Ti cast frameworks bonded with PF or RXU resinous agents. All groups were within the clinically acceptable misfit range. Key words:Dental alloy, laser sintering, implant-supported prostheses, vertical discrepancy, vertical misfit. PMID:22322524

FOS EXPRESSION IN PONTOMEDULLARY CATECHOLAMINERGIC CELLS FOLLOWING REM SLEEP-LIKE EPISODES ELICITED BY PONTINE CARBACHOL IN URETHANE-ANESTHETIZED RATS

PubMed Central

RUKHADZE, Irma; FENIK, Victor B.; BRANCONI, Jennifer L.; KUBIN, Leszek

2008-01-01

Pontine noradrenergic neurons of the locus coeruleus (LC) and sub-coeruleus (SubC) region cease firing during rapid eye movement sleep (REMS). This plays a permissive role in the generation of REMS and may contribute to state-dependent modulation of transmission in the central nervous system. Whether all pontomedullary catecholaminergic neurons, including those in the A1/C1, A2/C2 and A7 groups, have REMS-related suppression of activity has not been tested. We used Fos protein expression as an indirect marker of the level of neuronal activity and linear regression analysis to determine whether pontomedullary cells identified by tyrosine hydroxylase (TH) immunohistochemistry have reduced Fos expression following REMS-like state induced by pontine microinjections of a cholinergic agonist, carbachol in urethane-anesthetized rats. The percentage of Fos-positive TH cells was negatively correlated with the cumulative duration of REMS-like episodes induced during 140 min prior to brain harvesting in the A7 and rostral A5 groups bilaterally (p<0.01 for both), and in SubC neurons on the side opposite to carbachol injection (p<0.05). Dorsal medullary A2/C2 neurons did not exhibit such correlation, but their Fos expression (and that in A7, rostral A5 and SubC neurons) was positively correlated with the duration of the interval between the last REMS-like episode and the time of sacrifice (p<0.05). In contrast, neither of these correlations was significant for A1/C1 or caudal A5 neurons. These findings suggest that, similar to the prototypic LC neurons, neurons of the A7, rostral A5 and A2/C2 groups have reduced or abolished activity during REMS, whereas A1/C1 and caudal A5 neurons do not have this feature. The reduced during REMS activity in A2/C2, A5 and A7 neurons, and the associated decrements in norepinephrine release, may cause state-dependent modulation of transmission in brain somato- and viscerosensory, somatomotor, and cardiorespiratory pathways. PMID:18155849

l-Theanine inhibits proinflammatory PKC/ERK/ICAM-1/IL-33 signaling, apoptosis, and autophagy formation in substance P-induced hyperactive bladder in rats.

PubMed

Tsai, Wen-Hsin; Wu, Chung-Hsin; Yu, Hong-Jeng; Chien, Chiang-Ting

2017-02-01

Upregulation of substance P (SP) and neurokinin-1 receptor (NK1R) activation induces pro-inflammatory bladder hyperactivity through the PKC/ERK/NF-κB/ICAM-1/IL-33 signaling pathways to increase the leukocyte infiltration and adhesion leading to reactive oxygen species (ROS) production, autophagy, and apoptosis. l-Theanine is a unique non-protein-forming amino acid present in tea (Camellia sinensis [L.] O. Kuntze) with its antioxidant, anti-inflammatory, and relaxation effects to improve cognition, mood, gastric ulcer injury, and cerebral ischemia/reperfusion injury, and posttraumatic stress disorder. We explored the protective effect of l-theanine on SP-induced bladder hyperactivity. In urethane-anesthetized female Wistar rats, we explored the transcystometrogram, pelvic nerve activity, proinflammatory PKC/ERK/NF-κB/ICAM-1/IL-33 signaling, apoptosis-related Caspase 3/poly-(ADP-ribose)-polymerase (PARP), and autophagy-mediated LC3 II expression by Western blot, electrophoretic-mobility shift assay and immunohistochemistry, bladder ROS amount by a ultrasensitive chemiluminescence method, and possible ROS sources from the different leukocytes by specific stains in SP-evoked hyperactive bladder. l-Theanine dose-dependently depressed H 2 O 2 and HOCl activity in vitro. In urethane-anesthetized female Wistar rats, intra-arterial SP through NK1R activation increased voiding frequency (shortened intercontraction intervals) associated with the increase in bladder nerve activity, proinflammatory PKC/ERK/NF-κB/ICAM-1/IL-33 signaling, Caspase 3/PARP-mediated apoptosis, LC3 II-mediated autophagy, ROS amount, neutrophils adhesion, CD68 (monocyte/macrophage) infiltration, and mast cells degranulation in the hyperactive bladder. Intragastrical l-theanine (15 mg/kg) twice daily for 2 weeks efficiently ameliorated all the enhanced parameters in the SP-treated hyperactive bladder. In conclusion, l-theanine through antioxidant and anti-inflammatory actions ameliorates SP-induced bladder hyperactivity via the inhibition of proinflammatory PKC/ERK/NF-κB/ICAM-1/IL-33 signaling, oxidative stress, bladder nerve hyperactivity, apoptosis, and autophagy. Neurourol. Urodynam. 36:297-307, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature.

PubMed

Chaffin, Kimberly A; Wilson, Charles L; Himes, Adam K; Dawson, James W; Haddad, Tarek D; Buckalew, Adam J; Miller, Jennifer P; Untereker, Darrel F; Simha, Narendra K

2013-11-01

Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37-85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/Mn). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ≈ 16 kg/mole, where a smooth wear surface transitioned to a 'spalling-like' pattern, leaving the wear surface with ≈ 0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/Mn, after the molar mass was reduced below a critical value of ≈30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress-strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

Hemodynamic changes in post-suspension rats during gradual hemorrhage

NASA Astrophysics Data System (ADS)

Vinogradova, O. L.; Borovik, A. S.; Tsvirkoun, D. V.; Tarasova, O. S.

2005-08-01

In urethane-anasthetized rats the effects of 2-week tail suspension upon the hemodynamic changes during simulated orthostatism and during loss of blood were studied. Baseline values of mean arterial pressure (MAP) and pulse interval (PI) did not differ in cage control (C) and post-suspension rats (TS). In both groups 45o head-up tilt resulted in prominent decline of MAP. In C group this effect was followed by the compensatory phase, which was virtually lost in TS group. No significant postural changes of PI were observed. Gradual hemorrhage (30% blood loss during 30 min) resulted in similar MAP drop in C and TS (up to 40% of baseline level). Along with that, PI increase was less prominent in TS (25%) compared to C (60%) indicating higher resistance of the heart to hypovolemia after suspension.

Anti-genotoxicity of trans-anethole and eugenol in mice.

PubMed

Abraham, S K

2001-05-01

The naturally occurring flavouring agents trans-anethole and eugenol were evaluated for antigenotoxic effects in mice. The test doses of trans-anethole (40-400 mg/kg body weight) and eugenol (50-500 mg/kg weight) were administered by gavage 2 and 20 h before the genotoxins were injected intraperitoneally. Anti-genotoxic effects were assessed in the mouse bone marrow micronucleus test. Pretreatment with trans-anethole and eugenol led to significant antigenotoxic effects against cyclophosphamide (CPH), procarbazine (PCB), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and urethane (URE). In addition, trans-anethole inhibited the genotoxicity of ethyl methane sulfonate (EMS). Both trans-anethole and eugenol exerted dose-related antigenotoxic effects against PCB and URE. There was no significant increase in genotoxicity when trans-anethole (40-400 mg/kg body weight) and eugenol (50-500 mg/kg body weight) were administered alone.

Synthesis of chlorophyll-amino acid conjugates as models for modification of proteins with chromo/fluorophores.

PubMed

Tamiaki, Hitoshi; Isoda, Yasuaki; Tanaka, Takuya; Machida, Shinnosuke

2014-02-15

A chlorophyll-a derivative bonded directly with epoxide at the peripheral position of the chlorin π-system was reacted with N-urethane and C-ester protected amino acids bearing an alcoholic or phenolic hydroxy group as well as a carboxy group at the residue to give chlorophyll-amino acid conjugates. The carboxy residues of N,C-protected aspartic and glutamic acids were esterified with the epoxide in high yields. The synthetic conjugates in dichloromethane had absorption bands throughout the visible region including intense red-side Qy and blue-side Soret bands. By their excitation at the visible bands, strong and efficient fluorescence emission was observed up to the near-infrared region. The chromo/fluorophores are promising for preparation of functional peptides and modification of proteins. Copyright © 2013 Elsevier Ltd. All rights reserved.

Simultaneous imaging of intrinsic optical signals and cerebral vessel responses during cortical spreading depression in rats

NASA Astrophysics Data System (ADS)

Li, Pengcheng; Chen, Shangbin; Luo, Weihua; Luo, Qingming

2003-12-01

Cortical spreading depression (CSD) is an important disease model for migraine and cerebral ischemia. We investigated the spatio-temporal characteristics of the intrinsic optical signals (IOS) at 570 nm and the cerebral blood vessel responses during CSD simultaneously by optical reflectance imaging in vivo. The CSD were induced by pinprick in 10 α-chloralose/urethane anesthetized Sprague-Dawley rats. A four-phasic IOS response was observed at pial arteries and parenchymal sites in all experimental animals and an initial slight pial arteries dilation (21.5%+/-13.6%) and constriction (-4.2%+/-3.5%) precedes the dramatic dilation (69.2%+/-26.1%) of pial arterioles was recorded. Our experimental results show a high correlation (r = 0.89+/-0.025) between the IOS response and the diameter changes of the cerebral blood vessels during CSD in rats.

Actuators based on polyurethanes with different types of polyol

NASA Astrophysics Data System (ADS)

Lim, Hyun-Ok; Bark, Geong-Mi; Jo, Nam-Ju

2007-07-01

This study dealt with the electrostrictive responses of polyurethane (PU) actuators with different microphase separation structure, which was a promising candidate for a material used in polymer actuators. In order to construct PUs with different higher-order structure, we synthesized PUs with different diols; poly(neopentyl glycol adipate) (PNAD), poly(tetramethylene glycol) (PTMG), and poly(dimethyl siloxnae) (PDMS). Synthesized PU was characterized by FT-IR spectroscopy and GPC. Thermal analysis and mechanical properties of PU films were carried out with DSC and UTM, respectively. And PU actuator was formed in a monomorph type which made by carbon black electrodes on the both surfaces of PU film by spin coating method. Actuation behavior was mainly influenced on microphase separation structure and mechanical property of PU. In result, PU actuator with PNAD, polyester urethane, had the largest field-induced displacement.

Simultaneous two-photon imaging of cerebral oxygenation and capillary blood flow in atherosclerotic mice

NASA Astrophysics Data System (ADS)

Lu, Xuecong; Li, Baoqiang; Moeini, Mohammad; Lesage, Frédéric

2017-02-01

Gradual changes in brain microvasculature and cerebral capillary blood flow occurring with atherosclerosis may significantly contribute to cognition decline due to their role in brain tissue oxygenation. However, previous stud- ies of the relationship between cerebral capillary blood flow and brain tissue oxygenation are limited. This study aimed to investigate vascular and concomitant changes in brain tissue pO2 with atherosclerosis. Experiments in young healthy C57B1/6 mice (n=6 , WT), young atherosclerotic mice (n=6 , ATX Y) and old atherosclerotic mice (n=6 , ATX O) were performed imaging on the left sensory-motor cortex at resting state under urethane (1.5 g/kg) anesthesia using two-photon fluorescence microscopy. The results showed that pO2 around capillaries, correlated with red blood cell (RBC) flux, increased with atherosclerosis.

Method for providing mirror surfaces with protective strippable polymeric film

DOEpatents

Edwards, Charlene C.; Day, Jack R.

1980-01-01

This invention is a method for forming a protective, strippable, elastomeric film on a highly reflective surface. The method is especially well suited for protecting diamond-machined metallic mirrors, which are susceptible not only to abrasion and mechanical damage but also to contamination and corrosion by various fluids. In a typical use of the invention, a diamond-machined copper mirror surface is coated uniformly with a solution comprising a completely polymerized and completely cured thermoplastic urethane elastomer dissolved in tetrahydrofuran. The applied coating is evaporated to dryness, forming a tough, adherent, impermeable, and transparent film which encapsulates dust and other particulates on the surface. The film may be left in place for many months. When desired, the film may be stripped intact, removing the entrapped particulates and leaving no residue on the mirror surface.

A comparison of the effects of morphine, enkephalin, kyotorphin and D-phenylalanine on rat central neurones.

PubMed Central

Stone, T. W.

1983-01-01

1 Morphine, Met-enkephalin, kyotorphin and D-phenylalanine have been applied by microiontophoresis to neurones in the globus pallidus and cerebral cortex of rats anaesthetized with urethane. 2 In the pallidum, most cells were inhibited by all the agonists, with a high correspondence between cells inhibited by Met-enkephalin and D-phenylalanine and by Met-enkephalin and kyotorphin. Whereas responses to Met-enkephalin were readily antagonized by naloxone, responses to kyotorphin and D-phenylalanine were not. 3 In the cerebral cortex a high proportion of cells was excited by all four agonists and antagonism by naloxone was less consistent than in pallidum. 4 It is concluded that the naloxone-reversible analgesic effects of kyotorphin and D-phenylalanine may be mediated indirectly, rather through an activation of opiate receptors. PMID:6871550

A comparison of the effects of morphine, enkephalin, kyotorphin and D-phenylalanine on rat central neurones.

PubMed

Stone, T W

1983-05-01

1 Morphine, Met-enkephalin, kyotorphin and D-phenylalanine have been applied by microiontophoresis to neurones in the globus pallidus and cerebral cortex of rats anaesthetized with urethane. 2 In the pallidum, most cells were inhibited by all the agonists, with a high correspondence between cells inhibited by Met-enkephalin and D-phenylalanine and by Met-enkephalin and kyotorphin. Whereas responses to Met-enkephalin were readily antagonized by naloxone, responses to kyotorphin and D-phenylalanine were not. 3 In the cerebral cortex a high proportion of cells was excited by all four agonists and antagonism by naloxone was less consistent than in pallidum. 4 It is concluded that the naloxone-reversible analgesic effects of kyotorphin and D-phenylalanine may be mediated indirectly, rather through an activation of opiate receptors.

Mechanical properties of woven glass fiber-reinforced composites.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2006-06-01

The aim of this investigation was to measure the flexural and compressive strengths and the corresponding moduli of cylindrical composite specimens reinforced with woven glass fiber. Test specimens were made by light-curing urethane dimethacrylate oligomer with woven glass fiber of 0.18-mm standard thickness. Tests were conducted using four reinforcement methods and two specimen diameters. Flexural strength and modulus of woven glass fiber-reinforced specimens were significantly greater than those without woven glass fiber (p < 0.01). Likewise, compressive strength of reinforced specimens was significantly greater than those without woven glass fiber (p < 0.01), except for specimens reinforced with woven glass fiber oriented at a tilt direction in the texture (p > 0.05). In terms of comparison between the two specimen diameters, no statistically significant differences in flexural strength and compressive strength (p > 0.05) were observed.

Epoxy hydantoins as matrix resins

NASA Technical Reports Server (NTRS)

Weiss, J.

1983-01-01

Tensile strength and fracture toughness of castings of the hydantoin resins cured with methylenedianiline are significantly higher than MY 720 control castings. Water absorption of an ethyl, amyl hydantoin formulation is 2.1 percent at equilibrium and Tg's are about 160 C, approximately 15 deg below the final cure temperature. Two series of urethane and ester-extended hydantoin epoxy resins were synthesized to determine the effect of crosslink density and functional groups on properties. Castings cured with methylenedianiline or with hexahydrophthalic anhydride were made from these compounds and evaluated. The glass transition temperatures, tensile strengths and moduli, and fracture toughness values were all much lower than that of the simple hydantoin epoxy resins. Using a methylene bishydantoin epoxy with a more rigid structure gave brittle, low-energy fractures, while a more flexible, ethoxy-extended hydantoin epoxy resin gave a very low Tg.

Fabrication and design of bioactive agent coated, highly-aligned electrospun matrices for nerve tissue engineering: Preparation, characterization and application

NASA Astrophysics Data System (ADS)

Lee, Sang Jin; Heo, Min; Lee, Donghyun; Heo, Dong Nyoung; Lim, Ho-Nam; Kwon, Il Keun

2017-12-01

In this study, we designed highly-aligned thermoplastic polycarbonate urethane (PCU) fibrous scaffolds coated with bioactive compounds, such as Poly-L-Lysine (PLL) and Poly-L-Ornithine (PLO), to enhance cellular adhesion and directivity. These products were characterized by scanning electron microscope (SEM) analysis which demonstrated that highly aligned fiber strands were formed without beads when coated onto a mandrel rotating at 1800 rpm. During in vitro cell test, PLO-coated, aligned PCU scaffolds were found to have significantly higher proliferation rates than PLL coated and bare PCU scaffolds. Interestingly, dental pulp stem cells (DPSCs) were observed to stretch along the longitudinal axis parallel to the cell direction on highly aligned scaffolds. These results clearly confirm that our strategy may suggest a useful paradigm by inducing neural tissue repair as a means to remodeling and healing of tissue for restorative procedures in neural tissue engineering.

Antimutagenic action of the triterpene betulinic acid isolated from Scoparia dulcis (Scrophulariaceae).

PubMed

de Freitas, P L; Dias, A C S; Moreira, V R; Monteiro, S G; Pereira, S R F

2015-08-19

The mutagenic and antimutagenic activities of triterpene betulinic acid {3b-3-hydroxy-lup-20(29)-en-28-oic} isolated from the roots of Scoparia dulcis (Scrophulariaceae) were analyzed using the somatic mutation and recombination test (SMART) in the wings of Drosophila melanogaster. The mutagenic potential of betulinic acid was evaluated at 3 different concentrations (1.64, 3.28, and 6.57 mM). Antimutagenic activity evaluation was performed by co-treatment trials in which the flies received betulinic acid at 3 different concentrations in addition to 10 mM pro-mutagenic urethane. The results demonstrated that betulinic acid was not capable of causing DNA damage. However, the frequency of small single spots, large spots, and twin spots was significantly reduced. In the high bioactivation cross, betulinic acid was significantly active and exerted enhanced antimutagenic activity, possibly as a desmutagen.

Unlocking the Potential of Phenacyl Protecting Groups: CO2-Based Formation and Photocatalytic Release of Caged Amines.

PubMed

Speckmeier, Elisabeth; Klimkait, Michael; Zeitler, Kirsten

2018-04-06

Orthogonal protection and deprotection of amines remain important tools in synthetic design as well as in chemical biology and material research applications. A robust, highly efficient, and sustainable method for the formation of phenacyl-based carbamate esters was developed using CO 2 for the in situ preparation of the intermediate carbamates. Our mild and broadly applicable protocol allows for the formation of phenacyl urethanes of anilines, primary amines, including amino acids, and secondary amines in high to excellent yields. Moreover, we demonstrate the utility by a mild and convenient photocatalytic deprotection protocol using visible light. A key feature of the [Ru(bpy) 3 ](PF 6 ) 2 -catalyzed method is the use of ascorbic acid as reductive quencher in a neutral, buffered, two-phase acetonitrile/water mixture, granting fast and highly selective deprotection for all presented examples.

The possible mechanism of enhanced carcinogenesis induced by genotoxic carcinogens in rasH2 mice.

PubMed

Okamura, Miwa; Unami, Akira; Moto, Mitsuyoshi; Muguruma, Masako; Ito, Tadashi; Jin, Meilan; Oishi, Yuji; Kashida, Yoko; Mitsumori, Kunitoshi

2007-01-08

Microarray and RT-PCR analyses were performed for the transgene and Ras-related genes in forestomach squamous cell carcinomas (SCCs) induced by 7,12-dimethylbenz[a]anthracene (DMBA) in rasH2 mice; these results were compared with our previous molecular data of N-ethyl-N-nitrosourea-induced forestomach SCCs and urethane-induced lung adenomas in rasH2 mice. Overexpression of the transgene was detected in the DMBA-induced SCCs, suggesting that the transgene plays an important role in enhanced carcinogenesis in rasH2 mice. In addition, the mouse endogenous ras genes were up-regulated in the DMBA-induced SCCs, and are probably involved in the tumorigenesis of forestomach SCCs. Genes such as osteopontin, Cks1b, Tpm1, Reck, gelsolin, and amphiregulin that were commonly altered in these three different carcinogen-induced tumors may contribute to the development of tumors in rasH2 mice.

[Effects of stimulation of dorso-medial area of nucleus facialis on respiration related units in ventro-lateral region of nucleus tractus solitaris in rabbits].

PubMed

Gao, J X; Liu, L

1990-10-01

In urethane-anesthetized, vagotomized and paralyzed rabbits, effects of electrical stimulation of the dorso-medial area of the nucleus facialis (DMNF) on the respiration-related units (RRUs) in ventro-lateral region of nucleus tractus solitaris (VLNTS) were observed. The experimental results showed that during electrical stimulation of DMNF the majority of the inspiratory (I) neurons (64.4%) were increased in frequency and duration of discharge, some to a marked extent. During electrical stimulation of DMNF the expiratory neurons (35%) were decreased in their frequency and duration of discharge, some to a marked extent too. The responses of RRUs in ipsilateral and contralateral VLNTS to stimulation of DMNF was not statistically significant (P greater than 0.05). It is suggested that DMNF may have a facilitating effect on the inspiratory neurons and an inhibiting effect on the expiratory neurons in VLNTS.

Flame resistant elastomeric polymer development. [for use in space shuttle instrument packaging

NASA Technical Reports Server (NTRS)

Howarth, J. T.; Sheth, S. G.; Sidman, K. R.

1975-01-01

Elastomeric products were developed for use in the space shuttle program, and investigations were conducted to improve the properties of elastomers developed in previous programs, and to evaluate the possibility of using lower-cost general purpose polymers. Products were fabricated and processed on conventional processing equipment; these products include: foams based on fluorinated rubber flame-retarded compounds with a density of 20-30 pounds/cubic foot for use as padding and in helmets; foams based on urethane for use in instrument packaging in the space shuttle; flexible and semi-rigid films of fluorinated rubber and neoprene compounds that would not burn in a 70% nitrogen, 30% oxygen atmosphere, and in a 30% nitrogen, 70% oxygen atmosphere, respectively for use in packaging or in laminates; coated fabrics which used both nylon and Kelvar fabric substrates, coated with either fluorinated or neoprene polymer compositions to meet specific levels of flame retardancy; and other flame-resistant materials.

Acceleration of a ground-state reaction by selective femtosecond-infrared-laser-pulse excitation

NASA Astrophysics Data System (ADS)

Stensitzki, Till; Yang, Yang; Kozich, Valeri; Ahmed, Ashour A.; Kössl, Florian; Kühn, Oliver; Heyne, Karsten

2018-02-01

Infrared (IR) excitation of vibrations that participate in the reaction coordinate of an otherwise thermally driven chemical reaction are believed to lead to its acceleration. Attempts at the practical realization of this concept have been hampered so far by competing processes leading to sample heating. Here we demonstrate, using femtosecond IR-pump IR-probe experiments, the acceleration of urethane and polyurethane formation due to vibrational excitation of the reactants for 1:1 mixtures of phenylisocyanate and cyclohexanol, and toluene-2,4-diisocyanate and 2,2,2-trichloroethane-1,1-diol, respectively. We measured reaction rate changes upon selective vibrational excitation with negligible heating of the sample and observed an increase of the reaction rate up to 24%. The observation is rationalized using reactant and transition-state structures obtained from quantum chemical calculations. We subsequently used IR-driven reaction acceleration to write a polyurethane square on sample windows using a femtosecond IR pulse.

Self-repairable polyurethane networks by atmospheric carbon dioxide and water.

PubMed

Yang, Ying; Urban, Marek W

2014-11-03

Sugar moieties were incorporated into cross-linked polyurethane (PUR) networks in an effort to achieve self-repairing in the presence of atmospheric carbon dioxide (CO2) and water (H2O). When methyl-α-D-glucopyranoside (MGP) molecules are reacted with hexamethylene diisocyanate trimer (HDI) and polyethylene glycol (PEG) to form cross-linked MGP-polyurethane (PUR) networks, these materials are capable of self-repairing in air. This process requires atmospheric amounts of CO2 and H2O, thus resembling plant behavior of carbon fixation during the photosynthesis cycle. Molecular processes responsible for this unique self-repair process involve physical diffusion of cleaved network segments as well as the formation of carbonate and urethane linkages. Unlike plants, MGP-PUR networks require no photo-initiated reactions, and they are thus capable of repair in darkness under atmospheric conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic urea bond for the design of reversible and self-healing polymers

NASA Astrophysics Data System (ADS)

Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

2014-02-01

Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

Dynamic urea bond for the design of reversible and self-healing polymers

PubMed Central

Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

2014-01-01

Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-ureas) capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials. PMID:24492620

Novel carboxy functionalized sol-gel precursors

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

Wolter, H.; Storch, W.; Gellermann, C.

1996-12-31

A novel family of inorganic-organic copolymers (ORMOCER`s) derived from urethane- and thioether(meth)acrylate alkoxysilanes has been successfully exploited for a variety of diverse applications. In order to widen the range of applications an additional functionality (carboxy group) has been incorporated int his silane type. Conventional sol-gel processing facilitates the formation of an inorganic Si-O-Si-network via hydrolysis and polycondensation reactions of alkoxysilyl moieties and in addition, the (meth)acrylate groups are available for radically induced polymerization to obtain a complementary organic polymer structure. The presence of a carboxy group would appear to have great potential for a range of diverse areas of application,more » such as an internal catalyst for the sol-gel process, complexation of elements such as Zr and Ti, increasing the adhesion to various substrates and modification of solubility. A number of novel silanes and their syntheses will be described in this paper.« less

Materials SIG quantification and characterization of surface contaminants

NASA Technical Reports Server (NTRS)

Crutcher, E. Russ

1992-01-01

When LDEF entered orbit its cleanliness was approximately a MIL-STD-1246B Level 2000C. Its burden of contaminants included particles from every part of its history including a relatively small contribution from the shuttle bay itself. Although this satellite was far from what is normally considered clean in the aerospace industry, contaminating events in orbit and from processing after recovery were easily detected. The molecular contaminants carried into orbit were dwarfed by the heavy deposition of UV polymerized films from outgassing urethane paints and silicone based materials. Impacts by relatively small objects in orbit could create particulate contaminants that easily dominated the particle counts within a centimeter of the impact site. During the recovery activities LDEF was 'sprayed' with a liquid high in organics and water soluble salts. With reentry turbulence, vibration, and gravitational loading particulate contaminants were redistributed about LDEF and the shuttle bay.

Use of Synthetic Osteochondral Implants to Treat Bilateral Shoulder Osteochondritis Dissecans in a Dog.

PubMed

Danielski, Alan; Farrell, Michael

2018-06-20

 An 8-month-old American Bulldog was presented for assessment of bilateral thoracic limb lameness. Computed tomographic imaging revealed large, deep osteochondritis dissecans lesions in both humeral heads.  The osteochondritis dissecans lesions were debrided and the exposed subchondral defects were prepared to receive synthetic grafts. Circular implants consisting of a surface layer of polycarbonate urethane and a deep layer of lattice-type titanium were implanted into the osteochondral defects to reconstruct the articular surface topography. Follow-up clinical examination 1.5, 3 and 9months postoperatively revealed a lack of signs of shoulder pain and resolution of thoracic limb lameness. Nine-month follow-up radiographs showed radiographic evidence of osteointegration of both implants.  Synthetic osteochondral implantation in the caudocentral aspect of the humeral head appeared technically feasible and effective in resolving lameness caused by humeral head osteochondritis dissecans. Schattauer GmbH Stuttgart.

Preparation and properties of poly HTBN-based urethane-urea/organo reactive montmorillonite nanocomposites

NASA Astrophysics Data System (ADS)

Li, Zai-Feng; Wu, Yuan; Zhang, Fu-Tao; Cao, Yu-Yang; Wu, Shou-Peng; Wang, Ting

2012-12-01

With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane-urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T g of the soft segment and tan δ of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.

[Neuromuscular blocking and respiratory depressing actions of sodium ammonium dimethyl-2-(propano-1,3-dithiosulfate) monohydrate].

PubMed

Cao, B J; Chen, Z K; Chi, Z Q

1990-05-01

The neuromuscular blocking and respiratory depressing actions of the new insecticide sodium ammonium dimethyl-2-(propano-1,3-dithiosulfate) monohydrate (SCD) were investigated. In peroneal-tibialis anterior nerve-muscle preparations of urethane anesthetized rabbit, SCD 6.5 mg/kg iv completely depressed the indirectly elicited twitch tension but not the directly elicited one. This compound also caused initial potentiation of the indirectly elicited twitch tension. In the partially paralyzed preparations, potentiation of contractions occurred following a brief period of indirectly tetanic stimulation. Nereistoxin but not SCD blocked the indirectly elicited twitch tension of isolated rat diaphragm. The neuromuscular blockade induced by SCD and nereistoxin was antagonized by neostigmine and 4-aminopyridine. SCD and nereistoxin had little or no effect on arterial blood pressure and phrenic nerve discharge of rabbits. The results indicated that SCD-poisoned rabbits died of respiratory paralysis following the neuromuscular blockade.

PUA/PSS multilayer coated CaCO3 microparticles as smart drug delivery vehicles.

PubMed

Du, Chao; Shi, Jun; Shi, Jin; Zhang, Li; Cao, Shaokui

2013-10-01

Hybrid CaCO3 microparticles coated by sodium poly(styrene sulfonate) (PSS) and aliphatic poly(urethane-amine) (PUA) were developed as thermal-/pH-responsive drug delivery vehicles via LbL self-assembly technique. The DOX release from the CaCO3 microparticles was higher than 60% within 36 h, whereas the value of PUA/PSS-coated microparticles was only 20%. The results demonstrated that the PUA/PSS multilayer coating could reduce the drug release rate and significantly assuage the initial burst release of DOX. In addition, the drug release of the hybrid microparticles was found to be thermal-/pH-dual responsive. More interestingly, more than 90% of DOX was released in 36 h at pH2.1 and 55 °C owing to the combined action of the dissolution of the CaCO3 core and the shrinkage of aliphatic PUA. Copyright © 2013 Elsevier B.V. All rights reserved.

The effect of polyether functional polydimethylsiloxane on surface and thermal properties of waterborne polyurethane

NASA Astrophysics Data System (ADS)

Zheng, Guikai; Lu, Ming; Rui, Xiaoping

2017-03-01

Waterborne polyurethanes (WPU) modified with polyether functional polydimethylsiloxane (PDMS) were synthesized by pre-polymerization method using isophorone diisocyanate (IPDI) and 1,4-butanediol (BDO) as hard segments and polybutylene adipate glycol (PBA) and polyether functional PDMS as soft segments. The effect of polyether functional PDMS on phase separation, thermal properties, surface properties including surface composition, morphology and wettability were investigated by FTIR, contact angle measurements, ARXPS, SEM-EDS, AFM, TG and DSC. The results showed that the compatibility between urethane hard segment and PDMS modified with polyether was good, and there was no distinct phase separation in both bulk and surface of WPU films. The degradation temperature and low temperature flexibility increased with increasing amounts of polyether functional PDMS. The enrichment of polyether functional PDMS with low surface energy on the surface imparted excellent hydrophobicity to WPU films.

Prediction of crosslink density of solid propellant binders. [curing of elastomers

NASA Technical Reports Server (NTRS)

Marsh, H. E., Jr.

1976-01-01

A quantitative theory is outlined which allows calculation of crosslink density of solid propellant binders from a small number of predetermined parameters such as the binder composition, the functionality distributions of the ingredients, and the extent of the curing reaction. The parameter which is partly dependent on process conditions is the extent of reaction. The proposed theoretical model is verified by independent measurement of effective chain concentration and sol and gel fractions in simple compositions prepared from model compounds. The model is shown to correlate tensile data with composition in the case of urethane-cured polyether and certain solid propellants. A formula for the branching coefficient is provided according to which if one knows the functionality distributions of the ingredients and the corresponding equivalent weights and can measure or predict the extent of reaction, he can calculate the branching coefficient of such a system for any desired composition.

Non-shivering thermogenesis during prostaglandin E1 fever in rats: role of the cerebral cortex.

PubMed

Monda, M; Amaro, S; De Luca, B

1994-07-18

We have tested the hypothesis that there is a role for the cerebral cortex in the control of non-shivering thermogenesis during fever induced by prostaglandin E1 (PGE1). While under urethan anesthesia, the firing rate of nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic temperatures (TIBAT and Tc) and oxygen (O2) consumption were monitored during the fever from PGE1 injection (400 and 800 ng) in a lateral cerebral ventricle in controls and in functionally decorticated Sprague-Dawley rats. Rats were functionally decorticated by applying 3.3 M KCl solution on the frontal cortex which causes cortical spreading depression (CSD). Pyrogen injections caused dose-related increases in firing rate, TIBAT, Tc and O2 consumption and CSD reduced these enhancements. Our findings indicate that the cerebral cortex could be involved in the control of non-shivering thermogenesis during PGE1-induced febrile response.

REGULATORY MECHANISMS OF CELLULAR RESPIRATION

PubMed Central

Barron, E. S. Guzman; Nelson, Leonard; Ardao, Maria Isabel

1948-01-01

Oxidizing agents of sulfhydryl groups such as iodosobenzoate, alkylating agents such as iodoacetamide, and mercaptide-forming agents such as cadmium chloride, mercuric chloride, p-chloromercuribenzoate, sodium arsenite, and p-carboxyphenylarsine oxide, added in small concentrations to a suspension of sea urchin sperm produced an increase in respiration. When the concentration was increased there was an inhibition. These effects are explained by postulating the presence in the cells of two kinds of sulfhydryl groups: soluble sulfhydryl groups, which regulate cellular respiration, and fixed sulfhydryl groups, present in the protein moiety of enzymes. Small concentrations of sulfhydryl reagents combine only with the first, thus producing an increase in respiration; when the concentration is increased, the fixed sulfhydryl groups are also attacked and inhibition of respiration is the consequence. Other inhibitors of cell respiration, such as cyanide and urethanes, which do not combine with —SH groups, did not stimulate respiration in small concentration. PMID:18891144

Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties on new epoxy and urethane adhesives

NASA Technical Reports Server (NTRS)

Glasgow, D. G.; Garthwait, C.

1977-01-01

Aromatic diamines based on diphenyl sulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m prime-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m prime-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p prime-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m prime-methylene dianiline-cured epoxy appeared to be equivalent to the p,p prime-methylene dianiline-cured epoxy as judged by short beam shear tests.

Hydrogen Bond Induces Hierarchical Self-Assembly in Liquid-Crystalline Block Copolymers.

PubMed

Huang, Shuai; Pang, Linlin; Chen, Yuxuan; Zhou, Liming; Fang, Shaoming; Yu, Haifeng

2018-03-01

Microphase-separated structures of block copolymers (BCs) with a size of sub-10 nm are usually obtained by hydrogen-bond-induced self-assembly of BCs through doping with small molecules as functional additives. Here, fabrication of hierarchically self-assembled sub-10 nm structures upon microphase separation of amphiphilic liquid-crystalline BCs (LCBCs) at the existence of hydrogen bonds but without any dopants is reported. The newly introduced urethane groups in the side chain of the hydrophobic block of LCBCs interact with the ether groups of the hydrophilic poly(ethylene oxide) (PEO) block, leading to imperfect crystallization of the PEO blocks. Both crystalline and amorphous domains coexist in the separated PEO phase, enabling a lamellar structure to appear inside the PEO nanocylinders. This provides an elegant method to fabricate controllable sub-10 nm microstructures in well-defined polymer systems without the introduction of any dopants. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture.

PubMed

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-05-01

Voltage-gated Ca(2+) channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca(2+) channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca(2+) channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca(2+) channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3(-/-) mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca(2+) influx into RTN neurons can trigger small-conductance Ca(2+)-activated K(+)-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca(2+) channels in rodent sleep. The role of CaV2.3 Ca(2+) channels was analyzed in CaV2.3(-/-) mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3(-/-) mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca(2+) channel expression. The detailed mechanisms of SWS increase in CaV2.3(-/-) mice remain to be determined. Low-voltage activated CaV2.3 R-type Ca(2+) channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future.

Anticorrosive organic/inorganic hybrid coatings

NASA Astrophysics Data System (ADS)

Gao, Tongzhai

Organic/inorganic hybrid coating system was developed for anticorrosion applications using polyurea, polyurethane or epoxide as the organic phase and polysiloxane, formed by sol-gel process, as the inorganic phase. Polyurea/polysiloxane hybrid coatings were formulated and moisture cured using HDI isocyanurate, alkoxysilane-functionalized HDI isocyanurate, and tetraethyl orthosilicate (TEOS) oligomers. Two urethanes were prepared using the same components as abovementioned in addition to the oligoesters derived from either cyclohexane diacids (CHDA) and 2-butyl-2-ethyl-1,3-propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6-hexanediol (HD), and trimethylol propane (TMP). Accelerated weathering and outdoor exposure were performed to study the weatherability of the polyurethane/polysiloxane hybrid coating system. FTIR and solid-state 13C NMR revealed that the degradation of the hybrid coatings occurred at the urethane and ester functionalities of the organic phase. DMA and DSC analyses showed the glass transition temperature increased and broadened after weathering. SEM was employed to observe the change of morphology of the hybrid coatings and correlated with the gloss variation after weathering. Rutile TiO2 was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the effect of pigmentation on the coating properties and the sol-gel precursor. Chemical interaction between the TiO2 and the sol-gel precursor was investigated using solid-state 29Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings were evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment were observed to be well dispersed in the polymer matrix. The thermal stability, the tensile modulus and strength of the coatings were enhanced with increasing PVC, whereas the pull-off adhesion and flexibility were reduced with increasing PVC. Finally, the pigmented coatings were evaluated by electrochemical impedance spectroscopy (EIS) and the results showed that 10 wt% pigmentation improved the corrosion resistance of the entire coating system. The effect of pigmentation on epoxide/polysiloxane hybrid coatings was also investigated. The epoxide was successfully modified using 3-(triethoxysilyl) propyl isocyanate (TEOSPI) as indicated by FTIR and NMR. Good dispersion of the pigment particles was achieved as revealed by the SEM images. The tensile modulus, tensile strength, pencil hardness and thermal stability of the hybrid coatings were improved while the flexibility and pull-off adhesion were deteriorated when increasing PVC.

Mixed-mode fatigue fracture of adhesive joints in harsh environments and nonlinear viscoelastic modeling of the adhesive

NASA Astrophysics Data System (ADS)

Arzoumanidis, Alexis Gerasimos

A four point bend, mixed-mode, reinforced, cracked lap shear specimen experimentally simulated adhesive joints between load bearing composite parts in automotive components. The experiments accounted for fatigue, solvent and temperature effects on a swirled glass fiber composite adherend/urethane adhesive system. Crack length measurements based on compliance facilitated determination of da/dN curves. A digital image processing technique was also utilized to monitor crack growth from in situ images of the side of the specimen. Linear elastic fracture mechanics and finite elements were used to determine energy release rate and mode-mix as a function of crack length for this specimen. Experiments were conducted in air and in a salt water bath at 10, 26 and 90°C. Joints tested in the solvent were fully saturated. In air, both increasing and decreasing temperature relative to 26°C accelerated crack growth rates. In salt water, crack growth rates increased with increasing temperature. Threshold energy release rate is shown to be the most appropriate design criteria for joints of this system. In addition, path of the crack is discussed and fracture surfaces are examined on three length scales. Three linear viscoelastic properties were measured for the neat urethane adhesive. Dynamic tensile compliance (D*) was found using a novel extensometer and results were considerably more accurate and precise than standard DMTA testing. Dynamic shear compliance (J*) was determined using an Arcan specimen. Dynamic Poisson's ratio (nu*) was extracted from strain gage data analyzed to include gage reinforcement. Experiments spanned three frequency decades and isothermal data was shifted by time-temperature superposition to create master curves spanning thirty decades. Master curves were fit to time domain Prony series. Shear compliance inferred from D* and nu* compared well with measured J*, forming a basis for finding the complete time dependent material property matrix for this isotropic material. A constitutive model is introduced which replaces time with internal energy in time-temperature superposition. Internal energy for mechanical loading was calculated from stress history and time domain Prony series representation of compliance. The model also included pressure and volume effects. Ramp loading experiments conducted at strain rates spanning three decades were effectively predicted, but unloading predictions were poor.

Tribological evaluation of biomedical polycarbonate urethanes against articular cartilage.

PubMed

Kanca, Yusuf; Milner, Piers; Dini, Daniele; Amis, Andrew A

2018-06-01

This research investigated the in-vitro wear and friction performance of polycarbonate urethane (PCU) 80A as they interact with articular cartilage, using a customised multidirectional pin-on-plate tester. Condyles were articulated against PCU 80A discs (Bionate ® I and Bionate ® II) (configuration 1) and the results arising from these tests were compared to those recorded during the sliding of PCU pins against cartilage plates (configuration 2). Configuration 1 produced steadily increasing coefficient of friction (COF) (up to 0.64 ± 0.05) and had the same trend as the cartilage-on-stainless steel articulation (positive control). When synovial fluid rather than bovine calf serum was used as lubricant, average COF significantly decreased from 0.50 ± 0.02-0.38 ± 0.06 for condyle-on-Bionate ® I (80AI) and from 0.41 ± 0.02-0.24 ± 0.04 for condyle-on-Bionate ® II (80AII) test configurations (p < 0.05). After 15 h testing, the cartilage-on-cartilage articulation (negative control) tests showed no cartilage degeneration. However, different levels of cartilage volume loss were found on the condyles from the positive control (12.5 ± 4.2 mm 3 ) and the PCUs (20.1 ± 3.6 mm 3 for 80 AI and 19.0 ± 2.3 mm 3 for 80AII) (p > 0.05). A good correlation (R 2 =0.84) was found between the levels of average COF and the volume of cartilage lost during testing; increasing wear was found at higher levels of COF. Configuration 2 showed low and constant COF values (0.04 ± 0.01), which were closer to the negative control (0.03 ± 0.01) and significantly lower than configuration 1 (p < 0.05). The investigation showed that PCU is a good candidate for use in hemiarthroplasty components, where only one of the two articulating surfaces is replaced, as long as the synthetic material is implanted in a region where migrating cartilage contact is achieved. Bionate ® II showed better tribological performance, which suggests it is more favourable for use in hemiarthroplasty design. Copyright © 2018 Elsevier Ltd. All rights reserved.

Contact Mechanics and Failure Modes of Compliant Polymeric Bearing Materials for Knee Cartilage Replacement

NASA Astrophysics Data System (ADS)

Tohfafarosh, Mariya Shabbir

Osteoarthritis (OA) is the most common cause of disability affecting millions of people worldwide. Total knee replacement is the current state-of-the-art treatment to alleviate pain and improve mobility among patients in the late stage of knee OA. The current gold standard materials for total knee arthroplasty are cobalt-chromium and ultra-high molecular weight polyethylene (UHMWPE). However, wear debris and implant loosening-related revision persists; consequently, total knee replacements are not universally recommended for all patient subgroups with OA. This work explores the potential of using compliant polymeric materials in knee cartilage replacement devices, which are closer in lubrication and mechanical properties of articular cartilage, to prevent excessive removal of underlying bone and prolong the need for a total knee replacement. Two materials investigated in this thesis are polycarbonate urethane, Bionate 80A, and a novel hydrogel, Cyborgel, both of which have shown promising wear and lubrication properties under physiological loads. Polycarbonate urethane has been previously tested for the effects of gamma sterilization and has shown no significant changes in its mechanical strength or chemical bonds. Since an important aspect of medical device development is the sterilization process, this thesis first evaluated the effect of 30-35 kGy electron beam and gamma radiation on the polymer swell ratio, and the mechanical, chemical and tribological behavior of the novel hydrogel. Three different formulations were mechanically tested, and biphasic material properties were identified using finite element analysis. Fourier transform infrared spectroscopy was used to investigate chemical changes, while the wear properties were tested for 2 million cycles in bovine serum. The results showed no significant difference (p > 0.05) in the swell ratio, mechanical and tribological properties of the electron beam and gamma sterilized hydrogel sample as compared to the control samples. However, chemical spectra of electron beam sterilized samples revealed minor changes, which were absent in unsterilized and gamma sterilized samples. Upon successful sterilization evaluation, both polycarbonate urethane and the novel hydrogel were investigated for the contact mechanics of compliant-on-compliant artificial knee bearings using a finite element analysis approach. A simplified, axisymmetric, finite element model of a medial knee compartment was developed and validated, and a design of simulation experiments was carried out to evaluate the effect of implant conformity, implant thickness and material properties on the contact mechanics of compliant knee bearings under normal walking and stair climbing loads. All input parameters, namely, implant conformity, implant thickness and material properties, significantly (p<0.001) affected the maximum principal stress, Von Mises stress, maximum shear stress, maximum principal strain, maximum contact pressure and contact area. The knee implant contact mechanics demonstrated sensitivity to all the three design factors, and a correlation between resulting stresses and implant conformity as well as thickness was observed. However, the conformity had the highest effect-size on the contact mechanics. The maximum principal stress value halves and the contact area doubles when ≥ 95% implant conformity (i.e. the ratio of femoral to tibial surface’s radii of curvature) and ≥ 3mm thickness was used, hence, these parameters were recommended for the design of compliant knee bearings. Finally, a battery of mechanical tests was carried out to evaluate the failure criteria of the proposed compliant polymers under physiological loads and strain rates. Uniaxial tests, including tension and unconfined compression, and biaxial tests, such as plane strain compression, were carried out to characterize the mechanical behavior of different material formulations at physiologically relevant testing rates. The materials failed under tension between 250 - 750% true strain, while those under uniaxial and biaxial compression test sustained compression of 50 - 70% engineering strain (39 - 53% true strain) without any signs of cracking or fracture. The tension was determined to be the primary failure mode for the proposed materials, and the tensile test was used to define the failure criteria of the materials. The unconfined compression tests were used to define the yield stresses and strains under compression, which is the main mode of loading for the knee joint. The results of the plane strain compression were modeled using a finite element model and the maximum principal stress, von Mises stress, maximum shear stress, and maximum principal strain failure criteria were predicted at the corresponding yield strain of each material formulation. Upon comparing the knee model contact stress and strain prediction under normal walking and stair climbing loads with those of the empirical failure criteria at yield, the polycarbonate urethane showed better overall potential for use in compliant knee implants, while the hydrogels exhibited higher potential for delamination or fracture, especially if appropriate implant conformity and thickness are not employed. The outcome of this study and the previous parametric model results helped to determine a niche design space within which designing a knee implant with compliant bearing materials may be feasible. In summary, the potential of compliant bearing materials was thoroughly examined in this thesis, and the results provided a foundation for future testing and development of a compliant cartilage replacement implant. Such an implant would be a promising improvement and alternative to conventional total knee replacements.

Atmospheric Concentrations of Persistent Organic Pollutants in the Southern Ocean

NASA Astrophysics Data System (ADS)

Vlahos, P.; Edson, J.; Cifuentes, A.; McGillis, W. R.; Zappa, C.

2008-12-01

Long-range transport of persistent organic pollutant (POPs) is a global concern. Remote regions such as the Southern Ocean are greatly under-sampled though critical components in understanding POPs cycling. Over 20 high-volume air samples were collected in the Southern Ocean aboard the RV Brown during the GASEX III experiment between Mar 05 to April 9 2008. The relatively stationary platform (51S,38W) enabled the collection of a unique atmospheric time series at this open ocean station. Air sampling was also conducted across transects from Punto Arenas, Chile and to Montevideo, Uruguay. Samples were collected using glass sleeves packed with poly-urethane foam plugs and C-18 resin in order to collect target organic pollutants (per-fluorinated compounds, currently and historically used pesticides) in this under-sampled region. Here we present POPs concentrations and trends over the sampled period and compare variations with air parcel back trajectories to establish potential origins of their long-range transport.

A centrifuge CO2 pellet cleaning system

NASA Technical Reports Server (NTRS)

Foster, C. A.; Fisher, P. W.; Nelson, W. D.; Schechter, D. E.

1995-01-01

An advanced turbine/CO2 pellet accelerator is being evaluated as a depaint technology at Oak Ridge National Laboratory (ORNL). The program, sponsored by Warner Robins Air Logistics Center (ALC), Robins Air Force Base, Georgia, has developed a robot-compatible apparatus that efficiently accelerates pellets of dry ice with a high-speed rotating wheel. In comparison to the more conventional compressed air 'sandblast' pellet accelerators, the turbine system can achieve higher pellet speeds, has precise speed control, and is more than ten times as efficient. A preliminary study of the apparatus as a depaint technology has been undertaken. Depaint rates of military epoxy/urethane paint systems on 2024 and 7075 aluminum panels as a function of pellet speed and throughput have been measured. In addition, methods of enhancing the strip rate by combining infra-red heat lamps with pellet blasting and by combining the use of environmentally benign solvents with the pellet blasting have also been studied. The design and operation of the apparatus will be discussed along with data obtained from the depaint studies.

Thermal properties of poly(urethane-ester-siloxane)s based on hyperbranched polyester

NASA Astrophysics Data System (ADS)

Pergal, M. V.; Džunuzović, J. V.; Kićanović, M.; Vodnik, V.; Pergal, M. M.; Jovanović, S.

2011-12-01

Novel polyurethanes (PUs) were synthesized using hydroxy-terminated hyperbranched polyester (BH-20) and 4,4'-methylenediphenyl diisocyanate (MDI) as hard segments and hydroxy-terminated ethylene oxide-poly(dimethylsiloxane)-ethylene oxide triblock copolymer (PDMS-EO) as soft segment, with soft segment content ranging from 30 to 60 wt %. The PUs were synthesized by two-step solution polymerization method. The influence of the soft segment content on the structure, swelling behavior and thermal properties of PUs was investigated. According to the results obtained by swelling measurements, the increase of the hard segment content resulted in the increase of the crosslinking density of synthesized samples. DSC results showed that the glass transition temperatures increase from 36 to 65°C with increasing hard segment content. It was demonstrated using thermogravimetric analysis (TGA) that thermal stability of investigated PUs increases with increase of the soft PDMS-EO content. This was concluded from the temperatures corresponding to the 10 wt % loss, which represents the beginning of thermal degradation of samples.

THE QUESTION "RECOVERY SPEED OR RESISTANCE INCREASE" OF THE X-IRRADIATED SKIN OF FROGS (RANA ESCULENTA) IN SMALL FRACTIONATION (in German)

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

Amoroso, C.; Lorenz, W.

1959-01-01

Sixty-one frogs (Rana esculenta) were irradiated in urethan anesthesia. The right upper leg was irradiated with a surface dose of 12,000 r. The left upper legs of the same animals were irradiated subsequently with a surface dose of 2 times 6000 r, respectively 3 times 4000 r at intervals of 1, 3, 6, 24, or 72 hours. The single irradiation of 12,000 r caused changes of the pigentation and formation of ulcers after 3 weeks. After 8 weeks 35 out of 61 animals had formation of ulcers. The first tendency for healing was observed after 10 weeks. By the usemore » of divided doses of 3 times 4000 r or 2 tirees 6000 r, with intervals as short as one hour, the effect of the irradiation caused less damage, probably due to increased resistence, which may have developed during the intervals between irradiations. (auth)« less

Effect of basal forebrain stimulation on extracellular acetylcholine release and blood flow in the olfactory bulb.

PubMed

Uchida, Sae; Kagitani, Fusako

2017-05-12

The olfactory bulb receives cholinergic basal forebrain input, as does the neocortex; however, the in vivo physiological functions regarding the release of extracellular acetylcholine and regulation of regional blood flow in the olfactory bulb are unclear. We used in vivo microdialysis to measure the extracellular acetylcholine levels in the olfactory bulb of urethane-anesthetized rats. Focal chemical stimulation by microinjection of L-glutamate into the horizontal limb of the diagonal band of Broca (HDB) in the basal forebrain, which is the main source of cholinergic input to the olfactory bulb, increased extracellular acetylcholine release in the ipsilateral olfactory bulb. When the regional cerebral blood flow was measured using laser speckle contrast imaging, the focal chemical stimulation of the HDB did not significantly alter the blood flow in the olfactory bulb, while increases were observed in the neocortex. Our results suggest a functional difference between the olfactory bulb and neocortex regarding cerebral blood flow regulation through the release of acetylcholine by cholinergic basal forebrain input.

Tooling Foam for Structural Composite Applications

NASA Technical Reports Server (NTRS)

DeLay, Tom; Smith, Brett H.; Ely, Kevin; MacArthur, Doug

1998-01-01

Tooling technology applications for composite structures fabrication have been expanded at MSFC's Productivity Enhancement Complex (PEC). Engineers from NASA/MSFC and Lockheed Martin Corporation have developed a tooling foam for use in composite materials processing and manufacturing that exhibits superior thermal and mechanical properties in comparison with other tooling foam materials. This tooling foam is also compatible with most preimpregnated composite resins such as epoxy, bismaleimide, phenolic and their associated cure cycles. MARCORE tooling foam has excellent processability for applications requiring either integral or removable tooling. It can also be tailored to meet the requirements for composite processing of parts with unlimited cross sectional area. A shelf life of at least six months is easily maintained when components are stored between 50F - 70F. The MARCORE tooling foam system is a two component urethane-modified polyisocyanurate, high density rigid foam with zero ozone depletion potential. This readily machineable, lightweight tooling foam is ideal for composite structures fabrication and is dimensionally stable at temperatures up to 350F and pressures of 100 psi.

Effect of ultraviolet light irradiation period on bond strengths between fiber-reinforced composite post and core build-up composite resin.

PubMed

Asakawa, Yuya; Takahashi, Hidekazu; Iwasaki, Naohiko; Kobayashi, Masahiro

2014-01-01

The aim of the present study was to characterize the effects of the ultraviolet light (UV) irradiation period on the bond strength of fiber-reinforced composite (FRC) posts to core build-up resin. Three types of FRC posts were prepared using polymethyl methacrylate, urethane dimethacrylate, and epoxy resin. The surfaces of these posts were treated using UV irradiation at a distance of 15 mm for 0 to 600 s. The pull-out bond strength was measured and analyzed with the Dunnett's comparison test (α=0.05). The bond strengths of the post surfaces without irradiation were 6.9 to 7.4 MPa; those after irradiation were 4.2 to 26.1 MPa. The bond strengths significantly increased after 15 to 120-s irradiation. UV irradiation on the FRC posts improved the bond strengths between the FRC posts and core build-up resin regardless of the type of matrix resin.

Objective evaluation of insert material for diabetic and athletic footwear.

PubMed

Brodsky, J W; Kourosh, S; Stills, M; Mooney, V

1988-12-01

Five of the most commonly used materials for shoe inserts (soft Plastazote, medium Pelite, PPT, Spenco, and Sorbothane) were objectively evaluated in the laboratory to characterize their behavior in the following three specific functions that correspond to clinical use: (1) the effect on the materials of repeated compression. (2) the effect of a combination of repetitive shear and compression. (3) the force-distribution (force-attenuation) properties of these materials, both when new and after repeated compression. The last function represents a model for relief of pressure beneath plantar bony prominences, a topic of special concern for the insensitive foot. All materials were effective in reducing transmitted force over the simulated bony prominence with a rank order of effectiveness. Other factors considered were: amount and rate of permanent deformation offset by considerations of enhanced moldability when comparing the neoprene and urethane materials with the polyethylene foams. The ideal insert represents a combination of material to achieve both durability and moldability.

Site-Selective Modification of Cellulose Nanocrystals with Isophorone Diisocyanate and Formation of Polyurethane-CNC Composites.

PubMed

Girouard, Natalie M; Xu, Shanhong; Schueneman, Gregory T; Shofner, Meisha L; Meredith, J Carson

2016-01-20

The unequal reactivity of the two isocyanate groups in an isophorone diisocyante (IPDI) monomer was exploited to yield modified cellulose nanocrystals (CNCs) with both urethane and isocyanate functionality. The chemical functionality of the modified CNCs was verified with ATR-FTIR analysis and elemental analysis. The selectivity for the secondary isocyanate group using dibutyl tin dilaurate (DBTDL) as the reaction catalyst was confirmed with (13)C NMR. The modified CNCs showed improvements in the onset of thermal degradation by 35 °C compared to the unmodified CNCs. Polyurethane composites based on IPDI and a trifunctional polyether alcohol were synthesized using unmodified (um-CNC) and modified CNCs (m-CNC). The degree of nanoparticle dispersion was qualitatively assessed with polarized optical microscopy. It was found that the modification step facilitated superior nanoparticle dispersion compared to the um-CNCs, which resulted in increases in the tensile strength and work of fracture of over 200% compared to the neat matrix without degradation of elongation at break.

Effect of amphiphilic polyurethane nanoparticles on sorption-desorption of phenanthrene in aquifer material.

PubMed

Kim, Ju-Young; Shim, Sun-Bo; Shim, Jin-Kie

2003-03-17

Micelle-like amphiphilic nano-sized polyurethane (APU) nanoparticles were synthesized via chemical cross-linking reaction of nano-aggregates of urethane acrylate nonionomer (UAN) chain and were tested for extraction efficiency of sorbed phenanthrene from aquifer material. Even though the solubilizing performance and interfacial activity of APU nanoparticles were inferior to that of Triton X-100, in the low concentration region, APU nanoparticles could effectively reduce phenanthrene sorption on the aquifer material and extracted sorbed phenanthrene from the aquifer material, whereas Triton X-100 could not extract sorbed phenanthrene and rather increased phenanthrene sorption onto the aquifer materials. At higher concentrations, APU nanoparticles and Triton X-100 had almost the same soil washing effectiveness. This interesting result is mainly due to a lower degree of sorption of APU nanoparticles onto the aquifer material. The sorption of APU nanoparticles onto aquifer sand is largely hindered by their chemically cross-linked nature, resulting in better soil-washing performance of APU nanoparticles than Triton X-100. Copyright 2003 Elsevier Science B.V.

Suprachiasmatic nuclei and Circadian rhythms. The role of suprachiasmatic nuclei on rhythmic activity of neurons in the lateral hypothalamic area, ventromedian nuclei and pineal gland

NASA Technical Reports Server (NTRS)

Nishino, H.

1977-01-01

Unit activity of lateral hypothalamic area (LHA) and Ventromedian nuclei (VMN) was recorded in urethane anesthetized male rats. A 5 to 10 sec. a 3-5 min and a circadian rhythmicity were observed. In about 15% of all neurons, spontaneous activity of LHA and VMN showed reciprocal relationships. Subthreshold stimuli applied at a slow rate in the septum and the suprachiasmatic nuclei (SCN) suppressed the rhythms without changing firing rates. On the other hand, stimulation of the optic nerve at a rate of 5 to 10/sec increased firing rates in 1/3 of neurons of SCN. Iontophoretically applied acetylcholine increased 80% of tested neurons of SCN, whereas norepinephrine, dopamine and 5 HT inhibited 64, 60 and 75% of SCN neurons respectively. These inhibitions were much stronger in neurons, the activity of which was increased by optic nerve stimulation. Stimulation of the SCN inhibited the tonic activity in cervical sympathetic nerves.

Use of a simplified method of optical recording to identify foci of maximal neuron activity in the somatosensory cortex of white rats.

PubMed

Inyushin, M Y; Volnova, A B; Lenkov, D N

2001-01-01

Eight mongrel white male rats were studied under urethane anesthesia, and neuron activity evoked by mechanical and/or electrical stimulation of the contralateral whiskers was recorded in the primary somatosensory cortex. Recordings were made using a digital USB chamber attached to the printer port of a Pentium 200MMX computer running standard programs. Optical images were obtained in the barrel-field zone using a differential signal, i.e., the difference signal for cortex images in control and experimental animals. The results obtained here showed that subtraction of averaged sequences of frames yielded images consisting of spots reflecting the probable position of activated groups of neurons. The most effective stimulation consisted of natural low-frequency stimulation of the whiskers. The method can be used for preliminary mapping of cortical zones, as it provides for rapid and reproducible testing of the activity of neuron ensembles over large areas of the cortex.

AKT1E¹⁷K Is Oncogenic in Mouse Lung and Cooperates with Chemical Carcinogens in Inducing Lung Cancer.

PubMed

Malanga, Donatella; Belmonte, Stefania; Colelli, Fabiana; Scarfò, Marzia; De Marco, Carmela; Oliveira, Duarte Mendes; Mirante, Teresa; Camastra, Caterina; Gagliardi, Monica; Rizzuto, Antonia; Mignogna, Chiara; Paciello, Orlando; Papparella, Serenella; Fagman, Henrik; Viglietto, Giuseppe

2016-01-01

The hotspot AKT1E17K mutation in the pleckstrin homology domain of AKT1 occurs in approximately 0.6-2% of human lung cancers. Recently, we have demonstrated that AKT1E17K transforms immortalized human bronchial cells. Here by use of a transgenic Cre-inducible murine strain in the wild type Rosa26 (R26) locus (R26-AKT1E17K mice) we demonstrate that AKT1E17K is a bona-fide oncogene and plays a role in the development of lung cancer in vivo. In fact, we report that mutant AKT1E17K induces bronchial and/or bronchiolar hyperplastic lesions in murine lung epithelium, which progress to frank carcinoma at very low frequency, and accelerates tumor formation induced by chemical carcinogens. In conclusion, AKT1E17K induces hyperplasia of mouse lung epithelium in vivo and cooperates with urethane to induce the fully malignant phenotype.

Characteristics of low polymerization shrinkage flowable resin composites in newly-developed cavity base materials for bulk filling technique.

PubMed

Nitta, Keiko; Nomoto, Rie; Tsubota, Yuji; Tsuchikawa, Masuji; Hayakawa, Tohru

2017-11-29

The purpose of this study was to evaluate polymerization shrinkage and other physical properties of newly-developed cavity base materials for bulk filling technique, with the brand name BULK BASE (BBS). Polymerization shrinkage was measured according to ISO/FDIS 17304. BBS showed the significantly lowest polymerization shrinkage and significantly higher depth of cure than conventional flowable resin composites (p<0.05). The Knoop hardness, flexural strength and elastic modulus of that were significantly lower than conventional flowable resin composites (p<0.05). BBS had the significantly greatest filler content (p<0.05). SEM images of the surface showed failure of fillers. The lowest polymerization shrinkage was due to the incorporation of a new type of low shrinkage monomer, which has urethane moieties. There were no clear correlations between inorganic filler contents and polymerization shrinkage, flexural strength and elastic modulus. In conclusion, the low polymerization shrinkage of BBS will be useful for cavity treatment in dental clinics.

Investigation of kinetics and morphology development for polyurethane-urea extended by DMTDA

NASA Astrophysics Data System (ADS)

Li, Zai-feng; Li, Jin-yan; Sun, Jian; Sun, Bao-qun; Wang, Jin-jing; Shen, Qiang

2008-06-01

The relationship between the reactions kinetics and morphology development during the polyurethaneurea (PUU) curing process has been investigated simultaneously by in situ Fourier transform infrared spectroscopy (FTIR). The data of the FTIR spectra showed that with the increase of conversion, the absorbance of NH bands increases and its band sites shifts to lower wavenumbers; the absorbance of free urethane carbonyl kept nearly constant at low conversion, and then decreased much because of the interaction of the formed urea links, and then changed little at high conversion owing to the diffuse control. The band sites of hydrogen bonded urea carbonyl similarly shifted to lower wavenumbers and the absorbance of the hydrogen bonded urea carbonyl, associated with the phase separation of hard segments, became stronger with buildup of hydrogen bond between urea links. The carbonyl bands available during curing process were further assigned. Both interactions, such as hydrogenised effect and phase separation, played a major role in the matrix formation of the PUU polymer.

Infrared microspectroscopic study of the thermo-oxidative degradation of hydroxy-terminated polybutadiene/isophorone diisocyanate polyurethane rubber

DOE PAGES

Nagle, Dylan J.; Celina, Mathew; Rintoul, Llewellyn; ...

2007-05-21

In this work, hydroxy-terminated polybutadiene/isophorone diisocyanate (HTPB/IPDI) polyurethane rubber which was aged in air at elevated temperatures has been studied by infrared microspectroscopy. Spectra were collected in transmission mode on microtomed samples. Analysis of sets of spectra taken across the sectioned material showed that most of the degradation occurred in the polybutadiene part of the polymer and that the urethane linkage was essentially unchanged. The trans isomer of the polybutadiene appears to be preferentially degraded compared with the vinyl isomer. The IR technique does not provide significant information about the cis isomer. The IR spectra indicated that likely degradation productsmore » included acids, esters, alcohols, and small amounts of other products containing a carbonyl functional group. Band area ratios, supported by a principal components analysis, were used to derive degradation profiles for the material. Lastly, these profiles were steep-sided indicating an oxygen diffusion limited process.« less

Acetazolamide on the ventral medulla of the cat increases phrenic output and delays the ventilatory response to CO2.

PubMed Central

Coates, E L; Li, A H; Nattie, E E

1991-01-01

1. Acetazolamide (0.1 mM) applied to the surface of the rostral ventrolateral medulla or microinjected beneath the medullary surface in chloralose-urethane-anaesthetized, vagotomized, carotid-denervated, paralysed, servo-ventilated cats produced a long-lasting increase in integrated phrenic nerve activity. 2. Extracellular pH measured beneath the rostral ventrolateral medulla exhibited a long-lasting decrease after surface acetazolamide but was not a good predictor, in each individual animal, of changes in phrenic activity. 3. Medullary carbonic anhydrase inhibition reduced the slope and the half-time of the phrenic response to rapid step CO2 increases. Conversely, acetazolamide did not affect the phrenic response to steady-state CO2 increases. 4. These data indicate that localized inhibition of medullary carbonic anhydrase causes a centrally mediated increase in ventilation that we attribute to medullary tissue hypercapnia and acidosis. In addition, these data indicate that medullary carbonic anhydrase may play a role in central CO2 chemotransduction. Images Fig. 8 PMID:1816381

Facile preparation of mussel-inspired polyurethane hydrogel and its rapid curing behavior.

PubMed

Sun, Peiyu; Wang, Jing; Yao, Xiong; Peng, Ying; Tu, Xiaoxiong; Du, Pengfei; Zheng, Zhen; Wang, Xinling

2014-08-13

A facile method was found to incorporate a mussel-inspired adhesive moiety into synthetic polymers, and mussel mimetic polyurethanes were developed as adhesive hydrogels. In these polymers, a urethane backbone was substituted for the polyamide chain of mussel adhesive proteins, and dopamine was appended to mimic the adhesive moiety of adhesive proteins. A series of mussel mimetic polyurethanes were created through a step-growth polymerization based on hexamethylene diisocyanate as a hard segment, PEG having different molecular weights as a soft segment, and lysine-dopamine as a chain extender. Upon a treatment with Fe(3+), the aqueous mussel mimetic polyurethane solutions can be triggered by pH adjustment to form adhesive hydrogels instantaneously; these materials can be used as injectable adhesive hydrogels. Upon a treatment with NaIO4, the mussel mimetic polyurethane solutions can be cured in a controllable period of time. The successful combination of the unique mussel-inspired adhesive moiety with a tunable polyurethane structure can result in a new kind of mussel-inspired adhesive polymers.

Characterization of drug-eluting stent (DES) materials with cluster secondary ion mass spectrometry (SIMS)

NASA Astrophysics Data System (ADS)

Mahoney, Christine M.; Patwardhan, Dinesh V.; Ken McDermott, M.

2006-07-01

Secondary ion mass spectrometry (SIMS) employing an SF 5+ polyatomic primary ion source was utilized to analyze several materials commonly used in drug-eluting stents (DES). Poly(ethylene- co-vinyl acetate) (PEVA), poly(lactic- co-glycolic acid) (PLGA) and various poly(urethanes) were successfully depth profiled using SF 5+ bombardment. The resultant molecular depth profiles obtained from these polymeric films showed very little degradation in molecular signal as a function of increasing SF 5+ primary ion dose when experiments were performed at low temperatures (signal was maintained for doses up to ˜5 × 10 15 ions/cm 2). Temperature was determined to be an important parameter in both the success of the depth profiles and the mass spectral analysis of the polymers. In addition to the pristine polymer films, paclitaxel (drug released in Taxus™ stent) containing PLGA films were also characterized, where it was confirmed that both drug and polymer signals could be monitored as a function of depth at lower paclitaxel concentrations (10 wt%).

Guinea pig cochlear blood flow under definite sound exposure-hydrogen clearance measurement.

PubMed

Meyer, P; Kuhl, K D; Schmidt, R; Grützmacher, W

1991-01-01

Blood flow measurements were carried out on 18 coloured guinea pigs (8 animals served as control group) before and during definite sound exposure (12 kHz, 110 dB SPL). The exposure time amounted to 60 min. The anaesthesia was carried out according to the following schedule: a mixture consisting of 70 mg alpha-chloralose/kg b.w. and 400 mg urethane/kg b.w. was injected intraperitoneally. The relaxation was performed by means of i.p. application of 3 mg Tricuran/kg b.w./h. The hydrogen clearance measurements (HCM) were carried out under artificial respiration with control of arterial pH, endexpiratory CO2 content, as well as blood pressure and body temperature. After a duration of noise exposure of 30-45 min the cochlear blood flow reached an average level of 80% of the initial point. This level remained mainly unchanged until the end of noise exposure (60 min). Our HMC's confirm Laser Doppler flowmetry findings.

Evaluation on biocompatibility of biomedical polyurethanes with different hard segment contents

NASA Astrophysics Data System (ADS)

Ma, Dai-Wei; Zhu, Rong; Wang, Yi-Yu; Zhang, Zong-Rui; Wang, Xin-Yu

2015-12-01

In this paper, polyurethane (PU) materials with different contents of hard segment (20%, 25%, 30%) were prepared based on hexamethylene diisocyanate and polycarbonate diols by solution polymerization. The obtained polycarbonate-urethane (PCU) elastomers were characterized by very good hydrophobic property and excellent resistance to hydrolysis. Hemolysis, recalification time and platelet-rich plasma adhesion were used to evaluate the blood compatibility of the materials. L929 cells cultured with leach liquor of these PU membranes were selected to perform the cytotoxicity experiments. The results indicate that the hemolysis rates of PU membranes are all less than 5%, which can meet the requirement of the national standards for biomaterials. However, compared with 20% and 30% groups, the recalification time of the sample containing 25% hard segment is longer, while the number of platelet adhesion is less. Additionally, cells cultured in the leach liquor of PU membranes with 25% hard segment proliferated relatively more thriving, meaning that this proportion of the material has the lowest cytotoxicity.

Deformation and flexural properties of denture base polymer reinforced with glass fiber sheet.

PubMed

Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2005-09-01

The purpose of this study was to investigate the deformation and flexural properties of acrylic and urethane polymers reinforced with glass fiber sheet. Four types of specimen--self-curing resin plate (R), light-curing oligomer plate containing a reinforcement (GO), and self-curing resin plate containing a reinforcement on one (GR) or both (GRG) sides--were prepared with three thicknesses: 1.5, 2.4, and 3.0 mm. Gaps between polymerized test specimen and a standard metal plate were measured at the corner (C), middle of the long sides (LS), and middle of the short sides (SS). The gaps for R were 0-2.0 microm. GO and GR markedly deformed at Points C, LS, and SS, and the degree of deformation increased as GO became thinner. Flexural strength was significantly increased by the reinforcement (p < 0.05). The flexural moduli of 3.0-mm thick R, GO, and GR were significantly smaller than that of 1.5-mm thick specimens.

Respiratory pattern changes during costovertebral joint movement.

PubMed

Shannon, R

1980-05-01

Experiments were conducted to determine if costovertebral joint manipulation (CVJM) could influence the respiratory pattern. Phrenic efferent activity (PA) was monitored in dogs that were anesthetized with Dial-urethane, vagotomized, paralyzed, and artificially ventilated. Ribs 6-10 (bilaterally) were cut and separated from ribs 5-11. Branches of thoracic nerves 5-11 were cut, leaving only the joint nerve supply intact. Manual joint movement in an inspiratory or expiratory direction had an inhibitory effect on PA. Sustained displacement of the ribs could inhibit PA for a duration equal to numerous respiratory cycles. CVJM in synchrony with PA resulted in an increased respiratory rate. The inspiratory inhibitory effect of joint receptor stimulation was elicited with manual chest compression in vagotomized spontaneously breathing dogs, but not with artificial lung inflation or deflation. It is concluded that the effect of CVJM on the respiratory pattern is due to stimulation of joint mechanoreceptors, and that they exert their influence in part via the medullary-pontine rhythm generator.

Development of ultraviolet rigidizable materials. [expandable space erectable structures

NASA Technical Reports Server (NTRS)

Salisbury, D. P.

1979-01-01

A series of tests was performed to determine an optimum resin to be used as a UV rigidizable matrix in expandable rigidizable space structures. Commercially available resins including several types of polyesters, epoxies, epoxy-acrylics, an acrylic and a urethane were used as well as a polyester, produced by 3M Company's Solar Laboratory facility, which was found the best from the standpoint of physical properties and ability to be 'B' staged. Two other synthesized materials were also tested, but were not found to be superior to the Solar resin. An optimum fabric for use with the preferred resin was not found; however, the 15 ounce fabric from Solar Laboratories has the best combination of physical properties with respect to handling and processing characteristics. Expansion techniques for tubular structures, 'B' staging of the solar resin, and stowage techniques for up to 5 months were developed. A one meter high tetrahedron preprototype structure was prepared to evaluate and demonstrate stowage, deployment, and rigidization techniques.

Maleate/vinyl ether UV-cured coatings: Effects of composition on curing and properties

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

Noren, G.K.

1996-10-01

The effect of the composition of the maleate polyester and the vinyl ether terminated compound on their UV-curing and properties has been investigated. Linear unsaturated polyester resins based on maleic anhydride and 1,5-pentane diol were synthesized. The molecular weight of the unsaturated polyesters was varied by changing the ratio of maleic anhydride to 1,5-pentane diol and the double bond equivalent weight was varied by replacing maleic anhydride with succinic anhydride. Coating formulations containing these unsaturated polyesters, triethylene glycol divinyl ether and a free radical photoinitiator were crosslinked in the presence of UV light. The coatings were very brittle, exhibiting tensilemore » strengths in the range of 1.5-4.0 MPa and elongations of only 3-7%. Diethyl maleate and isobutyl vinyl ether were effective diluents for reducing viscosity but reduced the cure speed. A vinyl ether urethane oligomer was synthesized and enhanced the flexibility and toughness of the coatings when substituted for triethylene glycol divinyl ether.« less

AKT1E17K Is Oncogenic in Mouse Lung and Cooperates with Chemical Carcinogens in Inducing Lung Cancer

PubMed Central

Malanga, Donatella; Belmonte, Stefania; Colelli, Fabiana; Scarfò, Marzia; De Marco, Carmela; Oliveira, Duarte Mendes; Mirante, Teresa; Camastra, Caterina; Gagliardi, Monica; Rizzuto, Antonia; Mignogna, Chiara; Paciello, Orlando; Papparella, Serenella; Fagman, Henrik; Viglietto, Giuseppe

2016-01-01

The hotspot AKT1E17K mutation in the pleckstrin homology domain of AKT1 occurs in approximately 0.6–2% of human lung cancers. Recently, we have demonstrated that AKT1E17K transforms immortalized human bronchial cells. Here by use of a transgenic Cre-inducible murine strain in the wild type Rosa26 (R26) locus (R26-AKT1E17K mice) we demonstrate that AKT1E17K is a bona-fide oncogene and plays a role in the development of lung cancer in vivo. In fact, we report that mutant AKT1E17K induces bronchial and/or bronchiolar hyperplastic lesions in murine lung epithelium, which progress to frank carcinoma at very low frequency, and accelerates tumor formation induced by chemical carcinogens. In conclusion, AKT1E17K induces hyperplasia of mouse lung epithelium in vivo and cooperates with urethane to induce the fully malignant phenotype. PMID:26859676

Effects of morphine, physostigmine and raphe nuclei stimulation on 5-hydroxytryptamine release from the cerebral cortex of the cat.

PubMed Central

Aiello-Malmberg, P; Bartolini, A; Bartolini, R; Galli, A

1979-01-01

1. The release of 5-hydroxytryptamine (5-HT) from the cerebral cortex and caudate nucleus of brainstem-transected cats and from the cerebral cortex of rats anaesthetized with urethane was determined by radioenzymatic and biological assay. 2. The stimulation of nucleus linearis intermedius of raphe doubles the basal 5-HT release in the caudate nucleus and increases it 3 fold in the cerebral cortex. The effects of the electrical stimulation of the raphe are potentiated by chlorimipramine. 3. Brain 5-HT release is greatly increased by morphine hydrochloride (6 mg/kg i.v.) and by physostigmine (100 microgram/kg i.v.), but not by DL-DOPA (50 mg/kg i.v.). 4. It is suggested that the 5-HT releasing action of physostigmine can contribute to some of its pharmacological effects such as the analgesic effect so far attributed exclusively to its indirect cholinomimetic activity. 5. The 5-HT releasing action of physostigmine seems unrelated to its anticholinesterase activity. PMID:435680

Motorcycle helmets: What about their coating?

PubMed

Schnegg, Michaël; Massonnet, Geneviève; Gueissaz, Line

2015-07-01

In traffic accidents involving motorcycles, paint traces can be transferred from the rider's helmet or smeared onto its surface. These traces are usually in the form of chips or smears and are frequently collected for comparison purposes. This research investigates the physical and chemical characteristics of the coatings found on motorcycles helmets. An evaluation of the similarities between helmet and automotive coating systems was also performed.Twenty-seven helmet coatings from 15 different brands and 22 models were considered. One sample per helmet was collected and observed using optical microscopy. FTIR spectroscopy was then used and seven replicate measurements per layer were carried out to study the variability of each coating system (intravariability). Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were also performed on the infrared spectra of the clearcoats and basecoats of the data set. The most common systems were composed of two or three layers, consistently involving a clearcoat and basecoat. The coating systems of helmets with composite shells systematically contained a minimum of three layers. FTIR spectroscopy results showed that acrylic urethane and alkyd urethane were the most frequent binders used for clearcoats and basecoats. A high proportion of the coatings were differentiated (more than 95%) based on microscopic examinations. The chemical and physical characteristics of the coatings allowed the differentiation of all but one pair of helmets of the same brand, model and color. Chemometrics (PCA and HCA) corroborated classification based on visual comparisons of the spectra and allowed the study of the whole data set at once (i.e., all spectra of the same layer). Thus, the intravariability of each helmet and its proximity to the others (intervariability) could be more readily assessed. It was also possible to determine the most discriminative chemical variables based on the study of the PCA loadings. Chemometrics could therefore be used as a complementary decision-making tool when many spectra and replicates have to be taken into account. Similarities between automotive and helmet coating systems were highlighted, in particular with regard to automotive coating systems on plastic substrates (microscopy and FTIR). However, the primer layer of helmet coatings was shown to differ from the automotive primer. If the paint trace contains this layer, the risk of misclassification (i.e., helmet versus vehicle) is reduced. Nevertheless, a paint examiner should pay close attention to these similarities when analyzing paint traces, especially regarding smears or paint chips presenting an incomplete layer system. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The CaV2.3 R-Type Voltage-Gated Ca2+ Channel in Mouse Sleep Architecture

PubMed Central

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-01-01

Study Objectives: Voltage-gated Ca2+ channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca2+ channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca2+ channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca2+ channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3−/− mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca2+ influx into RTN neurons can trigger small-conductance Ca2+-activated K+-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca2+ channels in rodent sleep. Methods: The role of CaV2.3 Ca2+ channels was analyzed in CaV2.3−/− mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. Results: CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3−/− mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca2+ channel expression. The detailed mechanisms of SWS increase in CaV2.3−/− mice remain to be determined. Conclusions: Low-voltage activated CaV2.3 R-type Ca2+ channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future. Citation: Siwek ME, Müller R, Henseler C, Broich K, Papazoglou A, Weiergräber M. The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture. SLEEP 2014;37(5):881-892. PMID:24790266

Femtosecond laser direct-write of optofluidics in polymer-coated optical fiber

NASA Astrophysics Data System (ADS)

Joseph, Kevin A. J.; Haque, Moez; Ho, Stephen; Aitchison, J. Stewart; Herman, Peter R.

2017-03-01

Multifunctional lab in fiber technology seeks to translate the accomplishments of optofluidic, lab on chip devices into silica fibers. a robust, flexible, and ubiquitous optical communication platform that can underpin the `Internet of Things' with distributed sensors, or enable lab on chip functions deep inside our bodies. Femtosecond lasers have driven significant advances in three-dimensional processing, enabling optical circuits, microfluidics, and micro-mechanical structures to be formed around the core of the fiber. However, such processing typically requires the stripping and recoating of the polymer buffer or jacket, increasing processing time and mechanically weakening the device. This paper reports on a comprehensive assessment of laser damage in urethane-acrylate-coated fiber. The results show a sufficient processing window is available for femtosecond laser processing of the fiber without damaging the polymer jacket. The fiber core, cladding, and buffer could be simultaneously processed without removal of the buffer jacket. Three-dimensional lab in fiber devices were successfully fabricated by distortion-free immersionlens focusing, presenting fiber-cladding optical circuits and progress towards chemically-etched channels, microfluidic cavities, and MEMS structure inside buffer-coated fiber.

A strategy to synthesize graphene-incorporated lignin polymer composite materials with uniform graphene dispersion and covalently bonded interface engineering

NASA Astrophysics Data System (ADS)

Wang, Mei; Duong, Le Dai; Ma, Yifei; Sun, Yan; Hong, Sung Yong; Kim, Ye Chan; Suhr, Jonghwan; Nam, Jae-Do

2017-08-01

Graphene-incorporated polymer composites have been demonstrated to have excellent mechanical and electrical properties. In the field of graphene-incorporated composite material synthesis, there are two main obstacles: Non-uniform dispersion of graphene filler in the matrix and weak interface bonding between the graphene filler and polymer matrix. To overcome these problems, we develop an in-situ polymerization strategy to synthesize uniformly dispersed and covalently bonded graphene/lignin composites. Graphene oxide (GO) was chemically modified by 4,4'-methylene diphenyl diisocyanate (MDI) to introduce isocyanate groups and form the urethane bonds with lignin macromonomers. Subsequential polycondensation reactions of lignin groups with caprolactone and sebacoyl chloride bring about a covalent network of modified GO and lignin-based polymers. The flexible and robust lignin polycaprolactone polycondensate/modified GO (Lig-GOm) composite membranes are achieved after vacuum filtration, which have tunable hydrophilicity and electrical resistance according to the contents of GOm. This research transforms lignin from an abundant biomass into film-state composite materials, paving a new way for the utilization of biomass wastes.

3D Printing of Highly Stretchable, Shape-Memory, and Self-Healing Elastomer toward Novel 4D Printing.

PubMed

Kuang, Xiao; Chen, Kaijuan; Dunn, Conner K; Wu, Jiangtao; Li, Vincent C F; Qi, H Jerry

2018-02-28

The three-dimensional (3D) printing of flexible and stretchable materials with smart functions such as shape memory (SM) and self-healing (SH) is highly desirable for the development of future 4D printing technology for myriad applications, such as soft actuators, deployable smart medical devices, and flexible electronics. Here, we report a novel ink that can be used for the 3D printing of highly stretchable, SM, and SH elastomer via UV-light-assisted direct-ink-write printing. An ink containing urethane diacrylate and a linear semicrystalline polymer is developed for the 3D printing of a semi-interpenetrating polymer network elastomer that can be stretched by up to 600%. The 3D-printed complex structures show interesting functional properties, such as high strain SM and SM -assisted SH capability. We demonstrate that such a 3D-printed SM elastomer has the potential application for biomedical devices, such as vascular repair devices. This research paves a new way for the further development of novel 4D printing, soft robotics, and biomedical devices.

Dextran and gelatin based photocrosslinkable tissue adhesive.

PubMed

Wang, Tao; Nie, Jun; Yang, Dongzhi

2012-11-06

A two-component tissue adhesive based on biocompatible and bio-degradable polymers (oxidized urethane dextran (Dex-U-AD) and gelatin) was prepared and photocrosslinked under the ultraviolet (UV) irradiation. The adhesive could adhere to surface of gelatin, which simulated the human tissue steadily. The structures of above Dex-U-AD were characterized by FTIR, (1)H NMR spectroscopy and XRD. The adhesion property of result products was evaluated by lap-shear test. The maximum adhesion strength could reach to 4.16±0.72 MPa which was significantly higher than that of fibrin glue. The photopolymerization process of Dex-U-AD/gelatin was monitored by real time infrared spectroscopy (RTIR). It took less than 5 min to complete the curing process. The cytotoxicity of Dex-U-AD/gelatin also was evaluated which indicated that Dex-U-AD/gelatin gels were nontoxic to L929 cell. The relationship between all the above-mentioned properties and degree of oxidization of Dex-U-AD was assessed. The obtained products have the potential to serve as tissue adhesive in the future. Copyright © 2012 Elsevier Ltd. All rights reserved.

After-effects of anodal transcranial direct current stimulation on the excitability of the motor cortex in rats.

PubMed

Koo, Ho; Kim, Min Sun; Han, Sang Who; Paulus, Walter; Nitche, Michael A; Kim, Yun-Hee; Kim, Hyoung-Ihl; Ko, Sung-Hwa; Shin, Yong-Il

2016-09-21

Transcranial direct current stimulation (tDCS) is increasingly seen as a useful tool for noninvasive cortical neuromodulation. A number of studies in humans have shown that when tDCS is applied to the motor cortex it can modulate cortical excitability. It is especially interesting to note that when applied with sufficient duration and intensity, tDCS can enable long-lasting neuroplastic effects. However, the mechanism by which tDCS exerts its effects on the cortex is not fully understood. We investigated the effects of anodal tDCS under urethane anesthesia on field potentials in in vivo rats. These were measured on the skull over the right motor cortex of rats immediately after stimulating the left corpus callosum. Evoked field potentials in the motor cortex were gradually increased for more than one hour after anodal tDCS. To induce these long-lasting effects, a sufficient duration of stimulation (20 minutes or more) was found to may be required rather than high stimulation intensity. We propose that anodal tDCS with a sufficient duration of stimulation may modulate transcallosal plasticity.

Lightweight custom composite prosthetic components using an additive manufacturing-based molding technique.

PubMed

Leddy, Michael T; Belter, Joseph T; Gemmell, Kevin D; Dollar, Aaron M

2015-01-01

Additive manufacturing techniques are becoming more prominent and cost-effective as 3D printing becomes higher quality and more inexpensive. The idea of 3D printed prosthetics components promises affordable, customizable devices, but these systems currently have major shortcomings in durability and function. In this paper, we propose a fabrication method for custom composite prostheses utilizing additive manufacturing, allowing for customizability, as well the durability of professional prosthetics. The manufacturing process is completed using 3D printed molds in a multi-stage molding system, which creates a custom finger or palm with a lightweight epoxy foam core, a durable composite outer shell, and soft urethane gripping surfaces. The composite material was compared to 3D printed and aluminum materials using a three-point bending test to compare stiffness, as well as gravimetric measurements to compare weight. The composite finger demonstrates the largest stiffness with the lowest weight compared to other tested fingers, as well as having customizability and lower cost, proving to potentially be a substantial benefit to the development of upper-limb prostheses.

Bioactive glass/polymer composite materials with mechanical properties matching those of cortical bone.

PubMed

Koleganova, Veronika A; Bernier, Suzanne M; Dixon, S Jeffrey; Rizkalla, Amin S

2006-06-01

Stress shielding resulting from mismatch in dynamic mechanical properties contributes to the reduced stability of osseous implants. Our objective was to develop biocompatible composites having mechanical properties similar to those of cortical bone. Polymers of urethane dimethacrylate (UDMA) and 2-hydroxyethyl methacrylate (HEMA, 0-20%) and composites containing bioactive glass particles (70% SiO(2), 25% CaO, and 5% P(2)O(5)), with or without silane treatment were prepared. Young's moduli of composites containing silane-treated glass (16 GPa) were significantly greater than those of composites containing untreated glass (12-13 GPa) or of unfilled polymers (5-6 GPa). Bioactive glass reduced water sorption by the composites and incorporation of silane-treated glass prevented HEMA-induced increases in water sorption. Osteoblast-like cells attached equally well to UDMA polymer and composite containing silane-treated bioactive glass. Thus, silane treatment improved the mechanical properties of bioactive glass composites without compromising biocompatibility. This material has a Young's modulus comparable to that of cortical bone. Therefore, silane-treated bioactive glass composites, when used as implant or cement materials, would reduce stress shielding and improve implant stability.

Compatibility of Halthane 88-3 urethane adhesive with the replacement cleaning solvent D-Limonene

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

LeMay, J.D.; Mendoza, B.

1991-08-01

D-Limonene, (R)1-methyl-4-isopropenyl-1-cyclohexene, has been identified as a leading replacement for chlorinated solvents traditionally used to clean electrical assemblies and critical components in some phases of weapons production. Unfortunately, d-limonene has a much lower vapor pressure than the chlorinated solvents if replaces (<2 torr at ambient). This makes its complete elimination from cleaned subassemblies potentially difficult, and gives rise to concerns about the compatibility of d-limonene with materials in the warhead. During the past year many WR polymers and adhesives have been surveyed for their compatibility with d-limonene. Preliminary test results obtained at Sandia (Albuquerque) and Allied-Signal (KCD) showed that Aluminum/Halthanemore » 88-3/Aluminum joints were destroyed during exposure to saturated d-limonene vapor. The cause of bond failure appeared to be d-limonene induced swelling of the Halthane polymer. This report describes recent work performed at LLNL to study the swelling behavior and bond strength degradation of Halthane 88-3 resulting from exposure to d-limonene vapor.« less

Design and Evaluation of Glass/epoxy Composite Blade and Composite Tower Applied to Wind Turbine

NASA Astrophysics Data System (ADS)

Park, Hyunbum

2018-02-01

In the study, the analysis and manufacturing of small class wind turbine blade was performed. In the structural design, firstly the loading conditions are defined through the load case analysis. The proposed structural configuration of blade has a sandwich type composite structure with the E-glass/Epoxy face sheets and the Urethane foam core for lightness, structural stability, low manufacturing cost and easy manufacturing process. And also, this work proposes a design procedure and results of tower for the small scale wind turbine systems. Structural analysis of blade including load cases, stress, deformation, buckling, vibration and fatigue life was performed using the finite element method, the load spectrum analysis and the Miner rule. Moreover, investigation on structural safety of tower was verified through structural analysis by FEM. The manufacturing of blade and tower was performed based on structural design. In order to investigate the designed structure, the structural tests were conducted and its results were compared with the calculated results. It is confirmed that the final proposed blade and tower meet the design requirements.

FTIR and molecular mechanics studies of H-bonds in aliphatic polyurethane and polyamide-66 model molecules.

PubMed

Wang, Guoqing; Zhang, Chunxia; Guo, Xiaohe; Ren, Zhiyong

2008-02-01

Model aliphatic polyurethane (APU) hard segment based on 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) were prepared. FTIR and molecular mechanics (MM) simulation were used to conduct the systematic studies on APU and polyamide-66 (PA-66) whose sole difference lies in the alkoxyl oxygen. It was found that the introduction of the alkoxyl not only increases the conformations in APU, makes it a possible H-bond acceptor, but also weakens the H-bond between NH and O=C in APU. There are two conformers stably existed in APU with lowest energy, leading to eight H-bond complexes based on NH as donor and (1) O=C as acceptor, and another two complexes based on (2) alkoxyl O and (3) urethane N as acceptors, whereas there is only one stable conformer in PA-66, leading to one H-bond complex. One predominant H-bond complex has been found in APU with probability of about 95%. The simulated results are consistent with the nuNH and nuC=O band shifting in FTIR.

FTIR and molecular mechanics studies of H-bonds in aliphatic polyurethane and polyamide-66 model molecules

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Zhang, Chunxia; Guo, Xiaohe; Ren, Zhiyong

2008-02-01

Model aliphatic polyurethane (APU) hard segment based on 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) were prepared. FTIR and molecular mechanics (MM) simulation were used to conduct the systematic studies on APU and polyamide-66 (PA-66) whose sole difference lies in the alkoxyl oxygen. It was found that the introduction of the alkoxyl not only increases the conformations in APU, makes it a possible H-bond acceptor, but also weakens the H-bond between NH and O dbnd C in APU. There are two conformers stably existed in APU with lowest energy, leading to eight H-bond complexes based on NH as donor and (1) O dbnd C as acceptor, and another two complexes based on (2) alkoxyl O and (3) urethane N as acceptors, whereas there is only one stable conformer in PA-66, leading to one H-bond complex. One predominant H-bond complex has been found in APU with probability of about 95%. The simulated results are consistent with the νNH and νC dbnd O band shifting in FTIR.

Comparison of amphiphilic polyurethane nanoparticles to nonionic surfactants for flushing phenanthrene from soil.

PubMed

Kim, Ju-Young; Shim, Sun-Bo; Shim, Jin-Kie

2004-12-31

Amphiphilic polyurethane (APU) nanoparticles were synthesized through crosslinking polymerization of nano-aggregates of urethane acrylate nonionomer (UAN). The efficiency of in situ extraction of sorbed phenanthrene from aquifer material was tested using soil columns and compared with that of surfactants such as Triton X-100, Brij 30, and Tween 80. The extraction efficiency of those washing materials strongly depended on their concentration, flow rate, and the degree of sorption within soil column. That is, the extraction efficiency increased with the decrease of flow rate and the degree of sorption and the increase of the concentration. Even though the surfactants are superior to APU nanoparticles at solubilizing phenanthrene, at the same flow rate (0.02 mL/min) and concentration (4000 mg/L), the effectiveness of in situ soil washing of APU nanoparticles was about two times higher than those of surfactants. This is because, at the lower flow rates, the degree of sorption of APU nanoparticles was lower than that of surfactants, owing to the chemically crosslinked nature of APU nanoparticles.

Structure-Based Design of Novel HIV-1 Protease Inhibitors to Combat Drug Resistance

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

Ghosh,A.; Sridhar, P.; Leshchenko, S.

2006-01-01

Structure-based design and synthesis of novel HIV protease inhibitors are described. The inhibitors are designed specifically to interact with the backbone of HIV protease active site to combat drug resistance. Inhibitor 3 has exhibited exceedingly potent enzyme inhibitory and antiviral potency. Furthermore, this inhibitor maintains impressive potency against a wide spectrum of HIV including a variety of multi-PI-resistant clinical strains. The inhibitors incorporated a stereochemically defined 5-hexahydrocyclopenta[b]furanyl urethane as the P2-ligand into the (R)-(hydroxyethylamino)sulfonamide isostere. Optically active (3aS,5R,6aR)-5-hydroxy-hexahydrocyclopenta[b]furan was prepared by an enzymatic asymmetrization of meso-diacetate with acetyl cholinesterase, radical cyclization, and Lewis acid-catalyzed anomeric reduction as the key steps.more » A protein-ligand X-ray crystal structure of inhibitor 3-bound HIV-1 protease (1.35 Angstroms resolution) revealed extensive interactions in the HIV protease active site including strong hydrogen bonding interactions with the backbone. This design strategy may lead to novel inhibitors that can combat drug resistance.« less

Next generation brain implant coatings and nerve regeneration via novel conductive nanocomposite development.

PubMed

Antoniadou, Eleni V; Ahmad, Rezal K; Jackman, Richard B; Seifalian, Alexander M

2011-01-01

Composite materials based on the coupling of conductive organic polymers and carbon nanotubes have shown that they possess properties of the individual components with a synergistic effect. Multi-wall carbon nanotube (MWCNT)/ polymer composites are hybrid materials that combine numerous mechanical, electrical and chemical properties and thus, constitute ideal biomaterials for a wide range of regenerative medicine applications. Although, complete dispersion of CNT in a polymer matrix has rarely been achieved, in this study we have succeeded high dispersibility of CNT in POSS-PCU and POSS-PCL, novel polymers based on polyprolactone and polycarbonate polyurethane (PCU) and poly(caprolactoneurea)urethane both having incorporated polyhedral oligomeric silsesquioxane (POSS). We report the synthesis and characterization of a novel biomaterial that possesses unique properties of being electrically conducting and thus being capable of electronic interfacing with tissue. To this end, POSS-PCU/MWCNT composite can be used as a biomaterial for the development of nerve guidance channels to promote nerve regeneration and POSS-PCL/MWCNT as a substrate to increase electronic interfacing between neurons and micro-machined electrodes for potential applications in neural probes, prosthetic devices and brain implants.

Laser polymerization-based novel lift-off technique

NASA Astrophysics Data System (ADS)

Bhuian, B.; Winfield, R. J.; Crean, G. M.

2009-03-01

The fabrication of microstructures by two-photon polymerization has been widely reported as a means of directly writing three-dimensional nanoscale structures. In the majority of cases a single point serial writing technique is used to form a polymer model. Single layer writing can also be used to fabricate two-dimensional patterns and we report an extension of this capability by using two-photon polymerization to form a template that can be used as a sacrificial layer for a novel lift-off process. A Ti:sapphire laser, with wavelength 795 nm, 80 MHz repetition rate, 100 fs pulse duration and an average power of 700 mW, was used to write 2D grid patterns with pitches of 0.8 and 1.0 μm in a urethane acrylate resin that was spun on to a lift-off base layer. This was overcoated with gold and the grid lifted away to leave an array of gold islands. The optical transmission properties of the gold arrays were measured and found to be in agreement with a rigorous coupled-wave analysis simulation.

Rostral dorsolateral pontine neurons with sympathetic nerve-related activity.

PubMed

Barman, S M; Gebber, G L; Kitchens, H

1999-02-01

Spike-triggered averaging, arterial pulse-triggered analysis, and coherence analysis were used to classify rostral dorsolateral pontine (RDLP) neurons into groups whose naturally occurring discharges were correlated to only the 10-Hz rhythm (n = 29), to only the cardiac-related rhythm (n = 15), and to both rhythms (n = 15) in inferior cardiac sympathetic nerve discharge (SND) of urethan-anesthetized cats. Most of the neurons with activity correlated to only the cardiac-related rhythm were located medial to the other two groups of neurons. The firing rates of most RDLP neurons with activity correlated to only the 10-Hz rhythm (9 of 12) or both rhythms (7 of 8) were decreased during baroreceptor reflex-induced inhibition of SND produced by aortic obstruction; thus, they are presumed to be sympathoexcitatory. The firing rates of four of seven RDLP neurons with activity correlated to only the cardiac-related rhythm increased during baroreceptor reflex activation; thus, they may be sympathoinhibitory. We conclude that the RDLP contains a functionally heterogeneous population of neurons with sympathetic nerve-related activity. These neurons could not be antidromically activated by stimulation of the thoracic spinal cord.

Fabrication and characterization of a novel hydrophobic CaCO3 grafted by hydroxylated poly(vinyl chloride) chains

NASA Astrophysics Data System (ADS)

Bao, Lixia; Yang, Simei; Luo, Xin; Lei, Jingxin; Cao, Qiue; Wang, Jiliang

2015-12-01

The hydroxylated PVC (PVC-OH) was successfully synthesized by a suspension polymerization of vinyl chloride (VC), butyl acrylate (BA) and hydroxyethyl acrylate (HEA). Novel hydrophobic CaCO3 was then prepared by a urethane formation reaction between methylene diphenyl diisocyanate (MDI) and the sbnd OH groups both in the PVC-OH chains and on the surface of pristine CaCO3 particles. The effect of the PVC-OH content on the grafting ratio of treated CaCO3 particles was extensively investigated. Combining the result of Fourier transform infrared (FTIR) with that of water contact angle, it can be concluded that the hydrophobicity of CaCO3 had been efficiently improved by the PVC-OH segments grafted on the surface of CaCO3 particles. X-ray diffraction (XRD), thermal gravity analysis (TGA), scanning electron microscope (SEM) and transmission electron microscope (TEM) were also used to study crystalline behaviors, thermal stability and surface morphology of the modified CaCO3 particles, respectively. The change of specific surface area implying surface modification was investigated as well.

Simultaneous Measurement of Fluorescence, Conversion and Physical/mechanical Properties for Monitoring Bulk and Localized Photopolymerization Reactions in Heterogeneous Systems

PubMed Central

Medel, S.; Bosch, P.; Grabchev, I.; Shah, P. K.; Liu, J.; Aguirre-Soto, A.; Stansbury, J. W.

2016-01-01

An FT-NIR spectrometer, rheometer and fluorescence spectrophotometer were coupled for the real-time monitoring of polymerization reactions, allowing the simultaneous tracking of polymerization kinetics, storage modulus as well as fluorescence. In this study, a methacrylate functionalized dansyl chromophore (DANSMA) was synthesized and two different nanogels were made from urethane dimethacrylate and isobornyl methacrylate. Two series of resin formulations were prepared using the DANSMA probe, ethoxylated bisphenol A dimethacrylate as the matrix monomer, Irgacure® 651 as the initiator and the dispersed, monomer-swollen nanogels to give clear UV-curable resins. Placement of the fluorescent probe either throughout the resin or linked into the nanogel before its dispersion in the matrix provides a tool to study how the nanogel structure affects local network development by means of fluorescence from the DANSMA probe. We demonstrate the potential of this new technique using a composite as the two phase system (resin and polymerizable nanogel) including a dansyl derivative as a polymerizable probe to follow the reactions that are taking places in both phases. PMID:27213038

Chemical Kinetics of the TPS and Base Bleeding During Flight Test

NASA Technical Reports Server (NTRS)

Osipov, Viatcheslav; Ponizhovskaya, Ekaterina; Hafiychuck, Halyna; Luchinsky, Dmitry; Smelyanskiy, Vadim; Dagostino, Mark; Canabal, Francisco; Mobley, Brandon L.

2012-01-01

The present research deals with thermal degradation of polyurethane foam (PUF) during flight test. Model of thermal decomposition was developed that accounts for polyurethane kinetics parameters extracted from thermogravimetric analyses and radial heat losses to the surrounding environment. The model predicts mass loss of foam, the temperature and kinetic of release of the exhaust gases and char as function of heat and radiation loads. When PUF is heated, urethane bond break into polyol and isocyanate. In the first stage, isocyanate pyrolyses and oxidizes. As a result, the thermo-char and oil droplets (yellow smoke) are released. In the second decomposition stage, pyrolysis and oxidization of liquid polyol occur. Next, the kinetics of chemical compound release and the information about the reactions occurring in the base area are coupled to the CFD simulations of the base flow in a single first stage motor vertically stacked vehicle configuration. The CFD simulations are performed to estimate the contribution of the hot out-gassing, chemical reactions, and char oxidation to the temperature rise of the base flow. The results of simulations are compared with the flight test data.

Simultaneous recording of brain extracellular glucose, spike and local field potential in real time using an implantable microelectrode array with nano-materials

NASA Astrophysics Data System (ADS)

Wei, Wenjing; Song, Yilin; Fan, Xinyi; Zhang, Song; Wang, Li; Xu, Shengwei; Wang, Mixia; Cai, Xinxia

2016-03-01

Glucose is the main substrate for neurons in the central nervous system. In order to efficiently characterize the brain glucose mechanism, it is desirable to determine the extracellular glucose dynamics as well as the corresponding neuroelectrical activity in vivo. In the present study, we fabricated an implantable microelectrode array (MEA) probe composed of platinum electrochemical and electrophysiology microelectrodes by standard micro electromechanical system (MEMS) processes. The MEA probe was modified with nano-materials and implanted in a urethane-anesthetized rat for simultaneous recording of striatal extracellular glucose, local field potential (LFP) and spike on the same spatiotemporal scale when the rat was in normoglycemia, hypoglycemia and hyperglycemia. During these dual-mode recordings, we observed that increase of extracellular glucose enhanced the LFP power and spike firing rate, while decrease of glucose had an opposite effect. This dual mode MEA probe is capable of examining specific spatiotemporal relationships between electrical and chemical signaling in the brain, which will contribute significantly to improve our understanding of the neuron physiology.

Secondary barrier construction for vessels carrying spherical low temperature liquefied gas storage tanks

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

Okamoto, T.; Nishimoto, T.; Sawada, K.

1978-05-16

To simplify and thus reduce the cost of the secondary barrier for spherical LNG storage tanks onboard ocean-transport vessels, Japan's Hitachi Shipbuilding and Engineering Co., Ltd., has developed a new secondary-containment system that allows easy installation directly on the cargo hold's bottom plate beneath the spherical tank. The new system comprises at least two layers of rigid-foam synthetic resin sprayed on the hold plates and covered by a layer of glass mesh and adhesive. Alternatively, the layers of synthetic resin, glass mesh, and adhesive are applied to plywood attached to the hold plates by joists, thus forming an air spacemore » between the secondary barrier and the hold plates. Where the hold plates have a multisurface construction, (1) laminated rigid urethane foam blocks are butted end-to-end and are bonded to each other and to the plywood sheets at the corners between adjacent hold plates, (2) the spray-formed layers are applied between the blocks, and (3) the entire assembly is covered by a protective layer of glass mesh and adhesive.« less

Put the lid on VOC emissions from maintenance coatings

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

Morgan, R.E.

1996-11-01

After the coating film is applied to the substrate, the solvents evaporate and generally become an environmental liability. Solvents used by the coatings industry have been a major environmental issue for many years. Over the years, regulations have been aimed at reducing or eliminating photochemically reactive solvents--those that react in the atmosphere with nitrogen oxides in the atmosphere with nitrogen oxides in the presence of sunlight and heat to form ozones. Many of the solvents used in the coatings industry are, in fact, photochemically reactive. The rules regulating the maintenance coatings industry can generally be divided into three categories: 1.more » Rules aimed at restricting the VOCs in steel fabricating shops and paint shops. 2. Rules aimed at regulating the emission of VOCs from coatings applied in the field such as on bridges or industrial structures. 3. Rules aimed at the shipbuilding industry where coatings are applied to marine vessels. The paper discusses reducing VOCs, penetrating sealers, mastics, tank linings, inorganic zincs, topcoats--waterborne acrylics, zero-VOC urethane/water systems, and solventless topcoats.« less

Conjugation of diisocyanate side chains to dimethacrylate reduces polymerization shrinkage and increases the hardness of composite resins.

PubMed

Jan, Yih-Dean; Lee, Bor-Shiunn; Lin, Chun-Pin; Tseng, Wan-Yu

2014-04-01

Polymerization shrinkage is one of the main causes of dental restoration failure. This study tried to conjugate two diisocyanate side chains to dimethacrylate resins in order to reduce polymerization shrinkage and increase the hardness of composite resins. Diisocyanate, 2-hydroxyethyl methacrylate, and bisphenol A dimethacrylate were reacted in different ratios to form urethane-modified new resin matrices, and then mixed with 50 wt.% silica fillers. The viscosities of matrices, polymerization shrinkage, surface hardness, and degrees of conversion of experimental composite resins were then evaluated and compared with a non-modified control group. The viscosities of resin matrices increased with increasing diisocyanate side chain density. Polymerization shrinkage and degree of conversion, however, decreased with increasing diisocyanate side chain density. The surface hardness of all diisocyanate-modified groups was equal to or significantly higher than that of the control group. Conjugation of diisocyanate side chains to dimethacrylate represents an effective means of reducing polymerization shrinkage and increasing the surface hardness of dental composite resins. Copyright © 2012. Published by Elsevier B.V.

Parylene C coating for high-performance replica molding.

PubMed

Heyries, Kevin A; Hansen, Carl L

2011-12-07

This paper presents an improvement to the soft lithography fabrication process that uses chemical vapor deposition of poly(chloro-p-xylylene) (parylene C) to protect microfabricated masters and to improve the release of polymer devices following replica molding. Chemical vapor deposition creates nanometre thick conformal coatings of parylene C on silicon wafers having arrays of 30 μm high SU8 pillars with densities ranging from 278 to 10,040 features per mm(2) and aspect ratios (height : width) from 1 : 1 to 6 : 1. A single coating of parylene C was sufficient to permanently promote poly(dimethyl)siloxane (PDMS) mold release and to protect masters for an indefinite number of molding cycles. We also show that the improved release properties of parylene treated masters allow for fabrication with hard polymers, such as poly(urethane), that would otherwise not be compatible with SU8 on silicon masters. Parylene C provides a robust and high performance mold release coating for soft lithography microfabrication that extends the life of microfabricated masters and improves the achievable density and aspect ratio of replicated features.

Exploratory Study on the Effects of Novel Diamine Curing Agents and Isocyanate Precursors on the Properties of New Epoxy and Urethane Adhesives

NASA Technical Reports Server (NTRS)

Glasgow, D. Gerald; Garthwait, Clayborn

1977-01-01

This report covers the results of investigations directed toward studying the effects of novel aromatic diamine structures on epoxy adhesive properties and includes work done under a modification to the original contract. Three aromatic diamines based on diphenylsulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m'-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m'-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p'-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m'-methylene dianiline-cured epoxy appeared to be equivalent to the p,p'-methylene dianiline-cured epoxy as judged by short beam shear tests.

Sorption of Aromatic Compounds with Copolymer Sorbent Materials Containing β-Cyclodextrin.

PubMed

Wilson, Lee D; Mohamed, Mohamed H; Berhaut, Christopher L

2011-08-29

Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid) have been evaluated. The sorption properties of granular activated carbon (GAC) were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (< 10¹ m²/g), CDI-X copolymers (< 10¹ m²/g), and granular activated carbon (GAC ~10³ m²/g). The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i) surface area of the sorbent; (ii) CD content and accessibility; and (iii) and the chemical nature of the sorbent material.

Activity-Dependent Downscaling of Subthreshold Synaptic Inputs during Slow-Wave-Sleep-like Activity In Vivo.

PubMed

González-Rueda, Ana; Pedrosa, Victor; Feord, Rachael C; Clopath, Claudia; Paulsen, Ole

2018-03-21

Activity-dependent synaptic plasticity is critical for cortical circuit refinement. The synaptic homeostasis hypothesis suggests that synaptic connections are strengthened during wake and downscaled during sleep; however, it is not obvious how the same plasticity rules could explain both outcomes. Using whole-cell recordings and optogenetic stimulation of presynaptic input in urethane-anesthetized mice, which exhibit slow-wave-sleep (SWS)-like activity, we show that synaptic plasticity rules are gated by cortical dynamics in vivo. While Down states support conventional spike timing-dependent plasticity, Up states are biased toward depression such that presynaptic stimulation alone leads to synaptic depression, while connections contributing to postsynaptic spiking are protected against this synaptic weakening. We find that this novel activity-dependent and input-specific downscaling mechanism has two important computational advantages: (1) improved signal-to-noise ratio, and (2) preservation of previously stored information. Thus, these synaptic plasticity rules provide an attractive mechanism for SWS-related synaptic downscaling and circuit refinement. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Integrated antibacterial and antifouling surfaces via cross-linking chitosan-g-eugenol/zwitterionic copolymer on electrospun membranes.

PubMed

Li, Zhenguang; Hu, Wenhong; Zhao, Yunhui; Ren, Lixia; Yuan, Xiaoyan

2018-04-27

Integrated antibacterial and antifouling surfaces in favor of avoiding implant-related infections are necessarily required for biomaterials when they contact with the body fluid. In this work, an antibacterial and antifouling membrane was developed via cross-linking chitosan-g-eugenol and the zwitterionic copolymer poly(sulfobetaine methylacrylate-co-2-aminoethyl methacrylate) on the electrospun polycarbonate urethane substrate using genipin as a cross-linker. Antibacterial assays demonstrated that the prepared membranes had efficient antibacterial activity with 92.8 ± 2.5% and 95.2 ± 1.3% growth inhibition rates against Escherichia coli and Staphylococcus aureus, respectively. The investigations on antifouling activity and hemocompatibility of the membranes showed significant resistances to bacterial attachment, non-specific protein adsorption and platelet adhesion, and presented lower hemolytic activity and good anticoagulant activity as well. Moreover, cell culture assays indicated that the prepared membranes exerted no obvious cytotoxicity with more than 80% of relative L929 fibroblast viability. Therefore, the membranes with integrated antibacterial and antifouling properties could be potentially applied in promising indwelling devices. Copyright © 2018 Elsevier B.V. All rights reserved.

Material selection and evaluation of new encapsulation compounds for electric cables for launch support system

NASA Technical Reports Server (NTRS)

Ray, Asit K.

1992-01-01

Eight urethane compounds were evaluated as possible replacement for the existing encapsulating compoounds for electrical cables for the Launch Support System at Kennedy Space Center (KSC). The existing encapsulating compound, PR-1535, contains the curative MOCA 4-4'-Methylene-BIS (2-chloroaniline), which is a suspect carcinogen and hence may be the subject of further restrictions of its use by the Occupational Safety and Health Administration (OSHA). The samples made in the configuration of cable joints and in the form of disks were evaluated for flammability and hypergolic compatibility. These also underwent accelerated weatherability tests that measured the residual hardness of the exposed samples. Three candidates and the existing compound passed the hardness test. Of these, only one candidate and the existing compound passed the flammability test. The thermal and hydrolytic stability (weatherability) of these samples was studied using thermogravimetric analysis (DSC) techniques. The TMA and DSC data correlated with the residual hardness data; whereas, the TGA data showed no correlation. A hypergolic compatibility test will be conducted on the compound V-356-HE80, which passed both the flammability and accelerated weatherability tests.

Effect of hindlimb suspension on cardiovascular responses to sympathomimetics and lower body negative pressure

NASA Technical Reports Server (NTRS)

Overton, J. Michael; Tipton, Charles M.

1990-01-01

To determine whether hindlimb suspension is associated with the development of cardiovascular deconditioning, male rats were studied before and after undergoing one of three treatment conditions for 9 days: (1) cage control (n = 15, CON), (2) horizontal suspension (n = 15, HOZ), and (3) head-down suspension (n = 18, HDS). Testing included lower body negative pressure administered during chloralose-urethan anesthesia and graded doses of sympathomimetic agents (norepinephrine, phenylephrine, and tyramine) administered to conscious unrestrained animals. Both HDS and HOZ were associated with a small decrease in the hypotensive response to lower body negative pressure. The HOZ group, but not the HDS group, exhibited augmented reflex tachycardia. Furthermore, both HDS and HOZ groups manifested reduced pressor responses to phenylephrine after treatment. These reductions were associated with significantly attenuated increases in mesenteric vascular resistance. However, baroreflex control of heart rate was not altered by the treatment conditions. Collectively, these results indicate that 9 days of HDS in rats does not elicit hemodynamic response patterns generally associated with cardiovascular deconditioning induced by hypogravic conditions.

Lateral parabrachial nucleus mediates shortening of expiration during hypoxia.

PubMed

Song, Gang; Poon, Chi-Sang

2009-01-01

Acute hypoxia elicits complex time-dependent responses including rapid augmentation of inspiratory drive, shortening of inspiratory and expiratory durations (T(I), T(E)), and short-term potentiation and depression. The central pathways mediating these varied effects are largely unknown. Here, we show that the lateral parabrachial nucleus (LPBN) of the dorsolateral pons specifically mediates T(E)-shortening during hypoxia and not other hypoxic response components. Twelve urethane-anesthetized and vagotomized adult Sprague-Dawley rats were exposed to 1-min poikilocapnic hypoxia before and after unilateral kainic acid or bilateral electrolytic lesioning of the LPBN. Bilateral lesions resulted in a significant increase in baseline T(E) under hyperoxia. After unilateral or bilateral lesions, the decrease in T(E) during hypoxia was markedly attenuated without appreciable changes in all other hypoxic response components. These findings add to the mounting evidence that the central processing of peripheral chemoafferent inputs is segregated into parallel integrator and differentiator (low-pass and high-pass filter) pathways that separately modulate inspiratory drive, T(I), T(E) and resultant short-term potentiation and depression.

Sorption of Aromatic Compounds with Copolymer Sorbent Materials Containing β-Cyclodextrin

PubMed Central

Wilson, Lee D.; Mohamed, Mohamed H.; Berhaut, Christopher L.

2011-01-01

Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid) have been evaluated. The sorption properties of granular activated carbon (GAC) were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (< 101 m2/g), CDI-X copolymers (< 101 m2/g), and granular activated carbon (GAC ~103 m2/g). The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i) surface area of the sorbent; (ii) CD content and accessibility; and (iii) and the chemical nature of the sorbent material. PMID:28824156

Novel strategy for synthesis of magnetic dummy molecularly imprinted nanoparticles based on functionalized silica as an efficient sorbent for the determination of acrylamide in potato chips: Optimization by experimental design methodology.

PubMed

Arabi, Maryam; Ostovan, Abbas; Ghaedi, Mehrorang; Purkait, Mihir K

2016-07-01

This study discusses a novel and simple method for the preparation of magnetic dummy molecularly imprinted nanoparticles (MDMINPs). Firstly, Fe3O4 magnetic nanoparticles (MNPs) were synthesized as a magnetic component. Subsequently, MDMINPs were constructed via the sol-gel strategy using APTMS as the functional monomer. Urethane was considered as dummy template to avoid residual template and TEOS as the cross linker. The prepared MDMINPs were used for the pre-concentration of acrylamide from potato chips. Quantification was carried out by high performance liquid chromatography with UV detection (HPLC-UV). The impact of influential variables such as pH, amount of sorbent, sonication time and eluent volume were well investigated and optimized using a central composite design. The particles had excellent magnetic property and high selectivity to the targeted molecule. In optimized conditions, the recovery ranged from 94.0% to 98.0% with the detection limit of 0.35µgkg(-1). Copyright © 2016 Elsevier B.V. All rights reserved.

Polyurethane/fluor-hydroxyapatite nanocomposite scaffolds for bone tissue engineering. Part I: morphological, physical, and mechanical characterization

PubMed Central

Asefnejad, Azadeh; Behnamghader, Aliasghar; Khorasani, Mohammad Taghi; Farsadzadeh, Babak

2011-01-01

In this study, new nano-fluor-hydroxyapatite (nFHA)/polyurethane composite scaffolds were fabricated for potential use in bone tissue engineering. Polyester urethane samples were synthesized from polycaprolactone, hexamethylene diisocyanate, and 1,4-butanediol as chain extender. Nano fluor-hydroxyapatite (nFHA) was successfully synthesized by sol-gel method. The solid–liquid phase separation and solvent sublimation methods were used for preparation of the porous composites. Mechanical properties, chemical structure, and morphological characteristics of the samples were investigated by compressive test, Fourier transform infrared, and scanning electron microscopy (SEM) techniques, respectively. The effect of nFHA powder content on porosity and pore morphology was investigated. SEM images demonstrated that the scaffolds were constituted of interconnected and homogeneously distributed pores. The pore size of the scaffolds was in the range 50–250 μm. The result obtained in this research revealed that the porosity and pore average size decreased and compressive modulus increased with nFHA percentage. Considering morphological, physical, and mechanical properties, the scaffold with a higher ratio of nFHA has suitable potential use in tissue regeneration. PMID:21289986

Platelet adhesive resistance of segmented polyurethane film surface-grafted with vinyl benzyl sulfo monomer of ammonium zwitterions.

PubMed

Zhang, Jun; Yuan, Jiang; Yuan, Youling; Zang, Xiaopeng; Shen, Jian; Lin, Sicong

2003-10-01

Platelet from human plasma adhered on the segmented poly(ether urethane) (SPEU) film grafted with N,N-dimethyl-N-(p-vinylbenyl)-N-(3-sulfopropyl) ammonium (DMVSA) was studied. SPEU films were hydroxylated by potassium peroxosulfate (KPS) and then grafted with DMVSA using ceric ammonium nitrate (CAN) as initiator. The mixing time of hydroxylated SPEU/CAN and the monomer concentration effect on graft polymerization yield were determined by ATR-FTIR. Surface analysis of the grafted films by ATR-FTIR and ESCA confirmed that DMVSA was successfully grafted onto the SPEU film surface. The grafted film possessed a relatively hydrophilic surface, as revealed by water contact angle measurement. The improved blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion study and scanning electron microscopy, using original SPEU and hydroxylated SPEU films as the controls. The results showed that platelet attachment was decreased greatly on the segmented polyurethane films grafted with DMVSA. This kind of new biomaterials grafted with sulfo ammonium zwitterionic monomers might have potential for biomedical applications.

Direct writing of bio-functional coatings for cardiovascular applications.

PubMed

Perkins, Jessica; Hong, Yi; Ye, Sang-Ho; Wagner, William R; Desai, Salil

2014-12-01

The surface modification of metallic biomaterials is of critical importance to enhance the biocompatibility of surgical implant materials and devices. This article investigates the use of a direct-write inkjet technique for multilayer coatings of a biodegradable polymer (polyester urethane urea (PEUU)) embedded with an anti-proliferation drug paclitaxel (Taxol). The direct-write inkjet technique provides selective patterning capability for depositing multimaterial coatings on three-dimensional implant devices such as pins, screws, and stents for orthopedic and vascular applications. Drug release profiles were studied to observe the influence of drug loading and coating thickness for obtaining tunable release kinetics. Platelet deposition studies were conducted following ovine blood contact and significant reduction in platelet deposition was observed on the Taxol loaded PEUU substrate compared with the unloaded control. Rat smooth muscle cells were used for cell proliferation studies. Significant reduction in cell growth was observed following the release of anti-proliferative drug from the biopolymer thin film. This research provides a basis for developing anti-proliferative biocompatible coatings for different biomedical device applications. © 2014 Wiley Periodicals, Inc.

Studies on the trigeminal antidromic vasodilatation and plasma extravasation in the rat.

PubMed Central

Couture, R; Cuello, A C

1984-01-01

Antidromic stimulation of sensory peripheral branches of the trigeminal system (mental nerve) led to cutaneous vasodilatation and increased vascular permeability in rats anaesthetized with urethane. The antidromic vasodilatation observed in intact animals was not altered by decentralization or sympathectomy. Both antidromic vasodilatation and neurogenic plasma extravasation remained unaffected by pre-treatment with cimetidine, indomethacin, baclofen, guanethidine plus phentolamine and propranolol, but were significantly reduced by cimetidine plus mepyramine and atropine, suggesting that cholinergic and histaminergic components might be involved in the sensory neurogenic responses. Methysergide reduced only the extravasation, suggesting that probably serotonin liberated by mast cells upon sensory stimulation can contribute to the neurogenic responses. In tests using substance P (SP) antagonists (D-pro4, D- trp 7, 9, 10)-SP (4-11) and (D-pro2, D-trp 7, 9)-SP it was found that they are more active in reducing the neurogenic extravasation than the vasodilatation. In addition it was observed that (D-pro 4, D-trp 7, 9, 10)-SP (4-11) was the most potent substance P antagonist in reducing the plasma extravasation and antidromic vasodilatation resulting from sensory stimulation. PMID:6199494

Effects of the Acrylic Polyol Structure and the Selectivity of the Employed Catalyst on the Performance of Two-Component Aqueous Polyurethane Coatings

PubMed Central

Cakic, Suzana; Lacnjevac, Caslav; Stamenkovic, Jakov; Ristic, Nikola; Takic, Ljiljana; Barac, Miroljub; Gligoric, Miladin

2007-01-01

Two kinds of aqueous acrylic polyols (single step and multi step synthesis type) have been investigated for their performance in the two-component aqueous polyurethane application, by using more selective catalysts. The aliphatic polyfunctional isocyanates based on hexamethylen diisocyanates have been employed as suitable hardeners. The complex of zirconium, commercially known as K-KAT®XC-6212, and manganese (III) complexes with mixed ligands based on the derivative of maleic acid have been used as catalysts in this study. Both of the aqueous polyols give good results, in terms of application and hardness, when elevated temperatures and more selective catalysts are applied. A more selective catalyst promotes the reaction between the isocyanate and polyol component. This increases the percentage of urethane bonds and the degree of hardness in the films formed from the two components of aqueous polyurethane lacquers. The polyol based on the single step synthesis route is favourable concerning potlife and hardness. The obtained results show that the performance of the two-component aqueous polyurethane coatings depends on the polymer structure of the polyols as well as on the selectivity of the employed catalyst.

On impedance measurement of reinforced concrete on the surface for estimate of corroded rebar

NASA Astrophysics Data System (ADS)

Sasamoto, Akira; Yu, Jun; Harada, Yoshihisa; Iwata, Masahiro; Noguchi, Kazuhiro

2017-04-01

In an estimate of health monitoring for reinforced concrete, corrosion degree of rebar is important parameter but is not easy to be estimated by non destructive testing. A few test method such as half cell method or polarization resistance method could be a 'perfect' nondestructive method if luckily having had wired connection to rebar without destructing target concrete. In this presentation it is reported the experimental result that an impedance measurement on surface of reinforced concretes is able to distinguish corroded rebar from healthy rebar. The contact electrode on concrete surface are simple structure made of urethane sponge and needle. Impedance measurement are carried out with frequency response analyzer with frequency range from 0.01Hz to 1MHz, typical amplitude of imposed voltage are 10 volt. We made concrete specimens under two different corrosion process. One process(pre corrosion) has rebars corroded by electrolysis in salty water before concrete casting and another process (post corrosion) has concrete specimens being corroded during the curing. The results of application of developed method to these corroded specimens show the method is useful to estimate corrosion level of rebars.

Effects of a beta-adrenergic blocking agent timolol on intra ocular pressure responses induced by stimulation of cervical sympathetic nerve in the cat.

PubMed

Naito, A; Izumi, H; Karita, K; Tamai, M

2001-12-01

We clarified whether the intraocular pressure (IOP) response elicited by stimulation of the cervical sympathetic nerve (CSN) is influenced by changes in the baseline of IOP level and by beta-adrenergic blockade. The CSN was stimulated electrically for 30 seconds (10 V, 0.1-100 Hz, 2 milliseconds pulse duration) in urethane (100 mg/kg i.v.)-chloralose (50 mg/kg i.v.)-anesthetized, paralyzed cats. The IOP was monitored manometrically, and a controlled saline infusion was delivered into the anterior chamber to gradually increase IOP. CSN stimulation was delivered at the various baseline IOP levels so obtained. When required, a beta-adrenergic blocker timolol (2%) was delivered into the conjunctival cul-de-sac. The normal IOP in our cats was 25+/-3 mmHg. This value decreased transiently on CSN stimulation. The amplitude of this IOP response depended on stimulus frequency and the pre-stimulus baseline IOP level. Topical administration of timolol increased the IOP response to CSN stimulation at a given baseline level. These results suggest that beta-adrenergic blockade increases the alpha-adrenergic mediated-IOP reduction elicited by CSN stimulation at given baseline IOP level.

Study of Crystal Formation and Nitric Oxide (NO) Release Mechanism from S-Nitroso-N-acetylpenicillamine (SNAP)-Doped CarboSil Polymer Composites for Potential Antimicrobial Applications.

PubMed

Wo, Yaqi; Li, Zi; Colletta, Alessandro; Wu, Jianfeng; Xi, Chuanwu; Matzger, Adam J; Brisbois, Elizabeth J; Bartlett, Robert H; Meyerhoff, Mark E

2017-07-15

Stable and long-term nitric oxide (NO) releasing polymeric materials have many potential biomedical applications. Herein, we report the real-time observation of the crystallization process of the NO donor, S -nitroso- N -acetylpenicillamine (SNAP), within a thermoplastic silicone-polycarbonate-urethane biomedical polymer, CarboSil 20 80A. It is demonstrated that the NO release rate from this composite material is directly correlated with the surface area that the CarboSil polymer film is exposed to when in contact with aqueous solution. The decomposition of SNAP in solution (e.g. PBS, ethanol, THF, etc.) is a pseudo-first-order reaction proportional to the SNAP concentration. Further, catheters fabricated with this novel NO releasing composite material are shown to exhibit significant effects on preventing biofilm formation on catheter surface by Pseudomonas aeruginosa and Proteus mirabilis grown in CDC bioreactor over 14 days, with a 2 and 3 log-unit reduction in number of live bacteria on their surfaces, respectively. Therefore, the SNAP-CarboSil composite is a promising new material to develop antimicrobial catheters, as well as other biomedical devices.

A new cyclodextrin-grafted viscose loaded with aescin formulations for a cosmeto-textile approach to chronic venous insufficiency.

PubMed

Cravotto, G; Beltramo, L; Sapino, S; Binello, A; Carlotti, M E

2011-10-01

Cosmeto-textile applications can be used in the treatment of chronic venous insufficiency in legs by means of elastic bandages loaded with natural products which possess flebotonic properties. We have developed an efficient synthetic procedure for the preparation of β-cyclodextrin (β-CD)-grafted viscose by means of a 2-step ultrasound-assisted reaction. The highly grafted fabric bearing bis-urethane bridged β-CD has been characterized by ATR-FTIR and CP-MAS spectra and by an empiric colorimetric method which used phenolphthalein as the CD guest. We have also developed a suitable cosmetic preparation containing natural substances and extracts (aescin, menthol, Centella asiatica and Ginkgo biloba) to recharge the CD-grafted textile. The efficacy of the new cosmeto-textile has been corroborated by in vitro studies of diffusion through membranes, cutaneous permeation and accumulation in porcine skin. Aescin was taken as a reference compound and its concentration in the different compartments was monitored by HPLC analysis. This cost effective cosmeto-textile shows excellent application compliance and is easily recharged and so has the strong base characteristics needed for possible industrial production.

Facilitation of the arterial baroreflex by the preoptic area in anaesthetized rats.

PubMed Central

Inui, K; Nomura, J; Murase, S; Nosaka, S

1995-01-01

1. Activation of cell bodies in the ventrolateral part of the midbrain periaqueductal grey matter (PAG) facilitates the arterial baroreflex via the nucleus raphe magnus. The facilitatory effects of stimulation within the hypothalamus on the arterial baroreflex and their relation to the PAG and nucleus raphe magnus were studied in urethane- and chloralose-anaesthetized rats. 2. Systematic mapping experiments revealed that the preoptic area (POA) is the principal location in the hypothalamus of neuronal cell bodies that are responsible for the potentiation of the baroreflex. In addition to provoking hypotension and vagal bradycardia, both electrical and chemical stimulation of the POA produced facilitation of baroreflex vagal bradycardia (BVB) that was evoked by electrical stimulation of the aortic depressor nerve. Baroreflex hypotension was slightly augmented during activation of the POA in vagotomized rats. 3. Selective destruction of cell bodies either in the ventrolateral PAG or in the nucleus raphe magnus reduced facilitation of BVB by the POA. Hypotension and bradycardia due to POA stimulation were also markedly attenuated after such selective destruction. 4. In conclusion, the POA, the ventrolateral PAG and the nucleus raphe magnus constitute a functional complex that produces cardiovascular trophotropic effects including hypotension, vagal bradycardia and baroreflex facilitation. PMID:8568691

[Intranasal epitalon infusion modulates neuronal activity in the rat neocortex].

PubMed

Sibarov, D A; Vol'nova, A B; Frolov, D S; Nosdrachev, A D

2006-08-01

Properties of tetrapeptide epitalon (Ala-Glu-Asp-Gly) constructed on the basis of pineal peptide extract, have been studied. The intranasal infusions: a noninvasive way to deliver this peptide to CNS hypassing the blood-brain barrier, was used. The aim of the study is to estimate epitalon action on rat motor cortex spontaneous activity. Wistar male rats were anesthetized with urethane (1 g/kg). Extracellular unit recording was made using glass microelectrodes (1-2 MOhm). After recording of spontaneous activity (10-15 min), epitalon intranasal infusion (2 ng) was followed by 30-minute recording. Within a few minutes after the infusion, significant activation of neural activity was observed (2-2.5-fold higher frequency of neuronal spikes). Complex response consisting of several phases was identified in some recordings. The spikes frequency growth during 5 to 7 min (first phase) after the infusion was followed by the second (11-12 min) and the third (17-18 min) phases. An increase of neuronal spontaneous activity was conditioned by the higher frequency of already active units and by the involvement of previously silent cells. At least the first phase of epitalon action can be explained by direct action of the peptide on the cells of the motor cortex.

Hydrothermal Growth of ZnO Nanowires on UV-Nanoimprinted Polymer Structures.

PubMed

Park, Sooyeon; Moore, Sean A; Lee, Jaejong; Song, In-Hyouk; Farshchian, Bahador; Kim, Namwon

2018-05-01

Integration of zinc oxide (ZnO) nanowires on miniaturized polymer structures can broaden its application in multi-functional polymer devices by taking advantages of unique physical properties of ZnO nanowires and recent development of polymer microstructures in analytical systems. In this paper, we demonstrate the hydrothermal growth of ZnO nanowires on polymer microstructures fabricated by UV nanoimprinting lithography (NIL) using a polyurethane acrylate (PUA). Since PUA is a siloxane-urethane-acrylate compound containing the alpha-hydroxyl ketone, UV-cured PUA include carboxyl groups, which inhibit and suppress the nucleation and growth of ZnO nanowires on polymer structures. The presence of carboxyl groups in UV-cured PUA was substantiated by Fourier transform infrared spectroscopy (FTIR), and a Ag thin film was deposited on the nanoimprinted polymer structures to limit their inhibitive influence on the growth of ZnO nanowires. Furthermore, the naturally oxidized Ag layer (Ag2O) reduced crystalline lattice mismatches at the interface between ZnO-Ag during the seed annealing process. The ZnO nanowires grown on the Ag-deposited PUA microstructures were found to have comparable morphological characteristics with ZnO nanowires grown on a Si wafer.

Dermal oncogenicity bioassays of monofunctional and multifunctional acrylates and acrylate-based oligomers.

PubMed

DePass, L R; Maronpot, R R; Weil, C S

1985-01-01

Several important components of photocurable coatings were studied for dermal tumorigenic activity by repeated application to the skin of mice. The substances tested were 2-ethylhexyl acrylate (EHA) and methylcarbamoyloxyethyl acrylate (MCEA) (monomers); neopentyl glycol diacrylate (NPGDA), esterdiol-204-diacrylate (EDDA), and pentaerythritol tri(tetra)acrylate (PETA) (cross-linkers); and three acrylated urethane oligomers. For each bioassay, 40 C3H/HeJ male mice were dosed 3 times weekly on the dorsal skin for their lifetime with the highest dose of the test agent that caused no local irritation or reduction in body weight gain. Two negative control groups received acetone (diluent) only. A positive control group received 0.2% methylcholanthrene (MC). NPGDA and EHA had significant tumorigenic activity with tumor yields of eight and six tumor-bearing mice (three and two malignancies), respectively. The MC group had 34 mice with carcinomas and 1 additional mouse with a papilloma. MCEA had no dermal tumorigenic activity but resulted in early mortality. No skin tumors in the treatment area were observed in the other groups. Additional studies will be necessary to elucidate possible relationships between structure and tumorigenic activity for the acrylates.

Improved wettability and adhesion of polylactic acid/chitosan coating for bio-based multilayer film development

NASA Astrophysics Data System (ADS)

Gartner, Hunter; Li, Yana; Almenar, Eva

2015-03-01

The objective of this study was to investigate the effect of methyldiphenyl diisocyanate (MDI) concentration (0, 0.2, 1, 2, and 3%) on the wettability and adhesion of blend solutions of poly(lactic acid) (PLA) and chitosan (CS) when coated on PLA film for development of a bio-based multi-layer film suitable for food packaging and other applications. Characterization was carried out by attenuated total reflectance infrared spectrometry (ATR-FTIR), contact angle (θ), mechanical adhesion pull-off testing, and scanning electron microscopy (SEM). The θ of the PLA/CS blend shifted to a lower value (41-35°) with increasing MDI concentration showing that the surface tension was modified between the PLA/CS blend solution and PLA film and better wettability was achieved. The increase in MDI also resulted in an increased breaking strength (228-303 kPa) due to the increased H-bonding resulting from the more urethane groups formed within the PLA/CS blend as shown by ATR-FTIR. The improved adhesion was also shown by the increased number of physical entanglements observed by SEM. It can be concluded that MDI can be used to improve wettability and adhesion between PLA/CS coating and PLA film.

Tensile bond strength of silicone-based soft denture liner to two chemically different denture base resins after various surface treatments.

PubMed

Akin, Hakan; Tugut, Faik; Guney, Umit; Kirmali, Omer; Akar, Turker

2013-01-01

This study evaluated the effect of various surface treatments on the tensile bond strength of a silicone-based soft denture liner to two chemically different denture base resins, heat-cured polymethyl methacrylate (PMMA), and light-activated urethane dimethacrylate or Eclipse denture base resin. PMMA test specimens were fabricated and relined with a silicone-based soft denture liner (group AC). Eclipse test specimens were prepared according to the manufacturer's recommendation. Before they were relined with a silicone-based soft denture liner, each received one of three surface treatments: untreated (control, group EC), Eclipse bonding agent applied (group EB), and laser-irradiated (group EL). Tensile bond strength tests (crosshead speed = 5 mm/min) were performed for all specimens, and the results were analyzed using the analysis of variance followed by Tukey's test (p = 0.05). Eclipse denture base and PMMA resins presented similar bond strengths to the silicone-based soft denture liner. The highest mean force was observed in group EL specimens, and the tensile bond strengths in group EL were significantly different (p < 0.05) from those in the other groups.

Evaluation of a new composite prosthesis for the repair of abdominal wall defects.

PubMed

Losi, Paola; Munaò, Antonella; Spiller, Dario; Briganti, Enrica; Martinelli, Ilaria; Scoccianti, Marco; Soldani, Giorgio

2007-10-01

The degree of integration of biomaterials used in the repair of abdominal wall defects seems to depend upon the structure of the prosthesis. The present investigation evaluates the behaviour in terms of adhesion formation and integration of a new composite prosthesis that could be employed in this clinical application. Full-thickness abdominal wall defects (7 x 5 cm) were created in 16 anaesthetized New Zealand white rabbits and the prosthesis were placed in direct contact with the visceral peritoneum during the experiment. The defects were repaired with a composite prosthesis or pure polypropylene mesh to establish two study groups (n = 8 each). The composite device was constituted by a polypropylene mesh physically attached to a poly(ether)urethane-polydimethylsiloxane laminar sheet. Animals were sacrificed 7, 14, 21 and 30 days after implant and prosthesis/surrounding tissue specimens subjected to light and electron microscopy. Firm adhesions were detected in the polypropylene implants, while they were not present in the composite implants. The excellent behaviour of the composite prosthesis shown in this study warrants further investigation on its use for the repair of abdominal wall defects when a prosthetic device needs to be placed in contact with the intestinal loops.

Experimental study of noise transmission into a general aviation aircraft

NASA Technical Reports Server (NTRS)

Vaicaitis, R.; Bofilios, D. A.; Eisler, R.

1984-01-01

The effect of add-on treatments on noise transmission into a cabin of a light aircraft was studied under laboratory conditions for diffuse and localized noise inputs. Results indicate that stiffening skin panels with honeycomb would provide on the average 3dB to 7 dB insertion loss over the most of selected frequency range H1 to 1000 Hz. Addition of damping tape on top of the honeycomb treatment increases insertion loss by 2dB to 3dB. Porous acoustic blankets show no attenuation of transmitted noise for frequencies below 300 Hz. Insertion of impervious vinyl septa between the layers of porous acoustic blankets do not provide additional noise reduction for frequencies up to about 500 Hz. Similar behavior was observed for noise barriers composed of urethane elastomer, decoupler foam and acoustic foam. A treatment composed from several layers of acoustic foams does not increase noise attenuation for the entire frequency range studied. An acoustic treatment composed of honeycomb panels, constrained layer damping tape, 2 to 3 inches of porous acoustic blankets, and limptrim which is isolated from the vibrations of the main fuselage structure seems to provide the best option for noise control.

NASA Tech Briefs, May 2004

NASA Technical Reports Server (NTRS)

2004-01-01

Topics include: Embedded Heaters for Joining or Separating Plastic Parts; Curing Composite Materials Using Lower-Energy Electron Beams; Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites; Fibrous-Ceramic/Aerogel Composite Insulating Tiles; Urethane/Silicone Adhesives for Bonding Flexing Metal Parts; Scalable Architecture for Multihop Wireless ad Hoc Networks; Improved Thermoplastic/Iron-Particle Transformer Cores; Cooperative Lander-Surface/Aerial Microflyer Missions for Mars Exploration Dual-Frequency Airborne Scanning Rain Radar Antenna System Eight-Channel Continuous Timer Reduction of Phase Ambiguity in an Offset-QPSK Receiver Ambient-Light-Canceling Camera Using Subtraction of Frames Lightweight, Flexible, Thin, Integrated Solar-Power Packs Windows(Registered Trademark)-Based Software Models Cyclic Oxidation Behavior Software for Analyzing Sequences of Flow-Related Images Improved Ball-and-Socket Docking Mechanism Two-Stage Solenoid Ordered Nanostructures Made Using Chaperonin Polypeptides Low-Temperature Plasma Functionalization of Carbon Nanotubes Improved Cryostat for Cooling a Wide Panel Current Pulses Momentarily Enhance Thermoelectric Cooling Hand-Held Color Meters Based on Interference Filters Calculating Mass Diffusion in High-Pressure Binary Fluids Fresnel Lenses for Wide-Aperture Optical Receivers Increasing Accuracy in Computed Inviscid Boundary Conditions Higher-Order Finite Elements for Computing Thermal Radiation Radar for Monitoring Hurricanes from Geostationary Orbit Time-Transfer System for Two Orbiting Spacecraft

Characteristics of the mechanosensitive bladder afferent activities in relation with microcontractions in male rats with bladder outlet obstruction.

PubMed

Aizawa, Naoki; Ichihara, Koji; Fukuhara, Hiroshi; Fujimura, Tetsuya; Andersson, Karl-Erik; Homma, Yukio; Igawa, Yasuhiko

2017-08-09

We investigated the characteristics of bladder mechanosensitive single-unit afferent activities (SAAs) in rats with a bladder outlet obstruction (BOO) and their relationship with bladder microcontractions. Male Wistar rats were divided into Sham and BOO groups. Four or 10 days after the surgery, rats were anesthetized with urethane. The SAAs of Aδ- or C-fibers from the L6 dorsal roots were recorded during bladder filling. The BOO group showed a higher number of microcontractions and lower SAAs of Aδ-fibers compared with those of the Sham group. These findings were significant at day 10 post-operatively. In contrast, SAAs of C-fibers were not significantly different between the groups at either day 4 or 10. In the BOO group at day 10, the SAAs of both Aδ- and C-fibers at the "ascending" phase of microcontractions were significantly higher than those at the other phases (descending or stationary), and a similar tendency was also observed at day 4. Taken together, during bladder filling, the bladder mechanosensitive SAAs of Aδ-fibers were attenuated, but SAAs of both Aδ- and C-fibers were intermittently enhanced by propagation of microcontractions.

Enhancing gelation ability of a dendritic gelator through complexation with a polyelectrolyte.

PubMed

Zhang, Zijian; Yang, Miao; Zhang, Xinjun; Zhang, Lichu; Liu, Bo; Zheng, Ping; Wang, Wei

2009-01-01

A poly(urethane amide) (PUA) dendron with long alkyl chains on its periphery was synthesized and then attached to the backbone of a polyelectrolyte, in which each unit contained a positive charge, by ionizing the carboxyl groups on the apexes of the dendrons to form a dendronized polymer. We found that both the PUA dendron and the dendronized polymer could form organogels in toluene. Interestingly, both the minimum gelation concentration and the gelation time of the dendronized polymer gelator were greatly reduced compared with the dendron alone. Our investigations showed that in the gel phase the intermolecular hydrogen bonding between adjacent dendrons creates similar supramolecular structures in both the dendron and the dendronized polymer gelator, which immobilize solvent molecules by means of interactions between dendrons and solvent molecules. Further studies on the gelation kinetics indicated that the polyelectrolyte backbone plays an important role in prearranging the attached dendritic gelators orderly and quickly into the supramolecular structures through a nucleation-elongation mechanism. Therefore, the gel-forming ability of the dendritic PUA gelator is enhanced by being complexed with the polyelectrolyte. In this work, this positive macromolecular effect is discussed in detail.

Evaluation of the polymerization shrinkage of experimental flowable composite resins through optical coherence tomography

NASA Astrophysics Data System (ADS)

Carneiro, Vanda S. M.; Mota, Cláudia C. B. O.; Souza, Alex F.; Cajazeira, Marlus R. R.; Gerbi, Marleny E. M. M.; Gomes, Anderson S. L.

2018-02-01

This study evaluated the polymerization shrinkage of two experimental flowable composite resins (CR) with different proportions of Urethane dimethacrylate (UDMA)/triethylene glycol dimethacrylate (TEGDMA) monomers in the organic matrix (50:50 and 60:40, respectively). A commercially available flowable CR, Tetric N-Flow (Ivoclair Vivadent, Liechtenstein, Germany), was employed as the control group. The resins were inserted in a cylindrical teflon mold (7 mm diameter, 0.6 mm height) and scanned with OCT before photoactivation, immediately after and 15 minutes after light-curing (Radii-Cal, SDI, Australia, 1,200 mW/cm2 ) exposure. A Callisto SD-OCT system (Thorlabs Inc, USA), operating at 930 nm central wavelength was employed for imaging acquisition. Cross-sectional OCT images were captured with 8 mm transverse scanning (2000x512 matrix), and processed by the ImageJ software, for comparison between the scanning times and between groups. Pearson correlation showed significant shrinkage for all groups in each time analyzed. Kruskal-Wallis test showed greater polymerization shrinkage for the 50:50 UDMA/TEGDMA group (p=0.001), followed by the control group (p=0.018). TEGDMA concentration was proportionally related to the polymerization shrinkage of the flowable composite resins.

Antiparallel Self-Association of a γ,α-Hybrid Peptide: More Relevance of Weak Interactions.

PubMed

Venugopalan, Paloth; Kishore, Raghuvansh

2015-08-01

To learn how a preorganized peptide-based molecular template, together with diverse weak non-covalent interactions, leads to an effective self-association, we investigated the conformational characteristics of a simple γ,α-hybrid model peptide, Boc-γ-Abz-Gly-OMe. The single-crystal X-ray diffraction analysis revealed the existence of a fully extended β-strand-like structure stabilized by two non-conventional C-H⋅⋅⋅O=C intramolecular H-bonds. The 2D (1) H NMR ROESY experiment led us to propose that the flat topology of the urethane-γ-Abz-amide moiety is predominantly preserved in a non-polar environment. The self-association of the energetically more favorable antiparallel β-strand-mimic in solid-state engenders an unusual 'flight of stairs' fabricated through face-to-face and edge-to-edge Ar⋅⋅⋅Ar interactions. In conjunction with FT-IR spectroscopic analysis in chloroform, we highlight that conformationally semi-rigid γ-Abz foldamer in appositely designed peptides may encourage unusual β-strand or β-sheet-like self-association and supramolecular organization stabilized via weak attractive forces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of carbon quantum dots based high photostability luminescent membranes.

PubMed

Zhao, Jinxing; Liu, Cui; Li, Yunchuan; Liang, Jiyuan; Liu, Jiyan; Qian, Tonghui; Ding, Jianjun; Cao, Yuan-Cheng

2017-06-01

Urethane acrylate (UA) was used to prepare carbon quantum dots (C-dots) luminescent membranes and the resultants were examined with FT-IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT-IR results showed the polyurethane acrylate (PUA) prepolymer -C = C-vibration at 1101 cm -1 disappeared but there was strong vibration at1687cm -1 which was contributed from the-C = O groups in cross-linking PUA. Mechanical strength results showed that the different quantity of C-dots loadings and UV-curing time affect the strength. SEM observations on the cross-sections of the membranes are uniform and have no structural defects, which prove that the C-dots are compatible with the water-soluble PUA resin. The C-dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C-dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C-dots photoluminescent film is the promising material for the flexible devices in the future applications. Copyright © 2016 John Wiley & Sons, Ltd.

Continuous and scalable fabrication of bioinspired dry adhesives via a roll-to-roll process with modulated ultraviolet-curable resin.

PubMed

Yi, Hoon; Hwang, Insol; Lee, Jeong Hyeon; Lee, Dael; Lim, Haneol; Tahk, Dongha; Sung, Minho; Bae, Won-Gyu; Choi, Se-Jin; Kwak, Moon Kyu; Jeong, Hoon Eui

2014-08-27

A simple yet scalable strategy for fabricating dry adhesives with mushroom-shaped micropillars is achieved by a combination of the roll-to-roll process and modulated UV-curable elastic poly(urethane acrylate) (e-PUA) resin. The e-PUA combines the major benefits of commercial PUA and poly(dimethylsiloxane) (PDMS). It not only can be cured within a few seconds like commercial PUA but also possesses good mechanical properties comparable to those of PDMS. A roll-type fabrication system equipped with a rollable mold and a UV exposure unit is also developed for the continuous process. By integrating the roll-to-roll process with the e-PUA, dry adhesives with spatulate tips in the form of a thin flexible film can be generated in a highly continuous and scalable manner. The fabricated dry adhesives with mushroom-shaped microstructures exhibit a strong pull-off strength of up to ∼38.7 N cm(-2) on the glass surface as well as high durability without any noticeable degradation. Furthermore, an automated substrate transportation system equipped with the dry adhesives can transport a 300 mm Si wafer over 10,000 repeating cycles with high accuracy.

Flexural properties of ethyl or methyl methacrylate-UDMA blend polymers.

PubMed

Kanie, Takahito; Kadokawa, Akihiko; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

2010-10-01

Light-curing polyethyl methacrylate (PEMA)-urethane dimethacrylate (UDMA) resins and polymethyl methacrylate (PMMA)-UDMA resins were prepared by two processes. For first step, PEMA or PMMA powders were fully dissolved in ethyl methacrylate (EMA) or methyl methacrylate (MMA) and then the PEMA-EMA/PMMA-MMA mixtures were mixed with UDMA. The flexural properties of cured PEMA-UDMA and PMMA-UDMA polymers were measured using two PEMA (Mw: 300,000-400,000 and 650,000-1,000,000) and three PMMA (Mw: 30,000-60,000, 350,000 and 650,000-1,000,000) powders with different molecular weight, four mixing ratios of PMMA-MMA, and three mixing ratios of PMMA-MMA mixture and UDMA oligomer. Polymers with PMMA(Mw: 350,000) MMA=25/50, and with PMMA(Mw: 350,000)-MMA/UDMA=1/2 and =1/1, showed no-fracture in a flexural test at 1 mm/min and flexural strength and flexural modulus showed no significant difference compared with those of commercially available heat- and self-curing acrylic resins (p>0.01). Within limitation of this investigation, methyl methacrylate-UDMA blend polymer of this composition is available for denture base resin.

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

Severini, Aldo; Mantero, Sara; Tanzi, Maria Cristina

Purpose: Prototypes of Gianturco-Rosch Z-stents coated with polycarbonate urethane (PCU) were placed in the biliary tree of pigs, in order to test their biomechanical behavior, stability, and biocompatibility. Methods: The stents were surgically implanted in the common bile duct of three pairs of pigs, which were killed after 1, 3, and 6 months respectively. Explanted livers from pigs of the same race, age, and size were used to provide comparative data. The bile ducts were radiologically and histopathologically examined; the stents were processed and examined by scanning electron microscopy. Results: No complications occurred and the animals showed a normal weightmore » gain. The main bile duct appeared radiologically and macroscopically dilated, but the stents proved to be in place. Histologically, the bile duct epithelium was destroyed, but neither hyperplastic nor inflammatory fibrotic reactions of the wall were evident. Both the metallic structure and the polymeric coating of the stents were intact. A layer of organic material with a maximum thickness of approximately 3 {mu}m was evident on the inner surface of the stents. Conclusion: The present in vivo study demonstrates the biocompatibility, efficacy, and stability of PCU-coated Gianturco-Rosch stents in the biliary environment.« less

A review of plastic waste biodegradation.

PubMed

Zheng, Ying; Yanful, Ernest K; Bassi, Amarjeet S

2005-01-01

With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.

Green and selective polycondensation methods toward linear sorbitol-based polyesters: enzymatic versus organic and metal-based catalysis.

PubMed

Gustini, Liliana; Lavilla, Cristina; Janssen, William W T J; Martínez de Ilarduya, Antxon; Muñoz-Guerra, Sebastián; Koning, Cor E

2016-08-23

Renewable polyesters derived from a sugar alcohol (i.e., sorbitol) were synthesized by solvent-free polycondensation. The aim was to prepare linear polyesters with pendant hydroxyl groups along the polymer backbone. The performance of the sustainable biocatalyst SPRIN liposorb CALB [an immobilized form of Candida antarctica lipase B (CALB); SPRIN technologies] and the organo-base catalyst 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) were compared with two metal-based catalysts: dibutyl tin oxide (DBTO) and scandium trifluoromethanesulfonate [also known as scandium triflate, Sc(OTf)3 ]. For the four catalytic systems, the efficiency and selectivity for the incorporation of sorbitol were studied, mainly using (13) C and (31) P NMR spectroscopies, whereas side reactions, such as ether formation and dehydration of sorbitol, were evaluated using MALDI-TOF-MS. Especially the biocatalyst SPRIN liposorb CALB succeeded in incorporating sorbitol in a selective way without side reactions, leading to close-to-linear polyesters. By using a renewable hydroxyl-reactive curing agent based on l-lysine, transparent and glossy poly(ester urethane) networks were successfully synthesized offering a tangible example of bio-based coatings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Fast-Starting Robotic Fish

NASA Astrophysics Data System (ADS)

Modarres-Sadeghi, Yahya; Watts, Matthew; Conte, Joe; Hover, Franz; Triantafyllou, Michael

2009-11-01

We have built a simple mechanical system to emulate the fast-start performance of fish. The system consisted of a thin metal beam covered by a urethane rubber fish body. The body form of the mechanical fish in this work was modeled from a pike species, which is the most successfully studied fast-start specialist species. The mechanical fish was held in curvature and hung in water by two restraining lines, which were simultaneously released by pneumatic cutting mechanisms. The potential energy in the beam was transferred into the fluid, thereby accelerating the fish, similar to a pike. We measured the resulting velocity and acceleration, as well as the efficiency of propulsion for the mechanical fish model and also ran a series of flow visualization tests to observe the resulting flow pattern. We also studied the influence of stiffness and geometry of the tail on the efficiency of propulsion and flow pattern. The hydrodynamic efficiency of the fish, calculated by the transfer of energy, was around 10%. Flow visualization of the mechanical fast-start wake was also analyzed, showing that the acceleration is associated with the fast movement of an intense vortex in a near-lateral direction.

Modulation of dendrodendritic interactions and mitral cell excitability in the mouse accessory olfactory bulb by vaginocervical stimulation.

PubMed

Otsuka, T; Ishii, K; Osako, Y; Okutani, F; Taniguchi, M; Oka, T; Kaba, H

2001-05-01

When female mice are mated, they form a memory to the pheromonal signal of their male partner. The neural changes underlying this memory occur in the accessory olfactory bulb, depend upon vaginocervical stimulation at mating and involve changes at the reciprocal synapses between mitral and granule cells. However, the action of vaginocervical stimulation on the reciprocal interactions between mitral and granule cells remains to be elucidated. We have examined the effects of vaginocervical stimulation on paired-pulse depression of amygdala-evoked field potentials recorded in the external plexiform layer of the accessory olfactory bulb (AOB) and the single-unit activity of mitral cells antidromically stimulated from the amygdala in urethane-anaesthetized female mice. Artificial vaginocervical stimulation reduced paired-pulse depression (considered to be due to feedback inhibition of the mitral cell dendrites from the granule cells via reciprocal dendrodendritic synapses) recorded in the AOB external plexiform layer. As would be expected from this result, vaginocervical stimulation also enhanced the spontaneous activity of a proportion of the mitral cells tested. These results suggest that vaginocervical stimulation reduces dendrodendritic feedback inhibition to mitral cells and enhances their activity.

The Influence of Phosphor and Binder Chemistry on the Aging Characteristics of Remote Phosphor Products

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

Davis, Lynn; Yaga, Robert; Lamvik, Michael

The influence of phosphor and binder layer chemistries on the lumen maintenance and color stability of remote phosphor disks were examined using wet high-temperature operational lifetime testing (WHTOL). As part of the experimental matrix, two different correlated color temperature (CCT) values, 2700 K and 5000 K, were studied and each had a different binder chemistry. The 2700 K samples used a urethane binder whereas the 5000 K samples used an acrylate binder. Experimental conditions were chosen to enable study of the binder and phosphor chemistries and to minimize photo-oxidation of the polycarbonate substrate. Under the more severe WHTOL conditions ofmore » 85°C and 85% relative humidity (RH), absorption in the binder layer significantly reduced luminous flux and produced a blue color shift. The milder WHTOL conditions of 75°C and 75% RH, resulted in chemical changes in the binder layer that may alter its index of refraction. As a result, lumen maintenance remained high, but a slight yellow shift was found. The aging of remote phosphor products provides insights into the impact of materials on the performance of phosphors in an LED lighting system.« less

Optimization of Multilayer Laminated Film and Absorbent of Vacuum Insulation Panel for Use at High Temperature

NASA Astrophysics Data System (ADS)

Araki, Kuninari; Echigoya, Wataru; Tsuruga, Toshimitsu; Kamoto, Daigorou; Matsuoka, Shin-Ichi

For the energy saving regulation and larger capacity, Vacuum Insulation Panel (VIP) has been used in refrigerators with urethane foam in recent years. VIP for low temperature is constructed by laminated plastic film, using heat welding of each neighboring part for keeping vacuum, so that the performance decrement is very large under high temperature. But recently high efficiency insulation material is desired for high temperature water holding devices (automatic vending machine, heat pump water heater, electric hot-water pot water, etc.), and we especially focused on cost and ability of the laminated plastic film and absorbent for high temperature VIP. We measured the heatproof temperature of plastic films and checked the amount of water vapor and out coming gas on temperature-programmed adsorption in absorbent. These results suggest the suitable laminated film and absorbent system for VIP use at high temperature, and the long-term reliability was evaluated by measuring thermal conductivity of high temperature. As a result it was found that high-retort pouch of CPP (cast polypropylene film) and adding of aluminum coating are the most suitable materials for use in the welded layers of high-temperature VIPs (105°C).

Human Mesenchymal Stem Cell Behavior on Segmented Polyurethanes Prepared with Biologically Active Chain Extenders

PubMed Central

Kavanaugh, Taylor E.; Clark, Amy Y.; Chan-Chan, Lerma H.; Ramírez-Saldaña, Maricela; Vargas-Coronado, Rossana F.; Cervantes-Uc, José M.; Hernández-Sánchez, Fernando; García, Andrés J.; Cauich-Rodríguez, Juan V.

2016-01-01

The development of elastomeric, bioresorbable and biocompatible segmented polyurethanes (SPUs) for use in tissue-engineering applications has attracted considerable interest because of the existing need of mechanically tunable scaffolds for regeneration of different tissues, but the incorporation of osteoinductive molecules into SPUs has been limited. In this study, segmented polyurethanes were synthesized from poly (ε-caprolactone)diol, 4,4’-methylene bis(cyclohexyl isocyanate) (HMDI) using biologically active compounds such as ascorbic acid, L-glutamine, β-glycerol phosphate, and dexamethasone as chain extenders. Fourier Transform Infrared Spectroscopy (FTIR) revealed the formation of both urethanes and urea linkages while Differential Scanning Calorimetry, Dynamic Mechanical Analysis, X-ray Diffraction and mechanical testing showed that these polyurethanes were semi-crystalline polymers exhibiting high deformations. Cytocompatibility studies showed that only SPUs containing β-glycerol phosphate supported human mesenchymal stem cell (hMSC) adhesion, growth, and osteogenic differentiation, rendering them potentially suitable for bone tissue regeneration, whereas other SPUs failed to support either cell growth or osteogenic differentiation, or both. This study demonstrates that modification of SPUs with osteogenic compounds can lead to new cytocompatible polymers for regenerative medicine applications. PMID:26704555

Implementing and Quantifying the Shape-Memory Effect of Single Polymeric Micro/Nanowires with an Atomic Force Microscope.

PubMed

Fang, Liang; Gould, Oliver E C; Lysyakova, Liudmila; Jiang, Yi; Sauter, Tilman; Frank, Oliver; Becker, Tino; Schossig, Michael; Kratz, Karl; Lendlein, Andreas

2018-04-23

The implementation of shape-memory effects (SME) in polymeric micro- or nano-objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro- and nano-objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro-spun poly(ether urethane) (PEU) micro- or nanowires freely suspended between two micropillars on a micro-structured silicon substrate. In this way, programming strains of 10±1% or 21±1% were realized, which could be successfully fixed. An almost complete restoration of the original free-suspended shape during heating confirmed the excellent shape-memory performance of the PEU wires. Apparent recovery stresses of σ max,app =1.2±0.1 and 33.3±0.1 MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro- and nanosystems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal and chemical stabilization of ethylene/vinyl acetate/vinyl alcohol (EVA-OH) terpolymers under nitroplasticizer environments

DOE PAGES

Yang, Dali; Hubbard, Kevin M.; Henderson, Kevin C.; ...

2014-09-17

Here, we compare the aging behaviors of cross-linked ethylene/vinyl acetate/vinyl alcohol terpolymers, also referred to as EVA-OH, when they are either immersed in nitroplasticizer (NP) liquid or exposed to NP vapor at different temperatures. And while thermogravimetric analysis and differential scanning calorimetry are used to probe the thermal stability of aged NP and polymers, Fourier transform infrared, gel permeation chromatography, ultra-violet/vis, and nuclear magnetic resonance are used to probe their structural changes over the aging process. Our study confirms that NP degrades through C[BOND]N cleavage, and releases HONO molecules at a slightly elevated temperature (<75°C). As these molecules accumulate inmore » the vapor phase, they react among themselves to create an acidic environment. Therefore, these chemical constituents in the NP vapor significantly accelerate the hydrolysis of EVA-OH polymer. When the hydrolysis occurs in both vinyl acetate and urethane groups and the scission at the cross-linker progresses, EVA-OH becomes vulnerable to further degradation in the NP vapor environment. Finally, through the comprehensive characterization, the possible degradation mechanisms of the terpolymers are proposed.« less

Optogenetic activation of septal cholinergic neurons suppresses sharp wave ripples and enhances theta oscillations in the hippocampus.

PubMed

Vandecasteele, Marie; Varga, Viktor; Berényi, Antal; Papp, Edit; Barthó, Péter; Venance, Laurent; Freund, Tamás F; Buzsáki, György

2014-09-16

Theta oscillations in the limbic system depend on the integrity of the medial septum. The different populations of medial septal neurons (cholinergic and GABAergic) are assumed to affect different aspects of theta oscillations. Using optogenetic stimulation of cholinergic neurons in ChAT-Cre mice, we investigated their effects on hippocampal local field potentials in both anesthetized and behaving mice. Cholinergic stimulation completely blocked sharp wave ripples and strongly suppressed the power of both slow oscillations (0.5-2 Hz in anesthetized, 0.5-4 Hz in behaving animals) and supratheta (6-10 Hz in anesthetized, 10-25 Hz in behaving animals) bands. The same stimulation robustly increased both the power and coherence of theta oscillations (2-6 Hz) in urethane-anesthetized mice. In behaving mice, cholinergic stimulation was less effective in the theta (4-10 Hz) band yet it also increased the ratio of theta/slow oscillation and theta coherence. The effects on gamma oscillations largely mirrored those of theta. These findings show that medial septal cholinergic activation can both enhance theta rhythm and suppress peri-theta frequency bands, allowing theta oscillations to dominate.

[Role of rostral ventrolateral medulla in the pressor response to intraventricular (4th) injection of substance P].

PubMed

Zhang, X H; Ni, H

1998-04-01

Experiments were done in rabbits anaesthetized with urethane and immobilized under artificial respiration. It was found that substance P (SP, 0.8 ng/kg dissolved in 100 microliters artificial cerebro-spinal fluid, CSF) injected into the 4th ventricle induced either a rise or a drop of pulmonary arterial pressure (PAP) with predominated pressor response. In addition, a rise in carotid arterial pressure (CAP) and reduction in heart rate (HR) were also observed, whereas no significant alteration in PAP, CAP and HR was observed. Microinjection of SP receptor antagonist [D-Pro2, D-Phe7, D-Trp9]--SP (5-10 ng dissolved in 0.5 microliter CSF) or phentolamine (2-3 micrograms dissolved in 0.5 microliter CSF) into the bilateral rostral ventrolateral medulla (rVLM) prior to intraventricular injection of SP could block the SP-induced pressor responses in pulmonary and carotid arteries, while microinjection of SP receptor antagonist or phentolamine into bilateral caudal ventrolateral medulla (cVLM) at the same dosage had no effect. The results show that SP-induced pulmonary and carotid pressor responses may be mediated through SP-receptor and alpha-adrenergic receptors in the rostral ventro-lateral medulla (rVLM).

Transcranial direct-current stimulation increases extracellular dopamine levels in the rat striatum

PubMed Central

Tanaka, Tomoko; Takano, Yuji; Tanaka, Satoshi; Hironaka, Naoyuki; Kobayashi, Kazuto; Hanakawa, Takashi; Watanabe, Katsumi; Honda, Manabu

2013-01-01

Background: Transcranial direct-current stimulation (tDCS) is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo. Objective/Hypothesis: To investigate whether the application of cathodal or anodal tDCS affects extracellular dopamine and serotonin levels in the rat striatum. Methods: Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal tDCS was applied continuously for 10 min with a current intensity of 800 μA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation. Results: Following the application of cathodal, but not anodal, tDCS for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels. Conclusion: These findings suggest that tDCS has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia. PMID:23596399

Peripheral functional organisation of vagally evoked gastric motor responses in the ferret.

PubMed Central

Andrews, P L; Lawes, I N; Bower, A J

1980-01-01

The aims of the present study were to determine the relative amplitudes of intragastric motor responses evoked by different vagal branches and to establish whether the effects of acute or chronic vagotomy could be predicted from these data. Intragastric pressure responses to electrical stimulation of the vagus were measured in urethane-anaesthetised ferrets and acute or chronic vagotomies were performed. The results show that the left and right cervical vagi were equipotential and fully overlaped each other. Their contributions to the dorsal trunk were equipotential and fully overlapping and so were their contributions to the ventral trunk. The dorsal trunk was more effective than the ventral trunk and there was total functional overlap between these two trunks. Vagal evoked gastric motor responses of the ferret are apparently organised in a different way from vagally induced acid secretion or hormone release in the cat. Acute removal of a trunk led to a reduction in evoked responses that was not linear function of the effect of stimulation of that trunk. In contrast, chronic removal caused a relative increase in evoked responses that ws inversely related to the decrease caused by acute removal. The implications of total functional overlap and neuromuscular reorganisation after chronic vagotomy are discussed. PMID:7439800

Material and fabrication strategies for artificial muscles (Conference Presentation)

NASA Astrophysics Data System (ADS)

Spinks, Geoffrey M.

2017-04-01

Soft robotic and wearable robotic devices seek to exploit polymer based artificial muscles and sensor materials to generate biomimetic movements and forces. A challenge is to integrate the active materials into a complex, three-dimensional device with integrated electronics, power supplies and support structures. Both 3D printing and textiles technologies offer attractive fabrication strategies, but require suitable functional materials. 3D printing of actuating hydrogels has been developed to produce simple devices, such as a prototype valve. Tough hydrogels based on interpenetrating networks of ionicially crosslinked alginate and covalently crosslinked polyacrylamide and poly(N-isopropylacrylamide) have been developed in a form suitable for extrusion printing with UV curing. Combined with UV-curable and extrudable rigid acrylated urethanes, the tough hydrogels can be 3D printed into composite materials or complex shapes with multiple different materials. An actuating valve was printed that operated thermally to open or close the flow path using 6 parallel hydrogel actuators. Textile processing methods such as knitting and weaving can be used to generate assemblies of actuating fibres. Low cost and high performance coiled fibres made from oriented polymers have been used for developing actuating textiles. Similarly, braiding methods have been developed to fabricate new forms of McKibben muscles that operate without any external apparatus, such as pumps, compressors or piping.

Choleretic activity of Gentiana lutea ssp. symphyandra in rats.

PubMed

Oztürk, N; Herekman-Demir, T; Oztürk, Y; Bozan, B; Başer, K H

1998-08-01

Effects of an ethanolic extract prepared from G. lutea ssp. symphyandra roots on the bile production and liver in rats were investigated. Bile flows of rats which were treated by a single i.p. dose of CCl(4) 24 h prior to experiments were measured after the cannulation of bile duct under urethane anaesthesia. After an equilibration period of 1 h, the lyophilized extract were administered intraduodenally (500 mg/kg i.p.), while control animals received physiological saline only. To monitor the effect of multiple dose therapy, rats received the same dose of G. lutea ssp. symphyandra extract for 3 days (2 days prior to CCl(4) administration) and their bile flows were measured after the cannulation. In all groups, bile samples were collected for 3 h with 15 min intervals. After the completion of bile flow experiment, rat livers were removed and put in neutral formaldehyde solution (10%) for the histological examination. According to results obtained, multiple dose treatment of rats with the plant extract normalized the decreased bile flow due CCl(4), whereas single dose therapy was ineffective on the impaired bile flow. These data indicate that the extract prepared from Gentiana lutea ssp. symphyandra roots has a hepatoprotective activity. Copyright © 1998 Gustav Fischer Verlag. Published by Elsevier GmbH.. All rights reserved.

Study on the Antimicrobial Properties of Citrate-Based Biodegradable Polymers

PubMed Central

Su, Lee-Chun; Xie, Zhiwei; Zhang, Yi; Nguyen, Kytai Truong; Yang, Jian

2014-01-01

Citrate-based polymers possess unique advantages for various biomedical applications since citric acid is a natural metabolism product, which is biocompatible and antimicrobial. In polymer synthesis, citric acid also provides multiple functional groups to control the crosslinking of polymers and active binding sites for further conjugation of biomolecules. Our group recently developed a number of citrate-based polymers for various biomedical applications by taking advantage of their controllable chemical, mechanical, and biological characteristics. In this study, various citric acid derived biodegradable polymers were synthesized and investigated for their physicochemical and antimicrobial properties. Results indicate that citric acid derived polymers reduced bacterial proliferation to different degrees based on their chemical composition. Among the studied polymers, poly(octamethylene citrate) showed ~70–80% suppression to microbe proliferation, owing to its relatively higher ratio of citric acid contents. Crosslinked urethane-doped polyester elastomers and biodegradable photoluminescent polymers also exhibited significant bacteria reduction of ~20 and ~50% for Staphylococcus aureus and Escherichia coli, respectively. Thus, the intrinsic antibacterial properties in citrate-based polymers enable them to inhibit bacteria growth without incorporation of antibiotics, silver nanoparticles, and other traditional bacteria-killing agents suggesting that the citrate-based polymers are unique beneficial materials for wound dressing, tissue engineering, and other potential medical applications where antimicrobial property is desired. PMID:25023605

Localization of needle tip with color doppler during pericardiocentesis: In vitro validation and initial clinical application

NASA Technical Reports Server (NTRS)

Armstrong, G.; Cardon, L.; Vilkomerson, D.; Lipson, D.; Wong, J.; Rodriguez, L. L.; Thomas, J. D.; Griffin, B. P.

2001-01-01

This study evaluates a new device that uses color Doppler ultrasonography to enable real-time image guidance of the aspirating needle, which has not been possible until now. The ColorMark device (EchoCath Inc, Princeton, NJ) induces high-frequency, low-amplitude vibrations in the needle to enable localization with color Doppler. We studied this technique in 25 consecutive patients undergoing pericardiocentesis, and in vitro, in a urethane phantom with which the accuracy of color Doppler localization of the needle tip was compared with that obtained by direct measurement. Tip localization was excellent in vitro; errors axial to the ultrasound beam (velocity Doppler -0.13 +/- 0.90 mm, power Doppler -0.05 +/- 1.7 mm) were less than lateral errors (velocity -0.36 +/- 1.8 mm, power -0.02 +/- 2.8 mm). In 18 of 25 patients, the needle was identified and guided into the pericardial space with the ColorMark technique, and it allowed successful, uncomplicated drainage of fluid. Initial failures were the result of incorrect settings on the echocardiographic machine and inappropriate combinations of the needle puncture site and imaging window. This study demonstrates a novel color Doppler technique that is highly accurate at localizing a needle tip. The technique is feasible for guiding pericardiocentesis. Further clinical validation of this technique is required.

Changes in the frequency of swallowing during electrical stimulation of superior laryngeal nerve in rats.

PubMed

Tsuji, Kojun; Tsujimura, Takanori; Magara, Jin; Sakai, Shogo; Nakamura, Yuki; Inoue, Makoto

2015-02-01

The aim of the present study was to investigate the adaptation of the swallowing reflex in terms of reduced swallowing reflex initiation following continuous superior laryngeal nerve stimulation. Forty-four male Sprague Dawley rats were anesthetized with urethane. To identify swallowing, electromyographic activity of the left mylohyoid and thyrohyoid muscles was recorded. To evoke the swallowing response, the superior laryngeal nerve (SLN), recurrent laryngeal nerve, or cortical swallowing area was electrically stimulated. Repetitive swallowing evoked by continuous SLN stimulation was gradually reduced, and this reduction was dependent on the resting time duration between stimulations. Prior SLN stimulation also suppressed subsequent swallowing initiation. The reduction in evoked swallows induced by recurrent laryngeal nerve or cortical swallowing area stimulation was less than that following superior laryngeal nerve stimulation. Decerebration had no effect on the reduction in evoked swallows. Prior subthreshold stimulation reduced subsequent initiation of swallowing, suggesting that there was no relationship between swallowing movement evoked by prior stimulation and the subsequent reduction in swallowing initiation. Overall, these data suggest that reduced sensory afferent nerve firing and/or trans-synaptic responses, as well as part of the brainstem central pattern generator, are involved in adaptation of the swallowing reflex following continuous stimulation of swallow-inducing peripheral nerves and cortical areas. Copyright © 2014 Elsevier Inc. All rights reserved.

Development of polyether urethane intravaginal rings for the sustained delivery of hydroxychloroquine

PubMed Central

Chen, Yufei; Traore, Yannick Leandre; Li, Amanda; Fowke, Keith R; Ho, Emmanuel A

2014-01-01

Hydroxychloroquine (HCQ) has been shown to demonstrate anti-inflammatory properties and direct anti-HIV activity. In this study, we describe for the first time the fabrication and in vitro evaluation of two types of intravaginal ring (IVR) devices (a surfaced-modified matrix IVR and a reservoir segmental IVR) for achieving sustained delivery (>14 days) of HCQ as a strategy for preventing male-to-female transmission of HIV. Both IVRs were fabricated by hot-melt injection molding. Surface-modified matrix IVRs with polyvinylpyrrolidone or poly(vinyl alcohol) coatings exhibited significantly reduced burst release on the first day (6.45% and 15.72% reduction, respectively). Reservoir IVR segments designed to release lower amounts of HCQ displayed near-zero-order release kinetics with an average release rate of 28.38 μg/mL per day for IVRs loaded with aqueous HCQ and 32.23 μg/mL per day for IVRs loaded with HCQ mixed with a rate-controlling excipient. Stability studies demonstrated that HCQ was stable in coated or noncoated IVRs for 30 days. The IVR segments had no significant effect on cell viability, pro-inflammatory cytokine production, or colony formation of vaginal and ectocervical epithelial cells. Both IVR systems may be suitable for the prevention of HIV transmission and other sexually transmitted infections. PMID:25336923

Effect of midodrine on chlorpromazine-induced orthostatic hypotension in rabbits: comparison with amezinium, etilefrine and droxidopa.

PubMed

Kurihara, J; Takata, Y; Suzuki, S; Okubo, Y; Kato, H

2000-12-01

Orthostatic hypotension was produced in urethane-anesthetized rabbit by a combination of chlorpromazine (0.1 mg/kg, i.v.) and 45 degrees head-up tilt. The effect of midodrine (1 and 3 mg/kg, i.d.) was investigated in comparison with amezinium (10 and 30 mg/kg, i.d.), etilefrine (10 and 30 mg/kg, i.d.) and droxidopa (30 and 100 mg/kg, i.d.). The higher doses of each drug significantly mitigated the chlorpromazine-induced orthostatic hypotension, while none of the lower doses caused a significant effect. The effect of midodrine developed most rapidly; a significant effect was observed 25 min after administration. The order of onset time was midodrine < etilefrine < amezinium < droxidopa. The effect of droxidopa was significant only at 130 to 160 min after administration. The amplitude of effect was in the following order; midodrine = droxidopa > or = etilefrine > amezinium. Midodrine (3 mg/kg, i.d.) mitigated orthostatic hypotension induced by prazosin (0.1 mg/kg, i.v.), but not by pentolinium (0.6 mg/kg, i.v.). It is suggested that midodrine competes with chlorpromazine at alpha1-adrenoceptors and subsequently recovers reflex vasoconstriction. Midodrine may be useful to protect patients with impaired baroreflex activity from accidental orthostatic hypotension during treatment with neuroleptics.

Development and validation of cryogenic foam insulation for LH2 subsonic transports

NASA Technical Reports Server (NTRS)

Anthony, F. M.; Colt, J. Z.; Helenbrook, R. G.

1981-01-01

Fourteen foam insulation specimens were tested. Some were plain foam while others contained flame retardants, chopped fiberglass reinforcement and/or vapor barriers. The thermal performance of the insulation was determined by measuring the rate at which LH2 boiled from an aluminum tank insulated with the test material. The test specimens were approximately 50 mm (2 in.) thick. They were structurally scaled so that the test cycle would duplicate the maximum thermal stresses predicted for the thicker insulation of an aircraft liquid hydrogen fuel tank during a typical subsonic flight. The simulated flight cycle of approximately 10 minutes duration heated the other insulation surface to 316 K (110 F) and cooled it to 226 K (20 F) while the inner insulation surface remained at liquid hydrogen temperature of 20 K (-423 F). Two urethane foam insulations exceeded the initial life goal of 2400 simulated flight cycles and sustained 4400 cycles with only minor damage. The addition of fiberglass reinforcement of flame retardant materials to an insulation degraded thermal performance and/or the life of the foam material. Installation of vapor barriers enhanced the structural integrity of the material but did not improve thermal performance. All of the foams tested were available materials; none were developed specifically for LH2 service.

Surface chemistry of a pine-oil cleaner and other terpene mixtures with ozone on vinyl flooring tiles.

PubMed

Ham, Jason E; Wells, J Raymond

2011-04-01

Indoor environments are dynamic reactors where consumer products (such as cleaning agents, deodorants, and air fresheners) emit volatile organic compounds (VOCs) that can subsequently interact with indoor oxidants such as ozone (O(3)), hydroxyl radicals, and nitrate radicals. Typically, consumer products consist of mixtures of VOCs and semi-VOCs which can react in the gas-phase or on surfaces with these oxidants to generate a variety of oxygenated products. In this study, the reaction of a pine-oil cleaner (POC) with O(3) (100ppb) on a urethane-coated vinyl flooring tile was investigated at 5% and 50% relative humidity. These results were compared to previous α-terpineol+O(3) reactions on glass and vinyl surfaces. Additionally, other terpene and terpene alcohol mixtures were formulated to understand the emission profiles as seen in the POC data. Results showed that the α-terpineol+O(3) reaction products were the prominent species that were also observed in the POC/O(3) surface experiments. Furthermore, α-terpineol+O(3) reactions generate the largest fraction of oxygenated products even in equal mixtures of other terpene alcohols. This finding suggests that the judicial choice of terpene alcohols for inclusion in product formulations may be useful in reducing oxidation product emissions. Published by Elsevier Ltd.

Salivary contamination during bonding procedures with a one-bottle adhesive system.

PubMed

Fritz, U B; Finger, W J; Stean, H

1998-09-01

The effect of salivary contamination of enamel and dentin on bonding efficacy of an experimental one-bottle resin adhesive was investigated. The adhesive was a light-curing urethane dimethacrylate/hydroxyethyl methacrylate/4-methacryloxyethyl trimellitate anhydride mixture dissolved in acetone. Evaluation parameters were shear bond strength and marginal gap width in a dental cavity. Apart from a control group without contamination (group 1), etched enamel and dentin were (2) contaminated with saliva and air dried; (3) contaminated, rinsed, and blot dried; (4) coated with adhesive, contaminated, rinsed, and blot dried; (5) coated with adhesive, light cured, contaminated, rinsed, and air dried; or (6) treated as in group 5, with additional adhesive application after air drying. There was no negative effect in groups 3 and 4, compared with control. Air drying after salivary contamination (group 2) resulted in low shear bond strengths and wide marginal gaps. Contamination of the cured adhesive layer (groups 5 and 6) had no adverse effect on enamel shear bond strengths, but resulted in 50% reduced dentin shear bond strengths and wide marginal gaps. The one-bottle adhesive system is relatively insensitive to salivary contamination, provided that the contamination occurs prior to light curing of the adhesive and is carefully rinsed and blot dried. Salivary contact after adhesive curing must be avoided.

Distribution of phenanthrene between soil and an aqueous phase in the presence of anionic micelle-like amphiphilic polyurethane particles.

PubMed

Lee, Kangtaek; Choi, Heon-Sik; Kim, Ju-Young; Ahn, Ik-Sung

2003-12-12

Sorption of micelle-like amphiphilic polyurethane (APU) particles to soil was studied and compared to that of a model anionic surfactant, sodium dodecyl sulfate (SDS). Three types of APU particles with different hydrophobicity were synthesized from urethane acrylate anionomers (UAA) and used in this study. Due to the chemically cross-linked structure, APU exhibited less sorption to the soil than SDS and a greater reduction in the sorption of phenanthrene, a model soil contaminant, to the soil was observed in the presence of APU than SDS even though the solubility of phenanthrene was higher in the presence of SDS than APU. A mathematical model was developed to describe the phenanthrene distribution between soil and an aqueous phase containing APU particles. The sorption of phenanthrene to the test soil could be well described by Linear isotherm. APU sorption to the soil was successfully described by Langmuir and Freundlich isotherms. The partition of phenanthrene between water and APU were successfully explained with a single partition coefficient. The model, which accounts for the limited solubilization of phenanthrene in sorbed APU particles, successfully described the experimental data for the distribution of phenanthrene between the soil and the aqueous phase in the presence of APU.

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

Nahum, T.; Dodiuk, H.; Dotan, A.

Superhydrophobic surfaces with contact angle (CA) >150 and sliding angle (SA) <10 have been aroused curiosity over the years due to their various applications. Superhydrophobicity can be obtained tailoring the chemistry and the roughness of the surface, mimicking the Lotus flower. Most superhydrophobic surfaces based on secondary bonding lose their roughness in harsh conditions and are unsuitable for practical applications. Photoreactive SiO{sub 2} nanoparticles (NPs) based on benzophenone (BP) can be a very effective tool for formation of reactive species that function as a molecular bridge by covalent bonding between the NP and any polymer matrix with C-C and C-Hmore » bonds. The present work focused on thermoset radiation curing urethane acrylate. Upon UV irradiation reactive excited nπ* triplet benzophenone species are formed and react through hydrogen abstraction to form ketyl radicals which interact with a radicals from the UV irradiated polymer matrix to yield covalent bonding. Roughness was achieved by dipping the substrate in SiO{sub 2}@BPs NPs dispersion followed by irradiation. Fluoroalkylsilane was used to obtain hydrophobic top layer. AFM nano manipulation was used to verify the immobilization of NPs. Evaluation of durability was made using air flow at 300 km/hr. Preliminary results indicate the formation of super hydrophobic surfaces (CA>150 and SA<10) with improved stability.« less

Indoor cultivation and cultural characteristics of Wolfiporia cocos sclerotia using mushroom culture bottles.

PubMed

Kubo, Toshiyuki; Terabayashi, Susumu; Takeda, Shuichi; Sasaki, Hiroshi; Aburada, Masaki; Miyamoto, Ken-ichi

2006-06-01

We newly developed an indoor cultivation technique for Wolfiporia cocos (Wolf) Ryvarden et Gilbertson (Syn. Poria cocos Wolf), not with soil, but using mushroom culture bottles with pine logs, and clarified some cultural characteristics of sclerotia in the laboratory. To determine the optimum conditions for sclerotia growth, the weight of sclerotia and concentration of CO2 in three different air filters; cloth, paper and urethane resin, and closed bottles were tested. When the cloth air filter was used, the growth rate was the fastest and the yield was maximal. These results suggested that the aeration was an important environmental factor for cultivation. To clarify the characteristics of culture in the cloth air filtered and closed bottles, the weight of sclerotia, the compositions of pine logs and the contents of pachymic acid and dehydropachymic acid were examined during 24 weeks. The growth of scleroia and the wood decaying efficiency in the cloth air filtered bottles were better than those in the closed bottles. Also, it was found that W. cocos was a brown rot fungus due to the alkaline solubility of pine logs in the wood decay process. In addition, the contents of pachymic acid and dehydropachymic acid and the TLC pattern between the cultivated and commercial sclerotia did not differ remarkably.

Use of tripolar electrodes for minimization of current spread in uncut peripheral nerve stimulation.

PubMed

Ohsawa, Ichiro; Inui, Koji

2009-05-01

The electrical stimulation of an uncut peripheral nerve requires a countermeasure to avoid the spread of current through a loop pathway formed outside the electrode array. Here the use of tripolar electrodes (TE) is proposed. By binding the two end poles, current spread through the loop pathway can theoretically be eliminated since both end poles are held equipotential. Experimentally, we tested the validity of this approach. In chloralose-urethane anesthetized rats, the left cervical vagus (LCV) was placed on TE which could function as such or as bipolar electrodes (BE) by the use of a selector switch. The spread of current to the adjacent tissues (rectus capitis muscle underlying the LCV, and the right cervical vagus (RCV) incised and translocated beside the target, LCV) was compared between TE and BE. When the stimulus intensity was increased, contraction occurred in the capitis muscle with BE, but not TE. Compound spike potentials of A fiber origin were evoked in the non-target RCV on high-intensity stimulation with BE, but not TE. Constant voltage stimulation of the LCV with TE produced bradycardia of the same magnitude as that with BE. In conclusion, constant voltage stimulation using TE can minimize current spread without changing the stimulus's effects.

Understanding the effects of PEMFC contamination from balance of plant assembly aids materials: In situ studies

DOE PAGES

Opu, Md.; Bender, G.; Macomber, Clay S.; ...

2015-06-29

In this study, in situ performance data were measured to assess the degree of contamination from leachates of five families of balance of plant (BOP) materials (i.e., 2-part adhesive, grease, thread lock/seal, silicone adhesive/seal and urethane adhesive/seal) broadly classified as assembly aids that may be used as adhesives and lubricants in polymer electrolyte membrane fuel cell (PEMFC) systems. Leachate solutions, derived from soaking the materials in deionized (DI) water at elevated temperature, were infused into the fuel cell to determine the effect of the leachates on fuel cell performance. During the contamination phase of the experiments, leachate solution was introducedmore » through a nebulizer into the cathode feed stream of a 50 cm 2 PEMFC operating at 0.2 A/cm 2 at 80°C and 32%RH. Voltage loss and high frequency resistance (HFR) were measured as a function of time and electrochemical surface area (ECA) before and after contamination were compared. Two procedures of recovery, one self-induced recovery with DI water and one driven recovery through cyclic voltammetry (CV) were investigated. Finally, performance results measured before and after contamination and after CV recovery are compared and discussed.« less

Durability of switchable QR code carriers under hydrolytic and photolytic conditions

NASA Astrophysics Data System (ADS)

Ecker, Melanie; Pretsch, Thorsten

2013-09-01

Following a guest diffusion approach, the surface of a shape memory poly(ester urethane) (PEU) was either black or blue colored. Bowtie-shaped quick response (QR) code carriers were then obtained from laser engraving and cutting, before thermo-mechanical functionalization (programming) was applied to stabilize the PEU in a thermo-responsive (switchable) state. The stability of the dye within the polymer surface and long-term functionality of the polymer were investigated against UVA and hydrolytic ageing. Spectrophotometric investigations verified UVA ageing-related color shifts from black to yellow-brownish and blue to petrol-greenish whereas hydrolytically aged samples changed from black to greenish and blue to light blue. In the case of UVA ageing, color changes were accompanied by dye decolorization, whereas hydrolytic ageing led to contrast declines due to dye diffusion. The Michelson contrast could be identified as an effective tool to follow ageing-related contrast changes between surface-dyed and laser-ablated (undyed) polymer regions. As soon as the Michelson contrast fell below a crucial value of 0.1 due to ageing, the QR code was no longer decipherable with a scanning device. Remarkably, the PEU information carrier base material could even then be adequately fixed and recovered. Hence, the surface contrast turned out to be the decisive parameter for QR code carrier applicability.

Bladder volume-dependent excitatory and inhibitory influence of lumbosacral dorsal and ventral roots on bladder activity in rats

PubMed Central

Sugaya, Kimio; de Groat, William C.

2011-01-01

This study was undertaken to examine the role of the afferent and efferent pathways of the lumbosacral spinal nerve roots in the tonic control of bladder activity. Changes of isovolumetric bladder activity were recorded in 21 sympathectomized female rats under urethane anesthesia following transection of the dorsal (DRT) and ventral (VRT) lumbosacral spinal roots, and after intraperitoneal administration of hexamethonium. DRT altered the baseline intravesical pressure in a bladder volume-dependent manner in each animal. The percent change of baseline pressure after VRT following DRT was also dependent upon bladder volume. The percent change of baseline pressure after VRT alone was similarly dependent on bladder volume, but not after VRT followed by DRT. The percent change of baseline intravesical pressure (y)(−9 to +8 cm H2O, −56 to +46%) after DRT and VRT depended upon bladder volume (x)(y = 44.7 x −40.4) in all rats. Hexamethonium increased the amplitude of small myogenic bladder contractions after DRT and VRT. In conclusion, the bladder is tonically excited or inhibited by a local reflex pathway and by a parasympathetic reflex pathway that depends on connections with the lumbosacral spinal cord and the pelvic nerves. Both reflex mechanisms are influenced by bladder volume. PMID:17878597

Mediterranean report/heated pipeline offloads tankers

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

Not Available

1979-08-01

The first heated submarine pipeline in Europe, according to Anonima Petroli Italiana, is now in operation from their Falconara Refinery near Ancona, Italy, to an existing offshore loading facility. The 3850 m long, 24 inch wide line, laid on the seabottom at 3-14 m depths, was built to offload high pour/high viscosity crudes requiring a minimum constant discharge temperature of 45-65 C. Four 3.5 mm heating pipes (three operating and one spare) were stretch-welded to the outside of the line at 45 degree angles to each other; they are heated at about 100 m/m by a parasitic current formed onmore » the pipe while 1500 volt current is passed through a cable inside the pipe. The heating system is equipped with an electric feeding installation, automatic power regulation, and remote sensors applied along the sea line. The heating pipes were protected with a coat of epoxy tar paint, a 50 mm thick and 70 kg/cm dense sprayed-on urethane foam coat, a sheath of butyric elastomer covered with an adhering 3 mm coat of polyethylene, and a concrete coat for protection and weighting. Specially designed water stops were placed at both ends of every line section under the waterproofing. Industria Construzioni Opere Publiche prefabricated the line on shore and laid it from shore.« less

Effect of stimulation and hyperpolarization on non-electrolyte and sodium permeability in perfused axons of squid.

PubMed

Hidalgo, C; Latorre, R

1970-11-01

1. The permeability for micro-injected [(3)H]ethylene glycol was measured in resting state and during stimulation at 100/sec in squid giant axons. No detectable changes during electrical activity were observed.2. The influxes of urethane, tritiated water, ethylene glycol, urea and sodium were measured in internally perfused squid axons. Ethylene glycol and urea influxes were determined simultaneously with sodium influxes. The electrical stimulation of the fibre produced an increase in the influx of sodium but did not alter the influxes of the non-electrolytes listed above.3. Experiments were done with the combined voltage clamp-perfusion technique. The influxes of ethylene glycol and sodium were simultaneously measured in resting state and during maximum sodium current under stimulation at 10/sec. The influx of sodium increased in these conditions but the influx of ethylene glycol remained constant. In some experiments, the fibre was hyperpolarized to 10 or 20 mV, above the resting potential and the influxes of ethylene glycol and sodium were measured. The sodium influx decreased to 60% at 20 mV above the resting potential whereas the influx of ethylene glycol remained constant.4. These results indicate that in the giant axons of the squid Dosidicus gigas, sodium and non-electrolytes fluxes are not coupled.

Effect of stimulation and hyperpolarization on non-electrolyte and sodium permeability in perfused axons of squid

PubMed Central

Hidalgo, Cecilia; Latorre, Ramón

1970-01-01

1. The permeability for micro-injected [3H]ethylene glycol was measured in resting state and during stimulation at 100/sec in squid giant axons. No detectable changes during electrical activity were observed. 2. The influxes of urethane, tritiated water, ethylene glycol, urea and sodium were measured in internally perfused squid axons. Ethylene glycol and urea influxes were determined simultaneously with sodium influxes. The electrical stimulation of the fibre produced an increase in the influx of sodium but did not alter the influxes of the non-electrolytes listed above. 3. Experiments were done with the combined voltage clamp—perfusion technique. The influxes of ethylene glycol and sodium were simultaneously measured in resting state and during maximum sodium current under stimulation at 10/sec. The influx of sodium increased in these conditions but the influx of ethylene glycol remained constant. In some experiments, the fibre was hyperpolarized to 10 or 20 mV, above the resting potential and the influxes of ethylene glycol and sodium were measured. The sodium influx decreased to 60% at 20 mV above the resting potential whereas the influx of ethylene glycol remained constant. 4. These results indicate that in the giant axons of the squid Dosidicus gigas, sodium and non-electrolytes fluxes are not coupled. PMID:5500991

Substance P in the dorsal vagal complex inhibits medullary TRH-induced gastric acid secretion in rats.

PubMed

Yang, H; Taché, Y

1997-05-01

Neurons that contain substance P (SP) and thyrotropin-releasing hormone (TRH) in medullary midline raphe nuclei project to the dorsal vagal complex (DVC). The modulatory role of SP on basal gastric acid secretion (GAS) and TRH on DVC-induced stimulation of GAS was studied in urethan-anesthetized rats. The stable SP agonist, DiMe-C7 ([pGlu5, MePhe8, MeGly9]SP5-11, 50 and 100 pmol), injected unilaterally into the DVC reduced the GAS response (47 +/- 12 mumol/60 min) to coinjected TRH analog, RX 77368 (25 pmol), by 53% and 85%, respectively, whereas DiMe-C7 (100 pmol) alone had no effect on basal and pentagastrin-stimulated GAS. DiMe-C7 (100 pmol/site) inhibited the GAS response to kainic acid injected into the raphe pallidus (Rpa) when it was injected bilaterally into the DVC but not the hypoglossal nuclei. The SP nourokinin-1-receptor antagonist, CP-96,345, injected bilaterally into the DVC (1 nmol/ site) increased basal GAS (33 +/- 8 mumol/90 min) and potentiated the GAS response to kainic acid injected into the Rpa by 40%. These results suggest that SP acts on neurokinin-1 receptors in the DVC to reduce medullary TRH-induced stimulation of GAS in rats.

Cardiovascular effects of substance P receptor stimulation in the ventrolateral medullary pressor and depressor areas.

PubMed

Urbanski, R W; Murugaian, J; Krieger, A J; Sapru, H N

1989-07-10

The pressor (VLPA) and the depressor (VLDA) areas in the ventrolateral medulla were identified with the microinjection of L-glutamate (1.77 nmol/site) in artificially ventilated urethane-anesthetized male Wistar rats. Bilateral microinjection of a stable substance P (SP) agonist [pGlu5, MePhe8, Sar9]-SP(5-11)], abbreviated as DiMe, into the VLPA (6-600 pmol/site) produced a dose-dependent increase in blood pressure (BP). The effects on heart rate (HR) were variable. Intravenous pretreatment with a ganglionic blocker chlorisondamine (3.0 mg/kg, i.v.), but not with a vasopressin antagonist, blocked these responses. Similar microinjection of DiMe (6-600 pmol/site) into the VLDA produced a dose-dependent decrease in HR but had no effect on BP levels. The DiMe-induced bradycardic response elicited from the VLDA was blocked by i.v. pretreatment with atropine methylbromide (0.5 mg/kg, i.v.). These findings indicate that there are SP receptors localized on sympathoexcitatory neurons in the VLPA and that SP may be an excitatory neurotransmitter in this area. In the VLDA, the SP receptors appear to be localized on a subpopulation of neurons that affect vagal, but not sympathetic, outflow to the heart.

NK1 receptor activation in rat rostral ventrolateral medulla selectively attenuates somato-sympathetic reflex while antagonism attenuates sympathetic chemoreflex.

PubMed

Makeham, John M; Goodchild, Ann K; Pilowsky, Paul M

2005-06-01

The effects of activation and blockade of the neurokinin 1 (NK1) receptor in the rostral ventrolateral medulla (RVLM) on arterial blood pressure (ABP), splanchnic sympathetic nerve activity (sSNA), phrenic nerve activity, the somato-sympathetic reflex, baroreflex, and chemoreflex were studied in urethane-anesthetized and artificially ventilated Sprague-Dawley rats. Bilateral microinjection of either the stable substance P analog (pGlu5, MePhe8, Sar9)SP(5-11) (DiMe-SP) or the highly selective NK1 agonist [Sar9, Met (O(2))11]SP into the RVLM resulted in an increase in ABP, sSNA, and heart rate and an abolition of phrenic nerve activity. The effects of [Sar9, Met (O(2))11]SP were blocked by the selective nonpeptide NK1 receptor antagonist WIN 51708. NK1 receptor activation also dramatically attenuated the somato-sympathetic reflex elicited by tibial nerve stimulation, while leaving the baroreflex and chemoreflex unaffected. This effect was again blocked by WIN 51708. NK1 receptor antagonism in the RVLM, with WIN 51708 significantly attenuated the sympathoexcitatory response to hypoxia but had no effect on baseline respiratory function. Our findings suggest that substance P and the NK1 receptor play a significant role in the cardiorespiratory reflexes integrated within the RVLM.

Simultaneous determination of components released from dental composite resins in human saliva by liquid chromatography/multiple-stage ion trap mass spectrometry.

PubMed

Hsu, Wei-Yi; Wang, Ven-Shing; Lai, Chien-Chen; Tsai, Fuu-Jen

2012-02-01

Dental composite resins are widely used for fixing teeth; however, the monomers used in dental composite resins have been found to be cytotoxic and genotoxic, namely triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A glycol dimethacrylate (Bis-GMA). In this study, we incubated dental composite resins with human saliva for demonstrating the released monomers and biodegradation products. A simple saliva sample dilution method without purification or derivatization was used for quantification. We found that liquid chromatography coupled with multiple-stage ion trap mass spectrometry (LC-MS(n) ) operated in selected reaction monitoring (SRM) mode was able to separate the three monomers within 10 min. The calibration curves were linear (R² >0.996) over a wide range for each monomer in saliva: TEGDMA, 5-500 ppb; UDMA, 5-100 ppb, and Bis-GMA, 5-700 ppb. Furthermore, several biodegradation products were discovered with data-dependent MS/MS scan techniques. Although TEGMA degradation products have previously been reported, we identified two previously unknown UDMA degradation products. The LC-MS/MS method developed in this study was able to successfully quantify monomers and their principal biodegradation products from dental composite resins in human saliva. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct effects of endogenous pyrogen on medullary temperature-responsive neurons in rabbits.

PubMed

Sakata, Y; Morimoto, A; Takase, Y; Murakami, N

1981-01-01

The effect of endogenous pyrogen (E.P.) injected directly into the tissue near the recording site were examined on the activities of the medullary temperature-responsive (TR) neurons in rabbits anesthetized with urethane. Endogenous pyrogen prepared from rabbit's whole blood was administered by a fine glass cannula (100-200 micrometer in diameter) in a fluid volume of 1 to 4 microliter. The cannula was fixed to the manipulator in parallel with a microelectrode and their tips were less than 0.05 mm apart. In rabbits with the intact preoptic/anterior hypothalamic (PO/AH) region, 4 warm-responsive neurons out of 7 were inhibited and 6 cold-responsive neuron out of 7 were excited by the direct administration of the E.P. In rabbits with lesions of the PO/AH, 5 warm-responsive neurons out of 9 were inhibited and 6 cold-responsive neurons out of 8 were facilitated by E.P. Antipyretics administered locally after the E.P. antagonized the pyretic effect, causing a return of the discharge of TR neuron to the control rate within 2.4 +/- 1.2 (mean +/- S.D.) min. The medullary TR neuron itself has the ability to respond to the E.P. and contributes to the development of fever.

Remediation of hydrocarbons polluted water by hydrophobic functionalized cellulose.

PubMed

Tursi, Antonio; Beneduci, Amerigo; Chidichimo, Francesco; De Vietro, Nicoletta; Chidichimo, Giuseppe

2018-06-01

Remediation of water bodies from petroleum hydrocarbons is of the utmost importance due to health risks related to the high toxicity, mutagenicity and carcinogenicity of the hydrocarbons components that may enter into the food chain. Though several methods were proposed to face up this challenge, they are generally not easily feasible at a contaminated site and quite costly. Here we propose a green, cost-effective technology based on hydrophobized Spanish Broom (SB) cellulose fiber. The natural cellulose fiber was extracted by alkaline digestion of the raw vegetable. The hydrophilic cellulose surface was transformed into a hydrophobic one by the reaction with 4,4'-diphenylmethane diisocyanate (MDI) forming a very stable urethane linkage with the hydroxyl groups of cellulose emerging from the fibers surface. Chemical functionalization was performed with a novel solvent-free technology based on a home-made still reactor were the fiber was kept under vortex stirring and the MDI reactant then spread onto the fiber surface by nebulizing it in form of micrometer-sized droplets. The functionalized fiber, characterized by means of WCA measurements, XPS and ATR-FTIR spectroscopy, shows fast adsorption kinetics adsorption capacity as high as 220 mg/g, among the highest ever reported so far in the literature for cellulosic materials. Copyright © 2018 Elsevier Ltd. All rights reserved.

High-Throughput In Vivo Genotoxicity Testing: An Automated Readout System for the Somatic Mutation and Recombination Test (SMART)

PubMed Central

Kwak, Jihoon; Genovesio, Auguste; Kang, Myungjoo; Hansen, Michael Adsett Edberg; Han, Sung-Jun

2015-01-01

Genotoxicity testing is an important component of toxicity assessment. As illustrated by the European registration, evaluation, authorization, and restriction of chemicals (REACH) directive, it concerns all the chemicals used in industry. The commonly used in vivo mammalian tests appear to be ill adapted to tackle the large compound sets involved, due to throughput, cost, and ethical issues. The somatic mutation and recombination test (SMART) represents a more scalable alternative, since it uses Drosophila, which develops faster and requires less infrastructure. Despite these advantages, the manual scoring of the hairs on Drosophila wings required for the SMART limits its usage. To overcome this limitation, we have developed an automated SMART readout. It consists of automated imaging, followed by an image analysis pipeline that measures individual wing genotoxicity scores. Finally, we have developed a wing score-based dose-dependency approach that can provide genotoxicity profiles. We have validated our method using 6 compounds, obtaining profiles almost identical to those obtained from manual measures, even for low-genotoxicity compounds such as urethane. The automated SMART, with its faster and more reliable readout, fulfills the need for a high-throughput in vivo test. The flexible imaging strategy we describe and the analysis tools we provide should facilitate the optimization and dissemination of our methods. PMID:25830368

Real-time dynamics of high-velocity micro-particle impact

NASA Astrophysics Data System (ADS)

Veysset, David; Hsieh, Alex; Kooi, Steve; Maznev, Alex A.; Tang, Shengchang; Olsen, Bradley D.; Nelson, Keith A.

High-velocity micro-particle impact is important for many areas of science and technology, from space exploration to the development of novel drug delivery platforms. We present real-time observations of supersonic micro-particle impacts using multi-frame imaging. In an all optical laser-induced projectile impact test, a monolayer of micro-particles is placed on a transparent substrate coated with a laser absorbing polymer layer. Ablation of a laser-irradiated polymer region accelerates the micro-particles into free space with speeds up to 1.0 km/s. The particles are monitored during the impact on the target with an ultrahigh-speed multi-frame camera that can record up to 16 images with time resolution as short as 3 ns. In particular, we investigated the high-velocity impact deformation response of poly(urethane urea) (PUU) elastomers to further the fundamental understanding of the molecular influence on dynamical behaviors of PUUs. We show the dynamic-stiffening response of the PUUs and demonstrate the significance of segmental dynamics in the response. We also present movies capturing individual particle impact and penetration in gels, and discuss the observed dynamics. The results will provide an impetus for modeling high-velocity microscale impact responses and high strain rate deformation in polymers, gels, and other materials.

An Evaluation of Transplacental Carcinogenesis for Human ...

EPA Pesticide Factsheets

Risk assessments take into account the sensitivity of the postnatal period to carcinogens through the application of age-dependent adjustment factors (ADAFs) (Barton et al. 2005). The prenatal period is also recognized to be sensitive but is typically not included into risk assessments (NRC, 2009). An analysis by California OEHHA (2008) contrasted prenatal, postnatal and adult sensitivity to 23 different carcinogens across 37 studies. That analysis found a wide range of transplacental sensitivity with some agents nearly 100 fold more potent in utero than in adults while others had an in utero/adult ratio adult only exposure). Five carcinogens had more modest ratios to adult potency in both pre- and postnatal testing (vinyl chloride, ethylnitroso biuret, 3-methylcholanthrene, urethane, diethylnitrosamine, 3-10 fold). Only one chemical showed a pre- vs postnatal divergence (butylnitrosourea, prenataladult). Based upon this limited set of genotoxic carcinogens, it appears that the prenatal period often has a sensitivity that approximates what has been found for postnatal, and the maternal system does not offer substantial protection against transplacental carcinogenesis in most cases. This suggests that the system of ADAFs developed for postnatal exposure may be considered for prenatal exposures as well. An alternative approach may be to calculate cancer risk for the period of pregnancy rather than blend this risk into the calculation of lifetime risk. This

Responses of dorsal spinal cord blood flow to noxious mechanical stimulation of the skin in anesthetized rats.

PubMed

Toda, Hiroko; Maruyama, Hitoshi; Budgell, Brian; Kurosawa, Mieko

2008-08-01

In urethane-anesthetized, artificially ventilated rats, alterations in dorsal spinal cord blood flow (SCBF) at the L4-6 level were measured with laser Doppler flowmetry in response to noxious mechanical cutaneous stimulation (pinching) of either a forepaw or a hindpaw. The stimulation was delivered ipsilaterally or contralaterally to the site of blood flow measurement. Pinching of the forepaw or the hindpaw on either side increased mean arterial pressure (MAP) to the same degree. However, the SCBF response to pinching of the ipsilateral hindpaw was significantly greater than that to other stimulations. These responses were not influenced by denervation of the baroreceptors. The responses of SCBF to pinching of the ipsilateral hindpaw persisted both after treatment with phenoxybenzamine and after spinalization at the C1-2 level, whereas the responses to pinching at other sites disappeared. The responses of MAP to stimulation at all four sites became negligible after treatment with phenoxybenzamine and after spinalization at the C1-2 level. These results indicate that noxious mechanical stimulation of the skin produces increases in SCBF via two mechanisms: one is via an elevation of systemic arterial pressure; the other is via a localized spinal mechanism evoked by ipsilateral, segmental inputs.

Biocompatibility Evaluation of Four Dentin Adhesives Used as Indirect Pulp Capping Materials

PubMed Central

Cortés, Olga; Bernabé, Antonia

2017-01-01

Background In many cases, the indirect pulp treatment (IPT) is an acceptable treatment for deciduous teeth with reversible pulp inflammation. Various medicaments have been used for IPT, ranging from calcium hydroxide and glass ionomers to dentin adhesives. Objective This in vitro trial aimed to measure cytotoxicity in a cell culture, comparing the following four adhesives: Xeno® V (XE), Excite® F DSC (EX), Adhese® OneF (AD) and Prime & Bond NT (PB). Materials and methods The adhesives were prepared according to the manufacturer’s instructions. After 24 hours of exposure, the cell viability was evaluated using a photometrical test (MTT test). Data were subjected to analysis of variance (ANOVA). Results Adhesives, the main component of which was 2-hydroxyethyl methacrylate (HEMA), were found to be less cytotoxic, while those that included the monomer urethane dimethacrylate (UDMA were the most cytotoxic) in their composition. The effects on cell viability assay varied between the adhesives assayed with statistically significant differences. Conclusions The results may support the argument that Adhese® OneF is the least cytotoxic of the adhesives assayed, and may be considered as an adhesive agent for indirect pulp treatment. However, Prime and Bond NT showed a reduced biocompatibility under the same conditions. PMID:28827848

The role of nitric oxide in the reversal of hemorrhagic shock by oxotremorine.

PubMed

Gören, M Z; Akici, A; Karaalp, A; Aker, R; Oktay, S

2001-10-05

In the present study, the effect of the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methylester (L-NAME), on the antishock actions of oxotremorine was investigated in rats subjected to hemorrhagic shock under urethane anesthesia. L-citrulline production in the AV3V region, as an indicator of nitric oxide (NO) synthesis, was assayed by high-performance liquid chromatography (HPLC) with fluorescent detection throughout the experiment. The rats were pretreated with either intravenous (i.v.) physiological saline or L-NAME (2.5 mg/kg) before bleeding. L-NAME potentiated the reversal of hypotension by oxotremorine (25 microg/kg, i.v.). However, oxotremorine either alone or in combination with L-NAME did not produce any significant change in 60-min survival rate at this low dose. Analysis of microdialysis samples collected from the AV3V region showed that L-citrulline concentration increased during bleeding and that this increase was abolished by L-NAME pretreatment. These results may suggest that nitric oxide production contributes to hypotension in rats bled to shock since nitric oxide levels in the AV3V region increased in response to bleeding and nitric oxide synthase (NOS) inhibition abolished this increase and potentiated the oxotremorine-induced reversal of hypotension.

Allergic contact dermatitis caused by acrylic-based medical dressings and adhesives.

PubMed

Mestach, Lien; Huygens, Sara; Goossens, An; Gilissen, Liesbeth

2018-06-11

Acrylates and methacrylates are acrylic resin monomers that are known to induce skin sensitization as a result of their presence in different materials, such as nail cosmetics, dental materials, printing inks, and adhesives. Allergic contact dermatitis resulting from the use of modern wound dressings containing them has only rarely been reported. To describe 2 patients who developed allergic contact dermatitis caused by acrylic-based modern medical dressings and/or adhesives. The medical charts of patients observed since 1990 were retrospectively reviewed for (meth)acrylate allergy resulting from contact with such materials, and their demographic characteristics and patch test results were analysed. Two patients were observed in 2014 and 2016 who had presented with positive patch test reactions to several acrylic-based dressings and/or adhesive materials, and to several (meth)acrylates, that is, hydroxyethyl acrylate, hydroxyethyl methacrylate, ethyleneglycol dimethacrylate, bisphenol A-glycidyl methacrylate/epoxy-acrylate, urethane diacrylate, and/or penta-erythritol acrylate. Allergic contact dermatitis needs to be considered in patients with eczematous reactions or delayed healing following the use of acrylic-based modern dressings or adhesives. However, identification of the culprit allergen is hampered by poor cooperation from the producers, so adequate labelling of medical devices is an urgent necessity. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Vestibular stimulation leads to distinct hemodynamic patterning

NASA Technical Reports Server (NTRS)

Kerman, I. A.; Emanuel, B. A.; Yates, B. J.

2000-01-01

Previous studies demonstrated that responses of a particular sympathetic nerve to vestibular stimulation depend on the type of tissue the nerve innervates as well as its anatomic location. In the present study, we sought to determine whether such precise patterning of vestibulosympathetic reflexes could lead to specific hemodynamic alterations in response to vestibular afferent activation. We simultaneously measured changes in systemic blood pressure and blood flow (with the use of Doppler flowmetry) to the hindlimb (femoral artery), forelimb (brachial artery), and kidney (renal artery) in chloralose-urethane-anesthetized, baroreceptor-denervated cats. Electrical vestibular stimulation led to depressor responses, 8 +/- 2 mmHg (mean +/- SE) in magnitude, that were accompanied by decreases in femoral vasoconstriction (23 +/- 4% decrease in vascular resistance or 36 +/- 7% increase in vascular conductance) and increases in brachial vascular tone (resistance increase of 10 +/- 6% and conductance decrease of 11 +/- 4%). Relatively small changes (<5%) in renal vascular tone were observed. In contrast, electrical stimulation of muscle and cutaneous afferents produced pressor responses (20 +/- 6 mmHg) that were accompanied by vasoconstriction in all three beds. These data suggest that vestibular inputs lead to a complex pattern of cardiovascular changes that is distinct from that which occurs in response to activation of other types of somatic afferents.

Modification of GABA-mediated inhibition by various injectable anesthetics.

PubMed

Albertson, T E; Walby, W F; Joy, R M

1992-09-01

Increasing doses of the injectable anesthetics etomidate, Saffan, thiopental, ketamine, and xylazine and the vehicles saline and propylene glycol were administered to urethane-anesthetized rats. Their effects in vivo on perforant pathway-evoked field excitatory post-synaptic potentials and population spikes in the hippocampal dentate gyrus were determined. The primary purpose was to ascertain whether these compounds affect hippocampal excitability in a manner consistent with their proposed mechanisms of action. Compared with their respective vehicles, thiopental, etomidate, and xylazine reduced the amplitude of population spikes to single perforant pathway stimulation by 20-30% at the highest doses tested. Xylazine also increased the latency to onset of the population spike. No other effects were observed. Using paired pulse paradigms, it was determined that etomidate produced a dramatic, prolonged reduction in granule cell excitability at interpulse intervals of 10-100 ms. The magnitude of the effect was dose related and was reversible with the discontinuance of administration of the drug. Similar changes occurred with Saffan (althesin) and thiopental. Ketamine produced a small but significant depression in granule cell excitability during intervals of 10-200 ms. Xylazine had no effect. These data corroborate the importance of a prolongation of gamma-aminobutyric acid A-mediated inhibition to the mechanism of actions of etomidate, thiopental, and Saffan at relevant exposure concentrations in vivo.

Amphetamine Augments Action Potential-Dependent Dopaminergic Signaling in the Striatum in Vivo

PubMed Central

Ramsson, Eric S.; Covey, Daniel P.; Daberkow, David P.; Litherland, Melissa T.; Juliano, Steven A.; Garris, Paul A.

2011-01-01

Amphetamine (AMPH) is thought to disrupt normal patterns of action potential-dependent dopaminergic signaling by depleting dopamine (DA) vesicular stores and promoting non-exocytotic DA efflux. Voltammetry in brain slices concurrently demonstrates these key drug effects, along with competitive inhibition of neuronal DA uptake. Here we perform comparable kinetic and voltammetric analyses in vivo to determine whether AMPH acts qualitatively and quantitatively similar in the intact brain. Fast-scan cyclic voltammetry measured extracellular DA in dorsal and ventral striata of urethane-anesthetized rats. Electrically evoked recordings were analyzed to determine Km and Vmax for DA uptake and vesicular DA release, while background voltammetric current indexed basal DA concentration. AMPH (0.5, 3, and 10 mg/kg i.p.) robustly increased evoked DA responses in both striatal subregions. The predominant contributor to these elevated levels was competitive uptake inhibition, as exocytotic release was unchanged in the ventral striatum and only modestly decreased in the dorsal striatum. Increases in basal DA levels were not detected. These results are consistent with AMPH augmenting action potential-dependent dopaminergic signaling in vivo across a wide, behaviorally relevant dose range. Future work should be directed at possible causes for the distinct in vitro and in vivo pharmacology of AMPH. PMID:21443523

Skin application of urea-containing cream affected cutaneous arterial sympathetic nerve activity, blood flow, and water evaporation.

PubMed

Horii, Yuko; Tanida, Mamoru; Shen, Jiao; Fujisaki, Yosiyuki; Fuyuki, Risa; Hashimoto, Kazuko; Niijima, Akira; Nakashima, Toshihiro; Nagai, Katsuya

2011-02-01

We observed that olfactory stimulation with scent of grapefruit oil elevated the activities of sympathetic nerves, and increased the plasma glycerol concentration and blood pressure. In contrast, olfactory stimulation with scent of lavender oil had opposite effects in rats. These suggest that changes in autonomic activities cause physiological functions via histaminergic H1 and H3 receptor. Moreover, it has been reported that somatic sensory stimulation affected autonomic neurotransmission. To examine effects of skin application of urea-containing cream on cutaneous arterial sympathetic nerve activity (CASNA), blood flow, and transepidermal water loss (TEWL). The activity of CASNA was determined by electrophysiological method, and cutaneous blood flow was determined using laser flowmeter in urethane-anesthetized rats, TEWL was measured using VapoMeter in the back skin of HWY hairless rats. CASNA was markedly and significantly inhibited by skin application of 10% urea-containing cream, whereas cutaneous blood flow was significantly elevated via histaminergic H3-receptor. In conscious hairless rats, TEWL was significantly decreased 24 h after application of 10% urea-containing cream to the back skin. These findings suggest that skin application of 10% urea-containing cream increases the cutaneous blood flow and water retaining ability, and that histaminergic H3-receptors may mediate these effects. © 2010 John Wiley & Sons A/S.